1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2021 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{} 1988-2021 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 @*
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) 1988-2021 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 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share GDB
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 Many options have both long and short forms; both are shown in the
966 following list. @value{GDBN} also recognizes the long forms if you truncate
967 them, so long as enough of the option is present to be unambiguous.
968 (If you prefer, you can flag option arguments with @samp{--} rather
969 than @samp{-}, though we illustrate the more usual convention.)
971 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
972 @c way, both those who look for -foo and --foo in the index, will find
976 @item -symbols @var{file}
978 @cindex @code{--symbols}
980 Read symbol table from file @var{file}.
982 @item -exec @var{file}
984 @cindex @code{--exec}
986 Use file @var{file} as the executable file to execute when appropriate,
987 and for examining pure data in conjunction with a core dump.
991 Read symbol table from file @var{file} and use it as the executable
994 @item -core @var{file}
996 @cindex @code{--core}
998 Use file @var{file} as a core dump to examine.
1000 @item -pid @var{number}
1001 @itemx -p @var{number}
1002 @cindex @code{--pid}
1004 Connect to process ID @var{number}, as with the @code{attach} command.
1006 @item -command @var{file}
1007 @itemx -x @var{file}
1008 @cindex @code{--command}
1010 Execute commands from file @var{file}. The contents of this file is
1011 evaluated exactly as the @code{source} command would.
1012 @xref{Command Files,, Command files}.
1014 @item -eval-command @var{command}
1015 @itemx -ex @var{command}
1016 @cindex @code{--eval-command}
1018 Execute a single @value{GDBN} command.
1020 This option may be used multiple times to call multiple commands. It may
1021 also be interleaved with @samp{-command} as required.
1024 @value{GDBP} -ex 'target sim' -ex 'load' \
1025 -x setbreakpoints -ex 'run' a.out
1028 @item -init-command @var{file}
1029 @itemx -ix @var{file}
1030 @cindex @code{--init-command}
1032 Execute commands from file @var{file} before loading the inferior (but
1033 after loading gdbinit files).
1036 @item -init-eval-command @var{command}
1037 @itemx -iex @var{command}
1038 @cindex @code{--init-eval-command}
1040 Execute a single @value{GDBN} command before loading the inferior (but
1041 after loading gdbinit files).
1044 @item -early-init-command @var{file}
1045 @itemx -eix @var{file}
1046 @cindex @code{--early-init-command}
1048 Execute commands from @var{file} very early in the initialization
1049 process, before any output is produced. @xref{Startup}.
1051 @item -early-init-eval-command @var{command}
1052 @itemx -eiex @var{command}
1053 @cindex @code{--early-init-eval-command}
1054 @cindex @code{-eiex}
1055 Execute a single @value{GDBN} command very early in the initialization
1056 process, before any output is produced.
1058 @item -directory @var{directory}
1059 @itemx -d @var{directory}
1060 @cindex @code{--directory}
1062 Add @var{directory} to the path to search for source and script files.
1066 @cindex @code{--readnow}
1068 Read each symbol file's entire symbol table immediately, rather than
1069 the default, which is to read it incrementally as it is needed.
1070 This makes startup slower, but makes future operations faster.
1073 @anchor{--readnever}
1074 @cindex @code{--readnever}, command-line option
1075 Do not read each symbol file's symbolic debug information. This makes
1076 startup faster but at the expense of not being able to perform
1077 symbolic debugging. DWARF unwind information is also not read,
1078 meaning backtraces may become incomplete or inaccurate. One use of
1079 this is when a user simply wants to do the following sequence: attach,
1080 dump core, detach. Loading the debugging information in this case is
1081 an unnecessary cause of delay.
1085 @subsection Choosing Modes
1087 You can run @value{GDBN} in various alternative modes---for example, in
1088 batch mode or quiet mode.
1096 Do not execute commands found in any initialization files
1097 (@pxref{Initialization Files}).
1102 Do not execute commands found in any home directory initialization
1103 file (@pxref{Initialization Files,,Home directory initialization
1104 file}). The system wide and current directory initialization files
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1116 @kindex set startup-quietly
1117 @kindex show startup-quietly
1118 This can also be enabled using @code{set startup-quietly on}. The
1119 default is @code{off}. Use @code{show startup-quietly} to see the
1120 current setting. Place @code{set startup-quietly on} into your early
1121 initialization file (@pxref{Initialization Files,,Initialization
1122 Files}) to have future @value{GDBN} sessions startup quietly.
1125 @cindex @code{--batch}
1126 Run in batch mode. Exit with status @code{0} after processing all the
1127 command files specified with @samp{-x} (and all commands from
1128 initialization files, if not inhibited with @samp{-n}). Exit with
1129 nonzero status if an error occurs in executing the @value{GDBN} commands
1130 in the command files. Batch mode also disables pagination, sets unlimited
1131 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1132 off} were in effect (@pxref{Messages/Warnings}).
1134 Batch mode may be useful for running @value{GDBN} as a filter, for
1135 example to download and run a program on another computer; in order to
1136 make this more useful, the message
1139 Program exited normally.
1143 (which is ordinarily issued whenever a program running under
1144 @value{GDBN} control terminates) is not issued when running in batch
1148 @cindex @code{--batch-silent}
1149 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1150 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1151 unaffected). This is much quieter than @samp{-silent} and would be useless
1152 for an interactive session.
1154 This is particularly useful when using targets that give @samp{Loading section}
1155 messages, for example.
1157 Note that targets that give their output via @value{GDBN}, as opposed to
1158 writing directly to @code{stdout}, will also be made silent.
1160 @item -return-child-result
1161 @cindex @code{--return-child-result}
1162 The return code from @value{GDBN} will be the return code from the child
1163 process (the process being debugged), with the following exceptions:
1167 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1168 internal error. In this case the exit code is the same as it would have been
1169 without @samp{-return-child-result}.
1171 The user quits with an explicit value. E.g., @samp{quit 1}.
1173 The child process never runs, or is not allowed to terminate, in which case
1174 the exit code will be -1.
1177 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1178 when @value{GDBN} is being used as a remote program loader or simulator
1183 @cindex @code{--nowindows}
1185 ``No windows''. If @value{GDBN} comes with a graphical user interface
1186 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1187 interface. If no GUI is available, this option has no effect.
1191 @cindex @code{--windows}
1193 If @value{GDBN} includes a GUI, then this option requires it to be
1196 @item -cd @var{directory}
1198 Run @value{GDBN} using @var{directory} as its working directory,
1199 instead of the current directory.
1201 @item -data-directory @var{directory}
1202 @itemx -D @var{directory}
1203 @cindex @code{--data-directory}
1205 Run @value{GDBN} using @var{directory} as its data directory.
1206 The data directory is where @value{GDBN} searches for its
1207 auxiliary files. @xref{Data Files}.
1211 @cindex @code{--fullname}
1213 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1214 subprocess. It tells @value{GDBN} to output the full file name and line
1215 number in a standard, recognizable fashion each time a stack frame is
1216 displayed (which includes each time your program stops). This
1217 recognizable format looks like two @samp{\032} characters, followed by
1218 the file name, line number and character position separated by colons,
1219 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1220 @samp{\032} characters as a signal to display the source code for the
1223 @item -annotate @var{level}
1224 @cindex @code{--annotate}
1225 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1226 effect is identical to using @samp{set annotate @var{level}}
1227 (@pxref{Annotations}). The annotation @var{level} controls how much
1228 information @value{GDBN} prints together with its prompt, values of
1229 expressions, source lines, and other types of output. Level 0 is the
1230 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1231 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1232 that control @value{GDBN}, and level 2 has been deprecated.
1234 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1238 @cindex @code{--args}
1239 Change interpretation of command line so that arguments following the
1240 executable file are passed as command line arguments to the inferior.
1241 This option stops option processing.
1243 @item -baud @var{bps}
1245 @cindex @code{--baud}
1247 Set the line speed (baud rate or bits per second) of any serial
1248 interface used by @value{GDBN} for remote debugging.
1250 @item -l @var{timeout}
1252 Set the timeout (in seconds) of any communication used by @value{GDBN}
1253 for remote debugging.
1255 @item -tty @var{device}
1256 @itemx -t @var{device}
1257 @cindex @code{--tty}
1259 Run using @var{device} for your program's standard input and output.
1260 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1262 @c resolve the situation of these eventually
1264 @cindex @code{--tui}
1265 Activate the @dfn{Text User Interface} when starting. The Text User
1266 Interface manages several text windows on the terminal, showing
1267 source, assembly, registers and @value{GDBN} command outputs
1268 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1269 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1270 Using @value{GDBN} under @sc{gnu} Emacs}).
1272 @item -interpreter @var{interp}
1273 @cindex @code{--interpreter}
1274 Use the interpreter @var{interp} for interface with the controlling
1275 program or device. This option is meant to be set by programs which
1276 communicate with @value{GDBN} using it as a back end.
1277 @xref{Interpreters, , Command Interpreters}.
1279 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1280 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1281 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1282 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1283 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1284 interfaces are no longer supported.
1287 @cindex @code{--write}
1288 Open the executable and core files for both reading and writing. This
1289 is equivalent to the @samp{set write on} command inside @value{GDBN}
1293 @cindex @code{--statistics}
1294 This option causes @value{GDBN} to print statistics about time and
1295 memory usage after it completes each command and returns to the prompt.
1298 @cindex @code{--version}
1299 This option causes @value{GDBN} to print its version number and
1300 no-warranty blurb, and exit.
1302 @item -configuration
1303 @cindex @code{--configuration}
1304 This option causes @value{GDBN} to print details about its build-time
1305 configuration parameters, and then exit. These details can be
1306 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1311 @subsection What @value{GDBN} Does During Startup
1312 @cindex @value{GDBN} startup
1314 Here's the description of what @value{GDBN} does during session startup:
1319 Performs minimal setup required to initialize basic internal state.
1322 @cindex early initialization file
1323 Reads commands from the early initialization file (if any) in your
1324 home directory. Only a restricted set of commands can be placed into
1325 an early initialization file, see @ref{Initialization Files}, for
1329 Executes commands and command files specified by the @samp{-eiex} and
1330 @samp{-eix} command line options in their specified order. Only a
1331 restricted set of commands can be used with @samp{-eiex} and
1332 @samp{eix}, see @ref{Initialization Files}, for details.
1335 Sets up the command interpreter as specified by the command line
1336 (@pxref{Mode Options, interpreter}).
1340 Reads the system wide initialization file and the files from the
1341 system wide initialization directory, @pxref{System Wide Init Files}.
1344 Reads the initialization file (if any) in your home directory and
1345 executes all the commands in that file, @pxref{Home Directory Init
1348 @anchor{Option -init-eval-command}
1350 Executes commands and command files specified by the @samp{-iex} and
1351 @samp{-ix} options in their specified order. Usually you should use the
1352 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1353 settings before @value{GDBN} init files get executed and before inferior
1357 Processes command line options and operands.
1360 Reads and executes the commands from the initialization file (if any)
1361 in the current working directory as long as @samp{set auto-load
1362 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1363 Directory}). This is only done if the current directory is different
1364 from your home directory. Thus, you can have more than one init file,
1365 one generic in your home directory, and another, specific to the
1366 program you are debugging, in the directory where you invoke
1367 @value{GDBN}. @xref{Init File in the Current Directory during
1371 If the command line specified a program to debug, or a process to
1372 attach to, or a core file, @value{GDBN} loads any auto-loaded
1373 scripts provided for the program or for its loaded shared libraries.
1374 @xref{Auto-loading}.
1376 If you wish to disable the auto-loading during startup,
1377 you must do something like the following:
1380 $ gdb -iex "set auto-load python-scripts off" myprogram
1383 Option @samp{-ex} does not work because the auto-loading is then turned
1387 Executes commands and command files specified by the @samp{-ex} and
1388 @samp{-x} options in their specified order. @xref{Command Files}, for
1389 more details about @value{GDBN} command files.
1392 Reads the command history recorded in the @dfn{history file}.
1393 @xref{Command History}, for more details about the command history and the
1394 files where @value{GDBN} records it.
1397 @node Initialization Files
1398 @subsection Initialization Files
1399 @cindex init file name
1401 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1402 from several initialization files. These initialization files use the
1403 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1404 processed by @value{GDBN} in the same way.
1406 To display the list of initialization files loaded by @value{GDBN} at
1407 startup, in the order they will be loaded, you can use @kbd{gdb
1410 @cindex early initialization
1411 The @dfn{early initialization} file is loaded very early in
1412 @value{GDBN}'s initialization process, before the interpreter
1413 (@pxref{Interpreters}) has been initialized, and before the default
1414 target (@pxref{Targets}) is initialized. Only @code{set} or
1415 @code{source} commands should be placed into an early initialization
1416 file, and the only @code{set} commands that can be used are those that
1417 control how @value{GDBN} starts up.
1419 Commands that can be placed into an early initialization file will be
1420 documented as such throughout this manual. Any command that is not
1421 documented as being suitable for an early initialization file should
1422 instead be placed into a general initialization file. Command files
1423 passed to @code{--early-init-command} or @code{-eix} are also early
1424 initialization files, with the same command restrictions. Only
1425 commands that can appear in an early initialization file should be
1426 passed to @code{--early-init-eval-command} or @code{-eiex}.
1428 @cindex general initialization
1429 In contrast, the @dfn{general initialization} files are processed
1430 later, after @value{GDBN} has finished its own internal initialization
1431 process, any valid command can be used in these files.
1433 @cindex initialization file
1434 Throughout the rest of this document the term @dfn{initialization
1435 file} refers to one of the general initialization files, not the early
1436 initialization file. Any discussion of the early initialization file
1437 will specifically mention that it is the early initialization file
1440 As the system wide and home directory initialization files are
1441 processed before most command line options, changes to settings
1442 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1443 command line options and operands.
1445 The following sections describe where @value{GDBN} looks for the early
1446 initialization and initialization files, and the order that the files
1449 @subsubsection Home directory early initialization files
1451 @value{GDBN} initially looks for an early initialization file in the
1452 users home directory@footnote{On DOS/Windows systems, the home
1453 directory is the one pointed to by the @env{HOME} environment
1454 variable.}. There are a number of locations that @value{GDBN} will
1455 search in the home directory, these locations are searched in order
1456 and @value{GDBN} will load the first file that it finds, and
1457 subsequent locations will not be checked.
1459 On non-macOS hosts the locations searched are:
1462 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1463 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1465 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1466 by the environment variable @env{HOME}, if it is defined.
1468 The file @file{.gdbearlyinit} within the directory pointed to by the
1469 environment variable @env{HOME}, if it is defined.
1472 By contrast, on macOS hosts the locations searched are:
1475 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1476 directory pointed to by the environment variable @env{HOME}, if it is
1479 The file @file{.gdbearlyinit} within the directory pointed to by the
1480 environment variable @env{HOME}, if it is defined.
1483 It is possible to prevent the home directory early initialization file
1484 from being loaded using the @samp{-nx} or @samp{-nh} command line
1485 options, @pxref{Mode Options,,Choosing Modes}.
1487 @anchor{System Wide Init Files}
1488 @subsubsection System wide initialization files
1490 There are two locations that are searched for system wide
1491 initialization files. Both of these locations are always checked:
1495 @item @file{system.gdbinit}
1496 This is a single system-wide initialization file. Its location is
1497 specified with the @code{--with-system-gdbinit} configure option
1498 (@pxref{System-wide configuration}). It is loaded first when
1499 @value{GDBN} starts, before command line options have been processed.
1501 @item @file{system.gdbinit.d}
1502 This is the system-wide initialization directory. Its location is
1503 specified with the @code{--with-system-gdbinit-dir} configure option
1504 (@pxref{System-wide configuration}). Files in this directory are
1505 loaded in alphabetical order immediately after @file{system.gdbinit}
1506 (if enabled) when @value{GDBN} starts, before command line options
1507 have been processed. Files need to have a recognized scripting
1508 language extension (@file{.py}/@file{.scm}) or be named with a
1509 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1510 commands. @value{GDBN} will not recurse into any subdirectories of
1515 It is possible to prevent the system wide initialization files from
1516 being loaded using the @samp{-nx} command line option, @pxref{Mode
1517 Options,,Choosing Modes}.
1519 @anchor{Home Directory Init File}
1520 @subsubsection Home directory initialization file
1521 @cindex @file{gdbinit}
1522 @cindex @file{.gdbinit}
1523 @cindex @file{gdb.ini}
1525 After loading the system wide initialization files @value{GDBN} will
1526 look for an initialization file in the users home
1527 directory@footnote{On DOS/Windows systems, the home directory is the
1528 one pointed to by the @env{HOME} environment variable.}. There are a
1529 number of locations that @value{GDBN} will search in the home
1530 directory, these locations are searched in order and @value{GDBN} will
1531 load the first file that it finds, and subsequent locations will not
1534 On non-Apple hosts the locations searched are:
1536 @item $XDG_CONFIG_HOME/gdb/gdbinit
1537 @item $HOME/.config/gdb/gdbinit
1538 @item $HOME/.gdbinit
1541 While on Apple hosts the locations searched are:
1543 @item $HOME/Library/Preferences/gdb/gdbinit
1544 @item $HOME/.gdbinit
1547 It is possible to prevent the home directory initialization file from
1548 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1549 @pxref{Mode Options,,Choosing Modes}.
1551 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1552 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1553 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1554 uses the standard name, but if it finds a @file{gdb.ini} file in your
1555 home directory, it warns you about that and suggests to rename the
1556 file to the standard name.
1558 @anchor{Init File in the Current Directory during Startup}
1559 @subsubsection Local directory initialization file
1561 @value{GDBN} will check the current directory for a file called
1562 @file{.gdbinit}. It is loaded last, after command line options
1563 other than @samp{-x} and @samp{-ex} have been processed. The command
1564 line options @samp{-x} and @samp{-ex} are processed last, after
1565 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1568 If the file in the current directory was already loaded as the home
1569 directory initialization file then it will not be loaded a second
1572 It is possible to prevent the local directory initialization file from
1573 being loaded using the @samp{-nx} command line option, @pxref{Mode
1574 Options,,Choosing Modes}.
1577 @section Quitting @value{GDBN}
1578 @cindex exiting @value{GDBN}
1579 @cindex leaving @value{GDBN}
1582 @kindex quit @r{[}@var{expression}@r{]}
1583 @kindex exit @r{[}@var{expression}@r{]}
1584 @kindex q @r{(@code{quit})}
1585 @item quit @r{[}@var{expression}@r{]}
1586 @itemx exit @r{[}@var{expression}@r{]}
1588 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1589 @code{q}), the @code{exit} command, or type an end-of-file
1590 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1591 @value{GDBN} will terminate normally; otherwise it will terminate using
1592 the result of @var{expression} as the error code.
1596 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1597 terminates the action of any @value{GDBN} command that is in progress and
1598 returns to @value{GDBN} command level. It is safe to type the interrupt
1599 character at any time because @value{GDBN} does not allow it to take effect
1600 until a time when it is safe.
1602 If you have been using @value{GDBN} to control an attached process or
1603 device, you can release it with the @code{detach} command
1604 (@pxref{Attach, ,Debugging an Already-running Process}).
1606 @node Shell Commands
1607 @section Shell Commands
1609 If you need to execute occasional shell commands during your
1610 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1611 just use the @code{shell} command.
1616 @cindex shell escape
1617 @item shell @var{command-string}
1618 @itemx !@var{command-string}
1619 Invoke a standard shell to execute @var{command-string}.
1620 Note that no space is needed between @code{!} and @var{command-string}.
1621 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1622 exists, determines which shell to run. Otherwise @value{GDBN} uses
1623 the default shell (@file{/bin/sh} on GNU and Unix systems,
1624 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1627 The utility @code{make} is often needed in development environments.
1628 You do not have to use the @code{shell} command for this purpose in
1633 @cindex calling make
1634 @item make @var{make-args}
1635 Execute the @code{make} program with the specified
1636 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1642 @cindex send the output of a gdb command to a shell command
1644 @item pipe [@var{command}] | @var{shell_command}
1645 @itemx | [@var{command}] | @var{shell_command}
1646 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1647 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1648 Executes @var{command} and sends its output to @var{shell_command}.
1649 Note that no space is needed around @code{|}.
1650 If no @var{command} is provided, the last command executed is repeated.
1652 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1653 can be used to specify an alternate delimiter string @var{delim} that separates
1654 the @var{command} from the @var{shell_command}.
1687 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1688 this contains a PIPE char
1689 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1690 this contains a PIPE char!
1696 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1697 can be used to examine the exit status of the last shell command launched
1698 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1699 @xref{Convenience Vars,, Convenience Variables}.
1701 @node Logging Output
1702 @section Logging Output
1703 @cindex logging @value{GDBN} output
1704 @cindex save @value{GDBN} output to a file
1706 You may want to save the output of @value{GDBN} commands to a file.
1707 There are several commands to control @value{GDBN}'s logging.
1710 @kindex set logging enabled
1711 @item set logging enabled [on|off]
1712 Enable or disable logging.
1713 @cindex logging file name
1714 @item set logging file @var{file}
1715 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1716 @item set logging overwrite [on|off]
1717 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1718 you want @code{set logging enabled on} to overwrite the logfile instead.
1719 @item set logging redirect [on|off]
1720 By default, @value{GDBN} output will go to both the terminal and the logfile.
1721 Set @code{redirect} if you want output to go only to the log file.
1722 @item set logging debugredirect [on|off]
1723 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1724 Set @code{debugredirect} if you want debug output to go only to the log file.
1725 @kindex show logging
1727 Show the current values of the logging settings.
1730 You can also redirect the output of a @value{GDBN} command to a
1731 shell command. @xref{pipe}.
1733 @chapter @value{GDBN} Commands
1735 You can abbreviate a @value{GDBN} command to the first few letters of the command
1736 name, if that abbreviation is unambiguous; and you can repeat certain
1737 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1738 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1739 show you the alternatives available, if there is more than one possibility).
1742 * Command Syntax:: How to give commands to @value{GDBN}
1743 * Command Settings:: How to change default behavior of commands
1744 * Completion:: Command completion
1745 * Command Options:: Command options
1746 * Help:: How to ask @value{GDBN} for help
1749 @node Command Syntax
1750 @section Command Syntax
1752 A @value{GDBN} command is a single line of input. There is no limit on
1753 how long it can be. It starts with a command name, which is followed by
1754 arguments whose meaning depends on the command name. For example, the
1755 command @code{step} accepts an argument which is the number of times to
1756 step, as in @samp{step 5}. You can also use the @code{step} command
1757 with no arguments. Some commands do not allow any arguments.
1759 @cindex abbreviation
1760 @value{GDBN} command names may always be truncated if that abbreviation is
1761 unambiguous. Other possible command abbreviations are listed in the
1762 documentation for individual commands. In some cases, even ambiguous
1763 abbreviations are allowed; for example, @code{s} is specially defined as
1764 equivalent to @code{step} even though there are other commands whose
1765 names start with @code{s}. You can test abbreviations by using them as
1766 arguments to the @code{help} command.
1768 @cindex repeating commands
1769 @kindex RET @r{(repeat last command)}
1770 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1771 repeat the previous command. Certain commands (for example, @code{run})
1772 will not repeat this way; these are commands whose unintentional
1773 repetition might cause trouble and which you are unlikely to want to
1774 repeat. User-defined commands can disable this feature; see
1775 @ref{Define, dont-repeat}.
1777 The @code{list} and @code{x} commands, when you repeat them with
1778 @key{RET}, construct new arguments rather than repeating
1779 exactly as typed. This permits easy scanning of source or memory.
1781 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1782 output, in a way similar to the common utility @code{more}
1783 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1784 @key{RET} too many in this situation, @value{GDBN} disables command
1785 repetition after any command that generates this sort of display.
1787 @kindex # @r{(a comment)}
1789 Any text from a @kbd{#} to the end of the line is a comment; it does
1790 nothing. This is useful mainly in command files (@pxref{Command
1791 Files,,Command Files}).
1793 @cindex repeating command sequences
1794 @kindex Ctrl-o @r{(operate-and-get-next)}
1795 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1796 commands. This command accepts the current line, like @key{RET}, and
1797 then fetches the next line relative to the current line from the history
1801 @node Command Settings
1802 @section Command Settings
1803 @cindex default behavior of commands, changing
1804 @cindex default settings, changing
1806 Many commands change their behavior according to command-specific
1807 variables or settings. These settings can be changed with the
1808 @code{set} subcommands. For example, the @code{print} command
1809 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1810 settings changeable with the commands @code{set print elements
1811 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1813 You can change these settings to your preference in the gdbinit files
1814 loaded at @value{GDBN} startup. @xref{Startup}.
1816 The settings can also be changed interactively during the debugging
1817 session. For example, to change the limit of array elements to print,
1818 you can do the following:
1820 (@value{GDBN}) set print elements 10
1821 (@value{GDBN}) print some_array
1822 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1825 The above @code{set print elements 10} command changes the number of
1826 elements to print from the default of 200 to 10. If you only intend
1827 this limit of 10 to be used for printing @code{some_array}, then you
1828 must restore the limit back to 200, with @code{set print elements
1831 Some commands allow overriding settings with command options. For
1832 example, the @code{print} command supports a number of options that
1833 allow overriding relevant global print settings as set by @code{set
1834 print} subcommands. @xref{print options}. The example above could be
1837 (@value{GDBN}) print -elements 10 -- some_array
1838 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1841 Alternatively, you can use the @code{with} command to change a setting
1842 temporarily, for the duration of a command invocation.
1845 @kindex with command
1846 @kindex w @r{(@code{with})}
1848 @cindex temporarily change settings
1849 @item with @var{setting} [@var{value}] [-- @var{command}]
1850 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1851 Temporarily set @var{setting} to @var{value} for the duration of
1854 @var{setting} is any setting you can change with the @code{set}
1855 subcommands. @var{value} is the value to assign to @code{setting}
1856 while running @code{command}.
1858 If no @var{command} is provided, the last command executed is
1861 If a @var{command} is provided, it must be preceded by a double dash
1862 (@code{--}) separator. This is required because some settings accept
1863 free-form arguments, such as expressions or filenames.
1865 For example, the command
1867 (@value{GDBN}) with print array on -- print some_array
1870 is equivalent to the following 3 commands:
1872 (@value{GDBN}) set print array on
1873 (@value{GDBN}) print some_array
1874 (@value{GDBN}) set print array off
1877 The @code{with} command is particularly useful when you want to
1878 override a setting while running user-defined commands, or commands
1879 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1882 (@value{GDBN}) with print pretty on -- my_complex_command
1885 To change several settings for the same command, you can nest
1886 @code{with} commands. For example, @code{with language ada -- with
1887 print elements 10} temporarily changes the language to Ada and sets a
1888 limit of 10 elements to print for arrays and strings.
1893 @section Command Completion
1896 @cindex word completion
1897 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1898 only one possibility; it can also show you what the valid possibilities
1899 are for the next word in a command, at any time. This works for @value{GDBN}
1900 commands, @value{GDBN} subcommands, command options, and the names of symbols
1903 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1904 of a word. If there is only one possibility, @value{GDBN} fills in the
1905 word, and waits for you to finish the command (or press @key{RET} to
1906 enter it). For example, if you type
1908 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1909 @c complete accuracy in these examples; space introduced for clarity.
1910 @c If texinfo enhancements make it unnecessary, it would be nice to
1911 @c replace " @key" by "@key" in the following...
1913 (@value{GDBP}) info bre @key{TAB}
1917 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1918 the only @code{info} subcommand beginning with @samp{bre}:
1921 (@value{GDBP}) info breakpoints
1925 You can either press @key{RET} at this point, to run the @code{info
1926 breakpoints} command, or backspace and enter something else, if
1927 @samp{breakpoints} does not look like the command you expected. (If you
1928 were sure you wanted @code{info breakpoints} in the first place, you
1929 might as well just type @key{RET} immediately after @samp{info bre},
1930 to exploit command abbreviations rather than command completion).
1932 If there is more than one possibility for the next word when you press
1933 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1934 characters and try again, or just press @key{TAB} a second time;
1935 @value{GDBN} displays all the possible completions for that word. For
1936 example, you might want to set a breakpoint on a subroutine whose name
1937 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1938 just sounds the bell. Typing @key{TAB} again displays all the
1939 function names in your program that begin with those characters, for
1943 (@value{GDBP}) b make_ @key{TAB}
1944 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1945 make_a_section_from_file make_environ
1946 make_abs_section make_function_type
1947 make_blockvector make_pointer_type
1948 make_cleanup make_reference_type
1949 make_command make_symbol_completion_list
1950 (@value{GDBP}) b make_
1954 After displaying the available possibilities, @value{GDBN} copies your
1955 partial input (@samp{b make_} in the example) so you can finish the
1958 If you just want to see the list of alternatives in the first place, you
1959 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1960 means @kbd{@key{META} ?}. You can type this either by holding down a
1961 key designated as the @key{META} shift on your keyboard (if there is
1962 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1964 If the number of possible completions is large, @value{GDBN} will
1965 print as much of the list as it has collected, as well as a message
1966 indicating that the list may be truncated.
1969 (@value{GDBP}) b m@key{TAB}@key{TAB}
1971 <... the rest of the possible completions ...>
1972 *** List may be truncated, max-completions reached. ***
1977 This behavior can be controlled with the following commands:
1980 @kindex set max-completions
1981 @item set max-completions @var{limit}
1982 @itemx set max-completions unlimited
1983 Set the maximum number of completion candidates. @value{GDBN} will
1984 stop looking for more completions once it collects this many candidates.
1985 This is useful when completing on things like function names as collecting
1986 all the possible candidates can be time consuming.
1987 The default value is 200. A value of zero disables tab-completion.
1988 Note that setting either no limit or a very large limit can make
1990 @kindex show max-completions
1991 @item show max-completions
1992 Show the maximum number of candidates that @value{GDBN} will collect and show
1996 @cindex quotes in commands
1997 @cindex completion of quoted strings
1998 Sometimes the string you need, while logically a ``word'', may contain
1999 parentheses or other characters that @value{GDBN} normally excludes from
2000 its notion of a word. To permit word completion to work in this
2001 situation, you may enclose words in @code{'} (single quote marks) in
2002 @value{GDBN} commands.
2004 A likely situation where you might need this is in typing an
2005 expression that involves a C@t{++} symbol name with template
2006 parameters. This is because when completing expressions, GDB treats
2007 the @samp{<} character as word delimiter, assuming that it's the
2008 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2011 For example, when you want to call a C@t{++} template function
2012 interactively using the @code{print} or @code{call} commands, you may
2013 need to distinguish whether you mean the version of @code{name} that
2014 was specialized for @code{int}, @code{name<int>()}, or the version
2015 that was specialized for @code{float}, @code{name<float>()}. To use
2016 the word-completion facilities in this situation, type a single quote
2017 @code{'} at the beginning of the function name. This alerts
2018 @value{GDBN} that it may need to consider more information than usual
2019 when you press @key{TAB} or @kbd{M-?} to request word completion:
2022 (@value{GDBP}) p 'func< @kbd{M-?}
2023 func<int>() func<float>()
2024 (@value{GDBP}) p 'func<
2027 When setting breakpoints however (@pxref{Specify Location}), you don't
2028 usually need to type a quote before the function name, because
2029 @value{GDBN} understands that you want to set a breakpoint on a
2033 (@value{GDBP}) b func< @kbd{M-?}
2034 func<int>() func<float>()
2035 (@value{GDBP}) b func<
2038 This is true even in the case of typing the name of C@t{++} overloaded
2039 functions (multiple definitions of the same function, distinguished by
2040 argument type). For example, when you want to set a breakpoint you
2041 don't need to distinguish whether you mean the version of @code{name}
2042 that takes an @code{int} parameter, @code{name(int)}, or the version
2043 that takes a @code{float} parameter, @code{name(float)}.
2046 (@value{GDBP}) b bubble( @kbd{M-?}
2047 bubble(int) bubble(double)
2048 (@value{GDBP}) b bubble(dou @kbd{M-?}
2052 See @ref{quoting names} for a description of other scenarios that
2055 For more information about overloaded functions, see @ref{C Plus Plus
2056 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2057 overload-resolution off} to disable overload resolution;
2058 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2060 @cindex completion of structure field names
2061 @cindex structure field name completion
2062 @cindex completion of union field names
2063 @cindex union field name completion
2064 When completing in an expression which looks up a field in a
2065 structure, @value{GDBN} also tries@footnote{The completer can be
2066 confused by certain kinds of invalid expressions. Also, it only
2067 examines the static type of the expression, not the dynamic type.} to
2068 limit completions to the field names available in the type of the
2072 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2073 magic to_fputs to_rewind
2074 to_data to_isatty to_write
2075 to_delete to_put to_write_async_safe
2080 This is because the @code{gdb_stdout} is a variable of the type
2081 @code{struct ui_file} that is defined in @value{GDBN} sources as
2088 ui_file_flush_ftype *to_flush;
2089 ui_file_write_ftype *to_write;
2090 ui_file_write_async_safe_ftype *to_write_async_safe;
2091 ui_file_fputs_ftype *to_fputs;
2092 ui_file_read_ftype *to_read;
2093 ui_file_delete_ftype *to_delete;
2094 ui_file_isatty_ftype *to_isatty;
2095 ui_file_rewind_ftype *to_rewind;
2096 ui_file_put_ftype *to_put;
2101 @node Command Options
2102 @section Command options
2104 @cindex command options
2105 Some commands accept options starting with a leading dash. For
2106 example, @code{print -pretty}. Similarly to command names, you can
2107 abbreviate a @value{GDBN} option to the first few letters of the
2108 option name, if that abbreviation is unambiguous, and you can also use
2109 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2110 in an option (or to show you the alternatives available, if there is
2111 more than one possibility).
2113 @cindex command options, raw input
2114 Some commands take raw input as argument. For example, the print
2115 command processes arbitrary expressions in any of the languages
2116 supported by @value{GDBN}. With such commands, because raw input may
2117 start with a leading dash that would be confused with an option or any
2118 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2119 -pretty} or printing negative @code{p}?), if you specify any command
2120 option, then you must use a double-dash (@code{--}) delimiter to
2121 indicate the end of options.
2123 @cindex command options, boolean
2125 Some options are described as accepting an argument which can be
2126 either @code{on} or @code{off}. These are known as @dfn{boolean
2127 options}. Similarly to boolean settings commands---@code{on} and
2128 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2129 @code{enable} can also be used as ``true'' value, and any of @code{0},
2130 @code{no} and @code{disable} can also be used as ``false'' value. You
2131 can also omit a ``true'' value, as it is implied by default.
2133 For example, these are equivalent:
2136 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2137 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2140 You can discover the set of options some command accepts by completing
2141 on @code{-} after the command name. For example:
2144 (@value{GDBP}) print -@key{TAB}@key{TAB}
2145 -address -max-depth -pretty -symbol
2146 -array -memory-tag-violations -raw-values -union
2147 -array-indexes -null-stop -repeats -vtbl
2148 -elements -object -static-members
2151 Completion will in some cases guide you with a suggestion of what kind
2152 of argument an option expects. For example:
2155 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2159 Here, the option expects a number (e.g., @code{100}), not literal
2160 @code{NUMBER}. Such metasyntactical arguments are always presented in
2163 (For more on using the @code{print} command, see @ref{Data, ,Examining
2167 @section Getting Help
2168 @cindex online documentation
2171 You can always ask @value{GDBN} itself for information on its commands,
2172 using the command @code{help}.
2175 @kindex h @r{(@code{help})}
2178 You can use @code{help} (abbreviated @code{h}) with no arguments to
2179 display a short list of named classes of commands:
2183 List of classes of commands:
2185 aliases -- User-defined aliases of other commands
2186 breakpoints -- Making program stop at certain points
2187 data -- Examining data
2188 files -- Specifying and examining files
2189 internals -- Maintenance commands
2190 obscure -- Obscure features
2191 running -- Running the program
2192 stack -- Examining the stack
2193 status -- Status inquiries
2194 support -- Support facilities
2195 tracepoints -- Tracing of program execution without
2196 stopping the program
2197 user-defined -- User-defined commands
2199 Type "help" followed by a class name for a list of
2200 commands in that class.
2201 Type "help" followed by command name for full
2203 Command name abbreviations are allowed if unambiguous.
2206 @c the above line break eliminates huge line overfull...
2208 @item help @var{class}
2209 Using one of the general help classes as an argument, you can get a
2210 list of the individual commands in that class. If a command has
2211 aliases, the aliases are given after the command name, separated by
2212 commas. If an alias has default arguments, the full definition of
2213 the alias is given after the first line.
2214 For example, here is the help display for the class @code{status}:
2217 (@value{GDBP}) help status
2222 @c Line break in "show" line falsifies real output, but needed
2223 @c to fit in smallbook page size.
2224 info, inf, i -- Generic command for showing things
2225 about the program being debugged
2226 info address, iamain -- Describe where symbol SYM is stored.
2227 alias iamain = info address main
2228 info all-registers -- List of all registers and their contents,
2229 for selected stack frame.
2231 show, info set -- Generic command for showing things
2234 Type "help" followed by command name for full
2236 Command name abbreviations are allowed if unambiguous.
2240 @item help @var{command}
2241 With a command name as @code{help} argument, @value{GDBN} displays a
2242 short paragraph on how to use that command. If that command has
2243 one or more aliases, @value{GDBN} will display a first line with
2244 the command name and all its aliases separated by commas.
2245 This first line will be followed by the full definition of all aliases
2246 having default arguments.
2249 @item apropos [-v] @var{regexp}
2250 The @code{apropos} command searches through all of the @value{GDBN}
2251 commands, and their documentation, for the regular expression specified in
2252 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2253 which stands for @samp{verbose}, indicates to output the full documentation
2254 of the matching commands and highlight the parts of the documentation
2255 matching @var{regexp}. For example:
2266 alias -- Define a new command that is an alias of an existing command
2267 aliases -- User-defined aliases of other commands
2275 apropos -v cut.*thread apply
2279 results in the below output, where @samp{cut for 'thread apply}
2280 is highlighted if styling is enabled.
2284 taas -- Apply a command to all threads (ignoring errors
2287 shortcut for 'thread apply all -s COMMAND'
2289 tfaas -- Apply a command to all frames of all threads
2290 (ignoring errors and empty output).
2291 Usage: tfaas COMMAND
2292 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2297 @item complete @var{args}
2298 The @code{complete @var{args}} command lists all the possible completions
2299 for the beginning of a command. Use @var{args} to specify the beginning of the
2300 command you want completed. For example:
2306 @noindent results in:
2317 @noindent This is intended for use by @sc{gnu} Emacs.
2320 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2321 and @code{show} to inquire about the state of your program, or the state
2322 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2323 manual introduces each of them in the appropriate context. The listings
2324 under @code{info} and under @code{show} in the Command, Variable, and
2325 Function Index point to all the sub-commands. @xref{Command and Variable
2331 @kindex i @r{(@code{info})}
2333 This command (abbreviated @code{i}) is for describing the state of your
2334 program. For example, you can show the arguments passed to a function
2335 with @code{info args}, list the registers currently in use with @code{info
2336 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2337 You can get a complete list of the @code{info} sub-commands with
2338 @w{@code{help info}}.
2342 You can assign the result of an expression to an environment variable with
2343 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2344 @code{set prompt $}.
2348 In contrast to @code{info}, @code{show} is for describing the state of
2349 @value{GDBN} itself.
2350 You can change most of the things you can @code{show}, by using the
2351 related command @code{set}; for example, you can control what number
2352 system is used for displays with @code{set radix}, or simply inquire
2353 which is currently in use with @code{show radix}.
2356 To display all the settable parameters and their current
2357 values, you can use @code{show} with no arguments; you may also use
2358 @code{info set}. Both commands produce the same display.
2359 @c FIXME: "info set" violates the rule that "info" is for state of
2360 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2361 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2365 Here are several miscellaneous @code{show} subcommands, all of which are
2366 exceptional in lacking corresponding @code{set} commands:
2369 @kindex show version
2370 @cindex @value{GDBN} version number
2372 Show what version of @value{GDBN} is running. You should include this
2373 information in @value{GDBN} bug-reports. If multiple versions of
2374 @value{GDBN} are in use at your site, you may need to determine which
2375 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2376 commands are introduced, and old ones may wither away. Also, many
2377 system vendors ship variant versions of @value{GDBN}, and there are
2378 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2379 The version number is the same as the one announced when you start
2382 @kindex show copying
2383 @kindex info copying
2384 @cindex display @value{GDBN} copyright
2387 Display information about permission for copying @value{GDBN}.
2389 @kindex show warranty
2390 @kindex info warranty
2392 @itemx info warranty
2393 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2394 if your version of @value{GDBN} comes with one.
2396 @kindex show configuration
2397 @item show configuration
2398 Display detailed information about the way @value{GDBN} was configured
2399 when it was built. This displays the optional arguments passed to the
2400 @file{configure} script and also configuration parameters detected
2401 automatically by @command{configure}. When reporting a @value{GDBN}
2402 bug (@pxref{GDB Bugs}), it is important to include this information in
2408 @chapter Running Programs Under @value{GDBN}
2410 When you run a program under @value{GDBN}, you must first generate
2411 debugging information when you compile it.
2413 You may start @value{GDBN} with its arguments, if any, in an environment
2414 of your choice. If you are doing native debugging, you may redirect
2415 your program's input and output, debug an already running process, or
2416 kill a child process.
2419 * Compilation:: Compiling for debugging
2420 * Starting:: Starting your program
2421 * Arguments:: Your program's arguments
2422 * Environment:: Your program's environment
2424 * Working Directory:: Your program's working directory
2425 * Input/Output:: Your program's input and output
2426 * Attach:: Debugging an already-running process
2427 * Kill Process:: Killing the child process
2428 * Inferiors Connections and Programs:: Debugging multiple inferiors
2429 connections and programs
2430 * Threads:: Debugging programs with multiple threads
2431 * Forks:: Debugging forks
2432 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2436 @section Compiling for Debugging
2438 In order to debug a program effectively, you need to generate
2439 debugging information when you compile it. This debugging information
2440 is stored in the object file; it describes the data type of each
2441 variable or function and the correspondence between source line numbers
2442 and addresses in the executable code.
2444 To request debugging information, specify the @samp{-g} option when you run
2447 Programs that are to be shipped to your customers are compiled with
2448 optimizations, using the @samp{-O} compiler option. However, some
2449 compilers are unable to handle the @samp{-g} and @samp{-O} options
2450 together. Using those compilers, you cannot generate optimized
2451 executables containing debugging information.
2453 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2454 without @samp{-O}, making it possible to debug optimized code. We
2455 recommend that you @emph{always} use @samp{-g} whenever you compile a
2456 program. You may think your program is correct, but there is no sense
2457 in pushing your luck. For more information, see @ref{Optimized Code}.
2459 Older versions of the @sc{gnu} C compiler permitted a variant option
2460 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2461 format; if your @sc{gnu} C compiler has this option, do not use it.
2463 @value{GDBN} knows about preprocessor macros and can show you their
2464 expansion (@pxref{Macros}). Most compilers do not include information
2465 about preprocessor macros in the debugging information if you specify
2466 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2467 the @sc{gnu} C compiler, provides macro information if you are using
2468 the DWARF debugging format, and specify the option @option{-g3}.
2470 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2471 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2472 information on @value{NGCC} options affecting debug information.
2474 You will have the best debugging experience if you use the latest
2475 version of the DWARF debugging format that your compiler supports.
2476 DWARF is currently the most expressive and best supported debugging
2477 format in @value{GDBN}.
2481 @section Starting your Program
2487 @kindex r @r{(@code{run})}
2490 Use the @code{run} command to start your program under @value{GDBN}.
2491 You must first specify the program name with an argument to
2492 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2493 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2494 command (@pxref{Files, ,Commands to Specify Files}).
2498 If you are running your program in an execution environment that
2499 supports processes, @code{run} creates an inferior process and makes
2500 that process run your program. In some environments without processes,
2501 @code{run} jumps to the start of your program. Other targets,
2502 like @samp{remote}, are always running. If you get an error
2503 message like this one:
2506 The "remote" target does not support "run".
2507 Try "help target" or "continue".
2511 then use @code{continue} to run your program. You may need @code{load}
2512 first (@pxref{load}).
2514 The execution of a program is affected by certain information it
2515 receives from its superior. @value{GDBN} provides ways to specify this
2516 information, which you must do @emph{before} starting your program. (You
2517 can change it after starting your program, but such changes only affect
2518 your program the next time you start it.) This information may be
2519 divided into four categories:
2522 @item The @emph{arguments.}
2523 Specify the arguments to give your program as the arguments of the
2524 @code{run} command. If a shell is available on your target, the shell
2525 is used to pass the arguments, so that you may use normal conventions
2526 (such as wildcard expansion or variable substitution) in describing
2528 In Unix systems, you can control which shell is used with the
2529 @env{SHELL} environment variable. If you do not define @env{SHELL},
2530 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2531 use of any shell with the @code{set startup-with-shell} command (see
2534 @item The @emph{environment.}
2535 Your program normally inherits its environment from @value{GDBN}, but you can
2536 use the @value{GDBN} commands @code{set environment} and @code{unset
2537 environment} to change parts of the environment that affect
2538 your program. @xref{Environment, ,Your Program's Environment}.
2540 @item The @emph{working directory.}
2541 You can set your program's working directory with the command
2542 @kbd{set cwd}. If you do not set any working directory with this
2543 command, your program will inherit @value{GDBN}'s working directory if
2544 native debugging, or the remote server's working directory if remote
2545 debugging. @xref{Working Directory, ,Your Program's Working
2548 @item The @emph{standard input and output.}
2549 Your program normally uses the same device for standard input and
2550 standard output as @value{GDBN} is using. You can redirect input and output
2551 in the @code{run} command line, or you can use the @code{tty} command to
2552 set a different device for your program.
2553 @xref{Input/Output, ,Your Program's Input and Output}.
2556 @emph{Warning:} While input and output redirection work, you cannot use
2557 pipes to pass the output of the program you are debugging to another
2558 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2562 When you issue the @code{run} command, your program begins to execute
2563 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2564 of how to arrange for your program to stop. Once your program has
2565 stopped, you may call functions in your program, using the @code{print}
2566 or @code{call} commands. @xref{Data, ,Examining Data}.
2568 If the modification time of your symbol file has changed since the last
2569 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2570 table, and reads it again. When it does this, @value{GDBN} tries to retain
2571 your current breakpoints.
2576 @cindex run to main procedure
2577 The name of the main procedure can vary from language to language.
2578 With C or C@t{++}, the main procedure name is always @code{main}, but
2579 other languages such as Ada do not require a specific name for their
2580 main procedure. The debugger provides a convenient way to start the
2581 execution of the program and to stop at the beginning of the main
2582 procedure, depending on the language used.
2584 The @samp{start} command does the equivalent of setting a temporary
2585 breakpoint at the beginning of the main procedure and then invoking
2586 the @samp{run} command.
2588 @cindex elaboration phase
2589 Some programs contain an @dfn{elaboration} phase where some startup code is
2590 executed before the main procedure is called. This depends on the
2591 languages used to write your program. In C@t{++}, for instance,
2592 constructors for static and global objects are executed before
2593 @code{main} is called. It is therefore possible that the debugger stops
2594 before reaching the main procedure. However, the temporary breakpoint
2595 will remain to halt execution.
2597 Specify the arguments to give to your program as arguments to the
2598 @samp{start} command. These arguments will be given verbatim to the
2599 underlying @samp{run} command. Note that the same arguments will be
2600 reused if no argument is provided during subsequent calls to
2601 @samp{start} or @samp{run}.
2603 It is sometimes necessary to debug the program during elaboration. In
2604 these cases, using the @code{start} command would stop the execution
2605 of your program too late, as the program would have already completed
2606 the elaboration phase. Under these circumstances, either insert
2607 breakpoints in your elaboration code before running your program or
2608 use the @code{starti} command.
2612 @cindex run to first instruction
2613 The @samp{starti} command does the equivalent of setting a temporary
2614 breakpoint at the first instruction of a program's execution and then
2615 invoking the @samp{run} command. For programs containing an
2616 elaboration phase, the @code{starti} command will stop execution at
2617 the start of the elaboration phase.
2619 @anchor{set exec-wrapper}
2620 @kindex set exec-wrapper
2621 @item set exec-wrapper @var{wrapper}
2622 @itemx show exec-wrapper
2623 @itemx unset exec-wrapper
2624 When @samp{exec-wrapper} is set, the specified wrapper is used to
2625 launch programs for debugging. @value{GDBN} starts your program
2626 with a shell command of the form @kbd{exec @var{wrapper}
2627 @var{program}}. Quoting is added to @var{program} and its
2628 arguments, but not to @var{wrapper}, so you should add quotes if
2629 appropriate for your shell. The wrapper runs until it executes
2630 your program, and then @value{GDBN} takes control.
2632 You can use any program that eventually calls @code{execve} with
2633 its arguments as a wrapper. Several standard Unix utilities do
2634 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2635 with @code{exec "$@@"} will also work.
2637 For example, you can use @code{env} to pass an environment variable to
2638 the debugged program, without setting the variable in your shell's
2642 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2646 This command is available when debugging locally on most targets, excluding
2647 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2649 @kindex set startup-with-shell
2650 @anchor{set startup-with-shell}
2651 @item set startup-with-shell
2652 @itemx set startup-with-shell on
2653 @itemx set startup-with-shell off
2654 @itemx show startup-with-shell
2655 On Unix systems, by default, if a shell is available on your target,
2656 @value{GDBN}) uses it to start your program. Arguments of the
2657 @code{run} command are passed to the shell, which does variable
2658 substitution, expands wildcard characters and performs redirection of
2659 I/O. In some circumstances, it may be useful to disable such use of a
2660 shell, for example, when debugging the shell itself or diagnosing
2661 startup failures such as:
2665 Starting program: ./a.out
2666 During startup program terminated with signal SIGSEGV, Segmentation fault.
2670 which indicates the shell or the wrapper specified with
2671 @samp{exec-wrapper} crashed, not your program. Most often, this is
2672 caused by something odd in your shell's non-interactive mode
2673 initialization file---such as @file{.cshrc} for C-shell,
2674 $@file{.zshenv} for the Z shell, or the file specified in the
2675 @env{BASH_ENV} environment variable for BASH.
2677 @anchor{set auto-connect-native-target}
2678 @kindex set auto-connect-native-target
2679 @item set auto-connect-native-target
2680 @itemx set auto-connect-native-target on
2681 @itemx set auto-connect-native-target off
2682 @itemx show auto-connect-native-target
2684 By default, if the current inferior is not connected to any target yet
2685 (e.g., with @code{target remote}), the @code{run} command starts your
2686 program as a native process under @value{GDBN}, on your local machine.
2687 If you're sure you don't want to debug programs on your local machine,
2688 you can tell @value{GDBN} to not connect to the native target
2689 automatically with the @code{set auto-connect-native-target off}
2692 If @code{on}, which is the default, and if the current inferior is not
2693 connected to a target already, the @code{run} command automaticaly
2694 connects to the native target, if one is available.
2696 If @code{off}, and if the current inferior is not connected to a
2697 target already, the @code{run} command fails with an error:
2701 Don't know how to run. Try "help target".
2704 If the current inferior is already connected to a target, @value{GDBN}
2705 always uses it with the @code{run} command.
2707 In any case, you can explicitly connect to the native target with the
2708 @code{target native} command. For example,
2711 (@value{GDBP}) set auto-connect-native-target off
2713 Don't know how to run. Try "help target".
2714 (@value{GDBP}) target native
2716 Starting program: ./a.out
2717 [Inferior 1 (process 10421) exited normally]
2720 In case you connected explicitly to the @code{native} target,
2721 @value{GDBN} remains connected even if all inferiors exit, ready for
2722 the next @code{run} command. Use the @code{disconnect} command to
2725 Examples of other commands that likewise respect the
2726 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2727 proc}, @code{info os}.
2729 @kindex set disable-randomization
2730 @item set disable-randomization
2731 @itemx set disable-randomization on
2732 This option (enabled by default in @value{GDBN}) will turn off the native
2733 randomization of the virtual address space of the started program. This option
2734 is useful for multiple debugging sessions to make the execution better
2735 reproducible and memory addresses reusable across debugging sessions.
2737 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2738 On @sc{gnu}/Linux you can get the same behavior using
2741 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2744 @item set disable-randomization off
2745 Leave the behavior of the started executable unchanged. Some bugs rear their
2746 ugly heads only when the program is loaded at certain addresses. If your bug
2747 disappears when you run the program under @value{GDBN}, that might be because
2748 @value{GDBN} by default disables the address randomization on platforms, such
2749 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2750 disable-randomization off} to try to reproduce such elusive bugs.
2752 On targets where it is available, virtual address space randomization
2753 protects the programs against certain kinds of security attacks. In these
2754 cases the attacker needs to know the exact location of a concrete executable
2755 code. Randomizing its location makes it impossible to inject jumps misusing
2756 a code at its expected addresses.
2758 Prelinking shared libraries provides a startup performance advantage but it
2759 makes addresses in these libraries predictable for privileged processes by
2760 having just unprivileged access at the target system. Reading the shared
2761 library binary gives enough information for assembling the malicious code
2762 misusing it. Still even a prelinked shared library can get loaded at a new
2763 random address just requiring the regular relocation process during the
2764 startup. Shared libraries not already prelinked are always loaded at
2765 a randomly chosen address.
2767 Position independent executables (PIE) contain position independent code
2768 similar to the shared libraries and therefore such executables get loaded at
2769 a randomly chosen address upon startup. PIE executables always load even
2770 already prelinked shared libraries at a random address. You can build such
2771 executable using @command{gcc -fPIE -pie}.
2773 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2774 (as long as the randomization is enabled).
2776 @item show disable-randomization
2777 Show the current setting of the explicit disable of the native randomization of
2778 the virtual address space of the started program.
2783 @section Your Program's Arguments
2785 @cindex arguments (to your program)
2786 The arguments to your program can be specified by the arguments of the
2788 They are passed to a shell, which expands wildcard characters and
2789 performs redirection of I/O, and thence to your program. Your
2790 @env{SHELL} environment variable (if it exists) specifies what shell
2791 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2792 the default shell (@file{/bin/sh} on Unix).
2794 On non-Unix systems, the program is usually invoked directly by
2795 @value{GDBN}, which emulates I/O redirection via the appropriate system
2796 calls, and the wildcard characters are expanded by the startup code of
2797 the program, not by the shell.
2799 @code{run} with no arguments uses the same arguments used by the previous
2800 @code{run}, or those set by the @code{set args} command.
2805 Specify the arguments to be used the next time your program is run. If
2806 @code{set args} has no arguments, @code{run} executes your program
2807 with no arguments. Once you have run your program with arguments,
2808 using @code{set args} before the next @code{run} is the only way to run
2809 it again without arguments.
2813 Show the arguments to give your program when it is started.
2817 @section Your Program's Environment
2819 @cindex environment (of your program)
2820 The @dfn{environment} consists of a set of environment variables and
2821 their values. Environment variables conventionally record such things as
2822 your user name, your home directory, your terminal type, and your search
2823 path for programs to run. Usually you set up environment variables with
2824 the shell and they are inherited by all the other programs you run. When
2825 debugging, it can be useful to try running your program with a modified
2826 environment without having to start @value{GDBN} over again.
2830 @item path @var{directory}
2831 Add @var{directory} to the front of the @env{PATH} environment variable
2832 (the search path for executables) that will be passed to your program.
2833 The value of @env{PATH} used by @value{GDBN} does not change.
2834 You may specify several directory names, separated by whitespace or by a
2835 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2836 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2837 is moved to the front, so it is searched sooner.
2839 You can use the string @samp{$cwd} to refer to whatever is the current
2840 working directory at the time @value{GDBN} searches the path. If you
2841 use @samp{.} instead, it refers to the directory where you executed the
2842 @code{path} command. @value{GDBN} replaces @samp{.} in the
2843 @var{directory} argument (with the current path) before adding
2844 @var{directory} to the search path.
2845 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2846 @c document that, since repeating it would be a no-op.
2850 Display the list of search paths for executables (the @env{PATH}
2851 environment variable).
2853 @kindex show environment
2854 @item show environment @r{[}@var{varname}@r{]}
2855 Print the value of environment variable @var{varname} to be given to
2856 your program when it starts. If you do not supply @var{varname},
2857 print the names and values of all environment variables to be given to
2858 your program. You can abbreviate @code{environment} as @code{env}.
2860 @kindex set environment
2861 @anchor{set environment}
2862 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2863 Set environment variable @var{varname} to @var{value}. The value
2864 changes for your program (and the shell @value{GDBN} uses to launch
2865 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2866 values of environment variables are just strings, and any
2867 interpretation is supplied by your program itself. The @var{value}
2868 parameter is optional; if it is eliminated, the variable is set to a
2870 @c "any string" here does not include leading, trailing
2871 @c blanks. Gnu asks: does anyone care?
2873 For example, this command:
2880 tells the debugged program, when subsequently run, that its user is named
2881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2882 are not actually required.)
2884 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2885 which also inherits the environment set with @code{set environment}.
2886 If necessary, you can avoid that by using the @samp{env} program as a
2887 wrapper instead of using @code{set environment}. @xref{set
2888 exec-wrapper}, for an example doing just that.
2890 Environment variables that are set by the user are also transmitted to
2891 @command{gdbserver} to be used when starting the remote inferior.
2892 @pxref{QEnvironmentHexEncoded}.
2894 @kindex unset environment
2895 @anchor{unset environment}
2896 @item unset environment @var{varname}
2897 Remove variable @var{varname} from the environment to be passed to your
2898 program. This is different from @samp{set env @var{varname} =};
2899 @code{unset environment} removes the variable from the environment,
2900 rather than assigning it an empty value.
2902 Environment variables that are unset by the user are also unset on
2903 @command{gdbserver} when starting the remote inferior.
2904 @pxref{QEnvironmentUnset}.
2907 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2908 the shell indicated by your @env{SHELL} environment variable if it
2909 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2910 names a shell that runs an initialization file when started
2911 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2912 for the Z shell, or the file specified in the @env{BASH_ENV}
2913 environment variable for BASH---any variables you set in that file
2914 affect your program. You may wish to move setting of environment
2915 variables to files that are only run when you sign on, such as
2916 @file{.login} or @file{.profile}.
2918 @node Working Directory
2919 @section Your Program's Working Directory
2921 @cindex working directory (of your program)
2922 Each time you start your program with @code{run}, the inferior will be
2923 initialized with the current working directory specified by the
2924 @kbd{set cwd} command. If no directory has been specified by this
2925 command, then the inferior will inherit @value{GDBN}'s current working
2926 directory as its working directory if native debugging, or it will
2927 inherit the remote server's current working directory if remote
2932 @cindex change inferior's working directory
2933 @anchor{set cwd command}
2934 @item set cwd @r{[}@var{directory}@r{]}
2935 Set the inferior's working directory to @var{directory}, which will be
2936 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2937 argument has been specified, the command clears the setting and resets
2938 it to an empty state. This setting has no effect on @value{GDBN}'s
2939 working directory, and it only takes effect the next time you start
2940 the inferior. The @file{~} in @var{directory} is a short for the
2941 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2942 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2943 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2946 You can also change @value{GDBN}'s current working directory by using
2947 the @code{cd} command.
2951 @cindex show inferior's working directory
2953 Show the inferior's working directory. If no directory has been
2954 specified by @kbd{set cwd}, then the default inferior's working
2955 directory is the same as @value{GDBN}'s working directory.
2958 @cindex change @value{GDBN}'s working directory
2960 @item cd @r{[}@var{directory}@r{]}
2961 Set the @value{GDBN} working directory to @var{directory}. If not
2962 given, @var{directory} uses @file{'~'}.
2964 The @value{GDBN} working directory serves as a default for the
2965 commands that specify files for @value{GDBN} to operate on.
2966 @xref{Files, ,Commands to Specify Files}.
2967 @xref{set cwd command}.
2971 Print the @value{GDBN} working directory.
2974 It is generally impossible to find the current working directory of
2975 the process being debugged (since a program can change its directory
2976 during its run). If you work on a system where @value{GDBN} supports
2977 the @code{info proc} command (@pxref{Process Information}), you can
2978 use the @code{info proc} command to find out the
2979 current working directory of the debuggee.
2982 @section Your Program's Input and Output
2987 By default, the program you run under @value{GDBN} does input and output to
2988 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2989 to its own terminal modes to interact with you, but it records the terminal
2990 modes your program was using and switches back to them when you continue
2991 running your program.
2994 @kindex info terminal
2996 Displays information recorded by @value{GDBN} about the terminal modes your
3000 You can redirect your program's input and/or output using shell
3001 redirection with the @code{run} command. For example,
3008 starts your program, diverting its output to the file @file{outfile}.
3011 @cindex controlling terminal
3012 Another way to specify where your program should do input and output is
3013 with the @code{tty} command. This command accepts a file name as
3014 argument, and causes this file to be the default for future @code{run}
3015 commands. It also resets the controlling terminal for the child
3016 process, for future @code{run} commands. For example,
3023 directs that processes started with subsequent @code{run} commands
3024 default to do input and output on the terminal @file{/dev/ttyb} and have
3025 that as their controlling terminal.
3027 An explicit redirection in @code{run} overrides the @code{tty} command's
3028 effect on the input/output device, but not its effect on the controlling
3031 When you use the @code{tty} command or redirect input in the @code{run}
3032 command, only the input @emph{for your program} is affected. The input
3033 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3034 for @code{set inferior-tty}.
3036 @cindex inferior tty
3037 @cindex set inferior controlling terminal
3038 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3039 display the name of the terminal that will be used for future runs of your
3043 @item set inferior-tty [ @var{tty} ]
3044 @kindex set inferior-tty
3045 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3046 restores the default behavior, which is to use the same terminal as
3049 @item show inferior-tty
3050 @kindex show inferior-tty
3051 Show the current tty for the program being debugged.
3055 @section Debugging an Already-running Process
3060 @item attach @var{process-id}
3061 This command attaches to a running process---one that was started
3062 outside @value{GDBN}. (@code{info files} shows your active
3063 targets.) The command takes as argument a process ID. The usual way to
3064 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3065 or with the @samp{jobs -l} shell command.
3067 @code{attach} does not repeat if you press @key{RET} a second time after
3068 executing the command.
3071 To use @code{attach}, your program must be running in an environment
3072 which supports processes; for example, @code{attach} does not work for
3073 programs on bare-board targets that lack an operating system. You must
3074 also have permission to send the process a signal.
3076 When you use @code{attach}, the debugger finds the program running in
3077 the process first by looking in the current working directory, then (if
3078 the program is not found) by using the source file search path
3079 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3080 the @code{file} command to load the program. @xref{Files, ,Commands to
3083 @anchor{set exec-file-mismatch}
3084 If the debugger can determine that the executable file running in the
3085 process it is attaching to does not match the current exec-file loaded
3086 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3087 handle the mismatch. @value{GDBN} tries to compare the files by
3088 comparing their build IDs (@pxref{build ID}), if available.
3091 @kindex exec-file-mismatch
3092 @cindex set exec-file-mismatch
3093 @item set exec-file-mismatch @samp{ask|warn|off}
3095 Whether to detect mismatch between the current executable file loaded
3096 by @value{GDBN} and the executable file used to start the process. If
3097 @samp{ask}, the default, display a warning and ask the user whether to
3098 load the process executable file; if @samp{warn}, just display a
3099 warning; if @samp{off}, don't attempt to detect a mismatch.
3100 If the user confirms loading the process executable file, then its symbols
3101 will be loaded as well.
3103 @cindex show exec-file-mismatch
3104 @item show exec-file-mismatch
3105 Show the current value of @code{exec-file-mismatch}.
3109 The first thing @value{GDBN} does after arranging to debug the specified
3110 process is to stop it. You can examine and modify an attached process
3111 with all the @value{GDBN} commands that are ordinarily available when
3112 you start processes with @code{run}. You can insert breakpoints; you
3113 can step and continue; you can modify storage. If you would rather the
3114 process continue running, you may use the @code{continue} command after
3115 attaching @value{GDBN} to the process.
3120 When you have finished debugging the attached process, you can use the
3121 @code{detach} command to release it from @value{GDBN} control. Detaching
3122 the process continues its execution. After the @code{detach} command,
3123 that process and @value{GDBN} become completely independent once more, and you
3124 are ready to @code{attach} another process or start one with @code{run}.
3125 @code{detach} does not repeat if you press @key{RET} again after
3126 executing the command.
3129 If you exit @value{GDBN} while you have an attached process, you detach
3130 that process. If you use the @code{run} command, you kill that process.
3131 By default, @value{GDBN} asks for confirmation if you try to do either of these
3132 things; you can control whether or not you need to confirm by using the
3133 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3137 @section Killing the Child Process
3142 Kill the child process in which your program is running under @value{GDBN}.
3145 This command is useful if you wish to debug a core dump instead of a
3146 running process. @value{GDBN} ignores any core dump file while your program
3149 On some operating systems, a program cannot be executed outside @value{GDBN}
3150 while you have breakpoints set on it inside @value{GDBN}. You can use the
3151 @code{kill} command in this situation to permit running your program
3152 outside the debugger.
3154 The @code{kill} command is also useful if you wish to recompile and
3155 relink your program, since on many systems it is impossible to modify an
3156 executable file while it is running in a process. In this case, when you
3157 next type @code{run}, @value{GDBN} notices that the file has changed, and
3158 reads the symbol table again (while trying to preserve your current
3159 breakpoint settings).
3161 @node Inferiors Connections and Programs
3162 @section Debugging Multiple Inferiors Connections and Programs
3164 @value{GDBN} lets you run and debug multiple programs in a single
3165 session. In addition, @value{GDBN} on some systems may let you run
3166 several programs simultaneously (otherwise you have to exit from one
3167 before starting another). On some systems @value{GDBN} may even let
3168 you debug several programs simultaneously on different remote systems.
3169 In the most general case, you can have multiple threads of execution
3170 in each of multiple processes, launched from multiple executables,
3171 running on different machines.
3174 @value{GDBN} represents the state of each program execution with an
3175 object called an @dfn{inferior}. An inferior typically corresponds to
3176 a process, but is more general and applies also to targets that do not
3177 have processes. Inferiors may be created before a process runs, and
3178 may be retained after a process exits. Inferiors have unique
3179 identifiers that are different from process ids. Usually each
3180 inferior will also have its own distinct address space, although some
3181 embedded targets may have several inferiors running in different parts
3182 of a single address space. Each inferior may in turn have multiple
3183 threads running in it.
3185 To find out what inferiors exist at any moment, use @w{@code{info
3189 @kindex info inferiors [ @var{id}@dots{} ]
3190 @item info inferiors
3191 Print a list of all inferiors currently being managed by @value{GDBN}.
3192 By default all inferiors are printed, but the argument @var{id}@dots{}
3193 -- a space separated list of inferior numbers -- can be used to limit
3194 the display to just the requested inferiors.
3196 @value{GDBN} displays for each inferior (in this order):
3200 the inferior number assigned by @value{GDBN}
3203 the target system's inferior identifier
3206 the target connection the inferior is bound to, including the unique
3207 connection number assigned by @value{GDBN}, and the protocol used by
3211 the name of the executable the inferior is running.
3216 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3217 indicates the current inferior.
3221 @c end table here to get a little more width for example
3224 (@value{GDBP}) info inferiors
3225 Num Description Connection Executable
3226 * 1 process 3401 1 (native) goodbye
3227 2 process 2307 2 (extended-remote host:10000) hello
3230 To get informations about the current inferior, use @code{inferior}:
3235 Shows information about the current inferior.
3239 @c end table here to get a little more width for example
3242 (@value{GDBP}) inferior
3243 [Current inferior is 1 [process 3401] (helloworld)]
3246 To find out what open target connections exist at any moment, use
3247 @w{@code{info connections}}:
3250 @kindex info connections [ @var{id}@dots{} ]
3251 @item info connections
3252 Print a list of all open target connections currently being managed by
3253 @value{GDBN}. By default all connections are printed, but the
3254 argument @var{id}@dots{} -- a space separated list of connections
3255 numbers -- can be used to limit the display to just the requested
3258 @value{GDBN} displays for each connection (in this order):
3262 the connection number assigned by @value{GDBN}.
3265 the protocol used by the connection.
3268 a textual description of the protocol used by the connection.
3273 An asterisk @samp{*} preceding the connection number indicates the
3274 connection of the current inferior.
3278 @c end table here to get a little more width for example
3281 (@value{GDBP}) info connections
3282 Num What Description
3283 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3284 2 native Native process
3285 3 core Local core dump file
3288 To switch focus between inferiors, use the @code{inferior} command:
3291 @kindex inferior @var{infno}
3292 @item inferior @var{infno}
3293 Make inferior number @var{infno} the current inferior. The argument
3294 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3295 in the first field of the @samp{info inferiors} display.
3298 @vindex $_inferior@r{, convenience variable}
3299 The debugger convenience variable @samp{$_inferior} contains the
3300 number of the current inferior. You may find this useful in writing
3301 breakpoint conditional expressions, command scripts, and so forth.
3302 @xref{Convenience Vars,, Convenience Variables}, for general
3303 information on convenience variables.
3305 You can get multiple executables into a debugging session via the
3306 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3307 systems @value{GDBN} can add inferiors to the debug session
3308 automatically by following calls to @code{fork} and @code{exec}. To
3309 remove inferiors from the debugging session use the
3310 @w{@code{remove-inferiors}} command.
3313 @kindex add-inferior
3314 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3315 Adds @var{n} inferiors to be run using @var{executable} as the
3316 executable; @var{n} defaults to 1. If no executable is specified,
3317 the inferiors begins empty, with no program. You can still assign or
3318 change the program assigned to the inferior at any time by using the
3319 @code{file} command with the executable name as its argument.
3321 By default, the new inferior begins connected to the same target
3322 connection as the current inferior. For example, if the current
3323 inferior was connected to @code{gdbserver} with @code{target remote},
3324 then the new inferior will be connected to the same @code{gdbserver}
3325 instance. The @samp{-no-connection} option starts the new inferior
3326 with no connection yet. You can then for example use the @code{target
3327 remote} command to connect to some other @code{gdbserver} instance,
3328 use @code{run} to spawn a local program, etc.
3330 @kindex clone-inferior
3331 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3332 Adds @var{n} inferiors ready to execute the same program as inferior
3333 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3334 number of the current inferior. This is a convenient command when you
3335 want to run another instance of the inferior you are debugging.
3338 (@value{GDBP}) info inferiors
3339 Num Description Connection Executable
3340 * 1 process 29964 1 (native) helloworld
3341 (@value{GDBP}) clone-inferior
3344 (@value{GDBP}) info inferiors
3345 Num Description Connection Executable
3346 * 1 process 29964 1 (native) helloworld
3347 2 <null> 1 (native) helloworld
3350 You can now simply switch focus to inferior 2 and run it.
3352 @kindex remove-inferiors
3353 @item remove-inferiors @var{infno}@dots{}
3354 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3355 possible to remove an inferior that is running with this command. For
3356 those, use the @code{kill} or @code{detach} command first.
3360 To quit debugging one of the running inferiors that is not the current
3361 inferior, you can either detach from it by using the @w{@code{detach
3362 inferior}} command (allowing it to run independently), or kill it
3363 using the @w{@code{kill inferiors}} command:
3366 @kindex detach inferiors @var{infno}@dots{}
3367 @item detach inferior @var{infno}@dots{}
3368 Detach from the inferior or inferiors identified by @value{GDBN}
3369 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3370 still stays on the list of inferiors shown by @code{info inferiors},
3371 but its Description will show @samp{<null>}.
3373 @kindex kill inferiors @var{infno}@dots{}
3374 @item kill inferiors @var{infno}@dots{}
3375 Kill the inferior or inferiors identified by @value{GDBN} inferior
3376 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3377 stays on the list of inferiors shown by @code{info inferiors}, but its
3378 Description will show @samp{<null>}.
3381 After the successful completion of a command such as @code{detach},
3382 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3383 a normal process exit, the inferior is still valid and listed with
3384 @code{info inferiors}, ready to be restarted.
3387 To be notified when inferiors are started or exit under @value{GDBN}'s
3388 control use @w{@code{set print inferior-events}}:
3391 @kindex set print inferior-events
3392 @cindex print messages on inferior start and exit
3393 @item set print inferior-events
3394 @itemx set print inferior-events on
3395 @itemx set print inferior-events off
3396 The @code{set print inferior-events} command allows you to enable or
3397 disable printing of messages when @value{GDBN} notices that new
3398 inferiors have started or that inferiors have exited or have been
3399 detached. By default, these messages will be printed.
3401 @kindex show print inferior-events
3402 @item show print inferior-events
3403 Show whether messages will be printed when @value{GDBN} detects that
3404 inferiors have started, exited or have been detached.
3407 Many commands will work the same with multiple programs as with a
3408 single program: e.g., @code{print myglobal} will simply display the
3409 value of @code{myglobal} in the current inferior.
3412 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3413 get more info about the relationship of inferiors, programs, address
3414 spaces in a debug session. You can do that with the @w{@code{maint
3415 info program-spaces}} command.
3418 @kindex maint info program-spaces
3419 @item maint info program-spaces
3420 Print a list of all program spaces currently being managed by
3423 @value{GDBN} displays for each program space (in this order):
3427 the program space number assigned by @value{GDBN}
3430 the name of the executable loaded into the program space, with e.g.,
3431 the @code{file} command.
3436 An asterisk @samp{*} preceding the @value{GDBN} program space number
3437 indicates the current program space.
3439 In addition, below each program space line, @value{GDBN} prints extra
3440 information that isn't suitable to display in tabular form. For
3441 example, the list of inferiors bound to the program space.
3444 (@value{GDBP}) maint info program-spaces
3448 Bound inferiors: ID 1 (process 21561)
3451 Here we can see that no inferior is running the program @code{hello},
3452 while @code{process 21561} is running the program @code{goodbye}. On
3453 some targets, it is possible that multiple inferiors are bound to the
3454 same program space. The most common example is that of debugging both
3455 the parent and child processes of a @code{vfork} call. For example,
3458 (@value{GDBP}) maint info program-spaces
3461 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3464 Here, both inferior 2 and inferior 1 are running in the same program
3465 space as a result of inferior 1 having executed a @code{vfork} call.
3469 @section Debugging Programs with Multiple Threads
3471 @cindex threads of execution
3472 @cindex multiple threads
3473 @cindex switching threads
3474 In some operating systems, such as GNU/Linux and Solaris, a single program
3475 may have more than one @dfn{thread} of execution. The precise semantics
3476 of threads differ from one operating system to another, but in general
3477 the threads of a single program are akin to multiple processes---except
3478 that they share one address space (that is, they can all examine and
3479 modify the same variables). On the other hand, each thread has its own
3480 registers and execution stack, and perhaps private memory.
3482 @value{GDBN} provides these facilities for debugging multi-thread
3486 @item automatic notification of new threads
3487 @item @samp{thread @var{thread-id}}, a command to switch among threads
3488 @item @samp{info threads}, a command to inquire about existing threads
3489 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3490 a command to apply a command to a list of threads
3491 @item thread-specific breakpoints
3492 @item @samp{set print thread-events}, which controls printing of
3493 messages on thread start and exit.
3494 @item @samp{set libthread-db-search-path @var{path}}, which lets
3495 the user specify which @code{libthread_db} to use if the default choice
3496 isn't compatible with the program.
3499 @cindex focus of debugging
3500 @cindex current thread
3501 The @value{GDBN} thread debugging facility allows you to observe all
3502 threads while your program runs---but whenever @value{GDBN} takes
3503 control, one thread in particular is always the focus of debugging.
3504 This thread is called the @dfn{current thread}. Debugging commands show
3505 program information from the perspective of the current thread.
3507 @cindex @code{New} @var{systag} message
3508 @cindex thread identifier (system)
3509 @c FIXME-implementors!! It would be more helpful if the [New...] message
3510 @c included GDB's numeric thread handle, so you could just go to that
3511 @c thread without first checking `info threads'.
3512 Whenever @value{GDBN} detects a new thread in your program, it displays
3513 the target system's identification for the thread with a message in the
3514 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3515 whose form varies depending on the particular system. For example, on
3516 @sc{gnu}/Linux, you might see
3519 [New Thread 0x41e02940 (LWP 25582)]
3523 when @value{GDBN} notices a new thread. In contrast, on other systems,
3524 the @var{systag} is simply something like @samp{process 368}, with no
3527 @c FIXME!! (1) Does the [New...] message appear even for the very first
3528 @c thread of a program, or does it only appear for the
3529 @c second---i.e.@: when it becomes obvious we have a multithread
3531 @c (2) *Is* there necessarily a first thread always? Or do some
3532 @c multithread systems permit starting a program with multiple
3533 @c threads ab initio?
3535 @anchor{thread numbers}
3536 @cindex thread number, per inferior
3537 @cindex thread identifier (GDB)
3538 For debugging purposes, @value{GDBN} associates its own thread number
3539 ---always a single integer---with each thread of an inferior. This
3540 number is unique between all threads of an inferior, but not unique
3541 between threads of different inferiors.
3543 @cindex qualified thread ID
3544 You can refer to a given thread in an inferior using the qualified
3545 @var{inferior-num}.@var{thread-num} syntax, also known as
3546 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3547 number and @var{thread-num} being the thread number of the given
3548 inferior. For example, thread @code{2.3} refers to thread number 3 of
3549 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3550 then @value{GDBN} infers you're referring to a thread of the current
3553 Until you create a second inferior, @value{GDBN} does not show the
3554 @var{inferior-num} part of thread IDs, even though you can always use
3555 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3556 of inferior 1, the initial inferior.
3558 @anchor{thread ID lists}
3559 @cindex thread ID lists
3560 Some commands accept a space-separated @dfn{thread ID list} as
3561 argument. A list element can be:
3565 A thread ID as shown in the first field of the @samp{info threads}
3566 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3570 A range of thread numbers, again with or without an inferior
3571 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3572 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3575 All threads of an inferior, specified with a star wildcard, with or
3576 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3577 @samp{1.*}) or @code{*}. The former refers to all threads of the
3578 given inferior, and the latter form without an inferior qualifier
3579 refers to all threads of the current inferior.
3583 For example, if the current inferior is 1, and inferior 7 has one
3584 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3585 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3586 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3587 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3591 @anchor{global thread numbers}
3592 @cindex global thread number
3593 @cindex global thread identifier (GDB)
3594 In addition to a @emph{per-inferior} number, each thread is also
3595 assigned a unique @emph{global} number, also known as @dfn{global
3596 thread ID}, a single integer. Unlike the thread number component of
3597 the thread ID, no two threads have the same global ID, even when
3598 you're debugging multiple inferiors.
3600 From @value{GDBN}'s perspective, a process always has at least one
3601 thread. In other words, @value{GDBN} assigns a thread number to the
3602 program's ``main thread'' even if the program is not multi-threaded.
3604 @vindex $_thread@r{, convenience variable}
3605 @vindex $_gthread@r{, convenience variable}
3606 The debugger convenience variables @samp{$_thread} and
3607 @samp{$_gthread} contain, respectively, the per-inferior thread number
3608 and the global thread number of the current thread. You may find this
3609 useful in writing breakpoint conditional expressions, command scripts,
3610 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3611 general information on convenience variables.
3613 If @value{GDBN} detects the program is multi-threaded, it augments the
3614 usual message about stopping at a breakpoint with the ID and name of
3615 the thread that hit the breakpoint.
3618 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3621 Likewise when the program receives a signal:
3624 Thread 1 "main" received signal SIGINT, Interrupt.
3628 @kindex info threads
3629 @item info threads @r{[}@var{thread-id-list}@r{]}
3631 Display information about one or more threads. With no arguments
3632 displays information about all threads. You can specify the list of
3633 threads that you want to display using the thread ID list syntax
3634 (@pxref{thread ID lists}).
3636 @value{GDBN} displays for each thread (in this order):
3640 the per-inferior thread number assigned by @value{GDBN}
3643 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3644 option was specified
3647 the target system's thread identifier (@var{systag})
3650 the thread's name, if one is known. A thread can either be named by
3651 the user (see @code{thread name}, below), or, in some cases, by the
3655 the current stack frame summary for that thread
3659 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3660 indicates the current thread.
3664 @c end table here to get a little more width for example
3667 (@value{GDBP}) info threads
3669 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3670 2 process 35 thread 23 0x34e5 in sigpause ()
3671 3 process 35 thread 27 0x34e5 in sigpause ()
3675 If you're debugging multiple inferiors, @value{GDBN} displays thread
3676 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3677 Otherwise, only @var{thread-num} is shown.
3679 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3680 indicating each thread's global thread ID:
3683 (@value{GDBP}) info threads
3684 Id GId Target Id Frame
3685 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3686 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3687 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3688 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3691 On Solaris, you can display more information about user threads with a
3692 Solaris-specific command:
3695 @item maint info sol-threads
3696 @kindex maint info sol-threads
3697 @cindex thread info (Solaris)
3698 Display info on Solaris user threads.
3702 @kindex thread @var{thread-id}
3703 @item thread @var{thread-id}
3704 Make thread ID @var{thread-id} the current thread. The command
3705 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3706 the first field of the @samp{info threads} display, with or without an
3707 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3709 @value{GDBN} responds by displaying the system identifier of the
3710 thread you selected, and its current stack frame summary:
3713 (@value{GDBP}) thread 2
3714 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3715 #0 some_function (ignore=0x0) at example.c:8
3716 8 printf ("hello\n");
3720 As with the @samp{[New @dots{}]} message, the form of the text after
3721 @samp{Switching to} depends on your system's conventions for identifying
3724 @anchor{thread apply all}
3725 @kindex thread apply
3726 @cindex apply command to several threads
3727 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3728 The @code{thread apply} command allows you to apply the named
3729 @var{command} to one or more threads. Specify the threads that you
3730 want affected using the thread ID list syntax (@pxref{thread ID
3731 lists}), or specify @code{all} to apply to all threads. To apply a
3732 command to all threads in descending order, type @kbd{thread apply all
3733 @var{command}}. To apply a command to all threads in ascending order,
3734 type @kbd{thread apply all -ascending @var{command}}.
3736 The @var{flag} arguments control what output to produce and how to handle
3737 errors raised when applying @var{command} to a thread. @var{flag}
3738 must start with a @code{-} directly followed by one letter in
3739 @code{qcs}. If several flags are provided, they must be given
3740 individually, such as @code{-c -q}.
3742 By default, @value{GDBN} displays some thread information before the
3743 output produced by @var{command}, and an error raised during the
3744 execution of a @var{command} will abort @code{thread apply}. The
3745 following flags can be used to fine-tune this behavior:
3749 The flag @code{-c}, which stands for @samp{continue}, causes any
3750 errors in @var{command} to be displayed, and the execution of
3751 @code{thread apply} then continues.
3753 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3754 or empty output produced by a @var{command} to be silently ignored.
3755 That is, the execution continues, but the thread information and errors
3758 The flag @code{-q} (@samp{quiet}) disables printing the thread
3762 Flags @code{-c} and @code{-s} cannot be used together.
3765 @cindex apply command to all threads (ignoring errors and empty output)
3766 @item taas [@var{option}]@dots{} @var{command}
3767 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3768 Applies @var{command} on all threads, ignoring errors and empty output.
3770 The @code{taas} command accepts the same options as the @code{thread
3771 apply all} command. @xref{thread apply all}.
3774 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3775 @item tfaas [@var{option}]@dots{} @var{command}
3776 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3777 Applies @var{command} on all frames of all threads, ignoring errors
3778 and empty output. Note that the flag @code{-s} is specified twice:
3779 The first @code{-s} ensures that @code{thread apply} only shows the thread
3780 information of the threads for which @code{frame apply} produces
3781 some output. The second @code{-s} is needed to ensure that @code{frame
3782 apply} shows the frame information of a frame only if the
3783 @var{command} successfully produced some output.
3785 It can for example be used to print a local variable or a function
3786 argument without knowing the thread or frame where this variable or argument
3789 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3792 The @code{tfaas} command accepts the same options as the @code{frame
3793 apply} command. @xref{Frame Apply,,frame apply}.
3796 @cindex name a thread
3797 @item thread name [@var{name}]
3798 This command assigns a name to the current thread. If no argument is
3799 given, any existing user-specified name is removed. The thread name
3800 appears in the @samp{info threads} display.
3802 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3803 determine the name of the thread as given by the OS. On these
3804 systems, a name specified with @samp{thread name} will override the
3805 system-give name, and removing the user-specified name will cause
3806 @value{GDBN} to once again display the system-specified name.
3809 @cindex search for a thread
3810 @item thread find [@var{regexp}]
3811 Search for and display thread ids whose name or @var{systag}
3812 matches the supplied regular expression.
3814 As well as being the complement to the @samp{thread name} command,
3815 this command also allows you to identify a thread by its target
3816 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3820 (@value{GDBN}) thread find 26688
3821 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3822 (@value{GDBN}) info thread 4
3824 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3827 @kindex set print thread-events
3828 @cindex print messages on thread start and exit
3829 @item set print thread-events
3830 @itemx set print thread-events on
3831 @itemx set print thread-events off
3832 The @code{set print thread-events} command allows you to enable or
3833 disable printing of messages when @value{GDBN} notices that new threads have
3834 started or that threads have exited. By default, these messages will
3835 be printed if detection of these events is supported by the target.
3836 Note that these messages cannot be disabled on all targets.
3838 @kindex show print thread-events
3839 @item show print thread-events
3840 Show whether messages will be printed when @value{GDBN} detects that threads
3841 have started and exited.
3844 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3845 more information about how @value{GDBN} behaves when you stop and start
3846 programs with multiple threads.
3848 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3849 watchpoints in programs with multiple threads.
3851 @anchor{set libthread-db-search-path}
3853 @kindex set libthread-db-search-path
3854 @cindex search path for @code{libthread_db}
3855 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3856 If this variable is set, @var{path} is a colon-separated list of
3857 directories @value{GDBN} will use to search for @code{libthread_db}.
3858 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3859 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3860 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3863 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3864 @code{libthread_db} library to obtain information about threads in the
3865 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3866 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3867 specific thread debugging library loading is enabled
3868 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3871 refers to the default system directories that are
3872 normally searched for loading shared libraries. The @samp{$sdir} entry
3873 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3874 (@pxref{libthread_db.so.1 file}).
3876 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3877 refers to the directory from which @code{libpthread}
3878 was loaded in the inferior process.
3880 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3881 @value{GDBN} attempts to initialize it with the current inferior process.
3882 If this initialization fails (which could happen because of a version
3883 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3884 will unload @code{libthread_db}, and continue with the next directory.
3885 If none of @code{libthread_db} libraries initialize successfully,
3886 @value{GDBN} will issue a warning and thread debugging will be disabled.
3888 Setting @code{libthread-db-search-path} is currently implemented
3889 only on some platforms.
3891 @kindex show libthread-db-search-path
3892 @item show libthread-db-search-path
3893 Display current libthread_db search path.
3895 @kindex set debug libthread-db
3896 @kindex show debug libthread-db
3897 @cindex debugging @code{libthread_db}
3898 @item set debug libthread-db
3899 @itemx show debug libthread-db
3900 Turns on or off display of @code{libthread_db}-related events.
3901 Use @code{1} to enable, @code{0} to disable.
3903 @kindex set debug threads
3904 @kindex show debug threads
3905 @cindex debugging @code{threads}
3906 @item set debug threads @r{[}on@r{|}off@r{]}
3907 @itemx show debug threads
3908 When @samp{on} @value{GDBN} will print additional messages when
3909 threads are created and deleted.
3913 @section Debugging Forks
3915 @cindex fork, debugging programs which call
3916 @cindex multiple processes
3917 @cindex processes, multiple
3918 On most systems, @value{GDBN} has no special support for debugging
3919 programs which create additional processes using the @code{fork}
3920 function. When a program forks, @value{GDBN} will continue to debug the
3921 parent process and the child process will run unimpeded. If you have
3922 set a breakpoint in any code which the child then executes, the child
3923 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3924 will cause it to terminate.
3926 However, if you want to debug the child process there is a workaround
3927 which isn't too painful. Put a call to @code{sleep} in the code which
3928 the child process executes after the fork. It may be useful to sleep
3929 only if a certain environment variable is set, or a certain file exists,
3930 so that the delay need not occur when you don't want to run @value{GDBN}
3931 on the child. While the child is sleeping, use the @code{ps} program to
3932 get its process ID. Then tell @value{GDBN} (a new invocation of
3933 @value{GDBN} if you are also debugging the parent process) to attach to
3934 the child process (@pxref{Attach}). From that point on you can debug
3935 the child process just like any other process which you attached to.
3937 On some systems, @value{GDBN} provides support for debugging programs
3938 that create additional processes using the @code{fork} or @code{vfork}
3939 functions. On @sc{gnu}/Linux platforms, this feature is supported
3940 with kernel version 2.5.46 and later.
3942 The fork debugging commands are supported in native mode and when
3943 connected to @code{gdbserver} in either @code{target remote} mode or
3944 @code{target extended-remote} mode.
3946 By default, when a program forks, @value{GDBN} will continue to debug
3947 the parent process and the child process will run unimpeded.
3949 If you want to follow the child process instead of the parent process,
3950 use the command @w{@code{set follow-fork-mode}}.
3953 @kindex set follow-fork-mode
3954 @item set follow-fork-mode @var{mode}
3955 Set the debugger response to a program call of @code{fork} or
3956 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3957 process. The @var{mode} argument can be:
3961 The original process is debugged after a fork. The child process runs
3962 unimpeded. This is the default.
3965 The new process is debugged after a fork. The parent process runs
3970 @kindex show follow-fork-mode
3971 @item show follow-fork-mode
3972 Display the current debugger response to a @code{fork} or @code{vfork} call.
3975 @cindex debugging multiple processes
3976 On Linux, if you want to debug both the parent and child processes, use the
3977 command @w{@code{set detach-on-fork}}.
3980 @kindex set detach-on-fork
3981 @item set detach-on-fork @var{mode}
3982 Tells gdb whether to detach one of the processes after a fork, or
3983 retain debugger control over them both.
3987 The child process (or parent process, depending on the value of
3988 @code{follow-fork-mode}) will be detached and allowed to run
3989 independently. This is the default.
3992 Both processes will be held under the control of @value{GDBN}.
3993 One process (child or parent, depending on the value of
3994 @code{follow-fork-mode}) is debugged as usual, while the other
3999 @kindex show detach-on-fork
4000 @item show detach-on-fork
4001 Show whether detach-on-fork mode is on/off.
4004 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4005 will retain control of all forked processes (including nested forks).
4006 You can list the forked processes under the control of @value{GDBN} by
4007 using the @w{@code{info inferiors}} command, and switch from one fork
4008 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4009 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4011 To quit debugging one of the forked processes, you can either detach
4012 from it by using the @w{@code{detach inferiors}} command (allowing it
4013 to run independently), or kill it using the @w{@code{kill inferiors}}
4014 command. @xref{Inferiors Connections and Programs, ,Debugging
4015 Multiple Inferiors Connections and Programs}.
4017 If you ask to debug a child process and a @code{vfork} is followed by an
4018 @code{exec}, @value{GDBN} executes the new target up to the first
4019 breakpoint in the new target. If you have a breakpoint set on
4020 @code{main} in your original program, the breakpoint will also be set on
4021 the child process's @code{main}.
4023 On some systems, when a child process is spawned by @code{vfork}, you
4024 cannot debug the child or parent until an @code{exec} call completes.
4026 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4027 call executes, the new target restarts. To restart the parent
4028 process, use the @code{file} command with the parent executable name
4029 as its argument. By default, after an @code{exec} call executes,
4030 @value{GDBN} discards the symbols of the previous executable image.
4031 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4035 @kindex set follow-exec-mode
4036 @item set follow-exec-mode @var{mode}
4038 Set debugger response to a program call of @code{exec}. An
4039 @code{exec} call replaces the program image of a process.
4041 @code{follow-exec-mode} can be:
4045 @value{GDBN} creates a new inferior and rebinds the process to this
4046 new inferior. The program the process was running before the
4047 @code{exec} call can be restarted afterwards by restarting the
4053 (@value{GDBP}) info inferiors
4055 Id Description Executable
4058 process 12020 is executing new program: prog2
4059 Program exited normally.
4060 (@value{GDBP}) info inferiors
4061 Id Description Executable
4067 @value{GDBN} keeps the process bound to the same inferior. The new
4068 executable image replaces the previous executable loaded in the
4069 inferior. Restarting the inferior after the @code{exec} call, with
4070 e.g., the @code{run} command, restarts the executable the process was
4071 running after the @code{exec} call. This is the default mode.
4076 (@value{GDBP}) info inferiors
4077 Id Description Executable
4080 process 12020 is executing new program: prog2
4081 Program exited normally.
4082 (@value{GDBP}) info inferiors
4083 Id Description Executable
4090 @code{follow-exec-mode} is supported in native mode and
4091 @code{target extended-remote} mode.
4093 You can use the @code{catch} command to make @value{GDBN} stop whenever
4094 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4095 Catchpoints, ,Setting Catchpoints}.
4097 @node Checkpoint/Restart
4098 @section Setting a @emph{Bookmark} to Return to Later
4103 @cindex snapshot of a process
4104 @cindex rewind program state
4106 On certain operating systems@footnote{Currently, only
4107 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4108 program's state, called a @dfn{checkpoint}, and come back to it
4111 Returning to a checkpoint effectively undoes everything that has
4112 happened in the program since the @code{checkpoint} was saved. This
4113 includes changes in memory, registers, and even (within some limits)
4114 system state. Effectively, it is like going back in time to the
4115 moment when the checkpoint was saved.
4117 Thus, if you're stepping thru a program and you think you're
4118 getting close to the point where things go wrong, you can save
4119 a checkpoint. Then, if you accidentally go too far and miss
4120 the critical statement, instead of having to restart your program
4121 from the beginning, you can just go back to the checkpoint and
4122 start again from there.
4124 This can be especially useful if it takes a lot of time or
4125 steps to reach the point where you think the bug occurs.
4127 To use the @code{checkpoint}/@code{restart} method of debugging:
4132 Save a snapshot of the debugged program's current execution state.
4133 The @code{checkpoint} command takes no arguments, but each checkpoint
4134 is assigned a small integer id, similar to a breakpoint id.
4136 @kindex info checkpoints
4137 @item info checkpoints
4138 List the checkpoints that have been saved in the current debugging
4139 session. For each checkpoint, the following information will be
4146 @item Source line, or label
4149 @kindex restart @var{checkpoint-id}
4150 @item restart @var{checkpoint-id}
4151 Restore the program state that was saved as checkpoint number
4152 @var{checkpoint-id}. All program variables, registers, stack frames
4153 etc.@: will be returned to the values that they had when the checkpoint
4154 was saved. In essence, gdb will ``wind back the clock'' to the point
4155 in time when the checkpoint was saved.
4157 Note that breakpoints, @value{GDBN} variables, command history etc.
4158 are not affected by restoring a checkpoint. In general, a checkpoint
4159 only restores things that reside in the program being debugged, not in
4162 @kindex delete checkpoint @var{checkpoint-id}
4163 @item delete checkpoint @var{checkpoint-id}
4164 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4168 Returning to a previously saved checkpoint will restore the user state
4169 of the program being debugged, plus a significant subset of the system
4170 (OS) state, including file pointers. It won't ``un-write'' data from
4171 a file, but it will rewind the file pointer to the previous location,
4172 so that the previously written data can be overwritten. For files
4173 opened in read mode, the pointer will also be restored so that the
4174 previously read data can be read again.
4176 Of course, characters that have been sent to a printer (or other
4177 external device) cannot be ``snatched back'', and characters received
4178 from eg.@: a serial device can be removed from internal program buffers,
4179 but they cannot be ``pushed back'' into the serial pipeline, ready to
4180 be received again. Similarly, the actual contents of files that have
4181 been changed cannot be restored (at this time).
4183 However, within those constraints, you actually can ``rewind'' your
4184 program to a previously saved point in time, and begin debugging it
4185 again --- and you can change the course of events so as to debug a
4186 different execution path this time.
4188 @cindex checkpoints and process id
4189 Finally, there is one bit of internal program state that will be
4190 different when you return to a checkpoint --- the program's process
4191 id. Each checkpoint will have a unique process id (or @var{pid}),
4192 and each will be different from the program's original @var{pid}.
4193 If your program has saved a local copy of its process id, this could
4194 potentially pose a problem.
4196 @subsection A Non-obvious Benefit of Using Checkpoints
4198 On some systems such as @sc{gnu}/Linux, address space randomization
4199 is performed on new processes for security reasons. This makes it
4200 difficult or impossible to set a breakpoint, or watchpoint, on an
4201 absolute address if you have to restart the program, since the
4202 absolute location of a symbol will change from one execution to the
4205 A checkpoint, however, is an @emph{identical} copy of a process.
4206 Therefore if you create a checkpoint at (eg.@:) the start of main,
4207 and simply return to that checkpoint instead of restarting the
4208 process, you can avoid the effects of address randomization and
4209 your symbols will all stay in the same place.
4212 @chapter Stopping and Continuing
4214 The principal purposes of using a debugger are so that you can stop your
4215 program before it terminates; or so that, if your program runs into
4216 trouble, you can investigate and find out why.
4218 Inside @value{GDBN}, your program may stop for any of several reasons,
4219 such as a signal, a breakpoint, or reaching a new line after a
4220 @value{GDBN} command such as @code{step}. You may then examine and
4221 change variables, set new breakpoints or remove old ones, and then
4222 continue execution. Usually, the messages shown by @value{GDBN} provide
4223 ample explanation of the status of your program---but you can also
4224 explicitly request this information at any time.
4227 @kindex info program
4229 Display information about the status of your program: whether it is
4230 running or not, what process it is, and why it stopped.
4234 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4235 * Continuing and Stepping:: Resuming execution
4236 * Skipping Over Functions and Files::
4237 Skipping over functions and files
4239 * Thread Stops:: Stopping and starting multi-thread programs
4243 @section Breakpoints, Watchpoints, and Catchpoints
4246 A @dfn{breakpoint} makes your program stop whenever a certain point in
4247 the program is reached. For each breakpoint, you can add conditions to
4248 control in finer detail whether your program stops. You can set
4249 breakpoints with the @code{break} command and its variants (@pxref{Set
4250 Breaks, ,Setting Breakpoints}), to specify the place where your program
4251 should stop by line number, function name or exact address in the
4254 On some systems, you can set breakpoints in shared libraries before
4255 the executable is run.
4258 @cindex data breakpoints
4259 @cindex memory tracing
4260 @cindex breakpoint on memory address
4261 @cindex breakpoint on variable modification
4262 A @dfn{watchpoint} is a special breakpoint that stops your program
4263 when the value of an expression changes. The expression may be a value
4264 of a variable, or it could involve values of one or more variables
4265 combined by operators, such as @samp{a + b}. This is sometimes called
4266 @dfn{data breakpoints}. You must use a different command to set
4267 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4268 from that, you can manage a watchpoint like any other breakpoint: you
4269 enable, disable, and delete both breakpoints and watchpoints using the
4272 You can arrange to have values from your program displayed automatically
4273 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4277 @cindex breakpoint on events
4278 A @dfn{catchpoint} is another special breakpoint that stops your program
4279 when a certain kind of event occurs, such as the throwing of a C@t{++}
4280 exception or the loading of a library. As with watchpoints, you use a
4281 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4282 Catchpoints}), but aside from that, you can manage a catchpoint like any
4283 other breakpoint. (To stop when your program receives a signal, use the
4284 @code{handle} command; see @ref{Signals, ,Signals}.)
4286 @cindex breakpoint numbers
4287 @cindex numbers for breakpoints
4288 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4289 catchpoint when you create it; these numbers are successive integers
4290 starting with one. In many of the commands for controlling various
4291 features of breakpoints you use the breakpoint number to say which
4292 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4293 @dfn{disabled}; if disabled, it has no effect on your program until you
4296 @cindex breakpoint ranges
4297 @cindex breakpoint lists
4298 @cindex ranges of breakpoints
4299 @cindex lists of breakpoints
4300 Some @value{GDBN} commands accept a space-separated list of breakpoints
4301 on which to operate. A list element can be either a single breakpoint number,
4302 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4303 When a breakpoint list is given to a command, all breakpoints in that list
4307 * Set Breaks:: Setting breakpoints
4308 * Set Watchpoints:: Setting watchpoints
4309 * Set Catchpoints:: Setting catchpoints
4310 * Delete Breaks:: Deleting breakpoints
4311 * Disabling:: Disabling breakpoints
4312 * Conditions:: Break conditions
4313 * Break Commands:: Breakpoint command lists
4314 * Dynamic Printf:: Dynamic printf
4315 * Save Breakpoints:: How to save breakpoints in a file
4316 * Static Probe Points:: Listing static probe points
4317 * Error in Breakpoints:: ``Cannot insert breakpoints''
4318 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4322 @subsection Setting Breakpoints
4324 @c FIXME LMB what does GDB do if no code on line of breakpt?
4325 @c consider in particular declaration with/without initialization.
4327 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4330 @kindex b @r{(@code{break})}
4331 @vindex $bpnum@r{, convenience variable}
4332 @cindex latest breakpoint
4333 Breakpoints are set with the @code{break} command (abbreviated
4334 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4335 number of the breakpoint you've set most recently; see @ref{Convenience
4336 Vars,, Convenience Variables}, for a discussion of what you can do with
4337 convenience variables.
4340 @item break @var{location}
4341 Set a breakpoint at the given @var{location}, which can specify a
4342 function name, a line number, or an address of an instruction.
4343 (@xref{Specify Location}, for a list of all the possible ways to
4344 specify a @var{location}.) The breakpoint will stop your program just
4345 before it executes any of the code in the specified @var{location}.
4347 When using source languages that permit overloading of symbols, such as
4348 C@t{++}, a function name may refer to more than one possible place to break.
4349 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4352 It is also possible to insert a breakpoint that will stop the program
4353 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4354 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4357 When called without any arguments, @code{break} sets a breakpoint at
4358 the next instruction to be executed in the selected stack frame
4359 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4360 innermost, this makes your program stop as soon as control
4361 returns to that frame. This is similar to the effect of a
4362 @code{finish} command in the frame inside the selected frame---except
4363 that @code{finish} does not leave an active breakpoint. If you use
4364 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4365 the next time it reaches the current location; this may be useful
4368 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4369 least one instruction has been executed. If it did not do this, you
4370 would be unable to proceed past a breakpoint without first disabling the
4371 breakpoint. This rule applies whether or not the breakpoint already
4372 existed when your program stopped.
4374 @item break @dots{} if @var{cond}
4375 Set a breakpoint with condition @var{cond}; evaluate the expression
4376 @var{cond} each time the breakpoint is reached, and stop only if the
4377 value is nonzero---that is, if @var{cond} evaluates as true.
4378 @samp{@dots{}} stands for one of the possible arguments described
4379 above (or no argument) specifying where to break. @xref{Conditions,
4380 ,Break Conditions}, for more information on breakpoint conditions.
4382 The breakpoint may be mapped to multiple locations. If the breakpoint
4383 condition @var{cond} is invalid at some but not all of the locations,
4384 the locations for which the condition is invalid are disabled. For
4385 example, @value{GDBN} reports below that two of the three locations
4389 (@value{GDBP}) break func if a == 10
4390 warning: failed to validate condition at location 0x11ce, disabling:
4391 No symbol "a" in current context.
4392 warning: failed to validate condition at location 0x11b6, disabling:
4393 No symbol "a" in current context.
4394 Breakpoint 1 at 0x11b6: func. (3 locations)
4397 Locations that are disabled because of the condition are denoted by an
4398 uppercase @code{N} in the output of the @code{info breakpoints}
4402 (@value{GDBP}) info breakpoints
4403 Num Type Disp Enb Address What
4404 1 breakpoint keep y <MULTIPLE>
4405 stop only if a == 10
4406 1.1 N* 0x00000000000011b6 in ...
4407 1.2 y 0x00000000000011c2 in ...
4408 1.3 N* 0x00000000000011ce in ...
4409 (*): Breakpoint condition is invalid at this location.
4412 If the breakpoint condition @var{cond} is invalid in the context of
4413 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4414 define the breakpoint. For example, if variable @code{foo} is an
4418 (@value{GDBP}) break func if foo
4419 No symbol "foo" in current context.
4422 @item break @dots{} -force-condition if @var{cond}
4423 There may be cases where the condition @var{cond} is invalid at all
4424 the current locations, but the user knows that it will be valid at a
4425 future location; for example, because of a library load. In such
4426 cases, by using the @code{-force-condition} keyword before @samp{if},
4427 @value{GDBN} can be forced to define the breakpoint with the given
4428 condition expression instead of refusing it.
4431 (@value{GDBP}) break func -force-condition if foo
4432 warning: failed to validate condition at location 1, disabling:
4433 No symbol "foo" in current context.
4434 warning: failed to validate condition at location 2, disabling:
4435 No symbol "foo" in current context.
4436 warning: failed to validate condition at location 3, disabling:
4437 No symbol "foo" in current context.
4438 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4441 This causes all the present locations where the breakpoint would
4442 otherwise be inserted, to be disabled, as seen in the example above.
4443 However, if there exist locations at which the condition is valid, the
4444 @code{-force-condition} keyword has no effect.
4447 @item tbreak @var{args}
4448 Set a breakpoint enabled only for one stop. The @var{args} are the
4449 same as for the @code{break} command, and the breakpoint is set in the same
4450 way, but the breakpoint is automatically deleted after the first time your
4451 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4454 @cindex hardware breakpoints
4455 @item hbreak @var{args}
4456 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4457 @code{break} command and the breakpoint is set in the same way, but the
4458 breakpoint requires hardware support and some target hardware may not
4459 have this support. The main purpose of this is EPROM/ROM code
4460 debugging, so you can set a breakpoint at an instruction without
4461 changing the instruction. This can be used with the new trap-generation
4462 provided by SPARClite DSU and most x86-based targets. These targets
4463 will generate traps when a program accesses some data or instruction
4464 address that is assigned to the debug registers. However the hardware
4465 breakpoint registers can take a limited number of breakpoints. For
4466 example, on the DSU, only two data breakpoints can be set at a time, and
4467 @value{GDBN} will reject this command if more than two are used. Delete
4468 or disable unused hardware breakpoints before setting new ones
4469 (@pxref{Disabling, ,Disabling Breakpoints}).
4470 @xref{Conditions, ,Break Conditions}.
4471 For remote targets, you can restrict the number of hardware
4472 breakpoints @value{GDBN} will use, see @ref{set remote
4473 hardware-breakpoint-limit}.
4476 @item thbreak @var{args}
4477 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4478 are the same as for the @code{hbreak} command and the breakpoint is set in
4479 the same way. However, like the @code{tbreak} command,
4480 the breakpoint is automatically deleted after the
4481 first time your program stops there. Also, like the @code{hbreak}
4482 command, the breakpoint requires hardware support and some target hardware
4483 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4484 See also @ref{Conditions, ,Break Conditions}.
4487 @cindex regular expression
4488 @cindex breakpoints at functions matching a regexp
4489 @cindex set breakpoints in many functions
4490 @item rbreak @var{regex}
4491 Set breakpoints on all functions matching the regular expression
4492 @var{regex}. This command sets an unconditional breakpoint on all
4493 matches, printing a list of all breakpoints it set. Once these
4494 breakpoints are set, they are treated just like the breakpoints set with
4495 the @code{break} command. You can delete them, disable them, or make
4496 them conditional the same way as any other breakpoint.
4498 In programs using different languages, @value{GDBN} chooses the syntax
4499 to print the list of all breakpoints it sets according to the
4500 @samp{set language} value: using @samp{set language auto}
4501 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4502 language of the breakpoint's function, other values mean to use
4503 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4505 The syntax of the regular expression is the standard one used with tools
4506 like @file{grep}. Note that this is different from the syntax used by
4507 shells, so for instance @code{foo*} matches all functions that include
4508 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4509 @code{.*} leading and trailing the regular expression you supply, so to
4510 match only functions that begin with @code{foo}, use @code{^foo}.
4512 @cindex non-member C@t{++} functions, set breakpoint in
4513 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4514 breakpoints on overloaded functions that are not members of any special
4517 @cindex set breakpoints on all functions
4518 The @code{rbreak} command can be used to set breakpoints in
4519 @strong{all} the functions in a program, like this:
4522 (@value{GDBP}) rbreak .
4525 @item rbreak @var{file}:@var{regex}
4526 If @code{rbreak} is called with a filename qualification, it limits
4527 the search for functions matching the given regular expression to the
4528 specified @var{file}. This can be used, for example, to set breakpoints on
4529 every function in a given file:
4532 (@value{GDBP}) rbreak file.c:.
4535 The colon separating the filename qualifier from the regex may
4536 optionally be surrounded by spaces.
4538 @kindex info breakpoints
4539 @cindex @code{$_} and @code{info breakpoints}
4540 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4541 @itemx info break @r{[}@var{list}@dots{}@r{]}
4542 Print a table of all breakpoints, watchpoints, and catchpoints set and
4543 not deleted. Optional argument @var{n} means print information only
4544 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4545 For each breakpoint, following columns are printed:
4548 @item Breakpoint Numbers
4550 Breakpoint, watchpoint, or catchpoint.
4552 Whether the breakpoint is marked to be disabled or deleted when hit.
4553 @item Enabled or Disabled
4554 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4555 that are not enabled.
4557 Where the breakpoint is in your program, as a memory address. For a
4558 pending breakpoint whose address is not yet known, this field will
4559 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4560 library that has the symbol or line referred by breakpoint is loaded.
4561 See below for details. A breakpoint with several locations will
4562 have @samp{<MULTIPLE>} in this field---see below for details.
4564 Where the breakpoint is in the source for your program, as a file and
4565 line number. For a pending breakpoint, the original string passed to
4566 the breakpoint command will be listed as it cannot be resolved until
4567 the appropriate shared library is loaded in the future.
4571 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4572 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4573 @value{GDBN} on the host's side. If it is ``target'', then the condition
4574 is evaluated by the target. The @code{info break} command shows
4575 the condition on the line following the affected breakpoint, together with
4576 its condition evaluation mode in between parentheses.
4578 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4579 allowed to have a condition specified for it. The condition is not parsed for
4580 validity until a shared library is loaded that allows the pending
4581 breakpoint to resolve to a valid location.
4584 @code{info break} with a breakpoint
4585 number @var{n} as argument lists only that breakpoint. The
4586 convenience variable @code{$_} and the default examining-address for
4587 the @code{x} command are set to the address of the last breakpoint
4588 listed (@pxref{Memory, ,Examining Memory}).
4591 @code{info break} displays a count of the number of times the breakpoint
4592 has been hit. This is especially useful in conjunction with the
4593 @code{ignore} command. You can ignore a large number of breakpoint
4594 hits, look at the breakpoint info to see how many times the breakpoint
4595 was hit, and then run again, ignoring one less than that number. This
4596 will get you quickly to the last hit of that breakpoint.
4599 For a breakpoints with an enable count (xref) greater than 1,
4600 @code{info break} also displays that count.
4604 @value{GDBN} allows you to set any number of breakpoints at the same place in
4605 your program. There is nothing silly or meaningless about this. When
4606 the breakpoints are conditional, this is even useful
4607 (@pxref{Conditions, ,Break Conditions}).
4609 @cindex multiple locations, breakpoints
4610 @cindex breakpoints, multiple locations
4611 It is possible that a breakpoint corresponds to several locations
4612 in your program. Examples of this situation are:
4616 Multiple functions in the program may have the same name.
4619 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4620 instances of the function body, used in different cases.
4623 For a C@t{++} template function, a given line in the function can
4624 correspond to any number of instantiations.
4627 For an inlined function, a given source line can correspond to
4628 several places where that function is inlined.
4631 In all those cases, @value{GDBN} will insert a breakpoint at all
4632 the relevant locations.
4634 A breakpoint with multiple locations is displayed in the breakpoint
4635 table using several rows---one header row, followed by one row for
4636 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4637 address column. The rows for individual locations contain the actual
4638 addresses for locations, and show the functions to which those
4639 locations belong. The number column for a location is of the form
4640 @var{breakpoint-number}.@var{location-number}.
4645 Num Type Disp Enb Address What
4646 1 breakpoint keep y <MULTIPLE>
4648 breakpoint already hit 1 time
4649 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4650 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4653 You cannot delete the individual locations from a breakpoint. However,
4654 each location can be individually enabled or disabled by passing
4655 @var{breakpoint-number}.@var{location-number} as argument to the
4656 @code{enable} and @code{disable} commands. It's also possible to
4657 @code{enable} and @code{disable} a range of @var{location-number}
4658 locations using a @var{breakpoint-number} and two @var{location-number}s,
4659 in increasing order, separated by a hyphen, like
4660 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4661 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4662 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4663 all of the locations that belong to that breakpoint.
4665 @cindex pending breakpoints
4666 It's quite common to have a breakpoint inside a shared library.
4667 Shared libraries can be loaded and unloaded explicitly,
4668 and possibly repeatedly, as the program is executed. To support
4669 this use case, @value{GDBN} updates breakpoint locations whenever
4670 any shared library is loaded or unloaded. Typically, you would
4671 set a breakpoint in a shared library at the beginning of your
4672 debugging session, when the library is not loaded, and when the
4673 symbols from the library are not available. When you try to set
4674 breakpoint, @value{GDBN} will ask you if you want to set
4675 a so called @dfn{pending breakpoint}---breakpoint whose address
4676 is not yet resolved.
4678 After the program is run, whenever a new shared library is loaded,
4679 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4680 shared library contains the symbol or line referred to by some
4681 pending breakpoint, that breakpoint is resolved and becomes an
4682 ordinary breakpoint. When a library is unloaded, all breakpoints
4683 that refer to its symbols or source lines become pending again.
4685 This logic works for breakpoints with multiple locations, too. For
4686 example, if you have a breakpoint in a C@t{++} template function, and
4687 a newly loaded shared library has an instantiation of that template,
4688 a new location is added to the list of locations for the breakpoint.
4690 Except for having unresolved address, pending breakpoints do not
4691 differ from regular breakpoints. You can set conditions or commands,
4692 enable and disable them and perform other breakpoint operations.
4694 @value{GDBN} provides some additional commands for controlling what
4695 happens when the @samp{break} command cannot resolve breakpoint
4696 address specification to an address:
4698 @kindex set breakpoint pending
4699 @kindex show breakpoint pending
4701 @item set breakpoint pending auto
4702 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4703 location, it queries you whether a pending breakpoint should be created.
4705 @item set breakpoint pending on
4706 This indicates that an unrecognized breakpoint location should automatically
4707 result in a pending breakpoint being created.
4709 @item set breakpoint pending off
4710 This indicates that pending breakpoints are not to be created. Any
4711 unrecognized breakpoint location results in an error. This setting does
4712 not affect any pending breakpoints previously created.
4714 @item show breakpoint pending
4715 Show the current behavior setting for creating pending breakpoints.
4718 The settings above only affect the @code{break} command and its
4719 variants. Once breakpoint is set, it will be automatically updated
4720 as shared libraries are loaded and unloaded.
4722 @cindex automatic hardware breakpoints
4723 For some targets, @value{GDBN} can automatically decide if hardware or
4724 software breakpoints should be used, depending on whether the
4725 breakpoint address is read-only or read-write. This applies to
4726 breakpoints set with the @code{break} command as well as to internal
4727 breakpoints set by commands like @code{next} and @code{finish}. For
4728 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4731 You can control this automatic behaviour with the following commands:
4733 @kindex set breakpoint auto-hw
4734 @kindex show breakpoint auto-hw
4736 @item set breakpoint auto-hw on
4737 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4738 will try to use the target memory map to decide if software or hardware
4739 breakpoint must be used.
4741 @item set breakpoint auto-hw off
4742 This indicates @value{GDBN} should not automatically select breakpoint
4743 type. If the target provides a memory map, @value{GDBN} will warn when
4744 trying to set software breakpoint at a read-only address.
4747 @value{GDBN} normally implements breakpoints by replacing the program code
4748 at the breakpoint address with a special instruction, which, when
4749 executed, given control to the debugger. By default, the program
4750 code is so modified only when the program is resumed. As soon as
4751 the program stops, @value{GDBN} restores the original instructions. This
4752 behaviour guards against leaving breakpoints inserted in the
4753 target should gdb abrubptly disconnect. However, with slow remote
4754 targets, inserting and removing breakpoint can reduce the performance.
4755 This behavior can be controlled with the following commands::
4757 @kindex set breakpoint always-inserted
4758 @kindex show breakpoint always-inserted
4760 @item set breakpoint always-inserted off
4761 All breakpoints, including newly added by the user, are inserted in
4762 the target only when the target is resumed. All breakpoints are
4763 removed from the target when it stops. This is the default mode.
4765 @item set breakpoint always-inserted on
4766 Causes all breakpoints to be inserted in the target at all times. If
4767 the user adds a new breakpoint, or changes an existing breakpoint, the
4768 breakpoints in the target are updated immediately. A breakpoint is
4769 removed from the target only when breakpoint itself is deleted.
4772 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4773 when a breakpoint breaks. If the condition is true, then the process being
4774 debugged stops, otherwise the process is resumed.
4776 If the target supports evaluating conditions on its end, @value{GDBN} may
4777 download the breakpoint, together with its conditions, to it.
4779 This feature can be controlled via the following commands:
4781 @kindex set breakpoint condition-evaluation
4782 @kindex show breakpoint condition-evaluation
4784 @item set breakpoint condition-evaluation host
4785 This option commands @value{GDBN} to evaluate the breakpoint
4786 conditions on the host's side. Unconditional breakpoints are sent to
4787 the target which in turn receives the triggers and reports them back to GDB
4788 for condition evaluation. This is the standard evaluation mode.
4790 @item set breakpoint condition-evaluation target
4791 This option commands @value{GDBN} to download breakpoint conditions
4792 to the target at the moment of their insertion. The target
4793 is responsible for evaluating the conditional expression and reporting
4794 breakpoint stop events back to @value{GDBN} whenever the condition
4795 is true. Due to limitations of target-side evaluation, some conditions
4796 cannot be evaluated there, e.g., conditions that depend on local data
4797 that is only known to the host. Examples include
4798 conditional expressions involving convenience variables, complex types
4799 that cannot be handled by the agent expression parser and expressions
4800 that are too long to be sent over to the target, specially when the
4801 target is a remote system. In these cases, the conditions will be
4802 evaluated by @value{GDBN}.
4804 @item set breakpoint condition-evaluation auto
4805 This is the default mode. If the target supports evaluating breakpoint
4806 conditions on its end, @value{GDBN} will download breakpoint conditions to
4807 the target (limitations mentioned previously apply). If the target does
4808 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4809 to evaluating all these conditions on the host's side.
4813 @cindex negative breakpoint numbers
4814 @cindex internal @value{GDBN} breakpoints
4815 @value{GDBN} itself sometimes sets breakpoints in your program for
4816 special purposes, such as proper handling of @code{longjmp} (in C
4817 programs). These internal breakpoints are assigned negative numbers,
4818 starting with @code{-1}; @samp{info breakpoints} does not display them.
4819 You can see these breakpoints with the @value{GDBN} maintenance command
4820 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4823 @node Set Watchpoints
4824 @subsection Setting Watchpoints
4826 @cindex setting watchpoints
4827 You can use a watchpoint to stop execution whenever the value of an
4828 expression changes, without having to predict a particular place where
4829 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4830 The expression may be as simple as the value of a single variable, or
4831 as complex as many variables combined by operators. Examples include:
4835 A reference to the value of a single variable.
4838 An address cast to an appropriate data type. For example,
4839 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4840 address (assuming an @code{int} occupies 4 bytes).
4843 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4844 expression can use any operators valid in the program's native
4845 language (@pxref{Languages}).
4848 You can set a watchpoint on an expression even if the expression can
4849 not be evaluated yet. For instance, you can set a watchpoint on
4850 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4851 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4852 the expression produces a valid value. If the expression becomes
4853 valid in some other way than changing a variable (e.g.@: if the memory
4854 pointed to by @samp{*global_ptr} becomes readable as the result of a
4855 @code{malloc} call), @value{GDBN} may not stop until the next time
4856 the expression changes.
4858 @cindex software watchpoints
4859 @cindex hardware watchpoints
4860 Depending on your system, watchpoints may be implemented in software or
4861 hardware. @value{GDBN} does software watchpointing by single-stepping your
4862 program and testing the variable's value each time, which is hundreds of
4863 times slower than normal execution. (But this may still be worth it, to
4864 catch errors where you have no clue what part of your program is the
4867 On some systems, such as most PowerPC or x86-based targets,
4868 @value{GDBN} includes support for hardware watchpoints, which do not
4869 slow down the running of your program.
4873 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
4874 Set a watchpoint for an expression. @value{GDBN} will break when the
4875 expression @var{expr} is written into by the program and its value
4876 changes. The simplest (and the most popular) use of this command is
4877 to watch the value of a single variable:
4880 (@value{GDBP}) watch foo
4883 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4884 argument, @value{GDBN} breaks only when the thread identified by
4885 @var{thread-id} changes the value of @var{expr}. If any other threads
4886 change the value of @var{expr}, @value{GDBN} will not break. Note
4887 that watchpoints restricted to a single thread in this way only work
4888 with Hardware Watchpoints.
4890 Similarly, if the @code{task} argument is given, then the watchpoint
4891 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4893 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4894 (see below). The @code{-location} argument tells @value{GDBN} to
4895 instead watch the memory referred to by @var{expr}. In this case,
4896 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4897 and watch the memory at that address. The type of the result is used
4898 to determine the size of the watched memory. If the expression's
4899 result does not have an address, then @value{GDBN} will print an
4902 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4903 of masked watchpoints, if the current architecture supports this
4904 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4905 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4906 to an address to watch. The mask specifies that some bits of an address
4907 (the bits which are reset in the mask) should be ignored when matching
4908 the address accessed by the inferior against the watchpoint address.
4909 Thus, a masked watchpoint watches many addresses simultaneously---those
4910 addresses whose unmasked bits are identical to the unmasked bits in the
4911 watchpoint address. The @code{mask} argument implies @code{-location}.
4915 (@value{GDBP}) watch foo mask 0xffff00ff
4916 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4920 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4921 Set a watchpoint that will break when the value of @var{expr} is read
4925 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4926 Set a watchpoint that will break when @var{expr} is either read from
4927 or written into by the program.
4929 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4930 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4931 This command prints a list of watchpoints, using the same format as
4932 @code{info break} (@pxref{Set Breaks}).
4935 If you watch for a change in a numerically entered address you need to
4936 dereference it, as the address itself is just a constant number which will
4937 never change. @value{GDBN} refuses to create a watchpoint that watches
4938 a never-changing value:
4941 (@value{GDBP}) watch 0x600850
4942 Cannot watch constant value 0x600850.
4943 (@value{GDBP}) watch *(int *) 0x600850
4944 Watchpoint 1: *(int *) 6293584
4947 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4948 watchpoints execute very quickly, and the debugger reports a change in
4949 value at the exact instruction where the change occurs. If @value{GDBN}
4950 cannot set a hardware watchpoint, it sets a software watchpoint, which
4951 executes more slowly and reports the change in value at the next
4952 @emph{statement}, not the instruction, after the change occurs.
4954 @cindex use only software watchpoints
4955 You can force @value{GDBN} to use only software watchpoints with the
4956 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4957 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4958 the underlying system supports them. (Note that hardware-assisted
4959 watchpoints that were set @emph{before} setting
4960 @code{can-use-hw-watchpoints} to zero will still use the hardware
4961 mechanism of watching expression values.)
4964 @item set can-use-hw-watchpoints
4965 @kindex set can-use-hw-watchpoints
4966 Set whether or not to use hardware watchpoints.
4968 @item show can-use-hw-watchpoints
4969 @kindex show can-use-hw-watchpoints
4970 Show the current mode of using hardware watchpoints.
4973 For remote targets, you can restrict the number of hardware
4974 watchpoints @value{GDBN} will use, see @ref{set remote
4975 hardware-breakpoint-limit}.
4977 When you issue the @code{watch} command, @value{GDBN} reports
4980 Hardware watchpoint @var{num}: @var{expr}
4984 if it was able to set a hardware watchpoint.
4986 Currently, the @code{awatch} and @code{rwatch} commands can only set
4987 hardware watchpoints, because accesses to data that don't change the
4988 value of the watched expression cannot be detected without examining
4989 every instruction as it is being executed, and @value{GDBN} does not do
4990 that currently. If @value{GDBN} finds that it is unable to set a
4991 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4992 will print a message like this:
4995 Expression cannot be implemented with read/access watchpoint.
4998 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4999 data type of the watched expression is wider than what a hardware
5000 watchpoint on the target machine can handle. For example, some systems
5001 can only watch regions that are up to 4 bytes wide; on such systems you
5002 cannot set hardware watchpoints for an expression that yields a
5003 double-precision floating-point number (which is typically 8 bytes
5004 wide). As a work-around, it might be possible to break the large region
5005 into a series of smaller ones and watch them with separate watchpoints.
5007 If you set too many hardware watchpoints, @value{GDBN} might be unable
5008 to insert all of them when you resume the execution of your program.
5009 Since the precise number of active watchpoints is unknown until such
5010 time as the program is about to be resumed, @value{GDBN} might not be
5011 able to warn you about this when you set the watchpoints, and the
5012 warning will be printed only when the program is resumed:
5015 Hardware watchpoint @var{num}: Could not insert watchpoint
5019 If this happens, delete or disable some of the watchpoints.
5021 Watching complex expressions that reference many variables can also
5022 exhaust the resources available for hardware-assisted watchpoints.
5023 That's because @value{GDBN} needs to watch every variable in the
5024 expression with separately allocated resources.
5026 If you call a function interactively using @code{print} or @code{call},
5027 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5028 kind of breakpoint or the call completes.
5030 @value{GDBN} automatically deletes watchpoints that watch local
5031 (automatic) variables, or expressions that involve such variables, when
5032 they go out of scope, that is, when the execution leaves the block in
5033 which these variables were defined. In particular, when the program
5034 being debugged terminates, @emph{all} local variables go out of scope,
5035 and so only watchpoints that watch global variables remain set. If you
5036 rerun the program, you will need to set all such watchpoints again. One
5037 way of doing that would be to set a code breakpoint at the entry to the
5038 @code{main} function and when it breaks, set all the watchpoints.
5040 @cindex watchpoints and threads
5041 @cindex threads and watchpoints
5042 In multi-threaded programs, watchpoints will detect changes to the
5043 watched expression from every thread.
5046 @emph{Warning:} In multi-threaded programs, software watchpoints
5047 have only limited usefulness. If @value{GDBN} creates a software
5048 watchpoint, it can only watch the value of an expression @emph{in a
5049 single thread}. If you are confident that the expression can only
5050 change due to the current thread's activity (and if you are also
5051 confident that no other thread can become current), then you can use
5052 software watchpoints as usual. However, @value{GDBN} may not notice
5053 when a non-current thread's activity changes the expression. (Hardware
5054 watchpoints, in contrast, watch an expression in all threads.)
5057 @xref{set remote hardware-watchpoint-limit}.
5059 @node Set Catchpoints
5060 @subsection Setting Catchpoints
5061 @cindex catchpoints, setting
5062 @cindex exception handlers
5063 @cindex event handling
5065 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5066 kinds of program events, such as C@t{++} exceptions or the loading of a
5067 shared library. Use the @code{catch} command to set a catchpoint.
5071 @item catch @var{event}
5072 Stop when @var{event} occurs. The @var{event} can be any of the following:
5075 @item throw @r{[}@var{regexp}@r{]}
5076 @itemx rethrow @r{[}@var{regexp}@r{]}
5077 @itemx catch @r{[}@var{regexp}@r{]}
5079 @kindex catch rethrow
5081 @cindex stop on C@t{++} exceptions
5082 The throwing, re-throwing, or catching of a C@t{++} exception.
5084 If @var{regexp} is given, then only exceptions whose type matches the
5085 regular expression will be caught.
5087 @vindex $_exception@r{, convenience variable}
5088 The convenience variable @code{$_exception} is available at an
5089 exception-related catchpoint, on some systems. This holds the
5090 exception being thrown.
5092 There are currently some limitations to C@t{++} exception handling in
5097 The support for these commands is system-dependent. Currently, only
5098 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5102 The regular expression feature and the @code{$_exception} convenience
5103 variable rely on the presence of some SDT probes in @code{libstdc++}.
5104 If these probes are not present, then these features cannot be used.
5105 These probes were first available in the GCC 4.8 release, but whether
5106 or not they are available in your GCC also depends on how it was
5110 The @code{$_exception} convenience variable is only valid at the
5111 instruction at which an exception-related catchpoint is set.
5114 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5115 location in the system library which implements runtime exception
5116 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5117 (@pxref{Selection}) to get to your code.
5120 If you call a function interactively, @value{GDBN} normally returns
5121 control to you when the function has finished executing. If the call
5122 raises an exception, however, the call may bypass the mechanism that
5123 returns control to you and cause your program either to abort or to
5124 simply continue running until it hits a breakpoint, catches a signal
5125 that @value{GDBN} is listening for, or exits. This is the case even if
5126 you set a catchpoint for the exception; catchpoints on exceptions are
5127 disabled within interactive calls. @xref{Calling}, for information on
5128 controlling this with @code{set unwind-on-terminating-exception}.
5131 You cannot raise an exception interactively.
5134 You cannot install an exception handler interactively.
5137 @item exception @r{[}@var{name}@r{]}
5138 @kindex catch exception
5139 @cindex Ada exception catching
5140 @cindex catch Ada exceptions
5141 An Ada exception being raised. If an exception name is specified
5142 at the end of the command (eg @code{catch exception Program_Error}),
5143 the debugger will stop only when this specific exception is raised.
5144 Otherwise, the debugger stops execution when any Ada exception is raised.
5146 When inserting an exception catchpoint on a user-defined exception whose
5147 name is identical to one of the exceptions defined by the language, the
5148 fully qualified name must be used as the exception name. Otherwise,
5149 @value{GDBN} will assume that it should stop on the pre-defined exception
5150 rather than the user-defined one. For instance, assuming an exception
5151 called @code{Constraint_Error} is defined in package @code{Pck}, then
5152 the command to use to catch such exceptions is @kbd{catch exception
5153 Pck.Constraint_Error}.
5155 @vindex $_ada_exception@r{, convenience variable}
5156 The convenience variable @code{$_ada_exception} holds the address of
5157 the exception being thrown. This can be useful when setting a
5158 condition for such a catchpoint.
5160 @item exception unhandled
5161 @kindex catch exception unhandled
5162 An exception that was raised but is not handled by the program. The
5163 convenience variable @code{$_ada_exception} is set as for @code{catch
5166 @item handlers @r{[}@var{name}@r{]}
5167 @kindex catch handlers
5168 @cindex Ada exception handlers catching
5169 @cindex catch Ada exceptions when handled
5170 An Ada exception being handled. If an exception name is
5171 specified at the end of the command
5172 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5173 only when this specific exception is handled.
5174 Otherwise, the debugger stops execution when any Ada exception is handled.
5176 When inserting a handlers catchpoint on a user-defined
5177 exception whose name is identical to one of the exceptions
5178 defined by the language, the fully qualified name must be used
5179 as the exception name. Otherwise, @value{GDBN} will assume that it
5180 should stop on the pre-defined exception rather than the
5181 user-defined one. For instance, assuming an exception called
5182 @code{Constraint_Error} is defined in package @code{Pck}, then the
5183 command to use to catch such exceptions handling is
5184 @kbd{catch handlers Pck.Constraint_Error}.
5186 The convenience variable @code{$_ada_exception} is set as for
5187 @code{catch exception}.
5190 @kindex catch assert
5191 A failed Ada assertion. Note that the convenience variable
5192 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5196 @cindex break on fork/exec
5197 A call to @code{exec}.
5199 @anchor{catch syscall}
5201 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5202 @kindex catch syscall
5203 @cindex break on a system call.
5204 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5205 syscall is a mechanism for application programs to request a service
5206 from the operating system (OS) or one of the OS system services.
5207 @value{GDBN} can catch some or all of the syscalls issued by the
5208 debuggee, and show the related information for each syscall. If no
5209 argument is specified, calls to and returns from all system calls
5212 @var{name} can be any system call name that is valid for the
5213 underlying OS. Just what syscalls are valid depends on the OS. On
5214 GNU and Unix systems, you can find the full list of valid syscall
5215 names on @file{/usr/include/asm/unistd.h}.
5217 @c For MS-Windows, the syscall names and the corresponding numbers
5218 @c can be found, e.g., on this URL:
5219 @c http://www.metasploit.com/users/opcode/syscalls.html
5220 @c but we don't support Windows syscalls yet.
5222 Normally, @value{GDBN} knows in advance which syscalls are valid for
5223 each OS, so you can use the @value{GDBN} command-line completion
5224 facilities (@pxref{Completion,, command completion}) to list the
5227 You may also specify the system call numerically. A syscall's
5228 number is the value passed to the OS's syscall dispatcher to
5229 identify the requested service. When you specify the syscall by its
5230 name, @value{GDBN} uses its database of syscalls to convert the name
5231 into the corresponding numeric code, but using the number directly
5232 may be useful if @value{GDBN}'s database does not have the complete
5233 list of syscalls on your system (e.g., because @value{GDBN} lags
5234 behind the OS upgrades).
5236 You may specify a group of related syscalls to be caught at once using
5237 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5238 instance, on some platforms @value{GDBN} allows you to catch all
5239 network related syscalls, by passing the argument @code{group:network}
5240 to @code{catch syscall}. Note that not all syscall groups are
5241 available in every system. You can use the command completion
5242 facilities (@pxref{Completion,, command completion}) to list the
5243 syscall groups available on your environment.
5245 The example below illustrates how this command works if you don't provide
5249 (@value{GDBP}) catch syscall
5250 Catchpoint 1 (syscall)
5252 Starting program: /tmp/catch-syscall
5254 Catchpoint 1 (call to syscall 'close'), \
5255 0xffffe424 in __kernel_vsyscall ()
5259 Catchpoint 1 (returned from syscall 'close'), \
5260 0xffffe424 in __kernel_vsyscall ()
5264 Here is an example of catching a system call by name:
5267 (@value{GDBP}) catch syscall chroot
5268 Catchpoint 1 (syscall 'chroot' [61])
5270 Starting program: /tmp/catch-syscall
5272 Catchpoint 1 (call to syscall 'chroot'), \
5273 0xffffe424 in __kernel_vsyscall ()
5277 Catchpoint 1 (returned from syscall 'chroot'), \
5278 0xffffe424 in __kernel_vsyscall ()
5282 An example of specifying a system call numerically. In the case
5283 below, the syscall number has a corresponding entry in the XML
5284 file, so @value{GDBN} finds its name and prints it:
5287 (@value{GDBP}) catch syscall 252
5288 Catchpoint 1 (syscall(s) 'exit_group')
5290 Starting program: /tmp/catch-syscall
5292 Catchpoint 1 (call to syscall 'exit_group'), \
5293 0xffffe424 in __kernel_vsyscall ()
5297 Program exited normally.
5301 Here is an example of catching a syscall group:
5304 (@value{GDBP}) catch syscall group:process
5305 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5306 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5307 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5309 Starting program: /tmp/catch-syscall
5311 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5312 from /lib64/ld-linux-x86-64.so.2
5318 However, there can be situations when there is no corresponding name
5319 in XML file for that syscall number. In this case, @value{GDBN} prints
5320 a warning message saying that it was not able to find the syscall name,
5321 but the catchpoint will be set anyway. See the example below:
5324 (@value{GDBP}) catch syscall 764
5325 warning: The number '764' does not represent a known syscall.
5326 Catchpoint 2 (syscall 764)
5330 If you configure @value{GDBN} using the @samp{--without-expat} option,
5331 it will not be able to display syscall names. Also, if your
5332 architecture does not have an XML file describing its system calls,
5333 you will not be able to see the syscall names. It is important to
5334 notice that these two features are used for accessing the syscall
5335 name database. In either case, you will see a warning like this:
5338 (@value{GDBP}) catch syscall
5339 warning: Could not open "syscalls/i386-linux.xml"
5340 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5341 GDB will not be able to display syscall names.
5342 Catchpoint 1 (syscall)
5346 Of course, the file name will change depending on your architecture and system.
5348 Still using the example above, you can also try to catch a syscall by its
5349 number. In this case, you would see something like:
5352 (@value{GDBP}) catch syscall 252
5353 Catchpoint 1 (syscall(s) 252)
5356 Again, in this case @value{GDBN} would not be able to display syscall's names.
5360 A call to @code{fork}.
5364 A call to @code{vfork}.
5366 @item load @r{[}@var{regexp}@r{]}
5367 @itemx unload @r{[}@var{regexp}@r{]}
5369 @kindex catch unload
5370 The loading or unloading of a shared library. If @var{regexp} is
5371 given, then the catchpoint will stop only if the regular expression
5372 matches one of the affected libraries.
5374 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5375 @kindex catch signal
5376 The delivery of a signal.
5378 With no arguments, this catchpoint will catch any signal that is not
5379 used internally by @value{GDBN}, specifically, all signals except
5380 @samp{SIGTRAP} and @samp{SIGINT}.
5382 With the argument @samp{all}, all signals, including those used by
5383 @value{GDBN}, will be caught. This argument cannot be used with other
5386 Otherwise, the arguments are a list of signal names as given to
5387 @code{handle} (@pxref{Signals}). Only signals specified in this list
5390 One reason that @code{catch signal} can be more useful than
5391 @code{handle} is that you can attach commands and conditions to the
5394 When a signal is caught by a catchpoint, the signal's @code{stop} and
5395 @code{print} settings, as specified by @code{handle}, are ignored.
5396 However, whether the signal is still delivered to the inferior depends
5397 on the @code{pass} setting; this can be changed in the catchpoint's
5402 @item tcatch @var{event}
5404 Set a catchpoint that is enabled only for one stop. The catchpoint is
5405 automatically deleted after the first time the event is caught.
5409 Use the @code{info break} command to list the current catchpoints.
5413 @subsection Deleting Breakpoints
5415 @cindex clearing breakpoints, watchpoints, catchpoints
5416 @cindex deleting breakpoints, watchpoints, catchpoints
5417 It is often necessary to eliminate a breakpoint, watchpoint, or
5418 catchpoint once it has done its job and you no longer want your program
5419 to stop there. This is called @dfn{deleting} the breakpoint. A
5420 breakpoint that has been deleted no longer exists; it is forgotten.
5422 With the @code{clear} command you can delete breakpoints according to
5423 where they are in your program. With the @code{delete} command you can
5424 delete individual breakpoints, watchpoints, or catchpoints by specifying
5425 their breakpoint numbers.
5427 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5428 automatically ignores breakpoints on the first instruction to be executed
5429 when you continue execution without changing the execution address.
5434 Delete any breakpoints at the next instruction to be executed in the
5435 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5436 the innermost frame is selected, this is a good way to delete a
5437 breakpoint where your program just stopped.
5439 @item clear @var{location}
5440 Delete any breakpoints set at the specified @var{location}.
5441 @xref{Specify Location}, for the various forms of @var{location}; the
5442 most useful ones are listed below:
5445 @item clear @var{function}
5446 @itemx clear @var{filename}:@var{function}
5447 Delete any breakpoints set at entry to the named @var{function}.
5449 @item clear @var{linenum}
5450 @itemx clear @var{filename}:@var{linenum}
5451 Delete any breakpoints set at or within the code of the specified
5452 @var{linenum} of the specified @var{filename}.
5455 @cindex delete breakpoints
5457 @kindex d @r{(@code{delete})}
5458 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5459 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5460 list specified as argument. If no argument is specified, delete all
5461 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5462 confirm off}). You can abbreviate this command as @code{d}.
5466 @subsection Disabling Breakpoints
5468 @cindex enable/disable a breakpoint
5469 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5470 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5471 it had been deleted, but remembers the information on the breakpoint so
5472 that you can @dfn{enable} it again later.
5474 You disable and enable breakpoints, watchpoints, and catchpoints with
5475 the @code{enable} and @code{disable} commands, optionally specifying
5476 one or more breakpoint numbers as arguments. Use @code{info break} to
5477 print a list of all breakpoints, watchpoints, and catchpoints if you
5478 do not know which numbers to use.
5480 Disabling and enabling a breakpoint that has multiple locations
5481 affects all of its locations.
5483 A breakpoint, watchpoint, or catchpoint can have any of several
5484 different states of enablement:
5488 Enabled. The breakpoint stops your program. A breakpoint set
5489 with the @code{break} command starts out in this state.
5491 Disabled. The breakpoint has no effect on your program.
5493 Enabled once. The breakpoint stops your program, but then becomes
5496 Enabled for a count. The breakpoint stops your program for the next
5497 N times, then becomes disabled.
5499 Enabled for deletion. The breakpoint stops your program, but
5500 immediately after it does so it is deleted permanently. A breakpoint
5501 set with the @code{tbreak} command starts out in this state.
5504 You can use the following commands to enable or disable breakpoints,
5505 watchpoints, and catchpoints:
5509 @kindex dis @r{(@code{disable})}
5510 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5511 Disable the specified breakpoints---or all breakpoints, if none are
5512 listed. A disabled breakpoint has no effect but is not forgotten. All
5513 options such as ignore-counts, conditions and commands are remembered in
5514 case the breakpoint is enabled again later. You may abbreviate
5515 @code{disable} as @code{dis}.
5518 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5519 Enable the specified breakpoints (or all defined breakpoints). They
5520 become effective once again in stopping your program.
5522 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5523 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5524 of these breakpoints immediately after stopping your program.
5526 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5527 Enable the specified breakpoints temporarily. @value{GDBN} records
5528 @var{count} with each of the specified breakpoints, and decrements a
5529 breakpoint's count when it is hit. When any count reaches 0,
5530 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5531 count (@pxref{Conditions, ,Break Conditions}), that will be
5532 decremented to 0 before @var{count} is affected.
5534 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5535 Enable the specified breakpoints to work once, then die. @value{GDBN}
5536 deletes any of these breakpoints as soon as your program stops there.
5537 Breakpoints set by the @code{tbreak} command start out in this state.
5540 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5541 @c confusing: tbreak is also initially enabled.
5542 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5543 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5544 subsequently, they become disabled or enabled only when you use one of
5545 the commands above. (The command @code{until} can set and delete a
5546 breakpoint of its own, but it does not change the state of your other
5547 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5551 @subsection Break Conditions
5552 @cindex conditional breakpoints
5553 @cindex breakpoint conditions
5555 @c FIXME what is scope of break condition expr? Context where wanted?
5556 @c in particular for a watchpoint?
5557 The simplest sort of breakpoint breaks every time your program reaches a
5558 specified place. You can also specify a @dfn{condition} for a
5559 breakpoint. A condition is just a Boolean expression in your
5560 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5561 a condition evaluates the expression each time your program reaches it,
5562 and your program stops only if the condition is @emph{true}.
5564 This is the converse of using assertions for program validation; in that
5565 situation, you want to stop when the assertion is violated---that is,
5566 when the condition is false. In C, if you want to test an assertion expressed
5567 by the condition @var{assert}, you should set the condition
5568 @samp{! @var{assert}} on the appropriate breakpoint.
5570 Conditions are also accepted for watchpoints; you may not need them,
5571 since a watchpoint is inspecting the value of an expression anyhow---but
5572 it might be simpler, say, to just set a watchpoint on a variable name,
5573 and specify a condition that tests whether the new value is an interesting
5576 Break conditions can have side effects, and may even call functions in
5577 your program. This can be useful, for example, to activate functions
5578 that log program progress, or to use your own print functions to
5579 format special data structures. The effects are completely predictable
5580 unless there is another enabled breakpoint at the same address. (In
5581 that case, @value{GDBN} might see the other breakpoint first and stop your
5582 program without checking the condition of this one.) Note that
5583 breakpoint commands are usually more convenient and flexible than break
5585 purpose of performing side effects when a breakpoint is reached
5586 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5588 Breakpoint conditions can also be evaluated on the target's side if
5589 the target supports it. Instead of evaluating the conditions locally,
5590 @value{GDBN} encodes the expression into an agent expression
5591 (@pxref{Agent Expressions}) suitable for execution on the target,
5592 independently of @value{GDBN}. Global variables become raw memory
5593 locations, locals become stack accesses, and so forth.
5595 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5596 when its condition evaluates to true. This mechanism may provide faster
5597 response times depending on the performance characteristics of the target
5598 since it does not need to keep @value{GDBN} informed about
5599 every breakpoint trigger, even those with false conditions.
5601 Break conditions can be specified when a breakpoint is set, by using
5602 @samp{if} in the arguments to the @code{break} command. @xref{Set
5603 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5604 with the @code{condition} command.
5606 You can also use the @code{if} keyword with the @code{watch} command.
5607 The @code{catch} command does not recognize the @code{if} keyword;
5608 @code{condition} is the only way to impose a further condition on a
5613 @item condition @var{bnum} @var{expression}
5614 Specify @var{expression} as the break condition for breakpoint,
5615 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5616 breakpoint @var{bnum} stops your program only if the value of
5617 @var{expression} is true (nonzero, in C). When you use
5618 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5619 syntactic correctness, and to determine whether symbols in it have
5620 referents in the context of your breakpoint. If @var{expression} uses
5621 symbols not referenced in the context of the breakpoint, @value{GDBN}
5622 prints an error message:
5625 No symbol "foo" in current context.
5630 not actually evaluate @var{expression} at the time the @code{condition}
5631 command (or a command that sets a breakpoint with a condition, like
5632 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5634 @item condition -force @var{bnum} @var{expression}
5635 When the @code{-force} flag is used, define the condition even if
5636 @var{expression} is invalid at all the current locations of breakpoint
5637 @var{bnum}. This is similar to the @code{-force-condition} option
5638 of the @code{break} command.
5640 @item condition @var{bnum}
5641 Remove the condition from breakpoint number @var{bnum}. It becomes
5642 an ordinary unconditional breakpoint.
5645 @cindex ignore count (of breakpoint)
5646 A special case of a breakpoint condition is to stop only when the
5647 breakpoint has been reached a certain number of times. This is so
5648 useful that there is a special way to do it, using the @dfn{ignore
5649 count} of the breakpoint. Every breakpoint has an ignore count, which
5650 is an integer. Most of the time, the ignore count is zero, and
5651 therefore has no effect. But if your program reaches a breakpoint whose
5652 ignore count is positive, then instead of stopping, it just decrements
5653 the ignore count by one and continues. As a result, if the ignore count
5654 value is @var{n}, the breakpoint does not stop the next @var{n} times
5655 your program reaches it.
5659 @item ignore @var{bnum} @var{count}
5660 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5661 The next @var{count} times the breakpoint is reached, your program's
5662 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5665 To make the breakpoint stop the next time it is reached, specify
5668 When you use @code{continue} to resume execution of your program from a
5669 breakpoint, you can specify an ignore count directly as an argument to
5670 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5671 Stepping,,Continuing and Stepping}.
5673 If a breakpoint has a positive ignore count and a condition, the
5674 condition is not checked. Once the ignore count reaches zero,
5675 @value{GDBN} resumes checking the condition.
5677 You could achieve the effect of the ignore count with a condition such
5678 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5679 is decremented each time. @xref{Convenience Vars, ,Convenience
5683 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5686 @node Break Commands
5687 @subsection Breakpoint Command Lists
5689 @cindex breakpoint commands
5690 You can give any breakpoint (or watchpoint or catchpoint) a series of
5691 commands to execute when your program stops due to that breakpoint. For
5692 example, you might want to print the values of certain expressions, or
5693 enable other breakpoints.
5697 @kindex end@r{ (breakpoint commands)}
5698 @item commands @r{[}@var{list}@dots{}@r{]}
5699 @itemx @dots{} @var{command-list} @dots{}
5701 Specify a list of commands for the given breakpoints. The commands
5702 themselves appear on the following lines. Type a line containing just
5703 @code{end} to terminate the commands.
5705 To remove all commands from a breakpoint, type @code{commands} and
5706 follow it immediately with @code{end}; that is, give no commands.
5708 With no argument, @code{commands} refers to the last breakpoint,
5709 watchpoint, or catchpoint set (not to the breakpoint most recently
5710 encountered). If the most recent breakpoints were set with a single
5711 command, then the @code{commands} will apply to all the breakpoints
5712 set by that command. This applies to breakpoints set by
5713 @code{rbreak}, and also applies when a single @code{break} command
5714 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5718 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5719 disabled within a @var{command-list}.
5721 You can use breakpoint commands to start your program up again. Simply
5722 use the @code{continue} command, or @code{step}, or any other command
5723 that resumes execution.
5725 Any other commands in the command list, after a command that resumes
5726 execution, are ignored. This is because any time you resume execution
5727 (even with a simple @code{next} or @code{step}), you may encounter
5728 another breakpoint---which could have its own command list, leading to
5729 ambiguities about which list to execute.
5732 If the first command you specify in a command list is @code{silent}, the
5733 usual message about stopping at a breakpoint is not printed. This may
5734 be desirable for breakpoints that are to print a specific message and
5735 then continue. If none of the remaining commands print anything, you
5736 see no sign that the breakpoint was reached. @code{silent} is
5737 meaningful only at the beginning of a breakpoint command list.
5739 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5740 print precisely controlled output, and are often useful in silent
5741 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5743 For example, here is how you could use breakpoint commands to print the
5744 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5750 printf "x is %d\n",x
5755 One application for breakpoint commands is to compensate for one bug so
5756 you can test for another. Put a breakpoint just after the erroneous line
5757 of code, give it a condition to detect the case in which something
5758 erroneous has been done, and give it commands to assign correct values
5759 to any variables that need them. End with the @code{continue} command
5760 so that your program does not stop, and start with the @code{silent}
5761 command so that no output is produced. Here is an example:
5772 @node Dynamic Printf
5773 @subsection Dynamic Printf
5775 @cindex dynamic printf
5777 The dynamic printf command @code{dprintf} combines a breakpoint with
5778 formatted printing of your program's data to give you the effect of
5779 inserting @code{printf} calls into your program on-the-fly, without
5780 having to recompile it.
5782 In its most basic form, the output goes to the GDB console. However,
5783 you can set the variable @code{dprintf-style} for alternate handling.
5784 For instance, you can ask to format the output by calling your
5785 program's @code{printf} function. This has the advantage that the
5786 characters go to the program's output device, so they can recorded in
5787 redirects to files and so forth.
5789 If you are doing remote debugging with a stub or agent, you can also
5790 ask to have the printf handled by the remote agent. In addition to
5791 ensuring that the output goes to the remote program's device along
5792 with any other output the program might produce, you can also ask that
5793 the dprintf remain active even after disconnecting from the remote
5794 target. Using the stub/agent is also more efficient, as it can do
5795 everything without needing to communicate with @value{GDBN}.
5799 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5800 Whenever execution reaches @var{location}, print the values of one or
5801 more @var{expressions} under the control of the string @var{template}.
5802 To print several values, separate them with commas.
5804 @item set dprintf-style @var{style}
5805 Set the dprintf output to be handled in one of several different
5806 styles enumerated below. A change of style affects all existing
5807 dynamic printfs immediately. (If you need individual control over the
5808 print commands, simply define normal breakpoints with
5809 explicitly-supplied command lists.)
5813 @kindex dprintf-style gdb
5814 Handle the output using the @value{GDBN} @code{printf} command.
5817 @kindex dprintf-style call
5818 Handle the output by calling a function in your program (normally
5822 @kindex dprintf-style agent
5823 Have the remote debugging agent (such as @code{gdbserver}) handle
5824 the output itself. This style is only available for agents that
5825 support running commands on the target.
5828 @item set dprintf-function @var{function}
5829 Set the function to call if the dprintf style is @code{call}. By
5830 default its value is @code{printf}. You may set it to any expression.
5831 that @value{GDBN} can evaluate to a function, as per the @code{call}
5834 @item set dprintf-channel @var{channel}
5835 Set a ``channel'' for dprintf. If set to a non-empty value,
5836 @value{GDBN} will evaluate it as an expression and pass the result as
5837 a first argument to the @code{dprintf-function}, in the manner of
5838 @code{fprintf} and similar functions. Otherwise, the dprintf format
5839 string will be the first argument, in the manner of @code{printf}.
5841 As an example, if you wanted @code{dprintf} output to go to a logfile
5842 that is a standard I/O stream assigned to the variable @code{mylog},
5843 you could do the following:
5846 (gdb) set dprintf-style call
5847 (gdb) set dprintf-function fprintf
5848 (gdb) set dprintf-channel mylog
5849 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5850 Dprintf 1 at 0x123456: file main.c, line 25.
5852 1 dprintf keep y 0x00123456 in main at main.c:25
5853 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5858 Note that the @code{info break} displays the dynamic printf commands
5859 as normal breakpoint commands; you can thus easily see the effect of
5860 the variable settings.
5862 @item set disconnected-dprintf on
5863 @itemx set disconnected-dprintf off
5864 @kindex set disconnected-dprintf
5865 Choose whether @code{dprintf} commands should continue to run if
5866 @value{GDBN} has disconnected from the target. This only applies
5867 if the @code{dprintf-style} is @code{agent}.
5869 @item show disconnected-dprintf off
5870 @kindex show disconnected-dprintf
5871 Show the current choice for disconnected @code{dprintf}.
5875 @value{GDBN} does not check the validity of function and channel,
5876 relying on you to supply values that are meaningful for the contexts
5877 in which they are being used. For instance, the function and channel
5878 may be the values of local variables, but if that is the case, then
5879 all enabled dynamic prints must be at locations within the scope of
5880 those locals. If evaluation fails, @value{GDBN} will report an error.
5882 @node Save Breakpoints
5883 @subsection How to save breakpoints to a file
5885 To save breakpoint definitions to a file use the @w{@code{save
5886 breakpoints}} command.
5889 @kindex save breakpoints
5890 @cindex save breakpoints to a file for future sessions
5891 @item save breakpoints [@var{filename}]
5892 This command saves all current breakpoint definitions together with
5893 their commands and ignore counts, into a file @file{@var{filename}}
5894 suitable for use in a later debugging session. This includes all
5895 types of breakpoints (breakpoints, watchpoints, catchpoints,
5896 tracepoints). To read the saved breakpoint definitions, use the
5897 @code{source} command (@pxref{Command Files}). Note that watchpoints
5898 with expressions involving local variables may fail to be recreated
5899 because it may not be possible to access the context where the
5900 watchpoint is valid anymore. Because the saved breakpoint definitions
5901 are simply a sequence of @value{GDBN} commands that recreate the
5902 breakpoints, you can edit the file in your favorite editing program,
5903 and remove the breakpoint definitions you're not interested in, or
5904 that can no longer be recreated.
5907 @node Static Probe Points
5908 @subsection Static Probe Points
5910 @cindex static probe point, SystemTap
5911 @cindex static probe point, DTrace
5912 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5913 for Statically Defined Tracing, and the probes are designed to have a tiny
5914 runtime code and data footprint, and no dynamic relocations.
5916 Currently, the following types of probes are supported on
5917 ELF-compatible systems:
5921 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5922 @acronym{SDT} probes@footnote{See
5923 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5924 for more information on how to add @code{SystemTap} @acronym{SDT}
5925 probes in your applications.}. @code{SystemTap} probes are usable
5926 from assembly, C and C@t{++} languages@footnote{See
5927 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5928 for a good reference on how the @acronym{SDT} probes are implemented.}.
5930 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5931 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5935 @cindex semaphores on static probe points
5936 Some @code{SystemTap} probes have an associated semaphore variable;
5937 for instance, this happens automatically if you defined your probe
5938 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5939 @value{GDBN} will automatically enable it when you specify a
5940 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5941 breakpoint at a probe's location by some other method (e.g.,
5942 @code{break file:line}), then @value{GDBN} will not automatically set
5943 the semaphore. @code{DTrace} probes do not support semaphores.
5945 You can examine the available static static probes using @code{info
5946 probes}, with optional arguments:
5950 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5951 If given, @var{type} is either @code{stap} for listing
5952 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5953 probes. If omitted all probes are listed regardless of their types.
5955 If given, @var{provider} is a regular expression used to match against provider
5956 names when selecting which probes to list. If omitted, probes by all
5957 probes from all providers are listed.
5959 If given, @var{name} is a regular expression to match against probe names
5960 when selecting which probes to list. If omitted, probe names are not
5961 considered when deciding whether to display them.
5963 If given, @var{objfile} is a regular expression used to select which
5964 object files (executable or shared libraries) to examine. If not
5965 given, all object files are considered.
5967 @item info probes all
5968 List the available static probes, from all types.
5971 @cindex enabling and disabling probes
5972 Some probe points can be enabled and/or disabled. The effect of
5973 enabling or disabling a probe depends on the type of probe being
5974 handled. Some @code{DTrace} probes can be enabled or
5975 disabled, but @code{SystemTap} probes cannot be disabled.
5977 You can enable (or disable) one or more probes using the following
5978 commands, with optional arguments:
5981 @kindex enable probes
5982 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5983 If given, @var{provider} is a regular expression used to match against
5984 provider names when selecting which probes to enable. If omitted,
5985 all probes from all providers are enabled.
5987 If given, @var{name} is a regular expression to match against probe
5988 names when selecting which probes to enable. If omitted, probe names
5989 are not considered when deciding whether to enable them.
5991 If given, @var{objfile} is a regular expression used to select which
5992 object files (executable or shared libraries) to examine. If not
5993 given, all object files are considered.
5995 @kindex disable probes
5996 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5997 See the @code{enable probes} command above for a description of the
5998 optional arguments accepted by this command.
6001 @vindex $_probe_arg@r{, convenience variable}
6002 A probe may specify up to twelve arguments. These are available at the
6003 point at which the probe is defined---that is, when the current PC is
6004 at the probe's location. The arguments are available using the
6005 convenience variables (@pxref{Convenience Vars})
6006 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6007 probes each probe argument is an integer of the appropriate size;
6008 types are not preserved. In @code{DTrace} probes types are preserved
6009 provided that they are recognized as such by @value{GDBN}; otherwise
6010 the value of the probe argument will be a long integer. The
6011 convenience variable @code{$_probe_argc} holds the number of arguments
6012 at the current probe point.
6014 These variables are always available, but attempts to access them at
6015 any location other than a probe point will cause @value{GDBN} to give
6019 @c @ifclear BARETARGET
6020 @node Error in Breakpoints
6021 @subsection ``Cannot insert breakpoints''
6023 If you request too many active hardware-assisted breakpoints and
6024 watchpoints, you will see this error message:
6026 @c FIXME: the precise wording of this message may change; the relevant
6027 @c source change is not committed yet (Sep 3, 1999).
6029 Stopped; cannot insert breakpoints.
6030 You may have requested too many hardware breakpoints and watchpoints.
6034 This message is printed when you attempt to resume the program, since
6035 only then @value{GDBN} knows exactly how many hardware breakpoints and
6036 watchpoints it needs to insert.
6038 When this message is printed, you need to disable or remove some of the
6039 hardware-assisted breakpoints and watchpoints, and then continue.
6041 @node Breakpoint-related Warnings
6042 @subsection ``Breakpoint address adjusted...''
6043 @cindex breakpoint address adjusted
6045 Some processor architectures place constraints on the addresses at
6046 which breakpoints may be placed. For architectures thus constrained,
6047 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6048 with the constraints dictated by the architecture.
6050 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6051 a VLIW architecture in which a number of RISC-like instructions may be
6052 bundled together for parallel execution. The FR-V architecture
6053 constrains the location of a breakpoint instruction within such a
6054 bundle to the instruction with the lowest address. @value{GDBN}
6055 honors this constraint by adjusting a breakpoint's address to the
6056 first in the bundle.
6058 It is not uncommon for optimized code to have bundles which contain
6059 instructions from different source statements, thus it may happen that
6060 a breakpoint's address will be adjusted from one source statement to
6061 another. Since this adjustment may significantly alter @value{GDBN}'s
6062 breakpoint related behavior from what the user expects, a warning is
6063 printed when the breakpoint is first set and also when the breakpoint
6066 A warning like the one below is printed when setting a breakpoint
6067 that's been subject to address adjustment:
6070 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6073 Such warnings are printed both for user settable and @value{GDBN}'s
6074 internal breakpoints. If you see one of these warnings, you should
6075 verify that a breakpoint set at the adjusted address will have the
6076 desired affect. If not, the breakpoint in question may be removed and
6077 other breakpoints may be set which will have the desired behavior.
6078 E.g., it may be sufficient to place the breakpoint at a later
6079 instruction. A conditional breakpoint may also be useful in some
6080 cases to prevent the breakpoint from triggering too often.
6082 @value{GDBN} will also issue a warning when stopping at one of these
6083 adjusted breakpoints:
6086 warning: Breakpoint 1 address previously adjusted from 0x00010414
6090 When this warning is encountered, it may be too late to take remedial
6091 action except in cases where the breakpoint is hit earlier or more
6092 frequently than expected.
6094 @node Continuing and Stepping
6095 @section Continuing and Stepping
6099 @cindex resuming execution
6100 @dfn{Continuing} means resuming program execution until your program
6101 completes normally. In contrast, @dfn{stepping} means executing just
6102 one more ``step'' of your program, where ``step'' may mean either one
6103 line of source code, or one machine instruction (depending on what
6104 particular command you use). Either when continuing or when stepping,
6105 your program may stop even sooner, due to a breakpoint or a signal. (If
6106 it stops due to a signal, you may want to use @code{handle}, or use
6107 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6108 or you may step into the signal's handler (@pxref{stepping and signal
6113 @kindex c @r{(@code{continue})}
6114 @kindex fg @r{(resume foreground execution)}
6115 @item continue @r{[}@var{ignore-count}@r{]}
6116 @itemx c @r{[}@var{ignore-count}@r{]}
6117 @itemx fg @r{[}@var{ignore-count}@r{]}
6118 Resume program execution, at the address where your program last stopped;
6119 any breakpoints set at that address are bypassed. The optional argument
6120 @var{ignore-count} allows you to specify a further number of times to
6121 ignore a breakpoint at this location; its effect is like that of
6122 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6124 The argument @var{ignore-count} is meaningful only when your program
6125 stopped due to a breakpoint. At other times, the argument to
6126 @code{continue} is ignored.
6128 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6129 debugged program is deemed to be the foreground program) are provided
6130 purely for convenience, and have exactly the same behavior as
6134 To resume execution at a different place, you can use @code{return}
6135 (@pxref{Returning, ,Returning from a Function}) to go back to the
6136 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6137 Different Address}) to go to an arbitrary location in your program.
6139 A typical technique for using stepping is to set a breakpoint
6140 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6141 beginning of the function or the section of your program where a problem
6142 is believed to lie, run your program until it stops at that breakpoint,
6143 and then step through the suspect area, examining the variables that are
6144 interesting, until you see the problem happen.
6148 @kindex s @r{(@code{step})}
6150 Continue running your program until control reaches a different source
6151 line, then stop it and return control to @value{GDBN}. This command is
6152 abbreviated @code{s}.
6155 @c "without debugging information" is imprecise; actually "without line
6156 @c numbers in the debugging information". (gcc -g1 has debugging info but
6157 @c not line numbers). But it seems complex to try to make that
6158 @c distinction here.
6159 @emph{Warning:} If you use the @code{step} command while control is
6160 within a function that was compiled without debugging information,
6161 execution proceeds until control reaches a function that does have
6162 debugging information. Likewise, it will not step into a function which
6163 is compiled without debugging information. To step through functions
6164 without debugging information, use the @code{stepi} command, described
6168 The @code{step} command only stops at the first instruction of a source
6169 line. This prevents the multiple stops that could otherwise occur in
6170 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6171 to stop if a function that has debugging information is called within
6172 the line. In other words, @code{step} @emph{steps inside} any functions
6173 called within the line.
6175 Also, the @code{step} command only enters a function if there is line
6176 number information for the function. Otherwise it acts like the
6177 @code{next} command. This avoids problems when using @code{cc -gl}
6178 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6179 was any debugging information about the routine.
6181 @item step @var{count}
6182 Continue running as in @code{step}, but do so @var{count} times. If a
6183 breakpoint is reached, or a signal not related to stepping occurs before
6184 @var{count} steps, stepping stops right away.
6187 @kindex n @r{(@code{next})}
6188 @item next @r{[}@var{count}@r{]}
6189 Continue to the next source line in the current (innermost) stack frame.
6190 This is similar to @code{step}, but function calls that appear within
6191 the line of code are executed without stopping. Execution stops when
6192 control reaches a different line of code at the original stack level
6193 that was executing when you gave the @code{next} command. This command
6194 is abbreviated @code{n}.
6196 An argument @var{count} is a repeat count, as for @code{step}.
6199 @c FIX ME!! Do we delete this, or is there a way it fits in with
6200 @c the following paragraph? --- Vctoria
6202 @c @code{next} within a function that lacks debugging information acts like
6203 @c @code{step}, but any function calls appearing within the code of the
6204 @c function are executed without stopping.
6206 The @code{next} command only stops at the first instruction of a
6207 source line. This prevents multiple stops that could otherwise occur in
6208 @code{switch} statements, @code{for} loops, etc.
6210 @kindex set step-mode
6212 @cindex functions without line info, and stepping
6213 @cindex stepping into functions with no line info
6214 @itemx set step-mode on
6215 The @code{set step-mode on} command causes the @code{step} command to
6216 stop at the first instruction of a function which contains no debug line
6217 information rather than stepping over it.
6219 This is useful in cases where you may be interested in inspecting the
6220 machine instructions of a function which has no symbolic info and do not
6221 want @value{GDBN} to automatically skip over this function.
6223 @item set step-mode off
6224 Causes the @code{step} command to step over any functions which contains no
6225 debug information. This is the default.
6227 @item show step-mode
6228 Show whether @value{GDBN} will stop in or step over functions without
6229 source line debug information.
6232 @kindex fin @r{(@code{finish})}
6234 Continue running until just after function in the selected stack frame
6235 returns. Print the returned value (if any). This command can be
6236 abbreviated as @code{fin}.
6238 Contrast this with the @code{return} command (@pxref{Returning,
6239 ,Returning from a Function}).
6241 @kindex set print finish
6242 @kindex show print finish
6243 @item set print finish @r{[}on|off@r{]}
6244 @itemx show print finish
6245 By default the @code{finish} command will show the value that is
6246 returned by the function. This can be disabled using @code{set print
6247 finish off}. When disabled, the value is still entered into the value
6248 history (@pxref{Value History}), but not displayed.
6251 @kindex u @r{(@code{until})}
6252 @cindex run until specified location
6255 Continue running until a source line past the current line, in the
6256 current stack frame, is reached. This command is used to avoid single
6257 stepping through a loop more than once. It is like the @code{next}
6258 command, except that when @code{until} encounters a jump, it
6259 automatically continues execution until the program counter is greater
6260 than the address of the jump.
6262 This means that when you reach the end of a loop after single stepping
6263 though it, @code{until} makes your program continue execution until it
6264 exits the loop. In contrast, a @code{next} command at the end of a loop
6265 simply steps back to the beginning of the loop, which forces you to step
6266 through the next iteration.
6268 @code{until} always stops your program if it attempts to exit the current
6271 @code{until} may produce somewhat counterintuitive results if the order
6272 of machine code does not match the order of the source lines. For
6273 example, in the following excerpt from a debugging session, the @code{f}
6274 (@code{frame}) command shows that execution is stopped at line
6275 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6279 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6281 (@value{GDBP}) until
6282 195 for ( ; argc > 0; NEXTARG) @{
6285 This happened because, for execution efficiency, the compiler had
6286 generated code for the loop closure test at the end, rather than the
6287 start, of the loop---even though the test in a C @code{for}-loop is
6288 written before the body of the loop. The @code{until} command appeared
6289 to step back to the beginning of the loop when it advanced to this
6290 expression; however, it has not really gone to an earlier
6291 statement---not in terms of the actual machine code.
6293 @code{until} with no argument works by means of single
6294 instruction stepping, and hence is slower than @code{until} with an
6297 @item until @var{location}
6298 @itemx u @var{location}
6299 Continue running your program until either the specified @var{location} is
6300 reached, or the current stack frame returns. The location is any of
6301 the forms described in @ref{Specify Location}.
6302 This form of the command uses temporary breakpoints, and
6303 hence is quicker than @code{until} without an argument. The specified
6304 location is actually reached only if it is in the current frame. This
6305 implies that @code{until} can be used to skip over recursive function
6306 invocations. For instance in the code below, if the current location is
6307 line @code{96}, issuing @code{until 99} will execute the program up to
6308 line @code{99} in the same invocation of factorial, i.e., after the inner
6309 invocations have returned.
6312 94 int factorial (int value)
6314 96 if (value > 1) @{
6315 97 value *= factorial (value - 1);
6322 @kindex advance @var{location}
6323 @item advance @var{location}
6324 Continue running the program up to the given @var{location}. An argument is
6325 required, which should be of one of the forms described in
6326 @ref{Specify Location}.
6327 Execution will also stop upon exit from the current stack
6328 frame. This command is similar to @code{until}, but @code{advance} will
6329 not skip over recursive function calls, and the target location doesn't
6330 have to be in the same frame as the current one.
6334 @kindex si @r{(@code{stepi})}
6336 @itemx stepi @var{arg}
6338 Execute one machine instruction, then stop and return to the debugger.
6340 It is often useful to do @samp{display/i $pc} when stepping by machine
6341 instructions. This makes @value{GDBN} automatically display the next
6342 instruction to be executed, each time your program stops. @xref{Auto
6343 Display,, Automatic Display}.
6345 An argument is a repeat count, as in @code{step}.
6349 @kindex ni @r{(@code{nexti})}
6351 @itemx nexti @var{arg}
6353 Execute one machine instruction, but if it is a function call,
6354 proceed until the function returns.
6356 An argument is a repeat count, as in @code{next}.
6360 @anchor{range stepping}
6361 @cindex range stepping
6362 @cindex target-assisted range stepping
6363 By default, and if available, @value{GDBN} makes use of
6364 target-assisted @dfn{range stepping}. In other words, whenever you
6365 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6366 tells the target to step the corresponding range of instruction
6367 addresses instead of issuing multiple single-steps. This speeds up
6368 line stepping, particularly for remote targets. Ideally, there should
6369 be no reason you would want to turn range stepping off. However, it's
6370 possible that a bug in the debug info, a bug in the remote stub (for
6371 remote targets), or even a bug in @value{GDBN} could make line
6372 stepping behave incorrectly when target-assisted range stepping is
6373 enabled. You can use the following command to turn off range stepping
6377 @kindex set range-stepping
6378 @kindex show range-stepping
6379 @item set range-stepping
6380 @itemx show range-stepping
6381 Control whether range stepping is enabled.
6383 If @code{on}, and the target supports it, @value{GDBN} tells the
6384 target to step a range of addresses itself, instead of issuing
6385 multiple single-steps. If @code{off}, @value{GDBN} always issues
6386 single-steps, even if range stepping is supported by the target. The
6387 default is @code{on}.
6391 @node Skipping Over Functions and Files
6392 @section Skipping Over Functions and Files
6393 @cindex skipping over functions and files
6395 The program you are debugging may contain some functions which are
6396 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6397 skip a function, all functions in a file or a particular function in
6398 a particular file when stepping.
6400 For example, consider the following C function:
6411 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6412 are not interested in stepping through @code{boring}. If you run @code{step}
6413 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6414 step over both @code{foo} and @code{boring}!
6416 One solution is to @code{step} into @code{boring} and use the @code{finish}
6417 command to immediately exit it. But this can become tedious if @code{boring}
6418 is called from many places.
6420 A more flexible solution is to execute @kbd{skip boring}. This instructs
6421 @value{GDBN} never to step into @code{boring}. Now when you execute
6422 @code{step} at line 103, you'll step over @code{boring} and directly into
6425 Functions may be skipped by providing either a function name, linespec
6426 (@pxref{Specify Location}), regular expression that matches the function's
6427 name, file name or a @code{glob}-style pattern that matches the file name.
6429 On Posix systems the form of the regular expression is
6430 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6431 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6432 expression is whatever is provided by the @code{regcomp} function of
6433 the underlying system.
6434 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6435 description of @code{glob}-style patterns.
6439 @item skip @r{[}@var{options}@r{]}
6440 The basic form of the @code{skip} command takes zero or more options
6441 that specify what to skip.
6442 The @var{options} argument is any useful combination of the following:
6445 @item -file @var{file}
6446 @itemx -fi @var{file}
6447 Functions in @var{file} will be skipped over when stepping.
6449 @item -gfile @var{file-glob-pattern}
6450 @itemx -gfi @var{file-glob-pattern}
6451 @cindex skipping over files via glob-style patterns
6452 Functions in files matching @var{file-glob-pattern} will be skipped
6456 (gdb) skip -gfi utils/*.c
6459 @item -function @var{linespec}
6460 @itemx -fu @var{linespec}
6461 Functions named by @var{linespec} or the function containing the line
6462 named by @var{linespec} will be skipped over when stepping.
6463 @xref{Specify Location}.
6465 @item -rfunction @var{regexp}
6466 @itemx -rfu @var{regexp}
6467 @cindex skipping over functions via regular expressions
6468 Functions whose name matches @var{regexp} will be skipped over when stepping.
6470 This form is useful for complex function names.
6471 For example, there is generally no need to step into C@t{++} @code{std::string}
6472 constructors or destructors. Plus with C@t{++} templates it can be hard to
6473 write out the full name of the function, and often it doesn't matter what
6474 the template arguments are. Specifying the function to be skipped as a
6475 regular expression makes this easier.
6478 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6481 If you want to skip every templated C@t{++} constructor and destructor
6482 in the @code{std} namespace you can do:
6485 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6489 If no options are specified, the function you're currently debugging
6492 @kindex skip function
6493 @item skip function @r{[}@var{linespec}@r{]}
6494 After running this command, the function named by @var{linespec} or the
6495 function containing the line named by @var{linespec} will be skipped over when
6496 stepping. @xref{Specify Location}.
6498 If you do not specify @var{linespec}, the function you're currently debugging
6501 (If you have a function called @code{file} that you want to skip, use
6502 @kbd{skip function file}.)
6505 @item skip file @r{[}@var{filename}@r{]}
6506 After running this command, any function whose source lives in @var{filename}
6507 will be skipped over when stepping.
6510 (gdb) skip file boring.c
6511 File boring.c will be skipped when stepping.
6514 If you do not specify @var{filename}, functions whose source lives in the file
6515 you're currently debugging will be skipped.
6518 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6519 These are the commands for managing your list of skips:
6523 @item info skip @r{[}@var{range}@r{]}
6524 Print details about the specified skip(s). If @var{range} is not specified,
6525 print a table with details about all functions and files marked for skipping.
6526 @code{info skip} prints the following information about each skip:
6530 A number identifying this skip.
6531 @item Enabled or Disabled
6532 Enabled skips are marked with @samp{y}.
6533 Disabled skips are marked with @samp{n}.
6535 If the file name is a @samp{glob} pattern this is @samp{y}.
6536 Otherwise it is @samp{n}.
6538 The name or @samp{glob} pattern of the file to be skipped.
6539 If no file is specified this is @samp{<none>}.
6541 If the function name is a @samp{regular expression} this is @samp{y}.
6542 Otherwise it is @samp{n}.
6544 The name or regular expression of the function to skip.
6545 If no function is specified this is @samp{<none>}.
6549 @item skip delete @r{[}@var{range}@r{]}
6550 Delete the specified skip(s). If @var{range} is not specified, delete all
6554 @item skip enable @r{[}@var{range}@r{]}
6555 Enable the specified skip(s). If @var{range} is not specified, enable all
6558 @kindex skip disable
6559 @item skip disable @r{[}@var{range}@r{]}
6560 Disable the specified skip(s). If @var{range} is not specified, disable all
6563 @kindex set debug skip
6564 @item set debug skip @r{[}on|off@r{]}
6565 Set whether to print the debug output about skipping files and functions.
6567 @kindex show debug skip
6568 @item show debug skip
6569 Show whether the debug output about skipping files and functions is printed.
6577 A signal is an asynchronous event that can happen in a program. The
6578 operating system defines the possible kinds of signals, and gives each
6579 kind a name and a number. For example, in Unix @code{SIGINT} is the
6580 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6581 @code{SIGSEGV} is the signal a program gets from referencing a place in
6582 memory far away from all the areas in use; @code{SIGALRM} occurs when
6583 the alarm clock timer goes off (which happens only if your program has
6584 requested an alarm).
6586 @cindex fatal signals
6587 Some signals, including @code{SIGALRM}, are a normal part of the
6588 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6589 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6590 program has not specified in advance some other way to handle the signal.
6591 @code{SIGINT} does not indicate an error in your program, but it is normally
6592 fatal so it can carry out the purpose of the interrupt: to kill the program.
6594 @value{GDBN} has the ability to detect any occurrence of a signal in your
6595 program. You can tell @value{GDBN} in advance what to do for each kind of
6598 @cindex handling signals
6599 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6600 @code{SIGALRM} be silently passed to your program
6601 (so as not to interfere with their role in the program's functioning)
6602 but to stop your program immediately whenever an error signal happens.
6603 You can change these settings with the @code{handle} command.
6606 @kindex info signals
6610 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6611 handle each one. You can use this to see the signal numbers of all
6612 the defined types of signals.
6614 @item info signals @var{sig}
6615 Similar, but print information only about the specified signal number.
6617 @code{info handle} is an alias for @code{info signals}.
6619 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6620 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6621 for details about this command.
6624 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6625 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6626 can be the number of a signal or its name (with or without the
6627 @samp{SIG} at the beginning); a list of signal numbers of the form
6628 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6629 known signals. Optional arguments @var{keywords}, described below,
6630 say what change to make.
6634 The keywords allowed by the @code{handle} command can be abbreviated.
6635 Their full names are:
6639 @value{GDBN} should not stop your program when this signal happens. It may
6640 still print a message telling you that the signal has come in.
6643 @value{GDBN} should stop your program when this signal happens. This implies
6644 the @code{print} keyword as well.
6647 @value{GDBN} should print a message when this signal happens.
6650 @value{GDBN} should not mention the occurrence of the signal at all. This
6651 implies the @code{nostop} keyword as well.
6655 @value{GDBN} should allow your program to see this signal; your program
6656 can handle the signal, or else it may terminate if the signal is fatal
6657 and not handled. @code{pass} and @code{noignore} are synonyms.
6661 @value{GDBN} should not allow your program to see this signal.
6662 @code{nopass} and @code{ignore} are synonyms.
6666 When a signal stops your program, the signal is not visible to the
6668 continue. Your program sees the signal then, if @code{pass} is in
6669 effect for the signal in question @emph{at that time}. In other words,
6670 after @value{GDBN} reports a signal, you can use the @code{handle}
6671 command with @code{pass} or @code{nopass} to control whether your
6672 program sees that signal when you continue.
6674 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6675 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6676 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6679 You can also use the @code{signal} command to prevent your program from
6680 seeing a signal, or cause it to see a signal it normally would not see,
6681 or to give it any signal at any time. For example, if your program stopped
6682 due to some sort of memory reference error, you might store correct
6683 values into the erroneous variables and continue, hoping to see more
6684 execution; but your program would probably terminate immediately as
6685 a result of the fatal signal once it saw the signal. To prevent this,
6686 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6689 @cindex stepping and signal handlers
6690 @anchor{stepping and signal handlers}
6692 @value{GDBN} optimizes for stepping the mainline code. If a signal
6693 that has @code{handle nostop} and @code{handle pass} set arrives while
6694 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6695 in progress, @value{GDBN} lets the signal handler run and then resumes
6696 stepping the mainline code once the signal handler returns. In other
6697 words, @value{GDBN} steps over the signal handler. This prevents
6698 signals that you've specified as not interesting (with @code{handle
6699 nostop}) from changing the focus of debugging unexpectedly. Note that
6700 the signal handler itself may still hit a breakpoint, stop for another
6701 signal that has @code{handle stop} in effect, or for any other event
6702 that normally results in stopping the stepping command sooner. Also
6703 note that @value{GDBN} still informs you that the program received a
6704 signal if @code{handle print} is set.
6706 @anchor{stepping into signal handlers}
6708 If you set @code{handle pass} for a signal, and your program sets up a
6709 handler for it, then issuing a stepping command, such as @code{step}
6710 or @code{stepi}, when your program is stopped due to the signal will
6711 step @emph{into} the signal handler (if the target supports that).
6713 Likewise, if you use the @code{queue-signal} command to queue a signal
6714 to be delivered to the current thread when execution of the thread
6715 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6716 stepping command will step into the signal handler.
6718 Here's an example, using @code{stepi} to step to the first instruction
6719 of @code{SIGUSR1}'s handler:
6722 (@value{GDBP}) handle SIGUSR1
6723 Signal Stop Print Pass to program Description
6724 SIGUSR1 Yes Yes Yes User defined signal 1
6728 Program received signal SIGUSR1, User defined signal 1.
6729 main () sigusr1.c:28
6732 sigusr1_handler () at sigusr1.c:9
6736 The same, but using @code{queue-signal} instead of waiting for the
6737 program to receive the signal first:
6742 (@value{GDBP}) queue-signal SIGUSR1
6744 sigusr1_handler () at sigusr1.c:9
6749 @cindex extra signal information
6750 @anchor{extra signal information}
6752 On some targets, @value{GDBN} can inspect extra signal information
6753 associated with the intercepted signal, before it is actually
6754 delivered to the program being debugged. This information is exported
6755 by the convenience variable @code{$_siginfo}, and consists of data
6756 that is passed by the kernel to the signal handler at the time of the
6757 receipt of a signal. The data type of the information itself is
6758 target dependent. You can see the data type using the @code{ptype
6759 $_siginfo} command. On Unix systems, it typically corresponds to the
6760 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6763 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6764 referenced address that raised a segmentation fault.
6768 (@value{GDBP}) continue
6769 Program received signal SIGSEGV, Segmentation fault.
6770 0x0000000000400766 in main ()
6772 (@value{GDBP}) ptype $_siginfo
6779 struct @{...@} _kill;
6780 struct @{...@} _timer;
6782 struct @{...@} _sigchld;
6783 struct @{...@} _sigfault;
6784 struct @{...@} _sigpoll;
6787 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6791 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6792 $1 = (void *) 0x7ffff7ff7000
6796 Depending on target support, @code{$_siginfo} may also be writable.
6798 @cindex Intel MPX boundary violations
6799 @cindex boundary violations, Intel MPX
6800 On some targets, a @code{SIGSEGV} can be caused by a boundary
6801 violation, i.e., accessing an address outside of the allowed range.
6802 In those cases @value{GDBN} may displays additional information,
6803 depending on how @value{GDBN} has been told to handle the signal.
6804 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6805 kind: "Upper" or "Lower", the memory address accessed and the
6806 bounds, while with @code{handle nostop SIGSEGV} no additional
6807 information is displayed.
6809 The usual output of a segfault is:
6811 Program received signal SIGSEGV, Segmentation fault
6812 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6813 68 value = *(p + len);
6816 While a bound violation is presented as:
6818 Program received signal SIGSEGV, Segmentation fault
6819 Upper bound violation while accessing address 0x7fffffffc3b3
6820 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6821 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6822 68 value = *(p + len);
6826 @section Stopping and Starting Multi-thread Programs
6828 @cindex stopped threads
6829 @cindex threads, stopped
6831 @cindex continuing threads
6832 @cindex threads, continuing
6834 @value{GDBN} supports debugging programs with multiple threads
6835 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6836 are two modes of controlling execution of your program within the
6837 debugger. In the default mode, referred to as @dfn{all-stop mode},
6838 when any thread in your program stops (for example, at a breakpoint
6839 or while being stepped), all other threads in the program are also stopped by
6840 @value{GDBN}. On some targets, @value{GDBN} also supports
6841 @dfn{non-stop mode}, in which other threads can continue to run freely while
6842 you examine the stopped thread in the debugger.
6845 * All-Stop Mode:: All threads stop when GDB takes control
6846 * Non-Stop Mode:: Other threads continue to execute
6847 * Background Execution:: Running your program asynchronously
6848 * Thread-Specific Breakpoints:: Controlling breakpoints
6849 * Interrupted System Calls:: GDB may interfere with system calls
6850 * Observer Mode:: GDB does not alter program behavior
6854 @subsection All-Stop Mode
6856 @cindex all-stop mode
6858 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6859 @emph{all} threads of execution stop, not just the current thread. This
6860 allows you to examine the overall state of the program, including
6861 switching between threads, without worrying that things may change
6864 Conversely, whenever you restart the program, @emph{all} threads start
6865 executing. @emph{This is true even when single-stepping} with commands
6866 like @code{step} or @code{next}.
6868 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6869 Since thread scheduling is up to your debugging target's operating
6870 system (not controlled by @value{GDBN}), other threads may
6871 execute more than one statement while the current thread completes a
6872 single step. Moreover, in general other threads stop in the middle of a
6873 statement, rather than at a clean statement boundary, when the program
6876 You might even find your program stopped in another thread after
6877 continuing or even single-stepping. This happens whenever some other
6878 thread runs into a breakpoint, a signal, or an exception before the
6879 first thread completes whatever you requested.
6881 @cindex automatic thread selection
6882 @cindex switching threads automatically
6883 @cindex threads, automatic switching
6884 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6885 signal, it automatically selects the thread where that breakpoint or
6886 signal happened. @value{GDBN} alerts you to the context switch with a
6887 message such as @samp{[Switching to Thread @var{n}]} to identify the
6890 On some OSes, you can modify @value{GDBN}'s default behavior by
6891 locking the OS scheduler to allow only a single thread to run.
6894 @item set scheduler-locking @var{mode}
6895 @cindex scheduler locking mode
6896 @cindex lock scheduler
6897 Set the scheduler locking mode. It applies to normal execution,
6898 record mode, and replay mode. If it is @code{off}, then there is no
6899 locking and any thread may run at any time. If @code{on}, then only
6900 the current thread may run when the inferior is resumed. The
6901 @code{step} mode optimizes for single-stepping; it prevents other
6902 threads from preempting the current thread while you are stepping, so
6903 that the focus of debugging does not change unexpectedly. Other
6904 threads never get a chance to run when you step, and they are
6905 completely free to run when you use commands like @samp{continue},
6906 @samp{until}, or @samp{finish}. However, unless another thread hits a
6907 breakpoint during its timeslice, @value{GDBN} does not change the
6908 current thread away from the thread that you are debugging. The
6909 @code{replay} mode behaves like @code{off} in record mode and like
6910 @code{on} in replay mode.
6912 @item show scheduler-locking
6913 Display the current scheduler locking mode.
6916 @cindex resume threads of multiple processes simultaneously
6917 By default, when you issue one of the execution commands such as
6918 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6919 threads of the current inferior to run. For example, if @value{GDBN}
6920 is attached to two inferiors, each with two threads, the
6921 @code{continue} command resumes only the two threads of the current
6922 inferior. This is useful, for example, when you debug a program that
6923 forks and you want to hold the parent stopped (so that, for instance,
6924 it doesn't run to exit), while you debug the child. In other
6925 situations, you may not be interested in inspecting the current state
6926 of any of the processes @value{GDBN} is attached to, and you may want
6927 to resume them all until some breakpoint is hit. In the latter case,
6928 you can instruct @value{GDBN} to allow all threads of all the
6929 inferiors to run with the @w{@code{set schedule-multiple}} command.
6932 @kindex set schedule-multiple
6933 @item set schedule-multiple
6934 Set the mode for allowing threads of multiple processes to be resumed
6935 when an execution command is issued. When @code{on}, all threads of
6936 all processes are allowed to run. When @code{off}, only the threads
6937 of the current process are resumed. The default is @code{off}. The
6938 @code{scheduler-locking} mode takes precedence when set to @code{on},
6939 or while you are stepping and set to @code{step}.
6941 @item show schedule-multiple
6942 Display the current mode for resuming the execution of threads of
6947 @subsection Non-Stop Mode
6949 @cindex non-stop mode
6951 @c This section is really only a place-holder, and needs to be expanded
6952 @c with more details.
6954 For some multi-threaded targets, @value{GDBN} supports an optional
6955 mode of operation in which you can examine stopped program threads in
6956 the debugger while other threads continue to execute freely. This
6957 minimizes intrusion when debugging live systems, such as programs
6958 where some threads have real-time constraints or must continue to
6959 respond to external events. This is referred to as @dfn{non-stop} mode.
6961 In non-stop mode, when a thread stops to report a debugging event,
6962 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6963 threads as well, in contrast to the all-stop mode behavior. Additionally,
6964 execution commands such as @code{continue} and @code{step} apply by default
6965 only to the current thread in non-stop mode, rather than all threads as
6966 in all-stop mode. This allows you to control threads explicitly in
6967 ways that are not possible in all-stop mode --- for example, stepping
6968 one thread while allowing others to run freely, stepping
6969 one thread while holding all others stopped, or stepping several threads
6970 independently and simultaneously.
6972 To enter non-stop mode, use this sequence of commands before you run
6973 or attach to your program:
6976 # If using the CLI, pagination breaks non-stop.
6979 # Finally, turn it on!
6983 You can use these commands to manipulate the non-stop mode setting:
6986 @kindex set non-stop
6987 @item set non-stop on
6988 Enable selection of non-stop mode.
6989 @item set non-stop off
6990 Disable selection of non-stop mode.
6991 @kindex show non-stop
6993 Show the current non-stop enablement setting.
6996 Note these commands only reflect whether non-stop mode is enabled,
6997 not whether the currently-executing program is being run in non-stop mode.
6998 In particular, the @code{set non-stop} preference is only consulted when
6999 @value{GDBN} starts or connects to the target program, and it is generally
7000 not possible to switch modes once debugging has started. Furthermore,
7001 since not all targets support non-stop mode, even when you have enabled
7002 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7005 In non-stop mode, all execution commands apply only to the current thread
7006 by default. That is, @code{continue} only continues one thread.
7007 To continue all threads, issue @code{continue -a} or @code{c -a}.
7009 You can use @value{GDBN}'s background execution commands
7010 (@pxref{Background Execution}) to run some threads in the background
7011 while you continue to examine or step others from @value{GDBN}.
7012 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7013 always executed asynchronously in non-stop mode.
7015 Suspending execution is done with the @code{interrupt} command when
7016 running in the background, or @kbd{Ctrl-c} during foreground execution.
7017 In all-stop mode, this stops the whole process;
7018 but in non-stop mode the interrupt applies only to the current thread.
7019 To stop the whole program, use @code{interrupt -a}.
7021 Other execution commands do not currently support the @code{-a} option.
7023 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7024 that thread current, as it does in all-stop mode. This is because the
7025 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7026 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7027 changed to a different thread just as you entered a command to operate on the
7028 previously current thread.
7030 @node Background Execution
7031 @subsection Background Execution
7033 @cindex foreground execution
7034 @cindex background execution
7035 @cindex asynchronous execution
7036 @cindex execution, foreground, background and asynchronous
7038 @value{GDBN}'s execution commands have two variants: the normal
7039 foreground (synchronous) behavior, and a background
7040 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7041 the program to report that some thread has stopped before prompting for
7042 another command. In background execution, @value{GDBN} immediately gives
7043 a command prompt so that you can issue other commands while your program runs.
7045 If the target doesn't support async mode, @value{GDBN} issues an error
7046 message if you attempt to use the background execution commands.
7048 @cindex @code{&}, background execution of commands
7049 To specify background execution, add a @code{&} to the command. For example,
7050 the background form of the @code{continue} command is @code{continue&}, or
7051 just @code{c&}. The execution commands that accept background execution
7057 @xref{Starting, , Starting your Program}.
7061 @xref{Attach, , Debugging an Already-running Process}.
7065 @xref{Continuing and Stepping, step}.
7069 @xref{Continuing and Stepping, stepi}.
7073 @xref{Continuing and Stepping, next}.
7077 @xref{Continuing and Stepping, nexti}.
7081 @xref{Continuing and Stepping, continue}.
7085 @xref{Continuing and Stepping, finish}.
7089 @xref{Continuing and Stepping, until}.
7093 Background execution is especially useful in conjunction with non-stop
7094 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7095 However, you can also use these commands in the normal all-stop mode with
7096 the restriction that you cannot issue another execution command until the
7097 previous one finishes. Examples of commands that are valid in all-stop
7098 mode while the program is running include @code{help} and @code{info break}.
7100 You can interrupt your program while it is running in the background by
7101 using the @code{interrupt} command.
7108 Suspend execution of the running program. In all-stop mode,
7109 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7110 only the current thread. To stop the whole program in non-stop mode,
7111 use @code{interrupt -a}.
7114 @node Thread-Specific Breakpoints
7115 @subsection Thread-Specific Breakpoints
7117 When your program has multiple threads (@pxref{Threads,, Debugging
7118 Programs with Multiple Threads}), you can choose whether to set
7119 breakpoints on all threads, or on a particular thread.
7122 @cindex breakpoints and threads
7123 @cindex thread breakpoints
7124 @kindex break @dots{} thread @var{thread-id}
7125 @item break @var{location} thread @var{thread-id}
7126 @itemx break @var{location} thread @var{thread-id} if @dots{}
7127 @var{location} specifies source lines; there are several ways of
7128 writing them (@pxref{Specify Location}), but the effect is always to
7129 specify some source line.
7131 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7132 to specify that you only want @value{GDBN} to stop the program when a
7133 particular thread reaches this breakpoint. The @var{thread-id} specifier
7134 is one of the thread identifiers assigned by @value{GDBN}, shown
7135 in the first column of the @samp{info threads} display.
7137 If you do not specify @samp{thread @var{thread-id}} when you set a
7138 breakpoint, the breakpoint applies to @emph{all} threads of your
7141 You can use the @code{thread} qualifier on conditional breakpoints as
7142 well; in this case, place @samp{thread @var{thread-id}} before or
7143 after the breakpoint condition, like this:
7146 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7151 Thread-specific breakpoints are automatically deleted when
7152 @value{GDBN} detects the corresponding thread is no longer in the
7153 thread list. For example:
7157 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7160 There are several ways for a thread to disappear, such as a regular
7161 thread exit, but also when you detach from the process with the
7162 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7163 Process}), or if @value{GDBN} loses the remote connection
7164 (@pxref{Remote Debugging}), etc. Note that with some targets,
7165 @value{GDBN} is only able to detect a thread has exited when the user
7166 explictly asks for the thread list with the @code{info threads}
7169 @node Interrupted System Calls
7170 @subsection Interrupted System Calls
7172 @cindex thread breakpoints and system calls
7173 @cindex system calls and thread breakpoints
7174 @cindex premature return from system calls
7175 There is an unfortunate side effect when using @value{GDBN} to debug
7176 multi-threaded programs. If one thread stops for a
7177 breakpoint, or for some other reason, and another thread is blocked in a
7178 system call, then the system call may return prematurely. This is a
7179 consequence of the interaction between multiple threads and the signals
7180 that @value{GDBN} uses to implement breakpoints and other events that
7183 To handle this problem, your program should check the return value of
7184 each system call and react appropriately. This is good programming
7187 For example, do not write code like this:
7193 The call to @code{sleep} will return early if a different thread stops
7194 at a breakpoint or for some other reason.
7196 Instead, write this:
7201 unslept = sleep (unslept);
7204 A system call is allowed to return early, so the system is still
7205 conforming to its specification. But @value{GDBN} does cause your
7206 multi-threaded program to behave differently than it would without
7209 Also, @value{GDBN} uses internal breakpoints in the thread library to
7210 monitor certain events such as thread creation and thread destruction.
7211 When such an event happens, a system call in another thread may return
7212 prematurely, even though your program does not appear to stop.
7215 @subsection Observer Mode
7217 If you want to build on non-stop mode and observe program behavior
7218 without any chance of disruption by @value{GDBN}, you can set
7219 variables to disable all of the debugger's attempts to modify state,
7220 whether by writing memory, inserting breakpoints, etc. These operate
7221 at a low level, intercepting operations from all commands.
7223 When all of these are set to @code{off}, then @value{GDBN} is said to
7224 be @dfn{observer mode}. As a convenience, the variable
7225 @code{observer} can be set to disable these, plus enable non-stop
7228 Note that @value{GDBN} will not prevent you from making nonsensical
7229 combinations of these settings. For instance, if you have enabled
7230 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7231 then breakpoints that work by writing trap instructions into the code
7232 stream will still not be able to be placed.
7237 @item set observer on
7238 @itemx set observer off
7239 When set to @code{on}, this disables all the permission variables
7240 below (except for @code{insert-fast-tracepoints}), plus enables
7241 non-stop debugging. Setting this to @code{off} switches back to
7242 normal debugging, though remaining in non-stop mode.
7245 Show whether observer mode is on or off.
7247 @kindex may-write-registers
7248 @item set may-write-registers on
7249 @itemx set may-write-registers off
7250 This controls whether @value{GDBN} will attempt to alter the values of
7251 registers, such as with assignment expressions in @code{print}, or the
7252 @code{jump} command. It defaults to @code{on}.
7254 @item show may-write-registers
7255 Show the current permission to write registers.
7257 @kindex may-write-memory
7258 @item set may-write-memory on
7259 @itemx set may-write-memory off
7260 This controls whether @value{GDBN} will attempt to alter the contents
7261 of memory, such as with assignment expressions in @code{print}. It
7262 defaults to @code{on}.
7264 @item show may-write-memory
7265 Show the current permission to write memory.
7267 @kindex may-insert-breakpoints
7268 @item set may-insert-breakpoints on
7269 @itemx set may-insert-breakpoints off
7270 This controls whether @value{GDBN} will attempt to insert breakpoints.
7271 This affects all breakpoints, including internal breakpoints defined
7272 by @value{GDBN}. It defaults to @code{on}.
7274 @item show may-insert-breakpoints
7275 Show the current permission to insert breakpoints.
7277 @kindex may-insert-tracepoints
7278 @item set may-insert-tracepoints on
7279 @itemx set may-insert-tracepoints off
7280 This controls whether @value{GDBN} will attempt to insert (regular)
7281 tracepoints at the beginning of a tracing experiment. It affects only
7282 non-fast tracepoints, fast tracepoints being under the control of
7283 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7285 @item show may-insert-tracepoints
7286 Show the current permission to insert tracepoints.
7288 @kindex may-insert-fast-tracepoints
7289 @item set may-insert-fast-tracepoints on
7290 @itemx set may-insert-fast-tracepoints off
7291 This controls whether @value{GDBN} will attempt to insert fast
7292 tracepoints at the beginning of a tracing experiment. It affects only
7293 fast tracepoints, regular (non-fast) tracepoints being under the
7294 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7296 @item show may-insert-fast-tracepoints
7297 Show the current permission to insert fast tracepoints.
7299 @kindex may-interrupt
7300 @item set may-interrupt on
7301 @itemx set may-interrupt off
7302 This controls whether @value{GDBN} will attempt to interrupt or stop
7303 program execution. When this variable is @code{off}, the
7304 @code{interrupt} command will have no effect, nor will
7305 @kbd{Ctrl-c}. It defaults to @code{on}.
7307 @item show may-interrupt
7308 Show the current permission to interrupt or stop the program.
7312 @node Reverse Execution
7313 @chapter Running programs backward
7314 @cindex reverse execution
7315 @cindex running programs backward
7317 When you are debugging a program, it is not unusual to realize that
7318 you have gone too far, and some event of interest has already happened.
7319 If the target environment supports it, @value{GDBN} can allow you to
7320 ``rewind'' the program by running it backward.
7322 A target environment that supports reverse execution should be able
7323 to ``undo'' the changes in machine state that have taken place as the
7324 program was executing normally. Variables, registers etc.@: should
7325 revert to their previous values. Obviously this requires a great
7326 deal of sophistication on the part of the target environment; not
7327 all target environments can support reverse execution.
7329 When a program is executed in reverse, the instructions that
7330 have most recently been executed are ``un-executed'', in reverse
7331 order. The program counter runs backward, following the previous
7332 thread of execution in reverse. As each instruction is ``un-executed'',
7333 the values of memory and/or registers that were changed by that
7334 instruction are reverted to their previous states. After executing
7335 a piece of source code in reverse, all side effects of that code
7336 should be ``undone'', and all variables should be returned to their
7337 prior values@footnote{
7338 Note that some side effects are easier to undo than others. For instance,
7339 memory and registers are relatively easy, but device I/O is hard. Some
7340 targets may be able undo things like device I/O, and some may not.
7342 The contract between @value{GDBN} and the reverse executing target
7343 requires only that the target do something reasonable when
7344 @value{GDBN} tells it to execute backwards, and then report the
7345 results back to @value{GDBN}. Whatever the target reports back to
7346 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7347 assumes that the memory and registers that the target reports are in a
7348 consistent state, but @value{GDBN} accepts whatever it is given.
7351 On some platforms, @value{GDBN} has built-in support for reverse
7352 execution, activated with the @code{record} or @code{record btrace}
7353 commands. @xref{Process Record and Replay}. Some remote targets,
7354 typically full system emulators, support reverse execution directly
7355 without requiring any special command.
7357 If you are debugging in a target environment that supports
7358 reverse execution, @value{GDBN} provides the following commands.
7361 @kindex reverse-continue
7362 @kindex rc @r{(@code{reverse-continue})}
7363 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7364 @itemx rc @r{[}@var{ignore-count}@r{]}
7365 Beginning at the point where your program last stopped, start executing
7366 in reverse. Reverse execution will stop for breakpoints and synchronous
7367 exceptions (signals), just like normal execution. Behavior of
7368 asynchronous signals depends on the target environment.
7370 @kindex reverse-step
7371 @kindex rs @r{(@code{step})}
7372 @item reverse-step @r{[}@var{count}@r{]}
7373 Run the program backward until control reaches the start of a
7374 different source line; then stop it, and return control to @value{GDBN}.
7376 Like the @code{step} command, @code{reverse-step} will only stop
7377 at the beginning of a source line. It ``un-executes'' the previously
7378 executed source line. If the previous source line included calls to
7379 debuggable functions, @code{reverse-step} will step (backward) into
7380 the called function, stopping at the beginning of the @emph{last}
7381 statement in the called function (typically a return statement).
7383 Also, as with the @code{step} command, if non-debuggable functions are
7384 called, @code{reverse-step} will run thru them backward without stopping.
7386 @kindex reverse-stepi
7387 @kindex rsi @r{(@code{reverse-stepi})}
7388 @item reverse-stepi @r{[}@var{count}@r{]}
7389 Reverse-execute one machine instruction. Note that the instruction
7390 to be reverse-executed is @emph{not} the one pointed to by the program
7391 counter, but the instruction executed prior to that one. For instance,
7392 if the last instruction was a jump, @code{reverse-stepi} will take you
7393 back from the destination of the jump to the jump instruction itself.
7395 @kindex reverse-next
7396 @kindex rn @r{(@code{reverse-next})}
7397 @item reverse-next @r{[}@var{count}@r{]}
7398 Run backward to the beginning of the previous line executed in
7399 the current (innermost) stack frame. If the line contains function
7400 calls, they will be ``un-executed'' without stopping. Starting from
7401 the first line of a function, @code{reverse-next} will take you back
7402 to the caller of that function, @emph{before} the function was called,
7403 just as the normal @code{next} command would take you from the last
7404 line of a function back to its return to its caller
7405 @footnote{Unless the code is too heavily optimized.}.
7407 @kindex reverse-nexti
7408 @kindex rni @r{(@code{reverse-nexti})}
7409 @item reverse-nexti @r{[}@var{count}@r{]}
7410 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7411 in reverse, except that called functions are ``un-executed'' atomically.
7412 That is, if the previously executed instruction was a return from
7413 another function, @code{reverse-nexti} will continue to execute
7414 in reverse until the call to that function (from the current stack
7417 @kindex reverse-finish
7418 @item reverse-finish
7419 Just as the @code{finish} command takes you to the point where the
7420 current function returns, @code{reverse-finish} takes you to the point
7421 where it was called. Instead of ending up at the end of the current
7422 function invocation, you end up at the beginning.
7424 @kindex set exec-direction
7425 @item set exec-direction
7426 Set the direction of target execution.
7427 @item set exec-direction reverse
7428 @cindex execute forward or backward in time
7429 @value{GDBN} will perform all execution commands in reverse, until the
7430 exec-direction mode is changed to ``forward''. Affected commands include
7431 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7432 command cannot be used in reverse mode.
7433 @item set exec-direction forward
7434 @value{GDBN} will perform all execution commands in the normal fashion.
7435 This is the default.
7439 @node Process Record and Replay
7440 @chapter Recording Inferior's Execution and Replaying It
7441 @cindex process record and replay
7442 @cindex recording inferior's execution and replaying it
7444 On some platforms, @value{GDBN} provides a special @dfn{process record
7445 and replay} target that can record a log of the process execution, and
7446 replay it later with both forward and reverse execution commands.
7449 When this target is in use, if the execution log includes the record
7450 for the next instruction, @value{GDBN} will debug in @dfn{replay
7451 mode}. In the replay mode, the inferior does not really execute code
7452 instructions. Instead, all the events that normally happen during
7453 code execution are taken from the execution log. While code is not
7454 really executed in replay mode, the values of registers (including the
7455 program counter register) and the memory of the inferior are still
7456 changed as they normally would. Their contents are taken from the
7460 If the record for the next instruction is not in the execution log,
7461 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7462 inferior executes normally, and @value{GDBN} records the execution log
7465 The process record and replay target supports reverse execution
7466 (@pxref{Reverse Execution}), even if the platform on which the
7467 inferior runs does not. However, the reverse execution is limited in
7468 this case by the range of the instructions recorded in the execution
7469 log. In other words, reverse execution on platforms that don't
7470 support it directly can only be done in the replay mode.
7472 When debugging in the reverse direction, @value{GDBN} will work in
7473 replay mode as long as the execution log includes the record for the
7474 previous instruction; otherwise, it will work in record mode, if the
7475 platform supports reverse execution, or stop if not.
7477 Currently, process record and replay is supported on ARM, Aarch64,
7478 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7479 GNU/Linux. Process record and replay can be used both when native
7480 debugging, and when remote debugging via @code{gdbserver}.
7482 For architecture environments that support process record and replay,
7483 @value{GDBN} provides the following commands:
7486 @kindex target record
7487 @kindex target record-full
7488 @kindex target record-btrace
7491 @kindex record btrace
7492 @kindex record btrace bts
7493 @kindex record btrace pt
7499 @kindex rec btrace bts
7500 @kindex rec btrace pt
7503 @item record @var{method}
7504 This command starts the process record and replay target. The
7505 recording method can be specified as parameter. Without a parameter
7506 the command uses the @code{full} recording method. The following
7507 recording methods are available:
7511 Full record/replay recording using @value{GDBN}'s software record and
7512 replay implementation. This method allows replaying and reverse
7515 @item btrace @var{format}
7516 Hardware-supported instruction recording, supported on Intel
7517 processors. This method does not record data. Further, the data is
7518 collected in a ring buffer so old data will be overwritten when the
7519 buffer is full. It allows limited reverse execution. Variables and
7520 registers are not available during reverse execution. In remote
7521 debugging, recording continues on disconnect. Recorded data can be
7522 inspected after reconnecting. The recording may be stopped using
7525 The recording format can be specified as parameter. Without a parameter
7526 the command chooses the recording format. The following recording
7527 formats are available:
7531 @cindex branch trace store
7532 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7533 this format, the processor stores a from/to record for each executed
7534 branch in the btrace ring buffer.
7537 @cindex Intel Processor Trace
7538 Use the @dfn{Intel Processor Trace} recording format. In this
7539 format, the processor stores the execution trace in a compressed form
7540 that is afterwards decoded by @value{GDBN}.
7542 The trace can be recorded with very low overhead. The compressed
7543 trace format also allows small trace buffers to already contain a big
7544 number of instructions compared to @acronym{BTS}.
7546 Decoding the recorded execution trace, on the other hand, is more
7547 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7548 increased number of instructions to process. You should increase the
7549 buffer-size with care.
7552 Not all recording formats may be available on all processors.
7555 The process record and replay target can only debug a process that is
7556 already running. Therefore, you need first to start the process with
7557 the @kbd{run} or @kbd{start} commands, and then start the recording
7558 with the @kbd{record @var{method}} command.
7560 @cindex displaced stepping, and process record and replay
7561 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7562 will be automatically disabled when process record and replay target
7563 is started. That's because the process record and replay target
7564 doesn't support displaced stepping.
7566 @cindex non-stop mode, and process record and replay
7567 @cindex asynchronous execution, and process record and replay
7568 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7569 the asynchronous execution mode (@pxref{Background Execution}), not
7570 all recording methods are available. The @code{full} recording method
7571 does not support these two modes.
7576 Stop the process record and replay target. When process record and
7577 replay target stops, the entire execution log will be deleted and the
7578 inferior will either be terminated, or will remain in its final state.
7580 When you stop the process record and replay target in record mode (at
7581 the end of the execution log), the inferior will be stopped at the
7582 next instruction that would have been recorded. In other words, if
7583 you record for a while and then stop recording, the inferior process
7584 will be left in the same state as if the recording never happened.
7586 On the other hand, if the process record and replay target is stopped
7587 while in replay mode (that is, not at the end of the execution log,
7588 but at some earlier point), the inferior process will become ``live''
7589 at that earlier state, and it will then be possible to continue the
7590 usual ``live'' debugging of the process from that state.
7592 When the inferior process exits, or @value{GDBN} detaches from it,
7593 process record and replay target will automatically stop itself.
7597 Go to a specific location in the execution log. There are several
7598 ways to specify the location to go to:
7601 @item record goto begin
7602 @itemx record goto start
7603 Go to the beginning of the execution log.
7605 @item record goto end
7606 Go to the end of the execution log.
7608 @item record goto @var{n}
7609 Go to instruction number @var{n} in the execution log.
7613 @item record save @var{filename}
7614 Save the execution log to a file @file{@var{filename}}.
7615 Default filename is @file{gdb_record.@var{process_id}}, where
7616 @var{process_id} is the process ID of the inferior.
7618 This command may not be available for all recording methods.
7620 @kindex record restore
7621 @item record restore @var{filename}
7622 Restore the execution log from a file @file{@var{filename}}.
7623 File must have been created with @code{record save}.
7625 @kindex set record full
7626 @item set record full insn-number-max @var{limit}
7627 @itemx set record full insn-number-max unlimited
7628 Set the limit of instructions to be recorded for the @code{full}
7629 recording method. Default value is 200000.
7631 If @var{limit} is a positive number, then @value{GDBN} will start
7632 deleting instructions from the log once the number of the record
7633 instructions becomes greater than @var{limit}. For every new recorded
7634 instruction, @value{GDBN} will delete the earliest recorded
7635 instruction to keep the number of recorded instructions at the limit.
7636 (Since deleting recorded instructions loses information, @value{GDBN}
7637 lets you control what happens when the limit is reached, by means of
7638 the @code{stop-at-limit} option, described below.)
7640 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7641 delete recorded instructions from the execution log. The number of
7642 recorded instructions is limited only by the available memory.
7644 @kindex show record full
7645 @item show record full insn-number-max
7646 Show the limit of instructions to be recorded with the @code{full}
7649 @item set record full stop-at-limit
7650 Control the behavior of the @code{full} recording method when the
7651 number of recorded instructions reaches the limit. If ON (the
7652 default), @value{GDBN} will stop when the limit is reached for the
7653 first time and ask you whether you want to stop the inferior or
7654 continue running it and recording the execution log. If you decide
7655 to continue recording, each new recorded instruction will cause the
7656 oldest one to be deleted.
7658 If this option is OFF, @value{GDBN} will automatically delete the
7659 oldest record to make room for each new one, without asking.
7661 @item show record full stop-at-limit
7662 Show the current setting of @code{stop-at-limit}.
7664 @item set record full memory-query
7665 Control the behavior when @value{GDBN} is unable to record memory
7666 changes caused by an instruction for the @code{full} recording method.
7667 If ON, @value{GDBN} will query whether to stop the inferior in that
7670 If this option is OFF (the default), @value{GDBN} will automatically
7671 ignore the effect of such instructions on memory. Later, when
7672 @value{GDBN} replays this execution log, it will mark the log of this
7673 instruction as not accessible, and it will not affect the replay
7676 @item show record full memory-query
7677 Show the current setting of @code{memory-query}.
7679 @kindex set record btrace
7680 The @code{btrace} record target does not trace data. As a
7681 convenience, when replaying, @value{GDBN} reads read-only memory off
7682 the live program directly, assuming that the addresses of the
7683 read-only areas don't change. This for example makes it possible to
7684 disassemble code while replaying, but not to print variables.
7685 In some cases, being able to inspect variables might be useful.
7686 You can use the following command for that:
7688 @item set record btrace replay-memory-access
7689 Control the behavior of the @code{btrace} recording method when
7690 accessing memory during replay. If @code{read-only} (the default),
7691 @value{GDBN} will only allow accesses to read-only memory.
7692 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7693 and to read-write memory. Beware that the accessed memory corresponds
7694 to the live target and not necessarily to the current replay
7697 @item set record btrace cpu @var{identifier}
7698 Set the processor to be used for enabling workarounds for processor
7699 errata when decoding the trace.
7701 Processor errata are defects in processor operation, caused by its
7702 design or manufacture. They can cause a trace not to match the
7703 specification. This, in turn, may cause trace decode to fail.
7704 @value{GDBN} can detect erroneous trace packets and correct them, thus
7705 avoiding the decoding failures. These corrections are known as
7706 @dfn{errata workarounds}, and are enabled based on the processor on
7707 which the trace was recorded.
7709 By default, @value{GDBN} attempts to detect the processor
7710 automatically, and apply the necessary workarounds for it. However,
7711 you may need to specify the processor if @value{GDBN} does not yet
7712 support it. This command allows you to do that, and also allows to
7713 disable the workarounds.
7715 The argument @var{identifier} identifies the @sc{cpu} and is of the
7716 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7717 there are two special identifiers, @code{none} and @code{auto}
7720 The following vendor identifiers and corresponding processor
7721 identifiers are currently supported:
7723 @multitable @columnfractions .1 .9
7726 @tab @var{family}/@var{model}[/@var{stepping}]
7730 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7731 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7733 If @var{identifier} is @code{auto}, enable errata workarounds for the
7734 processor on which the trace was recorded. If @var{identifier} is
7735 @code{none}, errata workarounds are disabled.
7737 For example, when using an old @value{GDBN} on a new system, decode
7738 may fail because @value{GDBN} does not support the new processor. It
7739 often suffices to specify an older processor that @value{GDBN}
7744 Active record target: record-btrace
7745 Recording format: Intel Processor Trace.
7747 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7748 (gdb) set record btrace cpu intel:6/158
7750 Active record target: record-btrace
7751 Recording format: Intel Processor Trace.
7753 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7756 @kindex show record btrace
7757 @item show record btrace replay-memory-access
7758 Show the current setting of @code{replay-memory-access}.
7760 @item show record btrace cpu
7761 Show the processor to be used for enabling trace decode errata
7764 @kindex set record btrace bts
7765 @item set record btrace bts buffer-size @var{size}
7766 @itemx set record btrace bts buffer-size unlimited
7767 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7768 format. Default is 64KB.
7770 If @var{size} is a positive number, then @value{GDBN} will try to
7771 allocate a buffer of at least @var{size} bytes for each new thread
7772 that uses the btrace recording method and the @acronym{BTS} format.
7773 The actually obtained buffer size may differ from the requested
7774 @var{size}. Use the @code{info record} command to see the actual
7775 buffer size for each thread that uses the btrace recording method and
7776 the @acronym{BTS} format.
7778 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7779 allocate a buffer of 4MB.
7781 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7782 also need longer to process the branch trace data before it can be used.
7784 @item show record btrace bts buffer-size @var{size}
7785 Show the current setting of the requested ring buffer size for branch
7786 tracing in @acronym{BTS} format.
7788 @kindex set record btrace pt
7789 @item set record btrace pt buffer-size @var{size}
7790 @itemx set record btrace pt buffer-size unlimited
7791 Set the requested ring buffer size for branch tracing in Intel
7792 Processor Trace format. Default is 16KB.
7794 If @var{size} is a positive number, then @value{GDBN} will try to
7795 allocate a buffer of at least @var{size} bytes for each new thread
7796 that uses the btrace recording method and the Intel Processor Trace
7797 format. The actually obtained buffer size may differ from the
7798 requested @var{size}. Use the @code{info record} command to see the
7799 actual buffer size for each thread.
7801 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7802 allocate a buffer of 4MB.
7804 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7805 also need longer to process the branch trace data before it can be used.
7807 @item show record btrace pt buffer-size @var{size}
7808 Show the current setting of the requested ring buffer size for branch
7809 tracing in Intel Processor Trace format.
7813 Show various statistics about the recording depending on the recording
7818 For the @code{full} recording method, it shows the state of process
7819 record and its in-memory execution log buffer, including:
7823 Whether in record mode or replay mode.
7825 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7827 Highest recorded instruction number.
7829 Current instruction about to be replayed (if in replay mode).
7831 Number of instructions contained in the execution log.
7833 Maximum number of instructions that may be contained in the execution log.
7837 For the @code{btrace} recording method, it shows:
7843 Number of instructions that have been recorded.
7845 Number of blocks of sequential control-flow formed by the recorded
7848 Whether in record mode or replay mode.
7851 For the @code{bts} recording format, it also shows:
7854 Size of the perf ring buffer.
7857 For the @code{pt} recording format, it also shows:
7860 Size of the perf ring buffer.
7864 @kindex record delete
7867 When record target runs in replay mode (``in the past''), delete the
7868 subsequent execution log and begin to record a new execution log starting
7869 from the current address. This means you will abandon the previously
7870 recorded ``future'' and begin recording a new ``future''.
7872 @kindex record instruction-history
7873 @kindex rec instruction-history
7874 @item record instruction-history
7875 Disassembles instructions from the recorded execution log. By
7876 default, ten instructions are disassembled. This can be changed using
7877 the @code{set record instruction-history-size} command. Instructions
7878 are printed in execution order.
7880 It can also print mixed source+disassembly if you specify the the
7881 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7882 as well as in symbolic form by specifying the @code{/r} modifier.
7884 The current position marker is printed for the instruction at the
7885 current program counter value. This instruction can appear multiple
7886 times in the trace and the current position marker will be printed
7887 every time. To omit the current position marker, specify the
7890 To better align the printed instructions when the trace contains
7891 instructions from more than one function, the function name may be
7892 omitted by specifying the @code{/f} modifier.
7894 Speculatively executed instructions are prefixed with @samp{?}. This
7895 feature is not available for all recording formats.
7897 There are several ways to specify what part of the execution log to
7901 @item record instruction-history @var{insn}
7902 Disassembles ten instructions starting from instruction number
7905 @item record instruction-history @var{insn}, +/-@var{n}
7906 Disassembles @var{n} instructions around instruction number
7907 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7908 @var{n} instructions after instruction number @var{insn}. If
7909 @var{n} is preceded with @code{-}, disassembles @var{n}
7910 instructions before instruction number @var{insn}.
7912 @item record instruction-history
7913 Disassembles ten more instructions after the last disassembly.
7915 @item record instruction-history -
7916 Disassembles ten more instructions before the last disassembly.
7918 @item record instruction-history @var{begin}, @var{end}
7919 Disassembles instructions beginning with instruction number
7920 @var{begin} until instruction number @var{end}. The instruction
7921 number @var{end} is included.
7924 This command may not be available for all recording methods.
7927 @item set record instruction-history-size @var{size}
7928 @itemx set record instruction-history-size unlimited
7929 Define how many instructions to disassemble in the @code{record
7930 instruction-history} command. The default value is 10.
7931 A @var{size} of @code{unlimited} means unlimited instructions.
7934 @item show record instruction-history-size
7935 Show how many instructions to disassemble in the @code{record
7936 instruction-history} command.
7938 @kindex record function-call-history
7939 @kindex rec function-call-history
7940 @item record function-call-history
7941 Prints the execution history at function granularity. For each sequence
7942 of instructions that belong to the same function, it prints the name of
7943 that function, the source lines for this instruction sequence (if the
7944 @code{/l} modifier is specified), and the instructions numbers that form
7945 the sequence (if the @code{/i} modifier is specified). The function names
7946 are indented to reflect the call stack depth if the @code{/c} modifier is
7947 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7951 (@value{GDBP}) @b{list 1, 10}
7962 (@value{GDBP}) @b{record function-call-history /ilc}
7963 1 bar inst 1,4 at foo.c:6,8
7964 2 foo inst 5,10 at foo.c:2,3
7965 3 bar inst 11,13 at foo.c:9,10
7968 By default, ten functions are printed. This can be changed using the
7969 @code{set record function-call-history-size} command. Functions are
7970 printed in execution order. There are several ways to specify what
7974 @item record function-call-history @var{func}
7975 Prints ten functions starting from function number @var{func}.
7977 @item record function-call-history @var{func}, +/-@var{n}
7978 Prints @var{n} functions around function number @var{func}. If
7979 @var{n} is preceded with @code{+}, prints @var{n} functions after
7980 function number @var{func}. If @var{n} is preceded with @code{-},
7981 prints @var{n} functions before function number @var{func}.
7983 @item record function-call-history
7984 Prints ten more functions after the last ten-function print.
7986 @item record function-call-history -
7987 Prints ten more functions before the last ten-function print.
7989 @item record function-call-history @var{begin}, @var{end}
7990 Prints functions beginning with function number @var{begin} until
7991 function number @var{end}. The function number @var{end} is included.
7994 This command may not be available for all recording methods.
7996 @item set record function-call-history-size @var{size}
7997 @itemx set record function-call-history-size unlimited
7998 Define how many functions to print in the
7999 @code{record function-call-history} command. The default value is 10.
8000 A size of @code{unlimited} means unlimited functions.
8002 @item show record function-call-history-size
8003 Show how many functions to print in the
8004 @code{record function-call-history} command.
8009 @chapter Examining the Stack
8011 When your program has stopped, the first thing you need to know is where it
8012 stopped and how it got there.
8015 Each time your program performs a function call, information about the call
8017 That information includes the location of the call in your program,
8018 the arguments of the call,
8019 and the local variables of the function being called.
8020 The information is saved in a block of data called a @dfn{stack frame}.
8021 The stack frames are allocated in a region of memory called the @dfn{call
8024 When your program stops, the @value{GDBN} commands for examining the
8025 stack allow you to see all of this information.
8027 @cindex selected frame
8028 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8029 @value{GDBN} commands refer implicitly to the selected frame. In
8030 particular, whenever you ask @value{GDBN} for the value of a variable in
8031 your program, the value is found in the selected frame. There are
8032 special @value{GDBN} commands to select whichever frame you are
8033 interested in. @xref{Selection, ,Selecting a Frame}.
8035 When your program stops, @value{GDBN} automatically selects the
8036 currently executing frame and describes it briefly, similar to the
8037 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8040 * Frames:: Stack frames
8041 * Backtrace:: Backtraces
8042 * Selection:: Selecting a frame
8043 * Frame Info:: Information on a frame
8044 * Frame Apply:: Applying a command to several frames
8045 * Frame Filter Management:: Managing frame filters
8050 @section Stack Frames
8052 @cindex frame, definition
8054 The call stack is divided up into contiguous pieces called @dfn{stack
8055 frames}, or @dfn{frames} for short; each frame is the data associated
8056 with one call to one function. The frame contains the arguments given
8057 to the function, the function's local variables, and the address at
8058 which the function is executing.
8060 @cindex initial frame
8061 @cindex outermost frame
8062 @cindex innermost frame
8063 When your program is started, the stack has only one frame, that of the
8064 function @code{main}. This is called the @dfn{initial} frame or the
8065 @dfn{outermost} frame. Each time a function is called, a new frame is
8066 made. Each time a function returns, the frame for that function invocation
8067 is eliminated. If a function is recursive, there can be many frames for
8068 the same function. The frame for the function in which execution is
8069 actually occurring is called the @dfn{innermost} frame. This is the most
8070 recently created of all the stack frames that still exist.
8072 @cindex frame pointer
8073 Inside your program, stack frames are identified by their addresses. A
8074 stack frame consists of many bytes, each of which has its own address; each
8075 kind of computer has a convention for choosing one byte whose
8076 address serves as the address of the frame. Usually this address is kept
8077 in a register called the @dfn{frame pointer register}
8078 (@pxref{Registers, $fp}) while execution is going on in that frame.
8081 @cindex frame number
8082 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8083 number that is zero for the innermost frame, one for the frame that
8084 called it, and so on upward. These level numbers give you a way of
8085 designating stack frames in @value{GDBN} commands. The terms
8086 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8087 describe this number.
8089 @c The -fomit-frame-pointer below perennially causes hbox overflow
8090 @c underflow problems.
8091 @cindex frameless execution
8092 Some compilers provide a way to compile functions so that they operate
8093 without stack frames. (For example, the @value{NGCC} option
8095 @samp{-fomit-frame-pointer}
8097 generates functions without a frame.)
8098 This is occasionally done with heavily used library functions to save
8099 the frame setup time. @value{GDBN} has limited facilities for dealing
8100 with these function invocations. If the innermost function invocation
8101 has no stack frame, @value{GDBN} nevertheless regards it as though
8102 it had a separate frame, which is numbered zero as usual, allowing
8103 correct tracing of the function call chain. However, @value{GDBN} has
8104 no provision for frameless functions elsewhere in the stack.
8110 @cindex call stack traces
8111 A backtrace is a summary of how your program got where it is. It shows one
8112 line per frame, for many frames, starting with the currently executing
8113 frame (frame zero), followed by its caller (frame one), and on up the
8116 @anchor{backtrace-command}
8118 @kindex bt @r{(@code{backtrace})}
8119 To print a backtrace of the entire stack, use the @code{backtrace}
8120 command, or its alias @code{bt}. This command will print one line per
8121 frame for frames in the stack. By default, all stack frames are
8122 printed. You can stop the backtrace at any time by typing the system
8123 interrupt character, normally @kbd{Ctrl-c}.
8126 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8127 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8128 Print the backtrace of the entire stack.
8130 The optional @var{count} can be one of the following:
8135 Print only the innermost @var{n} frames, where @var{n} is a positive
8140 Print only the outermost @var{n} frames, where @var{n} is a positive
8148 Print the values of the local variables also. This can be combined
8149 with the optional @var{count} to limit the number of frames shown.
8152 Do not run Python frame filters on this backtrace. @xref{Frame
8153 Filter API}, for more information. Additionally use @ref{disable
8154 frame-filter all} to turn off all frame filters. This is only
8155 relevant when @value{GDBN} has been configured with @code{Python}
8159 A Python frame filter might decide to ``elide'' some frames. Normally
8160 such elided frames are still printed, but they are indented relative
8161 to the filtered frames that cause them to be elided. The @code{-hide}
8162 option causes elided frames to not be printed at all.
8165 The @code{backtrace} command also supports a number of options that
8166 allow overriding relevant global print settings as set by @code{set
8167 backtrace} and @code{set print} subcommands:
8170 @item -past-main [@code{on}|@code{off}]
8171 Set whether backtraces should continue past @code{main}. Related setting:
8172 @ref{set backtrace past-main}.
8174 @item -past-entry [@code{on}|@code{off}]
8175 Set whether backtraces should continue past the entry point of a program.
8176 Related setting: @ref{set backtrace past-entry}.
8178 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8179 Set printing of function arguments at function entry.
8180 Related setting: @ref{set print entry-values}.
8182 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8183 Set printing of non-scalar frame arguments.
8184 Related setting: @ref{set print frame-arguments}.
8186 @item -raw-frame-arguments [@code{on}|@code{off}]
8187 Set whether to print frame arguments in raw form.
8188 Related setting: @ref{set print raw-frame-arguments}.
8190 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8191 Set printing of frame information.
8192 Related setting: @ref{set print frame-info}.
8195 The optional @var{qualifier} is maintained for backward compatibility.
8196 It can be one of the following:
8200 Equivalent to the @code{-full} option.
8203 Equivalent to the @code{-no-filters} option.
8206 Equivalent to the @code{-hide} option.
8213 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8214 are additional aliases for @code{backtrace}.
8216 @cindex multiple threads, backtrace
8217 In a multi-threaded program, @value{GDBN} by default shows the
8218 backtrace only for the current thread. To display the backtrace for
8219 several or all of the threads, use the command @code{thread apply}
8220 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8221 apply all backtrace}, @value{GDBN} will display the backtrace for all
8222 the threads; this is handy when you debug a core dump of a
8223 multi-threaded program.
8225 Each line in the backtrace shows the frame number and the function name.
8226 The program counter value is also shown---unless you use @code{set
8227 print address off}. The backtrace also shows the source file name and
8228 line number, as well as the arguments to the function. The program
8229 counter value is omitted if it is at the beginning of the code for that
8232 Here is an example of a backtrace. It was made with the command
8233 @samp{bt 3}, so it shows the innermost three frames.
8237 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8239 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8240 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8242 (More stack frames follow...)
8247 The display for frame zero does not begin with a program counter
8248 value, indicating that your program has stopped at the beginning of the
8249 code for line @code{993} of @code{builtin.c}.
8252 The value of parameter @code{data} in frame 1 has been replaced by
8253 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8254 only if it is a scalar (integer, pointer, enumeration, etc). See command
8255 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8256 on how to configure the way function parameter values are printed.
8257 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8258 what frame information is printed.
8260 @cindex optimized out, in backtrace
8261 @cindex function call arguments, optimized out
8262 If your program was compiled with optimizations, some compilers will
8263 optimize away arguments passed to functions if those arguments are
8264 never used after the call. Such optimizations generate code that
8265 passes arguments through registers, but doesn't store those arguments
8266 in the stack frame. @value{GDBN} has no way of displaying such
8267 arguments in stack frames other than the innermost one. Here's what
8268 such a backtrace might look like:
8272 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8274 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8275 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8277 (More stack frames follow...)
8282 The values of arguments that were not saved in their stack frames are
8283 shown as @samp{<optimized out>}.
8285 If you need to display the values of such optimized-out arguments,
8286 either deduce that from other variables whose values depend on the one
8287 you are interested in, or recompile without optimizations.
8289 @cindex backtrace beyond @code{main} function
8290 @cindex program entry point
8291 @cindex startup code, and backtrace
8292 Most programs have a standard user entry point---a place where system
8293 libraries and startup code transition into user code. For C this is
8294 @code{main}@footnote{
8295 Note that embedded programs (the so-called ``free-standing''
8296 environment) are not required to have a @code{main} function as the
8297 entry point. They could even have multiple entry points.}.
8298 When @value{GDBN} finds the entry function in a backtrace
8299 it will terminate the backtrace, to avoid tracing into highly
8300 system-specific (and generally uninteresting) code.
8302 If you need to examine the startup code, or limit the number of levels
8303 in a backtrace, you can change this behavior:
8306 @item set backtrace past-main
8307 @itemx set backtrace past-main on
8308 @anchor{set backtrace past-main}
8309 @kindex set backtrace
8310 Backtraces will continue past the user entry point.
8312 @item set backtrace past-main off
8313 Backtraces will stop when they encounter the user entry point. This is the
8316 @item show backtrace past-main
8317 @kindex show backtrace
8318 Display the current user entry point backtrace policy.
8320 @item set backtrace past-entry
8321 @itemx set backtrace past-entry on
8322 @anchor{set backtrace past-entry}
8323 Backtraces will continue past the internal entry point of an application.
8324 This entry point is encoded by the linker when the application is built,
8325 and is likely before the user entry point @code{main} (or equivalent) is called.
8327 @item set backtrace past-entry off
8328 Backtraces will stop when they encounter the internal entry point of an
8329 application. This is the default.
8331 @item show backtrace past-entry
8332 Display the current internal entry point backtrace policy.
8334 @item set backtrace limit @var{n}
8335 @itemx set backtrace limit 0
8336 @itemx set backtrace limit unlimited
8337 @anchor{set backtrace limit}
8338 @cindex backtrace limit
8339 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8340 or zero means unlimited levels.
8342 @item show backtrace limit
8343 Display the current limit on backtrace levels.
8346 You can control how file names are displayed.
8349 @item set filename-display
8350 @itemx set filename-display relative
8351 @cindex filename-display
8352 Display file names relative to the compilation directory. This is the default.
8354 @item set filename-display basename
8355 Display only basename of a filename.
8357 @item set filename-display absolute
8358 Display an absolute filename.
8360 @item show filename-display
8361 Show the current way to display filenames.
8365 @section Selecting a Frame
8367 Most commands for examining the stack and other data in your program work on
8368 whichever stack frame is selected at the moment. Here are the commands for
8369 selecting a stack frame; all of them finish by printing a brief description
8370 of the stack frame just selected.
8373 @kindex frame@r{, selecting}
8374 @kindex f @r{(@code{frame})}
8375 @item frame @r{[} @var{frame-selection-spec} @r{]}
8376 @item f @r{[} @var{frame-selection-spec} @r{]}
8377 The @command{frame} command allows different stack frames to be
8378 selected. The @var{frame-selection-spec} can be any of the following:
8383 @item level @var{num}
8384 Select frame level @var{num}. Recall that frame zero is the innermost
8385 (currently executing) frame, frame one is the frame that called the
8386 innermost one, and so on. The highest level frame is usually the one
8389 As this is the most common method of navigating the frame stack, the
8390 string @command{level} can be omitted. For example, the following two
8391 commands are equivalent:
8394 (@value{GDBP}) frame 3
8395 (@value{GDBP}) frame level 3
8398 @kindex frame address
8399 @item address @var{stack-address}
8400 Select the frame with stack address @var{stack-address}. The
8401 @var{stack-address} for a frame can be seen in the output of
8402 @command{info frame}, for example:
8406 Stack level 1, frame at 0x7fffffffda30:
8407 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8408 tail call frame, caller of frame at 0x7fffffffda30
8409 source language c++.
8410 Arglist at unknown address.
8411 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8414 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8415 indicated by the line:
8418 Stack level 1, frame at 0x7fffffffda30:
8421 @kindex frame function
8422 @item function @var{function-name}
8423 Select the stack frame for function @var{function-name}. If there are
8424 multiple stack frames for function @var{function-name} then the inner
8425 most stack frame is selected.
8428 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8429 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8430 viewed has stack address @var{stack-addr}, and optionally, a program
8431 counter address of @var{pc-addr}.
8433 This is useful mainly if the chaining of stack frames has been
8434 damaged by a bug, making it impossible for @value{GDBN} to assign
8435 numbers properly to all frames. In addition, this can be useful
8436 when your program has multiple stacks and switches between them.
8438 When viewing a frame outside the current backtrace using
8439 @command{frame view} then you can always return to the original
8440 stack using one of the previous stack frame selection instructions,
8441 for example @command{frame level 0}.
8447 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8448 numbers @var{n}, this advances toward the outermost frame, to higher
8449 frame numbers, to frames that have existed longer.
8452 @kindex do @r{(@code{down})}
8454 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8455 positive numbers @var{n}, this advances toward the innermost frame, to
8456 lower frame numbers, to frames that were created more recently.
8457 You may abbreviate @code{down} as @code{do}.
8460 All of these commands end by printing two lines of output describing the
8461 frame. The first line shows the frame number, the function name, the
8462 arguments, and the source file and line number of execution in that
8463 frame. The second line shows the text of that source line.
8471 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8473 10 read_input_file (argv[i]);
8477 After such a printout, the @code{list} command with no arguments
8478 prints ten lines centered on the point of execution in the frame.
8479 You can also edit the program at the point of execution with your favorite
8480 editing program by typing @code{edit}.
8481 @xref{List, ,Printing Source Lines},
8485 @kindex select-frame
8486 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8487 The @code{select-frame} command is a variant of @code{frame} that does
8488 not display the new frame after selecting it. This command is
8489 intended primarily for use in @value{GDBN} command scripts, where the
8490 output might be unnecessary and distracting. The
8491 @var{frame-selection-spec} is as for the @command{frame} command
8492 described in @ref{Selection, ,Selecting a Frame}.
8494 @kindex down-silently
8496 @item up-silently @var{n}
8497 @itemx down-silently @var{n}
8498 These two commands are variants of @code{up} and @code{down},
8499 respectively; they differ in that they do their work silently, without
8500 causing display of the new frame. They are intended primarily for use
8501 in @value{GDBN} command scripts, where the output might be unnecessary and
8506 @section Information About a Frame
8508 There are several other commands to print information about the selected
8514 When used without any argument, this command does not change which
8515 frame is selected, but prints a brief description of the currently
8516 selected stack frame. It can be abbreviated @code{f}. With an
8517 argument, this command is used to select a stack frame.
8518 @xref{Selection, ,Selecting a Frame}.
8521 @kindex info f @r{(@code{info frame})}
8524 This command prints a verbose description of the selected stack frame,
8529 the address of the frame
8531 the address of the next frame down (called by this frame)
8533 the address of the next frame up (caller of this frame)
8535 the language in which the source code corresponding to this frame is written
8537 the address of the frame's arguments
8539 the address of the frame's local variables
8541 the program counter saved in it (the address of execution in the caller frame)
8543 which registers were saved in the frame
8546 @noindent The verbose description is useful when
8547 something has gone wrong that has made the stack format fail to fit
8548 the usual conventions.
8550 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8551 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8552 Print a verbose description of the frame selected by
8553 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8554 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8555 a Frame}). The selected frame remains unchanged by this command.
8558 @item info args [-q]
8559 Print the arguments of the selected frame, each on a separate line.
8561 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8562 printing header information and messages explaining why no argument
8565 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8566 Like @kbd{info args}, but only print the arguments selected
8567 with the provided regexp(s).
8569 If @var{regexp} is provided, print only the arguments whose names
8570 match the regular expression @var{regexp}.
8572 If @var{type_regexp} is provided, print only the arguments whose
8573 types, as printed by the @code{whatis} command, match
8574 the regular expression @var{type_regexp}.
8575 If @var{type_regexp} contains space(s), it should be enclosed in
8576 quote characters. If needed, use backslash to escape the meaning
8577 of special characters or quotes.
8579 If both @var{regexp} and @var{type_regexp} are provided, an argument
8580 is printed only if its name matches @var{regexp} and its type matches
8583 @item info locals [-q]
8585 Print the local variables of the selected frame, each on a separate
8586 line. These are all variables (declared either static or automatic)
8587 accessible at the point of execution of the selected frame.
8589 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8590 printing header information and messages explaining why no local variables
8593 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8594 Like @kbd{info locals}, but only print the local variables selected
8595 with the provided regexp(s).
8597 If @var{regexp} is provided, print only the local variables whose names
8598 match the regular expression @var{regexp}.
8600 If @var{type_regexp} is provided, print only the local variables whose
8601 types, as printed by the @code{whatis} command, match
8602 the regular expression @var{type_regexp}.
8603 If @var{type_regexp} contains space(s), it should be enclosed in
8604 quote characters. If needed, use backslash to escape the meaning
8605 of special characters or quotes.
8607 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8608 is printed only if its name matches @var{regexp} and its type matches
8611 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8612 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8613 For example, your program might use Resource Acquisition Is
8614 Initialization types (RAII) such as @code{lock_something_t}: each
8615 local variable of type @code{lock_something_t} automatically places a
8616 lock that is destroyed when the variable goes out of scope. You can
8617 then list all acquired locks in your program by doing
8619 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8622 or the equivalent shorter form
8624 tfaas i lo -q -t lock_something_t
8630 @section Applying a Command to Several Frames.
8632 @cindex apply command to several frames
8634 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8635 The @code{frame apply} command allows you to apply the named
8636 @var{command} to one or more frames.
8640 Specify @code{all} to apply @var{command} to all frames.
8643 Use @var{count} to apply @var{command} to the innermost @var{count}
8644 frames, where @var{count} is a positive number.
8647 Use @var{-count} to apply @var{command} to the outermost @var{count}
8648 frames, where @var{count} is a positive number.
8651 Use @code{level} to apply @var{command} to the set of frames identified
8652 by the @var{level} list. @var{level} is a frame level or a range of frame
8653 levels as @var{level1}-@var{level2}. The frame level is the number shown
8654 in the first field of the @samp{backtrace} command output.
8655 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8656 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8660 Note that the frames on which @code{frame apply} applies a command are
8661 also influenced by the @code{set backtrace} settings such as @code{set
8662 backtrace past-main} and @code{set backtrace limit N}.
8663 @xref{Backtrace,,Backtraces}.
8665 The @code{frame apply} command also supports a number of options that
8666 allow overriding relevant @code{set backtrace} settings:
8669 @item -past-main [@code{on}|@code{off}]
8670 Whether backtraces should continue past @code{main}.
8671 Related setting: @ref{set backtrace past-main}.
8673 @item -past-entry [@code{on}|@code{off}]
8674 Whether backtraces should continue past the entry point of a program.
8675 Related setting: @ref{set backtrace past-entry}.
8678 By default, @value{GDBN} displays some frame information before the
8679 output produced by @var{command}, and an error raised during the
8680 execution of a @var{command} will abort @code{frame apply}. The
8681 following options can be used to fine-tune these behaviors:
8685 The flag @code{-c}, which stands for @samp{continue}, causes any
8686 errors in @var{command} to be displayed, and the execution of
8687 @code{frame apply} then continues.
8689 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8690 or empty output produced by a @var{command} to be silently ignored.
8691 That is, the execution continues, but the frame information and errors
8694 The flag @code{-q} (@samp{quiet}) disables printing the frame
8698 The following example shows how the flags @code{-c} and @code{-s} are
8699 working when applying the command @code{p j} to all frames, where
8700 variable @code{j} can only be successfully printed in the outermost
8701 @code{#1 main} frame.
8705 (gdb) frame apply all p j
8706 #0 some_function (i=5) at fun.c:4
8707 No symbol "j" in current context.
8708 (gdb) frame apply all -c p j
8709 #0 some_function (i=5) at fun.c:4
8710 No symbol "j" in current context.
8711 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8713 (gdb) frame apply all -s p j
8714 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8720 By default, @samp{frame apply}, prints the frame location
8721 information before the command output:
8725 (gdb) frame apply all p $sp
8726 #0 some_function (i=5) at fun.c:4
8727 $4 = (void *) 0xffffd1e0
8728 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8729 $5 = (void *) 0xffffd1f0
8734 If the flag @code{-q} is given, no frame information is printed:
8737 (gdb) frame apply all -q p $sp
8738 $12 = (void *) 0xffffd1e0
8739 $13 = (void *) 0xffffd1f0
8749 @cindex apply a command to all frames (ignoring errors and empty output)
8750 @item faas @var{command}
8751 Shortcut for @code{frame apply all -s @var{command}}.
8752 Applies @var{command} on all frames, ignoring errors and empty output.
8754 It can for example be used to print a local variable or a function
8755 argument without knowing the frame where this variable or argument
8758 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8761 The @code{faas} command accepts the same options as the @code{frame
8762 apply} command. @xref{Frame Apply,,frame apply}.
8764 Note that the command @code{tfaas @var{command}} applies @var{command}
8765 on all frames of all threads. See @xref{Threads,,Threads}.
8769 @node Frame Filter Management
8770 @section Management of Frame Filters.
8771 @cindex managing frame filters
8773 Frame filters are Python based utilities to manage and decorate the
8774 output of frames. @xref{Frame Filter API}, for further information.
8776 Managing frame filters is performed by several commands available
8777 within @value{GDBN}, detailed here.
8780 @kindex info frame-filter
8781 @item info frame-filter
8782 Print a list of installed frame filters from all dictionaries, showing
8783 their name, priority and enabled status.
8785 @kindex disable frame-filter
8786 @anchor{disable frame-filter all}
8787 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8788 Disable a frame filter in the dictionary matching
8789 @var{filter-dictionary} and @var{filter-name}. The
8790 @var{filter-dictionary} may be @code{all}, @code{global},
8791 @code{progspace}, or the name of the object file where the frame filter
8792 dictionary resides. When @code{all} is specified, all frame filters
8793 across all dictionaries are disabled. The @var{filter-name} is the name
8794 of the frame filter and is used when @code{all} is not the option for
8795 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8796 may be enabled again later.
8798 @kindex enable frame-filter
8799 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8800 Enable a frame filter in the dictionary matching
8801 @var{filter-dictionary} and @var{filter-name}. The
8802 @var{filter-dictionary} may be @code{all}, @code{global},
8803 @code{progspace} or the name of the object file where the frame filter
8804 dictionary resides. When @code{all} is specified, all frame filters across
8805 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8806 filter and is used when @code{all} is not the option for
8807 @var{filter-dictionary}.
8812 (gdb) info frame-filter
8814 global frame-filters:
8815 Priority Enabled Name
8816 1000 No PrimaryFunctionFilter
8819 progspace /build/test frame-filters:
8820 Priority Enabled Name
8821 100 Yes ProgspaceFilter
8823 objfile /build/test frame-filters:
8824 Priority Enabled Name
8825 999 Yes BuildProgramFilter
8827 (gdb) disable frame-filter /build/test BuildProgramFilter
8828 (gdb) info frame-filter
8830 global frame-filters:
8831 Priority Enabled Name
8832 1000 No PrimaryFunctionFilter
8835 progspace /build/test frame-filters:
8836 Priority Enabled Name
8837 100 Yes ProgspaceFilter
8839 objfile /build/test frame-filters:
8840 Priority Enabled Name
8841 999 No BuildProgramFilter
8843 (gdb) enable frame-filter global PrimaryFunctionFilter
8844 (gdb) info frame-filter
8846 global frame-filters:
8847 Priority Enabled Name
8848 1000 Yes PrimaryFunctionFilter
8851 progspace /build/test frame-filters:
8852 Priority Enabled Name
8853 100 Yes ProgspaceFilter
8855 objfile /build/test frame-filters:
8856 Priority Enabled Name
8857 999 No BuildProgramFilter
8860 @kindex set frame-filter priority
8861 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8862 Set the @var{priority} of a frame filter in the dictionary matching
8863 @var{filter-dictionary}, and the frame filter name matching
8864 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8865 @code{progspace} or the name of the object file where the frame filter
8866 dictionary resides. The @var{priority} is an integer.
8868 @kindex show frame-filter priority
8869 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8870 Show the @var{priority} of a frame filter in the dictionary matching
8871 @var{filter-dictionary}, and the frame filter name matching
8872 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8873 @code{progspace} or the name of the object file where the frame filter
8879 (gdb) info frame-filter
8881 global frame-filters:
8882 Priority Enabled Name
8883 1000 Yes PrimaryFunctionFilter
8886 progspace /build/test frame-filters:
8887 Priority Enabled Name
8888 100 Yes ProgspaceFilter
8890 objfile /build/test frame-filters:
8891 Priority Enabled Name
8892 999 No BuildProgramFilter
8894 (gdb) set frame-filter priority global Reverse 50
8895 (gdb) info frame-filter
8897 global frame-filters:
8898 Priority Enabled Name
8899 1000 Yes PrimaryFunctionFilter
8902 progspace /build/test frame-filters:
8903 Priority Enabled Name
8904 100 Yes ProgspaceFilter
8906 objfile /build/test frame-filters:
8907 Priority Enabled Name
8908 999 No BuildProgramFilter
8913 @chapter Examining Source Files
8915 @value{GDBN} can print parts of your program's source, since the debugging
8916 information recorded in the program tells @value{GDBN} what source files were
8917 used to build it. When your program stops, @value{GDBN} spontaneously prints
8918 the line where it stopped. Likewise, when you select a stack frame
8919 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8920 execution in that frame has stopped. You can print other portions of
8921 source files by explicit command.
8923 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8924 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8925 @value{GDBN} under @sc{gnu} Emacs}.
8928 * List:: Printing source lines
8929 * Specify Location:: How to specify code locations
8930 * Edit:: Editing source files
8931 * Search:: Searching source files
8932 * Source Path:: Specifying source directories
8933 * Machine Code:: Source and machine code
8934 * Disable Reading Source:: Disable Reading Source Code
8938 @section Printing Source Lines
8941 @kindex l @r{(@code{list})}
8942 To print lines from a source file, use the @code{list} command
8943 (abbreviated @code{l}). By default, ten lines are printed.
8944 There are several ways to specify what part of the file you want to
8945 print; see @ref{Specify Location}, for the full list.
8947 Here are the forms of the @code{list} command most commonly used:
8950 @item list @var{linenum}
8951 Print lines centered around line number @var{linenum} in the
8952 current source file.
8954 @item list @var{function}
8955 Print lines centered around the beginning of function
8959 Print more lines. If the last lines printed were printed with a
8960 @code{list} command, this prints lines following the last lines
8961 printed; however, if the last line printed was a solitary line printed
8962 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8963 Stack}), this prints lines centered around that line.
8966 Print lines just before the lines last printed.
8969 @cindex @code{list}, how many lines to display
8970 By default, @value{GDBN} prints ten source lines with any of these forms of
8971 the @code{list} command. You can change this using @code{set listsize}:
8974 @kindex set listsize
8975 @item set listsize @var{count}
8976 @itemx set listsize unlimited
8977 Make the @code{list} command display @var{count} source lines (unless
8978 the @code{list} argument explicitly specifies some other number).
8979 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8981 @kindex show listsize
8983 Display the number of lines that @code{list} prints.
8986 Repeating a @code{list} command with @key{RET} discards the argument,
8987 so it is equivalent to typing just @code{list}. This is more useful
8988 than listing the same lines again. An exception is made for an
8989 argument of @samp{-}; that argument is preserved in repetition so that
8990 each repetition moves up in the source file.
8992 In general, the @code{list} command expects you to supply zero, one or two
8993 @dfn{locations}. Locations specify source lines; there are several ways
8994 of writing them (@pxref{Specify Location}), but the effect is always
8995 to specify some source line.
8997 Here is a complete description of the possible arguments for @code{list}:
9000 @item list @var{location}
9001 Print lines centered around the line specified by @var{location}.
9003 @item list @var{first},@var{last}
9004 Print lines from @var{first} to @var{last}. Both arguments are
9005 locations. When a @code{list} command has two locations, and the
9006 source file of the second location is omitted, this refers to
9007 the same source file as the first location.
9009 @item list ,@var{last}
9010 Print lines ending with @var{last}.
9012 @item list @var{first},
9013 Print lines starting with @var{first}.
9016 Print lines just after the lines last printed.
9019 Print lines just before the lines last printed.
9022 As described in the preceding table.
9025 @node Specify Location
9026 @section Specifying a Location
9027 @cindex specifying location
9029 @cindex source location
9031 Several @value{GDBN} commands accept arguments that specify a location
9032 of your program's code. Since @value{GDBN} is a source-level
9033 debugger, a location usually specifies some line in the source code.
9034 Locations may be specified using three different formats:
9035 linespec locations, explicit locations, or address locations.
9038 * Linespec Locations:: Linespec locations
9039 * Explicit Locations:: Explicit locations
9040 * Address Locations:: Address locations
9043 @node Linespec Locations
9044 @subsection Linespec Locations
9045 @cindex linespec locations
9047 A @dfn{linespec} is a colon-separated list of source location parameters such
9048 as file name, function name, etc. Here are all the different ways of
9049 specifying a linespec:
9053 Specifies the line number @var{linenum} of the current source file.
9056 @itemx +@var{offset}
9057 Specifies the line @var{offset} lines before or after the @dfn{current
9058 line}. For the @code{list} command, the current line is the last one
9059 printed; for the breakpoint commands, this is the line at which
9060 execution stopped in the currently selected @dfn{stack frame}
9061 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9062 used as the second of the two linespecs in a @code{list} command,
9063 this specifies the line @var{offset} lines up or down from the first
9066 @item @var{filename}:@var{linenum}
9067 Specifies the line @var{linenum} in the source file @var{filename}.
9068 If @var{filename} is a relative file name, then it will match any
9069 source file name with the same trailing components. For example, if
9070 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9071 name of @file{/build/trunk/gcc/expr.c}, but not
9072 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9074 @item @var{function}
9075 Specifies the line that begins the body of the function @var{function}.
9076 For example, in C, this is the line with the open brace.
9078 By default, in C@t{++} and Ada, @var{function} is interpreted as
9079 specifying all functions named @var{function} in all scopes. For
9080 C@t{++}, this means in all namespaces and classes. For Ada, this
9081 means in all packages.
9083 For example, assuming a program with C@t{++} symbols named
9084 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9085 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9087 Commands that accept a linespec let you override this with the
9088 @code{-qualified} option. For example, @w{@kbd{break -qualified
9089 func}} sets a breakpoint on a free-function named @code{func} ignoring
9090 any C@t{++} class methods and namespace functions called @code{func}.
9092 @xref{Explicit Locations}.
9094 @item @var{function}:@var{label}
9095 Specifies the line where @var{label} appears in @var{function}.
9097 @item @var{filename}:@var{function}
9098 Specifies the line that begins the body of the function @var{function}
9099 in the file @var{filename}. You only need the file name with a
9100 function name to avoid ambiguity when there are identically named
9101 functions in different source files.
9104 Specifies the line at which the label named @var{label} appears
9105 in the function corresponding to the currently selected stack frame.
9106 If there is no current selected stack frame (for instance, if the inferior
9107 is not running), then @value{GDBN} will not search for a label.
9109 @cindex breakpoint at static probe point
9110 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9111 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9112 applications to embed static probes. @xref{Static Probe Points}, for more
9113 information on finding and using static probes. This form of linespec
9114 specifies the location of such a static probe.
9116 If @var{objfile} is given, only probes coming from that shared library
9117 or executable matching @var{objfile} as a regular expression are considered.
9118 If @var{provider} is given, then only probes from that provider are considered.
9119 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9120 each one of those probes.
9123 @node Explicit Locations
9124 @subsection Explicit Locations
9125 @cindex explicit locations
9127 @dfn{Explicit locations} allow the user to directly specify the source
9128 location's parameters using option-value pairs.
9130 Explicit locations are useful when several functions, labels, or
9131 file names have the same name (base name for files) in the program's
9132 sources. In these cases, explicit locations point to the source
9133 line you meant more accurately and unambiguously. Also, using
9134 explicit locations might be faster in large programs.
9136 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9137 defined in the file named @file{foo} or the label @code{bar} in a function
9138 named @code{foo}. @value{GDBN} must search either the file system or
9139 the symbol table to know.
9141 The list of valid explicit location options is summarized in the
9145 @item -source @var{filename}
9146 The value specifies the source file name. To differentiate between
9147 files with the same base name, prepend as many directories as is necessary
9148 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9149 @value{GDBN} will use the first file it finds with the given base
9150 name. This option requires the use of either @code{-function} or @code{-line}.
9152 @item -function @var{function}
9153 The value specifies the name of a function. Operations
9154 on function locations unmodified by other options (such as @code{-label}
9155 or @code{-line}) refer to the line that begins the body of the function.
9156 In C, for example, this is the line with the open brace.
9158 By default, in C@t{++} and Ada, @var{function} is interpreted as
9159 specifying all functions named @var{function} in all scopes. For
9160 C@t{++}, this means in all namespaces and classes. For Ada, this
9161 means in all packages.
9163 For example, assuming a program with C@t{++} symbols named
9164 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9165 -function func}} and @w{@kbd{break -function B::func}} set a
9166 breakpoint on both symbols.
9168 You can use the @kbd{-qualified} flag to override this (see below).
9172 This flag makes @value{GDBN} interpret a function name specified with
9173 @kbd{-function} as a complete fully-qualified name.
9175 For example, assuming a C@t{++} program with symbols named
9176 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9177 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9179 (Note: the @kbd{-qualified} option can precede a linespec as well
9180 (@pxref{Linespec Locations}), so the particular example above could be
9181 simplified as @w{@kbd{break -qualified B::func}}.)
9183 @item -label @var{label}
9184 The value specifies the name of a label. When the function
9185 name is not specified, the label is searched in the function of the currently
9186 selected stack frame.
9188 @item -line @var{number}
9189 The value specifies a line offset for the location. The offset may either
9190 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9191 the command. When specified without any other options, the line offset is
9192 relative to the current line.
9195 Explicit location options may be abbreviated by omitting any non-unique
9196 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9198 @node Address Locations
9199 @subsection Address Locations
9200 @cindex address locations
9202 @dfn{Address locations} indicate a specific program address. They have
9203 the generalized form *@var{address}.
9205 For line-oriented commands, such as @code{list} and @code{edit}, this
9206 specifies a source line that contains @var{address}. For @code{break} and
9207 other breakpoint-oriented commands, this can be used to set breakpoints in
9208 parts of your program which do not have debugging information or
9211 Here @var{address} may be any expression valid in the current working
9212 language (@pxref{Languages, working language}) that specifies a code
9213 address. In addition, as a convenience, @value{GDBN} extends the
9214 semantics of expressions used in locations to cover several situations
9215 that frequently occur during debugging. Here are the various forms
9219 @item @var{expression}
9220 Any expression valid in the current working language.
9222 @item @var{funcaddr}
9223 An address of a function or procedure derived from its name. In C,
9224 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9225 simply the function's name @var{function} (and actually a special case
9226 of a valid expression). In Pascal and Modula-2, this is
9227 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9228 (although the Pascal form also works).
9230 This form specifies the address of the function's first instruction,
9231 before the stack frame and arguments have been set up.
9233 @item '@var{filename}':@var{funcaddr}
9234 Like @var{funcaddr} above, but also specifies the name of the source
9235 file explicitly. This is useful if the name of the function does not
9236 specify the function unambiguously, e.g., if there are several
9237 functions with identical names in different source files.
9241 @section Editing Source Files
9242 @cindex editing source files
9245 @kindex e @r{(@code{edit})}
9246 To edit the lines in a source file, use the @code{edit} command.
9247 The editing program of your choice
9248 is invoked with the current line set to
9249 the active line in the program.
9250 Alternatively, there are several ways to specify what part of the file you
9251 want to print if you want to see other parts of the program:
9254 @item edit @var{location}
9255 Edit the source file specified by @code{location}. Editing starts at
9256 that @var{location}, e.g., at the specified source line of the
9257 specified file. @xref{Specify Location}, for all the possible forms
9258 of the @var{location} argument; here are the forms of the @code{edit}
9259 command most commonly used:
9262 @item edit @var{number}
9263 Edit the current source file with @var{number} as the active line number.
9265 @item edit @var{function}
9266 Edit the file containing @var{function} at the beginning of its definition.
9271 @subsection Choosing your Editor
9272 You can customize @value{GDBN} to use any editor you want
9274 The only restriction is that your editor (say @code{ex}), recognizes the
9275 following command-line syntax:
9277 ex +@var{number} file
9279 The optional numeric value +@var{number} specifies the number of the line in
9280 the file where to start editing.}.
9281 By default, it is @file{@value{EDITOR}}, but you can change this
9282 by setting the environment variable @env{EDITOR} before using
9283 @value{GDBN}. For example, to configure @value{GDBN} to use the
9284 @code{vi} editor, you could use these commands with the @code{sh} shell:
9290 or in the @code{csh} shell,
9292 setenv EDITOR /usr/bin/vi
9297 @section Searching Source Files
9298 @cindex searching source files
9300 There are two commands for searching through the current source file for a
9305 @kindex forward-search
9306 @kindex fo @r{(@code{forward-search})}
9307 @item forward-search @var{regexp}
9308 @itemx search @var{regexp}
9309 The command @samp{forward-search @var{regexp}} checks each line,
9310 starting with the one following the last line listed, for a match for
9311 @var{regexp}. It lists the line that is found. You can use the
9312 synonym @samp{search @var{regexp}} or abbreviate the command name as
9315 @kindex reverse-search
9316 @item reverse-search @var{regexp}
9317 The command @samp{reverse-search @var{regexp}} checks each line, starting
9318 with the one before the last line listed and going backward, for a match
9319 for @var{regexp}. It lists the line that is found. You can abbreviate
9320 this command as @code{rev}.
9324 @section Specifying Source Directories
9327 @cindex directories for source files
9328 Executable programs sometimes do not record the directories of the source
9329 files from which they were compiled, just the names. Even when they do,
9330 the directories could be moved between the compilation and your debugging
9331 session. @value{GDBN} has a list of directories to search for source files;
9332 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9333 it tries all the directories in the list, in the order they are present
9334 in the list, until it finds a file with the desired name.
9336 For example, suppose an executable references the file
9337 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9338 directory, and the @dfn{source path} is @file{/mnt/cross}.
9339 @value{GDBN} would look for the source file in the following
9344 @item @file{/usr/src/foo-1.0/lib/foo.c}
9345 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9346 @item @file{/mnt/cross/foo.c}
9350 If the source file is not present at any of the above locations then
9351 an error is printed. @value{GDBN} does not look up the parts of the
9352 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9353 Likewise, the subdirectories of the source path are not searched: if
9354 the source path is @file{/mnt/cross}, and the binary refers to
9355 @file{foo.c}, @value{GDBN} would not find it under
9356 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9358 Plain file names, relative file names with leading directories, file
9359 names containing dots, etc.@: are all treated as described above,
9360 except that non-absolute file names are not looked up literally. If
9361 the @dfn{source path} is @file{/mnt/cross}, the source file is
9362 recorded as @file{../lib/foo.c}, and no compilation directory is
9363 recorded, then @value{GDBN} will search in the following locations:
9367 @item @file{/mnt/cross/../lib/foo.c}
9368 @item @file{/mnt/cross/foo.c}
9374 @vindex $cdir@r{, convenience variable}
9375 @vindex $cwd@r{, convenience variable}
9376 @cindex compilation directory
9377 @cindex current directory
9378 @cindex working directory
9379 @cindex directory, current
9380 @cindex directory, compilation
9381 The @dfn{source path} will always include two special entries
9382 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9383 (if one is recorded) and the current working directory respectively.
9385 @samp{$cdir} causes @value{GDBN} to search within the compilation
9386 directory, if one is recorded in the debug information. If no
9387 compilation directory is recorded in the debug information then
9388 @samp{$cdir} is ignored.
9390 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9391 current working directory as it changes during your @value{GDBN}
9392 session, while the latter is immediately expanded to the current
9393 directory at the time you add an entry to the source path.
9395 If a compilation directory is recorded in the debug information, and
9396 @value{GDBN} has not found the source file after the first search
9397 using @dfn{source path}, then @value{GDBN} will combine the
9398 compilation directory and the filename, and then search for the source
9399 file again using the @dfn{source path}.
9401 For example, if the executable records the source file as
9402 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9403 recorded as @file{/project/build}, and the @dfn{source path} is
9404 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9405 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9406 search for the source file in the following locations:
9410 @item @file{/usr/src/foo-1.0/lib/foo.c}
9411 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9412 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9413 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9414 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9415 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9416 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9417 @item @file{/mnt/cross/foo.c}
9418 @item @file{/project/build/foo.c}
9419 @item @file{/home/user/foo.c}
9423 If the file name in the previous example had been recorded in the
9424 executable as a relative path rather than an absolute path, then the
9425 first look up would not have occurred, but all of the remaining steps
9428 When searching for source files on MS-DOS and MS-Windows, where
9429 absolute paths start with a drive letter (e.g.@:
9430 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9431 from the file name before appending it to a search directory from
9432 @dfn{source path}; for instance if the executable references the
9433 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9434 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9435 locations for the source file:
9439 @item @file{C:/project/foo.c}
9440 @item @file{D:/mnt/cross/project/foo.c}
9441 @item @file{D:/mnt/cross/foo.c}
9445 Note that the executable search path is @emph{not} used to locate the
9448 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9449 any information it has cached about where source files are found and where
9450 each line is in the file.
9454 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9455 and @samp{$cwd}, in that order.
9456 To add other directories, use the @code{directory} command.
9458 The search path is used to find both program source files and @value{GDBN}
9459 script files (read using the @samp{-command} option and @samp{source} command).
9461 In addition to the source path, @value{GDBN} provides a set of commands
9462 that manage a list of source path substitution rules. A @dfn{substitution
9463 rule} specifies how to rewrite source directories stored in the program's
9464 debug information in case the sources were moved to a different
9465 directory between compilation and debugging. A rule is made of
9466 two strings, the first specifying what needs to be rewritten in
9467 the path, and the second specifying how it should be rewritten.
9468 In @ref{set substitute-path}, we name these two parts @var{from} and
9469 @var{to} respectively. @value{GDBN} does a simple string replacement
9470 of @var{from} with @var{to} at the start of the directory part of the
9471 source file name, and uses that result instead of the original file
9472 name to look up the sources.
9474 Using the previous example, suppose the @file{foo-1.0} tree has been
9475 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9476 @value{GDBN} to replace @file{/usr/src} in all source path names with
9477 @file{/mnt/cross}. The first lookup will then be
9478 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9479 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9480 substitution rule, use the @code{set substitute-path} command
9481 (@pxref{set substitute-path}).
9483 To avoid unexpected substitution results, a rule is applied only if the
9484 @var{from} part of the directory name ends at a directory separator.
9485 For instance, a rule substituting @file{/usr/source} into
9486 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9487 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9488 is applied only at the beginning of the directory name, this rule will
9489 not be applied to @file{/root/usr/source/baz.c} either.
9491 In many cases, you can achieve the same result using the @code{directory}
9492 command. However, @code{set substitute-path} can be more efficient in
9493 the case where the sources are organized in a complex tree with multiple
9494 subdirectories. With the @code{directory} command, you need to add each
9495 subdirectory of your project. If you moved the entire tree while
9496 preserving its internal organization, then @code{set substitute-path}
9497 allows you to direct the debugger to all the sources with one single
9500 @code{set substitute-path} is also more than just a shortcut command.
9501 The source path is only used if the file at the original location no
9502 longer exists. On the other hand, @code{set substitute-path} modifies
9503 the debugger behavior to look at the rewritten location instead. So, if
9504 for any reason a source file that is not relevant to your executable is
9505 located at the original location, a substitution rule is the only
9506 method available to point @value{GDBN} at the new location.
9508 @cindex @samp{--with-relocated-sources}
9509 @cindex default source path substitution
9510 You can configure a default source path substitution rule by
9511 configuring @value{GDBN} with the
9512 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9513 should be the name of a directory under @value{GDBN}'s configured
9514 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9515 directory names in debug information under @var{dir} will be adjusted
9516 automatically if the installed @value{GDBN} is moved to a new
9517 location. This is useful if @value{GDBN}, libraries or executables
9518 with debug information and corresponding source code are being moved
9522 @item directory @var{dirname} @dots{}
9523 @item dir @var{dirname} @dots{}
9524 Add directory @var{dirname} to the front of the source path. Several
9525 directory names may be given to this command, separated by @samp{:}
9526 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9527 part of absolute file names) or
9528 whitespace. You may specify a directory that is already in the source
9529 path; this moves it forward, so @value{GDBN} searches it sooner.
9531 The special strings @samp{$cdir} (to refer to the compilation
9532 directory, if one is recorded), and @samp{$cwd} (to refer to the
9533 current working directory) can also be included in the list of
9534 directories @var{dirname}. Though these will already be in the source
9535 path they will be moved forward in the list so @value{GDBN} searches
9539 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9541 @c RET-repeat for @code{directory} is explicitly disabled, but since
9542 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9544 @item set directories @var{path-list}
9545 @kindex set directories
9546 Set the source path to @var{path-list}.
9547 @samp{$cdir:$cwd} are added if missing.
9549 @item show directories
9550 @kindex show directories
9551 Print the source path: show which directories it contains.
9553 @anchor{set substitute-path}
9554 @item set substitute-path @var{from} @var{to}
9555 @kindex set substitute-path
9556 Define a source path substitution rule, and add it at the end of the
9557 current list of existing substitution rules. If a rule with the same
9558 @var{from} was already defined, then the old rule is also deleted.
9560 For example, if the file @file{/foo/bar/baz.c} was moved to
9561 @file{/mnt/cross/baz.c}, then the command
9564 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9568 will tell @value{GDBN} to replace @samp{/foo/bar} with
9569 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9570 @file{baz.c} even though it was moved.
9572 In the case when more than one substitution rule have been defined,
9573 the rules are evaluated one by one in the order where they have been
9574 defined. The first one matching, if any, is selected to perform
9577 For instance, if we had entered the following commands:
9580 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9581 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9585 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9586 @file{/mnt/include/defs.h} by using the first rule. However, it would
9587 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9588 @file{/mnt/src/lib/foo.c}.
9591 @item unset substitute-path [path]
9592 @kindex unset substitute-path
9593 If a path is specified, search the current list of substitution rules
9594 for a rule that would rewrite that path. Delete that rule if found.
9595 A warning is emitted by the debugger if no rule could be found.
9597 If no path is specified, then all substitution rules are deleted.
9599 @item show substitute-path [path]
9600 @kindex show substitute-path
9601 If a path is specified, then print the source path substitution rule
9602 which would rewrite that path, if any.
9604 If no path is specified, then print all existing source path substitution
9609 If your source path is cluttered with directories that are no longer of
9610 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9611 versions of source. You can correct the situation as follows:
9615 Use @code{directory} with no argument to reset the source path to its default value.
9618 Use @code{directory} with suitable arguments to reinstall the
9619 directories you want in the source path. You can add all the
9620 directories in one command.
9624 @section Source and Machine Code
9625 @cindex source line and its code address
9627 You can use the command @code{info line} to map source lines to program
9628 addresses (and vice versa), and the command @code{disassemble} to display
9629 a range of addresses as machine instructions. You can use the command
9630 @code{set disassemble-next-line} to set whether to disassemble next
9631 source line when execution stops. When run under @sc{gnu} Emacs
9632 mode, the @code{info line} command causes the arrow to point to the
9633 line specified. Also, @code{info line} prints addresses in symbolic form as
9639 @itemx info line @var{location}
9640 Print the starting and ending addresses of the compiled code for
9641 source line @var{location}. You can specify source lines in any of
9642 the ways documented in @ref{Specify Location}. With no @var{location}
9643 information about the current source line is printed.
9646 For example, we can use @code{info line} to discover the location of
9647 the object code for the first line of function
9648 @code{m4_changequote}:
9651 (@value{GDBP}) info line m4_changequote
9652 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9653 ends at 0x6350 <m4_changequote+4>.
9657 @cindex code address and its source line
9658 We can also inquire (using @code{*@var{addr}} as the form for
9659 @var{location}) what source line covers a particular address:
9661 (@value{GDBP}) info line *0x63ff
9662 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9663 ends at 0x6404 <m4_changequote+184>.
9666 @cindex @code{$_} and @code{info line}
9667 @cindex @code{x} command, default address
9668 @kindex x@r{(examine), and} info line
9669 After @code{info line}, the default address for the @code{x} command
9670 is changed to the starting address of the line, so that @samp{x/i} is
9671 sufficient to begin examining the machine code (@pxref{Memory,
9672 ,Examining Memory}). Also, this address is saved as the value of the
9673 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9676 @cindex info line, repeated calls
9677 After @code{info line}, using @code{info line} again without
9678 specifying a location will display information about the next source
9683 @cindex assembly instructions
9684 @cindex instructions, assembly
9685 @cindex machine instructions
9686 @cindex listing machine instructions
9688 @itemx disassemble /m
9689 @itemx disassemble /s
9690 @itemx disassemble /r
9691 This specialized command dumps a range of memory as machine
9692 instructions. It can also print mixed source+disassembly by specifying
9693 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9694 as well as in symbolic form by specifying the @code{/r} modifier.
9695 The default memory range is the function surrounding the
9696 program counter of the selected frame. A single argument to this
9697 command is a program counter value; @value{GDBN} dumps the function
9698 surrounding this value. When two arguments are given, they should
9699 be separated by a comma, possibly surrounded by whitespace. The
9700 arguments specify a range of addresses to dump, in one of two forms:
9703 @item @var{start},@var{end}
9704 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9705 @item @var{start},+@var{length}
9706 the addresses from @var{start} (inclusive) to
9707 @code{@var{start}+@var{length}} (exclusive).
9711 When 2 arguments are specified, the name of the function is also
9712 printed (since there could be several functions in the given range).
9714 The argument(s) can be any expression yielding a numeric value, such as
9715 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9717 If the range of memory being disassembled contains current program counter,
9718 the instruction at that location is shown with a @code{=>} marker.
9721 The following example shows the disassembly of a range of addresses of
9722 HP PA-RISC 2.0 code:
9725 (@value{GDBP}) disas 0x32c4, 0x32e4
9726 Dump of assembler code from 0x32c4 to 0x32e4:
9727 0x32c4 <main+204>: addil 0,dp
9728 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9729 0x32cc <main+212>: ldil 0x3000,r31
9730 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9731 0x32d4 <main+220>: ldo 0(r31),rp
9732 0x32d8 <main+224>: addil -0x800,dp
9733 0x32dc <main+228>: ldo 0x588(r1),r26
9734 0x32e0 <main+232>: ldil 0x3000,r31
9735 End of assembler dump.
9738 Here is an example showing mixed source+assembly for Intel x86
9739 with @code{/m} or @code{/s}, when the program is stopped just after
9740 function prologue in a non-optimized function with no inline code.
9743 (@value{GDBP}) disas /m main
9744 Dump of assembler code for function main:
9746 0x08048330 <+0>: push %ebp
9747 0x08048331 <+1>: mov %esp,%ebp
9748 0x08048333 <+3>: sub $0x8,%esp
9749 0x08048336 <+6>: and $0xfffffff0,%esp
9750 0x08048339 <+9>: sub $0x10,%esp
9752 6 printf ("Hello.\n");
9753 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9754 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9758 0x08048348 <+24>: mov $0x0,%eax
9759 0x0804834d <+29>: leave
9760 0x0804834e <+30>: ret
9762 End of assembler dump.
9765 The @code{/m} option is deprecated as its output is not useful when
9766 there is either inlined code or re-ordered code.
9767 The @code{/s} option is the preferred choice.
9768 Here is an example for AMD x86-64 showing the difference between
9769 @code{/m} output and @code{/s} output.
9770 This example has one inline function defined in a header file,
9771 and the code is compiled with @samp{-O2} optimization.
9772 Note how the @code{/m} output is missing the disassembly of
9773 several instructions that are present in the @code{/s} output.
9803 (@value{GDBP}) disas /m main
9804 Dump of assembler code for function main:
9808 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9809 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9813 0x000000000040041d <+29>: xor %eax,%eax
9814 0x000000000040041f <+31>: retq
9815 0x0000000000400420 <+32>: add %eax,%eax
9816 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9818 End of assembler dump.
9819 (@value{GDBP}) disas /s main
9820 Dump of assembler code for function main:
9824 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9828 0x0000000000400406 <+6>: test %eax,%eax
9829 0x0000000000400408 <+8>: js 0x400420 <main+32>
9834 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9835 0x000000000040040d <+13>: test %eax,%eax
9836 0x000000000040040f <+15>: mov $0x1,%eax
9837 0x0000000000400414 <+20>: cmovne %edx,%eax
9841 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9845 0x000000000040041d <+29>: xor %eax,%eax
9846 0x000000000040041f <+31>: retq
9850 0x0000000000400420 <+32>: add %eax,%eax
9851 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9852 End of assembler dump.
9855 Here is another example showing raw instructions in hex for AMD x86-64,
9858 (gdb) disas /r 0x400281,+10
9859 Dump of assembler code from 0x400281 to 0x40028b:
9860 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9861 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9862 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9863 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9864 End of assembler dump.
9867 Addresses cannot be specified as a location (@pxref{Specify Location}).
9868 So, for example, if you want to disassemble function @code{bar}
9869 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9870 and not @samp{disassemble foo.c:bar}.
9872 Some architectures have more than one commonly-used set of instruction
9873 mnemonics or other syntax.
9875 For programs that were dynamically linked and use shared libraries,
9876 instructions that call functions or branch to locations in the shared
9877 libraries might show a seemingly bogus location---it's actually a
9878 location of the relocation table. On some architectures, @value{GDBN}
9879 might be able to resolve these to actual function names.
9882 @kindex set disassembler-options
9883 @cindex disassembler options
9884 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9885 This command controls the passing of target specific information to
9886 the disassembler. For a list of valid options, please refer to the
9887 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9888 manual and/or the output of @kbd{objdump --help}
9889 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9890 The default value is the empty string.
9892 If it is necessary to specify more than one disassembler option, then
9893 multiple options can be placed together into a comma separated list.
9894 Currently this command is only supported on targets ARC, ARM, MIPS,
9897 @kindex show disassembler-options
9898 @item show disassembler-options
9899 Show the current setting of the disassembler options.
9903 @kindex set disassembly-flavor
9904 @cindex Intel disassembly flavor
9905 @cindex AT&T disassembly flavor
9906 @item set disassembly-flavor @var{instruction-set}
9907 Select the instruction set to use when disassembling the
9908 program via the @code{disassemble} or @code{x/i} commands.
9910 Currently this command is only defined for the Intel x86 family. You
9911 can set @var{instruction-set} to either @code{intel} or @code{att}.
9912 The default is @code{att}, the AT&T flavor used by default by Unix
9913 assemblers for x86-based targets.
9915 @kindex show disassembly-flavor
9916 @item show disassembly-flavor
9917 Show the current setting of the disassembly flavor.
9921 @kindex set disassemble-next-line
9922 @kindex show disassemble-next-line
9923 @item set disassemble-next-line
9924 @itemx show disassemble-next-line
9925 Control whether or not @value{GDBN} will disassemble the next source
9926 line or instruction when execution stops. If ON, @value{GDBN} will
9927 display disassembly of the next source line when execution of the
9928 program being debugged stops. This is @emph{in addition} to
9929 displaying the source line itself, which @value{GDBN} always does if
9930 possible. If the next source line cannot be displayed for some reason
9931 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9932 info in the debug info), @value{GDBN} will display disassembly of the
9933 next @emph{instruction} instead of showing the next source line. If
9934 AUTO, @value{GDBN} will display disassembly of next instruction only
9935 if the source line cannot be displayed. This setting causes
9936 @value{GDBN} to display some feedback when you step through a function
9937 with no line info or whose source file is unavailable. The default is
9938 OFF, which means never display the disassembly of the next line or
9942 @node Disable Reading Source
9943 @section Disable Reading Source Code
9944 @cindex source code, disable access
9946 In some cases it can be desirable to prevent @value{GDBN} from
9947 accessing source code files. One case where this might be desirable
9948 is if the source code files are located over a slow network
9951 The following command can be used to control whether @value{GDBN}
9952 should access source code files or not:
9955 @kindex set source open
9956 @kindex show source open
9957 @item set source open @r{[}on@r{|}off@r{]}
9958 @itemx show source open
9959 When this option is @code{on}, which is the default, @value{GDBN} will
9960 access source code files when needed, for example to print source
9961 lines when @value{GDBN} stops, or in response to the @code{list}
9964 When this option is @code{off}, @value{GDBN} will not access source
9969 @chapter Examining Data
9971 @cindex printing data
9972 @cindex examining data
9975 The usual way to examine data in your program is with the @code{print}
9976 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9977 evaluates and prints the value of an expression of the language your
9978 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9979 Different Languages}). It may also print the expression using a
9980 Python-based pretty-printer (@pxref{Pretty Printing}).
9983 @item print [[@var{options}] --] @var{expr}
9984 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9985 @var{expr} is an expression (in the source language). By default the
9986 value of @var{expr} is printed in a format appropriate to its data type;
9987 you can choose a different format by specifying @samp{/@var{f}}, where
9988 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9991 @anchor{print options}
9992 The @code{print} command supports a number of options that allow
9993 overriding relevant global print settings as set by @code{set print}
9997 @item -address [@code{on}|@code{off}]
9998 Set printing of addresses.
9999 Related setting: @ref{set print address}.
10001 @item -array [@code{on}|@code{off}]
10002 Pretty formatting of arrays.
10003 Related setting: @ref{set print array}.
10005 @item -array-indexes [@code{on}|@code{off}]
10006 Set printing of array indexes.
10007 Related setting: @ref{set print array-indexes}.
10009 @item -elements @var{number-of-elements}|@code{unlimited}
10010 Set limit on string chars or array elements to print. The value
10011 @code{unlimited} causes there to be no limit. Related setting:
10012 @ref{set print elements}.
10014 @item -max-depth @var{depth}|@code{unlimited}
10015 Set the threshold after which nested structures are replaced with
10016 ellipsis. Related setting: @ref{set print max-depth}.
10018 @item -memory-tag-violations [@code{on}|@code{off}]
10019 Set printing of additional information about memory tag violations.
10020 @xref{set print memory-tag-violations}.
10022 @item -null-stop [@code{on}|@code{off}]
10023 Set printing of char arrays to stop at first null char. Related
10024 setting: @ref{set print null-stop}.
10026 @item -object [@code{on}|@code{off}]
10027 Set printing C@t{++} virtual function tables. Related setting:
10028 @ref{set print object}.
10030 @item -pretty [@code{on}|@code{off}]
10031 Set pretty formatting of structures. Related setting: @ref{set print
10034 @item -raw-values [@code{on}|@code{off}]
10035 Set whether to print values in raw form, bypassing any
10036 pretty-printers for that value. Related setting: @ref{set print
10039 @item -repeats @var{number-of-repeats}|@code{unlimited}
10040 Set threshold for repeated print elements. @code{unlimited} causes
10041 all elements to be individually printed. Related setting: @ref{set
10044 @item -static-members [@code{on}|@code{off}]
10045 Set printing C@t{++} static members. Related setting: @ref{set print
10048 @item -symbol [@code{on}|@code{off}]
10049 Set printing of symbol names when printing pointers. Related setting:
10050 @ref{set print symbol}.
10052 @item -union [@code{on}|@code{off}]
10053 Set printing of unions interior to structures. Related setting:
10054 @ref{set print union}.
10056 @item -vtbl [@code{on}|@code{off}]
10057 Set printing of C++ virtual function tables. Related setting:
10058 @ref{set print vtbl}.
10061 Because the @code{print} command accepts arbitrary expressions which
10062 may look like options (including abbreviations), if you specify any
10063 command option, then you must use a double dash (@code{--}) to mark
10064 the end of option processing.
10066 For example, this prints the value of the @code{-p} expression:
10069 (@value{GDBP}) print -p
10072 While this repeats the last value in the value history (see below)
10073 with the @code{-pretty} option in effect:
10076 (@value{GDBP}) print -p --
10079 Here is an example including both on option and an expression:
10083 (@value{GDBP}) print -pretty -- *myptr
10095 @item print [@var{options}]
10096 @itemx print [@var{options}] /@var{f}
10097 @cindex reprint the last value
10098 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10099 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10100 conveniently inspect the same value in an alternative format.
10103 If the architecture supports memory tagging, the @code{print} command will
10104 display pointer/memory tag mismatches if what is being printed is a pointer
10105 or reference type. @xref{Memory Tagging}.
10107 A more low-level way of examining data is with the @code{x} command.
10108 It examines data in memory at a specified address and prints it in a
10109 specified format. @xref{Memory, ,Examining Memory}.
10111 If you are interested in information about types, or about how the
10112 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
10113 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10116 @cindex exploring hierarchical data structures
10118 Another way of examining values of expressions and type information is
10119 through the Python extension command @code{explore} (available only if
10120 the @value{GDBN} build is configured with @code{--with-python}). It
10121 offers an interactive way to start at the highest level (or, the most
10122 abstract level) of the data type of an expression (or, the data type
10123 itself) and explore all the way down to leaf scalar values/fields
10124 embedded in the higher level data types.
10127 @item explore @var{arg}
10128 @var{arg} is either an expression (in the source language), or a type
10129 visible in the current context of the program being debugged.
10132 The working of the @code{explore} command can be illustrated with an
10133 example. If a data type @code{struct ComplexStruct} is defined in your
10137 struct SimpleStruct
10143 struct ComplexStruct
10145 struct SimpleStruct *ss_p;
10151 followed by variable declarations as
10154 struct SimpleStruct ss = @{ 10, 1.11 @};
10155 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10159 then, the value of the variable @code{cs} can be explored using the
10160 @code{explore} command as follows.
10164 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10165 the following fields:
10167 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10168 arr = <Enter 1 to explore this field of type `int [10]'>
10170 Enter the field number of choice:
10174 Since the fields of @code{cs} are not scalar values, you are being
10175 prompted to chose the field you want to explore. Let's say you choose
10176 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10177 pointer, you will be asked if it is pointing to a single value. From
10178 the declaration of @code{cs} above, it is indeed pointing to a single
10179 value, hence you enter @code{y}. If you enter @code{n}, then you will
10180 be asked if it were pointing to an array of values, in which case this
10181 field will be explored as if it were an array.
10184 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10185 Continue exploring it as a pointer to a single value [y/n]: y
10186 The value of `*(cs.ss_p)' is a struct/class of type `struct
10187 SimpleStruct' with the following fields:
10189 i = 10 .. (Value of type `int')
10190 d = 1.1100000000000001 .. (Value of type `double')
10192 Press enter to return to parent value:
10196 If the field @code{arr} of @code{cs} was chosen for exploration by
10197 entering @code{1} earlier, then since it is as array, you will be
10198 prompted to enter the index of the element in the array that you want
10202 `cs.arr' is an array of `int'.
10203 Enter the index of the element you want to explore in `cs.arr': 5
10205 `(cs.arr)[5]' is a scalar value of type `int'.
10209 Press enter to return to parent value:
10212 In general, at any stage of exploration, you can go deeper towards the
10213 leaf values by responding to the prompts appropriately, or hit the
10214 return key to return to the enclosing data structure (the @i{higher}
10215 level data structure).
10217 Similar to exploring values, you can use the @code{explore} command to
10218 explore types. Instead of specifying a value (which is typically a
10219 variable name or an expression valid in the current context of the
10220 program being debugged), you specify a type name. If you consider the
10221 same example as above, your can explore the type
10222 @code{struct ComplexStruct} by passing the argument
10223 @code{struct ComplexStruct} to the @code{explore} command.
10226 (gdb) explore struct ComplexStruct
10230 By responding to the prompts appropriately in the subsequent interactive
10231 session, you can explore the type @code{struct ComplexStruct} in a
10232 manner similar to how the value @code{cs} was explored in the above
10235 The @code{explore} command also has two sub-commands,
10236 @code{explore value} and @code{explore type}. The former sub-command is
10237 a way to explicitly specify that value exploration of the argument is
10238 being invoked, while the latter is a way to explicitly specify that type
10239 exploration of the argument is being invoked.
10242 @item explore value @var{expr}
10243 @cindex explore value
10244 This sub-command of @code{explore} explores the value of the
10245 expression @var{expr} (if @var{expr} is an expression valid in the
10246 current context of the program being debugged). The behavior of this
10247 command is identical to that of the behavior of the @code{explore}
10248 command being passed the argument @var{expr}.
10250 @item explore type @var{arg}
10251 @cindex explore type
10252 This sub-command of @code{explore} explores the type of @var{arg} (if
10253 @var{arg} is a type visible in the current context of program being
10254 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10255 is an expression valid in the current context of the program being
10256 debugged). If @var{arg} is a type, then the behavior of this command is
10257 identical to that of the @code{explore} command being passed the
10258 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10259 this command will be identical to that of the @code{explore} command
10260 being passed the type of @var{arg} as the argument.
10264 * Expressions:: Expressions
10265 * Ambiguous Expressions:: Ambiguous Expressions
10266 * Variables:: Program variables
10267 * Arrays:: Artificial arrays
10268 * Output Formats:: Output formats
10269 * Memory:: Examining memory
10270 * Memory Tagging:: Memory Tagging
10271 * Auto Display:: Automatic display
10272 * Print Settings:: Print settings
10273 * Pretty Printing:: Python pretty printing
10274 * Value History:: Value history
10275 * Convenience Vars:: Convenience variables
10276 * Convenience Funs:: Convenience functions
10277 * Registers:: Registers
10278 * Floating Point Hardware:: Floating point hardware
10279 * Vector Unit:: Vector Unit
10280 * OS Information:: Auxiliary data provided by operating system
10281 * Memory Region Attributes:: Memory region attributes
10282 * Dump/Restore Files:: Copy between memory and a file
10283 * Core File Generation:: Cause a program dump its core
10284 * Character Sets:: Debugging programs that use a different
10285 character set than GDB does
10286 * Caching Target Data:: Data caching for targets
10287 * Searching Memory:: Searching memory for a sequence of bytes
10288 * Value Sizes:: Managing memory allocated for values
10292 @section Expressions
10294 @cindex expressions
10295 @code{print} and many other @value{GDBN} commands accept an expression and
10296 compute its value. Any kind of constant, variable or operator defined
10297 by the programming language you are using is valid in an expression in
10298 @value{GDBN}. This includes conditional expressions, function calls,
10299 casts, and string constants. It also includes preprocessor macros, if
10300 you compiled your program to include this information; see
10303 @cindex arrays in expressions
10304 @value{GDBN} supports array constants in expressions input by
10305 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10306 you can use the command @code{print @{1, 2, 3@}} to create an array
10307 of three integers. If you pass an array to a function or assign it
10308 to a program variable, @value{GDBN} copies the array to memory that
10309 is @code{malloc}ed in the target program.
10311 Because C is so widespread, most of the expressions shown in examples in
10312 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10313 Languages}, for information on how to use expressions in other
10316 In this section, we discuss operators that you can use in @value{GDBN}
10317 expressions regardless of your programming language.
10319 @cindex casts, in expressions
10320 Casts are supported in all languages, not just in C, because it is so
10321 useful to cast a number into a pointer in order to examine a structure
10322 at that address in memory.
10323 @c FIXME: casts supported---Mod2 true?
10325 @value{GDBN} supports these operators, in addition to those common
10326 to programming languages:
10330 @samp{@@} is a binary operator for treating parts of memory as arrays.
10331 @xref{Arrays, ,Artificial Arrays}, for more information.
10334 @samp{::} allows you to specify a variable in terms of the file or
10335 function where it is defined. @xref{Variables, ,Program Variables}.
10337 @cindex @{@var{type}@}
10338 @cindex type casting memory
10339 @cindex memory, viewing as typed object
10340 @cindex casts, to view memory
10341 @item @{@var{type}@} @var{addr}
10342 Refers to an object of type @var{type} stored at address @var{addr} in
10343 memory. The address @var{addr} may be any expression whose value is
10344 an integer or pointer (but parentheses are required around binary
10345 operators, just as in a cast). This construct is allowed regardless
10346 of what kind of data is normally supposed to reside at @var{addr}.
10349 @node Ambiguous Expressions
10350 @section Ambiguous Expressions
10351 @cindex ambiguous expressions
10353 Expressions can sometimes contain some ambiguous elements. For instance,
10354 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10355 a single function name to be defined several times, for application in
10356 different contexts. This is called @dfn{overloading}. Another example
10357 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10358 templates and is typically instantiated several times, resulting in
10359 the same function name being defined in different contexts.
10361 In some cases and depending on the language, it is possible to adjust
10362 the expression to remove the ambiguity. For instance in C@t{++}, you
10363 can specify the signature of the function you want to break on, as in
10364 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10365 qualified name of your function often makes the expression unambiguous
10368 When an ambiguity that needs to be resolved is detected, the debugger
10369 has the capability to display a menu of numbered choices for each
10370 possibility, and then waits for the selection with the prompt @samp{>}.
10371 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10372 aborts the current command. If the command in which the expression was
10373 used allows more than one choice to be selected, the next option in the
10374 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10377 For example, the following session excerpt shows an attempt to set a
10378 breakpoint at the overloaded symbol @code{String::after}.
10379 We choose three particular definitions of that function name:
10381 @c FIXME! This is likely to change to show arg type lists, at least
10384 (@value{GDBP}) b String::after
10387 [2] file:String.cc; line number:867
10388 [3] file:String.cc; line number:860
10389 [4] file:String.cc; line number:875
10390 [5] file:String.cc; line number:853
10391 [6] file:String.cc; line number:846
10392 [7] file:String.cc; line number:735
10394 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10395 Breakpoint 2 at 0xb344: file String.cc, line 875.
10396 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10397 Multiple breakpoints were set.
10398 Use the "delete" command to delete unwanted
10405 @kindex set multiple-symbols
10406 @item set multiple-symbols @var{mode}
10407 @cindex multiple-symbols menu
10409 This option allows you to adjust the debugger behavior when an expression
10412 By default, @var{mode} is set to @code{all}. If the command with which
10413 the expression is used allows more than one choice, then @value{GDBN}
10414 automatically selects all possible choices. For instance, inserting
10415 a breakpoint on a function using an ambiguous name results in a breakpoint
10416 inserted on each possible match. However, if a unique choice must be made,
10417 then @value{GDBN} uses the menu to help you disambiguate the expression.
10418 For instance, printing the address of an overloaded function will result
10419 in the use of the menu.
10421 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10422 when an ambiguity is detected.
10424 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10425 an error due to the ambiguity and the command is aborted.
10427 @kindex show multiple-symbols
10428 @item show multiple-symbols
10429 Show the current value of the @code{multiple-symbols} setting.
10433 @section Program Variables
10435 The most common kind of expression to use is the name of a variable
10438 Variables in expressions are understood in the selected stack frame
10439 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10443 global (or file-static)
10450 visible according to the scope rules of the
10451 programming language from the point of execution in that frame
10454 @noindent This means that in the function
10469 you can examine and use the variable @code{a} whenever your program is
10470 executing within the function @code{foo}, but you can only use or
10471 examine the variable @code{b} while your program is executing inside
10472 the block where @code{b} is declared.
10474 @cindex variable name conflict
10475 There is an exception: you can refer to a variable or function whose
10476 scope is a single source file even if the current execution point is not
10477 in this file. But it is possible to have more than one such variable or
10478 function with the same name (in different source files). If that
10479 happens, referring to that name has unpredictable effects. If you wish,
10480 you can specify a static variable in a particular function or file by
10481 using the colon-colon (@code{::}) notation:
10483 @cindex colon-colon, context for variables/functions
10485 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10486 @cindex @code{::}, context for variables/functions
10489 @var{file}::@var{variable}
10490 @var{function}::@var{variable}
10494 Here @var{file} or @var{function} is the name of the context for the
10495 static @var{variable}. In the case of file names, you can use quotes to
10496 make sure @value{GDBN} parses the file name as a single word---for example,
10497 to print a global value of @code{x} defined in @file{f2.c}:
10500 (@value{GDBP}) p 'f2.c'::x
10503 The @code{::} notation is normally used for referring to
10504 static variables, since you typically disambiguate uses of local variables
10505 in functions by selecting the appropriate frame and using the
10506 simple name of the variable. However, you may also use this notation
10507 to refer to local variables in frames enclosing the selected frame:
10516 process (a); /* Stop here */
10527 For example, if there is a breakpoint at the commented line,
10528 here is what you might see
10529 when the program stops after executing the call @code{bar(0)}:
10534 (@value{GDBP}) p bar::a
10536 (@value{GDBP}) up 2
10537 #2 0x080483d0 in foo (a=5) at foobar.c:12
10540 (@value{GDBP}) p bar::a
10544 @cindex C@t{++} scope resolution
10545 These uses of @samp{::} are very rarely in conflict with the very
10546 similar use of the same notation in C@t{++}. When they are in
10547 conflict, the C@t{++} meaning takes precedence; however, this can be
10548 overridden by quoting the file or function name with single quotes.
10550 For example, suppose the program is stopped in a method of a class
10551 that has a field named @code{includefile}, and there is also an
10552 include file named @file{includefile} that defines a variable,
10553 @code{some_global}.
10556 (@value{GDBP}) p includefile
10558 (@value{GDBP}) p includefile::some_global
10559 A syntax error in expression, near `'.
10560 (@value{GDBP}) p 'includefile'::some_global
10564 @cindex wrong values
10565 @cindex variable values, wrong
10566 @cindex function entry/exit, wrong values of variables
10567 @cindex optimized code, wrong values of variables
10569 @emph{Warning:} Occasionally, a local variable may appear to have the
10570 wrong value at certain points in a function---just after entry to a new
10571 scope, and just before exit.
10573 You may see this problem when you are stepping by machine instructions.
10574 This is because, on most machines, it takes more than one instruction to
10575 set up a stack frame (including local variable definitions); if you are
10576 stepping by machine instructions, variables may appear to have the wrong
10577 values until the stack frame is completely built. On exit, it usually
10578 also takes more than one machine instruction to destroy a stack frame;
10579 after you begin stepping through that group of instructions, local
10580 variable definitions may be gone.
10582 This may also happen when the compiler does significant optimizations.
10583 To be sure of always seeing accurate values, turn off all optimization
10586 @cindex ``No symbol "foo" in current context''
10587 Another possible effect of compiler optimizations is to optimize
10588 unused variables out of existence, or assign variables to registers (as
10589 opposed to memory addresses). Depending on the support for such cases
10590 offered by the debug info format used by the compiler, @value{GDBN}
10591 might not be able to display values for such local variables. If that
10592 happens, @value{GDBN} will print a message like this:
10595 No symbol "foo" in current context.
10598 To solve such problems, either recompile without optimizations, or use a
10599 different debug info format, if the compiler supports several such
10600 formats. @xref{Compilation}, for more information on choosing compiler
10601 options. @xref{C, ,C and C@t{++}}, for more information about debug
10602 info formats that are best suited to C@t{++} programs.
10604 If you ask to print an object whose contents are unknown to
10605 @value{GDBN}, e.g., because its data type is not completely specified
10606 by the debug information, @value{GDBN} will say @samp{<incomplete
10607 type>}. @xref{Symbols, incomplete type}, for more about this.
10609 @cindex no debug info variables
10610 If you try to examine or use the value of a (global) variable for
10611 which @value{GDBN} has no type information, e.g., because the program
10612 includes no debug information, @value{GDBN} displays an error message.
10613 @xref{Symbols, unknown type}, for more about unknown types. If you
10614 cast the variable to its declared type, @value{GDBN} gets the
10615 variable's value using the cast-to type as the variable's type. For
10616 example, in a C program:
10619 (@value{GDBP}) p var
10620 'var' has unknown type; cast it to its declared type
10621 (@value{GDBP}) p (float) var
10625 If you append @kbd{@@entry} string to a function parameter name you get its
10626 value at the time the function got called. If the value is not available an
10627 error message is printed. Entry values are available only with some compilers.
10628 Entry values are normally also printed at the function parameter list according
10629 to @ref{set print entry-values}.
10632 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10638 (gdb) print i@@entry
10642 Strings are identified as arrays of @code{char} values without specified
10643 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10644 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10645 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10646 defines literal string type @code{"char"} as @code{char} without a sign.
10651 signed char var1[] = "A";
10654 You get during debugging
10659 $2 = @{65 'A', 0 '\0'@}
10663 @section Artificial Arrays
10665 @cindex artificial array
10667 @kindex @@@r{, referencing memory as an array}
10668 It is often useful to print out several successive objects of the
10669 same type in memory; a section of an array, or an array of
10670 dynamically determined size for which only a pointer exists in the
10673 You can do this by referring to a contiguous span of memory as an
10674 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10675 operand of @samp{@@} should be the first element of the desired array
10676 and be an individual object. The right operand should be the desired length
10677 of the array. The result is an array value whose elements are all of
10678 the type of the left argument. The first element is actually the left
10679 argument; the second element comes from bytes of memory immediately
10680 following those that hold the first element, and so on. Here is an
10681 example. If a program says
10684 int *array = (int *) malloc (len * sizeof (int));
10688 you can print the contents of @code{array} with
10694 The left operand of @samp{@@} must reside in memory. Array values made
10695 with @samp{@@} in this way behave just like other arrays in terms of
10696 subscripting, and are coerced to pointers when used in expressions.
10697 Artificial arrays most often appear in expressions via the value history
10698 (@pxref{Value History, ,Value History}), after printing one out.
10700 Another way to create an artificial array is to use a cast.
10701 This re-interprets a value as if it were an array.
10702 The value need not be in memory:
10704 (@value{GDBP}) p/x (short[2])0x12345678
10705 $1 = @{0x1234, 0x5678@}
10708 As a convenience, if you leave the array length out (as in
10709 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10710 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10712 (@value{GDBP}) p/x (short[])0x12345678
10713 $2 = @{0x1234, 0x5678@}
10716 Sometimes the artificial array mechanism is not quite enough; in
10717 moderately complex data structures, the elements of interest may not
10718 actually be adjacent---for example, if you are interested in the values
10719 of pointers in an array. One useful work-around in this situation is
10720 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10721 Variables}) as a counter in an expression that prints the first
10722 interesting value, and then repeat that expression via @key{RET}. For
10723 instance, suppose you have an array @code{dtab} of pointers to
10724 structures, and you are interested in the values of a field @code{fv}
10725 in each structure. Here is an example of what you might type:
10735 @node Output Formats
10736 @section Output Formats
10738 @cindex formatted output
10739 @cindex output formats
10740 By default, @value{GDBN} prints a value according to its data type. Sometimes
10741 this is not what you want. For example, you might want to print a number
10742 in hex, or a pointer in decimal. Or you might want to view data in memory
10743 at a certain address as a character string or as an instruction. To do
10744 these things, specify an @dfn{output format} when you print a value.
10746 The simplest use of output formats is to say how to print a value
10747 already computed. This is done by starting the arguments of the
10748 @code{print} command with a slash and a format letter. The format
10749 letters supported are:
10753 Regard the bits of the value as an integer, and print the integer in
10757 Print as integer in signed decimal.
10760 Print as integer in unsigned decimal.
10763 Print as integer in octal.
10766 Print as integer in binary. The letter @samp{t} stands for ``two''.
10767 @footnote{@samp{b} cannot be used because these format letters are also
10768 used with the @code{x} command, where @samp{b} stands for ``byte'';
10769 see @ref{Memory,,Examining Memory}.}
10772 @cindex unknown address, locating
10773 @cindex locate address
10774 Print as an address, both absolute in hexadecimal and as an offset from
10775 the nearest preceding symbol. You can use this format used to discover
10776 where (in what function) an unknown address is located:
10779 (@value{GDBP}) p/a 0x54320
10780 $3 = 0x54320 <_initialize_vx+396>
10784 The command @code{info symbol 0x54320} yields similar results.
10785 @xref{Symbols, info symbol}.
10788 Regard as an integer and print it as a character constant. This
10789 prints both the numerical value and its character representation. The
10790 character representation is replaced with the octal escape @samp{\nnn}
10791 for characters outside the 7-bit @sc{ascii} range.
10793 Without this format, @value{GDBN} displays @code{char},
10794 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10795 constants. Single-byte members of vectors are displayed as integer
10799 Regard the bits of the value as a floating point number and print
10800 using typical floating point syntax.
10803 @cindex printing strings
10804 @cindex printing byte arrays
10805 Regard as a string, if possible. With this format, pointers to single-byte
10806 data are displayed as null-terminated strings and arrays of single-byte data
10807 are displayed as fixed-length strings. Other values are displayed in their
10810 Without this format, @value{GDBN} displays pointers to and arrays of
10811 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10812 strings. Single-byte members of a vector are displayed as an integer
10816 Like @samp{x} formatting, the value is treated as an integer and
10817 printed as hexadecimal, but leading zeros are printed to pad the value
10818 to the size of the integer type.
10821 @cindex raw printing
10822 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10823 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10824 Printing}). This typically results in a higher-level display of the
10825 value's contents. The @samp{r} format bypasses any Python
10826 pretty-printer which might exist.
10829 For example, to print the program counter in hex (@pxref{Registers}), type
10836 Note that no space is required before the slash; this is because command
10837 names in @value{GDBN} cannot contain a slash.
10839 To reprint the last value in the value history with a different format,
10840 you can use the @code{print} command with just a format and no
10841 expression. For example, @samp{p/x} reprints the last value in hex.
10844 @section Examining Memory
10846 You can use the command @code{x} (for ``examine'') to examine memory in
10847 any of several formats, independently of your program's data types.
10849 @cindex examining memory
10851 @kindex x @r{(examine memory)}
10852 @item x/@var{nfu} @var{addr}
10853 @itemx x @var{addr}
10855 Use the @code{x} command to examine memory.
10858 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10859 much memory to display and how to format it; @var{addr} is an
10860 expression giving the address where you want to start displaying memory.
10861 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10862 Several commands set convenient defaults for @var{addr}.
10865 @item @var{n}, the repeat count
10866 The repeat count is a decimal integer; the default is 1. It specifies
10867 how much memory (counting by units @var{u}) to display. If a negative
10868 number is specified, memory is examined backward from @var{addr}.
10869 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10872 @item @var{f}, the display format
10873 The display format is one of the formats used by @code{print}
10874 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10875 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
10876 @samp{m} (for displaying memory tags).
10877 The default is @samp{x} (hexadecimal) initially. The default changes
10878 each time you use either @code{x} or @code{print}.
10880 @item @var{u}, the unit size
10881 The unit size is any of
10887 Halfwords (two bytes).
10889 Words (four bytes). This is the initial default.
10891 Giant words (eight bytes).
10894 Each time you specify a unit size with @code{x}, that size becomes the
10895 default unit the next time you use @code{x}. For the @samp{i} format,
10896 the unit size is ignored and is normally not written. For the @samp{s} format,
10897 the unit size defaults to @samp{b}, unless it is explicitly given.
10898 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10899 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10900 Note that the results depend on the programming language of the
10901 current compilation unit. If the language is C, the @samp{s}
10902 modifier will use the UTF-16 encoding while @samp{w} will use
10903 UTF-32. The encoding is set by the programming language and cannot
10906 @item @var{addr}, starting display address
10907 @var{addr} is the address where you want @value{GDBN} to begin displaying
10908 memory. The expression need not have a pointer value (though it may);
10909 it is always interpreted as an integer address of a byte of memory.
10910 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10911 @var{addr} is usually just after the last address examined---but several
10912 other commands also set the default address: @code{info breakpoints} (to
10913 the address of the last breakpoint listed), @code{info line} (to the
10914 starting address of a line), and @code{print} (if you use it to display
10915 a value from memory).
10918 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10919 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10920 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10921 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10922 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10924 You can also specify a negative repeat count to examine memory backward
10925 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10926 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
10928 Since the letters indicating unit sizes are all distinct from the
10929 letters specifying output formats, you do not have to remember whether
10930 unit size or format comes first; either order works. The output
10931 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10932 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10934 Even though the unit size @var{u} is ignored for the formats @samp{s}
10935 and @samp{i}, you might still want to use a count @var{n}; for example,
10936 @samp{3i} specifies that you want to see three machine instructions,
10937 including any operands. For convenience, especially when used with
10938 the @code{display} command, the @samp{i} format also prints branch delay
10939 slot instructions, if any, beyond the count specified, which immediately
10940 follow the last instruction that is within the count. The command
10941 @code{disassemble} gives an alternative way of inspecting machine
10942 instructions; see @ref{Machine Code,,Source and Machine Code}.
10944 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10945 the command displays null-terminated strings or instructions before the given
10946 address as many as the absolute value of the given number. For the @samp{i}
10947 format, we use line number information in the debug info to accurately locate
10948 instruction boundaries while disassembling backward. If line info is not
10949 available, the command stops examining memory with an error message.
10951 All the defaults for the arguments to @code{x} are designed to make it
10952 easy to continue scanning memory with minimal specifications each time
10953 you use @code{x}. For example, after you have inspected three machine
10954 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10955 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10956 the repeat count @var{n} is used again; the other arguments default as
10957 for successive uses of @code{x}.
10959 When examining machine instructions, the instruction at current program
10960 counter is shown with a @code{=>} marker. For example:
10963 (@value{GDBP}) x/5i $pc-6
10964 0x804837f <main+11>: mov %esp,%ebp
10965 0x8048381 <main+13>: push %ecx
10966 0x8048382 <main+14>: sub $0x4,%esp
10967 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10968 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10971 If the architecture supports memory tagging, the tags can be displayed by
10972 using @samp{m}. @xref{Memory Tagging}.
10974 The information will be displayed once per granule size
10975 (the amount of bytes a particular memory tag covers). For example, AArch64
10976 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
10978 Due to the way @value{GDBN} prints information with the @code{x} command (not
10979 aligned to a particular boundary), the tag information will refer to the
10980 initial address displayed on a particular line. If a memory tag boundary
10981 is crossed in the middle of a line displayed by the @code{x} command, it
10982 will be displayed on the next line.
10984 The @samp{m} format doesn't affect any other specified formats that were
10985 passed to the @code{x} command.
10987 @cindex @code{$_}, @code{$__}, and value history
10988 The addresses and contents printed by the @code{x} command are not saved
10989 in the value history because there is often too much of them and they
10990 would get in the way. Instead, @value{GDBN} makes these values available for
10991 subsequent use in expressions as values of the convenience variables
10992 @code{$_} and @code{$__}. After an @code{x} command, the last address
10993 examined is available for use in expressions in the convenience variable
10994 @code{$_}. The contents of that address, as examined, are available in
10995 the convenience variable @code{$__}.
10997 If the @code{x} command has a repeat count, the address and contents saved
10998 are from the last memory unit printed; this is not the same as the last
10999 address printed if several units were printed on the last line of output.
11001 @anchor{addressable memory unit}
11002 @cindex addressable memory unit
11003 Most targets have an addressable memory unit size of 8 bits. This means
11004 that to each memory address are associated 8 bits of data. Some
11005 targets, however, have other addressable memory unit sizes.
11006 Within @value{GDBN} and this document, the term
11007 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11008 when explicitly referring to a chunk of data of that size. The word
11009 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11010 the addressable memory unit size of the target. For most systems,
11011 addressable memory unit is a synonym of byte.
11013 @cindex remote memory comparison
11014 @cindex target memory comparison
11015 @cindex verify remote memory image
11016 @cindex verify target memory image
11017 When you are debugging a program running on a remote target machine
11018 (@pxref{Remote Debugging}), you may wish to verify the program's image
11019 in the remote machine's memory against the executable file you
11020 downloaded to the target. Or, on any target, you may want to check
11021 whether the program has corrupted its own read-only sections. The
11022 @code{compare-sections} command is provided for such situations.
11025 @kindex compare-sections
11026 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11027 Compare the data of a loadable section @var{section-name} in the
11028 executable file of the program being debugged with the same section in
11029 the target machine's memory, and report any mismatches. With no
11030 arguments, compares all loadable sections. With an argument of
11031 @code{-r}, compares all loadable read-only sections.
11033 Note: for remote targets, this command can be accelerated if the
11034 target supports computing the CRC checksum of a block of memory
11035 (@pxref{qCRC packet}).
11038 @node Memory Tagging
11039 @section Memory Tagging
11041 Memory tagging is a memory protection technology that uses a pair of tags to
11042 validate memory accesses through pointers. The tags are integer values
11043 usually comprised of a few bits, depending on the architecture.
11045 There are two types of tags that are used in this setup: logical and
11046 allocation. A logical tag is stored in the pointers themselves, usually at the
11047 higher bits of the pointers. An allocation tag is the tag associated
11048 with particular ranges of memory in the physical address space, against which
11049 the logical tags from pointers are compared.
11051 The pointer tag (logical tag) must match the memory tag (allocation tag)
11052 for the memory access to be valid. If the logical tag does not match the
11053 allocation tag, that will raise a memory violation.
11055 Allocation tags cover multiple contiguous bytes of physical memory. This
11056 range of bytes is called a memory tag granule and is architecture-specific.
11057 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11058 tag spans 16 bytes of memory.
11060 If the underlying architecture supports memory tagging, like AArch64 MTE
11061 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11062 against memory allocation tags.
11064 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11065 display tag information when appropriate, and a command prefix of
11066 @code{memory-tag} gives access to the various memory tagging commands.
11068 The @code{memory-tag} commands are the following:
11071 @kindex memory-tag print-logical-tag
11072 @item memory-tag print-logical-tag @var{pointer_expression}
11073 Print the logical tag stored in @var{pointer_expression}.
11074 @kindex memory-tag with-logical-tag
11075 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11076 Print the pointer given by @var{pointer_expression}, augmented with a logical
11077 tag of @var{tag_bytes}.
11078 @kindex memory-tag print-allocation-tag
11079 @item memory-tag print-allocation-tag @var{address_expression}
11080 Print the allocation tag associated with the memory address given by
11081 @var{address_expression}.
11082 @kindex memory-tag setatag
11083 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11084 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11085 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11086 @kindex memory-tag check
11087 @item memory-tag check @var{pointer_expression}
11088 Check if the logical tag in the pointer given by @var{pointer_expression}
11089 matches the allocation tag for the memory referenced by the pointer.
11091 This essentially emulates the hardware validation that is done when tagged
11092 memory is accessed through a pointer, but does not cause a memory fault as
11093 it would during hardware validation.
11095 It can be used to inspect potential memory tagging violations in the running
11096 process, before any faults get triggered.
11100 @section Automatic Display
11101 @cindex automatic display
11102 @cindex display of expressions
11104 If you find that you want to print the value of an expression frequently
11105 (to see how it changes), you might want to add it to the @dfn{automatic
11106 display list} so that @value{GDBN} prints its value each time your program stops.
11107 Each expression added to the list is given a number to identify it;
11108 to remove an expression from the list, you specify that number.
11109 The automatic display looks like this:
11113 3: bar[5] = (struct hack *) 0x3804
11117 This display shows item numbers, expressions and their current values. As with
11118 displays you request manually using @code{x} or @code{print}, you can
11119 specify the output format you prefer; in fact, @code{display} decides
11120 whether to use @code{print} or @code{x} depending your format
11121 specification---it uses @code{x} if you specify either the @samp{i}
11122 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11126 @item display @var{expr}
11127 Add the expression @var{expr} to the list of expressions to display
11128 each time your program stops. @xref{Expressions, ,Expressions}.
11130 @code{display} does not repeat if you press @key{RET} again after using it.
11132 @item display/@var{fmt} @var{expr}
11133 For @var{fmt} specifying only a display format and not a size or
11134 count, add the expression @var{expr} to the auto-display list but
11135 arrange to display it each time in the specified format @var{fmt}.
11136 @xref{Output Formats,,Output Formats}.
11138 @item display/@var{fmt} @var{addr}
11139 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11140 number of units, add the expression @var{addr} as a memory address to
11141 be examined each time your program stops. Examining means in effect
11142 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11145 For example, @samp{display/i $pc} can be helpful, to see the machine
11146 instruction about to be executed each time execution stops (@samp{$pc}
11147 is a common name for the program counter; @pxref{Registers, ,Registers}).
11150 @kindex delete display
11152 @item undisplay @var{dnums}@dots{}
11153 @itemx delete display @var{dnums}@dots{}
11154 Remove items from the list of expressions to display. Specify the
11155 numbers of the displays that you want affected with the command
11156 argument @var{dnums}. It can be a single display number, one of the
11157 numbers shown in the first field of the @samp{info display} display;
11158 or it could be a range of display numbers, as in @code{2-4}.
11160 @code{undisplay} does not repeat if you press @key{RET} after using it.
11161 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11163 @kindex disable display
11164 @item disable display @var{dnums}@dots{}
11165 Disable the display of item numbers @var{dnums}. A disabled display
11166 item is not printed automatically, but is not forgotten. It may be
11167 enabled again later. Specify the numbers of the displays that you
11168 want affected with the command argument @var{dnums}. It can be a
11169 single display number, one of the numbers shown in the first field of
11170 the @samp{info display} display; or it could be a range of display
11171 numbers, as in @code{2-4}.
11173 @kindex enable display
11174 @item enable display @var{dnums}@dots{}
11175 Enable display of item numbers @var{dnums}. It becomes effective once
11176 again in auto display of its expression, until you specify otherwise.
11177 Specify the numbers of the displays that you want affected with the
11178 command argument @var{dnums}. It can be a single display number, one
11179 of the numbers shown in the first field of the @samp{info display}
11180 display; or it could be a range of display numbers, as in @code{2-4}.
11183 Display the current values of the expressions on the list, just as is
11184 done when your program stops.
11186 @kindex info display
11188 Print the list of expressions previously set up to display
11189 automatically, each one with its item number, but without showing the
11190 values. This includes disabled expressions, which are marked as such.
11191 It also includes expressions which would not be displayed right now
11192 because they refer to automatic variables not currently available.
11195 @cindex display disabled out of scope
11196 If a display expression refers to local variables, then it does not make
11197 sense outside the lexical context for which it was set up. Such an
11198 expression is disabled when execution enters a context where one of its
11199 variables is not defined. For example, if you give the command
11200 @code{display last_char} while inside a function with an argument
11201 @code{last_char}, @value{GDBN} displays this argument while your program
11202 continues to stop inside that function. When it stops elsewhere---where
11203 there is no variable @code{last_char}---the display is disabled
11204 automatically. The next time your program stops where @code{last_char}
11205 is meaningful, you can enable the display expression once again.
11207 @node Print Settings
11208 @section Print Settings
11210 @cindex format options
11211 @cindex print settings
11212 @value{GDBN} provides the following ways to control how arrays, structures,
11213 and symbols are printed.
11216 These settings are useful for debugging programs in any language:
11220 @anchor{set print address}
11221 @item set print address
11222 @itemx set print address on
11223 @cindex print/don't print memory addresses
11224 @value{GDBN} prints memory addresses showing the location of stack
11225 traces, structure values, pointer values, breakpoints, and so forth,
11226 even when it also displays the contents of those addresses. The default
11227 is @code{on}. For example, this is what a stack frame display looks like with
11228 @code{set print address on}:
11233 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11235 530 if (lquote != def_lquote)
11239 @item set print address off
11240 Do not print addresses when displaying their contents. For example,
11241 this is the same stack frame displayed with @code{set print address off}:
11245 (@value{GDBP}) set print addr off
11247 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11248 530 if (lquote != def_lquote)
11252 You can use @samp{set print address off} to eliminate all machine
11253 dependent displays from the @value{GDBN} interface. For example, with
11254 @code{print address off}, you should get the same text for backtraces on
11255 all machines---whether or not they involve pointer arguments.
11258 @item show print address
11259 Show whether or not addresses are to be printed.
11262 When @value{GDBN} prints a symbolic address, it normally prints the
11263 closest earlier symbol plus an offset. If that symbol does not uniquely
11264 identify the address (for example, it is a name whose scope is a single
11265 source file), you may need to clarify. One way to do this is with
11266 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11267 you can set @value{GDBN} to print the source file and line number when
11268 it prints a symbolic address:
11271 @item set print symbol-filename on
11272 @cindex source file and line of a symbol
11273 @cindex symbol, source file and line
11274 Tell @value{GDBN} to print the source file name and line number of a
11275 symbol in the symbolic form of an address.
11277 @item set print symbol-filename off
11278 Do not print source file name and line number of a symbol. This is the
11281 @item show print symbol-filename
11282 Show whether or not @value{GDBN} will print the source file name and
11283 line number of a symbol in the symbolic form of an address.
11286 Another situation where it is helpful to show symbol filenames and line
11287 numbers is when disassembling code; @value{GDBN} shows you the line
11288 number and source file that corresponds to each instruction.
11290 Also, you may wish to see the symbolic form only if the address being
11291 printed is reasonably close to the closest earlier symbol:
11294 @item set print max-symbolic-offset @var{max-offset}
11295 @itemx set print max-symbolic-offset unlimited
11296 @cindex maximum value for offset of closest symbol
11297 Tell @value{GDBN} to only display the symbolic form of an address if the
11298 offset between the closest earlier symbol and the address is less than
11299 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11300 to always print the symbolic form of an address if any symbol precedes
11301 it. Zero is equivalent to @code{unlimited}.
11303 @item show print max-symbolic-offset
11304 Ask how large the maximum offset is that @value{GDBN} prints in a
11308 @cindex wild pointer, interpreting
11309 @cindex pointer, finding referent
11310 If you have a pointer and you are not sure where it points, try
11311 @samp{set print symbol-filename on}. Then you can determine the name
11312 and source file location of the variable where it points, using
11313 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11314 For example, here @value{GDBN} shows that a variable @code{ptt} points
11315 at another variable @code{t}, defined in @file{hi2.c}:
11318 (@value{GDBP}) set print symbol-filename on
11319 (@value{GDBP}) p/a ptt
11320 $4 = 0xe008 <t in hi2.c>
11324 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11325 does not show the symbol name and filename of the referent, even with
11326 the appropriate @code{set print} options turned on.
11329 You can also enable @samp{/a}-like formatting all the time using
11330 @samp{set print symbol on}:
11332 @anchor{set print symbol}
11334 @item set print symbol on
11335 Tell @value{GDBN} to print the symbol corresponding to an address, if
11338 @item set print symbol off
11339 Tell @value{GDBN} not to print the symbol corresponding to an
11340 address. In this mode, @value{GDBN} will still print the symbol
11341 corresponding to pointers to functions. This is the default.
11343 @item show print symbol
11344 Show whether @value{GDBN} will display the symbol corresponding to an
11348 Other settings control how different kinds of objects are printed:
11351 @anchor{set print array}
11352 @item set print array
11353 @itemx set print array on
11354 @cindex pretty print arrays
11355 Pretty print arrays. This format is more convenient to read,
11356 but uses more space. The default is off.
11358 @item set print array off
11359 Return to compressed format for arrays.
11361 @item show print array
11362 Show whether compressed or pretty format is selected for displaying
11365 @cindex print array indexes
11366 @anchor{set print array-indexes}
11367 @item set print array-indexes
11368 @itemx set print array-indexes on
11369 Print the index of each element when displaying arrays. May be more
11370 convenient to locate a given element in the array or quickly find the
11371 index of a given element in that printed array. The default is off.
11373 @item set print array-indexes off
11374 Stop printing element indexes when displaying arrays.
11376 @item show print array-indexes
11377 Show whether the index of each element is printed when displaying
11380 @anchor{set print elements}
11381 @item set print elements @var{number-of-elements}
11382 @itemx set print elements unlimited
11383 @cindex number of array elements to print
11384 @cindex limit on number of printed array elements
11385 Set a limit on how many elements of an array @value{GDBN} will print.
11386 If @value{GDBN} is printing a large array, it stops printing after it has
11387 printed the number of elements set by the @code{set print elements} command.
11388 This limit also applies to the display of strings.
11389 When @value{GDBN} starts, this limit is set to 200.
11390 Setting @var{number-of-elements} to @code{unlimited} or zero means
11391 that the number of elements to print is unlimited.
11393 @item show print elements
11394 Display the number of elements of a large array that @value{GDBN} will print.
11396 @anchor{set print frame-arguments}
11397 @item set print frame-arguments @var{value}
11398 @kindex set print frame-arguments
11399 @cindex printing frame argument values
11400 @cindex print all frame argument values
11401 @cindex print frame argument values for scalars only
11402 @cindex do not print frame arguments
11403 This command allows to control how the values of arguments are printed
11404 when the debugger prints a frame (@pxref{Frames}). The possible
11409 The values of all arguments are printed.
11412 Print the value of an argument only if it is a scalar. The value of more
11413 complex arguments such as arrays, structures, unions, etc, is replaced
11414 by @code{@dots{}}. This is the default. Here is an example where
11415 only scalar arguments are shown:
11418 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11423 None of the argument values are printed. Instead, the value of each argument
11424 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11427 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11432 Only the presence of arguments is indicated by @code{@dots{}}.
11433 The @code{@dots{}} are not printed for function without any arguments.
11434 None of the argument names and values are printed.
11435 In this case, the example above now becomes:
11438 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11443 By default, only scalar arguments are printed. This command can be used
11444 to configure the debugger to print the value of all arguments, regardless
11445 of their type. However, it is often advantageous to not print the value
11446 of more complex parameters. For instance, it reduces the amount of
11447 information printed in each frame, making the backtrace more readable.
11448 Also, it improves performance when displaying Ada frames, because
11449 the computation of large arguments can sometimes be CPU-intensive,
11450 especially in large applications. Setting @code{print frame-arguments}
11451 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11452 this computation, thus speeding up the display of each Ada frame.
11454 @item show print frame-arguments
11455 Show how the value of arguments should be displayed when printing a frame.
11457 @anchor{set print raw-frame-arguments}
11458 @item set print raw-frame-arguments on
11459 Print frame arguments in raw, non pretty-printed, form.
11461 @item set print raw-frame-arguments off
11462 Print frame arguments in pretty-printed form, if there is a pretty-printer
11463 for the value (@pxref{Pretty Printing}),
11464 otherwise print the value in raw form.
11465 This is the default.
11467 @item show print raw-frame-arguments
11468 Show whether to print frame arguments in raw form.
11470 @anchor{set print entry-values}
11471 @item set print entry-values @var{value}
11472 @kindex set print entry-values
11473 Set printing of frame argument values at function entry. In some cases
11474 @value{GDBN} can determine the value of function argument which was passed by
11475 the function caller, even if the value was modified inside the called function
11476 and therefore is different. With optimized code, the current value could be
11477 unavailable, but the entry value may still be known.
11479 The default value is @code{default} (see below for its description). Older
11480 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11481 this feature will behave in the @code{default} setting the same way as with the
11484 This functionality is currently supported only by DWARF 2 debugging format and
11485 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11486 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11489 The @var{value} parameter can be one of the following:
11493 Print only actual parameter values, never print values from function entry
11497 #0 different (val=6)
11498 #0 lost (val=<optimized out>)
11500 #0 invalid (val=<optimized out>)
11504 Print only parameter values from function entry point. The actual parameter
11505 values are never printed.
11507 #0 equal (val@@entry=5)
11508 #0 different (val@@entry=5)
11509 #0 lost (val@@entry=5)
11510 #0 born (val@@entry=<optimized out>)
11511 #0 invalid (val@@entry=<optimized out>)
11515 Print only parameter values from function entry point. If value from function
11516 entry point is not known while the actual value is known, print the actual
11517 value for such parameter.
11519 #0 equal (val@@entry=5)
11520 #0 different (val@@entry=5)
11521 #0 lost (val@@entry=5)
11523 #0 invalid (val@@entry=<optimized out>)
11527 Print actual parameter values. If actual parameter value is not known while
11528 value from function entry point is known, print the entry point value for such
11532 #0 different (val=6)
11533 #0 lost (val@@entry=5)
11535 #0 invalid (val=<optimized out>)
11539 Always print both the actual parameter value and its value from function entry
11540 point, even if values of one or both are not available due to compiler
11543 #0 equal (val=5, val@@entry=5)
11544 #0 different (val=6, val@@entry=5)
11545 #0 lost (val=<optimized out>, val@@entry=5)
11546 #0 born (val=10, val@@entry=<optimized out>)
11547 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11551 Print the actual parameter value if it is known and also its value from
11552 function entry point if it is known. If neither is known, print for the actual
11553 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11554 values are known and identical, print the shortened
11555 @code{param=param@@entry=VALUE} notation.
11557 #0 equal (val=val@@entry=5)
11558 #0 different (val=6, val@@entry=5)
11559 #0 lost (val@@entry=5)
11561 #0 invalid (val=<optimized out>)
11565 Always print the actual parameter value. Print also its value from function
11566 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11567 if both values are known and identical, print the shortened
11568 @code{param=param@@entry=VALUE} notation.
11570 #0 equal (val=val@@entry=5)
11571 #0 different (val=6, val@@entry=5)
11572 #0 lost (val=<optimized out>, val@@entry=5)
11574 #0 invalid (val=<optimized out>)
11578 For analysis messages on possible failures of frame argument values at function
11579 entry resolution see @ref{set debug entry-values}.
11581 @item show print entry-values
11582 Show the method being used for printing of frame argument values at function
11585 @anchor{set print frame-info}
11586 @item set print frame-info @var{value}
11587 @kindex set print frame-info
11588 @cindex printing frame information
11589 @cindex frame information, printing
11590 This command allows to control the information printed when
11591 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11592 for a general explanation about frames and frame information.
11593 Note that some other settings (such as @code{set print frame-arguments}
11594 and @code{set print address}) are also influencing if and how some frame
11595 information is displayed. In particular, the frame program counter is never
11596 printed if @code{set print address} is off.
11598 The possible values for @code{set print frame-info} are:
11600 @item short-location
11601 Print the frame level, the program counter (if not at the
11602 beginning of the location source line), the function, the function
11605 Same as @code{short-location} but also print the source file and source line
11607 @item location-and-address
11608 Same as @code{location} but print the program counter even if located at the
11609 beginning of the location source line.
11611 Print the program counter (if not at the beginning of the location
11612 source line), the line number and the source line.
11613 @item source-and-location
11614 Print what @code{location} and @code{source-line} are printing.
11616 The information printed for a frame is decided automatically
11617 by the @value{GDBN} command that prints a frame.
11618 For example, @code{frame} prints the information printed by
11619 @code{source-and-location} while @code{stepi} will switch between
11620 @code{source-line} and @code{source-and-location} depending on the program
11622 The default value is @code{auto}.
11625 @anchor{set print repeats}
11626 @item set print repeats @var{number-of-repeats}
11627 @itemx set print repeats unlimited
11628 @cindex repeated array elements
11629 Set the threshold for suppressing display of repeated array
11630 elements. When the number of consecutive identical elements of an
11631 array exceeds the threshold, @value{GDBN} prints the string
11632 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11633 identical repetitions, instead of displaying the identical elements
11634 themselves. Setting the threshold to @code{unlimited} or zero will
11635 cause all elements to be individually printed. The default threshold
11638 @item show print repeats
11639 Display the current threshold for printing repeated identical
11642 @anchor{set print max-depth}
11643 @item set print max-depth @var{depth}
11644 @item set print max-depth unlimited
11645 @cindex printing nested structures
11646 Set the threshold after which nested structures are replaced with
11647 ellipsis, this can make visualising deeply nested structures easier.
11649 For example, given this C code
11652 typedef struct s1 @{ int a; @} s1;
11653 typedef struct s2 @{ s1 b; @} s2;
11654 typedef struct s3 @{ s2 c; @} s3;
11655 typedef struct s4 @{ s3 d; @} s4;
11657 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11660 The following table shows how different values of @var{depth} will
11661 effect how @code{var} is printed by @value{GDBN}:
11663 @multitable @columnfractions .3 .7
11664 @headitem @var{depth} setting @tab Result of @samp{p var}
11666 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11668 @tab @code{$1 = @{...@}}
11670 @tab @code{$1 = @{d = @{...@}@}}
11672 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11674 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11676 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11679 To see the contents of structures that have been hidden the user can
11680 either increase the print max-depth, or they can print the elements of
11681 the structure that are visible, for example
11684 (gdb) set print max-depth 2
11686 $1 = @{d = @{c = @{...@}@}@}
11688 $2 = @{c = @{b = @{...@}@}@}
11690 $3 = @{b = @{a = 3@}@}
11693 The pattern used to replace nested structures varies based on
11694 language, for most languages @code{@{...@}} is used, but Fortran uses
11697 @item show print max-depth
11698 Display the current threshold after which nested structures are
11699 replaces with ellipsis.
11701 @anchor{set print memory-tag-violations}
11702 @cindex printing memory tag violation information
11703 @item set print memory-tag-violations
11704 @itemx set print memory-tag-violations on
11705 Cause @value{GDBN} to display additional information about memory tag violations
11706 when printing pointers and addresses.
11708 @item set print memory-tag-violations off
11709 Stop printing memory tag violation information.
11711 @item show print memory-tag-violations
11712 Show whether memory tag violation information is displayed when printing
11713 pointers and addresses.
11715 @anchor{set print null-stop}
11716 @item set print null-stop
11717 @cindex @sc{null} elements in arrays
11718 Cause @value{GDBN} to stop printing the characters of an array when the first
11719 @sc{null} is encountered. This is useful when large arrays actually
11720 contain only short strings.
11721 The default is off.
11723 @item show print null-stop
11724 Show whether @value{GDBN} stops printing an array on the first
11725 @sc{null} character.
11727 @anchor{set print pretty}
11728 @item set print pretty on
11729 @cindex print structures in indented form
11730 @cindex indentation in structure display
11731 Cause @value{GDBN} to print structures in an indented format with one member
11732 per line, like this:
11747 @item set print pretty off
11748 Cause @value{GDBN} to print structures in a compact format, like this:
11752 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11753 meat = 0x54 "Pork"@}
11758 This is the default format.
11760 @item show print pretty
11761 Show which format @value{GDBN} is using to print structures.
11763 @anchor{set print raw-values}
11764 @item set print raw-values on
11765 Print values in raw form, without applying the pretty
11766 printers for the value.
11768 @item set print raw-values off
11769 Print values in pretty-printed form, if there is a pretty-printer
11770 for the value (@pxref{Pretty Printing}),
11771 otherwise print the value in raw form.
11773 The default setting is ``off''.
11775 @item show print raw-values
11776 Show whether to print values in raw form.
11778 @item set print sevenbit-strings on
11779 @cindex eight-bit characters in strings
11780 @cindex octal escapes in strings
11781 Print using only seven-bit characters; if this option is set,
11782 @value{GDBN} displays any eight-bit characters (in strings or
11783 character values) using the notation @code{\}@var{nnn}. This setting is
11784 best if you are working in English (@sc{ascii}) and you use the
11785 high-order bit of characters as a marker or ``meta'' bit.
11787 @item set print sevenbit-strings off
11788 Print full eight-bit characters. This allows the use of more
11789 international character sets, and is the default.
11791 @item show print sevenbit-strings
11792 Show whether or not @value{GDBN} is printing only seven-bit characters.
11794 @anchor{set print union}
11795 @item set print union on
11796 @cindex unions in structures, printing
11797 Tell @value{GDBN} to print unions which are contained in structures
11798 and other unions. This is the default setting.
11800 @item set print union off
11801 Tell @value{GDBN} not to print unions which are contained in
11802 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11805 @item show print union
11806 Ask @value{GDBN} whether or not it will print unions which are contained in
11807 structures and other unions.
11809 For example, given the declarations
11812 typedef enum @{Tree, Bug@} Species;
11813 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11814 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11825 struct thing foo = @{Tree, @{Acorn@}@};
11829 with @code{set print union on} in effect @samp{p foo} would print
11832 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11836 and with @code{set print union off} in effect it would print
11839 $1 = @{it = Tree, form = @{...@}@}
11843 @code{set print union} affects programs written in C-like languages
11849 These settings are of interest when debugging C@t{++} programs:
11852 @cindex demangling C@t{++} names
11853 @item set print demangle
11854 @itemx set print demangle on
11855 Print C@t{++} names in their source form rather than in the encoded
11856 (``mangled'') form passed to the assembler and linker for type-safe
11857 linkage. The default is on.
11859 @item show print demangle
11860 Show whether C@t{++} names are printed in mangled or demangled form.
11862 @item set print asm-demangle
11863 @itemx set print asm-demangle on
11864 Print C@t{++} names in their source form rather than their mangled form, even
11865 in assembler code printouts such as instruction disassemblies.
11866 The default is off.
11868 @item show print asm-demangle
11869 Show whether C@t{++} names in assembly listings are printed in mangled
11872 @cindex C@t{++} symbol decoding style
11873 @cindex symbol decoding style, C@t{++}
11874 @kindex set demangle-style
11875 @item set demangle-style @var{style}
11876 Choose among several encoding schemes used by different compilers to represent
11877 C@t{++} names. If you omit @var{style}, you will see a list of possible
11878 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11879 decoding style by inspecting your program.
11881 @item show demangle-style
11882 Display the encoding style currently in use for decoding C@t{++} symbols.
11884 @anchor{set print object}
11885 @item set print object
11886 @itemx set print object on
11887 @cindex derived type of an object, printing
11888 @cindex display derived types
11889 When displaying a pointer to an object, identify the @emph{actual}
11890 (derived) type of the object rather than the @emph{declared} type, using
11891 the virtual function table. Note that the virtual function table is
11892 required---this feature can only work for objects that have run-time
11893 type identification; a single virtual method in the object's declared
11894 type is sufficient. Note that this setting is also taken into account when
11895 working with variable objects via MI (@pxref{GDB/MI}).
11897 @item set print object off
11898 Display only the declared type of objects, without reference to the
11899 virtual function table. This is the default setting.
11901 @item show print object
11902 Show whether actual, or declared, object types are displayed.
11904 @anchor{set print static-members}
11905 @item set print static-members
11906 @itemx set print static-members on
11907 @cindex static members of C@t{++} objects
11908 Print static members when displaying a C@t{++} object. The default is on.
11910 @item set print static-members off
11911 Do not print static members when displaying a C@t{++} object.
11913 @item show print static-members
11914 Show whether C@t{++} static members are printed or not.
11916 @item set print pascal_static-members
11917 @itemx set print pascal_static-members on
11918 @cindex static members of Pascal objects
11919 @cindex Pascal objects, static members display
11920 Print static members when displaying a Pascal object. The default is on.
11922 @item set print pascal_static-members off
11923 Do not print static members when displaying a Pascal object.
11925 @item show print pascal_static-members
11926 Show whether Pascal static members are printed or not.
11928 @c These don't work with HP ANSI C++ yet.
11929 @anchor{set print vtbl}
11930 @item set print vtbl
11931 @itemx set print vtbl on
11932 @cindex pretty print C@t{++} virtual function tables
11933 @cindex virtual functions (C@t{++}) display
11934 @cindex VTBL display
11935 Pretty print C@t{++} virtual function tables. The default is off.
11936 (The @code{vtbl} commands do not work on programs compiled with the HP
11937 ANSI C@t{++} compiler (@code{aCC}).)
11939 @item set print vtbl off
11940 Do not pretty print C@t{++} virtual function tables.
11942 @item show print vtbl
11943 Show whether C@t{++} virtual function tables are pretty printed, or not.
11946 @node Pretty Printing
11947 @section Pretty Printing
11949 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11950 Python code. It greatly simplifies the display of complex objects. This
11951 mechanism works for both MI and the CLI.
11954 * Pretty-Printer Introduction:: Introduction to pretty-printers
11955 * Pretty-Printer Example:: An example pretty-printer
11956 * Pretty-Printer Commands:: Pretty-printer commands
11959 @node Pretty-Printer Introduction
11960 @subsection Pretty-Printer Introduction
11962 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11963 registered for the value. If there is then @value{GDBN} invokes the
11964 pretty-printer to print the value. Otherwise the value is printed normally.
11966 Pretty-printers are normally named. This makes them easy to manage.
11967 The @samp{info pretty-printer} command will list all the installed
11968 pretty-printers with their names.
11969 If a pretty-printer can handle multiple data types, then its
11970 @dfn{subprinters} are the printers for the individual data types.
11971 Each such subprinter has its own name.
11972 The format of the name is @var{printer-name};@var{subprinter-name}.
11974 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11975 Typically they are automatically loaded and registered when the corresponding
11976 debug information is loaded, thus making them available without having to
11977 do anything special.
11979 There are three places where a pretty-printer can be registered.
11983 Pretty-printers registered globally are available when debugging
11987 Pretty-printers registered with a program space are available only
11988 when debugging that program.
11989 @xref{Progspaces In Python}, for more details on program spaces in Python.
11992 Pretty-printers registered with an objfile are loaded and unloaded
11993 with the corresponding objfile (e.g., shared library).
11994 @xref{Objfiles In Python}, for more details on objfiles in Python.
11997 @xref{Selecting Pretty-Printers}, for further information on how
11998 pretty-printers are selected,
12000 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12003 @node Pretty-Printer Example
12004 @subsection Pretty-Printer Example
12006 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12009 (@value{GDBP}) print s
12011 static npos = 4294967295,
12013 <std::allocator<char>> = @{
12014 <__gnu_cxx::new_allocator<char>> = @{
12015 <No data fields>@}, <No data fields>
12017 members of std::basic_string<char, std::char_traits<char>,
12018 std::allocator<char> >::_Alloc_hider:
12019 _M_p = 0x804a014 "abcd"
12024 With a pretty-printer for @code{std::string} only the contents are printed:
12027 (@value{GDBP}) print s
12031 @node Pretty-Printer Commands
12032 @subsection Pretty-Printer Commands
12033 @cindex pretty-printer commands
12036 @kindex info pretty-printer
12037 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12038 Print the list of installed pretty-printers.
12039 This includes disabled pretty-printers, which are marked as such.
12041 @var{object-regexp} is a regular expression matching the objects
12042 whose pretty-printers to list.
12043 Objects can be @code{global}, the program space's file
12044 (@pxref{Progspaces In Python}),
12045 and the object files within that program space (@pxref{Objfiles In Python}).
12046 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12047 looks up a printer from these three objects.
12049 @var{name-regexp} is a regular expression matching the name of the printers
12052 @kindex disable pretty-printer
12053 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12054 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12055 A disabled pretty-printer is not forgotten, it may be enabled again later.
12057 @kindex enable pretty-printer
12058 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12059 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12064 Suppose we have three pretty-printers installed: one from library1.so
12065 named @code{foo} that prints objects of type @code{foo}, and
12066 another from library2.so named @code{bar} that prints two types of objects,
12067 @code{bar1} and @code{bar2}.
12070 (gdb) info pretty-printer
12077 (gdb) info pretty-printer library2
12082 (gdb) disable pretty-printer library1
12084 2 of 3 printers enabled
12085 (gdb) info pretty-printer
12092 (gdb) disable pretty-printer library2 bar;bar1
12094 1 of 3 printers enabled
12095 (gdb) info pretty-printer library2
12102 (gdb) disable pretty-printer library2 bar
12104 0 of 3 printers enabled
12105 (gdb) info pretty-printer library2
12114 Note that for @code{bar} the entire printer can be disabled,
12115 as can each individual subprinter.
12117 Printing values and frame arguments is done by default using
12118 the enabled pretty printers.
12120 The print option @code{-raw-values} and @value{GDBN} setting
12121 @code{set print raw-values} (@pxref{set print raw-values}) can be
12122 used to print values without applying the enabled pretty printers.
12124 Similarly, the backtrace option @code{-raw-frame-arguments} and
12125 @value{GDBN} setting @code{set print raw-frame-arguments}
12126 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12127 enabled pretty printers when printing frame argument values.
12129 @node Value History
12130 @section Value History
12132 @cindex value history
12133 @cindex history of values printed by @value{GDBN}
12134 Values printed by the @code{print} command are saved in the @value{GDBN}
12135 @dfn{value history}. This allows you to refer to them in other expressions.
12136 Values are kept until the symbol table is re-read or discarded
12137 (for example with the @code{file} or @code{symbol-file} commands).
12138 When the symbol table changes, the value history is discarded,
12139 since the values may contain pointers back to the types defined in the
12144 @cindex history number
12145 The values printed are given @dfn{history numbers} by which you can
12146 refer to them. These are successive integers starting with one.
12147 @code{print} shows you the history number assigned to a value by
12148 printing @samp{$@var{num} = } before the value; here @var{num} is the
12151 To refer to any previous value, use @samp{$} followed by the value's
12152 history number. The way @code{print} labels its output is designed to
12153 remind you of this. Just @code{$} refers to the most recent value in
12154 the history, and @code{$$} refers to the value before that.
12155 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12156 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12157 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12159 For example, suppose you have just printed a pointer to a structure and
12160 want to see the contents of the structure. It suffices to type
12166 If you have a chain of structures where the component @code{next} points
12167 to the next one, you can print the contents of the next one with this:
12174 You can print successive links in the chain by repeating this
12175 command---which you can do by just typing @key{RET}.
12177 Note that the history records values, not expressions. If the value of
12178 @code{x} is 4 and you type these commands:
12186 then the value recorded in the value history by the @code{print} command
12187 remains 4 even though the value of @code{x} has changed.
12190 @kindex show values
12192 Print the last ten values in the value history, with their item numbers.
12193 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12194 values} does not change the history.
12196 @item show values @var{n}
12197 Print ten history values centered on history item number @var{n}.
12199 @item show values +
12200 Print ten history values just after the values last printed. If no more
12201 values are available, @code{show values +} produces no display.
12204 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12205 same effect as @samp{show values +}.
12207 @node Convenience Vars
12208 @section Convenience Variables
12210 @cindex convenience variables
12211 @cindex user-defined variables
12212 @value{GDBN} provides @dfn{convenience variables} that you can use within
12213 @value{GDBN} to hold on to a value and refer to it later. These variables
12214 exist entirely within @value{GDBN}; they are not part of your program, and
12215 setting a convenience variable has no direct effect on further execution
12216 of your program. That is why you can use them freely.
12218 Convenience variables are prefixed with @samp{$}. Any name preceded by
12219 @samp{$} can be used for a convenience variable, unless it is one of
12220 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12221 (Value history references, in contrast, are @emph{numbers} preceded
12222 by @samp{$}. @xref{Value History, ,Value History}.)
12224 You can save a value in a convenience variable with an assignment
12225 expression, just as you would set a variable in your program.
12229 set $foo = *object_ptr
12233 would save in @code{$foo} the value contained in the object pointed to by
12236 Using a convenience variable for the first time creates it, but its
12237 value is @code{void} until you assign a new value. You can alter the
12238 value with another assignment at any time.
12240 Convenience variables have no fixed types. You can assign a convenience
12241 variable any type of value, including structures and arrays, even if
12242 that variable already has a value of a different type. The convenience
12243 variable, when used as an expression, has the type of its current value.
12246 @kindex show convenience
12247 @cindex show all user variables and functions
12248 @item show convenience
12249 Print a list of convenience variables used so far, and their values,
12250 as well as a list of the convenience functions.
12251 Abbreviated @code{show conv}.
12253 @kindex init-if-undefined
12254 @cindex convenience variables, initializing
12255 @item init-if-undefined $@var{variable} = @var{expression}
12256 Set a convenience variable if it has not already been set. This is useful
12257 for user-defined commands that keep some state. It is similar, in concept,
12258 to using local static variables with initializers in C (except that
12259 convenience variables are global). It can also be used to allow users to
12260 override default values used in a command script.
12262 If the variable is already defined then the expression is not evaluated so
12263 any side-effects do not occur.
12266 One of the ways to use a convenience variable is as a counter to be
12267 incremented or a pointer to be advanced. For example, to print
12268 a field from successive elements of an array of structures:
12272 print bar[$i++]->contents
12276 Repeat that command by typing @key{RET}.
12278 Some convenience variables are created automatically by @value{GDBN} and given
12279 values likely to be useful.
12282 @vindex $_@r{, convenience variable}
12284 The variable @code{$_} is automatically set by the @code{x} command to
12285 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12286 commands which provide a default address for @code{x} to examine also
12287 set @code{$_} to that address; these commands include @code{info line}
12288 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12289 except when set by the @code{x} command, in which case it is a pointer
12290 to the type of @code{$__}.
12292 @vindex $__@r{, convenience variable}
12294 The variable @code{$__} is automatically set by the @code{x} command
12295 to the value found in the last address examined. Its type is chosen
12296 to match the format in which the data was printed.
12299 @vindex $_exitcode@r{, convenience variable}
12300 When the program being debugged terminates normally, @value{GDBN}
12301 automatically sets this variable to the exit code of the program, and
12302 resets @code{$_exitsignal} to @code{void}.
12305 @vindex $_exitsignal@r{, convenience variable}
12306 When the program being debugged dies due to an uncaught signal,
12307 @value{GDBN} automatically sets this variable to that signal's number,
12308 and resets @code{$_exitcode} to @code{void}.
12310 To distinguish between whether the program being debugged has exited
12311 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12312 @code{$_exitsignal} is not @code{void}), the convenience function
12313 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12314 Functions}). For example, considering the following source code:
12317 #include <signal.h>
12320 main (int argc, char *argv[])
12327 A valid way of telling whether the program being debugged has exited
12328 or signalled would be:
12331 (@value{GDBP}) define has_exited_or_signalled
12332 Type commands for definition of ``has_exited_or_signalled''.
12333 End with a line saying just ``end''.
12334 >if $_isvoid ($_exitsignal)
12335 >echo The program has exited\n
12337 >echo The program has signalled\n
12343 Program terminated with signal SIGALRM, Alarm clock.
12344 The program no longer exists.
12345 (@value{GDBP}) has_exited_or_signalled
12346 The program has signalled
12349 As can be seen, @value{GDBN} correctly informs that the program being
12350 debugged has signalled, since it calls @code{raise} and raises a
12351 @code{SIGALRM} signal. If the program being debugged had not called
12352 @code{raise}, then @value{GDBN} would report a normal exit:
12355 (@value{GDBP}) has_exited_or_signalled
12356 The program has exited
12360 The variable @code{$_exception} is set to the exception object being
12361 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12363 @item $_ada_exception
12364 The variable @code{$_ada_exception} is set to the address of the
12365 exception being caught or thrown at an Ada exception-related
12366 catchpoint. @xref{Set Catchpoints}.
12369 @itemx $_probe_arg0@dots{}$_probe_arg11
12370 Arguments to a static probe. @xref{Static Probe Points}.
12373 @vindex $_sdata@r{, inspect, convenience variable}
12374 The variable @code{$_sdata} contains extra collected static tracepoint
12375 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12376 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12377 if extra static tracepoint data has not been collected.
12380 @vindex $_siginfo@r{, convenience variable}
12381 The variable @code{$_siginfo} contains extra signal information
12382 (@pxref{extra signal information}). Note that @code{$_siginfo}
12383 could be empty, if the application has not yet received any signals.
12384 For example, it will be empty before you execute the @code{run} command.
12387 @vindex $_tlb@r{, convenience variable}
12388 The variable @code{$_tlb} is automatically set when debugging
12389 applications running on MS-Windows in native mode or connected to
12390 gdbserver that supports the @code{qGetTIBAddr} request.
12391 @xref{General Query Packets}.
12392 This variable contains the address of the thread information block.
12395 The number of the current inferior. @xref{Inferiors Connections and
12396 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12399 The thread number of the current thread. @xref{thread numbers}.
12402 The global number of the current thread. @xref{global thread numbers}.
12406 @vindex $_gdb_major@r{, convenience variable}
12407 @vindex $_gdb_minor@r{, convenience variable}
12408 The major and minor version numbers of the running @value{GDBN}.
12409 Development snapshots and pretest versions have their minor version
12410 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12411 the value 12 for @code{$_gdb_minor}. These variables allow you to
12412 write scripts that work with different versions of @value{GDBN}
12413 without errors caused by features unavailable in some of those
12416 @item $_shell_exitcode
12417 @itemx $_shell_exitsignal
12418 @vindex $_shell_exitcode@r{, convenience variable}
12419 @vindex $_shell_exitsignal@r{, convenience variable}
12420 @cindex shell command, exit code
12421 @cindex shell command, exit signal
12422 @cindex exit status of shell commands
12423 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12424 shell commands. When a launched command terminates, @value{GDBN}
12425 automatically maintains the variables @code{$_shell_exitcode}
12426 and @code{$_shell_exitsignal} according to the exit status of the last
12427 launched command. These variables are set and used similarly to
12428 the variables @code{$_exitcode} and @code{$_exitsignal}.
12432 @node Convenience Funs
12433 @section Convenience Functions
12435 @cindex convenience functions
12436 @value{GDBN} also supplies some @dfn{convenience functions}. These
12437 have a syntax similar to convenience variables. A convenience
12438 function can be used in an expression just like an ordinary function;
12439 however, a convenience function is implemented internally to
12442 These functions do not require @value{GDBN} to be configured with
12443 @code{Python} support, which means that they are always available.
12447 @item $_isvoid (@var{expr})
12448 @findex $_isvoid@r{, convenience function}
12449 Return one if the expression @var{expr} is @code{void}. Otherwise it
12452 A @code{void} expression is an expression where the type of the result
12453 is @code{void}. For example, you can examine a convenience variable
12454 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12458 (@value{GDBP}) print $_exitcode
12460 (@value{GDBP}) print $_isvoid ($_exitcode)
12463 Starting program: ./a.out
12464 [Inferior 1 (process 29572) exited normally]
12465 (@value{GDBP}) print $_exitcode
12467 (@value{GDBP}) print $_isvoid ($_exitcode)
12471 In the example above, we used @code{$_isvoid} to check whether
12472 @code{$_exitcode} is @code{void} before and after the execution of the
12473 program being debugged. Before the execution there is no exit code to
12474 be examined, therefore @code{$_exitcode} is @code{void}. After the
12475 execution the program being debugged returned zero, therefore
12476 @code{$_exitcode} is zero, which means that it is not @code{void}
12479 The @code{void} expression can also be a call of a function from the
12480 program being debugged. For example, given the following function:
12489 The result of calling it inside @value{GDBN} is @code{void}:
12492 (@value{GDBP}) print foo ()
12494 (@value{GDBP}) print $_isvoid (foo ())
12496 (@value{GDBP}) set $v = foo ()
12497 (@value{GDBP}) print $v
12499 (@value{GDBP}) print $_isvoid ($v)
12503 @item $_gdb_setting_str (@var{setting})
12504 @findex $_gdb_setting_str@r{, convenience function}
12505 Return the value of the @value{GDBN} @var{setting} as a string.
12506 @var{setting} is any setting that can be used in a @code{set} or
12507 @code{show} command (@pxref{Controlling GDB}).
12510 (@value{GDBP}) show print frame-arguments
12511 Printing of non-scalar frame arguments is "scalars".
12512 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12514 (@value{GDBP}) p $_gdb_setting_str("height")
12519 @item $_gdb_setting (@var{setting})
12520 @findex $_gdb_setting@r{, convenience function}
12521 Return the value of the @value{GDBN} @var{setting}.
12522 The type of the returned value depends on the setting.
12524 The value type for boolean and auto boolean settings is @code{int}.
12525 The boolean values @code{off} and @code{on} are converted to
12526 the integer values @code{0} and @code{1}. The value @code{auto} is
12527 converted to the value @code{-1}.
12529 The value type for integer settings is either @code{unsigned int}
12530 or @code{int}, depending on the setting.
12532 Some integer settings accept an @code{unlimited} value.
12533 Depending on the setting, the @code{set} command also accepts
12534 the value @code{0} or the value @code{@minus{}1} as a synonym for
12536 For example, @code{set height unlimited} is equivalent to
12537 @code{set height 0}.
12539 Some other settings that accept the @code{unlimited} value
12540 use the value @code{0} to literally mean zero.
12541 For example, @code{set history size 0} indicates to not
12542 record any @value{GDBN} commands in the command history.
12543 For such settings, @code{@minus{}1} is the synonym
12544 for @code{unlimited}.
12546 See the documentation of the corresponding @code{set} command for
12547 the numerical value equivalent to @code{unlimited}.
12549 The @code{$_gdb_setting} function converts the unlimited value
12550 to a @code{0} or a @code{@minus{}1} value according to what the
12551 @code{set} command uses.
12555 (@value{GDBP}) p $_gdb_setting_str("height")
12557 (@value{GDBP}) p $_gdb_setting("height")
12559 (@value{GDBP}) set height unlimited
12560 (@value{GDBP}) p $_gdb_setting_str("height")
12562 (@value{GDBP}) p $_gdb_setting("height")
12566 (@value{GDBP}) p $_gdb_setting_str("history size")
12568 (@value{GDBP}) p $_gdb_setting("history size")
12570 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12572 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12578 Other setting types (enum, filename, optional filename, string, string noescape)
12579 are returned as string values.
12582 @item $_gdb_maint_setting_str (@var{setting})
12583 @findex $_gdb_maint_setting_str@r{, convenience function}
12584 Like the @code{$_gdb_setting_str} function, but works with
12585 @code{maintenance set} variables.
12587 @item $_gdb_maint_setting (@var{setting})
12588 @findex $_gdb_maint_setting@r{, convenience function}
12589 Like the @code{$_gdb_setting} function, but works with
12590 @code{maintenance set} variables.
12594 The following functions require @value{GDBN} to be configured with
12595 @code{Python} support.
12599 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12600 @findex $_memeq@r{, convenience function}
12601 Returns one if the @var{length} bytes at the addresses given by
12602 @var{buf1} and @var{buf2} are equal.
12603 Otherwise it returns zero.
12605 @item $_regex(@var{str}, @var{regex})
12606 @findex $_regex@r{, convenience function}
12607 Returns one if the string @var{str} matches the regular expression
12608 @var{regex}. Otherwise it returns zero.
12609 The syntax of the regular expression is that specified by @code{Python}'s
12610 regular expression support.
12612 @item $_streq(@var{str1}, @var{str2})
12613 @findex $_streq@r{, convenience function}
12614 Returns one if the strings @var{str1} and @var{str2} are equal.
12615 Otherwise it returns zero.
12617 @item $_strlen(@var{str})
12618 @findex $_strlen@r{, convenience function}
12619 Returns the length of string @var{str}.
12621 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12622 @findex $_caller_is@r{, convenience function}
12623 Returns one if the calling function's name is equal to @var{name}.
12624 Otherwise it returns zero.
12626 If the optional argument @var{number_of_frames} is provided,
12627 it is the number of frames up in the stack to look.
12635 at testsuite/gdb.python/py-caller-is.c:21
12636 #1 0x00000000004005a0 in middle_func ()
12637 at testsuite/gdb.python/py-caller-is.c:27
12638 #2 0x00000000004005ab in top_func ()
12639 at testsuite/gdb.python/py-caller-is.c:33
12640 #3 0x00000000004005b6 in main ()
12641 at testsuite/gdb.python/py-caller-is.c:39
12642 (gdb) print $_caller_is ("middle_func")
12644 (gdb) print $_caller_is ("top_func", 2)
12648 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12649 @findex $_caller_matches@r{, convenience function}
12650 Returns one if the calling function's name matches the regular expression
12651 @var{regexp}. Otherwise it returns zero.
12653 If the optional argument @var{number_of_frames} is provided,
12654 it is the number of frames up in the stack to look.
12657 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12658 @findex $_any_caller_is@r{, convenience function}
12659 Returns one if any calling function's name is equal to @var{name}.
12660 Otherwise it returns zero.
12662 If the optional argument @var{number_of_frames} is provided,
12663 it is the number of frames up in the stack to look.
12666 This function differs from @code{$_caller_is} in that this function
12667 checks all stack frames from the immediate caller to the frame specified
12668 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12669 frame specified by @var{number_of_frames}.
12671 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12672 @findex $_any_caller_matches@r{, convenience function}
12673 Returns one if any calling function's name matches the regular expression
12674 @var{regexp}. Otherwise it returns zero.
12676 If the optional argument @var{number_of_frames} is provided,
12677 it is the number of frames up in the stack to look.
12680 This function differs from @code{$_caller_matches} in that this function
12681 checks all stack frames from the immediate caller to the frame specified
12682 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12683 frame specified by @var{number_of_frames}.
12685 @item $_as_string(@var{value})
12686 @findex $_as_string@r{, convenience function}
12687 Return the string representation of @var{value}.
12689 This function is useful to obtain the textual label (enumerator) of an
12690 enumeration value. For example, assuming the variable @var{node} is of
12691 an enumerated type:
12694 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12695 Visiting node of type NODE_INTEGER
12698 @item $_cimag(@var{value})
12699 @itemx $_creal(@var{value})
12700 @findex $_cimag@r{, convenience function}
12701 @findex $_creal@r{, convenience function}
12702 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12703 the complex number @var{value}.
12705 The type of the imaginary or real part depends on the type of the
12706 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12707 will return an imaginary part of type @code{float}.
12711 @value{GDBN} provides the ability to list and get help on
12712 convenience functions.
12715 @item help function
12716 @kindex help function
12717 @cindex show all convenience functions
12718 Print a list of all convenience functions.
12725 You can refer to machine register contents, in expressions, as variables
12726 with names starting with @samp{$}. The names of registers are different
12727 for each machine; use @code{info registers} to see the names used on
12731 @kindex info registers
12732 @item info registers
12733 Print the names and values of all registers except floating-point
12734 and vector registers (in the selected stack frame).
12736 @kindex info all-registers
12737 @cindex floating point registers
12738 @item info all-registers
12739 Print the names and values of all registers, including floating-point
12740 and vector registers (in the selected stack frame).
12742 @anchor{info_registers_reggroup}
12743 @item info registers @var{reggroup} @dots{}
12744 Print the name and value of the registers in each of the specified
12745 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12746 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12748 @item info registers @var{regname} @dots{}
12749 Print the @dfn{relativized} value of each specified register @var{regname}.
12750 As discussed in detail below, register values are normally relative to
12751 the selected stack frame. The @var{regname} may be any register name valid on
12752 the machine you are using, with or without the initial @samp{$}.
12755 @anchor{standard registers}
12756 @cindex stack pointer register
12757 @cindex program counter register
12758 @cindex process status register
12759 @cindex frame pointer register
12760 @cindex standard registers
12761 @value{GDBN} has four ``standard'' register names that are available (in
12762 expressions) on most machines---whenever they do not conflict with an
12763 architecture's canonical mnemonics for registers. The register names
12764 @code{$pc} and @code{$sp} are used for the program counter register and
12765 the stack pointer. @code{$fp} is used for a register that contains a
12766 pointer to the current stack frame, and @code{$ps} is used for a
12767 register that contains the processor status. For example,
12768 you could print the program counter in hex with
12775 or print the instruction to be executed next with
12782 or add four to the stack pointer@footnote{This is a way of removing
12783 one word from the stack, on machines where stacks grow downward in
12784 memory (most machines, nowadays). This assumes that the innermost
12785 stack frame is selected; setting @code{$sp} is not allowed when other
12786 stack frames are selected. To pop entire frames off the stack,
12787 regardless of machine architecture, use @code{return};
12788 see @ref{Returning, ,Returning from a Function}.} with
12794 Whenever possible, these four standard register names are available on
12795 your machine even though the machine has different canonical mnemonics,
12796 so long as there is no conflict. The @code{info registers} command
12797 shows the canonical names. For example, on the SPARC, @code{info
12798 registers} displays the processor status register as @code{$psr} but you
12799 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12800 is an alias for the @sc{eflags} register.
12802 @value{GDBN} always considers the contents of an ordinary register as an
12803 integer when the register is examined in this way. Some machines have
12804 special registers which can hold nothing but floating point; these
12805 registers are considered to have floating point values. There is no way
12806 to refer to the contents of an ordinary register as floating point value
12807 (although you can @emph{print} it as a floating point value with
12808 @samp{print/f $@var{regname}}).
12810 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12811 means that the data format in which the register contents are saved by
12812 the operating system is not the same one that your program normally
12813 sees. For example, the registers of the 68881 floating point
12814 coprocessor are always saved in ``extended'' (raw) format, but all C
12815 programs expect to work with ``double'' (virtual) format. In such
12816 cases, @value{GDBN} normally works with the virtual format only (the format
12817 that makes sense for your program), but the @code{info registers} command
12818 prints the data in both formats.
12820 @cindex SSE registers (x86)
12821 @cindex MMX registers (x86)
12822 Some machines have special registers whose contents can be interpreted
12823 in several different ways. For example, modern x86-based machines
12824 have SSE and MMX registers that can hold several values packed
12825 together in several different formats. @value{GDBN} refers to such
12826 registers in @code{struct} notation:
12829 (@value{GDBP}) print $xmm1
12831 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12832 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12833 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12834 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12835 v4_int32 = @{0, 20657912, 11, 13@},
12836 v2_int64 = @{88725056443645952, 55834574859@},
12837 uint128 = 0x0000000d0000000b013b36f800000000
12842 To set values of such registers, you need to tell @value{GDBN} which
12843 view of the register you wish to change, as if you were assigning
12844 value to a @code{struct} member:
12847 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12850 Normally, register values are relative to the selected stack frame
12851 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12852 value that the register would contain if all stack frames farther in
12853 were exited and their saved registers restored. In order to see the
12854 true contents of hardware registers, you must select the innermost
12855 frame (with @samp{frame 0}).
12857 @cindex caller-saved registers
12858 @cindex call-clobbered registers
12859 @cindex volatile registers
12860 @cindex <not saved> values
12861 Usually ABIs reserve some registers as not needed to be saved by the
12862 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12863 registers). It may therefore not be possible for @value{GDBN} to know
12864 the value a register had before the call (in other words, in the outer
12865 frame), if the register value has since been changed by the callee.
12866 @value{GDBN} tries to deduce where the inner frame saved
12867 (``callee-saved'') registers, from the debug info, unwind info, or the
12868 machine code generated by your compiler. If some register is not
12869 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12870 its own knowledge of the ABI, or because the debug/unwind info
12871 explicitly says the register's value is undefined), @value{GDBN}
12872 displays @w{@samp{<not saved>}} as the register's value. With targets
12873 that @value{GDBN} has no knowledge of the register saving convention,
12874 if a register was not saved by the callee, then its value and location
12875 in the outer frame are assumed to be the same of the inner frame.
12876 This is usually harmless, because if the register is call-clobbered,
12877 the caller either does not care what is in the register after the
12878 call, or has code to restore the value that it does care about. Note,
12879 however, that if you change such a register in the outer frame, you
12880 may also be affecting the inner frame. Also, the more ``outer'' the
12881 frame is you're looking at, the more likely a call-clobbered
12882 register's value is to be wrong, in the sense that it doesn't actually
12883 represent the value the register had just before the call.
12885 @node Floating Point Hardware
12886 @section Floating Point Hardware
12887 @cindex floating point
12889 Depending on the configuration, @value{GDBN} may be able to give
12890 you more information about the status of the floating point hardware.
12895 Display hardware-dependent information about the floating
12896 point unit. The exact contents and layout vary depending on the
12897 floating point chip. Currently, @samp{info float} is supported on
12898 the ARM and x86 machines.
12902 @section Vector Unit
12903 @cindex vector unit
12905 Depending on the configuration, @value{GDBN} may be able to give you
12906 more information about the status of the vector unit.
12909 @kindex info vector
12911 Display information about the vector unit. The exact contents and
12912 layout vary depending on the hardware.
12915 @node OS Information
12916 @section Operating System Auxiliary Information
12917 @cindex OS information
12919 @value{GDBN} provides interfaces to useful OS facilities that can help
12920 you debug your program.
12922 @cindex auxiliary vector
12923 @cindex vector, auxiliary
12924 Some operating systems supply an @dfn{auxiliary vector} to programs at
12925 startup. This is akin to the arguments and environment that you
12926 specify for a program, but contains a system-dependent variety of
12927 binary values that tell system libraries important details about the
12928 hardware, operating system, and process. Each value's purpose is
12929 identified by an integer tag; the meanings are well-known but system-specific.
12930 Depending on the configuration and operating system facilities,
12931 @value{GDBN} may be able to show you this information. For remote
12932 targets, this functionality may further depend on the remote stub's
12933 support of the @samp{qXfer:auxv:read} packet, see
12934 @ref{qXfer auxiliary vector read}.
12939 Display the auxiliary vector of the inferior, which can be either a
12940 live process or a core dump file. @value{GDBN} prints each tag value
12941 numerically, and also shows names and text descriptions for recognized
12942 tags. Some values in the vector are numbers, some bit masks, and some
12943 pointers to strings or other data. @value{GDBN} displays each value in the
12944 most appropriate form for a recognized tag, and in hexadecimal for
12945 an unrecognized tag.
12948 On some targets, @value{GDBN} can access operating system-specific
12949 information and show it to you. The types of information available
12950 will differ depending on the type of operating system running on the
12951 target. The mechanism used to fetch the data is described in
12952 @ref{Operating System Information}. For remote targets, this
12953 functionality depends on the remote stub's support of the
12954 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12958 @item info os @var{infotype}
12960 Display OS information of the requested type.
12962 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12964 @anchor{linux info os infotypes}
12966 @kindex info os cpus
12968 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12969 the available fields from /proc/cpuinfo. For each supported architecture
12970 different fields are available. Two common entries are processor which gives
12971 CPU number and bogomips; a system constant that is calculated during
12972 kernel initialization.
12974 @kindex info os files
12976 Display the list of open file descriptors on the target. For each
12977 file descriptor, @value{GDBN} prints the identifier of the process
12978 owning the descriptor, the command of the owning process, the value
12979 of the descriptor, and the target of the descriptor.
12981 @kindex info os modules
12983 Display the list of all loaded kernel modules on the target. For each
12984 module, @value{GDBN} prints the module name, the size of the module in
12985 bytes, the number of times the module is used, the dependencies of the
12986 module, the status of the module, and the address of the loaded module
12989 @kindex info os msg
12991 Display the list of all System V message queues on the target. For each
12992 message queue, @value{GDBN} prints the message queue key, the message
12993 queue identifier, the access permissions, the current number of bytes
12994 on the queue, the current number of messages on the queue, the processes
12995 that last sent and received a message on the queue, the user and group
12996 of the owner and creator of the message queue, the times at which a
12997 message was last sent and received on the queue, and the time at which
12998 the message queue was last changed.
13000 @kindex info os processes
13002 Display the list of processes on the target. For each process,
13003 @value{GDBN} prints the process identifier, the name of the user, the
13004 command corresponding to the process, and the list of processor cores
13005 that the process is currently running on. (To understand what these
13006 properties mean, for this and the following info types, please consult
13007 the general @sc{gnu}/Linux documentation.)
13009 @kindex info os procgroups
13011 Display the list of process groups on the target. For each process,
13012 @value{GDBN} prints the identifier of the process group that it belongs
13013 to, the command corresponding to the process group leader, the process
13014 identifier, and the command line of the process. The list is sorted
13015 first by the process group identifier, then by the process identifier,
13016 so that processes belonging to the same process group are grouped together
13017 and the process group leader is listed first.
13019 @kindex info os semaphores
13021 Display the list of all System V semaphore sets on the target. For each
13022 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13023 set identifier, the access permissions, the number of semaphores in the
13024 set, the user and group of the owner and creator of the semaphore set,
13025 and the times at which the semaphore set was operated upon and changed.
13027 @kindex info os shm
13029 Display the list of all System V shared-memory regions on the target.
13030 For each shared-memory region, @value{GDBN} prints the region key,
13031 the shared-memory identifier, the access permissions, the size of the
13032 region, the process that created the region, the process that last
13033 attached to or detached from the region, the current number of live
13034 attaches to the region, and the times at which the region was last
13035 attached to, detach from, and changed.
13037 @kindex info os sockets
13039 Display the list of Internet-domain sockets on the target. For each
13040 socket, @value{GDBN} prints the address and port of the local and
13041 remote endpoints, the current state of the connection, the creator of
13042 the socket, the IP address family of the socket, and the type of the
13045 @kindex info os threads
13047 Display the list of threads running on the target. For each thread,
13048 @value{GDBN} prints the identifier of the process that the thread
13049 belongs to, the command of the process, the thread identifier, and the
13050 processor core that it is currently running on. The main thread of a
13051 process is not listed.
13055 If @var{infotype} is omitted, then list the possible values for
13056 @var{infotype} and the kind of OS information available for each
13057 @var{infotype}. If the target does not return a list of possible
13058 types, this command will report an error.
13061 @node Memory Region Attributes
13062 @section Memory Region Attributes
13063 @cindex memory region attributes
13065 @dfn{Memory region attributes} allow you to describe special handling
13066 required by regions of your target's memory. @value{GDBN} uses
13067 attributes to determine whether to allow certain types of memory
13068 accesses; whether to use specific width accesses; and whether to cache
13069 target memory. By default the description of memory regions is
13070 fetched from the target (if the current target supports this), but the
13071 user can override the fetched regions.
13073 Defined memory regions can be individually enabled and disabled. When a
13074 memory region is disabled, @value{GDBN} uses the default attributes when
13075 accessing memory in that region. Similarly, if no memory regions have
13076 been defined, @value{GDBN} uses the default attributes when accessing
13079 When a memory region is defined, it is given a number to identify it;
13080 to enable, disable, or remove a memory region, you specify that number.
13084 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13085 Define a memory region bounded by @var{lower} and @var{upper} with
13086 attributes @var{attributes}@dots{}, and add it to the list of regions
13087 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13088 case: it is treated as the target's maximum memory address.
13089 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13092 Discard any user changes to the memory regions and use target-supplied
13093 regions, if available, or no regions if the target does not support.
13096 @item delete mem @var{nums}@dots{}
13097 Remove memory regions @var{nums}@dots{} from the list of regions
13098 monitored by @value{GDBN}.
13100 @kindex disable mem
13101 @item disable mem @var{nums}@dots{}
13102 Disable monitoring of memory regions @var{nums}@dots{}.
13103 A disabled memory region is not forgotten.
13104 It may be enabled again later.
13107 @item enable mem @var{nums}@dots{}
13108 Enable monitoring of memory regions @var{nums}@dots{}.
13112 Print a table of all defined memory regions, with the following columns
13116 @item Memory Region Number
13117 @item Enabled or Disabled.
13118 Enabled memory regions are marked with @samp{y}.
13119 Disabled memory regions are marked with @samp{n}.
13122 The address defining the inclusive lower bound of the memory region.
13125 The address defining the exclusive upper bound of the memory region.
13128 The list of attributes set for this memory region.
13133 @subsection Attributes
13135 @subsubsection Memory Access Mode
13136 The access mode attributes set whether @value{GDBN} may make read or
13137 write accesses to a memory region.
13139 While these attributes prevent @value{GDBN} from performing invalid
13140 memory accesses, they do nothing to prevent the target system, I/O DMA,
13141 etc.@: from accessing memory.
13145 Memory is read only.
13147 Memory is write only.
13149 Memory is read/write. This is the default.
13152 @subsubsection Memory Access Size
13153 The access size attribute tells @value{GDBN} to use specific sized
13154 accesses in the memory region. Often memory mapped device registers
13155 require specific sized accesses. If no access size attribute is
13156 specified, @value{GDBN} may use accesses of any size.
13160 Use 8 bit memory accesses.
13162 Use 16 bit memory accesses.
13164 Use 32 bit memory accesses.
13166 Use 64 bit memory accesses.
13169 @c @subsubsection Hardware/Software Breakpoints
13170 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13171 @c will use hardware or software breakpoints for the internal breakpoints
13172 @c used by the step, next, finish, until, etc. commands.
13176 @c Always use hardware breakpoints
13177 @c @item swbreak (default)
13180 @subsubsection Data Cache
13181 The data cache attributes set whether @value{GDBN} will cache target
13182 memory. While this generally improves performance by reducing debug
13183 protocol overhead, it can lead to incorrect results because @value{GDBN}
13184 does not know about volatile variables or memory mapped device
13189 Enable @value{GDBN} to cache target memory.
13191 Disable @value{GDBN} from caching target memory. This is the default.
13194 @subsection Memory Access Checking
13195 @value{GDBN} can be instructed to refuse accesses to memory that is
13196 not explicitly described. This can be useful if accessing such
13197 regions has undesired effects for a specific target, or to provide
13198 better error checking. The following commands control this behaviour.
13201 @kindex set mem inaccessible-by-default
13202 @item set mem inaccessible-by-default [on|off]
13203 If @code{on} is specified, make @value{GDBN} treat memory not
13204 explicitly described by the memory ranges as non-existent and refuse accesses
13205 to such memory. The checks are only performed if there's at least one
13206 memory range defined. If @code{off} is specified, make @value{GDBN}
13207 treat the memory not explicitly described by the memory ranges as RAM.
13208 The default value is @code{on}.
13209 @kindex show mem inaccessible-by-default
13210 @item show mem inaccessible-by-default
13211 Show the current handling of accesses to unknown memory.
13215 @c @subsubsection Memory Write Verification
13216 @c The memory write verification attributes set whether @value{GDBN}
13217 @c will re-reads data after each write to verify the write was successful.
13221 @c @item noverify (default)
13224 @node Dump/Restore Files
13225 @section Copy Between Memory and a File
13226 @cindex dump/restore files
13227 @cindex append data to a file
13228 @cindex dump data to a file
13229 @cindex restore data from a file
13231 You can use the commands @code{dump}, @code{append}, and
13232 @code{restore} to copy data between target memory and a file. The
13233 @code{dump} and @code{append} commands write data to a file, and the
13234 @code{restore} command reads data from a file back into the inferior's
13235 memory. Files may be in binary, Motorola S-record, Intel hex,
13236 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13237 append to binary files, and cannot read from Verilog Hex files.
13242 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13243 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13244 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13245 or the value of @var{expr}, to @var{filename} in the given format.
13247 The @var{format} parameter may be any one of:
13254 Motorola S-record format.
13256 Tektronix Hex format.
13258 Verilog Hex format.
13261 @value{GDBN} uses the same definitions of these formats as the
13262 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13263 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13267 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13268 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13269 Append the contents of memory from @var{start_addr} to @var{end_addr},
13270 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13271 (@value{GDBN} can only append data to files in raw binary form.)
13274 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13275 Restore the contents of file @var{filename} into memory. The
13276 @code{restore} command can automatically recognize any known @sc{bfd}
13277 file format, except for raw binary. To restore a raw binary file you
13278 must specify the optional keyword @code{binary} after the filename.
13280 If @var{bias} is non-zero, its value will be added to the addresses
13281 contained in the file. Binary files always start at address zero, so
13282 they will be restored at address @var{bias}. Other bfd files have
13283 a built-in location; they will be restored at offset @var{bias}
13284 from that location.
13286 If @var{start} and/or @var{end} are non-zero, then only data between
13287 file offset @var{start} and file offset @var{end} will be restored.
13288 These offsets are relative to the addresses in the file, before
13289 the @var{bias} argument is applied.
13293 @node Core File Generation
13294 @section How to Produce a Core File from Your Program
13295 @cindex dump core from inferior
13297 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13298 image of a running process and its process status (register values
13299 etc.). Its primary use is post-mortem debugging of a program that
13300 crashed while it ran outside a debugger. A program that crashes
13301 automatically produces a core file, unless this feature is disabled by
13302 the user. @xref{Files}, for information on invoking @value{GDBN} in
13303 the post-mortem debugging mode.
13305 Occasionally, you may wish to produce a core file of the program you
13306 are debugging in order to preserve a snapshot of its state.
13307 @value{GDBN} has a special command for that.
13311 @kindex generate-core-file
13312 @item generate-core-file [@var{file}]
13313 @itemx gcore [@var{file}]
13314 Produce a core dump of the inferior process. The optional argument
13315 @var{file} specifies the file name where to put the core dump. If not
13316 specified, the file name defaults to @file{core.@var{pid}}, where
13317 @var{pid} is the inferior process ID.
13319 Note that this command is implemented only for some systems (as of
13320 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13322 On @sc{gnu}/Linux, this command can take into account the value of the
13323 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13324 dump (@pxref{set use-coredump-filter}), and by default honors the
13325 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13326 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13328 @kindex set use-coredump-filter
13329 @anchor{set use-coredump-filter}
13330 @item set use-coredump-filter on
13331 @itemx set use-coredump-filter off
13332 Enable or disable the use of the file
13333 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13334 files. This file is used by the Linux kernel to decide what types of
13335 memory mappings will be dumped or ignored when generating a core dump
13336 file. @var{pid} is the process ID of a currently running process.
13338 To make use of this feature, you have to write in the
13339 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13340 which is a bit mask representing the memory mapping types. If a bit
13341 is set in the bit mask, then the memory mappings of the corresponding
13342 types will be dumped; otherwise, they will be ignored. This
13343 configuration is inherited by child processes. For more information
13344 about the bits that can be set in the
13345 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13346 manpage of @code{core(5)}.
13348 By default, this option is @code{on}. If this option is turned
13349 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13350 and instead uses the same default value as the Linux kernel in order
13351 to decide which pages will be dumped in the core dump file. This
13352 value is currently @code{0x33}, which means that bits @code{0}
13353 (anonymous private mappings), @code{1} (anonymous shared mappings),
13354 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13355 This will cause these memory mappings to be dumped automatically.
13357 @kindex set dump-excluded-mappings
13358 @anchor{set dump-excluded-mappings}
13359 @item set dump-excluded-mappings on
13360 @itemx set dump-excluded-mappings off
13361 If @code{on} is specified, @value{GDBN} will dump memory mappings
13362 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13363 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13365 The default value is @code{off}.
13368 @node Character Sets
13369 @section Character Sets
13370 @cindex character sets
13372 @cindex translating between character sets
13373 @cindex host character set
13374 @cindex target character set
13376 If the program you are debugging uses a different character set to
13377 represent characters and strings than the one @value{GDBN} uses itself,
13378 @value{GDBN} can automatically translate between the character sets for
13379 you. The character set @value{GDBN} uses we call the @dfn{host
13380 character set}; the one the inferior program uses we call the
13381 @dfn{target character set}.
13383 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13384 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13385 remote protocol (@pxref{Remote Debugging}) to debug a program
13386 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13387 then the host character set is Latin-1, and the target character set is
13388 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13389 target-charset EBCDIC-US}, then @value{GDBN} translates between
13390 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13391 character and string literals in expressions.
13393 @value{GDBN} has no way to automatically recognize which character set
13394 the inferior program uses; you must tell it, using the @code{set
13395 target-charset} command, described below.
13397 Here are the commands for controlling @value{GDBN}'s character set
13401 @item set target-charset @var{charset}
13402 @kindex set target-charset
13403 Set the current target character set to @var{charset}. To display the
13404 list of supported target character sets, type
13405 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13407 @item set host-charset @var{charset}
13408 @kindex set host-charset
13409 Set the current host character set to @var{charset}.
13411 By default, @value{GDBN} uses a host character set appropriate to the
13412 system it is running on; you can override that default using the
13413 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13414 automatically determine the appropriate host character set. In this
13415 case, @value{GDBN} uses @samp{UTF-8}.
13417 @value{GDBN} can only use certain character sets as its host character
13418 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13419 @value{GDBN} will list the host character sets it supports.
13421 @item set charset @var{charset}
13422 @kindex set charset
13423 Set the current host and target character sets to @var{charset}. As
13424 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13425 @value{GDBN} will list the names of the character sets that can be used
13426 for both host and target.
13429 @kindex show charset
13430 Show the names of the current host and target character sets.
13432 @item show host-charset
13433 @kindex show host-charset
13434 Show the name of the current host character set.
13436 @item show target-charset
13437 @kindex show target-charset
13438 Show the name of the current target character set.
13440 @item set target-wide-charset @var{charset}
13441 @kindex set target-wide-charset
13442 Set the current target's wide character set to @var{charset}. This is
13443 the character set used by the target's @code{wchar_t} type. To
13444 display the list of supported wide character sets, type
13445 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13447 @item show target-wide-charset
13448 @kindex show target-wide-charset
13449 Show the name of the current target's wide character set.
13452 Here is an example of @value{GDBN}'s character set support in action.
13453 Assume that the following source code has been placed in the file
13454 @file{charset-test.c}:
13460 = @{72, 101, 108, 108, 111, 44, 32, 119,
13461 111, 114, 108, 100, 33, 10, 0@};
13462 char ibm1047_hello[]
13463 = @{200, 133, 147, 147, 150, 107, 64, 166,
13464 150, 153, 147, 132, 90, 37, 0@};
13468 printf ("Hello, world!\n");
13472 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13473 containing the string @samp{Hello, world!} followed by a newline,
13474 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13476 We compile the program, and invoke the debugger on it:
13479 $ gcc -g charset-test.c -o charset-test
13480 $ gdb -nw charset-test
13481 GNU gdb 2001-12-19-cvs
13482 Copyright 2001 Free Software Foundation, Inc.
13487 We can use the @code{show charset} command to see what character sets
13488 @value{GDBN} is currently using to interpret and display characters and
13492 (@value{GDBP}) show charset
13493 The current host and target character set is `ISO-8859-1'.
13497 For the sake of printing this manual, let's use @sc{ascii} as our
13498 initial character set:
13500 (@value{GDBP}) set charset ASCII
13501 (@value{GDBP}) show charset
13502 The current host and target character set is `ASCII'.
13506 Let's assume that @sc{ascii} is indeed the correct character set for our
13507 host system --- in other words, let's assume that if @value{GDBN} prints
13508 characters using the @sc{ascii} character set, our terminal will display
13509 them properly. Since our current target character set is also
13510 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13513 (@value{GDBP}) print ascii_hello
13514 $1 = 0x401698 "Hello, world!\n"
13515 (@value{GDBP}) print ascii_hello[0]
13520 @value{GDBN} uses the target character set for character and string
13521 literals you use in expressions:
13524 (@value{GDBP}) print '+'
13529 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13532 @value{GDBN} relies on the user to tell it which character set the
13533 target program uses. If we print @code{ibm1047_hello} while our target
13534 character set is still @sc{ascii}, we get jibberish:
13537 (@value{GDBP}) print ibm1047_hello
13538 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13539 (@value{GDBP}) print ibm1047_hello[0]
13544 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13545 @value{GDBN} tells us the character sets it supports:
13548 (@value{GDBP}) set target-charset
13549 ASCII EBCDIC-US IBM1047 ISO-8859-1
13550 (@value{GDBP}) set target-charset
13553 We can select @sc{ibm1047} as our target character set, and examine the
13554 program's strings again. Now the @sc{ascii} string is wrong, but
13555 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13556 target character set, @sc{ibm1047}, to the host character set,
13557 @sc{ascii}, and they display correctly:
13560 (@value{GDBP}) set target-charset IBM1047
13561 (@value{GDBP}) show charset
13562 The current host character set is `ASCII'.
13563 The current target character set is `IBM1047'.
13564 (@value{GDBP}) print ascii_hello
13565 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13566 (@value{GDBP}) print ascii_hello[0]
13568 (@value{GDBP}) print ibm1047_hello
13569 $8 = 0x4016a8 "Hello, world!\n"
13570 (@value{GDBP}) print ibm1047_hello[0]
13575 As above, @value{GDBN} uses the target character set for character and
13576 string literals you use in expressions:
13579 (@value{GDBP}) print '+'
13584 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13587 @node Caching Target Data
13588 @section Caching Data of Targets
13589 @cindex caching data of targets
13591 @value{GDBN} caches data exchanged between the debugger and a target.
13592 Each cache is associated with the address space of the inferior.
13593 @xref{Inferiors Connections and Programs}, about inferior and address space.
13594 Such caching generally improves performance in remote debugging
13595 (@pxref{Remote Debugging}), because it reduces the overhead of the
13596 remote protocol by bundling memory reads and writes into large chunks.
13597 Unfortunately, simply caching everything would lead to incorrect results,
13598 since @value{GDBN} does not necessarily know anything about volatile
13599 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13600 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13602 Therefore, by default, @value{GDBN} only caches data
13603 known to be on the stack@footnote{In non-stop mode, it is moderately
13604 rare for a running thread to modify the stack of a stopped thread
13605 in a way that would interfere with a backtrace, and caching of
13606 stack reads provides a significant speed up of remote backtraces.} or
13607 in the code segment.
13608 Other regions of memory can be explicitly marked as
13609 cacheable; @pxref{Memory Region Attributes}.
13612 @kindex set remotecache
13613 @item set remotecache on
13614 @itemx set remotecache off
13615 This option no longer does anything; it exists for compatibility
13618 @kindex show remotecache
13619 @item show remotecache
13620 Show the current state of the obsolete remotecache flag.
13622 @kindex set stack-cache
13623 @item set stack-cache on
13624 @itemx set stack-cache off
13625 Enable or disable caching of stack accesses. When @code{on}, use
13626 caching. By default, this option is @code{on}.
13628 @kindex show stack-cache
13629 @item show stack-cache
13630 Show the current state of data caching for memory accesses.
13632 @kindex set code-cache
13633 @item set code-cache on
13634 @itemx set code-cache off
13635 Enable or disable caching of code segment accesses. When @code{on},
13636 use caching. By default, this option is @code{on}. This improves
13637 performance of disassembly in remote debugging.
13639 @kindex show code-cache
13640 @item show code-cache
13641 Show the current state of target memory cache for code segment
13644 @kindex info dcache
13645 @item info dcache @r{[}line@r{]}
13646 Print the information about the performance of data cache of the
13647 current inferior's address space. The information displayed
13648 includes the dcache width and depth, and for each cache line, its
13649 number, address, and how many times it was referenced. This
13650 command is useful for debugging the data cache operation.
13652 If a line number is specified, the contents of that line will be
13655 @item set dcache size @var{size}
13656 @cindex dcache size
13657 @kindex set dcache size
13658 Set maximum number of entries in dcache (dcache depth above).
13660 @item set dcache line-size @var{line-size}
13661 @cindex dcache line-size
13662 @kindex set dcache line-size
13663 Set number of bytes each dcache entry caches (dcache width above).
13664 Must be a power of 2.
13666 @item show dcache size
13667 @kindex show dcache size
13668 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13670 @item show dcache line-size
13671 @kindex show dcache line-size
13672 Show default size of dcache lines.
13674 @item maint flush dcache
13675 @cindex dcache, flushing
13676 @kindex maint flush dcache
13677 Flush the contents (if any) of the dcache. This maintainer command is
13678 useful when debugging the dcache implementation.
13682 @node Searching Memory
13683 @section Search Memory
13684 @cindex searching memory
13686 Memory can be searched for a particular sequence of bytes with the
13687 @code{find} command.
13691 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13692 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13693 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13694 etc. The search begins at address @var{start_addr} and continues for either
13695 @var{len} bytes or through to @var{end_addr} inclusive.
13698 @var{s} and @var{n} are optional parameters.
13699 They may be specified in either order, apart or together.
13702 @item @var{s}, search query size
13703 The size of each search query value.
13709 halfwords (two bytes)
13713 giant words (eight bytes)
13716 All values are interpreted in the current language.
13717 This means, for example, that if the current source language is C/C@t{++}
13718 then searching for the string ``hello'' includes the trailing '\0'.
13719 The null terminator can be removed from searching by using casts,
13720 e.g.: @samp{@{char[5]@}"hello"}.
13722 If the value size is not specified, it is taken from the
13723 value's type in the current language.
13724 This is useful when one wants to specify the search
13725 pattern as a mixture of types.
13726 Note that this means, for example, that in the case of C-like languages
13727 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13728 which is typically four bytes.
13730 @item @var{n}, maximum number of finds
13731 The maximum number of matches to print. The default is to print all finds.
13734 You can use strings as search values. Quote them with double-quotes
13736 The string value is copied into the search pattern byte by byte,
13737 regardless of the endianness of the target and the size specification.
13739 The address of each match found is printed as well as a count of the
13740 number of matches found.
13742 The address of the last value found is stored in convenience variable
13744 A count of the number of matches is stored in @samp{$numfound}.
13746 For example, if stopped at the @code{printf} in this function:
13752 static char hello[] = "hello-hello";
13753 static struct @{ char c; short s; int i; @}
13754 __attribute__ ((packed)) mixed
13755 = @{ 'c', 0x1234, 0x87654321 @};
13756 printf ("%s\n", hello);
13761 you get during debugging:
13764 (gdb) find &hello[0], +sizeof(hello), "hello"
13765 0x804956d <hello.1620+6>
13767 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13768 0x8049567 <hello.1620>
13769 0x804956d <hello.1620+6>
13771 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13772 0x8049567 <hello.1620>
13773 0x804956d <hello.1620+6>
13775 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13776 0x8049567 <hello.1620>
13778 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13779 0x8049560 <mixed.1625>
13781 (gdb) print $numfound
13784 $2 = (void *) 0x8049560
13788 @section Value Sizes
13790 Whenever @value{GDBN} prints a value memory will be allocated within
13791 @value{GDBN} to hold the contents of the value. It is possible in
13792 some languages with dynamic typing systems, that an invalid program
13793 may indicate a value that is incorrectly large, this in turn may cause
13794 @value{GDBN} to try and allocate an overly large amount of memory.
13797 @kindex set max-value-size
13798 @item set max-value-size @var{bytes}
13799 @itemx set max-value-size unlimited
13800 Set the maximum size of memory that @value{GDBN} will allocate for the
13801 contents of a value to @var{bytes}, trying to display a value that
13802 requires more memory than that will result in an error.
13804 Setting this variable does not effect values that have already been
13805 allocated within @value{GDBN}, only future allocations.
13807 There's a minimum size that @code{max-value-size} can be set to in
13808 order that @value{GDBN} can still operate correctly, this minimum is
13809 currently 16 bytes.
13811 The limit applies to the results of some subexpressions as well as to
13812 complete expressions. For example, an expression denoting a simple
13813 integer component, such as @code{x.y.z}, may fail if the size of
13814 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13815 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13816 @var{A} is an array variable with non-constant size, will generally
13817 succeed regardless of the bounds on @var{A}, as long as the component
13818 size is less than @var{bytes}.
13820 The default value of @code{max-value-size} is currently 64k.
13822 @kindex show max-value-size
13823 @item show max-value-size
13824 Show the maximum size of memory, in bytes, that @value{GDBN} will
13825 allocate for the contents of a value.
13828 @node Optimized Code
13829 @chapter Debugging Optimized Code
13830 @cindex optimized code, debugging
13831 @cindex debugging optimized code
13833 Almost all compilers support optimization. With optimization
13834 disabled, the compiler generates assembly code that corresponds
13835 directly to your source code, in a simplistic way. As the compiler
13836 applies more powerful optimizations, the generated assembly code
13837 diverges from your original source code. With help from debugging
13838 information generated by the compiler, @value{GDBN} can map from
13839 the running program back to constructs from your original source.
13841 @value{GDBN} is more accurate with optimization disabled. If you
13842 can recompile without optimization, it is easier to follow the
13843 progress of your program during debugging. But, there are many cases
13844 where you may need to debug an optimized version.
13846 When you debug a program compiled with @samp{-g -O}, remember that the
13847 optimizer has rearranged your code; the debugger shows you what is
13848 really there. Do not be too surprised when the execution path does not
13849 exactly match your source file! An extreme example: if you define a
13850 variable, but never use it, @value{GDBN} never sees that
13851 variable---because the compiler optimizes it out of existence.
13853 Some things do not work as well with @samp{-g -O} as with just
13854 @samp{-g}, particularly on machines with instruction scheduling. If in
13855 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13856 please report it to us as a bug (including a test case!).
13857 @xref{Variables}, for more information about debugging optimized code.
13860 * Inline Functions:: How @value{GDBN} presents inlining
13861 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13864 @node Inline Functions
13865 @section Inline Functions
13866 @cindex inline functions, debugging
13868 @dfn{Inlining} is an optimization that inserts a copy of the function
13869 body directly at each call site, instead of jumping to a shared
13870 routine. @value{GDBN} displays inlined functions just like
13871 non-inlined functions. They appear in backtraces. You can view their
13872 arguments and local variables, step into them with @code{step}, skip
13873 them with @code{next}, and escape from them with @code{finish}.
13874 You can check whether a function was inlined by using the
13875 @code{info frame} command.
13877 For @value{GDBN} to support inlined functions, the compiler must
13878 record information about inlining in the debug information ---
13879 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13880 other compilers do also. @value{GDBN} only supports inlined functions
13881 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13882 do not emit two required attributes (@samp{DW_AT_call_file} and
13883 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13884 function calls with earlier versions of @value{NGCC}. It instead
13885 displays the arguments and local variables of inlined functions as
13886 local variables in the caller.
13888 The body of an inlined function is directly included at its call site;
13889 unlike a non-inlined function, there are no instructions devoted to
13890 the call. @value{GDBN} still pretends that the call site and the
13891 start of the inlined function are different instructions. Stepping to
13892 the call site shows the call site, and then stepping again shows
13893 the first line of the inlined function, even though no additional
13894 instructions are executed.
13896 This makes source-level debugging much clearer; you can see both the
13897 context of the call and then the effect of the call. Only stepping by
13898 a single instruction using @code{stepi} or @code{nexti} does not do
13899 this; single instruction steps always show the inlined body.
13901 There are some ways that @value{GDBN} does not pretend that inlined
13902 function calls are the same as normal calls:
13906 Setting breakpoints at the call site of an inlined function may not
13907 work, because the call site does not contain any code. @value{GDBN}
13908 may incorrectly move the breakpoint to the next line of the enclosing
13909 function, after the call. This limitation will be removed in a future
13910 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13911 or inside the inlined function instead.
13914 @value{GDBN} cannot locate the return value of inlined calls after
13915 using the @code{finish} command. This is a limitation of compiler-generated
13916 debugging information; after @code{finish}, you can step to the next line
13917 and print a variable where your program stored the return value.
13921 @node Tail Call Frames
13922 @section Tail Call Frames
13923 @cindex tail call frames, debugging
13925 Function @code{B} can call function @code{C} in its very last statement. In
13926 unoptimized compilation the call of @code{C} is immediately followed by return
13927 instruction at the end of @code{B} code. Optimizing compiler may replace the
13928 call and return in function @code{B} into one jump to function @code{C}
13929 instead. Such use of a jump instruction is called @dfn{tail call}.
13931 During execution of function @code{C}, there will be no indication in the
13932 function call stack frames that it was tail-called from @code{B}. If function
13933 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13934 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13935 some cases @value{GDBN} can determine that @code{C} was tail-called from
13936 @code{B}, and it will then create fictitious call frame for that, with the
13937 return address set up as if @code{B} called @code{C} normally.
13939 This functionality is currently supported only by DWARF 2 debugging format and
13940 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13941 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13944 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13945 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13949 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13951 Stack level 1, frame at 0x7fffffffda30:
13952 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13953 tail call frame, caller of frame at 0x7fffffffda30
13954 source language c++.
13955 Arglist at unknown address.
13956 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13959 The detection of all the possible code path executions can find them ambiguous.
13960 There is no execution history stored (possible @ref{Reverse Execution} is never
13961 used for this purpose) and the last known caller could have reached the known
13962 callee by multiple different jump sequences. In such case @value{GDBN} still
13963 tries to show at least all the unambiguous top tail callers and all the
13964 unambiguous bottom tail calees, if any.
13967 @anchor{set debug entry-values}
13968 @item set debug entry-values
13969 @kindex set debug entry-values
13970 When set to on, enables printing of analysis messages for both frame argument
13971 values at function entry and tail calls. It will show all the possible valid
13972 tail calls code paths it has considered. It will also print the intersection
13973 of them with the final unambiguous (possibly partial or even empty) code path
13976 @item show debug entry-values
13977 @kindex show debug entry-values
13978 Show the current state of analysis messages printing for both frame argument
13979 values at function entry and tail calls.
13982 The analysis messages for tail calls can for example show why the virtual tail
13983 call frame for function @code{c} has not been recognized (due to the indirect
13984 reference by variable @code{x}):
13987 static void __attribute__((noinline, noclone)) c (void);
13988 void (*x) (void) = c;
13989 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13990 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13991 int main (void) @{ x (); return 0; @}
13993 Breakpoint 1, DW_OP_entry_value resolving cannot find
13994 DW_TAG_call_site 0x40039a in main
13996 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13999 #1 0x000000000040039a in main () at t.c:5
14002 Another possibility is an ambiguous virtual tail call frames resolution:
14006 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14007 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14008 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14009 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14010 static void __attribute__((noinline, noclone)) b (void)
14011 @{ if (i) c (); else e (); @}
14012 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14013 int main (void) @{ a (); return 0; @}
14015 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14016 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14017 tailcall: reduced: 0x4004d2(a) |
14020 #1 0x00000000004004d2 in a () at t.c:8
14021 #2 0x0000000000400395 in main () at t.c:9
14024 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14025 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14027 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14028 @ifset HAVE_MAKEINFO_CLICK
14029 @set ARROW @click{}
14030 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14031 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14033 @ifclear HAVE_MAKEINFO_CLICK
14035 @set CALLSEQ1B @value{CALLSEQ1A}
14036 @set CALLSEQ2B @value{CALLSEQ2A}
14039 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14040 The code can have possible execution paths @value{CALLSEQ1B} or
14041 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14043 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14044 has found. It then finds another possible calling sequence - that one is
14045 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14046 printed as the @code{reduced:} calling sequence. That one could have many
14047 further @code{compare:} and @code{reduced:} statements as long as there remain
14048 any non-ambiguous sequence entries.
14050 For the frame of function @code{b} in both cases there are different possible
14051 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14052 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14053 therefore this one is displayed to the user while the ambiguous frames are
14056 There can be also reasons why printing of frame argument values at function
14061 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14062 static void __attribute__((noinline, noclone)) a (int i);
14063 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14064 static void __attribute__((noinline, noclone)) a (int i)
14065 @{ if (i) b (i - 1); else c (0); @}
14066 int main (void) @{ a (5); return 0; @}
14069 #0 c (i=i@@entry=0) at t.c:2
14070 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14071 function "a" at 0x400420 can call itself via tail calls
14072 i=<optimized out>) at t.c:6
14073 #2 0x000000000040036e in main () at t.c:7
14076 @value{GDBN} cannot find out from the inferior state if and how many times did
14077 function @code{a} call itself (via function @code{b}) as these calls would be
14078 tail calls. Such tail calls would modify the @code{i} variable, therefore
14079 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14080 prints @code{<optimized out>} instead.
14083 @chapter C Preprocessor Macros
14085 Some languages, such as C and C@t{++}, provide a way to define and invoke
14086 ``preprocessor macros'' which expand into strings of tokens.
14087 @value{GDBN} can evaluate expressions containing macro invocations, show
14088 the result of macro expansion, and show a macro's definition, including
14089 where it was defined.
14091 You may need to compile your program specially to provide @value{GDBN}
14092 with information about preprocessor macros. Most compilers do not
14093 include macros in their debugging information, even when you compile
14094 with the @option{-g} flag. @xref{Compilation}.
14096 A program may define a macro at one point, remove that definition later,
14097 and then provide a different definition after that. Thus, at different
14098 points in the program, a macro may have different definitions, or have
14099 no definition at all. If there is a current stack frame, @value{GDBN}
14100 uses the macros in scope at that frame's source code line. Otherwise,
14101 @value{GDBN} uses the macros in scope at the current listing location;
14104 Whenever @value{GDBN} evaluates an expression, it always expands any
14105 macro invocations present in the expression. @value{GDBN} also provides
14106 the following commands for working with macros explicitly.
14110 @kindex macro expand
14111 @cindex macro expansion, showing the results of preprocessor
14112 @cindex preprocessor macro expansion, showing the results of
14113 @cindex expanding preprocessor macros
14114 @item macro expand @var{expression}
14115 @itemx macro exp @var{expression}
14116 Show the results of expanding all preprocessor macro invocations in
14117 @var{expression}. Since @value{GDBN} simply expands macros, but does
14118 not parse the result, @var{expression} need not be a valid expression;
14119 it can be any string of tokens.
14122 @item macro expand-once @var{expression}
14123 @itemx macro exp1 @var{expression}
14124 @cindex expand macro once
14125 @i{(This command is not yet implemented.)} Show the results of
14126 expanding those preprocessor macro invocations that appear explicitly in
14127 @var{expression}. Macro invocations appearing in that expansion are
14128 left unchanged. This command allows you to see the effect of a
14129 particular macro more clearly, without being confused by further
14130 expansions. Since @value{GDBN} simply expands macros, but does not
14131 parse the result, @var{expression} need not be a valid expression; it
14132 can be any string of tokens.
14135 @cindex macro definition, showing
14136 @cindex definition of a macro, showing
14137 @cindex macros, from debug info
14138 @item info macro [-a|-all] [--] @var{macro}
14139 Show the current definition or all definitions of the named @var{macro},
14140 and describe the source location or compiler command-line where that
14141 definition was established. The optional double dash is to signify the end of
14142 argument processing and the beginning of @var{macro} for non C-like macros where
14143 the macro may begin with a hyphen.
14145 @kindex info macros
14146 @item info macros @var{location}
14147 Show all macro definitions that are in effect at the location specified
14148 by @var{location}, and describe the source location or compiler
14149 command-line where those definitions were established.
14151 @kindex macro define
14152 @cindex user-defined macros
14153 @cindex defining macros interactively
14154 @cindex macros, user-defined
14155 @item macro define @var{macro} @var{replacement-list}
14156 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14157 Introduce a definition for a preprocessor macro named @var{macro},
14158 invocations of which are replaced by the tokens given in
14159 @var{replacement-list}. The first form of this command defines an
14160 ``object-like'' macro, which takes no arguments; the second form
14161 defines a ``function-like'' macro, which takes the arguments given in
14164 A definition introduced by this command is in scope in every
14165 expression evaluated in @value{GDBN}, until it is removed with the
14166 @code{macro undef} command, described below. The definition overrides
14167 all definitions for @var{macro} present in the program being debugged,
14168 as well as any previous user-supplied definition.
14170 @kindex macro undef
14171 @item macro undef @var{macro}
14172 Remove any user-supplied definition for the macro named @var{macro}.
14173 This command only affects definitions provided with the @code{macro
14174 define} command, described above; it cannot remove definitions present
14175 in the program being debugged.
14179 List all the macros defined using the @code{macro define} command.
14182 @cindex macros, example of debugging with
14183 Here is a transcript showing the above commands in action. First, we
14184 show our source files:
14189 #include "sample.h"
14192 #define ADD(x) (M + x)
14197 printf ("Hello, world!\n");
14199 printf ("We're so creative.\n");
14201 printf ("Goodbye, world!\n");
14208 Now, we compile the program using the @sc{gnu} C compiler,
14209 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14210 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14211 and @option{-gdwarf-4}; we recommend always choosing the most recent
14212 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14213 includes information about preprocessor macros in the debugging
14217 $ gcc -gdwarf-2 -g3 sample.c -o sample
14221 Now, we start @value{GDBN} on our sample program:
14225 GNU gdb 2002-05-06-cvs
14226 Copyright 2002 Free Software Foundation, Inc.
14227 GDB is free software, @dots{}
14231 We can expand macros and examine their definitions, even when the
14232 program is not running. @value{GDBN} uses the current listing position
14233 to decide which macro definitions are in scope:
14236 (@value{GDBP}) list main
14239 5 #define ADD(x) (M + x)
14244 10 printf ("Hello, world!\n");
14246 12 printf ("We're so creative.\n");
14247 (@value{GDBP}) info macro ADD
14248 Defined at /home/jimb/gdb/macros/play/sample.c:5
14249 #define ADD(x) (M + x)
14250 (@value{GDBP}) info macro Q
14251 Defined at /home/jimb/gdb/macros/play/sample.h:1
14252 included at /home/jimb/gdb/macros/play/sample.c:2
14254 (@value{GDBP}) macro expand ADD(1)
14255 expands to: (42 + 1)
14256 (@value{GDBP}) macro expand-once ADD(1)
14257 expands to: once (M + 1)
14261 In the example above, note that @code{macro expand-once} expands only
14262 the macro invocation explicit in the original text --- the invocation of
14263 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14264 which was introduced by @code{ADD}.
14266 Once the program is running, @value{GDBN} uses the macro definitions in
14267 force at the source line of the current stack frame:
14270 (@value{GDBP}) break main
14271 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14273 Starting program: /home/jimb/gdb/macros/play/sample
14275 Breakpoint 1, main () at sample.c:10
14276 10 printf ("Hello, world!\n");
14280 At line 10, the definition of the macro @code{N} at line 9 is in force:
14283 (@value{GDBP}) info macro N
14284 Defined at /home/jimb/gdb/macros/play/sample.c:9
14286 (@value{GDBP}) macro expand N Q M
14287 expands to: 28 < 42
14288 (@value{GDBP}) print N Q M
14293 As we step over directives that remove @code{N}'s definition, and then
14294 give it a new definition, @value{GDBN} finds the definition (or lack
14295 thereof) in force at each point:
14298 (@value{GDBP}) next
14300 12 printf ("We're so creative.\n");
14301 (@value{GDBP}) info macro N
14302 The symbol `N' has no definition as a C/C++ preprocessor macro
14303 at /home/jimb/gdb/macros/play/sample.c:12
14304 (@value{GDBP}) next
14306 14 printf ("Goodbye, world!\n");
14307 (@value{GDBP}) info macro N
14308 Defined at /home/jimb/gdb/macros/play/sample.c:13
14310 (@value{GDBP}) macro expand N Q M
14311 expands to: 1729 < 42
14312 (@value{GDBP}) print N Q M
14317 In addition to source files, macros can be defined on the compilation command
14318 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14319 such a way, @value{GDBN} displays the location of their definition as line zero
14320 of the source file submitted to the compiler.
14323 (@value{GDBP}) info macro __STDC__
14324 Defined at /home/jimb/gdb/macros/play/sample.c:0
14331 @chapter Tracepoints
14332 @c This chapter is based on the documentation written by Michael
14333 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14335 @cindex tracepoints
14336 In some applications, it is not feasible for the debugger to interrupt
14337 the program's execution long enough for the developer to learn
14338 anything helpful about its behavior. If the program's correctness
14339 depends on its real-time behavior, delays introduced by a debugger
14340 might cause the program to change its behavior drastically, or perhaps
14341 fail, even when the code itself is correct. It is useful to be able
14342 to observe the program's behavior without interrupting it.
14344 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14345 specify locations in the program, called @dfn{tracepoints}, and
14346 arbitrary expressions to evaluate when those tracepoints are reached.
14347 Later, using the @code{tfind} command, you can examine the values
14348 those expressions had when the program hit the tracepoints. The
14349 expressions may also denote objects in memory---structures or arrays,
14350 for example---whose values @value{GDBN} should record; while visiting
14351 a particular tracepoint, you may inspect those objects as if they were
14352 in memory at that moment. However, because @value{GDBN} records these
14353 values without interacting with you, it can do so quickly and
14354 unobtrusively, hopefully not disturbing the program's behavior.
14356 The tracepoint facility is currently available only for remote
14357 targets. @xref{Targets}. In addition, your remote target must know
14358 how to collect trace data. This functionality is implemented in the
14359 remote stub; however, none of the stubs distributed with @value{GDBN}
14360 support tracepoints as of this writing. The format of the remote
14361 packets used to implement tracepoints are described in @ref{Tracepoint
14364 It is also possible to get trace data from a file, in a manner reminiscent
14365 of corefiles; you specify the filename, and use @code{tfind} to search
14366 through the file. @xref{Trace Files}, for more details.
14368 This chapter describes the tracepoint commands and features.
14371 * Set Tracepoints::
14372 * Analyze Collected Data::
14373 * Tracepoint Variables::
14377 @node Set Tracepoints
14378 @section Commands to Set Tracepoints
14380 Before running such a @dfn{trace experiment}, an arbitrary number of
14381 tracepoints can be set. A tracepoint is actually a special type of
14382 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14383 standard breakpoint commands. For instance, as with breakpoints,
14384 tracepoint numbers are successive integers starting from one, and many
14385 of the commands associated with tracepoints take the tracepoint number
14386 as their argument, to identify which tracepoint to work on.
14388 For each tracepoint, you can specify, in advance, some arbitrary set
14389 of data that you want the target to collect in the trace buffer when
14390 it hits that tracepoint. The collected data can include registers,
14391 local variables, or global data. Later, you can use @value{GDBN}
14392 commands to examine the values these data had at the time the
14393 tracepoint was hit.
14395 Tracepoints do not support every breakpoint feature. Ignore counts on
14396 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14397 commands when they are hit. Tracepoints may not be thread-specific
14400 @cindex fast tracepoints
14401 Some targets may support @dfn{fast tracepoints}, which are inserted in
14402 a different way (such as with a jump instead of a trap), that is
14403 faster but possibly restricted in where they may be installed.
14405 @cindex static tracepoints
14406 @cindex markers, static tracepoints
14407 @cindex probing markers, static tracepoints
14408 Regular and fast tracepoints are dynamic tracing facilities, meaning
14409 that they can be used to insert tracepoints at (almost) any location
14410 in the target. Some targets may also support controlling @dfn{static
14411 tracepoints} from @value{GDBN}. With static tracing, a set of
14412 instrumentation points, also known as @dfn{markers}, are embedded in
14413 the target program, and can be activated or deactivated by name or
14414 address. These are usually placed at locations which facilitate
14415 investigating what the target is actually doing. @value{GDBN}'s
14416 support for static tracing includes being able to list instrumentation
14417 points, and attach them with @value{GDBN} defined high level
14418 tracepoints that expose the whole range of convenience of
14419 @value{GDBN}'s tracepoints support. Namely, support for collecting
14420 registers values and values of global or local (to the instrumentation
14421 point) variables; tracepoint conditions and trace state variables.
14422 The act of installing a @value{GDBN} static tracepoint on an
14423 instrumentation point, or marker, is referred to as @dfn{probing} a
14424 static tracepoint marker.
14426 @code{gdbserver} supports tracepoints on some target systems.
14427 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14429 This section describes commands to set tracepoints and associated
14430 conditions and actions.
14433 * Create and Delete Tracepoints::
14434 * Enable and Disable Tracepoints::
14435 * Tracepoint Passcounts::
14436 * Tracepoint Conditions::
14437 * Trace State Variables::
14438 * Tracepoint Actions::
14439 * Listing Tracepoints::
14440 * Listing Static Tracepoint Markers::
14441 * Starting and Stopping Trace Experiments::
14442 * Tracepoint Restrictions::
14445 @node Create and Delete Tracepoints
14446 @subsection Create and Delete Tracepoints
14449 @cindex set tracepoint
14451 @item trace @var{location}
14452 The @code{trace} command is very similar to the @code{break} command.
14453 Its argument @var{location} can be any valid location.
14454 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14455 which is a point in the target program where the debugger will briefly stop,
14456 collect some data, and then allow the program to continue. Setting a tracepoint
14457 or changing its actions takes effect immediately if the remote stub
14458 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14460 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14461 these changes don't take effect until the next @code{tstart}
14462 command, and once a trace experiment is running, further changes will
14463 not have any effect until the next trace experiment starts. In addition,
14464 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14465 address is not yet resolved. (This is similar to pending breakpoints.)
14466 Pending tracepoints are not downloaded to the target and not installed
14467 until they are resolved. The resolution of pending tracepoints requires
14468 @value{GDBN} support---when debugging with the remote target, and
14469 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14470 tracing}), pending tracepoints can not be resolved (and downloaded to
14471 the remote stub) while @value{GDBN} is disconnected.
14473 Here are some examples of using the @code{trace} command:
14476 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14478 (@value{GDBP}) @b{trace +2} // 2 lines forward
14480 (@value{GDBP}) @b{trace my_function} // first source line of function
14482 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14484 (@value{GDBP}) @b{trace *0x2117c4} // an address
14488 You can abbreviate @code{trace} as @code{tr}.
14490 @item trace @var{location} if @var{cond}
14491 Set a tracepoint with condition @var{cond}; evaluate the expression
14492 @var{cond} each time the tracepoint is reached, and collect data only
14493 if the value is nonzero---that is, if @var{cond} evaluates as true.
14494 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14495 information on tracepoint conditions.
14497 @item ftrace @var{location} [ if @var{cond} ]
14498 @cindex set fast tracepoint
14499 @cindex fast tracepoints, setting
14501 The @code{ftrace} command sets a fast tracepoint. For targets that
14502 support them, fast tracepoints will use a more efficient but possibly
14503 less general technique to trigger data collection, such as a jump
14504 instruction instead of a trap, or some sort of hardware support. It
14505 may not be possible to create a fast tracepoint at the desired
14506 location, in which case the command will exit with an explanatory
14509 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14512 On 32-bit x86-architecture systems, fast tracepoints normally need to
14513 be placed at an instruction that is 5 bytes or longer, but can be
14514 placed at 4-byte instructions if the low 64K of memory of the target
14515 program is available to install trampolines. Some Unix-type systems,
14516 such as @sc{gnu}/Linux, exclude low addresses from the program's
14517 address space; but for instance with the Linux kernel it is possible
14518 to let @value{GDBN} use this area by doing a @command{sysctl} command
14519 to set the @code{mmap_min_addr} kernel parameter, as in
14522 sudo sysctl -w vm.mmap_min_addr=32768
14526 which sets the low address to 32K, which leaves plenty of room for
14527 trampolines. The minimum address should be set to a page boundary.
14529 @item strace @var{location} [ if @var{cond} ]
14530 @cindex set static tracepoint
14531 @cindex static tracepoints, setting
14532 @cindex probe static tracepoint marker
14534 The @code{strace} command sets a static tracepoint. For targets that
14535 support it, setting a static tracepoint probes a static
14536 instrumentation point, or marker, found at @var{location}. It may not
14537 be possible to set a static tracepoint at the desired location, in
14538 which case the command will exit with an explanatory message.
14540 @value{GDBN} handles arguments to @code{strace} exactly as for
14541 @code{trace}, with the addition that the user can also specify
14542 @code{-m @var{marker}} as @var{location}. This probes the marker
14543 identified by the @var{marker} string identifier. This identifier
14544 depends on the static tracepoint backend library your program is
14545 using. You can find all the marker identifiers in the @samp{ID} field
14546 of the @code{info static-tracepoint-markers} command output.
14547 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14548 Markers}. For example, in the following small program using the UST
14554 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14559 the marker id is composed of joining the first two arguments to the
14560 @code{trace_mark} call with a slash, which translates to:
14563 (@value{GDBP}) info static-tracepoint-markers
14564 Cnt Enb ID Address What
14565 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14571 so you may probe the marker above with:
14574 (@value{GDBP}) strace -m ust/bar33
14577 Static tracepoints accept an extra collect action --- @code{collect
14578 $_sdata}. This collects arbitrary user data passed in the probe point
14579 call to the tracing library. In the UST example above, you'll see
14580 that the third argument to @code{trace_mark} is a printf-like format
14581 string. The user data is then the result of running that formatting
14582 string against the following arguments. Note that @code{info
14583 static-tracepoint-markers} command output lists that format string in
14584 the @samp{Data:} field.
14586 You can inspect this data when analyzing the trace buffer, by printing
14587 the $_sdata variable like any other variable available to
14588 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14591 @cindex last tracepoint number
14592 @cindex recent tracepoint number
14593 @cindex tracepoint number
14594 The convenience variable @code{$tpnum} records the tracepoint number
14595 of the most recently set tracepoint.
14597 @kindex delete tracepoint
14598 @cindex tracepoint deletion
14599 @item delete tracepoint @r{[}@var{num}@r{]}
14600 Permanently delete one or more tracepoints. With no argument, the
14601 default is to delete all tracepoints. Note that the regular
14602 @code{delete} command can remove tracepoints also.
14607 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14609 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14613 You can abbreviate this command as @code{del tr}.
14616 @node Enable and Disable Tracepoints
14617 @subsection Enable and Disable Tracepoints
14619 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14622 @kindex disable tracepoint
14623 @item disable tracepoint @r{[}@var{num}@r{]}
14624 Disable tracepoint @var{num}, or all tracepoints if no argument
14625 @var{num} is given. A disabled tracepoint will have no effect during
14626 a trace experiment, but it is not forgotten. You can re-enable
14627 a disabled tracepoint using the @code{enable tracepoint} command.
14628 If the command is issued during a trace experiment and the debug target
14629 has support for disabling tracepoints during a trace experiment, then the
14630 change will be effective immediately. Otherwise, it will be applied to the
14631 next trace experiment.
14633 @kindex enable tracepoint
14634 @item enable tracepoint @r{[}@var{num}@r{]}
14635 Enable tracepoint @var{num}, or all tracepoints. If this command is
14636 issued during a trace experiment and the debug target supports enabling
14637 tracepoints during a trace experiment, then the enabled tracepoints will
14638 become effective immediately. Otherwise, they will become effective the
14639 next time a trace experiment is run.
14642 @node Tracepoint Passcounts
14643 @subsection Tracepoint Passcounts
14647 @cindex tracepoint pass count
14648 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14649 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14650 automatically stop a trace experiment. If a tracepoint's passcount is
14651 @var{n}, then the trace experiment will be automatically stopped on
14652 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14653 @var{num} is not specified, the @code{passcount} command sets the
14654 passcount of the most recently defined tracepoint. If no passcount is
14655 given, the trace experiment will run until stopped explicitly by the
14661 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14662 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14664 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14665 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14666 (@value{GDBP}) @b{trace foo}
14667 (@value{GDBP}) @b{pass 3}
14668 (@value{GDBP}) @b{trace bar}
14669 (@value{GDBP}) @b{pass 2}
14670 (@value{GDBP}) @b{trace baz}
14671 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14672 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14673 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14674 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14678 @node Tracepoint Conditions
14679 @subsection Tracepoint Conditions
14680 @cindex conditional tracepoints
14681 @cindex tracepoint conditions
14683 The simplest sort of tracepoint collects data every time your program
14684 reaches a specified place. You can also specify a @dfn{condition} for
14685 a tracepoint. A condition is just a Boolean expression in your
14686 programming language (@pxref{Expressions, ,Expressions}). A
14687 tracepoint with a condition evaluates the expression each time your
14688 program reaches it, and data collection happens only if the condition
14691 Tracepoint conditions can be specified when a tracepoint is set, by
14692 using @samp{if} in the arguments to the @code{trace} command.
14693 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14694 also be set or changed at any time with the @code{condition} command,
14695 just as with breakpoints.
14697 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14698 the conditional expression itself. Instead, @value{GDBN} encodes the
14699 expression into an agent expression (@pxref{Agent Expressions})
14700 suitable for execution on the target, independently of @value{GDBN}.
14701 Global variables become raw memory locations, locals become stack
14702 accesses, and so forth.
14704 For instance, suppose you have a function that is usually called
14705 frequently, but should not be called after an error has occurred. You
14706 could use the following tracepoint command to collect data about calls
14707 of that function that happen while the error code is propagating
14708 through the program; an unconditional tracepoint could end up
14709 collecting thousands of useless trace frames that you would have to
14713 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14716 @node Trace State Variables
14717 @subsection Trace State Variables
14718 @cindex trace state variables
14720 A @dfn{trace state variable} is a special type of variable that is
14721 created and managed by target-side code. The syntax is the same as
14722 that for GDB's convenience variables (a string prefixed with ``$''),
14723 but they are stored on the target. They must be created explicitly,
14724 using a @code{tvariable} command. They are always 64-bit signed
14727 Trace state variables are remembered by @value{GDBN}, and downloaded
14728 to the target along with tracepoint information when the trace
14729 experiment starts. There are no intrinsic limits on the number of
14730 trace state variables, beyond memory limitations of the target.
14732 @cindex convenience variables, and trace state variables
14733 Although trace state variables are managed by the target, you can use
14734 them in print commands and expressions as if they were convenience
14735 variables; @value{GDBN} will get the current value from the target
14736 while the trace experiment is running. Trace state variables share
14737 the same namespace as other ``$'' variables, which means that you
14738 cannot have trace state variables with names like @code{$23} or
14739 @code{$pc}, nor can you have a trace state variable and a convenience
14740 variable with the same name.
14744 @item tvariable $@var{name} [ = @var{expression} ]
14746 The @code{tvariable} command creates a new trace state variable named
14747 @code{$@var{name}}, and optionally gives it an initial value of
14748 @var{expression}. The @var{expression} is evaluated when this command is
14749 entered; the result will be converted to an integer if possible,
14750 otherwise @value{GDBN} will report an error. A subsequent
14751 @code{tvariable} command specifying the same name does not create a
14752 variable, but instead assigns the supplied initial value to the
14753 existing variable of that name, overwriting any previous initial
14754 value. The default initial value is 0.
14756 @item info tvariables
14757 @kindex info tvariables
14758 List all the trace state variables along with their initial values.
14759 Their current values may also be displayed, if the trace experiment is
14762 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14763 @kindex delete tvariable
14764 Delete the given trace state variables, or all of them if no arguments
14769 @node Tracepoint Actions
14770 @subsection Tracepoint Action Lists
14774 @cindex tracepoint actions
14775 @item actions @r{[}@var{num}@r{]}
14776 This command will prompt for a list of actions to be taken when the
14777 tracepoint is hit. If the tracepoint number @var{num} is not
14778 specified, this command sets the actions for the one that was most
14779 recently defined (so that you can define a tracepoint and then say
14780 @code{actions} without bothering about its number). You specify the
14781 actions themselves on the following lines, one action at a time, and
14782 terminate the actions list with a line containing just @code{end}. So
14783 far, the only defined actions are @code{collect}, @code{teval}, and
14784 @code{while-stepping}.
14786 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14787 Commands, ,Breakpoint Command Lists}), except that only the defined
14788 actions are allowed; any other @value{GDBN} command is rejected.
14790 @cindex remove actions from a tracepoint
14791 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14792 and follow it immediately with @samp{end}.
14795 (@value{GDBP}) @b{collect @var{data}} // collect some data
14797 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14799 (@value{GDBP}) @b{end} // signals the end of actions.
14802 In the following example, the action list begins with @code{collect}
14803 commands indicating the things to be collected when the tracepoint is
14804 hit. Then, in order to single-step and collect additional data
14805 following the tracepoint, a @code{while-stepping} command is used,
14806 followed by the list of things to be collected after each step in a
14807 sequence of single steps. The @code{while-stepping} command is
14808 terminated by its own separate @code{end} command. Lastly, the action
14809 list is terminated by an @code{end} command.
14812 (@value{GDBP}) @b{trace foo}
14813 (@value{GDBP}) @b{actions}
14814 Enter actions for tracepoint 1, one per line:
14817 > while-stepping 12
14818 > collect $pc, arr[i]
14823 @kindex collect @r{(tracepoints)}
14824 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14825 Collect values of the given expressions when the tracepoint is hit.
14826 This command accepts a comma-separated list of any valid expressions.
14827 In addition to global, static, or local variables, the following
14828 special arguments are supported:
14832 Collect all registers.
14835 Collect all function arguments.
14838 Collect all local variables.
14841 Collect the return address. This is helpful if you want to see more
14844 @emph{Note:} The return address location can not always be reliably
14845 determined up front, and the wrong address / registers may end up
14846 collected instead. On some architectures the reliability is higher
14847 for tracepoints at function entry, while on others it's the opposite.
14848 When this happens, backtracing will stop because the return address is
14849 found unavailable (unless another collect rule happened to match it).
14852 Collects the number of arguments from the static probe at which the
14853 tracepoint is located.
14854 @xref{Static Probe Points}.
14856 @item $_probe_arg@var{n}
14857 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14858 from the static probe at which the tracepoint is located.
14859 @xref{Static Probe Points}.
14862 @vindex $_sdata@r{, collect}
14863 Collect static tracepoint marker specific data. Only available for
14864 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14865 Lists}. On the UST static tracepoints library backend, an
14866 instrumentation point resembles a @code{printf} function call. The
14867 tracing library is able to collect user specified data formatted to a
14868 character string using the format provided by the programmer that
14869 instrumented the program. Other backends have similar mechanisms.
14870 Here's an example of a UST marker call:
14873 const char master_name[] = "$your_name";
14874 trace_mark(channel1, marker1, "hello %s", master_name)
14877 In this case, collecting @code{$_sdata} collects the string
14878 @samp{hello $yourname}. When analyzing the trace buffer, you can
14879 inspect @samp{$_sdata} like any other variable available to
14883 You can give several consecutive @code{collect} commands, each one
14884 with a single argument, or one @code{collect} command with several
14885 arguments separated by commas; the effect is the same.
14887 The optional @var{mods} changes the usual handling of the arguments.
14888 @code{s} requests that pointers to chars be handled as strings, in
14889 particular collecting the contents of the memory being pointed at, up
14890 to the first zero. The upper bound is by default the value of the
14891 @code{print elements} variable; if @code{s} is followed by a decimal
14892 number, that is the upper bound instead. So for instance
14893 @samp{collect/s25 mystr} collects as many as 25 characters at
14896 The command @code{info scope} (@pxref{Symbols, info scope}) is
14897 particularly useful for figuring out what data to collect.
14899 @kindex teval @r{(tracepoints)}
14900 @item teval @var{expr1}, @var{expr2}, @dots{}
14901 Evaluate the given expressions when the tracepoint is hit. This
14902 command accepts a comma-separated list of expressions. The results
14903 are discarded, so this is mainly useful for assigning values to trace
14904 state variables (@pxref{Trace State Variables}) without adding those
14905 values to the trace buffer, as would be the case if the @code{collect}
14908 @kindex while-stepping @r{(tracepoints)}
14909 @item while-stepping @var{n}
14910 Perform @var{n} single-step instruction traces after the tracepoint,
14911 collecting new data after each step. The @code{while-stepping}
14912 command is followed by the list of what to collect while stepping
14913 (followed by its own @code{end} command):
14916 > while-stepping 12
14917 > collect $regs, myglobal
14923 Note that @code{$pc} is not automatically collected by
14924 @code{while-stepping}; you need to explicitly collect that register if
14925 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14928 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14929 @kindex set default-collect
14930 @cindex default collection action
14931 This variable is a list of expressions to collect at each tracepoint
14932 hit. It is effectively an additional @code{collect} action prepended
14933 to every tracepoint action list. The expressions are parsed
14934 individually for each tracepoint, so for instance a variable named
14935 @code{xyz} may be interpreted as a global for one tracepoint, and a
14936 local for another, as appropriate to the tracepoint's location.
14938 @item show default-collect
14939 @kindex show default-collect
14940 Show the list of expressions that are collected by default at each
14945 @node Listing Tracepoints
14946 @subsection Listing Tracepoints
14949 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14950 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14951 @cindex information about tracepoints
14952 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14953 Display information about the tracepoint @var{num}. If you don't
14954 specify a tracepoint number, displays information about all the
14955 tracepoints defined so far. The format is similar to that used for
14956 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14957 command, simply restricting itself to tracepoints.
14959 A tracepoint's listing may include additional information specific to
14964 its passcount as given by the @code{passcount @var{n}} command
14967 the state about installed on target of each location
14971 (@value{GDBP}) @b{info trace}
14972 Num Type Disp Enb Address What
14973 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14975 collect globfoo, $regs
14980 2 tracepoint keep y <MULTIPLE>
14982 2.1 y 0x0804859c in func4 at change-loc.h:35
14983 installed on target
14984 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14985 installed on target
14986 2.3 y <PENDING> set_tracepoint
14987 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14988 not installed on target
14993 This command can be abbreviated @code{info tp}.
14996 @node Listing Static Tracepoint Markers
14997 @subsection Listing Static Tracepoint Markers
15000 @kindex info static-tracepoint-markers
15001 @cindex information about static tracepoint markers
15002 @item info static-tracepoint-markers
15003 Display information about all static tracepoint markers defined in the
15006 For each marker, the following columns are printed:
15010 An incrementing counter, output to help readability. This is not a
15013 The marker ID, as reported by the target.
15014 @item Enabled or Disabled
15015 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15016 that are not enabled.
15018 Where the marker is in your program, as a memory address.
15020 Where the marker is in the source for your program, as a file and line
15021 number. If the debug information included in the program does not
15022 allow @value{GDBN} to locate the source of the marker, this column
15023 will be left blank.
15027 In addition, the following information may be printed for each marker:
15031 User data passed to the tracing library by the marker call. In the
15032 UST backend, this is the format string passed as argument to the
15034 @item Static tracepoints probing the marker
15035 The list of static tracepoints attached to the marker.
15039 (@value{GDBP}) info static-tracepoint-markers
15040 Cnt ID Enb Address What
15041 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15042 Data: number1 %d number2 %d
15043 Probed by static tracepoints: #2
15044 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15050 @node Starting and Stopping Trace Experiments
15051 @subsection Starting and Stopping Trace Experiments
15054 @kindex tstart [ @var{notes} ]
15055 @cindex start a new trace experiment
15056 @cindex collected data discarded
15058 This command starts the trace experiment, and begins collecting data.
15059 It has the side effect of discarding all the data collected in the
15060 trace buffer during the previous trace experiment. If any arguments
15061 are supplied, they are taken as a note and stored with the trace
15062 experiment's state. The notes may be arbitrary text, and are
15063 especially useful with disconnected tracing in a multi-user context;
15064 the notes can explain what the trace is doing, supply user contact
15065 information, and so forth.
15067 @kindex tstop [ @var{notes} ]
15068 @cindex stop a running trace experiment
15070 This command stops the trace experiment. If any arguments are
15071 supplied, they are recorded with the experiment as a note. This is
15072 useful if you are stopping a trace started by someone else, for
15073 instance if the trace is interfering with the system's behavior and
15074 needs to be stopped quickly.
15076 @strong{Note}: a trace experiment and data collection may stop
15077 automatically if any tracepoint's passcount is reached
15078 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15081 @cindex status of trace data collection
15082 @cindex trace experiment, status of
15084 This command displays the status of the current trace data
15088 Here is an example of the commands we described so far:
15091 (@value{GDBP}) @b{trace gdb_c_test}
15092 (@value{GDBP}) @b{actions}
15093 Enter actions for tracepoint #1, one per line.
15094 > collect $regs,$locals,$args
15095 > while-stepping 11
15099 (@value{GDBP}) @b{tstart}
15100 [time passes @dots{}]
15101 (@value{GDBP}) @b{tstop}
15104 @anchor{disconnected tracing}
15105 @cindex disconnected tracing
15106 You can choose to continue running the trace experiment even if
15107 @value{GDBN} disconnects from the target, voluntarily or
15108 involuntarily. For commands such as @code{detach}, the debugger will
15109 ask what you want to do with the trace. But for unexpected
15110 terminations (@value{GDBN} crash, network outage), it would be
15111 unfortunate to lose hard-won trace data, so the variable
15112 @code{disconnected-tracing} lets you decide whether the trace should
15113 continue running without @value{GDBN}.
15116 @item set disconnected-tracing on
15117 @itemx set disconnected-tracing off
15118 @kindex set disconnected-tracing
15119 Choose whether a tracing run should continue to run if @value{GDBN}
15120 has disconnected from the target. Note that @code{detach} or
15121 @code{quit} will ask you directly what to do about a running trace no
15122 matter what this variable's setting, so the variable is mainly useful
15123 for handling unexpected situations, such as loss of the network.
15125 @item show disconnected-tracing
15126 @kindex show disconnected-tracing
15127 Show the current choice for disconnected tracing.
15131 When you reconnect to the target, the trace experiment may or may not
15132 still be running; it might have filled the trace buffer in the
15133 meantime, or stopped for one of the other reasons. If it is running,
15134 it will continue after reconnection.
15136 Upon reconnection, the target will upload information about the
15137 tracepoints in effect. @value{GDBN} will then compare that
15138 information to the set of tracepoints currently defined, and attempt
15139 to match them up, allowing for the possibility that the numbers may
15140 have changed due to creation and deletion in the meantime. If one of
15141 the target's tracepoints does not match any in @value{GDBN}, the
15142 debugger will create a new tracepoint, so that you have a number with
15143 which to specify that tracepoint. This matching-up process is
15144 necessarily heuristic, and it may result in useless tracepoints being
15145 created; you may simply delete them if they are of no use.
15147 @cindex circular trace buffer
15148 If your target agent supports a @dfn{circular trace buffer}, then you
15149 can run a trace experiment indefinitely without filling the trace
15150 buffer; when space runs out, the agent deletes already-collected trace
15151 frames, oldest first, until there is enough room to continue
15152 collecting. This is especially useful if your tracepoints are being
15153 hit too often, and your trace gets terminated prematurely because the
15154 buffer is full. To ask for a circular trace buffer, simply set
15155 @samp{circular-trace-buffer} to on. You can set this at any time,
15156 including during tracing; if the agent can do it, it will change
15157 buffer handling on the fly, otherwise it will not take effect until
15161 @item set circular-trace-buffer on
15162 @itemx set circular-trace-buffer off
15163 @kindex set circular-trace-buffer
15164 Choose whether a tracing run should use a linear or circular buffer
15165 for trace data. A linear buffer will not lose any trace data, but may
15166 fill up prematurely, while a circular buffer will discard old trace
15167 data, but it will have always room for the latest tracepoint hits.
15169 @item show circular-trace-buffer
15170 @kindex show circular-trace-buffer
15171 Show the current choice for the trace buffer. Note that this may not
15172 match the agent's current buffer handling, nor is it guaranteed to
15173 match the setting that might have been in effect during a past run,
15174 for instance if you are looking at frames from a trace file.
15179 @item set trace-buffer-size @var{n}
15180 @itemx set trace-buffer-size unlimited
15181 @kindex set trace-buffer-size
15182 Request that the target use a trace buffer of @var{n} bytes. Not all
15183 targets will honor the request; they may have a compiled-in size for
15184 the trace buffer, or some other limitation. Set to a value of
15185 @code{unlimited} or @code{-1} to let the target use whatever size it
15186 likes. This is also the default.
15188 @item show trace-buffer-size
15189 @kindex show trace-buffer-size
15190 Show the current requested size for the trace buffer. Note that this
15191 will only match the actual size if the target supports size-setting,
15192 and was able to handle the requested size. For instance, if the
15193 target can only change buffer size between runs, this variable will
15194 not reflect the change until the next run starts. Use @code{tstatus}
15195 to get a report of the actual buffer size.
15199 @item set trace-user @var{text}
15200 @kindex set trace-user
15202 @item show trace-user
15203 @kindex show trace-user
15205 @item set trace-notes @var{text}
15206 @kindex set trace-notes
15207 Set the trace run's notes.
15209 @item show trace-notes
15210 @kindex show trace-notes
15211 Show the trace run's notes.
15213 @item set trace-stop-notes @var{text}
15214 @kindex set trace-stop-notes
15215 Set the trace run's stop notes. The handling of the note is as for
15216 @code{tstop} arguments; the set command is convenient way to fix a
15217 stop note that is mistaken or incomplete.
15219 @item show trace-stop-notes
15220 @kindex show trace-stop-notes
15221 Show the trace run's stop notes.
15225 @node Tracepoint Restrictions
15226 @subsection Tracepoint Restrictions
15228 @cindex tracepoint restrictions
15229 There are a number of restrictions on the use of tracepoints. As
15230 described above, tracepoint data gathering occurs on the target
15231 without interaction from @value{GDBN}. Thus the full capabilities of
15232 the debugger are not available during data gathering, and then at data
15233 examination time, you will be limited by only having what was
15234 collected. The following items describe some common problems, but it
15235 is not exhaustive, and you may run into additional difficulties not
15241 Tracepoint expressions are intended to gather objects (lvalues). Thus
15242 the full flexibility of GDB's expression evaluator is not available.
15243 You cannot call functions, cast objects to aggregate types, access
15244 convenience variables or modify values (except by assignment to trace
15245 state variables). Some language features may implicitly call
15246 functions (for instance Objective-C fields with accessors), and therefore
15247 cannot be collected either.
15250 Collection of local variables, either individually or in bulk with
15251 @code{$locals} or @code{$args}, during @code{while-stepping} may
15252 behave erratically. The stepping action may enter a new scope (for
15253 instance by stepping into a function), or the location of the variable
15254 may change (for instance it is loaded into a register). The
15255 tracepoint data recorded uses the location information for the
15256 variables that is correct for the tracepoint location. When the
15257 tracepoint is created, it is not possible, in general, to determine
15258 where the steps of a @code{while-stepping} sequence will advance the
15259 program---particularly if a conditional branch is stepped.
15262 Collection of an incompletely-initialized or partially-destroyed object
15263 may result in something that @value{GDBN} cannot display, or displays
15264 in a misleading way.
15267 When @value{GDBN} displays a pointer to character it automatically
15268 dereferences the pointer to also display characters of the string
15269 being pointed to. However, collecting the pointer during tracing does
15270 not automatically collect the string. You need to explicitly
15271 dereference the pointer and provide size information if you want to
15272 collect not only the pointer, but the memory pointed to. For example,
15273 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15277 It is not possible to collect a complete stack backtrace at a
15278 tracepoint. Instead, you may collect the registers and a few hundred
15279 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15280 (adjust to use the name of the actual stack pointer register on your
15281 target architecture, and the amount of stack you wish to capture).
15282 Then the @code{backtrace} command will show a partial backtrace when
15283 using a trace frame. The number of stack frames that can be examined
15284 depends on the sizes of the frames in the collected stack. Note that
15285 if you ask for a block so large that it goes past the bottom of the
15286 stack, the target agent may report an error trying to read from an
15290 If you do not collect registers at a tracepoint, @value{GDBN} can
15291 infer that the value of @code{$pc} must be the same as the address of
15292 the tracepoint and use that when you are looking at a trace frame
15293 for that tracepoint. However, this cannot work if the tracepoint has
15294 multiple locations (for instance if it was set in a function that was
15295 inlined), or if it has a @code{while-stepping} loop. In those cases
15296 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15301 @node Analyze Collected Data
15302 @section Using the Collected Data
15304 After the tracepoint experiment ends, you use @value{GDBN} commands
15305 for examining the trace data. The basic idea is that each tracepoint
15306 collects a trace @dfn{snapshot} every time it is hit and another
15307 snapshot every time it single-steps. All these snapshots are
15308 consecutively numbered from zero and go into a buffer, and you can
15309 examine them later. The way you examine them is to @dfn{focus} on a
15310 specific trace snapshot. When the remote stub is focused on a trace
15311 snapshot, it will respond to all @value{GDBN} requests for memory and
15312 registers by reading from the buffer which belongs to that snapshot,
15313 rather than from @emph{real} memory or registers of the program being
15314 debugged. This means that @strong{all} @value{GDBN} commands
15315 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15316 behave as if we were currently debugging the program state as it was
15317 when the tracepoint occurred. Any requests for data that are not in
15318 the buffer will fail.
15321 * tfind:: How to select a trace snapshot
15322 * tdump:: How to display all data for a snapshot
15323 * save tracepoints:: How to save tracepoints for a future run
15327 @subsection @code{tfind @var{n}}
15330 @cindex select trace snapshot
15331 @cindex find trace snapshot
15332 The basic command for selecting a trace snapshot from the buffer is
15333 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15334 counting from zero. If no argument @var{n} is given, the next
15335 snapshot is selected.
15337 Here are the various forms of using the @code{tfind} command.
15341 Find the first snapshot in the buffer. This is a synonym for
15342 @code{tfind 0} (since 0 is the number of the first snapshot).
15345 Stop debugging trace snapshots, resume @emph{live} debugging.
15348 Same as @samp{tfind none}.
15351 No argument means find the next trace snapshot or find the first
15352 one if no trace snapshot is selected.
15355 Find the previous trace snapshot before the current one. This permits
15356 retracing earlier steps.
15358 @item tfind tracepoint @var{num}
15359 Find the next snapshot associated with tracepoint @var{num}. Search
15360 proceeds forward from the last examined trace snapshot. If no
15361 argument @var{num} is given, it means find the next snapshot collected
15362 for the same tracepoint as the current snapshot.
15364 @item tfind pc @var{addr}
15365 Find the next snapshot associated with the value @var{addr} of the
15366 program counter. Search proceeds forward from the last examined trace
15367 snapshot. If no argument @var{addr} is given, it means find the next
15368 snapshot with the same value of PC as the current snapshot.
15370 @item tfind outside @var{addr1}, @var{addr2}
15371 Find the next snapshot whose PC is outside the given range of
15372 addresses (exclusive).
15374 @item tfind range @var{addr1}, @var{addr2}
15375 Find the next snapshot whose PC is between @var{addr1} and
15376 @var{addr2} (inclusive).
15378 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15379 Find the next snapshot associated with the source line @var{n}. If
15380 the optional argument @var{file} is given, refer to line @var{n} in
15381 that source file. Search proceeds forward from the last examined
15382 trace snapshot. If no argument @var{n} is given, it means find the
15383 next line other than the one currently being examined; thus saying
15384 @code{tfind line} repeatedly can appear to have the same effect as
15385 stepping from line to line in a @emph{live} debugging session.
15388 The default arguments for the @code{tfind} commands are specifically
15389 designed to make it easy to scan through the trace buffer. For
15390 instance, @code{tfind} with no argument selects the next trace
15391 snapshot, and @code{tfind -} with no argument selects the previous
15392 trace snapshot. So, by giving one @code{tfind} command, and then
15393 simply hitting @key{RET} repeatedly you can examine all the trace
15394 snapshots in order. Or, by saying @code{tfind -} and then hitting
15395 @key{RET} repeatedly you can examine the snapshots in reverse order.
15396 The @code{tfind line} command with no argument selects the snapshot
15397 for the next source line executed. The @code{tfind pc} command with
15398 no argument selects the next snapshot with the same program counter
15399 (PC) as the current frame. The @code{tfind tracepoint} command with
15400 no argument selects the next trace snapshot collected by the same
15401 tracepoint as the current one.
15403 In addition to letting you scan through the trace buffer manually,
15404 these commands make it easy to construct @value{GDBN} scripts that
15405 scan through the trace buffer and print out whatever collected data
15406 you are interested in. Thus, if we want to examine the PC, FP, and SP
15407 registers from each trace frame in the buffer, we can say this:
15410 (@value{GDBP}) @b{tfind start}
15411 (@value{GDBP}) @b{while ($trace_frame != -1)}
15412 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15413 $trace_frame, $pc, $sp, $fp
15417 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15418 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15419 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15420 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15421 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15422 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15423 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15424 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15425 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15426 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15427 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15430 Or, if we want to examine the variable @code{X} at each source line in
15434 (@value{GDBP}) @b{tfind start}
15435 (@value{GDBP}) @b{while ($trace_frame != -1)}
15436 > printf "Frame %d, X == %d\n", $trace_frame, X
15446 @subsection @code{tdump}
15448 @cindex dump all data collected at tracepoint
15449 @cindex tracepoint data, display
15451 This command takes no arguments. It prints all the data collected at
15452 the current trace snapshot.
15455 (@value{GDBP}) @b{trace 444}
15456 (@value{GDBP}) @b{actions}
15457 Enter actions for tracepoint #2, one per line:
15458 > collect $regs, $locals, $args, gdb_long_test
15461 (@value{GDBP}) @b{tstart}
15463 (@value{GDBP}) @b{tfind line 444}
15464 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15466 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15468 (@value{GDBP}) @b{tdump}
15469 Data collected at tracepoint 2, trace frame 1:
15470 d0 0xc4aa0085 -995491707
15474 d4 0x71aea3d 119204413
15477 d7 0x380035 3670069
15478 a0 0x19e24a 1696330
15479 a1 0x3000668 50333288
15481 a3 0x322000 3284992
15482 a4 0x3000698 50333336
15483 a5 0x1ad3cc 1758156
15484 fp 0x30bf3c 0x30bf3c
15485 sp 0x30bf34 0x30bf34
15487 pc 0x20b2c8 0x20b2c8
15491 p = 0x20e5b4 "gdb-test"
15498 gdb_long_test = 17 '\021'
15503 @code{tdump} works by scanning the tracepoint's current collection
15504 actions and printing the value of each expression listed. So
15505 @code{tdump} can fail, if after a run, you change the tracepoint's
15506 actions to mention variables that were not collected during the run.
15508 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15509 uses the collected value of @code{$pc} to distinguish between trace
15510 frames that were collected at the tracepoint hit, and frames that were
15511 collected while stepping. This allows it to correctly choose whether
15512 to display the basic list of collections, or the collections from the
15513 body of the while-stepping loop. However, if @code{$pc} was not collected,
15514 then @code{tdump} will always attempt to dump using the basic collection
15515 list, and may fail if a while-stepping frame does not include all the
15516 same data that is collected at the tracepoint hit.
15517 @c This is getting pretty arcane, example would be good.
15519 @node save tracepoints
15520 @subsection @code{save tracepoints @var{filename}}
15521 @kindex save tracepoints
15522 @kindex save-tracepoints
15523 @cindex save tracepoints for future sessions
15525 This command saves all current tracepoint definitions together with
15526 their actions and passcounts, into a file @file{@var{filename}}
15527 suitable for use in a later debugging session. To read the saved
15528 tracepoint definitions, use the @code{source} command (@pxref{Command
15529 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15530 alias for @w{@code{save tracepoints}}
15532 @node Tracepoint Variables
15533 @section Convenience Variables for Tracepoints
15534 @cindex tracepoint variables
15535 @cindex convenience variables for tracepoints
15538 @vindex $trace_frame
15539 @item (int) $trace_frame
15540 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15541 snapshot is selected.
15543 @vindex $tracepoint
15544 @item (int) $tracepoint
15545 The tracepoint for the current trace snapshot.
15547 @vindex $trace_line
15548 @item (int) $trace_line
15549 The line number for the current trace snapshot.
15551 @vindex $trace_file
15552 @item (char []) $trace_file
15553 The source file for the current trace snapshot.
15555 @vindex $trace_func
15556 @item (char []) $trace_func
15557 The name of the function containing @code{$tracepoint}.
15560 Note: @code{$trace_file} is not suitable for use in @code{printf},
15561 use @code{output} instead.
15563 Here's a simple example of using these convenience variables for
15564 stepping through all the trace snapshots and printing some of their
15565 data. Note that these are not the same as trace state variables,
15566 which are managed by the target.
15569 (@value{GDBP}) @b{tfind start}
15571 (@value{GDBP}) @b{while $trace_frame != -1}
15572 > output $trace_file
15573 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15579 @section Using Trace Files
15580 @cindex trace files
15582 In some situations, the target running a trace experiment may no
15583 longer be available; perhaps it crashed, or the hardware was needed
15584 for a different activity. To handle these cases, you can arrange to
15585 dump the trace data into a file, and later use that file as a source
15586 of trace data, via the @code{target tfile} command.
15591 @item tsave [ -r ] @var{filename}
15592 @itemx tsave [-ctf] @var{dirname}
15593 Save the trace data to @var{filename}. By default, this command
15594 assumes that @var{filename} refers to the host filesystem, so if
15595 necessary @value{GDBN} will copy raw trace data up from the target and
15596 then save it. If the target supports it, you can also supply the
15597 optional argument @code{-r} (``remote'') to direct the target to save
15598 the data directly into @var{filename} in its own filesystem, which may be
15599 more efficient if the trace buffer is very large. (Note, however, that
15600 @code{target tfile} can only read from files accessible to the host.)
15601 By default, this command will save trace frame in tfile format.
15602 You can supply the optional argument @code{-ctf} to save data in CTF
15603 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15604 that can be shared by multiple debugging and tracing tools. Please go to
15605 @indicateurl{http://www.efficios.com/ctf} to get more information.
15607 @kindex target tfile
15611 @item target tfile @var{filename}
15612 @itemx target ctf @var{dirname}
15613 Use the file named @var{filename} or directory named @var{dirname} as
15614 a source of trace data. Commands that examine data work as they do with
15615 a live target, but it is not possible to run any new trace experiments.
15616 @code{tstatus} will report the state of the trace run at the moment
15617 the data was saved, as well as the current trace frame you are examining.
15618 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15622 (@value{GDBP}) target ctf ctf.ctf
15623 (@value{GDBP}) tfind
15624 Found trace frame 0, tracepoint 2
15625 39 ++a; /* set tracepoint 1 here */
15626 (@value{GDBP}) tdump
15627 Data collected at tracepoint 2, trace frame 0:
15631 c = @{"123", "456", "789", "123", "456", "789"@}
15632 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15640 @chapter Debugging Programs That Use Overlays
15643 If your program is too large to fit completely in your target system's
15644 memory, you can sometimes use @dfn{overlays} to work around this
15645 problem. @value{GDBN} provides some support for debugging programs that
15649 * How Overlays Work:: A general explanation of overlays.
15650 * Overlay Commands:: Managing overlays in @value{GDBN}.
15651 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15652 mapped by asking the inferior.
15653 * Overlay Sample Program:: A sample program using overlays.
15656 @node How Overlays Work
15657 @section How Overlays Work
15658 @cindex mapped overlays
15659 @cindex unmapped overlays
15660 @cindex load address, overlay's
15661 @cindex mapped address
15662 @cindex overlay area
15664 Suppose you have a computer whose instruction address space is only 64
15665 kilobytes long, but which has much more memory which can be accessed by
15666 other means: special instructions, segment registers, or memory
15667 management hardware, for example. Suppose further that you want to
15668 adapt a program which is larger than 64 kilobytes to run on this system.
15670 One solution is to identify modules of your program which are relatively
15671 independent, and need not call each other directly; call these modules
15672 @dfn{overlays}. Separate the overlays from the main program, and place
15673 their machine code in the larger memory. Place your main program in
15674 instruction memory, but leave at least enough space there to hold the
15675 largest overlay as well.
15677 Now, to call a function located in an overlay, you must first copy that
15678 overlay's machine code from the large memory into the space set aside
15679 for it in the instruction memory, and then jump to its entry point
15682 @c NB: In the below the mapped area's size is greater or equal to the
15683 @c size of all overlays. This is intentional to remind the developer
15684 @c that overlays don't necessarily need to be the same size.
15688 Data Instruction Larger
15689 Address Space Address Space Address Space
15690 +-----------+ +-----------+ +-----------+
15692 +-----------+ +-----------+ +-----------+<-- overlay 1
15693 | program | | main | .----| overlay 1 | load address
15694 | variables | | program | | +-----------+
15695 | and heap | | | | | |
15696 +-----------+ | | | +-----------+<-- overlay 2
15697 | | +-----------+ | | | load address
15698 +-----------+ | | | .-| overlay 2 |
15700 mapped --->+-----------+ | | +-----------+
15701 address | | | | | |
15702 | overlay | <-' | | |
15703 | area | <---' +-----------+<-- overlay 3
15704 | | <---. | | load address
15705 +-----------+ `--| overlay 3 |
15712 @anchor{A code overlay}A code overlay
15716 The diagram (@pxref{A code overlay}) shows a system with separate data
15717 and instruction address spaces. To map an overlay, the program copies
15718 its code from the larger address space to the instruction address space.
15719 Since the overlays shown here all use the same mapped address, only one
15720 may be mapped at a time. For a system with a single address space for
15721 data and instructions, the diagram would be similar, except that the
15722 program variables and heap would share an address space with the main
15723 program and the overlay area.
15725 An overlay loaded into instruction memory and ready for use is called a
15726 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15727 instruction memory. An overlay not present (or only partially present)
15728 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15729 is its address in the larger memory. The mapped address is also called
15730 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15731 called the @dfn{load memory address}, or @dfn{LMA}.
15733 Unfortunately, overlays are not a completely transparent way to adapt a
15734 program to limited instruction memory. They introduce a new set of
15735 global constraints you must keep in mind as you design your program:
15740 Before calling or returning to a function in an overlay, your program
15741 must make sure that overlay is actually mapped. Otherwise, the call or
15742 return will transfer control to the right address, but in the wrong
15743 overlay, and your program will probably crash.
15746 If the process of mapping an overlay is expensive on your system, you
15747 will need to choose your overlays carefully to minimize their effect on
15748 your program's performance.
15751 The executable file you load onto your system must contain each
15752 overlay's instructions, appearing at the overlay's load address, not its
15753 mapped address. However, each overlay's instructions must be relocated
15754 and its symbols defined as if the overlay were at its mapped address.
15755 You can use GNU linker scripts to specify different load and relocation
15756 addresses for pieces of your program; see @ref{Overlay Description,,,
15757 ld.info, Using ld: the GNU linker}.
15760 The procedure for loading executable files onto your system must be able
15761 to load their contents into the larger address space as well as the
15762 instruction and data spaces.
15766 The overlay system described above is rather simple, and could be
15767 improved in many ways:
15772 If your system has suitable bank switch registers or memory management
15773 hardware, you could use those facilities to make an overlay's load area
15774 contents simply appear at their mapped address in instruction space.
15775 This would probably be faster than copying the overlay to its mapped
15776 area in the usual way.
15779 If your overlays are small enough, you could set aside more than one
15780 overlay area, and have more than one overlay mapped at a time.
15783 You can use overlays to manage data, as well as instructions. In
15784 general, data overlays are even less transparent to your design than
15785 code overlays: whereas code overlays only require care when you call or
15786 return to functions, data overlays require care every time you access
15787 the data. Also, if you change the contents of a data overlay, you
15788 must copy its contents back out to its load address before you can copy a
15789 different data overlay into the same mapped area.
15794 @node Overlay Commands
15795 @section Overlay Commands
15797 To use @value{GDBN}'s overlay support, each overlay in your program must
15798 correspond to a separate section of the executable file. The section's
15799 virtual memory address and load memory address must be the overlay's
15800 mapped and load addresses. Identifying overlays with sections allows
15801 @value{GDBN} to determine the appropriate address of a function or
15802 variable, depending on whether the overlay is mapped or not.
15804 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15805 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15810 Disable @value{GDBN}'s overlay support. When overlay support is
15811 disabled, @value{GDBN} assumes that all functions and variables are
15812 always present at their mapped addresses. By default, @value{GDBN}'s
15813 overlay support is disabled.
15815 @item overlay manual
15816 @cindex manual overlay debugging
15817 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15818 relies on you to tell it which overlays are mapped, and which are not,
15819 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15820 commands described below.
15822 @item overlay map-overlay @var{overlay}
15823 @itemx overlay map @var{overlay}
15824 @cindex map an overlay
15825 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15826 be the name of the object file section containing the overlay. When an
15827 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15828 functions and variables at their mapped addresses. @value{GDBN} assumes
15829 that any other overlays whose mapped ranges overlap that of
15830 @var{overlay} are now unmapped.
15832 @item overlay unmap-overlay @var{overlay}
15833 @itemx overlay unmap @var{overlay}
15834 @cindex unmap an overlay
15835 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15836 must be the name of the object file section containing the overlay.
15837 When an overlay is unmapped, @value{GDBN} assumes it can find the
15838 overlay's functions and variables at their load addresses.
15841 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15842 consults a data structure the overlay manager maintains in the inferior
15843 to see which overlays are mapped. For details, see @ref{Automatic
15844 Overlay Debugging}.
15846 @item overlay load-target
15847 @itemx overlay load
15848 @cindex reloading the overlay table
15849 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15850 re-reads the table @value{GDBN} automatically each time the inferior
15851 stops, so this command should only be necessary if you have changed the
15852 overlay mapping yourself using @value{GDBN}. This command is only
15853 useful when using automatic overlay debugging.
15855 @item overlay list-overlays
15856 @itemx overlay list
15857 @cindex listing mapped overlays
15858 Display a list of the overlays currently mapped, along with their mapped
15859 addresses, load addresses, and sizes.
15863 Normally, when @value{GDBN} prints a code address, it includes the name
15864 of the function the address falls in:
15867 (@value{GDBP}) print main
15868 $3 = @{int ()@} 0x11a0 <main>
15871 When overlay debugging is enabled, @value{GDBN} recognizes code in
15872 unmapped overlays, and prints the names of unmapped functions with
15873 asterisks around them. For example, if @code{foo} is a function in an
15874 unmapped overlay, @value{GDBN} prints it this way:
15877 (@value{GDBP}) overlay list
15878 No sections are mapped.
15879 (@value{GDBP}) print foo
15880 $5 = @{int (int)@} 0x100000 <*foo*>
15883 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15887 (@value{GDBP}) overlay list
15888 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15889 mapped at 0x1016 - 0x104a
15890 (@value{GDBP}) print foo
15891 $6 = @{int (int)@} 0x1016 <foo>
15894 When overlay debugging is enabled, @value{GDBN} can find the correct
15895 address for functions and variables in an overlay, whether or not the
15896 overlay is mapped. This allows most @value{GDBN} commands, like
15897 @code{break} and @code{disassemble}, to work normally, even on unmapped
15898 code. However, @value{GDBN}'s breakpoint support has some limitations:
15902 @cindex breakpoints in overlays
15903 @cindex overlays, setting breakpoints in
15904 You can set breakpoints in functions in unmapped overlays, as long as
15905 @value{GDBN} can write to the overlay at its load address.
15907 @value{GDBN} can not set hardware or simulator-based breakpoints in
15908 unmapped overlays. However, if you set a breakpoint at the end of your
15909 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15910 you are using manual overlay management), @value{GDBN} will re-set its
15911 breakpoints properly.
15915 @node Automatic Overlay Debugging
15916 @section Automatic Overlay Debugging
15917 @cindex automatic overlay debugging
15919 @value{GDBN} can automatically track which overlays are mapped and which
15920 are not, given some simple co-operation from the overlay manager in the
15921 inferior. If you enable automatic overlay debugging with the
15922 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15923 looks in the inferior's memory for certain variables describing the
15924 current state of the overlays.
15926 Here are the variables your overlay manager must define to support
15927 @value{GDBN}'s automatic overlay debugging:
15931 @item @code{_ovly_table}:
15932 This variable must be an array of the following structures:
15937 /* The overlay's mapped address. */
15940 /* The size of the overlay, in bytes. */
15941 unsigned long size;
15943 /* The overlay's load address. */
15946 /* Non-zero if the overlay is currently mapped;
15948 unsigned long mapped;
15952 @item @code{_novlys}:
15953 This variable must be a four-byte signed integer, holding the total
15954 number of elements in @code{_ovly_table}.
15958 To decide whether a particular overlay is mapped or not, @value{GDBN}
15959 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15960 @code{lma} members equal the VMA and LMA of the overlay's section in the
15961 executable file. When @value{GDBN} finds a matching entry, it consults
15962 the entry's @code{mapped} member to determine whether the overlay is
15965 In addition, your overlay manager may define a function called
15966 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15967 will silently set a breakpoint there. If the overlay manager then
15968 calls this function whenever it has changed the overlay table, this
15969 will enable @value{GDBN} to accurately keep track of which overlays
15970 are in program memory, and update any breakpoints that may be set
15971 in overlays. This will allow breakpoints to work even if the
15972 overlays are kept in ROM or other non-writable memory while they
15973 are not being executed.
15975 @node Overlay Sample Program
15976 @section Overlay Sample Program
15977 @cindex overlay example program
15979 When linking a program which uses overlays, you must place the overlays
15980 at their load addresses, while relocating them to run at their mapped
15981 addresses. To do this, you must write a linker script (@pxref{Overlay
15982 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15983 since linker scripts are specific to a particular host system, target
15984 architecture, and target memory layout, this manual cannot provide
15985 portable sample code demonstrating @value{GDBN}'s overlay support.
15987 However, the @value{GDBN} source distribution does contain an overlaid
15988 program, with linker scripts for a few systems, as part of its test
15989 suite. The program consists of the following files from
15990 @file{gdb/testsuite/gdb.base}:
15994 The main program file.
15996 A simple overlay manager, used by @file{overlays.c}.
16001 Overlay modules, loaded and used by @file{overlays.c}.
16004 Linker scripts for linking the test program on the @code{d10v-elf}
16005 and @code{m32r-elf} targets.
16008 You can build the test program using the @code{d10v-elf} GCC
16009 cross-compiler like this:
16012 $ d10v-elf-gcc -g -c overlays.c
16013 $ d10v-elf-gcc -g -c ovlymgr.c
16014 $ d10v-elf-gcc -g -c foo.c
16015 $ d10v-elf-gcc -g -c bar.c
16016 $ d10v-elf-gcc -g -c baz.c
16017 $ d10v-elf-gcc -g -c grbx.c
16018 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16019 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16022 The build process is identical for any other architecture, except that
16023 you must substitute the appropriate compiler and linker script for the
16024 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16028 @chapter Using @value{GDBN} with Different Languages
16031 Although programming languages generally have common aspects, they are
16032 rarely expressed in the same manner. For instance, in ANSI C,
16033 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16034 Modula-2, it is accomplished by @code{p^}. Values can also be
16035 represented (and displayed) differently. Hex numbers in C appear as
16036 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16038 @cindex working language
16039 Language-specific information is built into @value{GDBN} for some languages,
16040 allowing you to express operations like the above in your program's
16041 native language, and allowing @value{GDBN} to output values in a manner
16042 consistent with the syntax of your program's native language. The
16043 language you use to build expressions is called the @dfn{working
16047 * Setting:: Switching between source languages
16048 * Show:: Displaying the language
16049 * Checks:: Type and range checks
16050 * Supported Languages:: Supported languages
16051 * Unsupported Languages:: Unsupported languages
16055 @section Switching Between Source Languages
16057 There are two ways to control the working language---either have @value{GDBN}
16058 set it automatically, or select it manually yourself. You can use the
16059 @code{set language} command for either purpose. On startup, @value{GDBN}
16060 defaults to setting the language automatically. The working language is
16061 used to determine how expressions you type are interpreted, how values
16064 In addition to the working language, every source file that
16065 @value{GDBN} knows about has its own working language. For some object
16066 file formats, the compiler might indicate which language a particular
16067 source file is in. However, most of the time @value{GDBN} infers the
16068 language from the name of the file. The language of a source file
16069 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16070 show each frame appropriately for its own language. There is no way to
16071 set the language of a source file from within @value{GDBN}, but you can
16072 set the language associated with a filename extension. @xref{Show, ,
16073 Displaying the Language}.
16075 This is most commonly a problem when you use a program, such
16076 as @code{cfront} or @code{f2c}, that generates C but is written in
16077 another language. In that case, make the
16078 program use @code{#line} directives in its C output; that way
16079 @value{GDBN} will know the correct language of the source code of the original
16080 program, and will display that source code, not the generated C code.
16083 * Filenames:: Filename extensions and languages.
16084 * Manually:: Setting the working language manually
16085 * Automatically:: Having @value{GDBN} infer the source language
16089 @subsection List of Filename Extensions and Languages
16091 If a source file name ends in one of the following extensions, then
16092 @value{GDBN} infers that its language is the one indicated.
16110 C@t{++} source file
16116 Objective-C source file
16120 Fortran source file
16123 Modula-2 source file
16127 Assembler source file. This actually behaves almost like C, but
16128 @value{GDBN} does not skip over function prologues when stepping.
16131 In addition, you may set the language associated with a filename
16132 extension. @xref{Show, , Displaying the Language}.
16135 @subsection Setting the Working Language
16137 If you allow @value{GDBN} to set the language automatically,
16138 expressions are interpreted the same way in your debugging session and
16141 @kindex set language
16142 If you wish, you may set the language manually. To do this, issue the
16143 command @samp{set language @var{lang}}, where @var{lang} is the name of
16144 a language, such as
16145 @code{c} or @code{modula-2}.
16146 For a list of the supported languages, type @samp{set language}.
16148 Setting the language manually prevents @value{GDBN} from updating the working
16149 language automatically. This can lead to confusion if you try
16150 to debug a program when the working language is not the same as the
16151 source language, when an expression is acceptable to both
16152 languages---but means different things. For instance, if the current
16153 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16161 might not have the effect you intended. In C, this means to add
16162 @code{b} and @code{c} and place the result in @code{a}. The result
16163 printed would be the value of @code{a}. In Modula-2, this means to compare
16164 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16166 @node Automatically
16167 @subsection Having @value{GDBN} Infer the Source Language
16169 To have @value{GDBN} set the working language automatically, use
16170 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16171 then infers the working language. That is, when your program stops in a
16172 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16173 working language to the language recorded for the function in that
16174 frame. If the language for a frame is unknown (that is, if the function
16175 or block corresponding to the frame was defined in a source file that
16176 does not have a recognized extension), the current working language is
16177 not changed, and @value{GDBN} issues a warning.
16179 This may not seem necessary for most programs, which are written
16180 entirely in one source language. However, program modules and libraries
16181 written in one source language can be used by a main program written in
16182 a different source language. Using @samp{set language auto} in this
16183 case frees you from having to set the working language manually.
16186 @section Displaying the Language
16188 The following commands help you find out which language is the
16189 working language, and also what language source files were written in.
16192 @item show language
16193 @anchor{show language}
16194 @kindex show language
16195 Display the current working language. This is the
16196 language you can use with commands such as @code{print} to
16197 build and compute expressions that may involve variables in your program.
16200 @kindex info frame@r{, show the source language}
16201 Display the source language for this frame. This language becomes the
16202 working language if you use an identifier from this frame.
16203 @xref{Frame Info, ,Information about a Frame}, to identify the other
16204 information listed here.
16207 @kindex info source@r{, show the source language}
16208 Display the source language of this source file.
16209 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16210 information listed here.
16213 In unusual circumstances, you may have source files with extensions
16214 not in the standard list. You can then set the extension associated
16215 with a language explicitly:
16218 @item set extension-language @var{ext} @var{language}
16219 @kindex set extension-language
16220 Tell @value{GDBN} that source files with extension @var{ext} are to be
16221 assumed as written in the source language @var{language}.
16223 @item info extensions
16224 @kindex info extensions
16225 List all the filename extensions and the associated languages.
16229 @section Type and Range Checking
16231 Some languages are designed to guard you against making seemingly common
16232 errors through a series of compile- and run-time checks. These include
16233 checking the type of arguments to functions and operators and making
16234 sure mathematical overflows are caught at run time. Checks such as
16235 these help to ensure a program's correctness once it has been compiled
16236 by eliminating type mismatches and providing active checks for range
16237 errors when your program is running.
16239 By default @value{GDBN} checks for these errors according to the
16240 rules of the current source language. Although @value{GDBN} does not check
16241 the statements in your program, it can check expressions entered directly
16242 into @value{GDBN} for evaluation via the @code{print} command, for example.
16245 * Type Checking:: An overview of type checking
16246 * Range Checking:: An overview of range checking
16249 @cindex type checking
16250 @cindex checks, type
16251 @node Type Checking
16252 @subsection An Overview of Type Checking
16254 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16255 arguments to operators and functions have to be of the correct type,
16256 otherwise an error occurs. These checks prevent type mismatch
16257 errors from ever causing any run-time problems. For example,
16260 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16262 (@value{GDBP}) print obj.my_method (0)
16265 (@value{GDBP}) print obj.my_method (0x1234)
16266 Cannot resolve method klass::my_method to any overloaded instance
16269 The second example fails because in C@t{++} the integer constant
16270 @samp{0x1234} is not type-compatible with the pointer parameter type.
16272 For the expressions you use in @value{GDBN} commands, you can tell
16273 @value{GDBN} to not enforce strict type checking or
16274 to treat any mismatches as errors and abandon the expression;
16275 When type checking is disabled, @value{GDBN} successfully evaluates
16276 expressions like the second example above.
16278 Even if type checking is off, there may be other reasons
16279 related to type that prevent @value{GDBN} from evaluating an expression.
16280 For instance, @value{GDBN} does not know how to add an @code{int} and
16281 a @code{struct foo}. These particular type errors have nothing to do
16282 with the language in use and usually arise from expressions which make
16283 little sense to evaluate anyway.
16285 @value{GDBN} provides some additional commands for controlling type checking:
16287 @kindex set check type
16288 @kindex show check type
16290 @item set check type on
16291 @itemx set check type off
16292 Set strict type checking on or off. If any type mismatches occur in
16293 evaluating an expression while type checking is on, @value{GDBN} prints a
16294 message and aborts evaluation of the expression.
16296 @item show check type
16297 Show the current setting of type checking and whether @value{GDBN}
16298 is enforcing strict type checking rules.
16301 @cindex range checking
16302 @cindex checks, range
16303 @node Range Checking
16304 @subsection An Overview of Range Checking
16306 In some languages (such as Modula-2), it is an error to exceed the
16307 bounds of a type; this is enforced with run-time checks. Such range
16308 checking is meant to ensure program correctness by making sure
16309 computations do not overflow, or indices on an array element access do
16310 not exceed the bounds of the array.
16312 For expressions you use in @value{GDBN} commands, you can tell
16313 @value{GDBN} to treat range errors in one of three ways: ignore them,
16314 always treat them as errors and abandon the expression, or issue
16315 warnings but evaluate the expression anyway.
16317 A range error can result from numerical overflow, from exceeding an
16318 array index bound, or when you type a constant that is not a member
16319 of any type. Some languages, however, do not treat overflows as an
16320 error. In many implementations of C, mathematical overflow causes the
16321 result to ``wrap around'' to lower values---for example, if @var{m} is
16322 the largest integer value, and @var{s} is the smallest, then
16325 @var{m} + 1 @result{} @var{s}
16328 This, too, is specific to individual languages, and in some cases
16329 specific to individual compilers or machines. @xref{Supported Languages, ,
16330 Supported Languages}, for further details on specific languages.
16332 @value{GDBN} provides some additional commands for controlling the range checker:
16334 @kindex set check range
16335 @kindex show check range
16337 @item set check range auto
16338 Set range checking on or off based on the current working language.
16339 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16342 @item set check range on
16343 @itemx set check range off
16344 Set range checking on or off, overriding the default setting for the
16345 current working language. A warning is issued if the setting does not
16346 match the language default. If a range error occurs and range checking is on,
16347 then a message is printed and evaluation of the expression is aborted.
16349 @item set check range warn
16350 Output messages when the @value{GDBN} range checker detects a range error,
16351 but attempt to evaluate the expression anyway. Evaluating the
16352 expression may still be impossible for other reasons, such as accessing
16353 memory that the process does not own (a typical example from many Unix
16356 @item show check range
16357 Show the current setting of the range checker, and whether or not it is
16358 being set automatically by @value{GDBN}.
16361 @node Supported Languages
16362 @section Supported Languages
16364 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16365 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16366 @c This is false ...
16367 Some @value{GDBN} features may be used in expressions regardless of the
16368 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16369 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16370 ,Expressions}) can be used with the constructs of any supported
16373 The following sections detail to what degree each source language is
16374 supported by @value{GDBN}. These sections are not meant to be language
16375 tutorials or references, but serve only as a reference guide to what the
16376 @value{GDBN} expression parser accepts, and what input and output
16377 formats should look like for different languages. There are many good
16378 books written on each of these languages; please look to these for a
16379 language reference or tutorial.
16382 * C:: C and C@t{++}
16385 * Objective-C:: Objective-C
16386 * OpenCL C:: OpenCL C
16387 * Fortran:: Fortran
16390 * Modula-2:: Modula-2
16395 @subsection C and C@t{++}
16397 @cindex C and C@t{++}
16398 @cindex expressions in C or C@t{++}
16400 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16401 to both languages. Whenever this is the case, we discuss those languages
16405 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16406 @cindex @sc{gnu} C@t{++}
16407 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16408 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16409 effectively, you must compile your C@t{++} programs with a supported
16410 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16411 compiler (@code{aCC}).
16414 * C Operators:: C and C@t{++} operators
16415 * C Constants:: C and C@t{++} constants
16416 * C Plus Plus Expressions:: C@t{++} expressions
16417 * C Defaults:: Default settings for C and C@t{++}
16418 * C Checks:: C and C@t{++} type and range checks
16419 * Debugging C:: @value{GDBN} and C
16420 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16421 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16425 @subsubsection C and C@t{++} Operators
16427 @cindex C and C@t{++} operators
16429 Operators must be defined on values of specific types. For instance,
16430 @code{+} is defined on numbers, but not on structures. Operators are
16431 often defined on groups of types.
16433 For the purposes of C and C@t{++}, the following definitions hold:
16438 @emph{Integral types} include @code{int} with any of its storage-class
16439 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16442 @emph{Floating-point types} include @code{float}, @code{double}, and
16443 @code{long double} (if supported by the target platform).
16446 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16449 @emph{Scalar types} include all of the above.
16454 The following operators are supported. They are listed here
16455 in order of increasing precedence:
16459 The comma or sequencing operator. Expressions in a comma-separated list
16460 are evaluated from left to right, with the result of the entire
16461 expression being the last expression evaluated.
16464 Assignment. The value of an assignment expression is the value
16465 assigned. Defined on scalar types.
16468 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16469 and translated to @w{@code{@var{a} = @var{a op b}}}.
16470 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16471 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16472 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16475 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16476 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16477 should be of an integral type.
16480 Logical @sc{or}. Defined on integral types.
16483 Logical @sc{and}. Defined on integral types.
16486 Bitwise @sc{or}. Defined on integral types.
16489 Bitwise exclusive-@sc{or}. Defined on integral types.
16492 Bitwise @sc{and}. Defined on integral types.
16495 Equality and inequality. Defined on scalar types. The value of these
16496 expressions is 0 for false and non-zero for true.
16498 @item <@r{, }>@r{, }<=@r{, }>=
16499 Less than, greater than, less than or equal, greater than or equal.
16500 Defined on scalar types. The value of these expressions is 0 for false
16501 and non-zero for true.
16504 left shift, and right shift. Defined on integral types.
16507 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16510 Addition and subtraction. Defined on integral types, floating-point types and
16513 @item *@r{, }/@r{, }%
16514 Multiplication, division, and modulus. Multiplication and division are
16515 defined on integral and floating-point types. Modulus is defined on
16519 Increment and decrement. When appearing before a variable, the
16520 operation is performed before the variable is used in an expression;
16521 when appearing after it, the variable's value is used before the
16522 operation takes place.
16525 Pointer dereferencing. Defined on pointer types. Same precedence as
16529 Address operator. Defined on variables. Same precedence as @code{++}.
16531 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16532 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16533 to examine the address
16534 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16538 Negative. Defined on integral and floating-point types. Same
16539 precedence as @code{++}.
16542 Logical negation. Defined on integral types. Same precedence as
16546 Bitwise complement operator. Defined on integral types. Same precedence as
16551 Structure member, and pointer-to-structure member. For convenience,
16552 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16553 pointer based on the stored type information.
16554 Defined on @code{struct} and @code{union} data.
16557 Dereferences of pointers to members.
16560 Array indexing. @code{@var{a}[@var{i}]} is defined as
16561 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16564 Function parameter list. Same precedence as @code{->}.
16567 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16568 and @code{class} types.
16571 Doubled colons also represent the @value{GDBN} scope operator
16572 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16576 If an operator is redefined in the user code, @value{GDBN} usually
16577 attempts to invoke the redefined version instead of using the operator's
16578 predefined meaning.
16581 @subsubsection C and C@t{++} Constants
16583 @cindex C and C@t{++} constants
16585 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16590 Integer constants are a sequence of digits. Octal constants are
16591 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16592 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16593 @samp{l}, specifying that the constant should be treated as a
16597 Floating point constants are a sequence of digits, followed by a decimal
16598 point, followed by a sequence of digits, and optionally followed by an
16599 exponent. An exponent is of the form:
16600 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16601 sequence of digits. The @samp{+} is optional for positive exponents.
16602 A floating-point constant may also end with a letter @samp{f} or
16603 @samp{F}, specifying that the constant should be treated as being of
16604 the @code{float} (as opposed to the default @code{double}) type; or with
16605 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16609 Enumerated constants consist of enumerated identifiers, or their
16610 integral equivalents.
16613 Character constants are a single character surrounded by single quotes
16614 (@code{'}), or a number---the ordinal value of the corresponding character
16615 (usually its @sc{ascii} value). Within quotes, the single character may
16616 be represented by a letter or by @dfn{escape sequences}, which are of
16617 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16618 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16619 @samp{@var{x}} is a predefined special character---for example,
16620 @samp{\n} for newline.
16622 Wide character constants can be written by prefixing a character
16623 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16624 form of @samp{x}. The target wide character set is used when
16625 computing the value of this constant (@pxref{Character Sets}).
16628 String constants are a sequence of character constants surrounded by
16629 double quotes (@code{"}). Any valid character constant (as described
16630 above) may appear. Double quotes within the string must be preceded by
16631 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16634 Wide string constants can be written by prefixing a string constant
16635 with @samp{L}, as in C. The target wide character set is used when
16636 computing the value of this constant (@pxref{Character Sets}).
16639 Pointer constants are an integral value. You can also write pointers
16640 to constants using the C operator @samp{&}.
16643 Array constants are comma-separated lists surrounded by braces @samp{@{}
16644 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16645 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16646 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16649 @node C Plus Plus Expressions
16650 @subsubsection C@t{++} Expressions
16652 @cindex expressions in C@t{++}
16653 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16655 @cindex debugging C@t{++} programs
16656 @cindex C@t{++} compilers
16657 @cindex debug formats and C@t{++}
16658 @cindex @value{NGCC} and C@t{++}
16660 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16661 the proper compiler and the proper debug format. Currently,
16662 @value{GDBN} works best when debugging C@t{++} code that is compiled
16663 with the most recent version of @value{NGCC} possible. The DWARF
16664 debugging format is preferred; @value{NGCC} defaults to this on most
16665 popular platforms. Other compilers and/or debug formats are likely to
16666 work badly or not at all when using @value{GDBN} to debug C@t{++}
16667 code. @xref{Compilation}.
16672 @cindex member functions
16674 Member function calls are allowed; you can use expressions like
16677 count = aml->GetOriginal(x, y)
16680 @vindex this@r{, inside C@t{++} member functions}
16681 @cindex namespace in C@t{++}
16683 While a member function is active (in the selected stack frame), your
16684 expressions have the same namespace available as the member function;
16685 that is, @value{GDBN} allows implicit references to the class instance
16686 pointer @code{this} following the same rules as C@t{++}. @code{using}
16687 declarations in the current scope are also respected by @value{GDBN}.
16689 @cindex call overloaded functions
16690 @cindex overloaded functions, calling
16691 @cindex type conversions in C@t{++}
16693 You can call overloaded functions; @value{GDBN} resolves the function
16694 call to the right definition, with some restrictions. @value{GDBN} does not
16695 perform overload resolution involving user-defined type conversions,
16696 calls to constructors, or instantiations of templates that do not exist
16697 in the program. It also cannot handle ellipsis argument lists or
16700 It does perform integral conversions and promotions, floating-point
16701 promotions, arithmetic conversions, pointer conversions, conversions of
16702 class objects to base classes, and standard conversions such as those of
16703 functions or arrays to pointers; it requires an exact match on the
16704 number of function arguments.
16706 Overload resolution is always performed, unless you have specified
16707 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16708 ,@value{GDBN} Features for C@t{++}}.
16710 You must specify @code{set overload-resolution off} in order to use an
16711 explicit function signature to call an overloaded function, as in
16713 p 'foo(char,int)'('x', 13)
16716 The @value{GDBN} command-completion facility can simplify this;
16717 see @ref{Completion, ,Command Completion}.
16719 @cindex reference declarations
16721 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16722 references; you can use them in expressions just as you do in C@t{++}
16723 source---they are automatically dereferenced.
16725 In the parameter list shown when @value{GDBN} displays a frame, the values of
16726 reference variables are not displayed (unlike other variables); this
16727 avoids clutter, since references are often used for large structures.
16728 The @emph{address} of a reference variable is always shown, unless
16729 you have specified @samp{set print address off}.
16732 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16733 expressions can use it just as expressions in your program do. Since
16734 one scope may be defined in another, you can use @code{::} repeatedly if
16735 necessary, for example in an expression like
16736 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16737 resolving name scope by reference to source files, in both C and C@t{++}
16738 debugging (@pxref{Variables, ,Program Variables}).
16741 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16746 @subsubsection C and C@t{++} Defaults
16748 @cindex C and C@t{++} defaults
16750 If you allow @value{GDBN} to set range checking automatically, it
16751 defaults to @code{off} whenever the working language changes to
16752 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16753 selects the working language.
16755 If you allow @value{GDBN} to set the language automatically, it
16756 recognizes source files whose names end with @file{.c}, @file{.C}, or
16757 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16758 these files, it sets the working language to C or C@t{++}.
16759 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16760 for further details.
16763 @subsubsection C and C@t{++} Type and Range Checks
16765 @cindex C and C@t{++} checks
16767 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16768 checking is used. However, if you turn type checking off, @value{GDBN}
16769 will allow certain non-standard conversions, such as promoting integer
16770 constants to pointers.
16772 Range checking, if turned on, is done on mathematical operations. Array
16773 indices are not checked, since they are often used to index a pointer
16774 that is not itself an array.
16777 @subsubsection @value{GDBN} and C
16779 The @code{set print union} and @code{show print union} commands apply to
16780 the @code{union} type. When set to @samp{on}, any @code{union} that is
16781 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16782 appears as @samp{@{...@}}.
16784 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16785 with pointers and a memory allocation function. @xref{Expressions,
16788 @node Debugging C Plus Plus
16789 @subsubsection @value{GDBN} Features for C@t{++}
16791 @cindex commands for C@t{++}
16793 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16794 designed specifically for use with C@t{++}. Here is a summary:
16797 @cindex break in overloaded functions
16798 @item @r{breakpoint menus}
16799 When you want a breakpoint in a function whose name is overloaded,
16800 @value{GDBN} has the capability to display a menu of possible breakpoint
16801 locations to help you specify which function definition you want.
16802 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16804 @cindex overloading in C@t{++}
16805 @item rbreak @var{regex}
16806 Setting breakpoints using regular expressions is helpful for setting
16807 breakpoints on overloaded functions that are not members of any special
16809 @xref{Set Breaks, ,Setting Breakpoints}.
16811 @cindex C@t{++} exception handling
16813 @itemx catch rethrow
16815 Debug C@t{++} exception handling using these commands. @xref{Set
16816 Catchpoints, , Setting Catchpoints}.
16818 @cindex inheritance
16819 @item ptype @var{typename}
16820 Print inheritance relationships as well as other information for type
16822 @xref{Symbols, ,Examining the Symbol Table}.
16824 @item info vtbl @var{expression}.
16825 The @code{info vtbl} command can be used to display the virtual
16826 method tables of the object computed by @var{expression}. This shows
16827 one entry per virtual table; there may be multiple virtual tables when
16828 multiple inheritance is in use.
16830 @cindex C@t{++} demangling
16831 @item demangle @var{name}
16832 Demangle @var{name}.
16833 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16835 @cindex C@t{++} symbol display
16836 @item set print demangle
16837 @itemx show print demangle
16838 @itemx set print asm-demangle
16839 @itemx show print asm-demangle
16840 Control whether C@t{++} symbols display in their source form, both when
16841 displaying code as C@t{++} source and when displaying disassemblies.
16842 @xref{Print Settings, ,Print Settings}.
16844 @item set print object
16845 @itemx show print object
16846 Choose whether to print derived (actual) or declared types of objects.
16847 @xref{Print Settings, ,Print Settings}.
16849 @item set print vtbl
16850 @itemx show print vtbl
16851 Control the format for printing virtual function tables.
16852 @xref{Print Settings, ,Print Settings}.
16853 (The @code{vtbl} commands do not work on programs compiled with the HP
16854 ANSI C@t{++} compiler (@code{aCC}).)
16856 @kindex set overload-resolution
16857 @cindex overloaded functions, overload resolution
16858 @item set overload-resolution on
16859 Enable overload resolution for C@t{++} expression evaluation. The default
16860 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16861 and searches for a function whose signature matches the argument types,
16862 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16863 Expressions, ,C@t{++} Expressions}, for details).
16864 If it cannot find a match, it emits a message.
16866 @item set overload-resolution off
16867 Disable overload resolution for C@t{++} expression evaluation. For
16868 overloaded functions that are not class member functions, @value{GDBN}
16869 chooses the first function of the specified name that it finds in the
16870 symbol table, whether or not its arguments are of the correct type. For
16871 overloaded functions that are class member functions, @value{GDBN}
16872 searches for a function whose signature @emph{exactly} matches the
16875 @kindex show overload-resolution
16876 @item show overload-resolution
16877 Show the current setting of overload resolution.
16879 @item @r{Overloaded symbol names}
16880 You can specify a particular definition of an overloaded symbol, using
16881 the same notation that is used to declare such symbols in C@t{++}: type
16882 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16883 also use the @value{GDBN} command-line word completion facilities to list the
16884 available choices, or to finish the type list for you.
16885 @xref{Completion,, Command Completion}, for details on how to do this.
16887 @item @r{Breakpoints in functions with ABI tags}
16889 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16890 correspond to changes in the ABI of a type, function, or variable that
16891 would not otherwise be reflected in a mangled name. See
16892 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16895 The ABI tags are visible in C@t{++} demangled names. For example, a
16896 function that returns a std::string:
16899 std::string function(int);
16903 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16904 tag, and @value{GDBN} displays the symbol like this:
16907 function[abi:cxx11](int)
16910 You can set a breakpoint on such functions simply as if they had no
16914 (gdb) b function(int)
16915 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16916 (gdb) info breakpoints
16917 Num Type Disp Enb Address What
16918 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16922 On the rare occasion you need to disambiguate between different ABI
16923 tags, you can do so by simply including the ABI tag in the function
16927 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16931 @node Decimal Floating Point
16932 @subsubsection Decimal Floating Point format
16933 @cindex decimal floating point format
16935 @value{GDBN} can examine, set and perform computations with numbers in
16936 decimal floating point format, which in the C language correspond to the
16937 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16938 specified by the extension to support decimal floating-point arithmetic.
16940 There are two encodings in use, depending on the architecture: BID (Binary
16941 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16942 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16945 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16946 to manipulate decimal floating point numbers, it is not possible to convert
16947 (using a cast, for example) integers wider than 32-bit to decimal float.
16949 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16950 point computations, error checking in decimal float operations ignores
16951 underflow, overflow and divide by zero exceptions.
16953 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16954 to inspect @code{_Decimal128} values stored in floating point registers.
16955 See @ref{PowerPC,,PowerPC} for more details.
16961 @value{GDBN} can be used to debug programs written in D and compiled with
16962 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16963 specific feature --- dynamic arrays.
16968 @cindex Go (programming language)
16969 @value{GDBN} can be used to debug programs written in Go and compiled with
16970 @file{gccgo} or @file{6g} compilers.
16972 Here is a summary of the Go-specific features and restrictions:
16975 @cindex current Go package
16976 @item The current Go package
16977 The name of the current package does not need to be specified when
16978 specifying global variables and functions.
16980 For example, given the program:
16984 var myglob = "Shall we?"
16990 When stopped inside @code{main} either of these work:
16994 (gdb) p main.myglob
16997 @cindex builtin Go types
16998 @item Builtin Go types
16999 The @code{string} type is recognized by @value{GDBN} and is printed
17002 @cindex builtin Go functions
17003 @item Builtin Go functions
17004 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17005 function and handles it internally.
17007 @cindex restrictions on Go expressions
17008 @item Restrictions on Go expressions
17009 All Go operators are supported except @code{&^}.
17010 The Go @code{_} ``blank identifier'' is not supported.
17011 Automatic dereferencing of pointers is not supported.
17015 @subsection Objective-C
17017 @cindex Objective-C
17018 This section provides information about some commands and command
17019 options that are useful for debugging Objective-C code. See also
17020 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17021 few more commands specific to Objective-C support.
17024 * Method Names in Commands::
17025 * The Print Command with Objective-C::
17028 @node Method Names in Commands
17029 @subsubsection Method Names in Commands
17031 The following commands have been extended to accept Objective-C method
17032 names as line specifications:
17034 @kindex clear@r{, and Objective-C}
17035 @kindex break@r{, and Objective-C}
17036 @kindex info line@r{, and Objective-C}
17037 @kindex jump@r{, and Objective-C}
17038 @kindex list@r{, and Objective-C}
17042 @item @code{info line}
17047 A fully qualified Objective-C method name is specified as
17050 -[@var{Class} @var{methodName}]
17053 where the minus sign is used to indicate an instance method and a
17054 plus sign (not shown) is used to indicate a class method. The class
17055 name @var{Class} and method name @var{methodName} are enclosed in
17056 brackets, similar to the way messages are specified in Objective-C
17057 source code. For example, to set a breakpoint at the @code{create}
17058 instance method of class @code{Fruit} in the program currently being
17062 break -[Fruit create]
17065 To list ten program lines around the @code{initialize} class method,
17069 list +[NSText initialize]
17072 In the current version of @value{GDBN}, the plus or minus sign is
17073 required. In future versions of @value{GDBN}, the plus or minus
17074 sign will be optional, but you can use it to narrow the search. It
17075 is also possible to specify just a method name:
17081 You must specify the complete method name, including any colons. If
17082 your program's source files contain more than one @code{create} method,
17083 you'll be presented with a numbered list of classes that implement that
17084 method. Indicate your choice by number, or type @samp{0} to exit if
17087 As another example, to clear a breakpoint established at the
17088 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17091 clear -[NSWindow makeKeyAndOrderFront:]
17094 @node The Print Command with Objective-C
17095 @subsubsection The Print Command With Objective-C
17096 @cindex Objective-C, print objects
17097 @kindex print-object
17098 @kindex po @r{(@code{print-object})}
17100 The print command has also been extended to accept methods. For example:
17103 print -[@var{object} hash]
17106 @cindex print an Objective-C object description
17107 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17109 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17110 and print the result. Also, an additional command has been added,
17111 @code{print-object} or @code{po} for short, which is meant to print
17112 the description of an object. However, this command may only work
17113 with certain Objective-C libraries that have a particular hook
17114 function, @code{_NSPrintForDebugger}, defined.
17117 @subsection OpenCL C
17120 This section provides information about @value{GDBN}s OpenCL C support.
17123 * OpenCL C Datatypes::
17124 * OpenCL C Expressions::
17125 * OpenCL C Operators::
17128 @node OpenCL C Datatypes
17129 @subsubsection OpenCL C Datatypes
17131 @cindex OpenCL C Datatypes
17132 @value{GDBN} supports the builtin scalar and vector datatypes specified
17133 by OpenCL 1.1. In addition the half- and double-precision floating point
17134 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17135 extensions are also known to @value{GDBN}.
17137 @node OpenCL C Expressions
17138 @subsubsection OpenCL C Expressions
17140 @cindex OpenCL C Expressions
17141 @value{GDBN} supports accesses to vector components including the access as
17142 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17143 supported by @value{GDBN} can be used as well.
17145 @node OpenCL C Operators
17146 @subsubsection OpenCL C Operators
17148 @cindex OpenCL C Operators
17149 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17153 @subsection Fortran
17154 @cindex Fortran-specific support in @value{GDBN}
17156 @value{GDBN} can be used to debug programs written in Fortran, but it
17157 currently supports only the features of Fortran 77 language.
17159 @cindex trailing underscore, in Fortran symbols
17160 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17161 among them) append an underscore to the names of variables and
17162 functions. When you debug programs compiled by those compilers, you
17163 will need to refer to variables and functions with a trailing
17167 * Fortran Operators:: Fortran operators and expressions
17168 * Fortran Defaults:: Default settings for Fortran
17169 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17172 @node Fortran Operators
17173 @subsubsection Fortran Operators and Expressions
17175 @cindex Fortran operators and expressions
17177 Operators must be defined on values of specific types. For instance,
17178 @code{+} is defined on numbers, but not on characters or other non-
17179 arithmetic types. Operators are often defined on groups of types.
17183 The exponentiation operator. It raises the first operand to the power
17187 The range operator. Normally used in the form of array(low:high) to
17188 represent a section of array.
17191 The access component operator. Normally used to access elements in derived
17192 types. Also suitable for unions. As unions aren't part of regular Fortran,
17193 this can only happen when accessing a register that uses a gdbarch-defined
17196 The scope operator. Normally used to access variables in modules or
17197 to set breakpoints on subroutines nested in modules or in other
17198 subroutines (internal subroutines).
17201 @node Fortran Defaults
17202 @subsubsection Fortran Defaults
17204 @cindex Fortran Defaults
17206 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17207 default uses case-insensitive matches for Fortran symbols. You can
17208 change that with the @samp{set case-insensitive} command, see
17209 @ref{Symbols}, for the details.
17211 @node Special Fortran Commands
17212 @subsubsection Special Fortran Commands
17214 @cindex Special Fortran commands
17216 @value{GDBN} has some commands to support Fortran-specific features,
17217 such as displaying common blocks.
17220 @cindex @code{COMMON} blocks, Fortran
17221 @kindex info common
17222 @item info common @r{[}@var{common-name}@r{]}
17223 This command prints the values contained in the Fortran @code{COMMON}
17224 block whose name is @var{common-name}. With no argument, the names of
17225 all @code{COMMON} blocks visible at the current program location are
17227 @cindex arrays slices (Fortran)
17228 @kindex set fortran repack-array-slices
17229 @kindex show fortran repack-array-slices
17230 @item set fortran repack-array-slices [on|off]
17231 @item show fortran repack-array-slices
17232 When taking a slice from an array, a Fortran compiler can choose to
17233 either produce an array descriptor that describes the slice in place,
17234 or it may repack the slice, copying the elements of the slice into a
17235 new region of memory.
17237 When this setting is on, then @value{GDBN} will also repack array
17238 slices in some situations. When this setting is off, then
17239 @value{GDBN} will create array descriptors for slices that reference
17240 the original data in place.
17242 @value{GDBN} will never repack an array slice if the data for the
17243 slice is contiguous within the original array.
17245 @value{GDBN} will always repack string slices if the data for the
17246 slice is non-contiguous within the original string as @value{GDBN}
17247 does not support printing non-contiguous strings.
17249 The default for this setting is @code{off}.
17255 @cindex Pascal support in @value{GDBN}, limitations
17256 Debugging Pascal programs which use sets, subranges, file variables, or
17257 nested functions does not currently work. @value{GDBN} does not support
17258 entering expressions, printing values, or similar features using Pascal
17261 The Pascal-specific command @code{set print pascal_static-members}
17262 controls whether static members of Pascal objects are displayed.
17263 @xref{Print Settings, pascal_static-members}.
17268 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17269 Programming Language}. Type- and value-printing, and expression
17270 parsing, are reasonably complete. However, there are a few
17271 peculiarities and holes to be aware of.
17275 Linespecs (@pxref{Specify Location}) are never relative to the current
17276 crate. Instead, they act as if there were a global namespace of
17277 crates, somewhat similar to the way @code{extern crate} behaves.
17279 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17280 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17281 to set a breakpoint in a function named @samp{f} in a crate named
17284 As a consequence of this approach, linespecs also cannot refer to
17285 items using @samp{self::} or @samp{super::}.
17288 Because @value{GDBN} implements Rust name-lookup semantics in
17289 expressions, it will sometimes prepend the current crate to a name.
17290 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17291 @samp{K}, then @code{print ::x::y} will try to find the symbol
17294 However, since it is useful to be able to refer to other crates when
17295 debugging, @value{GDBN} provides the @code{extern} extension to
17296 circumvent this. To use the extension, just put @code{extern} before
17297 a path expression to refer to the otherwise unavailable ``global''
17300 In the above example, if you wanted to refer to the symbol @samp{y} in
17301 the crate @samp{x}, you would use @code{print extern x::y}.
17304 The Rust expression evaluator does not support ``statement-like''
17305 expressions such as @code{if} or @code{match}, or lambda expressions.
17308 Tuple expressions are not implemented.
17311 The Rust expression evaluator does not currently implement the
17312 @code{Drop} trait. Objects that may be created by the evaluator will
17313 never be destroyed.
17316 @value{GDBN} does not implement type inference for generics. In order
17317 to call generic functions or otherwise refer to generic items, you
17318 will have to specify the type parameters manually.
17321 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17322 cases this does not cause any problems. However, in an expression
17323 context, completing a generic function name will give syntactically
17324 invalid results. This happens because Rust requires the @samp{::}
17325 operator between the function name and its generic arguments. For
17326 example, @value{GDBN} might provide a completion like
17327 @code{crate::f<u32>}, where the parser would require
17328 @code{crate::f::<u32>}.
17331 As of this writing, the Rust compiler (version 1.8) has a few holes in
17332 the debugging information it generates. These holes prevent certain
17333 features from being implemented by @value{GDBN}:
17337 Method calls cannot be made via traits.
17340 Operator overloading is not implemented.
17343 When debugging in a monomorphized function, you cannot use the generic
17347 The type @code{Self} is not available.
17350 @code{use} statements are not available, so some names may not be
17351 available in the crate.
17356 @subsection Modula-2
17358 @cindex Modula-2, @value{GDBN} support
17360 The extensions made to @value{GDBN} to support Modula-2 only support
17361 output from the @sc{gnu} Modula-2 compiler (which is currently being
17362 developed). Other Modula-2 compilers are not currently supported, and
17363 attempting to debug executables produced by them is most likely
17364 to give an error as @value{GDBN} reads in the executable's symbol
17367 @cindex expressions in Modula-2
17369 * M2 Operators:: Built-in operators
17370 * Built-In Func/Proc:: Built-in functions and procedures
17371 * M2 Constants:: Modula-2 constants
17372 * M2 Types:: Modula-2 types
17373 * M2 Defaults:: Default settings for Modula-2
17374 * Deviations:: Deviations from standard Modula-2
17375 * M2 Checks:: Modula-2 type and range checks
17376 * M2 Scope:: The scope operators @code{::} and @code{.}
17377 * GDB/M2:: @value{GDBN} and Modula-2
17381 @subsubsection Operators
17382 @cindex Modula-2 operators
17384 Operators must be defined on values of specific types. For instance,
17385 @code{+} is defined on numbers, but not on structures. Operators are
17386 often defined on groups of types. For the purposes of Modula-2, the
17387 following definitions hold:
17392 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17396 @emph{Character types} consist of @code{CHAR} and its subranges.
17399 @emph{Floating-point types} consist of @code{REAL}.
17402 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17406 @emph{Scalar types} consist of all of the above.
17409 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17412 @emph{Boolean types} consist of @code{BOOLEAN}.
17416 The following operators are supported, and appear in order of
17417 increasing precedence:
17421 Function argument or array index separator.
17424 Assignment. The value of @var{var} @code{:=} @var{value} is
17428 Less than, greater than on integral, floating-point, or enumerated
17432 Less than or equal to, greater than or equal to
17433 on integral, floating-point and enumerated types, or set inclusion on
17434 set types. Same precedence as @code{<}.
17436 @item =@r{, }<>@r{, }#
17437 Equality and two ways of expressing inequality, valid on scalar types.
17438 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17439 available for inequality, since @code{#} conflicts with the script
17443 Set membership. Defined on set types and the types of their members.
17444 Same precedence as @code{<}.
17447 Boolean disjunction. Defined on boolean types.
17450 Boolean conjunction. Defined on boolean types.
17453 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17456 Addition and subtraction on integral and floating-point types, or union
17457 and difference on set types.
17460 Multiplication on integral and floating-point types, or set intersection
17464 Division on floating-point types, or symmetric set difference on set
17465 types. Same precedence as @code{*}.
17468 Integer division and remainder. Defined on integral types. Same
17469 precedence as @code{*}.
17472 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17475 Pointer dereferencing. Defined on pointer types.
17478 Boolean negation. Defined on boolean types. Same precedence as
17482 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17483 precedence as @code{^}.
17486 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17489 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17493 @value{GDBN} and Modula-2 scope operators.
17497 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17498 treats the use of the operator @code{IN}, or the use of operators
17499 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17500 @code{<=}, and @code{>=} on sets as an error.
17504 @node Built-In Func/Proc
17505 @subsubsection Built-in Functions and Procedures
17506 @cindex Modula-2 built-ins
17508 Modula-2 also makes available several built-in procedures and functions.
17509 In describing these, the following metavariables are used:
17514 represents an @code{ARRAY} variable.
17517 represents a @code{CHAR} constant or variable.
17520 represents a variable or constant of integral type.
17523 represents an identifier that belongs to a set. Generally used in the
17524 same function with the metavariable @var{s}. The type of @var{s} should
17525 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17528 represents a variable or constant of integral or floating-point type.
17531 represents a variable or constant of floating-point type.
17537 represents a variable.
17540 represents a variable or constant of one of many types. See the
17541 explanation of the function for details.
17544 All Modula-2 built-in procedures also return a result, described below.
17548 Returns the absolute value of @var{n}.
17551 If @var{c} is a lower case letter, it returns its upper case
17552 equivalent, otherwise it returns its argument.
17555 Returns the character whose ordinal value is @var{i}.
17558 Decrements the value in the variable @var{v} by one. Returns the new value.
17560 @item DEC(@var{v},@var{i})
17561 Decrements the value in the variable @var{v} by @var{i}. Returns the
17564 @item EXCL(@var{m},@var{s})
17565 Removes the element @var{m} from the set @var{s}. Returns the new
17568 @item FLOAT(@var{i})
17569 Returns the floating point equivalent of the integer @var{i}.
17571 @item HIGH(@var{a})
17572 Returns the index of the last member of @var{a}.
17575 Increments the value in the variable @var{v} by one. Returns the new value.
17577 @item INC(@var{v},@var{i})
17578 Increments the value in the variable @var{v} by @var{i}. Returns the
17581 @item INCL(@var{m},@var{s})
17582 Adds the element @var{m} to the set @var{s} if it is not already
17583 there. Returns the new set.
17586 Returns the maximum value of the type @var{t}.
17589 Returns the minimum value of the type @var{t}.
17592 Returns boolean TRUE if @var{i} is an odd number.
17595 Returns the ordinal value of its argument. For example, the ordinal
17596 value of a character is its @sc{ascii} value (on machines supporting
17597 the @sc{ascii} character set). The argument @var{x} must be of an
17598 ordered type, which include integral, character and enumerated types.
17600 @item SIZE(@var{x})
17601 Returns the size of its argument. The argument @var{x} can be a
17602 variable or a type.
17604 @item TRUNC(@var{r})
17605 Returns the integral part of @var{r}.
17607 @item TSIZE(@var{x})
17608 Returns the size of its argument. The argument @var{x} can be a
17609 variable or a type.
17611 @item VAL(@var{t},@var{i})
17612 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17616 @emph{Warning:} Sets and their operations are not yet supported, so
17617 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17621 @cindex Modula-2 constants
17623 @subsubsection Constants
17625 @value{GDBN} allows you to express the constants of Modula-2 in the following
17631 Integer constants are simply a sequence of digits. When used in an
17632 expression, a constant is interpreted to be type-compatible with the
17633 rest of the expression. Hexadecimal integers are specified by a
17634 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17637 Floating point constants appear as a sequence of digits, followed by a
17638 decimal point and another sequence of digits. An optional exponent can
17639 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17640 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17641 digits of the floating point constant must be valid decimal (base 10)
17645 Character constants consist of a single character enclosed by a pair of
17646 like quotes, either single (@code{'}) or double (@code{"}). They may
17647 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17648 followed by a @samp{C}.
17651 String constants consist of a sequence of characters enclosed by a
17652 pair of like quotes, either single (@code{'}) or double (@code{"}).
17653 Escape sequences in the style of C are also allowed. @xref{C
17654 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17658 Enumerated constants consist of an enumerated identifier.
17661 Boolean constants consist of the identifiers @code{TRUE} and
17665 Pointer constants consist of integral values only.
17668 Set constants are not yet supported.
17672 @subsubsection Modula-2 Types
17673 @cindex Modula-2 types
17675 Currently @value{GDBN} can print the following data types in Modula-2
17676 syntax: array types, record types, set types, pointer types, procedure
17677 types, enumerated types, subrange types and base types. You can also
17678 print the contents of variables declared using these type.
17679 This section gives a number of simple source code examples together with
17680 sample @value{GDBN} sessions.
17682 The first example contains the following section of code:
17691 and you can request @value{GDBN} to interrogate the type and value of
17692 @code{r} and @code{s}.
17695 (@value{GDBP}) print s
17697 (@value{GDBP}) ptype s
17699 (@value{GDBP}) print r
17701 (@value{GDBP}) ptype r
17706 Likewise if your source code declares @code{s} as:
17710 s: SET ['A'..'Z'] ;
17714 then you may query the type of @code{s} by:
17717 (@value{GDBP}) ptype s
17718 type = SET ['A'..'Z']
17722 Note that at present you cannot interactively manipulate set
17723 expressions using the debugger.
17725 The following example shows how you might declare an array in Modula-2
17726 and how you can interact with @value{GDBN} to print its type and contents:
17730 s: ARRAY [-10..10] OF CHAR ;
17734 (@value{GDBP}) ptype s
17735 ARRAY [-10..10] OF CHAR
17738 Note that the array handling is not yet complete and although the type
17739 is printed correctly, expression handling still assumes that all
17740 arrays have a lower bound of zero and not @code{-10} as in the example
17743 Here are some more type related Modula-2 examples:
17747 colour = (blue, red, yellow, green) ;
17748 t = [blue..yellow] ;
17756 The @value{GDBN} interaction shows how you can query the data type
17757 and value of a variable.
17760 (@value{GDBP}) print s
17762 (@value{GDBP}) ptype t
17763 type = [blue..yellow]
17767 In this example a Modula-2 array is declared and its contents
17768 displayed. Observe that the contents are written in the same way as
17769 their @code{C} counterparts.
17773 s: ARRAY [1..5] OF CARDINAL ;
17779 (@value{GDBP}) print s
17780 $1 = @{1, 0, 0, 0, 0@}
17781 (@value{GDBP}) ptype s
17782 type = ARRAY [1..5] OF CARDINAL
17785 The Modula-2 language interface to @value{GDBN} also understands
17786 pointer types as shown in this example:
17790 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17797 and you can request that @value{GDBN} describes the type of @code{s}.
17800 (@value{GDBP}) ptype s
17801 type = POINTER TO ARRAY [1..5] OF CARDINAL
17804 @value{GDBN} handles compound types as we can see in this example.
17805 Here we combine array types, record types, pointer types and subrange
17816 myarray = ARRAY myrange OF CARDINAL ;
17817 myrange = [-2..2] ;
17819 s: POINTER TO ARRAY myrange OF foo ;
17823 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17827 (@value{GDBP}) ptype s
17828 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17831 f3 : ARRAY [-2..2] OF CARDINAL;
17836 @subsubsection Modula-2 Defaults
17837 @cindex Modula-2 defaults
17839 If type and range checking are set automatically by @value{GDBN}, they
17840 both default to @code{on} whenever the working language changes to
17841 Modula-2. This happens regardless of whether you or @value{GDBN}
17842 selected the working language.
17844 If you allow @value{GDBN} to set the language automatically, then entering
17845 code compiled from a file whose name ends with @file{.mod} sets the
17846 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17847 Infer the Source Language}, for further details.
17850 @subsubsection Deviations from Standard Modula-2
17851 @cindex Modula-2, deviations from
17853 A few changes have been made to make Modula-2 programs easier to debug.
17854 This is done primarily via loosening its type strictness:
17858 Unlike in standard Modula-2, pointer constants can be formed by
17859 integers. This allows you to modify pointer variables during
17860 debugging. (In standard Modula-2, the actual address contained in a
17861 pointer variable is hidden from you; it can only be modified
17862 through direct assignment to another pointer variable or expression that
17863 returned a pointer.)
17866 C escape sequences can be used in strings and characters to represent
17867 non-printable characters. @value{GDBN} prints out strings with these
17868 escape sequences embedded. Single non-printable characters are
17869 printed using the @samp{CHR(@var{nnn})} format.
17872 The assignment operator (@code{:=}) returns the value of its right-hand
17876 All built-in procedures both modify @emph{and} return their argument.
17880 @subsubsection Modula-2 Type and Range Checks
17881 @cindex Modula-2 checks
17884 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17887 @c FIXME remove warning when type/range checks added
17889 @value{GDBN} considers two Modula-2 variables type equivalent if:
17893 They are of types that have been declared equivalent via a @code{TYPE
17894 @var{t1} = @var{t2}} statement
17897 They have been declared on the same line. (Note: This is true of the
17898 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17901 As long as type checking is enabled, any attempt to combine variables
17902 whose types are not equivalent is an error.
17904 Range checking is done on all mathematical operations, assignment, array
17905 index bounds, and all built-in functions and procedures.
17908 @subsubsection The Scope Operators @code{::} and @code{.}
17910 @cindex @code{.}, Modula-2 scope operator
17911 @cindex colon, doubled as scope operator
17913 @vindex colon-colon@r{, in Modula-2}
17914 @c Info cannot handle :: but TeX can.
17917 @vindex ::@r{, in Modula-2}
17920 There are a few subtle differences between the Modula-2 scope operator
17921 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17926 @var{module} . @var{id}
17927 @var{scope} :: @var{id}
17931 where @var{scope} is the name of a module or a procedure,
17932 @var{module} the name of a module, and @var{id} is any declared
17933 identifier within your program, except another module.
17935 Using the @code{::} operator makes @value{GDBN} search the scope
17936 specified by @var{scope} for the identifier @var{id}. If it is not
17937 found in the specified scope, then @value{GDBN} searches all scopes
17938 enclosing the one specified by @var{scope}.
17940 Using the @code{.} operator makes @value{GDBN} search the current scope for
17941 the identifier specified by @var{id} that was imported from the
17942 definition module specified by @var{module}. With this operator, it is
17943 an error if the identifier @var{id} was not imported from definition
17944 module @var{module}, or if @var{id} is not an identifier in
17948 @subsubsection @value{GDBN} and Modula-2
17950 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17951 Five subcommands of @code{set print} and @code{show print} apply
17952 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17953 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17954 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17955 analogue in Modula-2.
17957 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17958 with any language, is not useful with Modula-2. Its
17959 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17960 created in Modula-2 as they can in C or C@t{++}. However, because an
17961 address can be specified by an integral constant, the construct
17962 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17964 @cindex @code{#} in Modula-2
17965 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17966 interpreted as the beginning of a comment. Use @code{<>} instead.
17972 The extensions made to @value{GDBN} for Ada only support
17973 output from the @sc{gnu} Ada (GNAT) compiler.
17974 Other Ada compilers are not currently supported, and
17975 attempting to debug executables produced by them is most likely
17979 @cindex expressions in Ada
17981 * Ada Mode Intro:: General remarks on the Ada syntax
17982 and semantics supported by Ada mode
17984 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17985 * Additions to Ada:: Extensions of the Ada expression syntax.
17986 * Overloading support for Ada:: Support for expressions involving overloaded
17988 * Stopping Before Main Program:: Debugging the program during elaboration.
17989 * Ada Exceptions:: Ada Exceptions
17990 * Ada Tasks:: Listing and setting breakpoints in tasks.
17991 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17992 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17994 * Ada Settings:: New settable GDB parameters for Ada.
17995 * Ada Glitches:: Known peculiarities of Ada mode.
17998 @node Ada Mode Intro
17999 @subsubsection Introduction
18000 @cindex Ada mode, general
18002 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18003 syntax, with some extensions.
18004 The philosophy behind the design of this subset is
18008 That @value{GDBN} should provide basic literals and access to operations for
18009 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18010 leaving more sophisticated computations to subprograms written into the
18011 program (which therefore may be called from @value{GDBN}).
18014 That type safety and strict adherence to Ada language restrictions
18015 are not particularly important to the @value{GDBN} user.
18018 That brevity is important to the @value{GDBN} user.
18021 Thus, for brevity, the debugger acts as if all names declared in
18022 user-written packages are directly visible, even if they are not visible
18023 according to Ada rules, thus making it unnecessary to fully qualify most
18024 names with their packages, regardless of context. Where this causes
18025 ambiguity, @value{GDBN} asks the user's intent.
18027 The debugger will start in Ada mode if it detects an Ada main program.
18028 As for other languages, it will enter Ada mode when stopped in a program that
18029 was translated from an Ada source file.
18031 While in Ada mode, you may use `@t{--}' for comments. This is useful
18032 mostly for documenting command files. The standard @value{GDBN} comment
18033 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18034 middle (to allow based literals).
18036 @node Omissions from Ada
18037 @subsubsection Omissions from Ada
18038 @cindex Ada, omissions from
18040 Here are the notable omissions from the subset:
18044 Only a subset of the attributes are supported:
18048 @t{'First}, @t{'Last}, and @t{'Length}
18049 on array objects (not on types and subtypes).
18052 @t{'Min} and @t{'Max}.
18055 @t{'Pos} and @t{'Val}.
18061 @t{'Range} on array objects (not subtypes), but only as the right
18062 operand of the membership (@code{in}) operator.
18065 @t{'Access}, @t{'Unchecked_Access}, and
18066 @t{'Unrestricted_Access} (a GNAT extension).
18074 @code{Characters.Latin_1} are not available and
18075 concatenation is not implemented. Thus, escape characters in strings are
18076 not currently available.
18079 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18080 equality of representations. They will generally work correctly
18081 for strings and arrays whose elements have integer or enumeration types.
18082 They may not work correctly for arrays whose element
18083 types have user-defined equality, for arrays of real values
18084 (in particular, IEEE-conformant floating point, because of negative
18085 zeroes and NaNs), and for arrays whose elements contain unused bits with
18086 indeterminate values.
18089 The other component-by-component array operations (@code{and}, @code{or},
18090 @code{xor}, @code{not}, and relational tests other than equality)
18091 are not implemented.
18094 @cindex array aggregates (Ada)
18095 @cindex record aggregates (Ada)
18096 @cindex aggregates (Ada)
18097 There is limited support for array and record aggregates. They are
18098 permitted only on the right sides of assignments, as in these examples:
18101 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18102 (@value{GDBP}) set An_Array := (1, others => 0)
18103 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18104 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18105 (@value{GDBP}) set A_Record := (1, "Peter", True);
18106 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18110 discriminant's value by assigning an aggregate has an
18111 undefined effect if that discriminant is used within the record.
18112 However, you can first modify discriminants by directly assigning to
18113 them (which normally would not be allowed in Ada), and then performing an
18114 aggregate assignment. For example, given a variable @code{A_Rec}
18115 declared to have a type such as:
18118 type Rec (Len : Small_Integer := 0) is record
18120 Vals : IntArray (1 .. Len);
18124 you can assign a value with a different size of @code{Vals} with two
18128 (@value{GDBP}) set A_Rec.Len := 4
18129 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18132 As this example also illustrates, @value{GDBN} is very loose about the usual
18133 rules concerning aggregates. You may leave out some of the
18134 components of an array or record aggregate (such as the @code{Len}
18135 component in the assignment to @code{A_Rec} above); they will retain their
18136 original values upon assignment. You may freely use dynamic values as
18137 indices in component associations. You may even use overlapping or
18138 redundant component associations, although which component values are
18139 assigned in such cases is not defined.
18142 Calls to dispatching subprograms are not implemented.
18145 The overloading algorithm is much more limited (i.e., less selective)
18146 than that of real Ada. It makes only limited use of the context in
18147 which a subexpression appears to resolve its meaning, and it is much
18148 looser in its rules for allowing type matches. As a result, some
18149 function calls will be ambiguous, and the user will be asked to choose
18150 the proper resolution.
18153 The @code{new} operator is not implemented.
18156 Entry calls are not implemented.
18159 Aside from printing, arithmetic operations on the native VAX floating-point
18160 formats are not supported.
18163 It is not possible to slice a packed array.
18166 The names @code{True} and @code{False}, when not part of a qualified name,
18167 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18169 Should your program
18170 redefine these names in a package or procedure (at best a dubious practice),
18171 you will have to use fully qualified names to access their new definitions.
18174 @node Additions to Ada
18175 @subsubsection Additions to Ada
18176 @cindex Ada, deviations from
18178 As it does for other languages, @value{GDBN} makes certain generic
18179 extensions to Ada (@pxref{Expressions}):
18183 If the expression @var{E} is a variable residing in memory (typically
18184 a local variable or array element) and @var{N} is a positive integer,
18185 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18186 @var{N}-1 adjacent variables following it in memory as an array. In
18187 Ada, this operator is generally not necessary, since its prime use is
18188 in displaying parts of an array, and slicing will usually do this in
18189 Ada. However, there are occasional uses when debugging programs in
18190 which certain debugging information has been optimized away.
18193 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18194 appears in function or file @var{B}.'' When @var{B} is a file name,
18195 you must typically surround it in single quotes.
18198 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18199 @var{type} that appears at address @var{addr}.''
18202 A name starting with @samp{$} is a convenience variable
18203 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18206 In addition, @value{GDBN} provides a few other shortcuts and outright
18207 additions specific to Ada:
18211 The assignment statement is allowed as an expression, returning
18212 its right-hand operand as its value. Thus, you may enter
18215 (@value{GDBP}) set x := y + 3
18216 (@value{GDBP}) print A(tmp := y + 1)
18220 The semicolon is allowed as an ``operator,'' returning as its value
18221 the value of its right-hand operand.
18222 This allows, for example,
18223 complex conditional breaks:
18226 (@value{GDBP}) break f
18227 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18231 Rather than use catenation and symbolic character names to introduce special
18232 characters into strings, one may instead use a special bracket notation,
18233 which is also used to print strings. A sequence of characters of the form
18234 @samp{["@var{XX}"]} within a string or character literal denotes the
18235 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18236 sequence of characters @samp{["""]} also denotes a single quotation mark
18237 in strings. For example,
18239 "One line.["0a"]Next line.["0a"]"
18242 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18246 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18247 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18251 (@value{GDBP}) print 'max(x, y)
18255 When printing arrays, @value{GDBN} uses positional notation when the
18256 array has a lower bound of 1, and uses a modified named notation otherwise.
18257 For example, a one-dimensional array of three integers with a lower bound
18258 of 3 might print as
18265 That is, in contrast to valid Ada, only the first component has a @code{=>}
18269 You may abbreviate attributes in expressions with any unique,
18270 multi-character subsequence of
18271 their names (an exact match gets preference).
18272 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18273 in place of @t{a'length}.
18276 @cindex quoting Ada internal identifiers
18277 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18278 to lower case. The GNAT compiler uses upper-case characters for
18279 some of its internal identifiers, which are normally of no interest to users.
18280 For the rare occasions when you actually have to look at them,
18281 enclose them in angle brackets to avoid the lower-case mapping.
18284 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18288 Printing an object of class-wide type or dereferencing an
18289 access-to-class-wide value will display all the components of the object's
18290 specific type (as indicated by its run-time tag). Likewise, component
18291 selection on such a value will operate on the specific type of the
18296 @node Overloading support for Ada
18297 @subsubsection Overloading support for Ada
18298 @cindex overloading, Ada
18300 The debugger supports limited overloading. Given a subprogram call in which
18301 the function symbol has multiple definitions, it will use the number of
18302 actual parameters and some information about their types to attempt to narrow
18303 the set of definitions. It also makes very limited use of context, preferring
18304 procedures to functions in the context of the @code{call} command, and
18305 functions to procedures elsewhere.
18307 If, after narrowing, the set of matching definitions still contains more than
18308 one definition, @value{GDBN} will display a menu to query which one it should
18312 (@value{GDBP}) print f(1)
18313 Multiple matches for f
18315 [1] foo.f (integer) return boolean at foo.adb:23
18316 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18320 In this case, just select one menu entry either to cancel expression evaluation
18321 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18322 instance (type the corresponding number and press @key{RET}).
18324 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18329 @kindex set ada print-signatures
18330 @item set ada print-signatures
18331 Control whether parameter types and return types are displayed in overloads
18332 selection menus. It is @code{on} by default.
18333 @xref{Overloading support for Ada}.
18335 @kindex show ada print-signatures
18336 @item show ada print-signatures
18337 Show the current setting for displaying parameter types and return types in
18338 overloads selection menu.
18339 @xref{Overloading support for Ada}.
18343 @node Stopping Before Main Program
18344 @subsubsection Stopping at the Very Beginning
18346 @cindex breakpointing Ada elaboration code
18347 It is sometimes necessary to debug the program during elaboration, and
18348 before reaching the main procedure.
18349 As defined in the Ada Reference
18350 Manual, the elaboration code is invoked from a procedure called
18351 @code{adainit}. To run your program up to the beginning of
18352 elaboration, simply use the following two commands:
18353 @code{tbreak adainit} and @code{run}.
18355 @node Ada Exceptions
18356 @subsubsection Ada Exceptions
18358 A command is provided to list all Ada exceptions:
18361 @kindex info exceptions
18362 @item info exceptions
18363 @itemx info exceptions @var{regexp}
18364 The @code{info exceptions} command allows you to list all Ada exceptions
18365 defined within the program being debugged, as well as their addresses.
18366 With a regular expression, @var{regexp}, as argument, only those exceptions
18367 whose names match @var{regexp} are listed.
18370 Below is a small example, showing how the command can be used, first
18371 without argument, and next with a regular expression passed as an
18375 (@value{GDBP}) info exceptions
18376 All defined Ada exceptions:
18377 constraint_error: 0x613da0
18378 program_error: 0x613d20
18379 storage_error: 0x613ce0
18380 tasking_error: 0x613ca0
18381 const.aint_global_e: 0x613b00
18382 (@value{GDBP}) info exceptions const.aint
18383 All Ada exceptions matching regular expression "const.aint":
18384 constraint_error: 0x613da0
18385 const.aint_global_e: 0x613b00
18388 It is also possible to ask @value{GDBN} to stop your program's execution
18389 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18392 @subsubsection Extensions for Ada Tasks
18393 @cindex Ada, tasking
18395 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18396 @value{GDBN} provides the following task-related commands:
18401 This command shows a list of current Ada tasks, as in the following example:
18408 (@value{GDBP}) info tasks
18409 ID TID P-ID Pri State Name
18410 1 8088000 0 15 Child Activation Wait main_task
18411 2 80a4000 1 15 Accept Statement b
18412 3 809a800 1 15 Child Activation Wait a
18413 * 4 80ae800 3 15 Runnable c
18418 In this listing, the asterisk before the last task indicates it to be the
18419 task currently being inspected.
18423 Represents @value{GDBN}'s internal task number.
18429 The parent's task ID (@value{GDBN}'s internal task number).
18432 The base priority of the task.
18435 Current state of the task.
18439 The task has been created but has not been activated. It cannot be
18443 The task is not blocked for any reason known to Ada. (It may be waiting
18444 for a mutex, though.) It is conceptually "executing" in normal mode.
18447 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18448 that were waiting on terminate alternatives have been awakened and have
18449 terminated themselves.
18451 @item Child Activation Wait
18452 The task is waiting for created tasks to complete activation.
18454 @item Accept Statement
18455 The task is waiting on an accept or selective wait statement.
18457 @item Waiting on entry call
18458 The task is waiting on an entry call.
18460 @item Async Select Wait
18461 The task is waiting to start the abortable part of an asynchronous
18465 The task is waiting on a select statement with only a delay
18468 @item Child Termination Wait
18469 The task is sleeping having completed a master within itself, and is
18470 waiting for the tasks dependent on that master to become terminated or
18471 waiting on a terminate Phase.
18473 @item Wait Child in Term Alt
18474 The task is sleeping waiting for tasks on terminate alternatives to
18475 finish terminating.
18477 @item Accepting RV with @var{taskno}
18478 The task is accepting a rendez-vous with the task @var{taskno}.
18482 Name of the task in the program.
18486 @kindex info task @var{taskno}
18487 @item info task @var{taskno}
18488 This command shows detailed informations on the specified task, as in
18489 the following example:
18494 (@value{GDBP}) info tasks
18495 ID TID P-ID Pri State Name
18496 1 8077880 0 15 Child Activation Wait main_task
18497 * 2 807c468 1 15 Runnable task_1
18498 (@value{GDBP}) info task 2
18499 Ada Task: 0x807c468
18503 Parent: 1 ("main_task")
18509 @kindex task@r{ (Ada)}
18510 @cindex current Ada task ID
18511 This command prints the ID and name of the current task.
18517 (@value{GDBP}) info tasks
18518 ID TID P-ID Pri State Name
18519 1 8077870 0 15 Child Activation Wait main_task
18520 * 2 807c458 1 15 Runnable some_task
18521 (@value{GDBP}) task
18522 [Current task is 2 "some_task"]
18525 @item task @var{taskno}
18526 @cindex Ada task switching
18527 This command is like the @code{thread @var{thread-id}}
18528 command (@pxref{Threads}). It switches the context of debugging
18529 from the current task to the given task.
18535 (@value{GDBP}) info tasks
18536 ID TID P-ID Pri State Name
18537 1 8077870 0 15 Child Activation Wait main_task
18538 * 2 807c458 1 15 Runnable some_task
18539 (@value{GDBP}) task 1
18540 [Switching to task 1 "main_task"]
18541 #0 0x8067726 in pthread_cond_wait ()
18543 #0 0x8067726 in pthread_cond_wait ()
18544 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18545 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18546 #3 0x806153e in system.tasking.stages.activate_tasks ()
18547 #4 0x804aacc in un () at un.adb:5
18550 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18551 The @code{task apply} command is the Ada tasking analogue of
18552 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18553 named @var{command} to one or more tasks. Specify the tasks that you
18554 want affected using a list of task IDs, or specify @code{all} to apply
18557 The @var{flag} arguments control what output to produce and how to
18558 handle errors raised when applying @var{command} to a task.
18559 @var{flag} must start with a @code{-} directly followed by one letter
18560 in @code{qcs}. If several flags are provided, they must be given
18561 individually, such as @code{-c -q}.
18563 By default, @value{GDBN} displays some task information before the
18564 output produced by @var{command}, and an error raised during the
18565 execution of a @var{command} will abort @code{task apply}. The
18566 following flags can be used to fine-tune this behavior:
18570 The flag @code{-c}, which stands for @samp{continue}, causes any
18571 errors in @var{command} to be displayed, and the execution of
18572 @code{task apply} then continues.
18574 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18575 or empty output produced by a @var{command} to be silently ignored.
18576 That is, the execution continues, but the task information and errors
18579 The flag @code{-q} (@samp{quiet}) disables printing the task
18583 Flags @code{-c} and @code{-s} cannot be used together.
18585 @item break @var{location} task @var{taskno}
18586 @itemx break @var{location} task @var{taskno} if @dots{}
18587 @cindex breakpoints and tasks, in Ada
18588 @cindex task breakpoints, in Ada
18589 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18590 These commands are like the @code{break @dots{} thread @dots{}}
18591 command (@pxref{Thread Stops}). The
18592 @var{location} argument specifies source lines, as described
18593 in @ref{Specify Location}.
18595 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18596 to specify that you only want @value{GDBN} to stop the program when a
18597 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18598 numeric task identifiers assigned by @value{GDBN}, shown in the first
18599 column of the @samp{info tasks} display.
18601 If you do not specify @samp{task @var{taskno}} when you set a
18602 breakpoint, the breakpoint applies to @emph{all} tasks of your
18605 You can use the @code{task} qualifier on conditional breakpoints as
18606 well; in this case, place @samp{task @var{taskno}} before the
18607 breakpoint condition (before the @code{if}).
18615 (@value{GDBP}) info tasks
18616 ID TID P-ID Pri State Name
18617 1 140022020 0 15 Child Activation Wait main_task
18618 2 140045060 1 15 Accept/Select Wait t2
18619 3 140044840 1 15 Runnable t1
18620 * 4 140056040 1 15 Runnable t3
18621 (@value{GDBP}) b 15 task 2
18622 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18623 (@value{GDBP}) cont
18628 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18630 (@value{GDBP}) info tasks
18631 ID TID P-ID Pri State Name
18632 1 140022020 0 15 Child Activation Wait main_task
18633 * 2 140045060 1 15 Runnable t2
18634 3 140044840 1 15 Runnable t1
18635 4 140056040 1 15 Delay Sleep t3
18639 @node Ada Tasks and Core Files
18640 @subsubsection Tasking Support when Debugging Core Files
18641 @cindex Ada tasking and core file debugging
18643 When inspecting a core file, as opposed to debugging a live program,
18644 tasking support may be limited or even unavailable, depending on
18645 the platform being used.
18646 For instance, on x86-linux, the list of tasks is available, but task
18647 switching is not supported.
18649 On certain platforms, the debugger needs to perform some
18650 memory writes in order to provide Ada tasking support. When inspecting
18651 a core file, this means that the core file must be opened with read-write
18652 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18653 Under these circumstances, you should make a backup copy of the core
18654 file before inspecting it with @value{GDBN}.
18656 @node Ravenscar Profile
18657 @subsubsection Tasking Support when using the Ravenscar Profile
18658 @cindex Ravenscar Profile
18660 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18661 specifically designed for systems with safety-critical real-time
18665 @kindex set ravenscar task-switching on
18666 @cindex task switching with program using Ravenscar Profile
18667 @item set ravenscar task-switching on
18668 Allows task switching when debugging a program that uses the Ravenscar
18669 Profile. This is the default.
18671 @kindex set ravenscar task-switching off
18672 @item set ravenscar task-switching off
18673 Turn off task switching when debugging a program that uses the Ravenscar
18674 Profile. This is mostly intended to disable the code that adds support
18675 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18676 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18677 To be effective, this command should be run before the program is started.
18679 @kindex show ravenscar task-switching
18680 @item show ravenscar task-switching
18681 Show whether it is possible to switch from task to task in a program
18682 using the Ravenscar Profile.
18686 @cindex Ravenscar thread
18687 When Ravenscar task-switching is enabled, Ravenscar tasks are
18688 announced by @value{GDBN} as if they were threads:
18692 [New Ravenscar Thread 0x2b8f0]
18695 Both Ravenscar tasks and the underlying CPU threads will show up in
18696 the output of @code{info threads}:
18701 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18702 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18703 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18704 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18705 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18706 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18709 One known limitation of the Ravenscar support in @value{GDBN} is that
18710 it isn't currently possible to single-step through the runtime
18711 initialization sequence. If you need to debug this code, you should
18712 use @code{set ravenscar task-switching off}.
18715 @subsubsection Ada Settings
18716 @cindex Ada settings
18719 @kindex set varsize-limit
18720 @item set varsize-limit @var{size}
18721 Prevent @value{GDBN} from attempting to evaluate objects whose size
18722 is above the given limit (@var{size}) when those sizes are computed
18723 from run-time quantities. This is typically the case when the object
18724 has a variable size, such as an array whose bounds are not known at
18725 compile time for example. Setting @var{size} to @code{unlimited}
18726 removes the size limitation. By default, the limit is about 65KB.
18728 The purpose of having such a limit is to prevent @value{GDBN} from
18729 trying to grab enormous chunks of virtual memory when asked to evaluate
18730 a quantity whose bounds have been corrupted or have not yet been fully
18731 initialized. The limit applies to the results of some subexpressions
18732 as well as to complete expressions. For example, an expression denoting
18733 a simple integer component, such as @code{x.y.z}, may fail if the size of
18734 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18735 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18736 @code{A} is an array variable with non-constant size, will generally
18737 succeed regardless of the bounds on @code{A}, as long as the component
18738 size is less than @var{size}.
18740 @kindex show varsize-limit
18741 @item show varsize-limit
18742 Show the limit on types whose size is determined by run-time quantities.
18746 @subsubsection Known Peculiarities of Ada Mode
18747 @cindex Ada, problems
18749 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18750 we know of several problems with and limitations of Ada mode in
18752 some of which will be fixed with planned future releases of the debugger
18753 and the GNU Ada compiler.
18757 Static constants that the compiler chooses not to materialize as objects in
18758 storage are invisible to the debugger.
18761 Named parameter associations in function argument lists are ignored (the
18762 argument lists are treated as positional).
18765 Many useful library packages are currently invisible to the debugger.
18768 Fixed-point arithmetic, conversions, input, and output is carried out using
18769 floating-point arithmetic, and may give results that only approximate those on
18773 The GNAT compiler never generates the prefix @code{Standard} for any of
18774 the standard symbols defined by the Ada language. @value{GDBN} knows about
18775 this: it will strip the prefix from names when you use it, and will never
18776 look for a name you have so qualified among local symbols, nor match against
18777 symbols in other packages or subprograms. If you have
18778 defined entities anywhere in your program other than parameters and
18779 local variables whose simple names match names in @code{Standard},
18780 GNAT's lack of qualification here can cause confusion. When this happens,
18781 you can usually resolve the confusion
18782 by qualifying the problematic names with package
18783 @code{Standard} explicitly.
18786 Older versions of the compiler sometimes generate erroneous debugging
18787 information, resulting in the debugger incorrectly printing the value
18788 of affected entities. In some cases, the debugger is able to work
18789 around an issue automatically. In other cases, the debugger is able
18790 to work around the issue, but the work-around has to be specifically
18793 @kindex set ada trust-PAD-over-XVS
18794 @kindex show ada trust-PAD-over-XVS
18797 @item set ada trust-PAD-over-XVS on
18798 Configure GDB to strictly follow the GNAT encoding when computing the
18799 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18800 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18801 a complete description of the encoding used by the GNAT compiler).
18802 This is the default.
18804 @item set ada trust-PAD-over-XVS off
18805 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18806 sometimes prints the wrong value for certain entities, changing @code{ada
18807 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18808 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18809 @code{off}, but this incurs a slight performance penalty, so it is
18810 recommended to leave this setting to @code{on} unless necessary.
18814 @cindex GNAT descriptive types
18815 @cindex GNAT encoding
18816 Internally, the debugger also relies on the compiler following a number
18817 of conventions known as the @samp{GNAT Encoding}, all documented in
18818 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18819 how the debugging information should be generated for certain types.
18820 In particular, this convention makes use of @dfn{descriptive types},
18821 which are artificial types generated purely to help the debugger.
18823 These encodings were defined at a time when the debugging information
18824 format used was not powerful enough to describe some of the more complex
18825 types available in Ada. Since DWARF allows us to express nearly all
18826 Ada features, the long-term goal is to slowly replace these descriptive
18827 types by their pure DWARF equivalent. To facilitate that transition,
18828 a new maintenance option is available to force the debugger to ignore
18829 those descriptive types. It allows the user to quickly evaluate how
18830 well @value{GDBN} works without them.
18834 @kindex maint ada set ignore-descriptive-types
18835 @item maintenance ada set ignore-descriptive-types [on|off]
18836 Control whether the debugger should ignore descriptive types.
18837 The default is not to ignore descriptives types (@code{off}).
18839 @kindex maint ada show ignore-descriptive-types
18840 @item maintenance ada show ignore-descriptive-types
18841 Show if descriptive types are ignored by @value{GDBN}.
18845 @node Unsupported Languages
18846 @section Unsupported Languages
18848 @cindex unsupported languages
18849 @cindex minimal language
18850 In addition to the other fully-supported programming languages,
18851 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18852 It does not represent a real programming language, but provides a set
18853 of capabilities close to what the C or assembly languages provide.
18854 This should allow most simple operations to be performed while debugging
18855 an application that uses a language currently not supported by @value{GDBN}.
18857 If the language is set to @code{auto}, @value{GDBN} will automatically
18858 select this language if the current frame corresponds to an unsupported
18862 @chapter Examining the Symbol Table
18864 The commands described in this chapter allow you to inquire about the
18865 symbols (names of variables, functions and types) defined in your
18866 program. This information is inherent in the text of your program and
18867 does not change as your program executes. @value{GDBN} finds it in your
18868 program's symbol table, in the file indicated when you started @value{GDBN}
18869 (@pxref{File Options, ,Choosing Files}), or by one of the
18870 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18872 @cindex symbol names
18873 @cindex names of symbols
18874 @cindex quoting names
18875 @anchor{quoting names}
18876 Occasionally, you may need to refer to symbols that contain unusual
18877 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18878 most frequent case is in referring to static variables in other
18879 source files (@pxref{Variables,,Program Variables}). File names
18880 are recorded in object files as debugging symbols, but @value{GDBN} would
18881 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18882 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18883 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18890 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18893 @cindex case-insensitive symbol names
18894 @cindex case sensitivity in symbol names
18895 @kindex set case-sensitive
18896 @item set case-sensitive on
18897 @itemx set case-sensitive off
18898 @itemx set case-sensitive auto
18899 Normally, when @value{GDBN} looks up symbols, it matches their names
18900 with case sensitivity determined by the current source language.
18901 Occasionally, you may wish to control that. The command @code{set
18902 case-sensitive} lets you do that by specifying @code{on} for
18903 case-sensitive matches or @code{off} for case-insensitive ones. If
18904 you specify @code{auto}, case sensitivity is reset to the default
18905 suitable for the source language. The default is case-sensitive
18906 matches for all languages except for Fortran, for which the default is
18907 case-insensitive matches.
18909 @kindex show case-sensitive
18910 @item show case-sensitive
18911 This command shows the current setting of case sensitivity for symbols
18914 @kindex set print type methods
18915 @item set print type methods
18916 @itemx set print type methods on
18917 @itemx set print type methods off
18918 Normally, when @value{GDBN} prints a class, it displays any methods
18919 declared in that class. You can control this behavior either by
18920 passing the appropriate flag to @code{ptype}, or using @command{set
18921 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18922 display the methods; this is the default. Specifying @code{off} will
18923 cause @value{GDBN} to omit the methods.
18925 @kindex show print type methods
18926 @item show print type methods
18927 This command shows the current setting of method display when printing
18930 @kindex set print type nested-type-limit
18931 @item set print type nested-type-limit @var{limit}
18932 @itemx set print type nested-type-limit unlimited
18933 Set the limit of displayed nested types that the type printer will
18934 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18935 nested definitions. By default, the type printer will not show any nested
18936 types defined in classes.
18938 @kindex show print type nested-type-limit
18939 @item show print type nested-type-limit
18940 This command shows the current display limit of nested types when
18943 @kindex set print type typedefs
18944 @item set print type typedefs
18945 @itemx set print type typedefs on
18946 @itemx set print type typedefs off
18948 Normally, when @value{GDBN} prints a class, it displays any typedefs
18949 defined in that class. You can control this behavior either by
18950 passing the appropriate flag to @code{ptype}, or using @command{set
18951 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18952 display the typedef definitions; this is the default. Specifying
18953 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18954 Note that this controls whether the typedef definition itself is
18955 printed, not whether typedef names are substituted when printing other
18958 @kindex show print type typedefs
18959 @item show print type typedefs
18960 This command shows the current setting of typedef display when
18963 @kindex set print type hex
18964 @item set print type hex
18965 @itemx set print type hex on
18966 @itemx set print type hex off
18968 When @value{GDBN} prints sizes and offsets of struct members, it can use
18969 either the decimal or hexadecimal notation. You can select one or the
18970 other either by passing the appropriate flag to @code{ptype}, or by using
18971 the @command{set print type hex} command.
18973 @kindex show print type hex
18974 @item show print type hex
18975 This command shows whether the sizes and offsets of struct members are
18976 printed in decimal or hexadecimal notation.
18978 @kindex info address
18979 @cindex address of a symbol
18980 @item info address @var{symbol}
18981 Describe where the data for @var{symbol} is stored. For a register
18982 variable, this says which register it is kept in. For a non-register
18983 local variable, this prints the stack-frame offset at which the variable
18986 Note the contrast with @samp{print &@var{symbol}}, which does not work
18987 at all for a register variable, and for a stack local variable prints
18988 the exact address of the current instantiation of the variable.
18990 @kindex info symbol
18991 @cindex symbol from address
18992 @cindex closest symbol and offset for an address
18993 @item info symbol @var{addr}
18994 Print the name of a symbol which is stored at the address @var{addr}.
18995 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18996 nearest symbol and an offset from it:
18999 (@value{GDBP}) info symbol 0x54320
19000 _initialize_vx + 396 in section .text
19004 This is the opposite of the @code{info address} command. You can use
19005 it to find out the name of a variable or a function given its address.
19007 For dynamically linked executables, the name of executable or shared
19008 library containing the symbol is also printed:
19011 (@value{GDBP}) info symbol 0x400225
19012 _start + 5 in section .text of /tmp/a.out
19013 (@value{GDBP}) info symbol 0x2aaaac2811cf
19014 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19019 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19020 Demangle @var{name}.
19021 If @var{language} is provided it is the name of the language to demangle
19022 @var{name} in. Otherwise @var{name} is demangled in the current language.
19024 The @samp{--} option specifies the end of options,
19025 and is useful when @var{name} begins with a dash.
19027 The parameter @code{demangle-style} specifies how to interpret the kind
19028 of mangling used. @xref{Print Settings}.
19031 @item whatis[/@var{flags}] [@var{arg}]
19032 Print the data type of @var{arg}, which can be either an expression
19033 or a name of a data type. With no argument, print the data type of
19034 @code{$}, the last value in the value history.
19036 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19037 is not actually evaluated, and any side-effecting operations (such as
19038 assignments or function calls) inside it do not take place.
19040 If @var{arg} is a variable or an expression, @code{whatis} prints its
19041 literal type as it is used in the source code. If the type was
19042 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19043 the data type underlying the @code{typedef}. If the type of the
19044 variable or the expression is a compound data type, such as
19045 @code{struct} or @code{class}, @code{whatis} never prints their
19046 fields or methods. It just prints the @code{struct}/@code{class}
19047 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19048 such a compound data type, use @code{ptype}.
19050 If @var{arg} is a type name that was defined using @code{typedef},
19051 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19052 Unrolling means that @code{whatis} will show the underlying type used
19053 in the @code{typedef} declaration of @var{arg}. However, if that
19054 underlying type is also a @code{typedef}, @code{whatis} will not
19057 For C code, the type names may also have the form @samp{class
19058 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19059 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19061 @var{flags} can be used to modify how the type is displayed.
19062 Available flags are:
19066 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19067 parameters and typedefs defined in a class when printing the class'
19068 members. The @code{/r} flag disables this.
19071 Do not print methods defined in the class.
19074 Print methods defined in the class. This is the default, but the flag
19075 exists in case you change the default with @command{set print type methods}.
19078 Do not print typedefs defined in the class. Note that this controls
19079 whether the typedef definition itself is printed, not whether typedef
19080 names are substituted when printing other types.
19083 Print typedefs defined in the class. This is the default, but the flag
19084 exists in case you change the default with @command{set print type typedefs}.
19087 Print the offsets and sizes of fields in a struct, similar to what the
19088 @command{pahole} tool does. This option implies the @code{/tm} flags.
19091 Use hexadecimal notation when printing offsets and sizes of fields in a
19095 Use decimal notation when printing offsets and sizes of fields in a
19098 For example, given the following declarations:
19134 Issuing a @kbd{ptype /o struct tuv} command would print:
19137 (@value{GDBP}) ptype /o struct tuv
19138 /* offset | size */ type = struct tuv @{
19139 /* 0 | 4 */ int a1;
19140 /* XXX 4-byte hole */
19141 /* 8 | 8 */ char *a2;
19142 /* 16 | 4 */ int a3;
19144 /* total size (bytes): 24 */
19148 Notice the format of the first column of comments. There, you can
19149 find two parts separated by the @samp{|} character: the @emph{offset},
19150 which indicates where the field is located inside the struct, in
19151 bytes, and the @emph{size} of the field. Another interesting line is
19152 the marker of a @emph{hole} in the struct, indicating that it may be
19153 possible to pack the struct and make it use less space by reorganizing
19156 It is also possible to print offsets inside an union:
19159 (@value{GDBP}) ptype /o union qwe
19160 /* offset | size */ type = union qwe @{
19161 /* 24 */ struct tuv @{
19162 /* 0 | 4 */ int a1;
19163 /* XXX 4-byte hole */
19164 /* 8 | 8 */ char *a2;
19165 /* 16 | 4 */ int a3;
19167 /* total size (bytes): 24 */
19169 /* 40 */ struct xyz @{
19170 /* 0 | 4 */ int f1;
19171 /* 4 | 1 */ char f2;
19172 /* XXX 3-byte hole */
19173 /* 8 | 8 */ void *f3;
19174 /* 16 | 24 */ struct tuv @{
19175 /* 16 | 4 */ int a1;
19176 /* XXX 4-byte hole */
19177 /* 24 | 8 */ char *a2;
19178 /* 32 | 4 */ int a3;
19180 /* total size (bytes): 24 */
19183 /* total size (bytes): 40 */
19186 /* total size (bytes): 40 */
19190 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19191 same space (because we are dealing with an union), the offset is not
19192 printed for them. However, you can still examine the offset of each
19193 of these structures' fields.
19195 Another useful scenario is printing the offsets of a struct containing
19199 (@value{GDBP}) ptype /o struct tyu
19200 /* offset | size */ type = struct tyu @{
19201 /* 0:31 | 4 */ int a1 : 1;
19202 /* 0:28 | 4 */ int a2 : 3;
19203 /* 0: 5 | 4 */ int a3 : 23;
19204 /* 3: 3 | 1 */ signed char a4 : 2;
19205 /* XXX 3-bit hole */
19206 /* XXX 4-byte hole */
19207 /* 8 | 8 */ int64_t a5;
19208 /* 16: 0 | 4 */ int a6 : 5;
19209 /* 16: 5 | 8 */ int64_t a7 : 3;
19210 /* XXX 7-byte padding */
19212 /* total size (bytes): 24 */
19216 Note how the offset information is now extended to also include the
19217 first bit of the bitfield.
19221 @item ptype[/@var{flags}] [@var{arg}]
19222 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19223 detailed description of the type, instead of just the name of the type.
19224 @xref{Expressions, ,Expressions}.
19226 Contrary to @code{whatis}, @code{ptype} always unrolls any
19227 @code{typedef}s in its argument declaration, whether the argument is
19228 a variable, expression, or a data type. This means that @code{ptype}
19229 of a variable or an expression will not print literally its type as
19230 present in the source code---use @code{whatis} for that. @code{typedef}s at
19231 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19232 fields, methods and inner @code{class typedef}s of @code{struct}s,
19233 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19235 For example, for this variable declaration:
19238 typedef double real_t;
19239 struct complex @{ real_t real; double imag; @};
19240 typedef struct complex complex_t;
19242 real_t *real_pointer_var;
19246 the two commands give this output:
19250 (@value{GDBP}) whatis var
19252 (@value{GDBP}) ptype var
19253 type = struct complex @{
19257 (@value{GDBP}) whatis complex_t
19258 type = struct complex
19259 (@value{GDBP}) whatis struct complex
19260 type = struct complex
19261 (@value{GDBP}) ptype struct complex
19262 type = struct complex @{
19266 (@value{GDBP}) whatis real_pointer_var
19268 (@value{GDBP}) ptype real_pointer_var
19274 As with @code{whatis}, using @code{ptype} without an argument refers to
19275 the type of @code{$}, the last value in the value history.
19277 @cindex incomplete type
19278 Sometimes, programs use opaque data types or incomplete specifications
19279 of complex data structure. If the debug information included in the
19280 program does not allow @value{GDBN} to display a full declaration of
19281 the data type, it will say @samp{<incomplete type>}. For example,
19282 given these declarations:
19286 struct foo *fooptr;
19290 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19293 (@value{GDBP}) ptype foo
19294 $1 = <incomplete type>
19298 ``Incomplete type'' is C terminology for data types that are not
19299 completely specified.
19301 @cindex unknown type
19302 Othertimes, information about a variable's type is completely absent
19303 from the debug information included in the program. This most often
19304 happens when the program or library where the variable is defined
19305 includes no debug information at all. @value{GDBN} knows the variable
19306 exists from inspecting the linker/loader symbol table (e.g., the ELF
19307 dynamic symbol table), but such symbols do not contain type
19308 information. Inspecting the type of a (global) variable for which
19309 @value{GDBN} has no type information shows:
19312 (@value{GDBP}) ptype var
19313 type = <data variable, no debug info>
19316 @xref{Variables, no debug info variables}, for how to print the values
19320 @item info types [-q] [@var{regexp}]
19321 Print a brief description of all types whose names match the regular
19322 expression @var{regexp} (or all types in your program, if you supply
19323 no argument). Each complete typename is matched as though it were a
19324 complete line; thus, @samp{i type value} gives information on all
19325 types in your program whose names include the string @code{value}, but
19326 @samp{i type ^value$} gives information only on types whose complete
19327 name is @code{value}.
19329 In programs using different languages, @value{GDBN} chooses the syntax
19330 to print the type description according to the
19331 @samp{set language} value: using @samp{set language auto}
19332 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19333 language of the type, other values mean to use
19334 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19336 This command differs from @code{ptype} in two ways: first, like
19337 @code{whatis}, it does not print a detailed description; second, it
19338 lists all source files and line numbers where a type is defined.
19340 The output from @samp{into types} is proceeded with a header line
19341 describing what types are being listed. The optional flag @samp{-q},
19342 which stands for @samp{quiet}, disables printing this header
19345 @kindex info type-printers
19346 @item info type-printers
19347 Versions of @value{GDBN} that ship with Python scripting enabled may
19348 have ``type printers'' available. When using @command{ptype} or
19349 @command{whatis}, these printers are consulted when the name of a type
19350 is needed. @xref{Type Printing API}, for more information on writing
19353 @code{info type-printers} displays all the available type printers.
19355 @kindex enable type-printer
19356 @kindex disable type-printer
19357 @item enable type-printer @var{name}@dots{}
19358 @item disable type-printer @var{name}@dots{}
19359 These commands can be used to enable or disable type printers.
19362 @cindex local variables
19363 @item info scope @var{location}
19364 List all the variables local to a particular scope. This command
19365 accepts a @var{location} argument---a function name, a source line, or
19366 an address preceded by a @samp{*}, and prints all the variables local
19367 to the scope defined by that location. (@xref{Specify Location}, for
19368 details about supported forms of @var{location}.) For example:
19371 (@value{GDBP}) @b{info scope command_line_handler}
19372 Scope for command_line_handler:
19373 Symbol rl is an argument at stack/frame offset 8, length 4.
19374 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19375 Symbol linelength is in static storage at address 0x150a1c, length 4.
19376 Symbol p is a local variable in register $esi, length 4.
19377 Symbol p1 is a local variable in register $ebx, length 4.
19378 Symbol nline is a local variable in register $edx, length 4.
19379 Symbol repeat is a local variable at frame offset -8, length 4.
19383 This command is especially useful for determining what data to collect
19384 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19387 @kindex info source
19389 Show information about the current source file---that is, the source file for
19390 the function containing the current point of execution:
19393 the name of the source file, and the directory containing it,
19395 the directory it was compiled in,
19397 its length, in lines,
19399 which programming language it is written in,
19401 if the debug information provides it, the program that compiled the file
19402 (which may include, e.g., the compiler version and command line arguments),
19404 whether the executable includes debugging information for that file, and
19405 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19407 whether the debugging information includes information about
19408 preprocessor macros.
19412 @kindex info sources
19413 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19416 With no options @samp{info sources} prints the names of all source
19417 files in your program for which there is debugging information. The
19418 source files are presented based on a list of object files
19419 (executables and libraries) currently loaded into @value{GDBN}. For
19420 each object file all of the associated source files are listed.
19422 Each source file will only be printed once for each object file, but a
19423 single source file can be repeated in the output if it is part of
19424 multiple object files.
19426 If the optional @var{regexp} is provided, then only source files that
19427 match the regular expression will be printed. The matching is
19428 case-sensitive, except on operating systems that have case-insensitive
19429 filesystem (e.g., MS-Windows). @samp{--} can be used before
19430 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19431 command option (e.g. if @var{regexp} starts with @samp{-}).
19433 By default, the @var{regexp} is used to match anywhere in the
19434 filename. If @code{-dirname}, only files having a dirname matching
19435 @var{regexp} are shown. If @code{-basename}, only files having a
19436 basename matching @var{regexp} are shown.
19438 It is possible that an object file may be printed in the list with no
19439 associated source files. This can happen when either no source files
19440 match @var{regexp}, or, the object file was compiled without debug
19441 information and so @value{GDBN} is unable to find any source file
19444 @kindex info functions
19445 @item info functions [-q] [-n]
19446 Print the names and data types of all defined functions.
19447 Similarly to @samp{info types}, this command groups its output by source
19448 files and annotates each function definition with its source line
19451 In programs using different languages, @value{GDBN} chooses the syntax
19452 to print the function name and type according to the
19453 @samp{set language} value: using @samp{set language auto}
19454 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19455 language of the function, other values mean to use
19456 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19458 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19459 results. A non-debugging symbol is a symbol that comes from the
19460 executable's symbol table, not from the debug information (for
19461 example, DWARF) associated with the executable.
19463 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19464 printing header information and messages explaining why no functions
19467 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19468 Like @samp{info functions}, but only print the names and data types
19469 of the functions selected with the provided regexp(s).
19471 If @var{regexp} is provided, print only the functions whose names
19472 match the regular expression @var{regexp}.
19473 Thus, @samp{info fun step} finds all functions whose
19474 names include @code{step}; @samp{info fun ^step} finds those whose names
19475 start with @code{step}. If a function name contains characters that
19476 conflict with the regular expression language (e.g.@:
19477 @samp{operator*()}), they may be quoted with a backslash.
19479 If @var{type_regexp} is provided, print only the functions whose
19480 types, as printed by the @code{whatis} command, match
19481 the regular expression @var{type_regexp}.
19482 If @var{type_regexp} contains space(s), it should be enclosed in
19483 quote characters. If needed, use backslash to escape the meaning
19484 of special characters or quotes.
19485 Thus, @samp{info fun -t '^int ('} finds the functions that return
19486 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19487 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19488 finds the functions whose names start with @code{step} and that return
19491 If both @var{regexp} and @var{type_regexp} are provided, a function
19492 is printed only if its name matches @var{regexp} and its type matches
19496 @kindex info variables
19497 @item info variables [-q] [-n]
19498 Print the names and data types of all variables that are defined
19499 outside of functions (i.e.@: excluding local variables).
19500 The printed variables are grouped by source files and annotated with
19501 their respective source line numbers.
19503 In programs using different languages, @value{GDBN} chooses the syntax
19504 to print the variable name and type according to the
19505 @samp{set language} value: using @samp{set language auto}
19506 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19507 language of the variable, other values mean to use
19508 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19510 The @samp{-n} flag excludes non-debugging symbols from the results.
19512 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19513 printing header information and messages explaining why no variables
19516 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19517 Like @kbd{info variables}, but only print the variables selected
19518 with the provided regexp(s).
19520 If @var{regexp} is provided, print only the variables whose names
19521 match the regular expression @var{regexp}.
19523 If @var{type_regexp} is provided, print only the variables whose
19524 types, as printed by the @code{whatis} command, match
19525 the regular expression @var{type_regexp}.
19526 If @var{type_regexp} contains space(s), it should be enclosed in
19527 quote characters. If needed, use backslash to escape the meaning
19528 of special characters or quotes.
19530 If both @var{regexp} and @var{type_regexp} are provided, an argument
19531 is printed only if its name matches @var{regexp} and its type matches
19534 @kindex info modules
19536 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19537 List all Fortran modules in the program, or all modules matching the
19538 optional regular expression @var{regexp}.
19540 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19541 printing header information and messages explaining why no modules
19544 @kindex info module
19545 @cindex Fortran modules, information about
19546 @cindex functions and variables by Fortran module
19547 @cindex module functions and variables
19548 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19549 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19550 List all functions or variables within all Fortran modules. The set
19551 of functions or variables listed can be limited by providing some or
19552 all of the optional regular expressions. If @var{module-regexp} is
19553 provided, then only Fortran modules matching @var{module-regexp} will
19554 be searched. Only functions or variables whose type matches the
19555 optional regular expression @var{type-regexp} will be listed. And
19556 only functions or variables whose name matches the optional regular
19557 expression @var{regexp} will be listed.
19559 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19560 printing header information and messages explaining why no functions
19561 or variables have been printed.
19563 @kindex info classes
19564 @cindex Objective-C, classes and selectors
19566 @itemx info classes @var{regexp}
19567 Display all Objective-C classes in your program, or
19568 (with the @var{regexp} argument) all those matching a particular regular
19571 @kindex info selectors
19572 @item info selectors
19573 @itemx info selectors @var{regexp}
19574 Display all Objective-C selectors in your program, or
19575 (with the @var{regexp} argument) all those matching a particular regular
19579 This was never implemented.
19580 @kindex info methods
19582 @itemx info methods @var{regexp}
19583 The @code{info methods} command permits the user to examine all defined
19584 methods within C@t{++} program, or (with the @var{regexp} argument) a
19585 specific set of methods found in the various C@t{++} classes. Many
19586 C@t{++} classes provide a large number of methods. Thus, the output
19587 from the @code{ptype} command can be overwhelming and hard to use. The
19588 @code{info-methods} command filters the methods, printing only those
19589 which match the regular-expression @var{regexp}.
19592 @cindex opaque data types
19593 @kindex set opaque-type-resolution
19594 @item set opaque-type-resolution on
19595 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19596 declared as a pointer to a @code{struct}, @code{class}, or
19597 @code{union}---for example, @code{struct MyType *}---that is used in one
19598 source file although the full declaration of @code{struct MyType} is in
19599 another source file. The default is on.
19601 A change in the setting of this subcommand will not take effect until
19602 the next time symbols for a file are loaded.
19604 @item set opaque-type-resolution off
19605 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19606 is printed as follows:
19608 @{<no data fields>@}
19611 @kindex show opaque-type-resolution
19612 @item show opaque-type-resolution
19613 Show whether opaque types are resolved or not.
19615 @kindex set print symbol-loading
19616 @cindex print messages when symbols are loaded
19617 @item set print symbol-loading
19618 @itemx set print symbol-loading full
19619 @itemx set print symbol-loading brief
19620 @itemx set print symbol-loading off
19621 The @code{set print symbol-loading} command allows you to control the
19622 printing of messages when @value{GDBN} loads symbol information.
19623 By default a message is printed for the executable and one for each
19624 shared library, and normally this is what you want. However, when
19625 debugging apps with large numbers of shared libraries these messages
19627 When set to @code{brief} a message is printed for each executable,
19628 and when @value{GDBN} loads a collection of shared libraries at once
19629 it will only print one message regardless of the number of shared
19630 libraries. When set to @code{off} no messages are printed.
19632 @kindex show print symbol-loading
19633 @item show print symbol-loading
19634 Show whether messages will be printed when a @value{GDBN} command
19635 entered from the keyboard causes symbol information to be loaded.
19637 @kindex maint print symbols
19638 @cindex symbol dump
19639 @kindex maint print psymbols
19640 @cindex partial symbol dump
19641 @kindex maint print msymbols
19642 @cindex minimal symbol dump
19643 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19644 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19645 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19646 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19647 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19648 Write a dump of debugging symbol data into the file @var{filename} or
19649 the terminal if @var{filename} is unspecified.
19650 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19652 If @code{-pc @var{address}} is specified, only dump symbols for the file
19653 with code at that address. Note that @var{address} may be a symbol like
19655 If @code{-source @var{source}} is specified, only dump symbols for that
19658 These commands are used to debug the @value{GDBN} symbol-reading code.
19659 These commands do not modify internal @value{GDBN} state, therefore
19660 @samp{maint print symbols} will only print symbols for already expanded symbol
19662 You can use the command @code{info sources} to find out which files these are.
19663 If you use @samp{maint print psymbols} instead, the dump shows information
19664 about symbols that @value{GDBN} only knows partially---that is, symbols
19665 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19666 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19669 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19670 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19672 @kindex maint info symtabs
19673 @kindex maint info psymtabs
19674 @cindex listing @value{GDBN}'s internal symbol tables
19675 @cindex symbol tables, listing @value{GDBN}'s internal
19676 @cindex full symbol tables, listing @value{GDBN}'s internal
19677 @cindex partial symbol tables, listing @value{GDBN}'s internal
19678 @item maint info symtabs @r{[} @var{regexp} @r{]}
19679 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19681 List the @code{struct symtab} or @code{struct partial_symtab}
19682 structures whose names match @var{regexp}. If @var{regexp} is not
19683 given, list them all. The output includes expressions which you can
19684 copy into a @value{GDBN} debugging this one to examine a particular
19685 structure in more detail. For example:
19688 (@value{GDBP}) maint info psymtabs dwarf2read
19689 @{ objfile /home/gnu/build/gdb/gdb
19690 ((struct objfile *) 0x82e69d0)
19691 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19692 ((struct partial_symtab *) 0x8474b10)
19695 text addresses 0x814d3c8 -- 0x8158074
19696 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19697 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19698 dependencies (none)
19701 (@value{GDBP}) maint info symtabs
19705 We see that there is one partial symbol table whose filename contains
19706 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19707 and we see that @value{GDBN} has not read in any symtabs yet at all.
19708 If we set a breakpoint on a function, that will cause @value{GDBN} to
19709 read the symtab for the compilation unit containing that function:
19712 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19713 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19715 (@value{GDBP}) maint info symtabs
19716 @{ objfile /home/gnu/build/gdb/gdb
19717 ((struct objfile *) 0x82e69d0)
19718 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19719 ((struct symtab *) 0x86c1f38)
19722 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19723 linetable ((struct linetable *) 0x8370fa0)
19724 debugformat DWARF 2
19730 @kindex maint info line-table
19731 @cindex listing @value{GDBN}'s internal line tables
19732 @cindex line tables, listing @value{GDBN}'s internal
19733 @item maint info line-table @r{[} @var{regexp} @r{]}
19735 List the @code{struct linetable} from all @code{struct symtab}
19736 instances whose name matches @var{regexp}. If @var{regexp} is not
19737 given, list the @code{struct linetable} from all @code{struct symtab}.
19739 @kindex maint set symbol-cache-size
19740 @cindex symbol cache size
19741 @item maint set symbol-cache-size @var{size}
19742 Set the size of the symbol cache to @var{size}.
19743 The default size is intended to be good enough for debugging
19744 most applications. This option exists to allow for experimenting
19745 with different sizes.
19747 @kindex maint show symbol-cache-size
19748 @item maint show symbol-cache-size
19749 Show the size of the symbol cache.
19751 @kindex maint print symbol-cache
19752 @cindex symbol cache, printing its contents
19753 @item maint print symbol-cache
19754 Print the contents of the symbol cache.
19755 This is useful when debugging symbol cache issues.
19757 @kindex maint print symbol-cache-statistics
19758 @cindex symbol cache, printing usage statistics
19759 @item maint print symbol-cache-statistics
19760 Print symbol cache usage statistics.
19761 This helps determine how well the cache is being utilized.
19763 @kindex maint flush symbol-cache
19764 @kindex maint flush-symbol-cache
19765 @cindex symbol cache, flushing
19766 @item maint flush symbol-cache
19767 @itemx maint flush-symbol-cache
19768 Flush the contents of the symbol cache, all entries are removed. This
19769 command is useful when debugging the symbol cache. It is also useful
19770 when collecting performance data. The command @code{maint
19771 flush-symbol-cache} is deprecated in favor of @code{maint flush
19777 @chapter Altering Execution
19779 Once you think you have found an error in your program, you might want to
19780 find out for certain whether correcting the apparent error would lead to
19781 correct results in the rest of the run. You can find the answer by
19782 experiment, using the @value{GDBN} features for altering execution of the
19785 For example, you can store new values into variables or memory
19786 locations, give your program a signal, restart it at a different
19787 address, or even return prematurely from a function.
19790 * Assignment:: Assignment to variables
19791 * Jumping:: Continuing at a different address
19792 * Signaling:: Giving your program a signal
19793 * Returning:: Returning from a function
19794 * Calling:: Calling your program's functions
19795 * Patching:: Patching your program
19796 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19800 @section Assignment to Variables
19803 @cindex setting variables
19804 To alter the value of a variable, evaluate an assignment expression.
19805 @xref{Expressions, ,Expressions}. For example,
19812 stores the value 4 into the variable @code{x}, and then prints the
19813 value of the assignment expression (which is 4).
19814 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19815 information on operators in supported languages.
19817 @kindex set variable
19818 @cindex variables, setting
19819 If you are not interested in seeing the value of the assignment, use the
19820 @code{set} command instead of the @code{print} command. @code{set} is
19821 really the same as @code{print} except that the expression's value is
19822 not printed and is not put in the value history (@pxref{Value History,
19823 ,Value History}). The expression is evaluated only for its effects.
19825 If the beginning of the argument string of the @code{set} command
19826 appears identical to a @code{set} subcommand, use the @code{set
19827 variable} command instead of just @code{set}. This command is identical
19828 to @code{set} except for its lack of subcommands. For example, if your
19829 program has a variable @code{width}, you get an error if you try to set
19830 a new value with just @samp{set width=13}, because @value{GDBN} has the
19831 command @code{set width}:
19834 (@value{GDBP}) whatis width
19836 (@value{GDBP}) p width
19838 (@value{GDBP}) set width=47
19839 Invalid syntax in expression.
19843 The invalid expression, of course, is @samp{=47}. In
19844 order to actually set the program's variable @code{width}, use
19847 (@value{GDBP}) set var width=47
19850 Because the @code{set} command has many subcommands that can conflict
19851 with the names of program variables, it is a good idea to use the
19852 @code{set variable} command instead of just @code{set}. For example, if
19853 your program has a variable @code{g}, you run into problems if you try
19854 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19855 the command @code{set gnutarget}, abbreviated @code{set g}:
19859 (@value{GDBP}) whatis g
19863 (@value{GDBP}) set g=4
19867 The program being debugged has been started already.
19868 Start it from the beginning? (y or n) y
19869 Starting program: /home/smith/cc_progs/a.out
19870 "/home/smith/cc_progs/a.out": can't open to read symbols:
19871 Invalid bfd target.
19872 (@value{GDBP}) show g
19873 The current BFD target is "=4".
19878 The program variable @code{g} did not change, and you silently set the
19879 @code{gnutarget} to an invalid value. In order to set the variable
19883 (@value{GDBP}) set var g=4
19886 @value{GDBN} allows more implicit conversions in assignments than C; you can
19887 freely store an integer value into a pointer variable or vice versa,
19888 and you can convert any structure to any other structure that is the
19889 same length or shorter.
19890 @comment FIXME: how do structs align/pad in these conversions?
19891 @comment /doc@cygnus.com 18dec1990
19893 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19894 construct to generate a value of specified type at a specified address
19895 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19896 to memory location @code{0x83040} as an integer (which implies a certain size
19897 and representation in memory), and
19900 set @{int@}0x83040 = 4
19904 stores the value 4 into that memory location.
19907 @section Continuing at a Different Address
19909 Ordinarily, when you continue your program, you do so at the place where
19910 it stopped, with the @code{continue} command. You can instead continue at
19911 an address of your own choosing, with the following commands:
19915 @kindex j @r{(@code{jump})}
19916 @item jump @var{location}
19917 @itemx j @var{location}
19918 Resume execution at @var{location}. Execution stops again immediately
19919 if there is a breakpoint there. @xref{Specify Location}, for a description
19920 of the different forms of @var{location}. It is common
19921 practice to use the @code{tbreak} command in conjunction with
19922 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19924 The @code{jump} command does not change the current stack frame, or
19925 the stack pointer, or the contents of any memory location or any
19926 register other than the program counter. If @var{location} is in
19927 a different function from the one currently executing, the results may
19928 be bizarre if the two functions expect different patterns of arguments or
19929 of local variables. For this reason, the @code{jump} command requests
19930 confirmation if the specified line is not in the function currently
19931 executing. However, even bizarre results are predictable if you are
19932 well acquainted with the machine-language code of your program.
19935 On many systems, you can get much the same effect as the @code{jump}
19936 command by storing a new value into the register @code{$pc}. The
19937 difference is that this does not start your program running; it only
19938 changes the address of where it @emph{will} run when you continue. For
19946 makes the next @code{continue} command or stepping command execute at
19947 address @code{0x485}, rather than at the address where your program stopped.
19948 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19950 The most common occasion to use the @code{jump} command is to back
19951 up---perhaps with more breakpoints set---over a portion of a program
19952 that has already executed, in order to examine its execution in more
19957 @section Giving your Program a Signal
19958 @cindex deliver a signal to a program
19962 @item signal @var{signal}
19963 Resume execution where your program is stopped, but immediately give it the
19964 signal @var{signal}. The @var{signal} can be the name or the number of a
19965 signal. For example, on many systems @code{signal 2} and @code{signal
19966 SIGINT} are both ways of sending an interrupt signal.
19968 Alternatively, if @var{signal} is zero, continue execution without
19969 giving a signal. This is useful when your program stopped on account of
19970 a signal and would ordinarily see the signal when resumed with the
19971 @code{continue} command; @samp{signal 0} causes it to resume without a
19974 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19975 delivered to the currently selected thread, not the thread that last
19976 reported a stop. This includes the situation where a thread was
19977 stopped due to a signal. So if you want to continue execution
19978 suppressing the signal that stopped a thread, you should select that
19979 same thread before issuing the @samp{signal 0} command. If you issue
19980 the @samp{signal 0} command with another thread as the selected one,
19981 @value{GDBN} detects that and asks for confirmation.
19983 Invoking the @code{signal} command is not the same as invoking the
19984 @code{kill} utility from the shell. Sending a signal with @code{kill}
19985 causes @value{GDBN} to decide what to do with the signal depending on
19986 the signal handling tables (@pxref{Signals}). The @code{signal} command
19987 passes the signal directly to your program.
19989 @code{signal} does not repeat when you press @key{RET} a second time
19990 after executing the command.
19992 @kindex queue-signal
19993 @item queue-signal @var{signal}
19994 Queue @var{signal} to be delivered immediately to the current thread
19995 when execution of the thread resumes. The @var{signal} can be the name or
19996 the number of a signal. For example, on many systems @code{signal 2} and
19997 @code{signal SIGINT} are both ways of sending an interrupt signal.
19998 The handling of the signal must be set to pass the signal to the program,
19999 otherwise @value{GDBN} will report an error.
20000 You can control the handling of signals from @value{GDBN} with the
20001 @code{handle} command (@pxref{Signals}).
20003 Alternatively, if @var{signal} is zero, any currently queued signal
20004 for the current thread is discarded and when execution resumes no signal
20005 will be delivered. This is useful when your program stopped on account
20006 of a signal and would ordinarily see the signal when resumed with the
20007 @code{continue} command.
20009 This command differs from the @code{signal} command in that the signal
20010 is just queued, execution is not resumed. And @code{queue-signal} cannot
20011 be used to pass a signal whose handling state has been set to @code{nopass}
20016 @xref{stepping into signal handlers}, for information on how stepping
20017 commands behave when the thread has a signal queued.
20020 @section Returning from a Function
20023 @cindex returning from a function
20026 @itemx return @var{expression}
20027 You can cancel execution of a function call with the @code{return}
20028 command. If you give an
20029 @var{expression} argument, its value is used as the function's return
20033 When you use @code{return}, @value{GDBN} discards the selected stack frame
20034 (and all frames within it). You can think of this as making the
20035 discarded frame return prematurely. If you wish to specify a value to
20036 be returned, give that value as the argument to @code{return}.
20038 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20039 Frame}), and any other frames inside of it, leaving its caller as the
20040 innermost remaining frame. That frame becomes selected. The
20041 specified value is stored in the registers used for returning values
20044 The @code{return} command does not resume execution; it leaves the
20045 program stopped in the state that would exist if the function had just
20046 returned. In contrast, the @code{finish} command (@pxref{Continuing
20047 and Stepping, ,Continuing and Stepping}) resumes execution until the
20048 selected stack frame returns naturally.
20050 @value{GDBN} needs to know how the @var{expression} argument should be set for
20051 the inferior. The concrete registers assignment depends on the OS ABI and the
20052 type being returned by the selected stack frame. For example it is common for
20053 OS ABI to return floating point values in FPU registers while integer values in
20054 CPU registers. Still some ABIs return even floating point values in CPU
20055 registers. Larger integer widths (such as @code{long long int}) also have
20056 specific placement rules. @value{GDBN} already knows the OS ABI from its
20057 current target so it needs to find out also the type being returned to make the
20058 assignment into the right register(s).
20060 Normally, the selected stack frame has debug info. @value{GDBN} will always
20061 use the debug info instead of the implicit type of @var{expression} when the
20062 debug info is available. For example, if you type @kbd{return -1}, and the
20063 function in the current stack frame is declared to return a @code{long long
20064 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20065 into a @code{long long int}:
20068 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20070 (@value{GDBP}) return -1
20071 Make func return now? (y or n) y
20072 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20073 43 printf ("result=%lld\n", func ());
20077 However, if the selected stack frame does not have a debug info, e.g., if the
20078 function was compiled without debug info, @value{GDBN} has to find out the type
20079 to return from user. Specifying a different type by mistake may set the value
20080 in different inferior registers than the caller code expects. For example,
20081 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20082 of a @code{long long int} result for a debug info less function (on 32-bit
20083 architectures). Therefore the user is required to specify the return type by
20084 an appropriate cast explicitly:
20087 Breakpoint 2, 0x0040050b in func ()
20088 (@value{GDBP}) return -1
20089 Return value type not available for selected stack frame.
20090 Please use an explicit cast of the value to return.
20091 (@value{GDBP}) return (long long int) -1
20092 Make selected stack frame return now? (y or n) y
20093 #0 0x00400526 in main ()
20098 @section Calling Program Functions
20101 @cindex calling functions
20102 @cindex inferior functions, calling
20103 @item print @var{expr}
20104 Evaluate the expression @var{expr} and display the resulting value.
20105 The expression may include calls to functions in the program being
20109 @item call @var{expr}
20110 Evaluate the expression @var{expr} without displaying @code{void}
20113 You can use this variant of the @code{print} command if you want to
20114 execute a function from your program that does not return anything
20115 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20116 with @code{void} returned values that @value{GDBN} will otherwise
20117 print. If the result is not void, it is printed and saved in the
20121 It is possible for the function you call via the @code{print} or
20122 @code{call} command to generate a signal (e.g., if there's a bug in
20123 the function, or if you passed it incorrect arguments). What happens
20124 in that case is controlled by the @code{set unwindonsignal} command.
20126 Similarly, with a C@t{++} program it is possible for the function you
20127 call via the @code{print} or @code{call} command to generate an
20128 exception that is not handled due to the constraints of the dummy
20129 frame. In this case, any exception that is raised in the frame, but has
20130 an out-of-frame exception handler will not be found. GDB builds a
20131 dummy-frame for the inferior function call, and the unwinder cannot
20132 seek for exception handlers outside of this dummy-frame. What happens
20133 in that case is controlled by the
20134 @code{set unwind-on-terminating-exception} command.
20137 @item set unwindonsignal
20138 @kindex set unwindonsignal
20139 @cindex unwind stack in called functions
20140 @cindex call dummy stack unwinding
20141 Set unwinding of the stack if a signal is received while in a function
20142 that @value{GDBN} called in the program being debugged. If set to on,
20143 @value{GDBN} unwinds the stack it created for the call and restores
20144 the context to what it was before the call. If set to off (the
20145 default), @value{GDBN} stops in the frame where the signal was
20148 @item show unwindonsignal
20149 @kindex show unwindonsignal
20150 Show the current setting of stack unwinding in the functions called by
20153 @item set unwind-on-terminating-exception
20154 @kindex set unwind-on-terminating-exception
20155 @cindex unwind stack in called functions with unhandled exceptions
20156 @cindex call dummy stack unwinding on unhandled exception.
20157 Set unwinding of the stack if a C@t{++} exception is raised, but left
20158 unhandled while in a function that @value{GDBN} called in the program being
20159 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20160 it created for the call and restores the context to what it was before
20161 the call. If set to off, @value{GDBN} the exception is delivered to
20162 the default C@t{++} exception handler and the inferior terminated.
20164 @item show unwind-on-terminating-exception
20165 @kindex show unwind-on-terminating-exception
20166 Show the current setting of stack unwinding in the functions called by
20169 @item set may-call-functions
20170 @kindex set may-call-functions
20171 @cindex disabling calling functions in the program
20172 @cindex calling functions in the program, disabling
20173 Set permission to call functions in the program.
20174 This controls whether @value{GDBN} will attempt to call functions in
20175 the program, such as with expressions in the @code{print} command. It
20176 defaults to @code{on}.
20178 To call a function in the program, @value{GDBN} has to temporarily
20179 modify the state of the inferior. This has potentially undesired side
20180 effects. Also, having @value{GDBN} call nested functions is likely to
20181 be erroneous and may even crash the program being debugged. You can
20182 avoid such hazards by forbidding @value{GDBN} from calling functions
20183 in the program being debugged. If calling functions in the program
20184 is forbidden, GDB will throw an error when a command (such as printing
20185 an expression) starts a function call in the program.
20187 @item show may-call-functions
20188 @kindex show may-call-functions
20189 Show permission to call functions in the program.
20193 @subsection Calling functions with no debug info
20195 @cindex no debug info functions
20196 Sometimes, a function you wish to call is missing debug information.
20197 In such case, @value{GDBN} does not know the type of the function,
20198 including the types of the function's parameters. To avoid calling
20199 the inferior function incorrectly, which could result in the called
20200 function functioning erroneously and even crash, @value{GDBN} refuses
20201 to call the function unless you tell it the type of the function.
20203 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20204 to do that. The simplest is to cast the call to the function's
20205 declared return type. For example:
20208 (@value{GDBP}) p getenv ("PATH")
20209 'getenv' has unknown return type; cast the call to its declared return type
20210 (@value{GDBP}) p (char *) getenv ("PATH")
20211 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20214 Casting the return type of a no-debug function is equivalent to
20215 casting the function to a pointer to a prototyped function that has a
20216 prototype that matches the types of the passed-in arguments, and
20217 calling that. I.e., the call above is equivalent to:
20220 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20224 and given this prototyped C or C++ function with float parameters:
20227 float multiply (float v1, float v2) @{ return v1 * v2; @}
20231 these calls are equivalent:
20234 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20235 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20238 If the function you wish to call is declared as unprototyped (i.e.@:
20239 old K&R style), you must use the cast-to-function-pointer syntax, so
20240 that @value{GDBN} knows that it needs to apply default argument
20241 promotions (promote float arguments to double). @xref{ABI, float
20242 promotion}. For example, given this unprototyped C function with
20243 float parameters, and no debug info:
20247 multiply_noproto (v1, v2)
20255 you call it like this:
20258 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20262 @section Patching Programs
20264 @cindex patching binaries
20265 @cindex writing into executables
20266 @cindex writing into corefiles
20268 By default, @value{GDBN} opens the file containing your program's
20269 executable code (or the corefile) read-only. This prevents accidental
20270 alterations to machine code; but it also prevents you from intentionally
20271 patching your program's binary.
20273 If you'd like to be able to patch the binary, you can specify that
20274 explicitly with the @code{set write} command. For example, you might
20275 want to turn on internal debugging flags, or even to make emergency
20281 @itemx set write off
20282 If you specify @samp{set write on}, @value{GDBN} opens executable and
20283 core files for both reading and writing; if you specify @kbd{set write
20284 off} (the default), @value{GDBN} opens them read-only.
20286 If you have already loaded a file, you must load it again (using the
20287 @code{exec-file} or @code{core-file} command) after changing @code{set
20288 write}, for your new setting to take effect.
20292 Display whether executable files and core files are opened for writing
20293 as well as reading.
20296 @node Compiling and Injecting Code
20297 @section Compiling and injecting code in @value{GDBN}
20298 @cindex injecting code
20299 @cindex writing into executables
20300 @cindex compiling code
20302 @value{GDBN} supports on-demand compilation and code injection into
20303 programs running under @value{GDBN}. GCC 5.0 or higher built with
20304 @file{libcc1.so} must be installed for this functionality to be enabled.
20305 This functionality is implemented with the following commands.
20308 @kindex compile code
20309 @item compile code @var{source-code}
20310 @itemx compile code -raw @var{--} @var{source-code}
20311 Compile @var{source-code} with the compiler language found as the current
20312 language in @value{GDBN} (@pxref{Languages}). If compilation and
20313 injection is not supported with the current language specified in
20314 @value{GDBN}, or the compiler does not support this feature, an error
20315 message will be printed. If @var{source-code} compiles and links
20316 successfully, @value{GDBN} will load the object-code emitted,
20317 and execute it within the context of the currently selected inferior.
20318 It is important to note that the compiled code is executed immediately.
20319 After execution, the compiled code is removed from @value{GDBN} and any
20320 new types or variables you have defined will be deleted.
20322 The command allows you to specify @var{source-code} in two ways.
20323 The simplest method is to provide a single line of code to the command.
20327 compile code printf ("hello world\n");
20330 If you specify options on the command line as well as source code, they
20331 may conflict. The @samp{--} delimiter can be used to separate options
20332 from actual source code. E.g.:
20335 compile code -r -- printf ("hello world\n");
20338 Alternatively you can enter source code as multiple lines of text. To
20339 enter this mode, invoke the @samp{compile code} command without any text
20340 following the command. This will start the multiple-line editor and
20341 allow you to type as many lines of source code as required. When you
20342 have completed typing, enter @samp{end} on its own line to exit the
20347 >printf ("hello\n");
20348 >printf ("world\n");
20352 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20353 provided @var{source-code} in a callable scope. In this case, you must
20354 specify the entry point of the code by defining a function named
20355 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20356 inferior. Using @samp{-raw} option may be needed for example when
20357 @var{source-code} requires @samp{#include} lines which may conflict with
20358 inferior symbols otherwise.
20360 @kindex compile file
20361 @item compile file @var{filename}
20362 @itemx compile file -raw @var{filename}
20363 Like @code{compile code}, but take the source code from @var{filename}.
20366 compile file /home/user/example.c
20371 @item compile print [[@var{options}] --] @var{expr}
20372 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20373 Compile and execute @var{expr} with the compiler language found as the
20374 current language in @value{GDBN} (@pxref{Languages}). By default the
20375 value of @var{expr} is printed in a format appropriate to its data type;
20376 you can choose a different format by specifying @samp{/@var{f}}, where
20377 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20378 Formats}. The @code{compile print} command accepts the same options
20379 as the @code{print} command; see @ref{print options}.
20381 @item compile print [[@var{options}] --]
20382 @itemx compile print [[@var{options}] --] /@var{f}
20383 @cindex reprint the last value
20384 Alternatively you can enter the expression (source code producing it) as
20385 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20386 command without any text following the command. This will start the
20387 multiple-line editor.
20391 The process of compiling and injecting the code can be inspected using:
20394 @anchor{set debug compile}
20395 @item set debug compile
20396 @cindex compile command debugging info
20397 Turns on or off display of @value{GDBN} process of compiling and
20398 injecting the code. The default is off.
20400 @item show debug compile
20401 Displays the current state of displaying @value{GDBN} process of
20402 compiling and injecting the code.
20404 @anchor{set debug compile-cplus-types}
20405 @item set debug compile-cplus-types
20406 @cindex compile C@t{++} type conversion
20407 Turns on or off the display of C@t{++} type conversion debugging information.
20408 The default is off.
20410 @item show debug compile-cplus-types
20411 Displays the current state of displaying debugging information for
20412 C@t{++} type conversion.
20415 @subsection Compilation options for the @code{compile} command
20417 @value{GDBN} needs to specify the right compilation options for the code
20418 to be injected, in part to make its ABI compatible with the inferior
20419 and in part to make the injected code compatible with @value{GDBN}'s
20423 The options used, in increasing precedence:
20426 @item target architecture and OS options (@code{gdbarch})
20427 These options depend on target processor type and target operating
20428 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20429 (@code{-m64}) compilation option.
20431 @item compilation options recorded in the target
20432 @value{NGCC} (since version 4.7) stores the options used for compilation
20433 into @code{DW_AT_producer} part of DWARF debugging information according
20434 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20435 explicitly specify @code{-g} during inferior compilation otherwise
20436 @value{NGCC} produces no DWARF. This feature is only relevant for
20437 platforms where @code{-g} produces DWARF by default, otherwise one may
20438 try to enforce DWARF by using @code{-gdwarf-4}.
20440 @item compilation options set by @code{set compile-args}
20444 You can override compilation options using the following command:
20447 @item set compile-args
20448 @cindex compile command options override
20449 Set compilation options used for compiling and injecting code with the
20450 @code{compile} commands. These options override any conflicting ones
20451 from the target architecture and/or options stored during inferior
20454 @item show compile-args
20455 Displays the current state of compilation options override.
20456 This does not show all the options actually used during compilation,
20457 use @ref{set debug compile} for that.
20460 @subsection Caveats when using the @code{compile} command
20462 There are a few caveats to keep in mind when using the @code{compile}
20463 command. As the caveats are different per language, the table below
20464 highlights specific issues on a per language basis.
20467 @item C code examples and caveats
20468 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20469 attempt to compile the source code with a @samp{C} compiler. The source
20470 code provided to the @code{compile} command will have much the same
20471 access to variables and types as it normally would if it were part of
20472 the program currently being debugged in @value{GDBN}.
20474 Below is a sample program that forms the basis of the examples that
20475 follow. This program has been compiled and loaded into @value{GDBN},
20476 much like any other normal debugging session.
20479 void function1 (void)
20482 printf ("function 1\n");
20485 void function2 (void)
20500 For the purposes of the examples in this section, the program above has
20501 been compiled, loaded into @value{GDBN}, stopped at the function
20502 @code{main}, and @value{GDBN} is awaiting input from the user.
20504 To access variables and types for any program in @value{GDBN}, the
20505 program must be compiled and packaged with debug information. The
20506 @code{compile} command is not an exception to this rule. Without debug
20507 information, you can still use the @code{compile} command, but you will
20508 be very limited in what variables and types you can access.
20510 So with that in mind, the example above has been compiled with debug
20511 information enabled. The @code{compile} command will have access to
20512 all variables and types (except those that may have been optimized
20513 out). Currently, as @value{GDBN} has stopped the program in the
20514 @code{main} function, the @code{compile} command would have access to
20515 the variable @code{k}. You could invoke the @code{compile} command
20516 and type some source code to set the value of @code{k}. You can also
20517 read it, or do anything with that variable you would normally do in
20518 @code{C}. Be aware that changes to inferior variables in the
20519 @code{compile} command are persistent. In the following example:
20522 compile code k = 3;
20526 the variable @code{k} is now 3. It will retain that value until
20527 something else in the example program changes it, or another
20528 @code{compile} command changes it.
20530 Normal scope and access rules apply to source code compiled and
20531 injected by the @code{compile} command. In the example, the variables
20532 @code{j} and @code{k} are not accessible yet, because the program is
20533 currently stopped in the @code{main} function, where these variables
20534 are not in scope. Therefore, the following command
20537 compile code j = 3;
20541 will result in a compilation error message.
20543 Once the program is continued, execution will bring these variables in
20544 scope, and they will become accessible; then the code you specify via
20545 the @code{compile} command will be able to access them.
20547 You can create variables and types with the @code{compile} command as
20548 part of your source code. Variables and types that are created as part
20549 of the @code{compile} command are not visible to the rest of the program for
20550 the duration of its run. This example is valid:
20553 compile code int ff = 5; printf ("ff is %d\n", ff);
20556 However, if you were to type the following into @value{GDBN} after that
20557 command has completed:
20560 compile code printf ("ff is %d\n'', ff);
20564 a compiler error would be raised as the variable @code{ff} no longer
20565 exists. Object code generated and injected by the @code{compile}
20566 command is removed when its execution ends. Caution is advised
20567 when assigning to program variables values of variables created by the
20568 code submitted to the @code{compile} command. This example is valid:
20571 compile code int ff = 5; k = ff;
20574 The value of the variable @code{ff} is assigned to @code{k}. The variable
20575 @code{k} does not require the existence of @code{ff} to maintain the value
20576 it has been assigned. However, pointers require particular care in
20577 assignment. If the source code compiled with the @code{compile} command
20578 changed the address of a pointer in the example program, perhaps to a
20579 variable created in the @code{compile} command, that pointer would point
20580 to an invalid location when the command exits. The following example
20581 would likely cause issues with your debugged program:
20584 compile code int ff = 5; p = &ff;
20587 In this example, @code{p} would point to @code{ff} when the
20588 @code{compile} command is executing the source code provided to it.
20589 However, as variables in the (example) program persist with their
20590 assigned values, the variable @code{p} would point to an invalid
20591 location when the command exists. A general rule should be followed
20592 in that you should either assign @code{NULL} to any assigned pointers,
20593 or restore a valid location to the pointer before the command exits.
20595 Similar caution must be exercised with any structs, unions, and typedefs
20596 defined in @code{compile} command. Types defined in the @code{compile}
20597 command will no longer be available in the next @code{compile} command.
20598 Therefore, if you cast a variable to a type defined in the
20599 @code{compile} command, care must be taken to ensure that any future
20600 need to resolve the type can be achieved.
20603 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20604 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20605 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20606 Compilation failed.
20607 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20611 Variables that have been optimized away by the compiler are not
20612 accessible to the code submitted to the @code{compile} command.
20613 Access to those variables will generate a compiler error which @value{GDBN}
20614 will print to the console.
20617 @subsection Compiler search for the @code{compile} command
20619 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20620 which may not be obvious for remote targets of different architecture
20621 than where @value{GDBN} is running. Environment variable @env{PATH} on
20622 @value{GDBN} host is searched for @value{NGCC} binary matching the
20623 target architecture and operating system. This search can be overriden
20624 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
20625 taken from shell that executed @value{GDBN}, it is not the value set by
20626 @value{GDBN} command @code{set environment}). @xref{Environment}.
20629 Specifically @env{PATH} is searched for binaries matching regular expression
20630 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20631 debugged. @var{arch} is processor name --- multiarch is supported, so for
20632 example both @code{i386} and @code{x86_64} targets look for pattern
20633 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20634 for pattern @code{s390x?}. @var{os} is currently supported only for
20635 pattern @code{linux(-gnu)?}.
20637 On Posix hosts the compiler driver @value{GDBN} needs to find also
20638 shared library @file{libcc1.so} from the compiler. It is searched in
20639 default shared library search path (overridable with usual environment
20640 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
20641 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20642 according to the installation of the found compiler --- as possibly
20643 specified by the @code{set compile-gcc} command.
20646 @item set compile-gcc
20647 @cindex compile command driver filename override
20648 Set compilation command used for compiling and injecting code with the
20649 @code{compile} commands. If this option is not set (it is set to
20650 an empty string), the search described above will occur --- that is the
20653 @item show compile-gcc
20654 Displays the current compile command @value{NGCC} driver filename.
20655 If set, it is the main command @command{gcc}, found usually for example
20656 under name @file{x86_64-linux-gnu-gcc}.
20660 @chapter @value{GDBN} Files
20662 @value{GDBN} needs to know the file name of the program to be debugged,
20663 both in order to read its symbol table and in order to start your
20664 program. To debug a core dump of a previous run, you must also tell
20665 @value{GDBN} the name of the core dump file.
20668 * Files:: Commands to specify files
20669 * File Caching:: Information about @value{GDBN}'s file caching
20670 * Separate Debug Files:: Debugging information in separate files
20671 * MiniDebugInfo:: Debugging information in a special section
20672 * Index Files:: Index files speed up GDB
20673 * Symbol Errors:: Errors reading symbol files
20674 * Data Files:: GDB data files
20678 @section Commands to Specify Files
20680 @cindex symbol table
20681 @cindex core dump file
20683 You may want to specify executable and core dump file names. The usual
20684 way to do this is at start-up time, using the arguments to
20685 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20686 Out of @value{GDBN}}).
20688 Occasionally it is necessary to change to a different file during a
20689 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20690 specify a file you want to use. Or you are debugging a remote target
20691 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20692 Program}). In these situations the @value{GDBN} commands to specify
20693 new files are useful.
20696 @cindex executable file
20698 @item file @var{filename}
20699 Use @var{filename} as the program to be debugged. It is read for its
20700 symbols and for the contents of pure memory. It is also the program
20701 executed when you use the @code{run} command. If you do not specify a
20702 directory and the file is not found in the @value{GDBN} working directory,
20703 @value{GDBN} uses the environment variable @env{PATH} as a list of
20704 directories to search, just as the shell does when looking for a program
20705 to run. You can change the value of this variable, for both @value{GDBN}
20706 and your program, using the @code{path} command.
20708 @cindex unlinked object files
20709 @cindex patching object files
20710 You can load unlinked object @file{.o} files into @value{GDBN} using
20711 the @code{file} command. You will not be able to ``run'' an object
20712 file, but you can disassemble functions and inspect variables. Also,
20713 if the underlying BFD functionality supports it, you could use
20714 @kbd{gdb -write} to patch object files using this technique. Note
20715 that @value{GDBN} can neither interpret nor modify relocations in this
20716 case, so branches and some initialized variables will appear to go to
20717 the wrong place. But this feature is still handy from time to time.
20720 @code{file} with no argument makes @value{GDBN} discard any information it
20721 has on both executable file and the symbol table.
20724 @item exec-file @r{[} @var{filename} @r{]}
20725 Specify that the program to be run (but not the symbol table) is found
20726 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
20727 if necessary to locate your program. Omitting @var{filename} means to
20728 discard information on the executable file.
20730 @kindex symbol-file
20731 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20732 Read symbol table information from file @var{filename}. @env{PATH} is
20733 searched when necessary. Use the @code{file} command to get both symbol
20734 table and program to run from the same file.
20736 If an optional @var{offset} is specified, it is added to the start
20737 address of each section in the symbol file. This is useful if the
20738 program is relocated at runtime, such as the Linux kernel with kASLR
20741 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20742 program's symbol table.
20744 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20745 some breakpoints and auto-display expressions. This is because they may
20746 contain pointers to the internal data recording symbols and data types,
20747 which are part of the old symbol table data being discarded inside
20750 @code{symbol-file} does not repeat if you press @key{RET} again after
20753 When @value{GDBN} is configured for a particular environment, it
20754 understands debugging information in whatever format is the standard
20755 generated for that environment; you may use either a @sc{gnu} compiler, or
20756 other compilers that adhere to the local conventions.
20757 Best results are usually obtained from @sc{gnu} compilers; for example,
20758 using @code{@value{NGCC}} you can generate debugging information for
20761 For most kinds of object files, with the exception of old SVR3 systems
20762 using COFF, the @code{symbol-file} command does not normally read the
20763 symbol table in full right away. Instead, it scans the symbol table
20764 quickly to find which source files and which symbols are present. The
20765 details are read later, one source file at a time, as they are needed.
20767 The purpose of this two-stage reading strategy is to make @value{GDBN}
20768 start up faster. For the most part, it is invisible except for
20769 occasional pauses while the symbol table details for a particular source
20770 file are being read. (The @code{set verbose} command can turn these
20771 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20772 Warnings and Messages}.)
20774 We have not implemented the two-stage strategy for COFF yet. When the
20775 symbol table is stored in COFF format, @code{symbol-file} reads the
20776 symbol table data in full right away. Note that ``stabs-in-COFF''
20777 still does the two-stage strategy, since the debug info is actually
20781 @cindex reading symbols immediately
20782 @cindex symbols, reading immediately
20783 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20784 @itemx file @r{[} -readnow @r{]} @var{filename}
20785 You can override the @value{GDBN} two-stage strategy for reading symbol
20786 tables by using the @samp{-readnow} option with any of the commands that
20787 load symbol table information, if you want to be sure @value{GDBN} has the
20788 entire symbol table available.
20790 @cindex @code{-readnever}, option for symbol-file command
20791 @cindex never read symbols
20792 @cindex symbols, never read
20793 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20794 @itemx file @r{[} -readnever @r{]} @var{filename}
20795 You can instruct @value{GDBN} to never read the symbolic information
20796 contained in @var{filename} by using the @samp{-readnever} option.
20797 @xref{--readnever}.
20799 @c FIXME: for now no mention of directories, since this seems to be in
20800 @c flux. 13mar1992 status is that in theory GDB would look either in
20801 @c current dir or in same dir as myprog; but issues like competing
20802 @c GDB's, or clutter in system dirs, mean that in practice right now
20803 @c only current dir is used. FFish says maybe a special GDB hierarchy
20804 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20808 @item core-file @r{[}@var{filename}@r{]}
20810 Specify the whereabouts of a core dump file to be used as the ``contents
20811 of memory''. Traditionally, core files contain only some parts of the
20812 address space of the process that generated them; @value{GDBN} can access the
20813 executable file itself for other parts.
20815 @code{core-file} with no argument specifies that no core file is
20818 Note that the core file is ignored when your program is actually running
20819 under @value{GDBN}. So, if you have been running your program and you
20820 wish to debug a core file instead, you must kill the subprocess in which
20821 the program is running. To do this, use the @code{kill} command
20822 (@pxref{Kill Process, ,Killing the Child Process}).
20824 @kindex add-symbol-file
20825 @cindex dynamic linking
20826 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
20827 The @code{add-symbol-file} command reads additional symbol table
20828 information from the file @var{filename}. You would use this command
20829 when @var{filename} has been dynamically loaded (by some other means)
20830 into the program that is running. The @var{textaddress} parameter gives
20831 the memory address at which the file's text section has been loaded.
20832 You can additionally specify the base address of other sections using
20833 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20834 If a section is omitted, @value{GDBN} will use its default addresses
20835 as found in @var{filename}. Any @var{address} or @var{textaddress}
20836 can be given as an expression.
20838 If an optional @var{offset} is specified, it is added to the start
20839 address of each section, except those for which the address was
20840 specified explicitly.
20842 The symbol table of the file @var{filename} is added to the symbol table
20843 originally read with the @code{symbol-file} command. You can use the
20844 @code{add-symbol-file} command any number of times; the new symbol data
20845 thus read is kept in addition to the old.
20847 Changes can be reverted using the command @code{remove-symbol-file}.
20849 @cindex relocatable object files, reading symbols from
20850 @cindex object files, relocatable, reading symbols from
20851 @cindex reading symbols from relocatable object files
20852 @cindex symbols, reading from relocatable object files
20853 @cindex @file{.o} files, reading symbols from
20854 Although @var{filename} is typically a shared library file, an
20855 executable file, or some other object file which has been fully
20856 relocated for loading into a process, you can also load symbolic
20857 information from relocatable @file{.o} files, as long as:
20861 the file's symbolic information refers only to linker symbols defined in
20862 that file, not to symbols defined by other object files,
20864 every section the file's symbolic information refers to has actually
20865 been loaded into the inferior, as it appears in the file, and
20867 you can determine the address at which every section was loaded, and
20868 provide these to the @code{add-symbol-file} command.
20872 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20873 relocatable files into an already running program; such systems
20874 typically make the requirements above easy to meet. However, it's
20875 important to recognize that many native systems use complex link
20876 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20877 assembly, for example) that make the requirements difficult to meet. In
20878 general, one cannot assume that using @code{add-symbol-file} to read a
20879 relocatable object file's symbolic information will have the same effect
20880 as linking the relocatable object file into the program in the normal
20883 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20885 @kindex remove-symbol-file
20886 @item remove-symbol-file @var{filename}
20887 @item remove-symbol-file -a @var{address}
20888 Remove a symbol file added via the @code{add-symbol-file} command. The
20889 file to remove can be identified by its @var{filename} or by an @var{address}
20890 that lies within the boundaries of this symbol file in memory. Example:
20893 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20894 add symbol table from file "/home/user/gdb/mylib.so" at
20895 .text_addr = 0x7ffff7ff9480
20897 Reading symbols from /home/user/gdb/mylib.so...
20898 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20899 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20904 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20906 @kindex add-symbol-file-from-memory
20907 @cindex @code{syscall DSO}
20908 @cindex load symbols from memory
20909 @item add-symbol-file-from-memory @var{address}
20910 Load symbols from the given @var{address} in a dynamically loaded
20911 object file whose image is mapped directly into the inferior's memory.
20912 For example, the Linux kernel maps a @code{syscall DSO} into each
20913 process's address space; this DSO provides kernel-specific code for
20914 some system calls. The argument can be any expression whose
20915 evaluation yields the address of the file's shared object file header.
20916 For this command to work, you must have used @code{symbol-file} or
20917 @code{exec-file} commands in advance.
20920 @item section @var{section} @var{addr}
20921 The @code{section} command changes the base address of the named
20922 @var{section} of the exec file to @var{addr}. This can be used if the
20923 exec file does not contain section addresses, (such as in the
20924 @code{a.out} format), or when the addresses specified in the file
20925 itself are wrong. Each section must be changed separately. The
20926 @code{info files} command, described below, lists all the sections and
20930 @kindex info target
20933 @code{info files} and @code{info target} are synonymous; both print the
20934 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20935 including the names of the executable and core dump files currently in
20936 use by @value{GDBN}, and the files from which symbols were loaded. The
20937 command @code{help target} lists all possible targets rather than
20940 @kindex maint info sections
20941 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
20942 Another command that can give you extra information about program sections
20943 is @code{maint info sections}. In addition to the section information
20944 displayed by @code{info files}, this command displays the flags and file
20945 offset of each section in the executable and core dump files.
20947 When @samp{-all-objects} is passed then sections from all loaded object
20948 files, including shared libraries, are printed.
20950 The optional @var{filter-list} is a space separated list of filter
20951 keywords. Sections that match any one of the filter criteria will be
20952 printed. There are two types of filter:
20955 @item @var{section-name}
20956 Display information about any section named @var{section-name}.
20957 @item @var{section-flag}
20958 Display information for any section with @var{section-flag}. The
20959 section flags that @value{GDBN} currently knows about are:
20962 Section will have space allocated in the process when loaded.
20963 Set for all sections except those containing debug information.
20965 Section will be loaded from the file into the child process memory.
20966 Set for pre-initialized code and data, clear for @code{.bss} sections.
20968 Section needs to be relocated before loading.
20970 Section cannot be modified by the child process.
20972 Section contains executable code only.
20974 Section contains data only (no executable code).
20976 Section will reside in ROM.
20978 Section contains data for constructor/destructor lists.
20980 Section is not empty.
20982 An instruction to the linker to not output the section.
20983 @item COFF_SHARED_LIBRARY
20984 A notification to the linker that the section contains
20985 COFF shared library information.
20987 Section contains common symbols.
20991 @kindex maint info target-sections
20992 @item maint info target-sections
20993 This command prints @value{GDBN}'s internal section table. For each
20994 target @value{GDBN} maintains a table containing the allocatable
20995 sections from all currently mapped objects, along with information
20996 about where the section is mapped.
20998 @kindex set trust-readonly-sections
20999 @cindex read-only sections
21000 @item set trust-readonly-sections on
21001 Tell @value{GDBN} that readonly sections in your object file
21002 really are read-only (i.e.@: that their contents will not change).
21003 In that case, @value{GDBN} can fetch values from these sections
21004 out of the object file, rather than from the target program.
21005 For some targets (notably embedded ones), this can be a significant
21006 enhancement to debugging performance.
21008 The default is off.
21010 @item set trust-readonly-sections off
21011 Tell @value{GDBN} not to trust readonly sections. This means that
21012 the contents of the section might change while the program is running,
21013 and must therefore be fetched from the target when needed.
21015 @item show trust-readonly-sections
21016 Show the current setting of trusting readonly sections.
21019 All file-specifying commands allow both absolute and relative file names
21020 as arguments. @value{GDBN} always converts the file name to an absolute file
21021 name and remembers it that way.
21023 @cindex shared libraries
21024 @anchor{Shared Libraries}
21025 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21026 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21027 DSBT (TIC6X) shared libraries.
21029 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21030 shared libraries. @xref{Expat}.
21032 @value{GDBN} automatically loads symbol definitions from shared libraries
21033 when you use the @code{run} command, or when you examine a core file.
21034 (Before you issue the @code{run} command, @value{GDBN} does not understand
21035 references to a function in a shared library, however---unless you are
21036 debugging a core file).
21038 @c FIXME: some @value{GDBN} release may permit some refs to undef
21039 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21040 @c FIXME...lib; check this from time to time when updating manual
21042 There are times, however, when you may wish to not automatically load
21043 symbol definitions from shared libraries, such as when they are
21044 particularly large or there are many of them.
21046 To control the automatic loading of shared library symbols, use the
21050 @kindex set auto-solib-add
21051 @item set auto-solib-add @var{mode}
21052 If @var{mode} is @code{on}, symbols from all shared object libraries
21053 will be loaded automatically when the inferior begins execution, you
21054 attach to an independently started inferior, or when the dynamic linker
21055 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21056 is @code{off}, symbols must be loaded manually, using the
21057 @code{sharedlibrary} command. The default value is @code{on}.
21059 @cindex memory used for symbol tables
21060 If your program uses lots of shared libraries with debug info that
21061 takes large amounts of memory, you can decrease the @value{GDBN}
21062 memory footprint by preventing it from automatically loading the
21063 symbols from shared libraries. To that end, type @kbd{set
21064 auto-solib-add off} before running the inferior, then load each
21065 library whose debug symbols you do need with @kbd{sharedlibrary
21066 @var{regexp}}, where @var{regexp} is a regular expression that matches
21067 the libraries whose symbols you want to be loaded.
21069 @kindex show auto-solib-add
21070 @item show auto-solib-add
21071 Display the current autoloading mode.
21074 @cindex load shared library
21075 To explicitly load shared library symbols, use the @code{sharedlibrary}
21079 @kindex info sharedlibrary
21081 @item info share @var{regex}
21082 @itemx info sharedlibrary @var{regex}
21083 Print the names of the shared libraries which are currently loaded
21084 that match @var{regex}. If @var{regex} is omitted then print
21085 all shared libraries that are loaded.
21088 @item info dll @var{regex}
21089 This is an alias of @code{info sharedlibrary}.
21091 @kindex sharedlibrary
21093 @item sharedlibrary @var{regex}
21094 @itemx share @var{regex}
21095 Load shared object library symbols for files matching a
21096 Unix regular expression.
21097 As with files loaded automatically, it only loads shared libraries
21098 required by your program for a core file or after typing @code{run}. If
21099 @var{regex} is omitted all shared libraries required by your program are
21102 @item nosharedlibrary
21103 @kindex nosharedlibrary
21104 @cindex unload symbols from shared libraries
21105 Unload all shared object library symbols. This discards all symbols
21106 that have been loaded from all shared libraries. Symbols from shared
21107 libraries that were loaded by explicit user requests are not
21111 Sometimes you may wish that @value{GDBN} stops and gives you control
21112 when any of shared library events happen. The best way to do this is
21113 to use @code{catch load} and @code{catch unload} (@pxref{Set
21116 @value{GDBN} also supports the @code{set stop-on-solib-events}
21117 command for this. This command exists for historical reasons. It is
21118 less useful than setting a catchpoint, because it does not allow for
21119 conditions or commands as a catchpoint does.
21122 @item set stop-on-solib-events
21123 @kindex set stop-on-solib-events
21124 This command controls whether @value{GDBN} should give you control
21125 when the dynamic linker notifies it about some shared library event.
21126 The most common event of interest is loading or unloading of a new
21129 @item show stop-on-solib-events
21130 @kindex show stop-on-solib-events
21131 Show whether @value{GDBN} stops and gives you control when shared
21132 library events happen.
21135 Shared libraries are also supported in many cross or remote debugging
21136 configurations. @value{GDBN} needs to have access to the target's libraries;
21137 this can be accomplished either by providing copies of the libraries
21138 on the host system, or by asking @value{GDBN} to automatically retrieve the
21139 libraries from the target. If copies of the target libraries are
21140 provided, they need to be the same as the target libraries, although the
21141 copies on the target can be stripped as long as the copies on the host are
21144 @cindex where to look for shared libraries
21145 For remote debugging, you need to tell @value{GDBN} where the target
21146 libraries are, so that it can load the correct copies---otherwise, it
21147 may try to load the host's libraries. @value{GDBN} has two variables
21148 to specify the search directories for target libraries.
21151 @cindex prefix for executable and shared library file names
21152 @cindex system root, alternate
21153 @kindex set solib-absolute-prefix
21154 @kindex set sysroot
21155 @item set sysroot @var{path}
21156 Use @var{path} as the system root for the program being debugged. Any
21157 absolute shared library paths will be prefixed with @var{path}; many
21158 runtime loaders store the absolute paths to the shared library in the
21159 target program's memory. When starting processes remotely, and when
21160 attaching to already-running processes (local or remote), their
21161 executable filenames will be prefixed with @var{path} if reported to
21162 @value{GDBN} as absolute by the operating system. If you use
21163 @code{set sysroot} to find executables and shared libraries, they need
21164 to be laid out in the same way that they are on the target, with
21165 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21168 If @var{path} starts with the sequence @file{target:} and the target
21169 system is remote then @value{GDBN} will retrieve the target binaries
21170 from the remote system. This is only supported when using a remote
21171 target that supports the @code{remote get} command (@pxref{File
21172 Transfer,,Sending files to a remote system}). The part of @var{path}
21173 following the initial @file{target:} (if present) is used as system
21174 root prefix on the remote file system. If @var{path} starts with the
21175 sequence @file{remote:} this is converted to the sequence
21176 @file{target:} by @code{set sysroot}@footnote{Historically the
21177 functionality to retrieve binaries from the remote system was
21178 provided by prefixing @var{path} with @file{remote:}}. If you want
21179 to specify a local system root using a directory that happens to be
21180 named @file{target:} or @file{remote:}, you need to use some
21181 equivalent variant of the name like @file{./target:}.
21183 For targets with an MS-DOS based filesystem, such as MS-Windows,
21184 @value{GDBN} tries prefixing a few variants of the target
21185 absolute file name with @var{path}. But first, on Unix hosts,
21186 @value{GDBN} converts all backslash directory separators into forward
21187 slashes, because the backslash is not a directory separator on Unix:
21190 c:\foo\bar.dll @result{} c:/foo/bar.dll
21193 Then, @value{GDBN} attempts prefixing the target file name with
21194 @var{path}, and looks for the resulting file name in the host file
21198 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21201 If that does not find the binary, @value{GDBN} tries removing
21202 the @samp{:} character from the drive spec, both for convenience, and,
21203 for the case of the host file system not supporting file names with
21207 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21210 This makes it possible to have a system root that mirrors a target
21211 with more than one drive. E.g., you may want to setup your local
21212 copies of the target system shared libraries like so (note @samp{c} vs
21216 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21217 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21218 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21222 and point the system root at @file{/path/to/sysroot}, so that
21223 @value{GDBN} can find the correct copies of both
21224 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21226 If that still does not find the binary, @value{GDBN} tries
21227 removing the whole drive spec from the target file name:
21230 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21233 This last lookup makes it possible to not care about the drive name,
21234 if you don't want or need to.
21236 The @code{set solib-absolute-prefix} command is an alias for @code{set
21239 @cindex default system root
21240 @cindex @samp{--with-sysroot}
21241 You can set the default system root by using the configure-time
21242 @samp{--with-sysroot} option. If the system root is inside
21243 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21244 @samp{--exec-prefix}), then the default system root will be updated
21245 automatically if the installed @value{GDBN} is moved to a new
21248 @kindex show sysroot
21250 Display the current executable and shared library prefix.
21252 @kindex set solib-search-path
21253 @item set solib-search-path @var{path}
21254 If this variable is set, @var{path} is a colon-separated list of
21255 directories to search for shared libraries. @samp{solib-search-path}
21256 is used after @samp{sysroot} fails to locate the library, or if the
21257 path to the library is relative instead of absolute. If you want to
21258 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21259 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21260 finding your host's libraries. @samp{sysroot} is preferred; setting
21261 it to a nonexistent directory may interfere with automatic loading
21262 of shared library symbols.
21264 @kindex show solib-search-path
21265 @item show solib-search-path
21266 Display the current shared library search path.
21268 @cindex DOS file-name semantics of file names.
21269 @kindex set target-file-system-kind (unix|dos-based|auto)
21270 @kindex show target-file-system-kind
21271 @item set target-file-system-kind @var{kind}
21272 Set assumed file system kind for target reported file names.
21274 Shared library file names as reported by the target system may not
21275 make sense as is on the system @value{GDBN} is running on. For
21276 example, when remote debugging a target that has MS-DOS based file
21277 system semantics, from a Unix host, the target may be reporting to
21278 @value{GDBN} a list of loaded shared libraries with file names such as
21279 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21280 drive letters, so the @samp{c:\} prefix is not normally understood as
21281 indicating an absolute file name, and neither is the backslash
21282 normally considered a directory separator character. In that case,
21283 the native file system would interpret this whole absolute file name
21284 as a relative file name with no directory components. This would make
21285 it impossible to point @value{GDBN} at a copy of the remote target's
21286 shared libraries on the host using @code{set sysroot}, and impractical
21287 with @code{set solib-search-path}. Setting
21288 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21289 to interpret such file names similarly to how the target would, and to
21290 map them to file names valid on @value{GDBN}'s native file system
21291 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21292 to one of the supported file system kinds. In that case, @value{GDBN}
21293 tries to determine the appropriate file system variant based on the
21294 current target's operating system (@pxref{ABI, ,Configuring the
21295 Current ABI}). The supported file system settings are:
21299 Instruct @value{GDBN} to assume the target file system is of Unix
21300 kind. Only file names starting the forward slash (@samp{/}) character
21301 are considered absolute, and the directory separator character is also
21305 Instruct @value{GDBN} to assume the target file system is DOS based.
21306 File names starting with either a forward slash, or a drive letter
21307 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21308 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21309 considered directory separators.
21312 Instruct @value{GDBN} to use the file system kind associated with the
21313 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21314 This is the default.
21318 @cindex file name canonicalization
21319 @cindex base name differences
21320 When processing file names provided by the user, @value{GDBN}
21321 frequently needs to compare them to the file names recorded in the
21322 program's debug info. Normally, @value{GDBN} compares just the
21323 @dfn{base names} of the files as strings, which is reasonably fast
21324 even for very large programs. (The base name of a file is the last
21325 portion of its name, after stripping all the leading directories.)
21326 This shortcut in comparison is based upon the assumption that files
21327 cannot have more than one base name. This is usually true, but
21328 references to files that use symlinks or similar filesystem
21329 facilities violate that assumption. If your program records files
21330 using such facilities, or if you provide file names to @value{GDBN}
21331 using symlinks etc., you can set @code{basenames-may-differ} to
21332 @code{true} to instruct @value{GDBN} to completely canonicalize each
21333 pair of file names it needs to compare. This will make file-name
21334 comparisons accurate, but at a price of a significant slowdown.
21337 @item set basenames-may-differ
21338 @kindex set basenames-may-differ
21339 Set whether a source file may have multiple base names.
21341 @item show basenames-may-differ
21342 @kindex show basenames-may-differ
21343 Show whether a source file may have multiple base names.
21347 @section File Caching
21348 @cindex caching of opened files
21349 @cindex caching of bfd objects
21351 To speed up file loading, and reduce memory usage, @value{GDBN} will
21352 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21353 BFD, bfd, The Binary File Descriptor Library}. The following commands
21354 allow visibility and control of the caching behavior.
21357 @kindex maint info bfds
21358 @item maint info bfds
21359 This prints information about each @code{bfd} object that is known to
21362 @kindex maint set bfd-sharing
21363 @kindex maint show bfd-sharing
21364 @kindex bfd caching
21365 @item maint set bfd-sharing
21366 @item maint show bfd-sharing
21367 Control whether @code{bfd} objects can be shared. When sharing is
21368 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21369 than reopening the same file. Turning sharing off does not cause
21370 already shared @code{bfd} objects to be unshared, but all future files
21371 that are opened will create a new @code{bfd} object. Similarly,
21372 re-enabling sharing does not cause multiple existing @code{bfd}
21373 objects to be collapsed into a single shared @code{bfd} object.
21375 @kindex set debug bfd-cache @var{level}
21376 @kindex bfd caching
21377 @item set debug bfd-cache @var{level}
21378 Turns on debugging of the bfd cache, setting the level to @var{level}.
21380 @kindex show debug bfd-cache
21381 @kindex bfd caching
21382 @item show debug bfd-cache
21383 Show the current debugging level of the bfd cache.
21386 @node Separate Debug Files
21387 @section Debugging Information in Separate Files
21388 @cindex separate debugging information files
21389 @cindex debugging information in separate files
21390 @cindex @file{.debug} subdirectories
21391 @cindex debugging information directory, global
21392 @cindex global debugging information directories
21393 @cindex build ID, and separate debugging files
21394 @cindex @file{.build-id} directory
21396 @value{GDBN} allows you to put a program's debugging information in a
21397 file separate from the executable itself, in a way that allows
21398 @value{GDBN} to find and load the debugging information automatically.
21399 Since debugging information can be very large---sometimes larger
21400 than the executable code itself---some systems distribute debugging
21401 information for their executables in separate files, which users can
21402 install only when they need to debug a problem.
21404 @value{GDBN} supports two ways of specifying the separate debug info
21409 The executable contains a @dfn{debug link} that specifies the name of
21410 the separate debug info file. The separate debug file's name is
21411 usually @file{@var{executable}.debug}, where @var{executable} is the
21412 name of the corresponding executable file without leading directories
21413 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21414 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21415 checksum for the debug file, which @value{GDBN} uses to validate that
21416 the executable and the debug file came from the same build.
21420 The executable contains a @dfn{build ID}, a unique bit string that is
21421 also present in the corresponding debug info file. (This is supported
21422 only on some operating systems, when using the ELF or PE file formats
21423 for binary files and the @sc{gnu} Binutils.) For more details about
21424 this feature, see the description of the @option{--build-id}
21425 command-line option in @ref{Options, , Command Line Options, ld,
21426 The GNU Linker}. The debug info file's name is not specified
21427 explicitly by the build ID, but can be computed from the build ID, see
21431 Depending on the way the debug info file is specified, @value{GDBN}
21432 uses two different methods of looking for the debug file:
21436 For the ``debug link'' method, @value{GDBN} looks up the named file in
21437 the directory of the executable file, then in a subdirectory of that
21438 directory named @file{.debug}, and finally under each one of the
21439 global debug directories, in a subdirectory whose name is identical to
21440 the leading directories of the executable's absolute file name. (On
21441 MS-Windows/MS-DOS, the drive letter of the executable's leading
21442 directories is converted to a one-letter subdirectory, i.e.@:
21443 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21444 filesystems disallow colons in file names.)
21447 For the ``build ID'' method, @value{GDBN} looks in the
21448 @file{.build-id} subdirectory of each one of the global debug directories for
21449 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21450 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21451 are the rest of the bit string. (Real build ID strings are 32 or more
21452 hex characters, not 10.) @value{GDBN} can automatically query
21453 @code{debuginfod} servers using build IDs in order to download separate debug
21454 files that cannot be found locally. For more information see @ref{Debuginfod}.
21457 So, for example, suppose you ask @value{GDBN} to debug
21458 @file{/usr/bin/ls}, which has a debug link that specifies the
21459 file @file{ls.debug}, and a build ID whose value in hex is
21460 @code{abcdef1234}. If the list of the global debug directories includes
21461 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21462 debug information files, in the indicated order:
21466 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21468 @file{/usr/bin/ls.debug}
21470 @file{/usr/bin/.debug/ls.debug}
21472 @file{/usr/lib/debug/usr/bin/ls.debug}.
21475 If the debug file still has not been found and @code{debuginfod}
21476 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21477 file from @code{debuginfod} servers.
21479 @anchor{debug-file-directory}
21480 Global debugging info directories default to what is set by @value{GDBN}
21481 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21482 you can also set the global debugging info directories, and view the list
21483 @value{GDBN} is currently using.
21487 @kindex set debug-file-directory
21488 @item set debug-file-directory @var{directories}
21489 Set the directories which @value{GDBN} searches for separate debugging
21490 information files to @var{directory}. Multiple path components can be set
21491 concatenating them by a path separator.
21493 @kindex show debug-file-directory
21494 @item show debug-file-directory
21495 Show the directories @value{GDBN} searches for separate debugging
21500 @cindex @code{.gnu_debuglink} sections
21501 @cindex debug link sections
21502 A debug link is a special section of the executable file named
21503 @code{.gnu_debuglink}. The section must contain:
21507 A filename, with any leading directory components removed, followed by
21510 zero to three bytes of padding, as needed to reach the next four-byte
21511 boundary within the section, and
21513 a four-byte CRC checksum, stored in the same endianness used for the
21514 executable file itself. The checksum is computed on the debugging
21515 information file's full contents by the function given below, passing
21516 zero as the @var{crc} argument.
21519 Any executable file format can carry a debug link, as long as it can
21520 contain a section named @code{.gnu_debuglink} with the contents
21523 @cindex @code{.note.gnu.build-id} sections
21524 @cindex build ID sections
21525 The build ID is a special section in the executable file (and in other
21526 ELF binary files that @value{GDBN} may consider). This section is
21527 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21528 It contains unique identification for the built files---the ID remains
21529 the same across multiple builds of the same build tree. The default
21530 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21531 content for the build ID string. The same section with an identical
21532 value is present in the original built binary with symbols, in its
21533 stripped variant, and in the separate debugging information file.
21535 The debugging information file itself should be an ordinary
21536 executable, containing a full set of linker symbols, sections, and
21537 debugging information. The sections of the debugging information file
21538 should have the same names, addresses, and sizes as the original file,
21539 but they need not contain any data---much like a @code{.bss} section
21540 in an ordinary executable.
21542 The @sc{gnu} binary utilities (Binutils) package includes the
21543 @samp{objcopy} utility that can produce
21544 the separated executable / debugging information file pairs using the
21545 following commands:
21548 @kbd{objcopy --only-keep-debug foo foo.debug}
21553 These commands remove the debugging
21554 information from the executable file @file{foo} and place it in the file
21555 @file{foo.debug}. You can use the first, second or both methods to link the
21560 The debug link method needs the following additional command to also leave
21561 behind a debug link in @file{foo}:
21564 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21567 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21568 a version of the @code{strip} command such that the command @kbd{strip foo -f
21569 foo.debug} has the same functionality as the two @code{objcopy} commands and
21570 the @code{ln -s} command above, together.
21573 Build ID gets embedded into the main executable using @code{ld --build-id} or
21574 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21575 compatibility fixes for debug files separation are present in @sc{gnu} binary
21576 utilities (Binutils) package since version 2.18.
21581 @cindex CRC algorithm definition
21582 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21583 IEEE 802.3 using the polynomial:
21585 @c TexInfo requires naked braces for multi-digit exponents for Tex
21586 @c output, but this causes HTML output to barf. HTML has to be set using
21587 @c raw commands. So we end up having to specify this equation in 2
21592 <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>
21593 + <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
21599 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21600 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21604 The function is computed byte at a time, taking the least
21605 significant bit of each byte first. The initial pattern
21606 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21607 the final result is inverted to ensure trailing zeros also affect the
21610 @emph{Note:} This is the same CRC polynomial as used in handling the
21611 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21612 However in the case of the Remote Serial Protocol, the CRC is computed
21613 @emph{most} significant bit first, and the result is not inverted, so
21614 trailing zeros have no effect on the CRC value.
21616 To complete the description, we show below the code of the function
21617 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21618 initially supplied @code{crc} argument means that an initial call to
21619 this function passing in zero will start computing the CRC using
21622 @kindex gnu_debuglink_crc32
21625 gnu_debuglink_crc32 (unsigned long crc,
21626 unsigned char *buf, size_t len)
21628 static const unsigned long crc32_table[256] =
21630 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21631 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21632 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21633 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21634 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21635 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21636 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21637 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21638 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21639 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21640 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21641 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21642 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21643 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21644 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21645 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21646 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21647 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21648 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21649 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21650 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21651 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21652 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21653 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21654 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21655 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21656 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21657 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21658 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21659 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21660 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21661 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21662 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21663 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21664 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21665 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21666 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21667 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21668 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21669 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21670 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21671 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21672 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21673 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21674 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21675 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21676 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21677 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21678 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21679 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21680 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21683 unsigned char *end;
21685 crc = ~crc & 0xffffffff;
21686 for (end = buf + len; buf < end; ++buf)
21687 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21688 return ~crc & 0xffffffff;
21693 This computation does not apply to the ``build ID'' method.
21695 @node MiniDebugInfo
21696 @section Debugging information in a special section
21697 @cindex separate debug sections
21698 @cindex @samp{.gnu_debugdata} section
21700 Some systems ship pre-built executables and libraries that have a
21701 special @samp{.gnu_debugdata} section. This feature is called
21702 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21703 is used to supply extra symbols for backtraces.
21705 The intent of this section is to provide extra minimal debugging
21706 information for use in simple backtraces. It is not intended to be a
21707 replacement for full separate debugging information (@pxref{Separate
21708 Debug Files}). The example below shows the intended use; however,
21709 @value{GDBN} does not currently put restrictions on what sort of
21710 debugging information might be included in the section.
21712 @value{GDBN} has support for this extension. If the section exists,
21713 then it is used provided that no other source of debugging information
21714 can be found, and that @value{GDBN} was configured with LZMA support.
21716 This section can be easily created using @command{objcopy} and other
21717 standard utilities:
21720 # Extract the dynamic symbols from the main binary, there is no need
21721 # to also have these in the normal symbol table.
21722 nm -D @var{binary} --format=posix --defined-only \
21723 | awk '@{ print $1 @}' | sort > dynsyms
21725 # Extract all the text (i.e. function) symbols from the debuginfo.
21726 # (Note that we actually also accept "D" symbols, for the benefit
21727 # of platforms like PowerPC64 that use function descriptors.)
21728 nm @var{binary} --format=posix --defined-only \
21729 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21732 # Keep all the function symbols not already in the dynamic symbol
21734 comm -13 dynsyms funcsyms > keep_symbols
21736 # Separate full debug info into debug binary.
21737 objcopy --only-keep-debug @var{binary} debug
21739 # Copy the full debuginfo, keeping only a minimal set of symbols and
21740 # removing some unnecessary sections.
21741 objcopy -S --remove-section .gdb_index --remove-section .comment \
21742 --keep-symbols=keep_symbols debug mini_debuginfo
21744 # Drop the full debug info from the original binary.
21745 strip --strip-all -R .comment @var{binary}
21747 # Inject the compressed data into the .gnu_debugdata section of the
21750 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21754 @section Index Files Speed Up @value{GDBN}
21755 @cindex index files
21756 @cindex @samp{.gdb_index} section
21758 When @value{GDBN} finds a symbol file, it scans the symbols in the
21759 file in order to construct an internal symbol table. This lets most
21760 @value{GDBN} operations work quickly---at the cost of a delay early
21761 on. For large programs, this delay can be quite lengthy, so
21762 @value{GDBN} provides a way to build an index, which speeds up
21765 For convenience, @value{GDBN} comes with a program,
21766 @command{gdb-add-index}, which can be used to add the index to a
21767 symbol file. It takes the symbol file as its only argument:
21770 $ gdb-add-index symfile
21773 @xref{gdb-add-index}.
21775 It is also possible to do the work manually. Here is what
21776 @command{gdb-add-index} does behind the curtains.
21778 The index is stored as a section in the symbol file. @value{GDBN} can
21779 write the index to a file, then you can put it into the symbol file
21780 using @command{objcopy}.
21782 To create an index file, use the @code{save gdb-index} command:
21785 @item save gdb-index [-dwarf-5] @var{directory}
21786 @kindex save gdb-index
21787 Create index files for all symbol files currently known by
21788 @value{GDBN}. For each known @var{symbol-file}, this command by
21789 default creates it produces a single file
21790 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21791 the @option{-dwarf-5} option, it produces 2 files:
21792 @file{@var{symbol-file}.debug_names} and
21793 @file{@var{symbol-file}.debug_str}. The files are created in the
21794 given @var{directory}.
21797 Once you have created an index file you can merge it into your symbol
21798 file, here named @file{symfile}, using @command{objcopy}:
21801 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21802 --set-section-flags .gdb_index=readonly symfile symfile
21805 Or for @code{-dwarf-5}:
21808 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21809 $ cat symfile.debug_str >>symfile.debug_str.new
21810 $ objcopy --add-section .debug_names=symfile.gdb-index \
21811 --set-section-flags .debug_names=readonly \
21812 --update-section .debug_str=symfile.debug_str.new symfile symfile
21815 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21816 sections that have been deprecated. Usually they are deprecated because
21817 they are missing a new feature or have performance issues.
21818 To tell @value{GDBN} to use a deprecated index section anyway
21819 specify @code{set use-deprecated-index-sections on}.
21820 The default is @code{off}.
21821 This can speed up startup, but may result in some functionality being lost.
21822 @xref{Index Section Format}.
21824 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21825 must be done before gdb reads the file. The following will not work:
21828 $ gdb -ex "set use-deprecated-index-sections on" <program>
21831 Instead you must do, for example,
21834 $ gdb -iex "set use-deprecated-index-sections on" <program>
21837 Indices only work when using DWARF debugging information, not stabs.
21839 @subsection Automatic symbol index cache
21841 @cindex automatic symbol index cache
21842 It is possible for @value{GDBN} to automatically save a copy of this index in a
21843 cache on disk and retrieve it from there when loading the same binary in the
21844 future. This feature can be turned on with @kbd{set index-cache enabled on}.
21845 The following commands can be used to tweak the behavior of the index cache.
21849 @kindex set index-cache
21850 @item set index-cache enabled on
21851 @itemx set index-cache enabled off
21852 Enable or disable the use of the symbol index cache.
21854 @item set index-cache directory @var{directory}
21855 @kindex show index-cache
21856 @itemx show index-cache directory
21857 Set/show the directory where index files will be saved.
21859 The default value for this directory depends on the host platform. On
21860 most systems, the index is cached in the @file{gdb} subdirectory of
21861 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21862 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21863 of your home directory. However, on some systems, the default may
21864 differ according to local convention.
21866 There is no limit on the disk space used by index cache. It is perfectly safe
21867 to delete the content of that directory to free up disk space.
21869 @item show index-cache stats
21870 Print the number of cache hits and misses since the launch of @value{GDBN}.
21874 @node Symbol Errors
21875 @section Errors Reading Symbol Files
21877 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21878 such as symbol types it does not recognize, or known bugs in compiler
21879 output. By default, @value{GDBN} does not notify you of such problems, since
21880 they are relatively common and primarily of interest to people
21881 debugging compilers. If you are interested in seeing information
21882 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21883 only one message about each such type of problem, no matter how many
21884 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21885 to see how many times the problems occur, with the @code{set
21886 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21889 The messages currently printed, and their meanings, include:
21892 @item inner block not inside outer block in @var{symbol}
21894 The symbol information shows where symbol scopes begin and end
21895 (such as at the start of a function or a block of statements). This
21896 error indicates that an inner scope block is not fully contained
21897 in its outer scope blocks.
21899 @value{GDBN} circumvents the problem by treating the inner block as if it had
21900 the same scope as the outer block. In the error message, @var{symbol}
21901 may be shown as ``@code{(don't know)}'' if the outer block is not a
21904 @item block at @var{address} out of order
21906 The symbol information for symbol scope blocks should occur in
21907 order of increasing addresses. This error indicates that it does not
21910 @value{GDBN} does not circumvent this problem, and has trouble
21911 locating symbols in the source file whose symbols it is reading. (You
21912 can often determine what source file is affected by specifying
21913 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21916 @item bad block start address patched
21918 The symbol information for a symbol scope block has a start address
21919 smaller than the address of the preceding source line. This is known
21920 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21922 @value{GDBN} circumvents the problem by treating the symbol scope block as
21923 starting on the previous source line.
21925 @item bad string table offset in symbol @var{n}
21928 Symbol number @var{n} contains a pointer into the string table which is
21929 larger than the size of the string table.
21931 @value{GDBN} circumvents the problem by considering the symbol to have the
21932 name @code{foo}, which may cause other problems if many symbols end up
21935 @item unknown symbol type @code{0x@var{nn}}
21937 The symbol information contains new data types that @value{GDBN} does
21938 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21939 uncomprehended information, in hexadecimal.
21941 @value{GDBN} circumvents the error by ignoring this symbol information.
21942 This usually allows you to debug your program, though certain symbols
21943 are not accessible. If you encounter such a problem and feel like
21944 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21945 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21946 and examine @code{*bufp} to see the symbol.
21948 @item stub type has NULL name
21950 @value{GDBN} could not find the full definition for a struct or class.
21952 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21953 The symbol information for a C@t{++} member function is missing some
21954 information that recent versions of the compiler should have output for
21957 @item info mismatch between compiler and debugger
21959 @value{GDBN} could not parse a type specification output by the compiler.
21964 @section GDB Data Files
21966 @cindex prefix for data files
21967 @value{GDBN} will sometimes read an auxiliary data file. These files
21968 are kept in a directory known as the @dfn{data directory}.
21970 You can set the data directory's name, and view the name @value{GDBN}
21971 is currently using.
21974 @kindex set data-directory
21975 @item set data-directory @var{directory}
21976 Set the directory which @value{GDBN} searches for auxiliary data files
21977 to @var{directory}.
21979 @kindex show data-directory
21980 @item show data-directory
21981 Show the directory @value{GDBN} searches for auxiliary data files.
21984 @cindex default data directory
21985 @cindex @samp{--with-gdb-datadir}
21986 You can set the default data directory by using the configure-time
21987 @samp{--with-gdb-datadir} option. If the data directory is inside
21988 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21989 @samp{--exec-prefix}), then the default data directory will be updated
21990 automatically if the installed @value{GDBN} is moved to a new
21993 The data directory may also be specified with the
21994 @code{--data-directory} command line option.
21995 @xref{Mode Options}.
21998 @chapter Specifying a Debugging Target
22000 @cindex debugging target
22001 A @dfn{target} is the execution environment occupied by your program.
22003 Often, @value{GDBN} runs in the same host environment as your program;
22004 in that case, the debugging target is specified as a side effect when
22005 you use the @code{file} or @code{core} commands. When you need more
22006 flexibility---for example, running @value{GDBN} on a physically separate
22007 host, or controlling a standalone system over a serial port or a
22008 realtime system over a TCP/IP connection---you can use the @code{target}
22009 command to specify one of the target types configured for @value{GDBN}
22010 (@pxref{Target Commands, ,Commands for Managing Targets}).
22012 @cindex target architecture
22013 It is possible to build @value{GDBN} for several different @dfn{target
22014 architectures}. When @value{GDBN} is built like that, you can choose
22015 one of the available architectures with the @kbd{set architecture}
22019 @kindex set architecture
22020 @kindex show architecture
22021 @item set architecture @var{arch}
22022 This command sets the current target architecture to @var{arch}. The
22023 value of @var{arch} can be @code{"auto"}, in addition to one of the
22024 supported architectures.
22026 @item show architecture
22027 Show the current target architecture.
22029 @item set processor
22031 @kindex set processor
22032 @kindex show processor
22033 These are alias commands for, respectively, @code{set architecture}
22034 and @code{show architecture}.
22038 * Active Targets:: Active targets
22039 * Target Commands:: Commands for managing targets
22040 * Byte Order:: Choosing target byte order
22043 @node Active Targets
22044 @section Active Targets
22046 @cindex stacking targets
22047 @cindex active targets
22048 @cindex multiple targets
22050 There are multiple classes of targets such as: processes, executable files or
22051 recording sessions. Core files belong to the process class, making core file
22052 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22053 on multiple active targets, one in each class. This allows you to (for
22054 example) start a process and inspect its activity, while still having access to
22055 the executable file after the process finishes. Or if you start process
22056 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22057 presented a virtual layer of the recording target, while the process target
22058 remains stopped at the chronologically last point of the process execution.
22060 Use the @code{core-file} and @code{exec-file} commands to select a new core
22061 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22062 specify as a target a process that is already running, use the @code{attach}
22063 command (@pxref{Attach, ,Debugging an Already-running Process}).
22065 @node Target Commands
22066 @section Commands for Managing Targets
22069 @item target @var{type} @var{parameters}
22070 Connects the @value{GDBN} host environment to a target machine or
22071 process. A target is typically a protocol for talking to debugging
22072 facilities. You use the argument @var{type} to specify the type or
22073 protocol of the target machine.
22075 Further @var{parameters} are interpreted by the target protocol, but
22076 typically include things like device names or host names to connect
22077 with, process numbers, and baud rates.
22079 The @code{target} command does not repeat if you press @key{RET} again
22080 after executing the command.
22082 @kindex help target
22084 Displays the names of all targets available. To display targets
22085 currently selected, use either @code{info target} or @code{info files}
22086 (@pxref{Files, ,Commands to Specify Files}).
22088 @item help target @var{name}
22089 Describe a particular target, including any parameters necessary to
22092 @kindex set gnutarget
22093 @item set gnutarget @var{args}
22094 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22095 knows whether it is reading an @dfn{executable},
22096 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22097 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22098 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22101 @emph{Warning:} To specify a file format with @code{set gnutarget},
22102 you must know the actual BFD name.
22106 @xref{Files, , Commands to Specify Files}.
22108 @kindex show gnutarget
22109 @item show gnutarget
22110 Use the @code{show gnutarget} command to display what file format
22111 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22112 @value{GDBN} will determine the file format for each file automatically,
22113 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22116 @cindex common targets
22117 Here are some common targets (available, or not, depending on the GDB
22122 @item target exec @var{program}
22123 @cindex executable file target
22124 An executable file. @samp{target exec @var{program}} is the same as
22125 @samp{exec-file @var{program}}.
22127 @item target core @var{filename}
22128 @cindex core dump file target
22129 A core dump file. @samp{target core @var{filename}} is the same as
22130 @samp{core-file @var{filename}}.
22132 @item target remote @var{medium}
22133 @cindex remote target
22134 A remote system connected to @value{GDBN} via a serial line or network
22135 connection. This command tells @value{GDBN} to use its own remote
22136 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22138 For example, if you have a board connected to @file{/dev/ttya} on the
22139 machine running @value{GDBN}, you could say:
22142 target remote /dev/ttya
22145 @code{target remote} supports the @code{load} command. This is only
22146 useful if you have some other way of getting the stub to the target
22147 system, and you can put it somewhere in memory where it won't get
22148 clobbered by the download.
22150 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22151 @cindex built-in simulator target
22152 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22160 works; however, you cannot assume that a specific memory map, device
22161 drivers, or even basic I/O is available, although some simulators do
22162 provide these. For info about any processor-specific simulator details,
22163 see the appropriate section in @ref{Embedded Processors, ,Embedded
22166 @item target native
22167 @cindex native target
22168 Setup for local/native process debugging. Useful to make the
22169 @code{run} command spawn native processes (likewise @code{attach},
22170 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22171 (@pxref{set auto-connect-native-target}).
22175 Different targets are available on different configurations of @value{GDBN};
22176 your configuration may have more or fewer targets.
22178 Many remote targets require you to download the executable's code once
22179 you've successfully established a connection. You may wish to control
22180 various aspects of this process.
22185 @kindex set hash@r{, for remote monitors}
22186 @cindex hash mark while downloading
22187 This command controls whether a hash mark @samp{#} is displayed while
22188 downloading a file to the remote monitor. If on, a hash mark is
22189 displayed after each S-record is successfully downloaded to the
22193 @kindex show hash@r{, for remote monitors}
22194 Show the current status of displaying the hash mark.
22196 @item set debug monitor
22197 @kindex set debug monitor
22198 @cindex display remote monitor communications
22199 Enable or disable display of communications messages between
22200 @value{GDBN} and the remote monitor.
22202 @item show debug monitor
22203 @kindex show debug monitor
22204 Show the current status of displaying communications between
22205 @value{GDBN} and the remote monitor.
22210 @kindex load @var{filename} @var{offset}
22211 @item load @var{filename} @var{offset}
22213 Depending on what remote debugging facilities are configured into
22214 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22215 is meant to make @var{filename} (an executable) available for debugging
22216 on the remote system---by downloading, or dynamic linking, for example.
22217 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22218 the @code{add-symbol-file} command.
22220 If your @value{GDBN} does not have a @code{load} command, attempting to
22221 execute it gets the error message ``@code{You can't do that when your
22222 target is @dots{}}''
22224 The file is loaded at whatever address is specified in the executable.
22225 For some object file formats, you can specify the load address when you
22226 link the program; for other formats, like a.out, the object file format
22227 specifies a fixed address.
22228 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22230 It is also possible to tell @value{GDBN} to load the executable file at a
22231 specific offset described by the optional argument @var{offset}. When
22232 @var{offset} is provided, @var{filename} must also be provided.
22234 Depending on the remote side capabilities, @value{GDBN} may be able to
22235 load programs into flash memory.
22237 @code{load} does not repeat if you press @key{RET} again after using it.
22242 @kindex flash-erase
22244 @anchor{flash-erase}
22246 Erases all known flash memory regions on the target.
22251 @section Choosing Target Byte Order
22253 @cindex choosing target byte order
22254 @cindex target byte order
22256 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22257 offer the ability to run either big-endian or little-endian byte
22258 orders. Usually the executable or symbol will include a bit to
22259 designate the endian-ness, and you will not need to worry about
22260 which to use. However, you may still find it useful to adjust
22261 @value{GDBN}'s idea of processor endian-ness manually.
22265 @item set endian big
22266 Instruct @value{GDBN} to assume the target is big-endian.
22268 @item set endian little
22269 Instruct @value{GDBN} to assume the target is little-endian.
22271 @item set endian auto
22272 Instruct @value{GDBN} to use the byte order associated with the
22276 Display @value{GDBN}'s current idea of the target byte order.
22280 If the @code{set endian auto} mode is in effect and no executable has
22281 been selected, then the endianness used is the last one chosen either
22282 by one of the @code{set endian big} and @code{set endian little}
22283 commands or by inferring from the last executable used. If no
22284 endianness has been previously chosen, then the default for this mode
22285 is inferred from the target @value{GDBN} has been built for, and is
22286 @code{little} if the name of the target CPU has an @code{el} suffix
22287 and @code{big} otherwise.
22289 Note that these commands merely adjust interpretation of symbolic
22290 data on the host, and that they have absolutely no effect on the
22294 @node Remote Debugging
22295 @chapter Debugging Remote Programs
22296 @cindex remote debugging
22298 If you are trying to debug a program running on a machine that cannot run
22299 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22300 For example, you might use remote debugging on an operating system kernel,
22301 or on a small system which does not have a general purpose operating system
22302 powerful enough to run a full-featured debugger.
22304 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22305 to make this work with particular debugging targets. In addition,
22306 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22307 but not specific to any particular target system) which you can use if you
22308 write the remote stubs---the code that runs on the remote system to
22309 communicate with @value{GDBN}.
22311 Other remote targets may be available in your
22312 configuration of @value{GDBN}; use @code{help target} to list them.
22315 * Connecting:: Connecting to a remote target
22316 * File Transfer:: Sending files to a remote system
22317 * Server:: Using the gdbserver program
22318 * Remote Configuration:: Remote configuration
22319 * Remote Stub:: Implementing a remote stub
22323 @section Connecting to a Remote Target
22324 @cindex remote debugging, connecting
22325 @cindex @code{gdbserver}, connecting
22326 @cindex remote debugging, types of connections
22327 @cindex @code{gdbserver}, types of connections
22328 @cindex @code{gdbserver}, @code{target remote} mode
22329 @cindex @code{gdbserver}, @code{target extended-remote} mode
22331 This section describes how to connect to a remote target, including the
22332 types of connections and their differences, how to set up executable and
22333 symbol files on the host and target, and the commands used for
22334 connecting to and disconnecting from the remote target.
22336 @subsection Types of Remote Connections
22338 @value{GDBN} supports two types of remote connections, @code{target remote}
22339 mode and @code{target extended-remote} mode. Note that many remote targets
22340 support only @code{target remote} mode. There are several major
22341 differences between the two types of connections, enumerated here:
22345 @cindex remote debugging, detach and program exit
22346 @item Result of detach or program exit
22347 @strong{With target remote mode:} When the debugged program exits or you
22348 detach from it, @value{GDBN} disconnects from the target. When using
22349 @code{gdbserver}, @code{gdbserver} will exit.
22351 @strong{With target extended-remote mode:} When the debugged program exits or
22352 you detach from it, @value{GDBN} remains connected to the target, even
22353 though no program is running. You can rerun the program, attach to a
22354 running program, or use @code{monitor} commands specific to the target.
22356 When using @code{gdbserver} in this case, it does not exit unless it was
22357 invoked using the @option{--once} option. If the @option{--once} option
22358 was not used, you can ask @code{gdbserver} to exit using the
22359 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22361 @item Specifying the program to debug
22362 For both connection types you use the @code{file} command to specify the
22363 program on the host system. If you are using @code{gdbserver} there are
22364 some differences in how to specify the location of the program on the
22367 @strong{With target remote mode:} You must either specify the program to debug
22368 on the @code{gdbserver} command line or use the @option{--attach} option
22369 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22371 @cindex @option{--multi}, @code{gdbserver} option
22372 @strong{With target extended-remote mode:} You may specify the program to debug
22373 on the @code{gdbserver} command line, or you can load the program or attach
22374 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22376 @anchor{--multi Option in Types of Remote Connnections}
22377 You can start @code{gdbserver} without supplying an initial command to run
22378 or process ID to attach. To do this, use the @option{--multi} command line
22379 option. Then you can connect using @code{target extended-remote} and start
22380 the program you want to debug (see below for details on using the
22381 @code{run} command in this scenario). Note that the conditions under which
22382 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22383 (@code{target remote} or @code{target extended-remote}). The
22384 @option{--multi} option to @code{gdbserver} has no influence on that.
22386 @item The @code{run} command
22387 @strong{With target remote mode:} The @code{run} command is not
22388 supported. Once a connection has been established, you can use all
22389 the usual @value{GDBN} commands to examine and change data. The
22390 remote program is already running, so you can use commands like
22391 @kbd{step} and @kbd{continue}.
22393 @strong{With target extended-remote mode:} The @code{run} command is
22394 supported. The @code{run} command uses the value set by
22395 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22396 the program to run. Command line arguments are supported, except for
22397 wildcard expansion and I/O redirection (@pxref{Arguments}).
22399 If you specify the program to debug on the command line, then the
22400 @code{run} command is not required to start execution, and you can
22401 resume using commands like @kbd{step} and @kbd{continue} as with
22402 @code{target remote} mode.
22404 @anchor{Attaching in Types of Remote Connections}
22406 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22407 not supported. To attach to a running program using @code{gdbserver}, you
22408 must use the @option{--attach} option (@pxref{Running gdbserver}).
22410 @strong{With target extended-remote mode:} To attach to a running program,
22411 you may use the @code{attach} command after the connection has been
22412 established. If you are using @code{gdbserver}, you may also invoke
22413 @code{gdbserver} using the @option{--attach} option
22414 (@pxref{Running gdbserver}).
22416 Some remote targets allow @value{GDBN} to determine the executable file running
22417 in the process the debugger is attaching to. In such a case, @value{GDBN}
22418 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22419 between the executable file name running in the process and the name of the
22420 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22424 @anchor{Host and target files}
22425 @subsection Host and Target Files
22426 @cindex remote debugging, symbol files
22427 @cindex symbol files, remote debugging
22429 @value{GDBN}, running on the host, needs access to symbol and debugging
22430 information for your program running on the target. This requires
22431 access to an unstripped copy of your program, and possibly any associated
22432 symbol files. Note that this section applies equally to both @code{target
22433 remote} mode and @code{target extended-remote} mode.
22435 Some remote targets (@pxref{qXfer executable filename read}, and
22436 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22437 the same connection used to communicate with @value{GDBN}. With such a
22438 target, if the remote program is unstripped, the only command you need is
22439 @code{target remote} (or @code{target extended-remote}).
22441 If the remote program is stripped, or the target does not support remote
22442 program file access, start up @value{GDBN} using the name of the local
22443 unstripped copy of your program as the first argument, or use the
22444 @code{file} command. Use @code{set sysroot} to specify the location (on
22445 the host) of target libraries (unless your @value{GDBN} was compiled with
22446 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22447 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22450 The symbol file and target libraries must exactly match the executable
22451 and libraries on the target, with one exception: the files on the host
22452 system should not be stripped, even if the files on the target system
22453 are. Mismatched or missing files will lead to confusing results
22454 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22455 files may also prevent @code{gdbserver} from debugging multi-threaded
22458 @subsection Remote Connection Commands
22459 @cindex remote connection commands
22460 @value{GDBN} can communicate with the target over a serial line, a
22461 local Unix domain socket, or
22462 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22463 each case, @value{GDBN} uses the same protocol for debugging your
22464 program; only the medium carrying the debugging packets varies. The
22465 @code{target remote} and @code{target extended-remote} commands
22466 establish a connection to the target. Both commands accept the same
22467 arguments, which indicate the medium to use:
22471 @item target remote @var{serial-device}
22472 @itemx target extended-remote @var{serial-device}
22473 @cindex serial line, @code{target remote}
22474 Use @var{serial-device} to communicate with the target. For example,
22475 to use a serial line connected to the device named @file{/dev/ttyb}:
22478 target remote /dev/ttyb
22481 If you're using a serial line, you may want to give @value{GDBN} the
22482 @samp{--baud} option, or use the @code{set serial baud} command
22483 (@pxref{Remote Configuration, set serial baud}) before the
22484 @code{target} command.
22486 @item target remote @var{local-socket}
22487 @itemx target extended-remote @var{local-socket}
22488 @cindex local socket, @code{target remote}
22489 @cindex Unix domain socket
22490 Use @var{local-socket} to communicate with the target. For example,
22491 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22494 target remote /tmp/gdb-socket0
22497 Note that this command has the same form as the command to connect
22498 to a serial line. @value{GDBN} will automatically determine which
22499 kind of file you have specified and will make the appropriate kind
22501 This feature is not available if the host system does not support
22502 Unix domain sockets.
22504 @item target remote @code{@var{host}:@var{port}}
22505 @itemx target remote @code{[@var{host}]:@var{port}}
22506 @itemx target remote @code{tcp:@var{host}:@var{port}}
22507 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22508 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22509 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22510 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22511 @itemx target extended-remote @code{@var{host}:@var{port}}
22512 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22513 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22514 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22515 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22516 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22517 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22518 @cindex @acronym{TCP} port, @code{target remote}
22519 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22520 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22521 address, or a numeric @acronym{IPv6} address (with or without the
22522 square brackets to separate the address from the port); @var{port}
22523 must be a decimal number. The @var{host} could be the target machine
22524 itself, if it is directly connected to the net, or it might be a
22525 terminal server which in turn has a serial line to the target.
22527 For example, to connect to port 2828 on a terminal server named
22531 target remote manyfarms:2828
22534 To connect to port 2828 on a terminal server whose address is
22535 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22536 square bracket syntax:
22539 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22543 or explicitly specify the @acronym{IPv6} protocol:
22546 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22549 This last example may be confusing to the reader, because there is no
22550 visible separation between the hostname and the port number.
22551 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22552 using square brackets for clarity. However, it is important to
22553 mention that for @value{GDBN} there is no ambiguity: the number after
22554 the last colon is considered to be the port number.
22556 If your remote target is actually running on the same machine as your
22557 debugger session (e.g.@: a simulator for your target running on the
22558 same host), you can omit the hostname. For example, to connect to
22559 port 1234 on your local machine:
22562 target remote :1234
22566 Note that the colon is still required here.
22568 @item target remote @code{udp:@var{host}:@var{port}}
22569 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22570 @itemx target remote @code{udp4:@var{host}:@var{port}}
22571 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22572 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22573 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22574 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22575 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22576 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22577 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22578 @cindex @acronym{UDP} port, @code{target remote}
22579 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22580 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22583 target remote udp:manyfarms:2828
22586 When using a @acronym{UDP} connection for remote debugging, you should
22587 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22588 can silently drop packets on busy or unreliable networks, which will
22589 cause havoc with your debugging session.
22591 @item target remote | @var{command}
22592 @itemx target extended-remote | @var{command}
22593 @cindex pipe, @code{target remote} to
22594 Run @var{command} in the background and communicate with it using a
22595 pipe. The @var{command} is a shell command, to be parsed and expanded
22596 by the system's command shell, @code{/bin/sh}; it should expect remote
22597 protocol packets on its standard input, and send replies on its
22598 standard output. You could use this to run a stand-alone simulator
22599 that speaks the remote debugging protocol, to make net connections
22600 using programs like @code{ssh}, or for other similar tricks.
22602 If @var{command} closes its standard output (perhaps by exiting),
22603 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22604 program has already exited, this will have no effect.)
22608 @cindex interrupting remote programs
22609 @cindex remote programs, interrupting
22610 Whenever @value{GDBN} is waiting for the remote program, if you type the
22611 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22612 program. This may or may not succeed, depending in part on the hardware
22613 and the serial drivers the remote system uses. If you type the
22614 interrupt character once again, @value{GDBN} displays this prompt:
22617 Interrupted while waiting for the program.
22618 Give up (and stop debugging it)? (y or n)
22621 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22622 the remote debugging session. (If you decide you want to try again later,
22623 you can use @kbd{target remote} again to connect once more.) If you type
22624 @kbd{n}, @value{GDBN} goes back to waiting.
22626 In @code{target extended-remote} mode, typing @kbd{n} will leave
22627 @value{GDBN} connected to the target.
22630 @kindex detach (remote)
22632 When you have finished debugging the remote program, you can use the
22633 @code{detach} command to release it from @value{GDBN} control.
22634 Detaching from the target normally resumes its execution, but the results
22635 will depend on your particular remote stub. After the @code{detach}
22636 command in @code{target remote} mode, @value{GDBN} is free to connect to
22637 another target. In @code{target extended-remote} mode, @value{GDBN} is
22638 still connected to the target.
22642 The @code{disconnect} command closes the connection to the target, and
22643 the target is generally not resumed. It will wait for @value{GDBN}
22644 (this instance or another one) to connect and continue debugging. After
22645 the @code{disconnect} command, @value{GDBN} is again free to connect to
22648 @cindex send command to remote monitor
22649 @cindex extend @value{GDBN} for remote targets
22650 @cindex add new commands for external monitor
22652 @item monitor @var{cmd}
22653 This command allows you to send arbitrary commands directly to the
22654 remote monitor. Since @value{GDBN} doesn't care about the commands it
22655 sends like this, this command is the way to extend @value{GDBN}---you
22656 can add new commands that only the external monitor will understand
22660 @node File Transfer
22661 @section Sending files to a remote system
22662 @cindex remote target, file transfer
22663 @cindex file transfer
22664 @cindex sending files to remote systems
22666 Some remote targets offer the ability to transfer files over the same
22667 connection used to communicate with @value{GDBN}. This is convenient
22668 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22669 running @code{gdbserver} over a network interface. For other targets,
22670 e.g.@: embedded devices with only a single serial port, this may be
22671 the only way to upload or download files.
22673 Not all remote targets support these commands.
22677 @item remote put @var{hostfile} @var{targetfile}
22678 Copy file @var{hostfile} from the host system (the machine running
22679 @value{GDBN}) to @var{targetfile} on the target system.
22682 @item remote get @var{targetfile} @var{hostfile}
22683 Copy file @var{targetfile} from the target system to @var{hostfile}
22684 on the host system.
22686 @kindex remote delete
22687 @item remote delete @var{targetfile}
22688 Delete @var{targetfile} from the target system.
22693 @section Using the @code{gdbserver} Program
22696 @cindex remote connection without stubs
22697 @code{gdbserver} is a control program for Unix-like systems, which
22698 allows you to connect your program with a remote @value{GDBN} via
22699 @code{target remote} or @code{target extended-remote}---but without
22700 linking in the usual debugging stub.
22702 @code{gdbserver} is not a complete replacement for the debugging stubs,
22703 because it requires essentially the same operating-system facilities
22704 that @value{GDBN} itself does. In fact, a system that can run
22705 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22706 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22707 because it is a much smaller program than @value{GDBN} itself. It is
22708 also easier to port than all of @value{GDBN}, so you may be able to get
22709 started more quickly on a new system by using @code{gdbserver}.
22710 Finally, if you develop code for real-time systems, you may find that
22711 the tradeoffs involved in real-time operation make it more convenient to
22712 do as much development work as possible on another system, for example
22713 by cross-compiling. You can use @code{gdbserver} to make a similar
22714 choice for debugging.
22716 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22717 or a TCP connection, using the standard @value{GDBN} remote serial
22721 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22722 Do not run @code{gdbserver} connected to any public network; a
22723 @value{GDBN} connection to @code{gdbserver} provides access to the
22724 target system with the same privileges as the user running
22728 @anchor{Running gdbserver}
22729 @subsection Running @code{gdbserver}
22730 @cindex arguments, to @code{gdbserver}
22731 @cindex @code{gdbserver}, command-line arguments
22733 Run @code{gdbserver} on the target system. You need a copy of the
22734 program you want to debug, including any libraries it requires.
22735 @code{gdbserver} does not need your program's symbol table, so you can
22736 strip the program if necessary to save space. @value{GDBN} on the host
22737 system does all the symbol handling.
22739 To use the server, you must tell it how to communicate with @value{GDBN};
22740 the name of your program; and the arguments for your program. The usual
22744 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22747 @var{comm} is either a device name (to use a serial line), or a TCP
22748 hostname and portnumber, or @code{-} or @code{stdio} to use
22749 stdin/stdout of @code{gdbserver}.
22750 For example, to debug Emacs with the argument
22751 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22755 target> gdbserver /dev/com1 emacs foo.txt
22758 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22761 To use a TCP connection instead of a serial line:
22764 target> gdbserver host:2345 emacs foo.txt
22767 The only difference from the previous example is the first argument,
22768 specifying that you are communicating with the host @value{GDBN} via
22769 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22770 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22771 (Currently, the @samp{host} part is ignored.) You can choose any number
22772 you want for the port number as long as it does not conflict with any
22773 TCP ports already in use on the target system (for example, @code{23} is
22774 reserved for @code{telnet}).@footnote{If you choose a port number that
22775 conflicts with another service, @code{gdbserver} prints an error message
22776 and exits.} You must use the same port number with the host @value{GDBN}
22777 @code{target remote} command.
22779 The @code{stdio} connection is useful when starting @code{gdbserver}
22783 (gdb) target remote | ssh -T hostname gdbserver - hello
22786 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22787 and we don't want escape-character handling. Ssh does this by default when
22788 a command is provided, the flag is provided to make it explicit.
22789 You could elide it if you want to.
22791 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22792 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22793 display through a pipe connected to gdbserver.
22794 Both @code{stdout} and @code{stderr} use the same pipe.
22796 @anchor{Attaching to a program}
22797 @subsubsection Attaching to a Running Program
22798 @cindex attach to a program, @code{gdbserver}
22799 @cindex @option{--attach}, @code{gdbserver} option
22801 On some targets, @code{gdbserver} can also attach to running programs.
22802 This is accomplished via the @code{--attach} argument. The syntax is:
22805 target> gdbserver --attach @var{comm} @var{pid}
22808 @var{pid} is the process ID of a currently running process. It isn't
22809 necessary to point @code{gdbserver} at a binary for the running process.
22811 In @code{target extended-remote} mode, you can also attach using the
22812 @value{GDBN} attach command
22813 (@pxref{Attaching in Types of Remote Connections}).
22816 You can debug processes by name instead of process ID if your target has the
22817 @code{pidof} utility:
22820 target> gdbserver --attach @var{comm} `pidof @var{program}`
22823 In case more than one copy of @var{program} is running, or @var{program}
22824 has multiple threads, most versions of @code{pidof} support the
22825 @code{-s} option to only return the first process ID.
22827 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22829 This section applies only when @code{gdbserver} is run to listen on a TCP
22832 @code{gdbserver} normally terminates after all of its debugged processes have
22833 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22834 extended-remote}, @code{gdbserver} stays running even with no processes left.
22835 @value{GDBN} normally terminates the spawned debugged process on its exit,
22836 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22837 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22838 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22839 stays running even in the @kbd{target remote} mode.
22841 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22842 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22843 completeness, at most one @value{GDBN} can be connected at a time.
22845 @cindex @option{--once}, @code{gdbserver} option
22846 By default, @code{gdbserver} keeps the listening TCP port open, so that
22847 subsequent connections are possible. However, if you start @code{gdbserver}
22848 with the @option{--once} option, it will stop listening for any further
22849 connection attempts after connecting to the first @value{GDBN} session. This
22850 means no further connections to @code{gdbserver} will be possible after the
22851 first one. It also means @code{gdbserver} will terminate after the first
22852 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22853 connections and even in the @kbd{target extended-remote} mode. The
22854 @option{--once} option allows reusing the same port number for connecting to
22855 multiple instances of @code{gdbserver} running on the same host, since each
22856 instance closes its port after the first connection.
22858 @anchor{Other Command-Line Arguments for gdbserver}
22859 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22861 You can use the @option{--multi} option to start @code{gdbserver} without
22862 specifying a program to debug or a process to attach to. Then you can
22863 attach in @code{target extended-remote} mode and run or attach to a
22864 program. For more information,
22865 @pxref{--multi Option in Types of Remote Connnections}.
22867 @cindex @option{--debug}, @code{gdbserver} option
22868 The @option{--debug} option tells @code{gdbserver} to display extra
22869 status information about the debugging process.
22870 @cindex @option{--remote-debug}, @code{gdbserver} option
22871 The @option{--remote-debug} option tells @code{gdbserver} to display
22872 remote protocol debug output.
22873 @cindex @option{--debug-file}, @code{gdbserver} option
22874 @cindex @code{gdbserver}, send all debug output to a single file
22875 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22876 write any debug output to the given @var{filename}. These options are intended
22877 for @code{gdbserver} development and for bug reports to the developers.
22879 @cindex @option{--debug-format}, @code{gdbserver} option
22880 The @option{--debug-format=option1[,option2,...]} option tells
22881 @code{gdbserver} to include additional information in each output.
22882 Possible options are:
22886 Turn off all extra information in debugging output.
22888 Turn on all extra information in debugging output.
22890 Include a timestamp in each line of debugging output.
22893 Options are processed in order. Thus, for example, if @option{none}
22894 appears last then no additional information is added to debugging output.
22896 @cindex @option{--wrapper}, @code{gdbserver} option
22897 The @option{--wrapper} option specifies a wrapper to launch programs
22898 for debugging. The option should be followed by the name of the
22899 wrapper, then any command-line arguments to pass to the wrapper, then
22900 @kbd{--} indicating the end of the wrapper arguments.
22902 @code{gdbserver} runs the specified wrapper program with a combined
22903 command line including the wrapper arguments, then the name of the
22904 program to debug, then any arguments to the program. The wrapper
22905 runs until it executes your program, and then @value{GDBN} gains control.
22907 You can use any program that eventually calls @code{execve} with
22908 its arguments as a wrapper. Several standard Unix utilities do
22909 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22910 with @code{exec "$@@"} will also work.
22912 For example, you can use @code{env} to pass an environment variable to
22913 the debugged program, without setting the variable in @code{gdbserver}'s
22917 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22920 @cindex @option{--selftest}
22921 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22924 $ gdbserver --selftest
22925 Ran 2 unit tests, 0 failed
22928 These tests are disabled in release.
22929 @subsection Connecting to @code{gdbserver}
22931 The basic procedure for connecting to the remote target is:
22935 Run @value{GDBN} on the host system.
22938 Make sure you have the necessary symbol files
22939 (@pxref{Host and target files}).
22940 Load symbols for your application using the @code{file} command before you
22941 connect. Use @code{set sysroot} to locate target libraries (unless your
22942 @value{GDBN} was compiled with the correct sysroot using
22943 @code{--with-sysroot}).
22946 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22947 For TCP connections, you must start up @code{gdbserver} prior to using
22948 the @code{target} command. Otherwise you may get an error whose
22949 text depends on the host system, but which usually looks something like
22950 @samp{Connection refused}. Don't use the @code{load}
22951 command in @value{GDBN} when using @code{target remote} mode, since the
22952 program is already on the target.
22956 @anchor{Monitor Commands for gdbserver}
22957 @subsection Monitor Commands for @code{gdbserver}
22958 @cindex monitor commands, for @code{gdbserver}
22960 During a @value{GDBN} session using @code{gdbserver}, you can use the
22961 @code{monitor} command to send special requests to @code{gdbserver}.
22962 Here are the available commands.
22966 List the available monitor commands.
22968 @item monitor set debug 0
22969 @itemx monitor set debug 1
22970 Disable or enable general debugging messages.
22972 @item monitor set remote-debug 0
22973 @itemx monitor set remote-debug 1
22974 Disable or enable specific debugging messages associated with the remote
22975 protocol (@pxref{Remote Protocol}).
22977 @item monitor set debug-file filename
22978 @itemx monitor set debug-file
22979 Send any debug output to the given file, or to stderr.
22981 @item monitor set debug-format option1@r{[},option2,...@r{]}
22982 Specify additional text to add to debugging messages.
22983 Possible options are:
22987 Turn off all extra information in debugging output.
22989 Turn on all extra information in debugging output.
22991 Include a timestamp in each line of debugging output.
22994 Options are processed in order. Thus, for example, if @option{none}
22995 appears last then no additional information is added to debugging output.
22997 @item monitor set libthread-db-search-path [PATH]
22998 @cindex gdbserver, search path for @code{libthread_db}
22999 When this command is issued, @var{path} is a colon-separated list of
23000 directories to search for @code{libthread_db} (@pxref{Threads,,set
23001 libthread-db-search-path}). If you omit @var{path},
23002 @samp{libthread-db-search-path} will be reset to its default value.
23004 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23005 not supported in @code{gdbserver}.
23008 Tell gdbserver to exit immediately. This command should be followed by
23009 @code{disconnect} to close the debugging session. @code{gdbserver} will
23010 detach from any attached processes and kill any processes it created.
23011 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23012 of a multi-process mode debug session.
23016 @subsection Tracepoints support in @code{gdbserver}
23017 @cindex tracepoints support in @code{gdbserver}
23019 On some targets, @code{gdbserver} supports tracepoints, fast
23020 tracepoints and static tracepoints.
23022 For fast or static tracepoints to work, a special library called the
23023 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23024 This library is built and distributed as an integral part of
23025 @code{gdbserver}. In addition, support for static tracepoints
23026 requires building the in-process agent library with static tracepoints
23027 support. At present, the UST (LTTng Userspace Tracer,
23028 @url{http://lttng.org/ust}) tracing engine is supported. This support
23029 is automatically available if UST development headers are found in the
23030 standard include path when @code{gdbserver} is built, or if
23031 @code{gdbserver} was explicitly configured using @option{--with-ust}
23032 to point at such headers. You can explicitly disable the support
23033 using @option{--with-ust=no}.
23035 There are several ways to load the in-process agent in your program:
23038 @item Specifying it as dependency at link time
23040 You can link your program dynamically with the in-process agent
23041 library. On most systems, this is accomplished by adding
23042 @code{-linproctrace} to the link command.
23044 @item Using the system's preloading mechanisms
23046 You can force loading the in-process agent at startup time by using
23047 your system's support for preloading shared libraries. Many Unixes
23048 support the concept of preloading user defined libraries. In most
23049 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23050 in the environment. See also the description of @code{gdbserver}'s
23051 @option{--wrapper} command line option.
23053 @item Using @value{GDBN} to force loading the agent at run time
23055 On some systems, you can force the inferior to load a shared library,
23056 by calling a dynamic loader function in the inferior that takes care
23057 of dynamically looking up and loading a shared library. On most Unix
23058 systems, the function is @code{dlopen}. You'll use the @code{call}
23059 command for that. For example:
23062 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23065 Note that on most Unix systems, for the @code{dlopen} function to be
23066 available, the program needs to be linked with @code{-ldl}.
23069 On systems that have a userspace dynamic loader, like most Unix
23070 systems, when you connect to @code{gdbserver} using @code{target
23071 remote}, you'll find that the program is stopped at the dynamic
23072 loader's entry point, and no shared library has been loaded in the
23073 program's address space yet, including the in-process agent. In that
23074 case, before being able to use any of the fast or static tracepoints
23075 features, you need to let the loader run and load the shared
23076 libraries. The simplest way to do that is to run the program to the
23077 main procedure. E.g., if debugging a C or C@t{++} program, start
23078 @code{gdbserver} like so:
23081 $ gdbserver :9999 myprogram
23084 Start GDB and connect to @code{gdbserver} like so, and run to main:
23088 (@value{GDBP}) target remote myhost:9999
23089 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23090 (@value{GDBP}) b main
23091 (@value{GDBP}) continue
23094 The in-process tracing agent library should now be loaded into the
23095 process; you can confirm it with the @code{info sharedlibrary}
23096 command, which will list @file{libinproctrace.so} as loaded in the
23097 process. You are now ready to install fast tracepoints, list static
23098 tracepoint markers, probe static tracepoints markers, and start
23101 @node Remote Configuration
23102 @section Remote Configuration
23105 @kindex show remote
23106 This section documents the configuration options available when
23107 debugging remote programs. For the options related to the File I/O
23108 extensions of the remote protocol, see @ref{system,
23109 system-call-allowed}.
23112 @item set remoteaddresssize @var{bits}
23113 @cindex address size for remote targets
23114 @cindex bits in remote address
23115 Set the maximum size of address in a memory packet to the specified
23116 number of bits. @value{GDBN} will mask off the address bits above
23117 that number, when it passes addresses to the remote target. The
23118 default value is the number of bits in the target's address.
23120 @item show remoteaddresssize
23121 Show the current value of remote address size in bits.
23123 @item set serial baud @var{n}
23124 @cindex baud rate for remote targets
23125 Set the baud rate for the remote serial I/O to @var{n} baud. The
23126 value is used to set the speed of the serial port used for debugging
23129 @item show serial baud
23130 Show the current speed of the remote connection.
23132 @item set serial parity @var{parity}
23133 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23134 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23136 @item show serial parity
23137 Show the current parity of the serial port.
23139 @item set remotebreak
23140 @cindex interrupt remote programs
23141 @cindex BREAK signal instead of Ctrl-C
23142 @anchor{set remotebreak}
23143 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23144 when you type @kbd{Ctrl-c} to interrupt the program running
23145 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23146 character instead. The default is off, since most remote systems
23147 expect to see @samp{Ctrl-C} as the interrupt signal.
23149 @item show remotebreak
23150 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23151 interrupt the remote program.
23153 @item set remoteflow on
23154 @itemx set remoteflow off
23155 @kindex set remoteflow
23156 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23157 on the serial port used to communicate to the remote target.
23159 @item show remoteflow
23160 @kindex show remoteflow
23161 Show the current setting of hardware flow control.
23163 @item set remotelogbase @var{base}
23164 Set the base (a.k.a.@: radix) of logging serial protocol
23165 communications to @var{base}. Supported values of @var{base} are:
23166 @code{ascii}, @code{octal}, and @code{hex}. The default is
23169 @item show remotelogbase
23170 Show the current setting of the radix for logging remote serial
23173 @item set remotelogfile @var{file}
23174 @cindex record serial communications on file
23175 Record remote serial communications on the named @var{file}. The
23176 default is not to record at all.
23178 @item show remotelogfile
23179 Show the current setting of the file name on which to record the
23180 serial communications.
23182 @item set remotetimeout @var{num}
23183 @cindex timeout for serial communications
23184 @cindex remote timeout
23185 Set the timeout limit to wait for the remote target to respond to
23186 @var{num} seconds. The default is 2 seconds.
23188 @item show remotetimeout
23189 Show the current number of seconds to wait for the remote target
23192 @cindex limit hardware breakpoints and watchpoints
23193 @cindex remote target, limit break- and watchpoints
23194 @anchor{set remote hardware-watchpoint-limit}
23195 @anchor{set remote hardware-breakpoint-limit}
23196 @item set remote hardware-watchpoint-limit @var{limit}
23197 @itemx set remote hardware-breakpoint-limit @var{limit}
23198 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23199 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23200 watchpoints or breakpoints, and @code{unlimited} for unlimited
23201 watchpoints or breakpoints.
23203 @item show remote hardware-watchpoint-limit
23204 @itemx show remote hardware-breakpoint-limit
23205 Show the current limit for the number of hardware watchpoints or
23206 breakpoints that @value{GDBN} can use.
23208 @cindex limit hardware watchpoints length
23209 @cindex remote target, limit watchpoints length
23210 @anchor{set remote hardware-watchpoint-length-limit}
23211 @item set remote hardware-watchpoint-length-limit @var{limit}
23212 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23213 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23214 hardware watchpoints and @code{unlimited} allows watchpoints of any
23217 @item show remote hardware-watchpoint-length-limit
23218 Show the current limit (in bytes) of the maximum length of
23219 a remote hardware watchpoint.
23221 @item set remote exec-file @var{filename}
23222 @itemx show remote exec-file
23223 @anchor{set remote exec-file}
23224 @cindex executable file, for remote target
23225 Select the file used for @code{run} with @code{target
23226 extended-remote}. This should be set to a filename valid on the
23227 target system. If it is not set, the target will use a default
23228 filename (e.g.@: the last program run).
23230 @item set remote interrupt-sequence
23231 @cindex interrupt remote programs
23232 @cindex select Ctrl-C, BREAK or BREAK-g
23233 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23234 @samp{BREAK-g} as the
23235 sequence to the remote target in order to interrupt the execution.
23236 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23237 is high level of serial line for some certain time.
23238 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23239 It is @code{BREAK} signal followed by character @code{g}.
23241 @item show remote interrupt-sequence
23242 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23243 is sent by @value{GDBN} to interrupt the remote program.
23244 @code{BREAK-g} is BREAK signal followed by @code{g} and
23245 also known as Magic SysRq g.
23247 @item set remote interrupt-on-connect
23248 @cindex send interrupt-sequence on start
23249 Specify whether interrupt-sequence is sent to remote target when
23250 @value{GDBN} connects to it. This is mostly needed when you debug
23251 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23252 which is known as Magic SysRq g in order to connect @value{GDBN}.
23254 @item show remote interrupt-on-connect
23255 Show whether interrupt-sequence is sent
23256 to remote target when @value{GDBN} connects to it.
23260 @item set tcp auto-retry on
23261 @cindex auto-retry, for remote TCP target
23262 Enable auto-retry for remote TCP connections. This is useful if the remote
23263 debugging agent is launched in parallel with @value{GDBN}; there is a race
23264 condition because the agent may not become ready to accept the connection
23265 before @value{GDBN} attempts to connect. When auto-retry is
23266 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23267 to establish the connection using the timeout specified by
23268 @code{set tcp connect-timeout}.
23270 @item set tcp auto-retry off
23271 Do not auto-retry failed TCP connections.
23273 @item show tcp auto-retry
23274 Show the current auto-retry setting.
23276 @item set tcp connect-timeout @var{seconds}
23277 @itemx set tcp connect-timeout unlimited
23278 @cindex connection timeout, for remote TCP target
23279 @cindex timeout, for remote target connection
23280 Set the timeout for establishing a TCP connection to the remote target to
23281 @var{seconds}. The timeout affects both polling to retry failed connections
23282 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23283 that are merely slow to complete, and represents an approximate cumulative
23284 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23285 @value{GDBN} will keep attempting to establish a connection forever,
23286 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23288 @item show tcp connect-timeout
23289 Show the current connection timeout setting.
23292 @cindex remote packets, enabling and disabling
23293 The @value{GDBN} remote protocol autodetects the packets supported by
23294 your debugging stub. If you need to override the autodetection, you
23295 can use these commands to enable or disable individual packets. Each
23296 packet can be set to @samp{on} (the remote target supports this
23297 packet), @samp{off} (the remote target does not support this packet),
23298 or @samp{auto} (detect remote target support for this packet). They
23299 all default to @samp{auto}. For more information about each packet,
23300 see @ref{Remote Protocol}.
23302 During normal use, you should not have to use any of these commands.
23303 If you do, that may be a bug in your remote debugging stub, or a bug
23304 in @value{GDBN}. You may want to report the problem to the
23305 @value{GDBN} developers.
23307 For each packet @var{name}, the command to enable or disable the
23308 packet is @code{set remote @var{name}-packet}. The available settings
23311 @multitable @columnfractions 0.28 0.32 0.25
23314 @tab Related Features
23316 @item @code{fetch-register}
23318 @tab @code{info registers}
23320 @item @code{set-register}
23324 @item @code{binary-download}
23326 @tab @code{load}, @code{set}
23328 @item @code{read-aux-vector}
23329 @tab @code{qXfer:auxv:read}
23330 @tab @code{info auxv}
23332 @item @code{symbol-lookup}
23333 @tab @code{qSymbol}
23334 @tab Detecting multiple threads
23336 @item @code{attach}
23337 @tab @code{vAttach}
23340 @item @code{verbose-resume}
23342 @tab Stepping or resuming multiple threads
23348 @item @code{software-breakpoint}
23352 @item @code{hardware-breakpoint}
23356 @item @code{write-watchpoint}
23360 @item @code{read-watchpoint}
23364 @item @code{access-watchpoint}
23368 @item @code{pid-to-exec-file}
23369 @tab @code{qXfer:exec-file:read}
23370 @tab @code{attach}, @code{run}
23372 @item @code{target-features}
23373 @tab @code{qXfer:features:read}
23374 @tab @code{set architecture}
23376 @item @code{library-info}
23377 @tab @code{qXfer:libraries:read}
23378 @tab @code{info sharedlibrary}
23380 @item @code{memory-map}
23381 @tab @code{qXfer:memory-map:read}
23382 @tab @code{info mem}
23384 @item @code{read-sdata-object}
23385 @tab @code{qXfer:sdata:read}
23386 @tab @code{print $_sdata}
23388 @item @code{read-siginfo-object}
23389 @tab @code{qXfer:siginfo:read}
23390 @tab @code{print $_siginfo}
23392 @item @code{write-siginfo-object}
23393 @tab @code{qXfer:siginfo:write}
23394 @tab @code{set $_siginfo}
23396 @item @code{threads}
23397 @tab @code{qXfer:threads:read}
23398 @tab @code{info threads}
23400 @item @code{get-thread-local-@*storage-address}
23401 @tab @code{qGetTLSAddr}
23402 @tab Displaying @code{__thread} variables
23404 @item @code{get-thread-information-block-address}
23405 @tab @code{qGetTIBAddr}
23406 @tab Display MS-Windows Thread Information Block.
23408 @item @code{search-memory}
23409 @tab @code{qSearch:memory}
23412 @item @code{supported-packets}
23413 @tab @code{qSupported}
23414 @tab Remote communications parameters
23416 @item @code{catch-syscalls}
23417 @tab @code{QCatchSyscalls}
23418 @tab @code{catch syscall}
23420 @item @code{pass-signals}
23421 @tab @code{QPassSignals}
23422 @tab @code{handle @var{signal}}
23424 @item @code{program-signals}
23425 @tab @code{QProgramSignals}
23426 @tab @code{handle @var{signal}}
23428 @item @code{hostio-close-packet}
23429 @tab @code{vFile:close}
23430 @tab @code{remote get}, @code{remote put}
23432 @item @code{hostio-open-packet}
23433 @tab @code{vFile:open}
23434 @tab @code{remote get}, @code{remote put}
23436 @item @code{hostio-pread-packet}
23437 @tab @code{vFile:pread}
23438 @tab @code{remote get}, @code{remote put}
23440 @item @code{hostio-pwrite-packet}
23441 @tab @code{vFile:pwrite}
23442 @tab @code{remote get}, @code{remote put}
23444 @item @code{hostio-unlink-packet}
23445 @tab @code{vFile:unlink}
23446 @tab @code{remote delete}
23448 @item @code{hostio-readlink-packet}
23449 @tab @code{vFile:readlink}
23452 @item @code{hostio-fstat-packet}
23453 @tab @code{vFile:fstat}
23456 @item @code{hostio-setfs-packet}
23457 @tab @code{vFile:setfs}
23460 @item @code{noack-packet}
23461 @tab @code{QStartNoAckMode}
23462 @tab Packet acknowledgment
23464 @item @code{osdata}
23465 @tab @code{qXfer:osdata:read}
23466 @tab @code{info os}
23468 @item @code{query-attached}
23469 @tab @code{qAttached}
23470 @tab Querying remote process attach state.
23472 @item @code{trace-buffer-size}
23473 @tab @code{QTBuffer:size}
23474 @tab @code{set trace-buffer-size}
23476 @item @code{trace-status}
23477 @tab @code{qTStatus}
23478 @tab @code{tstatus}
23480 @item @code{traceframe-info}
23481 @tab @code{qXfer:traceframe-info:read}
23482 @tab Traceframe info
23484 @item @code{install-in-trace}
23485 @tab @code{InstallInTrace}
23486 @tab Install tracepoint in tracing
23488 @item @code{disable-randomization}
23489 @tab @code{QDisableRandomization}
23490 @tab @code{set disable-randomization}
23492 @item @code{startup-with-shell}
23493 @tab @code{QStartupWithShell}
23494 @tab @code{set startup-with-shell}
23496 @item @code{environment-hex-encoded}
23497 @tab @code{QEnvironmentHexEncoded}
23498 @tab @code{set environment}
23500 @item @code{environment-unset}
23501 @tab @code{QEnvironmentUnset}
23502 @tab @code{unset environment}
23504 @item @code{environment-reset}
23505 @tab @code{QEnvironmentReset}
23506 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23508 @item @code{set-working-dir}
23509 @tab @code{QSetWorkingDir}
23510 @tab @code{set cwd}
23512 @item @code{conditional-breakpoints-packet}
23513 @tab @code{Z0 and Z1}
23514 @tab @code{Support for target-side breakpoint condition evaluation}
23516 @item @code{multiprocess-extensions}
23517 @tab @code{multiprocess extensions}
23518 @tab Debug multiple processes and remote process PID awareness
23520 @item @code{swbreak-feature}
23521 @tab @code{swbreak stop reason}
23524 @item @code{hwbreak-feature}
23525 @tab @code{hwbreak stop reason}
23528 @item @code{fork-event-feature}
23529 @tab @code{fork stop reason}
23532 @item @code{vfork-event-feature}
23533 @tab @code{vfork stop reason}
23536 @item @code{exec-event-feature}
23537 @tab @code{exec stop reason}
23540 @item @code{thread-events}
23541 @tab @code{QThreadEvents}
23542 @tab Tracking thread lifetime.
23544 @item @code{no-resumed-stop-reply}
23545 @tab @code{no resumed thread left stop reply}
23546 @tab Tracking thread lifetime.
23551 @section Implementing a Remote Stub
23553 @cindex debugging stub, example
23554 @cindex remote stub, example
23555 @cindex stub example, remote debugging
23556 The stub files provided with @value{GDBN} implement the target side of the
23557 communication protocol, and the @value{GDBN} side is implemented in the
23558 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23559 these subroutines to communicate, and ignore the details. (If you're
23560 implementing your own stub file, you can still ignore the details: start
23561 with one of the existing stub files. @file{sparc-stub.c} is the best
23562 organized, and therefore the easiest to read.)
23564 @cindex remote serial debugging, overview
23565 To debug a program running on another machine (the debugging
23566 @dfn{target} machine), you must first arrange for all the usual
23567 prerequisites for the program to run by itself. For example, for a C
23572 A startup routine to set up the C runtime environment; these usually
23573 have a name like @file{crt0}. The startup routine may be supplied by
23574 your hardware supplier, or you may have to write your own.
23577 A C subroutine library to support your program's
23578 subroutine calls, notably managing input and output.
23581 A way of getting your program to the other machine---for example, a
23582 download program. These are often supplied by the hardware
23583 manufacturer, but you may have to write your own from hardware
23587 The next step is to arrange for your program to use a serial port to
23588 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23589 machine). In general terms, the scheme looks like this:
23593 @value{GDBN} already understands how to use this protocol; when everything
23594 else is set up, you can simply use the @samp{target remote} command
23595 (@pxref{Targets,,Specifying a Debugging Target}).
23597 @item On the target,
23598 you must link with your program a few special-purpose subroutines that
23599 implement the @value{GDBN} remote serial protocol. The file containing these
23600 subroutines is called a @dfn{debugging stub}.
23602 On certain remote targets, you can use an auxiliary program
23603 @code{gdbserver} instead of linking a stub into your program.
23604 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23607 The debugging stub is specific to the architecture of the remote
23608 machine; for example, use @file{sparc-stub.c} to debug programs on
23611 @cindex remote serial stub list
23612 These working remote stubs are distributed with @value{GDBN}:
23617 @cindex @file{i386-stub.c}
23620 For Intel 386 and compatible architectures.
23623 @cindex @file{m68k-stub.c}
23624 @cindex Motorola 680x0
23626 For Motorola 680x0 architectures.
23629 @cindex @file{sh-stub.c}
23632 For Renesas SH architectures.
23635 @cindex @file{sparc-stub.c}
23637 For @sc{sparc} architectures.
23639 @item sparcl-stub.c
23640 @cindex @file{sparcl-stub.c}
23643 For Fujitsu @sc{sparclite} architectures.
23647 The @file{README} file in the @value{GDBN} distribution may list other
23648 recently added stubs.
23651 * Stub Contents:: What the stub can do for you
23652 * Bootstrapping:: What you must do for the stub
23653 * Debug Session:: Putting it all together
23656 @node Stub Contents
23657 @subsection What the Stub Can Do for You
23659 @cindex remote serial stub
23660 The debugging stub for your architecture supplies these three
23664 @item set_debug_traps
23665 @findex set_debug_traps
23666 @cindex remote serial stub, initialization
23667 This routine arranges for @code{handle_exception} to run when your
23668 program stops. You must call this subroutine explicitly in your
23669 program's startup code.
23671 @item handle_exception
23672 @findex handle_exception
23673 @cindex remote serial stub, main routine
23674 This is the central workhorse, but your program never calls it
23675 explicitly---the setup code arranges for @code{handle_exception} to
23676 run when a trap is triggered.
23678 @code{handle_exception} takes control when your program stops during
23679 execution (for example, on a breakpoint), and mediates communications
23680 with @value{GDBN} on the host machine. This is where the communications
23681 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23682 representative on the target machine. It begins by sending summary
23683 information on the state of your program, then continues to execute,
23684 retrieving and transmitting any information @value{GDBN} needs, until you
23685 execute a @value{GDBN} command that makes your program resume; at that point,
23686 @code{handle_exception} returns control to your own code on the target
23690 @cindex @code{breakpoint} subroutine, remote
23691 Use this auxiliary subroutine to make your program contain a
23692 breakpoint. Depending on the particular situation, this may be the only
23693 way for @value{GDBN} to get control. For instance, if your target
23694 machine has some sort of interrupt button, you won't need to call this;
23695 pressing the interrupt button transfers control to
23696 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23697 simply receiving characters on the serial port may also trigger a trap;
23698 again, in that situation, you don't need to call @code{breakpoint} from
23699 your own program---simply running @samp{target remote} from the host
23700 @value{GDBN} session gets control.
23702 Call @code{breakpoint} if none of these is true, or if you simply want
23703 to make certain your program stops at a predetermined point for the
23704 start of your debugging session.
23707 @node Bootstrapping
23708 @subsection What You Must Do for the Stub
23710 @cindex remote stub, support routines
23711 The debugging stubs that come with @value{GDBN} are set up for a particular
23712 chip architecture, but they have no information about the rest of your
23713 debugging target machine.
23715 First of all you need to tell the stub how to communicate with the
23719 @item int getDebugChar()
23720 @findex getDebugChar
23721 Write this subroutine to read a single character from the serial port.
23722 It may be identical to @code{getchar} for your target system; a
23723 different name is used to allow you to distinguish the two if you wish.
23725 @item void putDebugChar(int)
23726 @findex putDebugChar
23727 Write this subroutine to write a single character to the serial port.
23728 It may be identical to @code{putchar} for your target system; a
23729 different name is used to allow you to distinguish the two if you wish.
23732 @cindex control C, and remote debugging
23733 @cindex interrupting remote targets
23734 If you want @value{GDBN} to be able to stop your program while it is
23735 running, you need to use an interrupt-driven serial driver, and arrange
23736 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23737 character). That is the character which @value{GDBN} uses to tell the
23738 remote system to stop.
23740 Getting the debugging target to return the proper status to @value{GDBN}
23741 probably requires changes to the standard stub; one quick and dirty way
23742 is to just execute a breakpoint instruction (the ``dirty'' part is that
23743 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23745 Other routines you need to supply are:
23748 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23749 @findex exceptionHandler
23750 Write this function to install @var{exception_address} in the exception
23751 handling tables. You need to do this because the stub does not have any
23752 way of knowing what the exception handling tables on your target system
23753 are like (for example, the processor's table might be in @sc{rom},
23754 containing entries which point to a table in @sc{ram}).
23755 The @var{exception_number} specifies the exception which should be changed;
23756 its meaning is architecture-dependent (for example, different numbers
23757 might represent divide by zero, misaligned access, etc). When this
23758 exception occurs, control should be transferred directly to
23759 @var{exception_address}, and the processor state (stack, registers,
23760 and so on) should be just as it is when a processor exception occurs. So if
23761 you want to use a jump instruction to reach @var{exception_address}, it
23762 should be a simple jump, not a jump to subroutine.
23764 For the 386, @var{exception_address} should be installed as an interrupt
23765 gate so that interrupts are masked while the handler runs. The gate
23766 should be at privilege level 0 (the most privileged level). The
23767 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23768 help from @code{exceptionHandler}.
23770 @item void flush_i_cache()
23771 @findex flush_i_cache
23772 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23773 instruction cache, if any, on your target machine. If there is no
23774 instruction cache, this subroutine may be a no-op.
23776 On target machines that have instruction caches, @value{GDBN} requires this
23777 function to make certain that the state of your program is stable.
23781 You must also make sure this library routine is available:
23784 @item void *memset(void *, int, int)
23786 This is the standard library function @code{memset} that sets an area of
23787 memory to a known value. If you have one of the free versions of
23788 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23789 either obtain it from your hardware manufacturer, or write your own.
23792 If you do not use the GNU C compiler, you may need other standard
23793 library subroutines as well; this varies from one stub to another,
23794 but in general the stubs are likely to use any of the common library
23795 subroutines which @code{@value{NGCC}} generates as inline code.
23798 @node Debug Session
23799 @subsection Putting it All Together
23801 @cindex remote serial debugging summary
23802 In summary, when your program is ready to debug, you must follow these
23807 Make sure you have defined the supporting low-level routines
23808 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23810 @code{getDebugChar}, @code{putDebugChar},
23811 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23815 Insert these lines in your program's startup code, before the main
23816 procedure is called:
23823 On some machines, when a breakpoint trap is raised, the hardware
23824 automatically makes the PC point to the instruction after the
23825 breakpoint. If your machine doesn't do that, you may need to adjust
23826 @code{handle_exception} to arrange for it to return to the instruction
23827 after the breakpoint on this first invocation, so that your program
23828 doesn't keep hitting the initial breakpoint instead of making
23832 For the 680x0 stub only, you need to provide a variable called
23833 @code{exceptionHook}. Normally you just use:
23836 void (*exceptionHook)() = 0;
23840 but if before calling @code{set_debug_traps}, you set it to point to a
23841 function in your program, that function is called when
23842 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23843 error). The function indicated by @code{exceptionHook} is called with
23844 one parameter: an @code{int} which is the exception number.
23847 Compile and link together: your program, the @value{GDBN} debugging stub for
23848 your target architecture, and the supporting subroutines.
23851 Make sure you have a serial connection between your target machine and
23852 the @value{GDBN} host, and identify the serial port on the host.
23855 @c The "remote" target now provides a `load' command, so we should
23856 @c document that. FIXME.
23857 Download your program to your target machine (or get it there by
23858 whatever means the manufacturer provides), and start it.
23861 Start @value{GDBN} on the host, and connect to the target
23862 (@pxref{Connecting,,Connecting to a Remote Target}).
23866 @node Configurations
23867 @chapter Configuration-Specific Information
23869 While nearly all @value{GDBN} commands are available for all native and
23870 cross versions of the debugger, there are some exceptions. This chapter
23871 describes things that are only available in certain configurations.
23873 There are three major categories of configurations: native
23874 configurations, where the host and target are the same, embedded
23875 operating system configurations, which are usually the same for several
23876 different processor architectures, and bare embedded processors, which
23877 are quite different from each other.
23882 * Embedded Processors::
23889 This section describes details specific to particular native
23893 * BSD libkvm Interface:: Debugging BSD kernel memory images
23894 * Process Information:: Process information
23895 * DJGPP Native:: Features specific to the DJGPP port
23896 * Cygwin Native:: Features specific to the Cygwin port
23897 * Hurd Native:: Features specific to @sc{gnu} Hurd
23898 * Darwin:: Features specific to Darwin
23899 * FreeBSD:: Features specific to FreeBSD
23902 @node BSD libkvm Interface
23903 @subsection BSD libkvm Interface
23906 @cindex kernel memory image
23907 @cindex kernel crash dump
23909 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23910 interface that provides a uniform interface for accessing kernel virtual
23911 memory images, including live systems and crash dumps. @value{GDBN}
23912 uses this interface to allow you to debug live kernels and kernel crash
23913 dumps on many native BSD configurations. This is implemented as a
23914 special @code{kvm} debugging target. For debugging a live system, load
23915 the currently running kernel into @value{GDBN} and connect to the
23919 (@value{GDBP}) @b{target kvm}
23922 For debugging crash dumps, provide the file name of the crash dump as an
23926 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23929 Once connected to the @code{kvm} target, the following commands are
23935 Set current context from the @dfn{Process Control Block} (PCB) address.
23938 Set current context from proc address. This command isn't available on
23939 modern FreeBSD systems.
23942 @node Process Information
23943 @subsection Process Information
23945 @cindex examine process image
23946 @cindex process info via @file{/proc}
23948 Some operating systems provide interfaces to fetch additional
23949 information about running processes beyond memory and per-thread
23950 register state. If @value{GDBN} is configured for an operating system
23951 with a supported interface, the command @code{info proc} is available
23952 to report information about the process running your program, or about
23953 any process running on your system.
23955 One supported interface is a facility called @samp{/proc} that can be
23956 used to examine the image of a running process using file-system
23957 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23960 On FreeBSD and NetBSD systems, system control nodes are used to query
23961 process information.
23963 In addition, some systems may provide additional process information
23964 in core files. Note that a core file may include a subset of the
23965 information available from a live process. Process information is
23966 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23973 @itemx info proc @var{process-id}
23974 Summarize available information about a process. If a
23975 process ID is specified by @var{process-id}, display information about
23976 that process; otherwise display information about the program being
23977 debugged. The summary includes the debugged process ID, the command
23978 line used to invoke it, its current working directory, and its
23979 executable file's absolute file name.
23981 On some systems, @var{process-id} can be of the form
23982 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23983 within a process. If the optional @var{pid} part is missing, it means
23984 a thread from the process being debugged (the leading @samp{/} still
23985 needs to be present, or else @value{GDBN} will interpret the number as
23986 a process ID rather than a thread ID).
23988 @item info proc cmdline
23989 @cindex info proc cmdline
23990 Show the original command line of the process. This command is
23991 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23993 @item info proc cwd
23994 @cindex info proc cwd
23995 Show the current working directory of the process. This command is
23996 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23998 @item info proc exe
23999 @cindex info proc exe
24000 Show the name of executable of the process. This command is supported
24001 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24003 @item info proc files
24004 @cindex info proc files
24005 Show the file descriptors open by the process. For each open file
24006 descriptor, @value{GDBN} shows its number, type (file, directory,
24007 character device, socket), file pointer offset, and the name of the
24008 resource open on the descriptor. The resource name can be a file name
24009 (for files, directories, and devices) or a protocol followed by socket
24010 address (for network connections). This command is supported on
24013 This example shows the open file descriptors for a process using a
24014 tty for standard input and output as well as two network sockets:
24017 (gdb) info proc files 22136
24021 FD Type Offset Flags Name
24022 text file - r-------- /usr/bin/ssh
24023 ctty chr - rw------- /dev/pts/20
24024 cwd dir - r-------- /usr/home/john
24025 root dir - r-------- /
24026 0 chr 0x32933a4 rw------- /dev/pts/20
24027 1 chr 0x32933a4 rw------- /dev/pts/20
24028 2 chr 0x32933a4 rw------- /dev/pts/20
24029 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24030 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24033 @item info proc mappings
24034 @cindex memory address space mappings
24035 Report the memory address space ranges accessible in a process. On
24036 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24037 on whether the process has read, write, or execute access rights to each
24038 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24039 includes the object file which is mapped to that range.
24041 @item info proc stat
24042 @itemx info proc status
24043 @cindex process detailed status information
24044 Show additional process-related information, including the user ID and
24045 group ID; virtual memory usage; the signals that are pending, blocked,
24046 and ignored; its TTY; its consumption of system and user time; its
24047 stack size; its @samp{nice} value; etc. These commands are supported
24048 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24050 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24051 information (type @kbd{man 5 proc} from your shell prompt).
24053 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24054 @code{info proc status}.
24056 @item info proc all
24057 Show all the information about the process described under all of the
24058 above @code{info proc} subcommands.
24061 @comment These sub-options of 'info proc' were not included when
24062 @comment procfs.c was re-written. Keep their descriptions around
24063 @comment against the day when someone finds the time to put them back in.
24064 @kindex info proc times
24065 @item info proc times
24066 Starting time, user CPU time, and system CPU time for your program and
24069 @kindex info proc id
24071 Report on the process IDs related to your program: its own process ID,
24072 the ID of its parent, the process group ID, and the session ID.
24075 @item set procfs-trace
24076 @kindex set procfs-trace
24077 @cindex @code{procfs} API calls
24078 This command enables and disables tracing of @code{procfs} API calls.
24080 @item show procfs-trace
24081 @kindex show procfs-trace
24082 Show the current state of @code{procfs} API call tracing.
24084 @item set procfs-file @var{file}
24085 @kindex set procfs-file
24086 Tell @value{GDBN} to write @code{procfs} API trace to the named
24087 @var{file}. @value{GDBN} appends the trace info to the previous
24088 contents of the file. The default is to display the trace on the
24091 @item show procfs-file
24092 @kindex show procfs-file
24093 Show the file to which @code{procfs} API trace is written.
24095 @item proc-trace-entry
24096 @itemx proc-trace-exit
24097 @itemx proc-untrace-entry
24098 @itemx proc-untrace-exit
24099 @kindex proc-trace-entry
24100 @kindex proc-trace-exit
24101 @kindex proc-untrace-entry
24102 @kindex proc-untrace-exit
24103 These commands enable and disable tracing of entries into and exits
24104 from the @code{syscall} interface.
24107 @kindex info pidlist
24108 @cindex process list, QNX Neutrino
24109 For QNX Neutrino only, this command displays the list of all the
24110 processes and all the threads within each process.
24113 @kindex info meminfo
24114 @cindex mapinfo list, QNX Neutrino
24115 For QNX Neutrino only, this command displays the list of all mapinfos.
24119 @subsection Features for Debugging @sc{djgpp} Programs
24120 @cindex @sc{djgpp} debugging
24121 @cindex native @sc{djgpp} debugging
24122 @cindex MS-DOS-specific commands
24125 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24126 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24127 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24128 top of real-mode DOS systems and their emulations.
24130 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24131 defines a few commands specific to the @sc{djgpp} port. This
24132 subsection describes those commands.
24137 This is a prefix of @sc{djgpp}-specific commands which print
24138 information about the target system and important OS structures.
24141 @cindex MS-DOS system info
24142 @cindex free memory information (MS-DOS)
24143 @item info dos sysinfo
24144 This command displays assorted information about the underlying
24145 platform: the CPU type and features, the OS version and flavor, the
24146 DPMI version, and the available conventional and DPMI memory.
24151 @cindex segment descriptor tables
24152 @cindex descriptor tables display
24154 @itemx info dos ldt
24155 @itemx info dos idt
24156 These 3 commands display entries from, respectively, Global, Local,
24157 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24158 tables are data structures which store a descriptor for each segment
24159 that is currently in use. The segment's selector is an index into a
24160 descriptor table; the table entry for that index holds the
24161 descriptor's base address and limit, and its attributes and access
24164 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24165 segment (used for both data and the stack), and a DOS segment (which
24166 allows access to DOS/BIOS data structures and absolute addresses in
24167 conventional memory). However, the DPMI host will usually define
24168 additional segments in order to support the DPMI environment.
24170 @cindex garbled pointers
24171 These commands allow to display entries from the descriptor tables.
24172 Without an argument, all entries from the specified table are
24173 displayed. An argument, which should be an integer expression, means
24174 display a single entry whose index is given by the argument. For
24175 example, here's a convenient way to display information about the
24176 debugged program's data segment:
24179 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24180 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24184 This comes in handy when you want to see whether a pointer is outside
24185 the data segment's limit (i.e.@: @dfn{garbled}).
24187 @cindex page tables display (MS-DOS)
24189 @itemx info dos pte
24190 These two commands display entries from, respectively, the Page
24191 Directory and the Page Tables. Page Directories and Page Tables are
24192 data structures which control how virtual memory addresses are mapped
24193 into physical addresses. A Page Table includes an entry for every
24194 page of memory that is mapped into the program's address space; there
24195 may be several Page Tables, each one holding up to 4096 entries. A
24196 Page Directory has up to 4096 entries, one each for every Page Table
24197 that is currently in use.
24199 Without an argument, @kbd{info dos pde} displays the entire Page
24200 Directory, and @kbd{info dos pte} displays all the entries in all of
24201 the Page Tables. An argument, an integer expression, given to the
24202 @kbd{info dos pde} command means display only that entry from the Page
24203 Directory table. An argument given to the @kbd{info dos pte} command
24204 means display entries from a single Page Table, the one pointed to by
24205 the specified entry in the Page Directory.
24207 @cindex direct memory access (DMA) on MS-DOS
24208 These commands are useful when your program uses @dfn{DMA} (Direct
24209 Memory Access), which needs physical addresses to program the DMA
24212 These commands are supported only with some DPMI servers.
24214 @cindex physical address from linear address
24215 @item info dos address-pte @var{addr}
24216 This command displays the Page Table entry for a specified linear
24217 address. The argument @var{addr} is a linear address which should
24218 already have the appropriate segment's base address added to it,
24219 because this command accepts addresses which may belong to @emph{any}
24220 segment. For example, here's how to display the Page Table entry for
24221 the page where a variable @code{i} is stored:
24224 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24225 @exdent @code{Page Table entry for address 0x11a00d30:}
24226 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24230 This says that @code{i} is stored at offset @code{0xd30} from the page
24231 whose physical base address is @code{0x02698000}, and shows all the
24232 attributes of that page.
24234 Note that you must cast the addresses of variables to a @code{char *},
24235 since otherwise the value of @code{__djgpp_base_address}, the base
24236 address of all variables and functions in a @sc{djgpp} program, will
24237 be added using the rules of C pointer arithmetics: if @code{i} is
24238 declared an @code{int}, @value{GDBN} will add 4 times the value of
24239 @code{__djgpp_base_address} to the address of @code{i}.
24241 Here's another example, it displays the Page Table entry for the
24245 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24246 @exdent @code{Page Table entry for address 0x29110:}
24247 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24251 (The @code{+ 3} offset is because the transfer buffer's address is the
24252 3rd member of the @code{_go32_info_block} structure.) The output
24253 clearly shows that this DPMI server maps the addresses in conventional
24254 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24255 linear (@code{0x29110}) addresses are identical.
24257 This command is supported only with some DPMI servers.
24260 @cindex DOS serial data link, remote debugging
24261 In addition to native debugging, the DJGPP port supports remote
24262 debugging via a serial data link. The following commands are specific
24263 to remote serial debugging in the DJGPP port of @value{GDBN}.
24266 @kindex set com1base
24267 @kindex set com1irq
24268 @kindex set com2base
24269 @kindex set com2irq
24270 @kindex set com3base
24271 @kindex set com3irq
24272 @kindex set com4base
24273 @kindex set com4irq
24274 @item set com1base @var{addr}
24275 This command sets the base I/O port address of the @file{COM1} serial
24278 @item set com1irq @var{irq}
24279 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24280 for the @file{COM1} serial port.
24282 There are similar commands @samp{set com2base}, @samp{set com3irq},
24283 etc.@: for setting the port address and the @code{IRQ} lines for the
24286 @kindex show com1base
24287 @kindex show com1irq
24288 @kindex show com2base
24289 @kindex show com2irq
24290 @kindex show com3base
24291 @kindex show com3irq
24292 @kindex show com4base
24293 @kindex show com4irq
24294 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24295 display the current settings of the base address and the @code{IRQ}
24296 lines used by the COM ports.
24299 @kindex info serial
24300 @cindex DOS serial port status
24301 This command prints the status of the 4 DOS serial ports. For each
24302 port, it prints whether it's active or not, its I/O base address and
24303 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24304 counts of various errors encountered so far.
24308 @node Cygwin Native
24309 @subsection Features for Debugging MS Windows PE Executables
24310 @cindex MS Windows debugging
24311 @cindex native Cygwin debugging
24312 @cindex Cygwin-specific commands
24314 @value{GDBN} supports native debugging of MS Windows programs, including
24315 DLLs with and without symbolic debugging information.
24317 @cindex Ctrl-BREAK, MS-Windows
24318 @cindex interrupt debuggee on MS-Windows
24319 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24320 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24321 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24322 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24323 sequence, which can be used to interrupt the debuggee even if it
24326 There are various additional Cygwin-specific commands, described in
24327 this section. Working with DLLs that have no debugging symbols is
24328 described in @ref{Non-debug DLL Symbols}.
24333 This is a prefix of MS Windows-specific commands which print
24334 information about the target system and important OS structures.
24336 @item info w32 selector
24337 This command displays information returned by
24338 the Win32 API @code{GetThreadSelectorEntry} function.
24339 It takes an optional argument that is evaluated to
24340 a long value to give the information about this given selector.
24341 Without argument, this command displays information
24342 about the six segment registers.
24344 @item info w32 thread-information-block
24345 This command displays thread specific information stored in the
24346 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24347 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24349 @kindex signal-event
24350 @item signal-event @var{id}
24351 This command signals an event with user-provided @var{id}. Used to resume
24352 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24354 To use it, create or edit the following keys in
24355 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24356 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24357 (for x86_64 versions):
24361 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24362 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24363 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24365 The first @code{%ld} will be replaced by the process ID of the
24366 crashing process, the second @code{%ld} will be replaced by the ID of
24367 the event that blocks the crashing process, waiting for @value{GDBN}
24371 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24372 make the system run debugger specified by the Debugger key
24373 automatically, @code{0} will cause a dialog box with ``OK'' and
24374 ``Cancel'' buttons to appear, which allows the user to either
24375 terminate the crashing process (OK) or debug it (Cancel).
24378 @kindex set cygwin-exceptions
24379 @cindex debugging the Cygwin DLL
24380 @cindex Cygwin DLL, debugging
24381 @item set cygwin-exceptions @var{mode}
24382 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24383 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24384 @value{GDBN} will delay recognition of exceptions, and may ignore some
24385 exceptions which seem to be caused by internal Cygwin DLL
24386 ``bookkeeping''. This option is meant primarily for debugging the
24387 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24388 @value{GDBN} users with false @code{SIGSEGV} signals.
24390 @kindex show cygwin-exceptions
24391 @item show cygwin-exceptions
24392 Displays whether @value{GDBN} will break on exceptions that happen
24393 inside the Cygwin DLL itself.
24395 @kindex set new-console
24396 @item set new-console @var{mode}
24397 If @var{mode} is @code{on} the debuggee will
24398 be started in a new console on next start.
24399 If @var{mode} is @code{off}, the debuggee will
24400 be started in the same console as the debugger.
24402 @kindex show new-console
24403 @item show new-console
24404 Displays whether a new console is used
24405 when the debuggee is started.
24407 @kindex set new-group
24408 @item set new-group @var{mode}
24409 This boolean value controls whether the debuggee should
24410 start a new group or stay in the same group as the debugger.
24411 This affects the way the Windows OS handles
24414 @kindex show new-group
24415 @item show new-group
24416 Displays current value of new-group boolean.
24418 @kindex set debugevents
24419 @item set debugevents
24420 This boolean value adds debug output concerning kernel events related
24421 to the debuggee seen by the debugger. This includes events that
24422 signal thread and process creation and exit, DLL loading and
24423 unloading, console interrupts, and debugging messages produced by the
24424 Windows @code{OutputDebugString} API call.
24426 @kindex set debugexec
24427 @item set debugexec
24428 This boolean value adds debug output concerning execute events
24429 (such as resume thread) seen by the debugger.
24431 @kindex set debugexceptions
24432 @item set debugexceptions
24433 This boolean value adds debug output concerning exceptions in the
24434 debuggee seen by the debugger.
24436 @kindex set debugmemory
24437 @item set debugmemory
24438 This boolean value adds debug output concerning debuggee memory reads
24439 and writes by the debugger.
24443 This boolean values specifies whether the debuggee is called
24444 via a shell or directly (default value is on).
24448 Displays if the debuggee will be started with a shell.
24453 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24456 @node Non-debug DLL Symbols
24457 @subsubsection Support for DLLs without Debugging Symbols
24458 @cindex DLLs with no debugging symbols
24459 @cindex Minimal symbols and DLLs
24461 Very often on windows, some of the DLLs that your program relies on do
24462 not include symbolic debugging information (for example,
24463 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24464 symbols in a DLL, it relies on the minimal amount of symbolic
24465 information contained in the DLL's export table. This section
24466 describes working with such symbols, known internally to @value{GDBN} as
24467 ``minimal symbols''.
24469 Note that before the debugged program has started execution, no DLLs
24470 will have been loaded. The easiest way around this problem is simply to
24471 start the program --- either by setting a breakpoint or letting the
24472 program run once to completion.
24474 @subsubsection DLL Name Prefixes
24476 In keeping with the naming conventions used by the Microsoft debugging
24477 tools, DLL export symbols are made available with a prefix based on the
24478 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24479 also entered into the symbol table, so @code{CreateFileA} is often
24480 sufficient. In some cases there will be name clashes within a program
24481 (particularly if the executable itself includes full debugging symbols)
24482 necessitating the use of the fully qualified name when referring to the
24483 contents of the DLL. Use single-quotes around the name to avoid the
24484 exclamation mark (``!'') being interpreted as a language operator.
24486 Note that the internal name of the DLL may be all upper-case, even
24487 though the file name of the DLL is lower-case, or vice-versa. Since
24488 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24489 some confusion. If in doubt, try the @code{info functions} and
24490 @code{info variables} commands or even @code{maint print msymbols}
24491 (@pxref{Symbols}). Here's an example:
24494 (@value{GDBP}) info function CreateFileA
24495 All functions matching regular expression "CreateFileA":
24497 Non-debugging symbols:
24498 0x77e885f4 CreateFileA
24499 0x77e885f4 KERNEL32!CreateFileA
24503 (@value{GDBP}) info function !
24504 All functions matching regular expression "!":
24506 Non-debugging symbols:
24507 0x6100114c cygwin1!__assert
24508 0x61004034 cygwin1!_dll_crt0@@0
24509 0x61004240 cygwin1!dll_crt0(per_process *)
24513 @subsubsection Working with Minimal Symbols
24515 Symbols extracted from a DLL's export table do not contain very much
24516 type information. All that @value{GDBN} can do is guess whether a symbol
24517 refers to a function or variable depending on the linker section that
24518 contains the symbol. Also note that the actual contents of the memory
24519 contained in a DLL are not available unless the program is running. This
24520 means that you cannot examine the contents of a variable or disassemble
24521 a function within a DLL without a running program.
24523 Variables are generally treated as pointers and dereferenced
24524 automatically. For this reason, it is often necessary to prefix a
24525 variable name with the address-of operator (``&'') and provide explicit
24526 type information in the command. Here's an example of the type of
24530 (@value{GDBP}) print 'cygwin1!__argv'
24531 'cygwin1!__argv' has unknown type; cast it to its declared type
24535 (@value{GDBP}) x 'cygwin1!__argv'
24536 'cygwin1!__argv' has unknown type; cast it to its declared type
24539 And two possible solutions:
24542 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24543 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24547 (@value{GDBP}) x/2x &'cygwin1!__argv'
24548 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24549 (@value{GDBP}) x/x 0x10021608
24550 0x10021608: 0x0022fd98
24551 (@value{GDBP}) x/s 0x0022fd98
24552 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24555 Setting a break point within a DLL is possible even before the program
24556 starts execution. However, under these circumstances, @value{GDBN} can't
24557 examine the initial instructions of the function in order to skip the
24558 function's frame set-up code. You can work around this by using ``*&''
24559 to set the breakpoint at a raw memory address:
24562 (@value{GDBP}) break *&'python22!PyOS_Readline'
24563 Breakpoint 1 at 0x1e04eff0
24566 The author of these extensions is not entirely convinced that setting a
24567 break point within a shared DLL like @file{kernel32.dll} is completely
24571 @subsection Commands Specific to @sc{gnu} Hurd Systems
24572 @cindex @sc{gnu} Hurd debugging
24574 This subsection describes @value{GDBN} commands specific to the
24575 @sc{gnu} Hurd native debugging.
24580 @kindex set signals@r{, Hurd command}
24581 @kindex set sigs@r{, Hurd command}
24582 This command toggles the state of inferior signal interception by
24583 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24584 affected by this command. @code{sigs} is a shorthand alias for
24589 @kindex show signals@r{, Hurd command}
24590 @kindex show sigs@r{, Hurd command}
24591 Show the current state of intercepting inferior's signals.
24593 @item set signal-thread
24594 @itemx set sigthread
24595 @kindex set signal-thread
24596 @kindex set sigthread
24597 This command tells @value{GDBN} which thread is the @code{libc} signal
24598 thread. That thread is run when a signal is delivered to a running
24599 process. @code{set sigthread} is the shorthand alias of @code{set
24602 @item show signal-thread
24603 @itemx show sigthread
24604 @kindex show signal-thread
24605 @kindex show sigthread
24606 These two commands show which thread will run when the inferior is
24607 delivered a signal.
24610 @kindex set stopped@r{, Hurd command}
24611 This commands tells @value{GDBN} that the inferior process is stopped,
24612 as with the @code{SIGSTOP} signal. The stopped process can be
24613 continued by delivering a signal to it.
24616 @kindex show stopped@r{, Hurd command}
24617 This command shows whether @value{GDBN} thinks the debuggee is
24620 @item set exceptions
24621 @kindex set exceptions@r{, Hurd command}
24622 Use this command to turn off trapping of exceptions in the inferior.
24623 When exception trapping is off, neither breakpoints nor
24624 single-stepping will work. To restore the default, set exception
24627 @item show exceptions
24628 @kindex show exceptions@r{, Hurd command}
24629 Show the current state of trapping exceptions in the inferior.
24631 @item set task pause
24632 @kindex set task@r{, Hurd commands}
24633 @cindex task attributes (@sc{gnu} Hurd)
24634 @cindex pause current task (@sc{gnu} Hurd)
24635 This command toggles task suspension when @value{GDBN} has control.
24636 Setting it to on takes effect immediately, and the task is suspended
24637 whenever @value{GDBN} gets control. Setting it to off will take
24638 effect the next time the inferior is continued. If this option is set
24639 to off, you can use @code{set thread default pause on} or @code{set
24640 thread pause on} (see below) to pause individual threads.
24642 @item show task pause
24643 @kindex show task@r{, Hurd commands}
24644 Show the current state of task suspension.
24646 @item set task detach-suspend-count
24647 @cindex task suspend count
24648 @cindex detach from task, @sc{gnu} Hurd
24649 This command sets the suspend count the task will be left with when
24650 @value{GDBN} detaches from it.
24652 @item show task detach-suspend-count
24653 Show the suspend count the task will be left with when detaching.
24655 @item set task exception-port
24656 @itemx set task excp
24657 @cindex task exception port, @sc{gnu} Hurd
24658 This command sets the task exception port to which @value{GDBN} will
24659 forward exceptions. The argument should be the value of the @dfn{send
24660 rights} of the task. @code{set task excp} is a shorthand alias.
24662 @item set noninvasive
24663 @cindex noninvasive task options
24664 This command switches @value{GDBN} to a mode that is the least
24665 invasive as far as interfering with the inferior is concerned. This
24666 is the same as using @code{set task pause}, @code{set exceptions}, and
24667 @code{set signals} to values opposite to the defaults.
24669 @item info send-rights
24670 @itemx info receive-rights
24671 @itemx info port-rights
24672 @itemx info port-sets
24673 @itemx info dead-names
24676 @cindex send rights, @sc{gnu} Hurd
24677 @cindex receive rights, @sc{gnu} Hurd
24678 @cindex port rights, @sc{gnu} Hurd
24679 @cindex port sets, @sc{gnu} Hurd
24680 @cindex dead names, @sc{gnu} Hurd
24681 These commands display information about, respectively, send rights,
24682 receive rights, port rights, port sets, and dead names of a task.
24683 There are also shorthand aliases: @code{info ports} for @code{info
24684 port-rights} and @code{info psets} for @code{info port-sets}.
24686 @item set thread pause
24687 @kindex set thread@r{, Hurd command}
24688 @cindex thread properties, @sc{gnu} Hurd
24689 @cindex pause current thread (@sc{gnu} Hurd)
24690 This command toggles current thread suspension when @value{GDBN} has
24691 control. Setting it to on takes effect immediately, and the current
24692 thread is suspended whenever @value{GDBN} gets control. Setting it to
24693 off will take effect the next time the inferior is continued.
24694 Normally, this command has no effect, since when @value{GDBN} has
24695 control, the whole task is suspended. However, if you used @code{set
24696 task pause off} (see above), this command comes in handy to suspend
24697 only the current thread.
24699 @item show thread pause
24700 @kindex show thread@r{, Hurd command}
24701 This command shows the state of current thread suspension.
24703 @item set thread run
24704 This command sets whether the current thread is allowed to run.
24706 @item show thread run
24707 Show whether the current thread is allowed to run.
24709 @item set thread detach-suspend-count
24710 @cindex thread suspend count, @sc{gnu} Hurd
24711 @cindex detach from thread, @sc{gnu} Hurd
24712 This command sets the suspend count @value{GDBN} will leave on a
24713 thread when detaching. This number is relative to the suspend count
24714 found by @value{GDBN} when it notices the thread; use @code{set thread
24715 takeover-suspend-count} to force it to an absolute value.
24717 @item show thread detach-suspend-count
24718 Show the suspend count @value{GDBN} will leave on the thread when
24721 @item set thread exception-port
24722 @itemx set thread excp
24723 Set the thread exception port to which to forward exceptions. This
24724 overrides the port set by @code{set task exception-port} (see above).
24725 @code{set thread excp} is the shorthand alias.
24727 @item set thread takeover-suspend-count
24728 Normally, @value{GDBN}'s thread suspend counts are relative to the
24729 value @value{GDBN} finds when it notices each thread. This command
24730 changes the suspend counts to be absolute instead.
24732 @item set thread default
24733 @itemx show thread default
24734 @cindex thread default settings, @sc{gnu} Hurd
24735 Each of the above @code{set thread} commands has a @code{set thread
24736 default} counterpart (e.g., @code{set thread default pause}, @code{set
24737 thread default exception-port}, etc.). The @code{thread default}
24738 variety of commands sets the default thread properties for all
24739 threads; you can then change the properties of individual threads with
24740 the non-default commands.
24747 @value{GDBN} provides the following commands specific to the Darwin target:
24750 @item set debug darwin @var{num}
24751 @kindex set debug darwin
24752 When set to a non zero value, enables debugging messages specific to
24753 the Darwin support. Higher values produce more verbose output.
24755 @item show debug darwin
24756 @kindex show debug darwin
24757 Show the current state of Darwin messages.
24759 @item set debug mach-o @var{num}
24760 @kindex set debug mach-o
24761 When set to a non zero value, enables debugging messages while
24762 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24763 file format used on Darwin for object and executable files.) Higher
24764 values produce more verbose output. This is a command to diagnose
24765 problems internal to @value{GDBN} and should not be needed in normal
24768 @item show debug mach-o
24769 @kindex show debug mach-o
24770 Show the current state of Mach-O file messages.
24772 @item set mach-exceptions on
24773 @itemx set mach-exceptions off
24774 @kindex set mach-exceptions
24775 On Darwin, faults are first reported as a Mach exception and are then
24776 mapped to a Posix signal. Use this command to turn on trapping of
24777 Mach exceptions in the inferior. This might be sometimes useful to
24778 better understand the cause of a fault. The default is off.
24780 @item show mach-exceptions
24781 @kindex show mach-exceptions
24782 Show the current state of exceptions trapping.
24786 @subsection FreeBSD
24789 When the ABI of a system call is changed in the FreeBSD kernel, this
24790 is implemented by leaving a compatibility system call using the old
24791 ABI at the existing number and allocating a new system call number for
24792 the version using the new ABI. As a convenience, when a system call
24793 is caught by name (@pxref{catch syscall}), compatibility system calls
24796 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24797 system call and catching the @code{kevent} system call by name catches
24801 (@value{GDBP}) catch syscall kevent
24802 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24808 @section Embedded Operating Systems
24810 This section describes configurations involving the debugging of
24811 embedded operating systems that are available for several different
24814 @value{GDBN} includes the ability to debug programs running on
24815 various real-time operating systems.
24817 @node Embedded Processors
24818 @section Embedded Processors
24820 This section goes into details specific to particular embedded
24823 @cindex send command to simulator
24824 Whenever a specific embedded processor has a simulator, @value{GDBN}
24825 allows to send an arbitrary command to the simulator.
24828 @item sim @var{command}
24829 @kindex sim@r{, a command}
24830 Send an arbitrary @var{command} string to the simulator. Consult the
24831 documentation for the specific simulator in use for information about
24832 acceptable commands.
24837 * ARC:: Synopsys ARC
24840 * M68K:: Motorola M68K
24841 * MicroBlaze:: Xilinx MicroBlaze
24842 * MIPS Embedded:: MIPS Embedded
24843 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24844 * PowerPC Embedded:: PowerPC Embedded
24847 * Super-H:: Renesas Super-H
24851 @subsection Synopsys ARC
24852 @cindex Synopsys ARC
24853 @cindex ARC specific commands
24859 @value{GDBN} provides the following ARC-specific commands:
24862 @item set debug arc
24863 @kindex set debug arc
24864 Control the level of ARC specific debug messages. Use 0 for no messages (the
24865 default), 1 for debug messages, and 2 for even more debug messages.
24867 @item show debug arc
24868 @kindex show debug arc
24869 Show the level of ARC specific debugging in operation.
24871 @item maint print arc arc-instruction @var{address}
24872 @kindex maint print arc arc-instruction
24873 Print internal disassembler information about instruction at a given address.
24880 @value{GDBN} provides the following ARM-specific commands:
24883 @item set arm disassembler
24885 This commands selects from a list of disassembly styles. The
24886 @code{"std"} style is the standard style.
24888 @item show arm disassembler
24890 Show the current disassembly style.
24892 @item set arm apcs32
24893 @cindex ARM 32-bit mode
24894 This command toggles ARM operation mode between 32-bit and 26-bit.
24896 @item show arm apcs32
24897 Display the current usage of the ARM 32-bit mode.
24899 @item set arm fpu @var{fputype}
24900 This command sets the ARM floating-point unit (FPU) type. The
24901 argument @var{fputype} can be one of these:
24905 Determine the FPU type by querying the OS ABI.
24907 Software FPU, with mixed-endian doubles on little-endian ARM
24910 GCC-compiled FPA co-processor.
24912 Software FPU with pure-endian doubles.
24918 Show the current type of the FPU.
24921 This command forces @value{GDBN} to use the specified ABI.
24924 Show the currently used ABI.
24926 @item set arm fallback-mode (arm|thumb|auto)
24927 @value{GDBN} uses the symbol table, when available, to determine
24928 whether instructions are ARM or Thumb. This command controls
24929 @value{GDBN}'s default behavior when the symbol table is not
24930 available. The default is @samp{auto}, which causes @value{GDBN} to
24931 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24934 @item show arm fallback-mode
24935 Show the current fallback instruction mode.
24937 @item set arm force-mode (arm|thumb|auto)
24938 This command overrides use of the symbol table to determine whether
24939 instructions are ARM or Thumb. The default is @samp{auto}, which
24940 causes @value{GDBN} to use the symbol table and then the setting
24941 of @samp{set arm fallback-mode}.
24943 @item show arm force-mode
24944 Show the current forced instruction mode.
24946 @item set debug arm
24947 Toggle whether to display ARM-specific debugging messages from the ARM
24948 target support subsystem.
24950 @item show debug arm
24951 Show whether ARM-specific debugging messages are enabled.
24955 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24956 The @value{GDBN} ARM simulator accepts the following optional arguments.
24959 @item --swi-support=@var{type}
24960 Tell the simulator which SWI interfaces to support. The argument
24961 @var{type} may be a comma separated list of the following values.
24962 The default value is @code{all}.
24978 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24979 The @value{GDBN} BPF simulator accepts the following optional arguments.
24982 @item --skb-data-offset=@var{offset}
24983 Tell the simulator the offset, measured in bytes, of the
24984 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
24985 This offset is used by some BPF specific-purpose load/store
24986 instructions. Defaults to 0.
24993 The Motorola m68k configuration includes ColdFire support.
24996 @subsection MicroBlaze
24997 @cindex Xilinx MicroBlaze
24998 @cindex XMD, Xilinx Microprocessor Debugger
25000 The MicroBlaze is a soft-core processor supported on various Xilinx
25001 FPGAs, such as Spartan or Virtex series. Boards with these processors
25002 usually have JTAG ports which connect to a host system running the Xilinx
25003 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25004 This host system is used to download the configuration bitstream to
25005 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25006 communicates with the target board using the JTAG interface and
25007 presents a @code{gdbserver} interface to the board. By default
25008 @code{xmd} uses port @code{1234}. (While it is possible to change
25009 this default port, it requires the use of undocumented @code{xmd}
25010 commands. Contact Xilinx support if you need to do this.)
25012 Use these GDB commands to connect to the MicroBlaze target processor.
25015 @item target remote :1234
25016 Use this command to connect to the target if you are running @value{GDBN}
25017 on the same system as @code{xmd}.
25019 @item target remote @var{xmd-host}:1234
25020 Use this command to connect to the target if it is connected to @code{xmd}
25021 running on a different system named @var{xmd-host}.
25024 Use this command to download a program to the MicroBlaze target.
25026 @item set debug microblaze @var{n}
25027 Enable MicroBlaze-specific debugging messages if non-zero.
25029 @item show debug microblaze @var{n}
25030 Show MicroBlaze-specific debugging level.
25033 @node MIPS Embedded
25034 @subsection @acronym{MIPS} Embedded
25037 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25040 @item set mipsfpu double
25041 @itemx set mipsfpu single
25042 @itemx set mipsfpu none
25043 @itemx set mipsfpu auto
25044 @itemx show mipsfpu
25045 @kindex set mipsfpu
25046 @kindex show mipsfpu
25047 @cindex @acronym{MIPS} remote floating point
25048 @cindex floating point, @acronym{MIPS} remote
25049 If your target board does not support the @acronym{MIPS} floating point
25050 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25051 need this, you may wish to put the command in your @value{GDBN} init
25052 file). This tells @value{GDBN} how to find the return value of
25053 functions which return floating point values. It also allows
25054 @value{GDBN} to avoid saving the floating point registers when calling
25055 functions on the board. If you are using a floating point coprocessor
25056 with only single precision floating point support, as on the @sc{r4650}
25057 processor, use the command @samp{set mipsfpu single}. The default
25058 double precision floating point coprocessor may be selected using
25059 @samp{set mipsfpu double}.
25061 In previous versions the only choices were double precision or no
25062 floating point, so @samp{set mipsfpu on} will select double precision
25063 and @samp{set mipsfpu off} will select no floating point.
25065 As usual, you can inquire about the @code{mipsfpu} variable with
25066 @samp{show mipsfpu}.
25069 @node OpenRISC 1000
25070 @subsection OpenRISC 1000
25071 @cindex OpenRISC 1000
25074 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25075 mainly provided as a soft-core which can run on Xilinx, Altera and other
25078 @value{GDBN} for OpenRISC supports the below commands when connecting to
25086 Runs the builtin CPU simulator which can run very basic
25087 programs but does not support most hardware functions like MMU.
25088 For more complex use cases the user is advised to run an external
25089 target, and connect using @samp{target remote}.
25091 Example: @code{target sim}
25093 @item set debug or1k
25094 Toggle whether to display OpenRISC-specific debugging messages from the
25095 OpenRISC target support subsystem.
25097 @item show debug or1k
25098 Show whether OpenRISC-specific debugging messages are enabled.
25101 @node PowerPC Embedded
25102 @subsection PowerPC Embedded
25104 @cindex DVC register
25105 @value{GDBN} supports using the DVC (Data Value Compare) register to
25106 implement in hardware simple hardware watchpoint conditions of the form:
25109 (@value{GDBP}) watch @var{address|variable} \
25110 if @var{address|variable} == @var{constant expression}
25113 The DVC register will be automatically used when @value{GDBN} detects
25114 such pattern in a condition expression, and the created watchpoint uses one
25115 debug register (either the @code{exact-watchpoints} option is on and the
25116 variable is scalar, or the variable has a length of one byte). This feature
25117 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25120 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25121 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25122 in which case watchpoints using only one debug register are created when
25123 watching variables of scalar types.
25125 You can create an artificial array to watch an arbitrary memory
25126 region using one of the following commands (@pxref{Expressions}):
25129 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25130 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25133 PowerPC embedded processors support masked watchpoints. See the discussion
25134 about the @code{mask} argument in @ref{Set Watchpoints}.
25136 @cindex ranged breakpoint
25137 PowerPC embedded processors support hardware accelerated
25138 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25139 the inferior whenever it executes an instruction at any address within
25140 the range it specifies. To set a ranged breakpoint in @value{GDBN},
25141 use the @code{break-range} command.
25143 @value{GDBN} provides the following PowerPC-specific commands:
25146 @kindex break-range
25147 @item break-range @var{start-location}, @var{end-location}
25148 Set a breakpoint for an address range given by
25149 @var{start-location} and @var{end-location}, which can specify a function name,
25150 a line number, an offset of lines from the current line or from the start
25151 location, or an address of an instruction (see @ref{Specify Location},
25152 for a list of all the possible ways to specify a @var{location}.)
25153 The breakpoint will stop execution of the inferior whenever it
25154 executes an instruction at any address within the specified range,
25155 (including @var{start-location} and @var{end-location}.)
25157 @kindex set powerpc
25158 @item set powerpc soft-float
25159 @itemx show powerpc soft-float
25160 Force @value{GDBN} to use (or not use) a software floating point calling
25161 convention. By default, @value{GDBN} selects the calling convention based
25162 on the selected architecture and the provided executable file.
25164 @item set powerpc vector-abi
25165 @itemx show powerpc vector-abi
25166 Force @value{GDBN} to use the specified calling convention for vector
25167 arguments and return values. The valid options are @samp{auto};
25168 @samp{generic}, to avoid vector registers even if they are present;
25169 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25170 registers. By default, @value{GDBN} selects the calling convention
25171 based on the selected architecture and the provided executable file.
25173 @item set powerpc exact-watchpoints
25174 @itemx show powerpc exact-watchpoints
25175 Allow @value{GDBN} to use only one debug register when watching a variable
25176 of scalar type, thus assuming that the variable is accessed through the
25177 address of its first byte.
25182 @subsection Atmel AVR
25185 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25186 following AVR-specific commands:
25189 @item info io_registers
25190 @kindex info io_registers@r{, AVR}
25191 @cindex I/O registers (Atmel AVR)
25192 This command displays information about the AVR I/O registers. For
25193 each register, @value{GDBN} prints its number and value.
25200 When configured for debugging CRIS, @value{GDBN} provides the
25201 following CRIS-specific commands:
25204 @item set cris-version @var{ver}
25205 @cindex CRIS version
25206 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25207 The CRIS version affects register names and sizes. This command is useful in
25208 case autodetection of the CRIS version fails.
25210 @item show cris-version
25211 Show the current CRIS version.
25213 @item set cris-dwarf2-cfi
25214 @cindex DWARF-2 CFI and CRIS
25215 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25216 Change to @samp{off} when using @code{gcc-cris} whose version is below
25219 @item show cris-dwarf2-cfi
25220 Show the current state of using DWARF-2 CFI.
25222 @item set cris-mode @var{mode}
25224 Set the current CRIS mode to @var{mode}. It should only be changed when
25225 debugging in guru mode, in which case it should be set to
25226 @samp{guru} (the default is @samp{normal}).
25228 @item show cris-mode
25229 Show the current CRIS mode.
25233 @subsection Renesas Super-H
25236 For the Renesas Super-H processor, @value{GDBN} provides these
25240 @item set sh calling-convention @var{convention}
25241 @kindex set sh calling-convention
25242 Set the calling-convention used when calling functions from @value{GDBN}.
25243 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25244 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25245 convention. If the DWARF-2 information of the called function specifies
25246 that the function follows the Renesas calling convention, the function
25247 is called using the Renesas calling convention. If the calling convention
25248 is set to @samp{renesas}, the Renesas calling convention is always used,
25249 regardless of the DWARF-2 information. This can be used to override the
25250 default of @samp{gcc} if debug information is missing, or the compiler
25251 does not emit the DWARF-2 calling convention entry for a function.
25253 @item show sh calling-convention
25254 @kindex show sh calling-convention
25255 Show the current calling convention setting.
25260 @node Architectures
25261 @section Architectures
25263 This section describes characteristics of architectures that affect
25264 all uses of @value{GDBN} with the architecture, both native and cross.
25271 * HPPA:: HP PA architecture
25279 @subsection AArch64
25280 @cindex AArch64 support
25282 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25283 following special commands:
25286 @item set debug aarch64
25287 @kindex set debug aarch64
25288 This command determines whether AArch64 architecture-specific debugging
25289 messages are to be displayed.
25291 @item show debug aarch64
25292 Show whether AArch64 debugging messages are displayed.
25296 @subsubsection AArch64 SVE.
25297 @cindex AArch64 SVE.
25299 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25300 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25301 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25302 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25303 @code{$vg} will be provided. This is the vector granule for the current thread
25304 and represents the number of 64-bit chunks in an SVE @code{z} register.
25306 If the vector length changes, then the @code{$vg} register will be updated,
25307 but the lengths of the @code{z} and @code{p} registers will not change. This
25308 is a known limitation of @value{GDBN} and does not affect the execution of the
25311 @subsubsection AArch64 Pointer Authentication.
25312 @cindex AArch64 Pointer Authentication.
25314 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25315 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25316 register @code{$lr} is pointing to an PAC function its value will be masked.
25317 When GDB prints a backtrace, any addresses that required unmasking will be
25318 postfixed with the marker [PAC]. When using the MI, this is printed as part
25319 of the @code{addr_flags} field.
25321 @subsubsection AArch64 Memory Tagging Extension.
25322 @cindex AArch64 Memory Tagging Extension.
25324 When @value{GDBN} is debugging the AArch64 architecture, the program is
25325 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25326 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25327 available for inspection and editing of logical and allocation tags.
25328 @xref{Memory Tagging}.
25330 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25331 signals are generated as a result of memory tag failures.
25333 If the tag violation is synchronous, the following will be shown:
25336 Program received signal SIGSEGV, Segmentation fault
25337 Memory tag violation while accessing address 0x0500fffff7ff8000
25342 If the tag violation is asynchronous, the fault address is not available.
25343 In this case @value{GDBN} will show the following:
25346 Program received signal SIGSEGV, Segmentation fault
25347 Memory tag violation
25348 Fault address unavailable.
25351 A special register, @code{tag_ctl}, is made available through the
25352 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25353 options that can be controlled at runtime and emulates the @code{prctl}
25354 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25355 documentation in the Linux kernel.
25358 @subsection x86 Architecture-specific Issues
25361 @item set struct-convention @var{mode}
25362 @kindex set struct-convention
25363 @cindex struct return convention
25364 @cindex struct/union returned in registers
25365 Set the convention used by the inferior to return @code{struct}s and
25366 @code{union}s from functions to @var{mode}. Possible values of
25367 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25368 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25369 are returned on the stack, while @code{"reg"} means that a
25370 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25371 be returned in a register.
25373 @item show struct-convention
25374 @kindex show struct-convention
25375 Show the current setting of the convention to return @code{struct}s
25380 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25381 @cindex Intel Memory Protection Extensions (MPX).
25383 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25384 @footnote{The register named with capital letters represent the architecture
25385 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25386 which are the lower bound and upper bound. Bounds are effective addresses or
25387 memory locations. The upper bounds are architecturally represented in 1's
25388 complement form. A bound having lower bound = 0, and upper bound = 0
25389 (1's complement of all bits set) will allow access to the entire address space.
25391 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25392 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25393 display the upper bound performing the complement of one operation on the
25394 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25395 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25396 can also be noted that the upper bounds are inclusive.
25398 As an example, assume that the register BND0 holds bounds for a pointer having
25399 access allowed for the range between 0x32 and 0x71. The values present on
25400 bnd0raw and bnd registers are presented as follows:
25403 bnd0raw = @{0x32, 0xffffffff8e@}
25404 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25407 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25408 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25409 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25410 Python, the display includes the memory size, in bits, accessible to
25413 Bounds can also be stored in bounds tables, which are stored in
25414 application memory. These tables store bounds for pointers by specifying
25415 the bounds pointer's value along with its bounds. Evaluating and changing
25416 bounds located in bound tables is therefore interesting while investigating
25417 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25420 @item show mpx bound @var{pointer}
25421 @kindex show mpx bound
25422 Display bounds of the given @var{pointer}.
25424 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25425 @kindex set mpx bound
25426 Set the bounds of a pointer in the bound table.
25427 This command takes three parameters: @var{pointer} is the pointers
25428 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25429 for lower and upper bounds respectively.
25432 When you call an inferior function on an Intel MPX enabled program,
25433 GDB sets the inferior's bound registers to the init (disabled) state
25434 before calling the function. As a consequence, bounds checks for the
25435 pointer arguments passed to the function will always pass.
25437 This is necessary because when you call an inferior function, the
25438 program is usually in the middle of the execution of other function.
25439 Since at that point bound registers are in an arbitrary state, not
25440 clearing them would lead to random bound violations in the called
25443 You can still examine the influence of the bound registers on the
25444 execution of the called function by stopping the execution of the
25445 called function at its prologue, setting bound registers, and
25446 continuing the execution. For example:
25450 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25451 $ print upper (a, b, c, d, 1)
25452 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25454 @{lbound = 0x0, ubound = ffffffff@} : size -1
25457 At this last step the value of bnd0 can be changed for investigation of bound
25458 violations caused along the execution of the call. In order to know how to
25459 set the bound registers or bound table for the call consult the ABI.
25464 See the following section.
25467 @subsection @acronym{MIPS}
25469 @cindex stack on Alpha
25470 @cindex stack on @acronym{MIPS}
25471 @cindex Alpha stack
25472 @cindex @acronym{MIPS} stack
25473 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25474 sometimes requires @value{GDBN} to search backward in the object code to
25475 find the beginning of a function.
25477 @cindex response time, @acronym{MIPS} debugging
25478 To improve response time (especially for embedded applications, where
25479 @value{GDBN} may be restricted to a slow serial line for this search)
25480 you may want to limit the size of this search, using one of these
25484 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25485 @item set heuristic-fence-post @var{limit}
25486 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25487 search for the beginning of a function. A value of @var{0} (the
25488 default) means there is no limit. However, except for @var{0}, the
25489 larger the limit the more bytes @code{heuristic-fence-post} must search
25490 and therefore the longer it takes to run. You should only need to use
25491 this command when debugging a stripped executable.
25493 @item show heuristic-fence-post
25494 Display the current limit.
25498 These commands are available @emph{only} when @value{GDBN} is configured
25499 for debugging programs on Alpha or @acronym{MIPS} processors.
25501 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25505 @item set mips abi @var{arg}
25506 @kindex set mips abi
25507 @cindex set ABI for @acronym{MIPS}
25508 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25509 values of @var{arg} are:
25513 The default ABI associated with the current binary (this is the
25523 @item show mips abi
25524 @kindex show mips abi
25525 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25527 @item set mips compression @var{arg}
25528 @kindex set mips compression
25529 @cindex code compression, @acronym{MIPS}
25530 Tell @value{GDBN} which @acronym{MIPS} compressed
25531 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25532 inferior. @value{GDBN} uses this for code disassembly and other
25533 internal interpretation purposes. This setting is only referred to
25534 when no executable has been associated with the debugging session or
25535 the executable does not provide information about the encoding it uses.
25536 Otherwise this setting is automatically updated from information
25537 provided by the executable.
25539 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25540 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25541 executables containing @acronym{MIPS16} code frequently are not
25542 identified as such.
25544 This setting is ``sticky''; that is, it retains its value across
25545 debugging sessions until reset either explicitly with this command or
25546 implicitly from an executable.
25548 The compiler and/or assembler typically add symbol table annotations to
25549 identify functions compiled for the @acronym{MIPS16} or
25550 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25551 are present, @value{GDBN} uses them in preference to the global
25552 compressed @acronym{ISA} encoding setting.
25554 @item show mips compression
25555 @kindex show mips compression
25556 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25557 @value{GDBN} to debug the inferior.
25560 @itemx show mipsfpu
25561 @xref{MIPS Embedded, set mipsfpu}.
25563 @item set mips mask-address @var{arg}
25564 @kindex set mips mask-address
25565 @cindex @acronym{MIPS} addresses, masking
25566 This command determines whether the most-significant 32 bits of 64-bit
25567 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25568 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25569 setting, which lets @value{GDBN} determine the correct value.
25571 @item show mips mask-address
25572 @kindex show mips mask-address
25573 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25576 @item set remote-mips64-transfers-32bit-regs
25577 @kindex set remote-mips64-transfers-32bit-regs
25578 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25579 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25580 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25581 and 64 bits for other registers, set this option to @samp{on}.
25583 @item show remote-mips64-transfers-32bit-regs
25584 @kindex show remote-mips64-transfers-32bit-regs
25585 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25587 @item set debug mips
25588 @kindex set debug mips
25589 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25590 target code in @value{GDBN}.
25592 @item show debug mips
25593 @kindex show debug mips
25594 Show the current setting of @acronym{MIPS} debugging messages.
25600 @cindex HPPA support
25602 When @value{GDBN} is debugging the HP PA architecture, it provides the
25603 following special commands:
25606 @item set debug hppa
25607 @kindex set debug hppa
25608 This command determines whether HPPA architecture-specific debugging
25609 messages are to be displayed.
25611 @item show debug hppa
25612 Show whether HPPA debugging messages are displayed.
25614 @item maint print unwind @var{address}
25615 @kindex maint print unwind@r{, HPPA}
25616 This command displays the contents of the unwind table entry at the
25617 given @var{address}.
25623 @subsection PowerPC
25624 @cindex PowerPC architecture
25626 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25627 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25628 numbers stored in the floating point registers. These values must be stored
25629 in two consecutive registers, always starting at an even register like
25630 @code{f0} or @code{f2}.
25632 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25633 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25634 @code{f2} and @code{f3} for @code{$dl1} and so on.
25636 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25637 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25640 @subsection Nios II
25641 @cindex Nios II architecture
25643 When @value{GDBN} is debugging the Nios II architecture,
25644 it provides the following special commands:
25648 @item set debug nios2
25649 @kindex set debug nios2
25650 This command turns on and off debugging messages for the Nios II
25651 target code in @value{GDBN}.
25653 @item show debug nios2
25654 @kindex show debug nios2
25655 Show the current setting of Nios II debugging messages.
25659 @subsection Sparc64
25660 @cindex Sparc64 support
25661 @cindex Application Data Integrity
25662 @subsubsection ADI Support
25664 The M7 processor supports an Application Data Integrity (ADI) feature that
25665 detects invalid data accesses. When software allocates memory and enables
25666 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25667 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25668 the 4-bit version in every cacheline of that data. Hardware saves the latter
25669 in spare bits in the cache and memory hierarchy. On each load and store,
25670 the processor compares the upper 4 VA (virtual address) bits to the
25671 cacheline's version. If there is a mismatch, the processor generates a
25672 version mismatch trap which can be either precise or disrupting. The trap
25673 is an error condition which the kernel delivers to the process as a SIGSEGV
25676 Note that only 64-bit applications can use ADI and need to be built with
25679 Values of the ADI version tags, which are in granularity of a
25680 cacheline (64 bytes), can be viewed or modified.
25684 @kindex adi examine
25685 @item adi (examine | x) [ / @var{n} ] @var{addr}
25687 The @code{adi examine} command displays the value of one ADI version tag per
25690 @var{n} is a decimal integer specifying the number in bytes; the default
25691 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25692 block size, to display.
25694 @var{addr} is the address in user address space where you want @value{GDBN}
25695 to begin displaying the ADI version tags.
25697 Below is an example of displaying ADI versions of variable "shmaddr".
25700 (@value{GDBP}) adi x/100 shmaddr
25701 0xfff800010002c000: 0 0
25705 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25707 The @code{adi assign} command is used to assign new ADI version tag
25710 @var{n} is a decimal integer specifying the number in bytes;
25711 the default is 1. It specifies how much ADI version information, at the
25712 ratio of 1:ADI block size, to modify.
25714 @var{addr} is the address in user address space where you want @value{GDBN}
25715 to begin modifying the ADI version tags.
25717 @var{tag} is the new ADI version tag.
25719 For example, do the following to modify then verify ADI versions of
25720 variable "shmaddr":
25723 (@value{GDBP}) adi a/100 shmaddr = 7
25724 (@value{GDBP}) adi x/100 shmaddr
25725 0xfff800010002c000: 7 7
25732 @cindex S12Z support
25734 When @value{GDBN} is debugging the S12Z architecture,
25735 it provides the following special command:
25738 @item maint info bdccsr
25739 @kindex maint info bdccsr@r{, S12Z}
25740 This command displays the current value of the microprocessor's
25745 @node Controlling GDB
25746 @chapter Controlling @value{GDBN}
25748 You can alter the way @value{GDBN} interacts with you by using the
25749 @code{set} command. For commands controlling how @value{GDBN} displays
25750 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25755 * Editing:: Command editing
25756 * Command History:: Command history
25757 * Screen Size:: Screen size
25758 * Output Styling:: Output styling
25759 * Numbers:: Numbers
25760 * ABI:: Configuring the current ABI
25761 * Auto-loading:: Automatically loading associated files
25762 * Messages/Warnings:: Optional warnings and messages
25763 * Debugging Output:: Optional messages about internal happenings
25764 * Other Misc Settings:: Other Miscellaneous Settings
25772 @value{GDBN} indicates its readiness to read a command by printing a string
25773 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25774 can change the prompt string with the @code{set prompt} command. For
25775 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25776 the prompt in one of the @value{GDBN} sessions so that you can always tell
25777 which one you are talking to.
25779 @emph{Note:} @code{set prompt} does not add a space for you after the
25780 prompt you set. This allows you to set a prompt which ends in a space
25781 or a prompt that does not.
25785 @item set prompt @var{newprompt}
25786 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25788 @kindex show prompt
25790 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25793 Versions of @value{GDBN} that ship with Python scripting enabled have
25794 prompt extensions. The commands for interacting with these extensions
25798 @kindex set extended-prompt
25799 @item set extended-prompt @var{prompt}
25800 Set an extended prompt that allows for substitutions.
25801 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25802 substitution. Any escape sequences specified as part of the prompt
25803 string are replaced with the corresponding strings each time the prompt
25809 set extended-prompt Current working directory: \w (gdb)
25812 Note that when an extended-prompt is set, it takes control of the
25813 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25815 @kindex show extended-prompt
25816 @item show extended-prompt
25817 Prints the extended prompt. Any escape sequences specified as part of
25818 the prompt string with @code{set extended-prompt}, are replaced with the
25819 corresponding strings each time the prompt is displayed.
25823 @section Command Editing
25825 @cindex command line editing
25827 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25828 @sc{gnu} library provides consistent behavior for programs which provide a
25829 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25830 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25831 substitution, and a storage and recall of command history across
25832 debugging sessions.
25834 You may control the behavior of command line editing in @value{GDBN} with the
25835 command @code{set}.
25838 @kindex set editing
25841 @itemx set editing on
25842 Enable command line editing (enabled by default).
25844 @item set editing off
25845 Disable command line editing.
25847 @kindex show editing
25849 Show whether command line editing is enabled.
25852 @ifset SYSTEM_READLINE
25853 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25855 @ifclear SYSTEM_READLINE
25856 @xref{Command Line Editing},
25858 for more details about the Readline
25859 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25860 encouraged to read that chapter.
25862 @cindex Readline application name
25863 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25864 is useful for conditions in @file{.inputrc}.
25866 @cindex operate-and-get-next
25867 @value{GDBN} defines a bindable Readline command,
25868 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25869 This command accepts the current line for execution and fetches the
25870 next line relative to the current line from the history for editing.
25871 Any argument is ignored.
25873 @node Command History
25874 @section Command History
25875 @cindex command history
25877 @value{GDBN} can keep track of the commands you type during your
25878 debugging sessions, so that you can be certain of precisely what
25879 happened. Use these commands to manage the @value{GDBN} command
25882 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25883 package, to provide the history facility.
25884 @ifset SYSTEM_READLINE
25885 @xref{Using History Interactively, , , history, GNU History Library},
25887 @ifclear SYSTEM_READLINE
25888 @xref{Using History Interactively},
25890 for the detailed description of the History library.
25892 To issue a command to @value{GDBN} without affecting certain aspects of
25893 the state which is seen by users, prefix it with @samp{server }
25894 (@pxref{Server Prefix}). This
25895 means that this command will not affect the command history, nor will it
25896 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25897 pressed on a line by itself.
25899 @cindex @code{server}, command prefix
25900 The server prefix does not affect the recording of values into the value
25901 history; to print a value without recording it into the value history,
25902 use the @code{output} command instead of the @code{print} command.
25904 Here is the description of @value{GDBN} commands related to command
25908 @cindex history substitution
25909 @cindex history file
25910 @kindex set history filename
25911 @cindex @env{GDBHISTFILE}, environment variable
25912 @item set history filename @r{[}@var{fname}@r{]}
25913 Set the name of the @value{GDBN} command history file to @var{fname}.
25914 This is the file where @value{GDBN} reads an initial command history
25915 list, and where it writes the command history from this session when it
25916 exits. You can access this list through history expansion or through
25917 the history command editing characters listed below. This file defaults
25918 to the value of the environment variable @env{GDBHISTFILE}, or to
25919 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25922 The @env{GDBHISTFILE} environment variable is read after processing
25923 any @value{GDBN} initialization files (@pxref{Startup}) and after
25924 processing any commands passed using command line options (for
25925 example, @code{-ex}).
25927 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
25928 is the empty string then @value{GDBN} will neither try to load an
25929 existing history file, nor will it try to save the history on exit.
25931 @cindex save command history
25932 @kindex set history save
25933 @item set history save
25934 @itemx set history save on
25935 Record command history in a file, whose name may be specified with the
25936 @code{set history filename} command. By default, this option is
25937 disabled. The command history will be recorded when @value{GDBN}
25938 exits. If @code{set history filename} is set to the empty string then
25939 history saving is disabled, even when @code{set history save} is
25942 @item set history save off
25943 Don't record the command history into the file specified by @code{set
25944 history filename} when @value{GDBN} exits.
25946 @cindex history size
25947 @kindex set history size
25948 @cindex @env{GDBHISTSIZE}, environment variable
25949 @item set history size @var{size}
25950 @itemx set history size unlimited
25951 Set the number of commands which @value{GDBN} keeps in its history list.
25952 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25953 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25954 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25955 either a negative number or the empty string, then the number of commands
25956 @value{GDBN} keeps in the history list is unlimited.
25958 The @env{GDBHISTSIZE} environment variable is read after processing
25959 any @value{GDBN} initialization files (@pxref{Startup}) and after
25960 processing any commands passed using command line options (for
25961 example, @code{-ex}).
25963 @cindex remove duplicate history
25964 @kindex set history remove-duplicates
25965 @item set history remove-duplicates @var{count}
25966 @itemx set history remove-duplicates unlimited
25967 Control the removal of duplicate history entries in the command history list.
25968 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25969 history entries and remove the first entry that is a duplicate of the current
25970 entry being added to the command history list. If @var{count} is
25971 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25972 removal of duplicate history entries is disabled.
25974 Only history entries added during the current session are considered for
25975 removal. This option is set to 0 by default.
25979 History expansion assigns special meaning to the character @kbd{!}.
25980 @ifset SYSTEM_READLINE
25981 @xref{Event Designators, , , history, GNU History Library},
25983 @ifclear SYSTEM_READLINE
25984 @xref{Event Designators},
25988 @cindex history expansion, turn on/off
25989 Since @kbd{!} is also the logical not operator in C, history expansion
25990 is off by default. If you decide to enable history expansion with the
25991 @code{set history expansion on} command, you may sometimes need to
25992 follow @kbd{!} (when it is used as logical not, in an expression) with
25993 a space or a tab to prevent it from being expanded. The readline
25994 history facilities do not attempt substitution on the strings
25995 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25997 The commands to control history expansion are:
26000 @item set history expansion on
26001 @itemx set history expansion
26002 @kindex set history expansion
26003 Enable history expansion. History expansion is off by default.
26005 @item set history expansion off
26006 Disable history expansion.
26009 @kindex show history
26011 @itemx show history filename
26012 @itemx show history save
26013 @itemx show history size
26014 @itemx show history expansion
26015 These commands display the state of the @value{GDBN} history parameters.
26016 @code{show history} by itself displays all four states.
26021 @kindex show commands
26022 @cindex show last commands
26023 @cindex display command history
26024 @item show commands
26025 Display the last ten commands in the command history.
26027 @item show commands @var{n}
26028 Print ten commands centered on command number @var{n}.
26030 @item show commands +
26031 Print ten commands just after the commands last printed.
26035 @section Screen Size
26036 @cindex size of screen
26037 @cindex screen size
26040 @cindex pauses in output
26042 Certain commands to @value{GDBN} may produce large amounts of
26043 information output to the screen. To help you read all of it,
26044 @value{GDBN} pauses and asks you for input at the end of each page of
26045 output. Type @key{RET} when you want to see one more page of output,
26046 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26047 without paging for the rest of the current command. Also, the screen
26048 width setting determines when to wrap lines of output. Depending on
26049 what is being printed, @value{GDBN} tries to break the line at a
26050 readable place, rather than simply letting it overflow onto the
26053 Normally @value{GDBN} knows the size of the screen from the terminal
26054 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26055 together with the value of the @env{TERM} environment variable and the
26056 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26057 you can override it with the @code{set height} and @code{set
26064 @kindex show height
26065 @item set height @var{lpp}
26066 @itemx set height unlimited
26068 @itemx set width @var{cpl}
26069 @itemx set width unlimited
26071 These @code{set} commands specify a screen height of @var{lpp} lines and
26072 a screen width of @var{cpl} characters. The associated @code{show}
26073 commands display the current settings.
26075 If you specify a height of either @code{unlimited} or zero lines,
26076 @value{GDBN} does not pause during output no matter how long the
26077 output is. This is useful if output is to a file or to an editor
26080 Likewise, you can specify @samp{set width unlimited} or @samp{set
26081 width 0} to prevent @value{GDBN} from wrapping its output.
26083 @item set pagination on
26084 @itemx set pagination off
26085 @kindex set pagination
26086 Turn the output pagination on or off; the default is on. Turning
26087 pagination off is the alternative to @code{set height unlimited}. Note that
26088 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26089 Options, -batch}) also automatically disables pagination.
26091 @item show pagination
26092 @kindex show pagination
26093 Show the current pagination mode.
26096 @node Output Styling
26097 @section Output Styling
26103 @value{GDBN} can style its output on a capable terminal. This is
26104 enabled by default on most systems, but disabled by default when in
26105 batch mode (@pxref{Mode Options}). Various style settings are available;
26106 and styles can also be disabled entirely.
26109 @item set style enabled @samp{on|off}
26110 Enable or disable all styling. The default is host-dependent, with
26111 most hosts defaulting to @samp{on}.
26113 @item show style enabled
26114 Show the current state of styling.
26116 @item set style sources @samp{on|off}
26117 Enable or disable source code styling. This affects whether source
26118 code, such as the output of the @code{list} command, is styled. The
26119 default is @samp{on}. Note that source styling only works if styling
26120 in general is enabled, and if a source highlighting library is
26121 available to @value{GDBN}.
26123 There are two ways that highlighting can be done. First, if
26124 @value{GDBN} was linked with the GNU Source Highlight library, then it
26125 is used. Otherwise, if @value{GDBN} was configured with Python
26126 scripting support, and if the Python Pygments package is available,
26127 then it will be used.
26129 @item show style sources
26130 Show the current state of source code styling.
26133 Subcommands of @code{set style} control specific forms of styling.
26134 These subcommands all follow the same pattern: each style-able object
26135 can be styled with a foreground color, a background color, and an
26138 For example, the style of file names can be controlled using the
26139 @code{set style filename} group of commands:
26142 @item set style filename background @var{color}
26143 Set the background to @var{color}. Valid colors are @samp{none}
26144 (meaning the terminal's default color), @samp{black}, @samp{red},
26145 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26148 @item set style filename foreground @var{color}
26149 Set the foreground to @var{color}. Valid colors are @samp{none}
26150 (meaning the terminal's default color), @samp{black}, @samp{red},
26151 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26154 @item set style filename intensity @var{value}
26155 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26156 (the default), @samp{bold}, and @samp{dim}.
26159 The @code{show style} command and its subcommands are styling
26160 a style name in their output using its own style.
26161 So, use @command{show style} to see the complete list of styles,
26162 their characteristics and the visual aspect of each style.
26164 The style-able objects are:
26167 Control the styling of file names. By default, this style's
26168 foreground color is green.
26171 Control the styling of function names. These are managed with the
26172 @code{set style function} family of commands. By default, this
26173 style's foreground color is yellow.
26176 Control the styling of variable names. These are managed with the
26177 @code{set style variable} family of commands. By default, this style's
26178 foreground color is cyan.
26181 Control the styling of addresses. These are managed with the
26182 @code{set style address} family of commands. By default, this style's
26183 foreground color is blue.
26186 Control the styling of @value{GDBN}'s version number text. By
26187 default, this style's foreground color is magenta and it has bold
26188 intensity. The version number is displayed in two places, the output
26189 of @command{show version}, and when @value{GDBN} starts up.
26191 In order to control how @value{GDBN} styles the version number at
26192 startup, add the @code{set style version} family of commands to the
26193 early initialization command file (@pxref{Initialization
26197 Control the styling of titles. These are managed with the
26198 @code{set style title} family of commands. By default, this style's
26199 intensity is bold. Commands are using the title style to improve
26200 the readability of large output. For example, the commands
26201 @command{apropos} and @command{help} are using the title style
26202 for the command names.
26205 Control the styling of highlightings. These are managed with the
26206 @code{set style highlight} family of commands. By default, this style's
26207 foreground color is red. Commands are using the highlight style to draw
26208 the user attention to some specific parts of their output. For example,
26209 the command @command{apropos -v REGEXP} uses the highlight style to
26210 mark the documentation parts matching @var{regexp}.
26213 Control the styling of the TUI border. Note that, unlike other
26214 styling options, only the color of the border can be controlled via
26215 @code{set style}. This was done for compatibility reasons, as TUI
26216 controls to set the border's intensity predated the addition of
26217 general styling to @value{GDBN}. @xref{TUI Configuration}.
26219 @item tui-active-border
26220 Control the styling of the active TUI border; that is, the TUI window
26221 that has the focus.
26227 @cindex number representation
26228 @cindex entering numbers
26230 You can always enter numbers in octal, decimal, or hexadecimal in
26231 @value{GDBN} by the usual conventions: octal numbers begin with
26232 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26233 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26234 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26235 10; likewise, the default display for numbers---when no particular
26236 format is specified---is base 10. You can change the default base for
26237 both input and output with the commands described below.
26240 @kindex set input-radix
26241 @item set input-radix @var{base}
26242 Set the default base for numeric input. Supported choices
26243 for @var{base} are decimal 8, 10, or 16. The base must itself be
26244 specified either unambiguously or using the current input radix; for
26248 set input-radix 012
26249 set input-radix 10.
26250 set input-radix 0xa
26254 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26255 leaves the input radix unchanged, no matter what it was, since
26256 @samp{10}, being without any leading or trailing signs of its base, is
26257 interpreted in the current radix. Thus, if the current radix is 16,
26258 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26261 @kindex set output-radix
26262 @item set output-radix @var{base}
26263 Set the default base for numeric display. Supported choices
26264 for @var{base} are decimal 8, 10, or 16. The base must itself be
26265 specified either unambiguously or using the current input radix.
26267 @kindex show input-radix
26268 @item show input-radix
26269 Display the current default base for numeric input.
26271 @kindex show output-radix
26272 @item show output-radix
26273 Display the current default base for numeric display.
26275 @item set radix @r{[}@var{base}@r{]}
26279 These commands set and show the default base for both input and output
26280 of numbers. @code{set radix} sets the radix of input and output to
26281 the same base; without an argument, it resets the radix back to its
26282 default value of 10.
26287 @section Configuring the Current ABI
26289 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26290 application automatically. However, sometimes you need to override its
26291 conclusions. Use these commands to manage @value{GDBN}'s view of the
26297 @cindex Newlib OS ABI and its influence on the longjmp handling
26299 One @value{GDBN} configuration can debug binaries for multiple operating
26300 system targets, either via remote debugging or native emulation.
26301 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26302 but you can override its conclusion using the @code{set osabi} command.
26303 One example where this is useful is in debugging of binaries which use
26304 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26305 not have the same identifying marks that the standard C library for your
26308 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26309 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26310 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26311 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26315 Show the OS ABI currently in use.
26318 With no argument, show the list of registered available OS ABI's.
26320 @item set osabi @var{abi}
26321 Set the current OS ABI to @var{abi}.
26324 @cindex float promotion
26326 Generally, the way that an argument of type @code{float} is passed to a
26327 function depends on whether the function is prototyped. For a prototyped
26328 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26329 according to the architecture's convention for @code{float}. For unprototyped
26330 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26331 @code{double} and then passed.
26333 Unfortunately, some forms of debug information do not reliably indicate whether
26334 a function is prototyped. If @value{GDBN} calls a function that is not marked
26335 as prototyped, it consults @kbd{set coerce-float-to-double}.
26338 @kindex set coerce-float-to-double
26339 @item set coerce-float-to-double
26340 @itemx set coerce-float-to-double on
26341 Arguments of type @code{float} will be promoted to @code{double} when passed
26342 to an unprototyped function. This is the default setting.
26344 @item set coerce-float-to-double off
26345 Arguments of type @code{float} will be passed directly to unprototyped
26348 @kindex show coerce-float-to-double
26349 @item show coerce-float-to-double
26350 Show the current setting of promoting @code{float} to @code{double}.
26354 @kindex show cp-abi
26355 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26356 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26357 used to build your application. @value{GDBN} only fully supports
26358 programs with a single C@t{++} ABI; if your program contains code using
26359 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26360 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26361 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26362 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26363 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26364 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26369 Show the C@t{++} ABI currently in use.
26372 With no argument, show the list of supported C@t{++} ABI's.
26374 @item set cp-abi @var{abi}
26375 @itemx set cp-abi auto
26376 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26380 @section Automatically loading associated files
26381 @cindex auto-loading
26383 @value{GDBN} sometimes reads files with commands and settings automatically,
26384 without being explicitly told so by the user. We call this feature
26385 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26386 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26387 results or introduce security risks (e.g., if the file comes from untrusted
26390 There are various kinds of files @value{GDBN} can automatically load.
26391 In addition to these files, @value{GDBN} supports auto-loading code written
26392 in various extension languages. @xref{Auto-loading extensions}.
26394 Note that loading of these associated files (including the local @file{.gdbinit}
26395 file) requires accordingly configured @code{auto-load safe-path}
26396 (@pxref{Auto-loading safe path}).
26398 For these reasons, @value{GDBN} includes commands and options to let you
26399 control when to auto-load files and which files should be auto-loaded.
26402 @anchor{set auto-load off}
26403 @kindex set auto-load off
26404 @item set auto-load off
26405 Globally disable loading of all auto-loaded files.
26406 You may want to use this command with the @samp{-iex} option
26407 (@pxref{Option -init-eval-command}) such as:
26409 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26412 Be aware that system init file (@pxref{System-wide configuration})
26413 and init files from your home directory (@pxref{Home Directory Init File})
26414 still get read (as they come from generally trusted directories).
26415 To prevent @value{GDBN} from auto-loading even those init files, use the
26416 @option{-nx} option (@pxref{Mode Options}), in addition to
26417 @code{set auto-load no}.
26419 @anchor{show auto-load}
26420 @kindex show auto-load
26421 @item show auto-load
26422 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26426 (gdb) show auto-load
26427 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26428 libthread-db: Auto-loading of inferior specific libthread_db is on.
26429 local-gdbinit: Auto-loading of .gdbinit script from current directory
26431 python-scripts: Auto-loading of Python scripts is on.
26432 safe-path: List of directories from which it is safe to auto-load files
26433 is $debugdir:$datadir/auto-load.
26434 scripts-directory: List of directories from which to load auto-loaded scripts
26435 is $debugdir:$datadir/auto-load.
26438 @anchor{info auto-load}
26439 @kindex info auto-load
26440 @item info auto-load
26441 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26445 (gdb) info auto-load
26448 Yes /home/user/gdb/gdb-gdb.gdb
26449 libthread-db: No auto-loaded libthread-db.
26450 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26454 Yes /home/user/gdb/gdb-gdb.py
26458 These are @value{GDBN} control commands for the auto-loading:
26460 @multitable @columnfractions .5 .5
26461 @item @xref{set auto-load off}.
26462 @tab Disable auto-loading globally.
26463 @item @xref{show auto-load}.
26464 @tab Show setting of all kinds of files.
26465 @item @xref{info auto-load}.
26466 @tab Show state of all kinds of files.
26467 @item @xref{set auto-load gdb-scripts}.
26468 @tab Control for @value{GDBN} command scripts.
26469 @item @xref{show auto-load gdb-scripts}.
26470 @tab Show setting of @value{GDBN} command scripts.
26471 @item @xref{info auto-load gdb-scripts}.
26472 @tab Show state of @value{GDBN} command scripts.
26473 @item @xref{set auto-load python-scripts}.
26474 @tab Control for @value{GDBN} Python scripts.
26475 @item @xref{show auto-load python-scripts}.
26476 @tab Show setting of @value{GDBN} Python scripts.
26477 @item @xref{info auto-load python-scripts}.
26478 @tab Show state of @value{GDBN} Python scripts.
26479 @item @xref{set auto-load guile-scripts}.
26480 @tab Control for @value{GDBN} Guile scripts.
26481 @item @xref{show auto-load guile-scripts}.
26482 @tab Show setting of @value{GDBN} Guile scripts.
26483 @item @xref{info auto-load guile-scripts}.
26484 @tab Show state of @value{GDBN} Guile scripts.
26485 @item @xref{set auto-load scripts-directory}.
26486 @tab Control for @value{GDBN} auto-loaded scripts location.
26487 @item @xref{show auto-load scripts-directory}.
26488 @tab Show @value{GDBN} auto-loaded scripts location.
26489 @item @xref{add-auto-load-scripts-directory}.
26490 @tab Add directory for auto-loaded scripts location list.
26491 @item @xref{set auto-load local-gdbinit}.
26492 @tab Control for init file in the current directory.
26493 @item @xref{show auto-load local-gdbinit}.
26494 @tab Show setting of init file in the current directory.
26495 @item @xref{info auto-load local-gdbinit}.
26496 @tab Show state of init file in the current directory.
26497 @item @xref{set auto-load libthread-db}.
26498 @tab Control for thread debugging library.
26499 @item @xref{show auto-load libthread-db}.
26500 @tab Show setting of thread debugging library.
26501 @item @xref{info auto-load libthread-db}.
26502 @tab Show state of thread debugging library.
26503 @item @xref{set auto-load safe-path}.
26504 @tab Control directories trusted for automatic loading.
26505 @item @xref{show auto-load safe-path}.
26506 @tab Show directories trusted for automatic loading.
26507 @item @xref{add-auto-load-safe-path}.
26508 @tab Add directory trusted for automatic loading.
26512 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26513 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26515 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26516 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26519 @node Init File in the Current Directory
26520 @subsection Automatically loading init file in the current directory
26521 @cindex auto-loading init file in the current directory
26523 By default, @value{GDBN} reads and executes the canned sequences of commands
26524 from init file (if any) in the current working directory,
26525 see @ref{Init File in the Current Directory during Startup}.
26527 Note that loading of this local @file{.gdbinit} file also requires accordingly
26528 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26531 @anchor{set auto-load local-gdbinit}
26532 @kindex set auto-load local-gdbinit
26533 @item set auto-load local-gdbinit [on|off]
26534 Enable or disable the auto-loading of canned sequences of commands
26535 (@pxref{Sequences}) found in init file in the current directory.
26537 @anchor{show auto-load local-gdbinit}
26538 @kindex show auto-load local-gdbinit
26539 @item show auto-load local-gdbinit
26540 Show whether auto-loading of canned sequences of commands from init file in the
26541 current directory is enabled or disabled.
26543 @anchor{info auto-load local-gdbinit}
26544 @kindex info auto-load local-gdbinit
26545 @item info auto-load local-gdbinit
26546 Print whether canned sequences of commands from init file in the
26547 current directory have been auto-loaded.
26550 @node libthread_db.so.1 file
26551 @subsection Automatically loading thread debugging library
26552 @cindex auto-loading libthread_db.so.1
26554 This feature is currently present only on @sc{gnu}/Linux native hosts.
26556 @value{GDBN} reads in some cases thread debugging library from places specific
26557 to the inferior (@pxref{set libthread-db-search-path}).
26559 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26560 without checking this @samp{set auto-load libthread-db} switch as system
26561 libraries have to be trusted in general. In all other cases of
26562 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26563 auto-load libthread-db} is enabled before trying to open such thread debugging
26566 Note that loading of this debugging library also requires accordingly configured
26567 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26570 @anchor{set auto-load libthread-db}
26571 @kindex set auto-load libthread-db
26572 @item set auto-load libthread-db [on|off]
26573 Enable or disable the auto-loading of inferior specific thread debugging library.
26575 @anchor{show auto-load libthread-db}
26576 @kindex show auto-load libthread-db
26577 @item show auto-load libthread-db
26578 Show whether auto-loading of inferior specific thread debugging library is
26579 enabled or disabled.
26581 @anchor{info auto-load libthread-db}
26582 @kindex info auto-load libthread-db
26583 @item info auto-load libthread-db
26584 Print the list of all loaded inferior specific thread debugging libraries and
26585 for each such library print list of inferior @var{pid}s using it.
26588 @node Auto-loading safe path
26589 @subsection Security restriction for auto-loading
26590 @cindex auto-loading safe-path
26592 As the files of inferior can come from untrusted source (such as submitted by
26593 an application user) @value{GDBN} does not always load any files automatically.
26594 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26595 directories trusted for loading files not explicitly requested by user.
26596 Each directory can also be a shell wildcard pattern.
26598 If the path is not set properly you will see a warning and the file will not
26603 Reading symbols from /home/user/gdb/gdb...
26604 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26605 declined by your `auto-load safe-path' set
26606 to "$debugdir:$datadir/auto-load".
26607 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26608 declined by your `auto-load safe-path' set
26609 to "$debugdir:$datadir/auto-load".
26613 To instruct @value{GDBN} to go ahead and use the init files anyway,
26614 invoke @value{GDBN} like this:
26617 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26620 The list of trusted directories is controlled by the following commands:
26623 @anchor{set auto-load safe-path}
26624 @kindex set auto-load safe-path
26625 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26626 Set the list of directories (and their subdirectories) trusted for automatic
26627 loading and execution of scripts. You can also enter a specific trusted file.
26628 Each directory can also be a shell wildcard pattern; wildcards do not match
26629 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26630 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26631 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26632 its default value as specified during @value{GDBN} compilation.
26634 The list of directories uses path separator (@samp{:} on GNU and Unix
26635 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26636 to the @env{PATH} environment variable.
26638 @anchor{show auto-load safe-path}
26639 @kindex show auto-load safe-path
26640 @item show auto-load safe-path
26641 Show the list of directories trusted for automatic loading and execution of
26644 @anchor{add-auto-load-safe-path}
26645 @kindex add-auto-load-safe-path
26646 @item add-auto-load-safe-path
26647 Add an entry (or list of entries) to the list of directories trusted for
26648 automatic loading and execution of scripts. Multiple entries may be delimited
26649 by the host platform path separator in use.
26652 This variable defaults to what @code{--with-auto-load-dir} has been configured
26653 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26654 substitution applies the same as for @ref{set auto-load scripts-directory}.
26655 The default @code{set auto-load safe-path} value can be also overriden by
26656 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26658 Setting this variable to @file{/} disables this security protection,
26659 corresponding @value{GDBN} configuration option is
26660 @option{--without-auto-load-safe-path}.
26661 This variable is supposed to be set to the system directories writable by the
26662 system superuser only. Users can add their source directories in init files in
26663 their home directories (@pxref{Home Directory Init File}). See also deprecated
26664 init file in the current directory
26665 (@pxref{Init File in the Current Directory during Startup}).
26667 To force @value{GDBN} to load the files it declined to load in the previous
26668 example, you could use one of the following ways:
26671 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26672 Specify this trusted directory (or a file) as additional component of the list.
26673 You have to specify also any existing directories displayed by
26674 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26676 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26677 Specify this directory as in the previous case but just for a single
26678 @value{GDBN} session.
26680 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26681 Disable auto-loading safety for a single @value{GDBN} session.
26682 This assumes all the files you debug during this @value{GDBN} session will come
26683 from trusted sources.
26685 @item @kbd{./configure --without-auto-load-safe-path}
26686 During compilation of @value{GDBN} you may disable any auto-loading safety.
26687 This assumes all the files you will ever debug with this @value{GDBN} come from
26691 On the other hand you can also explicitly forbid automatic files loading which
26692 also suppresses any such warning messages:
26695 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26696 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26698 @item @file{~/.gdbinit}: @samp{set auto-load no}
26699 Disable auto-loading globally for the user
26700 (@pxref{Home Directory Init File}). While it is improbable, you could also
26701 use system init file instead (@pxref{System-wide configuration}).
26704 This setting applies to the file names as entered by user. If no entry matches
26705 @value{GDBN} tries as a last resort to also resolve all the file names into
26706 their canonical form (typically resolving symbolic links) and compare the
26707 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26708 own before starting the comparison so a canonical form of directories is
26709 recommended to be entered.
26711 @node Auto-loading verbose mode
26712 @subsection Displaying files tried for auto-load
26713 @cindex auto-loading verbose mode
26715 For better visibility of all the file locations where you can place scripts to
26716 be auto-loaded with inferior --- or to protect yourself against accidental
26717 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26718 all the files attempted to be loaded. Both existing and non-existing files may
26721 For example the list of directories from which it is safe to auto-load files
26722 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26723 may not be too obvious while setting it up.
26726 (gdb) set debug auto-load on
26727 (gdb) file ~/src/t/true
26728 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26729 for objfile "/tmp/true".
26730 auto-load: Updating directories of "/usr:/opt".
26731 auto-load: Using directory "/usr".
26732 auto-load: Using directory "/opt".
26733 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26734 by your `auto-load safe-path' set to "/usr:/opt".
26738 @anchor{set debug auto-load}
26739 @kindex set debug auto-load
26740 @item set debug auto-load [on|off]
26741 Set whether to print the filenames attempted to be auto-loaded.
26743 @anchor{show debug auto-load}
26744 @kindex show debug auto-load
26745 @item show debug auto-load
26746 Show whether printing of the filenames attempted to be auto-loaded is turned
26750 @node Messages/Warnings
26751 @section Optional Warnings and Messages
26753 @cindex verbose operation
26754 @cindex optional warnings
26755 By default, @value{GDBN} is silent about its inner workings. If you are
26756 running on a slow machine, you may want to use the @code{set verbose}
26757 command. This makes @value{GDBN} tell you when it does a lengthy
26758 internal operation, so you will not think it has crashed.
26760 Currently, the messages controlled by @code{set verbose} are those
26761 which announce that the symbol table for a source file is being read;
26762 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26765 @kindex set verbose
26766 @item set verbose on
26767 Enables @value{GDBN} output of certain informational messages.
26769 @item set verbose off
26770 Disables @value{GDBN} output of certain informational messages.
26772 @kindex show verbose
26774 Displays whether @code{set verbose} is on or off.
26777 By default, if @value{GDBN} encounters bugs in the symbol table of an
26778 object file, it is silent; but if you are debugging a compiler, you may
26779 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26784 @kindex set complaints
26785 @item set complaints @var{limit}
26786 Permits @value{GDBN} to output @var{limit} complaints about each type of
26787 unusual symbols before becoming silent about the problem. Set
26788 @var{limit} to zero to suppress all complaints; set it to a large number
26789 to prevent complaints from being suppressed.
26791 @kindex show complaints
26792 @item show complaints
26793 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26797 @anchor{confirmation requests}
26798 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26799 lot of stupid questions to confirm certain commands. For example, if
26800 you try to run a program which is already running:
26804 The program being debugged has been started already.
26805 Start it from the beginning? (y or n)
26808 If you are willing to unflinchingly face the consequences of your own
26809 commands, you can disable this ``feature'':
26813 @kindex set confirm
26815 @cindex confirmation
26816 @cindex stupid questions
26817 @item set confirm off
26818 Disables confirmation requests. Note that running @value{GDBN} with
26819 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26820 automatically disables confirmation requests.
26822 @item set confirm on
26823 Enables confirmation requests (the default).
26825 @kindex show confirm
26827 Displays state of confirmation requests.
26831 @cindex command tracing
26832 If you need to debug user-defined commands or sourced files you may find it
26833 useful to enable @dfn{command tracing}. In this mode each command will be
26834 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26835 quantity denoting the call depth of each command.
26838 @kindex set trace-commands
26839 @cindex command scripts, debugging
26840 @item set trace-commands on
26841 Enable command tracing.
26842 @item set trace-commands off
26843 Disable command tracing.
26844 @item show trace-commands
26845 Display the current state of command tracing.
26848 @node Debugging Output
26849 @section Optional Messages about Internal Happenings
26850 @cindex optional debugging messages
26852 @value{GDBN} has commands that enable optional debugging messages from
26853 various @value{GDBN} subsystems; normally these commands are of
26854 interest to @value{GDBN} maintainers, or when reporting a bug. This
26855 section documents those commands.
26858 @kindex set exec-done-display
26859 @item set exec-done-display
26860 Turns on or off the notification of asynchronous commands'
26861 completion. When on, @value{GDBN} will print a message when an
26862 asynchronous command finishes its execution. The default is off.
26863 @kindex show exec-done-display
26864 @item show exec-done-display
26865 Displays the current setting of asynchronous command completion
26869 @cindex ARM AArch64
26870 @item set debug aarch64
26871 Turns on or off display of debugging messages related to ARM AArch64.
26872 The default is off.
26874 @item show debug aarch64
26875 Displays the current state of displaying debugging messages related to
26878 @cindex gdbarch debugging info
26879 @cindex architecture debugging info
26880 @item set debug arch
26881 Turns on or off display of gdbarch debugging info. The default is off
26882 @item show debug arch
26883 Displays the current state of displaying gdbarch debugging info.
26885 @item set debug aix-solib
26886 @cindex AIX shared library debugging
26887 Control display of debugging messages from the AIX shared library
26888 support module. The default is off.
26889 @item show debug aix-solib
26890 Show the current state of displaying AIX shared library debugging messages.
26892 @item set debug aix-thread
26893 @cindex AIX threads
26894 Display debugging messages about inner workings of the AIX thread
26896 @item show debug aix-thread
26897 Show the current state of AIX thread debugging info display.
26899 @item set debug check-physname
26901 Check the results of the ``physname'' computation. When reading DWARF
26902 debugging information for C@t{++}, @value{GDBN} attempts to compute
26903 each entity's name. @value{GDBN} can do this computation in two
26904 different ways, depending on exactly what information is present.
26905 When enabled, this setting causes @value{GDBN} to compute the names
26906 both ways and display any discrepancies.
26907 @item show debug check-physname
26908 Show the current state of ``physname'' checking.
26910 @item set debug coff-pe-read
26911 @cindex COFF/PE exported symbols
26912 Control display of debugging messages related to reading of COFF/PE
26913 exported symbols. The default is off.
26914 @item show debug coff-pe-read
26915 Displays the current state of displaying debugging messages related to
26916 reading of COFF/PE exported symbols.
26918 @item set debug dwarf-die
26920 Dump DWARF DIEs after they are read in.
26921 The value is the number of nesting levels to print.
26922 A value of zero turns off the display.
26923 @item show debug dwarf-die
26924 Show the current state of DWARF DIE debugging.
26926 @item set debug dwarf-line
26927 @cindex DWARF Line Tables
26928 Turns on or off display of debugging messages related to reading
26929 DWARF line tables. The default is 0 (off).
26930 A value of 1 provides basic information.
26931 A value greater than 1 provides more verbose information.
26932 @item show debug dwarf-line
26933 Show the current state of DWARF line table debugging.
26935 @item set debug dwarf-read
26936 @cindex DWARF Reading
26937 Turns on or off display of debugging messages related to reading
26938 DWARF debug info. The default is 0 (off).
26939 A value of 1 provides basic information.
26940 A value greater than 1 provides more verbose information.
26941 @item show debug dwarf-read
26942 Show the current state of DWARF reader debugging.
26944 @item set debug displaced
26945 @cindex displaced stepping debugging info
26946 Turns on or off display of @value{GDBN} debugging info for the
26947 displaced stepping support. The default is off.
26948 @item show debug displaced
26949 Displays the current state of displaying @value{GDBN} debugging info
26950 related to displaced stepping.
26952 @item set debug event
26953 @cindex event debugging info
26954 Turns on or off display of @value{GDBN} event debugging info. The
26956 @item show debug event
26957 Displays the current state of displaying @value{GDBN} event debugging
26960 @item set debug event-loop
26961 @cindex event-loop debugging
26962 Controls output of debugging info about the event loop. The possible
26963 values are @samp{off}, @samp{all} (shows all debugging info) and
26964 @samp{all-except-ui} (shows all debugging info except those about
26965 UI-related events).
26966 @item show debug event-loop
26967 Shows the current state of displaying debugging info about the event
26970 @item set debug expression
26971 @cindex expression debugging info
26972 Turns on or off display of debugging info about @value{GDBN}
26973 expression parsing. The default is off.
26974 @item show debug expression
26975 Displays the current state of displaying debugging info about
26976 @value{GDBN} expression parsing.
26978 @item set debug fbsd-lwp
26979 @cindex FreeBSD LWP debug messages
26980 Turns on or off debugging messages from the FreeBSD LWP debug support.
26981 @item show debug fbsd-lwp
26982 Show the current state of FreeBSD LWP debugging messages.
26984 @item set debug fbsd-nat
26985 @cindex FreeBSD native target debug messages
26986 Turns on or off debugging messages from the FreeBSD native target.
26987 @item show debug fbsd-nat
26988 Show the current state of FreeBSD native target debugging messages.
26990 @item set debug fortran-array-slicing
26991 @cindex fortran array slicing debugging info
26992 Turns on or off display of @value{GDBN} Fortran array slicing
26993 debugging info. The default is off.
26995 @item show debug fortran-array-slicing
26996 Displays the current state of displaying @value{GDBN} Fortran array
26997 slicing debugging info.
26999 @item set debug frame
27000 @cindex frame debugging info
27001 Turns on or off display of @value{GDBN} frame debugging info. The
27003 @item show debug frame
27004 Displays the current state of displaying @value{GDBN} frame debugging
27007 @item set debug gnu-nat
27008 @cindex @sc{gnu}/Hurd debug messages
27009 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27010 @item show debug gnu-nat
27011 Show the current state of @sc{gnu}/Hurd debugging messages.
27013 @item set debug infrun
27014 @cindex inferior debugging info
27015 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27016 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27017 for implementing operations such as single-stepping the inferior.
27018 @item show debug infrun
27019 Displays the current state of @value{GDBN} inferior debugging.
27021 @item set debug jit
27022 @cindex just-in-time compilation, debugging messages
27023 Turn on or off debugging messages from JIT debug support.
27024 @item show debug jit
27025 Displays the current state of @value{GDBN} JIT debugging.
27027 @item set debug lin-lwp
27028 @cindex @sc{gnu}/Linux LWP debug messages
27029 @cindex Linux lightweight processes
27030 Turn on or off debugging messages from the Linux LWP debug support.
27031 @item show debug lin-lwp
27032 Show the current state of Linux LWP debugging messages.
27034 @item set debug linux-namespaces
27035 @cindex @sc{gnu}/Linux namespaces debug messages
27036 Turn on or off debugging messages from the Linux namespaces debug support.
27037 @item show debug linux-namespaces
27038 Show the current state of Linux namespaces debugging messages.
27040 @item set debug mach-o
27041 @cindex Mach-O symbols processing
27042 Control display of debugging messages related to Mach-O symbols
27043 processing. The default is off.
27044 @item show debug mach-o
27045 Displays the current state of displaying debugging messages related to
27046 reading of COFF/PE exported symbols.
27048 @item set debug notification
27049 @cindex remote async notification debugging info
27050 Turn on or off debugging messages about remote async notification.
27051 The default is off.
27052 @item show debug notification
27053 Displays the current state of remote async notification debugging messages.
27055 @item set debug observer
27056 @cindex observer debugging info
27057 Turns on or off display of @value{GDBN} observer debugging. This
27058 includes info such as the notification of observable events.
27059 @item show debug observer
27060 Displays the current state of observer debugging.
27062 @item set debug overload
27063 @cindex C@t{++} overload debugging info
27064 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27065 info. This includes info such as ranking of functions, etc. The default
27067 @item show debug overload
27068 Displays the current state of displaying @value{GDBN} C@t{++} overload
27071 @cindex expression parser, debugging info
27072 @cindex debug expression parser
27073 @item set debug parser
27074 Turns on or off the display of expression parser debugging output.
27075 Internally, this sets the @code{yydebug} variable in the expression
27076 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27077 details. The default is off.
27078 @item show debug parser
27079 Show the current state of expression parser debugging.
27081 @cindex packets, reporting on stdout
27082 @cindex serial connections, debugging
27083 @cindex debug remote protocol
27084 @cindex remote protocol debugging
27085 @cindex display remote packets
27086 @item set debug remote
27087 Turns on or off display of reports on all packets sent back and forth across
27088 the serial line to the remote machine. The info is printed on the
27089 @value{GDBN} standard output stream. The default is off.
27090 @item show debug remote
27091 Displays the state of display of remote packets.
27093 @item set debug remote-packet-max-chars
27094 Sets the maximum number of characters to display for each remote packet when
27095 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27096 displaying lengthy remote packets and polluting the console.
27098 The default value is @code{512}, which means @value{GDBN} will truncate each
27099 remote packet after 512 bytes.
27101 Setting this option to @code{unlimited} will disable truncation and will output
27102 the full length of the remote packets.
27103 @item show debug remote-packet-max-chars
27104 Displays the number of bytes to output for remote packet debugging.
27106 @item set debug separate-debug-file
27107 Turns on or off display of debug output about separate debug file search.
27108 @item show debug separate-debug-file
27109 Displays the state of separate debug file search debug output.
27111 @item set debug serial
27112 Turns on or off display of @value{GDBN} serial debugging info. The
27114 @item show debug serial
27115 Displays the current state of displaying @value{GDBN} serial debugging
27118 @item set debug solib-frv
27119 @cindex FR-V shared-library debugging
27120 Turn on or off debugging messages for FR-V shared-library code.
27121 @item show debug solib-frv
27122 Display the current state of FR-V shared-library code debugging
27125 @item set debug symbol-lookup
27126 @cindex symbol lookup
27127 Turns on or off display of debugging messages related to symbol lookup.
27128 The default is 0 (off).
27129 A value of 1 provides basic information.
27130 A value greater than 1 provides more verbose information.
27131 @item show debug symbol-lookup
27132 Show the current state of symbol lookup debugging messages.
27134 @item set debug symfile
27135 @cindex symbol file functions
27136 Turns on or off display of debugging messages related to symbol file functions.
27137 The default is off. @xref{Files}.
27138 @item show debug symfile
27139 Show the current state of symbol file debugging messages.
27141 @item set debug symtab-create
27142 @cindex symbol table creation
27143 Turns on or off display of debugging messages related to symbol table creation.
27144 The default is 0 (off).
27145 A value of 1 provides basic information.
27146 A value greater than 1 provides more verbose information.
27147 @item show debug symtab-create
27148 Show the current state of symbol table creation debugging.
27150 @item set debug target
27151 @cindex target debugging info
27152 Turns on or off display of @value{GDBN} target debugging info. This info
27153 includes what is going on at the target level of GDB, as it happens. The
27154 default is 0. Set it to 1 to track events, and to 2 to also track the
27155 value of large memory transfers.
27156 @item show debug target
27157 Displays the current state of displaying @value{GDBN} target debugging
27160 @item set debug timestamp
27161 @cindex timestamping debugging info
27162 Turns on or off display of timestamps with @value{GDBN} debugging info.
27163 When enabled, seconds and microseconds are displayed before each debugging
27165 @item show debug timestamp
27166 Displays the current state of displaying timestamps with @value{GDBN}
27169 @item set debug varobj
27170 @cindex variable object debugging info
27171 Turns on or off display of @value{GDBN} variable object debugging
27172 info. The default is off.
27173 @item show debug varobj
27174 Displays the current state of displaying @value{GDBN} variable object
27177 @item set debug xml
27178 @cindex XML parser debugging
27179 Turn on or off debugging messages for built-in XML parsers.
27180 @item show debug xml
27181 Displays the current state of XML debugging messages.
27184 @node Other Misc Settings
27185 @section Other Miscellaneous Settings
27186 @cindex miscellaneous settings
27189 @kindex set interactive-mode
27190 @item set interactive-mode
27191 If @code{on}, forces @value{GDBN} to assume that GDB was started
27192 in a terminal. In practice, this means that @value{GDBN} should wait
27193 for the user to answer queries generated by commands entered at
27194 the command prompt. If @code{off}, forces @value{GDBN} to operate
27195 in the opposite mode, and it uses the default answers to all queries.
27196 If @code{auto} (the default), @value{GDBN} tries to determine whether
27197 its standard input is a terminal, and works in interactive-mode if it
27198 is, non-interactively otherwise.
27200 In the vast majority of cases, the debugger should be able to guess
27201 correctly which mode should be used. But this setting can be useful
27202 in certain specific cases, such as running a MinGW @value{GDBN}
27203 inside a cygwin window.
27205 @kindex show interactive-mode
27206 @item show interactive-mode
27207 Displays whether the debugger is operating in interactive mode or not.
27210 @node Extending GDB
27211 @chapter Extending @value{GDBN}
27212 @cindex extending GDB
27214 @value{GDBN} provides several mechanisms for extension.
27215 @value{GDBN} also provides the ability to automatically load
27216 extensions when it reads a file for debugging. This allows the
27217 user to automatically customize @value{GDBN} for the program
27220 To facilitate the use of extension languages, @value{GDBN} is capable
27221 of evaluating the contents of a file. When doing so, @value{GDBN}
27222 can recognize which extension language is being used by looking at
27223 the filename extension. Files with an unrecognized filename extension
27224 are always treated as a @value{GDBN} Command Files.
27225 @xref{Command Files,, Command files}.
27227 You can control how @value{GDBN} evaluates these files with the following
27231 @kindex set script-extension
27232 @kindex show script-extension
27233 @item set script-extension off
27234 All scripts are always evaluated as @value{GDBN} Command Files.
27236 @item set script-extension soft
27237 The debugger determines the scripting language based on filename
27238 extension. If this scripting language is supported, @value{GDBN}
27239 evaluates the script using that language. Otherwise, it evaluates
27240 the file as a @value{GDBN} Command File.
27242 @item set script-extension strict
27243 The debugger determines the scripting language based on filename
27244 extension, and evaluates the script using that language. If the
27245 language is not supported, then the evaluation fails.
27247 @item show script-extension
27248 Display the current value of the @code{script-extension} option.
27252 @ifset SYSTEM_GDBINIT_DIR
27253 This setting is not used for files in the system-wide gdbinit directory.
27254 Files in that directory must have an extension matching their language,
27255 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27256 commands. @xref{Startup}.
27260 * Sequences:: Canned Sequences of @value{GDBN} Commands
27261 * Aliases:: Command Aliases
27262 * Python:: Extending @value{GDBN} using Python
27263 * Guile:: Extending @value{GDBN} using Guile
27264 * Auto-loading extensions:: Automatically loading extensions
27265 * Multiple Extension Languages:: Working with multiple extension languages
27269 @section Canned Sequences of Commands
27271 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27272 Command Lists}), @value{GDBN} provides two ways to store sequences of
27273 commands for execution as a unit: user-defined commands and command
27277 * Define:: How to define your own commands
27278 * Hooks:: Hooks for user-defined commands
27279 * Command Files:: How to write scripts of commands to be stored in a file
27280 * Output:: Commands for controlled output
27281 * Auto-loading sequences:: Controlling auto-loaded command files
27285 @subsection User-defined Commands
27287 @cindex user-defined command
27288 @cindex arguments, to user-defined commands
27289 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27290 which you assign a new name as a command. This is done with the
27291 @code{define} command. User commands may accept an unlimited number of arguments
27292 separated by whitespace. Arguments are accessed within the user command
27293 via @code{$arg0@dots{}$argN}. A trivial example:
27297 print $arg0 + $arg1 + $arg2
27302 To execute the command use:
27309 This defines the command @code{adder}, which prints the sum of
27310 its three arguments. Note the arguments are text substitutions, so they may
27311 reference variables, use complex expressions, or even perform inferior
27314 @cindex argument count in user-defined commands
27315 @cindex how many arguments (user-defined commands)
27316 In addition, @code{$argc} may be used to find out how many arguments have
27322 print $arg0 + $arg1
27325 print $arg0 + $arg1 + $arg2
27330 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27331 to process a variable number of arguments:
27338 eval "set $sum = $sum + $arg%d", $i
27348 @item define @var{commandname}
27349 Define a command named @var{commandname}. If there is already a command
27350 by that name, you are asked to confirm that you want to redefine it.
27351 The argument @var{commandname} may be a bare command name consisting of letters,
27352 numbers, dashes, dots, and underscores. It may also start with any
27353 predefined or user-defined prefix command.
27354 For example, @samp{define target my-target} creates
27355 a user-defined @samp{target my-target} command.
27357 The definition of the command is made up of other @value{GDBN} command lines,
27358 which are given following the @code{define} command. The end of these
27359 commands is marked by a line containing @code{end}.
27362 @kindex end@r{ (user-defined commands)}
27363 @item document @var{commandname}
27364 Document the user-defined command @var{commandname}, so that it can be
27365 accessed by @code{help}. The command @var{commandname} must already be
27366 defined. This command reads lines of documentation just as @code{define}
27367 reads the lines of the command definition, ending with @code{end}.
27368 After the @code{document} command is finished, @code{help} on command
27369 @var{commandname} displays the documentation you have written.
27371 You may use the @code{document} command again to change the
27372 documentation of a command. Redefining the command with @code{define}
27373 does not change the documentation.
27375 @kindex define-prefix
27376 @item define-prefix @var{commandname}
27377 Define or mark the command @var{commandname} as a user-defined prefix
27378 command. Once marked, @var{commandname} can be used as prefix command
27379 by the @code{define} command.
27380 Note that @code{define-prefix} can be used with a not yet defined
27381 @var{commandname}. In such a case, @var{commandname} is defined as
27382 an empty user-defined command.
27383 In case you redefine a command that was marked as a user-defined
27384 prefix command, the subcommands of the redefined command are kept
27385 (and @value{GDBN} indicates so to the user).
27389 (gdb) define-prefix abc
27390 (gdb) define-prefix abc def
27391 (gdb) define abc def
27392 Type commands for definition of "abc def".
27393 End with a line saying just "end".
27394 >echo command initial def\n
27396 (gdb) define abc def ghi
27397 Type commands for definition of "abc def ghi".
27398 End with a line saying just "end".
27399 >echo command ghi\n
27401 (gdb) define abc def
27402 Keeping subcommands of prefix command "def".
27403 Redefine command "def"? (y or n) y
27404 Type commands for definition of "abc def".
27405 End with a line saying just "end".
27406 >echo command def\n
27415 @kindex dont-repeat
27416 @cindex don't repeat command
27418 Used inside a user-defined command, this tells @value{GDBN} that this
27419 command should not be repeated when the user hits @key{RET}
27420 (@pxref{Command Syntax, repeat last command}).
27422 @kindex help user-defined
27423 @item help user-defined
27424 List all user-defined commands and all python commands defined in class
27425 COMMAND_USER. The first line of the documentation or docstring is
27430 @itemx show user @var{commandname}
27431 Display the @value{GDBN} commands used to define @var{commandname} (but
27432 not its documentation). If no @var{commandname} is given, display the
27433 definitions for all user-defined commands.
27434 This does not work for user-defined python commands.
27436 @cindex infinite recursion in user-defined commands
27437 @kindex show max-user-call-depth
27438 @kindex set max-user-call-depth
27439 @item show max-user-call-depth
27440 @itemx set max-user-call-depth
27441 The value of @code{max-user-call-depth} controls how many recursion
27442 levels are allowed in user-defined commands before @value{GDBN} suspects an
27443 infinite recursion and aborts the command.
27444 This does not apply to user-defined python commands.
27447 In addition to the above commands, user-defined commands frequently
27448 use control flow commands, described in @ref{Command Files}.
27450 When user-defined commands are executed, the
27451 commands of the definition are not printed. An error in any command
27452 stops execution of the user-defined command.
27454 If used interactively, commands that would ask for confirmation proceed
27455 without asking when used inside a user-defined command. Many @value{GDBN}
27456 commands that normally print messages to say what they are doing omit the
27457 messages when used in a user-defined command.
27460 @subsection User-defined Command Hooks
27461 @cindex command hooks
27462 @cindex hooks, for commands
27463 @cindex hooks, pre-command
27466 You may define @dfn{hooks}, which are a special kind of user-defined
27467 command. Whenever you run the command @samp{foo}, if the user-defined
27468 command @samp{hook-foo} exists, it is executed (with no arguments)
27469 before that command.
27471 @cindex hooks, post-command
27473 A hook may also be defined which is run after the command you executed.
27474 Whenever you run the command @samp{foo}, if the user-defined command
27475 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27476 that command. Post-execution hooks may exist simultaneously with
27477 pre-execution hooks, for the same command.
27479 It is valid for a hook to call the command which it hooks. If this
27480 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27482 @c It would be nice if hookpost could be passed a parameter indicating
27483 @c if the command it hooks executed properly or not. FIXME!
27485 @kindex stop@r{, a pseudo-command}
27486 In addition, a pseudo-command, @samp{stop} exists. Defining
27487 (@samp{hook-stop}) makes the associated commands execute every time
27488 execution stops in your program: before breakpoint commands are run,
27489 displays are printed, or the stack frame is printed.
27491 For example, to ignore @code{SIGALRM} signals while
27492 single-stepping, but treat them normally during normal execution,
27497 handle SIGALRM nopass
27501 handle SIGALRM pass
27504 define hook-continue
27505 handle SIGALRM pass
27509 As a further example, to hook at the beginning and end of the @code{echo}
27510 command, and to add extra text to the beginning and end of the message,
27518 define hookpost-echo
27522 (@value{GDBP}) echo Hello World
27523 <<<---Hello World--->>>
27528 You can define a hook for any single-word command in @value{GDBN}, but
27529 not for command aliases; you should define a hook for the basic command
27530 name, e.g.@: @code{backtrace} rather than @code{bt}.
27531 @c FIXME! So how does Joe User discover whether a command is an alias
27533 You can hook a multi-word command by adding @code{hook-} or
27534 @code{hookpost-} to the last word of the command, e.g.@:
27535 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27537 If an error occurs during the execution of your hook, execution of
27538 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27539 (before the command that you actually typed had a chance to run).
27541 If you try to define a hook which does not match any known command, you
27542 get a warning from the @code{define} command.
27544 @node Command Files
27545 @subsection Command Files
27547 @cindex command files
27548 @cindex scripting commands
27549 A command file for @value{GDBN} is a text file made of lines that are
27550 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27551 also be included. An empty line in a command file does nothing; it
27552 does not mean to repeat the last command, as it would from the
27555 You can request the execution of a command file with the @code{source}
27556 command. Note that the @code{source} command is also used to evaluate
27557 scripts that are not Command Files. The exact behavior can be configured
27558 using the @code{script-extension} setting.
27559 @xref{Extending GDB,, Extending GDB}.
27563 @cindex execute commands from a file
27564 @item source [-s] [-v] @var{filename}
27565 Execute the command file @var{filename}.
27568 The lines in a command file are generally executed sequentially,
27569 unless the order of execution is changed by one of the
27570 @emph{flow-control commands} described below. The commands are not
27571 printed as they are executed. An error in any command terminates
27572 execution of the command file and control is returned to the console.
27574 @value{GDBN} first searches for @var{filename} in the current directory.
27575 If the file is not found there, and @var{filename} does not specify a
27576 directory, then @value{GDBN} also looks for the file on the source search path
27577 (specified with the @samp{directory} command);
27578 except that @file{$cdir} is not searched because the compilation directory
27579 is not relevant to scripts.
27581 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27582 on the search path even if @var{filename} specifies a directory.
27583 The search is done by appending @var{filename} to each element of the
27584 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27585 and the search path contains @file{/home/user} then @value{GDBN} will
27586 look for the script @file{/home/user/mylib/myscript}.
27587 The search is also done if @var{filename} is an absolute path.
27588 For example, if @var{filename} is @file{/tmp/myscript} and
27589 the search path contains @file{/home/user} then @value{GDBN} will
27590 look for the script @file{/home/user/tmp/myscript}.
27591 For DOS-like systems, if @var{filename} contains a drive specification,
27592 it is stripped before concatenation. For example, if @var{filename} is
27593 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27594 will look for the script @file{c:/tmp/myscript}.
27596 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27597 each command as it is executed. The option must be given before
27598 @var{filename}, and is interpreted as part of the filename anywhere else.
27600 Commands that would ask for confirmation if used interactively proceed
27601 without asking when used in a command file. Many @value{GDBN} commands that
27602 normally print messages to say what they are doing omit the messages
27603 when called from command files.
27605 @value{GDBN} also accepts command input from standard input. In this
27606 mode, normal output goes to standard output and error output goes to
27607 standard error. Errors in a command file supplied on standard input do
27608 not terminate execution of the command file---execution continues with
27612 gdb < cmds > log 2>&1
27615 (The syntax above will vary depending on the shell used.) This example
27616 will execute commands from the file @file{cmds}. All output and errors
27617 would be directed to @file{log}.
27619 Since commands stored on command files tend to be more general than
27620 commands typed interactively, they frequently need to deal with
27621 complicated situations, such as different or unexpected values of
27622 variables and symbols, changes in how the program being debugged is
27623 built, etc. @value{GDBN} provides a set of flow-control commands to
27624 deal with these complexities. Using these commands, you can write
27625 complex scripts that loop over data structures, execute commands
27626 conditionally, etc.
27633 This command allows to include in your script conditionally executed
27634 commands. The @code{if} command takes a single argument, which is an
27635 expression to evaluate. It is followed by a series of commands that
27636 are executed only if the expression is true (its value is nonzero).
27637 There can then optionally be an @code{else} line, followed by a series
27638 of commands that are only executed if the expression was false. The
27639 end of the list is marked by a line containing @code{end}.
27643 This command allows to write loops. Its syntax is similar to
27644 @code{if}: the command takes a single argument, which is an expression
27645 to evaluate, and must be followed by the commands to execute, one per
27646 line, terminated by an @code{end}. These commands are called the
27647 @dfn{body} of the loop. The commands in the body of @code{while} are
27648 executed repeatedly as long as the expression evaluates to true.
27652 This command exits the @code{while} loop in whose body it is included.
27653 Execution of the script continues after that @code{while}s @code{end}
27656 @kindex loop_continue
27657 @item loop_continue
27658 This command skips the execution of the rest of the body of commands
27659 in the @code{while} loop in whose body it is included. Execution
27660 branches to the beginning of the @code{while} loop, where it evaluates
27661 the controlling expression.
27663 @kindex end@r{ (if/else/while commands)}
27665 Terminate the block of commands that are the body of @code{if},
27666 @code{else}, or @code{while} flow-control commands.
27671 @subsection Commands for Controlled Output
27673 During the execution of a command file or a user-defined command, normal
27674 @value{GDBN} output is suppressed; the only output that appears is what is
27675 explicitly printed by the commands in the definition. This section
27676 describes three commands useful for generating exactly the output you
27681 @item echo @var{text}
27682 @c I do not consider backslash-space a standard C escape sequence
27683 @c because it is not in ANSI.
27684 Print @var{text}. Nonprinting characters can be included in
27685 @var{text} using C escape sequences, such as @samp{\n} to print a
27686 newline. @strong{No newline is printed unless you specify one.}
27687 In addition to the standard C escape sequences, a backslash followed
27688 by a space stands for a space. This is useful for displaying a
27689 string with spaces at the beginning or the end, since leading and
27690 trailing spaces are otherwise trimmed from all arguments.
27691 To print @samp{@w{ }and foo =@w{ }}, use the command
27692 @samp{echo \@w{ }and foo = \@w{ }}.
27694 A backslash at the end of @var{text} can be used, as in C, to continue
27695 the command onto subsequent lines. For example,
27698 echo This is some text\n\
27699 which is continued\n\
27700 onto several lines.\n
27703 produces the same output as
27706 echo This is some text\n
27707 echo which is continued\n
27708 echo onto several lines.\n
27712 @item output @var{expression}
27713 Print the value of @var{expression} and nothing but that value: no
27714 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27715 value history either. @xref{Expressions, ,Expressions}, for more information
27718 @item output/@var{fmt} @var{expression}
27719 Print the value of @var{expression} in format @var{fmt}. You can use
27720 the same formats as for @code{print}. @xref{Output Formats,,Output
27721 Formats}, for more information.
27724 @item printf @var{template}, @var{expressions}@dots{}
27725 Print the values of one or more @var{expressions} under the control of
27726 the string @var{template}. To print several values, make
27727 @var{expressions} be a comma-separated list of individual expressions,
27728 which may be either numbers or pointers. Their values are printed as
27729 specified by @var{template}, exactly as a C program would do by
27730 executing the code below:
27733 printf (@var{template}, @var{expressions}@dots{});
27736 As in @code{C} @code{printf}, ordinary characters in @var{template}
27737 are printed verbatim, while @dfn{conversion specification} introduced
27738 by the @samp{%} character cause subsequent @var{expressions} to be
27739 evaluated, their values converted and formatted according to type and
27740 style information encoded in the conversion specifications, and then
27743 For example, you can print two values in hex like this:
27746 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27749 @code{printf} supports all the standard @code{C} conversion
27750 specifications, including the flags and modifiers between the @samp{%}
27751 character and the conversion letter, with the following exceptions:
27755 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27758 The modifier @samp{*} is not supported for specifying precision or
27762 The @samp{'} flag (for separation of digits into groups according to
27763 @code{LC_NUMERIC'}) is not supported.
27766 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27770 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27773 The conversion letters @samp{a} and @samp{A} are not supported.
27777 Note that the @samp{ll} type modifier is supported only if the
27778 underlying @code{C} implementation used to build @value{GDBN} supports
27779 the @code{long long int} type, and the @samp{L} type modifier is
27780 supported only if @code{long double} type is available.
27782 As in @code{C}, @code{printf} supports simple backslash-escape
27783 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27784 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27785 single character. Octal and hexadecimal escape sequences are not
27788 Additionally, @code{printf} supports conversion specifications for DFP
27789 (@dfn{Decimal Floating Point}) types using the following length modifiers
27790 together with a floating point specifier.
27795 @samp{H} for printing @code{Decimal32} types.
27798 @samp{D} for printing @code{Decimal64} types.
27801 @samp{DD} for printing @code{Decimal128} types.
27804 If the underlying @code{C} implementation used to build @value{GDBN} has
27805 support for the three length modifiers for DFP types, other modifiers
27806 such as width and precision will also be available for @value{GDBN} to use.
27808 In case there is no such @code{C} support, no additional modifiers will be
27809 available and the value will be printed in the standard way.
27811 Here's an example of printing DFP types using the above conversion letters:
27813 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27818 @item eval @var{template}, @var{expressions}@dots{}
27819 Convert the values of one or more @var{expressions} under the control of
27820 the string @var{template} to a command line, and call it.
27824 @node Auto-loading sequences
27825 @subsection Controlling auto-loading native @value{GDBN} scripts
27826 @cindex native script auto-loading
27828 When a new object file is read (for example, due to the @code{file}
27829 command, or because the inferior has loaded a shared library),
27830 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27831 @xref{Auto-loading extensions}.
27833 Auto-loading can be enabled or disabled,
27834 and the list of auto-loaded scripts can be printed.
27837 @anchor{set auto-load gdb-scripts}
27838 @kindex set auto-load gdb-scripts
27839 @item set auto-load gdb-scripts [on|off]
27840 Enable or disable the auto-loading of canned sequences of commands scripts.
27842 @anchor{show auto-load gdb-scripts}
27843 @kindex show auto-load gdb-scripts
27844 @item show auto-load gdb-scripts
27845 Show whether auto-loading of canned sequences of commands scripts is enabled or
27848 @anchor{info auto-load gdb-scripts}
27849 @kindex info auto-load gdb-scripts
27850 @cindex print list of auto-loaded canned sequences of commands scripts
27851 @item info auto-load gdb-scripts [@var{regexp}]
27852 Print the list of all canned sequences of commands scripts that @value{GDBN}
27856 If @var{regexp} is supplied only canned sequences of commands scripts with
27857 matching names are printed.
27860 @section Command Aliases
27861 @cindex aliases for commands
27863 Aliases allow you to define alternate spellings for existing commands.
27864 For example, if a new @value{GDBN} command defined in Python
27865 (@pxref{Python}) has a long name, it is handy to have an abbreviated
27866 version of it that involves less typing.
27868 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27869 of the @samp{step} command even though it is otherwise an ambiguous
27870 abbreviation of other commands like @samp{set} and @samp{show}.
27872 Aliases are also used to provide shortened or more common versions
27873 of multi-word commands. For example, @value{GDBN} provides the
27874 @samp{tty} alias of the @samp{set inferior-tty} command.
27876 You can define a new alias with the @samp{alias} command.
27881 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
27885 @var{alias} specifies the name of the new alias. Each word of
27886 @var{alias} must consist of letters, numbers, dashes and underscores.
27888 @var{command} specifies the name of an existing command
27889 that is being aliased.
27891 @var{command} can also be the name of an existing alias. In this
27892 case, @var{command} cannot be an alias that has default arguments.
27894 The @samp{-a} option specifies that the new alias is an abbreviation
27895 of the command. Abbreviations are not used in command completion.
27897 The @samp{--} option specifies the end of options,
27898 and is useful when @var{alias} begins with a dash.
27900 You can specify @var{default-args} for your alias. These
27901 @var{default-args} will be automatically added before the alias
27902 arguments typed explicitly on the command line.
27904 For example, the below defines an alias @code{btfullall} that shows all local
27905 variables and all frame arguments:
27907 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
27910 For more information about @var{default-args}, see @ref{Command
27911 aliases default args, ,Default Arguments}.
27913 Here is a simple example showing how to make an abbreviation of a
27914 command so that there is less to type. Suppose you were tired of
27915 typing @samp{disas}, the current shortest unambiguous abbreviation of
27916 the @samp{disassemble} command and you wanted an even shorter version
27917 named @samp{di}. The following will accomplish this.
27920 (gdb) alias -a di = disas
27923 Note that aliases are different from user-defined commands. With a
27924 user-defined command, you also need to write documentation for it with
27925 the @samp{document} command. An alias automatically picks up the
27926 documentation of the existing command.
27928 Here is an example where we make @samp{elms} an abbreviation of
27929 @samp{elements} in the @samp{set print elements} command.
27930 This is to show that you can make an abbreviation of any part
27934 (gdb) alias -a set print elms = set print elements
27935 (gdb) alias -a show print elms = show print elements
27936 (gdb) set p elms 20
27938 Limit on string chars or array elements to print is 200.
27941 Note that if you are defining an alias of a @samp{set} command,
27942 and you want to have an alias for the corresponding @samp{show}
27943 command, then you need to define the latter separately.
27945 Unambiguously abbreviated commands are allowed in @var{command} and
27946 @var{alias}, just as they are normally.
27949 (gdb) alias -a set pr elms = set p ele
27952 Finally, here is an example showing the creation of a one word
27953 alias for a more complex command.
27954 This creates alias @samp{spe} of the command @samp{set print elements}.
27957 (gdb) alias spe = set print elements
27962 * Command aliases default args:: Default arguments for aliases
27965 @node Command aliases default args
27966 @subsection Default Arguments
27967 @cindex aliases for commands, default arguments
27969 You can tell @value{GDBN} to always prepend some default arguments to
27970 the list of arguments provided explicitly by the user when using a
27971 user-defined alias.
27973 If you repeatedly use the same arguments or options for a command, you
27974 can define an alias for this command and tell @value{GDBN} to
27975 automatically prepend these arguments or options to the list of
27976 arguments you type explicitly when using the alias@footnote{@value{GDBN}
27977 could easily accept default arguments for pre-defined commands and aliases,
27978 but it was deemed this would be confusing, and so is not allowed.}.
27980 For example, if you often use the command @code{thread apply all}
27981 specifying to work on the threads in ascending order and to continue in case it
27982 encounters an error, you can tell @value{GDBN} to automatically preprend
27983 the @code{-ascending} and @code{-c} options by using:
27986 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
27989 Once you have defined this alias with its default args, any time you type
27990 the @code{thread apply asc-all} followed by @code{some arguments},
27991 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
27993 To have even less to type, you can also define a one word alias:
27995 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
27998 As usual, unambiguous abbreviations can be used for @var{alias}
27999 and @var{default-args}.
28001 The different aliases of a command do not share their default args.
28002 For example, you define a new alias @code{bt_ALL} showing all possible
28003 information and another alias @code{bt_SMALL} showing very limited information
28006 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28007 -past-main -past-entry -full
28008 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28009 -past-main off -past-entry off
28012 (For more on using the @code{alias} command, see @ref{Aliases}.)
28014 Default args are not limited to the arguments and options of @var{command},
28015 but can specify nested commands if @var{command} accepts such a nested command
28017 For example, the below defines @code{faalocalsoftype} that lists the
28018 frames having locals of a certain type, together with the matching
28021 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28022 (@value{GDBP}) faalocalsoftype int
28023 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28028 This is also very useful to define an alias for a set of nested @code{with}
28029 commands to have a particular combination of temporary settings. For example,
28030 the below defines the alias @code{pp10} that pretty prints an expression
28031 argument, with a maximum of 10 elements if the expression is a string or
28034 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28036 This defines the alias @code{pp10} as being a sequence of 3 commands.
28037 The first part @code{with print pretty --} temporarily activates the setting
28038 @code{set print pretty}, then launches the command that follows the separator
28040 The command following the first part is also a @code{with} command that
28041 temporarily changes the setting @code{set print elements} to 10, then
28042 launches the command that follows the second separator @code{--}.
28043 The third part @code{print} is the command the @code{pp10} alias will launch,
28044 using the temporary values of the settings and the arguments explicitly given
28046 For more information about the @code{with} command usage,
28047 see @ref{Command Settings}.
28049 @c Python docs live in a separate file.
28050 @include python.texi
28052 @c Guile docs live in a separate file.
28053 @include guile.texi
28055 @node Auto-loading extensions
28056 @section Auto-loading extensions
28057 @cindex auto-loading extensions
28059 @value{GDBN} provides two mechanisms for automatically loading
28060 extensions when a new object file is read (for example, due to the
28061 @code{file} command, or because the inferior has loaded a shared
28062 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28063 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28064 @code{.debug_gdb_scripts} section of modern file formats like ELF
28065 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28066 section}). For a discussion of the differences between these two
28067 approaches see @ref{Which flavor to choose?}.
28069 The auto-loading feature is useful for supplying application-specific
28070 debugging commands and features.
28072 Auto-loading can be enabled or disabled,
28073 and the list of auto-loaded scripts can be printed.
28074 See the @samp{auto-loading} section of each extension language
28075 for more information.
28076 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28077 For Python files see @ref{Python Auto-loading}.
28079 Note that loading of this script file also requires accordingly configured
28080 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28083 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28084 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28085 * Which flavor to choose?:: Choosing between these approaches
28088 @node objfile-gdbdotext file
28089 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28090 @cindex @file{@var{objfile}-gdb.gdb}
28091 @cindex @file{@var{objfile}-gdb.py}
28092 @cindex @file{@var{objfile}-gdb.scm}
28094 When a new object file is read, @value{GDBN} looks for a file named
28095 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28096 where @var{objfile} is the object file's name and
28097 where @var{ext} is the file extension for the extension language:
28100 @item @file{@var{objfile}-gdb.gdb}
28101 GDB's own command language
28102 @item @file{@var{objfile}-gdb.py}
28104 @item @file{@var{objfile}-gdb.scm}
28108 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28109 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28110 components, and appending the @file{-gdb.@var{ext}} suffix.
28111 If this file exists and is readable, @value{GDBN} will evaluate it as a
28112 script in the specified extension language.
28114 If this file does not exist, then @value{GDBN} will look for
28115 @var{script-name} file in all of the directories as specified below.
28116 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28117 directories is converted to a one-letter subdirectory, i.e.@:
28118 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28119 filesystems disallow colons in file names.)
28121 Note that loading of these files requires an accordingly configured
28122 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28124 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28125 scripts normally according to its @file{.exe} filename. But if no scripts are
28126 found @value{GDBN} also tries script filenames matching the object file without
28127 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28128 is attempted on any platform. This makes the script filenames compatible
28129 between Unix and MS-Windows hosts.
28132 @anchor{set auto-load scripts-directory}
28133 @kindex set auto-load scripts-directory
28134 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28135 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28136 may be delimited by the host platform path separator in use
28137 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28139 Each entry here needs to be covered also by the security setting
28140 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28142 @anchor{with-auto-load-dir}
28143 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28144 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28145 configuration option @option{--with-auto-load-dir}.
28147 Any reference to @file{$debugdir} will get replaced by
28148 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28149 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28150 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28151 @file{$datadir} must be placed as a directory component --- either alone or
28152 delimited by @file{/} or @file{\} directory separators, depending on the host
28155 The list of directories uses path separator (@samp{:} on GNU and Unix
28156 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28157 to the @env{PATH} environment variable.
28159 @anchor{show auto-load scripts-directory}
28160 @kindex show auto-load scripts-directory
28161 @item show auto-load scripts-directory
28162 Show @value{GDBN} auto-loaded scripts location.
28164 @anchor{add-auto-load-scripts-directory}
28165 @kindex add-auto-load-scripts-directory
28166 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28167 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28168 Multiple entries may be delimited by the host platform path separator in use.
28171 @value{GDBN} does not track which files it has already auto-loaded this way.
28172 @value{GDBN} will load the associated script every time the corresponding
28173 @var{objfile} is opened.
28174 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28175 is evaluated more than once.
28177 @node dotdebug_gdb_scripts section
28178 @subsection The @code{.debug_gdb_scripts} section
28179 @cindex @code{.debug_gdb_scripts} section
28181 For systems using file formats like ELF and COFF,
28182 when @value{GDBN} loads a new object file
28183 it will look for a special section named @code{.debug_gdb_scripts}.
28184 If this section exists, its contents is a list of null-terminated entries
28185 specifying scripts to load. Each entry begins with a non-null prefix byte that
28186 specifies the kind of entry, typically the extension language and whether the
28187 script is in a file or inlined in @code{.debug_gdb_scripts}.
28189 The following entries are supported:
28192 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28193 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28194 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28195 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28198 @subsubsection Script File Entries
28200 If the entry specifies a file, @value{GDBN} will look for the file first
28201 in the current directory and then along the source search path
28202 (@pxref{Source Path, ,Specifying Source Directories}),
28203 except that @file{$cdir} is not searched, since the compilation
28204 directory is not relevant to scripts.
28206 File entries can be placed in section @code{.debug_gdb_scripts} with,
28207 for example, this GCC macro for Python scripts.
28210 /* Note: The "MS" section flags are to remove duplicates. */
28211 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28213 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28214 .byte 1 /* Python */\n\
28215 .asciz \"" script_name "\"\n\
28221 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28222 Then one can reference the macro in a header or source file like this:
28225 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28228 The script name may include directories if desired.
28230 Note that loading of this script file also requires accordingly configured
28231 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28233 If the macro invocation is put in a header, any application or library
28234 using this header will get a reference to the specified script,
28235 and with the use of @code{"MS"} attributes on the section, the linker
28236 will remove duplicates.
28238 @subsubsection Script Text Entries
28240 Script text entries allow to put the executable script in the entry
28241 itself instead of loading it from a file.
28242 The first line of the entry, everything after the prefix byte and up to
28243 the first newline (@code{0xa}) character, is the script name, and must not
28244 contain any kind of space character, e.g., spaces or tabs.
28245 The rest of the entry, up to the trailing null byte, is the script to
28246 execute in the specified language. The name needs to be unique among
28247 all script names, as @value{GDBN} executes each script only once based
28250 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28254 #include "symcat.h"
28255 #include "gdb/section-scripts.h"
28257 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28258 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28259 ".ascii \"gdb.inlined-script\\n\"\n"
28260 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28261 ".ascii \" def __init__ (self):\\n\"\n"
28262 ".ascii \" super (test_cmd, self).__init__ ("
28263 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28264 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28265 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28266 ".ascii \"test_cmd ()\\n\"\n"
28272 Loading of inlined scripts requires a properly configured
28273 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28274 The path to specify in @code{auto-load safe-path} is the path of the file
28275 containing the @code{.debug_gdb_scripts} section.
28277 @node Which flavor to choose?
28278 @subsection Which flavor to choose?
28280 Given the multiple ways of auto-loading extensions, it might not always
28281 be clear which one to choose. This section provides some guidance.
28284 Benefits of the @file{-gdb.@var{ext}} way:
28288 Can be used with file formats that don't support multiple sections.
28291 Ease of finding scripts for public libraries.
28293 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28294 in the source search path.
28295 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28296 isn't a source directory in which to find the script.
28299 Doesn't require source code additions.
28303 Benefits of the @code{.debug_gdb_scripts} way:
28307 Works with static linking.
28309 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28310 trigger their loading. When an application is statically linked the only
28311 objfile available is the executable, and it is cumbersome to attach all the
28312 scripts from all the input libraries to the executable's
28313 @file{-gdb.@var{ext}} script.
28316 Works with classes that are entirely inlined.
28318 Some classes can be entirely inlined, and thus there may not be an associated
28319 shared library to attach a @file{-gdb.@var{ext}} script to.
28322 Scripts needn't be copied out of the source tree.
28324 In some circumstances, apps can be built out of large collections of internal
28325 libraries, and the build infrastructure necessary to install the
28326 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28327 cumbersome. It may be easier to specify the scripts in the
28328 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28329 top of the source tree to the source search path.
28332 @node Multiple Extension Languages
28333 @section Multiple Extension Languages
28335 The Guile and Python extension languages do not share any state,
28336 and generally do not interfere with each other.
28337 There are some things to be aware of, however.
28339 @subsection Python comes first
28341 Python was @value{GDBN}'s first extension language, and to avoid breaking
28342 existing behaviour Python comes first. This is generally solved by the
28343 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28344 extension languages, and when it makes a call to an extension language,
28345 (say to pretty-print a value), it tries each in turn until an extension
28346 language indicates it has performed the request (e.g., has returned the
28347 pretty-printed form of a value).
28348 This extends to errors while performing such requests: If an error happens
28349 while, for example, trying to pretty-print an object then the error is
28350 reported and any following extension languages are not tried.
28353 @chapter Command Interpreters
28354 @cindex command interpreters
28356 @value{GDBN} supports multiple command interpreters, and some command
28357 infrastructure to allow users or user interface writers to switch
28358 between interpreters or run commands in other interpreters.
28360 @value{GDBN} currently supports two command interpreters, the console
28361 interpreter (sometimes called the command-line interpreter or @sc{cli})
28362 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28363 describes both of these interfaces in great detail.
28365 By default, @value{GDBN} will start with the console interpreter.
28366 However, the user may choose to start @value{GDBN} with another
28367 interpreter by specifying the @option{-i} or @option{--interpreter}
28368 startup options. Defined interpreters include:
28372 @cindex console interpreter
28373 The traditional console or command-line interpreter. This is the most often
28374 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28375 @value{GDBN} will use this interpreter.
28378 @cindex mi interpreter
28379 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28380 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28381 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28385 @cindex mi3 interpreter
28386 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28389 @cindex mi2 interpreter
28390 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28393 @cindex mi1 interpreter
28394 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28398 @cindex invoke another interpreter
28400 @kindex interpreter-exec
28401 You may execute commands in any interpreter from the current
28402 interpreter using the appropriate command. If you are running the
28403 console interpreter, simply use the @code{interpreter-exec} command:
28406 interpreter-exec mi "-data-list-register-names"
28409 @sc{gdb/mi} has a similar command, although it is only available in versions of
28410 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28412 Note that @code{interpreter-exec} only changes the interpreter for the
28413 duration of the specified command. It does not change the interpreter
28416 @cindex start a new independent interpreter
28418 Although you may only choose a single interpreter at startup, it is
28419 possible to run an independent interpreter on a specified input/output
28420 device (usually a tty).
28422 For example, consider a debugger GUI or IDE that wants to provide a
28423 @value{GDBN} console view. It may do so by embedding a terminal
28424 emulator widget in its GUI, starting @value{GDBN} in the traditional
28425 command-line mode with stdin/stdout/stderr redirected to that
28426 terminal, and then creating an MI interpreter running on a specified
28427 input/output device. The console interpreter created by @value{GDBN}
28428 at startup handles commands the user types in the terminal widget,
28429 while the GUI controls and synchronizes state with @value{GDBN} using
28430 the separate MI interpreter.
28432 To start a new secondary @dfn{user interface} running MI, use the
28433 @code{new-ui} command:
28436 @cindex new user interface
28438 new-ui @var{interpreter} @var{tty}
28441 The @var{interpreter} parameter specifies the interpreter to run.
28442 This accepts the same values as the @code{interpreter-exec} command.
28443 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28444 @var{tty} parameter specifies the name of the bidirectional file the
28445 interpreter uses for input/output, usually the name of a
28446 pseudoterminal slave on Unix systems. For example:
28449 (@value{GDBP}) new-ui mi /dev/pts/9
28453 runs an MI interpreter on @file{/dev/pts/9}.
28456 @chapter @value{GDBN} Text User Interface
28458 @cindex Text User Interface
28460 The @value{GDBN} Text User Interface (TUI) is a terminal
28461 interface which uses the @code{curses} library to show the source
28462 file, the assembly output, the program registers and @value{GDBN}
28463 commands in separate text windows. The TUI mode is supported only
28464 on platforms where a suitable version of the @code{curses} library
28467 The TUI mode is enabled by default when you invoke @value{GDBN} as
28468 @samp{@value{GDBP} -tui}.
28469 You can also switch in and out of TUI mode while @value{GDBN} runs by
28470 using various TUI commands and key bindings, such as @command{tui
28471 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28472 @ref{TUI Keys, ,TUI Key Bindings}.
28475 * TUI Overview:: TUI overview
28476 * TUI Keys:: TUI key bindings
28477 * TUI Single Key Mode:: TUI single key mode
28478 * TUI Mouse Support:: TUI mouse support
28479 * TUI Commands:: TUI-specific commands
28480 * TUI Configuration:: TUI configuration variables
28484 @section TUI Overview
28486 In TUI mode, @value{GDBN} can display several text windows:
28490 This window is the @value{GDBN} command window with the @value{GDBN}
28491 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28492 managed using readline.
28495 The source window shows the source file of the program. The current
28496 line and active breakpoints are displayed in this window.
28499 The assembly window shows the disassembly output of the program.
28502 This window shows the processor registers. Registers are highlighted
28503 when their values change.
28506 The source and assembly windows show the current program position
28507 by highlighting the current line and marking it with a @samp{>} marker.
28508 Breakpoints are indicated with two markers. The first marker
28509 indicates the breakpoint type:
28513 Breakpoint which was hit at least once.
28516 Breakpoint which was never hit.
28519 Hardware breakpoint which was hit at least once.
28522 Hardware breakpoint which was never hit.
28525 The second marker indicates whether the breakpoint is enabled or not:
28529 Breakpoint is enabled.
28532 Breakpoint is disabled.
28535 The source, assembly and register windows are updated when the current
28536 thread changes, when the frame changes, or when the program counter
28539 These windows are not all visible at the same time. The command
28540 window is always visible. The others can be arranged in several
28551 source and assembly,
28554 source and registers, or
28557 assembly and registers.
28560 These are the standard layouts, but other layouts can be defined.
28562 A status line above the command window shows the following information:
28566 Indicates the current @value{GDBN} target.
28567 (@pxref{Targets, ,Specifying a Debugging Target}).
28570 Gives the current process or thread number.
28571 When no process is being debugged, this field is set to @code{No process}.
28574 Gives the current function name for the selected frame.
28575 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28576 When there is no symbol corresponding to the current program counter,
28577 the string @code{??} is displayed.
28580 Indicates the current line number for the selected frame.
28581 When the current line number is not known, the string @code{??} is displayed.
28584 Indicates the current program counter address.
28588 @section TUI Key Bindings
28589 @cindex TUI key bindings
28591 The TUI installs several key bindings in the readline keymaps
28592 @ifset SYSTEM_READLINE
28593 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28595 @ifclear SYSTEM_READLINE
28596 (@pxref{Command Line Editing}).
28598 The following key bindings are installed for both TUI mode and the
28599 @value{GDBN} standard mode.
28608 Enter or leave the TUI mode. When leaving the TUI mode,
28609 the curses window management stops and @value{GDBN} operates using
28610 its standard mode, writing on the terminal directly. When reentering
28611 the TUI mode, control is given back to the curses windows.
28612 The screen is then refreshed.
28614 This key binding uses the bindable Readline function
28615 @code{tui-switch-mode}.
28619 Use a TUI layout with only one window. The layout will
28620 either be @samp{source} or @samp{assembly}. When the TUI mode
28621 is not active, it will switch to the TUI mode.
28623 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28625 This key binding uses the bindable Readline function
28626 @code{tui-delete-other-windows}.
28630 Use a TUI layout with at least two windows. When the current
28631 layout already has two windows, the next layout with two windows is used.
28632 When a new layout is chosen, one window will always be common to the
28633 previous layout and the new one.
28635 Think of it as the Emacs @kbd{C-x 2} binding.
28637 This key binding uses the bindable Readline function
28638 @code{tui-change-windows}.
28642 Change the active window. The TUI associates several key bindings
28643 (like scrolling and arrow keys) with the active window. This command
28644 gives the focus to the next TUI window.
28646 Think of it as the Emacs @kbd{C-x o} binding.
28648 This key binding uses the bindable Readline function
28649 @code{tui-other-window}.
28653 Switch in and out of the TUI SingleKey mode that binds single
28654 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28656 This key binding uses the bindable Readline function
28657 @code{next-keymap}.
28660 The following key bindings only work in the TUI mode:
28665 Scroll the active window one page up.
28669 Scroll the active window one page down.
28673 Scroll the active window one line up.
28677 Scroll the active window one line down.
28681 Scroll the active window one column left.
28685 Scroll the active window one column right.
28689 Refresh the screen.
28692 Because the arrow keys scroll the active window in the TUI mode, they
28693 are not available for their normal use by readline unless the command
28694 window has the focus. When another window is active, you must use
28695 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28696 and @kbd{C-f} to control the command window.
28698 @node TUI Single Key Mode
28699 @section TUI Single Key Mode
28700 @cindex TUI single key mode
28702 The TUI also provides a @dfn{SingleKey} mode, which binds several
28703 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28704 switch into this mode, where the following key bindings are used:
28707 @kindex c @r{(SingleKey TUI key)}
28711 @kindex d @r{(SingleKey TUI key)}
28715 @kindex f @r{(SingleKey TUI key)}
28719 @kindex n @r{(SingleKey TUI key)}
28723 @kindex o @r{(SingleKey TUI key)}
28725 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28727 @kindex q @r{(SingleKey TUI key)}
28729 exit the SingleKey mode.
28731 @kindex r @r{(SingleKey TUI key)}
28735 @kindex s @r{(SingleKey TUI key)}
28739 @kindex i @r{(SingleKey TUI key)}
28741 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28743 @kindex u @r{(SingleKey TUI key)}
28747 @kindex v @r{(SingleKey TUI key)}
28751 @kindex w @r{(SingleKey TUI key)}
28756 Other keys temporarily switch to the @value{GDBN} command prompt.
28757 The key that was pressed is inserted in the editing buffer so that
28758 it is possible to type most @value{GDBN} commands without interaction
28759 with the TUI SingleKey mode. Once the command is entered the TUI
28760 SingleKey mode is restored. The only way to permanently leave
28761 this mode is by typing @kbd{q} or @kbd{C-x s}.
28763 @cindex SingleKey keymap name
28764 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28765 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28766 @file{.inputrc} to add additional bindings to this keymap.
28768 @node TUI Mouse Support
28769 @section TUI Mouse Support
28770 @cindex TUI mouse support
28772 If the curses library supports the mouse, the TUI supports mouse
28775 The mouse wheel scrolls the appropriate window under the mouse cursor.
28777 The TUI itself does not directly support copying/pasting with the
28778 mouse. However, on Unix terminals, you can typically press and hold
28779 the @key{SHIFT} key on your keyboard to temporarily bypass
28780 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
28781 functionality (commonly, click-drag-release or double-click to select
28782 text, middle-click to paste). This copy/paste works with the
28783 terminal's selection buffer, as opposed to the TUI's buffer.
28786 @section TUI-specific Commands
28787 @cindex TUI commands
28789 The TUI has specific commands to control the text windows.
28790 These commands are always available, even when @value{GDBN} is not in
28791 the TUI mode. When @value{GDBN} is in the standard mode, most
28792 of these commands will automatically switch to the TUI mode.
28794 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28795 terminal, or @value{GDBN} has been started with the machine interface
28796 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28797 these commands will fail with an error, because it would not be
28798 possible or desirable to enable curses window management.
28803 Activate TUI mode. The last active TUI window layout will be used if
28804 TUI mode has previously been used in the current debugging session,
28805 otherwise a default layout is used.
28808 @kindex tui disable
28809 Disable TUI mode, returning to the console interpreter.
28813 List and give the size of all displayed windows.
28815 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28816 @kindex tui new-layout
28817 Create a new TUI layout. The new layout will be named @var{name}, and
28818 can be accessed using the @code{layout} command (see below).
28820 Each @var{window} parameter is either the name of a window to display,
28821 or a window description. The windows will be displayed from top to
28822 bottom in the order listed.
28824 The names of the windows are the same as the ones given to the
28825 @code{focus} command (see below); additional, the @code{status}
28826 window can be specified. Note that, because it is of fixed height,
28827 the weight assigned to the status window is of no importance. It is
28828 conventional to use @samp{0} here.
28830 A window description looks a bit like an invocation of @code{tui
28831 new-layout}, and is of the form
28832 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28834 This specifies a sub-layout. If @code{-horizontal} is given, the
28835 windows in this description will be arranged side-by-side, rather than
28838 Each @var{weight} is an integer. It is the weight of this window
28839 relative to all the other windows in the layout. These numbers are
28840 used to calculate how much of the screen is given to each window.
28845 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28848 Here, the new layout is called @samp{example}. It shows the source
28849 and register windows, followed by the status window, and then finally
28850 the command window. The non-status windows all have the same weight,
28851 so the terminal will be split into three roughly equal sections.
28853 Here is a more complex example, showing a horizontal layout:
28856 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28859 This will result in side-by-side source and assembly windows; with the
28860 status and command window being beneath these, filling the entire
28861 width of the terminal. Because they have weight 2, the source and
28862 assembly windows will be twice the height of the command window.
28864 @item layout @var{name}
28866 Changes which TUI windows are displayed. The @var{name} parameter
28867 controls which layout is shown. It can be either one of the built-in
28868 layout names, or the name of a layout defined by the user using
28869 @code{tui new-layout}.
28871 The built-in layouts are as follows:
28875 Display the next layout.
28878 Display the previous layout.
28881 Display the source and command windows.
28884 Display the assembly and command windows.
28887 Display the source, assembly, and command windows.
28890 When in @code{src} layout display the register, source, and command
28891 windows. When in @code{asm} or @code{split} layout display the
28892 register, assembler, and command windows.
28895 @item focus @var{name}
28897 Changes which TUI window is currently active for scrolling. The
28898 @var{name} parameter can be any of the following:
28902 Make the next window active for scrolling.
28905 Make the previous window active for scrolling.
28908 Make the source window active for scrolling.
28911 Make the assembly window active for scrolling.
28914 Make the register window active for scrolling.
28917 Make the command window active for scrolling.
28922 Refresh the screen. This is similar to typing @kbd{C-L}.
28924 @item tui reg @var{group}
28926 Changes the register group displayed in the tui register window to
28927 @var{group}. If the register window is not currently displayed this
28928 command will cause the register window to be displayed. The list of
28929 register groups, as well as their order is target specific. The
28930 following groups are available on most targets:
28933 Repeatedly selecting this group will cause the display to cycle
28934 through all of the available register groups.
28937 Repeatedly selecting this group will cause the display to cycle
28938 through all of the available register groups in the reverse order to
28942 Display the general registers.
28944 Display the floating point registers.
28946 Display the system registers.
28948 Display the vector registers.
28950 Display all registers.
28955 Update the source window and the current execution point.
28957 @item winheight @var{name} +@var{count}
28958 @itemx winheight @var{name} -@var{count}
28960 Change the height of the window @var{name} by @var{count}
28961 lines. Positive counts increase the height, while negative counts
28962 decrease it. The @var{name} parameter can be one of @code{src} (the
28963 source window), @code{cmd} (the command window), @code{asm} (the
28964 disassembly window), or @code{regs} (the register display window).
28967 @node TUI Configuration
28968 @section TUI Configuration Variables
28969 @cindex TUI configuration variables
28971 Several configuration variables control the appearance of TUI windows.
28974 @item set tui border-kind @var{kind}
28975 @kindex set tui border-kind
28976 Select the border appearance for the source, assembly and register windows.
28977 The possible values are the following:
28980 Use a space character to draw the border.
28983 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28986 Use the Alternate Character Set to draw the border. The border is
28987 drawn using character line graphics if the terminal supports them.
28990 @item set tui border-mode @var{mode}
28991 @kindex set tui border-mode
28992 @itemx set tui active-border-mode @var{mode}
28993 @kindex set tui active-border-mode
28994 Select the display attributes for the borders of the inactive windows
28995 or the active window. The @var{mode} can be one of the following:
28998 Use normal attributes to display the border.
29004 Use reverse video mode.
29007 Use half bright mode.
29009 @item half-standout
29010 Use half bright and standout mode.
29013 Use extra bright or bold mode.
29015 @item bold-standout
29016 Use extra bright or bold and standout mode.
29019 @item set tui tab-width @var{nchars}
29020 @kindex set tui tab-width
29022 Set the width of tab stops to be @var{nchars} characters. This
29023 setting affects the display of TAB characters in the source and
29026 @item set tui compact-source @r{[}on@r{|}off@r{]}
29027 @kindex set tui compact-source
29028 Set whether the TUI source window is displayed in ``compact'' form.
29029 The default display uses more space for line numbers and starts the
29030 source text at the next tab stop; the compact display uses only as
29031 much space as is needed for the line numbers in the current file, and
29032 only a single space to separate the line numbers from the source.
29035 Note that the colors of the TUI borders can be controlled using the
29036 appropriate @code{set style} commands. @xref{Output Styling}.
29039 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29042 @cindex @sc{gnu} Emacs
29043 A special interface allows you to use @sc{gnu} Emacs to view (and
29044 edit) the source files for the program you are debugging with
29047 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29048 executable file you want to debug as an argument. This command starts
29049 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29050 created Emacs buffer.
29051 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29053 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29058 All ``terminal'' input and output goes through an Emacs buffer, called
29061 This applies both to @value{GDBN} commands and their output, and to the input
29062 and output done by the program you are debugging.
29064 This is useful because it means that you can copy the text of previous
29065 commands and input them again; you can even use parts of the output
29068 All the facilities of Emacs' Shell mode are available for interacting
29069 with your program. In particular, you can send signals the usual
29070 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29074 @value{GDBN} displays source code through Emacs.
29076 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29077 source file for that frame and puts an arrow (@samp{=>}) at the
29078 left margin of the current line. Emacs uses a separate buffer for
29079 source display, and splits the screen to show both your @value{GDBN} session
29082 Explicit @value{GDBN} @code{list} or search commands still produce output as
29083 usual, but you probably have no reason to use them from Emacs.
29086 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29087 a graphical mode, enabled by default, which provides further buffers
29088 that can control the execution and describe the state of your program.
29089 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29091 If you specify an absolute file name when prompted for the @kbd{M-x
29092 gdb} argument, then Emacs sets your current working directory to where
29093 your program resides. If you only specify the file name, then Emacs
29094 sets your current working directory to the directory associated
29095 with the previous buffer. In this case, @value{GDBN} may find your
29096 program by searching your environment's @env{PATH} variable, but on
29097 some operating systems it might not find the source. So, although the
29098 @value{GDBN} input and output session proceeds normally, the auxiliary
29099 buffer does not display the current source and line of execution.
29101 The initial working directory of @value{GDBN} is printed on the top
29102 line of the GUD buffer and this serves as a default for the commands
29103 that specify files for @value{GDBN} to operate on. @xref{Files,
29104 ,Commands to Specify Files}.
29106 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29107 need to call @value{GDBN} by a different name (for example, if you
29108 keep several configurations around, with different names) you can
29109 customize the Emacs variable @code{gud-gdb-command-name} to run the
29112 In the GUD buffer, you can use these special Emacs commands in
29113 addition to the standard Shell mode commands:
29117 Describe the features of Emacs' GUD Mode.
29120 Execute to another source line, like the @value{GDBN} @code{step} command; also
29121 update the display window to show the current file and location.
29124 Execute to next source line in this function, skipping all function
29125 calls, like the @value{GDBN} @code{next} command. Then update the display window
29126 to show the current file and location.
29129 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29130 display window accordingly.
29133 Execute until exit from the selected stack frame, like the @value{GDBN}
29134 @code{finish} command.
29137 Continue execution of your program, like the @value{GDBN} @code{continue}
29141 Go up the number of frames indicated by the numeric argument
29142 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29143 like the @value{GDBN} @code{up} command.
29146 Go down the number of frames indicated by the numeric argument, like the
29147 @value{GDBN} @code{down} command.
29150 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29151 tells @value{GDBN} to set a breakpoint on the source line point is on.
29153 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29154 separate frame which shows a backtrace when the GUD buffer is current.
29155 Move point to any frame in the stack and type @key{RET} to make it
29156 become the current frame and display the associated source in the
29157 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29158 selected frame become the current one. In graphical mode, the
29159 speedbar displays watch expressions.
29161 If you accidentally delete the source-display buffer, an easy way to get
29162 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29163 request a frame display; when you run under Emacs, this recreates
29164 the source buffer if necessary to show you the context of the current
29167 The source files displayed in Emacs are in ordinary Emacs buffers
29168 which are visiting the source files in the usual way. You can edit
29169 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29170 communicates with Emacs in terms of line numbers. If you add or
29171 delete lines from the text, the line numbers that @value{GDBN} knows cease
29172 to correspond properly with the code.
29174 A more detailed description of Emacs' interaction with @value{GDBN} is
29175 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29179 @chapter The @sc{gdb/mi} Interface
29181 @unnumberedsec Function and Purpose
29183 @cindex @sc{gdb/mi}, its purpose
29184 @sc{gdb/mi} is a line based machine oriented text interface to
29185 @value{GDBN} and is activated by specifying using the
29186 @option{--interpreter} command line option (@pxref{Mode Options}). It
29187 is specifically intended to support the development of systems which
29188 use the debugger as just one small component of a larger system.
29190 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29191 in the form of a reference manual.
29193 Note that @sc{gdb/mi} is still under construction, so some of the
29194 features described below are incomplete and subject to change
29195 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29197 @unnumberedsec Notation and Terminology
29199 @cindex notational conventions, for @sc{gdb/mi}
29200 This chapter uses the following notation:
29204 @code{|} separates two alternatives.
29207 @code{[ @var{something} ]} indicates that @var{something} is optional:
29208 it may or may not be given.
29211 @code{( @var{group} )*} means that @var{group} inside the parentheses
29212 may repeat zero or more times.
29215 @code{( @var{group} )+} means that @var{group} inside the parentheses
29216 may repeat one or more times.
29219 @code{"@var{string}"} means a literal @var{string}.
29223 @heading Dependencies
29227 * GDB/MI General Design::
29228 * GDB/MI Command Syntax::
29229 * GDB/MI Compatibility with CLI::
29230 * GDB/MI Development and Front Ends::
29231 * GDB/MI Output Records::
29232 * GDB/MI Simple Examples::
29233 * GDB/MI Command Description Format::
29234 * GDB/MI Breakpoint Commands::
29235 * GDB/MI Catchpoint Commands::
29236 * GDB/MI Program Context::
29237 * GDB/MI Thread Commands::
29238 * GDB/MI Ada Tasking Commands::
29239 * GDB/MI Program Execution::
29240 * GDB/MI Stack Manipulation::
29241 * GDB/MI Variable Objects::
29242 * GDB/MI Data Manipulation::
29243 * GDB/MI Tracepoint Commands::
29244 * GDB/MI Symbol Query::
29245 * GDB/MI File Commands::
29247 * GDB/MI Kod Commands::
29248 * GDB/MI Memory Overlay Commands::
29249 * GDB/MI Signal Handling Commands::
29251 * GDB/MI Target Manipulation::
29252 * GDB/MI File Transfer Commands::
29253 * GDB/MI Ada Exceptions Commands::
29254 * GDB/MI Support Commands::
29255 * GDB/MI Miscellaneous Commands::
29258 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29259 @node GDB/MI General Design
29260 @section @sc{gdb/mi} General Design
29261 @cindex GDB/MI General Design
29263 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29264 parts---commands sent to @value{GDBN}, responses to those commands
29265 and notifications. Each command results in exactly one response,
29266 indicating either successful completion of the command, or an error.
29267 For the commands that do not resume the target, the response contains the
29268 requested information. For the commands that resume the target, the
29269 response only indicates whether the target was successfully resumed.
29270 Notifications is the mechanism for reporting changes in the state of the
29271 target, or in @value{GDBN} state, that cannot conveniently be associated with
29272 a command and reported as part of that command response.
29274 The important examples of notifications are:
29278 Exec notifications. These are used to report changes in
29279 target state---when a target is resumed, or stopped. It would not
29280 be feasible to include this information in response of resuming
29281 commands, because one resume commands can result in multiple events in
29282 different threads. Also, quite some time may pass before any event
29283 happens in the target, while a frontend needs to know whether the resuming
29284 command itself was successfully executed.
29287 Console output, and status notifications. Console output
29288 notifications are used to report output of CLI commands, as well as
29289 diagnostics for other commands. Status notifications are used to
29290 report the progress of a long-running operation. Naturally, including
29291 this information in command response would mean no output is produced
29292 until the command is finished, which is undesirable.
29295 General notifications. Commands may have various side effects on
29296 the @value{GDBN} or target state beyond their official purpose. For example,
29297 a command may change the selected thread. Although such changes can
29298 be included in command response, using notification allows for more
29299 orthogonal frontend design.
29303 There's no guarantee that whenever an MI command reports an error,
29304 @value{GDBN} or the target are in any specific state, and especially,
29305 the state is not reverted to the state before the MI command was
29306 processed. Therefore, whenever an MI command results in an error,
29307 we recommend that the frontend refreshes all the information shown in
29308 the user interface.
29312 * Context management::
29313 * Asynchronous and non-stop modes::
29317 @node Context management
29318 @subsection Context management
29320 @subsubsection Threads and Frames
29322 In most cases when @value{GDBN} accesses the target, this access is
29323 done in context of a specific thread and frame (@pxref{Frames}).
29324 Often, even when accessing global data, the target requires that a thread
29325 be specified. The CLI interface maintains the selected thread and frame,
29326 and supplies them to target on each command. This is convenient,
29327 because a command line user would not want to specify that information
29328 explicitly on each command, and because user interacts with
29329 @value{GDBN} via a single terminal, so no confusion is possible as
29330 to what thread and frame are the current ones.
29332 In the case of MI, the concept of selected thread and frame is less
29333 useful. First, a frontend can easily remember this information
29334 itself. Second, a graphical frontend can have more than one window,
29335 each one used for debugging a different thread, and the frontend might
29336 want to access additional threads for internal purposes. This
29337 increases the risk that by relying on implicitly selected thread, the
29338 frontend may be operating on a wrong one. Therefore, each MI command
29339 should explicitly specify which thread and frame to operate on. To
29340 make it possible, each MI command accepts the @samp{--thread} and
29341 @samp{--frame} options, the value to each is @value{GDBN} global
29342 identifier for thread and frame to operate on.
29344 Usually, each top-level window in a frontend allows the user to select
29345 a thread and a frame, and remembers the user selection for further
29346 operations. However, in some cases @value{GDBN} may suggest that the
29347 current thread or frame be changed. For example, when stopping on a
29348 breakpoint it is reasonable to switch to the thread where breakpoint is
29349 hit. For another example, if the user issues the CLI @samp{thread} or
29350 @samp{frame} commands via the frontend, it is desirable to change the
29351 frontend's selection to the one specified by user. @value{GDBN}
29352 communicates the suggestion to change current thread and frame using the
29353 @samp{=thread-selected} notification.
29355 Note that historically, MI shares the selected thread with CLI, so
29356 frontends used the @code{-thread-select} to execute commands in the
29357 right context. However, getting this to work right is cumbersome. The
29358 simplest way is for frontend to emit @code{-thread-select} command
29359 before every command. This doubles the number of commands that need
29360 to be sent. The alternative approach is to suppress @code{-thread-select}
29361 if the selected thread in @value{GDBN} is supposed to be identical to the
29362 thread the frontend wants to operate on. However, getting this
29363 optimization right can be tricky. In particular, if the frontend
29364 sends several commands to @value{GDBN}, and one of the commands changes the
29365 selected thread, then the behaviour of subsequent commands will
29366 change. So, a frontend should either wait for response from such
29367 problematic commands, or explicitly add @code{-thread-select} for
29368 all subsequent commands. No frontend is known to do this exactly
29369 right, so it is suggested to just always pass the @samp{--thread} and
29370 @samp{--frame} options.
29372 @subsubsection Language
29374 The execution of several commands depends on which language is selected.
29375 By default, the current language (@pxref{show language}) is used.
29376 But for commands known to be language-sensitive, it is recommended
29377 to use the @samp{--language} option. This option takes one argument,
29378 which is the name of the language to use while executing the command.
29382 -data-evaluate-expression --language c "sizeof (void*)"
29387 The valid language names are the same names accepted by the
29388 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29389 @samp{local} or @samp{unknown}.
29391 @node Asynchronous and non-stop modes
29392 @subsection Asynchronous command execution and non-stop mode
29394 On some targets, @value{GDBN} is capable of processing MI commands
29395 even while the target is running. This is called @dfn{asynchronous
29396 command execution} (@pxref{Background Execution}). The frontend may
29397 specify a preference for asynchronous execution using the
29398 @code{-gdb-set mi-async 1} command, which should be emitted before
29399 either running the executable or attaching to the target. After the
29400 frontend has started the executable or attached to the target, it can
29401 find if asynchronous execution is enabled using the
29402 @code{-list-target-features} command.
29405 @item -gdb-set mi-async on
29406 @item -gdb-set mi-async off
29407 Set whether MI is in asynchronous mode.
29409 When @code{off}, which is the default, MI execution commands (e.g.,
29410 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29411 for the program to stop before processing further commands.
29413 When @code{on}, MI execution commands are background execution
29414 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29415 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29416 MI commands even while the target is running.
29418 @item -gdb-show mi-async
29419 Show whether MI asynchronous mode is enabled.
29422 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29423 @code{target-async} instead of @code{mi-async}, and it had the effect
29424 of both putting MI in asynchronous mode and making CLI background
29425 commands possible. CLI background commands are now always possible
29426 ``out of the box'' if the target supports them. The old spelling is
29427 kept as a deprecated alias for backwards compatibility.
29429 Even if @value{GDBN} can accept a command while target is running,
29430 many commands that access the target do not work when the target is
29431 running. Therefore, asynchronous command execution is most useful
29432 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29433 it is possible to examine the state of one thread, while other threads
29436 When a given thread is running, MI commands that try to access the
29437 target in the context of that thread may not work, or may work only on
29438 some targets. In particular, commands that try to operate on thread's
29439 stack will not work, on any target. Commands that read memory, or
29440 modify breakpoints, may work or not work, depending on the target. Note
29441 that even commands that operate on global state, such as @code{print},
29442 @code{set}, and breakpoint commands, still access the target in the
29443 context of a specific thread, so frontend should try to find a
29444 stopped thread and perform the operation on that thread (using the
29445 @samp{--thread} option).
29447 Which commands will work in the context of a running thread is
29448 highly target dependent. However, the two commands
29449 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29450 to find the state of a thread, will always work.
29452 @node Thread groups
29453 @subsection Thread groups
29454 @value{GDBN} may be used to debug several processes at the same time.
29455 On some platforms, @value{GDBN} may support debugging of several
29456 hardware systems, each one having several cores with several different
29457 processes running on each core. This section describes the MI
29458 mechanism to support such debugging scenarios.
29460 The key observation is that regardless of the structure of the
29461 target, MI can have a global list of threads, because most commands that
29462 accept the @samp{--thread} option do not need to know what process that
29463 thread belongs to. Therefore, it is not necessary to introduce
29464 neither additional @samp{--process} option, nor an notion of the
29465 current process in the MI interface. The only strictly new feature
29466 that is required is the ability to find how the threads are grouped
29469 To allow the user to discover such grouping, and to support arbitrary
29470 hierarchy of machines/cores/processes, MI introduces the concept of a
29471 @dfn{thread group}. Thread group is a collection of threads and other
29472 thread groups. A thread group always has a string identifier, a type,
29473 and may have additional attributes specific to the type. A new
29474 command, @code{-list-thread-groups}, returns the list of top-level
29475 thread groups, which correspond to processes that @value{GDBN} is
29476 debugging at the moment. By passing an identifier of a thread group
29477 to the @code{-list-thread-groups} command, it is possible to obtain
29478 the members of specific thread group.
29480 To allow the user to easily discover processes, and other objects, he
29481 wishes to debug, a concept of @dfn{available thread group} is
29482 introduced. Available thread group is an thread group that
29483 @value{GDBN} is not debugging, but that can be attached to, using the
29484 @code{-target-attach} command. The list of available top-level thread
29485 groups can be obtained using @samp{-list-thread-groups --available}.
29486 In general, the content of a thread group may be only retrieved only
29487 after attaching to that thread group.
29489 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29490 Programs}). Each inferior corresponds to a thread group of a special
29491 type @samp{process}, and some additional operations are permitted on
29492 such thread groups.
29494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29495 @node GDB/MI Command Syntax
29496 @section @sc{gdb/mi} Command Syntax
29499 * GDB/MI Input Syntax::
29500 * GDB/MI Output Syntax::
29503 @node GDB/MI Input Syntax
29504 @subsection @sc{gdb/mi} Input Syntax
29506 @cindex input syntax for @sc{gdb/mi}
29507 @cindex @sc{gdb/mi}, input syntax
29509 @item @var{command} @expansion{}
29510 @code{@var{cli-command} | @var{mi-command}}
29512 @item @var{cli-command} @expansion{}
29513 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29514 @var{cli-command} is any existing @value{GDBN} CLI command.
29516 @item @var{mi-command} @expansion{}
29517 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29518 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29520 @item @var{token} @expansion{}
29521 "any sequence of digits"
29523 @item @var{option} @expansion{}
29524 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29526 @item @var{parameter} @expansion{}
29527 @code{@var{non-blank-sequence} | @var{c-string}}
29529 @item @var{operation} @expansion{}
29530 @emph{any of the operations described in this chapter}
29532 @item @var{non-blank-sequence} @expansion{}
29533 @emph{anything, provided it doesn't contain special characters such as
29534 "-", @var{nl}, """ and of course " "}
29536 @item @var{c-string} @expansion{}
29537 @code{""" @var{seven-bit-iso-c-string-content} """}
29539 @item @var{nl} @expansion{}
29548 The CLI commands are still handled by the @sc{mi} interpreter; their
29549 output is described below.
29552 The @code{@var{token}}, when present, is passed back when the command
29556 Some @sc{mi} commands accept optional arguments as part of the parameter
29557 list. Each option is identified by a leading @samp{-} (dash) and may be
29558 followed by an optional argument parameter. Options occur first in the
29559 parameter list and can be delimited from normal parameters using
29560 @samp{--} (this is useful when some parameters begin with a dash).
29567 We want easy access to the existing CLI syntax (for debugging).
29570 We want it to be easy to spot a @sc{mi} operation.
29573 @node GDB/MI Output Syntax
29574 @subsection @sc{gdb/mi} Output Syntax
29576 @cindex output syntax of @sc{gdb/mi}
29577 @cindex @sc{gdb/mi}, output syntax
29578 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29579 followed, optionally, by a single result record. This result record
29580 is for the most recent command. The sequence of output records is
29581 terminated by @samp{(gdb)}.
29583 If an input command was prefixed with a @code{@var{token}} then the
29584 corresponding output for that command will also be prefixed by that same
29588 @item @var{output} @expansion{}
29589 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29591 @item @var{result-record} @expansion{}
29592 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29594 @item @var{out-of-band-record} @expansion{}
29595 @code{@var{async-record} | @var{stream-record}}
29597 @item @var{async-record} @expansion{}
29598 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29600 @item @var{exec-async-output} @expansion{}
29601 @code{[ @var{token} ] "*" @var{async-output nl}}
29603 @item @var{status-async-output} @expansion{}
29604 @code{[ @var{token} ] "+" @var{async-output nl}}
29606 @item @var{notify-async-output} @expansion{}
29607 @code{[ @var{token} ] "=" @var{async-output nl}}
29609 @item @var{async-output} @expansion{}
29610 @code{@var{async-class} ( "," @var{result} )*}
29612 @item @var{result-class} @expansion{}
29613 @code{"done" | "running" | "connected" | "error" | "exit"}
29615 @item @var{async-class} @expansion{}
29616 @code{"stopped" | @var{others}} (where @var{others} will be added
29617 depending on the needs---this is still in development).
29619 @item @var{result} @expansion{}
29620 @code{ @var{variable} "=" @var{value}}
29622 @item @var{variable} @expansion{}
29623 @code{ @var{string} }
29625 @item @var{value} @expansion{}
29626 @code{ @var{const} | @var{tuple} | @var{list} }
29628 @item @var{const} @expansion{}
29629 @code{@var{c-string}}
29631 @item @var{tuple} @expansion{}
29632 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29634 @item @var{list} @expansion{}
29635 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29636 @var{result} ( "," @var{result} )* "]" }
29638 @item @var{stream-record} @expansion{}
29639 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29641 @item @var{console-stream-output} @expansion{}
29642 @code{"~" @var{c-string nl}}
29644 @item @var{target-stream-output} @expansion{}
29645 @code{"@@" @var{c-string nl}}
29647 @item @var{log-stream-output} @expansion{}
29648 @code{"&" @var{c-string nl}}
29650 @item @var{nl} @expansion{}
29653 @item @var{token} @expansion{}
29654 @emph{any sequence of digits}.
29662 All output sequences end in a single line containing a period.
29665 The @code{@var{token}} is from the corresponding request. Note that
29666 for all async output, while the token is allowed by the grammar and
29667 may be output by future versions of @value{GDBN} for select async
29668 output messages, it is generally omitted. Frontends should treat
29669 all async output as reporting general changes in the state of the
29670 target and there should be no need to associate async output to any
29674 @cindex status output in @sc{gdb/mi}
29675 @var{status-async-output} contains on-going status information about the
29676 progress of a slow operation. It can be discarded. All status output is
29677 prefixed by @samp{+}.
29680 @cindex async output in @sc{gdb/mi}
29681 @var{exec-async-output} contains asynchronous state change on the target
29682 (stopped, started, disappeared). All async output is prefixed by
29686 @cindex notify output in @sc{gdb/mi}
29687 @var{notify-async-output} contains supplementary information that the
29688 client should handle (e.g., a new breakpoint information). All notify
29689 output is prefixed by @samp{=}.
29692 @cindex console output in @sc{gdb/mi}
29693 @var{console-stream-output} is output that should be displayed as is in the
29694 console. It is the textual response to a CLI command. All the console
29695 output is prefixed by @samp{~}.
29698 @cindex target output in @sc{gdb/mi}
29699 @var{target-stream-output} is the output produced by the target program.
29700 All the target output is prefixed by @samp{@@}.
29703 @cindex log output in @sc{gdb/mi}
29704 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29705 instance messages that should be displayed as part of an error log. All
29706 the log output is prefixed by @samp{&}.
29709 @cindex list output in @sc{gdb/mi}
29710 New @sc{gdb/mi} commands should only output @var{lists} containing
29716 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29717 details about the various output records.
29719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29720 @node GDB/MI Compatibility with CLI
29721 @section @sc{gdb/mi} Compatibility with CLI
29723 @cindex compatibility, @sc{gdb/mi} and CLI
29724 @cindex @sc{gdb/mi}, compatibility with CLI
29726 For the developers convenience CLI commands can be entered directly,
29727 but there may be some unexpected behaviour. For example, commands
29728 that query the user will behave as if the user replied yes, breakpoint
29729 command lists are not executed and some CLI commands, such as
29730 @code{if}, @code{when} and @code{define}, prompt for further input with
29731 @samp{>}, which is not valid MI output.
29733 This feature may be removed at some stage in the future and it is
29734 recommended that front ends use the @code{-interpreter-exec} command
29735 (@pxref{-interpreter-exec}).
29737 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29738 @node GDB/MI Development and Front Ends
29739 @section @sc{gdb/mi} Development and Front Ends
29740 @cindex @sc{gdb/mi} development
29742 The application which takes the MI output and presents the state of the
29743 program being debugged to the user is called a @dfn{front end}.
29745 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29746 to the MI interface may break existing usage. This section describes how the
29747 protocol changes and how to request previous version of the protocol when it
29750 Some changes in MI need not break a carefully designed front end, and
29751 for these the MI version will remain unchanged. The following is a
29752 list of changes that may occur within one level, so front ends should
29753 parse MI output in a way that can handle them:
29757 New MI commands may be added.
29760 New fields may be added to the output of any MI command.
29763 The range of values for fields with specified values, e.g.,
29764 @code{in_scope} (@pxref{-var-update}) may be extended.
29766 @c The format of field's content e.g type prefix, may change so parse it
29767 @c at your own risk. Yes, in general?
29769 @c The order of fields may change? Shouldn't really matter but it might
29770 @c resolve inconsistencies.
29773 If the changes are likely to break front ends, the MI version level
29774 will be increased by one. The new versions of the MI protocol are not compatible
29775 with the old versions. Old versions of MI remain available, allowing front ends
29776 to keep using them until they are modified to use the latest MI version.
29778 Since @code{--interpreter=mi} always points to the latest MI version, it is
29779 recommended that front ends request a specific version of MI when launching
29780 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
29781 interpreter with the MI version they expect.
29783 The following table gives a summary of the released versions of the MI
29784 interface: the version number, the version of GDB in which it first appeared
29785 and the breaking changes compared to the previous version.
29787 @multitable @columnfractions .05 .05 .9
29788 @headitem MI version @tab GDB version @tab Breaking changes
29805 The @code{-environment-pwd}, @code{-environment-directory} and
29806 @code{-environment-path} commands now returns values using the MI output
29807 syntax, rather than CLI output syntax.
29810 @code{-var-list-children}'s @code{children} result field is now a list, rather
29814 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29826 The output of information about multi-location breakpoints has changed in the
29827 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29828 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29829 The multiple locations are now placed in a @code{locations} field, whose value
29835 If your front end cannot yet migrate to a more recent version of the
29836 MI protocol, you can nevertheless selectively enable specific features
29837 available in those recent MI versions, using the following commands:
29841 @item -fix-multi-location-breakpoint-output
29842 Use the output for multi-location breakpoints which was introduced by
29843 MI 3, even when using MI versions 2 or 1. This command has no
29844 effect when using MI version 3 or later.
29848 The best way to avoid unexpected changes in MI that might break your front
29849 end is to make your project known to @value{GDBN} developers and
29850 follow development on @email{gdb@@sourceware.org} and
29851 @email{gdb-patches@@sourceware.org}.
29852 @cindex mailing lists
29854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29855 @node GDB/MI Output Records
29856 @section @sc{gdb/mi} Output Records
29859 * GDB/MI Result Records::
29860 * GDB/MI Stream Records::
29861 * GDB/MI Async Records::
29862 * GDB/MI Breakpoint Information::
29863 * GDB/MI Frame Information::
29864 * GDB/MI Thread Information::
29865 * GDB/MI Ada Exception Information::
29868 @node GDB/MI Result Records
29869 @subsection @sc{gdb/mi} Result Records
29871 @cindex result records in @sc{gdb/mi}
29872 @cindex @sc{gdb/mi}, result records
29873 In addition to a number of out-of-band notifications, the response to a
29874 @sc{gdb/mi} command includes one of the following result indications:
29878 @item "^done" [ "," @var{results} ]
29879 The synchronous operation was successful, @code{@var{results}} are the return
29884 This result record is equivalent to @samp{^done}. Historically, it
29885 was output instead of @samp{^done} if the command has resumed the
29886 target. This behaviour is maintained for backward compatibility, but
29887 all frontends should treat @samp{^done} and @samp{^running}
29888 identically and rely on the @samp{*running} output record to determine
29889 which threads are resumed.
29893 @value{GDBN} has connected to a remote target.
29895 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29897 The operation failed. The @code{msg=@var{c-string}} variable contains
29898 the corresponding error message.
29900 If present, the @code{code=@var{c-string}} variable provides an error
29901 code on which consumers can rely on to detect the corresponding
29902 error condition. At present, only one error code is defined:
29905 @item "undefined-command"
29906 Indicates that the command causing the error does not exist.
29911 @value{GDBN} has terminated.
29915 @node GDB/MI Stream Records
29916 @subsection @sc{gdb/mi} Stream Records
29918 @cindex @sc{gdb/mi}, stream records
29919 @cindex stream records in @sc{gdb/mi}
29920 @value{GDBN} internally maintains a number of output streams: the console, the
29921 target, and the log. The output intended for each of these streams is
29922 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29924 Each stream record begins with a unique @dfn{prefix character} which
29925 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29926 Syntax}). In addition to the prefix, each stream record contains a
29927 @code{@var{string-output}}. This is either raw text (with an implicit new
29928 line) or a quoted C string (which does not contain an implicit newline).
29931 @item "~" @var{string-output}
29932 The console output stream contains text that should be displayed in the
29933 CLI console window. It contains the textual responses to CLI commands.
29935 @item "@@" @var{string-output}
29936 The target output stream contains any textual output from the running
29937 target. This is only present when GDB's event loop is truly
29938 asynchronous, which is currently only the case for remote targets.
29940 @item "&" @var{string-output}
29941 The log stream contains debugging messages being produced by @value{GDBN}'s
29945 @node GDB/MI Async Records
29946 @subsection @sc{gdb/mi} Async Records
29948 @cindex async records in @sc{gdb/mi}
29949 @cindex @sc{gdb/mi}, async records
29950 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29951 additional changes that have occurred. Those changes can either be a
29952 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29953 target activity (e.g., target stopped).
29955 The following is the list of possible async records:
29959 @item *running,thread-id="@var{thread}"
29960 The target is now running. The @var{thread} field can be the global
29961 thread ID of the thread that is now running, and it can be
29962 @samp{all} if all threads are running. The frontend should assume
29963 that no interaction with a running thread is possible after this
29964 notification is produced. The frontend should not assume that this
29965 notification is output only once for any command. @value{GDBN} may
29966 emit this notification several times, either for different threads,
29967 because it cannot resume all threads together, or even for a single
29968 thread, if the thread must be stepped though some code before letting
29971 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29972 The target has stopped. The @var{reason} field can have one of the
29976 @item breakpoint-hit
29977 A breakpoint was reached.
29978 @item watchpoint-trigger
29979 A watchpoint was triggered.
29980 @item read-watchpoint-trigger
29981 A read watchpoint was triggered.
29982 @item access-watchpoint-trigger
29983 An access watchpoint was triggered.
29984 @item function-finished
29985 An -exec-finish or similar CLI command was accomplished.
29986 @item location-reached
29987 An -exec-until or similar CLI command was accomplished.
29988 @item watchpoint-scope
29989 A watchpoint has gone out of scope.
29990 @item end-stepping-range
29991 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29992 similar CLI command was accomplished.
29993 @item exited-signalled
29994 The inferior exited because of a signal.
29996 The inferior exited.
29997 @item exited-normally
29998 The inferior exited normally.
29999 @item signal-received
30000 A signal was received by the inferior.
30002 The inferior has stopped due to a library being loaded or unloaded.
30003 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30004 set or when a @code{catch load} or @code{catch unload} catchpoint is
30005 in use (@pxref{Set Catchpoints}).
30007 The inferior has forked. This is reported when @code{catch fork}
30008 (@pxref{Set Catchpoints}) has been used.
30010 The inferior has vforked. This is reported in when @code{catch vfork}
30011 (@pxref{Set Catchpoints}) has been used.
30012 @item syscall-entry
30013 The inferior entered a system call. This is reported when @code{catch
30014 syscall} (@pxref{Set Catchpoints}) has been used.
30015 @item syscall-return
30016 The inferior returned from a system call. This is reported when
30017 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30019 The inferior called @code{exec}. This is reported when @code{catch exec}
30020 (@pxref{Set Catchpoints}) has been used.
30023 The @var{id} field identifies the global thread ID of the thread
30024 that directly caused the stop -- for example by hitting a breakpoint.
30025 Depending on whether all-stop
30026 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30027 stop all threads, or only the thread that directly triggered the stop.
30028 If all threads are stopped, the @var{stopped} field will have the
30029 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30030 field will be a list of thread identifiers. Presently, this list will
30031 always include a single thread, but frontend should be prepared to see
30032 several threads in the list. The @var{core} field reports the
30033 processor core on which the stop event has happened. This field may be absent
30034 if such information is not available.
30036 @item =thread-group-added,id="@var{id}"
30037 @itemx =thread-group-removed,id="@var{id}"
30038 A thread group was either added or removed. The @var{id} field
30039 contains the @value{GDBN} identifier of the thread group. When a thread
30040 group is added, it generally might not be associated with a running
30041 process. When a thread group is removed, its id becomes invalid and
30042 cannot be used in any way.
30044 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30045 A thread group became associated with a running program,
30046 either because the program was just started or the thread group
30047 was attached to a program. The @var{id} field contains the
30048 @value{GDBN} identifier of the thread group. The @var{pid} field
30049 contains process identifier, specific to the operating system.
30051 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30052 A thread group is no longer associated with a running program,
30053 either because the program has exited, or because it was detached
30054 from. The @var{id} field contains the @value{GDBN} identifier of the
30055 thread group. The @var{code} field is the exit code of the inferior; it exists
30056 only when the inferior exited with some code.
30058 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30059 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30060 A thread either was created, or has exited. The @var{id} field
30061 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30062 field identifies the thread group this thread belongs to.
30064 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30065 Informs that the selected thread or frame were changed. This notification
30066 is not emitted as result of the @code{-thread-select} or
30067 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30068 that is not documented to change the selected thread and frame actually
30069 changes them. In particular, invoking, directly or indirectly
30070 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30071 will generate this notification. Changing the thread or frame from another
30072 user interface (see @ref{Interpreters}) will also generate this notification.
30074 The @var{frame} field is only present if the newly selected thread is
30075 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30077 We suggest that in response to this notification, front ends
30078 highlight the selected thread and cause subsequent commands to apply to
30081 @item =library-loaded,...
30082 Reports that a new library file was loaded by the program. This
30083 notification has 5 fields---@var{id}, @var{target-name},
30084 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30085 opaque identifier of the library. For remote debugging case,
30086 @var{target-name} and @var{host-name} fields give the name of the
30087 library file on the target, and on the host respectively. For native
30088 debugging, both those fields have the same value. The
30089 @var{symbols-loaded} field is emitted only for backward compatibility
30090 and should not be relied on to convey any useful information. The
30091 @var{thread-group} field, if present, specifies the id of the thread
30092 group in whose context the library was loaded. If the field is
30093 absent, it means the library was loaded in the context of all present
30094 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30097 @item =library-unloaded,...
30098 Reports that a library was unloaded by the program. This notification
30099 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30100 the same meaning as for the @code{=library-loaded} notification.
30101 The @var{thread-group} field, if present, specifies the id of the
30102 thread group in whose context the library was unloaded. If the field is
30103 absent, it means the library was unloaded in the context of all present
30106 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30107 @itemx =traceframe-changed,end
30108 Reports that the trace frame was changed and its new number is
30109 @var{tfnum}. The number of the tracepoint associated with this trace
30110 frame is @var{tpnum}.
30112 @item =tsv-created,name=@var{name},initial=@var{initial}
30113 Reports that the new trace state variable @var{name} is created with
30114 initial value @var{initial}.
30116 @item =tsv-deleted,name=@var{name}
30117 @itemx =tsv-deleted
30118 Reports that the trace state variable @var{name} is deleted or all
30119 trace state variables are deleted.
30121 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30122 Reports that the trace state variable @var{name} is modified with
30123 the initial value @var{initial}. The current value @var{current} of
30124 trace state variable is optional and is reported if the current
30125 value of trace state variable is known.
30127 @item =breakpoint-created,bkpt=@{...@}
30128 @itemx =breakpoint-modified,bkpt=@{...@}
30129 @itemx =breakpoint-deleted,id=@var{number}
30130 Reports that a breakpoint was created, modified, or deleted,
30131 respectively. Only user-visible breakpoints are reported to the MI
30134 The @var{bkpt} argument is of the same form as returned by the various
30135 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30136 @var{number} is the ordinal number of the breakpoint.
30138 Note that if a breakpoint is emitted in the result record of a
30139 command, then it will not also be emitted in an async record.
30141 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30142 @itemx =record-stopped,thread-group="@var{id}"
30143 Execution log recording was either started or stopped on an
30144 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30145 group corresponding to the affected inferior.
30147 The @var{method} field indicates the method used to record execution. If the
30148 method in use supports multiple recording formats, @var{format} will be present
30149 and contain the currently used format. @xref{Process Record and Replay},
30150 for existing method and format values.
30152 @item =cmd-param-changed,param=@var{param},value=@var{value}
30153 Reports that a parameter of the command @code{set @var{param}} is
30154 changed to @var{value}. In the multi-word @code{set} command,
30155 the @var{param} is the whole parameter list to @code{set} command.
30156 For example, In command @code{set check type on}, @var{param}
30157 is @code{check type} and @var{value} is @code{on}.
30159 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30160 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30161 written in an inferior. The @var{id} is the identifier of the
30162 thread group corresponding to the affected inferior. The optional
30163 @code{type="code"} part is reported if the memory written to holds
30167 @node GDB/MI Breakpoint Information
30168 @subsection @sc{gdb/mi} Breakpoint Information
30170 When @value{GDBN} reports information about a breakpoint, a
30171 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30176 The breakpoint number.
30179 The type of the breakpoint. For ordinary breakpoints this will be
30180 @samp{breakpoint}, but many values are possible.
30183 If the type of the breakpoint is @samp{catchpoint}, then this
30184 indicates the exact type of catchpoint.
30187 This is the breakpoint disposition---either @samp{del}, meaning that
30188 the breakpoint will be deleted at the next stop, or @samp{keep},
30189 meaning that the breakpoint will not be deleted.
30192 This indicates whether the breakpoint is enabled, in which case the
30193 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30194 Note that this is not the same as the field @code{enable}.
30197 The address of the breakpoint. This may be a hexidecimal number,
30198 giving the address; or the string @samp{<PENDING>}, for a pending
30199 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30200 multiple locations. This field will not be present if no address can
30201 be determined. For example, a watchpoint does not have an address.
30204 Optional field containing any flags related to the address. These flags are
30205 architecture-dependent; see @ref{Architectures} for their meaning for a
30209 If known, the function in which the breakpoint appears.
30210 If not known, this field is not present.
30213 The name of the source file which contains this function, if known.
30214 If not known, this field is not present.
30217 The full file name of the source file which contains this function, if
30218 known. If not known, this field is not present.
30221 The line number at which this breakpoint appears, if known.
30222 If not known, this field is not present.
30225 If the source file is not known, this field may be provided. If
30226 provided, this holds the address of the breakpoint, possibly followed
30230 If this breakpoint is pending, this field is present and holds the
30231 text used to set the breakpoint, as entered by the user.
30234 Where this breakpoint's condition is evaluated, either @samp{host} or
30238 If this is a thread-specific breakpoint, then this identifies the
30239 thread in which the breakpoint can trigger.
30242 If this breakpoint is restricted to a particular Ada task, then this
30243 field will hold the task identifier.
30246 If the breakpoint is conditional, this is the condition expression.
30249 The ignore count of the breakpoint.
30252 The enable count of the breakpoint.
30254 @item traceframe-usage
30257 @item static-tracepoint-marker-string-id
30258 For a static tracepoint, the name of the static tracepoint marker.
30261 For a masked watchpoint, this is the mask.
30264 A tracepoint's pass count.
30266 @item original-location
30267 The location of the breakpoint as originally specified by the user.
30268 This field is optional.
30271 The number of times the breakpoint has been hit.
30274 This field is only given for tracepoints. This is either @samp{y},
30275 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30279 Some extra data, the exact contents of which are type-dependent.
30282 This field is present if the breakpoint has multiple locations. It is also
30283 exceptionally present if the breakpoint is enabled and has a single, disabled
30286 The value is a list of locations. The format of a location is described below.
30290 A location in a multi-location breakpoint is represented as a tuple with the
30296 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30297 number of the parent breakpoint. The second digit is the number of the
30298 location within that breakpoint.
30301 There are three possible values, with the following meanings:
30304 The location is enabled.
30306 The location is disabled by the user.
30308 The location is disabled because the breakpoint condition is invalid
30313 The address of this location as an hexidecimal number.
30316 Optional field containing any flags related to the address. These flags are
30317 architecture-dependent; see @ref{Architectures} for their meaning for a
30321 If known, the function in which the location appears.
30322 If not known, this field is not present.
30325 The name of the source file which contains this location, if known.
30326 If not known, this field is not present.
30329 The full file name of the source file which contains this location, if
30330 known. If not known, this field is not present.
30333 The line number at which this location appears, if known.
30334 If not known, this field is not present.
30336 @item thread-groups
30337 The thread groups this location is in.
30341 For example, here is what the output of @code{-break-insert}
30342 (@pxref{GDB/MI Breakpoint Commands}) might be:
30345 -> -break-insert main
30346 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30347 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30348 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30353 @node GDB/MI Frame Information
30354 @subsection @sc{gdb/mi} Frame Information
30356 Response from many MI commands includes an information about stack
30357 frame. This information is a tuple that may have the following
30362 The level of the stack frame. The innermost frame has the level of
30363 zero. This field is always present.
30366 The name of the function corresponding to the frame. This field may
30367 be absent if @value{GDBN} is unable to determine the function name.
30370 The code address for the frame. This field is always present.
30373 Optional field containing any flags related to the address. These flags are
30374 architecture-dependent; see @ref{Architectures} for their meaning for a
30378 The name of the source files that correspond to the frame's code
30379 address. This field may be absent.
30382 The source line corresponding to the frames' code address. This field
30386 The name of the binary file (either executable or shared library) the
30387 corresponds to the frame's code address. This field may be absent.
30391 @node GDB/MI Thread Information
30392 @subsection @sc{gdb/mi} Thread Information
30394 Whenever @value{GDBN} has to report an information about a thread, it
30395 uses a tuple with the following fields. The fields are always present unless
30400 The global numeric id assigned to the thread by @value{GDBN}.
30403 The target-specific string identifying the thread.
30406 Additional information about the thread provided by the target.
30407 It is supposed to be human-readable and not interpreted by the
30408 frontend. This field is optional.
30411 The name of the thread. If the user specified a name using the
30412 @code{thread name} command, then this name is given. Otherwise, if
30413 @value{GDBN} can extract the thread name from the target, then that
30414 name is given. If @value{GDBN} cannot find the thread name, then this
30418 The execution state of the thread, either @samp{stopped} or @samp{running},
30419 depending on whether the thread is presently running.
30422 The stack frame currently executing in the thread. This field is only present
30423 if the thread is stopped. Its format is documented in
30424 @ref{GDB/MI Frame Information}.
30427 The value of this field is an integer number of the processor core the
30428 thread was last seen on. This field is optional.
30431 @node GDB/MI Ada Exception Information
30432 @subsection @sc{gdb/mi} Ada Exception Information
30434 Whenever a @code{*stopped} record is emitted because the program
30435 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30436 @value{GDBN} provides the name of the exception that was raised via
30437 the @code{exception-name} field. Also, for exceptions that were raised
30438 with an exception message, @value{GDBN} provides that message via
30439 the @code{exception-message} field.
30441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30442 @node GDB/MI Simple Examples
30443 @section Simple Examples of @sc{gdb/mi} Interaction
30444 @cindex @sc{gdb/mi}, simple examples
30446 This subsection presents several simple examples of interaction using
30447 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30448 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30449 the output received from @sc{gdb/mi}.
30451 Note the line breaks shown in the examples are here only for
30452 readability, they don't appear in the real output.
30454 @subheading Setting a Breakpoint
30456 Setting a breakpoint generates synchronous output which contains detailed
30457 information of the breakpoint.
30460 -> -break-insert main
30461 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30462 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30463 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30468 @subheading Program Execution
30470 Program execution generates asynchronous records and MI gives the
30471 reason that execution stopped.
30477 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30478 frame=@{addr="0x08048564",func="main",
30479 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30480 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30481 arch="i386:x86_64"@}
30486 <- *stopped,reason="exited-normally"
30490 @subheading Quitting @value{GDBN}
30492 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30500 Please note that @samp{^exit} is printed immediately, but it might
30501 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30502 performs necessary cleanups, including killing programs being debugged
30503 or disconnecting from debug hardware, so the frontend should wait till
30504 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30505 fails to exit in reasonable time.
30507 @subheading A Bad Command
30509 Here's what happens if you pass a non-existent command:
30513 <- ^error,msg="Undefined MI command: rubbish"
30518 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30519 @node GDB/MI Command Description Format
30520 @section @sc{gdb/mi} Command Description Format
30522 The remaining sections describe blocks of commands. Each block of
30523 commands is laid out in a fashion similar to this section.
30525 @subheading Motivation
30527 The motivation for this collection of commands.
30529 @subheading Introduction
30531 A brief introduction to this collection of commands as a whole.
30533 @subheading Commands
30535 For each command in the block, the following is described:
30537 @subsubheading Synopsis
30540 -command @var{args}@dots{}
30543 @subsubheading Result
30545 @subsubheading @value{GDBN} Command
30547 The corresponding @value{GDBN} CLI command(s), if any.
30549 @subsubheading Example
30551 Example(s) formatted for readability. Some of the described commands have
30552 not been implemented yet and these are labeled N.A.@: (not available).
30555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30556 @node GDB/MI Breakpoint Commands
30557 @section @sc{gdb/mi} Breakpoint Commands
30559 @cindex breakpoint commands for @sc{gdb/mi}
30560 @cindex @sc{gdb/mi}, breakpoint commands
30561 This section documents @sc{gdb/mi} commands for manipulating
30564 @subheading The @code{-break-after} Command
30565 @findex -break-after
30567 @subsubheading Synopsis
30570 -break-after @var{number} @var{count}
30573 The breakpoint number @var{number} is not in effect until it has been
30574 hit @var{count} times. To see how this is reflected in the output of
30575 the @samp{-break-list} command, see the description of the
30576 @samp{-break-list} command below.
30578 @subsubheading @value{GDBN} Command
30580 The corresponding @value{GDBN} command is @samp{ignore}.
30582 @subsubheading Example
30587 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30588 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30589 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30597 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30598 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30599 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30600 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30601 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30602 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30603 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30604 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30605 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30606 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30611 @subheading The @code{-break-catch} Command
30612 @findex -break-catch
30615 @subheading The @code{-break-commands} Command
30616 @findex -break-commands
30618 @subsubheading Synopsis
30621 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30624 Specifies the CLI commands that should be executed when breakpoint
30625 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30626 are the commands. If no command is specified, any previously-set
30627 commands are cleared. @xref{Break Commands}. Typical use of this
30628 functionality is tracing a program, that is, printing of values of
30629 some variables whenever breakpoint is hit and then continuing.
30631 @subsubheading @value{GDBN} Command
30633 The corresponding @value{GDBN} command is @samp{commands}.
30635 @subsubheading Example
30640 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30641 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30642 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30645 -break-commands 1 "print v" "continue"
30650 @subheading The @code{-break-condition} Command
30651 @findex -break-condition
30653 @subsubheading Synopsis
30656 -break-condition [ --force ] @var{number} [ @var{expr} ]
30659 Breakpoint @var{number} will stop the program only if the condition in
30660 @var{expr} is true. The condition becomes part of the
30661 @samp{-break-list} output (see the description of the @samp{-break-list}
30662 command below). If the @samp{--force} flag is passed, the condition
30663 is forcibly defined even when it is invalid for all locations of
30664 breakpoint @var{number}. If the @var{expr} argument is omitted,
30665 breakpoint @var{number} becomes unconditional.
30667 @subsubheading @value{GDBN} Command
30669 The corresponding @value{GDBN} command is @samp{condition}.
30671 @subsubheading Example
30675 -break-condition 1 1
30679 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30680 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30681 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30682 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30683 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30684 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30685 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30686 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30687 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30688 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30692 @subheading The @code{-break-delete} Command
30693 @findex -break-delete
30695 @subsubheading Synopsis
30698 -break-delete ( @var{breakpoint} )+
30701 Delete the breakpoint(s) whose number(s) are specified in the argument
30702 list. This is obviously reflected in the breakpoint list.
30704 @subsubheading @value{GDBN} Command
30706 The corresponding @value{GDBN} command is @samp{delete}.
30708 @subsubheading Example
30716 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30717 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30718 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30719 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30720 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30721 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30722 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30727 @subheading The @code{-break-disable} Command
30728 @findex -break-disable
30730 @subsubheading Synopsis
30733 -break-disable ( @var{breakpoint} )+
30736 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30737 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30739 @subsubheading @value{GDBN} Command
30741 The corresponding @value{GDBN} command is @samp{disable}.
30743 @subsubheading Example
30751 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30752 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30753 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30754 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30755 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30756 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30757 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30758 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30759 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30760 line="5",thread-groups=["i1"],times="0"@}]@}
30764 @subheading The @code{-break-enable} Command
30765 @findex -break-enable
30767 @subsubheading Synopsis
30770 -break-enable ( @var{breakpoint} )+
30773 Enable (previously disabled) @var{breakpoint}(s).
30775 @subsubheading @value{GDBN} Command
30777 The corresponding @value{GDBN} command is @samp{enable}.
30779 @subsubheading Example
30787 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30788 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30789 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30790 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30791 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30792 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30793 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30794 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30795 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30796 line="5",thread-groups=["i1"],times="0"@}]@}
30800 @subheading The @code{-break-info} Command
30801 @findex -break-info
30803 @subsubheading Synopsis
30806 -break-info @var{breakpoint}
30810 Get information about a single breakpoint.
30812 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30813 Information}, for details on the format of each breakpoint in the
30816 @subsubheading @value{GDBN} Command
30818 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30820 @subsubheading Example
30823 @subheading The @code{-break-insert} Command
30824 @findex -break-insert
30825 @anchor{-break-insert}
30827 @subsubheading Synopsis
30830 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
30831 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
30832 [ -p @var{thread-id} ] [ @var{location} ]
30836 If specified, @var{location}, can be one of:
30839 @item linespec location
30840 A linespec location. @xref{Linespec Locations}.
30842 @item explicit location
30843 An explicit location. @sc{gdb/mi} explicit locations are
30844 analogous to the CLI's explicit locations using the option names
30845 listed below. @xref{Explicit Locations}.
30848 @item --source @var{filename}
30849 The source file name of the location. This option requires the use
30850 of either @samp{--function} or @samp{--line}.
30852 @item --function @var{function}
30853 The name of a function or method.
30855 @item --label @var{label}
30856 The name of a label.
30858 @item --line @var{lineoffset}
30859 An absolute or relative line offset from the start of the location.
30862 @item address location
30863 An address location, *@var{address}. @xref{Address Locations}.
30867 The possible optional parameters of this command are:
30871 Insert a temporary breakpoint.
30873 Insert a hardware breakpoint.
30875 If @var{location} cannot be parsed (for example if it
30876 refers to unknown files or functions), create a pending
30877 breakpoint. Without this flag, @value{GDBN} will report
30878 an error, and won't create a breakpoint, if @var{location}
30881 Create a disabled breakpoint.
30883 Create a tracepoint. @xref{Tracepoints}. When this parameter
30884 is used together with @samp{-h}, a fast tracepoint is created.
30885 @item -c @var{condition}
30886 Make the breakpoint conditional on @var{condition}.
30887 @item --force-condition
30888 Forcibly define the breakpoint even if the condition is invalid at
30889 all of the breakpoint locations.
30890 @item -i @var{ignore-count}
30891 Initialize the @var{ignore-count}.
30892 @item -p @var{thread-id}
30893 Restrict the breakpoint to the thread with the specified global
30896 This option makes @value{GDBN} interpret a function name specified as
30897 a complete fully-qualified name.
30900 @subsubheading Result
30902 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30903 resulting breakpoint.
30905 Note: this format is open to change.
30906 @c An out-of-band breakpoint instead of part of the result?
30908 @subsubheading @value{GDBN} Command
30910 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30911 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30913 @subsubheading Example
30918 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30919 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30922 -break-insert -t foo
30923 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30924 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30928 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30929 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30930 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30931 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30932 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30933 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30934 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30935 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30936 addr="0x0001072c", func="main",file="recursive2.c",
30937 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30939 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30940 addr="0x00010774",func="foo",file="recursive2.c",
30941 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30944 @c -break-insert -r foo.*
30945 @c ~int foo(int, int);
30946 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30947 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30952 @subheading The @code{-dprintf-insert} Command
30953 @findex -dprintf-insert
30955 @subsubheading Synopsis
30958 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
30959 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
30960 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30965 If supplied, @var{location} and @code{--qualified} may be specified
30966 the same way as for the @code{-break-insert} command.
30967 @xref{-break-insert}.
30969 The possible optional parameters of this command are:
30973 Insert a temporary breakpoint.
30975 If @var{location} cannot be parsed (for example, if it
30976 refers to unknown files or functions), create a pending
30977 breakpoint. Without this flag, @value{GDBN} will report
30978 an error, and won't create a breakpoint, if @var{location}
30981 Create a disabled breakpoint.
30982 @item -c @var{condition}
30983 Make the breakpoint conditional on @var{condition}.
30984 @item --force-condition
30985 Forcibly define the breakpoint even if the condition is invalid at
30986 all of the breakpoint locations.
30987 @item -i @var{ignore-count}
30988 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30989 to @var{ignore-count}.
30990 @item -p @var{thread-id}
30991 Restrict the breakpoint to the thread with the specified global
30995 @subsubheading Result
30997 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30998 resulting breakpoint.
31000 @c An out-of-band breakpoint instead of part of the result?
31002 @subsubheading @value{GDBN} Command
31004 The corresponding @value{GDBN} command is @samp{dprintf}.
31006 @subsubheading Example
31010 4-dprintf-insert foo "At foo entry\n"
31011 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31012 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31013 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31014 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31015 original-location="foo"@}
31017 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31018 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31019 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31020 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31021 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31022 original-location="mi-dprintf.c:26"@}
31026 @subheading The @code{-break-list} Command
31027 @findex -break-list
31029 @subsubheading Synopsis
31035 Displays the list of inserted breakpoints, showing the following fields:
31039 number of the breakpoint
31041 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31043 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31046 is the breakpoint enabled or no: @samp{y} or @samp{n}
31048 memory location at which the breakpoint is set
31050 logical location of the breakpoint, expressed by function name, file
31052 @item Thread-groups
31053 list of thread groups to which this breakpoint applies
31055 number of times the breakpoint has been hit
31058 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31059 @code{body} field is an empty list.
31061 @subsubheading @value{GDBN} Command
31063 The corresponding @value{GDBN} command is @samp{info break}.
31065 @subsubheading Example
31070 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31077 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31078 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31080 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31081 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31082 line="13",thread-groups=["i1"],times="0"@}]@}
31086 Here's an example of the result when there are no breakpoints:
31091 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31102 @subheading The @code{-break-passcount} Command
31103 @findex -break-passcount
31105 @subsubheading Synopsis
31108 -break-passcount @var{tracepoint-number} @var{passcount}
31111 Set the passcount for tracepoint @var{tracepoint-number} to
31112 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31113 is not a tracepoint, error is emitted. This corresponds to CLI
31114 command @samp{passcount}.
31116 @subheading The @code{-break-watch} Command
31117 @findex -break-watch
31119 @subsubheading Synopsis
31122 -break-watch [ -a | -r ]
31125 Create a watchpoint. With the @samp{-a} option it will create an
31126 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31127 read from or on a write to the memory location. With the @samp{-r}
31128 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31129 trigger only when the memory location is accessed for reading. Without
31130 either of the options, the watchpoint created is a regular watchpoint,
31131 i.e., it will trigger when the memory location is accessed for writing.
31132 @xref{Set Watchpoints, , Setting Watchpoints}.
31134 Note that @samp{-break-list} will report a single list of watchpoints and
31135 breakpoints inserted.
31137 @subsubheading @value{GDBN} Command
31139 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31142 @subsubheading Example
31144 Setting a watchpoint on a variable in the @code{main} function:
31149 ^done,wpt=@{number="2",exp="x"@}
31154 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31155 value=@{old="-268439212",new="55"@},
31156 frame=@{func="main",args=[],file="recursive2.c",
31157 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31161 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31162 the program execution twice: first for the variable changing value, then
31163 for the watchpoint going out of scope.
31168 ^done,wpt=@{number="5",exp="C"@}
31173 *stopped,reason="watchpoint-trigger",
31174 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31175 frame=@{func="callee4",args=[],
31176 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31177 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31178 arch="i386:x86_64"@}
31183 *stopped,reason="watchpoint-scope",wpnum="5",
31184 frame=@{func="callee3",args=[@{name="strarg",
31185 value="0x11940 \"A string argument.\""@}],
31186 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31187 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31188 arch="i386:x86_64"@}
31192 Listing breakpoints and watchpoints, at different points in the program
31193 execution. Note that once the watchpoint goes out of scope, it is
31199 ^done,wpt=@{number="2",exp="C"@}
31202 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31203 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31204 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31205 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31206 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31207 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31208 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31209 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31210 addr="0x00010734",func="callee4",
31211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31212 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31214 bkpt=@{number="2",type="watchpoint",disp="keep",
31215 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31220 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31221 value=@{old="-276895068",new="3"@},
31222 frame=@{func="callee4",args=[],
31223 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31224 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31225 arch="i386:x86_64"@}
31228 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31229 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31230 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31231 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31232 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31233 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31234 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31235 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31236 addr="0x00010734",func="callee4",
31237 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31238 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31240 bkpt=@{number="2",type="watchpoint",disp="keep",
31241 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31245 ^done,reason="watchpoint-scope",wpnum="2",
31246 frame=@{func="callee3",args=[@{name="strarg",
31247 value="0x11940 \"A string argument.\""@}],
31248 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31249 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31250 arch="i386:x86_64"@}
31253 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31254 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31255 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31256 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31257 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31258 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31259 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31260 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31261 addr="0x00010734",func="callee4",
31262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31263 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31264 thread-groups=["i1"],times="1"@}]@}
31269 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31270 @node GDB/MI Catchpoint Commands
31271 @section @sc{gdb/mi} Catchpoint Commands
31273 This section documents @sc{gdb/mi} commands for manipulating
31277 * Shared Library GDB/MI Catchpoint Commands::
31278 * Ada Exception GDB/MI Catchpoint Commands::
31279 * C++ Exception GDB/MI Catchpoint Commands::
31282 @node Shared Library GDB/MI Catchpoint Commands
31283 @subsection Shared Library @sc{gdb/mi} Catchpoints
31285 @subheading The @code{-catch-load} Command
31286 @findex -catch-load
31288 @subsubheading Synopsis
31291 -catch-load [ -t ] [ -d ] @var{regexp}
31294 Add a catchpoint for library load events. If the @samp{-t} option is used,
31295 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31296 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31297 in a disabled state. The @samp{regexp} argument is a regular
31298 expression used to match the name of the loaded library.
31301 @subsubheading @value{GDBN} Command
31303 The corresponding @value{GDBN} command is @samp{catch load}.
31305 @subsubheading Example
31308 -catch-load -t foo.so
31309 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31310 what="load of library matching foo.so",catch-type="load",times="0"@}
31315 @subheading The @code{-catch-unload} Command
31316 @findex -catch-unload
31318 @subsubheading Synopsis
31321 -catch-unload [ -t ] [ -d ] @var{regexp}
31324 Add a catchpoint for library unload events. If the @samp{-t} option is
31325 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31326 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31327 created in a disabled state. The @samp{regexp} argument is a regular
31328 expression used to match the name of the unloaded library.
31330 @subsubheading @value{GDBN} Command
31332 The corresponding @value{GDBN} command is @samp{catch unload}.
31334 @subsubheading Example
31337 -catch-unload -d bar.so
31338 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31339 what="load of library matching bar.so",catch-type="unload",times="0"@}
31343 @node Ada Exception GDB/MI Catchpoint Commands
31344 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31346 The following @sc{gdb/mi} commands can be used to create catchpoints
31347 that stop the execution when Ada exceptions are being raised.
31349 @subheading The @code{-catch-assert} Command
31350 @findex -catch-assert
31352 @subsubheading Synopsis
31355 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31358 Add a catchpoint for failed Ada assertions.
31360 The possible optional parameters for this command are:
31363 @item -c @var{condition}
31364 Make the catchpoint conditional on @var{condition}.
31366 Create a disabled catchpoint.
31368 Create a temporary catchpoint.
31371 @subsubheading @value{GDBN} Command
31373 The corresponding @value{GDBN} command is @samp{catch assert}.
31375 @subsubheading Example
31379 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31380 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31381 thread-groups=["i1"],times="0",
31382 original-location="__gnat_debug_raise_assert_failure"@}
31386 @subheading The @code{-catch-exception} Command
31387 @findex -catch-exception
31389 @subsubheading Synopsis
31392 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31396 Add a catchpoint stopping when Ada exceptions are raised.
31397 By default, the command stops the program when any Ada exception
31398 gets raised. But it is also possible, by using some of the
31399 optional parameters described below, to create more selective
31402 The possible optional parameters for this command are:
31405 @item -c @var{condition}
31406 Make the catchpoint conditional on @var{condition}.
31408 Create a disabled catchpoint.
31409 @item -e @var{exception-name}
31410 Only stop when @var{exception-name} is raised. This option cannot
31411 be used combined with @samp{-u}.
31413 Create a temporary catchpoint.
31415 Stop only when an unhandled exception gets raised. This option
31416 cannot be used combined with @samp{-e}.
31419 @subsubheading @value{GDBN} Command
31421 The corresponding @value{GDBN} commands are @samp{catch exception}
31422 and @samp{catch exception unhandled}.
31424 @subsubheading Example
31427 -catch-exception -e Program_Error
31428 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31429 enabled="y",addr="0x0000000000404874",
31430 what="`Program_Error' Ada exception", thread-groups=["i1"],
31431 times="0",original-location="__gnat_debug_raise_exception"@}
31435 @subheading The @code{-catch-handlers} Command
31436 @findex -catch-handlers
31438 @subsubheading Synopsis
31441 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31445 Add a catchpoint stopping when Ada exceptions are handled.
31446 By default, the command stops the program when any Ada exception
31447 gets handled. But it is also possible, by using some of the
31448 optional parameters described below, to create more selective
31451 The possible optional parameters for this command are:
31454 @item -c @var{condition}
31455 Make the catchpoint conditional on @var{condition}.
31457 Create a disabled catchpoint.
31458 @item -e @var{exception-name}
31459 Only stop when @var{exception-name} is handled.
31461 Create a temporary catchpoint.
31464 @subsubheading @value{GDBN} Command
31466 The corresponding @value{GDBN} command is @samp{catch handlers}.
31468 @subsubheading Example
31471 -catch-handlers -e Constraint_Error
31472 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31473 enabled="y",addr="0x0000000000402f68",
31474 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31475 times="0",original-location="__gnat_begin_handler"@}
31479 @node C++ Exception GDB/MI Catchpoint Commands
31480 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31482 The following @sc{gdb/mi} commands can be used to create catchpoints
31483 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31486 @subheading The @code{-catch-throw} Command
31487 @findex -catch-throw
31489 @subsubheading Synopsis
31492 -catch-throw [ -t ] [ -r @var{regexp}]
31495 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31496 given, then only exceptions whose type matches the regular expression
31499 If @samp{-t} is given, then the catchpoint is enabled only for one
31500 stop, the catchpoint is automatically deleted after stopping once for
31503 @subsubheading @value{GDBN} Command
31505 The corresponding @value{GDBN} commands are @samp{catch throw}
31506 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31508 @subsubheading Example
31511 -catch-throw -r exception_type
31512 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31513 what="exception throw",catch-type="throw",
31514 thread-groups=["i1"],
31515 regexp="exception_type",times="0"@}
31521 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31522 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31523 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31524 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31525 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31526 thread-id="1",stopped-threads="all",core="6"
31530 @subheading The @code{-catch-rethrow} Command
31531 @findex -catch-rethrow
31533 @subsubheading Synopsis
31536 -catch-rethrow [ -t ] [ -r @var{regexp}]
31539 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31540 then only exceptions whose type matches the regular expression will be
31543 If @samp{-t} is given, then the catchpoint is enabled only for one
31544 stop, the catchpoint is automatically deleted after the first event is
31547 @subsubheading @value{GDBN} Command
31549 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31550 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31552 @subsubheading Example
31555 -catch-rethrow -r exception_type
31556 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31557 what="exception rethrow",catch-type="rethrow",
31558 thread-groups=["i1"],
31559 regexp="exception_type",times="0"@}
31565 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31566 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31567 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31568 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31569 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31570 thread-id="1",stopped-threads="all",core="6"
31574 @subheading The @code{-catch-catch} Command
31575 @findex -catch-catch
31577 @subsubheading Synopsis
31580 -catch-catch [ -t ] [ -r @var{regexp}]
31583 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31584 is given, then only exceptions whose type matches the regular
31585 expression will be caught.
31587 If @samp{-t} is given, then the catchpoint is enabled only for one
31588 stop, the catchpoint is automatically deleted after the first event is
31591 @subsubheading @value{GDBN} Command
31593 The corresponding @value{GDBN} commands are @samp{catch catch}
31594 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31596 @subsubheading Example
31599 -catch-catch -r exception_type
31600 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31601 what="exception catch",catch-type="catch",
31602 thread-groups=["i1"],
31603 regexp="exception_type",times="0"@}
31609 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31610 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31611 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31612 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31613 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31614 thread-id="1",stopped-threads="all",core="6"
31618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31619 @node GDB/MI Program Context
31620 @section @sc{gdb/mi} Program Context
31622 @subheading The @code{-exec-arguments} Command
31623 @findex -exec-arguments
31626 @subsubheading Synopsis
31629 -exec-arguments @var{args}
31632 Set the inferior program arguments, to be used in the next
31635 @subsubheading @value{GDBN} Command
31637 The corresponding @value{GDBN} command is @samp{set args}.
31639 @subsubheading Example
31643 -exec-arguments -v word
31650 @subheading The @code{-exec-show-arguments} Command
31651 @findex -exec-show-arguments
31653 @subsubheading Synopsis
31656 -exec-show-arguments
31659 Print the arguments of the program.
31661 @subsubheading @value{GDBN} Command
31663 The corresponding @value{GDBN} command is @samp{show args}.
31665 @subsubheading Example
31670 @subheading The @code{-environment-cd} Command
31671 @findex -environment-cd
31673 @subsubheading Synopsis
31676 -environment-cd @var{pathdir}
31679 Set @value{GDBN}'s working directory.
31681 @subsubheading @value{GDBN} Command
31683 The corresponding @value{GDBN} command is @samp{cd}.
31685 @subsubheading Example
31689 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31695 @subheading The @code{-environment-directory} Command
31696 @findex -environment-directory
31698 @subsubheading Synopsis
31701 -environment-directory [ -r ] [ @var{pathdir} ]+
31704 Add directories @var{pathdir} to beginning of search path for source files.
31705 If the @samp{-r} option is used, the search path is reset to the default
31706 search path. If directories @var{pathdir} are supplied in addition to the
31707 @samp{-r} option, the search path is first reset and then addition
31709 Multiple directories may be specified, separated by blanks. Specifying
31710 multiple directories in a single command
31711 results in the directories added to the beginning of the
31712 search path in the same order they were presented in the command.
31713 If blanks are needed as
31714 part of a directory name, double-quotes should be used around
31715 the name. In the command output, the path will show up separated
31716 by the system directory-separator character. The directory-separator
31717 character must not be used
31718 in any directory name.
31719 If no directories are specified, the current search path is displayed.
31721 @subsubheading @value{GDBN} Command
31723 The corresponding @value{GDBN} command is @samp{dir}.
31725 @subsubheading Example
31729 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31730 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31732 -environment-directory ""
31733 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31735 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31736 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31738 -environment-directory -r
31739 ^done,source-path="$cdir:$cwd"
31744 @subheading The @code{-environment-path} Command
31745 @findex -environment-path
31747 @subsubheading Synopsis
31750 -environment-path [ -r ] [ @var{pathdir} ]+
31753 Add directories @var{pathdir} to beginning of search path for object files.
31754 If the @samp{-r} option is used, the search path is reset to the original
31755 search path that existed at gdb start-up. If directories @var{pathdir} are
31756 supplied in addition to the
31757 @samp{-r} option, the search path is first reset and then addition
31759 Multiple directories may be specified, separated by blanks. Specifying
31760 multiple directories in a single command
31761 results in the directories added to the beginning of the
31762 search path in the same order they were presented in the command.
31763 If blanks are needed as
31764 part of a directory name, double-quotes should be used around
31765 the name. In the command output, the path will show up separated
31766 by the system directory-separator character. The directory-separator
31767 character must not be used
31768 in any directory name.
31769 If no directories are specified, the current path is displayed.
31772 @subsubheading @value{GDBN} Command
31774 The corresponding @value{GDBN} command is @samp{path}.
31776 @subsubheading Example
31781 ^done,path="/usr/bin"
31783 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31784 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31786 -environment-path -r /usr/local/bin
31787 ^done,path="/usr/local/bin:/usr/bin"
31792 @subheading The @code{-environment-pwd} Command
31793 @findex -environment-pwd
31795 @subsubheading Synopsis
31801 Show the current working directory.
31803 @subsubheading @value{GDBN} Command
31805 The corresponding @value{GDBN} command is @samp{pwd}.
31807 @subsubheading Example
31812 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31816 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31817 @node GDB/MI Thread Commands
31818 @section @sc{gdb/mi} Thread Commands
31821 @subheading The @code{-thread-info} Command
31822 @findex -thread-info
31824 @subsubheading Synopsis
31827 -thread-info [ @var{thread-id} ]
31830 Reports information about either a specific thread, if the
31831 @var{thread-id} parameter is present, or about all threads.
31832 @var{thread-id} is the thread's global thread ID. When printing
31833 information about all threads, also reports the global ID of the
31836 @subsubheading @value{GDBN} Command
31838 The @samp{info thread} command prints the same information
31841 @subsubheading Result
31843 The result contains the following attributes:
31847 A list of threads. The format of the elements of the list is described in
31848 @ref{GDB/MI Thread Information}.
31850 @item current-thread-id
31851 The global id of the currently selected thread. This field is omitted if there
31852 is no selected thread (for example, when the selected inferior is not running,
31853 and therefore has no threads) or if a @var{thread-id} argument was passed to
31858 @subsubheading Example
31863 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31864 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31865 args=[]@},state="running"@},
31866 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31867 frame=@{level="0",addr="0x0804891f",func="foo",
31868 args=[@{name="i",value="10"@}],
31869 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31870 state="running"@}],
31871 current-thread-id="1"
31875 @subheading The @code{-thread-list-ids} Command
31876 @findex -thread-list-ids
31878 @subsubheading Synopsis
31884 Produces a list of the currently known global @value{GDBN} thread ids.
31885 At the end of the list it also prints the total number of such
31888 This command is retained for historical reasons, the
31889 @code{-thread-info} command should be used instead.
31891 @subsubheading @value{GDBN} Command
31893 Part of @samp{info threads} supplies the same information.
31895 @subsubheading Example
31900 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31901 current-thread-id="1",number-of-threads="3"
31906 @subheading The @code{-thread-select} Command
31907 @findex -thread-select
31909 @subsubheading Synopsis
31912 -thread-select @var{thread-id}
31915 Make thread with global thread number @var{thread-id} the current
31916 thread. It prints the number of the new current thread, and the
31917 topmost frame for that thread.
31919 This command is deprecated in favor of explicitly using the
31920 @samp{--thread} option to each command.
31922 @subsubheading @value{GDBN} Command
31924 The corresponding @value{GDBN} command is @samp{thread}.
31926 @subsubheading Example
31933 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31934 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31938 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31939 number-of-threads="3"
31942 ^done,new-thread-id="3",
31943 frame=@{level="0",func="vprintf",
31944 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31945 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31949 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31950 @node GDB/MI Ada Tasking Commands
31951 @section @sc{gdb/mi} Ada Tasking Commands
31953 @subheading The @code{-ada-task-info} Command
31954 @findex -ada-task-info
31956 @subsubheading Synopsis
31959 -ada-task-info [ @var{task-id} ]
31962 Reports information about either a specific Ada task, if the
31963 @var{task-id} parameter is present, or about all Ada tasks.
31965 @subsubheading @value{GDBN} Command
31967 The @samp{info tasks} command prints the same information
31968 about all Ada tasks (@pxref{Ada Tasks}).
31970 @subsubheading Result
31972 The result is a table of Ada tasks. The following columns are
31973 defined for each Ada task:
31977 This field exists only for the current thread. It has the value @samp{*}.
31980 The identifier that @value{GDBN} uses to refer to the Ada task.
31983 The identifier that the target uses to refer to the Ada task.
31986 The global thread identifier of the thread corresponding to the Ada
31989 This field should always exist, as Ada tasks are always implemented
31990 on top of a thread. But if @value{GDBN} cannot find this corresponding
31991 thread for any reason, the field is omitted.
31994 This field exists only when the task was created by another task.
31995 In this case, it provides the ID of the parent task.
31998 The base priority of the task.
32001 The current state of the task. For a detailed description of the
32002 possible states, see @ref{Ada Tasks}.
32005 The name of the task.
32009 @subsubheading Example
32013 ^done,tasks=@{nr_rows="3",nr_cols="8",
32014 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32015 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32016 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32017 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32018 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32019 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32020 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32021 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32022 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32023 state="Child Termination Wait",name="main_task"@}]@}
32027 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32028 @node GDB/MI Program Execution
32029 @section @sc{gdb/mi} Program Execution
32031 These are the asynchronous commands which generate the out-of-band
32032 record @samp{*stopped}. Currently @value{GDBN} only really executes
32033 asynchronously with remote targets and this interaction is mimicked in
32036 @subheading The @code{-exec-continue} Command
32037 @findex -exec-continue
32039 @subsubheading Synopsis
32042 -exec-continue [--reverse] [--all|--thread-group N]
32045 Resumes the execution of the inferior program, which will continue
32046 to execute until it reaches a debugger stop event. If the
32047 @samp{--reverse} option is specified, execution resumes in reverse until
32048 it reaches a stop event. Stop events may include
32051 breakpoints or watchpoints
32053 signals or exceptions
32055 the end of the process (or its beginning under @samp{--reverse})
32057 the end or beginning of a replay log if one is being used.
32059 In all-stop mode (@pxref{All-Stop
32060 Mode}), may resume only one thread, or all threads, depending on the
32061 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32062 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32063 ignored in all-stop mode. If the @samp{--thread-group} options is
32064 specified, then all threads in that thread group are resumed.
32066 @subsubheading @value{GDBN} Command
32068 The corresponding @value{GDBN} corresponding is @samp{continue}.
32070 @subsubheading Example
32077 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32078 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32079 line="13",arch="i386:x86_64"@}
32084 @subheading The @code{-exec-finish} Command
32085 @findex -exec-finish
32087 @subsubheading Synopsis
32090 -exec-finish [--reverse]
32093 Resumes the execution of the inferior program until the current
32094 function is exited. Displays the results returned by the function.
32095 If the @samp{--reverse} option is specified, resumes the reverse
32096 execution of the inferior program until the point where current
32097 function was called.
32099 @subsubheading @value{GDBN} Command
32101 The corresponding @value{GDBN} command is @samp{finish}.
32103 @subsubheading Example
32105 Function returning @code{void}.
32112 *stopped,reason="function-finished",frame=@{func="main",args=[],
32113 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32117 Function returning other than @code{void}. The name of the internal
32118 @value{GDBN} variable storing the result is printed, together with the
32125 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32126 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32127 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32128 arch="i386:x86_64"@},
32129 gdb-result-var="$1",return-value="0"
32134 @subheading The @code{-exec-interrupt} Command
32135 @findex -exec-interrupt
32137 @subsubheading Synopsis
32140 -exec-interrupt [--all|--thread-group N]
32143 Interrupts the background execution of the target. Note how the token
32144 associated with the stop message is the one for the execution command
32145 that has been interrupted. The token for the interrupt itself only
32146 appears in the @samp{^done} output. If the user is trying to
32147 interrupt a non-running program, an error message will be printed.
32149 Note that when asynchronous execution is enabled, this command is
32150 asynchronous just like other execution commands. That is, first the
32151 @samp{^done} response will be printed, and the target stop will be
32152 reported after that using the @samp{*stopped} notification.
32154 In non-stop mode, only the context thread is interrupted by default.
32155 All threads (in all inferiors) will be interrupted if the
32156 @samp{--all} option is specified. If the @samp{--thread-group}
32157 option is specified, all threads in that group will be interrupted.
32159 @subsubheading @value{GDBN} Command
32161 The corresponding @value{GDBN} command is @samp{interrupt}.
32163 @subsubheading Example
32174 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32175 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32176 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32181 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32185 @subheading The @code{-exec-jump} Command
32188 @subsubheading Synopsis
32191 -exec-jump @var{location}
32194 Resumes execution of the inferior program at the location specified by
32195 parameter. @xref{Specify Location}, for a description of the
32196 different forms of @var{location}.
32198 @subsubheading @value{GDBN} Command
32200 The corresponding @value{GDBN} command is @samp{jump}.
32202 @subsubheading Example
32205 -exec-jump foo.c:10
32206 *running,thread-id="all"
32211 @subheading The @code{-exec-next} Command
32214 @subsubheading Synopsis
32217 -exec-next [--reverse]
32220 Resumes execution of the inferior program, stopping when the beginning
32221 of the next source line is reached.
32223 If the @samp{--reverse} option is specified, resumes reverse execution
32224 of the inferior program, stopping at the beginning of the previous
32225 source line. If you issue this command on the first line of a
32226 function, it will take you back to the caller of that function, to the
32227 source line where the function was called.
32230 @subsubheading @value{GDBN} Command
32232 The corresponding @value{GDBN} command is @samp{next}.
32234 @subsubheading Example
32240 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32245 @subheading The @code{-exec-next-instruction} Command
32246 @findex -exec-next-instruction
32248 @subsubheading Synopsis
32251 -exec-next-instruction [--reverse]
32254 Executes one machine instruction. If the instruction is a function
32255 call, continues until the function returns. If the program stops at an
32256 instruction in the middle of a source line, the address will be
32259 If the @samp{--reverse} option is specified, resumes reverse execution
32260 of the inferior program, stopping at the previous instruction. If the
32261 previously executed instruction was a return from another function,
32262 it will continue to execute in reverse until the call to that function
32263 (from the current stack frame) is reached.
32265 @subsubheading @value{GDBN} Command
32267 The corresponding @value{GDBN} command is @samp{nexti}.
32269 @subsubheading Example
32273 -exec-next-instruction
32277 *stopped,reason="end-stepping-range",
32278 addr="0x000100d4",line="5",file="hello.c"
32283 @subheading The @code{-exec-return} Command
32284 @findex -exec-return
32286 @subsubheading Synopsis
32292 Makes current function return immediately. Doesn't execute the inferior.
32293 Displays the new current frame.
32295 @subsubheading @value{GDBN} Command
32297 The corresponding @value{GDBN} command is @samp{return}.
32299 @subsubheading Example
32303 200-break-insert callee4
32304 200^done,bkpt=@{number="1",addr="0x00010734",
32305 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32310 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32311 frame=@{func="callee4",args=[],
32312 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32313 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32314 arch="i386:x86_64"@}
32320 111^done,frame=@{level="0",func="callee3",
32321 args=[@{name="strarg",
32322 value="0x11940 \"A string argument.\""@}],
32323 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32324 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32325 arch="i386:x86_64"@}
32330 @subheading The @code{-exec-run} Command
32333 @subsubheading Synopsis
32336 -exec-run [ --all | --thread-group N ] [ --start ]
32339 Starts execution of the inferior from the beginning. The inferior
32340 executes until either a breakpoint is encountered or the program
32341 exits. In the latter case the output will include an exit code, if
32342 the program has exited exceptionally.
32344 When neither the @samp{--all} nor the @samp{--thread-group} option
32345 is specified, the current inferior is started. If the
32346 @samp{--thread-group} option is specified, it should refer to a thread
32347 group of type @samp{process}, and that thread group will be started.
32348 If the @samp{--all} option is specified, then all inferiors will be started.
32350 Using the @samp{--start} option instructs the debugger to stop
32351 the execution at the start of the inferior's main subprogram,
32352 following the same behavior as the @code{start} command
32353 (@pxref{Starting}).
32355 @subsubheading @value{GDBN} Command
32357 The corresponding @value{GDBN} command is @samp{run}.
32359 @subsubheading Examples
32364 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32369 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32370 frame=@{func="main",args=[],file="recursive2.c",
32371 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32376 Program exited normally:
32384 *stopped,reason="exited-normally"
32389 Program exited exceptionally:
32397 *stopped,reason="exited",exit-code="01"
32401 Another way the program can terminate is if it receives a signal such as
32402 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32406 *stopped,reason="exited-signalled",signal-name="SIGINT",
32407 signal-meaning="Interrupt"
32411 @c @subheading -exec-signal
32414 @subheading The @code{-exec-step} Command
32417 @subsubheading Synopsis
32420 -exec-step [--reverse]
32423 Resumes execution of the inferior program, stopping when the beginning
32424 of the next source line is reached, if the next source line is not a
32425 function call. If it is, stop at the first instruction of the called
32426 function. If the @samp{--reverse} option is specified, resumes reverse
32427 execution of the inferior program, stopping at the beginning of the
32428 previously executed source line.
32430 @subsubheading @value{GDBN} Command
32432 The corresponding @value{GDBN} command is @samp{step}.
32434 @subsubheading Example
32436 Stepping into a function:
32442 *stopped,reason="end-stepping-range",
32443 frame=@{func="foo",args=[@{name="a",value="10"@},
32444 @{name="b",value="0"@}],file="recursive2.c",
32445 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32455 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32460 @subheading The @code{-exec-step-instruction} Command
32461 @findex -exec-step-instruction
32463 @subsubheading Synopsis
32466 -exec-step-instruction [--reverse]
32469 Resumes the inferior which executes one machine instruction. If the
32470 @samp{--reverse} option is specified, resumes reverse execution of the
32471 inferior program, stopping at the previously executed instruction.
32472 The output, once @value{GDBN} has stopped, will vary depending on
32473 whether we have stopped in the middle of a source line or not. In the
32474 former case, the address at which the program stopped will be printed
32477 @subsubheading @value{GDBN} Command
32479 The corresponding @value{GDBN} command is @samp{stepi}.
32481 @subsubheading Example
32485 -exec-step-instruction
32489 *stopped,reason="end-stepping-range",
32490 frame=@{func="foo",args=[],file="try.c",
32491 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32493 -exec-step-instruction
32497 *stopped,reason="end-stepping-range",
32498 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32499 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32504 @subheading The @code{-exec-until} Command
32505 @findex -exec-until
32507 @subsubheading Synopsis
32510 -exec-until [ @var{location} ]
32513 Executes the inferior until the @var{location} specified in the
32514 argument is reached. If there is no argument, the inferior executes
32515 until a source line greater than the current one is reached. The
32516 reason for stopping in this case will be @samp{location-reached}.
32518 @subsubheading @value{GDBN} Command
32520 The corresponding @value{GDBN} command is @samp{until}.
32522 @subsubheading Example
32526 -exec-until recursive2.c:6
32530 *stopped,reason="location-reached",frame=@{func="main",args=[],
32531 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32532 arch="i386:x86_64"@}
32537 @subheading -file-clear
32538 Is this going away????
32541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32542 @node GDB/MI Stack Manipulation
32543 @section @sc{gdb/mi} Stack Manipulation Commands
32545 @subheading The @code{-enable-frame-filters} Command
32546 @findex -enable-frame-filters
32549 -enable-frame-filters
32552 @value{GDBN} allows Python-based frame filters to affect the output of
32553 the MI commands relating to stack traces. As there is no way to
32554 implement this in a fully backward-compatible way, a front end must
32555 request that this functionality be enabled.
32557 Once enabled, this feature cannot be disabled.
32559 Note that if Python support has not been compiled into @value{GDBN},
32560 this command will still succeed (and do nothing).
32562 @subheading The @code{-stack-info-frame} Command
32563 @findex -stack-info-frame
32565 @subsubheading Synopsis
32571 Get info on the selected frame.
32573 @subsubheading @value{GDBN} Command
32575 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32576 (without arguments).
32578 @subsubheading Example
32583 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32586 arch="i386:x86_64"@}
32590 @subheading The @code{-stack-info-depth} Command
32591 @findex -stack-info-depth
32593 @subsubheading Synopsis
32596 -stack-info-depth [ @var{max-depth} ]
32599 Return the depth of the stack. If the integer argument @var{max-depth}
32600 is specified, do not count beyond @var{max-depth} frames.
32602 @subsubheading @value{GDBN} Command
32604 There's no equivalent @value{GDBN} command.
32606 @subsubheading Example
32608 For a stack with frame levels 0 through 11:
32615 -stack-info-depth 4
32618 -stack-info-depth 12
32621 -stack-info-depth 11
32624 -stack-info-depth 13
32629 @anchor{-stack-list-arguments}
32630 @subheading The @code{-stack-list-arguments} Command
32631 @findex -stack-list-arguments
32633 @subsubheading Synopsis
32636 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32637 [ @var{low-frame} @var{high-frame} ]
32640 Display a list of the arguments for the frames between @var{low-frame}
32641 and @var{high-frame} (inclusive). If @var{low-frame} and
32642 @var{high-frame} are not provided, list the arguments for the whole
32643 call stack. If the two arguments are equal, show the single frame
32644 at the corresponding level. It is an error if @var{low-frame} is
32645 larger than the actual number of frames. On the other hand,
32646 @var{high-frame} may be larger than the actual number of frames, in
32647 which case only existing frames will be returned.
32649 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32650 the variables; if it is 1 or @code{--all-values}, print also their
32651 values; and if it is 2 or @code{--simple-values}, print the name,
32652 type and value for simple data types, and the name and type for arrays,
32653 structures and unions. If the option @code{--no-frame-filters} is
32654 supplied, then Python frame filters will not be executed.
32656 If the @code{--skip-unavailable} option is specified, arguments that
32657 are not available are not listed. Partially available arguments
32658 are still displayed, however.
32660 Use of this command to obtain arguments in a single frame is
32661 deprecated in favor of the @samp{-stack-list-variables} command.
32663 @subsubheading @value{GDBN} Command
32665 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32666 @samp{gdb_get_args} command which partially overlaps with the
32667 functionality of @samp{-stack-list-arguments}.
32669 @subsubheading Example
32676 frame=@{level="0",addr="0x00010734",func="callee4",
32677 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32678 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32679 arch="i386:x86_64"@},
32680 frame=@{level="1",addr="0x0001076c",func="callee3",
32681 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32682 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32683 arch="i386:x86_64"@},
32684 frame=@{level="2",addr="0x0001078c",func="callee2",
32685 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32686 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32687 arch="i386:x86_64"@},
32688 frame=@{level="3",addr="0x000107b4",func="callee1",
32689 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32690 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32691 arch="i386:x86_64"@},
32692 frame=@{level="4",addr="0x000107e0",func="main",
32693 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32694 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32695 arch="i386:x86_64"@}]
32697 -stack-list-arguments 0
32700 frame=@{level="0",args=[]@},
32701 frame=@{level="1",args=[name="strarg"]@},
32702 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32703 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32704 frame=@{level="4",args=[]@}]
32706 -stack-list-arguments 1
32709 frame=@{level="0",args=[]@},
32711 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32712 frame=@{level="2",args=[
32713 @{name="intarg",value="2"@},
32714 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32715 @{frame=@{level="3",args=[
32716 @{name="intarg",value="2"@},
32717 @{name="strarg",value="0x11940 \"A string argument.\""@},
32718 @{name="fltarg",value="3.5"@}]@},
32719 frame=@{level="4",args=[]@}]
32721 -stack-list-arguments 0 2 2
32722 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32724 -stack-list-arguments 1 2 2
32725 ^done,stack-args=[frame=@{level="2",
32726 args=[@{name="intarg",value="2"@},
32727 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32731 @c @subheading -stack-list-exception-handlers
32734 @anchor{-stack-list-frames}
32735 @subheading The @code{-stack-list-frames} Command
32736 @findex -stack-list-frames
32738 @subsubheading Synopsis
32741 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32744 List the frames currently on the stack. For each frame it displays the
32749 The frame number, 0 being the topmost frame, i.e., the innermost function.
32751 The @code{$pc} value for that frame.
32755 File name of the source file where the function lives.
32756 @item @var{fullname}
32757 The full file name of the source file where the function lives.
32759 Line number corresponding to the @code{$pc}.
32761 The shared library where this function is defined. This is only given
32762 if the frame's function is not known.
32764 Frame's architecture.
32767 If invoked without arguments, this command prints a backtrace for the
32768 whole stack. If given two integer arguments, it shows the frames whose
32769 levels are between the two arguments (inclusive). If the two arguments
32770 are equal, it shows the single frame at the corresponding level. It is
32771 an error if @var{low-frame} is larger than the actual number of
32772 frames. On the other hand, @var{high-frame} may be larger than the
32773 actual number of frames, in which case only existing frames will be
32774 returned. If the option @code{--no-frame-filters} is supplied, then
32775 Python frame filters will not be executed.
32777 @subsubheading @value{GDBN} Command
32779 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32781 @subsubheading Example
32783 Full stack backtrace:
32789 [frame=@{level="0",addr="0x0001076c",func="foo",
32790 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32791 arch="i386:x86_64"@},
32792 frame=@{level="1",addr="0x000107a4",func="foo",
32793 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32794 arch="i386:x86_64"@},
32795 frame=@{level="2",addr="0x000107a4",func="foo",
32796 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32797 arch="i386:x86_64"@},
32798 frame=@{level="3",addr="0x000107a4",func="foo",
32799 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32800 arch="i386:x86_64"@},
32801 frame=@{level="4",addr="0x000107a4",func="foo",
32802 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32803 arch="i386:x86_64"@},
32804 frame=@{level="5",addr="0x000107a4",func="foo",
32805 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32806 arch="i386:x86_64"@},
32807 frame=@{level="6",addr="0x000107a4",func="foo",
32808 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32809 arch="i386:x86_64"@},
32810 frame=@{level="7",addr="0x000107a4",func="foo",
32811 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32812 arch="i386:x86_64"@},
32813 frame=@{level="8",addr="0x000107a4",func="foo",
32814 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32815 arch="i386:x86_64"@},
32816 frame=@{level="9",addr="0x000107a4",func="foo",
32817 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32818 arch="i386:x86_64"@},
32819 frame=@{level="10",addr="0x000107a4",func="foo",
32820 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32821 arch="i386:x86_64"@},
32822 frame=@{level="11",addr="0x00010738",func="main",
32823 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32824 arch="i386:x86_64"@}]
32828 Show frames between @var{low_frame} and @var{high_frame}:
32832 -stack-list-frames 3 5
32834 [frame=@{level="3",addr="0x000107a4",func="foo",
32835 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32836 arch="i386:x86_64"@},
32837 frame=@{level="4",addr="0x000107a4",func="foo",
32838 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32839 arch="i386:x86_64"@},
32840 frame=@{level="5",addr="0x000107a4",func="foo",
32841 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32842 arch="i386:x86_64"@}]
32846 Show a single frame:
32850 -stack-list-frames 3 3
32852 [frame=@{level="3",addr="0x000107a4",func="foo",
32853 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32854 arch="i386:x86_64"@}]
32859 @subheading The @code{-stack-list-locals} Command
32860 @findex -stack-list-locals
32861 @anchor{-stack-list-locals}
32863 @subsubheading Synopsis
32866 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32869 Display the local variable names for the selected frame. If
32870 @var{print-values} is 0 or @code{--no-values}, print only the names of
32871 the variables; if it is 1 or @code{--all-values}, print also their
32872 values; and if it is 2 or @code{--simple-values}, print the name,
32873 type and value for simple data types, and the name and type for arrays,
32874 structures and unions. In this last case, a frontend can immediately
32875 display the value of simple data types and create variable objects for
32876 other data types when the user wishes to explore their values in
32877 more detail. If the option @code{--no-frame-filters} is supplied, then
32878 Python frame filters will not be executed.
32880 If the @code{--skip-unavailable} option is specified, local variables
32881 that are not available are not listed. Partially available local
32882 variables are still displayed, however.
32884 This command is deprecated in favor of the
32885 @samp{-stack-list-variables} command.
32887 @subsubheading @value{GDBN} Command
32889 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32891 @subsubheading Example
32895 -stack-list-locals 0
32896 ^done,locals=[name="A",name="B",name="C"]
32898 -stack-list-locals --all-values
32899 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32900 @{name="C",value="@{1, 2, 3@}"@}]
32901 -stack-list-locals --simple-values
32902 ^done,locals=[@{name="A",type="int",value="1"@},
32903 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32907 @anchor{-stack-list-variables}
32908 @subheading The @code{-stack-list-variables} Command
32909 @findex -stack-list-variables
32911 @subsubheading Synopsis
32914 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32917 Display the names of local variables and function arguments for the selected frame. If
32918 @var{print-values} is 0 or @code{--no-values}, print only the names of
32919 the variables; if it is 1 or @code{--all-values}, print also their
32920 values; and if it is 2 or @code{--simple-values}, print the name,
32921 type and value for simple data types, and the name and type for arrays,
32922 structures and unions. If the option @code{--no-frame-filters} is
32923 supplied, then Python frame filters will not be executed.
32925 If the @code{--skip-unavailable} option is specified, local variables
32926 and arguments that are not available are not listed. Partially
32927 available arguments and local variables are still displayed, however.
32929 @subsubheading Example
32933 -stack-list-variables --thread 1 --frame 0 --all-values
32934 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32939 @subheading The @code{-stack-select-frame} Command
32940 @findex -stack-select-frame
32942 @subsubheading Synopsis
32945 -stack-select-frame @var{framenum}
32948 Change the selected frame. Select a different frame @var{framenum} on
32951 This command in deprecated in favor of passing the @samp{--frame}
32952 option to every command.
32954 @subsubheading @value{GDBN} Command
32956 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32957 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32959 @subsubheading Example
32963 -stack-select-frame 2
32968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32969 @node GDB/MI Variable Objects
32970 @section @sc{gdb/mi} Variable Objects
32974 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32976 For the implementation of a variable debugger window (locals, watched
32977 expressions, etc.), we are proposing the adaptation of the existing code
32978 used by @code{Insight}.
32980 The two main reasons for that are:
32984 It has been proven in practice (it is already on its second generation).
32987 It will shorten development time (needless to say how important it is
32991 The original interface was designed to be used by Tcl code, so it was
32992 slightly changed so it could be used through @sc{gdb/mi}. This section
32993 describes the @sc{gdb/mi} operations that will be available and gives some
32994 hints about their use.
32996 @emph{Note}: In addition to the set of operations described here, we
32997 expect the @sc{gui} implementation of a variable window to require, at
32998 least, the following operations:
33001 @item @code{-gdb-show} @code{output-radix}
33002 @item @code{-stack-list-arguments}
33003 @item @code{-stack-list-locals}
33004 @item @code{-stack-select-frame}
33009 @subheading Introduction to Variable Objects
33011 @cindex variable objects in @sc{gdb/mi}
33013 Variable objects are "object-oriented" MI interface for examining and
33014 changing values of expressions. Unlike some other MI interfaces that
33015 work with expressions, variable objects are specifically designed for
33016 simple and efficient presentation in the frontend. A variable object
33017 is identified by string name. When a variable object is created, the
33018 frontend specifies the expression for that variable object. The
33019 expression can be a simple variable, or it can be an arbitrary complex
33020 expression, and can even involve CPU registers. After creating a
33021 variable object, the frontend can invoke other variable object
33022 operations---for example to obtain or change the value of a variable
33023 object, or to change display format.
33025 Variable objects have hierarchical tree structure. Any variable object
33026 that corresponds to a composite type, such as structure in C, has
33027 a number of child variable objects, for example corresponding to each
33028 element of a structure. A child variable object can itself have
33029 children, recursively. Recursion ends when we reach
33030 leaf variable objects, which always have built-in types. Child variable
33031 objects are created only by explicit request, so if a frontend
33032 is not interested in the children of a particular variable object, no
33033 child will be created.
33035 For a leaf variable object it is possible to obtain its value as a
33036 string, or set the value from a string. String value can be also
33037 obtained for a non-leaf variable object, but it's generally a string
33038 that only indicates the type of the object, and does not list its
33039 contents. Assignment to a non-leaf variable object is not allowed.
33041 A frontend does not need to read the values of all variable objects each time
33042 the program stops. Instead, MI provides an update command that lists all
33043 variable objects whose values has changed since the last update
33044 operation. This considerably reduces the amount of data that must
33045 be transferred to the frontend. As noted above, children variable
33046 objects are created on demand, and only leaf variable objects have a
33047 real value. As result, gdb will read target memory only for leaf
33048 variables that frontend has created.
33050 The automatic update is not always desirable. For example, a frontend
33051 might want to keep a value of some expression for future reference,
33052 and never update it. For another example, fetching memory is
33053 relatively slow for embedded targets, so a frontend might want
33054 to disable automatic update for the variables that are either not
33055 visible on the screen, or ``closed''. This is possible using so
33056 called ``frozen variable objects''. Such variable objects are never
33057 implicitly updated.
33059 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33060 fixed variable object, the expression is parsed when the variable
33061 object is created, including associating identifiers to specific
33062 variables. The meaning of expression never changes. For a floating
33063 variable object the values of variables whose names appear in the
33064 expressions are re-evaluated every time in the context of the current
33065 frame. Consider this example:
33070 struct work_state state;
33077 If a fixed variable object for the @code{state} variable is created in
33078 this function, and we enter the recursive call, the variable
33079 object will report the value of @code{state} in the top-level
33080 @code{do_work} invocation. On the other hand, a floating variable
33081 object will report the value of @code{state} in the current frame.
33083 If an expression specified when creating a fixed variable object
33084 refers to a local variable, the variable object becomes bound to the
33085 thread and frame in which the variable object is created. When such
33086 variable object is updated, @value{GDBN} makes sure that the
33087 thread/frame combination the variable object is bound to still exists,
33088 and re-evaluates the variable object in context of that thread/frame.
33090 The following is the complete set of @sc{gdb/mi} operations defined to
33091 access this functionality:
33093 @multitable @columnfractions .4 .6
33094 @item @strong{Operation}
33095 @tab @strong{Description}
33097 @item @code{-enable-pretty-printing}
33098 @tab enable Python-based pretty-printing
33099 @item @code{-var-create}
33100 @tab create a variable object
33101 @item @code{-var-delete}
33102 @tab delete the variable object and/or its children
33103 @item @code{-var-set-format}
33104 @tab set the display format of this variable
33105 @item @code{-var-show-format}
33106 @tab show the display format of this variable
33107 @item @code{-var-info-num-children}
33108 @tab tells how many children this object has
33109 @item @code{-var-list-children}
33110 @tab return a list of the object's children
33111 @item @code{-var-info-type}
33112 @tab show the type of this variable object
33113 @item @code{-var-info-expression}
33114 @tab print parent-relative expression that this variable object represents
33115 @item @code{-var-info-path-expression}
33116 @tab print full expression that this variable object represents
33117 @item @code{-var-show-attributes}
33118 @tab is this variable editable? does it exist here?
33119 @item @code{-var-evaluate-expression}
33120 @tab get the value of this variable
33121 @item @code{-var-assign}
33122 @tab set the value of this variable
33123 @item @code{-var-update}
33124 @tab update the variable and its children
33125 @item @code{-var-set-frozen}
33126 @tab set frozenness attribute
33127 @item @code{-var-set-update-range}
33128 @tab set range of children to display on update
33131 In the next subsection we describe each operation in detail and suggest
33132 how it can be used.
33134 @subheading Description And Use of Operations on Variable Objects
33136 @subheading The @code{-enable-pretty-printing} Command
33137 @findex -enable-pretty-printing
33140 -enable-pretty-printing
33143 @value{GDBN} allows Python-based visualizers to affect the output of the
33144 MI variable object commands. However, because there was no way to
33145 implement this in a fully backward-compatible way, a front end must
33146 request that this functionality be enabled.
33148 Once enabled, this feature cannot be disabled.
33150 Note that if Python support has not been compiled into @value{GDBN},
33151 this command will still succeed (and do nothing).
33153 This feature is currently (as of @value{GDBN} 7.0) experimental, and
33154 may work differently in future versions of @value{GDBN}.
33156 @subheading The @code{-var-create} Command
33157 @findex -var-create
33159 @subsubheading Synopsis
33162 -var-create @{@var{name} | "-"@}
33163 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33166 This operation creates a variable object, which allows the monitoring of
33167 a variable, the result of an expression, a memory cell or a CPU
33170 The @var{name} parameter is the string by which the object can be
33171 referenced. It must be unique. If @samp{-} is specified, the varobj
33172 system will generate a string ``varNNNNNN'' automatically. It will be
33173 unique provided that one does not specify @var{name} of that format.
33174 The command fails if a duplicate name is found.
33176 The frame under which the expression should be evaluated can be
33177 specified by @var{frame-addr}. A @samp{*} indicates that the current
33178 frame should be used. A @samp{@@} indicates that a floating variable
33179 object must be created.
33181 @var{expression} is any expression valid on the current language set (must not
33182 begin with a @samp{*}), or one of the following:
33186 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33189 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33192 @samp{$@var{regname}} --- a CPU register name
33195 @cindex dynamic varobj
33196 A varobj's contents may be provided by a Python-based pretty-printer. In this
33197 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33198 have slightly different semantics in some cases. If the
33199 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33200 will never create a dynamic varobj. This ensures backward
33201 compatibility for existing clients.
33203 @subsubheading Result
33205 This operation returns attributes of the newly-created varobj. These
33210 The name of the varobj.
33213 The number of children of the varobj. This number is not necessarily
33214 reliable for a dynamic varobj. Instead, you must examine the
33215 @samp{has_more} attribute.
33218 The varobj's scalar value. For a varobj whose type is some sort of
33219 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33220 will not be interesting.
33223 The varobj's type. This is a string representation of the type, as
33224 would be printed by the @value{GDBN} CLI. If @samp{print object}
33225 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33226 @emph{actual} (derived) type of the object is shown rather than the
33227 @emph{declared} one.
33230 If a variable object is bound to a specific thread, then this is the
33231 thread's global identifier.
33234 For a dynamic varobj, this indicates whether there appear to be any
33235 children available. For a non-dynamic varobj, this will be 0.
33238 This attribute will be present and have the value @samp{1} if the
33239 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33240 then this attribute will not be present.
33243 A dynamic varobj can supply a display hint to the front end. The
33244 value comes directly from the Python pretty-printer object's
33245 @code{display_hint} method. @xref{Pretty Printing API}.
33248 Typical output will look like this:
33251 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33252 has_more="@var{has_more}"
33256 @subheading The @code{-var-delete} Command
33257 @findex -var-delete
33259 @subsubheading Synopsis
33262 -var-delete [ -c ] @var{name}
33265 Deletes a previously created variable object and all of its children.
33266 With the @samp{-c} option, just deletes the children.
33268 Returns an error if the object @var{name} is not found.
33271 @subheading The @code{-var-set-format} Command
33272 @findex -var-set-format
33274 @subsubheading Synopsis
33277 -var-set-format @var{name} @var{format-spec}
33280 Sets the output format for the value of the object @var{name} to be
33283 @anchor{-var-set-format}
33284 The syntax for the @var{format-spec} is as follows:
33287 @var{format-spec} @expansion{}
33288 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33291 The natural format is the default format choosen automatically
33292 based on the variable type (like decimal for an @code{int}, hex
33293 for pointers, etc.).
33295 The zero-hexadecimal format has a representation similar to hexadecimal
33296 but with padding zeroes to the left of the value. For example, a 32-bit
33297 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33298 zero-hexadecimal format.
33300 For a variable with children, the format is set only on the
33301 variable itself, and the children are not affected.
33303 @subheading The @code{-var-show-format} Command
33304 @findex -var-show-format
33306 @subsubheading Synopsis
33309 -var-show-format @var{name}
33312 Returns the format used to display the value of the object @var{name}.
33315 @var{format} @expansion{}
33320 @subheading The @code{-var-info-num-children} Command
33321 @findex -var-info-num-children
33323 @subsubheading Synopsis
33326 -var-info-num-children @var{name}
33329 Returns the number of children of a variable object @var{name}:
33335 Note that this number is not completely reliable for a dynamic varobj.
33336 It will return the current number of children, but more children may
33340 @subheading The @code{-var-list-children} Command
33341 @findex -var-list-children
33343 @subsubheading Synopsis
33346 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33348 @anchor{-var-list-children}
33350 Return a list of the children of the specified variable object and
33351 create variable objects for them, if they do not already exist. With
33352 a single argument or if @var{print-values} has a value of 0 or
33353 @code{--no-values}, print only the names of the variables; if
33354 @var{print-values} is 1 or @code{--all-values}, also print their
33355 values; and if it is 2 or @code{--simple-values} print the name and
33356 value for simple data types and just the name for arrays, structures
33359 @var{from} and @var{to}, if specified, indicate the range of children
33360 to report. If @var{from} or @var{to} is less than zero, the range is
33361 reset and all children will be reported. Otherwise, children starting
33362 at @var{from} (zero-based) and up to and excluding @var{to} will be
33365 If a child range is requested, it will only affect the current call to
33366 @code{-var-list-children}, but not future calls to @code{-var-update}.
33367 For this, you must instead use @code{-var-set-update-range}. The
33368 intent of this approach is to enable a front end to implement any
33369 update approach it likes; for example, scrolling a view may cause the
33370 front end to request more children with @code{-var-list-children}, and
33371 then the front end could call @code{-var-set-update-range} with a
33372 different range to ensure that future updates are restricted to just
33375 For each child the following results are returned:
33380 Name of the variable object created for this child.
33383 The expression to be shown to the user by the front end to designate this child.
33384 For example this may be the name of a structure member.
33386 For a dynamic varobj, this value cannot be used to form an
33387 expression. There is no way to do this at all with a dynamic varobj.
33389 For C/C@t{++} structures there are several pseudo children returned to
33390 designate access qualifiers. For these pseudo children @var{exp} is
33391 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33392 type and value are not present.
33394 A dynamic varobj will not report the access qualifying
33395 pseudo-children, regardless of the language. This information is not
33396 available at all with a dynamic varobj.
33399 Number of children this child has. For a dynamic varobj, this will be
33403 The type of the child. If @samp{print object}
33404 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33405 @emph{actual} (derived) type of the object is shown rather than the
33406 @emph{declared} one.
33409 If values were requested, this is the value.
33412 If this variable object is associated with a thread, this is the
33413 thread's global thread id. Otherwise this result is not present.
33416 If the variable object is frozen, this variable will be present with a value of 1.
33419 A dynamic varobj can supply a display hint to the front end. The
33420 value comes directly from the Python pretty-printer object's
33421 @code{display_hint} method. @xref{Pretty Printing API}.
33424 This attribute will be present and have the value @samp{1} if the
33425 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33426 then this attribute will not be present.
33430 The result may have its own attributes:
33434 A dynamic varobj can supply a display hint to the front end. The
33435 value comes directly from the Python pretty-printer object's
33436 @code{display_hint} method. @xref{Pretty Printing API}.
33439 This is an integer attribute which is nonzero if there are children
33440 remaining after the end of the selected range.
33443 @subsubheading Example
33447 -var-list-children n
33448 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33449 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33451 -var-list-children --all-values n
33452 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33453 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33457 @subheading The @code{-var-info-type} Command
33458 @findex -var-info-type
33460 @subsubheading Synopsis
33463 -var-info-type @var{name}
33466 Returns the type of the specified variable @var{name}. The type is
33467 returned as a string in the same format as it is output by the
33471 type=@var{typename}
33475 @subheading The @code{-var-info-expression} Command
33476 @findex -var-info-expression
33478 @subsubheading Synopsis
33481 -var-info-expression @var{name}
33484 Returns a string that is suitable for presenting this
33485 variable object in user interface. The string is generally
33486 not valid expression in the current language, and cannot be evaluated.
33488 For example, if @code{a} is an array, and variable object
33489 @code{A} was created for @code{a}, then we'll get this output:
33492 (gdb) -var-info-expression A.1
33493 ^done,lang="C",exp="1"
33497 Here, the value of @code{lang} is the language name, which can be
33498 found in @ref{Supported Languages}.
33500 Note that the output of the @code{-var-list-children} command also
33501 includes those expressions, so the @code{-var-info-expression} command
33504 @subheading The @code{-var-info-path-expression} Command
33505 @findex -var-info-path-expression
33507 @subsubheading Synopsis
33510 -var-info-path-expression @var{name}
33513 Returns an expression that can be evaluated in the current
33514 context and will yield the same value that a variable object has.
33515 Compare this with the @code{-var-info-expression} command, which
33516 result can be used only for UI presentation. Typical use of
33517 the @code{-var-info-path-expression} command is creating a
33518 watchpoint from a variable object.
33520 This command is currently not valid for children of a dynamic varobj,
33521 and will give an error when invoked on one.
33523 For example, suppose @code{C} is a C@t{++} class, derived from class
33524 @code{Base}, and that the @code{Base} class has a member called
33525 @code{m_size}. Assume a variable @code{c} is has the type of
33526 @code{C} and a variable object @code{C} was created for variable
33527 @code{c}. Then, we'll get this output:
33529 (gdb) -var-info-path-expression C.Base.public.m_size
33530 ^done,path_expr=((Base)c).m_size)
33533 @subheading The @code{-var-show-attributes} Command
33534 @findex -var-show-attributes
33536 @subsubheading Synopsis
33539 -var-show-attributes @var{name}
33542 List attributes of the specified variable object @var{name}:
33545 status=@var{attr} [ ( ,@var{attr} )* ]
33549 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33551 @subheading The @code{-var-evaluate-expression} Command
33552 @findex -var-evaluate-expression
33554 @subsubheading Synopsis
33557 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33560 Evaluates the expression that is represented by the specified variable
33561 object and returns its value as a string. The format of the string
33562 can be specified with the @samp{-f} option. The possible values of
33563 this option are the same as for @code{-var-set-format}
33564 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33565 the current display format will be used. The current display format
33566 can be changed using the @code{-var-set-format} command.
33572 Note that one must invoke @code{-var-list-children} for a variable
33573 before the value of a child variable can be evaluated.
33575 @subheading The @code{-var-assign} Command
33576 @findex -var-assign
33578 @subsubheading Synopsis
33581 -var-assign @var{name} @var{expression}
33584 Assigns the value of @var{expression} to the variable object specified
33585 by @var{name}. The object must be @samp{editable}. If the variable's
33586 value is altered by the assign, the variable will show up in any
33587 subsequent @code{-var-update} list.
33589 @subsubheading Example
33597 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33601 @subheading The @code{-var-update} Command
33602 @findex -var-update
33604 @subsubheading Synopsis
33607 -var-update [@var{print-values}] @{@var{name} | "*"@}
33610 Reevaluate the expressions corresponding to the variable object
33611 @var{name} and all its direct and indirect children, and return the
33612 list of variable objects whose values have changed; @var{name} must
33613 be a root variable object. Here, ``changed'' means that the result of
33614 @code{-var-evaluate-expression} before and after the
33615 @code{-var-update} is different. If @samp{*} is used as the variable
33616 object names, all existing variable objects are updated, except
33617 for frozen ones (@pxref{-var-set-frozen}). The option
33618 @var{print-values} determines whether both names and values, or just
33619 names are printed. The possible values of this option are the same
33620 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33621 recommended to use the @samp{--all-values} option, to reduce the
33622 number of MI commands needed on each program stop.
33624 With the @samp{*} parameter, if a variable object is bound to a
33625 currently running thread, it will not be updated, without any
33628 If @code{-var-set-update-range} was previously used on a varobj, then
33629 only the selected range of children will be reported.
33631 @code{-var-update} reports all the changed varobjs in a tuple named
33634 Each item in the change list is itself a tuple holding:
33638 The name of the varobj.
33641 If values were requested for this update, then this field will be
33642 present and will hold the value of the varobj.
33645 @anchor{-var-update}
33646 This field is a string which may take one of three values:
33650 The variable object's current value is valid.
33653 The variable object does not currently hold a valid value but it may
33654 hold one in the future if its associated expression comes back into
33658 The variable object no longer holds a valid value.
33659 This can occur when the executable file being debugged has changed,
33660 either through recompilation or by using the @value{GDBN} @code{file}
33661 command. The front end should normally choose to delete these variable
33665 In the future new values may be added to this list so the front should
33666 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33669 This is only present if the varobj is still valid. If the type
33670 changed, then this will be the string @samp{true}; otherwise it will
33673 When a varobj's type changes, its children are also likely to have
33674 become incorrect. Therefore, the varobj's children are automatically
33675 deleted when this attribute is @samp{true}. Also, the varobj's update
33676 range, when set using the @code{-var-set-update-range} command, is
33680 If the varobj's type changed, then this field will be present and will
33683 @item new_num_children
33684 For a dynamic varobj, if the number of children changed, or if the
33685 type changed, this will be the new number of children.
33687 The @samp{numchild} field in other varobj responses is generally not
33688 valid for a dynamic varobj -- it will show the number of children that
33689 @value{GDBN} knows about, but because dynamic varobjs lazily
33690 instantiate their children, this will not reflect the number of
33691 children which may be available.
33693 The @samp{new_num_children} attribute only reports changes to the
33694 number of children known by @value{GDBN}. This is the only way to
33695 detect whether an update has removed children (which necessarily can
33696 only happen at the end of the update range).
33699 The display hint, if any.
33702 This is an integer value, which will be 1 if there are more children
33703 available outside the varobj's update range.
33706 This attribute will be present and have the value @samp{1} if the
33707 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33708 then this attribute will not be present.
33711 If new children were added to a dynamic varobj within the selected
33712 update range (as set by @code{-var-set-update-range}), then they will
33713 be listed in this attribute.
33716 @subsubheading Example
33723 -var-update --all-values var1
33724 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33725 type_changed="false"@}]
33729 @subheading The @code{-var-set-frozen} Command
33730 @findex -var-set-frozen
33731 @anchor{-var-set-frozen}
33733 @subsubheading Synopsis
33736 -var-set-frozen @var{name} @var{flag}
33739 Set the frozenness flag on the variable object @var{name}. The
33740 @var{flag} parameter should be either @samp{1} to make the variable
33741 frozen or @samp{0} to make it unfrozen. If a variable object is
33742 frozen, then neither itself, nor any of its children, are
33743 implicitly updated by @code{-var-update} of
33744 a parent variable or by @code{-var-update *}. Only
33745 @code{-var-update} of the variable itself will update its value and
33746 values of its children. After a variable object is unfrozen, it is
33747 implicitly updated by all subsequent @code{-var-update} operations.
33748 Unfreezing a variable does not update it, only subsequent
33749 @code{-var-update} does.
33751 @subsubheading Example
33755 -var-set-frozen V 1
33760 @subheading The @code{-var-set-update-range} command
33761 @findex -var-set-update-range
33762 @anchor{-var-set-update-range}
33764 @subsubheading Synopsis
33767 -var-set-update-range @var{name} @var{from} @var{to}
33770 Set the range of children to be returned by future invocations of
33771 @code{-var-update}.
33773 @var{from} and @var{to} indicate the range of children to report. If
33774 @var{from} or @var{to} is less than zero, the range is reset and all
33775 children will be reported. Otherwise, children starting at @var{from}
33776 (zero-based) and up to and excluding @var{to} will be reported.
33778 @subsubheading Example
33782 -var-set-update-range V 1 2
33786 @subheading The @code{-var-set-visualizer} command
33787 @findex -var-set-visualizer
33788 @anchor{-var-set-visualizer}
33790 @subsubheading Synopsis
33793 -var-set-visualizer @var{name} @var{visualizer}
33796 Set a visualizer for the variable object @var{name}.
33798 @var{visualizer} is the visualizer to use. The special value
33799 @samp{None} means to disable any visualizer in use.
33801 If not @samp{None}, @var{visualizer} must be a Python expression.
33802 This expression must evaluate to a callable object which accepts a
33803 single argument. @value{GDBN} will call this object with the value of
33804 the varobj @var{name} as an argument (this is done so that the same
33805 Python pretty-printing code can be used for both the CLI and MI).
33806 When called, this object must return an object which conforms to the
33807 pretty-printing interface (@pxref{Pretty Printing API}).
33809 The pre-defined function @code{gdb.default_visualizer} may be used to
33810 select a visualizer by following the built-in process
33811 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33812 a varobj is created, and so ordinarily is not needed.
33814 This feature is only available if Python support is enabled. The MI
33815 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33816 can be used to check this.
33818 @subsubheading Example
33820 Resetting the visualizer:
33824 -var-set-visualizer V None
33828 Reselecting the default (type-based) visualizer:
33832 -var-set-visualizer V gdb.default_visualizer
33836 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33837 can be used to instantiate this class for a varobj:
33841 -var-set-visualizer V "lambda val: SomeClass()"
33845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33846 @node GDB/MI Data Manipulation
33847 @section @sc{gdb/mi} Data Manipulation
33849 @cindex data manipulation, in @sc{gdb/mi}
33850 @cindex @sc{gdb/mi}, data manipulation
33851 This section describes the @sc{gdb/mi} commands that manipulate data:
33852 examine memory and registers, evaluate expressions, etc.
33854 For details about what an addressable memory unit is,
33855 @pxref{addressable memory unit}.
33857 @c REMOVED FROM THE INTERFACE.
33858 @c @subheading -data-assign
33859 @c Change the value of a program variable. Plenty of side effects.
33860 @c @subsubheading GDB Command
33862 @c @subsubheading Example
33865 @subheading The @code{-data-disassemble} Command
33866 @findex -data-disassemble
33868 @subsubheading Synopsis
33872 [ -s @var{start-addr} -e @var{end-addr} ]
33873 | [ -a @var{addr} ]
33874 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33882 @item @var{start-addr}
33883 is the beginning address (or @code{$pc})
33884 @item @var{end-addr}
33887 is an address anywhere within (or the name of) the function to
33888 disassemble. If an address is specified, the whole function
33889 surrounding that address will be disassembled. If a name is
33890 specified, the whole function with that name will be disassembled.
33891 @item @var{filename}
33892 is the name of the file to disassemble
33893 @item @var{linenum}
33894 is the line number to disassemble around
33896 is the number of disassembly lines to be produced. If it is -1,
33897 the whole function will be disassembled, in case no @var{end-addr} is
33898 specified. If @var{end-addr} is specified as a non-zero value, and
33899 @var{lines} is lower than the number of disassembly lines between
33900 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33901 displayed; if @var{lines} is higher than the number of lines between
33902 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33907 @item 0 disassembly only
33908 @item 1 mixed source and disassembly (deprecated)
33909 @item 2 disassembly with raw opcodes
33910 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33911 @item 4 mixed source and disassembly
33912 @item 5 mixed source and disassembly with raw opcodes
33915 Modes 1 and 3 are deprecated. The output is ``source centric''
33916 which hasn't proved useful in practice.
33917 @xref{Machine Code}, for a discussion of the difference between
33918 @code{/m} and @code{/s} output of the @code{disassemble} command.
33921 @subsubheading Result
33923 The result of the @code{-data-disassemble} command will be a list named
33924 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33925 used with the @code{-data-disassemble} command.
33927 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33932 The address at which this instruction was disassembled.
33935 The name of the function this instruction is within.
33938 The decimal offset in bytes from the start of @samp{func-name}.
33941 The text disassembly for this @samp{address}.
33944 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33945 bytes for the @samp{inst} field.
33949 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33950 @samp{src_and_asm_line}, each of which has the following fields:
33954 The line number within @samp{file}.
33957 The file name from the compilation unit. This might be an absolute
33958 file name or a relative file name depending on the compile command
33962 Absolute file name of @samp{file}. It is converted to a canonical form
33963 using the source file search path
33964 (@pxref{Source Path, ,Specifying Source Directories})
33965 and after resolving all the symbolic links.
33967 If the source file is not found this field will contain the path as
33968 present in the debug information.
33970 @item line_asm_insn
33971 This is a list of tuples containing the disassembly for @samp{line} in
33972 @samp{file}. The fields of each tuple are the same as for
33973 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33974 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33979 Note that whatever included in the @samp{inst} field, is not
33980 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33983 @subsubheading @value{GDBN} Command
33985 The corresponding @value{GDBN} command is @samp{disassemble}.
33987 @subsubheading Example
33989 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33993 -data-disassemble -s $pc -e "$pc + 20" -- 0
33996 @{address="0x000107c0",func-name="main",offset="4",
33997 inst="mov 2, %o0"@},
33998 @{address="0x000107c4",func-name="main",offset="8",
33999 inst="sethi %hi(0x11800), %o2"@},
34000 @{address="0x000107c8",func-name="main",offset="12",
34001 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34002 @{address="0x000107cc",func-name="main",offset="16",
34003 inst="sethi %hi(0x11800), %o2"@},
34004 @{address="0x000107d0",func-name="main",offset="20",
34005 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34009 Disassemble the whole @code{main} function. Line 32 is part of
34013 -data-disassemble -f basics.c -l 32 -- 0
34015 @{address="0x000107bc",func-name="main",offset="0",
34016 inst="save %sp, -112, %sp"@},
34017 @{address="0x000107c0",func-name="main",offset="4",
34018 inst="mov 2, %o0"@},
34019 @{address="0x000107c4",func-name="main",offset="8",
34020 inst="sethi %hi(0x11800), %o2"@},
34022 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34023 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34027 Disassemble 3 instructions from the start of @code{main}:
34031 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34033 @{address="0x000107bc",func-name="main",offset="0",
34034 inst="save %sp, -112, %sp"@},
34035 @{address="0x000107c0",func-name="main",offset="4",
34036 inst="mov 2, %o0"@},
34037 @{address="0x000107c4",func-name="main",offset="8",
34038 inst="sethi %hi(0x11800), %o2"@}]
34042 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34046 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34048 src_and_asm_line=@{line="31",
34049 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34050 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34051 line_asm_insn=[@{address="0x000107bc",
34052 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34053 src_and_asm_line=@{line="32",
34054 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34055 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34056 line_asm_insn=[@{address="0x000107c0",
34057 func-name="main",offset="4",inst="mov 2, %o0"@},
34058 @{address="0x000107c4",func-name="main",offset="8",
34059 inst="sethi %hi(0x11800), %o2"@}]@}]
34064 @subheading The @code{-data-evaluate-expression} Command
34065 @findex -data-evaluate-expression
34067 @subsubheading Synopsis
34070 -data-evaluate-expression @var{expr}
34073 Evaluate @var{expr} as an expression. The expression could contain an
34074 inferior function call. The function call will execute synchronously.
34075 If the expression contains spaces, it must be enclosed in double quotes.
34077 @subsubheading @value{GDBN} Command
34079 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34080 @samp{call}. In @code{gdbtk} only, there's a corresponding
34081 @samp{gdb_eval} command.
34083 @subsubheading Example
34085 In the following example, the numbers that precede the commands are the
34086 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34087 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34091 211-data-evaluate-expression A
34094 311-data-evaluate-expression &A
34095 311^done,value="0xefffeb7c"
34097 411-data-evaluate-expression A+3
34100 511-data-evaluate-expression "A + 3"
34106 @subheading The @code{-data-list-changed-registers} Command
34107 @findex -data-list-changed-registers
34109 @subsubheading Synopsis
34112 -data-list-changed-registers
34115 Display a list of the registers that have changed.
34117 @subsubheading @value{GDBN} Command
34119 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34120 has the corresponding command @samp{gdb_changed_register_list}.
34122 @subsubheading Example
34124 On a PPC MBX board:
34132 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34133 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34134 line="5",arch="powerpc"@}
34136 -data-list-changed-registers
34137 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34138 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34139 "24","25","26","27","28","30","31","64","65","66","67","69"]
34144 @subheading The @code{-data-list-register-names} Command
34145 @findex -data-list-register-names
34147 @subsubheading Synopsis
34150 -data-list-register-names [ ( @var{regno} )+ ]
34153 Show a list of register names for the current target. If no arguments
34154 are given, it shows a list of the names of all the registers. If
34155 integer numbers are given as arguments, it will print a list of the
34156 names of the registers corresponding to the arguments. To ensure
34157 consistency between a register name and its number, the output list may
34158 include empty register names.
34160 @subsubheading @value{GDBN} Command
34162 @value{GDBN} does not have a command which corresponds to
34163 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34164 corresponding command @samp{gdb_regnames}.
34166 @subsubheading Example
34168 For the PPC MBX board:
34171 -data-list-register-names
34172 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34173 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34174 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34175 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34176 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34177 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34178 "", "pc","ps","cr","lr","ctr","xer"]
34180 -data-list-register-names 1 2 3
34181 ^done,register-names=["r1","r2","r3"]
34185 @subheading The @code{-data-list-register-values} Command
34186 @findex -data-list-register-values
34188 @subsubheading Synopsis
34191 -data-list-register-values
34192 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34195 Display the registers' contents. The format according to which the
34196 registers' contents are to be returned is given by @var{fmt}, followed
34197 by an optional list of numbers specifying the registers to display. A
34198 missing list of numbers indicates that the contents of all the
34199 registers must be returned. The @code{--skip-unavailable} option
34200 indicates that only the available registers are to be returned.
34202 Allowed formats for @var{fmt} are:
34219 @subsubheading @value{GDBN} Command
34221 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34222 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34224 @subsubheading Example
34226 For a PPC MBX board (note: line breaks are for readability only, they
34227 don't appear in the actual output):
34231 -data-list-register-values r 64 65
34232 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34233 @{number="65",value="0x00029002"@}]
34235 -data-list-register-values x
34236 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34237 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34238 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34239 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34240 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34241 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34242 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34243 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34244 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34245 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34246 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34247 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34248 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34249 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34250 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34251 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34252 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34253 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34254 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34255 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34256 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34257 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34258 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34259 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34260 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34261 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34262 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34263 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34264 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34265 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34266 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34267 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34268 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34269 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34270 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34271 @{number="69",value="0x20002b03"@}]
34276 @subheading The @code{-data-read-memory} Command
34277 @findex -data-read-memory
34279 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34281 @subsubheading Synopsis
34284 -data-read-memory [ -o @var{byte-offset} ]
34285 @var{address} @var{word-format} @var{word-size}
34286 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34293 @item @var{address}
34294 An expression specifying the address of the first memory word to be
34295 read. Complex expressions containing embedded white space should be
34296 quoted using the C convention.
34298 @item @var{word-format}
34299 The format to be used to print the memory words. The notation is the
34300 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34303 @item @var{word-size}
34304 The size of each memory word in bytes.
34306 @item @var{nr-rows}
34307 The number of rows in the output table.
34309 @item @var{nr-cols}
34310 The number of columns in the output table.
34313 If present, indicates that each row should include an @sc{ascii} dump. The
34314 value of @var{aschar} is used as a padding character when a byte is not a
34315 member of the printable @sc{ascii} character set (printable @sc{ascii}
34316 characters are those whose code is between 32 and 126, inclusively).
34318 @item @var{byte-offset}
34319 An offset to add to the @var{address} before fetching memory.
34322 This command displays memory contents as a table of @var{nr-rows} by
34323 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34324 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34325 (returned as @samp{total-bytes}). Should less than the requested number
34326 of bytes be returned by the target, the missing words are identified
34327 using @samp{N/A}. The number of bytes read from the target is returned
34328 in @samp{nr-bytes} and the starting address used to read memory in
34331 The address of the next/previous row or page is available in
34332 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34335 @subsubheading @value{GDBN} Command
34337 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34338 @samp{gdb_get_mem} memory read command.
34340 @subsubheading Example
34342 Read six bytes of memory starting at @code{bytes+6} but then offset by
34343 @code{-6} bytes. Format as three rows of two columns. One byte per
34344 word. Display each word in hex.
34348 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34349 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34350 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34351 prev-page="0x0000138a",memory=[
34352 @{addr="0x00001390",data=["0x00","0x01"]@},
34353 @{addr="0x00001392",data=["0x02","0x03"]@},
34354 @{addr="0x00001394",data=["0x04","0x05"]@}]
34358 Read two bytes of memory starting at address @code{shorts + 64} and
34359 display as a single word formatted in decimal.
34363 5-data-read-memory shorts+64 d 2 1 1
34364 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34365 next-row="0x00001512",prev-row="0x0000150e",
34366 next-page="0x00001512",prev-page="0x0000150e",memory=[
34367 @{addr="0x00001510",data=["128"]@}]
34371 Read thirty two bytes of memory starting at @code{bytes+16} and format
34372 as eight rows of four columns. Include a string encoding with @samp{x}
34373 used as the non-printable character.
34377 4-data-read-memory bytes+16 x 1 8 4 x
34378 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34379 next-row="0x000013c0",prev-row="0x0000139c",
34380 next-page="0x000013c0",prev-page="0x00001380",memory=[
34381 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34382 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34383 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34384 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34385 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34386 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34387 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34388 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34392 @subheading The @code{-data-read-memory-bytes} Command
34393 @findex -data-read-memory-bytes
34395 @subsubheading Synopsis
34398 -data-read-memory-bytes [ -o @var{offset} ]
34399 @var{address} @var{count}
34406 @item @var{address}
34407 An expression specifying the address of the first addressable memory unit
34408 to be read. Complex expressions containing embedded white space should be
34409 quoted using the C convention.
34412 The number of addressable memory units to read. This should be an integer
34416 The offset relative to @var{address} at which to start reading. This
34417 should be an integer literal. This option is provided so that a frontend
34418 is not required to first evaluate address and then perform address
34419 arithmetics itself.
34423 This command attempts to read all accessible memory regions in the
34424 specified range. First, all regions marked as unreadable in the memory
34425 map (if one is defined) will be skipped. @xref{Memory Region
34426 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34427 regions. For each one, if reading full region results in an errors,
34428 @value{GDBN} will try to read a subset of the region.
34430 In general, every single memory unit in the region may be readable or not,
34431 and the only way to read every readable unit is to try a read at
34432 every address, which is not practical. Therefore, @value{GDBN} will
34433 attempt to read all accessible memory units at either beginning or the end
34434 of the region, using a binary division scheme. This heuristic works
34435 well for reading across a memory map boundary. Note that if a region
34436 has a readable range that is neither at the beginning or the end,
34437 @value{GDBN} will not read it.
34439 The result record (@pxref{GDB/MI Result Records}) that is output of
34440 the command includes a field named @samp{memory} whose content is a
34441 list of tuples. Each tuple represent a successfully read memory block
34442 and has the following fields:
34446 The start address of the memory block, as hexadecimal literal.
34449 The end address of the memory block, as hexadecimal literal.
34452 The offset of the memory block, as hexadecimal literal, relative to
34453 the start address passed to @code{-data-read-memory-bytes}.
34456 The contents of the memory block, in hex.
34462 @subsubheading @value{GDBN} Command
34464 The corresponding @value{GDBN} command is @samp{x}.
34466 @subsubheading Example
34470 -data-read-memory-bytes &a 10
34471 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34473 contents="01000000020000000300"@}]
34478 @subheading The @code{-data-write-memory-bytes} Command
34479 @findex -data-write-memory-bytes
34481 @subsubheading Synopsis
34484 -data-write-memory-bytes @var{address} @var{contents}
34485 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34492 @item @var{address}
34493 An expression specifying the address of the first addressable memory unit
34494 to be written. Complex expressions containing embedded white space should
34495 be quoted using the C convention.
34497 @item @var{contents}
34498 The hex-encoded data to write. It is an error if @var{contents} does
34499 not represent an integral number of addressable memory units.
34502 Optional argument indicating the number of addressable memory units to be
34503 written. If @var{count} is greater than @var{contents}' length,
34504 @value{GDBN} will repeatedly write @var{contents} until it fills
34505 @var{count} memory units.
34509 @subsubheading @value{GDBN} Command
34511 There's no corresponding @value{GDBN} command.
34513 @subsubheading Example
34517 -data-write-memory-bytes &a "aabbccdd"
34524 -data-write-memory-bytes &a "aabbccdd" 16e
34529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34530 @node GDB/MI Tracepoint Commands
34531 @section @sc{gdb/mi} Tracepoint Commands
34533 The commands defined in this section implement MI support for
34534 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34536 @subheading The @code{-trace-find} Command
34537 @findex -trace-find
34539 @subsubheading Synopsis
34542 -trace-find @var{mode} [@var{parameters}@dots{}]
34545 Find a trace frame using criteria defined by @var{mode} and
34546 @var{parameters}. The following table lists permissible
34547 modes and their parameters. For details of operation, see @ref{tfind}.
34552 No parameters are required. Stops examining trace frames.
34555 An integer is required as parameter. Selects tracepoint frame with
34558 @item tracepoint-number
34559 An integer is required as parameter. Finds next
34560 trace frame that corresponds to tracepoint with the specified number.
34563 An address is required as parameter. Finds
34564 next trace frame that corresponds to any tracepoint at the specified
34567 @item pc-inside-range
34568 Two addresses are required as parameters. Finds next trace
34569 frame that corresponds to a tracepoint at an address inside the
34570 specified range. Both bounds are considered to be inside the range.
34572 @item pc-outside-range
34573 Two addresses are required as parameters. Finds
34574 next trace frame that corresponds to a tracepoint at an address outside
34575 the specified range. Both bounds are considered to be inside the range.
34578 Line specification is required as parameter. @xref{Specify Location}.
34579 Finds next trace frame that corresponds to a tracepoint at
34580 the specified location.
34584 If @samp{none} was passed as @var{mode}, the response does not
34585 have fields. Otherwise, the response may have the following fields:
34589 This field has either @samp{0} or @samp{1} as the value, depending
34590 on whether a matching tracepoint was found.
34593 The index of the found traceframe. This field is present iff
34594 the @samp{found} field has value of @samp{1}.
34597 The index of the found tracepoint. This field is present iff
34598 the @samp{found} field has value of @samp{1}.
34601 The information about the frame corresponding to the found trace
34602 frame. This field is present only if a trace frame was found.
34603 @xref{GDB/MI Frame Information}, for description of this field.
34607 @subsubheading @value{GDBN} Command
34609 The corresponding @value{GDBN} command is @samp{tfind}.
34611 @subheading -trace-define-variable
34612 @findex -trace-define-variable
34614 @subsubheading Synopsis
34617 -trace-define-variable @var{name} [ @var{value} ]
34620 Create trace variable @var{name} if it does not exist. If
34621 @var{value} is specified, sets the initial value of the specified
34622 trace variable to that value. Note that the @var{name} should start
34623 with the @samp{$} character.
34625 @subsubheading @value{GDBN} Command
34627 The corresponding @value{GDBN} command is @samp{tvariable}.
34629 @subheading The @code{-trace-frame-collected} Command
34630 @findex -trace-frame-collected
34632 @subsubheading Synopsis
34635 -trace-frame-collected
34636 [--var-print-values @var{var_pval}]
34637 [--comp-print-values @var{comp_pval}]
34638 [--registers-format @var{regformat}]
34639 [--memory-contents]
34642 This command returns the set of collected objects, register names,
34643 trace state variable names, memory ranges and computed expressions
34644 that have been collected at a particular trace frame. The optional
34645 parameters to the command affect the output format in different ways.
34646 See the output description table below for more details.
34648 The reported names can be used in the normal manner to create
34649 varobjs and inspect the objects themselves. The items returned by
34650 this command are categorized so that it is clear which is a variable,
34651 which is a register, which is a trace state variable, which is a
34652 memory range and which is a computed expression.
34654 For instance, if the actions were
34656 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34657 collect *(int*)0xaf02bef0@@40
34661 the object collected in its entirety would be @code{myVar}. The
34662 object @code{myArray} would be partially collected, because only the
34663 element at index @code{myIndex} would be collected. The remaining
34664 objects would be computed expressions.
34666 An example output would be:
34670 -trace-frame-collected
34672 explicit-variables=[@{name="myVar",value="1"@}],
34673 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34674 @{name="myObj.field",value="0"@},
34675 @{name="myPtr->field",value="1"@},
34676 @{name="myCount + 2",value="3"@},
34677 @{name="$tvar1 + 1",value="43970027"@}],
34678 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34679 @{number="1",value="0x0"@},
34680 @{number="2",value="0x4"@},
34682 @{number="125",value="0x0"@}],
34683 tvars=[@{name="$tvar1",current="43970026"@}],
34684 memory=[@{address="0x0000000000602264",length="4"@},
34685 @{address="0x0000000000615bc0",length="4"@}]
34692 @item explicit-variables
34693 The set of objects that have been collected in their entirety (as
34694 opposed to collecting just a few elements of an array or a few struct
34695 members). For each object, its name and value are printed.
34696 The @code{--var-print-values} option affects how or whether the value
34697 field is output. If @var{var_pval} is 0, then print only the names;
34698 if it is 1, print also their values; and if it is 2, print the name,
34699 type and value for simple data types, and the name and type for
34700 arrays, structures and unions.
34702 @item computed-expressions
34703 The set of computed expressions that have been collected at the
34704 current trace frame. The @code{--comp-print-values} option affects
34705 this set like the @code{--var-print-values} option affects the
34706 @code{explicit-variables} set. See above.
34709 The registers that have been collected at the current trace frame.
34710 For each register collected, the name and current value are returned.
34711 The value is formatted according to the @code{--registers-format}
34712 option. See the @command{-data-list-register-values} command for a
34713 list of the allowed formats. The default is @samp{x}.
34716 The trace state variables that have been collected at the current
34717 trace frame. For each trace state variable collected, the name and
34718 current value are returned.
34721 The set of memory ranges that have been collected at the current trace
34722 frame. Its content is a list of tuples. Each tuple represents a
34723 collected memory range and has the following fields:
34727 The start address of the memory range, as hexadecimal literal.
34730 The length of the memory range, as decimal literal.
34733 The contents of the memory block, in hex. This field is only present
34734 if the @code{--memory-contents} option is specified.
34740 @subsubheading @value{GDBN} Command
34742 There is no corresponding @value{GDBN} command.
34744 @subsubheading Example
34746 @subheading -trace-list-variables
34747 @findex -trace-list-variables
34749 @subsubheading Synopsis
34752 -trace-list-variables
34755 Return a table of all defined trace variables. Each element of the
34756 table has the following fields:
34760 The name of the trace variable. This field is always present.
34763 The initial value. This is a 64-bit signed integer. This
34764 field is always present.
34767 The value the trace variable has at the moment. This is a 64-bit
34768 signed integer. This field is absent iff current value is
34769 not defined, for example if the trace was never run, or is
34774 @subsubheading @value{GDBN} Command
34776 The corresponding @value{GDBN} command is @samp{tvariables}.
34778 @subsubheading Example
34782 -trace-list-variables
34783 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34784 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34785 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34786 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34787 body=[variable=@{name="$trace_timestamp",initial="0"@}
34788 variable=@{name="$foo",initial="10",current="15"@}]@}
34792 @subheading -trace-save
34793 @findex -trace-save
34795 @subsubheading Synopsis
34798 -trace-save [ -r ] [ -ctf ] @var{filename}
34801 Saves the collected trace data to @var{filename}. Without the
34802 @samp{-r} option, the data is downloaded from the target and saved
34803 in a local file. With the @samp{-r} option the target is asked
34804 to perform the save.
34806 By default, this command will save the trace in the tfile format. You can
34807 supply the optional @samp{-ctf} argument to save it the CTF format. See
34808 @ref{Trace Files} for more information about CTF.
34810 @subsubheading @value{GDBN} Command
34812 The corresponding @value{GDBN} command is @samp{tsave}.
34815 @subheading -trace-start
34816 @findex -trace-start
34818 @subsubheading Synopsis
34824 Starts a tracing experiment. The result of this command does not
34827 @subsubheading @value{GDBN} Command
34829 The corresponding @value{GDBN} command is @samp{tstart}.
34831 @subheading -trace-status
34832 @findex -trace-status
34834 @subsubheading Synopsis
34840 Obtains the status of a tracing experiment. The result may include
34841 the following fields:
34846 May have a value of either @samp{0}, when no tracing operations are
34847 supported, @samp{1}, when all tracing operations are supported, or
34848 @samp{file} when examining trace file. In the latter case, examining
34849 of trace frame is possible but new tracing experiement cannot be
34850 started. This field is always present.
34853 May have a value of either @samp{0} or @samp{1} depending on whether
34854 tracing experiement is in progress on target. This field is present
34855 if @samp{supported} field is not @samp{0}.
34858 Report the reason why the tracing was stopped last time. This field
34859 may be absent iff tracing was never stopped on target yet. The
34860 value of @samp{request} means the tracing was stopped as result of
34861 the @code{-trace-stop} command. The value of @samp{overflow} means
34862 the tracing buffer is full. The value of @samp{disconnection} means
34863 tracing was automatically stopped when @value{GDBN} has disconnected.
34864 The value of @samp{passcount} means tracing was stopped when a
34865 tracepoint was passed a maximal number of times for that tracepoint.
34866 This field is present if @samp{supported} field is not @samp{0}.
34868 @item stopping-tracepoint
34869 The number of tracepoint whose passcount as exceeded. This field is
34870 present iff the @samp{stop-reason} field has the value of
34874 @itemx frames-created
34875 The @samp{frames} field is a count of the total number of trace frames
34876 in the trace buffer, while @samp{frames-created} is the total created
34877 during the run, including ones that were discarded, such as when a
34878 circular trace buffer filled up. Both fields are optional.
34882 These fields tell the current size of the tracing buffer and the
34883 remaining space. These fields are optional.
34886 The value of the circular trace buffer flag. @code{1} means that the
34887 trace buffer is circular and old trace frames will be discarded if
34888 necessary to make room, @code{0} means that the trace buffer is linear
34892 The value of the disconnected tracing flag. @code{1} means that
34893 tracing will continue after @value{GDBN} disconnects, @code{0} means
34894 that the trace run will stop.
34897 The filename of the trace file being examined. This field is
34898 optional, and only present when examining a trace file.
34902 @subsubheading @value{GDBN} Command
34904 The corresponding @value{GDBN} command is @samp{tstatus}.
34906 @subheading -trace-stop
34907 @findex -trace-stop
34909 @subsubheading Synopsis
34915 Stops a tracing experiment. The result of this command has the same
34916 fields as @code{-trace-status}, except that the @samp{supported} and
34917 @samp{running} fields are not output.
34919 @subsubheading @value{GDBN} Command
34921 The corresponding @value{GDBN} command is @samp{tstop}.
34924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34925 @node GDB/MI Symbol Query
34926 @section @sc{gdb/mi} Symbol Query Commands
34930 @subheading The @code{-symbol-info-address} Command
34931 @findex -symbol-info-address
34933 @subsubheading Synopsis
34936 -symbol-info-address @var{symbol}
34939 Describe where @var{symbol} is stored.
34941 @subsubheading @value{GDBN} Command
34943 The corresponding @value{GDBN} command is @samp{info address}.
34945 @subsubheading Example
34949 @subheading The @code{-symbol-info-file} Command
34950 @findex -symbol-info-file
34952 @subsubheading Synopsis
34958 Show the file for the symbol.
34960 @subsubheading @value{GDBN} Command
34962 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34963 @samp{gdb_find_file}.
34965 @subsubheading Example
34969 @subheading The @code{-symbol-info-functions} Command
34970 @findex -symbol-info-functions
34971 @anchor{-symbol-info-functions}
34973 @subsubheading Synopsis
34976 -symbol-info-functions [--include-nondebug]
34977 [--type @var{type_regexp}]
34978 [--name @var{name_regexp}]
34979 [--max-results @var{limit}]
34983 Return a list containing the names and types for all global functions
34984 taken from the debug information. The functions are grouped by source
34985 file, and shown with the line number on which each function is
34988 The @code{--include-nondebug} option causes the output to include
34989 code symbols from the symbol table.
34991 The options @code{--type} and @code{--name} allow the symbols returned
34992 to be filtered based on either the name of the function, or the type
34993 signature of the function.
34995 The option @code{--max-results} restricts the command to return no
34996 more than @var{limit} results. If exactly @var{limit} results are
34997 returned then there might be additional results available if a higher
35000 @subsubheading @value{GDBN} Command
35002 The corresponding @value{GDBN} command is @samp{info functions}.
35004 @subsubheading Example
35008 -symbol-info-functions
35011 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35012 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35013 symbols=[@{line="36", name="f4", type="void (int *)",
35014 description="void f4(int *);"@},
35015 @{line="42", name="main", type="int ()",
35016 description="int main();"@},
35017 @{line="30", name="f1", type="my_int_t (int, int)",
35018 description="static my_int_t f1(int, int);"@}]@},
35019 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35020 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35021 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35022 description="float f2(another_float_t);"@},
35023 @{line="39", name="f3", type="int (another_int_t)",
35024 description="int f3(another_int_t);"@},
35025 @{line="27", name="f1", type="another_float_t (int)",
35026 description="static another_float_t f1(int);"@}]@}]@}
35030 -symbol-info-functions --name f1
35033 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35034 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35035 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35036 description="static my_int_t f1(int, int);"@}]@},
35037 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35038 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35039 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35040 description="static another_float_t f1(int);"@}]@}]@}
35044 -symbol-info-functions --type void
35047 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35048 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35049 symbols=[@{line="36", name="f4", type="void (int *)",
35050 description="void f4(int *);"@}]@}]@}
35054 -symbol-info-functions --include-nondebug
35057 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35058 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35059 symbols=[@{line="36", name="f4", type="void (int *)",
35060 description="void f4(int *);"@},
35061 @{line="42", name="main", type="int ()",
35062 description="int main();"@},
35063 @{line="30", name="f1", type="my_int_t (int, int)",
35064 description="static my_int_t f1(int, int);"@}]@},
35065 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35066 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35067 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35068 description="float f2(another_float_t);"@},
35069 @{line="39", name="f3", type="int (another_int_t)",
35070 description="int f3(another_int_t);"@},
35071 @{line="27", name="f1", type="another_float_t (int)",
35072 description="static another_float_t f1(int);"@}]@}],
35074 [@{address="0x0000000000400398",name="_init"@},
35075 @{address="0x00000000004003b0",name="_start"@},
35081 @subheading The @code{-symbol-info-module-functions} Command
35082 @findex -symbol-info-module-functions
35083 @anchor{-symbol-info-module-functions}
35085 @subsubheading Synopsis
35088 -symbol-info-module-functions [--module @var{module_regexp}]
35089 [--name @var{name_regexp}]
35090 [--type @var{type_regexp}]
35094 Return a list containing the names of all known functions within all
35095 know Fortran modules. The functions are grouped by source file and
35096 containing module, and shown with the line number on which each
35097 function is defined.
35099 The option @code{--module} only returns results for modules matching
35100 @var{module_regexp}. The option @code{--name} only returns functions
35101 whose name matches @var{name_regexp}, and @code{--type} only returns
35102 functions whose type matches @var{type_regexp}.
35104 @subsubheading @value{GDBN} Command
35106 The corresponding @value{GDBN} command is @samp{info module functions}.
35108 @subsubheading Example
35113 -symbol-info-module-functions
35116 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35117 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35118 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35119 description="void mod1::check_all(void);"@}]@}]@},
35121 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35122 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35123 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35124 description="void mod2::check_var_i(void);"@}]@}]@},
35126 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35127 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35128 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35129 description="void mod3::check_all(void);"@},
35130 @{line="27",name="mod3::check_mod2",type="void (void)",
35131 description="void mod3::check_mod2(void);"@}]@}]@},
35132 @{module="modmany",
35133 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35134 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35135 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35136 description="void modmany::check_some(void);"@}]@}]@},
35138 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35139 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35140 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35141 description="void moduse::check_all(void);"@},
35142 @{line="49",name="moduse::check_var_x",type="void (void)",
35143 description="void moduse::check_var_x(void);"@}]@}]@}]
35147 @subheading The @code{-symbol-info-module-variables} Command
35148 @findex -symbol-info-module-variables
35149 @anchor{-symbol-info-module-variables}
35151 @subsubheading Synopsis
35154 -symbol-info-module-variables [--module @var{module_regexp}]
35155 [--name @var{name_regexp}]
35156 [--type @var{type_regexp}]
35160 Return a list containing the names of all known variables within all
35161 know Fortran modules. The variables are grouped by source file and
35162 containing module, and shown with the line number on which each
35163 variable is defined.
35165 The option @code{--module} only returns results for modules matching
35166 @var{module_regexp}. The option @code{--name} only returns variables
35167 whose name matches @var{name_regexp}, and @code{--type} only returns
35168 variables whose type matches @var{type_regexp}.
35170 @subsubheading @value{GDBN} Command
35172 The corresponding @value{GDBN} command is @samp{info module variables}.
35174 @subsubheading Example
35179 -symbol-info-module-variables
35182 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35183 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35184 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35185 description="integer(kind=4) mod1::var_const;"@},
35186 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35187 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35189 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35190 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35191 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35192 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35194 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35195 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35196 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35197 description="integer(kind=4) mod3::mod1;"@},
35198 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35199 description="integer(kind=4) mod3::mod2;"@},
35200 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35201 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35202 @{module="modmany",
35203 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35204 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35205 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35206 description="integer(kind=4) modmany::var_a;"@},
35207 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35208 description="integer(kind=4) modmany::var_b;"@},
35209 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35210 description="integer(kind=4) modmany::var_c;"@},
35211 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35212 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35214 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35215 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35216 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35217 description="integer(kind=4) moduse::var_x;"@},
35218 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35219 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35223 @subheading The @code{-symbol-info-modules} Command
35224 @findex -symbol-info-modules
35225 @anchor{-symbol-info-modules}
35227 @subsubheading Synopsis
35230 -symbol-info-modules [--name @var{name_regexp}]
35231 [--max-results @var{limit}]
35236 Return a list containing the names of all known Fortran modules. The
35237 modules are grouped by source file, and shown with the line number on
35238 which each modules is defined.
35240 The option @code{--name} allows the modules returned to be filtered
35241 based the name of the module.
35243 The option @code{--max-results} restricts the command to return no
35244 more than @var{limit} results. If exactly @var{limit} results are
35245 returned then there might be additional results available if a higher
35248 @subsubheading @value{GDBN} Command
35250 The corresponding @value{GDBN} command is @samp{info modules}.
35252 @subsubheading Example
35256 -symbol-info-modules
35259 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35260 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35261 symbols=[@{line="16",name="mod1"@},
35262 @{line="22",name="mod2"@}]@},
35263 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35264 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35265 symbols=[@{line="16",name="mod3"@},
35266 @{line="22",name="modmany"@},
35267 @{line="26",name="moduse"@}]@}]@}
35271 -symbol-info-modules --name mod[123]
35274 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35275 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35276 symbols=[@{line="16",name="mod1"@},
35277 @{line="22",name="mod2"@}]@},
35278 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35279 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35280 symbols=[@{line="16",name="mod3"@}]@}]@}
35284 @subheading The @code{-symbol-info-types} Command
35285 @findex -symbol-info-types
35286 @anchor{-symbol-info-types}
35288 @subsubheading Synopsis
35291 -symbol-info-types [--name @var{name_regexp}]
35292 [--max-results @var{limit}]
35297 Return a list of all defined types. The types are grouped by source
35298 file, and shown with the line number on which each user defined type
35299 is defined. Some base types are not defined in the source code but
35300 are added to the debug information by the compiler, for example
35301 @code{int}, @code{float}, etc.; these types do not have an associated
35304 The option @code{--name} allows the list of types returned to be
35307 The option @code{--max-results} restricts the command to return no
35308 more than @var{limit} results. If exactly @var{limit} results are
35309 returned then there might be additional results available if a higher
35312 @subsubheading @value{GDBN} Command
35314 The corresponding @value{GDBN} command is @samp{info types}.
35316 @subsubheading Example
35323 [@{filename="gdb.mi/mi-sym-info-1.c",
35324 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35325 symbols=[@{name="float"@},
35327 @{line="27",name="typedef int my_int_t;"@}]@},
35328 @{filename="gdb.mi/mi-sym-info-2.c",
35329 fullname="/project/gdb.mi/mi-sym-info-2.c",
35330 symbols=[@{line="24",name="typedef float another_float_t;"@},
35331 @{line="23",name="typedef int another_int_t;"@},
35333 @{name="int"@}]@}]@}
35337 -symbol-info-types --name _int_
35340 [@{filename="gdb.mi/mi-sym-info-1.c",
35341 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35342 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35343 @{filename="gdb.mi/mi-sym-info-2.c",
35344 fullname="/project/gdb.mi/mi-sym-info-2.c",
35345 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35349 @subheading The @code{-symbol-info-variables} Command
35350 @findex -symbol-info-variables
35351 @anchor{-symbol-info-variables}
35353 @subsubheading Synopsis
35356 -symbol-info-variables [--include-nondebug]
35357 [--type @var{type_regexp}]
35358 [--name @var{name_regexp}]
35359 [--max-results @var{limit}]
35364 Return a list containing the names and types for all global variables
35365 taken from the debug information. The variables are grouped by source
35366 file, and shown with the line number on which each variable is
35369 The @code{--include-nondebug} option causes the output to include
35370 data symbols from the symbol table.
35372 The options @code{--type} and @code{--name} allow the symbols returned
35373 to be filtered based on either the name of the variable, or the type
35376 The option @code{--max-results} restricts the command to return no
35377 more than @var{limit} results. If exactly @var{limit} results are
35378 returned then there might be additional results available if a higher
35381 @subsubheading @value{GDBN} Command
35383 The corresponding @value{GDBN} command is @samp{info variables}.
35385 @subsubheading Example
35389 -symbol-info-variables
35392 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35393 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35394 symbols=[@{line="25",name="global_f1",type="float",
35395 description="static float global_f1;"@},
35396 @{line="24",name="global_i1",type="int",
35397 description="static int global_i1;"@}]@},
35398 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35399 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35400 symbols=[@{line="21",name="global_f2",type="int",
35401 description="int global_f2;"@},
35402 @{line="20",name="global_i2",type="int",
35403 description="int global_i2;"@},
35404 @{line="19",name="global_f1",type="float",
35405 description="static float global_f1;"@},
35406 @{line="18",name="global_i1",type="int",
35407 description="static int global_i1;"@}]@}]@}
35411 -symbol-info-variables --name f1
35414 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35415 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35416 symbols=[@{line="25",name="global_f1",type="float",
35417 description="static float global_f1;"@}]@},
35418 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35419 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35420 symbols=[@{line="19",name="global_f1",type="float",
35421 description="static float global_f1;"@}]@}]@}
35425 -symbol-info-variables --type float
35428 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35429 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35430 symbols=[@{line="25",name="global_f1",type="float",
35431 description="static float global_f1;"@}]@},
35432 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35433 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35434 symbols=[@{line="19",name="global_f1",type="float",
35435 description="static float global_f1;"@}]@}]@}
35439 -symbol-info-variables --include-nondebug
35442 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35443 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35444 symbols=[@{line="25",name="global_f1",type="float",
35445 description="static float global_f1;"@},
35446 @{line="24",name="global_i1",type="int",
35447 description="static int global_i1;"@}]@},
35448 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35449 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35450 symbols=[@{line="21",name="global_f2",type="int",
35451 description="int global_f2;"@},
35452 @{line="20",name="global_i2",type="int",
35453 description="int global_i2;"@},
35454 @{line="19",name="global_f1",type="float",
35455 description="static float global_f1;"@},
35456 @{line="18",name="global_i1",type="int",
35457 description="static int global_i1;"@}]@}],
35459 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35460 @{address="0x00000000004005d8",name="__dso_handle"@}
35467 @subheading The @code{-symbol-info-line} Command
35468 @findex -symbol-info-line
35470 @subsubheading Synopsis
35476 Show the core addresses of the code for a source line.
35478 @subsubheading @value{GDBN} Command
35480 The corresponding @value{GDBN} command is @samp{info line}.
35481 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35483 @subsubheading Example
35487 @subheading The @code{-symbol-info-symbol} Command
35488 @findex -symbol-info-symbol
35490 @subsubheading Synopsis
35493 -symbol-info-symbol @var{addr}
35496 Describe what symbol is at location @var{addr}.
35498 @subsubheading @value{GDBN} Command
35500 The corresponding @value{GDBN} command is @samp{info symbol}.
35502 @subsubheading Example
35506 @subheading The @code{-symbol-list-functions} Command
35507 @findex -symbol-list-functions
35509 @subsubheading Synopsis
35512 -symbol-list-functions
35515 List the functions in the executable.
35517 @subsubheading @value{GDBN} Command
35519 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35520 @samp{gdb_search} in @code{gdbtk}.
35522 @subsubheading Example
35527 @subheading The @code{-symbol-list-lines} Command
35528 @findex -symbol-list-lines
35530 @subsubheading Synopsis
35533 -symbol-list-lines @var{filename}
35536 Print the list of lines that contain code and their associated program
35537 addresses for the given source filename. The entries are sorted in
35538 ascending PC order.
35540 @subsubheading @value{GDBN} Command
35542 There is no corresponding @value{GDBN} command.
35544 @subsubheading Example
35547 -symbol-list-lines basics.c
35548 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35554 @subheading The @code{-symbol-list-types} Command
35555 @findex -symbol-list-types
35557 @subsubheading Synopsis
35563 List all the type names.
35565 @subsubheading @value{GDBN} Command
35567 The corresponding commands are @samp{info types} in @value{GDBN},
35568 @samp{gdb_search} in @code{gdbtk}.
35570 @subsubheading Example
35574 @subheading The @code{-symbol-list-variables} Command
35575 @findex -symbol-list-variables
35577 @subsubheading Synopsis
35580 -symbol-list-variables
35583 List all the global and static variable names.
35585 @subsubheading @value{GDBN} Command
35587 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35589 @subsubheading Example
35593 @subheading The @code{-symbol-locate} Command
35594 @findex -symbol-locate
35596 @subsubheading Synopsis
35602 @subsubheading @value{GDBN} Command
35604 @samp{gdb_loc} in @code{gdbtk}.
35606 @subsubheading Example
35610 @subheading The @code{-symbol-type} Command
35611 @findex -symbol-type
35613 @subsubheading Synopsis
35616 -symbol-type @var{variable}
35619 Show type of @var{variable}.
35621 @subsubheading @value{GDBN} Command
35623 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35624 @samp{gdb_obj_variable}.
35626 @subsubheading Example
35631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35632 @node GDB/MI File Commands
35633 @section @sc{gdb/mi} File Commands
35635 This section describes the GDB/MI commands to specify executable file names
35636 and to read in and obtain symbol table information.
35638 @subheading The @code{-file-exec-and-symbols} Command
35639 @findex -file-exec-and-symbols
35641 @subsubheading Synopsis
35644 -file-exec-and-symbols @var{file}
35647 Specify the executable file to be debugged. This file is the one from
35648 which the symbol table is also read. If no file is specified, the
35649 command clears the executable and symbol information. If breakpoints
35650 are set when using this command with no arguments, @value{GDBN} will produce
35651 error messages. Otherwise, no output is produced, except a completion
35654 @subsubheading @value{GDBN} Command
35656 The corresponding @value{GDBN} command is @samp{file}.
35658 @subsubheading Example
35662 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35668 @subheading The @code{-file-exec-file} Command
35669 @findex -file-exec-file
35671 @subsubheading Synopsis
35674 -file-exec-file @var{file}
35677 Specify the executable file to be debugged. Unlike
35678 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35679 from this file. If used without argument, @value{GDBN} clears the information
35680 about the executable file. No output is produced, except a completion
35683 @subsubheading @value{GDBN} Command
35685 The corresponding @value{GDBN} command is @samp{exec-file}.
35687 @subsubheading Example
35691 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35698 @subheading The @code{-file-list-exec-sections} Command
35699 @findex -file-list-exec-sections
35701 @subsubheading Synopsis
35704 -file-list-exec-sections
35707 List the sections of the current executable file.
35709 @subsubheading @value{GDBN} Command
35711 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35712 information as this command. @code{gdbtk} has a corresponding command
35713 @samp{gdb_load_info}.
35715 @subsubheading Example
35720 @subheading The @code{-file-list-exec-source-file} Command
35721 @findex -file-list-exec-source-file
35723 @subsubheading Synopsis
35726 -file-list-exec-source-file
35729 List the line number, the current source file, and the absolute path
35730 to the current source file for the current executable. The macro
35731 information field has a value of @samp{1} or @samp{0} depending on
35732 whether or not the file includes preprocessor macro information.
35734 @subsubheading @value{GDBN} Command
35736 The @value{GDBN} equivalent is @samp{info source}
35738 @subsubheading Example
35742 123-file-list-exec-source-file
35743 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35748 @subheading The @code{-file-list-exec-source-files} Command
35749 @kindex info sources
35750 @findex -file-list-exec-source-files
35752 @subsubheading Synopsis
35755 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
35756 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
35758 @r{[} @var{regexp} @r{]}
35761 This command returns information about the source files @value{GDBN}
35762 knows about, it will output both the filename and fullname (absolute
35763 file name) of a source file, though the fullname can be elided if this
35764 information is not known to @value{GDBN}.
35766 With no arguments this command returns a list of source files. Each
35767 source file is represented by a tuple with the fields; @var{file},
35768 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
35769 display name for the file, while @var{fullname} is the absolute name
35770 of the file. The @var{fullname} field can be elided if the absolute
35771 name of the source file can't be computed. The field
35772 @var{debug-fully-read} will be a string, either @code{true} or
35773 @code{false}. When @code{true}, this indicates the full debug
35774 information for the compilation unit describing this file has been
35775 read in. When @code{false}, the full debug information has not yet
35776 been read in. While reading in the full debug information it is
35777 possible that @value{GDBN} could become aware of additional source
35780 The optional @var{regexp} can be used to filter the list of source
35781 files returned. The @var{regexp} will be matched against the full
35782 source file name. The matching is case-sensitive, except on operating
35783 systems that have case-insensitive filesystem (e.g.,
35784 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
35785 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
35786 @var{regexp} starts with @samp{-}).
35788 If @code{--dirname} is provided, then @var{regexp} is matched only
35789 against the directory name of each source file. If @code{--basename}
35790 is provided, then @var{regexp} is matched against the basename of each
35791 source file. Only one of @code{--dirname} or @code{--basename} may be
35792 given, and if either is given then @var{regexp} is required.
35794 If @code{--group-by-objfile} is used then the format of the results is
35795 changed. The results will now be a list of tuples, with each tuple
35796 representing an object file (executable or shared library) loaded into
35797 @value{GDBN}. The fields of these tuples are; @var{filename},
35798 @var{debug-info}, and @var{sources}. The @var{filename} is the
35799 absolute name of the object file, @var{debug-info} is a string with
35800 one of the following values:
35804 This object file has no debug information.
35805 @item partially-read
35806 This object file has debug information, but it is not fully read in
35807 yet. When it is read in later, GDB might become aware of additional
35810 This object file has debug information, and this information is fully
35811 read into GDB. The list of source files is complete.
35814 The @var{sources} is a list or tuples, with each tuple describing a
35815 single source file with the same fields as described previously. The
35816 @var{sources} list can be empty for object files that have no debug
35819 @subsubheading @value{GDBN} Command
35821 The @value{GDBN} equivalent is @samp{info sources}.
35822 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35824 @subsubheading Example
35827 -file-list-exec-source-files
35828 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
35829 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
35830 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
35832 -file-list-exec-source-files
35833 ^done,files=[@{file="test.c",
35834 fullname="/tmp/info-sources/test.c",
35835 debug-fully-read="true"@},
35836 @{file="/usr/include/stdc-predef.h",
35837 fullname="/usr/include/stdc-predef.h",
35838 debug-fully-read="true"@},
35840 fullname="/tmp/info-sources/header.h",
35841 debug-fully-read="true"@},
35843 fullname="/tmp/info-sources/helper.c",
35844 debug-fully-read="true"@}]
35846 -file-list-exec-source-files -- \\.c
35847 ^done,files=[@{file="test.c",
35848 fullname="/tmp/info-sources/test.c",
35849 debug-fully-read="true"@},
35851 fullname="/tmp/info-sources/helper.c",
35852 debug-fully-read="true"@}]
35854 -file-list-exec-source-files --group-by-objfile
35855 ^done,files=[@{filename="/tmp/info-sources/test.x",
35856 debug-info="fully-read",
35857 sources=[@{file="test.c",
35858 fullname="/tmp/info-sources/test.c",
35859 debug-fully-read="true"@},
35860 @{file="/usr/include/stdc-predef.h",
35861 fullname="/usr/include/stdc-predef.h",
35862 debug-fully-read="true"@},
35864 fullname="/tmp/info-sources/header.h",
35865 debug-fully-read="true"@}]@},
35866 @{filename="/lib64/ld-linux-x86-64.so.2",
35869 @{filename="system-supplied DSO at 0x7ffff7fcf000",
35872 @{filename="/tmp/info-sources/libhelper.so",
35873 debug-info="fully-read",
35874 sources=[@{file="helper.c",
35875 fullname="/tmp/info-sources/helper.c",
35876 debug-fully-read="true"@},
35877 @{file="/usr/include/stdc-predef.h",
35878 fullname="/usr/include/stdc-predef.h",
35879 debug-fully-read="true"@},
35881 fullname="/tmp/info-sources/header.h",
35882 debug-fully-read="true"@}]@},
35883 @{filename="/lib64/libc.so.6",
35888 @subheading The @code{-file-list-shared-libraries} Command
35889 @findex -file-list-shared-libraries
35891 @subsubheading Synopsis
35894 -file-list-shared-libraries [ @var{regexp} ]
35897 List the shared libraries in the program.
35898 With a regular expression @var{regexp}, only those libraries whose
35899 names match @var{regexp} are listed.
35901 @subsubheading @value{GDBN} Command
35903 The corresponding @value{GDBN} command is @samp{info shared}. The fields
35904 have a similar meaning to the @code{=library-loaded} notification.
35905 The @code{ranges} field specifies the multiple segments belonging to this
35906 library. Each range has the following fields:
35910 The address defining the inclusive lower bound of the segment.
35912 The address defining the exclusive upper bound of the segment.
35915 @subsubheading Example
35918 -file-list-exec-source-files
35919 ^done,shared-libraries=[
35920 @{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"@}]@},
35921 @{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"@}]@}]
35927 @subheading The @code{-file-list-symbol-files} Command
35928 @findex -file-list-symbol-files
35930 @subsubheading Synopsis
35933 -file-list-symbol-files
35938 @subsubheading @value{GDBN} Command
35940 The corresponding @value{GDBN} command is @samp{info file} (part of it).
35942 @subsubheading Example
35947 @subheading The @code{-file-symbol-file} Command
35948 @findex -file-symbol-file
35950 @subsubheading Synopsis
35953 -file-symbol-file @var{file}
35956 Read symbol table info from the specified @var{file} argument. When
35957 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35958 produced, except for a completion notification.
35960 @subsubheading @value{GDBN} Command
35962 The corresponding @value{GDBN} command is @samp{symbol-file}.
35964 @subsubheading Example
35968 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35975 @node GDB/MI Memory Overlay Commands
35976 @section @sc{gdb/mi} Memory Overlay Commands
35978 The memory overlay commands are not implemented.
35980 @c @subheading -overlay-auto
35982 @c @subheading -overlay-list-mapping-state
35984 @c @subheading -overlay-list-overlays
35986 @c @subheading -overlay-map
35988 @c @subheading -overlay-off
35990 @c @subheading -overlay-on
35992 @c @subheading -overlay-unmap
35994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35995 @node GDB/MI Signal Handling Commands
35996 @section @sc{gdb/mi} Signal Handling Commands
35998 Signal handling commands are not implemented.
36000 @c @subheading -signal-handle
36002 @c @subheading -signal-list-handle-actions
36004 @c @subheading -signal-list-signal-types
36008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36009 @node GDB/MI Target Manipulation
36010 @section @sc{gdb/mi} Target Manipulation Commands
36013 @subheading The @code{-target-attach} Command
36014 @findex -target-attach
36016 @subsubheading Synopsis
36019 -target-attach @var{pid} | @var{gid} | @var{file}
36022 Attach to a process @var{pid} or a file @var{file} outside of
36023 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36024 group, the id previously returned by
36025 @samp{-list-thread-groups --available} must be used.
36027 @subsubheading @value{GDBN} Command
36029 The corresponding @value{GDBN} command is @samp{attach}.
36031 @subsubheading Example
36035 =thread-created,id="1"
36036 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36042 @subheading The @code{-target-compare-sections} Command
36043 @findex -target-compare-sections
36045 @subsubheading Synopsis
36048 -target-compare-sections [ @var{section} ]
36051 Compare data of section @var{section} on target to the exec file.
36052 Without the argument, all sections are compared.
36054 @subsubheading @value{GDBN} Command
36056 The @value{GDBN} equivalent is @samp{compare-sections}.
36058 @subsubheading Example
36063 @subheading The @code{-target-detach} Command
36064 @findex -target-detach
36066 @subsubheading Synopsis
36069 -target-detach [ @var{pid} | @var{gid} ]
36072 Detach from the remote target which normally resumes its execution.
36073 If either @var{pid} or @var{gid} is specified, detaches from either
36074 the specified process, or specified thread group. There's no output.
36076 @subsubheading @value{GDBN} Command
36078 The corresponding @value{GDBN} command is @samp{detach}.
36080 @subsubheading Example
36090 @subheading The @code{-target-disconnect} Command
36091 @findex -target-disconnect
36093 @subsubheading Synopsis
36099 Disconnect from the remote target. There's no output and the target is
36100 generally not resumed.
36102 @subsubheading @value{GDBN} Command
36104 The corresponding @value{GDBN} command is @samp{disconnect}.
36106 @subsubheading Example
36116 @subheading The @code{-target-download} Command
36117 @findex -target-download
36119 @subsubheading Synopsis
36125 Loads the executable onto the remote target.
36126 It prints out an update message every half second, which includes the fields:
36130 The name of the section.
36132 The size of what has been sent so far for that section.
36134 The size of the section.
36136 The total size of what was sent so far (the current and the previous sections).
36138 The size of the overall executable to download.
36142 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36143 @sc{gdb/mi} Output Syntax}).
36145 In addition, it prints the name and size of the sections, as they are
36146 downloaded. These messages include the following fields:
36150 The name of the section.
36152 The size of the section.
36154 The size of the overall executable to download.
36158 At the end, a summary is printed.
36160 @subsubheading @value{GDBN} Command
36162 The corresponding @value{GDBN} command is @samp{load}.
36164 @subsubheading Example
36166 Note: each status message appears on a single line. Here the messages
36167 have been broken down so that they can fit onto a page.
36172 +download,@{section=".text",section-size="6668",total-size="9880"@}
36173 +download,@{section=".text",section-sent="512",section-size="6668",
36174 total-sent="512",total-size="9880"@}
36175 +download,@{section=".text",section-sent="1024",section-size="6668",
36176 total-sent="1024",total-size="9880"@}
36177 +download,@{section=".text",section-sent="1536",section-size="6668",
36178 total-sent="1536",total-size="9880"@}
36179 +download,@{section=".text",section-sent="2048",section-size="6668",
36180 total-sent="2048",total-size="9880"@}
36181 +download,@{section=".text",section-sent="2560",section-size="6668",
36182 total-sent="2560",total-size="9880"@}
36183 +download,@{section=".text",section-sent="3072",section-size="6668",
36184 total-sent="3072",total-size="9880"@}
36185 +download,@{section=".text",section-sent="3584",section-size="6668",
36186 total-sent="3584",total-size="9880"@}
36187 +download,@{section=".text",section-sent="4096",section-size="6668",
36188 total-sent="4096",total-size="9880"@}
36189 +download,@{section=".text",section-sent="4608",section-size="6668",
36190 total-sent="4608",total-size="9880"@}
36191 +download,@{section=".text",section-sent="5120",section-size="6668",
36192 total-sent="5120",total-size="9880"@}
36193 +download,@{section=".text",section-sent="5632",section-size="6668",
36194 total-sent="5632",total-size="9880"@}
36195 +download,@{section=".text",section-sent="6144",section-size="6668",
36196 total-sent="6144",total-size="9880"@}
36197 +download,@{section=".text",section-sent="6656",section-size="6668",
36198 total-sent="6656",total-size="9880"@}
36199 +download,@{section=".init",section-size="28",total-size="9880"@}
36200 +download,@{section=".fini",section-size="28",total-size="9880"@}
36201 +download,@{section=".data",section-size="3156",total-size="9880"@}
36202 +download,@{section=".data",section-sent="512",section-size="3156",
36203 total-sent="7236",total-size="9880"@}
36204 +download,@{section=".data",section-sent="1024",section-size="3156",
36205 total-sent="7748",total-size="9880"@}
36206 +download,@{section=".data",section-sent="1536",section-size="3156",
36207 total-sent="8260",total-size="9880"@}
36208 +download,@{section=".data",section-sent="2048",section-size="3156",
36209 total-sent="8772",total-size="9880"@}
36210 +download,@{section=".data",section-sent="2560",section-size="3156",
36211 total-sent="9284",total-size="9880"@}
36212 +download,@{section=".data",section-sent="3072",section-size="3156",
36213 total-sent="9796",total-size="9880"@}
36214 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36221 @subheading The @code{-target-exec-status} Command
36222 @findex -target-exec-status
36224 @subsubheading Synopsis
36227 -target-exec-status
36230 Provide information on the state of the target (whether it is running or
36231 not, for instance).
36233 @subsubheading @value{GDBN} Command
36235 There's no equivalent @value{GDBN} command.
36237 @subsubheading Example
36241 @subheading The @code{-target-list-available-targets} Command
36242 @findex -target-list-available-targets
36244 @subsubheading Synopsis
36247 -target-list-available-targets
36250 List the possible targets to connect to.
36252 @subsubheading @value{GDBN} Command
36254 The corresponding @value{GDBN} command is @samp{help target}.
36256 @subsubheading Example
36260 @subheading The @code{-target-list-current-targets} Command
36261 @findex -target-list-current-targets
36263 @subsubheading Synopsis
36266 -target-list-current-targets
36269 Describe the current target.
36271 @subsubheading @value{GDBN} Command
36273 The corresponding information is printed by @samp{info file} (among
36276 @subsubheading Example
36280 @subheading The @code{-target-list-parameters} Command
36281 @findex -target-list-parameters
36283 @subsubheading Synopsis
36286 -target-list-parameters
36292 @subsubheading @value{GDBN} Command
36296 @subsubheading Example
36299 @subheading The @code{-target-flash-erase} Command
36300 @findex -target-flash-erase
36302 @subsubheading Synopsis
36305 -target-flash-erase
36308 Erases all known flash memory regions on the target.
36310 The corresponding @value{GDBN} command is @samp{flash-erase}.
36312 The output is a list of flash regions that have been erased, with starting
36313 addresses and memory region sizes.
36317 -target-flash-erase
36318 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36322 @subheading The @code{-target-select} Command
36323 @findex -target-select
36325 @subsubheading Synopsis
36328 -target-select @var{type} @var{parameters @dots{}}
36331 Connect @value{GDBN} to the remote target. This command takes two args:
36335 The type of target, for instance @samp{remote}, etc.
36336 @item @var{parameters}
36337 Device names, host names and the like. @xref{Target Commands, ,
36338 Commands for Managing Targets}, for more details.
36341 The output is a connection notification, followed by the address at
36342 which the target program is, in the following form:
36345 ^connected,addr="@var{address}",func="@var{function name}",
36346 args=[@var{arg list}]
36349 @subsubheading @value{GDBN} Command
36351 The corresponding @value{GDBN} command is @samp{target}.
36353 @subsubheading Example
36357 -target-select remote /dev/ttya
36358 ^connected,addr="0xfe00a300",func="??",args=[]
36362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36363 @node GDB/MI File Transfer Commands
36364 @section @sc{gdb/mi} File Transfer Commands
36367 @subheading The @code{-target-file-put} Command
36368 @findex -target-file-put
36370 @subsubheading Synopsis
36373 -target-file-put @var{hostfile} @var{targetfile}
36376 Copy file @var{hostfile} from the host system (the machine running
36377 @value{GDBN}) to @var{targetfile} on the target system.
36379 @subsubheading @value{GDBN} Command
36381 The corresponding @value{GDBN} command is @samp{remote put}.
36383 @subsubheading Example
36387 -target-file-put localfile remotefile
36393 @subheading The @code{-target-file-get} Command
36394 @findex -target-file-get
36396 @subsubheading Synopsis
36399 -target-file-get @var{targetfile} @var{hostfile}
36402 Copy file @var{targetfile} from the target system to @var{hostfile}
36403 on the host system.
36405 @subsubheading @value{GDBN} Command
36407 The corresponding @value{GDBN} command is @samp{remote get}.
36409 @subsubheading Example
36413 -target-file-get remotefile localfile
36419 @subheading The @code{-target-file-delete} Command
36420 @findex -target-file-delete
36422 @subsubheading Synopsis
36425 -target-file-delete @var{targetfile}
36428 Delete @var{targetfile} from the target system.
36430 @subsubheading @value{GDBN} Command
36432 The corresponding @value{GDBN} command is @samp{remote delete}.
36434 @subsubheading Example
36438 -target-file-delete remotefile
36444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36445 @node GDB/MI Ada Exceptions Commands
36446 @section Ada Exceptions @sc{gdb/mi} Commands
36448 @subheading The @code{-info-ada-exceptions} Command
36449 @findex -info-ada-exceptions
36451 @subsubheading Synopsis
36454 -info-ada-exceptions [ @var{regexp}]
36457 List all Ada exceptions defined within the program being debugged.
36458 With a regular expression @var{regexp}, only those exceptions whose
36459 names match @var{regexp} are listed.
36461 @subsubheading @value{GDBN} Command
36463 The corresponding @value{GDBN} command is @samp{info exceptions}.
36465 @subsubheading Result
36467 The result is a table of Ada exceptions. The following columns are
36468 defined for each exception:
36472 The name of the exception.
36475 The address of the exception.
36479 @subsubheading Example
36482 -info-ada-exceptions aint
36483 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
36484 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
36485 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
36486 body=[@{name="constraint_error",address="0x0000000000613da0"@},
36487 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
36490 @subheading Catching Ada Exceptions
36492 The commands describing how to ask @value{GDBN} to stop when a program
36493 raises an exception are described at @ref{Ada Exception GDB/MI
36494 Catchpoint Commands}.
36497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36498 @node GDB/MI Support Commands
36499 @section @sc{gdb/mi} Support Commands
36501 Since new commands and features get regularly added to @sc{gdb/mi},
36502 some commands are available to help front-ends query the debugger
36503 about support for these capabilities. Similarly, it is also possible
36504 to query @value{GDBN} about target support of certain features.
36506 @subheading The @code{-info-gdb-mi-command} Command
36507 @cindex @code{-info-gdb-mi-command}
36508 @findex -info-gdb-mi-command
36510 @subsubheading Synopsis
36513 -info-gdb-mi-command @var{cmd_name}
36516 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
36518 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
36519 is technically not part of the command name (@pxref{GDB/MI Input
36520 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36521 for ease of use, this command also accepts the form with the leading
36524 @subsubheading @value{GDBN} Command
36526 There is no corresponding @value{GDBN} command.
36528 @subsubheading Result
36530 The result is a tuple. There is currently only one field:
36534 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36535 @code{"false"} otherwise.
36539 @subsubheading Example
36541 Here is an example where the @sc{gdb/mi} command does not exist:
36544 -info-gdb-mi-command unsupported-command
36545 ^done,command=@{exists="false"@}
36549 And here is an example where the @sc{gdb/mi} command is known
36553 -info-gdb-mi-command symbol-list-lines
36554 ^done,command=@{exists="true"@}
36557 @subheading The @code{-list-features} Command
36558 @findex -list-features
36559 @cindex supported @sc{gdb/mi} features, list
36561 Returns a list of particular features of the MI protocol that
36562 this version of gdb implements. A feature can be a command,
36563 or a new field in an output of some command, or even an
36564 important bugfix. While a frontend can sometimes detect presence
36565 of a feature at runtime, it is easier to perform detection at debugger
36568 The command returns a list of strings, with each string naming an
36569 available feature. Each returned string is just a name, it does not
36570 have any internal structure. The list of possible feature names
36576 (gdb) -list-features
36577 ^done,result=["feature1","feature2"]
36580 The current list of features is:
36583 @item frozen-varobjs
36584 Indicates support for the @code{-var-set-frozen} command, as well
36585 as possible presence of the @code{frozen} field in the output
36586 of @code{-varobj-create}.
36587 @item pending-breakpoints
36588 Indicates support for the @option{-f} option to the @code{-break-insert}
36591 Indicates Python scripting support, Python-based
36592 pretty-printing commands, and possible presence of the
36593 @samp{display_hint} field in the output of @code{-var-list-children}
36595 Indicates support for the @code{-thread-info} command.
36596 @item data-read-memory-bytes
36597 Indicates support for the @code{-data-read-memory-bytes} and the
36598 @code{-data-write-memory-bytes} commands.
36599 @item breakpoint-notifications
36600 Indicates that changes to breakpoints and breakpoints created via the
36601 CLI will be announced via async records.
36602 @item ada-task-info
36603 Indicates support for the @code{-ada-task-info} command.
36604 @item language-option
36605 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36606 option (@pxref{Context management}).
36607 @item info-gdb-mi-command
36608 Indicates support for the @code{-info-gdb-mi-command} command.
36609 @item undefined-command-error-code
36610 Indicates support for the "undefined-command" error code in error result
36611 records, produced when trying to execute an undefined @sc{gdb/mi} command
36612 (@pxref{GDB/MI Result Records}).
36613 @item exec-run-start-option
36614 Indicates that the @code{-exec-run} command supports the @option{--start}
36615 option (@pxref{GDB/MI Program Execution}).
36616 @item data-disassemble-a-option
36617 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36618 option (@pxref{GDB/MI Data Manipulation}).
36621 @subheading The @code{-list-target-features} Command
36622 @findex -list-target-features
36624 Returns a list of particular features that are supported by the
36625 target. Those features affect the permitted MI commands, but
36626 unlike the features reported by the @code{-list-features} command, the
36627 features depend on which target GDB is using at the moment. Whenever
36628 a target can change, due to commands such as @code{-target-select},
36629 @code{-target-attach} or @code{-exec-run}, the list of target features
36630 may change, and the frontend should obtain it again.
36634 (gdb) -list-target-features
36635 ^done,result=["async"]
36638 The current list of features is:
36642 Indicates that the target is capable of asynchronous command
36643 execution, which means that @value{GDBN} will accept further commands
36644 while the target is running.
36647 Indicates that the target is capable of reverse execution.
36648 @xref{Reverse Execution}, for more information.
36652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36653 @node GDB/MI Miscellaneous Commands
36654 @section Miscellaneous @sc{gdb/mi} Commands
36656 @c @subheading -gdb-complete
36658 @subheading The @code{-gdb-exit} Command
36661 @subsubheading Synopsis
36667 Exit @value{GDBN} immediately.
36669 @subsubheading @value{GDBN} Command
36671 Approximately corresponds to @samp{quit}.
36673 @subsubheading Example
36683 @subheading The @code{-exec-abort} Command
36684 @findex -exec-abort
36686 @subsubheading Synopsis
36692 Kill the inferior running program.
36694 @subsubheading @value{GDBN} Command
36696 The corresponding @value{GDBN} command is @samp{kill}.
36698 @subsubheading Example
36703 @subheading The @code{-gdb-set} Command
36706 @subsubheading Synopsis
36712 Set an internal @value{GDBN} variable.
36713 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
36715 @subsubheading @value{GDBN} Command
36717 The corresponding @value{GDBN} command is @samp{set}.
36719 @subsubheading Example
36729 @subheading The @code{-gdb-show} Command
36732 @subsubheading Synopsis
36738 Show the current value of a @value{GDBN} variable.
36740 @subsubheading @value{GDBN} Command
36742 The corresponding @value{GDBN} command is @samp{show}.
36744 @subsubheading Example
36753 @c @subheading -gdb-source
36756 @subheading The @code{-gdb-version} Command
36757 @findex -gdb-version
36759 @subsubheading Synopsis
36765 Show version information for @value{GDBN}. Used mostly in testing.
36767 @subsubheading @value{GDBN} Command
36769 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36770 default shows this information when you start an interactive session.
36772 @subsubheading Example
36774 @c This example modifies the actual output from GDB to avoid overfull
36780 ~Copyright 2000 Free Software Foundation, Inc.
36781 ~GDB is free software, covered by the GNU General Public License, and
36782 ~you are welcome to change it and/or distribute copies of it under
36783 ~ certain conditions.
36784 ~Type "show copying" to see the conditions.
36785 ~There is absolutely no warranty for GDB. Type "show warranty" for
36787 ~This GDB was configured as
36788 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36793 @subheading The @code{-list-thread-groups} Command
36794 @findex -list-thread-groups
36796 @subheading Synopsis
36799 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36802 Lists thread groups (@pxref{Thread groups}). When a single thread
36803 group is passed as the argument, lists the children of that group.
36804 When several thread group are passed, lists information about those
36805 thread groups. Without any parameters, lists information about all
36806 top-level thread groups.
36808 Normally, thread groups that are being debugged are reported.
36809 With the @samp{--available} option, @value{GDBN} reports thread groups
36810 available on the target.
36812 The output of this command may have either a @samp{threads} result or
36813 a @samp{groups} result. The @samp{thread} result has a list of tuples
36814 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
36815 Information}). The @samp{groups} result has a list of tuples as value,
36816 each tuple describing a thread group. If top-level groups are
36817 requested (that is, no parameter is passed), or when several groups
36818 are passed, the output always has a @samp{groups} result. The format
36819 of the @samp{group} result is described below.
36821 To reduce the number of roundtrips it's possible to list thread groups
36822 together with their children, by passing the @samp{--recurse} option
36823 and the recursion depth. Presently, only recursion depth of 1 is
36824 permitted. If this option is present, then every reported thread group
36825 will also include its children, either as @samp{group} or
36826 @samp{threads} field.
36828 In general, any combination of option and parameters is permitted, with
36829 the following caveats:
36833 When a single thread group is passed, the output will typically
36834 be the @samp{threads} result. Because threads may not contain
36835 anything, the @samp{recurse} option will be ignored.
36838 When the @samp{--available} option is passed, limited information may
36839 be available. In particular, the list of threads of a process might
36840 be inaccessible. Further, specifying specific thread groups might
36841 not give any performance advantage over listing all thread groups.
36842 The frontend should assume that @samp{-list-thread-groups --available}
36843 is always an expensive operation and cache the results.
36847 The @samp{groups} result is a list of tuples, where each tuple may
36848 have the following fields:
36852 Identifier of the thread group. This field is always present.
36853 The identifier is an opaque string; frontends should not try to
36854 convert it to an integer, even though it might look like one.
36857 The type of the thread group. At present, only @samp{process} is a
36861 The target-specific process identifier. This field is only present
36862 for thread groups of type @samp{process} and only if the process exists.
36865 The exit code of this group's last exited thread, formatted in octal.
36866 This field is only present for thread groups of type @samp{process} and
36867 only if the process is not running.
36870 The number of children this thread group has. This field may be
36871 absent for an available thread group.
36874 This field has a list of tuples as value, each tuple describing a
36875 thread. It may be present if the @samp{--recurse} option is
36876 specified, and it's actually possible to obtain the threads.
36879 This field is a list of integers, each identifying a core that one
36880 thread of the group is running on. This field may be absent if
36881 such information is not available.
36884 The name of the executable file that corresponds to this thread group.
36885 The field is only present for thread groups of type @samp{process},
36886 and only if there is a corresponding executable file.
36890 @subheading Example
36894 -list-thread-groups
36895 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
36896 -list-thread-groups 17
36897 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
36898 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
36899 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
36900 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
36901 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
36902 -list-thread-groups --available
36903 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
36904 -list-thread-groups --available --recurse 1
36905 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36906 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36907 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
36908 -list-thread-groups --available --recurse 1 17 18
36909 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36910 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36911 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
36914 @subheading The @code{-info-os} Command
36917 @subsubheading Synopsis
36920 -info-os [ @var{type} ]
36923 If no argument is supplied, the command returns a table of available
36924 operating-system-specific information types. If one of these types is
36925 supplied as an argument @var{type}, then the command returns a table
36926 of data of that type.
36928 The types of information available depend on the target operating
36931 @subsubheading @value{GDBN} Command
36933 The corresponding @value{GDBN} command is @samp{info os}.
36935 @subsubheading Example
36937 When run on a @sc{gnu}/Linux system, the output will look something
36943 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
36944 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
36945 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
36946 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
36947 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36949 item=@{col0="files",col1="Listing of all file descriptors",
36950 col2="File descriptors"@},
36951 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36952 col2="Kernel modules"@},
36953 item=@{col0="msg",col1="Listing of all message queues",
36954 col2="Message queues"@},
36955 item=@{col0="processes",col1="Listing of all processes",
36956 col2="Processes"@},
36957 item=@{col0="procgroups",col1="Listing of all process groups",
36958 col2="Process groups"@},
36959 item=@{col0="semaphores",col1="Listing of all semaphores",
36960 col2="Semaphores"@},
36961 item=@{col0="shm",col1="Listing of all shared-memory regions",
36962 col2="Shared-memory regions"@},
36963 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36965 item=@{col0="threads",col1="Listing of all threads",
36969 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36970 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36971 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36972 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36973 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36974 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36975 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36976 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36978 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36979 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36983 (Note that the MI output here includes a @code{"Title"} column that
36984 does not appear in command-line @code{info os}; this column is useful
36985 for MI clients that want to enumerate the types of data, such as in a
36986 popup menu, but is needless clutter on the command line, and
36987 @code{info os} omits it.)
36989 @subheading The @code{-add-inferior} Command
36990 @findex -add-inferior
36992 @subheading Synopsis
36998 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36999 inferior is not associated with any executable. Such association may
37000 be established with the @samp{-file-exec-and-symbols} command
37001 (@pxref{GDB/MI File Commands}). The command response has a single
37002 field, @samp{inferior}, whose value is the identifier of the
37003 thread group corresponding to the new inferior.
37005 @subheading Example
37010 ^done,inferior="i3"
37013 @subheading The @code{-interpreter-exec} Command
37014 @findex -interpreter-exec
37016 @subheading Synopsis
37019 -interpreter-exec @var{interpreter} @var{command}
37021 @anchor{-interpreter-exec}
37023 Execute the specified @var{command} in the given @var{interpreter}.
37025 @subheading @value{GDBN} Command
37027 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37029 @subheading Example
37033 -interpreter-exec console "break main"
37034 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37035 &"During symbol reading, bad structure-type format.\n"
37036 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37041 @subheading The @code{-inferior-tty-set} Command
37042 @findex -inferior-tty-set
37044 @subheading Synopsis
37047 -inferior-tty-set /dev/pts/1
37050 Set terminal for future runs of the program being debugged.
37052 @subheading @value{GDBN} Command
37054 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37056 @subheading Example
37060 -inferior-tty-set /dev/pts/1
37065 @subheading The @code{-inferior-tty-show} Command
37066 @findex -inferior-tty-show
37068 @subheading Synopsis
37074 Show terminal for future runs of program being debugged.
37076 @subheading @value{GDBN} Command
37078 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37080 @subheading Example
37084 -inferior-tty-set /dev/pts/1
37088 ^done,inferior_tty_terminal="/dev/pts/1"
37092 @subheading The @code{-enable-timings} Command
37093 @findex -enable-timings
37095 @subheading Synopsis
37098 -enable-timings [yes | no]
37101 Toggle the printing of the wallclock, user and system times for an MI
37102 command as a field in its output. This command is to help frontend
37103 developers optimize the performance of their code. No argument is
37104 equivalent to @samp{yes}.
37106 @subheading @value{GDBN} Command
37110 @subheading Example
37118 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37119 addr="0x080484ed",func="main",file="myprog.c",
37120 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37122 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37130 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37131 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37132 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37133 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37137 @subheading The @code{-complete} Command
37140 @subheading Synopsis
37143 -complete @var{command}
37146 Show a list of completions for partially typed CLI @var{command}.
37148 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37149 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37150 because @value{GDBN} is used remotely via a SSH connection.
37154 The result consists of two or three fields:
37158 This field contains the completed @var{command}. If @var{command}
37159 has no known completions, this field is omitted.
37162 This field contains a (possibly empty) array of matches. It is always present.
37164 @item max_completions_reached
37165 This field contains @code{1} if number of known completions is above
37166 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37167 @code{0}. It is always present.
37171 @subheading @value{GDBN} Command
37173 The corresponding @value{GDBN} command is @samp{complete}.
37175 @subheading Example
37180 ^done,completion="break",
37181 matches=["break","break-range"],
37182 max_completions_reached="0"
37185 ^done,completion="b ma",
37186 matches=["b madvise","b main"],max_completions_reached="0"
37188 -complete "b push_b"
37189 ^done,completion="b push_back(",
37191 "b A::push_back(void*)",
37192 "b std::string::push_back(char)",
37193 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37194 max_completions_reached="0"
37196 -complete "nonexist"
37197 ^done,matches=[],max_completions_reached="0"
37203 @chapter @value{GDBN} Annotations
37205 This chapter describes annotations in @value{GDBN}. Annotations were
37206 designed to interface @value{GDBN} to graphical user interfaces or other
37207 similar programs which want to interact with @value{GDBN} at a
37208 relatively high level.
37210 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37214 This is Edition @value{EDITION}, @value{DATE}.
37218 * Annotations Overview:: What annotations are; the general syntax.
37219 * Server Prefix:: Issuing a command without affecting user state.
37220 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37221 * Errors:: Annotations for error messages.
37222 * Invalidation:: Some annotations describe things now invalid.
37223 * Annotations for Running::
37224 Whether the program is running, how it stopped, etc.
37225 * Source Annotations:: Annotations describing source code.
37228 @node Annotations Overview
37229 @section What is an Annotation?
37230 @cindex annotations
37232 Annotations start with a newline character, two @samp{control-z}
37233 characters, and the name of the annotation. If there is no additional
37234 information associated with this annotation, the name of the annotation
37235 is followed immediately by a newline. If there is additional
37236 information, the name of the annotation is followed by a space, the
37237 additional information, and a newline. The additional information
37238 cannot contain newline characters.
37240 Any output not beginning with a newline and two @samp{control-z}
37241 characters denotes literal output from @value{GDBN}. Currently there is
37242 no need for @value{GDBN} to output a newline followed by two
37243 @samp{control-z} characters, but if there was such a need, the
37244 annotations could be extended with an @samp{escape} annotation which
37245 means those three characters as output.
37247 The annotation @var{level}, which is specified using the
37248 @option{--annotate} command line option (@pxref{Mode Options}), controls
37249 how much information @value{GDBN} prints together with its prompt,
37250 values of expressions, source lines, and other types of output. Level 0
37251 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37252 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37253 for programs that control @value{GDBN}, and level 2 annotations have
37254 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37255 Interface, annotate, GDB's Obsolete Annotations}).
37258 @kindex set annotate
37259 @item set annotate @var{level}
37260 The @value{GDBN} command @code{set annotate} sets the level of
37261 annotations to the specified @var{level}.
37263 @item show annotate
37264 @kindex show annotate
37265 Show the current annotation level.
37268 This chapter describes level 3 annotations.
37270 A simple example of starting up @value{GDBN} with annotations is:
37273 $ @kbd{gdb --annotate=3}
37275 Copyright 2003 Free Software Foundation, Inc.
37276 GDB is free software, covered by the GNU General Public License,
37277 and you are welcome to change it and/or distribute copies of it
37278 under certain conditions.
37279 Type "show copying" to see the conditions.
37280 There is absolutely no warranty for GDB. Type "show warranty"
37282 This GDB was configured as "i386-pc-linux-gnu"
37293 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37294 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37295 denotes a @samp{control-z} character) are annotations; the rest is
37296 output from @value{GDBN}.
37298 @node Server Prefix
37299 @section The Server Prefix
37300 @cindex server prefix
37302 If you prefix a command with @samp{server } then it will not affect
37303 the command history, nor will it affect @value{GDBN}'s notion of which
37304 command to repeat if @key{RET} is pressed on a line by itself. This
37305 means that commands can be run behind a user's back by a front-end in
37306 a transparent manner.
37308 The @code{server } prefix does not affect the recording of values into
37309 the value history; to print a value without recording it into the
37310 value history, use the @code{output} command instead of the
37311 @code{print} command.
37313 Using this prefix also disables confirmation requests
37314 (@pxref{confirmation requests}).
37317 @section Annotation for @value{GDBN} Input
37319 @cindex annotations for prompts
37320 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37321 to know when to send output, when the output from a given command is
37324 Different kinds of input each have a different @dfn{input type}. Each
37325 input type has three annotations: a @code{pre-} annotation, which
37326 denotes the beginning of any prompt which is being output, a plain
37327 annotation, which denotes the end of the prompt, and then a @code{post-}
37328 annotation which denotes the end of any echo which may (or may not) be
37329 associated with the input. For example, the @code{prompt} input type
37330 features the following annotations:
37338 The input types are
37341 @findex pre-prompt annotation
37342 @findex prompt annotation
37343 @findex post-prompt annotation
37345 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37347 @findex pre-commands annotation
37348 @findex commands annotation
37349 @findex post-commands annotation
37351 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37352 command. The annotations are repeated for each command which is input.
37354 @findex pre-overload-choice annotation
37355 @findex overload-choice annotation
37356 @findex post-overload-choice annotation
37357 @item overload-choice
37358 When @value{GDBN} wants the user to select between various overloaded functions.
37360 @findex pre-query annotation
37361 @findex query annotation
37362 @findex post-query annotation
37364 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37366 @findex pre-prompt-for-continue annotation
37367 @findex prompt-for-continue annotation
37368 @findex post-prompt-for-continue annotation
37369 @item prompt-for-continue
37370 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37371 expect this to work well; instead use @code{set height 0} to disable
37372 prompting. This is because the counting of lines is buggy in the
37373 presence of annotations.
37378 @cindex annotations for errors, warnings and interrupts
37380 @findex quit annotation
37385 This annotation occurs right before @value{GDBN} responds to an interrupt.
37387 @findex error annotation
37392 This annotation occurs right before @value{GDBN} responds to an error.
37394 Quit and error annotations indicate that any annotations which @value{GDBN} was
37395 in the middle of may end abruptly. For example, if a
37396 @code{value-history-begin} annotation is followed by a @code{error}, one
37397 cannot expect to receive the matching @code{value-history-end}. One
37398 cannot expect not to receive it either, however; an error annotation
37399 does not necessarily mean that @value{GDBN} is immediately returning all the way
37402 @findex error-begin annotation
37403 A quit or error annotation may be preceded by
37409 Any output between that and the quit or error annotation is the error
37412 Warning messages are not yet annotated.
37413 @c If we want to change that, need to fix warning(), type_error(),
37414 @c range_error(), and possibly other places.
37417 @section Invalidation Notices
37419 @cindex annotations for invalidation messages
37420 The following annotations say that certain pieces of state may have
37424 @findex frames-invalid annotation
37425 @item ^Z^Zframes-invalid
37427 The frames (for example, output from the @code{backtrace} command) may
37430 @findex breakpoints-invalid annotation
37431 @item ^Z^Zbreakpoints-invalid
37433 The breakpoints may have changed. For example, the user just added or
37434 deleted a breakpoint.
37437 @node Annotations for Running
37438 @section Running the Program
37439 @cindex annotations for running programs
37441 @findex starting annotation
37442 @findex stopping annotation
37443 When the program starts executing due to a @value{GDBN} command such as
37444 @code{step} or @code{continue},
37450 is output. When the program stops,
37456 is output. Before the @code{stopped} annotation, a variety of
37457 annotations describe how the program stopped.
37460 @findex exited annotation
37461 @item ^Z^Zexited @var{exit-status}
37462 The program exited, and @var{exit-status} is the exit status (zero for
37463 successful exit, otherwise nonzero).
37465 @findex signalled annotation
37466 @findex signal-name annotation
37467 @findex signal-name-end annotation
37468 @findex signal-string annotation
37469 @findex signal-string-end annotation
37470 @item ^Z^Zsignalled
37471 The program exited with a signal. After the @code{^Z^Zsignalled}, the
37472 annotation continues:
37478 ^Z^Zsignal-name-end
37482 ^Z^Zsignal-string-end
37487 where @var{name} is the name of the signal, such as @code{SIGILL} or
37488 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
37489 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
37490 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
37491 user's benefit and have no particular format.
37493 @findex signal annotation
37495 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
37496 just saying that the program received the signal, not that it was
37497 terminated with it.
37499 @findex breakpoint annotation
37500 @item ^Z^Zbreakpoint @var{number}
37501 The program hit breakpoint number @var{number}.
37503 @findex watchpoint annotation
37504 @item ^Z^Zwatchpoint @var{number}
37505 The program hit watchpoint number @var{number}.
37508 @node Source Annotations
37509 @section Displaying Source
37510 @cindex annotations for source display
37512 @findex source annotation
37513 The following annotation is used instead of displaying source code:
37516 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
37519 where @var{filename} is an absolute file name indicating which source
37520 file, @var{line} is the line number within that file (where 1 is the
37521 first line in the file), @var{character} is the character position
37522 within the file (where 0 is the first character in the file) (for most
37523 debug formats this will necessarily point to the beginning of a line),
37524 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37525 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37526 @var{addr} is the address in the target program associated with the
37527 source which is being displayed. The @var{addr} is in the form @samp{0x}
37528 followed by one or more lowercase hex digits (note that this does not
37529 depend on the language).
37531 @node JIT Interface
37532 @chapter JIT Compilation Interface
37533 @cindex just-in-time compilation
37534 @cindex JIT compilation interface
37536 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37537 interface. A JIT compiler is a program or library that generates native
37538 executable code at runtime and executes it, usually in order to achieve good
37539 performance while maintaining platform independence.
37541 Programs that use JIT compilation are normally difficult to debug because
37542 portions of their code are generated at runtime, instead of being loaded from
37543 object files, which is where @value{GDBN} normally finds the program's symbols
37544 and debug information. In order to debug programs that use JIT compilation,
37545 @value{GDBN} has an interface that allows the program to register in-memory
37546 symbol files with @value{GDBN} at runtime.
37548 If you are using @value{GDBN} to debug a program that uses this interface, then
37549 it should work transparently so long as you have not stripped the binary. If
37550 you are developing a JIT compiler, then the interface is documented in the rest
37551 of this chapter. At this time, the only known client of this interface is the
37554 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37555 JIT compiler communicates with @value{GDBN} by writing data into a global
37556 variable and calling a function at a well-known symbol. When @value{GDBN}
37557 attaches, it reads a linked list of symbol files from the global variable to
37558 find existing code, and puts a breakpoint in the function so that it can find
37559 out about additional code.
37562 * Declarations:: Relevant C struct declarations
37563 * Registering Code:: Steps to register code
37564 * Unregistering Code:: Steps to unregister code
37565 * Custom Debug Info:: Emit debug information in a custom format
37569 @section JIT Declarations
37571 These are the relevant struct declarations that a C program should include to
37572 implement the interface:
37582 struct jit_code_entry
37584 struct jit_code_entry *next_entry;
37585 struct jit_code_entry *prev_entry;
37586 const char *symfile_addr;
37587 uint64_t symfile_size;
37590 struct jit_descriptor
37593 /* This type should be jit_actions_t, but we use uint32_t
37594 to be explicit about the bitwidth. */
37595 uint32_t action_flag;
37596 struct jit_code_entry *relevant_entry;
37597 struct jit_code_entry *first_entry;
37600 /* GDB puts a breakpoint in this function. */
37601 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37603 /* Make sure to specify the version statically, because the
37604 debugger may check the version before we can set it. */
37605 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37608 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37609 modifications to this global data properly, which can easily be done by putting
37610 a global mutex around modifications to these structures.
37612 @node Registering Code
37613 @section Registering Code
37615 To register code with @value{GDBN}, the JIT should follow this protocol:
37619 Generate an object file in memory with symbols and other desired debug
37620 information. The file must include the virtual addresses of the sections.
37623 Create a code entry for the file, which gives the start and size of the symbol
37627 Add it to the linked list in the JIT descriptor.
37630 Point the relevant_entry field of the descriptor at the entry.
37633 Set @code{action_flag} to @code{JIT_REGISTER} and call
37634 @code{__jit_debug_register_code}.
37637 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37638 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37639 new code. However, the linked list must still be maintained in order to allow
37640 @value{GDBN} to attach to a running process and still find the symbol files.
37642 @node Unregistering Code
37643 @section Unregistering Code
37645 If code is freed, then the JIT should use the following protocol:
37649 Remove the code entry corresponding to the code from the linked list.
37652 Point the @code{relevant_entry} field of the descriptor at the code entry.
37655 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
37656 @code{__jit_debug_register_code}.
37659 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
37660 and the JIT will leak the memory used for the associated symbol files.
37662 @node Custom Debug Info
37663 @section Custom Debug Info
37664 @cindex custom JIT debug info
37665 @cindex JIT debug info reader
37667 Generating debug information in platform-native file formats (like ELF
37668 or COFF) may be an overkill for JIT compilers; especially if all the
37669 debug info is used for is displaying a meaningful backtrace. The
37670 issue can be resolved by having the JIT writers decide on a debug info
37671 format and also provide a reader that parses the debug info generated
37672 by the JIT compiler. This section gives a brief overview on writing
37673 such a parser. More specific details can be found in the source file
37674 @file{gdb/jit-reader.in}, which is also installed as a header at
37675 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
37677 The reader is implemented as a shared object (so this functionality is
37678 not available on platforms which don't allow loading shared objects at
37679 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
37680 @code{jit-reader-unload} are provided, to be used to load and unload
37681 the readers from a preconfigured directory. Once loaded, the shared
37682 object is used the parse the debug information emitted by the JIT
37686 * Using JIT Debug Info Readers:: How to use supplied readers correctly
37687 * Writing JIT Debug Info Readers:: Creating a debug-info reader
37690 @node Using JIT Debug Info Readers
37691 @subsection Using JIT Debug Info Readers
37692 @kindex jit-reader-load
37693 @kindex jit-reader-unload
37695 Readers can be loaded and unloaded using the @code{jit-reader-load}
37696 and @code{jit-reader-unload} commands.
37699 @item jit-reader-load @var{reader}
37700 Load the JIT reader named @var{reader}, which is a shared
37701 object specified as either an absolute or a relative file name. In
37702 the latter case, @value{GDBN} will try to load the reader from a
37703 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
37704 system (here @var{libdir} is the system library directory, often
37705 @file{/usr/local/lib}).
37707 Only one reader can be active at a time; trying to load a second
37708 reader when one is already loaded will result in @value{GDBN}
37709 reporting an error. A new JIT reader can be loaded by first unloading
37710 the current one using @code{jit-reader-unload} and then invoking
37711 @code{jit-reader-load}.
37713 @item jit-reader-unload
37714 Unload the currently loaded JIT reader.
37718 @node Writing JIT Debug Info Readers
37719 @subsection Writing JIT Debug Info Readers
37720 @cindex writing JIT debug info readers
37722 As mentioned, a reader is essentially a shared object conforming to a
37723 certain ABI. This ABI is described in @file{jit-reader.h}.
37725 @file{jit-reader.h} defines the structures, macros and functions
37726 required to write a reader. It is installed (along with
37727 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
37728 the system include directory.
37730 Readers need to be released under a GPL compatible license. A reader
37731 can be declared as released under such a license by placing the macro
37732 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37734 The entry point for readers is the symbol @code{gdb_init_reader},
37735 which is expected to be a function with the prototype
37737 @findex gdb_init_reader
37739 extern struct gdb_reader_funcs *gdb_init_reader (void);
37742 @cindex @code{struct gdb_reader_funcs}
37744 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37745 functions. These functions are executed to read the debug info
37746 generated by the JIT compiler (@code{read}), to unwind stack frames
37747 (@code{unwind}) and to create canonical frame IDs
37748 (@code{get_frame_id}). It also has a callback that is called when the
37749 reader is being unloaded (@code{destroy}). The struct looks like this
37752 struct gdb_reader_funcs
37754 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37755 int reader_version;
37757 /* For use by the reader. */
37760 gdb_read_debug_info *read;
37761 gdb_unwind_frame *unwind;
37762 gdb_get_frame_id *get_frame_id;
37763 gdb_destroy_reader *destroy;
37767 @cindex @code{struct gdb_symbol_callbacks}
37768 @cindex @code{struct gdb_unwind_callbacks}
37770 The callbacks are provided with another set of callbacks by
37771 @value{GDBN} to do their job. For @code{read}, these callbacks are
37772 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37773 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37774 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37775 files and new symbol tables inside those object files. @code{struct
37776 gdb_unwind_callbacks} has callbacks to read registers off the current
37777 frame and to write out the values of the registers in the previous
37778 frame. Both have a callback (@code{target_read}) to read bytes off the
37779 target's address space.
37781 @node In-Process Agent
37782 @chapter In-Process Agent
37783 @cindex debugging agent
37784 The traditional debugging model is conceptually low-speed, but works fine,
37785 because most bugs can be reproduced in debugging-mode execution. However,
37786 as multi-core or many-core processors are becoming mainstream, and
37787 multi-threaded programs become more and more popular, there should be more
37788 and more bugs that only manifest themselves at normal-mode execution, for
37789 example, thread races, because debugger's interference with the program's
37790 timing may conceal the bugs. On the other hand, in some applications,
37791 it is not feasible for the debugger to interrupt the program's execution
37792 long enough for the developer to learn anything helpful about its behavior.
37793 If the program's correctness depends on its real-time behavior, delays
37794 introduced by a debugger might cause the program to fail, even when the
37795 code itself is correct. It is useful to be able to observe the program's
37796 behavior without interrupting it.
37798 Therefore, traditional debugging model is too intrusive to reproduce
37799 some bugs. In order to reduce the interference with the program, we can
37800 reduce the number of operations performed by debugger. The
37801 @dfn{In-Process Agent}, a shared library, is running within the same
37802 process with inferior, and is able to perform some debugging operations
37803 itself. As a result, debugger is only involved when necessary, and
37804 performance of debugging can be improved accordingly. Note that
37805 interference with program can be reduced but can't be removed completely,
37806 because the in-process agent will still stop or slow down the program.
37808 The in-process agent can interpret and execute Agent Expressions
37809 (@pxref{Agent Expressions}) during performing debugging operations. The
37810 agent expressions can be used for different purposes, such as collecting
37811 data in tracepoints, and condition evaluation in breakpoints.
37813 @anchor{Control Agent}
37814 You can control whether the in-process agent is used as an aid for
37815 debugging with the following commands:
37818 @kindex set agent on
37820 Causes the in-process agent to perform some operations on behalf of the
37821 debugger. Just which operations requested by the user will be done
37822 by the in-process agent depends on the its capabilities. For example,
37823 if you request to evaluate breakpoint conditions in the in-process agent,
37824 and the in-process agent has such capability as well, then breakpoint
37825 conditions will be evaluated in the in-process agent.
37827 @kindex set agent off
37828 @item set agent off
37829 Disables execution of debugging operations by the in-process agent. All
37830 of the operations will be performed by @value{GDBN}.
37834 Display the current setting of execution of debugging operations by
37835 the in-process agent.
37839 * In-Process Agent Protocol::
37842 @node In-Process Agent Protocol
37843 @section In-Process Agent Protocol
37844 @cindex in-process agent protocol
37846 The in-process agent is able to communicate with both @value{GDBN} and
37847 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37848 used for communications between @value{GDBN} or GDBserver and the IPA.
37849 In general, @value{GDBN} or GDBserver sends commands
37850 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37851 in-process agent replies back with the return result of the command, or
37852 some other information. The data sent to in-process agent is composed
37853 of primitive data types, such as 4-byte or 8-byte type, and composite
37854 types, which are called objects (@pxref{IPA Protocol Objects}).
37857 * IPA Protocol Objects::
37858 * IPA Protocol Commands::
37861 @node IPA Protocol Objects
37862 @subsection IPA Protocol Objects
37863 @cindex ipa protocol objects
37865 The commands sent to and results received from agent may contain some
37866 complex data types called @dfn{objects}.
37868 The in-process agent is running on the same machine with @value{GDBN}
37869 or GDBserver, so it doesn't have to handle as much differences between
37870 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
37871 However, there are still some differences of two ends in two processes:
37875 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
37876 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
37878 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
37879 GDBserver is compiled with one, and in-process agent is compiled with
37883 Here are the IPA Protocol Objects:
37887 agent expression object. It represents an agent expression
37888 (@pxref{Agent Expressions}).
37889 @anchor{agent expression object}
37891 tracepoint action object. It represents a tracepoint action
37892 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
37893 memory, static trace data and to evaluate expression.
37894 @anchor{tracepoint action object}
37896 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
37897 @anchor{tracepoint object}
37901 The following table describes important attributes of each IPA protocol
37904 @multitable @columnfractions .30 .20 .50
37905 @headitem Name @tab Size @tab Description
37906 @item @emph{agent expression object} @tab @tab
37907 @item length @tab 4 @tab length of bytes code
37908 @item byte code @tab @var{length} @tab contents of byte code
37909 @item @emph{tracepoint action for collecting memory} @tab @tab
37910 @item 'M' @tab 1 @tab type of tracepoint action
37911 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
37912 address of the lowest byte to collect, otherwise @var{addr} is the offset
37913 of @var{basereg} for memory collecting.
37914 @item len @tab 8 @tab length of memory for collecting
37915 @item basereg @tab 4 @tab the register number containing the starting
37916 memory address for collecting.
37917 @item @emph{tracepoint action for collecting registers} @tab @tab
37918 @item 'R' @tab 1 @tab type of tracepoint action
37919 @item @emph{tracepoint action for collecting static trace data} @tab @tab
37920 @item 'L' @tab 1 @tab type of tracepoint action
37921 @item @emph{tracepoint action for expression evaluation} @tab @tab
37922 @item 'X' @tab 1 @tab type of tracepoint action
37923 @item agent expression @tab length of @tab @ref{agent expression object}
37924 @item @emph{tracepoint object} @tab @tab
37925 @item number @tab 4 @tab number of tracepoint
37926 @item address @tab 8 @tab address of tracepoint inserted on
37927 @item type @tab 4 @tab type of tracepoint
37928 @item enabled @tab 1 @tab enable or disable of tracepoint
37929 @item step_count @tab 8 @tab step
37930 @item pass_count @tab 8 @tab pass
37931 @item numactions @tab 4 @tab number of tracepoint actions
37932 @item hit count @tab 8 @tab hit count
37933 @item trace frame usage @tab 8 @tab trace frame usage
37934 @item compiled_cond @tab 8 @tab compiled condition
37935 @item orig_size @tab 8 @tab orig size
37936 @item condition @tab 4 if condition is NULL otherwise length of
37937 @ref{agent expression object}
37938 @tab zero if condition is NULL, otherwise is
37939 @ref{agent expression object}
37940 @item actions @tab variable
37941 @tab numactions number of @ref{tracepoint action object}
37944 @node IPA Protocol Commands
37945 @subsection IPA Protocol Commands
37946 @cindex ipa protocol commands
37948 The spaces in each command are delimiters to ease reading this commands
37949 specification. They don't exist in real commands.
37953 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37954 Installs a new fast tracepoint described by @var{tracepoint_object}
37955 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37956 head of @dfn{jumppad}, which is used to jump to data collection routine
37961 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37962 @var{target_address} is address of tracepoint in the inferior.
37963 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37964 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37965 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37966 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37973 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37974 is about to kill inferiors.
37982 @item probe_marker_at:@var{address}
37983 Asks in-process agent to probe the marker at @var{address}.
37990 @item unprobe_marker_at:@var{address}
37991 Asks in-process agent to unprobe the marker at @var{address}.
37995 @chapter Reporting Bugs in @value{GDBN}
37996 @cindex bugs in @value{GDBN}
37997 @cindex reporting bugs in @value{GDBN}
37999 Your bug reports play an essential role in making @value{GDBN} reliable.
38001 Reporting a bug may help you by bringing a solution to your problem, or it
38002 may not. But in any case the principal function of a bug report is to help
38003 the entire community by making the next version of @value{GDBN} work better. Bug
38004 reports are your contribution to the maintenance of @value{GDBN}.
38006 In order for a bug report to serve its purpose, you must include the
38007 information that enables us to fix the bug.
38010 * Bug Criteria:: Have you found a bug?
38011 * Bug Reporting:: How to report bugs
38015 @section Have You Found a Bug?
38016 @cindex bug criteria
38018 If you are not sure whether you have found a bug, here are some guidelines:
38021 @cindex fatal signal
38022 @cindex debugger crash
38023 @cindex crash of debugger
38025 If the debugger gets a fatal signal, for any input whatever, that is a
38026 @value{GDBN} bug. Reliable debuggers never crash.
38028 @cindex error on valid input
38030 If @value{GDBN} produces an error message for valid input, that is a
38031 bug. (Note that if you're cross debugging, the problem may also be
38032 somewhere in the connection to the target.)
38034 @cindex invalid input
38036 If @value{GDBN} does not produce an error message for invalid input,
38037 that is a bug. However, you should note that your idea of
38038 ``invalid input'' might be our idea of ``an extension'' or ``support
38039 for traditional practice''.
38042 If you are an experienced user of debugging tools, your suggestions
38043 for improvement of @value{GDBN} are welcome in any case.
38046 @node Bug Reporting
38047 @section How to Report Bugs
38048 @cindex bug reports
38049 @cindex @value{GDBN} bugs, reporting
38051 A number of companies and individuals offer support for @sc{gnu} products.
38052 If you obtained @value{GDBN} from a support organization, we recommend you
38053 contact that organization first.
38055 You can find contact information for many support companies and
38056 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38058 @c should add a web page ref...
38061 @ifset BUGURL_DEFAULT
38062 In any event, we also recommend that you submit bug reports for
38063 @value{GDBN}. The preferred method is to submit them directly using
38064 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38065 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38068 @strong{Do not send bug reports to @samp{info-gdb}, or to
38069 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38070 not want to receive bug reports. Those that do have arranged to receive
38073 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38074 serves as a repeater. The mailing list and the newsgroup carry exactly
38075 the same messages. Often people think of posting bug reports to the
38076 newsgroup instead of mailing them. This appears to work, but it has one
38077 problem which can be crucial: a newsgroup posting often lacks a mail
38078 path back to the sender. Thus, if we need to ask for more information,
38079 we may be unable to reach you. For this reason, it is better to send
38080 bug reports to the mailing list.
38082 @ifclear BUGURL_DEFAULT
38083 In any event, we also recommend that you submit bug reports for
38084 @value{GDBN} to @value{BUGURL}.
38088 The fundamental principle of reporting bugs usefully is this:
38089 @strong{report all the facts}. If you are not sure whether to state a
38090 fact or leave it out, state it!
38092 Often people omit facts because they think they know what causes the
38093 problem and assume that some details do not matter. Thus, you might
38094 assume that the name of the variable you use in an example does not matter.
38095 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38096 stray memory reference which happens to fetch from the location where that
38097 name is stored in memory; perhaps, if the name were different, the contents
38098 of that location would fool the debugger into doing the right thing despite
38099 the bug. Play it safe and give a specific, complete example. That is the
38100 easiest thing for you to do, and the most helpful.
38102 Keep in mind that the purpose of a bug report is to enable us to fix the
38103 bug. It may be that the bug has been reported previously, but neither
38104 you nor we can know that unless your bug report is complete and
38107 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38108 bell?'' Those bug reports are useless, and we urge everyone to
38109 @emph{refuse to respond to them} except to chide the sender to report
38112 To enable us to fix the bug, you should include all these things:
38116 The version of @value{GDBN}. @value{GDBN} announces it if you start
38117 with no arguments; you can also print it at any time using @code{show
38120 Without this, we will not know whether there is any point in looking for
38121 the bug in the current version of @value{GDBN}.
38124 The type of machine you are using, and the operating system name and
38128 The details of the @value{GDBN} build-time configuration.
38129 @value{GDBN} shows these details if you invoke it with the
38130 @option{--configuration} command-line option, or if you type
38131 @code{show configuration} at @value{GDBN}'s prompt.
38134 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38135 ``@value{GCC}--2.8.1''.
38138 What compiler (and its version) was used to compile the program you are
38139 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38140 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38141 to get this information; for other compilers, see the documentation for
38145 The command arguments you gave the compiler to compile your example and
38146 observe the bug. For example, did you use @samp{-O}? To guarantee
38147 you will not omit something important, list them all. A copy of the
38148 Makefile (or the output from make) is sufficient.
38150 If we were to try to guess the arguments, we would probably guess wrong
38151 and then we might not encounter the bug.
38154 A complete input script, and all necessary source files, that will
38158 A description of what behavior you observe that you believe is
38159 incorrect. For example, ``It gets a fatal signal.''
38161 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38162 will certainly notice it. But if the bug is incorrect output, we might
38163 not notice unless it is glaringly wrong. You might as well not give us
38164 a chance to make a mistake.
38166 Even if the problem you experience is a fatal signal, you should still
38167 say so explicitly. Suppose something strange is going on, such as, your
38168 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38169 the C library on your system. (This has happened!) Your copy might
38170 crash and ours would not. If you told us to expect a crash, then when
38171 ours fails to crash, we would know that the bug was not happening for
38172 us. If you had not told us to expect a crash, then we would not be able
38173 to draw any conclusion from our observations.
38176 @cindex recording a session script
38177 To collect all this information, you can use a session recording program
38178 such as @command{script}, which is available on many Unix systems.
38179 Just run your @value{GDBN} session inside @command{script} and then
38180 include the @file{typescript} file with your bug report.
38182 Another way to record a @value{GDBN} session is to run @value{GDBN}
38183 inside Emacs and then save the entire buffer to a file.
38186 If you wish to suggest changes to the @value{GDBN} source, send us context
38187 diffs. If you even discuss something in the @value{GDBN} source, refer to
38188 it by context, not by line number.
38190 The line numbers in our development sources will not match those in your
38191 sources. Your line numbers would convey no useful information to us.
38195 Here are some things that are not necessary:
38199 A description of the envelope of the bug.
38201 Often people who encounter a bug spend a lot of time investigating
38202 which changes to the input file will make the bug go away and which
38203 changes will not affect it.
38205 This is often time consuming and not very useful, because the way we
38206 will find the bug is by running a single example under the debugger
38207 with breakpoints, not by pure deduction from a series of examples.
38208 We recommend that you save your time for something else.
38210 Of course, if you can find a simpler example to report @emph{instead}
38211 of the original one, that is a convenience for us. Errors in the
38212 output will be easier to spot, running under the debugger will take
38213 less time, and so on.
38215 However, simplification is not vital; if you do not want to do this,
38216 report the bug anyway and send us the entire test case you used.
38219 A patch for the bug.
38221 A patch for the bug does help us if it is a good one. But do not omit
38222 the necessary information, such as the test case, on the assumption that
38223 a patch is all we need. We might see problems with your patch and decide
38224 to fix the problem another way, or we might not understand it at all.
38226 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38227 construct an example that will make the program follow a certain path
38228 through the code. If you do not send us the example, we will not be able
38229 to construct one, so we will not be able to verify that the bug is fixed.
38231 And if we cannot understand what bug you are trying to fix, or why your
38232 patch should be an improvement, we will not install it. A test case will
38233 help us to understand.
38236 A guess about what the bug is or what it depends on.
38238 Such guesses are usually wrong. Even we cannot guess right about such
38239 things without first using the debugger to find the facts.
38242 @c The readline documentation is distributed with the readline code
38243 @c and consists of the two following files:
38246 @c Use -I with makeinfo to point to the appropriate directory,
38247 @c environment var TEXINPUTS with TeX.
38248 @ifclear SYSTEM_READLINE
38249 @include rluser.texi
38250 @include hsuser.texi
38254 @appendix In Memoriam
38256 The @value{GDBN} project mourns the loss of the following long-time
38261 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38262 to Free Software in general. Outside of @value{GDBN}, he was known in
38263 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38265 @item Michael Snyder
38266 Michael was one of the Global Maintainers of the @value{GDBN} project,
38267 with contributions recorded as early as 1996, until 2011. In addition
38268 to his day to day participation, he was a large driving force behind
38269 adding Reverse Debugging to @value{GDBN}.
38272 Beyond their technical contributions to the project, they were also
38273 enjoyable members of the Free Software Community. We will miss them.
38275 @node Formatting Documentation
38276 @appendix Formatting Documentation
38278 @cindex @value{GDBN} reference card
38279 @cindex reference card
38280 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38281 for printing with PostScript or Ghostscript, in the @file{gdb}
38282 subdirectory of the main source directory@footnote{In
38283 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38284 release.}. If you can use PostScript or Ghostscript with your printer,
38285 you can print the reference card immediately with @file{refcard.ps}.
38287 The release also includes the source for the reference card. You
38288 can format it, using @TeX{}, by typing:
38294 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38295 mode on US ``letter'' size paper;
38296 that is, on a sheet 11 inches wide by 8.5 inches
38297 high. You will need to specify this form of printing as an option to
38298 your @sc{dvi} output program.
38300 @cindex documentation
38302 All the documentation for @value{GDBN} comes as part of the machine-readable
38303 distribution. The documentation is written in Texinfo format, which is
38304 a documentation system that uses a single source file to produce both
38305 on-line information and a printed manual. You can use one of the Info
38306 formatting commands to create the on-line version of the documentation
38307 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38309 @value{GDBN} includes an already formatted copy of the on-line Info
38310 version of this manual in the @file{gdb} subdirectory. The main Info
38311 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38312 subordinate files matching @samp{gdb.info*} in the same directory. If
38313 necessary, you can print out these files, or read them with any editor;
38314 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38315 Emacs or the standalone @code{info} program, available as part of the
38316 @sc{gnu} Texinfo distribution.
38318 If you want to format these Info files yourself, you need one of the
38319 Info formatting programs, such as @code{texinfo-format-buffer} or
38322 If you have @code{makeinfo} installed, and are in the top level
38323 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38324 version @value{GDBVN}), you can make the Info file by typing:
38331 If you want to typeset and print copies of this manual, you need @TeX{},
38332 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38333 Texinfo definitions file.
38335 @TeX{} is a typesetting program; it does not print files directly, but
38336 produces output files called @sc{dvi} files. To print a typeset
38337 document, you need a program to print @sc{dvi} files. If your system
38338 has @TeX{} installed, chances are it has such a program. The precise
38339 command to use depends on your system; @kbd{lpr -d} is common; another
38340 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38341 require a file name without any extension or a @samp{.dvi} extension.
38343 @TeX{} also requires a macro definitions file called
38344 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38345 written in Texinfo format. On its own, @TeX{} cannot either read or
38346 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38347 and is located in the @file{gdb-@var{version-number}/texinfo}
38350 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38351 typeset and print this manual. First switch to the @file{gdb}
38352 subdirectory of the main source directory (for example, to
38353 @file{gdb-@value{GDBVN}/gdb}) and type:
38359 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38361 @node Installing GDB
38362 @appendix Installing @value{GDBN}
38363 @cindex installation
38366 * Requirements:: Requirements for building @value{GDBN}
38367 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38368 * Separate Objdir:: Compiling @value{GDBN} in another directory
38369 * Config Names:: Specifying names for hosts and targets
38370 * Configure Options:: Summary of options for configure
38371 * System-wide configuration:: Having a system-wide init file
38375 @section Requirements for Building @value{GDBN}
38376 @cindex building @value{GDBN}, requirements for
38378 Building @value{GDBN} requires various tools and packages to be available.
38379 Other packages will be used only if they are found.
38381 @heading Tools/Packages Necessary for Building @value{GDBN}
38383 @item C@t{++}11 compiler
38384 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38385 recent C@t{++}11 compiler, e.g.@: GCC.
38388 @value{GDBN}'s build system relies on features only found in the GNU
38389 make program. Other variants of @code{make} will not work.
38391 @item GMP (The GNU Multiple Precision Arithmetic Library)
38392 @value{GDBN} now uses GMP to perform some of its arithmetics.
38393 This library may be included with your operating system distribution;
38394 if it is not, you can get the latest version from
38395 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38396 you can use the @option{--with-libgmp-prefix} option to specify
38401 @heading Tools/Packages Optional for Building @value{GDBN}
38405 @value{GDBN} can use the Expat XML parsing library. This library may be
38406 included with your operating system distribution; if it is not, you
38407 can get the latest version from @url{http://expat.sourceforge.net}.
38408 The @file{configure} script will search for this library in several
38409 standard locations; if it is installed in an unusual path, you can
38410 use the @option{--with-libexpat-prefix} option to specify its location.
38416 Remote protocol memory maps (@pxref{Memory Map Format})
38418 Target descriptions (@pxref{Target Descriptions})
38420 Remote shared library lists (@xref{Library List Format},
38421 or alternatively @pxref{Library List Format for SVR4 Targets})
38423 MS-Windows shared libraries (@pxref{Shared Libraries})
38425 Traceframe info (@pxref{Traceframe Info Format})
38427 Branch trace (@pxref{Branch Trace Format},
38428 @pxref{Branch Trace Configuration Format})
38432 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38433 default, @value{GDBN} will be compiled if the Guile libraries are
38434 installed and are found by @file{configure}. You can use the
38435 @code{--with-guile} option to request Guile, and pass either the Guile
38436 version number or the file name of the relevant @code{pkg-config}
38437 program to choose a particular version of Guile.
38440 @value{GDBN}'s features related to character sets (@pxref{Character
38441 Sets}) require a functioning @code{iconv} implementation. If you are
38442 on a GNU system, then this is provided by the GNU C Library. Some
38443 other systems also provide a working @code{iconv}.
38445 If @value{GDBN} is using the @code{iconv} program which is installed
38446 in a non-standard place, you will need to tell @value{GDBN} where to
38447 find it. This is done with @option{--with-iconv-bin} which specifies
38448 the directory that contains the @code{iconv} program. This program is
38449 run in order to make a list of the available character sets.
38451 On systems without @code{iconv}, you can install GNU Libiconv. If
38452 Libiconv is installed in a standard place, @value{GDBN} will
38453 automatically use it if it is needed. If you have previously
38454 installed Libiconv in a non-standard place, you can use the
38455 @option{--with-libiconv-prefix} option to @file{configure}.
38457 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
38458 arrange to build Libiconv if a directory named @file{libiconv} appears
38459 in the top-most source directory. If Libiconv is built this way, and
38460 if the operating system does not provide a suitable @code{iconv}
38461 implementation, then the just-built library will automatically be used
38462 by @value{GDBN}. One easy way to set this up is to download GNU
38463 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
38464 source tree, and then rename the directory holding the Libiconv source
38465 code to @samp{libiconv}.
38468 @value{GDBN} can support debugging sections that are compressed with
38469 the LZMA library. @xref{MiniDebugInfo}. If this library is not
38470 included with your operating system, you can find it in the xz package
38471 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
38472 the usual place, then the @file{configure} script will use it
38473 automatically. If it is installed in an unusual path, you can use the
38474 @option{--with-lzma-prefix} option to specify its location.
38478 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
38479 library. This library may be included with your operating system
38480 distribution; if it is not, you can get the latest version from
38481 @url{http://www.mpfr.org}. The @file{configure} script will search
38482 for this library in several standard locations; if it is installed
38483 in an unusual path, you can use the @option{--with-libmpfr-prefix}
38484 option to specify its location.
38486 GNU MPFR is used to emulate target floating-point arithmetic during
38487 expression evaluation when the target uses different floating-point
38488 formats than the host. If GNU MPFR it is not available, @value{GDBN}
38489 will fall back to using host floating-point arithmetic.
38492 @value{GDBN} can be scripted using Python language. @xref{Python}.
38493 By default, @value{GDBN} will be compiled if the Python libraries are
38494 installed and are found by @file{configure}. You can use the
38495 @code{--with-python} option to request Python, and pass either the
38496 file name of the relevant @code{python} executable, or the name of the
38497 directory in which Python is installed, to choose a particular
38498 installation of Python.
38501 @cindex compressed debug sections
38502 @value{GDBN} will use the @samp{zlib} library, if available, to read
38503 compressed debug sections. Some linkers, such as GNU gold, are capable
38504 of producing binaries with compressed debug sections. If @value{GDBN}
38505 is compiled with @samp{zlib}, it will be able to read the debug
38506 information in such binaries.
38508 The @samp{zlib} library is likely included with your operating system
38509 distribution; if it is not, you can get the latest version from
38510 @url{http://zlib.net}.
38513 @node Running Configure
38514 @section Invoking the @value{GDBN} @file{configure} Script
38515 @cindex configuring @value{GDBN}
38516 @value{GDBN} comes with a @file{configure} script that automates the process
38517 of preparing @value{GDBN} for installation; you can then use @code{make} to
38518 build the @code{gdb} program.
38520 @c irrelevant in info file; it's as current as the code it lives with.
38521 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38522 look at the @file{README} file in the sources; we may have improved the
38523 installation procedures since publishing this manual.}
38526 The @value{GDBN} distribution includes all the source code you need for
38527 @value{GDBN} in a single directory, whose name is usually composed by
38528 appending the version number to @samp{gdb}.
38530 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38531 @file{gdb-@value{GDBVN}} directory. That directory contains:
38534 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38535 script for configuring @value{GDBN} and all its supporting libraries
38537 @item gdb-@value{GDBVN}/gdb
38538 the source specific to @value{GDBN} itself
38540 @item gdb-@value{GDBVN}/bfd
38541 source for the Binary File Descriptor library
38543 @item gdb-@value{GDBVN}/include
38544 @sc{gnu} include files
38546 @item gdb-@value{GDBVN}/libiberty
38547 source for the @samp{-liberty} free software library
38549 @item gdb-@value{GDBVN}/opcodes
38550 source for the library of opcode tables and disassemblers
38552 @item gdb-@value{GDBVN}/readline
38553 source for the @sc{gnu} command-line interface
38556 There may be other subdirectories as well.
38558 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38559 from the @file{gdb-@var{version-number}} source directory, which in
38560 this example is the @file{gdb-@value{GDBVN}} directory.
38562 First switch to the @file{gdb-@var{version-number}} source directory
38563 if you are not already in it; then run @file{configure}. Pass the
38564 identifier for the platform on which @value{GDBN} will run as an
38570 cd gdb-@value{GDBVN}
38575 Running @samp{configure} and then running @code{make} builds the
38576 included supporting libraries, then @code{gdb} itself. The configured
38577 source files, and the binaries, are left in the corresponding source
38581 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38582 system does not recognize this automatically when you run a different
38583 shell, you may need to run @code{sh} on it explicitly:
38589 You should run the @file{configure} script from the top directory in the
38590 source tree, the @file{gdb-@var{version-number}} directory. If you run
38591 @file{configure} from one of the subdirectories, you will configure only
38592 that subdirectory. That is usually not what you want. In particular,
38593 if you run the first @file{configure} from the @file{gdb} subdirectory
38594 of the @file{gdb-@var{version-number}} directory, you will omit the
38595 configuration of @file{bfd}, @file{readline}, and other sibling
38596 directories of the @file{gdb} subdirectory. This leads to build errors
38597 about missing include files such as @file{bfd/bfd.h}.
38599 You can install @code{@value{GDBN}} anywhere. The best way to do this
38600 is to pass the @code{--prefix} option to @code{configure}, and then
38601 install it with @code{make install}.
38603 @node Separate Objdir
38604 @section Compiling @value{GDBN} in Another Directory
38606 If you want to run @value{GDBN} versions for several host or target machines,
38607 you need a different @code{gdb} compiled for each combination of
38608 host and target. @file{configure} is designed to make this easy by
38609 allowing you to generate each configuration in a separate subdirectory,
38610 rather than in the source directory. If your @code{make} program
38611 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38612 @code{make} in each of these directories builds the @code{gdb}
38613 program specified there.
38615 To build @code{gdb} in a separate directory, run @file{configure}
38616 with the @samp{--srcdir} option to specify where to find the source.
38617 (You also need to specify a path to find @file{configure}
38618 itself from your working directory. If the path to @file{configure}
38619 would be the same as the argument to @samp{--srcdir}, you can leave out
38620 the @samp{--srcdir} option; it is assumed.)
38622 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38623 separate directory for a Sun 4 like this:
38627 cd gdb-@value{GDBVN}
38630 ../gdb-@value{GDBVN}/configure
38635 When @file{configure} builds a configuration using a remote source
38636 directory, it creates a tree for the binaries with the same structure
38637 (and using the same names) as the tree under the source directory. In
38638 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38639 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38640 @file{gdb-sun4/gdb}.
38642 Make sure that your path to the @file{configure} script has just one
38643 instance of @file{gdb} in it. If your path to @file{configure} looks
38644 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38645 one subdirectory of @value{GDBN}, not the whole package. This leads to
38646 build errors about missing include files such as @file{bfd/bfd.h}.
38648 One popular reason to build several @value{GDBN} configurations in separate
38649 directories is to configure @value{GDBN} for cross-compiling (where
38650 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
38651 programs that run on another machine---the @dfn{target}).
38652 You specify a cross-debugging target by
38653 giving the @samp{--target=@var{target}} option to @file{configure}.
38655 When you run @code{make} to build a program or library, you must run
38656 it in a configured directory---whatever directory you were in when you
38657 called @file{configure} (or one of its subdirectories).
38659 The @code{Makefile} that @file{configure} generates in each source
38660 directory also runs recursively. If you type @code{make} in a source
38661 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
38662 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
38663 will build all the required libraries, and then build GDB.
38665 When you have multiple hosts or targets configured in separate
38666 directories, you can run @code{make} on them in parallel (for example,
38667 if they are NFS-mounted on each of the hosts); they will not interfere
38671 @section Specifying Names for Hosts and Targets
38673 The specifications used for hosts and targets in the @file{configure}
38674 script are based on a three-part naming scheme, but some short predefined
38675 aliases are also supported. The full naming scheme encodes three pieces
38676 of information in the following pattern:
38679 @var{architecture}-@var{vendor}-@var{os}
38682 For example, you can use the alias @code{sun4} as a @var{host} argument,
38683 or as the value for @var{target} in a @code{--target=@var{target}}
38684 option. The equivalent full name is @samp{sparc-sun-sunos4}.
38686 The @file{configure} script accompanying @value{GDBN} does not provide
38687 any query facility to list all supported host and target names or
38688 aliases. @file{configure} calls the Bourne shell script
38689 @code{config.sub} to map abbreviations to full names; you can read the
38690 script, if you wish, or you can use it to test your guesses on
38691 abbreviations---for example:
38694 % sh config.sub i386-linux
38696 % sh config.sub alpha-linux
38697 alpha-unknown-linux-gnu
38698 % sh config.sub hp9k700
38700 % sh config.sub sun4
38701 sparc-sun-sunos4.1.1
38702 % sh config.sub sun3
38703 m68k-sun-sunos4.1.1
38704 % sh config.sub i986v
38705 Invalid configuration `i986v': machine `i986v' not recognized
38709 @code{config.sub} is also distributed in the @value{GDBN} source
38710 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
38712 @node Configure Options
38713 @section @file{configure} Options
38715 Here is a summary of the @file{configure} options and arguments that
38716 are most often useful for building @value{GDBN}. @file{configure}
38717 also has several other options not listed here. @xref{Running
38718 configure Scripts,,,autoconf}, for a full
38719 explanation of @file{configure}.
38722 configure @r{[}--help@r{]}
38723 @r{[}--prefix=@var{dir}@r{]}
38724 @r{[}--exec-prefix=@var{dir}@r{]}
38725 @r{[}--srcdir=@var{dirname}@r{]}
38726 @r{[}--target=@var{target}@r{]}
38730 You may introduce options with a single @samp{-} rather than
38731 @samp{--} if you prefer; but you may abbreviate option names if you use
38736 Display a quick summary of how to invoke @file{configure}.
38738 @item --prefix=@var{dir}
38739 Configure the source to install programs and files under directory
38742 @item --exec-prefix=@var{dir}
38743 Configure the source to install programs under directory
38746 @c avoid splitting the warning from the explanation:
38748 @item --srcdir=@var{dirname}
38749 Use this option to make configurations in directories separate from the
38750 @value{GDBN} source directories. Among other things, you can use this to
38751 build (or maintain) several configurations simultaneously, in separate
38752 directories. @file{configure} writes configuration-specific files in
38753 the current directory, but arranges for them to use the source in the
38754 directory @var{dirname}. @file{configure} creates directories under
38755 the working directory in parallel to the source directories below
38758 @item --target=@var{target}
38759 Configure @value{GDBN} for cross-debugging programs running on the specified
38760 @var{target}. Without this option, @value{GDBN} is configured to debug
38761 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38763 There is no convenient way to generate a list of all available
38764 targets. Also see the @code{--enable-targets} option, below.
38767 There are many other options that are specific to @value{GDBN}. This
38768 lists just the most common ones; there are some very specialized
38769 options not described here.
38772 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38773 @itemx --enable-targets=all
38774 Configure @value{GDBN} for cross-debugging programs running on the
38775 specified list of targets. The special value @samp{all} configures
38776 @value{GDBN} for debugging programs running on any target it supports.
38778 @item --with-gdb-datadir=@var{path}
38779 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
38780 here for certain supporting files or scripts. This defaults to the
38781 @file{gdb} subdirectory of @samp{datadir} (which can be set using
38784 @item --with-relocated-sources=@var{dir}
38785 Sets up the default source path substitution rule so that directory
38786 names recorded in debug information will be automatically adjusted for
38787 any directory under @var{dir}. @var{dir} should be a subdirectory of
38788 @value{GDBN}'s configured prefix, the one mentioned in the
38789 @code{--prefix} or @code{--exec-prefix} options to configure. This
38790 option is useful if GDB is supposed to be moved to a different place
38793 @item --enable-64-bit-bfd
38794 Enable 64-bit support in BFD on 32-bit hosts.
38796 @item --disable-gdbmi
38797 Build @value{GDBN} without the GDB/MI machine interface
38801 Build @value{GDBN} with the text-mode full-screen user interface
38802 (TUI). Requires a curses library (ncurses and cursesX are also
38805 @item --with-curses
38806 Use the curses library instead of the termcap library, for text-mode
38807 terminal operations.
38809 @item --with-debuginfod
38810 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
38811 library. Used to automatically fetch ELF, DWARF and source files from
38812 @code{debuginfod} servers using build IDs associated with any missing
38813 files. Enabled by default if @file{libdebuginfod} is installed and found
38814 at configure time. For more information regarding @code{debuginfod} see
38817 @item --with-libunwind-ia64
38818 Use the libunwind library for unwinding function call stack on ia64
38819 target platforms. See http://www.nongnu.org/libunwind/index.html for
38822 @item --with-system-readline
38823 Use the readline library installed on the host, rather than the
38824 library supplied as part of @value{GDBN}. Readline 7 or newer is
38825 required; this is enforced by the build system.
38827 @item --with-system-zlib
38828 Use the zlib library installed on the host, rather than the library
38829 supplied as part of @value{GDBN}.
38832 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38833 default if libexpat is installed and found at configure time.) This
38834 library is used to read XML files supplied with @value{GDBN}. If it
38835 is unavailable, some features, such as remote protocol memory maps,
38836 target descriptions, and shared library lists, that are based on XML
38837 files, will not be available in @value{GDBN}. If your host does not
38838 have libexpat installed, you can get the latest version from
38839 `http://expat.sourceforge.net'.
38841 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38843 Build @value{GDBN} with GNU libiconv, a character set encoding
38844 conversion library. This is not done by default, as on GNU systems
38845 the @code{iconv} that is built in to the C library is sufficient. If
38846 your host does not have a working @code{iconv}, you can get the latest
38847 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38849 @value{GDBN}'s build system also supports building GNU libiconv as
38850 part of the overall build. @xref{Requirements}.
38853 Build @value{GDBN} with LZMA, a compression library. (Done by default
38854 if liblzma is installed and found at configure time.) LZMA is used by
38855 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38856 platforms using the ELF object file format. If your host does not
38857 have liblzma installed, you can get the latest version from
38858 `https://tukaani.org/xz/'.
38861 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38862 floating-point computation with correct rounding. (Done by default if
38863 GNU MPFR is installed and found at configure time.) This library is
38864 used to emulate target floating-point arithmetic during expression
38865 evaluation when the target uses different floating-point formats than
38866 the host. If GNU MPFR is not available, @value{GDBN} will fall back
38867 to using host floating-point arithmetic. If your host does not have
38868 GNU MPFR installed, you can get the latest version from
38869 `http://www.mpfr.org'.
38871 @item --with-python@r{[}=@var{python}@r{]}
38872 Build @value{GDBN} with Python scripting support. (Done by default if
38873 libpython is present and found at configure time.) Python makes
38874 @value{GDBN} scripting much more powerful than the restricted CLI
38875 scripting language. If your host does not have Python installed, you
38876 can find it on `http://www.python.org/download/'. The oldest version
38877 of Python supported by GDB is 2.6. The optional argument @var{python}
38878 is used to find the Python headers and libraries. It can be either
38879 the name of a Python executable, or the name of the directory in which
38880 Python is installed.
38882 @item --with-guile[=GUILE]'
38883 Build @value{GDBN} with GNU Guile scripting support. (Done by default
38884 if libguile is present and found at configure time.) If your host
38885 does not have Guile installed, you can find it at
38886 `https://www.gnu.org/software/guile/'. The optional argument GUILE
38887 can be a version number, which will cause @code{configure} to try to
38888 use that version of Guile; or the file name of a @code{pkg-config}
38889 executable, which will be queried to find the information needed to
38890 compile and link against Guile.
38892 @item --without-included-regex
38893 Don't use the regex library included with @value{GDBN} (as part of the
38894 libiberty library). This is the default on hosts with version 2 of
38897 @item --with-sysroot=@var{dir}
38898 Use @var{dir} as the default system root directory for libraries whose
38899 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
38900 @var{dir} can be modified at run time by using the @command{set
38901 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
38902 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
38903 default system root will be automatically adjusted if and when
38904 @value{GDBN} is moved to a different location.
38906 @item --with-system-gdbinit=@var{file}
38907 Configure @value{GDBN} to automatically load a system-wide init file.
38908 @var{file} should be an absolute file name. If @var{file} is in a
38909 directory under the configured prefix, and @value{GDBN} is moved to
38910 another location after being built, the location of the system-wide
38911 init file will be adjusted accordingly.
38913 @item --with-system-gdbinit-dir=@var{directory}
38914 Configure @value{GDBN} to automatically load init files from a
38915 system-wide directory. @var{directory} should be an absolute directory
38916 name. If @var{directory} is in a directory under the configured
38917 prefix, and @value{GDBN} is moved to another location after being
38918 built, the location of the system-wide init directory will be
38919 adjusted accordingly.
38921 @item --enable-build-warnings
38922 When building the @value{GDBN} sources, ask the compiler to warn about
38923 any code which looks even vaguely suspicious. It passes many
38924 different warning flags, depending on the exact version of the
38925 compiler you are using.
38927 @item --enable-werror
38928 Treat compiler warnings as errors. It adds the @code{-Werror} flag
38929 to the compiler, which will fail the compilation if the compiler
38930 outputs any warning messages.
38932 @item --enable-ubsan
38933 Enable the GCC undefined behavior sanitizer. This is disabled by
38934 default, but passing @code{--enable-ubsan=yes} or
38935 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
38936 undefined behavior sanitizer checks for C@t{++} undefined behavior.
38937 It has a performance cost, so if you are looking at @value{GDBN}'s
38938 performance, you should disable it. The undefined behavior sanitizer
38939 was first introduced in GCC 4.9.
38942 @node System-wide configuration
38943 @section System-wide configuration and settings
38944 @cindex system-wide init file
38946 @value{GDBN} can be configured to have a system-wide init file and a
38947 system-wide init file directory; this file and files in that directory
38948 (if they have a recognized file extension) will be read and executed at
38949 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
38951 Here are the corresponding configure options:
38954 @item --with-system-gdbinit=@var{file}
38955 Specify that the default location of the system-wide init file is
38957 @item --with-system-gdbinit-dir=@var{directory}
38958 Specify that the default location of the system-wide init file directory
38959 is @var{directory}.
38962 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
38963 they may be subject to relocation. Two possible cases:
38967 If the default location of this init file/directory contains @file{$prefix},
38968 it will be subject to relocation. Suppose that the configure options
38969 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38970 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38971 init file is looked for as @file{$install/etc/gdbinit} instead of
38972 @file{$prefix/etc/gdbinit}.
38975 By contrast, if the default location does not contain the prefix,
38976 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38977 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38978 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38979 wherever @value{GDBN} is installed.
38982 If the configured location of the system-wide init file (as given by the
38983 @option{--with-system-gdbinit} option at configure time) is in the
38984 data-directory (as specified by @option{--with-gdb-datadir} at configure
38985 time) or in one of its subdirectories, then @value{GDBN} will look for the
38986 system-wide init file in the directory specified by the
38987 @option{--data-directory} command-line option.
38988 Note that the system-wide init file is only read once, during @value{GDBN}
38989 initialization. If the data-directory is changed after @value{GDBN} has
38990 started with the @code{set data-directory} command, the file will not be
38993 This applies similarly to the system-wide directory specified in
38994 @option{--with-system-gdbinit-dir}.
38996 Any supported scripting language can be used for these init files, as long
38997 as the file extension matches the scripting language. To be interpreted
38998 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39002 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39005 @node System-wide Configuration Scripts
39006 @subsection Installed System-wide Configuration Scripts
39007 @cindex system-wide configuration scripts
39009 The @file{system-gdbinit} directory, located inside the data-directory
39010 (as specified by @option{--with-gdb-datadir} at configure time) contains
39011 a number of scripts which can be used as system-wide init files. To
39012 automatically source those scripts at startup, @value{GDBN} should be
39013 configured with @option{--with-system-gdbinit}. Otherwise, any user
39014 should be able to source them by hand as needed.
39016 The following scripts are currently available:
39019 @item @file{elinos.py}
39021 @cindex ELinOS system-wide configuration script
39022 This script is useful when debugging a program on an ELinOS target.
39023 It takes advantage of the environment variables defined in a standard
39024 ELinOS environment in order to determine the location of the system
39025 shared libraries, and then sets the @samp{solib-absolute-prefix}
39026 and @samp{solib-search-path} variables appropriately.
39028 @item @file{wrs-linux.py}
39029 @pindex wrs-linux.py
39030 @cindex Wind River Linux system-wide configuration script
39031 This script is useful when debugging a program on a target running
39032 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39033 the host-side sysroot used by the target system.
39037 @node Maintenance Commands
39038 @appendix Maintenance Commands
39039 @cindex maintenance commands
39040 @cindex internal commands
39042 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39043 includes a number of commands intended for @value{GDBN} developers,
39044 that are not documented elsewhere in this manual. These commands are
39045 provided here for reference. (For commands that turn on debugging
39046 messages, see @ref{Debugging Output}.)
39049 @kindex maint agent
39050 @kindex maint agent-eval
39051 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39052 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39053 Translate the given @var{expression} into remote agent bytecodes.
39054 This command is useful for debugging the Agent Expression mechanism
39055 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39056 expression useful for data collection, such as by tracepoints, while
39057 @samp{maint agent-eval} produces an expression that evaluates directly
39058 to a result. For instance, a collection expression for @code{globa +
39059 globb} will include bytecodes to record four bytes of memory at each
39060 of the addresses of @code{globa} and @code{globb}, while discarding
39061 the result of the addition, while an evaluation expression will do the
39062 addition and return the sum.
39063 If @code{-at} is given, generate remote agent bytecode for @var{location}.
39064 If not, generate remote agent bytecode for current frame PC address.
39066 @kindex maint agent-printf
39067 @item maint agent-printf @var{format},@var{expr},...
39068 Translate the given format string and list of argument expressions
39069 into remote agent bytecodes and display them as a disassembled list.
39070 This command is useful for debugging the agent version of dynamic
39071 printf (@pxref{Dynamic Printf}).
39073 @kindex maint info breakpoints
39074 @item @anchor{maint info breakpoints}maint info breakpoints
39075 Using the same format as @samp{info breakpoints}, display both the
39076 breakpoints you've set explicitly, and those @value{GDBN} is using for
39077 internal purposes. Internal breakpoints are shown with negative
39078 breakpoint numbers. The type column identifies what kind of breakpoint
39083 Normal, explicitly set breakpoint.
39086 Normal, explicitly set watchpoint.
39089 Internal breakpoint, used to handle correctly stepping through
39090 @code{longjmp} calls.
39092 @item longjmp resume
39093 Internal breakpoint at the target of a @code{longjmp}.
39096 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39099 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39102 Shared library events.
39106 @kindex maint info btrace
39107 @item maint info btrace
39108 Pint information about raw branch tracing data.
39110 @kindex maint btrace packet-history
39111 @item maint btrace packet-history
39112 Print the raw branch trace packets that are used to compute the
39113 execution history for the @samp{record btrace} command. Both the
39114 information and the format in which it is printed depend on the btrace
39119 For the BTS recording format, print a list of blocks of sequential
39120 code. For each block, the following information is printed:
39124 Newer blocks have higher numbers. The oldest block has number zero.
39125 @item Lowest @samp{PC}
39126 @item Highest @samp{PC}
39130 For the Intel Processor Trace recording format, print a list of
39131 Intel Processor Trace packets. For each packet, the following
39132 information is printed:
39135 @item Packet number
39136 Newer packets have higher numbers. The oldest packet has number zero.
39138 The packet's offset in the trace stream.
39139 @item Packet opcode and payload
39143 @kindex maint btrace clear-packet-history
39144 @item maint btrace clear-packet-history
39145 Discards the cached packet history printed by the @samp{maint btrace
39146 packet-history} command. The history will be computed again when
39149 @kindex maint btrace clear
39150 @item maint btrace clear
39151 Discard the branch trace data. The data will be fetched anew and the
39152 branch trace will be recomputed when needed.
39154 This implicitly truncates the branch trace to a single branch trace
39155 buffer. When updating branch trace incrementally, the branch trace
39156 available to @value{GDBN} may be bigger than a single branch trace
39159 @kindex maint set btrace pt skip-pad
39160 @item maint set btrace pt skip-pad
39161 @kindex maint show btrace pt skip-pad
39162 @item maint show btrace pt skip-pad
39163 Control whether @value{GDBN} will skip PAD packets when computing the
39166 @kindex maint info jit
39167 @item maint info jit
39168 Print information about JIT code objects loaded in the current inferior.
39170 @kindex set displaced-stepping
39171 @kindex show displaced-stepping
39172 @cindex displaced stepping support
39173 @cindex out-of-line single-stepping
39174 @item set displaced-stepping
39175 @itemx show displaced-stepping
39176 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39177 if the target supports it. Displaced stepping is a way to single-step
39178 over breakpoints without removing them from the inferior, by executing
39179 an out-of-line copy of the instruction that was originally at the
39180 breakpoint location. It is also known as out-of-line single-stepping.
39183 @item set displaced-stepping on
39184 If the target architecture supports it, @value{GDBN} will use
39185 displaced stepping to step over breakpoints.
39187 @item set displaced-stepping off
39188 @value{GDBN} will not use displaced stepping to step over breakpoints,
39189 even if such is supported by the target architecture.
39191 @cindex non-stop mode, and @samp{set displaced-stepping}
39192 @item set displaced-stepping auto
39193 This is the default mode. @value{GDBN} will use displaced stepping
39194 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39195 architecture supports displaced stepping.
39198 @kindex maint check-psymtabs
39199 @item maint check-psymtabs
39200 Check the consistency of currently expanded psymtabs versus symtabs.
39201 Use this to check, for example, whether a symbol is in one but not the other.
39203 @kindex maint check-symtabs
39204 @item maint check-symtabs
39205 Check the consistency of currently expanded symtabs.
39207 @kindex maint expand-symtabs
39208 @item maint expand-symtabs [@var{regexp}]
39209 Expand symbol tables.
39210 If @var{regexp} is specified, only expand symbol tables for file
39211 names matching @var{regexp}.
39213 @kindex maint set catch-demangler-crashes
39214 @kindex maint show catch-demangler-crashes
39215 @cindex demangler crashes
39216 @item maint set catch-demangler-crashes [on|off]
39217 @itemx maint show catch-demangler-crashes
39218 Control whether @value{GDBN} should attempt to catch crashes in the
39219 symbol name demangler. The default is to attempt to catch crashes.
39220 If enabled, the first time a crash is caught, a core file is created,
39221 the offending symbol is displayed and the user is presented with the
39222 option to terminate the current session.
39224 @kindex maint cplus first_component
39225 @item maint cplus first_component @var{name}
39226 Print the first C@t{++} class/namespace component of @var{name}.
39228 @kindex maint cplus namespace
39229 @item maint cplus namespace
39230 Print the list of possible C@t{++} namespaces.
39232 @kindex maint deprecate
39233 @kindex maint undeprecate
39234 @cindex deprecated commands
39235 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39236 @itemx maint undeprecate @var{command}
39237 Deprecate or undeprecate the named @var{command}. Deprecated commands
39238 cause @value{GDBN} to issue a warning when you use them. The optional
39239 argument @var{replacement} says which newer command should be used in
39240 favor of the deprecated one; if it is given, @value{GDBN} will mention
39241 the replacement as part of the warning.
39243 @kindex maint dump-me
39244 @item maint dump-me
39245 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39246 Cause a fatal signal in the debugger and force it to dump its core.
39247 This is supported only on systems which support aborting a program
39248 with the @code{SIGQUIT} signal.
39250 @kindex maint internal-error
39251 @kindex maint internal-warning
39252 @kindex maint demangler-warning
39253 @cindex demangler crashes
39254 @item maint internal-error @r{[}@var{message-text}@r{]}
39255 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39256 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39258 Cause @value{GDBN} to call the internal function @code{internal_error},
39259 @code{internal_warning} or @code{demangler_warning} and hence behave
39260 as though an internal problem has been detected. In addition to
39261 reporting the internal problem, these functions give the user the
39262 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39263 and @code{internal_warning}) create a core file of the current
39264 @value{GDBN} session.
39266 These commands take an optional parameter @var{message-text} that is
39267 used as the text of the error or warning message.
39269 Here's an example of using @code{internal-error}:
39272 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39273 @dots{}/maint.c:121: internal-error: testing, 1, 2
39274 A problem internal to GDB has been detected. Further
39275 debugging may prove unreliable.
39276 Quit this debugging session? (y or n) @kbd{n}
39277 Create a core file? (y or n) @kbd{n}
39281 @cindex @value{GDBN} internal error
39282 @cindex internal errors, control of @value{GDBN} behavior
39283 @cindex demangler crashes
39285 @kindex maint set internal-error
39286 @kindex maint show internal-error
39287 @kindex maint set internal-warning
39288 @kindex maint show internal-warning
39289 @kindex maint set demangler-warning
39290 @kindex maint show demangler-warning
39291 @item maint set internal-error @var{action} [ask|yes|no]
39292 @itemx maint show internal-error @var{action}
39293 @itemx maint set internal-warning @var{action} [ask|yes|no]
39294 @itemx maint show internal-warning @var{action}
39295 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39296 @itemx maint show demangler-warning @var{action}
39297 When @value{GDBN} reports an internal problem (error or warning) it
39298 gives the user the opportunity to both quit @value{GDBN} and create a
39299 core file of the current @value{GDBN} session. These commands let you
39300 override the default behaviour for each particular @var{action},
39301 described in the table below.
39305 You can specify that @value{GDBN} should always (yes) or never (no)
39306 quit. The default is to ask the user what to do.
39309 You can specify that @value{GDBN} should always (yes) or never (no)
39310 create a core file. The default is to ask the user what to do. Note
39311 that there is no @code{corefile} option for @code{demangler-warning}:
39312 demangler warnings always create a core file and this cannot be
39316 @kindex maint set internal-error
39317 @kindex maint show internal-error
39318 @kindex maint set internal-warning
39319 @kindex maint show internal-warning
39320 @item maint set internal-error backtrace @r{[}on|off@r{]}
39321 @itemx maint show internal-error backtrace
39322 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
39323 @itemx maint show internal-warning backtrace
39324 When @value{GDBN} reports an internal problem (error or warning) it is
39325 possible to have a backtrace of @value{GDBN} printed to the standard
39326 error stream. This is @samp{on} by default for @code{internal-error}
39327 and @samp{off} by default for @code{internal-warning}.
39329 @anchor{maint packet}
39330 @kindex maint packet
39331 @item maint packet @var{text}
39332 If @value{GDBN} is talking to an inferior via the serial protocol,
39333 then this command sends the string @var{text} to the inferior, and
39334 displays the response packet. @value{GDBN} supplies the initial
39335 @samp{$} character, the terminating @samp{#} character, and the
39338 Any non-printable characters in the reply are printed as escaped hex,
39339 e.g. @samp{\x00}, @samp{\x01}, etc.
39341 @kindex maint print architecture
39342 @item maint print architecture @r{[}@var{file}@r{]}
39343 Print the entire architecture configuration. The optional argument
39344 @var{file} names the file where the output goes.
39346 @kindex maint print c-tdesc
39347 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39348 Print the target description (@pxref{Target Descriptions}) as
39349 a C source file. By default, the target description is for the current
39350 target, but if the optional argument @var{file} is provided, that file
39351 is used to produce the description. The @var{file} should be an XML
39352 document, of the form described in @ref{Target Description Format}.
39353 The created source file is built into @value{GDBN} when @value{GDBN} is
39354 built again. This command is used by developers after they add or
39355 modify XML target descriptions.
39357 When the optional flag @samp{-single-feature} is provided then the
39358 target description being processed (either the default, or from
39359 @var{file}) must only contain a single feature. The source file
39360 produced is different in this case.
39362 @kindex maint print xml-tdesc
39363 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39364 Print the target description (@pxref{Target Descriptions}) as an XML
39365 file. By default print the target description for the current target,
39366 but if the optional argument @var{file} is provided, then that file is
39367 read in by GDB and then used to produce the description. The
39368 @var{file} should be an XML document, of the form described in
39369 @ref{Target Description Format}.
39371 @kindex maint check xml-descriptions
39372 @item maint check xml-descriptions @var{dir}
39373 Check that the target descriptions dynamically created by @value{GDBN}
39374 equal the descriptions created from XML files found in @var{dir}.
39376 @anchor{maint check libthread-db}
39377 @kindex maint check libthread-db
39378 @item maint check libthread-db
39379 Run integrity checks on the current inferior's thread debugging
39380 library. This exercises all @code{libthread_db} functionality used by
39381 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39382 @code{proc_service} functions provided by @value{GDBN} that
39383 @code{libthread_db} uses. Note that parts of the test may be skipped
39384 on some platforms when debugging core files.
39386 @kindex maint print core-file-backed-mappings
39387 @cindex memory address space mappings
39388 @item maint print core-file-backed-mappings
39389 Print the file-backed mappings which were loaded from a core file note.
39390 This output represents state internal to @value{GDBN} and should be
39391 similar to the mappings displayed by the @code{info proc mappings}
39394 @kindex maint print dummy-frames
39395 @item maint print dummy-frames
39396 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
39399 (@value{GDBP}) @kbd{b add}
39401 (@value{GDBP}) @kbd{print add(2,3)}
39402 Breakpoint 2, add (a=2, b=3) at @dots{}
39404 The program being debugged stopped while in a function called from GDB.
39406 (@value{GDBP}) @kbd{maint print dummy-frames}
39407 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
39411 Takes an optional file parameter.
39413 @kindex maint print registers
39414 @kindex maint print raw-registers
39415 @kindex maint print cooked-registers
39416 @kindex maint print register-groups
39417 @kindex maint print remote-registers
39418 @item maint print registers @r{[}@var{file}@r{]}
39419 @itemx maint print raw-registers @r{[}@var{file}@r{]}
39420 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
39421 @itemx maint print register-groups @r{[}@var{file}@r{]}
39422 @itemx maint print remote-registers @r{[}@var{file}@r{]}
39423 Print @value{GDBN}'s internal register data structures.
39425 The command @code{maint print raw-registers} includes the contents of
39426 the raw register cache; the command @code{maint print
39427 cooked-registers} includes the (cooked) value of all registers,
39428 including registers which aren't available on the target nor visible
39429 to user; the command @code{maint print register-groups} includes the
39430 groups that each register is a member of; and the command @code{maint
39431 print remote-registers} includes the remote target's register numbers
39432 and offsets in the `G' packets.
39434 These commands take an optional parameter, a file name to which to
39435 write the information.
39437 @kindex maint print reggroups
39438 @item maint print reggroups @r{[}@var{file}@r{]}
39439 Print @value{GDBN}'s internal register group data structures. The
39440 optional argument @var{file} tells to what file to write the
39443 The register groups info looks like this:
39446 (@value{GDBP}) @kbd{maint print reggroups}
39457 @kindex maint flush register-cache
39459 @cindex register cache, flushing
39460 @item maint flush register-cache
39462 Flush the contents of the register cache and as a consequence the
39463 frame cache. This command is useful when debugging issues related to
39464 register fetching, or frame unwinding. The command @code{flushregs}
39465 is deprecated in favor of @code{maint flush register-cache}.
39467 @kindex maint print objfiles
39468 @cindex info for known object files
39469 @item maint print objfiles @r{[}@var{regexp}@r{]}
39470 Print a dump of all known object files.
39471 If @var{regexp} is specified, only print object files whose names
39472 match @var{regexp}. For each object file, this command prints its name,
39473 address in memory, and all of its psymtabs and symtabs.
39475 @kindex maint print user-registers
39476 @cindex user registers
39477 @item maint print user-registers
39478 List all currently available @dfn{user registers}. User registers
39479 typically provide alternate names for actual hardware registers. They
39480 include the four ``standard'' registers @code{$fp}, @code{$pc},
39481 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
39482 registers can be used in expressions in the same way as the canonical
39483 register names, but only the latter are listed by the @code{info
39484 registers} and @code{maint print registers} commands.
39486 @kindex maint print section-scripts
39487 @cindex info for known .debug_gdb_scripts-loaded scripts
39488 @item maint print section-scripts [@var{regexp}]
39489 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
39490 If @var{regexp} is specified, only print scripts loaded by object files
39491 matching @var{regexp}.
39492 For each script, this command prints its name as specified in the objfile,
39493 and the full path if known.
39494 @xref{dotdebug_gdb_scripts section}.
39496 @kindex maint print statistics
39497 @cindex bcache statistics
39498 @item maint print statistics
39499 This command prints, for each object file in the program, various data
39500 about that object file followed by the byte cache (@dfn{bcache})
39501 statistics for the object file. The objfile data includes the number
39502 of minimal, partial, full, and stabs symbols, the number of types
39503 defined by the objfile, the number of as yet unexpanded psym tables,
39504 the number of line tables and string tables, and the amount of memory
39505 used by the various tables. The bcache statistics include the counts,
39506 sizes, and counts of duplicates of all and unique objects, max,
39507 average, and median entry size, total memory used and its overhead and
39508 savings, and various measures of the hash table size and chain
39511 @kindex maint print target-stack
39512 @cindex target stack description
39513 @item maint print target-stack
39514 A @dfn{target} is an interface between the debugger and a particular
39515 kind of file or process. Targets can be stacked in @dfn{strata},
39516 so that more than one target can potentially respond to a request.
39517 In particular, memory accesses will walk down the stack of targets
39518 until they find a target that is interested in handling that particular
39521 This command prints a short description of each layer that was pushed on
39522 the @dfn{target stack}, starting from the top layer down to the bottom one.
39524 @kindex maint print type
39525 @cindex type chain of a data type
39526 @item maint print type @var{expr}
39527 Print the type chain for a type specified by @var{expr}. The argument
39528 can be either a type name or a symbol. If it is a symbol, the type of
39529 that symbol is described. The type chain produced by this command is
39530 a recursive definition of the data type as stored in @value{GDBN}'s
39531 data structures, including its flags and contained types.
39533 @kindex maint selftest
39535 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
39536 Run any self tests that were compiled in to @value{GDBN}. This will
39537 print a message showing how many tests were run, and how many failed.
39538 If a @var{filter} is passed, only the tests with @var{filter} in their
39539 name will be ran. If @code{-verbose} is passed, the self tests can be
39542 @kindex maint set selftest verbose
39543 @kindex maint show selftest verbose
39545 @item maint set selftest verbose
39546 @item maint show selftest verbose
39547 Control whether self tests are run verbosely or not.
39549 @kindex maint info selftests
39551 @item maint info selftests
39552 List the selftests compiled in to @value{GDBN}.
39554 @kindex maint set dwarf always-disassemble
39555 @kindex maint show dwarf always-disassemble
39556 @item maint set dwarf always-disassemble
39557 @item maint show dwarf always-disassemble
39558 Control the behavior of @code{info address} when using DWARF debugging
39561 The default is @code{off}, which means that @value{GDBN} should try to
39562 describe a variable's location in an easily readable format. When
39563 @code{on}, @value{GDBN} will instead display the DWARF location
39564 expression in an assembly-like format. Note that some locations are
39565 too complex for @value{GDBN} to describe simply; in this case you will
39566 always see the disassembly form.
39568 Here is an example of the resulting disassembly:
39571 (gdb) info addr argc
39572 Symbol "argc" is a complex DWARF expression:
39576 For more information on these expressions, see
39577 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39579 @kindex maint set dwarf max-cache-age
39580 @kindex maint show dwarf max-cache-age
39581 @item maint set dwarf max-cache-age
39582 @itemx maint show dwarf max-cache-age
39583 Control the DWARF compilation unit cache.
39585 @cindex DWARF compilation units cache
39586 In object files with inter-compilation-unit references, such as those
39587 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39588 reader needs to frequently refer to previously read compilation units.
39589 This setting controls how long a compilation unit will remain in the
39590 cache if it is not referenced. A higher limit means that cached
39591 compilation units will be stored in memory longer, and more total
39592 memory will be used. Setting it to zero disables caching, which will
39593 slow down @value{GDBN} startup, but reduce memory consumption.
39595 @kindex maint set dwarf unwinders
39596 @kindex maint show dwarf unwinders
39597 @item maint set dwarf unwinders
39598 @itemx maint show dwarf unwinders
39599 Control use of the DWARF frame unwinders.
39601 @cindex DWARF frame unwinders
39602 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39603 frame unwinders to build the backtrace. Many of these targets will
39604 also have a second mechanism for building the backtrace for use in
39605 cases where DWARF information is not available, this second mechanism
39606 is often an analysis of a function's prologue.
39608 In order to extend testing coverage of the second level stack
39609 unwinding mechanisms it is helpful to be able to disable the DWARF
39610 stack unwinders, this can be done with this switch.
39612 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39613 advisable, there are cases that are better handled through DWARF than
39614 prologue analysis, and the debug experience is likely to be better
39615 with the DWARF frame unwinders enabled.
39617 If DWARF frame unwinders are not supported for a particular target
39618 architecture, then enabling this flag does not cause them to be used.
39620 @kindex maint set worker-threads
39621 @kindex maint show worker-threads
39622 @item maint set worker-threads
39623 @item maint show worker-threads
39624 Control the number of worker threads that may be used by @value{GDBN}.
39625 On capable hosts, @value{GDBN} may use multiple threads to speed up
39626 certain CPU-intensive operations, such as demangling symbol names.
39627 While the number of threads used by @value{GDBN} may vary, this
39628 command can be used to set an upper bound on this number. The default
39629 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39630 number. Note that this only controls worker threads started by
39631 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39634 @kindex maint set profile
39635 @kindex maint show profile
39636 @cindex profiling GDB
39637 @item maint set profile
39638 @itemx maint show profile
39639 Control profiling of @value{GDBN}.
39641 Profiling will be disabled until you use the @samp{maint set profile}
39642 command to enable it. When you enable profiling, the system will begin
39643 collecting timing and execution count data; when you disable profiling or
39644 exit @value{GDBN}, the results will be written to a log file. Remember that
39645 if you use profiling, @value{GDBN} will overwrite the profiling log file
39646 (often called @file{gmon.out}). If you have a record of important profiling
39647 data in a @file{gmon.out} file, be sure to move it to a safe location.
39649 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
39650 compiled with the @samp{-pg} compiler option.
39652 @kindex maint set show-debug-regs
39653 @kindex maint show show-debug-regs
39654 @cindex hardware debug registers
39655 @item maint set show-debug-regs
39656 @itemx maint show show-debug-regs
39657 Control whether to show variables that mirror the hardware debug
39658 registers. Use @code{on} to enable, @code{off} to disable. If
39659 enabled, the debug registers values are shown when @value{GDBN} inserts or
39660 removes a hardware breakpoint or watchpoint, and when the inferior
39661 triggers a hardware-assisted breakpoint or watchpoint.
39663 @kindex maint set show-all-tib
39664 @kindex maint show show-all-tib
39665 @item maint set show-all-tib
39666 @itemx maint show show-all-tib
39667 Control whether to show all non zero areas within a 1k block starting
39668 at thread local base, when using the @samp{info w32 thread-information-block}
39671 @kindex maint set target-async
39672 @kindex maint show target-async
39673 @item maint set target-async
39674 @itemx maint show target-async
39675 This controls whether @value{GDBN} targets operate in synchronous or
39676 asynchronous mode (@pxref{Background Execution}). Normally the
39677 default is asynchronous, if it is available; but this can be changed
39678 to more easily debug problems occurring only in synchronous mode.
39680 @kindex maint set target-non-stop @var{mode} [on|off|auto]
39681 @kindex maint show target-non-stop
39682 @item maint set target-non-stop
39683 @itemx maint show target-non-stop
39685 This controls whether @value{GDBN} targets always operate in non-stop
39686 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
39687 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
39688 if supported by the target.
39691 @item maint set target-non-stop auto
39692 This is the default mode. @value{GDBN} controls the target in
39693 non-stop mode if the target supports it.
39695 @item maint set target-non-stop on
39696 @value{GDBN} controls the target in non-stop mode even if the target
39697 does not indicate support.
39699 @item maint set target-non-stop off
39700 @value{GDBN} does not control the target in non-stop mode even if the
39701 target supports it.
39704 @kindex maint set tui-resize-message
39705 @kindex maint show tui-resize-message
39706 @item maint set tui-resize-message
39707 @item maint show tui-resize-message
39708 Control whether @value{GDBN} displays a message each time the terminal
39709 is resized when in TUI mode. The default is @code{off}, which means
39710 that @value{GDBN} is silent during resizes. When @code{on},
39711 @value{GDBN} will display a message after a resize is completed; the
39712 message will include a number indicating how many times the terminal
39713 has been resized. This setting is intended for use by the test suite,
39714 where it would otherwise be difficult to determine when a resize and
39715 refresh has been completed.
39717 @kindex maint set per-command
39718 @kindex maint show per-command
39719 @item maint set per-command
39720 @itemx maint show per-command
39721 @cindex resources used by commands
39723 @value{GDBN} can display the resources used by each command.
39724 This is useful in debugging performance problems.
39727 @item maint set per-command space [on|off]
39728 @itemx maint show per-command space
39729 Enable or disable the printing of the memory used by GDB for each command.
39730 If enabled, @value{GDBN} will display how much memory each command
39731 took, following the command's own output.
39732 This can also be requested by invoking @value{GDBN} with the
39733 @option{--statistics} command-line switch (@pxref{Mode Options}).
39735 @item maint set per-command time [on|off]
39736 @itemx maint show per-command time
39737 Enable or disable the printing of the execution time of @value{GDBN}
39739 If enabled, @value{GDBN} will display how much time it
39740 took to execute each command, following the command's own output.
39741 Both CPU time and wallclock time are printed.
39742 Printing both is useful when trying to determine whether the cost is
39743 CPU or, e.g., disk/network latency.
39744 Note that the CPU time printed is for @value{GDBN} only, it does not include
39745 the execution time of the inferior because there's no mechanism currently
39746 to compute how much time was spent by @value{GDBN} and how much time was
39747 spent by the program been debugged.
39748 This can also be requested by invoking @value{GDBN} with the
39749 @option{--statistics} command-line switch (@pxref{Mode Options}).
39751 @item maint set per-command symtab [on|off]
39752 @itemx maint show per-command symtab
39753 Enable or disable the printing of basic symbol table statistics
39755 If enabled, @value{GDBN} will display the following information:
39759 number of symbol tables
39761 number of primary symbol tables
39763 number of blocks in the blockvector
39767 @kindex maint set check-libthread-db
39768 @kindex maint show check-libthread-db
39769 @item maint set check-libthread-db [on|off]
39770 @itemx maint show check-libthread-db
39771 Control whether @value{GDBN} should run integrity checks on inferior
39772 specific thread debugging libraries as they are loaded. The default
39773 is not to perform such checks. If any check fails @value{GDBN} will
39774 unload the library and continue searching for a suitable candidate as
39775 described in @ref{set libthread-db-search-path}. For more information
39776 about the tests, see @ref{maint check libthread-db}.
39778 @kindex maint space
39779 @cindex memory used by commands
39780 @item maint space @var{value}
39781 An alias for @code{maint set per-command space}.
39782 A non-zero value enables it, zero disables it.
39785 @cindex time of command execution
39786 @item maint time @var{value}
39787 An alias for @code{maint set per-command time}.
39788 A non-zero value enables it, zero disables it.
39790 @kindex maint translate-address
39791 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
39792 Find the symbol stored at the location specified by the address
39793 @var{addr} and an optional section name @var{section}. If found,
39794 @value{GDBN} prints the name of the closest symbol and an offset from
39795 the symbol's location to the specified address. This is similar to
39796 the @code{info address} command (@pxref{Symbols}), except that this
39797 command also allows to find symbols in other sections.
39799 If section was not specified, the section in which the symbol was found
39800 is also printed. For dynamically linked executables, the name of
39801 executable or shared library containing the symbol is printed as well.
39803 @kindex maint test-options
39804 @item maint test-options require-delimiter
39805 @itemx maint test-options unknown-is-error
39806 @itemx maint test-options unknown-is-operand
39807 These commands are used by the testsuite to validate the command
39808 options framework. The @code{require-delimiter} variant requires a
39809 double-dash delimiter to indicate end of options. The
39810 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
39811 @code{unknown-is-error} variant throws an error on unknown option,
39812 while @code{unknown-is-operand} treats unknown options as the start of
39813 the command's operands. When run, the commands output the result of
39814 the processed options. When completed, the commands store the
39815 internal result of completion in a variable exposed by the @code{maint
39816 show test-options-completion-result} command.
39818 @kindex maint show test-options-completion-result
39819 @item maint show test-options-completion-result
39820 Shows the result of completing the @code{maint test-options}
39821 subcommands. This is used by the testsuite to validate completion
39822 support in the command options framework.
39824 @kindex maint set test-settings
39825 @kindex maint show test-settings
39826 @item maint set test-settings @var{kind}
39827 @itemx maint show test-settings @var{kind}
39828 These are representative commands for each @var{kind} of setting type
39829 @value{GDBN} supports. They are used by the testsuite for exercising
39830 the settings infrastructure.
39832 @kindex maint set backtrace-on-fatal-signal
39833 @kindex maint show backtrace-on-fatal-signal
39834 @item maint set backtrace-on-fatal-signal [on|off]
39835 @itemx maint show backtrace-on-fatal-signal
39836 When this setting is @code{on}, if @value{GDBN} itself terminates with
39837 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
39838 printed to the standard error stream. This backtrace can be used to
39839 help diagnose crashes within @value{GDBN} in situations where a user
39840 is unable to share a corefile with the @value{GDBN} developers.
39842 If the functionality to provide this backtrace is not available for
39843 the platform on which GDB is running then this feature will be
39844 @code{off} by default, and attempting to turn this feature on will
39847 For platforms that do support creating the backtrace this feature is
39848 @code{on} by default.
39851 @item maint with @var{setting} [@var{value}] [-- @var{command}]
39852 Like the @code{with} command, but works with @code{maintenance set}
39853 variables. This is used by the testsuite to exercise the @code{with}
39854 command's infrastructure.
39858 The following command is useful for non-interactive invocations of
39859 @value{GDBN}, such as in the test suite.
39862 @item set watchdog @var{nsec}
39863 @kindex set watchdog
39864 @cindex watchdog timer
39865 @cindex timeout for commands
39866 Set the maximum number of seconds @value{GDBN} will wait for the
39867 target operation to finish. If this time expires, @value{GDBN}
39868 reports and error and the command is aborted.
39870 @item show watchdog
39871 Show the current setting of the target wait timeout.
39874 @node Remote Protocol
39875 @appendix @value{GDBN} Remote Serial Protocol
39880 * Stop Reply Packets::
39881 * General Query Packets::
39882 * Architecture-Specific Protocol Details::
39883 * Tracepoint Packets::
39884 * Host I/O Packets::
39886 * Notification Packets::
39887 * Remote Non-Stop::
39888 * Packet Acknowledgment::
39890 * File-I/O Remote Protocol Extension::
39891 * Library List Format::
39892 * Library List Format for SVR4 Targets::
39893 * Memory Map Format::
39894 * Thread List Format::
39895 * Traceframe Info Format::
39896 * Branch Trace Format::
39897 * Branch Trace Configuration Format::
39903 There may be occasions when you need to know something about the
39904 protocol---for example, if there is only one serial port to your target
39905 machine, you might want your program to do something special if it
39906 recognizes a packet meant for @value{GDBN}.
39908 In the examples below, @samp{->} and @samp{<-} are used to indicate
39909 transmitted and received data, respectively.
39911 @cindex protocol, @value{GDBN} remote serial
39912 @cindex serial protocol, @value{GDBN} remote
39913 @cindex remote serial protocol
39914 All @value{GDBN} commands and responses (other than acknowledgments
39915 and notifications, see @ref{Notification Packets}) are sent as a
39916 @var{packet}. A @var{packet} is introduced with the character
39917 @samp{$}, the actual @var{packet-data}, and the terminating character
39918 @samp{#} followed by a two-digit @var{checksum}:
39921 @code{$}@var{packet-data}@code{#}@var{checksum}
39925 @cindex checksum, for @value{GDBN} remote
39927 The two-digit @var{checksum} is computed as the modulo 256 sum of all
39928 characters between the leading @samp{$} and the trailing @samp{#} (an
39929 eight bit unsigned checksum).
39931 Implementors should note that prior to @value{GDBN} 5.0 the protocol
39932 specification also included an optional two-digit @var{sequence-id}:
39935 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
39938 @cindex sequence-id, for @value{GDBN} remote
39940 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
39941 has never output @var{sequence-id}s. Stubs that handle packets added
39942 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
39944 When either the host or the target machine receives a packet, the first
39945 response expected is an acknowledgment: either @samp{+} (to indicate
39946 the package was received correctly) or @samp{-} (to request
39950 -> @code{$}@var{packet-data}@code{#}@var{checksum}
39955 The @samp{+}/@samp{-} acknowledgments can be disabled
39956 once a connection is established.
39957 @xref{Packet Acknowledgment}, for details.
39959 The host (@value{GDBN}) sends @var{command}s, and the target (the
39960 debugging stub incorporated in your program) sends a @var{response}. In
39961 the case of step and continue @var{command}s, the response is only sent
39962 when the operation has completed, and the target has again stopped all
39963 threads in all attached processes. This is the default all-stop mode
39964 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
39965 execution mode; see @ref{Remote Non-Stop}, for details.
39967 @var{packet-data} consists of a sequence of characters with the
39968 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
39971 @cindex remote protocol, field separator
39972 Fields within the packet should be separated using @samp{,} @samp{;} or
39973 @samp{:}. Except where otherwise noted all numbers are represented in
39974 @sc{hex} with leading zeros suppressed.
39976 Implementors should note that prior to @value{GDBN} 5.0, the character
39977 @samp{:} could not appear as the third character in a packet (as it
39978 would potentially conflict with the @var{sequence-id}).
39980 @cindex remote protocol, binary data
39981 @anchor{Binary Data}
39982 Binary data in most packets is encoded either as two hexadecimal
39983 digits per byte of binary data. This allowed the traditional remote
39984 protocol to work over connections which were only seven-bit clean.
39985 Some packets designed more recently assume an eight-bit clean
39986 connection, and use a more efficient encoding to send and receive
39989 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
39990 as an escape character. Any escaped byte is transmitted as the escape
39991 character followed by the original character XORed with @code{0x20}.
39992 For example, the byte @code{0x7d} would be transmitted as the two
39993 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
39994 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
39995 @samp{@}}) must always be escaped. Responses sent by the stub
39996 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
39997 is not interpreted as the start of a run-length encoded sequence
40000 Response @var{data} can be run-length encoded to save space.
40001 Run-length encoding replaces runs of identical characters with one
40002 instance of the repeated character, followed by a @samp{*} and a
40003 repeat count. The repeat count is itself sent encoded, to avoid
40004 binary characters in @var{data}: a value of @var{n} is sent as
40005 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40006 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40007 code 32) for a repeat count of 3. (This is because run-length
40008 encoding starts to win for counts 3 or more.) Thus, for example,
40009 @samp{0* } is a run-length encoding of ``0000'': the space character
40010 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40013 The printable characters @samp{#} and @samp{$} or with a numeric value
40014 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40015 seven repeats (@samp{$}) can be expanded using a repeat count of only
40016 five (@samp{"}). For example, @samp{00000000} can be encoded as
40019 The error response returned for some packets includes a two character
40020 error number. That number is not well defined.
40022 @cindex empty response, for unsupported packets
40023 For any @var{command} not supported by the stub, an empty response
40024 (@samp{$#00}) should be returned. That way it is possible to extend the
40025 protocol. A newer @value{GDBN} can tell if a packet is supported based
40028 At a minimum, a stub is required to support the @samp{?} command to
40029 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40030 commands for register access, and the @samp{m} and @samp{M} commands
40031 for memory access. Stubs that only control single-threaded targets
40032 can implement run control with the @samp{c} (continue) command, and if
40033 the target architecture supports hardware-assisted single-stepping,
40034 the @samp{s} (step) command. Stubs that support multi-threading
40035 targets should support the @samp{vCont} command. All other commands
40041 The following table provides a complete list of all currently defined
40042 @var{command}s and their corresponding response @var{data}.
40043 @xref{File-I/O Remote Protocol Extension}, for details about the File
40044 I/O extension of the remote protocol.
40046 Each packet's description has a template showing the packet's overall
40047 syntax, followed by an explanation of the packet's meaning. We
40048 include spaces in some of the templates for clarity; these are not
40049 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40050 separate its components. For example, a template like @samp{foo
40051 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40052 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40053 @var{baz}. @value{GDBN} does not transmit a space character between the
40054 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40057 @cindex @var{thread-id}, in remote protocol
40058 @anchor{thread-id syntax}
40059 Several packets and replies include a @var{thread-id} field to identify
40060 a thread. Normally these are positive numbers with a target-specific
40061 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40062 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40065 In addition, the remote protocol supports a multiprocess feature in
40066 which the @var{thread-id} syntax is extended to optionally include both
40067 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40068 The @var{pid} (process) and @var{tid} (thread) components each have the
40069 format described above: a positive number with target-specific
40070 interpretation formatted as a big-endian hex string, literal @samp{-1}
40071 to indicate all processes or threads (respectively), or @samp{0} to
40072 indicate an arbitrary process or thread. Specifying just a process, as
40073 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40074 error to specify all processes but a specific thread, such as
40075 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40076 for those packets and replies explicitly documented to include a process
40077 ID, rather than a @var{thread-id}.
40079 The multiprocess @var{thread-id} syntax extensions are only used if both
40080 @value{GDBN} and the stub report support for the @samp{multiprocess}
40081 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40084 Note that all packet forms beginning with an upper- or lower-case
40085 letter, other than those described here, are reserved for future use.
40087 Here are the packet descriptions.
40092 @cindex @samp{!} packet
40093 @anchor{extended mode}
40094 Enable extended mode. In extended mode, the remote server is made
40095 persistent. The @samp{R} packet is used to restart the program being
40101 The remote target both supports and has enabled extended mode.
40105 @cindex @samp{?} packet
40107 This is sent when connection is first established to query the reason
40108 the target halted. The reply is the same as for step and continue.
40109 This packet has a special interpretation when the target is in
40110 non-stop mode; see @ref{Remote Non-Stop}.
40113 @xref{Stop Reply Packets}, for the reply specifications.
40115 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40116 @cindex @samp{A} packet
40117 Initialized @code{argv[]} array passed into program. @var{arglen}
40118 specifies the number of bytes in the hex encoded byte stream
40119 @var{arg}. See @code{gdbserver} for more details.
40124 The arguments were set.
40130 @cindex @samp{b} packet
40131 (Don't use this packet; its behavior is not well-defined.)
40132 Change the serial line speed to @var{baud}.
40134 JTC: @emph{When does the transport layer state change? When it's
40135 received, or after the ACK is transmitted. In either case, there are
40136 problems if the command or the acknowledgment packet is dropped.}
40138 Stan: @emph{If people really wanted to add something like this, and get
40139 it working for the first time, they ought to modify ser-unix.c to send
40140 some kind of out-of-band message to a specially-setup stub and have the
40141 switch happen "in between" packets, so that from remote protocol's point
40142 of view, nothing actually happened.}
40144 @item B @var{addr},@var{mode}
40145 @cindex @samp{B} packet
40146 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40147 breakpoint at @var{addr}.
40149 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40150 (@pxref{insert breakpoint or watchpoint packet}).
40152 @cindex @samp{bc} packet
40155 Backward continue. Execute the target system in reverse. No parameter.
40156 @xref{Reverse Execution}, for more information.
40159 @xref{Stop Reply Packets}, for the reply specifications.
40161 @cindex @samp{bs} packet
40164 Backward single step. Execute one instruction in reverse. No parameter.
40165 @xref{Reverse Execution}, for more information.
40168 @xref{Stop Reply Packets}, for the reply specifications.
40170 @item c @r{[}@var{addr}@r{]}
40171 @cindex @samp{c} packet
40172 Continue at @var{addr}, which is the address to resume. If @var{addr}
40173 is omitted, resume at current address.
40175 This packet is deprecated for multi-threading support. @xref{vCont
40179 @xref{Stop Reply Packets}, for the reply specifications.
40181 @item C @var{sig}@r{[};@var{addr}@r{]}
40182 @cindex @samp{C} packet
40183 Continue with signal @var{sig} (hex signal number). If
40184 @samp{;@var{addr}} is omitted, resume at same address.
40186 This packet is deprecated for multi-threading support. @xref{vCont
40190 @xref{Stop Reply Packets}, for the reply specifications.
40193 @cindex @samp{d} packet
40196 Don't use this packet; instead, define a general set packet
40197 (@pxref{General Query Packets}).
40201 @cindex @samp{D} packet
40202 The first form of the packet is used to detach @value{GDBN} from the
40203 remote system. It is sent to the remote target
40204 before @value{GDBN} disconnects via the @code{detach} command.
40206 The second form, including a process ID, is used when multiprocess
40207 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40208 detach only a specific process. The @var{pid} is specified as a
40209 big-endian hex string.
40219 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40220 @cindex @samp{F} packet
40221 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40222 This is part of the File-I/O protocol extension. @xref{File-I/O
40223 Remote Protocol Extension}, for the specification.
40226 @anchor{read registers packet}
40227 @cindex @samp{g} packet
40228 Read general registers.
40232 @item @var{XX@dots{}}
40233 Each byte of register data is described by two hex digits. The bytes
40234 with the register are transmitted in target byte order. The size of
40235 each register and their position within the @samp{g} packet are
40236 determined by the @value{GDBN} internal gdbarch functions
40237 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40239 When reading registers from a trace frame (@pxref{Analyze Collected
40240 Data,,Using the Collected Data}), the stub may also return a string of
40241 literal @samp{x}'s in place of the register data digits, to indicate
40242 that the corresponding register has not been collected, thus its value
40243 is unavailable. For example, for an architecture with 4 registers of
40244 4 bytes each, the following reply indicates to @value{GDBN} that
40245 registers 0 and 2 have not been collected, while registers 1 and 3
40246 have been collected, and both have zero value:
40250 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40257 @item G @var{XX@dots{}}
40258 @cindex @samp{G} packet
40259 Write general registers. @xref{read registers packet}, for a
40260 description of the @var{XX@dots{}} data.
40270 @item H @var{op} @var{thread-id}
40271 @cindex @samp{H} packet
40272 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40273 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40274 should be @samp{c} for step and continue operations (note that this
40275 is deprecated, supporting the @samp{vCont} command is a better
40276 option), and @samp{g} for other operations. The thread designator
40277 @var{thread-id} has the format and interpretation described in
40278 @ref{thread-id syntax}.
40289 @c 'H': How restrictive (or permissive) is the thread model. If a
40290 @c thread is selected and stopped, are other threads allowed
40291 @c to continue to execute? As I mentioned above, I think the
40292 @c semantics of each command when a thread is selected must be
40293 @c described. For example:
40295 @c 'g': If the stub supports threads and a specific thread is
40296 @c selected, returns the register block from that thread;
40297 @c otherwise returns current registers.
40299 @c 'G' If the stub supports threads and a specific thread is
40300 @c selected, sets the registers of the register block of
40301 @c that thread; otherwise sets current registers.
40303 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40304 @anchor{cycle step packet}
40305 @cindex @samp{i} packet
40306 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40307 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40308 step starting at that address.
40311 @cindex @samp{I} packet
40312 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40316 @cindex @samp{k} packet
40319 The exact effect of this packet is not specified.
40321 For a bare-metal target, it may power cycle or reset the target
40322 system. For that reason, the @samp{k} packet has no reply.
40324 For a single-process target, it may kill that process if possible.
40326 A multiple-process target may choose to kill just one process, or all
40327 that are under @value{GDBN}'s control. For more precise control, use
40328 the vKill packet (@pxref{vKill packet}).
40330 If the target system immediately closes the connection in response to
40331 @samp{k}, @value{GDBN} does not consider the lack of packet
40332 acknowledgment to be an error, and assumes the kill was successful.
40334 If connected using @kbd{target extended-remote}, and the target does
40335 not close the connection in response to a kill request, @value{GDBN}
40336 probes the target state as if a new connection was opened
40337 (@pxref{? packet}).
40339 @item m @var{addr},@var{length}
40340 @cindex @samp{m} packet
40341 Read @var{length} addressable memory units starting at address @var{addr}
40342 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40343 any particular boundary.
40345 The stub need not use any particular size or alignment when gathering
40346 data from memory for the response; even if @var{addr} is word-aligned
40347 and @var{length} is a multiple of the word size, the stub is free to
40348 use byte accesses, or not. For this reason, this packet may not be
40349 suitable for accessing memory-mapped I/O devices.
40350 @cindex alignment of remote memory accesses
40351 @cindex size of remote memory accesses
40352 @cindex memory, alignment and size of remote accesses
40356 @item @var{XX@dots{}}
40357 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40358 The reply may contain fewer addressable memory units than requested if the
40359 server was able to read only part of the region of memory.
40364 @item M @var{addr},@var{length}:@var{XX@dots{}}
40365 @cindex @samp{M} packet
40366 Write @var{length} addressable memory units starting at address @var{addr}
40367 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
40368 byte is transmitted as a two-digit hexadecimal number.
40375 for an error (this includes the case where only part of the data was
40380 @cindex @samp{p} packet
40381 Read the value of register @var{n}; @var{n} is in hex.
40382 @xref{read registers packet}, for a description of how the returned
40383 register value is encoded.
40387 @item @var{XX@dots{}}
40388 the register's value
40392 Indicating an unrecognized @var{query}.
40395 @item P @var{n@dots{}}=@var{r@dots{}}
40396 @anchor{write register packet}
40397 @cindex @samp{P} packet
40398 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
40399 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
40400 digits for each byte in the register (target byte order).
40410 @item q @var{name} @var{params}@dots{}
40411 @itemx Q @var{name} @var{params}@dots{}
40412 @cindex @samp{q} packet
40413 @cindex @samp{Q} packet
40414 General query (@samp{q}) and set (@samp{Q}). These packets are
40415 described fully in @ref{General Query Packets}.
40418 @cindex @samp{r} packet
40419 Reset the entire system.
40421 Don't use this packet; use the @samp{R} packet instead.
40424 @cindex @samp{R} packet
40425 Restart the program being debugged. The @var{XX}, while needed, is ignored.
40426 This packet is only available in extended mode (@pxref{extended mode}).
40428 The @samp{R} packet has no reply.
40430 @item s @r{[}@var{addr}@r{]}
40431 @cindex @samp{s} packet
40432 Single step, resuming at @var{addr}. If
40433 @var{addr} is omitted, resume at same address.
40435 This packet is deprecated for multi-threading support. @xref{vCont
40439 @xref{Stop Reply Packets}, for the reply specifications.
40441 @item S @var{sig}@r{[};@var{addr}@r{]}
40442 @anchor{step with signal packet}
40443 @cindex @samp{S} packet
40444 Step with signal. This is analogous to the @samp{C} packet, but
40445 requests a single-step, rather than a normal resumption of execution.
40447 This packet is deprecated for multi-threading support. @xref{vCont
40451 @xref{Stop Reply Packets}, for the reply specifications.
40453 @item t @var{addr}:@var{PP},@var{MM}
40454 @cindex @samp{t} packet
40455 Search backwards starting at address @var{addr} for a match with pattern
40456 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
40457 There must be at least 3 digits in @var{addr}.
40459 @item T @var{thread-id}
40460 @cindex @samp{T} packet
40461 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
40466 thread is still alive
40472 Packets starting with @samp{v} are identified by a multi-letter name,
40473 up to the first @samp{;} or @samp{?} (or the end of the packet).
40475 @item vAttach;@var{pid}
40476 @cindex @samp{vAttach} packet
40477 Attach to a new process with the specified process ID @var{pid}.
40478 The process ID is a
40479 hexadecimal integer identifying the process. In all-stop mode, all
40480 threads in the attached process are stopped; in non-stop mode, it may be
40481 attached without being stopped if that is supported by the target.
40483 @c In non-stop mode, on a successful vAttach, the stub should set the
40484 @c current thread to a thread of the newly-attached process. After
40485 @c attaching, GDB queries for the attached process's thread ID with qC.
40486 @c Also note that, from a user perspective, whether or not the
40487 @c target is stopped on attach in non-stop mode depends on whether you
40488 @c use the foreground or background version of the attach command, not
40489 @c on what vAttach does; GDB does the right thing with respect to either
40490 @c stopping or restarting threads.
40492 This packet is only available in extended mode (@pxref{extended mode}).
40498 @item @r{Any stop packet}
40499 for success in all-stop mode (@pxref{Stop Reply Packets})
40501 for success in non-stop mode (@pxref{Remote Non-Stop})
40504 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
40505 @cindex @samp{vCont} packet
40506 @anchor{vCont packet}
40507 Resume the inferior, specifying different actions for each thread.
40509 For each inferior thread, the leftmost action with a matching
40510 @var{thread-id} is applied. Threads that don't match any action
40511 remain in their current state. Thread IDs are specified using the
40512 syntax described in @ref{thread-id syntax}. If multiprocess
40513 extensions (@pxref{multiprocess extensions}) are supported, actions
40514 can be specified to match all threads in a process by using the
40515 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
40516 @var{thread-id} matches all threads. Specifying no actions is an
40519 Currently supported actions are:
40525 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
40529 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
40532 @item r @var{start},@var{end}
40533 Step once, and then keep stepping as long as the thread stops at
40534 addresses between @var{start} (inclusive) and @var{end} (exclusive).
40535 The remote stub reports a stop reply when either the thread goes out
40536 of the range or is stopped due to an unrelated reason, such as hitting
40537 a breakpoint. @xref{range stepping}.
40539 If the range is empty (@var{start} == @var{end}), then the action
40540 becomes equivalent to the @samp{s} action. In other words,
40541 single-step once, and report the stop (even if the stepped instruction
40542 jumps to @var{start}).
40544 (A stop reply may be sent at any point even if the PC is still within
40545 the stepping range; for example, it is valid to implement this packet
40546 in a degenerate way as a single instruction step operation.)
40550 The optional argument @var{addr} normally associated with the
40551 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
40552 not supported in @samp{vCont}.
40554 The @samp{t} action is only relevant in non-stop mode
40555 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
40556 A stop reply should be generated for any affected thread not already stopped.
40557 When a thread is stopped by means of a @samp{t} action,
40558 the corresponding stop reply should indicate that the thread has stopped with
40559 signal @samp{0}, regardless of whether the target uses some other signal
40560 as an implementation detail.
40562 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
40563 @samp{r} actions for threads that are already running. Conversely,
40564 the server must ignore @samp{t} actions for threads that are already
40567 @emph{Note:} In non-stop mode, a thread is considered running until
40568 @value{GDBN} acknowledges an asynchronous stop notification for it with
40569 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40571 The stub must support @samp{vCont} if it reports support for
40572 multiprocess extensions (@pxref{multiprocess extensions}).
40575 @xref{Stop Reply Packets}, for the reply specifications.
40578 @cindex @samp{vCont?} packet
40579 Request a list of actions supported by the @samp{vCont} packet.
40583 @item vCont@r{[};@var{action}@dots{}@r{]}
40584 The @samp{vCont} packet is supported. Each @var{action} is a supported
40585 command in the @samp{vCont} packet.
40587 The @samp{vCont} packet is not supported.
40590 @anchor{vCtrlC packet}
40592 @cindex @samp{vCtrlC} packet
40593 Interrupt remote target as if a control-C was pressed on the remote
40594 terminal. This is the equivalent to reacting to the @code{^C}
40595 (@samp{\003}, the control-C character) character in all-stop mode
40596 while the target is running, except this works in non-stop mode.
40597 @xref{interrupting remote targets}, for more info on the all-stop
40608 @item vFile:@var{operation}:@var{parameter}@dots{}
40609 @cindex @samp{vFile} packet
40610 Perform a file operation on the target system. For details,
40611 see @ref{Host I/O Packets}.
40613 @item vFlashErase:@var{addr},@var{length}
40614 @cindex @samp{vFlashErase} packet
40615 Direct the stub to erase @var{length} bytes of flash starting at
40616 @var{addr}. The region may enclose any number of flash blocks, but
40617 its start and end must fall on block boundaries, as indicated by the
40618 flash block size appearing in the memory map (@pxref{Memory Map
40619 Format}). @value{GDBN} groups flash memory programming operations
40620 together, and sends a @samp{vFlashDone} request after each group; the
40621 stub is allowed to delay erase operation until the @samp{vFlashDone}
40622 packet is received.
40632 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
40633 @cindex @samp{vFlashWrite} packet
40634 Direct the stub to write data to flash address @var{addr}. The data
40635 is passed in binary form using the same encoding as for the @samp{X}
40636 packet (@pxref{Binary Data}). The memory ranges specified by
40637 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
40638 not overlap, and must appear in order of increasing addresses
40639 (although @samp{vFlashErase} packets for higher addresses may already
40640 have been received; the ordering is guaranteed only between
40641 @samp{vFlashWrite} packets). If a packet writes to an address that was
40642 neither erased by a preceding @samp{vFlashErase} packet nor by some other
40643 target-specific method, the results are unpredictable.
40651 for vFlashWrite addressing non-flash memory
40657 @cindex @samp{vFlashDone} packet
40658 Indicate to the stub that flash programming operation is finished.
40659 The stub is permitted to delay or batch the effects of a group of
40660 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
40661 @samp{vFlashDone} packet is received. The contents of the affected
40662 regions of flash memory are unpredictable until the @samp{vFlashDone}
40663 request is completed.
40665 @item vKill;@var{pid}
40666 @cindex @samp{vKill} packet
40667 @anchor{vKill packet}
40668 Kill the process with the specified process ID @var{pid}, which is a
40669 hexadecimal integer identifying the process. This packet is used in
40670 preference to @samp{k} when multiprocess protocol extensions are
40671 supported; see @ref{multiprocess extensions}.
40681 @item vMustReplyEmpty
40682 @cindex @samp{vMustReplyEmpty} packet
40683 The correct reply to an unknown @samp{v} packet is to return the empty
40684 string, however, some older versions of @command{gdbserver} would
40685 incorrectly return @samp{OK} for unknown @samp{v} packets.
40687 The @samp{vMustReplyEmpty} is used as a feature test to check how
40688 @command{gdbserver} handles unknown packets, it is important that this
40689 packet be handled in the same way as other unknown @samp{v} packets.
40690 If this packet is handled differently to other unknown @samp{v}
40691 packets then it is possible that @value{GDBN} may run into problems in
40692 other areas, specifically around use of @samp{vFile:setfs:}.
40694 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
40695 @cindex @samp{vRun} packet
40696 Run the program @var{filename}, passing it each @var{argument} on its
40697 command line. The file and arguments are hex-encoded strings. If
40698 @var{filename} is an empty string, the stub may use a default program
40699 (e.g.@: the last program run). The program is created in the stopped
40702 @c FIXME: What about non-stop mode?
40704 This packet is only available in extended mode (@pxref{extended mode}).
40710 @item @r{Any stop packet}
40711 for success (@pxref{Stop Reply Packets})
40715 @cindex @samp{vStopped} packet
40716 @xref{Notification Packets}.
40718 @item X @var{addr},@var{length}:@var{XX@dots{}}
40720 @cindex @samp{X} packet
40721 Write data to memory, where the data is transmitted in binary.
40722 Memory is specified by its address @var{addr} and number of addressable memory
40723 units @var{length} (@pxref{addressable memory unit});
40724 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
40734 @item z @var{type},@var{addr},@var{kind}
40735 @itemx Z @var{type},@var{addr},@var{kind}
40736 @anchor{insert breakpoint or watchpoint packet}
40737 @cindex @samp{z} packet
40738 @cindex @samp{Z} packets
40739 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
40740 watchpoint starting at address @var{address} of kind @var{kind}.
40742 Each breakpoint and watchpoint packet @var{type} is documented
40745 @emph{Implementation notes: A remote target shall return an empty string
40746 for an unrecognized breakpoint or watchpoint packet @var{type}. A
40747 remote target shall support either both or neither of a given
40748 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
40749 avoid potential problems with duplicate packets, the operations should
40750 be implemented in an idempotent way.}
40752 @item z0,@var{addr},@var{kind}
40753 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40754 @cindex @samp{z0} packet
40755 @cindex @samp{Z0} packet
40756 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
40757 @var{addr} of type @var{kind}.
40759 A software breakpoint is implemented by replacing the instruction at
40760 @var{addr} with a software breakpoint or trap instruction. The
40761 @var{kind} is target-specific and typically indicates the size of the
40762 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
40763 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
40764 architectures have additional meanings for @var{kind}
40765 (@pxref{Architecture-Specific Protocol Details}); if no
40766 architecture-specific value is being used, it should be @samp{0}.
40767 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
40768 conditional expressions in bytecode form that should be evaluated on
40769 the target's side. These are the conditions that should be taken into
40770 consideration when deciding if the breakpoint trigger should be
40771 reported back to @value{GDBN}.
40773 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
40774 for how to best report a software breakpoint event to @value{GDBN}.
40776 The @var{cond_list} parameter is comprised of a series of expressions,
40777 concatenated without separators. Each expression has the following form:
40781 @item X @var{len},@var{expr}
40782 @var{len} is the length of the bytecode expression and @var{expr} is the
40783 actual conditional expression in bytecode form.
40787 The optional @var{cmd_list} parameter introduces commands that may be
40788 run on the target, rather than being reported back to @value{GDBN}.
40789 The parameter starts with a numeric flag @var{persist}; if the flag is
40790 nonzero, then the breakpoint may remain active and the commands
40791 continue to be run even when @value{GDBN} disconnects from the target.
40792 Following this flag is a series of expressions concatenated with no
40793 separators. Each expression has the following form:
40797 @item X @var{len},@var{expr}
40798 @var{len} is the length of the bytecode expression and @var{expr} is the
40799 actual commands expression in bytecode form.
40803 @emph{Implementation note: It is possible for a target to copy or move
40804 code that contains software breakpoints (e.g., when implementing
40805 overlays). The behavior of this packet, in the presence of such a
40806 target, is not defined.}
40818 @item z1,@var{addr},@var{kind}
40819 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40820 @cindex @samp{z1} packet
40821 @cindex @samp{Z1} packet
40822 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
40823 address @var{addr}.
40825 A hardware breakpoint is implemented using a mechanism that is not
40826 dependent on being able to modify the target's memory. The
40827 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
40828 same meaning as in @samp{Z0} packets.
40830 @emph{Implementation note: A hardware breakpoint is not affected by code
40843 @item z2,@var{addr},@var{kind}
40844 @itemx Z2,@var{addr},@var{kind}
40845 @cindex @samp{z2} packet
40846 @cindex @samp{Z2} packet
40847 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
40848 The number of bytes to watch is specified by @var{kind}.
40860 @item z3,@var{addr},@var{kind}
40861 @itemx Z3,@var{addr},@var{kind}
40862 @cindex @samp{z3} packet
40863 @cindex @samp{Z3} packet
40864 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
40865 The number of bytes to watch is specified by @var{kind}.
40877 @item z4,@var{addr},@var{kind}
40878 @itemx Z4,@var{addr},@var{kind}
40879 @cindex @samp{z4} packet
40880 @cindex @samp{Z4} packet
40881 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
40882 The number of bytes to watch is specified by @var{kind}.
40896 @node Stop Reply Packets
40897 @section Stop Reply Packets
40898 @cindex stop reply packets
40900 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
40901 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
40902 receive any of the below as a reply. Except for @samp{?}
40903 and @samp{vStopped}, that reply is only returned
40904 when the target halts. In the below the exact meaning of @dfn{signal
40905 number} is defined by the header @file{include/gdb/signals.h} in the
40906 @value{GDBN} source code.
40908 In non-stop mode, the server will simply reply @samp{OK} to commands
40909 such as @samp{vCont}; any stop will be the subject of a future
40910 notification. @xref{Remote Non-Stop}.
40912 As in the description of request packets, we include spaces in the
40913 reply templates for clarity; these are not part of the reply packet's
40914 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
40920 The program received signal number @var{AA} (a two-digit hexadecimal
40921 number). This is equivalent to a @samp{T} response with no
40922 @var{n}:@var{r} pairs.
40924 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
40925 @cindex @samp{T} packet reply
40926 The program received signal number @var{AA} (a two-digit hexadecimal
40927 number). This is equivalent to an @samp{S} response, except that the
40928 @samp{@var{n}:@var{r}} pairs can carry values of important registers
40929 and other information directly in the stop reply packet, reducing
40930 round-trip latency. Single-step and breakpoint traps are reported
40931 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
40935 If @var{n} is a hexadecimal number, it is a register number, and the
40936 corresponding @var{r} gives that register's value. The data @var{r} is a
40937 series of bytes in target byte order, with each byte given by a
40938 two-digit hex number.
40941 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
40942 the stopped thread, as specified in @ref{thread-id syntax}.
40945 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
40946 the core on which the stop event was detected.
40949 If @var{n} is a recognized @dfn{stop reason}, it describes a more
40950 specific event that stopped the target. The currently defined stop
40951 reasons are listed below. The @var{aa} should be @samp{05}, the trap
40952 signal. At most one stop reason should be present.
40955 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
40956 and go on to the next; this allows us to extend the protocol in the
40960 The currently defined stop reasons are:
40966 The packet indicates a watchpoint hit, and @var{r} is the data address, in
40969 @item syscall_entry
40970 @itemx syscall_return
40971 The packet indicates a syscall entry or return, and @var{r} is the
40972 syscall number, in hex.
40974 @cindex shared library events, remote reply
40976 The packet indicates that the loaded libraries have changed.
40977 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
40978 list of loaded libraries. The @var{r} part is ignored.
40980 @cindex replay log events, remote reply
40982 The packet indicates that the target cannot continue replaying
40983 logged execution events, because it has reached the end (or the
40984 beginning when executing backward) of the log. The value of @var{r}
40985 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
40986 for more information.
40989 @anchor{swbreak stop reason}
40990 The packet indicates a software breakpoint instruction was executed,
40991 irrespective of whether it was @value{GDBN} that planted the
40992 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
40993 part must be left empty.
40995 On some architectures, such as x86, at the architecture level, when a
40996 breakpoint instruction executes the program counter points at the
40997 breakpoint address plus an offset. On such targets, the stub is
40998 responsible for adjusting the PC to point back at the breakpoint
41001 This packet should not be sent by default; older @value{GDBN} versions
41002 did not support it. @value{GDBN} requests it, by supplying an
41003 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41004 remote stub must also supply the appropriate @samp{qSupported} feature
41005 indicating support.
41007 This packet is required for correct non-stop mode operation.
41010 The packet indicates the target stopped for a hardware breakpoint.
41011 The @var{r} part must be left empty.
41013 The same remarks about @samp{qSupported} and non-stop mode above
41016 @cindex fork events, remote reply
41018 The packet indicates that @code{fork} was called, and @var{r}
41019 is the thread ID of the new child process. Refer to
41020 @ref{thread-id syntax} for the format of the @var{thread-id}
41021 field. This packet is only applicable to targets that support
41024 This packet should not be sent by default; older @value{GDBN} versions
41025 did not support it. @value{GDBN} requests it, by supplying an
41026 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41027 remote stub must also supply the appropriate @samp{qSupported} feature
41028 indicating support.
41030 @cindex vfork events, remote reply
41032 The packet indicates that @code{vfork} was called, and @var{r}
41033 is the thread ID of the new child process. Refer to
41034 @ref{thread-id syntax} for the format of the @var{thread-id}
41035 field. This packet is only applicable to targets that support
41038 This packet should not be sent by default; older @value{GDBN} versions
41039 did not support it. @value{GDBN} requests it, by supplying an
41040 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41041 remote stub must also supply the appropriate @samp{qSupported} feature
41042 indicating support.
41044 @cindex vforkdone events, remote reply
41046 The packet indicates that a child process created by a vfork
41047 has either called @code{exec} or terminated, so that the
41048 address spaces of the parent and child process are no longer
41049 shared. The @var{r} part is ignored. This packet is only
41050 applicable to targets that support vforkdone events.
41052 This packet should not be sent by default; older @value{GDBN} versions
41053 did not support it. @value{GDBN} requests it, by supplying an
41054 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41055 remote stub must also supply the appropriate @samp{qSupported} feature
41056 indicating support.
41058 @cindex exec events, remote reply
41060 The packet indicates that @code{execve} was called, and @var{r}
41061 is the absolute pathname of the file that was executed, in hex.
41062 This packet is only applicable to targets that support exec events.
41064 This packet should not be sent by default; older @value{GDBN} versions
41065 did not support it. @value{GDBN} requests it, by supplying an
41066 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41067 remote stub must also supply the appropriate @samp{qSupported} feature
41068 indicating support.
41070 @cindex thread create event, remote reply
41071 @anchor{thread create event}
41073 The packet indicates that the thread was just created. The new thread
41074 is stopped until @value{GDBN} sets it running with a resumption packet
41075 (@pxref{vCont packet}). This packet should not be sent by default;
41076 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41077 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41078 @var{r} part is ignored.
41083 @itemx W @var{AA} ; process:@var{pid}
41084 The process exited, and @var{AA} is the exit status. This is only
41085 applicable to certain targets.
41087 The second form of the response, including the process ID of the
41088 exited process, can be used only when @value{GDBN} has reported
41089 support for multiprocess protocol extensions; see @ref{multiprocess
41090 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41094 @itemx X @var{AA} ; process:@var{pid}
41095 The process terminated with signal @var{AA}.
41097 The second form of the response, including the process ID of the
41098 terminated process, can be used only when @value{GDBN} has reported
41099 support for multiprocess protocol extensions; see @ref{multiprocess
41100 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41103 @anchor{thread exit event}
41104 @cindex thread exit event, remote reply
41105 @item w @var{AA} ; @var{tid}
41107 The thread exited, and @var{AA} is the exit status. This response
41108 should not be sent by default; @value{GDBN} requests it with the
41109 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41110 @var{AA} is formatted as a big-endian hex string.
41113 There are no resumed threads left in the target. In other words, even
41114 though the process is alive, the last resumed thread has exited. For
41115 example, say the target process has two threads: thread 1 and thread
41116 2. The client leaves thread 1 stopped, and resumes thread 2, which
41117 subsequently exits. At this point, even though the process is still
41118 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41119 executing either. The @samp{N} stop reply thus informs the client
41120 that it can stop waiting for stop replies. This packet should not be
41121 sent by default; older @value{GDBN} versions did not support it.
41122 @value{GDBN} requests it, by supplying an appropriate
41123 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41124 also supply the appropriate @samp{qSupported} feature indicating
41127 @item O @var{XX}@dots{}
41128 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41129 written as the program's console output. This can happen at any time
41130 while the program is running and the debugger should continue to wait
41131 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41133 @item F @var{call-id},@var{parameter}@dots{}
41134 @var{call-id} is the identifier which says which host system call should
41135 be called. This is just the name of the function. Translation into the
41136 correct system call is only applicable as it's defined in @value{GDBN}.
41137 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41140 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41141 this very system call.
41143 The target replies with this packet when it expects @value{GDBN} to
41144 call a host system call on behalf of the target. @value{GDBN} replies
41145 with an appropriate @samp{F} packet and keeps up waiting for the next
41146 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41147 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41148 Protocol Extension}, for more details.
41152 @node General Query Packets
41153 @section General Query Packets
41154 @cindex remote query requests
41156 Packets starting with @samp{q} are @dfn{general query packets};
41157 packets starting with @samp{Q} are @dfn{general set packets}. General
41158 query and set packets are a semi-unified form for retrieving and
41159 sending information to and from the stub.
41161 The initial letter of a query or set packet is followed by a name
41162 indicating what sort of thing the packet applies to. For example,
41163 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41164 definitions with the stub. These packet names follow some
41169 The name must not contain commas, colons or semicolons.
41171 Most @value{GDBN} query and set packets have a leading upper case
41174 The names of custom vendor packets should use a company prefix, in
41175 lower case, followed by a period. For example, packets designed at
41176 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41177 foos) or @samp{Qacme.bar} (for setting bars).
41180 The name of a query or set packet should be separated from any
41181 parameters by a @samp{:}; the parameters themselves should be
41182 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41183 full packet name, and check for a separator or the end of the packet,
41184 in case two packet names share a common prefix. New packets should not begin
41185 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41186 packets predate these conventions, and have arguments without any terminator
41187 for the packet name; we suspect they are in widespread use in places that
41188 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41189 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41192 Like the descriptions of the other packets, each description here
41193 has a template showing the packet's overall syntax, followed by an
41194 explanation of the packet's meaning. We include spaces in some of the
41195 templates for clarity; these are not part of the packet's syntax. No
41196 @value{GDBN} packet uses spaces to separate its components.
41198 Here are the currently defined query and set packets:
41204 Turn on or off the agent as a helper to perform some debugging operations
41205 delegated from @value{GDBN} (@pxref{Control Agent}).
41207 @item QAllow:@var{op}:@var{val}@dots{}
41208 @cindex @samp{QAllow} packet
41209 Specify which operations @value{GDBN} expects to request of the
41210 target, as a semicolon-separated list of operation name and value
41211 pairs. Possible values for @var{op} include @samp{WriteReg},
41212 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41213 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41214 indicating that @value{GDBN} will not request the operation, or 1,
41215 indicating that it may. (The target can then use this to set up its
41216 own internals optimally, for instance if the debugger never expects to
41217 insert breakpoints, it may not need to install its own trap handler.)
41220 @cindex current thread, remote request
41221 @cindex @samp{qC} packet
41222 Return the current thread ID.
41226 @item QC @var{thread-id}
41227 Where @var{thread-id} is a thread ID as documented in
41228 @ref{thread-id syntax}.
41229 @item @r{(anything else)}
41230 Any other reply implies the old thread ID.
41233 @item qCRC:@var{addr},@var{length}
41234 @cindex CRC of memory block, remote request
41235 @cindex @samp{qCRC} packet
41236 @anchor{qCRC packet}
41237 Compute the CRC checksum of a block of memory using CRC-32 defined in
41238 IEEE 802.3. The CRC is computed byte at a time, taking the most
41239 significant bit of each byte first. The initial pattern code
41240 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41242 @emph{Note:} This is the same CRC used in validating separate debug
41243 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41244 Files}). However the algorithm is slightly different. When validating
41245 separate debug files, the CRC is computed taking the @emph{least}
41246 significant bit of each byte first, and the final result is inverted to
41247 detect trailing zeros.
41252 An error (such as memory fault)
41253 @item C @var{crc32}
41254 The specified memory region's checksum is @var{crc32}.
41257 @item QDisableRandomization:@var{value}
41258 @cindex disable address space randomization, remote request
41259 @cindex @samp{QDisableRandomization} packet
41260 Some target operating systems will randomize the virtual address space
41261 of the inferior process as a security feature, but provide a feature
41262 to disable such randomization, e.g.@: to allow for a more deterministic
41263 debugging experience. On such systems, this packet with a @var{value}
41264 of 1 directs the target to disable address space randomization for
41265 processes subsequently started via @samp{vRun} packets, while a packet
41266 with a @var{value} of 0 tells the target to enable address space
41269 This packet is only available in extended mode (@pxref{extended mode}).
41274 The request succeeded.
41277 An error occurred. The error number @var{nn} is given as hex digits.
41280 An empty reply indicates that @samp{QDisableRandomization} is not supported
41284 This packet is not probed by default; the remote stub must request it,
41285 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41286 This should only be done on targets that actually support disabling
41287 address space randomization.
41289 @item QStartupWithShell:@var{value}
41290 @cindex startup with shell, remote request
41291 @cindex @samp{QStartupWithShell} packet
41292 On UNIX-like targets, it is possible to start the inferior using a
41293 shell program. This is the default behavior on both @value{GDBN} and
41294 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41295 used to inform @command{gdbserver} whether it should start the
41296 inferior using a shell or not.
41298 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41299 to start the inferior. If @var{value} is @samp{1},
41300 @command{gdbserver} will use a shell to start the inferior. All other
41301 values are considered an error.
41303 This packet is only available in extended mode (@pxref{extended
41309 The request succeeded.
41312 An error occurred. The error number @var{nn} is given as hex digits.
41315 This packet is not probed by default; the remote stub must request it,
41316 by supplying an appropriate @samp{qSupported} response
41317 (@pxref{qSupported}). This should only be done on targets that
41318 actually support starting the inferior using a shell.
41320 Use of this packet is controlled by the @code{set startup-with-shell}
41321 command; @pxref{set startup-with-shell}.
41323 @item QEnvironmentHexEncoded:@var{hex-value}
41324 @anchor{QEnvironmentHexEncoded}
41325 @cindex set environment variable, remote request
41326 @cindex @samp{QEnvironmentHexEncoded} packet
41327 On UNIX-like targets, it is possible to set environment variables that
41328 will be passed to the inferior during the startup process. This
41329 packet is used to inform @command{gdbserver} of an environment
41330 variable that has been defined by the user on @value{GDBN} (@pxref{set
41333 The packet is composed by @var{hex-value}, an hex encoded
41334 representation of the @var{name=value} format representing an
41335 environment variable. The name of the environment variable is
41336 represented by @var{name}, and the value to be assigned to the
41337 environment variable is represented by @var{value}. If the variable
41338 has no value (i.e., the value is @code{null}), then @var{value} will
41341 This packet is only available in extended mode (@pxref{extended
41347 The request succeeded.
41350 This packet is not probed by default; the remote stub must request it,
41351 by supplying an appropriate @samp{qSupported} response
41352 (@pxref{qSupported}). This should only be done on targets that
41353 actually support passing environment variables to the starting
41356 This packet is related to the @code{set environment} command;
41357 @pxref{set environment}.
41359 @item QEnvironmentUnset:@var{hex-value}
41360 @anchor{QEnvironmentUnset}
41361 @cindex unset environment variable, remote request
41362 @cindex @samp{QEnvironmentUnset} packet
41363 On UNIX-like targets, it is possible to unset environment variables
41364 before starting the inferior in the remote target. This packet is
41365 used to inform @command{gdbserver} of an environment variable that has
41366 been unset by the user on @value{GDBN} (@pxref{unset environment}).
41368 The packet is composed by @var{hex-value}, an hex encoded
41369 representation of the name of the environment variable to be unset.
41371 This packet is only available in extended mode (@pxref{extended
41377 The request succeeded.
41380 This packet is not probed by default; the remote stub must request it,
41381 by supplying an appropriate @samp{qSupported} response
41382 (@pxref{qSupported}). This should only be done on targets that
41383 actually support passing environment variables to the starting
41386 This packet is related to the @code{unset environment} command;
41387 @pxref{unset environment}.
41389 @item QEnvironmentReset
41390 @anchor{QEnvironmentReset}
41391 @cindex reset environment, remote request
41392 @cindex @samp{QEnvironmentReset} packet
41393 On UNIX-like targets, this packet is used to reset the state of
41394 environment variables in the remote target before starting the
41395 inferior. In this context, reset means unsetting all environment
41396 variables that were previously set by the user (i.e., were not
41397 initially present in the environment). It is sent to
41398 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
41399 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
41400 (@pxref{QEnvironmentUnset}) packets.
41402 This packet is only available in extended mode (@pxref{extended
41408 The request succeeded.
41411 This packet is not probed by default; the remote stub must request it,
41412 by supplying an appropriate @samp{qSupported} response
41413 (@pxref{qSupported}). This should only be done on targets that
41414 actually support passing environment variables to the starting
41417 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
41418 @anchor{QSetWorkingDir packet}
41419 @cindex set working directory, remote request
41420 @cindex @samp{QSetWorkingDir} packet
41421 This packet is used to inform the remote server of the intended
41422 current working directory for programs that are going to be executed.
41424 The packet is composed by @var{directory}, an hex encoded
41425 representation of the directory that the remote inferior will use as
41426 its current working directory. If @var{directory} is an empty string,
41427 the remote server should reset the inferior's current working
41428 directory to its original, empty value.
41430 This packet is only available in extended mode (@pxref{extended
41436 The request succeeded.
41440 @itemx qsThreadInfo
41441 @cindex list active threads, remote request
41442 @cindex @samp{qfThreadInfo} packet
41443 @cindex @samp{qsThreadInfo} packet
41444 Obtain a list of all active thread IDs from the target (OS). Since there
41445 may be too many active threads to fit into one reply packet, this query
41446 works iteratively: it may require more than one query/reply sequence to
41447 obtain the entire list of threads. The first query of the sequence will
41448 be the @samp{qfThreadInfo} query; subsequent queries in the
41449 sequence will be the @samp{qsThreadInfo} query.
41451 NOTE: This packet replaces the @samp{qL} query (see below).
41455 @item m @var{thread-id}
41457 @item m @var{thread-id},@var{thread-id}@dots{}
41458 a comma-separated list of thread IDs
41460 (lower case letter @samp{L}) denotes end of list.
41463 In response to each query, the target will reply with a list of one or
41464 more thread IDs, separated by commas.
41465 @value{GDBN} will respond to each reply with a request for more thread
41466 ids (using the @samp{qs} form of the query), until the target responds
41467 with @samp{l} (lower-case ell, for @dfn{last}).
41468 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
41471 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
41472 initial connection with the remote target, and the very first thread ID
41473 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
41474 message. Therefore, the stub should ensure that the first thread ID in
41475 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
41477 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
41478 @cindex get thread-local storage address, remote request
41479 @cindex @samp{qGetTLSAddr} packet
41480 Fetch the address associated with thread local storage specified
41481 by @var{thread-id}, @var{offset}, and @var{lm}.
41483 @var{thread-id} is the thread ID associated with the
41484 thread for which to fetch the TLS address. @xref{thread-id syntax}.
41486 @var{offset} is the (big endian, hex encoded) offset associated with the
41487 thread local variable. (This offset is obtained from the debug
41488 information associated with the variable.)
41490 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
41491 load module associated with the thread local storage. For example,
41492 a @sc{gnu}/Linux system will pass the link map address of the shared
41493 object associated with the thread local storage under consideration.
41494 Other operating environments may choose to represent the load module
41495 differently, so the precise meaning of this parameter will vary.
41499 @item @var{XX}@dots{}
41500 Hex encoded (big endian) bytes representing the address of the thread
41501 local storage requested.
41504 An error occurred. The error number @var{nn} is given as hex digits.
41507 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
41510 @item qGetTIBAddr:@var{thread-id}
41511 @cindex get thread information block address
41512 @cindex @samp{qGetTIBAddr} packet
41513 Fetch address of the Windows OS specific Thread Information Block.
41515 @var{thread-id} is the thread ID associated with the thread.
41519 @item @var{XX}@dots{}
41520 Hex encoded (big endian) bytes representing the linear address of the
41521 thread information block.
41524 An error occured. This means that either the thread was not found, or the
41525 address could not be retrieved.
41528 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
41531 @item qL @var{startflag} @var{threadcount} @var{nextthread}
41532 Obtain thread information from RTOS. Where: @var{startflag} (one hex
41533 digit) is one to indicate the first query and zero to indicate a
41534 subsequent query; @var{threadcount} (two hex digits) is the maximum
41535 number of threads the response packet can contain; and @var{nextthread}
41536 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
41537 returned in the response as @var{argthread}.
41539 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
41543 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
41544 Where: @var{count} (two hex digits) is the number of threads being
41545 returned; @var{done} (one hex digit) is zero to indicate more threads
41546 and one indicates no further threads; @var{argthreadid} (eight hex
41547 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
41548 is a sequence of thread IDs, @var{threadid} (eight hex
41549 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
41552 @item qMemTags:@var{start address},@var{length}:@var{type}
41554 @cindex fetch memory tags
41555 @cindex @samp{qMemTags} packet
41556 Fetch memory tags of type @var{type} from the address range
41557 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41558 target is responsible for calculating how many tags will be returned, as this
41559 is architecture-specific.
41561 @var{start address} is the starting address of the memory range.
41563 @var{length} is the length, in bytes, of the memory range.
41565 @var{type} is the type of tag the request wants to fetch. The type is a signed
41570 @item @var{mxx}@dots{}
41571 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
41572 tags found in the requested memory range.
41575 An error occured. This means that fetching of memory tags failed for some
41579 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
41580 although this should not happen given @value{GDBN} will only send this packet
41581 if the stub has advertised support for memory tagging via @samp{qSupported}.
41584 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
41586 @cindex store memory tags
41587 @cindex @samp{QMemTags} packet
41588 Store memory tags of type @var{type} to the address range
41589 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41590 target is responsible for interpreting the type, the tag bytes and modifying
41591 the memory tag granules accordingly, given this is architecture-specific.
41593 The interpretation of how many tags (@var{nt}) should be written to how many
41594 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
41595 implementation-specific, but the following is suggested.
41597 If the number of memory tags, @var{nt}, is greater than or equal to the
41598 number of memory tag granules, @var{ng}, only @var{ng} tags will be
41601 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
41602 and the tag bytes will be used as a pattern that will get repeated until
41603 @var{ng} tags are stored.
41605 @var{start address} is the starting address of the memory range. The address
41606 does not have any restriction on alignment or size.
41608 @var{length} is the length, in bytes, of the memory range.
41610 @var{type} is the type of tag the request wants to fetch. The type is a signed
41613 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
41614 interpreted by the target. Each pair of hex digits is interpreted as a
41620 The request was successful and the memory tag granules were modified
41624 An error occured. This means that modifying the memory tag granules failed
41628 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
41629 although this should not happen given @value{GDBN} will only send this packet
41630 if the stub has advertised support for memory tagging via @samp{qSupported}.
41634 @cindex section offsets, remote request
41635 @cindex @samp{qOffsets} packet
41636 Get section offsets that the target used when relocating the downloaded
41641 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
41642 Relocate the @code{Text} section by @var{xxx} from its original address.
41643 Relocate the @code{Data} section by @var{yyy} from its original address.
41644 If the object file format provides segment information (e.g.@: @sc{elf}
41645 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
41646 segments by the supplied offsets.
41648 @emph{Note: while a @code{Bss} offset may be included in the response,
41649 @value{GDBN} ignores this and instead applies the @code{Data} offset
41650 to the @code{Bss} section.}
41652 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
41653 Relocate the first segment of the object file, which conventionally
41654 contains program code, to a starting address of @var{xxx}. If
41655 @samp{DataSeg} is specified, relocate the second segment, which
41656 conventionally contains modifiable data, to a starting address of
41657 @var{yyy}. @value{GDBN} will report an error if the object file
41658 does not contain segment information, or does not contain at least
41659 as many segments as mentioned in the reply. Extra segments are
41660 kept at fixed offsets relative to the last relocated segment.
41663 @item qP @var{mode} @var{thread-id}
41664 @cindex thread information, remote request
41665 @cindex @samp{qP} packet
41666 Returns information on @var{thread-id}. Where: @var{mode} is a hex
41667 encoded 32 bit mode; @var{thread-id} is a thread ID
41668 (@pxref{thread-id syntax}).
41670 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
41673 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
41677 @cindex non-stop mode, remote request
41678 @cindex @samp{QNonStop} packet
41680 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
41681 @xref{Remote Non-Stop}, for more information.
41686 The request succeeded.
41689 An error occurred. The error number @var{nn} is given as hex digits.
41692 An empty reply indicates that @samp{QNonStop} is not supported by
41696 This packet is not probed by default; the remote stub must request it,
41697 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41698 Use of this packet is controlled by the @code{set non-stop} command;
41699 @pxref{Non-Stop Mode}.
41701 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
41702 @itemx QCatchSyscalls:0
41703 @cindex catch syscalls from inferior, remote request
41704 @cindex @samp{QCatchSyscalls} packet
41705 @anchor{QCatchSyscalls}
41706 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
41707 catching syscalls from the inferior process.
41709 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
41710 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
41711 is listed, every system call should be reported.
41713 Note that if a syscall not in the list is reported, @value{GDBN} will
41714 still filter the event according to its own list from all corresponding
41715 @code{catch syscall} commands. However, it is more efficient to only
41716 report the requested syscalls.
41718 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
41719 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
41721 If the inferior process execs, the state of @samp{QCatchSyscalls} is
41722 kept for the new process too. On targets where exec may affect syscall
41723 numbers, for example with exec between 32 and 64-bit processes, the
41724 client should send a new packet with the new syscall list.
41729 The request succeeded.
41732 An error occurred. @var{nn} are hex digits.
41735 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
41739 Use of this packet is controlled by the @code{set remote catch-syscalls}
41740 command (@pxref{Remote Configuration, set remote catch-syscalls}).
41741 This packet is not probed by default; the remote stub must request it,
41742 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41744 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41745 @cindex pass signals to inferior, remote request
41746 @cindex @samp{QPassSignals} packet
41747 @anchor{QPassSignals}
41748 Each listed @var{signal} should be passed directly to the inferior process.
41749 Signals are numbered identically to continue packets and stop replies
41750 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41751 strictly greater than the previous item. These signals do not need to stop
41752 the inferior, or be reported to @value{GDBN}. All other signals should be
41753 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
41754 combine; any earlier @samp{QPassSignals} list is completely replaced by the
41755 new list. This packet improves performance when using @samp{handle
41756 @var{signal} nostop noprint pass}.
41761 The request succeeded.
41764 An error occurred. The error number @var{nn} is given as hex digits.
41767 An empty reply indicates that @samp{QPassSignals} is not supported by
41771 Use of this packet is controlled by the @code{set remote pass-signals}
41772 command (@pxref{Remote Configuration, set remote pass-signals}).
41773 This packet is not probed by default; the remote stub must request it,
41774 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41776 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41777 @cindex signals the inferior may see, remote request
41778 @cindex @samp{QProgramSignals} packet
41779 @anchor{QProgramSignals}
41780 Each listed @var{signal} may be delivered to the inferior process.
41781 Others should be silently discarded.
41783 In some cases, the remote stub may need to decide whether to deliver a
41784 signal to the program or not without @value{GDBN} involvement. One
41785 example of that is while detaching --- the program's threads may have
41786 stopped for signals that haven't yet had a chance of being reported to
41787 @value{GDBN}, and so the remote stub can use the signal list specified
41788 by this packet to know whether to deliver or ignore those pending
41791 This does not influence whether to deliver a signal as requested by a
41792 resumption packet (@pxref{vCont packet}).
41794 Signals are numbered identically to continue packets and stop replies
41795 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41796 strictly greater than the previous item. Multiple
41797 @samp{QProgramSignals} packets do not combine; any earlier
41798 @samp{QProgramSignals} list is completely replaced by the new list.
41803 The request succeeded.
41806 An error occurred. The error number @var{nn} is given as hex digits.
41809 An empty reply indicates that @samp{QProgramSignals} is not supported
41813 Use of this packet is controlled by the @code{set remote program-signals}
41814 command (@pxref{Remote Configuration, set remote program-signals}).
41815 This packet is not probed by default; the remote stub must request it,
41816 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41818 @anchor{QThreadEvents}
41819 @item QThreadEvents:1
41820 @itemx QThreadEvents:0
41821 @cindex thread create/exit events, remote request
41822 @cindex @samp{QThreadEvents} packet
41824 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
41825 reporting of thread create and exit events. @xref{thread create
41826 event}, for the reply specifications. For example, this is used in
41827 non-stop mode when @value{GDBN} stops a set of threads and
41828 synchronously waits for the their corresponding stop replies. Without
41829 exit events, if one of the threads exits, @value{GDBN} would hang
41830 forever not knowing that it should no longer expect a stop for that
41831 same thread. @value{GDBN} does not enable this feature unless the
41832 stub reports that it supports it by including @samp{QThreadEvents+} in
41833 its @samp{qSupported} reply.
41838 The request succeeded.
41841 An error occurred. The error number @var{nn} is given as hex digits.
41844 An empty reply indicates that @samp{QThreadEvents} is not supported by
41848 Use of this packet is controlled by the @code{set remote thread-events}
41849 command (@pxref{Remote Configuration, set remote thread-events}).
41851 @item qRcmd,@var{command}
41852 @cindex execute remote command, remote request
41853 @cindex @samp{qRcmd} packet
41854 @var{command} (hex encoded) is passed to the local interpreter for
41855 execution. Invalid commands should be reported using the output
41856 string. Before the final result packet, the target may also respond
41857 with a number of intermediate @samp{O@var{output}} console output
41858 packets. @emph{Implementors should note that providing access to a
41859 stubs's interpreter may have security implications}.
41864 A command response with no output.
41866 A command response with the hex encoded output string @var{OUTPUT}.
41868 Indicate a badly formed request.
41870 An empty reply indicates that @samp{qRcmd} is not recognized.
41873 (Note that the @code{qRcmd} packet's name is separated from the
41874 command by a @samp{,}, not a @samp{:}, contrary to the naming
41875 conventions above. Please don't use this packet as a model for new
41878 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
41879 @cindex searching memory, in remote debugging
41881 @cindex @samp{qSearch:memory} packet
41883 @cindex @samp{qSearch memory} packet
41884 @anchor{qSearch memory}
41885 Search @var{length} bytes at @var{address} for @var{search-pattern}.
41886 Both @var{address} and @var{length} are encoded in hex;
41887 @var{search-pattern} is a sequence of bytes, also hex encoded.
41892 The pattern was not found.
41894 The pattern was found at @var{address}.
41896 A badly formed request or an error was encountered while searching memory.
41898 An empty reply indicates that @samp{qSearch:memory} is not recognized.
41901 @item QStartNoAckMode
41902 @cindex @samp{QStartNoAckMode} packet
41903 @anchor{QStartNoAckMode}
41904 Request that the remote stub disable the normal @samp{+}/@samp{-}
41905 protocol acknowledgments (@pxref{Packet Acknowledgment}).
41910 The stub has switched to no-acknowledgment mode.
41911 @value{GDBN} acknowledges this response,
41912 but neither the stub nor @value{GDBN} shall send or expect further
41913 @samp{+}/@samp{-} acknowledgments in the current connection.
41915 An empty reply indicates that the stub does not support no-acknowledgment mode.
41918 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
41919 @cindex supported packets, remote query
41920 @cindex features of the remote protocol
41921 @cindex @samp{qSupported} packet
41922 @anchor{qSupported}
41923 Tell the remote stub about features supported by @value{GDBN}, and
41924 query the stub for features it supports. This packet allows
41925 @value{GDBN} and the remote stub to take advantage of each others'
41926 features. @samp{qSupported} also consolidates multiple feature probes
41927 at startup, to improve @value{GDBN} performance---a single larger
41928 packet performs better than multiple smaller probe packets on
41929 high-latency links. Some features may enable behavior which must not
41930 be on by default, e.g.@: because it would confuse older clients or
41931 stubs. Other features may describe packets which could be
41932 automatically probed for, but are not. These features must be
41933 reported before @value{GDBN} will use them. This ``default
41934 unsupported'' behavior is not appropriate for all packets, but it
41935 helps to keep the initial connection time under control with new
41936 versions of @value{GDBN} which support increasing numbers of packets.
41940 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
41941 The stub supports or does not support each returned @var{stubfeature},
41942 depending on the form of each @var{stubfeature} (see below for the
41945 An empty reply indicates that @samp{qSupported} is not recognized,
41946 or that no features needed to be reported to @value{GDBN}.
41949 The allowed forms for each feature (either a @var{gdbfeature} in the
41950 @samp{qSupported} packet, or a @var{stubfeature} in the response)
41954 @item @var{name}=@var{value}
41955 The remote protocol feature @var{name} is supported, and associated
41956 with the specified @var{value}. The format of @var{value} depends
41957 on the feature, but it must not include a semicolon.
41959 The remote protocol feature @var{name} is supported, and does not
41960 need an associated value.
41962 The remote protocol feature @var{name} is not supported.
41964 The remote protocol feature @var{name} may be supported, and
41965 @value{GDBN} should auto-detect support in some other way when it is
41966 needed. This form will not be used for @var{gdbfeature} notifications,
41967 but may be used for @var{stubfeature} responses.
41970 Whenever the stub receives a @samp{qSupported} request, the
41971 supplied set of @value{GDBN} features should override any previous
41972 request. This allows @value{GDBN} to put the stub in a known
41973 state, even if the stub had previously been communicating with
41974 a different version of @value{GDBN}.
41976 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
41981 This feature indicates whether @value{GDBN} supports multiprocess
41982 extensions to the remote protocol. @value{GDBN} does not use such
41983 extensions unless the stub also reports that it supports them by
41984 including @samp{multiprocess+} in its @samp{qSupported} reply.
41985 @xref{multiprocess extensions}, for details.
41988 This feature indicates that @value{GDBN} supports the XML target
41989 description. If the stub sees @samp{xmlRegisters=} with target
41990 specific strings separated by a comma, it will report register
41994 This feature indicates whether @value{GDBN} supports the
41995 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
41996 instruction reply packet}).
41999 This feature indicates whether @value{GDBN} supports the swbreak stop
42000 reason in stop replies. @xref{swbreak stop reason}, for details.
42003 This feature indicates whether @value{GDBN} supports the hwbreak stop
42004 reason in stop replies. @xref{swbreak stop reason}, for details.
42007 This feature indicates whether @value{GDBN} supports fork event
42008 extensions to the remote protocol. @value{GDBN} does not use such
42009 extensions unless the stub also reports that it supports them by
42010 including @samp{fork-events+} in its @samp{qSupported} reply.
42013 This feature indicates whether @value{GDBN} supports vfork event
42014 extensions to the remote protocol. @value{GDBN} does not use such
42015 extensions unless the stub also reports that it supports them by
42016 including @samp{vfork-events+} in its @samp{qSupported} reply.
42019 This feature indicates whether @value{GDBN} supports exec event
42020 extensions to the remote protocol. @value{GDBN} does not use such
42021 extensions unless the stub also reports that it supports them by
42022 including @samp{exec-events+} in its @samp{qSupported} reply.
42024 @item vContSupported
42025 This feature indicates whether @value{GDBN} wants to know the
42026 supported actions in the reply to @samp{vCont?} packet.
42029 Stubs should ignore any unknown values for
42030 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42031 packet supports receiving packets of unlimited length (earlier
42032 versions of @value{GDBN} may reject overly long responses). Additional values
42033 for @var{gdbfeature} may be defined in the future to let the stub take
42034 advantage of new features in @value{GDBN}, e.g.@: incompatible
42035 improvements in the remote protocol---the @samp{multiprocess} feature is
42036 an example of such a feature. The stub's reply should be independent
42037 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42038 describes all the features it supports, and then the stub replies with
42039 all the features it supports.
42041 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42042 responses, as long as each response uses one of the standard forms.
42044 Some features are flags. A stub which supports a flag feature
42045 should respond with a @samp{+} form response. Other features
42046 require values, and the stub should respond with an @samp{=}
42049 Each feature has a default value, which @value{GDBN} will use if
42050 @samp{qSupported} is not available or if the feature is not mentioned
42051 in the @samp{qSupported} response. The default values are fixed; a
42052 stub is free to omit any feature responses that match the defaults.
42054 Not all features can be probed, but for those which can, the probing
42055 mechanism is useful: in some cases, a stub's internal
42056 architecture may not allow the protocol layer to know some information
42057 about the underlying target in advance. This is especially common in
42058 stubs which may be configured for multiple targets.
42060 These are the currently defined stub features and their properties:
42062 @multitable @columnfractions 0.35 0.2 0.12 0.2
42063 @c NOTE: The first row should be @headitem, but we do not yet require
42064 @c a new enough version of Texinfo (4.7) to use @headitem.
42066 @tab Value Required
42070 @item @samp{PacketSize}
42075 @item @samp{qXfer:auxv:read}
42080 @item @samp{qXfer:btrace:read}
42085 @item @samp{qXfer:btrace-conf:read}
42090 @item @samp{qXfer:exec-file:read}
42095 @item @samp{qXfer:features:read}
42100 @item @samp{qXfer:libraries:read}
42105 @item @samp{qXfer:libraries-svr4:read}
42110 @item @samp{augmented-libraries-svr4-read}
42115 @item @samp{qXfer:memory-map:read}
42120 @item @samp{qXfer:sdata:read}
42125 @item @samp{qXfer:siginfo:read}
42130 @item @samp{qXfer:siginfo:write}
42135 @item @samp{qXfer:threads:read}
42140 @item @samp{qXfer:traceframe-info:read}
42145 @item @samp{qXfer:uib:read}
42150 @item @samp{qXfer:fdpic:read}
42155 @item @samp{Qbtrace:off}
42160 @item @samp{Qbtrace:bts}
42165 @item @samp{Qbtrace:pt}
42170 @item @samp{Qbtrace-conf:bts:size}
42175 @item @samp{Qbtrace-conf:pt:size}
42180 @item @samp{QNonStop}
42185 @item @samp{QCatchSyscalls}
42190 @item @samp{QPassSignals}
42195 @item @samp{QStartNoAckMode}
42200 @item @samp{multiprocess}
42205 @item @samp{ConditionalBreakpoints}
42210 @item @samp{ConditionalTracepoints}
42215 @item @samp{ReverseContinue}
42220 @item @samp{ReverseStep}
42225 @item @samp{TracepointSource}
42230 @item @samp{QAgent}
42235 @item @samp{QAllow}
42240 @item @samp{QDisableRandomization}
42245 @item @samp{EnableDisableTracepoints}
42250 @item @samp{QTBuffer:size}
42255 @item @samp{tracenz}
42260 @item @samp{BreakpointCommands}
42265 @item @samp{swbreak}
42270 @item @samp{hwbreak}
42275 @item @samp{fork-events}
42280 @item @samp{vfork-events}
42285 @item @samp{exec-events}
42290 @item @samp{QThreadEvents}
42295 @item @samp{no-resumed}
42300 @item @samp{memory-tagging}
42307 These are the currently defined stub features, in more detail:
42310 @cindex packet size, remote protocol
42311 @item PacketSize=@var{bytes}
42312 The remote stub can accept packets up to at least @var{bytes} in
42313 length. @value{GDBN} will send packets up to this size for bulk
42314 transfers, and will never send larger packets. This is a limit on the
42315 data characters in the packet, including the frame and checksum.
42316 There is no trailing NUL byte in a remote protocol packet; if the stub
42317 stores packets in a NUL-terminated format, it should allow an extra
42318 byte in its buffer for the NUL. If this stub feature is not supported,
42319 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42321 @item qXfer:auxv:read
42322 The remote stub understands the @samp{qXfer:auxv:read} packet
42323 (@pxref{qXfer auxiliary vector read}).
42325 @item qXfer:btrace:read
42326 The remote stub understands the @samp{qXfer:btrace:read}
42327 packet (@pxref{qXfer btrace read}).
42329 @item qXfer:btrace-conf:read
42330 The remote stub understands the @samp{qXfer:btrace-conf:read}
42331 packet (@pxref{qXfer btrace-conf read}).
42333 @item qXfer:exec-file:read
42334 The remote stub understands the @samp{qXfer:exec-file:read} packet
42335 (@pxref{qXfer executable filename read}).
42337 @item qXfer:features:read
42338 The remote stub understands the @samp{qXfer:features:read} packet
42339 (@pxref{qXfer target description read}).
42341 @item qXfer:libraries:read
42342 The remote stub understands the @samp{qXfer:libraries:read} packet
42343 (@pxref{qXfer library list read}).
42345 @item qXfer:libraries-svr4:read
42346 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42347 (@pxref{qXfer svr4 library list read}).
42349 @item augmented-libraries-svr4-read
42350 The remote stub understands the augmented form of the
42351 @samp{qXfer:libraries-svr4:read} packet
42352 (@pxref{qXfer svr4 library list read}).
42354 @item qXfer:memory-map:read
42355 The remote stub understands the @samp{qXfer:memory-map:read} packet
42356 (@pxref{qXfer memory map read}).
42358 @item qXfer:sdata:read
42359 The remote stub understands the @samp{qXfer:sdata:read} packet
42360 (@pxref{qXfer sdata read}).
42362 @item qXfer:siginfo:read
42363 The remote stub understands the @samp{qXfer:siginfo:read} packet
42364 (@pxref{qXfer siginfo read}).
42366 @item qXfer:siginfo:write
42367 The remote stub understands the @samp{qXfer:siginfo:write} packet
42368 (@pxref{qXfer siginfo write}).
42370 @item qXfer:threads:read
42371 The remote stub understands the @samp{qXfer:threads:read} packet
42372 (@pxref{qXfer threads read}).
42374 @item qXfer:traceframe-info:read
42375 The remote stub understands the @samp{qXfer:traceframe-info:read}
42376 packet (@pxref{qXfer traceframe info read}).
42378 @item qXfer:uib:read
42379 The remote stub understands the @samp{qXfer:uib:read}
42380 packet (@pxref{qXfer unwind info block}).
42382 @item qXfer:fdpic:read
42383 The remote stub understands the @samp{qXfer:fdpic:read}
42384 packet (@pxref{qXfer fdpic loadmap read}).
42387 The remote stub understands the @samp{QNonStop} packet
42388 (@pxref{QNonStop}).
42390 @item QCatchSyscalls
42391 The remote stub understands the @samp{QCatchSyscalls} packet
42392 (@pxref{QCatchSyscalls}).
42395 The remote stub understands the @samp{QPassSignals} packet
42396 (@pxref{QPassSignals}).
42398 @item QStartNoAckMode
42399 The remote stub understands the @samp{QStartNoAckMode} packet and
42400 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
42403 @anchor{multiprocess extensions}
42404 @cindex multiprocess extensions, in remote protocol
42405 The remote stub understands the multiprocess extensions to the remote
42406 protocol syntax. The multiprocess extensions affect the syntax of
42407 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
42408 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
42409 replies. Note that reporting this feature indicates support for the
42410 syntactic extensions only, not that the stub necessarily supports
42411 debugging of more than one process at a time. The stub must not use
42412 multiprocess extensions in packet replies unless @value{GDBN} has also
42413 indicated it supports them in its @samp{qSupported} request.
42415 @item qXfer:osdata:read
42416 The remote stub understands the @samp{qXfer:osdata:read} packet
42417 ((@pxref{qXfer osdata read}).
42419 @item ConditionalBreakpoints
42420 The target accepts and implements evaluation of conditional expressions
42421 defined for breakpoints. The target will only report breakpoint triggers
42422 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
42424 @item ConditionalTracepoints
42425 The remote stub accepts and implements conditional expressions defined
42426 for tracepoints (@pxref{Tracepoint Conditions}).
42428 @item ReverseContinue
42429 The remote stub accepts and implements the reverse continue packet
42433 The remote stub accepts and implements the reverse step packet
42436 @item TracepointSource
42437 The remote stub understands the @samp{QTDPsrc} packet that supplies
42438 the source form of tracepoint definitions.
42441 The remote stub understands the @samp{QAgent} packet.
42444 The remote stub understands the @samp{QAllow} packet.
42446 @item QDisableRandomization
42447 The remote stub understands the @samp{QDisableRandomization} packet.
42449 @item StaticTracepoint
42450 @cindex static tracepoints, in remote protocol
42451 The remote stub supports static tracepoints.
42453 @item InstallInTrace
42454 @anchor{install tracepoint in tracing}
42455 The remote stub supports installing tracepoint in tracing.
42457 @item EnableDisableTracepoints
42458 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
42459 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
42460 to be enabled and disabled while a trace experiment is running.
42462 @item QTBuffer:size
42463 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
42464 packet that allows to change the size of the trace buffer.
42467 @cindex string tracing, in remote protocol
42468 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
42469 See @ref{Bytecode Descriptions} for details about the bytecode.
42471 @item BreakpointCommands
42472 @cindex breakpoint commands, in remote protocol
42473 The remote stub supports running a breakpoint's command list itself,
42474 rather than reporting the hit to @value{GDBN}.
42477 The remote stub understands the @samp{Qbtrace:off} packet.
42480 The remote stub understands the @samp{Qbtrace:bts} packet.
42483 The remote stub understands the @samp{Qbtrace:pt} packet.
42485 @item Qbtrace-conf:bts:size
42486 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
42488 @item Qbtrace-conf:pt:size
42489 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
42492 The remote stub reports the @samp{swbreak} stop reason for memory
42496 The remote stub reports the @samp{hwbreak} stop reason for hardware
42500 The remote stub reports the @samp{fork} stop reason for fork events.
42503 The remote stub reports the @samp{vfork} stop reason for vfork events
42504 and vforkdone events.
42507 The remote stub reports the @samp{exec} stop reason for exec events.
42509 @item vContSupported
42510 The remote stub reports the supported actions in the reply to
42511 @samp{vCont?} packet.
42513 @item QThreadEvents
42514 The remote stub understands the @samp{QThreadEvents} packet.
42517 The remote stub reports the @samp{N} stop reply.
42520 @item memory-tagging
42521 The remote stub supports and implements the required memory tagging
42522 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
42523 @samp{QMemTags} (@pxref{QMemTags}) packets.
42525 For AArch64 GNU/Linux systems, this feature also requires access to the
42526 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
42527 This is done via the @samp{vFile} requests.
42532 @cindex symbol lookup, remote request
42533 @cindex @samp{qSymbol} packet
42534 Notify the target that @value{GDBN} is prepared to serve symbol lookup
42535 requests. Accept requests from the target for the values of symbols.
42540 The target does not need to look up any (more) symbols.
42541 @item qSymbol:@var{sym_name}
42542 The target requests the value of symbol @var{sym_name} (hex encoded).
42543 @value{GDBN} may provide the value by using the
42544 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
42548 @item qSymbol:@var{sym_value}:@var{sym_name}
42549 Set the value of @var{sym_name} to @var{sym_value}.
42551 @var{sym_name} (hex encoded) is the name of a symbol whose value the
42552 target has previously requested.
42554 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
42555 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
42561 The target does not need to look up any (more) symbols.
42562 @item qSymbol:@var{sym_name}
42563 The target requests the value of a new symbol @var{sym_name} (hex
42564 encoded). @value{GDBN} will continue to supply the values of symbols
42565 (if available), until the target ceases to request them.
42570 @itemx QTDisconnected
42577 @itemx qTMinFTPILen
42579 @xref{Tracepoint Packets}.
42581 @item qThreadExtraInfo,@var{thread-id}
42582 @cindex thread attributes info, remote request
42583 @cindex @samp{qThreadExtraInfo} packet
42584 Obtain from the target OS a printable string description of thread
42585 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
42586 for the forms of @var{thread-id}. This
42587 string may contain anything that the target OS thinks is interesting
42588 for @value{GDBN} to tell the user about the thread. The string is
42589 displayed in @value{GDBN}'s @code{info threads} display. Some
42590 examples of possible thread extra info strings are @samp{Runnable}, or
42591 @samp{Blocked on Mutex}.
42595 @item @var{XX}@dots{}
42596 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
42597 comprising the printable string containing the extra information about
42598 the thread's attributes.
42601 (Note that the @code{qThreadExtraInfo} packet's name is separated from
42602 the command by a @samp{,}, not a @samp{:}, contrary to the naming
42603 conventions above. Please don't use this packet as a model for new
42622 @xref{Tracepoint Packets}.
42624 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
42625 @cindex read special object, remote request
42626 @cindex @samp{qXfer} packet
42627 @anchor{qXfer read}
42628 Read uninterpreted bytes from the target's special data area
42629 identified by the keyword @var{object}. Request @var{length} bytes
42630 starting at @var{offset} bytes into the data. The content and
42631 encoding of @var{annex} is specific to @var{object}; it can supply
42632 additional details about what data to access.
42637 Data @var{data} (@pxref{Binary Data}) has been read from the
42638 target. There may be more data at a higher address (although
42639 it is permitted to return @samp{m} even for the last valid
42640 block of data, as long as at least one byte of data was read).
42641 It is possible for @var{data} to have fewer bytes than the @var{length} in the
42645 Data @var{data} (@pxref{Binary Data}) has been read from the target.
42646 There is no more data to be read. It is possible for @var{data} to
42647 have fewer bytes than the @var{length} in the request.
42650 The @var{offset} in the request is at the end of the data.
42651 There is no more data to be read.
42654 The request was malformed, or @var{annex} was invalid.
42657 The offset was invalid, or there was an error encountered reading the data.
42658 The @var{nn} part is a hex-encoded @code{errno} value.
42661 An empty reply indicates the @var{object} string was not recognized by
42662 the stub, or that the object does not support reading.
42665 Here are the specific requests of this form defined so far. All the
42666 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
42667 formats, listed above.
42670 @item qXfer:auxv:read::@var{offset},@var{length}
42671 @anchor{qXfer auxiliary vector read}
42672 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
42673 auxiliary vector}. Note @var{annex} must be empty.
42675 This packet is not probed by default; the remote stub must request it,
42676 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42678 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
42679 @anchor{qXfer btrace read}
42681 Return a description of the current branch trace.
42682 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
42683 packet may have one of the following values:
42687 Returns all available branch trace.
42690 Returns all available branch trace if the branch trace changed since
42691 the last read request.
42694 Returns the new branch trace since the last read request. Adds a new
42695 block to the end of the trace that begins at zero and ends at the source
42696 location of the first branch in the trace buffer. This extra block is
42697 used to stitch traces together.
42699 If the trace buffer overflowed, returns an error indicating the overflow.
42702 This packet is not probed by default; the remote stub must request it
42703 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42705 @item qXfer:btrace-conf:read::@var{offset},@var{length}
42706 @anchor{qXfer btrace-conf read}
42708 Return a description of the current branch trace configuration.
42709 @xref{Branch Trace Configuration Format}.
42711 This packet is not probed by default; the remote stub must request it
42712 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42714 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
42715 @anchor{qXfer executable filename read}
42716 Return the full absolute name of the file that was executed to create
42717 a process running on the remote system. The annex specifies the
42718 numeric process ID of the process to query, encoded as a hexadecimal
42719 number. If the annex part is empty the remote stub should return the
42720 filename corresponding to the currently executing process.
42722 This packet is not probed by default; the remote stub must request it,
42723 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42725 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
42726 @anchor{qXfer target description read}
42727 Access the @dfn{target description}. @xref{Target Descriptions}. The
42728 annex specifies which XML document to access. The main description is
42729 always loaded from the @samp{target.xml} annex.
42731 This packet is not probed by default; the remote stub must request it,
42732 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42734 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
42735 @anchor{qXfer library list read}
42736 Access the target's list of loaded libraries. @xref{Library List Format}.
42737 The annex part of the generic @samp{qXfer} packet must be empty
42738 (@pxref{qXfer read}).
42740 Targets which maintain a list of libraries in the program's memory do
42741 not need to implement this packet; it is designed for platforms where
42742 the operating system manages the list of loaded libraries.
42744 This packet is not probed by default; the remote stub must request it,
42745 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42747 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
42748 @anchor{qXfer svr4 library list read}
42749 Access the target's list of loaded libraries when the target is an SVR4
42750 platform. @xref{Library List Format for SVR4 Targets}. The annex part
42751 of the generic @samp{qXfer} packet must be empty unless the remote
42752 stub indicated it supports the augmented form of this packet
42753 by supplying an appropriate @samp{qSupported} response
42754 (@pxref{qXfer read}, @ref{qSupported}).
42756 This packet is optional for better performance on SVR4 targets.
42757 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
42759 This packet is not probed by default; the remote stub must request it,
42760 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42762 If the remote stub indicates it supports the augmented form of this
42763 packet then the annex part of the generic @samp{qXfer} packet may
42764 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
42765 arguments. The currently supported arguments are:
42768 @item start=@var{address}
42769 A hexadecimal number specifying the address of the @samp{struct
42770 link_map} to start reading the library list from. If unset or zero
42771 then the first @samp{struct link_map} in the library list will be
42772 chosen as the starting point.
42774 @item prev=@var{address}
42775 A hexadecimal number specifying the address of the @samp{struct
42776 link_map} immediately preceding the @samp{struct link_map}
42777 specified by the @samp{start} argument. If unset or zero then
42778 the remote stub will expect that no @samp{struct link_map}
42779 exists prior to the starting point.
42783 Arguments that are not understood by the remote stub will be silently
42786 @item qXfer:memory-map:read::@var{offset},@var{length}
42787 @anchor{qXfer memory map read}
42788 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
42789 annex part of the generic @samp{qXfer} packet must be empty
42790 (@pxref{qXfer read}).
42792 This packet is not probed by default; the remote stub must request it,
42793 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42795 @item qXfer:sdata:read::@var{offset},@var{length}
42796 @anchor{qXfer sdata read}
42798 Read contents of the extra collected static tracepoint marker
42799 information. The annex part of the generic @samp{qXfer} packet must
42800 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
42803 This packet is not probed by default; the remote stub must request it,
42804 by supplying an appropriate @samp{qSupported} response
42805 (@pxref{qSupported}).
42807 @item qXfer:siginfo:read::@var{offset},@var{length}
42808 @anchor{qXfer siginfo read}
42809 Read contents of the extra signal information on the target
42810 system. The annex part of the generic @samp{qXfer} packet must be
42811 empty (@pxref{qXfer read}).
42813 This packet is not probed by default; the remote stub must request it,
42814 by supplying an appropriate @samp{qSupported} response
42815 (@pxref{qSupported}).
42817 @item qXfer:threads:read::@var{offset},@var{length}
42818 @anchor{qXfer threads read}
42819 Access the list of threads on target. @xref{Thread List Format}. The
42820 annex part of the generic @samp{qXfer} packet must be empty
42821 (@pxref{qXfer read}).
42823 This packet is not probed by default; the remote stub must request it,
42824 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42826 @item qXfer:traceframe-info:read::@var{offset},@var{length}
42827 @anchor{qXfer traceframe info read}
42829 Return a description of the current traceframe's contents.
42830 @xref{Traceframe Info Format}. The annex part of the generic
42831 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
42833 This packet is not probed by default; the remote stub must request it,
42834 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42836 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
42837 @anchor{qXfer unwind info block}
42839 Return the unwind information block for @var{pc}. This packet is used
42840 on OpenVMS/ia64 to ask the kernel unwind information.
42842 This packet is not probed by default.
42844 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
42845 @anchor{qXfer fdpic loadmap read}
42846 Read contents of @code{loadmap}s on the target system. The
42847 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
42848 executable @code{loadmap} or interpreter @code{loadmap} to read.
42850 This packet is not probed by default; the remote stub must request it,
42851 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42853 @item qXfer:osdata:read::@var{offset},@var{length}
42854 @anchor{qXfer osdata read}
42855 Access the target's @dfn{operating system information}.
42856 @xref{Operating System Information}.
42860 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
42861 @cindex write data into object, remote request
42862 @anchor{qXfer write}
42863 Write uninterpreted bytes into the target's special data area
42864 identified by the keyword @var{object}, starting at @var{offset} bytes
42865 into the data. The binary-encoded data (@pxref{Binary Data}) to be
42866 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
42867 is specific to @var{object}; it can supply additional details about what data
42873 @var{nn} (hex encoded) is the number of bytes written.
42874 This may be fewer bytes than supplied in the request.
42877 The request was malformed, or @var{annex} was invalid.
42880 The offset was invalid, or there was an error encountered writing the data.
42881 The @var{nn} part is a hex-encoded @code{errno} value.
42884 An empty reply indicates the @var{object} string was not
42885 recognized by the stub, or that the object does not support writing.
42888 Here are the specific requests of this form defined so far. All the
42889 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
42890 formats, listed above.
42893 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
42894 @anchor{qXfer siginfo write}
42895 Write @var{data} to the extra signal information on the target system.
42896 The annex part of the generic @samp{qXfer} packet must be
42897 empty (@pxref{qXfer write}).
42899 This packet is not probed by default; the remote stub must request it,
42900 by supplying an appropriate @samp{qSupported} response
42901 (@pxref{qSupported}).
42904 @item qXfer:@var{object}:@var{operation}:@dots{}
42905 Requests of this form may be added in the future. When a stub does
42906 not recognize the @var{object} keyword, or its support for
42907 @var{object} does not recognize the @var{operation} keyword, the stub
42908 must respond with an empty packet.
42910 @item qAttached:@var{pid}
42911 @cindex query attached, remote request
42912 @cindex @samp{qAttached} packet
42913 Return an indication of whether the remote server attached to an
42914 existing process or created a new process. When the multiprocess
42915 protocol extensions are supported (@pxref{multiprocess extensions}),
42916 @var{pid} is an integer in hexadecimal format identifying the target
42917 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
42918 the query packet will be simplified as @samp{qAttached}.
42920 This query is used, for example, to know whether the remote process
42921 should be detached or killed when a @value{GDBN} session is ended with
42922 the @code{quit} command.
42927 The remote server attached to an existing process.
42929 The remote server created a new process.
42931 A badly formed request or an error was encountered.
42935 Enable branch tracing for the current thread using Branch Trace Store.
42940 Branch tracing has been enabled.
42942 A badly formed request or an error was encountered.
42946 Enable branch tracing for the current thread using Intel Processor Trace.
42951 Branch tracing has been enabled.
42953 A badly formed request or an error was encountered.
42957 Disable branch tracing for the current thread.
42962 Branch tracing has been disabled.
42964 A badly formed request or an error was encountered.
42967 @item Qbtrace-conf:bts:size=@var{value}
42968 Set the requested ring buffer size for new threads that use the
42969 btrace recording method in bts format.
42974 The ring buffer size has been set.
42976 A badly formed request or an error was encountered.
42979 @item Qbtrace-conf:pt:size=@var{value}
42980 Set the requested ring buffer size for new threads that use the
42981 btrace recording method in pt format.
42986 The ring buffer size has been set.
42988 A badly formed request or an error was encountered.
42993 @node Architecture-Specific Protocol Details
42994 @section Architecture-Specific Protocol Details
42996 This section describes how the remote protocol is applied to specific
42997 target architectures. Also see @ref{Standard Target Features}, for
42998 details of XML target descriptions for each architecture.
43001 * ARM-Specific Protocol Details::
43002 * MIPS-Specific Protocol Details::
43005 @node ARM-Specific Protocol Details
43006 @subsection @acronym{ARM}-specific Protocol Details
43009 * ARM Breakpoint Kinds::
43010 * ARM Memory Tag Types::
43013 @node ARM Breakpoint Kinds
43014 @subsubsection @acronym{ARM} Breakpoint Kinds
43015 @cindex breakpoint kinds, @acronym{ARM}
43017 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43022 16-bit Thumb mode breakpoint.
43025 32-bit Thumb mode (Thumb-2) breakpoint.
43028 32-bit @acronym{ARM} mode breakpoint.
43032 @node ARM Memory Tag Types
43033 @subsubsection @acronym{ARM} Memory Tag Types
43034 @cindex memory tag types, @acronym{ARM}
43036 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43049 @node MIPS-Specific Protocol Details
43050 @subsection @acronym{MIPS}-specific Protocol Details
43053 * MIPS Register packet Format::
43054 * MIPS Breakpoint Kinds::
43057 @node MIPS Register packet Format
43058 @subsubsection @acronym{MIPS} Register Packet Format
43059 @cindex register packet format, @acronym{MIPS}
43061 The following @code{g}/@code{G} packets have previously been defined.
43062 In the below, some thirty-two bit registers are transferred as
43063 sixty-four bits. Those registers should be zero/sign extended (which?)
43064 to fill the space allocated. Register bytes are transferred in target
43065 byte order. The two nibbles within a register byte are transferred
43066 most-significant -- least-significant.
43071 All registers are transferred as thirty-two bit quantities in the order:
43072 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43073 registers; fsr; fir; fp.
43076 All registers are transferred as sixty-four bit quantities (including
43077 thirty-two bit registers such as @code{sr}). The ordering is the same
43082 @node MIPS Breakpoint Kinds
43083 @subsubsection @acronym{MIPS} Breakpoint Kinds
43084 @cindex breakpoint kinds, @acronym{MIPS}
43086 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43091 16-bit @acronym{MIPS16} mode breakpoint.
43094 16-bit @acronym{microMIPS} mode breakpoint.
43097 32-bit standard @acronym{MIPS} mode breakpoint.
43100 32-bit @acronym{microMIPS} mode breakpoint.
43104 @node Tracepoint Packets
43105 @section Tracepoint Packets
43106 @cindex tracepoint packets
43107 @cindex packets, tracepoint
43109 Here we describe the packets @value{GDBN} uses to implement
43110 tracepoints (@pxref{Tracepoints}).
43114 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43115 @cindex @samp{QTDP} packet
43116 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43117 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43118 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43119 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43120 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43121 the number of bytes that the target should copy elsewhere to make room
43122 for the tracepoint. If an @samp{X} is present, it introduces a
43123 tracepoint condition, which consists of a hexadecimal length, followed
43124 by a comma and hex-encoded bytes, in a manner similar to action
43125 encodings as described below. If the trailing @samp{-} is present,
43126 further @samp{QTDP} packets will follow to specify this tracepoint's
43132 The packet was understood and carried out.
43134 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43136 The packet was not recognized.
43139 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43140 Define actions to be taken when a tracepoint is hit. The @var{n} and
43141 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43142 this tracepoint. This packet may only be sent immediately after
43143 another @samp{QTDP} packet that ended with a @samp{-}. If the
43144 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43145 specifying more actions for this tracepoint.
43147 In the series of action packets for a given tracepoint, at most one
43148 can have an @samp{S} before its first @var{action}. If such a packet
43149 is sent, it and the following packets define ``while-stepping''
43150 actions. Any prior packets define ordinary actions --- that is, those
43151 taken when the tracepoint is first hit. If no action packet has an
43152 @samp{S}, then all the packets in the series specify ordinary
43153 tracepoint actions.
43155 The @samp{@var{action}@dots{}} portion of the packet is a series of
43156 actions, concatenated without separators. Each action has one of the
43162 Collect the registers whose bits are set in @var{mask},
43163 a hexadecimal number whose @var{i}'th bit is set if register number
43164 @var{i} should be collected. (The least significant bit is numbered
43165 zero.) Note that @var{mask} may be any number of digits long; it may
43166 not fit in a 32-bit word.
43168 @item M @var{basereg},@var{offset},@var{len}
43169 Collect @var{len} bytes of memory starting at the address in register
43170 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43171 @samp{-1}, then the range has a fixed address: @var{offset} is the
43172 address of the lowest byte to collect. The @var{basereg},
43173 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43174 values (the @samp{-1} value for @var{basereg} is a special case).
43176 @item X @var{len},@var{expr}
43177 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43178 it directs. The agent expression @var{expr} is as described in
43179 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43180 two-digit hex number in the packet; @var{len} is the number of bytes
43181 in the expression (and thus one-half the number of hex digits in the
43186 Any number of actions may be packed together in a single @samp{QTDP}
43187 packet, as long as the packet does not exceed the maximum packet
43188 length (400 bytes, for many stubs). There may be only one @samp{R}
43189 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43190 actions. Any registers referred to by @samp{M} and @samp{X} actions
43191 must be collected by a preceding @samp{R} action. (The
43192 ``while-stepping'' actions are treated as if they were attached to a
43193 separate tracepoint, as far as these restrictions are concerned.)
43198 The packet was understood and carried out.
43200 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43202 The packet was not recognized.
43205 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43206 @cindex @samp{QTDPsrc} packet
43207 Specify a source string of tracepoint @var{n} at address @var{addr}.
43208 This is useful to get accurate reproduction of the tracepoints
43209 originally downloaded at the beginning of the trace run. The @var{type}
43210 is the name of the tracepoint part, such as @samp{cond} for the
43211 tracepoint's conditional expression (see below for a list of types), while
43212 @var{bytes} is the string, encoded in hexadecimal.
43214 @var{start} is the offset of the @var{bytes} within the overall source
43215 string, while @var{slen} is the total length of the source string.
43216 This is intended for handling source strings that are longer than will
43217 fit in a single packet.
43218 @c Add detailed example when this info is moved into a dedicated
43219 @c tracepoint descriptions section.
43221 The available string types are @samp{at} for the location,
43222 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43223 @value{GDBN} sends a separate packet for each command in the action
43224 list, in the same order in which the commands are stored in the list.
43226 The target does not need to do anything with source strings except
43227 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43230 Although this packet is optional, and @value{GDBN} will only send it
43231 if the target replies with @samp{TracepointSource} @xref{General
43232 Query Packets}, it makes both disconnected tracing and trace files
43233 much easier to use. Otherwise the user must be careful that the
43234 tracepoints in effect while looking at trace frames are identical to
43235 the ones in effect during the trace run; even a small discrepancy
43236 could cause @samp{tdump} not to work, or a particular trace frame not
43239 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43240 @cindex define trace state variable, remote request
43241 @cindex @samp{QTDV} packet
43242 Create a new trace state variable, number @var{n}, with an initial
43243 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43244 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43245 the option of not using this packet for initial values of zero; the
43246 target should simply create the trace state variables as they are
43247 mentioned in expressions. The value @var{builtin} should be 1 (one)
43248 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43249 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43250 @samp{qTsV} packet had it set. The contents of @var{name} is the
43251 hex-encoded name (without the leading @samp{$}) of the trace state
43254 @item QTFrame:@var{n}
43255 @cindex @samp{QTFrame} packet
43256 Select the @var{n}'th tracepoint frame from the buffer, and use the
43257 register and memory contents recorded there to answer subsequent
43258 request packets from @value{GDBN}.
43260 A successful reply from the stub indicates that the stub has found the
43261 requested frame. The response is a series of parts, concatenated
43262 without separators, describing the frame we selected. Each part has
43263 one of the following forms:
43267 The selected frame is number @var{n} in the trace frame buffer;
43268 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43269 was no frame matching the criteria in the request packet.
43272 The selected trace frame records a hit of tracepoint number @var{t};
43273 @var{t} is a hexadecimal number.
43277 @item QTFrame:pc:@var{addr}
43278 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43279 currently selected frame whose PC is @var{addr};
43280 @var{addr} is a hexadecimal number.
43282 @item QTFrame:tdp:@var{t}
43283 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43284 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43285 is a hexadecimal number.
43287 @item QTFrame:range:@var{start}:@var{end}
43288 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43289 currently selected frame whose PC is between @var{start} (inclusive)
43290 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43293 @item QTFrame:outside:@var{start}:@var{end}
43294 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43295 frame @emph{outside} the given range of addresses (exclusive).
43298 @cindex @samp{qTMinFTPILen} packet
43299 This packet requests the minimum length of instruction at which a fast
43300 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43301 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43302 it depends on the target system being able to create trampolines in
43303 the first 64K of memory, which might or might not be possible for that
43304 system. So the reply to this packet will be 4 if it is able to
43311 The minimum instruction length is currently unknown.
43313 The minimum instruction length is @var{length}, where @var{length}
43314 is a hexadecimal number greater or equal to 1. A reply
43315 of 1 means that a fast tracepoint may be placed on any instruction
43316 regardless of size.
43318 An error has occurred.
43320 An empty reply indicates that the request is not supported by the stub.
43324 @cindex @samp{QTStart} packet
43325 Begin the tracepoint experiment. Begin collecting data from
43326 tracepoint hits in the trace frame buffer. This packet supports the
43327 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43328 instruction reply packet}).
43331 @cindex @samp{QTStop} packet
43332 End the tracepoint experiment. Stop collecting trace frames.
43334 @item QTEnable:@var{n}:@var{addr}
43336 @cindex @samp{QTEnable} packet
43337 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43338 experiment. If the tracepoint was previously disabled, then collection
43339 of data from it will resume.
43341 @item QTDisable:@var{n}:@var{addr}
43343 @cindex @samp{QTDisable} packet
43344 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43345 experiment. No more data will be collected from the tracepoint unless
43346 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43349 @cindex @samp{QTinit} packet
43350 Clear the table of tracepoints, and empty the trace frame buffer.
43352 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43353 @cindex @samp{QTro} packet
43354 Establish the given ranges of memory as ``transparent''. The stub
43355 will answer requests for these ranges from memory's current contents,
43356 if they were not collected as part of the tracepoint hit.
43358 @value{GDBN} uses this to mark read-only regions of memory, like those
43359 containing program code. Since these areas never change, they should
43360 still have the same contents they did when the tracepoint was hit, so
43361 there's no reason for the stub to refuse to provide their contents.
43363 @item QTDisconnected:@var{value}
43364 @cindex @samp{QTDisconnected} packet
43365 Set the choice to what to do with the tracing run when @value{GDBN}
43366 disconnects from the target. A @var{value} of 1 directs the target to
43367 continue the tracing run, while 0 tells the target to stop tracing if
43368 @value{GDBN} is no longer in the picture.
43371 @cindex @samp{qTStatus} packet
43372 Ask the stub if there is a trace experiment running right now.
43374 The reply has the form:
43378 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
43379 @var{running} is a single digit @code{1} if the trace is presently
43380 running, or @code{0} if not. It is followed by semicolon-separated
43381 optional fields that an agent may use to report additional status.
43385 If the trace is not running, the agent may report any of several
43386 explanations as one of the optional fields:
43391 No trace has been run yet.
43393 @item tstop[:@var{text}]:0
43394 The trace was stopped by a user-originated stop command. The optional
43395 @var{text} field is a user-supplied string supplied as part of the
43396 stop command (for instance, an explanation of why the trace was
43397 stopped manually). It is hex-encoded.
43400 The trace stopped because the trace buffer filled up.
43402 @item tdisconnected:0
43403 The trace stopped because @value{GDBN} disconnected from the target.
43405 @item tpasscount:@var{tpnum}
43406 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
43408 @item terror:@var{text}:@var{tpnum}
43409 The trace stopped because tracepoint @var{tpnum} had an error. The
43410 string @var{text} is available to describe the nature of the error
43411 (for instance, a divide by zero in the condition expression); it
43415 The trace stopped for some other reason.
43419 Additional optional fields supply statistical and other information.
43420 Although not required, they are extremely useful for users monitoring
43421 the progress of a trace run. If a trace has stopped, and these
43422 numbers are reported, they must reflect the state of the just-stopped
43427 @item tframes:@var{n}
43428 The number of trace frames in the buffer.
43430 @item tcreated:@var{n}
43431 The total number of trace frames created during the run. This may
43432 be larger than the trace frame count, if the buffer is circular.
43434 @item tsize:@var{n}
43435 The total size of the trace buffer, in bytes.
43437 @item tfree:@var{n}
43438 The number of bytes still unused in the buffer.
43440 @item circular:@var{n}
43441 The value of the circular trace buffer flag. @code{1} means that the
43442 trace buffer is circular and old trace frames will be discarded if
43443 necessary to make room, @code{0} means that the trace buffer is linear
43446 @item disconn:@var{n}
43447 The value of the disconnected tracing flag. @code{1} means that
43448 tracing will continue after @value{GDBN} disconnects, @code{0} means
43449 that the trace run will stop.
43453 @item qTP:@var{tp}:@var{addr}
43454 @cindex tracepoint status, remote request
43455 @cindex @samp{qTP} packet
43456 Ask the stub for the current state of tracepoint number @var{tp} at
43457 address @var{addr}.
43461 @item V@var{hits}:@var{usage}
43462 The tracepoint has been hit @var{hits} times so far during the trace
43463 run, and accounts for @var{usage} in the trace buffer. Note that
43464 @code{while-stepping} steps are not counted as separate hits, but the
43465 steps' space consumption is added into the usage number.
43469 @item qTV:@var{var}
43470 @cindex trace state variable value, remote request
43471 @cindex @samp{qTV} packet
43472 Ask the stub for the value of the trace state variable number @var{var}.
43477 The value of the variable is @var{value}. This will be the current
43478 value of the variable if the user is examining a running target, or a
43479 saved value if the variable was collected in the trace frame that the
43480 user is looking at. Note that multiple requests may result in
43481 different reply values, such as when requesting values while the
43482 program is running.
43485 The value of the variable is unknown. This would occur, for example,
43486 if the user is examining a trace frame in which the requested variable
43491 @cindex @samp{qTfP} packet
43493 @cindex @samp{qTsP} packet
43494 These packets request data about tracepoints that are being used by
43495 the target. @value{GDBN} sends @code{qTfP} to get the first piece
43496 of data, and multiple @code{qTsP} to get additional pieces. Replies
43497 to these packets generally take the form of the @code{QTDP} packets
43498 that define tracepoints. (FIXME add detailed syntax)
43501 @cindex @samp{qTfV} packet
43503 @cindex @samp{qTsV} packet
43504 These packets request data about trace state variables that are on the
43505 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
43506 and multiple @code{qTsV} to get additional variables. Replies to
43507 these packets follow the syntax of the @code{QTDV} packets that define
43508 trace state variables.
43514 @cindex @samp{qTfSTM} packet
43515 @cindex @samp{qTsSTM} packet
43516 These packets request data about static tracepoint markers that exist
43517 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
43518 first piece of data, and multiple @code{qTsSTM} to get additional
43519 pieces. Replies to these packets take the following form:
43523 @item m @var{address}:@var{id}:@var{extra}
43525 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
43526 a comma-separated list of markers
43528 (lower case letter @samp{L}) denotes end of list.
43530 An error occurred. The error number @var{nn} is given as hex digits.
43532 An empty reply indicates that the request is not supported by the
43536 The @var{address} is encoded in hex;
43537 @var{id} and @var{extra} are strings encoded in hex.
43539 In response to each query, the target will reply with a list of one or
43540 more markers, separated by commas. @value{GDBN} will respond to each
43541 reply with a request for more markers (using the @samp{qs} form of the
43542 query), until the target responds with @samp{l} (lower-case ell, for
43545 @item qTSTMat:@var{address}
43547 @cindex @samp{qTSTMat} packet
43548 This packets requests data about static tracepoint markers in the
43549 target program at @var{address}. Replies to this packet follow the
43550 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
43551 tracepoint markers.
43553 @item QTSave:@var{filename}
43554 @cindex @samp{QTSave} packet
43555 This packet directs the target to save trace data to the file name
43556 @var{filename} in the target's filesystem. The @var{filename} is encoded
43557 as a hex string; the interpretation of the file name (relative vs
43558 absolute, wild cards, etc) is up to the target.
43560 @item qTBuffer:@var{offset},@var{len}
43561 @cindex @samp{qTBuffer} packet
43562 Return up to @var{len} bytes of the current contents of trace buffer,
43563 starting at @var{offset}. The trace buffer is treated as if it were
43564 a contiguous collection of traceframes, as per the trace file format.
43565 The reply consists as many hex-encoded bytes as the target can deliver
43566 in a packet; it is not an error to return fewer than were asked for.
43567 A reply consisting of just @code{l} indicates that no bytes are
43570 @item QTBuffer:circular:@var{value}
43571 This packet directs the target to use a circular trace buffer if
43572 @var{value} is 1, or a linear buffer if the value is 0.
43574 @item QTBuffer:size:@var{size}
43575 @anchor{QTBuffer-size}
43576 @cindex @samp{QTBuffer size} packet
43577 This packet directs the target to make the trace buffer be of size
43578 @var{size} if possible. A value of @code{-1} tells the target to
43579 use whatever size it prefers.
43581 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
43582 @cindex @samp{QTNotes} packet
43583 This packet adds optional textual notes to the trace run. Allowable
43584 types include @code{user}, @code{notes}, and @code{tstop}, the
43585 @var{text} fields are arbitrary strings, hex-encoded.
43589 @subsection Relocate instruction reply packet
43590 When installing fast tracepoints in memory, the target may need to
43591 relocate the instruction currently at the tracepoint address to a
43592 different address in memory. For most instructions, a simple copy is
43593 enough, but, for example, call instructions that implicitly push the
43594 return address on the stack, and relative branches or other
43595 PC-relative instructions require offset adjustment, so that the effect
43596 of executing the instruction at a different address is the same as if
43597 it had executed in the original location.
43599 In response to several of the tracepoint packets, the target may also
43600 respond with a number of intermediate @samp{qRelocInsn} request
43601 packets before the final result packet, to have @value{GDBN} handle
43602 this relocation operation. If a packet supports this mechanism, its
43603 documentation will explicitly say so. See for example the above
43604 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
43605 format of the request is:
43608 @item qRelocInsn:@var{from};@var{to}
43610 This requests @value{GDBN} to copy instruction at address @var{from}
43611 to address @var{to}, possibly adjusted so that executing the
43612 instruction at @var{to} has the same effect as executing it at
43613 @var{from}. @value{GDBN} writes the adjusted instruction to target
43614 memory starting at @var{to}.
43619 @item qRelocInsn:@var{adjusted_size}
43620 Informs the stub the relocation is complete. The @var{adjusted_size} is
43621 the length in bytes of resulting relocated instruction sequence.
43623 A badly formed request was detected, or an error was encountered while
43624 relocating the instruction.
43627 @node Host I/O Packets
43628 @section Host I/O Packets
43629 @cindex Host I/O, remote protocol
43630 @cindex file transfer, remote protocol
43632 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
43633 operations on the far side of a remote link. For example, Host I/O is
43634 used to upload and download files to a remote target with its own
43635 filesystem. Host I/O uses the same constant values and data structure
43636 layout as the target-initiated File-I/O protocol. However, the
43637 Host I/O packets are structured differently. The target-initiated
43638 protocol relies on target memory to store parameters and buffers.
43639 Host I/O requests are initiated by @value{GDBN}, and the
43640 target's memory is not involved. @xref{File-I/O Remote Protocol
43641 Extension}, for more details on the target-initiated protocol.
43643 The Host I/O request packets all encode a single operation along with
43644 its arguments. They have this format:
43648 @item vFile:@var{operation}: @var{parameter}@dots{}
43649 @var{operation} is the name of the particular request; the target
43650 should compare the entire packet name up to the second colon when checking
43651 for a supported operation. The format of @var{parameter} depends on
43652 the operation. Numbers are always passed in hexadecimal. Negative
43653 numbers have an explicit minus sign (i.e.@: two's complement is not
43654 used). Strings (e.g.@: filenames) are encoded as a series of
43655 hexadecimal bytes. The last argument to a system call may be a
43656 buffer of escaped binary data (@pxref{Binary Data}).
43660 The valid responses to Host I/O packets are:
43664 @item F @var{result} [, @var{errno}] [; @var{attachment}]
43665 @var{result} is the integer value returned by this operation, usually
43666 non-negative for success and -1 for errors. If an error has occured,
43667 @var{errno} will be included in the result specifying a
43668 value defined by the File-I/O protocol (@pxref{Errno Values}). For
43669 operations which return data, @var{attachment} supplies the data as a
43670 binary buffer. Binary buffers in response packets are escaped in the
43671 normal way (@pxref{Binary Data}). See the individual packet
43672 documentation for the interpretation of @var{result} and
43676 An empty response indicates that this operation is not recognized.
43680 These are the supported Host I/O operations:
43683 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
43684 Open a file at @var{filename} and return a file descriptor for it, or
43685 return -1 if an error occurs. The @var{filename} is a string,
43686 @var{flags} is an integer indicating a mask of open flags
43687 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
43688 of mode bits to use if the file is created (@pxref{mode_t Values}).
43689 @xref{open}, for details of the open flags and mode values.
43691 @item vFile:close: @var{fd}
43692 Close the open file corresponding to @var{fd} and return 0, or
43693 -1 if an error occurs.
43695 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
43696 Read data from the open file corresponding to @var{fd}. Up to
43697 @var{count} bytes will be read from the file, starting at @var{offset}
43698 relative to the start of the file. The target may read fewer bytes;
43699 common reasons include packet size limits and an end-of-file
43700 condition. The number of bytes read is returned. Zero should only be
43701 returned for a successful read at the end of the file, or if
43702 @var{count} was zero.
43704 The data read should be returned as a binary attachment on success.
43705 If zero bytes were read, the response should include an empty binary
43706 attachment (i.e.@: a trailing semicolon). The return value is the
43707 number of target bytes read; the binary attachment may be longer if
43708 some characters were escaped.
43710 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
43711 Write @var{data} (a binary buffer) to the open file corresponding
43712 to @var{fd}. Start the write at @var{offset} from the start of the
43713 file. Unlike many @code{write} system calls, there is no
43714 separate @var{count} argument; the length of @var{data} in the
43715 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
43716 which may be shorter than the length of @var{data}, or -1 if an
43719 @item vFile:fstat: @var{fd}
43720 Get information about the open file corresponding to @var{fd}.
43721 On success the information is returned as a binary attachment
43722 and the return value is the size of this attachment in bytes.
43723 If an error occurs the return value is -1. The format of the
43724 returned binary attachment is as described in @ref{struct stat}.
43726 @item vFile:unlink: @var{filename}
43727 Delete the file at @var{filename} on the target. Return 0,
43728 or -1 if an error occurs. The @var{filename} is a string.
43730 @item vFile:readlink: @var{filename}
43731 Read value of symbolic link @var{filename} on the target. Return
43732 the number of bytes read, or -1 if an error occurs.
43734 The data read should be returned as a binary attachment on success.
43735 If zero bytes were read, the response should include an empty binary
43736 attachment (i.e.@: a trailing semicolon). The return value is the
43737 number of target bytes read; the binary attachment may be longer if
43738 some characters were escaped.
43740 @item vFile:setfs: @var{pid}
43741 Select the filesystem on which @code{vFile} operations with
43742 @var{filename} arguments will operate. This is required for
43743 @value{GDBN} to be able to access files on remote targets where
43744 the remote stub does not share a common filesystem with the
43747 If @var{pid} is nonzero, select the filesystem as seen by process
43748 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
43749 the remote stub. Return 0 on success, or -1 if an error occurs.
43750 If @code{vFile:setfs:} indicates success, the selected filesystem
43751 remains selected until the next successful @code{vFile:setfs:}
43757 @section Interrupts
43758 @cindex interrupts (remote protocol)
43759 @anchor{interrupting remote targets}
43761 In all-stop mode, when a program on the remote target is running,
43762 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
43763 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
43764 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
43766 The precise meaning of @code{BREAK} is defined by the transport
43767 mechanism and may, in fact, be undefined. @value{GDBN} does not
43768 currently define a @code{BREAK} mechanism for any of the network
43769 interfaces except for TCP, in which case @value{GDBN} sends the
43770 @code{telnet} BREAK sequence.
43772 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
43773 transport mechanisms. It is represented by sending the single byte
43774 @code{0x03} without any of the usual packet overhead described in
43775 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
43776 transmitted as part of a packet, it is considered to be packet data
43777 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
43778 (@pxref{X packet}), used for binary downloads, may include an unescaped
43779 @code{0x03} as part of its packet.
43781 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
43782 When Linux kernel receives this sequence from serial port,
43783 it stops execution and connects to gdb.
43785 In non-stop mode, because packet resumptions are asynchronous
43786 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
43787 command to the remote stub, even when the target is running. For that
43788 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
43789 packet}) with the usual packet framing instead of the single byte
43792 Stubs are not required to recognize these interrupt mechanisms and the
43793 precise meaning associated with receipt of the interrupt is
43794 implementation defined. If the target supports debugging of multiple
43795 threads and/or processes, it should attempt to interrupt all
43796 currently-executing threads and processes.
43797 If the stub is successful at interrupting the
43798 running program, it should send one of the stop
43799 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
43800 of successfully stopping the program in all-stop mode, and a stop reply
43801 for each stopped thread in non-stop mode.
43802 Interrupts received while the
43803 program is stopped are queued and the program will be interrupted when
43804 it is resumed next time.
43806 @node Notification Packets
43807 @section Notification Packets
43808 @cindex notification packets
43809 @cindex packets, notification
43811 The @value{GDBN} remote serial protocol includes @dfn{notifications},
43812 packets that require no acknowledgment. Both the GDB and the stub
43813 may send notifications (although the only notifications defined at
43814 present are sent by the stub). Notifications carry information
43815 without incurring the round-trip latency of an acknowledgment, and so
43816 are useful for low-impact communications where occasional packet loss
43819 A notification packet has the form @samp{% @var{data} #
43820 @var{checksum}}, where @var{data} is the content of the notification,
43821 and @var{checksum} is a checksum of @var{data}, computed and formatted
43822 as for ordinary @value{GDBN} packets. A notification's @var{data}
43823 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
43824 receiving a notification, the recipient sends no @samp{+} or @samp{-}
43825 to acknowledge the notification's receipt or to report its corruption.
43827 Every notification's @var{data} begins with a name, which contains no
43828 colon characters, followed by a colon character.
43830 Recipients should silently ignore corrupted notifications and
43831 notifications they do not understand. Recipients should restart
43832 timeout periods on receipt of a well-formed notification, whether or
43833 not they understand it.
43835 Senders should only send the notifications described here when this
43836 protocol description specifies that they are permitted. In the
43837 future, we may extend the protocol to permit existing notifications in
43838 new contexts; this rule helps older senders avoid confusing newer
43841 (Older versions of @value{GDBN} ignore bytes received until they see
43842 the @samp{$} byte that begins an ordinary packet, so new stubs may
43843 transmit notifications without fear of confusing older clients. There
43844 are no notifications defined for @value{GDBN} to send at the moment, but we
43845 assume that most older stubs would ignore them, as well.)
43847 Each notification is comprised of three parts:
43849 @item @var{name}:@var{event}
43850 The notification packet is sent by the side that initiates the
43851 exchange (currently, only the stub does that), with @var{event}
43852 carrying the specific information about the notification, and
43853 @var{name} specifying the name of the notification.
43855 The acknowledge sent by the other side, usually @value{GDBN}, to
43856 acknowledge the exchange and request the event.
43859 The purpose of an asynchronous notification mechanism is to report to
43860 @value{GDBN} that something interesting happened in the remote stub.
43862 The remote stub may send notification @var{name}:@var{event}
43863 at any time, but @value{GDBN} acknowledges the notification when
43864 appropriate. The notification event is pending before @value{GDBN}
43865 acknowledges. Only one notification at a time may be pending; if
43866 additional events occur before @value{GDBN} has acknowledged the
43867 previous notification, they must be queued by the stub for later
43868 synchronous transmission in response to @var{ack} packets from
43869 @value{GDBN}. Because the notification mechanism is unreliable,
43870 the stub is permitted to resend a notification if it believes
43871 @value{GDBN} may not have received it.
43873 Specifically, notifications may appear when @value{GDBN} is not
43874 otherwise reading input from the stub, or when @value{GDBN} is
43875 expecting to read a normal synchronous response or a
43876 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
43877 Notification packets are distinct from any other communication from
43878 the stub so there is no ambiguity.
43880 After receiving a notification, @value{GDBN} shall acknowledge it by
43881 sending a @var{ack} packet as a regular, synchronous request to the
43882 stub. Such acknowledgment is not required to happen immediately, as
43883 @value{GDBN} is permitted to send other, unrelated packets to the
43884 stub first, which the stub should process normally.
43886 Upon receiving a @var{ack} packet, if the stub has other queued
43887 events to report to @value{GDBN}, it shall respond by sending a
43888 normal @var{event}. @value{GDBN} shall then send another @var{ack}
43889 packet to solicit further responses; again, it is permitted to send
43890 other, unrelated packets as well which the stub should process
43893 If the stub receives a @var{ack} packet and there are no additional
43894 @var{event} to report, the stub shall return an @samp{OK} response.
43895 At this point, @value{GDBN} has finished processing a notification
43896 and the stub has completed sending any queued events. @value{GDBN}
43897 won't accept any new notifications until the final @samp{OK} is
43898 received . If further notification events occur, the stub shall send
43899 a new notification, @value{GDBN} shall accept the notification, and
43900 the process shall be repeated.
43902 The process of asynchronous notification can be illustrated by the
43905 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
43908 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
43910 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
43915 The following notifications are defined:
43916 @multitable @columnfractions 0.12 0.12 0.38 0.38
43925 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
43926 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
43927 for information on how these notifications are acknowledged by
43929 @tab Report an asynchronous stop event in non-stop mode.
43933 @node Remote Non-Stop
43934 @section Remote Protocol Support for Non-Stop Mode
43936 @value{GDBN}'s remote protocol supports non-stop debugging of
43937 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
43938 supports non-stop mode, it should report that to @value{GDBN} by including
43939 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
43941 @value{GDBN} typically sends a @samp{QNonStop} packet only when
43942 establishing a new connection with the stub. Entering non-stop mode
43943 does not alter the state of any currently-running threads, but targets
43944 must stop all threads in any already-attached processes when entering
43945 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
43946 probe the target state after a mode change.
43948 In non-stop mode, when an attached process encounters an event that
43949 would otherwise be reported with a stop reply, it uses the
43950 asynchronous notification mechanism (@pxref{Notification Packets}) to
43951 inform @value{GDBN}. In contrast to all-stop mode, where all threads
43952 in all processes are stopped when a stop reply is sent, in non-stop
43953 mode only the thread reporting the stop event is stopped. That is,
43954 when reporting a @samp{S} or @samp{T} response to indicate completion
43955 of a step operation, hitting a breakpoint, or a fault, only the
43956 affected thread is stopped; any other still-running threads continue
43957 to run. When reporting a @samp{W} or @samp{X} response, all running
43958 threads belonging to other attached processes continue to run.
43960 In non-stop mode, the target shall respond to the @samp{?} packet as
43961 follows. First, any incomplete stop reply notification/@samp{vStopped}
43962 sequence in progress is abandoned. The target must begin a new
43963 sequence reporting stop events for all stopped threads, whether or not
43964 it has previously reported those events to @value{GDBN}. The first
43965 stop reply is sent as a synchronous reply to the @samp{?} packet, and
43966 subsequent stop replies are sent as responses to @samp{vStopped} packets
43967 using the mechanism described above. The target must not send
43968 asynchronous stop reply notifications until the sequence is complete.
43969 If all threads are running when the target receives the @samp{?} packet,
43970 or if the target is not attached to any process, it shall respond
43973 If the stub supports non-stop mode, it should also support the
43974 @samp{swbreak} stop reason if software breakpoints are supported, and
43975 the @samp{hwbreak} stop reason if hardware breakpoints are supported
43976 (@pxref{swbreak stop reason}). This is because given the asynchronous
43977 nature of non-stop mode, between the time a thread hits a breakpoint
43978 and the time the event is finally processed by @value{GDBN}, the
43979 breakpoint may have already been removed from the target. Due to
43980 this, @value{GDBN} needs to be able to tell whether a trap stop was
43981 caused by a delayed breakpoint event, which should be ignored, as
43982 opposed to a random trap signal, which should be reported to the user.
43983 Note the @samp{swbreak} feature implies that the target is responsible
43984 for adjusting the PC when a software breakpoint triggers, if
43985 necessary, such as on the x86 architecture.
43987 @node Packet Acknowledgment
43988 @section Packet Acknowledgment
43990 @cindex acknowledgment, for @value{GDBN} remote
43991 @cindex packet acknowledgment, for @value{GDBN} remote
43992 By default, when either the host or the target machine receives a packet,
43993 the first response expected is an acknowledgment: either @samp{+} (to indicate
43994 the package was received correctly) or @samp{-} (to request retransmission).
43995 This mechanism allows the @value{GDBN} remote protocol to operate over
43996 unreliable transport mechanisms, such as a serial line.
43998 In cases where the transport mechanism is itself reliable (such as a pipe or
43999 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44000 It may be desirable to disable them in that case to reduce communication
44001 overhead, or for other reasons. This can be accomplished by means of the
44002 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44004 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44005 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44006 and response format still includes the normal checksum, as described in
44007 @ref{Overview}, but the checksum may be ignored by the receiver.
44009 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44010 no-acknowledgment mode, it should report that to @value{GDBN}
44011 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44012 @pxref{qSupported}.
44013 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44014 disabled via the @code{set remote noack-packet off} command
44015 (@pxref{Remote Configuration}),
44016 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44017 Only then may the stub actually turn off packet acknowledgments.
44018 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44019 response, which can be safely ignored by the stub.
44021 Note that @code{set remote noack-packet} command only affects negotiation
44022 between @value{GDBN} and the stub when subsequent connections are made;
44023 it does not affect the protocol acknowledgment state for any current
44025 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44026 new connection is established,
44027 there is also no protocol request to re-enable the acknowledgments
44028 for the current connection, once disabled.
44033 Example sequence of a target being re-started. Notice how the restart
44034 does not get any direct output:
44039 @emph{target restarts}
44042 <- @code{T001:1234123412341234}
44046 Example sequence of a target being stepped by a single instruction:
44049 -> @code{G1445@dots{}}
44054 <- @code{T001:1234123412341234}
44058 <- @code{1455@dots{}}
44062 @node File-I/O Remote Protocol Extension
44063 @section File-I/O Remote Protocol Extension
44064 @cindex File-I/O remote protocol extension
44067 * File-I/O Overview::
44068 * Protocol Basics::
44069 * The F Request Packet::
44070 * The F Reply Packet::
44071 * The Ctrl-C Message::
44073 * List of Supported Calls::
44074 * Protocol-specific Representation of Datatypes::
44076 * File-I/O Examples::
44079 @node File-I/O Overview
44080 @subsection File-I/O Overview
44081 @cindex file-i/o overview
44083 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44084 target to use the host's file system and console I/O to perform various
44085 system calls. System calls on the target system are translated into a
44086 remote protocol packet to the host system, which then performs the needed
44087 actions and returns a response packet to the target system.
44088 This simulates file system operations even on targets that lack file systems.
44090 The protocol is defined to be independent of both the host and target systems.
44091 It uses its own internal representation of datatypes and values. Both
44092 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44093 translating the system-dependent value representations into the internal
44094 protocol representations when data is transmitted.
44096 The communication is synchronous. A system call is possible only when
44097 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44098 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44099 the target is stopped to allow deterministic access to the target's
44100 memory. Therefore File-I/O is not interruptible by target signals. On
44101 the other hand, it is possible to interrupt File-I/O by a user interrupt
44102 (@samp{Ctrl-C}) within @value{GDBN}.
44104 The target's request to perform a host system call does not finish
44105 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44106 after finishing the system call, the target returns to continuing the
44107 previous activity (continue, step). No additional continue or step
44108 request from @value{GDBN} is required.
44111 (@value{GDBP}) continue
44112 <- target requests 'system call X'
44113 target is stopped, @value{GDBN} executes system call
44114 -> @value{GDBN} returns result
44115 ... target continues, @value{GDBN} returns to wait for the target
44116 <- target hits breakpoint and sends a Txx packet
44119 The protocol only supports I/O on the console and to regular files on
44120 the host file system. Character or block special devices, pipes,
44121 named pipes, sockets or any other communication method on the host
44122 system are not supported by this protocol.
44124 File I/O is not supported in non-stop mode.
44126 @node Protocol Basics
44127 @subsection Protocol Basics
44128 @cindex protocol basics, file-i/o
44130 The File-I/O protocol uses the @code{F} packet as the request as well
44131 as reply packet. Since a File-I/O system call can only occur when
44132 @value{GDBN} is waiting for a response from the continuing or stepping target,
44133 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44134 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44135 This @code{F} packet contains all information needed to allow @value{GDBN}
44136 to call the appropriate host system call:
44140 A unique identifier for the requested system call.
44143 All parameters to the system call. Pointers are given as addresses
44144 in the target memory address space. Pointers to strings are given as
44145 pointer/length pair. Numerical values are given as they are.
44146 Numerical control flags are given in a protocol-specific representation.
44150 At this point, @value{GDBN} has to perform the following actions.
44154 If the parameters include pointer values to data needed as input to a
44155 system call, @value{GDBN} requests this data from the target with a
44156 standard @code{m} packet request. This additional communication has to be
44157 expected by the target implementation and is handled as any other @code{m}
44161 @value{GDBN} translates all value from protocol representation to host
44162 representation as needed. Datatypes are coerced into the host types.
44165 @value{GDBN} calls the system call.
44168 It then coerces datatypes back to protocol representation.
44171 If the system call is expected to return data in buffer space specified
44172 by pointer parameters to the call, the data is transmitted to the
44173 target using a @code{M} or @code{X} packet. This packet has to be expected
44174 by the target implementation and is handled as any other @code{M} or @code{X}
44179 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44180 necessary information for the target to continue. This at least contains
44187 @code{errno}, if has been changed by the system call.
44194 After having done the needed type and value coercion, the target continues
44195 the latest continue or step action.
44197 @node The F Request Packet
44198 @subsection The @code{F} Request Packet
44199 @cindex file-i/o request packet
44200 @cindex @code{F} request packet
44202 The @code{F} request packet has the following format:
44205 @item F@var{call-id},@var{parameter@dots{}}
44207 @var{call-id} is the identifier to indicate the host system call to be called.
44208 This is just the name of the function.
44210 @var{parameter@dots{}} are the parameters to the system call.
44211 Parameters are hexadecimal integer values, either the actual values in case
44212 of scalar datatypes, pointers to target buffer space in case of compound
44213 datatypes and unspecified memory areas, or pointer/length pairs in case
44214 of string parameters. These are appended to the @var{call-id} as a
44215 comma-delimited list. All values are transmitted in ASCII
44216 string representation, pointer/length pairs separated by a slash.
44222 @node The F Reply Packet
44223 @subsection The @code{F} Reply Packet
44224 @cindex file-i/o reply packet
44225 @cindex @code{F} reply packet
44227 The @code{F} reply packet has the following format:
44231 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44233 @var{retcode} is the return code of the system call as hexadecimal value.
44235 @var{errno} is the @code{errno} set by the call, in protocol-specific
44237 This parameter can be omitted if the call was successful.
44239 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44240 case, @var{errno} must be sent as well, even if the call was successful.
44241 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44248 or, if the call was interrupted before the host call has been performed:
44255 assuming 4 is the protocol-specific representation of @code{EINTR}.
44260 @node The Ctrl-C Message
44261 @subsection The @samp{Ctrl-C} Message
44262 @cindex ctrl-c message, in file-i/o protocol
44264 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44265 reply packet (@pxref{The F Reply Packet}),
44266 the target should behave as if it had
44267 gotten a break message. The meaning for the target is ``system call
44268 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44269 (as with a break message) and return to @value{GDBN} with a @code{T02}
44272 It's important for the target to know in which
44273 state the system call was interrupted. There are two possible cases:
44277 The system call hasn't been performed on the host yet.
44280 The system call on the host has been finished.
44284 These two states can be distinguished by the target by the value of the
44285 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44286 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44287 on POSIX systems. In any other case, the target may presume that the
44288 system call has been finished --- successfully or not --- and should behave
44289 as if the break message arrived right after the system call.
44291 @value{GDBN} must behave reliably. If the system call has not been called
44292 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44293 @code{errno} in the packet. If the system call on the host has been finished
44294 before the user requests a break, the full action must be finished by
44295 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44296 The @code{F} packet may only be sent when either nothing has happened
44297 or the full action has been completed.
44300 @subsection Console I/O
44301 @cindex console i/o as part of file-i/o
44303 By default and if not explicitly closed by the target system, the file
44304 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44305 on the @value{GDBN} console is handled as any other file output operation
44306 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44307 by @value{GDBN} so that after the target read request from file descriptor
44308 0 all following typing is buffered until either one of the following
44313 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44315 system call is treated as finished.
44318 The user presses @key{RET}. This is treated as end of input with a trailing
44322 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44323 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44327 If the user has typed more characters than fit in the buffer given to
44328 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44329 either another @code{read(0, @dots{})} is requested by the target, or debugging
44330 is stopped at the user's request.
44333 @node List of Supported Calls
44334 @subsection List of Supported Calls
44335 @cindex list of supported file-i/o calls
44352 @unnumberedsubsubsec open
44353 @cindex open, file-i/o system call
44358 int open(const char *pathname, int flags);
44359 int open(const char *pathname, int flags, mode_t mode);
44363 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
44366 @var{flags} is the bitwise @code{OR} of the following values:
44370 If the file does not exist it will be created. The host
44371 rules apply as far as file ownership and time stamps
44375 When used with @code{O_CREAT}, if the file already exists it is
44376 an error and open() fails.
44379 If the file already exists and the open mode allows
44380 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
44381 truncated to zero length.
44384 The file is opened in append mode.
44387 The file is opened for reading only.
44390 The file is opened for writing only.
44393 The file is opened for reading and writing.
44397 Other bits are silently ignored.
44401 @var{mode} is the bitwise @code{OR} of the following values:
44405 User has read permission.
44408 User has write permission.
44411 Group has read permission.
44414 Group has write permission.
44417 Others have read permission.
44420 Others have write permission.
44424 Other bits are silently ignored.
44427 @item Return value:
44428 @code{open} returns the new file descriptor or -1 if an error
44435 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
44438 @var{pathname} refers to a directory.
44441 The requested access is not allowed.
44444 @var{pathname} was too long.
44447 A directory component in @var{pathname} does not exist.
44450 @var{pathname} refers to a device, pipe, named pipe or socket.
44453 @var{pathname} refers to a file on a read-only filesystem and
44454 write access was requested.
44457 @var{pathname} is an invalid pointer value.
44460 No space on device to create the file.
44463 The process already has the maximum number of files open.
44466 The limit on the total number of files open on the system
44470 The call was interrupted by the user.
44476 @unnumberedsubsubsec close
44477 @cindex close, file-i/o system call
44486 @samp{Fclose,@var{fd}}
44488 @item Return value:
44489 @code{close} returns zero on success, or -1 if an error occurred.
44495 @var{fd} isn't a valid open file descriptor.
44498 The call was interrupted by the user.
44504 @unnumberedsubsubsec read
44505 @cindex read, file-i/o system call
44510 int read(int fd, void *buf, unsigned int count);
44514 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
44516 @item Return value:
44517 On success, the number of bytes read is returned.
44518 Zero indicates end of file. If count is zero, read
44519 returns zero as well. On error, -1 is returned.
44525 @var{fd} is not a valid file descriptor or is not open for
44529 @var{bufptr} is an invalid pointer value.
44532 The call was interrupted by the user.
44538 @unnumberedsubsubsec write
44539 @cindex write, file-i/o system call
44544 int write(int fd, const void *buf, unsigned int count);
44548 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
44550 @item Return value:
44551 On success, the number of bytes written are returned.
44552 Zero indicates nothing was written. On error, -1
44559 @var{fd} is not a valid file descriptor or is not open for
44563 @var{bufptr} is an invalid pointer value.
44566 An attempt was made to write a file that exceeds the
44567 host-specific maximum file size allowed.
44570 No space on device to write the data.
44573 The call was interrupted by the user.
44579 @unnumberedsubsubsec lseek
44580 @cindex lseek, file-i/o system call
44585 long lseek (int fd, long offset, int flag);
44589 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
44591 @var{flag} is one of:
44595 The offset is set to @var{offset} bytes.
44598 The offset is set to its current location plus @var{offset}
44602 The offset is set to the size of the file plus @var{offset}
44606 @item Return value:
44607 On success, the resulting unsigned offset in bytes from
44608 the beginning of the file is returned. Otherwise, a
44609 value of -1 is returned.
44615 @var{fd} is not a valid open file descriptor.
44618 @var{fd} is associated with the @value{GDBN} console.
44621 @var{flag} is not a proper value.
44624 The call was interrupted by the user.
44630 @unnumberedsubsubsec rename
44631 @cindex rename, file-i/o system call
44636 int rename(const char *oldpath, const char *newpath);
44640 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
44642 @item Return value:
44643 On success, zero is returned. On error, -1 is returned.
44649 @var{newpath} is an existing directory, but @var{oldpath} is not a
44653 @var{newpath} is a non-empty directory.
44656 @var{oldpath} or @var{newpath} is a directory that is in use by some
44660 An attempt was made to make a directory a subdirectory
44664 A component used as a directory in @var{oldpath} or new
44665 path is not a directory. Or @var{oldpath} is a directory
44666 and @var{newpath} exists but is not a directory.
44669 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
44672 No access to the file or the path of the file.
44676 @var{oldpath} or @var{newpath} was too long.
44679 A directory component in @var{oldpath} or @var{newpath} does not exist.
44682 The file is on a read-only filesystem.
44685 The device containing the file has no room for the new
44689 The call was interrupted by the user.
44695 @unnumberedsubsubsec unlink
44696 @cindex unlink, file-i/o system call
44701 int unlink(const char *pathname);
44705 @samp{Funlink,@var{pathnameptr}/@var{len}}
44707 @item Return value:
44708 On success, zero is returned. On error, -1 is returned.
44714 No access to the file or the path of the file.
44717 The system does not allow unlinking of directories.
44720 The file @var{pathname} cannot be unlinked because it's
44721 being used by another process.
44724 @var{pathnameptr} is an invalid pointer value.
44727 @var{pathname} was too long.
44730 A directory component in @var{pathname} does not exist.
44733 A component of the path is not a directory.
44736 The file is on a read-only filesystem.
44739 The call was interrupted by the user.
44745 @unnumberedsubsubsec stat/fstat
44746 @cindex fstat, file-i/o system call
44747 @cindex stat, file-i/o system call
44752 int stat(const char *pathname, struct stat *buf);
44753 int fstat(int fd, struct stat *buf);
44757 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
44758 @samp{Ffstat,@var{fd},@var{bufptr}}
44760 @item Return value:
44761 On success, zero is returned. On error, -1 is returned.
44767 @var{fd} is not a valid open file.
44770 A directory component in @var{pathname} does not exist or the
44771 path is an empty string.
44774 A component of the path is not a directory.
44777 @var{pathnameptr} is an invalid pointer value.
44780 No access to the file or the path of the file.
44783 @var{pathname} was too long.
44786 The call was interrupted by the user.
44792 @unnumberedsubsubsec gettimeofday
44793 @cindex gettimeofday, file-i/o system call
44798 int gettimeofday(struct timeval *tv, void *tz);
44802 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
44804 @item Return value:
44805 On success, 0 is returned, -1 otherwise.
44811 @var{tz} is a non-NULL pointer.
44814 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
44820 @unnumberedsubsubsec isatty
44821 @cindex isatty, file-i/o system call
44826 int isatty(int fd);
44830 @samp{Fisatty,@var{fd}}
44832 @item Return value:
44833 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
44839 The call was interrupted by the user.
44844 Note that the @code{isatty} call is treated as a special case: it returns
44845 1 to the target if the file descriptor is attached
44846 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
44847 would require implementing @code{ioctl} and would be more complex than
44852 @unnumberedsubsubsec system
44853 @cindex system, file-i/o system call
44858 int system(const char *command);
44862 @samp{Fsystem,@var{commandptr}/@var{len}}
44864 @item Return value:
44865 If @var{len} is zero, the return value indicates whether a shell is
44866 available. A zero return value indicates a shell is not available.
44867 For non-zero @var{len}, the value returned is -1 on error and the
44868 return status of the command otherwise. Only the exit status of the
44869 command is returned, which is extracted from the host's @code{system}
44870 return value by calling @code{WEXITSTATUS(retval)}. In case
44871 @file{/bin/sh} could not be executed, 127 is returned.
44877 The call was interrupted by the user.
44882 @value{GDBN} takes over the full task of calling the necessary host calls
44883 to perform the @code{system} call. The return value of @code{system} on
44884 the host is simplified before it's returned
44885 to the target. Any termination signal information from the child process
44886 is discarded, and the return value consists
44887 entirely of the exit status of the called command.
44889 Due to security concerns, the @code{system} call is by default refused
44890 by @value{GDBN}. The user has to allow this call explicitly with the
44891 @code{set remote system-call-allowed 1} command.
44894 @item set remote system-call-allowed
44895 @kindex set remote system-call-allowed
44896 Control whether to allow the @code{system} calls in the File I/O
44897 protocol for the remote target. The default is zero (disabled).
44899 @item show remote system-call-allowed
44900 @kindex show remote system-call-allowed
44901 Show whether the @code{system} calls are allowed in the File I/O
44905 @node Protocol-specific Representation of Datatypes
44906 @subsection Protocol-specific Representation of Datatypes
44907 @cindex protocol-specific representation of datatypes, in file-i/o protocol
44910 * Integral Datatypes::
44912 * Memory Transfer::
44917 @node Integral Datatypes
44918 @unnumberedsubsubsec Integral Datatypes
44919 @cindex integral datatypes, in file-i/o protocol
44921 The integral datatypes used in the system calls are @code{int},
44922 @code{unsigned int}, @code{long}, @code{unsigned long},
44923 @code{mode_t}, and @code{time_t}.
44925 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
44926 implemented as 32 bit values in this protocol.
44928 @code{long} and @code{unsigned long} are implemented as 64 bit types.
44930 @xref{Limits}, for corresponding MIN and MAX values (similar to those
44931 in @file{limits.h}) to allow range checking on host and target.
44933 @code{time_t} datatypes are defined as seconds since the Epoch.
44935 All integral datatypes transferred as part of a memory read or write of a
44936 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
44939 @node Pointer Values
44940 @unnumberedsubsubsec Pointer Values
44941 @cindex pointer values, in file-i/o protocol
44943 Pointers to target data are transmitted as they are. An exception
44944 is made for pointers to buffers for which the length isn't
44945 transmitted as part of the function call, namely strings. Strings
44946 are transmitted as a pointer/length pair, both as hex values, e.g.@:
44953 which is a pointer to data of length 18 bytes at position 0x1aaf.
44954 The length is defined as the full string length in bytes, including
44955 the trailing null byte. For example, the string @code{"hello world"}
44956 at address 0x123456 is transmitted as
44962 @node Memory Transfer
44963 @unnumberedsubsubsec Memory Transfer
44964 @cindex memory transfer, in file-i/o protocol
44966 Structured data which is transferred using a memory read or write (for
44967 example, a @code{struct stat}) is expected to be in a protocol-specific format
44968 with all scalar multibyte datatypes being big endian. Translation to
44969 this representation needs to be done both by the target before the @code{F}
44970 packet is sent, and by @value{GDBN} before
44971 it transfers memory to the target. Transferred pointers to structured
44972 data should point to the already-coerced data at any time.
44976 @unnumberedsubsubsec struct stat
44977 @cindex struct stat, in file-i/o protocol
44979 The buffer of type @code{struct stat} used by the target and @value{GDBN}
44980 is defined as follows:
44984 unsigned int st_dev; /* device */
44985 unsigned int st_ino; /* inode */
44986 mode_t st_mode; /* protection */
44987 unsigned int st_nlink; /* number of hard links */
44988 unsigned int st_uid; /* user ID of owner */
44989 unsigned int st_gid; /* group ID of owner */
44990 unsigned int st_rdev; /* device type (if inode device) */
44991 unsigned long st_size; /* total size, in bytes */
44992 unsigned long st_blksize; /* blocksize for filesystem I/O */
44993 unsigned long st_blocks; /* number of blocks allocated */
44994 time_t st_atime; /* time of last access */
44995 time_t st_mtime; /* time of last modification */
44996 time_t st_ctime; /* time of last change */
45000 The integral datatypes conform to the definitions given in the
45001 appropriate section (see @ref{Integral Datatypes}, for details) so this
45002 structure is of size 64 bytes.
45004 The values of several fields have a restricted meaning and/or
45010 A value of 0 represents a file, 1 the console.
45013 No valid meaning for the target. Transmitted unchanged.
45016 Valid mode bits are described in @ref{Constants}. Any other
45017 bits have currently no meaning for the target.
45022 No valid meaning for the target. Transmitted unchanged.
45027 These values have a host and file system dependent
45028 accuracy. Especially on Windows hosts, the file system may not
45029 support exact timing values.
45032 The target gets a @code{struct stat} of the above representation and is
45033 responsible for coercing it to the target representation before
45036 Note that due to size differences between the host, target, and protocol
45037 representations of @code{struct stat} members, these members could eventually
45038 get truncated on the target.
45040 @node struct timeval
45041 @unnumberedsubsubsec struct timeval
45042 @cindex struct timeval, in file-i/o protocol
45044 The buffer of type @code{struct timeval} used by the File-I/O protocol
45045 is defined as follows:
45049 time_t tv_sec; /* second */
45050 long tv_usec; /* microsecond */
45054 The integral datatypes conform to the definitions given in the
45055 appropriate section (see @ref{Integral Datatypes}, for details) so this
45056 structure is of size 8 bytes.
45059 @subsection Constants
45060 @cindex constants, in file-i/o protocol
45062 The following values are used for the constants inside of the
45063 protocol. @value{GDBN} and target are responsible for translating these
45064 values before and after the call as needed.
45075 @unnumberedsubsubsec Open Flags
45076 @cindex open flags, in file-i/o protocol
45078 All values are given in hexadecimal representation.
45090 @node mode_t Values
45091 @unnumberedsubsubsec mode_t Values
45092 @cindex mode_t values, in file-i/o protocol
45094 All values are given in octal representation.
45111 @unnumberedsubsubsec Errno Values
45112 @cindex errno values, in file-i/o protocol
45114 All values are given in decimal representation.
45139 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45140 any error value not in the list of supported error numbers.
45143 @unnumberedsubsubsec Lseek Flags
45144 @cindex lseek flags, in file-i/o protocol
45153 @unnumberedsubsubsec Limits
45154 @cindex limits, in file-i/o protocol
45156 All values are given in decimal representation.
45159 INT_MIN -2147483648
45161 UINT_MAX 4294967295
45162 LONG_MIN -9223372036854775808
45163 LONG_MAX 9223372036854775807
45164 ULONG_MAX 18446744073709551615
45167 @node File-I/O Examples
45168 @subsection File-I/O Examples
45169 @cindex file-i/o examples
45171 Example sequence of a write call, file descriptor 3, buffer is at target
45172 address 0x1234, 6 bytes should be written:
45175 <- @code{Fwrite,3,1234,6}
45176 @emph{request memory read from target}
45179 @emph{return "6 bytes written"}
45183 Example sequence of a read call, file descriptor 3, buffer is at target
45184 address 0x1234, 6 bytes should be read:
45187 <- @code{Fread,3,1234,6}
45188 @emph{request memory write to target}
45189 -> @code{X1234,6:XXXXXX}
45190 @emph{return "6 bytes read"}
45194 Example sequence of a read call, call fails on the host due to invalid
45195 file descriptor (@code{EBADF}):
45198 <- @code{Fread,3,1234,6}
45202 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45206 <- @code{Fread,3,1234,6}
45211 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45215 <- @code{Fread,3,1234,6}
45216 -> @code{X1234,6:XXXXXX}
45220 @node Library List Format
45221 @section Library List Format
45222 @cindex library list format, remote protocol
45224 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45225 same process as your application to manage libraries. In this case,
45226 @value{GDBN} can use the loader's symbol table and normal memory
45227 operations to maintain a list of shared libraries. On other
45228 platforms, the operating system manages loaded libraries.
45229 @value{GDBN} can not retrieve the list of currently loaded libraries
45230 through memory operations, so it uses the @samp{qXfer:libraries:read}
45231 packet (@pxref{qXfer library list read}) instead. The remote stub
45232 queries the target's operating system and reports which libraries
45235 The @samp{qXfer:libraries:read} packet returns an XML document which
45236 lists loaded libraries and their offsets. Each library has an
45237 associated name and one or more segment or section base addresses,
45238 which report where the library was loaded in memory.
45240 For the common case of libraries that are fully linked binaries, the
45241 library should have a list of segments. If the target supports
45242 dynamic linking of a relocatable object file, its library XML element
45243 should instead include a list of allocated sections. The segment or
45244 section bases are start addresses, not relocation offsets; they do not
45245 depend on the library's link-time base addresses.
45247 @value{GDBN} must be linked with the Expat library to support XML
45248 library lists. @xref{Expat}.
45250 A simple memory map, with one loaded library relocated by a single
45251 offset, looks like this:
45255 <library name="/lib/libc.so.6">
45256 <segment address="0x10000000"/>
45261 Another simple memory map, with one loaded library with three
45262 allocated sections (.text, .data, .bss), looks like this:
45266 <library name="sharedlib.o">
45267 <section address="0x10000000"/>
45268 <section address="0x20000000"/>
45269 <section address="0x30000000"/>
45274 The format of a library list is described by this DTD:
45277 <!-- library-list: Root element with versioning -->
45278 <!ELEMENT library-list (library)*>
45279 <!ATTLIST library-list version CDATA #FIXED "1.0">
45280 <!ELEMENT library (segment*, section*)>
45281 <!ATTLIST library name CDATA #REQUIRED>
45282 <!ELEMENT segment EMPTY>
45283 <!ATTLIST segment address CDATA #REQUIRED>
45284 <!ELEMENT section EMPTY>
45285 <!ATTLIST section address CDATA #REQUIRED>
45288 In addition, segments and section descriptors cannot be mixed within a
45289 single library element, and you must supply at least one segment or
45290 section for each library.
45292 @node Library List Format for SVR4 Targets
45293 @section Library List Format for SVR4 Targets
45294 @cindex library list format, remote protocol
45296 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45297 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45298 shared libraries. Still a special library list provided by this packet is
45299 more efficient for the @value{GDBN} remote protocol.
45301 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45302 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45303 target, the following parameters are reported:
45307 @code{name}, the absolute file name from the @code{l_name} field of
45308 @code{struct link_map}.
45310 @code{lm} with address of @code{struct link_map} used for TLS
45311 (Thread Local Storage) access.
45313 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45314 @code{struct link_map}. For prelinked libraries this is not an absolute
45315 memory address. It is a displacement of absolute memory address against
45316 address the file was prelinked to during the library load.
45318 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45321 Additionally the single @code{main-lm} attribute specifies address of
45322 @code{struct link_map} used for the main executable. This parameter is used
45323 for TLS access and its presence is optional.
45325 @value{GDBN} must be linked with the Expat library to support XML
45326 SVR4 library lists. @xref{Expat}.
45328 A simple memory map, with two loaded libraries (which do not use prelink),
45332 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45333 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45335 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45337 </library-list-svr>
45340 The format of an SVR4 library list is described by this DTD:
45343 <!-- library-list-svr4: Root element with versioning -->
45344 <!ELEMENT library-list-svr4 (library)*>
45345 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45346 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45347 <!ELEMENT library EMPTY>
45348 <!ATTLIST library name CDATA #REQUIRED>
45349 <!ATTLIST library lm CDATA #REQUIRED>
45350 <!ATTLIST library l_addr CDATA #REQUIRED>
45351 <!ATTLIST library l_ld CDATA #REQUIRED>
45354 @node Memory Map Format
45355 @section Memory Map Format
45356 @cindex memory map format
45358 To be able to write into flash memory, @value{GDBN} needs to obtain a
45359 memory map from the target. This section describes the format of the
45362 The memory map is obtained using the @samp{qXfer:memory-map:read}
45363 (@pxref{qXfer memory map read}) packet and is an XML document that
45364 lists memory regions.
45366 @value{GDBN} must be linked with the Expat library to support XML
45367 memory maps. @xref{Expat}.
45369 The top-level structure of the document is shown below:
45372 <?xml version="1.0"?>
45373 <!DOCTYPE memory-map
45374 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45375 "http://sourceware.org/gdb/gdb-memory-map.dtd">
45381 Each region can be either:
45386 A region of RAM starting at @var{addr} and extending for @var{length}
45390 <memory type="ram" start="@var{addr}" length="@var{length}"/>
45395 A region of read-only memory:
45398 <memory type="rom" start="@var{addr}" length="@var{length}"/>
45403 A region of flash memory, with erasure blocks @var{blocksize}
45407 <memory type="flash" start="@var{addr}" length="@var{length}">
45408 <property name="blocksize">@var{blocksize}</property>
45414 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
45415 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
45416 packets to write to addresses in such ranges.
45418 The formal DTD for memory map format is given below:
45421 <!-- ................................................... -->
45422 <!-- Memory Map XML DTD ................................ -->
45423 <!-- File: memory-map.dtd .............................. -->
45424 <!-- .................................... .............. -->
45425 <!-- memory-map.dtd -->
45426 <!-- memory-map: Root element with versioning -->
45427 <!ELEMENT memory-map (memory)*>
45428 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
45429 <!ELEMENT memory (property)*>
45430 <!-- memory: Specifies a memory region,
45431 and its type, or device. -->
45432 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
45433 start CDATA #REQUIRED
45434 length CDATA #REQUIRED>
45435 <!-- property: Generic attribute tag -->
45436 <!ELEMENT property (#PCDATA | property)*>
45437 <!ATTLIST property name (blocksize) #REQUIRED>
45440 @node Thread List Format
45441 @section Thread List Format
45442 @cindex thread list format
45444 To efficiently update the list of threads and their attributes,
45445 @value{GDBN} issues the @samp{qXfer:threads:read} packet
45446 (@pxref{qXfer threads read}) and obtains the XML document with
45447 the following structure:
45450 <?xml version="1.0"?>
45452 <thread id="id" core="0" name="name">
45453 ... description ...
45458 Each @samp{thread} element must have the @samp{id} attribute that
45459 identifies the thread (@pxref{thread-id syntax}). The
45460 @samp{core} attribute, if present, specifies which processor core
45461 the thread was last executing on. The @samp{name} attribute, if
45462 present, specifies the human-readable name of the thread. The content
45463 of the of @samp{thread} element is interpreted as human-readable
45464 auxiliary information. The @samp{handle} attribute, if present,
45465 is a hex encoded representation of the thread handle.
45468 @node Traceframe Info Format
45469 @section Traceframe Info Format
45470 @cindex traceframe info format
45472 To be able to know which objects in the inferior can be examined when
45473 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
45474 memory ranges, registers and trace state variables that have been
45475 collected in a traceframe.
45477 This list is obtained using the @samp{qXfer:traceframe-info:read}
45478 (@pxref{qXfer traceframe info read}) packet and is an XML document.
45480 @value{GDBN} must be linked with the Expat library to support XML
45481 traceframe info discovery. @xref{Expat}.
45483 The top-level structure of the document is shown below:
45486 <?xml version="1.0"?>
45487 <!DOCTYPE traceframe-info
45488 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45489 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
45495 Each traceframe block can be either:
45500 A region of collected memory starting at @var{addr} and extending for
45501 @var{length} bytes from there:
45504 <memory start="@var{addr}" length="@var{length}"/>
45508 A block indicating trace state variable numbered @var{number} has been
45512 <tvar id="@var{number}"/>
45517 The formal DTD for the traceframe info format is given below:
45520 <!ELEMENT traceframe-info (memory | tvar)* >
45521 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
45523 <!ELEMENT memory EMPTY>
45524 <!ATTLIST memory start CDATA #REQUIRED
45525 length CDATA #REQUIRED>
45527 <!ATTLIST tvar id CDATA #REQUIRED>
45530 @node Branch Trace Format
45531 @section Branch Trace Format
45532 @cindex branch trace format
45534 In order to display the branch trace of an inferior thread,
45535 @value{GDBN} needs to obtain the list of branches. This list is
45536 represented as list of sequential code blocks that are connected via
45537 branches. The code in each block has been executed sequentially.
45539 This list is obtained using the @samp{qXfer:btrace:read}
45540 (@pxref{qXfer btrace read}) packet and is an XML document.
45542 @value{GDBN} must be linked with the Expat library to support XML
45543 traceframe info discovery. @xref{Expat}.
45545 The top-level structure of the document is shown below:
45548 <?xml version="1.0"?>
45550 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
45551 "http://sourceware.org/gdb/gdb-btrace.dtd">
45560 A block of sequentially executed instructions starting at @var{begin}
45561 and ending at @var{end}:
45564 <block begin="@var{begin}" end="@var{end}"/>
45569 The formal DTD for the branch trace format is given below:
45572 <!ELEMENT btrace (block* | pt) >
45573 <!ATTLIST btrace version CDATA #FIXED "1.0">
45575 <!ELEMENT block EMPTY>
45576 <!ATTLIST block begin CDATA #REQUIRED
45577 end CDATA #REQUIRED>
45579 <!ELEMENT pt (pt-config?, raw?)>
45581 <!ELEMENT pt-config (cpu?)>
45583 <!ELEMENT cpu EMPTY>
45584 <!ATTLIST cpu vendor CDATA #REQUIRED
45585 family CDATA #REQUIRED
45586 model CDATA #REQUIRED
45587 stepping CDATA #REQUIRED>
45589 <!ELEMENT raw (#PCDATA)>
45592 @node Branch Trace Configuration Format
45593 @section Branch Trace Configuration Format
45594 @cindex branch trace configuration format
45596 For each inferior thread, @value{GDBN} can obtain the branch trace
45597 configuration using the @samp{qXfer:btrace-conf:read}
45598 (@pxref{qXfer btrace-conf read}) packet.
45600 The configuration describes the branch trace format and configuration
45601 settings for that format. The following information is described:
45605 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
45608 The size of the @acronym{BTS} ring buffer in bytes.
45611 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
45615 The size of the @acronym{Intel PT} ring buffer in bytes.
45619 @value{GDBN} must be linked with the Expat library to support XML
45620 branch trace configuration discovery. @xref{Expat}.
45622 The formal DTD for the branch trace configuration format is given below:
45625 <!ELEMENT btrace-conf (bts?, pt?)>
45626 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
45628 <!ELEMENT bts EMPTY>
45629 <!ATTLIST bts size CDATA #IMPLIED>
45631 <!ELEMENT pt EMPTY>
45632 <!ATTLIST pt size CDATA #IMPLIED>
45635 @include agentexpr.texi
45637 @node Target Descriptions
45638 @appendix Target Descriptions
45639 @cindex target descriptions
45641 One of the challenges of using @value{GDBN} to debug embedded systems
45642 is that there are so many minor variants of each processor
45643 architecture in use. It is common practice for vendors to start with
45644 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
45645 and then make changes to adapt it to a particular market niche. Some
45646 architectures have hundreds of variants, available from dozens of
45647 vendors. This leads to a number of problems:
45651 With so many different customized processors, it is difficult for
45652 the @value{GDBN} maintainers to keep up with the changes.
45654 Since individual variants may have short lifetimes or limited
45655 audiences, it may not be worthwhile to carry information about every
45656 variant in the @value{GDBN} source tree.
45658 When @value{GDBN} does support the architecture of the embedded system
45659 at hand, the task of finding the correct architecture name to give the
45660 @command{set architecture} command can be error-prone.
45663 To address these problems, the @value{GDBN} remote protocol allows a
45664 target system to not only identify itself to @value{GDBN}, but to
45665 actually describe its own features. This lets @value{GDBN} support
45666 processor variants it has never seen before --- to the extent that the
45667 descriptions are accurate, and that @value{GDBN} understands them.
45669 @value{GDBN} must be linked with the Expat library to support XML
45670 target descriptions. @xref{Expat}.
45673 * Retrieving Descriptions:: How descriptions are fetched from a target.
45674 * Target Description Format:: The contents of a target description.
45675 * Predefined Target Types:: Standard types available for target
45677 * Enum Target Types:: How to define enum target types.
45678 * Standard Target Features:: Features @value{GDBN} knows about.
45681 @node Retrieving Descriptions
45682 @section Retrieving Descriptions
45684 Target descriptions can be read from the target automatically, or
45685 specified by the user manually. The default behavior is to read the
45686 description from the target. @value{GDBN} retrieves it via the remote
45687 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
45688 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
45689 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
45690 XML document, of the form described in @ref{Target Description
45693 Alternatively, you can specify a file to read for the target description.
45694 If a file is set, the target will not be queried. The commands to
45695 specify a file are:
45698 @cindex set tdesc filename
45699 @item set tdesc filename @var{path}
45700 Read the target description from @var{path}.
45702 @cindex unset tdesc filename
45703 @item unset tdesc filename
45704 Do not read the XML target description from a file. @value{GDBN}
45705 will use the description supplied by the current target.
45707 @cindex show tdesc filename
45708 @item show tdesc filename
45709 Show the filename to read for a target description, if any.
45713 @node Target Description Format
45714 @section Target Description Format
45715 @cindex target descriptions, XML format
45717 A target description annex is an @uref{http://www.w3.org/XML/, XML}
45718 document which complies with the Document Type Definition provided in
45719 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
45720 means you can use generally available tools like @command{xmllint} to
45721 check that your feature descriptions are well-formed and valid.
45722 However, to help people unfamiliar with XML write descriptions for
45723 their targets, we also describe the grammar here.
45725 Target descriptions can identify the architecture of the remote target
45726 and (for some architectures) provide information about custom register
45727 sets. They can also identify the OS ABI of the remote target.
45728 @value{GDBN} can use this information to autoconfigure for your
45729 target, or to warn you if you connect to an unsupported target.
45731 Here is a simple target description:
45734 <target version="1.0">
45735 <architecture>i386:x86-64</architecture>
45740 This minimal description only says that the target uses
45741 the x86-64 architecture.
45743 A target description has the following overall form, with [ ] marking
45744 optional elements and @dots{} marking repeatable elements. The elements
45745 are explained further below.
45748 <?xml version="1.0"?>
45749 <!DOCTYPE target SYSTEM "gdb-target.dtd">
45750 <target version="1.0">
45751 @r{[}@var{architecture}@r{]}
45752 @r{[}@var{osabi}@r{]}
45753 @r{[}@var{compatible}@r{]}
45754 @r{[}@var{feature}@dots{}@r{]}
45759 The description is generally insensitive to whitespace and line
45760 breaks, under the usual common-sense rules. The XML version
45761 declaration and document type declaration can generally be omitted
45762 (@value{GDBN} does not require them), but specifying them may be
45763 useful for XML validation tools. The @samp{version} attribute for
45764 @samp{<target>} may also be omitted, but we recommend
45765 including it; if future versions of @value{GDBN} use an incompatible
45766 revision of @file{gdb-target.dtd}, they will detect and report
45767 the version mismatch.
45769 @subsection Inclusion
45770 @cindex target descriptions, inclusion
45773 @cindex <xi:include>
45776 It can sometimes be valuable to split a target description up into
45777 several different annexes, either for organizational purposes, or to
45778 share files between different possible target descriptions. You can
45779 divide a description into multiple files by replacing any element of
45780 the target description with an inclusion directive of the form:
45783 <xi:include href="@var{document}"/>
45787 When @value{GDBN} encounters an element of this form, it will retrieve
45788 the named XML @var{document}, and replace the inclusion directive with
45789 the contents of that document. If the current description was read
45790 using @samp{qXfer}, then so will be the included document;
45791 @var{document} will be interpreted as the name of an annex. If the
45792 current description was read from a file, @value{GDBN} will look for
45793 @var{document} as a file in the same directory where it found the
45794 original description.
45796 @subsection Architecture
45797 @cindex <architecture>
45799 An @samp{<architecture>} element has this form:
45802 <architecture>@var{arch}</architecture>
45805 @var{arch} is one of the architectures from the set accepted by
45806 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45809 @cindex @code{<osabi>}
45811 This optional field was introduced in @value{GDBN} version 7.0.
45812 Previous versions of @value{GDBN} ignore it.
45814 An @samp{<osabi>} element has this form:
45817 <osabi>@var{abi-name}</osabi>
45820 @var{abi-name} is an OS ABI name from the same selection accepted by
45821 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
45823 @subsection Compatible Architecture
45824 @cindex @code{<compatible>}
45826 This optional field was introduced in @value{GDBN} version 7.0.
45827 Previous versions of @value{GDBN} ignore it.
45829 A @samp{<compatible>} element has this form:
45832 <compatible>@var{arch}</compatible>
45835 @var{arch} is one of the architectures from the set accepted by
45836 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45838 A @samp{<compatible>} element is used to specify that the target
45839 is able to run binaries in some other than the main target architecture
45840 given by the @samp{<architecture>} element. For example, on the
45841 Cell Broadband Engine, the main architecture is @code{powerpc:common}
45842 or @code{powerpc:common64}, but the system is able to run binaries
45843 in the @code{spu} architecture as well. The way to describe this
45844 capability with @samp{<compatible>} is as follows:
45847 <architecture>powerpc:common</architecture>
45848 <compatible>spu</compatible>
45851 @subsection Features
45854 Each @samp{<feature>} describes some logical portion of the target
45855 system. Features are currently used to describe available CPU
45856 registers and the types of their contents. A @samp{<feature>} element
45860 <feature name="@var{name}">
45861 @r{[}@var{type}@dots{}@r{]}
45867 Each feature's name should be unique within the description. The name
45868 of a feature does not matter unless @value{GDBN} has some special
45869 knowledge of the contents of that feature; if it does, the feature
45870 should have its standard name. @xref{Standard Target Features}.
45874 Any register's value is a collection of bits which @value{GDBN} must
45875 interpret. The default interpretation is a two's complement integer,
45876 but other types can be requested by name in the register description.
45877 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
45878 Target Types}), and the description can define additional composite
45881 Each type element must have an @samp{id} attribute, which gives
45882 a unique (within the containing @samp{<feature>}) name to the type.
45883 Types must be defined before they are used.
45886 Some targets offer vector registers, which can be treated as arrays
45887 of scalar elements. These types are written as @samp{<vector>} elements,
45888 specifying the array element type, @var{type}, and the number of elements,
45892 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
45896 If a register's value is usefully viewed in multiple ways, define it
45897 with a union type containing the useful representations. The
45898 @samp{<union>} element contains one or more @samp{<field>} elements,
45899 each of which has a @var{name} and a @var{type}:
45902 <union id="@var{id}">
45903 <field name="@var{name}" type="@var{type}"/>
45910 If a register's value is composed from several separate values, define
45911 it with either a structure type or a flags type.
45912 A flags type may only contain bitfields.
45913 A structure type may either contain only bitfields or contain no bitfields.
45914 If the value contains only bitfields, its total size in bytes must be
45917 Non-bitfield values have a @var{name} and @var{type}.
45920 <struct id="@var{id}">
45921 <field name="@var{name}" type="@var{type}"/>
45926 Both @var{name} and @var{type} values are required.
45927 No implicit padding is added.
45929 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
45932 <struct id="@var{id}" size="@var{size}">
45933 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45939 <flags id="@var{id}" size="@var{size}">
45940 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45945 The @var{name} value is required.
45946 Bitfield values may be named with the empty string, @samp{""},
45947 in which case the field is ``filler'' and its value is not printed.
45948 Not all bits need to be specified, so ``filler'' fields are optional.
45950 The @var{start} and @var{end} values are required, and @var{type}
45952 The field's @var{start} must be less than or equal to its @var{end},
45953 and zero represents the least significant bit.
45955 The default value of @var{type} is @code{bool} for single bit fields,
45956 and an unsigned integer otherwise.
45958 Which to choose? Structures or flags?
45960 Registers defined with @samp{flags} have these advantages over
45961 defining them with @samp{struct}:
45965 Arithmetic may be performed on them as if they were integers.
45967 They are printed in a more readable fashion.
45970 Registers defined with @samp{struct} have one advantage over
45971 defining them with @samp{flags}:
45975 One can fetch individual fields like in @samp{C}.
45978 (gdb) print $my_struct_reg.field3
45984 @subsection Registers
45987 Each register is represented as an element with this form:
45990 <reg name="@var{name}"
45991 bitsize="@var{size}"
45992 @r{[}regnum="@var{num}"@r{]}
45993 @r{[}save-restore="@var{save-restore}"@r{]}
45994 @r{[}type="@var{type}"@r{]}
45995 @r{[}group="@var{group}"@r{]}/>
45999 The components are as follows:
46004 The register's name; it must be unique within the target description.
46007 The register's size, in bits.
46010 The register's number. If omitted, a register's number is one greater
46011 than that of the previous register (either in the current feature or in
46012 a preceding feature); the first register in the target description
46013 defaults to zero. This register number is used to read or write
46014 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46015 packets, and registers appear in the @code{g} and @code{G} packets
46016 in order of increasing register number.
46019 Whether the register should be preserved across inferior function
46020 calls; this must be either @code{yes} or @code{no}. The default is
46021 @code{yes}, which is appropriate for most registers except for
46022 some system control registers; this is not related to the target's
46026 The type of the register. It may be a predefined type, a type
46027 defined in the current feature, or one of the special types @code{int}
46028 and @code{float}. @code{int} is an integer type of the correct size
46029 for @var{bitsize}, and @code{float} is a floating point type (in the
46030 architecture's normal floating point format) of the correct size for
46031 @var{bitsize}. The default is @code{int}.
46034 The register group to which this register belongs. It can be one of the
46035 standard register groups @code{general}, @code{float}, @code{vector} or an
46036 arbitrary string. Group names should be limited to alphanumeric characters.
46037 If a group name is made up of multiple words the words may be separated by
46038 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46039 @var{group} is specified, @value{GDBN} will not display the register in
46040 @code{info registers}.
46044 @node Predefined Target Types
46045 @section Predefined Target Types
46046 @cindex target descriptions, predefined types
46048 Type definitions in the self-description can build up composite types
46049 from basic building blocks, but can not define fundamental types. Instead,
46050 standard identifiers are provided by @value{GDBN} for the fundamental
46051 types. The currently supported types are:
46056 Boolean type, occupying a single bit.
46064 Signed integer types holding the specified number of bits.
46072 Unsigned integer types holding the specified number of bits.
46076 Pointers to unspecified code and data. The program counter and
46077 any dedicated return address register may be marked as code
46078 pointers; printing a code pointer converts it into a symbolic
46079 address. The stack pointer and any dedicated address registers
46080 may be marked as data pointers.
46083 Half precision IEEE floating point.
46086 Single precision IEEE floating point.
46089 Double precision IEEE floating point.
46092 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46095 The 12-byte extended precision format used by ARM FPA registers.
46098 The 10-byte extended precision format used by x87 registers.
46101 32bit @sc{eflags} register used by x86.
46104 32bit @sc{mxcsr} register used by x86.
46108 @node Enum Target Types
46109 @section Enum Target Types
46110 @cindex target descriptions, enum types
46112 Enum target types are useful in @samp{struct} and @samp{flags}
46113 register descriptions. @xref{Target Description Format}.
46115 Enum types have a name, size and a list of name/value pairs.
46118 <enum id="@var{id}" size="@var{size}">
46119 <evalue name="@var{name}" value="@var{value}"/>
46124 Enums must be defined before they are used.
46127 <enum id="levels_type" size="4">
46128 <evalue name="low" value="0"/>
46129 <evalue name="high" value="1"/>
46131 <flags id="flags_type" size="4">
46132 <field name="X" start="0"/>
46133 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46135 <reg name="flags" bitsize="32" type="flags_type"/>
46138 Given that description, a value of 3 for the @samp{flags} register
46139 would be printed as:
46142 (gdb) info register flags
46143 flags 0x3 [ X LEVEL=high ]
46146 @node Standard Target Features
46147 @section Standard Target Features
46148 @cindex target descriptions, standard features
46150 A target description must contain either no registers or all the
46151 target's registers. If the description contains no registers, then
46152 @value{GDBN} will assume a default register layout, selected based on
46153 the architecture. If the description contains any registers, the
46154 default layout will not be used; the standard registers must be
46155 described in the target description, in such a way that @value{GDBN}
46156 can recognize them.
46158 This is accomplished by giving specific names to feature elements
46159 which contain standard registers. @value{GDBN} will look for features
46160 with those names and verify that they contain the expected registers;
46161 if any known feature is missing required registers, or if any required
46162 feature is missing, @value{GDBN} will reject the target
46163 description. You can add additional registers to any of the
46164 standard features --- @value{GDBN} will display them just as if
46165 they were added to an unrecognized feature.
46167 This section lists the known features and their expected contents.
46168 Sample XML documents for these features are included in the
46169 @value{GDBN} source tree, in the directory @file{gdb/features}.
46171 Names recognized by @value{GDBN} should include the name of the
46172 company or organization which selected the name, and the overall
46173 architecture to which the feature applies; so e.g.@: the feature
46174 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46176 The names of registers are not case sensitive for the purpose
46177 of recognizing standard features, but @value{GDBN} will only display
46178 registers using the capitalization used in the description.
46181 * AArch64 Features::
46185 * MicroBlaze Features::
46189 * Nios II Features::
46190 * OpenRISC 1000 Features::
46191 * PowerPC Features::
46192 * RISC-V Features::
46194 * S/390 and System z Features::
46200 @node AArch64 Features
46201 @subsection AArch64 Features
46202 @cindex target descriptions, AArch64 features
46204 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46205 targets. It should contain registers @samp{x0} through @samp{x30},
46206 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46208 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46209 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46212 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46213 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46214 through @samp{p15}, @samp{ffr} and @samp{vg}.
46216 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46217 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46220 @subsection ARC Features
46221 @cindex target descriptions, ARC Features
46223 ARC processors are so configurable that even core registers and their numbers
46224 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46225 registers, which are important to @value{GDBN}, are not ``core'' registers in
46226 ARC. Therefore, there are two features that their presence is mandatory:
46227 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46229 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46234 @samp{r0} through @samp{r25} for normal register file targets.
46236 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46237 register file targets.
46239 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46240 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46243 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46244 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46245 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46246 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46247 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46248 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46249 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46250 because of their inaccessibility during user space debugging sessions.
46252 Extension core registers @samp{r32} through @samp{r59} are optional and their
46253 existence depends on the configuration. When debugging GNU/Linux applications,
46254 i.e.@: user space debugging, these core registers are not available.
46256 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46257 is the list of registers pertinent to this feature:
46261 mandatory: @samp{pc} and @samp{status32}.
46263 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46267 @subsection ARM Features
46268 @cindex target descriptions, ARM features
46270 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46272 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46273 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46275 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46276 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46277 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46280 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46281 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46283 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
46284 must contain register @samp{vpr}.
46286 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
46287 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
46289 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
46290 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
46291 synthesize the @samp{q} pseudo registers from @samp{d} register
46294 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46295 it should contain at least registers @samp{wR0} through @samp{wR15} and
46296 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46297 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46299 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46300 should contain at least registers @samp{d0} through @samp{d15}. If
46301 they are present, @samp{d16} through @samp{d31} should also be included.
46302 @value{GDBN} will synthesize the single-precision registers from
46303 halves of the double-precision registers.
46305 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46306 need to contain registers; it instructs @value{GDBN} to display the
46307 VFP double-precision registers as vectors and to synthesize the
46308 quad-precision registers from pairs of double-precision registers.
46309 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46310 be present and include 32 double-precision registers.
46312 @node i386 Features
46313 @subsection i386 Features
46314 @cindex target descriptions, i386 features
46316 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46317 targets. It should describe the following registers:
46321 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46323 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46325 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46326 @samp{fs}, @samp{gs}
46328 @samp{st0} through @samp{st7}
46330 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46331 @samp{foseg}, @samp{fooff} and @samp{fop}
46334 The register sets may be different, depending on the target.
46336 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46337 describe registers:
46341 @samp{xmm0} through @samp{xmm7} for i386
46343 @samp{xmm0} through @samp{xmm15} for amd64
46348 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46349 @samp{org.gnu.gdb.i386.sse} feature. It should
46350 describe the upper 128 bits of @sc{ymm} registers:
46354 @samp{ymm0h} through @samp{ymm7h} for i386
46356 @samp{ymm0h} through @samp{ymm15h} for amd64
46359 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
46360 Memory Protection Extension (MPX). It should describe the following registers:
46364 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
46366 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
46369 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
46370 describe a single register, @samp{orig_eax}.
46372 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
46373 describe two system registers: @samp{fs_base} and @samp{gs_base}.
46375 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
46376 @samp{org.gnu.gdb.i386.avx} feature. It should
46377 describe additional @sc{xmm} registers:
46381 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
46384 It should describe the upper 128 bits of additional @sc{ymm} registers:
46388 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
46392 describe the upper 256 bits of @sc{zmm} registers:
46396 @samp{zmm0h} through @samp{zmm7h} for i386.
46398 @samp{zmm0h} through @samp{zmm15h} for amd64.
46402 describe the additional @sc{zmm} registers:
46406 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
46409 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
46410 describe a single register, @samp{pkru}. It is a 32-bit register
46411 valid for i386 and amd64.
46413 @node MicroBlaze Features
46414 @subsection MicroBlaze Features
46415 @cindex target descriptions, MicroBlaze features
46417 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
46418 targets. It should contain registers @samp{r0} through @samp{r31},
46419 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
46420 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
46421 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
46423 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
46424 If present, it should contain registers @samp{rshr} and @samp{rslr}
46426 @node MIPS Features
46427 @subsection @acronym{MIPS} Features
46428 @cindex target descriptions, @acronym{MIPS} features
46430 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
46431 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
46432 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
46435 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
46436 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
46437 registers. They may be 32-bit or 64-bit depending on the target.
46439 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
46440 it may be optional in a future version of @value{GDBN}. It should
46441 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
46442 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
46444 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
46445 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
46446 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
46447 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
46449 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
46450 contain a single register, @samp{restart}, which is used by the
46451 Linux kernel to control restartable syscalls.
46453 @node M68K Features
46454 @subsection M68K Features
46455 @cindex target descriptions, M68K features
46458 @item @samp{org.gnu.gdb.m68k.core}
46459 @itemx @samp{org.gnu.gdb.coldfire.core}
46460 @itemx @samp{org.gnu.gdb.fido.core}
46461 One of those features must be always present.
46462 The feature that is present determines which flavor of m68k is
46463 used. The feature that is present should contain registers
46464 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
46465 @samp{sp}, @samp{ps} and @samp{pc}.
46467 @item @samp{org.gnu.gdb.coldfire.fp}
46468 This feature is optional. If present, it should contain registers
46469 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
46472 Note that, despite the fact that this feature's name says
46473 @samp{coldfire}, it is used to describe any floating point registers.
46474 The size of the registers must match the main m68k flavor; so, for
46475 example, if the primary feature is reported as @samp{coldfire}, then
46476 64-bit floating point registers are required.
46479 @node NDS32 Features
46480 @subsection NDS32 Features
46481 @cindex target descriptions, NDS32 features
46483 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
46484 targets. It should contain at least registers @samp{r0} through
46485 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
46488 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
46489 it should contain 64-bit double-precision floating-point registers
46490 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
46491 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
46493 @emph{Note:} The first sixteen 64-bit double-precision floating-point
46494 registers are overlapped with the thirty-two 32-bit single-precision
46495 floating-point registers. The 32-bit single-precision registers, if
46496 not being listed explicitly, will be synthesized from halves of the
46497 overlapping 64-bit double-precision registers. Listing 32-bit
46498 single-precision registers explicitly is deprecated, and the
46499 support to it could be totally removed some day.
46501 @node Nios II Features
46502 @subsection Nios II Features
46503 @cindex target descriptions, Nios II features
46505 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
46506 targets. It should contain the 32 core registers (@samp{zero},
46507 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
46508 @samp{pc}, and the 16 control registers (@samp{status} through
46511 @node OpenRISC 1000 Features
46512 @subsection Openrisc 1000 Features
46513 @cindex target descriptions, OpenRISC 1000 features
46515 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
46516 targets. It should contain the 32 general purpose registers (@samp{r0}
46517 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
46519 @node PowerPC Features
46520 @subsection PowerPC Features
46521 @cindex target descriptions, PowerPC features
46523 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
46524 targets. It should contain registers @samp{r0} through @samp{r31},
46525 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
46526 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
46528 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
46529 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
46531 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
46532 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
46533 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
46534 through @samp{v31} as aliases for the corresponding @samp{vrX}
46537 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
46538 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
46539 combine these registers with the floating point registers (@samp{f0}
46540 through @samp{f31}) and the altivec registers (@samp{vr0} through
46541 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
46542 @samp{vs63}, the set of vector-scalar registers for POWER7.
46543 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
46544 @samp{org.gnu.gdb.power.altivec}.
46546 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
46547 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
46548 @samp{spefscr}. SPE targets should provide 32-bit registers in
46549 @samp{org.gnu.gdb.power.core} and provide the upper halves in
46550 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
46551 these to present registers @samp{ev0} through @samp{ev31} to the
46554 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
46555 contain the 64-bit register @samp{ppr}.
46557 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
46558 contain the 64-bit register @samp{dscr}.
46560 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
46561 contain the 64-bit register @samp{tar}.
46563 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
46564 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
46567 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
46568 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
46569 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
46570 server PMU registers provided by @sc{gnu}/Linux.
46572 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
46573 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
46576 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
46577 contain the checkpointed general-purpose registers @samp{cr0} through
46578 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
46579 @samp{cctr}. These registers may all be either 32-bit or 64-bit
46580 depending on the target. It should also contain the checkpointed
46581 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
46584 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
46585 contain the checkpointed 64-bit floating-point registers @samp{cf0}
46586 through @samp{cf31}, as well as the checkpointed 64-bit register
46589 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
46590 should contain the checkpointed altivec registers @samp{cvr0} through
46591 @samp{cvr31}, all 128-bit wide. It should also contain the
46592 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
46595 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
46596 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
46597 will combine these registers with the checkpointed floating point
46598 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
46599 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
46600 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
46601 @samp{cvs63}. Therefore, this feature requires both
46602 @samp{org.gnu.gdb.power.htm.altivec} and
46603 @samp{org.gnu.gdb.power.htm.fpu}.
46605 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
46606 contain the 64-bit checkpointed register @samp{cppr}.
46608 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
46609 contain the 64-bit checkpointed register @samp{cdscr}.
46611 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
46612 contain the 64-bit checkpointed register @samp{ctar}.
46615 @node RISC-V Features
46616 @subsection RISC-V Features
46617 @cindex target descriptions, RISC-V Features
46619 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
46620 targets. It should contain the registers @samp{x0} through
46621 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
46622 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
46625 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
46626 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
46627 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
46628 architectural register names, or the ABI names can be used.
46630 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
46631 it should contain registers that are not backed by real registers on
46632 the target, but are instead virtual, where the register value is
46633 derived from other target state. In many ways these are like
46634 @value{GDBN}s pseudo-registers, except implemented by the target.
46635 Currently the only register expected in this set is the one byte
46636 @samp{priv} register that contains the target's privilege level in the
46637 least significant two bits.
46639 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
46640 should contain all of the target's standard CSRs. Standard CSRs are
46641 those defined in the RISC-V specification documents. There is some
46642 overlap between this feature and the fpu feature; the @samp{fflags},
46643 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
46644 expectation is that these registers will be in the fpu feature if the
46645 target has floating point hardware, but can be moved into the csr
46646 feature if the target has the floating point control registers, but no
46647 other floating point hardware.
46649 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
46650 it should contain registers @samp{v0} through @samp{v31}, all of which
46651 must be the same size. These requirements are based on the v0.10
46652 draft vector extension, as the vector extension is not yet final. In
46653 the event that the register set of the vector extension changes for
46654 the final specification, the requirements given here could change for
46655 future releases of @value{GDBN}.
46658 @subsection RX Features
46659 @cindex target descriptions, RX Features
46661 The @samp{org.gnu.gdb.rx.core} feature is required for RX
46662 targets. It should contain the registers @samp{r0} through
46663 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
46664 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
46666 @node S/390 and System z Features
46667 @subsection S/390 and System z Features
46668 @cindex target descriptions, S/390 features
46669 @cindex target descriptions, System z features
46671 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
46672 System z targets. It should contain the PSW and the 16 general
46673 registers. In particular, System z targets should provide the 64-bit
46674 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
46675 S/390 targets should provide the 32-bit versions of these registers.
46676 A System z target that runs in 31-bit addressing mode should provide
46677 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
46678 register's upper halves @samp{r0h} through @samp{r15h}, and their
46679 lower halves @samp{r0l} through @samp{r15l}.
46681 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
46682 contain the 64-bit registers @samp{f0} through @samp{f15}, and
46685 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
46686 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
46688 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
46689 contain the register @samp{orig_r2}, which is 64-bit wide on System z
46690 targets and 32-bit otherwise. In addition, the feature may contain
46691 the @samp{last_break} register, whose width depends on the addressing
46692 mode, as well as the @samp{system_call} register, which is always
46695 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
46696 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
46697 @samp{atia}, and @samp{tr0} through @samp{tr15}.
46699 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
46700 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
46701 combined by @value{GDBN} with the floating point registers @samp{f0}
46702 through @samp{f15} to present the 128-bit wide vector registers
46703 @samp{v0} through @samp{v15}. In addition, this feature should
46704 contain the 128-bit wide vector registers @samp{v16} through
46707 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
46708 the 64-bit wide guarded-storage-control registers @samp{gsd},
46709 @samp{gssm}, and @samp{gsepla}.
46711 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
46712 the 64-bit wide guarded-storage broadcast control registers
46713 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
46715 @node Sparc Features
46716 @subsection Sparc Features
46717 @cindex target descriptions, sparc32 features
46718 @cindex target descriptions, sparc64 features
46719 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
46720 targets. It should describe the following registers:
46724 @samp{g0} through @samp{g7}
46726 @samp{o0} through @samp{o7}
46728 @samp{l0} through @samp{l7}
46730 @samp{i0} through @samp{i7}
46733 They may be 32-bit or 64-bit depending on the target.
46735 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
46736 targets. It should describe the following registers:
46740 @samp{f0} through @samp{f31}
46742 @samp{f32} through @samp{f62} for sparc64
46745 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
46746 targets. It should describe the following registers:
46750 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
46751 @samp{fsr}, and @samp{csr} for sparc32
46753 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
46757 @node TIC6x Features
46758 @subsection TMS320C6x Features
46759 @cindex target descriptions, TIC6x features
46760 @cindex target descriptions, TMS320C6x features
46761 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
46762 targets. It should contain registers @samp{A0} through @samp{A15},
46763 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
46765 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
46766 contain registers @samp{A16} through @samp{A31} and @samp{B16}
46767 through @samp{B31}.
46769 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
46770 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
46772 @node Operating System Information
46773 @appendix Operating System Information
46774 @cindex operating system information
46776 Users of @value{GDBN} often wish to obtain information about the state of
46777 the operating system running on the target---for example the list of
46778 processes, or the list of open files. This section describes the
46779 mechanism that makes it possible. This mechanism is similar to the
46780 target features mechanism (@pxref{Target Descriptions}), but focuses
46781 on a different aspect of target.
46783 Operating system information is retrieved from the target via the
46784 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
46785 read}). The object name in the request should be @samp{osdata}, and
46786 the @var{annex} identifies the data to be fetched.
46793 @appendixsection Process list
46794 @cindex operating system information, process list
46796 When requesting the process list, the @var{annex} field in the
46797 @samp{qXfer} request should be @samp{processes}. The returned data is
46798 an XML document. The formal syntax of this document is defined in
46799 @file{gdb/features/osdata.dtd}.
46801 An example document is:
46804 <?xml version="1.0"?>
46805 <!DOCTYPE target SYSTEM "osdata.dtd">
46806 <osdata type="processes">
46808 <column name="pid">1</column>
46809 <column name="user">root</column>
46810 <column name="command">/sbin/init</column>
46811 <column name="cores">1,2,3</column>
46816 Each item should include a column whose name is @samp{pid}. The value
46817 of that column should identify the process on the target. The
46818 @samp{user} and @samp{command} columns are optional, and will be
46819 displayed by @value{GDBN}. The @samp{cores} column, if present,
46820 should contain a comma-separated list of cores that this process
46821 is running on. Target may provide additional columns,
46822 which @value{GDBN} currently ignores.
46824 @node Trace File Format
46825 @appendix Trace File Format
46826 @cindex trace file format
46828 The trace file comes in three parts: a header, a textual description
46829 section, and a trace frame section with binary data.
46831 The header has the form @code{\x7fTRACE0\n}. The first byte is
46832 @code{0x7f} so as to indicate that the file contains binary data,
46833 while the @code{0} is a version number that may have different values
46836 The description section consists of multiple lines of @sc{ascii} text
46837 separated by newline characters (@code{0xa}). The lines may include a
46838 variety of optional descriptive or context-setting information, such
46839 as tracepoint definitions or register set size. @value{GDBN} will
46840 ignore any line that it does not recognize. An empty line marks the end
46845 Specifies the size of a register block in bytes. This is equal to the
46846 size of a @code{g} packet payload in the remote protocol. @var{size}
46847 is an ascii decimal number. There should be only one such line in
46848 a single trace file.
46850 @item status @var{status}
46851 Trace status. @var{status} has the same format as a @code{qTStatus}
46852 remote packet reply. There should be only one such line in a single trace
46855 @item tp @var{payload}
46856 Tracepoint definition. The @var{payload} has the same format as
46857 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
46858 may take multiple lines of definition, corresponding to the multiple
46861 @item tsv @var{payload}
46862 Trace state variable definition. The @var{payload} has the same format as
46863 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
46864 may take multiple lines of definition, corresponding to the multiple
46867 @item tdesc @var{payload}
46868 Target description in XML format. The @var{payload} is a single line of
46869 the XML file. All such lines should be concatenated together to get
46870 the original XML file. This file is in the same format as @code{qXfer}
46871 @code{features} payload, and corresponds to the main @code{target.xml}
46872 file. Includes are not allowed.
46876 The trace frame section consists of a number of consecutive frames.
46877 Each frame begins with a two-byte tracepoint number, followed by a
46878 four-byte size giving the amount of data in the frame. The data in
46879 the frame consists of a number of blocks, each introduced by a
46880 character indicating its type (at least register, memory, and trace
46881 state variable). The data in this section is raw binary, not a
46882 hexadecimal or other encoding; its endianness matches the target's
46885 @c FIXME bi-arch may require endianness/arch info in description section
46888 @item R @var{bytes}
46889 Register block. The number and ordering of bytes matches that of a
46890 @code{g} packet in the remote protocol. Note that these are the
46891 actual bytes, in target order, not a hexadecimal encoding.
46893 @item M @var{address} @var{length} @var{bytes}...
46894 Memory block. This is a contiguous block of memory, at the 8-byte
46895 address @var{address}, with a 2-byte length @var{length}, followed by
46896 @var{length} bytes.
46898 @item V @var{number} @var{value}
46899 Trace state variable block. This records the 8-byte signed value
46900 @var{value} of trace state variable numbered @var{number}.
46904 Future enhancements of the trace file format may include additional types
46907 @node Index Section Format
46908 @appendix @code{.gdb_index} section format
46909 @cindex .gdb_index section format
46910 @cindex index section format
46912 This section documents the index section that is created by @code{save
46913 gdb-index} (@pxref{Index Files}). The index section is
46914 DWARF-specific; some knowledge of DWARF is assumed in this
46917 The mapped index file format is designed to be directly
46918 @code{mmap}able on any architecture. In most cases, a datum is
46919 represented using a little-endian 32-bit integer value, called an
46920 @code{offset_type}. Big endian machines must byte-swap the values
46921 before using them. Exceptions to this rule are noted. The data is
46922 laid out such that alignment is always respected.
46924 A mapped index consists of several areas, laid out in order.
46928 The file header. This is a sequence of values, of @code{offset_type}
46929 unless otherwise noted:
46933 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
46934 Version 4 uses a different hashing function from versions 5 and 6.
46935 Version 6 includes symbols for inlined functions, whereas versions 4
46936 and 5 do not. Version 7 adds attributes to the CU indices in the
46937 symbol table. Version 8 specifies that symbols from DWARF type units
46938 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
46939 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
46941 @value{GDBN} will only read version 4, 5, or 6 indices
46942 by specifying @code{set use-deprecated-index-sections on}.
46943 GDB has a workaround for potentially broken version 7 indices so it is
46944 currently not flagged as deprecated.
46947 The offset, from the start of the file, of the CU list.
46950 The offset, from the start of the file, of the types CU list. Note
46951 that this area can be empty, in which case this offset will be equal
46952 to the next offset.
46955 The offset, from the start of the file, of the address area.
46958 The offset, from the start of the file, of the symbol table.
46961 The offset, from the start of the file, of the constant pool.
46965 The CU list. This is a sequence of pairs of 64-bit little-endian
46966 values, sorted by the CU offset. The first element in each pair is
46967 the offset of a CU in the @code{.debug_info} section. The second
46968 element in each pair is the length of that CU. References to a CU
46969 elsewhere in the map are done using a CU index, which is just the
46970 0-based index into this table. Note that if there are type CUs, then
46971 conceptually CUs and type CUs form a single list for the purposes of
46975 The types CU list. This is a sequence of triplets of 64-bit
46976 little-endian values. In a triplet, the first value is the CU offset,
46977 the second value is the type offset in the CU, and the third value is
46978 the type signature. The types CU list is not sorted.
46981 The address area. The address area consists of a sequence of address
46982 entries. Each address entry has three elements:
46986 The low address. This is a 64-bit little-endian value.
46989 The high address. This is a 64-bit little-endian value. Like
46990 @code{DW_AT_high_pc}, the value is one byte beyond the end.
46993 The CU index. This is an @code{offset_type} value.
46997 The symbol table. This is an open-addressed hash table. The size of
46998 the hash table is always a power of 2.
47000 Each slot in the hash table consists of a pair of @code{offset_type}
47001 values. The first value is the offset of the symbol's name in the
47002 constant pool. The second value is the offset of the CU vector in the
47005 If both values are 0, then this slot in the hash table is empty. This
47006 is ok because while 0 is a valid constant pool index, it cannot be a
47007 valid index for both a string and a CU vector.
47009 The hash value for a table entry is computed by applying an
47010 iterative hash function to the symbol's name. Starting with an
47011 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47012 the string is incorporated into the hash using the formula depending on the
47017 The formula is @code{r = r * 67 + c - 113}.
47019 @item Versions 5 to 7
47020 The formula is @code{r = r * 67 + tolower (c) - 113}.
47023 The terminating @samp{\0} is not incorporated into the hash.
47025 The step size used in the hash table is computed via
47026 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47027 value, and @samp{size} is the size of the hash table. The step size
47028 is used to find the next candidate slot when handling a hash
47031 The names of C@t{++} symbols in the hash table are canonicalized. We
47032 don't currently have a simple description of the canonicalization
47033 algorithm; if you intend to create new index sections, you must read
47037 The constant pool. This is simply a bunch of bytes. It is organized
47038 so that alignment is correct: CU vectors are stored first, followed by
47041 A CU vector in the constant pool is a sequence of @code{offset_type}
47042 values. The first value is the number of CU indices in the vector.
47043 Each subsequent value is the index and symbol attributes of a CU in
47044 the CU list. This element in the hash table is used to indicate which
47045 CUs define the symbol and how the symbol is used.
47046 See below for the format of each CU index+attributes entry.
47048 A string in the constant pool is zero-terminated.
47051 Attributes were added to CU index values in @code{.gdb_index} version 7.
47052 If a symbol has multiple uses within a CU then there is one
47053 CU index+attributes value for each use.
47055 The format of each CU index+attributes entry is as follows
47061 This is the index of the CU in the CU list.
47063 These bits are reserved for future purposes and must be zero.
47065 The kind of the symbol in the CU.
47069 This value is reserved and should not be used.
47070 By reserving zero the full @code{offset_type} value is backwards compatible
47071 with previous versions of the index.
47073 The symbol is a type.
47075 The symbol is a variable or an enum value.
47077 The symbol is a function.
47079 Any other kind of symbol.
47081 These values are reserved.
47085 This bit is zero if the value is global and one if it is static.
47087 The determination of whether a symbol is global or static is complicated.
47088 The authorative reference is the file @file{dwarf2read.c} in
47089 @value{GDBN} sources.
47093 This pseudo-code describes the computation of a symbol's kind and
47094 global/static attributes in the index.
47097 is_external = get_attribute (die, DW_AT_external);
47098 language = get_attribute (cu_die, DW_AT_language);
47101 case DW_TAG_typedef:
47102 case DW_TAG_base_type:
47103 case DW_TAG_subrange_type:
47107 case DW_TAG_enumerator:
47109 is_static = language != CPLUS;
47111 case DW_TAG_subprogram:
47113 is_static = ! (is_external || language == ADA);
47115 case DW_TAG_constant:
47117 is_static = ! is_external;
47119 case DW_TAG_variable:
47121 is_static = ! is_external;
47123 case DW_TAG_namespace:
47127 case DW_TAG_class_type:
47128 case DW_TAG_interface_type:
47129 case DW_TAG_structure_type:
47130 case DW_TAG_union_type:
47131 case DW_TAG_enumeration_type:
47133 is_static = language != CPLUS;
47141 @appendix Download debugging resources with Debuginfod
47144 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47147 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47148 can query servers using the build IDs associated with missing debug info,
47149 executables and source files in order to download them on demand.
47151 For instructions on building @value{GDBN} with @file{libdebuginfod},
47152 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47153 with @code{elfutils}, starting with version 0.178. See
47154 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47155 regarding @code{debuginfod}.
47158 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47161 @node Debuginfod Settings
47162 @section Debuginfod Settings
47164 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47167 @kindex set debuginfod enabled
47168 @anchor{set debuginfod enabled}
47169 @item set debuginfod enabled
47170 @itemx set debuginfod enabled on
47171 @cindex enable debuginfod
47172 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47173 info or source files.
47175 @item set debuginfod enabled off
47176 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47177 debug info or source files. By default, @code{debuginfod enabled} is set to
47178 @code{off} for non-interactive sessions.
47180 @item set debuginfod enabled ask
47181 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47182 attempting to perform the next query. By default, @code{debuginfod enabled}
47183 is set to @code{ask} for interactive sessions.
47185 @kindex show debuginfod enabled
47186 @item show debuginfod enabled
47187 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47190 @kindex set debuginfod urls
47191 @cindex configure debuginfod URLs
47192 @item set debuginfod urls
47193 @itemx set debuginfod urls @var{urls}
47194 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47195 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47196 should be used. The default value of @code{debuginfod urls} is copied from
47197 the @var{DEBUGINFOD_URLS} environment variable.
47199 @kindex show debuginfod urls
47200 @item show debuginfod urls
47201 Display the list of URLs that @code{debuginfod} will attempt to query.
47203 @kindex set debuginfod verbose
47204 @cindex debuginfod verbosity
47205 @item set debuginfod verbose
47206 @itemx set debuginfod verbose @var{n}
47207 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47208 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47211 @kindex show debuginfod verbose
47212 @item show debuginfod verbose
47213 Show the current verbosity setting.
47218 @appendix Manual pages
47222 * gdb man:: The GNU Debugger man page
47223 * gdbserver man:: Remote Server for the GNU Debugger man page
47224 * gcore man:: Generate a core file of a running program
47225 * gdbinit man:: gdbinit scripts
47226 * gdb-add-index man:: Add index files to speed up GDB
47232 @c man title gdb The GNU Debugger
47234 @c man begin SYNOPSIS gdb
47235 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
47238 @c man begin DESCRIPTION gdb
47239 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
47240 going on ``inside'' another program while it executes -- or what another
47241 program was doing at the moment it crashed.
47243 @value{GDBN} can do four main kinds of things (plus other things in support of
47244 these) to help you catch bugs in the act:
47248 Start your program, specifying anything that might affect its behavior.
47251 Make your program stop on specified conditions.
47254 Examine what has happened, when your program has stopped.
47257 Change things in your program, so you can experiment with correcting the
47258 effects of one bug and go on to learn about another.
47261 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47264 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47265 commands from the terminal until you tell it to exit with the @value{GDBN}
47266 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
47267 by using the command @code{help}.
47269 You can run @code{gdb} with no arguments or options; but the most
47270 usual way to start @value{GDBN} is with one argument or two, specifying an
47271 executable program as the argument:
47277 You can also start with both an executable program and a core file specified:
47283 You can, instead, specify a process ID as a second argument or use option
47284 @code{-p}, if you want to debug a running process:
47292 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47293 can omit the @var{program} filename.
47295 Here are some of the most frequently needed @value{GDBN} commands:
47297 @c pod2man highlights the right hand side of the @item lines.
47299 @item break [@var{file}:][@var{function}|@var{line}]
47300 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
47302 @item run [@var{arglist}]
47303 Start your program (with @var{arglist}, if specified).
47306 Backtrace: display the program stack.
47308 @item print @var{expr}
47309 Display the value of an expression.
47312 Continue running your program (after stopping, e.g.@: at a breakpoint).
47315 Execute next program line (after stopping); step @emph{over} any
47316 function calls in the line.
47318 @item edit [@var{file}:]@var{function}
47319 look at the program line where it is presently stopped.
47321 @item list [@var{file}:]@var{function}
47322 type the text of the program in the vicinity of where it is presently stopped.
47325 Execute next program line (after stopping); step @emph{into} any
47326 function calls in the line.
47328 @item help [@var{name}]
47329 Show information about @value{GDBN} command @var{name}, or general information
47330 about using @value{GDBN}.
47334 Exit from @value{GDBN}.
47338 For full details on @value{GDBN},
47339 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47340 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47341 as the @code{gdb} entry in the @code{info} program.
47345 @c man begin OPTIONS gdb
47346 Any arguments other than options specify an executable
47347 file and core file (or process ID); that is, the first argument
47348 encountered with no
47349 associated option flag is equivalent to a @option{--se} option, and the second,
47350 if any, is equivalent to a @option{-c} option if it's the name of a file.
47352 both long and abbreviated forms; both are shown here. The long forms are also
47353 recognized if you truncate them, so long as enough of the option is
47354 present to be unambiguous.
47356 The abbreviated forms are shown here with @samp{-} and long forms are shown
47357 with @samp{--} to reflect how they are shown in @option{--help}. However,
47358 @value{GDBN} recognizes all of the following conventions for most options:
47361 @item --option=@var{value}
47362 @item --option @var{value}
47363 @item -option=@var{value}
47364 @item -option @var{value}
47365 @item --o=@var{value}
47366 @item --o @var{value}
47367 @item -o=@var{value}
47368 @item -o @var{value}
47371 All the options and command line arguments you give are processed
47372 in sequential order. The order makes a difference when the @option{-x}
47378 List all options, with brief explanations.
47380 @item --symbols=@var{file}
47381 @itemx -s @var{file}
47382 Read symbol table from @var{file}.
47385 Enable writing into executable and core files.
47387 @item --exec=@var{file}
47388 @itemx -e @var{file}
47389 Use @var{file} as the executable file to execute when
47390 appropriate, and for examining pure data in conjunction with a core
47393 @item --se=@var{file}
47394 Read symbol table from @var{file} and use it as the executable
47397 @item --core=@var{file}
47398 @itemx -c @var{file}
47399 Use @var{file} as a core dump to examine.
47401 @item --command=@var{file}
47402 @itemx -x @var{file}
47403 Execute @value{GDBN} commands from @var{file}.
47405 @item --eval-command=@var{command}
47406 @item -ex @var{command}
47407 Execute given @value{GDBN} @var{command}.
47409 @item --init-eval-command=@var{command}
47411 Execute @value{GDBN} @var{command} before loading the inferior.
47413 @item --directory=@var{directory}
47414 @itemx -d @var{directory}
47415 Add @var{directory} to the path to search for source files.
47418 Do not execute commands from @file{~/.config/gdb/gdbinit},
47419 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
47420 @file{~/.gdbearlyinit}
47424 Do not execute commands from any @file{.gdbinit} or
47425 @file{.gdbearlyinit} initialization files.
47430 ``Quiet''. Do not print the introductory and copyright messages. These
47431 messages are also suppressed in batch mode.
47434 Run in batch mode. Exit with status @code{0} after processing all the command
47435 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
47436 Exit with nonzero status if an error occurs in executing the @value{GDBN}
47437 commands in the command files.
47439 Batch mode may be useful for running @value{GDBN} as a filter, for example to
47440 download and run a program on another computer; in order to make this
47441 more useful, the message
47444 Program exited normally.
47448 (which is ordinarily issued whenever a program running under @value{GDBN} control
47449 terminates) is not issued when running in batch mode.
47451 @item --batch-silent
47452 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
47453 output is supressed (stderr is unaffected). This is much quieter than
47454 @option{--silent} and would be useless for an interactive session.
47456 This is particularly useful when using targets that give @samp{Loading section}
47457 messages, for example.
47459 Note that targets that give their output via @value{GDBN}, as opposed to writing
47460 directly to @code{stdout}, will also be made silent.
47462 @item --args @var{prog} [@var{arglist}]
47463 Change interpretation of command line so that arguments following this
47464 option are passed as arguments to the inferior. As an example, take
47465 the following command:
47472 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
47473 the other hand, using:
47476 gdb --args ./a.out -q
47480 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
47482 @item --pid=@var{pid}
47483 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
47486 Open the terminal user interface.
47489 Read all symbols from the given symfile on the first access.
47492 Do not read symbol files.
47495 Run in DBX compatibility mode.
47497 @item --return-child-result
47498 @value{GDBN}'s exit code will be the same as the child's exit code.
47500 @item --configuration
47501 Print details about GDB configuration and then exit.
47504 Print version information and then exit.
47506 @item --cd=@var{directory}
47507 Run @value{GDBN} using @var{directory} as its working directory,
47508 instead of the current directory.
47510 @item --data-directory=@var{directory}
47512 Run @value{GDBN} using @var{directory} as its data directory. The data
47513 directory is where @value{GDBN} searches for its auxiliary files.
47517 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
47518 @value{GDBN} to output the full file name and line number in a standard,
47519 recognizable fashion each time a stack frame is displayed (which
47520 includes each time the program stops). This recognizable format looks
47521 like two @samp{\032} characters, followed by the file name, line number
47522 and character position separated by colons, and a newline. The
47523 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
47524 characters as a signal to display the source code for the frame.
47526 @item -b @var{baudrate}
47527 Set the line speed (baud rate or bits per second) of any serial
47528 interface used by @value{GDBN} for remote debugging.
47530 @item -l @var{timeout}
47531 Set timeout, in seconds, for remote debugging.
47533 @item --tty=@var{device}
47534 Run using @var{device} for your program's standard input and output.
47538 @c man begin SEEALSO gdb
47540 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47541 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47542 documentation are properly installed at your site, the command
47549 should give you access to the complete manual.
47551 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47552 Richard M. Stallman and Roland H. Pesch, July 1991.
47556 @node gdbserver man
47557 @heading gdbserver man
47559 @c man title gdbserver Remote Server for the GNU Debugger
47561 @c man begin SYNOPSIS gdbserver
47562 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47564 gdbserver --attach @var{comm} @var{pid}
47566 gdbserver --multi @var{comm}
47570 @c man begin DESCRIPTION gdbserver
47571 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
47572 than the one which is running the program being debugged.
47575 @subheading Usage (server (target) side)
47578 Usage (server (target) side):
47581 First, you need to have a copy of the program you want to debug put onto
47582 the target system. The program can be stripped to save space if needed, as
47583 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
47584 the @value{GDBN} running on the host system.
47586 To use the server, you log on to the target system, and run the @command{gdbserver}
47587 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
47588 your program, and (c) its arguments. The general syntax is:
47591 target> gdbserver @var{comm} @var{program} [@var{args} ...]
47594 For example, using a serial port, you might say:
47598 @c @file would wrap it as F</dev/com1>.
47599 target> gdbserver /dev/com1 emacs foo.txt
47602 target> gdbserver @file{/dev/com1} emacs foo.txt
47606 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
47607 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
47608 waits patiently for the host @value{GDBN} to communicate with it.
47610 To use a TCP connection, you could say:
47613 target> gdbserver host:2345 emacs foo.txt
47616 This says pretty much the same thing as the last example, except that we are
47617 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
47618 that we are expecting to see a TCP connection from @code{host} to local TCP port
47619 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
47620 want for the port number as long as it does not conflict with any existing TCP
47621 ports on the target system. This same port number must be used in the host
47622 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
47623 you chose a port number that conflicts with another service, @command{gdbserver} will
47624 print an error message and exit.
47626 @command{gdbserver} can also attach to running programs.
47627 This is accomplished via the @option{--attach} argument. The syntax is:
47630 target> gdbserver --attach @var{comm} @var{pid}
47633 @var{pid} is the process ID of a currently running process. It isn't
47634 necessary to point @command{gdbserver} at a binary for the running process.
47636 To start @code{gdbserver} without supplying an initial command to run
47637 or process ID to attach, use the @option{--multi} command line option.
47638 In such case you should connect using @kbd{target extended-remote} to start
47639 the program you want to debug.
47642 target> gdbserver --multi @var{comm}
47646 @subheading Usage (host side)
47652 You need an unstripped copy of the target program on your host system, since
47653 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
47654 would, with the target program as the first argument. (You may need to use the
47655 @option{--baud} option if the serial line is running at anything except 9600 baud.)
47656 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
47657 new command you need to know about is @code{target remote}
47658 (or @code{target extended-remote}). Its argument is either
47659 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
47660 descriptor. For example:
47664 @c @file would wrap it as F</dev/ttyb>.
47665 (gdb) target remote /dev/ttyb
47668 (gdb) target remote @file{/dev/ttyb}
47673 communicates with the server via serial line @file{/dev/ttyb}, and:
47676 (gdb) target remote the-target:2345
47680 communicates via a TCP connection to port 2345 on host `the-target', where
47681 you previously started up @command{gdbserver} with the same port number. Note that for
47682 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
47683 command, otherwise you may get an error that looks something like
47684 `Connection refused'.
47686 @command{gdbserver} can also debug multiple inferiors at once,
47689 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
47690 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
47693 @ref{Inferiors Connections and Programs}.
47695 In such case use the @code{extended-remote} @value{GDBN} command variant:
47698 (gdb) target extended-remote the-target:2345
47701 The @command{gdbserver} option @option{--multi} may or may not be used in such
47705 @c man begin OPTIONS gdbserver
47706 There are three different modes for invoking @command{gdbserver}:
47711 Debug a specific program specified by its program name:
47714 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47717 The @var{comm} parameter specifies how should the server communicate
47718 with @value{GDBN}; it is either a device name (to use a serial line),
47719 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
47720 stdin/stdout of @code{gdbserver}. Specify the name of the program to
47721 debug in @var{prog}. Any remaining arguments will be passed to the
47722 program verbatim. When the program exits, @value{GDBN} will close the
47723 connection, and @code{gdbserver} will exit.
47726 Debug a specific program by specifying the process ID of a running
47730 gdbserver --attach @var{comm} @var{pid}
47733 The @var{comm} parameter is as described above. Supply the process ID
47734 of a running program in @var{pid}; @value{GDBN} will do everything
47735 else. Like with the previous mode, when the process @var{pid} exits,
47736 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
47739 Multi-process mode -- debug more than one program/process:
47742 gdbserver --multi @var{comm}
47745 In this mode, @value{GDBN} can instruct @command{gdbserver} which
47746 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
47747 close the connection when a process being debugged exits, so you can
47748 debug several processes in the same session.
47751 In each of the modes you may specify these options:
47756 List all options, with brief explanations.
47759 This option causes @command{gdbserver} to print its version number and exit.
47762 @command{gdbserver} will attach to a running program. The syntax is:
47765 target> gdbserver --attach @var{comm} @var{pid}
47768 @var{pid} is the process ID of a currently running process. It isn't
47769 necessary to point @command{gdbserver} at a binary for the running process.
47772 To start @code{gdbserver} without supplying an initial command to run
47773 or process ID to attach, use this command line option.
47774 Then you can connect using @kbd{target extended-remote} and start
47775 the program you want to debug. The syntax is:
47778 target> gdbserver --multi @var{comm}
47782 Instruct @code{gdbserver} to display extra status information about the debugging
47784 This option is intended for @code{gdbserver} development and for bug reports to
47787 @item --remote-debug
47788 Instruct @code{gdbserver} to display remote protocol debug output.
47789 This option is intended for @code{gdbserver} development and for bug reports to
47792 @item --debug-file=@var{filename}
47793 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
47794 This option is intended for @code{gdbserver} development and for bug reports to
47797 @item --debug-format=option1@r{[},option2,...@r{]}
47798 Instruct @code{gdbserver} to include extra information in each line
47799 of debugging output.
47800 @xref{Other Command-Line Arguments for gdbserver}.
47803 Specify a wrapper to launch programs
47804 for debugging. The option should be followed by the name of the
47805 wrapper, then any command-line arguments to pass to the wrapper, then
47806 @kbd{--} indicating the end of the wrapper arguments.
47809 By default, @command{gdbserver} keeps the listening TCP port open, so that
47810 additional connections are possible. However, if you start @code{gdbserver}
47811 with the @option{--once} option, it will stop listening for any further
47812 connection attempts after connecting to the first @value{GDBN} session.
47814 @c --disable-packet is not documented for users.
47816 @c --disable-randomization and --no-disable-randomization are superseded by
47817 @c QDisableRandomization.
47822 @c man begin SEEALSO gdbserver
47824 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47825 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47826 documentation are properly installed at your site, the command
47832 should give you access to the complete manual.
47834 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47835 Richard M. Stallman and Roland H. Pesch, July 1991.
47842 @c man title gcore Generate a core file of a running program
47845 @c man begin SYNOPSIS gcore
47846 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
47850 @c man begin DESCRIPTION gcore
47851 Generate core dumps of one or more running programs with process IDs
47852 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
47853 is equivalent to one produced by the kernel when the process crashes
47854 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
47855 limit). However, unlike after a crash, after @command{gcore} finishes
47856 its job the program remains running without any change.
47859 @c man begin OPTIONS gcore
47862 Dump all memory mappings. The actual effect of this option depends on
47863 the Operating System. On @sc{gnu}/Linux, it will disable
47864 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
47865 enable @code{dump-excluded-mappings} (@pxref{set
47866 dump-excluded-mappings}).
47868 @item -o @var{prefix}
47869 The optional argument @var{prefix} specifies the prefix to be used
47870 when composing the file names of the core dumps. The file name is
47871 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
47872 process ID of the running program being analyzed by @command{gcore}.
47873 If not specified, @var{prefix} defaults to @var{gcore}.
47877 @c man begin SEEALSO gcore
47879 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47880 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47881 documentation are properly installed at your site, the command
47888 should give you access to the complete manual.
47890 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47891 Richard M. Stallman and Roland H. Pesch, July 1991.
47898 @c man title gdbinit GDB initialization scripts
47901 @c man begin SYNOPSIS gdbinit
47902 @ifset SYSTEM_GDBINIT
47903 @value{SYSTEM_GDBINIT}
47906 @ifset SYSTEM_GDBINIT_DIR
47907 @value{SYSTEM_GDBINIT_DIR}/*
47910 ~/.config/gdb/gdbinit
47918 @c man begin DESCRIPTION gdbinit
47919 These files contain @value{GDBN} commands to automatically execute during
47920 @value{GDBN} startup. The lines of contents are canned sequences of commands,
47923 the @value{GDBN} manual in node @code{Sequences}
47924 -- shell command @code{info -f gdb -n Sequences}.
47930 Please read more in
47932 the @value{GDBN} manual in node @code{Startup}
47933 -- shell command @code{info -f gdb -n Startup}.
47940 @ifset SYSTEM_GDBINIT
47941 @item @value{SYSTEM_GDBINIT}
47943 @ifclear SYSTEM_GDBINIT
47944 @item (not enabled with @code{--with-system-gdbinit} during compilation)
47946 System-wide initialization file. It is executed unless user specified
47947 @value{GDBN} option @code{-nx} or @code{-n}.
47950 the @value{GDBN} manual in node @code{System-wide configuration}
47951 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47953 @ifset SYSTEM_GDBINIT_DIR
47954 @item @value{SYSTEM_GDBINIT_DIR}
47956 @ifclear SYSTEM_GDBINIT_DIR
47957 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
47959 System-wide initialization directory. All files in this directory are
47960 executed on startup unless user specified @value{GDBN} option @code{-nx} or
47961 @code{-n}, as long as they have a recognized file extension.
47964 the @value{GDBN} manual in node @code{System-wide configuration}
47965 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
47968 @ref{System-wide configuration}.
47971 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
47972 User initialization file. It is executed unless user specified
47973 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
47975 @item @file{.gdbinit}
47976 Initialization file for current directory. It may need to be enabled with
47977 @value{GDBN} security command @code{set auto-load local-gdbinit}.
47980 the @value{GDBN} manual in node @code{Init File in the Current Directory}
47981 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
47984 @ref{Init File in the Current Directory}.
47989 @c man begin SEEALSO gdbinit
47991 gdb(1), @code{info -f gdb -n Startup}
47993 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47994 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47995 documentation are properly installed at your site, the command
48001 should give you access to the complete manual.
48003 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48004 Richard M. Stallman and Roland H. Pesch, July 1991.
48008 @node gdb-add-index man
48009 @heading gdb-add-index
48010 @pindex gdb-add-index
48011 @anchor{gdb-add-index}
48013 @c man title gdb-add-index Add index files to speed up GDB
48015 @c man begin SYNOPSIS gdb-add-index
48016 gdb-add-index @var{filename}
48019 @c man begin DESCRIPTION gdb-add-index
48020 When @value{GDBN} finds a symbol file, it scans the symbols in the
48021 file in order to construct an internal symbol table. This lets most
48022 @value{GDBN} operations work quickly--at the cost of a delay early on.
48023 For large programs, this delay can be quite lengthy, so @value{GDBN}
48024 provides a way to build an index, which speeds up startup.
48026 To determine whether a file contains such an index, use the command
48027 @kbd{readelf -S filename}: the index is stored in a section named
48028 @code{.gdb_index}. The index file can only be produced on systems
48029 which use ELF binaries and DWARF debug information (i.e., sections
48030 named @code{.debug_*}).
48032 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48033 in the @env{PATH} environment variable. If you want to use different
48034 versions of these programs, you can specify them through the
48035 @env{GDB} and @env{OBJDUMP} environment variables.
48039 the @value{GDBN} manual in node @code{Index Files}
48040 -- shell command @kbd{info -f gdb -n "Index Files"}.
48047 @c man begin SEEALSO gdb-add-index
48049 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48050 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48051 documentation are properly installed at your site, the command
48057 should give you access to the complete manual.
48059 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48060 Richard M. Stallman and Roland H. Pesch, July 1991.
48066 @node GNU Free Documentation License
48067 @appendix GNU Free Documentation License
48070 @node Concept Index
48071 @unnumbered Concept Index
48075 @node Command and Variable Index
48076 @unnumbered Command, Variable, and Function Index
48081 % I think something like @@colophon should be in texinfo. In the
48083 \long\def\colophon{\hbox to0pt{}\vfill
48084 \centerline{The body of this manual is set in}
48085 \centerline{\fontname\tenrm,}
48086 \centerline{with headings in {\bf\fontname\tenbf}}
48087 \centerline{and examples in {\tt\fontname\tentt}.}
48088 \centerline{{\it\fontname\tenit\/},}
48089 \centerline{{\bf\fontname\tenbf}, and}
48090 \centerline{{\sl\fontname\tensl\/}}
48091 \centerline{are used for emphasis.}\vfill}
48093 % Blame: doc@@cygnus.com, 1991.