1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2023 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{} 1988-2023 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) 1988-2023 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 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
966 form equivalents, the method used to search the file system for the
967 symbol and/or executable file is the same as that used by the
968 @code{file} command. @xref{Files, ,file}.
970 Many options have both long and short forms; both are shown in the
971 following list. @value{GDBN} also recognizes the long forms if you truncate
972 them, so long as enough of the option is present to be unambiguous.
973 (If you prefer, you can flag option arguments with @samp{--} rather
974 than @samp{-}, though we illustrate the more usual convention.)
976 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
977 @c way, both those who look for -foo and --foo in the index, will find
981 @item -symbols @var{file}
983 @cindex @code{--symbols}
985 Read symbol table from file @var{file}.
987 @item -exec @var{file}
989 @cindex @code{--exec}
991 Use file @var{file} as the executable file to execute when appropriate,
992 and for examining pure data in conjunction with a core dump.
996 Read symbol table from file @var{file} and use it as the executable
999 @item -core @var{file}
1000 @itemx -c @var{file}
1001 @cindex @code{--core}
1003 Use file @var{file} as a core dump to examine.
1005 @item -pid @var{number}
1006 @itemx -p @var{number}
1007 @cindex @code{--pid}
1009 Connect to process ID @var{number}, as with the @code{attach} command.
1011 @item -command @var{file}
1012 @itemx -x @var{file}
1013 @cindex @code{--command}
1015 Execute commands from file @var{file}. The contents of this file is
1016 evaluated exactly as the @code{source} command would.
1017 @xref{Command Files,, Command files}.
1019 @item -eval-command @var{command}
1020 @itemx -ex @var{command}
1021 @cindex @code{--eval-command}
1023 Execute a single @value{GDBN} command.
1025 This option may be used multiple times to call multiple commands. It may
1026 also be interleaved with @samp{-command} as required.
1029 @value{GDBP} -ex 'target sim' -ex 'load' \
1030 -x setbreakpoints -ex 'run' a.out
1033 @item -init-command @var{file}
1034 @itemx -ix @var{file}
1035 @cindex @code{--init-command}
1037 Execute commands from file @var{file} before loading the inferior (but
1038 after loading gdbinit files).
1041 @item -init-eval-command @var{command}
1042 @itemx -iex @var{command}
1043 @cindex @code{--init-eval-command}
1045 Execute a single @value{GDBN} command before loading the inferior (but
1046 after loading gdbinit files).
1049 @item -early-init-command @var{file}
1050 @itemx -eix @var{file}
1051 @cindex @code{--early-init-command}
1053 Execute commands from @var{file} very early in the initialization
1054 process, before any output is produced. @xref{Startup}.
1056 @item -early-init-eval-command @var{command}
1057 @itemx -eiex @var{command}
1058 @cindex @code{--early-init-eval-command}
1059 @cindex @code{-eiex}
1060 Execute a single @value{GDBN} command very early in the initialization
1061 process, before any output is produced.
1063 @item -directory @var{directory}
1064 @itemx -d @var{directory}
1065 @cindex @code{--directory}
1067 Add @var{directory} to the path to search for source and script files.
1071 @cindex @code{--readnow}
1073 Read each symbol file's entire symbol table immediately, rather than
1074 the default, which is to read it incrementally as it is needed.
1075 This makes startup slower, but makes future operations faster.
1078 @anchor{--readnever}
1079 @cindex @code{--readnever}, command-line option
1080 Do not read each symbol file's symbolic debug information. This makes
1081 startup faster but at the expense of not being able to perform
1082 symbolic debugging. DWARF unwind information is also not read,
1083 meaning backtraces may become incomplete or inaccurate. One use of
1084 this is when a user simply wants to do the following sequence: attach,
1085 dump core, detach. Loading the debugging information in this case is
1086 an unnecessary cause of delay.
1090 @subsection Choosing Modes
1092 You can run @value{GDBN} in various alternative modes---for example, in
1093 batch mode or quiet mode.
1101 Do not execute commands found in any initialization files
1102 (@pxref{Initialization Files}).
1107 Do not execute commands found in any home directory initialization
1108 file (@pxref{Initialization Files,,Home directory initialization
1109 file}). The system wide and current directory initialization files
1115 @cindex @code{--quiet}
1116 @cindex @code{--silent}
1118 ``Quiet''. Do not print the introductory and copyright messages. These
1119 messages are also suppressed in batch mode.
1121 @kindex set startup-quietly
1122 @kindex show startup-quietly
1123 This can also be enabled using @code{set startup-quietly on}. The
1124 default is @code{off}. Use @code{show startup-quietly} to see the
1125 current setting. Place @code{set startup-quietly on} into your early
1126 initialization file (@pxref{Initialization Files,,Initialization
1127 Files}) to have future @value{GDBN} sessions startup quietly.
1130 @cindex @code{--batch}
1131 Run in batch mode. Exit with status @code{0} after processing all the
1132 command files specified with @samp{-x} (and all commands from
1133 initialization files, if not inhibited with @samp{-n}). Exit with
1134 nonzero status if an error occurs in executing the @value{GDBN} commands
1135 in the command files. Batch mode also disables pagination, sets unlimited
1136 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1137 off} were in effect (@pxref{Messages/Warnings}).
1139 Batch mode may be useful for running @value{GDBN} as a filter, for
1140 example to download and run a program on another computer; in order to
1141 make this more useful, the message
1144 Program exited normally.
1148 (which is ordinarily issued whenever a program running under
1149 @value{GDBN} control terminates) is not issued when running in batch
1153 @cindex @code{--batch-silent}
1154 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1155 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1156 unaffected). This is much quieter than @samp{-silent} and would be useless
1157 for an interactive session.
1159 This is particularly useful when using targets that give @samp{Loading section}
1160 messages, for example.
1162 Note that targets that give their output via @value{GDBN}, as opposed to
1163 writing directly to @code{stdout}, will also be made silent.
1165 @item -return-child-result
1166 @cindex @code{--return-child-result}
1167 The return code from @value{GDBN} will be the return code from the child
1168 process (the process being debugged), with the following exceptions:
1172 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1173 internal error. In this case the exit code is the same as it would have been
1174 without @samp{-return-child-result}.
1176 The user quits with an explicit value. E.g., @samp{quit 1}.
1178 The child process never runs, or is not allowed to terminate, in which case
1179 the exit code will be -1.
1182 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1183 when @value{GDBN} is being used as a remote program loader or simulator
1188 @cindex @code{--nowindows}
1190 ``No windows''. If @value{GDBN} comes with a graphical user interface
1191 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1192 interface. If no GUI is available, this option has no effect.
1196 @cindex @code{--windows}
1198 If @value{GDBN} includes a GUI, then this option requires it to be
1201 @item -cd @var{directory}
1203 Run @value{GDBN} using @var{directory} as its working directory,
1204 instead of the current directory.
1206 @item -data-directory @var{directory}
1207 @itemx -D @var{directory}
1208 @cindex @code{--data-directory}
1210 Run @value{GDBN} using @var{directory} as its data directory.
1211 The data directory is where @value{GDBN} searches for its
1212 auxiliary files. @xref{Data Files}.
1216 @cindex @code{--fullname}
1218 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1219 subprocess. It tells @value{GDBN} to output the full file name and line
1220 number in a standard, recognizable fashion each time a stack frame is
1221 displayed (which includes each time your program stops). This
1222 recognizable format looks like two @samp{\032} characters, followed by
1223 the file name, line number and character position separated by colons,
1224 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1225 @samp{\032} characters as a signal to display the source code for the
1228 @item -annotate @var{level}
1229 @cindex @code{--annotate}
1230 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1231 effect is identical to using @samp{set annotate @var{level}}
1232 (@pxref{Annotations}). The annotation @var{level} controls how much
1233 information @value{GDBN} prints together with its prompt, values of
1234 expressions, source lines, and other types of output. Level 0 is the
1235 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1236 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1237 that control @value{GDBN}, and level 2 has been deprecated.
1239 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1243 @cindex @code{--args}
1244 Change interpretation of command line so that arguments following the
1245 executable file are passed as command line arguments to the inferior.
1246 This option stops option processing.
1248 @item -baud @var{bps}
1250 @cindex @code{--baud}
1252 Set the line speed (baud rate or bits per second) of any serial
1253 interface used by @value{GDBN} for remote debugging.
1255 @item -l @var{timeout}
1257 Set the timeout (in seconds) of any communication used by @value{GDBN}
1258 for remote debugging.
1260 @item -tty @var{device}
1261 @itemx -t @var{device}
1262 @cindex @code{--tty}
1264 Run using @var{device} for your program's standard input and output.
1265 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1267 @c resolve the situation of these eventually
1269 @cindex @code{--tui}
1270 Activate the @dfn{Text User Interface} when starting. The Text User
1271 Interface manages several text windows on the terminal, showing
1272 source, assembly, registers and @value{GDBN} command outputs
1273 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1274 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1275 Using @value{GDBN} under @sc{gnu} Emacs}).
1277 @item -interpreter @var{interp}
1278 @cindex @code{--interpreter}
1279 Use the interpreter @var{interp} for interface with the controlling
1280 program or device. This option is meant to be set by programs which
1281 communicate with @value{GDBN} using it as a back end.
1282 @xref{Interpreters, , Command Interpreters}.
1284 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1285 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1286 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1287 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1288 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1289 interfaces are no longer supported.
1292 @cindex @code{--write}
1293 Open the executable and core files for both reading and writing. This
1294 is equivalent to the @samp{set write on} command inside @value{GDBN}
1298 @cindex @code{--statistics}
1299 This option causes @value{GDBN} to print statistics about time and
1300 memory usage after it completes each command and returns to the prompt.
1303 @cindex @code{--version}
1304 This option causes @value{GDBN} to print its version number and
1305 no-warranty blurb, and exit.
1307 @item -configuration
1308 @cindex @code{--configuration}
1309 This option causes @value{GDBN} to print details about its build-time
1310 configuration parameters, and then exit. These details can be
1311 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1316 @subsection What @value{GDBN} Does During Startup
1317 @cindex @value{GDBN} startup
1319 Here's the description of what @value{GDBN} does during session startup:
1324 Performs minimal setup required to initialize basic internal state.
1327 @cindex early initialization file
1328 Reads commands from the early initialization file (if any) in your
1329 home directory. Only a restricted set of commands can be placed into
1330 an early initialization file, see @ref{Initialization Files}, for
1334 Executes commands and command files specified by the @samp{-eiex} and
1335 @samp{-eix} command line options in their specified order. Only a
1336 restricted set of commands can be used with @samp{-eiex} and
1337 @samp{eix}, see @ref{Initialization Files}, for details.
1340 Sets up the command interpreter as specified by the command line
1341 (@pxref{Mode Options, interpreter}).
1345 Reads the system wide initialization file and the files from the
1346 system wide initialization directory, @pxref{System Wide Init Files}.
1349 Reads the initialization file (if any) in your home directory and
1350 executes all the commands in that file, @pxref{Home Directory Init
1353 @anchor{Option -init-eval-command}
1355 Executes commands and command files specified by the @samp{-iex} and
1356 @samp{-ix} options in their specified order. Usually you should use the
1357 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1358 settings before @value{GDBN} init files get executed and before inferior
1362 Processes command line options and operands.
1365 Reads and executes the commands from the initialization file (if any)
1366 in the current working directory as long as @samp{set auto-load
1367 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1368 Directory}). This is only done if the current directory is different
1369 from your home directory. Thus, you can have more than one init file,
1370 one generic in your home directory, and another, specific to the
1371 program you are debugging, in the directory where you invoke
1372 @value{GDBN}. @xref{Init File in the Current Directory during
1376 If the command line specified a program to debug, or a process to
1377 attach to, or a core file, @value{GDBN} loads any auto-loaded
1378 scripts provided for the program or for its loaded shared libraries.
1379 @xref{Auto-loading}.
1381 If you wish to disable the auto-loading during startup,
1382 you must do something like the following:
1385 $ gdb -iex "set auto-load python-scripts off" myprogram
1388 Option @samp{-ex} does not work because the auto-loading is then turned
1392 Executes commands and command files specified by the @samp{-ex} and
1393 @samp{-x} options in their specified order. @xref{Command Files}, for
1394 more details about @value{GDBN} command files.
1397 Reads the command history recorded in the @dfn{history file}.
1398 @xref{Command History}, for more details about the command history and the
1399 files where @value{GDBN} records it.
1402 @node Initialization Files
1403 @subsection Initialization Files
1404 @cindex init file name
1406 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1407 from several initialization files. These initialization files use the
1408 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1409 processed by @value{GDBN} in the same way.
1411 To display the list of initialization files loaded by @value{GDBN} at
1412 startup, in the order they will be loaded, you can use @kbd{gdb
1415 @cindex early initialization
1416 The @dfn{early initialization} file is loaded very early in
1417 @value{GDBN}'s initialization process, before the interpreter
1418 (@pxref{Interpreters}) has been initialized, and before the default
1419 target (@pxref{Targets}) is initialized. Only @code{set} or
1420 @code{source} commands should be placed into an early initialization
1421 file, and the only @code{set} commands that can be used are those that
1422 control how @value{GDBN} starts up.
1424 Commands that can be placed into an early initialization file will be
1425 documented as such throughout this manual. Any command that is not
1426 documented as being suitable for an early initialization file should
1427 instead be placed into a general initialization file. Command files
1428 passed to @code{--early-init-command} or @code{-eix} are also early
1429 initialization files, with the same command restrictions. Only
1430 commands that can appear in an early initialization file should be
1431 passed to @code{--early-init-eval-command} or @code{-eiex}.
1433 @cindex general initialization
1434 In contrast, the @dfn{general initialization} files are processed
1435 later, after @value{GDBN} has finished its own internal initialization
1436 process, any valid command can be used in these files.
1438 @cindex initialization file
1439 Throughout the rest of this document the term @dfn{initialization
1440 file} refers to one of the general initialization files, not the early
1441 initialization file. Any discussion of the early initialization file
1442 will specifically mention that it is the early initialization file
1445 As the system wide and home directory initialization files are
1446 processed before most command line options, changes to settings
1447 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1448 command line options and operands.
1450 The following sections describe where @value{GDBN} looks for the early
1451 initialization and initialization files, and the order that the files
1454 @subsubsection Home directory early initialization files
1456 @value{GDBN} initially looks for an early initialization file in the
1457 users home directory@footnote{On DOS/Windows systems, the home
1458 directory is the one pointed to by the @env{HOME} environment
1459 variable.}. There are a number of locations that @value{GDBN} will
1460 search in the home directory, these locations are searched in order
1461 and @value{GDBN} will load the first file that it finds, and
1462 subsequent locations will not be checked.
1464 On non-macOS hosts the locations searched are:
1467 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1470 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1471 by the environment variable @env{HOME}, if it is defined.
1473 The file @file{.gdbearlyinit} within the directory pointed to by the
1474 environment variable @env{HOME}, if it is defined.
1477 By contrast, on macOS hosts the locations searched are:
1480 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1481 directory pointed to by the environment variable @env{HOME}, if it is
1484 The file @file{.gdbearlyinit} within the directory pointed to by the
1485 environment variable @env{HOME}, if it is defined.
1488 It is possible to prevent the home directory early initialization file
1489 from being loaded using the @samp{-nx} or @samp{-nh} command line
1490 options, @pxref{Mode Options,,Choosing Modes}.
1492 @anchor{System Wide Init Files}
1493 @subsubsection System wide initialization files
1495 There are two locations that are searched for system wide
1496 initialization files. Both of these locations are always checked:
1500 @item @file{system.gdbinit}
1501 This is a single system-wide initialization file. Its location is
1502 specified with the @code{--with-system-gdbinit} configure option
1503 (@pxref{System-wide configuration}). It is loaded first when
1504 @value{GDBN} starts, before command line options have been processed.
1506 @item @file{system.gdbinit.d}
1507 This is the system-wide initialization directory. Its location is
1508 specified with the @code{--with-system-gdbinit-dir} configure option
1509 (@pxref{System-wide configuration}). Files in this directory are
1510 loaded in alphabetical order immediately after @file{system.gdbinit}
1511 (if enabled) when @value{GDBN} starts, before command line options
1512 have been processed. Files need to have a recognized scripting
1513 language extension (@file{.py}/@file{.scm}) or be named with a
1514 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1515 commands. @value{GDBN} will not recurse into any subdirectories of
1520 It is possible to prevent the system wide initialization files from
1521 being loaded using the @samp{-nx} command line option, @pxref{Mode
1522 Options,,Choosing Modes}.
1524 @anchor{Home Directory Init File}
1525 @subsubsection Home directory initialization file
1526 @cindex @file{gdbinit}
1527 @cindex @file{.gdbinit}
1528 @cindex @file{gdb.ini}
1530 After loading the system wide initialization files @value{GDBN} will
1531 look for an initialization file in the users home
1532 directory@footnote{On DOS/Windows systems, the home directory is the
1533 one pointed to by the @env{HOME} environment variable.}. There are a
1534 number of locations that @value{GDBN} will search in the home
1535 directory, these locations are searched in order and @value{GDBN} will
1536 load the first file that it finds, and subsequent locations will not
1539 On non-Apple hosts the locations searched are:
1541 @item $XDG_CONFIG_HOME/gdb/gdbinit
1542 @item $HOME/.config/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 While on Apple hosts the locations searched are:
1548 @item $HOME/Library/Preferences/gdb/gdbinit
1549 @item $HOME/.gdbinit
1552 It is possible to prevent the home directory initialization file from
1553 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1554 @pxref{Mode Options,,Choosing Modes}.
1556 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1557 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1558 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1559 uses the standard name, but if it finds a @file{gdb.ini} file in your
1560 home directory, it warns you about that and suggests to rename the
1561 file to the standard name.
1563 @anchor{Init File in the Current Directory during Startup}
1564 @subsubsection Local directory initialization file
1566 @value{GDBN} will check the current directory for a file called
1567 @file{.gdbinit}. It is loaded last, after command line options
1568 other than @samp{-x} and @samp{-ex} have been processed. The command
1569 line options @samp{-x} and @samp{-ex} are processed last, after
1570 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1573 If the file in the current directory was already loaded as the home
1574 directory initialization file then it will not be loaded a second
1577 It is possible to prevent the local directory initialization file from
1578 being loaded using the @samp{-nx} command line option, @pxref{Mode
1579 Options,,Choosing Modes}.
1582 @section Quitting @value{GDBN}
1583 @cindex exiting @value{GDBN}
1584 @cindex leaving @value{GDBN}
1587 @kindex quit @r{[}@var{expression}@r{]}
1588 @kindex exit @r{[}@var{expression}@r{]}
1589 @kindex q @r{(@code{quit})}
1590 @item quit @r{[}@var{expression}@r{]}
1591 @itemx exit @r{[}@var{expression}@r{]}
1593 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1594 @code{q}), the @code{exit} command, or type an end-of-file
1595 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1596 @value{GDBN} will terminate normally; otherwise it will terminate using
1597 the result of @var{expression} as the error code.
1601 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1602 terminates the action of any @value{GDBN} command that is in progress and
1603 returns to @value{GDBN} command level. It is safe to type the interrupt
1604 character at any time because @value{GDBN} does not allow it to take effect
1605 until a time when it is safe.
1607 If you have been using @value{GDBN} to control an attached process or
1608 device, you can release it with the @code{detach} command
1609 (@pxref{Attach, ,Debugging an Already-running Process}).
1611 @node Shell Commands
1612 @section Shell Commands
1614 If you need to execute occasional shell commands during your
1615 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1616 just use the @code{shell} command.
1621 @cindex shell escape
1622 @item shell @var{command-string}
1623 @itemx !@var{command-string}
1624 Invoke a standard shell to execute @var{command-string}.
1625 Note that no space is needed between @code{!} and @var{command-string}.
1626 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1627 exists, determines which shell to run. Otherwise @value{GDBN} uses
1628 the default shell (@file{/bin/sh} on GNU and Unix systems,
1629 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1632 The utility @code{make} is often needed in development environments.
1633 You do not have to use the @code{shell} command for this purpose in
1638 @cindex calling make
1639 @item make @var{make-args}
1640 Execute the @code{make} program with the specified
1641 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1647 @cindex send the output of a gdb command to a shell command
1649 @item pipe [@var{command}] | @var{shell_command}
1650 @itemx | [@var{command}] | @var{shell_command}
1651 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1652 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1653 Executes @var{command} and sends its output to @var{shell_command}.
1654 Note that no space is needed around @code{|}.
1655 If no @var{command} is provided, the last command executed is repeated.
1657 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1658 can be used to specify an alternate delimiter string @var{delim} that separates
1659 the @var{command} from the @var{shell_command}.
1692 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1693 this contains a PIPE char
1694 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1695 this contains a PIPE char!
1701 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1702 can be used to examine the exit status of the last shell command launched
1703 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1704 @xref{Convenience Vars,, Convenience Variables}.
1706 @node Logging Output
1707 @section Logging Output
1708 @cindex logging @value{GDBN} output
1709 @cindex save @value{GDBN} output to a file
1711 You may want to save the output of @value{GDBN} commands to a file.
1712 There are several commands to control @value{GDBN}'s logging.
1715 @kindex set logging enabled
1716 @item set logging enabled [on|off]
1717 Enable or disable logging.
1718 @cindex logging file name
1719 @item set logging file @var{file}
1720 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1721 @item set logging overwrite [on|off]
1722 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1723 you want @code{set logging enabled on} to overwrite the logfile instead.
1724 @item set logging redirect [on|off]
1725 By default, @value{GDBN} output will go to both the terminal and the logfile.
1726 Set @code{redirect} if you want output to go only to the log file.
1727 @item set logging debugredirect [on|off]
1728 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1729 Set @code{debugredirect} if you want debug output to go only to the log file.
1730 @kindex show logging
1732 Show the current values of the logging settings.
1735 You can also redirect the output of a @value{GDBN} command to a
1736 shell command. @xref{pipe}.
1738 @chapter @value{GDBN} Commands
1740 You can abbreviate a @value{GDBN} command to the first few letters of the command
1741 name, if that abbreviation is unambiguous; and you can repeat certain
1742 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1743 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1744 show you the alternatives available, if there is more than one possibility).
1747 * Command Syntax:: How to give commands to @value{GDBN}
1748 * Command Settings:: How to change default behavior of commands
1749 * Completion:: Command completion
1750 * Command Options:: Command options
1751 * Help:: How to ask @value{GDBN} for help
1754 @node Command Syntax
1755 @section Command Syntax
1757 A @value{GDBN} command is a single line of input. There is no limit on
1758 how long it can be. It starts with a command name, which is followed by
1759 arguments whose meaning depends on the command name. For example, the
1760 command @code{step} accepts an argument which is the number of times to
1761 step, as in @samp{step 5}. You can also use the @code{step} command
1762 with no arguments. Some commands do not allow any arguments.
1764 @cindex abbreviation
1765 @value{GDBN} command names may always be truncated if that abbreviation is
1766 unambiguous. Other possible command abbreviations are listed in the
1767 documentation for individual commands. In some cases, even ambiguous
1768 abbreviations are allowed; for example, @code{s} is specially defined as
1769 equivalent to @code{step} even though there are other commands whose
1770 names start with @code{s}. You can test abbreviations by using them as
1771 arguments to the @code{help} command.
1773 @cindex repeating commands
1774 @kindex RET @r{(repeat last command)}
1775 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1776 repeat the previous command. Certain commands (for example, @code{run})
1777 will not repeat this way; these are commands whose unintentional
1778 repetition might cause trouble and which you are unlikely to want to
1779 repeat. User-defined commands can disable this feature; see
1780 @ref{Define, dont-repeat}.
1782 The @code{list} and @code{x} commands, when you repeat them with
1783 @key{RET}, construct new arguments rather than repeating
1784 exactly as typed. This permits easy scanning of source or memory.
1786 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1787 output, in a way similar to the common utility @code{more}
1788 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1789 @key{RET} too many in this situation, @value{GDBN} disables command
1790 repetition after any command that generates this sort of display.
1792 @kindex # @r{(a comment)}
1794 Any text from a @kbd{#} to the end of the line is a comment; it does
1795 nothing. This is useful mainly in command files (@pxref{Command
1796 Files,,Command Files}).
1798 @cindex repeating command sequences
1799 @kindex Ctrl-o @r{(operate-and-get-next)}
1800 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1801 commands. This command accepts the current line, like @key{RET}, and
1802 then fetches the next line relative to the current line from the history
1806 @node Command Settings
1807 @section Command Settings
1808 @cindex default behavior of commands, changing
1809 @cindex default settings, changing
1811 Many commands change their behavior according to command-specific
1812 variables or settings. These settings can be changed with the
1813 @code{set} subcommands. For example, the @code{print} command
1814 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1815 settings changeable with the commands @code{set print elements
1816 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1818 You can change these settings to your preference in the gdbinit files
1819 loaded at @value{GDBN} startup. @xref{Startup}.
1821 The settings can also be changed interactively during the debugging
1822 session. For example, to change the limit of array elements to print,
1823 you can do the following:
1825 (@value{GDBN}) set print elements 10
1826 (@value{GDBN}) print some_array
1827 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1830 The above @code{set print elements 10} command changes the number of
1831 elements to print from the default of 200 to 10. If you only intend
1832 this limit of 10 to be used for printing @code{some_array}, then you
1833 must restore the limit back to 200, with @code{set print elements
1836 Some commands allow overriding settings with command options. For
1837 example, the @code{print} command supports a number of options that
1838 allow overriding relevant global print settings as set by @code{set
1839 print} subcommands. @xref{print options}. The example above could be
1842 (@value{GDBN}) print -elements 10 -- some_array
1843 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1846 Alternatively, you can use the @code{with} command to change a setting
1847 temporarily, for the duration of a command invocation.
1850 @kindex with command
1851 @kindex w @r{(@code{with})}
1853 @cindex temporarily change settings
1854 @item with @var{setting} [@var{value}] [-- @var{command}]
1855 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1856 Temporarily set @var{setting} to @var{value} for the duration of
1859 @var{setting} is any setting you can change with the @code{set}
1860 subcommands. @var{value} is the value to assign to @code{setting}
1861 while running @code{command}.
1863 If no @var{command} is provided, the last command executed is
1866 If a @var{command} is provided, it must be preceded by a double dash
1867 (@code{--}) separator. This is required because some settings accept
1868 free-form arguments, such as expressions or filenames.
1870 For example, the command
1872 (@value{GDBN}) with print array on -- print some_array
1875 is equivalent to the following 3 commands:
1877 (@value{GDBN}) set print array on
1878 (@value{GDBN}) print some_array
1879 (@value{GDBN}) set print array off
1882 The @code{with} command is particularly useful when you want to
1883 override a setting while running user-defined commands, or commands
1884 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1887 (@value{GDBN}) with print pretty on -- my_complex_command
1890 To change several settings for the same command, you can nest
1891 @code{with} commands. For example, @code{with language ada -- with
1892 print elements 10} temporarily changes the language to Ada and sets a
1893 limit of 10 elements to print for arrays and strings.
1898 @section Command Completion
1901 @cindex word completion
1902 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1903 only one possibility; it can also show you what the valid possibilities
1904 are for the next word in a command, at any time. This works for @value{GDBN}
1905 commands, @value{GDBN} subcommands, command options, and the names of symbols
1908 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1909 of a word. If there is only one possibility, @value{GDBN} fills in the
1910 word, and waits for you to finish the command (or press @key{RET} to
1911 enter it). For example, if you type
1913 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1914 @c complete accuracy in these examples; space introduced for clarity.
1915 @c If texinfo enhancements make it unnecessary, it would be nice to
1916 @c replace " @key" by "@key" in the following...
1918 (@value{GDBP}) info bre@key{TAB}
1922 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1923 the only @code{info} subcommand beginning with @samp{bre}:
1926 (@value{GDBP}) info breakpoints
1930 You can either press @key{RET} at this point, to run the @code{info
1931 breakpoints} command, or backspace and enter something else, if
1932 @samp{breakpoints} does not look like the command you expected. (If you
1933 were sure you wanted @code{info breakpoints} in the first place, you
1934 might as well just type @key{RET} immediately after @samp{info bre},
1935 to exploit command abbreviations rather than command completion).
1937 If there is more than one possibility for the next word when you press
1938 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1939 characters and try again, or just press @key{TAB} a second time;
1940 @value{GDBN} displays all the possible completions for that word. For
1941 example, you might want to set a breakpoint on a subroutine whose name
1942 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1943 just sounds the bell. Typing @key{TAB} again displays all the
1944 function names in your program that begin with those characters, for
1948 (@value{GDBP}) b make_@key{TAB}
1949 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1950 make_a_section_from_file make_environ
1951 make_abs_section make_function_type
1952 make_blockvector make_pointer_type
1953 make_cleanup make_reference_type
1954 make_command make_symbol_completion_list
1955 (@value{GDBP}) b make_
1959 After displaying the available possibilities, @value{GDBN} copies your
1960 partial input (@samp{b make_} in the example) so you can finish the
1963 If the command you are trying to complete expects either a keyword or a
1964 number to follow, then @samp{NUMBER} will be shown among the available
1965 completions, for example:
1968 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1970 (@value{GDBP}) print -elements@tie{}
1974 Here, the option expects a number (e.g., @code{100}), not literal
1975 @code{NUMBER}. Such metasyntactical arguments are always presented in
1978 If you just want to see the list of alternatives in the first place, you
1979 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1980 means @kbd{@key{META} ?}. You can type this either by holding down a
1981 key designated as the @key{META} shift on your keyboard (if there is
1982 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1984 If the number of possible completions is large, @value{GDBN} will
1985 print as much of the list as it has collected, as well as a message
1986 indicating that the list may be truncated.
1989 (@value{GDBP}) b m@key{TAB}@key{TAB}
1991 <... the rest of the possible completions ...>
1992 *** List may be truncated, max-completions reached. ***
1997 This behavior can be controlled with the following commands:
2000 @kindex set max-completions
2001 @item set max-completions @var{limit}
2002 @itemx set max-completions unlimited
2003 Set the maximum number of completion candidates. @value{GDBN} will
2004 stop looking for more completions once it collects this many candidates.
2005 This is useful when completing on things like function names as collecting
2006 all the possible candidates can be time consuming.
2007 The default value is 200. A value of zero disables tab-completion.
2008 Note that setting either no limit or a very large limit can make
2010 @kindex show max-completions
2011 @item show max-completions
2012 Show the maximum number of candidates that @value{GDBN} will collect and show
2016 @cindex quotes in commands
2017 @cindex completion of quoted strings
2018 Sometimes the string you need, while logically a ``word'', may contain
2019 parentheses or other characters that @value{GDBN} normally excludes from
2020 its notion of a word. To permit word completion to work in this
2021 situation, you may enclose words in @code{'} (single quote marks) in
2022 @value{GDBN} commands.
2024 A likely situation where you might need this is in typing an
2025 expression that involves a C@t{++} symbol name with template
2026 parameters. This is because when completing expressions, GDB treats
2027 the @samp{<} character as word delimiter, assuming that it's the
2028 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2031 For example, when you want to call a C@t{++} template function
2032 interactively using the @code{print} or @code{call} commands, you may
2033 need to distinguish whether you mean the version of @code{name} that
2034 was specialized for @code{int}, @code{name<int>()}, or the version
2035 that was specialized for @code{float}, @code{name<float>()}. To use
2036 the word-completion facilities in this situation, type a single quote
2037 @code{'} at the beginning of the function name. This alerts
2038 @value{GDBN} that it may need to consider more information than usual
2039 when you press @key{TAB} or @kbd{M-?} to request word completion:
2042 (@value{GDBP}) p 'func<@kbd{M-?}
2043 func<int>() func<float>()
2044 (@value{GDBP}) p 'func<
2047 When setting breakpoints however (@pxref{Location Specifications}), you don't
2048 usually need to type a quote before the function name, because
2049 @value{GDBN} understands that you want to set a breakpoint on a
2053 (@value{GDBP}) b func<@kbd{M-?}
2054 func<int>() func<float>()
2055 (@value{GDBP}) b func<
2058 This is true even in the case of typing the name of C@t{++} overloaded
2059 functions (multiple definitions of the same function, distinguished by
2060 argument type). For example, when you want to set a breakpoint you
2061 don't need to distinguish whether you mean the version of @code{name}
2062 that takes an @code{int} parameter, @code{name(int)}, or the version
2063 that takes a @code{float} parameter, @code{name(float)}.
2066 (@value{GDBP}) b bubble(@kbd{M-?}
2067 bubble(int) bubble(double)
2068 (@value{GDBP}) b bubble(dou@kbd{M-?}
2072 See @ref{quoting names} for a description of other scenarios that
2075 For more information about overloaded functions, see @ref{C Plus Plus
2076 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2077 overload-resolution off} to disable overload resolution;
2078 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2080 @cindex completion of structure field names
2081 @cindex structure field name completion
2082 @cindex completion of union field names
2083 @cindex union field name completion
2084 When completing in an expression which looks up a field in a
2085 structure, @value{GDBN} also tries@footnote{The completer can be
2086 confused by certain kinds of invalid expressions. Also, it only
2087 examines the static type of the expression, not the dynamic type.} to
2088 limit completions to the field names available in the type of the
2092 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2093 magic to_fputs to_rewind
2094 to_data to_isatty to_write
2095 to_delete to_put to_write_async_safe
2100 This is because the @code{gdb_stdout} is a variable of the type
2101 @code{struct ui_file} that is defined in @value{GDBN} sources as
2108 ui_file_flush_ftype *to_flush;
2109 ui_file_write_ftype *to_write;
2110 ui_file_write_async_safe_ftype *to_write_async_safe;
2111 ui_file_fputs_ftype *to_fputs;
2112 ui_file_read_ftype *to_read;
2113 ui_file_delete_ftype *to_delete;
2114 ui_file_isatty_ftype *to_isatty;
2115 ui_file_rewind_ftype *to_rewind;
2116 ui_file_put_ftype *to_put;
2121 @node Command Options
2122 @section Command options
2124 @cindex command options
2125 Some commands accept options starting with a leading dash. For
2126 example, @code{print -pretty}. Similarly to command names, you can
2127 abbreviate a @value{GDBN} option to the first few letters of the
2128 option name, if that abbreviation is unambiguous, and you can also use
2129 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2130 in an option (or to show you the alternatives available, if there is
2131 more than one possibility).
2133 @cindex command options, raw input
2134 Some commands take raw input as argument. For example, the print
2135 command processes arbitrary expressions in any of the languages
2136 supported by @value{GDBN}. With such commands, because raw input may
2137 start with a leading dash that would be confused with an option or any
2138 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2139 -pretty} or printing negative @code{p}?), if you specify any command
2140 option, then you must use a double-dash (@code{--}) delimiter to
2141 indicate the end of options.
2143 @cindex command options, boolean
2145 Some options are described as accepting an argument which can be
2146 either @code{on} or @code{off}. These are known as @dfn{boolean
2147 options}. Similarly to boolean settings commands---@code{on} and
2148 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2149 @code{enable} can also be used as ``true'' value, and any of @code{0},
2150 @code{no} and @code{disable} can also be used as ``false'' value. You
2151 can also omit a ``true'' value, as it is implied by default.
2153 For example, these are equivalent:
2156 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2157 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2160 You can discover the set of options some command accepts by completing
2161 on @code{-} after the command name. For example:
2164 (@value{GDBP}) print -@key{TAB}@key{TAB}
2165 -address -max-depth -object -static-members
2166 -array -memory-tag-violations -pretty -symbol
2167 -array-indexes -nibbles -raw-values -union
2168 -elements -null-stop -repeats -vtbl
2171 Completion will in some cases guide you with a suggestion of what kind
2172 of argument an option expects. For example:
2175 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2180 Here, the option expects a number (e.g., @code{100}), not literal
2181 @code{NUMBER}. Such metasyntactical arguments are always presented in
2184 (For more on using the @code{print} command, see @ref{Data, ,Examining
2188 @section Getting Help
2189 @cindex online documentation
2192 You can always ask @value{GDBN} itself for information on its commands,
2193 using the command @code{help}.
2196 @kindex h @r{(@code{help})}
2199 You can use @code{help} (abbreviated @code{h}) with no arguments to
2200 display a short list of named classes of commands:
2204 List of classes of commands:
2206 aliases -- User-defined aliases of other commands
2207 breakpoints -- Making program stop at certain points
2208 data -- Examining data
2209 files -- Specifying and examining files
2210 internals -- Maintenance commands
2211 obscure -- Obscure features
2212 running -- Running the program
2213 stack -- Examining the stack
2214 status -- Status inquiries
2215 support -- Support facilities
2216 tracepoints -- Tracing of program execution without
2217 stopping the program
2218 user-defined -- User-defined commands
2220 Type "help" followed by a class name for a list of
2221 commands in that class.
2222 Type "help" followed by command name for full
2224 Command name abbreviations are allowed if unambiguous.
2227 @c the above line break eliminates huge line overfull...
2229 @item help @var{class}
2230 Using one of the general help classes as an argument, you can get a
2231 list of the individual commands in that class. If a command has
2232 aliases, the aliases are given after the command name, separated by
2233 commas. If an alias has default arguments, the full definition of
2234 the alias is given after the first line.
2235 For example, here is the help display for the class @code{status}:
2238 (@value{GDBP}) help status
2243 @c Line break in "show" line falsifies real output, but needed
2244 @c to fit in smallbook page size.
2245 info, inf, i -- Generic command for showing things
2246 about the program being debugged
2247 info address, iamain -- Describe where symbol SYM is stored.
2248 alias iamain = info address main
2249 info all-registers -- List of all registers and their contents,
2250 for selected stack frame.
2252 show, info set -- Generic command for showing things
2255 Type "help" followed by command name for full
2257 Command name abbreviations are allowed if unambiguous.
2261 @item help @var{command}
2262 With a command name as @code{help} argument, @value{GDBN} displays a
2263 short paragraph on how to use that command. If that command has
2264 one or more aliases, @value{GDBN} will display a first line with
2265 the command name and all its aliases separated by commas.
2266 This first line will be followed by the full definition of all aliases
2267 having default arguments.
2268 When asking the help for an alias, the documentation for the aliased
2271 A user-defined alias can optionally be documented using the
2272 @code{document} command (@pxref{Define, document}). @value{GDBN} then
2273 considers this alias as different from the aliased command: this alias
2274 is not listed in the aliased command help output, and asking help for
2275 this alias will show the documentation provided for the alias instead of
2276 the documentation of the aliased command.
2279 @item apropos [-v] @var{regexp}
2280 The @code{apropos} command searches through all of the @value{GDBN}
2281 commands and aliases, and their documentation, for the regular expression specified in
2282 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2283 which stands for @samp{verbose}, indicates to output the full documentation
2284 of the matching commands and highlight the parts of the documentation
2285 matching @var{regexp}. For example:
2296 alias -- Define a new command that is an alias of an existing command
2297 aliases -- User-defined aliases of other commands
2305 apropos -v cut.*thread apply
2309 results in the below output, where @samp{cut for 'thread apply}
2310 is highlighted if styling is enabled.
2314 taas -- Apply a command to all threads (ignoring errors
2317 shortcut for 'thread apply all -s COMMAND'
2319 tfaas -- Apply a command to all frames of all threads
2320 (ignoring errors and empty output).
2321 Usage: tfaas COMMAND
2322 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2327 @item complete @var{args}
2328 The @code{complete @var{args}} command lists all the possible completions
2329 for the beginning of a command. Use @var{args} to specify the beginning of the
2330 command you want completed. For example:
2336 @noindent results in:
2347 @noindent This is intended for use by @sc{gnu} Emacs.
2350 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2351 and @code{show} to inquire about the state of your program, or the state
2352 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2353 manual introduces each of them in the appropriate context. The listings
2354 under @code{info} and under @code{show} in the Command, Variable, and
2355 Function Index point to all the sub-commands. @xref{Command and Variable
2361 @kindex i @r{(@code{info})}
2363 This command (abbreviated @code{i}) is for describing the state of your
2364 program. For example, you can show the arguments passed to a function
2365 with @code{info args}, list the registers currently in use with @code{info
2366 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2367 You can get a complete list of the @code{info} sub-commands with
2368 @w{@code{help info}}.
2372 You can assign the result of an expression to an environment variable with
2373 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2374 @code{set prompt $}.
2378 In contrast to @code{info}, @code{show} is for describing the state of
2379 @value{GDBN} itself.
2380 You can change most of the things you can @code{show}, by using the
2381 related command @code{set}; for example, you can control what number
2382 system is used for displays with @code{set radix}, or simply inquire
2383 which is currently in use with @code{show radix}.
2386 To display all the settable parameters and their current
2387 values, you can use @code{show} with no arguments; you may also use
2388 @code{info set}. Both commands produce the same display.
2389 @c FIXME: "info set" violates the rule that "info" is for state of
2390 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2391 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2395 Here are several miscellaneous @code{show} subcommands, all of which are
2396 exceptional in lacking corresponding @code{set} commands:
2399 @kindex show version
2400 @cindex @value{GDBN} version number
2402 Show what version of @value{GDBN} is running. You should include this
2403 information in @value{GDBN} bug-reports. If multiple versions of
2404 @value{GDBN} are in use at your site, you may need to determine which
2405 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2406 commands are introduced, and old ones may wither away. Also, many
2407 system vendors ship variant versions of @value{GDBN}, and there are
2408 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2409 The version number is the same as the one announced when you start
2412 @kindex show copying
2413 @kindex info copying
2414 @cindex display @value{GDBN} copyright
2417 Display information about permission for copying @value{GDBN}.
2419 @kindex show warranty
2420 @kindex info warranty
2422 @itemx info warranty
2423 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2424 if your version of @value{GDBN} comes with one.
2426 @kindex show configuration
2427 @item show configuration
2428 Display detailed information about the way @value{GDBN} was configured
2429 when it was built. This displays the optional arguments passed to the
2430 @file{configure} script and also configuration parameters detected
2431 automatically by @command{configure}. When reporting a @value{GDBN}
2432 bug (@pxref{GDB Bugs}), it is important to include this information in
2438 @chapter Running Programs Under @value{GDBN}
2440 When you run a program under @value{GDBN}, you must first generate
2441 debugging information when you compile it.
2443 You may start @value{GDBN} with its arguments, if any, in an environment
2444 of your choice. If you are doing native debugging, you may redirect
2445 your program's input and output, debug an already running process, or
2446 kill a child process.
2449 * Compilation:: Compiling for debugging
2450 * Starting:: Starting your program
2451 * Arguments:: Your program's arguments
2452 * Environment:: Your program's environment
2454 * Working Directory:: Your program's working directory
2455 * Input/Output:: Your program's input and output
2456 * Attach:: Debugging an already-running process
2457 * Kill Process:: Killing the child process
2458 * Inferiors Connections and Programs:: Debugging multiple inferiors
2459 connections and programs
2460 * Threads:: Debugging programs with multiple threads
2461 * Forks:: Debugging forks
2462 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2466 @section Compiling for Debugging
2468 In order to debug a program effectively, you need to generate
2469 debugging information when you compile it. This debugging information
2470 is stored in the object file; it describes the data type of each
2471 variable or function and the correspondence between source line numbers
2472 and addresses in the executable code.
2474 To request debugging information, specify the @samp{-g} option when you run
2477 Programs that are to be shipped to your customers are compiled with
2478 optimizations, using the @samp{-O} compiler option. However, some
2479 compilers are unable to handle the @samp{-g} and @samp{-O} options
2480 together. Using those compilers, you cannot generate optimized
2481 executables containing debugging information.
2483 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2484 without @samp{-O}, making it possible to debug optimized code. We
2485 recommend that you @emph{always} use @samp{-g} whenever you compile a
2486 program. You may think your program is correct, but there is no sense
2487 in pushing your luck. For more information, see @ref{Optimized Code}.
2489 Older versions of the @sc{gnu} C compiler permitted a variant option
2490 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2491 format; if your @sc{gnu} C compiler has this option, do not use it.
2493 @value{GDBN} knows about preprocessor macros and can show you their
2494 expansion (@pxref{Macros}). Most compilers do not include information
2495 about preprocessor macros in the debugging information if you specify
2496 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2497 the @sc{gnu} C compiler, provides macro information if you are using
2498 the DWARF debugging format, and specify the option @option{-g3}.
2500 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2501 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2502 information on @value{NGCC} options affecting debug information.
2504 You will have the best debugging experience if you use the latest
2505 version of the DWARF debugging format that your compiler supports.
2506 DWARF is currently the most expressive and best supported debugging
2507 format in @value{GDBN}.
2511 @section Starting your Program
2517 @kindex r @r{(@code{run})}
2520 Use the @code{run} command to start your program under @value{GDBN}.
2521 You must first specify the program name with an argument to
2522 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2523 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2524 command (@pxref{Files, ,Commands to Specify Files}).
2528 If you are running your program in an execution environment that
2529 supports processes, @code{run} creates an inferior process and makes
2530 that process run your program. In some environments without processes,
2531 @code{run} jumps to the start of your program. Other targets,
2532 like @samp{remote}, are always running. If you get an error
2533 message like this one:
2536 The "remote" target does not support "run".
2537 Try "help target" or "continue".
2541 then use @code{continue} to run your program. You may need @code{load}
2542 first (@pxref{load}).
2544 The execution of a program is affected by certain information it
2545 receives from its superior. @value{GDBN} provides ways to specify this
2546 information, which you must do @emph{before} starting your program. (You
2547 can change it after starting your program, but such changes only affect
2548 your program the next time you start it.) This information may be
2549 divided into four categories:
2552 @item The @emph{arguments.}
2553 Specify the arguments to give your program as the arguments of the
2554 @code{run} command. If a shell is available on your target, the shell
2555 is used to pass the arguments, so that you may use normal conventions
2556 (such as wildcard expansion or variable substitution) in describing
2558 In Unix systems, you can control which shell is used with the
2559 @env{SHELL} environment variable. If you do not define @env{SHELL},
2560 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2561 use of any shell with the @code{set startup-with-shell} command (see
2564 @item The @emph{environment.}
2565 Your program normally inherits its environment from @value{GDBN}, but you can
2566 use the @value{GDBN} commands @code{set environment} and @code{unset
2567 environment} to change parts of the environment that affect
2568 your program. @xref{Environment, ,Your Program's Environment}.
2570 @item The @emph{working directory.}
2571 You can set your program's working directory with the command
2572 @kbd{set cwd}. If you do not set any working directory with this
2573 command, your program will inherit @value{GDBN}'s working directory if
2574 native debugging, or the remote server's working directory if remote
2575 debugging. @xref{Working Directory, ,Your Program's Working
2578 @item The @emph{standard input and output.}
2579 Your program normally uses the same device for standard input and
2580 standard output as @value{GDBN} is using. You can redirect input and output
2581 in the @code{run} command line, or you can use the @code{tty} command to
2582 set a different device for your program.
2583 @xref{Input/Output, ,Your Program's Input and Output}.
2586 @emph{Warning:} While input and output redirection work, you cannot use
2587 pipes to pass the output of the program you are debugging to another
2588 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2592 When you issue the @code{run} command, your program begins to execute
2593 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2594 of how to arrange for your program to stop. Once your program has
2595 stopped, you may call functions in your program, using the @code{print}
2596 or @code{call} commands. @xref{Data, ,Examining Data}.
2598 If the modification time of your symbol file has changed since the last
2599 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2600 table, and reads it again. When it does this, @value{GDBN} tries to retain
2601 your current breakpoints.
2606 @cindex run to main procedure
2607 The name of the main procedure can vary from language to language.
2608 With C or C@t{++}, the main procedure name is always @code{main}, but
2609 other languages such as Ada do not require a specific name for their
2610 main procedure. The debugger provides a convenient way to start the
2611 execution of the program and to stop at the beginning of the main
2612 procedure, depending on the language used.
2614 The @samp{start} command does the equivalent of setting a temporary
2615 breakpoint at the beginning of the main procedure and then invoking
2616 the @samp{run} command.
2618 @cindex elaboration phase
2619 Some programs contain an @dfn{elaboration} phase where some startup code is
2620 executed before the main procedure is called. This depends on the
2621 languages used to write your program. In C@t{++}, for instance,
2622 constructors for static and global objects are executed before
2623 @code{main} is called. It is therefore possible that the debugger stops
2624 before reaching the main procedure. However, the temporary breakpoint
2625 will remain to halt execution.
2627 Specify the arguments to give to your program as arguments to the
2628 @samp{start} command. These arguments will be given verbatim to the
2629 underlying @samp{run} command. Note that the same arguments will be
2630 reused if no argument is provided during subsequent calls to
2631 @samp{start} or @samp{run}.
2633 It is sometimes necessary to debug the program during elaboration. In
2634 these cases, using the @code{start} command would stop the execution
2635 of your program too late, as the program would have already completed
2636 the elaboration phase. Under these circumstances, either insert
2637 breakpoints in your elaboration code before running your program or
2638 use the @code{starti} command.
2642 @cindex run to first instruction
2643 The @samp{starti} command does the equivalent of setting a temporary
2644 breakpoint at the first instruction of a program's execution and then
2645 invoking the @samp{run} command. For programs containing an
2646 elaboration phase, the @code{starti} command will stop execution at
2647 the start of the elaboration phase.
2649 @anchor{set exec-wrapper}
2650 @kindex set exec-wrapper
2651 @item set exec-wrapper @var{wrapper}
2652 @itemx show exec-wrapper
2653 @itemx unset exec-wrapper
2654 When @samp{exec-wrapper} is set, the specified wrapper is used to
2655 launch programs for debugging. @value{GDBN} starts your program
2656 with a shell command of the form @kbd{exec @var{wrapper}
2657 @var{program}}. Quoting is added to @var{program} and its
2658 arguments, but not to @var{wrapper}, so you should add quotes if
2659 appropriate for your shell. The wrapper runs until it executes
2660 your program, and then @value{GDBN} takes control.
2662 You can use any program that eventually calls @code{execve} with
2663 its arguments as a wrapper. Several standard Unix utilities do
2664 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2665 with @code{exec "$@@"} will also work.
2667 For example, you can use @code{env} to pass an environment variable to
2668 the debugged program, without setting the variable in your shell's
2672 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2676 This command is available when debugging locally on most targets, excluding
2677 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2679 @kindex set startup-with-shell
2680 @anchor{set startup-with-shell}
2681 @item set startup-with-shell
2682 @itemx set startup-with-shell on
2683 @itemx set startup-with-shell off
2684 @itemx show startup-with-shell
2685 On Unix systems, by default, if a shell is available on your target,
2686 @value{GDBN}) uses it to start your program. Arguments of the
2687 @code{run} command are passed to the shell, which does variable
2688 substitution, expands wildcard characters and performs redirection of
2689 I/O. In some circumstances, it may be useful to disable such use of a
2690 shell, for example, when debugging the shell itself or diagnosing
2691 startup failures such as:
2695 Starting program: ./a.out
2696 During startup program terminated with signal SIGSEGV, Segmentation fault.
2700 which indicates the shell or the wrapper specified with
2701 @samp{exec-wrapper} crashed, not your program. Most often, this is
2702 caused by something odd in your shell's non-interactive mode
2703 initialization file---such as @file{.cshrc} for C-shell,
2704 $@file{.zshenv} for the Z shell, or the file specified in the
2705 @env{BASH_ENV} environment variable for BASH.
2707 @anchor{set auto-connect-native-target}
2708 @kindex set auto-connect-native-target
2709 @item set auto-connect-native-target
2710 @itemx set auto-connect-native-target on
2711 @itemx set auto-connect-native-target off
2712 @itemx show auto-connect-native-target
2714 By default, if the current inferior is not connected to any target yet
2715 (e.g., with @code{target remote}), the @code{run} command starts your
2716 program as a native process under @value{GDBN}, on your local machine.
2717 If you're sure you don't want to debug programs on your local machine,
2718 you can tell @value{GDBN} to not connect to the native target
2719 automatically with the @code{set auto-connect-native-target off}
2722 If @code{on}, which is the default, and if the current inferior is not
2723 connected to a target already, the @code{run} command automaticaly
2724 connects to the native target, if one is available.
2726 If @code{off}, and if the current inferior is not connected to a
2727 target already, the @code{run} command fails with an error:
2731 Don't know how to run. Try "help target".
2734 If the current inferior is already connected to a target, @value{GDBN}
2735 always uses it with the @code{run} command.
2737 In any case, you can explicitly connect to the native target with the
2738 @code{target native} command. For example,
2741 (@value{GDBP}) set auto-connect-native-target off
2743 Don't know how to run. Try "help target".
2744 (@value{GDBP}) target native
2746 Starting program: ./a.out
2747 [Inferior 1 (process 10421) exited normally]
2750 In case you connected explicitly to the @code{native} target,
2751 @value{GDBN} remains connected even if all inferiors exit, ready for
2752 the next @code{run} command. Use the @code{disconnect} command to
2755 Examples of other commands that likewise respect the
2756 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2757 proc}, @code{info os}.
2759 @kindex set disable-randomization
2760 @item set disable-randomization
2761 @itemx set disable-randomization on
2762 This option (enabled by default in @value{GDBN}) will turn off the native
2763 randomization of the virtual address space of the started program. This option
2764 is useful for multiple debugging sessions to make the execution better
2765 reproducible and memory addresses reusable across debugging sessions.
2767 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2768 On @sc{gnu}/Linux you can get the same behavior using
2771 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2774 @item set disable-randomization off
2775 Leave the behavior of the started executable unchanged. Some bugs rear their
2776 ugly heads only when the program is loaded at certain addresses. If your bug
2777 disappears when you run the program under @value{GDBN}, that might be because
2778 @value{GDBN} by default disables the address randomization on platforms, such
2779 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2780 disable-randomization off} to try to reproduce such elusive bugs.
2782 On targets where it is available, virtual address space randomization
2783 protects the programs against certain kinds of security attacks. In these
2784 cases the attacker needs to know the exact location of a concrete executable
2785 code. Randomizing its location makes it impossible to inject jumps misusing
2786 a code at its expected addresses.
2788 Prelinking shared libraries provides a startup performance advantage but it
2789 makes addresses in these libraries predictable for privileged processes by
2790 having just unprivileged access at the target system. Reading the shared
2791 library binary gives enough information for assembling the malicious code
2792 misusing it. Still even a prelinked shared library can get loaded at a new
2793 random address just requiring the regular relocation process during the
2794 startup. Shared libraries not already prelinked are always loaded at
2795 a randomly chosen address.
2797 Position independent executables (PIE) contain position independent code
2798 similar to the shared libraries and therefore such executables get loaded at
2799 a randomly chosen address upon startup. PIE executables always load even
2800 already prelinked shared libraries at a random address. You can build such
2801 executable using @command{gcc -fPIE -pie}.
2803 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2804 (as long as the randomization is enabled).
2806 @item show disable-randomization
2807 Show the current setting of the explicit disable of the native randomization of
2808 the virtual address space of the started program.
2813 @section Your Program's Arguments
2815 @cindex arguments (to your program)
2816 The arguments to your program can be specified by the arguments of the
2818 They are passed to a shell, which expands wildcard characters and
2819 performs redirection of I/O, and thence to your program. Your
2820 @env{SHELL} environment variable (if it exists) specifies what shell
2821 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2822 the default shell (@file{/bin/sh} on Unix).
2824 On non-Unix systems, the program is usually invoked directly by
2825 @value{GDBN}, which emulates I/O redirection via the appropriate system
2826 calls, and the wildcard characters are expanded by the startup code of
2827 the program, not by the shell.
2829 @code{run} with no arguments uses the same arguments used by the previous
2830 @code{run}, or those set by the @code{set args} command.
2835 Specify the arguments to be used the next time your program is run. If
2836 @code{set args} has no arguments, @code{run} executes your program
2837 with no arguments. Once you have run your program with arguments,
2838 using @code{set args} before the next @code{run} is the only way to run
2839 it again without arguments.
2843 Show the arguments to give your program when it is started.
2847 @section Your Program's Environment
2849 @cindex environment (of your program)
2850 The @dfn{environment} consists of a set of environment variables and
2851 their values. Environment variables conventionally record such things as
2852 your user name, your home directory, your terminal type, and your search
2853 path for programs to run. Usually you set up environment variables with
2854 the shell and they are inherited by all the other programs you run. When
2855 debugging, it can be useful to try running your program with a modified
2856 environment without having to start @value{GDBN} over again.
2860 @item path @var{directory}
2861 Add @var{directory} to the front of the @env{PATH} environment variable
2862 (the search path for executables) that will be passed to your program.
2863 The value of @env{PATH} used by @value{GDBN} does not change.
2864 You may specify several directory names, separated by whitespace or by a
2865 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2866 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2867 is moved to the front, so it is searched sooner.
2869 You can use the string @samp{$cwd} to refer to whatever is the current
2870 working directory at the time @value{GDBN} searches the path. If you
2871 use @samp{.} instead, it refers to the directory where you executed the
2872 @code{path} command. @value{GDBN} replaces @samp{.} in the
2873 @var{directory} argument (with the current path) before adding
2874 @var{directory} to the search path.
2875 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2876 @c document that, since repeating it would be a no-op.
2880 Display the list of search paths for executables (the @env{PATH}
2881 environment variable).
2883 @kindex show environment
2884 @item show environment @r{[}@var{varname}@r{]}
2885 Print the value of environment variable @var{varname} to be given to
2886 your program when it starts. If you do not supply @var{varname},
2887 print the names and values of all environment variables to be given to
2888 your program. You can abbreviate @code{environment} as @code{env}.
2890 @kindex set environment
2891 @anchor{set environment}
2892 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2893 Set environment variable @var{varname} to @var{value}. The value
2894 changes for your program (and the shell @value{GDBN} uses to launch
2895 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2896 values of environment variables are just strings, and any
2897 interpretation is supplied by your program itself. The @var{value}
2898 parameter is optional; if it is eliminated, the variable is set to a
2900 @c "any string" here does not include leading, trailing
2901 @c blanks. Gnu asks: does anyone care?
2903 For example, this command:
2910 tells the debugged program, when subsequently run, that its user is named
2911 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2912 are not actually required.)
2914 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2915 which also inherits the environment set with @code{set environment}.
2916 If necessary, you can avoid that by using the @samp{env} program as a
2917 wrapper instead of using @code{set environment}. @xref{set
2918 exec-wrapper}, for an example doing just that.
2920 Environment variables that are set by the user are also transmitted to
2921 @command{gdbserver} to be used when starting the remote inferior.
2922 @pxref{QEnvironmentHexEncoded}.
2924 @kindex unset environment
2925 @anchor{unset environment}
2926 @item unset environment @var{varname}
2927 Remove variable @var{varname} from the environment to be passed to your
2928 program. This is different from @samp{set env @var{varname} =};
2929 @code{unset environment} removes the variable from the environment,
2930 rather than assigning it an empty value.
2932 Environment variables that are unset by the user are also unset on
2933 @command{gdbserver} when starting the remote inferior.
2934 @pxref{QEnvironmentUnset}.
2937 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2938 the shell indicated by your @env{SHELL} environment variable if it
2939 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2940 names a shell that runs an initialization file when started
2941 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2942 for the Z shell, or the file specified in the @env{BASH_ENV}
2943 environment variable for BASH---any variables you set in that file
2944 affect your program. You may wish to move setting of environment
2945 variables to files that are only run when you sign on, such as
2946 @file{.login} or @file{.profile}.
2948 @node Working Directory
2949 @section Your Program's Working Directory
2951 @cindex working directory (of your program)
2952 Each time you start your program with @code{run}, the inferior will be
2953 initialized with the current working directory specified by the
2954 @kbd{set cwd} command. If no directory has been specified by this
2955 command, then the inferior will inherit @value{GDBN}'s current working
2956 directory as its working directory if native debugging, or it will
2957 inherit the remote server's current working directory if remote
2962 @cindex change inferior's working directory
2963 @anchor{set cwd command}
2964 @item set cwd @r{[}@var{directory}@r{]}
2965 Set the inferior's working directory to @var{directory}, which will be
2966 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2967 argument has been specified, the command clears the setting and resets
2968 it to an empty state. This setting has no effect on @value{GDBN}'s
2969 working directory, and it only takes effect the next time you start
2970 the inferior. The @file{~} in @var{directory} is a short for the
2971 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2972 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2973 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2976 You can also change @value{GDBN}'s current working directory by using
2977 the @code{cd} command.
2981 @cindex show inferior's working directory
2983 Show the inferior's working directory. If no directory has been
2984 specified by @kbd{set cwd}, then the default inferior's working
2985 directory is the same as @value{GDBN}'s working directory.
2988 @cindex change @value{GDBN}'s working directory
2990 @item cd @r{[}@var{directory}@r{]}
2991 Set the @value{GDBN} working directory to @var{directory}. If not
2992 given, @var{directory} uses @file{'~'}.
2994 The @value{GDBN} working directory serves as a default for the
2995 commands that specify files for @value{GDBN} to operate on.
2996 @xref{Files, ,Commands to Specify Files}.
2997 @xref{set cwd command}.
3001 Print the @value{GDBN} working directory.
3004 It is generally impossible to find the current working directory of
3005 the process being debugged (since a program can change its directory
3006 during its run). If you work on a system where @value{GDBN} supports
3007 the @code{info proc} command (@pxref{Process Information}), you can
3008 use the @code{info proc} command to find out the
3009 current working directory of the debuggee.
3012 @section Your Program's Input and Output
3017 By default, the program you run under @value{GDBN} does input and output to
3018 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3019 to its own terminal modes to interact with you, but it records the terminal
3020 modes your program was using and switches back to them when you continue
3021 running your program.
3024 @kindex info terminal
3026 Displays information recorded by @value{GDBN} about the terminal modes your
3030 You can redirect your program's input and/or output using shell
3031 redirection with the @code{run} command. For example,
3038 starts your program, diverting its output to the file @file{outfile}.
3041 @cindex controlling terminal
3042 Another way to specify where your program should do input and output is
3043 with the @code{tty} command. This command accepts a file name as
3044 argument, and causes this file to be the default for future @code{run}
3045 commands. It also resets the controlling terminal for the child
3046 process, for future @code{run} commands. For example,
3053 directs that processes started with subsequent @code{run} commands
3054 default to do input and output on the terminal @file{/dev/ttyb} and have
3055 that as their controlling terminal.
3057 An explicit redirection in @code{run} overrides the @code{tty} command's
3058 effect on the input/output device, but not its effect on the controlling
3061 When you use the @code{tty} command or redirect input in the @code{run}
3062 command, only the input @emph{for your program} is affected. The input
3063 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3064 for @code{set inferior-tty}.
3066 @cindex inferior tty
3067 @cindex set inferior controlling terminal
3068 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3069 display the name of the terminal that will be used for future runs of your
3073 @item set inferior-tty [ @var{tty} ]
3074 @kindex set inferior-tty
3075 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3076 restores the default behavior, which is to use the same terminal as
3079 @item show inferior-tty
3080 @kindex show inferior-tty
3081 Show the current tty for the program being debugged.
3085 @section Debugging an Already-running Process
3090 @item attach @var{process-id}
3091 This command attaches to a running process---one that was started
3092 outside @value{GDBN}. (@code{info files} shows your active
3093 targets.) The command takes as argument a process ID. The usual way to
3094 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3095 or with the @samp{jobs -l} shell command.
3097 @code{attach} does not repeat if you press @key{RET} a second time after
3098 executing the command.
3101 To use @code{attach}, your program must be running in an environment
3102 which supports processes; for example, @code{attach} does not work for
3103 programs on bare-board targets that lack an operating system. You must
3104 also have permission to send the process a signal.
3106 When you use @code{attach}, the debugger finds the program running in
3107 the process first by looking in the current working directory, then (if
3108 the program is not found) by using the source file search path
3109 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3110 the @code{file} command to load the program. @xref{Files, ,Commands to
3113 @anchor{set exec-file-mismatch}
3114 If the debugger can determine that the executable file running in the
3115 process it is attaching to does not match the current exec-file loaded
3116 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3117 handle the mismatch. @value{GDBN} tries to compare the files by
3118 comparing their build IDs (@pxref{build ID}), if available.
3121 @kindex exec-file-mismatch
3122 @cindex set exec-file-mismatch
3123 @item set exec-file-mismatch @samp{ask|warn|off}
3125 Whether to detect mismatch between the current executable file loaded
3126 by @value{GDBN} and the executable file used to start the process. If
3127 @samp{ask}, the default, display a warning and ask the user whether to
3128 load the process executable file; if @samp{warn}, just display a
3129 warning; if @samp{off}, don't attempt to detect a mismatch.
3130 If the user confirms loading the process executable file, then its symbols
3131 will be loaded as well.
3133 @cindex show exec-file-mismatch
3134 @item show exec-file-mismatch
3135 Show the current value of @code{exec-file-mismatch}.
3139 The first thing @value{GDBN} does after arranging to debug the specified
3140 process is to stop it. You can examine and modify an attached process
3141 with all the @value{GDBN} commands that are ordinarily available when
3142 you start processes with @code{run}. You can insert breakpoints; you
3143 can step and continue; you can modify storage. If you would rather the
3144 process continue running, you may use the @code{continue} command after
3145 attaching @value{GDBN} to the process.
3150 When you have finished debugging the attached process, you can use the
3151 @code{detach} command to release it from @value{GDBN} control. Detaching
3152 the process continues its execution. After the @code{detach} command,
3153 that process and @value{GDBN} become completely independent once more, and you
3154 are ready to @code{attach} another process or start one with @code{run}.
3155 @code{detach} does not repeat if you press @key{RET} again after
3156 executing the command.
3159 If you exit @value{GDBN} while you have an attached process, you detach
3160 that process. If you use the @code{run} command, you kill that process.
3161 By default, @value{GDBN} asks for confirmation if you try to do either of these
3162 things; you can control whether or not you need to confirm by using the
3163 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3167 @section Killing the Child Process
3172 Kill the child process in which your program is running under @value{GDBN}.
3175 This command is useful if you wish to debug a core dump instead of a
3176 running process. @value{GDBN} ignores any core dump file while your program
3179 On some operating systems, a program cannot be executed outside @value{GDBN}
3180 while you have breakpoints set on it inside @value{GDBN}. You can use the
3181 @code{kill} command in this situation to permit running your program
3182 outside the debugger.
3184 The @code{kill} command is also useful if you wish to recompile and
3185 relink your program, since on many systems it is impossible to modify an
3186 executable file while it is running in a process. In this case, when you
3187 next type @code{run}, @value{GDBN} notices that the file has changed, and
3188 reads the symbol table again (while trying to preserve your current
3189 breakpoint settings).
3191 @node Inferiors Connections and Programs
3192 @section Debugging Multiple Inferiors Connections and Programs
3194 @value{GDBN} lets you run and debug multiple programs in a single
3195 session. In addition, @value{GDBN} on some systems may let you run
3196 several programs simultaneously (otherwise you have to exit from one
3197 before starting another). On some systems @value{GDBN} may even let
3198 you debug several programs simultaneously on different remote systems.
3199 In the most general case, you can have multiple threads of execution
3200 in each of multiple processes, launched from multiple executables,
3201 running on different machines.
3204 @value{GDBN} represents the state of each program execution with an
3205 object called an @dfn{inferior}. An inferior typically corresponds to
3206 a process, but is more general and applies also to targets that do not
3207 have processes. Inferiors may be created before a process runs, and
3208 may be retained after a process exits. Inferiors have unique
3209 identifiers that are different from process ids. Usually each
3210 inferior will also have its own distinct address space, although some
3211 embedded targets may have several inferiors running in different parts
3212 of a single address space. Each inferior may in turn have multiple
3213 threads running in it.
3215 To find out what inferiors exist at any moment, use @w{@code{info
3219 @kindex info inferiors [ @var{id}@dots{} ]
3220 @item info inferiors
3221 Print a list of all inferiors currently being managed by @value{GDBN}.
3222 By default all inferiors are printed, but the argument @var{id}@dots{}
3223 -- a space separated list of inferior numbers -- can be used to limit
3224 the display to just the requested inferiors.
3226 @value{GDBN} displays for each inferior (in this order):
3230 the inferior number assigned by @value{GDBN}
3233 the target system's inferior identifier
3236 the target connection the inferior is bound to, including the unique
3237 connection number assigned by @value{GDBN}, and the protocol used by
3241 the name of the executable the inferior is running.
3246 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3247 indicates the current inferior.
3251 @c end table here to get a little more width for example
3254 (@value{GDBP}) info inferiors
3255 Num Description Connection Executable
3256 * 1 process 3401 1 (native) goodbye
3257 2 process 2307 2 (extended-remote host:10000) hello
3260 To get informations about the current inferior, use @code{inferior}:
3265 Shows information about the current inferior.
3269 @c end table here to get a little more width for example
3272 (@value{GDBP}) inferior
3273 [Current inferior is 1 [process 3401] (helloworld)]
3276 To find out what open target connections exist at any moment, use
3277 @w{@code{info connections}}:
3280 @kindex info connections [ @var{id}@dots{} ]
3281 @item info connections
3282 Print a list of all open target connections currently being managed by
3283 @value{GDBN}. By default all connections are printed, but the
3284 argument @var{id}@dots{} -- a space separated list of connections
3285 numbers -- can be used to limit the display to just the requested
3288 @value{GDBN} displays for each connection (in this order):
3292 the connection number assigned by @value{GDBN}.
3295 the protocol used by the connection.
3298 a textual description of the protocol used by the connection.
3303 An asterisk @samp{*} preceding the connection number indicates the
3304 connection of the current inferior.
3308 @c end table here to get a little more width for example
3311 (@value{GDBP}) info connections
3312 Num What Description
3313 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3314 2 native Native process
3315 3 core Local core dump file
3318 To switch focus between inferiors, use the @code{inferior} command:
3321 @kindex inferior @var{infno}
3322 @item inferior @var{infno}
3323 Make inferior number @var{infno} the current inferior. The argument
3324 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3325 in the first field of the @samp{info inferiors} display.
3328 @vindex $_inferior@r{, convenience variable}
3329 The debugger convenience variable @samp{$_inferior} contains the
3330 number of the current inferior. You may find this useful in writing
3331 breakpoint conditional expressions, command scripts, and so forth.
3332 @xref{Convenience Vars,, Convenience Variables}, for general
3333 information on convenience variables.
3335 You can get multiple executables into a debugging session via the
3336 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3337 systems @value{GDBN} can add inferiors to the debug session
3338 automatically by following calls to @code{fork} and @code{exec}. To
3339 remove inferiors from the debugging session use the
3340 @w{@code{remove-inferiors}} command.
3343 @anchor{add_inferior_cli}
3344 @kindex add-inferior
3345 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3346 Adds @var{n} inferiors to be run using @var{executable} as the
3347 executable; @var{n} defaults to 1. If no executable is specified,
3348 the inferiors begins empty, with no program. You can still assign or
3349 change the program assigned to the inferior at any time by using the
3350 @code{file} command with the executable name as its argument.
3352 By default, the new inferior begins connected to the same target
3353 connection as the current inferior. For example, if the current
3354 inferior was connected to @code{gdbserver} with @code{target remote},
3355 then the new inferior will be connected to the same @code{gdbserver}
3356 instance. The @samp{-no-connection} option starts the new inferior
3357 with no connection yet. You can then for example use the @code{target
3358 remote} command to connect to some other @code{gdbserver} instance,
3359 use @code{run} to spawn a local program, etc.
3361 @kindex clone-inferior
3362 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3363 Adds @var{n} inferiors ready to execute the same program as inferior
3364 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3365 number of the current inferior. This command copies the values of the
3366 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3367 current inferior to the new one. It also propagates changes the user
3368 made to environment variables using the @w{@code{set environment}} and
3369 @w{@code{unset environment}} commands. This is a convenient command
3370 when you want to run another instance of the inferior you are debugging.
3373 (@value{GDBP}) info inferiors
3374 Num Description Connection Executable
3375 * 1 process 29964 1 (native) helloworld
3376 (@value{GDBP}) clone-inferior
3379 (@value{GDBP}) info inferiors
3380 Num Description Connection Executable
3381 * 1 process 29964 1 (native) helloworld
3382 2 <null> 1 (native) helloworld
3385 You can now simply switch focus to inferior 2 and run it.
3387 @kindex remove-inferiors
3388 @item remove-inferiors @var{infno}@dots{}
3389 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3390 possible to remove an inferior that is running with this command. For
3391 those, use the @code{kill} or @code{detach} command first.
3395 To quit debugging one of the running inferiors that is not the current
3396 inferior, you can either detach from it by using the @w{@code{detach
3397 inferior}} command (allowing it to run independently), or kill it
3398 using the @w{@code{kill inferiors}} command:
3401 @kindex detach inferiors @var{infno}@dots{}
3402 @item detach inferior @var{infno}@dots{}
3403 Detach from the inferior or inferiors identified by @value{GDBN}
3404 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3405 still stays on the list of inferiors shown by @code{info inferiors},
3406 but its Description will show @samp{<null>}.
3408 @kindex kill inferiors @var{infno}@dots{}
3409 @item kill inferiors @var{infno}@dots{}
3410 Kill the inferior or inferiors identified by @value{GDBN} inferior
3411 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3412 stays on the list of inferiors shown by @code{info inferiors}, but its
3413 Description will show @samp{<null>}.
3416 After the successful completion of a command such as @code{detach},
3417 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3418 a normal process exit, the inferior is still valid and listed with
3419 @code{info inferiors}, ready to be restarted.
3422 To be notified when inferiors are started or exit under @value{GDBN}'s
3423 control use @w{@code{set print inferior-events}}:
3426 @kindex set print inferior-events
3427 @cindex print messages on inferior start and exit
3428 @item set print inferior-events
3429 @itemx set print inferior-events on
3430 @itemx set print inferior-events off
3431 The @code{set print inferior-events} command allows you to enable or
3432 disable printing of messages when @value{GDBN} notices that new
3433 inferiors have started or that inferiors have exited or have been
3434 detached. By default, these messages will be printed.
3436 @kindex show print inferior-events
3437 @item show print inferior-events
3438 Show whether messages will be printed when @value{GDBN} detects that
3439 inferiors have started, exited or have been detached.
3442 Many commands will work the same with multiple programs as with a
3443 single program: e.g., @code{print myglobal} will simply display the
3444 value of @code{myglobal} in the current inferior.
3447 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3448 get more info about the relationship of inferiors, programs, address
3449 spaces in a debug session. You can do that with the @w{@code{maint
3450 info program-spaces}} command.
3453 @kindex maint info program-spaces
3454 @item maint info program-spaces
3455 Print a list of all program spaces currently being managed by
3458 @value{GDBN} displays for each program space (in this order):
3462 the program space number assigned by @value{GDBN}
3465 the name of the executable loaded into the program space, with e.g.,
3466 the @code{file} command.
3469 the name of the core file loaded into the program space, with e.g.,
3470 the @code{core-file} command.
3475 An asterisk @samp{*} preceding the @value{GDBN} program space number
3476 indicates the current program space.
3478 In addition, below each program space line, @value{GDBN} prints extra
3479 information that isn't suitable to display in tabular form. For
3480 example, the list of inferiors bound to the program space.
3483 (@value{GDBP}) maint info program-spaces
3484 Id Executable Core File
3487 Bound inferiors: ID 1 (process 21561)
3490 Here we can see that no inferior is running the program @code{hello},
3491 while @code{process 21561} is running the program @code{goodbye}. On
3492 some targets, it is possible that multiple inferiors are bound to the
3493 same program space. The most common example is that of debugging both
3494 the parent and child processes of a @code{vfork} call. For example,
3497 (@value{GDBP}) maint info program-spaces
3498 Id Executable Core File
3500 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3503 Here, both inferior 2 and inferior 1 are running in the same program
3504 space as a result of inferior 1 having executed a @code{vfork} call.
3508 @section Debugging Programs with Multiple Threads
3510 @cindex threads of execution
3511 @cindex multiple threads
3512 @cindex switching threads
3513 In some operating systems, such as GNU/Linux and Solaris, a single program
3514 may have more than one @dfn{thread} of execution. The precise semantics
3515 of threads differ from one operating system to another, but in general
3516 the threads of a single program are akin to multiple processes---except
3517 that they share one address space (that is, they can all examine and
3518 modify the same variables). On the other hand, each thread has its own
3519 registers and execution stack, and perhaps private memory.
3521 @value{GDBN} provides these facilities for debugging multi-thread
3525 @item automatic notification of new threads
3526 @item @samp{thread @var{thread-id}}, a command to switch among threads
3527 @item @samp{info threads}, a command to inquire about existing threads
3528 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3529 a command to apply a command to a list of threads
3530 @item thread-specific breakpoints
3531 @item @samp{set print thread-events}, which controls printing of
3532 messages on thread start and exit.
3533 @item @samp{set libthread-db-search-path @var{path}}, which lets
3534 the user specify which @code{libthread_db} to use if the default choice
3535 isn't compatible with the program.
3538 @cindex focus of debugging
3539 @cindex current thread
3540 The @value{GDBN} thread debugging facility allows you to observe all
3541 threads while your program runs---but whenever @value{GDBN} takes
3542 control, one thread in particular is always the focus of debugging.
3543 This thread is called the @dfn{current thread}. Debugging commands show
3544 program information from the perspective of the current thread.
3546 @cindex @code{New} @var{systag} message
3547 @cindex thread identifier (system)
3548 @c FIXME-implementors!! It would be more helpful if the [New...] message
3549 @c included GDB's numeric thread handle, so you could just go to that
3550 @c thread without first checking `info threads'.
3551 Whenever @value{GDBN} detects a new thread in your program, it displays
3552 the target system's identification for the thread with a message in the
3553 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3554 whose form varies depending on the particular system. For example, on
3555 @sc{gnu}/Linux, you might see
3558 [New Thread 0x41e02940 (LWP 25582)]
3562 when @value{GDBN} notices a new thread. In contrast, on other systems,
3563 the @var{systag} is simply something like @samp{process 368}, with no
3566 @c FIXME!! (1) Does the [New...] message appear even for the very first
3567 @c thread of a program, or does it only appear for the
3568 @c second---i.e.@: when it becomes obvious we have a multithread
3570 @c (2) *Is* there necessarily a first thread always? Or do some
3571 @c multithread systems permit starting a program with multiple
3572 @c threads ab initio?
3574 @anchor{thread numbers}
3575 @cindex thread number, per inferior
3576 @cindex thread identifier (GDB)
3577 For debugging purposes, @value{GDBN} associates its own thread number
3578 ---always a single integer---with each thread of an inferior. This
3579 number is unique between all threads of an inferior, but not unique
3580 between threads of different inferiors.
3582 @cindex qualified thread ID
3583 You can refer to a given thread in an inferior using the qualified
3584 @var{inferior-num}.@var{thread-num} syntax, also known as
3585 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3586 number and @var{thread-num} being the thread number of the given
3587 inferior. For example, thread @code{2.3} refers to thread number 3 of
3588 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3589 then @value{GDBN} infers you're referring to a thread of the current
3592 Until you create a second inferior, @value{GDBN} does not show the
3593 @var{inferior-num} part of thread IDs, even though you can always use
3594 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3595 of inferior 1, the initial inferior.
3597 @anchor{thread ID lists}
3598 @cindex thread ID lists
3599 Some commands accept a space-separated @dfn{thread ID list} as
3600 argument. A list element can be:
3604 A thread ID as shown in the first field of the @samp{info threads}
3605 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3609 A range of thread numbers, again with or without an inferior
3610 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3611 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3614 All threads of an inferior, specified with a star wildcard, with or
3615 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3616 @samp{1.*}) or @code{*}. The former refers to all threads of the
3617 given inferior, and the latter form without an inferior qualifier
3618 refers to all threads of the current inferior.
3622 For example, if the current inferior is 1, and inferior 7 has one
3623 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3624 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3625 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3626 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3630 @anchor{global thread numbers}
3631 @cindex global thread number
3632 @cindex global thread identifier (GDB)
3633 In addition to a @emph{per-inferior} number, each thread is also
3634 assigned a unique @emph{global} number, also known as @dfn{global
3635 thread ID}, a single integer. Unlike the thread number component of
3636 the thread ID, no two threads have the same global ID, even when
3637 you're debugging multiple inferiors.
3639 From @value{GDBN}'s perspective, a process always has at least one
3640 thread. In other words, @value{GDBN} assigns a thread number to the
3641 program's ``main thread'' even if the program is not multi-threaded.
3643 @vindex $_thread@r{, convenience variable}
3644 @vindex $_gthread@r{, convenience variable}
3645 The debugger convenience variables @samp{$_thread} and
3646 @samp{$_gthread} contain, respectively, the per-inferior thread number
3647 and the global thread number of the current thread. You may find this
3648 useful in writing breakpoint conditional expressions, command scripts,
3649 and so forth. The convenience variable @samp{$_inferior_thread_count}
3650 contains the number of live threads in the current inferior.
3651 @xref{Convenience Vars,, Convenience Variables}, for general
3652 information on convenience variables.
3654 When running in non-stop mode (@pxref{Non-Stop Mode}), where new
3655 threads can be created, and existing threads exit, at any time,
3656 @samp{$_inferior_thread_count} could return a different value each
3657 time it is evaluated.
3659 If @value{GDBN} detects the program is multi-threaded, it augments the
3660 usual message about stopping at a breakpoint with the ID and name of
3661 the thread that hit the breakpoint.
3664 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3667 Likewise when the program receives a signal:
3670 Thread 1 "main" received signal SIGINT, Interrupt.
3674 @anchor{info_threads}
3675 @kindex info threads
3676 @item info threads @r{[}@var{thread-id-list}@r{]}
3678 Display information about one or more threads. With no arguments
3679 displays information about all threads. You can specify the list of
3680 threads that you want to display using the thread ID list syntax
3681 (@pxref{thread ID lists}).
3683 @value{GDBN} displays for each thread (in this order):
3687 the per-inferior thread number assigned by @value{GDBN}
3690 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3691 option was specified
3694 the target system's thread identifier (@var{systag})
3697 the thread's name, if one is known. A thread can either be named by
3698 the user (see @code{thread name}, below), or, in some cases, by the
3702 the current stack frame summary for that thread
3706 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3707 indicates the current thread.
3711 @c end table here to get a little more width for example
3714 (@value{GDBP}) info threads
3716 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3717 2 process 35 thread 23 0x34e5 in sigpause ()
3718 3 process 35 thread 27 0x34e5 in sigpause ()
3722 If you're debugging multiple inferiors, @value{GDBN} displays thread
3723 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3724 Otherwise, only @var{thread-num} is shown.
3726 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3727 indicating each thread's global thread ID:
3730 (@value{GDBP}) info threads
3731 Id GId Target Id Frame
3732 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3733 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3734 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3735 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3738 On Solaris, you can display more information about user threads with a
3739 Solaris-specific command:
3742 @item maint info sol-threads
3743 @kindex maint info sol-threads
3744 @cindex thread info (Solaris)
3745 Display info on Solaris user threads.
3749 @kindex thread @var{thread-id}
3750 @item thread @var{thread-id}
3751 Make thread ID @var{thread-id} the current thread. The command
3752 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3753 the first field of the @samp{info threads} display, with or without an
3754 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3756 @value{GDBN} responds by displaying the system identifier of the
3757 thread you selected, and its current stack frame summary:
3760 (@value{GDBP}) thread 2
3761 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3762 #0 some_function (ignore=0x0) at example.c:8
3763 8 printf ("hello\n");
3767 As with the @samp{[New @dots{}]} message, the form of the text after
3768 @samp{Switching to} depends on your system's conventions for identifying
3771 @anchor{thread apply all}
3772 @kindex thread apply
3773 @cindex apply command to several threads
3774 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3775 The @code{thread apply} command allows you to apply the named
3776 @var{command} to one or more threads. Specify the threads that you
3777 want affected using the thread ID list syntax (@pxref{thread ID
3778 lists}), or specify @code{all} to apply to all threads. To apply a
3779 command to all threads in descending order, type @kbd{thread apply all
3780 @var{command}}. To apply a command to all threads in ascending order,
3781 type @kbd{thread apply all -ascending @var{command}}.
3783 The @var{flag} arguments control what output to produce and how to handle
3784 errors raised when applying @var{command} to a thread. @var{flag}
3785 must start with a @code{-} directly followed by one letter in
3786 @code{qcs}. If several flags are provided, they must be given
3787 individually, such as @code{-c -q}.
3789 By default, @value{GDBN} displays some thread information before the
3790 output produced by @var{command}, and an error raised during the
3791 execution of a @var{command} will abort @code{thread apply}. The
3792 following flags can be used to fine-tune this behavior:
3796 The flag @code{-c}, which stands for @samp{continue}, causes any
3797 errors in @var{command} to be displayed, and the execution of
3798 @code{thread apply} then continues.
3800 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3801 or empty output produced by a @var{command} to be silently ignored.
3802 That is, the execution continues, but the thread information and errors
3805 The flag @code{-q} (@samp{quiet}) disables printing the thread
3809 Flags @code{-c} and @code{-s} cannot be used together.
3812 @cindex apply command to all threads (ignoring errors and empty output)
3813 @item taas [@var{option}]@dots{} @var{command}
3814 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3815 Applies @var{command} on all threads, ignoring errors and empty output.
3817 The @code{taas} command accepts the same options as the @code{thread
3818 apply all} command. @xref{thread apply all}.
3821 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3822 @item tfaas [@var{option}]@dots{} @var{command}
3823 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3824 Applies @var{command} on all frames of all threads, ignoring errors
3825 and empty output. Note that the flag @code{-s} is specified twice:
3826 The first @code{-s} ensures that @code{thread apply} only shows the thread
3827 information of the threads for which @code{frame apply} produces
3828 some output. The second @code{-s} is needed to ensure that @code{frame
3829 apply} shows the frame information of a frame only if the
3830 @var{command} successfully produced some output.
3832 It can for example be used to print a local variable or a function
3833 argument without knowing the thread or frame where this variable or argument
3836 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3839 The @code{tfaas} command accepts the same options as the @code{frame
3840 apply} command. @xref{Frame Apply,,frame apply}.
3843 @cindex name a thread
3844 @item thread name [@var{name}]
3845 This command assigns a name to the current thread. If no argument is
3846 given, any existing user-specified name is removed. The thread name
3847 appears in the @samp{info threads} display.
3849 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3850 determine the name of the thread as given by the OS. On these
3851 systems, a name specified with @samp{thread name} will override the
3852 system-give name, and removing the user-specified name will cause
3853 @value{GDBN} to once again display the system-specified name.
3856 @cindex search for a thread
3857 @item thread find [@var{regexp}]
3858 Search for and display thread ids whose name or @var{systag}
3859 matches the supplied regular expression.
3861 As well as being the complement to the @samp{thread name} command,
3862 this command also allows you to identify a thread by its target
3863 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3867 (@value{GDBN}) thread find 26688
3868 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3869 (@value{GDBN}) info thread 4
3871 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3874 @kindex set print thread-events
3875 @cindex print messages on thread start and exit
3876 @item set print thread-events
3877 @itemx set print thread-events on
3878 @itemx set print thread-events off
3879 The @code{set print thread-events} command allows you to enable or
3880 disable printing of messages when @value{GDBN} notices that new threads have
3881 started or that threads have exited. By default, these messages will
3882 be printed if detection of these events is supported by the target.
3883 Note that these messages cannot be disabled on all targets.
3885 @kindex show print thread-events
3886 @item show print thread-events
3887 Show whether messages will be printed when @value{GDBN} detects that threads
3888 have started and exited.
3891 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3892 more information about how @value{GDBN} behaves when you stop and start
3893 programs with multiple threads.
3895 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3896 watchpoints in programs with multiple threads.
3898 @anchor{set libthread-db-search-path}
3900 @kindex set libthread-db-search-path
3901 @cindex search path for @code{libthread_db}
3902 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3903 If this variable is set, @var{path} is a colon-separated list of
3904 directories @value{GDBN} will use to search for @code{libthread_db}.
3905 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3906 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3907 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3910 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3911 @code{libthread_db} library to obtain information about threads in the
3912 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3913 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3914 specific thread debugging library loading is enabled
3915 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3917 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3918 refers to the default system directories that are
3919 normally searched for loading shared libraries. The @samp{$sdir} entry
3920 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3921 (@pxref{libthread_db.so.1 file}).
3923 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3924 refers to the directory from which @code{libpthread}
3925 was loaded in the inferior process.
3927 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3928 @value{GDBN} attempts to initialize it with the current inferior process.
3929 If this initialization fails (which could happen because of a version
3930 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3931 will unload @code{libthread_db}, and continue with the next directory.
3932 If none of @code{libthread_db} libraries initialize successfully,
3933 @value{GDBN} will issue a warning and thread debugging will be disabled.
3935 Setting @code{libthread-db-search-path} is currently implemented
3936 only on some platforms.
3938 @kindex show libthread-db-search-path
3939 @item show libthread-db-search-path
3940 Display current libthread_db search path.
3942 @kindex set debug libthread-db
3943 @kindex show debug libthread-db
3944 @cindex debugging @code{libthread_db}
3945 @item set debug libthread-db
3946 @itemx show debug libthread-db
3947 Turns on or off display of @code{libthread_db}-related events.
3948 Use @code{1} to enable, @code{0} to disable.
3950 @kindex set debug threads
3951 @kindex show debug threads
3952 @cindex debugging @code{threads}
3953 @item set debug threads @r{[}on@r{|}off@r{]}
3954 @itemx show debug threads
3955 When @samp{on} @value{GDBN} will print additional messages when
3956 threads are created and deleted.
3960 @section Debugging Forks
3962 @cindex fork, debugging programs which call
3963 @cindex multiple processes
3964 @cindex processes, multiple
3965 On most systems, @value{GDBN} has no special support for debugging
3966 programs which create additional processes using the @code{fork}
3967 function. When a program forks, @value{GDBN} will continue to debug the
3968 parent process and the child process will run unimpeded. If you have
3969 set a breakpoint in any code which the child then executes, the child
3970 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3971 will cause it to terminate.
3973 However, if you want to debug the child process there is a workaround
3974 which isn't too painful. Put a call to @code{sleep} in the code which
3975 the child process executes after the fork. It may be useful to sleep
3976 only if a certain environment variable is set, or a certain file exists,
3977 so that the delay need not occur when you don't want to run @value{GDBN}
3978 on the child. While the child is sleeping, use the @code{ps} program to
3979 get its process ID. Then tell @value{GDBN} (a new invocation of
3980 @value{GDBN} if you are also debugging the parent process) to attach to
3981 the child process (@pxref{Attach}). From that point on you can debug
3982 the child process just like any other process which you attached to.
3984 On some systems, @value{GDBN} provides support for debugging programs
3985 that create additional processes using the @code{fork} or @code{vfork}
3986 functions. On @sc{gnu}/Linux platforms, this feature is supported
3987 with kernel version 2.5.46 and later.
3989 The fork debugging commands are supported in native mode and when
3990 connected to @code{gdbserver} in either @code{target remote} mode or
3991 @code{target extended-remote} mode.
3993 By default, when a program forks, @value{GDBN} will continue to debug
3994 the parent process and the child process will run unimpeded.
3996 If you want to follow the child process instead of the parent process,
3997 use the command @w{@code{set follow-fork-mode}}.
4000 @kindex set follow-fork-mode
4001 @item set follow-fork-mode @var{mode}
4002 Set the debugger response to a program call of @code{fork} or
4003 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
4004 process. The @var{mode} argument can be:
4008 The original process is debugged after a fork. The child process runs
4009 unimpeded. This is the default.
4012 The new process is debugged after a fork. The parent process runs
4017 @kindex show follow-fork-mode
4018 @item show follow-fork-mode
4019 Display the current debugger response to a @code{fork} or @code{vfork} call.
4022 @cindex debugging multiple processes
4023 On Linux, if you want to debug both the parent and child processes, use the
4024 command @w{@code{set detach-on-fork}}.
4027 @kindex set detach-on-fork
4028 @item set detach-on-fork @var{mode}
4029 Tells gdb whether to detach one of the processes after a fork, or
4030 retain debugger control over them both.
4034 The child process (or parent process, depending on the value of
4035 @code{follow-fork-mode}) will be detached and allowed to run
4036 independently. This is the default.
4039 Both processes will be held under the control of @value{GDBN}.
4040 One process (child or parent, depending on the value of
4041 @code{follow-fork-mode}) is debugged as usual, while the other
4046 @kindex show detach-on-fork
4047 @item show detach-on-fork
4048 Show whether detach-on-fork mode is on/off.
4051 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4052 will retain control of all forked processes (including nested forks).
4053 You can list the forked processes under the control of @value{GDBN} by
4054 using the @w{@code{info inferiors}} command, and switch from one fork
4055 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4056 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4058 To quit debugging one of the forked processes, you can either detach
4059 from it by using the @w{@code{detach inferiors}} command (allowing it
4060 to run independently), or kill it using the @w{@code{kill inferiors}}
4061 command. @xref{Inferiors Connections and Programs, ,Debugging
4062 Multiple Inferiors Connections and Programs}.
4064 If you ask to debug a child process and a @code{vfork} is followed by an
4065 @code{exec}, @value{GDBN} executes the new target up to the first
4066 breakpoint in the new target. If you have a breakpoint set on
4067 @code{main} in your original program, the breakpoint will also be set on
4068 the child process's @code{main}.
4070 On some systems, when a child process is spawned by @code{vfork}, you
4071 cannot debug the child or parent until an @code{exec} call completes.
4073 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4074 call executes, the new target restarts. To restart the parent
4075 process, use the @code{file} command with the parent executable name
4076 as its argument. By default, after an @code{exec} call executes,
4077 @value{GDBN} discards the symbols of the previous executable image.
4078 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4082 @kindex set follow-exec-mode
4083 @item set follow-exec-mode @var{mode}
4085 Set debugger response to a program call of @code{exec}. An
4086 @code{exec} call replaces the program image of a process.
4088 @code{follow-exec-mode} can be:
4092 @value{GDBN} creates a new inferior and rebinds the process to this
4093 new inferior. The program the process was running before the
4094 @code{exec} call can be restarted afterwards by restarting the
4100 (@value{GDBP}) info inferiors
4102 Id Description Executable
4105 process 12020 is executing new program: prog2
4106 Program exited normally.
4107 (@value{GDBP}) info inferiors
4108 Id Description Executable
4114 @value{GDBN} keeps the process bound to the same inferior. The new
4115 executable image replaces the previous executable loaded in the
4116 inferior. Restarting the inferior after the @code{exec} call, with
4117 e.g., the @code{run} command, restarts the executable the process was
4118 running after the @code{exec} call. This is the default mode.
4123 (@value{GDBP}) info inferiors
4124 Id Description Executable
4127 process 12020 is executing new program: prog2
4128 Program exited normally.
4129 (@value{GDBP}) info inferiors
4130 Id Description Executable
4137 @code{follow-exec-mode} is supported in native mode and
4138 @code{target extended-remote} mode.
4140 You can use the @code{catch} command to make @value{GDBN} stop whenever
4141 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4142 Catchpoints, ,Setting Catchpoints}.
4144 @node Checkpoint/Restart
4145 @section Setting a @emph{Bookmark} to Return to Later
4150 @cindex snapshot of a process
4151 @cindex rewind program state
4153 On certain operating systems@footnote{Currently, only
4154 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4155 program's state, called a @dfn{checkpoint}, and come back to it
4158 Returning to a checkpoint effectively undoes everything that has
4159 happened in the program since the @code{checkpoint} was saved. This
4160 includes changes in memory, registers, and even (within some limits)
4161 system state. Effectively, it is like going back in time to the
4162 moment when the checkpoint was saved.
4164 Thus, if you're stepping thru a program and you think you're
4165 getting close to the point where things go wrong, you can save
4166 a checkpoint. Then, if you accidentally go too far and miss
4167 the critical statement, instead of having to restart your program
4168 from the beginning, you can just go back to the checkpoint and
4169 start again from there.
4171 This can be especially useful if it takes a lot of time or
4172 steps to reach the point where you think the bug occurs.
4174 To use the @code{checkpoint}/@code{restart} method of debugging:
4179 Save a snapshot of the debugged program's current execution state.
4180 The @code{checkpoint} command takes no arguments, but each checkpoint
4181 is assigned a small integer id, similar to a breakpoint id.
4183 @kindex info checkpoints
4184 @item info checkpoints
4185 List the checkpoints that have been saved in the current debugging
4186 session. For each checkpoint, the following information will be
4193 @item Source line, or label
4196 @kindex restart @var{checkpoint-id}
4197 @item restart @var{checkpoint-id}
4198 Restore the program state that was saved as checkpoint number
4199 @var{checkpoint-id}. All program variables, registers, stack frames
4200 etc.@: will be returned to the values that they had when the checkpoint
4201 was saved. In essence, gdb will ``wind back the clock'' to the point
4202 in time when the checkpoint was saved.
4204 Note that breakpoints, @value{GDBN} variables, command history etc.
4205 are not affected by restoring a checkpoint. In general, a checkpoint
4206 only restores things that reside in the program being debugged, not in
4209 @kindex delete checkpoint @var{checkpoint-id}
4210 @item delete checkpoint @var{checkpoint-id}
4211 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4215 Returning to a previously saved checkpoint will restore the user state
4216 of the program being debugged, plus a significant subset of the system
4217 (OS) state, including file pointers. It won't ``un-write'' data from
4218 a file, but it will rewind the file pointer to the previous location,
4219 so that the previously written data can be overwritten. For files
4220 opened in read mode, the pointer will also be restored so that the
4221 previously read data can be read again.
4223 Of course, characters that have been sent to a printer (or other
4224 external device) cannot be ``snatched back'', and characters received
4225 from eg.@: a serial device can be removed from internal program buffers,
4226 but they cannot be ``pushed back'' into the serial pipeline, ready to
4227 be received again. Similarly, the actual contents of files that have
4228 been changed cannot be restored (at this time).
4230 However, within those constraints, you actually can ``rewind'' your
4231 program to a previously saved point in time, and begin debugging it
4232 again --- and you can change the course of events so as to debug a
4233 different execution path this time.
4235 @cindex checkpoints and process id
4236 Finally, there is one bit of internal program state that will be
4237 different when you return to a checkpoint --- the program's process
4238 id. Each checkpoint will have a unique process id (or @var{pid}),
4239 and each will be different from the program's original @var{pid}.
4240 If your program has saved a local copy of its process id, this could
4241 potentially pose a problem.
4243 @subsection A Non-obvious Benefit of Using Checkpoints
4245 On some systems such as @sc{gnu}/Linux, address space randomization
4246 is performed on new processes for security reasons. This makes it
4247 difficult or impossible to set a breakpoint, or watchpoint, on an
4248 absolute address if you have to restart the program, since the
4249 absolute location of a symbol will change from one execution to the
4252 A checkpoint, however, is an @emph{identical} copy of a process.
4253 Therefore if you create a checkpoint at (eg.@:) the start of main,
4254 and simply return to that checkpoint instead of restarting the
4255 process, you can avoid the effects of address randomization and
4256 your symbols will all stay in the same place.
4259 @chapter Stopping and Continuing
4261 The principal purposes of using a debugger are so that you can stop your
4262 program before it terminates; or so that, if your program runs into
4263 trouble, you can investigate and find out why.
4265 Inside @value{GDBN}, your program may stop for any of several reasons,
4266 such as a signal, a breakpoint, or reaching a new line after a
4267 @value{GDBN} command such as @code{step}. You may then examine and
4268 change variables, set new breakpoints or remove old ones, and then
4269 continue execution. Usually, the messages shown by @value{GDBN} provide
4270 ample explanation of the status of your program---but you can also
4271 explicitly request this information at any time.
4274 @kindex info program
4276 Display information about the status of your program: whether it is
4277 running or not, what process it is, and why it stopped.
4281 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4282 * Continuing and Stepping:: Resuming execution
4283 * Skipping Over Functions and Files::
4284 Skipping over functions and files
4286 * Thread Stops:: Stopping and starting multi-thread programs
4290 @section Breakpoints, Watchpoints, and Catchpoints
4293 A @dfn{breakpoint} makes your program stop whenever a certain point in
4294 the program is reached. For each breakpoint, you can add conditions to
4295 control in finer detail whether your program stops. You can set
4296 breakpoints with the @code{break} command and its variants (@pxref{Set
4297 Breaks, ,Setting Breakpoints}), to specify the place where your program
4298 should stop by line number, function name or exact address in the
4301 On some systems, you can set breakpoints in shared libraries before
4302 the executable is run.
4305 @cindex data breakpoints
4306 @cindex memory tracing
4307 @cindex breakpoint on memory address
4308 @cindex breakpoint on variable modification
4309 A @dfn{watchpoint} is a special breakpoint that stops your program
4310 when the value of an expression changes. The expression may be a value
4311 of a variable, or it could involve values of one or more variables
4312 combined by operators, such as @samp{a + b}. This is sometimes called
4313 @dfn{data breakpoints}. You must use a different command to set
4314 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4315 from that, you can manage a watchpoint like any other breakpoint: you
4316 enable, disable, and delete both breakpoints and watchpoints using the
4319 You can arrange to have values from your program displayed automatically
4320 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4324 @cindex breakpoint on events
4325 A @dfn{catchpoint} is another special breakpoint that stops your program
4326 when a certain kind of event occurs, such as the throwing of a C@t{++}
4327 exception or the loading of a library. As with watchpoints, you use a
4328 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4329 Catchpoints}), but aside from that, you can manage a catchpoint like any
4330 other breakpoint. (To stop when your program receives a signal, use the
4331 @code{handle} command; see @ref{Signals, ,Signals}.)
4333 @cindex breakpoint numbers
4334 @cindex numbers for breakpoints
4335 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4336 catchpoint when you create it; these numbers are successive integers
4337 starting with one. In many of the commands for controlling various
4338 features of breakpoints you use the breakpoint number to say which
4339 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4340 @dfn{disabled}; if disabled, it has no effect on your program until you
4343 @cindex breakpoint ranges
4344 @cindex breakpoint lists
4345 @cindex ranges of breakpoints
4346 @cindex lists of breakpoints
4347 Some @value{GDBN} commands accept a space-separated list of breakpoints
4348 on which to operate. A list element can be either a single breakpoint number,
4349 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4350 When a breakpoint list is given to a command, all breakpoints in that list
4354 * Set Breaks:: Setting breakpoints
4355 * Set Watchpoints:: Setting watchpoints
4356 * Set Catchpoints:: Setting catchpoints
4357 * Delete Breaks:: Deleting breakpoints
4358 * Disabling:: Disabling breakpoints
4359 * Conditions:: Break conditions
4360 * Break Commands:: Breakpoint command lists
4361 * Dynamic Printf:: Dynamic printf
4362 * Save Breakpoints:: How to save breakpoints in a file
4363 * Static Probe Points:: Listing static probe points
4364 * Error in Breakpoints:: ``Cannot insert breakpoints''
4365 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4369 @subsection Setting Breakpoints
4371 @c FIXME LMB what does GDB do if no code on line of breakpt?
4372 @c consider in particular declaration with/without initialization.
4374 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4377 @kindex b @r{(@code{break})}
4378 @vindex $bpnum@r{, convenience variable}
4379 @cindex latest breakpoint
4380 Breakpoints are set with the @code{break} command (abbreviated
4381 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4382 number of the breakpoint you've set most recently:
4385 Breakpoint 1 at 0x11c6: file zeoes.c, line 24.
4390 A breakpoint may be mapped to multiple code locations for example with
4391 inlined functions, Ada generics, C@t{++} templates or overloaded function names.
4392 @value{GDBN} then indicates the number of code locations in the breakpoint
4396 Breakpoint 2 at 0x1179: some_func. (3 locations)
4402 @vindex $_hit_bpnum@r{, convenience variable}
4403 @vindex $_hit_locno@r{, convenience variable}
4404 When your program stops on a breakpoint, the convenience variables
4405 @samp{$_hit_bpnum} and @samp{$_hit_locno} are respectively set to the number of
4406 the encountered breakpoint and the number of the breakpoint's code location:
4408 Thread 1 "zeoes" hit Breakpoint 2.1, some_func () at zeoes.c:8
4409 8 printf("some func\n");
4417 Note that @samp{$_hit_bpnum} and @samp{$bpnum} are not equivalent:
4418 @samp{$_hit_bpnum} is set to the breakpoint number @b{last hit}, while
4419 @samp{$bpnum} is set to the breakpoint number @b{last set}.
4422 If the encountered breakpoint has only one code location, @samp{$_hit_locno}
4425 Breakpoint 1, main (argc=1, argv=0x7fffffffe018) at zeoes.c:24
4434 The @samp{$_hit_bpnum} and @samp{$_hit_locno} variables can typically be used
4435 in a breakpoint command list.
4436 (@pxref{Break Commands, ,Breakpoint Command Lists}). For example, as
4437 part of the breakpoint command list, you can disable completely the
4438 encountered breakpoint using @kbd{disable $_hit_bpnum} or disable the
4439 specific encountered breakpoint location using
4440 @kbd{disable $_hit_bpnum.$_hit_locno}.
4441 If a breakpoint has only one location, @samp{$_hit_locno} is set to 1
4442 and the commands @kbd{disable $_hit_bpnum} and
4443 @kbd{disable $_hit_bpnum.$_hit_locno} both disable the breakpoint.
4445 You can also define aliases to easily disable the last hit location or
4446 last hit breakpoint:
4448 (gdb) alias lld = disable $_hit_bpnum.$_hit_locno
4449 (gdb) alias lbd = disable $_hit_bpnum
4453 @item break @var{locspec}
4454 Set a breakpoint at all the code locations in your program that result
4455 from resolving the given @var{locspec}. @var{locspec} can specify a
4456 function name, a line number, an address of an instruction, and more.
4457 @xref{Location Specifications}, for the various forms of
4458 @var{locspec}. The breakpoint will stop your program just before it
4459 executes the instruction at the address of any of the breakpoint's
4462 When using source languages that permit overloading of symbols, such
4463 as C@t{++}, a function name may refer to more than one symbol, and
4464 thus more than one place to break. @xref{Ambiguous
4465 Expressions,,Ambiguous Expressions}, for a discussion of that
4468 It is also possible to insert a breakpoint that will stop the program
4469 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4470 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4473 When called without any arguments, @code{break} sets a breakpoint at
4474 the next instruction to be executed in the selected stack frame
4475 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4476 innermost, this makes your program stop as soon as control
4477 returns to that frame. This is similar to the effect of a
4478 @code{finish} command in the frame inside the selected frame---except
4479 that @code{finish} does not leave an active breakpoint. If you use
4480 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4481 the next time it reaches the current location; this may be useful
4484 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4485 least one instruction has been executed. If it did not do this, you
4486 would be unable to proceed past a breakpoint without first disabling the
4487 breakpoint. This rule applies whether or not the breakpoint already
4488 existed when your program stopped.
4490 @item break @dots{} if @var{cond}
4491 Set a breakpoint with condition @var{cond}; evaluate the expression
4492 @var{cond} each time the breakpoint is reached, and stop only if the
4493 value is nonzero---that is, if @var{cond} evaluates as true.
4494 @samp{@dots{}} stands for one of the possible arguments described
4495 above (or no argument) specifying where to break. @xref{Conditions,
4496 ,Break Conditions}, for more information on breakpoint conditions.
4498 The breakpoint may be mapped to multiple locations. If the breakpoint
4499 condition @var{cond} is invalid at some but not all of the locations,
4500 the locations for which the condition is invalid are disabled. For
4501 example, @value{GDBN} reports below that two of the three locations
4505 (@value{GDBP}) break func if a == 10
4506 warning: failed to validate condition at location 0x11ce, disabling:
4507 No symbol "a" in current context.
4508 warning: failed to validate condition at location 0x11b6, disabling:
4509 No symbol "a" in current context.
4510 Breakpoint 1 at 0x11b6: func. (3 locations)
4513 Locations that are disabled because of the condition are denoted by an
4514 uppercase @code{N} in the output of the @code{info breakpoints}
4518 (@value{GDBP}) info breakpoints
4519 Num Type Disp Enb Address What
4520 1 breakpoint keep y <MULTIPLE>
4521 stop only if a == 10
4522 1.1 N* 0x00000000000011b6 in ...
4523 1.2 y 0x00000000000011c2 in ...
4524 1.3 N* 0x00000000000011ce in ...
4525 (*): Breakpoint condition is invalid at this location.
4528 If the breakpoint condition @var{cond} is invalid in the context of
4529 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4530 define the breakpoint. For example, if variable @code{foo} is an
4534 (@value{GDBP}) break func if foo
4535 No symbol "foo" in current context.
4538 @item break @dots{} -force-condition if @var{cond}
4539 There may be cases where the condition @var{cond} is invalid at all
4540 the current locations, but the user knows that it will be valid at a
4541 future location; for example, because of a library load. In such
4542 cases, by using the @code{-force-condition} keyword before @samp{if},
4543 @value{GDBN} can be forced to define the breakpoint with the given
4544 condition expression instead of refusing it.
4547 (@value{GDBP}) break func -force-condition if foo
4548 warning: failed to validate condition at location 1, disabling:
4549 No symbol "foo" in current context.
4550 warning: failed to validate condition at location 2, disabling:
4551 No symbol "foo" in current context.
4552 warning: failed to validate condition at location 3, disabling:
4553 No symbol "foo" in current context.
4554 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4557 This causes all the present locations where the breakpoint would
4558 otherwise be inserted, to be disabled, as seen in the example above.
4559 However, if there exist locations at which the condition is valid, the
4560 @code{-force-condition} keyword has no effect.
4563 @item tbreak @var{args}
4564 Set a breakpoint enabled only for one stop. The @var{args} are the
4565 same as for the @code{break} command, and the breakpoint is set in the same
4566 way, but the breakpoint is automatically deleted after the first time your
4567 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4570 @cindex hardware breakpoints
4571 @item hbreak @var{args}
4572 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4573 @code{break} command and the breakpoint is set in the same way, but the
4574 breakpoint requires hardware support and some target hardware may not
4575 have this support. The main purpose of this is EPROM/ROM code
4576 debugging, so you can set a breakpoint at an instruction without
4577 changing the instruction. This can be used with the new trap-generation
4578 provided by SPARClite DSU and most x86-based targets. These targets
4579 will generate traps when a program accesses some data or instruction
4580 address that is assigned to the debug registers. However the hardware
4581 breakpoint registers can take a limited number of breakpoints. For
4582 example, on the DSU, only two data breakpoints can be set at a time, and
4583 @value{GDBN} will reject this command if more than two are used. Delete
4584 or disable unused hardware breakpoints before setting new ones
4585 (@pxref{Disabling, ,Disabling Breakpoints}).
4586 @xref{Conditions, ,Break Conditions}.
4587 For remote targets, you can restrict the number of hardware
4588 breakpoints @value{GDBN} will use, see @ref{set remote
4589 hardware-breakpoint-limit}.
4592 @item thbreak @var{args}
4593 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4594 are the same as for the @code{hbreak} command and the breakpoint is set in
4595 the same way. However, like the @code{tbreak} command,
4596 the breakpoint is automatically deleted after the
4597 first time your program stops there. Also, like the @code{hbreak}
4598 command, the breakpoint requires hardware support and some target hardware
4599 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4600 See also @ref{Conditions, ,Break Conditions}.
4603 @cindex regular expression
4604 @cindex breakpoints at functions matching a regexp
4605 @cindex set breakpoints in many functions
4606 @item rbreak @var{regex}
4607 Set breakpoints on all functions matching the regular expression
4608 @var{regex}. This command sets an unconditional breakpoint on all
4609 matches, printing a list of all breakpoints it set. Once these
4610 breakpoints are set, they are treated just like the breakpoints set with
4611 the @code{break} command. You can delete them, disable them, or make
4612 them conditional the same way as any other breakpoint.
4614 In programs using different languages, @value{GDBN} chooses the syntax
4615 to print the list of all breakpoints it sets according to the
4616 @samp{set language} value: using @samp{set language auto}
4617 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4618 language of the breakpoint's function, other values mean to use
4619 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4621 The syntax of the regular expression is the standard one used with tools
4622 like @file{grep}. Note that this is different from the syntax used by
4623 shells, so for instance @code{foo*} matches all functions that include
4624 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4625 @code{.*} leading and trailing the regular expression you supply, so to
4626 match only functions that begin with @code{foo}, use @code{^foo}.
4628 @cindex non-member C@t{++} functions, set breakpoint in
4629 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4630 breakpoints on overloaded functions that are not members of any special
4633 @cindex set breakpoints on all functions
4634 The @code{rbreak} command can be used to set breakpoints in
4635 @strong{all} the functions in a program, like this:
4638 (@value{GDBP}) rbreak .
4641 @item rbreak @var{file}:@var{regex}
4642 If @code{rbreak} is called with a filename qualification, it limits
4643 the search for functions matching the given regular expression to the
4644 specified @var{file}. This can be used, for example, to set breakpoints on
4645 every function in a given file:
4648 (@value{GDBP}) rbreak file.c:.
4651 The colon separating the filename qualifier from the regex may
4652 optionally be surrounded by spaces.
4654 @kindex info breakpoints
4655 @cindex @code{$_} and @code{info breakpoints}
4656 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4657 @itemx info break @r{[}@var{list}@dots{}@r{]}
4658 Print a table of all breakpoints, watchpoints, and catchpoints set and
4659 not deleted. Optional argument @var{n} means print information only
4660 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4661 For each breakpoint, following columns are printed:
4664 @item Breakpoint Numbers
4666 Breakpoint, watchpoint, or catchpoint.
4668 Whether the breakpoint is marked to be disabled or deleted when hit.
4669 @item Enabled or Disabled
4670 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4671 that are not enabled.
4673 Where the breakpoint is in your program, as a memory address. For a
4674 pending breakpoint whose address is not yet known, this field will
4675 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4676 library that has the symbol or line referred by breakpoint is loaded.
4677 See below for details. A breakpoint with several locations will
4678 have @samp{<MULTIPLE>} in this field---see below for details.
4680 Where the breakpoint is in the source for your program, as a file and
4681 line number. For a pending breakpoint, the original string passed to
4682 the breakpoint command will be listed as it cannot be resolved until
4683 the appropriate shared library is loaded in the future.
4687 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4688 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4689 @value{GDBN} on the host's side. If it is ``target'', then the condition
4690 is evaluated by the target. The @code{info break} command shows
4691 the condition on the line following the affected breakpoint, together with
4692 its condition evaluation mode in between parentheses.
4694 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4695 allowed to have a condition specified for it. The condition is not parsed for
4696 validity until a shared library is loaded that allows the pending
4697 breakpoint to resolve to a valid location.
4700 @code{info break} with a breakpoint
4701 number @var{n} as argument lists only that breakpoint. The
4702 convenience variable @code{$_} and the default examining-address for
4703 the @code{x} command are set to the address of the last breakpoint
4704 listed (@pxref{Memory, ,Examining Memory}).
4707 @code{info break} displays a count of the number of times the breakpoint
4708 has been hit. This is especially useful in conjunction with the
4709 @code{ignore} command. You can ignore a large number of breakpoint
4710 hits, look at the breakpoint info to see how many times the breakpoint
4711 was hit, and then run again, ignoring one less than that number. This
4712 will get you quickly to the last hit of that breakpoint.
4715 For a breakpoints with an enable count (xref) greater than 1,
4716 @code{info break} also displays that count.
4720 @value{GDBN} allows you to set any number of breakpoints at the same place in
4721 your program. There is nothing silly or meaningless about this. When
4722 the breakpoints are conditional, this is even useful
4723 (@pxref{Conditions, ,Break Conditions}).
4725 @cindex multiple locations, breakpoints
4726 @cindex breakpoints, multiple locations
4727 It is possible that a single logical breakpoint is set at several code
4728 locations in your program. @xref{Location Specifications}, for
4731 A breakpoint with multiple code locations is displayed in the
4732 breakpoint table using several rows---one header row, followed by one
4733 row for each code location. The header row has @samp{<MULTIPLE>} in
4734 the address column. Each code location row contains the actual
4735 address, source file, source line and function of its code location.
4736 The number column for a code location is of the form
4737 @var{breakpoint-number}.@var{location-number}.
4742 Num Type Disp Enb Address What
4743 1 breakpoint keep y <MULTIPLE>
4745 breakpoint already hit 1 time
4746 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4747 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4750 You cannot delete the individual locations from a breakpoint. However,
4751 each location can be individually enabled or disabled by passing
4752 @var{breakpoint-number}.@var{location-number} as argument to the
4753 @code{enable} and @code{disable} commands. It's also possible to
4754 @code{enable} and @code{disable} a range of @var{location-number}
4755 locations using a @var{breakpoint-number} and two @var{location-number}s,
4756 in increasing order, separated by a hyphen, like
4757 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4758 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4759 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4760 all of the locations that belong to that breakpoint.
4762 Locations that are enabled while their parent breakpoint is disabled
4763 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4764 column. For example:
4767 (@value{GDBP}) info breakpoints
4768 Num Type Disp Enb Address What
4769 1 breakpoint keep n <MULTIPLE>
4770 1.1 y- 0x00000000000011b6 in ...
4771 1.2 y- 0x00000000000011c2 in ...
4772 1.3 n 0x00000000000011ce in ...
4775 @cindex pending breakpoints
4776 It's quite common to have a breakpoint inside a shared library.
4777 Shared libraries can be loaded and unloaded explicitly,
4778 and possibly repeatedly, as the program is executed. To support
4779 this use case, @value{GDBN} updates breakpoint locations whenever
4780 any shared library is loaded or unloaded. Typically, you would
4781 set a breakpoint in a shared library at the beginning of your
4782 debugging session, when the library is not loaded, and when the
4783 symbols from the library are not available. When you try to set
4784 breakpoint, @value{GDBN} will ask you if you want to set
4785 a so called @dfn{pending breakpoint}---breakpoint whose address
4786 is not yet resolved.
4788 After the program is run, whenever a new shared library is loaded,
4789 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4790 shared library contains the symbol or line referred to by some
4791 pending breakpoint, that breakpoint is resolved and becomes an
4792 ordinary breakpoint. When a library is unloaded, all breakpoints
4793 that refer to its symbols or source lines become pending again.
4795 This logic works for breakpoints with multiple locations, too. For
4796 example, if you have a breakpoint in a C@t{++} template function, and
4797 a newly loaded shared library has an instantiation of that template,
4798 a new location is added to the list of locations for the breakpoint.
4800 Except for having unresolved address, pending breakpoints do not
4801 differ from regular breakpoints. You can set conditions or commands,
4802 enable and disable them and perform other breakpoint operations.
4804 @value{GDBN} provides some additional commands for controlling what
4805 happens when the @samp{break} command cannot resolve the location spec
4806 to any code location in your program (@pxref{Location
4809 @kindex set breakpoint pending
4810 @kindex show breakpoint pending
4812 @item set breakpoint pending auto
4813 This is the default behavior. When @value{GDBN} cannot resolve the
4814 location spec, it queries you whether a pending breakpoint should be
4817 @item set breakpoint pending on
4818 This indicates that when @value{GDBN} cannot resolve the location
4819 spec, it should create a pending breakpoint without confirmation.
4821 @item set breakpoint pending off
4822 This indicates that pending breakpoints are not to be created. If
4823 @value{GDBN} cannot resolve the location spec, it aborts the
4824 breakpoint creation with an error. This setting does not affect any
4825 pending breakpoints previously created.
4827 @item show breakpoint pending
4828 Show the current behavior setting for creating pending breakpoints.
4831 The settings above only affect the @code{break} command and its
4832 variants. Once a breakpoint is set, it will be automatically updated
4833 as shared libraries are loaded and unloaded.
4835 @cindex automatic hardware breakpoints
4836 For some targets, @value{GDBN} can automatically decide if hardware or
4837 software breakpoints should be used, depending on whether the
4838 breakpoint address is read-only or read-write. This applies to
4839 breakpoints set with the @code{break} command as well as to internal
4840 breakpoints set by commands like @code{next} and @code{finish}. For
4841 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4844 You can control this automatic behaviour with the following commands:
4846 @kindex set breakpoint auto-hw
4847 @kindex show breakpoint auto-hw
4849 @item set breakpoint auto-hw on
4850 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4851 will try to use the target memory map to decide if software or hardware
4852 breakpoint must be used.
4854 @item set breakpoint auto-hw off
4855 This indicates @value{GDBN} should not automatically select breakpoint
4856 type. If the target provides a memory map, @value{GDBN} will warn when
4857 trying to set software breakpoint at a read-only address.
4860 @value{GDBN} normally implements breakpoints by replacing the program code
4861 at the breakpoint address with a special instruction, which, when
4862 executed, given control to the debugger. By default, the program
4863 code is so modified only when the program is resumed. As soon as
4864 the program stops, @value{GDBN} restores the original instructions. This
4865 behaviour guards against leaving breakpoints inserted in the
4866 target should gdb abrubptly disconnect. However, with slow remote
4867 targets, inserting and removing breakpoint can reduce the performance.
4868 This behavior can be controlled with the following commands::
4870 @kindex set breakpoint always-inserted
4871 @kindex show breakpoint always-inserted
4873 @item set breakpoint always-inserted off
4874 All breakpoints, including newly added by the user, are inserted in
4875 the target only when the target is resumed. All breakpoints are
4876 removed from the target when it stops. This is the default mode.
4878 @item set breakpoint always-inserted on
4879 Causes all breakpoints to be inserted in the target at all times. If
4880 the user adds a new breakpoint, or changes an existing breakpoint, the
4881 breakpoints in the target are updated immediately. A breakpoint is
4882 removed from the target only when breakpoint itself is deleted.
4885 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4886 when a breakpoint breaks. If the condition is true, then the process being
4887 debugged stops, otherwise the process is resumed.
4889 If the target supports evaluating conditions on its end, @value{GDBN} may
4890 download the breakpoint, together with its conditions, to it.
4892 This feature can be controlled via the following commands:
4894 @kindex set breakpoint condition-evaluation
4895 @kindex show breakpoint condition-evaluation
4897 @item set breakpoint condition-evaluation host
4898 This option commands @value{GDBN} to evaluate the breakpoint
4899 conditions on the host's side. Unconditional breakpoints are sent to
4900 the target which in turn receives the triggers and reports them back to GDB
4901 for condition evaluation. This is the standard evaluation mode.
4903 @item set breakpoint condition-evaluation target
4904 This option commands @value{GDBN} to download breakpoint conditions
4905 to the target at the moment of their insertion. The target
4906 is responsible for evaluating the conditional expression and reporting
4907 breakpoint stop events back to @value{GDBN} whenever the condition
4908 is true. Due to limitations of target-side evaluation, some conditions
4909 cannot be evaluated there, e.g., conditions that depend on local data
4910 that is only known to the host. Examples include
4911 conditional expressions involving convenience variables, complex types
4912 that cannot be handled by the agent expression parser and expressions
4913 that are too long to be sent over to the target, specially when the
4914 target is a remote system. In these cases, the conditions will be
4915 evaluated by @value{GDBN}.
4917 @item set breakpoint condition-evaluation auto
4918 This is the default mode. If the target supports evaluating breakpoint
4919 conditions on its end, @value{GDBN} will download breakpoint conditions to
4920 the target (limitations mentioned previously apply). If the target does
4921 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4922 to evaluating all these conditions on the host's side.
4926 @cindex negative breakpoint numbers
4927 @cindex internal @value{GDBN} breakpoints
4928 @value{GDBN} itself sometimes sets breakpoints in your program for
4929 special purposes, such as proper handling of @code{longjmp} (in C
4930 programs). These internal breakpoints are assigned negative numbers,
4931 starting with @code{-1}; @samp{info breakpoints} does not display them.
4932 You can see these breakpoints with the @value{GDBN} maintenance command
4933 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4936 @node Set Watchpoints
4937 @subsection Setting Watchpoints
4939 @cindex setting watchpoints
4940 You can use a watchpoint to stop execution whenever the value of an
4941 expression changes, without having to predict a particular place where
4942 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4943 The expression may be as simple as the value of a single variable, or
4944 as complex as many variables combined by operators. Examples include:
4948 A reference to the value of a single variable.
4951 An address cast to an appropriate data type. For example,
4952 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4953 address (assuming an @code{int} occupies 4 bytes).
4956 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4957 expression can use any operators valid in the program's native
4958 language (@pxref{Languages}).
4961 You can set a watchpoint on an expression even if the expression can
4962 not be evaluated yet. For instance, you can set a watchpoint on
4963 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4964 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4965 the expression produces a valid value. If the expression becomes
4966 valid in some other way than changing a variable (e.g.@: if the memory
4967 pointed to by @samp{*global_ptr} becomes readable as the result of a
4968 @code{malloc} call), @value{GDBN} may not stop until the next time
4969 the expression changes.
4971 @cindex software watchpoints
4972 @cindex hardware watchpoints
4973 Depending on your system, watchpoints may be implemented in software or
4974 hardware. @value{GDBN} does software watchpointing by single-stepping your
4975 program and testing the variable's value each time, which is hundreds of
4976 times slower than normal execution. (But this may still be worth it, to
4977 catch errors where you have no clue what part of your program is the
4980 On some systems, such as most PowerPC or x86-based targets,
4981 @value{GDBN} includes support for hardware watchpoints, which do not
4982 slow down the running of your program.
4986 @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{]}
4987 Set a watchpoint for an expression. @value{GDBN} will break when the
4988 expression @var{expr} is written into by the program and its value
4989 changes. The simplest (and the most popular) use of this command is
4990 to watch the value of a single variable:
4993 (@value{GDBP}) watch foo
4996 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4997 argument, @value{GDBN} breaks only when the thread identified by
4998 @var{thread-id} changes the value of @var{expr}. If any other threads
4999 change the value of @var{expr}, @value{GDBN} will not break. Note
5000 that watchpoints restricted to a single thread in this way only work
5001 with Hardware Watchpoints.
5003 Similarly, if the @code{task} argument is given, then the watchpoint
5004 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
5006 Ordinarily a watchpoint respects the scope of variables in @var{expr}
5007 (see below). The @code{-location} argument tells @value{GDBN} to
5008 instead watch the memory referred to by @var{expr}. In this case,
5009 @value{GDBN} will evaluate @var{expr}, take the address of the result,
5010 and watch the memory at that address. The type of the result is used
5011 to determine the size of the watched memory. If the expression's
5012 result does not have an address, then @value{GDBN} will print an
5015 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
5016 of masked watchpoints, if the current architecture supports this
5017 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
5018 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
5019 to an address to watch. The mask specifies that some bits of an address
5020 (the bits which are reset in the mask) should be ignored when matching
5021 the address accessed by the inferior against the watchpoint address.
5022 Thus, a masked watchpoint watches many addresses simultaneously---those
5023 addresses whose unmasked bits are identical to the unmasked bits in the
5024 watchpoint address. The @code{mask} argument implies @code{-location}.
5028 (@value{GDBP}) watch foo mask 0xffff00ff
5029 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
5033 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5034 Set a watchpoint that will break when the value of @var{expr} is read
5038 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5039 Set a watchpoint that will break when @var{expr} is either read from
5040 or written into by the program.
5042 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
5043 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
5044 This command prints a list of watchpoints, using the same format as
5045 @code{info break} (@pxref{Set Breaks}).
5048 If you watch for a change in a numerically entered address you need to
5049 dereference it, as the address itself is just a constant number which will
5050 never change. @value{GDBN} refuses to create a watchpoint that watches
5051 a never-changing value:
5054 (@value{GDBP}) watch 0x600850
5055 Cannot watch constant value 0x600850.
5056 (@value{GDBP}) watch *(int *) 0x600850
5057 Watchpoint 1: *(int *) 6293584
5060 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
5061 watchpoints execute very quickly, and the debugger reports a change in
5062 value at the exact instruction where the change occurs. If @value{GDBN}
5063 cannot set a hardware watchpoint, it sets a software watchpoint, which
5064 executes more slowly and reports the change in value at the next
5065 @emph{statement}, not the instruction, after the change occurs.
5067 @cindex use only software watchpoints
5068 You can force @value{GDBN} to use only software watchpoints with the
5069 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
5070 zero, @value{GDBN} will never try to use hardware watchpoints, even if
5071 the underlying system supports them. (Note that hardware-assisted
5072 watchpoints that were set @emph{before} setting
5073 @code{can-use-hw-watchpoints} to zero will still use the hardware
5074 mechanism of watching expression values.)
5077 @item set can-use-hw-watchpoints
5078 @kindex set can-use-hw-watchpoints
5079 Set whether or not to use hardware watchpoints.
5081 @item show can-use-hw-watchpoints
5082 @kindex show can-use-hw-watchpoints
5083 Show the current mode of using hardware watchpoints.
5086 For remote targets, you can restrict the number of hardware
5087 watchpoints @value{GDBN} will use, see @ref{set remote
5088 hardware-breakpoint-limit}.
5090 When you issue the @code{watch} command, @value{GDBN} reports
5093 Hardware watchpoint @var{num}: @var{expr}
5097 if it was able to set a hardware watchpoint.
5099 Currently, the @code{awatch} and @code{rwatch} commands can only set
5100 hardware watchpoints, because accesses to data that don't change the
5101 value of the watched expression cannot be detected without examining
5102 every instruction as it is being executed, and @value{GDBN} does not do
5103 that currently. If @value{GDBN} finds that it is unable to set a
5104 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5105 will print a message like this:
5108 Expression cannot be implemented with read/access watchpoint.
5111 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5112 data type of the watched expression is wider than what a hardware
5113 watchpoint on the target machine can handle. For example, some systems
5114 can only watch regions that are up to 4 bytes wide; on such systems you
5115 cannot set hardware watchpoints for an expression that yields a
5116 double-precision floating-point number (which is typically 8 bytes
5117 wide). As a work-around, it might be possible to break the large region
5118 into a series of smaller ones and watch them with separate watchpoints.
5120 If you set too many hardware watchpoints, @value{GDBN} might be unable
5121 to insert all of them when you resume the execution of your program.
5122 Since the precise number of active watchpoints is unknown until such
5123 time as the program is about to be resumed, @value{GDBN} might not be
5124 able to warn you about this when you set the watchpoints, and the
5125 warning will be printed only when the program is resumed:
5128 Hardware watchpoint @var{num}: Could not insert watchpoint
5132 If this happens, delete or disable some of the watchpoints.
5134 Watching complex expressions that reference many variables can also
5135 exhaust the resources available for hardware-assisted watchpoints.
5136 That's because @value{GDBN} needs to watch every variable in the
5137 expression with separately allocated resources.
5139 If you call a function interactively using @code{print} or @code{call},
5140 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5141 kind of breakpoint or the call completes.
5143 @value{GDBN} automatically deletes watchpoints that watch local
5144 (automatic) variables, or expressions that involve such variables, when
5145 they go out of scope, that is, when the execution leaves the block in
5146 which these variables were defined. In particular, when the program
5147 being debugged terminates, @emph{all} local variables go out of scope,
5148 and so only watchpoints that watch global variables remain set. If you
5149 rerun the program, you will need to set all such watchpoints again. One
5150 way of doing that would be to set a code breakpoint at the entry to the
5151 @code{main} function and when it breaks, set all the watchpoints.
5153 @cindex watchpoints and threads
5154 @cindex threads and watchpoints
5155 In multi-threaded programs, watchpoints will detect changes to the
5156 watched expression from every thread.
5159 @emph{Warning:} In multi-threaded programs, software watchpoints
5160 have only limited usefulness. If @value{GDBN} creates a software
5161 watchpoint, it can only watch the value of an expression @emph{in a
5162 single thread}. If you are confident that the expression can only
5163 change due to the current thread's activity (and if you are also
5164 confident that no other thread can become current), then you can use
5165 software watchpoints as usual. However, @value{GDBN} may not notice
5166 when a non-current thread's activity changes the expression. (Hardware
5167 watchpoints, in contrast, watch an expression in all threads.)
5170 @xref{set remote hardware-watchpoint-limit}.
5172 @node Set Catchpoints
5173 @subsection Setting Catchpoints
5174 @cindex catchpoints, setting
5175 @cindex exception handlers
5176 @cindex event handling
5178 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5179 kinds of program events, such as C@t{++} exceptions or the loading of a
5180 shared library. Use the @code{catch} command to set a catchpoint.
5184 @item catch @var{event}
5185 Stop when @var{event} occurs. The @var{event} can be any of the following:
5188 @item throw @r{[}@var{regexp}@r{]}
5189 @itemx rethrow @r{[}@var{regexp}@r{]}
5190 @itemx catch @r{[}@var{regexp}@r{]}
5192 @kindex catch rethrow
5194 @cindex stop on C@t{++} exceptions
5195 The throwing, re-throwing, or catching of a C@t{++} exception.
5197 If @var{regexp} is given, then only exceptions whose type matches the
5198 regular expression will be caught.
5200 @vindex $_exception@r{, convenience variable}
5201 The convenience variable @code{$_exception} is available at an
5202 exception-related catchpoint, on some systems. This holds the
5203 exception being thrown.
5205 There are currently some limitations to C@t{++} exception handling in
5210 The support for these commands is system-dependent. Currently, only
5211 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5215 The regular expression feature and the @code{$_exception} convenience
5216 variable rely on the presence of some SDT probes in @code{libstdc++}.
5217 If these probes are not present, then these features cannot be used.
5218 These probes were first available in the GCC 4.8 release, but whether
5219 or not they are available in your GCC also depends on how it was
5223 The @code{$_exception} convenience variable is only valid at the
5224 instruction at which an exception-related catchpoint is set.
5227 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5228 location in the system library which implements runtime exception
5229 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5230 (@pxref{Selection}) to get to your code.
5233 If you call a function interactively, @value{GDBN} normally returns
5234 control to you when the function has finished executing. If the call
5235 raises an exception, however, the call may bypass the mechanism that
5236 returns control to you and cause your program either to abort or to
5237 simply continue running until it hits a breakpoint, catches a signal
5238 that @value{GDBN} is listening for, or exits. This is the case even if
5239 you set a catchpoint for the exception; catchpoints on exceptions are
5240 disabled within interactive calls. @xref{Calling}, for information on
5241 controlling this with @code{set unwind-on-terminating-exception}.
5244 You cannot raise an exception interactively.
5247 You cannot install an exception handler interactively.
5250 @item exception @r{[}@var{name}@r{]}
5251 @kindex catch exception
5252 @cindex Ada exception catching
5253 @cindex catch Ada exceptions
5254 An Ada exception being raised. If an exception name is specified
5255 at the end of the command (eg @code{catch exception Program_Error}),
5256 the debugger will stop only when this specific exception is raised.
5257 Otherwise, the debugger stops execution when any Ada exception is raised.
5259 When inserting an exception catchpoint on a user-defined exception whose
5260 name is identical to one of the exceptions defined by the language, the
5261 fully qualified name must be used as the exception name. Otherwise,
5262 @value{GDBN} will assume that it should stop on the pre-defined exception
5263 rather than the user-defined one. For instance, assuming an exception
5264 called @code{Constraint_Error} is defined in package @code{Pck}, then
5265 the command to use to catch such exceptions is @kbd{catch exception
5266 Pck.Constraint_Error}.
5268 @vindex $_ada_exception@r{, convenience variable}
5269 The convenience variable @code{$_ada_exception} holds the address of
5270 the exception being thrown. This can be useful when setting a
5271 condition for such a catchpoint.
5273 @item exception unhandled
5274 @kindex catch exception unhandled
5275 An exception that was raised but is not handled by the program. The
5276 convenience variable @code{$_ada_exception} is set as for @code{catch
5279 @item handlers @r{[}@var{name}@r{]}
5280 @kindex catch handlers
5281 @cindex Ada exception handlers catching
5282 @cindex catch Ada exceptions when handled
5283 An Ada exception being handled. If an exception name is
5284 specified at the end of the command
5285 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5286 only when this specific exception is handled.
5287 Otherwise, the debugger stops execution when any Ada exception is handled.
5289 When inserting a handlers catchpoint on a user-defined
5290 exception whose name is identical to one of the exceptions
5291 defined by the language, the fully qualified name must be used
5292 as the exception name. Otherwise, @value{GDBN} will assume that it
5293 should stop on the pre-defined exception rather than the
5294 user-defined one. For instance, assuming an exception called
5295 @code{Constraint_Error} is defined in package @code{Pck}, then the
5296 command to use to catch such exceptions handling is
5297 @kbd{catch handlers Pck.Constraint_Error}.
5299 The convenience variable @code{$_ada_exception} is set as for
5300 @code{catch exception}.
5303 @kindex catch assert
5304 A failed Ada assertion. Note that the convenience variable
5305 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5309 @cindex break on fork/exec
5310 A call to @code{exec}.
5312 @anchor{catch syscall}
5314 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5315 @kindex catch syscall
5316 @cindex break on a system call.
5317 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5318 syscall is a mechanism for application programs to request a service
5319 from the operating system (OS) or one of the OS system services.
5320 @value{GDBN} can catch some or all of the syscalls issued by the
5321 debuggee, and show the related information for each syscall. If no
5322 argument is specified, calls to and returns from all system calls
5325 @var{name} can be any system call name that is valid for the
5326 underlying OS. Just what syscalls are valid depends on the OS. On
5327 GNU and Unix systems, you can find the full list of valid syscall
5328 names on @file{/usr/include/asm/unistd.h}.
5330 @c For MS-Windows, the syscall names and the corresponding numbers
5331 @c can be found, e.g., on this URL:
5332 @c http://www.metasploit.com/users/opcode/syscalls.html
5333 @c but we don't support Windows syscalls yet.
5335 Normally, @value{GDBN} knows in advance which syscalls are valid for
5336 each OS, so you can use the @value{GDBN} command-line completion
5337 facilities (@pxref{Completion,, command completion}) to list the
5340 You may also specify the system call numerically. A syscall's
5341 number is the value passed to the OS's syscall dispatcher to
5342 identify the requested service. When you specify the syscall by its
5343 name, @value{GDBN} uses its database of syscalls to convert the name
5344 into the corresponding numeric code, but using the number directly
5345 may be useful if @value{GDBN}'s database does not have the complete
5346 list of syscalls on your system (e.g., because @value{GDBN} lags
5347 behind the OS upgrades).
5349 You may specify a group of related syscalls to be caught at once using
5350 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5351 instance, on some platforms @value{GDBN} allows you to catch all
5352 network related syscalls, by passing the argument @code{group:network}
5353 to @code{catch syscall}. Note that not all syscall groups are
5354 available in every system. You can use the command completion
5355 facilities (@pxref{Completion,, command completion}) to list the
5356 syscall groups available on your environment.
5358 The example below illustrates how this command works if you don't provide
5362 (@value{GDBP}) catch syscall
5363 Catchpoint 1 (syscall)
5365 Starting program: /tmp/catch-syscall
5367 Catchpoint 1 (call to syscall 'close'), \
5368 0xffffe424 in __kernel_vsyscall ()
5372 Catchpoint 1 (returned from syscall 'close'), \
5373 0xffffe424 in __kernel_vsyscall ()
5377 Here is an example of catching a system call by name:
5380 (@value{GDBP}) catch syscall chroot
5381 Catchpoint 1 (syscall 'chroot' [61])
5383 Starting program: /tmp/catch-syscall
5385 Catchpoint 1 (call to syscall 'chroot'), \
5386 0xffffe424 in __kernel_vsyscall ()
5390 Catchpoint 1 (returned from syscall 'chroot'), \
5391 0xffffe424 in __kernel_vsyscall ()
5395 An example of specifying a system call numerically. In the case
5396 below, the syscall number has a corresponding entry in the XML
5397 file, so @value{GDBN} finds its name and prints it:
5400 (@value{GDBP}) catch syscall 252
5401 Catchpoint 1 (syscall(s) 'exit_group')
5403 Starting program: /tmp/catch-syscall
5405 Catchpoint 1 (call to syscall 'exit_group'), \
5406 0xffffe424 in __kernel_vsyscall ()
5410 Program exited normally.
5414 Here is an example of catching a syscall group:
5417 (@value{GDBP}) catch syscall group:process
5418 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5419 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5420 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5422 Starting program: /tmp/catch-syscall
5424 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5425 from /lib64/ld-linux-x86-64.so.2
5431 However, there can be situations when there is no corresponding name
5432 in XML file for that syscall number. In this case, @value{GDBN} prints
5433 a warning message saying that it was not able to find the syscall name,
5434 but the catchpoint will be set anyway. See the example below:
5437 (@value{GDBP}) catch syscall 764
5438 warning: The number '764' does not represent a known syscall.
5439 Catchpoint 2 (syscall 764)
5443 If you configure @value{GDBN} using the @samp{--without-expat} option,
5444 it will not be able to display syscall names. Also, if your
5445 architecture does not have an XML file describing its system calls,
5446 you will not be able to see the syscall names. It is important to
5447 notice that these two features are used for accessing the syscall
5448 name database. In either case, you will see a warning like this:
5451 (@value{GDBP}) catch syscall
5452 warning: Could not open "syscalls/i386-linux.xml"
5453 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5454 GDB will not be able to display syscall names.
5455 Catchpoint 1 (syscall)
5459 Of course, the file name will change depending on your architecture and system.
5461 Still using the example above, you can also try to catch a syscall by its
5462 number. In this case, you would see something like:
5465 (@value{GDBP}) catch syscall 252
5466 Catchpoint 1 (syscall(s) 252)
5469 Again, in this case @value{GDBN} would not be able to display syscall's names.
5473 A call to @code{fork}.
5477 A call to @code{vfork}.
5479 @item load @r{[}@var{regexp}@r{]}
5480 @itemx unload @r{[}@var{regexp}@r{]}
5482 @kindex catch unload
5483 The loading or unloading of a shared library. If @var{regexp} is
5484 given, then the catchpoint will stop only if the regular expression
5485 matches one of the affected libraries.
5487 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5488 @kindex catch signal
5489 The delivery of a signal.
5491 With no arguments, this catchpoint will catch any signal that is not
5492 used internally by @value{GDBN}, specifically, all signals except
5493 @samp{SIGTRAP} and @samp{SIGINT}.
5495 With the argument @samp{all}, all signals, including those used by
5496 @value{GDBN}, will be caught. This argument cannot be used with other
5499 Otherwise, the arguments are a list of signal names as given to
5500 @code{handle} (@pxref{Signals}). Only signals specified in this list
5503 One reason that @code{catch signal} can be more useful than
5504 @code{handle} is that you can attach commands and conditions to the
5507 When a signal is caught by a catchpoint, the signal's @code{stop} and
5508 @code{print} settings, as specified by @code{handle}, are ignored.
5509 However, whether the signal is still delivered to the inferior depends
5510 on the @code{pass} setting; this can be changed in the catchpoint's
5515 @item tcatch @var{event}
5517 Set a catchpoint that is enabled only for one stop. The catchpoint is
5518 automatically deleted after the first time the event is caught.
5522 Use the @code{info break} command to list the current catchpoints.
5526 @subsection Deleting Breakpoints
5528 @cindex clearing breakpoints, watchpoints, catchpoints
5529 @cindex deleting breakpoints, watchpoints, catchpoints
5530 It is often necessary to eliminate a breakpoint, watchpoint, or
5531 catchpoint once it has done its job and you no longer want your program
5532 to stop there. This is called @dfn{deleting} the breakpoint. A
5533 breakpoint that has been deleted no longer exists; it is forgotten.
5535 With the @code{clear} command you can delete breakpoints according to
5536 where they are in your program. With the @code{delete} command you can
5537 delete individual breakpoints, watchpoints, or catchpoints by specifying
5538 their breakpoint numbers.
5540 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5541 automatically ignores breakpoints on the first instruction to be executed
5542 when you continue execution without changing the execution address.
5547 Delete any breakpoints at the next instruction to be executed in the
5548 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5549 the innermost frame is selected, this is a good way to delete a
5550 breakpoint where your program just stopped.
5552 @item clear @var{locspec}
5553 Delete any breakpoint with a code location that corresponds to
5554 @var{locspec}. @xref{Location Specifications}, for the various forms
5555 of @var{locspec}. Which code locations correspond to @var{locspec}
5556 depends on the form used in the location specification @var{locspec}:
5560 @itemx @var{filename}:@var{linenum}
5561 @itemx -line @var{linenum}
5562 @itemx -source @var{filename} -line @var{linenum}
5563 If @var{locspec} specifies a line number, with or without a file name,
5564 the command deletes any breakpoint with a code location that is at or
5565 within the specified line @var{linenum} in files that match the
5566 specified @var{filename}. If @var{filename} is omitted, it defaults
5567 to the current source file.
5569 @item *@var{address}
5570 If @var{locspec} specifies an address, the command deletes any
5571 breakpoint with a code location that is at the given @var{address}.
5573 @item @var{function}
5574 @itemx -function @var{function}
5575 If @var{locspec} specifies a function, the command deletes any
5576 breakpoint with a code location that is at the entry to any function
5577 whose name matches @var{function}.
5580 Ambiguity in names of files and functions can be resolved as described
5581 in @ref{Location Specifications}.
5583 @cindex delete breakpoints
5585 @kindex d @r{(@code{delete})}
5586 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5587 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5588 list specified as argument. If no argument is specified, delete all
5589 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5590 confirm off}). You can abbreviate this command as @code{d}.
5594 @subsection Disabling Breakpoints
5596 @cindex enable/disable a breakpoint
5597 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5598 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5599 it had been deleted, but remembers the information on the breakpoint so
5600 that you can @dfn{enable} it again later.
5602 You disable and enable breakpoints, watchpoints, and catchpoints with
5603 the @code{enable} and @code{disable} commands, optionally specifying
5604 one or more breakpoint numbers as arguments. Use @code{info break} to
5605 print a list of all breakpoints, watchpoints, and catchpoints if you
5606 do not know which numbers to use.
5608 Disabling and enabling a breakpoint that has multiple locations
5609 affects all of its locations.
5611 A breakpoint, watchpoint, or catchpoint can have any of several
5612 different states of enablement:
5616 Enabled. The breakpoint stops your program. A breakpoint set
5617 with the @code{break} command starts out in this state.
5619 Disabled. The breakpoint has no effect on your program.
5621 Enabled once. The breakpoint stops your program, but then becomes
5624 Enabled for a count. The breakpoint stops your program for the next
5625 N times, then becomes disabled.
5627 Enabled for deletion. The breakpoint stops your program, but
5628 immediately after it does so it is deleted permanently. A breakpoint
5629 set with the @code{tbreak} command starts out in this state.
5632 You can use the following commands to enable or disable breakpoints,
5633 watchpoints, and catchpoints:
5637 @kindex dis @r{(@code{disable})}
5638 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5639 Disable the specified breakpoints---or all breakpoints, if none are
5640 listed. A disabled breakpoint has no effect but is not forgotten. All
5641 options such as ignore-counts, conditions and commands are remembered in
5642 case the breakpoint is enabled again later. You may abbreviate
5643 @code{disable} as @code{dis}.
5646 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5647 Enable the specified breakpoints (or all defined breakpoints). They
5648 become effective once again in stopping your program.
5650 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5651 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5652 of these breakpoints immediately after stopping your program.
5654 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5655 Enable the specified breakpoints temporarily. @value{GDBN} records
5656 @var{count} with each of the specified breakpoints, and decrements a
5657 breakpoint's count when it is hit. When any count reaches 0,
5658 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5659 count (@pxref{Conditions, ,Break Conditions}), that will be
5660 decremented to 0 before @var{count} is affected.
5662 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5663 Enable the specified breakpoints to work once, then die. @value{GDBN}
5664 deletes any of these breakpoints as soon as your program stops there.
5665 Breakpoints set by the @code{tbreak} command start out in this state.
5668 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5669 @c confusing: tbreak is also initially enabled.
5670 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5671 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5672 subsequently, they become disabled or enabled only when you use one of
5673 the commands above. (The command @code{until} can set and delete a
5674 breakpoint of its own, but it does not change the state of your other
5675 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5679 @subsection Break Conditions
5680 @cindex conditional breakpoints
5681 @cindex breakpoint conditions
5683 @c FIXME what is scope of break condition expr? Context where wanted?
5684 @c in particular for a watchpoint?
5685 The simplest sort of breakpoint breaks every time your program reaches a
5686 specified place. You can also specify a @dfn{condition} for a
5687 breakpoint. A condition is just a Boolean expression in your
5688 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5689 a condition evaluates the expression each time your program reaches it,
5690 and your program stops only if the condition is @emph{true}.
5692 This is the converse of using assertions for program validation; in that
5693 situation, you want to stop when the assertion is violated---that is,
5694 when the condition is false. In C, if you want to test an assertion expressed
5695 by the condition @var{assert}, you should set the condition
5696 @samp{! @var{assert}} on the appropriate breakpoint.
5698 Conditions are also accepted for watchpoints; you may not need them,
5699 since a watchpoint is inspecting the value of an expression anyhow---but
5700 it might be simpler, say, to just set a watchpoint on a variable name,
5701 and specify a condition that tests whether the new value is an interesting
5704 Break conditions can have side effects, and may even call functions in
5705 your program. This can be useful, for example, to activate functions
5706 that log program progress, or to use your own print functions to
5707 format special data structures. The effects are completely predictable
5708 unless there is another enabled breakpoint at the same address. (In
5709 that case, @value{GDBN} might see the other breakpoint first and stop your
5710 program without checking the condition of this one.) Note that
5711 breakpoint commands are usually more convenient and flexible than break
5713 purpose of performing side effects when a breakpoint is reached
5714 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5716 Breakpoint conditions can also be evaluated on the target's side if
5717 the target supports it. Instead of evaluating the conditions locally,
5718 @value{GDBN} encodes the expression into an agent expression
5719 (@pxref{Agent Expressions}) suitable for execution on the target,
5720 independently of @value{GDBN}. Global variables become raw memory
5721 locations, locals become stack accesses, and so forth.
5723 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5724 when its condition evaluates to true. This mechanism may provide faster
5725 response times depending on the performance characteristics of the target
5726 since it does not need to keep @value{GDBN} informed about
5727 every breakpoint trigger, even those with false conditions.
5729 Break conditions can be specified when a breakpoint is set, by using
5730 @samp{if} in the arguments to the @code{break} command. @xref{Set
5731 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5732 with the @code{condition} command.
5734 You can also use the @code{if} keyword with the @code{watch} command.
5735 The @code{catch} command does not recognize the @code{if} keyword;
5736 @code{condition} is the only way to impose a further condition on a
5741 @item condition @var{bnum} @var{expression}
5742 Specify @var{expression} as the break condition for breakpoint,
5743 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5744 breakpoint @var{bnum} stops your program only if the value of
5745 @var{expression} is true (nonzero, in C). When you use
5746 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5747 syntactic correctness, and to determine whether symbols in it have
5748 referents in the context of your breakpoint. If @var{expression} uses
5749 symbols not referenced in the context of the breakpoint, @value{GDBN}
5750 prints an error message:
5753 No symbol "foo" in current context.
5758 not actually evaluate @var{expression} at the time the @code{condition}
5759 command (or a command that sets a breakpoint with a condition, like
5760 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5762 @item condition -force @var{bnum} @var{expression}
5763 When the @code{-force} flag is used, define the condition even if
5764 @var{expression} is invalid at all the current locations of breakpoint
5765 @var{bnum}. This is similar to the @code{-force-condition} option
5766 of the @code{break} command.
5768 @item condition @var{bnum}
5769 Remove the condition from breakpoint number @var{bnum}. It becomes
5770 an ordinary unconditional breakpoint.
5773 @cindex ignore count (of breakpoint)
5774 A special case of a breakpoint condition is to stop only when the
5775 breakpoint has been reached a certain number of times. This is so
5776 useful that there is a special way to do it, using the @dfn{ignore
5777 count} of the breakpoint. Every breakpoint has an ignore count, which
5778 is an integer. Most of the time, the ignore count is zero, and
5779 therefore has no effect. But if your program reaches a breakpoint whose
5780 ignore count is positive, then instead of stopping, it just decrements
5781 the ignore count by one and continues. As a result, if the ignore count
5782 value is @var{n}, the breakpoint does not stop the next @var{n} times
5783 your program reaches it.
5787 @item ignore @var{bnum} @var{count}
5788 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5789 The next @var{count} times the breakpoint is reached, your program's
5790 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5793 To make the breakpoint stop the next time it is reached, specify
5796 When you use @code{continue} to resume execution of your program from a
5797 breakpoint, you can specify an ignore count directly as an argument to
5798 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5799 Stepping,,Continuing and Stepping}.
5801 If a breakpoint has a positive ignore count and a condition, the
5802 condition is not checked. Once the ignore count reaches zero,
5803 @value{GDBN} resumes checking the condition.
5805 You could achieve the effect of the ignore count with a condition such
5806 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5807 is decremented each time. @xref{Convenience Vars, ,Convenience
5811 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5814 @node Break Commands
5815 @subsection Breakpoint Command Lists
5817 @cindex breakpoint commands
5818 You can give any breakpoint (or watchpoint or catchpoint) a series of
5819 commands to execute when your program stops due to that breakpoint. For
5820 example, you might want to print the values of certain expressions, or
5821 enable other breakpoints.
5825 @kindex end@r{ (breakpoint commands)}
5826 @item commands @r{[}@var{list}@dots{}@r{]}
5827 @itemx @dots{} @var{command-list} @dots{}
5829 Specify a list of commands for the given breakpoints. The commands
5830 themselves appear on the following lines. Type a line containing just
5831 @code{end} to terminate the commands.
5833 To remove all commands from a breakpoint, type @code{commands} and
5834 follow it immediately with @code{end}; that is, give no commands.
5836 With no argument, @code{commands} refers to the last breakpoint,
5837 watchpoint, or catchpoint set (not to the breakpoint most recently
5838 encountered). If the most recent breakpoints were set with a single
5839 command, then the @code{commands} will apply to all the breakpoints
5840 set by that command. This applies to breakpoints set by
5841 @code{rbreak}, and also applies when a single @code{break} command
5842 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5846 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5847 disabled within a @var{command-list}.
5849 Inside a command list, you can use the command
5850 @kbd{disable $_hit_bpnum} to disable the encountered breakpoint.
5852 If your breakpoint has several code locations, the command
5853 @kbd{disable $_hit_bpnum.$_hit_locno} will disable the specific breakpoint
5854 code location encountered. If the breakpoint has only one location,
5855 this command will disable the encountered breakpoint.
5857 You can use breakpoint commands to start your program up again. Simply
5858 use the @code{continue} command, or @code{step}, or any other command
5859 that resumes execution.
5861 Any other commands in the command list, after a command that resumes
5862 execution, are ignored. This is because any time you resume execution
5863 (even with a simple @code{next} or @code{step}), you may encounter
5864 another breakpoint---which could have its own command list, leading to
5865 ambiguities about which list to execute.
5868 If the first command you specify in a command list is @code{silent}, the
5869 usual message about stopping at a breakpoint is not printed. This may
5870 be desirable for breakpoints that are to print a specific message and
5871 then continue. If none of the remaining commands print anything, you
5872 see no sign that the breakpoint was reached. @code{silent} is
5873 meaningful only at the beginning of a breakpoint command list.
5875 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5876 print precisely controlled output, and are often useful in silent
5877 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5879 For example, here is how you could use breakpoint commands to print the
5880 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5886 printf "x is %d\n",x
5891 One application for breakpoint commands is to compensate for one bug so
5892 you can test for another. Put a breakpoint just after the erroneous line
5893 of code, give it a condition to detect the case in which something
5894 erroneous has been done, and give it commands to assign correct values
5895 to any variables that need them. End with the @code{continue} command
5896 so that your program does not stop, and start with the @code{silent}
5897 command so that no output is produced. Here is an example:
5908 @node Dynamic Printf
5909 @subsection Dynamic Printf
5911 @cindex dynamic printf
5913 The dynamic printf command @code{dprintf} combines a breakpoint with
5914 formatted printing of your program's data to give you the effect of
5915 inserting @code{printf} calls into your program on-the-fly, without
5916 having to recompile it.
5918 In its most basic form, the output goes to the GDB console. However,
5919 you can set the variable @code{dprintf-style} for alternate handling.
5920 For instance, you can ask to format the output by calling your
5921 program's @code{printf} function. This has the advantage that the
5922 characters go to the program's output device, so they can recorded in
5923 redirects to files and so forth.
5925 If you are doing remote debugging with a stub or agent, you can also
5926 ask to have the printf handled by the remote agent. In addition to
5927 ensuring that the output goes to the remote program's device along
5928 with any other output the program might produce, you can also ask that
5929 the dprintf remain active even after disconnecting from the remote
5930 target. Using the stub/agent is also more efficient, as it can do
5931 everything without needing to communicate with @value{GDBN}.
5935 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
5936 Whenever execution reaches a code location that results from resolving
5937 @var{locspec}, print the values of one or more @var{expressions} under
5938 the control of the string @var{template}. To print several values,
5939 separate them with commas.
5941 @item set dprintf-style @var{style}
5942 Set the dprintf output to be handled in one of several different
5943 styles enumerated below. A change of style affects all existing
5944 dynamic printfs immediately. (If you need individual control over the
5945 print commands, simply define normal breakpoints with
5946 explicitly-supplied command lists.)
5950 @kindex dprintf-style gdb
5951 Handle the output using the @value{GDBN} @code{printf} command.
5954 @kindex dprintf-style call
5955 Handle the output by calling a function in your program (normally
5959 @kindex dprintf-style agent
5960 Have the remote debugging agent (such as @code{gdbserver}) handle
5961 the output itself. This style is only available for agents that
5962 support running commands on the target.
5965 @item set dprintf-function @var{function}
5966 Set the function to call if the dprintf style is @code{call}. By
5967 default its value is @code{printf}. You may set it to any expression.
5968 that @value{GDBN} can evaluate to a function, as per the @code{call}
5971 @item set dprintf-channel @var{channel}
5972 Set a ``channel'' for dprintf. If set to a non-empty value,
5973 @value{GDBN} will evaluate it as an expression and pass the result as
5974 a first argument to the @code{dprintf-function}, in the manner of
5975 @code{fprintf} and similar functions. Otherwise, the dprintf format
5976 string will be the first argument, in the manner of @code{printf}.
5978 As an example, if you wanted @code{dprintf} output to go to a logfile
5979 that is a standard I/O stream assigned to the variable @code{mylog},
5980 you could do the following:
5983 (gdb) set dprintf-style call
5984 (gdb) set dprintf-function fprintf
5985 (gdb) set dprintf-channel mylog
5986 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5987 Dprintf 1 at 0x123456: file main.c, line 25.
5989 1 dprintf keep y 0x00123456 in main at main.c:25
5990 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5995 Note that the @code{info break} displays the dynamic printf commands
5996 as normal breakpoint commands; you can thus easily see the effect of
5997 the variable settings.
5999 @item set disconnected-dprintf on
6000 @itemx set disconnected-dprintf off
6001 @kindex set disconnected-dprintf
6002 Choose whether @code{dprintf} commands should continue to run if
6003 @value{GDBN} has disconnected from the target. This only applies
6004 if the @code{dprintf-style} is @code{agent}.
6006 @item show disconnected-dprintf off
6007 @kindex show disconnected-dprintf
6008 Show the current choice for disconnected @code{dprintf}.
6012 @value{GDBN} does not check the validity of function and channel,
6013 relying on you to supply values that are meaningful for the contexts
6014 in which they are being used. For instance, the function and channel
6015 may be the values of local variables, but if that is the case, then
6016 all enabled dynamic prints must be at locations within the scope of
6017 those locals. If evaluation fails, @value{GDBN} will report an error.
6019 @node Save Breakpoints
6020 @subsection How to save breakpoints to a file
6022 To save breakpoint definitions to a file use the @w{@code{save
6023 breakpoints}} command.
6026 @kindex save breakpoints
6027 @cindex save breakpoints to a file for future sessions
6028 @item save breakpoints [@var{filename}]
6029 This command saves all current breakpoint definitions together with
6030 their commands and ignore counts, into a file @file{@var{filename}}
6031 suitable for use in a later debugging session. This includes all
6032 types of breakpoints (breakpoints, watchpoints, catchpoints,
6033 tracepoints). To read the saved breakpoint definitions, use the
6034 @code{source} command (@pxref{Command Files}). Note that watchpoints
6035 with expressions involving local variables may fail to be recreated
6036 because it may not be possible to access the context where the
6037 watchpoint is valid anymore. Because the saved breakpoint definitions
6038 are simply a sequence of @value{GDBN} commands that recreate the
6039 breakpoints, you can edit the file in your favorite editing program,
6040 and remove the breakpoint definitions you're not interested in, or
6041 that can no longer be recreated.
6044 @node Static Probe Points
6045 @subsection Static Probe Points
6047 @cindex static probe point, SystemTap
6048 @cindex static probe point, DTrace
6049 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
6050 for Statically Defined Tracing, and the probes are designed to have a tiny
6051 runtime code and data footprint, and no dynamic relocations.
6053 Currently, the following types of probes are supported on
6054 ELF-compatible systems:
6058 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
6059 @acronym{SDT} probes@footnote{See
6060 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
6061 for more information on how to add @code{SystemTap} @acronym{SDT}
6062 probes in your applications.}. @code{SystemTap} probes are usable
6063 from assembly, C and C@t{++} languages@footnote{See
6064 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
6065 for a good reference on how the @acronym{SDT} probes are implemented.}.
6067 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
6068 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
6072 @cindex semaphores on static probe points
6073 Some @code{SystemTap} probes have an associated semaphore variable;
6074 for instance, this happens automatically if you defined your probe
6075 using a DTrace-style @file{.d} file. If your probe has a semaphore,
6076 @value{GDBN} will automatically enable it when you specify a
6077 breakpoint using the @samp{-probe-stap} notation. But, if you put a
6078 breakpoint at a probe's location by some other method (e.g.,
6079 @code{break file:line}), then @value{GDBN} will not automatically set
6080 the semaphore. @code{DTrace} probes do not support semaphores.
6082 You can examine the available static static probes using @code{info
6083 probes}, with optional arguments:
6087 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6088 If given, @var{type} is either @code{stap} for listing
6089 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
6090 probes. If omitted all probes are listed regardless of their types.
6092 If given, @var{provider} is a regular expression used to match against provider
6093 names when selecting which probes to list. If omitted, probes by all
6094 probes from all providers are listed.
6096 If given, @var{name} is a regular expression to match against probe names
6097 when selecting which probes to list. If omitted, probe names are not
6098 considered when deciding whether to display them.
6100 If given, @var{objfile} is a regular expression used to select which
6101 object files (executable or shared libraries) to examine. If not
6102 given, all object files are considered.
6104 @item info probes all
6105 List the available static probes, from all types.
6108 @cindex enabling and disabling probes
6109 Some probe points can be enabled and/or disabled. The effect of
6110 enabling or disabling a probe depends on the type of probe being
6111 handled. Some @code{DTrace} probes can be enabled or
6112 disabled, but @code{SystemTap} probes cannot be disabled.
6114 You can enable (or disable) one or more probes using the following
6115 commands, with optional arguments:
6117 @anchor{enable probes}
6119 @kindex enable probes
6120 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6121 If given, @var{provider} is a regular expression used to match against
6122 provider names when selecting which probes to enable. If omitted,
6123 all probes from all providers are enabled.
6125 If given, @var{name} is a regular expression to match against probe
6126 names when selecting which probes to enable. If omitted, probe names
6127 are not considered when deciding whether to enable them.
6129 If given, @var{objfile} is a regular expression used to select which
6130 object files (executable or shared libraries) to examine. If not
6131 given, all object files are considered.
6133 @kindex disable probes
6134 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6135 See the @code{enable probes} command above for a description of the
6136 optional arguments accepted by this command.
6139 @vindex $_probe_arg@r{, convenience variable}
6140 A probe may specify up to twelve arguments. These are available at the
6141 point at which the probe is defined---that is, when the current PC is
6142 at the probe's location. The arguments are available using the
6143 convenience variables (@pxref{Convenience Vars})
6144 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6145 probes each probe argument is an integer of the appropriate size;
6146 types are not preserved. In @code{DTrace} probes types are preserved
6147 provided that they are recognized as such by @value{GDBN}; otherwise
6148 the value of the probe argument will be a long integer. The
6149 convenience variable @code{$_probe_argc} holds the number of arguments
6150 at the current probe point.
6152 These variables are always available, but attempts to access them at
6153 any location other than a probe point will cause @value{GDBN} to give
6157 @c @ifclear BARETARGET
6158 @node Error in Breakpoints
6159 @subsection ``Cannot insert breakpoints''
6161 If you request too many active hardware-assisted breakpoints and
6162 watchpoints, you will see this error message:
6164 @c FIXME: the precise wording of this message may change; the relevant
6165 @c source change is not committed yet (Sep 3, 1999).
6167 Stopped; cannot insert breakpoints.
6168 You may have requested too many hardware breakpoints and watchpoints.
6172 This message is printed when you attempt to resume the program, since
6173 only then @value{GDBN} knows exactly how many hardware breakpoints and
6174 watchpoints it needs to insert.
6176 When this message is printed, you need to disable or remove some of the
6177 hardware-assisted breakpoints and watchpoints, and then continue.
6179 @node Breakpoint-related Warnings
6180 @subsection ``Breakpoint address adjusted...''
6181 @cindex breakpoint address adjusted
6183 Some processor architectures place constraints on the addresses at
6184 which breakpoints may be placed. For architectures thus constrained,
6185 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6186 with the constraints dictated by the architecture.
6188 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6189 a VLIW architecture in which a number of RISC-like instructions may be
6190 bundled together for parallel execution. The FR-V architecture
6191 constrains the location of a breakpoint instruction within such a
6192 bundle to the instruction with the lowest address. @value{GDBN}
6193 honors this constraint by adjusting a breakpoint's address to the
6194 first in the bundle.
6196 It is not uncommon for optimized code to have bundles which contain
6197 instructions from different source statements, thus it may happen that
6198 a breakpoint's address will be adjusted from one source statement to
6199 another. Since this adjustment may significantly alter @value{GDBN}'s
6200 breakpoint related behavior from what the user expects, a warning is
6201 printed when the breakpoint is first set and also when the breakpoint
6204 A warning like the one below is printed when setting a breakpoint
6205 that's been subject to address adjustment:
6208 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6211 Such warnings are printed both for user settable and @value{GDBN}'s
6212 internal breakpoints. If you see one of these warnings, you should
6213 verify that a breakpoint set at the adjusted address will have the
6214 desired affect. If not, the breakpoint in question may be removed and
6215 other breakpoints may be set which will have the desired behavior.
6216 E.g., it may be sufficient to place the breakpoint at a later
6217 instruction. A conditional breakpoint may also be useful in some
6218 cases to prevent the breakpoint from triggering too often.
6220 @value{GDBN} will also issue a warning when stopping at one of these
6221 adjusted breakpoints:
6224 warning: Breakpoint 1 address previously adjusted from 0x00010414
6228 When this warning is encountered, it may be too late to take remedial
6229 action except in cases where the breakpoint is hit earlier or more
6230 frequently than expected.
6232 @node Continuing and Stepping
6233 @section Continuing and Stepping
6237 @cindex resuming execution
6238 @dfn{Continuing} means resuming program execution until your program
6239 completes normally. In contrast, @dfn{stepping} means executing just
6240 one more ``step'' of your program, where ``step'' may mean either one
6241 line of source code, or one machine instruction (depending on what
6242 particular command you use). Either when continuing or when stepping,
6243 your program may stop even sooner, due to a breakpoint or a signal. (If
6244 it stops due to a signal, you may want to use @code{handle}, or use
6245 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6246 or you may step into the signal's handler (@pxref{stepping and signal
6251 @kindex c @r{(@code{continue})}
6252 @kindex fg @r{(resume foreground execution)}
6253 @item continue @r{[}@var{ignore-count}@r{]}
6254 @itemx c @r{[}@var{ignore-count}@r{]}
6255 @itemx fg @r{[}@var{ignore-count}@r{]}
6256 Resume program execution, at the address where your program last stopped;
6257 any breakpoints set at that address are bypassed. The optional argument
6258 @var{ignore-count} allows you to specify a further number of times to
6259 ignore a breakpoint at this location; its effect is like that of
6260 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6262 The argument @var{ignore-count} is meaningful only when your program
6263 stopped due to a breakpoint. At other times, the argument to
6264 @code{continue} is ignored.
6266 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6267 debugged program is deemed to be the foreground program) are provided
6268 purely for convenience, and have exactly the same behavior as
6272 To resume execution at a different place, you can use @code{return}
6273 (@pxref{Returning, ,Returning from a Function}) to go back to the
6274 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6275 Different Address}) to go to an arbitrary location in your program.
6277 A typical technique for using stepping is to set a breakpoint
6278 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6279 beginning of the function or the section of your program where a problem
6280 is believed to lie, run your program until it stops at that breakpoint,
6281 and then step through the suspect area, examining the variables that are
6282 interesting, until you see the problem happen.
6286 @kindex s @r{(@code{step})}
6288 Continue running your program until control reaches a different source
6289 line, then stop it and return control to @value{GDBN}. This command is
6290 abbreviated @code{s}.
6293 @c "without debugging information" is imprecise; actually "without line
6294 @c numbers in the debugging information". (gcc -g1 has debugging info but
6295 @c not line numbers). But it seems complex to try to make that
6296 @c distinction here.
6297 @emph{Warning:} If you use the @code{step} command while control is
6298 within a function that was compiled without debugging information,
6299 execution proceeds until control reaches a function that does have
6300 debugging information. Likewise, it will not step into a function which
6301 is compiled without debugging information. To step through functions
6302 without debugging information, use the @code{stepi} command, described
6306 The @code{step} command only stops at the first instruction of a source
6307 line. This prevents the multiple stops that could otherwise occur in
6308 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6309 to stop if a function that has debugging information is called within
6310 the line. In other words, @code{step} @emph{steps inside} any functions
6311 called within the line.
6313 Also, the @code{step} command only enters a function if there is line
6314 number information for the function. Otherwise it acts like the
6315 @code{next} command. This avoids problems when using @code{cc -gl}
6316 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6317 was any debugging information about the routine.
6319 @item step @var{count}
6320 Continue running as in @code{step}, but do so @var{count} times. If a
6321 breakpoint is reached, or a signal not related to stepping occurs before
6322 @var{count} steps, stepping stops right away.
6325 @kindex n @r{(@code{next})}
6326 @item next @r{[}@var{count}@r{]}
6327 Continue to the next source line in the current (innermost) stack frame.
6328 This is similar to @code{step}, but function calls that appear within
6329 the line of code are executed without stopping. Execution stops when
6330 control reaches a different line of code at the original stack level
6331 that was executing when you gave the @code{next} command. This command
6332 is abbreviated @code{n}.
6334 An argument @var{count} is a repeat count, as for @code{step}.
6337 @c FIX ME!! Do we delete this, or is there a way it fits in with
6338 @c the following paragraph? --- Vctoria
6340 @c @code{next} within a function that lacks debugging information acts like
6341 @c @code{step}, but any function calls appearing within the code of the
6342 @c function are executed without stopping.
6344 The @code{next} command only stops at the first instruction of a
6345 source line. This prevents multiple stops that could otherwise occur in
6346 @code{switch} statements, @code{for} loops, etc.
6348 @kindex set step-mode
6350 @cindex functions without line info, and stepping
6351 @cindex stepping into functions with no line info
6352 @itemx set step-mode on
6353 The @code{set step-mode on} command causes the @code{step} command to
6354 stop at the first instruction of a function which contains no debug line
6355 information rather than stepping over it.
6357 This is useful in cases where you may be interested in inspecting the
6358 machine instructions of a function which has no symbolic info and do not
6359 want @value{GDBN} to automatically skip over this function.
6361 @item set step-mode off
6362 Causes the @code{step} command to step over any functions which contains no
6363 debug information. This is the default.
6365 @item show step-mode
6366 Show whether @value{GDBN} will stop in or step over functions without
6367 source line debug information.
6370 @kindex fin @r{(@code{finish})}
6372 Continue running until just after function in the selected stack frame
6373 returns. Print the returned value (if any). This command can be
6374 abbreviated as @code{fin}.
6376 Contrast this with the @code{return} command (@pxref{Returning,
6377 ,Returning from a Function}).
6379 @kindex set print finish
6380 @kindex show print finish
6381 @item set print finish @r{[}on|off@r{]}
6382 @itemx show print finish
6383 By default the @code{finish} command will show the value that is
6384 returned by the function. This can be disabled using @code{set print
6385 finish off}. When disabled, the value is still entered into the value
6386 history (@pxref{Value History}), but not displayed.
6389 @kindex u @r{(@code{until})}
6390 @cindex run until specified location
6393 Continue running until a source line past the current line, in the
6394 current stack frame, is reached. This command is used to avoid single
6395 stepping through a loop more than once. It is like the @code{next}
6396 command, except that when @code{until} encounters a jump, it
6397 automatically continues execution until the program counter is greater
6398 than the address of the jump.
6400 This means that when you reach the end of a loop after single stepping
6401 though it, @code{until} makes your program continue execution until it
6402 exits the loop. In contrast, a @code{next} command at the end of a loop
6403 simply steps back to the beginning of the loop, which forces you to step
6404 through the next iteration.
6406 @code{until} always stops your program if it attempts to exit the current
6409 @code{until} may produce somewhat counterintuitive results if the order
6410 of machine code does not match the order of the source lines. For
6411 example, in the following excerpt from a debugging session, the @code{f}
6412 (@code{frame}) command shows that execution is stopped at line
6413 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6417 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6419 (@value{GDBP}) until
6420 195 for ( ; argc > 0; NEXTARG) @{
6423 This happened because, for execution efficiency, the compiler had
6424 generated code for the loop closure test at the end, rather than the
6425 start, of the loop---even though the test in a C @code{for}-loop is
6426 written before the body of the loop. The @code{until} command appeared
6427 to step back to the beginning of the loop when it advanced to this
6428 expression; however, it has not really gone to an earlier
6429 statement---not in terms of the actual machine code.
6431 @code{until} with no argument works by means of single
6432 instruction stepping, and hence is slower than @code{until} with an
6435 @item until @var{locspec}
6436 @itemx u @var{locspec}
6437 Continue running your program until either it reaches a code location
6438 that results from resolving @var{locspec}, or the current stack frame
6439 returns. @var{locspec} is any of the forms described in @ref{Location
6441 This form of the command uses temporary breakpoints, and
6442 hence is quicker than @code{until} without an argument. The specified
6443 location is actually reached only if it is in the current frame. This
6444 implies that @code{until} can be used to skip over recursive function
6445 invocations. For instance in the code below, if the current location is
6446 line @code{96}, issuing @code{until 99} will execute the program up to
6447 line @code{99} in the same invocation of factorial, i.e., after the inner
6448 invocations have returned.
6451 94 int factorial (int value)
6453 96 if (value > 1) @{
6454 97 value *= factorial (value - 1);
6461 @kindex advance @var{locspec}
6462 @item advance @var{locspec}
6463 Continue running your program until either it reaches a code location
6464 that results from resolving @var{locspec}, or the current stack frame
6465 returns. @var{locspec} is any of the forms described in @ref{Location
6466 Specifications}. This command is similar to @code{until}, but
6467 @code{advance} will not skip over recursive function calls, and the
6468 target code location doesn't have to be in the same frame as the
6473 @kindex si @r{(@code{stepi})}
6475 @itemx stepi @var{arg}
6477 Execute one machine instruction, then stop and return to the debugger.
6479 It is often useful to do @samp{display/i $pc} when stepping by machine
6480 instructions. This makes @value{GDBN} automatically display the next
6481 instruction to be executed, each time your program stops. @xref{Auto
6482 Display,, Automatic Display}.
6484 An argument is a repeat count, as in @code{step}.
6488 @kindex ni @r{(@code{nexti})}
6490 @itemx nexti @var{arg}
6492 Execute one machine instruction, but if it is a function call,
6493 proceed until the function returns.
6495 An argument is a repeat count, as in @code{next}.
6499 @anchor{range stepping}
6500 @cindex range stepping
6501 @cindex target-assisted range stepping
6502 By default, and if available, @value{GDBN} makes use of
6503 target-assisted @dfn{range stepping}. In other words, whenever you
6504 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6505 tells the target to step the corresponding range of instruction
6506 addresses instead of issuing multiple single-steps. This speeds up
6507 line stepping, particularly for remote targets. Ideally, there should
6508 be no reason you would want to turn range stepping off. However, it's
6509 possible that a bug in the debug info, a bug in the remote stub (for
6510 remote targets), or even a bug in @value{GDBN} could make line
6511 stepping behave incorrectly when target-assisted range stepping is
6512 enabled. You can use the following command to turn off range stepping
6516 @kindex set range-stepping
6517 @kindex show range-stepping
6518 @item set range-stepping
6519 @itemx show range-stepping
6520 Control whether range stepping is enabled.
6522 If @code{on}, and the target supports it, @value{GDBN} tells the
6523 target to step a range of addresses itself, instead of issuing
6524 multiple single-steps. If @code{off}, @value{GDBN} always issues
6525 single-steps, even if range stepping is supported by the target. The
6526 default is @code{on}.
6530 @node Skipping Over Functions and Files
6531 @section Skipping Over Functions and Files
6532 @cindex skipping over functions and files
6534 The program you are debugging may contain some functions which are
6535 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6536 skip a function, all functions in a file or a particular function in
6537 a particular file when stepping.
6539 For example, consider the following C function:
6550 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6551 are not interested in stepping through @code{boring}. If you run @code{step}
6552 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6553 step over both @code{foo} and @code{boring}!
6555 One solution is to @code{step} into @code{boring} and use the @code{finish}
6556 command to immediately exit it. But this can become tedious if @code{boring}
6557 is called from many places.
6559 A more flexible solution is to execute @kbd{skip boring}. This instructs
6560 @value{GDBN} never to step into @code{boring}. Now when you execute
6561 @code{step} at line 103, you'll step over @code{boring} and directly into
6564 Functions may be skipped by providing either a function name, linespec
6565 (@pxref{Location Specifications}), regular expression that matches the function's
6566 name, file name or a @code{glob}-style pattern that matches the file name.
6568 On Posix systems the form of the regular expression is
6569 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6570 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6571 expression is whatever is provided by the @code{regcomp} function of
6572 the underlying system.
6573 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6574 description of @code{glob}-style patterns.
6578 @item skip @r{[}@var{options}@r{]}
6579 The basic form of the @code{skip} command takes zero or more options
6580 that specify what to skip.
6581 The @var{options} argument is any useful combination of the following:
6584 @item -file @var{file}
6585 @itemx -fi @var{file}
6586 Functions in @var{file} will be skipped over when stepping.
6588 @item -gfile @var{file-glob-pattern}
6589 @itemx -gfi @var{file-glob-pattern}
6590 @cindex skipping over files via glob-style patterns
6591 Functions in files matching @var{file-glob-pattern} will be skipped
6595 (gdb) skip -gfi utils/*.c
6598 @item -function @var{linespec}
6599 @itemx -fu @var{linespec}
6600 Functions named by @var{linespec} or the function containing the line
6601 named by @var{linespec} will be skipped over when stepping.
6602 @xref{Location Specifications}.
6604 @item -rfunction @var{regexp}
6605 @itemx -rfu @var{regexp}
6606 @cindex skipping over functions via regular expressions
6607 Functions whose name matches @var{regexp} will be skipped over when stepping.
6609 This form is useful for complex function names.
6610 For example, there is generally no need to step into C@t{++} @code{std::string}
6611 constructors or destructors. Plus with C@t{++} templates it can be hard to
6612 write out the full name of the function, and often it doesn't matter what
6613 the template arguments are. Specifying the function to be skipped as a
6614 regular expression makes this easier.
6617 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6620 If you want to skip every templated C@t{++} constructor and destructor
6621 in the @code{std} namespace you can do:
6624 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6628 If no options are specified, the function you're currently debugging
6631 @kindex skip function
6632 @item skip function @r{[}@var{linespec}@r{]}
6633 After running this command, the function named by @var{linespec} or the
6634 function containing the line named by @var{linespec} will be skipped over when
6635 stepping. @xref{Location Specifications}.
6637 If you do not specify @var{linespec}, the function you're currently debugging
6640 (If you have a function called @code{file} that you want to skip, use
6641 @kbd{skip function file}.)
6644 @item skip file @r{[}@var{filename}@r{]}
6645 After running this command, any function whose source lives in @var{filename}
6646 will be skipped over when stepping.
6649 (gdb) skip file boring.c
6650 File boring.c will be skipped when stepping.
6653 If you do not specify @var{filename}, functions whose source lives in the file
6654 you're currently debugging will be skipped.
6657 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6658 These are the commands for managing your list of skips:
6662 @item info skip @r{[}@var{range}@r{]}
6663 Print details about the specified skip(s). If @var{range} is not specified,
6664 print a table with details about all functions and files marked for skipping.
6665 @code{info skip} prints the following information about each skip:
6669 A number identifying this skip.
6670 @item Enabled or Disabled
6671 Enabled skips are marked with @samp{y}.
6672 Disabled skips are marked with @samp{n}.
6674 If the file name is a @samp{glob} pattern this is @samp{y}.
6675 Otherwise it is @samp{n}.
6677 The name or @samp{glob} pattern of the file to be skipped.
6678 If no file is specified this is @samp{<none>}.
6680 If the function name is a @samp{regular expression} this is @samp{y}.
6681 Otherwise it is @samp{n}.
6683 The name or regular expression of the function to skip.
6684 If no function is specified this is @samp{<none>}.
6688 @item skip delete @r{[}@var{range}@r{]}
6689 Delete the specified skip(s). If @var{range} is not specified, delete all
6693 @item skip enable @r{[}@var{range}@r{]}
6694 Enable the specified skip(s). If @var{range} is not specified, enable all
6697 @kindex skip disable
6698 @item skip disable @r{[}@var{range}@r{]}
6699 Disable the specified skip(s). If @var{range} is not specified, disable all
6702 @kindex set debug skip
6703 @item set debug skip @r{[}on|off@r{]}
6704 Set whether to print the debug output about skipping files and functions.
6706 @kindex show debug skip
6707 @item show debug skip
6708 Show whether the debug output about skipping files and functions is printed.
6716 A signal is an asynchronous event that can happen in a program. The
6717 operating system defines the possible kinds of signals, and gives each
6718 kind a name and a number. For example, in Unix @code{SIGINT} is the
6719 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6720 @code{SIGSEGV} is the signal a program gets from referencing a place in
6721 memory far away from all the areas in use; @code{SIGALRM} occurs when
6722 the alarm clock timer goes off (which happens only if your program has
6723 requested an alarm).
6725 @cindex fatal signals
6726 Some signals, including @code{SIGALRM}, are a normal part of the
6727 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6728 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6729 program has not specified in advance some other way to handle the signal.
6730 @code{SIGINT} does not indicate an error in your program, but it is normally
6731 fatal so it can carry out the purpose of the interrupt: to kill the program.
6733 @value{GDBN} has the ability to detect any occurrence of a signal in your
6734 program. You can tell @value{GDBN} in advance what to do for each kind of
6737 @cindex handling signals
6738 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6739 @code{SIGALRM} be silently passed to your program
6740 (so as not to interfere with their role in the program's functioning)
6741 but to stop your program immediately whenever an error signal happens.
6742 You can change these settings with the @code{handle} command.
6745 @kindex info signals
6749 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6750 handle each one. You can use this to see the signal numbers of all
6751 the defined types of signals.
6753 @item info signals @var{sig}
6754 Similar, but print information only about the specified signal number.
6756 @code{info handle} is an alias for @code{info signals}.
6758 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6759 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6760 for details about this command.
6763 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6764 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6765 can be the number of a signal or its name (with or without the
6766 @samp{SIG} at the beginning); a list of signal numbers of the form
6767 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6768 known signals. Optional arguments @var{keywords}, described below,
6769 say what change to make.
6773 The keywords allowed by the @code{handle} command can be abbreviated.
6774 Their full names are:
6778 @value{GDBN} should not stop your program when this signal happens. It may
6779 still print a message telling you that the signal has come in.
6782 @value{GDBN} should stop your program when this signal happens. This implies
6783 the @code{print} keyword as well.
6786 @value{GDBN} should print a message when this signal happens.
6789 @value{GDBN} should not mention the occurrence of the signal at all. This
6790 implies the @code{nostop} keyword as well.
6794 @value{GDBN} should allow your program to see this signal; your program
6795 can handle the signal, or else it may terminate if the signal is fatal
6796 and not handled. @code{pass} and @code{noignore} are synonyms.
6800 @value{GDBN} should not allow your program to see this signal.
6801 @code{nopass} and @code{ignore} are synonyms.
6805 When a signal stops your program, the signal is not visible to the
6807 continue. Your program sees the signal then, if @code{pass} is in
6808 effect for the signal in question @emph{at that time}. In other words,
6809 after @value{GDBN} reports a signal, you can use the @code{handle}
6810 command with @code{pass} or @code{nopass} to control whether your
6811 program sees that signal when you continue.
6813 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6814 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6815 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6818 You can also use the @code{signal} command to prevent your program from
6819 seeing a signal, or cause it to see a signal it normally would not see,
6820 or to give it any signal at any time. For example, if your program stopped
6821 due to some sort of memory reference error, you might store correct
6822 values into the erroneous variables and continue, hoping to see more
6823 execution; but your program would probably terminate immediately as
6824 a result of the fatal signal once it saw the signal. To prevent this,
6825 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6828 @cindex stepping and signal handlers
6829 @anchor{stepping and signal handlers}
6831 @value{GDBN} optimizes for stepping the mainline code. If a signal
6832 that has @code{handle nostop} and @code{handle pass} set arrives while
6833 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6834 in progress, @value{GDBN} lets the signal handler run and then resumes
6835 stepping the mainline code once the signal handler returns. In other
6836 words, @value{GDBN} steps over the signal handler. This prevents
6837 signals that you've specified as not interesting (with @code{handle
6838 nostop}) from changing the focus of debugging unexpectedly. Note that
6839 the signal handler itself may still hit a breakpoint, stop for another
6840 signal that has @code{handle stop} in effect, or for any other event
6841 that normally results in stopping the stepping command sooner. Also
6842 note that @value{GDBN} still informs you that the program received a
6843 signal if @code{handle print} is set.
6845 @anchor{stepping into signal handlers}
6847 If you set @code{handle pass} for a signal, and your program sets up a
6848 handler for it, then issuing a stepping command, such as @code{step}
6849 or @code{stepi}, when your program is stopped due to the signal will
6850 step @emph{into} the signal handler (if the target supports that).
6852 Likewise, if you use the @code{queue-signal} command to queue a signal
6853 to be delivered to the current thread when execution of the thread
6854 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6855 stepping command will step into the signal handler.
6857 Here's an example, using @code{stepi} to step to the first instruction
6858 of @code{SIGUSR1}'s handler:
6861 (@value{GDBP}) handle SIGUSR1
6862 Signal Stop Print Pass to program Description
6863 SIGUSR1 Yes Yes Yes User defined signal 1
6867 Program received signal SIGUSR1, User defined signal 1.
6868 main () sigusr1.c:28
6871 sigusr1_handler () at sigusr1.c:9
6875 The same, but using @code{queue-signal} instead of waiting for the
6876 program to receive the signal first:
6881 (@value{GDBP}) queue-signal SIGUSR1
6883 sigusr1_handler () at sigusr1.c:9
6888 @cindex extra signal information
6889 @anchor{extra signal information}
6891 On some targets, @value{GDBN} can inspect extra signal information
6892 associated with the intercepted signal, before it is actually
6893 delivered to the program being debugged. This information is exported
6894 by the convenience variable @code{$_siginfo}, and consists of data
6895 that is passed by the kernel to the signal handler at the time of the
6896 receipt of a signal. The data type of the information itself is
6897 target dependent. You can see the data type using the @code{ptype
6898 $_siginfo} command. On Unix systems, it typically corresponds to the
6899 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6902 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6903 referenced address that raised a segmentation fault.
6907 (@value{GDBP}) continue
6908 Program received signal SIGSEGV, Segmentation fault.
6909 0x0000000000400766 in main ()
6911 (@value{GDBP}) ptype $_siginfo
6918 struct @{...@} _kill;
6919 struct @{...@} _timer;
6921 struct @{...@} _sigchld;
6922 struct @{...@} _sigfault;
6923 struct @{...@} _sigpoll;
6926 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6930 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6931 $1 = (void *) 0x7ffff7ff7000
6935 Depending on target support, @code{$_siginfo} may also be writable.
6937 @cindex Intel MPX boundary violations
6938 @cindex boundary violations, Intel MPX
6939 On some targets, a @code{SIGSEGV} can be caused by a boundary
6940 violation, i.e., accessing an address outside of the allowed range.
6941 In those cases @value{GDBN} may displays additional information,
6942 depending on how @value{GDBN} has been told to handle the signal.
6943 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6944 kind: "Upper" or "Lower", the memory address accessed and the
6945 bounds, while with @code{handle nostop SIGSEGV} no additional
6946 information is displayed.
6948 The usual output of a segfault is:
6950 Program received signal SIGSEGV, Segmentation fault
6951 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6952 68 value = *(p + len);
6955 While a bound violation is presented as:
6957 Program received signal SIGSEGV, Segmentation fault
6958 Upper bound violation while accessing address 0x7fffffffc3b3
6959 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6960 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6961 68 value = *(p + len);
6965 @section Stopping and Starting Multi-thread Programs
6967 @cindex stopped threads
6968 @cindex threads, stopped
6970 @cindex continuing threads
6971 @cindex threads, continuing
6973 @value{GDBN} supports debugging programs with multiple threads
6974 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6975 are two modes of controlling execution of your program within the
6976 debugger. In the default mode, referred to as @dfn{all-stop mode},
6977 when any thread in your program stops (for example, at a breakpoint
6978 or while being stepped), all other threads in the program are also stopped by
6979 @value{GDBN}. On some targets, @value{GDBN} also supports
6980 @dfn{non-stop mode}, in which other threads can continue to run freely while
6981 you examine the stopped thread in the debugger.
6984 * All-Stop Mode:: All threads stop when GDB takes control
6985 * Non-Stop Mode:: Other threads continue to execute
6986 * Background Execution:: Running your program asynchronously
6987 * Thread-Specific Breakpoints:: Controlling breakpoints
6988 * Interrupted System Calls:: GDB may interfere with system calls
6989 * Observer Mode:: GDB does not alter program behavior
6993 @subsection All-Stop Mode
6995 @cindex all-stop mode
6997 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6998 @emph{all} threads of execution stop, not just the current thread. This
6999 allows you to examine the overall state of the program, including
7000 switching between threads, without worrying that things may change
7003 Conversely, whenever you restart the program, @emph{all} threads start
7004 executing. @emph{This is true even when single-stepping} with commands
7005 like @code{step} or @code{next}.
7007 In particular, @value{GDBN} cannot single-step all threads in lockstep.
7008 Since thread scheduling is up to your debugging target's operating
7009 system (not controlled by @value{GDBN}), other threads may
7010 execute more than one statement while the current thread completes a
7011 single step. Moreover, in general other threads stop in the middle of a
7012 statement, rather than at a clean statement boundary, when the program
7015 You might even find your program stopped in another thread after
7016 continuing or even single-stepping. This happens whenever some other
7017 thread runs into a breakpoint, a signal, or an exception before the
7018 first thread completes whatever you requested.
7020 @cindex automatic thread selection
7021 @cindex switching threads automatically
7022 @cindex threads, automatic switching
7023 Whenever @value{GDBN} stops your program, due to a breakpoint or a
7024 signal, it automatically selects the thread where that breakpoint or
7025 signal happened. @value{GDBN} alerts you to the context switch with a
7026 message such as @samp{[Switching to Thread @var{n}]} to identify the
7029 On some OSes, you can modify @value{GDBN}'s default behavior by
7030 locking the OS scheduler to allow only a single thread to run.
7033 @item set scheduler-locking @var{mode}
7034 @cindex scheduler locking mode
7035 @cindex lock scheduler
7036 Set the scheduler locking mode. It applies to normal execution,
7037 record mode, and replay mode. @var{mode} can be one of
7042 There is no locking and any thread may run at any time.
7045 Only the current thread may run when the inferior is resumed.
7048 Behaves like @code{on} when stepping, and @code{off} otherwise.
7049 Threads other than the current never get a chance to run when you
7050 step, and they are completely free to run when you use commands like
7051 @samp{continue}, @samp{until}, or @samp{finish}.
7053 This mode optimizes for single-stepping; it prevents other threads
7054 from preempting the current thread while you are stepping, so that the
7055 focus of debugging does not change unexpectedly. However, unless
7056 another thread hits a breakpoint during its timeslice, @value{GDBN}
7057 does not change the current thread away from the thread that you are
7061 Behaves like @code{on} in replay mode, and @code{off} in either record
7062 mode or during normal execution. This is the default mode.
7065 @item show scheduler-locking
7066 Display the current scheduler locking mode.
7069 @cindex resume threads of multiple processes simultaneously
7070 By default, when you issue one of the execution commands such as
7071 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
7072 threads of the current inferior to run. For example, if @value{GDBN}
7073 is attached to two inferiors, each with two threads, the
7074 @code{continue} command resumes only the two threads of the current
7075 inferior. This is useful, for example, when you debug a program that
7076 forks and you want to hold the parent stopped (so that, for instance,
7077 it doesn't run to exit), while you debug the child. In other
7078 situations, you may not be interested in inspecting the current state
7079 of any of the processes @value{GDBN} is attached to, and you may want
7080 to resume them all until some breakpoint is hit. In the latter case,
7081 you can instruct @value{GDBN} to allow all threads of all the
7082 inferiors to run with the @w{@code{set schedule-multiple}} command.
7085 @kindex set schedule-multiple
7086 @item set schedule-multiple
7087 Set the mode for allowing threads of multiple processes to be resumed
7088 when an execution command is issued. When @code{on}, all threads of
7089 all processes are allowed to run. When @code{off}, only the threads
7090 of the current process are resumed. The default is @code{off}. The
7091 @code{scheduler-locking} mode takes precedence when set to @code{on},
7092 or while you are stepping and set to @code{step}.
7094 @item show schedule-multiple
7095 Display the current mode for resuming the execution of threads of
7100 @subsection Non-Stop Mode
7102 @cindex non-stop mode
7104 @c This section is really only a place-holder, and needs to be expanded
7105 @c with more details.
7107 For some multi-threaded targets, @value{GDBN} supports an optional
7108 mode of operation in which you can examine stopped program threads in
7109 the debugger while other threads continue to execute freely. This
7110 minimizes intrusion when debugging live systems, such as programs
7111 where some threads have real-time constraints or must continue to
7112 respond to external events. This is referred to as @dfn{non-stop} mode.
7114 In non-stop mode, when a thread stops to report a debugging event,
7115 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7116 threads as well, in contrast to the all-stop mode behavior. Additionally,
7117 execution commands such as @code{continue} and @code{step} apply by default
7118 only to the current thread in non-stop mode, rather than all threads as
7119 in all-stop mode. This allows you to control threads explicitly in
7120 ways that are not possible in all-stop mode --- for example, stepping
7121 one thread while allowing others to run freely, stepping
7122 one thread while holding all others stopped, or stepping several threads
7123 independently and simultaneously.
7125 To enter non-stop mode, use this sequence of commands before you run
7126 or attach to your program:
7129 # If using the CLI, pagination breaks non-stop.
7132 # Finally, turn it on!
7136 You can use these commands to manipulate the non-stop mode setting:
7139 @kindex set non-stop
7140 @item set non-stop on
7141 Enable selection of non-stop mode.
7142 @item set non-stop off
7143 Disable selection of non-stop mode.
7144 @kindex show non-stop
7146 Show the current non-stop enablement setting.
7149 Note these commands only reflect whether non-stop mode is enabled,
7150 not whether the currently-executing program is being run in non-stop mode.
7151 In particular, the @code{set non-stop} preference is only consulted when
7152 @value{GDBN} starts or connects to the target program, and it is generally
7153 not possible to switch modes once debugging has started. Furthermore,
7154 since not all targets support non-stop mode, even when you have enabled
7155 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7158 In non-stop mode, all execution commands apply only to the current thread
7159 by default. That is, @code{continue} only continues one thread.
7160 To continue all threads, issue @code{continue -a} or @code{c -a}.
7162 You can use @value{GDBN}'s background execution commands
7163 (@pxref{Background Execution}) to run some threads in the background
7164 while you continue to examine or step others from @value{GDBN}.
7165 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7166 always executed asynchronously in non-stop mode.
7168 Suspending execution is done with the @code{interrupt} command when
7169 running in the background, or @kbd{Ctrl-c} during foreground execution.
7170 In all-stop mode, this stops the whole process;
7171 but in non-stop mode the interrupt applies only to the current thread.
7172 To stop the whole program, use @code{interrupt -a}.
7174 Other execution commands do not currently support the @code{-a} option.
7176 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7177 that thread current, as it does in all-stop mode. This is because the
7178 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7179 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7180 changed to a different thread just as you entered a command to operate on the
7181 previously current thread.
7183 @node Background Execution
7184 @subsection Background Execution
7186 @cindex foreground execution
7187 @cindex background execution
7188 @cindex asynchronous execution
7189 @cindex execution, foreground, background and asynchronous
7191 @value{GDBN}'s execution commands have two variants: the normal
7192 foreground (synchronous) behavior, and a background
7193 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7194 the program to report that some thread has stopped before prompting for
7195 another command. In background execution, @value{GDBN} immediately gives
7196 a command prompt so that you can issue other commands while your program runs.
7198 If the target doesn't support async mode, @value{GDBN} issues an error
7199 message if you attempt to use the background execution commands.
7201 @cindex @code{&}, background execution of commands
7202 To specify background execution, add a @code{&} to the command. For example,
7203 the background form of the @code{continue} command is @code{continue&}, or
7204 just @code{c&}. The execution commands that accept background execution
7210 @xref{Starting, , Starting your Program}.
7214 @xref{Attach, , Debugging an Already-running Process}.
7218 @xref{Continuing and Stepping, step}.
7222 @xref{Continuing and Stepping, stepi}.
7226 @xref{Continuing and Stepping, next}.
7230 @xref{Continuing and Stepping, nexti}.
7234 @xref{Continuing and Stepping, continue}.
7238 @xref{Continuing and Stepping, finish}.
7242 @xref{Continuing and Stepping, until}.
7246 Background execution is especially useful in conjunction with non-stop
7247 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7248 However, you can also use these commands in the normal all-stop mode with
7249 the restriction that you cannot issue another execution command until the
7250 previous one finishes. Examples of commands that are valid in all-stop
7251 mode while the program is running include @code{help} and @code{info break}.
7253 You can interrupt your program while it is running in the background by
7254 using the @code{interrupt} command.
7261 Suspend execution of the running program. In all-stop mode,
7262 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7263 only the current thread. To stop the whole program in non-stop mode,
7264 use @code{interrupt -a}.
7267 @node Thread-Specific Breakpoints
7268 @subsection Thread-Specific Breakpoints
7270 When your program has multiple threads (@pxref{Threads,, Debugging
7271 Programs with Multiple Threads}), you can choose whether to set
7272 breakpoints on all threads, or on a particular thread.
7275 @cindex breakpoints and threads
7276 @cindex thread breakpoints
7277 @kindex break @dots{} thread @var{thread-id}
7278 @item break @var{locspec} thread @var{thread-id}
7279 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7280 @var{locspec} specifies a code location or locations in your program.
7281 @xref{Location Specifications}, for details.
7283 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7284 to specify that you only want @value{GDBN} to stop the program when a
7285 particular thread reaches this breakpoint. The @var{thread-id} specifier
7286 is one of the thread identifiers assigned by @value{GDBN}, shown
7287 in the first column of the @samp{info threads} display.
7289 If you do not specify @samp{thread @var{thread-id}} when you set a
7290 breakpoint, the breakpoint applies to @emph{all} threads of your
7293 You can use the @code{thread} qualifier on conditional breakpoints as
7294 well; in this case, place @samp{thread @var{thread-id}} before or
7295 after the breakpoint condition, like this:
7298 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7303 Thread-specific breakpoints are automatically deleted when
7304 @value{GDBN} detects the corresponding thread is no longer in the
7305 thread list. For example:
7309 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7312 There are several ways for a thread to disappear, such as a regular
7313 thread exit, but also when you detach from the process with the
7314 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7315 Process}), or if @value{GDBN} loses the remote connection
7316 (@pxref{Remote Debugging}), etc. Note that with some targets,
7317 @value{GDBN} is only able to detect a thread has exited when the user
7318 explictly asks for the thread list with the @code{info threads}
7321 @node Interrupted System Calls
7322 @subsection Interrupted System Calls
7324 @cindex thread breakpoints and system calls
7325 @cindex system calls and thread breakpoints
7326 @cindex premature return from system calls
7327 There is an unfortunate side effect when using @value{GDBN} to debug
7328 multi-threaded programs. If one thread stops for a
7329 breakpoint, or for some other reason, and another thread is blocked in a
7330 system call, then the system call may return prematurely. This is a
7331 consequence of the interaction between multiple threads and the signals
7332 that @value{GDBN} uses to implement breakpoints and other events that
7335 To handle this problem, your program should check the return value of
7336 each system call and react appropriately. This is good programming
7339 For example, do not write code like this:
7345 The call to @code{sleep} will return early if a different thread stops
7346 at a breakpoint or for some other reason.
7348 Instead, write this:
7353 unslept = sleep (unslept);
7356 A system call is allowed to return early, so the system is still
7357 conforming to its specification. But @value{GDBN} does cause your
7358 multi-threaded program to behave differently than it would without
7361 Also, @value{GDBN} uses internal breakpoints in the thread library to
7362 monitor certain events such as thread creation and thread destruction.
7363 When such an event happens, a system call in another thread may return
7364 prematurely, even though your program does not appear to stop.
7367 @subsection Observer Mode
7369 If you want to build on non-stop mode and observe program behavior
7370 without any chance of disruption by @value{GDBN}, you can set
7371 variables to disable all of the debugger's attempts to modify state,
7372 whether by writing memory, inserting breakpoints, etc. These operate
7373 at a low level, intercepting operations from all commands.
7375 When all of these are set to @code{off}, then @value{GDBN} is said to
7376 be @dfn{observer mode}. As a convenience, the variable
7377 @code{observer} can be set to disable these, plus enable non-stop
7380 Note that @value{GDBN} will not prevent you from making nonsensical
7381 combinations of these settings. For instance, if you have enabled
7382 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7383 then breakpoints that work by writing trap instructions into the code
7384 stream will still not be able to be placed.
7389 @item set observer on
7390 @itemx set observer off
7391 When set to @code{on}, this disables all the permission variables
7392 below (except for @code{insert-fast-tracepoints}), plus enables
7393 non-stop debugging. Setting this to @code{off} switches back to
7394 normal debugging, though remaining in non-stop mode.
7397 Show whether observer mode is on or off.
7399 @kindex may-write-registers
7400 @item set may-write-registers on
7401 @itemx set may-write-registers off
7402 This controls whether @value{GDBN} will attempt to alter the values of
7403 registers, such as with assignment expressions in @code{print}, or the
7404 @code{jump} command. It defaults to @code{on}.
7406 @item show may-write-registers
7407 Show the current permission to write registers.
7409 @kindex may-write-memory
7410 @item set may-write-memory on
7411 @itemx set may-write-memory off
7412 This controls whether @value{GDBN} will attempt to alter the contents
7413 of memory, such as with assignment expressions in @code{print}. It
7414 defaults to @code{on}.
7416 @item show may-write-memory
7417 Show the current permission to write memory.
7419 @kindex may-insert-breakpoints
7420 @item set may-insert-breakpoints on
7421 @itemx set may-insert-breakpoints off
7422 This controls whether @value{GDBN} will attempt to insert breakpoints.
7423 This affects all breakpoints, including internal breakpoints defined
7424 by @value{GDBN}. It defaults to @code{on}.
7426 @item show may-insert-breakpoints
7427 Show the current permission to insert breakpoints.
7429 @kindex may-insert-tracepoints
7430 @item set may-insert-tracepoints on
7431 @itemx set may-insert-tracepoints off
7432 This controls whether @value{GDBN} will attempt to insert (regular)
7433 tracepoints at the beginning of a tracing experiment. It affects only
7434 non-fast tracepoints, fast tracepoints being under the control of
7435 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7437 @item show may-insert-tracepoints
7438 Show the current permission to insert tracepoints.
7440 @kindex may-insert-fast-tracepoints
7441 @item set may-insert-fast-tracepoints on
7442 @itemx set may-insert-fast-tracepoints off
7443 This controls whether @value{GDBN} will attempt to insert fast
7444 tracepoints at the beginning of a tracing experiment. It affects only
7445 fast tracepoints, regular (non-fast) tracepoints being under the
7446 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7448 @item show may-insert-fast-tracepoints
7449 Show the current permission to insert fast tracepoints.
7451 @kindex may-interrupt
7452 @item set may-interrupt on
7453 @itemx set may-interrupt off
7454 This controls whether @value{GDBN} will attempt to interrupt or stop
7455 program execution. When this variable is @code{off}, the
7456 @code{interrupt} command will have no effect, nor will
7457 @kbd{Ctrl-c}. It defaults to @code{on}.
7459 @item show may-interrupt
7460 Show the current permission to interrupt or stop the program.
7464 @node Reverse Execution
7465 @chapter Running programs backward
7466 @cindex reverse execution
7467 @cindex running programs backward
7469 When you are debugging a program, it is not unusual to realize that
7470 you have gone too far, and some event of interest has already happened.
7471 If the target environment supports it, @value{GDBN} can allow you to
7472 ``rewind'' the program by running it backward.
7474 A target environment that supports reverse execution should be able
7475 to ``undo'' the changes in machine state that have taken place as the
7476 program was executing normally. Variables, registers etc.@: should
7477 revert to their previous values. Obviously this requires a great
7478 deal of sophistication on the part of the target environment; not
7479 all target environments can support reverse execution.
7481 When a program is executed in reverse, the instructions that
7482 have most recently been executed are ``un-executed'', in reverse
7483 order. The program counter runs backward, following the previous
7484 thread of execution in reverse. As each instruction is ``un-executed'',
7485 the values of memory and/or registers that were changed by that
7486 instruction are reverted to their previous states. After executing
7487 a piece of source code in reverse, all side effects of that code
7488 should be ``undone'', and all variables should be returned to their
7489 prior values@footnote{
7490 Note that some side effects are easier to undo than others. For instance,
7491 memory and registers are relatively easy, but device I/O is hard. Some
7492 targets may be able undo things like device I/O, and some may not.
7494 The contract between @value{GDBN} and the reverse executing target
7495 requires only that the target do something reasonable when
7496 @value{GDBN} tells it to execute backwards, and then report the
7497 results back to @value{GDBN}. Whatever the target reports back to
7498 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7499 assumes that the memory and registers that the target reports are in a
7500 consistent state, but @value{GDBN} accepts whatever it is given.
7503 On some platforms, @value{GDBN} has built-in support for reverse
7504 execution, activated with the @code{record} or @code{record btrace}
7505 commands. @xref{Process Record and Replay}. Some remote targets,
7506 typically full system emulators, support reverse execution directly
7507 without requiring any special command.
7509 If you are debugging in a target environment that supports
7510 reverse execution, @value{GDBN} provides the following commands.
7513 @kindex reverse-continue
7514 @kindex rc @r{(@code{reverse-continue})}
7515 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7516 @itemx rc @r{[}@var{ignore-count}@r{]}
7517 Beginning at the point where your program last stopped, start executing
7518 in reverse. Reverse execution will stop for breakpoints and synchronous
7519 exceptions (signals), just like normal execution. Behavior of
7520 asynchronous signals depends on the target environment.
7522 @kindex reverse-step
7523 @kindex rs @r{(@code{step})}
7524 @item reverse-step @r{[}@var{count}@r{]}
7525 Run the program backward until control reaches the start of a
7526 different source line; then stop it, and return control to @value{GDBN}.
7528 Like the @code{step} command, @code{reverse-step} will only stop
7529 at the beginning of a source line. It ``un-executes'' the previously
7530 executed source line. If the previous source line included calls to
7531 debuggable functions, @code{reverse-step} will step (backward) into
7532 the called function, stopping at the beginning of the @emph{last}
7533 statement in the called function (typically a return statement).
7535 Also, as with the @code{step} command, if non-debuggable functions are
7536 called, @code{reverse-step} will run thru them backward without stopping.
7538 @kindex reverse-stepi
7539 @kindex rsi @r{(@code{reverse-stepi})}
7540 @item reverse-stepi @r{[}@var{count}@r{]}
7541 Reverse-execute one machine instruction. Note that the instruction
7542 to be reverse-executed is @emph{not} the one pointed to by the program
7543 counter, but the instruction executed prior to that one. For instance,
7544 if the last instruction was a jump, @code{reverse-stepi} will take you
7545 back from the destination of the jump to the jump instruction itself.
7547 @kindex reverse-next
7548 @kindex rn @r{(@code{reverse-next})}
7549 @item reverse-next @r{[}@var{count}@r{]}
7550 Run backward to the beginning of the previous line executed in
7551 the current (innermost) stack frame. If the line contains function
7552 calls, they will be ``un-executed'' without stopping. Starting from
7553 the first line of a function, @code{reverse-next} will take you back
7554 to the caller of that function, @emph{before} the function was called,
7555 just as the normal @code{next} command would take you from the last
7556 line of a function back to its return to its caller
7557 @footnote{Unless the code is too heavily optimized.}.
7559 @kindex reverse-nexti
7560 @kindex rni @r{(@code{reverse-nexti})}
7561 @item reverse-nexti @r{[}@var{count}@r{]}
7562 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7563 in reverse, except that called functions are ``un-executed'' atomically.
7564 That is, if the previously executed instruction was a return from
7565 another function, @code{reverse-nexti} will continue to execute
7566 in reverse until the call to that function (from the current stack
7569 @kindex reverse-finish
7570 @item reverse-finish
7571 Just as the @code{finish} command takes you to the point where the
7572 current function returns, @code{reverse-finish} takes you to the point
7573 where it was called. Instead of ending up at the end of the current
7574 function invocation, you end up at the beginning.
7576 @kindex set exec-direction
7577 @item set exec-direction
7578 Set the direction of target execution.
7579 @item set exec-direction reverse
7580 @cindex execute forward or backward in time
7581 @value{GDBN} will perform all execution commands in reverse, until the
7582 exec-direction mode is changed to ``forward''. Affected commands include
7583 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7584 command cannot be used in reverse mode.
7585 @item set exec-direction forward
7586 @value{GDBN} will perform all execution commands in the normal fashion.
7587 This is the default.
7591 @node Process Record and Replay
7592 @chapter Recording Inferior's Execution and Replaying It
7593 @cindex process record and replay
7594 @cindex recording inferior's execution and replaying it
7596 On some platforms, @value{GDBN} provides a special @dfn{process record
7597 and replay} target that can record a log of the process execution, and
7598 replay it later with both forward and reverse execution commands.
7601 When this target is in use, if the execution log includes the record
7602 for the next instruction, @value{GDBN} will debug in @dfn{replay
7603 mode}. In the replay mode, the inferior does not really execute code
7604 instructions. Instead, all the events that normally happen during
7605 code execution are taken from the execution log. While code is not
7606 really executed in replay mode, the values of registers (including the
7607 program counter register) and the memory of the inferior are still
7608 changed as they normally would. Their contents are taken from the
7612 If the record for the next instruction is not in the execution log,
7613 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7614 inferior executes normally, and @value{GDBN} records the execution log
7617 The process record and replay target supports reverse execution
7618 (@pxref{Reverse Execution}), even if the platform on which the
7619 inferior runs does not. However, the reverse execution is limited in
7620 this case by the range of the instructions recorded in the execution
7621 log. In other words, reverse execution on platforms that don't
7622 support it directly can only be done in the replay mode.
7624 When debugging in the reverse direction, @value{GDBN} will work in
7625 replay mode as long as the execution log includes the record for the
7626 previous instruction; otherwise, it will work in record mode, if the
7627 platform supports reverse execution, or stop if not.
7629 Currently, process record and replay is supported on ARM, Aarch64,
7630 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7631 GNU/Linux. Process record and replay can be used both when native
7632 debugging, and when remote debugging via @code{gdbserver}.
7634 For architecture environments that support process record and replay,
7635 @value{GDBN} provides the following commands:
7638 @kindex target record
7639 @kindex target record-full
7640 @kindex target record-btrace
7643 @kindex record btrace
7644 @kindex record btrace bts
7645 @kindex record btrace pt
7651 @kindex rec btrace bts
7652 @kindex rec btrace pt
7655 @item record @var{method}
7656 This command starts the process record and replay target. The
7657 recording method can be specified as parameter. Without a parameter
7658 the command uses the @code{full} recording method. The following
7659 recording methods are available:
7663 Full record/replay recording using @value{GDBN}'s software record and
7664 replay implementation. This method allows replaying and reverse
7667 @item btrace @var{format}
7668 Hardware-supported instruction recording, supported on Intel
7669 processors. This method does not record data. Further, the data is
7670 collected in a ring buffer so old data will be overwritten when the
7671 buffer is full. It allows limited reverse execution. Variables and
7672 registers are not available during reverse execution. In remote
7673 debugging, recording continues on disconnect. Recorded data can be
7674 inspected after reconnecting. The recording may be stopped using
7677 The recording format can be specified as parameter. Without a parameter
7678 the command chooses the recording format. The following recording
7679 formats are available:
7683 @cindex branch trace store
7684 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7685 this format, the processor stores a from/to record for each executed
7686 branch in the btrace ring buffer.
7689 @cindex Intel Processor Trace
7690 Use the @dfn{Intel Processor Trace} recording format. In this
7691 format, the processor stores the execution trace in a compressed form
7692 that is afterwards decoded by @value{GDBN}.
7694 The trace can be recorded with very low overhead. The compressed
7695 trace format also allows small trace buffers to already contain a big
7696 number of instructions compared to @acronym{BTS}.
7698 Decoding the recorded execution trace, on the other hand, is more
7699 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7700 increased number of instructions to process. You should increase the
7701 buffer-size with care.
7704 Not all recording formats may be available on all processors.
7707 The process record and replay target can only debug a process that is
7708 already running. Therefore, you need first to start the process with
7709 the @kbd{run} or @kbd{start} commands, and then start the recording
7710 with the @kbd{record @var{method}} command.
7712 @cindex displaced stepping, and process record and replay
7713 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7714 will be automatically disabled when process record and replay target
7715 is started. That's because the process record and replay target
7716 doesn't support displaced stepping.
7718 @cindex non-stop mode, and process record and replay
7719 @cindex asynchronous execution, and process record and replay
7720 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7721 the asynchronous execution mode (@pxref{Background Execution}), not
7722 all recording methods are available. The @code{full} recording method
7723 does not support these two modes.
7728 Stop the process record and replay target. When process record and
7729 replay target stops, the entire execution log will be deleted and the
7730 inferior will either be terminated, or will remain in its final state.
7732 When you stop the process record and replay target in record mode (at
7733 the end of the execution log), the inferior will be stopped at the
7734 next instruction that would have been recorded. In other words, if
7735 you record for a while and then stop recording, the inferior process
7736 will be left in the same state as if the recording never happened.
7738 On the other hand, if the process record and replay target is stopped
7739 while in replay mode (that is, not at the end of the execution log,
7740 but at some earlier point), the inferior process will become ``live''
7741 at that earlier state, and it will then be possible to continue the
7742 usual ``live'' debugging of the process from that state.
7744 When the inferior process exits, or @value{GDBN} detaches from it,
7745 process record and replay target will automatically stop itself.
7749 Go to a specific location in the execution log. There are several
7750 ways to specify the location to go to:
7753 @item record goto begin
7754 @itemx record goto start
7755 Go to the beginning of the execution log.
7757 @item record goto end
7758 Go to the end of the execution log.
7760 @item record goto @var{n}
7761 Go to instruction number @var{n} in the execution log.
7765 @item record save @var{filename}
7766 Save the execution log to a file @file{@var{filename}}.
7767 Default filename is @file{gdb_record.@var{process_id}}, where
7768 @var{process_id} is the process ID of the inferior.
7770 This command may not be available for all recording methods.
7772 @kindex record restore
7773 @item record restore @var{filename}
7774 Restore the execution log from a file @file{@var{filename}}.
7775 File must have been created with @code{record save}.
7777 @kindex set record full
7778 @item set record full insn-number-max @var{limit}
7779 @itemx set record full insn-number-max unlimited
7780 Set the limit of instructions to be recorded for the @code{full}
7781 recording method. Default value is 200000.
7783 If @var{limit} is a positive number, then @value{GDBN} will start
7784 deleting instructions from the log once the number of the record
7785 instructions becomes greater than @var{limit}. For every new recorded
7786 instruction, @value{GDBN} will delete the earliest recorded
7787 instruction to keep the number of recorded instructions at the limit.
7788 (Since deleting recorded instructions loses information, @value{GDBN}
7789 lets you control what happens when the limit is reached, by means of
7790 the @code{stop-at-limit} option, described below.)
7792 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7793 delete recorded instructions from the execution log. The number of
7794 recorded instructions is limited only by the available memory.
7796 @kindex show record full
7797 @item show record full insn-number-max
7798 Show the limit of instructions to be recorded with the @code{full}
7801 @item set record full stop-at-limit
7802 Control the behavior of the @code{full} recording method when the
7803 number of recorded instructions reaches the limit. If ON (the
7804 default), @value{GDBN} will stop when the limit is reached for the
7805 first time and ask you whether you want to stop the inferior or
7806 continue running it and recording the execution log. If you decide
7807 to continue recording, each new recorded instruction will cause the
7808 oldest one to be deleted.
7810 If this option is OFF, @value{GDBN} will automatically delete the
7811 oldest record to make room for each new one, without asking.
7813 @item show record full stop-at-limit
7814 Show the current setting of @code{stop-at-limit}.
7816 @item set record full memory-query
7817 Control the behavior when @value{GDBN} is unable to record memory
7818 changes caused by an instruction for the @code{full} recording method.
7819 If ON, @value{GDBN} will query whether to stop the inferior in that
7822 If this option is OFF (the default), @value{GDBN} will automatically
7823 ignore the effect of such instructions on memory. Later, when
7824 @value{GDBN} replays this execution log, it will mark the log of this
7825 instruction as not accessible, and it will not affect the replay
7828 @item show record full memory-query
7829 Show the current setting of @code{memory-query}.
7831 @kindex set record btrace
7832 The @code{btrace} record target does not trace data. As a
7833 convenience, when replaying, @value{GDBN} reads read-only memory off
7834 the live program directly, assuming that the addresses of the
7835 read-only areas don't change. This for example makes it possible to
7836 disassemble code while replaying, but not to print variables.
7837 In some cases, being able to inspect variables might be useful.
7838 You can use the following command for that:
7840 @item set record btrace replay-memory-access
7841 Control the behavior of the @code{btrace} recording method when
7842 accessing memory during replay. If @code{read-only} (the default),
7843 @value{GDBN} will only allow accesses to read-only memory.
7844 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7845 and to read-write memory. Beware that the accessed memory corresponds
7846 to the live target and not necessarily to the current replay
7849 @item set record btrace cpu @var{identifier}
7850 Set the processor to be used for enabling workarounds for processor
7851 errata when decoding the trace.
7853 Processor errata are defects in processor operation, caused by its
7854 design or manufacture. They can cause a trace not to match the
7855 specification. This, in turn, may cause trace decode to fail.
7856 @value{GDBN} can detect erroneous trace packets and correct them, thus
7857 avoiding the decoding failures. These corrections are known as
7858 @dfn{errata workarounds}, and are enabled based on the processor on
7859 which the trace was recorded.
7861 By default, @value{GDBN} attempts to detect the processor
7862 automatically, and apply the necessary workarounds for it. However,
7863 you may need to specify the processor if @value{GDBN} does not yet
7864 support it. This command allows you to do that, and also allows to
7865 disable the workarounds.
7867 The argument @var{identifier} identifies the @sc{cpu} and is of the
7868 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7869 there are two special identifiers, @code{none} and @code{auto}
7872 The following vendor identifiers and corresponding processor
7873 identifiers are currently supported:
7875 @multitable @columnfractions .1 .9
7878 @tab @var{family}/@var{model}[/@var{stepping}]
7882 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7883 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7885 If @var{identifier} is @code{auto}, enable errata workarounds for the
7886 processor on which the trace was recorded. If @var{identifier} is
7887 @code{none}, errata workarounds are disabled.
7889 For example, when using an old @value{GDBN} on a new system, decode
7890 may fail because @value{GDBN} does not support the new processor. It
7891 often suffices to specify an older processor that @value{GDBN}
7896 Active record target: record-btrace
7897 Recording format: Intel Processor Trace.
7899 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7900 (gdb) set record btrace cpu intel:6/158
7902 Active record target: record-btrace
7903 Recording format: Intel Processor Trace.
7905 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7908 @kindex show record btrace
7909 @item show record btrace replay-memory-access
7910 Show the current setting of @code{replay-memory-access}.
7912 @item show record btrace cpu
7913 Show the processor to be used for enabling trace decode errata
7916 @kindex set record btrace bts
7917 @item set record btrace bts buffer-size @var{size}
7918 @itemx set record btrace bts buffer-size unlimited
7919 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7920 format. Default is 64KB.
7922 If @var{size} is a positive number, then @value{GDBN} will try to
7923 allocate a buffer of at least @var{size} bytes for each new thread
7924 that uses the btrace recording method and the @acronym{BTS} format.
7925 The actually obtained buffer size may differ from the requested
7926 @var{size}. Use the @code{info record} command to see the actual
7927 buffer size for each thread that uses the btrace recording method and
7928 the @acronym{BTS} format.
7930 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7931 allocate a buffer of 4MB.
7933 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7934 also need longer to process the branch trace data before it can be used.
7936 @item show record btrace bts buffer-size @var{size}
7937 Show the current setting of the requested ring buffer size for branch
7938 tracing in @acronym{BTS} format.
7940 @kindex set record btrace pt
7941 @item set record btrace pt buffer-size @var{size}
7942 @itemx set record btrace pt buffer-size unlimited
7943 Set the requested ring buffer size for branch tracing in Intel
7944 Processor Trace format. Default is 16KB.
7946 If @var{size} is a positive number, then @value{GDBN} will try to
7947 allocate a buffer of at least @var{size} bytes for each new thread
7948 that uses the btrace recording method and the Intel Processor Trace
7949 format. The actually obtained buffer size may differ from the
7950 requested @var{size}. Use the @code{info record} command to see the
7951 actual buffer size for each thread.
7953 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7954 allocate a buffer of 4MB.
7956 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7957 also need longer to process the branch trace data before it can be used.
7959 @item show record btrace pt buffer-size @var{size}
7960 Show the current setting of the requested ring buffer size for branch
7961 tracing in Intel Processor Trace format.
7965 Show various statistics about the recording depending on the recording
7970 For the @code{full} recording method, it shows the state of process
7971 record and its in-memory execution log buffer, including:
7975 Whether in record mode or replay mode.
7977 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7979 Highest recorded instruction number.
7981 Current instruction about to be replayed (if in replay mode).
7983 Number of instructions contained in the execution log.
7985 Maximum number of instructions that may be contained in the execution log.
7989 For the @code{btrace} recording method, it shows:
7995 Number of instructions that have been recorded.
7997 Number of blocks of sequential control-flow formed by the recorded
8000 Whether in record mode or replay mode.
8003 For the @code{bts} recording format, it also shows:
8006 Size of the perf ring buffer.
8009 For the @code{pt} recording format, it also shows:
8012 Size of the perf ring buffer.
8016 @kindex record delete
8019 When record target runs in replay mode (``in the past''), delete the
8020 subsequent execution log and begin to record a new execution log starting
8021 from the current address. This means you will abandon the previously
8022 recorded ``future'' and begin recording a new ``future''.
8024 @kindex record instruction-history
8025 @kindex rec instruction-history
8026 @item record instruction-history
8027 Disassembles instructions from the recorded execution log. By
8028 default, ten instructions are disassembled. This can be changed using
8029 the @code{set record instruction-history-size} command. Instructions
8030 are printed in execution order.
8032 It can also print mixed source+disassembly if you specify the the
8033 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
8034 as well as in symbolic form by specifying the @code{/r} or @code{/b}
8035 modifier. The behaviour of the @code{/m}, @code{/s}, @code{/r}, and
8036 @code{/b} modifiers are the same as for the @kbd{disassemble} command
8037 (@pxref{disassemble,,@kbd{disassemble}}).
8039 The current position marker is printed for the instruction at the
8040 current program counter value. This instruction can appear multiple
8041 times in the trace and the current position marker will be printed
8042 every time. To omit the current position marker, specify the
8045 To better align the printed instructions when the trace contains
8046 instructions from more than one function, the function name may be
8047 omitted by specifying the @code{/f} modifier.
8049 Speculatively executed instructions are prefixed with @samp{?}. This
8050 feature is not available for all recording formats.
8052 There are several ways to specify what part of the execution log to
8056 @item record instruction-history @var{insn}
8057 Disassembles ten instructions starting from instruction number
8060 @item record instruction-history @var{insn}, +/-@var{n}
8061 Disassembles @var{n} instructions around instruction number
8062 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
8063 @var{n} instructions after instruction number @var{insn}. If
8064 @var{n} is preceded with @code{-}, disassembles @var{n}
8065 instructions before instruction number @var{insn}.
8067 @item record instruction-history
8068 Disassembles ten more instructions after the last disassembly.
8070 @item record instruction-history -
8071 Disassembles ten more instructions before the last disassembly.
8073 @item record instruction-history @var{begin}, @var{end}
8074 Disassembles instructions beginning with instruction number
8075 @var{begin} until instruction number @var{end}. The instruction
8076 number @var{end} is included.
8079 This command may not be available for all recording methods.
8082 @item set record instruction-history-size @var{size}
8083 @itemx set record instruction-history-size unlimited
8084 Define how many instructions to disassemble in the @code{record
8085 instruction-history} command. The default value is 10.
8086 A @var{size} of @code{unlimited} means unlimited instructions.
8089 @item show record instruction-history-size
8090 Show how many instructions to disassemble in the @code{record
8091 instruction-history} command.
8093 @kindex record function-call-history
8094 @kindex rec function-call-history
8095 @item record function-call-history
8096 Prints the execution history at function granularity. For each sequence
8097 of instructions that belong to the same function, it prints the name of
8098 that function, the source lines for this instruction sequence (if the
8099 @code{/l} modifier is specified), and the instructions numbers that form
8100 the sequence (if the @code{/i} modifier is specified). The function names
8101 are indented to reflect the call stack depth if the @code{/c} modifier is
8102 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
8106 (@value{GDBP}) @b{list 1, 10}
8117 (@value{GDBP}) @b{record function-call-history /ilc}
8118 1 bar inst 1,4 at foo.c:6,8
8119 2 foo inst 5,10 at foo.c:2,3
8120 3 bar inst 11,13 at foo.c:9,10
8123 By default, ten functions are printed. This can be changed using the
8124 @code{set record function-call-history-size} command. Functions are
8125 printed in execution order. There are several ways to specify what
8129 @item record function-call-history @var{func}
8130 Prints ten functions starting from function number @var{func}.
8132 @item record function-call-history @var{func}, +/-@var{n}
8133 Prints @var{n} functions around function number @var{func}. If
8134 @var{n} is preceded with @code{+}, prints @var{n} functions after
8135 function number @var{func}. If @var{n} is preceded with @code{-},
8136 prints @var{n} functions before function number @var{func}.
8138 @item record function-call-history
8139 Prints ten more functions after the last ten-function print.
8141 @item record function-call-history -
8142 Prints ten more functions before the last ten-function print.
8144 @item record function-call-history @var{begin}, @var{end}
8145 Prints functions beginning with function number @var{begin} until
8146 function number @var{end}. The function number @var{end} is included.
8149 This command may not be available for all recording methods.
8151 @item set record function-call-history-size @var{size}
8152 @itemx set record function-call-history-size unlimited
8153 Define how many functions to print in the
8154 @code{record function-call-history} command. The default value is 10.
8155 A size of @code{unlimited} means unlimited functions.
8157 @item show record function-call-history-size
8158 Show how many functions to print in the
8159 @code{record function-call-history} command.
8164 @chapter Examining the Stack
8166 When your program has stopped, the first thing you need to know is where it
8167 stopped and how it got there.
8170 Each time your program performs a function call, information about the call
8172 That information includes the location of the call in your program,
8173 the arguments of the call,
8174 and the local variables of the function being called.
8175 The information is saved in a block of data called a @dfn{stack frame}.
8176 The stack frames are allocated in a region of memory called the @dfn{call
8179 When your program stops, the @value{GDBN} commands for examining the
8180 stack allow you to see all of this information.
8182 @cindex selected frame
8183 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8184 @value{GDBN} commands refer implicitly to the selected frame. In
8185 particular, whenever you ask @value{GDBN} for the value of a variable in
8186 your program, the value is found in the selected frame. There are
8187 special @value{GDBN} commands to select whichever frame you are
8188 interested in. @xref{Selection, ,Selecting a Frame}.
8190 When your program stops, @value{GDBN} automatically selects the
8191 currently executing frame and describes it briefly, similar to the
8192 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8195 * Frames:: Stack frames
8196 * Backtrace:: Backtraces
8197 * Selection:: Selecting a frame
8198 * Frame Info:: Information on a frame
8199 * Frame Apply:: Applying a command to several frames
8200 * Frame Filter Management:: Managing frame filters
8205 @section Stack Frames
8207 @cindex frame, definition
8209 The call stack is divided up into contiguous pieces called @dfn{stack
8210 frames}, or @dfn{frames} for short; each frame is the data associated
8211 with one call to one function. The frame contains the arguments given
8212 to the function, the function's local variables, and the address at
8213 which the function is executing.
8215 @cindex initial frame
8216 @cindex outermost frame
8217 @cindex innermost frame
8218 When your program is started, the stack has only one frame, that of the
8219 function @code{main}. This is called the @dfn{initial} frame or the
8220 @dfn{outermost} frame. Each time a function is called, a new frame is
8221 made. Each time a function returns, the frame for that function invocation
8222 is eliminated. If a function is recursive, there can be many frames for
8223 the same function. The frame for the function in which execution is
8224 actually occurring is called the @dfn{innermost} frame. This is the most
8225 recently created of all the stack frames that still exist.
8227 @cindex frame pointer
8228 Inside your program, stack frames are identified by their addresses. A
8229 stack frame consists of many bytes, each of which has its own address; each
8230 kind of computer has a convention for choosing one byte whose
8231 address serves as the address of the frame. Usually this address is kept
8232 in a register called the @dfn{frame pointer register}
8233 (@pxref{Registers, $fp}) while execution is going on in that frame.
8236 @cindex frame number
8237 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8238 number that is zero for the innermost frame, one for the frame that
8239 called it, and so on upward. These level numbers give you a way of
8240 designating stack frames in @value{GDBN} commands. The terms
8241 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8242 describe this number.
8244 @c The -fomit-frame-pointer below perennially causes hbox overflow
8245 @c underflow problems.
8246 @cindex frameless execution
8247 Some compilers provide a way to compile functions so that they operate
8248 without stack frames. (For example, the @value{NGCC} option
8250 @samp{-fomit-frame-pointer}
8252 generates functions without a frame.)
8253 This is occasionally done with heavily used library functions to save
8254 the frame setup time. @value{GDBN} has limited facilities for dealing
8255 with these function invocations. If the innermost function invocation
8256 has no stack frame, @value{GDBN} nevertheless regards it as though
8257 it had a separate frame, which is numbered zero as usual, allowing
8258 correct tracing of the function call chain. However, @value{GDBN} has
8259 no provision for frameless functions elsewhere in the stack.
8265 @cindex call stack traces
8266 A backtrace is a summary of how your program got where it is. It shows one
8267 line per frame, for many frames, starting with the currently executing
8268 frame (frame zero), followed by its caller (frame one), and on up the
8271 @anchor{backtrace-command}
8273 @kindex bt @r{(@code{backtrace})}
8274 To print a backtrace of the entire stack, use the @code{backtrace}
8275 command, or its alias @code{bt}. This command will print one line per
8276 frame for frames in the stack. By default, all stack frames are
8277 printed. You can stop the backtrace at any time by typing the system
8278 interrupt character, normally @kbd{Ctrl-c}.
8281 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8282 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8283 Print the backtrace of the entire stack.
8285 The optional @var{count} can be one of the following:
8290 Print only the innermost @var{n} frames, where @var{n} is a positive
8295 Print only the outermost @var{n} frames, where @var{n} is a positive
8303 Print the values of the local variables also. This can be combined
8304 with the optional @var{count} to limit the number of frames shown.
8307 Do not run Python frame filters on this backtrace. @xref{Frame
8308 Filter API}, for more information. Additionally use @ref{disable
8309 frame-filter all} to turn off all frame filters. This is only
8310 relevant when @value{GDBN} has been configured with @code{Python}
8314 A Python frame filter might decide to ``elide'' some frames. Normally
8315 such elided frames are still printed, but they are indented relative
8316 to the filtered frames that cause them to be elided. The @code{-hide}
8317 option causes elided frames to not be printed at all.
8320 The @code{backtrace} command also supports a number of options that
8321 allow overriding relevant global print settings as set by @code{set
8322 backtrace} and @code{set print} subcommands:
8325 @item -past-main [@code{on}|@code{off}]
8326 Set whether backtraces should continue past @code{main}. Related setting:
8327 @ref{set backtrace past-main}.
8329 @item -past-entry [@code{on}|@code{off}]
8330 Set whether backtraces should continue past the entry point of a program.
8331 Related setting: @ref{set backtrace past-entry}.
8333 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8334 Set printing of function arguments at function entry.
8335 Related setting: @ref{set print entry-values}.
8337 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8338 Set printing of non-scalar frame arguments.
8339 Related setting: @ref{set print frame-arguments}.
8341 @item -raw-frame-arguments [@code{on}|@code{off}]
8342 Set whether to print frame arguments in raw form.
8343 Related setting: @ref{set print raw-frame-arguments}.
8345 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8346 Set printing of frame information.
8347 Related setting: @ref{set print frame-info}.
8350 The optional @var{qualifier} is maintained for backward compatibility.
8351 It can be one of the following:
8355 Equivalent to the @code{-full} option.
8358 Equivalent to the @code{-no-filters} option.
8361 Equivalent to the @code{-hide} option.
8368 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8369 are additional aliases for @code{backtrace}.
8371 @cindex multiple threads, backtrace
8372 In a multi-threaded program, @value{GDBN} by default shows the
8373 backtrace only for the current thread. To display the backtrace for
8374 several or all of the threads, use the command @code{thread apply}
8375 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8376 apply all backtrace}, @value{GDBN} will display the backtrace for all
8377 the threads; this is handy when you debug a core dump of a
8378 multi-threaded program.
8380 Each line in the backtrace shows the frame number and the function name.
8381 The program counter value is also shown---unless you use @code{set
8382 print address off}. The backtrace also shows the source file name and
8383 line number, as well as the arguments to the function. The program
8384 counter value is omitted if it is at the beginning of the code for that
8387 Here is an example of a backtrace. It was made with the command
8388 @samp{bt 3}, so it shows the innermost three frames.
8392 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8394 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8395 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8397 (More stack frames follow...)
8402 The display for frame zero does not begin with a program counter
8403 value, indicating that your program has stopped at the beginning of the
8404 code for line @code{993} of @code{builtin.c}.
8407 The value of parameter @code{data} in frame 1 has been replaced by
8408 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8409 only if it is a scalar (integer, pointer, enumeration, etc). See command
8410 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8411 on how to configure the way function parameter values are printed.
8412 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8413 what frame information is printed.
8415 @cindex optimized out, in backtrace
8416 @cindex function call arguments, optimized out
8417 If your program was compiled with optimizations, some compilers will
8418 optimize away arguments passed to functions if those arguments are
8419 never used after the call. Such optimizations generate code that
8420 passes arguments through registers, but doesn't store those arguments
8421 in the stack frame. @value{GDBN} has no way of displaying such
8422 arguments in stack frames other than the innermost one. Here's what
8423 such a backtrace might look like:
8427 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8429 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8430 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8432 (More stack frames follow...)
8437 The values of arguments that were not saved in their stack frames are
8438 shown as @samp{<optimized out>}.
8440 If you need to display the values of such optimized-out arguments,
8441 either deduce that from other variables whose values depend on the one
8442 you are interested in, or recompile without optimizations.
8444 @cindex backtrace beyond @code{main} function
8445 @cindex program entry point
8446 @cindex startup code, and backtrace
8447 Most programs have a standard user entry point---a place where system
8448 libraries and startup code transition into user code. For C this is
8449 @code{main}@footnote{
8450 Note that embedded programs (the so-called ``free-standing''
8451 environment) are not required to have a @code{main} function as the
8452 entry point. They could even have multiple entry points.}.
8453 When @value{GDBN} finds the entry function in a backtrace
8454 it will terminate the backtrace, to avoid tracing into highly
8455 system-specific (and generally uninteresting) code.
8457 If you need to examine the startup code, or limit the number of levels
8458 in a backtrace, you can change this behavior:
8461 @item set backtrace past-main
8462 @itemx set backtrace past-main on
8463 @anchor{set backtrace past-main}
8464 @kindex set backtrace
8465 Backtraces will continue past the user entry point.
8467 @item set backtrace past-main off
8468 Backtraces will stop when they encounter the user entry point. This is the
8471 @item show backtrace past-main
8472 @kindex show backtrace
8473 Display the current user entry point backtrace policy.
8475 @item set backtrace past-entry
8476 @itemx set backtrace past-entry on
8477 @anchor{set backtrace past-entry}
8478 Backtraces will continue past the internal entry point of an application.
8479 This entry point is encoded by the linker when the application is built,
8480 and is likely before the user entry point @code{main} (or equivalent) is called.
8482 @item set backtrace past-entry off
8483 Backtraces will stop when they encounter the internal entry point of an
8484 application. This is the default.
8486 @item show backtrace past-entry
8487 Display the current internal entry point backtrace policy.
8489 @item set backtrace limit @var{n}
8490 @itemx set backtrace limit 0
8491 @itemx set backtrace limit unlimited
8492 @anchor{set backtrace limit}
8493 @cindex backtrace limit
8494 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8495 or zero means unlimited levels.
8497 @item show backtrace limit
8498 Display the current limit on backtrace levels.
8501 You can control how file names are displayed.
8504 @item set filename-display
8505 @itemx set filename-display relative
8506 @cindex filename-display
8507 Display file names relative to the compilation directory. This is the default.
8509 @item set filename-display basename
8510 Display only basename of a filename.
8512 @item set filename-display absolute
8513 Display an absolute filename.
8515 @item show filename-display
8516 Show the current way to display filenames.
8520 @section Selecting a Frame
8522 Most commands for examining the stack and other data in your program work on
8523 whichever stack frame is selected at the moment. Here are the commands for
8524 selecting a stack frame; all of them finish by printing a brief description
8525 of the stack frame just selected.
8528 @kindex frame@r{, selecting}
8529 @kindex f @r{(@code{frame})}
8530 @item frame @r{[} @var{frame-selection-spec} @r{]}
8531 @item f @r{[} @var{frame-selection-spec} @r{]}
8532 The @command{frame} command allows different stack frames to be
8533 selected. The @var{frame-selection-spec} can be any of the following:
8538 @item level @var{num}
8539 Select frame level @var{num}. Recall that frame zero is the innermost
8540 (currently executing) frame, frame one is the frame that called the
8541 innermost one, and so on. The highest level frame is usually the one
8544 As this is the most common method of navigating the frame stack, the
8545 string @command{level} can be omitted. For example, the following two
8546 commands are equivalent:
8549 (@value{GDBP}) frame 3
8550 (@value{GDBP}) frame level 3
8553 @kindex frame address
8554 @item address @var{stack-address}
8555 Select the frame with stack address @var{stack-address}. The
8556 @var{stack-address} for a frame can be seen in the output of
8557 @command{info frame}, for example:
8561 Stack level 1, frame at 0x7fffffffda30:
8562 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8563 tail call frame, caller of frame at 0x7fffffffda30
8564 source language c++.
8565 Arglist at unknown address.
8566 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8569 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8570 indicated by the line:
8573 Stack level 1, frame at 0x7fffffffda30:
8576 @kindex frame function
8577 @item function @var{function-name}
8578 Select the stack frame for function @var{function-name}. If there are
8579 multiple stack frames for function @var{function-name} then the inner
8580 most stack frame is selected.
8583 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8584 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8585 viewed has stack address @var{stack-addr}, and optionally, a program
8586 counter address of @var{pc-addr}.
8588 This is useful mainly if the chaining of stack frames has been
8589 damaged by a bug, making it impossible for @value{GDBN} to assign
8590 numbers properly to all frames. In addition, this can be useful
8591 when your program has multiple stacks and switches between them.
8593 When viewing a frame outside the current backtrace using
8594 @command{frame view} then you can always return to the original
8595 stack using one of the previous stack frame selection instructions,
8596 for example @command{frame level 0}.
8602 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8603 numbers @var{n}, this advances toward the outermost frame, to higher
8604 frame numbers, to frames that have existed longer.
8607 @kindex do @r{(@code{down})}
8609 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8610 positive numbers @var{n}, this advances toward the innermost frame, to
8611 lower frame numbers, to frames that were created more recently.
8612 You may abbreviate @code{down} as @code{do}.
8615 All of these commands end by printing two lines of output describing the
8616 frame. The first line shows the frame number, the function name, the
8617 arguments, and the source file and line number of execution in that
8618 frame. The second line shows the text of that source line.
8626 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8628 10 read_input_file (argv[i]);
8632 After such a printout, the @code{list} command with no arguments
8633 prints ten lines centered on the point of execution in the frame.
8634 You can also edit the program at the point of execution with your favorite
8635 editing program by typing @code{edit}.
8636 @xref{List, ,Printing Source Lines},
8640 @kindex select-frame
8641 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8642 The @code{select-frame} command is a variant of @code{frame} that does
8643 not display the new frame after selecting it. This command is
8644 intended primarily for use in @value{GDBN} command scripts, where the
8645 output might be unnecessary and distracting. The
8646 @var{frame-selection-spec} is as for the @command{frame} command
8647 described in @ref{Selection, ,Selecting a Frame}.
8649 @kindex down-silently
8651 @item up-silently @var{n}
8652 @itemx down-silently @var{n}
8653 These two commands are variants of @code{up} and @code{down},
8654 respectively; they differ in that they do their work silently, without
8655 causing display of the new frame. They are intended primarily for use
8656 in @value{GDBN} command scripts, where the output might be unnecessary and
8661 @section Information About a Frame
8663 There are several other commands to print information about the selected
8669 When used without any argument, this command does not change which
8670 frame is selected, but prints a brief description of the currently
8671 selected stack frame. It can be abbreviated @code{f}. With an
8672 argument, this command is used to select a stack frame.
8673 @xref{Selection, ,Selecting a Frame}.
8676 @kindex info f @r{(@code{info frame})}
8679 This command prints a verbose description of the selected stack frame,
8684 the address of the frame
8686 the address of the next frame down (called by this frame)
8688 the address of the next frame up (caller of this frame)
8690 the language in which the source code corresponding to this frame is written
8692 the address of the frame's arguments
8694 the address of the frame's local variables
8696 the program counter saved in it (the address of execution in the caller frame)
8698 which registers were saved in the frame
8701 @noindent The verbose description is useful when
8702 something has gone wrong that has made the stack format fail to fit
8703 the usual conventions.
8705 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8706 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8707 Print a verbose description of the frame selected by
8708 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8709 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8710 a Frame}). The selected frame remains unchanged by this command.
8713 @item info args [-q]
8714 Print the arguments of the selected frame, each on a separate line.
8716 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8717 printing header information and messages explaining why no argument
8720 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8721 Like @kbd{info args}, but only print the arguments selected
8722 with the provided regexp(s).
8724 If @var{regexp} is provided, print only the arguments whose names
8725 match the regular expression @var{regexp}.
8727 If @var{type_regexp} is provided, print only the arguments whose
8728 types, as printed by the @code{whatis} command, match
8729 the regular expression @var{type_regexp}.
8730 If @var{type_regexp} contains space(s), it should be enclosed in
8731 quote characters. If needed, use backslash to escape the meaning
8732 of special characters or quotes.
8734 If both @var{regexp} and @var{type_regexp} are provided, an argument
8735 is printed only if its name matches @var{regexp} and its type matches
8738 @item info locals [-q]
8740 Print the local variables of the selected frame, each on a separate
8741 line. These are all variables (declared either static or automatic)
8742 accessible at the point of execution of the selected frame.
8744 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8745 printing header information and messages explaining why no local variables
8748 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8749 Like @kbd{info locals}, but only print the local variables selected
8750 with the provided regexp(s).
8752 If @var{regexp} is provided, print only the local variables whose names
8753 match the regular expression @var{regexp}.
8755 If @var{type_regexp} is provided, print only the local variables whose
8756 types, as printed by the @code{whatis} command, match
8757 the regular expression @var{type_regexp}.
8758 If @var{type_regexp} contains space(s), it should be enclosed in
8759 quote characters. If needed, use backslash to escape the meaning
8760 of special characters or quotes.
8762 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8763 is printed only if its name matches @var{regexp} and its type matches
8766 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8767 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8768 For example, your program might use Resource Acquisition Is
8769 Initialization types (RAII) such as @code{lock_something_t}: each
8770 local variable of type @code{lock_something_t} automatically places a
8771 lock that is destroyed when the variable goes out of scope. You can
8772 then list all acquired locks in your program by doing
8774 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8777 or the equivalent shorter form
8779 tfaas i lo -q -t lock_something_t
8785 @section Applying a Command to Several Frames.
8787 @cindex apply command to several frames
8789 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8790 The @code{frame apply} command allows you to apply the named
8791 @var{command} to one or more frames.
8795 Specify @code{all} to apply @var{command} to all frames.
8798 Use @var{count} to apply @var{command} to the innermost @var{count}
8799 frames, where @var{count} is a positive number.
8802 Use @var{-count} to apply @var{command} to the outermost @var{count}
8803 frames, where @var{count} is a positive number.
8806 Use @code{level} to apply @var{command} to the set of frames identified
8807 by the @var{level} list. @var{level} is a frame level or a range of frame
8808 levels as @var{level1}-@var{level2}. The frame level is the number shown
8809 in the first field of the @samp{backtrace} command output.
8810 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8811 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8815 Note that the frames on which @code{frame apply} applies a command are
8816 also influenced by the @code{set backtrace} settings such as @code{set
8817 backtrace past-main} and @code{set backtrace limit N}.
8818 @xref{Backtrace,,Backtraces}.
8820 The @code{frame apply} command also supports a number of options that
8821 allow overriding relevant @code{set backtrace} settings:
8824 @item -past-main [@code{on}|@code{off}]
8825 Whether backtraces should continue past @code{main}.
8826 Related setting: @ref{set backtrace past-main}.
8828 @item -past-entry [@code{on}|@code{off}]
8829 Whether backtraces should continue past the entry point of a program.
8830 Related setting: @ref{set backtrace past-entry}.
8833 By default, @value{GDBN} displays some frame information before the
8834 output produced by @var{command}, and an error raised during the
8835 execution of a @var{command} will abort @code{frame apply}. The
8836 following options can be used to fine-tune these behaviors:
8840 The flag @code{-c}, which stands for @samp{continue}, causes any
8841 errors in @var{command} to be displayed, and the execution of
8842 @code{frame apply} then continues.
8844 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8845 or empty output produced by a @var{command} to be silently ignored.
8846 That is, the execution continues, but the frame information and errors
8849 The flag @code{-q} (@samp{quiet}) disables printing the frame
8853 The following example shows how the flags @code{-c} and @code{-s} are
8854 working when applying the command @code{p j} to all frames, where
8855 variable @code{j} can only be successfully printed in the outermost
8856 @code{#1 main} frame.
8860 (gdb) frame apply all p j
8861 #0 some_function (i=5) at fun.c:4
8862 No symbol "j" in current context.
8863 (gdb) frame apply all -c p j
8864 #0 some_function (i=5) at fun.c:4
8865 No symbol "j" in current context.
8866 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8868 (gdb) frame apply all -s p j
8869 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8875 By default, @samp{frame apply}, prints the frame location
8876 information before the command output:
8880 (gdb) frame apply all p $sp
8881 #0 some_function (i=5) at fun.c:4
8882 $4 = (void *) 0xffffd1e0
8883 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8884 $5 = (void *) 0xffffd1f0
8889 If the flag @code{-q} is given, no frame information is printed:
8892 (gdb) frame apply all -q p $sp
8893 $12 = (void *) 0xffffd1e0
8894 $13 = (void *) 0xffffd1f0
8904 @cindex apply a command to all frames (ignoring errors and empty output)
8905 @item faas @var{command}
8906 Shortcut for @code{frame apply all -s @var{command}}.
8907 Applies @var{command} on all frames, ignoring errors and empty output.
8909 It can for example be used to print a local variable or a function
8910 argument without knowing the frame where this variable or argument
8913 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8916 The @code{faas} command accepts the same options as the @code{frame
8917 apply} command. @xref{Frame Apply,,frame apply}.
8919 Note that the command @code{tfaas @var{command}} applies @var{command}
8920 on all frames of all threads. See @xref{Threads,,Threads}.
8924 @node Frame Filter Management
8925 @section Management of Frame Filters.
8926 @cindex managing frame filters
8928 Frame filters are Python based utilities to manage and decorate the
8929 output of frames. @xref{Frame Filter API}, for further information.
8931 Managing frame filters is performed by several commands available
8932 within @value{GDBN}, detailed here.
8935 @kindex info frame-filter
8936 @item info frame-filter
8937 Print a list of installed frame filters from all dictionaries, showing
8938 their name, priority and enabled status.
8940 @kindex disable frame-filter
8941 @anchor{disable frame-filter all}
8942 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8943 Disable a frame filter in the dictionary matching
8944 @var{filter-dictionary} and @var{filter-name}. The
8945 @var{filter-dictionary} may be @code{all}, @code{global},
8946 @code{progspace}, or the name of the object file where the frame filter
8947 dictionary resides. When @code{all} is specified, all frame filters
8948 across all dictionaries are disabled. The @var{filter-name} is the name
8949 of the frame filter and is used when @code{all} is not the option for
8950 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8951 may be enabled again later.
8953 @kindex enable frame-filter
8954 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8955 Enable a frame filter in the dictionary matching
8956 @var{filter-dictionary} and @var{filter-name}. The
8957 @var{filter-dictionary} may be @code{all}, @code{global},
8958 @code{progspace} or the name of the object file where the frame filter
8959 dictionary resides. When @code{all} is specified, all frame filters across
8960 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8961 filter and is used when @code{all} is not the option for
8962 @var{filter-dictionary}.
8967 (gdb) info frame-filter
8969 global frame-filters:
8970 Priority Enabled Name
8971 1000 No PrimaryFunctionFilter
8974 progspace /build/test frame-filters:
8975 Priority Enabled Name
8976 100 Yes ProgspaceFilter
8978 objfile /build/test frame-filters:
8979 Priority Enabled Name
8980 999 Yes BuildProgramFilter
8982 (gdb) disable frame-filter /build/test BuildProgramFilter
8983 (gdb) info frame-filter
8985 global frame-filters:
8986 Priority Enabled Name
8987 1000 No PrimaryFunctionFilter
8990 progspace /build/test frame-filters:
8991 Priority Enabled Name
8992 100 Yes ProgspaceFilter
8994 objfile /build/test frame-filters:
8995 Priority Enabled Name
8996 999 No BuildProgramFilter
8998 (gdb) enable frame-filter global PrimaryFunctionFilter
8999 (gdb) info frame-filter
9001 global frame-filters:
9002 Priority Enabled Name
9003 1000 Yes PrimaryFunctionFilter
9006 progspace /build/test frame-filters:
9007 Priority Enabled Name
9008 100 Yes ProgspaceFilter
9010 objfile /build/test frame-filters:
9011 Priority Enabled Name
9012 999 No BuildProgramFilter
9015 @kindex set frame-filter priority
9016 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
9017 Set the @var{priority} of a frame filter in the dictionary matching
9018 @var{filter-dictionary}, and the frame filter name matching
9019 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9020 @code{progspace} or the name of the object file where the frame filter
9021 dictionary resides. The @var{priority} is an integer.
9023 @kindex show frame-filter priority
9024 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
9025 Show the @var{priority} of a frame filter in the dictionary matching
9026 @var{filter-dictionary}, and the frame filter name matching
9027 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9028 @code{progspace} or the name of the object file where the frame filter
9034 (gdb) info frame-filter
9036 global frame-filters:
9037 Priority Enabled Name
9038 1000 Yes PrimaryFunctionFilter
9041 progspace /build/test frame-filters:
9042 Priority Enabled Name
9043 100 Yes ProgspaceFilter
9045 objfile /build/test frame-filters:
9046 Priority Enabled Name
9047 999 No BuildProgramFilter
9049 (gdb) set frame-filter priority global Reverse 50
9050 (gdb) info frame-filter
9052 global frame-filters:
9053 Priority Enabled Name
9054 1000 Yes PrimaryFunctionFilter
9057 progspace /build/test frame-filters:
9058 Priority Enabled Name
9059 100 Yes ProgspaceFilter
9061 objfile /build/test frame-filters:
9062 Priority Enabled Name
9063 999 No BuildProgramFilter
9068 @chapter Examining Source Files
9070 @value{GDBN} can print parts of your program's source, since the debugging
9071 information recorded in the program tells @value{GDBN} what source files were
9072 used to build it. When your program stops, @value{GDBN} spontaneously prints
9073 the line where it stopped. Likewise, when you select a stack frame
9074 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
9075 execution in that frame has stopped. You can print other portions of
9076 source files by explicit command.
9078 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
9079 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
9080 @value{GDBN} under @sc{gnu} Emacs}.
9083 * List:: Printing source lines
9084 * Location Specifications:: How to specify code locations
9085 * Edit:: Editing source files
9086 * Search:: Searching source files
9087 * Source Path:: Specifying source directories
9088 * Machine Code:: Source and machine code
9089 * Disable Reading Source:: Disable Reading Source Code
9093 @section Printing Source Lines
9096 @kindex l @r{(@code{list})}
9097 To print lines from a source file, use the @code{list} command
9098 (abbreviated @code{l}). By default, ten lines are printed.
9099 There are several ways to specify what part of the file you want to
9100 print; see @ref{Location Specifications}, for the full list.
9102 Here are the forms of the @code{list} command most commonly used:
9105 @item list @var{linenum}
9106 Print lines centered around line number @var{linenum} in the
9107 current source file.
9109 @item list @var{function}
9110 Print lines centered around the beginning of function
9114 Print more lines. If the last lines printed were printed with a
9115 @code{list} command, this prints lines following the last lines
9116 printed; however, if the last line printed was a solitary line printed
9117 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9118 Stack}), this prints lines centered around that line.
9121 Print lines just before the lines last printed.
9124 @cindex @code{list}, how many lines to display
9125 By default, @value{GDBN} prints ten source lines with any of these forms of
9126 the @code{list} command. You can change this using @code{set listsize}:
9129 @kindex set listsize
9130 @item set listsize @var{count}
9131 @itemx set listsize unlimited
9132 Make the @code{list} command display @var{count} source lines (unless
9133 the @code{list} argument explicitly specifies some other number).
9134 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9136 @kindex show listsize
9138 Display the number of lines that @code{list} prints.
9141 Repeating a @code{list} command with @key{RET} discards the argument,
9142 so it is equivalent to typing just @code{list}. This is more useful
9143 than listing the same lines again. An exception is made for an
9144 argument of @samp{-}; that argument is preserved in repetition so that
9145 each repetition moves up in the source file.
9147 In general, the @code{list} command expects you to supply zero, one or
9148 two location specs. These location specs are interpreted to resolve
9149 to source code lines; there are several ways of writing them
9150 (@pxref{Location Specifications}), but the effect is always to resolve
9151 to some source lines to display.
9153 Here is a complete description of the possible arguments for @code{list}:
9156 @item list @var{locspec}
9157 Print lines centered around the line or lines of all the code
9158 locations that result from resolving @var{locspec}.
9160 @item list @var{first},@var{last}
9161 Print lines from @var{first} to @var{last}. Both arguments are
9162 location specs. When a @code{list} command has two location specs,
9163 and the source file of the second location spec is omitted, this
9164 refers to the same source file as the first location spec. If either
9165 @var{first} or @var{last} resolve to more than one source line in the
9166 program, then the list command shows the list of resolved source
9167 lines and does not proceed with the source code listing.
9169 @item list ,@var{last}
9170 Print lines ending with @var{last}.
9172 Likewise, if @var{last} resolves to more than one source line in the
9173 program, then the list command prints the list of resolved source
9174 lines and does not proceed with the source code listing.
9176 @item list @var{first},
9177 Print lines starting with @var{first}.
9180 Print lines just after the lines last printed.
9183 Print lines just before the lines last printed.
9186 As described in the preceding table.
9189 @node Location Specifications
9190 @section Location Specifications
9191 @cindex specifying location
9193 @cindex source location
9194 @cindex code location
9196 @cindex location spec
9197 Several @value{GDBN} commands accept arguments that specify a location
9198 or locations of your program's code. Many times locations are
9199 specified using a source line number, but they can also be specified
9200 by a function name, an address, a label, etc. The different
9201 forms of specifying a location that @value{GDBN} recognizes are
9202 collectively known as forms of @dfn{location specification}, or
9203 @dfn{location spec}. This section documents the forms of specifying
9204 locations that @value{GDBN} recognizes.
9206 @cindex location resolution
9207 @cindex resolution of location spec
9208 When you specify a location, @value{GDBN} needs to find the place in
9209 your program, known as @dfn{code location}, that corresponds to the
9210 given location spec. We call this process of finding actual code
9211 locations corresponding to a location spec @dfn{location resolution}.
9213 A concrete code location in your program is uniquely identifiable by a
9214 set of several attributes: its source line number, the name of its
9215 source file, the fully-qualified and prototyped function in which it
9216 is defined, and an instruction address. Because each inferior has its
9217 own address space, the inferior number is also a necessary part of
9220 By contrast, location specs you type will many times omit some of
9221 these attributes. For example, it is customary to specify just the
9222 source line number to mean a line in the current source file, or
9223 specify just the basename of the file, omitting its directories. In
9224 other words, a location spec is usually incomplete, a kind of
9225 blueprint, and @value{GDBN} needs to complete the missing attributes
9226 by using the implied defaults, and by considering the source code and
9227 the debug information available to it. This is what location
9228 resolution is about.
9230 The resolution of an incomplete location spec can produce more than a
9231 single code location, if the spec doesn't allow distinguishing between
9232 them. Here are some examples of situations that result in a location
9233 spec matching multiple code locations in your program:
9237 The location spec specifies a function name, and there are several
9238 functions in the program which have that name. (To distinguish
9239 between them, you can specify a fully-qualified and prototyped
9240 function name, such as @code{A::func(int)} instead of just
9244 The location spec specifies a source file name, and there are several
9245 source files in the program that share the same name, for example
9246 several files with the same basename in different subdirectories. (To
9247 distinguish between them, specify enough leading directories with the
9251 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9252 instances of the function body, used in different cases, but their
9253 source-level names are identical.
9256 For a C@t{++} template function, a given line in the function can
9257 correspond to any number of instantiations.
9260 For an inlined function, a given source line can correspond to several
9261 actual code locations with that function's inlined code.
9264 Resolution of a location spec can also fail to produce a complete code
9265 location, or even fail to produce any code location. Here are some
9266 examples of such situations:
9270 Some parts of the program lack detailed enough debug info, so the
9271 resolved code location lacks some attributes, like source file name
9272 and line number, leaving just the instruction address and perhaps also
9273 a function name. Such an incomplete code location is only usable in
9274 contexts that work with addresses and/or function names. Some
9275 commands can only work with complete code locations.
9278 The location spec specifies a function name, and there are no
9279 functions in the program by that name, or they only exist in a
9280 yet-unloaded shared library.
9283 The location spec specifies a source file name, and there are no
9284 source files in the program by that name, or they only exist in a
9285 yet-unloaded shared library.
9288 The location spec specifies both a source file name and a source line
9289 number, and even though there are source files in the program that
9290 match the file name, none of those files has the specified line
9294 Locations may be specified using three different formats: linespec
9295 locations, explicit locations, or address locations. The following
9296 subsections describe these formats.
9299 * Linespec Locations:: Linespec locations
9300 * Explicit Locations:: Explicit locations
9301 * Address Locations:: Address locations
9304 @node Linespec Locations
9305 @subsection Linespec Locations
9306 @cindex linespec locations
9308 A @dfn{linespec} is a colon-separated list of source location parameters such
9309 as file name, function name, etc. Here are all the different ways of
9310 specifying a linespec:
9314 Specifies the line number @var{linenum} of the current source file.
9317 @itemx +@var{offset}
9318 Specifies the line @var{offset} lines before or after the @dfn{current
9319 line}. For the @code{list} command, the current line is the last one
9320 printed; for the breakpoint commands, this is the line at which
9321 execution stopped in the currently selected @dfn{stack frame}
9322 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9323 used as the second of the two linespecs in a @code{list} command,
9324 this specifies the line @var{offset} lines up or down from the first
9327 @item @var{filename}:@var{linenum}
9328 Specifies the line @var{linenum} in the source file @var{filename}.
9329 If @var{filename} is a relative file name, then it will match any
9330 source file name with the same trailing components. For example, if
9331 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9332 name of @file{/build/trunk/gcc/expr.c}, but not
9333 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9335 @item @var{function}
9336 Specifies the line that begins the body of the function @var{function}.
9337 For example, in C, this is the line with the open brace.
9339 By default, in C@t{++} and Ada, @var{function} is interpreted as
9340 specifying all functions named @var{function} in all scopes. For
9341 C@t{++}, this means in all namespaces and classes. For Ada, this
9342 means in all packages.
9344 For example, assuming a program with C@t{++} symbols named
9345 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9346 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9348 Commands that accept a linespec let you override this with the
9349 @code{-qualified} option. For example, @w{@kbd{break -qualified
9350 func}} sets a breakpoint on a free-function named @code{func} ignoring
9351 any C@t{++} class methods and namespace functions called @code{func}.
9353 @xref{Explicit Locations}.
9355 @item @var{function}:@var{label}
9356 Specifies the line where @var{label} appears in @var{function}.
9358 @item @var{filename}:@var{function}
9359 Specifies the line that begins the body of the function @var{function}
9360 in the file @var{filename}. You only need the file name with a
9361 function name to avoid ambiguity when there are identically named
9362 functions in different source files.
9365 Specifies the line at which the label named @var{label} appears
9366 in the function corresponding to the currently selected stack frame.
9367 If there is no current selected stack frame (for instance, if the inferior
9368 is not running), then @value{GDBN} will not search for a label.
9370 @cindex breakpoint at static probe point
9371 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9372 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9373 applications to embed static probes. @xref{Static Probe Points}, for more
9374 information on finding and using static probes. This form of linespec
9375 specifies the location of such a static probe.
9377 If @var{objfile} is given, only probes coming from that shared library
9378 or executable matching @var{objfile} as a regular expression are considered.
9379 If @var{provider} is given, then only probes from that provider are considered.
9380 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9381 each one of those probes.
9384 @node Explicit Locations
9385 @subsection Explicit Locations
9386 @cindex explicit locations
9388 @dfn{Explicit locations} allow the user to directly specify the source
9389 location's parameters using option-value pairs.
9391 Explicit locations are useful when several functions, labels, or
9392 file names have the same name (base name for files) in the program's
9393 sources. In these cases, explicit locations point to the source
9394 line you meant more accurately and unambiguously. Also, using
9395 explicit locations might be faster in large programs.
9397 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9398 defined in the file named @file{foo} or the label @code{bar} in a function
9399 named @code{foo}. @value{GDBN} must search either the file system or
9400 the symbol table to know.
9402 The list of valid explicit location options is summarized in the
9406 @item -source @var{filename}
9407 The value specifies the source file name. To differentiate between
9408 files with the same base name, prepend as many directories as is necessary
9409 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9410 @value{GDBN} will use the first file it finds with the given base
9411 name. This option requires the use of either @code{-function} or @code{-line}.
9413 @item -function @var{function}
9414 The value specifies the name of a function. Operations
9415 on function locations unmodified by other options (such as @code{-label}
9416 or @code{-line}) refer to the line that begins the body of the function.
9417 In C, for example, this is the line with the open brace.
9419 By default, in C@t{++} and Ada, @var{function} is interpreted as
9420 specifying all functions named @var{function} in all scopes. For
9421 C@t{++}, this means in all namespaces and classes. For Ada, this
9422 means in all packages.
9424 For example, assuming a program with C@t{++} symbols named
9425 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9426 -function func}} and @w{@kbd{break -function B::func}} set a
9427 breakpoint on both symbols.
9429 You can use the @kbd{-qualified} flag to override this (see below).
9433 This flag makes @value{GDBN} interpret a function name specified with
9434 @kbd{-function} as a complete fully-qualified name.
9436 For example, assuming a C@t{++} program with symbols named
9437 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9438 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9440 (Note: the @kbd{-qualified} option can precede a linespec as well
9441 (@pxref{Linespec Locations}), so the particular example above could be
9442 simplified as @w{@kbd{break -qualified B::func}}.)
9444 @item -label @var{label}
9445 The value specifies the name of a label. When the function
9446 name is not specified, the label is searched in the function of the currently
9447 selected stack frame.
9449 @item -line @var{number}
9450 The value specifies a line offset for the location. The offset may either
9451 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9452 the command. When specified without any other options, the line offset is
9453 relative to the current line.
9456 Explicit location options may be abbreviated by omitting any non-unique
9457 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9459 @node Address Locations
9460 @subsection Address Locations
9461 @cindex address locations
9463 @dfn{Address locations} indicate a specific program address. They have
9464 the generalized form *@var{address}.
9466 For line-oriented commands, such as @code{list} and @code{edit}, this
9467 specifies a source line that contains @var{address}. For @code{break} and
9468 other breakpoint-oriented commands, this can be used to set breakpoints in
9469 parts of your program which do not have debugging information or
9472 Here @var{address} may be any expression valid in the current working
9473 language (@pxref{Languages, working language}) that specifies a code
9474 address. In addition, as a convenience, @value{GDBN} extends the
9475 semantics of expressions used in locations to cover several situations
9476 that frequently occur during debugging. Here are the various forms
9480 @item @var{expression}
9481 Any expression valid in the current working language.
9483 @item @var{funcaddr}
9484 An address of a function or procedure derived from its name. In C,
9485 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9486 simply the function's name @var{function} (and actually a special case
9487 of a valid expression). In Pascal and Modula-2, this is
9488 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9489 (although the Pascal form also works).
9491 This form specifies the address of the function's first instruction,
9492 before the stack frame and arguments have been set up.
9494 @item '@var{filename}':@var{funcaddr}
9495 Like @var{funcaddr} above, but also specifies the name of the source
9496 file explicitly. This is useful if the name of the function does not
9497 specify the function unambiguously, e.g., if there are several
9498 functions with identical names in different source files.
9502 @section Editing Source Files
9503 @cindex editing source files
9506 @kindex e @r{(@code{edit})}
9507 To edit the lines in a source file, use the @code{edit} command.
9508 The editing program of your choice
9509 is invoked with the current line set to
9510 the active line in the program.
9511 Alternatively, there are several ways to specify what part of the file you
9512 want to print if you want to see other parts of the program:
9515 @item edit @var{locspec}
9516 Edit the source file of the code location that results from resolving
9517 @code{locspec}. Editing starts at the source file and source line
9518 @code{locspec} resolves to.
9519 @xref{Location Specifications}, for all the possible forms of the
9520 @var{locspec} argument.
9522 If @code{locspec} resolves to more than one source line in your
9523 program, then the command prints the list of resolved source lines and
9524 does not proceed with the editing.
9526 Here are the forms of the @code{edit} command most commonly used:
9529 @item edit @var{number}
9530 Edit the current source file with @var{number} as the active line number.
9532 @item edit @var{function}
9533 Edit the file containing @var{function} at the beginning of its definition.
9538 @subsection Choosing your Editor
9539 You can customize @value{GDBN} to use any editor you want
9541 The only restriction is that your editor (say @code{ex}), recognizes the
9542 following command-line syntax:
9544 ex +@var{number} file
9546 The optional numeric value +@var{number} specifies the number of the line in
9547 the file where to start editing.}.
9548 By default, it is @file{@value{EDITOR}}, but you can change this
9549 by setting the environment variable @env{EDITOR} before using
9550 @value{GDBN}. For example, to configure @value{GDBN} to use the
9551 @code{vi} editor, you could use these commands with the @code{sh} shell:
9557 or in the @code{csh} shell,
9559 setenv EDITOR /usr/bin/vi
9564 @section Searching Source Files
9565 @cindex searching source files
9567 There are two commands for searching through the current source file for a
9572 @kindex forward-search
9573 @kindex fo @r{(@code{forward-search})}
9574 @item forward-search @var{regexp}
9575 @itemx search @var{regexp}
9576 The command @samp{forward-search @var{regexp}} checks each line,
9577 starting with the one following the last line listed, for a match for
9578 @var{regexp}. It lists the line that is found. You can use the
9579 synonym @samp{search @var{regexp}} or abbreviate the command name as
9582 @kindex reverse-search
9583 @item reverse-search @var{regexp}
9584 The command @samp{reverse-search @var{regexp}} checks each line, starting
9585 with the one before the last line listed and going backward, for a match
9586 for @var{regexp}. It lists the line that is found. You can abbreviate
9587 this command as @code{rev}.
9591 @section Specifying Source Directories
9594 @cindex directories for source files
9595 Executable programs sometimes do not record the directories of the source
9596 files from which they were compiled, just the names. Even when they do,
9597 the directories could be moved between the compilation and your debugging
9598 session. @value{GDBN} has a list of directories to search for source files;
9599 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9600 it tries all the directories in the list, in the order they are present
9601 in the list, until it finds a file with the desired name.
9603 For example, suppose an executable references the file
9604 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9605 directory, and the @dfn{source path} is @file{/mnt/cross}.
9606 @value{GDBN} would look for the source file in the following
9611 @item @file{/usr/src/foo-1.0/lib/foo.c}
9612 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9613 @item @file{/mnt/cross/foo.c}
9617 If the source file is not present at any of the above locations then
9618 an error is printed. @value{GDBN} does not look up the parts of the
9619 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9620 Likewise, the subdirectories of the source path are not searched: if
9621 the source path is @file{/mnt/cross}, and the binary refers to
9622 @file{foo.c}, @value{GDBN} would not find it under
9623 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9625 Plain file names, relative file names with leading directories, file
9626 names containing dots, etc.@: are all treated as described above,
9627 except that non-absolute file names are not looked up literally. If
9628 the @dfn{source path} is @file{/mnt/cross}, the source file is
9629 recorded as @file{../lib/foo.c}, and no compilation directory is
9630 recorded, then @value{GDBN} will search in the following locations:
9634 @item @file{/mnt/cross/../lib/foo.c}
9635 @item @file{/mnt/cross/foo.c}
9641 @vindex $cdir@r{, convenience variable}
9642 @vindex $cwd@r{, convenience variable}
9643 @cindex compilation directory
9644 @cindex current directory
9645 @cindex working directory
9646 @cindex directory, current
9647 @cindex directory, compilation
9648 The @dfn{source path} will always include two special entries
9649 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9650 (if one is recorded) and the current working directory respectively.
9652 @samp{$cdir} causes @value{GDBN} to search within the compilation
9653 directory, if one is recorded in the debug information. If no
9654 compilation directory is recorded in the debug information then
9655 @samp{$cdir} is ignored.
9657 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9658 current working directory as it changes during your @value{GDBN}
9659 session, while the latter is immediately expanded to the current
9660 directory at the time you add an entry to the source path.
9662 If a compilation directory is recorded in the debug information, and
9663 @value{GDBN} has not found the source file after the first search
9664 using @dfn{source path}, then @value{GDBN} will combine the
9665 compilation directory and the filename, and then search for the source
9666 file again using the @dfn{source path}.
9668 For example, if the executable records the source file as
9669 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9670 recorded as @file{/project/build}, and the @dfn{source path} is
9671 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9672 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9673 search for the source file in the following locations:
9677 @item @file{/usr/src/foo-1.0/lib/foo.c}
9678 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9679 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9680 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9681 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9682 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9683 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9684 @item @file{/mnt/cross/foo.c}
9685 @item @file{/project/build/foo.c}
9686 @item @file{/home/user/foo.c}
9690 If the file name in the previous example had been recorded in the
9691 executable as a relative path rather than an absolute path, then the
9692 first look up would not have occurred, but all of the remaining steps
9695 When searching for source files on MS-DOS and MS-Windows, where
9696 absolute paths start with a drive letter (e.g.@:
9697 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9698 from the file name before appending it to a search directory from
9699 @dfn{source path}; for instance if the executable references the
9700 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9701 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9702 locations for the source file:
9706 @item @file{C:/project/foo.c}
9707 @item @file{D:/mnt/cross/project/foo.c}
9708 @item @file{D:/mnt/cross/foo.c}
9712 Note that the executable search path is @emph{not} used to locate the
9715 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9716 any information it has cached about where source files are found and where
9717 each line is in the file.
9721 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9722 and @samp{$cwd}, in that order.
9723 To add other directories, use the @code{directory} command.
9725 The search path is used to find both program source files and @value{GDBN}
9726 script files (read using the @samp{-command} option and @samp{source} command).
9728 In addition to the source path, @value{GDBN} provides a set of commands
9729 that manage a list of source path substitution rules. A @dfn{substitution
9730 rule} specifies how to rewrite source directories stored in the program's
9731 debug information in case the sources were moved to a different
9732 directory between compilation and debugging. A rule is made of
9733 two strings, the first specifying what needs to be rewritten in
9734 the path, and the second specifying how it should be rewritten.
9735 In @ref{set substitute-path}, we name these two parts @var{from} and
9736 @var{to} respectively. @value{GDBN} does a simple string replacement
9737 of @var{from} with @var{to} at the start of the directory part of the
9738 source file name, and uses that result instead of the original file
9739 name to look up the sources.
9741 Using the previous example, suppose the @file{foo-1.0} tree has been
9742 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9743 @value{GDBN} to replace @file{/usr/src} in all source path names with
9744 @file{/mnt/cross}. The first lookup will then be
9745 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9746 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9747 substitution rule, use the @code{set substitute-path} command
9748 (@pxref{set substitute-path}).
9750 To avoid unexpected substitution results, a rule is applied only if the
9751 @var{from} part of the directory name ends at a directory separator.
9752 For instance, a rule substituting @file{/usr/source} into
9753 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9754 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9755 is applied only at the beginning of the directory name, this rule will
9756 not be applied to @file{/root/usr/source/baz.c} either.
9758 In many cases, you can achieve the same result using the @code{directory}
9759 command. However, @code{set substitute-path} can be more efficient in
9760 the case where the sources are organized in a complex tree with multiple
9761 subdirectories. With the @code{directory} command, you need to add each
9762 subdirectory of your project. If you moved the entire tree while
9763 preserving its internal organization, then @code{set substitute-path}
9764 allows you to direct the debugger to all the sources with one single
9767 @code{set substitute-path} is also more than just a shortcut command.
9768 The source path is only used if the file at the original location no
9769 longer exists. On the other hand, @code{set substitute-path} modifies
9770 the debugger behavior to look at the rewritten location instead. So, if
9771 for any reason a source file that is not relevant to your executable is
9772 located at the original location, a substitution rule is the only
9773 method available to point @value{GDBN} at the new location.
9775 @cindex @samp{--with-relocated-sources}
9776 @cindex default source path substitution
9777 You can configure a default source path substitution rule by
9778 configuring @value{GDBN} with the
9779 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9780 should be the name of a directory under @value{GDBN}'s configured
9781 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9782 directory names in debug information under @var{dir} will be adjusted
9783 automatically if the installed @value{GDBN} is moved to a new
9784 location. This is useful if @value{GDBN}, libraries or executables
9785 with debug information and corresponding source code are being moved
9789 @item directory @var{dirname} @dots{}
9790 @item dir @var{dirname} @dots{}
9791 Add directory @var{dirname} to the front of the source path. Several
9792 directory names may be given to this command, separated by @samp{:}
9793 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9794 part of absolute file names) or
9795 whitespace. You may specify a directory that is already in the source
9796 path; this moves it forward, so @value{GDBN} searches it sooner.
9798 The special strings @samp{$cdir} (to refer to the compilation
9799 directory, if one is recorded), and @samp{$cwd} (to refer to the
9800 current working directory) can also be included in the list of
9801 directories @var{dirname}. Though these will already be in the source
9802 path they will be moved forward in the list so @value{GDBN} searches
9806 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9808 @c RET-repeat for @code{directory} is explicitly disabled, but since
9809 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9811 @item set directories @var{path-list}
9812 @kindex set directories
9813 Set the source path to @var{path-list}.
9814 @samp{$cdir:$cwd} are added if missing.
9816 @item show directories
9817 @kindex show directories
9818 Print the source path: show which directories it contains.
9820 @anchor{set substitute-path}
9821 @item set substitute-path @var{from} @var{to}
9822 @kindex set substitute-path
9823 Define a source path substitution rule, and add it at the end of the
9824 current list of existing substitution rules. If a rule with the same
9825 @var{from} was already defined, then the old rule is also deleted.
9827 For example, if the file @file{/foo/bar/baz.c} was moved to
9828 @file{/mnt/cross/baz.c}, then the command
9831 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9835 will tell @value{GDBN} to replace @samp{/foo/bar} with
9836 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9837 @file{baz.c} even though it was moved.
9839 In the case when more than one substitution rule have been defined,
9840 the rules are evaluated one by one in the order where they have been
9841 defined. The first one matching, if any, is selected to perform
9844 For instance, if we had entered the following commands:
9847 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9848 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9852 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9853 @file{/mnt/include/defs.h} by using the first rule. However, it would
9854 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9855 @file{/mnt/src/lib/foo.c}.
9858 @item unset substitute-path [path]
9859 @kindex unset substitute-path
9860 If a path is specified, search the current list of substitution rules
9861 for a rule that would rewrite that path. Delete that rule if found.
9862 A warning is emitted by the debugger if no rule could be found.
9864 If no path is specified, then all substitution rules are deleted.
9866 @item show substitute-path [path]
9867 @kindex show substitute-path
9868 If a path is specified, then print the source path substitution rule
9869 which would rewrite that path, if any.
9871 If no path is specified, then print all existing source path substitution
9876 If your source path is cluttered with directories that are no longer of
9877 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9878 versions of source. You can correct the situation as follows:
9882 Use @code{directory} with no argument to reset the source path to its default value.
9885 Use @code{directory} with suitable arguments to reinstall the
9886 directories you want in the source path. You can add all the
9887 directories in one command.
9891 @section Source and Machine Code
9892 @cindex source line and its code address
9894 You can use the command @code{info line} to map source lines to program
9895 addresses (and vice versa), and the command @code{disassemble} to display
9896 a range of addresses as machine instructions. You can use the command
9897 @code{set disassemble-next-line} to set whether to disassemble next
9898 source line when execution stops. When run under @sc{gnu} Emacs
9899 mode, the @code{info line} command causes the arrow to point to the
9900 line specified. Also, @code{info line} prints addresses in symbolic form as
9906 @itemx info line @var{locspec}
9907 Print the starting and ending addresses of the compiled code for the
9908 source lines of the code locations that result from resolving
9909 @var{locspec}. @xref{Location Specifications}, for the various forms
9911 With no @var{locspec}, information about the current source line is
9915 For example, we can use @code{info line} to discover the location of
9916 the object code for the first line of function
9917 @code{m4_changequote}:
9920 (@value{GDBP}) info line m4_changequote
9921 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9922 ends at 0x6350 <m4_changequote+4>.
9926 @cindex code address and its source line
9927 We can also inquire, using @code{*@var{addr}} as the form for
9928 @var{locspec}, what source line covers a particular address
9931 (@value{GDBP}) info line *0x63ff
9932 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9933 ends at 0x6404 <m4_changequote+184>.
9936 @cindex @code{$_} and @code{info line}
9937 @cindex @code{x} command, default address
9938 @kindex x@r{(examine), and} info line
9939 After @code{info line}, the default address for the @code{x} command
9940 is changed to the starting address of the line, so that @samp{x/i} is
9941 sufficient to begin examining the machine code (@pxref{Memory,
9942 ,Examining Memory}). Also, this address is saved as the value of the
9943 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9946 @cindex info line, repeated calls
9947 After @code{info line}, using @code{info line} again without
9948 specifying a location will display information about the next source
9951 @anchor{disassemble}
9954 @cindex assembly instructions
9955 @cindex instructions, assembly
9956 @cindex machine instructions
9957 @cindex listing machine instructions
9959 @itemx disassemble /m
9960 @itemx disassemble /s
9961 @itemx disassemble /r
9962 @itemx disassemble /b
9963 This specialized command dumps a range of memory as machine
9964 instructions. It can also print mixed source+disassembly by specifying
9965 the @code{/m} or @code{/s} modifier and print the raw instructions in
9966 hex as well as in symbolic form by specifying the @code{/r} or @code{/b}
9967 modifier. The default memory range is the function surrounding the
9968 program counter of the selected frame. A single argument to this
9969 command is a program counter value; @value{GDBN} dumps the function
9970 surrounding this value. When two arguments are given, they should be
9971 separated by a comma, possibly surrounded by whitespace. The arguments
9972 specify a range of addresses to dump, in one of two forms:
9975 @item @var{start},@var{end}
9976 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9977 @item @var{start},+@var{length}
9978 the addresses from @var{start} (inclusive) to
9979 @code{@var{start}+@var{length}} (exclusive).
9983 When 2 arguments are specified, the name of the function is also
9984 printed (since there could be several functions in the given range).
9986 The argument(s) can be any expression yielding a numeric value, such as
9987 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9989 If the range of memory being disassembled contains current program counter,
9990 the instruction at that location is shown with a @code{=>} marker.
9993 The following example shows the disassembly of a range of addresses of
9994 HP PA-RISC 2.0 code:
9997 (@value{GDBP}) disas 0x32c4, 0x32e4
9998 Dump of assembler code from 0x32c4 to 0x32e4:
9999 0x32c4 <main+204>: addil 0,dp
10000 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
10001 0x32cc <main+212>: ldil 0x3000,r31
10002 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
10003 0x32d4 <main+220>: ldo 0(r31),rp
10004 0x32d8 <main+224>: addil -0x800,dp
10005 0x32dc <main+228>: ldo 0x588(r1),r26
10006 0x32e0 <main+232>: ldil 0x3000,r31
10007 End of assembler dump.
10010 The following two examples are for RISC-V, and demonstrates the
10011 difference between the @code{/r} and @code{/b} modifiers. First with
10012 @code{/b}, the bytes of the instruction are printed, in hex, in memory
10016 (@value{GDBP}) disassemble /b 0x00010150,0x0001015c
10017 Dump of assembler code from 0x10150 to 0x1015c:
10018 0x00010150 <call_me+4>: 22 dc sw s0,56(sp)
10019 0x00010152 <call_me+6>: 80 00 addi s0,sp,64
10020 0x00010154 <call_me+8>: 23 26 a4 fe sw a0,-20(s0)
10021 0x00010158 <call_me+12>: 23 24 b4 fe sw a1,-24(s0)
10022 End of assembler dump.
10025 In contrast, with @code{/r} the bytes of the instruction are displayed
10026 in the instruction order, for RISC-V this means that the bytes have been
10027 swapped to little-endian order:
10030 (@value{GDBP}) disassemble /r 0x00010150,0x0001015c
10031 Dump of assembler code from 0x10150 to 0x1015c:
10032 0x00010150 <call_me+4>: dc22 sw s0,56(sp)
10033 0x00010152 <call_me+6>: 0080 addi s0,sp,64
10034 0x00010154 <call_me+8>: fea42623 sw a0,-20(s0)
10035 0x00010158 <call_me+12>: feb42423 sw a1,-24(s0)
10036 End of assembler dump.
10039 Here is an example showing mixed source+assembly for Intel x86
10040 with @code{/m} or @code{/s}, when the program is stopped just after
10041 function prologue in a non-optimized function with no inline code.
10044 (@value{GDBP}) disas /m main
10045 Dump of assembler code for function main:
10047 0x08048330 <+0>: push %ebp
10048 0x08048331 <+1>: mov %esp,%ebp
10049 0x08048333 <+3>: sub $0x8,%esp
10050 0x08048336 <+6>: and $0xfffffff0,%esp
10051 0x08048339 <+9>: sub $0x10,%esp
10053 6 printf ("Hello.\n");
10054 => 0x0804833c <+12>: movl $0x8048440,(%esp)
10055 0x08048343 <+19>: call 0x8048284 <puts@@plt>
10059 0x08048348 <+24>: mov $0x0,%eax
10060 0x0804834d <+29>: leave
10061 0x0804834e <+30>: ret
10063 End of assembler dump.
10066 The @code{/m} option is deprecated as its output is not useful when
10067 there is either inlined code or re-ordered code.
10068 The @code{/s} option is the preferred choice.
10069 Here is an example for AMD x86-64 showing the difference between
10070 @code{/m} output and @code{/s} output.
10071 This example has one inline function defined in a header file,
10072 and the code is compiled with @samp{-O2} optimization.
10073 Note how the @code{/m} output is missing the disassembly of
10074 several instructions that are present in the @code{/s} output.
10104 (@value{GDBP}) disas /m main
10105 Dump of assembler code for function main:
10109 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10110 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10114 0x000000000040041d <+29>: xor %eax,%eax
10115 0x000000000040041f <+31>: retq
10116 0x0000000000400420 <+32>: add %eax,%eax
10117 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10119 End of assembler dump.
10120 (@value{GDBP}) disas /s main
10121 Dump of assembler code for function main:
10125 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10129 0x0000000000400406 <+6>: test %eax,%eax
10130 0x0000000000400408 <+8>: js 0x400420 <main+32>
10135 0x000000000040040a <+10>: lea 0xa(%rax),%edx
10136 0x000000000040040d <+13>: test %eax,%eax
10137 0x000000000040040f <+15>: mov $0x1,%eax
10138 0x0000000000400414 <+20>: cmovne %edx,%eax
10142 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10146 0x000000000040041d <+29>: xor %eax,%eax
10147 0x000000000040041f <+31>: retq
10151 0x0000000000400420 <+32>: add %eax,%eax
10152 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10153 End of assembler dump.
10156 Here is another example showing raw instructions in hex for AMD x86-64,
10159 (gdb) disas /r 0x400281,+10
10160 Dump of assembler code from 0x400281 to 0x40028b:
10161 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10162 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10163 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10164 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10165 End of assembler dump.
10168 Note that the @samp{disassemble} command's address arguments are
10169 specified using expressions in your programming language
10170 (@pxref{Expressions, ,Expressions}), not location specs
10171 (@pxref{Location Specifications}). So, for example, if you want to
10172 disassemble function @code{bar} in file @file{foo.c}, you must type
10173 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10175 Some architectures have more than one commonly-used set of instruction
10176 mnemonics or other syntax.
10178 For programs that were dynamically linked and use shared libraries,
10179 instructions that call functions or branch to locations in the shared
10180 libraries might show a seemingly bogus location---it's actually a
10181 location of the relocation table. On some architectures, @value{GDBN}
10182 might be able to resolve these to actual function names.
10185 @kindex set disassembler-options
10186 @cindex disassembler options
10187 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10188 This command controls the passing of target specific information to
10189 the disassembler. For a list of valid options, please refer to the
10190 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10191 manual and/or the output of @kbd{objdump --help}
10192 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10193 The default value is the empty string.
10195 If it is necessary to specify more than one disassembler option, then
10196 multiple options can be placed together into a comma separated list.
10197 Currently this command is only supported on targets ARC, ARM, MIPS,
10200 @kindex show disassembler-options
10201 @item show disassembler-options
10202 Show the current setting of the disassembler options.
10206 @kindex set disassembly-flavor
10207 @cindex Intel disassembly flavor
10208 @cindex AT&T disassembly flavor
10209 @item set disassembly-flavor @var{instruction-set}
10210 Select the instruction set to use when disassembling the
10211 program via the @code{disassemble} or @code{x/i} commands.
10213 Currently this command is only defined for the Intel x86 family. You
10214 can set @var{instruction-set} to either @code{intel} or @code{att}.
10215 The default is @code{att}, the AT&T flavor used by default by Unix
10216 assemblers for x86-based targets.
10218 @kindex show disassembly-flavor
10219 @item show disassembly-flavor
10220 Show the current setting of the disassembly flavor.
10224 @kindex set disassemble-next-line
10225 @kindex show disassemble-next-line
10226 @item set disassemble-next-line
10227 @itemx show disassemble-next-line
10228 Control whether or not @value{GDBN} will disassemble the next source
10229 line or instruction when execution stops. If ON, @value{GDBN} will
10230 display disassembly of the next source line when execution of the
10231 program being debugged stops. This is @emph{in addition} to
10232 displaying the source line itself, which @value{GDBN} always does if
10233 possible. If the next source line cannot be displayed for some reason
10234 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10235 info in the debug info), @value{GDBN} will display disassembly of the
10236 next @emph{instruction} instead of showing the next source line. If
10237 AUTO, @value{GDBN} will display disassembly of next instruction only
10238 if the source line cannot be displayed. This setting causes
10239 @value{GDBN} to display some feedback when you step through a function
10240 with no line info or whose source file is unavailable. The default is
10241 OFF, which means never display the disassembly of the next line or
10245 @node Disable Reading Source
10246 @section Disable Reading Source Code
10247 @cindex source code, disable access
10249 In some cases it can be desirable to prevent @value{GDBN} from
10250 accessing source code files. One case where this might be desirable
10251 is if the source code files are located over a slow network
10254 The following command can be used to control whether @value{GDBN}
10255 should access source code files or not:
10258 @kindex set source open
10259 @kindex show source open
10260 @item set source open @r{[}on@r{|}off@r{]}
10261 @itemx show source open
10262 When this option is @code{on}, which is the default, @value{GDBN} will
10263 access source code files when needed, for example to print source
10264 lines when @value{GDBN} stops, or in response to the @code{list}
10267 When this option is @code{off}, @value{GDBN} will not access source
10272 @chapter Examining Data
10274 @cindex printing data
10275 @cindex examining data
10278 The usual way to examine data in your program is with the @code{print}
10279 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10280 evaluates and prints the value of an expression of the language your
10281 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10282 Different Languages}). It may also print the expression using a
10283 Python-based pretty-printer (@pxref{Pretty Printing}).
10286 @item print [[@var{options}] --] @var{expr}
10287 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10288 @var{expr} is an expression (in the source language). By default the
10289 value of @var{expr} is printed in a format appropriate to its data type;
10290 you can choose a different format by specifying @samp{/@var{f}}, where
10291 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10294 @anchor{print options}
10295 The @code{print} command supports a number of options that allow
10296 overriding relevant global print settings as set by @code{set print}
10300 @item -address [@code{on}|@code{off}]
10301 Set printing of addresses.
10302 Related setting: @ref{set print address}.
10304 @item -array [@code{on}|@code{off}]
10305 Pretty formatting of arrays.
10306 Related setting: @ref{set print array}.
10308 @item -array-indexes [@code{on}|@code{off}]
10309 Set printing of array indexes.
10310 Related setting: @ref{set print array-indexes}.
10312 @item -elements @var{number-of-elements}|@code{unlimited}
10313 Set limit on string chars or array elements to print. The value
10314 @code{unlimited} causes there to be no limit. Related setting:
10315 @ref{set print elements}.
10317 @item -max-depth @var{depth}|@code{unlimited}
10318 Set the threshold after which nested structures are replaced with
10319 ellipsis. Related setting: @ref{set print max-depth}.
10321 @item -nibbles [@code{on}|@code{off}]
10322 Set whether to print binary values in groups of four bits, known
10323 as ``nibbles''. @xref{set print nibbles}.
10325 @item -memory-tag-violations [@code{on}|@code{off}]
10326 Set printing of additional information about memory tag violations.
10327 @xref{set print memory-tag-violations}.
10329 @item -null-stop [@code{on}|@code{off}]
10330 Set printing of char arrays to stop at first null char. Related
10331 setting: @ref{set print null-stop}.
10333 @item -object [@code{on}|@code{off}]
10334 Set printing C@t{++} virtual function tables. Related setting:
10335 @ref{set print object}.
10337 @item -pretty [@code{on}|@code{off}]
10338 Set pretty formatting of structures. Related setting: @ref{set print
10341 @item -raw-values [@code{on}|@code{off}]
10342 Set whether to print values in raw form, bypassing any
10343 pretty-printers for that value. Related setting: @ref{set print
10346 @item -repeats @var{number-of-repeats}|@code{unlimited}
10347 Set threshold for repeated print elements. @code{unlimited} causes
10348 all elements to be individually printed. Related setting: @ref{set
10351 @item -static-members [@code{on}|@code{off}]
10352 Set printing C@t{++} static members. Related setting: @ref{set print
10355 @item -symbol [@code{on}|@code{off}]
10356 Set printing of symbol names when printing pointers. Related setting:
10357 @ref{set print symbol}.
10359 @item -union [@code{on}|@code{off}]
10360 Set printing of unions interior to structures. Related setting:
10361 @ref{set print union}.
10363 @item -vtbl [@code{on}|@code{off}]
10364 Set printing of C++ virtual function tables. Related setting:
10365 @ref{set print vtbl}.
10368 Because the @code{print} command accepts arbitrary expressions which
10369 may look like options (including abbreviations), if you specify any
10370 command option, then you must use a double dash (@code{--}) to mark
10371 the end of option processing.
10373 For example, this prints the value of the @code{-p} expression:
10376 (@value{GDBP}) print -p
10379 While this repeats the last value in the value history (see below)
10380 with the @code{-pretty} option in effect:
10383 (@value{GDBP}) print -p --
10386 Here is an example including both on option and an expression:
10390 (@value{GDBP}) print -pretty -- *myptr
10402 @item print [@var{options}]
10403 @itemx print [@var{options}] /@var{f}
10404 @cindex reprint the last value
10405 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10406 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10407 conveniently inspect the same value in an alternative format.
10410 If the architecture supports memory tagging, the @code{print} command will
10411 display pointer/memory tag mismatches if what is being printed is a pointer
10412 or reference type. @xref{Memory Tagging}.
10414 A more low-level way of examining data is with the @code{x} command.
10415 It examines data in memory at a specified address and prints it in a
10416 specified format. @xref{Memory, ,Examining Memory}.
10418 If you are interested in information about types, or about how the
10419 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10420 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10423 @cindex exploring hierarchical data structures
10425 Another way of examining values of expressions and type information is
10426 through the Python extension command @code{explore} (available only if
10427 the @value{GDBN} build is configured with @code{--with-python}). It
10428 offers an interactive way to start at the highest level (or, the most
10429 abstract level) of the data type of an expression (or, the data type
10430 itself) and explore all the way down to leaf scalar values/fields
10431 embedded in the higher level data types.
10434 @item explore @var{arg}
10435 @var{arg} is either an expression (in the source language), or a type
10436 visible in the current context of the program being debugged.
10439 The working of the @code{explore} command can be illustrated with an
10440 example. If a data type @code{struct ComplexStruct} is defined in your
10444 struct SimpleStruct
10450 struct ComplexStruct
10452 struct SimpleStruct *ss_p;
10458 followed by variable declarations as
10461 struct SimpleStruct ss = @{ 10, 1.11 @};
10462 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10466 then, the value of the variable @code{cs} can be explored using the
10467 @code{explore} command as follows.
10471 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10472 the following fields:
10474 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10475 arr = <Enter 1 to explore this field of type `int [10]'>
10477 Enter the field number of choice:
10481 Since the fields of @code{cs} are not scalar values, you are being
10482 prompted to chose the field you want to explore. Let's say you choose
10483 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10484 pointer, you will be asked if it is pointing to a single value. From
10485 the declaration of @code{cs} above, it is indeed pointing to a single
10486 value, hence you enter @code{y}. If you enter @code{n}, then you will
10487 be asked if it were pointing to an array of values, in which case this
10488 field will be explored as if it were an array.
10491 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10492 Continue exploring it as a pointer to a single value [y/n]: y
10493 The value of `*(cs.ss_p)' is a struct/class of type `struct
10494 SimpleStruct' with the following fields:
10496 i = 10 .. (Value of type `int')
10497 d = 1.1100000000000001 .. (Value of type `double')
10499 Press enter to return to parent value:
10503 If the field @code{arr} of @code{cs} was chosen for exploration by
10504 entering @code{1} earlier, then since it is as array, you will be
10505 prompted to enter the index of the element in the array that you want
10509 `cs.arr' is an array of `int'.
10510 Enter the index of the element you want to explore in `cs.arr': 5
10512 `(cs.arr)[5]' is a scalar value of type `int'.
10516 Press enter to return to parent value:
10519 In general, at any stage of exploration, you can go deeper towards the
10520 leaf values by responding to the prompts appropriately, or hit the
10521 return key to return to the enclosing data structure (the @i{higher}
10522 level data structure).
10524 Similar to exploring values, you can use the @code{explore} command to
10525 explore types. Instead of specifying a value (which is typically a
10526 variable name or an expression valid in the current context of the
10527 program being debugged), you specify a type name. If you consider the
10528 same example as above, your can explore the type
10529 @code{struct ComplexStruct} by passing the argument
10530 @code{struct ComplexStruct} to the @code{explore} command.
10533 (gdb) explore struct ComplexStruct
10537 By responding to the prompts appropriately in the subsequent interactive
10538 session, you can explore the type @code{struct ComplexStruct} in a
10539 manner similar to how the value @code{cs} was explored in the above
10542 The @code{explore} command also has two sub-commands,
10543 @code{explore value} and @code{explore type}. The former sub-command is
10544 a way to explicitly specify that value exploration of the argument is
10545 being invoked, while the latter is a way to explicitly specify that type
10546 exploration of the argument is being invoked.
10549 @item explore value @var{expr}
10550 @cindex explore value
10551 This sub-command of @code{explore} explores the value of the
10552 expression @var{expr} (if @var{expr} is an expression valid in the
10553 current context of the program being debugged). The behavior of this
10554 command is identical to that of the behavior of the @code{explore}
10555 command being passed the argument @var{expr}.
10557 @item explore type @var{arg}
10558 @cindex explore type
10559 This sub-command of @code{explore} explores the type of @var{arg} (if
10560 @var{arg} is a type visible in the current context of program being
10561 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10562 is an expression valid in the current context of the program being
10563 debugged). If @var{arg} is a type, then the behavior of this command is
10564 identical to that of the @code{explore} command being passed the
10565 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10566 this command will be identical to that of the @code{explore} command
10567 being passed the type of @var{arg} as the argument.
10571 * Expressions:: Expressions
10572 * Ambiguous Expressions:: Ambiguous Expressions
10573 * Variables:: Program variables
10574 * Arrays:: Artificial arrays
10575 * Output Formats:: Output formats
10576 * Memory:: Examining memory
10577 * Memory Tagging:: Memory Tagging
10578 * Auto Display:: Automatic display
10579 * Print Settings:: Print settings
10580 * Pretty Printing:: Python pretty printing
10581 * Value History:: Value history
10582 * Convenience Vars:: Convenience variables
10583 * Convenience Funs:: Convenience functions
10584 * Registers:: Registers
10585 * Floating Point Hardware:: Floating point hardware
10586 * Vector Unit:: Vector Unit
10587 * OS Information:: Auxiliary data provided by operating system
10588 * Memory Region Attributes:: Memory region attributes
10589 * Dump/Restore Files:: Copy between memory and a file
10590 * Core File Generation:: Cause a program dump its core
10591 * Character Sets:: Debugging programs that use a different
10592 character set than GDB does
10593 * Caching Target Data:: Data caching for targets
10594 * Searching Memory:: Searching memory for a sequence of bytes
10595 * Value Sizes:: Managing memory allocated for values
10599 @section Expressions
10601 @cindex expressions
10602 @code{print} and many other @value{GDBN} commands accept an expression and
10603 compute its value. Any kind of constant, variable or operator defined
10604 by the programming language you are using is valid in an expression in
10605 @value{GDBN}. This includes conditional expressions, function calls,
10606 casts, and string constants. It also includes preprocessor macros, if
10607 you compiled your program to include this information; see
10610 @cindex arrays in expressions
10611 @value{GDBN} supports array constants in expressions input by
10612 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10613 you can use the command @code{print @{1, 2, 3@}} to create an array
10614 of three integers. If you pass an array to a function or assign it
10615 to a program variable, @value{GDBN} copies the array to memory that
10616 is @code{malloc}ed in the target program.
10618 Because C is so widespread, most of the expressions shown in examples in
10619 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10620 Languages}, for information on how to use expressions in other
10623 In this section, we discuss operators that you can use in @value{GDBN}
10624 expressions regardless of your programming language.
10626 @cindex casts, in expressions
10627 Casts are supported in all languages, not just in C, because it is so
10628 useful to cast a number into a pointer in order to examine a structure
10629 at that address in memory.
10630 @c FIXME: casts supported---Mod2 true?
10632 @value{GDBN} supports these operators, in addition to those common
10633 to programming languages:
10637 @samp{@@} is a binary operator for treating parts of memory as arrays.
10638 @xref{Arrays, ,Artificial Arrays}, for more information.
10641 @samp{::} allows you to specify a variable in terms of the file or
10642 function where it is defined. @xref{Variables, ,Program Variables}.
10644 @cindex @{@var{type}@}
10645 @cindex type casting memory
10646 @cindex memory, viewing as typed object
10647 @cindex casts, to view memory
10648 @item @{@var{type}@} @var{addr}
10649 Refers to an object of type @var{type} stored at address @var{addr} in
10650 memory. The address @var{addr} may be any expression whose value is
10651 an integer or pointer (but parentheses are required around binary
10652 operators, just as in a cast). This construct is allowed regardless
10653 of what kind of data is normally supposed to reside at @var{addr}.
10656 @node Ambiguous Expressions
10657 @section Ambiguous Expressions
10658 @cindex ambiguous expressions
10660 Expressions can sometimes contain some ambiguous elements. For instance,
10661 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10662 a single function name to be defined several times, for application in
10663 different contexts. This is called @dfn{overloading}. Another example
10664 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10665 templates and is typically instantiated several times, resulting in
10666 the same function name being defined in different contexts.
10668 In some cases and depending on the language, it is possible to adjust
10669 the expression to remove the ambiguity. For instance in C@t{++}, you
10670 can specify the signature of the function you want to break on, as in
10671 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10672 qualified name of your function often makes the expression unambiguous
10675 When an ambiguity that needs to be resolved is detected, the debugger
10676 has the capability to display a menu of numbered choices for each
10677 possibility, and then waits for the selection with the prompt @samp{>}.
10678 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10679 aborts the current command. If the command in which the expression was
10680 used allows more than one choice to be selected, the next option in the
10681 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10684 For example, the following session excerpt shows an attempt to set a
10685 breakpoint at the overloaded symbol @code{String::after}.
10686 We choose three particular definitions of that function name:
10688 @c FIXME! This is likely to change to show arg type lists, at least
10691 (@value{GDBP}) b String::after
10694 [2] file:String.cc; line number:867
10695 [3] file:String.cc; line number:860
10696 [4] file:String.cc; line number:875
10697 [5] file:String.cc; line number:853
10698 [6] file:String.cc; line number:846
10699 [7] file:String.cc; line number:735
10701 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10702 Breakpoint 2 at 0xb344: file String.cc, line 875.
10703 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10704 Multiple breakpoints were set.
10705 Use the "delete" command to delete unwanted
10712 @kindex set multiple-symbols
10713 @item set multiple-symbols @var{mode}
10714 @cindex multiple-symbols menu
10716 This option allows you to adjust the debugger behavior when an expression
10719 By default, @var{mode} is set to @code{all}. If the command with which
10720 the expression is used allows more than one choice, then @value{GDBN}
10721 automatically selects all possible choices. For instance, inserting
10722 a breakpoint on a function using an ambiguous name results in a breakpoint
10723 inserted on each possible match. However, if a unique choice must be made,
10724 then @value{GDBN} uses the menu to help you disambiguate the expression.
10725 For instance, printing the address of an overloaded function will result
10726 in the use of the menu.
10728 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10729 when an ambiguity is detected.
10731 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10732 an error due to the ambiguity and the command is aborted.
10734 @kindex show multiple-symbols
10735 @item show multiple-symbols
10736 Show the current value of the @code{multiple-symbols} setting.
10740 @section Program Variables
10742 The most common kind of expression to use is the name of a variable
10745 Variables in expressions are understood in the selected stack frame
10746 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10750 global (or file-static)
10757 visible according to the scope rules of the
10758 programming language from the point of execution in that frame
10761 @noindent This means that in the function
10776 you can examine and use the variable @code{a} whenever your program is
10777 executing within the function @code{foo}, but you can only use or
10778 examine the variable @code{b} while your program is executing inside
10779 the block where @code{b} is declared.
10781 @cindex variable name conflict
10782 There is an exception: you can refer to a variable or function whose
10783 scope is a single source file even if the current execution point is not
10784 in this file. But it is possible to have more than one such variable or
10785 function with the same name (in different source files). If that
10786 happens, referring to that name has unpredictable effects. If you wish,
10787 you can specify a static variable in a particular function or file by
10788 using the colon-colon (@code{::}) notation:
10790 @cindex colon-colon, context for variables/functions
10792 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10793 @cindex @code{::}, context for variables/functions
10796 @var{file}::@var{variable}
10797 @var{function}::@var{variable}
10801 Here @var{file} or @var{function} is the name of the context for the
10802 static @var{variable}. In the case of file names, you can use quotes to
10803 make sure @value{GDBN} parses the file name as a single word---for example,
10804 to print a global value of @code{x} defined in @file{f2.c}:
10807 (@value{GDBP}) p 'f2.c'::x
10810 The @code{::} notation is normally used for referring to
10811 static variables, since you typically disambiguate uses of local variables
10812 in functions by selecting the appropriate frame and using the
10813 simple name of the variable. However, you may also use this notation
10814 to refer to local variables in frames enclosing the selected frame:
10823 process (a); /* Stop here */
10834 For example, if there is a breakpoint at the commented line,
10835 here is what you might see
10836 when the program stops after executing the call @code{bar(0)}:
10841 (@value{GDBP}) p bar::a
10843 (@value{GDBP}) up 2
10844 #2 0x080483d0 in foo (a=5) at foobar.c:12
10847 (@value{GDBP}) p bar::a
10851 @cindex C@t{++} scope resolution
10852 These uses of @samp{::} are very rarely in conflict with the very
10853 similar use of the same notation in C@t{++}. When they are in
10854 conflict, the C@t{++} meaning takes precedence; however, this can be
10855 overridden by quoting the file or function name with single quotes.
10857 For example, suppose the program is stopped in a method of a class
10858 that has a field named @code{includefile}, and there is also an
10859 include file named @file{includefile} that defines a variable,
10860 @code{some_global}.
10863 (@value{GDBP}) p includefile
10865 (@value{GDBP}) p includefile::some_global
10866 A syntax error in expression, near `'.
10867 (@value{GDBP}) p 'includefile'::some_global
10871 @cindex wrong values
10872 @cindex variable values, wrong
10873 @cindex function entry/exit, wrong values of variables
10874 @cindex optimized code, wrong values of variables
10876 @emph{Warning:} Occasionally, a local variable may appear to have the
10877 wrong value at certain points in a function---just after entry to a new
10878 scope, and just before exit.
10880 You may see this problem when you are stepping by machine instructions.
10881 This is because, on most machines, it takes more than one instruction to
10882 set up a stack frame (including local variable definitions); if you are
10883 stepping by machine instructions, variables may appear to have the wrong
10884 values until the stack frame is completely built. On exit, it usually
10885 also takes more than one machine instruction to destroy a stack frame;
10886 after you begin stepping through that group of instructions, local
10887 variable definitions may be gone.
10889 This may also happen when the compiler does significant optimizations.
10890 To be sure of always seeing accurate values, turn off all optimization
10893 @cindex ``No symbol "foo" in current context''
10894 Another possible effect of compiler optimizations is to optimize
10895 unused variables out of existence, or assign variables to registers (as
10896 opposed to memory addresses). Depending on the support for such cases
10897 offered by the debug info format used by the compiler, @value{GDBN}
10898 might not be able to display values for such local variables. If that
10899 happens, @value{GDBN} will print a message like this:
10902 No symbol "foo" in current context.
10905 To solve such problems, either recompile without optimizations, or use a
10906 different debug info format, if the compiler supports several such
10907 formats. @xref{Compilation}, for more information on choosing compiler
10908 options. @xref{C, ,C and C@t{++}}, for more information about debug
10909 info formats that are best suited to C@t{++} programs.
10911 If you ask to print an object whose contents are unknown to
10912 @value{GDBN}, e.g., because its data type is not completely specified
10913 by the debug information, @value{GDBN} will say @samp{<incomplete
10914 type>}. @xref{Symbols, incomplete type}, for more about this.
10916 @cindex no debug info variables
10917 If you try to examine or use the value of a (global) variable for
10918 which @value{GDBN} has no type information, e.g., because the program
10919 includes no debug information, @value{GDBN} displays an error message.
10920 @xref{Symbols, unknown type}, for more about unknown types. If you
10921 cast the variable to its declared type, @value{GDBN} gets the
10922 variable's value using the cast-to type as the variable's type. For
10923 example, in a C program:
10926 (@value{GDBP}) p var
10927 'var' has unknown type; cast it to its declared type
10928 (@value{GDBP}) p (float) var
10932 If you append @kbd{@@entry} string to a function parameter name you get its
10933 value at the time the function got called. If the value is not available an
10934 error message is printed. Entry values are available only with some compilers.
10935 Entry values are normally also printed at the function parameter list according
10936 to @ref{set print entry-values}.
10939 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10945 (gdb) print i@@entry
10949 Strings are identified as arrays of @code{char} values without specified
10950 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10951 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10952 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10953 defines literal string type @code{"char"} as @code{char} without a sign.
10958 signed char var1[] = "A";
10961 You get during debugging
10966 $2 = @{65 'A', 0 '\0'@}
10970 @section Artificial Arrays
10972 @cindex artificial array
10974 @kindex @@@r{, referencing memory as an array}
10975 It is often useful to print out several successive objects of the
10976 same type in memory; a section of an array, or an array of
10977 dynamically determined size for which only a pointer exists in the
10980 You can do this by referring to a contiguous span of memory as an
10981 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10982 operand of @samp{@@} should be the first element of the desired array
10983 and be an individual object. The right operand should be the desired length
10984 of the array. The result is an array value whose elements are all of
10985 the type of the left argument. The first element is actually the left
10986 argument; the second element comes from bytes of memory immediately
10987 following those that hold the first element, and so on. Here is an
10988 example. If a program says
10991 int *array = (int *) malloc (len * sizeof (int));
10995 you can print the contents of @code{array} with
11001 The left operand of @samp{@@} must reside in memory. Array values made
11002 with @samp{@@} in this way behave just like other arrays in terms of
11003 subscripting, and are coerced to pointers when used in expressions.
11004 Artificial arrays most often appear in expressions via the value history
11005 (@pxref{Value History, ,Value History}), after printing one out.
11007 Another way to create an artificial array is to use a cast.
11008 This re-interprets a value as if it were an array.
11009 The value need not be in memory:
11011 (@value{GDBP}) p/x (short[2])0x12345678
11012 $1 = @{0x1234, 0x5678@}
11015 As a convenience, if you leave the array length out (as in
11016 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
11017 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
11019 (@value{GDBP}) p/x (short[])0x12345678
11020 $2 = @{0x1234, 0x5678@}
11023 Sometimes the artificial array mechanism is not quite enough; in
11024 moderately complex data structures, the elements of interest may not
11025 actually be adjacent---for example, if you are interested in the values
11026 of pointers in an array. One useful work-around in this situation is
11027 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
11028 Variables}) as a counter in an expression that prints the first
11029 interesting value, and then repeat that expression via @key{RET}. For
11030 instance, suppose you have an array @code{dtab} of pointers to
11031 structures, and you are interested in the values of a field @code{fv}
11032 in each structure. Here is an example of what you might type:
11042 @node Output Formats
11043 @section Output Formats
11045 @cindex formatted output
11046 @cindex output formats
11047 By default, @value{GDBN} prints a value according to its data type. Sometimes
11048 this is not what you want. For example, you might want to print a number
11049 in hex, or a pointer in decimal. Or you might want to view data in memory
11050 at a certain address as a character string or as an instruction. To do
11051 these things, specify an @dfn{output format} when you print a value.
11053 The simplest use of output formats is to say how to print a value
11054 already computed. This is done by starting the arguments of the
11055 @code{print} command with a slash and a format letter. The format
11056 letters supported are:
11060 Print the binary representation of the value in hexadecimal.
11063 Print the binary representation of the value in decimal.
11066 Print the binary representation of the value as an decimal, as if it
11070 Print the binary representation of the value in octal.
11073 Print the binary representation of the value in binary. The letter
11074 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
11075 because these format letters are also used with the @code{x} command,
11076 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
11080 @cindex unknown address, locating
11081 @cindex locate address
11082 Print as an address, both absolute in hexadecimal and as an offset from
11083 the nearest preceding symbol. You can use this format used to discover
11084 where (in what function) an unknown address is located:
11087 (@value{GDBP}) p/a 0x54320
11088 $3 = 0x54320 <_initialize_vx+396>
11092 The command @code{info symbol 0x54320} yields similar results.
11093 @xref{Symbols, info symbol}.
11096 Cast the value to an integer (unlike other formats, this does not just
11097 reinterpret the underlying bits) and print it as a character constant.
11098 This prints both the numerical value and its character representation.
11099 The character representation is replaced with the octal escape
11100 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
11102 Without this format, @value{GDBN} displays @code{char},
11103 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
11104 constants. Single-byte members of vectors are displayed as integer
11108 Regard the bits of the value as a floating point number and print
11109 using typical floating point syntax.
11112 @cindex printing strings
11113 @cindex printing byte arrays
11114 Regard as a string, if possible. With this format, pointers to single-byte
11115 data are displayed as null-terminated strings and arrays of single-byte data
11116 are displayed as fixed-length strings. Other values are displayed in their
11119 Without this format, @value{GDBN} displays pointers to and arrays of
11120 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
11121 strings. Single-byte members of a vector are displayed as an integer
11125 Like @samp{x} formatting, the value is treated as an integer and
11126 printed as hexadecimal, but leading zeros are printed to pad the value
11127 to the size of the integer type.
11130 @cindex raw printing
11131 Print using the @samp{raw} formatting. By default, @value{GDBN} will
11132 use a Python-based pretty-printer, if one is available (@pxref{Pretty
11133 Printing}). This typically results in a higher-level display of the
11134 value's contents. The @samp{r} format bypasses any Python
11135 pretty-printer which might exist.
11138 For example, to print the program counter in hex (@pxref{Registers}), type
11145 Note that no space is required before the slash; this is because command
11146 names in @value{GDBN} cannot contain a slash.
11148 To reprint the last value in the value history with a different format,
11149 you can use the @code{print} command with just a format and no
11150 expression. For example, @samp{p/x} reprints the last value in hex.
11153 @section Examining Memory
11155 You can use the command @code{x} (for ``examine'') to examine memory in
11156 any of several formats, independently of your program's data types.
11158 @cindex examining memory
11160 @kindex x @r{(examine memory)}
11161 @item x/@var{nfu} @var{addr}
11162 @itemx x @var{addr}
11164 Use the @code{x} command to examine memory.
11167 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11168 much memory to display and how to format it; @var{addr} is an
11169 expression giving the address where you want to start displaying memory.
11170 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11171 Several commands set convenient defaults for @var{addr}.
11174 @item @var{n}, the repeat count
11175 The repeat count is a decimal integer; the default is 1. It specifies
11176 how much memory (counting by units @var{u}) to display. If a negative
11177 number is specified, memory is examined backward from @var{addr}.
11178 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11181 @item @var{f}, the display format
11182 The display format is one of the formats used by @code{print}
11183 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11184 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11185 @samp{m} (for displaying memory tags).
11186 The default is @samp{x} (hexadecimal) initially. The default changes
11187 each time you use either @code{x} or @code{print}.
11189 @item @var{u}, the unit size
11190 The unit size is any of
11196 Halfwords (two bytes).
11198 Words (four bytes). This is the initial default.
11200 Giant words (eight bytes).
11203 Each time you specify a unit size with @code{x}, that size becomes the
11204 default unit the next time you use @code{x}. For the @samp{i} format,
11205 the unit size is ignored and is normally not written. For the @samp{s} format,
11206 the unit size defaults to @samp{b}, unless it is explicitly given.
11207 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11208 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11209 Note that the results depend on the programming language of the
11210 current compilation unit. If the language is C, the @samp{s}
11211 modifier will use the UTF-16 encoding while @samp{w} will use
11212 UTF-32. The encoding is set by the programming language and cannot
11215 @item @var{addr}, starting display address
11216 @var{addr} is the address where you want @value{GDBN} to begin displaying
11217 memory. The expression need not have a pointer value (though it may);
11218 it is always interpreted as an integer address of a byte of memory.
11219 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11220 @var{addr} is usually just after the last address examined---but several
11221 other commands also set the default address: @code{info breakpoints} (to
11222 the address of the last breakpoint listed), @code{info line} (to the
11223 starting address of a line), and @code{print} (if you use it to display
11224 a value from memory).
11227 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11228 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11229 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11230 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11231 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11233 You can also specify a negative repeat count to examine memory backward
11234 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11235 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11237 Since the letters indicating unit sizes are all distinct from the
11238 letters specifying output formats, you do not have to remember whether
11239 unit size or format comes first; either order works. The output
11240 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11241 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11243 Even though the unit size @var{u} is ignored for the formats @samp{s}
11244 and @samp{i}, you might still want to use a count @var{n}; for example,
11245 @samp{3i} specifies that you want to see three machine instructions,
11246 including any operands. For convenience, especially when used with
11247 the @code{display} command, the @samp{i} format also prints branch delay
11248 slot instructions, if any, beyond the count specified, which immediately
11249 follow the last instruction that is within the count. The command
11250 @code{disassemble} gives an alternative way of inspecting machine
11251 instructions; see @ref{Machine Code,,Source and Machine Code}.
11253 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11254 the command displays null-terminated strings or instructions before the given
11255 address as many as the absolute value of the given number. For the @samp{i}
11256 format, we use line number information in the debug info to accurately locate
11257 instruction boundaries while disassembling backward. If line info is not
11258 available, the command stops examining memory with an error message.
11260 All the defaults for the arguments to @code{x} are designed to make it
11261 easy to continue scanning memory with minimal specifications each time
11262 you use @code{x}. For example, after you have inspected three machine
11263 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11264 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11265 the repeat count @var{n} is used again; the other arguments default as
11266 for successive uses of @code{x}.
11268 When examining machine instructions, the instruction at current program
11269 counter is shown with a @code{=>} marker. For example:
11272 (@value{GDBP}) x/5i $pc-6
11273 0x804837f <main+11>: mov %esp,%ebp
11274 0x8048381 <main+13>: push %ecx
11275 0x8048382 <main+14>: sub $0x4,%esp
11276 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11277 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11280 If the architecture supports memory tagging, the tags can be displayed by
11281 using @samp{m}. @xref{Memory Tagging}.
11283 The information will be displayed once per granule size
11284 (the amount of bytes a particular memory tag covers). For example, AArch64
11285 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11287 Due to the way @value{GDBN} prints information with the @code{x} command (not
11288 aligned to a particular boundary), the tag information will refer to the
11289 initial address displayed on a particular line. If a memory tag boundary
11290 is crossed in the middle of a line displayed by the @code{x} command, it
11291 will be displayed on the next line.
11293 The @samp{m} format doesn't affect any other specified formats that were
11294 passed to the @code{x} command.
11296 @cindex @code{$_}, @code{$__}, and value history
11297 The addresses and contents printed by the @code{x} command are not saved
11298 in the value history because there is often too much of them and they
11299 would get in the way. Instead, @value{GDBN} makes these values available for
11300 subsequent use in expressions as values of the convenience variables
11301 @code{$_} and @code{$__}. After an @code{x} command, the last address
11302 examined is available for use in expressions in the convenience variable
11303 @code{$_}. The contents of that address, as examined, are available in
11304 the convenience variable @code{$__}.
11306 If the @code{x} command has a repeat count, the address and contents saved
11307 are from the last memory unit printed; this is not the same as the last
11308 address printed if several units were printed on the last line of output.
11310 @anchor{addressable memory unit}
11311 @cindex addressable memory unit
11312 Most targets have an addressable memory unit size of 8 bits. This means
11313 that to each memory address are associated 8 bits of data. Some
11314 targets, however, have other addressable memory unit sizes.
11315 Within @value{GDBN} and this document, the term
11316 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11317 when explicitly referring to a chunk of data of that size. The word
11318 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11319 the addressable memory unit size of the target. For most systems,
11320 addressable memory unit is a synonym of byte.
11322 @cindex remote memory comparison
11323 @cindex target memory comparison
11324 @cindex verify remote memory image
11325 @cindex verify target memory image
11326 When you are debugging a program running on a remote target machine
11327 (@pxref{Remote Debugging}), you may wish to verify the program's image
11328 in the remote machine's memory against the executable file you
11329 downloaded to the target. Or, on any target, you may want to check
11330 whether the program has corrupted its own read-only sections. The
11331 @code{compare-sections} command is provided for such situations.
11334 @kindex compare-sections
11335 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11336 Compare the data of a loadable section @var{section-name} in the
11337 executable file of the program being debugged with the same section in
11338 the target machine's memory, and report any mismatches. With no
11339 arguments, compares all loadable sections. With an argument of
11340 @code{-r}, compares all loadable read-only sections.
11342 Note: for remote targets, this command can be accelerated if the
11343 target supports computing the CRC checksum of a block of memory
11344 (@pxref{qCRC packet}).
11347 @node Memory Tagging
11348 @section Memory Tagging
11350 Memory tagging is a memory protection technology that uses a pair of tags to
11351 validate memory accesses through pointers. The tags are integer values
11352 usually comprised of a few bits, depending on the architecture.
11354 There are two types of tags that are used in this setup: logical and
11355 allocation. A logical tag is stored in the pointers themselves, usually at the
11356 higher bits of the pointers. An allocation tag is the tag associated
11357 with particular ranges of memory in the physical address space, against which
11358 the logical tags from pointers are compared.
11360 The pointer tag (logical tag) must match the memory tag (allocation tag)
11361 for the memory access to be valid. If the logical tag does not match the
11362 allocation tag, that will raise a memory violation.
11364 Allocation tags cover multiple contiguous bytes of physical memory. This
11365 range of bytes is called a memory tag granule and is architecture-specific.
11366 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11367 tag spans 16 bytes of memory.
11369 If the underlying architecture supports memory tagging, like AArch64 MTE
11370 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11371 against memory allocation tags.
11373 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11374 display tag information when appropriate, and a command prefix of
11375 @code{memory-tag} gives access to the various memory tagging commands.
11377 The @code{memory-tag} commands are the following:
11380 @kindex memory-tag print-logical-tag
11381 @item memory-tag print-logical-tag @var{pointer_expression}
11382 Print the logical tag stored in @var{pointer_expression}.
11383 @kindex memory-tag with-logical-tag
11384 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11385 Print the pointer given by @var{pointer_expression}, augmented with a logical
11386 tag of @var{tag_bytes}.
11387 @kindex memory-tag print-allocation-tag
11388 @item memory-tag print-allocation-tag @var{address_expression}
11389 Print the allocation tag associated with the memory address given by
11390 @var{address_expression}.
11391 @kindex memory-tag setatag
11392 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11393 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11394 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11395 @kindex memory-tag check
11396 @item memory-tag check @var{pointer_expression}
11397 Check if the logical tag in the pointer given by @var{pointer_expression}
11398 matches the allocation tag for the memory referenced by the pointer.
11400 This essentially emulates the hardware validation that is done when tagged
11401 memory is accessed through a pointer, but does not cause a memory fault as
11402 it would during hardware validation.
11404 It can be used to inspect potential memory tagging violations in the running
11405 process, before any faults get triggered.
11409 @section Automatic Display
11410 @cindex automatic display
11411 @cindex display of expressions
11413 If you find that you want to print the value of an expression frequently
11414 (to see how it changes), you might want to add it to the @dfn{automatic
11415 display list} so that @value{GDBN} prints its value each time your program stops.
11416 Each expression added to the list is given a number to identify it;
11417 to remove an expression from the list, you specify that number.
11418 The automatic display looks like this:
11422 3: bar[5] = (struct hack *) 0x3804
11426 This display shows item numbers, expressions and their current values. As with
11427 displays you request manually using @code{x} or @code{print}, you can
11428 specify the output format you prefer; in fact, @code{display} decides
11429 whether to use @code{print} or @code{x} depending your format
11430 specification---it uses @code{x} if you specify either the @samp{i}
11431 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11435 @item display @var{expr}
11436 Add the expression @var{expr} to the list of expressions to display
11437 each time your program stops. @xref{Expressions, ,Expressions}.
11439 @code{display} does not repeat if you press @key{RET} again after using it.
11441 @item display/@var{fmt} @var{expr}
11442 For @var{fmt} specifying only a display format and not a size or
11443 count, add the expression @var{expr} to the auto-display list but
11444 arrange to display it each time in the specified format @var{fmt}.
11445 @xref{Output Formats,,Output Formats}.
11447 @item display/@var{fmt} @var{addr}
11448 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11449 number of units, add the expression @var{addr} as a memory address to
11450 be examined each time your program stops. Examining means in effect
11451 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11454 For example, @samp{display/i $pc} can be helpful, to see the machine
11455 instruction about to be executed each time execution stops (@samp{$pc}
11456 is a common name for the program counter; @pxref{Registers, ,Registers}).
11459 @kindex delete display
11461 @item undisplay @var{dnums}@dots{}
11462 @itemx delete display @var{dnums}@dots{}
11463 Remove items from the list of expressions to display. Specify the
11464 numbers of the displays that you want affected with the command
11465 argument @var{dnums}. It can be a single display number, one of the
11466 numbers shown in the first field of the @samp{info display} display;
11467 or it could be a range of display numbers, as in @code{2-4}.
11469 @code{undisplay} does not repeat if you press @key{RET} after using it.
11470 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11472 @kindex disable display
11473 @item disable display @var{dnums}@dots{}
11474 Disable the display of item numbers @var{dnums}. A disabled display
11475 item is not printed automatically, but is not forgotten. It may be
11476 enabled again later. Specify the numbers of the displays that you
11477 want affected with the command argument @var{dnums}. It can be a
11478 single display number, one of the numbers shown in the first field of
11479 the @samp{info display} display; or it could be a range of display
11480 numbers, as in @code{2-4}.
11482 @kindex enable display
11483 @item enable display @var{dnums}@dots{}
11484 Enable display of item numbers @var{dnums}. It becomes effective once
11485 again in auto display of its expression, until you specify otherwise.
11486 Specify the numbers of the displays that you want affected with the
11487 command argument @var{dnums}. It can be a single display number, one
11488 of the numbers shown in the first field of the @samp{info display}
11489 display; or it could be a range of display numbers, as in @code{2-4}.
11492 Display the current values of the expressions on the list, just as is
11493 done when your program stops.
11495 @kindex info display
11497 Print the list of expressions previously set up to display
11498 automatically, each one with its item number, but without showing the
11499 values. This includes disabled expressions, which are marked as such.
11500 It also includes expressions which would not be displayed right now
11501 because they refer to automatic variables not currently available.
11504 @cindex display disabled out of scope
11505 If a display expression refers to local variables, then it does not make
11506 sense outside the lexical context for which it was set up. Such an
11507 expression is disabled when execution enters a context where one of its
11508 variables is not defined. For example, if you give the command
11509 @code{display last_char} while inside a function with an argument
11510 @code{last_char}, @value{GDBN} displays this argument while your program
11511 continues to stop inside that function. When it stops elsewhere---where
11512 there is no variable @code{last_char}---the display is disabled
11513 automatically. The next time your program stops where @code{last_char}
11514 is meaningful, you can enable the display expression once again.
11516 @node Print Settings
11517 @section Print Settings
11519 @cindex format options
11520 @cindex print settings
11521 @value{GDBN} provides the following ways to control how arrays, structures,
11522 and symbols are printed.
11525 These settings are useful for debugging programs in any language:
11529 @anchor{set print address}
11530 @item set print address
11531 @itemx set print address on
11532 @cindex print/don't print memory addresses
11533 @value{GDBN} prints memory addresses showing the location of stack
11534 traces, structure values, pointer values, breakpoints, and so forth,
11535 even when it also displays the contents of those addresses. The default
11536 is @code{on}. For example, this is what a stack frame display looks like with
11537 @code{set print address on}:
11542 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11544 530 if (lquote != def_lquote)
11548 @item set print address off
11549 Do not print addresses when displaying their contents. For example,
11550 this is the same stack frame displayed with @code{set print address off}:
11554 (@value{GDBP}) set print addr off
11556 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11557 530 if (lquote != def_lquote)
11561 You can use @samp{set print address off} to eliminate all machine
11562 dependent displays from the @value{GDBN} interface. For example, with
11563 @code{print address off}, you should get the same text for backtraces on
11564 all machines---whether or not they involve pointer arguments.
11567 @item show print address
11568 Show whether or not addresses are to be printed.
11571 When @value{GDBN} prints a symbolic address, it normally prints the
11572 closest earlier symbol plus an offset. If that symbol does not uniquely
11573 identify the address (for example, it is a name whose scope is a single
11574 source file), you may need to clarify. One way to do this is with
11575 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11576 you can set @value{GDBN} to print the source file and line number when
11577 it prints a symbolic address:
11580 @item set print symbol-filename on
11581 @cindex source file and line of a symbol
11582 @cindex symbol, source file and line
11583 Tell @value{GDBN} to print the source file name and line number of a
11584 symbol in the symbolic form of an address.
11586 @item set print symbol-filename off
11587 Do not print source file name and line number of a symbol. This is the
11590 @item show print symbol-filename
11591 Show whether or not @value{GDBN} will print the source file name and
11592 line number of a symbol in the symbolic form of an address.
11595 Another situation where it is helpful to show symbol filenames and line
11596 numbers is when disassembling code; @value{GDBN} shows you the line
11597 number and source file that corresponds to each instruction.
11599 Also, you may wish to see the symbolic form only if the address being
11600 printed is reasonably close to the closest earlier symbol:
11603 @item set print max-symbolic-offset @var{max-offset}
11604 @itemx set print max-symbolic-offset unlimited
11605 @cindex maximum value for offset of closest symbol
11606 Tell @value{GDBN} to only display the symbolic form of an address if the
11607 offset between the closest earlier symbol and the address is less than
11608 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11609 to always print the symbolic form of an address if any symbol precedes
11610 it. Zero is equivalent to @code{unlimited}.
11612 @item show print max-symbolic-offset
11613 Ask how large the maximum offset is that @value{GDBN} prints in a
11617 @cindex wild pointer, interpreting
11618 @cindex pointer, finding referent
11619 If you have a pointer and you are not sure where it points, try
11620 @samp{set print symbol-filename on}. Then you can determine the name
11621 and source file location of the variable where it points, using
11622 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11623 For example, here @value{GDBN} shows that a variable @code{ptt} points
11624 at another variable @code{t}, defined in @file{hi2.c}:
11627 (@value{GDBP}) set print symbol-filename on
11628 (@value{GDBP}) p/a ptt
11629 $4 = 0xe008 <t in hi2.c>
11633 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11634 does not show the symbol name and filename of the referent, even with
11635 the appropriate @code{set print} options turned on.
11638 You can also enable @samp{/a}-like formatting all the time using
11639 @samp{set print symbol on}:
11641 @anchor{set print symbol}
11643 @item set print symbol on
11644 Tell @value{GDBN} to print the symbol corresponding to an address, if
11647 @item set print symbol off
11648 Tell @value{GDBN} not to print the symbol corresponding to an
11649 address. In this mode, @value{GDBN} will still print the symbol
11650 corresponding to pointers to functions. This is the default.
11652 @item show print symbol
11653 Show whether @value{GDBN} will display the symbol corresponding to an
11657 Other settings control how different kinds of objects are printed:
11660 @anchor{set print array}
11661 @item set print array
11662 @itemx set print array on
11663 @cindex pretty print arrays
11664 Pretty print arrays. This format is more convenient to read,
11665 but uses more space. The default is off.
11667 @item set print array off
11668 Return to compressed format for arrays.
11670 @item show print array
11671 Show whether compressed or pretty format is selected for displaying
11674 @cindex print array indexes
11675 @anchor{set print array-indexes}
11676 @item set print array-indexes
11677 @itemx set print array-indexes on
11678 Print the index of each element when displaying arrays. May be more
11679 convenient to locate a given element in the array or quickly find the
11680 index of a given element in that printed array. The default is off.
11682 @item set print array-indexes off
11683 Stop printing element indexes when displaying arrays.
11685 @item show print array-indexes
11686 Show whether the index of each element is printed when displaying
11689 @anchor{set print nibbles}
11690 @item set print nibbles
11691 @itemx set print nibbles on
11692 @cindex print binary values in groups of four bits
11693 Print binary values in groups of four bits, known as @dfn{nibbles},
11694 when using the print command of @value{GDBN} with the option @samp{/t}.
11695 For example, this is what it looks like with @code{set print nibbles on}:
11699 (@value{GDBP}) print val_flags
11701 (@value{GDBP}) print/t val_flags
11702 $2 = 0100 1100 1110
11706 @item set print nibbles off
11707 Don't printing binary values in groups. This is the default.
11709 @item show print nibbles
11710 Show whether to print binary values in groups of four bits.
11712 @anchor{set print elements}
11713 @item set print elements @var{number-of-elements}
11714 @itemx set print elements unlimited
11715 @cindex number of array elements to print
11716 @cindex limit on number of printed array elements
11717 Set a limit on how many elements of an array @value{GDBN} will print.
11718 If @value{GDBN} is printing a large array, it stops printing after it has
11719 printed the number of elements set by the @code{set print elements} command.
11720 This limit also applies to the display of strings.
11721 When @value{GDBN} starts, this limit is set to 200.
11722 Setting @var{number-of-elements} to @code{unlimited} or zero means
11723 that the number of elements to print is unlimited.
11725 @item show print elements
11726 Display the number of elements of a large array that @value{GDBN} will print.
11728 @anchor{set print frame-arguments}
11729 @item set print frame-arguments @var{value}
11730 @kindex set print frame-arguments
11731 @cindex printing frame argument values
11732 @cindex print all frame argument values
11733 @cindex print frame argument values for scalars only
11734 @cindex do not print frame arguments
11735 This command allows to control how the values of arguments are printed
11736 when the debugger prints a frame (@pxref{Frames}). The possible
11741 The values of all arguments are printed.
11744 Print the value of an argument only if it is a scalar. The value of more
11745 complex arguments such as arrays, structures, unions, etc, is replaced
11746 by @code{@dots{}}. This is the default. Here is an example where
11747 only scalar arguments are shown:
11750 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11755 None of the argument values are printed. Instead, the value of each argument
11756 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11759 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11764 Only the presence of arguments is indicated by @code{@dots{}}.
11765 The @code{@dots{}} are not printed for function without any arguments.
11766 None of the argument names and values are printed.
11767 In this case, the example above now becomes:
11770 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11775 By default, only scalar arguments are printed. This command can be used
11776 to configure the debugger to print the value of all arguments, regardless
11777 of their type. However, it is often advantageous to not print the value
11778 of more complex parameters. For instance, it reduces the amount of
11779 information printed in each frame, making the backtrace more readable.
11780 Also, it improves performance when displaying Ada frames, because
11781 the computation of large arguments can sometimes be CPU-intensive,
11782 especially in large applications. Setting @code{print frame-arguments}
11783 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11784 this computation, thus speeding up the display of each Ada frame.
11786 @item show print frame-arguments
11787 Show how the value of arguments should be displayed when printing a frame.
11789 @anchor{set print raw-frame-arguments}
11790 @item set print raw-frame-arguments on
11791 Print frame arguments in raw, non pretty-printed, form.
11793 @item set print raw-frame-arguments off
11794 Print frame arguments in pretty-printed form, if there is a pretty-printer
11795 for the value (@pxref{Pretty Printing}),
11796 otherwise print the value in raw form.
11797 This is the default.
11799 @item show print raw-frame-arguments
11800 Show whether to print frame arguments in raw form.
11802 @anchor{set print entry-values}
11803 @item set print entry-values @var{value}
11804 @kindex set print entry-values
11805 Set printing of frame argument values at function entry. In some cases
11806 @value{GDBN} can determine the value of function argument which was passed by
11807 the function caller, even if the value was modified inside the called function
11808 and therefore is different. With optimized code, the current value could be
11809 unavailable, but the entry value may still be known.
11811 The default value is @code{default} (see below for its description). Older
11812 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11813 this feature will behave in the @code{default} setting the same way as with the
11816 This functionality is currently supported only by DWARF 2 debugging format and
11817 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11818 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11821 The @var{value} parameter can be one of the following:
11825 Print only actual parameter values, never print values from function entry
11829 #0 different (val=6)
11830 #0 lost (val=<optimized out>)
11832 #0 invalid (val=<optimized out>)
11836 Print only parameter values from function entry point. The actual parameter
11837 values are never printed.
11839 #0 equal (val@@entry=5)
11840 #0 different (val@@entry=5)
11841 #0 lost (val@@entry=5)
11842 #0 born (val@@entry=<optimized out>)
11843 #0 invalid (val@@entry=<optimized out>)
11847 Print only parameter values from function entry point. If value from function
11848 entry point is not known while the actual value is known, print the actual
11849 value for such parameter.
11851 #0 equal (val@@entry=5)
11852 #0 different (val@@entry=5)
11853 #0 lost (val@@entry=5)
11855 #0 invalid (val@@entry=<optimized out>)
11859 Print actual parameter values. If actual parameter value is not known while
11860 value from function entry point is known, print the entry point value for such
11864 #0 different (val=6)
11865 #0 lost (val@@entry=5)
11867 #0 invalid (val=<optimized out>)
11871 Always print both the actual parameter value and its value from function entry
11872 point, even if values of one or both are not available due to compiler
11875 #0 equal (val=5, val@@entry=5)
11876 #0 different (val=6, val@@entry=5)
11877 #0 lost (val=<optimized out>, val@@entry=5)
11878 #0 born (val=10, val@@entry=<optimized out>)
11879 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11883 Print the actual parameter value if it is known and also its value from
11884 function entry point if it is known. If neither is known, print for the actual
11885 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11886 values are known and identical, print the shortened
11887 @code{param=param@@entry=VALUE} notation.
11889 #0 equal (val=val@@entry=5)
11890 #0 different (val=6, val@@entry=5)
11891 #0 lost (val@@entry=5)
11893 #0 invalid (val=<optimized out>)
11897 Always print the actual parameter value. Print also its value from function
11898 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11899 if both values are known and identical, print the shortened
11900 @code{param=param@@entry=VALUE} notation.
11902 #0 equal (val=val@@entry=5)
11903 #0 different (val=6, val@@entry=5)
11904 #0 lost (val=<optimized out>, val@@entry=5)
11906 #0 invalid (val=<optimized out>)
11910 For analysis messages on possible failures of frame argument values at function
11911 entry resolution see @ref{set debug entry-values}.
11913 @item show print entry-values
11914 Show the method being used for printing of frame argument values at function
11917 @anchor{set print frame-info}
11918 @item set print frame-info @var{value}
11919 @kindex set print frame-info
11920 @cindex printing frame information
11921 @cindex frame information, printing
11922 This command allows to control the information printed when
11923 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11924 for a general explanation about frames and frame information.
11925 Note that some other settings (such as @code{set print frame-arguments}
11926 and @code{set print address}) are also influencing if and how some frame
11927 information is displayed. In particular, the frame program counter is never
11928 printed if @code{set print address} is off.
11930 The possible values for @code{set print frame-info} are:
11932 @item short-location
11933 Print the frame level, the program counter (if not at the
11934 beginning of the location source line), the function, the function
11937 Same as @code{short-location} but also print the source file and source line
11939 @item location-and-address
11940 Same as @code{location} but print the program counter even if located at the
11941 beginning of the location source line.
11943 Print the program counter (if not at the beginning of the location
11944 source line), the line number and the source line.
11945 @item source-and-location
11946 Print what @code{location} and @code{source-line} are printing.
11948 The information printed for a frame is decided automatically
11949 by the @value{GDBN} command that prints a frame.
11950 For example, @code{frame} prints the information printed by
11951 @code{source-and-location} while @code{stepi} will switch between
11952 @code{source-line} and @code{source-and-location} depending on the program
11954 The default value is @code{auto}.
11957 @anchor{set print repeats}
11958 @item set print repeats @var{number-of-repeats}
11959 @itemx set print repeats unlimited
11960 @cindex repeated array elements
11961 Set the threshold for suppressing display of repeated array
11962 elements. When the number of consecutive identical elements of an
11963 array exceeds the threshold, @value{GDBN} prints the string
11964 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11965 identical repetitions, instead of displaying the identical elements
11966 themselves. Setting the threshold to @code{unlimited} or zero will
11967 cause all elements to be individually printed. The default threshold
11970 @item show print repeats
11971 Display the current threshold for printing repeated identical
11974 @anchor{set print max-depth}
11975 @item set print max-depth @var{depth}
11976 @item set print max-depth unlimited
11977 @cindex printing nested structures
11978 Set the threshold after which nested structures are replaced with
11979 ellipsis, this can make visualising deeply nested structures easier.
11981 For example, given this C code
11984 typedef struct s1 @{ int a; @} s1;
11985 typedef struct s2 @{ s1 b; @} s2;
11986 typedef struct s3 @{ s2 c; @} s3;
11987 typedef struct s4 @{ s3 d; @} s4;
11989 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11992 The following table shows how different values of @var{depth} will
11993 effect how @code{var} is printed by @value{GDBN}:
11995 @multitable @columnfractions .3 .7
11996 @headitem @var{depth} setting @tab Result of @samp{p var}
11998 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12000 @tab @code{$1 = @{...@}}
12002 @tab @code{$1 = @{d = @{...@}@}}
12004 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
12006 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
12008 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12011 To see the contents of structures that have been hidden the user can
12012 either increase the print max-depth, or they can print the elements of
12013 the structure that are visible, for example
12016 (gdb) set print max-depth 2
12018 $1 = @{d = @{c = @{...@}@}@}
12020 $2 = @{c = @{b = @{...@}@}@}
12022 $3 = @{b = @{a = 3@}@}
12025 The pattern used to replace nested structures varies based on
12026 language, for most languages @code{@{...@}} is used, but Fortran uses
12029 @item show print max-depth
12030 Display the current threshold after which nested structures are
12031 replaces with ellipsis.
12033 @anchor{set print memory-tag-violations}
12034 @cindex printing memory tag violation information
12035 @item set print memory-tag-violations
12036 @itemx set print memory-tag-violations on
12037 Cause @value{GDBN} to display additional information about memory tag violations
12038 when printing pointers and addresses.
12040 @item set print memory-tag-violations off
12041 Stop printing memory tag violation information.
12043 @item show print memory-tag-violations
12044 Show whether memory tag violation information is displayed when printing
12045 pointers and addresses.
12047 @anchor{set print null-stop}
12048 @item set print null-stop
12049 @cindex @sc{null} elements in arrays
12050 Cause @value{GDBN} to stop printing the characters of an array when the first
12051 @sc{null} is encountered. This is useful when large arrays actually
12052 contain only short strings.
12053 The default is off.
12055 @item show print null-stop
12056 Show whether @value{GDBN} stops printing an array on the first
12057 @sc{null} character.
12059 @anchor{set print pretty}
12060 @item set print pretty on
12061 @cindex print structures in indented form
12062 @cindex indentation in structure display
12063 Cause @value{GDBN} to print structures in an indented format with one member
12064 per line, like this:
12079 @item set print pretty off
12080 Cause @value{GDBN} to print structures in a compact format, like this:
12084 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
12085 meat = 0x54 "Pork"@}
12090 This is the default format.
12092 @item show print pretty
12093 Show which format @value{GDBN} is using to print structures.
12095 @anchor{set print raw-values}
12096 @item set print raw-values on
12097 Print values in raw form, without applying the pretty
12098 printers for the value.
12100 @item set print raw-values off
12101 Print values in pretty-printed form, if there is a pretty-printer
12102 for the value (@pxref{Pretty Printing}),
12103 otherwise print the value in raw form.
12105 The default setting is ``off''.
12107 @item show print raw-values
12108 Show whether to print values in raw form.
12110 @item set print sevenbit-strings on
12111 @cindex eight-bit characters in strings
12112 @cindex octal escapes in strings
12113 Print using only seven-bit characters; if this option is set,
12114 @value{GDBN} displays any eight-bit characters (in strings or
12115 character values) using the notation @code{\}@var{nnn}. This setting is
12116 best if you are working in English (@sc{ascii}) and you use the
12117 high-order bit of characters as a marker or ``meta'' bit.
12119 @item set print sevenbit-strings off
12120 Print full eight-bit characters. This allows the use of more
12121 international character sets, and is the default.
12123 @item show print sevenbit-strings
12124 Show whether or not @value{GDBN} is printing only seven-bit characters.
12126 @anchor{set print union}
12127 @item set print union on
12128 @cindex unions in structures, printing
12129 Tell @value{GDBN} to print unions which are contained in structures
12130 and other unions. This is the default setting.
12132 @item set print union off
12133 Tell @value{GDBN} not to print unions which are contained in
12134 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
12137 @item show print union
12138 Ask @value{GDBN} whether or not it will print unions which are contained in
12139 structures and other unions.
12141 For example, given the declarations
12144 typedef enum @{Tree, Bug@} Species;
12145 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12146 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12157 struct thing foo = @{Tree, @{Acorn@}@};
12161 with @code{set print union on} in effect @samp{p foo} would print
12164 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12168 and with @code{set print union off} in effect it would print
12171 $1 = @{it = Tree, form = @{...@}@}
12175 @code{set print union} affects programs written in C-like languages
12181 These settings are of interest when debugging C@t{++} programs:
12184 @cindex demangling C@t{++} names
12185 @item set print demangle
12186 @itemx set print demangle on
12187 Print C@t{++} names in their source form rather than in the encoded
12188 (``mangled'') form passed to the assembler and linker for type-safe
12189 linkage. The default is on.
12191 @item show print demangle
12192 Show whether C@t{++} names are printed in mangled or demangled form.
12194 @item set print asm-demangle
12195 @itemx set print asm-demangle on
12196 Print C@t{++} names in their source form rather than their mangled form, even
12197 in assembler code printouts such as instruction disassemblies.
12198 The default is off.
12200 @item show print asm-demangle
12201 Show whether C@t{++} names in assembly listings are printed in mangled
12204 @cindex C@t{++} symbol decoding style
12205 @cindex symbol decoding style, C@t{++}
12206 @kindex set demangle-style
12207 @item set demangle-style @var{style}
12208 Choose among several encoding schemes used by different compilers to represent
12209 C@t{++} names. If you omit @var{style}, you will see a list of possible
12210 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12211 decoding style by inspecting your program.
12213 @item show demangle-style
12214 Display the encoding style currently in use for decoding C@t{++} symbols.
12216 @anchor{set print object}
12217 @item set print object
12218 @itemx set print object on
12219 @cindex derived type of an object, printing
12220 @cindex display derived types
12221 When displaying a pointer to an object, identify the @emph{actual}
12222 (derived) type of the object rather than the @emph{declared} type, using
12223 the virtual function table. Note that the virtual function table is
12224 required---this feature can only work for objects that have run-time
12225 type identification; a single virtual method in the object's declared
12226 type is sufficient. Note that this setting is also taken into account when
12227 working with variable objects via MI (@pxref{GDB/MI}).
12229 @item set print object off
12230 Display only the declared type of objects, without reference to the
12231 virtual function table. This is the default setting.
12233 @item show print object
12234 Show whether actual, or declared, object types are displayed.
12236 @anchor{set print static-members}
12237 @item set print static-members
12238 @itemx set print static-members on
12239 @cindex static members of C@t{++} objects
12240 Print static members when displaying a C@t{++} object. The default is on.
12242 @item set print static-members off
12243 Do not print static members when displaying a C@t{++} object.
12245 @item show print static-members
12246 Show whether C@t{++} static members are printed or not.
12248 @item set print pascal_static-members
12249 @itemx set print pascal_static-members on
12250 @cindex static members of Pascal objects
12251 @cindex Pascal objects, static members display
12252 Print static members when displaying a Pascal object. The default is on.
12254 @item set print pascal_static-members off
12255 Do not print static members when displaying a Pascal object.
12257 @item show print pascal_static-members
12258 Show whether Pascal static members are printed or not.
12260 @c These don't work with HP ANSI C++ yet.
12261 @anchor{set print vtbl}
12262 @item set print vtbl
12263 @itemx set print vtbl on
12264 @cindex pretty print C@t{++} virtual function tables
12265 @cindex virtual functions (C@t{++}) display
12266 @cindex VTBL display
12267 Pretty print C@t{++} virtual function tables. The default is off.
12268 (The @code{vtbl} commands do not work on programs compiled with the HP
12269 ANSI C@t{++} compiler (@code{aCC}).)
12271 @item set print vtbl off
12272 Do not pretty print C@t{++} virtual function tables.
12274 @item show print vtbl
12275 Show whether C@t{++} virtual function tables are pretty printed, or not.
12278 @node Pretty Printing
12279 @section Pretty Printing
12281 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12282 Python code. It greatly simplifies the display of complex objects. This
12283 mechanism works for both MI and the CLI.
12286 * Pretty-Printer Introduction:: Introduction to pretty-printers
12287 * Pretty-Printer Example:: An example pretty-printer
12288 * Pretty-Printer Commands:: Pretty-printer commands
12291 @node Pretty-Printer Introduction
12292 @subsection Pretty-Printer Introduction
12294 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12295 registered for the value. If there is then @value{GDBN} invokes the
12296 pretty-printer to print the value. Otherwise the value is printed normally.
12298 Pretty-printers are normally named. This makes them easy to manage.
12299 The @samp{info pretty-printer} command will list all the installed
12300 pretty-printers with their names.
12301 If a pretty-printer can handle multiple data types, then its
12302 @dfn{subprinters} are the printers for the individual data types.
12303 Each such subprinter has its own name.
12304 The format of the name is @var{printer-name};@var{subprinter-name}.
12306 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12307 Typically they are automatically loaded and registered when the corresponding
12308 debug information is loaded, thus making them available without having to
12309 do anything special.
12311 There are three places where a pretty-printer can be registered.
12315 Pretty-printers registered globally are available when debugging
12319 Pretty-printers registered with a program space are available only
12320 when debugging that program.
12321 @xref{Progspaces In Python}, for more details on program spaces in Python.
12324 Pretty-printers registered with an objfile are loaded and unloaded
12325 with the corresponding objfile (e.g., shared library).
12326 @xref{Objfiles In Python}, for more details on objfiles in Python.
12329 @xref{Selecting Pretty-Printers}, for further information on how
12330 pretty-printers are selected,
12332 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12335 @node Pretty-Printer Example
12336 @subsection Pretty-Printer Example
12338 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12341 (@value{GDBP}) print s
12343 static npos = 4294967295,
12345 <std::allocator<char>> = @{
12346 <__gnu_cxx::new_allocator<char>> = @{
12347 <No data fields>@}, <No data fields>
12349 members of std::basic_string<char, std::char_traits<char>,
12350 std::allocator<char> >::_Alloc_hider:
12351 _M_p = 0x804a014 "abcd"
12356 With a pretty-printer for @code{std::string} only the contents are printed:
12359 (@value{GDBP}) print s
12363 @node Pretty-Printer Commands
12364 @subsection Pretty-Printer Commands
12365 @cindex pretty-printer commands
12368 @kindex info pretty-printer
12369 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12370 Print the list of installed pretty-printers.
12371 This includes disabled pretty-printers, which are marked as such.
12373 @var{object-regexp} is a regular expression matching the objects
12374 whose pretty-printers to list.
12375 Objects can be @code{global}, the program space's file
12376 (@pxref{Progspaces In Python}),
12377 and the object files within that program space (@pxref{Objfiles In Python}).
12378 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12379 looks up a printer from these three objects.
12381 @var{name-regexp} is a regular expression matching the name of the printers
12384 @kindex disable pretty-printer
12385 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12386 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12387 A disabled pretty-printer is not forgotten, it may be enabled again later.
12389 @kindex enable pretty-printer
12390 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12391 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12396 Suppose we have three pretty-printers installed: one from library1.so
12397 named @code{foo} that prints objects of type @code{foo}, and
12398 another from library2.so named @code{bar} that prints two types of objects,
12399 @code{bar1} and @code{bar2}.
12403 (@value{GDBP}) info pretty-printer
12412 (@value{GDBP}) info pretty-printer library2
12419 (@value{GDBP}) disable pretty-printer library1
12421 2 of 3 printers enabled
12422 (@value{GDBP}) info pretty-printer
12431 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12433 1 of 3 printers enabled
12434 (@value{GDBP}) info pretty-printer library2
12441 (@value{GDBP}) disable pretty-printer library2 bar
12443 0 of 3 printers enabled
12444 (@value{GDBP}) info pretty-printer
12454 Note that for @code{bar} the entire printer can be disabled,
12455 as can each individual subprinter.
12457 Printing values and frame arguments is done by default using
12458 the enabled pretty printers.
12460 The print option @code{-raw-values} and @value{GDBN} setting
12461 @code{set print raw-values} (@pxref{set print raw-values}) can be
12462 used to print values without applying the enabled pretty printers.
12464 Similarly, the backtrace option @code{-raw-frame-arguments} and
12465 @value{GDBN} setting @code{set print raw-frame-arguments}
12466 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12467 enabled pretty printers when printing frame argument values.
12469 @node Value History
12470 @section Value History
12472 @cindex value history
12473 @cindex history of values printed by @value{GDBN}
12474 Values printed by the @code{print} command are saved in the @value{GDBN}
12475 @dfn{value history}. This allows you to refer to them in other expressions.
12476 Values are kept until the symbol table is re-read or discarded
12477 (for example with the @code{file} or @code{symbol-file} commands).
12478 When the symbol table changes, the value history is discarded,
12479 since the values may contain pointers back to the types defined in the
12484 @cindex history number
12485 The values printed are given @dfn{history numbers} by which you can
12486 refer to them. These are successive integers starting with one.
12487 @code{print} shows you the history number assigned to a value by
12488 printing @samp{$@var{num} = } before the value; here @var{num} is the
12491 To refer to any previous value, use @samp{$} followed by the value's
12492 history number. The way @code{print} labels its output is designed to
12493 remind you of this. Just @code{$} refers to the most recent value in
12494 the history, and @code{$$} refers to the value before that.
12495 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12496 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12497 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12499 For example, suppose you have just printed a pointer to a structure and
12500 want to see the contents of the structure. It suffices to type
12506 If you have a chain of structures where the component @code{next} points
12507 to the next one, you can print the contents of the next one with this:
12514 You can print successive links in the chain by repeating this
12515 command---which you can do by just typing @key{RET}.
12517 Note that the history records values, not expressions. If the value of
12518 @code{x} is 4 and you type these commands:
12526 then the value recorded in the value history by the @code{print} command
12527 remains 4 even though the value of @code{x} has changed.
12530 @kindex show values
12532 Print the last ten values in the value history, with their item numbers.
12533 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12534 values} does not change the history.
12536 @item show values @var{n}
12537 Print ten history values centered on history item number @var{n}.
12539 @item show values +
12540 Print ten history values just after the values last printed. If no more
12541 values are available, @code{show values +} produces no display.
12544 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12545 same effect as @samp{show values +}.
12547 @node Convenience Vars
12548 @section Convenience Variables
12550 @cindex convenience variables
12551 @cindex user-defined variables
12552 @value{GDBN} provides @dfn{convenience variables} that you can use within
12553 @value{GDBN} to hold on to a value and refer to it later. These variables
12554 exist entirely within @value{GDBN}; they are not part of your program, and
12555 setting a convenience variable has no direct effect on further execution
12556 of your program. That is why you can use them freely.
12558 Convenience variables are prefixed with @samp{$}. Any name preceded by
12559 @samp{$} can be used for a convenience variable, unless it is one of
12560 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12561 (Value history references, in contrast, are @emph{numbers} preceded
12562 by @samp{$}. @xref{Value History, ,Value History}.)
12564 You can save a value in a convenience variable with an assignment
12565 expression, just as you would set a variable in your program.
12569 set $foo = *object_ptr
12573 would save in @code{$foo} the value contained in the object pointed to by
12576 Using a convenience variable for the first time creates it, but its
12577 value is @code{void} until you assign a new value. You can alter the
12578 value with another assignment at any time.
12580 Convenience variables have no fixed types. You can assign a convenience
12581 variable any type of value, including structures and arrays, even if
12582 that variable already has a value of a different type. The convenience
12583 variable, when used as an expression, has the type of its current value.
12586 @kindex show convenience
12587 @cindex show all user variables and functions
12588 @item show convenience
12589 Print a list of convenience variables used so far, and their values,
12590 as well as a list of the convenience functions.
12591 Abbreviated @code{show conv}.
12593 @kindex init-if-undefined
12594 @cindex convenience variables, initializing
12595 @item init-if-undefined $@var{variable} = @var{expression}
12596 Set a convenience variable if it has not already been set. This is useful
12597 for user-defined commands that keep some state. It is similar, in concept,
12598 to using local static variables with initializers in C (except that
12599 convenience variables are global). It can also be used to allow users to
12600 override default values used in a command script.
12602 If the variable is already defined then the expression is not evaluated so
12603 any side-effects do not occur.
12606 One of the ways to use a convenience variable is as a counter to be
12607 incremented or a pointer to be advanced. For example, to print
12608 a field from successive elements of an array of structures:
12612 print bar[$i++]->contents
12616 Repeat that command by typing @key{RET}.
12618 Some convenience variables are created automatically by @value{GDBN} and given
12619 values likely to be useful.
12622 @vindex $_@r{, convenience variable}
12624 The variable @code{$_} is automatically set by the @code{x} command to
12625 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12626 commands which provide a default address for @code{x} to examine also
12627 set @code{$_} to that address; these commands include @code{info line}
12628 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12629 except when set by the @code{x} command, in which case it is a pointer
12630 to the type of @code{$__}.
12632 @vindex $__@r{, convenience variable}
12634 The variable @code{$__} is automatically set by the @code{x} command
12635 to the value found in the last address examined. Its type is chosen
12636 to match the format in which the data was printed.
12639 @vindex $_exitcode@r{, convenience variable}
12640 When the program being debugged terminates normally, @value{GDBN}
12641 automatically sets this variable to the exit code of the program, and
12642 resets @code{$_exitsignal} to @code{void}.
12645 @vindex $_exitsignal@r{, convenience variable}
12646 When the program being debugged dies due to an uncaught signal,
12647 @value{GDBN} automatically sets this variable to that signal's number,
12648 and resets @code{$_exitcode} to @code{void}.
12650 To distinguish between whether the program being debugged has exited
12651 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12652 @code{$_exitsignal} is not @code{void}), the convenience function
12653 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12654 Functions}). For example, considering the following source code:
12657 #include <signal.h>
12660 main (int argc, char *argv[])
12667 A valid way of telling whether the program being debugged has exited
12668 or signalled would be:
12671 (@value{GDBP}) define has_exited_or_signalled
12672 Type commands for definition of ``has_exited_or_signalled''.
12673 End with a line saying just ``end''.
12674 >if $_isvoid ($_exitsignal)
12675 >echo The program has exited\n
12677 >echo The program has signalled\n
12683 Program terminated with signal SIGALRM, Alarm clock.
12684 The program no longer exists.
12685 (@value{GDBP}) has_exited_or_signalled
12686 The program has signalled
12689 As can be seen, @value{GDBN} correctly informs that the program being
12690 debugged has signalled, since it calls @code{raise} and raises a
12691 @code{SIGALRM} signal. If the program being debugged had not called
12692 @code{raise}, then @value{GDBN} would report a normal exit:
12695 (@value{GDBP}) has_exited_or_signalled
12696 The program has exited
12700 The variable @code{$_exception} is set to the exception object being
12701 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12703 @item $_ada_exception
12704 The variable @code{$_ada_exception} is set to the address of the
12705 exception being caught or thrown at an Ada exception-related
12706 catchpoint. @xref{Set Catchpoints}.
12709 @itemx $_probe_arg0@dots{}$_probe_arg11
12710 Arguments to a static probe. @xref{Static Probe Points}.
12713 @vindex $_sdata@r{, inspect, convenience variable}
12714 The variable @code{$_sdata} contains extra collected static tracepoint
12715 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12716 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12717 if extra static tracepoint data has not been collected.
12720 @vindex $_siginfo@r{, convenience variable}
12721 The variable @code{$_siginfo} contains extra signal information
12722 (@pxref{extra signal information}). Note that @code{$_siginfo}
12723 could be empty, if the application has not yet received any signals.
12724 For example, it will be empty before you execute the @code{run} command.
12727 @vindex $_tlb@r{, convenience variable}
12728 The variable @code{$_tlb} is automatically set when debugging
12729 applications running on MS-Windows in native mode or connected to
12730 gdbserver that supports the @code{qGetTIBAddr} request.
12731 @xref{General Query Packets}.
12732 This variable contains the address of the thread information block.
12735 The number of the current inferior. @xref{Inferiors Connections and
12736 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12739 The thread number of the current thread. @xref{thread numbers}.
12742 The global number of the current thread. @xref{global thread numbers}.
12744 @item $_inferior_thread_count
12745 The number of live threads in the current inferior. @xref{Threads}.
12749 @vindex $_gdb_major@r{, convenience variable}
12750 @vindex $_gdb_minor@r{, convenience variable}
12751 The major and minor version numbers of the running @value{GDBN}.
12752 Development snapshots and pretest versions have their minor version
12753 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12754 the value 12 for @code{$_gdb_minor}. These variables allow you to
12755 write scripts that work with different versions of @value{GDBN}
12756 without errors caused by features unavailable in some of those
12759 @item $_shell_exitcode
12760 @itemx $_shell_exitsignal
12761 @vindex $_shell_exitcode@r{, convenience variable}
12762 @vindex $_shell_exitsignal@r{, convenience variable}
12763 @cindex shell command, exit code
12764 @cindex shell command, exit signal
12765 @cindex exit status of shell commands
12766 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12767 shell commands. When a launched command terminates, @value{GDBN}
12768 automatically maintains the variables @code{$_shell_exitcode}
12769 and @code{$_shell_exitsignal} according to the exit status of the last
12770 launched command. These variables are set and used similarly to
12771 the variables @code{$_exitcode} and @code{$_exitsignal}.
12775 @node Convenience Funs
12776 @section Convenience Functions
12778 @cindex convenience functions
12779 @value{GDBN} also supplies some @dfn{convenience functions}. These
12780 have a syntax similar to convenience variables. A convenience
12781 function can be used in an expression just like an ordinary function;
12782 however, a convenience function is implemented internally to
12785 These functions do not require @value{GDBN} to be configured with
12786 @code{Python} support, which means that they are always available.
12790 @item $_isvoid (@var{expr})
12791 @findex $_isvoid@r{, convenience function}
12792 Return one if the expression @var{expr} is @code{void}. Otherwise it
12795 A @code{void} expression is an expression where the type of the result
12796 is @code{void}. For example, you can examine a convenience variable
12797 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12801 (@value{GDBP}) print $_exitcode
12803 (@value{GDBP}) print $_isvoid ($_exitcode)
12806 Starting program: ./a.out
12807 [Inferior 1 (process 29572) exited normally]
12808 (@value{GDBP}) print $_exitcode
12810 (@value{GDBP}) print $_isvoid ($_exitcode)
12814 In the example above, we used @code{$_isvoid} to check whether
12815 @code{$_exitcode} is @code{void} before and after the execution of the
12816 program being debugged. Before the execution there is no exit code to
12817 be examined, therefore @code{$_exitcode} is @code{void}. After the
12818 execution the program being debugged returned zero, therefore
12819 @code{$_exitcode} is zero, which means that it is not @code{void}
12822 The @code{void} expression can also be a call of a function from the
12823 program being debugged. For example, given the following function:
12832 The result of calling it inside @value{GDBN} is @code{void}:
12835 (@value{GDBP}) print foo ()
12837 (@value{GDBP}) print $_isvoid (foo ())
12839 (@value{GDBP}) set $v = foo ()
12840 (@value{GDBP}) print $v
12842 (@value{GDBP}) print $_isvoid ($v)
12846 @item $_gdb_setting_str (@var{setting})
12847 @findex $_gdb_setting_str@r{, convenience function}
12848 Return the value of the @value{GDBN} @var{setting} as a string.
12849 @var{setting} is any setting that can be used in a @code{set} or
12850 @code{show} command (@pxref{Controlling GDB}).
12853 (@value{GDBP}) show print frame-arguments
12854 Printing of non-scalar frame arguments is "scalars".
12855 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12857 (@value{GDBP}) p $_gdb_setting_str("height")
12862 @item $_gdb_setting (@var{setting})
12863 @findex $_gdb_setting@r{, convenience function}
12864 Return the value of the @value{GDBN} @var{setting}.
12865 The type of the returned value depends on the setting.
12867 The value type for boolean and auto boolean settings is @code{int}.
12868 The boolean values @code{off} and @code{on} are converted to
12869 the integer values @code{0} and @code{1}. The value @code{auto} is
12870 converted to the value @code{-1}.
12872 The value type for integer settings is either @code{unsigned int}
12873 or @code{int}, depending on the setting.
12875 Some integer settings accept an @code{unlimited} value.
12876 Depending on the setting, the @code{set} command also accepts
12877 the value @code{0} or the value @code{@minus{}1} as a synonym for
12879 For example, @code{set height unlimited} is equivalent to
12880 @code{set height 0}.
12882 Some other settings that accept the @code{unlimited} value
12883 use the value @code{0} to literally mean zero.
12884 For example, @code{set history size 0} indicates to not
12885 record any @value{GDBN} commands in the command history.
12886 For such settings, @code{@minus{}1} is the synonym
12887 for @code{unlimited}.
12889 See the documentation of the corresponding @code{set} command for
12890 the numerical value equivalent to @code{unlimited}.
12892 The @code{$_gdb_setting} function converts the unlimited value
12893 to a @code{0} or a @code{@minus{}1} value according to what the
12894 @code{set} command uses.
12898 (@value{GDBP}) p $_gdb_setting_str("height")
12900 (@value{GDBP}) p $_gdb_setting("height")
12902 (@value{GDBP}) set height unlimited
12903 (@value{GDBP}) p $_gdb_setting_str("height")
12905 (@value{GDBP}) p $_gdb_setting("height")
12909 (@value{GDBP}) p $_gdb_setting_str("history size")
12911 (@value{GDBP}) p $_gdb_setting("history size")
12913 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12915 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12921 Other setting types (enum, filename, optional filename, string, string noescape)
12922 are returned as string values.
12925 @item $_gdb_maint_setting_str (@var{setting})
12926 @findex $_gdb_maint_setting_str@r{, convenience function}
12927 Like the @code{$_gdb_setting_str} function, but works with
12928 @code{maintenance set} variables.
12930 @item $_gdb_maint_setting (@var{setting})
12931 @findex $_gdb_maint_setting@r{, convenience function}
12932 Like the @code{$_gdb_setting} function, but works with
12933 @code{maintenance set} variables.
12937 The following functions require @value{GDBN} to be configured with
12938 @code{Python} support.
12942 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12943 @findex $_memeq@r{, convenience function}
12944 Returns one if the @var{length} bytes at the addresses given by
12945 @var{buf1} and @var{buf2} are equal.
12946 Otherwise it returns zero.
12948 @item $_regex(@var{str}, @var{regex})
12949 @findex $_regex@r{, convenience function}
12950 Returns one if the string @var{str} matches the regular expression
12951 @var{regex}. Otherwise it returns zero.
12952 The syntax of the regular expression is that specified by @code{Python}'s
12953 regular expression support.
12955 @item $_streq(@var{str1}, @var{str2})
12956 @findex $_streq@r{, convenience function}
12957 Returns one if the strings @var{str1} and @var{str2} are equal.
12958 Otherwise it returns zero.
12960 @item $_strlen(@var{str})
12961 @findex $_strlen@r{, convenience function}
12962 Returns the length of string @var{str}.
12964 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12965 @findex $_caller_is@r{, convenience function}
12966 Returns one if the calling function's name is equal to @var{name}.
12967 Otherwise it returns zero.
12969 If the optional argument @var{number_of_frames} is provided,
12970 it is the number of frames up in the stack to look.
12978 at testsuite/gdb.python/py-caller-is.c:21
12979 #1 0x00000000004005a0 in middle_func ()
12980 at testsuite/gdb.python/py-caller-is.c:27
12981 #2 0x00000000004005ab in top_func ()
12982 at testsuite/gdb.python/py-caller-is.c:33
12983 #3 0x00000000004005b6 in main ()
12984 at testsuite/gdb.python/py-caller-is.c:39
12985 (gdb) print $_caller_is ("middle_func")
12987 (gdb) print $_caller_is ("top_func", 2)
12991 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12992 @findex $_caller_matches@r{, convenience function}
12993 Returns one if the calling function's name matches the regular expression
12994 @var{regexp}. Otherwise it returns zero.
12996 If the optional argument @var{number_of_frames} is provided,
12997 it is the number of frames up in the stack to look.
13000 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
13001 @findex $_any_caller_is@r{, convenience function}
13002 Returns one if any calling function's name is equal to @var{name}.
13003 Otherwise it returns zero.
13005 If the optional argument @var{number_of_frames} is provided,
13006 it is the number of frames up in the stack to look.
13009 This function differs from @code{$_caller_is} in that this function
13010 checks all stack frames from the immediate caller to the frame specified
13011 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
13012 frame specified by @var{number_of_frames}.
13014 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
13015 @findex $_any_caller_matches@r{, convenience function}
13016 Returns one if any calling function's name matches the regular expression
13017 @var{regexp}. Otherwise it returns zero.
13019 If the optional argument @var{number_of_frames} is provided,
13020 it is the number of frames up in the stack to look.
13023 This function differs from @code{$_caller_matches} in that this function
13024 checks all stack frames from the immediate caller to the frame specified
13025 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
13026 frame specified by @var{number_of_frames}.
13028 @item $_as_string(@var{value})
13029 @findex $_as_string@r{, convenience function}
13030 Return the string representation of @var{value}.
13032 This function is useful to obtain the textual label (enumerator) of an
13033 enumeration value. For example, assuming the variable @var{node} is of
13034 an enumerated type:
13037 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
13038 Visiting node of type NODE_INTEGER
13041 @item $_cimag(@var{value})
13042 @itemx $_creal(@var{value})
13043 @findex $_cimag@r{, convenience function}
13044 @findex $_creal@r{, convenience function}
13045 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
13046 the complex number @var{value}.
13048 The type of the imaginary or real part depends on the type of the
13049 complex number, e.g., using @code{$_cimag} on a @code{float complex}
13050 will return an imaginary part of type @code{float}.
13054 @value{GDBN} provides the ability to list and get help on
13055 convenience functions.
13058 @item help function
13059 @kindex help function
13060 @cindex show all convenience functions
13061 Print a list of all convenience functions.
13068 You can refer to machine register contents, in expressions, as variables
13069 with names starting with @samp{$}. The names of registers are different
13070 for each machine; use @code{info registers} to see the names used on
13074 @kindex info registers
13075 @item info registers
13076 Print the names and values of all registers except floating-point
13077 and vector registers (in the selected stack frame).
13079 @kindex info all-registers
13080 @cindex floating point registers
13081 @item info all-registers
13082 Print the names and values of all registers, including floating-point
13083 and vector registers (in the selected stack frame).
13085 @anchor{info_registers_reggroup}
13086 @item info registers @var{reggroup} @dots{}
13087 Print the name and value of the registers in each of the specified
13088 @var{reggroup}s. The @var{reggroup} can be any of those returned by
13089 @code{maint print reggroups} (@pxref{Maintenance Commands}).
13091 @item info registers @var{regname} @dots{}
13092 Print the @dfn{relativized} value of each specified register @var{regname}.
13093 As discussed in detail below, register values are normally relative to
13094 the selected stack frame. The @var{regname} may be any register name valid on
13095 the machine you are using, with or without the initial @samp{$}.
13098 @anchor{standard registers}
13099 @cindex stack pointer register
13100 @cindex program counter register
13101 @cindex process status register
13102 @cindex frame pointer register
13103 @cindex standard registers
13104 @value{GDBN} has four ``standard'' register names that are available (in
13105 expressions) on most machines---whenever they do not conflict with an
13106 architecture's canonical mnemonics for registers. The register names
13107 @code{$pc} and @code{$sp} are used for the program counter register and
13108 the stack pointer. @code{$fp} is used for a register that contains a
13109 pointer to the current stack frame, and @code{$ps} is used for a
13110 register that contains the processor status. For example,
13111 you could print the program counter in hex with
13118 or print the instruction to be executed next with
13125 or add four to the stack pointer@footnote{This is a way of removing
13126 one word from the stack, on machines where stacks grow downward in
13127 memory (most machines, nowadays). This assumes that the innermost
13128 stack frame is selected; setting @code{$sp} is not allowed when other
13129 stack frames are selected. To pop entire frames off the stack,
13130 regardless of machine architecture, use @code{return};
13131 see @ref{Returning, ,Returning from a Function}.} with
13137 Whenever possible, these four standard register names are available on
13138 your machine even though the machine has different canonical mnemonics,
13139 so long as there is no conflict. The @code{info registers} command
13140 shows the canonical names. For example, on the SPARC, @code{info
13141 registers} displays the processor status register as @code{$psr} but you
13142 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
13143 is an alias for the @sc{eflags} register.
13145 @value{GDBN} always considers the contents of an ordinary register as an
13146 integer when the register is examined in this way. Some machines have
13147 special registers which can hold nothing but floating point; these
13148 registers are considered to have floating point values. There is no way
13149 to refer to the contents of an ordinary register as floating point value
13150 (although you can @emph{print} it as a floating point value with
13151 @samp{print/f $@var{regname}}).
13153 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13154 means that the data format in which the register contents are saved by
13155 the operating system is not the same one that your program normally
13156 sees. For example, the registers of the 68881 floating point
13157 coprocessor are always saved in ``extended'' (raw) format, but all C
13158 programs expect to work with ``double'' (virtual) format. In such
13159 cases, @value{GDBN} normally works with the virtual format only (the format
13160 that makes sense for your program), but the @code{info registers} command
13161 prints the data in both formats.
13163 @cindex SSE registers (x86)
13164 @cindex MMX registers (x86)
13165 Some machines have special registers whose contents can be interpreted
13166 in several different ways. For example, modern x86-based machines
13167 have SSE and MMX registers that can hold several values packed
13168 together in several different formats. @value{GDBN} refers to such
13169 registers in @code{struct} notation:
13172 (@value{GDBP}) print $xmm1
13174 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13175 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13176 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13177 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13178 v4_int32 = @{0, 20657912, 11, 13@},
13179 v2_int64 = @{88725056443645952, 55834574859@},
13180 uint128 = 0x0000000d0000000b013b36f800000000
13185 To set values of such registers, you need to tell @value{GDBN} which
13186 view of the register you wish to change, as if you were assigning
13187 value to a @code{struct} member:
13190 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13193 Normally, register values are relative to the selected stack frame
13194 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13195 value that the register would contain if all stack frames farther in
13196 were exited and their saved registers restored. In order to see the
13197 true contents of hardware registers, you must select the innermost
13198 frame (with @samp{frame 0}).
13200 @cindex caller-saved registers
13201 @cindex call-clobbered registers
13202 @cindex volatile registers
13203 @cindex <not saved> values
13204 Usually ABIs reserve some registers as not needed to be saved by the
13205 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13206 registers). It may therefore not be possible for @value{GDBN} to know
13207 the value a register had before the call (in other words, in the outer
13208 frame), if the register value has since been changed by the callee.
13209 @value{GDBN} tries to deduce where the inner frame saved
13210 (``callee-saved'') registers, from the debug info, unwind info, or the
13211 machine code generated by your compiler. If some register is not
13212 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13213 its own knowledge of the ABI, or because the debug/unwind info
13214 explicitly says the register's value is undefined), @value{GDBN}
13215 displays @w{@samp{<not saved>}} as the register's value. With targets
13216 that @value{GDBN} has no knowledge of the register saving convention,
13217 if a register was not saved by the callee, then its value and location
13218 in the outer frame are assumed to be the same of the inner frame.
13219 This is usually harmless, because if the register is call-clobbered,
13220 the caller either does not care what is in the register after the
13221 call, or has code to restore the value that it does care about. Note,
13222 however, that if you change such a register in the outer frame, you
13223 may also be affecting the inner frame. Also, the more ``outer'' the
13224 frame is you're looking at, the more likely a call-clobbered
13225 register's value is to be wrong, in the sense that it doesn't actually
13226 represent the value the register had just before the call.
13228 @node Floating Point Hardware
13229 @section Floating Point Hardware
13230 @cindex floating point
13232 Depending on the configuration, @value{GDBN} may be able to give
13233 you more information about the status of the floating point hardware.
13238 Display hardware-dependent information about the floating
13239 point unit. The exact contents and layout vary depending on the
13240 floating point chip. Currently, @samp{info float} is supported on
13241 the ARM and x86 machines.
13245 @section Vector Unit
13246 @cindex vector unit
13248 Depending on the configuration, @value{GDBN} may be able to give you
13249 more information about the status of the vector unit.
13252 @kindex info vector
13254 Display information about the vector unit. The exact contents and
13255 layout vary depending on the hardware.
13258 @node OS Information
13259 @section Operating System Auxiliary Information
13260 @cindex OS information
13262 @value{GDBN} provides interfaces to useful OS facilities that can help
13263 you debug your program.
13265 @cindex auxiliary vector
13266 @cindex vector, auxiliary
13267 Some operating systems supply an @dfn{auxiliary vector} to programs at
13268 startup. This is akin to the arguments and environment that you
13269 specify for a program, but contains a system-dependent variety of
13270 binary values that tell system libraries important details about the
13271 hardware, operating system, and process. Each value's purpose is
13272 identified by an integer tag; the meanings are well-known but system-specific.
13273 Depending on the configuration and operating system facilities,
13274 @value{GDBN} may be able to show you this information. For remote
13275 targets, this functionality may further depend on the remote stub's
13276 support of the @samp{qXfer:auxv:read} packet, see
13277 @ref{qXfer auxiliary vector read}.
13282 Display the auxiliary vector of the inferior, which can be either a
13283 live process or a core dump file. @value{GDBN} prints each tag value
13284 numerically, and also shows names and text descriptions for recognized
13285 tags. Some values in the vector are numbers, some bit masks, and some
13286 pointers to strings or other data. @value{GDBN} displays each value in the
13287 most appropriate form for a recognized tag, and in hexadecimal for
13288 an unrecognized tag.
13291 On some targets, @value{GDBN} can access operating system-specific
13292 information and show it to you. The types of information available
13293 will differ depending on the type of operating system running on the
13294 target. The mechanism used to fetch the data is described in
13295 @ref{Operating System Information}. For remote targets, this
13296 functionality depends on the remote stub's support of the
13297 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13301 @item info os @var{infotype}
13303 Display OS information of the requested type.
13305 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13307 @anchor{linux info os infotypes}
13309 @kindex info os cpus
13311 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13312 the available fields from /proc/cpuinfo. For each supported architecture
13313 different fields are available. Two common entries are processor which gives
13314 CPU number and bogomips; a system constant that is calculated during
13315 kernel initialization.
13317 @kindex info os files
13319 Display the list of open file descriptors on the target. For each
13320 file descriptor, @value{GDBN} prints the identifier of the process
13321 owning the descriptor, the command of the owning process, the value
13322 of the descriptor, and the target of the descriptor.
13324 @kindex info os modules
13326 Display the list of all loaded kernel modules on the target. For each
13327 module, @value{GDBN} prints the module name, the size of the module in
13328 bytes, the number of times the module is used, the dependencies of the
13329 module, the status of the module, and the address of the loaded module
13332 @kindex info os msg
13334 Display the list of all System V message queues on the target. For each
13335 message queue, @value{GDBN} prints the message queue key, the message
13336 queue identifier, the access permissions, the current number of bytes
13337 on the queue, the current number of messages on the queue, the processes
13338 that last sent and received a message on the queue, the user and group
13339 of the owner and creator of the message queue, the times at which a
13340 message was last sent and received on the queue, and the time at which
13341 the message queue was last changed.
13343 @kindex info os processes
13345 Display the list of processes on the target. For each process,
13346 @value{GDBN} prints the process identifier, the name of the user, the
13347 command corresponding to the process, and the list of processor cores
13348 that the process is currently running on. (To understand what these
13349 properties mean, for this and the following info types, please consult
13350 the general @sc{gnu}/Linux documentation.)
13352 @kindex info os procgroups
13354 Display the list of process groups on the target. For each process,
13355 @value{GDBN} prints the identifier of the process group that it belongs
13356 to, the command corresponding to the process group leader, the process
13357 identifier, and the command line of the process. The list is sorted
13358 first by the process group identifier, then by the process identifier,
13359 so that processes belonging to the same process group are grouped together
13360 and the process group leader is listed first.
13362 @kindex info os semaphores
13364 Display the list of all System V semaphore sets on the target. For each
13365 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13366 set identifier, the access permissions, the number of semaphores in the
13367 set, the user and group of the owner and creator of the semaphore set,
13368 and the times at which the semaphore set was operated upon and changed.
13370 @kindex info os shm
13372 Display the list of all System V shared-memory regions on the target.
13373 For each shared-memory region, @value{GDBN} prints the region key,
13374 the shared-memory identifier, the access permissions, the size of the
13375 region, the process that created the region, the process that last
13376 attached to or detached from the region, the current number of live
13377 attaches to the region, and the times at which the region was last
13378 attached to, detach from, and changed.
13380 @kindex info os sockets
13382 Display the list of Internet-domain sockets on the target. For each
13383 socket, @value{GDBN} prints the address and port of the local and
13384 remote endpoints, the current state of the connection, the creator of
13385 the socket, the IP address family of the socket, and the type of the
13388 @kindex info os threads
13390 Display the list of threads running on the target. For each thread,
13391 @value{GDBN} prints the identifier of the process that the thread
13392 belongs to, the command of the process, the thread identifier, and the
13393 processor core that it is currently running on. The main thread of a
13394 process is not listed.
13398 If @var{infotype} is omitted, then list the possible values for
13399 @var{infotype} and the kind of OS information available for each
13400 @var{infotype}. If the target does not return a list of possible
13401 types, this command will report an error.
13404 @node Memory Region Attributes
13405 @section Memory Region Attributes
13406 @cindex memory region attributes
13408 @dfn{Memory region attributes} allow you to describe special handling
13409 required by regions of your target's memory. @value{GDBN} uses
13410 attributes to determine whether to allow certain types of memory
13411 accesses; whether to use specific width accesses; and whether to cache
13412 target memory. By default the description of memory regions is
13413 fetched from the target (if the current target supports this), but the
13414 user can override the fetched regions.
13416 Defined memory regions can be individually enabled and disabled. When a
13417 memory region is disabled, @value{GDBN} uses the default attributes when
13418 accessing memory in that region. Similarly, if no memory regions have
13419 been defined, @value{GDBN} uses the default attributes when accessing
13422 When a memory region is defined, it is given a number to identify it;
13423 to enable, disable, or remove a memory region, you specify that number.
13427 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13428 Define a memory region bounded by @var{lower} and @var{upper} with
13429 attributes @var{attributes}@dots{}, and add it to the list of regions
13430 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13431 case: it is treated as the target's maximum memory address.
13432 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13435 Discard any user changes to the memory regions and use target-supplied
13436 regions, if available, or no regions if the target does not support.
13439 @item delete mem @var{nums}@dots{}
13440 Remove memory regions @var{nums}@dots{} from the list of regions
13441 monitored by @value{GDBN}.
13443 @kindex disable mem
13444 @item disable mem @var{nums}@dots{}
13445 Disable monitoring of memory regions @var{nums}@dots{}.
13446 A disabled memory region is not forgotten.
13447 It may be enabled again later.
13450 @item enable mem @var{nums}@dots{}
13451 Enable monitoring of memory regions @var{nums}@dots{}.
13455 Print a table of all defined memory regions, with the following columns
13459 @item Memory Region Number
13460 @item Enabled or Disabled.
13461 Enabled memory regions are marked with @samp{y}.
13462 Disabled memory regions are marked with @samp{n}.
13465 The address defining the inclusive lower bound of the memory region.
13468 The address defining the exclusive upper bound of the memory region.
13471 The list of attributes set for this memory region.
13476 @subsection Attributes
13478 @subsubsection Memory Access Mode
13479 The access mode attributes set whether @value{GDBN} may make read or
13480 write accesses to a memory region.
13482 While these attributes prevent @value{GDBN} from performing invalid
13483 memory accesses, they do nothing to prevent the target system, I/O DMA,
13484 etc.@: from accessing memory.
13488 Memory is read only.
13490 Memory is write only.
13492 Memory is read/write. This is the default.
13495 @subsubsection Memory Access Size
13496 The access size attribute tells @value{GDBN} to use specific sized
13497 accesses in the memory region. Often memory mapped device registers
13498 require specific sized accesses. If no access size attribute is
13499 specified, @value{GDBN} may use accesses of any size.
13503 Use 8 bit memory accesses.
13505 Use 16 bit memory accesses.
13507 Use 32 bit memory accesses.
13509 Use 64 bit memory accesses.
13512 @c @subsubsection Hardware/Software Breakpoints
13513 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13514 @c will use hardware or software breakpoints for the internal breakpoints
13515 @c used by the step, next, finish, until, etc. commands.
13519 @c Always use hardware breakpoints
13520 @c @item swbreak (default)
13523 @subsubsection Data Cache
13524 The data cache attributes set whether @value{GDBN} will cache target
13525 memory. While this generally improves performance by reducing debug
13526 protocol overhead, it can lead to incorrect results because @value{GDBN}
13527 does not know about volatile variables or memory mapped device
13532 Enable @value{GDBN} to cache target memory.
13534 Disable @value{GDBN} from caching target memory. This is the default.
13537 @subsection Memory Access Checking
13538 @value{GDBN} can be instructed to refuse accesses to memory that is
13539 not explicitly described. This can be useful if accessing such
13540 regions has undesired effects for a specific target, or to provide
13541 better error checking. The following commands control this behaviour.
13544 @kindex set mem inaccessible-by-default
13545 @item set mem inaccessible-by-default [on|off]
13546 If @code{on} is specified, make @value{GDBN} treat memory not
13547 explicitly described by the memory ranges as non-existent and refuse accesses
13548 to such memory. The checks are only performed if there's at least one
13549 memory range defined. If @code{off} is specified, make @value{GDBN}
13550 treat the memory not explicitly described by the memory ranges as RAM.
13551 The default value is @code{on}.
13552 @kindex show mem inaccessible-by-default
13553 @item show mem inaccessible-by-default
13554 Show the current handling of accesses to unknown memory.
13558 @c @subsubsection Memory Write Verification
13559 @c The memory write verification attributes set whether @value{GDBN}
13560 @c will re-reads data after each write to verify the write was successful.
13564 @c @item noverify (default)
13567 @node Dump/Restore Files
13568 @section Copy Between Memory and a File
13569 @cindex dump/restore files
13570 @cindex append data to a file
13571 @cindex dump data to a file
13572 @cindex restore data from a file
13574 You can use the commands @code{dump}, @code{append}, and
13575 @code{restore} to copy data between target memory and a file. The
13576 @code{dump} and @code{append} commands write data to a file, and the
13577 @code{restore} command reads data from a file back into the inferior's
13578 memory. Files may be in binary, Motorola S-record, Intel hex,
13579 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13580 append to binary files, and cannot read from Verilog Hex files.
13585 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13586 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13587 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13588 or the value of @var{expr}, to @var{filename} in the given format.
13590 The @var{format} parameter may be any one of:
13597 Motorola S-record format.
13599 Tektronix Hex format.
13601 Verilog Hex format.
13604 @value{GDBN} uses the same definitions of these formats as the
13605 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13606 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13610 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13611 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13612 Append the contents of memory from @var{start_addr} to @var{end_addr},
13613 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13614 (@value{GDBN} can only append data to files in raw binary form.)
13617 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13618 Restore the contents of file @var{filename} into memory. The
13619 @code{restore} command can automatically recognize any known @sc{bfd}
13620 file format, except for raw binary. To restore a raw binary file you
13621 must specify the optional keyword @code{binary} after the filename.
13623 If @var{bias} is non-zero, its value will be added to the addresses
13624 contained in the file. Binary files always start at address zero, so
13625 they will be restored at address @var{bias}. Other bfd files have
13626 a built-in location; they will be restored at offset @var{bias}
13627 from that location.
13629 If @var{start} and/or @var{end} are non-zero, then only data between
13630 file offset @var{start} and file offset @var{end} will be restored.
13631 These offsets are relative to the addresses in the file, before
13632 the @var{bias} argument is applied.
13636 @node Core File Generation
13637 @section How to Produce a Core File from Your Program
13638 @cindex dump core from inferior
13640 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13641 image of a running process and its process status (register values
13642 etc.). Its primary use is post-mortem debugging of a program that
13643 crashed while it ran outside a debugger. A program that crashes
13644 automatically produces a core file, unless this feature is disabled by
13645 the user. @xref{Files}, for information on invoking @value{GDBN} in
13646 the post-mortem debugging mode.
13648 Occasionally, you may wish to produce a core file of the program you
13649 are debugging in order to preserve a snapshot of its state.
13650 @value{GDBN} has a special command for that.
13654 @kindex generate-core-file
13655 @item generate-core-file [@var{file}]
13656 @itemx gcore [@var{file}]
13657 Produce a core dump of the inferior process. The optional argument
13658 @var{file} specifies the file name where to put the core dump. If not
13659 specified, the file name defaults to @file{core.@var{pid}}, where
13660 @var{pid} is the inferior process ID.
13662 Note that this command is implemented only for some systems (as of
13663 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13665 On @sc{gnu}/Linux, this command can take into account the value of the
13666 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13667 dump (@pxref{set use-coredump-filter}), and by default honors the
13668 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13669 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13671 @kindex set use-coredump-filter
13672 @anchor{set use-coredump-filter}
13673 @item set use-coredump-filter on
13674 @itemx set use-coredump-filter off
13675 Enable or disable the use of the file
13676 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13677 files. This file is used by the Linux kernel to decide what types of
13678 memory mappings will be dumped or ignored when generating a core dump
13679 file. @var{pid} is the process ID of a currently running process.
13681 To make use of this feature, you have to write in the
13682 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13683 which is a bit mask representing the memory mapping types. If a bit
13684 is set in the bit mask, then the memory mappings of the corresponding
13685 types will be dumped; otherwise, they will be ignored. This
13686 configuration is inherited by child processes. For more information
13687 about the bits that can be set in the
13688 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13689 manpage of @code{core(5)}.
13691 By default, this option is @code{on}. If this option is turned
13692 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13693 and instead uses the same default value as the Linux kernel in order
13694 to decide which pages will be dumped in the core dump file. This
13695 value is currently @code{0x33}, which means that bits @code{0}
13696 (anonymous private mappings), @code{1} (anonymous shared mappings),
13697 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13698 This will cause these memory mappings to be dumped automatically.
13700 @kindex set dump-excluded-mappings
13701 @anchor{set dump-excluded-mappings}
13702 @item set dump-excluded-mappings on
13703 @itemx set dump-excluded-mappings off
13704 If @code{on} is specified, @value{GDBN} will dump memory mappings
13705 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13706 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13708 The default value is @code{off}.
13711 @node Character Sets
13712 @section Character Sets
13713 @cindex character sets
13715 @cindex translating between character sets
13716 @cindex host character set
13717 @cindex target character set
13719 If the program you are debugging uses a different character set to
13720 represent characters and strings than the one @value{GDBN} uses itself,
13721 @value{GDBN} can automatically translate between the character sets for
13722 you. The character set @value{GDBN} uses we call the @dfn{host
13723 character set}; the one the inferior program uses we call the
13724 @dfn{target character set}.
13726 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13727 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13728 remote protocol (@pxref{Remote Debugging}) to debug a program
13729 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13730 then the host character set is Latin-1, and the target character set is
13731 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13732 target-charset EBCDIC-US}, then @value{GDBN} translates between
13733 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13734 character and string literals in expressions.
13736 @value{GDBN} has no way to automatically recognize which character set
13737 the inferior program uses; you must tell it, using the @code{set
13738 target-charset} command, described below.
13740 Here are the commands for controlling @value{GDBN}'s character set
13744 @item set target-charset @var{charset}
13745 @kindex set target-charset
13746 Set the current target character set to @var{charset}. To display the
13747 list of supported target character sets, type
13748 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13750 @item set host-charset @var{charset}
13751 @kindex set host-charset
13752 Set the current host character set to @var{charset}.
13754 By default, @value{GDBN} uses a host character set appropriate to the
13755 system it is running on; you can override that default using the
13756 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13757 automatically determine the appropriate host character set. In this
13758 case, @value{GDBN} uses @samp{UTF-8}.
13760 @value{GDBN} can only use certain character sets as its host character
13761 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13762 @value{GDBN} will list the host character sets it supports.
13764 @item set charset @var{charset}
13765 @kindex set charset
13766 Set the current host and target character sets to @var{charset}. As
13767 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13768 @value{GDBN} will list the names of the character sets that can be used
13769 for both host and target.
13772 @kindex show charset
13773 Show the names of the current host and target character sets.
13775 @item show host-charset
13776 @kindex show host-charset
13777 Show the name of the current host character set.
13779 @item show target-charset
13780 @kindex show target-charset
13781 Show the name of the current target character set.
13783 @item set target-wide-charset @var{charset}
13784 @kindex set target-wide-charset
13785 Set the current target's wide character set to @var{charset}. This is
13786 the character set used by the target's @code{wchar_t} type. To
13787 display the list of supported wide character sets, type
13788 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13790 @item show target-wide-charset
13791 @kindex show target-wide-charset
13792 Show the name of the current target's wide character set.
13795 Here is an example of @value{GDBN}'s character set support in action.
13796 Assume that the following source code has been placed in the file
13797 @file{charset-test.c}:
13803 = @{72, 101, 108, 108, 111, 44, 32, 119,
13804 111, 114, 108, 100, 33, 10, 0@};
13805 char ibm1047_hello[]
13806 = @{200, 133, 147, 147, 150, 107, 64, 166,
13807 150, 153, 147, 132, 90, 37, 0@};
13811 printf ("Hello, world!\n");
13815 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13816 containing the string @samp{Hello, world!} followed by a newline,
13817 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13819 We compile the program, and invoke the debugger on it:
13822 $ gcc -g charset-test.c -o charset-test
13823 $ gdb -nw charset-test
13824 GNU gdb 2001-12-19-cvs
13825 Copyright 2001 Free Software Foundation, Inc.
13830 We can use the @code{show charset} command to see what character sets
13831 @value{GDBN} is currently using to interpret and display characters and
13835 (@value{GDBP}) show charset
13836 The current host and target character set is `ISO-8859-1'.
13840 For the sake of printing this manual, let's use @sc{ascii} as our
13841 initial character set:
13843 (@value{GDBP}) set charset ASCII
13844 (@value{GDBP}) show charset
13845 The current host and target character set is `ASCII'.
13849 Let's assume that @sc{ascii} is indeed the correct character set for our
13850 host system --- in other words, let's assume that if @value{GDBN} prints
13851 characters using the @sc{ascii} character set, our terminal will display
13852 them properly. Since our current target character set is also
13853 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13856 (@value{GDBP}) print ascii_hello
13857 $1 = 0x401698 "Hello, world!\n"
13858 (@value{GDBP}) print ascii_hello[0]
13863 @value{GDBN} uses the target character set for character and string
13864 literals you use in expressions:
13867 (@value{GDBP}) print '+'
13872 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13875 @value{GDBN} relies on the user to tell it which character set the
13876 target program uses. If we print @code{ibm1047_hello} while our target
13877 character set is still @sc{ascii}, we get jibberish:
13880 (@value{GDBP}) print ibm1047_hello
13881 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13882 (@value{GDBP}) print ibm1047_hello[0]
13887 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13888 @value{GDBN} tells us the character sets it supports:
13891 (@value{GDBP}) set target-charset
13892 ASCII EBCDIC-US IBM1047 ISO-8859-1
13893 (@value{GDBP}) set target-charset
13896 We can select @sc{ibm1047} as our target character set, and examine the
13897 program's strings again. Now the @sc{ascii} string is wrong, but
13898 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13899 target character set, @sc{ibm1047}, to the host character set,
13900 @sc{ascii}, and they display correctly:
13903 (@value{GDBP}) set target-charset IBM1047
13904 (@value{GDBP}) show charset
13905 The current host character set is `ASCII'.
13906 The current target character set is `IBM1047'.
13907 (@value{GDBP}) print ascii_hello
13908 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13909 (@value{GDBP}) print ascii_hello[0]
13911 (@value{GDBP}) print ibm1047_hello
13912 $8 = 0x4016a8 "Hello, world!\n"
13913 (@value{GDBP}) print ibm1047_hello[0]
13918 As above, @value{GDBN} uses the target character set for character and
13919 string literals you use in expressions:
13922 (@value{GDBP}) print '+'
13927 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13930 @node Caching Target Data
13931 @section Caching Data of Targets
13932 @cindex caching data of targets
13934 @value{GDBN} caches data exchanged between the debugger and a target.
13935 Each cache is associated with the address space of the inferior.
13936 @xref{Inferiors Connections and Programs}, about inferior and address space.
13937 Such caching generally improves performance in remote debugging
13938 (@pxref{Remote Debugging}), because it reduces the overhead of the
13939 remote protocol by bundling memory reads and writes into large chunks.
13940 Unfortunately, simply caching everything would lead to incorrect results,
13941 since @value{GDBN} does not necessarily know anything about volatile
13942 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13943 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13945 Therefore, by default, @value{GDBN} only caches data
13946 known to be on the stack@footnote{In non-stop mode, it is moderately
13947 rare for a running thread to modify the stack of a stopped thread
13948 in a way that would interfere with a backtrace, and caching of
13949 stack reads provides a significant speed up of remote backtraces.} or
13950 in the code segment.
13951 Other regions of memory can be explicitly marked as
13952 cacheable; @pxref{Memory Region Attributes}.
13955 @kindex set remotecache
13956 @item set remotecache on
13957 @itemx set remotecache off
13958 This option no longer does anything; it exists for compatibility
13961 @kindex show remotecache
13962 @item show remotecache
13963 Show the current state of the obsolete remotecache flag.
13965 @kindex set stack-cache
13966 @item set stack-cache on
13967 @itemx set stack-cache off
13968 Enable or disable caching of stack accesses. When @code{on}, use
13969 caching. By default, this option is @code{on}.
13971 @kindex show stack-cache
13972 @item show stack-cache
13973 Show the current state of data caching for memory accesses.
13975 @kindex set code-cache
13976 @item set code-cache on
13977 @itemx set code-cache off
13978 Enable or disable caching of code segment accesses. When @code{on},
13979 use caching. By default, this option is @code{on}. This improves
13980 performance of disassembly in remote debugging.
13982 @kindex show code-cache
13983 @item show code-cache
13984 Show the current state of target memory cache for code segment
13987 @kindex info dcache
13988 @item info dcache @r{[}line@r{]}
13989 Print the information about the performance of data cache of the
13990 current inferior's address space. The information displayed
13991 includes the dcache width and depth, and for each cache line, its
13992 number, address, and how many times it was referenced. This
13993 command is useful for debugging the data cache operation.
13995 If a line number is specified, the contents of that line will be
13998 @item set dcache size @var{size}
13999 @cindex dcache size
14000 @kindex set dcache size
14001 Set maximum number of entries in dcache (dcache depth above).
14003 @item set dcache line-size @var{line-size}
14004 @cindex dcache line-size
14005 @kindex set dcache line-size
14006 Set number of bytes each dcache entry caches (dcache width above).
14007 Must be a power of 2.
14009 @item show dcache size
14010 @kindex show dcache size
14011 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
14013 @item show dcache line-size
14014 @kindex show dcache line-size
14015 Show default size of dcache lines.
14017 @item maint flush dcache
14018 @cindex dcache, flushing
14019 @kindex maint flush dcache
14020 Flush the contents (if any) of the dcache. This maintainer command is
14021 useful when debugging the dcache implementation.
14025 @node Searching Memory
14026 @section Search Memory
14027 @cindex searching memory
14029 Memory can be searched for a particular sequence of bytes with the
14030 @code{find} command.
14034 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14035 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14036 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
14037 etc. The search begins at address @var{start_addr} and continues for either
14038 @var{len} bytes or through to @var{end_addr} inclusive.
14041 @var{s} and @var{n} are optional parameters.
14042 They may be specified in either order, apart or together.
14045 @item @var{s}, search query size
14046 The size of each search query value.
14052 halfwords (two bytes)
14056 giant words (eight bytes)
14059 All values are interpreted in the current language.
14060 This means, for example, that if the current source language is C/C@t{++}
14061 then searching for the string ``hello'' includes the trailing '\0'.
14062 The null terminator can be removed from searching by using casts,
14063 e.g.: @samp{@{char[5]@}"hello"}.
14065 If the value size is not specified, it is taken from the
14066 value's type in the current language.
14067 This is useful when one wants to specify the search
14068 pattern as a mixture of types.
14069 Note that this means, for example, that in the case of C-like languages
14070 a search for an untyped 0x42 will search for @samp{(int) 0x42}
14071 which is typically four bytes.
14073 @item @var{n}, maximum number of finds
14074 The maximum number of matches to print. The default is to print all finds.
14077 You can use strings as search values. Quote them with double-quotes
14079 The string value is copied into the search pattern byte by byte,
14080 regardless of the endianness of the target and the size specification.
14082 The address of each match found is printed as well as a count of the
14083 number of matches found.
14085 The address of the last value found is stored in convenience variable
14087 A count of the number of matches is stored in @samp{$numfound}.
14089 For example, if stopped at the @code{printf} in this function:
14095 static char hello[] = "hello-hello";
14096 static struct @{ char c; short s; int i; @}
14097 __attribute__ ((packed)) mixed
14098 = @{ 'c', 0x1234, 0x87654321 @};
14099 printf ("%s\n", hello);
14104 you get during debugging:
14107 (gdb) find &hello[0], +sizeof(hello), "hello"
14108 0x804956d <hello.1620+6>
14110 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
14111 0x8049567 <hello.1620>
14112 0x804956d <hello.1620+6>
14114 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
14115 0x8049567 <hello.1620>
14116 0x804956d <hello.1620+6>
14118 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
14119 0x8049567 <hello.1620>
14121 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
14122 0x8049560 <mixed.1625>
14124 (gdb) print $numfound
14127 $2 = (void *) 0x8049560
14131 @section Value Sizes
14133 Whenever @value{GDBN} prints a value memory will be allocated within
14134 @value{GDBN} to hold the contents of the value. It is possible in
14135 some languages with dynamic typing systems, that an invalid program
14136 may indicate a value that is incorrectly large, this in turn may cause
14137 @value{GDBN} to try and allocate an overly large amount of memory.
14140 @kindex set max-value-size
14141 @item set max-value-size @var{bytes}
14142 @itemx set max-value-size unlimited
14143 Set the maximum size of memory that @value{GDBN} will allocate for the
14144 contents of a value to @var{bytes}, trying to display a value that
14145 requires more memory than that will result in an error.
14147 Setting this variable does not effect values that have already been
14148 allocated within @value{GDBN}, only future allocations.
14150 There's a minimum size that @code{max-value-size} can be set to in
14151 order that @value{GDBN} can still operate correctly, this minimum is
14152 currently 16 bytes.
14154 The limit applies to the results of some subexpressions as well as to
14155 complete expressions. For example, an expression denoting a simple
14156 integer component, such as @code{x.y.z}, may fail if the size of
14157 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14158 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14159 @var{A} is an array variable with non-constant size, will generally
14160 succeed regardless of the bounds on @var{A}, as long as the component
14161 size is less than @var{bytes}.
14163 The default value of @code{max-value-size} is currently 64k.
14165 @kindex show max-value-size
14166 @item show max-value-size
14167 Show the maximum size of memory, in bytes, that @value{GDBN} will
14168 allocate for the contents of a value.
14171 @node Optimized Code
14172 @chapter Debugging Optimized Code
14173 @cindex optimized code, debugging
14174 @cindex debugging optimized code
14176 Almost all compilers support optimization. With optimization
14177 disabled, the compiler generates assembly code that corresponds
14178 directly to your source code, in a simplistic way. As the compiler
14179 applies more powerful optimizations, the generated assembly code
14180 diverges from your original source code. With help from debugging
14181 information generated by the compiler, @value{GDBN} can map from
14182 the running program back to constructs from your original source.
14184 @value{GDBN} is more accurate with optimization disabled. If you
14185 can recompile without optimization, it is easier to follow the
14186 progress of your program during debugging. But, there are many cases
14187 where you may need to debug an optimized version.
14189 When you debug a program compiled with @samp{-g -O}, remember that the
14190 optimizer has rearranged your code; the debugger shows you what is
14191 really there. Do not be too surprised when the execution path does not
14192 exactly match your source file! An extreme example: if you define a
14193 variable, but never use it, @value{GDBN} never sees that
14194 variable---because the compiler optimizes it out of existence.
14196 Some things do not work as well with @samp{-g -O} as with just
14197 @samp{-g}, particularly on machines with instruction scheduling. If in
14198 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14199 please report it to us as a bug (including a test case!).
14200 @xref{Variables}, for more information about debugging optimized code.
14203 * Inline Functions:: How @value{GDBN} presents inlining
14204 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14207 @node Inline Functions
14208 @section Inline Functions
14209 @cindex inline functions, debugging
14211 @dfn{Inlining} is an optimization that inserts a copy of the function
14212 body directly at each call site, instead of jumping to a shared
14213 routine. @value{GDBN} displays inlined functions just like
14214 non-inlined functions. They appear in backtraces. You can view their
14215 arguments and local variables, step into them with @code{step}, skip
14216 them with @code{next}, and escape from them with @code{finish}.
14217 You can check whether a function was inlined by using the
14218 @code{info frame} command.
14220 For @value{GDBN} to support inlined functions, the compiler must
14221 record information about inlining in the debug information ---
14222 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14223 other compilers do also. @value{GDBN} only supports inlined functions
14224 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14225 do not emit two required attributes (@samp{DW_AT_call_file} and
14226 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14227 function calls with earlier versions of @value{NGCC}. It instead
14228 displays the arguments and local variables of inlined functions as
14229 local variables in the caller.
14231 The body of an inlined function is directly included at its call site;
14232 unlike a non-inlined function, there are no instructions devoted to
14233 the call. @value{GDBN} still pretends that the call site and the
14234 start of the inlined function are different instructions. Stepping to
14235 the call site shows the call site, and then stepping again shows
14236 the first line of the inlined function, even though no additional
14237 instructions are executed.
14239 This makes source-level debugging much clearer; you can see both the
14240 context of the call and then the effect of the call. Only stepping by
14241 a single instruction using @code{stepi} or @code{nexti} does not do
14242 this; single instruction steps always show the inlined body.
14244 There are some ways that @value{GDBN} does not pretend that inlined
14245 function calls are the same as normal calls:
14249 Setting breakpoints at the call site of an inlined function may not
14250 work, because the call site does not contain any code. @value{GDBN}
14251 may incorrectly move the breakpoint to the next line of the enclosing
14252 function, after the call. This limitation will be removed in a future
14253 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14254 or inside the inlined function instead.
14257 @value{GDBN} cannot locate the return value of inlined calls after
14258 using the @code{finish} command. This is a limitation of compiler-generated
14259 debugging information; after @code{finish}, you can step to the next line
14260 and print a variable where your program stored the return value.
14264 @node Tail Call Frames
14265 @section Tail Call Frames
14266 @cindex tail call frames, debugging
14268 Function @code{B} can call function @code{C} in its very last statement. In
14269 unoptimized compilation the call of @code{C} is immediately followed by return
14270 instruction at the end of @code{B} code. Optimizing compiler may replace the
14271 call and return in function @code{B} into one jump to function @code{C}
14272 instead. Such use of a jump instruction is called @dfn{tail call}.
14274 During execution of function @code{C}, there will be no indication in the
14275 function call stack frames that it was tail-called from @code{B}. If function
14276 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14277 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14278 some cases @value{GDBN} can determine that @code{C} was tail-called from
14279 @code{B}, and it will then create fictitious call frame for that, with the
14280 return address set up as if @code{B} called @code{C} normally.
14282 This functionality is currently supported only by DWARF 2 debugging format and
14283 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14284 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14287 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14288 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14292 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14294 Stack level 1, frame at 0x7fffffffda30:
14295 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14296 tail call frame, caller of frame at 0x7fffffffda30
14297 source language c++.
14298 Arglist at unknown address.
14299 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14302 The detection of all the possible code path executions can find them ambiguous.
14303 There is no execution history stored (possible @ref{Reverse Execution} is never
14304 used for this purpose) and the last known caller could have reached the known
14305 callee by multiple different jump sequences. In such case @value{GDBN} still
14306 tries to show at least all the unambiguous top tail callers and all the
14307 unambiguous bottom tail calees, if any.
14310 @anchor{set debug entry-values}
14311 @item set debug entry-values
14312 @kindex set debug entry-values
14313 When set to on, enables printing of analysis messages for both frame argument
14314 values at function entry and tail calls. It will show all the possible valid
14315 tail calls code paths it has considered. It will also print the intersection
14316 of them with the final unambiguous (possibly partial or even empty) code path
14319 @item show debug entry-values
14320 @kindex show debug entry-values
14321 Show the current state of analysis messages printing for both frame argument
14322 values at function entry and tail calls.
14325 The analysis messages for tail calls can for example show why the virtual tail
14326 call frame for function @code{c} has not been recognized (due to the indirect
14327 reference by variable @code{x}):
14330 static void __attribute__((noinline, noclone)) c (void);
14331 void (*x) (void) = c;
14332 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14333 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14334 int main (void) @{ x (); return 0; @}
14336 Breakpoint 1, DW_OP_entry_value resolving cannot find
14337 DW_TAG_call_site 0x40039a in main
14339 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14342 #1 0x000000000040039a in main () at t.c:5
14345 Another possibility is an ambiguous virtual tail call frames resolution:
14349 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14350 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14351 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14352 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14353 static void __attribute__((noinline, noclone)) b (void)
14354 @{ if (i) c (); else e (); @}
14355 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14356 int main (void) @{ a (); return 0; @}
14358 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14359 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14360 tailcall: reduced: 0x4004d2(a) |
14363 #1 0x00000000004004d2 in a () at t.c:8
14364 #2 0x0000000000400395 in main () at t.c:9
14367 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14368 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14370 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14371 @ifset HAVE_MAKEINFO_CLICK
14372 @set ARROW @click{}
14373 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14374 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14376 @ifclear HAVE_MAKEINFO_CLICK
14378 @set CALLSEQ1B @value{CALLSEQ1A}
14379 @set CALLSEQ2B @value{CALLSEQ2A}
14382 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14383 The code can have possible execution paths @value{CALLSEQ1B} or
14384 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14386 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14387 has found. It then finds another possible calling sequence - that one is
14388 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14389 printed as the @code{reduced:} calling sequence. That one could have many
14390 further @code{compare:} and @code{reduced:} statements as long as there remain
14391 any non-ambiguous sequence entries.
14393 For the frame of function @code{b} in both cases there are different possible
14394 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14395 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14396 therefore this one is displayed to the user while the ambiguous frames are
14399 There can be also reasons why printing of frame argument values at function
14404 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14405 static void __attribute__((noinline, noclone)) a (int i);
14406 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14407 static void __attribute__((noinline, noclone)) a (int i)
14408 @{ if (i) b (i - 1); else c (0); @}
14409 int main (void) @{ a (5); return 0; @}
14412 #0 c (i=i@@entry=0) at t.c:2
14413 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14414 function "a" at 0x400420 can call itself via tail calls
14415 i=<optimized out>) at t.c:6
14416 #2 0x000000000040036e in main () at t.c:7
14419 @value{GDBN} cannot find out from the inferior state if and how many times did
14420 function @code{a} call itself (via function @code{b}) as these calls would be
14421 tail calls. Such tail calls would modify the @code{i} variable, therefore
14422 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14423 prints @code{<optimized out>} instead.
14426 @chapter C Preprocessor Macros
14428 Some languages, such as C and C@t{++}, provide a way to define and invoke
14429 ``preprocessor macros'' which expand into strings of tokens.
14430 @value{GDBN} can evaluate expressions containing macro invocations, show
14431 the result of macro expansion, and show a macro's definition, including
14432 where it was defined.
14434 You may need to compile your program specially to provide @value{GDBN}
14435 with information about preprocessor macros. Most compilers do not
14436 include macros in their debugging information, even when you compile
14437 with the @option{-g} flag. @xref{Compilation}.
14439 A program may define a macro at one point, remove that definition later,
14440 and then provide a different definition after that. Thus, at different
14441 points in the program, a macro may have different definitions, or have
14442 no definition at all. If there is a current stack frame, @value{GDBN}
14443 uses the macros in scope at that frame's source code line. Otherwise,
14444 @value{GDBN} uses the macros in scope at the current listing location;
14447 Whenever @value{GDBN} evaluates an expression, it always expands any
14448 macro invocations present in the expression. @value{GDBN} also provides
14449 the following commands for working with macros explicitly.
14453 @kindex macro expand
14454 @cindex macro expansion, showing the results of preprocessor
14455 @cindex preprocessor macro expansion, showing the results of
14456 @cindex expanding preprocessor macros
14457 @item macro expand @var{expression}
14458 @itemx macro exp @var{expression}
14459 Show the results of expanding all preprocessor macro invocations in
14460 @var{expression}. Since @value{GDBN} simply expands macros, but does
14461 not parse the result, @var{expression} need not be a valid expression;
14462 it can be any string of tokens.
14465 @item macro expand-once @var{expression}
14466 @itemx macro exp1 @var{expression}
14467 @cindex expand macro once
14468 @i{(This command is not yet implemented.)} Show the results of
14469 expanding those preprocessor macro invocations that appear explicitly in
14470 @var{expression}. Macro invocations appearing in that expansion are
14471 left unchanged. This command allows you to see the effect of a
14472 particular macro more clearly, without being confused by further
14473 expansions. Since @value{GDBN} simply expands macros, but does not
14474 parse the result, @var{expression} need not be a valid expression; it
14475 can be any string of tokens.
14478 @cindex macro definition, showing
14479 @cindex definition of a macro, showing
14480 @cindex macros, from debug info
14481 @item info macro [-a|-all] [--] @var{macro}
14482 Show the current definition or all definitions of the named @var{macro},
14483 and describe the source location or compiler command-line where that
14484 definition was established. The optional double dash is to signify the end of
14485 argument processing and the beginning of @var{macro} for non C-like macros where
14486 the macro may begin with a hyphen.
14488 @kindex info macros
14489 @item info macros @var{locspec}
14490 Show all macro definitions that are in effect at the source line of
14491 the code location that results from resolving @var{locspec}, and
14492 describe the source location or compiler command-line where those
14493 definitions were established.
14495 @kindex macro define
14496 @cindex user-defined macros
14497 @cindex defining macros interactively
14498 @cindex macros, user-defined
14499 @item macro define @var{macro} @var{replacement-list}
14500 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14501 Introduce a definition for a preprocessor macro named @var{macro},
14502 invocations of which are replaced by the tokens given in
14503 @var{replacement-list}. The first form of this command defines an
14504 ``object-like'' macro, which takes no arguments; the second form
14505 defines a ``function-like'' macro, which takes the arguments given in
14508 A definition introduced by this command is in scope in every
14509 expression evaluated in @value{GDBN}, until it is removed with the
14510 @code{macro undef} command, described below. The definition overrides
14511 all definitions for @var{macro} present in the program being debugged,
14512 as well as any previous user-supplied definition.
14514 @kindex macro undef
14515 @item macro undef @var{macro}
14516 Remove any user-supplied definition for the macro named @var{macro}.
14517 This command only affects definitions provided with the @code{macro
14518 define} command, described above; it cannot remove definitions present
14519 in the program being debugged.
14523 List all the macros defined using the @code{macro define} command.
14526 @cindex macros, example of debugging with
14527 Here is a transcript showing the above commands in action. First, we
14528 show our source files:
14533 #include "sample.h"
14536 #define ADD(x) (M + x)
14541 printf ("Hello, world!\n");
14543 printf ("We're so creative.\n");
14545 printf ("Goodbye, world!\n");
14552 Now, we compile the program using the @sc{gnu} C compiler,
14553 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14554 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14555 and @option{-gdwarf-4}; we recommend always choosing the most recent
14556 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14557 includes information about preprocessor macros in the debugging
14561 $ gcc -gdwarf-2 -g3 sample.c -o sample
14565 Now, we start @value{GDBN} on our sample program:
14569 GNU gdb 2002-05-06-cvs
14570 Copyright 2002 Free Software Foundation, Inc.
14571 GDB is free software, @dots{}
14575 We can expand macros and examine their definitions, even when the
14576 program is not running. @value{GDBN} uses the current listing position
14577 to decide which macro definitions are in scope:
14580 (@value{GDBP}) list main
14583 5 #define ADD(x) (M + x)
14588 10 printf ("Hello, world!\n");
14590 12 printf ("We're so creative.\n");
14591 (@value{GDBP}) info macro ADD
14592 Defined at /home/jimb/gdb/macros/play/sample.c:5
14593 #define ADD(x) (M + x)
14594 (@value{GDBP}) info macro Q
14595 Defined at /home/jimb/gdb/macros/play/sample.h:1
14596 included at /home/jimb/gdb/macros/play/sample.c:2
14598 (@value{GDBP}) macro expand ADD(1)
14599 expands to: (42 + 1)
14600 (@value{GDBP}) macro expand-once ADD(1)
14601 expands to: once (M + 1)
14605 In the example above, note that @code{macro expand-once} expands only
14606 the macro invocation explicit in the original text --- the invocation of
14607 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14608 which was introduced by @code{ADD}.
14610 Once the program is running, @value{GDBN} uses the macro definitions in
14611 force at the source line of the current stack frame:
14614 (@value{GDBP}) break main
14615 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14617 Starting program: /home/jimb/gdb/macros/play/sample
14619 Breakpoint 1, main () at sample.c:10
14620 10 printf ("Hello, world!\n");
14624 At line 10, the definition of the macro @code{N} at line 9 is in force:
14627 (@value{GDBP}) info macro N
14628 Defined at /home/jimb/gdb/macros/play/sample.c:9
14630 (@value{GDBP}) macro expand N Q M
14631 expands to: 28 < 42
14632 (@value{GDBP}) print N Q M
14637 As we step over directives that remove @code{N}'s definition, and then
14638 give it a new definition, @value{GDBN} finds the definition (or lack
14639 thereof) in force at each point:
14642 (@value{GDBP}) next
14644 12 printf ("We're so creative.\n");
14645 (@value{GDBP}) info macro N
14646 The symbol `N' has no definition as a C/C++ preprocessor macro
14647 at /home/jimb/gdb/macros/play/sample.c:12
14648 (@value{GDBP}) next
14650 14 printf ("Goodbye, world!\n");
14651 (@value{GDBP}) info macro N
14652 Defined at /home/jimb/gdb/macros/play/sample.c:13
14654 (@value{GDBP}) macro expand N Q M
14655 expands to: 1729 < 42
14656 (@value{GDBP}) print N Q M
14661 In addition to source files, macros can be defined on the compilation command
14662 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14663 such a way, @value{GDBN} displays the location of their definition as line zero
14664 of the source file submitted to the compiler.
14667 (@value{GDBP}) info macro __STDC__
14668 Defined at /home/jimb/gdb/macros/play/sample.c:0
14675 @chapter Tracepoints
14676 @c This chapter is based on the documentation written by Michael
14677 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14679 @cindex tracepoints
14680 In some applications, it is not feasible for the debugger to interrupt
14681 the program's execution long enough for the developer to learn
14682 anything helpful about its behavior. If the program's correctness
14683 depends on its real-time behavior, delays introduced by a debugger
14684 might cause the program to change its behavior drastically, or perhaps
14685 fail, even when the code itself is correct. It is useful to be able
14686 to observe the program's behavior without interrupting it.
14688 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14689 specify locations in the program, called @dfn{tracepoints}, and
14690 arbitrary expressions to evaluate when those tracepoints are reached.
14691 Later, using the @code{tfind} command, you can examine the values
14692 those expressions had when the program hit the tracepoints. The
14693 expressions may also denote objects in memory---structures or arrays,
14694 for example---whose values @value{GDBN} should record; while visiting
14695 a particular tracepoint, you may inspect those objects as if they were
14696 in memory at that moment. However, because @value{GDBN} records these
14697 values without interacting with you, it can do so quickly and
14698 unobtrusively, hopefully not disturbing the program's behavior.
14700 The tracepoint facility is currently available only for remote
14701 targets. @xref{Targets}. In addition, your remote target must know
14702 how to collect trace data. This functionality is implemented in the
14703 remote stub; however, none of the stubs distributed with @value{GDBN}
14704 support tracepoints as of this writing. The format of the remote
14705 packets used to implement tracepoints are described in @ref{Tracepoint
14708 It is also possible to get trace data from a file, in a manner reminiscent
14709 of corefiles; you specify the filename, and use @code{tfind} to search
14710 through the file. @xref{Trace Files}, for more details.
14712 This chapter describes the tracepoint commands and features.
14715 * Set Tracepoints::
14716 * Analyze Collected Data::
14717 * Tracepoint Variables::
14721 @node Set Tracepoints
14722 @section Commands to Set Tracepoints
14724 Before running such a @dfn{trace experiment}, an arbitrary number of
14725 tracepoints can be set. A tracepoint is actually a special type of
14726 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14727 standard breakpoint commands. For instance, as with breakpoints,
14728 tracepoint numbers are successive integers starting from one, and many
14729 of the commands associated with tracepoints take the tracepoint number
14730 as their argument, to identify which tracepoint to work on.
14732 For each tracepoint, you can specify, in advance, some arbitrary set
14733 of data that you want the target to collect in the trace buffer when
14734 it hits that tracepoint. The collected data can include registers,
14735 local variables, or global data. Later, you can use @value{GDBN}
14736 commands to examine the values these data had at the time the
14737 tracepoint was hit.
14739 Tracepoints do not support every breakpoint feature. Ignore counts on
14740 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14741 commands when they are hit. Tracepoints may not be thread-specific
14744 @cindex fast tracepoints
14745 Some targets may support @dfn{fast tracepoints}, which are inserted in
14746 a different way (such as with a jump instead of a trap), that is
14747 faster but possibly restricted in where they may be installed.
14749 @cindex static tracepoints
14750 @cindex markers, static tracepoints
14751 @cindex probing markers, static tracepoints
14752 Regular and fast tracepoints are dynamic tracing facilities, meaning
14753 that they can be used to insert tracepoints at (almost) any location
14754 in the target. Some targets may also support controlling @dfn{static
14755 tracepoints} from @value{GDBN}. With static tracing, a set of
14756 instrumentation points, also known as @dfn{markers}, are embedded in
14757 the target program, and can be activated or deactivated by name or
14758 address. These are usually placed at locations which facilitate
14759 investigating what the target is actually doing. @value{GDBN}'s
14760 support for static tracing includes being able to list instrumentation
14761 points, and attach them with @value{GDBN} defined high level
14762 tracepoints that expose the whole range of convenience of
14763 @value{GDBN}'s tracepoints support. Namely, support for collecting
14764 registers values and values of global or local (to the instrumentation
14765 point) variables; tracepoint conditions and trace state variables.
14766 The act of installing a @value{GDBN} static tracepoint on an
14767 instrumentation point, or marker, is referred to as @dfn{probing} a
14768 static tracepoint marker.
14770 @code{gdbserver} supports tracepoints on some target systems.
14771 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14773 This section describes commands to set tracepoints and associated
14774 conditions and actions.
14777 * Create and Delete Tracepoints::
14778 * Enable and Disable Tracepoints::
14779 * Tracepoint Passcounts::
14780 * Tracepoint Conditions::
14781 * Trace State Variables::
14782 * Tracepoint Actions::
14783 * Listing Tracepoints::
14784 * Listing Static Tracepoint Markers::
14785 * Starting and Stopping Trace Experiments::
14786 * Tracepoint Restrictions::
14789 @node Create and Delete Tracepoints
14790 @subsection Create and Delete Tracepoints
14793 @cindex set tracepoint
14795 @item trace @var{locspec}
14796 The @code{trace} command is very similar to the @code{break} command.
14797 Its argument @var{locspec} can be any valid location specification.
14798 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
14799 which is a point in the target program where the debugger will briefly stop,
14800 collect some data, and then allow the program to continue. Setting a tracepoint
14801 or changing its actions takes effect immediately if the remote stub
14802 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14804 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14805 these changes don't take effect until the next @code{tstart}
14806 command, and once a trace experiment is running, further changes will
14807 not have any effect until the next trace experiment starts. In addition,
14808 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14809 address is not yet resolved. (This is similar to pending breakpoints.)
14810 Pending tracepoints are not downloaded to the target and not installed
14811 until they are resolved. The resolution of pending tracepoints requires
14812 @value{GDBN} support---when debugging with the remote target, and
14813 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14814 tracing}), pending tracepoints can not be resolved (and downloaded to
14815 the remote stub) while @value{GDBN} is disconnected.
14817 Here are some examples of using the @code{trace} command:
14820 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14822 (@value{GDBP}) @b{trace +2} // 2 lines forward
14824 (@value{GDBP}) @b{trace my_function} // first source line of function
14826 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14828 (@value{GDBP}) @b{trace *0x2117c4} // an address
14832 You can abbreviate @code{trace} as @code{tr}.
14834 @item trace @var{locspec} if @var{cond}
14835 Set a tracepoint with condition @var{cond}; evaluate the expression
14836 @var{cond} each time the tracepoint is reached, and collect data only
14837 if the value is nonzero---that is, if @var{cond} evaluates as true.
14838 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14839 information on tracepoint conditions.
14841 @item ftrace @var{locspec} [ if @var{cond} ]
14842 @cindex set fast tracepoint
14843 @cindex fast tracepoints, setting
14845 The @code{ftrace} command sets a fast tracepoint. For targets that
14846 support them, fast tracepoints will use a more efficient but possibly
14847 less general technique to trigger data collection, such as a jump
14848 instruction instead of a trap, or some sort of hardware support. It
14849 may not be possible to create a fast tracepoint at the desired
14850 location, in which case the command will exit with an explanatory
14853 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14856 On 32-bit x86-architecture systems, fast tracepoints normally need to
14857 be placed at an instruction that is 5 bytes or longer, but can be
14858 placed at 4-byte instructions if the low 64K of memory of the target
14859 program is available to install trampolines. Some Unix-type systems,
14860 such as @sc{gnu}/Linux, exclude low addresses from the program's
14861 address space; but for instance with the Linux kernel it is possible
14862 to let @value{GDBN} use this area by doing a @command{sysctl} command
14863 to set the @code{mmap_min_addr} kernel parameter, as in
14866 sudo sysctl -w vm.mmap_min_addr=32768
14870 which sets the low address to 32K, which leaves plenty of room for
14871 trampolines. The minimum address should be set to a page boundary.
14873 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
14874 @cindex set static tracepoint
14875 @cindex static tracepoints, setting
14876 @cindex probe static tracepoint marker
14878 The @code{strace} command sets a static tracepoint. For targets that
14879 support it, setting a static tracepoint probes a static
14880 instrumentation point, or marker, found at the code locations that
14881 result from resolving @var{locspec}. It may not be possible to set a
14882 static tracepoint at the desired code location, in which case the
14883 command will exit with an explanatory message.
14885 @value{GDBN} handles arguments to @code{strace} exactly as for
14886 @code{trace}, with the addition that the user can also specify
14887 @code{-m @var{marker}} instead of a location spec. This probes the marker
14888 identified by the @var{marker} string identifier. This identifier
14889 depends on the static tracepoint backend library your program is
14890 using. You can find all the marker identifiers in the @samp{ID} field
14891 of the @code{info static-tracepoint-markers} command output.
14892 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14893 Markers}. For example, in the following small program using the UST
14899 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14904 the marker id is composed of joining the first two arguments to the
14905 @code{trace_mark} call with a slash, which translates to:
14908 (@value{GDBP}) info static-tracepoint-markers
14909 Cnt Enb ID Address What
14910 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14916 so you may probe the marker above with:
14919 (@value{GDBP}) strace -m ust/bar33
14922 Static tracepoints accept an extra collect action --- @code{collect
14923 $_sdata}. This collects arbitrary user data passed in the probe point
14924 call to the tracing library. In the UST example above, you'll see
14925 that the third argument to @code{trace_mark} is a printf-like format
14926 string. The user data is then the result of running that formatting
14927 string against the following arguments. Note that @code{info
14928 static-tracepoint-markers} command output lists that format string in
14929 the @samp{Data:} field.
14931 You can inspect this data when analyzing the trace buffer, by printing
14932 the $_sdata variable like any other variable available to
14933 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14936 @cindex last tracepoint number
14937 @cindex recent tracepoint number
14938 @cindex tracepoint number
14939 The convenience variable @code{$tpnum} records the tracepoint number
14940 of the most recently set tracepoint.
14942 @kindex delete tracepoint
14943 @cindex tracepoint deletion
14944 @item delete tracepoint @r{[}@var{num}@r{]}
14945 Permanently delete one or more tracepoints. With no argument, the
14946 default is to delete all tracepoints. Note that the regular
14947 @code{delete} command can remove tracepoints also.
14952 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14954 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14958 You can abbreviate this command as @code{del tr}.
14961 @node Enable and Disable Tracepoints
14962 @subsection Enable and Disable Tracepoints
14964 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14967 @kindex disable tracepoint
14968 @item disable tracepoint @r{[}@var{num}@r{]}
14969 Disable tracepoint @var{num}, or all tracepoints if no argument
14970 @var{num} is given. A disabled tracepoint will have no effect during
14971 a trace experiment, but it is not forgotten. You can re-enable
14972 a disabled tracepoint using the @code{enable tracepoint} command.
14973 If the command is issued during a trace experiment and the debug target
14974 has support for disabling tracepoints during a trace experiment, then the
14975 change will be effective immediately. Otherwise, it will be applied to the
14976 next trace experiment.
14978 @kindex enable tracepoint
14979 @item enable tracepoint @r{[}@var{num}@r{]}
14980 Enable tracepoint @var{num}, or all tracepoints. If this command is
14981 issued during a trace experiment and the debug target supports enabling
14982 tracepoints during a trace experiment, then the enabled tracepoints will
14983 become effective immediately. Otherwise, they will become effective the
14984 next time a trace experiment is run.
14987 @node Tracepoint Passcounts
14988 @subsection Tracepoint Passcounts
14992 @cindex tracepoint pass count
14993 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14994 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14995 automatically stop a trace experiment. If a tracepoint's passcount is
14996 @var{n}, then the trace experiment will be automatically stopped on
14997 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14998 @var{num} is not specified, the @code{passcount} command sets the
14999 passcount of the most recently defined tracepoint. If no passcount is
15000 given, the trace experiment will run until stopped explicitly by the
15006 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
15007 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
15009 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
15010 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
15011 (@value{GDBP}) @b{trace foo}
15012 (@value{GDBP}) @b{pass 3}
15013 (@value{GDBP}) @b{trace bar}
15014 (@value{GDBP}) @b{pass 2}
15015 (@value{GDBP}) @b{trace baz}
15016 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
15017 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
15018 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
15019 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
15023 @node Tracepoint Conditions
15024 @subsection Tracepoint Conditions
15025 @cindex conditional tracepoints
15026 @cindex tracepoint conditions
15028 The simplest sort of tracepoint collects data every time your program
15029 reaches a specified place. You can also specify a @dfn{condition} for
15030 a tracepoint. A condition is just a Boolean expression in your
15031 programming language (@pxref{Expressions, ,Expressions}). A
15032 tracepoint with a condition evaluates the expression each time your
15033 program reaches it, and data collection happens only if the condition
15036 Tracepoint conditions can be specified when a tracepoint is set, by
15037 using @samp{if} in the arguments to the @code{trace} command.
15038 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
15039 also be set or changed at any time with the @code{condition} command,
15040 just as with breakpoints.
15042 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
15043 the conditional expression itself. Instead, @value{GDBN} encodes the
15044 expression into an agent expression (@pxref{Agent Expressions})
15045 suitable for execution on the target, independently of @value{GDBN}.
15046 Global variables become raw memory locations, locals become stack
15047 accesses, and so forth.
15049 For instance, suppose you have a function that is usually called
15050 frequently, but should not be called after an error has occurred. You
15051 could use the following tracepoint command to collect data about calls
15052 of that function that happen while the error code is propagating
15053 through the program; an unconditional tracepoint could end up
15054 collecting thousands of useless trace frames that you would have to
15058 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
15061 @node Trace State Variables
15062 @subsection Trace State Variables
15063 @cindex trace state variables
15065 A @dfn{trace state variable} is a special type of variable that is
15066 created and managed by target-side code. The syntax is the same as
15067 that for GDB's convenience variables (a string prefixed with ``$''),
15068 but they are stored on the target. They must be created explicitly,
15069 using a @code{tvariable} command. They are always 64-bit signed
15072 Trace state variables are remembered by @value{GDBN}, and downloaded
15073 to the target along with tracepoint information when the trace
15074 experiment starts. There are no intrinsic limits on the number of
15075 trace state variables, beyond memory limitations of the target.
15077 @cindex convenience variables, and trace state variables
15078 Although trace state variables are managed by the target, you can use
15079 them in print commands and expressions as if they were convenience
15080 variables; @value{GDBN} will get the current value from the target
15081 while the trace experiment is running. Trace state variables share
15082 the same namespace as other ``$'' variables, which means that you
15083 cannot have trace state variables with names like @code{$23} or
15084 @code{$pc}, nor can you have a trace state variable and a convenience
15085 variable with the same name.
15089 @item tvariable $@var{name} [ = @var{expression} ]
15091 The @code{tvariable} command creates a new trace state variable named
15092 @code{$@var{name}}, and optionally gives it an initial value of
15093 @var{expression}. The @var{expression} is evaluated when this command is
15094 entered; the result will be converted to an integer if possible,
15095 otherwise @value{GDBN} will report an error. A subsequent
15096 @code{tvariable} command specifying the same name does not create a
15097 variable, but instead assigns the supplied initial value to the
15098 existing variable of that name, overwriting any previous initial
15099 value. The default initial value is 0.
15101 @item info tvariables
15102 @kindex info tvariables
15103 List all the trace state variables along with their initial values.
15104 Their current values may also be displayed, if the trace experiment is
15107 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
15108 @kindex delete tvariable
15109 Delete the given trace state variables, or all of them if no arguments
15114 @node Tracepoint Actions
15115 @subsection Tracepoint Action Lists
15119 @cindex tracepoint actions
15120 @item actions @r{[}@var{num}@r{]}
15121 This command will prompt for a list of actions to be taken when the
15122 tracepoint is hit. If the tracepoint number @var{num} is not
15123 specified, this command sets the actions for the one that was most
15124 recently defined (so that you can define a tracepoint and then say
15125 @code{actions} without bothering about its number). You specify the
15126 actions themselves on the following lines, one action at a time, and
15127 terminate the actions list with a line containing just @code{end}. So
15128 far, the only defined actions are @code{collect}, @code{teval}, and
15129 @code{while-stepping}.
15131 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
15132 Commands, ,Breakpoint Command Lists}), except that only the defined
15133 actions are allowed; any other @value{GDBN} command is rejected.
15135 @cindex remove actions from a tracepoint
15136 To remove all actions from a tracepoint, type @samp{actions @var{num}}
15137 and follow it immediately with @samp{end}.
15140 (@value{GDBP}) @b{collect @var{data}} // collect some data
15142 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
15144 (@value{GDBP}) @b{end} // signals the end of actions.
15147 In the following example, the action list begins with @code{collect}
15148 commands indicating the things to be collected when the tracepoint is
15149 hit. Then, in order to single-step and collect additional data
15150 following the tracepoint, a @code{while-stepping} command is used,
15151 followed by the list of things to be collected after each step in a
15152 sequence of single steps. The @code{while-stepping} command is
15153 terminated by its own separate @code{end} command. Lastly, the action
15154 list is terminated by an @code{end} command.
15157 (@value{GDBP}) @b{trace foo}
15158 (@value{GDBP}) @b{actions}
15159 Enter actions for tracepoint 1, one per line:
15162 > while-stepping 12
15163 > collect $pc, arr[i]
15168 @kindex collect @r{(tracepoints)}
15169 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15170 Collect values of the given expressions when the tracepoint is hit.
15171 This command accepts a comma-separated list of any valid expressions.
15172 In addition to global, static, or local variables, the following
15173 special arguments are supported:
15177 Collect all registers.
15180 Collect all function arguments.
15183 Collect all local variables.
15186 Collect the return address. This is helpful if you want to see more
15189 @emph{Note:} The return address location can not always be reliably
15190 determined up front, and the wrong address / registers may end up
15191 collected instead. On some architectures the reliability is higher
15192 for tracepoints at function entry, while on others it's the opposite.
15193 When this happens, backtracing will stop because the return address is
15194 found unavailable (unless another collect rule happened to match it).
15197 Collects the number of arguments from the static probe at which the
15198 tracepoint is located.
15199 @xref{Static Probe Points}.
15201 @item $_probe_arg@var{n}
15202 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15203 from the static probe at which the tracepoint is located.
15204 @xref{Static Probe Points}.
15207 @vindex $_sdata@r{, collect}
15208 Collect static tracepoint marker specific data. Only available for
15209 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15210 Lists}. On the UST static tracepoints library backend, an
15211 instrumentation point resembles a @code{printf} function call. The
15212 tracing library is able to collect user specified data formatted to a
15213 character string using the format provided by the programmer that
15214 instrumented the program. Other backends have similar mechanisms.
15215 Here's an example of a UST marker call:
15218 const char master_name[] = "$your_name";
15219 trace_mark(channel1, marker1, "hello %s", master_name)
15222 In this case, collecting @code{$_sdata} collects the string
15223 @samp{hello $yourname}. When analyzing the trace buffer, you can
15224 inspect @samp{$_sdata} like any other variable available to
15228 You can give several consecutive @code{collect} commands, each one
15229 with a single argument, or one @code{collect} command with several
15230 arguments separated by commas; the effect is the same.
15232 The optional @var{mods} changes the usual handling of the arguments.
15233 @code{s} requests that pointers to chars be handled as strings, in
15234 particular collecting the contents of the memory being pointed at, up
15235 to the first zero. The upper bound is by default the value of the
15236 @code{print elements} variable; if @code{s} is followed by a decimal
15237 number, that is the upper bound instead. So for instance
15238 @samp{collect/s25 mystr} collects as many as 25 characters at
15241 The command @code{info scope} (@pxref{Symbols, info scope}) is
15242 particularly useful for figuring out what data to collect.
15244 @kindex teval @r{(tracepoints)}
15245 @item teval @var{expr1}, @var{expr2}, @dots{}
15246 Evaluate the given expressions when the tracepoint is hit. This
15247 command accepts a comma-separated list of expressions. The results
15248 are discarded, so this is mainly useful for assigning values to trace
15249 state variables (@pxref{Trace State Variables}) without adding those
15250 values to the trace buffer, as would be the case if the @code{collect}
15253 @kindex while-stepping @r{(tracepoints)}
15254 @item while-stepping @var{n}
15255 Perform @var{n} single-step instruction traces after the tracepoint,
15256 collecting new data after each step. The @code{while-stepping}
15257 command is followed by the list of what to collect while stepping
15258 (followed by its own @code{end} command):
15261 > while-stepping 12
15262 > collect $regs, myglobal
15268 Note that @code{$pc} is not automatically collected by
15269 @code{while-stepping}; you need to explicitly collect that register if
15270 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15273 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15274 @kindex set default-collect
15275 @cindex default collection action
15276 This variable is a list of expressions to collect at each tracepoint
15277 hit. It is effectively an additional @code{collect} action prepended
15278 to every tracepoint action list. The expressions are parsed
15279 individually for each tracepoint, so for instance a variable named
15280 @code{xyz} may be interpreted as a global for one tracepoint, and a
15281 local for another, as appropriate to the tracepoint's location.
15283 @item show default-collect
15284 @kindex show default-collect
15285 Show the list of expressions that are collected by default at each
15290 @node Listing Tracepoints
15291 @subsection Listing Tracepoints
15294 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15295 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15296 @cindex information about tracepoints
15297 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15298 Display information about the tracepoint @var{num}. If you don't
15299 specify a tracepoint number, displays information about all the
15300 tracepoints defined so far. The format is similar to that used for
15301 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15302 command, simply restricting itself to tracepoints.
15304 A tracepoint's listing may include additional information specific to
15309 its passcount as given by the @code{passcount @var{n}} command
15312 the state about installed on target of each location
15316 (@value{GDBP}) @b{info trace}
15317 Num Type Disp Enb Address What
15318 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15320 collect globfoo, $regs
15325 2 tracepoint keep y <MULTIPLE>
15327 2.1 y 0x0804859c in func4 at change-loc.h:35
15328 installed on target
15329 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15330 installed on target
15331 2.3 y <PENDING> set_tracepoint
15332 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15333 not installed on target
15338 This command can be abbreviated @code{info tp}.
15341 @node Listing Static Tracepoint Markers
15342 @subsection Listing Static Tracepoint Markers
15345 @kindex info static-tracepoint-markers
15346 @cindex information about static tracepoint markers
15347 @item info static-tracepoint-markers
15348 Display information about all static tracepoint markers defined in the
15351 For each marker, the following columns are printed:
15355 An incrementing counter, output to help readability. This is not a
15358 The marker ID, as reported by the target.
15359 @item Enabled or Disabled
15360 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15361 that are not enabled.
15363 Where the marker is in your program, as a memory address.
15365 Where the marker is in the source for your program, as a file and line
15366 number. If the debug information included in the program does not
15367 allow @value{GDBN} to locate the source of the marker, this column
15368 will be left blank.
15372 In addition, the following information may be printed for each marker:
15376 User data passed to the tracing library by the marker call. In the
15377 UST backend, this is the format string passed as argument to the
15379 @item Static tracepoints probing the marker
15380 The list of static tracepoints attached to the marker.
15384 (@value{GDBP}) info static-tracepoint-markers
15385 Cnt ID Enb Address What
15386 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15387 Data: number1 %d number2 %d
15388 Probed by static tracepoints: #2
15389 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15395 @node Starting and Stopping Trace Experiments
15396 @subsection Starting and Stopping Trace Experiments
15399 @kindex tstart [ @var{notes} ]
15400 @cindex start a new trace experiment
15401 @cindex collected data discarded
15403 This command starts the trace experiment, and begins collecting data.
15404 It has the side effect of discarding all the data collected in the
15405 trace buffer during the previous trace experiment. If any arguments
15406 are supplied, they are taken as a note and stored with the trace
15407 experiment's state. The notes may be arbitrary text, and are
15408 especially useful with disconnected tracing in a multi-user context;
15409 the notes can explain what the trace is doing, supply user contact
15410 information, and so forth.
15412 @kindex tstop [ @var{notes} ]
15413 @cindex stop a running trace experiment
15415 This command stops the trace experiment. If any arguments are
15416 supplied, they are recorded with the experiment as a note. This is
15417 useful if you are stopping a trace started by someone else, for
15418 instance if the trace is interfering with the system's behavior and
15419 needs to be stopped quickly.
15421 @strong{Note}: a trace experiment and data collection may stop
15422 automatically if any tracepoint's passcount is reached
15423 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15426 @cindex status of trace data collection
15427 @cindex trace experiment, status of
15429 This command displays the status of the current trace data
15433 Here is an example of the commands we described so far:
15436 (@value{GDBP}) @b{trace gdb_c_test}
15437 (@value{GDBP}) @b{actions}
15438 Enter actions for tracepoint #1, one per line.
15439 > collect $regs,$locals,$args
15440 > while-stepping 11
15444 (@value{GDBP}) @b{tstart}
15445 [time passes @dots{}]
15446 (@value{GDBP}) @b{tstop}
15449 @anchor{disconnected tracing}
15450 @cindex disconnected tracing
15451 You can choose to continue running the trace experiment even if
15452 @value{GDBN} disconnects from the target, voluntarily or
15453 involuntarily. For commands such as @code{detach}, the debugger will
15454 ask what you want to do with the trace. But for unexpected
15455 terminations (@value{GDBN} crash, network outage), it would be
15456 unfortunate to lose hard-won trace data, so the variable
15457 @code{disconnected-tracing} lets you decide whether the trace should
15458 continue running without @value{GDBN}.
15461 @item set disconnected-tracing on
15462 @itemx set disconnected-tracing off
15463 @kindex set disconnected-tracing
15464 Choose whether a tracing run should continue to run if @value{GDBN}
15465 has disconnected from the target. Note that @code{detach} or
15466 @code{quit} will ask you directly what to do about a running trace no
15467 matter what this variable's setting, so the variable is mainly useful
15468 for handling unexpected situations, such as loss of the network.
15470 @item show disconnected-tracing
15471 @kindex show disconnected-tracing
15472 Show the current choice for disconnected tracing.
15476 When you reconnect to the target, the trace experiment may or may not
15477 still be running; it might have filled the trace buffer in the
15478 meantime, or stopped for one of the other reasons. If it is running,
15479 it will continue after reconnection.
15481 Upon reconnection, the target will upload information about the
15482 tracepoints in effect. @value{GDBN} will then compare that
15483 information to the set of tracepoints currently defined, and attempt
15484 to match them up, allowing for the possibility that the numbers may
15485 have changed due to creation and deletion in the meantime. If one of
15486 the target's tracepoints does not match any in @value{GDBN}, the
15487 debugger will create a new tracepoint, so that you have a number with
15488 which to specify that tracepoint. This matching-up process is
15489 necessarily heuristic, and it may result in useless tracepoints being
15490 created; you may simply delete them if they are of no use.
15492 @cindex circular trace buffer
15493 If your target agent supports a @dfn{circular trace buffer}, then you
15494 can run a trace experiment indefinitely without filling the trace
15495 buffer; when space runs out, the agent deletes already-collected trace
15496 frames, oldest first, until there is enough room to continue
15497 collecting. This is especially useful if your tracepoints are being
15498 hit too often, and your trace gets terminated prematurely because the
15499 buffer is full. To ask for a circular trace buffer, simply set
15500 @samp{circular-trace-buffer} to on. You can set this at any time,
15501 including during tracing; if the agent can do it, it will change
15502 buffer handling on the fly, otherwise it will not take effect until
15506 @item set circular-trace-buffer on
15507 @itemx set circular-trace-buffer off
15508 @kindex set circular-trace-buffer
15509 Choose whether a tracing run should use a linear or circular buffer
15510 for trace data. A linear buffer will not lose any trace data, but may
15511 fill up prematurely, while a circular buffer will discard old trace
15512 data, but it will have always room for the latest tracepoint hits.
15514 @item show circular-trace-buffer
15515 @kindex show circular-trace-buffer
15516 Show the current choice for the trace buffer. Note that this may not
15517 match the agent's current buffer handling, nor is it guaranteed to
15518 match the setting that might have been in effect during a past run,
15519 for instance if you are looking at frames from a trace file.
15524 @item set trace-buffer-size @var{n}
15525 @itemx set trace-buffer-size unlimited
15526 @kindex set trace-buffer-size
15527 Request that the target use a trace buffer of @var{n} bytes. Not all
15528 targets will honor the request; they may have a compiled-in size for
15529 the trace buffer, or some other limitation. Set to a value of
15530 @code{unlimited} or @code{-1} to let the target use whatever size it
15531 likes. This is also the default.
15533 @item show trace-buffer-size
15534 @kindex show trace-buffer-size
15535 Show the current requested size for the trace buffer. Note that this
15536 will only match the actual size if the target supports size-setting,
15537 and was able to handle the requested size. For instance, if the
15538 target can only change buffer size between runs, this variable will
15539 not reflect the change until the next run starts. Use @code{tstatus}
15540 to get a report of the actual buffer size.
15544 @item set trace-user @var{text}
15545 @kindex set trace-user
15547 @item show trace-user
15548 @kindex show trace-user
15550 @item set trace-notes @var{text}
15551 @kindex set trace-notes
15552 Set the trace run's notes.
15554 @item show trace-notes
15555 @kindex show trace-notes
15556 Show the trace run's notes.
15558 @item set trace-stop-notes @var{text}
15559 @kindex set trace-stop-notes
15560 Set the trace run's stop notes. The handling of the note is as for
15561 @code{tstop} arguments; the set command is convenient way to fix a
15562 stop note that is mistaken or incomplete.
15564 @item show trace-stop-notes
15565 @kindex show trace-stop-notes
15566 Show the trace run's stop notes.
15570 @node Tracepoint Restrictions
15571 @subsection Tracepoint Restrictions
15573 @cindex tracepoint restrictions
15574 There are a number of restrictions on the use of tracepoints. As
15575 described above, tracepoint data gathering occurs on the target
15576 without interaction from @value{GDBN}. Thus the full capabilities of
15577 the debugger are not available during data gathering, and then at data
15578 examination time, you will be limited by only having what was
15579 collected. The following items describe some common problems, but it
15580 is not exhaustive, and you may run into additional difficulties not
15586 Tracepoint expressions are intended to gather objects (lvalues). Thus
15587 the full flexibility of GDB's expression evaluator is not available.
15588 You cannot call functions, cast objects to aggregate types, access
15589 convenience variables or modify values (except by assignment to trace
15590 state variables). Some language features may implicitly call
15591 functions (for instance Objective-C fields with accessors), and therefore
15592 cannot be collected either.
15595 Collection of local variables, either individually or in bulk with
15596 @code{$locals} or @code{$args}, during @code{while-stepping} may
15597 behave erratically. The stepping action may enter a new scope (for
15598 instance by stepping into a function), or the location of the variable
15599 may change (for instance it is loaded into a register). The
15600 tracepoint data recorded uses the location information for the
15601 variables that is correct for the tracepoint location. When the
15602 tracepoint is created, it is not possible, in general, to determine
15603 where the steps of a @code{while-stepping} sequence will advance the
15604 program---particularly if a conditional branch is stepped.
15607 Collection of an incompletely-initialized or partially-destroyed object
15608 may result in something that @value{GDBN} cannot display, or displays
15609 in a misleading way.
15612 When @value{GDBN} displays a pointer to character it automatically
15613 dereferences the pointer to also display characters of the string
15614 being pointed to. However, collecting the pointer during tracing does
15615 not automatically collect the string. You need to explicitly
15616 dereference the pointer and provide size information if you want to
15617 collect not only the pointer, but the memory pointed to. For example,
15618 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15622 It is not possible to collect a complete stack backtrace at a
15623 tracepoint. Instead, you may collect the registers and a few hundred
15624 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15625 (adjust to use the name of the actual stack pointer register on your
15626 target architecture, and the amount of stack you wish to capture).
15627 Then the @code{backtrace} command will show a partial backtrace when
15628 using a trace frame. The number of stack frames that can be examined
15629 depends on the sizes of the frames in the collected stack. Note that
15630 if you ask for a block so large that it goes past the bottom of the
15631 stack, the target agent may report an error trying to read from an
15635 If you do not collect registers at a tracepoint, @value{GDBN} can
15636 infer that the value of @code{$pc} must be the same as the address of
15637 the tracepoint and use that when you are looking at a trace frame
15638 for that tracepoint. However, this cannot work if the tracepoint has
15639 multiple locations (for instance if it was set in a function that was
15640 inlined), or if it has a @code{while-stepping} loop. In those cases
15641 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15646 @node Analyze Collected Data
15647 @section Using the Collected Data
15649 After the tracepoint experiment ends, you use @value{GDBN} commands
15650 for examining the trace data. The basic idea is that each tracepoint
15651 collects a trace @dfn{snapshot} every time it is hit and another
15652 snapshot every time it single-steps. All these snapshots are
15653 consecutively numbered from zero and go into a buffer, and you can
15654 examine them later. The way you examine them is to @dfn{focus} on a
15655 specific trace snapshot. When the remote stub is focused on a trace
15656 snapshot, it will respond to all @value{GDBN} requests for memory and
15657 registers by reading from the buffer which belongs to that snapshot,
15658 rather than from @emph{real} memory or registers of the program being
15659 debugged. This means that @strong{all} @value{GDBN} commands
15660 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15661 behave as if we were currently debugging the program state as it was
15662 when the tracepoint occurred. Any requests for data that are not in
15663 the buffer will fail.
15666 * tfind:: How to select a trace snapshot
15667 * tdump:: How to display all data for a snapshot
15668 * save tracepoints:: How to save tracepoints for a future run
15672 @subsection @code{tfind @var{n}}
15675 @cindex select trace snapshot
15676 @cindex find trace snapshot
15677 The basic command for selecting a trace snapshot from the buffer is
15678 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15679 counting from zero. If no argument @var{n} is given, the next
15680 snapshot is selected.
15682 Here are the various forms of using the @code{tfind} command.
15686 Find the first snapshot in the buffer. This is a synonym for
15687 @code{tfind 0} (since 0 is the number of the first snapshot).
15690 Stop debugging trace snapshots, resume @emph{live} debugging.
15693 Same as @samp{tfind none}.
15696 No argument means find the next trace snapshot or find the first
15697 one if no trace snapshot is selected.
15700 Find the previous trace snapshot before the current one. This permits
15701 retracing earlier steps.
15703 @item tfind tracepoint @var{num}
15704 Find the next snapshot associated with tracepoint @var{num}. Search
15705 proceeds forward from the last examined trace snapshot. If no
15706 argument @var{num} is given, it means find the next snapshot collected
15707 for the same tracepoint as the current snapshot.
15709 @item tfind pc @var{addr}
15710 Find the next snapshot associated with the value @var{addr} of the
15711 program counter. Search proceeds forward from the last examined trace
15712 snapshot. If no argument @var{addr} is given, it means find the next
15713 snapshot with the same value of PC as the current snapshot.
15715 @item tfind outside @var{addr1}, @var{addr2}
15716 Find the next snapshot whose PC is outside the given range of
15717 addresses (exclusive).
15719 @item tfind range @var{addr1}, @var{addr2}
15720 Find the next snapshot whose PC is between @var{addr1} and
15721 @var{addr2} (inclusive).
15723 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15724 Find the next snapshot associated with the source line @var{n}. If
15725 the optional argument @var{file} is given, refer to line @var{n} in
15726 that source file. Search proceeds forward from the last examined
15727 trace snapshot. If no argument @var{n} is given, it means find the
15728 next line other than the one currently being examined; thus saying
15729 @code{tfind line} repeatedly can appear to have the same effect as
15730 stepping from line to line in a @emph{live} debugging session.
15733 The default arguments for the @code{tfind} commands are specifically
15734 designed to make it easy to scan through the trace buffer. For
15735 instance, @code{tfind} with no argument selects the next trace
15736 snapshot, and @code{tfind -} with no argument selects the previous
15737 trace snapshot. So, by giving one @code{tfind} command, and then
15738 simply hitting @key{RET} repeatedly you can examine all the trace
15739 snapshots in order. Or, by saying @code{tfind -} and then hitting
15740 @key{RET} repeatedly you can examine the snapshots in reverse order.
15741 The @code{tfind line} command with no argument selects the snapshot
15742 for the next source line executed. The @code{tfind pc} command with
15743 no argument selects the next snapshot with the same program counter
15744 (PC) as the current frame. The @code{tfind tracepoint} command with
15745 no argument selects the next trace snapshot collected by the same
15746 tracepoint as the current one.
15748 In addition to letting you scan through the trace buffer manually,
15749 these commands make it easy to construct @value{GDBN} scripts that
15750 scan through the trace buffer and print out whatever collected data
15751 you are interested in. Thus, if we want to examine the PC, FP, and SP
15752 registers from each trace frame in the buffer, we can say this:
15755 (@value{GDBP}) @b{tfind start}
15756 (@value{GDBP}) @b{while ($trace_frame != -1)}
15757 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15758 $trace_frame, $pc, $sp, $fp
15762 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15763 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15764 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15765 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15766 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15767 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15768 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15769 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15770 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15771 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15772 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15775 Or, if we want to examine the variable @code{X} at each source line in
15779 (@value{GDBP}) @b{tfind start}
15780 (@value{GDBP}) @b{while ($trace_frame != -1)}
15781 > printf "Frame %d, X == %d\n", $trace_frame, X
15791 @subsection @code{tdump}
15793 @cindex dump all data collected at tracepoint
15794 @cindex tracepoint data, display
15796 This command takes no arguments. It prints all the data collected at
15797 the current trace snapshot.
15800 (@value{GDBP}) @b{trace 444}
15801 (@value{GDBP}) @b{actions}
15802 Enter actions for tracepoint #2, one per line:
15803 > collect $regs, $locals, $args, gdb_long_test
15806 (@value{GDBP}) @b{tstart}
15808 (@value{GDBP}) @b{tfind line 444}
15809 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15811 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15813 (@value{GDBP}) @b{tdump}
15814 Data collected at tracepoint 2, trace frame 1:
15815 d0 0xc4aa0085 -995491707
15819 d4 0x71aea3d 119204413
15822 d7 0x380035 3670069
15823 a0 0x19e24a 1696330
15824 a1 0x3000668 50333288
15826 a3 0x322000 3284992
15827 a4 0x3000698 50333336
15828 a5 0x1ad3cc 1758156
15829 fp 0x30bf3c 0x30bf3c
15830 sp 0x30bf34 0x30bf34
15832 pc 0x20b2c8 0x20b2c8
15836 p = 0x20e5b4 "gdb-test"
15843 gdb_long_test = 17 '\021'
15848 @code{tdump} works by scanning the tracepoint's current collection
15849 actions and printing the value of each expression listed. So
15850 @code{tdump} can fail, if after a run, you change the tracepoint's
15851 actions to mention variables that were not collected during the run.
15853 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15854 uses the collected value of @code{$pc} to distinguish between trace
15855 frames that were collected at the tracepoint hit, and frames that were
15856 collected while stepping. This allows it to correctly choose whether
15857 to display the basic list of collections, or the collections from the
15858 body of the while-stepping loop. However, if @code{$pc} was not collected,
15859 then @code{tdump} will always attempt to dump using the basic collection
15860 list, and may fail if a while-stepping frame does not include all the
15861 same data that is collected at the tracepoint hit.
15862 @c This is getting pretty arcane, example would be good.
15864 @node save tracepoints
15865 @subsection @code{save tracepoints @var{filename}}
15866 @kindex save tracepoints
15867 @kindex save-tracepoints
15868 @cindex save tracepoints for future sessions
15870 This command saves all current tracepoint definitions together with
15871 their actions and passcounts, into a file @file{@var{filename}}
15872 suitable for use in a later debugging session. To read the saved
15873 tracepoint definitions, use the @code{source} command (@pxref{Command
15874 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15875 alias for @w{@code{save tracepoints}}
15877 @node Tracepoint Variables
15878 @section Convenience Variables for Tracepoints
15879 @cindex tracepoint variables
15880 @cindex convenience variables for tracepoints
15883 @vindex $trace_frame
15884 @item (int) $trace_frame
15885 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15886 snapshot is selected.
15888 @vindex $tracepoint
15889 @item (int) $tracepoint
15890 The tracepoint for the current trace snapshot.
15892 @vindex $trace_line
15893 @item (int) $trace_line
15894 The line number for the current trace snapshot.
15896 @vindex $trace_file
15897 @item (char []) $trace_file
15898 The source file for the current trace snapshot.
15900 @vindex $trace_func
15901 @item (char []) $trace_func
15902 The name of the function containing @code{$tracepoint}.
15905 Note: @code{$trace_file} is not suitable for use in @code{printf},
15906 use @code{output} instead.
15908 Here's a simple example of using these convenience variables for
15909 stepping through all the trace snapshots and printing some of their
15910 data. Note that these are not the same as trace state variables,
15911 which are managed by the target.
15914 (@value{GDBP}) @b{tfind start}
15916 (@value{GDBP}) @b{while $trace_frame != -1}
15917 > output $trace_file
15918 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15924 @section Using Trace Files
15925 @cindex trace files
15927 In some situations, the target running a trace experiment may no
15928 longer be available; perhaps it crashed, or the hardware was needed
15929 for a different activity. To handle these cases, you can arrange to
15930 dump the trace data into a file, and later use that file as a source
15931 of trace data, via the @code{target tfile} command.
15936 @item tsave [ -r ] @var{filename}
15937 @itemx tsave [-ctf] @var{dirname}
15938 Save the trace data to @var{filename}. By default, this command
15939 assumes that @var{filename} refers to the host filesystem, so if
15940 necessary @value{GDBN} will copy raw trace data up from the target and
15941 then save it. If the target supports it, you can also supply the
15942 optional argument @code{-r} (``remote'') to direct the target to save
15943 the data directly into @var{filename} in its own filesystem, which may be
15944 more efficient if the trace buffer is very large. (Note, however, that
15945 @code{target tfile} can only read from files accessible to the host.)
15946 By default, this command will save trace frame in tfile format.
15947 You can supply the optional argument @code{-ctf} to save data in CTF
15948 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15949 that can be shared by multiple debugging and tracing tools. Please go to
15950 @indicateurl{http://www.efficios.com/ctf} to get more information.
15952 @kindex target tfile
15956 @item target tfile @var{filename}
15957 @itemx target ctf @var{dirname}
15958 Use the file named @var{filename} or directory named @var{dirname} as
15959 a source of trace data. Commands that examine data work as they do with
15960 a live target, but it is not possible to run any new trace experiments.
15961 @code{tstatus} will report the state of the trace run at the moment
15962 the data was saved, as well as the current trace frame you are examining.
15963 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15967 (@value{GDBP}) target ctf ctf.ctf
15968 (@value{GDBP}) tfind
15969 Found trace frame 0, tracepoint 2
15970 39 ++a; /* set tracepoint 1 here */
15971 (@value{GDBP}) tdump
15972 Data collected at tracepoint 2, trace frame 0:
15976 c = @{"123", "456", "789", "123", "456", "789"@}
15977 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15985 @chapter Debugging Programs That Use Overlays
15988 If your program is too large to fit completely in your target system's
15989 memory, you can sometimes use @dfn{overlays} to work around this
15990 problem. @value{GDBN} provides some support for debugging programs that
15994 * How Overlays Work:: A general explanation of overlays.
15995 * Overlay Commands:: Managing overlays in @value{GDBN}.
15996 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15997 mapped by asking the inferior.
15998 * Overlay Sample Program:: A sample program using overlays.
16001 @node How Overlays Work
16002 @section How Overlays Work
16003 @cindex mapped overlays
16004 @cindex unmapped overlays
16005 @cindex load address, overlay's
16006 @cindex mapped address
16007 @cindex overlay area
16009 Suppose you have a computer whose instruction address space is only 64
16010 kilobytes long, but which has much more memory which can be accessed by
16011 other means: special instructions, segment registers, or memory
16012 management hardware, for example. Suppose further that you want to
16013 adapt a program which is larger than 64 kilobytes to run on this system.
16015 One solution is to identify modules of your program which are relatively
16016 independent, and need not call each other directly; call these modules
16017 @dfn{overlays}. Separate the overlays from the main program, and place
16018 their machine code in the larger memory. Place your main program in
16019 instruction memory, but leave at least enough space there to hold the
16020 largest overlay as well.
16022 Now, to call a function located in an overlay, you must first copy that
16023 overlay's machine code from the large memory into the space set aside
16024 for it in the instruction memory, and then jump to its entry point
16027 @c NB: In the below the mapped area's size is greater or equal to the
16028 @c size of all overlays. This is intentional to remind the developer
16029 @c that overlays don't necessarily need to be the same size.
16033 Data Instruction Larger
16034 Address Space Address Space Address Space
16035 +-----------+ +-----------+ +-----------+
16037 +-----------+ +-----------+ +-----------+<-- overlay 1
16038 | program | | main | .----| overlay 1 | load address
16039 | variables | | program | | +-----------+
16040 | and heap | | | | | |
16041 +-----------+ | | | +-----------+<-- overlay 2
16042 | | +-----------+ | | | load address
16043 +-----------+ | | | .-| overlay 2 |
16045 mapped --->+-----------+ | | +-----------+
16046 address | | | | | |
16047 | overlay | <-' | | |
16048 | area | <---' +-----------+<-- overlay 3
16049 | | <---. | | load address
16050 +-----------+ `--| overlay 3 |
16057 @anchor{A code overlay}A code overlay
16061 The diagram (@pxref{A code overlay}) shows a system with separate data
16062 and instruction address spaces. To map an overlay, the program copies
16063 its code from the larger address space to the instruction address space.
16064 Since the overlays shown here all use the same mapped address, only one
16065 may be mapped at a time. For a system with a single address space for
16066 data and instructions, the diagram would be similar, except that the
16067 program variables and heap would share an address space with the main
16068 program and the overlay area.
16070 An overlay loaded into instruction memory and ready for use is called a
16071 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
16072 instruction memory. An overlay not present (or only partially present)
16073 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
16074 is its address in the larger memory. The mapped address is also called
16075 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
16076 called the @dfn{load memory address}, or @dfn{LMA}.
16078 Unfortunately, overlays are not a completely transparent way to adapt a
16079 program to limited instruction memory. They introduce a new set of
16080 global constraints you must keep in mind as you design your program:
16085 Before calling or returning to a function in an overlay, your program
16086 must make sure that overlay is actually mapped. Otherwise, the call or
16087 return will transfer control to the right address, but in the wrong
16088 overlay, and your program will probably crash.
16091 If the process of mapping an overlay is expensive on your system, you
16092 will need to choose your overlays carefully to minimize their effect on
16093 your program's performance.
16096 The executable file you load onto your system must contain each
16097 overlay's instructions, appearing at the overlay's load address, not its
16098 mapped address. However, each overlay's instructions must be relocated
16099 and its symbols defined as if the overlay were at its mapped address.
16100 You can use GNU linker scripts to specify different load and relocation
16101 addresses for pieces of your program; see @ref{Overlay Description,,,
16102 ld.info, Using ld: the GNU linker}.
16105 The procedure for loading executable files onto your system must be able
16106 to load their contents into the larger address space as well as the
16107 instruction and data spaces.
16111 The overlay system described above is rather simple, and could be
16112 improved in many ways:
16117 If your system has suitable bank switch registers or memory management
16118 hardware, you could use those facilities to make an overlay's load area
16119 contents simply appear at their mapped address in instruction space.
16120 This would probably be faster than copying the overlay to its mapped
16121 area in the usual way.
16124 If your overlays are small enough, you could set aside more than one
16125 overlay area, and have more than one overlay mapped at a time.
16128 You can use overlays to manage data, as well as instructions. In
16129 general, data overlays are even less transparent to your design than
16130 code overlays: whereas code overlays only require care when you call or
16131 return to functions, data overlays require care every time you access
16132 the data. Also, if you change the contents of a data overlay, you
16133 must copy its contents back out to its load address before you can copy a
16134 different data overlay into the same mapped area.
16139 @node Overlay Commands
16140 @section Overlay Commands
16142 To use @value{GDBN}'s overlay support, each overlay in your program must
16143 correspond to a separate section of the executable file. The section's
16144 virtual memory address and load memory address must be the overlay's
16145 mapped and load addresses. Identifying overlays with sections allows
16146 @value{GDBN} to determine the appropriate address of a function or
16147 variable, depending on whether the overlay is mapped or not.
16149 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16150 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16155 Disable @value{GDBN}'s overlay support. When overlay support is
16156 disabled, @value{GDBN} assumes that all functions and variables are
16157 always present at their mapped addresses. By default, @value{GDBN}'s
16158 overlay support is disabled.
16160 @item overlay manual
16161 @cindex manual overlay debugging
16162 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16163 relies on you to tell it which overlays are mapped, and which are not,
16164 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16165 commands described below.
16167 @item overlay map-overlay @var{overlay}
16168 @itemx overlay map @var{overlay}
16169 @cindex map an overlay
16170 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16171 be the name of the object file section containing the overlay. When an
16172 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16173 functions and variables at their mapped addresses. @value{GDBN} assumes
16174 that any other overlays whose mapped ranges overlap that of
16175 @var{overlay} are now unmapped.
16177 @item overlay unmap-overlay @var{overlay}
16178 @itemx overlay unmap @var{overlay}
16179 @cindex unmap an overlay
16180 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16181 must be the name of the object file section containing the overlay.
16182 When an overlay is unmapped, @value{GDBN} assumes it can find the
16183 overlay's functions and variables at their load addresses.
16186 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16187 consults a data structure the overlay manager maintains in the inferior
16188 to see which overlays are mapped. For details, see @ref{Automatic
16189 Overlay Debugging}.
16191 @item overlay load-target
16192 @itemx overlay load
16193 @cindex reloading the overlay table
16194 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16195 re-reads the table @value{GDBN} automatically each time the inferior
16196 stops, so this command should only be necessary if you have changed the
16197 overlay mapping yourself using @value{GDBN}. This command is only
16198 useful when using automatic overlay debugging.
16200 @item overlay list-overlays
16201 @itemx overlay list
16202 @cindex listing mapped overlays
16203 Display a list of the overlays currently mapped, along with their mapped
16204 addresses, load addresses, and sizes.
16208 Normally, when @value{GDBN} prints a code address, it includes the name
16209 of the function the address falls in:
16212 (@value{GDBP}) print main
16213 $3 = @{int ()@} 0x11a0 <main>
16216 When overlay debugging is enabled, @value{GDBN} recognizes code in
16217 unmapped overlays, and prints the names of unmapped functions with
16218 asterisks around them. For example, if @code{foo} is a function in an
16219 unmapped overlay, @value{GDBN} prints it this way:
16222 (@value{GDBP}) overlay list
16223 No sections are mapped.
16224 (@value{GDBP}) print foo
16225 $5 = @{int (int)@} 0x100000 <*foo*>
16228 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16232 (@value{GDBP}) overlay list
16233 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16234 mapped at 0x1016 - 0x104a
16235 (@value{GDBP}) print foo
16236 $6 = @{int (int)@} 0x1016 <foo>
16239 When overlay debugging is enabled, @value{GDBN} can find the correct
16240 address for functions and variables in an overlay, whether or not the
16241 overlay is mapped. This allows most @value{GDBN} commands, like
16242 @code{break} and @code{disassemble}, to work normally, even on unmapped
16243 code. However, @value{GDBN}'s breakpoint support has some limitations:
16247 @cindex breakpoints in overlays
16248 @cindex overlays, setting breakpoints in
16249 You can set breakpoints in functions in unmapped overlays, as long as
16250 @value{GDBN} can write to the overlay at its load address.
16252 @value{GDBN} can not set hardware or simulator-based breakpoints in
16253 unmapped overlays. However, if you set a breakpoint at the end of your
16254 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16255 you are using manual overlay management), @value{GDBN} will re-set its
16256 breakpoints properly.
16260 @node Automatic Overlay Debugging
16261 @section Automatic Overlay Debugging
16262 @cindex automatic overlay debugging
16264 @value{GDBN} can automatically track which overlays are mapped and which
16265 are not, given some simple co-operation from the overlay manager in the
16266 inferior. If you enable automatic overlay debugging with the
16267 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16268 looks in the inferior's memory for certain variables describing the
16269 current state of the overlays.
16271 Here are the variables your overlay manager must define to support
16272 @value{GDBN}'s automatic overlay debugging:
16276 @item @code{_ovly_table}:
16277 This variable must be an array of the following structures:
16282 /* The overlay's mapped address. */
16285 /* The size of the overlay, in bytes. */
16286 unsigned long size;
16288 /* The overlay's load address. */
16291 /* Non-zero if the overlay is currently mapped;
16293 unsigned long mapped;
16297 @item @code{_novlys}:
16298 This variable must be a four-byte signed integer, holding the total
16299 number of elements in @code{_ovly_table}.
16303 To decide whether a particular overlay is mapped or not, @value{GDBN}
16304 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16305 @code{lma} members equal the VMA and LMA of the overlay's section in the
16306 executable file. When @value{GDBN} finds a matching entry, it consults
16307 the entry's @code{mapped} member to determine whether the overlay is
16310 In addition, your overlay manager may define a function called
16311 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16312 will silently set a breakpoint there. If the overlay manager then
16313 calls this function whenever it has changed the overlay table, this
16314 will enable @value{GDBN} to accurately keep track of which overlays
16315 are in program memory, and update any breakpoints that may be set
16316 in overlays. This will allow breakpoints to work even if the
16317 overlays are kept in ROM or other non-writable memory while they
16318 are not being executed.
16320 @node Overlay Sample Program
16321 @section Overlay Sample Program
16322 @cindex overlay example program
16324 When linking a program which uses overlays, you must place the overlays
16325 at their load addresses, while relocating them to run at their mapped
16326 addresses. To do this, you must write a linker script (@pxref{Overlay
16327 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16328 since linker scripts are specific to a particular host system, target
16329 architecture, and target memory layout, this manual cannot provide
16330 portable sample code demonstrating @value{GDBN}'s overlay support.
16332 However, the @value{GDBN} source distribution does contain an overlaid
16333 program, with linker scripts for a few systems, as part of its test
16334 suite. The program consists of the following files from
16335 @file{gdb/testsuite/gdb.base}:
16339 The main program file.
16341 A simple overlay manager, used by @file{overlays.c}.
16346 Overlay modules, loaded and used by @file{overlays.c}.
16349 Linker scripts for linking the test program on the @code{d10v-elf}
16350 and @code{m32r-elf} targets.
16353 You can build the test program using the @code{d10v-elf} GCC
16354 cross-compiler like this:
16357 $ d10v-elf-gcc -g -c overlays.c
16358 $ d10v-elf-gcc -g -c ovlymgr.c
16359 $ d10v-elf-gcc -g -c foo.c
16360 $ d10v-elf-gcc -g -c bar.c
16361 $ d10v-elf-gcc -g -c baz.c
16362 $ d10v-elf-gcc -g -c grbx.c
16363 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16364 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16367 The build process is identical for any other architecture, except that
16368 you must substitute the appropriate compiler and linker script for the
16369 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16373 @chapter Using @value{GDBN} with Different Languages
16376 Although programming languages generally have common aspects, they are
16377 rarely expressed in the same manner. For instance, in ANSI C,
16378 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16379 Modula-2, it is accomplished by @code{p^}. Values can also be
16380 represented (and displayed) differently. Hex numbers in C appear as
16381 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16383 @cindex working language
16384 Language-specific information is built into @value{GDBN} for some languages,
16385 allowing you to express operations like the above in your program's
16386 native language, and allowing @value{GDBN} to output values in a manner
16387 consistent with the syntax of your program's native language. The
16388 language you use to build expressions is called the @dfn{working
16392 * Setting:: Switching between source languages
16393 * Show:: Displaying the language
16394 * Checks:: Type and range checks
16395 * Supported Languages:: Supported languages
16396 * Unsupported Languages:: Unsupported languages
16400 @section Switching Between Source Languages
16402 There are two ways to control the working language---either have @value{GDBN}
16403 set it automatically, or select it manually yourself. You can use the
16404 @code{set language} command for either purpose. On startup, @value{GDBN}
16405 defaults to setting the language automatically. The working language is
16406 used to determine how expressions you type are interpreted, how values
16409 In addition to the working language, every source file that
16410 @value{GDBN} knows about has its own working language. For some object
16411 file formats, the compiler might indicate which language a particular
16412 source file is in. However, most of the time @value{GDBN} infers the
16413 language from the name of the file. The language of a source file
16414 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16415 show each frame appropriately for its own language. There is no way to
16416 set the language of a source file from within @value{GDBN}, but you can
16417 set the language associated with a filename extension. @xref{Show, ,
16418 Displaying the Language}.
16420 This is most commonly a problem when you use a program, such
16421 as @code{cfront} or @code{f2c}, that generates C but is written in
16422 another language. In that case, make the
16423 program use @code{#line} directives in its C output; that way
16424 @value{GDBN} will know the correct language of the source code of the original
16425 program, and will display that source code, not the generated C code.
16428 * Filenames:: Filename extensions and languages.
16429 * Manually:: Setting the working language manually
16430 * Automatically:: Having @value{GDBN} infer the source language
16434 @subsection List of Filename Extensions and Languages
16436 If a source file name ends in one of the following extensions, then
16437 @value{GDBN} infers that its language is the one indicated.
16455 C@t{++} source file
16461 Objective-C source file
16465 Fortran source file
16468 Modula-2 source file
16472 Assembler source file. This actually behaves almost like C, but
16473 @value{GDBN} does not skip over function prologues when stepping.
16476 In addition, you may set the language associated with a filename
16477 extension. @xref{Show, , Displaying the Language}.
16480 @subsection Setting the Working Language
16482 If you allow @value{GDBN} to set the language automatically,
16483 expressions are interpreted the same way in your debugging session and
16486 @kindex set language
16487 If you wish, you may set the language manually. To do this, issue the
16488 command @samp{set language @var{lang}}, where @var{lang} is the name of
16489 a language, such as
16490 @code{c} or @code{modula-2}.
16491 For a list of the supported languages, type @samp{set language}.
16493 Setting the language manually prevents @value{GDBN} from updating the working
16494 language automatically. This can lead to confusion if you try
16495 to debug a program when the working language is not the same as the
16496 source language, when an expression is acceptable to both
16497 languages---but means different things. For instance, if the current
16498 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16506 might not have the effect you intended. In C, this means to add
16507 @code{b} and @code{c} and place the result in @code{a}. The result
16508 printed would be the value of @code{a}. In Modula-2, this means to compare
16509 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16511 @node Automatically
16512 @subsection Having @value{GDBN} Infer the Source Language
16514 To have @value{GDBN} set the working language automatically, use
16515 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16516 then infers the working language. That is, when your program stops in a
16517 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16518 working language to the language recorded for the function in that
16519 frame. If the language for a frame is unknown (that is, if the function
16520 or block corresponding to the frame was defined in a source file that
16521 does not have a recognized extension), the current working language is
16522 not changed, and @value{GDBN} issues a warning.
16524 This may not seem necessary for most programs, which are written
16525 entirely in one source language. However, program modules and libraries
16526 written in one source language can be used by a main program written in
16527 a different source language. Using @samp{set language auto} in this
16528 case frees you from having to set the working language manually.
16531 @section Displaying the Language
16533 The following commands help you find out which language is the
16534 working language, and also what language source files were written in.
16537 @item show language
16538 @anchor{show language}
16539 @kindex show language
16540 Display the current working language. This is the
16541 language you can use with commands such as @code{print} to
16542 build and compute expressions that may involve variables in your program.
16545 @kindex info frame@r{, show the source language}
16546 Display the source language for this frame. This language becomes the
16547 working language if you use an identifier from this frame.
16548 @xref{Frame Info, ,Information about a Frame}, to identify the other
16549 information listed here.
16552 @kindex info source@r{, show the source language}
16553 Display the source language of this source file.
16554 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16555 information listed here.
16558 In unusual circumstances, you may have source files with extensions
16559 not in the standard list. You can then set the extension associated
16560 with a language explicitly:
16563 @item set extension-language @var{ext} @var{language}
16564 @kindex set extension-language
16565 Tell @value{GDBN} that source files with extension @var{ext} are to be
16566 assumed as written in the source language @var{language}.
16568 @item info extensions
16569 @kindex info extensions
16570 List all the filename extensions and the associated languages.
16574 @section Type and Range Checking
16576 Some languages are designed to guard you against making seemingly common
16577 errors through a series of compile- and run-time checks. These include
16578 checking the type of arguments to functions and operators and making
16579 sure mathematical overflows are caught at run time. Checks such as
16580 these help to ensure a program's correctness once it has been compiled
16581 by eliminating type mismatches and providing active checks for range
16582 errors when your program is running.
16584 By default @value{GDBN} checks for these errors according to the
16585 rules of the current source language. Although @value{GDBN} does not check
16586 the statements in your program, it can check expressions entered directly
16587 into @value{GDBN} for evaluation via the @code{print} command, for example.
16590 * Type Checking:: An overview of type checking
16591 * Range Checking:: An overview of range checking
16594 @cindex type checking
16595 @cindex checks, type
16596 @node Type Checking
16597 @subsection An Overview of Type Checking
16599 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16600 arguments to operators and functions have to be of the correct type,
16601 otherwise an error occurs. These checks prevent type mismatch
16602 errors from ever causing any run-time problems. For example,
16605 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16607 (@value{GDBP}) print obj.my_method (0)
16610 (@value{GDBP}) print obj.my_method (0x1234)
16611 Cannot resolve method klass::my_method to any overloaded instance
16614 The second example fails because in C@t{++} the integer constant
16615 @samp{0x1234} is not type-compatible with the pointer parameter type.
16617 For the expressions you use in @value{GDBN} commands, you can tell
16618 @value{GDBN} to not enforce strict type checking or
16619 to treat any mismatches as errors and abandon the expression;
16620 When type checking is disabled, @value{GDBN} successfully evaluates
16621 expressions like the second example above.
16623 Even if type checking is off, there may be other reasons
16624 related to type that prevent @value{GDBN} from evaluating an expression.
16625 For instance, @value{GDBN} does not know how to add an @code{int} and
16626 a @code{struct foo}. These particular type errors have nothing to do
16627 with the language in use and usually arise from expressions which make
16628 little sense to evaluate anyway.
16630 @value{GDBN} provides some additional commands for controlling type checking:
16632 @kindex set check type
16633 @kindex show check type
16635 @item set check type on
16636 @itemx set check type off
16637 Set strict type checking on or off. If any type mismatches occur in
16638 evaluating an expression while type checking is on, @value{GDBN} prints a
16639 message and aborts evaluation of the expression.
16641 @item show check type
16642 Show the current setting of type checking and whether @value{GDBN}
16643 is enforcing strict type checking rules.
16646 @cindex range checking
16647 @cindex checks, range
16648 @node Range Checking
16649 @subsection An Overview of Range Checking
16651 In some languages (such as Modula-2), it is an error to exceed the
16652 bounds of a type; this is enforced with run-time checks. Such range
16653 checking is meant to ensure program correctness by making sure
16654 computations do not overflow, or indices on an array element access do
16655 not exceed the bounds of the array.
16657 For expressions you use in @value{GDBN} commands, you can tell
16658 @value{GDBN} to treat range errors in one of three ways: ignore them,
16659 always treat them as errors and abandon the expression, or issue
16660 warnings but evaluate the expression anyway.
16662 A range error can result from numerical overflow, from exceeding an
16663 array index bound, or when you type a constant that is not a member
16664 of any type. Some languages, however, do not treat overflows as an
16665 error. In many implementations of C, mathematical overflow causes the
16666 result to ``wrap around'' to lower values---for example, if @var{m} is
16667 the largest integer value, and @var{s} is the smallest, then
16670 @var{m} + 1 @result{} @var{s}
16673 This, too, is specific to individual languages, and in some cases
16674 specific to individual compilers or machines. @xref{Supported Languages, ,
16675 Supported Languages}, for further details on specific languages.
16677 @value{GDBN} provides some additional commands for controlling the range checker:
16679 @kindex set check range
16680 @kindex show check range
16682 @item set check range auto
16683 Set range checking on or off based on the current working language.
16684 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16687 @item set check range on
16688 @itemx set check range off
16689 Set range checking on or off, overriding the default setting for the
16690 current working language. A warning is issued if the setting does not
16691 match the language default. If a range error occurs and range checking is on,
16692 then a message is printed and evaluation of the expression is aborted.
16694 @item set check range warn
16695 Output messages when the @value{GDBN} range checker detects a range error,
16696 but attempt to evaluate the expression anyway. Evaluating the
16697 expression may still be impossible for other reasons, such as accessing
16698 memory that the process does not own (a typical example from many Unix
16701 @item show check range
16702 Show the current setting of the range checker, and whether or not it is
16703 being set automatically by @value{GDBN}.
16706 @node Supported Languages
16707 @section Supported Languages
16709 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16710 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16711 @c This is false ...
16712 Some @value{GDBN} features may be used in expressions regardless of the
16713 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16714 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16715 ,Expressions}) can be used with the constructs of any supported
16718 The following sections detail to what degree each source language is
16719 supported by @value{GDBN}. These sections are not meant to be language
16720 tutorials or references, but serve only as a reference guide to what the
16721 @value{GDBN} expression parser accepts, and what input and output
16722 formats should look like for different languages. There are many good
16723 books written on each of these languages; please look to these for a
16724 language reference or tutorial.
16727 * C:: C and C@t{++}
16730 * Objective-C:: Objective-C
16731 * OpenCL C:: OpenCL C
16732 * Fortran:: Fortran
16735 * Modula-2:: Modula-2
16740 @subsection C and C@t{++}
16742 @cindex C and C@t{++}
16743 @cindex expressions in C or C@t{++}
16745 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16746 to both languages. Whenever this is the case, we discuss those languages
16750 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16751 @cindex @sc{gnu} C@t{++}
16752 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16753 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16754 effectively, you must compile your C@t{++} programs with a supported
16755 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16756 compiler (@code{aCC}).
16759 * C Operators:: C and C@t{++} operators
16760 * C Constants:: C and C@t{++} constants
16761 * C Plus Plus Expressions:: C@t{++} expressions
16762 * C Defaults:: Default settings for C and C@t{++}
16763 * C Checks:: C and C@t{++} type and range checks
16764 * Debugging C:: @value{GDBN} and C
16765 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16766 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16770 @subsubsection C and C@t{++} Operators
16772 @cindex C and C@t{++} operators
16774 Operators must be defined on values of specific types. For instance,
16775 @code{+} is defined on numbers, but not on structures. Operators are
16776 often defined on groups of types.
16778 For the purposes of C and C@t{++}, the following definitions hold:
16783 @emph{Integral types} include @code{int} with any of its storage-class
16784 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16787 @emph{Floating-point types} include @code{float}, @code{double}, and
16788 @code{long double} (if supported by the target platform).
16791 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16794 @emph{Scalar types} include all of the above.
16799 The following operators are supported. They are listed here
16800 in order of increasing precedence:
16804 The comma or sequencing operator. Expressions in a comma-separated list
16805 are evaluated from left to right, with the result of the entire
16806 expression being the last expression evaluated.
16809 Assignment. The value of an assignment expression is the value
16810 assigned. Defined on scalar types.
16813 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16814 and translated to @w{@code{@var{a} = @var{a op b}}}.
16815 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16816 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16817 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16820 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16821 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16822 should be of an integral type.
16825 Logical @sc{or}. Defined on integral types.
16828 Logical @sc{and}. Defined on integral types.
16831 Bitwise @sc{or}. Defined on integral types.
16834 Bitwise exclusive-@sc{or}. Defined on integral types.
16837 Bitwise @sc{and}. Defined on integral types.
16840 Equality and inequality. Defined on scalar types. The value of these
16841 expressions is 0 for false and non-zero for true.
16843 @item <@r{, }>@r{, }<=@r{, }>=
16844 Less than, greater than, less than or equal, greater than or equal.
16845 Defined on scalar types. The value of these expressions is 0 for false
16846 and non-zero for true.
16849 left shift, and right shift. Defined on integral types.
16852 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16855 Addition and subtraction. Defined on integral types, floating-point types and
16858 @item *@r{, }/@r{, }%
16859 Multiplication, division, and modulus. Multiplication and division are
16860 defined on integral and floating-point types. Modulus is defined on
16864 Increment and decrement. When appearing before a variable, the
16865 operation is performed before the variable is used in an expression;
16866 when appearing after it, the variable's value is used before the
16867 operation takes place.
16870 Pointer dereferencing. Defined on pointer types. Same precedence as
16874 Address operator. Defined on variables. Same precedence as @code{++}.
16876 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16877 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16878 to examine the address
16879 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16883 Negative. Defined on integral and floating-point types. Same
16884 precedence as @code{++}.
16887 Logical negation. Defined on integral types. Same precedence as
16891 Bitwise complement operator. Defined on integral types. Same precedence as
16896 Structure member, and pointer-to-structure member. For convenience,
16897 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16898 pointer based on the stored type information.
16899 Defined on @code{struct} and @code{union} data.
16902 Dereferences of pointers to members.
16905 Array indexing. @code{@var{a}[@var{i}]} is defined as
16906 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16909 Function parameter list. Same precedence as @code{->}.
16912 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16913 and @code{class} types.
16916 Doubled colons also represent the @value{GDBN} scope operator
16917 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16921 If an operator is redefined in the user code, @value{GDBN} usually
16922 attempts to invoke the redefined version instead of using the operator's
16923 predefined meaning.
16926 @subsubsection C and C@t{++} Constants
16928 @cindex C and C@t{++} constants
16930 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16935 Integer constants are a sequence of digits. Octal constants are
16936 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16937 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16938 @samp{l}, specifying that the constant should be treated as a
16942 Floating point constants are a sequence of digits, followed by a decimal
16943 point, followed by a sequence of digits, and optionally followed by an
16944 exponent. An exponent is of the form:
16945 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16946 sequence of digits. The @samp{+} is optional for positive exponents.
16947 A floating-point constant may also end with a letter @samp{f} or
16948 @samp{F}, specifying that the constant should be treated as being of
16949 the @code{float} (as opposed to the default @code{double}) type; or with
16950 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16954 Enumerated constants consist of enumerated identifiers, or their
16955 integral equivalents.
16958 Character constants are a single character surrounded by single quotes
16959 (@code{'}), or a number---the ordinal value of the corresponding character
16960 (usually its @sc{ascii} value). Within quotes, the single character may
16961 be represented by a letter or by @dfn{escape sequences}, which are of
16962 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16963 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16964 @samp{@var{x}} is a predefined special character---for example,
16965 @samp{\n} for newline.
16967 Wide character constants can be written by prefixing a character
16968 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16969 form of @samp{x}. The target wide character set is used when
16970 computing the value of this constant (@pxref{Character Sets}).
16973 String constants are a sequence of character constants surrounded by
16974 double quotes (@code{"}). Any valid character constant (as described
16975 above) may appear. Double quotes within the string must be preceded by
16976 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16979 Wide string constants can be written by prefixing a string constant
16980 with @samp{L}, as in C. The target wide character set is used when
16981 computing the value of this constant (@pxref{Character Sets}).
16984 Pointer constants are an integral value. You can also write pointers
16985 to constants using the C operator @samp{&}.
16988 Array constants are comma-separated lists surrounded by braces @samp{@{}
16989 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16990 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16991 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16994 @node C Plus Plus Expressions
16995 @subsubsection C@t{++} Expressions
16997 @cindex expressions in C@t{++}
16998 @value{GDBN} expression handling can interpret most C@t{++} expressions.
17000 @cindex debugging C@t{++} programs
17001 @cindex C@t{++} compilers
17002 @cindex debug formats and C@t{++}
17003 @cindex @value{NGCC} and C@t{++}
17005 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
17006 the proper compiler and the proper debug format. Currently,
17007 @value{GDBN} works best when debugging C@t{++} code that is compiled
17008 with the most recent version of @value{NGCC} possible. The DWARF
17009 debugging format is preferred; @value{NGCC} defaults to this on most
17010 popular platforms. Other compilers and/or debug formats are likely to
17011 work badly or not at all when using @value{GDBN} to debug C@t{++}
17012 code. @xref{Compilation}.
17017 @cindex member functions
17019 Member function calls are allowed; you can use expressions like
17022 count = aml->GetOriginal(x, y)
17025 @vindex this@r{, inside C@t{++} member functions}
17026 @cindex namespace in C@t{++}
17028 While a member function is active (in the selected stack frame), your
17029 expressions have the same namespace available as the member function;
17030 that is, @value{GDBN} allows implicit references to the class instance
17031 pointer @code{this} following the same rules as C@t{++}. @code{using}
17032 declarations in the current scope are also respected by @value{GDBN}.
17034 @cindex call overloaded functions
17035 @cindex overloaded functions, calling
17036 @cindex type conversions in C@t{++}
17038 You can call overloaded functions; @value{GDBN} resolves the function
17039 call to the right definition, with some restrictions. @value{GDBN} does not
17040 perform overload resolution involving user-defined type conversions,
17041 calls to constructors, or instantiations of templates that do not exist
17042 in the program. It also cannot handle ellipsis argument lists or
17045 It does perform integral conversions and promotions, floating-point
17046 promotions, arithmetic conversions, pointer conversions, conversions of
17047 class objects to base classes, and standard conversions such as those of
17048 functions or arrays to pointers; it requires an exact match on the
17049 number of function arguments.
17051 Overload resolution is always performed, unless you have specified
17052 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
17053 ,@value{GDBN} Features for C@t{++}}.
17055 You must specify @code{set overload-resolution off} in order to use an
17056 explicit function signature to call an overloaded function, as in
17058 p 'foo(char,int)'('x', 13)
17061 The @value{GDBN} command-completion facility can simplify this;
17062 see @ref{Completion, ,Command Completion}.
17064 @cindex reference declarations
17066 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
17067 references; you can use them in expressions just as you do in C@t{++}
17068 source---they are automatically dereferenced.
17070 In the parameter list shown when @value{GDBN} displays a frame, the values of
17071 reference variables are not displayed (unlike other variables); this
17072 avoids clutter, since references are often used for large structures.
17073 The @emph{address} of a reference variable is always shown, unless
17074 you have specified @samp{set print address off}.
17077 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
17078 expressions can use it just as expressions in your program do. Since
17079 one scope may be defined in another, you can use @code{::} repeatedly if
17080 necessary, for example in an expression like
17081 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
17082 resolving name scope by reference to source files, in both C and C@t{++}
17083 debugging (@pxref{Variables, ,Program Variables}).
17086 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
17091 @subsubsection C and C@t{++} Defaults
17093 @cindex C and C@t{++} defaults
17095 If you allow @value{GDBN} to set range checking automatically, it
17096 defaults to @code{off} whenever the working language changes to
17097 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
17098 selects the working language.
17100 If you allow @value{GDBN} to set the language automatically, it
17101 recognizes source files whose names end with @file{.c}, @file{.C}, or
17102 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
17103 these files, it sets the working language to C or C@t{++}.
17104 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
17105 for further details.
17108 @subsubsection C and C@t{++} Type and Range Checks
17110 @cindex C and C@t{++} checks
17112 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
17113 checking is used. However, if you turn type checking off, @value{GDBN}
17114 will allow certain non-standard conversions, such as promoting integer
17115 constants to pointers.
17117 Range checking, if turned on, is done on mathematical operations. Array
17118 indices are not checked, since they are often used to index a pointer
17119 that is not itself an array.
17122 @subsubsection @value{GDBN} and C
17124 The @code{set print union} and @code{show print union} commands apply to
17125 the @code{union} type. When set to @samp{on}, any @code{union} that is
17126 inside a @code{struct} or @code{class} is also printed. Otherwise, it
17127 appears as @samp{@{...@}}.
17129 The @code{@@} operator aids in the debugging of dynamic arrays, formed
17130 with pointers and a memory allocation function. @xref{Expressions,
17133 @node Debugging C Plus Plus
17134 @subsubsection @value{GDBN} Features for C@t{++}
17136 @cindex commands for C@t{++}
17138 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
17139 designed specifically for use with C@t{++}. Here is a summary:
17142 @cindex break in overloaded functions
17143 @item @r{breakpoint menus}
17144 When you want a breakpoint in a function whose name is overloaded,
17145 @value{GDBN} has the capability to display a menu of possible breakpoint
17146 locations to help you specify which function definition you want.
17147 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17149 @cindex overloading in C@t{++}
17150 @item rbreak @var{regex}
17151 Setting breakpoints using regular expressions is helpful for setting
17152 breakpoints on overloaded functions that are not members of any special
17154 @xref{Set Breaks, ,Setting Breakpoints}.
17156 @cindex C@t{++} exception handling
17158 @itemx catch rethrow
17160 Debug C@t{++} exception handling using these commands. @xref{Set
17161 Catchpoints, , Setting Catchpoints}.
17163 @cindex inheritance
17164 @item ptype @var{typename}
17165 Print inheritance relationships as well as other information for type
17167 @xref{Symbols, ,Examining the Symbol Table}.
17169 @item info vtbl @var{expression}.
17170 The @code{info vtbl} command can be used to display the virtual
17171 method tables of the object computed by @var{expression}. This shows
17172 one entry per virtual table; there may be multiple virtual tables when
17173 multiple inheritance is in use.
17175 @cindex C@t{++} demangling
17176 @item demangle @var{name}
17177 Demangle @var{name}.
17178 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17180 @cindex C@t{++} symbol display
17181 @item set print demangle
17182 @itemx show print demangle
17183 @itemx set print asm-demangle
17184 @itemx show print asm-demangle
17185 Control whether C@t{++} symbols display in their source form, both when
17186 displaying code as C@t{++} source and when displaying disassemblies.
17187 @xref{Print Settings, ,Print Settings}.
17189 @item set print object
17190 @itemx show print object
17191 Choose whether to print derived (actual) or declared types of objects.
17192 @xref{Print Settings, ,Print Settings}.
17194 @item set print vtbl
17195 @itemx show print vtbl
17196 Control the format for printing virtual function tables.
17197 @xref{Print Settings, ,Print Settings}.
17198 (The @code{vtbl} commands do not work on programs compiled with the HP
17199 ANSI C@t{++} compiler (@code{aCC}).)
17201 @kindex set overload-resolution
17202 @cindex overloaded functions, overload resolution
17203 @item set overload-resolution on
17204 Enable overload resolution for C@t{++} expression evaluation. The default
17205 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17206 and searches for a function whose signature matches the argument types,
17207 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17208 Expressions, ,C@t{++} Expressions}, for details).
17209 If it cannot find a match, it emits a message.
17211 @item set overload-resolution off
17212 Disable overload resolution for C@t{++} expression evaluation. For
17213 overloaded functions that are not class member functions, @value{GDBN}
17214 chooses the first function of the specified name that it finds in the
17215 symbol table, whether or not its arguments are of the correct type. For
17216 overloaded functions that are class member functions, @value{GDBN}
17217 searches for a function whose signature @emph{exactly} matches the
17220 @kindex show overload-resolution
17221 @item show overload-resolution
17222 Show the current setting of overload resolution.
17224 @item @r{Overloaded symbol names}
17225 You can specify a particular definition of an overloaded symbol, using
17226 the same notation that is used to declare such symbols in C@t{++}: type
17227 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17228 also use the @value{GDBN} command-line word completion facilities to list the
17229 available choices, or to finish the type list for you.
17230 @xref{Completion,, Command Completion}, for details on how to do this.
17232 @item @r{Breakpoints in template functions}
17234 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17235 template parameter lists when it encounters a symbol which includes a
17236 C@t{++} template. This permits setting breakpoints on families of template functions
17237 or functions whose parameters include template types.
17239 The @kbd{-qualified} flag may be used to override this behavior, causing
17240 @value{GDBN} to search for a specific function or type.
17242 The @value{GDBN} command-line word completion facility also understands
17243 template parameters and may be used to list available choices or finish
17244 template parameter lists for you. @xref{Completion,, Command Completion}, for
17245 details on how to do this.
17247 @item @r{Breakpoints in functions with ABI tags}
17249 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17250 correspond to changes in the ABI of a type, function, or variable that
17251 would not otherwise be reflected in a mangled name. See
17252 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17255 The ABI tags are visible in C@t{++} demangled names. For example, a
17256 function that returns a std::string:
17259 std::string function(int);
17263 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17264 tag, and @value{GDBN} displays the symbol like this:
17267 function[abi:cxx11](int)
17270 You can set a breakpoint on such functions simply as if they had no
17274 (gdb) b function(int)
17275 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17276 (gdb) info breakpoints
17277 Num Type Disp Enb Address What
17278 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17282 On the rare occasion you need to disambiguate between different ABI
17283 tags, you can do so by simply including the ABI tag in the function
17287 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17291 @node Decimal Floating Point
17292 @subsubsection Decimal Floating Point format
17293 @cindex decimal floating point format
17295 @value{GDBN} can examine, set and perform computations with numbers in
17296 decimal floating point format, which in the C language correspond to the
17297 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17298 specified by the extension to support decimal floating-point arithmetic.
17300 There are two encodings in use, depending on the architecture: BID (Binary
17301 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17302 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17305 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17306 to manipulate decimal floating point numbers, it is not possible to convert
17307 (using a cast, for example) integers wider than 32-bit to decimal float.
17309 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17310 point computations, error checking in decimal float operations ignores
17311 underflow, overflow and divide by zero exceptions.
17313 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17314 to inspect @code{_Decimal128} values stored in floating point registers.
17315 See @ref{PowerPC,,PowerPC} for more details.
17321 @value{GDBN} can be used to debug programs written in D and compiled with
17322 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17323 specific feature --- dynamic arrays.
17328 @cindex Go (programming language)
17329 @value{GDBN} can be used to debug programs written in Go and compiled with
17330 @file{gccgo} or @file{6g} compilers.
17332 Here is a summary of the Go-specific features and restrictions:
17335 @cindex current Go package
17336 @item The current Go package
17337 The name of the current package does not need to be specified when
17338 specifying global variables and functions.
17340 For example, given the program:
17344 var myglob = "Shall we?"
17350 When stopped inside @code{main} either of these work:
17354 (gdb) p main.myglob
17357 @cindex builtin Go types
17358 @item Builtin Go types
17359 The @code{string} type is recognized by @value{GDBN} and is printed
17362 @cindex builtin Go functions
17363 @item Builtin Go functions
17364 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17365 function and handles it internally.
17367 @cindex restrictions on Go expressions
17368 @item Restrictions on Go expressions
17369 All Go operators are supported except @code{&^}.
17370 The Go @code{_} ``blank identifier'' is not supported.
17371 Automatic dereferencing of pointers is not supported.
17375 @subsection Objective-C
17377 @cindex Objective-C
17378 This section provides information about some commands and command
17379 options that are useful for debugging Objective-C code. See also
17380 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17381 few more commands specific to Objective-C support.
17384 * Method Names in Commands::
17385 * The Print Command with Objective-C::
17388 @node Method Names in Commands
17389 @subsubsection Method Names in Commands
17391 The following commands have been extended to accept Objective-C method
17392 names as line specifications:
17394 @kindex clear@r{, and Objective-C}
17395 @kindex break@r{, and Objective-C}
17396 @kindex info line@r{, and Objective-C}
17397 @kindex jump@r{, and Objective-C}
17398 @kindex list@r{, and Objective-C}
17402 @item @code{info line}
17407 A fully qualified Objective-C method name is specified as
17410 -[@var{Class} @var{methodName}]
17413 where the minus sign is used to indicate an instance method and a
17414 plus sign (not shown) is used to indicate a class method. The class
17415 name @var{Class} and method name @var{methodName} are enclosed in
17416 brackets, similar to the way messages are specified in Objective-C
17417 source code. For example, to set a breakpoint at the @code{create}
17418 instance method of class @code{Fruit} in the program currently being
17422 break -[Fruit create]
17425 To list ten program lines around the @code{initialize} class method,
17429 list +[NSText initialize]
17432 In the current version of @value{GDBN}, the plus or minus sign is
17433 required. In future versions of @value{GDBN}, the plus or minus
17434 sign will be optional, but you can use it to narrow the search. It
17435 is also possible to specify just a method name:
17441 You must specify the complete method name, including any colons. If
17442 your program's source files contain more than one @code{create} method,
17443 you'll be presented with a numbered list of classes that implement that
17444 method. Indicate your choice by number, or type @samp{0} to exit if
17447 As another example, to clear a breakpoint established at the
17448 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17451 clear -[NSWindow makeKeyAndOrderFront:]
17454 @node The Print Command with Objective-C
17455 @subsubsection The Print Command With Objective-C
17456 @cindex Objective-C, print objects
17457 @kindex print-object
17458 @kindex po @r{(@code{print-object})}
17460 The print command has also been extended to accept methods. For example:
17463 print -[@var{object} hash]
17466 @cindex print an Objective-C object description
17467 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17469 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17470 and print the result. Also, an additional command has been added,
17471 @code{print-object} or @code{po} for short, which is meant to print
17472 the description of an object. However, this command may only work
17473 with certain Objective-C libraries that have a particular hook
17474 function, @code{_NSPrintForDebugger}, defined.
17477 @subsection OpenCL C
17480 This section provides information about @value{GDBN}s OpenCL C support.
17483 * OpenCL C Datatypes::
17484 * OpenCL C Expressions::
17485 * OpenCL C Operators::
17488 @node OpenCL C Datatypes
17489 @subsubsection OpenCL C Datatypes
17491 @cindex OpenCL C Datatypes
17492 @value{GDBN} supports the builtin scalar and vector datatypes specified
17493 by OpenCL 1.1. In addition the half- and double-precision floating point
17494 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17495 extensions are also known to @value{GDBN}.
17497 @node OpenCL C Expressions
17498 @subsubsection OpenCL C Expressions
17500 @cindex OpenCL C Expressions
17501 @value{GDBN} supports accesses to vector components including the access as
17502 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17503 supported by @value{GDBN} can be used as well.
17505 @node OpenCL C Operators
17506 @subsubsection OpenCL C Operators
17508 @cindex OpenCL C Operators
17509 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17513 @subsection Fortran
17514 @cindex Fortran-specific support in @value{GDBN}
17516 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17517 all Fortran language features are available yet.
17519 @cindex trailing underscore, in Fortran symbols
17520 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17521 among them) append an underscore to the names of variables and
17522 functions. When you debug programs compiled by those compilers, you
17523 will need to refer to variables and functions with a trailing
17526 @cindex Fortran Defaults
17527 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17528 default uses case-insensitive matching for Fortran symbols. You can
17529 change that with the @samp{set case-insensitive} command, see
17530 @ref{Symbols}, for the details.
17533 * Fortran Types:: Fortran builtin types
17534 * Fortran Operators:: Fortran operators and expressions
17535 * Fortran Intrinsics:: Fortran intrinsic functions
17536 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17539 @node Fortran Types
17540 @subsubsection Fortran Types
17542 @cindex Fortran Types
17544 In Fortran the primitive data-types have an associated @code{KIND} type
17545 parameter, written as @samp{@var{type}*@var{kindparam}},
17546 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17547 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17548 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17549 The kind of a type can be retrieved by using the intrinsic function
17550 @code{KIND}, see @ref{Fortran Intrinsics}.
17552 Generally, the actual implementation of the @code{KIND} type parameter is
17553 compiler specific. In @value{GDBN} the kind parameter is implemented in
17554 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17555 kind parameter for a given @var{type} specifies its size in memory --- a
17556 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17557 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17558 type for which the kind of the type does not specify its entire size, but
17559 the size of each of the two @code{Real}'s it is composed of. A
17560 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17563 For every type there is also a default kind associated with it, e.g.@
17564 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17565 table below for default types). The default types are the same as in @sc{gnu}
17566 compilers but note, that the @sc{gnu} default types can actually be changed by
17567 compiler flags such as @option{-fdefault-integer-8} and
17568 @option{-fdefault-real-8}.
17570 Not every kind parameter is valid for every type and in @value{GDBN} the
17571 following type kinds are available.
17575 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17576 @code{Integer} = @code{Integer*4}.
17579 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17580 @code{Logical} = @code{Logical*4}.
17583 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17586 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17591 @node Fortran Operators
17592 @subsubsection Fortran Operators and Expressions
17594 @cindex Fortran operators and expressions
17596 Operators must be defined on values of specific types. For instance,
17597 @code{+} is defined on numbers, but not on characters or other non-
17598 arithmetic types. Operators are often defined on groups of types.
17602 The exponentiation operator. It raises the first operand to the power
17606 The range operator. Normally used in the form of array(low:high) to
17607 represent a section of array.
17610 The access component operator. Normally used to access elements in derived
17611 types. Also suitable for unions. As unions aren't part of regular Fortran,
17612 this can only happen when accessing a register that uses a gdbarch-defined
17615 The scope operator. Normally used to access variables in modules or
17616 to set breakpoints on subroutines nested in modules or in other
17617 subroutines (internal subroutines).
17620 @node Fortran Intrinsics
17621 @subsubsection Fortran Intrinsics
17623 @cindex Fortran Intrinsics
17625 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17626 an incomplete subset of those procedures and their overloads. Some of these
17627 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17631 Computes the absolute value of its argument @var{a}. Currently not supported
17632 for @code{Complex} arguments.
17634 @item ALLOCATE(@var{array})
17635 Returns whether @var{array} is allocated or not.
17637 @item ASSOCIATED(@var{pointer} [, @var{target}])
17638 Returns the association status of the pointer @var{pointer} or, if @var{target}
17639 is present, whether @var{pointer} is associated with the target @var{target}.
17641 @item CEILING(@var{a} [, @var{kind}])
17642 Computes the least integer greater than or equal to @var{a}. The optional
17643 parameter @var{kind} specifies the kind of the return type
17644 @code{Integer(@var{kind})}.
17646 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17647 Returns a complex number where @var{x} is converted to the real component. If
17648 @var{y} is present it is converted to the imaginary component. If @var{y} is
17649 not present then the imaginary component is set to @code{0.0} except if @var{x}
17650 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17651 the kind of the return type @code{Complex(@var{kind})}.
17653 @item FLOOR(@var{a} [, @var{kind}])
17654 Computes the greatest integer less than or equal to @var{a}. The optional
17655 parameter @var{kind} specifies the kind of the return type
17656 @code{Integer(@var{kind})}.
17658 @item KIND(@var{a})
17659 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17661 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17662 Returns the lower bounds of an @var{array}, or a single lower bound along the
17663 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17664 the kind of the return type @code{Integer(@var{kind})}.
17667 Returns the address of @var{x} as an @code{Integer}.
17669 @item MOD(@var{a}, @var{p})
17670 Computes the remainder of the division of @var{a} by @var{p}.
17672 @item MODULO(@var{a}, @var{p})
17673 Computes the @var{a} modulo @var{p}.
17675 @item RANK(@var{a})
17676 Returns the rank of a scalar or array (scalars have rank @code{0}).
17678 @item SHAPE(@var{a})
17679 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17681 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17682 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17683 total number of elements in @var{array} if @var{dim} is absent. The optional
17684 parameter @var{kind} specifies the kind of the return type
17685 @code{Integer(@var{kind})}.
17687 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17688 Returns the upper bounds of an @var{array}, or a single upper bound along the
17689 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17690 the kind of the return type @code{Integer(@var{kind})}.
17694 @node Special Fortran Commands
17695 @subsubsection Special Fortran Commands
17697 @cindex Special Fortran commands
17699 @value{GDBN} has some commands to support Fortran-specific features,
17700 such as displaying common blocks.
17703 @cindex @code{COMMON} blocks, Fortran
17704 @kindex info common
17705 @item info common @r{[}@var{common-name}@r{]}
17706 This command prints the values contained in the Fortran @code{COMMON}
17707 block whose name is @var{common-name}. With no argument, the names of
17708 all @code{COMMON} blocks visible at the current program location are
17710 @cindex arrays slices (Fortran)
17711 @kindex set fortran repack-array-slices
17712 @kindex show fortran repack-array-slices
17713 @item set fortran repack-array-slices [on|off]
17714 @item show fortran repack-array-slices
17715 When taking a slice from an array, a Fortran compiler can choose to
17716 either produce an array descriptor that describes the slice in place,
17717 or it may repack the slice, copying the elements of the slice into a
17718 new region of memory.
17720 When this setting is on, then @value{GDBN} will also repack array
17721 slices in some situations. When this setting is off, then
17722 @value{GDBN} will create array descriptors for slices that reference
17723 the original data in place.
17725 @value{GDBN} will never repack an array slice if the data for the
17726 slice is contiguous within the original array.
17728 @value{GDBN} will always repack string slices if the data for the
17729 slice is non-contiguous within the original string as @value{GDBN}
17730 does not support printing non-contiguous strings.
17732 The default for this setting is @code{off}.
17738 @cindex Pascal support in @value{GDBN}, limitations
17739 Debugging Pascal programs which use sets, subranges, file variables, or
17740 nested functions does not currently work. @value{GDBN} does not support
17741 entering expressions, printing values, or similar features using Pascal
17744 The Pascal-specific command @code{set print pascal_static-members}
17745 controls whether static members of Pascal objects are displayed.
17746 @xref{Print Settings, pascal_static-members}.
17751 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17752 Programming Language}. Type- and value-printing, and expression
17753 parsing, are reasonably complete. However, there are a few
17754 peculiarities and holes to be aware of.
17758 Linespecs (@pxref{Location Specifications}) are never relative to the
17759 current crate. Instead, they act as if there were a global namespace
17760 of crates, somewhat similar to the way @code{extern crate} behaves.
17762 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17763 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17764 to set a breakpoint in a function named @samp{f} in a crate named
17767 As a consequence of this approach, linespecs also cannot refer to
17768 items using @samp{self::} or @samp{super::}.
17771 Because @value{GDBN} implements Rust name-lookup semantics in
17772 expressions, it will sometimes prepend the current crate to a name.
17773 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17774 @samp{K}, then @code{print ::x::y} will try to find the symbol
17777 However, since it is useful to be able to refer to other crates when
17778 debugging, @value{GDBN} provides the @code{extern} extension to
17779 circumvent this. To use the extension, just put @code{extern} before
17780 a path expression to refer to the otherwise unavailable ``global''
17783 In the above example, if you wanted to refer to the symbol @samp{y} in
17784 the crate @samp{x}, you would use @code{print extern x::y}.
17787 The Rust expression evaluator does not support ``statement-like''
17788 expressions such as @code{if} or @code{match}, or lambda expressions.
17791 Tuple expressions are not implemented.
17794 The Rust expression evaluator does not currently implement the
17795 @code{Drop} trait. Objects that may be created by the evaluator will
17796 never be destroyed.
17799 @value{GDBN} does not implement type inference for generics. In order
17800 to call generic functions or otherwise refer to generic items, you
17801 will have to specify the type parameters manually.
17804 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17805 cases this does not cause any problems. However, in an expression
17806 context, completing a generic function name will give syntactically
17807 invalid results. This happens because Rust requires the @samp{::}
17808 operator between the function name and its generic arguments. For
17809 example, @value{GDBN} might provide a completion like
17810 @code{crate::f<u32>}, where the parser would require
17811 @code{crate::f::<u32>}.
17814 As of this writing, the Rust compiler (version 1.8) has a few holes in
17815 the debugging information it generates. These holes prevent certain
17816 features from being implemented by @value{GDBN}:
17820 Method calls cannot be made via traits.
17823 Operator overloading is not implemented.
17826 When debugging in a monomorphized function, you cannot use the generic
17830 The type @code{Self} is not available.
17833 @code{use} statements are not available, so some names may not be
17834 available in the crate.
17839 @subsection Modula-2
17841 @cindex Modula-2, @value{GDBN} support
17843 The extensions made to @value{GDBN} to support Modula-2 only support
17844 output from the @sc{gnu} Modula-2 compiler (which is currently being
17845 developed). Other Modula-2 compilers are not currently supported, and
17846 attempting to debug executables produced by them is most likely
17847 to give an error as @value{GDBN} reads in the executable's symbol
17850 @cindex expressions in Modula-2
17852 * M2 Operators:: Built-in operators
17853 * Built-In Func/Proc:: Built-in functions and procedures
17854 * M2 Constants:: Modula-2 constants
17855 * M2 Types:: Modula-2 types
17856 * M2 Defaults:: Default settings for Modula-2
17857 * Deviations:: Deviations from standard Modula-2
17858 * M2 Checks:: Modula-2 type and range checks
17859 * M2 Scope:: The scope operators @code{::} and @code{.}
17860 * GDB/M2:: @value{GDBN} and Modula-2
17864 @subsubsection Operators
17865 @cindex Modula-2 operators
17867 Operators must be defined on values of specific types. For instance,
17868 @code{+} is defined on numbers, but not on structures. Operators are
17869 often defined on groups of types. For the purposes of Modula-2, the
17870 following definitions hold:
17875 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17879 @emph{Character types} consist of @code{CHAR} and its subranges.
17882 @emph{Floating-point types} consist of @code{REAL}.
17885 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17889 @emph{Scalar types} consist of all of the above.
17892 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17895 @emph{Boolean types} consist of @code{BOOLEAN}.
17899 The following operators are supported, and appear in order of
17900 increasing precedence:
17904 Function argument or array index separator.
17907 Assignment. The value of @var{var} @code{:=} @var{value} is
17911 Less than, greater than on integral, floating-point, or enumerated
17915 Less than or equal to, greater than or equal to
17916 on integral, floating-point and enumerated types, or set inclusion on
17917 set types. Same precedence as @code{<}.
17919 @item =@r{, }<>@r{, }#
17920 Equality and two ways of expressing inequality, valid on scalar types.
17921 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17922 available for inequality, since @code{#} conflicts with the script
17926 Set membership. Defined on set types and the types of their members.
17927 Same precedence as @code{<}.
17930 Boolean disjunction. Defined on boolean types.
17933 Boolean conjunction. Defined on boolean types.
17936 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17939 Addition and subtraction on integral and floating-point types, or union
17940 and difference on set types.
17943 Multiplication on integral and floating-point types, or set intersection
17947 Division on floating-point types, or symmetric set difference on set
17948 types. Same precedence as @code{*}.
17951 Integer division and remainder. Defined on integral types. Same
17952 precedence as @code{*}.
17955 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17958 Pointer dereferencing. Defined on pointer types.
17961 Boolean negation. Defined on boolean types. Same precedence as
17965 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17966 precedence as @code{^}.
17969 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17972 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17976 @value{GDBN} and Modula-2 scope operators.
17980 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17981 treats the use of the operator @code{IN}, or the use of operators
17982 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17983 @code{<=}, and @code{>=} on sets as an error.
17987 @node Built-In Func/Proc
17988 @subsubsection Built-in Functions and Procedures
17989 @cindex Modula-2 built-ins
17991 Modula-2 also makes available several built-in procedures and functions.
17992 In describing these, the following metavariables are used:
17997 represents an @code{ARRAY} variable.
18000 represents a @code{CHAR} constant or variable.
18003 represents a variable or constant of integral type.
18006 represents an identifier that belongs to a set. Generally used in the
18007 same function with the metavariable @var{s}. The type of @var{s} should
18008 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
18011 represents a variable or constant of integral or floating-point type.
18014 represents a variable or constant of floating-point type.
18020 represents a variable.
18023 represents a variable or constant of one of many types. See the
18024 explanation of the function for details.
18027 All Modula-2 built-in procedures also return a result, described below.
18031 Returns the absolute value of @var{n}.
18034 If @var{c} is a lower case letter, it returns its upper case
18035 equivalent, otherwise it returns its argument.
18038 Returns the character whose ordinal value is @var{i}.
18041 Decrements the value in the variable @var{v} by one. Returns the new value.
18043 @item DEC(@var{v},@var{i})
18044 Decrements the value in the variable @var{v} by @var{i}. Returns the
18047 @item EXCL(@var{m},@var{s})
18048 Removes the element @var{m} from the set @var{s}. Returns the new
18051 @item FLOAT(@var{i})
18052 Returns the floating point equivalent of the integer @var{i}.
18054 @item HIGH(@var{a})
18055 Returns the index of the last member of @var{a}.
18058 Increments the value in the variable @var{v} by one. Returns the new value.
18060 @item INC(@var{v},@var{i})
18061 Increments the value in the variable @var{v} by @var{i}. Returns the
18064 @item INCL(@var{m},@var{s})
18065 Adds the element @var{m} to the set @var{s} if it is not already
18066 there. Returns the new set.
18069 Returns the maximum value of the type @var{t}.
18072 Returns the minimum value of the type @var{t}.
18075 Returns boolean TRUE if @var{i} is an odd number.
18078 Returns the ordinal value of its argument. For example, the ordinal
18079 value of a character is its @sc{ascii} value (on machines supporting
18080 the @sc{ascii} character set). The argument @var{x} must be of an
18081 ordered type, which include integral, character and enumerated types.
18083 @item SIZE(@var{x})
18084 Returns the size of its argument. The argument @var{x} can be a
18085 variable or a type.
18087 @item TRUNC(@var{r})
18088 Returns the integral part of @var{r}.
18090 @item TSIZE(@var{x})
18091 Returns the size of its argument. The argument @var{x} can be a
18092 variable or a type.
18094 @item VAL(@var{t},@var{i})
18095 Returns the member of the type @var{t} whose ordinal value is @var{i}.
18099 @emph{Warning:} Sets and their operations are not yet supported, so
18100 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
18104 @cindex Modula-2 constants
18106 @subsubsection Constants
18108 @value{GDBN} allows you to express the constants of Modula-2 in the following
18114 Integer constants are simply a sequence of digits. When used in an
18115 expression, a constant is interpreted to be type-compatible with the
18116 rest of the expression. Hexadecimal integers are specified by a
18117 trailing @samp{H}, and octal integers by a trailing @samp{B}.
18120 Floating point constants appear as a sequence of digits, followed by a
18121 decimal point and another sequence of digits. An optional exponent can
18122 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
18123 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
18124 digits of the floating point constant must be valid decimal (base 10)
18128 Character constants consist of a single character enclosed by a pair of
18129 like quotes, either single (@code{'}) or double (@code{"}). They may
18130 also be expressed by their ordinal value (their @sc{ascii} value, usually)
18131 followed by a @samp{C}.
18134 String constants consist of a sequence of characters enclosed by a
18135 pair of like quotes, either single (@code{'}) or double (@code{"}).
18136 Escape sequences in the style of C are also allowed. @xref{C
18137 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
18141 Enumerated constants consist of an enumerated identifier.
18144 Boolean constants consist of the identifiers @code{TRUE} and
18148 Pointer constants consist of integral values only.
18151 Set constants are not yet supported.
18155 @subsubsection Modula-2 Types
18156 @cindex Modula-2 types
18158 Currently @value{GDBN} can print the following data types in Modula-2
18159 syntax: array types, record types, set types, pointer types, procedure
18160 types, enumerated types, subrange types and base types. You can also
18161 print the contents of variables declared using these type.
18162 This section gives a number of simple source code examples together with
18163 sample @value{GDBN} sessions.
18165 The first example contains the following section of code:
18174 and you can request @value{GDBN} to interrogate the type and value of
18175 @code{r} and @code{s}.
18178 (@value{GDBP}) print s
18180 (@value{GDBP}) ptype s
18182 (@value{GDBP}) print r
18184 (@value{GDBP}) ptype r
18189 Likewise if your source code declares @code{s} as:
18193 s: SET ['A'..'Z'] ;
18197 then you may query the type of @code{s} by:
18200 (@value{GDBP}) ptype s
18201 type = SET ['A'..'Z']
18205 Note that at present you cannot interactively manipulate set
18206 expressions using the debugger.
18208 The following example shows how you might declare an array in Modula-2
18209 and how you can interact with @value{GDBN} to print its type and contents:
18213 s: ARRAY [-10..10] OF CHAR ;
18217 (@value{GDBP}) ptype s
18218 ARRAY [-10..10] OF CHAR
18221 Note that the array handling is not yet complete and although the type
18222 is printed correctly, expression handling still assumes that all
18223 arrays have a lower bound of zero and not @code{-10} as in the example
18226 Here are some more type related Modula-2 examples:
18230 colour = (blue, red, yellow, green) ;
18231 t = [blue..yellow] ;
18239 The @value{GDBN} interaction shows how you can query the data type
18240 and value of a variable.
18243 (@value{GDBP}) print s
18245 (@value{GDBP}) ptype t
18246 type = [blue..yellow]
18250 In this example a Modula-2 array is declared and its contents
18251 displayed. Observe that the contents are written in the same way as
18252 their @code{C} counterparts.
18256 s: ARRAY [1..5] OF CARDINAL ;
18262 (@value{GDBP}) print s
18263 $1 = @{1, 0, 0, 0, 0@}
18264 (@value{GDBP}) ptype s
18265 type = ARRAY [1..5] OF CARDINAL
18268 The Modula-2 language interface to @value{GDBN} also understands
18269 pointer types as shown in this example:
18273 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18280 and you can request that @value{GDBN} describes the type of @code{s}.
18283 (@value{GDBP}) ptype s
18284 type = POINTER TO ARRAY [1..5] OF CARDINAL
18287 @value{GDBN} handles compound types as we can see in this example.
18288 Here we combine array types, record types, pointer types and subrange
18299 myarray = ARRAY myrange OF CARDINAL ;
18300 myrange = [-2..2] ;
18302 s: POINTER TO ARRAY myrange OF foo ;
18306 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18310 (@value{GDBP}) ptype s
18311 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18314 f3 : ARRAY [-2..2] OF CARDINAL;
18319 @subsubsection Modula-2 Defaults
18320 @cindex Modula-2 defaults
18322 If type and range checking are set automatically by @value{GDBN}, they
18323 both default to @code{on} whenever the working language changes to
18324 Modula-2. This happens regardless of whether you or @value{GDBN}
18325 selected the working language.
18327 If you allow @value{GDBN} to set the language automatically, then entering
18328 code compiled from a file whose name ends with @file{.mod} sets the
18329 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18330 Infer the Source Language}, for further details.
18333 @subsubsection Deviations from Standard Modula-2
18334 @cindex Modula-2, deviations from
18336 A few changes have been made to make Modula-2 programs easier to debug.
18337 This is done primarily via loosening its type strictness:
18341 Unlike in standard Modula-2, pointer constants can be formed by
18342 integers. This allows you to modify pointer variables during
18343 debugging. (In standard Modula-2, the actual address contained in a
18344 pointer variable is hidden from you; it can only be modified
18345 through direct assignment to another pointer variable or expression that
18346 returned a pointer.)
18349 C escape sequences can be used in strings and characters to represent
18350 non-printable characters. @value{GDBN} prints out strings with these
18351 escape sequences embedded. Single non-printable characters are
18352 printed using the @samp{CHR(@var{nnn})} format.
18355 The assignment operator (@code{:=}) returns the value of its right-hand
18359 All built-in procedures both modify @emph{and} return their argument.
18363 @subsubsection Modula-2 Type and Range Checks
18364 @cindex Modula-2 checks
18367 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18370 @c FIXME remove warning when type/range checks added
18372 @value{GDBN} considers two Modula-2 variables type equivalent if:
18376 They are of types that have been declared equivalent via a @code{TYPE
18377 @var{t1} = @var{t2}} statement
18380 They have been declared on the same line. (Note: This is true of the
18381 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18384 As long as type checking is enabled, any attempt to combine variables
18385 whose types are not equivalent is an error.
18387 Range checking is done on all mathematical operations, assignment, array
18388 index bounds, and all built-in functions and procedures.
18391 @subsubsection The Scope Operators @code{::} and @code{.}
18393 @cindex @code{.}, Modula-2 scope operator
18394 @cindex colon, doubled as scope operator
18396 @vindex colon-colon@r{, in Modula-2}
18397 @c Info cannot handle :: but TeX can.
18400 @vindex ::@r{, in Modula-2}
18403 There are a few subtle differences between the Modula-2 scope operator
18404 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18409 @var{module} . @var{id}
18410 @var{scope} :: @var{id}
18414 where @var{scope} is the name of a module or a procedure,
18415 @var{module} the name of a module, and @var{id} is any declared
18416 identifier within your program, except another module.
18418 Using the @code{::} operator makes @value{GDBN} search the scope
18419 specified by @var{scope} for the identifier @var{id}. If it is not
18420 found in the specified scope, then @value{GDBN} searches all scopes
18421 enclosing the one specified by @var{scope}.
18423 Using the @code{.} operator makes @value{GDBN} search the current scope for
18424 the identifier specified by @var{id} that was imported from the
18425 definition module specified by @var{module}. With this operator, it is
18426 an error if the identifier @var{id} was not imported from definition
18427 module @var{module}, or if @var{id} is not an identifier in
18431 @subsubsection @value{GDBN} and Modula-2
18433 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18434 Five subcommands of @code{set print} and @code{show print} apply
18435 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18436 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18437 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18438 analogue in Modula-2.
18440 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18441 with any language, is not useful with Modula-2. Its
18442 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18443 created in Modula-2 as they can in C or C@t{++}. However, because an
18444 address can be specified by an integral constant, the construct
18445 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18447 @cindex @code{#} in Modula-2
18448 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18449 interpreted as the beginning of a comment. Use @code{<>} instead.
18455 The extensions made to @value{GDBN} for Ada only support
18456 output from the @sc{gnu} Ada (GNAT) compiler.
18457 Other Ada compilers are not currently supported, and
18458 attempting to debug executables produced by them is most likely
18462 @cindex expressions in Ada
18464 * Ada Mode Intro:: General remarks on the Ada syntax
18465 and semantics supported by Ada mode
18467 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18468 * Additions to Ada:: Extensions of the Ada expression syntax.
18469 * Overloading support for Ada:: Support for expressions involving overloaded
18471 * Stopping Before Main Program:: Debugging the program during elaboration.
18472 * Ada Exceptions:: Ada Exceptions
18473 * Ada Tasks:: Listing and setting breakpoints in tasks.
18474 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18475 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18477 * Ada Source Character Set:: Character set of Ada source files.
18478 * Ada Glitches:: Known peculiarities of Ada mode.
18481 @node Ada Mode Intro
18482 @subsubsection Introduction
18483 @cindex Ada mode, general
18485 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18486 syntax, with some extensions.
18487 The philosophy behind the design of this subset is
18491 That @value{GDBN} should provide basic literals and access to operations for
18492 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18493 leaving more sophisticated computations to subprograms written into the
18494 program (which therefore may be called from @value{GDBN}).
18497 That type safety and strict adherence to Ada language restrictions
18498 are not particularly important to the @value{GDBN} user.
18501 That brevity is important to the @value{GDBN} user.
18504 Thus, for brevity, the debugger acts as if all names declared in
18505 user-written packages are directly visible, even if they are not visible
18506 according to Ada rules, thus making it unnecessary to fully qualify most
18507 names with their packages, regardless of context. Where this causes
18508 ambiguity, @value{GDBN} asks the user's intent.
18510 The debugger will start in Ada mode if it detects an Ada main program.
18511 As for other languages, it will enter Ada mode when stopped in a program that
18512 was translated from an Ada source file.
18514 While in Ada mode, you may use `@t{--}' for comments. This is useful
18515 mostly for documenting command files. The standard @value{GDBN} comment
18516 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18517 middle (to allow based literals).
18519 @node Omissions from Ada
18520 @subsubsection Omissions from Ada
18521 @cindex Ada, omissions from
18523 Here are the notable omissions from the subset:
18527 Only a subset of the attributes are supported:
18531 @t{'First}, @t{'Last}, and @t{'Length}
18532 on array objects (not on types and subtypes).
18535 @t{'Min} and @t{'Max}.
18538 @t{'Pos} and @t{'Val}.
18544 @t{'Range} on array objects (not subtypes), but only as the right
18545 operand of the membership (@code{in}) operator.
18548 @t{'Access}, @t{'Unchecked_Access}, and
18549 @t{'Unrestricted_Access} (a GNAT extension).
18556 The names in @code{Characters.Latin_1} are not available.
18559 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18560 equality of representations. They will generally work correctly
18561 for strings and arrays whose elements have integer or enumeration types.
18562 They may not work correctly for arrays whose element
18563 types have user-defined equality, for arrays of real values
18564 (in particular, IEEE-conformant floating point, because of negative
18565 zeroes and NaNs), and for arrays whose elements contain unused bits with
18566 indeterminate values.
18569 The other component-by-component array operations (@code{and}, @code{or},
18570 @code{xor}, @code{not}, and relational tests other than equality)
18571 are not implemented.
18574 @cindex array aggregates (Ada)
18575 @cindex record aggregates (Ada)
18576 @cindex aggregates (Ada)
18577 There is limited support for array and record aggregates. They are
18578 permitted only on the right sides of assignments, as in these examples:
18581 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18582 (@value{GDBP}) set An_Array := (1, others => 0)
18583 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18584 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18585 (@value{GDBP}) set A_Record := (1, "Peter", True);
18586 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18590 discriminant's value by assigning an aggregate has an
18591 undefined effect if that discriminant is used within the record.
18592 However, you can first modify discriminants by directly assigning to
18593 them (which normally would not be allowed in Ada), and then performing an
18594 aggregate assignment. For example, given a variable @code{A_Rec}
18595 declared to have a type such as:
18598 type Rec (Len : Small_Integer := 0) is record
18600 Vals : IntArray (1 .. Len);
18604 you can assign a value with a different size of @code{Vals} with two
18608 (@value{GDBP}) set A_Rec.Len := 4
18609 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18612 As this example also illustrates, @value{GDBN} is very loose about the usual
18613 rules concerning aggregates. You may leave out some of the
18614 components of an array or record aggregate (such as the @code{Len}
18615 component in the assignment to @code{A_Rec} above); they will retain their
18616 original values upon assignment. You may freely use dynamic values as
18617 indices in component associations. You may even use overlapping or
18618 redundant component associations, although which component values are
18619 assigned in such cases is not defined.
18622 Calls to dispatching subprograms are not implemented.
18625 The overloading algorithm is much more limited (i.e., less selective)
18626 than that of real Ada. It makes only limited use of the context in
18627 which a subexpression appears to resolve its meaning, and it is much
18628 looser in its rules for allowing type matches. As a result, some
18629 function calls will be ambiguous, and the user will be asked to choose
18630 the proper resolution.
18633 The @code{new} operator is not implemented.
18636 Entry calls are not implemented.
18639 Aside from printing, arithmetic operations on the native VAX floating-point
18640 formats are not supported.
18643 It is not possible to slice a packed array.
18646 The names @code{True} and @code{False}, when not part of a qualified name,
18647 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18649 Should your program
18650 redefine these names in a package or procedure (at best a dubious practice),
18651 you will have to use fully qualified names to access their new definitions.
18654 Based real literals are not implemented.
18657 @node Additions to Ada
18658 @subsubsection Additions to Ada
18659 @cindex Ada, deviations from
18661 As it does for other languages, @value{GDBN} makes certain generic
18662 extensions to Ada (@pxref{Expressions}):
18666 If the expression @var{E} is a variable residing in memory (typically
18667 a local variable or array element) and @var{N} is a positive integer,
18668 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18669 @var{N}-1 adjacent variables following it in memory as an array. In
18670 Ada, this operator is generally not necessary, since its prime use is
18671 in displaying parts of an array, and slicing will usually do this in
18672 Ada. However, there are occasional uses when debugging programs in
18673 which certain debugging information has been optimized away.
18676 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18677 appears in function or file @var{B}.'' When @var{B} is a file name,
18678 you must typically surround it in single quotes.
18681 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18682 @var{type} that appears at address @var{addr}.''
18685 A name starting with @samp{$} is a convenience variable
18686 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18689 In addition, @value{GDBN} provides a few other shortcuts and outright
18690 additions specific to Ada:
18694 The assignment statement is allowed as an expression, returning
18695 its right-hand operand as its value. Thus, you may enter
18698 (@value{GDBP}) set x := y + 3
18699 (@value{GDBP}) print A(tmp := y + 1)
18703 The semicolon is allowed as an ``operator,'' returning as its value
18704 the value of its right-hand operand.
18705 This allows, for example,
18706 complex conditional breaks:
18709 (@value{GDBP}) break f
18710 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18714 An extension to based literals can be used to specify the exact byte
18715 contents of a floating-point literal. After the base, you can use
18716 from zero to two @samp{l} characters, followed by an @samp{f}. The
18717 number of @samp{l} characters controls the width of the resulting real
18718 constant: zero means @code{Float} is used, one means
18719 @code{Long_Float}, and two means @code{Long_Long_Float}.
18722 (@value{GDBP}) print 16f#41b80000#
18727 Rather than use catenation and symbolic character names to introduce special
18728 characters into strings, one may instead use a special bracket notation,
18729 which is also used to print strings. A sequence of characters of the form
18730 @samp{["@var{XX}"]} within a string or character literal denotes the
18731 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18732 sequence of characters @samp{["""]} also denotes a single quotation mark
18733 in strings. For example,
18735 "One line.["0a"]Next line.["0a"]"
18738 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18742 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18743 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18747 (@value{GDBP}) print 'max(x, y)
18751 When printing arrays, @value{GDBN} uses positional notation when the
18752 array has a lower bound of 1, and uses a modified named notation otherwise.
18753 For example, a one-dimensional array of three integers with a lower bound
18754 of 3 might print as
18761 That is, in contrast to valid Ada, only the first component has a @code{=>}
18765 You may abbreviate attributes in expressions with any unique,
18766 multi-character subsequence of
18767 their names (an exact match gets preference).
18768 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18769 in place of @t{a'length}.
18772 @cindex quoting Ada internal identifiers
18773 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18774 to lower case. The GNAT compiler uses upper-case characters for
18775 some of its internal identifiers, which are normally of no interest to users.
18776 For the rare occasions when you actually have to look at them,
18777 enclose them in angle brackets to avoid the lower-case mapping.
18780 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18784 Printing an object of class-wide type or dereferencing an
18785 access-to-class-wide value will display all the components of the object's
18786 specific type (as indicated by its run-time tag). Likewise, component
18787 selection on such a value will operate on the specific type of the
18792 @node Overloading support for Ada
18793 @subsubsection Overloading support for Ada
18794 @cindex overloading, Ada
18796 The debugger supports limited overloading. Given a subprogram call in which
18797 the function symbol has multiple definitions, it will use the number of
18798 actual parameters and some information about their types to attempt to narrow
18799 the set of definitions. It also makes very limited use of context, preferring
18800 procedures to functions in the context of the @code{call} command, and
18801 functions to procedures elsewhere.
18803 If, after narrowing, the set of matching definitions still contains more than
18804 one definition, @value{GDBN} will display a menu to query which one it should
18808 (@value{GDBP}) print f(1)
18809 Multiple matches for f
18811 [1] foo.f (integer) return boolean at foo.adb:23
18812 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18816 In this case, just select one menu entry either to cancel expression evaluation
18817 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18818 instance (type the corresponding number and press @key{RET}).
18820 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18825 @kindex set ada print-signatures
18826 @item set ada print-signatures
18827 Control whether parameter types and return types are displayed in overloads
18828 selection menus. It is @code{on} by default.
18829 @xref{Overloading support for Ada}.
18831 @kindex show ada print-signatures
18832 @item show ada print-signatures
18833 Show the current setting for displaying parameter types and return types in
18834 overloads selection menu.
18835 @xref{Overloading support for Ada}.
18839 @node Stopping Before Main Program
18840 @subsubsection Stopping at the Very Beginning
18842 @cindex breakpointing Ada elaboration code
18843 It is sometimes necessary to debug the program during elaboration, and
18844 before reaching the main procedure.
18845 As defined in the Ada Reference
18846 Manual, the elaboration code is invoked from a procedure called
18847 @code{adainit}. To run your program up to the beginning of
18848 elaboration, simply use the following two commands:
18849 @code{tbreak adainit} and @code{run}.
18851 @node Ada Exceptions
18852 @subsubsection Ada Exceptions
18854 A command is provided to list all Ada exceptions:
18857 @kindex info exceptions
18858 @item info exceptions
18859 @itemx info exceptions @var{regexp}
18860 The @code{info exceptions} command allows you to list all Ada exceptions
18861 defined within the program being debugged, as well as their addresses.
18862 With a regular expression, @var{regexp}, as argument, only those exceptions
18863 whose names match @var{regexp} are listed.
18866 Below is a small example, showing how the command can be used, first
18867 without argument, and next with a regular expression passed as an
18871 (@value{GDBP}) info exceptions
18872 All defined Ada exceptions:
18873 constraint_error: 0x613da0
18874 program_error: 0x613d20
18875 storage_error: 0x613ce0
18876 tasking_error: 0x613ca0
18877 const.aint_global_e: 0x613b00
18878 (@value{GDBP}) info exceptions const.aint
18879 All Ada exceptions matching regular expression "const.aint":
18880 constraint_error: 0x613da0
18881 const.aint_global_e: 0x613b00
18884 It is also possible to ask @value{GDBN} to stop your program's execution
18885 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18888 @subsubsection Extensions for Ada Tasks
18889 @cindex Ada, tasking
18891 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18892 @value{GDBN} provides the following task-related commands:
18897 This command shows a list of current Ada tasks, as in the following example:
18904 (@value{GDBP}) info tasks
18905 ID TID P-ID Pri State Name
18906 1 8088000 0 15 Child Activation Wait main_task
18907 2 80a4000 1 15 Accept Statement b
18908 3 809a800 1 15 Child Activation Wait a
18909 * 4 80ae800 3 15 Runnable c
18914 In this listing, the asterisk before the last task indicates it to be the
18915 task currently being inspected.
18919 Represents @value{GDBN}'s internal task number.
18925 The parent's task ID (@value{GDBN}'s internal task number).
18928 The base priority of the task.
18931 Current state of the task.
18935 The task has been created but has not been activated. It cannot be
18939 The task is not blocked for any reason known to Ada. (It may be waiting
18940 for a mutex, though.) It is conceptually "executing" in normal mode.
18943 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18944 that were waiting on terminate alternatives have been awakened and have
18945 terminated themselves.
18947 @item Child Activation Wait
18948 The task is waiting for created tasks to complete activation.
18950 @item Accept or Select Term
18951 The task is waiting on an accept or selective wait statement.
18953 @item Waiting on entry call
18954 The task is waiting on an entry call.
18956 @item Async Select Wait
18957 The task is waiting to start the abortable part of an asynchronous
18961 The task is waiting on a select statement with only a delay
18964 @item Child Termination Wait
18965 The task is sleeping having completed a master within itself, and is
18966 waiting for the tasks dependent on that master to become terminated or
18967 waiting on a terminate Phase.
18969 @item Wait Child in Term Alt
18970 The task is sleeping waiting for tasks on terminate alternatives to
18971 finish terminating.
18973 @item Asynchronous Hold
18974 The task has been held by @code{Ada.Asynchronous_Task_Control.Hold_Task}.
18977 The task has been created and is being made runnable.
18979 @item Selective Wait
18980 The task is waiting in a selective wait statement.
18982 @item Accepting RV with @var{taskno}
18983 The task is accepting a rendez-vous with the task @var{taskno}.
18985 @item Waiting on RV with @var{taskno}
18986 The task is waiting for a rendez-vous with the task @var{taskno}.
18990 Name of the task in the program.
18994 @kindex info task @var{taskno}
18995 @item info task @var{taskno}
18996 This command shows detailed informations on the specified task, as in
18997 the following example:
19002 (@value{GDBP}) info tasks
19003 ID TID P-ID Pri State Name
19004 1 8077880 0 15 Child Activation Wait main_task
19005 * 2 807c468 1 15 Runnable task_1
19006 (@value{GDBP}) info task 2
19007 Ada Task: 0x807c468
19011 Parent: 1 ("main_task")
19017 @kindex task@r{ (Ada)}
19018 @cindex current Ada task ID
19019 This command prints the ID and name of the current task.
19025 (@value{GDBP}) info tasks
19026 ID TID P-ID Pri State Name
19027 1 8077870 0 15 Child Activation Wait main_task
19028 * 2 807c458 1 15 Runnable some_task
19029 (@value{GDBP}) task
19030 [Current task is 2 "some_task"]
19033 @item task @var{taskno}
19034 @cindex Ada task switching
19035 This command is like the @code{thread @var{thread-id}}
19036 command (@pxref{Threads}). It switches the context of debugging
19037 from the current task to the given task.
19043 (@value{GDBP}) info tasks
19044 ID TID P-ID Pri State Name
19045 1 8077870 0 15 Child Activation Wait main_task
19046 * 2 807c458 1 15 Runnable some_task
19047 (@value{GDBP}) task 1
19048 [Switching to task 1 "main_task"]
19049 #0 0x8067726 in pthread_cond_wait ()
19051 #0 0x8067726 in pthread_cond_wait ()
19052 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
19053 #2 0x805cb63 in system.task_primitives.operations.sleep ()
19054 #3 0x806153e in system.tasking.stages.activate_tasks ()
19055 #4 0x804aacc in un () at un.adb:5
19058 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
19059 The @code{task apply} command is the Ada tasking analogue of
19060 @code{thread apply} (@pxref{Threads}). It allows you to apply the
19061 named @var{command} to one or more tasks. Specify the tasks that you
19062 want affected using a list of task IDs, or specify @code{all} to apply
19065 The @var{flag} arguments control what output to produce and how to
19066 handle errors raised when applying @var{command} to a task.
19067 @var{flag} must start with a @code{-} directly followed by one letter
19068 in @code{qcs}. If several flags are provided, they must be given
19069 individually, such as @code{-c -q}.
19071 By default, @value{GDBN} displays some task information before the
19072 output produced by @var{command}, and an error raised during the
19073 execution of a @var{command} will abort @code{task apply}. The
19074 following flags can be used to fine-tune this behavior:
19078 The flag @code{-c}, which stands for @samp{continue}, causes any
19079 errors in @var{command} to be displayed, and the execution of
19080 @code{task apply} then continues.
19082 The flag @code{-s}, which stands for @samp{silent}, causes any errors
19083 or empty output produced by a @var{command} to be silently ignored.
19084 That is, the execution continues, but the task information and errors
19087 The flag @code{-q} (@samp{quiet}) disables printing the task
19091 Flags @code{-c} and @code{-s} cannot be used together.
19093 @item break @var{locspec} task @var{taskno}
19094 @itemx break @var{locspec} task @var{taskno} if @dots{}
19095 @cindex breakpoints and tasks, in Ada
19096 @cindex task breakpoints, in Ada
19097 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
19098 These commands are like the @code{break @dots{} thread @dots{}}
19099 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
19100 the various forms of @var{locspec}.
19102 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
19103 to specify that you only want @value{GDBN} to stop the program when a
19104 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
19105 numeric task identifiers assigned by @value{GDBN}, shown in the first
19106 column of the @samp{info tasks} display.
19108 If you do not specify @samp{task @var{taskno}} when you set a
19109 breakpoint, the breakpoint applies to @emph{all} tasks of your
19112 You can use the @code{task} qualifier on conditional breakpoints as
19113 well; in this case, place @samp{task @var{taskno}} before the
19114 breakpoint condition (before the @code{if}).
19122 (@value{GDBP}) info tasks
19123 ID TID P-ID Pri State Name
19124 1 140022020 0 15 Child Activation Wait main_task
19125 2 140045060 1 15 Accept/Select Wait t2
19126 3 140044840 1 15 Runnable t1
19127 * 4 140056040 1 15 Runnable t3
19128 (@value{GDBP}) b 15 task 2
19129 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
19130 (@value{GDBP}) cont
19135 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
19137 (@value{GDBP}) info tasks
19138 ID TID P-ID Pri State Name
19139 1 140022020 0 15 Child Activation Wait main_task
19140 * 2 140045060 1 15 Runnable t2
19141 3 140044840 1 15 Runnable t1
19142 4 140056040 1 15 Delay Sleep t3
19146 @node Ada Tasks and Core Files
19147 @subsubsection Tasking Support when Debugging Core Files
19148 @cindex Ada tasking and core file debugging
19150 When inspecting a core file, as opposed to debugging a live program,
19151 tasking support may be limited or even unavailable, depending on
19152 the platform being used.
19153 For instance, on x86-linux, the list of tasks is available, but task
19154 switching is not supported.
19156 On certain platforms, the debugger needs to perform some
19157 memory writes in order to provide Ada tasking support. When inspecting
19158 a core file, this means that the core file must be opened with read-write
19159 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19160 Under these circumstances, you should make a backup copy of the core
19161 file before inspecting it with @value{GDBN}.
19163 @node Ravenscar Profile
19164 @subsubsection Tasking Support when using the Ravenscar Profile
19165 @cindex Ravenscar Profile
19167 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19168 specifically designed for systems with safety-critical real-time
19172 @kindex set ravenscar task-switching on
19173 @cindex task switching with program using Ravenscar Profile
19174 @item set ravenscar task-switching on
19175 Allows task switching when debugging a program that uses the Ravenscar
19176 Profile. This is the default.
19178 @kindex set ravenscar task-switching off
19179 @item set ravenscar task-switching off
19180 Turn off task switching when debugging a program that uses the Ravenscar
19181 Profile. This is mostly intended to disable the code that adds support
19182 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19183 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19184 To be effective, this command should be run before the program is started.
19186 @kindex show ravenscar task-switching
19187 @item show ravenscar task-switching
19188 Show whether it is possible to switch from task to task in a program
19189 using the Ravenscar Profile.
19193 @cindex Ravenscar thread
19194 When Ravenscar task-switching is enabled, Ravenscar tasks are
19195 announced by @value{GDBN} as if they were threads:
19199 [New Ravenscar Thread 0x2b8f0]
19202 Both Ravenscar tasks and the underlying CPU threads will show up in
19203 the output of @code{info threads}:
19208 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19209 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19210 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19211 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19212 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19213 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19216 One known limitation of the Ravenscar support in @value{GDBN} is that
19217 it isn't currently possible to single-step through the runtime
19218 initialization sequence. If you need to debug this code, you should
19219 use @code{set ravenscar task-switching off}.
19221 @node Ada Source Character Set
19222 @subsubsection Ada Source Character Set
19223 @cindex Ada, source character set
19225 The GNAT compiler supports a number of character sets for source
19226 files. @xref{Character Set Control, , Character Set Control,
19227 gnat_ugn}. @value{GDBN} includes support for this as well.
19230 @item set ada source-charset @var{charset}
19231 @kindex set ada source-charset
19232 Set the source character set for Ada. The character set must be
19233 supported by GNAT. Because this setting affects the decoding of
19234 symbols coming from the debug information in your program, the setting
19235 should be set as early as possible. The default is @code{ISO-8859-1},
19236 because that is also GNAT's default.
19238 @item show ada source-charset
19239 @kindex show ada source-charset
19240 Show the current source character set for Ada.
19244 @subsubsection Known Peculiarities of Ada Mode
19245 @cindex Ada, problems
19247 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19248 we know of several problems with and limitations of Ada mode in
19250 some of which will be fixed with planned future releases of the debugger
19251 and the GNU Ada compiler.
19255 Static constants that the compiler chooses not to materialize as objects in
19256 storage are invisible to the debugger.
19259 Named parameter associations in function argument lists are ignored (the
19260 argument lists are treated as positional).
19263 Many useful library packages are currently invisible to the debugger.
19266 Fixed-point arithmetic, conversions, input, and output is carried out using
19267 floating-point arithmetic, and may give results that only approximate those on
19271 The GNAT compiler never generates the prefix @code{Standard} for any of
19272 the standard symbols defined by the Ada language. @value{GDBN} knows about
19273 this: it will strip the prefix from names when you use it, and will never
19274 look for a name you have so qualified among local symbols, nor match against
19275 symbols in other packages or subprograms. If you have
19276 defined entities anywhere in your program other than parameters and
19277 local variables whose simple names match names in @code{Standard},
19278 GNAT's lack of qualification here can cause confusion. When this happens,
19279 you can usually resolve the confusion
19280 by qualifying the problematic names with package
19281 @code{Standard} explicitly.
19284 Older versions of the compiler sometimes generate erroneous debugging
19285 information, resulting in the debugger incorrectly printing the value
19286 of affected entities. In some cases, the debugger is able to work
19287 around an issue automatically. In other cases, the debugger is able
19288 to work around the issue, but the work-around has to be specifically
19291 @kindex set ada trust-PAD-over-XVS
19292 @kindex show ada trust-PAD-over-XVS
19295 @item set ada trust-PAD-over-XVS on
19296 Configure GDB to strictly follow the GNAT encoding when computing the
19297 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19298 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19299 a complete description of the encoding used by the GNAT compiler).
19300 This is the default.
19302 @item set ada trust-PAD-over-XVS off
19303 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19304 sometimes prints the wrong value for certain entities, changing @code{ada
19305 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19306 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19307 @code{off}, but this incurs a slight performance penalty, so it is
19308 recommended to leave this setting to @code{on} unless necessary.
19312 @cindex GNAT descriptive types
19313 @cindex GNAT encoding
19314 Internally, the debugger also relies on the compiler following a number
19315 of conventions known as the @samp{GNAT Encoding}, all documented in
19316 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19317 how the debugging information should be generated for certain types.
19318 In particular, this convention makes use of @dfn{descriptive types},
19319 which are artificial types generated purely to help the debugger.
19321 These encodings were defined at a time when the debugging information
19322 format used was not powerful enough to describe some of the more complex
19323 types available in Ada. Since DWARF allows us to express nearly all
19324 Ada features, the long-term goal is to slowly replace these descriptive
19325 types by their pure DWARF equivalent. To facilitate that transition,
19326 a new maintenance option is available to force the debugger to ignore
19327 those descriptive types. It allows the user to quickly evaluate how
19328 well @value{GDBN} works without them.
19332 @kindex maint ada set ignore-descriptive-types
19333 @item maintenance ada set ignore-descriptive-types [on|off]
19334 Control whether the debugger should ignore descriptive types.
19335 The default is not to ignore descriptives types (@code{off}).
19337 @kindex maint ada show ignore-descriptive-types
19338 @item maintenance ada show ignore-descriptive-types
19339 Show if descriptive types are ignored by @value{GDBN}.
19343 @node Unsupported Languages
19344 @section Unsupported Languages
19346 @cindex unsupported languages
19347 @cindex minimal language
19348 In addition to the other fully-supported programming languages,
19349 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19350 It does not represent a real programming language, but provides a set
19351 of capabilities close to what the C or assembly languages provide.
19352 This should allow most simple operations to be performed while debugging
19353 an application that uses a language currently not supported by @value{GDBN}.
19355 If the language is set to @code{auto}, @value{GDBN} will automatically
19356 select this language if the current frame corresponds to an unsupported
19360 @chapter Examining the Symbol Table
19362 The commands described in this chapter allow you to inquire about the
19363 symbols (names of variables, functions and types) defined in your
19364 program. This information is inherent in the text of your program and
19365 does not change as your program executes. @value{GDBN} finds it in your
19366 program's symbol table, in the file indicated when you started @value{GDBN}
19367 (@pxref{File Options, ,Choosing Files}), or by one of the
19368 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19370 @cindex symbol names
19371 @cindex names of symbols
19372 @cindex quoting names
19373 @anchor{quoting names}
19374 Occasionally, you may need to refer to symbols that contain unusual
19375 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19376 most frequent case is in referring to static variables in other
19377 source files (@pxref{Variables,,Program Variables}). File names
19378 are recorded in object files as debugging symbols, but @value{GDBN} would
19379 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19380 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19381 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19388 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19391 @cindex case-insensitive symbol names
19392 @cindex case sensitivity in symbol names
19393 @kindex set case-sensitive
19394 @item set case-sensitive on
19395 @itemx set case-sensitive off
19396 @itemx set case-sensitive auto
19397 Normally, when @value{GDBN} looks up symbols, it matches their names
19398 with case sensitivity determined by the current source language.
19399 Occasionally, you may wish to control that. The command @code{set
19400 case-sensitive} lets you do that by specifying @code{on} for
19401 case-sensitive matches or @code{off} for case-insensitive ones. If
19402 you specify @code{auto}, case sensitivity is reset to the default
19403 suitable for the source language. The default is case-sensitive
19404 matches for all languages except for Fortran, for which the default is
19405 case-insensitive matches.
19407 @kindex show case-sensitive
19408 @item show case-sensitive
19409 This command shows the current setting of case sensitivity for symbols
19412 @kindex set print type methods
19413 @item set print type methods
19414 @itemx set print type methods on
19415 @itemx set print type methods off
19416 Normally, when @value{GDBN} prints a class, it displays any methods
19417 declared in that class. You can control this behavior either by
19418 passing the appropriate flag to @code{ptype}, or using @command{set
19419 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19420 display the methods; this is the default. Specifying @code{off} will
19421 cause @value{GDBN} to omit the methods.
19423 @kindex show print type methods
19424 @item show print type methods
19425 This command shows the current setting of method display when printing
19428 @kindex set print type nested-type-limit
19429 @item set print type nested-type-limit @var{limit}
19430 @itemx set print type nested-type-limit unlimited
19431 Set the limit of displayed nested types that the type printer will
19432 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19433 nested definitions. By default, the type printer will not show any nested
19434 types defined in classes.
19436 @kindex show print type nested-type-limit
19437 @item show print type nested-type-limit
19438 This command shows the current display limit of nested types when
19441 @kindex set print type typedefs
19442 @item set print type typedefs
19443 @itemx set print type typedefs on
19444 @itemx set print type typedefs off
19446 Normally, when @value{GDBN} prints a class, it displays any typedefs
19447 defined in that class. You can control this behavior either by
19448 passing the appropriate flag to @code{ptype}, or using @command{set
19449 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19450 display the typedef definitions; this is the default. Specifying
19451 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19452 Note that this controls whether the typedef definition itself is
19453 printed, not whether typedef names are substituted when printing other
19456 @kindex show print type typedefs
19457 @item show print type typedefs
19458 This command shows the current setting of typedef display when
19461 @kindex set print type hex
19462 @item set print type hex
19463 @itemx set print type hex on
19464 @itemx set print type hex off
19466 When @value{GDBN} prints sizes and offsets of struct members, it can use
19467 either the decimal or hexadecimal notation. You can select one or the
19468 other either by passing the appropriate flag to @code{ptype}, or by using
19469 the @command{set print type hex} command.
19471 @kindex show print type hex
19472 @item show print type hex
19473 This command shows whether the sizes and offsets of struct members are
19474 printed in decimal or hexadecimal notation.
19476 @kindex info address
19477 @cindex address of a symbol
19478 @item info address @var{symbol}
19479 Describe where the data for @var{symbol} is stored. For a register
19480 variable, this says which register it is kept in. For a non-register
19481 local variable, this prints the stack-frame offset at which the variable
19484 Note the contrast with @samp{print &@var{symbol}}, which does not work
19485 at all for a register variable, and for a stack local variable prints
19486 the exact address of the current instantiation of the variable.
19488 @kindex info symbol
19489 @cindex symbol from address
19490 @cindex closest symbol and offset for an address
19491 @item info symbol @var{addr}
19492 Print the name of a symbol which is stored at the address @var{addr}.
19493 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19494 nearest symbol and an offset from it:
19497 (@value{GDBP}) info symbol 0x54320
19498 _initialize_vx + 396 in section .text
19502 This is the opposite of the @code{info address} command. You can use
19503 it to find out the name of a variable or a function given its address.
19505 For dynamically linked executables, the name of executable or shared
19506 library containing the symbol is also printed:
19509 (@value{GDBP}) info symbol 0x400225
19510 _start + 5 in section .text of /tmp/a.out
19511 (@value{GDBP}) info symbol 0x2aaaac2811cf
19512 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19517 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19518 Demangle @var{name}.
19519 If @var{language} is provided it is the name of the language to demangle
19520 @var{name} in. Otherwise @var{name} is demangled in the current language.
19522 The @samp{--} option specifies the end of options,
19523 and is useful when @var{name} begins with a dash.
19525 The parameter @code{demangle-style} specifies how to interpret the kind
19526 of mangling used. @xref{Print Settings}.
19529 @item whatis[/@var{flags}] [@var{arg}]
19530 Print the data type of @var{arg}, which can be either an expression
19531 or a name of a data type. With no argument, print the data type of
19532 @code{$}, the last value in the value history.
19534 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19535 is not actually evaluated, and any side-effecting operations (such as
19536 assignments or function calls) inside it do not take place.
19538 If @var{arg} is a variable or an expression, @code{whatis} prints its
19539 literal type as it is used in the source code. If the type was
19540 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19541 the data type underlying the @code{typedef}. If the type of the
19542 variable or the expression is a compound data type, such as
19543 @code{struct} or @code{class}, @code{whatis} never prints their
19544 fields or methods. It just prints the @code{struct}/@code{class}
19545 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19546 such a compound data type, use @code{ptype}.
19548 If @var{arg} is a type name that was defined using @code{typedef},
19549 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19550 Unrolling means that @code{whatis} will show the underlying type used
19551 in the @code{typedef} declaration of @var{arg}. However, if that
19552 underlying type is also a @code{typedef}, @code{whatis} will not
19555 For C code, the type names may also have the form @samp{class
19556 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19557 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19559 @var{flags} can be used to modify how the type is displayed.
19560 Available flags are:
19564 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19565 parameters and typedefs defined in a class when printing the class'
19566 members. The @code{/r} flag disables this.
19569 Do not print methods defined in the class.
19572 Print methods defined in the class. This is the default, but the flag
19573 exists in case you change the default with @command{set print type methods}.
19576 Do not print typedefs defined in the class. Note that this controls
19577 whether the typedef definition itself is printed, not whether typedef
19578 names are substituted when printing other types.
19581 Print typedefs defined in the class. This is the default, but the flag
19582 exists in case you change the default with @command{set print type typedefs}.
19585 Print the offsets and sizes of fields in a struct, similar to what the
19586 @command{pahole} tool does. This option implies the @code{/tm} flags.
19589 Use hexadecimal notation when printing offsets and sizes of fields in a
19593 Use decimal notation when printing offsets and sizes of fields in a
19596 For example, given the following declarations:
19632 Issuing a @kbd{ptype /o struct tuv} command would print:
19635 (@value{GDBP}) ptype /o struct tuv
19636 /* offset | size */ type = struct tuv @{
19637 /* 0 | 4 */ int a1;
19638 /* XXX 4-byte hole */
19639 /* 8 | 8 */ char *a2;
19640 /* 16 | 4 */ int a3;
19642 /* total size (bytes): 24 */
19646 Notice the format of the first column of comments. There, you can
19647 find two parts separated by the @samp{|} character: the @emph{offset},
19648 which indicates where the field is located inside the struct, in
19649 bytes, and the @emph{size} of the field. Another interesting line is
19650 the marker of a @emph{hole} in the struct, indicating that it may be
19651 possible to pack the struct and make it use less space by reorganizing
19654 It is also possible to print offsets inside an union:
19657 (@value{GDBP}) ptype /o union qwe
19658 /* offset | size */ type = union qwe @{
19659 /* 24 */ struct tuv @{
19660 /* 0 | 4 */ int a1;
19661 /* XXX 4-byte hole */
19662 /* 8 | 8 */ char *a2;
19663 /* 16 | 4 */ int a3;
19665 /* total size (bytes): 24 */
19667 /* 40 */ struct xyz @{
19668 /* 0 | 4 */ int f1;
19669 /* 4 | 1 */ char f2;
19670 /* XXX 3-byte hole */
19671 /* 8 | 8 */ void *f3;
19672 /* 16 | 24 */ struct tuv @{
19673 /* 16 | 4 */ int a1;
19674 /* XXX 4-byte hole */
19675 /* 24 | 8 */ char *a2;
19676 /* 32 | 4 */ int a3;
19678 /* total size (bytes): 24 */
19681 /* total size (bytes): 40 */
19684 /* total size (bytes): 40 */
19688 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19689 same space (because we are dealing with an union), the offset is not
19690 printed for them. However, you can still examine the offset of each
19691 of these structures' fields.
19693 Another useful scenario is printing the offsets of a struct containing
19697 (@value{GDBP}) ptype /o struct tyu
19698 /* offset | size */ type = struct tyu @{
19699 /* 0:31 | 4 */ int a1 : 1;
19700 /* 0:28 | 4 */ int a2 : 3;
19701 /* 0: 5 | 4 */ int a3 : 23;
19702 /* 3: 3 | 1 */ signed char a4 : 2;
19703 /* XXX 3-bit hole */
19704 /* XXX 4-byte hole */
19705 /* 8 | 8 */ int64_t a5;
19706 /* 16: 0 | 4 */ int a6 : 5;
19707 /* 16: 5 | 8 */ int64_t a7 : 3;
19708 /* XXX 7-byte padding */
19710 /* total size (bytes): 24 */
19714 Note how the offset information is now extended to also include the
19715 first bit of the bitfield.
19719 @item ptype[/@var{flags}] [@var{arg}]
19720 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19721 detailed description of the type, instead of just the name of the type.
19722 @xref{Expressions, ,Expressions}.
19724 Contrary to @code{whatis}, @code{ptype} always unrolls any
19725 @code{typedef}s in its argument declaration, whether the argument is
19726 a variable, expression, or a data type. This means that @code{ptype}
19727 of a variable or an expression will not print literally its type as
19728 present in the source code---use @code{whatis} for that. @code{typedef}s at
19729 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19730 fields, methods and inner @code{class typedef}s of @code{struct}s,
19731 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19733 For example, for this variable declaration:
19736 typedef double real_t;
19737 struct complex @{ real_t real; double imag; @};
19738 typedef struct complex complex_t;
19740 real_t *real_pointer_var;
19744 the two commands give this output:
19748 (@value{GDBP}) whatis var
19750 (@value{GDBP}) ptype var
19751 type = struct complex @{
19755 (@value{GDBP}) whatis complex_t
19756 type = struct complex
19757 (@value{GDBP}) whatis struct complex
19758 type = struct complex
19759 (@value{GDBP}) ptype struct complex
19760 type = struct complex @{
19764 (@value{GDBP}) whatis real_pointer_var
19766 (@value{GDBP}) ptype real_pointer_var
19772 As with @code{whatis}, using @code{ptype} without an argument refers to
19773 the type of @code{$}, the last value in the value history.
19775 @cindex incomplete type
19776 Sometimes, programs use opaque data types or incomplete specifications
19777 of complex data structure. If the debug information included in the
19778 program does not allow @value{GDBN} to display a full declaration of
19779 the data type, it will say @samp{<incomplete type>}. For example,
19780 given these declarations:
19784 struct foo *fooptr;
19788 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19791 (@value{GDBP}) ptype foo
19792 $1 = <incomplete type>
19796 ``Incomplete type'' is C terminology for data types that are not
19797 completely specified.
19799 @cindex unknown type
19800 Othertimes, information about a variable's type is completely absent
19801 from the debug information included in the program. This most often
19802 happens when the program or library where the variable is defined
19803 includes no debug information at all. @value{GDBN} knows the variable
19804 exists from inspecting the linker/loader symbol table (e.g., the ELF
19805 dynamic symbol table), but such symbols do not contain type
19806 information. Inspecting the type of a (global) variable for which
19807 @value{GDBN} has no type information shows:
19810 (@value{GDBP}) ptype var
19811 type = <data variable, no debug info>
19814 @xref{Variables, no debug info variables}, for how to print the values
19818 @item info types [-q] [@var{regexp}]
19819 Print a brief description of all types whose names match the regular
19820 expression @var{regexp} (or all types in your program, if you supply
19821 no argument). Each complete typename is matched as though it were a
19822 complete line; thus, @samp{i type value} gives information on all
19823 types in your program whose names include the string @code{value}, but
19824 @samp{i type ^value$} gives information only on types whose complete
19825 name is @code{value}.
19827 In programs using different languages, @value{GDBN} chooses the syntax
19828 to print the type description according to the
19829 @samp{set language} value: using @samp{set language auto}
19830 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19831 language of the type, other values mean to use
19832 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19834 This command differs from @code{ptype} in two ways: first, like
19835 @code{whatis}, it does not print a detailed description; second, it
19836 lists all source files and line numbers where a type is defined.
19838 The output from @samp{into types} is proceeded with a header line
19839 describing what types are being listed. The optional flag @samp{-q},
19840 which stands for @samp{quiet}, disables printing this header
19843 @kindex info type-printers
19844 @item info type-printers
19845 Versions of @value{GDBN} that ship with Python scripting enabled may
19846 have ``type printers'' available. When using @command{ptype} or
19847 @command{whatis}, these printers are consulted when the name of a type
19848 is needed. @xref{Type Printing API}, for more information on writing
19851 @code{info type-printers} displays all the available type printers.
19853 @kindex enable type-printer
19854 @kindex disable type-printer
19855 @item enable type-printer @var{name}@dots{}
19856 @item disable type-printer @var{name}@dots{}
19857 These commands can be used to enable or disable type printers.
19860 @cindex local variables
19861 @item info scope @var{locspec}
19862 List all the variables local to the lexical scope of the code location
19863 that results from resolving @var{locspec}. @xref{Location
19864 Specifications}, for details about supported forms of @var{locspec}.
19868 (@value{GDBP}) @b{info scope command_line_handler}
19869 Scope for command_line_handler:
19870 Symbol rl is an argument at stack/frame offset 8, length 4.
19871 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19872 Symbol linelength is in static storage at address 0x150a1c, length 4.
19873 Symbol p is a local variable in register $esi, length 4.
19874 Symbol p1 is a local variable in register $ebx, length 4.
19875 Symbol nline is a local variable in register $edx, length 4.
19876 Symbol repeat is a local variable at frame offset -8, length 4.
19880 This command is especially useful for determining what data to collect
19881 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19884 @kindex info source
19886 Show information about the current source file---that is, the source file for
19887 the function containing the current point of execution:
19890 the name of the source file, and the directory containing it,
19892 the directory it was compiled in,
19894 its length, in lines,
19896 which programming language it is written in,
19898 if the debug information provides it, the program that compiled the file
19899 (which may include, e.g., the compiler version and command line arguments),
19901 whether the executable includes debugging information for that file, and
19902 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19904 whether the debugging information includes information about
19905 preprocessor macros.
19909 @kindex info sources
19910 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19913 With no options @samp{info sources} prints the names of all source
19914 files in your program for which there is debugging information. The
19915 source files are presented based on a list of object files
19916 (executables and libraries) currently loaded into @value{GDBN}. For
19917 each object file all of the associated source files are listed.
19919 Each source file will only be printed once for each object file, but a
19920 single source file can be repeated in the output if it is part of
19921 multiple object files.
19923 If the optional @var{regexp} is provided, then only source files that
19924 match the regular expression will be printed. The matching is
19925 case-sensitive, except on operating systems that have case-insensitive
19926 filesystem (e.g., MS-Windows). @samp{--} can be used before
19927 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19928 command option (e.g. if @var{regexp} starts with @samp{-}).
19930 By default, the @var{regexp} is used to match anywhere in the
19931 filename. If @code{-dirname}, only files having a dirname matching
19932 @var{regexp} are shown. If @code{-basename}, only files having a
19933 basename matching @var{regexp} are shown.
19935 It is possible that an object file may be printed in the list with no
19936 associated source files. This can happen when either no source files
19937 match @var{regexp}, or, the object file was compiled without debug
19938 information and so @value{GDBN} is unable to find any source file
19941 @kindex info functions
19942 @item info functions [-q] [-n]
19943 Print the names and data types of all defined functions.
19944 Similarly to @samp{info types}, this command groups its output by source
19945 files and annotates each function definition with its source line
19948 In programs using different languages, @value{GDBN} chooses the syntax
19949 to print the function name and type according to the
19950 @samp{set language} value: using @samp{set language auto}
19951 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19952 language of the function, other values mean to use
19953 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19955 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19956 results. A non-debugging symbol is a symbol that comes from the
19957 executable's symbol table, not from the debug information (for
19958 example, DWARF) associated with the executable.
19960 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19961 printing header information and messages explaining why no functions
19964 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19965 Like @samp{info functions}, but only print the names and data types
19966 of the functions selected with the provided regexp(s).
19968 If @var{regexp} is provided, print only the functions whose names
19969 match the regular expression @var{regexp}.
19970 Thus, @samp{info fun step} finds all functions whose
19971 names include @code{step}; @samp{info fun ^step} finds those whose names
19972 start with @code{step}. If a function name contains characters that
19973 conflict with the regular expression language (e.g.@:
19974 @samp{operator*()}), they may be quoted with a backslash.
19976 If @var{type_regexp} is provided, print only the functions whose
19977 types, as printed by the @code{whatis} command, match
19978 the regular expression @var{type_regexp}.
19979 If @var{type_regexp} contains space(s), it should be enclosed in
19980 quote characters. If needed, use backslash to escape the meaning
19981 of special characters or quotes.
19982 Thus, @samp{info fun -t '^int ('} finds the functions that return
19983 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19984 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19985 finds the functions whose names start with @code{step} and that return
19988 If both @var{regexp} and @var{type_regexp} are provided, a function
19989 is printed only if its name matches @var{regexp} and its type matches
19993 @kindex info variables
19994 @item info variables [-q] [-n]
19995 Print the names and data types of all variables that are defined
19996 outside of functions (i.e.@: excluding local variables).
19997 The printed variables are grouped by source files and annotated with
19998 their respective source line numbers.
20000 In programs using different languages, @value{GDBN} chooses the syntax
20001 to print the variable name and type according to the
20002 @samp{set language} value: using @samp{set language auto}
20003 (see @ref{Automatically, ,Set Language Automatically}) means to use the
20004 language of the variable, other values mean to use
20005 the manually specified language (see @ref{Manually, ,Set Language Manually}).
20007 The @samp{-n} flag excludes non-debugging symbols from the results.
20009 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20010 printing header information and messages explaining why no variables
20013 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
20014 Like @kbd{info variables}, but only print the variables selected
20015 with the provided regexp(s).
20017 If @var{regexp} is provided, print only the variables whose names
20018 match the regular expression @var{regexp}.
20020 If @var{type_regexp} is provided, print only the variables whose
20021 types, as printed by the @code{whatis} command, match
20022 the regular expression @var{type_regexp}.
20023 If @var{type_regexp} contains space(s), it should be enclosed in
20024 quote characters. If needed, use backslash to escape the meaning
20025 of special characters or quotes.
20027 If both @var{regexp} and @var{type_regexp} are provided, an argument
20028 is printed only if its name matches @var{regexp} and its type matches
20031 @kindex info modules
20033 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
20034 List all Fortran modules in the program, or all modules matching the
20035 optional regular expression @var{regexp}.
20037 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20038 printing header information and messages explaining why no modules
20041 @kindex info module
20042 @cindex Fortran modules, information about
20043 @cindex functions and variables by Fortran module
20044 @cindex module functions and variables
20045 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20046 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20047 List all functions or variables within all Fortran modules. The set
20048 of functions or variables listed can be limited by providing some or
20049 all of the optional regular expressions. If @var{module-regexp} is
20050 provided, then only Fortran modules matching @var{module-regexp} will
20051 be searched. Only functions or variables whose type matches the
20052 optional regular expression @var{type-regexp} will be listed. And
20053 only functions or variables whose name matches the optional regular
20054 expression @var{regexp} will be listed.
20056 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20057 printing header information and messages explaining why no functions
20058 or variables have been printed.
20060 @kindex info classes
20061 @cindex Objective-C, classes and selectors
20063 @itemx info classes @var{regexp}
20064 Display all Objective-C classes in your program, or
20065 (with the @var{regexp} argument) all those matching a particular regular
20068 @kindex info selectors
20069 @item info selectors
20070 @itemx info selectors @var{regexp}
20071 Display all Objective-C selectors in your program, or
20072 (with the @var{regexp} argument) all those matching a particular regular
20076 This was never implemented.
20077 @kindex info methods
20079 @itemx info methods @var{regexp}
20080 The @code{info methods} command permits the user to examine all defined
20081 methods within C@t{++} program, or (with the @var{regexp} argument) a
20082 specific set of methods found in the various C@t{++} classes. Many
20083 C@t{++} classes provide a large number of methods. Thus, the output
20084 from the @code{ptype} command can be overwhelming and hard to use. The
20085 @code{info-methods} command filters the methods, printing only those
20086 which match the regular-expression @var{regexp}.
20089 @cindex opaque data types
20090 @kindex set opaque-type-resolution
20091 @item set opaque-type-resolution on
20092 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
20093 declared as a pointer to a @code{struct}, @code{class}, or
20094 @code{union}---for example, @code{struct MyType *}---that is used in one
20095 source file although the full declaration of @code{struct MyType} is in
20096 another source file. The default is on.
20098 A change in the setting of this subcommand will not take effect until
20099 the next time symbols for a file are loaded.
20101 @item set opaque-type-resolution off
20102 Tell @value{GDBN} not to resolve opaque types. In this case, the type
20103 is printed as follows:
20105 @{<no data fields>@}
20108 @kindex show opaque-type-resolution
20109 @item show opaque-type-resolution
20110 Show whether opaque types are resolved or not.
20112 @kindex set print symbol-loading
20113 @cindex print messages when symbols are loaded
20114 @item set print symbol-loading
20115 @itemx set print symbol-loading full
20116 @itemx set print symbol-loading brief
20117 @itemx set print symbol-loading off
20118 The @code{set print symbol-loading} command allows you to control the
20119 printing of messages when @value{GDBN} loads symbol information.
20120 By default a message is printed for the executable and one for each
20121 shared library, and normally this is what you want. However, when
20122 debugging apps with large numbers of shared libraries these messages
20124 When set to @code{brief} a message is printed for each executable,
20125 and when @value{GDBN} loads a collection of shared libraries at once
20126 it will only print one message regardless of the number of shared
20127 libraries. When set to @code{off} no messages are printed.
20129 @kindex show print symbol-loading
20130 @item show print symbol-loading
20131 Show whether messages will be printed when a @value{GDBN} command
20132 entered from the keyboard causes symbol information to be loaded.
20134 @kindex maint print symbols
20135 @cindex symbol dump
20136 @kindex maint print psymbols
20137 @cindex partial symbol dump
20138 @kindex maint print msymbols
20139 @cindex minimal symbol dump
20140 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
20141 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20142 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20143 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20144 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20145 Write a dump of debugging symbol data into the file @var{filename} or
20146 the terminal if @var{filename} is unspecified.
20147 If @code{-objfile @var{objfile}} is specified, only dump symbols for
20149 If @code{-pc @var{address}} is specified, only dump symbols for the file
20150 with code at that address. Note that @var{address} may be a symbol like
20152 If @code{-source @var{source}} is specified, only dump symbols for that
20155 These commands are used to debug the @value{GDBN} symbol-reading code.
20156 These commands do not modify internal @value{GDBN} state, therefore
20157 @samp{maint print symbols} will only print symbols for already expanded symbol
20159 You can use the command @code{info sources} to find out which files these are.
20160 If you use @samp{maint print psymbols} instead, the dump shows information
20161 about symbols that @value{GDBN} only knows partially---that is, symbols
20162 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20163 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20166 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20167 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20169 @kindex maint info symtabs
20170 @kindex maint info psymtabs
20171 @cindex listing @value{GDBN}'s internal symbol tables
20172 @cindex symbol tables, listing @value{GDBN}'s internal
20173 @cindex full symbol tables, listing @value{GDBN}'s internal
20174 @cindex partial symbol tables, listing @value{GDBN}'s internal
20175 @item maint info symtabs @r{[} @var{regexp} @r{]}
20176 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20178 List the @code{struct symtab} or @code{struct partial_symtab}
20179 structures whose names match @var{regexp}. If @var{regexp} is not
20180 given, list them all. The output includes expressions which you can
20181 copy into a @value{GDBN} debugging this one to examine a particular
20182 structure in more detail. For example:
20185 (@value{GDBP}) maint info psymtabs dwarf2read
20186 @{ objfile /home/gnu/build/gdb/gdb
20187 ((struct objfile *) 0x82e69d0)
20188 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20189 ((struct partial_symtab *) 0x8474b10)
20192 text addresses 0x814d3c8 -- 0x8158074
20193 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20194 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20195 dependencies (none)
20198 (@value{GDBP}) maint info symtabs
20202 We see that there is one partial symbol table whose filename contains
20203 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20204 and we see that @value{GDBN} has not read in any symtabs yet at all.
20205 If we set a breakpoint on a function, that will cause @value{GDBN} to
20206 read the symtab for the compilation unit containing that function:
20209 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20210 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20212 (@value{GDBP}) maint info symtabs
20213 @{ objfile /home/gnu/build/gdb/gdb
20214 ((struct objfile *) 0x82e69d0)
20215 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20216 ((struct symtab *) 0x86c1f38)
20219 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20220 linetable ((struct linetable *) 0x8370fa0)
20221 debugformat DWARF 2
20227 @kindex maint info line-table
20228 @cindex listing @value{GDBN}'s internal line tables
20229 @cindex line tables, listing @value{GDBN}'s internal
20230 @item maint info line-table @r{[} @var{regexp} @r{]}
20232 List the @code{struct linetable} from all @code{struct symtab}
20233 instances whose name matches @var{regexp}. If @var{regexp} is not
20234 given, list the @code{struct linetable} from all @code{struct symtab}.
20238 (@value{GDBP}) maint info line-table
20239 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20240 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20241 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20242 linetable: ((struct linetable *) 0x62100012b760):
20243 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
20244 0 3 0x0000000000401110 Y
20245 1 4 0x0000000000401114 Y Y
20246 2 9 0x0000000000401120 Y
20247 3 10 0x0000000000401124 Y Y
20248 4 10 0x0000000000401129
20249 5 15 0x0000000000401130 Y
20250 6 16 0x0000000000401134 Y Y
20251 7 16 0x0000000000401139
20252 8 21 0x0000000000401140 Y
20253 9 22 0x000000000040114f Y Y
20254 10 22 0x0000000000401154
20255 11 END 0x000000000040115a Y
20258 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20259 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20260 indicates that a given address is an adequate place to set a breakpoint at the
20261 first instruction following a function prologue.
20263 @kindex maint set symbol-cache-size
20264 @cindex symbol cache size
20265 @item maint set symbol-cache-size @var{size}
20266 Set the size of the symbol cache to @var{size}.
20267 The default size is intended to be good enough for debugging
20268 most applications. This option exists to allow for experimenting
20269 with different sizes.
20271 @kindex maint show symbol-cache-size
20272 @item maint show symbol-cache-size
20273 Show the size of the symbol cache.
20275 @kindex maint print symbol-cache
20276 @cindex symbol cache, printing its contents
20277 @item maint print symbol-cache
20278 Print the contents of the symbol cache.
20279 This is useful when debugging symbol cache issues.
20281 @kindex maint print symbol-cache-statistics
20282 @cindex symbol cache, printing usage statistics
20283 @item maint print symbol-cache-statistics
20284 Print symbol cache usage statistics.
20285 This helps determine how well the cache is being utilized.
20287 @kindex maint flush symbol-cache
20288 @kindex maint flush-symbol-cache
20289 @cindex symbol cache, flushing
20290 @item maint flush symbol-cache
20291 @itemx maint flush-symbol-cache
20292 Flush the contents of the symbol cache, all entries are removed. This
20293 command is useful when debugging the symbol cache. It is also useful
20294 when collecting performance data. The command @code{maint
20295 flush-symbol-cache} is deprecated in favor of @code{maint flush
20298 @kindex maint set ignore-prologue-end-flag
20299 @cindex prologue-end
20300 @item maint set ignore-prologue-end-flag [on|off]
20301 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20302 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20303 to place breakpoints past the end of a function prologue. When @samp{on},
20304 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20307 @kindex maint show ignore-prologue-end-flag
20308 @item maint show ignore-prologue-end-flag
20309 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20314 @chapter Altering Execution
20316 Once you think you have found an error in your program, you might want to
20317 find out for certain whether correcting the apparent error would lead to
20318 correct results in the rest of the run. You can find the answer by
20319 experiment, using the @value{GDBN} features for altering execution of the
20322 For example, you can store new values into variables or memory
20323 locations, give your program a signal, restart it at a different
20324 address, or even return prematurely from a function.
20327 * Assignment:: Assignment to variables
20328 * Jumping:: Continuing at a different address
20329 * Signaling:: Giving your program a signal
20330 * Returning:: Returning from a function
20331 * Calling:: Calling your program's functions
20332 * Patching:: Patching your program
20333 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20337 @section Assignment to Variables
20340 @cindex setting variables
20341 To alter the value of a variable, evaluate an assignment expression.
20342 @xref{Expressions, ,Expressions}. For example,
20349 stores the value 4 into the variable @code{x}, and then prints the
20350 value of the assignment expression (which is 4).
20351 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20352 information on operators in supported languages.
20354 @kindex set variable
20355 @cindex variables, setting
20356 If you are not interested in seeing the value of the assignment, use the
20357 @code{set} command instead of the @code{print} command. @code{set} is
20358 really the same as @code{print} except that the expression's value is
20359 not printed and is not put in the value history (@pxref{Value History,
20360 ,Value History}). The expression is evaluated only for its effects.
20362 If the beginning of the argument string of the @code{set} command
20363 appears identical to a @code{set} subcommand, use the @code{set
20364 variable} command instead of just @code{set}. This command is identical
20365 to @code{set} except for its lack of subcommands. For example, if your
20366 program has a variable @code{width}, you get an error if you try to set
20367 a new value with just @samp{set width=13}, because @value{GDBN} has the
20368 command @code{set width}:
20371 (@value{GDBP}) whatis width
20373 (@value{GDBP}) p width
20375 (@value{GDBP}) set width=47
20376 Invalid syntax in expression.
20380 The invalid expression, of course, is @samp{=47}. In
20381 order to actually set the program's variable @code{width}, use
20384 (@value{GDBP}) set var width=47
20387 Because the @code{set} command has many subcommands that can conflict
20388 with the names of program variables, it is a good idea to use the
20389 @code{set variable} command instead of just @code{set}. For example, if
20390 your program has a variable @code{g}, you run into problems if you try
20391 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20392 the command @code{set gnutarget}, abbreviated @code{set g}:
20396 (@value{GDBP}) whatis g
20400 (@value{GDBP}) set g=4
20404 The program being debugged has been started already.
20405 Start it from the beginning? (y or n) y
20406 Starting program: /home/smith/cc_progs/a.out
20407 "/home/smith/cc_progs/a.out": can't open to read symbols:
20408 Invalid bfd target.
20409 (@value{GDBP}) show g
20410 The current BFD target is "=4".
20415 The program variable @code{g} did not change, and you silently set the
20416 @code{gnutarget} to an invalid value. In order to set the variable
20420 (@value{GDBP}) set var g=4
20423 @value{GDBN} allows more implicit conversions in assignments than C; you can
20424 freely store an integer value into a pointer variable or vice versa,
20425 and you can convert any structure to any other structure that is the
20426 same length or shorter.
20427 @comment FIXME: how do structs align/pad in these conversions?
20428 @comment /doc@cygnus.com 18dec1990
20430 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20431 construct to generate a value of specified type at a specified address
20432 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20433 to memory location @code{0x83040} as an integer (which implies a certain size
20434 and representation in memory), and
20437 set @{int@}0x83040 = 4
20441 stores the value 4 into that memory location.
20444 @section Continuing at a Different Address
20446 Ordinarily, when you continue your program, you do so at the place where
20447 it stopped, with the @code{continue} command. You can instead continue at
20448 an address of your own choosing, with the following commands:
20452 @kindex j @r{(@code{jump})}
20453 @item jump @var{locspec}
20454 @itemx j @var{locspec}
20455 Resume execution at the address of the code location that results from
20456 resolving @var{locspec}.
20457 @xref{Location Specifications}, for a description of the different
20458 forms of @var{locspec}. If @var{locspec} resolves to more than one
20459 address, the command aborts before jumping.
20460 Execution stops again immediately if there is a breakpoint there. It
20461 is common practice to use the @code{tbreak} command in conjunction
20462 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20464 The @code{jump} command does not change the current stack frame, or
20465 the stack pointer, or the contents of any memory location or any
20466 register other than the program counter. If @var{locspec} resolves to
20467 an address in a different function from the one currently executing, the
20468 results may be bizarre if the two functions expect different patterns
20469 of arguments or of local variables. For this reason, the @code{jump}
20470 command requests confirmation if the jump address is not in the
20471 function currently executing. However, even bizarre results are
20472 predictable if you are well acquainted with the machine-language code
20476 On many systems, you can get much the same effect as the @code{jump}
20477 command by storing a new value into the register @code{$pc}. The
20478 difference is that this does not start your program running; it only
20479 changes the address of where it @emph{will} run when you continue. For
20487 makes the next @code{continue} command or stepping command execute at
20488 address @code{0x485}, rather than at the address where your program stopped.
20489 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20491 The most common occasion to use the @code{jump} command is to back
20492 up---perhaps with more breakpoints set---over a portion of a program
20493 that has already executed, in order to examine its execution in more
20498 @section Giving your Program a Signal
20499 @cindex deliver a signal to a program
20503 @item signal @var{signal}
20504 Resume execution where your program is stopped, but immediately give it the
20505 signal @var{signal}. The @var{signal} can be the name or the number of a
20506 signal. For example, on many systems @code{signal 2} and @code{signal
20507 SIGINT} are both ways of sending an interrupt signal.
20509 Alternatively, if @var{signal} is zero, continue execution without
20510 giving a signal. This is useful when your program stopped on account of
20511 a signal and would ordinarily see the signal when resumed with the
20512 @code{continue} command; @samp{signal 0} causes it to resume without a
20515 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20516 delivered to the currently selected thread, not the thread that last
20517 reported a stop. This includes the situation where a thread was
20518 stopped due to a signal. So if you want to continue execution
20519 suppressing the signal that stopped a thread, you should select that
20520 same thread before issuing the @samp{signal 0} command. If you issue
20521 the @samp{signal 0} command with another thread as the selected one,
20522 @value{GDBN} detects that and asks for confirmation.
20524 Invoking the @code{signal} command is not the same as invoking the
20525 @code{kill} utility from the shell. Sending a signal with @code{kill}
20526 causes @value{GDBN} to decide what to do with the signal depending on
20527 the signal handling tables (@pxref{Signals}). The @code{signal} command
20528 passes the signal directly to your program.
20530 @code{signal} does not repeat when you press @key{RET} a second time
20531 after executing the command.
20533 @kindex queue-signal
20534 @item queue-signal @var{signal}
20535 Queue @var{signal} to be delivered immediately to the current thread
20536 when execution of the thread resumes. The @var{signal} can be the name or
20537 the number of a signal. For example, on many systems @code{signal 2} and
20538 @code{signal SIGINT} are both ways of sending an interrupt signal.
20539 The handling of the signal must be set to pass the signal to the program,
20540 otherwise @value{GDBN} will report an error.
20541 You can control the handling of signals from @value{GDBN} with the
20542 @code{handle} command (@pxref{Signals}).
20544 Alternatively, if @var{signal} is zero, any currently queued signal
20545 for the current thread is discarded and when execution resumes no signal
20546 will be delivered. This is useful when your program stopped on account
20547 of a signal and would ordinarily see the signal when resumed with the
20548 @code{continue} command.
20550 This command differs from the @code{signal} command in that the signal
20551 is just queued, execution is not resumed. And @code{queue-signal} cannot
20552 be used to pass a signal whose handling state has been set to @code{nopass}
20557 @xref{stepping into signal handlers}, for information on how stepping
20558 commands behave when the thread has a signal queued.
20561 @section Returning from a Function
20564 @cindex returning from a function
20567 @itemx return @var{expression}
20568 You can cancel execution of a function call with the @code{return}
20569 command. If you give an
20570 @var{expression} argument, its value is used as the function's return
20574 When you use @code{return}, @value{GDBN} discards the selected stack frame
20575 (and all frames within it). You can think of this as making the
20576 discarded frame return prematurely. If you wish to specify a value to
20577 be returned, give that value as the argument to @code{return}.
20579 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20580 Frame}), and any other frames inside of it, leaving its caller as the
20581 innermost remaining frame. That frame becomes selected. The
20582 specified value is stored in the registers used for returning values
20585 The @code{return} command does not resume execution; it leaves the
20586 program stopped in the state that would exist if the function had just
20587 returned. In contrast, the @code{finish} command (@pxref{Continuing
20588 and Stepping, ,Continuing and Stepping}) resumes execution until the
20589 selected stack frame returns naturally.
20591 @value{GDBN} needs to know how the @var{expression} argument should be set for
20592 the inferior. The concrete registers assignment depends on the OS ABI and the
20593 type being returned by the selected stack frame. For example it is common for
20594 OS ABI to return floating point values in FPU registers while integer values in
20595 CPU registers. Still some ABIs return even floating point values in CPU
20596 registers. Larger integer widths (such as @code{long long int}) also have
20597 specific placement rules. @value{GDBN} already knows the OS ABI from its
20598 current target so it needs to find out also the type being returned to make the
20599 assignment into the right register(s).
20601 Normally, the selected stack frame has debug info. @value{GDBN} will always
20602 use the debug info instead of the implicit type of @var{expression} when the
20603 debug info is available. For example, if you type @kbd{return -1}, and the
20604 function in the current stack frame is declared to return a @code{long long
20605 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20606 into a @code{long long int}:
20609 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20611 (@value{GDBP}) return -1
20612 Make func return now? (y or n) y
20613 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20614 43 printf ("result=%lld\n", func ());
20618 However, if the selected stack frame does not have a debug info, e.g., if the
20619 function was compiled without debug info, @value{GDBN} has to find out the type
20620 to return from user. Specifying a different type by mistake may set the value
20621 in different inferior registers than the caller code expects. For example,
20622 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20623 of a @code{long long int} result for a debug info less function (on 32-bit
20624 architectures). Therefore the user is required to specify the return type by
20625 an appropriate cast explicitly:
20628 Breakpoint 2, 0x0040050b in func ()
20629 (@value{GDBP}) return -1
20630 Return value type not available for selected stack frame.
20631 Please use an explicit cast of the value to return.
20632 (@value{GDBP}) return (long long int) -1
20633 Make selected stack frame return now? (y or n) y
20634 #0 0x00400526 in main ()
20639 @section Calling Program Functions
20642 @cindex calling functions
20643 @cindex inferior functions, calling
20644 @item print @var{expr}
20645 Evaluate the expression @var{expr} and display the resulting value.
20646 The expression may include calls to functions in the program being
20650 @item call @var{expr}
20651 Evaluate the expression @var{expr} without displaying @code{void}
20654 You can use this variant of the @code{print} command if you want to
20655 execute a function from your program that does not return anything
20656 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20657 with @code{void} returned values that @value{GDBN} will otherwise
20658 print. If the result is not void, it is printed and saved in the
20662 It is possible for the function you call via the @code{print} or
20663 @code{call} command to generate a signal (e.g., if there's a bug in
20664 the function, or if you passed it incorrect arguments). What happens
20665 in that case is controlled by the @code{set unwindonsignal} command.
20667 Similarly, with a C@t{++} program it is possible for the function you
20668 call via the @code{print} or @code{call} command to generate an
20669 exception that is not handled due to the constraints of the dummy
20670 frame. In this case, any exception that is raised in the frame, but has
20671 an out-of-frame exception handler will not be found. GDB builds a
20672 dummy-frame for the inferior function call, and the unwinder cannot
20673 seek for exception handlers outside of this dummy-frame. What happens
20674 in that case is controlled by the
20675 @code{set unwind-on-terminating-exception} command.
20678 @item set unwindonsignal
20679 @kindex set unwindonsignal
20680 @cindex unwind stack in called functions
20681 @cindex call dummy stack unwinding
20682 Set unwinding of the stack if a signal is received while in a function
20683 that @value{GDBN} called in the program being debugged. If set to on,
20684 @value{GDBN} unwinds the stack it created for the call and restores
20685 the context to what it was before the call. If set to off (the
20686 default), @value{GDBN} stops in the frame where the signal was
20689 @item show unwindonsignal
20690 @kindex show unwindonsignal
20691 Show the current setting of stack unwinding in the functions called by
20694 @item set unwind-on-terminating-exception
20695 @kindex set unwind-on-terminating-exception
20696 @cindex unwind stack in called functions with unhandled exceptions
20697 @cindex call dummy stack unwinding on unhandled exception.
20698 Set unwinding of the stack if a C@t{++} exception is raised, but left
20699 unhandled while in a function that @value{GDBN} called in the program being
20700 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20701 it created for the call and restores the context to what it was before
20702 the call. If set to off, @value{GDBN} the exception is delivered to
20703 the default C@t{++} exception handler and the inferior terminated.
20705 @item show unwind-on-terminating-exception
20706 @kindex show unwind-on-terminating-exception
20707 Show the current setting of stack unwinding in the functions called by
20710 @item set may-call-functions
20711 @kindex set may-call-functions
20712 @cindex disabling calling functions in the program
20713 @cindex calling functions in the program, disabling
20714 Set permission to call functions in the program.
20715 This controls whether @value{GDBN} will attempt to call functions in
20716 the program, such as with expressions in the @code{print} command. It
20717 defaults to @code{on}.
20719 To call a function in the program, @value{GDBN} has to temporarily
20720 modify the state of the inferior. This has potentially undesired side
20721 effects. Also, having @value{GDBN} call nested functions is likely to
20722 be erroneous and may even crash the program being debugged. You can
20723 avoid such hazards by forbidding @value{GDBN} from calling functions
20724 in the program being debugged. If calling functions in the program
20725 is forbidden, GDB will throw an error when a command (such as printing
20726 an expression) starts a function call in the program.
20728 @item show may-call-functions
20729 @kindex show may-call-functions
20730 Show permission to call functions in the program.
20734 @subsection Calling functions with no debug info
20736 @cindex no debug info functions
20737 Sometimes, a function you wish to call is missing debug information.
20738 In such case, @value{GDBN} does not know the type of the function,
20739 including the types of the function's parameters. To avoid calling
20740 the inferior function incorrectly, which could result in the called
20741 function functioning erroneously and even crash, @value{GDBN} refuses
20742 to call the function unless you tell it the type of the function.
20744 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20745 to do that. The simplest is to cast the call to the function's
20746 declared return type. For example:
20749 (@value{GDBP}) p getenv ("PATH")
20750 'getenv' has unknown return type; cast the call to its declared return type
20751 (@value{GDBP}) p (char *) getenv ("PATH")
20752 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20755 Casting the return type of a no-debug function is equivalent to
20756 casting the function to a pointer to a prototyped function that has a
20757 prototype that matches the types of the passed-in arguments, and
20758 calling that. I.e., the call above is equivalent to:
20761 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20765 and given this prototyped C or C++ function with float parameters:
20768 float multiply (float v1, float v2) @{ return v1 * v2; @}
20772 these calls are equivalent:
20775 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20776 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20779 If the function you wish to call is declared as unprototyped (i.e.@:
20780 old K&R style), you must use the cast-to-function-pointer syntax, so
20781 that @value{GDBN} knows that it needs to apply default argument
20782 promotions (promote float arguments to double). @xref{ABI, float
20783 promotion}. For example, given this unprototyped C function with
20784 float parameters, and no debug info:
20788 multiply_noproto (v1, v2)
20796 you call it like this:
20799 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20803 @section Patching Programs
20805 @cindex patching binaries
20806 @cindex writing into executables
20807 @cindex writing into corefiles
20809 By default, @value{GDBN} opens the file containing your program's
20810 executable code (or the corefile) read-only. This prevents accidental
20811 alterations to machine code; but it also prevents you from intentionally
20812 patching your program's binary.
20814 If you'd like to be able to patch the binary, you can specify that
20815 explicitly with the @code{set write} command. For example, you might
20816 want to turn on internal debugging flags, or even to make emergency
20822 @itemx set write off
20823 If you specify @samp{set write on}, @value{GDBN} opens executable and
20824 core files for both reading and writing; if you specify @kbd{set write
20825 off} (the default), @value{GDBN} opens them read-only.
20827 If you have already loaded a file, you must load it again (using the
20828 @code{exec-file} or @code{core-file} command) after changing @code{set
20829 write}, for your new setting to take effect.
20833 Display whether executable files and core files are opened for writing
20834 as well as reading.
20837 @node Compiling and Injecting Code
20838 @section Compiling and injecting code in @value{GDBN}
20839 @cindex injecting code
20840 @cindex writing into executables
20841 @cindex compiling code
20843 @value{GDBN} supports on-demand compilation and code injection into
20844 programs running under @value{GDBN}. GCC 5.0 or higher built with
20845 @file{libcc1.so} must be installed for this functionality to be enabled.
20846 This functionality is implemented with the following commands.
20849 @kindex compile code
20850 @item compile code @var{source-code}
20851 @itemx compile code -raw @var{--} @var{source-code}
20852 Compile @var{source-code} with the compiler language found as the current
20853 language in @value{GDBN} (@pxref{Languages}). If compilation and
20854 injection is not supported with the current language specified in
20855 @value{GDBN}, or the compiler does not support this feature, an error
20856 message will be printed. If @var{source-code} compiles and links
20857 successfully, @value{GDBN} will load the object-code emitted,
20858 and execute it within the context of the currently selected inferior.
20859 It is important to note that the compiled code is executed immediately.
20860 After execution, the compiled code is removed from @value{GDBN} and any
20861 new types or variables you have defined will be deleted.
20863 The command allows you to specify @var{source-code} in two ways.
20864 The simplest method is to provide a single line of code to the command.
20868 compile code printf ("hello world\n");
20871 If you specify options on the command line as well as source code, they
20872 may conflict. The @samp{--} delimiter can be used to separate options
20873 from actual source code. E.g.:
20876 compile code -r -- printf ("hello world\n");
20879 Alternatively you can enter source code as multiple lines of text. To
20880 enter this mode, invoke the @samp{compile code} command without any text
20881 following the command. This will start the multiple-line editor and
20882 allow you to type as many lines of source code as required. When you
20883 have completed typing, enter @samp{end} on its own line to exit the
20888 >printf ("hello\n");
20889 >printf ("world\n");
20893 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20894 provided @var{source-code} in a callable scope. In this case, you must
20895 specify the entry point of the code by defining a function named
20896 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20897 inferior. Using @samp{-raw} option may be needed for example when
20898 @var{source-code} requires @samp{#include} lines which may conflict with
20899 inferior symbols otherwise.
20901 @kindex compile file
20902 @item compile file @var{filename}
20903 @itemx compile file -raw @var{filename}
20904 Like @code{compile code}, but take the source code from @var{filename}.
20907 compile file /home/user/example.c
20912 @item compile print [[@var{options}] --] @var{expr}
20913 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20914 Compile and execute @var{expr} with the compiler language found as the
20915 current language in @value{GDBN} (@pxref{Languages}). By default the
20916 value of @var{expr} is printed in a format appropriate to its data type;
20917 you can choose a different format by specifying @samp{/@var{f}}, where
20918 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20919 Formats}. The @code{compile print} command accepts the same options
20920 as the @code{print} command; see @ref{print options}.
20922 @item compile print [[@var{options}] --]
20923 @itemx compile print [[@var{options}] --] /@var{f}
20924 @cindex reprint the last value
20925 Alternatively you can enter the expression (source code producing it) as
20926 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20927 command without any text following the command. This will start the
20928 multiple-line editor.
20932 The process of compiling and injecting the code can be inspected using:
20935 @anchor{set debug compile}
20936 @item set debug compile
20937 @cindex compile command debugging info
20938 Turns on or off display of @value{GDBN} process of compiling and
20939 injecting the code. The default is off.
20941 @item show debug compile
20942 Displays the current state of displaying @value{GDBN} process of
20943 compiling and injecting the code.
20945 @anchor{set debug compile-cplus-types}
20946 @item set debug compile-cplus-types
20947 @cindex compile C@t{++} type conversion
20948 Turns on or off the display of C@t{++} type conversion debugging information.
20949 The default is off.
20951 @item show debug compile-cplus-types
20952 Displays the current state of displaying debugging information for
20953 C@t{++} type conversion.
20956 @subsection Compilation options for the @code{compile} command
20958 @value{GDBN} needs to specify the right compilation options for the code
20959 to be injected, in part to make its ABI compatible with the inferior
20960 and in part to make the injected code compatible with @value{GDBN}'s
20964 The options used, in increasing precedence:
20967 @item target architecture and OS options (@code{gdbarch})
20968 These options depend on target processor type and target operating
20969 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20970 (@code{-m64}) compilation option.
20972 @item compilation options recorded in the target
20973 @value{NGCC} (since version 4.7) stores the options used for compilation
20974 into @code{DW_AT_producer} part of DWARF debugging information according
20975 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20976 explicitly specify @code{-g} during inferior compilation otherwise
20977 @value{NGCC} produces no DWARF. This feature is only relevant for
20978 platforms where @code{-g} produces DWARF by default, otherwise one may
20979 try to enforce DWARF by using @code{-gdwarf-4}.
20981 @item compilation options set by @code{set compile-args}
20985 You can override compilation options using the following command:
20988 @item set compile-args
20989 @cindex compile command options override
20990 Set compilation options used for compiling and injecting code with the
20991 @code{compile} commands. These options override any conflicting ones
20992 from the target architecture and/or options stored during inferior
20995 @item show compile-args
20996 Displays the current state of compilation options override.
20997 This does not show all the options actually used during compilation,
20998 use @ref{set debug compile} for that.
21001 @subsection Caveats when using the @code{compile} command
21003 There are a few caveats to keep in mind when using the @code{compile}
21004 command. As the caveats are different per language, the table below
21005 highlights specific issues on a per language basis.
21008 @item C code examples and caveats
21009 When the language in @value{GDBN} is set to @samp{C}, the compiler will
21010 attempt to compile the source code with a @samp{C} compiler. The source
21011 code provided to the @code{compile} command will have much the same
21012 access to variables and types as it normally would if it were part of
21013 the program currently being debugged in @value{GDBN}.
21015 Below is a sample program that forms the basis of the examples that
21016 follow. This program has been compiled and loaded into @value{GDBN},
21017 much like any other normal debugging session.
21020 void function1 (void)
21023 printf ("function 1\n");
21026 void function2 (void)
21041 For the purposes of the examples in this section, the program above has
21042 been compiled, loaded into @value{GDBN}, stopped at the function
21043 @code{main}, and @value{GDBN} is awaiting input from the user.
21045 To access variables and types for any program in @value{GDBN}, the
21046 program must be compiled and packaged with debug information. The
21047 @code{compile} command is not an exception to this rule. Without debug
21048 information, you can still use the @code{compile} command, but you will
21049 be very limited in what variables and types you can access.
21051 So with that in mind, the example above has been compiled with debug
21052 information enabled. The @code{compile} command will have access to
21053 all variables and types (except those that may have been optimized
21054 out). Currently, as @value{GDBN} has stopped the program in the
21055 @code{main} function, the @code{compile} command would have access to
21056 the variable @code{k}. You could invoke the @code{compile} command
21057 and type some source code to set the value of @code{k}. You can also
21058 read it, or do anything with that variable you would normally do in
21059 @code{C}. Be aware that changes to inferior variables in the
21060 @code{compile} command are persistent. In the following example:
21063 compile code k = 3;
21067 the variable @code{k} is now 3. It will retain that value until
21068 something else in the example program changes it, or another
21069 @code{compile} command changes it.
21071 Normal scope and access rules apply to source code compiled and
21072 injected by the @code{compile} command. In the example, the variables
21073 @code{j} and @code{k} are not accessible yet, because the program is
21074 currently stopped in the @code{main} function, where these variables
21075 are not in scope. Therefore, the following command
21078 compile code j = 3;
21082 will result in a compilation error message.
21084 Once the program is continued, execution will bring these variables in
21085 scope, and they will become accessible; then the code you specify via
21086 the @code{compile} command will be able to access them.
21088 You can create variables and types with the @code{compile} command as
21089 part of your source code. Variables and types that are created as part
21090 of the @code{compile} command are not visible to the rest of the program for
21091 the duration of its run. This example is valid:
21094 compile code int ff = 5; printf ("ff is %d\n", ff);
21097 However, if you were to type the following into @value{GDBN} after that
21098 command has completed:
21101 compile code printf ("ff is %d\n'', ff);
21105 a compiler error would be raised as the variable @code{ff} no longer
21106 exists. Object code generated and injected by the @code{compile}
21107 command is removed when its execution ends. Caution is advised
21108 when assigning to program variables values of variables created by the
21109 code submitted to the @code{compile} command. This example is valid:
21112 compile code int ff = 5; k = ff;
21115 The value of the variable @code{ff} is assigned to @code{k}. The variable
21116 @code{k} does not require the existence of @code{ff} to maintain the value
21117 it has been assigned. However, pointers require particular care in
21118 assignment. If the source code compiled with the @code{compile} command
21119 changed the address of a pointer in the example program, perhaps to a
21120 variable created in the @code{compile} command, that pointer would point
21121 to an invalid location when the command exits. The following example
21122 would likely cause issues with your debugged program:
21125 compile code int ff = 5; p = &ff;
21128 In this example, @code{p} would point to @code{ff} when the
21129 @code{compile} command is executing the source code provided to it.
21130 However, as variables in the (example) program persist with their
21131 assigned values, the variable @code{p} would point to an invalid
21132 location when the command exists. A general rule should be followed
21133 in that you should either assign @code{NULL} to any assigned pointers,
21134 or restore a valid location to the pointer before the command exits.
21136 Similar caution must be exercised with any structs, unions, and typedefs
21137 defined in @code{compile} command. Types defined in the @code{compile}
21138 command will no longer be available in the next @code{compile} command.
21139 Therefore, if you cast a variable to a type defined in the
21140 @code{compile} command, care must be taken to ensure that any future
21141 need to resolve the type can be achieved.
21144 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
21145 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
21146 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
21147 Compilation failed.
21148 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
21152 Variables that have been optimized away by the compiler are not
21153 accessible to the code submitted to the @code{compile} command.
21154 Access to those variables will generate a compiler error which @value{GDBN}
21155 will print to the console.
21158 @subsection Compiler search for the @code{compile} command
21160 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21161 which may not be obvious for remote targets of different architecture
21162 than where @value{GDBN} is running. Environment variable @env{PATH} on
21163 @value{GDBN} host is searched for @value{NGCC} binary matching the
21164 target architecture and operating system. This search can be overriden
21165 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21166 taken from shell that executed @value{GDBN}, it is not the value set by
21167 @value{GDBN} command @code{set environment}). @xref{Environment}.
21170 Specifically @env{PATH} is searched for binaries matching regular expression
21171 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21172 debugged. @var{arch} is processor name --- multiarch is supported, so for
21173 example both @code{i386} and @code{x86_64} targets look for pattern
21174 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21175 for pattern @code{s390x?}. @var{os} is currently supported only for
21176 pattern @code{linux(-gnu)?}.
21178 On Posix hosts the compiler driver @value{GDBN} needs to find also
21179 shared library @file{libcc1.so} from the compiler. It is searched in
21180 default shared library search path (overridable with usual environment
21181 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21182 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21183 according to the installation of the found compiler --- as possibly
21184 specified by the @code{set compile-gcc} command.
21187 @item set compile-gcc
21188 @cindex compile command driver filename override
21189 Set compilation command used for compiling and injecting code with the
21190 @code{compile} commands. If this option is not set (it is set to
21191 an empty string), the search described above will occur --- that is the
21194 @item show compile-gcc
21195 Displays the current compile command @value{NGCC} driver filename.
21196 If set, it is the main command @command{gcc}, found usually for example
21197 under name @file{x86_64-linux-gnu-gcc}.
21201 @chapter @value{GDBN} Files
21203 @value{GDBN} needs to know the file name of the program to be debugged,
21204 both in order to read its symbol table and in order to start your
21205 program. To debug a core dump of a previous run, you must also tell
21206 @value{GDBN} the name of the core dump file.
21209 * Files:: Commands to specify files
21210 * File Caching:: Information about @value{GDBN}'s file caching
21211 * Separate Debug Files:: Debugging information in separate files
21212 * MiniDebugInfo:: Debugging information in a special section
21213 * Index Files:: Index files speed up GDB
21214 * Symbol Errors:: Errors reading symbol files
21215 * Data Files:: GDB data files
21219 @section Commands to Specify Files
21221 @cindex symbol table
21222 @cindex core dump file
21224 You may want to specify executable and core dump file names. The usual
21225 way to do this is at start-up time, using the arguments to
21226 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21227 Out of @value{GDBN}}).
21229 Occasionally it is necessary to change to a different file during a
21230 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21231 specify a file you want to use. Or you are debugging a remote target
21232 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21233 Program}). In these situations the @value{GDBN} commands to specify
21234 new files are useful.
21237 @cindex executable file
21239 @item file @var{filename}
21240 Use @var{filename} as the program to be debugged. It is read for its
21241 symbols and for the contents of pure memory. It is also the program
21242 executed when you use the @code{run} command. If you do not specify a
21243 directory and the file is not found in the @value{GDBN} working directory,
21244 @value{GDBN} uses the environment variable @env{PATH} as a list of
21245 directories to search, just as the shell does when looking for a program
21246 to run. You can change the value of this variable, for both @value{GDBN}
21247 and your program, using the @code{path} command.
21249 @cindex unlinked object files
21250 @cindex patching object files
21251 You can load unlinked object @file{.o} files into @value{GDBN} using
21252 the @code{file} command. You will not be able to ``run'' an object
21253 file, but you can disassemble functions and inspect variables. Also,
21254 if the underlying BFD functionality supports it, you could use
21255 @kbd{gdb -write} to patch object files using this technique. Note
21256 that @value{GDBN} can neither interpret nor modify relocations in this
21257 case, so branches and some initialized variables will appear to go to
21258 the wrong place. But this feature is still handy from time to time.
21261 @code{file} with no argument makes @value{GDBN} discard any information it
21262 has on both executable file and the symbol table.
21265 @item exec-file @r{[} @var{filename} @r{]}
21266 Specify that the program to be run (but not the symbol table) is found
21267 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21268 if necessary to locate your program. Omitting @var{filename} means to
21269 discard information on the executable file.
21271 @kindex symbol-file
21272 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21273 Read symbol table information from file @var{filename}. @env{PATH} is
21274 searched when necessary. Use the @code{file} command to get both symbol
21275 table and program to run from the same file.
21277 If an optional @var{offset} is specified, it is added to the start
21278 address of each section in the symbol file. This is useful if the
21279 program is relocated at runtime, such as the Linux kernel with kASLR
21282 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21283 program's symbol table.
21285 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21286 some breakpoints and auto-display expressions. This is because they may
21287 contain pointers to the internal data recording symbols and data types,
21288 which are part of the old symbol table data being discarded inside
21291 @code{symbol-file} does not repeat if you press @key{RET} again after
21294 When @value{GDBN} is configured for a particular environment, it
21295 understands debugging information in whatever format is the standard
21296 generated for that environment; you may use either a @sc{gnu} compiler, or
21297 other compilers that adhere to the local conventions.
21298 Best results are usually obtained from @sc{gnu} compilers; for example,
21299 using @code{@value{NGCC}} you can generate debugging information for
21302 For most kinds of object files, with the exception of old SVR3 systems
21303 using COFF, the @code{symbol-file} command does not normally read the
21304 symbol table in full right away. Instead, it scans the symbol table
21305 quickly to find which source files and which symbols are present. The
21306 details are read later, one source file at a time, as they are needed.
21308 The purpose of this two-stage reading strategy is to make @value{GDBN}
21309 start up faster. For the most part, it is invisible except for
21310 occasional pauses while the symbol table details for a particular source
21311 file are being read. (The @code{set verbose} command can turn these
21312 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21313 Warnings and Messages}.)
21315 We have not implemented the two-stage strategy for COFF yet. When the
21316 symbol table is stored in COFF format, @code{symbol-file} reads the
21317 symbol table data in full right away. Note that ``stabs-in-COFF''
21318 still does the two-stage strategy, since the debug info is actually
21322 @cindex reading symbols immediately
21323 @cindex symbols, reading immediately
21324 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21325 @itemx file @r{[} -readnow @r{]} @var{filename}
21326 You can override the @value{GDBN} two-stage strategy for reading symbol
21327 tables by using the @samp{-readnow} option with any of the commands that
21328 load symbol table information, if you want to be sure @value{GDBN} has the
21329 entire symbol table available.
21331 @cindex @code{-readnever}, option for symbol-file command
21332 @cindex never read symbols
21333 @cindex symbols, never read
21334 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21335 @itemx file @r{[} -readnever @r{]} @var{filename}
21336 You can instruct @value{GDBN} to never read the symbolic information
21337 contained in @var{filename} by using the @samp{-readnever} option.
21338 @xref{--readnever}.
21340 @c FIXME: for now no mention of directories, since this seems to be in
21341 @c flux. 13mar1992 status is that in theory GDB would look either in
21342 @c current dir or in same dir as myprog; but issues like competing
21343 @c GDB's, or clutter in system dirs, mean that in practice right now
21344 @c only current dir is used. FFish says maybe a special GDB hierarchy
21345 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21349 @item core-file @r{[}@var{filename}@r{]}
21351 Specify the whereabouts of a core dump file to be used as the ``contents
21352 of memory''. Traditionally, core files contain only some parts of the
21353 address space of the process that generated them; @value{GDBN} can access the
21354 executable file itself for other parts.
21356 @code{core-file} with no argument specifies that no core file is
21359 Note that the core file is ignored when your program is actually running
21360 under @value{GDBN}. So, if you have been running your program and you
21361 wish to debug a core file instead, you must kill the subprocess in which
21362 the program is running. To do this, use the @code{kill} command
21363 (@pxref{Kill Process, ,Killing the Child Process}).
21365 @kindex add-symbol-file
21366 @cindex dynamic linking
21367 @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{]}
21368 The @code{add-symbol-file} command reads additional symbol table
21369 information from the file @var{filename}. You would use this command
21370 when @var{filename} has been dynamically loaded (by some other means)
21371 into the program that is running. The @var{textaddress} parameter gives
21372 the memory address at which the file's text section has been loaded.
21373 You can additionally specify the base address of other sections using
21374 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21375 If a section is omitted, @value{GDBN} will use its default addresses
21376 as found in @var{filename}. Any @var{address} or @var{textaddress}
21377 can be given as an expression.
21379 If an optional @var{offset} is specified, it is added to the start
21380 address of each section, except those for which the address was
21381 specified explicitly.
21383 The symbol table of the file @var{filename} is added to the symbol table
21384 originally read with the @code{symbol-file} command. You can use the
21385 @code{add-symbol-file} command any number of times; the new symbol data
21386 thus read is kept in addition to the old.
21388 Changes can be reverted using the command @code{remove-symbol-file}.
21390 @cindex relocatable object files, reading symbols from
21391 @cindex object files, relocatable, reading symbols from
21392 @cindex reading symbols from relocatable object files
21393 @cindex symbols, reading from relocatable object files
21394 @cindex @file{.o} files, reading symbols from
21395 Although @var{filename} is typically a shared library file, an
21396 executable file, or some other object file which has been fully
21397 relocated for loading into a process, you can also load symbolic
21398 information from relocatable @file{.o} files, as long as:
21402 the file's symbolic information refers only to linker symbols defined in
21403 that file, not to symbols defined by other object files,
21405 every section the file's symbolic information refers to has actually
21406 been loaded into the inferior, as it appears in the file, and
21408 you can determine the address at which every section was loaded, and
21409 provide these to the @code{add-symbol-file} command.
21413 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21414 relocatable files into an already running program; such systems
21415 typically make the requirements above easy to meet. However, it's
21416 important to recognize that many native systems use complex link
21417 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21418 assembly, for example) that make the requirements difficult to meet. In
21419 general, one cannot assume that using @code{add-symbol-file} to read a
21420 relocatable object file's symbolic information will have the same effect
21421 as linking the relocatable object file into the program in the normal
21424 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21426 @kindex remove-symbol-file
21427 @item remove-symbol-file @var{filename}
21428 @item remove-symbol-file -a @var{address}
21429 Remove a symbol file added via the @code{add-symbol-file} command. The
21430 file to remove can be identified by its @var{filename} or by an @var{address}
21431 that lies within the boundaries of this symbol file in memory. Example:
21434 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21435 add symbol table from file "/home/user/gdb/mylib.so" at
21436 .text_addr = 0x7ffff7ff9480
21438 Reading symbols from /home/user/gdb/mylib.so...
21439 (gdb) remove-symbol-file -a 0x7ffff7ff9480
21440 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21445 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21447 @kindex add-symbol-file-from-memory
21448 @cindex @code{syscall DSO}
21449 @cindex load symbols from memory
21450 @item add-symbol-file-from-memory @var{address}
21451 Load symbols from the given @var{address} in a dynamically loaded
21452 object file whose image is mapped directly into the inferior's memory.
21453 For example, the Linux kernel maps a @code{syscall DSO} into each
21454 process's address space; this DSO provides kernel-specific code for
21455 some system calls. The argument can be any expression whose
21456 evaluation yields the address of the file's shared object file header.
21457 For this command to work, you must have used @code{symbol-file} or
21458 @code{exec-file} commands in advance.
21461 @item section @var{section} @var{addr}
21462 The @code{section} command changes the base address of the named
21463 @var{section} of the exec file to @var{addr}. This can be used if the
21464 exec file does not contain section addresses, (such as in the
21465 @code{a.out} format), or when the addresses specified in the file
21466 itself are wrong. Each section must be changed separately. The
21467 @code{info files} command, described below, lists all the sections and
21471 @kindex info target
21474 @code{info files} and @code{info target} are synonymous; both print the
21475 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21476 including the names of the executable and core dump files currently in
21477 use by @value{GDBN}, and the files from which symbols were loaded. The
21478 command @code{help target} lists all possible targets rather than
21481 @kindex maint info sections
21482 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21483 Another command that can give you extra information about program sections
21484 is @code{maint info sections}. In addition to the section information
21485 displayed by @code{info files}, this command displays the flags and file
21486 offset of each section in the executable and core dump files.
21488 When @samp{-all-objects} is passed then sections from all loaded object
21489 files, including shared libraries, are printed.
21491 The optional @var{filter-list} is a space separated list of filter
21492 keywords. Sections that match any one of the filter criteria will be
21493 printed. There are two types of filter:
21496 @item @var{section-name}
21497 Display information about any section named @var{section-name}.
21498 @item @var{section-flag}
21499 Display information for any section with @var{section-flag}. The
21500 section flags that @value{GDBN} currently knows about are:
21503 Section will have space allocated in the process when loaded.
21504 Set for all sections except those containing debug information.
21506 Section will be loaded from the file into the child process memory.
21507 Set for pre-initialized code and data, clear for @code{.bss} sections.
21509 Section needs to be relocated before loading.
21511 Section cannot be modified by the child process.
21513 Section contains executable code only.
21515 Section contains data only (no executable code).
21517 Section will reside in ROM.
21519 Section contains data for constructor/destructor lists.
21521 Section is not empty.
21523 An instruction to the linker to not output the section.
21524 @item COFF_SHARED_LIBRARY
21525 A notification to the linker that the section contains
21526 COFF shared library information.
21528 Section contains common symbols.
21532 @kindex maint info target-sections
21533 @item maint info target-sections
21534 This command prints @value{GDBN}'s internal section table. For each
21535 target @value{GDBN} maintains a table containing the allocatable
21536 sections from all currently mapped objects, along with information
21537 about where the section is mapped.
21539 @kindex set trust-readonly-sections
21540 @cindex read-only sections
21541 @item set trust-readonly-sections on
21542 Tell @value{GDBN} that readonly sections in your object file
21543 really are read-only (i.e.@: that their contents will not change).
21544 In that case, @value{GDBN} can fetch values from these sections
21545 out of the object file, rather than from the target program.
21546 For some targets (notably embedded ones), this can be a significant
21547 enhancement to debugging performance.
21549 The default is off.
21551 @item set trust-readonly-sections off
21552 Tell @value{GDBN} not to trust readonly sections. This means that
21553 the contents of the section might change while the program is running,
21554 and must therefore be fetched from the target when needed.
21556 @item show trust-readonly-sections
21557 Show the current setting of trusting readonly sections.
21560 All file-specifying commands allow both absolute and relative file names
21561 as arguments. @value{GDBN} always converts the file name to an absolute file
21562 name and remembers it that way.
21564 @cindex shared libraries
21565 @anchor{Shared Libraries}
21566 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21567 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21568 DSBT (TIC6X) shared libraries.
21570 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21571 shared libraries. @xref{Expat}.
21573 @value{GDBN} automatically loads symbol definitions from shared libraries
21574 when you use the @code{run} command, or when you examine a core file.
21575 (Before you issue the @code{run} command, @value{GDBN} does not understand
21576 references to a function in a shared library, however---unless you are
21577 debugging a core file).
21579 @c FIXME: some @value{GDBN} release may permit some refs to undef
21580 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21581 @c FIXME...lib; check this from time to time when updating manual
21583 There are times, however, when you may wish to not automatically load
21584 symbol definitions from shared libraries, such as when they are
21585 particularly large or there are many of them.
21587 To control the automatic loading of shared library symbols, use the
21591 @kindex set auto-solib-add
21592 @item set auto-solib-add @var{mode}
21593 If @var{mode} is @code{on}, symbols from all shared object libraries
21594 will be loaded automatically when the inferior begins execution, you
21595 attach to an independently started inferior, or when the dynamic linker
21596 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21597 is @code{off}, symbols must be loaded manually, using the
21598 @code{sharedlibrary} command. The default value is @code{on}.
21600 @cindex memory used for symbol tables
21601 If your program uses lots of shared libraries with debug info that
21602 takes large amounts of memory, you can decrease the @value{GDBN}
21603 memory footprint by preventing it from automatically loading the
21604 symbols from shared libraries. To that end, type @kbd{set
21605 auto-solib-add off} before running the inferior, then load each
21606 library whose debug symbols you do need with @kbd{sharedlibrary
21607 @var{regexp}}, where @var{regexp} is a regular expression that matches
21608 the libraries whose symbols you want to be loaded.
21610 @kindex show auto-solib-add
21611 @item show auto-solib-add
21612 Display the current autoloading mode.
21615 @cindex load shared library
21616 To explicitly load shared library symbols, use the @code{sharedlibrary}
21620 @kindex info sharedlibrary
21622 @item info share @var{regex}
21623 @itemx info sharedlibrary @var{regex}
21624 Print the names of the shared libraries which are currently loaded
21625 that match @var{regex}. If @var{regex} is omitted then print
21626 all shared libraries that are loaded.
21629 @item info dll @var{regex}
21630 This is an alias of @code{info sharedlibrary}.
21632 @kindex sharedlibrary
21634 @item sharedlibrary @var{regex}
21635 @itemx share @var{regex}
21636 Load shared object library symbols for files matching a
21637 Unix regular expression.
21638 As with files loaded automatically, it only loads shared libraries
21639 required by your program for a core file or after typing @code{run}. If
21640 @var{regex} is omitted all shared libraries required by your program are
21643 @item nosharedlibrary
21644 @kindex nosharedlibrary
21645 @cindex unload symbols from shared libraries
21646 Unload all shared object library symbols. This discards all symbols
21647 that have been loaded from all shared libraries. Symbols from shared
21648 libraries that were loaded by explicit user requests are not
21652 Sometimes you may wish that @value{GDBN} stops and gives you control
21653 when any of shared library events happen. The best way to do this is
21654 to use @code{catch load} and @code{catch unload} (@pxref{Set
21657 @value{GDBN} also supports the @code{set stop-on-solib-events}
21658 command for this. This command exists for historical reasons. It is
21659 less useful than setting a catchpoint, because it does not allow for
21660 conditions or commands as a catchpoint does.
21663 @item set stop-on-solib-events
21664 @kindex set stop-on-solib-events
21665 This command controls whether @value{GDBN} should give you control
21666 when the dynamic linker notifies it about some shared library event.
21667 The most common event of interest is loading or unloading of a new
21670 @item show stop-on-solib-events
21671 @kindex show stop-on-solib-events
21672 Show whether @value{GDBN} stops and gives you control when shared
21673 library events happen.
21676 Shared libraries are also supported in many cross or remote debugging
21677 configurations. @value{GDBN} needs to have access to the target's libraries;
21678 this can be accomplished either by providing copies of the libraries
21679 on the host system, or by asking @value{GDBN} to automatically retrieve the
21680 libraries from the target. If copies of the target libraries are
21681 provided, they need to be the same as the target libraries, although the
21682 copies on the target can be stripped as long as the copies on the host are
21685 @cindex where to look for shared libraries
21686 For remote debugging, you need to tell @value{GDBN} where the target
21687 libraries are, so that it can load the correct copies---otherwise, it
21688 may try to load the host's libraries. @value{GDBN} has two variables
21689 to specify the search directories for target libraries.
21692 @cindex prefix for executable and shared library file names
21693 @cindex system root, alternate
21694 @kindex set solib-absolute-prefix
21695 @kindex set sysroot
21696 @item set sysroot @var{path}
21697 Use @var{path} as the system root for the program being debugged. Any
21698 absolute shared library paths will be prefixed with @var{path}; many
21699 runtime loaders store the absolute paths to the shared library in the
21700 target program's memory. When starting processes remotely, and when
21701 attaching to already-running processes (local or remote), their
21702 executable filenames will be prefixed with @var{path} if reported to
21703 @value{GDBN} as absolute by the operating system. If you use
21704 @code{set sysroot} to find executables and shared libraries, they need
21705 to be laid out in the same way that they are on the target, with
21706 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21709 If @var{path} starts with the sequence @file{target:} and the target
21710 system is remote then @value{GDBN} will retrieve the target binaries
21711 from the remote system. This is only supported when using a remote
21712 target that supports the @code{remote get} command (@pxref{File
21713 Transfer,,Sending files to a remote system}). The part of @var{path}
21714 following the initial @file{target:} (if present) is used as system
21715 root prefix on the remote file system. If @var{path} starts with the
21716 sequence @file{remote:} this is converted to the sequence
21717 @file{target:} by @code{set sysroot}@footnote{Historically the
21718 functionality to retrieve binaries from the remote system was
21719 provided by prefixing @var{path} with @file{remote:}}. If you want
21720 to specify a local system root using a directory that happens to be
21721 named @file{target:} or @file{remote:}, you need to use some
21722 equivalent variant of the name like @file{./target:}.
21724 For targets with an MS-DOS based filesystem, such as MS-Windows,
21725 @value{GDBN} tries prefixing a few variants of the target
21726 absolute file name with @var{path}. But first, on Unix hosts,
21727 @value{GDBN} converts all backslash directory separators into forward
21728 slashes, because the backslash is not a directory separator on Unix:
21731 c:\foo\bar.dll @result{} c:/foo/bar.dll
21734 Then, @value{GDBN} attempts prefixing the target file name with
21735 @var{path}, and looks for the resulting file name in the host file
21739 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21742 If that does not find the binary, @value{GDBN} tries removing
21743 the @samp{:} character from the drive spec, both for convenience, and,
21744 for the case of the host file system not supporting file names with
21748 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21751 This makes it possible to have a system root that mirrors a target
21752 with more than one drive. E.g., you may want to setup your local
21753 copies of the target system shared libraries like so (note @samp{c} vs
21757 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21758 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21759 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21763 and point the system root at @file{/path/to/sysroot}, so that
21764 @value{GDBN} can find the correct copies of both
21765 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21767 If that still does not find the binary, @value{GDBN} tries
21768 removing the whole drive spec from the target file name:
21771 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21774 This last lookup makes it possible to not care about the drive name,
21775 if you don't want or need to.
21777 The @code{set solib-absolute-prefix} command is an alias for @code{set
21780 @cindex default system root
21781 @cindex @samp{--with-sysroot}
21782 You can set the default system root by using the configure-time
21783 @samp{--with-sysroot} option. If the system root is inside
21784 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21785 @samp{--exec-prefix}), then the default system root will be updated
21786 automatically if the installed @value{GDBN} is moved to a new
21789 @kindex show sysroot
21791 Display the current executable and shared library prefix.
21793 @kindex set solib-search-path
21794 @item set solib-search-path @var{path}
21795 If this variable is set, @var{path} is a colon-separated list of
21796 directories to search for shared libraries. @samp{solib-search-path}
21797 is used after @samp{sysroot} fails to locate the library, or if the
21798 path to the library is relative instead of absolute. If you want to
21799 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21800 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21801 finding your host's libraries. @samp{sysroot} is preferred; setting
21802 it to a nonexistent directory may interfere with automatic loading
21803 of shared library symbols.
21805 @kindex show solib-search-path
21806 @item show solib-search-path
21807 Display the current shared library search path.
21809 @cindex DOS file-name semantics of file names.
21810 @kindex set target-file-system-kind (unix|dos-based|auto)
21811 @kindex show target-file-system-kind
21812 @item set target-file-system-kind @var{kind}
21813 Set assumed file system kind for target reported file names.
21815 Shared library file names as reported by the target system may not
21816 make sense as is on the system @value{GDBN} is running on. For
21817 example, when remote debugging a target that has MS-DOS based file
21818 system semantics, from a Unix host, the target may be reporting to
21819 @value{GDBN} a list of loaded shared libraries with file names such as
21820 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21821 drive letters, so the @samp{c:\} prefix is not normally understood as
21822 indicating an absolute file name, and neither is the backslash
21823 normally considered a directory separator character. In that case,
21824 the native file system would interpret this whole absolute file name
21825 as a relative file name with no directory components. This would make
21826 it impossible to point @value{GDBN} at a copy of the remote target's
21827 shared libraries on the host using @code{set sysroot}, and impractical
21828 with @code{set solib-search-path}. Setting
21829 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21830 to interpret such file names similarly to how the target would, and to
21831 map them to file names valid on @value{GDBN}'s native file system
21832 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21833 to one of the supported file system kinds. In that case, @value{GDBN}
21834 tries to determine the appropriate file system variant based on the
21835 current target's operating system (@pxref{ABI, ,Configuring the
21836 Current ABI}). The supported file system settings are:
21840 Instruct @value{GDBN} to assume the target file system is of Unix
21841 kind. Only file names starting the forward slash (@samp{/}) character
21842 are considered absolute, and the directory separator character is also
21846 Instruct @value{GDBN} to assume the target file system is DOS based.
21847 File names starting with either a forward slash, or a drive letter
21848 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21849 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21850 considered directory separators.
21853 Instruct @value{GDBN} to use the file system kind associated with the
21854 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21855 This is the default.
21859 @cindex file name canonicalization
21860 @cindex base name differences
21861 When processing file names provided by the user, @value{GDBN}
21862 frequently needs to compare them to the file names recorded in the
21863 program's debug info. Normally, @value{GDBN} compares just the
21864 @dfn{base names} of the files as strings, which is reasonably fast
21865 even for very large programs. (The base name of a file is the last
21866 portion of its name, after stripping all the leading directories.)
21867 This shortcut in comparison is based upon the assumption that files
21868 cannot have more than one base name. This is usually true, but
21869 references to files that use symlinks or similar filesystem
21870 facilities violate that assumption. If your program records files
21871 using such facilities, or if you provide file names to @value{GDBN}
21872 using symlinks etc., you can set @code{basenames-may-differ} to
21873 @code{true} to instruct @value{GDBN} to completely canonicalize each
21874 pair of file names it needs to compare. This will make file-name
21875 comparisons accurate, but at a price of a significant slowdown.
21878 @item set basenames-may-differ
21879 @kindex set basenames-may-differ
21880 Set whether a source file may have multiple base names.
21882 @item show basenames-may-differ
21883 @kindex show basenames-may-differ
21884 Show whether a source file may have multiple base names.
21888 @section File Caching
21889 @cindex caching of opened files
21890 @cindex caching of bfd objects
21892 To speed up file loading, and reduce memory usage, @value{GDBN} will
21893 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21894 BFD, bfd, The Binary File Descriptor Library}. The following commands
21895 allow visibility and control of the caching behavior.
21898 @kindex maint info bfds
21899 @item maint info bfds
21900 This prints information about each @code{bfd} object that is known to
21903 @kindex maint set bfd-sharing
21904 @kindex maint show bfd-sharing
21905 @kindex bfd caching
21906 @item maint set bfd-sharing
21907 @item maint show bfd-sharing
21908 Control whether @code{bfd} objects can be shared. When sharing is
21909 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21910 than reopening the same file. Turning sharing off does not cause
21911 already shared @code{bfd} objects to be unshared, but all future files
21912 that are opened will create a new @code{bfd} object. Similarly,
21913 re-enabling sharing does not cause multiple existing @code{bfd}
21914 objects to be collapsed into a single shared @code{bfd} object.
21916 @kindex set debug bfd-cache @var{level}
21917 @kindex bfd caching
21918 @item set debug bfd-cache @var{level}
21919 Turns on debugging of the bfd cache, setting the level to @var{level}.
21921 @kindex show debug bfd-cache
21922 @kindex bfd caching
21923 @item show debug bfd-cache
21924 Show the current debugging level of the bfd cache.
21927 @node Separate Debug Files
21928 @section Debugging Information in Separate Files
21929 @cindex separate debugging information files
21930 @cindex debugging information in separate files
21931 @cindex @file{.debug} subdirectories
21932 @cindex debugging information directory, global
21933 @cindex global debugging information directories
21934 @cindex build ID, and separate debugging files
21935 @cindex @file{.build-id} directory
21937 @value{GDBN} allows you to put a program's debugging information in a
21938 file separate from the executable itself, in a way that allows
21939 @value{GDBN} to find and load the debugging information automatically.
21940 Since debugging information can be very large---sometimes larger
21941 than the executable code itself---some systems distribute debugging
21942 information for their executables in separate files, which users can
21943 install only when they need to debug a problem.
21945 @value{GDBN} supports two ways of specifying the separate debug info
21950 The executable contains a @dfn{debug link} that specifies the name of
21951 the separate debug info file. The separate debug file's name is
21952 usually @file{@var{executable}.debug}, where @var{executable} is the
21953 name of the corresponding executable file without leading directories
21954 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21955 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21956 checksum for the debug file, which @value{GDBN} uses to validate that
21957 the executable and the debug file came from the same build.
21961 The executable contains a @dfn{build ID}, a unique bit string that is
21962 also present in the corresponding debug info file. (This is supported
21963 only on some operating systems, when using the ELF or PE file formats
21964 for binary files and the @sc{gnu} Binutils.) For more details about
21965 this feature, see the description of the @option{--build-id}
21966 command-line option in @ref{Options, , Command Line Options, ld,
21967 The GNU Linker}. The debug info file's name is not specified
21968 explicitly by the build ID, but can be computed from the build ID, see
21972 Depending on the way the debug info file is specified, @value{GDBN}
21973 uses two different methods of looking for the debug file:
21977 For the ``debug link'' method, @value{GDBN} looks up the named file in
21978 the directory of the executable file, then in a subdirectory of that
21979 directory named @file{.debug}, and finally under each one of the
21980 global debug directories, in a subdirectory whose name is identical to
21981 the leading directories of the executable's absolute file name. (On
21982 MS-Windows/MS-DOS, the drive letter of the executable's leading
21983 directories is converted to a one-letter subdirectory, i.e.@:
21984 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21985 filesystems disallow colons in file names.)
21988 For the ``build ID'' method, @value{GDBN} looks in the
21989 @file{.build-id} subdirectory of each one of the global debug directories for
21990 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21991 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21992 are the rest of the bit string. (Real build ID strings are 32 or more
21993 hex characters, not 10.) @value{GDBN} can automatically query
21994 @code{debuginfod} servers using build IDs in order to download separate debug
21995 files that cannot be found locally. For more information see @ref{Debuginfod}.
21998 So, for example, suppose you ask @value{GDBN} to debug
21999 @file{/usr/bin/ls}, which has a debug link that specifies the
22000 file @file{ls.debug}, and a build ID whose value in hex is
22001 @code{abcdef1234}. If the list of the global debug directories includes
22002 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
22003 debug information files, in the indicated order:
22007 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
22009 @file{/usr/bin/ls.debug}
22011 @file{/usr/bin/.debug/ls.debug}
22013 @file{/usr/lib/debug/usr/bin/ls.debug}.
22016 If the debug file still has not been found and @code{debuginfod}
22017 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
22018 file from @code{debuginfod} servers.
22020 @anchor{debug-file-directory}
22021 Global debugging info directories default to what is set by @value{GDBN}
22022 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
22023 you can also set the global debugging info directories, and view the list
22024 @value{GDBN} is currently using.
22028 @kindex set debug-file-directory
22029 @item set debug-file-directory @var{directories}
22030 Set the directories which @value{GDBN} searches for separate debugging
22031 information files to @var{directory}. Multiple path components can be set
22032 concatenating them by a path separator.
22034 @kindex show debug-file-directory
22035 @item show debug-file-directory
22036 Show the directories @value{GDBN} searches for separate debugging
22041 @cindex @code{.gnu_debuglink} sections
22042 @cindex debug link sections
22043 A debug link is a special section of the executable file named
22044 @code{.gnu_debuglink}. The section must contain:
22048 A filename, with any leading directory components removed, followed by
22051 zero to three bytes of padding, as needed to reach the next four-byte
22052 boundary within the section, and
22054 a four-byte CRC checksum, stored in the same endianness used for the
22055 executable file itself. The checksum is computed on the debugging
22056 information file's full contents by the function given below, passing
22057 zero as the @var{crc} argument.
22060 Any executable file format can carry a debug link, as long as it can
22061 contain a section named @code{.gnu_debuglink} with the contents
22064 @cindex @code{.note.gnu.build-id} sections
22065 @cindex build ID sections
22066 The build ID is a special section in the executable file (and in other
22067 ELF binary files that @value{GDBN} may consider). This section is
22068 often named @code{.note.gnu.build-id}, but that name is not mandatory.
22069 It contains unique identification for the built files---the ID remains
22070 the same across multiple builds of the same build tree. The default
22071 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
22072 content for the build ID string. The same section with an identical
22073 value is present in the original built binary with symbols, in its
22074 stripped variant, and in the separate debugging information file.
22076 The debugging information file itself should be an ordinary
22077 executable, containing a full set of linker symbols, sections, and
22078 debugging information. The sections of the debugging information file
22079 should have the same names, addresses, and sizes as the original file,
22080 but they need not contain any data---much like a @code{.bss} section
22081 in an ordinary executable.
22083 The @sc{gnu} binary utilities (Binutils) package includes the
22084 @samp{objcopy} utility that can produce
22085 the separated executable / debugging information file pairs using the
22086 following commands:
22089 @kbd{objcopy --only-keep-debug foo foo.debug}
22094 These commands remove the debugging
22095 information from the executable file @file{foo} and place it in the file
22096 @file{foo.debug}. You can use the first, second or both methods to link the
22101 The debug link method needs the following additional command to also leave
22102 behind a debug link in @file{foo}:
22105 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
22108 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
22109 a version of the @code{strip} command such that the command @kbd{strip foo -f
22110 foo.debug} has the same functionality as the two @code{objcopy} commands and
22111 the @code{ln -s} command above, together.
22114 Build ID gets embedded into the main executable using @code{ld --build-id} or
22115 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
22116 compatibility fixes for debug files separation are present in @sc{gnu} binary
22117 utilities (Binutils) package since version 2.18.
22122 @cindex CRC algorithm definition
22123 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
22124 IEEE 802.3 using the polynomial:
22126 @c TexInfo requires naked braces for multi-digit exponents for Tex
22127 @c output, but this causes HTML output to barf. HTML has to be set using
22128 @c raw commands. So we end up having to specify this equation in 2
22133 <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>
22134 + <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
22140 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
22141 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
22145 The function is computed byte at a time, taking the least
22146 significant bit of each byte first. The initial pattern
22147 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
22148 the final result is inverted to ensure trailing zeros also affect the
22151 @emph{Note:} This is the same CRC polynomial as used in handling the
22152 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
22153 However in the case of the Remote Serial Protocol, the CRC is computed
22154 @emph{most} significant bit first, and the result is not inverted, so
22155 trailing zeros have no effect on the CRC value.
22157 To complete the description, we show below the code of the function
22158 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22159 initially supplied @code{crc} argument means that an initial call to
22160 this function passing in zero will start computing the CRC using
22163 @kindex gnu_debuglink_crc32
22166 gnu_debuglink_crc32 (unsigned long crc,
22167 unsigned char *buf, size_t len)
22169 static const unsigned long crc32_table[256] =
22171 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22172 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22173 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22174 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22175 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22176 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22177 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22178 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22179 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22180 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22181 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22182 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22183 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22184 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22185 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22186 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22187 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22188 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22189 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22190 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22191 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22192 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22193 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22194 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22195 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22196 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22197 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22198 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22199 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22200 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22201 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22202 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22203 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22204 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22205 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22206 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22207 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22208 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22209 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22210 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22211 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22212 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22213 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22214 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22215 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22216 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22217 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22218 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22219 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22220 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22221 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22224 unsigned char *end;
22226 crc = ~crc & 0xffffffff;
22227 for (end = buf + len; buf < end; ++buf)
22228 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22229 return ~crc & 0xffffffff;
22234 This computation does not apply to the ``build ID'' method.
22236 @node MiniDebugInfo
22237 @section Debugging information in a special section
22238 @cindex separate debug sections
22239 @cindex @samp{.gnu_debugdata} section
22241 Some systems ship pre-built executables and libraries that have a
22242 special @samp{.gnu_debugdata} section. This feature is called
22243 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22244 is used to supply extra symbols for backtraces.
22246 The intent of this section is to provide extra minimal debugging
22247 information for use in simple backtraces. It is not intended to be a
22248 replacement for full separate debugging information (@pxref{Separate
22249 Debug Files}). The example below shows the intended use; however,
22250 @value{GDBN} does not currently put restrictions on what sort of
22251 debugging information might be included in the section.
22253 @value{GDBN} has support for this extension. If the section exists,
22254 then it is used provided that no other source of debugging information
22255 can be found, and that @value{GDBN} was configured with LZMA support.
22257 This section can be easily created using @command{objcopy} and other
22258 standard utilities:
22261 # Extract the dynamic symbols from the main binary, there is no need
22262 # to also have these in the normal symbol table.
22263 nm -D @var{binary} --format=posix --defined-only \
22264 | awk '@{ print $1 @}' | sort > dynsyms
22266 # Extract all the text (i.e. function) symbols from the debuginfo.
22267 # (Note that we actually also accept "D" symbols, for the benefit
22268 # of platforms like PowerPC64 that use function descriptors.)
22269 nm @var{binary} --format=posix --defined-only \
22270 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22273 # Keep all the function symbols not already in the dynamic symbol
22275 comm -13 dynsyms funcsyms > keep_symbols
22277 # Separate full debug info into debug binary.
22278 objcopy --only-keep-debug @var{binary} debug
22280 # Copy the full debuginfo, keeping only a minimal set of symbols and
22281 # removing some unnecessary sections.
22282 objcopy -S --remove-section .gdb_index --remove-section .comment \
22283 --keep-symbols=keep_symbols debug mini_debuginfo
22285 # Drop the full debug info from the original binary.
22286 strip --strip-all -R .comment @var{binary}
22288 # Inject the compressed data into the .gnu_debugdata section of the
22291 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22295 @section Index Files Speed Up @value{GDBN}
22296 @cindex index files
22297 @cindex @samp{.gdb_index} section
22299 When @value{GDBN} finds a symbol file, it scans the symbols in the
22300 file in order to construct an internal symbol table. This lets most
22301 @value{GDBN} operations work quickly---at the cost of a delay early
22302 on. For large programs, this delay can be quite lengthy, so
22303 @value{GDBN} provides a way to build an index, which speeds up
22306 For convenience, @value{GDBN} comes with a program,
22307 @command{gdb-add-index}, which can be used to add the index to a
22308 symbol file. It takes the symbol file as its only argument:
22311 $ gdb-add-index symfile
22314 @xref{gdb-add-index}.
22316 It is also possible to do the work manually. Here is what
22317 @command{gdb-add-index} does behind the curtains.
22319 The index is stored as a section in the symbol file. @value{GDBN} can
22320 write the index to a file, then you can put it into the symbol file
22321 using @command{objcopy}.
22323 To create an index file, use the @code{save gdb-index} command:
22326 @item save gdb-index [-dwarf-5] @var{directory}
22327 @kindex save gdb-index
22328 Create index files for all symbol files currently known by
22329 @value{GDBN}. For each known @var{symbol-file}, this command by
22330 default creates it produces a single file
22331 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22332 the @option{-dwarf-5} option, it produces 2 files:
22333 @file{@var{symbol-file}.debug_names} and
22334 @file{@var{symbol-file}.debug_str}. The files are created in the
22335 given @var{directory}.
22338 Once you have created an index file you can merge it into your symbol
22339 file, here named @file{symfile}, using @command{objcopy}:
22342 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22343 --set-section-flags .gdb_index=readonly symfile symfile
22346 Or for @code{-dwarf-5}:
22349 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22350 $ cat symfile.debug_str >>symfile.debug_str.new
22351 $ objcopy --add-section .debug_names=symfile.gdb-index \
22352 --set-section-flags .debug_names=readonly \
22353 --update-section .debug_str=symfile.debug_str.new symfile symfile
22356 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22357 sections that have been deprecated. Usually they are deprecated because
22358 they are missing a new feature or have performance issues.
22359 To tell @value{GDBN} to use a deprecated index section anyway
22360 specify @code{set use-deprecated-index-sections on}.
22361 The default is @code{off}.
22362 This can speed up startup, but may result in some functionality being lost.
22363 @xref{Index Section Format}.
22365 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22366 must be done before gdb reads the file. The following will not work:
22369 $ gdb -ex "set use-deprecated-index-sections on" <program>
22372 Instead you must do, for example,
22375 $ gdb -iex "set use-deprecated-index-sections on" <program>
22378 Indices only work when using DWARF debugging information, not stabs.
22380 @subsection Automatic symbol index cache
22382 @cindex automatic symbol index cache
22383 It is possible for @value{GDBN} to automatically save a copy of this index in a
22384 cache on disk and retrieve it from there when loading the same binary in the
22385 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22386 The following commands can be used to tweak the behavior of the index cache.
22390 @kindex set index-cache
22391 @item set index-cache enabled on
22392 @itemx set index-cache enabled off
22393 Enable or disable the use of the symbol index cache.
22395 @item set index-cache directory @var{directory}
22396 @kindex show index-cache
22397 @itemx show index-cache directory
22398 Set/show the directory where index files will be saved.
22400 The default value for this directory depends on the host platform. On
22401 most systems, the index is cached in the @file{gdb} subdirectory of
22402 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22403 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22404 of your home directory. However, on some systems, the default may
22405 differ according to local convention.
22407 There is no limit on the disk space used by index cache. It is perfectly safe
22408 to delete the content of that directory to free up disk space.
22410 @item show index-cache stats
22411 Print the number of cache hits and misses since the launch of @value{GDBN}.
22415 @node Symbol Errors
22416 @section Errors Reading Symbol Files
22418 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22419 such as symbol types it does not recognize, or known bugs in compiler
22420 output. By default, @value{GDBN} does not notify you of such problems, since
22421 they are relatively common and primarily of interest to people
22422 debugging compilers. If you are interested in seeing information
22423 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22424 only one message about each such type of problem, no matter how many
22425 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22426 to see how many times the problems occur, with the @code{set
22427 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22430 The messages currently printed, and their meanings, include:
22433 @item inner block not inside outer block in @var{symbol}
22435 The symbol information shows where symbol scopes begin and end
22436 (such as at the start of a function or a block of statements). This
22437 error indicates that an inner scope block is not fully contained
22438 in its outer scope blocks.
22440 @value{GDBN} circumvents the problem by treating the inner block as if it had
22441 the same scope as the outer block. In the error message, @var{symbol}
22442 may be shown as ``@code{(don't know)}'' if the outer block is not a
22445 @item block at @var{address} out of order
22447 The symbol information for symbol scope blocks should occur in
22448 order of increasing addresses. This error indicates that it does not
22451 @value{GDBN} does not circumvent this problem, and has trouble
22452 locating symbols in the source file whose symbols it is reading. (You
22453 can often determine what source file is affected by specifying
22454 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22457 @item bad block start address patched
22459 The symbol information for a symbol scope block has a start address
22460 smaller than the address of the preceding source line. This is known
22461 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22463 @value{GDBN} circumvents the problem by treating the symbol scope block as
22464 starting on the previous source line.
22466 @item bad string table offset in symbol @var{n}
22469 Symbol number @var{n} contains a pointer into the string table which is
22470 larger than the size of the string table.
22472 @value{GDBN} circumvents the problem by considering the symbol to have the
22473 name @code{foo}, which may cause other problems if many symbols end up
22476 @item unknown symbol type @code{0x@var{nn}}
22478 The symbol information contains new data types that @value{GDBN} does
22479 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22480 uncomprehended information, in hexadecimal.
22482 @value{GDBN} circumvents the error by ignoring this symbol information.
22483 This usually allows you to debug your program, though certain symbols
22484 are not accessible. If you encounter such a problem and feel like
22485 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22486 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22487 and examine @code{*bufp} to see the symbol.
22489 @item stub type has NULL name
22491 @value{GDBN} could not find the full definition for a struct or class.
22493 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22494 The symbol information for a C@t{++} member function is missing some
22495 information that recent versions of the compiler should have output for
22498 @item info mismatch between compiler and debugger
22500 @value{GDBN} could not parse a type specification output by the compiler.
22505 @section GDB Data Files
22507 @cindex prefix for data files
22508 @value{GDBN} will sometimes read an auxiliary data file. These files
22509 are kept in a directory known as the @dfn{data directory}.
22511 You can set the data directory's name, and view the name @value{GDBN}
22512 is currently using.
22515 @kindex set data-directory
22516 @item set data-directory @var{directory}
22517 Set the directory which @value{GDBN} searches for auxiliary data files
22518 to @var{directory}.
22520 @kindex show data-directory
22521 @item show data-directory
22522 Show the directory @value{GDBN} searches for auxiliary data files.
22525 @cindex default data directory
22526 @cindex @samp{--with-gdb-datadir}
22527 You can set the default data directory by using the configure-time
22528 @samp{--with-gdb-datadir} option. If the data directory is inside
22529 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22530 @samp{--exec-prefix}), then the default data directory will be updated
22531 automatically if the installed @value{GDBN} is moved to a new
22534 The data directory may also be specified with the
22535 @code{--data-directory} command line option.
22536 @xref{Mode Options}.
22539 @chapter Specifying a Debugging Target
22541 @cindex debugging target
22542 A @dfn{target} is the execution environment occupied by your program.
22544 Often, @value{GDBN} runs in the same host environment as your program;
22545 in that case, the debugging target is specified as a side effect when
22546 you use the @code{file} or @code{core} commands. When you need more
22547 flexibility---for example, running @value{GDBN} on a physically separate
22548 host, or controlling a standalone system over a serial port or a
22549 realtime system over a TCP/IP connection---you can use the @code{target}
22550 command to specify one of the target types configured for @value{GDBN}
22551 (@pxref{Target Commands, ,Commands for Managing Targets}).
22553 @cindex target architecture
22554 It is possible to build @value{GDBN} for several different @dfn{target
22555 architectures}. When @value{GDBN} is built like that, you can choose
22556 one of the available architectures with the @kbd{set architecture}
22560 @kindex set architecture
22561 @kindex show architecture
22562 @item set architecture @var{arch}
22563 This command sets the current target architecture to @var{arch}. The
22564 value of @var{arch} can be @code{"auto"}, in addition to one of the
22565 supported architectures.
22567 @item show architecture
22568 Show the current target architecture.
22570 @item set processor
22572 @kindex set processor
22573 @kindex show processor
22574 These are alias commands for, respectively, @code{set architecture}
22575 and @code{show architecture}.
22579 * Active Targets:: Active targets
22580 * Target Commands:: Commands for managing targets
22581 * Byte Order:: Choosing target byte order
22584 @node Active Targets
22585 @section Active Targets
22587 @cindex stacking targets
22588 @cindex active targets
22589 @cindex multiple targets
22591 There are multiple classes of targets such as: processes, executable files or
22592 recording sessions. Core files belong to the process class, making core file
22593 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22594 on multiple active targets, one in each class. This allows you to (for
22595 example) start a process and inspect its activity, while still having access to
22596 the executable file after the process finishes. Or if you start process
22597 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22598 presented a virtual layer of the recording target, while the process target
22599 remains stopped at the chronologically last point of the process execution.
22601 Use the @code{core-file} and @code{exec-file} commands to select a new core
22602 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22603 specify as a target a process that is already running, use the @code{attach}
22604 command (@pxref{Attach, ,Debugging an Already-running Process}).
22606 @node Target Commands
22607 @section Commands for Managing Targets
22610 @item target @var{type} @var{parameters}
22611 Connects the @value{GDBN} host environment to a target machine or
22612 process. A target is typically a protocol for talking to debugging
22613 facilities. You use the argument @var{type} to specify the type or
22614 protocol of the target machine.
22616 Further @var{parameters} are interpreted by the target protocol, but
22617 typically include things like device names or host names to connect
22618 with, process numbers, and baud rates.
22620 The @code{target} command does not repeat if you press @key{RET} again
22621 after executing the command.
22623 @kindex help target
22625 Displays the names of all targets available. To display targets
22626 currently selected, use either @code{info target} or @code{info files}
22627 (@pxref{Files, ,Commands to Specify Files}).
22629 @item help target @var{name}
22630 Describe a particular target, including any parameters necessary to
22633 @kindex set gnutarget
22634 @item set gnutarget @var{args}
22635 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22636 knows whether it is reading an @dfn{executable},
22637 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22638 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22639 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22642 @emph{Warning:} To specify a file format with @code{set gnutarget},
22643 you must know the actual BFD name.
22647 @xref{Files, , Commands to Specify Files}.
22649 @kindex show gnutarget
22650 @item show gnutarget
22651 Use the @code{show gnutarget} command to display what file format
22652 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22653 @value{GDBN} will determine the file format for each file automatically,
22654 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22657 @cindex common targets
22658 Here are some common targets (available, or not, depending on the GDB
22663 @item target exec @var{program}
22664 @cindex executable file target
22665 An executable file. @samp{target exec @var{program}} is the same as
22666 @samp{exec-file @var{program}}.
22668 @item target core @var{filename}
22669 @cindex core dump file target
22670 A core dump file. @samp{target core @var{filename}} is the same as
22671 @samp{core-file @var{filename}}.
22673 @item target remote @var{medium}
22674 @cindex remote target
22675 A remote system connected to @value{GDBN} via a serial line or network
22676 connection. This command tells @value{GDBN} to use its own remote
22677 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22679 For example, if you have a board connected to @file{/dev/ttya} on the
22680 machine running @value{GDBN}, you could say:
22683 target remote /dev/ttya
22686 @code{target remote} supports the @code{load} command. This is only
22687 useful if you have some other way of getting the stub to the target
22688 system, and you can put it somewhere in memory where it won't get
22689 clobbered by the download.
22691 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22692 @cindex built-in simulator target
22693 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22701 works; however, you cannot assume that a specific memory map, device
22702 drivers, or even basic I/O is available, although some simulators do
22703 provide these. For info about any processor-specific simulator details,
22704 see the appropriate section in @ref{Embedded Processors, ,Embedded
22707 @item target native
22708 @cindex native target
22709 Setup for local/native process debugging. Useful to make the
22710 @code{run} command spawn native processes (likewise @code{attach},
22711 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22712 (@pxref{set auto-connect-native-target}).
22716 Different targets are available on different configurations of @value{GDBN};
22717 your configuration may have more or fewer targets.
22719 Many remote targets require you to download the executable's code once
22720 you've successfully established a connection. You may wish to control
22721 various aspects of this process.
22726 @kindex set hash@r{, for remote monitors}
22727 @cindex hash mark while downloading
22728 This command controls whether a hash mark @samp{#} is displayed while
22729 downloading a file to the remote monitor. If on, a hash mark is
22730 displayed after each S-record is successfully downloaded to the
22734 @kindex show hash@r{, for remote monitors}
22735 Show the current status of displaying the hash mark.
22737 @item set debug monitor
22738 @kindex set debug monitor
22739 @cindex display remote monitor communications
22740 Enable or disable display of communications messages between
22741 @value{GDBN} and the remote monitor.
22743 @item show debug monitor
22744 @kindex show debug monitor
22745 Show the current status of displaying communications between
22746 @value{GDBN} and the remote monitor.
22751 @kindex load @var{filename} @var{offset}
22752 @item load @var{filename} @var{offset}
22754 Depending on what remote debugging facilities are configured into
22755 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22756 is meant to make @var{filename} (an executable) available for debugging
22757 on the remote system---by downloading, or dynamic linking, for example.
22758 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22759 the @code{add-symbol-file} command.
22761 If your @value{GDBN} does not have a @code{load} command, attempting to
22762 execute it gets the error message ``@code{You can't do that when your
22763 target is @dots{}}''
22765 The file is loaded at whatever address is specified in the executable.
22766 For some object file formats, you can specify the load address when you
22767 link the program; for other formats, like a.out, the object file format
22768 specifies a fixed address.
22769 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22771 It is also possible to tell @value{GDBN} to load the executable file at a
22772 specific offset described by the optional argument @var{offset}. When
22773 @var{offset} is provided, @var{filename} must also be provided.
22775 Depending on the remote side capabilities, @value{GDBN} may be able to
22776 load programs into flash memory.
22778 @code{load} does not repeat if you press @key{RET} again after using it.
22783 @kindex flash-erase
22785 @anchor{flash-erase}
22787 Erases all known flash memory regions on the target.
22792 @section Choosing Target Byte Order
22794 @cindex choosing target byte order
22795 @cindex target byte order
22797 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22798 offer the ability to run either big-endian or little-endian byte
22799 orders. Usually the executable or symbol will include a bit to
22800 designate the endian-ness, and you will not need to worry about
22801 which to use. However, you may still find it useful to adjust
22802 @value{GDBN}'s idea of processor endian-ness manually.
22806 @item set endian big
22807 Instruct @value{GDBN} to assume the target is big-endian.
22809 @item set endian little
22810 Instruct @value{GDBN} to assume the target is little-endian.
22812 @item set endian auto
22813 Instruct @value{GDBN} to use the byte order associated with the
22817 Display @value{GDBN}'s current idea of the target byte order.
22821 If the @code{set endian auto} mode is in effect and no executable has
22822 been selected, then the endianness used is the last one chosen either
22823 by one of the @code{set endian big} and @code{set endian little}
22824 commands or by inferring from the last executable used. If no
22825 endianness has been previously chosen, then the default for this mode
22826 is inferred from the target @value{GDBN} has been built for, and is
22827 @code{little} if the name of the target CPU has an @code{el} suffix
22828 and @code{big} otherwise.
22830 Note that these commands merely adjust interpretation of symbolic
22831 data on the host, and that they have absolutely no effect on the
22835 @node Remote Debugging
22836 @chapter Debugging Remote Programs
22837 @cindex remote debugging
22839 If you are trying to debug a program running on a machine that cannot run
22840 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22841 For example, you might use remote debugging on an operating system kernel,
22842 or on a small system which does not have a general purpose operating system
22843 powerful enough to run a full-featured debugger.
22845 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22846 to make this work with particular debugging targets. In addition,
22847 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22848 but not specific to any particular target system) which you can use if you
22849 write the remote stubs---the code that runs on the remote system to
22850 communicate with @value{GDBN}.
22852 Other remote targets may be available in your
22853 configuration of @value{GDBN}; use @code{help target} to list them.
22856 * Connecting:: Connecting to a remote target
22857 * File Transfer:: Sending files to a remote system
22858 * Server:: Using the gdbserver program
22859 * Remote Configuration:: Remote configuration
22860 * Remote Stub:: Implementing a remote stub
22864 @section Connecting to a Remote Target
22865 @cindex remote debugging, connecting
22866 @cindex @code{gdbserver}, connecting
22867 @cindex remote debugging, types of connections
22868 @cindex @code{gdbserver}, types of connections
22869 @cindex @code{gdbserver}, @code{target remote} mode
22870 @cindex @code{gdbserver}, @code{target extended-remote} mode
22872 This section describes how to connect to a remote target, including the
22873 types of connections and their differences, how to set up executable and
22874 symbol files on the host and target, and the commands used for
22875 connecting to and disconnecting from the remote target.
22877 @subsection Types of Remote Connections
22879 @value{GDBN} supports two types of remote connections, @code{target remote}
22880 mode and @code{target extended-remote} mode. Note that many remote targets
22881 support only @code{target remote} mode. There are several major
22882 differences between the two types of connections, enumerated here:
22886 @cindex remote debugging, detach and program exit
22887 @item Result of detach or program exit
22888 @strong{With target remote mode:} When the debugged program exits or you
22889 detach from it, @value{GDBN} disconnects from the target. When using
22890 @code{gdbserver}, @code{gdbserver} will exit.
22892 @strong{With target extended-remote mode:} When the debugged program exits or
22893 you detach from it, @value{GDBN} remains connected to the target, even
22894 though no program is running. You can rerun the program, attach to a
22895 running program, or use @code{monitor} commands specific to the target.
22897 When using @code{gdbserver} in this case, it does not exit unless it was
22898 invoked using the @option{--once} option. If the @option{--once} option
22899 was not used, you can ask @code{gdbserver} to exit using the
22900 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22902 @item Specifying the program to debug
22903 For both connection types you use the @code{file} command to specify the
22904 program on the host system. If you are using @code{gdbserver} there are
22905 some differences in how to specify the location of the program on the
22908 @strong{With target remote mode:} You must either specify the program to debug
22909 on the @code{gdbserver} command line or use the @option{--attach} option
22910 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22912 @cindex @option{--multi}, @code{gdbserver} option
22913 @strong{With target extended-remote mode:} You may specify the program to debug
22914 on the @code{gdbserver} command line, or you can load the program or attach
22915 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22917 @anchor{--multi Option in Types of Remote Connnections}
22918 You can start @code{gdbserver} without supplying an initial command to run
22919 or process ID to attach. To do this, use the @option{--multi} command line
22920 option. Then you can connect using @code{target extended-remote} and start
22921 the program you want to debug (see below for details on using the
22922 @code{run} command in this scenario). Note that the conditions under which
22923 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22924 (@code{target remote} or @code{target extended-remote}). The
22925 @option{--multi} option to @code{gdbserver} has no influence on that.
22927 @item The @code{run} command
22928 @strong{With target remote mode:} The @code{run} command is not
22929 supported. Once a connection has been established, you can use all
22930 the usual @value{GDBN} commands to examine and change data. The
22931 remote program is already running, so you can use commands like
22932 @kbd{step} and @kbd{continue}.
22934 @strong{With target extended-remote mode:} The @code{run} command is
22935 supported. The @code{run} command uses the value set by
22936 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22937 the program to run. Command line arguments are supported, except for
22938 wildcard expansion and I/O redirection (@pxref{Arguments}).
22940 If you specify the program to debug on the command line, then the
22941 @code{run} command is not required to start execution, and you can
22942 resume using commands like @kbd{step} and @kbd{continue} as with
22943 @code{target remote} mode.
22945 @anchor{Attaching in Types of Remote Connections}
22947 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22948 not supported. To attach to a running program using @code{gdbserver}, you
22949 must use the @option{--attach} option (@pxref{Running gdbserver}).
22951 @strong{With target extended-remote mode:} To attach to a running program,
22952 you may use the @code{attach} command after the connection has been
22953 established. If you are using @code{gdbserver}, you may also invoke
22954 @code{gdbserver} using the @option{--attach} option
22955 (@pxref{Running gdbserver}).
22957 Some remote targets allow @value{GDBN} to determine the executable file running
22958 in the process the debugger is attaching to. In such a case, @value{GDBN}
22959 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22960 between the executable file name running in the process and the name of the
22961 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22965 @anchor{Host and target files}
22966 @subsection Host and Target Files
22967 @cindex remote debugging, symbol files
22968 @cindex symbol files, remote debugging
22970 @value{GDBN}, running on the host, needs access to symbol and debugging
22971 information for your program running on the target. This requires
22972 access to an unstripped copy of your program, and possibly any associated
22973 symbol files. Note that this section applies equally to both @code{target
22974 remote} mode and @code{target extended-remote} mode.
22976 Some remote targets (@pxref{qXfer executable filename read}, and
22977 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22978 the same connection used to communicate with @value{GDBN}. With such a
22979 target, if the remote program is unstripped, the only command you need is
22980 @code{target remote} (or @code{target extended-remote}).
22982 If the remote program is stripped, or the target does not support remote
22983 program file access, start up @value{GDBN} using the name of the local
22984 unstripped copy of your program as the first argument, or use the
22985 @code{file} command. Use @code{set sysroot} to specify the location (on
22986 the host) of target libraries (unless your @value{GDBN} was compiled with
22987 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22988 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22991 The symbol file and target libraries must exactly match the executable
22992 and libraries on the target, with one exception: the files on the host
22993 system should not be stripped, even if the files on the target system
22994 are. Mismatched or missing files will lead to confusing results
22995 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22996 files may also prevent @code{gdbserver} from debugging multi-threaded
22999 @subsection Remote Connection Commands
23000 @cindex remote connection commands
23001 @value{GDBN} can communicate with the target over a serial line, a
23002 local Unix domain socket, or
23003 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
23004 each case, @value{GDBN} uses the same protocol for debugging your
23005 program; only the medium carrying the debugging packets varies. The
23006 @code{target remote} and @code{target extended-remote} commands
23007 establish a connection to the target. Both commands accept the same
23008 arguments, which indicate the medium to use:
23012 @item target remote @var{serial-device}
23013 @itemx target extended-remote @var{serial-device}
23014 @cindex serial line, @code{target remote}
23015 Use @var{serial-device} to communicate with the target. For example,
23016 to use a serial line connected to the device named @file{/dev/ttyb}:
23019 target remote /dev/ttyb
23022 If you're using a serial line, you may want to give @value{GDBN} the
23023 @samp{--baud} option, or use the @code{set serial baud} command
23024 (@pxref{Remote Configuration, set serial baud}) before the
23025 @code{target} command.
23027 @item target remote @var{local-socket}
23028 @itemx target extended-remote @var{local-socket}
23029 @cindex local socket, @code{target remote}
23030 @cindex Unix domain socket
23031 Use @var{local-socket} to communicate with the target. For example,
23032 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
23035 target remote /tmp/gdb-socket0
23038 Note that this command has the same form as the command to connect
23039 to a serial line. @value{GDBN} will automatically determine which
23040 kind of file you have specified and will make the appropriate kind
23042 This feature is not available if the host system does not support
23043 Unix domain sockets.
23045 @item target remote @code{@var{host}:@var{port}}
23046 @itemx target remote @code{[@var{host}]:@var{port}}
23047 @itemx target remote @code{tcp:@var{host}:@var{port}}
23048 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
23049 @itemx target remote @code{tcp4:@var{host}:@var{port}}
23050 @itemx target remote @code{tcp6:@var{host}:@var{port}}
23051 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
23052 @itemx target extended-remote @code{@var{host}:@var{port}}
23053 @itemx target extended-remote @code{[@var{host}]:@var{port}}
23054 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
23055 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
23056 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
23057 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
23058 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
23059 @cindex @acronym{TCP} port, @code{target remote}
23060 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
23061 The @var{host} may be either a host name, a numeric @acronym{IPv4}
23062 address, or a numeric @acronym{IPv6} address (with or without the
23063 square brackets to separate the address from the port); @var{port}
23064 must be a decimal number. The @var{host} could be the target machine
23065 itself, if it is directly connected to the net, or it might be a
23066 terminal server which in turn has a serial line to the target.
23068 For example, to connect to port 2828 on a terminal server named
23072 target remote manyfarms:2828
23075 To connect to port 2828 on a terminal server whose address is
23076 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
23077 square bracket syntax:
23080 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
23084 or explicitly specify the @acronym{IPv6} protocol:
23087 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
23090 This last example may be confusing to the reader, because there is no
23091 visible separation between the hostname and the port number.
23092 Therefore, we recommend the user to provide @acronym{IPv6} addresses
23093 using square brackets for clarity. However, it is important to
23094 mention that for @value{GDBN} there is no ambiguity: the number after
23095 the last colon is considered to be the port number.
23097 If your remote target is actually running on the same machine as your
23098 debugger session (e.g.@: a simulator for your target running on the
23099 same host), you can omit the hostname. For example, to connect to
23100 port 1234 on your local machine:
23103 target remote :1234
23107 Note that the colon is still required here.
23109 @item target remote @code{udp:@var{host}:@var{port}}
23110 @itemx target remote @code{udp:[@var{host}]:@var{port}}
23111 @itemx target remote @code{udp4:@var{host}:@var{port}}
23112 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
23113 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23114 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23115 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
23116 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
23117 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
23118 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
23119 @cindex @acronym{UDP} port, @code{target remote}
23120 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
23121 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
23124 target remote udp:manyfarms:2828
23127 When using a @acronym{UDP} connection for remote debugging, you should
23128 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
23129 can silently drop packets on busy or unreliable networks, which will
23130 cause havoc with your debugging session.
23132 @item target remote | @var{command}
23133 @itemx target extended-remote | @var{command}
23134 @cindex pipe, @code{target remote} to
23135 Run @var{command} in the background and communicate with it using a
23136 pipe. The @var{command} is a shell command, to be parsed and expanded
23137 by the system's command shell, @code{/bin/sh}; it should expect remote
23138 protocol packets on its standard input, and send replies on its
23139 standard output. You could use this to run a stand-alone simulator
23140 that speaks the remote debugging protocol, to make net connections
23141 using programs like @code{ssh}, or for other similar tricks.
23143 If @var{command} closes its standard output (perhaps by exiting),
23144 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
23145 program has already exited, this will have no effect.)
23149 @cindex interrupting remote programs
23150 @cindex remote programs, interrupting
23151 Whenever @value{GDBN} is waiting for the remote program, if you type the
23152 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
23153 program. This may or may not succeed, depending in part on the hardware
23154 and the serial drivers the remote system uses. If you type the
23155 interrupt character once again, @value{GDBN} displays this prompt:
23158 Interrupted while waiting for the program.
23159 Give up (and stop debugging it)? (y or n)
23162 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23163 the remote debugging session. (If you decide you want to try again later,
23164 you can use @kbd{target remote} again to connect once more.) If you type
23165 @kbd{n}, @value{GDBN} goes back to waiting.
23167 In @code{target extended-remote} mode, typing @kbd{n} will leave
23168 @value{GDBN} connected to the target.
23171 @kindex detach (remote)
23173 When you have finished debugging the remote program, you can use the
23174 @code{detach} command to release it from @value{GDBN} control.
23175 Detaching from the target normally resumes its execution, but the results
23176 will depend on your particular remote stub. After the @code{detach}
23177 command in @code{target remote} mode, @value{GDBN} is free to connect to
23178 another target. In @code{target extended-remote} mode, @value{GDBN} is
23179 still connected to the target.
23183 The @code{disconnect} command closes the connection to the target, and
23184 the target is generally not resumed. It will wait for @value{GDBN}
23185 (this instance or another one) to connect and continue debugging. After
23186 the @code{disconnect} command, @value{GDBN} is again free to connect to
23189 @cindex send command to remote monitor
23190 @cindex extend @value{GDBN} for remote targets
23191 @cindex add new commands for external monitor
23193 @item monitor @var{cmd}
23194 This command allows you to send arbitrary commands directly to the
23195 remote monitor. Since @value{GDBN} doesn't care about the commands it
23196 sends like this, this command is the way to extend @value{GDBN}---you
23197 can add new commands that only the external monitor will understand
23201 @node File Transfer
23202 @section Sending files to a remote system
23203 @cindex remote target, file transfer
23204 @cindex file transfer
23205 @cindex sending files to remote systems
23207 Some remote targets offer the ability to transfer files over the same
23208 connection used to communicate with @value{GDBN}. This is convenient
23209 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23210 running @code{gdbserver} over a network interface. For other targets,
23211 e.g.@: embedded devices with only a single serial port, this may be
23212 the only way to upload or download files.
23214 Not all remote targets support these commands.
23218 @item remote put @var{hostfile} @var{targetfile}
23219 Copy file @var{hostfile} from the host system (the machine running
23220 @value{GDBN}) to @var{targetfile} on the target system.
23223 @item remote get @var{targetfile} @var{hostfile}
23224 Copy file @var{targetfile} from the target system to @var{hostfile}
23225 on the host system.
23227 @kindex remote delete
23228 @item remote delete @var{targetfile}
23229 Delete @var{targetfile} from the target system.
23234 @section Using the @code{gdbserver} Program
23237 @cindex remote connection without stubs
23238 @code{gdbserver} is a control program for Unix-like systems, which
23239 allows you to connect your program with a remote @value{GDBN} via
23240 @code{target remote} or @code{target extended-remote}---but without
23241 linking in the usual debugging stub.
23243 @code{gdbserver} is not a complete replacement for the debugging stubs,
23244 because it requires essentially the same operating-system facilities
23245 that @value{GDBN} itself does. In fact, a system that can run
23246 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23247 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23248 because it is a much smaller program than @value{GDBN} itself. It is
23249 also easier to port than all of @value{GDBN}, so you may be able to get
23250 started more quickly on a new system by using @code{gdbserver}.
23251 Finally, if you develop code for real-time systems, you may find that
23252 the tradeoffs involved in real-time operation make it more convenient to
23253 do as much development work as possible on another system, for example
23254 by cross-compiling. You can use @code{gdbserver} to make a similar
23255 choice for debugging.
23257 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23258 or a TCP connection, using the standard @value{GDBN} remote serial
23262 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23263 Do not run @code{gdbserver} connected to any public network; a
23264 @value{GDBN} connection to @code{gdbserver} provides access to the
23265 target system with the same privileges as the user running
23269 @anchor{Running gdbserver}
23270 @subsection Running @code{gdbserver}
23271 @cindex arguments, to @code{gdbserver}
23272 @cindex @code{gdbserver}, command-line arguments
23274 Run @code{gdbserver} on the target system. You need a copy of the
23275 program you want to debug, including any libraries it requires.
23276 @code{gdbserver} does not need your program's symbol table, so you can
23277 strip the program if necessary to save space. @value{GDBN} on the host
23278 system does all the symbol handling.
23280 To use the server, you must tell it how to communicate with @value{GDBN};
23281 the name of your program; and the arguments for your program. The usual
23285 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23288 @var{comm} is either a device name (to use a serial line), or a TCP
23289 hostname and portnumber, or @code{-} or @code{stdio} to use
23290 stdin/stdout of @code{gdbserver}.
23291 For example, to debug Emacs with the argument
23292 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23296 target> gdbserver /dev/com1 emacs foo.txt
23299 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23302 To use a TCP connection instead of a serial line:
23305 target> gdbserver host:2345 emacs foo.txt
23308 The only difference from the previous example is the first argument,
23309 specifying that you are communicating with the host @value{GDBN} via
23310 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23311 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23312 (Currently, the @samp{host} part is ignored.) You can choose any number
23313 you want for the port number as long as it does not conflict with any
23314 TCP ports already in use on the target system (for example, @code{23} is
23315 reserved for @code{telnet}).@footnote{If you choose a port number that
23316 conflicts with another service, @code{gdbserver} prints an error message
23317 and exits.} You must use the same port number with the host @value{GDBN}
23318 @code{target remote} command.
23320 The @code{stdio} connection is useful when starting @code{gdbserver}
23324 (gdb) target remote | ssh -T hostname gdbserver - hello
23327 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23328 and we don't want escape-character handling. Ssh does this by default when
23329 a command is provided, the flag is provided to make it explicit.
23330 You could elide it if you want to.
23332 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23333 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23334 display through a pipe connected to gdbserver.
23335 Both @code{stdout} and @code{stderr} use the same pipe.
23337 @anchor{Attaching to a program}
23338 @subsubsection Attaching to a Running Program
23339 @cindex attach to a program, @code{gdbserver}
23340 @cindex @option{--attach}, @code{gdbserver} option
23342 On some targets, @code{gdbserver} can also attach to running programs.
23343 This is accomplished via the @code{--attach} argument. The syntax is:
23346 target> gdbserver --attach @var{comm} @var{pid}
23349 @var{pid} is the process ID of a currently running process. It isn't
23350 necessary to point @code{gdbserver} at a binary for the running process.
23352 In @code{target extended-remote} mode, you can also attach using the
23353 @value{GDBN} attach command
23354 (@pxref{Attaching in Types of Remote Connections}).
23357 You can debug processes by name instead of process ID if your target has the
23358 @code{pidof} utility:
23361 target> gdbserver --attach @var{comm} `pidof @var{program}`
23364 In case more than one copy of @var{program} is running, or @var{program}
23365 has multiple threads, most versions of @code{pidof} support the
23366 @code{-s} option to only return the first process ID.
23368 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23370 This section applies only when @code{gdbserver} is run to listen on a TCP
23373 @code{gdbserver} normally terminates after all of its debugged processes have
23374 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23375 extended-remote}, @code{gdbserver} stays running even with no processes left.
23376 @value{GDBN} normally terminates the spawned debugged process on its exit,
23377 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23378 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23379 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23380 stays running even in the @kbd{target remote} mode.
23382 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23383 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23384 completeness, at most one @value{GDBN} can be connected at a time.
23386 @cindex @option{--once}, @code{gdbserver} option
23387 By default, @code{gdbserver} keeps the listening TCP port open, so that
23388 subsequent connections are possible. However, if you start @code{gdbserver}
23389 with the @option{--once} option, it will stop listening for any further
23390 connection attempts after connecting to the first @value{GDBN} session. This
23391 means no further connections to @code{gdbserver} will be possible after the
23392 first one. It also means @code{gdbserver} will terminate after the first
23393 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23394 connections and even in the @kbd{target extended-remote} mode. The
23395 @option{--once} option allows reusing the same port number for connecting to
23396 multiple instances of @code{gdbserver} running on the same host, since each
23397 instance closes its port after the first connection.
23399 @anchor{Other Command-Line Arguments for gdbserver}
23400 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23402 You can use the @option{--multi} option to start @code{gdbserver} without
23403 specifying a program to debug or a process to attach to. Then you can
23404 attach in @code{target extended-remote} mode and run or attach to a
23405 program. For more information,
23406 @pxref{--multi Option in Types of Remote Connnections}.
23408 @cindex @option{--debug}, @code{gdbserver} option
23409 The @option{--debug} option tells @code{gdbserver} to display extra
23410 status information about the debugging process.
23411 @cindex @option{--remote-debug}, @code{gdbserver} option
23412 The @option{--remote-debug} option tells @code{gdbserver} to display
23413 remote protocol debug output.
23414 @cindex @option{--debug-file}, @code{gdbserver} option
23415 @cindex @code{gdbserver}, send all debug output to a single file
23416 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23417 write any debug output to the given @var{filename}. These options are intended
23418 for @code{gdbserver} development and for bug reports to the developers.
23420 @cindex @option{--debug-format}, @code{gdbserver} option
23421 The @option{--debug-format=option1[,option2,...]} option tells
23422 @code{gdbserver} to include additional information in each output.
23423 Possible options are:
23427 Turn off all extra information in debugging output.
23429 Turn on all extra information in debugging output.
23431 Include a timestamp in each line of debugging output.
23434 Options are processed in order. Thus, for example, if @option{none}
23435 appears last then no additional information is added to debugging output.
23437 @cindex @option{--wrapper}, @code{gdbserver} option
23438 The @option{--wrapper} option specifies a wrapper to launch programs
23439 for debugging. The option should be followed by the name of the
23440 wrapper, then any command-line arguments to pass to the wrapper, then
23441 @kbd{--} indicating the end of the wrapper arguments.
23443 @code{gdbserver} runs the specified wrapper program with a combined
23444 command line including the wrapper arguments, then the name of the
23445 program to debug, then any arguments to the program. The wrapper
23446 runs until it executes your program, and then @value{GDBN} gains control.
23448 You can use any program that eventually calls @code{execve} with
23449 its arguments as a wrapper. Several standard Unix utilities do
23450 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23451 with @code{exec "$@@"} will also work.
23453 For example, you can use @code{env} to pass an environment variable to
23454 the debugged program, without setting the variable in @code{gdbserver}'s
23458 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23461 @cindex @option{--selftest}
23462 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23465 $ gdbserver --selftest
23466 Ran 2 unit tests, 0 failed
23469 These tests are disabled in release.
23470 @subsection Connecting to @code{gdbserver}
23472 The basic procedure for connecting to the remote target is:
23476 Run @value{GDBN} on the host system.
23479 Make sure you have the necessary symbol files
23480 (@pxref{Host and target files}).
23481 Load symbols for your application using the @code{file} command before you
23482 connect. Use @code{set sysroot} to locate target libraries (unless your
23483 @value{GDBN} was compiled with the correct sysroot using
23484 @code{--with-sysroot}).
23487 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23488 For TCP connections, you must start up @code{gdbserver} prior to using
23489 the @code{target} command. Otherwise you may get an error whose
23490 text depends on the host system, but which usually looks something like
23491 @samp{Connection refused}. Don't use the @code{load}
23492 command in @value{GDBN} when using @code{target remote} mode, since the
23493 program is already on the target.
23497 @anchor{Monitor Commands for gdbserver}
23498 @subsection Monitor Commands for @code{gdbserver}
23499 @cindex monitor commands, for @code{gdbserver}
23501 During a @value{GDBN} session using @code{gdbserver}, you can use the
23502 @code{monitor} command to send special requests to @code{gdbserver}.
23503 Here are the available commands.
23507 List the available monitor commands.
23509 @item monitor set debug 0
23510 @itemx monitor set debug 1
23511 Disable or enable general debugging messages.
23513 @item monitor set remote-debug 0
23514 @itemx monitor set remote-debug 1
23515 Disable or enable specific debugging messages associated with the remote
23516 protocol (@pxref{Remote Protocol}).
23518 @item monitor set debug-file filename
23519 @itemx monitor set debug-file
23520 Send any debug output to the given file, or to stderr.
23522 @item monitor set debug-format option1@r{[},option2,...@r{]}
23523 Specify additional text to add to debugging messages.
23524 Possible options are:
23528 Turn off all extra information in debugging output.
23530 Turn on all extra information in debugging output.
23532 Include a timestamp in each line of debugging output.
23535 Options are processed in order. Thus, for example, if @option{none}
23536 appears last then no additional information is added to debugging output.
23538 @item monitor set libthread-db-search-path [PATH]
23539 @cindex gdbserver, search path for @code{libthread_db}
23540 When this command is issued, @var{path} is a colon-separated list of
23541 directories to search for @code{libthread_db} (@pxref{Threads,,set
23542 libthread-db-search-path}). If you omit @var{path},
23543 @samp{libthread-db-search-path} will be reset to its default value.
23545 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23546 not supported in @code{gdbserver}.
23549 Tell gdbserver to exit immediately. This command should be followed by
23550 @code{disconnect} to close the debugging session. @code{gdbserver} will
23551 detach from any attached processes and kill any processes it created.
23552 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23553 of a multi-process mode debug session.
23557 @subsection Tracepoints support in @code{gdbserver}
23558 @cindex tracepoints support in @code{gdbserver}
23560 On some targets, @code{gdbserver} supports tracepoints, fast
23561 tracepoints and static tracepoints.
23563 For fast or static tracepoints to work, a special library called the
23564 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23565 This library is built and distributed as an integral part of
23566 @code{gdbserver}. In addition, support for static tracepoints
23567 requires building the in-process agent library with static tracepoints
23568 support. At present, the UST (LTTng Userspace Tracer,
23569 @url{http://lttng.org/ust}) tracing engine is supported. This support
23570 is automatically available if UST development headers are found in the
23571 standard include path when @code{gdbserver} is built, or if
23572 @code{gdbserver} was explicitly configured using @option{--with-ust}
23573 to point at such headers. You can explicitly disable the support
23574 using @option{--with-ust=no}.
23576 There are several ways to load the in-process agent in your program:
23579 @item Specifying it as dependency at link time
23581 You can link your program dynamically with the in-process agent
23582 library. On most systems, this is accomplished by adding
23583 @code{-linproctrace} to the link command.
23585 @item Using the system's preloading mechanisms
23587 You can force loading the in-process agent at startup time by using
23588 your system's support for preloading shared libraries. Many Unixes
23589 support the concept of preloading user defined libraries. In most
23590 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23591 in the environment. See also the description of @code{gdbserver}'s
23592 @option{--wrapper} command line option.
23594 @item Using @value{GDBN} to force loading the agent at run time
23596 On some systems, you can force the inferior to load a shared library,
23597 by calling a dynamic loader function in the inferior that takes care
23598 of dynamically looking up and loading a shared library. On most Unix
23599 systems, the function is @code{dlopen}. You'll use the @code{call}
23600 command for that. For example:
23603 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23606 Note that on most Unix systems, for the @code{dlopen} function to be
23607 available, the program needs to be linked with @code{-ldl}.
23610 On systems that have a userspace dynamic loader, like most Unix
23611 systems, when you connect to @code{gdbserver} using @code{target
23612 remote}, you'll find that the program is stopped at the dynamic
23613 loader's entry point, and no shared library has been loaded in the
23614 program's address space yet, including the in-process agent. In that
23615 case, before being able to use any of the fast or static tracepoints
23616 features, you need to let the loader run and load the shared
23617 libraries. The simplest way to do that is to run the program to the
23618 main procedure. E.g., if debugging a C or C@t{++} program, start
23619 @code{gdbserver} like so:
23622 $ gdbserver :9999 myprogram
23625 Start GDB and connect to @code{gdbserver} like so, and run to main:
23629 (@value{GDBP}) target remote myhost:9999
23630 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23631 (@value{GDBP}) b main
23632 (@value{GDBP}) continue
23635 The in-process tracing agent library should now be loaded into the
23636 process; you can confirm it with the @code{info sharedlibrary}
23637 command, which will list @file{libinproctrace.so} as loaded in the
23638 process. You are now ready to install fast tracepoints, list static
23639 tracepoint markers, probe static tracepoints markers, and start
23642 @node Remote Configuration
23643 @section Remote Configuration
23646 @kindex show remote
23647 This section documents the configuration options available when
23648 debugging remote programs. For the options related to the File I/O
23649 extensions of the remote protocol, see @ref{system,
23650 system-call-allowed}.
23653 @item set remoteaddresssize @var{bits}
23654 @cindex address size for remote targets
23655 @cindex bits in remote address
23656 Set the maximum size of address in a memory packet to the specified
23657 number of bits. @value{GDBN} will mask off the address bits above
23658 that number, when it passes addresses to the remote target. The
23659 default value is the number of bits in the target's address.
23661 @item show remoteaddresssize
23662 Show the current value of remote address size in bits.
23664 @item set serial baud @var{n}
23665 @cindex baud rate for remote targets
23666 Set the baud rate for the remote serial I/O to @var{n} baud. The
23667 value is used to set the speed of the serial port used for debugging
23670 @item show serial baud
23671 Show the current speed of the remote connection.
23673 @item set serial parity @var{parity}
23674 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23675 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23677 @item show serial parity
23678 Show the current parity of the serial port.
23680 @item set remotebreak
23681 @cindex interrupt remote programs
23682 @cindex BREAK signal instead of Ctrl-C
23683 @anchor{set remotebreak}
23684 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23685 when you type @kbd{Ctrl-c} to interrupt the program running
23686 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23687 character instead. The default is off, since most remote systems
23688 expect to see @samp{Ctrl-C} as the interrupt signal.
23690 @item show remotebreak
23691 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23692 interrupt the remote program.
23694 @item set remoteflow on
23695 @itemx set remoteflow off
23696 @kindex set remoteflow
23697 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23698 on the serial port used to communicate to the remote target.
23700 @item show remoteflow
23701 @kindex show remoteflow
23702 Show the current setting of hardware flow control.
23704 @item set remotelogbase @var{base}
23705 Set the base (a.k.a.@: radix) of logging serial protocol
23706 communications to @var{base}. Supported values of @var{base} are:
23707 @code{ascii}, @code{octal}, and @code{hex}. The default is
23710 @item show remotelogbase
23711 Show the current setting of the radix for logging remote serial
23714 @item set remotelogfile @var{file}
23715 @cindex record serial communications on file
23716 Record remote serial communications on the named @var{file}. The
23717 default is not to record at all.
23719 @item show remotelogfile
23720 Show the current setting of the file name on which to record the
23721 serial communications.
23723 @item set remotetimeout @var{num}
23724 @cindex timeout for serial communications
23725 @cindex remote timeout
23726 Set the timeout limit to wait for the remote target to respond to
23727 @var{num} seconds. The default is 2 seconds.
23729 @item show remotetimeout
23730 Show the current number of seconds to wait for the remote target
23733 @cindex limit hardware breakpoints and watchpoints
23734 @cindex remote target, limit break- and watchpoints
23735 @anchor{set remote hardware-watchpoint-limit}
23736 @anchor{set remote hardware-breakpoint-limit}
23737 @item set remote hardware-watchpoint-limit @var{limit}
23738 @itemx set remote hardware-breakpoint-limit @var{limit}
23739 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23740 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23741 watchpoints or breakpoints, and @code{unlimited} for unlimited
23742 watchpoints or breakpoints.
23744 @item show remote hardware-watchpoint-limit
23745 @itemx show remote hardware-breakpoint-limit
23746 Show the current limit for the number of hardware watchpoints or
23747 breakpoints that @value{GDBN} can use.
23749 @cindex limit hardware watchpoints length
23750 @cindex remote target, limit watchpoints length
23751 @anchor{set remote hardware-watchpoint-length-limit}
23752 @item set remote hardware-watchpoint-length-limit @var{limit}
23753 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23754 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23755 hardware watchpoints and @code{unlimited} allows watchpoints of any
23758 @item show remote hardware-watchpoint-length-limit
23759 Show the current limit (in bytes) of the maximum length of
23760 a remote hardware watchpoint.
23762 @item set remote exec-file @var{filename}
23763 @itemx show remote exec-file
23764 @anchor{set remote exec-file}
23765 @cindex executable file, for remote target
23766 Select the file used for @code{run} with @code{target
23767 extended-remote}. This should be set to a filename valid on the
23768 target system. If it is not set, the target will use a default
23769 filename (e.g.@: the last program run).
23771 @item set remote interrupt-sequence
23772 @cindex interrupt remote programs
23773 @cindex select Ctrl-C, BREAK or BREAK-g
23774 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23775 @samp{BREAK-g} as the
23776 sequence to the remote target in order to interrupt the execution.
23777 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23778 is high level of serial line for some certain time.
23779 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23780 It is @code{BREAK} signal followed by character @code{g}.
23782 @item show remote interrupt-sequence
23783 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23784 is sent by @value{GDBN} to interrupt the remote program.
23785 @code{BREAK-g} is BREAK signal followed by @code{g} and
23786 also known as Magic SysRq g.
23788 @item set remote interrupt-on-connect
23789 @cindex send interrupt-sequence on start
23790 Specify whether interrupt-sequence is sent to remote target when
23791 @value{GDBN} connects to it. This is mostly needed when you debug
23792 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23793 which is known as Magic SysRq g in order to connect @value{GDBN}.
23795 @item show remote interrupt-on-connect
23796 Show whether interrupt-sequence is sent
23797 to remote target when @value{GDBN} connects to it.
23801 @item set tcp auto-retry on
23802 @cindex auto-retry, for remote TCP target
23803 Enable auto-retry for remote TCP connections. This is useful if the remote
23804 debugging agent is launched in parallel with @value{GDBN}; there is a race
23805 condition because the agent may not become ready to accept the connection
23806 before @value{GDBN} attempts to connect. When auto-retry is
23807 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23808 to establish the connection using the timeout specified by
23809 @code{set tcp connect-timeout}.
23811 @item set tcp auto-retry off
23812 Do not auto-retry failed TCP connections.
23814 @item show tcp auto-retry
23815 Show the current auto-retry setting.
23817 @item set tcp connect-timeout @var{seconds}
23818 @itemx set tcp connect-timeout unlimited
23819 @cindex connection timeout, for remote TCP target
23820 @cindex timeout, for remote target connection
23821 Set the timeout for establishing a TCP connection to the remote target to
23822 @var{seconds}. The timeout affects both polling to retry failed connections
23823 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23824 that are merely slow to complete, and represents an approximate cumulative
23825 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23826 @value{GDBN} will keep attempting to establish a connection forever,
23827 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23829 @item show tcp connect-timeout
23830 Show the current connection timeout setting.
23833 @cindex remote packets, enabling and disabling
23834 The @value{GDBN} remote protocol autodetects the packets supported by
23835 your debugging stub. If you need to override the autodetection, you
23836 can use these commands to enable or disable individual packets. Each
23837 packet can be set to @samp{on} (the remote target supports this
23838 packet), @samp{off} (the remote target does not support this packet),
23839 or @samp{auto} (detect remote target support for this packet). They
23840 all default to @samp{auto}. For more information about each packet,
23841 see @ref{Remote Protocol}.
23843 During normal use, you should not have to use any of these commands.
23844 If you do, that may be a bug in your remote debugging stub, or a bug
23845 in @value{GDBN}. You may want to report the problem to the
23846 @value{GDBN} developers.
23848 For each packet @var{name}, the command to enable or disable the
23849 packet is @code{set remote @var{name}-packet}. The available settings
23852 @multitable @columnfractions 0.28 0.32 0.25
23855 @tab Related Features
23857 @item @code{fetch-register}
23859 @tab @code{info registers}
23861 @item @code{set-register}
23865 @item @code{binary-download}
23867 @tab @code{load}, @code{set}
23869 @item @code{read-aux-vector}
23870 @tab @code{qXfer:auxv:read}
23871 @tab @code{info auxv}
23873 @item @code{symbol-lookup}
23874 @tab @code{qSymbol}
23875 @tab Detecting multiple threads
23877 @item @code{attach}
23878 @tab @code{vAttach}
23881 @item @code{verbose-resume}
23883 @tab Stepping or resuming multiple threads
23889 @item @code{software-breakpoint}
23893 @item @code{hardware-breakpoint}
23897 @item @code{write-watchpoint}
23901 @item @code{read-watchpoint}
23905 @item @code{access-watchpoint}
23909 @item @code{pid-to-exec-file}
23910 @tab @code{qXfer:exec-file:read}
23911 @tab @code{attach}, @code{run}
23913 @item @code{target-features}
23914 @tab @code{qXfer:features:read}
23915 @tab @code{set architecture}
23917 @item @code{library-info}
23918 @tab @code{qXfer:libraries:read}
23919 @tab @code{info sharedlibrary}
23921 @item @code{memory-map}
23922 @tab @code{qXfer:memory-map:read}
23923 @tab @code{info mem}
23925 @item @code{read-sdata-object}
23926 @tab @code{qXfer:sdata:read}
23927 @tab @code{print $_sdata}
23929 @item @code{read-siginfo-object}
23930 @tab @code{qXfer:siginfo:read}
23931 @tab @code{print $_siginfo}
23933 @item @code{write-siginfo-object}
23934 @tab @code{qXfer:siginfo:write}
23935 @tab @code{set $_siginfo}
23937 @item @code{threads}
23938 @tab @code{qXfer:threads:read}
23939 @tab @code{info threads}
23941 @item @code{get-thread-local-@*storage-address}
23942 @tab @code{qGetTLSAddr}
23943 @tab Displaying @code{__thread} variables
23945 @item @code{get-thread-information-block-address}
23946 @tab @code{qGetTIBAddr}
23947 @tab Display MS-Windows Thread Information Block.
23949 @item @code{search-memory}
23950 @tab @code{qSearch:memory}
23953 @item @code{supported-packets}
23954 @tab @code{qSupported}
23955 @tab Remote communications parameters
23957 @item @code{catch-syscalls}
23958 @tab @code{QCatchSyscalls}
23959 @tab @code{catch syscall}
23961 @item @code{pass-signals}
23962 @tab @code{QPassSignals}
23963 @tab @code{handle @var{signal}}
23965 @item @code{program-signals}
23966 @tab @code{QProgramSignals}
23967 @tab @code{handle @var{signal}}
23969 @item @code{hostio-close-packet}
23970 @tab @code{vFile:close}
23971 @tab @code{remote get}, @code{remote put}
23973 @item @code{hostio-open-packet}
23974 @tab @code{vFile:open}
23975 @tab @code{remote get}, @code{remote put}
23977 @item @code{hostio-pread-packet}
23978 @tab @code{vFile:pread}
23979 @tab @code{remote get}, @code{remote put}
23981 @item @code{hostio-pwrite-packet}
23982 @tab @code{vFile:pwrite}
23983 @tab @code{remote get}, @code{remote put}
23985 @item @code{hostio-unlink-packet}
23986 @tab @code{vFile:unlink}
23987 @tab @code{remote delete}
23989 @item @code{hostio-readlink-packet}
23990 @tab @code{vFile:readlink}
23993 @item @code{hostio-fstat-packet}
23994 @tab @code{vFile:fstat}
23997 @item @code{hostio-setfs-packet}
23998 @tab @code{vFile:setfs}
24001 @item @code{noack-packet}
24002 @tab @code{QStartNoAckMode}
24003 @tab Packet acknowledgment
24005 @item @code{osdata}
24006 @tab @code{qXfer:osdata:read}
24007 @tab @code{info os}
24009 @item @code{query-attached}
24010 @tab @code{qAttached}
24011 @tab Querying remote process attach state.
24013 @item @code{trace-buffer-size}
24014 @tab @code{QTBuffer:size}
24015 @tab @code{set trace-buffer-size}
24017 @item @code{trace-status}
24018 @tab @code{qTStatus}
24019 @tab @code{tstatus}
24021 @item @code{traceframe-info}
24022 @tab @code{qXfer:traceframe-info:read}
24023 @tab Traceframe info
24025 @item @code{install-in-trace}
24026 @tab @code{InstallInTrace}
24027 @tab Install tracepoint in tracing
24029 @item @code{disable-randomization}
24030 @tab @code{QDisableRandomization}
24031 @tab @code{set disable-randomization}
24033 @item @code{startup-with-shell}
24034 @tab @code{QStartupWithShell}
24035 @tab @code{set startup-with-shell}
24037 @item @code{environment-hex-encoded}
24038 @tab @code{QEnvironmentHexEncoded}
24039 @tab @code{set environment}
24041 @item @code{environment-unset}
24042 @tab @code{QEnvironmentUnset}
24043 @tab @code{unset environment}
24045 @item @code{environment-reset}
24046 @tab @code{QEnvironmentReset}
24047 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
24049 @item @code{set-working-dir}
24050 @tab @code{QSetWorkingDir}
24051 @tab @code{set cwd}
24053 @item @code{conditional-breakpoints-packet}
24054 @tab @code{Z0 and Z1}
24055 @tab @code{Support for target-side breakpoint condition evaluation}
24057 @item @code{multiprocess-extensions}
24058 @tab @code{multiprocess extensions}
24059 @tab Debug multiple processes and remote process PID awareness
24061 @item @code{swbreak-feature}
24062 @tab @code{swbreak stop reason}
24065 @item @code{hwbreak-feature}
24066 @tab @code{hwbreak stop reason}
24069 @item @code{fork-event-feature}
24070 @tab @code{fork stop reason}
24073 @item @code{vfork-event-feature}
24074 @tab @code{vfork stop reason}
24077 @item @code{exec-event-feature}
24078 @tab @code{exec stop reason}
24081 @item @code{thread-events}
24082 @tab @code{QThreadEvents}
24083 @tab Tracking thread lifetime.
24085 @item @code{no-resumed-stop-reply}
24086 @tab @code{no resumed thread left stop reply}
24087 @tab Tracking thread lifetime.
24092 @section Implementing a Remote Stub
24094 @cindex debugging stub, example
24095 @cindex remote stub, example
24096 @cindex stub example, remote debugging
24097 The stub files provided with @value{GDBN} implement the target side of the
24098 communication protocol, and the @value{GDBN} side is implemented in the
24099 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
24100 these subroutines to communicate, and ignore the details. (If you're
24101 implementing your own stub file, you can still ignore the details: start
24102 with one of the existing stub files. @file{sparc-stub.c} is the best
24103 organized, and therefore the easiest to read.)
24105 @cindex remote serial debugging, overview
24106 To debug a program running on another machine (the debugging
24107 @dfn{target} machine), you must first arrange for all the usual
24108 prerequisites for the program to run by itself. For example, for a C
24113 A startup routine to set up the C runtime environment; these usually
24114 have a name like @file{crt0}. The startup routine may be supplied by
24115 your hardware supplier, or you may have to write your own.
24118 A C subroutine library to support your program's
24119 subroutine calls, notably managing input and output.
24122 A way of getting your program to the other machine---for example, a
24123 download program. These are often supplied by the hardware
24124 manufacturer, but you may have to write your own from hardware
24128 The next step is to arrange for your program to use a serial port to
24129 communicate with the machine where @value{GDBN} is running (the @dfn{host}
24130 machine). In general terms, the scheme looks like this:
24134 @value{GDBN} already understands how to use this protocol; when everything
24135 else is set up, you can simply use the @samp{target remote} command
24136 (@pxref{Targets,,Specifying a Debugging Target}).
24138 @item On the target,
24139 you must link with your program a few special-purpose subroutines that
24140 implement the @value{GDBN} remote serial protocol. The file containing these
24141 subroutines is called a @dfn{debugging stub}.
24143 On certain remote targets, you can use an auxiliary program
24144 @code{gdbserver} instead of linking a stub into your program.
24145 @xref{Server,,Using the @code{gdbserver} Program}, for details.
24148 The debugging stub is specific to the architecture of the remote
24149 machine; for example, use @file{sparc-stub.c} to debug programs on
24152 @cindex remote serial stub list
24153 These working remote stubs are distributed with @value{GDBN}:
24158 @cindex @file{i386-stub.c}
24161 For Intel 386 and compatible architectures.
24164 @cindex @file{m68k-stub.c}
24165 @cindex Motorola 680x0
24167 For Motorola 680x0 architectures.
24170 @cindex @file{sh-stub.c}
24173 For Renesas SH architectures.
24176 @cindex @file{sparc-stub.c}
24178 For @sc{sparc} architectures.
24180 @item sparcl-stub.c
24181 @cindex @file{sparcl-stub.c}
24184 For Fujitsu @sc{sparclite} architectures.
24188 The @file{README} file in the @value{GDBN} distribution may list other
24189 recently added stubs.
24192 * Stub Contents:: What the stub can do for you
24193 * Bootstrapping:: What you must do for the stub
24194 * Debug Session:: Putting it all together
24197 @node Stub Contents
24198 @subsection What the Stub Can Do for You
24200 @cindex remote serial stub
24201 The debugging stub for your architecture supplies these three
24205 @item set_debug_traps
24206 @findex set_debug_traps
24207 @cindex remote serial stub, initialization
24208 This routine arranges for @code{handle_exception} to run when your
24209 program stops. You must call this subroutine explicitly in your
24210 program's startup code.
24212 @item handle_exception
24213 @findex handle_exception
24214 @cindex remote serial stub, main routine
24215 This is the central workhorse, but your program never calls it
24216 explicitly---the setup code arranges for @code{handle_exception} to
24217 run when a trap is triggered.
24219 @code{handle_exception} takes control when your program stops during
24220 execution (for example, on a breakpoint), and mediates communications
24221 with @value{GDBN} on the host machine. This is where the communications
24222 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24223 representative on the target machine. It begins by sending summary
24224 information on the state of your program, then continues to execute,
24225 retrieving and transmitting any information @value{GDBN} needs, until you
24226 execute a @value{GDBN} command that makes your program resume; at that point,
24227 @code{handle_exception} returns control to your own code on the target
24231 @cindex @code{breakpoint} subroutine, remote
24232 Use this auxiliary subroutine to make your program contain a
24233 breakpoint. Depending on the particular situation, this may be the only
24234 way for @value{GDBN} to get control. For instance, if your target
24235 machine has some sort of interrupt button, you won't need to call this;
24236 pressing the interrupt button transfers control to
24237 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24238 simply receiving characters on the serial port may also trigger a trap;
24239 again, in that situation, you don't need to call @code{breakpoint} from
24240 your own program---simply running @samp{target remote} from the host
24241 @value{GDBN} session gets control.
24243 Call @code{breakpoint} if none of these is true, or if you simply want
24244 to make certain your program stops at a predetermined point for the
24245 start of your debugging session.
24248 @node Bootstrapping
24249 @subsection What You Must Do for the Stub
24251 @cindex remote stub, support routines
24252 The debugging stubs that come with @value{GDBN} are set up for a particular
24253 chip architecture, but they have no information about the rest of your
24254 debugging target machine.
24256 First of all you need to tell the stub how to communicate with the
24260 @item int getDebugChar()
24261 @findex getDebugChar
24262 Write this subroutine to read a single character from the serial port.
24263 It may be identical to @code{getchar} for your target system; a
24264 different name is used to allow you to distinguish the two if you wish.
24266 @item void putDebugChar(int)
24267 @findex putDebugChar
24268 Write this subroutine to write a single character to the serial port.
24269 It may be identical to @code{putchar} for your target system; a
24270 different name is used to allow you to distinguish the two if you wish.
24273 @cindex control C, and remote debugging
24274 @cindex interrupting remote targets
24275 If you want @value{GDBN} to be able to stop your program while it is
24276 running, you need to use an interrupt-driven serial driver, and arrange
24277 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24278 character). That is the character which @value{GDBN} uses to tell the
24279 remote system to stop.
24281 Getting the debugging target to return the proper status to @value{GDBN}
24282 probably requires changes to the standard stub; one quick and dirty way
24283 is to just execute a breakpoint instruction (the ``dirty'' part is that
24284 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24286 Other routines you need to supply are:
24289 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24290 @findex exceptionHandler
24291 Write this function to install @var{exception_address} in the exception
24292 handling tables. You need to do this because the stub does not have any
24293 way of knowing what the exception handling tables on your target system
24294 are like (for example, the processor's table might be in @sc{rom},
24295 containing entries which point to a table in @sc{ram}).
24296 The @var{exception_number} specifies the exception which should be changed;
24297 its meaning is architecture-dependent (for example, different numbers
24298 might represent divide by zero, misaligned access, etc). When this
24299 exception occurs, control should be transferred directly to
24300 @var{exception_address}, and the processor state (stack, registers,
24301 and so on) should be just as it is when a processor exception occurs. So if
24302 you want to use a jump instruction to reach @var{exception_address}, it
24303 should be a simple jump, not a jump to subroutine.
24305 For the 386, @var{exception_address} should be installed as an interrupt
24306 gate so that interrupts are masked while the handler runs. The gate
24307 should be at privilege level 0 (the most privileged level). The
24308 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24309 help from @code{exceptionHandler}.
24311 @item void flush_i_cache()
24312 @findex flush_i_cache
24313 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24314 instruction cache, if any, on your target machine. If there is no
24315 instruction cache, this subroutine may be a no-op.
24317 On target machines that have instruction caches, @value{GDBN} requires this
24318 function to make certain that the state of your program is stable.
24322 You must also make sure this library routine is available:
24325 @item void *memset(void *, int, int)
24327 This is the standard library function @code{memset} that sets an area of
24328 memory to a known value. If you have one of the free versions of
24329 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24330 either obtain it from your hardware manufacturer, or write your own.
24333 If you do not use the GNU C compiler, you may need other standard
24334 library subroutines as well; this varies from one stub to another,
24335 but in general the stubs are likely to use any of the common library
24336 subroutines which @code{@value{NGCC}} generates as inline code.
24339 @node Debug Session
24340 @subsection Putting it All Together
24342 @cindex remote serial debugging summary
24343 In summary, when your program is ready to debug, you must follow these
24348 Make sure you have defined the supporting low-level routines
24349 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24351 @code{getDebugChar}, @code{putDebugChar},
24352 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24356 Insert these lines in your program's startup code, before the main
24357 procedure is called:
24364 On some machines, when a breakpoint trap is raised, the hardware
24365 automatically makes the PC point to the instruction after the
24366 breakpoint. If your machine doesn't do that, you may need to adjust
24367 @code{handle_exception} to arrange for it to return to the instruction
24368 after the breakpoint on this first invocation, so that your program
24369 doesn't keep hitting the initial breakpoint instead of making
24373 For the 680x0 stub only, you need to provide a variable called
24374 @code{exceptionHook}. Normally you just use:
24377 void (*exceptionHook)() = 0;
24381 but if before calling @code{set_debug_traps}, you set it to point to a
24382 function in your program, that function is called when
24383 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24384 error). The function indicated by @code{exceptionHook} is called with
24385 one parameter: an @code{int} which is the exception number.
24388 Compile and link together: your program, the @value{GDBN} debugging stub for
24389 your target architecture, and the supporting subroutines.
24392 Make sure you have a serial connection between your target machine and
24393 the @value{GDBN} host, and identify the serial port on the host.
24396 @c The "remote" target now provides a `load' command, so we should
24397 @c document that. FIXME.
24398 Download your program to your target machine (or get it there by
24399 whatever means the manufacturer provides), and start it.
24402 Start @value{GDBN} on the host, and connect to the target
24403 (@pxref{Connecting,,Connecting to a Remote Target}).
24407 @node Configurations
24408 @chapter Configuration-Specific Information
24410 While nearly all @value{GDBN} commands are available for all native and
24411 cross versions of the debugger, there are some exceptions. This chapter
24412 describes things that are only available in certain configurations.
24414 There are three major categories of configurations: native
24415 configurations, where the host and target are the same, embedded
24416 operating system configurations, which are usually the same for several
24417 different processor architectures, and bare embedded processors, which
24418 are quite different from each other.
24423 * Embedded Processors::
24430 This section describes details specific to particular native
24434 * BSD libkvm Interface:: Debugging BSD kernel memory images
24435 * Process Information:: Process information
24436 * DJGPP Native:: Features specific to the DJGPP port
24437 * Cygwin Native:: Features specific to the Cygwin port
24438 * Hurd Native:: Features specific to @sc{gnu} Hurd
24439 * Darwin:: Features specific to Darwin
24440 * FreeBSD:: Features specific to FreeBSD
24443 @node BSD libkvm Interface
24444 @subsection BSD libkvm Interface
24447 @cindex kernel memory image
24448 @cindex kernel crash dump
24450 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24451 interface that provides a uniform interface for accessing kernel virtual
24452 memory images, including live systems and crash dumps. @value{GDBN}
24453 uses this interface to allow you to debug live kernels and kernel crash
24454 dumps on many native BSD configurations. This is implemented as a
24455 special @code{kvm} debugging target. For debugging a live system, load
24456 the currently running kernel into @value{GDBN} and connect to the
24460 (@value{GDBP}) @b{target kvm}
24463 For debugging crash dumps, provide the file name of the crash dump as an
24467 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24470 Once connected to the @code{kvm} target, the following commands are
24476 Set current context from the @dfn{Process Control Block} (PCB) address.
24479 Set current context from proc address. This command isn't available on
24480 modern FreeBSD systems.
24483 @node Process Information
24484 @subsection Process Information
24486 @cindex examine process image
24487 @cindex process info via @file{/proc}
24489 Some operating systems provide interfaces to fetch additional
24490 information about running processes beyond memory and per-thread
24491 register state. If @value{GDBN} is configured for an operating system
24492 with a supported interface, the command @code{info proc} is available
24493 to report information about the process running your program, or about
24494 any process running on your system.
24496 One supported interface is a facility called @samp{/proc} that can be
24497 used to examine the image of a running process using file-system
24498 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24501 On FreeBSD and NetBSD systems, system control nodes are used to query
24502 process information.
24504 In addition, some systems may provide additional process information
24505 in core files. Note that a core file may include a subset of the
24506 information available from a live process. Process information is
24507 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24514 @itemx info proc @var{process-id}
24515 Summarize available information about a process. If a
24516 process ID is specified by @var{process-id}, display information about
24517 that process; otherwise display information about the program being
24518 debugged. The summary includes the debugged process ID, the command
24519 line used to invoke it, its current working directory, and its
24520 executable file's absolute file name.
24522 On some systems, @var{process-id} can be of the form
24523 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24524 within a process. If the optional @var{pid} part is missing, it means
24525 a thread from the process being debugged (the leading @samp{/} still
24526 needs to be present, or else @value{GDBN} will interpret the number as
24527 a process ID rather than a thread ID).
24529 @item info proc cmdline
24530 @cindex info proc cmdline
24531 Show the original command line of the process. This command is
24532 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24534 @item info proc cwd
24535 @cindex info proc cwd
24536 Show the current working directory of the process. This command is
24537 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24539 @item info proc exe
24540 @cindex info proc exe
24541 Show the name of executable of the process. This command is supported
24542 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24544 @item info proc files
24545 @cindex info proc files
24546 Show the file descriptors open by the process. For each open file
24547 descriptor, @value{GDBN} shows its number, type (file, directory,
24548 character device, socket), file pointer offset, and the name of the
24549 resource open on the descriptor. The resource name can be a file name
24550 (for files, directories, and devices) or a protocol followed by socket
24551 address (for network connections). This command is supported on
24554 This example shows the open file descriptors for a process using a
24555 tty for standard input and output as well as two network sockets:
24558 (gdb) info proc files 22136
24562 FD Type Offset Flags Name
24563 text file - r-------- /usr/bin/ssh
24564 ctty chr - rw------- /dev/pts/20
24565 cwd dir - r-------- /usr/home/john
24566 root dir - r-------- /
24567 0 chr 0x32933a4 rw------- /dev/pts/20
24568 1 chr 0x32933a4 rw------- /dev/pts/20
24569 2 chr 0x32933a4 rw------- /dev/pts/20
24570 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24571 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24574 @item info proc mappings
24575 @cindex memory address space mappings
24576 Report the memory address space ranges accessible in a process. On
24577 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24578 on whether the process has read, write, or execute access rights to each
24579 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24580 includes the object file which is mapped to that range.
24582 @item info proc stat
24583 @itemx info proc status
24584 @cindex process detailed status information
24585 Show additional process-related information, including the user ID and
24586 group ID; virtual memory usage; the signals that are pending, blocked,
24587 and ignored; its TTY; its consumption of system and user time; its
24588 stack size; its @samp{nice} value; etc. These commands are supported
24589 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24591 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24592 information (type @kbd{man 5 proc} from your shell prompt).
24594 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24595 @code{info proc status}.
24597 @item info proc all
24598 Show all the information about the process described under all of the
24599 above @code{info proc} subcommands.
24602 @comment These sub-options of 'info proc' were not included when
24603 @comment procfs.c was re-written. Keep their descriptions around
24604 @comment against the day when someone finds the time to put them back in.
24605 @kindex info proc times
24606 @item info proc times
24607 Starting time, user CPU time, and system CPU time for your program and
24610 @kindex info proc id
24612 Report on the process IDs related to your program: its own process ID,
24613 the ID of its parent, the process group ID, and the session ID.
24616 @item set procfs-trace
24617 @kindex set procfs-trace
24618 @cindex @code{procfs} API calls
24619 This command enables and disables tracing of @code{procfs} API calls.
24621 @item show procfs-trace
24622 @kindex show procfs-trace
24623 Show the current state of @code{procfs} API call tracing.
24625 @item set procfs-file @var{file}
24626 @kindex set procfs-file
24627 Tell @value{GDBN} to write @code{procfs} API trace to the named
24628 @var{file}. @value{GDBN} appends the trace info to the previous
24629 contents of the file. The default is to display the trace on the
24632 @item show procfs-file
24633 @kindex show procfs-file
24634 Show the file to which @code{procfs} API trace is written.
24636 @item proc-trace-entry
24637 @itemx proc-trace-exit
24638 @itemx proc-untrace-entry
24639 @itemx proc-untrace-exit
24640 @kindex proc-trace-entry
24641 @kindex proc-trace-exit
24642 @kindex proc-untrace-entry
24643 @kindex proc-untrace-exit
24644 These commands enable and disable tracing of entries into and exits
24645 from the @code{syscall} interface.
24648 @kindex info pidlist
24649 @cindex process list, QNX Neutrino
24650 For QNX Neutrino only, this command displays the list of all the
24651 processes and all the threads within each process.
24654 @kindex info meminfo
24655 @cindex mapinfo list, QNX Neutrino
24656 For QNX Neutrino only, this command displays the list of all mapinfos.
24660 @subsection Features for Debugging @sc{djgpp} Programs
24661 @cindex @sc{djgpp} debugging
24662 @cindex native @sc{djgpp} debugging
24663 @cindex MS-DOS-specific commands
24666 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24667 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24668 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24669 top of real-mode DOS systems and their emulations.
24671 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24672 defines a few commands specific to the @sc{djgpp} port. This
24673 subsection describes those commands.
24678 This is a prefix of @sc{djgpp}-specific commands which print
24679 information about the target system and important OS structures.
24682 @cindex MS-DOS system info
24683 @cindex free memory information (MS-DOS)
24684 @item info dos sysinfo
24685 This command displays assorted information about the underlying
24686 platform: the CPU type and features, the OS version and flavor, the
24687 DPMI version, and the available conventional and DPMI memory.
24692 @cindex segment descriptor tables
24693 @cindex descriptor tables display
24695 @itemx info dos ldt
24696 @itemx info dos idt
24697 These 3 commands display entries from, respectively, Global, Local,
24698 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24699 tables are data structures which store a descriptor for each segment
24700 that is currently in use. The segment's selector is an index into a
24701 descriptor table; the table entry for that index holds the
24702 descriptor's base address and limit, and its attributes and access
24705 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24706 segment (used for both data and the stack), and a DOS segment (which
24707 allows access to DOS/BIOS data structures and absolute addresses in
24708 conventional memory). However, the DPMI host will usually define
24709 additional segments in order to support the DPMI environment.
24711 @cindex garbled pointers
24712 These commands allow to display entries from the descriptor tables.
24713 Without an argument, all entries from the specified table are
24714 displayed. An argument, which should be an integer expression, means
24715 display a single entry whose index is given by the argument. For
24716 example, here's a convenient way to display information about the
24717 debugged program's data segment:
24720 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24721 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24725 This comes in handy when you want to see whether a pointer is outside
24726 the data segment's limit (i.e.@: @dfn{garbled}).
24728 @cindex page tables display (MS-DOS)
24730 @itemx info dos pte
24731 These two commands display entries from, respectively, the Page
24732 Directory and the Page Tables. Page Directories and Page Tables are
24733 data structures which control how virtual memory addresses are mapped
24734 into physical addresses. A Page Table includes an entry for every
24735 page of memory that is mapped into the program's address space; there
24736 may be several Page Tables, each one holding up to 4096 entries. A
24737 Page Directory has up to 4096 entries, one each for every Page Table
24738 that is currently in use.
24740 Without an argument, @kbd{info dos pde} displays the entire Page
24741 Directory, and @kbd{info dos pte} displays all the entries in all of
24742 the Page Tables. An argument, an integer expression, given to the
24743 @kbd{info dos pde} command means display only that entry from the Page
24744 Directory table. An argument given to the @kbd{info dos pte} command
24745 means display entries from a single Page Table, the one pointed to by
24746 the specified entry in the Page Directory.
24748 @cindex direct memory access (DMA) on MS-DOS
24749 These commands are useful when your program uses @dfn{DMA} (Direct
24750 Memory Access), which needs physical addresses to program the DMA
24753 These commands are supported only with some DPMI servers.
24755 @cindex physical address from linear address
24756 @item info dos address-pte @var{addr}
24757 This command displays the Page Table entry for a specified linear
24758 address. The argument @var{addr} is a linear address which should
24759 already have the appropriate segment's base address added to it,
24760 because this command accepts addresses which may belong to @emph{any}
24761 segment. For example, here's how to display the Page Table entry for
24762 the page where a variable @code{i} is stored:
24765 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24766 @exdent @code{Page Table entry for address 0x11a00d30:}
24767 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24771 This says that @code{i} is stored at offset @code{0xd30} from the page
24772 whose physical base address is @code{0x02698000}, and shows all the
24773 attributes of that page.
24775 Note that you must cast the addresses of variables to a @code{char *},
24776 since otherwise the value of @code{__djgpp_base_address}, the base
24777 address of all variables and functions in a @sc{djgpp} program, will
24778 be added using the rules of C pointer arithmetics: if @code{i} is
24779 declared an @code{int}, @value{GDBN} will add 4 times the value of
24780 @code{__djgpp_base_address} to the address of @code{i}.
24782 Here's another example, it displays the Page Table entry for the
24786 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24787 @exdent @code{Page Table entry for address 0x29110:}
24788 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24792 (The @code{+ 3} offset is because the transfer buffer's address is the
24793 3rd member of the @code{_go32_info_block} structure.) The output
24794 clearly shows that this DPMI server maps the addresses in conventional
24795 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24796 linear (@code{0x29110}) addresses are identical.
24798 This command is supported only with some DPMI servers.
24801 @cindex DOS serial data link, remote debugging
24802 In addition to native debugging, the DJGPP port supports remote
24803 debugging via a serial data link. The following commands are specific
24804 to remote serial debugging in the DJGPP port of @value{GDBN}.
24807 @kindex set com1base
24808 @kindex set com1irq
24809 @kindex set com2base
24810 @kindex set com2irq
24811 @kindex set com3base
24812 @kindex set com3irq
24813 @kindex set com4base
24814 @kindex set com4irq
24815 @item set com1base @var{addr}
24816 This command sets the base I/O port address of the @file{COM1} serial
24819 @item set com1irq @var{irq}
24820 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24821 for the @file{COM1} serial port.
24823 There are similar commands @samp{set com2base}, @samp{set com3irq},
24824 etc.@: for setting the port address and the @code{IRQ} lines for the
24827 @kindex show com1base
24828 @kindex show com1irq
24829 @kindex show com2base
24830 @kindex show com2irq
24831 @kindex show com3base
24832 @kindex show com3irq
24833 @kindex show com4base
24834 @kindex show com4irq
24835 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24836 display the current settings of the base address and the @code{IRQ}
24837 lines used by the COM ports.
24840 @kindex info serial
24841 @cindex DOS serial port status
24842 This command prints the status of the 4 DOS serial ports. For each
24843 port, it prints whether it's active or not, its I/O base address and
24844 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24845 counts of various errors encountered so far.
24849 @node Cygwin Native
24850 @subsection Features for Debugging MS Windows PE Executables
24851 @cindex MS Windows debugging
24852 @cindex native Cygwin debugging
24853 @cindex Cygwin-specific commands
24855 @value{GDBN} supports native debugging of MS Windows programs, including
24856 DLLs with and without symbolic debugging information.
24858 @cindex Ctrl-BREAK, MS-Windows
24859 @cindex interrupt debuggee on MS-Windows
24860 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24861 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24862 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24863 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24864 sequence, which can be used to interrupt the debuggee even if it
24867 There are various additional Cygwin-specific commands, described in
24868 this section. Working with DLLs that have no debugging symbols is
24869 described in @ref{Non-debug DLL Symbols}.
24874 This is a prefix of MS Windows-specific commands which print
24875 information about the target system and important OS structures.
24877 @item info w32 selector
24878 This command displays information returned by
24879 the Win32 API @code{GetThreadSelectorEntry} function.
24880 It takes an optional argument that is evaluated to
24881 a long value to give the information about this given selector.
24882 Without argument, this command displays information
24883 about the six segment registers.
24885 @item info w32 thread-information-block
24886 This command displays thread specific information stored in the
24887 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24888 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24890 @kindex signal-event
24891 @item signal-event @var{id}
24892 This command signals an event with user-provided @var{id}. Used to resume
24893 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24895 To use it, create or edit the following keys in
24896 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24897 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24898 (for x86_64 versions):
24902 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24903 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24904 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24906 The first @code{%ld} will be replaced by the process ID of the
24907 crashing process, the second @code{%ld} will be replaced by the ID of
24908 the event that blocks the crashing process, waiting for @value{GDBN}
24912 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24913 make the system run debugger specified by the Debugger key
24914 automatically, @code{0} will cause a dialog box with ``OK'' and
24915 ``Cancel'' buttons to appear, which allows the user to either
24916 terminate the crashing process (OK) or debug it (Cancel).
24919 @kindex set cygwin-exceptions
24920 @cindex debugging the Cygwin DLL
24921 @cindex Cygwin DLL, debugging
24922 @item set cygwin-exceptions @var{mode}
24923 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24924 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24925 @value{GDBN} will delay recognition of exceptions, and may ignore some
24926 exceptions which seem to be caused by internal Cygwin DLL
24927 ``bookkeeping''. This option is meant primarily for debugging the
24928 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24929 @value{GDBN} users with false @code{SIGSEGV} signals.
24931 @kindex show cygwin-exceptions
24932 @item show cygwin-exceptions
24933 Displays whether @value{GDBN} will break on exceptions that happen
24934 inside the Cygwin DLL itself.
24936 @kindex set new-console
24937 @item set new-console @var{mode}
24938 If @var{mode} is @code{on} the debuggee will
24939 be started in a new console on next start.
24940 If @var{mode} is @code{off}, the debuggee will
24941 be started in the same console as the debugger.
24943 @kindex show new-console
24944 @item show new-console
24945 Displays whether a new console is used
24946 when the debuggee is started.
24948 @kindex set new-group
24949 @item set new-group @var{mode}
24950 This boolean value controls whether the debuggee should
24951 start a new group or stay in the same group as the debugger.
24952 This affects the way the Windows OS handles
24955 @kindex show new-group
24956 @item show new-group
24957 Displays current value of new-group boolean.
24959 @kindex set debugevents
24960 @item set debugevents
24961 This boolean value adds debug output concerning kernel events related
24962 to the debuggee seen by the debugger. This includes events that
24963 signal thread and process creation and exit, DLL loading and
24964 unloading, console interrupts, and debugging messages produced by the
24965 Windows @code{OutputDebugString} API call.
24967 @kindex set debugexec
24968 @item set debugexec
24969 This boolean value adds debug output concerning execute events
24970 (such as resume thread) seen by the debugger.
24972 @kindex set debugexceptions
24973 @item set debugexceptions
24974 This boolean value adds debug output concerning exceptions in the
24975 debuggee seen by the debugger.
24977 @kindex set debugmemory
24978 @item set debugmemory
24979 This boolean value adds debug output concerning debuggee memory reads
24980 and writes by the debugger.
24984 This boolean values specifies whether the debuggee is called
24985 via a shell or directly (default value is on).
24989 Displays if the debuggee will be started with a shell.
24994 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24997 @node Non-debug DLL Symbols
24998 @subsubsection Support for DLLs without Debugging Symbols
24999 @cindex DLLs with no debugging symbols
25000 @cindex Minimal symbols and DLLs
25002 Very often on windows, some of the DLLs that your program relies on do
25003 not include symbolic debugging information (for example,
25004 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
25005 symbols in a DLL, it relies on the minimal amount of symbolic
25006 information contained in the DLL's export table. This section
25007 describes working with such symbols, known internally to @value{GDBN} as
25008 ``minimal symbols''.
25010 Note that before the debugged program has started execution, no DLLs
25011 will have been loaded. The easiest way around this problem is simply to
25012 start the program --- either by setting a breakpoint or letting the
25013 program run once to completion.
25015 @subsubsection DLL Name Prefixes
25017 In keeping with the naming conventions used by the Microsoft debugging
25018 tools, DLL export symbols are made available with a prefix based on the
25019 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
25020 also entered into the symbol table, so @code{CreateFileA} is often
25021 sufficient. In some cases there will be name clashes within a program
25022 (particularly if the executable itself includes full debugging symbols)
25023 necessitating the use of the fully qualified name when referring to the
25024 contents of the DLL. Use single-quotes around the name to avoid the
25025 exclamation mark (``!'') being interpreted as a language operator.
25027 Note that the internal name of the DLL may be all upper-case, even
25028 though the file name of the DLL is lower-case, or vice-versa. Since
25029 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
25030 some confusion. If in doubt, try the @code{info functions} and
25031 @code{info variables} commands or even @code{maint print msymbols}
25032 (@pxref{Symbols}). Here's an example:
25035 (@value{GDBP}) info function CreateFileA
25036 All functions matching regular expression "CreateFileA":
25038 Non-debugging symbols:
25039 0x77e885f4 CreateFileA
25040 0x77e885f4 KERNEL32!CreateFileA
25044 (@value{GDBP}) info function !
25045 All functions matching regular expression "!":
25047 Non-debugging symbols:
25048 0x6100114c cygwin1!__assert
25049 0x61004034 cygwin1!_dll_crt0@@0
25050 0x61004240 cygwin1!dll_crt0(per_process *)
25054 @subsubsection Working with Minimal Symbols
25056 Symbols extracted from a DLL's export table do not contain very much
25057 type information. All that @value{GDBN} can do is guess whether a symbol
25058 refers to a function or variable depending on the linker section that
25059 contains the symbol. Also note that the actual contents of the memory
25060 contained in a DLL are not available unless the program is running. This
25061 means that you cannot examine the contents of a variable or disassemble
25062 a function within a DLL without a running program.
25064 Variables are generally treated as pointers and dereferenced
25065 automatically. For this reason, it is often necessary to prefix a
25066 variable name with the address-of operator (``&'') and provide explicit
25067 type information in the command. Here's an example of the type of
25071 (@value{GDBP}) print 'cygwin1!__argv'
25072 'cygwin1!__argv' has unknown type; cast it to its declared type
25076 (@value{GDBP}) x 'cygwin1!__argv'
25077 'cygwin1!__argv' has unknown type; cast it to its declared type
25080 And two possible solutions:
25083 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
25084 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
25088 (@value{GDBP}) x/2x &'cygwin1!__argv'
25089 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
25090 (@value{GDBP}) x/x 0x10021608
25091 0x10021608: 0x0022fd98
25092 (@value{GDBP}) x/s 0x0022fd98
25093 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
25096 Setting a break point within a DLL is possible even before the program
25097 starts execution. However, under these circumstances, @value{GDBN} can't
25098 examine the initial instructions of the function in order to skip the
25099 function's frame set-up code. You can work around this by using ``*&''
25100 to set the breakpoint at a raw memory address:
25103 (@value{GDBP}) break *&'python22!PyOS_Readline'
25104 Breakpoint 1 at 0x1e04eff0
25107 The author of these extensions is not entirely convinced that setting a
25108 break point within a shared DLL like @file{kernel32.dll} is completely
25112 @subsection Commands Specific to @sc{gnu} Hurd Systems
25113 @cindex @sc{gnu} Hurd debugging
25115 This subsection describes @value{GDBN} commands specific to the
25116 @sc{gnu} Hurd native debugging.
25121 @kindex set signals@r{, Hurd command}
25122 @kindex set sigs@r{, Hurd command}
25123 This command toggles the state of inferior signal interception by
25124 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
25125 affected by this command. @code{sigs} is a shorthand alias for
25130 @kindex show signals@r{, Hurd command}
25131 @kindex show sigs@r{, Hurd command}
25132 Show the current state of intercepting inferior's signals.
25134 @item set signal-thread
25135 @itemx set sigthread
25136 @kindex set signal-thread
25137 @kindex set sigthread
25138 This command tells @value{GDBN} which thread is the @code{libc} signal
25139 thread. That thread is run when a signal is delivered to a running
25140 process. @code{set sigthread} is the shorthand alias of @code{set
25143 @item show signal-thread
25144 @itemx show sigthread
25145 @kindex show signal-thread
25146 @kindex show sigthread
25147 These two commands show which thread will run when the inferior is
25148 delivered a signal.
25151 @kindex set stopped@r{, Hurd command}
25152 This commands tells @value{GDBN} that the inferior process is stopped,
25153 as with the @code{SIGSTOP} signal. The stopped process can be
25154 continued by delivering a signal to it.
25157 @kindex show stopped@r{, Hurd command}
25158 This command shows whether @value{GDBN} thinks the debuggee is
25161 @item set exceptions
25162 @kindex set exceptions@r{, Hurd command}
25163 Use this command to turn off trapping of exceptions in the inferior.
25164 When exception trapping is off, neither breakpoints nor
25165 single-stepping will work. To restore the default, set exception
25168 @item show exceptions
25169 @kindex show exceptions@r{, Hurd command}
25170 Show the current state of trapping exceptions in the inferior.
25172 @item set task pause
25173 @kindex set task@r{, Hurd commands}
25174 @cindex task attributes (@sc{gnu} Hurd)
25175 @cindex pause current task (@sc{gnu} Hurd)
25176 This command toggles task suspension when @value{GDBN} has control.
25177 Setting it to on takes effect immediately, and the task is suspended
25178 whenever @value{GDBN} gets control. Setting it to off will take
25179 effect the next time the inferior is continued. If this option is set
25180 to off, you can use @code{set thread default pause on} or @code{set
25181 thread pause on} (see below) to pause individual threads.
25183 @item show task pause
25184 @kindex show task@r{, Hurd commands}
25185 Show the current state of task suspension.
25187 @item set task detach-suspend-count
25188 @cindex task suspend count
25189 @cindex detach from task, @sc{gnu} Hurd
25190 This command sets the suspend count the task will be left with when
25191 @value{GDBN} detaches from it.
25193 @item show task detach-suspend-count
25194 Show the suspend count the task will be left with when detaching.
25196 @item set task exception-port
25197 @itemx set task excp
25198 @cindex task exception port, @sc{gnu} Hurd
25199 This command sets the task exception port to which @value{GDBN} will
25200 forward exceptions. The argument should be the value of the @dfn{send
25201 rights} of the task. @code{set task excp} is a shorthand alias.
25203 @item set noninvasive
25204 @cindex noninvasive task options
25205 This command switches @value{GDBN} to a mode that is the least
25206 invasive as far as interfering with the inferior is concerned. This
25207 is the same as using @code{set task pause}, @code{set exceptions}, and
25208 @code{set signals} to values opposite to the defaults.
25210 @item info send-rights
25211 @itemx info receive-rights
25212 @itemx info port-rights
25213 @itemx info port-sets
25214 @itemx info dead-names
25217 @cindex send rights, @sc{gnu} Hurd
25218 @cindex receive rights, @sc{gnu} Hurd
25219 @cindex port rights, @sc{gnu} Hurd
25220 @cindex port sets, @sc{gnu} Hurd
25221 @cindex dead names, @sc{gnu} Hurd
25222 These commands display information about, respectively, send rights,
25223 receive rights, port rights, port sets, and dead names of a task.
25224 There are also shorthand aliases: @code{info ports} for @code{info
25225 port-rights} and @code{info psets} for @code{info port-sets}.
25227 @item set thread pause
25228 @kindex set thread@r{, Hurd command}
25229 @cindex thread properties, @sc{gnu} Hurd
25230 @cindex pause current thread (@sc{gnu} Hurd)
25231 This command toggles current thread suspension when @value{GDBN} has
25232 control. Setting it to on takes effect immediately, and the current
25233 thread is suspended whenever @value{GDBN} gets control. Setting it to
25234 off will take effect the next time the inferior is continued.
25235 Normally, this command has no effect, since when @value{GDBN} has
25236 control, the whole task is suspended. However, if you used @code{set
25237 task pause off} (see above), this command comes in handy to suspend
25238 only the current thread.
25240 @item show thread pause
25241 @kindex show thread@r{, Hurd command}
25242 This command shows the state of current thread suspension.
25244 @item set thread run
25245 This command sets whether the current thread is allowed to run.
25247 @item show thread run
25248 Show whether the current thread is allowed to run.
25250 @item set thread detach-suspend-count
25251 @cindex thread suspend count, @sc{gnu} Hurd
25252 @cindex detach from thread, @sc{gnu} Hurd
25253 This command sets the suspend count @value{GDBN} will leave on a
25254 thread when detaching. This number is relative to the suspend count
25255 found by @value{GDBN} when it notices the thread; use @code{set thread
25256 takeover-suspend-count} to force it to an absolute value.
25258 @item show thread detach-suspend-count
25259 Show the suspend count @value{GDBN} will leave on the thread when
25262 @item set thread exception-port
25263 @itemx set thread excp
25264 Set the thread exception port to which to forward exceptions. This
25265 overrides the port set by @code{set task exception-port} (see above).
25266 @code{set thread excp} is the shorthand alias.
25268 @item set thread takeover-suspend-count
25269 Normally, @value{GDBN}'s thread suspend counts are relative to the
25270 value @value{GDBN} finds when it notices each thread. This command
25271 changes the suspend counts to be absolute instead.
25273 @item set thread default
25274 @itemx show thread default
25275 @cindex thread default settings, @sc{gnu} Hurd
25276 Each of the above @code{set thread} commands has a @code{set thread
25277 default} counterpart (e.g., @code{set thread default pause}, @code{set
25278 thread default exception-port}, etc.). The @code{thread default}
25279 variety of commands sets the default thread properties for all
25280 threads; you can then change the properties of individual threads with
25281 the non-default commands.
25288 @value{GDBN} provides the following commands specific to the Darwin target:
25291 @item set debug darwin @var{num}
25292 @kindex set debug darwin
25293 When set to a non zero value, enables debugging messages specific to
25294 the Darwin support. Higher values produce more verbose output.
25296 @item show debug darwin
25297 @kindex show debug darwin
25298 Show the current state of Darwin messages.
25300 @item set debug mach-o @var{num}
25301 @kindex set debug mach-o
25302 When set to a non zero value, enables debugging messages while
25303 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25304 file format used on Darwin for object and executable files.) Higher
25305 values produce more verbose output. This is a command to diagnose
25306 problems internal to @value{GDBN} and should not be needed in normal
25309 @item show debug mach-o
25310 @kindex show debug mach-o
25311 Show the current state of Mach-O file messages.
25313 @item set mach-exceptions on
25314 @itemx set mach-exceptions off
25315 @kindex set mach-exceptions
25316 On Darwin, faults are first reported as a Mach exception and are then
25317 mapped to a Posix signal. Use this command to turn on trapping of
25318 Mach exceptions in the inferior. This might be sometimes useful to
25319 better understand the cause of a fault. The default is off.
25321 @item show mach-exceptions
25322 @kindex show mach-exceptions
25323 Show the current state of exceptions trapping.
25327 @subsection FreeBSD
25330 When the ABI of a system call is changed in the FreeBSD kernel, this
25331 is implemented by leaving a compatibility system call using the old
25332 ABI at the existing number and allocating a new system call number for
25333 the version using the new ABI. As a convenience, when a system call
25334 is caught by name (@pxref{catch syscall}), compatibility system calls
25337 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25338 system call and catching the @code{kevent} system call by name catches
25342 (@value{GDBP}) catch syscall kevent
25343 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25349 @section Embedded Operating Systems
25351 This section describes configurations involving the debugging of
25352 embedded operating systems that are available for several different
25355 @value{GDBN} includes the ability to debug programs running on
25356 various real-time operating systems.
25358 @node Embedded Processors
25359 @section Embedded Processors
25361 This section goes into details specific to particular embedded
25364 @cindex send command to simulator
25365 Whenever a specific embedded processor has a simulator, @value{GDBN}
25366 allows to send an arbitrary command to the simulator.
25369 @item sim @var{command}
25370 @kindex sim@r{, a command}
25371 Send an arbitrary @var{command} string to the simulator. Consult the
25372 documentation for the specific simulator in use for information about
25373 acceptable commands.
25378 * ARC:: Synopsys ARC
25381 * M68K:: Motorola M68K
25382 * MicroBlaze:: Xilinx MicroBlaze
25383 * MIPS Embedded:: MIPS Embedded
25384 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25385 * PowerPC Embedded:: PowerPC Embedded
25388 * Super-H:: Renesas Super-H
25392 @subsection Synopsys ARC
25393 @cindex Synopsys ARC
25394 @cindex ARC specific commands
25400 @value{GDBN} provides the following ARC-specific commands:
25403 @item set debug arc
25404 @kindex set debug arc
25405 Control the level of ARC specific debug messages. Use 0 for no messages (the
25406 default), 1 for debug messages, and 2 for even more debug messages.
25408 @item show debug arc
25409 @kindex show debug arc
25410 Show the level of ARC specific debugging in operation.
25412 @item maint print arc arc-instruction @var{address}
25413 @kindex maint print arc arc-instruction
25414 Print internal disassembler information about instruction at a given address.
25421 @value{GDBN} provides the following ARM-specific commands:
25424 @item set arm disassembler
25426 This commands selects from a list of disassembly styles. The
25427 @code{"std"} style is the standard style.
25429 @item show arm disassembler
25431 Show the current disassembly style.
25433 @item set arm apcs32
25434 @cindex ARM 32-bit mode
25435 This command toggles ARM operation mode between 32-bit and 26-bit.
25437 @item show arm apcs32
25438 Display the current usage of the ARM 32-bit mode.
25440 @item set arm fpu @var{fputype}
25441 This command sets the ARM floating-point unit (FPU) type. The
25442 argument @var{fputype} can be one of these:
25446 Determine the FPU type by querying the OS ABI.
25448 Software FPU, with mixed-endian doubles on little-endian ARM
25451 GCC-compiled FPA co-processor.
25453 Software FPU with pure-endian doubles.
25459 Show the current type of the FPU.
25462 This command forces @value{GDBN} to use the specified ABI.
25465 Show the currently used ABI.
25467 @item set arm fallback-mode (arm|thumb|auto)
25468 @value{GDBN} uses the symbol table, when available, to determine
25469 whether instructions are ARM or Thumb. This command controls
25470 @value{GDBN}'s default behavior when the symbol table is not
25471 available. The default is @samp{auto}, which causes @value{GDBN} to
25472 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25475 @item show arm fallback-mode
25476 Show the current fallback instruction mode.
25478 @item set arm force-mode (arm|thumb|auto)
25479 This command overrides use of the symbol table to determine whether
25480 instructions are ARM or Thumb. The default is @samp{auto}, which
25481 causes @value{GDBN} to use the symbol table and then the setting
25482 of @samp{set arm fallback-mode}.
25484 @item show arm force-mode
25485 Show the current forced instruction mode.
25487 @item set arm unwind-secure-frames
25488 This command enables unwinding from Non-secure to Secure mode on
25489 Cortex-M with Security extension.
25490 This can trigger security exceptions when unwinding the exception
25492 It is enabled by default.
25494 @item show arm unwind-secure-frames
25495 Show whether unwinding from Non-secure to Secure mode is enabled.
25497 @item set debug arm
25498 Toggle whether to display ARM-specific debugging messages from the ARM
25499 target support subsystem.
25501 @item show debug arm
25502 Show whether ARM-specific debugging messages are enabled.
25506 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25507 The @value{GDBN} ARM simulator accepts the following optional arguments.
25510 @item --swi-support=@var{type}
25511 Tell the simulator which SWI interfaces to support. The argument
25512 @var{type} may be a comma separated list of the following values.
25513 The default value is @code{all}.
25529 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25530 The @value{GDBN} BPF simulator accepts the following optional arguments.
25533 @item --skb-data-offset=@var{offset}
25534 Tell the simulator the offset, measured in bytes, of the
25535 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25536 This offset is used by some BPF specific-purpose load/store
25537 instructions. Defaults to 0.
25544 The Motorola m68k configuration includes ColdFire support.
25547 @subsection MicroBlaze
25548 @cindex Xilinx MicroBlaze
25549 @cindex XMD, Xilinx Microprocessor Debugger
25551 The MicroBlaze is a soft-core processor supported on various Xilinx
25552 FPGAs, such as Spartan or Virtex series. Boards with these processors
25553 usually have JTAG ports which connect to a host system running the Xilinx
25554 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25555 This host system is used to download the configuration bitstream to
25556 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25557 communicates with the target board using the JTAG interface and
25558 presents a @code{gdbserver} interface to the board. By default
25559 @code{xmd} uses port @code{1234}. (While it is possible to change
25560 this default port, it requires the use of undocumented @code{xmd}
25561 commands. Contact Xilinx support if you need to do this.)
25563 Use these GDB commands to connect to the MicroBlaze target processor.
25566 @item target remote :1234
25567 Use this command to connect to the target if you are running @value{GDBN}
25568 on the same system as @code{xmd}.
25570 @item target remote @var{xmd-host}:1234
25571 Use this command to connect to the target if it is connected to @code{xmd}
25572 running on a different system named @var{xmd-host}.
25575 Use this command to download a program to the MicroBlaze target.
25577 @item set debug microblaze @var{n}
25578 Enable MicroBlaze-specific debugging messages if non-zero.
25580 @item show debug microblaze @var{n}
25581 Show MicroBlaze-specific debugging level.
25584 @node MIPS Embedded
25585 @subsection @acronym{MIPS} Embedded
25588 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25591 @item set mipsfpu double
25592 @itemx set mipsfpu single
25593 @itemx set mipsfpu none
25594 @itemx set mipsfpu auto
25595 @itemx show mipsfpu
25596 @kindex set mipsfpu
25597 @kindex show mipsfpu
25598 @cindex @acronym{MIPS} remote floating point
25599 @cindex floating point, @acronym{MIPS} remote
25600 If your target board does not support the @acronym{MIPS} floating point
25601 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25602 need this, you may wish to put the command in your @value{GDBN} init
25603 file). This tells @value{GDBN} how to find the return value of
25604 functions which return floating point values. It also allows
25605 @value{GDBN} to avoid saving the floating point registers when calling
25606 functions on the board. If you are using a floating point coprocessor
25607 with only single precision floating point support, as on the @sc{r4650}
25608 processor, use the command @samp{set mipsfpu single}. The default
25609 double precision floating point coprocessor may be selected using
25610 @samp{set mipsfpu double}.
25612 In previous versions the only choices were double precision or no
25613 floating point, so @samp{set mipsfpu on} will select double precision
25614 and @samp{set mipsfpu off} will select no floating point.
25616 As usual, you can inquire about the @code{mipsfpu} variable with
25617 @samp{show mipsfpu}.
25620 @node OpenRISC 1000
25621 @subsection OpenRISC 1000
25622 @cindex OpenRISC 1000
25625 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25626 mainly provided as a soft-core which can run on Xilinx, Altera and other
25629 @value{GDBN} for OpenRISC supports the below commands when connecting to
25637 Runs the builtin CPU simulator which can run very basic
25638 programs but does not support most hardware functions like MMU.
25639 For more complex use cases the user is advised to run an external
25640 target, and connect using @samp{target remote}.
25642 Example: @code{target sim}
25644 @item set debug or1k
25645 Toggle whether to display OpenRISC-specific debugging messages from the
25646 OpenRISC target support subsystem.
25648 @item show debug or1k
25649 Show whether OpenRISC-specific debugging messages are enabled.
25652 @node PowerPC Embedded
25653 @subsection PowerPC Embedded
25655 @cindex DVC register
25656 @value{GDBN} supports using the DVC (Data Value Compare) register to
25657 implement in hardware simple hardware watchpoint conditions of the form:
25660 (@value{GDBP}) watch @var{address|variable} \
25661 if @var{address|variable} == @var{constant expression}
25664 The DVC register will be automatically used when @value{GDBN} detects
25665 such pattern in a condition expression, and the created watchpoint uses one
25666 debug register (either the @code{exact-watchpoints} option is on and the
25667 variable is scalar, or the variable has a length of one byte). This feature
25668 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25671 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25672 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25673 in which case watchpoints using only one debug register are created when
25674 watching variables of scalar types.
25676 You can create an artificial array to watch an arbitrary memory
25677 region using one of the following commands (@pxref{Expressions}):
25680 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25681 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25684 PowerPC embedded processors support masked watchpoints. See the discussion
25685 about the @code{mask} argument in @ref{Set Watchpoints}.
25687 @cindex ranged breakpoint
25688 PowerPC embedded processors support hardware accelerated
25689 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25690 the inferior whenever it executes an instruction at any address within
25691 the range it was set at. To set a ranged breakpoint in @value{GDBN},
25692 use the @code{break-range} command.
25694 @value{GDBN} provides the following PowerPC-specific commands:
25697 @kindex break-range
25698 @item break-range @var{start-locspec}, @var{end-locspec}
25699 Set a breakpoint for an address range given by @var{start-locspec} and
25700 @var{end-locspec}, which are location specs. @xref{Location
25701 Specifications}, for a list of all the possible forms of location
25702 specs. @value{GDBN} resolves both @var{start-locspec} and
25703 @var{end-locspec}, and uses the addresses of the resolved code
25704 locations as start and end addresses of the range to break at. The
25705 breakpoint will stop execution of the inferior whenever it executes an
25706 instruction at any address between the start and end addresses,
25707 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
25708 to multiple code locations in the program, then the command aborts
25709 with an error without creating a breakpoint.
25711 @kindex set powerpc
25712 @item set powerpc soft-float
25713 @itemx show powerpc soft-float
25714 Force @value{GDBN} to use (or not use) a software floating point calling
25715 convention. By default, @value{GDBN} selects the calling convention based
25716 on the selected architecture and the provided executable file.
25718 @item set powerpc vector-abi
25719 @itemx show powerpc vector-abi
25720 Force @value{GDBN} to use the specified calling convention for vector
25721 arguments and return values. The valid options are @samp{auto};
25722 @samp{generic}, to avoid vector registers even if they are present;
25723 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25724 registers. By default, @value{GDBN} selects the calling convention
25725 based on the selected architecture and the provided executable file.
25727 @item set powerpc exact-watchpoints
25728 @itemx show powerpc exact-watchpoints
25729 Allow @value{GDBN} to use only one debug register when watching a variable
25730 of scalar type, thus assuming that the variable is accessed through the
25731 address of its first byte.
25736 @subsection Atmel AVR
25739 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25740 following AVR-specific commands:
25743 @item info io_registers
25744 @kindex info io_registers@r{, AVR}
25745 @cindex I/O registers (Atmel AVR)
25746 This command displays information about the AVR I/O registers. For
25747 each register, @value{GDBN} prints its number and value.
25754 When configured for debugging CRIS, @value{GDBN} provides the
25755 following CRIS-specific commands:
25758 @item set cris-version @var{ver}
25759 @cindex CRIS version
25760 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25761 The CRIS version affects register names and sizes. This command is useful in
25762 case autodetection of the CRIS version fails.
25764 @item show cris-version
25765 Show the current CRIS version.
25767 @item set cris-dwarf2-cfi
25768 @cindex DWARF-2 CFI and CRIS
25769 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25770 Change to @samp{off} when using @code{gcc-cris} whose version is below
25773 @item show cris-dwarf2-cfi
25774 Show the current state of using DWARF-2 CFI.
25776 @item set cris-mode @var{mode}
25778 Set the current CRIS mode to @var{mode}. It should only be changed when
25779 debugging in guru mode, in which case it should be set to
25780 @samp{guru} (the default is @samp{normal}).
25782 @item show cris-mode
25783 Show the current CRIS mode.
25787 @subsection Renesas Super-H
25790 For the Renesas Super-H processor, @value{GDBN} provides these
25794 @item set sh calling-convention @var{convention}
25795 @kindex set sh calling-convention
25796 Set the calling-convention used when calling functions from @value{GDBN}.
25797 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25798 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25799 convention. If the DWARF-2 information of the called function specifies
25800 that the function follows the Renesas calling convention, the function
25801 is called using the Renesas calling convention. If the calling convention
25802 is set to @samp{renesas}, the Renesas calling convention is always used,
25803 regardless of the DWARF-2 information. This can be used to override the
25804 default of @samp{gcc} if debug information is missing, or the compiler
25805 does not emit the DWARF-2 calling convention entry for a function.
25807 @item show sh calling-convention
25808 @kindex show sh calling-convention
25809 Show the current calling convention setting.
25814 @node Architectures
25815 @section Architectures
25817 This section describes characteristics of architectures that affect
25818 all uses of @value{GDBN} with the architecture, both native and cross.
25825 * HPPA:: HP PA architecture
25833 @subsection AArch64
25834 @cindex AArch64 support
25836 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25837 following special commands:
25840 @item set debug aarch64
25841 @kindex set debug aarch64
25842 This command determines whether AArch64 architecture-specific debugging
25843 messages are to be displayed.
25845 @item show debug aarch64
25846 Show whether AArch64 debugging messages are displayed.
25850 @subsubsection AArch64 SVE.
25851 @cindex AArch64 SVE.
25853 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25854 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25855 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25856 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25857 @code{$vg} will be provided. This is the vector granule for the current thread
25858 and represents the number of 64-bit chunks in an SVE @code{z} register.
25860 If the vector length changes, then the @code{$vg} register will be updated,
25861 but the lengths of the @code{z} and @code{p} registers will not change. This
25862 is a known limitation of @value{GDBN} and does not affect the execution of the
25865 @subsubsection AArch64 Pointer Authentication.
25866 @cindex AArch64 Pointer Authentication.
25867 @anchor{AArch64 PAC}
25869 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25870 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25871 register @code{$lr} is pointing to an PAC function its value will be masked.
25872 When GDB prints a backtrace, any addresses that required unmasking will be
25873 postfixed with the marker [PAC]. When using the MI, this is printed as part
25874 of the @code{addr_flags} field.
25876 @subsubsection AArch64 Memory Tagging Extension.
25877 @cindex AArch64 Memory Tagging Extension.
25879 When @value{GDBN} is debugging the AArch64 architecture, the program is
25880 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25881 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25882 available for inspection and editing of logical and allocation tags.
25883 @xref{Memory Tagging}.
25885 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25886 signals are generated as a result of memory tag failures.
25888 If the tag violation is synchronous, the following will be shown:
25891 Program received signal SIGSEGV, Segmentation fault
25892 Memory tag violation while accessing address 0x0500fffff7ff8000
25897 If the tag violation is asynchronous, the fault address is not available.
25898 In this case @value{GDBN} will show the following:
25901 Program received signal SIGSEGV, Segmentation fault
25902 Memory tag violation
25903 Fault address unavailable.
25906 A special register, @code{tag_ctl}, is made available through the
25907 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25908 options that can be controlled at runtime and emulates the @code{prctl}
25909 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25910 documentation in the Linux kernel.
25912 @value{GDBN} supports dumping memory tag data to core files through the
25913 @command{gcore} command and reading memory tag data from core files generated
25914 by the @command{gcore} command or the Linux kernel.
25916 When a process uses memory-mapped pages protected by memory tags (for
25917 example, AArch64 MTE), this additional information will be recorded in
25918 the core file in the event of a crash or if @value{GDBN} generates a core file
25919 from the current process state.
25921 The memory tag data will be used so developers can display the memory
25922 tags from a particular memory region (using the @samp{m} modifier to the
25923 @command{x} command, using the @command{print} command or using the various
25924 @command{memory-tag} subcommands.
25926 In the case of a crash, @value{GDBN} will attempt to retrieve the memory tag
25927 information automatically from the core file, and will show one of the above
25928 messages depending on whether the synchronous or asynchronous mode is selected.
25929 @xref{Memory Tagging}. @xref{Memory}.
25932 @subsection x86 Architecture-specific Issues
25935 @item set struct-convention @var{mode}
25936 @kindex set struct-convention
25937 @cindex struct return convention
25938 @cindex struct/union returned in registers
25939 Set the convention used by the inferior to return @code{struct}s and
25940 @code{union}s from functions to @var{mode}. Possible values of
25941 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25942 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25943 are returned on the stack, while @code{"reg"} means that a
25944 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25945 be returned in a register.
25947 @item show struct-convention
25948 @kindex show struct-convention
25949 Show the current setting of the convention to return @code{struct}s
25954 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25955 @cindex Intel Memory Protection Extensions (MPX).
25957 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25958 @footnote{The register named with capital letters represent the architecture
25959 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25960 which are the lower bound and upper bound. Bounds are effective addresses or
25961 memory locations. The upper bounds are architecturally represented in 1's
25962 complement form. A bound having lower bound = 0, and upper bound = 0
25963 (1's complement of all bits set) will allow access to the entire address space.
25965 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25966 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25967 display the upper bound performing the complement of one operation on the
25968 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25969 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25970 can also be noted that the upper bounds are inclusive.
25972 As an example, assume that the register BND0 holds bounds for a pointer having
25973 access allowed for the range between 0x32 and 0x71. The values present on
25974 bnd0raw and bnd registers are presented as follows:
25977 bnd0raw = @{0x32, 0xffffffff8e@}
25978 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25981 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25982 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25983 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25984 Python, the display includes the memory size, in bits, accessible to
25987 Bounds can also be stored in bounds tables, which are stored in
25988 application memory. These tables store bounds for pointers by specifying
25989 the bounds pointer's value along with its bounds. Evaluating and changing
25990 bounds located in bound tables is therefore interesting while investigating
25991 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25994 @item show mpx bound @var{pointer}
25995 @kindex show mpx bound
25996 Display bounds of the given @var{pointer}.
25998 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25999 @kindex set mpx bound
26000 Set the bounds of a pointer in the bound table.
26001 This command takes three parameters: @var{pointer} is the pointers
26002 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
26003 for lower and upper bounds respectively.
26006 When you call an inferior function on an Intel MPX enabled program,
26007 GDB sets the inferior's bound registers to the init (disabled) state
26008 before calling the function. As a consequence, bounds checks for the
26009 pointer arguments passed to the function will always pass.
26011 This is necessary because when you call an inferior function, the
26012 program is usually in the middle of the execution of other function.
26013 Since at that point bound registers are in an arbitrary state, not
26014 clearing them would lead to random bound violations in the called
26017 You can still examine the influence of the bound registers on the
26018 execution of the called function by stopping the execution of the
26019 called function at its prologue, setting bound registers, and
26020 continuing the execution. For example:
26024 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
26025 $ print upper (a, b, c, d, 1)
26026 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
26028 @{lbound = 0x0, ubound = ffffffff@} : size -1
26031 At this last step the value of bnd0 can be changed for investigation of bound
26032 violations caused along the execution of the call. In order to know how to
26033 set the bound registers or bound table for the call consult the ABI.
26038 See the following section.
26041 @subsection @acronym{MIPS}
26043 @cindex stack on Alpha
26044 @cindex stack on @acronym{MIPS}
26045 @cindex Alpha stack
26046 @cindex @acronym{MIPS} stack
26047 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
26048 sometimes requires @value{GDBN} to search backward in the object code to
26049 find the beginning of a function.
26051 @cindex response time, @acronym{MIPS} debugging
26052 To improve response time (especially for embedded applications, where
26053 @value{GDBN} may be restricted to a slow serial line for this search)
26054 you may want to limit the size of this search, using one of these
26058 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
26059 @item set heuristic-fence-post @var{limit}
26060 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
26061 search for the beginning of a function. A value of @var{0} (the
26062 default) means there is no limit. However, except for @var{0}, the
26063 larger the limit the more bytes @code{heuristic-fence-post} must search
26064 and therefore the longer it takes to run. You should only need to use
26065 this command when debugging a stripped executable.
26067 @item show heuristic-fence-post
26068 Display the current limit.
26072 These commands are available @emph{only} when @value{GDBN} is configured
26073 for debugging programs on Alpha or @acronym{MIPS} processors.
26075 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
26079 @item set mips abi @var{arg}
26080 @kindex set mips abi
26081 @cindex set ABI for @acronym{MIPS}
26082 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
26083 values of @var{arg} are:
26087 The default ABI associated with the current binary (this is the
26097 @item show mips abi
26098 @kindex show mips abi
26099 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
26101 @item set mips compression @var{arg}
26102 @kindex set mips compression
26103 @cindex code compression, @acronym{MIPS}
26104 Tell @value{GDBN} which @acronym{MIPS} compressed
26105 @acronym{ISA, Instruction Set Architecture} encoding is used by the
26106 inferior. @value{GDBN} uses this for code disassembly and other
26107 internal interpretation purposes. This setting is only referred to
26108 when no executable has been associated with the debugging session or
26109 the executable does not provide information about the encoding it uses.
26110 Otherwise this setting is automatically updated from information
26111 provided by the executable.
26113 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
26114 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
26115 executables containing @acronym{MIPS16} code frequently are not
26116 identified as such.
26118 This setting is ``sticky''; that is, it retains its value across
26119 debugging sessions until reset either explicitly with this command or
26120 implicitly from an executable.
26122 The compiler and/or assembler typically add symbol table annotations to
26123 identify functions compiled for the @acronym{MIPS16} or
26124 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
26125 are present, @value{GDBN} uses them in preference to the global
26126 compressed @acronym{ISA} encoding setting.
26128 @item show mips compression
26129 @kindex show mips compression
26130 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
26131 @value{GDBN} to debug the inferior.
26134 @itemx show mipsfpu
26135 @xref{MIPS Embedded, set mipsfpu}.
26137 @item set mips mask-address @var{arg}
26138 @kindex set mips mask-address
26139 @cindex @acronym{MIPS} addresses, masking
26140 This command determines whether the most-significant 32 bits of 64-bit
26141 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
26142 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
26143 setting, which lets @value{GDBN} determine the correct value.
26145 @item show mips mask-address
26146 @kindex show mips mask-address
26147 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
26150 @item set remote-mips64-transfers-32bit-regs
26151 @kindex set remote-mips64-transfers-32bit-regs
26152 This command controls compatibility with 64-bit @acronym{MIPS} targets that
26153 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
26154 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
26155 and 64 bits for other registers, set this option to @samp{on}.
26157 @item show remote-mips64-transfers-32bit-regs
26158 @kindex show remote-mips64-transfers-32bit-regs
26159 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
26161 @item set debug mips
26162 @kindex set debug mips
26163 This command turns on and off debugging messages for the @acronym{MIPS}-specific
26164 target code in @value{GDBN}.
26166 @item show debug mips
26167 @kindex show debug mips
26168 Show the current setting of @acronym{MIPS} debugging messages.
26174 @cindex HPPA support
26176 When @value{GDBN} is debugging the HP PA architecture, it provides the
26177 following special commands:
26180 @item set debug hppa
26181 @kindex set debug hppa
26182 This command determines whether HPPA architecture-specific debugging
26183 messages are to be displayed.
26185 @item show debug hppa
26186 Show whether HPPA debugging messages are displayed.
26188 @item maint print unwind @var{address}
26189 @kindex maint print unwind@r{, HPPA}
26190 This command displays the contents of the unwind table entry at the
26191 given @var{address}.
26197 @subsection PowerPC
26198 @cindex PowerPC architecture
26200 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26201 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26202 numbers stored in the floating point registers. These values must be stored
26203 in two consecutive registers, always starting at an even register like
26204 @code{f0} or @code{f2}.
26206 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26207 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26208 @code{f2} and @code{f3} for @code{$dl1} and so on.
26210 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26211 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26214 @subsection Nios II
26215 @cindex Nios II architecture
26217 When @value{GDBN} is debugging the Nios II architecture,
26218 it provides the following special commands:
26222 @item set debug nios2
26223 @kindex set debug nios2
26224 This command turns on and off debugging messages for the Nios II
26225 target code in @value{GDBN}.
26227 @item show debug nios2
26228 @kindex show debug nios2
26229 Show the current setting of Nios II debugging messages.
26233 @subsection Sparc64
26234 @cindex Sparc64 support
26235 @cindex Application Data Integrity
26236 @subsubsection ADI Support
26238 The M7 processor supports an Application Data Integrity (ADI) feature that
26239 detects invalid data accesses. When software allocates memory and enables
26240 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26241 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26242 the 4-bit version in every cacheline of that data. Hardware saves the latter
26243 in spare bits in the cache and memory hierarchy. On each load and store,
26244 the processor compares the upper 4 VA (virtual address) bits to the
26245 cacheline's version. If there is a mismatch, the processor generates a
26246 version mismatch trap which can be either precise or disrupting. The trap
26247 is an error condition which the kernel delivers to the process as a SIGSEGV
26250 Note that only 64-bit applications can use ADI and need to be built with
26253 Values of the ADI version tags, which are in granularity of a
26254 cacheline (64 bytes), can be viewed or modified.
26258 @kindex adi examine
26259 @item adi (examine | x) [ / @var{n} ] @var{addr}
26261 The @code{adi examine} command displays the value of one ADI version tag per
26264 @var{n} is a decimal integer specifying the number in bytes; the default
26265 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26266 block size, to display.
26268 @var{addr} is the address in user address space where you want @value{GDBN}
26269 to begin displaying the ADI version tags.
26271 Below is an example of displaying ADI versions of variable "shmaddr".
26274 (@value{GDBP}) adi x/100 shmaddr
26275 0xfff800010002c000: 0 0
26279 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26281 The @code{adi assign} command is used to assign new ADI version tag
26284 @var{n} is a decimal integer specifying the number in bytes;
26285 the default is 1. It specifies how much ADI version information, at the
26286 ratio of 1:ADI block size, to modify.
26288 @var{addr} is the address in user address space where you want @value{GDBN}
26289 to begin modifying the ADI version tags.
26291 @var{tag} is the new ADI version tag.
26293 For example, do the following to modify then verify ADI versions of
26294 variable "shmaddr":
26297 (@value{GDBP}) adi a/100 shmaddr = 7
26298 (@value{GDBP}) adi x/100 shmaddr
26299 0xfff800010002c000: 7 7
26306 @cindex S12Z support
26308 When @value{GDBN} is debugging the S12Z architecture,
26309 it provides the following special command:
26312 @item maint info bdccsr
26313 @kindex maint info bdccsr@r{, S12Z}
26314 This command displays the current value of the microprocessor's
26319 @node Controlling GDB
26320 @chapter Controlling @value{GDBN}
26322 You can alter the way @value{GDBN} interacts with you by using the
26323 @code{set} command. For commands controlling how @value{GDBN} displays
26324 data, see @ref{Print Settings, ,Print Settings}. Other settings are
26329 * Editing:: Command editing
26330 * Command History:: Command history
26331 * Screen Size:: Screen size
26332 * Output Styling:: Output styling
26333 * Numbers:: Numbers
26334 * ABI:: Configuring the current ABI
26335 * Auto-loading:: Automatically loading associated files
26336 * Messages/Warnings:: Optional warnings and messages
26337 * Debugging Output:: Optional messages about internal happenings
26338 * Other Misc Settings:: Other Miscellaneous Settings
26346 @value{GDBN} indicates its readiness to read a command by printing a string
26347 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
26348 can change the prompt string with the @code{set prompt} command. For
26349 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
26350 the prompt in one of the @value{GDBN} sessions so that you can always tell
26351 which one you are talking to.
26353 @emph{Note:} @code{set prompt} does not add a space for you after the
26354 prompt you set. This allows you to set a prompt which ends in a space
26355 or a prompt that does not.
26359 @item set prompt @var{newprompt}
26360 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
26362 @kindex show prompt
26364 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
26367 Versions of @value{GDBN} that ship with Python scripting enabled have
26368 prompt extensions. The commands for interacting with these extensions
26372 @kindex set extended-prompt
26373 @item set extended-prompt @var{prompt}
26374 Set an extended prompt that allows for substitutions.
26375 @xref{gdb.prompt}, for a list of escape sequences that can be used for
26376 substitution. Any escape sequences specified as part of the prompt
26377 string are replaced with the corresponding strings each time the prompt
26383 set extended-prompt Current working directory: \w (gdb)
26386 Note that when an extended-prompt is set, it takes control of the
26387 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26389 @kindex show extended-prompt
26390 @item show extended-prompt
26391 Prints the extended prompt. Any escape sequences specified as part of
26392 the prompt string with @code{set extended-prompt}, are replaced with the
26393 corresponding strings each time the prompt is displayed.
26397 @section Command Editing
26399 @cindex command line editing
26401 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26402 @sc{gnu} library provides consistent behavior for programs which provide a
26403 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26404 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26405 substitution, and a storage and recall of command history across
26406 debugging sessions.
26408 You may control the behavior of command line editing in @value{GDBN} with the
26409 command @code{set}.
26412 @kindex set editing
26415 @itemx set editing on
26416 Enable command line editing (enabled by default).
26418 @item set editing off
26419 Disable command line editing.
26421 @kindex show editing
26423 Show whether command line editing is enabled.
26426 @ifset SYSTEM_READLINE
26427 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26429 @ifclear SYSTEM_READLINE
26430 @xref{Command Line Editing},
26432 for more details about the Readline
26433 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26434 encouraged to read that chapter.
26436 @cindex Readline application name
26437 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26438 is useful for conditions in @file{.inputrc}.
26440 @cindex operate-and-get-next
26441 @value{GDBN} defines a bindable Readline command,
26442 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26443 This command accepts the current line for execution and fetches the
26444 next line relative to the current line from the history for editing.
26445 Any argument is ignored.
26447 @node Command History
26448 @section Command History
26449 @cindex command history
26451 @value{GDBN} can keep track of the commands you type during your
26452 debugging sessions, so that you can be certain of precisely what
26453 happened. Use these commands to manage the @value{GDBN} command
26456 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26457 package, to provide the history facility.
26458 @ifset SYSTEM_READLINE
26459 @xref{Using History Interactively, , , history, GNU History Library},
26461 @ifclear SYSTEM_READLINE
26462 @xref{Using History Interactively},
26464 for the detailed description of the History library.
26466 To issue a command to @value{GDBN} without affecting certain aspects of
26467 the state which is seen by users, prefix it with @samp{server }
26468 (@pxref{Server Prefix}). This
26469 means that this command will not affect the command history, nor will it
26470 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26471 pressed on a line by itself.
26473 @cindex @code{server}, command prefix
26474 The server prefix does not affect the recording of values into the value
26475 history; to print a value without recording it into the value history,
26476 use the @code{output} command instead of the @code{print} command.
26478 Here is the description of @value{GDBN} commands related to command
26482 @cindex history substitution
26483 @cindex history file
26484 @kindex set history filename
26485 @cindex @env{GDBHISTFILE}, environment variable
26486 @item set history filename @r{[}@var{fname}@r{]}
26487 Set the name of the @value{GDBN} command history file to @var{fname}.
26488 This is the file where @value{GDBN} reads an initial command history
26489 list, and where it writes the command history from this session when it
26490 exits. You can access this list through history expansion or through
26491 the history command editing characters listed below. This file defaults
26492 to the value of the environment variable @env{GDBHISTFILE}, or to
26493 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26496 The @env{GDBHISTFILE} environment variable is read after processing
26497 any @value{GDBN} initialization files (@pxref{Startup}) and after
26498 processing any commands passed using command line options (for
26499 example, @code{-ex}).
26501 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26502 is the empty string then @value{GDBN} will neither try to load an
26503 existing history file, nor will it try to save the history on exit.
26505 @cindex save command history
26506 @kindex set history save
26507 @item set history save
26508 @itemx set history save on
26509 Record command history in a file, whose name may be specified with the
26510 @code{set history filename} command. By default, this option is
26511 disabled. The command history will be recorded when @value{GDBN}
26512 exits. If @code{set history filename} is set to the empty string then
26513 history saving is disabled, even when @code{set history save} is
26516 @item set history save off
26517 Don't record the command history into the file specified by @code{set
26518 history filename} when @value{GDBN} exits.
26520 @cindex history size
26521 @kindex set history size
26522 @cindex @env{GDBHISTSIZE}, environment variable
26523 @item set history size @var{size}
26524 @itemx set history size unlimited
26525 Set the number of commands which @value{GDBN} keeps in its history list.
26526 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26527 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26528 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26529 either a negative number or the empty string, then the number of commands
26530 @value{GDBN} keeps in the history list is unlimited.
26532 The @env{GDBHISTSIZE} environment variable is read after processing
26533 any @value{GDBN} initialization files (@pxref{Startup}) and after
26534 processing any commands passed using command line options (for
26535 example, @code{-ex}).
26537 @cindex remove duplicate history
26538 @kindex set history remove-duplicates
26539 @item set history remove-duplicates @var{count}
26540 @itemx set history remove-duplicates unlimited
26541 Control the removal of duplicate history entries in the command history list.
26542 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26543 history entries and remove the first entry that is a duplicate of the current
26544 entry being added to the command history list. If @var{count} is
26545 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26546 removal of duplicate history entries is disabled.
26548 Only history entries added during the current session are considered for
26549 removal. This option is set to 0 by default.
26553 History expansion assigns special meaning to the character @kbd{!}.
26554 @ifset SYSTEM_READLINE
26555 @xref{Event Designators, , , history, GNU History Library},
26557 @ifclear SYSTEM_READLINE
26558 @xref{Event Designators},
26562 @cindex history expansion, turn on/off
26563 Since @kbd{!} is also the logical not operator in C, history expansion
26564 is off by default. If you decide to enable history expansion with the
26565 @code{set history expansion on} command, you may sometimes need to
26566 follow @kbd{!} (when it is used as logical not, in an expression) with
26567 a space or a tab to prevent it from being expanded. The readline
26568 history facilities do not attempt substitution on the strings
26569 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26571 The commands to control history expansion are:
26574 @item set history expansion on
26575 @itemx set history expansion
26576 @kindex set history expansion
26577 Enable history expansion. History expansion is off by default.
26579 @item set history expansion off
26580 Disable history expansion.
26583 @kindex show history
26585 @itemx show history filename
26586 @itemx show history save
26587 @itemx show history size
26588 @itemx show history expansion
26589 These commands display the state of the @value{GDBN} history parameters.
26590 @code{show history} by itself displays all four states.
26595 @kindex show commands
26596 @cindex show last commands
26597 @cindex display command history
26598 @item show commands
26599 Display the last ten commands in the command history.
26601 @item show commands @var{n}
26602 Print ten commands centered on command number @var{n}.
26604 @item show commands +
26605 Print ten commands just after the commands last printed.
26609 @section Screen Size
26610 @cindex size of screen
26611 @cindex screen size
26614 @cindex pauses in output
26616 Certain commands to @value{GDBN} may produce large amounts of
26617 information output to the screen. To help you read all of it,
26618 @value{GDBN} pauses and asks you for input at the end of each page of
26619 output. Type @key{RET} when you want to see one more page of output,
26620 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26621 without paging for the rest of the current command. Also, the screen
26622 width setting determines when to wrap lines of output. Depending on
26623 what is being printed, @value{GDBN} tries to break the line at a
26624 readable place, rather than simply letting it overflow onto the
26627 Normally @value{GDBN} knows the size of the screen from the terminal
26628 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26629 together with the value of the @env{TERM} environment variable and the
26630 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26631 you can override it with the @code{set height} and @code{set
26638 @kindex show height
26639 @item set height @var{lpp}
26640 @itemx set height unlimited
26642 @itemx set width @var{cpl}
26643 @itemx set width unlimited
26645 These @code{set} commands specify a screen height of @var{lpp} lines and
26646 a screen width of @var{cpl} characters. The associated @code{show}
26647 commands display the current settings.
26649 If you specify a height of either @code{unlimited} or zero lines,
26650 @value{GDBN} does not pause during output no matter how long the
26651 output is. This is useful if output is to a file or to an editor
26654 Likewise, you can specify @samp{set width unlimited} or @samp{set
26655 width 0} to prevent @value{GDBN} from wrapping its output.
26657 @item set pagination on
26658 @itemx set pagination off
26659 @kindex set pagination
26660 Turn the output pagination on or off; the default is on. Turning
26661 pagination off is the alternative to @code{set height unlimited}. Note that
26662 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26663 Options, -batch}) also automatically disables pagination.
26665 @item show pagination
26666 @kindex show pagination
26667 Show the current pagination mode.
26670 @node Output Styling
26671 @section Output Styling
26677 @value{GDBN} can style its output on a capable terminal. This is
26678 enabled by default on most systems, but disabled by default when in
26679 batch mode (@pxref{Mode Options}). Various style settings are available;
26680 and styles can also be disabled entirely.
26683 @item set style enabled @samp{on|off}
26684 Enable or disable all styling. The default is host-dependent, with
26685 most hosts defaulting to @samp{on}.
26687 @item show style enabled
26688 Show the current state of styling.
26690 @item set style sources @samp{on|off}
26691 Enable or disable source code styling. This affects whether source
26692 code, such as the output of the @code{list} command, is styled. The
26693 default is @samp{on}. Note that source styling only works if styling
26694 in general is enabled, and if a source highlighting library is
26695 available to @value{GDBN}.
26697 There are two ways that highlighting can be done. First, if
26698 @value{GDBN} was linked with the GNU Source Highlight library, then it
26699 is used. Otherwise, if @value{GDBN} was configured with Python
26700 scripting support, and if the Python Pygments package is available,
26701 then it will be used.
26703 @item show style sources
26704 Show the current state of source code styling.
26706 @item set style tui-current-position @samp{on|off}
26707 Enable or disable styling of the source and assembly code highlighted
26708 by the TUI's current position indicator. The default is @samp{off}.
26709 @xref{TUI, ,@value{GDBN} Text User Interface}.
26711 @item show style tui-current-position
26712 Show whether the source and assembly code highlighted by the TUI's
26713 current position indicator is styled.
26715 @anchor{style_disassembler_enabled}
26716 @item set style disassembler enabled @samp{on|off}
26717 Enable or disable disassembler styling. This affects whether
26718 disassembler output, such as the output of the @code{disassemble}
26719 command, is styled. Disassembler styling only works if styling in
26720 general is enabled (with @code{set style enabled on}), and if a source
26721 highlighting library is available to @value{GDBN}.
26723 The two source highlighting libraries that @value{GDBN} could use to
26724 style disassembler output are; @value{GDBN}'s builtin disassembler, or
26725 the Python Pygments package.
26727 @value{GDBN}'s first choice will be to use the builtin disassembler
26728 for styling, this usually provides better results, being able to style
26729 different types of instruction operands differently. However, the
26730 builtin disassembler is not able to style all architectures.
26732 For architectures that the builtin disassembler is unable to style,
26733 @value{GDBN} will fall back to use the Python Pygments package where
26734 possible. In order to use the Python Pygments package, @value{GDBN}
26735 must be built with Python support, and the Pygments package must be
26738 If neither of these options are available then @value{GDBN} will
26739 produce unstyled disassembler output, even when this setting is
26742 To discover if the current architecture supports styling using the
26743 builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
26744 show libopcodes-styling enabled}}.
26746 @item show style disassembler enabled
26747 Show the current state of disassembler styling.
26751 Subcommands of @code{set style} control specific forms of styling.
26752 These subcommands all follow the same pattern: each style-able object
26753 can be styled with a foreground color, a background color, and an
26756 For example, the style of file names can be controlled using the
26757 @code{set style filename} group of commands:
26760 @item set style filename background @var{color}
26761 Set the background to @var{color}. Valid colors are @samp{none}
26762 (meaning the terminal's default color), @samp{black}, @samp{red},
26763 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26766 @item set style filename foreground @var{color}
26767 Set the foreground to @var{color}. Valid colors are @samp{none}
26768 (meaning the terminal's default color), @samp{black}, @samp{red},
26769 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26772 @item set style filename intensity @var{value}
26773 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26774 (the default), @samp{bold}, and @samp{dim}.
26777 The @code{show style} command and its subcommands are styling
26778 a style name in their output using its own style.
26779 So, use @command{show style} to see the complete list of styles,
26780 their characteristics and the visual aspect of each style.
26782 The style-able objects are:
26785 Control the styling of file names and URLs. By default, this style's
26786 foreground color is green.
26789 Control the styling of function names. These are managed with the
26790 @code{set style function} family of commands. By default, this
26791 style's foreground color is yellow.
26793 This style is also used for symbol names in styled disassembler output
26794 if @value{GDBN} is using its builtin disassembler library for styling
26795 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26799 Control the styling of variable names. These are managed with the
26800 @code{set style variable} family of commands. By default, this style's
26801 foreground color is cyan.
26804 Control the styling of addresses. These are managed with the
26805 @code{set style address} family of commands. By default, this style's
26806 foreground color is blue.
26808 This style is also used for addresses in styled disassembler output
26809 if @value{GDBN} is using its builtin disassembler library for styling
26810 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26814 Control the styling of @value{GDBN}'s version number text. By
26815 default, this style's foreground color is magenta and it has bold
26816 intensity. The version number is displayed in two places, the output
26817 of @command{show version}, and when @value{GDBN} starts up.
26819 In order to control how @value{GDBN} styles the version number at
26820 startup, add the @code{set style version} family of commands to the
26821 early initialization command file (@pxref{Initialization
26825 Control the styling of titles. These are managed with the
26826 @code{set style title} family of commands. By default, this style's
26827 intensity is bold. Commands are using the title style to improve
26828 the readability of large output. For example, the commands
26829 @command{apropos} and @command{help} are using the title style
26830 for the command names.
26833 Control the styling of highlightings. These are managed with the
26834 @code{set style highlight} family of commands. By default, this style's
26835 foreground color is red. Commands are using the highlight style to draw
26836 the user attention to some specific parts of their output. For example,
26837 the command @command{apropos -v REGEXP} uses the highlight style to
26838 mark the documentation parts matching @var{regexp}.
26841 Control the styling of data annotations added by @value{GDBN} to data
26842 it displays. By default, this style's intensity is dim. Metadata
26843 annotations include the @samp{repeats @var{n} times} annotation for
26844 suppressed display of repeated array elements (@pxref{Print Settings}),
26845 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
26846 for errors and @samp{<optimized-out>} annotations for optimized-out
26847 values in displaying stack frame information in backtraces
26848 (@pxref{Backtrace}), etc.
26851 Control the styling of the TUI border. Note that, unlike other
26852 styling options, only the color of the border can be controlled via
26853 @code{set style}. This was done for compatibility reasons, as TUI
26854 controls to set the border's intensity predated the addition of
26855 general styling to @value{GDBN}. @xref{TUI Configuration}.
26857 @item tui-active-border
26858 Control the styling of the active TUI border; that is, the TUI window
26859 that has the focus.
26861 @item disassembler comment
26862 Control the styling of comments in the disassembler output. These are
26863 managed with the @code{set style disassembler comment} family of
26864 commands. This style is only used when @value{GDBN} is styling using
26865 its builtin disassembler library
26866 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26867 enabled}}). By default, this style's intensity is dim, and its
26868 foreground color is white.
26870 @item disassembler immediate
26871 Control the styling of numeric operands in the disassembler output.
26872 These are managed with the @code{set style disassembler immediate}
26873 family of commands. This style is not used for instruction operands
26874 that represent addresses, in that case the @samp{disassembler address}
26875 style is used. This style is only used when @value{GDBN} is styling
26876 using its builtin disassembler library. By default, this style's
26877 foreground color is blue.
26879 @item disassembler address
26880 Control the styling of address operands in the disassembler output.
26881 This is an alias for the @samp{address} style.
26883 @item disassembler symbol
26884 Control the styling of symbol names in the disassembler output. This
26885 is an alias for the @samp{function} style.
26887 @item disassembler mnemonic
26888 Control the styling of instruction mnemonics in the disassembler
26889 output. These are managed with the @code{set style disassembler
26890 mnemonic} family of commands. This style is also used for assembler
26891 directives, e.g.@: @code{.byte}, @code{.word}, etc. This style is
26892 only used when @value{GDBN} is styling using its builtin disassembler
26893 library. By default, this style's foreground color is green.
26895 @item disassembler register
26896 Control the styling of register operands in the disassembler output.
26897 These are managed with the @code{set style disassembler register}
26898 family of commands. This style is only used when @value{GDBN} is
26899 styling using its builtin disassembler library. By default, this style's
26900 foreground color is red.
26906 @cindex number representation
26907 @cindex entering numbers
26909 You can always enter numbers in octal, decimal, or hexadecimal in
26910 @value{GDBN} by the usual conventions: octal numbers begin with
26911 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26912 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26913 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26914 10; likewise, the default display for numbers---when no particular
26915 format is specified---is base 10. You can change the default base for
26916 both input and output with the commands described below.
26919 @kindex set input-radix
26920 @item set input-radix @var{base}
26921 Set the default base for numeric input. Supported choices
26922 for @var{base} are decimal 8, 10, or 16. The base must itself be
26923 specified either unambiguously or using the current input radix; for
26927 set input-radix 012
26928 set input-radix 10.
26929 set input-radix 0xa
26933 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26934 leaves the input radix unchanged, no matter what it was, since
26935 @samp{10}, being without any leading or trailing signs of its base, is
26936 interpreted in the current radix. Thus, if the current radix is 16,
26937 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26940 @kindex set output-radix
26941 @item set output-radix @var{base}
26942 Set the default base for numeric display. Supported choices
26943 for @var{base} are decimal 8, 10, or 16. The base must itself be
26944 specified either unambiguously or using the current input radix.
26946 @kindex show input-radix
26947 @item show input-radix
26948 Display the current default base for numeric input.
26950 @kindex show output-radix
26951 @item show output-radix
26952 Display the current default base for numeric display.
26954 @item set radix @r{[}@var{base}@r{]}
26958 These commands set and show the default base for both input and output
26959 of numbers. @code{set radix} sets the radix of input and output to
26960 the same base; without an argument, it resets the radix back to its
26961 default value of 10.
26966 @section Configuring the Current ABI
26968 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26969 application automatically. However, sometimes you need to override its
26970 conclusions. Use these commands to manage @value{GDBN}'s view of the
26976 @cindex Newlib OS ABI and its influence on the longjmp handling
26978 One @value{GDBN} configuration can debug binaries for multiple operating
26979 system targets, either via remote debugging or native emulation.
26980 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26981 but you can override its conclusion using the @code{set osabi} command.
26982 One example where this is useful is in debugging of binaries which use
26983 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26984 not have the same identifying marks that the standard C library for your
26987 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26988 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26989 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26990 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26994 Show the OS ABI currently in use.
26997 With no argument, show the list of registered available OS ABI's.
26999 @item set osabi @var{abi}
27000 Set the current OS ABI to @var{abi}.
27003 @cindex float promotion
27005 Generally, the way that an argument of type @code{float} is passed to a
27006 function depends on whether the function is prototyped. For a prototyped
27007 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
27008 according to the architecture's convention for @code{float}. For unprototyped
27009 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
27010 @code{double} and then passed.
27012 Unfortunately, some forms of debug information do not reliably indicate whether
27013 a function is prototyped. If @value{GDBN} calls a function that is not marked
27014 as prototyped, it consults @kbd{set coerce-float-to-double}.
27017 @kindex set coerce-float-to-double
27018 @item set coerce-float-to-double
27019 @itemx set coerce-float-to-double on
27020 Arguments of type @code{float} will be promoted to @code{double} when passed
27021 to an unprototyped function. This is the default setting.
27023 @item set coerce-float-to-double off
27024 Arguments of type @code{float} will be passed directly to unprototyped
27027 @kindex show coerce-float-to-double
27028 @item show coerce-float-to-double
27029 Show the current setting of promoting @code{float} to @code{double}.
27033 @kindex show cp-abi
27034 @value{GDBN} needs to know the ABI used for your program's C@t{++}
27035 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
27036 used to build your application. @value{GDBN} only fully supports
27037 programs with a single C@t{++} ABI; if your program contains code using
27038 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
27039 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
27040 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
27041 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
27042 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
27043 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
27048 Show the C@t{++} ABI currently in use.
27051 With no argument, show the list of supported C@t{++} ABI's.
27053 @item set cp-abi @var{abi}
27054 @itemx set cp-abi auto
27055 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
27059 @section Automatically loading associated files
27060 @cindex auto-loading
27062 @value{GDBN} sometimes reads files with commands and settings automatically,
27063 without being explicitly told so by the user. We call this feature
27064 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
27065 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
27066 results or introduce security risks (e.g., if the file comes from untrusted
27069 There are various kinds of files @value{GDBN} can automatically load.
27070 In addition to these files, @value{GDBN} supports auto-loading code written
27071 in various extension languages. @xref{Auto-loading extensions}.
27073 Note that loading of these associated files (including the local @file{.gdbinit}
27074 file) requires accordingly configured @code{auto-load safe-path}
27075 (@pxref{Auto-loading safe path}).
27077 For these reasons, @value{GDBN} includes commands and options to let you
27078 control when to auto-load files and which files should be auto-loaded.
27081 @anchor{set auto-load off}
27082 @kindex set auto-load off
27083 @item set auto-load off
27084 Globally disable loading of all auto-loaded files.
27085 You may want to use this command with the @samp{-iex} option
27086 (@pxref{Option -init-eval-command}) such as:
27088 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
27091 Be aware that system init file (@pxref{System-wide configuration})
27092 and init files from your home directory (@pxref{Home Directory Init File})
27093 still get read (as they come from generally trusted directories).
27094 To prevent @value{GDBN} from auto-loading even those init files, use the
27095 @option{-nx} option (@pxref{Mode Options}), in addition to
27096 @code{set auto-load no}.
27098 @anchor{show auto-load}
27099 @kindex show auto-load
27100 @item show auto-load
27101 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
27105 (gdb) show auto-load
27106 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
27107 libthread-db: Auto-loading of inferior specific libthread_db is on.
27108 local-gdbinit: Auto-loading of .gdbinit script from current directory
27110 python-scripts: Auto-loading of Python scripts is on.
27111 safe-path: List of directories from which it is safe to auto-load files
27112 is $debugdir:$datadir/auto-load.
27113 scripts-directory: List of directories from which to load auto-loaded scripts
27114 is $debugdir:$datadir/auto-load.
27117 @anchor{info auto-load}
27118 @kindex info auto-load
27119 @item info auto-load
27120 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
27124 (gdb) info auto-load
27127 Yes /home/user/gdb/gdb-gdb.gdb
27128 libthread-db: No auto-loaded libthread-db.
27129 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
27133 Yes /home/user/gdb/gdb-gdb.py
27137 These are @value{GDBN} control commands for the auto-loading:
27139 @multitable @columnfractions .5 .5
27140 @item @xref{set auto-load off}.
27141 @tab Disable auto-loading globally.
27142 @item @xref{show auto-load}.
27143 @tab Show setting of all kinds of files.
27144 @item @xref{info auto-load}.
27145 @tab Show state of all kinds of files.
27146 @item @xref{set auto-load gdb-scripts}.
27147 @tab Control for @value{GDBN} command scripts.
27148 @item @xref{show auto-load gdb-scripts}.
27149 @tab Show setting of @value{GDBN} command scripts.
27150 @item @xref{info auto-load gdb-scripts}.
27151 @tab Show state of @value{GDBN} command scripts.
27152 @item @xref{set auto-load python-scripts}.
27153 @tab Control for @value{GDBN} Python scripts.
27154 @item @xref{show auto-load python-scripts}.
27155 @tab Show setting of @value{GDBN} Python scripts.
27156 @item @xref{info auto-load python-scripts}.
27157 @tab Show state of @value{GDBN} Python scripts.
27158 @item @xref{set auto-load guile-scripts}.
27159 @tab Control for @value{GDBN} Guile scripts.
27160 @item @xref{show auto-load guile-scripts}.
27161 @tab Show setting of @value{GDBN} Guile scripts.
27162 @item @xref{info auto-load guile-scripts}.
27163 @tab Show state of @value{GDBN} Guile scripts.
27164 @item @xref{set auto-load scripts-directory}.
27165 @tab Control for @value{GDBN} auto-loaded scripts location.
27166 @item @xref{show auto-load scripts-directory}.
27167 @tab Show @value{GDBN} auto-loaded scripts location.
27168 @item @xref{add-auto-load-scripts-directory}.
27169 @tab Add directory for auto-loaded scripts location list.
27170 @item @xref{set auto-load local-gdbinit}.
27171 @tab Control for init file in the current directory.
27172 @item @xref{show auto-load local-gdbinit}.
27173 @tab Show setting of init file in the current directory.
27174 @item @xref{info auto-load local-gdbinit}.
27175 @tab Show state of init file in the current directory.
27176 @item @xref{set auto-load libthread-db}.
27177 @tab Control for thread debugging library.
27178 @item @xref{show auto-load libthread-db}.
27179 @tab Show setting of thread debugging library.
27180 @item @xref{info auto-load libthread-db}.
27181 @tab Show state of thread debugging library.
27182 @item @xref{set auto-load safe-path}.
27183 @tab Control directories trusted for automatic loading.
27184 @item @xref{show auto-load safe-path}.
27185 @tab Show directories trusted for automatic loading.
27186 @item @xref{add-auto-load-safe-path}.
27187 @tab Add directory trusted for automatic loading.
27191 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
27192 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
27194 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
27195 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
27198 @node Init File in the Current Directory
27199 @subsection Automatically loading init file in the current directory
27200 @cindex auto-loading init file in the current directory
27202 By default, @value{GDBN} reads and executes the canned sequences of commands
27203 from init file (if any) in the current working directory,
27204 see @ref{Init File in the Current Directory during Startup}.
27206 Note that loading of this local @file{.gdbinit} file also requires accordingly
27207 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27210 @anchor{set auto-load local-gdbinit}
27211 @kindex set auto-load local-gdbinit
27212 @item set auto-load local-gdbinit [on|off]
27213 Enable or disable the auto-loading of canned sequences of commands
27214 (@pxref{Sequences}) found in init file in the current directory.
27216 @anchor{show auto-load local-gdbinit}
27217 @kindex show auto-load local-gdbinit
27218 @item show auto-load local-gdbinit
27219 Show whether auto-loading of canned sequences of commands from init file in the
27220 current directory is enabled or disabled.
27222 @anchor{info auto-load local-gdbinit}
27223 @kindex info auto-load local-gdbinit
27224 @item info auto-load local-gdbinit
27225 Print whether canned sequences of commands from init file in the
27226 current directory have been auto-loaded.
27229 @node libthread_db.so.1 file
27230 @subsection Automatically loading thread debugging library
27231 @cindex auto-loading libthread_db.so.1
27233 This feature is currently present only on @sc{gnu}/Linux native hosts.
27235 @value{GDBN} reads in some cases thread debugging library from places specific
27236 to the inferior (@pxref{set libthread-db-search-path}).
27238 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
27239 without checking this @samp{set auto-load libthread-db} switch as system
27240 libraries have to be trusted in general. In all other cases of
27241 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
27242 auto-load libthread-db} is enabled before trying to open such thread debugging
27245 Note that loading of this debugging library also requires accordingly configured
27246 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27249 @anchor{set auto-load libthread-db}
27250 @kindex set auto-load libthread-db
27251 @item set auto-load libthread-db [on|off]
27252 Enable or disable the auto-loading of inferior specific thread debugging library.
27254 @anchor{show auto-load libthread-db}
27255 @kindex show auto-load libthread-db
27256 @item show auto-load libthread-db
27257 Show whether auto-loading of inferior specific thread debugging library is
27258 enabled or disabled.
27260 @anchor{info auto-load libthread-db}
27261 @kindex info auto-load libthread-db
27262 @item info auto-load libthread-db
27263 Print the list of all loaded inferior specific thread debugging libraries and
27264 for each such library print list of inferior @var{pid}s using it.
27267 @node Auto-loading safe path
27268 @subsection Security restriction for auto-loading
27269 @cindex auto-loading safe-path
27271 As the files of inferior can come from untrusted source (such as submitted by
27272 an application user) @value{GDBN} does not always load any files automatically.
27273 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
27274 directories trusted for loading files not explicitly requested by user.
27275 Each directory can also be a shell wildcard pattern.
27277 If the path is not set properly you will see a warning and the file will not
27282 Reading symbols from /home/user/gdb/gdb...
27283 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
27284 declined by your `auto-load safe-path' set
27285 to "$debugdir:$datadir/auto-load".
27286 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
27287 declined by your `auto-load safe-path' set
27288 to "$debugdir:$datadir/auto-load".
27292 To instruct @value{GDBN} to go ahead and use the init files anyway,
27293 invoke @value{GDBN} like this:
27296 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
27299 The list of trusted directories is controlled by the following commands:
27302 @anchor{set auto-load safe-path}
27303 @kindex set auto-load safe-path
27304 @item set auto-load safe-path @r{[}@var{directories}@r{]}
27305 Set the list of directories (and their subdirectories) trusted for automatic
27306 loading and execution of scripts. You can also enter a specific trusted file.
27307 Each directory can also be a shell wildcard pattern; wildcards do not match
27308 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
27309 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
27310 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
27311 its default value as specified during @value{GDBN} compilation.
27313 The list of directories uses path separator (@samp{:} on GNU and Unix
27314 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27315 to the @env{PATH} environment variable.
27317 @anchor{show auto-load safe-path}
27318 @kindex show auto-load safe-path
27319 @item show auto-load safe-path
27320 Show the list of directories trusted for automatic loading and execution of
27323 @anchor{add-auto-load-safe-path}
27324 @kindex add-auto-load-safe-path
27325 @item add-auto-load-safe-path
27326 Add an entry (or list of entries) to the list of directories trusted for
27327 automatic loading and execution of scripts. Multiple entries may be delimited
27328 by the host platform path separator in use.
27331 This variable defaults to what @code{--with-auto-load-dir} has been configured
27332 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
27333 substitution applies the same as for @ref{set auto-load scripts-directory}.
27334 The default @code{set auto-load safe-path} value can be also overriden by
27335 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
27337 Setting this variable to @file{/} disables this security protection,
27338 corresponding @value{GDBN} configuration option is
27339 @option{--without-auto-load-safe-path}.
27340 This variable is supposed to be set to the system directories writable by the
27341 system superuser only. Users can add their source directories in init files in
27342 their home directories (@pxref{Home Directory Init File}). See also deprecated
27343 init file in the current directory
27344 (@pxref{Init File in the Current Directory during Startup}).
27346 To force @value{GDBN} to load the files it declined to load in the previous
27347 example, you could use one of the following ways:
27350 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
27351 Specify this trusted directory (or a file) as additional component of the list.
27352 You have to specify also any existing directories displayed by
27353 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
27355 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
27356 Specify this directory as in the previous case but just for a single
27357 @value{GDBN} session.
27359 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
27360 Disable auto-loading safety for a single @value{GDBN} session.
27361 This assumes all the files you debug during this @value{GDBN} session will come
27362 from trusted sources.
27364 @item @kbd{./configure --without-auto-load-safe-path}
27365 During compilation of @value{GDBN} you may disable any auto-loading safety.
27366 This assumes all the files you will ever debug with this @value{GDBN} come from
27370 On the other hand you can also explicitly forbid automatic files loading which
27371 also suppresses any such warning messages:
27374 @item @kbd{gdb -iex "set auto-load no" @dots{}}
27375 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
27377 @item @file{~/.gdbinit}: @samp{set auto-load no}
27378 Disable auto-loading globally for the user
27379 (@pxref{Home Directory Init File}). While it is improbable, you could also
27380 use system init file instead (@pxref{System-wide configuration}).
27383 This setting applies to the file names as entered by user. If no entry matches
27384 @value{GDBN} tries as a last resort to also resolve all the file names into
27385 their canonical form (typically resolving symbolic links) and compare the
27386 entries again. @value{GDBN} already canonicalizes most of the filenames on its
27387 own before starting the comparison so a canonical form of directories is
27388 recommended to be entered.
27390 @node Auto-loading verbose mode
27391 @subsection Displaying files tried for auto-load
27392 @cindex auto-loading verbose mode
27394 For better visibility of all the file locations where you can place scripts to
27395 be auto-loaded with inferior --- or to protect yourself against accidental
27396 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
27397 all the files attempted to be loaded. Both existing and non-existing files may
27400 For example the list of directories from which it is safe to auto-load files
27401 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
27402 may not be too obvious while setting it up.
27405 (gdb) set debug auto-load on
27406 (gdb) file ~/src/t/true
27407 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
27408 for objfile "/tmp/true".
27409 auto-load: Updating directories of "/usr:/opt".
27410 auto-load: Using directory "/usr".
27411 auto-load: Using directory "/opt".
27412 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
27413 by your `auto-load safe-path' set to "/usr:/opt".
27417 @anchor{set debug auto-load}
27418 @kindex set debug auto-load
27419 @item set debug auto-load [on|off]
27420 Set whether to print the filenames attempted to be auto-loaded.
27422 @anchor{show debug auto-load}
27423 @kindex show debug auto-load
27424 @item show debug auto-load
27425 Show whether printing of the filenames attempted to be auto-loaded is turned
27429 @node Messages/Warnings
27430 @section Optional Warnings and Messages
27432 @cindex verbose operation
27433 @cindex optional warnings
27434 By default, @value{GDBN} is silent about its inner workings. If you are
27435 running on a slow machine, you may want to use the @code{set verbose}
27436 command. This makes @value{GDBN} tell you when it does a lengthy
27437 internal operation, so you will not think it has crashed.
27439 Currently, the messages controlled by @code{set verbose} are those
27440 which announce that the symbol table for a source file is being read;
27441 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
27444 @kindex set verbose
27445 @item set verbose on
27446 Enables @value{GDBN} output of certain informational messages.
27448 @item set verbose off
27449 Disables @value{GDBN} output of certain informational messages.
27451 @kindex show verbose
27453 Displays whether @code{set verbose} is on or off.
27456 By default, if @value{GDBN} encounters bugs in the symbol table of an
27457 object file, it is silent; but if you are debugging a compiler, you may
27458 find this information useful (@pxref{Symbol Errors, ,Errors Reading
27463 @kindex set complaints
27464 @item set complaints @var{limit}
27465 Permits @value{GDBN} to output @var{limit} complaints about each type of
27466 unusual symbols before becoming silent about the problem. Set
27467 @var{limit} to zero to suppress all complaints; set it to a large number
27468 to prevent complaints from being suppressed.
27470 @kindex show complaints
27471 @item show complaints
27472 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27476 @anchor{confirmation requests}
27477 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27478 lot of stupid questions to confirm certain commands. For example, if
27479 you try to run a program which is already running:
27483 The program being debugged has been started already.
27484 Start it from the beginning? (y or n)
27487 If you are willing to unflinchingly face the consequences of your own
27488 commands, you can disable this ``feature'':
27492 @kindex set confirm
27494 @cindex confirmation
27495 @cindex stupid questions
27496 @item set confirm off
27497 Disables confirmation requests. Note that running @value{GDBN} with
27498 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27499 automatically disables confirmation requests.
27501 @item set confirm on
27502 Enables confirmation requests (the default).
27504 @kindex show confirm
27506 Displays state of confirmation requests.
27510 @cindex command tracing
27511 If you need to debug user-defined commands or sourced files you may find it
27512 useful to enable @dfn{command tracing}. In this mode each command will be
27513 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27514 quantity denoting the call depth of each command.
27517 @kindex set trace-commands
27518 @cindex command scripts, debugging
27519 @item set trace-commands on
27520 Enable command tracing.
27521 @item set trace-commands off
27522 Disable command tracing.
27523 @item show trace-commands
27524 Display the current state of command tracing.
27527 @node Debugging Output
27528 @section Optional Messages about Internal Happenings
27529 @cindex optional debugging messages
27531 @value{GDBN} has commands that enable optional debugging messages from
27532 various @value{GDBN} subsystems; normally these commands are of
27533 interest to @value{GDBN} maintainers, or when reporting a bug. This
27534 section documents those commands.
27537 @kindex set exec-done-display
27538 @item set exec-done-display
27539 Turns on or off the notification of asynchronous commands'
27540 completion. When on, @value{GDBN} will print a message when an
27541 asynchronous command finishes its execution. The default is off.
27542 @kindex show exec-done-display
27543 @item show exec-done-display
27544 Displays the current setting of asynchronous command completion
27548 @cindex ARM AArch64
27549 @item set debug aarch64
27550 Turns on or off display of debugging messages related to ARM AArch64.
27551 The default is off.
27553 @item show debug aarch64
27554 Displays the current state of displaying debugging messages related to
27557 @cindex gdbarch debugging info
27558 @cindex architecture debugging info
27559 @item set debug arch
27560 Turns on or off display of gdbarch debugging info. The default is off
27561 @item show debug arch
27562 Displays the current state of displaying gdbarch debugging info.
27564 @item set debug aix-thread
27565 @cindex AIX threads
27566 Display debugging messages about inner workings of the AIX thread
27568 @item show debug aix-thread
27569 Show the current state of AIX thread debugging info display.
27571 @item set debug check-physname
27573 Check the results of the ``physname'' computation. When reading DWARF
27574 debugging information for C@t{++}, @value{GDBN} attempts to compute
27575 each entity's name. @value{GDBN} can do this computation in two
27576 different ways, depending on exactly what information is present.
27577 When enabled, this setting causes @value{GDBN} to compute the names
27578 both ways and display any discrepancies.
27579 @item show debug check-physname
27580 Show the current state of ``physname'' checking.
27582 @item set debug coff-pe-read
27583 @cindex COFF/PE exported symbols
27584 Control display of debugging messages related to reading of COFF/PE
27585 exported symbols. The default is off.
27586 @item show debug coff-pe-read
27587 Displays the current state of displaying debugging messages related to
27588 reading of COFF/PE exported symbols.
27590 @item set debug dwarf-die
27592 Dump DWARF DIEs after they are read in.
27593 The value is the number of nesting levels to print.
27594 A value of zero turns off the display.
27595 @item show debug dwarf-die
27596 Show the current state of DWARF DIE debugging.
27598 @item set debug dwarf-line
27599 @cindex DWARF Line Tables
27600 Turns on or off display of debugging messages related to reading
27601 DWARF line tables. The default is 0 (off).
27602 A value of 1 provides basic information.
27603 A value greater than 1 provides more verbose information.
27604 @item show debug dwarf-line
27605 Show the current state of DWARF line table debugging.
27607 @item set debug dwarf-read
27608 @cindex DWARF Reading
27609 Turns on or off display of debugging messages related to reading
27610 DWARF debug info. The default is 0 (off).
27611 A value of 1 provides basic information.
27612 A value greater than 1 provides more verbose information.
27613 @item show debug dwarf-read
27614 Show the current state of DWARF reader debugging.
27616 @item set debug displaced
27617 @cindex displaced stepping debugging info
27618 Turns on or off display of @value{GDBN} debugging info for the
27619 displaced stepping support. The default is off.
27620 @item show debug displaced
27621 Displays the current state of displaying @value{GDBN} debugging info
27622 related to displaced stepping.
27624 @item set debug event
27625 @cindex event debugging info
27626 Turns on or off display of @value{GDBN} event debugging info. The
27628 @item show debug event
27629 Displays the current state of displaying @value{GDBN} event debugging
27632 @item set debug event-loop
27633 @cindex event-loop debugging
27634 Controls output of debugging info about the event loop. The possible
27635 values are @samp{off}, @samp{all} (shows all debugging info) and
27636 @samp{all-except-ui} (shows all debugging info except those about
27637 UI-related events).
27638 @item show debug event-loop
27639 Shows the current state of displaying debugging info about the event
27642 @item set debug expression
27643 @cindex expression debugging info
27644 Turns on or off display of debugging info about @value{GDBN}
27645 expression parsing. The default is off.
27646 @item show debug expression
27647 Displays the current state of displaying debugging info about
27648 @value{GDBN} expression parsing.
27650 @item set debug fbsd-lwp
27651 @cindex FreeBSD LWP debug messages
27652 Turns on or off debugging messages from the FreeBSD LWP debug support.
27653 @item show debug fbsd-lwp
27654 Show the current state of FreeBSD LWP debugging messages.
27656 @item set debug fbsd-nat
27657 @cindex FreeBSD native target debug messages
27658 Turns on or off debugging messages from the FreeBSD native target.
27659 @item show debug fbsd-nat
27660 Show the current state of FreeBSD native target debugging messages.
27662 @item set debug fortran-array-slicing
27663 @cindex fortran array slicing debugging info
27664 Turns on or off display of @value{GDBN} Fortran array slicing
27665 debugging info. The default is off.
27667 @item show debug fortran-array-slicing
27668 Displays the current state of displaying @value{GDBN} Fortran array
27669 slicing debugging info.
27671 @item set debug frame
27672 @cindex frame debugging info
27673 Turns on or off display of @value{GDBN} frame debugging info. The
27675 @item show debug frame
27676 Displays the current state of displaying @value{GDBN} frame debugging
27679 @item set debug gnu-nat
27680 @cindex @sc{gnu}/Hurd debug messages
27681 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27682 @item show debug gnu-nat
27683 Show the current state of @sc{gnu}/Hurd debugging messages.
27685 @item set debug infrun
27686 @cindex inferior debugging info
27687 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27688 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27689 for implementing operations such as single-stepping the inferior.
27690 @item show debug infrun
27691 Displays the current state of @value{GDBN} inferior debugging.
27693 @item set debug infcall
27694 @cindex inferior function call debugging info
27695 Turns on or off display of debugging info related to inferior function
27696 calls made by @value{GDBN}.
27697 @item show debug infcall
27698 Displays the current state of @value{GDBN} inferior function call debugging.
27700 @item set debug jit
27701 @cindex just-in-time compilation, debugging messages
27702 Turn on or off debugging messages from JIT debug support.
27703 @item show debug jit
27704 Displays the current state of @value{GDBN} JIT debugging.
27706 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27707 @cindex @sc{gnu}/Linux native target debug messages
27708 @cindex Linux native targets
27709 Turn on or off debugging messages from the Linux native target debug support.
27710 @item show debug linux-nat
27711 Show the current state of Linux native target debugging messages.
27713 @item set debug linux-namespaces
27714 @cindex @sc{gnu}/Linux namespaces debug messages
27715 Turn on or off debugging messages from the Linux namespaces debug support.
27716 @item show debug linux-namespaces
27717 Show the current state of Linux namespaces debugging messages.
27719 @item set debug mach-o
27720 @cindex Mach-O symbols processing
27721 Control display of debugging messages related to Mach-O symbols
27722 processing. The default is off.
27723 @item show debug mach-o
27724 Displays the current state of displaying debugging messages related to
27725 reading of COFF/PE exported symbols.
27727 @item set debug notification
27728 @cindex remote async notification debugging info
27729 Turn on or off debugging messages about remote async notification.
27730 The default is off.
27731 @item show debug notification
27732 Displays the current state of remote async notification debugging messages.
27734 @item set debug observer
27735 @cindex observer debugging info
27736 Turns on or off display of @value{GDBN} observer debugging. This
27737 includes info such as the notification of observable events.
27738 @item show debug observer
27739 Displays the current state of observer debugging.
27741 @item set debug overload
27742 @cindex C@t{++} overload debugging info
27743 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27744 info. This includes info such as ranking of functions, etc. The default
27746 @item show debug overload
27747 Displays the current state of displaying @value{GDBN} C@t{++} overload
27750 @cindex expression parser, debugging info
27751 @cindex debug expression parser
27752 @item set debug parser
27753 Turns on or off the display of expression parser debugging output.
27754 Internally, this sets the @code{yydebug} variable in the expression
27755 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27756 details. The default is off.
27757 @item show debug parser
27758 Show the current state of expression parser debugging.
27760 @cindex packets, reporting on stdout
27761 @cindex serial connections, debugging
27762 @cindex debug remote protocol
27763 @cindex remote protocol debugging
27764 @cindex display remote packets
27765 @item set debug remote
27766 Turns on or off display of reports on all packets sent back and forth across
27767 the serial line to the remote machine. The info is printed on the
27768 @value{GDBN} standard output stream. The default is off.
27769 @item show debug remote
27770 Displays the state of display of remote packets.
27772 @item set debug remote-packet-max-chars
27773 Sets the maximum number of characters to display for each remote packet when
27774 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27775 displaying lengthy remote packets and polluting the console.
27777 The default value is @code{512}, which means @value{GDBN} will truncate each
27778 remote packet after 512 bytes.
27780 Setting this option to @code{unlimited} will disable truncation and will output
27781 the full length of the remote packets.
27782 @item show debug remote-packet-max-chars
27783 Displays the number of bytes to output for remote packet debugging.
27785 @item set debug separate-debug-file
27786 Turns on or off display of debug output about separate debug file search.
27787 @item show debug separate-debug-file
27788 Displays the state of separate debug file search debug output.
27790 @item set debug serial
27791 Turns on or off display of @value{GDBN} serial debugging info. The
27793 @item show debug serial
27794 Displays the current state of displaying @value{GDBN} serial debugging
27797 @item set debug solib
27798 Turns on or off display of debugging messages related to shared libraries.
27799 The default is off.
27800 @item show debug solib
27801 Show the current state of solib debugging messages.
27803 @item set debug symbol-lookup
27804 @cindex symbol lookup
27805 Turns on or off display of debugging messages related to symbol lookup.
27806 The default is 0 (off).
27807 A value of 1 provides basic information.
27808 A value greater than 1 provides more verbose information.
27809 @item show debug symbol-lookup
27810 Show the current state of symbol lookup debugging messages.
27812 @item set debug symfile
27813 @cindex symbol file functions
27814 Turns on or off display of debugging messages related to symbol file functions.
27815 The default is off. @xref{Files}.
27816 @item show debug symfile
27817 Show the current state of symbol file debugging messages.
27819 @item set debug symtab-create
27820 @cindex symbol table creation
27821 Turns on or off display of debugging messages related to symbol table creation.
27822 The default is 0 (off).
27823 A value of 1 provides basic information.
27824 A value greater than 1 provides more verbose information.
27825 @item show debug symtab-create
27826 Show the current state of symbol table creation debugging.
27828 @item set debug target
27829 @cindex target debugging info
27830 Turns on or off display of @value{GDBN} target debugging info. This info
27831 includes what is going on at the target level of GDB, as it happens. The
27832 default is 0. Set it to 1 to track events, and to 2 to also track the
27833 value of large memory transfers.
27834 @item show debug target
27835 Displays the current state of displaying @value{GDBN} target debugging
27838 @item set debug timestamp
27839 @cindex timestamping debugging info
27840 Turns on or off display of timestamps with @value{GDBN} debugging info.
27841 When enabled, seconds and microseconds are displayed before each debugging
27843 @item show debug timestamp
27844 Displays the current state of displaying timestamps with @value{GDBN}
27847 @item set debug varobj
27848 @cindex variable object debugging info
27849 Turns on or off display of @value{GDBN} variable object debugging
27850 info. The default is off.
27851 @item show debug varobj
27852 Displays the current state of displaying @value{GDBN} variable object
27855 @item set debug xml
27856 @cindex XML parser debugging
27857 Turn on or off debugging messages for built-in XML parsers.
27858 @item show debug xml
27859 Displays the current state of XML debugging messages.
27862 @node Other Misc Settings
27863 @section Other Miscellaneous Settings
27864 @cindex miscellaneous settings
27867 @kindex set interactive-mode
27868 @item set interactive-mode
27869 If @code{on}, forces @value{GDBN} to assume that GDB was started
27870 in a terminal. In practice, this means that @value{GDBN} should wait
27871 for the user to answer queries generated by commands entered at
27872 the command prompt. If @code{off}, forces @value{GDBN} to operate
27873 in the opposite mode, and it uses the default answers to all queries.
27874 If @code{auto} (the default), @value{GDBN} tries to determine whether
27875 its standard input is a terminal, and works in interactive-mode if it
27876 is, non-interactively otherwise.
27878 In the vast majority of cases, the debugger should be able to guess
27879 correctly which mode should be used. But this setting can be useful
27880 in certain specific cases, such as running a MinGW @value{GDBN}
27881 inside a cygwin window.
27883 @kindex show interactive-mode
27884 @item show interactive-mode
27885 Displays whether the debugger is operating in interactive mode or not.
27889 @kindex set suppress-cli-notifications
27890 @item set suppress-cli-notifications
27891 If @code{on}, command-line-interface (CLI) notifications that are
27892 printed by @value{GDBN} are suppressed. If @code{off}, the
27893 notifications are printed as usual. The default value is @code{off}.
27894 CLI notifications occur when you change the selected context or when
27895 the program being debugged stops, as detailed below.
27898 @item User-selected context changes:
27899 When you change the selected context (i.e.@: the current inferior,
27900 thread and/or the frame), @value{GDBN} prints information about the
27901 new context. For example, the default behavior is below:
27905 [Switching to inferior 1 [process 634] (/tmp/test)]
27906 [Switching to thread 1 (process 634)]
27907 #0 main () at test.c:3
27912 When the notifications are suppressed, the new context is not printed:
27915 (gdb) set suppress-cli-notifications on
27920 @item The program being debugged stops:
27921 When the program you are debugging stops (e.g.@: because of hitting a
27922 breakpoint, completing source-stepping, an interrupt, etc.),
27923 @value{GDBN} prints information about the stop event. For example,
27924 below is a breakpoint hit:
27927 (gdb) break test.c:3
27928 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27932 Breakpoint 2, main () at test.c:3
27937 When the notifications are suppressed, the output becomes:
27940 (gdb) break test.c:3
27941 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27942 (gdb) set suppress-cli-notifications on
27948 Suppressing CLI notifications may be useful in scripts to obtain a
27949 reduced output from a list of commands.
27952 @kindex show suppress-cli-notifications
27953 @item show suppress-cli-notifications
27954 Displays whether printing CLI notifications is suppressed or not.
27957 @node Extending GDB
27958 @chapter Extending @value{GDBN}
27959 @cindex extending GDB
27961 @value{GDBN} provides several mechanisms for extension.
27962 @value{GDBN} also provides the ability to automatically load
27963 extensions when it reads a file for debugging. This allows the
27964 user to automatically customize @value{GDBN} for the program
27967 To facilitate the use of extension languages, @value{GDBN} is capable
27968 of evaluating the contents of a file. When doing so, @value{GDBN}
27969 can recognize which extension language is being used by looking at
27970 the filename extension. Files with an unrecognized filename extension
27971 are always treated as a @value{GDBN} Command Files.
27972 @xref{Command Files,, Command files}.
27974 You can control how @value{GDBN} evaluates these files with the following
27978 @kindex set script-extension
27979 @kindex show script-extension
27980 @item set script-extension off
27981 All scripts are always evaluated as @value{GDBN} Command Files.
27983 @item set script-extension soft
27984 The debugger determines the scripting language based on filename
27985 extension. If this scripting language is supported, @value{GDBN}
27986 evaluates the script using that language. Otherwise, it evaluates
27987 the file as a @value{GDBN} Command File.
27989 @item set script-extension strict
27990 The debugger determines the scripting language based on filename
27991 extension, and evaluates the script using that language. If the
27992 language is not supported, then the evaluation fails.
27994 @item show script-extension
27995 Display the current value of the @code{script-extension} option.
27999 @ifset SYSTEM_GDBINIT_DIR
28000 This setting is not used for files in the system-wide gdbinit directory.
28001 Files in that directory must have an extension matching their language,
28002 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
28003 commands. @xref{Startup}.
28007 * Sequences:: Canned Sequences of @value{GDBN} Commands
28008 * Aliases:: Command Aliases
28009 * Python:: Extending @value{GDBN} using Python
28010 * Guile:: Extending @value{GDBN} using Guile
28011 * Auto-loading extensions:: Automatically loading extensions
28012 * Multiple Extension Languages:: Working with multiple extension languages
28016 @section Canned Sequences of Commands
28018 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
28019 Command Lists}), @value{GDBN} provides two ways to store sequences of
28020 commands for execution as a unit: user-defined commands and command
28024 * Define:: How to define your own commands
28025 * Hooks:: Hooks for user-defined commands
28026 * Command Files:: How to write scripts of commands to be stored in a file
28027 * Output:: Commands for controlled output
28028 * Auto-loading sequences:: Controlling auto-loaded command files
28032 @subsection User-defined Commands
28034 @cindex user-defined command
28035 @cindex arguments, to user-defined commands
28036 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
28037 which you assign a new name as a command. This is done with the
28038 @code{define} command. User commands may accept an unlimited number of arguments
28039 separated by whitespace. Arguments are accessed within the user command
28040 via @code{$arg0@dots{}$argN}. A trivial example:
28044 print $arg0 + $arg1 + $arg2
28049 To execute the command use:
28056 This defines the command @code{adder}, which prints the sum of
28057 its three arguments. Note the arguments are text substitutions, so they may
28058 reference variables, use complex expressions, or even perform inferior
28061 @cindex argument count in user-defined commands
28062 @cindex how many arguments (user-defined commands)
28063 In addition, @code{$argc} may be used to find out how many arguments have
28069 print $arg0 + $arg1
28072 print $arg0 + $arg1 + $arg2
28077 Combining with the @code{eval} command (@pxref{eval}) makes it easier
28078 to process a variable number of arguments:
28085 eval "set $sum = $sum + $arg%d", $i
28095 @item define @var{commandname}
28096 Define a command named @var{commandname}. If there is already a command
28097 by that name, you are asked to confirm that you want to redefine it.
28098 The argument @var{commandname} may be a bare command name consisting of letters,
28099 numbers, dashes, dots, and underscores. It may also start with any
28100 predefined or user-defined prefix command.
28101 For example, @samp{define target my-target} creates
28102 a user-defined @samp{target my-target} command.
28104 The definition of the command is made up of other @value{GDBN} command lines,
28105 which are given following the @code{define} command. The end of these
28106 commands is marked by a line containing @code{end}.
28109 @kindex end@r{ (user-defined commands)}
28110 @item document @var{commandname}
28111 Document the user-defined command @var{commandname}, so that it can be
28112 accessed by @code{help}. The command @var{commandname} must already be
28113 defined. This command reads lines of documentation just as @code{define}
28114 reads the lines of the command definition, ending with @code{end}.
28115 After the @code{document} command is finished, @code{help} on command
28116 @var{commandname} displays the documentation you have written.
28118 You may use the @code{document} command again to change the
28119 documentation of a command. Redefining the command with @code{define}
28120 does not change the documentation.
28122 It is also possible to document user-defined aliases. The alias documentation
28123 will then be used by the @code{help} and @code{apropos} commands
28124 instead of the documentation of the aliased command.
28125 Documenting a user-defined alias is particularly useful when defining
28126 an alias as a set of nested @code{with} commands
28127 (@pxref{Command aliases default args}).
28129 @kindex define-prefix
28130 @item define-prefix @var{commandname}
28131 Define or mark the command @var{commandname} as a user-defined prefix
28132 command. Once marked, @var{commandname} can be used as prefix command
28133 by the @code{define} command.
28134 Note that @code{define-prefix} can be used with a not yet defined
28135 @var{commandname}. In such a case, @var{commandname} is defined as
28136 an empty user-defined command.
28137 In case you redefine a command that was marked as a user-defined
28138 prefix command, the subcommands of the redefined command are kept
28139 (and @value{GDBN} indicates so to the user).
28143 (gdb) define-prefix abc
28144 (gdb) define-prefix abc def
28145 (gdb) define abc def
28146 Type commands for definition of "abc def".
28147 End with a line saying just "end".
28148 >echo command initial def\n
28150 (gdb) define abc def ghi
28151 Type commands for definition of "abc def ghi".
28152 End with a line saying just "end".
28153 >echo command ghi\n
28155 (gdb) define abc def
28156 Keeping subcommands of prefix command "def".
28157 Redefine command "def"? (y or n) y
28158 Type commands for definition of "abc def".
28159 End with a line saying just "end".
28160 >echo command def\n
28169 @kindex dont-repeat
28170 @cindex don't repeat command
28172 Used inside a user-defined command, this tells @value{GDBN} that this
28173 command should not be repeated when the user hits @key{RET}
28174 (@pxref{Command Syntax, repeat last command}).
28176 @kindex help user-defined
28177 @item help user-defined
28178 List all user-defined commands and all python commands defined in class
28179 COMMAND_USER. The first line of the documentation or docstring is
28184 @itemx show user @var{commandname}
28185 Display the @value{GDBN} commands used to define @var{commandname} (but
28186 not its documentation). If no @var{commandname} is given, display the
28187 definitions for all user-defined commands.
28188 This does not work for user-defined python commands.
28190 @cindex infinite recursion in user-defined commands
28191 @kindex show max-user-call-depth
28192 @kindex set max-user-call-depth
28193 @item show max-user-call-depth
28194 @itemx set max-user-call-depth
28195 The value of @code{max-user-call-depth} controls how many recursion
28196 levels are allowed in user-defined commands before @value{GDBN} suspects an
28197 infinite recursion and aborts the command.
28198 This does not apply to user-defined python commands.
28201 In addition to the above commands, user-defined commands frequently
28202 use control flow commands, described in @ref{Command Files}.
28204 When user-defined commands are executed, the
28205 commands of the definition are not printed. An error in any command
28206 stops execution of the user-defined command.
28208 If used interactively, commands that would ask for confirmation proceed
28209 without asking when used inside a user-defined command. Many @value{GDBN}
28210 commands that normally print messages to say what they are doing omit the
28211 messages when used in a user-defined command.
28214 @subsection User-defined Command Hooks
28215 @cindex command hooks
28216 @cindex hooks, for commands
28217 @cindex hooks, pre-command
28220 You may define @dfn{hooks}, which are a special kind of user-defined
28221 command. Whenever you run the command @samp{foo}, if the user-defined
28222 command @samp{hook-foo} exists, it is executed (with no arguments)
28223 before that command.
28225 @cindex hooks, post-command
28227 A hook may also be defined which is run after the command you executed.
28228 Whenever you run the command @samp{foo}, if the user-defined command
28229 @samp{hookpost-foo} exists, it is executed (with no arguments) after
28230 that command. Post-execution hooks may exist simultaneously with
28231 pre-execution hooks, for the same command.
28233 It is valid for a hook to call the command which it hooks. If this
28234 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
28236 @c It would be nice if hookpost could be passed a parameter indicating
28237 @c if the command it hooks executed properly or not. FIXME!
28239 @kindex stop@r{, a pseudo-command}
28240 In addition, a pseudo-command, @samp{stop} exists. Defining
28241 (@samp{hook-stop}) makes the associated commands execute every time
28242 execution stops in your program: before breakpoint commands are run,
28243 displays are printed, or the stack frame is printed.
28245 For example, to ignore @code{SIGALRM} signals while
28246 single-stepping, but treat them normally during normal execution,
28251 handle SIGALRM nopass
28255 handle SIGALRM pass
28258 define hook-continue
28259 handle SIGALRM pass
28263 As a further example, to hook at the beginning and end of the @code{echo}
28264 command, and to add extra text to the beginning and end of the message,
28272 define hookpost-echo
28276 (@value{GDBP}) echo Hello World
28277 <<<---Hello World--->>>
28282 You can define a hook for any single-word command in @value{GDBN}, but
28283 not for command aliases; you should define a hook for the basic command
28284 name, e.g.@: @code{backtrace} rather than @code{bt}.
28285 @c FIXME! So how does Joe User discover whether a command is an alias
28287 You can hook a multi-word command by adding @code{hook-} or
28288 @code{hookpost-} to the last word of the command, e.g.@:
28289 @samp{define target hook-remote} to add a hook to @samp{target remote}.
28291 If an error occurs during the execution of your hook, execution of
28292 @value{GDBN} commands stops and @value{GDBN} issues a prompt
28293 (before the command that you actually typed had a chance to run).
28295 If you try to define a hook which does not match any known command, you
28296 get a warning from the @code{define} command.
28298 @node Command Files
28299 @subsection Command Files
28301 @cindex command files
28302 @cindex scripting commands
28303 A command file for @value{GDBN} is a text file made of lines that are
28304 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
28305 also be included. An empty line in a command file does nothing; it
28306 does not mean to repeat the last command, as it would from the
28309 You can request the execution of a command file with the @code{source}
28310 command. Note that the @code{source} command is also used to evaluate
28311 scripts that are not Command Files. The exact behavior can be configured
28312 using the @code{script-extension} setting.
28313 @xref{Extending GDB,, Extending GDB}.
28317 @cindex execute commands from a file
28318 @item source [-s] [-v] @var{filename}
28319 Execute the command file @var{filename}.
28322 The lines in a command file are generally executed sequentially,
28323 unless the order of execution is changed by one of the
28324 @emph{flow-control commands} described below. The commands are not
28325 printed as they are executed. An error in any command terminates
28326 execution of the command file and control is returned to the console.
28328 @value{GDBN} first searches for @var{filename} in the current directory.
28329 If the file is not found there, and @var{filename} does not specify a
28330 directory, then @value{GDBN} also looks for the file on the source search path
28331 (specified with the @samp{directory} command);
28332 except that @file{$cdir} is not searched because the compilation directory
28333 is not relevant to scripts.
28335 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
28336 on the search path even if @var{filename} specifies a directory.
28337 The search is done by appending @var{filename} to each element of the
28338 search path. So, for example, if @var{filename} is @file{mylib/myscript}
28339 and the search path contains @file{/home/user} then @value{GDBN} will
28340 look for the script @file{/home/user/mylib/myscript}.
28341 The search is also done if @var{filename} is an absolute path.
28342 For example, if @var{filename} is @file{/tmp/myscript} and
28343 the search path contains @file{/home/user} then @value{GDBN} will
28344 look for the script @file{/home/user/tmp/myscript}.
28345 For DOS-like systems, if @var{filename} contains a drive specification,
28346 it is stripped before concatenation. For example, if @var{filename} is
28347 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
28348 will look for the script @file{c:/tmp/myscript}.
28350 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
28351 each command as it is executed. The option must be given before
28352 @var{filename}, and is interpreted as part of the filename anywhere else.
28354 Commands that would ask for confirmation if used interactively proceed
28355 without asking when used in a command file. Many @value{GDBN} commands that
28356 normally print messages to say what they are doing omit the messages
28357 when called from command files.
28359 @value{GDBN} also accepts command input from standard input. In this
28360 mode, normal output goes to standard output and error output goes to
28361 standard error. Errors in a command file supplied on standard input do
28362 not terminate execution of the command file---execution continues with
28366 gdb < cmds > log 2>&1
28369 (The syntax above will vary depending on the shell used.) This example
28370 will execute commands from the file @file{cmds}. All output and errors
28371 would be directed to @file{log}.
28373 Since commands stored on command files tend to be more general than
28374 commands typed interactively, they frequently need to deal with
28375 complicated situations, such as different or unexpected values of
28376 variables and symbols, changes in how the program being debugged is
28377 built, etc. @value{GDBN} provides a set of flow-control commands to
28378 deal with these complexities. Using these commands, you can write
28379 complex scripts that loop over data structures, execute commands
28380 conditionally, etc.
28387 This command allows to include in your script conditionally executed
28388 commands. The @code{if} command takes a single argument, which is an
28389 expression to evaluate. It is followed by a series of commands that
28390 are executed only if the expression is true (its value is nonzero).
28391 There can then optionally be an @code{else} line, followed by a series
28392 of commands that are only executed if the expression was false. The
28393 end of the list is marked by a line containing @code{end}.
28397 This command allows to write loops. Its syntax is similar to
28398 @code{if}: the command takes a single argument, which is an expression
28399 to evaluate, and must be followed by the commands to execute, one per
28400 line, terminated by an @code{end}. These commands are called the
28401 @dfn{body} of the loop. The commands in the body of @code{while} are
28402 executed repeatedly as long as the expression evaluates to true.
28406 This command exits the @code{while} loop in whose body it is included.
28407 Execution of the script continues after that @code{while}s @code{end}
28410 @kindex loop_continue
28411 @item loop_continue
28412 This command skips the execution of the rest of the body of commands
28413 in the @code{while} loop in whose body it is included. Execution
28414 branches to the beginning of the @code{while} loop, where it evaluates
28415 the controlling expression.
28417 @kindex end@r{ (if/else/while commands)}
28419 Terminate the block of commands that are the body of @code{if},
28420 @code{else}, or @code{while} flow-control commands.
28425 @subsection Commands for Controlled Output
28427 During the execution of a command file or a user-defined command, normal
28428 @value{GDBN} output is suppressed; the only output that appears is what is
28429 explicitly printed by the commands in the definition. This section
28430 describes three commands useful for generating exactly the output you
28435 @item echo @var{text}
28436 @c I do not consider backslash-space a standard C escape sequence
28437 @c because it is not in ANSI.
28438 Print @var{text}. Nonprinting characters can be included in
28439 @var{text} using C escape sequences, such as @samp{\n} to print a
28440 newline. @strong{No newline is printed unless you specify one.}
28441 In addition to the standard C escape sequences, a backslash followed
28442 by a space stands for a space. This is useful for displaying a
28443 string with spaces at the beginning or the end, since leading and
28444 trailing spaces are otherwise trimmed from all arguments.
28445 To print @samp{@w{ }and foo =@w{ }}, use the command
28446 @samp{echo \@w{ }and foo = \@w{ }}.
28448 A backslash at the end of @var{text} can be used, as in C, to continue
28449 the command onto subsequent lines. For example,
28452 echo This is some text\n\
28453 which is continued\n\
28454 onto several lines.\n
28457 produces the same output as
28460 echo This is some text\n
28461 echo which is continued\n
28462 echo onto several lines.\n
28466 @item output @var{expression}
28467 Print the value of @var{expression} and nothing but that value: no
28468 newlines, no @samp{$@var{nn} = }. The value is not entered in the
28469 value history either. @xref{Expressions, ,Expressions}, for more information
28472 @item output/@var{fmt} @var{expression}
28473 Print the value of @var{expression} in format @var{fmt}. You can use
28474 the same formats as for @code{print}. @xref{Output Formats,,Output
28475 Formats}, for more information.
28478 @item printf @var{template}, @var{expressions}@dots{}
28479 Print the values of one or more @var{expressions} under the control of
28480 the string @var{template}. To print several values, make
28481 @var{expressions} be a comma-separated list of individual expressions,
28482 which may be either numbers or pointers. Their values are printed as
28483 specified by @var{template}, exactly as a C program would do by
28484 executing the code below:
28487 printf (@var{template}, @var{expressions}@dots{});
28490 As in @code{C} @code{printf}, ordinary characters in @var{template}
28491 are printed verbatim, while @dfn{conversion specification} introduced
28492 by the @samp{%} character cause subsequent @var{expressions} to be
28493 evaluated, their values converted and formatted according to type and
28494 style information encoded in the conversion specifications, and then
28497 For example, you can print two values in hex like this:
28500 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28503 @code{printf} supports all the standard @code{C} conversion
28504 specifications, including the flags and modifiers between the @samp{%}
28505 character and the conversion letter, with the following exceptions:
28509 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28512 The modifier @samp{*} is not supported for specifying precision or
28516 The @samp{'} flag (for separation of digits into groups according to
28517 @code{LC_NUMERIC'}) is not supported.
28520 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28524 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28527 The conversion letters @samp{a} and @samp{A} are not supported.
28531 Note that the @samp{ll} type modifier is supported only if the
28532 underlying @code{C} implementation used to build @value{GDBN} supports
28533 the @code{long long int} type, and the @samp{L} type modifier is
28534 supported only if @code{long double} type is available.
28536 As in @code{C}, @code{printf} supports simple backslash-escape
28537 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28538 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28539 single character. Octal and hexadecimal escape sequences are not
28542 Additionally, @code{printf} supports conversion specifications for DFP
28543 (@dfn{Decimal Floating Point}) types using the following length modifiers
28544 together with a floating point specifier.
28549 @samp{H} for printing @code{Decimal32} types.
28552 @samp{D} for printing @code{Decimal64} types.
28555 @samp{DD} for printing @code{Decimal128} types.
28558 If the underlying @code{C} implementation used to build @value{GDBN} has
28559 support for the three length modifiers for DFP types, other modifiers
28560 such as width and precision will also be available for @value{GDBN} to use.
28562 In case there is no such @code{C} support, no additional modifiers will be
28563 available and the value will be printed in the standard way.
28565 Here's an example of printing DFP types using the above conversion letters:
28567 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28572 @item eval @var{template}, @var{expressions}@dots{}
28573 Convert the values of one or more @var{expressions} under the control of
28574 the string @var{template} to a command line, and call it.
28578 @node Auto-loading sequences
28579 @subsection Controlling auto-loading native @value{GDBN} scripts
28580 @cindex native script auto-loading
28582 When a new object file is read (for example, due to the @code{file}
28583 command, or because the inferior has loaded a shared library),
28584 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28585 @xref{Auto-loading extensions}.
28587 Auto-loading can be enabled or disabled,
28588 and the list of auto-loaded scripts can be printed.
28591 @anchor{set auto-load gdb-scripts}
28592 @kindex set auto-load gdb-scripts
28593 @item set auto-load gdb-scripts [on|off]
28594 Enable or disable the auto-loading of canned sequences of commands scripts.
28596 @anchor{show auto-load gdb-scripts}
28597 @kindex show auto-load gdb-scripts
28598 @item show auto-load gdb-scripts
28599 Show whether auto-loading of canned sequences of commands scripts is enabled or
28602 @anchor{info auto-load gdb-scripts}
28603 @kindex info auto-load gdb-scripts
28604 @cindex print list of auto-loaded canned sequences of commands scripts
28605 @item info auto-load gdb-scripts [@var{regexp}]
28606 Print the list of all canned sequences of commands scripts that @value{GDBN}
28610 If @var{regexp} is supplied only canned sequences of commands scripts with
28611 matching names are printed.
28614 @section Command Aliases
28615 @cindex aliases for commands
28617 Aliases allow you to define alternate spellings for existing commands.
28618 For example, if a new @value{GDBN} command defined in Python
28619 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28620 version of it that involves less typing.
28622 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28623 of the @samp{step} command even though it is otherwise an ambiguous
28624 abbreviation of other commands like @samp{set} and @samp{show}.
28626 Aliases are also used to provide shortened or more common versions
28627 of multi-word commands. For example, @value{GDBN} provides the
28628 @samp{tty} alias of the @samp{set inferior-tty} command.
28630 You can define a new alias with the @samp{alias} command.
28635 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28639 @var{alias} specifies the name of the new alias. Each word of
28640 @var{alias} must consist of letters, numbers, dashes and underscores.
28642 @var{command} specifies the name of an existing command
28643 that is being aliased.
28645 @var{command} can also be the name of an existing alias. In this
28646 case, @var{command} cannot be an alias that has default arguments.
28648 The @samp{-a} option specifies that the new alias is an abbreviation
28649 of the command. Abbreviations are not used in command completion.
28651 The @samp{--} option specifies the end of options,
28652 and is useful when @var{alias} begins with a dash.
28654 You can specify @var{default-args} for your alias. These
28655 @var{default-args} will be automatically added before the alias
28656 arguments typed explicitly on the command line.
28658 For example, the below defines an alias @code{btfullall} that shows all local
28659 variables and all frame arguments:
28661 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28664 For more information about @var{default-args}, see @ref{Command
28665 aliases default args, ,Default Arguments}.
28667 Here is a simple example showing how to make an abbreviation of a
28668 command so that there is less to type. Suppose you were tired of
28669 typing @samp{disas}, the current shortest unambiguous abbreviation of
28670 the @samp{disassemble} command and you wanted an even shorter version
28671 named @samp{di}. The following will accomplish this.
28674 (gdb) alias -a di = disas
28677 Note that aliases are different from user-defined commands. With a
28678 user-defined command, you also need to write documentation for it with
28679 the @samp{document} command. An alias automatically picks up the
28680 documentation of the existing command.
28682 Here is an example where we make @samp{elms} an abbreviation of
28683 @samp{elements} in the @samp{set print elements} command.
28684 This is to show that you can make an abbreviation of any part
28688 (gdb) alias -a set print elms = set print elements
28689 (gdb) alias -a show print elms = show print elements
28690 (gdb) set p elms 200
28692 Limit on string chars or array elements to print is 200.
28695 Note that if you are defining an alias of a @samp{set} command,
28696 and you want to have an alias for the corresponding @samp{show}
28697 command, then you need to define the latter separately.
28699 Unambiguously abbreviated commands are allowed in @var{command} and
28700 @var{alias}, just as they are normally.
28703 (gdb) alias -a set pr elms = set p ele
28706 Finally, here is an example showing the creation of a one word
28707 alias for a more complex command.
28708 This creates alias @samp{spe} of the command @samp{set print elements}.
28711 (gdb) alias spe = set print elements
28716 * Command aliases default args:: Default arguments for aliases
28719 @node Command aliases default args
28720 @subsection Default Arguments
28721 @cindex aliases for commands, default arguments
28723 You can tell @value{GDBN} to always prepend some default arguments to
28724 the list of arguments provided explicitly by the user when using a
28725 user-defined alias.
28727 If you repeatedly use the same arguments or options for a command, you
28728 can define an alias for this command and tell @value{GDBN} to
28729 automatically prepend these arguments or options to the list of
28730 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28731 could easily accept default arguments for pre-defined commands and aliases,
28732 but it was deemed this would be confusing, and so is not allowed.}.
28734 For example, if you often use the command @code{thread apply all}
28735 specifying to work on the threads in ascending order and to continue in case it
28736 encounters an error, you can tell @value{GDBN} to automatically preprend
28737 the @code{-ascending} and @code{-c} options by using:
28740 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28743 Once you have defined this alias with its default args, any time you type
28744 the @code{thread apply asc-all} followed by @code{some arguments},
28745 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28747 To have even less to type, you can also define a one word alias:
28749 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28752 As usual, unambiguous abbreviations can be used for @var{alias}
28753 and @var{default-args}.
28755 The different aliases of a command do not share their default args.
28756 For example, you define a new alias @code{bt_ALL} showing all possible
28757 information and another alias @code{bt_SMALL} showing very limited information
28760 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28761 -past-main -past-entry -full
28762 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28763 -past-main off -past-entry off
28766 (For more on using the @code{alias} command, see @ref{Aliases}.)
28768 Default args are not limited to the arguments and options of @var{command},
28769 but can specify nested commands if @var{command} accepts such a nested command
28771 For example, the below defines @code{faalocalsoftype} that lists the
28772 frames having locals of a certain type, together with the matching
28775 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28776 (@value{GDBP}) faalocalsoftype int
28777 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28782 This is also very useful to define an alias for a set of nested @code{with}
28783 commands to have a particular combination of temporary settings. For example,
28784 the below defines the alias @code{pp10} that pretty prints an expression
28785 argument, with a maximum of 10 elements if the expression is a string or
28788 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28790 This defines the alias @code{pp10} as being a sequence of 3 commands.
28791 The first part @code{with print pretty --} temporarily activates the setting
28792 @code{set print pretty}, then launches the command that follows the separator
28794 The command following the first part is also a @code{with} command that
28795 temporarily changes the setting @code{set print elements} to 10, then
28796 launches the command that follows the second separator @code{--}.
28797 The third part @code{print} is the command the @code{pp10} alias will launch,
28798 using the temporary values of the settings and the arguments explicitly given
28800 For more information about the @code{with} command usage,
28801 see @ref{Command Settings}.
28803 By default, asking the help for an alias shows the documentation of
28804 the aliased command. When the alias is a set of nested commands, @code{help}
28805 of an alias shows the documentation of the first command. This help
28806 is not particularly useful for an alias such as @code{pp10}.
28807 For such an alias, it is useful to give a specific documentation
28808 using the @code{document} command (@pxref{Define, document}).
28811 @c Python docs live in a separate file.
28812 @include python.texi
28814 @c Guile docs live in a separate file.
28815 @include guile.texi
28817 @node Auto-loading extensions
28818 @section Auto-loading extensions
28819 @cindex auto-loading extensions
28821 @value{GDBN} provides two mechanisms for automatically loading
28822 extensions when a new object file is read (for example, due to the
28823 @code{file} command, or because the inferior has loaded a shared
28824 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28825 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28826 @code{.debug_gdb_scripts} section of modern file formats like ELF
28827 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28828 section}). For a discussion of the differences between these two
28829 approaches see @ref{Which flavor to choose?}.
28831 The auto-loading feature is useful for supplying application-specific
28832 debugging commands and features.
28834 Auto-loading can be enabled or disabled,
28835 and the list of auto-loaded scripts can be printed.
28836 See the @samp{auto-loading} section of each extension language
28837 for more information.
28838 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28839 For Python files see @ref{Python Auto-loading}.
28841 Note that loading of this script file also requires accordingly configured
28842 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28845 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28846 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28847 * Which flavor to choose?:: Choosing between these approaches
28850 @node objfile-gdbdotext file
28851 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28852 @cindex @file{@var{objfile}-gdb.gdb}
28853 @cindex @file{@var{objfile}-gdb.py}
28854 @cindex @file{@var{objfile}-gdb.scm}
28856 When a new object file is read, @value{GDBN} looks for a file named
28857 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28858 where @var{objfile} is the object file's name and
28859 where @var{ext} is the file extension for the extension language:
28862 @item @file{@var{objfile}-gdb.gdb}
28863 GDB's own command language
28864 @item @file{@var{objfile}-gdb.py}
28866 @item @file{@var{objfile}-gdb.scm}
28870 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28871 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28872 components, and appending the @file{-gdb.@var{ext}} suffix.
28873 If this file exists and is readable, @value{GDBN} will evaluate it as a
28874 script in the specified extension language.
28876 If this file does not exist, then @value{GDBN} will look for
28877 @var{script-name} file in all of the directories as specified below.
28878 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28879 directories is converted to a one-letter subdirectory, i.e.@:
28880 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28881 filesystems disallow colons in file names.)
28883 Note that loading of these files requires an accordingly configured
28884 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28886 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28887 scripts normally according to its @file{.exe} filename. But if no scripts are
28888 found @value{GDBN} also tries script filenames matching the object file without
28889 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28890 is attempted on any platform. This makes the script filenames compatible
28891 between Unix and MS-Windows hosts.
28894 @anchor{set auto-load scripts-directory}
28895 @kindex set auto-load scripts-directory
28896 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28897 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28898 may be delimited by the host platform path separator in use
28899 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28901 Each entry here needs to be covered also by the security setting
28902 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28904 @anchor{with-auto-load-dir}
28905 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28906 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28907 configuration option @option{--with-auto-load-dir}.
28909 Any reference to @file{$debugdir} will get replaced by
28910 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28911 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28912 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28913 @file{$datadir} must be placed as a directory component --- either alone or
28914 delimited by @file{/} or @file{\} directory separators, depending on the host
28917 The list of directories uses path separator (@samp{:} on GNU and Unix
28918 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28919 to the @env{PATH} environment variable.
28921 @anchor{show auto-load scripts-directory}
28922 @kindex show auto-load scripts-directory
28923 @item show auto-load scripts-directory
28924 Show @value{GDBN} auto-loaded scripts location.
28926 @anchor{add-auto-load-scripts-directory}
28927 @kindex add-auto-load-scripts-directory
28928 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28929 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28930 Multiple entries may be delimited by the host platform path separator in use.
28933 @value{GDBN} does not track which files it has already auto-loaded this way.
28934 @value{GDBN} will load the associated script every time the corresponding
28935 @var{objfile} is opened.
28936 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28937 is evaluated more than once.
28939 @node dotdebug_gdb_scripts section
28940 @subsection The @code{.debug_gdb_scripts} section
28941 @cindex @code{.debug_gdb_scripts} section
28943 For systems using file formats like ELF and COFF,
28944 when @value{GDBN} loads a new object file
28945 it will look for a special section named @code{.debug_gdb_scripts}.
28946 If this section exists, its contents is a list of null-terminated entries
28947 specifying scripts to load. Each entry begins with a non-null prefix byte that
28948 specifies the kind of entry, typically the extension language and whether the
28949 script is in a file or inlined in @code{.debug_gdb_scripts}.
28951 The following entries are supported:
28954 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28955 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28956 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28957 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28960 @subsubsection Script File Entries
28962 If the entry specifies a file, @value{GDBN} will look for the file first
28963 in the current directory and then along the source search path
28964 (@pxref{Source Path, ,Specifying Source Directories}),
28965 except that @file{$cdir} is not searched, since the compilation
28966 directory is not relevant to scripts.
28968 File entries can be placed in section @code{.debug_gdb_scripts} with,
28969 for example, this GCC macro for Python scripts.
28972 /* Note: The "MS" section flags are to remove duplicates. */
28973 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28975 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28976 .byte 1 /* Python */\n\
28977 .asciz \"" script_name "\"\n\
28983 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28984 Then one can reference the macro in a header or source file like this:
28987 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28990 The script name may include directories if desired.
28992 Note that loading of this script file also requires accordingly configured
28993 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28995 If the macro invocation is put in a header, any application or library
28996 using this header will get a reference to the specified script,
28997 and with the use of @code{"MS"} attributes on the section, the linker
28998 will remove duplicates.
29000 @subsubsection Script Text Entries
29002 Script text entries allow to put the executable script in the entry
29003 itself instead of loading it from a file.
29004 The first line of the entry, everything after the prefix byte and up to
29005 the first newline (@code{0xa}) character, is the script name, and must not
29006 contain any kind of space character, e.g., spaces or tabs.
29007 The rest of the entry, up to the trailing null byte, is the script to
29008 execute in the specified language. The name needs to be unique among
29009 all script names, as @value{GDBN} executes each script only once based
29012 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
29016 #include "symcat.h"
29017 #include "gdb/section-scripts.h"
29019 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
29020 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
29021 ".ascii \"gdb.inlined-script\\n\"\n"
29022 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
29023 ".ascii \" def __init__ (self):\\n\"\n"
29024 ".ascii \" super (test_cmd, self).__init__ ("
29025 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
29026 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
29027 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
29028 ".ascii \"test_cmd ()\\n\"\n"
29034 Loading of inlined scripts requires a properly configured
29035 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29036 The path to specify in @code{auto-load safe-path} is the path of the file
29037 containing the @code{.debug_gdb_scripts} section.
29039 @node Which flavor to choose?
29040 @subsection Which flavor to choose?
29042 Given the multiple ways of auto-loading extensions, it might not always
29043 be clear which one to choose. This section provides some guidance.
29046 Benefits of the @file{-gdb.@var{ext}} way:
29050 Can be used with file formats that don't support multiple sections.
29053 Ease of finding scripts for public libraries.
29055 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
29056 in the source search path.
29057 For publicly installed libraries, e.g., @file{libstdc++}, there typically
29058 isn't a source directory in which to find the script.
29061 Doesn't require source code additions.
29065 Benefits of the @code{.debug_gdb_scripts} way:
29069 Works with static linking.
29071 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
29072 trigger their loading. When an application is statically linked the only
29073 objfile available is the executable, and it is cumbersome to attach all the
29074 scripts from all the input libraries to the executable's
29075 @file{-gdb.@var{ext}} script.
29078 Works with classes that are entirely inlined.
29080 Some classes can be entirely inlined, and thus there may not be an associated
29081 shared library to attach a @file{-gdb.@var{ext}} script to.
29084 Scripts needn't be copied out of the source tree.
29086 In some circumstances, apps can be built out of large collections of internal
29087 libraries, and the build infrastructure necessary to install the
29088 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
29089 cumbersome. It may be easier to specify the scripts in the
29090 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
29091 top of the source tree to the source search path.
29094 @node Multiple Extension Languages
29095 @section Multiple Extension Languages
29097 The Guile and Python extension languages do not share any state,
29098 and generally do not interfere with each other.
29099 There are some things to be aware of, however.
29101 @subsection Python comes first
29103 Python was @value{GDBN}'s first extension language, and to avoid breaking
29104 existing behaviour Python comes first. This is generally solved by the
29105 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
29106 extension languages, and when it makes a call to an extension language,
29107 (say to pretty-print a value), it tries each in turn until an extension
29108 language indicates it has performed the request (e.g., has returned the
29109 pretty-printed form of a value).
29110 This extends to errors while performing such requests: If an error happens
29111 while, for example, trying to pretty-print an object then the error is
29112 reported and any following extension languages are not tried.
29115 @chapter Command Interpreters
29116 @cindex command interpreters
29118 @value{GDBN} supports multiple command interpreters, and some command
29119 infrastructure to allow users or user interface writers to switch
29120 between interpreters or run commands in other interpreters.
29122 @value{GDBN} currently supports two command interpreters, the console
29123 interpreter (sometimes called the command-line interpreter or @sc{cli})
29124 and the machine interface interpreter (or @sc{gdb/mi}). This manual
29125 describes both of these interfaces in great detail.
29127 By default, @value{GDBN} will start with the console interpreter.
29128 However, the user may choose to start @value{GDBN} with another
29129 interpreter by specifying the @option{-i} or @option{--interpreter}
29130 startup options. Defined interpreters include:
29134 @cindex console interpreter
29135 The traditional console or command-line interpreter. This is the most often
29136 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
29137 @value{GDBN} will use this interpreter.
29141 @cindex Debugger Adapter Protocol
29142 When @value{GDBN} has been built with Python support, it also supports
29143 the Debugger Adapter Protocol. This protocol can be used by a
29144 debugger GUI or an IDE to communicate with @value{GDBN}. This
29145 protocol is documented at
29146 @url{https://microsoft.github.io/debug-adapter-protocol/}.
29149 @cindex mi interpreter
29150 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
29151 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
29152 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
29156 @cindex mi3 interpreter
29157 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
29160 @cindex mi2 interpreter
29161 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
29165 @cindex invoke another interpreter
29167 @kindex interpreter-exec
29168 You may execute commands in any interpreter from the current
29169 interpreter using the appropriate command. If you are running the
29170 console interpreter, simply use the @code{interpreter-exec} command:
29173 interpreter-exec mi "-data-list-register-names"
29176 @sc{gdb/mi} has a similar command, although it is only available in versions of
29177 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
29179 Note that @code{interpreter-exec} only changes the interpreter for the
29180 duration of the specified command. It does not change the interpreter
29183 @cindex start a new independent interpreter
29185 Although you may only choose a single interpreter at startup, it is
29186 possible to run an independent interpreter on a specified input/output
29187 device (usually a tty).
29189 For example, consider a debugger GUI or IDE that wants to provide a
29190 @value{GDBN} console view. It may do so by embedding a terminal
29191 emulator widget in its GUI, starting @value{GDBN} in the traditional
29192 command-line mode with stdin/stdout/stderr redirected to that
29193 terminal, and then creating an MI interpreter running on a specified
29194 input/output device. The console interpreter created by @value{GDBN}
29195 at startup handles commands the user types in the terminal widget,
29196 while the GUI controls and synchronizes state with @value{GDBN} using
29197 the separate MI interpreter.
29199 To start a new secondary @dfn{user interface} running MI, use the
29200 @code{new-ui} command:
29203 @cindex new user interface
29205 new-ui @var{interpreter} @var{tty}
29208 The @var{interpreter} parameter specifies the interpreter to run.
29209 This accepts the same values as the @code{interpreter-exec} command.
29210 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
29211 @var{tty} parameter specifies the name of the bidirectional file the
29212 interpreter uses for input/output, usually the name of a
29213 pseudoterminal slave on Unix systems. For example:
29216 (@value{GDBP}) new-ui mi /dev/pts/9
29220 runs an MI interpreter on @file{/dev/pts/9}.
29223 @chapter @value{GDBN} Text User Interface
29225 @cindex Text User Interface
29227 The @value{GDBN} Text User Interface (TUI) is a terminal
29228 interface which uses the @code{curses} library to show the source
29229 file, the assembly output, the program registers and @value{GDBN}
29230 commands in separate text windows. The TUI mode is supported only
29231 on platforms where a suitable version of the @code{curses} library
29234 The TUI mode is enabled by default when you invoke @value{GDBN} as
29235 @samp{@value{GDBP} -tui}.
29236 You can also switch in and out of TUI mode while @value{GDBN} runs by
29237 using various TUI commands and key bindings, such as @command{tui
29238 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
29239 @ref{TUI Keys, ,TUI Key Bindings}.
29242 * TUI Overview:: TUI overview
29243 * TUI Keys:: TUI key bindings
29244 * TUI Single Key Mode:: TUI single key mode
29245 * TUI Mouse Support:: TUI mouse support
29246 * TUI Commands:: TUI-specific commands
29247 * TUI Configuration:: TUI configuration variables
29251 @section TUI Overview
29253 In TUI mode, @value{GDBN} can display several text windows:
29257 This window is the @value{GDBN} command window with the @value{GDBN}
29258 prompt and the @value{GDBN} output. The @value{GDBN} input is still
29259 managed using readline.
29262 The source window shows the source file of the program. The current
29263 line and active breakpoints are displayed in this window.
29266 The assembly window shows the disassembly output of the program.
29269 This window shows the processor registers. Registers are highlighted
29270 when their values change.
29273 The source and assembly windows show the current program position by
29274 highlighting the current line and marking it with a @samp{>} marker.
29275 By default, source and assembly code styling is disabled for the
29276 highlighted text, but you can enable it with the @code{set style
29277 tui-current-position on} command. @xref{Output Styling}.
29279 Breakpoints are indicated with two markers. The first marker
29280 indicates the breakpoint type:
29284 Breakpoint which was hit at least once.
29287 Breakpoint which was never hit.
29290 Hardware breakpoint which was hit at least once.
29293 Hardware breakpoint which was never hit.
29296 The second marker indicates whether the breakpoint is enabled or not:
29300 Breakpoint is enabled.
29303 Breakpoint is disabled.
29306 The source, assembly and register windows are updated when the current
29307 thread changes, when the frame changes, or when the program counter
29310 These windows are not all visible at the same time. The command
29311 window is always visible. The others can be arranged in several
29322 source and assembly,
29325 source and registers, or
29328 assembly and registers.
29331 These are the standard layouts, but other layouts can be defined.
29333 A status line above the command window shows the following information:
29337 Indicates the current @value{GDBN} target.
29338 (@pxref{Targets, ,Specifying a Debugging Target}).
29341 Gives the current process or thread number.
29342 When no process is being debugged, this field is set to @code{No process}.
29345 Gives the current function name for the selected frame.
29346 The name is demangled if demangling is turned on (@pxref{Print Settings}).
29347 When there is no symbol corresponding to the current program counter,
29348 the string @code{??} is displayed.
29351 Indicates the current line number for the selected frame.
29352 When the current line number is not known, the string @code{??} is displayed.
29355 Indicates the current program counter address.
29359 @section TUI Key Bindings
29360 @cindex TUI key bindings
29362 The TUI installs several key bindings in the readline keymaps
29363 @ifset SYSTEM_READLINE
29364 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
29366 @ifclear SYSTEM_READLINE
29367 (@pxref{Command Line Editing}).
29369 The following key bindings are installed for both TUI mode and the
29370 @value{GDBN} standard mode.
29379 Enter or leave the TUI mode. When leaving the TUI mode,
29380 the curses window management stops and @value{GDBN} operates using
29381 its standard mode, writing on the terminal directly. When reentering
29382 the TUI mode, control is given back to the curses windows.
29383 The screen is then refreshed.
29385 This key binding uses the bindable Readline function
29386 @code{tui-switch-mode}.
29390 Use a TUI layout with only one window. The layout will
29391 either be @samp{source} or @samp{assembly}. When the TUI mode
29392 is not active, it will switch to the TUI mode.
29394 Think of this key binding as the Emacs @kbd{C-x 1} binding.
29396 This key binding uses the bindable Readline function
29397 @code{tui-delete-other-windows}.
29401 Use a TUI layout with at least two windows. When the current
29402 layout already has two windows, the next layout with two windows is used.
29403 When a new layout is chosen, one window will always be common to the
29404 previous layout and the new one.
29406 Think of it as the Emacs @kbd{C-x 2} binding.
29408 This key binding uses the bindable Readline function
29409 @code{tui-change-windows}.
29413 Change the active window. The TUI associates several key bindings
29414 (like scrolling and arrow keys) with the active window. This command
29415 gives the focus to the next TUI window.
29417 Think of it as the Emacs @kbd{C-x o} binding.
29419 This key binding uses the bindable Readline function
29420 @code{tui-other-window}.
29424 Switch in and out of the TUI SingleKey mode that binds single
29425 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
29427 This key binding uses the bindable Readline function
29428 @code{next-keymap}.
29431 The following key bindings only work in the TUI mode:
29436 Scroll the active window one page up.
29440 Scroll the active window one page down.
29444 Scroll the active window one line up.
29448 Scroll the active window one line down.
29452 Scroll the active window one column left.
29456 Scroll the active window one column right.
29460 Refresh the screen.
29463 Because the arrow keys scroll the active window in the TUI mode, they
29464 are not available for their normal use by readline unless the command
29465 window has the focus. When another window is active, you must use
29466 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
29467 and @kbd{C-f} to control the command window.
29469 @node TUI Single Key Mode
29470 @section TUI Single Key Mode
29471 @cindex TUI single key mode
29473 The TUI also provides a @dfn{SingleKey} mode, which binds several
29474 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
29475 switch into this mode, where the following key bindings are used:
29478 @kindex c @r{(SingleKey TUI key)}
29482 @kindex d @r{(SingleKey TUI key)}
29486 @kindex f @r{(SingleKey TUI key)}
29490 @kindex n @r{(SingleKey TUI key)}
29494 @kindex o @r{(SingleKey TUI key)}
29496 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29498 @kindex q @r{(SingleKey TUI key)}
29500 exit the SingleKey mode.
29502 @kindex r @r{(SingleKey TUI key)}
29506 @kindex s @r{(SingleKey TUI key)}
29510 @kindex i @r{(SingleKey TUI key)}
29512 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29514 @kindex u @r{(SingleKey TUI key)}
29518 @kindex v @r{(SingleKey TUI key)}
29522 @kindex w @r{(SingleKey TUI key)}
29527 Other keys temporarily switch to the @value{GDBN} command prompt.
29528 The key that was pressed is inserted in the editing buffer so that
29529 it is possible to type most @value{GDBN} commands without interaction
29530 with the TUI SingleKey mode. Once the command is entered the TUI
29531 SingleKey mode is restored. The only way to permanently leave
29532 this mode is by typing @kbd{q} or @kbd{C-x s}.
29534 @cindex SingleKey keymap name
29535 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29536 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29537 @file{.inputrc} to add additional bindings to this keymap.
29539 @node TUI Mouse Support
29540 @section TUI Mouse Support
29541 @cindex TUI mouse support
29543 If the curses library supports the mouse, the TUI supports mouse
29546 The mouse wheel scrolls the appropriate window under the mouse cursor.
29548 The TUI itself does not directly support copying/pasting with the
29549 mouse. However, on Unix terminals, you can typically press and hold
29550 the @key{SHIFT} key on your keyboard to temporarily bypass
29551 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29552 functionality (commonly, click-drag-release or double-click to select
29553 text, middle-click to paste). This copy/paste works with the
29554 terminal's selection buffer, as opposed to the TUI's buffer.
29557 @section TUI-specific Commands
29558 @cindex TUI commands
29560 The TUI has specific commands to control the text windows.
29561 These commands are always available, even when @value{GDBN} is not in
29562 the TUI mode. When @value{GDBN} is in the standard mode, most
29563 of these commands will automatically switch to the TUI mode.
29565 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29566 terminal, or @value{GDBN} has been started with the machine interface
29567 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29568 these commands will fail with an error, because it would not be
29569 possible or desirable to enable curses window management.
29574 Activate TUI mode. The last active TUI window layout will be used if
29575 TUI mode has previously been used in the current debugging session,
29576 otherwise a default layout is used.
29579 @kindex tui disable
29580 Disable TUI mode, returning to the console interpreter.
29582 @anchor{info_win_command}
29585 List the names and sizes of all currently displayed windows.
29587 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29588 @kindex tui new-layout
29589 Create a new TUI layout. The new layout will be named @var{name}, and
29590 can be accessed using the @code{layout} command (see below).
29592 Each @var{window} parameter is either the name of a window to display,
29593 or a window description. The windows will be displayed from top to
29594 bottom in the order listed.
29596 The names of the windows are the same as the ones given to the
29597 @code{focus} command (see below); additional, the @code{status}
29598 window can be specified. Note that, because it is of fixed height,
29599 the weight assigned to the status window is of no importance. It is
29600 conventional to use @samp{0} here.
29602 A window description looks a bit like an invocation of @code{tui
29603 new-layout}, and is of the form
29604 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29606 This specifies a sub-layout. If @code{-horizontal} is given, the
29607 windows in this description will be arranged side-by-side, rather than
29610 Each @var{weight} is an integer. It is the weight of this window
29611 relative to all the other windows in the layout. These numbers are
29612 used to calculate how much of the screen is given to each window.
29617 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29620 Here, the new layout is called @samp{example}. It shows the source
29621 and register windows, followed by the status window, and then finally
29622 the command window. The non-status windows all have the same weight,
29623 so the terminal will be split into three roughly equal sections.
29625 Here is a more complex example, showing a horizontal layout:
29628 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29631 This will result in side-by-side source and assembly windows; with the
29632 status and command window being beneath these, filling the entire
29633 width of the terminal. Because they have weight 2, the source and
29634 assembly windows will be twice the height of the command window.
29638 @item tui layout @var{name}
29639 @itemx layout @var{name}
29640 Changes which TUI windows are displayed. The @var{name} parameter
29641 controls which layout is shown. It can be either one of the built-in
29642 layout names, or the name of a layout defined by the user using
29643 @code{tui new-layout}.
29645 The built-in layouts are as follows:
29649 Display the next layout.
29652 Display the previous layout.
29655 Display the source and command windows.
29658 Display the assembly and command windows.
29661 Display the source, assembly, and command windows.
29664 When in @code{src} layout display the register, source, and command
29665 windows. When in @code{asm} or @code{split} layout display the
29666 register, assembler, and command windows.
29670 @item tui focus @var{name}
29671 @itemx focus @var{name}
29672 Changes which TUI window is currently active for scrolling. The
29673 @var{name} parameter can be any of the following:
29677 Make the next window active for scrolling.
29680 Make the previous window active for scrolling.
29683 Make the source window active for scrolling.
29686 Make the assembly window active for scrolling.
29689 Make the register window active for scrolling.
29692 Make the command window active for scrolling.
29695 @kindex tui refresh
29699 Refresh the screen. This is similar to typing @kbd{C-L}.
29701 @item tui reg @var{group}
29703 Changes the register group displayed in the tui register window to
29704 @var{group}. If the register window is not currently displayed this
29705 command will cause the register window to be displayed. The list of
29706 register groups, as well as their order is target specific. The
29707 following groups are available on most targets:
29710 Repeatedly selecting this group will cause the display to cycle
29711 through all of the available register groups.
29714 Repeatedly selecting this group will cause the display to cycle
29715 through all of the available register groups in the reverse order to
29719 Display the general registers.
29721 Display the floating point registers.
29723 Display the system registers.
29725 Display the vector registers.
29727 Display all registers.
29732 Update the source window and the current execution point.
29734 @kindex tui window height
29736 @item tui window height @var{name} +@var{count}
29737 @itemx tui window height @var{name} -@var{count}
29738 @itemx winheight @var{name} +@var{count}
29739 @itemx winheight @var{name} -@var{count}
29740 Change the height of the window @var{name} by @var{count} lines.
29741 Positive counts increase the height, while negative counts decrease
29742 it. The @var{name} parameter can be the name of any currently visible
29743 window. The names of the currently visible windows can be discovered
29744 using @kbd{info win} (@pxref{info_win_command,,info win}).
29746 The set of currently visible windows must always fill the terminal,
29747 and so, it is only possible to resize on window if there are other
29748 visible windows that can either give or receive the extra terminal
29751 @kindex tui window width
29753 @item tui window width @var{name} +@var{count}
29754 @itemx tui window width @var{name} -@var{count}
29755 @itemx winwidth @var{name} +@var{count}
29756 @itemx winwidth @var{name} -@var{count}
29757 Change the width of the window @var{name} by @var{count} columns.
29758 Positive counts increase the width, while negative counts decrease it.
29759 The @var{name} parameter can be the name of any currently visible
29760 window. The names of the currently visible windows can be discovered
29761 using @code{info win} (@pxref{info_win_command,,info win}).
29763 The set of currently visible windows must always fill the terminal,
29764 and so, it is only possible to resize on window if there are other
29765 visible windows that can either give or receive the extra terminal
29769 @node TUI Configuration
29770 @section TUI Configuration Variables
29771 @cindex TUI configuration variables
29773 Several configuration variables control the appearance of TUI windows.
29776 @item set tui border-kind @var{kind}
29777 @kindex set tui border-kind
29778 Select the border appearance for the source, assembly and register windows.
29779 The possible values are the following:
29782 Use a space character to draw the border.
29785 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29788 Use the Alternate Character Set to draw the border. The border is
29789 drawn using character line graphics if the terminal supports them.
29792 @item set tui border-mode @var{mode}
29793 @kindex set tui border-mode
29794 @itemx set tui active-border-mode @var{mode}
29795 @kindex set tui active-border-mode
29796 Select the display attributes for the borders of the inactive windows
29797 or the active window. The @var{mode} can be one of the following:
29800 Use normal attributes to display the border.
29806 Use reverse video mode.
29809 Use half bright mode.
29811 @item half-standout
29812 Use half bright and standout mode.
29815 Use extra bright or bold mode.
29817 @item bold-standout
29818 Use extra bright or bold and standout mode.
29821 @item set tui tab-width @var{nchars}
29822 @kindex set tui tab-width
29824 Set the width of tab stops to be @var{nchars} characters. This
29825 setting affects the display of TAB characters in the source and
29828 @item set tui compact-source @r{[}on@r{|}off@r{]}
29829 @kindex set tui compact-source
29830 Set whether the TUI source window is displayed in ``compact'' form.
29831 The default display uses more space for line numbers and starts the
29832 source text at the next tab stop; the compact display uses only as
29833 much space as is needed for the line numbers in the current file, and
29834 only a single space to separate the line numbers from the source.
29836 @kindex set debug tui
29837 @item set debug tui @r{[}on|off@r{]}
29838 Turn on or off display of @value{GDBN} internal debug messages relating
29841 @kindex show debug tui
29842 @item show debug tui
29843 Show the current status of displaying @value{GDBN} internal debug
29844 messages relating to the TUI.
29848 Note that the colors of the TUI borders can be controlled using the
29849 appropriate @code{set style} commands. @xref{Output Styling}.
29852 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29855 @cindex @sc{gnu} Emacs
29856 A special interface allows you to use @sc{gnu} Emacs to view (and
29857 edit) the source files for the program you are debugging with
29860 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29861 executable file you want to debug as an argument. This command starts
29862 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29863 created Emacs buffer.
29864 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29866 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29871 All ``terminal'' input and output goes through an Emacs buffer, called
29874 This applies both to @value{GDBN} commands and their output, and to the input
29875 and output done by the program you are debugging.
29877 This is useful because it means that you can copy the text of previous
29878 commands and input them again; you can even use parts of the output
29881 All the facilities of Emacs' Shell mode are available for interacting
29882 with your program. In particular, you can send signals the usual
29883 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29887 @value{GDBN} displays source code through Emacs.
29889 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29890 source file for that frame and puts an arrow (@samp{=>}) at the
29891 left margin of the current line. Emacs uses a separate buffer for
29892 source display, and splits the screen to show both your @value{GDBN} session
29895 Explicit @value{GDBN} @code{list} or search commands still produce output as
29896 usual, but you probably have no reason to use them from Emacs.
29899 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29900 a graphical mode, enabled by default, which provides further buffers
29901 that can control the execution and describe the state of your program.
29902 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29904 If you specify an absolute file name when prompted for the @kbd{M-x
29905 gdb} argument, then Emacs sets your current working directory to where
29906 your program resides. If you only specify the file name, then Emacs
29907 sets your current working directory to the directory associated
29908 with the previous buffer. In this case, @value{GDBN} may find your
29909 program by searching your environment's @env{PATH} variable, but on
29910 some operating systems it might not find the source. So, although the
29911 @value{GDBN} input and output session proceeds normally, the auxiliary
29912 buffer does not display the current source and line of execution.
29914 The initial working directory of @value{GDBN} is printed on the top
29915 line of the GUD buffer and this serves as a default for the commands
29916 that specify files for @value{GDBN} to operate on. @xref{Files,
29917 ,Commands to Specify Files}.
29919 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29920 need to call @value{GDBN} by a different name (for example, if you
29921 keep several configurations around, with different names) you can
29922 customize the Emacs variable @code{gud-gdb-command-name} to run the
29925 In the GUD buffer, you can use these special Emacs commands in
29926 addition to the standard Shell mode commands:
29930 Describe the features of Emacs' GUD Mode.
29933 Execute to another source line, like the @value{GDBN} @code{step} command; also
29934 update the display window to show the current file and location.
29937 Execute to next source line in this function, skipping all function
29938 calls, like the @value{GDBN} @code{next} command. Then update the display window
29939 to show the current file and location.
29942 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29943 display window accordingly.
29946 Execute until exit from the selected stack frame, like the @value{GDBN}
29947 @code{finish} command.
29950 Continue execution of your program, like the @value{GDBN} @code{continue}
29954 Go up the number of frames indicated by the numeric argument
29955 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29956 like the @value{GDBN} @code{up} command.
29959 Go down the number of frames indicated by the numeric argument, like the
29960 @value{GDBN} @code{down} command.
29963 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29964 tells @value{GDBN} to set a breakpoint on the source line point is on.
29966 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29967 separate frame which shows a backtrace when the GUD buffer is current.
29968 Move point to any frame in the stack and type @key{RET} to make it
29969 become the current frame and display the associated source in the
29970 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29971 selected frame become the current one. In graphical mode, the
29972 speedbar displays watch expressions.
29974 If you accidentally delete the source-display buffer, an easy way to get
29975 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29976 request a frame display; when you run under Emacs, this recreates
29977 the source buffer if necessary to show you the context of the current
29980 The source files displayed in Emacs are in ordinary Emacs buffers
29981 which are visiting the source files in the usual way. You can edit
29982 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29983 communicates with Emacs in terms of line numbers. If you add or
29984 delete lines from the text, the line numbers that @value{GDBN} knows cease
29985 to correspond properly with the code.
29987 A more detailed description of Emacs' interaction with @value{GDBN} is
29988 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29992 @chapter The @sc{gdb/mi} Interface
29994 @unnumberedsec Function and Purpose
29996 @cindex @sc{gdb/mi}, its purpose
29997 @sc{gdb/mi} is a line based machine oriented text interface to
29998 @value{GDBN} and is activated by specifying using the
29999 @option{--interpreter} command line option (@pxref{Mode Options}). It
30000 is specifically intended to support the development of systems which
30001 use the debugger as just one small component of a larger system.
30003 This chapter is a specification of the @sc{gdb/mi} interface. It is written
30004 in the form of a reference manual.
30006 Note that @sc{gdb/mi} is still under construction, so some of the
30007 features described below are incomplete and subject to change
30008 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
30010 @unnumberedsec Notation and Terminology
30012 @cindex notational conventions, for @sc{gdb/mi}
30013 This chapter uses the following notation:
30017 @code{|} separates two alternatives.
30020 @code{[ @var{something} ]} indicates that @var{something} is optional:
30021 it may or may not be given.
30024 @code{( @var{group} )*} means that @var{group} inside the parentheses
30025 may repeat zero or more times.
30028 @code{( @var{group} )+} means that @var{group} inside the parentheses
30029 may repeat one or more times.
30032 @code{( @var{group} )} means that @var{group} inside the parentheses
30033 occurs exactly once.
30036 @code{"@var{string}"} means a literal @var{string}.
30040 @heading Dependencies
30044 * GDB/MI General Design::
30045 * GDB/MI Command Syntax::
30046 * GDB/MI Compatibility with CLI::
30047 * GDB/MI Development and Front Ends::
30048 * GDB/MI Output Records::
30049 * GDB/MI Simple Examples::
30050 * GDB/MI Command Description Format::
30051 * GDB/MI Breakpoint Commands::
30052 * GDB/MI Catchpoint Commands::
30053 * GDB/MI Program Context::
30054 * GDB/MI Thread Commands::
30055 * GDB/MI Ada Tasking Commands::
30056 * GDB/MI Program Execution::
30057 * GDB/MI Stack Manipulation::
30058 * GDB/MI Variable Objects::
30059 * GDB/MI Data Manipulation::
30060 * GDB/MI Tracepoint Commands::
30061 * GDB/MI Symbol Query::
30062 * GDB/MI File Commands::
30064 * GDB/MI Kod Commands::
30065 * GDB/MI Memory Overlay Commands::
30066 * GDB/MI Signal Handling Commands::
30068 * GDB/MI Target Manipulation::
30069 * GDB/MI File Transfer Commands::
30070 * GDB/MI Ada Exceptions Commands::
30071 * GDB/MI Support Commands::
30072 * GDB/MI Miscellaneous Commands::
30075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30076 @node GDB/MI General Design
30077 @section @sc{gdb/mi} General Design
30078 @cindex GDB/MI General Design
30080 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
30081 parts---commands sent to @value{GDBN}, responses to those commands
30082 and notifications. Each command results in exactly one response,
30083 indicating either successful completion of the command, or an error.
30084 For the commands that do not resume the target, the response contains the
30085 requested information. For the commands that resume the target, the
30086 response only indicates whether the target was successfully resumed.
30087 Notifications is the mechanism for reporting changes in the state of the
30088 target, or in @value{GDBN} state, that cannot conveniently be associated with
30089 a command and reported as part of that command response.
30091 The important examples of notifications are:
30095 Exec notifications. These are used to report changes in
30096 target state---when a target is resumed, or stopped. It would not
30097 be feasible to include this information in response of resuming
30098 commands, because one resume commands can result in multiple events in
30099 different threads. Also, quite some time may pass before any event
30100 happens in the target, while a frontend needs to know whether the resuming
30101 command itself was successfully executed.
30104 Console output, and status notifications. Console output
30105 notifications are used to report output of CLI commands, as well as
30106 diagnostics for other commands. Status notifications are used to
30107 report the progress of a long-running operation. Naturally, including
30108 this information in command response would mean no output is produced
30109 until the command is finished, which is undesirable.
30112 General notifications. Commands may have various side effects on
30113 the @value{GDBN} or target state beyond their official purpose. For example,
30114 a command may change the selected thread. Although such changes can
30115 be included in command response, using notification allows for more
30116 orthogonal frontend design.
30120 There's no guarantee that whenever an MI command reports an error,
30121 @value{GDBN} or the target are in any specific state, and especially,
30122 the state is not reverted to the state before the MI command was
30123 processed. Therefore, whenever an MI command results in an error,
30124 we recommend that the frontend refreshes all the information shown in
30125 the user interface.
30129 * Context management::
30130 * Asynchronous and non-stop modes::
30134 @node Context management
30135 @subsection Context management
30137 @subsubsection Threads and Frames
30139 In most cases when @value{GDBN} accesses the target, this access is
30140 done in context of a specific thread and frame (@pxref{Frames}).
30141 Often, even when accessing global data, the target requires that a thread
30142 be specified. The CLI interface maintains the selected thread and frame,
30143 and supplies them to target on each command. This is convenient,
30144 because a command line user would not want to specify that information
30145 explicitly on each command, and because user interacts with
30146 @value{GDBN} via a single terminal, so no confusion is possible as
30147 to what thread and frame are the current ones.
30149 In the case of MI, the concept of selected thread and frame is less
30150 useful. First, a frontend can easily remember this information
30151 itself. Second, a graphical frontend can have more than one window,
30152 each one used for debugging a different thread, and the frontend might
30153 want to access additional threads for internal purposes. This
30154 increases the risk that by relying on implicitly selected thread, the
30155 frontend may be operating on a wrong one. Therefore, each MI command
30156 should explicitly specify which thread and frame to operate on. To
30157 make it possible, each MI command accepts the @samp{--thread} and
30158 @samp{--frame} options, the value to each is @value{GDBN} global
30159 identifier for thread and frame to operate on.
30161 Usually, each top-level window in a frontend allows the user to select
30162 a thread and a frame, and remembers the user selection for further
30163 operations. However, in some cases @value{GDBN} may suggest that the
30164 current thread or frame be changed. For example, when stopping on a
30165 breakpoint it is reasonable to switch to the thread where breakpoint is
30166 hit. For another example, if the user issues the CLI @samp{thread} or
30167 @samp{frame} commands via the frontend, it is desirable to change the
30168 frontend's selection to the one specified by user. @value{GDBN}
30169 communicates the suggestion to change current thread and frame using the
30170 @samp{=thread-selected} notification.
30172 Note that historically, MI shares the selected thread with CLI, so
30173 frontends used the @code{-thread-select} to execute commands in the
30174 right context. However, getting this to work right is cumbersome. The
30175 simplest way is for frontend to emit @code{-thread-select} command
30176 before every command. This doubles the number of commands that need
30177 to be sent. The alternative approach is to suppress @code{-thread-select}
30178 if the selected thread in @value{GDBN} is supposed to be identical to the
30179 thread the frontend wants to operate on. However, getting this
30180 optimization right can be tricky. In particular, if the frontend
30181 sends several commands to @value{GDBN}, and one of the commands changes the
30182 selected thread, then the behaviour of subsequent commands will
30183 change. So, a frontend should either wait for response from such
30184 problematic commands, or explicitly add @code{-thread-select} for
30185 all subsequent commands. No frontend is known to do this exactly
30186 right, so it is suggested to just always pass the @samp{--thread} and
30187 @samp{--frame} options.
30189 @subsubsection Language
30191 The execution of several commands depends on which language is selected.
30192 By default, the current language (@pxref{show language}) is used.
30193 But for commands known to be language-sensitive, it is recommended
30194 to use the @samp{--language} option. This option takes one argument,
30195 which is the name of the language to use while executing the command.
30199 -data-evaluate-expression --language c "sizeof (void*)"
30204 The valid language names are the same names accepted by the
30205 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
30206 @samp{local} or @samp{unknown}.
30208 @node Asynchronous and non-stop modes
30209 @subsection Asynchronous command execution and non-stop mode
30211 On some targets, @value{GDBN} is capable of processing MI commands
30212 even while the target is running. This is called @dfn{asynchronous
30213 command execution} (@pxref{Background Execution}). The frontend may
30214 specify a preference for asynchronous execution using the
30215 @code{-gdb-set mi-async 1} command, which should be emitted before
30216 either running the executable or attaching to the target. After the
30217 frontend has started the executable or attached to the target, it can
30218 find if asynchronous execution is enabled using the
30219 @code{-list-target-features} command.
30222 @cindex foreground execution
30223 @cindex background execution
30224 @cindex asynchronous execution
30225 @cindex execution, foreground, background and asynchronous
30226 @kindex set mi-async
30227 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
30228 Set whether MI is in asynchronous mode.
30230 When @code{off}, which is the default, MI execution commands (e.g.,
30231 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
30232 for the program to stop before processing further commands.
30234 When @code{on}, MI execution commands are background execution
30235 commands (e.g., @code{-exec-continue} becomes the equivalent of the
30236 @code{c&} CLI command), and so @value{GDBN} is capable of processing
30237 MI commands even while the target is running.
30239 @kindex show mi-async
30240 @item -gdb-show mi-async
30241 Show whether MI asynchronous mode is enabled.
30244 Note: In @value{GDBN} version 7.7 and earlier, this option was called
30245 @code{target-async} instead of @code{mi-async}, and it had the effect
30246 of both putting MI in asynchronous mode and making CLI background
30247 commands possible. CLI background commands are now always possible
30248 ``out of the box'' if the target supports them. The old spelling is
30249 kept as a deprecated alias for backwards compatibility.
30251 Even if @value{GDBN} can accept a command while target is running,
30252 many commands that access the target do not work when the target is
30253 running. Therefore, asynchronous command execution is most useful
30254 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
30255 it is possible to examine the state of one thread, while other threads
30258 When a given thread is running, MI commands that try to access the
30259 target in the context of that thread may not work, or may work only on
30260 some targets. In particular, commands that try to operate on thread's
30261 stack will not work, on any target. Commands that read memory, or
30262 modify breakpoints, may work or not work, depending on the target. Note
30263 that even commands that operate on global state, such as @code{print},
30264 @code{set}, and breakpoint commands, still access the target in the
30265 context of a specific thread, so frontend should try to find a
30266 stopped thread and perform the operation on that thread (using the
30267 @samp{--thread} option).
30269 Which commands will work in the context of a running thread is
30270 highly target dependent. However, the two commands
30271 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
30272 to find the state of a thread, will always work.
30274 @node Thread groups
30275 @subsection Thread groups
30276 @value{GDBN} may be used to debug several processes at the same time.
30277 On some platforms, @value{GDBN} may support debugging of several
30278 hardware systems, each one having several cores with several different
30279 processes running on each core. This section describes the MI
30280 mechanism to support such debugging scenarios.
30282 The key observation is that regardless of the structure of the
30283 target, MI can have a global list of threads, because most commands that
30284 accept the @samp{--thread} option do not need to know what process that
30285 thread belongs to. Therefore, it is not necessary to introduce
30286 neither additional @samp{--process} option, nor an notion of the
30287 current process in the MI interface. The only strictly new feature
30288 that is required is the ability to find how the threads are grouped
30291 To allow the user to discover such grouping, and to support arbitrary
30292 hierarchy of machines/cores/processes, MI introduces the concept of a
30293 @dfn{thread group}. Thread group is a collection of threads and other
30294 thread groups. A thread group always has a string identifier, a type,
30295 and may have additional attributes specific to the type. A new
30296 command, @code{-list-thread-groups}, returns the list of top-level
30297 thread groups, which correspond to processes that @value{GDBN} is
30298 debugging at the moment. By passing an identifier of a thread group
30299 to the @code{-list-thread-groups} command, it is possible to obtain
30300 the members of specific thread group.
30302 To allow the user to easily discover processes, and other objects, he
30303 wishes to debug, a concept of @dfn{available thread group} is
30304 introduced. Available thread group is an thread group that
30305 @value{GDBN} is not debugging, but that can be attached to, using the
30306 @code{-target-attach} command. The list of available top-level thread
30307 groups can be obtained using @samp{-list-thread-groups --available}.
30308 In general, the content of a thread group may be only retrieved only
30309 after attaching to that thread group.
30311 Thread groups are related to inferiors (@pxref{Inferiors Connections and
30312 Programs}). Each inferior corresponds to a thread group of a special
30313 type @samp{process}, and some additional operations are permitted on
30314 such thread groups.
30316 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30317 @node GDB/MI Command Syntax
30318 @section @sc{gdb/mi} Command Syntax
30321 * GDB/MI Input Syntax::
30322 * GDB/MI Output Syntax::
30325 @node GDB/MI Input Syntax
30326 @subsection @sc{gdb/mi} Input Syntax
30328 @cindex input syntax for @sc{gdb/mi}
30329 @cindex @sc{gdb/mi}, input syntax
30331 @item @var{command} @expansion{}
30332 @code{@var{cli-command} | @var{mi-command}}
30334 @item @var{cli-command} @expansion{}
30335 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
30336 @var{cli-command} is any existing @value{GDBN} CLI command.
30338 @item @var{mi-command} @expansion{}
30339 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
30340 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
30342 @item @var{token} @expansion{}
30343 "any sequence of digits"
30345 @item @var{option} @expansion{}
30346 @code{"-" @var{parameter} [ " " @var{parameter} ]}
30348 @item @var{parameter} @expansion{}
30349 @code{@var{non-blank-sequence} | @var{c-string}}
30351 @item @var{operation} @expansion{}
30352 @emph{any of the operations described in this chapter}
30354 @item @var{non-blank-sequence} @expansion{}
30355 @emph{anything, provided it doesn't contain special characters such as
30356 "-", @var{nl}, """ and of course " "}
30358 @item @var{c-string} @expansion{}
30359 @code{""" @var{seven-bit-iso-c-string-content} """}
30361 @item @var{nl} @expansion{}
30370 The CLI commands are still handled by the @sc{mi} interpreter; their
30371 output is described below.
30374 The @code{@var{token}}, when present, is passed back when the command
30378 Some @sc{mi} commands accept optional arguments as part of the parameter
30379 list. Each option is identified by a leading @samp{-} (dash) and may be
30380 followed by an optional argument parameter. Options occur first in the
30381 parameter list and can be delimited from normal parameters using
30382 @samp{--} (this is useful when some parameters begin with a dash).
30389 We want easy access to the existing CLI syntax (for debugging).
30392 We want it to be easy to spot a @sc{mi} operation.
30395 @node GDB/MI Output Syntax
30396 @subsection @sc{gdb/mi} Output Syntax
30398 @cindex output syntax of @sc{gdb/mi}
30399 @cindex @sc{gdb/mi}, output syntax
30400 The output from @sc{gdb/mi} consists of zero or more out-of-band records
30401 followed, optionally, by a single result record. This result record
30402 is for the most recent command. The sequence of output records is
30403 terminated by @samp{(gdb)}.
30405 If an input command was prefixed with a @code{@var{token}} then the
30406 corresponding output for that command will also be prefixed by that same
30410 @item @var{output} @expansion{}
30411 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
30413 @item @var{result-record} @expansion{}
30414 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
30416 @item @var{out-of-band-record} @expansion{}
30417 @code{@var{async-record} | @var{stream-record}}
30419 @item @var{async-record} @expansion{}
30420 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
30422 @item @var{exec-async-output} @expansion{}
30423 @code{[ @var{token} ] "*" @var{async-output nl}}
30425 @item @var{status-async-output} @expansion{}
30426 @code{[ @var{token} ] "+" @var{async-output nl}}
30428 @item @var{notify-async-output} @expansion{}
30429 @code{[ @var{token} ] "=" @var{async-output nl}}
30431 @item @var{async-output} @expansion{}
30432 @code{@var{async-class} ( "," @var{result} )*}
30434 @item @var{result-class} @expansion{}
30435 @code{"done" | "running" | "connected" | "error" | "exit"}
30437 @item @var{async-class} @expansion{}
30438 @code{"stopped" | @var{others}} (where @var{others} will be added
30439 depending on the needs---this is still in development).
30441 @item @var{result} @expansion{}
30442 @code{ @var{variable} "=" @var{value}}
30444 @item @var{variable} @expansion{}
30445 @code{ @var{string} }
30447 @item @var{value} @expansion{}
30448 @code{ @var{const} | @var{tuple} | @var{list} }
30450 @item @var{const} @expansion{}
30451 @code{@var{c-string}}
30453 @item @var{tuple} @expansion{}
30454 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
30456 @item @var{list} @expansion{}
30457 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
30458 @var{result} ( "," @var{result} )* "]" }
30460 @item @var{stream-record} @expansion{}
30461 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
30463 @item @var{console-stream-output} @expansion{}
30464 @code{"~" @var{c-string nl}}
30466 @item @var{target-stream-output} @expansion{}
30467 @code{"@@" @var{c-string nl}}
30469 @item @var{log-stream-output} @expansion{}
30470 @code{"&" @var{c-string nl}}
30472 @item @var{nl} @expansion{}
30475 @item @var{token} @expansion{}
30476 @emph{any sequence of digits}.
30484 All output sequences end in a single line containing a period.
30487 The @code{@var{token}} is from the corresponding request. Note that
30488 for all async output, while the token is allowed by the grammar and
30489 may be output by future versions of @value{GDBN} for select async
30490 output messages, it is generally omitted. Frontends should treat
30491 all async output as reporting general changes in the state of the
30492 target and there should be no need to associate async output to any
30496 @cindex status output in @sc{gdb/mi}
30497 @var{status-async-output} contains on-going status information about the
30498 progress of a slow operation. It can be discarded. All status output is
30499 prefixed by @samp{+}.
30502 @cindex async output in @sc{gdb/mi}
30503 @var{exec-async-output} contains asynchronous state change on the target
30504 (stopped, started, disappeared). All async output is prefixed by
30508 @cindex notify output in @sc{gdb/mi}
30509 @var{notify-async-output} contains supplementary information that the
30510 client should handle (e.g., a new breakpoint information). All notify
30511 output is prefixed by @samp{=}.
30514 @cindex console output in @sc{gdb/mi}
30515 @var{console-stream-output} is output that should be displayed as is in the
30516 console. It is the textual response to a CLI command. All the console
30517 output is prefixed by @samp{~}.
30520 @cindex target output in @sc{gdb/mi}
30521 @var{target-stream-output} is the output produced by the target program.
30522 All the target output is prefixed by @samp{@@}.
30525 @cindex log output in @sc{gdb/mi}
30526 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30527 instance messages that should be displayed as part of an error log. All
30528 the log output is prefixed by @samp{&}.
30531 @cindex list output in @sc{gdb/mi}
30532 New @sc{gdb/mi} commands should only output @var{lists} containing
30538 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30539 details about the various output records.
30541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30542 @node GDB/MI Compatibility with CLI
30543 @section @sc{gdb/mi} Compatibility with CLI
30545 @cindex compatibility, @sc{gdb/mi} and CLI
30546 @cindex @sc{gdb/mi}, compatibility with CLI
30548 For the developers convenience CLI commands can be entered directly,
30549 but there may be some unexpected behaviour. For example, commands
30550 that query the user will behave as if the user replied yes, breakpoint
30551 command lists are not executed and some CLI commands, such as
30552 @code{if}, @code{when} and @code{define}, prompt for further input with
30553 @samp{>}, which is not valid MI output.
30555 This feature may be removed at some stage in the future and it is
30556 recommended that front ends use the @code{-interpreter-exec} command
30557 (@pxref{-interpreter-exec}).
30559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30560 @node GDB/MI Development and Front Ends
30561 @section @sc{gdb/mi} Development and Front Ends
30562 @cindex @sc{gdb/mi} development
30564 The application which takes the MI output and presents the state of the
30565 program being debugged to the user is called a @dfn{front end}.
30567 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30568 to the MI interface may break existing usage. This section describes how the
30569 protocol changes and how to request previous version of the protocol when it
30572 Some changes in MI need not break a carefully designed front end, and
30573 for these the MI version will remain unchanged. The following is a
30574 list of changes that may occur within one level, so front ends should
30575 parse MI output in a way that can handle them:
30579 New MI commands may be added.
30582 New fields may be added to the output of any MI command.
30585 The range of values for fields with specified values, e.g.,
30586 @code{in_scope} (@pxref{-var-update}) may be extended.
30588 @c The format of field's content e.g type prefix, may change so parse it
30589 @c at your own risk. Yes, in general?
30591 @c The order of fields may change? Shouldn't really matter but it might
30592 @c resolve inconsistencies.
30595 If the changes are likely to break front ends, the MI version level
30596 will be increased by one. The new versions of the MI protocol are not compatible
30597 with the old versions. Old versions of MI remain available, allowing front ends
30598 to keep using them until they are modified to use the latest MI version.
30600 Since @code{--interpreter=mi} always points to the latest MI version, it is
30601 recommended that front ends request a specific version of MI when launching
30602 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30603 interpreter with the MI version they expect.
30605 The following table gives a summary of the released versions of the MI
30606 interface: the version number, the version of GDB in which it first appeared
30607 and the breaking changes compared to the previous version.
30609 @multitable @columnfractions .1 .1 .8
30610 @headitem MI version @tab GDB version @tab Breaking changes
30627 The @code{-environment-pwd}, @code{-environment-directory} and
30628 @code{-environment-path} commands now returns values using the MI output
30629 syntax, rather than CLI output syntax.
30632 @code{-var-list-children}'s @code{children} result field is now a list, rather
30636 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30648 The output of information about multi-location breakpoints has changed in the
30649 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30650 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30651 The multiple locations are now placed in a @code{locations} field, whose value
30663 The syntax of the "script" field in breakpoint output has changed in the
30664 responses to the @code{-break-insert} and @code{-break-info} commands, as
30665 well as the @code{=breakpoint-created} and @code{=breakpoint-modified}
30666 events. The previous output was syntactically invalid. The new output is
30672 If your front end cannot yet migrate to a more recent version of the
30673 MI protocol, you can nevertheless selectively enable specific features
30674 available in those recent MI versions, using the following commands:
30678 @item -fix-multi-location-breakpoint-output
30679 Use the output for multi-location breakpoints which was introduced by
30680 MI 3, even when using MI versions below 3. This command has no
30681 effect when using MI version 3 or later.
30683 @item -fix-breakpoint-script-output
30684 Use the output for the breakpoint "script" field which was introduced by
30685 MI 4, even when using MI versions below 4. This command has no effect when
30686 using MI version 4 or later.
30690 The best way to avoid unexpected changes in MI that might break your front
30691 end is to make your project known to @value{GDBN} developers and
30692 follow development on @email{gdb@@sourceware.org} and
30693 @email{gdb-patches@@sourceware.org}.
30694 @cindex mailing lists
30696 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30697 @node GDB/MI Output Records
30698 @section @sc{gdb/mi} Output Records
30701 * GDB/MI Result Records::
30702 * GDB/MI Stream Records::
30703 * GDB/MI Async Records::
30704 * GDB/MI Breakpoint Information::
30705 * GDB/MI Frame Information::
30706 * GDB/MI Thread Information::
30707 * GDB/MI Ada Exception Information::
30710 @node GDB/MI Result Records
30711 @subsection @sc{gdb/mi} Result Records
30713 @cindex result records in @sc{gdb/mi}
30714 @cindex @sc{gdb/mi}, result records
30715 In addition to a number of out-of-band notifications, the response to a
30716 @sc{gdb/mi} command includes one of the following result indications:
30720 @item "^done" [ "," @var{results} ]
30721 The synchronous operation was successful, @code{@var{results}} are the return
30726 This result record is equivalent to @samp{^done}. Historically, it
30727 was output instead of @samp{^done} if the command has resumed the
30728 target. This behaviour is maintained for backward compatibility, but
30729 all frontends should treat @samp{^done} and @samp{^running}
30730 identically and rely on the @samp{*running} output record to determine
30731 which threads are resumed.
30735 @value{GDBN} has connected to a remote target.
30737 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30739 The operation failed. The @code{msg=@var{c-string}} variable contains
30740 the corresponding error message.
30742 If present, the @code{code=@var{c-string}} variable provides an error
30743 code on which consumers can rely on to detect the corresponding
30744 error condition. At present, only one error code is defined:
30747 @item "undefined-command"
30748 Indicates that the command causing the error does not exist.
30753 @value{GDBN} has terminated.
30757 @node GDB/MI Stream Records
30758 @subsection @sc{gdb/mi} Stream Records
30760 @cindex @sc{gdb/mi}, stream records
30761 @cindex stream records in @sc{gdb/mi}
30762 @value{GDBN} internally maintains a number of output streams: the console, the
30763 target, and the log. The output intended for each of these streams is
30764 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30766 Each stream record begins with a unique @dfn{prefix character} which
30767 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30768 Syntax}). In addition to the prefix, each stream record contains a
30769 @code{@var{string-output}}. This is either raw text (with an implicit new
30770 line) or a quoted C string (which does not contain an implicit newline).
30773 @item "~" @var{string-output}
30774 The console output stream contains text that should be displayed in the
30775 CLI console window. It contains the textual responses to CLI commands.
30777 @item "@@" @var{string-output}
30778 The target output stream contains any textual output from the running
30779 target. This is only present when GDB's event loop is truly
30780 asynchronous, which is currently only the case for remote targets.
30782 @item "&" @var{string-output}
30783 The log stream contains debugging messages being produced by @value{GDBN}'s
30787 @node GDB/MI Async Records
30788 @subsection @sc{gdb/mi} Async Records
30790 @cindex async records in @sc{gdb/mi}
30791 @cindex @sc{gdb/mi}, async records
30792 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30793 additional changes that have occurred. Those changes can either be a
30794 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30795 target activity (e.g., target stopped).
30797 The following is the list of possible async records:
30801 @item *running,thread-id="@var{thread}"
30802 The target is now running. The @var{thread} field can be the global
30803 thread ID of the thread that is now running, and it can be
30804 @samp{all} if all threads are running. The frontend should assume
30805 that no interaction with a running thread is possible after this
30806 notification is produced. The frontend should not assume that this
30807 notification is output only once for any command. @value{GDBN} may
30808 emit this notification several times, either for different threads,
30809 because it cannot resume all threads together, or even for a single
30810 thread, if the thread must be stepped though some code before letting
30813 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30814 The target has stopped. The @var{reason} field can have one of the
30818 @item breakpoint-hit
30819 A breakpoint was reached.
30820 @item watchpoint-trigger
30821 A watchpoint was triggered.
30822 @item read-watchpoint-trigger
30823 A read watchpoint was triggered.
30824 @item access-watchpoint-trigger
30825 An access watchpoint was triggered.
30826 @item function-finished
30827 An -exec-finish or similar CLI command was accomplished.
30828 @item location-reached
30829 An -exec-until or similar CLI command was accomplished.
30830 @item watchpoint-scope
30831 A watchpoint has gone out of scope.
30832 @item end-stepping-range
30833 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30834 similar CLI command was accomplished.
30835 @item exited-signalled
30836 The inferior exited because of a signal.
30838 The inferior exited.
30839 @item exited-normally
30840 The inferior exited normally.
30841 @item signal-received
30842 A signal was received by the inferior.
30844 The inferior has stopped due to a library being loaded or unloaded.
30845 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30846 set or when a @code{catch load} or @code{catch unload} catchpoint is
30847 in use (@pxref{Set Catchpoints}).
30849 The inferior has forked. This is reported when @code{catch fork}
30850 (@pxref{Set Catchpoints}) has been used.
30852 The inferior has vforked. This is reported in when @code{catch vfork}
30853 (@pxref{Set Catchpoints}) has been used.
30854 @item syscall-entry
30855 The inferior entered a system call. This is reported when @code{catch
30856 syscall} (@pxref{Set Catchpoints}) has been used.
30857 @item syscall-return
30858 The inferior returned from a system call. This is reported when
30859 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30861 The inferior called @code{exec}. This is reported when @code{catch exec}
30862 (@pxref{Set Catchpoints}) has been used.
30865 The @var{id} field identifies the global thread ID of the thread
30866 that directly caused the stop -- for example by hitting a breakpoint.
30867 Depending on whether all-stop
30868 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30869 stop all threads, or only the thread that directly triggered the stop.
30870 If all threads are stopped, the @var{stopped} field will have the
30871 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30872 field will be a list of thread identifiers. Presently, this list will
30873 always include a single thread, but frontend should be prepared to see
30874 several threads in the list. The @var{core} field reports the
30875 processor core on which the stop event has happened. This field may be absent
30876 if such information is not available.
30878 @item =thread-group-added,id="@var{id}"
30879 @itemx =thread-group-removed,id="@var{id}"
30880 A thread group was either added or removed. The @var{id} field
30881 contains the @value{GDBN} identifier of the thread group. When a thread
30882 group is added, it generally might not be associated with a running
30883 process. When a thread group is removed, its id becomes invalid and
30884 cannot be used in any way.
30886 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30887 A thread group became associated with a running program,
30888 either because the program was just started or the thread group
30889 was attached to a program. The @var{id} field contains the
30890 @value{GDBN} identifier of the thread group. The @var{pid} field
30891 contains process identifier, specific to the operating system.
30893 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30894 A thread group is no longer associated with a running program,
30895 either because the program has exited, or because it was detached
30896 from. The @var{id} field contains the @value{GDBN} identifier of the
30897 thread group. The @var{code} field is the exit code of the inferior; it exists
30898 only when the inferior exited with some code.
30900 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30901 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30902 A thread either was created, or has exited. The @var{id} field
30903 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30904 field identifies the thread group this thread belongs to.
30906 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30907 Informs that the selected thread or frame were changed. This notification
30908 is not emitted as result of the @code{-thread-select} or
30909 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30910 that is not documented to change the selected thread and frame actually
30911 changes them. In particular, invoking, directly or indirectly
30912 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30913 will generate this notification. Changing the thread or frame from another
30914 user interface (see @ref{Interpreters}) will also generate this notification.
30916 The @var{frame} field is only present if the newly selected thread is
30917 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30919 We suggest that in response to this notification, front ends
30920 highlight the selected thread and cause subsequent commands to apply to
30923 @item =library-loaded,...
30924 Reports that a new library file was loaded by the program. This
30925 notification has 5 fields---@var{id}, @var{target-name},
30926 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30927 opaque identifier of the library. For remote debugging case,
30928 @var{target-name} and @var{host-name} fields give the name of the
30929 library file on the target, and on the host respectively. For native
30930 debugging, both those fields have the same value. The
30931 @var{symbols-loaded} field is emitted only for backward compatibility
30932 and should not be relied on to convey any useful information. The
30933 @var{thread-group} field, if present, specifies the id of the thread
30934 group in whose context the library was loaded. If the field is
30935 absent, it means the library was loaded in the context of all present
30936 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30939 @item =library-unloaded,...
30940 Reports that a library was unloaded by the program. This notification
30941 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30942 the same meaning as for the @code{=library-loaded} notification.
30943 The @var{thread-group} field, if present, specifies the id of the
30944 thread group in whose context the library was unloaded. If the field is
30945 absent, it means the library was unloaded in the context of all present
30948 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30949 @itemx =traceframe-changed,end
30950 Reports that the trace frame was changed and its new number is
30951 @var{tfnum}. The number of the tracepoint associated with this trace
30952 frame is @var{tpnum}.
30954 @item =tsv-created,name=@var{name},initial=@var{initial}
30955 Reports that the new trace state variable @var{name} is created with
30956 initial value @var{initial}.
30958 @item =tsv-deleted,name=@var{name}
30959 @itemx =tsv-deleted
30960 Reports that the trace state variable @var{name} is deleted or all
30961 trace state variables are deleted.
30963 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30964 Reports that the trace state variable @var{name} is modified with
30965 the initial value @var{initial}. The current value @var{current} of
30966 trace state variable is optional and is reported if the current
30967 value of trace state variable is known.
30969 @item =breakpoint-created,bkpt=@{...@}
30970 @itemx =breakpoint-modified,bkpt=@{...@}
30971 @itemx =breakpoint-deleted,id=@var{number}
30972 Reports that a breakpoint was created, modified, or deleted,
30973 respectively. Only user-visible breakpoints are reported to the MI
30976 The @var{bkpt} argument is of the same form as returned by the various
30977 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30978 @var{number} is the ordinal number of the breakpoint.
30980 Note that if a breakpoint is emitted in the result record of a
30981 command, then it will not also be emitted in an async record.
30983 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30984 @itemx =record-stopped,thread-group="@var{id}"
30985 Execution log recording was either started or stopped on an
30986 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30987 group corresponding to the affected inferior.
30989 The @var{method} field indicates the method used to record execution. If the
30990 method in use supports multiple recording formats, @var{format} will be present
30991 and contain the currently used format. @xref{Process Record and Replay},
30992 for existing method and format values.
30994 @item =cmd-param-changed,param=@var{param},value=@var{value}
30995 Reports that a parameter of the command @code{set @var{param}} is
30996 changed to @var{value}. In the multi-word @code{set} command,
30997 the @var{param} is the whole parameter list to @code{set} command.
30998 For example, In command @code{set check type on}, @var{param}
30999 is @code{check type} and @var{value} is @code{on}.
31001 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
31002 Reports that bytes from @var{addr} to @var{data} + @var{len} were
31003 written in an inferior. The @var{id} is the identifier of the
31004 thread group corresponding to the affected inferior. The optional
31005 @code{type="code"} part is reported if the memory written to holds
31009 @node GDB/MI Breakpoint Information
31010 @subsection @sc{gdb/mi} Breakpoint Information
31012 When @value{GDBN} reports information about a breakpoint, a
31013 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
31018 The breakpoint number.
31021 The type of the breakpoint. For ordinary breakpoints this will be
31022 @samp{breakpoint}, but many values are possible.
31025 If the type of the breakpoint is @samp{catchpoint}, then this
31026 indicates the exact type of catchpoint.
31029 This is the breakpoint disposition---either @samp{del}, meaning that
31030 the breakpoint will be deleted at the next stop, or @samp{keep},
31031 meaning that the breakpoint will not be deleted.
31034 This indicates whether the breakpoint is enabled, in which case the
31035 value is @samp{y}, or disabled, in which case the value is @samp{n}.
31036 Note that this is not the same as the field @code{enable}.
31039 The address of the breakpoint. This may be a hexidecimal number,
31040 giving the address; or the string @samp{<PENDING>}, for a pending
31041 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
31042 multiple locations. This field will not be present if no address can
31043 be determined. For example, a watchpoint does not have an address.
31046 Optional field containing any flags related to the address. These flags are
31047 architecture-dependent; see @ref{Architectures} for their meaning for a
31051 If known, the function in which the breakpoint appears.
31052 If not known, this field is not present.
31055 The name of the source file which contains this function, if known.
31056 If not known, this field is not present.
31059 The full file name of the source file which contains this function, if
31060 known. If not known, this field is not present.
31063 The line number at which this breakpoint appears, if known.
31064 If not known, this field is not present.
31067 If the source file is not known, this field may be provided. If
31068 provided, this holds the address of the breakpoint, possibly followed
31072 If this breakpoint is pending, this field is present and holds the
31073 text used to set the breakpoint, as entered by the user.
31076 Where this breakpoint's condition is evaluated, either @samp{host} or
31080 If this is a thread-specific breakpoint, then this identifies the
31081 thread in which the breakpoint can trigger.
31084 If this breakpoint is restricted to a particular Ada task, then this
31085 field will hold the task identifier.
31088 If the breakpoint is conditional, this is the condition expression.
31091 The ignore count of the breakpoint.
31094 The enable count of the breakpoint.
31096 @item traceframe-usage
31099 @item static-tracepoint-marker-string-id
31100 For a static tracepoint, the name of the static tracepoint marker.
31103 For a masked watchpoint, this is the mask.
31106 A tracepoint's pass count.
31108 @item original-location
31109 The location of the breakpoint as originally specified by the user.
31110 This field is optional.
31113 The number of times the breakpoint has been hit.
31116 This field is only given for tracepoints. This is either @samp{y},
31117 meaning that the tracepoint is installed, or @samp{n}, meaning that it
31121 Some extra data, the exact contents of which are type-dependent.
31124 This field is present if the breakpoint has multiple locations. It is also
31125 exceptionally present if the breakpoint is enabled and has a single, disabled
31128 The value is a list of locations. The format of a location is described below.
31132 A location in a multi-location breakpoint is represented as a tuple with the
31138 The location number as a dotted pair, like @samp{1.2}. The first digit is the
31139 number of the parent breakpoint. The second digit is the number of the
31140 location within that breakpoint.
31143 There are three possible values, with the following meanings:
31146 The location is enabled.
31148 The location is disabled by the user.
31150 The location is disabled because the breakpoint condition is invalid
31155 The address of this location as an hexidecimal number.
31158 Optional field containing any flags related to the address. These flags are
31159 architecture-dependent; see @ref{Architectures} for their meaning for a
31163 If known, the function in which the location appears.
31164 If not known, this field is not present.
31167 The name of the source file which contains this location, if known.
31168 If not known, this field is not present.
31171 The full file name of the source file which contains this location, if
31172 known. If not known, this field is not present.
31175 The line number at which this location appears, if known.
31176 If not known, this field is not present.
31178 @item thread-groups
31179 The thread groups this location is in.
31183 For example, here is what the output of @code{-break-insert}
31184 (@pxref{GDB/MI Breakpoint Commands}) might be:
31187 -> -break-insert main
31188 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31189 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31190 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31195 @node GDB/MI Frame Information
31196 @subsection @sc{gdb/mi} Frame Information
31198 Response from many MI commands includes an information about stack
31199 frame. This information is a tuple that may have the following
31204 The level of the stack frame. The innermost frame has the level of
31205 zero. This field is always present.
31208 The name of the function corresponding to the frame. This field may
31209 be absent if @value{GDBN} is unable to determine the function name.
31212 The code address for the frame. This field is always present.
31215 Optional field containing any flags related to the address. These flags are
31216 architecture-dependent; see @ref{Architectures} for their meaning for a
31220 The name of the source files that correspond to the frame's code
31221 address. This field may be absent.
31224 The source line corresponding to the frames' code address. This field
31228 The name of the binary file (either executable or shared library) the
31229 corresponds to the frame's code address. This field may be absent.
31233 @node GDB/MI Thread Information
31234 @subsection @sc{gdb/mi} Thread Information
31236 Whenever @value{GDBN} has to report an information about a thread, it
31237 uses a tuple with the following fields. The fields are always present unless
31242 The global numeric id assigned to the thread by @value{GDBN}.
31245 The target-specific string identifying the thread.
31248 Additional information about the thread provided by the target.
31249 It is supposed to be human-readable and not interpreted by the
31250 frontend. This field is optional.
31253 The name of the thread. If the user specified a name using the
31254 @code{thread name} command, then this name is given. Otherwise, if
31255 @value{GDBN} can extract the thread name from the target, then that
31256 name is given. If @value{GDBN} cannot find the thread name, then this
31260 The execution state of the thread, either @samp{stopped} or @samp{running},
31261 depending on whether the thread is presently running.
31264 The stack frame currently executing in the thread. This field is only present
31265 if the thread is stopped. Its format is documented in
31266 @ref{GDB/MI Frame Information}.
31269 The value of this field is an integer number of the processor core the
31270 thread was last seen on. This field is optional.
31273 @node GDB/MI Ada Exception Information
31274 @subsection @sc{gdb/mi} Ada Exception Information
31276 Whenever a @code{*stopped} record is emitted because the program
31277 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
31278 @value{GDBN} provides the name of the exception that was raised via
31279 the @code{exception-name} field. Also, for exceptions that were raised
31280 with an exception message, @value{GDBN} provides that message via
31281 the @code{exception-message} field.
31283 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31284 @node GDB/MI Simple Examples
31285 @section Simple Examples of @sc{gdb/mi} Interaction
31286 @cindex @sc{gdb/mi}, simple examples
31288 This subsection presents several simple examples of interaction using
31289 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
31290 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
31291 the output received from @sc{gdb/mi}.
31293 Note the line breaks shown in the examples are here only for
31294 readability, they don't appear in the real output.
31296 @subheading Setting a Breakpoint
31298 Setting a breakpoint generates synchronous output which contains detailed
31299 information of the breakpoint.
31302 -> -break-insert main
31303 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31304 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31305 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31310 @subheading Program Execution
31312 Program execution generates asynchronous records and MI gives the
31313 reason that execution stopped.
31319 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31320 frame=@{addr="0x08048564",func="main",
31321 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
31322 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
31323 arch="i386:x86_64"@}
31328 <- *stopped,reason="exited-normally"
31332 @subheading Quitting @value{GDBN}
31334 Quitting @value{GDBN} just prints the result class @samp{^exit}.
31342 Please note that @samp{^exit} is printed immediately, but it might
31343 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
31344 performs necessary cleanups, including killing programs being debugged
31345 or disconnecting from debug hardware, so the frontend should wait till
31346 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
31347 fails to exit in reasonable time.
31349 @subheading A Bad Command
31351 Here's what happens if you pass a non-existent command:
31355 <- ^error,msg="Undefined MI command: rubbish"
31360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31361 @node GDB/MI Command Description Format
31362 @section @sc{gdb/mi} Command Description Format
31364 The remaining sections describe blocks of commands. Each block of
31365 commands is laid out in a fashion similar to this section.
31367 @subheading Motivation
31369 The motivation for this collection of commands.
31371 @subheading Introduction
31373 A brief introduction to this collection of commands as a whole.
31375 @subheading Commands
31377 For each command in the block, the following is described:
31379 @subsubheading Synopsis
31382 -command @var{args}@dots{}
31385 @subsubheading Result
31387 @subsubheading @value{GDBN} Command
31389 The corresponding @value{GDBN} CLI command(s), if any.
31391 @subsubheading Example
31393 Example(s) formatted for readability. Some of the described commands have
31394 not been implemented yet and these are labeled N.A.@: (not available).
31397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31398 @node GDB/MI Breakpoint Commands
31399 @section @sc{gdb/mi} Breakpoint Commands
31401 @cindex breakpoint commands for @sc{gdb/mi}
31402 @cindex @sc{gdb/mi}, breakpoint commands
31403 This section documents @sc{gdb/mi} commands for manipulating
31406 @subheading The @code{-break-after} Command
31407 @findex -break-after
31409 @subsubheading Synopsis
31412 -break-after @var{number} @var{count}
31415 The breakpoint number @var{number} is not in effect until it has been
31416 hit @var{count} times. To see how this is reflected in the output of
31417 the @samp{-break-list} command, see the description of the
31418 @samp{-break-list} command below.
31420 @subsubheading @value{GDBN} Command
31422 The corresponding @value{GDBN} command is @samp{ignore}.
31424 @subsubheading Example
31429 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31430 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31431 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31439 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31440 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31441 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31442 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31443 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31444 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31445 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31446 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31447 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31448 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
31453 @subheading The @code{-break-catch} Command
31454 @findex -break-catch
31457 @subheading The @code{-break-commands} Command
31458 @findex -break-commands
31460 @subsubheading Synopsis
31463 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
31466 Specifies the CLI commands that should be executed when breakpoint
31467 @var{number} is hit. The parameters @var{command1} to @var{commandN}
31468 are the commands. If no command is specified, any previously-set
31469 commands are cleared. @xref{Break Commands}. Typical use of this
31470 functionality is tracing a program, that is, printing of values of
31471 some variables whenever breakpoint is hit and then continuing.
31473 @subsubheading @value{GDBN} Command
31475 The corresponding @value{GDBN} command is @samp{commands}.
31477 @subsubheading Example
31482 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31483 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31484 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31487 -break-commands 1 "print v" "continue"
31492 @subheading The @code{-break-condition} Command
31493 @findex -break-condition
31495 @subsubheading Synopsis
31498 -break-condition [ --force ] @var{number} [ @var{expr} ]
31501 Breakpoint @var{number} will stop the program only if the condition in
31502 @var{expr} is true. The condition becomes part of the
31503 @samp{-break-list} output (see the description of the @samp{-break-list}
31504 command below). If the @samp{--force} flag is passed, the condition
31505 is forcibly defined even when it is invalid for all locations of
31506 breakpoint @var{number}. If the @var{expr} argument is omitted,
31507 breakpoint @var{number} becomes unconditional.
31509 @subsubheading @value{GDBN} Command
31511 The corresponding @value{GDBN} command is @samp{condition}.
31513 @subsubheading Example
31517 -break-condition 1 1
31521 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31522 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31523 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31524 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31525 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31526 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31527 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31528 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31529 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31530 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31534 @subheading The @code{-break-delete} Command
31535 @findex -break-delete
31537 @subsubheading Synopsis
31540 -break-delete ( @var{breakpoint} )+
31543 Delete the breakpoint(s) whose number(s) are specified in the argument
31544 list. This is obviously reflected in the breakpoint list.
31546 @subsubheading @value{GDBN} Command
31548 The corresponding @value{GDBN} command is @samp{delete}.
31550 @subsubheading Example
31558 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31559 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31560 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31561 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31562 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31563 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31564 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31569 @subheading The @code{-break-disable} Command
31570 @findex -break-disable
31572 @subsubheading Synopsis
31575 -break-disable ( @var{breakpoint} )+
31578 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31579 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31581 @subsubheading @value{GDBN} Command
31583 The corresponding @value{GDBN} command is @samp{disable}.
31585 @subsubheading Example
31593 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31594 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31595 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31596 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31597 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31598 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31599 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31600 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31601 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31602 line="5",thread-groups=["i1"],times="0"@}]@}
31606 @subheading The @code{-break-enable} Command
31607 @findex -break-enable
31609 @subsubheading Synopsis
31612 -break-enable ( @var{breakpoint} )+
31615 Enable (previously disabled) @var{breakpoint}(s).
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{enable}.
31621 @subsubheading Example
31629 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31630 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31631 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31632 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31633 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31634 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31635 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31636 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31637 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31638 line="5",thread-groups=["i1"],times="0"@}]@}
31642 @subheading The @code{-break-info} Command
31643 @findex -break-info
31645 @subsubheading Synopsis
31648 -break-info @var{breakpoint}
31652 Get information about a single breakpoint.
31654 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31655 Information}, for details on the format of each breakpoint in the
31658 @subsubheading @value{GDBN} Command
31660 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31662 @subsubheading Example
31665 @subheading The @code{-break-insert} Command
31666 @findex -break-insert
31667 @anchor{-break-insert}
31669 @subsubheading Synopsis
31672 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31673 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31674 [ -p @var{thread-id} ] [ @var{locspec} ]
31678 If specified, @var{locspec}, can be one of:
31681 @item linespec location
31682 A linespec location. @xref{Linespec Locations}.
31684 @item explicit location
31685 An explicit location. @sc{gdb/mi} explicit locations are
31686 analogous to the CLI's explicit locations using the option names
31687 listed below. @xref{Explicit Locations}.
31690 @item --source @var{filename}
31691 The source file name of the location. This option requires the use
31692 of either @samp{--function} or @samp{--line}.
31694 @item --function @var{function}
31695 The name of a function or method.
31697 @item --label @var{label}
31698 The name of a label.
31700 @item --line @var{lineoffset}
31701 An absolute or relative line offset from the start of the location.
31704 @item address location
31705 An address location, *@var{address}. @xref{Address Locations}.
31709 The possible optional parameters of this command are:
31713 Insert a temporary breakpoint.
31715 Insert a hardware breakpoint.
31717 If @var{locspec} cannot be resolved (for example if it
31718 refers to unknown files or functions), create a pending
31719 breakpoint. Without this flag, @value{GDBN} will report
31720 an error, and won't create a breakpoint, if @var{locspec}
31723 Create a disabled breakpoint.
31725 Create a tracepoint. @xref{Tracepoints}. When this parameter
31726 is used together with @samp{-h}, a fast tracepoint is created.
31727 @item -c @var{condition}
31728 Make the breakpoint conditional on @var{condition}.
31729 @item --force-condition
31730 Forcibly define the breakpoint even if the condition is invalid at
31731 all of the breakpoint locations.
31732 @item -i @var{ignore-count}
31733 Initialize the @var{ignore-count}.
31734 @item -p @var{thread-id}
31735 Restrict the breakpoint to the thread with the specified global
31738 This option makes @value{GDBN} interpret a function name specified as
31739 a complete fully-qualified name.
31742 @subsubheading Result
31744 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31745 resulting breakpoint.
31747 Note: this format is open to change.
31748 @c An out-of-band breakpoint instead of part of the result?
31750 @subsubheading @value{GDBN} Command
31752 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31753 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31755 @subsubheading Example
31760 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31761 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31764 -break-insert -t foo
31765 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31766 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31770 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31771 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31772 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31773 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31774 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31775 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31776 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31777 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31778 addr="0x0001072c", func="main",file="recursive2.c",
31779 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31781 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31782 addr="0x00010774",func="foo",file="recursive2.c",
31783 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31788 @subheading The @code{-dprintf-insert} Command
31789 @findex -dprintf-insert
31791 @subsubheading Synopsis
31794 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31795 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31796 [ -p @var{thread-id} ] [ @var{locspec} ] [ @var{format} ]
31801 If supplied, @var{locspec} and @code{--qualified} may be specified
31802 the same way as for the @code{-break-insert} command.
31803 @xref{-break-insert}.
31805 The possible optional parameters of this command are:
31809 Insert a temporary breakpoint.
31811 If @var{locspec} cannot be parsed (for example, if it
31812 refers to unknown files or functions), create a pending
31813 breakpoint. Without this flag, @value{GDBN} will report
31814 an error, and won't create a breakpoint, if @var{locspec}
31817 Create a disabled breakpoint.
31818 @item -c @var{condition}
31819 Make the breakpoint conditional on @var{condition}.
31820 @item --force-condition
31821 Forcibly define the breakpoint even if the condition is invalid at
31822 all of the breakpoint locations.
31823 @item -i @var{ignore-count}
31824 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31825 to @var{ignore-count}.
31826 @item -p @var{thread-id}
31827 Restrict the breakpoint to the thread with the specified global
31831 @subsubheading Result
31833 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31834 resulting breakpoint.
31836 @c An out-of-band breakpoint instead of part of the result?
31838 @subsubheading @value{GDBN} Command
31840 The corresponding @value{GDBN} command is @samp{dprintf}.
31842 @subsubheading Example
31846 4-dprintf-insert foo "At foo entry\n"
31847 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31848 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31849 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31850 times="0",script=["printf \"At foo entry\\n\"","continue"],
31851 original-location="foo"@}
31853 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31854 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31855 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31856 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31857 times="0",script=["printf \"arg=%d, g=%d\\n\", arg, g","continue"],
31858 original-location="mi-dprintf.c:26"@}
31862 @subheading The @code{-break-list} Command
31863 @findex -break-list
31865 @subsubheading Synopsis
31871 Displays the list of inserted breakpoints, showing the following fields:
31875 number of the breakpoint
31877 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31879 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31882 is the breakpoint enabled or no: @samp{y} or @samp{n}
31884 memory location at which the breakpoint is set
31886 logical location of the breakpoint, expressed by function name, file
31888 @item Thread-groups
31889 list of thread groups to which this breakpoint applies
31891 number of times the breakpoint has been hit
31894 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31895 @code{body} field is an empty list.
31897 @subsubheading @value{GDBN} Command
31899 The corresponding @value{GDBN} command is @samp{info break}.
31901 @subsubheading Example
31906 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31913 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31914 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31916 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31917 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31918 line="13",thread-groups=["i1"],times="0"@}]@}
31922 Here's an example of the result when there are no breakpoints:
31927 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31928 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31929 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31930 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31931 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31932 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31933 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31938 @subheading The @code{-break-passcount} Command
31939 @findex -break-passcount
31941 @subsubheading Synopsis
31944 -break-passcount @var{tracepoint-number} @var{passcount}
31947 Set the passcount for tracepoint @var{tracepoint-number} to
31948 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31949 is not a tracepoint, error is emitted. This corresponds to CLI
31950 command @samp{passcount}.
31952 @subheading The @code{-break-watch} Command
31953 @findex -break-watch
31955 @subsubheading Synopsis
31958 -break-watch [ -a | -r ]
31961 Create a watchpoint. With the @samp{-a} option it will create an
31962 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31963 read from or on a write to the memory location. With the @samp{-r}
31964 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31965 trigger only when the memory location is accessed for reading. Without
31966 either of the options, the watchpoint created is a regular watchpoint,
31967 i.e., it will trigger when the memory location is accessed for writing.
31968 @xref{Set Watchpoints, , Setting Watchpoints}.
31970 Note that @samp{-break-list} will report a single list of watchpoints and
31971 breakpoints inserted.
31973 @subsubheading @value{GDBN} Command
31975 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31978 @subsubheading Example
31980 Setting a watchpoint on a variable in the @code{main} function:
31985 ^done,wpt=@{number="2",exp="x"@}
31990 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31991 value=@{old="-268439212",new="55"@},
31992 frame=@{func="main",args=[],file="recursive2.c",
31993 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31997 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31998 the program execution twice: first for the variable changing value, then
31999 for the watchpoint going out of scope.
32004 ^done,wpt=@{number="5",exp="C"@}
32009 *stopped,reason="watchpoint-trigger",
32010 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
32011 frame=@{func="callee4",args=[],
32012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32013 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
32014 arch="i386:x86_64"@}
32019 *stopped,reason="watchpoint-scope",wpnum="5",
32020 frame=@{func="callee3",args=[@{name="strarg",
32021 value="0x11940 \"A string argument.\""@}],
32022 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32023 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32024 arch="i386:x86_64"@}
32028 Listing breakpoints and watchpoints, at different points in the program
32029 execution. Note that once the watchpoint goes out of scope, it is
32035 ^done,wpt=@{number="2",exp="C"@}
32038 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32039 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32040 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32041 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32042 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32043 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32044 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32045 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32046 addr="0x00010734",func="callee4",
32047 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32048 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
32050 bkpt=@{number="2",type="watchpoint",disp="keep",
32051 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
32056 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
32057 value=@{old="-276895068",new="3"@},
32058 frame=@{func="callee4",args=[],
32059 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32060 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
32061 arch="i386:x86_64"@}
32064 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32065 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32066 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32067 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32068 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32069 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32070 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32071 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32072 addr="0x00010734",func="callee4",
32073 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32074 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
32076 bkpt=@{number="2",type="watchpoint",disp="keep",
32077 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
32081 ^done,reason="watchpoint-scope",wpnum="2",
32082 frame=@{func="callee3",args=[@{name="strarg",
32083 value="0x11940 \"A string argument.\""@}],
32084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32085 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32086 arch="i386:x86_64"@}
32089 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32096 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32097 addr="0x00010734",func="callee4",
32098 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32099 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32100 thread-groups=["i1"],times="1"@}]@}
32105 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32106 @node GDB/MI Catchpoint Commands
32107 @section @sc{gdb/mi} Catchpoint Commands
32109 This section documents @sc{gdb/mi} commands for manipulating
32113 * Shared Library GDB/MI Catchpoint Commands::
32114 * Ada Exception GDB/MI Catchpoint Commands::
32115 * C++ Exception GDB/MI Catchpoint Commands::
32118 @node Shared Library GDB/MI Catchpoint Commands
32119 @subsection Shared Library @sc{gdb/mi} Catchpoints
32121 @subheading The @code{-catch-load} Command
32122 @findex -catch-load
32124 @subsubheading Synopsis
32127 -catch-load [ -t ] [ -d ] @var{regexp}
32130 Add a catchpoint for library load events. If the @samp{-t} option is used,
32131 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32132 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
32133 in a disabled state. The @samp{regexp} argument is a regular
32134 expression used to match the name of the loaded library.
32137 @subsubheading @value{GDBN} Command
32139 The corresponding @value{GDBN} command is @samp{catch load}.
32141 @subsubheading Example
32144 -catch-load -t foo.so
32145 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
32146 what="load of library matching foo.so",catch-type="load",times="0"@}
32151 @subheading The @code{-catch-unload} Command
32152 @findex -catch-unload
32154 @subsubheading Synopsis
32157 -catch-unload [ -t ] [ -d ] @var{regexp}
32160 Add a catchpoint for library unload events. If the @samp{-t} option is
32161 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32162 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
32163 created in a disabled state. The @samp{regexp} argument is a regular
32164 expression used to match the name of the unloaded library.
32166 @subsubheading @value{GDBN} Command
32168 The corresponding @value{GDBN} command is @samp{catch unload}.
32170 @subsubheading Example
32173 -catch-unload -d bar.so
32174 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
32175 what="load of library matching bar.so",catch-type="unload",times="0"@}
32179 @node Ada Exception GDB/MI Catchpoint Commands
32180 @subsection Ada Exception @sc{gdb/mi} Catchpoints
32182 The following @sc{gdb/mi} commands can be used to create catchpoints
32183 that stop the execution when Ada exceptions are being raised.
32185 @subheading The @code{-catch-assert} Command
32186 @findex -catch-assert
32188 @subsubheading Synopsis
32191 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
32194 Add a catchpoint for failed Ada assertions.
32196 The possible optional parameters for this command are:
32199 @item -c @var{condition}
32200 Make the catchpoint conditional on @var{condition}.
32202 Create a disabled catchpoint.
32204 Create a temporary catchpoint.
32207 @subsubheading @value{GDBN} Command
32209 The corresponding @value{GDBN} command is @samp{catch assert}.
32211 @subsubheading Example
32215 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
32216 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
32217 thread-groups=["i1"],times="0",
32218 original-location="__gnat_debug_raise_assert_failure"@}
32222 @subheading The @code{-catch-exception} Command
32223 @findex -catch-exception
32225 @subsubheading Synopsis
32228 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32232 Add a catchpoint stopping when Ada exceptions are raised.
32233 By default, the command stops the program when any Ada exception
32234 gets raised. But it is also possible, by using some of the
32235 optional parameters described below, to create more selective
32238 The possible optional parameters for this command are:
32241 @item -c @var{condition}
32242 Make the catchpoint conditional on @var{condition}.
32244 Create a disabled catchpoint.
32245 @item -e @var{exception-name}
32246 Only stop when @var{exception-name} is raised. This option cannot
32247 be used combined with @samp{-u}.
32249 Create a temporary catchpoint.
32251 Stop only when an unhandled exception gets raised. This option
32252 cannot be used combined with @samp{-e}.
32255 @subsubheading @value{GDBN} Command
32257 The corresponding @value{GDBN} commands are @samp{catch exception}
32258 and @samp{catch exception unhandled}.
32260 @subsubheading Example
32263 -catch-exception -e Program_Error
32264 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32265 enabled="y",addr="0x0000000000404874",
32266 what="`Program_Error' Ada exception", thread-groups=["i1"],
32267 times="0",original-location="__gnat_debug_raise_exception"@}
32271 @subheading The @code{-catch-handlers} Command
32272 @findex -catch-handlers
32274 @subsubheading Synopsis
32277 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32281 Add a catchpoint stopping when Ada exceptions are handled.
32282 By default, the command stops the program when any Ada exception
32283 gets handled. But it is also possible, by using some of the
32284 optional parameters described below, to create more selective
32287 The possible optional parameters for this command are:
32290 @item -c @var{condition}
32291 Make the catchpoint conditional on @var{condition}.
32293 Create a disabled catchpoint.
32294 @item -e @var{exception-name}
32295 Only stop when @var{exception-name} is handled.
32297 Create a temporary catchpoint.
32300 @subsubheading @value{GDBN} Command
32302 The corresponding @value{GDBN} command is @samp{catch handlers}.
32304 @subsubheading Example
32307 -catch-handlers -e Constraint_Error
32308 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32309 enabled="y",addr="0x0000000000402f68",
32310 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
32311 times="0",original-location="__gnat_begin_handler"@}
32315 @node C++ Exception GDB/MI Catchpoint Commands
32316 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
32318 The following @sc{gdb/mi} commands can be used to create catchpoints
32319 that stop the execution when C@t{++} exceptions are being throw, rethrown,
32322 @subheading The @code{-catch-throw} Command
32323 @findex -catch-throw
32325 @subsubheading Synopsis
32328 -catch-throw [ -t ] [ -r @var{regexp}]
32331 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
32332 given, then only exceptions whose type matches the regular expression
32335 If @samp{-t} is given, then the catchpoint is enabled only for one
32336 stop, the catchpoint is automatically deleted after stopping once for
32339 @subsubheading @value{GDBN} Command
32341 The corresponding @value{GDBN} commands are @samp{catch throw}
32342 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
32344 @subsubheading Example
32347 -catch-throw -r exception_type
32348 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32349 what="exception throw",catch-type="throw",
32350 thread-groups=["i1"],
32351 regexp="exception_type",times="0"@}
32357 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
32358 in __cxa_throw () from /lib64/libstdc++.so.6\n"
32359 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32360 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
32361 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32362 thread-id="1",stopped-threads="all",core="6"
32366 @subheading The @code{-catch-rethrow} Command
32367 @findex -catch-rethrow
32369 @subsubheading Synopsis
32372 -catch-rethrow [ -t ] [ -r @var{regexp}]
32375 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
32376 then only exceptions whose type matches the regular expression will be
32379 If @samp{-t} is given, then the catchpoint is enabled only for one
32380 stop, the catchpoint is automatically deleted after the first event is
32383 @subsubheading @value{GDBN} Command
32385 The corresponding @value{GDBN} commands are @samp{catch rethrow}
32386 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
32388 @subsubheading Example
32391 -catch-rethrow -r exception_type
32392 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32393 what="exception rethrow",catch-type="rethrow",
32394 thread-groups=["i1"],
32395 regexp="exception_type",times="0"@}
32401 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
32402 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
32403 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32404 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
32405 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32406 thread-id="1",stopped-threads="all",core="6"
32410 @subheading The @code{-catch-catch} Command
32411 @findex -catch-catch
32413 @subsubheading Synopsis
32416 -catch-catch [ -t ] [ -r @var{regexp}]
32419 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
32420 is given, then only exceptions whose type matches the regular
32421 expression will be caught.
32423 If @samp{-t} is given, then the catchpoint is enabled only for one
32424 stop, the catchpoint is automatically deleted after the first event is
32427 @subsubheading @value{GDBN} Command
32429 The corresponding @value{GDBN} commands are @samp{catch catch}
32430 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
32432 @subsubheading Example
32435 -catch-catch -r exception_type
32436 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32437 what="exception catch",catch-type="catch",
32438 thread-groups=["i1"],
32439 regexp="exception_type",times="0"@}
32445 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
32446 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
32447 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32448 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
32449 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32450 thread-id="1",stopped-threads="all",core="6"
32454 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32455 @node GDB/MI Program Context
32456 @section @sc{gdb/mi} Program Context
32458 @subheading The @code{-exec-arguments} Command
32459 @findex -exec-arguments
32462 @subsubheading Synopsis
32465 -exec-arguments @var{args}
32468 Set the inferior program arguments, to be used in the next
32471 @subsubheading @value{GDBN} Command
32473 The corresponding @value{GDBN} command is @samp{set args}.
32475 @subsubheading Example
32479 -exec-arguments -v word
32486 @subheading The @code{-exec-show-arguments} Command
32487 @findex -exec-show-arguments
32489 @subsubheading Synopsis
32492 -exec-show-arguments
32495 Print the arguments of the program.
32497 @subsubheading @value{GDBN} Command
32499 The corresponding @value{GDBN} command is @samp{show args}.
32501 @subsubheading Example
32506 @subheading The @code{-environment-cd} Command
32507 @findex -environment-cd
32509 @subsubheading Synopsis
32512 -environment-cd @var{pathdir}
32515 Set @value{GDBN}'s working directory.
32517 @subsubheading @value{GDBN} Command
32519 The corresponding @value{GDBN} command is @samp{cd}.
32521 @subsubheading Example
32525 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32531 @subheading The @code{-environment-directory} Command
32532 @findex -environment-directory
32534 @subsubheading Synopsis
32537 -environment-directory [ -r ] [ @var{pathdir} ]+
32540 Add directories @var{pathdir} to beginning of search path for source files.
32541 If the @samp{-r} option is used, the search path is reset to the default
32542 search path. If directories @var{pathdir} are supplied in addition to the
32543 @samp{-r} option, the search path is first reset and then addition
32545 Multiple directories may be specified, separated by blanks. Specifying
32546 multiple directories in a single command
32547 results in the directories added to the beginning of the
32548 search path in the same order they were presented in the command.
32549 If blanks are needed as
32550 part of a directory name, double-quotes should be used around
32551 the name. In the command output, the path will show up separated
32552 by the system directory-separator character. The directory-separator
32553 character must not be used
32554 in any directory name.
32555 If no directories are specified, the current search path is displayed.
32557 @subsubheading @value{GDBN} Command
32559 The corresponding @value{GDBN} command is @samp{dir}.
32561 @subsubheading Example
32565 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32566 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32568 -environment-directory ""
32569 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32571 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32572 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32574 -environment-directory -r
32575 ^done,source-path="$cdir:$cwd"
32580 @subheading The @code{-environment-path} Command
32581 @findex -environment-path
32583 @subsubheading Synopsis
32586 -environment-path [ -r ] [ @var{pathdir} ]+
32589 Add directories @var{pathdir} to beginning of search path for object files.
32590 If the @samp{-r} option is used, the search path is reset to the original
32591 search path that existed at gdb start-up. If directories @var{pathdir} are
32592 supplied in addition to the
32593 @samp{-r} option, the search path is first reset and then addition
32595 Multiple directories may be specified, separated by blanks. Specifying
32596 multiple directories in a single command
32597 results in the directories added to the beginning of the
32598 search path in the same order they were presented in the command.
32599 If blanks are needed as
32600 part of a directory name, double-quotes should be used around
32601 the name. In the command output, the path will show up separated
32602 by the system directory-separator character. The directory-separator
32603 character must not be used
32604 in any directory name.
32605 If no directories are specified, the current path is displayed.
32608 @subsubheading @value{GDBN} Command
32610 The corresponding @value{GDBN} command is @samp{path}.
32612 @subsubheading Example
32617 ^done,path="/usr/bin"
32619 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32620 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32622 -environment-path -r /usr/local/bin
32623 ^done,path="/usr/local/bin:/usr/bin"
32628 @subheading The @code{-environment-pwd} Command
32629 @findex -environment-pwd
32631 @subsubheading Synopsis
32637 Show the current working directory.
32639 @subsubheading @value{GDBN} Command
32641 The corresponding @value{GDBN} command is @samp{pwd}.
32643 @subsubheading Example
32648 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32653 @node GDB/MI Thread Commands
32654 @section @sc{gdb/mi} Thread Commands
32657 @subheading The @code{-thread-info} Command
32658 @findex -thread-info
32660 @subsubheading Synopsis
32663 -thread-info [ @var{thread-id} ]
32666 Reports information about either a specific thread, if the
32667 @var{thread-id} parameter is present, or about all threads.
32668 @var{thread-id} is the thread's global thread ID. When printing
32669 information about all threads, also reports the global ID of the
32672 @subsubheading @value{GDBN} Command
32674 The @samp{info thread} command prints the same information
32677 @subsubheading Result
32679 The result contains the following attributes:
32683 A list of threads. The format of the elements of the list is described in
32684 @ref{GDB/MI Thread Information}.
32686 @item current-thread-id
32687 The global id of the currently selected thread. This field is omitted if there
32688 is no selected thread (for example, when the selected inferior is not running,
32689 and therefore has no threads) or if a @var{thread-id} argument was passed to
32694 @subsubheading Example
32699 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32700 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32701 args=[]@},state="running"@},
32702 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32703 frame=@{level="0",addr="0x0804891f",func="foo",
32704 args=[@{name="i",value="10"@}],
32705 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32706 state="running"@}],
32707 current-thread-id="1"
32711 @subheading The @code{-thread-list-ids} Command
32712 @findex -thread-list-ids
32714 @subsubheading Synopsis
32720 Produces a list of the currently known global @value{GDBN} thread ids.
32721 At the end of the list it also prints the total number of such
32724 This command is retained for historical reasons, the
32725 @code{-thread-info} command should be used instead.
32727 @subsubheading @value{GDBN} Command
32729 Part of @samp{info threads} supplies the same information.
32731 @subsubheading Example
32736 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32737 current-thread-id="1",number-of-threads="3"
32742 @subheading The @code{-thread-select} Command
32743 @findex -thread-select
32745 @subsubheading Synopsis
32748 -thread-select @var{thread-id}
32751 Make thread with global thread number @var{thread-id} the current
32752 thread. It prints the number of the new current thread, and the
32753 topmost frame for that thread.
32755 This command is deprecated in favor of explicitly using the
32756 @samp{--thread} option to each command.
32758 @subsubheading @value{GDBN} Command
32760 The corresponding @value{GDBN} command is @samp{thread}.
32762 @subsubheading Example
32769 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32770 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32774 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32775 number-of-threads="3"
32778 ^done,new-thread-id="3",
32779 frame=@{level="0",func="vprintf",
32780 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32781 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32786 @node GDB/MI Ada Tasking Commands
32787 @section @sc{gdb/mi} Ada Tasking Commands
32789 @subheading The @code{-ada-task-info} Command
32790 @findex -ada-task-info
32792 @subsubheading Synopsis
32795 -ada-task-info [ @var{task-id} ]
32798 Reports information about either a specific Ada task, if the
32799 @var{task-id} parameter is present, or about all Ada tasks.
32801 @subsubheading @value{GDBN} Command
32803 The @samp{info tasks} command prints the same information
32804 about all Ada tasks (@pxref{Ada Tasks}).
32806 @subsubheading Result
32808 The result is a table of Ada tasks. The following columns are
32809 defined for each Ada task:
32813 This field exists only for the current thread. It has the value @samp{*}.
32816 The identifier that @value{GDBN} uses to refer to the Ada task.
32819 The identifier that the target uses to refer to the Ada task.
32822 The global thread identifier of the thread corresponding to the Ada
32825 This field should always exist, as Ada tasks are always implemented
32826 on top of a thread. But if @value{GDBN} cannot find this corresponding
32827 thread for any reason, the field is omitted.
32830 This field exists only when the task was created by another task.
32831 In this case, it provides the ID of the parent task.
32834 The base priority of the task.
32837 The current state of the task. For a detailed description of the
32838 possible states, see @ref{Ada Tasks}.
32841 The name of the task.
32845 @subsubheading Example
32849 ^done,tasks=@{nr_rows="3",nr_cols="8",
32850 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32851 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32852 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32853 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32854 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32855 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32856 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32857 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32858 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32859 state="Child Termination Wait",name="main_task"@}]@}
32863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32864 @node GDB/MI Program Execution
32865 @section @sc{gdb/mi} Program Execution
32867 These are the asynchronous commands which generate the out-of-band
32868 record @samp{*stopped}. Currently @value{GDBN} only really executes
32869 asynchronously with remote targets and this interaction is mimicked in
32872 @subheading The @code{-exec-continue} Command
32873 @findex -exec-continue
32875 @subsubheading Synopsis
32878 -exec-continue [--reverse] [--all|--thread-group N]
32881 Resumes the execution of the inferior program, which will continue
32882 to execute until it reaches a debugger stop event. If the
32883 @samp{--reverse} option is specified, execution resumes in reverse until
32884 it reaches a stop event. Stop events may include
32887 breakpoints or watchpoints
32889 signals or exceptions
32891 the end of the process (or its beginning under @samp{--reverse})
32893 the end or beginning of a replay log if one is being used.
32895 In all-stop mode (@pxref{All-Stop
32896 Mode}), may resume only one thread, or all threads, depending on the
32897 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32898 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32899 ignored in all-stop mode. If the @samp{--thread-group} options is
32900 specified, then all threads in that thread group are resumed.
32902 @subsubheading @value{GDBN} Command
32904 The corresponding @value{GDBN} corresponding is @samp{continue}.
32906 @subsubheading Example
32913 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32914 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32915 line="13",arch="i386:x86_64"@}
32919 For a @samp{breakpoint-hit} stopped reason, when the breakpoint
32920 encountered has multiple locations, the field @samp{bkptno} is
32921 followed by the field @samp{locno}.
32928 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",locno="3",frame=@{
32929 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32930 line="13",arch="i386:x86_64"@}
32934 @subheading The @code{-exec-finish} Command
32935 @findex -exec-finish
32937 @subsubheading Synopsis
32940 -exec-finish [--reverse]
32943 Resumes the execution of the inferior program until the current
32944 function is exited. Displays the results returned by the function.
32945 If the @samp{--reverse} option is specified, resumes the reverse
32946 execution of the inferior program until the point where current
32947 function was called.
32949 @subsubheading @value{GDBN} Command
32951 The corresponding @value{GDBN} command is @samp{finish}.
32953 @subsubheading Example
32955 Function returning @code{void}.
32962 *stopped,reason="function-finished",frame=@{func="main",args=[],
32963 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32967 Function returning other than @code{void}. The name of the internal
32968 @value{GDBN} variable storing the result is printed, together with the
32975 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32976 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32977 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32978 arch="i386:x86_64"@},
32979 gdb-result-var="$1",return-value="0"
32984 @subheading The @code{-exec-interrupt} Command
32985 @findex -exec-interrupt
32987 @subsubheading Synopsis
32990 -exec-interrupt [--all|--thread-group N]
32993 Interrupts the background execution of the target. Note how the token
32994 associated with the stop message is the one for the execution command
32995 that has been interrupted. The token for the interrupt itself only
32996 appears in the @samp{^done} output. If the user is trying to
32997 interrupt a non-running program, an error message will be printed.
32999 Note that when asynchronous execution is enabled, this command is
33000 asynchronous just like other execution commands. That is, first the
33001 @samp{^done} response will be printed, and the target stop will be
33002 reported after that using the @samp{*stopped} notification.
33004 In non-stop mode, only the context thread is interrupted by default.
33005 All threads (in all inferiors) will be interrupted if the
33006 @samp{--all} option is specified. If the @samp{--thread-group}
33007 option is specified, all threads in that group will be interrupted.
33009 @subsubheading @value{GDBN} Command
33011 The corresponding @value{GDBN} command is @samp{interrupt}.
33013 @subsubheading Example
33024 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
33025 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
33026 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
33031 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
33035 @subheading The @code{-exec-jump} Command
33038 @subsubheading Synopsis
33041 -exec-jump @var{locspec}
33044 Resumes execution of the inferior program at the address to
33045 which @var{locspec} resolves. @xref{Location Specifications},
33046 for a description of the different forms of @var{locspec}.
33048 @subsubheading @value{GDBN} Command
33050 The corresponding @value{GDBN} command is @samp{jump}.
33052 @subsubheading Example
33055 -exec-jump foo.c:10
33056 *running,thread-id="all"
33061 @subheading The @code{-exec-next} Command
33064 @subsubheading Synopsis
33067 -exec-next [--reverse]
33070 Resumes execution of the inferior program, stopping when the beginning
33071 of the next source line is reached.
33073 If the @samp{--reverse} option is specified, resumes reverse execution
33074 of the inferior program, stopping at the beginning of the previous
33075 source line. If you issue this command on the first line of a
33076 function, it will take you back to the caller of that function, to the
33077 source line where the function was called.
33080 @subsubheading @value{GDBN} Command
33082 The corresponding @value{GDBN} command is @samp{next}.
33084 @subsubheading Example
33090 *stopped,reason="end-stepping-range",line="8",file="hello.c"
33095 @subheading The @code{-exec-next-instruction} Command
33096 @findex -exec-next-instruction
33098 @subsubheading Synopsis
33101 -exec-next-instruction [--reverse]
33104 Executes one machine instruction. If the instruction is a function
33105 call, continues until the function returns. If the program stops at an
33106 instruction in the middle of a source line, the address will be
33109 If the @samp{--reverse} option is specified, resumes reverse execution
33110 of the inferior program, stopping at the previous instruction. If the
33111 previously executed instruction was a return from another function,
33112 it will continue to execute in reverse until the call to that function
33113 (from the current stack frame) is reached.
33115 @subsubheading @value{GDBN} Command
33117 The corresponding @value{GDBN} command is @samp{nexti}.
33119 @subsubheading Example
33123 -exec-next-instruction
33127 *stopped,reason="end-stepping-range",
33128 addr="0x000100d4",line="5",file="hello.c"
33133 @subheading The @code{-exec-return} Command
33134 @findex -exec-return
33136 @subsubheading Synopsis
33142 Makes current function return immediately. Doesn't execute the inferior.
33143 Displays the new current frame.
33145 @subsubheading @value{GDBN} Command
33147 The corresponding @value{GDBN} command is @samp{return}.
33149 @subsubheading Example
33153 200-break-insert callee4
33154 200^done,bkpt=@{number="1",addr="0x00010734",
33155 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
33160 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33161 frame=@{func="callee4",args=[],
33162 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33163 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33164 arch="i386:x86_64"@}
33170 111^done,frame=@{level="0",func="callee3",
33171 args=[@{name="strarg",
33172 value="0x11940 \"A string argument.\""@}],
33173 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33174 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
33175 arch="i386:x86_64"@}
33180 @subheading The @code{-exec-run} Command
33183 @subsubheading Synopsis
33186 -exec-run [ --all | --thread-group N ] [ --start ]
33189 Starts execution of the inferior from the beginning. The inferior
33190 executes until either a breakpoint is encountered or the program
33191 exits. In the latter case the output will include an exit code, if
33192 the program has exited exceptionally.
33194 When neither the @samp{--all} nor the @samp{--thread-group} option
33195 is specified, the current inferior is started. If the
33196 @samp{--thread-group} option is specified, it should refer to a thread
33197 group of type @samp{process}, and that thread group will be started.
33198 If the @samp{--all} option is specified, then all inferiors will be started.
33200 Using the @samp{--start} option instructs the debugger to stop
33201 the execution at the start of the inferior's main subprogram,
33202 following the same behavior as the @code{start} command
33203 (@pxref{Starting}).
33205 @subsubheading @value{GDBN} Command
33207 The corresponding @value{GDBN} command is @samp{run}.
33209 @subsubheading Examples
33214 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
33219 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33220 frame=@{func="main",args=[],file="recursive2.c",
33221 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
33226 Program exited normally:
33234 *stopped,reason="exited-normally"
33239 Program exited exceptionally:
33247 *stopped,reason="exited",exit-code="01"
33251 Another way the program can terminate is if it receives a signal such as
33252 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
33256 *stopped,reason="exited-signalled",signal-name="SIGINT",
33257 signal-meaning="Interrupt"
33261 @c @subheading -exec-signal
33264 @subheading The @code{-exec-step} Command
33267 @subsubheading Synopsis
33270 -exec-step [--reverse]
33273 Resumes execution of the inferior program, stopping when the beginning
33274 of the next source line is reached, if the next source line is not a
33275 function call. If it is, stop at the first instruction of the called
33276 function. If the @samp{--reverse} option is specified, resumes reverse
33277 execution of the inferior program, stopping at the beginning of the
33278 previously executed source line.
33280 @subsubheading @value{GDBN} Command
33282 The corresponding @value{GDBN} command is @samp{step}.
33284 @subsubheading Example
33286 Stepping into a function:
33292 *stopped,reason="end-stepping-range",
33293 frame=@{func="foo",args=[@{name="a",value="10"@},
33294 @{name="b",value="0"@}],file="recursive2.c",
33295 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
33305 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
33310 @subheading The @code{-exec-step-instruction} Command
33311 @findex -exec-step-instruction
33313 @subsubheading Synopsis
33316 -exec-step-instruction [--reverse]
33319 Resumes the inferior which executes one machine instruction. If the
33320 @samp{--reverse} option is specified, resumes reverse execution of the
33321 inferior program, stopping at the previously executed instruction.
33322 The output, once @value{GDBN} has stopped, will vary depending on
33323 whether we have stopped in the middle of a source line or not. In the
33324 former case, the address at which the program stopped will be printed
33327 @subsubheading @value{GDBN} Command
33329 The corresponding @value{GDBN} command is @samp{stepi}.
33331 @subsubheading Example
33335 -exec-step-instruction
33339 *stopped,reason="end-stepping-range",
33340 frame=@{func="foo",args=[],file="try.c",
33341 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33343 -exec-step-instruction
33347 *stopped,reason="end-stepping-range",
33348 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
33349 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33354 @subheading The @code{-exec-until} Command
33355 @findex -exec-until
33357 @subsubheading Synopsis
33360 -exec-until [ @var{locspec} ]
33363 Executes the inferior until it reaches the address to which
33364 @var{locspec} resolves. If there is no argument, the inferior
33365 executes until it reaches a source line greater than the current one.
33366 The reason for stopping in this case will be @samp{location-reached}.
33368 @subsubheading @value{GDBN} Command
33370 The corresponding @value{GDBN} command is @samp{until}.
33372 @subsubheading Example
33376 -exec-until recursive2.c:6
33380 *stopped,reason="location-reached",frame=@{func="main",args=[],
33381 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
33382 arch="i386:x86_64"@}
33387 @subheading -file-clear
33388 Is this going away????
33391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33392 @node GDB/MI Stack Manipulation
33393 @section @sc{gdb/mi} Stack Manipulation Commands
33395 @subheading The @code{-enable-frame-filters} Command
33396 @findex -enable-frame-filters
33399 -enable-frame-filters
33402 @value{GDBN} allows Python-based frame filters to affect the output of
33403 the MI commands relating to stack traces. As there is no way to
33404 implement this in a fully backward-compatible way, a front end must
33405 request that this functionality be enabled.
33407 Once enabled, this feature cannot be disabled.
33409 Note that if Python support has not been compiled into @value{GDBN},
33410 this command will still succeed (and do nothing).
33412 @subheading The @code{-stack-info-frame} Command
33413 @findex -stack-info-frame
33415 @subsubheading Synopsis
33421 Get info on the selected frame.
33423 @subsubheading @value{GDBN} Command
33425 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
33426 (without arguments).
33428 @subsubheading Example
33433 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
33434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33435 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33436 arch="i386:x86_64"@}
33440 @subheading The @code{-stack-info-depth} Command
33441 @findex -stack-info-depth
33443 @subsubheading Synopsis
33446 -stack-info-depth [ @var{max-depth} ]
33449 Return the depth of the stack. If the integer argument @var{max-depth}
33450 is specified, do not count beyond @var{max-depth} frames.
33452 @subsubheading @value{GDBN} Command
33454 There's no equivalent @value{GDBN} command.
33456 @subsubheading Example
33458 For a stack with frame levels 0 through 11:
33465 -stack-info-depth 4
33468 -stack-info-depth 12
33471 -stack-info-depth 11
33474 -stack-info-depth 13
33479 @anchor{-stack-list-arguments}
33480 @subheading The @code{-stack-list-arguments} Command
33481 @findex -stack-list-arguments
33483 @subsubheading Synopsis
33486 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33487 [ @var{low-frame} @var{high-frame} ]
33490 Display a list of the arguments for the frames between @var{low-frame}
33491 and @var{high-frame} (inclusive). If @var{low-frame} and
33492 @var{high-frame} are not provided, list the arguments for the whole
33493 call stack. If the two arguments are equal, show the single frame
33494 at the corresponding level. It is an error if @var{low-frame} is
33495 larger than the actual number of frames. On the other hand,
33496 @var{high-frame} may be larger than the actual number of frames, in
33497 which case only existing frames will be returned.
33499 If @var{print-values} is 0 or @code{--no-values}, print only the names of
33500 the variables; if it is 1 or @code{--all-values}, print also their
33501 values; and if it is 2 or @code{--simple-values}, print the name,
33502 type and value for simple data types, and the name and type for arrays,
33503 structures and unions. If the option @code{--no-frame-filters} is
33504 supplied, then Python frame filters will not be executed.
33506 If the @code{--skip-unavailable} option is specified, arguments that
33507 are not available are not listed. Partially available arguments
33508 are still displayed, however.
33510 Use of this command to obtain arguments in a single frame is
33511 deprecated in favor of the @samp{-stack-list-variables} command.
33513 @subsubheading @value{GDBN} Command
33515 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
33516 @samp{gdb_get_args} command which partially overlaps with the
33517 functionality of @samp{-stack-list-arguments}.
33519 @subsubheading Example
33526 frame=@{level="0",addr="0x00010734",func="callee4",
33527 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33528 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33529 arch="i386:x86_64"@},
33530 frame=@{level="1",addr="0x0001076c",func="callee3",
33531 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33532 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33533 arch="i386:x86_64"@},
33534 frame=@{level="2",addr="0x0001078c",func="callee2",
33535 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33536 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33537 arch="i386:x86_64"@},
33538 frame=@{level="3",addr="0x000107b4",func="callee1",
33539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33540 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33541 arch="i386:x86_64"@},
33542 frame=@{level="4",addr="0x000107e0",func="main",
33543 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33544 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33545 arch="i386:x86_64"@}]
33547 -stack-list-arguments 0
33550 frame=@{level="0",args=[]@},
33551 frame=@{level="1",args=[name="strarg"]@},
33552 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33553 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33554 frame=@{level="4",args=[]@}]
33556 -stack-list-arguments 1
33559 frame=@{level="0",args=[]@},
33561 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33562 frame=@{level="2",args=[
33563 @{name="intarg",value="2"@},
33564 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33565 @{frame=@{level="3",args=[
33566 @{name="intarg",value="2"@},
33567 @{name="strarg",value="0x11940 \"A string argument.\""@},
33568 @{name="fltarg",value="3.5"@}]@},
33569 frame=@{level="4",args=[]@}]
33571 -stack-list-arguments 0 2 2
33572 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33574 -stack-list-arguments 1 2 2
33575 ^done,stack-args=[frame=@{level="2",
33576 args=[@{name="intarg",value="2"@},
33577 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33581 @c @subheading -stack-list-exception-handlers
33584 @anchor{-stack-list-frames}
33585 @subheading The @code{-stack-list-frames} Command
33586 @findex -stack-list-frames
33588 @subsubheading Synopsis
33591 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33594 List the frames currently on the stack. For each frame it displays the
33599 The frame number, 0 being the topmost frame, i.e., the innermost function.
33601 The @code{$pc} value for that frame.
33605 File name of the source file where the function lives.
33606 @item @var{fullname}
33607 The full file name of the source file where the function lives.
33609 Line number corresponding to the @code{$pc}.
33611 The shared library where this function is defined. This is only given
33612 if the frame's function is not known.
33614 Frame's architecture.
33617 If invoked without arguments, this command prints a backtrace for the
33618 whole stack. If given two integer arguments, it shows the frames whose
33619 levels are between the two arguments (inclusive). If the two arguments
33620 are equal, it shows the single frame at the corresponding level. It is
33621 an error if @var{low-frame} is larger than the actual number of
33622 frames. On the other hand, @var{high-frame} may be larger than the
33623 actual number of frames, in which case only existing frames will be
33624 returned. If the option @code{--no-frame-filters} is supplied, then
33625 Python frame filters will not be executed.
33627 @subsubheading @value{GDBN} Command
33629 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33631 @subsubheading Example
33633 Full stack backtrace:
33639 [frame=@{level="0",addr="0x0001076c",func="foo",
33640 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33641 arch="i386:x86_64"@},
33642 frame=@{level="1",addr="0x000107a4",func="foo",
33643 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33644 arch="i386:x86_64"@},
33645 frame=@{level="2",addr="0x000107a4",func="foo",
33646 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33647 arch="i386:x86_64"@},
33648 frame=@{level="3",addr="0x000107a4",func="foo",
33649 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33650 arch="i386:x86_64"@},
33651 frame=@{level="4",addr="0x000107a4",func="foo",
33652 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33653 arch="i386:x86_64"@},
33654 frame=@{level="5",addr="0x000107a4",func="foo",
33655 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33656 arch="i386:x86_64"@},
33657 frame=@{level="6",addr="0x000107a4",func="foo",
33658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33659 arch="i386:x86_64"@},
33660 frame=@{level="7",addr="0x000107a4",func="foo",
33661 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33662 arch="i386:x86_64"@},
33663 frame=@{level="8",addr="0x000107a4",func="foo",
33664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33665 arch="i386:x86_64"@},
33666 frame=@{level="9",addr="0x000107a4",func="foo",
33667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33668 arch="i386:x86_64"@},
33669 frame=@{level="10",addr="0x000107a4",func="foo",
33670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33671 arch="i386:x86_64"@},
33672 frame=@{level="11",addr="0x00010738",func="main",
33673 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33674 arch="i386:x86_64"@}]
33678 Show frames between @var{low_frame} and @var{high_frame}:
33682 -stack-list-frames 3 5
33684 [frame=@{level="3",addr="0x000107a4",func="foo",
33685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33686 arch="i386:x86_64"@},
33687 frame=@{level="4",addr="0x000107a4",func="foo",
33688 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33689 arch="i386:x86_64"@},
33690 frame=@{level="5",addr="0x000107a4",func="foo",
33691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33692 arch="i386:x86_64"@}]
33696 Show a single frame:
33700 -stack-list-frames 3 3
33702 [frame=@{level="3",addr="0x000107a4",func="foo",
33703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33704 arch="i386:x86_64"@}]
33709 @subheading The @code{-stack-list-locals} Command
33710 @findex -stack-list-locals
33711 @anchor{-stack-list-locals}
33713 @subsubheading Synopsis
33716 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33719 Display the local variable names for the selected frame. If
33720 @var{print-values} is 0 or @code{--no-values}, print only the names of
33721 the variables; if it is 1 or @code{--all-values}, print also their
33722 values; and if it is 2 or @code{--simple-values}, print the name,
33723 type and value for simple data types, and the name and type for arrays,
33724 structures and unions. In this last case, a frontend can immediately
33725 display the value of simple data types and create variable objects for
33726 other data types when the user wishes to explore their values in
33727 more detail. If the option @code{--no-frame-filters} is supplied, then
33728 Python frame filters will not be executed.
33730 If the @code{--skip-unavailable} option is specified, local variables
33731 that are not available are not listed. Partially available local
33732 variables are still displayed, however.
33734 This command is deprecated in favor of the
33735 @samp{-stack-list-variables} command.
33737 @subsubheading @value{GDBN} Command
33739 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33741 @subsubheading Example
33745 -stack-list-locals 0
33746 ^done,locals=[name="A",name="B",name="C"]
33748 -stack-list-locals --all-values
33749 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33750 @{name="C",value="@{1, 2, 3@}"@}]
33751 -stack-list-locals --simple-values
33752 ^done,locals=[@{name="A",type="int",value="1"@},
33753 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33757 @anchor{-stack-list-variables}
33758 @subheading The @code{-stack-list-variables} Command
33759 @findex -stack-list-variables
33761 @subsubheading Synopsis
33764 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33767 Display the names of local variables and function arguments for the selected frame. If
33768 @var{print-values} is 0 or @code{--no-values}, print only the names of
33769 the variables; if it is 1 or @code{--all-values}, print also their
33770 values; and if it is 2 or @code{--simple-values}, print the name,
33771 type and value for simple data types, and the name and type for arrays,
33772 structures and unions. If the option @code{--no-frame-filters} is
33773 supplied, then Python frame filters will not be executed.
33775 If the @code{--skip-unavailable} option is specified, local variables
33776 and arguments that are not available are not listed. Partially
33777 available arguments and local variables are still displayed, however.
33779 @subsubheading Example
33783 -stack-list-variables --thread 1 --frame 0 --all-values
33784 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33789 @subheading The @code{-stack-select-frame} Command
33790 @findex -stack-select-frame
33792 @subsubheading Synopsis
33795 -stack-select-frame @var{framenum}
33798 Change the selected frame. Select a different frame @var{framenum} on
33801 This command in deprecated in favor of passing the @samp{--frame}
33802 option to every command.
33804 @subsubheading @value{GDBN} Command
33806 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33807 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33809 @subsubheading Example
33813 -stack-select-frame 2
33818 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33819 @node GDB/MI Variable Objects
33820 @section @sc{gdb/mi} Variable Objects
33824 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33826 For the implementation of a variable debugger window (locals, watched
33827 expressions, etc.), we are proposing the adaptation of the existing code
33828 used by @code{Insight}.
33830 The two main reasons for that are:
33834 It has been proven in practice (it is already on its second generation).
33837 It will shorten development time (needless to say how important it is
33841 The original interface was designed to be used by Tcl code, so it was
33842 slightly changed so it could be used through @sc{gdb/mi}. This section
33843 describes the @sc{gdb/mi} operations that will be available and gives some
33844 hints about their use.
33846 @emph{Note}: In addition to the set of operations described here, we
33847 expect the @sc{gui} implementation of a variable window to require, at
33848 least, the following operations:
33851 @item @code{-gdb-show} @code{output-radix}
33852 @item @code{-stack-list-arguments}
33853 @item @code{-stack-list-locals}
33854 @item @code{-stack-select-frame}
33859 @subheading Introduction to Variable Objects
33861 @cindex variable objects in @sc{gdb/mi}
33863 Variable objects are "object-oriented" MI interface for examining and
33864 changing values of expressions. Unlike some other MI interfaces that
33865 work with expressions, variable objects are specifically designed for
33866 simple and efficient presentation in the frontend. A variable object
33867 is identified by string name. When a variable object is created, the
33868 frontend specifies the expression for that variable object. The
33869 expression can be a simple variable, or it can be an arbitrary complex
33870 expression, and can even involve CPU registers. After creating a
33871 variable object, the frontend can invoke other variable object
33872 operations---for example to obtain or change the value of a variable
33873 object, or to change display format.
33875 Variable objects have hierarchical tree structure. Any variable object
33876 that corresponds to a composite type, such as structure in C, has
33877 a number of child variable objects, for example corresponding to each
33878 element of a structure. A child variable object can itself have
33879 children, recursively. Recursion ends when we reach
33880 leaf variable objects, which always have built-in types. Child variable
33881 objects are created only by explicit request, so if a frontend
33882 is not interested in the children of a particular variable object, no
33883 child will be created.
33885 For a leaf variable object it is possible to obtain its value as a
33886 string, or set the value from a string. String value can be also
33887 obtained for a non-leaf variable object, but it's generally a string
33888 that only indicates the type of the object, and does not list its
33889 contents. Assignment to a non-leaf variable object is not allowed.
33891 A frontend does not need to read the values of all variable objects each time
33892 the program stops. Instead, MI provides an update command that lists all
33893 variable objects whose values has changed since the last update
33894 operation. This considerably reduces the amount of data that must
33895 be transferred to the frontend. As noted above, children variable
33896 objects are created on demand, and only leaf variable objects have a
33897 real value. As result, gdb will read target memory only for leaf
33898 variables that frontend has created.
33900 The automatic update is not always desirable. For example, a frontend
33901 might want to keep a value of some expression for future reference,
33902 and never update it. For another example, fetching memory is
33903 relatively slow for embedded targets, so a frontend might want
33904 to disable automatic update for the variables that are either not
33905 visible on the screen, or ``closed''. This is possible using so
33906 called ``frozen variable objects''. Such variable objects are never
33907 implicitly updated.
33909 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33910 fixed variable object, the expression is parsed when the variable
33911 object is created, including associating identifiers to specific
33912 variables. The meaning of expression never changes. For a floating
33913 variable object the values of variables whose names appear in the
33914 expressions are re-evaluated every time in the context of the current
33915 frame. Consider this example:
33920 struct work_state state;
33927 If a fixed variable object for the @code{state} variable is created in
33928 this function, and we enter the recursive call, the variable
33929 object will report the value of @code{state} in the top-level
33930 @code{do_work} invocation. On the other hand, a floating variable
33931 object will report the value of @code{state} in the current frame.
33933 If an expression specified when creating a fixed variable object
33934 refers to a local variable, the variable object becomes bound to the
33935 thread and frame in which the variable object is created. When such
33936 variable object is updated, @value{GDBN} makes sure that the
33937 thread/frame combination the variable object is bound to still exists,
33938 and re-evaluates the variable object in context of that thread/frame.
33940 The following is the complete set of @sc{gdb/mi} operations defined to
33941 access this functionality:
33943 @multitable @columnfractions .4 .6
33944 @item @strong{Operation}
33945 @tab @strong{Description}
33947 @item @code{-enable-pretty-printing}
33948 @tab enable Python-based pretty-printing
33949 @item @code{-var-create}
33950 @tab create a variable object
33951 @item @code{-var-delete}
33952 @tab delete the variable object and/or its children
33953 @item @code{-var-set-format}
33954 @tab set the display format of this variable
33955 @item @code{-var-show-format}
33956 @tab show the display format of this variable
33957 @item @code{-var-info-num-children}
33958 @tab tells how many children this object has
33959 @item @code{-var-list-children}
33960 @tab return a list of the object's children
33961 @item @code{-var-info-type}
33962 @tab show the type of this variable object
33963 @item @code{-var-info-expression}
33964 @tab print parent-relative expression that this variable object represents
33965 @item @code{-var-info-path-expression}
33966 @tab print full expression that this variable object represents
33967 @item @code{-var-show-attributes}
33968 @tab is this variable editable? does it exist here?
33969 @item @code{-var-evaluate-expression}
33970 @tab get the value of this variable
33971 @item @code{-var-assign}
33972 @tab set the value of this variable
33973 @item @code{-var-update}
33974 @tab update the variable and its children
33975 @item @code{-var-set-frozen}
33976 @tab set frozenness attribute
33977 @item @code{-var-set-update-range}
33978 @tab set range of children to display on update
33981 In the next subsection we describe each operation in detail and suggest
33982 how it can be used.
33984 @subheading Description And Use of Operations on Variable Objects
33986 @subheading The @code{-enable-pretty-printing} Command
33987 @findex -enable-pretty-printing
33990 -enable-pretty-printing
33993 @value{GDBN} allows Python-based visualizers to affect the output of the
33994 MI variable object commands. However, because there was no way to
33995 implement this in a fully backward-compatible way, a front end must
33996 request that this functionality be enabled.
33998 Once enabled, this feature cannot be disabled.
34000 Note that if Python support has not been compiled into @value{GDBN},
34001 this command will still succeed (and do nothing).
34003 @subheading The @code{-var-create} Command
34004 @findex -var-create
34006 @subsubheading Synopsis
34009 -var-create @{@var{name} | "-"@}
34010 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
34013 This operation creates a variable object, which allows the monitoring of
34014 a variable, the result of an expression, a memory cell or a CPU
34017 The @var{name} parameter is the string by which the object can be
34018 referenced. It must be unique. If @samp{-} is specified, the varobj
34019 system will generate a string ``varNNNNNN'' automatically. It will be
34020 unique provided that one does not specify @var{name} of that format.
34021 The command fails if a duplicate name is found.
34023 The frame under which the expression should be evaluated can be
34024 specified by @var{frame-addr}. A @samp{*} indicates that the current
34025 frame should be used. A @samp{@@} indicates that a floating variable
34026 object must be created.
34028 @var{expression} is any expression valid on the current language set (must not
34029 begin with a @samp{*}), or one of the following:
34033 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
34036 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
34039 @samp{$@var{regname}} --- a CPU register name
34042 @cindex dynamic varobj
34043 A varobj's contents may be provided by a Python-based pretty-printer. In this
34044 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
34045 have slightly different semantics in some cases. If the
34046 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
34047 will never create a dynamic varobj. This ensures backward
34048 compatibility for existing clients.
34050 @subsubheading Result
34052 This operation returns attributes of the newly-created varobj. These
34057 The name of the varobj.
34060 The number of children of the varobj. This number is not necessarily
34061 reliable for a dynamic varobj. Instead, you must examine the
34062 @samp{has_more} attribute.
34065 The varobj's scalar value. For a varobj whose type is some sort of
34066 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
34067 will not be interesting.
34070 The varobj's type. This is a string representation of the type, as
34071 would be printed by the @value{GDBN} CLI. If @samp{print object}
34072 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34073 @emph{actual} (derived) type of the object is shown rather than the
34074 @emph{declared} one.
34077 If a variable object is bound to a specific thread, then this is the
34078 thread's global identifier.
34081 For a dynamic varobj, this indicates whether there appear to be any
34082 children available. For a non-dynamic varobj, this will be 0.
34085 This attribute will be present and have the value @samp{1} if the
34086 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34087 then this attribute will not be present.
34090 A dynamic varobj can supply a display hint to the front end. The
34091 value comes directly from the Python pretty-printer object's
34092 @code{display_hint} method. @xref{Pretty Printing API}.
34095 Typical output will look like this:
34098 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
34099 has_more="@var{has_more}"
34103 @subheading The @code{-var-delete} Command
34104 @findex -var-delete
34106 @subsubheading Synopsis
34109 -var-delete [ -c ] @var{name}
34112 Deletes a previously created variable object and all of its children.
34113 With the @samp{-c} option, just deletes the children.
34115 Returns an error if the object @var{name} is not found.
34118 @subheading The @code{-var-set-format} Command
34119 @findex -var-set-format
34121 @subsubheading Synopsis
34124 -var-set-format @var{name} @var{format-spec}
34127 Sets the output format for the value of the object @var{name} to be
34130 @anchor{-var-set-format}
34131 The syntax for the @var{format-spec} is as follows:
34134 @var{format-spec} @expansion{}
34135 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
34138 The natural format is the default format choosen automatically
34139 based on the variable type (like decimal for an @code{int}, hex
34140 for pointers, etc.).
34142 The zero-hexadecimal format has a representation similar to hexadecimal
34143 but with padding zeroes to the left of the value. For example, a 32-bit
34144 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
34145 zero-hexadecimal format.
34147 For a variable with children, the format is set only on the
34148 variable itself, and the children are not affected.
34150 @subheading The @code{-var-show-format} Command
34151 @findex -var-show-format
34153 @subsubheading Synopsis
34156 -var-show-format @var{name}
34159 Returns the format used to display the value of the object @var{name}.
34162 @var{format} @expansion{}
34167 @subheading The @code{-var-info-num-children} Command
34168 @findex -var-info-num-children
34170 @subsubheading Synopsis
34173 -var-info-num-children @var{name}
34176 Returns the number of children of a variable object @var{name}:
34182 Note that this number is not completely reliable for a dynamic varobj.
34183 It will return the current number of children, but more children may
34187 @subheading The @code{-var-list-children} Command
34188 @findex -var-list-children
34190 @subsubheading Synopsis
34193 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
34195 @anchor{-var-list-children}
34197 Return a list of the children of the specified variable object and
34198 create variable objects for them, if they do not already exist. With
34199 a single argument or if @var{print-values} has a value of 0 or
34200 @code{--no-values}, print only the names of the variables; if
34201 @var{print-values} is 1 or @code{--all-values}, also print their
34202 values; and if it is 2 or @code{--simple-values} print the name and
34203 value for simple data types and just the name for arrays, structures
34206 @var{from} and @var{to}, if specified, indicate the range of children
34207 to report. If @var{from} or @var{to} is less than zero, the range is
34208 reset and all children will be reported. Otherwise, children starting
34209 at @var{from} (zero-based) and up to and excluding @var{to} will be
34212 If a child range is requested, it will only affect the current call to
34213 @code{-var-list-children}, but not future calls to @code{-var-update}.
34214 For this, you must instead use @code{-var-set-update-range}. The
34215 intent of this approach is to enable a front end to implement any
34216 update approach it likes; for example, scrolling a view may cause the
34217 front end to request more children with @code{-var-list-children}, and
34218 then the front end could call @code{-var-set-update-range} with a
34219 different range to ensure that future updates are restricted to just
34222 For each child the following results are returned:
34227 Name of the variable object created for this child.
34230 The expression to be shown to the user by the front end to designate this child.
34231 For example this may be the name of a structure member.
34233 For a dynamic varobj, this value cannot be used to form an
34234 expression. There is no way to do this at all with a dynamic varobj.
34236 For C/C@t{++} structures there are several pseudo children returned to
34237 designate access qualifiers. For these pseudo children @var{exp} is
34238 @samp{public}, @samp{private}, or @samp{protected}. In this case the
34239 type and value are not present.
34241 A dynamic varobj will not report the access qualifying
34242 pseudo-children, regardless of the language. This information is not
34243 available at all with a dynamic varobj.
34246 Number of children this child has. For a dynamic varobj, this will be
34250 The type of the child. If @samp{print object}
34251 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34252 @emph{actual} (derived) type of the object is shown rather than the
34253 @emph{declared} one.
34256 If values were requested, this is the value.
34259 If this variable object is associated with a thread, this is the
34260 thread's global thread id. Otherwise this result is not present.
34263 If the variable object is frozen, this variable will be present with a value of 1.
34266 A dynamic varobj can supply a display hint to the front end. The
34267 value comes directly from the Python pretty-printer object's
34268 @code{display_hint} method. @xref{Pretty Printing API}.
34271 This attribute will be present and have the value @samp{1} if the
34272 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34273 then this attribute will not be present.
34277 The result may have its own attributes:
34281 A dynamic varobj can supply a display hint to the front end. The
34282 value comes directly from the Python pretty-printer object's
34283 @code{display_hint} method. @xref{Pretty Printing API}.
34286 This is an integer attribute which is nonzero if there are children
34287 remaining after the end of the selected range.
34290 @subsubheading Example
34294 -var-list-children n
34295 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34296 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
34298 -var-list-children --all-values n
34299 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34300 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
34304 @subheading The @code{-var-info-type} Command
34305 @findex -var-info-type
34307 @subsubheading Synopsis
34310 -var-info-type @var{name}
34313 Returns the type of the specified variable @var{name}. The type is
34314 returned as a string in the same format as it is output by the
34318 type=@var{typename}
34322 @subheading The @code{-var-info-expression} Command
34323 @findex -var-info-expression
34325 @subsubheading Synopsis
34328 -var-info-expression @var{name}
34331 Returns a string that is suitable for presenting this
34332 variable object in user interface. The string is generally
34333 not valid expression in the current language, and cannot be evaluated.
34335 For example, if @code{a} is an array, and variable object
34336 @code{A} was created for @code{a}, then we'll get this output:
34339 (gdb) -var-info-expression A.1
34340 ^done,lang="C",exp="1"
34344 Here, the value of @code{lang} is the language name, which can be
34345 found in @ref{Supported Languages}.
34347 Note that the output of the @code{-var-list-children} command also
34348 includes those expressions, so the @code{-var-info-expression} command
34351 @subheading The @code{-var-info-path-expression} Command
34352 @findex -var-info-path-expression
34354 @subsubheading Synopsis
34357 -var-info-path-expression @var{name}
34360 Returns an expression that can be evaluated in the current
34361 context and will yield the same value that a variable object has.
34362 Compare this with the @code{-var-info-expression} command, which
34363 result can be used only for UI presentation. Typical use of
34364 the @code{-var-info-path-expression} command is creating a
34365 watchpoint from a variable object.
34367 This command is currently not valid for children of a dynamic varobj,
34368 and will give an error when invoked on one.
34370 For example, suppose @code{C} is a C@t{++} class, derived from class
34371 @code{Base}, and that the @code{Base} class has a member called
34372 @code{m_size}. Assume a variable @code{c} is has the type of
34373 @code{C} and a variable object @code{C} was created for variable
34374 @code{c}. Then, we'll get this output:
34376 (gdb) -var-info-path-expression C.Base.public.m_size
34377 ^done,path_expr=((Base)c).m_size)
34380 @subheading The @code{-var-show-attributes} Command
34381 @findex -var-show-attributes
34383 @subsubheading Synopsis
34386 -var-show-attributes @var{name}
34389 List attributes of the specified variable object @var{name}:
34392 status=@var{attr} [ ( ,@var{attr} )* ]
34396 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
34398 @subheading The @code{-var-evaluate-expression} Command
34399 @findex -var-evaluate-expression
34401 @subsubheading Synopsis
34404 -var-evaluate-expression [-f @var{format-spec}] @var{name}
34407 Evaluates the expression that is represented by the specified variable
34408 object and returns its value as a string. The format of the string
34409 can be specified with the @samp{-f} option. The possible values of
34410 this option are the same as for @code{-var-set-format}
34411 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
34412 the current display format will be used. The current display format
34413 can be changed using the @code{-var-set-format} command.
34419 Note that one must invoke @code{-var-list-children} for a variable
34420 before the value of a child variable can be evaluated.
34422 @subheading The @code{-var-assign} Command
34423 @findex -var-assign
34425 @subsubheading Synopsis
34428 -var-assign @var{name} @var{expression}
34431 Assigns the value of @var{expression} to the variable object specified
34432 by @var{name}. The object must be @samp{editable}. If the variable's
34433 value is altered by the assign, the variable will show up in any
34434 subsequent @code{-var-update} list.
34436 @subsubheading Example
34444 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
34448 @subheading The @code{-var-update} Command
34449 @findex -var-update
34451 @subsubheading Synopsis
34454 -var-update [@var{print-values}] @{@var{name} | "*"@}
34457 Reevaluate the expressions corresponding to the variable object
34458 @var{name} and all its direct and indirect children, and return the
34459 list of variable objects whose values have changed; @var{name} must
34460 be a root variable object. Here, ``changed'' means that the result of
34461 @code{-var-evaluate-expression} before and after the
34462 @code{-var-update} is different. If @samp{*} is used as the variable
34463 object names, all existing variable objects are updated, except
34464 for frozen ones (@pxref{-var-set-frozen}). The option
34465 @var{print-values} determines whether both names and values, or just
34466 names are printed. The possible values of this option are the same
34467 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
34468 recommended to use the @samp{--all-values} option, to reduce the
34469 number of MI commands needed on each program stop.
34471 With the @samp{*} parameter, if a variable object is bound to a
34472 currently running thread, it will not be updated, without any
34475 If @code{-var-set-update-range} was previously used on a varobj, then
34476 only the selected range of children will be reported.
34478 @code{-var-update} reports all the changed varobjs in a tuple named
34481 Each item in the change list is itself a tuple holding:
34485 The name of the varobj.
34488 If values were requested for this update, then this field will be
34489 present and will hold the value of the varobj.
34492 @anchor{-var-update}
34493 This field is a string which may take one of three values:
34497 The variable object's current value is valid.
34500 The variable object does not currently hold a valid value but it may
34501 hold one in the future if its associated expression comes back into
34505 The variable object no longer holds a valid value.
34506 This can occur when the executable file being debugged has changed,
34507 either through recompilation or by using the @value{GDBN} @code{file}
34508 command. The front end should normally choose to delete these variable
34512 In the future new values may be added to this list so the front should
34513 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
34516 This is only present if the varobj is still valid. If the type
34517 changed, then this will be the string @samp{true}; otherwise it will
34520 When a varobj's type changes, its children are also likely to have
34521 become incorrect. Therefore, the varobj's children are automatically
34522 deleted when this attribute is @samp{true}. Also, the varobj's update
34523 range, when set using the @code{-var-set-update-range} command, is
34527 If the varobj's type changed, then this field will be present and will
34530 @item new_num_children
34531 For a dynamic varobj, if the number of children changed, or if the
34532 type changed, this will be the new number of children.
34534 The @samp{numchild} field in other varobj responses is generally not
34535 valid for a dynamic varobj -- it will show the number of children that
34536 @value{GDBN} knows about, but because dynamic varobjs lazily
34537 instantiate their children, this will not reflect the number of
34538 children which may be available.
34540 The @samp{new_num_children} attribute only reports changes to the
34541 number of children known by @value{GDBN}. This is the only way to
34542 detect whether an update has removed children (which necessarily can
34543 only happen at the end of the update range).
34546 The display hint, if any.
34549 This is an integer value, which will be 1 if there are more children
34550 available outside the varobj's update range.
34553 This attribute will be present and have the value @samp{1} if the
34554 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34555 then this attribute will not be present.
34558 If new children were added to a dynamic varobj within the selected
34559 update range (as set by @code{-var-set-update-range}), then they will
34560 be listed in this attribute.
34563 @subsubheading Example
34570 -var-update --all-values var1
34571 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34572 type_changed="false"@}]
34576 @subheading The @code{-var-set-frozen} Command
34577 @findex -var-set-frozen
34578 @anchor{-var-set-frozen}
34580 @subsubheading Synopsis
34583 -var-set-frozen @var{name} @var{flag}
34586 Set the frozenness flag on the variable object @var{name}. The
34587 @var{flag} parameter should be either @samp{1} to make the variable
34588 frozen or @samp{0} to make it unfrozen. If a variable object is
34589 frozen, then neither itself, nor any of its children, are
34590 implicitly updated by @code{-var-update} of
34591 a parent variable or by @code{-var-update *}. Only
34592 @code{-var-update} of the variable itself will update its value and
34593 values of its children. After a variable object is unfrozen, it is
34594 implicitly updated by all subsequent @code{-var-update} operations.
34595 Unfreezing a variable does not update it, only subsequent
34596 @code{-var-update} does.
34598 @subsubheading Example
34602 -var-set-frozen V 1
34607 @subheading The @code{-var-set-update-range} command
34608 @findex -var-set-update-range
34609 @anchor{-var-set-update-range}
34611 @subsubheading Synopsis
34614 -var-set-update-range @var{name} @var{from} @var{to}
34617 Set the range of children to be returned by future invocations of
34618 @code{-var-update}.
34620 @var{from} and @var{to} indicate the range of children to report. If
34621 @var{from} or @var{to} is less than zero, the range is reset and all
34622 children will be reported. Otherwise, children starting at @var{from}
34623 (zero-based) and up to and excluding @var{to} will be reported.
34625 @subsubheading Example
34629 -var-set-update-range V 1 2
34633 @subheading The @code{-var-set-visualizer} command
34634 @findex -var-set-visualizer
34635 @anchor{-var-set-visualizer}
34637 @subsubheading Synopsis
34640 -var-set-visualizer @var{name} @var{visualizer}
34643 Set a visualizer for the variable object @var{name}.
34645 @var{visualizer} is the visualizer to use. The special value
34646 @samp{None} means to disable any visualizer in use.
34648 If not @samp{None}, @var{visualizer} must be a Python expression.
34649 This expression must evaluate to a callable object which accepts a
34650 single argument. @value{GDBN} will call this object with the value of
34651 the varobj @var{name} as an argument (this is done so that the same
34652 Python pretty-printing code can be used for both the CLI and MI).
34653 When called, this object must return an object which conforms to the
34654 pretty-printing interface (@pxref{Pretty Printing API}).
34656 The pre-defined function @code{gdb.default_visualizer} may be used to
34657 select a visualizer by following the built-in process
34658 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34659 a varobj is created, and so ordinarily is not needed.
34661 This feature is only available if Python support is enabled. The MI
34662 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34663 can be used to check this.
34665 @subsubheading Example
34667 Resetting the visualizer:
34671 -var-set-visualizer V None
34675 Reselecting the default (type-based) visualizer:
34679 -var-set-visualizer V gdb.default_visualizer
34683 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34684 can be used to instantiate this class for a varobj:
34688 -var-set-visualizer V "lambda val: SomeClass()"
34692 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34693 @node GDB/MI Data Manipulation
34694 @section @sc{gdb/mi} Data Manipulation
34696 @cindex data manipulation, in @sc{gdb/mi}
34697 @cindex @sc{gdb/mi}, data manipulation
34698 This section describes the @sc{gdb/mi} commands that manipulate data:
34699 examine memory and registers, evaluate expressions, etc.
34701 For details about what an addressable memory unit is,
34702 @pxref{addressable memory unit}.
34704 @c REMOVED FROM THE INTERFACE.
34705 @c @subheading -data-assign
34706 @c Change the value of a program variable. Plenty of side effects.
34707 @c @subsubheading GDB Command
34709 @c @subsubheading Example
34712 @subheading The @code{-data-disassemble} Command
34713 @findex -data-disassemble
34715 @subsubheading Synopsis
34719 ( -s @var{start-addr} -e @var{end-addr}
34721 | -f @var{filename} -l @var{linenum} [ -n @var{lines} ] )
34722 [ --opcodes @var{opcodes-mode} ]
34731 @item @var{start-addr}
34732 is the beginning address (or @code{$pc})
34733 @item @var{end-addr}
34736 is an address anywhere within (or the name of) the function to
34737 disassemble. If an address is specified, the whole function
34738 surrounding that address will be disassembled. If a name is
34739 specified, the whole function with that name will be disassembled.
34740 @item @var{filename}
34741 is the name of the file to disassemble
34742 @item @var{linenum}
34743 is the line number to disassemble around
34745 is the number of disassembly lines to be produced. If it is -1,
34746 the whole function will be disassembled, in case no @var{end-addr} is
34747 specified. If @var{end-addr} is specified as a non-zero value, and
34748 @var{lines} is lower than the number of disassembly lines between
34749 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34750 displayed; if @var{lines} is higher than the number of lines between
34751 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34753 @item @var{opcodes-mode}
34754 can only be used with @var{mode} 0, and should be one of the following:
34757 no opcode information will be included in the result.
34760 opcodes will be included in the result, the opcodes will be formatted
34761 as for @kbd{disassemble /b}.
34764 opcodes will be included in the result, the opcodes will be formatted
34765 as for @kbd{disassemble /r}.
34768 the use of @var{mode} is deprecated in favour of using the
34769 @code{--opcodes} and @code{--source} options. When no @var{mode} is
34770 given, @var{mode} 0 will be assumed. However, the @var{mode} is still
34771 available for backward compatibility. The @var{mode} should be one of:
34774 @emph{disassembly only}, this is the default mode if no mode is
34778 @emph{mixed source and disassembly (deprecated)}, it is not possible
34779 to recreate this mode using @code{--opcodes} and @code{--source}
34783 @emph{disassembly with raw opcodes}, this mode is equivalent to using
34784 @var{mode} 0 and passing @code{--opcodes bytes} to the command.
34787 @emph{mixed source and disassembly with raw opcodes (deprecated)}, it
34788 is not possible to recreate this mode using @code{--opcodes} and
34789 @code{--source} options.
34792 @emph{mixed source and disassembly}, this mode is equivalent to using
34793 @var{mode} 0 and passing @code{--source} to the command.
34796 @emph{mixed source and disassembly with raw opcodes}, this mode is
34797 equivalent to using @var{mode} 0 and passing @code{--opcodes bytes}
34798 and @code{--source} to the command.
34800 Modes 1 and 3 are deprecated. The output is ``source centric''
34801 which hasn't proved useful in practice.
34802 @xref{Machine Code}, for a discussion of the difference between
34803 @code{/m} and @code{/s} output of the @code{disassemble} command.
34806 The @code{--source} can only be used with @var{mode} 0. Passing this
34807 option will include the source code in the disassembly result as if
34808 @var{mode} 4 or 5 had been used.
34810 @subsubheading Result
34812 The result of the @code{-data-disassemble} command will be a list named
34813 @samp{asm_insns}, the contents of this list depend on the options used
34814 with the @code{-data-disassemble} command.
34816 For modes 0 and 2, and when the @code{--source} option is not used, the
34817 @samp{asm_insns} list contains tuples with the following fields:
34821 The address at which this instruction was disassembled.
34824 The name of the function this instruction is within.
34827 The decimal offset in bytes from the start of @samp{func-name}.
34830 The text disassembly for this @samp{address}.
34833 This field is only present for modes 2, 3 and 5, or when the
34834 @code{--opcodes} option @samp{bytes} or @samp{display} is used. This
34835 contains the raw opcode bytes for the @samp{inst} field.
34837 When the @samp{--opcodes} option is not passed to
34838 @code{-data-disassemble}, or the @samp{bytes} value is passed to
34839 @samp{--opcodes}, then the bytes are formatted as a series of single
34840 bytes, in hex, in ascending address order, with a single space between
34841 each byte. This format is equivalent to the @samp{/b} option being
34842 used with the @kbd{disassemble} command
34843 (@pxref{disassemble,,@kbd{disassemble}}).
34845 When @samp{--opcodes} is passed the value @samp{display} then the bytes
34846 are formatted in the natural instruction display order. This means
34847 multiple bytes can be grouped together, and the bytes might be
34848 byte-swapped. This format is equivalent to the @samp{/r} option being
34849 used with the @kbd{disassemble} command.
34852 For modes 1, 3, 4 and 5, or when the @code{--source} option is used, the
34853 @samp{asm_insns} list contains tuples named @samp{src_and_asm_line},
34854 each of which has the following fields:
34858 The line number within @samp{file}.
34861 The file name from the compilation unit. This might be an absolute
34862 file name or a relative file name depending on the compile command
34866 Absolute file name of @samp{file}. It is converted to a canonical form
34867 using the source file search path
34868 (@pxref{Source Path, ,Specifying Source Directories})
34869 and after resolving all the symbolic links.
34871 If the source file is not found this field will contain the path as
34872 present in the debug information.
34874 @item line_asm_insn
34875 This is a list of tuples containing the disassembly for @samp{line} in
34876 @samp{file}. The fields of each tuple are the same as for
34877 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34878 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34883 Note that whatever included in the @samp{inst} field, is not
34884 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34887 @subsubheading @value{GDBN} Command
34889 The corresponding @value{GDBN} command is @samp{disassemble}.
34891 @subsubheading Example
34893 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34897 -data-disassemble -s $pc -e "$pc + 20" -- 0
34900 @{address="0x000107c0",func-name="main",offset="4",
34901 inst="mov 2, %o0"@},
34902 @{address="0x000107c4",func-name="main",offset="8",
34903 inst="sethi %hi(0x11800), %o2"@},
34904 @{address="0x000107c8",func-name="main",offset="12",
34905 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34906 @{address="0x000107cc",func-name="main",offset="16",
34907 inst="sethi %hi(0x11800), %o2"@},
34908 @{address="0x000107d0",func-name="main",offset="20",
34909 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34913 Disassemble the whole @code{main} function. Line 32 is part of
34917 -data-disassemble -f basics.c -l 32 -- 0
34919 @{address="0x000107bc",func-name="main",offset="0",
34920 inst="save %sp, -112, %sp"@},
34921 @{address="0x000107c0",func-name="main",offset="4",
34922 inst="mov 2, %o0"@},
34923 @{address="0x000107c4",func-name="main",offset="8",
34924 inst="sethi %hi(0x11800), %o2"@},
34926 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34927 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34931 Disassemble 3 instructions from the start of @code{main}:
34935 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34937 @{address="0x000107bc",func-name="main",offset="0",
34938 inst="save %sp, -112, %sp"@},
34939 @{address="0x000107c0",func-name="main",offset="4",
34940 inst="mov 2, %o0"@},
34941 @{address="0x000107c4",func-name="main",offset="8",
34942 inst="sethi %hi(0x11800), %o2"@}]
34946 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34950 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34952 src_and_asm_line=@{line="31",
34953 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34954 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34955 line_asm_insn=[@{address="0x000107bc",
34956 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34957 src_and_asm_line=@{line="32",
34958 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34959 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34960 line_asm_insn=[@{address="0x000107c0",
34961 func-name="main",offset="4",inst="mov 2, %o0"@},
34962 @{address="0x000107c4",func-name="main",offset="8",
34963 inst="sethi %hi(0x11800), %o2"@}]@}]
34968 @subheading The @code{-data-evaluate-expression} Command
34969 @findex -data-evaluate-expression
34971 @subsubheading Synopsis
34974 -data-evaluate-expression @var{expr}
34977 Evaluate @var{expr} as an expression. The expression could contain an
34978 inferior function call. The function call will execute synchronously.
34979 If the expression contains spaces, it must be enclosed in double quotes.
34981 @subsubheading @value{GDBN} Command
34983 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34984 @samp{call}. In @code{gdbtk} only, there's a corresponding
34985 @samp{gdb_eval} command.
34987 @subsubheading Example
34989 In the following example, the numbers that precede the commands are the
34990 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34991 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34995 211-data-evaluate-expression A
34998 311-data-evaluate-expression &A
34999 311^done,value="0xefffeb7c"
35001 411-data-evaluate-expression A+3
35004 511-data-evaluate-expression "A + 3"
35010 @subheading The @code{-data-list-changed-registers} Command
35011 @findex -data-list-changed-registers
35013 @subsubheading Synopsis
35016 -data-list-changed-registers
35019 Display a list of the registers that have changed.
35021 @subsubheading @value{GDBN} Command
35023 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
35024 has the corresponding command @samp{gdb_changed_register_list}.
35026 @subsubheading Example
35028 On a PPC MBX board:
35036 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
35037 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
35038 line="5",arch="powerpc"@}
35040 -data-list-changed-registers
35041 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
35042 "10","11","13","14","15","16","17","18","19","20","21","22","23",
35043 "24","25","26","27","28","30","31","64","65","66","67","69"]
35048 @subheading The @code{-data-list-register-names} Command
35049 @findex -data-list-register-names
35051 @subsubheading Synopsis
35054 -data-list-register-names [ ( @var{regno} )+ ]
35057 Show a list of register names for the current target. If no arguments
35058 are given, it shows a list of the names of all the registers. If
35059 integer numbers are given as arguments, it will print a list of the
35060 names of the registers corresponding to the arguments. To ensure
35061 consistency between a register name and its number, the output list may
35062 include empty register names.
35064 @subsubheading @value{GDBN} Command
35066 @value{GDBN} does not have a command which corresponds to
35067 @samp{-data-list-register-names}. In @code{gdbtk} there is a
35068 corresponding command @samp{gdb_regnames}.
35070 @subsubheading Example
35072 For the PPC MBX board:
35075 -data-list-register-names
35076 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
35077 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
35078 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
35079 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
35080 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
35081 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
35082 "", "pc","ps","cr","lr","ctr","xer"]
35084 -data-list-register-names 1 2 3
35085 ^done,register-names=["r1","r2","r3"]
35089 @subheading The @code{-data-list-register-values} Command
35090 @findex -data-list-register-values
35092 @subsubheading Synopsis
35095 -data-list-register-values
35096 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
35099 Display the registers' contents. The format according to which the
35100 registers' contents are to be returned is given by @var{fmt}, followed
35101 by an optional list of numbers specifying the registers to display. A
35102 missing list of numbers indicates that the contents of all the
35103 registers must be returned. The @code{--skip-unavailable} option
35104 indicates that only the available registers are to be returned.
35106 Allowed formats for @var{fmt} are:
35123 @subsubheading @value{GDBN} Command
35125 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
35126 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
35128 @subsubheading Example
35130 For a PPC MBX board (note: line breaks are for readability only, they
35131 don't appear in the actual output):
35135 -data-list-register-values r 64 65
35136 ^done,register-values=[@{number="64",value="0xfe00a300"@},
35137 @{number="65",value="0x00029002"@}]
35139 -data-list-register-values x
35140 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
35141 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
35142 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
35143 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
35144 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
35145 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
35146 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
35147 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
35148 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
35149 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
35150 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
35151 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
35152 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
35153 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
35154 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
35155 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
35156 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
35157 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
35158 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
35159 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
35160 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
35161 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
35162 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
35163 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
35164 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
35165 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
35166 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
35167 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
35168 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
35169 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
35170 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
35171 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
35172 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
35173 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
35174 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
35175 @{number="69",value="0x20002b03"@}]
35180 @subheading The @code{-data-read-memory} Command
35181 @findex -data-read-memory
35183 This command is deprecated, use @code{-data-read-memory-bytes} instead.
35185 @subsubheading Synopsis
35188 -data-read-memory [ -o @var{byte-offset} ]
35189 @var{address} @var{word-format} @var{word-size}
35190 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
35197 @item @var{address}
35198 An expression specifying the address of the first memory word to be
35199 read. Complex expressions containing embedded white space should be
35200 quoted using the C convention.
35202 @item @var{word-format}
35203 The format to be used to print the memory words. The notation is the
35204 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
35207 @item @var{word-size}
35208 The size of each memory word in bytes.
35210 @item @var{nr-rows}
35211 The number of rows in the output table.
35213 @item @var{nr-cols}
35214 The number of columns in the output table.
35217 If present, indicates that each row should include an @sc{ascii} dump. The
35218 value of @var{aschar} is used as a padding character when a byte is not a
35219 member of the printable @sc{ascii} character set (printable @sc{ascii}
35220 characters are those whose code is between 32 and 126, inclusively).
35222 @item @var{byte-offset}
35223 An offset to add to the @var{address} before fetching memory.
35226 This command displays memory contents as a table of @var{nr-rows} by
35227 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
35228 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
35229 (returned as @samp{total-bytes}). Should less than the requested number
35230 of bytes be returned by the target, the missing words are identified
35231 using @samp{N/A}. The number of bytes read from the target is returned
35232 in @samp{nr-bytes} and the starting address used to read memory in
35235 The address of the next/previous row or page is available in
35236 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
35239 @subsubheading @value{GDBN} Command
35241 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
35242 @samp{gdb_get_mem} memory read command.
35244 @subsubheading Example
35246 Read six bytes of memory starting at @code{bytes+6} but then offset by
35247 @code{-6} bytes. Format as three rows of two columns. One byte per
35248 word. Display each word in hex.
35252 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
35253 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
35254 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
35255 prev-page="0x0000138a",memory=[
35256 @{addr="0x00001390",data=["0x00","0x01"]@},
35257 @{addr="0x00001392",data=["0x02","0x03"]@},
35258 @{addr="0x00001394",data=["0x04","0x05"]@}]
35262 Read two bytes of memory starting at address @code{shorts + 64} and
35263 display as a single word formatted in decimal.
35267 5-data-read-memory shorts+64 d 2 1 1
35268 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
35269 next-row="0x00001512",prev-row="0x0000150e",
35270 next-page="0x00001512",prev-page="0x0000150e",memory=[
35271 @{addr="0x00001510",data=["128"]@}]
35275 Read thirty two bytes of memory starting at @code{bytes+16} and format
35276 as eight rows of four columns. Include a string encoding with @samp{x}
35277 used as the non-printable character.
35281 4-data-read-memory bytes+16 x 1 8 4 x
35282 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
35283 next-row="0x000013c0",prev-row="0x0000139c",
35284 next-page="0x000013c0",prev-page="0x00001380",memory=[
35285 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
35286 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
35287 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
35288 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
35289 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
35290 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
35291 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
35292 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
35296 @subheading The @code{-data-read-memory-bytes} Command
35297 @findex -data-read-memory-bytes
35299 @subsubheading Synopsis
35302 -data-read-memory-bytes [ -o @var{offset} ]
35303 @var{address} @var{count}
35310 @item @var{address}
35311 An expression specifying the address of the first addressable memory unit
35312 to be read. Complex expressions containing embedded white space should be
35313 quoted using the C convention.
35316 The number of addressable memory units to read. This should be an integer
35320 The offset relative to @var{address} at which to start reading. This
35321 should be an integer literal. This option is provided so that a frontend
35322 is not required to first evaluate address and then perform address
35323 arithmetics itself.
35327 This command attempts to read all accessible memory regions in the
35328 specified range. First, all regions marked as unreadable in the memory
35329 map (if one is defined) will be skipped. @xref{Memory Region
35330 Attributes}. Second, @value{GDBN} will attempt to read the remaining
35331 regions. For each one, if reading full region results in an errors,
35332 @value{GDBN} will try to read a subset of the region.
35334 In general, every single memory unit in the region may be readable or not,
35335 and the only way to read every readable unit is to try a read at
35336 every address, which is not practical. Therefore, @value{GDBN} will
35337 attempt to read all accessible memory units at either beginning or the end
35338 of the region, using a binary division scheme. This heuristic works
35339 well for reading across a memory map boundary. Note that if a region
35340 has a readable range that is neither at the beginning or the end,
35341 @value{GDBN} will not read it.
35343 The result record (@pxref{GDB/MI Result Records}) that is output of
35344 the command includes a field named @samp{memory} whose content is a
35345 list of tuples. Each tuple represent a successfully read memory block
35346 and has the following fields:
35350 The start address of the memory block, as hexadecimal literal.
35353 The end address of the memory block, as hexadecimal literal.
35356 The offset of the memory block, as hexadecimal literal, relative to
35357 the start address passed to @code{-data-read-memory-bytes}.
35360 The contents of the memory block, in hex.
35366 @subsubheading @value{GDBN} Command
35368 The corresponding @value{GDBN} command is @samp{x}.
35370 @subsubheading Example
35374 -data-read-memory-bytes &a 10
35375 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
35377 contents="01000000020000000300"@}]
35382 @subheading The @code{-data-write-memory-bytes} Command
35383 @findex -data-write-memory-bytes
35385 @subsubheading Synopsis
35388 -data-write-memory-bytes @var{address} @var{contents}
35389 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
35396 @item @var{address}
35397 An expression specifying the address of the first addressable memory unit
35398 to be written. Complex expressions containing embedded white space should
35399 be quoted using the C convention.
35401 @item @var{contents}
35402 The hex-encoded data to write. It is an error if @var{contents} does
35403 not represent an integral number of addressable memory units.
35406 Optional argument indicating the number of addressable memory units to be
35407 written. If @var{count} is greater than @var{contents}' length,
35408 @value{GDBN} will repeatedly write @var{contents} until it fills
35409 @var{count} memory units.
35413 @subsubheading @value{GDBN} Command
35415 There's no corresponding @value{GDBN} command.
35417 @subsubheading Example
35421 -data-write-memory-bytes &a "aabbccdd"
35428 -data-write-memory-bytes &a "aabbccdd" 16e
35433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35434 @node GDB/MI Tracepoint Commands
35435 @section @sc{gdb/mi} Tracepoint Commands
35437 The commands defined in this section implement MI support for
35438 tracepoints. For detailed introduction, see @ref{Tracepoints}.
35440 @subheading The @code{-trace-find} Command
35441 @findex -trace-find
35443 @subsubheading Synopsis
35446 -trace-find @var{mode} [@var{parameters}@dots{}]
35449 Find a trace frame using criteria defined by @var{mode} and
35450 @var{parameters}. The following table lists permissible
35451 modes and their parameters. For details of operation, see @ref{tfind}.
35456 No parameters are required. Stops examining trace frames.
35459 An integer is required as parameter. Selects tracepoint frame with
35462 @item tracepoint-number
35463 An integer is required as parameter. Finds next
35464 trace frame that corresponds to tracepoint with the specified number.
35467 An address is required as parameter. Finds
35468 next trace frame that corresponds to any tracepoint at the specified
35471 @item pc-inside-range
35472 Two addresses are required as parameters. Finds next trace
35473 frame that corresponds to a tracepoint at an address inside the
35474 specified range. Both bounds are considered to be inside the range.
35476 @item pc-outside-range
35477 Two addresses are required as parameters. Finds
35478 next trace frame that corresponds to a tracepoint at an address outside
35479 the specified range. Both bounds are considered to be inside the range.
35482 Location specification is required as parameter. @xref{Location Specifications}.
35483 Finds next trace frame that corresponds to a tracepoint at
35484 the specified location.
35488 If @samp{none} was passed as @var{mode}, the response does not
35489 have fields. Otherwise, the response may have the following fields:
35493 This field has either @samp{0} or @samp{1} as the value, depending
35494 on whether a matching tracepoint was found.
35497 The index of the found traceframe. This field is present iff
35498 the @samp{found} field has value of @samp{1}.
35501 The index of the found tracepoint. This field is present iff
35502 the @samp{found} field has value of @samp{1}.
35505 The information about the frame corresponding to the found trace
35506 frame. This field is present only if a trace frame was found.
35507 @xref{GDB/MI Frame Information}, for description of this field.
35511 @subsubheading @value{GDBN} Command
35513 The corresponding @value{GDBN} command is @samp{tfind}.
35515 @subheading -trace-define-variable
35516 @findex -trace-define-variable
35518 @subsubheading Synopsis
35521 -trace-define-variable @var{name} [ @var{value} ]
35524 Create trace variable @var{name} if it does not exist. If
35525 @var{value} is specified, sets the initial value of the specified
35526 trace variable to that value. Note that the @var{name} should start
35527 with the @samp{$} character.
35529 @subsubheading @value{GDBN} Command
35531 The corresponding @value{GDBN} command is @samp{tvariable}.
35533 @subheading The @code{-trace-frame-collected} Command
35534 @findex -trace-frame-collected
35536 @subsubheading Synopsis
35539 -trace-frame-collected
35540 [--var-print-values @var{var_pval}]
35541 [--comp-print-values @var{comp_pval}]
35542 [--registers-format @var{regformat}]
35543 [--memory-contents]
35546 This command returns the set of collected objects, register names,
35547 trace state variable names, memory ranges and computed expressions
35548 that have been collected at a particular trace frame. The optional
35549 parameters to the command affect the output format in different ways.
35550 See the output description table below for more details.
35552 The reported names can be used in the normal manner to create
35553 varobjs and inspect the objects themselves. The items returned by
35554 this command are categorized so that it is clear which is a variable,
35555 which is a register, which is a trace state variable, which is a
35556 memory range and which is a computed expression.
35558 For instance, if the actions were
35560 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
35561 collect *(int*)0xaf02bef0@@40
35565 the object collected in its entirety would be @code{myVar}. The
35566 object @code{myArray} would be partially collected, because only the
35567 element at index @code{myIndex} would be collected. The remaining
35568 objects would be computed expressions.
35570 An example output would be:
35574 -trace-frame-collected
35576 explicit-variables=[@{name="myVar",value="1"@}],
35577 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
35578 @{name="myObj.field",value="0"@},
35579 @{name="myPtr->field",value="1"@},
35580 @{name="myCount + 2",value="3"@},
35581 @{name="$tvar1 + 1",value="43970027"@}],
35582 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35583 @{number="1",value="0x0"@},
35584 @{number="2",value="0x4"@},
35586 @{number="125",value="0x0"@}],
35587 tvars=[@{name="$tvar1",current="43970026"@}],
35588 memory=[@{address="0x0000000000602264",length="4"@},
35589 @{address="0x0000000000615bc0",length="4"@}]
35596 @item explicit-variables
35597 The set of objects that have been collected in their entirety (as
35598 opposed to collecting just a few elements of an array or a few struct
35599 members). For each object, its name and value are printed.
35600 The @code{--var-print-values} option affects how or whether the value
35601 field is output. If @var{var_pval} is 0, then print only the names;
35602 if it is 1, print also their values; and if it is 2, print the name,
35603 type and value for simple data types, and the name and type for
35604 arrays, structures and unions.
35606 @item computed-expressions
35607 The set of computed expressions that have been collected at the
35608 current trace frame. The @code{--comp-print-values} option affects
35609 this set like the @code{--var-print-values} option affects the
35610 @code{explicit-variables} set. See above.
35613 The registers that have been collected at the current trace frame.
35614 For each register collected, the name and current value are returned.
35615 The value is formatted according to the @code{--registers-format}
35616 option. See the @command{-data-list-register-values} command for a
35617 list of the allowed formats. The default is @samp{x}.
35620 The trace state variables that have been collected at the current
35621 trace frame. For each trace state variable collected, the name and
35622 current value are returned.
35625 The set of memory ranges that have been collected at the current trace
35626 frame. Its content is a list of tuples. Each tuple represents a
35627 collected memory range and has the following fields:
35631 The start address of the memory range, as hexadecimal literal.
35634 The length of the memory range, as decimal literal.
35637 The contents of the memory block, in hex. This field is only present
35638 if the @code{--memory-contents} option is specified.
35644 @subsubheading @value{GDBN} Command
35646 There is no corresponding @value{GDBN} command.
35648 @subsubheading Example
35650 @subheading -trace-list-variables
35651 @findex -trace-list-variables
35653 @subsubheading Synopsis
35656 -trace-list-variables
35659 Return a table of all defined trace variables. Each element of the
35660 table has the following fields:
35664 The name of the trace variable. This field is always present.
35667 The initial value. This is a 64-bit signed integer. This
35668 field is always present.
35671 The value the trace variable has at the moment. This is a 64-bit
35672 signed integer. This field is absent iff current value is
35673 not defined, for example if the trace was never run, or is
35678 @subsubheading @value{GDBN} Command
35680 The corresponding @value{GDBN} command is @samp{tvariables}.
35682 @subsubheading Example
35686 -trace-list-variables
35687 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35688 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35689 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35690 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35691 body=[variable=@{name="$trace_timestamp",initial="0"@}
35692 variable=@{name="$foo",initial="10",current="15"@}]@}
35696 @subheading -trace-save
35697 @findex -trace-save
35699 @subsubheading Synopsis
35702 -trace-save [ -r ] [ -ctf ] @var{filename}
35705 Saves the collected trace data to @var{filename}. Without the
35706 @samp{-r} option, the data is downloaded from the target and saved
35707 in a local file. With the @samp{-r} option the target is asked
35708 to perform the save.
35710 By default, this command will save the trace in the tfile format. You can
35711 supply the optional @samp{-ctf} argument to save it the CTF format. See
35712 @ref{Trace Files} for more information about CTF.
35714 @subsubheading @value{GDBN} Command
35716 The corresponding @value{GDBN} command is @samp{tsave}.
35719 @subheading -trace-start
35720 @findex -trace-start
35722 @subsubheading Synopsis
35728 Starts a tracing experiment. The result of this command does not
35731 @subsubheading @value{GDBN} Command
35733 The corresponding @value{GDBN} command is @samp{tstart}.
35735 @subheading -trace-status
35736 @findex -trace-status
35738 @subsubheading Synopsis
35744 Obtains the status of a tracing experiment. The result may include
35745 the following fields:
35750 May have a value of either @samp{0}, when no tracing operations are
35751 supported, @samp{1}, when all tracing operations are supported, or
35752 @samp{file} when examining trace file. In the latter case, examining
35753 of trace frame is possible but new tracing experiement cannot be
35754 started. This field is always present.
35757 May have a value of either @samp{0} or @samp{1} depending on whether
35758 tracing experiement is in progress on target. This field is present
35759 if @samp{supported} field is not @samp{0}.
35762 Report the reason why the tracing was stopped last time. This field
35763 may be absent iff tracing was never stopped on target yet. The
35764 value of @samp{request} means the tracing was stopped as result of
35765 the @code{-trace-stop} command. The value of @samp{overflow} means
35766 the tracing buffer is full. The value of @samp{disconnection} means
35767 tracing was automatically stopped when @value{GDBN} has disconnected.
35768 The value of @samp{passcount} means tracing was stopped when a
35769 tracepoint was passed a maximal number of times for that tracepoint.
35770 This field is present if @samp{supported} field is not @samp{0}.
35772 @item stopping-tracepoint
35773 The number of tracepoint whose passcount as exceeded. This field is
35774 present iff the @samp{stop-reason} field has the value of
35778 @itemx frames-created
35779 The @samp{frames} field is a count of the total number of trace frames
35780 in the trace buffer, while @samp{frames-created} is the total created
35781 during the run, including ones that were discarded, such as when a
35782 circular trace buffer filled up. Both fields are optional.
35786 These fields tell the current size of the tracing buffer and the
35787 remaining space. These fields are optional.
35790 The value of the circular trace buffer flag. @code{1} means that the
35791 trace buffer is circular and old trace frames will be discarded if
35792 necessary to make room, @code{0} means that the trace buffer is linear
35796 The value of the disconnected tracing flag. @code{1} means that
35797 tracing will continue after @value{GDBN} disconnects, @code{0} means
35798 that the trace run will stop.
35801 The filename of the trace file being examined. This field is
35802 optional, and only present when examining a trace file.
35806 @subsubheading @value{GDBN} Command
35808 The corresponding @value{GDBN} command is @samp{tstatus}.
35810 @subheading -trace-stop
35811 @findex -trace-stop
35813 @subsubheading Synopsis
35819 Stops a tracing experiment. The result of this command has the same
35820 fields as @code{-trace-status}, except that the @samp{supported} and
35821 @samp{running} fields are not output.
35823 @subsubheading @value{GDBN} Command
35825 The corresponding @value{GDBN} command is @samp{tstop}.
35828 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35829 @node GDB/MI Symbol Query
35830 @section @sc{gdb/mi} Symbol Query Commands
35834 @subheading The @code{-symbol-info-address} Command
35835 @findex -symbol-info-address
35837 @subsubheading Synopsis
35840 -symbol-info-address @var{symbol}
35843 Describe where @var{symbol} is stored.
35845 @subsubheading @value{GDBN} Command
35847 The corresponding @value{GDBN} command is @samp{info address}.
35849 @subsubheading Example
35853 @subheading The @code{-symbol-info-file} Command
35854 @findex -symbol-info-file
35856 @subsubheading Synopsis
35862 Show the file for the symbol.
35864 @subsubheading @value{GDBN} Command
35866 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35867 @samp{gdb_find_file}.
35869 @subsubheading Example
35873 @subheading The @code{-symbol-info-functions} Command
35874 @findex -symbol-info-functions
35875 @anchor{-symbol-info-functions}
35877 @subsubheading Synopsis
35880 -symbol-info-functions [--include-nondebug]
35881 [--type @var{type_regexp}]
35882 [--name @var{name_regexp}]
35883 [--max-results @var{limit}]
35887 Return a list containing the names and types for all global functions
35888 taken from the debug information. The functions are grouped by source
35889 file, and shown with the line number on which each function is
35892 The @code{--include-nondebug} option causes the output to include
35893 code symbols from the symbol table.
35895 The options @code{--type} and @code{--name} allow the symbols returned
35896 to be filtered based on either the name of the function, or the type
35897 signature of the function.
35899 The option @code{--max-results} restricts the command to return no
35900 more than @var{limit} results. If exactly @var{limit} results are
35901 returned then there might be additional results available if a higher
35904 @subsubheading @value{GDBN} Command
35906 The corresponding @value{GDBN} command is @samp{info functions}.
35908 @subsubheading Example
35912 -symbol-info-functions
35915 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35916 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35917 symbols=[@{line="36", name="f4", type="void (int *)",
35918 description="void f4(int *);"@},
35919 @{line="42", name="main", type="int ()",
35920 description="int main();"@},
35921 @{line="30", name="f1", type="my_int_t (int, int)",
35922 description="static my_int_t f1(int, int);"@}]@},
35923 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35924 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35925 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35926 description="float f2(another_float_t);"@},
35927 @{line="39", name="f3", type="int (another_int_t)",
35928 description="int f3(another_int_t);"@},
35929 @{line="27", name="f1", type="another_float_t (int)",
35930 description="static another_float_t f1(int);"@}]@}]@}
35934 -symbol-info-functions --name f1
35937 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35938 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35939 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35940 description="static my_int_t f1(int, int);"@}]@},
35941 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35942 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35943 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35944 description="static another_float_t f1(int);"@}]@}]@}
35948 -symbol-info-functions --type void
35951 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35952 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35953 symbols=[@{line="36", name="f4", type="void (int *)",
35954 description="void f4(int *);"@}]@}]@}
35958 -symbol-info-functions --include-nondebug
35961 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35962 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35963 symbols=[@{line="36", name="f4", type="void (int *)",
35964 description="void f4(int *);"@},
35965 @{line="42", name="main", type="int ()",
35966 description="int main();"@},
35967 @{line="30", name="f1", type="my_int_t (int, int)",
35968 description="static my_int_t f1(int, int);"@}]@},
35969 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35970 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35971 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35972 description="float f2(another_float_t);"@},
35973 @{line="39", name="f3", type="int (another_int_t)",
35974 description="int f3(another_int_t);"@},
35975 @{line="27", name="f1", type="another_float_t (int)",
35976 description="static another_float_t f1(int);"@}]@}],
35978 [@{address="0x0000000000400398",name="_init"@},
35979 @{address="0x00000000004003b0",name="_start"@},
35985 @subheading The @code{-symbol-info-module-functions} Command
35986 @findex -symbol-info-module-functions
35987 @anchor{-symbol-info-module-functions}
35989 @subsubheading Synopsis
35992 -symbol-info-module-functions [--module @var{module_regexp}]
35993 [--name @var{name_regexp}]
35994 [--type @var{type_regexp}]
35998 Return a list containing the names of all known functions within all
35999 know Fortran modules. The functions are grouped by source file and
36000 containing module, and shown with the line number on which each
36001 function is defined.
36003 The option @code{--module} only returns results for modules matching
36004 @var{module_regexp}. The option @code{--name} only returns functions
36005 whose name matches @var{name_regexp}, and @code{--type} only returns
36006 functions whose type matches @var{type_regexp}.
36008 @subsubheading @value{GDBN} Command
36010 The corresponding @value{GDBN} command is @samp{info module functions}.
36012 @subsubheading Example
36017 -symbol-info-module-functions
36020 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36021 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36022 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
36023 description="void mod1::check_all(void);"@}]@}]@},
36025 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36026 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36027 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
36028 description="void mod2::check_var_i(void);"@}]@}]@},
36030 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36031 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36032 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
36033 description="void mod3::check_all(void);"@},
36034 @{line="27",name="mod3::check_mod2",type="void (void)",
36035 description="void mod3::check_mod2(void);"@}]@}]@},
36036 @{module="modmany",
36037 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36038 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36039 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
36040 description="void modmany::check_some(void);"@}]@}]@},
36042 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36043 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36044 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
36045 description="void moduse::check_all(void);"@},
36046 @{line="49",name="moduse::check_var_x",type="void (void)",
36047 description="void moduse::check_var_x(void);"@}]@}]@}]
36051 @subheading The @code{-symbol-info-module-variables} Command
36052 @findex -symbol-info-module-variables
36053 @anchor{-symbol-info-module-variables}
36055 @subsubheading Synopsis
36058 -symbol-info-module-variables [--module @var{module_regexp}]
36059 [--name @var{name_regexp}]
36060 [--type @var{type_regexp}]
36064 Return a list containing the names of all known variables within all
36065 know Fortran modules. The variables are grouped by source file and
36066 containing module, and shown with the line number on which each
36067 variable is defined.
36069 The option @code{--module} only returns results for modules matching
36070 @var{module_regexp}. The option @code{--name} only returns variables
36071 whose name matches @var{name_regexp}, and @code{--type} only returns
36072 variables whose type matches @var{type_regexp}.
36074 @subsubheading @value{GDBN} Command
36076 The corresponding @value{GDBN} command is @samp{info module variables}.
36078 @subsubheading Example
36083 -symbol-info-module-variables
36086 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36087 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36088 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
36089 description="integer(kind=4) mod1::var_const;"@},
36090 @{line="17",name="mod1::var_i",type="integer(kind=4)",
36091 description="integer(kind=4) mod1::var_i;"@}]@}]@},
36093 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36094 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36095 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
36096 description="integer(kind=4) mod2::var_i;"@}]@}]@},
36098 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36099 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36100 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
36101 description="integer(kind=4) mod3::mod1;"@},
36102 @{line="17",name="mod3::mod2",type="integer(kind=4)",
36103 description="integer(kind=4) mod3::mod2;"@},
36104 @{line="19",name="mod3::var_i",type="integer(kind=4)",
36105 description="integer(kind=4) mod3::var_i;"@}]@}]@},
36106 @{module="modmany",
36107 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36108 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36109 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
36110 description="integer(kind=4) modmany::var_a;"@},
36111 @{line="33",name="modmany::var_b",type="integer(kind=4)",
36112 description="integer(kind=4) modmany::var_b;"@},
36113 @{line="33",name="modmany::var_c",type="integer(kind=4)",
36114 description="integer(kind=4) modmany::var_c;"@},
36115 @{line="33",name="modmany::var_i",type="integer(kind=4)",
36116 description="integer(kind=4) modmany::var_i;"@}]@}]@},
36118 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36119 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36120 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
36121 description="integer(kind=4) moduse::var_x;"@},
36122 @{line="42",name="moduse::var_y",type="integer(kind=4)",
36123 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
36127 @subheading The @code{-symbol-info-modules} Command
36128 @findex -symbol-info-modules
36129 @anchor{-symbol-info-modules}
36131 @subsubheading Synopsis
36134 -symbol-info-modules [--name @var{name_regexp}]
36135 [--max-results @var{limit}]
36140 Return a list containing the names of all known Fortran modules. The
36141 modules are grouped by source file, and shown with the line number on
36142 which each modules is defined.
36144 The option @code{--name} allows the modules returned to be filtered
36145 based the name of the module.
36147 The option @code{--max-results} restricts the command to return no
36148 more than @var{limit} results. If exactly @var{limit} results are
36149 returned then there might be additional results available if a higher
36152 @subsubheading @value{GDBN} Command
36154 The corresponding @value{GDBN} command is @samp{info modules}.
36156 @subsubheading Example
36160 -symbol-info-modules
36163 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36164 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36165 symbols=[@{line="16",name="mod1"@},
36166 @{line="22",name="mod2"@}]@},
36167 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36168 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36169 symbols=[@{line="16",name="mod3"@},
36170 @{line="22",name="modmany"@},
36171 @{line="26",name="moduse"@}]@}]@}
36175 -symbol-info-modules --name mod[123]
36178 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36179 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36180 symbols=[@{line="16",name="mod1"@},
36181 @{line="22",name="mod2"@}]@},
36182 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36183 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36184 symbols=[@{line="16",name="mod3"@}]@}]@}
36188 @subheading The @code{-symbol-info-types} Command
36189 @findex -symbol-info-types
36190 @anchor{-symbol-info-types}
36192 @subsubheading Synopsis
36195 -symbol-info-types [--name @var{name_regexp}]
36196 [--max-results @var{limit}]
36201 Return a list of all defined types. The types are grouped by source
36202 file, and shown with the line number on which each user defined type
36203 is defined. Some base types are not defined in the source code but
36204 are added to the debug information by the compiler, for example
36205 @code{int}, @code{float}, etc.; these types do not have an associated
36208 The option @code{--name} allows the list of types returned to be
36211 The option @code{--max-results} restricts the command to return no
36212 more than @var{limit} results. If exactly @var{limit} results are
36213 returned then there might be additional results available if a higher
36216 @subsubheading @value{GDBN} Command
36218 The corresponding @value{GDBN} command is @samp{info types}.
36220 @subsubheading Example
36227 [@{filename="gdb.mi/mi-sym-info-1.c",
36228 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36229 symbols=[@{name="float"@},
36231 @{line="27",name="typedef int my_int_t;"@}]@},
36232 @{filename="gdb.mi/mi-sym-info-2.c",
36233 fullname="/project/gdb.mi/mi-sym-info-2.c",
36234 symbols=[@{line="24",name="typedef float another_float_t;"@},
36235 @{line="23",name="typedef int another_int_t;"@},
36237 @{name="int"@}]@}]@}
36241 -symbol-info-types --name _int_
36244 [@{filename="gdb.mi/mi-sym-info-1.c",
36245 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36246 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
36247 @{filename="gdb.mi/mi-sym-info-2.c",
36248 fullname="/project/gdb.mi/mi-sym-info-2.c",
36249 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
36253 @subheading The @code{-symbol-info-variables} Command
36254 @findex -symbol-info-variables
36255 @anchor{-symbol-info-variables}
36257 @subsubheading Synopsis
36260 -symbol-info-variables [--include-nondebug]
36261 [--type @var{type_regexp}]
36262 [--name @var{name_regexp}]
36263 [--max-results @var{limit}]
36268 Return a list containing the names and types for all global variables
36269 taken from the debug information. The variables are grouped by source
36270 file, and shown with the line number on which each variable is
36273 The @code{--include-nondebug} option causes the output to include
36274 data symbols from the symbol table.
36276 The options @code{--type} and @code{--name} allow the symbols returned
36277 to be filtered based on either the name of the variable, or the type
36280 The option @code{--max-results} restricts the command to return no
36281 more than @var{limit} results. If exactly @var{limit} results are
36282 returned then there might be additional results available if a higher
36285 @subsubheading @value{GDBN} Command
36287 The corresponding @value{GDBN} command is @samp{info variables}.
36289 @subsubheading Example
36293 -symbol-info-variables
36296 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36297 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36298 symbols=[@{line="25",name="global_f1",type="float",
36299 description="static float global_f1;"@},
36300 @{line="24",name="global_i1",type="int",
36301 description="static int global_i1;"@}]@},
36302 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36303 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36304 symbols=[@{line="21",name="global_f2",type="int",
36305 description="int global_f2;"@},
36306 @{line="20",name="global_i2",type="int",
36307 description="int global_i2;"@},
36308 @{line="19",name="global_f1",type="float",
36309 description="static float global_f1;"@},
36310 @{line="18",name="global_i1",type="int",
36311 description="static int global_i1;"@}]@}]@}
36315 -symbol-info-variables --name f1
36318 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36319 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36320 symbols=[@{line="25",name="global_f1",type="float",
36321 description="static float global_f1;"@}]@},
36322 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36323 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36324 symbols=[@{line="19",name="global_f1",type="float",
36325 description="static float global_f1;"@}]@}]@}
36329 -symbol-info-variables --type float
36332 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36333 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36334 symbols=[@{line="25",name="global_f1",type="float",
36335 description="static float global_f1;"@}]@},
36336 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36337 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36338 symbols=[@{line="19",name="global_f1",type="float",
36339 description="static float global_f1;"@}]@}]@}
36343 -symbol-info-variables --include-nondebug
36346 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36347 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36348 symbols=[@{line="25",name="global_f1",type="float",
36349 description="static float global_f1;"@},
36350 @{line="24",name="global_i1",type="int",
36351 description="static int global_i1;"@}]@},
36352 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36353 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36354 symbols=[@{line="21",name="global_f2",type="int",
36355 description="int global_f2;"@},
36356 @{line="20",name="global_i2",type="int",
36357 description="int global_i2;"@},
36358 @{line="19",name="global_f1",type="float",
36359 description="static float global_f1;"@},
36360 @{line="18",name="global_i1",type="int",
36361 description="static int global_i1;"@}]@}],
36363 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
36364 @{address="0x00000000004005d8",name="__dso_handle"@}
36371 @subheading The @code{-symbol-info-line} Command
36372 @findex -symbol-info-line
36374 @subsubheading Synopsis
36380 Show the core addresses of the code for a source line.
36382 @subsubheading @value{GDBN} Command
36384 The corresponding @value{GDBN} command is @samp{info line}.
36385 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
36387 @subsubheading Example
36391 @subheading The @code{-symbol-info-symbol} Command
36392 @findex -symbol-info-symbol
36394 @subsubheading Synopsis
36397 -symbol-info-symbol @var{addr}
36400 Describe what symbol is at location @var{addr}.
36402 @subsubheading @value{GDBN} Command
36404 The corresponding @value{GDBN} command is @samp{info symbol}.
36406 @subsubheading Example
36410 @subheading The @code{-symbol-list-functions} Command
36411 @findex -symbol-list-functions
36413 @subsubheading Synopsis
36416 -symbol-list-functions
36419 List the functions in the executable.
36421 @subsubheading @value{GDBN} Command
36423 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
36424 @samp{gdb_search} in @code{gdbtk}.
36426 @subsubheading Example
36431 @subheading The @code{-symbol-list-lines} Command
36432 @findex -symbol-list-lines
36434 @subsubheading Synopsis
36437 -symbol-list-lines @var{filename}
36440 Print the list of lines that contain code and their associated program
36441 addresses for the given source filename. The entries are sorted in
36442 ascending PC order.
36444 @subsubheading @value{GDBN} Command
36446 There is no corresponding @value{GDBN} command.
36448 @subsubheading Example
36451 -symbol-list-lines basics.c
36452 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
36458 @subheading The @code{-symbol-list-types} Command
36459 @findex -symbol-list-types
36461 @subsubheading Synopsis
36467 List all the type names.
36469 @subsubheading @value{GDBN} Command
36471 The corresponding commands are @samp{info types} in @value{GDBN},
36472 @samp{gdb_search} in @code{gdbtk}.
36474 @subsubheading Example
36478 @subheading The @code{-symbol-list-variables} Command
36479 @findex -symbol-list-variables
36481 @subsubheading Synopsis
36484 -symbol-list-variables
36487 List all the global and static variable names.
36489 @subsubheading @value{GDBN} Command
36491 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
36493 @subsubheading Example
36497 @subheading The @code{-symbol-locate} Command
36498 @findex -symbol-locate
36500 @subsubheading Synopsis
36506 @subsubheading @value{GDBN} Command
36508 @samp{gdb_loc} in @code{gdbtk}.
36510 @subsubheading Example
36514 @subheading The @code{-symbol-type} Command
36515 @findex -symbol-type
36517 @subsubheading Synopsis
36520 -symbol-type @var{variable}
36523 Show type of @var{variable}.
36525 @subsubheading @value{GDBN} Command
36527 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
36528 @samp{gdb_obj_variable}.
36530 @subsubheading Example
36535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36536 @node GDB/MI File Commands
36537 @section @sc{gdb/mi} File Commands
36539 This section describes the GDB/MI commands to specify executable file names
36540 and to read in and obtain symbol table information.
36542 @subheading The @code{-file-exec-and-symbols} Command
36543 @findex -file-exec-and-symbols
36545 @subsubheading Synopsis
36548 -file-exec-and-symbols @var{file}
36551 Specify the executable file to be debugged. This file is the one from
36552 which the symbol table is also read. If no file is specified, the
36553 command clears the executable and symbol information. If breakpoints
36554 are set when using this command with no arguments, @value{GDBN} will produce
36555 error messages. Otherwise, no output is produced, except a completion
36558 @subsubheading @value{GDBN} Command
36560 The corresponding @value{GDBN} command is @samp{file}.
36562 @subsubheading Example
36566 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36572 @subheading The @code{-file-exec-file} Command
36573 @findex -file-exec-file
36575 @subsubheading Synopsis
36578 -file-exec-file @var{file}
36581 Specify the executable file to be debugged. Unlike
36582 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36583 from this file. If used without argument, @value{GDBN} clears the information
36584 about the executable file. No output is produced, except a completion
36587 @subsubheading @value{GDBN} Command
36589 The corresponding @value{GDBN} command is @samp{exec-file}.
36591 @subsubheading Example
36595 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36602 @subheading The @code{-file-list-exec-sections} Command
36603 @findex -file-list-exec-sections
36605 @subsubheading Synopsis
36608 -file-list-exec-sections
36611 List the sections of the current executable file.
36613 @subsubheading @value{GDBN} Command
36615 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36616 information as this command. @code{gdbtk} has a corresponding command
36617 @samp{gdb_load_info}.
36619 @subsubheading Example
36624 @subheading The @code{-file-list-exec-source-file} Command
36625 @findex -file-list-exec-source-file
36627 @subsubheading Synopsis
36630 -file-list-exec-source-file
36633 List the line number, the current source file, and the absolute path
36634 to the current source file for the current executable. The macro
36635 information field has a value of @samp{1} or @samp{0} depending on
36636 whether or not the file includes preprocessor macro information.
36638 @subsubheading @value{GDBN} Command
36640 The @value{GDBN} equivalent is @samp{info source}
36642 @subsubheading Example
36646 123-file-list-exec-source-file
36647 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36652 @subheading The @code{-file-list-exec-source-files} Command
36653 @kindex info sources
36654 @findex -file-list-exec-source-files
36656 @subsubheading Synopsis
36659 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36660 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36662 @r{[} @var{regexp} @r{]}
36665 This command returns information about the source files @value{GDBN}
36666 knows about, it will output both the filename and fullname (absolute
36667 file name) of a source file, though the fullname can be elided if this
36668 information is not known to @value{GDBN}.
36670 With no arguments this command returns a list of source files. Each
36671 source file is represented by a tuple with the fields; @var{file},
36672 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36673 display name for the file, while @var{fullname} is the absolute name
36674 of the file. The @var{fullname} field can be elided if the absolute
36675 name of the source file can't be computed. The field
36676 @var{debug-fully-read} will be a string, either @code{true} or
36677 @code{false}. When @code{true}, this indicates the full debug
36678 information for the compilation unit describing this file has been
36679 read in. When @code{false}, the full debug information has not yet
36680 been read in. While reading in the full debug information it is
36681 possible that @value{GDBN} could become aware of additional source
36684 The optional @var{regexp} can be used to filter the list of source
36685 files returned. The @var{regexp} will be matched against the full
36686 source file name. The matching is case-sensitive, except on operating
36687 systems that have case-insensitive filesystem (e.g.,
36688 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36689 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36690 @var{regexp} starts with @samp{-}).
36692 If @code{--dirname} is provided, then @var{regexp} is matched only
36693 against the directory name of each source file. If @code{--basename}
36694 is provided, then @var{regexp} is matched against the basename of each
36695 source file. Only one of @code{--dirname} or @code{--basename} may be
36696 given, and if either is given then @var{regexp} is required.
36698 If @code{--group-by-objfile} is used then the format of the results is
36699 changed. The results will now be a list of tuples, with each tuple
36700 representing an object file (executable or shared library) loaded into
36701 @value{GDBN}. The fields of these tuples are; @var{filename},
36702 @var{debug-info}, and @var{sources}. The @var{filename} is the
36703 absolute name of the object file, @var{debug-info} is a string with
36704 one of the following values:
36708 This object file has no debug information.
36709 @item partially-read
36710 This object file has debug information, but it is not fully read in
36711 yet. When it is read in later, GDB might become aware of additional
36714 This object file has debug information, and this information is fully
36715 read into GDB. The list of source files is complete.
36718 The @var{sources} is a list or tuples, with each tuple describing a
36719 single source file with the same fields as described previously. The
36720 @var{sources} list can be empty for object files that have no debug
36723 @subsubheading @value{GDBN} Command
36725 The @value{GDBN} equivalent is @samp{info sources}.
36726 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36728 @subsubheading Example
36731 -file-list-exec-source-files
36732 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36733 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36734 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36736 -file-list-exec-source-files
36737 ^done,files=[@{file="test.c",
36738 fullname="/tmp/info-sources/test.c",
36739 debug-fully-read="true"@},
36740 @{file="/usr/include/stdc-predef.h",
36741 fullname="/usr/include/stdc-predef.h",
36742 debug-fully-read="true"@},
36744 fullname="/tmp/info-sources/header.h",
36745 debug-fully-read="true"@},
36747 fullname="/tmp/info-sources/helper.c",
36748 debug-fully-read="true"@}]
36750 -file-list-exec-source-files -- \\.c
36751 ^done,files=[@{file="test.c",
36752 fullname="/tmp/info-sources/test.c",
36753 debug-fully-read="true"@},
36755 fullname="/tmp/info-sources/helper.c",
36756 debug-fully-read="true"@}]
36758 -file-list-exec-source-files --group-by-objfile
36759 ^done,files=[@{filename="/tmp/info-sources/test.x",
36760 debug-info="fully-read",
36761 sources=[@{file="test.c",
36762 fullname="/tmp/info-sources/test.c",
36763 debug-fully-read="true"@},
36764 @{file="/usr/include/stdc-predef.h",
36765 fullname="/usr/include/stdc-predef.h",
36766 debug-fully-read="true"@},
36768 fullname="/tmp/info-sources/header.h",
36769 debug-fully-read="true"@}]@},
36770 @{filename="/lib64/ld-linux-x86-64.so.2",
36773 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36776 @{filename="/tmp/info-sources/libhelper.so",
36777 debug-info="fully-read",
36778 sources=[@{file="helper.c",
36779 fullname="/tmp/info-sources/helper.c",
36780 debug-fully-read="true"@},
36781 @{file="/usr/include/stdc-predef.h",
36782 fullname="/usr/include/stdc-predef.h",
36783 debug-fully-read="true"@},
36785 fullname="/tmp/info-sources/header.h",
36786 debug-fully-read="true"@}]@},
36787 @{filename="/lib64/libc.so.6",
36792 @subheading The @code{-file-list-shared-libraries} Command
36793 @findex -file-list-shared-libraries
36795 @subsubheading Synopsis
36798 -file-list-shared-libraries [ @var{regexp} ]
36801 List the shared libraries in the program.
36802 With a regular expression @var{regexp}, only those libraries whose
36803 names match @var{regexp} are listed.
36805 @subsubheading @value{GDBN} Command
36807 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36808 have a similar meaning to the @code{=library-loaded} notification.
36809 The @code{ranges} field specifies the multiple segments belonging to this
36810 library. Each range has the following fields:
36814 The address defining the inclusive lower bound of the segment.
36816 The address defining the exclusive upper bound of the segment.
36819 @subsubheading Example
36822 -file-list-exec-source-files
36823 ^done,shared-libraries=[
36824 @{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"@}]@},
36825 @{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"@}]@}]
36831 @subheading The @code{-file-list-symbol-files} Command
36832 @findex -file-list-symbol-files
36834 @subsubheading Synopsis
36837 -file-list-symbol-files
36842 @subsubheading @value{GDBN} Command
36844 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36846 @subsubheading Example
36851 @subheading The @code{-file-symbol-file} Command
36852 @findex -file-symbol-file
36854 @subsubheading Synopsis
36857 -file-symbol-file @var{file}
36860 Read symbol table info from the specified @var{file} argument. When
36861 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36862 produced, except for a completion notification.
36864 @subsubheading @value{GDBN} Command
36866 The corresponding @value{GDBN} command is @samp{symbol-file}.
36868 @subsubheading Example
36872 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36878 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36879 @node GDB/MI Memory Overlay Commands
36880 @section @sc{gdb/mi} Memory Overlay Commands
36882 The memory overlay commands are not implemented.
36884 @c @subheading -overlay-auto
36886 @c @subheading -overlay-list-mapping-state
36888 @c @subheading -overlay-list-overlays
36890 @c @subheading -overlay-map
36892 @c @subheading -overlay-off
36894 @c @subheading -overlay-on
36896 @c @subheading -overlay-unmap
36898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36899 @node GDB/MI Signal Handling Commands
36900 @section @sc{gdb/mi} Signal Handling Commands
36902 Signal handling commands are not implemented.
36904 @c @subheading -signal-handle
36906 @c @subheading -signal-list-handle-actions
36908 @c @subheading -signal-list-signal-types
36912 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36913 @node GDB/MI Target Manipulation
36914 @section @sc{gdb/mi} Target Manipulation Commands
36917 @subheading The @code{-target-attach} Command
36918 @findex -target-attach
36920 @subsubheading Synopsis
36923 -target-attach @var{pid} | @var{gid} | @var{file}
36926 Attach to a process @var{pid} or a file @var{file} outside of
36927 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36928 group, the id previously returned by
36929 @samp{-list-thread-groups --available} must be used.
36931 @subsubheading @value{GDBN} Command
36933 The corresponding @value{GDBN} command is @samp{attach}.
36935 @subsubheading Example
36939 =thread-created,id="1"
36940 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36946 @subheading The @code{-target-compare-sections} Command
36947 @findex -target-compare-sections
36949 @subsubheading Synopsis
36952 -target-compare-sections [ @var{section} ]
36955 Compare data of section @var{section} on target to the exec file.
36956 Without the argument, all sections are compared.
36958 @subsubheading @value{GDBN} Command
36960 The @value{GDBN} equivalent is @samp{compare-sections}.
36962 @subsubheading Example
36967 @subheading The @code{-target-detach} Command
36968 @findex -target-detach
36970 @subsubheading Synopsis
36973 -target-detach [ @var{pid} | @var{gid} ]
36976 Detach from the remote target which normally resumes its execution.
36977 If either @var{pid} or @var{gid} is specified, detaches from either
36978 the specified process, or specified thread group. There's no output.
36980 @subsubheading @value{GDBN} Command
36982 The corresponding @value{GDBN} command is @samp{detach}.
36984 @subsubheading Example
36994 @subheading The @code{-target-disconnect} Command
36995 @findex -target-disconnect
36997 @subsubheading Synopsis
37003 Disconnect from the remote target. There's no output and the target is
37004 generally not resumed.
37006 @subsubheading @value{GDBN} Command
37008 The corresponding @value{GDBN} command is @samp{disconnect}.
37010 @subsubheading Example
37020 @subheading The @code{-target-download} Command
37021 @findex -target-download
37023 @subsubheading Synopsis
37029 Loads the executable onto the remote target.
37030 It prints out an update message every half second, which includes the fields:
37034 The name of the section.
37036 The size of what has been sent so far for that section.
37038 The size of the section.
37040 The total size of what was sent so far (the current and the previous sections).
37042 The size of the overall executable to download.
37046 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
37047 @sc{gdb/mi} Output Syntax}).
37049 In addition, it prints the name and size of the sections, as they are
37050 downloaded. These messages include the following fields:
37054 The name of the section.
37056 The size of the section.
37058 The size of the overall executable to download.
37062 At the end, a summary is printed.
37064 @subsubheading @value{GDBN} Command
37066 The corresponding @value{GDBN} command is @samp{load}.
37068 @subsubheading Example
37070 Note: each status message appears on a single line. Here the messages
37071 have been broken down so that they can fit onto a page.
37076 +download,@{section=".text",section-size="6668",total-size="9880"@}
37077 +download,@{section=".text",section-sent="512",section-size="6668",
37078 total-sent="512",total-size="9880"@}
37079 +download,@{section=".text",section-sent="1024",section-size="6668",
37080 total-sent="1024",total-size="9880"@}
37081 +download,@{section=".text",section-sent="1536",section-size="6668",
37082 total-sent="1536",total-size="9880"@}
37083 +download,@{section=".text",section-sent="2048",section-size="6668",
37084 total-sent="2048",total-size="9880"@}
37085 +download,@{section=".text",section-sent="2560",section-size="6668",
37086 total-sent="2560",total-size="9880"@}
37087 +download,@{section=".text",section-sent="3072",section-size="6668",
37088 total-sent="3072",total-size="9880"@}
37089 +download,@{section=".text",section-sent="3584",section-size="6668",
37090 total-sent="3584",total-size="9880"@}
37091 +download,@{section=".text",section-sent="4096",section-size="6668",
37092 total-sent="4096",total-size="9880"@}
37093 +download,@{section=".text",section-sent="4608",section-size="6668",
37094 total-sent="4608",total-size="9880"@}
37095 +download,@{section=".text",section-sent="5120",section-size="6668",
37096 total-sent="5120",total-size="9880"@}
37097 +download,@{section=".text",section-sent="5632",section-size="6668",
37098 total-sent="5632",total-size="9880"@}
37099 +download,@{section=".text",section-sent="6144",section-size="6668",
37100 total-sent="6144",total-size="9880"@}
37101 +download,@{section=".text",section-sent="6656",section-size="6668",
37102 total-sent="6656",total-size="9880"@}
37103 +download,@{section=".init",section-size="28",total-size="9880"@}
37104 +download,@{section=".fini",section-size="28",total-size="9880"@}
37105 +download,@{section=".data",section-size="3156",total-size="9880"@}
37106 +download,@{section=".data",section-sent="512",section-size="3156",
37107 total-sent="7236",total-size="9880"@}
37108 +download,@{section=".data",section-sent="1024",section-size="3156",
37109 total-sent="7748",total-size="9880"@}
37110 +download,@{section=".data",section-sent="1536",section-size="3156",
37111 total-sent="8260",total-size="9880"@}
37112 +download,@{section=".data",section-sent="2048",section-size="3156",
37113 total-sent="8772",total-size="9880"@}
37114 +download,@{section=".data",section-sent="2560",section-size="3156",
37115 total-sent="9284",total-size="9880"@}
37116 +download,@{section=".data",section-sent="3072",section-size="3156",
37117 total-sent="9796",total-size="9880"@}
37118 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
37125 @subheading The @code{-target-exec-status} Command
37126 @findex -target-exec-status
37128 @subsubheading Synopsis
37131 -target-exec-status
37134 Provide information on the state of the target (whether it is running or
37135 not, for instance).
37137 @subsubheading @value{GDBN} Command
37139 There's no equivalent @value{GDBN} command.
37141 @subsubheading Example
37145 @subheading The @code{-target-list-available-targets} Command
37146 @findex -target-list-available-targets
37148 @subsubheading Synopsis
37151 -target-list-available-targets
37154 List the possible targets to connect to.
37156 @subsubheading @value{GDBN} Command
37158 The corresponding @value{GDBN} command is @samp{help target}.
37160 @subsubheading Example
37164 @subheading The @code{-target-list-current-targets} Command
37165 @findex -target-list-current-targets
37167 @subsubheading Synopsis
37170 -target-list-current-targets
37173 Describe the current target.
37175 @subsubheading @value{GDBN} Command
37177 The corresponding information is printed by @samp{info file} (among
37180 @subsubheading Example
37184 @subheading The @code{-target-list-parameters} Command
37185 @findex -target-list-parameters
37187 @subsubheading Synopsis
37190 -target-list-parameters
37196 @subsubheading @value{GDBN} Command
37200 @subsubheading Example
37203 @subheading The @code{-target-flash-erase} Command
37204 @findex -target-flash-erase
37206 @subsubheading Synopsis
37209 -target-flash-erase
37212 Erases all known flash memory regions on the target.
37214 The corresponding @value{GDBN} command is @samp{flash-erase}.
37216 The output is a list of flash regions that have been erased, with starting
37217 addresses and memory region sizes.
37221 -target-flash-erase
37222 ^done,erased-regions=@{address="0x0",size="0x40000"@}
37226 @subheading The @code{-target-select} Command
37227 @findex -target-select
37229 @subsubheading Synopsis
37232 -target-select @var{type} @var{parameters @dots{}}
37235 Connect @value{GDBN} to the remote target. This command takes two args:
37239 The type of target, for instance @samp{remote}, etc.
37240 @item @var{parameters}
37241 Device names, host names and the like. @xref{Target Commands, ,
37242 Commands for Managing Targets}, for more details.
37245 The output is a connection notification, followed by the address at
37246 which the target program is, in the following form:
37249 ^connected,addr="@var{address}",func="@var{function name}",
37250 args=[@var{arg list}]
37253 @subsubheading @value{GDBN} Command
37255 The corresponding @value{GDBN} command is @samp{target}.
37257 @subsubheading Example
37261 -target-select remote /dev/ttya
37262 ^connected,addr="0xfe00a300",func="??",args=[]
37266 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37267 @node GDB/MI File Transfer Commands
37268 @section @sc{gdb/mi} File Transfer Commands
37271 @subheading The @code{-target-file-put} Command
37272 @findex -target-file-put
37274 @subsubheading Synopsis
37277 -target-file-put @var{hostfile} @var{targetfile}
37280 Copy file @var{hostfile} from the host system (the machine running
37281 @value{GDBN}) to @var{targetfile} on the target system.
37283 @subsubheading @value{GDBN} Command
37285 The corresponding @value{GDBN} command is @samp{remote put}.
37287 @subsubheading Example
37291 -target-file-put localfile remotefile
37297 @subheading The @code{-target-file-get} Command
37298 @findex -target-file-get
37300 @subsubheading Synopsis
37303 -target-file-get @var{targetfile} @var{hostfile}
37306 Copy file @var{targetfile} from the target system to @var{hostfile}
37307 on the host system.
37309 @subsubheading @value{GDBN} Command
37311 The corresponding @value{GDBN} command is @samp{remote get}.
37313 @subsubheading Example
37317 -target-file-get remotefile localfile
37323 @subheading The @code{-target-file-delete} Command
37324 @findex -target-file-delete
37326 @subsubheading Synopsis
37329 -target-file-delete @var{targetfile}
37332 Delete @var{targetfile} from the target system.
37334 @subsubheading @value{GDBN} Command
37336 The corresponding @value{GDBN} command is @samp{remote delete}.
37338 @subsubheading Example
37342 -target-file-delete remotefile
37348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37349 @node GDB/MI Ada Exceptions Commands
37350 @section Ada Exceptions @sc{gdb/mi} Commands
37352 @subheading The @code{-info-ada-exceptions} Command
37353 @findex -info-ada-exceptions
37355 @subsubheading Synopsis
37358 -info-ada-exceptions [ @var{regexp}]
37361 List all Ada exceptions defined within the program being debugged.
37362 With a regular expression @var{regexp}, only those exceptions whose
37363 names match @var{regexp} are listed.
37365 @subsubheading @value{GDBN} Command
37367 The corresponding @value{GDBN} command is @samp{info exceptions}.
37369 @subsubheading Result
37371 The result is a table of Ada exceptions. The following columns are
37372 defined for each exception:
37376 The name of the exception.
37379 The address of the exception.
37383 @subsubheading Example
37386 -info-ada-exceptions aint
37387 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
37388 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
37389 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
37390 body=[@{name="constraint_error",address="0x0000000000613da0"@},
37391 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
37394 @subheading Catching Ada Exceptions
37396 The commands describing how to ask @value{GDBN} to stop when a program
37397 raises an exception are described at @ref{Ada Exception GDB/MI
37398 Catchpoint Commands}.
37401 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37402 @node GDB/MI Support Commands
37403 @section @sc{gdb/mi} Support Commands
37405 Since new commands and features get regularly added to @sc{gdb/mi},
37406 some commands are available to help front-ends query the debugger
37407 about support for these capabilities. Similarly, it is also possible
37408 to query @value{GDBN} about target support of certain features.
37410 @subheading The @code{-info-gdb-mi-command} Command
37411 @cindex @code{-info-gdb-mi-command}
37412 @findex -info-gdb-mi-command
37414 @subsubheading Synopsis
37417 -info-gdb-mi-command @var{cmd_name}
37420 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
37422 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
37423 is technically not part of the command name (@pxref{GDB/MI Input
37424 Syntax}), and thus should be omitted in @var{cmd_name}. However,
37425 for ease of use, this command also accepts the form with the leading
37428 @subsubheading @value{GDBN} Command
37430 There is no corresponding @value{GDBN} command.
37432 @subsubheading Result
37434 The result is a tuple. There is currently only one field:
37438 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
37439 @code{"false"} otherwise.
37443 @subsubheading Example
37445 Here is an example where the @sc{gdb/mi} command does not exist:
37448 -info-gdb-mi-command unsupported-command
37449 ^done,command=@{exists="false"@}
37453 And here is an example where the @sc{gdb/mi} command is known
37457 -info-gdb-mi-command symbol-list-lines
37458 ^done,command=@{exists="true"@}
37461 @subheading The @code{-list-features} Command
37462 @findex -list-features
37463 @cindex supported @sc{gdb/mi} features, list
37465 Returns a list of particular features of the MI protocol that
37466 this version of gdb implements. A feature can be a command,
37467 or a new field in an output of some command, or even an
37468 important bugfix. While a frontend can sometimes detect presence
37469 of a feature at runtime, it is easier to perform detection at debugger
37472 The command returns a list of strings, with each string naming an
37473 available feature. Each returned string is just a name, it does not
37474 have any internal structure. The list of possible feature names
37480 (gdb) -list-features
37481 ^done,result=["feature1","feature2"]
37484 The current list of features is:
37487 @item frozen-varobjs
37488 Indicates support for the @code{-var-set-frozen} command, as well
37489 as possible presence of the @code{frozen} field in the output
37490 of @code{-varobj-create}.
37491 @item pending-breakpoints
37492 Indicates support for the @option{-f} option to the @code{-break-insert}
37495 Indicates Python scripting support, Python-based
37496 pretty-printing commands, and possible presence of the
37497 @samp{display_hint} field in the output of @code{-var-list-children}
37499 Indicates support for the @code{-thread-info} command.
37500 @item data-read-memory-bytes
37501 Indicates support for the @code{-data-read-memory-bytes} and the
37502 @code{-data-write-memory-bytes} commands.
37503 @item breakpoint-notifications
37504 Indicates that changes to breakpoints and breakpoints created via the
37505 CLI will be announced via async records.
37506 @item ada-task-info
37507 Indicates support for the @code{-ada-task-info} command.
37508 @item language-option
37509 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
37510 option (@pxref{Context management}).
37511 @item info-gdb-mi-command
37512 Indicates support for the @code{-info-gdb-mi-command} command.
37513 @item undefined-command-error-code
37514 Indicates support for the "undefined-command" error code in error result
37515 records, produced when trying to execute an undefined @sc{gdb/mi} command
37516 (@pxref{GDB/MI Result Records}).
37517 @item exec-run-start-option
37518 Indicates that the @code{-exec-run} command supports the @option{--start}
37519 option (@pxref{GDB/MI Program Execution}).
37520 @item data-disassemble-a-option
37521 Indicates that the @code{-data-disassemble} command supports the @option{-a}
37522 option (@pxref{GDB/MI Data Manipulation}).
37525 @subheading The @code{-list-target-features} Command
37526 @findex -list-target-features
37528 Returns a list of particular features that are supported by the
37529 target. Those features affect the permitted MI commands, but
37530 unlike the features reported by the @code{-list-features} command, the
37531 features depend on which target GDB is using at the moment. Whenever
37532 a target can change, due to commands such as @code{-target-select},
37533 @code{-target-attach} or @code{-exec-run}, the list of target features
37534 may change, and the frontend should obtain it again.
37538 (gdb) -list-target-features
37539 ^done,result=["async"]
37542 The current list of features is:
37546 Indicates that the target is capable of asynchronous command
37547 execution, which means that @value{GDBN} will accept further commands
37548 while the target is running.
37551 Indicates that the target is capable of reverse execution.
37552 @xref{Reverse Execution}, for more information.
37556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37557 @node GDB/MI Miscellaneous Commands
37558 @section Miscellaneous @sc{gdb/mi} Commands
37560 @c @subheading -gdb-complete
37562 @subheading The @code{-gdb-exit} Command
37565 @subsubheading Synopsis
37571 Exit @value{GDBN} immediately.
37573 @subsubheading @value{GDBN} Command
37575 Approximately corresponds to @samp{quit}.
37577 @subsubheading Example
37587 @subheading The @code{-exec-abort} Command
37588 @findex -exec-abort
37590 @subsubheading Synopsis
37596 Kill the inferior running program.
37598 @subsubheading @value{GDBN} Command
37600 The corresponding @value{GDBN} command is @samp{kill}.
37602 @subsubheading Example
37607 @subheading The @code{-gdb-set} Command
37610 @subsubheading Synopsis
37616 Set an internal @value{GDBN} variable.
37617 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37619 @subsubheading @value{GDBN} Command
37621 The corresponding @value{GDBN} command is @samp{set}.
37623 @subsubheading Example
37633 @subheading The @code{-gdb-show} Command
37636 @subsubheading Synopsis
37642 Show the current value of a @value{GDBN} variable.
37644 @subsubheading @value{GDBN} Command
37646 The corresponding @value{GDBN} command is @samp{show}.
37648 @subsubheading Example
37657 @c @subheading -gdb-source
37660 @subheading The @code{-gdb-version} Command
37661 @findex -gdb-version
37663 @subsubheading Synopsis
37669 Show version information for @value{GDBN}. Used mostly in testing.
37671 @subsubheading @value{GDBN} Command
37673 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37674 default shows this information when you start an interactive session.
37676 @subsubheading Example
37678 @c This example modifies the actual output from GDB to avoid overfull
37684 ~Copyright 2000 Free Software Foundation, Inc.
37685 ~GDB is free software, covered by the GNU General Public License, and
37686 ~you are welcome to change it and/or distribute copies of it under
37687 ~ certain conditions.
37688 ~Type "show copying" to see the conditions.
37689 ~There is absolutely no warranty for GDB. Type "show warranty" for
37691 ~This GDB was configured as
37692 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37697 @subheading The @code{-list-thread-groups} Command
37698 @findex -list-thread-groups
37700 @subheading Synopsis
37703 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37706 Lists thread groups (@pxref{Thread groups}). When a single thread
37707 group is passed as the argument, lists the children of that group.
37708 When several thread group are passed, lists information about those
37709 thread groups. Without any parameters, lists information about all
37710 top-level thread groups.
37712 Normally, thread groups that are being debugged are reported.
37713 With the @samp{--available} option, @value{GDBN} reports thread groups
37714 available on the target.
37716 The output of this command may have either a @samp{threads} result or
37717 a @samp{groups} result. The @samp{thread} result has a list of tuples
37718 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37719 Information}). The @samp{groups} result has a list of tuples as value,
37720 each tuple describing a thread group. If top-level groups are
37721 requested (that is, no parameter is passed), or when several groups
37722 are passed, the output always has a @samp{groups} result. The format
37723 of the @samp{group} result is described below.
37725 To reduce the number of roundtrips it's possible to list thread groups
37726 together with their children, by passing the @samp{--recurse} option
37727 and the recursion depth. Presently, only recursion depth of 1 is
37728 permitted. If this option is present, then every reported thread group
37729 will also include its children, either as @samp{group} or
37730 @samp{threads} field.
37732 In general, any combination of option and parameters is permitted, with
37733 the following caveats:
37737 When a single thread group is passed, the output will typically
37738 be the @samp{threads} result. Because threads may not contain
37739 anything, the @samp{recurse} option will be ignored.
37742 When the @samp{--available} option is passed, limited information may
37743 be available. In particular, the list of threads of a process might
37744 be inaccessible. Further, specifying specific thread groups might
37745 not give any performance advantage over listing all thread groups.
37746 The frontend should assume that @samp{-list-thread-groups --available}
37747 is always an expensive operation and cache the results.
37751 The @samp{groups} result is a list of tuples, where each tuple may
37752 have the following fields:
37756 Identifier of the thread group. This field is always present.
37757 The identifier is an opaque string; frontends should not try to
37758 convert it to an integer, even though it might look like one.
37761 The type of the thread group. At present, only @samp{process} is a
37765 The target-specific process identifier. This field is only present
37766 for thread groups of type @samp{process} and only if the process exists.
37769 The exit code of this group's last exited thread, formatted in octal.
37770 This field is only present for thread groups of type @samp{process} and
37771 only if the process is not running.
37774 The number of children this thread group has. This field may be
37775 absent for an available thread group.
37778 This field has a list of tuples as value, each tuple describing a
37779 thread. It may be present if the @samp{--recurse} option is
37780 specified, and it's actually possible to obtain the threads.
37783 This field is a list of integers, each identifying a core that one
37784 thread of the group is running on. This field may be absent if
37785 such information is not available.
37788 The name of the executable file that corresponds to this thread group.
37789 The field is only present for thread groups of type @samp{process},
37790 and only if there is a corresponding executable file.
37794 @subheading Example
37798 -list-thread-groups
37799 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37800 -list-thread-groups 17
37801 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37802 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37803 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37804 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37805 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37806 -list-thread-groups --available
37807 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37808 -list-thread-groups --available --recurse 1
37809 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37810 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37811 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37812 -list-thread-groups --available --recurse 1 17 18
37813 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37814 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37815 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37818 @subheading The @code{-info-os} Command
37821 @subsubheading Synopsis
37824 -info-os [ @var{type} ]
37827 If no argument is supplied, the command returns a table of available
37828 operating-system-specific information types. If one of these types is
37829 supplied as an argument @var{type}, then the command returns a table
37830 of data of that type.
37832 The types of information available depend on the target operating
37835 @subsubheading @value{GDBN} Command
37837 The corresponding @value{GDBN} command is @samp{info os}.
37839 @subsubheading Example
37841 When run on a @sc{gnu}/Linux system, the output will look something
37847 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37848 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37849 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37850 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37851 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37853 item=@{col0="files",col1="Listing of all file descriptors",
37854 col2="File descriptors"@},
37855 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37856 col2="Kernel modules"@},
37857 item=@{col0="msg",col1="Listing of all message queues",
37858 col2="Message queues"@},
37859 item=@{col0="processes",col1="Listing of all processes",
37860 col2="Processes"@},
37861 item=@{col0="procgroups",col1="Listing of all process groups",
37862 col2="Process groups"@},
37863 item=@{col0="semaphores",col1="Listing of all semaphores",
37864 col2="Semaphores"@},
37865 item=@{col0="shm",col1="Listing of all shared-memory regions",
37866 col2="Shared-memory regions"@},
37867 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37869 item=@{col0="threads",col1="Listing of all threads",
37873 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37874 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37875 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37876 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37877 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37878 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37879 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37880 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37882 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37883 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37887 (Note that the MI output here includes a @code{"Title"} column that
37888 does not appear in command-line @code{info os}; this column is useful
37889 for MI clients that want to enumerate the types of data, such as in a
37890 popup menu, but is needless clutter on the command line, and
37891 @code{info os} omits it.)
37893 @subheading The @code{-add-inferior} Command
37894 @findex -add-inferior
37896 @subheading Synopsis
37899 -add-inferior [ --no-connection ]
37902 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37903 inferior is not associated with any executable. Such association may
37904 be established with the @samp{-file-exec-and-symbols} command
37905 (@pxref{GDB/MI File Commands}).
37907 By default, the new inferior begins connected to the same target
37908 connection as the current inferior. For example, if the current
37909 inferior was connected to @code{gdbserver} with @code{target remote},
37910 then the new inferior will be connected to the same @code{gdbserver}
37911 instance. The @samp{--no-connection} option starts the new inferior
37912 with no connection yet. You can then for example use the
37913 @code{-target-select remote} command to connect to some other
37914 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37917 The command response always has a field, @var{inferior}, whose value
37918 is the identifier of the thread group corresponding to the new
37921 An additional section field, @var{connection}, is optional. This
37922 field will only exist if the new inferior has a target connection. If
37923 this field exists, then its value will be a tuple containing the
37928 The number of the connection used for the new inferior.
37931 The name of the connection type used for the new inferior.
37934 @subheading @value{GDBN} Command
37936 The corresponding @value{GDBN} command is @samp{add-inferior}
37937 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37939 @subheading Example
37944 ^done,inferior="i3"
37947 @subheading The @code{-interpreter-exec} Command
37948 @findex -interpreter-exec
37950 @subheading Synopsis
37953 -interpreter-exec @var{interpreter} @var{command}
37955 @anchor{-interpreter-exec}
37957 Execute the specified @var{command} in the given @var{interpreter}.
37959 @subheading @value{GDBN} Command
37961 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37963 @subheading Example
37967 -interpreter-exec console "break main"
37968 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37969 &"During symbol reading, bad structure-type format.\n"
37970 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37975 @subheading The @code{-inferior-tty-set} Command
37976 @findex -inferior-tty-set
37978 @subheading Synopsis
37981 -inferior-tty-set /dev/pts/1
37984 Set terminal for future runs of the program being debugged.
37986 @subheading @value{GDBN} Command
37988 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37990 @subheading Example
37994 -inferior-tty-set /dev/pts/1
37999 @subheading The @code{-inferior-tty-show} Command
38000 @findex -inferior-tty-show
38002 @subheading Synopsis
38008 Show terminal for future runs of program being debugged.
38010 @subheading @value{GDBN} Command
38012 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
38014 @subheading Example
38018 -inferior-tty-set /dev/pts/1
38022 ^done,inferior_tty_terminal="/dev/pts/1"
38026 @subheading The @code{-enable-timings} Command
38027 @findex -enable-timings
38029 @subheading Synopsis
38032 -enable-timings [yes | no]
38035 Toggle the printing of the wallclock, user and system times for an MI
38036 command as a field in its output. This command is to help frontend
38037 developers optimize the performance of their code. No argument is
38038 equivalent to @samp{yes}.
38040 @subheading @value{GDBN} Command
38044 @subheading Example
38052 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
38053 addr="0x080484ed",func="main",file="myprog.c",
38054 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
38056 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
38064 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
38065 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
38066 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
38067 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
38071 @subheading The @code{-complete} Command
38074 @subheading Synopsis
38077 -complete @var{command}
38080 Show a list of completions for partially typed CLI @var{command}.
38082 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
38083 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
38084 because @value{GDBN} is used remotely via a SSH connection.
38088 The result consists of two or three fields:
38092 This field contains the completed @var{command}. If @var{command}
38093 has no known completions, this field is omitted.
38096 This field contains a (possibly empty) array of matches. It is always present.
38098 @item max_completions_reached
38099 This field contains @code{1} if number of known completions is above
38100 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
38101 @code{0}. It is always present.
38105 @subheading @value{GDBN} Command
38107 The corresponding @value{GDBN} command is @samp{complete}.
38109 @subheading Example
38114 ^done,completion="break",
38115 matches=["break","break-range"],
38116 max_completions_reached="0"
38119 ^done,completion="b ma",
38120 matches=["b madvise","b main"],max_completions_reached="0"
38122 -complete "b push_b"
38123 ^done,completion="b push_back(",
38125 "b A::push_back(void*)",
38126 "b std::string::push_back(char)",
38127 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
38128 max_completions_reached="0"
38130 -complete "nonexist"
38131 ^done,matches=[],max_completions_reached="0"
38137 @chapter @value{GDBN} Annotations
38139 This chapter describes annotations in @value{GDBN}. Annotations were
38140 designed to interface @value{GDBN} to graphical user interfaces or other
38141 similar programs which want to interact with @value{GDBN} at a
38142 relatively high level.
38144 The annotation mechanism has largely been superseded by @sc{gdb/mi}
38148 This is Edition @value{EDITION}, @value{DATE}.
38152 * Annotations Overview:: What annotations are; the general syntax.
38153 * Server Prefix:: Issuing a command without affecting user state.
38154 * Prompting:: Annotations marking @value{GDBN}'s need for input.
38155 * Errors:: Annotations for error messages.
38156 * Invalidation:: Some annotations describe things now invalid.
38157 * Annotations for Running::
38158 Whether the program is running, how it stopped, etc.
38159 * Source Annotations:: Annotations describing source code.
38162 @node Annotations Overview
38163 @section What is an Annotation?
38164 @cindex annotations
38166 Annotations start with a newline character, two @samp{control-z}
38167 characters, and the name of the annotation. If there is no additional
38168 information associated with this annotation, the name of the annotation
38169 is followed immediately by a newline. If there is additional
38170 information, the name of the annotation is followed by a space, the
38171 additional information, and a newline. The additional information
38172 cannot contain newline characters.
38174 Any output not beginning with a newline and two @samp{control-z}
38175 characters denotes literal output from @value{GDBN}. Currently there is
38176 no need for @value{GDBN} to output a newline followed by two
38177 @samp{control-z} characters, but if there was such a need, the
38178 annotations could be extended with an @samp{escape} annotation which
38179 means those three characters as output.
38181 The annotation @var{level}, which is specified using the
38182 @option{--annotate} command line option (@pxref{Mode Options}), controls
38183 how much information @value{GDBN} prints together with its prompt,
38184 values of expressions, source lines, and other types of output. Level 0
38185 is for no annotations, level 1 is for use when @value{GDBN} is run as a
38186 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
38187 for programs that control @value{GDBN}, and level 2 annotations have
38188 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
38189 Interface, annotate, GDB's Obsolete Annotations}).
38192 @kindex set annotate
38193 @item set annotate @var{level}
38194 The @value{GDBN} command @code{set annotate} sets the level of
38195 annotations to the specified @var{level}.
38197 @item show annotate
38198 @kindex show annotate
38199 Show the current annotation level.
38202 This chapter describes level 3 annotations.
38204 A simple example of starting up @value{GDBN} with annotations is:
38207 $ @kbd{gdb --annotate=3}
38209 Copyright 2003 Free Software Foundation, Inc.
38210 GDB is free software, covered by the GNU General Public License,
38211 and you are welcome to change it and/or distribute copies of it
38212 under certain conditions.
38213 Type "show copying" to see the conditions.
38214 There is absolutely no warranty for GDB. Type "show warranty"
38216 This GDB was configured as "i386-pc-linux-gnu"
38227 Here @samp{quit} is input to @value{GDBN}; the rest is output from
38228 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
38229 denotes a @samp{control-z} character) are annotations; the rest is
38230 output from @value{GDBN}.
38232 @node Server Prefix
38233 @section The Server Prefix
38234 @cindex server prefix
38236 If you prefix a command with @samp{server } then it will not affect
38237 the command history, nor will it affect @value{GDBN}'s notion of which
38238 command to repeat if @key{RET} is pressed on a line by itself. This
38239 means that commands can be run behind a user's back by a front-end in
38240 a transparent manner.
38242 The @code{server } prefix does not affect the recording of values into
38243 the value history; to print a value without recording it into the
38244 value history, use the @code{output} command instead of the
38245 @code{print} command.
38247 Using this prefix also disables confirmation requests
38248 (@pxref{confirmation requests}).
38251 @section Annotation for @value{GDBN} Input
38253 @cindex annotations for prompts
38254 When @value{GDBN} prompts for input, it annotates this fact so it is possible
38255 to know when to send output, when the output from a given command is
38258 Different kinds of input each have a different @dfn{input type}. Each
38259 input type has three annotations: a @code{pre-} annotation, which
38260 denotes the beginning of any prompt which is being output, a plain
38261 annotation, which denotes the end of the prompt, and then a @code{post-}
38262 annotation which denotes the end of any echo which may (or may not) be
38263 associated with the input. For example, the @code{prompt} input type
38264 features the following annotations:
38272 The input types are
38275 @findex pre-prompt annotation
38276 @findex prompt annotation
38277 @findex post-prompt annotation
38279 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
38281 @findex pre-commands annotation
38282 @findex commands annotation
38283 @findex post-commands annotation
38285 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
38286 command. The annotations are repeated for each command which is input.
38288 @findex pre-overload-choice annotation
38289 @findex overload-choice annotation
38290 @findex post-overload-choice annotation
38291 @item overload-choice
38292 When @value{GDBN} wants the user to select between various overloaded functions.
38294 @findex pre-query annotation
38295 @findex query annotation
38296 @findex post-query annotation
38298 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
38300 @findex pre-prompt-for-continue annotation
38301 @findex prompt-for-continue annotation
38302 @findex post-prompt-for-continue annotation
38303 @item prompt-for-continue
38304 When @value{GDBN} is asking the user to press return to continue. Note: Don't
38305 expect this to work well; instead use @code{set height 0} to disable
38306 prompting. This is because the counting of lines is buggy in the
38307 presence of annotations.
38312 @cindex annotations for errors, warnings and interrupts
38314 @findex quit annotation
38319 This annotation occurs right before @value{GDBN} responds to an interrupt.
38321 @findex error annotation
38326 This annotation occurs right before @value{GDBN} responds to an error.
38328 Quit and error annotations indicate that any annotations which @value{GDBN} was
38329 in the middle of may end abruptly. For example, if a
38330 @code{value-history-begin} annotation is followed by a @code{error}, one
38331 cannot expect to receive the matching @code{value-history-end}. One
38332 cannot expect not to receive it either, however; an error annotation
38333 does not necessarily mean that @value{GDBN} is immediately returning all the way
38336 @findex error-begin annotation
38337 A quit or error annotation may be preceded by
38343 Any output between that and the quit or error annotation is the error
38346 Warning messages are not yet annotated.
38347 @c If we want to change that, need to fix warning(), type_error(),
38348 @c range_error(), and possibly other places.
38351 @section Invalidation Notices
38353 @cindex annotations for invalidation messages
38354 The following annotations say that certain pieces of state may have
38358 @findex frames-invalid annotation
38359 @item ^Z^Zframes-invalid
38361 The frames (for example, output from the @code{backtrace} command) may
38364 @findex breakpoints-invalid annotation
38365 @item ^Z^Zbreakpoints-invalid
38367 The breakpoints may have changed. For example, the user just added or
38368 deleted a breakpoint.
38371 @node Annotations for Running
38372 @section Running the Program
38373 @cindex annotations for running programs
38375 @findex starting annotation
38376 @findex stopping annotation
38377 When the program starts executing due to a @value{GDBN} command such as
38378 @code{step} or @code{continue},
38384 is output. When the program stops,
38390 is output. Before the @code{stopped} annotation, a variety of
38391 annotations describe how the program stopped.
38394 @findex exited annotation
38395 @item ^Z^Zexited @var{exit-status}
38396 The program exited, and @var{exit-status} is the exit status (zero for
38397 successful exit, otherwise nonzero).
38399 @findex signalled annotation
38400 @findex signal-name annotation
38401 @findex signal-name-end annotation
38402 @findex signal-string annotation
38403 @findex signal-string-end annotation
38404 @item ^Z^Zsignalled
38405 The program exited with a signal. After the @code{^Z^Zsignalled}, the
38406 annotation continues:
38412 ^Z^Zsignal-name-end
38416 ^Z^Zsignal-string-end
38421 where @var{name} is the name of the signal, such as @code{SIGILL} or
38422 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
38423 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
38424 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
38425 user's benefit and have no particular format.
38427 @findex signal annotation
38429 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
38430 just saying that the program received the signal, not that it was
38431 terminated with it.
38433 @findex breakpoint annotation
38434 @item ^Z^Zbreakpoint @var{number}
38435 The program hit breakpoint number @var{number}.
38437 @findex watchpoint annotation
38438 @item ^Z^Zwatchpoint @var{number}
38439 The program hit watchpoint number @var{number}.
38442 @node Source Annotations
38443 @section Displaying Source
38444 @cindex annotations for source display
38446 @findex source annotation
38447 The following annotation is used instead of displaying source code:
38450 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
38453 where @var{filename} is an absolute file name indicating which source
38454 file, @var{line} is the line number within that file (where 1 is the
38455 first line in the file), @var{character} is the character position
38456 within the file (where 0 is the first character in the file) (for most
38457 debug formats this will necessarily point to the beginning of a line),
38458 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
38459 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
38460 @var{addr} is the address in the target program associated with the
38461 source which is being displayed. The @var{addr} is in the form @samp{0x}
38462 followed by one or more lowercase hex digits (note that this does not
38463 depend on the language).
38465 @node JIT Interface
38466 @chapter JIT Compilation Interface
38467 @cindex just-in-time compilation
38468 @cindex JIT compilation interface
38470 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
38471 interface. A JIT compiler is a program or library that generates native
38472 executable code at runtime and executes it, usually in order to achieve good
38473 performance while maintaining platform independence.
38475 Programs that use JIT compilation are normally difficult to debug because
38476 portions of their code are generated at runtime, instead of being loaded from
38477 object files, which is where @value{GDBN} normally finds the program's symbols
38478 and debug information. In order to debug programs that use JIT compilation,
38479 @value{GDBN} has an interface that allows the program to register in-memory
38480 symbol files with @value{GDBN} at runtime.
38482 If you are using @value{GDBN} to debug a program that uses this interface, then
38483 it should work transparently so long as you have not stripped the binary. If
38484 you are developing a JIT compiler, then the interface is documented in the rest
38485 of this chapter. At this time, the only known client of this interface is the
38488 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
38489 JIT compiler communicates with @value{GDBN} by writing data into a global
38490 variable and calling a function at a well-known symbol. When @value{GDBN}
38491 attaches, it reads a linked list of symbol files from the global variable to
38492 find existing code, and puts a breakpoint in the function so that it can find
38493 out about additional code.
38496 * Declarations:: Relevant C struct declarations
38497 * Registering Code:: Steps to register code
38498 * Unregistering Code:: Steps to unregister code
38499 * Custom Debug Info:: Emit debug information in a custom format
38503 @section JIT Declarations
38505 These are the relevant struct declarations that a C program should include to
38506 implement the interface:
38516 struct jit_code_entry
38518 struct jit_code_entry *next_entry;
38519 struct jit_code_entry *prev_entry;
38520 const char *symfile_addr;
38521 uint64_t symfile_size;
38524 struct jit_descriptor
38527 /* This type should be jit_actions_t, but we use uint32_t
38528 to be explicit about the bitwidth. */
38529 uint32_t action_flag;
38530 struct jit_code_entry *relevant_entry;
38531 struct jit_code_entry *first_entry;
38534 /* GDB puts a breakpoint in this function. */
38535 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
38537 /* Make sure to specify the version statically, because the
38538 debugger may check the version before we can set it. */
38539 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
38542 If the JIT is multi-threaded, then it is important that the JIT synchronize any
38543 modifications to this global data properly, which can easily be done by putting
38544 a global mutex around modifications to these structures.
38546 @node Registering Code
38547 @section Registering Code
38549 To register code with @value{GDBN}, the JIT should follow this protocol:
38553 Generate an object file in memory with symbols and other desired debug
38554 information. The file must include the virtual addresses of the sections.
38557 Create a code entry for the file, which gives the start and size of the symbol
38561 Add it to the linked list in the JIT descriptor.
38564 Point the relevant_entry field of the descriptor at the entry.
38567 Set @code{action_flag} to @code{JIT_REGISTER} and call
38568 @code{__jit_debug_register_code}.
38571 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
38572 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
38573 new code. However, the linked list must still be maintained in order to allow
38574 @value{GDBN} to attach to a running process and still find the symbol files.
38576 @node Unregistering Code
38577 @section Unregistering Code
38579 If code is freed, then the JIT should use the following protocol:
38583 Remove the code entry corresponding to the code from the linked list.
38586 Point the @code{relevant_entry} field of the descriptor at the code entry.
38589 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38590 @code{__jit_debug_register_code}.
38593 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38594 and the JIT will leak the memory used for the associated symbol files.
38596 @node Custom Debug Info
38597 @section Custom Debug Info
38598 @cindex custom JIT debug info
38599 @cindex JIT debug info reader
38601 Generating debug information in platform-native file formats (like ELF
38602 or COFF) may be an overkill for JIT compilers; especially if all the
38603 debug info is used for is displaying a meaningful backtrace. The
38604 issue can be resolved by having the JIT writers decide on a debug info
38605 format and also provide a reader that parses the debug info generated
38606 by the JIT compiler. This section gives a brief overview on writing
38607 such a parser. More specific details can be found in the source file
38608 @file{gdb/jit-reader.in}, which is also installed as a header at
38609 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38611 The reader is implemented as a shared object (so this functionality is
38612 not available on platforms which don't allow loading shared objects at
38613 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38614 @code{jit-reader-unload} are provided, to be used to load and unload
38615 the readers from a preconfigured directory. Once loaded, the shared
38616 object is used the parse the debug information emitted by the JIT
38620 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38621 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38624 @node Using JIT Debug Info Readers
38625 @subsection Using JIT Debug Info Readers
38626 @kindex jit-reader-load
38627 @kindex jit-reader-unload
38629 Readers can be loaded and unloaded using the @code{jit-reader-load}
38630 and @code{jit-reader-unload} commands.
38633 @item jit-reader-load @var{reader}
38634 Load the JIT reader named @var{reader}, which is a shared
38635 object specified as either an absolute or a relative file name. In
38636 the latter case, @value{GDBN} will try to load the reader from a
38637 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38638 system (here @var{libdir} is the system library directory, often
38639 @file{/usr/local/lib}).
38641 Only one reader can be active at a time; trying to load a second
38642 reader when one is already loaded will result in @value{GDBN}
38643 reporting an error. A new JIT reader can be loaded by first unloading
38644 the current one using @code{jit-reader-unload} and then invoking
38645 @code{jit-reader-load}.
38647 @item jit-reader-unload
38648 Unload the currently loaded JIT reader.
38652 @node Writing JIT Debug Info Readers
38653 @subsection Writing JIT Debug Info Readers
38654 @cindex writing JIT debug info readers
38656 As mentioned, a reader is essentially a shared object conforming to a
38657 certain ABI. This ABI is described in @file{jit-reader.h}.
38659 @file{jit-reader.h} defines the structures, macros and functions
38660 required to write a reader. It is installed (along with
38661 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38662 the system include directory.
38664 Readers need to be released under a GPL compatible license. A reader
38665 can be declared as released under such a license by placing the macro
38666 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38668 The entry point for readers is the symbol @code{gdb_init_reader},
38669 which is expected to be a function with the prototype
38671 @findex gdb_init_reader
38673 extern struct gdb_reader_funcs *gdb_init_reader (void);
38676 @cindex @code{struct gdb_reader_funcs}
38678 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38679 functions. These functions are executed to read the debug info
38680 generated by the JIT compiler (@code{read}), to unwind stack frames
38681 (@code{unwind}) and to create canonical frame IDs
38682 (@code{get_frame_id}). It also has a callback that is called when the
38683 reader is being unloaded (@code{destroy}). The struct looks like this
38686 struct gdb_reader_funcs
38688 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38689 int reader_version;
38691 /* For use by the reader. */
38694 gdb_read_debug_info *read;
38695 gdb_unwind_frame *unwind;
38696 gdb_get_frame_id *get_frame_id;
38697 gdb_destroy_reader *destroy;
38701 @cindex @code{struct gdb_symbol_callbacks}
38702 @cindex @code{struct gdb_unwind_callbacks}
38704 The callbacks are provided with another set of callbacks by
38705 @value{GDBN} to do their job. For @code{read}, these callbacks are
38706 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38707 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38708 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38709 files and new symbol tables inside those object files. @code{struct
38710 gdb_unwind_callbacks} has callbacks to read registers off the current
38711 frame and to write out the values of the registers in the previous
38712 frame. Both have a callback (@code{target_read}) to read bytes off the
38713 target's address space.
38715 @node In-Process Agent
38716 @chapter In-Process Agent
38717 @cindex debugging agent
38718 The traditional debugging model is conceptually low-speed, but works fine,
38719 because most bugs can be reproduced in debugging-mode execution. However,
38720 as multi-core or many-core processors are becoming mainstream, and
38721 multi-threaded programs become more and more popular, there should be more
38722 and more bugs that only manifest themselves at normal-mode execution, for
38723 example, thread races, because debugger's interference with the program's
38724 timing may conceal the bugs. On the other hand, in some applications,
38725 it is not feasible for the debugger to interrupt the program's execution
38726 long enough for the developer to learn anything helpful about its behavior.
38727 If the program's correctness depends on its real-time behavior, delays
38728 introduced by a debugger might cause the program to fail, even when the
38729 code itself is correct. It is useful to be able to observe the program's
38730 behavior without interrupting it.
38732 Therefore, traditional debugging model is too intrusive to reproduce
38733 some bugs. In order to reduce the interference with the program, we can
38734 reduce the number of operations performed by debugger. The
38735 @dfn{In-Process Agent}, a shared library, is running within the same
38736 process with inferior, and is able to perform some debugging operations
38737 itself. As a result, debugger is only involved when necessary, and
38738 performance of debugging can be improved accordingly. Note that
38739 interference with program can be reduced but can't be removed completely,
38740 because the in-process agent will still stop or slow down the program.
38742 The in-process agent can interpret and execute Agent Expressions
38743 (@pxref{Agent Expressions}) during performing debugging operations. The
38744 agent expressions can be used for different purposes, such as collecting
38745 data in tracepoints, and condition evaluation in breakpoints.
38747 @anchor{Control Agent}
38748 You can control whether the in-process agent is used as an aid for
38749 debugging with the following commands:
38752 @kindex set agent on
38754 Causes the in-process agent to perform some operations on behalf of the
38755 debugger. Just which operations requested by the user will be done
38756 by the in-process agent depends on the its capabilities. For example,
38757 if you request to evaluate breakpoint conditions in the in-process agent,
38758 and the in-process agent has such capability as well, then breakpoint
38759 conditions will be evaluated in the in-process agent.
38761 @kindex set agent off
38762 @item set agent off
38763 Disables execution of debugging operations by the in-process agent. All
38764 of the operations will be performed by @value{GDBN}.
38768 Display the current setting of execution of debugging operations by
38769 the in-process agent.
38773 * In-Process Agent Protocol::
38776 @node In-Process Agent Protocol
38777 @section In-Process Agent Protocol
38778 @cindex in-process agent protocol
38780 The in-process agent is able to communicate with both @value{GDBN} and
38781 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38782 used for communications between @value{GDBN} or GDBserver and the IPA.
38783 In general, @value{GDBN} or GDBserver sends commands
38784 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38785 in-process agent replies back with the return result of the command, or
38786 some other information. The data sent to in-process agent is composed
38787 of primitive data types, such as 4-byte or 8-byte type, and composite
38788 types, which are called objects (@pxref{IPA Protocol Objects}).
38791 * IPA Protocol Objects::
38792 * IPA Protocol Commands::
38795 @node IPA Protocol Objects
38796 @subsection IPA Protocol Objects
38797 @cindex ipa protocol objects
38799 The commands sent to and results received from agent may contain some
38800 complex data types called @dfn{objects}.
38802 The in-process agent is running on the same machine with @value{GDBN}
38803 or GDBserver, so it doesn't have to handle as much differences between
38804 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38805 However, there are still some differences of two ends in two processes:
38809 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38810 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38812 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38813 GDBserver is compiled with one, and in-process agent is compiled with
38817 Here are the IPA Protocol Objects:
38821 agent expression object. It represents an agent expression
38822 (@pxref{Agent Expressions}).
38823 @anchor{agent expression object}
38825 tracepoint action object. It represents a tracepoint action
38826 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38827 memory, static trace data and to evaluate expression.
38828 @anchor{tracepoint action object}
38830 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38831 @anchor{tracepoint object}
38835 The following table describes important attributes of each IPA protocol
38838 @multitable @columnfractions .30 .20 .50
38839 @headitem Name @tab Size @tab Description
38840 @item @emph{agent expression object} @tab @tab
38841 @item length @tab 4 @tab length of bytes code
38842 @item byte code @tab @var{length} @tab contents of byte code
38843 @item @emph{tracepoint action for collecting memory} @tab @tab
38844 @item 'M' @tab 1 @tab type of tracepoint action
38845 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38846 address of the lowest byte to collect, otherwise @var{addr} is the offset
38847 of @var{basereg} for memory collecting.
38848 @item len @tab 8 @tab length of memory for collecting
38849 @item basereg @tab 4 @tab the register number containing the starting
38850 memory address for collecting.
38851 @item @emph{tracepoint action for collecting registers} @tab @tab
38852 @item 'R' @tab 1 @tab type of tracepoint action
38853 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38854 @item 'L' @tab 1 @tab type of tracepoint action
38855 @item @emph{tracepoint action for expression evaluation} @tab @tab
38856 @item 'X' @tab 1 @tab type of tracepoint action
38857 @item agent expression @tab length of @tab @ref{agent expression object}
38858 @item @emph{tracepoint object} @tab @tab
38859 @item number @tab 4 @tab number of tracepoint
38860 @item address @tab 8 @tab address of tracepoint inserted on
38861 @item type @tab 4 @tab type of tracepoint
38862 @item enabled @tab 1 @tab enable or disable of tracepoint
38863 @item step_count @tab 8 @tab step
38864 @item pass_count @tab 8 @tab pass
38865 @item numactions @tab 4 @tab number of tracepoint actions
38866 @item hit count @tab 8 @tab hit count
38867 @item trace frame usage @tab 8 @tab trace frame usage
38868 @item compiled_cond @tab 8 @tab compiled condition
38869 @item orig_size @tab 8 @tab orig size
38870 @item condition @tab 4 if condition is NULL otherwise length of
38871 @ref{agent expression object}
38872 @tab zero if condition is NULL, otherwise is
38873 @ref{agent expression object}
38874 @item actions @tab variable
38875 @tab numactions number of @ref{tracepoint action object}
38878 @node IPA Protocol Commands
38879 @subsection IPA Protocol Commands
38880 @cindex ipa protocol commands
38882 The spaces in each command are delimiters to ease reading this commands
38883 specification. They don't exist in real commands.
38887 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38888 Installs a new fast tracepoint described by @var{tracepoint_object}
38889 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38890 head of @dfn{jumppad}, which is used to jump to data collection routine
38895 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38896 @var{target_address} is address of tracepoint in the inferior.
38897 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38898 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38899 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38900 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38907 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38908 is about to kill inferiors.
38916 @item probe_marker_at:@var{address}
38917 Asks in-process agent to probe the marker at @var{address}.
38924 @item unprobe_marker_at:@var{address}
38925 Asks in-process agent to unprobe the marker at @var{address}.
38929 @chapter Reporting Bugs in @value{GDBN}
38930 @cindex bugs in @value{GDBN}
38931 @cindex reporting bugs in @value{GDBN}
38933 Your bug reports play an essential role in making @value{GDBN} reliable.
38935 Reporting a bug may help you by bringing a solution to your problem, or it
38936 may not. But in any case the principal function of a bug report is to help
38937 the entire community by making the next version of @value{GDBN} work better. Bug
38938 reports are your contribution to the maintenance of @value{GDBN}.
38940 In order for a bug report to serve its purpose, you must include the
38941 information that enables us to fix the bug.
38944 * Bug Criteria:: Have you found a bug?
38945 * Bug Reporting:: How to report bugs
38949 @section Have You Found a Bug?
38950 @cindex bug criteria
38952 If you are not sure whether you have found a bug, here are some guidelines:
38955 @cindex fatal signal
38956 @cindex debugger crash
38957 @cindex crash of debugger
38959 If the debugger gets a fatal signal, for any input whatever, that is a
38960 @value{GDBN} bug. Reliable debuggers never crash.
38962 @cindex error on valid input
38964 If @value{GDBN} produces an error message for valid input, that is a
38965 bug. (Note that if you're cross debugging, the problem may also be
38966 somewhere in the connection to the target.)
38968 @cindex invalid input
38970 If @value{GDBN} does not produce an error message for invalid input,
38971 that is a bug. However, you should note that your idea of
38972 ``invalid input'' might be our idea of ``an extension'' or ``support
38973 for traditional practice''.
38976 If you are an experienced user of debugging tools, your suggestions
38977 for improvement of @value{GDBN} are welcome in any case.
38980 @node Bug Reporting
38981 @section How to Report Bugs
38982 @cindex bug reports
38983 @cindex @value{GDBN} bugs, reporting
38985 A number of companies and individuals offer support for @sc{gnu} products.
38986 If you obtained @value{GDBN} from a support organization, we recommend you
38987 contact that organization first.
38989 You can find contact information for many support companies and
38990 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38992 @c should add a web page ref...
38995 @ifset BUGURL_DEFAULT
38996 In any event, we also recommend that you submit bug reports for
38997 @value{GDBN}. The preferred method is to submit them directly using
38998 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38999 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
39002 @strong{Do not send bug reports to @samp{info-gdb}, or to
39003 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
39004 not want to receive bug reports. Those that do have arranged to receive
39007 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
39008 serves as a repeater. The mailing list and the newsgroup carry exactly
39009 the same messages. Often people think of posting bug reports to the
39010 newsgroup instead of mailing them. This appears to work, but it has one
39011 problem which can be crucial: a newsgroup posting often lacks a mail
39012 path back to the sender. Thus, if we need to ask for more information,
39013 we may be unable to reach you. For this reason, it is better to send
39014 bug reports to the mailing list.
39016 @ifclear BUGURL_DEFAULT
39017 In any event, we also recommend that you submit bug reports for
39018 @value{GDBN} to @value{BUGURL}.
39022 The fundamental principle of reporting bugs usefully is this:
39023 @strong{report all the facts}. If you are not sure whether to state a
39024 fact or leave it out, state it!
39026 Often people omit facts because they think they know what causes the
39027 problem and assume that some details do not matter. Thus, you might
39028 assume that the name of the variable you use in an example does not matter.
39029 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
39030 stray memory reference which happens to fetch from the location where that
39031 name is stored in memory; perhaps, if the name were different, the contents
39032 of that location would fool the debugger into doing the right thing despite
39033 the bug. Play it safe and give a specific, complete example. That is the
39034 easiest thing for you to do, and the most helpful.
39036 Keep in mind that the purpose of a bug report is to enable us to fix the
39037 bug. It may be that the bug has been reported previously, but neither
39038 you nor we can know that unless your bug report is complete and
39041 Sometimes people give a few sketchy facts and ask, ``Does this ring a
39042 bell?'' Those bug reports are useless, and we urge everyone to
39043 @emph{refuse to respond to them} except to chide the sender to report
39046 To enable us to fix the bug, you should include all these things:
39050 The version of @value{GDBN}. @value{GDBN} announces it if you start
39051 with no arguments; you can also print it at any time using @code{show
39054 Without this, we will not know whether there is any point in looking for
39055 the bug in the current version of @value{GDBN}.
39058 The type of machine you are using, and the operating system name and
39062 The details of the @value{GDBN} build-time configuration.
39063 @value{GDBN} shows these details if you invoke it with the
39064 @option{--configuration} command-line option, or if you type
39065 @code{show configuration} at @value{GDBN}'s prompt.
39068 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
39069 ``@value{GCC}--2.8.1''.
39072 What compiler (and its version) was used to compile the program you are
39073 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
39074 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
39075 to get this information; for other compilers, see the documentation for
39079 The command arguments you gave the compiler to compile your example and
39080 observe the bug. For example, did you use @samp{-O}? To guarantee
39081 you will not omit something important, list them all. A copy of the
39082 Makefile (or the output from make) is sufficient.
39084 If we were to try to guess the arguments, we would probably guess wrong
39085 and then we might not encounter the bug.
39088 A complete input script, and all necessary source files, that will
39092 A description of what behavior you observe that you believe is
39093 incorrect. For example, ``It gets a fatal signal.''
39095 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
39096 will certainly notice it. But if the bug is incorrect output, we might
39097 not notice unless it is glaringly wrong. You might as well not give us
39098 a chance to make a mistake.
39100 Even if the problem you experience is a fatal signal, you should still
39101 say so explicitly. Suppose something strange is going on, such as, your
39102 copy of @value{GDBN} is out of synch, or you have encountered a bug in
39103 the C library on your system. (This has happened!) Your copy might
39104 crash and ours would not. If you told us to expect a crash, then when
39105 ours fails to crash, we would know that the bug was not happening for
39106 us. If you had not told us to expect a crash, then we would not be able
39107 to draw any conclusion from our observations.
39110 @cindex recording a session script
39111 To collect all this information, you can use a session recording program
39112 such as @command{script}, which is available on many Unix systems.
39113 Just run your @value{GDBN} session inside @command{script} and then
39114 include the @file{typescript} file with your bug report.
39116 Another way to record a @value{GDBN} session is to run @value{GDBN}
39117 inside Emacs and then save the entire buffer to a file.
39120 If you wish to suggest changes to the @value{GDBN} source, send us context
39121 diffs. If you even discuss something in the @value{GDBN} source, refer to
39122 it by context, not by line number.
39124 The line numbers in our development sources will not match those in your
39125 sources. Your line numbers would convey no useful information to us.
39129 Here are some things that are not necessary:
39133 A description of the envelope of the bug.
39135 Often people who encounter a bug spend a lot of time investigating
39136 which changes to the input file will make the bug go away and which
39137 changes will not affect it.
39139 This is often time consuming and not very useful, because the way we
39140 will find the bug is by running a single example under the debugger
39141 with breakpoints, not by pure deduction from a series of examples.
39142 We recommend that you save your time for something else.
39144 Of course, if you can find a simpler example to report @emph{instead}
39145 of the original one, that is a convenience for us. Errors in the
39146 output will be easier to spot, running under the debugger will take
39147 less time, and so on.
39149 However, simplification is not vital; if you do not want to do this,
39150 report the bug anyway and send us the entire test case you used.
39153 A patch for the bug.
39155 A patch for the bug does help us if it is a good one. But do not omit
39156 the necessary information, such as the test case, on the assumption that
39157 a patch is all we need. We might see problems with your patch and decide
39158 to fix the problem another way, or we might not understand it at all.
39160 Sometimes with a program as complicated as @value{GDBN} it is very hard to
39161 construct an example that will make the program follow a certain path
39162 through the code. If you do not send us the example, we will not be able
39163 to construct one, so we will not be able to verify that the bug is fixed.
39165 And if we cannot understand what bug you are trying to fix, or why your
39166 patch should be an improvement, we will not install it. A test case will
39167 help us to understand.
39170 A guess about what the bug is or what it depends on.
39172 Such guesses are usually wrong. Even we cannot guess right about such
39173 things without first using the debugger to find the facts.
39176 @c The readline documentation is distributed with the readline code
39177 @c and consists of the two following files:
39180 @c Use -I with makeinfo to point to the appropriate directory,
39181 @c environment var TEXINPUTS with TeX.
39182 @ifclear SYSTEM_READLINE
39183 @include rluser.texi
39184 @include hsuser.texi
39188 @appendix In Memoriam
39190 The @value{GDBN} project mourns the loss of the following long-time
39195 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
39196 to Free Software in general. Outside of @value{GDBN}, he was known in
39197 the Amiga world for his series of Fish Disks, and the GeekGadget project.
39199 @item Michael Snyder
39200 Michael was one of the Global Maintainers of the @value{GDBN} project,
39201 with contributions recorded as early as 1996, until 2011. In addition
39202 to his day to day participation, he was a large driving force behind
39203 adding Reverse Debugging to @value{GDBN}.
39206 Beyond their technical contributions to the project, they were also
39207 enjoyable members of the Free Software Community. We will miss them.
39209 @node Formatting Documentation
39210 @appendix Formatting Documentation
39212 @cindex @value{GDBN} reference card
39213 @cindex reference card
39214 The @value{GDBN} 4 release includes an already-formatted reference card, ready
39215 for printing with PostScript or Ghostscript, in the @file{gdb}
39216 subdirectory of the main source directory@footnote{In
39217 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
39218 release.}. If you can use PostScript or Ghostscript with your printer,
39219 you can print the reference card immediately with @file{refcard.ps}.
39221 The release also includes the source for the reference card. You
39222 can format it, using @TeX{}, by typing:
39228 The @value{GDBN} reference card is designed to print in @dfn{landscape}
39229 mode on US ``letter'' size paper;
39230 that is, on a sheet 11 inches wide by 8.5 inches
39231 high. You will need to specify this form of printing as an option to
39232 your @sc{dvi} output program.
39234 @cindex documentation
39236 All the documentation for @value{GDBN} comes as part of the machine-readable
39237 distribution. The documentation is written in Texinfo format, which is
39238 a documentation system that uses a single source file to produce both
39239 on-line information and a printed manual. You can use one of the Info
39240 formatting commands to create the on-line version of the documentation
39241 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
39243 @value{GDBN} includes an already formatted copy of the on-line Info
39244 version of this manual in the @file{gdb} subdirectory. The main Info
39245 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
39246 subordinate files matching @samp{gdb.info*} in the same directory. If
39247 necessary, you can print out these files, or read them with any editor;
39248 but they are easier to read using the @code{info} subsystem in @sc{gnu}
39249 Emacs or the standalone @code{info} program, available as part of the
39250 @sc{gnu} Texinfo distribution.
39252 If you want to format these Info files yourself, you need one of the
39253 Info formatting programs, such as @code{texinfo-format-buffer} or
39256 If you have @code{makeinfo} installed, and are in the top level
39257 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
39258 version @value{GDBVN}), you can make the Info file by typing:
39265 If you want to typeset and print copies of this manual, you need @TeX{},
39266 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
39267 Texinfo definitions file.
39269 @TeX{} is a typesetting program; it does not print files directly, but
39270 produces output files called @sc{dvi} files. To print a typeset
39271 document, you need a program to print @sc{dvi} files. If your system
39272 has @TeX{} installed, chances are it has such a program. The precise
39273 command to use depends on your system; @kbd{lpr -d} is common; another
39274 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
39275 require a file name without any extension or a @samp{.dvi} extension.
39277 @TeX{} also requires a macro definitions file called
39278 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
39279 written in Texinfo format. On its own, @TeX{} cannot either read or
39280 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
39281 and is located in the @file{gdb-@var{version-number}/texinfo}
39284 If you have @TeX{} and a @sc{dvi} printer program installed, you can
39285 typeset and print this manual. First switch to the @file{gdb}
39286 subdirectory of the main source directory (for example, to
39287 @file{gdb-@value{GDBVN}/gdb}) and type:
39293 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
39295 @node Installing GDB
39296 @appendix Installing @value{GDBN}
39297 @cindex installation
39300 * Requirements:: Requirements for building @value{GDBN}
39301 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
39302 * Separate Objdir:: Compiling @value{GDBN} in another directory
39303 * Config Names:: Specifying names for hosts and targets
39304 * Configure Options:: Summary of options for configure
39305 * System-wide configuration:: Having a system-wide init file
39309 @section Requirements for Building @value{GDBN}
39310 @cindex building @value{GDBN}, requirements for
39312 Building @value{GDBN} requires various tools and packages to be available.
39313 Other packages will be used only if they are found.
39315 @heading Tools/Packages Necessary for Building @value{GDBN}
39317 @item C@t{++}11 compiler
39318 @value{GDBN} is written in C@t{++}11. It should be buildable with any
39319 recent C@t{++}11 compiler, e.g.@: GCC.
39322 @value{GDBN}'s build system relies on features only found in the GNU
39323 make program. Other variants of @code{make} will not work.
39325 @item GMP (The GNU Multiple Precision Arithmetic Library)
39326 @value{GDBN} now uses GMP to perform some of its arithmetics.
39327 This library may be included with your operating system distribution;
39328 if it is not, you can get the latest version from
39329 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
39330 you can use the @option{--with-gmp} option or options
39331 @option{--with-gmp-include} and @option{--with-gmp-lib} to specify
39336 @heading Tools/Packages Optional for Building @value{GDBN}
39340 @value{GDBN} can use the Expat XML parsing library. This library may be
39341 included with your operating system distribution; if it is not, you
39342 can get the latest version from @url{http://expat.sourceforge.net}.
39343 The @file{configure} script will search for this library in several
39344 standard locations; if it is installed in an unusual path, you can
39345 use the @option{--with-libexpat-prefix} option to specify its location.
39351 Remote protocol memory maps (@pxref{Memory Map Format})
39353 Target descriptions (@pxref{Target Descriptions})
39355 Remote shared library lists (@xref{Library List Format},
39356 or alternatively @pxref{Library List Format for SVR4 Targets})
39358 MS-Windows shared libraries (@pxref{Shared Libraries})
39360 Traceframe info (@pxref{Traceframe Info Format})
39362 Branch trace (@pxref{Branch Trace Format},
39363 @pxref{Branch Trace Configuration Format})
39367 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
39368 default, @value{GDBN} will be compiled if the Guile libraries are
39369 installed and are found by @file{configure}. You can use the
39370 @code{--with-guile} option to request Guile, and pass either the Guile
39371 version number or the file name of the relevant @code{pkg-config}
39372 program to choose a particular version of Guile.
39375 @value{GDBN}'s features related to character sets (@pxref{Character
39376 Sets}) require a functioning @code{iconv} implementation. If you are
39377 on a GNU system, then this is provided by the GNU C Library. Some
39378 other systems also provide a working @code{iconv}.
39380 If @value{GDBN} is using the @code{iconv} program which is installed
39381 in a non-standard place, you will need to tell @value{GDBN} where to
39382 find it. This is done with @option{--with-iconv-bin} which specifies
39383 the directory that contains the @code{iconv} program. This program is
39384 run in order to make a list of the available character sets.
39386 On systems without @code{iconv}, you can install GNU Libiconv. If
39387 Libiconv is installed in a standard place, @value{GDBN} will
39388 automatically use it if it is needed. If you have previously
39389 installed Libiconv in a non-standard place, you can use the
39390 @option{--with-libiconv-prefix} option to @file{configure}.
39392 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
39393 arrange to build Libiconv if a directory named @file{libiconv} appears
39394 in the top-most source directory. If Libiconv is built this way, and
39395 if the operating system does not provide a suitable @code{iconv}
39396 implementation, then the just-built library will automatically be used
39397 by @value{GDBN}. One easy way to set this up is to download GNU
39398 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
39399 source tree, and then rename the directory holding the Libiconv source
39400 code to @samp{libiconv}.
39403 @value{GDBN} can support debugging sections that are compressed with
39404 the LZMA library. @xref{MiniDebugInfo}. If this library is not
39405 included with your operating system, you can find it in the xz package
39406 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
39407 the usual place, then the @file{configure} script will use it
39408 automatically. If it is installed in an unusual path, you can use the
39409 @option{--with-liblzma-prefix} option to specify its location.
39413 @value{GDBN} now uses the GNU MPFR multiple-precision floating-point
39414 library. This library may be included with your operating system
39415 distribution; if it is not, you can get the latest version from
39416 @url{http://www.mpfr.org}. The @file{configure} script will search
39417 for this library in several standard locations; if it is installed
39418 in an unusual path, you can use the @option{--with-mpfr} option or options
39419 @option{--with-mpfr-include} and @option{--with-mpfr-lib} to specify
39422 GNU MPFR is used to emulate target floating-point arithmetic during
39423 expression evaluation when the target uses different floating-point
39424 formats than the host.
39427 @value{GDBN} can be scripted using Python language. @xref{Python}.
39428 By default, @value{GDBN} will be compiled if the Python libraries are
39429 installed and are found by @file{configure}. You can use the
39430 @code{--with-python} option to request Python, and pass either the
39431 file name of the relevant @code{python} executable, or the name of the
39432 directory in which Python is installed, to choose a particular
39433 installation of Python.
39436 @cindex compressed debug sections
39437 @value{GDBN} will use the @samp{zlib} library, if available, to read
39438 compressed debug sections. Some linkers, such as GNU gold, are capable
39439 of producing binaries with compressed debug sections. If @value{GDBN}
39440 is compiled with @samp{zlib}, it will be able to read the debug
39441 information in such binaries.
39443 The @samp{zlib} library is likely included with your operating system
39444 distribution; if it is not, you can get the latest version from
39445 @url{http://zlib.net}.
39448 @node Running Configure
39449 @section Invoking the @value{GDBN} @file{configure} Script
39450 @cindex configuring @value{GDBN}
39451 @value{GDBN} comes with a @file{configure} script that automates the process
39452 of preparing @value{GDBN} for installation; you can then use @code{make} to
39453 build the @code{gdb} program.
39455 @c irrelevant in info file; it's as current as the code it lives with.
39456 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
39457 look at the @file{README} file in the sources; we may have improved the
39458 installation procedures since publishing this manual.}
39461 The @value{GDBN} distribution includes all the source code you need for
39462 @value{GDBN} in a single directory, whose name is usually composed by
39463 appending the version number to @samp{gdb}.
39465 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
39466 @file{gdb-@value{GDBVN}} directory. That directory contains:
39469 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
39470 script for configuring @value{GDBN} and all its supporting libraries
39472 @item gdb-@value{GDBVN}/gdb
39473 the source specific to @value{GDBN} itself
39475 @item gdb-@value{GDBVN}/bfd
39476 source for the Binary File Descriptor library
39478 @item gdb-@value{GDBVN}/include
39479 @sc{gnu} include files
39481 @item gdb-@value{GDBVN}/libiberty
39482 source for the @samp{-liberty} free software library
39484 @item gdb-@value{GDBVN}/opcodes
39485 source for the library of opcode tables and disassemblers
39487 @item gdb-@value{GDBVN}/readline
39488 source for the @sc{gnu} command-line interface
39491 There may be other subdirectories as well.
39493 The simplest way to configure and build @value{GDBN} is to run @file{configure}
39494 from the @file{gdb-@var{version-number}} source directory, which in
39495 this example is the @file{gdb-@value{GDBVN}} directory.
39497 First switch to the @file{gdb-@var{version-number}} source directory
39498 if you are not already in it; then run @file{configure}. Pass the
39499 identifier for the platform on which @value{GDBN} will run as an
39505 cd gdb-@value{GDBVN}
39510 Running @samp{configure} and then running @code{make} builds the
39511 included supporting libraries, then @code{gdb} itself. The configured
39512 source files, and the binaries, are left in the corresponding source
39516 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
39517 system does not recognize this automatically when you run a different
39518 shell, you may need to run @code{sh} on it explicitly:
39524 You should run the @file{configure} script from the top directory in the
39525 source tree, the @file{gdb-@var{version-number}} directory. If you run
39526 @file{configure} from one of the subdirectories, you will configure only
39527 that subdirectory. That is usually not what you want. In particular,
39528 if you run the first @file{configure} from the @file{gdb} subdirectory
39529 of the @file{gdb-@var{version-number}} directory, you will omit the
39530 configuration of @file{bfd}, @file{readline}, and other sibling
39531 directories of the @file{gdb} subdirectory. This leads to build errors
39532 about missing include files such as @file{bfd/bfd.h}.
39534 You can install @code{@value{GDBN}} anywhere. The best way to do this
39535 is to pass the @code{--prefix} option to @code{configure}, and then
39536 install it with @code{make install}.
39538 @node Separate Objdir
39539 @section Compiling @value{GDBN} in Another Directory
39541 If you want to run @value{GDBN} versions for several host or target machines,
39542 you need a different @code{gdb} compiled for each combination of
39543 host and target. @file{configure} is designed to make this easy by
39544 allowing you to generate each configuration in a separate subdirectory,
39545 rather than in the source directory. If your @code{make} program
39546 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
39547 @code{make} in each of these directories builds the @code{gdb}
39548 program specified there.
39550 To build @code{gdb} in a separate directory, run @file{configure}
39551 with the @samp{--srcdir} option to specify where to find the source.
39552 (You also need to specify a path to find @file{configure}
39553 itself from your working directory. If the path to @file{configure}
39554 would be the same as the argument to @samp{--srcdir}, you can leave out
39555 the @samp{--srcdir} option; it is assumed.)
39557 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
39558 separate directory for a Sun 4 like this:
39562 cd gdb-@value{GDBVN}
39565 ../gdb-@value{GDBVN}/configure
39570 When @file{configure} builds a configuration using a remote source
39571 directory, it creates a tree for the binaries with the same structure
39572 (and using the same names) as the tree under the source directory. In
39573 the example, you'd find the Sun 4 library @file{libiberty.a} in the
39574 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
39575 @file{gdb-sun4/gdb}.
39577 Make sure that your path to the @file{configure} script has just one
39578 instance of @file{gdb} in it. If your path to @file{configure} looks
39579 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
39580 one subdirectory of @value{GDBN}, not the whole package. This leads to
39581 build errors about missing include files such as @file{bfd/bfd.h}.
39583 One popular reason to build several @value{GDBN} configurations in separate
39584 directories is to configure @value{GDBN} for cross-compiling (where
39585 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39586 programs that run on another machine---the @dfn{target}).
39587 You specify a cross-debugging target by
39588 giving the @samp{--target=@var{target}} option to @file{configure}.
39590 When you run @code{make} to build a program or library, you must run
39591 it in a configured directory---whatever directory you were in when you
39592 called @file{configure} (or one of its subdirectories).
39594 The @code{Makefile} that @file{configure} generates in each source
39595 directory also runs recursively. If you type @code{make} in a source
39596 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39597 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39598 will build all the required libraries, and then build GDB.
39600 When you have multiple hosts or targets configured in separate
39601 directories, you can run @code{make} on them in parallel (for example,
39602 if they are NFS-mounted on each of the hosts); they will not interfere
39606 @section Specifying Names for Hosts and Targets
39608 The specifications used for hosts and targets in the @file{configure}
39609 script are based on a three-part naming scheme, but some short predefined
39610 aliases are also supported. The full naming scheme encodes three pieces
39611 of information in the following pattern:
39614 @var{architecture}-@var{vendor}-@var{os}
39617 For example, you can use the alias @code{sun4} as a @var{host} argument,
39618 or as the value for @var{target} in a @code{--target=@var{target}}
39619 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39621 The @file{configure} script accompanying @value{GDBN} does not provide
39622 any query facility to list all supported host and target names or
39623 aliases. @file{configure} calls the Bourne shell script
39624 @code{config.sub} to map abbreviations to full names; you can read the
39625 script, if you wish, or you can use it to test your guesses on
39626 abbreviations---for example:
39629 % sh config.sub i386-linux
39631 % sh config.sub alpha-linux
39632 alpha-unknown-linux-gnu
39633 % sh config.sub hp9k700
39635 % sh config.sub sun4
39636 sparc-sun-sunos4.1.1
39637 % sh config.sub sun3
39638 m68k-sun-sunos4.1.1
39639 % sh config.sub i986v
39640 Invalid configuration `i986v': machine `i986v' not recognized
39644 @code{config.sub} is also distributed in the @value{GDBN} source
39645 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39647 @node Configure Options
39648 @section @file{configure} Options
39650 Here is a summary of the @file{configure} options and arguments that
39651 are most often useful for building @value{GDBN}. @file{configure}
39652 also has several other options not listed here. @xref{Running
39653 configure Scripts,,,autoconf}, for a full
39654 explanation of @file{configure}.
39657 configure @r{[}--help@r{]}
39658 @r{[}--prefix=@var{dir}@r{]}
39659 @r{[}--exec-prefix=@var{dir}@r{]}
39660 @r{[}--srcdir=@var{dirname}@r{]}
39661 @r{[}--target=@var{target}@r{]}
39665 You may introduce options with a single @samp{-} rather than
39666 @samp{--} if you prefer; but you may abbreviate option names if you use
39671 Display a quick summary of how to invoke @file{configure}.
39673 @item --prefix=@var{dir}
39674 Configure the source to install programs and files under directory
39677 @item --exec-prefix=@var{dir}
39678 Configure the source to install programs under directory
39681 @c avoid splitting the warning from the explanation:
39683 @item --srcdir=@var{dirname}
39684 Use this option to make configurations in directories separate from the
39685 @value{GDBN} source directories. Among other things, you can use this to
39686 build (or maintain) several configurations simultaneously, in separate
39687 directories. @file{configure} writes configuration-specific files in
39688 the current directory, but arranges for them to use the source in the
39689 directory @var{dirname}. @file{configure} creates directories under
39690 the working directory in parallel to the source directories below
39693 @item --target=@var{target}
39694 Configure @value{GDBN} for cross-debugging programs running on the specified
39695 @var{target}. Without this option, @value{GDBN} is configured to debug
39696 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39698 There is no convenient way to generate a list of all available
39699 targets. Also see the @code{--enable-targets} option, below.
39702 There are many other options that are specific to @value{GDBN}. This
39703 lists just the most common ones; there are some very specialized
39704 options not described here.
39707 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39708 @itemx --enable-targets=all
39709 Configure @value{GDBN} for cross-debugging programs running on the
39710 specified list of targets. The special value @samp{all} configures
39711 @value{GDBN} for debugging programs running on any target it supports.
39713 @item --with-gdb-datadir=@var{path}
39714 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39715 here for certain supporting files or scripts. This defaults to the
39716 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39719 @item --with-relocated-sources=@var{dir}
39720 Sets up the default source path substitution rule so that directory
39721 names recorded in debug information will be automatically adjusted for
39722 any directory under @var{dir}. @var{dir} should be a subdirectory of
39723 @value{GDBN}'s configured prefix, the one mentioned in the
39724 @code{--prefix} or @code{--exec-prefix} options to configure. This
39725 option is useful if GDB is supposed to be moved to a different place
39728 @item --enable-64-bit-bfd
39729 Enable 64-bit support in BFD on 32-bit hosts.
39731 @item --disable-gdbmi
39732 Build @value{GDBN} without the GDB/MI machine interface
39736 Build @value{GDBN} with the text-mode full-screen user interface
39737 (TUI). Requires a curses library (ncurses and cursesX are also
39740 @item --with-curses
39741 Use the curses library instead of the termcap library, for text-mode
39742 terminal operations.
39744 @item --with-debuginfod
39745 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39746 library. Used to automatically fetch ELF, DWARF and source files from
39747 @code{debuginfod} servers using build IDs associated with any missing
39748 files. Enabled by default if @file{libdebuginfod} is installed and found
39749 at configure time. For more information regarding @code{debuginfod} see
39752 @item --with-libunwind-ia64
39753 Use the libunwind library for unwinding function call stack on ia64
39754 target platforms. See http://www.nongnu.org/libunwind/index.html for
39757 @item --with-system-readline
39758 Use the readline library installed on the host, rather than the
39759 library supplied as part of @value{GDBN}. Readline 7 or newer is
39760 required; this is enforced by the build system.
39762 @item --with-system-zlib
39763 Use the zlib library installed on the host, rather than the library
39764 supplied as part of @value{GDBN}.
39767 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39768 default if libexpat is installed and found at configure time.) This
39769 library is used to read XML files supplied with @value{GDBN}. If it
39770 is unavailable, some features, such as remote protocol memory maps,
39771 target descriptions, and shared library lists, that are based on XML
39772 files, will not be available in @value{GDBN}. If your host does not
39773 have libexpat installed, you can get the latest version from
39774 `http://expat.sourceforge.net'.
39776 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39778 Build @value{GDBN} with GNU libiconv, a character set encoding
39779 conversion library. This is not done by default, as on GNU systems
39780 the @code{iconv} that is built in to the C library is sufficient. If
39781 your host does not have a working @code{iconv}, you can get the latest
39782 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39784 @value{GDBN}'s build system also supports building GNU libiconv as
39785 part of the overall build. @xref{Requirements}.
39788 Build @value{GDBN} with LZMA, a compression library. (Done by default
39789 if liblzma is installed and found at configure time.) LZMA is used by
39790 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39791 platforms using the ELF object file format. If your host does not
39792 have liblzma installed, you can get the latest version from
39793 `https://tukaani.org/xz/'.
39796 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39797 floating-point computation with correct rounding. (Done by default if
39798 GNU MPFR is installed and found at configure time.) This library is
39799 used to emulate target floating-point arithmetic during expression
39800 evaluation when the target uses different floating-point formats than
39801 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39802 to using host floating-point arithmetic. If your host does not have
39803 GNU MPFR installed, you can get the latest version from
39804 `http://www.mpfr.org'.
39806 @item --with-python@r{[}=@var{python}@r{]}
39807 Build @value{GDBN} with Python scripting support. (Done by default if
39808 libpython is present and found at configure time.) Python makes
39809 @value{GDBN} scripting much more powerful than the restricted CLI
39810 scripting language. If your host does not have Python installed, you
39811 can find it on `http://www.python.org/download/'. The oldest version
39812 of Python supported by GDB is 2.6. The optional argument @var{python}
39813 is used to find the Python headers and libraries. It can be either
39814 the name of a Python executable, or the name of the directory in which
39815 Python is installed.
39817 @item --with-guile[=GUILE]'
39818 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39819 if libguile is present and found at configure time.) If your host
39820 does not have Guile installed, you can find it at
39821 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39822 can be a version number, which will cause @code{configure} to try to
39823 use that version of Guile; or the file name of a @code{pkg-config}
39824 executable, which will be queried to find the information needed to
39825 compile and link against Guile.
39827 @item --without-included-regex
39828 Don't use the regex library included with @value{GDBN} (as part of the
39829 libiberty library). This is the default on hosts with version 2 of
39832 @item --with-sysroot=@var{dir}
39833 Use @var{dir} as the default system root directory for libraries whose
39834 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39835 @var{dir} can be modified at run time by using the @command{set
39836 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39837 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39838 default system root will be automatically adjusted if and when
39839 @value{GDBN} is moved to a different location.
39841 @item --with-system-gdbinit=@var{file}
39842 Configure @value{GDBN} to automatically load a system-wide init file.
39843 @var{file} should be an absolute file name. If @var{file} is in a
39844 directory under the configured prefix, and @value{GDBN} is moved to
39845 another location after being built, the location of the system-wide
39846 init file will be adjusted accordingly.
39848 @item --with-system-gdbinit-dir=@var{directory}
39849 Configure @value{GDBN} to automatically load init files from a
39850 system-wide directory. @var{directory} should be an absolute directory
39851 name. If @var{directory} is in a directory under the configured
39852 prefix, and @value{GDBN} is moved to another location after being
39853 built, the location of the system-wide init directory will be
39854 adjusted accordingly.
39856 @item --enable-build-warnings
39857 When building the @value{GDBN} sources, ask the compiler to warn about
39858 any code which looks even vaguely suspicious. It passes many
39859 different warning flags, depending on the exact version of the
39860 compiler you are using.
39862 @item --enable-werror
39863 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39864 to the compiler, which will fail the compilation if the compiler
39865 outputs any warning messages.
39867 @item --enable-ubsan
39868 Enable the GCC undefined behavior sanitizer. This is disabled by
39869 default, but passing @code{--enable-ubsan=yes} or
39870 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39871 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39872 It has a performance cost, so if you are looking at @value{GDBN}'s
39873 performance, you should disable it. The undefined behavior sanitizer
39874 was first introduced in GCC 4.9.
39877 @node System-wide configuration
39878 @section System-wide configuration and settings
39879 @cindex system-wide init file
39881 @value{GDBN} can be configured to have a system-wide init file and a
39882 system-wide init file directory; this file and files in that directory
39883 (if they have a recognized file extension) will be read and executed at
39884 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39886 Here are the corresponding configure options:
39889 @item --with-system-gdbinit=@var{file}
39890 Specify that the default location of the system-wide init file is
39892 @item --with-system-gdbinit-dir=@var{directory}
39893 Specify that the default location of the system-wide init file directory
39894 is @var{directory}.
39897 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39898 they may be subject to relocation. Two possible cases:
39902 If the default location of this init file/directory contains @file{$prefix},
39903 it will be subject to relocation. Suppose that the configure options
39904 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39905 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39906 init file is looked for as @file{$install/etc/gdbinit} instead of
39907 @file{$prefix/etc/gdbinit}.
39910 By contrast, if the default location does not contain the prefix,
39911 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39912 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39913 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39914 wherever @value{GDBN} is installed.
39917 If the configured location of the system-wide init file (as given by the
39918 @option{--with-system-gdbinit} option at configure time) is in the
39919 data-directory (as specified by @option{--with-gdb-datadir} at configure
39920 time) or in one of its subdirectories, then @value{GDBN} will look for the
39921 system-wide init file in the directory specified by the
39922 @option{--data-directory} command-line option.
39923 Note that the system-wide init file is only read once, during @value{GDBN}
39924 initialization. If the data-directory is changed after @value{GDBN} has
39925 started with the @code{set data-directory} command, the file will not be
39928 This applies similarly to the system-wide directory specified in
39929 @option{--with-system-gdbinit-dir}.
39931 Any supported scripting language can be used for these init files, as long
39932 as the file extension matches the scripting language. To be interpreted
39933 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39937 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39940 @node System-wide Configuration Scripts
39941 @subsection Installed System-wide Configuration Scripts
39942 @cindex system-wide configuration scripts
39944 The @file{system-gdbinit} directory, located inside the data-directory
39945 (as specified by @option{--with-gdb-datadir} at configure time) contains
39946 a number of scripts which can be used as system-wide init files. To
39947 automatically source those scripts at startup, @value{GDBN} should be
39948 configured with @option{--with-system-gdbinit}. Otherwise, any user
39949 should be able to source them by hand as needed.
39951 The following scripts are currently available:
39954 @item @file{elinos.py}
39956 @cindex ELinOS system-wide configuration script
39957 This script is useful when debugging a program on an ELinOS target.
39958 It takes advantage of the environment variables defined in a standard
39959 ELinOS environment in order to determine the location of the system
39960 shared libraries, and then sets the @samp{solib-absolute-prefix}
39961 and @samp{solib-search-path} variables appropriately.
39963 @item @file{wrs-linux.py}
39964 @pindex wrs-linux.py
39965 @cindex Wind River Linux system-wide configuration script
39966 This script is useful when debugging a program on a target running
39967 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39968 the host-side sysroot used by the target system.
39972 @node Maintenance Commands
39973 @appendix Maintenance Commands
39974 @cindex maintenance commands
39975 @cindex internal commands
39977 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39978 includes a number of commands intended for @value{GDBN} developers,
39979 that are not documented elsewhere in this manual. These commands are
39980 provided here for reference. (For commands that turn on debugging
39981 messages, see @ref{Debugging Output}.)
39984 @kindex maint agent
39985 @kindex maint agent-eval
39986 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39987 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
39988 Translate the given @var{expression} into remote agent bytecodes.
39989 This command is useful for debugging the Agent Expression mechanism
39990 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39991 expression useful for data collection, such as by tracepoints, while
39992 @samp{maint agent-eval} produces an expression that evaluates directly
39993 to a result. For instance, a collection expression for @code{globa +
39994 globb} will include bytecodes to record four bytes of memory at each
39995 of the addresses of @code{globa} and @code{globb}, while discarding
39996 the result of the addition, while an evaluation expression will do the
39997 addition and return the sum.
39998 If @code{-at} is given, generate remote agent bytecode for all the
39999 addresses to which @var{linespec} resolves (@pxref{Linespec
40001 If not, generate remote agent bytecode for current frame PC address.
40003 @kindex maint agent-printf
40004 @item maint agent-printf @var{format},@var{expr},...
40005 Translate the given format string and list of argument expressions
40006 into remote agent bytecodes and display them as a disassembled list.
40007 This command is useful for debugging the agent version of dynamic
40008 printf (@pxref{Dynamic Printf}).
40010 @kindex maint info breakpoints
40011 @item @anchor{maint info breakpoints}maint info breakpoints
40012 Using the same format as @samp{info breakpoints}, display both the
40013 breakpoints you've set explicitly, and those @value{GDBN} is using for
40014 internal purposes. Internal breakpoints are shown with negative
40015 breakpoint numbers. The type column identifies what kind of breakpoint
40020 Normal, explicitly set breakpoint.
40023 Normal, explicitly set watchpoint.
40026 Internal breakpoint, used to handle correctly stepping through
40027 @code{longjmp} calls.
40029 @item longjmp resume
40030 Internal breakpoint at the target of a @code{longjmp}.
40033 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
40036 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
40039 Shared library events.
40043 @kindex maint info btrace
40044 @item maint info btrace
40045 Pint information about raw branch tracing data.
40047 @kindex maint btrace packet-history
40048 @item maint btrace packet-history
40049 Print the raw branch trace packets that are used to compute the
40050 execution history for the @samp{record btrace} command. Both the
40051 information and the format in which it is printed depend on the btrace
40056 For the BTS recording format, print a list of blocks of sequential
40057 code. For each block, the following information is printed:
40061 Newer blocks have higher numbers. The oldest block has number zero.
40062 @item Lowest @samp{PC}
40063 @item Highest @samp{PC}
40067 For the Intel Processor Trace recording format, print a list of
40068 Intel Processor Trace packets. For each packet, the following
40069 information is printed:
40072 @item Packet number
40073 Newer packets have higher numbers. The oldest packet has number zero.
40075 The packet's offset in the trace stream.
40076 @item Packet opcode and payload
40080 @kindex maint btrace clear-packet-history
40081 @item maint btrace clear-packet-history
40082 Discards the cached packet history printed by the @samp{maint btrace
40083 packet-history} command. The history will be computed again when
40086 @kindex maint btrace clear
40087 @item maint btrace clear
40088 Discard the branch trace data. The data will be fetched anew and the
40089 branch trace will be recomputed when needed.
40091 This implicitly truncates the branch trace to a single branch trace
40092 buffer. When updating branch trace incrementally, the branch trace
40093 available to @value{GDBN} may be bigger than a single branch trace
40096 @kindex maint set btrace pt skip-pad
40097 @item maint set btrace pt skip-pad
40098 @kindex maint show btrace pt skip-pad
40099 @item maint show btrace pt skip-pad
40100 Control whether @value{GDBN} will skip PAD packets when computing the
40103 @kindex maint info jit
40104 @item maint info jit
40105 Print information about JIT code objects loaded in the current inferior.
40107 @anchor{maint info python-disassemblers}
40108 @kindex maint info python-disassemblers
40109 @item maint info python-disassemblers
40110 This command is defined within the @code{gdb.disassembler} Python
40111 module (@pxref{Disassembly In Python}), and will only be present after
40112 that module has been imported. To force the module to be imported do
40116 (@value{GDBP}) python import gdb.disassembler
40119 This command lists all the architectures for which a disassembler is
40120 currently registered, and the name of the disassembler. If a
40121 disassembler is registered for all architectures, then this is listed
40122 last against the @samp{GLOBAL} architecture.
40124 If one of the disassemblers would be selected for the architecture of
40125 the current inferior, then this disassembler will be marked.
40127 The following example shows a situation in which two disassemblers are
40128 registered, initially the @samp{i386} disassembler matches the current
40129 architecture, then the architecture is changed, now the @samp{GLOBAL}
40130 disassembler matches.
40134 (@value{GDBP}) show architecture
40135 The target architecture is set to "auto" (currently "i386").
40136 (@value{GDBP}) maint info python-disassemblers
40137 Architecture Disassember Name
40138 i386 Disassembler_1 (Matches current architecture)
40139 GLOBAL Disassembler_2
40142 (@value{GDBP}) set architecture arm
40143 The target architecture is set to "arm".
40144 (@value{GDBP}) maint info python-disassemblers
40146 Architecture Disassember Name
40147 i386 Disassembler_1
40148 GLOBAL Disassembler_2 (Matches current architecture)
40152 @kindex set displaced-stepping
40153 @kindex show displaced-stepping
40154 @cindex displaced stepping support
40155 @cindex out-of-line single-stepping
40156 @item set displaced-stepping
40157 @itemx show displaced-stepping
40158 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
40159 if the target supports it. Displaced stepping is a way to single-step
40160 over breakpoints without removing them from the inferior, by executing
40161 an out-of-line copy of the instruction that was originally at the
40162 breakpoint location. It is also known as out-of-line single-stepping.
40165 @item set displaced-stepping on
40166 If the target architecture supports it, @value{GDBN} will use
40167 displaced stepping to step over breakpoints.
40169 @item set displaced-stepping off
40170 @value{GDBN} will not use displaced stepping to step over breakpoints,
40171 even if such is supported by the target architecture.
40173 @cindex non-stop mode, and @samp{set displaced-stepping}
40174 @item set displaced-stepping auto
40175 This is the default mode. @value{GDBN} will use displaced stepping
40176 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
40177 architecture supports displaced stepping.
40180 @kindex maint check-psymtabs
40181 @item maint check-psymtabs
40182 Check the consistency of currently expanded psymtabs versus symtabs.
40183 Use this to check, for example, whether a symbol is in one but not the other.
40185 @kindex maint check-symtabs
40186 @item maint check-symtabs
40187 Check the consistency of currently expanded symtabs.
40189 @kindex maint expand-symtabs
40190 @item maint expand-symtabs [@var{regexp}]
40191 Expand symbol tables.
40192 If @var{regexp} is specified, only expand symbol tables for file
40193 names matching @var{regexp}.
40195 @kindex maint set catch-demangler-crashes
40196 @kindex maint show catch-demangler-crashes
40197 @cindex demangler crashes
40198 @item maint set catch-demangler-crashes [on|off]
40199 @itemx maint show catch-demangler-crashes
40200 Control whether @value{GDBN} should attempt to catch crashes in the
40201 symbol name demangler. The default is to attempt to catch crashes.
40202 If enabled, the first time a crash is caught, a core file is created,
40203 the offending symbol is displayed and the user is presented with the
40204 option to terminate the current session.
40206 @kindex maint cplus first_component
40207 @item maint cplus first_component @var{name}
40208 Print the first C@t{++} class/namespace component of @var{name}.
40210 @kindex maint cplus namespace
40211 @item maint cplus namespace
40212 Print the list of possible C@t{++} namespaces.
40214 @kindex maint deprecate
40215 @kindex maint undeprecate
40216 @cindex deprecated commands
40217 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
40218 @itemx maint undeprecate @var{command}
40219 Deprecate or undeprecate the named @var{command}. Deprecated commands
40220 cause @value{GDBN} to issue a warning when you use them. The optional
40221 argument @var{replacement} says which newer command should be used in
40222 favor of the deprecated one; if it is given, @value{GDBN} will mention
40223 the replacement as part of the warning.
40225 @kindex maint dump-me
40226 @item maint dump-me
40227 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
40228 Cause a fatal signal in the debugger and force it to dump its core.
40229 This is supported only on systems which support aborting a program
40230 with the @code{SIGQUIT} signal.
40232 @kindex maint internal-error
40233 @kindex maint internal-warning
40234 @kindex maint demangler-warning
40235 @cindex demangler crashes
40236 @item maint internal-error @r{[}@var{message-text}@r{]}
40237 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
40238 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
40240 Cause @value{GDBN} to call the internal function @code{internal_error},
40241 @code{internal_warning} or @code{demangler_warning} and hence behave
40242 as though an internal problem has been detected. In addition to
40243 reporting the internal problem, these functions give the user the
40244 opportunity to either quit @value{GDBN} or (for @code{internal_error}
40245 and @code{internal_warning}) create a core file of the current
40246 @value{GDBN} session.
40248 These commands take an optional parameter @var{message-text} that is
40249 used as the text of the error or warning message.
40251 Here's an example of using @code{internal-error}:
40254 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
40255 @dots{}/maint.c:121: internal-error: testing, 1, 2
40256 A problem internal to GDB has been detected. Further
40257 debugging may prove unreliable.
40258 Quit this debugging session? (y or n) @kbd{n}
40259 Create a core file? (y or n) @kbd{n}
40263 @cindex @value{GDBN} internal error
40264 @cindex internal errors, control of @value{GDBN} behavior
40265 @cindex demangler crashes
40267 @kindex maint set internal-error
40268 @kindex maint show internal-error
40269 @kindex maint set internal-warning
40270 @kindex maint show internal-warning
40271 @kindex maint set demangler-warning
40272 @kindex maint show demangler-warning
40273 @item maint set internal-error @var{action} [ask|yes|no]
40274 @itemx maint show internal-error @var{action}
40275 @itemx maint set internal-warning @var{action} [ask|yes|no]
40276 @itemx maint show internal-warning @var{action}
40277 @itemx maint set demangler-warning @var{action} [ask|yes|no]
40278 @itemx maint show demangler-warning @var{action}
40279 When @value{GDBN} reports an internal problem (error or warning) it
40280 gives the user the opportunity to both quit @value{GDBN} and create a
40281 core file of the current @value{GDBN} session. These commands let you
40282 override the default behaviour for each particular @var{action},
40283 described in the table below.
40287 You can specify that @value{GDBN} should always (yes) or never (no)
40288 quit. The default is to ask the user what to do.
40291 You can specify that @value{GDBN} should always (yes) or never (no)
40292 create a core file. The default is to ask the user what to do. Note
40293 that there is no @code{corefile} option for @code{demangler-warning}:
40294 demangler warnings always create a core file and this cannot be
40298 @kindex maint set internal-error
40299 @kindex maint show internal-error
40300 @kindex maint set internal-warning
40301 @kindex maint show internal-warning
40302 @item maint set internal-error backtrace @r{[}on|off@r{]}
40303 @itemx maint show internal-error backtrace
40304 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
40305 @itemx maint show internal-warning backtrace
40306 When @value{GDBN} reports an internal problem (error or warning) it is
40307 possible to have a backtrace of @value{GDBN} printed to the standard
40308 error stream. This is @samp{on} by default for @code{internal-error}
40309 and @samp{off} by default for @code{internal-warning}.
40311 @anchor{maint packet}
40312 @kindex maint packet
40313 @item maint packet @var{text}
40314 If @value{GDBN} is talking to an inferior via the serial protocol,
40315 then this command sends the string @var{text} to the inferior, and
40316 displays the response packet. @value{GDBN} supplies the initial
40317 @samp{$} character, the terminating @samp{#} character, and the
40320 Any non-printable characters in the reply are printed as escaped hex,
40321 e.g. @samp{\x00}, @samp{\x01}, etc.
40323 @kindex maint print architecture
40324 @item maint print architecture @r{[}@var{file}@r{]}
40325 Print the entire architecture configuration. The optional argument
40326 @var{file} names the file where the output goes.
40328 @kindex maint print c-tdesc
40329 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
40330 Print the target description (@pxref{Target Descriptions}) as
40331 a C source file. By default, the target description is for the current
40332 target, but if the optional argument @var{file} is provided, that file
40333 is used to produce the description. The @var{file} should be an XML
40334 document, of the form described in @ref{Target Description Format}.
40335 The created source file is built into @value{GDBN} when @value{GDBN} is
40336 built again. This command is used by developers after they add or
40337 modify XML target descriptions.
40339 When the optional flag @samp{-single-feature} is provided then the
40340 target description being processed (either the default, or from
40341 @var{file}) must only contain a single feature. The source file
40342 produced is different in this case.
40344 @kindex maint print xml-tdesc
40345 @item maint print xml-tdesc @r{[}@var{file}@r{]}
40346 Print the target description (@pxref{Target Descriptions}) as an XML
40347 file. By default print the target description for the current target,
40348 but if the optional argument @var{file} is provided, then that file is
40349 read in by GDB and then used to produce the description. The
40350 @var{file} should be an XML document, of the form described in
40351 @ref{Target Description Format}.
40353 @kindex maint check xml-descriptions
40354 @item maint check xml-descriptions @var{dir}
40355 Check that the target descriptions dynamically created by @value{GDBN}
40356 equal the descriptions created from XML files found in @var{dir}.
40358 @anchor{maint check libthread-db}
40359 @kindex maint check libthread-db
40360 @item maint check libthread-db
40361 Run integrity checks on the current inferior's thread debugging
40362 library. This exercises all @code{libthread_db} functionality used by
40363 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
40364 @code{proc_service} functions provided by @value{GDBN} that
40365 @code{libthread_db} uses. Note that parts of the test may be skipped
40366 on some platforms when debugging core files.
40368 @kindex maint print core-file-backed-mappings
40369 @cindex memory address space mappings
40370 @item maint print core-file-backed-mappings
40371 Print the file-backed mappings which were loaded from a core file note.
40372 This output represents state internal to @value{GDBN} and should be
40373 similar to the mappings displayed by the @code{info proc mappings}
40376 @kindex maint print dummy-frames
40377 @item maint print dummy-frames
40378 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
40381 (@value{GDBP}) @kbd{b add}
40383 (@value{GDBP}) @kbd{print add(2,3)}
40384 Breakpoint 2, add (a=2, b=3) at @dots{}
40386 The program being debugged stopped while in a function called from GDB.
40388 (@value{GDBP}) @kbd{maint print dummy-frames}
40389 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
40393 Takes an optional file parameter.
40395 @kindex maint print frame-id
40396 @item maint print frame-id
40397 @itemx maint print frame-id @var{level}
40398 Print @value{GDBN}'s internal frame-id for the frame at relative
40399 @var{level}, or for the currently selected frame when @var{level} is
40402 If used, @var{level} should be an integer, as displayed in the
40403 @command{backtrace} output.
40406 (@value{GDBP}) maint print frame-id
40407 frame-id for frame #0: @{stack=0x7fffffffac70,code=0x0000000000401106,!special@}
40408 (@value{GDBP}) maint print frame-id 2
40409 frame-id for frame #2: @{stack=0x7fffffffac90,code=0x000000000040111c,!special@}
40412 @kindex maint print registers
40413 @kindex maint print raw-registers
40414 @kindex maint print cooked-registers
40415 @kindex maint print register-groups
40416 @kindex maint print remote-registers
40417 @item maint print registers @r{[}@var{file}@r{]}
40418 @itemx maint print raw-registers @r{[}@var{file}@r{]}
40419 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
40420 @itemx maint print register-groups @r{[}@var{file}@r{]}
40421 @itemx maint print remote-registers @r{[}@var{file}@r{]}
40422 Print @value{GDBN}'s internal register data structures.
40424 The command @code{maint print raw-registers} includes the contents of
40425 the raw register cache; the command @code{maint print
40426 cooked-registers} includes the (cooked) value of all registers,
40427 including registers which aren't available on the target nor visible
40428 to user; the command @code{maint print register-groups} includes the
40429 groups that each register is a member of; and the command @code{maint
40430 print remote-registers} includes the remote target's register numbers
40431 and offsets in the `G' packets.
40433 These commands take an optional parameter, a file name to which to
40434 write the information.
40436 @kindex maint print reggroups
40437 @item maint print reggroups @r{[}@var{file}@r{]}
40438 Print @value{GDBN}'s internal register group data structures. The
40439 optional argument @var{file} tells to what file to write the
40442 The register groups info looks like this:
40445 (@value{GDBP}) @kbd{maint print reggroups}
40456 @kindex maint flush register-cache
40458 @cindex register cache, flushing
40459 @item maint flush register-cache
40461 Flush the contents of the register cache and as a consequence the
40462 frame cache. This command is useful when debugging issues related to
40463 register fetching, or frame unwinding. The command @code{flushregs}
40464 is deprecated in favor of @code{maint flush register-cache}.
40466 @kindex maint flush source-cache
40467 @cindex source code, caching
40468 @item maint flush source-cache
40469 Flush @value{GDBN}'s cache of source code file contents. After
40470 @value{GDBN} reads a source file, and optionally applies styling
40471 (@pxref{Output Styling}), the file contents are cached. This command
40472 clears that cache. The next time @value{GDBN} wants to show lines
40473 from a source file, the content will be re-read.
40475 This command is useful when debugging issues related to source code
40476 styling. After flushing the cache any source code displayed by
40477 @value{GDBN} will be re-read and re-styled.
40479 @kindex maint print objfiles
40480 @cindex info for known object files
40481 @item maint print objfiles @r{[}@var{regexp}@r{]}
40482 Print a dump of all known object files.
40483 If @var{regexp} is specified, only print object files whose names
40484 match @var{regexp}. For each object file, this command prints its name,
40485 address in memory, and all of its psymtabs and symtabs.
40487 @kindex maint print user-registers
40488 @cindex user registers
40489 @item maint print user-registers
40490 List all currently available @dfn{user registers}. User registers
40491 typically provide alternate names for actual hardware registers. They
40492 include the four ``standard'' registers @code{$fp}, @code{$pc},
40493 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
40494 registers can be used in expressions in the same way as the canonical
40495 register names, but only the latter are listed by the @code{info
40496 registers} and @code{maint print registers} commands.
40498 @kindex maint print section-scripts
40499 @cindex info for known .debug_gdb_scripts-loaded scripts
40500 @item maint print section-scripts [@var{regexp}]
40501 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
40502 If @var{regexp} is specified, only print scripts loaded by object files
40503 matching @var{regexp}.
40504 For each script, this command prints its name as specified in the objfile,
40505 and the full path if known.
40506 @xref{dotdebug_gdb_scripts section}.
40508 @kindex maint print statistics
40509 @cindex bcache statistics
40510 @item maint print statistics
40511 This command prints, for each object file in the program, various data
40512 about that object file followed by the byte cache (@dfn{bcache})
40513 statistics for the object file. The objfile data includes the number
40514 of minimal, partial, full, and stabs symbols, the number of types
40515 defined by the objfile, the number of as yet unexpanded psym tables,
40516 the number of line tables and string tables, and the amount of memory
40517 used by the various tables. The bcache statistics include the counts,
40518 sizes, and counts of duplicates of all and unique objects, max,
40519 average, and median entry size, total memory used and its overhead and
40520 savings, and various measures of the hash table size and chain
40523 @kindex maint print target-stack
40524 @cindex target stack description
40525 @item maint print target-stack
40526 A @dfn{target} is an interface between the debugger and a particular
40527 kind of file or process. Targets can be stacked in @dfn{strata},
40528 so that more than one target can potentially respond to a request.
40529 In particular, memory accesses will walk down the stack of targets
40530 until they find a target that is interested in handling that particular
40533 This command prints a short description of each layer that was pushed on
40534 the @dfn{target stack}, starting from the top layer down to the bottom one.
40536 @kindex maint print type
40537 @cindex type chain of a data type
40538 @item maint print type @var{expr}
40539 Print the type chain for a type specified by @var{expr}. The argument
40540 can be either a type name or a symbol. If it is a symbol, the type of
40541 that symbol is described. The type chain produced by this command is
40542 a recursive definition of the data type as stored in @value{GDBN}'s
40543 data structures, including its flags and contained types.
40545 @kindex maint selftest
40547 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
40548 Run any self tests that were compiled in to @value{GDBN}. This will
40549 print a message showing how many tests were run, and how many failed.
40550 If a @var{filter} is passed, only the tests with @var{filter} in their
40551 name will be ran. If @code{-verbose} is passed, the self tests can be
40554 @kindex maint set selftest verbose
40555 @kindex maint show selftest verbose
40557 @item maint set selftest verbose
40558 @item maint show selftest verbose
40559 Control whether self tests are run verbosely or not.
40561 @kindex maint info selftests
40563 @item maint info selftests
40564 List the selftests compiled in to @value{GDBN}.
40566 @kindex maint set dwarf always-disassemble
40567 @kindex maint show dwarf always-disassemble
40568 @item maint set dwarf always-disassemble
40569 @item maint show dwarf always-disassemble
40570 Control the behavior of @code{info address} when using DWARF debugging
40573 The default is @code{off}, which means that @value{GDBN} should try to
40574 describe a variable's location in an easily readable format. When
40575 @code{on}, @value{GDBN} will instead display the DWARF location
40576 expression in an assembly-like format. Note that some locations are
40577 too complex for @value{GDBN} to describe simply; in this case you will
40578 always see the disassembly form.
40580 Here is an example of the resulting disassembly:
40583 (gdb) info addr argc
40584 Symbol "argc" is a complex DWARF expression:
40588 For more information on these expressions, see
40589 @uref{http://www.dwarfstd.org/, the DWARF standard}.
40591 @kindex maint set dwarf max-cache-age
40592 @kindex maint show dwarf max-cache-age
40593 @item maint set dwarf max-cache-age
40594 @itemx maint show dwarf max-cache-age
40595 Control the DWARF compilation unit cache.
40597 @cindex DWARF compilation units cache
40598 In object files with inter-compilation-unit references, such as those
40599 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
40600 reader needs to frequently refer to previously read compilation units.
40601 This setting controls how long a compilation unit will remain in the
40602 cache if it is not referenced. A higher limit means that cached
40603 compilation units will be stored in memory longer, and more total
40604 memory will be used. Setting it to zero disables caching, which will
40605 slow down @value{GDBN} startup, but reduce memory consumption.
40607 @kindex maint set dwarf unwinders
40608 @kindex maint show dwarf unwinders
40609 @item maint set dwarf unwinders
40610 @itemx maint show dwarf unwinders
40611 Control use of the DWARF frame unwinders.
40613 @cindex DWARF frame unwinders
40614 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
40615 frame unwinders to build the backtrace. Many of these targets will
40616 also have a second mechanism for building the backtrace for use in
40617 cases where DWARF information is not available, this second mechanism
40618 is often an analysis of a function's prologue.
40620 In order to extend testing coverage of the second level stack
40621 unwinding mechanisms it is helpful to be able to disable the DWARF
40622 stack unwinders, this can be done with this switch.
40624 In normal use of @value{GDBN} disabling the DWARF unwinders is not
40625 advisable, there are cases that are better handled through DWARF than
40626 prologue analysis, and the debug experience is likely to be better
40627 with the DWARF frame unwinders enabled.
40629 If DWARF frame unwinders are not supported for a particular target
40630 architecture, then enabling this flag does not cause them to be used.
40632 @kindex maint set worker-threads
40633 @kindex maint show worker-threads
40634 @item maint set worker-threads
40635 @item maint show worker-threads
40636 Control the number of worker threads that may be used by @value{GDBN}.
40637 On capable hosts, @value{GDBN} may use multiple threads to speed up
40638 certain CPU-intensive operations, such as demangling symbol names.
40639 While the number of threads used by @value{GDBN} may vary, this
40640 command can be used to set an upper bound on this number. The default
40641 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
40642 number. Note that this only controls worker threads started by
40643 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
40646 @kindex maint set profile
40647 @kindex maint show profile
40648 @cindex profiling GDB
40649 @item maint set profile
40650 @itemx maint show profile
40651 Control profiling of @value{GDBN}.
40653 Profiling will be disabled until you use the @samp{maint set profile}
40654 command to enable it. When you enable profiling, the system will begin
40655 collecting timing and execution count data; when you disable profiling or
40656 exit @value{GDBN}, the results will be written to a log file. Remember that
40657 if you use profiling, @value{GDBN} will overwrite the profiling log file
40658 (often called @file{gmon.out}). If you have a record of important profiling
40659 data in a @file{gmon.out} file, be sure to move it to a safe location.
40661 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40662 compiled with the @samp{-pg} compiler option.
40664 @kindex maint set show-debug-regs
40665 @kindex maint show show-debug-regs
40666 @cindex hardware debug registers
40667 @item maint set show-debug-regs
40668 @itemx maint show show-debug-regs
40669 Control whether to show variables that mirror the hardware debug
40670 registers. Use @code{on} to enable, @code{off} to disable. If
40671 enabled, the debug registers values are shown when @value{GDBN} inserts or
40672 removes a hardware breakpoint or watchpoint, and when the inferior
40673 triggers a hardware-assisted breakpoint or watchpoint.
40675 @kindex maint set show-all-tib
40676 @kindex maint show show-all-tib
40677 @item maint set show-all-tib
40678 @itemx maint show show-all-tib
40679 Control whether to show all non zero areas within a 1k block starting
40680 at thread local base, when using the @samp{info w32 thread-information-block}
40683 @kindex maint set target-async
40684 @kindex maint show target-async
40685 @item maint set target-async
40686 @itemx maint show target-async
40687 This controls whether @value{GDBN} targets operate in synchronous or
40688 asynchronous mode (@pxref{Background Execution}). Normally the
40689 default is asynchronous, if it is available; but this can be changed
40690 to more easily debug problems occurring only in synchronous mode.
40692 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40693 @kindex maint show target-non-stop
40694 @item maint set target-non-stop
40695 @itemx maint show target-non-stop
40697 This controls whether @value{GDBN} targets always operate in non-stop
40698 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40699 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40700 if supported by the target.
40703 @item maint set target-non-stop auto
40704 This is the default mode. @value{GDBN} controls the target in
40705 non-stop mode if the target supports it.
40707 @item maint set target-non-stop on
40708 @value{GDBN} controls the target in non-stop mode even if the target
40709 does not indicate support.
40711 @item maint set target-non-stop off
40712 @value{GDBN} does not control the target in non-stop mode even if the
40713 target supports it.
40716 @kindex maint set tui-resize-message
40717 @kindex maint show tui-resize-message
40718 @item maint set tui-resize-message
40719 @item maint show tui-resize-message
40720 Control whether @value{GDBN} displays a message each time the terminal
40721 is resized when in TUI mode. The default is @code{off}, which means
40722 that @value{GDBN} is silent during resizes. When @code{on},
40723 @value{GDBN} will display a message after a resize is completed; the
40724 message will include a number indicating how many times the terminal
40725 has been resized. This setting is intended for use by the test suite,
40726 where it would otherwise be difficult to determine when a resize and
40727 refresh has been completed.
40729 @kindex maint set per-command
40730 @kindex maint show per-command
40731 @item maint set per-command
40732 @itemx maint show per-command
40733 @cindex resources used by commands
40735 @value{GDBN} can display the resources used by each command.
40736 This is useful in debugging performance problems.
40739 @item maint set per-command space [on|off]
40740 @itemx maint show per-command space
40741 Enable or disable the printing of the memory used by GDB for each command.
40742 If enabled, @value{GDBN} will display how much memory each command
40743 took, following the command's own output.
40744 This can also be requested by invoking @value{GDBN} with the
40745 @option{--statistics} command-line switch (@pxref{Mode Options}).
40747 @item maint set per-command time [on|off]
40748 @itemx maint show per-command time
40749 Enable or disable the printing of the execution time of @value{GDBN}
40751 If enabled, @value{GDBN} will display how much time it
40752 took to execute each command, following the command's own output.
40753 Both CPU time and wallclock time are printed.
40754 Printing both is useful when trying to determine whether the cost is
40755 CPU or, e.g., disk/network latency.
40756 Note that the CPU time printed is for @value{GDBN} only, it does not include
40757 the execution time of the inferior because there's no mechanism currently
40758 to compute how much time was spent by @value{GDBN} and how much time was
40759 spent by the program been debugged.
40760 This can also be requested by invoking @value{GDBN} with the
40761 @option{--statistics} command-line switch (@pxref{Mode Options}).
40763 @item maint set per-command symtab [on|off]
40764 @itemx maint show per-command symtab
40765 Enable or disable the printing of basic symbol table statistics
40767 If enabled, @value{GDBN} will display the following information:
40771 number of symbol tables
40773 number of primary symbol tables
40775 number of blocks in the blockvector
40779 @kindex maint set check-libthread-db
40780 @kindex maint show check-libthread-db
40781 @item maint set check-libthread-db [on|off]
40782 @itemx maint show check-libthread-db
40783 Control whether @value{GDBN} should run integrity checks on inferior
40784 specific thread debugging libraries as they are loaded. The default
40785 is not to perform such checks. If any check fails @value{GDBN} will
40786 unload the library and continue searching for a suitable candidate as
40787 described in @ref{set libthread-db-search-path}. For more information
40788 about the tests, see @ref{maint check libthread-db}.
40790 @kindex maint set gnu-source-highlight enabled
40791 @kindex maint show gnu-source-highlight enabled
40792 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40793 @itemx maint show gnu-source-highlight enabled
40794 Control whether @value{GDBN} should use the GNU Source Highlight
40795 library for applying styling to source code (@pxref{Output Styling}).
40796 This will be @samp{on} by default if the GNU Source Highlight library
40797 is available. If the GNU Source Highlight library is not available,
40798 then this will be @samp{off} by default, and attempting to change this
40799 value to @samp{on} will give an error.
40801 If the GNU Source Highlight library is not being used, then
40802 @value{GDBN} will use the Python Pygments package for source code
40803 styling, if it is available.
40805 This option is useful for debugging @value{GDBN}'s use of the Pygments
40806 library when @value{GDBN} is linked against the GNU Source Highlight
40809 @anchor{maint_libopcodes_styling}
40810 @kindex maint set libopcodes-styling enabled
40811 @kindex maint show libopcodes-styling enabled
40812 @item maint set libopcodes-styling enabled @r{[}on|off@r{]}
40813 @itemx maint show libopcodes-styling enabled
40814 Control whether @value{GDBN} should use its builtin disassembler
40815 (@file{libopcodes}) to style disassembler output (@pxref{Output
40816 Styling}). The builtin disassembler does not support styling for all
40819 When this option is @samp{off} the builtin disassembler will not be
40820 used for styling, @value{GDBN} will fall back to using the Python
40821 Pygments package if possible.
40823 Trying to set this option @samp{on} for an architecture that the
40824 builtin disassembler is unable to style will give an error, otherwise,
40825 the builtin disassembler will be used to style disassembler output.
40827 This option is @samp{on} by default for supported architectures.
40829 This option is useful for debugging @value{GDBN}'s use of the Pygments
40830 library when @value{GDBN} is built for an architecture that supports
40831 styling with the builtin disassembler
40832 @kindex maint space
40833 @cindex memory used by commands
40834 @item maint space @var{value}
40835 An alias for @code{maint set per-command space}.
40836 A non-zero value enables it, zero disables it.
40839 @cindex time of command execution
40840 @item maint time @var{value}
40841 An alias for @code{maint set per-command time}.
40842 A non-zero value enables it, zero disables it.
40844 @kindex maint translate-address
40845 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40846 Find the symbol stored at the location specified by the address
40847 @var{addr} and an optional section name @var{section}. If found,
40848 @value{GDBN} prints the name of the closest symbol and an offset from
40849 the symbol's location to the specified address. This is similar to
40850 the @code{info address} command (@pxref{Symbols}), except that this
40851 command also allows to find symbols in other sections.
40853 If section was not specified, the section in which the symbol was found
40854 is also printed. For dynamically linked executables, the name of
40855 executable or shared library containing the symbol is printed as well.
40857 @kindex maint test-options
40858 @item maint test-options require-delimiter
40859 @itemx maint test-options unknown-is-error
40860 @itemx maint test-options unknown-is-operand
40861 These commands are used by the testsuite to validate the command
40862 options framework. The @code{require-delimiter} variant requires a
40863 double-dash delimiter to indicate end of options. The
40864 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40865 @code{unknown-is-error} variant throws an error on unknown option,
40866 while @code{unknown-is-operand} treats unknown options as the start of
40867 the command's operands. When run, the commands output the result of
40868 the processed options. When completed, the commands store the
40869 internal result of completion in a variable exposed by the @code{maint
40870 show test-options-completion-result} command.
40872 @kindex maint show test-options-completion-result
40873 @item maint show test-options-completion-result
40874 Shows the result of completing the @code{maint test-options}
40875 subcommands. This is used by the testsuite to validate completion
40876 support in the command options framework.
40878 @kindex maint set test-settings
40879 @kindex maint show test-settings
40880 @item maint set test-settings @var{kind}
40881 @itemx maint show test-settings @var{kind}
40882 These are representative commands for each @var{kind} of setting type
40883 @value{GDBN} supports. They are used by the testsuite for exercising
40884 the settings infrastructure.
40886 @kindex maint set backtrace-on-fatal-signal
40887 @kindex maint show backtrace-on-fatal-signal
40888 @item maint set backtrace-on-fatal-signal [on|off]
40889 @itemx maint show backtrace-on-fatal-signal
40890 When this setting is @code{on}, if @value{GDBN} itself terminates with
40891 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40892 printed to the standard error stream. This backtrace can be used to
40893 help diagnose crashes within @value{GDBN} in situations where a user
40894 is unable to share a corefile with the @value{GDBN} developers.
40896 If the functionality to provide this backtrace is not available for
40897 the platform on which GDB is running then this feature will be
40898 @code{off} by default, and attempting to turn this feature on will
40901 For platforms that do support creating the backtrace this feature is
40902 @code{on} by default.
40905 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40906 Like the @code{with} command, but works with @code{maintenance set}
40907 variables. This is used by the testsuite to exercise the @code{with}
40908 command's infrastructure.
40910 @kindex maint ignore-probes
40911 @item maint ignore-probes [@var{-v}|@var{-verbose}] [@var{provider} [@var{name} [@var{objfile}]]]
40912 @itemx maint ignore-probes @var{-reset}
40913 Set or reset the ignore-probes filter. The @var{provider}, @var{name}
40914 and @var{objfile} arguments are as in @code{enable probes} and
40915 @code{disable probes} (@pxref{enable probes}). Only supported for
40918 Here's an example of using @code{maint ignore-probes}:
40920 (gdb) maint ignore-probes -verbose libc ^longjmp$
40921 ignore-probes filter has been set to:
40923 PROBE_NAME: '^longjmp$'
40926 <... more output ...>
40927 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40928 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40929 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40933 The following command is useful for non-interactive invocations of
40934 @value{GDBN}, such as in the test suite.
40937 @item set watchdog @var{nsec}
40938 @kindex set watchdog
40939 @cindex watchdog timer
40940 @cindex timeout for commands
40941 Set the maximum number of seconds @value{GDBN} will wait for the
40942 target operation to finish. If this time expires, @value{GDBN}
40943 reports and error and the command is aborted.
40945 @item show watchdog
40946 Show the current setting of the target wait timeout.
40949 @node Remote Protocol
40950 @appendix @value{GDBN} Remote Serial Protocol
40955 * Stop Reply Packets::
40956 * General Query Packets::
40957 * Architecture-Specific Protocol Details::
40958 * Tracepoint Packets::
40959 * Host I/O Packets::
40961 * Notification Packets::
40962 * Remote Non-Stop::
40963 * Packet Acknowledgment::
40965 * File-I/O Remote Protocol Extension::
40966 * Library List Format::
40967 * Library List Format for SVR4 Targets::
40968 * Memory Map Format::
40969 * Thread List Format::
40970 * Traceframe Info Format::
40971 * Branch Trace Format::
40972 * Branch Trace Configuration Format::
40978 There may be occasions when you need to know something about the
40979 protocol---for example, if there is only one serial port to your target
40980 machine, you might want your program to do something special if it
40981 recognizes a packet meant for @value{GDBN}.
40983 In the examples below, @samp{->} and @samp{<-} are used to indicate
40984 transmitted and received data, respectively.
40986 @cindex protocol, @value{GDBN} remote serial
40987 @cindex serial protocol, @value{GDBN} remote
40988 @cindex remote serial protocol
40989 All @value{GDBN} commands and responses (other than acknowledgments
40990 and notifications, see @ref{Notification Packets}) are sent as a
40991 @var{packet}. A @var{packet} is introduced with the character
40992 @samp{$}, the actual @var{packet-data}, and the terminating character
40993 @samp{#} followed by a two-digit @var{checksum}:
40996 @code{$}@var{packet-data}@code{#}@var{checksum}
41000 @cindex checksum, for @value{GDBN} remote
41002 The two-digit @var{checksum} is computed as the modulo 256 sum of all
41003 characters between the leading @samp{$} and the trailing @samp{#} (an
41004 eight bit unsigned checksum).
41006 Implementors should note that prior to @value{GDBN} 5.0 the protocol
41007 specification also included an optional two-digit @var{sequence-id}:
41010 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
41013 @cindex sequence-id, for @value{GDBN} remote
41015 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
41016 has never output @var{sequence-id}s. Stubs that handle packets added
41017 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
41019 When either the host or the target machine receives a packet, the first
41020 response expected is an acknowledgment: either @samp{+} (to indicate
41021 the package was received correctly) or @samp{-} (to request
41025 -> @code{$}@var{packet-data}@code{#}@var{checksum}
41030 The @samp{+}/@samp{-} acknowledgments can be disabled
41031 once a connection is established.
41032 @xref{Packet Acknowledgment}, for details.
41034 The host (@value{GDBN}) sends @var{command}s, and the target (the
41035 debugging stub incorporated in your program) sends a @var{response}. In
41036 the case of step and continue @var{command}s, the response is only sent
41037 when the operation has completed, and the target has again stopped all
41038 threads in all attached processes. This is the default all-stop mode
41039 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
41040 execution mode; see @ref{Remote Non-Stop}, for details.
41042 @var{packet-data} consists of a sequence of characters with the
41043 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
41046 @cindex remote protocol, field separator
41047 Fields within the packet should be separated using @samp{,} @samp{;} or
41048 @samp{:}. Except where otherwise noted all numbers are represented in
41049 @sc{hex} with leading zeros suppressed.
41051 Implementors should note that prior to @value{GDBN} 5.0, the character
41052 @samp{:} could not appear as the third character in a packet (as it
41053 would potentially conflict with the @var{sequence-id}).
41055 @cindex remote protocol, binary data
41056 @anchor{Binary Data}
41057 Binary data in most packets is encoded either as two hexadecimal
41058 digits per byte of binary data. This allowed the traditional remote
41059 protocol to work over connections which were only seven-bit clean.
41060 Some packets designed more recently assume an eight-bit clean
41061 connection, and use a more efficient encoding to send and receive
41064 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
41065 as an escape character. Any escaped byte is transmitted as the escape
41066 character followed by the original character XORed with @code{0x20}.
41067 For example, the byte @code{0x7d} would be transmitted as the two
41068 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
41069 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
41070 @samp{@}}) must always be escaped. Responses sent by the stub
41071 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
41072 is not interpreted as the start of a run-length encoded sequence
41075 Response @var{data} can be run-length encoded to save space.
41076 Run-length encoding replaces runs of identical characters with one
41077 instance of the repeated character, followed by a @samp{*} and a
41078 repeat count. The repeat count is itself sent encoded, to avoid
41079 binary characters in @var{data}: a value of @var{n} is sent as
41080 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
41081 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
41082 code 32) for a repeat count of 3. (This is because run-length
41083 encoding starts to win for counts 3 or more.) Thus, for example,
41084 @samp{0* } is a run-length encoding of ``0000'': the space character
41085 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
41088 The printable characters @samp{#} and @samp{$} or with a numeric value
41089 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
41090 seven repeats (@samp{$}) can be expanded using a repeat count of only
41091 five (@samp{"}). For example, @samp{00000000} can be encoded as
41094 The error response returned for some packets includes a two character
41095 error number. That number is not well defined.
41097 @cindex empty response, for unsupported packets
41098 For any @var{command} not supported by the stub, an empty response
41099 (@samp{$#00}) should be returned. That way it is possible to extend the
41100 protocol. A newer @value{GDBN} can tell if a packet is supported based
41103 At a minimum, a stub is required to support the @samp{?} command to
41104 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
41105 commands for register access, and the @samp{m} and @samp{M} commands
41106 for memory access. Stubs that only control single-threaded targets
41107 can implement run control with the @samp{c} (continue) command, and if
41108 the target architecture supports hardware-assisted single-stepping,
41109 the @samp{s} (step) command. Stubs that support multi-threading
41110 targets should support the @samp{vCont} command. All other commands
41116 The following table provides a complete list of all currently defined
41117 @var{command}s and their corresponding response @var{data}.
41118 @xref{File-I/O Remote Protocol Extension}, for details about the File
41119 I/O extension of the remote protocol.
41121 Each packet's description has a template showing the packet's overall
41122 syntax, followed by an explanation of the packet's meaning. We
41123 include spaces in some of the templates for clarity; these are not
41124 part of the packet's syntax. No @value{GDBN} packet uses spaces to
41125 separate its components. For example, a template like @samp{foo
41126 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
41127 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
41128 @var{baz}. @value{GDBN} does not transmit a space character between the
41129 @samp{foo} and the @var{bar}, or between the @var{bar} and the
41132 @cindex @var{thread-id}, in remote protocol
41133 @anchor{thread-id syntax}
41134 Several packets and replies include a @var{thread-id} field to identify
41135 a thread. Normally these are positive numbers with a target-specific
41136 interpretation, formatted as big-endian hex strings. A @var{thread-id}
41137 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
41140 In addition, the remote protocol supports a multiprocess feature in
41141 which the @var{thread-id} syntax is extended to optionally include both
41142 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
41143 The @var{pid} (process) and @var{tid} (thread) components each have the
41144 format described above: a positive number with target-specific
41145 interpretation formatted as a big-endian hex string, literal @samp{-1}
41146 to indicate all processes or threads (respectively), or @samp{0} to
41147 indicate an arbitrary process or thread. Specifying just a process, as
41148 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
41149 error to specify all processes but a specific thread, such as
41150 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
41151 for those packets and replies explicitly documented to include a process
41152 ID, rather than a @var{thread-id}.
41154 The multiprocess @var{thread-id} syntax extensions are only used if both
41155 @value{GDBN} and the stub report support for the @samp{multiprocess}
41156 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
41159 Note that all packet forms beginning with an upper- or lower-case
41160 letter, other than those described here, are reserved for future use.
41162 Here are the packet descriptions.
41167 @cindex @samp{!} packet
41168 @anchor{extended mode}
41169 Enable extended mode. In extended mode, the remote server is made
41170 persistent. The @samp{R} packet is used to restart the program being
41176 The remote target both supports and has enabled extended mode.
41180 @cindex @samp{?} packet
41182 This is sent when connection is first established to query the reason
41183 the target halted. The reply is the same as for step and continue.
41184 This packet has a special interpretation when the target is in
41185 non-stop mode; see @ref{Remote Non-Stop}.
41188 @xref{Stop Reply Packets}, for the reply specifications.
41190 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
41191 @cindex @samp{A} packet
41192 Initialized @code{argv[]} array passed into program. @var{arglen}
41193 specifies the number of bytes in the hex encoded byte stream
41194 @var{arg}. See @code{gdbserver} for more details.
41199 The arguments were set.
41205 @cindex @samp{b} packet
41206 (Don't use this packet; its behavior is not well-defined.)
41207 Change the serial line speed to @var{baud}.
41209 JTC: @emph{When does the transport layer state change? When it's
41210 received, or after the ACK is transmitted. In either case, there are
41211 problems if the command or the acknowledgment packet is dropped.}
41213 Stan: @emph{If people really wanted to add something like this, and get
41214 it working for the first time, they ought to modify ser-unix.c to send
41215 some kind of out-of-band message to a specially-setup stub and have the
41216 switch happen "in between" packets, so that from remote protocol's point
41217 of view, nothing actually happened.}
41219 @item B @var{addr},@var{mode}
41220 @cindex @samp{B} packet
41221 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
41222 breakpoint at @var{addr}.
41224 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
41225 (@pxref{insert breakpoint or watchpoint packet}).
41227 @cindex @samp{bc} packet
41230 Backward continue. Execute the target system in reverse. No parameter.
41231 @xref{Reverse Execution}, for more information.
41234 @xref{Stop Reply Packets}, for the reply specifications.
41236 @cindex @samp{bs} packet
41239 Backward single step. Execute one instruction in reverse. No parameter.
41240 @xref{Reverse Execution}, for more information.
41243 @xref{Stop Reply Packets}, for the reply specifications.
41245 @item c @r{[}@var{addr}@r{]}
41246 @cindex @samp{c} packet
41247 Continue at @var{addr}, which is the address to resume. If @var{addr}
41248 is omitted, resume at current address.
41250 This packet is deprecated for multi-threading support. @xref{vCont
41254 @xref{Stop Reply Packets}, for the reply specifications.
41256 @item C @var{sig}@r{[};@var{addr}@r{]}
41257 @cindex @samp{C} packet
41258 Continue with signal @var{sig} (hex signal number). If
41259 @samp{;@var{addr}} is omitted, resume at same address.
41261 This packet is deprecated for multi-threading support. @xref{vCont
41265 @xref{Stop Reply Packets}, for the reply specifications.
41268 @cindex @samp{d} packet
41271 Don't use this packet; instead, define a general set packet
41272 (@pxref{General Query Packets}).
41276 @cindex @samp{D} packet
41277 The first form of the packet is used to detach @value{GDBN} from the
41278 remote system. It is sent to the remote target
41279 before @value{GDBN} disconnects via the @code{detach} command.
41281 The second form, including a process ID, is used when multiprocess
41282 protocol extensions are enabled (@pxref{multiprocess extensions}), to
41283 detach only a specific process. The @var{pid} is specified as a
41284 big-endian hex string.
41294 @item F @var{RC},@var{EE},@var{CF};@var{XX}
41295 @cindex @samp{F} packet
41296 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
41297 This is part of the File-I/O protocol extension. @xref{File-I/O
41298 Remote Protocol Extension}, for the specification.
41301 @anchor{read registers packet}
41302 @cindex @samp{g} packet
41303 Read general registers.
41307 @item @var{XX@dots{}}
41308 Each byte of register data is described by two hex digits. The bytes
41309 with the register are transmitted in target byte order. The size of
41310 each register and their position within the @samp{g} packet are
41311 determined by the @value{GDBN} internal gdbarch functions
41312 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
41314 When reading registers from a trace frame (@pxref{Analyze Collected
41315 Data,,Using the Collected Data}), the stub may also return a string of
41316 literal @samp{x}'s in place of the register data digits, to indicate
41317 that the corresponding register has not been collected, thus its value
41318 is unavailable. For example, for an architecture with 4 registers of
41319 4 bytes each, the following reply indicates to @value{GDBN} that
41320 registers 0 and 2 have not been collected, while registers 1 and 3
41321 have been collected, and both have zero value:
41325 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
41332 @item G @var{XX@dots{}}
41333 @cindex @samp{G} packet
41334 Write general registers. @xref{read registers packet}, for a
41335 description of the @var{XX@dots{}} data.
41345 @item H @var{op} @var{thread-id}
41346 @cindex @samp{H} packet
41347 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
41348 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
41349 should be @samp{c} for step and continue operations (note that this
41350 is deprecated, supporting the @samp{vCont} command is a better
41351 option), and @samp{g} for other operations. The thread designator
41352 @var{thread-id} has the format and interpretation described in
41353 @ref{thread-id syntax}.
41364 @c 'H': How restrictive (or permissive) is the thread model. If a
41365 @c thread is selected and stopped, are other threads allowed
41366 @c to continue to execute? As I mentioned above, I think the
41367 @c semantics of each command when a thread is selected must be
41368 @c described. For example:
41370 @c 'g': If the stub supports threads and a specific thread is
41371 @c selected, returns the register block from that thread;
41372 @c otherwise returns current registers.
41374 @c 'G' If the stub supports threads and a specific thread is
41375 @c selected, sets the registers of the register block of
41376 @c that thread; otherwise sets current registers.
41378 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
41379 @anchor{cycle step packet}
41380 @cindex @samp{i} packet
41381 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
41382 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
41383 step starting at that address.
41386 @cindex @samp{I} packet
41387 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
41391 @cindex @samp{k} packet
41394 The exact effect of this packet is not specified.
41396 For a bare-metal target, it may power cycle or reset the target
41397 system. For that reason, the @samp{k} packet has no reply.
41399 For a single-process target, it may kill that process if possible.
41401 A multiple-process target may choose to kill just one process, or all
41402 that are under @value{GDBN}'s control. For more precise control, use
41403 the vKill packet (@pxref{vKill packet}).
41405 If the target system immediately closes the connection in response to
41406 @samp{k}, @value{GDBN} does not consider the lack of packet
41407 acknowledgment to be an error, and assumes the kill was successful.
41409 If connected using @kbd{target extended-remote}, and the target does
41410 not close the connection in response to a kill request, @value{GDBN}
41411 probes the target state as if a new connection was opened
41412 (@pxref{? packet}).
41414 @item m @var{addr},@var{length}
41415 @cindex @samp{m} packet
41416 Read @var{length} addressable memory units starting at address @var{addr}
41417 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
41418 any particular boundary.
41420 The stub need not use any particular size or alignment when gathering
41421 data from memory for the response; even if @var{addr} is word-aligned
41422 and @var{length} is a multiple of the word size, the stub is free to
41423 use byte accesses, or not. For this reason, this packet may not be
41424 suitable for accessing memory-mapped I/O devices.
41425 @cindex alignment of remote memory accesses
41426 @cindex size of remote memory accesses
41427 @cindex memory, alignment and size of remote accesses
41431 @item @var{XX@dots{}}
41432 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
41433 The reply may contain fewer addressable memory units than requested if the
41434 server was able to read only part of the region of memory.
41439 @item M @var{addr},@var{length}:@var{XX@dots{}}
41440 @cindex @samp{M} packet
41441 Write @var{length} addressable memory units starting at address @var{addr}
41442 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
41443 byte is transmitted as a two-digit hexadecimal number.
41450 for an error (this includes the case where only part of the data was
41455 @cindex @samp{p} packet
41456 Read the value of register @var{n}; @var{n} is in hex.
41457 @xref{read registers packet}, for a description of how the returned
41458 register value is encoded.
41462 @item @var{XX@dots{}}
41463 the register's value
41467 Indicating an unrecognized @var{query}.
41470 @item P @var{n@dots{}}=@var{r@dots{}}
41471 @anchor{write register packet}
41472 @cindex @samp{P} packet
41473 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
41474 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
41475 digits for each byte in the register (target byte order).
41485 @item q @var{name} @var{params}@dots{}
41486 @itemx Q @var{name} @var{params}@dots{}
41487 @cindex @samp{q} packet
41488 @cindex @samp{Q} packet
41489 General query (@samp{q}) and set (@samp{Q}). These packets are
41490 described fully in @ref{General Query Packets}.
41493 @cindex @samp{r} packet
41494 Reset the entire system.
41496 Don't use this packet; use the @samp{R} packet instead.
41499 @cindex @samp{R} packet
41500 Restart the program being debugged. The @var{XX}, while needed, is ignored.
41501 This packet is only available in extended mode (@pxref{extended mode}).
41503 The @samp{R} packet has no reply.
41505 @item s @r{[}@var{addr}@r{]}
41506 @cindex @samp{s} packet
41507 Single step, resuming at @var{addr}. If
41508 @var{addr} is omitted, resume at same address.
41510 This packet is deprecated for multi-threading support. @xref{vCont
41514 @xref{Stop Reply Packets}, for the reply specifications.
41516 @item S @var{sig}@r{[};@var{addr}@r{]}
41517 @anchor{step with signal packet}
41518 @cindex @samp{S} packet
41519 Step with signal. This is analogous to the @samp{C} packet, but
41520 requests a single-step, rather than a normal resumption of execution.
41522 This packet is deprecated for multi-threading support. @xref{vCont
41526 @xref{Stop Reply Packets}, for the reply specifications.
41528 @item t @var{addr}:@var{PP},@var{MM}
41529 @cindex @samp{t} packet
41530 Search backwards starting at address @var{addr} for a match with pattern
41531 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
41532 There must be at least 3 digits in @var{addr}.
41534 @item T @var{thread-id}
41535 @cindex @samp{T} packet
41536 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
41541 thread is still alive
41547 Packets starting with @samp{v} are identified by a multi-letter name,
41548 up to the first @samp{;} or @samp{?} (or the end of the packet).
41550 @item vAttach;@var{pid}
41551 @cindex @samp{vAttach} packet
41552 Attach to a new process with the specified process ID @var{pid}.
41553 The process ID is a
41554 hexadecimal integer identifying the process. In all-stop mode, all
41555 threads in the attached process are stopped; in non-stop mode, it may be
41556 attached without being stopped if that is supported by the target.
41558 @c In non-stop mode, on a successful vAttach, the stub should set the
41559 @c current thread to a thread of the newly-attached process. After
41560 @c attaching, GDB queries for the attached process's thread ID with qC.
41561 @c Also note that, from a user perspective, whether or not the
41562 @c target is stopped on attach in non-stop mode depends on whether you
41563 @c use the foreground or background version of the attach command, not
41564 @c on what vAttach does; GDB does the right thing with respect to either
41565 @c stopping or restarting threads.
41567 This packet is only available in extended mode (@pxref{extended mode}).
41573 @item @r{Any stop packet}
41574 for success in all-stop mode (@pxref{Stop Reply Packets})
41576 for success in non-stop mode (@pxref{Remote Non-Stop})
41579 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
41580 @cindex @samp{vCont} packet
41581 @anchor{vCont packet}
41582 Resume the inferior, specifying different actions for each thread.
41584 For each inferior thread, the leftmost action with a matching
41585 @var{thread-id} is applied. Threads that don't match any action
41586 remain in their current state. Thread IDs are specified using the
41587 syntax described in @ref{thread-id syntax}. If multiprocess
41588 extensions (@pxref{multiprocess extensions}) are supported, actions
41589 can be specified to match all threads in a process by using the
41590 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
41591 @var{thread-id} matches all threads. Specifying no actions is an
41594 Currently supported actions are:
41600 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
41604 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
41607 @item r @var{start},@var{end}
41608 Step once, and then keep stepping as long as the thread stops at
41609 addresses between @var{start} (inclusive) and @var{end} (exclusive).
41610 The remote stub reports a stop reply when either the thread goes out
41611 of the range or is stopped due to an unrelated reason, such as hitting
41612 a breakpoint. @xref{range stepping}.
41614 If the range is empty (@var{start} == @var{end}), then the action
41615 becomes equivalent to the @samp{s} action. In other words,
41616 single-step once, and report the stop (even if the stepped instruction
41617 jumps to @var{start}).
41619 (A stop reply may be sent at any point even if the PC is still within
41620 the stepping range; for example, it is valid to implement this packet
41621 in a degenerate way as a single instruction step operation.)
41625 The optional argument @var{addr} normally associated with the
41626 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
41627 not supported in @samp{vCont}.
41629 The @samp{t} action is only relevant in non-stop mode
41630 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
41631 A stop reply should be generated for any affected thread not already stopped.
41632 When a thread is stopped by means of a @samp{t} action,
41633 the corresponding stop reply should indicate that the thread has stopped with
41634 signal @samp{0}, regardless of whether the target uses some other signal
41635 as an implementation detail.
41637 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
41638 @samp{r} actions for threads that are already running. Conversely,
41639 the server must ignore @samp{t} actions for threads that are already
41642 @emph{Note:} In non-stop mode, a thread is considered running until
41643 @value{GDBN} acknowledges an asynchronous stop notification for it with
41644 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
41646 The stub must support @samp{vCont} if it reports support for
41647 multiprocess extensions (@pxref{multiprocess extensions}).
41650 @xref{Stop Reply Packets}, for the reply specifications.
41653 @cindex @samp{vCont?} packet
41654 Request a list of actions supported by the @samp{vCont} packet.
41658 @item vCont@r{[};@var{action}@dots{}@r{]}
41659 The @samp{vCont} packet is supported. Each @var{action} is a supported
41660 command in the @samp{vCont} packet.
41662 The @samp{vCont} packet is not supported.
41665 @anchor{vCtrlC packet}
41667 @cindex @samp{vCtrlC} packet
41668 Interrupt remote target as if a control-C was pressed on the remote
41669 terminal. This is the equivalent to reacting to the @code{^C}
41670 (@samp{\003}, the control-C character) character in all-stop mode
41671 while the target is running, except this works in non-stop mode.
41672 @xref{interrupting remote targets}, for more info on the all-stop
41683 @item vFile:@var{operation}:@var{parameter}@dots{}
41684 @cindex @samp{vFile} packet
41685 Perform a file operation on the target system. For details,
41686 see @ref{Host I/O Packets}.
41688 @item vFlashErase:@var{addr},@var{length}
41689 @cindex @samp{vFlashErase} packet
41690 Direct the stub to erase @var{length} bytes of flash starting at
41691 @var{addr}. The region may enclose any number of flash blocks, but
41692 its start and end must fall on block boundaries, as indicated by the
41693 flash block size appearing in the memory map (@pxref{Memory Map
41694 Format}). @value{GDBN} groups flash memory programming operations
41695 together, and sends a @samp{vFlashDone} request after each group; the
41696 stub is allowed to delay erase operation until the @samp{vFlashDone}
41697 packet is received.
41707 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41708 @cindex @samp{vFlashWrite} packet
41709 Direct the stub to write data to flash address @var{addr}. The data
41710 is passed in binary form using the same encoding as for the @samp{X}
41711 packet (@pxref{Binary Data}). The memory ranges specified by
41712 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41713 not overlap, and must appear in order of increasing addresses
41714 (although @samp{vFlashErase} packets for higher addresses may already
41715 have been received; the ordering is guaranteed only between
41716 @samp{vFlashWrite} packets). If a packet writes to an address that was
41717 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41718 target-specific method, the results are unpredictable.
41726 for vFlashWrite addressing non-flash memory
41732 @cindex @samp{vFlashDone} packet
41733 Indicate to the stub that flash programming operation is finished.
41734 The stub is permitted to delay or batch the effects of a group of
41735 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41736 @samp{vFlashDone} packet is received. The contents of the affected
41737 regions of flash memory are unpredictable until the @samp{vFlashDone}
41738 request is completed.
41740 @item vKill;@var{pid}
41741 @cindex @samp{vKill} packet
41742 @anchor{vKill packet}
41743 Kill the process with the specified process ID @var{pid}, which is a
41744 hexadecimal integer identifying the process. This packet is used in
41745 preference to @samp{k} when multiprocess protocol extensions are
41746 supported; see @ref{multiprocess extensions}.
41756 @item vMustReplyEmpty
41757 @cindex @samp{vMustReplyEmpty} packet
41758 The correct reply to an unknown @samp{v} packet is to return the empty
41759 string, however, some older versions of @command{gdbserver} would
41760 incorrectly return @samp{OK} for unknown @samp{v} packets.
41762 The @samp{vMustReplyEmpty} is used as a feature test to check how
41763 @command{gdbserver} handles unknown packets, it is important that this
41764 packet be handled in the same way as other unknown @samp{v} packets.
41765 If this packet is handled differently to other unknown @samp{v}
41766 packets then it is possible that @value{GDBN} may run into problems in
41767 other areas, specifically around use of @samp{vFile:setfs:}.
41769 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41770 @cindex @samp{vRun} packet
41771 Run the program @var{filename}, passing it each @var{argument} on its
41772 command line. The file and arguments are hex-encoded strings. If
41773 @var{filename} is an empty string, the stub may use a default program
41774 (e.g.@: the last program run). The program is created in the stopped
41777 @c FIXME: What about non-stop mode?
41779 This packet is only available in extended mode (@pxref{extended mode}).
41785 @item @r{Any stop packet}
41786 for success (@pxref{Stop Reply Packets})
41790 @cindex @samp{vStopped} packet
41791 @xref{Notification Packets}.
41793 @item X @var{addr},@var{length}:@var{XX@dots{}}
41795 @cindex @samp{X} packet
41796 Write data to memory, where the data is transmitted in binary.
41797 Memory is specified by its address @var{addr} and number of addressable memory
41798 units @var{length} (@pxref{addressable memory unit});
41799 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41809 @item z @var{type},@var{addr},@var{kind}
41810 @itemx Z @var{type},@var{addr},@var{kind}
41811 @anchor{insert breakpoint or watchpoint packet}
41812 @cindex @samp{z} packet
41813 @cindex @samp{Z} packets
41814 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41815 watchpoint starting at address @var{address} of kind @var{kind}.
41817 Each breakpoint and watchpoint packet @var{type} is documented
41820 @emph{Implementation notes: A remote target shall return an empty string
41821 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41822 remote target shall support either both or neither of a given
41823 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41824 avoid potential problems with duplicate packets, the operations should
41825 be implemented in an idempotent way.}
41827 @item z0,@var{addr},@var{kind}
41828 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41829 @cindex @samp{z0} packet
41830 @cindex @samp{Z0} packet
41831 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41832 @var{addr} of type @var{kind}.
41834 A software breakpoint is implemented by replacing the instruction at
41835 @var{addr} with a software breakpoint or trap instruction. The
41836 @var{kind} is target-specific and typically indicates the size of the
41837 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41838 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41839 architectures have additional meanings for @var{kind}
41840 (@pxref{Architecture-Specific Protocol Details}); if no
41841 architecture-specific value is being used, it should be @samp{0}.
41842 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41843 conditional expressions in bytecode form that should be evaluated on
41844 the target's side. These are the conditions that should be taken into
41845 consideration when deciding if the breakpoint trigger should be
41846 reported back to @value{GDBN}.
41848 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41849 for how to best report a software breakpoint event to @value{GDBN}.
41851 The @var{cond_list} parameter is comprised of a series of expressions,
41852 concatenated without separators. Each expression has the following form:
41856 @item X @var{len},@var{expr}
41857 @var{len} is the length of the bytecode expression and @var{expr} is the
41858 actual conditional expression in bytecode form.
41862 The optional @var{cmd_list} parameter introduces commands that may be
41863 run on the target, rather than being reported back to @value{GDBN}.
41864 The parameter starts with a numeric flag @var{persist}; if the flag is
41865 nonzero, then the breakpoint may remain active and the commands
41866 continue to be run even when @value{GDBN} disconnects from the target.
41867 Following this flag is a series of expressions concatenated with no
41868 separators. Each expression has the following form:
41872 @item X @var{len},@var{expr}
41873 @var{len} is the length of the bytecode expression and @var{expr} is the
41874 actual commands expression in bytecode form.
41878 @emph{Implementation note: It is possible for a target to copy or move
41879 code that contains software breakpoints (e.g., when implementing
41880 overlays). The behavior of this packet, in the presence of such a
41881 target, is not defined.}
41893 @item z1,@var{addr},@var{kind}
41894 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41895 @cindex @samp{z1} packet
41896 @cindex @samp{Z1} packet
41897 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41898 address @var{addr}.
41900 A hardware breakpoint is implemented using a mechanism that is not
41901 dependent on being able to modify the target's memory. The
41902 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41903 same meaning as in @samp{Z0} packets.
41905 @emph{Implementation note: A hardware breakpoint is not affected by code
41918 @item z2,@var{addr},@var{kind}
41919 @itemx Z2,@var{addr},@var{kind}
41920 @cindex @samp{z2} packet
41921 @cindex @samp{Z2} packet
41922 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41923 The number of bytes to watch is specified by @var{kind}.
41935 @item z3,@var{addr},@var{kind}
41936 @itemx Z3,@var{addr},@var{kind}
41937 @cindex @samp{z3} packet
41938 @cindex @samp{Z3} packet
41939 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41940 The number of bytes to watch is specified by @var{kind}.
41952 @item z4,@var{addr},@var{kind}
41953 @itemx Z4,@var{addr},@var{kind}
41954 @cindex @samp{z4} packet
41955 @cindex @samp{Z4} packet
41956 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41957 The number of bytes to watch is specified by @var{kind}.
41971 @node Stop Reply Packets
41972 @section Stop Reply Packets
41973 @cindex stop reply packets
41975 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41976 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41977 receive any of the below as a reply. Except for @samp{?}
41978 and @samp{vStopped}, that reply is only returned
41979 when the target halts. In the below the exact meaning of @dfn{signal
41980 number} is defined by the header @file{include/gdb/signals.h} in the
41981 @value{GDBN} source code.
41983 In non-stop mode, the server will simply reply @samp{OK} to commands
41984 such as @samp{vCont}; any stop will be the subject of a future
41985 notification. @xref{Remote Non-Stop}.
41987 As in the description of request packets, we include spaces in the
41988 reply templates for clarity; these are not part of the reply packet's
41989 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41995 The program received signal number @var{AA} (a two-digit hexadecimal
41996 number). This is equivalent to a @samp{T} response with no
41997 @var{n}:@var{r} pairs.
41999 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
42000 @cindex @samp{T} packet reply
42001 The program received signal number @var{AA} (a two-digit hexadecimal
42002 number). This is equivalent to an @samp{S} response, except that the
42003 @samp{@var{n}:@var{r}} pairs can carry values of important registers
42004 and other information directly in the stop reply packet, reducing
42005 round-trip latency. Single-step and breakpoint traps are reported
42006 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
42010 If @var{n} is a hexadecimal number, it is a register number, and the
42011 corresponding @var{r} gives that register's value. The data @var{r} is a
42012 series of bytes in target byte order, with each byte given by a
42013 two-digit hex number.
42016 If @var{n} is @samp{thread}, then @var{r} is the thread ID of
42017 the stopped thread, as specified in @ref{thread-id syntax}.
42020 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
42021 the core on which the stop event was detected.
42024 If @var{n} is a recognized @dfn{stop reason}, it describes a more
42025 specific event that stopped the target. The currently defined stop
42026 reasons are listed below. The @var{aa} should be @samp{05}, the trap
42027 signal. At most one stop reason should be present.
42030 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
42031 and go on to the next; this allows us to extend the protocol in the
42035 The currently defined stop reasons are:
42041 The packet indicates a watchpoint hit, and @var{r} is the data address, in
42044 @item syscall_entry
42045 @itemx syscall_return
42046 The packet indicates a syscall entry or return, and @var{r} is the
42047 syscall number, in hex.
42049 @cindex shared library events, remote reply
42051 The packet indicates that the loaded libraries have changed.
42052 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
42053 list of loaded libraries. The @var{r} part is ignored.
42055 @cindex replay log events, remote reply
42057 The packet indicates that the target cannot continue replaying
42058 logged execution events, because it has reached the end (or the
42059 beginning when executing backward) of the log. The value of @var{r}
42060 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
42061 for more information.
42064 @anchor{swbreak stop reason}
42065 The packet indicates a software breakpoint instruction was executed,
42066 irrespective of whether it was @value{GDBN} that planted the
42067 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
42068 part must be left empty.
42070 On some architectures, such as x86, at the architecture level, when a
42071 breakpoint instruction executes the program counter points at the
42072 breakpoint address plus an offset. On such targets, the stub is
42073 responsible for adjusting the PC to point back at the breakpoint
42076 This packet should not be sent by default; older @value{GDBN} versions
42077 did not support it. @value{GDBN} requests it, by supplying an
42078 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42079 remote stub must also supply the appropriate @samp{qSupported} feature
42080 indicating support.
42082 This packet is required for correct non-stop mode operation.
42085 The packet indicates the target stopped for a hardware breakpoint.
42086 The @var{r} part must be left empty.
42088 The same remarks about @samp{qSupported} and non-stop mode above
42091 @cindex fork events, remote reply
42093 The packet indicates that @code{fork} was called, and @var{r} is the
42094 thread ID of the new child process, as specified in @ref{thread-id
42095 syntax}. This packet is only applicable to targets that support fork
42098 This packet should not be sent by default; older @value{GDBN} versions
42099 did not support it. @value{GDBN} requests it, by supplying an
42100 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42101 remote stub must also supply the appropriate @samp{qSupported} feature
42102 indicating support.
42104 @cindex vfork events, remote reply
42106 The packet indicates that @code{vfork} was called, and @var{r} is the
42107 thread ID of the new child process, as specified in @ref{thread-id
42108 syntax}. This packet is only applicable to targets that support vfork
42111 This packet should not be sent by default; older @value{GDBN} versions
42112 did not support it. @value{GDBN} requests it, by supplying an
42113 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42114 remote stub must also supply the appropriate @samp{qSupported} feature
42115 indicating support.
42117 @cindex vforkdone events, remote reply
42119 The packet indicates that a child process created by a vfork
42120 has either called @code{exec} or terminated, so that the
42121 address spaces of the parent and child process are no longer
42122 shared. The @var{r} part is ignored. This packet is only
42123 applicable to targets that support vforkdone events.
42125 This packet should not be sent by default; older @value{GDBN} versions
42126 did not support it. @value{GDBN} requests it, by supplying an
42127 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42128 remote stub must also supply the appropriate @samp{qSupported} feature
42129 indicating support.
42131 @cindex exec events, remote reply
42133 The packet indicates that @code{execve} was called, and @var{r}
42134 is the absolute pathname of the file that was executed, in hex.
42135 This packet is only applicable to targets that support exec events.
42137 This packet should not be sent by default; older @value{GDBN} versions
42138 did not support it. @value{GDBN} requests it, by supplying an
42139 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42140 remote stub must also supply the appropriate @samp{qSupported} feature
42141 indicating support.
42143 @cindex thread create event, remote reply
42144 @anchor{thread create event}
42146 The packet indicates that the thread was just created. The new thread
42147 is stopped until @value{GDBN} sets it running with a resumption packet
42148 (@pxref{vCont packet}). This packet should not be sent by default;
42149 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
42150 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
42151 @var{r} part is ignored.
42156 @itemx W @var{AA} ; process:@var{pid}
42157 The process exited, and @var{AA} is the exit status. This is only
42158 applicable to certain targets.
42160 The second form of the response, including the process ID of the
42161 exited process, can be used only when @value{GDBN} has reported
42162 support for multiprocess protocol extensions; see @ref{multiprocess
42163 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
42167 @itemx X @var{AA} ; process:@var{pid}
42168 The process terminated with signal @var{AA}.
42170 The second form of the response, including the process ID of the
42171 terminated process, can be used only when @value{GDBN} has reported
42172 support for multiprocess protocol extensions; see @ref{multiprocess
42173 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
42176 @anchor{thread exit event}
42177 @cindex thread exit event, remote reply
42178 @item w @var{AA} ; @var{tid}
42180 The thread exited, and @var{AA} is the exit status. This response
42181 should not be sent by default; @value{GDBN} requests it with the
42182 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
42183 @var{AA} is formatted as a big-endian hex string.
42186 There are no resumed threads left in the target. In other words, even
42187 though the process is alive, the last resumed thread has exited. For
42188 example, say the target process has two threads: thread 1 and thread
42189 2. The client leaves thread 1 stopped, and resumes thread 2, which
42190 subsequently exits. At this point, even though the process is still
42191 alive, and thus no @samp{W} stop reply is sent, no thread is actually
42192 executing either. The @samp{N} stop reply thus informs the client
42193 that it can stop waiting for stop replies. This packet should not be
42194 sent by default; older @value{GDBN} versions did not support it.
42195 @value{GDBN} requests it, by supplying an appropriate
42196 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
42197 also supply the appropriate @samp{qSupported} feature indicating
42200 @item O @var{XX}@dots{}
42201 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
42202 written as the program's console output. This can happen at any time
42203 while the program is running and the debugger should continue to wait
42204 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
42206 @item F @var{call-id},@var{parameter}@dots{}
42207 @var{call-id} is the identifier which says which host system call should
42208 be called. This is just the name of the function. Translation into the
42209 correct system call is only applicable as it's defined in @value{GDBN}.
42210 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
42213 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
42214 this very system call.
42216 The target replies with this packet when it expects @value{GDBN} to
42217 call a host system call on behalf of the target. @value{GDBN} replies
42218 with an appropriate @samp{F} packet and keeps up waiting for the next
42219 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
42220 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
42221 Protocol Extension}, for more details.
42225 @node General Query Packets
42226 @section General Query Packets
42227 @cindex remote query requests
42229 Packets starting with @samp{q} are @dfn{general query packets};
42230 packets starting with @samp{Q} are @dfn{general set packets}. General
42231 query and set packets are a semi-unified form for retrieving and
42232 sending information to and from the stub.
42234 The initial letter of a query or set packet is followed by a name
42235 indicating what sort of thing the packet applies to. For example,
42236 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
42237 definitions with the stub. These packet names follow some
42242 The name must not contain commas, colons or semicolons.
42244 Most @value{GDBN} query and set packets have a leading upper case
42247 The names of custom vendor packets should use a company prefix, in
42248 lower case, followed by a period. For example, packets designed at
42249 the Acme Corporation might begin with @samp{qacme.foo} (for querying
42250 foos) or @samp{Qacme.bar} (for setting bars).
42253 The name of a query or set packet should be separated from any
42254 parameters by a @samp{:}; the parameters themselves should be
42255 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
42256 full packet name, and check for a separator or the end of the packet,
42257 in case two packet names share a common prefix. New packets should not begin
42258 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
42259 packets predate these conventions, and have arguments without any terminator
42260 for the packet name; we suspect they are in widespread use in places that
42261 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
42262 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
42265 Like the descriptions of the other packets, each description here
42266 has a template showing the packet's overall syntax, followed by an
42267 explanation of the packet's meaning. We include spaces in some of the
42268 templates for clarity; these are not part of the packet's syntax. No
42269 @value{GDBN} packet uses spaces to separate its components.
42271 Here are the currently defined query and set packets:
42277 Turn on or off the agent as a helper to perform some debugging operations
42278 delegated from @value{GDBN} (@pxref{Control Agent}).
42280 @item QAllow:@var{op}:@var{val}@dots{}
42281 @cindex @samp{QAllow} packet
42282 Specify which operations @value{GDBN} expects to request of the
42283 target, as a semicolon-separated list of operation name and value
42284 pairs. Possible values for @var{op} include @samp{WriteReg},
42285 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
42286 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
42287 indicating that @value{GDBN} will not request the operation, or 1,
42288 indicating that it may. (The target can then use this to set up its
42289 own internals optimally, for instance if the debugger never expects to
42290 insert breakpoints, it may not need to install its own trap handler.)
42293 @cindex current thread, remote request
42294 @cindex @samp{qC} packet
42295 Return the current thread ID.
42299 @item QC @var{thread-id}
42300 Where @var{thread-id} is a thread ID as documented in
42301 @ref{thread-id syntax}.
42302 @item @r{(anything else)}
42303 Any other reply implies the old thread ID.
42306 @item qCRC:@var{addr},@var{length}
42307 @cindex CRC of memory block, remote request
42308 @cindex @samp{qCRC} packet
42309 @anchor{qCRC packet}
42310 Compute the CRC checksum of a block of memory using CRC-32 defined in
42311 IEEE 802.3. The CRC is computed byte at a time, taking the most
42312 significant bit of each byte first. The initial pattern code
42313 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
42315 @emph{Note:} This is the same CRC used in validating separate debug
42316 files (@pxref{Separate Debug Files, , Debugging Information in Separate
42317 Files}). However the algorithm is slightly different. When validating
42318 separate debug files, the CRC is computed taking the @emph{least}
42319 significant bit of each byte first, and the final result is inverted to
42320 detect trailing zeros.
42325 An error (such as memory fault)
42326 @item C @var{crc32}
42327 The specified memory region's checksum is @var{crc32}.
42330 @item QDisableRandomization:@var{value}
42331 @cindex disable address space randomization, remote request
42332 @cindex @samp{QDisableRandomization} packet
42333 Some target operating systems will randomize the virtual address space
42334 of the inferior process as a security feature, but provide a feature
42335 to disable such randomization, e.g.@: to allow for a more deterministic
42336 debugging experience. On such systems, this packet with a @var{value}
42337 of 1 directs the target to disable address space randomization for
42338 processes subsequently started via @samp{vRun} packets, while a packet
42339 with a @var{value} of 0 tells the target to enable address space
42342 This packet is only available in extended mode (@pxref{extended mode}).
42347 The request succeeded.
42350 An error occurred. The error number @var{nn} is given as hex digits.
42353 An empty reply indicates that @samp{QDisableRandomization} is not supported
42357 This packet is not probed by default; the remote stub must request it,
42358 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42359 This should only be done on targets that actually support disabling
42360 address space randomization.
42362 @item QStartupWithShell:@var{value}
42363 @cindex startup with shell, remote request
42364 @cindex @samp{QStartupWithShell} packet
42365 On UNIX-like targets, it is possible to start the inferior using a
42366 shell program. This is the default behavior on both @value{GDBN} and
42367 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
42368 used to inform @command{gdbserver} whether it should start the
42369 inferior using a shell or not.
42371 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
42372 to start the inferior. If @var{value} is @samp{1},
42373 @command{gdbserver} will use a shell to start the inferior. All other
42374 values are considered an error.
42376 This packet is only available in extended mode (@pxref{extended
42382 The request succeeded.
42385 An error occurred. The error number @var{nn} is given as hex digits.
42388 This packet is not probed by default; the remote stub must request it,
42389 by supplying an appropriate @samp{qSupported} response
42390 (@pxref{qSupported}). This should only be done on targets that
42391 actually support starting the inferior using a shell.
42393 Use of this packet is controlled by the @code{set startup-with-shell}
42394 command; @pxref{set startup-with-shell}.
42396 @item QEnvironmentHexEncoded:@var{hex-value}
42397 @anchor{QEnvironmentHexEncoded}
42398 @cindex set environment variable, remote request
42399 @cindex @samp{QEnvironmentHexEncoded} packet
42400 On UNIX-like targets, it is possible to set environment variables that
42401 will be passed to the inferior during the startup process. This
42402 packet is used to inform @command{gdbserver} of an environment
42403 variable that has been defined by the user on @value{GDBN} (@pxref{set
42406 The packet is composed by @var{hex-value}, an hex encoded
42407 representation of the @var{name=value} format representing an
42408 environment variable. The name of the environment variable is
42409 represented by @var{name}, and the value to be assigned to the
42410 environment variable is represented by @var{value}. If the variable
42411 has no value (i.e., the value is @code{null}), then @var{value} will
42414 This packet is only available in extended mode (@pxref{extended
42420 The request succeeded.
42423 This packet is not probed by default; the remote stub must request it,
42424 by supplying an appropriate @samp{qSupported} response
42425 (@pxref{qSupported}). This should only be done on targets that
42426 actually support passing environment variables to the starting
42429 This packet is related to the @code{set environment} command;
42430 @pxref{set environment}.
42432 @item QEnvironmentUnset:@var{hex-value}
42433 @anchor{QEnvironmentUnset}
42434 @cindex unset environment variable, remote request
42435 @cindex @samp{QEnvironmentUnset} packet
42436 On UNIX-like targets, it is possible to unset environment variables
42437 before starting the inferior in the remote target. This packet is
42438 used to inform @command{gdbserver} of an environment variable that has
42439 been unset by the user on @value{GDBN} (@pxref{unset environment}).
42441 The packet is composed by @var{hex-value}, an hex encoded
42442 representation of the name of the environment variable to be unset.
42444 This packet is only available in extended mode (@pxref{extended
42450 The request succeeded.
42453 This packet is not probed by default; the remote stub must request it,
42454 by supplying an appropriate @samp{qSupported} response
42455 (@pxref{qSupported}). This should only be done on targets that
42456 actually support passing environment variables to the starting
42459 This packet is related to the @code{unset environment} command;
42460 @pxref{unset environment}.
42462 @item QEnvironmentReset
42463 @anchor{QEnvironmentReset}
42464 @cindex reset environment, remote request
42465 @cindex @samp{QEnvironmentReset} packet
42466 On UNIX-like targets, this packet is used to reset the state of
42467 environment variables in the remote target before starting the
42468 inferior. In this context, reset means unsetting all environment
42469 variables that were previously set by the user (i.e., were not
42470 initially present in the environment). It is sent to
42471 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
42472 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
42473 (@pxref{QEnvironmentUnset}) packets.
42475 This packet is only available in extended mode (@pxref{extended
42481 The request succeeded.
42484 This packet is not probed by default; the remote stub must request it,
42485 by supplying an appropriate @samp{qSupported} response
42486 (@pxref{qSupported}). This should only be done on targets that
42487 actually support passing environment variables to the starting
42490 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
42491 @anchor{QSetWorkingDir packet}
42492 @cindex set working directory, remote request
42493 @cindex @samp{QSetWorkingDir} packet
42494 This packet is used to inform the remote server of the intended
42495 current working directory for programs that are going to be executed.
42497 The packet is composed by @var{directory}, an hex encoded
42498 representation of the directory that the remote inferior will use as
42499 its current working directory. If @var{directory} is an empty string,
42500 the remote server should reset the inferior's current working
42501 directory to its original, empty value.
42503 This packet is only available in extended mode (@pxref{extended
42509 The request succeeded.
42513 @itemx qsThreadInfo
42514 @cindex list active threads, remote request
42515 @cindex @samp{qfThreadInfo} packet
42516 @cindex @samp{qsThreadInfo} packet
42517 Obtain a list of all active thread IDs from the target (OS). Since there
42518 may be too many active threads to fit into one reply packet, this query
42519 works iteratively: it may require more than one query/reply sequence to
42520 obtain the entire list of threads. The first query of the sequence will
42521 be the @samp{qfThreadInfo} query; subsequent queries in the
42522 sequence will be the @samp{qsThreadInfo} query.
42524 NOTE: This packet replaces the @samp{qL} query (see below).
42528 @item m @var{thread-id}
42530 @item m @var{thread-id},@var{thread-id}@dots{}
42531 a comma-separated list of thread IDs
42533 (lower case letter @samp{L}) denotes end of list.
42536 In response to each query, the target will reply with a list of one or
42537 more thread IDs, separated by commas.
42538 @value{GDBN} will respond to each reply with a request for more thread
42539 ids (using the @samp{qs} form of the query), until the target responds
42540 with @samp{l} (lower-case ell, for @dfn{last}).
42541 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
42544 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
42545 initial connection with the remote target, and the very first thread ID
42546 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
42547 message. Therefore, the stub should ensure that the first thread ID in
42548 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
42550 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
42551 @cindex get thread-local storage address, remote request
42552 @cindex @samp{qGetTLSAddr} packet
42553 Fetch the address associated with thread local storage specified
42554 by @var{thread-id}, @var{offset}, and @var{lm}.
42556 @var{thread-id} is the thread ID associated with the
42557 thread for which to fetch the TLS address. @xref{thread-id syntax}.
42559 @var{offset} is the (big endian, hex encoded) offset associated with the
42560 thread local variable. (This offset is obtained from the debug
42561 information associated with the variable.)
42563 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
42564 load module associated with the thread local storage. For example,
42565 a @sc{gnu}/Linux system will pass the link map address of the shared
42566 object associated with the thread local storage under consideration.
42567 Other operating environments may choose to represent the load module
42568 differently, so the precise meaning of this parameter will vary.
42572 @item @var{XX}@dots{}
42573 Hex encoded (big endian) bytes representing the address of the thread
42574 local storage requested.
42577 An error occurred. The error number @var{nn} is given as hex digits.
42580 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
42583 @item qGetTIBAddr:@var{thread-id}
42584 @cindex get thread information block address
42585 @cindex @samp{qGetTIBAddr} packet
42586 Fetch address of the Windows OS specific Thread Information Block.
42588 @var{thread-id} is the thread ID associated with the thread.
42592 @item @var{XX}@dots{}
42593 Hex encoded (big endian) bytes representing the linear address of the
42594 thread information block.
42597 An error occured. This means that either the thread was not found, or the
42598 address could not be retrieved.
42601 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
42604 @item qL @var{startflag} @var{threadcount} @var{nextthread}
42605 Obtain thread information from RTOS. Where: @var{startflag} (one hex
42606 digit) is one to indicate the first query and zero to indicate a
42607 subsequent query; @var{threadcount} (two hex digits) is the maximum
42608 number of threads the response packet can contain; and @var{nextthread}
42609 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
42610 returned in the response as @var{argthread}.
42612 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
42616 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
42617 Where: @var{count} (two hex digits) is the number of threads being
42618 returned; @var{done} (one hex digit) is zero to indicate more threads
42619 and one indicates no further threads; @var{argthreadid} (eight hex
42620 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
42621 is a sequence of thread IDs, @var{threadid} (eight hex
42622 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
42625 @item qMemTags:@var{start address},@var{length}:@var{type}
42627 @cindex fetch memory tags
42628 @cindex @samp{qMemTags} packet
42629 Fetch memory tags of type @var{type} from the address range
42630 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42631 target is responsible for calculating how many tags will be returned, as this
42632 is architecture-specific.
42634 @var{start address} is the starting address of the memory range.
42636 @var{length} is the length, in bytes, of the memory range.
42638 @var{type} is the type of tag the request wants to fetch. The type is a signed
42643 @item @var{mxx}@dots{}
42644 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
42645 tags found in the requested memory range.
42648 An error occured. This means that fetching of memory tags failed for some
42652 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
42653 although this should not happen given @value{GDBN} will only send this packet
42654 if the stub has advertised support for memory tagging via @samp{qSupported}.
42657 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
42659 @cindex store memory tags
42660 @cindex @samp{QMemTags} packet
42661 Store memory tags of type @var{type} to the address range
42662 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42663 target is responsible for interpreting the type, the tag bytes and modifying
42664 the memory tag granules accordingly, given this is architecture-specific.
42666 The interpretation of how many tags (@var{nt}) should be written to how many
42667 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
42668 implementation-specific, but the following is suggested.
42670 If the number of memory tags, @var{nt}, is greater than or equal to the
42671 number of memory tag granules, @var{ng}, only @var{ng} tags will be
42674 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
42675 and the tag bytes will be used as a pattern that will get repeated until
42676 @var{ng} tags are stored.
42678 @var{start address} is the starting address of the memory range. The address
42679 does not have any restriction on alignment or size.
42681 @var{length} is the length, in bytes, of the memory range.
42683 @var{type} is the type of tag the request wants to fetch. The type is a signed
42686 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
42687 interpreted by the target. Each pair of hex digits is interpreted as a
42693 The request was successful and the memory tag granules were modified
42697 An error occured. This means that modifying the memory tag granules failed
42701 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42702 although this should not happen given @value{GDBN} will only send this packet
42703 if the stub has advertised support for memory tagging via @samp{qSupported}.
42707 @cindex section offsets, remote request
42708 @cindex @samp{qOffsets} packet
42709 Get section offsets that the target used when relocating the downloaded
42714 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42715 Relocate the @code{Text} section by @var{xxx} from its original address.
42716 Relocate the @code{Data} section by @var{yyy} from its original address.
42717 If the object file format provides segment information (e.g.@: @sc{elf}
42718 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42719 segments by the supplied offsets.
42721 @emph{Note: while a @code{Bss} offset may be included in the response,
42722 @value{GDBN} ignores this and instead applies the @code{Data} offset
42723 to the @code{Bss} section.}
42725 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42726 Relocate the first segment of the object file, which conventionally
42727 contains program code, to a starting address of @var{xxx}. If
42728 @samp{DataSeg} is specified, relocate the second segment, which
42729 conventionally contains modifiable data, to a starting address of
42730 @var{yyy}. @value{GDBN} will report an error if the object file
42731 does not contain segment information, or does not contain at least
42732 as many segments as mentioned in the reply. Extra segments are
42733 kept at fixed offsets relative to the last relocated segment.
42736 @item qP @var{mode} @var{thread-id}
42737 @cindex thread information, remote request
42738 @cindex @samp{qP} packet
42739 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42740 encoded 32 bit mode; @var{thread-id} is a thread ID
42741 (@pxref{thread-id syntax}).
42743 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42746 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42750 @cindex non-stop mode, remote request
42751 @cindex @samp{QNonStop} packet
42753 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42754 @xref{Remote Non-Stop}, for more information.
42759 The request succeeded.
42762 An error occurred. The error number @var{nn} is given as hex digits.
42765 An empty reply indicates that @samp{QNonStop} is not supported by
42769 This packet is not probed by default; the remote stub must request it,
42770 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42771 Use of this packet is controlled by the @code{set non-stop} command;
42772 @pxref{Non-Stop Mode}.
42774 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42775 @itemx QCatchSyscalls:0
42776 @cindex catch syscalls from inferior, remote request
42777 @cindex @samp{QCatchSyscalls} packet
42778 @anchor{QCatchSyscalls}
42779 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42780 catching syscalls from the inferior process.
42782 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42783 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42784 is listed, every system call should be reported.
42786 Note that if a syscall not in the list is reported, @value{GDBN} will
42787 still filter the event according to its own list from all corresponding
42788 @code{catch syscall} commands. However, it is more efficient to only
42789 report the requested syscalls.
42791 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42792 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42794 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42795 kept for the new process too. On targets where exec may affect syscall
42796 numbers, for example with exec between 32 and 64-bit processes, the
42797 client should send a new packet with the new syscall list.
42802 The request succeeded.
42805 An error occurred. @var{nn} are hex digits.
42808 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42812 Use of this packet is controlled by the @code{set remote catch-syscalls}
42813 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42814 This packet is not probed by default; the remote stub must request it,
42815 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42817 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42818 @cindex pass signals to inferior, remote request
42819 @cindex @samp{QPassSignals} packet
42820 @anchor{QPassSignals}
42821 Each listed @var{signal} should be passed directly to the inferior process.
42822 Signals are numbered identically to continue packets and stop replies
42823 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42824 strictly greater than the previous item. These signals do not need to stop
42825 the inferior, or be reported to @value{GDBN}. All other signals should be
42826 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42827 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42828 new list. This packet improves performance when using @samp{handle
42829 @var{signal} nostop noprint pass}.
42834 The request succeeded.
42837 An error occurred. The error number @var{nn} is given as hex digits.
42840 An empty reply indicates that @samp{QPassSignals} is not supported by
42844 Use of this packet is controlled by the @code{set remote pass-signals}
42845 command (@pxref{Remote Configuration, set remote pass-signals}).
42846 This packet is not probed by default; the remote stub must request it,
42847 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42849 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42850 @cindex signals the inferior may see, remote request
42851 @cindex @samp{QProgramSignals} packet
42852 @anchor{QProgramSignals}
42853 Each listed @var{signal} may be delivered to the inferior process.
42854 Others should be silently discarded.
42856 In some cases, the remote stub may need to decide whether to deliver a
42857 signal to the program or not without @value{GDBN} involvement. One
42858 example of that is while detaching --- the program's threads may have
42859 stopped for signals that haven't yet had a chance of being reported to
42860 @value{GDBN}, and so the remote stub can use the signal list specified
42861 by this packet to know whether to deliver or ignore those pending
42864 This does not influence whether to deliver a signal as requested by a
42865 resumption packet (@pxref{vCont packet}).
42867 Signals are numbered identically to continue packets and stop replies
42868 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42869 strictly greater than the previous item. Multiple
42870 @samp{QProgramSignals} packets do not combine; any earlier
42871 @samp{QProgramSignals} list is completely replaced by the new list.
42876 The request succeeded.
42879 An error occurred. The error number @var{nn} is given as hex digits.
42882 An empty reply indicates that @samp{QProgramSignals} is not supported
42886 Use of this packet is controlled by the @code{set remote program-signals}
42887 command (@pxref{Remote Configuration, set remote program-signals}).
42888 This packet is not probed by default; the remote stub must request it,
42889 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42891 @anchor{QThreadEvents}
42892 @item QThreadEvents:1
42893 @itemx QThreadEvents:0
42894 @cindex thread create/exit events, remote request
42895 @cindex @samp{QThreadEvents} packet
42897 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42898 reporting of thread create and exit events. @xref{thread create
42899 event}, for the reply specifications. For example, this is used in
42900 non-stop mode when @value{GDBN} stops a set of threads and
42901 synchronously waits for the their corresponding stop replies. Without
42902 exit events, if one of the threads exits, @value{GDBN} would hang
42903 forever not knowing that it should no longer expect a stop for that
42904 same thread. @value{GDBN} does not enable this feature unless the
42905 stub reports that it supports it by including @samp{QThreadEvents+} in
42906 its @samp{qSupported} reply.
42911 The request succeeded.
42914 An error occurred. The error number @var{nn} is given as hex digits.
42917 An empty reply indicates that @samp{QThreadEvents} is not supported by
42921 Use of this packet is controlled by the @code{set remote thread-events}
42922 command (@pxref{Remote Configuration, set remote thread-events}).
42924 @item qRcmd,@var{command}
42925 @cindex execute remote command, remote request
42926 @cindex @samp{qRcmd} packet
42927 @var{command} (hex encoded) is passed to the local interpreter for
42928 execution. Invalid commands should be reported using the output
42929 string. Before the final result packet, the target may also respond
42930 with a number of intermediate @samp{O@var{output}} console output
42931 packets. @emph{Implementors should note that providing access to a
42932 stubs's interpreter may have security implications}.
42937 A command response with no output.
42939 A command response with the hex encoded output string @var{OUTPUT}.
42941 Indicate a badly formed request. The error number @var{NN} is given as
42944 An empty reply indicates that @samp{qRcmd} is not recognized.
42947 (Note that the @code{qRcmd} packet's name is separated from the
42948 command by a @samp{,}, not a @samp{:}, contrary to the naming
42949 conventions above. Please don't use this packet as a model for new
42952 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42953 @cindex searching memory, in remote debugging
42955 @cindex @samp{qSearch:memory} packet
42957 @cindex @samp{qSearch memory} packet
42958 @anchor{qSearch memory}
42959 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42960 Both @var{address} and @var{length} are encoded in hex;
42961 @var{search-pattern} is a sequence of bytes, also hex encoded.
42966 The pattern was not found.
42968 The pattern was found at @var{address}.
42970 A badly formed request or an error was encountered while searching memory.
42972 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42975 @item QStartNoAckMode
42976 @cindex @samp{QStartNoAckMode} packet
42977 @anchor{QStartNoAckMode}
42978 Request that the remote stub disable the normal @samp{+}/@samp{-}
42979 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42984 The stub has switched to no-acknowledgment mode.
42985 @value{GDBN} acknowledges this response,
42986 but neither the stub nor @value{GDBN} shall send or expect further
42987 @samp{+}/@samp{-} acknowledgments in the current connection.
42989 An empty reply indicates that the stub does not support no-acknowledgment mode.
42992 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42993 @cindex supported packets, remote query
42994 @cindex features of the remote protocol
42995 @cindex @samp{qSupported} packet
42996 @anchor{qSupported}
42997 Tell the remote stub about features supported by @value{GDBN}, and
42998 query the stub for features it supports. This packet allows
42999 @value{GDBN} and the remote stub to take advantage of each others'
43000 features. @samp{qSupported} also consolidates multiple feature probes
43001 at startup, to improve @value{GDBN} performance---a single larger
43002 packet performs better than multiple smaller probe packets on
43003 high-latency links. Some features may enable behavior which must not
43004 be on by default, e.g.@: because it would confuse older clients or
43005 stubs. Other features may describe packets which could be
43006 automatically probed for, but are not. These features must be
43007 reported before @value{GDBN} will use them. This ``default
43008 unsupported'' behavior is not appropriate for all packets, but it
43009 helps to keep the initial connection time under control with new
43010 versions of @value{GDBN} which support increasing numbers of packets.
43014 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
43015 The stub supports or does not support each returned @var{stubfeature},
43016 depending on the form of each @var{stubfeature} (see below for the
43019 An empty reply indicates that @samp{qSupported} is not recognized,
43020 or that no features needed to be reported to @value{GDBN}.
43023 The allowed forms for each feature (either a @var{gdbfeature} in the
43024 @samp{qSupported} packet, or a @var{stubfeature} in the response)
43028 @item @var{name}=@var{value}
43029 The remote protocol feature @var{name} is supported, and associated
43030 with the specified @var{value}. The format of @var{value} depends
43031 on the feature, but it must not include a semicolon.
43033 The remote protocol feature @var{name} is supported, and does not
43034 need an associated value.
43036 The remote protocol feature @var{name} is not supported.
43038 The remote protocol feature @var{name} may be supported, and
43039 @value{GDBN} should auto-detect support in some other way when it is
43040 needed. This form will not be used for @var{gdbfeature} notifications,
43041 but may be used for @var{stubfeature} responses.
43044 Whenever the stub receives a @samp{qSupported} request, the
43045 supplied set of @value{GDBN} features should override any previous
43046 request. This allows @value{GDBN} to put the stub in a known
43047 state, even if the stub had previously been communicating with
43048 a different version of @value{GDBN}.
43050 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
43055 This feature indicates whether @value{GDBN} supports multiprocess
43056 extensions to the remote protocol. @value{GDBN} does not use such
43057 extensions unless the stub also reports that it supports them by
43058 including @samp{multiprocess+} in its @samp{qSupported} reply.
43059 @xref{multiprocess extensions}, for details.
43062 This feature indicates that @value{GDBN} supports the XML target
43063 description. If the stub sees @samp{xmlRegisters=} with target
43064 specific strings separated by a comma, it will report register
43068 This feature indicates whether @value{GDBN} supports the
43069 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
43070 instruction reply packet}).
43073 This feature indicates whether @value{GDBN} supports the swbreak stop
43074 reason in stop replies. @xref{swbreak stop reason}, for details.
43077 This feature indicates whether @value{GDBN} supports the hwbreak stop
43078 reason in stop replies. @xref{swbreak stop reason}, for details.
43081 This feature indicates whether @value{GDBN} supports fork event
43082 extensions to the remote protocol. @value{GDBN} does not use such
43083 extensions unless the stub also reports that it supports them by
43084 including @samp{fork-events+} in its @samp{qSupported} reply.
43087 This feature indicates whether @value{GDBN} supports vfork event
43088 extensions to the remote protocol. @value{GDBN} does not use such
43089 extensions unless the stub also reports that it supports them by
43090 including @samp{vfork-events+} in its @samp{qSupported} reply.
43093 This feature indicates whether @value{GDBN} supports exec event
43094 extensions to the remote protocol. @value{GDBN} does not use such
43095 extensions unless the stub also reports that it supports them by
43096 including @samp{exec-events+} in its @samp{qSupported} reply.
43098 @item vContSupported
43099 This feature indicates whether @value{GDBN} wants to know the
43100 supported actions in the reply to @samp{vCont?} packet.
43103 Stubs should ignore any unknown values for
43104 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
43105 packet supports receiving packets of unlimited length (earlier
43106 versions of @value{GDBN} may reject overly long responses). Additional values
43107 for @var{gdbfeature} may be defined in the future to let the stub take
43108 advantage of new features in @value{GDBN}, e.g.@: incompatible
43109 improvements in the remote protocol---the @samp{multiprocess} feature is
43110 an example of such a feature. The stub's reply should be independent
43111 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
43112 describes all the features it supports, and then the stub replies with
43113 all the features it supports.
43115 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
43116 responses, as long as each response uses one of the standard forms.
43118 Some features are flags. A stub which supports a flag feature
43119 should respond with a @samp{+} form response. Other features
43120 require values, and the stub should respond with an @samp{=}
43123 Each feature has a default value, which @value{GDBN} will use if
43124 @samp{qSupported} is not available or if the feature is not mentioned
43125 in the @samp{qSupported} response. The default values are fixed; a
43126 stub is free to omit any feature responses that match the defaults.
43128 Not all features can be probed, but for those which can, the probing
43129 mechanism is useful: in some cases, a stub's internal
43130 architecture may not allow the protocol layer to know some information
43131 about the underlying target in advance. This is especially common in
43132 stubs which may be configured for multiple targets.
43134 These are the currently defined stub features and their properties:
43136 @multitable @columnfractions 0.35 0.2 0.12 0.2
43137 @c NOTE: The first row should be @headitem, but we do not yet require
43138 @c a new enough version of Texinfo (4.7) to use @headitem.
43140 @tab Value Required
43144 @item @samp{PacketSize}
43149 @item @samp{qXfer:auxv:read}
43154 @item @samp{qXfer:btrace:read}
43159 @item @samp{qXfer:btrace-conf:read}
43164 @item @samp{qXfer:exec-file:read}
43169 @item @samp{qXfer:features:read}
43174 @item @samp{qXfer:libraries:read}
43179 @item @samp{qXfer:libraries-svr4:read}
43184 @item @samp{augmented-libraries-svr4-read}
43189 @item @samp{qXfer:memory-map:read}
43194 @item @samp{qXfer:sdata:read}
43199 @item @samp{qXfer:siginfo:read}
43204 @item @samp{qXfer:siginfo:write}
43209 @item @samp{qXfer:threads:read}
43214 @item @samp{qXfer:traceframe-info:read}
43219 @item @samp{qXfer:uib:read}
43224 @item @samp{qXfer:fdpic:read}
43229 @item @samp{Qbtrace:off}
43234 @item @samp{Qbtrace:bts}
43239 @item @samp{Qbtrace:pt}
43244 @item @samp{Qbtrace-conf:bts:size}
43249 @item @samp{Qbtrace-conf:pt:size}
43254 @item @samp{QNonStop}
43259 @item @samp{QCatchSyscalls}
43264 @item @samp{QPassSignals}
43269 @item @samp{QStartNoAckMode}
43274 @item @samp{multiprocess}
43279 @item @samp{ConditionalBreakpoints}
43284 @item @samp{ConditionalTracepoints}
43289 @item @samp{ReverseContinue}
43294 @item @samp{ReverseStep}
43299 @item @samp{TracepointSource}
43304 @item @samp{QAgent}
43309 @item @samp{QAllow}
43314 @item @samp{QDisableRandomization}
43319 @item @samp{EnableDisableTracepoints}
43324 @item @samp{QTBuffer:size}
43329 @item @samp{tracenz}
43334 @item @samp{BreakpointCommands}
43339 @item @samp{swbreak}
43344 @item @samp{hwbreak}
43349 @item @samp{fork-events}
43354 @item @samp{vfork-events}
43359 @item @samp{exec-events}
43364 @item @samp{QThreadEvents}
43369 @item @samp{no-resumed}
43374 @item @samp{memory-tagging}
43381 These are the currently defined stub features, in more detail:
43384 @cindex packet size, remote protocol
43385 @item PacketSize=@var{bytes}
43386 The remote stub can accept packets up to at least @var{bytes} in
43387 length. @value{GDBN} will send packets up to this size for bulk
43388 transfers, and will never send larger packets. This is a limit on the
43389 data characters in the packet, including the frame and checksum.
43390 There is no trailing NUL byte in a remote protocol packet; if the stub
43391 stores packets in a NUL-terminated format, it should allow an extra
43392 byte in its buffer for the NUL. If this stub feature is not supported,
43393 @value{GDBN} guesses based on the size of the @samp{g} packet response.
43395 @item qXfer:auxv:read
43396 The remote stub understands the @samp{qXfer:auxv:read} packet
43397 (@pxref{qXfer auxiliary vector read}).
43399 @item qXfer:btrace:read
43400 The remote stub understands the @samp{qXfer:btrace:read}
43401 packet (@pxref{qXfer btrace read}).
43403 @item qXfer:btrace-conf:read
43404 The remote stub understands the @samp{qXfer:btrace-conf:read}
43405 packet (@pxref{qXfer btrace-conf read}).
43407 @item qXfer:exec-file:read
43408 The remote stub understands the @samp{qXfer:exec-file:read} packet
43409 (@pxref{qXfer executable filename read}).
43411 @item qXfer:features:read
43412 The remote stub understands the @samp{qXfer:features:read} packet
43413 (@pxref{qXfer target description read}).
43415 @item qXfer:libraries:read
43416 The remote stub understands the @samp{qXfer:libraries:read} packet
43417 (@pxref{qXfer library list read}).
43419 @item qXfer:libraries-svr4:read
43420 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
43421 (@pxref{qXfer svr4 library list read}).
43423 @item augmented-libraries-svr4-read
43424 The remote stub understands the augmented form of the
43425 @samp{qXfer:libraries-svr4:read} packet
43426 (@pxref{qXfer svr4 library list read}).
43428 @item qXfer:memory-map:read
43429 The remote stub understands the @samp{qXfer:memory-map:read} packet
43430 (@pxref{qXfer memory map read}).
43432 @item qXfer:sdata:read
43433 The remote stub understands the @samp{qXfer:sdata:read} packet
43434 (@pxref{qXfer sdata read}).
43436 @item qXfer:siginfo:read
43437 The remote stub understands the @samp{qXfer:siginfo:read} packet
43438 (@pxref{qXfer siginfo read}).
43440 @item qXfer:siginfo:write
43441 The remote stub understands the @samp{qXfer:siginfo:write} packet
43442 (@pxref{qXfer siginfo write}).
43444 @item qXfer:threads:read
43445 The remote stub understands the @samp{qXfer:threads:read} packet
43446 (@pxref{qXfer threads read}).
43448 @item qXfer:traceframe-info:read
43449 The remote stub understands the @samp{qXfer:traceframe-info:read}
43450 packet (@pxref{qXfer traceframe info read}).
43452 @item qXfer:uib:read
43453 The remote stub understands the @samp{qXfer:uib:read}
43454 packet (@pxref{qXfer unwind info block}).
43456 @item qXfer:fdpic:read
43457 The remote stub understands the @samp{qXfer:fdpic:read}
43458 packet (@pxref{qXfer fdpic loadmap read}).
43461 The remote stub understands the @samp{QNonStop} packet
43462 (@pxref{QNonStop}).
43464 @item QCatchSyscalls
43465 The remote stub understands the @samp{QCatchSyscalls} packet
43466 (@pxref{QCatchSyscalls}).
43469 The remote stub understands the @samp{QPassSignals} packet
43470 (@pxref{QPassSignals}).
43472 @item QStartNoAckMode
43473 The remote stub understands the @samp{QStartNoAckMode} packet and
43474 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
43477 @anchor{multiprocess extensions}
43478 @cindex multiprocess extensions, in remote protocol
43479 The remote stub understands the multiprocess extensions to the remote
43480 protocol syntax. The multiprocess extensions affect the syntax of
43481 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
43482 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
43483 replies. Note that reporting this feature indicates support for the
43484 syntactic extensions only, not that the stub necessarily supports
43485 debugging of more than one process at a time. The stub must not use
43486 multiprocess extensions in packet replies unless @value{GDBN} has also
43487 indicated it supports them in its @samp{qSupported} request.
43489 @item qXfer:osdata:read
43490 The remote stub understands the @samp{qXfer:osdata:read} packet
43491 ((@pxref{qXfer osdata read}).
43493 @item ConditionalBreakpoints
43494 The target accepts and implements evaluation of conditional expressions
43495 defined for breakpoints. The target will only report breakpoint triggers
43496 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
43498 @item ConditionalTracepoints
43499 The remote stub accepts and implements conditional expressions defined
43500 for tracepoints (@pxref{Tracepoint Conditions}).
43502 @item ReverseContinue
43503 The remote stub accepts and implements the reverse continue packet
43507 The remote stub accepts and implements the reverse step packet
43510 @item TracepointSource
43511 The remote stub understands the @samp{QTDPsrc} packet that supplies
43512 the source form of tracepoint definitions.
43515 The remote stub understands the @samp{QAgent} packet.
43518 The remote stub understands the @samp{QAllow} packet.
43520 @item QDisableRandomization
43521 The remote stub understands the @samp{QDisableRandomization} packet.
43523 @item StaticTracepoint
43524 @cindex static tracepoints, in remote protocol
43525 The remote stub supports static tracepoints.
43527 @item InstallInTrace
43528 @anchor{install tracepoint in tracing}
43529 The remote stub supports installing tracepoint in tracing.
43531 @item EnableDisableTracepoints
43532 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
43533 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
43534 to be enabled and disabled while a trace experiment is running.
43536 @item QTBuffer:size
43537 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
43538 packet that allows to change the size of the trace buffer.
43541 @cindex string tracing, in remote protocol
43542 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
43543 See @ref{Bytecode Descriptions} for details about the bytecode.
43545 @item BreakpointCommands
43546 @cindex breakpoint commands, in remote protocol
43547 The remote stub supports running a breakpoint's command list itself,
43548 rather than reporting the hit to @value{GDBN}.
43551 The remote stub understands the @samp{Qbtrace:off} packet.
43554 The remote stub understands the @samp{Qbtrace:bts} packet.
43557 The remote stub understands the @samp{Qbtrace:pt} packet.
43559 @item Qbtrace-conf:bts:size
43560 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
43562 @item Qbtrace-conf:pt:size
43563 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
43566 The remote stub reports the @samp{swbreak} stop reason for memory
43570 The remote stub reports the @samp{hwbreak} stop reason for hardware
43574 The remote stub reports the @samp{fork} stop reason for fork events.
43577 The remote stub reports the @samp{vfork} stop reason for vfork events
43578 and vforkdone events.
43581 The remote stub reports the @samp{exec} stop reason for exec events.
43583 @item vContSupported
43584 The remote stub reports the supported actions in the reply to
43585 @samp{vCont?} packet.
43587 @item QThreadEvents
43588 The remote stub understands the @samp{QThreadEvents} packet.
43591 The remote stub reports the @samp{N} stop reply.
43594 @item memory-tagging
43595 The remote stub supports and implements the required memory tagging
43596 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
43597 @samp{QMemTags} (@pxref{QMemTags}) packets.
43599 For AArch64 GNU/Linux systems, this feature also requires access to the
43600 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
43601 This is done via the @samp{vFile} requests.
43606 @cindex symbol lookup, remote request
43607 @cindex @samp{qSymbol} packet
43608 Notify the target that @value{GDBN} is prepared to serve symbol lookup
43609 requests. Accept requests from the target for the values of symbols.
43614 The target does not need to look up any (more) symbols.
43615 @item qSymbol:@var{sym_name}
43616 The target requests the value of symbol @var{sym_name} (hex encoded).
43617 @value{GDBN} may provide the value by using the
43618 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
43622 @item qSymbol:@var{sym_value}:@var{sym_name}
43623 Set the value of @var{sym_name} to @var{sym_value}.
43625 @var{sym_name} (hex encoded) is the name of a symbol whose value the
43626 target has previously requested.
43628 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
43629 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
43635 The target does not need to look up any (more) symbols.
43636 @item qSymbol:@var{sym_name}
43637 The target requests the value of a new symbol @var{sym_name} (hex
43638 encoded). @value{GDBN} will continue to supply the values of symbols
43639 (if available), until the target ceases to request them.
43644 @itemx QTDisconnected
43651 @itemx qTMinFTPILen
43653 @xref{Tracepoint Packets}.
43655 @anchor{qThreadExtraInfo}
43656 @item qThreadExtraInfo,@var{thread-id}
43657 @cindex thread attributes info, remote request
43658 @cindex @samp{qThreadExtraInfo} packet
43659 Obtain from the target OS a printable string description of thread
43660 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
43661 for the forms of @var{thread-id}. This
43662 string may contain anything that the target OS thinks is interesting
43663 for @value{GDBN} to tell the user about the thread. The string is
43664 displayed in @value{GDBN}'s @code{info threads} display. Some
43665 examples of possible thread extra info strings are @samp{Runnable}, or
43666 @samp{Blocked on Mutex}.
43670 @item @var{XX}@dots{}
43671 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
43672 comprising the printable string containing the extra information about
43673 the thread's attributes.
43676 (Note that the @code{qThreadExtraInfo} packet's name is separated from
43677 the command by a @samp{,}, not a @samp{:}, contrary to the naming
43678 conventions above. Please don't use this packet as a model for new
43697 @xref{Tracepoint Packets}.
43699 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43700 @cindex read special object, remote request
43701 @cindex @samp{qXfer} packet
43702 @anchor{qXfer read}
43703 Read uninterpreted bytes from the target's special data area
43704 identified by the keyword @var{object}. Request @var{length} bytes
43705 starting at @var{offset} bytes into the data. The content and
43706 encoding of @var{annex} is specific to @var{object}; it can supply
43707 additional details about what data to access.
43712 Data @var{data} (@pxref{Binary Data}) has been read from the
43713 target. There may be more data at a higher address (although
43714 it is permitted to return @samp{m} even for the last valid
43715 block of data, as long as at least one byte of data was read).
43716 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43720 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43721 There is no more data to be read. It is possible for @var{data} to
43722 have fewer bytes than the @var{length} in the request.
43725 The @var{offset} in the request is at the end of the data.
43726 There is no more data to be read.
43729 The request was malformed, or @var{annex} was invalid.
43732 The offset was invalid, or there was an error encountered reading the data.
43733 The @var{nn} part is a hex-encoded @code{errno} value.
43736 An empty reply indicates the @var{object} string was not recognized by
43737 the stub, or that the object does not support reading.
43740 Here are the specific requests of this form defined so far. All the
43741 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43742 formats, listed above.
43745 @item qXfer:auxv:read::@var{offset},@var{length}
43746 @anchor{qXfer auxiliary vector read}
43747 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43748 auxiliary vector}. Note @var{annex} must be empty.
43750 This packet is not probed by default; the remote stub must request it,
43751 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43753 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43754 @anchor{qXfer btrace read}
43756 Return a description of the current branch trace.
43757 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43758 packet may have one of the following values:
43762 Returns all available branch trace.
43765 Returns all available branch trace if the branch trace changed since
43766 the last read request.
43769 Returns the new branch trace since the last read request. Adds a new
43770 block to the end of the trace that begins at zero and ends at the source
43771 location of the first branch in the trace buffer. This extra block is
43772 used to stitch traces together.
43774 If the trace buffer overflowed, returns an error indicating the overflow.
43777 This packet is not probed by default; the remote stub must request it
43778 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43780 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43781 @anchor{qXfer btrace-conf read}
43783 Return a description of the current branch trace configuration.
43784 @xref{Branch Trace Configuration Format}.
43786 This packet is not probed by default; the remote stub must request it
43787 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43789 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43790 @anchor{qXfer executable filename read}
43791 Return the full absolute name of the file that was executed to create
43792 a process running on the remote system. The annex specifies the
43793 numeric process ID of the process to query, encoded as a hexadecimal
43794 number. If the annex part is empty the remote stub should return the
43795 filename corresponding to the currently executing process.
43797 This packet is not probed by default; the remote stub must request it,
43798 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43800 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43801 @anchor{qXfer target description read}
43802 Access the @dfn{target description}. @xref{Target Descriptions}. The
43803 annex specifies which XML document to access. The main description is
43804 always loaded from the @samp{target.xml} annex.
43806 This packet is not probed by default; the remote stub must request it,
43807 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43809 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43810 @anchor{qXfer library list read}
43811 Access the target's list of loaded libraries. @xref{Library List Format}.
43812 The annex part of the generic @samp{qXfer} packet must be empty
43813 (@pxref{qXfer read}).
43815 Targets which maintain a list of libraries in the program's memory do
43816 not need to implement this packet; it is designed for platforms where
43817 the operating system manages the list of loaded libraries.
43819 This packet is not probed by default; the remote stub must request it,
43820 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43822 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43823 @anchor{qXfer svr4 library list read}
43824 Access the target's list of loaded libraries when the target is an SVR4
43825 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43826 of the generic @samp{qXfer} packet must be empty unless the remote
43827 stub indicated it supports the augmented form of this packet
43828 by supplying an appropriate @samp{qSupported} response
43829 (@pxref{qXfer read}, @ref{qSupported}).
43831 This packet is optional for better performance on SVR4 targets.
43832 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43834 This packet is not probed by default; the remote stub must request it,
43835 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43837 If the remote stub indicates it supports the augmented form of this
43838 packet then the annex part of the generic @samp{qXfer} packet may
43839 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43840 arguments. The currently supported arguments are:
43843 @item start=@var{address}
43844 A hexadecimal number specifying the address of the @samp{struct
43845 link_map} to start reading the library list from. If unset or zero
43846 then the first @samp{struct link_map} in the library list will be
43847 chosen as the starting point.
43849 @item prev=@var{address}
43850 A hexadecimal number specifying the address of the @samp{struct
43851 link_map} immediately preceding the @samp{struct link_map}
43852 specified by the @samp{start} argument. If unset or zero then
43853 the remote stub will expect that no @samp{struct link_map}
43854 exists prior to the starting point.
43856 @item lmid=@var{lmid}
43857 A hexadecimal number specifying a namespace identifier. This is
43858 currently only used together with @samp{start} to provide the
43859 namespace identifier back to @value{GDBN} in the response.
43860 @value{GDBN} will only provide values that were previously reported to
43861 it. If unset, the response will include @samp{lmid="0x0"}.
43864 Arguments that are not understood by the remote stub will be silently
43867 @item qXfer:memory-map:read::@var{offset},@var{length}
43868 @anchor{qXfer memory map read}
43869 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43870 annex part of the generic @samp{qXfer} packet must be empty
43871 (@pxref{qXfer read}).
43873 This packet is not probed by default; the remote stub must request it,
43874 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43876 @item qXfer:sdata:read::@var{offset},@var{length}
43877 @anchor{qXfer sdata read}
43879 Read contents of the extra collected static tracepoint marker
43880 information. The annex part of the generic @samp{qXfer} packet must
43881 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43884 This packet is not probed by default; the remote stub must request it,
43885 by supplying an appropriate @samp{qSupported} response
43886 (@pxref{qSupported}).
43888 @item qXfer:siginfo:read::@var{offset},@var{length}
43889 @anchor{qXfer siginfo read}
43890 Read contents of the extra signal information on the target
43891 system. The annex part of the generic @samp{qXfer} packet must be
43892 empty (@pxref{qXfer read}).
43894 This packet is not probed by default; the remote stub must request it,
43895 by supplying an appropriate @samp{qSupported} response
43896 (@pxref{qSupported}).
43898 @item qXfer:threads:read::@var{offset},@var{length}
43899 @anchor{qXfer threads read}
43900 Access the list of threads on target. @xref{Thread List Format}. The
43901 annex part of the generic @samp{qXfer} packet must be empty
43902 (@pxref{qXfer read}).
43904 This packet is not probed by default; the remote stub must request it,
43905 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43907 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43908 @anchor{qXfer traceframe info read}
43910 Return a description of the current traceframe's contents.
43911 @xref{Traceframe Info Format}. The annex part of the generic
43912 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43914 This packet is not probed by default; the remote stub must request it,
43915 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43917 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43918 @anchor{qXfer unwind info block}
43920 Return the unwind information block for @var{pc}. This packet is used
43921 on OpenVMS/ia64 to ask the kernel unwind information.
43923 This packet is not probed by default.
43925 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43926 @anchor{qXfer fdpic loadmap read}
43927 Read contents of @code{loadmap}s on the target system. The
43928 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43929 executable @code{loadmap} or interpreter @code{loadmap} to read.
43931 This packet is not probed by default; the remote stub must request it,
43932 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43934 @item qXfer:osdata:read::@var{offset},@var{length}
43935 @anchor{qXfer osdata read}
43936 Access the target's @dfn{operating system information}.
43937 @xref{Operating System Information}.
43941 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43942 @cindex write data into object, remote request
43943 @anchor{qXfer write}
43944 Write uninterpreted bytes into the target's special data area
43945 identified by the keyword @var{object}, starting at @var{offset} bytes
43946 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43947 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43948 is specific to @var{object}; it can supply additional details about what data
43954 @var{nn} (hex encoded) is the number of bytes written.
43955 This may be fewer bytes than supplied in the request.
43958 The request was malformed, or @var{annex} was invalid.
43961 The offset was invalid, or there was an error encountered writing the data.
43962 The @var{nn} part is a hex-encoded @code{errno} value.
43965 An empty reply indicates the @var{object} string was not
43966 recognized by the stub, or that the object does not support writing.
43969 Here are the specific requests of this form defined so far. All the
43970 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43971 formats, listed above.
43974 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43975 @anchor{qXfer siginfo write}
43976 Write @var{data} to the extra signal information on the target system.
43977 The annex part of the generic @samp{qXfer} packet must be
43978 empty (@pxref{qXfer write}).
43980 This packet is not probed by default; the remote stub must request it,
43981 by supplying an appropriate @samp{qSupported} response
43982 (@pxref{qSupported}).
43985 @item qXfer:@var{object}:@var{operation}:@dots{}
43986 Requests of this form may be added in the future. When a stub does
43987 not recognize the @var{object} keyword, or its support for
43988 @var{object} does not recognize the @var{operation} keyword, the stub
43989 must respond with an empty packet.
43991 @item qAttached:@var{pid}
43992 @cindex query attached, remote request
43993 @cindex @samp{qAttached} packet
43994 Return an indication of whether the remote server attached to an
43995 existing process or created a new process. When the multiprocess
43996 protocol extensions are supported (@pxref{multiprocess extensions}),
43997 @var{pid} is an integer in hexadecimal format identifying the target
43998 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43999 the query packet will be simplified as @samp{qAttached}.
44001 This query is used, for example, to know whether the remote process
44002 should be detached or killed when a @value{GDBN} session is ended with
44003 the @code{quit} command.
44008 The remote server attached to an existing process.
44010 The remote server created a new process.
44012 A badly formed request or an error was encountered.
44016 Enable branch tracing for the current thread using Branch Trace Store.
44021 Branch tracing has been enabled.
44023 A badly formed request or an error was encountered.
44027 Enable branch tracing for the current thread using Intel Processor Trace.
44032 Branch tracing has been enabled.
44034 A badly formed request or an error was encountered.
44038 Disable branch tracing for the current thread.
44043 Branch tracing has been disabled.
44045 A badly formed request or an error was encountered.
44048 @item Qbtrace-conf:bts:size=@var{value}
44049 Set the requested ring buffer size for new threads that use the
44050 btrace recording method in bts format.
44055 The ring buffer size has been set.
44057 A badly formed request or an error was encountered.
44060 @item Qbtrace-conf:pt:size=@var{value}
44061 Set the requested ring buffer size for new threads that use the
44062 btrace recording method in pt format.
44067 The ring buffer size has been set.
44069 A badly formed request or an error was encountered.
44074 @node Architecture-Specific Protocol Details
44075 @section Architecture-Specific Protocol Details
44077 This section describes how the remote protocol is applied to specific
44078 target architectures. Also see @ref{Standard Target Features}, for
44079 details of XML target descriptions for each architecture.
44082 * ARM-Specific Protocol Details::
44083 * MIPS-Specific Protocol Details::
44086 @node ARM-Specific Protocol Details
44087 @subsection @acronym{ARM}-specific Protocol Details
44090 * ARM Breakpoint Kinds::
44091 * ARM Memory Tag Types::
44094 @node ARM Breakpoint Kinds
44095 @subsubsection @acronym{ARM} Breakpoint Kinds
44096 @cindex breakpoint kinds, @acronym{ARM}
44098 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
44103 16-bit Thumb mode breakpoint.
44106 32-bit Thumb mode (Thumb-2) breakpoint.
44109 32-bit @acronym{ARM} mode breakpoint.
44113 @node ARM Memory Tag Types
44114 @subsubsection @acronym{ARM} Memory Tag Types
44115 @cindex memory tag types, @acronym{ARM}
44117 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
44130 @node MIPS-Specific Protocol Details
44131 @subsection @acronym{MIPS}-specific Protocol Details
44134 * MIPS Register packet Format::
44135 * MIPS Breakpoint Kinds::
44138 @node MIPS Register packet Format
44139 @subsubsection @acronym{MIPS} Register Packet Format
44140 @cindex register packet format, @acronym{MIPS}
44142 The following @code{g}/@code{G} packets have previously been defined.
44143 In the below, some thirty-two bit registers are transferred as
44144 sixty-four bits. Those registers should be zero/sign extended (which?)
44145 to fill the space allocated. Register bytes are transferred in target
44146 byte order. The two nibbles within a register byte are transferred
44147 most-significant -- least-significant.
44152 All registers are transferred as thirty-two bit quantities in the order:
44153 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
44154 registers; fsr; fir; fp.
44157 All registers are transferred as sixty-four bit quantities (including
44158 thirty-two bit registers such as @code{sr}). The ordering is the same
44163 @node MIPS Breakpoint Kinds
44164 @subsubsection @acronym{MIPS} Breakpoint Kinds
44165 @cindex breakpoint kinds, @acronym{MIPS}
44167 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
44172 16-bit @acronym{MIPS16} mode breakpoint.
44175 16-bit @acronym{microMIPS} mode breakpoint.
44178 32-bit standard @acronym{MIPS} mode breakpoint.
44181 32-bit @acronym{microMIPS} mode breakpoint.
44185 @node Tracepoint Packets
44186 @section Tracepoint Packets
44187 @cindex tracepoint packets
44188 @cindex packets, tracepoint
44190 Here we describe the packets @value{GDBN} uses to implement
44191 tracepoints (@pxref{Tracepoints}).
44195 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
44196 @cindex @samp{QTDP} packet
44197 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
44198 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
44199 the tracepoint is disabled. The @var{step} gives the tracepoint's step
44200 count, and @var{pass} gives its pass count. If an @samp{F} is present,
44201 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
44202 the number of bytes that the target should copy elsewhere to make room
44203 for the tracepoint. If an @samp{X} is present, it introduces a
44204 tracepoint condition, which consists of a hexadecimal length, followed
44205 by a comma and hex-encoded bytes, in a manner similar to action
44206 encodings as described below. If the trailing @samp{-} is present,
44207 further @samp{QTDP} packets will follow to specify this tracepoint's
44213 The packet was understood and carried out.
44215 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
44217 The packet was not recognized.
44220 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
44221 Define actions to be taken when a tracepoint is hit. The @var{n} and
44222 @var{addr} must be the same as in the initial @samp{QTDP} packet for
44223 this tracepoint. This packet may only be sent immediately after
44224 another @samp{QTDP} packet that ended with a @samp{-}. If the
44225 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
44226 specifying more actions for this tracepoint.
44228 In the series of action packets for a given tracepoint, at most one
44229 can have an @samp{S} before its first @var{action}. If such a packet
44230 is sent, it and the following packets define ``while-stepping''
44231 actions. Any prior packets define ordinary actions --- that is, those
44232 taken when the tracepoint is first hit. If no action packet has an
44233 @samp{S}, then all the packets in the series specify ordinary
44234 tracepoint actions.
44236 The @samp{@var{action}@dots{}} portion of the packet is a series of
44237 actions, concatenated without separators. Each action has one of the
44243 Collect the registers whose bits are set in @var{mask},
44244 a hexadecimal number whose @var{i}'th bit is set if register number
44245 @var{i} should be collected. (The least significant bit is numbered
44246 zero.) Note that @var{mask} may be any number of digits long; it may
44247 not fit in a 32-bit word.
44249 @item M @var{basereg},@var{offset},@var{len}
44250 Collect @var{len} bytes of memory starting at the address in register
44251 number @var{basereg}, plus @var{offset}. If @var{basereg} is
44252 @samp{-1}, then the range has a fixed address: @var{offset} is the
44253 address of the lowest byte to collect. The @var{basereg},
44254 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
44255 values (the @samp{-1} value for @var{basereg} is a special case).
44257 @item X @var{len},@var{expr}
44258 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
44259 it directs. The agent expression @var{expr} is as described in
44260 @ref{Agent Expressions}. Each byte of the expression is encoded as a
44261 two-digit hex number in the packet; @var{len} is the number of bytes
44262 in the expression (and thus one-half the number of hex digits in the
44267 Any number of actions may be packed together in a single @samp{QTDP}
44268 packet, as long as the packet does not exceed the maximum packet
44269 length (400 bytes, for many stubs). There may be only one @samp{R}
44270 action per tracepoint, and it must precede any @samp{M} or @samp{X}
44271 actions. Any registers referred to by @samp{M} and @samp{X} actions
44272 must be collected by a preceding @samp{R} action. (The
44273 ``while-stepping'' actions are treated as if they were attached to a
44274 separate tracepoint, as far as these restrictions are concerned.)
44279 The packet was understood and carried out.
44281 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
44283 The packet was not recognized.
44286 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
44287 @cindex @samp{QTDPsrc} packet
44288 Specify a source string of tracepoint @var{n} at address @var{addr}.
44289 This is useful to get accurate reproduction of the tracepoints
44290 originally downloaded at the beginning of the trace run. The @var{type}
44291 is the name of the tracepoint part, such as @samp{cond} for the
44292 tracepoint's conditional expression (see below for a list of types), while
44293 @var{bytes} is the string, encoded in hexadecimal.
44295 @var{start} is the offset of the @var{bytes} within the overall source
44296 string, while @var{slen} is the total length of the source string.
44297 This is intended for handling source strings that are longer than will
44298 fit in a single packet.
44299 @c Add detailed example when this info is moved into a dedicated
44300 @c tracepoint descriptions section.
44302 The available string types are @samp{at} for the location,
44303 @samp{cond} for the conditional, and @samp{cmd} for an action command.
44304 @value{GDBN} sends a separate packet for each command in the action
44305 list, in the same order in which the commands are stored in the list.
44307 The target does not need to do anything with source strings except
44308 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
44311 Although this packet is optional, and @value{GDBN} will only send it
44312 if the target replies with @samp{TracepointSource} @xref{General
44313 Query Packets}, it makes both disconnected tracing and trace files
44314 much easier to use. Otherwise the user must be careful that the
44315 tracepoints in effect while looking at trace frames are identical to
44316 the ones in effect during the trace run; even a small discrepancy
44317 could cause @samp{tdump} not to work, or a particular trace frame not
44320 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
44321 @cindex define trace state variable, remote request
44322 @cindex @samp{QTDV} packet
44323 Create a new trace state variable, number @var{n}, with an initial
44324 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
44325 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
44326 the option of not using this packet for initial values of zero; the
44327 target should simply create the trace state variables as they are
44328 mentioned in expressions. The value @var{builtin} should be 1 (one)
44329 if the trace state variable is builtin and 0 (zero) if it is not builtin.
44330 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
44331 @samp{qTsV} packet had it set. The contents of @var{name} is the
44332 hex-encoded name (without the leading @samp{$}) of the trace state
44335 @item QTFrame:@var{n}
44336 @cindex @samp{QTFrame} packet
44337 Select the @var{n}'th tracepoint frame from the buffer, and use the
44338 register and memory contents recorded there to answer subsequent
44339 request packets from @value{GDBN}.
44341 A successful reply from the stub indicates that the stub has found the
44342 requested frame. The response is a series of parts, concatenated
44343 without separators, describing the frame we selected. Each part has
44344 one of the following forms:
44348 The selected frame is number @var{n} in the trace frame buffer;
44349 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
44350 was no frame matching the criteria in the request packet.
44353 The selected trace frame records a hit of tracepoint number @var{t};
44354 @var{t} is a hexadecimal number.
44358 @item QTFrame:pc:@var{addr}
44359 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44360 currently selected frame whose PC is @var{addr};
44361 @var{addr} is a hexadecimal number.
44363 @item QTFrame:tdp:@var{t}
44364 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44365 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
44366 is a hexadecimal number.
44368 @item QTFrame:range:@var{start}:@var{end}
44369 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44370 currently selected frame whose PC is between @var{start} (inclusive)
44371 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
44374 @item QTFrame:outside:@var{start}:@var{end}
44375 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
44376 frame @emph{outside} the given range of addresses (exclusive).
44379 @cindex @samp{qTMinFTPILen} packet
44380 This packet requests the minimum length of instruction at which a fast
44381 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
44382 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
44383 it depends on the target system being able to create trampolines in
44384 the first 64K of memory, which might or might not be possible for that
44385 system. So the reply to this packet will be 4 if it is able to
44392 The minimum instruction length is currently unknown.
44394 The minimum instruction length is @var{length}, where @var{length}
44395 is a hexadecimal number greater or equal to 1. A reply
44396 of 1 means that a fast tracepoint may be placed on any instruction
44397 regardless of size.
44399 An error has occurred.
44401 An empty reply indicates that the request is not supported by the stub.
44405 @cindex @samp{QTStart} packet
44406 Begin the tracepoint experiment. Begin collecting data from
44407 tracepoint hits in the trace frame buffer. This packet supports the
44408 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
44409 instruction reply packet}).
44412 @cindex @samp{QTStop} packet
44413 End the tracepoint experiment. Stop collecting trace frames.
44415 @item QTEnable:@var{n}:@var{addr}
44417 @cindex @samp{QTEnable} packet
44418 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
44419 experiment. If the tracepoint was previously disabled, then collection
44420 of data from it will resume.
44422 @item QTDisable:@var{n}:@var{addr}
44424 @cindex @samp{QTDisable} packet
44425 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
44426 experiment. No more data will be collected from the tracepoint unless
44427 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
44430 @cindex @samp{QTinit} packet
44431 Clear the table of tracepoints, and empty the trace frame buffer.
44433 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
44434 @cindex @samp{QTro} packet
44435 Establish the given ranges of memory as ``transparent''. The stub
44436 will answer requests for these ranges from memory's current contents,
44437 if they were not collected as part of the tracepoint hit.
44439 @value{GDBN} uses this to mark read-only regions of memory, like those
44440 containing program code. Since these areas never change, they should
44441 still have the same contents they did when the tracepoint was hit, so
44442 there's no reason for the stub to refuse to provide their contents.
44444 @item QTDisconnected:@var{value}
44445 @cindex @samp{QTDisconnected} packet
44446 Set the choice to what to do with the tracing run when @value{GDBN}
44447 disconnects from the target. A @var{value} of 1 directs the target to
44448 continue the tracing run, while 0 tells the target to stop tracing if
44449 @value{GDBN} is no longer in the picture.
44452 @cindex @samp{qTStatus} packet
44453 Ask the stub if there is a trace experiment running right now.
44455 The reply has the form:
44459 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
44460 @var{running} is a single digit @code{1} if the trace is presently
44461 running, or @code{0} if not. It is followed by semicolon-separated
44462 optional fields that an agent may use to report additional status.
44466 If the trace is not running, the agent may report any of several
44467 explanations as one of the optional fields:
44472 No trace has been run yet.
44474 @item tstop[:@var{text}]:0
44475 The trace was stopped by a user-originated stop command. The optional
44476 @var{text} field is a user-supplied string supplied as part of the
44477 stop command (for instance, an explanation of why the trace was
44478 stopped manually). It is hex-encoded.
44481 The trace stopped because the trace buffer filled up.
44483 @item tdisconnected:0
44484 The trace stopped because @value{GDBN} disconnected from the target.
44486 @item tpasscount:@var{tpnum}
44487 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
44489 @item terror:@var{text}:@var{tpnum}
44490 The trace stopped because tracepoint @var{tpnum} had an error. The
44491 string @var{text} is available to describe the nature of the error
44492 (for instance, a divide by zero in the condition expression); it
44496 The trace stopped for some other reason.
44500 Additional optional fields supply statistical and other information.
44501 Although not required, they are extremely useful for users monitoring
44502 the progress of a trace run. If a trace has stopped, and these
44503 numbers are reported, they must reflect the state of the just-stopped
44508 @item tframes:@var{n}
44509 The number of trace frames in the buffer.
44511 @item tcreated:@var{n}
44512 The total number of trace frames created during the run. This may
44513 be larger than the trace frame count, if the buffer is circular.
44515 @item tsize:@var{n}
44516 The total size of the trace buffer, in bytes.
44518 @item tfree:@var{n}
44519 The number of bytes still unused in the buffer.
44521 @item circular:@var{n}
44522 The value of the circular trace buffer flag. @code{1} means that the
44523 trace buffer is circular and old trace frames will be discarded if
44524 necessary to make room, @code{0} means that the trace buffer is linear
44527 @item disconn:@var{n}
44528 The value of the disconnected tracing flag. @code{1} means that
44529 tracing will continue after @value{GDBN} disconnects, @code{0} means
44530 that the trace run will stop.
44534 @item qTP:@var{tp}:@var{addr}
44535 @cindex tracepoint status, remote request
44536 @cindex @samp{qTP} packet
44537 Ask the stub for the current state of tracepoint number @var{tp} at
44538 address @var{addr}.
44542 @item V@var{hits}:@var{usage}
44543 The tracepoint has been hit @var{hits} times so far during the trace
44544 run, and accounts for @var{usage} in the trace buffer. Note that
44545 @code{while-stepping} steps are not counted as separate hits, but the
44546 steps' space consumption is added into the usage number.
44550 @item qTV:@var{var}
44551 @cindex trace state variable value, remote request
44552 @cindex @samp{qTV} packet
44553 Ask the stub for the value of the trace state variable number @var{var}.
44558 The value of the variable is @var{value}. This will be the current
44559 value of the variable if the user is examining a running target, or a
44560 saved value if the variable was collected in the trace frame that the
44561 user is looking at. Note that multiple requests may result in
44562 different reply values, such as when requesting values while the
44563 program is running.
44566 The value of the variable is unknown. This would occur, for example,
44567 if the user is examining a trace frame in which the requested variable
44572 @cindex @samp{qTfP} packet
44574 @cindex @samp{qTsP} packet
44575 These packets request data about tracepoints that are being used by
44576 the target. @value{GDBN} sends @code{qTfP} to get the first piece
44577 of data, and multiple @code{qTsP} to get additional pieces. Replies
44578 to these packets generally take the form of the @code{QTDP} packets
44579 that define tracepoints. (FIXME add detailed syntax)
44582 @cindex @samp{qTfV} packet
44584 @cindex @samp{qTsV} packet
44585 These packets request data about trace state variables that are on the
44586 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
44587 and multiple @code{qTsV} to get additional variables. Replies to
44588 these packets follow the syntax of the @code{QTDV} packets that define
44589 trace state variables.
44595 @cindex @samp{qTfSTM} packet
44596 @cindex @samp{qTsSTM} packet
44597 These packets request data about static tracepoint markers that exist
44598 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
44599 first piece of data, and multiple @code{qTsSTM} to get additional
44600 pieces. Replies to these packets take the following form:
44604 @item m @var{address}:@var{id}:@var{extra}
44606 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
44607 a comma-separated list of markers
44609 (lower case letter @samp{L}) denotes end of list.
44611 An error occurred. The error number @var{nn} is given as hex digits.
44613 An empty reply indicates that the request is not supported by the
44617 The @var{address} is encoded in hex;
44618 @var{id} and @var{extra} are strings encoded in hex.
44620 In response to each query, the target will reply with a list of one or
44621 more markers, separated by commas. @value{GDBN} will respond to each
44622 reply with a request for more markers (using the @samp{qs} form of the
44623 query), until the target responds with @samp{l} (lower-case ell, for
44626 @item qTSTMat:@var{address}
44628 @cindex @samp{qTSTMat} packet
44629 This packets requests data about static tracepoint markers in the
44630 target program at @var{address}. Replies to this packet follow the
44631 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
44632 tracepoint markers.
44634 @item QTSave:@var{filename}
44635 @cindex @samp{QTSave} packet
44636 This packet directs the target to save trace data to the file name
44637 @var{filename} in the target's filesystem. The @var{filename} is encoded
44638 as a hex string; the interpretation of the file name (relative vs
44639 absolute, wild cards, etc) is up to the target.
44641 @item qTBuffer:@var{offset},@var{len}
44642 @cindex @samp{qTBuffer} packet
44643 Return up to @var{len} bytes of the current contents of trace buffer,
44644 starting at @var{offset}. The trace buffer is treated as if it were
44645 a contiguous collection of traceframes, as per the trace file format.
44646 The reply consists as many hex-encoded bytes as the target can deliver
44647 in a packet; it is not an error to return fewer than were asked for.
44648 A reply consisting of just @code{l} indicates that no bytes are
44651 @item QTBuffer:circular:@var{value}
44652 This packet directs the target to use a circular trace buffer if
44653 @var{value} is 1, or a linear buffer if the value is 0.
44655 @item QTBuffer:size:@var{size}
44656 @anchor{QTBuffer-size}
44657 @cindex @samp{QTBuffer size} packet
44658 This packet directs the target to make the trace buffer be of size
44659 @var{size} if possible. A value of @code{-1} tells the target to
44660 use whatever size it prefers.
44662 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
44663 @cindex @samp{QTNotes} packet
44664 This packet adds optional textual notes to the trace run. Allowable
44665 types include @code{user}, @code{notes}, and @code{tstop}, the
44666 @var{text} fields are arbitrary strings, hex-encoded.
44670 @subsection Relocate instruction reply packet
44671 When installing fast tracepoints in memory, the target may need to
44672 relocate the instruction currently at the tracepoint address to a
44673 different address in memory. For most instructions, a simple copy is
44674 enough, but, for example, call instructions that implicitly push the
44675 return address on the stack, and relative branches or other
44676 PC-relative instructions require offset adjustment, so that the effect
44677 of executing the instruction at a different address is the same as if
44678 it had executed in the original location.
44680 In response to several of the tracepoint packets, the target may also
44681 respond with a number of intermediate @samp{qRelocInsn} request
44682 packets before the final result packet, to have @value{GDBN} handle
44683 this relocation operation. If a packet supports this mechanism, its
44684 documentation will explicitly say so. See for example the above
44685 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
44686 format of the request is:
44689 @item qRelocInsn:@var{from};@var{to}
44691 This requests @value{GDBN} to copy instruction at address @var{from}
44692 to address @var{to}, possibly adjusted so that executing the
44693 instruction at @var{to} has the same effect as executing it at
44694 @var{from}. @value{GDBN} writes the adjusted instruction to target
44695 memory starting at @var{to}.
44700 @item qRelocInsn:@var{adjusted_size}
44701 Informs the stub the relocation is complete. The @var{adjusted_size} is
44702 the length in bytes of resulting relocated instruction sequence.
44704 A badly formed request was detected, or an error was encountered while
44705 relocating the instruction.
44708 @node Host I/O Packets
44709 @section Host I/O Packets
44710 @cindex Host I/O, remote protocol
44711 @cindex file transfer, remote protocol
44713 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44714 operations on the far side of a remote link. For example, Host I/O is
44715 used to upload and download files to a remote target with its own
44716 filesystem. Host I/O uses the same constant values and data structure
44717 layout as the target-initiated File-I/O protocol. However, the
44718 Host I/O packets are structured differently. The target-initiated
44719 protocol relies on target memory to store parameters and buffers.
44720 Host I/O requests are initiated by @value{GDBN}, and the
44721 target's memory is not involved. @xref{File-I/O Remote Protocol
44722 Extension}, for more details on the target-initiated protocol.
44724 The Host I/O request packets all encode a single operation along with
44725 its arguments. They have this format:
44729 @item vFile:@var{operation}: @var{parameter}@dots{}
44730 @var{operation} is the name of the particular request; the target
44731 should compare the entire packet name up to the second colon when checking
44732 for a supported operation. The format of @var{parameter} depends on
44733 the operation. Numbers are always passed in hexadecimal. Negative
44734 numbers have an explicit minus sign (i.e.@: two's complement is not
44735 used). Strings (e.g.@: filenames) are encoded as a series of
44736 hexadecimal bytes. The last argument to a system call may be a
44737 buffer of escaped binary data (@pxref{Binary Data}).
44741 The valid responses to Host I/O packets are:
44745 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44746 @var{result} is the integer value returned by this operation, usually
44747 non-negative for success and -1 for errors. If an error has occured,
44748 @var{errno} will be included in the result specifying a
44749 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44750 operations which return data, @var{attachment} supplies the data as a
44751 binary buffer. Binary buffers in response packets are escaped in the
44752 normal way (@pxref{Binary Data}). See the individual packet
44753 documentation for the interpretation of @var{result} and
44757 An empty response indicates that this operation is not recognized.
44761 These are the supported Host I/O operations:
44764 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44765 Open a file at @var{filename} and return a file descriptor for it, or
44766 return -1 if an error occurs. The @var{filename} is a string,
44767 @var{flags} is an integer indicating a mask of open flags
44768 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44769 of mode bits to use if the file is created (@pxref{mode_t Values}).
44770 @xref{open}, for details of the open flags and mode values.
44772 @item vFile:close: @var{fd}
44773 Close the open file corresponding to @var{fd} and return 0, or
44774 -1 if an error occurs.
44776 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44777 Read data from the open file corresponding to @var{fd}. Up to
44778 @var{count} bytes will be read from the file, starting at @var{offset}
44779 relative to the start of the file. The target may read fewer bytes;
44780 common reasons include packet size limits and an end-of-file
44781 condition. The number of bytes read is returned. Zero should only be
44782 returned for a successful read at the end of the file, or if
44783 @var{count} was zero.
44785 The data read should be returned as a binary attachment on success.
44786 If zero bytes were read, the response should include an empty binary
44787 attachment (i.e.@: a trailing semicolon). The return value is the
44788 number of target bytes read; the binary attachment may be longer if
44789 some characters were escaped.
44791 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44792 Write @var{data} (a binary buffer) to the open file corresponding
44793 to @var{fd}. Start the write at @var{offset} from the start of the
44794 file. Unlike many @code{write} system calls, there is no
44795 separate @var{count} argument; the length of @var{data} in the
44796 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44797 which may be shorter than the length of @var{data}, or -1 if an
44800 @item vFile:fstat: @var{fd}
44801 Get information about the open file corresponding to @var{fd}.
44802 On success the information is returned as a binary attachment
44803 and the return value is the size of this attachment in bytes.
44804 If an error occurs the return value is -1. The format of the
44805 returned binary attachment is as described in @ref{struct stat}.
44807 @item vFile:unlink: @var{filename}
44808 Delete the file at @var{filename} on the target. Return 0,
44809 or -1 if an error occurs. The @var{filename} is a string.
44811 @item vFile:readlink: @var{filename}
44812 Read value of symbolic link @var{filename} on the target. Return
44813 the number of bytes read, or -1 if an error occurs.
44815 The data read should be returned as a binary attachment on success.
44816 If zero bytes were read, the response should include an empty binary
44817 attachment (i.e.@: a trailing semicolon). The return value is the
44818 number of target bytes read; the binary attachment may be longer if
44819 some characters were escaped.
44821 @item vFile:setfs: @var{pid}
44822 Select the filesystem on which @code{vFile} operations with
44823 @var{filename} arguments will operate. This is required for
44824 @value{GDBN} to be able to access files on remote targets where
44825 the remote stub does not share a common filesystem with the
44828 If @var{pid} is nonzero, select the filesystem as seen by process
44829 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44830 the remote stub. Return 0 on success, or -1 if an error occurs.
44831 If @code{vFile:setfs:} indicates success, the selected filesystem
44832 remains selected until the next successful @code{vFile:setfs:}
44838 @section Interrupts
44839 @cindex interrupts (remote protocol)
44840 @anchor{interrupting remote targets}
44842 In all-stop mode, when a program on the remote target is running,
44843 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44844 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44845 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44847 The precise meaning of @code{BREAK} is defined by the transport
44848 mechanism and may, in fact, be undefined. @value{GDBN} does not
44849 currently define a @code{BREAK} mechanism for any of the network
44850 interfaces except for TCP, in which case @value{GDBN} sends the
44851 @code{telnet} BREAK sequence.
44853 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44854 transport mechanisms. It is represented by sending the single byte
44855 @code{0x03} without any of the usual packet overhead described in
44856 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44857 transmitted as part of a packet, it is considered to be packet data
44858 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44859 (@pxref{X packet}), used for binary downloads, may include an unescaped
44860 @code{0x03} as part of its packet.
44862 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44863 When Linux kernel receives this sequence from serial port,
44864 it stops execution and connects to gdb.
44866 In non-stop mode, because packet resumptions are asynchronous
44867 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44868 command to the remote stub, even when the target is running. For that
44869 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44870 packet}) with the usual packet framing instead of the single byte
44873 Stubs are not required to recognize these interrupt mechanisms and the
44874 precise meaning associated with receipt of the interrupt is
44875 implementation defined. If the target supports debugging of multiple
44876 threads and/or processes, it should attempt to interrupt all
44877 currently-executing threads and processes.
44878 If the stub is successful at interrupting the
44879 running program, it should send one of the stop
44880 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44881 of successfully stopping the program in all-stop mode, and a stop reply
44882 for each stopped thread in non-stop mode.
44883 Interrupts received while the
44884 program is stopped are queued and the program will be interrupted when
44885 it is resumed next time.
44887 @node Notification Packets
44888 @section Notification Packets
44889 @cindex notification packets
44890 @cindex packets, notification
44892 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44893 packets that require no acknowledgment. Both the GDB and the stub
44894 may send notifications (although the only notifications defined at
44895 present are sent by the stub). Notifications carry information
44896 without incurring the round-trip latency of an acknowledgment, and so
44897 are useful for low-impact communications where occasional packet loss
44900 A notification packet has the form @samp{% @var{data} #
44901 @var{checksum}}, where @var{data} is the content of the notification,
44902 and @var{checksum} is a checksum of @var{data}, computed and formatted
44903 as for ordinary @value{GDBN} packets. A notification's @var{data}
44904 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44905 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44906 to acknowledge the notification's receipt or to report its corruption.
44908 Every notification's @var{data} begins with a name, which contains no
44909 colon characters, followed by a colon character.
44911 Recipients should silently ignore corrupted notifications and
44912 notifications they do not understand. Recipients should restart
44913 timeout periods on receipt of a well-formed notification, whether or
44914 not they understand it.
44916 Senders should only send the notifications described here when this
44917 protocol description specifies that they are permitted. In the
44918 future, we may extend the protocol to permit existing notifications in
44919 new contexts; this rule helps older senders avoid confusing newer
44922 (Older versions of @value{GDBN} ignore bytes received until they see
44923 the @samp{$} byte that begins an ordinary packet, so new stubs may
44924 transmit notifications without fear of confusing older clients. There
44925 are no notifications defined for @value{GDBN} to send at the moment, but we
44926 assume that most older stubs would ignore them, as well.)
44928 Each notification is comprised of three parts:
44930 @item @var{name}:@var{event}
44931 The notification packet is sent by the side that initiates the
44932 exchange (currently, only the stub does that), with @var{event}
44933 carrying the specific information about the notification, and
44934 @var{name} specifying the name of the notification.
44936 The acknowledge sent by the other side, usually @value{GDBN}, to
44937 acknowledge the exchange and request the event.
44940 The purpose of an asynchronous notification mechanism is to report to
44941 @value{GDBN} that something interesting happened in the remote stub.
44943 The remote stub may send notification @var{name}:@var{event}
44944 at any time, but @value{GDBN} acknowledges the notification when
44945 appropriate. The notification event is pending before @value{GDBN}
44946 acknowledges. Only one notification at a time may be pending; if
44947 additional events occur before @value{GDBN} has acknowledged the
44948 previous notification, they must be queued by the stub for later
44949 synchronous transmission in response to @var{ack} packets from
44950 @value{GDBN}. Because the notification mechanism is unreliable,
44951 the stub is permitted to resend a notification if it believes
44952 @value{GDBN} may not have received it.
44954 Specifically, notifications may appear when @value{GDBN} is not
44955 otherwise reading input from the stub, or when @value{GDBN} is
44956 expecting to read a normal synchronous response or a
44957 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44958 Notification packets are distinct from any other communication from
44959 the stub so there is no ambiguity.
44961 After receiving a notification, @value{GDBN} shall acknowledge it by
44962 sending a @var{ack} packet as a regular, synchronous request to the
44963 stub. Such acknowledgment is not required to happen immediately, as
44964 @value{GDBN} is permitted to send other, unrelated packets to the
44965 stub first, which the stub should process normally.
44967 Upon receiving a @var{ack} packet, if the stub has other queued
44968 events to report to @value{GDBN}, it shall respond by sending a
44969 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44970 packet to solicit further responses; again, it is permitted to send
44971 other, unrelated packets as well which the stub should process
44974 If the stub receives a @var{ack} packet and there are no additional
44975 @var{event} to report, the stub shall return an @samp{OK} response.
44976 At this point, @value{GDBN} has finished processing a notification
44977 and the stub has completed sending any queued events. @value{GDBN}
44978 won't accept any new notifications until the final @samp{OK} is
44979 received . If further notification events occur, the stub shall send
44980 a new notification, @value{GDBN} shall accept the notification, and
44981 the process shall be repeated.
44983 The process of asynchronous notification can be illustrated by the
44986 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44989 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44991 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44996 The following notifications are defined:
44997 @multitable @columnfractions 0.12 0.12 0.38 0.38
45006 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
45007 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
45008 for information on how these notifications are acknowledged by
45010 @tab Report an asynchronous stop event in non-stop mode.
45014 @node Remote Non-Stop
45015 @section Remote Protocol Support for Non-Stop Mode
45017 @value{GDBN}'s remote protocol supports non-stop debugging of
45018 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
45019 supports non-stop mode, it should report that to @value{GDBN} by including
45020 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
45022 @value{GDBN} typically sends a @samp{QNonStop} packet only when
45023 establishing a new connection with the stub. Entering non-stop mode
45024 does not alter the state of any currently-running threads, but targets
45025 must stop all threads in any already-attached processes when entering
45026 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
45027 probe the target state after a mode change.
45029 In non-stop mode, when an attached process encounters an event that
45030 would otherwise be reported with a stop reply, it uses the
45031 asynchronous notification mechanism (@pxref{Notification Packets}) to
45032 inform @value{GDBN}. In contrast to all-stop mode, where all threads
45033 in all processes are stopped when a stop reply is sent, in non-stop
45034 mode only the thread reporting the stop event is stopped. That is,
45035 when reporting a @samp{S} or @samp{T} response to indicate completion
45036 of a step operation, hitting a breakpoint, or a fault, only the
45037 affected thread is stopped; any other still-running threads continue
45038 to run. When reporting a @samp{W} or @samp{X} response, all running
45039 threads belonging to other attached processes continue to run.
45041 In non-stop mode, the target shall respond to the @samp{?} packet as
45042 follows. First, any incomplete stop reply notification/@samp{vStopped}
45043 sequence in progress is abandoned. The target must begin a new
45044 sequence reporting stop events for all stopped threads, whether or not
45045 it has previously reported those events to @value{GDBN}. The first
45046 stop reply is sent as a synchronous reply to the @samp{?} packet, and
45047 subsequent stop replies are sent as responses to @samp{vStopped} packets
45048 using the mechanism described above. The target must not send
45049 asynchronous stop reply notifications until the sequence is complete.
45050 If all threads are running when the target receives the @samp{?} packet,
45051 or if the target is not attached to any process, it shall respond
45054 If the stub supports non-stop mode, it should also support the
45055 @samp{swbreak} stop reason if software breakpoints are supported, and
45056 the @samp{hwbreak} stop reason if hardware breakpoints are supported
45057 (@pxref{swbreak stop reason}). This is because given the asynchronous
45058 nature of non-stop mode, between the time a thread hits a breakpoint
45059 and the time the event is finally processed by @value{GDBN}, the
45060 breakpoint may have already been removed from the target. Due to
45061 this, @value{GDBN} needs to be able to tell whether a trap stop was
45062 caused by a delayed breakpoint event, which should be ignored, as
45063 opposed to a random trap signal, which should be reported to the user.
45064 Note the @samp{swbreak} feature implies that the target is responsible
45065 for adjusting the PC when a software breakpoint triggers, if
45066 necessary, such as on the x86 architecture.
45068 @node Packet Acknowledgment
45069 @section Packet Acknowledgment
45071 @cindex acknowledgment, for @value{GDBN} remote
45072 @cindex packet acknowledgment, for @value{GDBN} remote
45073 By default, when either the host or the target machine receives a packet,
45074 the first response expected is an acknowledgment: either @samp{+} (to indicate
45075 the package was received correctly) or @samp{-} (to request retransmission).
45076 This mechanism allows the @value{GDBN} remote protocol to operate over
45077 unreliable transport mechanisms, such as a serial line.
45079 In cases where the transport mechanism is itself reliable (such as a pipe or
45080 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
45081 It may be desirable to disable them in that case to reduce communication
45082 overhead, or for other reasons. This can be accomplished by means of the
45083 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
45085 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
45086 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
45087 and response format still includes the normal checksum, as described in
45088 @ref{Overview}, but the checksum may be ignored by the receiver.
45090 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
45091 no-acknowledgment mode, it should report that to @value{GDBN}
45092 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
45093 @pxref{qSupported}.
45094 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
45095 disabled via the @code{set remote noack-packet off} command
45096 (@pxref{Remote Configuration}),
45097 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
45098 Only then may the stub actually turn off packet acknowledgments.
45099 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
45100 response, which can be safely ignored by the stub.
45102 Note that @code{set remote noack-packet} command only affects negotiation
45103 between @value{GDBN} and the stub when subsequent connections are made;
45104 it does not affect the protocol acknowledgment state for any current
45106 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
45107 new connection is established,
45108 there is also no protocol request to re-enable the acknowledgments
45109 for the current connection, once disabled.
45114 Example sequence of a target being re-started. Notice how the restart
45115 does not get any direct output:
45120 @emph{target restarts}
45123 <- @code{T001:1234123412341234}
45127 Example sequence of a target being stepped by a single instruction:
45130 -> @code{G1445@dots{}}
45135 <- @code{T001:1234123412341234}
45139 <- @code{1455@dots{}}
45143 @node File-I/O Remote Protocol Extension
45144 @section File-I/O Remote Protocol Extension
45145 @cindex File-I/O remote protocol extension
45148 * File-I/O Overview::
45149 * Protocol Basics::
45150 * The F Request Packet::
45151 * The F Reply Packet::
45152 * The Ctrl-C Message::
45154 * List of Supported Calls::
45155 * Protocol-specific Representation of Datatypes::
45157 * File-I/O Examples::
45160 @node File-I/O Overview
45161 @subsection File-I/O Overview
45162 @cindex file-i/o overview
45164 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
45165 target to use the host's file system and console I/O to perform various
45166 system calls. System calls on the target system are translated into a
45167 remote protocol packet to the host system, which then performs the needed
45168 actions and returns a response packet to the target system.
45169 This simulates file system operations even on targets that lack file systems.
45171 The protocol is defined to be independent of both the host and target systems.
45172 It uses its own internal representation of datatypes and values. Both
45173 @value{GDBN} and the target's @value{GDBN} stub are responsible for
45174 translating the system-dependent value representations into the internal
45175 protocol representations when data is transmitted.
45177 The communication is synchronous. A system call is possible only when
45178 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
45179 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
45180 the target is stopped to allow deterministic access to the target's
45181 memory. Therefore File-I/O is not interruptible by target signals. On
45182 the other hand, it is possible to interrupt File-I/O by a user interrupt
45183 (@samp{Ctrl-C}) within @value{GDBN}.
45185 The target's request to perform a host system call does not finish
45186 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
45187 after finishing the system call, the target returns to continuing the
45188 previous activity (continue, step). No additional continue or step
45189 request from @value{GDBN} is required.
45192 (@value{GDBP}) continue
45193 <- target requests 'system call X'
45194 target is stopped, @value{GDBN} executes system call
45195 -> @value{GDBN} returns result
45196 ... target continues, @value{GDBN} returns to wait for the target
45197 <- target hits breakpoint and sends a Txx packet
45200 The protocol only supports I/O on the console and to regular files on
45201 the host file system. Character or block special devices, pipes,
45202 named pipes, sockets or any other communication method on the host
45203 system are not supported by this protocol.
45205 File I/O is not supported in non-stop mode.
45207 @node Protocol Basics
45208 @subsection Protocol Basics
45209 @cindex protocol basics, file-i/o
45211 The File-I/O protocol uses the @code{F} packet as the request as well
45212 as reply packet. Since a File-I/O system call can only occur when
45213 @value{GDBN} is waiting for a response from the continuing or stepping target,
45214 the File-I/O request is a reply that @value{GDBN} has to expect as a result
45215 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
45216 This @code{F} packet contains all information needed to allow @value{GDBN}
45217 to call the appropriate host system call:
45221 A unique identifier for the requested system call.
45224 All parameters to the system call. Pointers are given as addresses
45225 in the target memory address space. Pointers to strings are given as
45226 pointer/length pair. Numerical values are given as they are.
45227 Numerical control flags are given in a protocol-specific representation.
45231 At this point, @value{GDBN} has to perform the following actions.
45235 If the parameters include pointer values to data needed as input to a
45236 system call, @value{GDBN} requests this data from the target with a
45237 standard @code{m} packet request. This additional communication has to be
45238 expected by the target implementation and is handled as any other @code{m}
45242 @value{GDBN} translates all value from protocol representation to host
45243 representation as needed. Datatypes are coerced into the host types.
45246 @value{GDBN} calls the system call.
45249 It then coerces datatypes back to protocol representation.
45252 If the system call is expected to return data in buffer space specified
45253 by pointer parameters to the call, the data is transmitted to the
45254 target using a @code{M} or @code{X} packet. This packet has to be expected
45255 by the target implementation and is handled as any other @code{M} or @code{X}
45260 Eventually @value{GDBN} replies with another @code{F} packet which contains all
45261 necessary information for the target to continue. This at least contains
45268 @code{errno}, if has been changed by the system call.
45275 After having done the needed type and value coercion, the target continues
45276 the latest continue or step action.
45278 @node The F Request Packet
45279 @subsection The @code{F} Request Packet
45280 @cindex file-i/o request packet
45281 @cindex @code{F} request packet
45283 The @code{F} request packet has the following format:
45286 @item F@var{call-id},@var{parameter@dots{}}
45288 @var{call-id} is the identifier to indicate the host system call to be called.
45289 This is just the name of the function.
45291 @var{parameter@dots{}} are the parameters to the system call.
45292 Parameters are hexadecimal integer values, either the actual values in case
45293 of scalar datatypes, pointers to target buffer space in case of compound
45294 datatypes and unspecified memory areas, or pointer/length pairs in case
45295 of string parameters. These are appended to the @var{call-id} as a
45296 comma-delimited list. All values are transmitted in ASCII
45297 string representation, pointer/length pairs separated by a slash.
45303 @node The F Reply Packet
45304 @subsection The @code{F} Reply Packet
45305 @cindex file-i/o reply packet
45306 @cindex @code{F} reply packet
45308 The @code{F} reply packet has the following format:
45312 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
45314 @var{retcode} is the return code of the system call as hexadecimal value.
45316 @var{errno} is the @code{errno} set by the call, in protocol-specific
45318 This parameter can be omitted if the call was successful.
45320 @var{Ctrl-C flag} is only sent if the user requested a break. In this
45321 case, @var{errno} must be sent as well, even if the call was successful.
45322 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
45329 or, if the call was interrupted before the host call has been performed:
45336 assuming 4 is the protocol-specific representation of @code{EINTR}.
45341 @node The Ctrl-C Message
45342 @subsection The @samp{Ctrl-C} Message
45343 @cindex ctrl-c message, in file-i/o protocol
45345 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
45346 reply packet (@pxref{The F Reply Packet}),
45347 the target should behave as if it had
45348 gotten a break message. The meaning for the target is ``system call
45349 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
45350 (as with a break message) and return to @value{GDBN} with a @code{T02}
45353 It's important for the target to know in which
45354 state the system call was interrupted. There are two possible cases:
45358 The system call hasn't been performed on the host yet.
45361 The system call on the host has been finished.
45365 These two states can be distinguished by the target by the value of the
45366 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
45367 call hasn't been performed. This is equivalent to the @code{EINTR} handling
45368 on POSIX systems. In any other case, the target may presume that the
45369 system call has been finished --- successfully or not --- and should behave
45370 as if the break message arrived right after the system call.
45372 @value{GDBN} must behave reliably. If the system call has not been called
45373 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
45374 @code{errno} in the packet. If the system call on the host has been finished
45375 before the user requests a break, the full action must be finished by
45376 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
45377 The @code{F} packet may only be sent when either nothing has happened
45378 or the full action has been completed.
45381 @subsection Console I/O
45382 @cindex console i/o as part of file-i/o
45384 By default and if not explicitly closed by the target system, the file
45385 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
45386 on the @value{GDBN} console is handled as any other file output operation
45387 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
45388 by @value{GDBN} so that after the target read request from file descriptor
45389 0 all following typing is buffered until either one of the following
45394 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
45396 system call is treated as finished.
45399 The user presses @key{RET}. This is treated as end of input with a trailing
45403 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
45404 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
45408 If the user has typed more characters than fit in the buffer given to
45409 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
45410 either another @code{read(0, @dots{})} is requested by the target, or debugging
45411 is stopped at the user's request.
45414 @node List of Supported Calls
45415 @subsection List of Supported Calls
45416 @cindex list of supported file-i/o calls
45433 @unnumberedsubsubsec open
45434 @cindex open, file-i/o system call
45439 int open(const char *pathname, int flags);
45440 int open(const char *pathname, int flags, mode_t mode);
45444 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
45447 @var{flags} is the bitwise @code{OR} of the following values:
45451 If the file does not exist it will be created. The host
45452 rules apply as far as file ownership and time stamps
45456 When used with @code{O_CREAT}, if the file already exists it is
45457 an error and open() fails.
45460 If the file already exists and the open mode allows
45461 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
45462 truncated to zero length.
45465 The file is opened in append mode.
45468 The file is opened for reading only.
45471 The file is opened for writing only.
45474 The file is opened for reading and writing.
45478 Other bits are silently ignored.
45482 @var{mode} is the bitwise @code{OR} of the following values:
45486 User has read permission.
45489 User has write permission.
45492 Group has read permission.
45495 Group has write permission.
45498 Others have read permission.
45501 Others have write permission.
45505 Other bits are silently ignored.
45508 @item Return value:
45509 @code{open} returns the new file descriptor or -1 if an error
45516 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
45519 @var{pathname} refers to a directory.
45522 The requested access is not allowed.
45525 @var{pathname} was too long.
45528 A directory component in @var{pathname} does not exist.
45531 @var{pathname} refers to a device, pipe, named pipe or socket.
45534 @var{pathname} refers to a file on a read-only filesystem and
45535 write access was requested.
45538 @var{pathname} is an invalid pointer value.
45541 No space on device to create the file.
45544 The process already has the maximum number of files open.
45547 The limit on the total number of files open on the system
45551 The call was interrupted by the user.
45557 @unnumberedsubsubsec close
45558 @cindex close, file-i/o system call
45567 @samp{Fclose,@var{fd}}
45569 @item Return value:
45570 @code{close} returns zero on success, or -1 if an error occurred.
45576 @var{fd} isn't a valid open file descriptor.
45579 The call was interrupted by the user.
45585 @unnumberedsubsubsec read
45586 @cindex read, file-i/o system call
45591 int read(int fd, void *buf, unsigned int count);
45595 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
45597 @item Return value:
45598 On success, the number of bytes read is returned.
45599 Zero indicates end of file. If count is zero, read
45600 returns zero as well. On error, -1 is returned.
45606 @var{fd} is not a valid file descriptor or is not open for
45610 @var{bufptr} is an invalid pointer value.
45613 The call was interrupted by the user.
45619 @unnumberedsubsubsec write
45620 @cindex write, file-i/o system call
45625 int write(int fd, const void *buf, unsigned int count);
45629 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
45631 @item Return value:
45632 On success, the number of bytes written are returned.
45633 Zero indicates nothing was written. On error, -1
45640 @var{fd} is not a valid file descriptor or is not open for
45644 @var{bufptr} is an invalid pointer value.
45647 An attempt was made to write a file that exceeds the
45648 host-specific maximum file size allowed.
45651 No space on device to write the data.
45654 The call was interrupted by the user.
45660 @unnumberedsubsubsec lseek
45661 @cindex lseek, file-i/o system call
45666 long lseek (int fd, long offset, int flag);
45670 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
45672 @var{flag} is one of:
45676 The offset is set to @var{offset} bytes.
45679 The offset is set to its current location plus @var{offset}
45683 The offset is set to the size of the file plus @var{offset}
45687 @item Return value:
45688 On success, the resulting unsigned offset in bytes from
45689 the beginning of the file is returned. Otherwise, a
45690 value of -1 is returned.
45696 @var{fd} is not a valid open file descriptor.
45699 @var{fd} is associated with the @value{GDBN} console.
45702 @var{flag} is not a proper value.
45705 The call was interrupted by the user.
45711 @unnumberedsubsubsec rename
45712 @cindex rename, file-i/o system call
45717 int rename(const char *oldpath, const char *newpath);
45721 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45723 @item Return value:
45724 On success, zero is returned. On error, -1 is returned.
45730 @var{newpath} is an existing directory, but @var{oldpath} is not a
45734 @var{newpath} is a non-empty directory.
45737 @var{oldpath} or @var{newpath} is a directory that is in use by some
45741 An attempt was made to make a directory a subdirectory
45745 A component used as a directory in @var{oldpath} or new
45746 path is not a directory. Or @var{oldpath} is a directory
45747 and @var{newpath} exists but is not a directory.
45750 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45753 No access to the file or the path of the file.
45757 @var{oldpath} or @var{newpath} was too long.
45760 A directory component in @var{oldpath} or @var{newpath} does not exist.
45763 The file is on a read-only filesystem.
45766 The device containing the file has no room for the new
45770 The call was interrupted by the user.
45776 @unnumberedsubsubsec unlink
45777 @cindex unlink, file-i/o system call
45782 int unlink(const char *pathname);
45786 @samp{Funlink,@var{pathnameptr}/@var{len}}
45788 @item Return value:
45789 On success, zero is returned. On error, -1 is returned.
45795 No access to the file or the path of the file.
45798 The system does not allow unlinking of directories.
45801 The file @var{pathname} cannot be unlinked because it's
45802 being used by another process.
45805 @var{pathnameptr} is an invalid pointer value.
45808 @var{pathname} was too long.
45811 A directory component in @var{pathname} does not exist.
45814 A component of the path is not a directory.
45817 The file is on a read-only filesystem.
45820 The call was interrupted by the user.
45826 @unnumberedsubsubsec stat/fstat
45827 @cindex fstat, file-i/o system call
45828 @cindex stat, file-i/o system call
45833 int stat(const char *pathname, struct stat *buf);
45834 int fstat(int fd, struct stat *buf);
45838 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45839 @samp{Ffstat,@var{fd},@var{bufptr}}
45841 @item Return value:
45842 On success, zero is returned. On error, -1 is returned.
45848 @var{fd} is not a valid open file.
45851 A directory component in @var{pathname} does not exist or the
45852 path is an empty string.
45855 A component of the path is not a directory.
45858 @var{pathnameptr} is an invalid pointer value.
45861 No access to the file or the path of the file.
45864 @var{pathname} was too long.
45867 The call was interrupted by the user.
45873 @unnumberedsubsubsec gettimeofday
45874 @cindex gettimeofday, file-i/o system call
45879 int gettimeofday(struct timeval *tv, void *tz);
45883 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45885 @item Return value:
45886 On success, 0 is returned, -1 otherwise.
45892 @var{tz} is a non-NULL pointer.
45895 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45901 @unnumberedsubsubsec isatty
45902 @cindex isatty, file-i/o system call
45907 int isatty(int fd);
45911 @samp{Fisatty,@var{fd}}
45913 @item Return value:
45914 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45920 The call was interrupted by the user.
45925 Note that the @code{isatty} call is treated as a special case: it returns
45926 1 to the target if the file descriptor is attached
45927 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45928 would require implementing @code{ioctl} and would be more complex than
45933 @unnumberedsubsubsec system
45934 @cindex system, file-i/o system call
45939 int system(const char *command);
45943 @samp{Fsystem,@var{commandptr}/@var{len}}
45945 @item Return value:
45946 If @var{len} is zero, the return value indicates whether a shell is
45947 available. A zero return value indicates a shell is not available.
45948 For non-zero @var{len}, the value returned is -1 on error and the
45949 return status of the command otherwise. Only the exit status of the
45950 command is returned, which is extracted from the host's @code{system}
45951 return value by calling @code{WEXITSTATUS(retval)}. In case
45952 @file{/bin/sh} could not be executed, 127 is returned.
45958 The call was interrupted by the user.
45963 @value{GDBN} takes over the full task of calling the necessary host calls
45964 to perform the @code{system} call. The return value of @code{system} on
45965 the host is simplified before it's returned
45966 to the target. Any termination signal information from the child process
45967 is discarded, and the return value consists
45968 entirely of the exit status of the called command.
45970 Due to security concerns, the @code{system} call is by default refused
45971 by @value{GDBN}. The user has to allow this call explicitly with the
45972 @code{set remote system-call-allowed 1} command.
45975 @item set remote system-call-allowed
45976 @kindex set remote system-call-allowed
45977 Control whether to allow the @code{system} calls in the File I/O
45978 protocol for the remote target. The default is zero (disabled).
45980 @item show remote system-call-allowed
45981 @kindex show remote system-call-allowed
45982 Show whether the @code{system} calls are allowed in the File I/O
45986 @node Protocol-specific Representation of Datatypes
45987 @subsection Protocol-specific Representation of Datatypes
45988 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45991 * Integral Datatypes::
45993 * Memory Transfer::
45998 @node Integral Datatypes
45999 @unnumberedsubsubsec Integral Datatypes
46000 @cindex integral datatypes, in file-i/o protocol
46002 The integral datatypes used in the system calls are @code{int},
46003 @code{unsigned int}, @code{long}, @code{unsigned long},
46004 @code{mode_t}, and @code{time_t}.
46006 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
46007 implemented as 32 bit values in this protocol.
46009 @code{long} and @code{unsigned long} are implemented as 64 bit types.
46011 @xref{Limits}, for corresponding MIN and MAX values (similar to those
46012 in @file{limits.h}) to allow range checking on host and target.
46014 @code{time_t} datatypes are defined as seconds since the Epoch.
46016 All integral datatypes transferred as part of a memory read or write of a
46017 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
46020 @node Pointer Values
46021 @unnumberedsubsubsec Pointer Values
46022 @cindex pointer values, in file-i/o protocol
46024 Pointers to target data are transmitted as they are. An exception
46025 is made for pointers to buffers for which the length isn't
46026 transmitted as part of the function call, namely strings. Strings
46027 are transmitted as a pointer/length pair, both as hex values, e.g.@:
46034 which is a pointer to data of length 18 bytes at position 0x1aaf.
46035 The length is defined as the full string length in bytes, including
46036 the trailing null byte. For example, the string @code{"hello world"}
46037 at address 0x123456 is transmitted as
46043 @node Memory Transfer
46044 @unnumberedsubsubsec Memory Transfer
46045 @cindex memory transfer, in file-i/o protocol
46047 Structured data which is transferred using a memory read or write (for
46048 example, a @code{struct stat}) is expected to be in a protocol-specific format
46049 with all scalar multibyte datatypes being big endian. Translation to
46050 this representation needs to be done both by the target before the @code{F}
46051 packet is sent, and by @value{GDBN} before
46052 it transfers memory to the target. Transferred pointers to structured
46053 data should point to the already-coerced data at any time.
46057 @unnumberedsubsubsec struct stat
46058 @cindex struct stat, in file-i/o protocol
46060 The buffer of type @code{struct stat} used by the target and @value{GDBN}
46061 is defined as follows:
46065 unsigned int st_dev; /* device */
46066 unsigned int st_ino; /* inode */
46067 mode_t st_mode; /* protection */
46068 unsigned int st_nlink; /* number of hard links */
46069 unsigned int st_uid; /* user ID of owner */
46070 unsigned int st_gid; /* group ID of owner */
46071 unsigned int st_rdev; /* device type (if inode device) */
46072 unsigned long st_size; /* total size, in bytes */
46073 unsigned long st_blksize; /* blocksize for filesystem I/O */
46074 unsigned long st_blocks; /* number of blocks allocated */
46075 time_t st_atime; /* time of last access */
46076 time_t st_mtime; /* time of last modification */
46077 time_t st_ctime; /* time of last change */
46081 The integral datatypes conform to the definitions given in the
46082 appropriate section (see @ref{Integral Datatypes}, for details) so this
46083 structure is of size 64 bytes.
46085 The values of several fields have a restricted meaning and/or
46091 A value of 0 represents a file, 1 the console.
46094 No valid meaning for the target. Transmitted unchanged.
46097 Valid mode bits are described in @ref{Constants}. Any other
46098 bits have currently no meaning for the target.
46103 No valid meaning for the target. Transmitted unchanged.
46108 These values have a host and file system dependent
46109 accuracy. Especially on Windows hosts, the file system may not
46110 support exact timing values.
46113 The target gets a @code{struct stat} of the above representation and is
46114 responsible for coercing it to the target representation before
46117 Note that due to size differences between the host, target, and protocol
46118 representations of @code{struct stat} members, these members could eventually
46119 get truncated on the target.
46121 @node struct timeval
46122 @unnumberedsubsubsec struct timeval
46123 @cindex struct timeval, in file-i/o protocol
46125 The buffer of type @code{struct timeval} used by the File-I/O protocol
46126 is defined as follows:
46130 time_t tv_sec; /* second */
46131 long tv_usec; /* microsecond */
46135 The integral datatypes conform to the definitions given in the
46136 appropriate section (see @ref{Integral Datatypes}, for details) so this
46137 structure is of size 8 bytes.
46140 @subsection Constants
46141 @cindex constants, in file-i/o protocol
46143 The following values are used for the constants inside of the
46144 protocol. @value{GDBN} and target are responsible for translating these
46145 values before and after the call as needed.
46156 @unnumberedsubsubsec Open Flags
46157 @cindex open flags, in file-i/o protocol
46159 All values are given in hexadecimal representation.
46171 @node mode_t Values
46172 @unnumberedsubsubsec mode_t Values
46173 @cindex mode_t values, in file-i/o protocol
46175 All values are given in octal representation.
46192 @unnumberedsubsubsec Errno Values
46193 @cindex errno values, in file-i/o protocol
46195 All values are given in decimal representation.
46220 @code{EUNKNOWN} is used as a fallback error value if a host system returns
46221 any error value not in the list of supported error numbers.
46224 @unnumberedsubsubsec Lseek Flags
46225 @cindex lseek flags, in file-i/o protocol
46234 @unnumberedsubsubsec Limits
46235 @cindex limits, in file-i/o protocol
46237 All values are given in decimal representation.
46240 INT_MIN -2147483648
46242 UINT_MAX 4294967295
46243 LONG_MIN -9223372036854775808
46244 LONG_MAX 9223372036854775807
46245 ULONG_MAX 18446744073709551615
46248 @node File-I/O Examples
46249 @subsection File-I/O Examples
46250 @cindex file-i/o examples
46252 Example sequence of a write call, file descriptor 3, buffer is at target
46253 address 0x1234, 6 bytes should be written:
46256 <- @code{Fwrite,3,1234,6}
46257 @emph{request memory read from target}
46260 @emph{return "6 bytes written"}
46264 Example sequence of a read call, file descriptor 3, buffer is at target
46265 address 0x1234, 6 bytes should be read:
46268 <- @code{Fread,3,1234,6}
46269 @emph{request memory write to target}
46270 -> @code{X1234,6:XXXXXX}
46271 @emph{return "6 bytes read"}
46275 Example sequence of a read call, call fails on the host due to invalid
46276 file descriptor (@code{EBADF}):
46279 <- @code{Fread,3,1234,6}
46283 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
46287 <- @code{Fread,3,1234,6}
46292 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
46296 <- @code{Fread,3,1234,6}
46297 -> @code{X1234,6:XXXXXX}
46301 @node Library List Format
46302 @section Library List Format
46303 @cindex library list format, remote protocol
46305 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
46306 same process as your application to manage libraries. In this case,
46307 @value{GDBN} can use the loader's symbol table and normal memory
46308 operations to maintain a list of shared libraries. On other
46309 platforms, the operating system manages loaded libraries.
46310 @value{GDBN} can not retrieve the list of currently loaded libraries
46311 through memory operations, so it uses the @samp{qXfer:libraries:read}
46312 packet (@pxref{qXfer library list read}) instead. The remote stub
46313 queries the target's operating system and reports which libraries
46316 The @samp{qXfer:libraries:read} packet returns an XML document which
46317 lists loaded libraries and their offsets. Each library has an
46318 associated name and one or more segment or section base addresses,
46319 which report where the library was loaded in memory.
46321 For the common case of libraries that are fully linked binaries, the
46322 library should have a list of segments. If the target supports
46323 dynamic linking of a relocatable object file, its library XML element
46324 should instead include a list of allocated sections. The segment or
46325 section bases are start addresses, not relocation offsets; they do not
46326 depend on the library's link-time base addresses.
46328 @value{GDBN} must be linked with the Expat library to support XML
46329 library lists. @xref{Expat}.
46331 A simple memory map, with one loaded library relocated by a single
46332 offset, looks like this:
46336 <library name="/lib/libc.so.6">
46337 <segment address="0x10000000"/>
46342 Another simple memory map, with one loaded library with three
46343 allocated sections (.text, .data, .bss), looks like this:
46347 <library name="sharedlib.o">
46348 <section address="0x10000000"/>
46349 <section address="0x20000000"/>
46350 <section address="0x30000000"/>
46355 The format of a library list is described by this DTD:
46358 <!-- library-list: Root element with versioning -->
46359 <!ELEMENT library-list (library)*>
46360 <!ATTLIST library-list version CDATA #FIXED "1.0">
46361 <!ELEMENT library (segment*, section*)>
46362 <!ATTLIST library name CDATA #REQUIRED>
46363 <!ELEMENT segment EMPTY>
46364 <!ATTLIST segment address CDATA #REQUIRED>
46365 <!ELEMENT section EMPTY>
46366 <!ATTLIST section address CDATA #REQUIRED>
46369 In addition, segments and section descriptors cannot be mixed within a
46370 single library element, and you must supply at least one segment or
46371 section for each library.
46373 @node Library List Format for SVR4 Targets
46374 @section Library List Format for SVR4 Targets
46375 @cindex library list format, remote protocol
46377 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
46378 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
46379 shared libraries. Still a special library list provided by this packet is
46380 more efficient for the @value{GDBN} remote protocol.
46382 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
46383 loaded libraries and their SVR4 linker parameters. For each library on SVR4
46384 target, the following parameters are reported:
46388 @code{name}, the absolute file name from the @code{l_name} field of
46389 @code{struct link_map}.
46391 @code{lm} with address of @code{struct link_map} used for TLS
46392 (Thread Local Storage) access.
46394 @code{l_addr}, the displacement as read from the field @code{l_addr} of
46395 @code{struct link_map}. For prelinked libraries this is not an absolute
46396 memory address. It is a displacement of absolute memory address against
46397 address the file was prelinked to during the library load.
46399 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
46401 @code{lmid}, which is an identifier for a linker namespace, such as
46402 the memory address of the @code{r_debug} object that contains this
46403 namespace's load map or the namespace identifier returned by
46407 Additionally the single @code{main-lm} attribute specifies address of
46408 @code{struct link_map} used for the main executable. This parameter is used
46409 for TLS access and its presence is optional.
46411 @value{GDBN} must be linked with the Expat library to support XML
46412 SVR4 library lists. @xref{Expat}.
46414 A simple memory map, with two loaded libraries (which do not use prelink),
46418 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
46419 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
46420 l_ld="0xe4eefc" lmid="0xfffe0"/>
46421 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
46422 l_ld="0x152350" lmid="0xfffe0"/>
46423 </library-list-svr>
46426 The format of an SVR4 library list is described by this DTD:
46429 <!-- library-list-svr4: Root element with versioning -->
46430 <!ELEMENT library-list-svr4 (library)*>
46431 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
46432 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
46433 <!ELEMENT library EMPTY>
46434 <!ATTLIST library name CDATA #REQUIRED>
46435 <!ATTLIST library lm CDATA #REQUIRED>
46436 <!ATTLIST library l_addr CDATA #REQUIRED>
46437 <!ATTLIST library l_ld CDATA #REQUIRED>
46438 <!ATTLIST library lmid CDATA #IMPLIED>
46441 @node Memory Map Format
46442 @section Memory Map Format
46443 @cindex memory map format
46445 To be able to write into flash memory, @value{GDBN} needs to obtain a
46446 memory map from the target. This section describes the format of the
46449 The memory map is obtained using the @samp{qXfer:memory-map:read}
46450 (@pxref{qXfer memory map read}) packet and is an XML document that
46451 lists memory regions.
46453 @value{GDBN} must be linked with the Expat library to support XML
46454 memory maps. @xref{Expat}.
46456 The top-level structure of the document is shown below:
46459 <?xml version="1.0"?>
46460 <!DOCTYPE memory-map
46461 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46462 "http://sourceware.org/gdb/gdb-memory-map.dtd">
46468 Each region can be either:
46473 A region of RAM starting at @var{addr} and extending for @var{length}
46477 <memory type="ram" start="@var{addr}" length="@var{length}"/>
46482 A region of read-only memory:
46485 <memory type="rom" start="@var{addr}" length="@var{length}"/>
46490 A region of flash memory, with erasure blocks @var{blocksize}
46494 <memory type="flash" start="@var{addr}" length="@var{length}">
46495 <property name="blocksize">@var{blocksize}</property>
46501 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
46502 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
46503 packets to write to addresses in such ranges.
46505 The formal DTD for memory map format is given below:
46508 <!-- ................................................... -->
46509 <!-- Memory Map XML DTD ................................ -->
46510 <!-- File: memory-map.dtd .............................. -->
46511 <!-- .................................... .............. -->
46512 <!-- memory-map.dtd -->
46513 <!-- memory-map: Root element with versioning -->
46514 <!ELEMENT memory-map (memory)*>
46515 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
46516 <!ELEMENT memory (property)*>
46517 <!-- memory: Specifies a memory region,
46518 and its type, or device. -->
46519 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
46520 start CDATA #REQUIRED
46521 length CDATA #REQUIRED>
46522 <!-- property: Generic attribute tag -->
46523 <!ELEMENT property (#PCDATA | property)*>
46524 <!ATTLIST property name (blocksize) #REQUIRED>
46527 @node Thread List Format
46528 @section Thread List Format
46529 @cindex thread list format
46531 To efficiently update the list of threads and their attributes,
46532 @value{GDBN} issues the @samp{qXfer:threads:read} packet
46533 (@pxref{qXfer threads read}) and obtains the XML document with
46534 the following structure:
46537 <?xml version="1.0"?>
46539 <thread id="id" core="0" name="name">
46540 ... description ...
46545 Each @samp{thread} element must have the @samp{id} attribute that
46546 identifies the thread (@pxref{thread-id syntax}). The
46547 @samp{core} attribute, if present, specifies which processor core
46548 the thread was last executing on. The @samp{name} attribute, if
46549 present, specifies the human-readable name of the thread. The content
46550 of the of @samp{thread} element is interpreted as human-readable
46551 auxiliary information. The @samp{handle} attribute, if present,
46552 is a hex encoded representation of the thread handle.
46555 @node Traceframe Info Format
46556 @section Traceframe Info Format
46557 @cindex traceframe info format
46559 To be able to know which objects in the inferior can be examined when
46560 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
46561 memory ranges, registers and trace state variables that have been
46562 collected in a traceframe.
46564 This list is obtained using the @samp{qXfer:traceframe-info:read}
46565 (@pxref{qXfer traceframe info read}) packet and is an XML document.
46567 @value{GDBN} must be linked with the Expat library to support XML
46568 traceframe info discovery. @xref{Expat}.
46570 The top-level structure of the document is shown below:
46573 <?xml version="1.0"?>
46574 <!DOCTYPE traceframe-info
46575 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46576 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
46582 Each traceframe block can be either:
46587 A region of collected memory starting at @var{addr} and extending for
46588 @var{length} bytes from there:
46591 <memory start="@var{addr}" length="@var{length}"/>
46595 A block indicating trace state variable numbered @var{number} has been
46599 <tvar id="@var{number}"/>
46604 The formal DTD for the traceframe info format is given below:
46607 <!ELEMENT traceframe-info (memory | tvar)* >
46608 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
46610 <!ELEMENT memory EMPTY>
46611 <!ATTLIST memory start CDATA #REQUIRED
46612 length CDATA #REQUIRED>
46614 <!ATTLIST tvar id CDATA #REQUIRED>
46617 @node Branch Trace Format
46618 @section Branch Trace Format
46619 @cindex branch trace format
46621 In order to display the branch trace of an inferior thread,
46622 @value{GDBN} needs to obtain the list of branches. This list is
46623 represented as list of sequential code blocks that are connected via
46624 branches. The code in each block has been executed sequentially.
46626 This list is obtained using the @samp{qXfer:btrace:read}
46627 (@pxref{qXfer btrace read}) packet and is an XML document.
46629 @value{GDBN} must be linked with the Expat library to support XML
46630 traceframe info discovery. @xref{Expat}.
46632 The top-level structure of the document is shown below:
46635 <?xml version="1.0"?>
46637 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
46638 "http://sourceware.org/gdb/gdb-btrace.dtd">
46647 A block of sequentially executed instructions starting at @var{begin}
46648 and ending at @var{end}:
46651 <block begin="@var{begin}" end="@var{end}"/>
46656 The formal DTD for the branch trace format is given below:
46659 <!ELEMENT btrace (block* | pt) >
46660 <!ATTLIST btrace version CDATA #FIXED "1.0">
46662 <!ELEMENT block EMPTY>
46663 <!ATTLIST block begin CDATA #REQUIRED
46664 end CDATA #REQUIRED>
46666 <!ELEMENT pt (pt-config?, raw?)>
46668 <!ELEMENT pt-config (cpu?)>
46670 <!ELEMENT cpu EMPTY>
46671 <!ATTLIST cpu vendor CDATA #REQUIRED
46672 family CDATA #REQUIRED
46673 model CDATA #REQUIRED
46674 stepping CDATA #REQUIRED>
46676 <!ELEMENT raw (#PCDATA)>
46679 @node Branch Trace Configuration Format
46680 @section Branch Trace Configuration Format
46681 @cindex branch trace configuration format
46683 For each inferior thread, @value{GDBN} can obtain the branch trace
46684 configuration using the @samp{qXfer:btrace-conf:read}
46685 (@pxref{qXfer btrace-conf read}) packet.
46687 The configuration describes the branch trace format and configuration
46688 settings for that format. The following information is described:
46692 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
46695 The size of the @acronym{BTS} ring buffer in bytes.
46698 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46702 The size of the @acronym{Intel PT} ring buffer in bytes.
46706 @value{GDBN} must be linked with the Expat library to support XML
46707 branch trace configuration discovery. @xref{Expat}.
46709 The formal DTD for the branch trace configuration format is given below:
46712 <!ELEMENT btrace-conf (bts?, pt?)>
46713 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46715 <!ELEMENT bts EMPTY>
46716 <!ATTLIST bts size CDATA #IMPLIED>
46718 <!ELEMENT pt EMPTY>
46719 <!ATTLIST pt size CDATA #IMPLIED>
46722 @include agentexpr.texi
46724 @node Target Descriptions
46725 @appendix Target Descriptions
46726 @cindex target descriptions
46728 One of the challenges of using @value{GDBN} to debug embedded systems
46729 is that there are so many minor variants of each processor
46730 architecture in use. It is common practice for vendors to start with
46731 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46732 and then make changes to adapt it to a particular market niche. Some
46733 architectures have hundreds of variants, available from dozens of
46734 vendors. This leads to a number of problems:
46738 With so many different customized processors, it is difficult for
46739 the @value{GDBN} maintainers to keep up with the changes.
46741 Since individual variants may have short lifetimes or limited
46742 audiences, it may not be worthwhile to carry information about every
46743 variant in the @value{GDBN} source tree.
46745 When @value{GDBN} does support the architecture of the embedded system
46746 at hand, the task of finding the correct architecture name to give the
46747 @command{set architecture} command can be error-prone.
46750 To address these problems, the @value{GDBN} remote protocol allows a
46751 target system to not only identify itself to @value{GDBN}, but to
46752 actually describe its own features. This lets @value{GDBN} support
46753 processor variants it has never seen before --- to the extent that the
46754 descriptions are accurate, and that @value{GDBN} understands them.
46756 @value{GDBN} must be linked with the Expat library to support XML
46757 target descriptions. @xref{Expat}.
46760 * Retrieving Descriptions:: How descriptions are fetched from a target.
46761 * Target Description Format:: The contents of a target description.
46762 * Predefined Target Types:: Standard types available for target
46764 * Enum Target Types:: How to define enum target types.
46765 * Standard Target Features:: Features @value{GDBN} knows about.
46768 @node Retrieving Descriptions
46769 @section Retrieving Descriptions
46771 Target descriptions can be read from the target automatically, or
46772 specified by the user manually. The default behavior is to read the
46773 description from the target. @value{GDBN} retrieves it via the remote
46774 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46775 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46776 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46777 XML document, of the form described in @ref{Target Description
46780 Alternatively, you can specify a file to read for the target description.
46781 If a file is set, the target will not be queried. The commands to
46782 specify a file are:
46785 @cindex set tdesc filename
46786 @item set tdesc filename @var{path}
46787 Read the target description from @var{path}.
46789 @cindex unset tdesc filename
46790 @item unset tdesc filename
46791 Do not read the XML target description from a file. @value{GDBN}
46792 will use the description supplied by the current target.
46794 @cindex show tdesc filename
46795 @item show tdesc filename
46796 Show the filename to read for a target description, if any.
46800 @node Target Description Format
46801 @section Target Description Format
46802 @cindex target descriptions, XML format
46804 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46805 document which complies with the Document Type Definition provided in
46806 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46807 means you can use generally available tools like @command{xmllint} to
46808 check that your feature descriptions are well-formed and valid.
46809 However, to help people unfamiliar with XML write descriptions for
46810 their targets, we also describe the grammar here.
46812 Target descriptions can identify the architecture of the remote target
46813 and (for some architectures) provide information about custom register
46814 sets. They can also identify the OS ABI of the remote target.
46815 @value{GDBN} can use this information to autoconfigure for your
46816 target, or to warn you if you connect to an unsupported target.
46818 Here is a simple target description:
46821 <target version="1.0">
46822 <architecture>i386:x86-64</architecture>
46827 This minimal description only says that the target uses
46828 the x86-64 architecture.
46830 A target description has the following overall form, with [ ] marking
46831 optional elements and @dots{} marking repeatable elements. The elements
46832 are explained further below.
46835 <?xml version="1.0"?>
46836 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46837 <target version="1.0">
46838 @r{[}@var{architecture}@r{]}
46839 @r{[}@var{osabi}@r{]}
46840 @r{[}@var{compatible}@r{]}
46841 @r{[}@var{feature}@dots{}@r{]}
46846 The description is generally insensitive to whitespace and line
46847 breaks, under the usual common-sense rules. The XML version
46848 declaration and document type declaration can generally be omitted
46849 (@value{GDBN} does not require them), but specifying them may be
46850 useful for XML validation tools. The @samp{version} attribute for
46851 @samp{<target>} may also be omitted, but we recommend
46852 including it; if future versions of @value{GDBN} use an incompatible
46853 revision of @file{gdb-target.dtd}, they will detect and report
46854 the version mismatch.
46856 @subsection Inclusion
46857 @cindex target descriptions, inclusion
46860 @cindex <xi:include>
46863 It can sometimes be valuable to split a target description up into
46864 several different annexes, either for organizational purposes, or to
46865 share files between different possible target descriptions. You can
46866 divide a description into multiple files by replacing any element of
46867 the target description with an inclusion directive of the form:
46870 <xi:include href="@var{document}"/>
46874 When @value{GDBN} encounters an element of this form, it will retrieve
46875 the named XML @var{document}, and replace the inclusion directive with
46876 the contents of that document. If the current description was read
46877 using @samp{qXfer}, then so will be the included document;
46878 @var{document} will be interpreted as the name of an annex. If the
46879 current description was read from a file, @value{GDBN} will look for
46880 @var{document} as a file in the same directory where it found the
46881 original description.
46883 @subsection Architecture
46884 @cindex <architecture>
46886 An @samp{<architecture>} element has this form:
46889 <architecture>@var{arch}</architecture>
46892 @var{arch} is one of the architectures from the set accepted by
46893 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46896 @cindex @code{<osabi>}
46898 This optional field was introduced in @value{GDBN} version 7.0.
46899 Previous versions of @value{GDBN} ignore it.
46901 An @samp{<osabi>} element has this form:
46904 <osabi>@var{abi-name}</osabi>
46907 @var{abi-name} is an OS ABI name from the same selection accepted by
46908 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46910 @subsection Compatible Architecture
46911 @cindex @code{<compatible>}
46913 This optional field was introduced in @value{GDBN} version 7.0.
46914 Previous versions of @value{GDBN} ignore it.
46916 A @samp{<compatible>} element has this form:
46919 <compatible>@var{arch}</compatible>
46922 @var{arch} is one of the architectures from the set accepted by
46923 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46925 A @samp{<compatible>} element is used to specify that the target
46926 is able to run binaries in some other than the main target architecture
46927 given by the @samp{<architecture>} element. For example, on the
46928 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46929 or @code{powerpc:common64}, but the system is able to run binaries
46930 in the @code{spu} architecture as well. The way to describe this
46931 capability with @samp{<compatible>} is as follows:
46934 <architecture>powerpc:common</architecture>
46935 <compatible>spu</compatible>
46938 @subsection Features
46941 Each @samp{<feature>} describes some logical portion of the target
46942 system. Features are currently used to describe available CPU
46943 registers and the types of their contents. A @samp{<feature>} element
46947 <feature name="@var{name}">
46948 @r{[}@var{type}@dots{}@r{]}
46954 Each feature's name should be unique within the description. The name
46955 of a feature does not matter unless @value{GDBN} has some special
46956 knowledge of the contents of that feature; if it does, the feature
46957 should have its standard name. @xref{Standard Target Features}.
46961 Any register's value is a collection of bits which @value{GDBN} must
46962 interpret. The default interpretation is a two's complement integer,
46963 but other types can be requested by name in the register description.
46964 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46965 Target Types}), and the description can define additional composite
46968 Each type element must have an @samp{id} attribute, which gives
46969 a unique (within the containing @samp{<feature>}) name to the type.
46970 Types must be defined before they are used.
46973 Some targets offer vector registers, which can be treated as arrays
46974 of scalar elements. These types are written as @samp{<vector>} elements,
46975 specifying the array element type, @var{type}, and the number of elements,
46979 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46983 If a register's value is usefully viewed in multiple ways, define it
46984 with a union type containing the useful representations. The
46985 @samp{<union>} element contains one or more @samp{<field>} elements,
46986 each of which has a @var{name} and a @var{type}:
46989 <union id="@var{id}">
46990 <field name="@var{name}" type="@var{type}"/>
46997 If a register's value is composed from several separate values, define
46998 it with either a structure type or a flags type.
46999 A flags type may only contain bitfields.
47000 A structure type may either contain only bitfields or contain no bitfields.
47001 If the value contains only bitfields, its total size in bytes must be
47004 Non-bitfield values have a @var{name} and @var{type}.
47007 <struct id="@var{id}">
47008 <field name="@var{name}" type="@var{type}"/>
47013 Both @var{name} and @var{type} values are required.
47014 No implicit padding is added.
47016 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
47019 <struct id="@var{id}" size="@var{size}">
47020 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
47026 <flags id="@var{id}" size="@var{size}">
47027 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
47032 The @var{name} value is required.
47033 Bitfield values may be named with the empty string, @samp{""},
47034 in which case the field is ``filler'' and its value is not printed.
47035 Not all bits need to be specified, so ``filler'' fields are optional.
47037 The @var{start} and @var{end} values are required, and @var{type}
47039 The field's @var{start} must be less than or equal to its @var{end},
47040 and zero represents the least significant bit.
47042 The default value of @var{type} is @code{bool} for single bit fields,
47043 and an unsigned integer otherwise.
47045 Which to choose? Structures or flags?
47047 Registers defined with @samp{flags} have these advantages over
47048 defining them with @samp{struct}:
47052 Arithmetic may be performed on them as if they were integers.
47054 They are printed in a more readable fashion.
47057 Registers defined with @samp{struct} have one advantage over
47058 defining them with @samp{flags}:
47062 One can fetch individual fields like in @samp{C}.
47065 (gdb) print $my_struct_reg.field3
47071 @subsection Registers
47074 Each register is represented as an element with this form:
47077 <reg name="@var{name}"
47078 bitsize="@var{size}"
47079 @r{[}regnum="@var{num}"@r{]}
47080 @r{[}save-restore="@var{save-restore}"@r{]}
47081 @r{[}type="@var{type}"@r{]}
47082 @r{[}group="@var{group}"@r{]}/>
47086 The components are as follows:
47091 The register's name; it must be unique within the target description.
47094 The register's size, in bits.
47097 The register's number. If omitted, a register's number is one greater
47098 than that of the previous register (either in the current feature or in
47099 a preceding feature); the first register in the target description
47100 defaults to zero. This register number is used to read or write
47101 the register; e.g.@: it is used in the remote @code{p} and @code{P}
47102 packets, and registers appear in the @code{g} and @code{G} packets
47103 in order of increasing register number.
47106 Whether the register should be preserved across inferior function
47107 calls; this must be either @code{yes} or @code{no}. The default is
47108 @code{yes}, which is appropriate for most registers except for
47109 some system control registers; this is not related to the target's
47113 The type of the register. It may be a predefined type, a type
47114 defined in the current feature, or one of the special types @code{int}
47115 and @code{float}. @code{int} is an integer type of the correct size
47116 for @var{bitsize}, and @code{float} is a floating point type (in the
47117 architecture's normal floating point format) of the correct size for
47118 @var{bitsize}. The default is @code{int}.
47121 The register group to which this register belongs. It can be one of the
47122 standard register groups @code{general}, @code{float}, @code{vector} or an
47123 arbitrary string. Group names should be limited to alphanumeric characters.
47124 If a group name is made up of multiple words the words may be separated by
47125 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
47126 @var{group} is specified, @value{GDBN} will not display the register in
47127 @code{info registers}.
47131 @node Predefined Target Types
47132 @section Predefined Target Types
47133 @cindex target descriptions, predefined types
47135 Type definitions in the self-description can build up composite types
47136 from basic building blocks, but can not define fundamental types. Instead,
47137 standard identifiers are provided by @value{GDBN} for the fundamental
47138 types. The currently supported types are:
47143 Boolean type, occupying a single bit.
47151 Signed integer types holding the specified number of bits.
47159 Unsigned integer types holding the specified number of bits.
47163 Pointers to unspecified code and data. The program counter and
47164 any dedicated return address register may be marked as code
47165 pointers; printing a code pointer converts it into a symbolic
47166 address. The stack pointer and any dedicated address registers
47167 may be marked as data pointers.
47170 Half precision IEEE floating point.
47173 Single precision IEEE floating point.
47176 Double precision IEEE floating point.
47179 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
47182 The 12-byte extended precision format used by ARM FPA registers.
47185 The 10-byte extended precision format used by x87 registers.
47188 32bit @sc{eflags} register used by x86.
47191 32bit @sc{mxcsr} register used by x86.
47195 @node Enum Target Types
47196 @section Enum Target Types
47197 @cindex target descriptions, enum types
47199 Enum target types are useful in @samp{struct} and @samp{flags}
47200 register descriptions. @xref{Target Description Format}.
47202 Enum types have a name, size and a list of name/value pairs.
47205 <enum id="@var{id}" size="@var{size}">
47206 <evalue name="@var{name}" value="@var{value}"/>
47211 Enums must be defined before they are used.
47214 <enum id="levels_type" size="4">
47215 <evalue name="low" value="0"/>
47216 <evalue name="high" value="1"/>
47218 <flags id="flags_type" size="4">
47219 <field name="X" start="0"/>
47220 <field name="LEVEL" start="1" end="1" type="levels_type"/>
47222 <reg name="flags" bitsize="32" type="flags_type"/>
47225 Given that description, a value of 3 for the @samp{flags} register
47226 would be printed as:
47229 (gdb) info register flags
47230 flags 0x3 [ X LEVEL=high ]
47233 @node Standard Target Features
47234 @section Standard Target Features
47235 @cindex target descriptions, standard features
47237 A target description must contain either no registers or all the
47238 target's registers. If the description contains no registers, then
47239 @value{GDBN} will assume a default register layout, selected based on
47240 the architecture. If the description contains any registers, the
47241 default layout will not be used; the standard registers must be
47242 described in the target description, in such a way that @value{GDBN}
47243 can recognize them.
47245 This is accomplished by giving specific names to feature elements
47246 which contain standard registers. @value{GDBN} will look for features
47247 with those names and verify that they contain the expected registers;
47248 if any known feature is missing required registers, or if any required
47249 feature is missing, @value{GDBN} will reject the target
47250 description. You can add additional registers to any of the
47251 standard features --- @value{GDBN} will display them just as if
47252 they were added to an unrecognized feature.
47254 This section lists the known features and their expected contents.
47255 Sample XML documents for these features are included in the
47256 @value{GDBN} source tree, in the directory @file{gdb/features}.
47258 Names recognized by @value{GDBN} should include the name of the
47259 company or organization which selected the name, and the overall
47260 architecture to which the feature applies; so e.g.@: the feature
47261 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
47263 The names of registers are not case sensitive for the purpose
47264 of recognizing standard features, but @value{GDBN} will only display
47265 registers using the capitalization used in the description.
47268 * AArch64 Features::
47272 * LoongArch Features::
47273 * MicroBlaze Features::
47277 * Nios II Features::
47278 * OpenRISC 1000 Features::
47279 * PowerPC Features::
47280 * RISC-V Features::
47282 * S/390 and System z Features::
47288 @node AArch64 Features
47289 @subsection AArch64 Features
47290 @cindex target descriptions, AArch64 features
47292 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
47293 targets. It should contain registers @samp{x0} through @samp{x30},
47294 @samp{sp}, @samp{pc}, and @samp{cpsr}.
47296 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
47297 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
47300 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
47301 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
47302 through @samp{p15}, @samp{ffr} and @samp{vg}.
47304 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
47305 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
47308 @subsection ARC Features
47309 @cindex target descriptions, ARC Features
47311 ARC processors are so configurable that even core registers and their numbers
47312 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
47313 registers, which are important to @value{GDBN}, are not ``core'' registers in
47314 ARC. Therefore, there are two features that their presence is mandatory:
47315 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
47317 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
47322 @samp{r0} through @samp{r25} for normal register file targets.
47324 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
47325 register file targets.
47327 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
47328 @samp{blink}, @samp{lp_count}, @samp{pcl}.
47331 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
47332 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
47333 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
47334 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
47335 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
47336 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
47337 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
47338 because of their inaccessibility during user space debugging sessions.
47340 Extension core registers @samp{r32} through @samp{r59} are optional and their
47341 existence depends on the configuration. When debugging GNU/Linux applications,
47342 i.e.@: user space debugging, these core registers are not available.
47344 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
47345 is the list of registers pertinent to this feature:
47349 mandatory: @samp{pc} and @samp{status32}.
47351 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
47355 @subsection ARM Features
47356 @cindex target descriptions, ARM features
47358 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
47360 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
47361 @samp{lr}, @samp{pc}, and @samp{cpsr}.
47363 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
47364 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
47365 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
47368 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
47369 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
47371 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
47372 must contain register @samp{vpr}.
47374 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
47375 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
47377 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
47378 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
47379 synthesize the @samp{q} pseudo registers from @samp{d} register
47382 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
47383 it should contain at least registers @samp{wR0} through @samp{wR15} and
47384 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
47385 @samp{wCSSF}, and @samp{wCASF} registers are optional.
47387 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
47388 should contain at least registers @samp{d0} through @samp{d15}. If
47389 they are present, @samp{d16} through @samp{d31} should also be included.
47390 @value{GDBN} will synthesize the single-precision registers from
47391 halves of the double-precision registers.
47393 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
47394 need to contain registers; it instructs @value{GDBN} to display the
47395 VFP double-precision registers as vectors and to synthesize the
47396 quad-precision registers from pairs of double-precision registers.
47397 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
47398 be present and include 32 double-precision registers.
47400 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
47401 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
47402 will track return address signing states and will decorate backtraces using
47403 the [PAC] marker, similar to AArch64's PAC extension.
47404 @xref{AArch64 PAC}.
47406 @node i386 Features
47407 @subsection i386 Features
47408 @cindex target descriptions, i386 features
47410 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
47411 targets. It should describe the following registers:
47415 @samp{eax} through @samp{edi} plus @samp{eip} for i386
47417 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
47419 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
47420 @samp{fs}, @samp{gs}
47422 @samp{st0} through @samp{st7}
47424 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
47425 @samp{foseg}, @samp{fooff} and @samp{fop}
47428 The register sets may be different, depending on the target.
47430 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
47431 describe registers:
47435 @samp{xmm0} through @samp{xmm7} for i386
47437 @samp{xmm0} through @samp{xmm15} for amd64
47442 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
47443 @samp{org.gnu.gdb.i386.sse} feature. It should
47444 describe the upper 128 bits of @sc{ymm} registers:
47448 @samp{ymm0h} through @samp{ymm7h} for i386
47450 @samp{ymm0h} through @samp{ymm15h} for amd64
47453 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
47454 Memory Protection Extension (MPX). It should describe the following registers:
47458 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
47460 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
47463 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
47464 describe a single register, @samp{orig_eax}.
47466 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
47467 describe two system registers: @samp{fs_base} and @samp{gs_base}.
47469 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
47470 @samp{org.gnu.gdb.i386.avx} feature. It should
47471 describe additional @sc{xmm} registers:
47475 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
47478 It should describe the upper 128 bits of additional @sc{ymm} registers:
47482 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
47486 describe the upper 256 bits of @sc{zmm} registers:
47490 @samp{zmm0h} through @samp{zmm7h} for i386.
47492 @samp{zmm0h} through @samp{zmm15h} for amd64.
47496 describe the additional @sc{zmm} registers:
47500 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
47503 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
47504 describe a single register, @samp{pkru}. It is a 32-bit register
47505 valid for i386 and amd64.
47507 @node LoongArch Features
47508 @subsection LoongArch Features
47509 @cindex target descriptions, LoongArch Features
47511 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
47512 targets. It should contain the registers @samp{r0} through @samp{r31},
47513 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
47514 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
47516 The @samp{org.gnu.gdb.loongarch.fpu} feature is optional. If present,
47517 it should contain registers @samp{f0} through @samp{f31}, @samp{fcc},
47520 @node MicroBlaze Features
47521 @subsection MicroBlaze Features
47522 @cindex target descriptions, MicroBlaze features
47524 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
47525 targets. It should contain registers @samp{r0} through @samp{r31},
47526 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
47527 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
47528 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
47530 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
47531 If present, it should contain registers @samp{rshr} and @samp{rslr}
47533 @node MIPS Features
47534 @subsection @acronym{MIPS} Features
47535 @cindex target descriptions, @acronym{MIPS} features
47537 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
47538 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
47539 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
47542 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
47543 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
47544 registers. They may be 32-bit or 64-bit depending on the target.
47546 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
47547 it may be optional in a future version of @value{GDBN}. It should
47548 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
47549 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
47551 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
47552 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
47553 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
47554 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
47556 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
47557 contain a single register, @samp{restart}, which is used by the
47558 Linux kernel to control restartable syscalls.
47560 @node M68K Features
47561 @subsection M68K Features
47562 @cindex target descriptions, M68K features
47565 @item @samp{org.gnu.gdb.m68k.core}
47566 @itemx @samp{org.gnu.gdb.coldfire.core}
47567 @itemx @samp{org.gnu.gdb.fido.core}
47568 One of those features must be always present.
47569 The feature that is present determines which flavor of m68k is
47570 used. The feature that is present should contain registers
47571 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
47572 @samp{sp}, @samp{ps} and @samp{pc}.
47574 @item @samp{org.gnu.gdb.coldfire.fp}
47575 This feature is optional. If present, it should contain registers
47576 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
47579 Note that, despite the fact that this feature's name says
47580 @samp{coldfire}, it is used to describe any floating point registers.
47581 The size of the registers must match the main m68k flavor; so, for
47582 example, if the primary feature is reported as @samp{coldfire}, then
47583 64-bit floating point registers are required.
47586 @node NDS32 Features
47587 @subsection NDS32 Features
47588 @cindex target descriptions, NDS32 features
47590 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
47591 targets. It should contain at least registers @samp{r0} through
47592 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
47595 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
47596 it should contain 64-bit double-precision floating-point registers
47597 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
47598 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
47600 @emph{Note:} The first sixteen 64-bit double-precision floating-point
47601 registers are overlapped with the thirty-two 32-bit single-precision
47602 floating-point registers. The 32-bit single-precision registers, if
47603 not being listed explicitly, will be synthesized from halves of the
47604 overlapping 64-bit double-precision registers. Listing 32-bit
47605 single-precision registers explicitly is deprecated, and the
47606 support to it could be totally removed some day.
47608 @node Nios II Features
47609 @subsection Nios II Features
47610 @cindex target descriptions, Nios II features
47612 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
47613 targets. It should contain the 32 core registers (@samp{zero},
47614 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
47615 @samp{pc}, and the 16 control registers (@samp{status} through
47618 @node OpenRISC 1000 Features
47619 @subsection Openrisc 1000 Features
47620 @cindex target descriptions, OpenRISC 1000 features
47622 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
47623 targets. It should contain the 32 general purpose registers (@samp{r0}
47624 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
47626 @node PowerPC Features
47627 @subsection PowerPC Features
47628 @cindex target descriptions, PowerPC features
47630 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
47631 targets. It should contain registers @samp{r0} through @samp{r31},
47632 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
47633 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
47635 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
47636 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
47638 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
47639 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
47640 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
47641 through @samp{v31} as aliases for the corresponding @samp{vrX}
47644 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
47645 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
47646 combine these registers with the floating point registers (@samp{f0}
47647 through @samp{f31}) and the altivec registers (@samp{vr0} through
47648 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
47649 @samp{vs63}, the set of vector-scalar registers for POWER7.
47650 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
47651 @samp{org.gnu.gdb.power.altivec}.
47653 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
47654 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
47655 @samp{spefscr}. SPE targets should provide 32-bit registers in
47656 @samp{org.gnu.gdb.power.core} and provide the upper halves in
47657 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
47658 these to present registers @samp{ev0} through @samp{ev31} to the
47661 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
47662 contain the 64-bit register @samp{ppr}.
47664 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
47665 contain the 64-bit register @samp{dscr}.
47667 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
47668 contain the 64-bit register @samp{tar}.
47670 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
47671 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
47674 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
47675 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
47676 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
47677 server PMU registers provided by @sc{gnu}/Linux.
47679 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
47680 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
47683 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
47684 contain the checkpointed general-purpose registers @samp{cr0} through
47685 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
47686 @samp{cctr}. These registers may all be either 32-bit or 64-bit
47687 depending on the target. It should also contain the checkpointed
47688 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
47691 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
47692 contain the checkpointed 64-bit floating-point registers @samp{cf0}
47693 through @samp{cf31}, as well as the checkpointed 64-bit register
47696 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
47697 should contain the checkpointed altivec registers @samp{cvr0} through
47698 @samp{cvr31}, all 128-bit wide. It should also contain the
47699 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
47702 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
47703 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
47704 will combine these registers with the checkpointed floating point
47705 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47706 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47707 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47708 @samp{cvs63}. Therefore, this feature requires both
47709 @samp{org.gnu.gdb.power.htm.altivec} and
47710 @samp{org.gnu.gdb.power.htm.fpu}.
47712 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47713 contain the 64-bit checkpointed register @samp{cppr}.
47715 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47716 contain the 64-bit checkpointed register @samp{cdscr}.
47718 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47719 contain the 64-bit checkpointed register @samp{ctar}.
47722 @node RISC-V Features
47723 @subsection RISC-V Features
47724 @cindex target descriptions, RISC-V Features
47726 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47727 targets. It should contain the registers @samp{x0} through
47728 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47729 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47732 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47733 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47734 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47735 architectural register names, or the ABI names can be used.
47737 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47738 it should contain registers that are not backed by real registers on
47739 the target, but are instead virtual, where the register value is
47740 derived from other target state. In many ways these are like
47741 @value{GDBN}s pseudo-registers, except implemented by the target.
47742 Currently the only register expected in this set is the one byte
47743 @samp{priv} register that contains the target's privilege level in the
47744 least significant two bits.
47746 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47747 should contain all of the target's standard CSRs. Standard CSRs are
47748 those defined in the RISC-V specification documents. There is some
47749 overlap between this feature and the fpu feature; the @samp{fflags},
47750 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47751 expectation is that these registers will be in the fpu feature if the
47752 target has floating point hardware, but can be moved into the csr
47753 feature if the target has the floating point control registers, but no
47754 other floating point hardware.
47756 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47757 it should contain registers @samp{v0} through @samp{v31}, all of which
47758 must be the same size. These requirements are based on the v0.10
47759 draft vector extension, as the vector extension is not yet final. In
47760 the event that the register set of the vector extension changes for
47761 the final specification, the requirements given here could change for
47762 future releases of @value{GDBN}.
47765 @subsection RX Features
47766 @cindex target descriptions, RX Features
47768 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47769 targets. It should contain the registers @samp{r0} through
47770 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47771 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47773 @node S/390 and System z Features
47774 @subsection S/390 and System z Features
47775 @cindex target descriptions, S/390 features
47776 @cindex target descriptions, System z features
47778 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47779 System z targets. It should contain the PSW and the 16 general
47780 registers. In particular, System z targets should provide the 64-bit
47781 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47782 S/390 targets should provide the 32-bit versions of these registers.
47783 A System z target that runs in 31-bit addressing mode should provide
47784 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47785 register's upper halves @samp{r0h} through @samp{r15h}, and their
47786 lower halves @samp{r0l} through @samp{r15l}.
47788 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47789 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47792 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47793 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47795 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47796 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47797 targets and 32-bit otherwise. In addition, the feature may contain
47798 the @samp{last_break} register, whose width depends on the addressing
47799 mode, as well as the @samp{system_call} register, which is always
47802 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47803 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47804 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47806 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47807 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47808 combined by @value{GDBN} with the floating point registers @samp{f0}
47809 through @samp{f15} to present the 128-bit wide vector registers
47810 @samp{v0} through @samp{v15}. In addition, this feature should
47811 contain the 128-bit wide vector registers @samp{v16} through
47814 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47815 the 64-bit wide guarded-storage-control registers @samp{gsd},
47816 @samp{gssm}, and @samp{gsepla}.
47818 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47819 the 64-bit wide guarded-storage broadcast control registers
47820 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47822 @node Sparc Features
47823 @subsection Sparc Features
47824 @cindex target descriptions, sparc32 features
47825 @cindex target descriptions, sparc64 features
47826 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47827 targets. It should describe the following registers:
47831 @samp{g0} through @samp{g7}
47833 @samp{o0} through @samp{o7}
47835 @samp{l0} through @samp{l7}
47837 @samp{i0} through @samp{i7}
47840 They may be 32-bit or 64-bit depending on the target.
47842 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47843 targets. It should describe the following registers:
47847 @samp{f0} through @samp{f31}
47849 @samp{f32} through @samp{f62} for sparc64
47852 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47853 targets. It should describe the following registers:
47857 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47858 @samp{fsr}, and @samp{csr} for sparc32
47860 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47864 @node TIC6x Features
47865 @subsection TMS320C6x Features
47866 @cindex target descriptions, TIC6x features
47867 @cindex target descriptions, TMS320C6x features
47868 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47869 targets. It should contain registers @samp{A0} through @samp{A15},
47870 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47872 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47873 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47874 through @samp{B31}.
47876 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47877 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47879 @node Operating System Information
47880 @appendix Operating System Information
47881 @cindex operating system information
47883 Users of @value{GDBN} often wish to obtain information about the state of
47884 the operating system running on the target---for example the list of
47885 processes, or the list of open files. This section describes the
47886 mechanism that makes it possible. This mechanism is similar to the
47887 target features mechanism (@pxref{Target Descriptions}), but focuses
47888 on a different aspect of target.
47890 Operating system information is retrieved from the target via the
47891 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47892 read}). The object name in the request should be @samp{osdata}, and
47893 the @var{annex} identifies the data to be fetched.
47900 @appendixsection Process list
47901 @cindex operating system information, process list
47903 When requesting the process list, the @var{annex} field in the
47904 @samp{qXfer} request should be @samp{processes}. The returned data is
47905 an XML document. The formal syntax of this document is defined in
47906 @file{gdb/features/osdata.dtd}.
47908 An example document is:
47911 <?xml version="1.0"?>
47912 <!DOCTYPE target SYSTEM "osdata.dtd">
47913 <osdata type="processes">
47915 <column name="pid">1</column>
47916 <column name="user">root</column>
47917 <column name="command">/sbin/init</column>
47918 <column name="cores">1,2,3</column>
47923 Each item should include a column whose name is @samp{pid}. The value
47924 of that column should identify the process on the target. The
47925 @samp{user} and @samp{command} columns are optional, and will be
47926 displayed by @value{GDBN}. The @samp{cores} column, if present,
47927 should contain a comma-separated list of cores that this process
47928 is running on. Target may provide additional columns,
47929 which @value{GDBN} currently ignores.
47931 @node Trace File Format
47932 @appendix Trace File Format
47933 @cindex trace file format
47935 The trace file comes in three parts: a header, a textual description
47936 section, and a trace frame section with binary data.
47938 The header has the form @code{\x7fTRACE0\n}. The first byte is
47939 @code{0x7f} so as to indicate that the file contains binary data,
47940 while the @code{0} is a version number that may have different values
47943 The description section consists of multiple lines of @sc{ascii} text
47944 separated by newline characters (@code{0xa}). The lines may include a
47945 variety of optional descriptive or context-setting information, such
47946 as tracepoint definitions or register set size. @value{GDBN} will
47947 ignore any line that it does not recognize. An empty line marks the end
47952 Specifies the size of a register block in bytes. This is equal to the
47953 size of a @code{g} packet payload in the remote protocol. @var{size}
47954 is an ascii decimal number. There should be only one such line in
47955 a single trace file.
47957 @item status @var{status}
47958 Trace status. @var{status} has the same format as a @code{qTStatus}
47959 remote packet reply. There should be only one such line in a single trace
47962 @item tp @var{payload}
47963 Tracepoint definition. The @var{payload} has the same format as
47964 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47965 may take multiple lines of definition, corresponding to the multiple
47968 @item tsv @var{payload}
47969 Trace state variable definition. The @var{payload} has the same format as
47970 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47971 may take multiple lines of definition, corresponding to the multiple
47974 @item tdesc @var{payload}
47975 Target description in XML format. The @var{payload} is a single line of
47976 the XML file. All such lines should be concatenated together to get
47977 the original XML file. This file is in the same format as @code{qXfer}
47978 @code{features} payload, and corresponds to the main @code{target.xml}
47979 file. Includes are not allowed.
47983 The trace frame section consists of a number of consecutive frames.
47984 Each frame begins with a two-byte tracepoint number, followed by a
47985 four-byte size giving the amount of data in the frame. The data in
47986 the frame consists of a number of blocks, each introduced by a
47987 character indicating its type (at least register, memory, and trace
47988 state variable). The data in this section is raw binary, not a
47989 hexadecimal or other encoding; its endianness matches the target's
47992 @c FIXME bi-arch may require endianness/arch info in description section
47995 @item R @var{bytes}
47996 Register block. The number and ordering of bytes matches that of a
47997 @code{g} packet in the remote protocol. Note that these are the
47998 actual bytes, in target order, not a hexadecimal encoding.
48000 @item M @var{address} @var{length} @var{bytes}...
48001 Memory block. This is a contiguous block of memory, at the 8-byte
48002 address @var{address}, with a 2-byte length @var{length}, followed by
48003 @var{length} bytes.
48005 @item V @var{number} @var{value}
48006 Trace state variable block. This records the 8-byte signed value
48007 @var{value} of trace state variable numbered @var{number}.
48011 Future enhancements of the trace file format may include additional types
48014 @node Index Section Format
48015 @appendix @code{.gdb_index} section format
48016 @cindex .gdb_index section format
48017 @cindex index section format
48019 This section documents the index section that is created by @code{save
48020 gdb-index} (@pxref{Index Files}). The index section is
48021 DWARF-specific; some knowledge of DWARF is assumed in this
48024 The mapped index file format is designed to be directly
48025 @code{mmap}able on any architecture. In most cases, a datum is
48026 represented using a little-endian 32-bit integer value, called an
48027 @code{offset_type}. Big endian machines must byte-swap the values
48028 before using them. Exceptions to this rule are noted. The data is
48029 laid out such that alignment is always respected.
48031 A mapped index consists of several areas, laid out in order.
48035 The file header. This is a sequence of values, of @code{offset_type}
48036 unless otherwise noted:
48040 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
48041 Version 4 uses a different hashing function from versions 5 and 6.
48042 Version 6 includes symbols for inlined functions, whereas versions 4
48043 and 5 do not. Version 7 adds attributes to the CU indices in the
48044 symbol table. Version 8 specifies that symbols from DWARF type units
48045 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
48046 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
48048 @value{GDBN} will only read version 4, 5, or 6 indices
48049 by specifying @code{set use-deprecated-index-sections on}.
48050 GDB has a workaround for potentially broken version 7 indices so it is
48051 currently not flagged as deprecated.
48054 The offset, from the start of the file, of the CU list.
48057 The offset, from the start of the file, of the types CU list. Note
48058 that this area can be empty, in which case this offset will be equal
48059 to the next offset.
48062 The offset, from the start of the file, of the address area.
48065 The offset, from the start of the file, of the symbol table.
48068 The offset, from the start of the file, of the constant pool.
48072 The CU list. This is a sequence of pairs of 64-bit little-endian
48073 values, sorted by the CU offset. The first element in each pair is
48074 the offset of a CU in the @code{.debug_info} section. The second
48075 element in each pair is the length of that CU. References to a CU
48076 elsewhere in the map are done using a CU index, which is just the
48077 0-based index into this table. Note that if there are type CUs, then
48078 conceptually CUs and type CUs form a single list for the purposes of
48082 The types CU list. This is a sequence of triplets of 64-bit
48083 little-endian values. In a triplet, the first value is the CU offset,
48084 the second value is the type offset in the CU, and the third value is
48085 the type signature. The types CU list is not sorted.
48088 The address area. The address area consists of a sequence of address
48089 entries. Each address entry has three elements:
48093 The low address. This is a 64-bit little-endian value.
48096 The high address. This is a 64-bit little-endian value. Like
48097 @code{DW_AT_high_pc}, the value is one byte beyond the end.
48100 The CU index. This is an @code{offset_type} value.
48104 The symbol table. This is an open-addressed hash table. The size of
48105 the hash table is always a power of 2.
48107 Each slot in the hash table consists of a pair of @code{offset_type}
48108 values. The first value is the offset of the symbol's name in the
48109 constant pool. The second value is the offset of the CU vector in the
48112 If both values are 0, then this slot in the hash table is empty. This
48113 is ok because while 0 is a valid constant pool index, it cannot be a
48114 valid index for both a string and a CU vector.
48116 The hash value for a table entry is computed by applying an
48117 iterative hash function to the symbol's name. Starting with an
48118 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
48119 the string is incorporated into the hash using the formula depending on the
48124 The formula is @code{r = r * 67 + c - 113}.
48126 @item Versions 5 to 7
48127 The formula is @code{r = r * 67 + tolower (c) - 113}.
48130 The terminating @samp{\0} is not incorporated into the hash.
48132 The step size used in the hash table is computed via
48133 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
48134 value, and @samp{size} is the size of the hash table. The step size
48135 is used to find the next candidate slot when handling a hash
48138 The names of C@t{++} symbols in the hash table are canonicalized. We
48139 don't currently have a simple description of the canonicalization
48140 algorithm; if you intend to create new index sections, you must read
48144 The constant pool. This is simply a bunch of bytes. It is organized
48145 so that alignment is correct: CU vectors are stored first, followed by
48148 A CU vector in the constant pool is a sequence of @code{offset_type}
48149 values. The first value is the number of CU indices in the vector.
48150 Each subsequent value is the index and symbol attributes of a CU in
48151 the CU list. This element in the hash table is used to indicate which
48152 CUs define the symbol and how the symbol is used.
48153 See below for the format of each CU index+attributes entry.
48155 A string in the constant pool is zero-terminated.
48158 Attributes were added to CU index values in @code{.gdb_index} version 7.
48159 If a symbol has multiple uses within a CU then there is one
48160 CU index+attributes value for each use.
48162 The format of each CU index+attributes entry is as follows
48168 This is the index of the CU in the CU list.
48170 These bits are reserved for future purposes and must be zero.
48172 The kind of the symbol in the CU.
48176 This value is reserved and should not be used.
48177 By reserving zero the full @code{offset_type} value is backwards compatible
48178 with previous versions of the index.
48180 The symbol is a type.
48182 The symbol is a variable or an enum value.
48184 The symbol is a function.
48186 Any other kind of symbol.
48188 These values are reserved.
48192 This bit is zero if the value is global and one if it is static.
48194 The determination of whether a symbol is global or static is complicated.
48195 The authorative reference is the file @file{dwarf2read.c} in
48196 @value{GDBN} sources.
48200 This pseudo-code describes the computation of a symbol's kind and
48201 global/static attributes in the index.
48204 is_external = get_attribute (die, DW_AT_external);
48205 language = get_attribute (cu_die, DW_AT_language);
48208 case DW_TAG_typedef:
48209 case DW_TAG_base_type:
48210 case DW_TAG_subrange_type:
48214 case DW_TAG_enumerator:
48216 is_static = language != CPLUS;
48218 case DW_TAG_subprogram:
48220 is_static = ! (is_external || language == ADA);
48222 case DW_TAG_constant:
48224 is_static = ! is_external;
48226 case DW_TAG_variable:
48228 is_static = ! is_external;
48230 case DW_TAG_namespace:
48234 case DW_TAG_class_type:
48235 case DW_TAG_interface_type:
48236 case DW_TAG_structure_type:
48237 case DW_TAG_union_type:
48238 case DW_TAG_enumeration_type:
48240 is_static = language != CPLUS;
48248 @appendix Download debugging resources with Debuginfod
48251 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
48254 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
48255 can query servers using the build IDs associated with missing debug info,
48256 executables and source files in order to download them on demand.
48258 For instructions on building @value{GDBN} with @file{libdebuginfod},
48259 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
48260 with @code{elfutils}, starting with version 0.178. See
48261 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
48262 regarding @code{debuginfod}.
48265 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
48268 @node Debuginfod Settings
48269 @section Debuginfod Settings
48271 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
48274 @kindex set debuginfod enabled
48275 @anchor{set debuginfod enabled}
48276 @item set debuginfod enabled
48277 @itemx set debuginfod enabled on
48278 @cindex enable debuginfod
48279 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
48280 info or source files.
48282 @item set debuginfod enabled off
48283 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
48284 debug info or source files. By default, @code{debuginfod enabled} is set to
48285 @code{off} for non-interactive sessions.
48287 @item set debuginfod enabled ask
48288 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
48289 attempting to perform the next query. By default, @code{debuginfod enabled}
48290 is set to @code{ask} for interactive sessions.
48292 @kindex show debuginfod enabled
48293 @item show debuginfod enabled
48294 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
48297 @kindex set debuginfod urls
48298 @cindex configure debuginfod URLs
48299 @item set debuginfod urls
48300 @itemx set debuginfod urls @var{urls}
48301 Set the space-separated list of URLs that @code{debuginfod} will attempt to
48302 query. Only @code{http://}, @code{https://} and @code{file://} protocols
48303 should be used. The default value of @code{debuginfod urls} is copied from
48304 the @var{DEBUGINFOD_URLS} environment variable.
48306 @kindex show debuginfod urls
48307 @item show debuginfod urls
48308 Display the list of URLs that @code{debuginfod} will attempt to query.
48310 @kindex set debuginfod verbose
48311 @cindex debuginfod verbosity
48312 @item set debuginfod verbose
48313 @itemx set debuginfod verbose @var{n}
48314 Enable or disable @code{debuginfod}-related output. Use a non-zero value
48315 to enable and @code{0} to disable. @code{debuginfod} output is shown by
48318 @kindex show debuginfod verbose
48319 @item show debuginfod verbose
48320 Show the current verbosity setting.
48325 @appendix Manual pages
48329 * gdb man:: The GNU Debugger man page
48330 * gdbserver man:: Remote Server for the GNU Debugger man page
48331 * gcore man:: Generate a core file of a running program
48332 * gdbinit man:: gdbinit scripts
48333 * gdb-add-index man:: Add index files to speed up GDB
48339 @c man title gdb The GNU Debugger
48341 @c man begin SYNOPSIS gdb
48342 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
48345 @c man begin DESCRIPTION gdb
48346 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
48347 going on ``inside'' another program while it executes -- or what another
48348 program was doing at the moment it crashed.
48350 @value{GDBN} can do four main kinds of things (plus other things in support of
48351 these) to help you catch bugs in the act:
48355 Start your program, specifying anything that might affect its behavior.
48358 Make your program stop on specified conditions.
48361 Examine what has happened, when your program has stopped.
48364 Change things in your program, so you can experiment with correcting the
48365 effects of one bug and go on to learn about another.
48368 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
48371 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
48372 commands from the terminal until you tell it to exit with the @value{GDBN}
48373 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
48374 by using the command @code{help}.
48376 You can run @code{gdb} with no arguments or options; but the most
48377 usual way to start @value{GDBN} is with one argument or two, specifying an
48378 executable program as the argument:
48384 You can also start with both an executable program and a core file specified:
48390 You can, instead, specify a process ID as a second argument or use option
48391 @code{-p}, if you want to debug a running process:
48399 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
48400 can omit the @var{program} filename.
48402 Here are some of the most frequently needed @value{GDBN} commands:
48404 @c pod2man highlights the right hand side of the @item lines.
48406 @item break [@var{file}:][@var{function}|@var{line}]
48407 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
48409 @item run [@var{arglist}]
48410 Start your program (with @var{arglist}, if specified).
48413 Backtrace: display the program stack.
48415 @item print @var{expr}
48416 Display the value of an expression.
48419 Continue running your program (after stopping, e.g.@: at a breakpoint).
48422 Execute next program line (after stopping); step @emph{over} any
48423 function calls in the line.
48425 @item edit [@var{file}:]@var{function}
48426 look at the program line where it is presently stopped.
48428 @item list [@var{file}:]@var{function}
48429 type the text of the program in the vicinity of where it is presently stopped.
48432 Execute next program line (after stopping); step @emph{into} any
48433 function calls in the line.
48435 @item help [@var{name}]
48436 Show information about @value{GDBN} command @var{name}, or general information
48437 about using @value{GDBN}.
48441 Exit from @value{GDBN}.
48445 For full details on @value{GDBN},
48446 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48447 by Richard M. Stallman and Roland H. Pesch. The same text is available online
48448 as the @code{gdb} entry in the @code{info} program.
48452 @c man begin OPTIONS gdb
48453 Any arguments other than options specify an executable
48454 file and core file (or process ID); that is, the first argument
48455 encountered with no
48456 associated option flag is equivalent to a @option{--se} option, and the second,
48457 if any, is equivalent to a @option{-c} option if it's the name of a file.
48459 both long and abbreviated forms; both are shown here. The long forms are also
48460 recognized if you truncate them, so long as enough of the option is
48461 present to be unambiguous.
48463 The abbreviated forms are shown here with @samp{-} and long forms are shown
48464 with @samp{--} to reflect how they are shown in @option{--help}. However,
48465 @value{GDBN} recognizes all of the following conventions for most options:
48468 @item --option=@var{value}
48469 @item --option @var{value}
48470 @item -option=@var{value}
48471 @item -option @var{value}
48472 @item --o=@var{value}
48473 @item --o @var{value}
48474 @item -o=@var{value}
48475 @item -o @var{value}
48478 All the options and command line arguments you give are processed
48479 in sequential order. The order makes a difference when the @option{-x}
48485 List all options, with brief explanations.
48487 @item --symbols=@var{file}
48488 @itemx -s @var{file}
48489 Read symbol table from @var{file}.
48492 Enable writing into executable and core files.
48494 @item --exec=@var{file}
48495 @itemx -e @var{file}
48496 Use @var{file} as the executable file to execute when
48497 appropriate, and for examining pure data in conjunction with a core
48500 @item --se=@var{file}
48501 Read symbol table from @var{file} and use it as the executable
48504 @item --core=@var{file}
48505 @itemx -c @var{file}
48506 Use @var{file} as a core dump to examine.
48508 @item --command=@var{file}
48509 @itemx -x @var{file}
48510 Execute @value{GDBN} commands from @var{file}.
48512 @item --eval-command=@var{command}
48513 @item -ex @var{command}
48514 Execute given @value{GDBN} @var{command}.
48516 @item --init-eval-command=@var{command}
48518 Execute @value{GDBN} @var{command} before loading the inferior.
48520 @item --directory=@var{directory}
48521 @itemx -d @var{directory}
48522 Add @var{directory} to the path to search for source files.
48525 Do not execute commands from @file{~/.config/gdb/gdbinit},
48526 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
48527 @file{~/.gdbearlyinit}
48531 Do not execute commands from any @file{.gdbinit} or
48532 @file{.gdbearlyinit} initialization files.
48537 ``Quiet''. Do not print the introductory and copyright messages. These
48538 messages are also suppressed in batch mode.
48541 Run in batch mode. Exit with status @code{0} after processing all the command
48542 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
48543 Exit with nonzero status if an error occurs in executing the @value{GDBN}
48544 commands in the command files.
48546 Batch mode may be useful for running @value{GDBN} as a filter, for example to
48547 download and run a program on another computer; in order to make this
48548 more useful, the message
48551 Program exited normally.
48555 (which is ordinarily issued whenever a program running under @value{GDBN} control
48556 terminates) is not issued when running in batch mode.
48558 @item --batch-silent
48559 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
48560 output is supressed (stderr is unaffected). This is much quieter than
48561 @option{--silent} and would be useless for an interactive session.
48563 This is particularly useful when using targets that give @samp{Loading section}
48564 messages, for example.
48566 Note that targets that give their output via @value{GDBN}, as opposed to writing
48567 directly to @code{stdout}, will also be made silent.
48569 @item --args @var{prog} [@var{arglist}]
48570 Change interpretation of command line so that arguments following this
48571 option are passed as arguments to the inferior. As an example, take
48572 the following command:
48579 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
48580 the other hand, using:
48583 gdb --args ./a.out -q
48587 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
48589 @item --pid=@var{pid}
48590 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
48593 Open the terminal user interface.
48596 Read all symbols from the given symfile on the first access.
48599 Do not read symbol files.
48601 @item --return-child-result
48602 @value{GDBN}'s exit code will be the same as the child's exit code.
48604 @item --configuration
48605 Print details about GDB configuration and then exit.
48608 Print version information and then exit.
48610 @item --cd=@var{directory}
48611 Run @value{GDBN} using @var{directory} as its working directory,
48612 instead of the current directory.
48614 @item --data-directory=@var{directory}
48616 Run @value{GDBN} using @var{directory} as its data directory. The data
48617 directory is where @value{GDBN} searches for its auxiliary files.
48621 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
48622 @value{GDBN} to output the full file name and line number in a standard,
48623 recognizable fashion each time a stack frame is displayed (which
48624 includes each time the program stops). This recognizable format looks
48625 like two @samp{\032} characters, followed by the file name, line number
48626 and character position separated by colons, and a newline. The
48627 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
48628 characters as a signal to display the source code for the frame.
48630 @item -b @var{baudrate}
48631 Set the line speed (baud rate or bits per second) of any serial
48632 interface used by @value{GDBN} for remote debugging.
48634 @item -l @var{timeout}
48635 Set timeout, in seconds, for remote debugging.
48637 @item --tty=@var{device}
48638 Run using @var{device} for your program's standard input and output.
48642 @c man begin SEEALSO gdb
48644 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48645 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48646 documentation are properly installed at your site, the command
48653 should give you access to the complete manual.
48655 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48656 Richard M. Stallman and Roland H. Pesch, July 1991.
48660 @node gdbserver man
48661 @heading gdbserver man
48663 @c man title gdbserver Remote Server for the GNU Debugger
48665 @c man begin SYNOPSIS gdbserver
48666 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48668 gdbserver --attach @var{comm} @var{pid}
48670 gdbserver --multi @var{comm}
48674 @c man begin DESCRIPTION gdbserver
48675 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
48676 than the one which is running the program being debugged.
48679 @subheading Usage (server (target) side)
48682 Usage (server (target) side):
48685 First, you need to have a copy of the program you want to debug put onto
48686 the target system. The program can be stripped to save space if needed, as
48687 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
48688 the @value{GDBN} running on the host system.
48690 To use the server, you log on to the target system, and run the @command{gdbserver}
48691 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
48692 your program, and (c) its arguments. The general syntax is:
48695 target> gdbserver @var{comm} @var{program} [@var{args} ...]
48698 For example, using a serial port, you might say:
48702 @c @file would wrap it as F</dev/com1>.
48703 target> gdbserver /dev/com1 emacs foo.txt
48706 target> gdbserver @file{/dev/com1} emacs foo.txt
48710 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48711 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48712 waits patiently for the host @value{GDBN} to communicate with it.
48714 To use a TCP connection, you could say:
48717 target> gdbserver host:2345 emacs foo.txt
48720 This says pretty much the same thing as the last example, except that we are
48721 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48722 that we are expecting to see a TCP connection from @code{host} to local TCP port
48723 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48724 want for the port number as long as it does not conflict with any existing TCP
48725 ports on the target system. This same port number must be used in the host
48726 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48727 you chose a port number that conflicts with another service, @command{gdbserver} will
48728 print an error message and exit.
48730 @command{gdbserver} can also attach to running programs.
48731 This is accomplished via the @option{--attach} argument. The syntax is:
48734 target> gdbserver --attach @var{comm} @var{pid}
48737 @var{pid} is the process ID of a currently running process. It isn't
48738 necessary to point @command{gdbserver} at a binary for the running process.
48740 To start @code{gdbserver} without supplying an initial command to run
48741 or process ID to attach, use the @option{--multi} command line option.
48742 In such case you should connect using @kbd{target extended-remote} to start
48743 the program you want to debug.
48746 target> gdbserver --multi @var{comm}
48750 @subheading Usage (host side)
48756 You need an unstripped copy of the target program on your host system, since
48757 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48758 would, with the target program as the first argument. (You may need to use the
48759 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48760 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48761 new command you need to know about is @code{target remote}
48762 (or @code{target extended-remote}). Its argument is either
48763 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48764 descriptor. For example:
48768 @c @file would wrap it as F</dev/ttyb>.
48769 (gdb) target remote /dev/ttyb
48772 (gdb) target remote @file{/dev/ttyb}
48777 communicates with the server via serial line @file{/dev/ttyb}, and:
48780 (gdb) target remote the-target:2345
48784 communicates via a TCP connection to port 2345 on host `the-target', where
48785 you previously started up @command{gdbserver} with the same port number. Note that for
48786 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48787 command, otherwise you may get an error that looks something like
48788 `Connection refused'.
48790 @command{gdbserver} can also debug multiple inferiors at once,
48793 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48794 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48797 @ref{Inferiors Connections and Programs}.
48799 In such case use the @code{extended-remote} @value{GDBN} command variant:
48802 (gdb) target extended-remote the-target:2345
48805 The @command{gdbserver} option @option{--multi} may or may not be used in such
48809 @c man begin OPTIONS gdbserver
48810 There are three different modes for invoking @command{gdbserver}:
48815 Debug a specific program specified by its program name:
48818 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48821 The @var{comm} parameter specifies how should the server communicate
48822 with @value{GDBN}; it is either a device name (to use a serial line),
48823 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48824 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48825 debug in @var{prog}. Any remaining arguments will be passed to the
48826 program verbatim. When the program exits, @value{GDBN} will close the
48827 connection, and @code{gdbserver} will exit.
48830 Debug a specific program by specifying the process ID of a running
48834 gdbserver --attach @var{comm} @var{pid}
48837 The @var{comm} parameter is as described above. Supply the process ID
48838 of a running program in @var{pid}; @value{GDBN} will do everything
48839 else. Like with the previous mode, when the process @var{pid} exits,
48840 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48843 Multi-process mode -- debug more than one program/process:
48846 gdbserver --multi @var{comm}
48849 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48850 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48851 close the connection when a process being debugged exits, so you can
48852 debug several processes in the same session.
48855 In each of the modes you may specify these options:
48860 List all options, with brief explanations.
48863 This option causes @command{gdbserver} to print its version number and exit.
48866 @command{gdbserver} will attach to a running program. The syntax is:
48869 target> gdbserver --attach @var{comm} @var{pid}
48872 @var{pid} is the process ID of a currently running process. It isn't
48873 necessary to point @command{gdbserver} at a binary for the running process.
48876 To start @code{gdbserver} without supplying an initial command to run
48877 or process ID to attach, use this command line option.
48878 Then you can connect using @kbd{target extended-remote} and start
48879 the program you want to debug. The syntax is:
48882 target> gdbserver --multi @var{comm}
48886 Instruct @code{gdbserver} to display extra status information about the debugging
48888 This option is intended for @code{gdbserver} development and for bug reports to
48891 @item --remote-debug
48892 Instruct @code{gdbserver} to display remote protocol debug output.
48893 This option is intended for @code{gdbserver} development and for bug reports to
48896 @item --debug-file=@var{filename}
48897 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48898 This option is intended for @code{gdbserver} development and for bug reports to
48901 @item --debug-format=option1@r{[},option2,...@r{]}
48902 Instruct @code{gdbserver} to include extra information in each line
48903 of debugging output.
48904 @xref{Other Command-Line Arguments for gdbserver}.
48907 Specify a wrapper to launch programs
48908 for debugging. The option should be followed by the name of the
48909 wrapper, then any command-line arguments to pass to the wrapper, then
48910 @kbd{--} indicating the end of the wrapper arguments.
48913 By default, @command{gdbserver} keeps the listening TCP port open, so that
48914 additional connections are possible. However, if you start @code{gdbserver}
48915 with the @option{--once} option, it will stop listening for any further
48916 connection attempts after connecting to the first @value{GDBN} session.
48918 @c --disable-packet is not documented for users.
48920 @c --disable-randomization and --no-disable-randomization are superseded by
48921 @c QDisableRandomization.
48926 @c man begin SEEALSO gdbserver
48928 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48929 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48930 documentation are properly installed at your site, the command
48936 should give you access to the complete manual.
48938 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48939 Richard M. Stallman and Roland H. Pesch, July 1991.
48946 @c man title gcore Generate a core file of a running program
48949 @c man begin SYNOPSIS gcore
48950 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48954 @c man begin DESCRIPTION gcore
48955 Generate core dumps of one or more running programs with process IDs
48956 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48957 is equivalent to one produced by the kernel when the process crashes
48958 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48959 limit). However, unlike after a crash, after @command{gcore} finishes
48960 its job the program remains running without any change.
48963 @c man begin OPTIONS gcore
48966 Dump all memory mappings. The actual effect of this option depends on
48967 the Operating System. On @sc{gnu}/Linux, it will disable
48968 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48969 enable @code{dump-excluded-mappings} (@pxref{set
48970 dump-excluded-mappings}).
48972 @item -o @var{prefix}
48973 The optional argument @var{prefix} specifies the prefix to be used
48974 when composing the file names of the core dumps. The file name is
48975 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48976 process ID of the running program being analyzed by @command{gcore}.
48977 If not specified, @var{prefix} defaults to @var{gcore}.
48981 @c man begin SEEALSO gcore
48983 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48984 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48985 documentation are properly installed at your site, the command
48992 should give you access to the complete manual.
48994 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48995 Richard M. Stallman and Roland H. Pesch, July 1991.
49002 @c man title gdbinit GDB initialization scripts
49005 @c man begin SYNOPSIS gdbinit
49006 @ifset SYSTEM_GDBINIT
49007 @value{SYSTEM_GDBINIT}
49010 @ifset SYSTEM_GDBINIT_DIR
49011 @value{SYSTEM_GDBINIT_DIR}/*
49014 ~/.config/gdb/gdbinit
49022 @c man begin DESCRIPTION gdbinit
49023 These files contain @value{GDBN} commands to automatically execute during
49024 @value{GDBN} startup. The lines of contents are canned sequences of commands,
49027 the @value{GDBN} manual in node @code{Sequences}
49028 -- shell command @code{info -f gdb -n Sequences}.
49034 Please read more in
49036 the @value{GDBN} manual in node @code{Startup}
49037 -- shell command @code{info -f gdb -n Startup}.
49044 @ifset SYSTEM_GDBINIT
49045 @item @value{SYSTEM_GDBINIT}
49047 @ifclear SYSTEM_GDBINIT
49048 @item (not enabled with @code{--with-system-gdbinit} during compilation)
49050 System-wide initialization file. It is executed unless user specified
49051 @value{GDBN} option @code{-nx} or @code{-n}.
49054 the @value{GDBN} manual in node @code{System-wide configuration}
49055 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
49057 @ifset SYSTEM_GDBINIT_DIR
49058 @item @value{SYSTEM_GDBINIT_DIR}
49060 @ifclear SYSTEM_GDBINIT_DIR
49061 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
49063 System-wide initialization directory. All files in this directory are
49064 executed on startup unless user specified @value{GDBN} option @code{-nx} or
49065 @code{-n}, as long as they have a recognized file extension.
49068 the @value{GDBN} manual in node @code{System-wide configuration}
49069 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
49072 @ref{System-wide configuration}.
49075 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
49076 User initialization file. It is executed unless user specified
49077 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
49079 @item @file{.gdbinit}
49080 Initialization file for current directory. It may need to be enabled with
49081 @value{GDBN} security command @code{set auto-load local-gdbinit}.
49084 the @value{GDBN} manual in node @code{Init File in the Current Directory}
49085 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
49088 @ref{Init File in the Current Directory}.
49093 @c man begin SEEALSO gdbinit
49095 gdb(1), @code{info -f gdb -n Startup}
49097 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
49098 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
49099 documentation are properly installed at your site, the command
49105 should give you access to the complete manual.
49107 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
49108 Richard M. Stallman and Roland H. Pesch, July 1991.
49112 @node gdb-add-index man
49113 @heading gdb-add-index
49114 @pindex gdb-add-index
49115 @anchor{gdb-add-index}
49117 @c man title gdb-add-index Add index files to speed up GDB
49119 @c man begin SYNOPSIS gdb-add-index
49120 gdb-add-index @var{filename}
49123 @c man begin DESCRIPTION gdb-add-index
49124 When @value{GDBN} finds a symbol file, it scans the symbols in the
49125 file in order to construct an internal symbol table. This lets most
49126 @value{GDBN} operations work quickly--at the cost of a delay early on.
49127 For large programs, this delay can be quite lengthy, so @value{GDBN}
49128 provides a way to build an index, which speeds up startup.
49130 To determine whether a file contains such an index, use the command
49131 @kbd{readelf -S filename}: the index is stored in a section named
49132 @code{.gdb_index}. The index file can only be produced on systems
49133 which use ELF binaries and DWARF debug information (i.e., sections
49134 named @code{.debug_*}).
49136 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
49137 in the @env{PATH} environment variable. If you want to use different
49138 versions of these programs, you can specify them through the
49139 @env{GDB} and @env{OBJDUMP} environment variables.
49143 the @value{GDBN} manual in node @code{Index Files}
49144 -- shell command @kbd{info -f gdb -n "Index Files"}.
49151 @c man begin SEEALSO gdb-add-index
49153 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
49154 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
49155 documentation are properly installed at your site, the command
49161 should give you access to the complete manual.
49163 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
49164 Richard M. Stallman and Roland H. Pesch, July 1991.
49170 @node GNU Free Documentation License
49171 @appendix GNU Free Documentation License
49174 @node Concept Index
49175 @unnumbered Concept Index
49179 @node Command and Variable Index
49180 @unnumbered Command, Variable, and Function Index
49185 % I think something like @@colophon should be in texinfo. In the
49187 \long\def\colophon{\hbox to0pt{}\vfill
49188 \centerline{The body of this manual is set in}
49189 \centerline{\fontname\tenrm,}
49190 \centerline{with headings in {\bf\fontname\tenbf}}
49191 \centerline{and examples in {\tt\fontname\tentt}.}
49192 \centerline{{\it\fontname\tenit\/},}
49193 \centerline{{\bf\fontname\tenbf}, and}
49194 \centerline{{\sl\fontname\tensl\/}}
49195 \centerline{are used for emphasis.}\vfill}
49197 % Blame: doc@@cygnus.com, 1991.