1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2020 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{} 1988-2020 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2020 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument or use option
878 @code{-p}, if you want to debug a running process:
881 @value{GDBP} @var{program} 1234
886 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
887 can omit the @var{program} filename.
889 Taking advantage of the second command-line argument requires a fairly
890 complete operating system; when you use @value{GDBN} as a remote
891 debugger attached to a bare board, there may not be any notion of
892 ``process'', and there is often no way to get a core dump. @value{GDBN}
893 will warn you if it is unable to attach or to read core dumps.
895 You can optionally have @code{@value{GDBP}} pass any arguments after the
896 executable file to the inferior using @code{--args}. This option stops
899 @value{GDBP} --args gcc -O2 -c foo.c
901 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
902 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
904 You can run @code{@value{GDBP}} without printing the front material, which describes
905 @value{GDBN}'s non-warranty, by specifying @code{--silent}
906 (or @code{-q}/@code{--quiet}):
909 @value{GDBP} --silent
913 You can further control how @value{GDBN} starts up by using command-line
914 options. @value{GDBN} itself can remind you of the options available.
924 to display all available options and briefly describe their use
925 (@samp{@value{GDBP} -h} is a shorter equivalent).
927 All options and command line arguments you give are processed
928 in sequential order. The order makes a difference when the
929 @samp{-x} option is used.
933 * File Options:: Choosing files
934 * Mode Options:: Choosing modes
935 * Startup:: What @value{GDBN} does during startup
939 @subsection Choosing Files
941 When @value{GDBN} starts, it reads any arguments other than options as
942 specifying an executable file and core file (or process ID). This is
943 the same as if the arguments were specified by the @samp{-se} and
944 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
945 first argument that does not have an associated option flag as
946 equivalent to the @samp{-se} option followed by that argument; and the
947 second argument that does not have an associated option flag, if any, as
948 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
949 If the second argument begins with a decimal digit, @value{GDBN} will
950 first attempt to attach to it as a process, and if that fails, attempt
951 to open it as a corefile. If you have a corefile whose name begins with
952 a digit, you can prevent @value{GDBN} from treating it as a pid by
953 prefixing it with @file{./}, e.g.@: @file{./12345}.
955 If @value{GDBN} has not been configured to included core file support,
956 such as for most embedded targets, then it will complain about a second
957 argument and ignore it.
959 Many options have both long and short forms; both are shown in the
960 following list. @value{GDBN} also recognizes the long forms if you truncate
961 them, so long as enough of the option is present to be unambiguous.
962 (If you prefer, you can flag option arguments with @samp{--} rather
963 than @samp{-}, though we illustrate the more usual convention.)
965 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
966 @c way, both those who look for -foo and --foo in the index, will find
970 @item -symbols @var{file}
972 @cindex @code{--symbols}
974 Read symbol table from file @var{file}.
976 @item -exec @var{file}
978 @cindex @code{--exec}
980 Use file @var{file} as the executable file to execute when appropriate,
981 and for examining pure data in conjunction with a core dump.
985 Read symbol table from file @var{file} and use it as the executable
988 @item -core @var{file}
990 @cindex @code{--core}
992 Use file @var{file} as a core dump to examine.
994 @item -pid @var{number}
995 @itemx -p @var{number}
998 Connect to process ID @var{number}, as with the @code{attach} command.
1000 @item -command @var{file}
1001 @itemx -x @var{file}
1002 @cindex @code{--command}
1004 Execute commands from file @var{file}. The contents of this file is
1005 evaluated exactly as the @code{source} command would.
1006 @xref{Command Files,, Command files}.
1008 @item -eval-command @var{command}
1009 @itemx -ex @var{command}
1010 @cindex @code{--eval-command}
1012 Execute a single @value{GDBN} command.
1014 This option may be used multiple times to call multiple commands. It may
1015 also be interleaved with @samp{-command} as required.
1018 @value{GDBP} -ex 'target sim' -ex 'load' \
1019 -x setbreakpoints -ex 'run' a.out
1022 @item -init-command @var{file}
1023 @itemx -ix @var{file}
1024 @cindex @code{--init-command}
1026 Execute commands from file @var{file} before loading the inferior (but
1027 after loading gdbinit files).
1030 @item -init-eval-command @var{command}
1031 @itemx -iex @var{command}
1032 @cindex @code{--init-eval-command}
1034 Execute a single @value{GDBN} command before loading the inferior (but
1035 after loading gdbinit files).
1038 @item -directory @var{directory}
1039 @itemx -d @var{directory}
1040 @cindex @code{--directory}
1042 Add @var{directory} to the path to search for source and script files.
1046 @cindex @code{--readnow}
1048 Read each symbol file's entire symbol table immediately, rather than
1049 the default, which is to read it incrementally as it is needed.
1050 This makes startup slower, but makes future operations faster.
1053 @anchor{--readnever}
1054 @cindex @code{--readnever}, command-line option
1055 Do not read each symbol file's symbolic debug information. This makes
1056 startup faster but at the expense of not being able to perform
1057 symbolic debugging. DWARF unwind information is also not read,
1058 meaning backtraces may become incomplete or inaccurate. One use of
1059 this is when a user simply wants to do the following sequence: attach,
1060 dump core, detach. Loading the debugging information in this case is
1061 an unnecessary cause of delay.
1065 @subsection Choosing Modes
1067 You can run @value{GDBN} in various alternative modes---for example, in
1068 batch mode or quiet mode.
1076 Do not execute commands found in any initialization file.
1077 There are three init files, loaded in the following order:
1080 @item @file{system.gdbinit}
1081 This is the system-wide init file.
1082 Its location is specified with the @code{--with-system-gdbinit}
1083 configure option (@pxref{System-wide configuration}).
1084 It is loaded first when @value{GDBN} starts, before command line options
1085 have been processed.
1086 @item @file{system.gdbinit.d}
1087 This is the system-wide init directory.
1088 Its location is specified with the @code{--with-system-gdbinit-dir}
1089 configure option (@pxref{System-wide configuration}).
1090 Files in this directory are loaded in alphabetical order immediately after
1091 system.gdbinit (if enabled) when @value{GDBN} starts, before command line
1092 options have been processed. Files need to have a recognized scripting
1093 language extension (@file{.py}/@file{.scm}) or be named with a @file{.gdb}
1094 extension to be interpreted as regular @value{GDBN} commands. @value{GDBN}
1095 will not recurse into any subdirectories of this directory.
1096 @item @file{~/.gdbinit}
1097 This is the init file in your home directory.
1098 It is loaded next, after @file{system.gdbinit}, and before
1099 command options have been processed.
1100 @item @file{./.gdbinit}
1101 This is the init file in the current directory.
1102 It is loaded last, after command line options other than @code{-x} and
1103 @code{-ex} have been processed. Command line options @code{-x} and
1104 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1107 For further documentation on startup processing, @xref{Startup}.
1108 For documentation on how to write command files,
1109 @xref{Command Files,,Command Files}.
1114 Do not execute commands found in @file{~/.gdbinit}, the init file
1115 in your home directory.
1121 @cindex @code{--quiet}
1122 @cindex @code{--silent}
1124 ``Quiet''. Do not print the introductory and copyright messages. These
1125 messages are also suppressed in batch mode.
1128 @cindex @code{--batch}
1129 Run in batch mode. Exit with status @code{0} after processing all the
1130 command files specified with @samp{-x} (and all commands from
1131 initialization files, if not inhibited with @samp{-n}). Exit with
1132 nonzero status if an error occurs in executing the @value{GDBN} commands
1133 in the command files. Batch mode also disables pagination, sets unlimited
1134 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1135 off} were in effect (@pxref{Messages/Warnings}).
1137 Batch mode may be useful for running @value{GDBN} as a filter, for
1138 example to download and run a program on another computer; in order to
1139 make this more useful, the message
1142 Program exited normally.
1146 (which is ordinarily issued whenever a program running under
1147 @value{GDBN} control terminates) is not issued when running in batch
1151 @cindex @code{--batch-silent}
1152 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1153 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1154 unaffected). This is much quieter than @samp{-silent} and would be useless
1155 for an interactive session.
1157 This is particularly useful when using targets that give @samp{Loading section}
1158 messages, for example.
1160 Note that targets that give their output via @value{GDBN}, as opposed to
1161 writing directly to @code{stdout}, will also be made silent.
1163 @item -return-child-result
1164 @cindex @code{--return-child-result}
1165 The return code from @value{GDBN} will be the return code from the child
1166 process (the process being debugged), with the following exceptions:
1170 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1171 internal error. In this case the exit code is the same as it would have been
1172 without @samp{-return-child-result}.
1174 The user quits with an explicit value. E.g., @samp{quit 1}.
1176 The child process never runs, or is not allowed to terminate, in which case
1177 the exit code will be -1.
1180 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1181 when @value{GDBN} is being used as a remote program loader or simulator
1186 @cindex @code{--nowindows}
1188 ``No windows''. If @value{GDBN} comes with a graphical user interface
1189 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1190 interface. If no GUI is available, this option has no effect.
1194 @cindex @code{--windows}
1196 If @value{GDBN} includes a GUI, then this option requires it to be
1199 @item -cd @var{directory}
1201 Run @value{GDBN} using @var{directory} as its working directory,
1202 instead of the current directory.
1204 @item -data-directory @var{directory}
1205 @itemx -D @var{directory}
1206 @cindex @code{--data-directory}
1208 Run @value{GDBN} using @var{directory} as its data directory.
1209 The data directory is where @value{GDBN} searches for its
1210 auxiliary files. @xref{Data Files}.
1214 @cindex @code{--fullname}
1216 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1217 subprocess. It tells @value{GDBN} to output the full file name and line
1218 number in a standard, recognizable fashion each time a stack frame is
1219 displayed (which includes each time your program stops). This
1220 recognizable format looks like two @samp{\032} characters, followed by
1221 the file name, line number and character position separated by colons,
1222 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1223 @samp{\032} characters as a signal to display the source code for the
1226 @item -annotate @var{level}
1227 @cindex @code{--annotate}
1228 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1229 effect is identical to using @samp{set annotate @var{level}}
1230 (@pxref{Annotations}). The annotation @var{level} controls how much
1231 information @value{GDBN} prints together with its prompt, values of
1232 expressions, source lines, and other types of output. Level 0 is the
1233 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1234 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1235 that control @value{GDBN}, and level 2 has been deprecated.
1237 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1241 @cindex @code{--args}
1242 Change interpretation of command line so that arguments following the
1243 executable file are passed as command line arguments to the inferior.
1244 This option stops option processing.
1246 @item -baud @var{bps}
1248 @cindex @code{--baud}
1250 Set the line speed (baud rate or bits per second) of any serial
1251 interface used by @value{GDBN} for remote debugging.
1253 @item -l @var{timeout}
1255 Set the timeout (in seconds) of any communication used by @value{GDBN}
1256 for remote debugging.
1258 @item -tty @var{device}
1259 @itemx -t @var{device}
1260 @cindex @code{--tty}
1262 Run using @var{device} for your program's standard input and output.
1263 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1265 @c resolve the situation of these eventually
1267 @cindex @code{--tui}
1268 Activate the @dfn{Text User Interface} when starting. The Text User
1269 Interface manages several text windows on the terminal, showing
1270 source, assembly, registers and @value{GDBN} command outputs
1271 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1272 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1273 Using @value{GDBN} under @sc{gnu} Emacs}).
1275 @item -interpreter @var{interp}
1276 @cindex @code{--interpreter}
1277 Use the interpreter @var{interp} for interface with the controlling
1278 program or device. This option is meant to be set by programs which
1279 communicate with @value{GDBN} using it as a back end.
1280 @xref{Interpreters, , Command Interpreters}.
1282 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1283 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1284 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1285 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1286 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1287 interfaces are no longer supported.
1290 @cindex @code{--write}
1291 Open the executable and core files for both reading and writing. This
1292 is equivalent to the @samp{set write on} command inside @value{GDBN}
1296 @cindex @code{--statistics}
1297 This option causes @value{GDBN} to print statistics about time and
1298 memory usage after it completes each command and returns to the prompt.
1301 @cindex @code{--version}
1302 This option causes @value{GDBN} to print its version number and
1303 no-warranty blurb, and exit.
1305 @item -configuration
1306 @cindex @code{--configuration}
1307 This option causes @value{GDBN} to print details about its build-time
1308 configuration parameters, and then exit. These details can be
1309 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1314 @subsection What @value{GDBN} Does During Startup
1315 @cindex @value{GDBN} startup
1317 Here's the description of what @value{GDBN} does during session startup:
1321 Sets up the command interpreter as specified by the command line
1322 (@pxref{Mode Options, interpreter}).
1326 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1327 used when building @value{GDBN}; @pxref{System-wide configuration,
1328 ,System-wide configuration and settings}) and the files in the system-wide
1329 gdbinit directory (if @option{--with-system-gdbinit-dir} was used) and executes
1330 all the commands in those files. The files need to be named with a @file{.gdb}
1331 extension to be interpreted as @value{GDBN} commands, or they can be written
1332 in a supported scripting language with an appropriate file extension.
1334 @anchor{Home Directory Init File}
1336 Reads the init file (if any) in your home directory@footnote{On
1337 DOS/Windows systems, the home directory is the one pointed to by the
1338 @code{HOME} environment variable.} and executes all the commands in
1341 @anchor{Option -init-eval-command}
1343 Executes commands and command files specified by the @samp{-iex} and
1344 @samp{-ix} options in their specified order. Usually you should use the
1345 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1346 settings before @value{GDBN} init files get executed and before inferior
1350 Processes command line options and operands.
1352 @anchor{Init File in the Current Directory during Startup}
1354 Reads and executes the commands from init file (if any) in the current
1355 working directory as long as @samp{set auto-load local-gdbinit} is set to
1356 @samp{on} (@pxref{Init File in the Current Directory}).
1357 This is only done if the current directory is
1358 different from your home directory. Thus, you can have more than one
1359 init file, one generic in your home directory, and another, specific
1360 to the program you are debugging, in the directory where you invoke
1364 If the command line specified a program to debug, or a process to
1365 attach to, or a core file, @value{GDBN} loads any auto-loaded
1366 scripts provided for the program or for its loaded shared libraries.
1367 @xref{Auto-loading}.
1369 If you wish to disable the auto-loading during startup,
1370 you must do something like the following:
1373 $ gdb -iex "set auto-load python-scripts off" myprogram
1376 Option @samp{-ex} does not work because the auto-loading is then turned
1380 Executes commands and command files specified by the @samp{-ex} and
1381 @samp{-x} options in their specified order. @xref{Command Files}, for
1382 more details about @value{GDBN} command files.
1385 Reads the command history recorded in the @dfn{history file}.
1386 @xref{Command History}, for more details about the command history and the
1387 files where @value{GDBN} records it.
1390 Init files use the same syntax as @dfn{command files} (@pxref{Command
1391 Files}) and are processed by @value{GDBN} in the same way. The init
1392 file in your home directory can set options (such as @samp{set
1393 complaints}) that affect subsequent processing of command line options
1394 and operands. Init files are not executed if you use the @samp{-nx}
1395 option (@pxref{Mode Options, ,Choosing Modes}).
1397 To display the list of init files loaded by gdb at startup, you
1398 can use @kbd{gdb --help}.
1400 @cindex init file name
1401 @cindex @file{.gdbinit}
1402 @cindex @file{gdb.ini}
1403 The @value{GDBN} init files are normally called @file{.gdbinit}.
1404 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1405 the limitations of file names imposed by DOS filesystems. The Windows
1406 port of @value{GDBN} uses the standard name, but if it finds a
1407 @file{gdb.ini} file in your home directory, it warns you about that
1408 and suggests to rename the file to the standard name.
1412 @section Quitting @value{GDBN}
1413 @cindex exiting @value{GDBN}
1414 @cindex leaving @value{GDBN}
1417 @kindex quit @r{[}@var{expression}@r{]}
1418 @kindex q @r{(@code{quit})}
1419 @item quit @r{[}@var{expression}@r{]}
1421 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1422 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1423 do not supply @var{expression}, @value{GDBN} will terminate normally;
1424 otherwise it will terminate using the result of @var{expression} as the
1429 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1430 terminates the action of any @value{GDBN} command that is in progress and
1431 returns to @value{GDBN} command level. It is safe to type the interrupt
1432 character at any time because @value{GDBN} does not allow it to take effect
1433 until a time when it is safe.
1435 If you have been using @value{GDBN} to control an attached process or
1436 device, you can release it with the @code{detach} command
1437 (@pxref{Attach, ,Debugging an Already-running Process}).
1439 @node Shell Commands
1440 @section Shell Commands
1442 If you need to execute occasional shell commands during your
1443 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1444 just use the @code{shell} command.
1449 @cindex shell escape
1450 @item shell @var{command-string}
1451 @itemx !@var{command-string}
1452 Invoke a standard shell to execute @var{command-string}.
1453 Note that no space is needed between @code{!} and @var{command-string}.
1454 If it exists, the environment variable @code{SHELL} determines which
1455 shell to run. Otherwise @value{GDBN} uses the default shell
1456 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1459 The utility @code{make} is often needed in development environments.
1460 You do not have to use the @code{shell} command for this purpose in
1465 @cindex calling make
1466 @item make @var{make-args}
1467 Execute the @code{make} program with the specified
1468 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1474 @cindex send the output of a gdb command to a shell command
1476 @item pipe [@var{command}] | @var{shell_command}
1477 @itemx | [@var{command}] | @var{shell_command}
1478 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1479 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1480 Executes @var{command} and sends its output to @var{shell_command}.
1481 Note that no space is needed around @code{|}.
1482 If no @var{command} is provided, the last command executed is repeated.
1484 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1485 can be used to specify an alternate delimiter string @var{delim} that separates
1486 the @var{command} from the @var{shell_command}.
1519 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1520 this contains a PIPE char
1521 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1522 this contains a PIPE char!
1528 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1529 can be used to examine the exit status of the last shell command launched
1530 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1531 @xref{Convenience Vars,, Convenience Variables}.
1533 @node Logging Output
1534 @section Logging Output
1535 @cindex logging @value{GDBN} output
1536 @cindex save @value{GDBN} output to a file
1538 You may want to save the output of @value{GDBN} commands to a file.
1539 There are several commands to control @value{GDBN}'s logging.
1543 @item set logging on
1545 @item set logging off
1547 @cindex logging file name
1548 @item set logging file @var{file}
1549 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1550 @item set logging overwrite [on|off]
1551 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1552 you want @code{set logging on} to overwrite the logfile instead.
1553 @item set logging redirect [on|off]
1554 By default, @value{GDBN} output will go to both the terminal and the logfile.
1555 Set @code{redirect} if you want output to go only to the log file.
1556 @item set logging debugredirect [on|off]
1557 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1558 Set @code{debugredirect} if you want debug output to go only to the log file.
1559 @kindex show logging
1561 Show the current values of the logging settings.
1564 You can also redirect the output of a @value{GDBN} command to a
1565 shell command. @xref{pipe}.
1567 @chapter @value{GDBN} Commands
1569 You can abbreviate a @value{GDBN} command to the first few letters of the command
1570 name, if that abbreviation is unambiguous; and you can repeat certain
1571 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1572 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1573 show you the alternatives available, if there is more than one possibility).
1576 * Command Syntax:: How to give commands to @value{GDBN}
1577 * Command Settings:: How to change default behavior of commands
1578 * Completion:: Command completion
1579 * Command Options:: Command options
1580 * Help:: How to ask @value{GDBN} for help
1583 @node Command Syntax
1584 @section Command Syntax
1586 A @value{GDBN} command is a single line of input. There is no limit on
1587 how long it can be. It starts with a command name, which is followed by
1588 arguments whose meaning depends on the command name. For example, the
1589 command @code{step} accepts an argument which is the number of times to
1590 step, as in @samp{step 5}. You can also use the @code{step} command
1591 with no arguments. Some commands do not allow any arguments.
1593 @cindex abbreviation
1594 @value{GDBN} command names may always be truncated if that abbreviation is
1595 unambiguous. Other possible command abbreviations are listed in the
1596 documentation for individual commands. In some cases, even ambiguous
1597 abbreviations are allowed; for example, @code{s} is specially defined as
1598 equivalent to @code{step} even though there are other commands whose
1599 names start with @code{s}. You can test abbreviations by using them as
1600 arguments to the @code{help} command.
1602 @cindex repeating commands
1603 @kindex RET @r{(repeat last command)}
1604 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1605 repeat the previous command. Certain commands (for example, @code{run})
1606 will not repeat this way; these are commands whose unintentional
1607 repetition might cause trouble and which you are unlikely to want to
1608 repeat. User-defined commands can disable this feature; see
1609 @ref{Define, dont-repeat}.
1611 The @code{list} and @code{x} commands, when you repeat them with
1612 @key{RET}, construct new arguments rather than repeating
1613 exactly as typed. This permits easy scanning of source or memory.
1615 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1616 output, in a way similar to the common utility @code{more}
1617 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1618 @key{RET} too many in this situation, @value{GDBN} disables command
1619 repetition after any command that generates this sort of display.
1621 @kindex # @r{(a comment)}
1623 Any text from a @kbd{#} to the end of the line is a comment; it does
1624 nothing. This is useful mainly in command files (@pxref{Command
1625 Files,,Command Files}).
1627 @cindex repeating command sequences
1628 @kindex Ctrl-o @r{(operate-and-get-next)}
1629 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1630 commands. This command accepts the current line, like @key{RET}, and
1631 then fetches the next line relative to the current line from the history
1635 @node Command Settings
1636 @section Command Settings
1637 @cindex default behavior of commands, changing
1638 @cindex default settings, changing
1640 Many commands change their behavior according to command-specific
1641 variables or settings. These settings can be changed with the
1642 @code{set} subcommands. For example, the @code{print} command
1643 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1644 settings changeable with the commands @code{set print elements
1645 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1647 You can change these settings to your preference in the gdbinit files
1648 loaded at @value{GDBN} startup. @xref{Startup}.
1650 The settings can also be changed interactively during the debugging
1651 session. For example, to change the limit of array elements to print,
1652 you can do the following:
1654 (@value{GDBN}) set print elements 10
1655 (@value{GDBN}) print some_array
1656 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1659 The above @code{set print elements 10} command changes the number of
1660 elements to print from the default of 200 to 10. If you only intend
1661 this limit of 10 to be used for printing @code{some_array}, then you
1662 must restore the limit back to 200, with @code{set print elements
1665 Some commands allow overriding settings with command options. For
1666 example, the @code{print} command supports a number of options that
1667 allow overriding relevant global print settings as set by @code{set
1668 print} subcommands. @xref{print options}. The example above could be
1671 (@value{GDBN}) print -elements 10 -- some_array
1672 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1675 Alternatively, you can use the @code{with} command to change a setting
1676 temporarily, for the duration of a command invocation.
1679 @kindex with command
1680 @kindex w @r{(@code{with})}
1682 @cindex temporarily change settings
1683 @item with @var{setting} [@var{value}] [-- @var{command}]
1684 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1685 Temporarily set @var{setting} to @var{value} for the duration of
1688 @var{setting} is any setting you can change with the @code{set}
1689 subcommands. @var{value} is the value to assign to @code{setting}
1690 while running @code{command}.
1692 If no @var{command} is provided, the last command executed is
1695 If a @var{command} is provided, it must be preceded by a double dash
1696 (@code{--}) separator. This is required because some settings accept
1697 free-form arguments, such as expressions or filenames.
1699 For example, the command
1701 (@value{GDBN}) with print array on -- print some_array
1704 is equivalent to the following 3 commands:
1706 (@value{GDBN}) set print array on
1707 (@value{GDBN}) print some_array
1708 (@value{GDBN}) set print array off
1711 The @code{with} command is particularly useful when you want to
1712 override a setting while running user-defined commands, or commands
1713 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1716 (@value{GDBN}) with print pretty on -- my_complex_command
1719 To change several settings for the same command, you can nest
1720 @code{with} commands. For example, @code{with language ada -- with
1721 print elements 10} temporarily changes the language to Ada and sets a
1722 limit of 10 elements to print for arrays and strings.
1727 @section Command Completion
1730 @cindex word completion
1731 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1732 only one possibility; it can also show you what the valid possibilities
1733 are for the next word in a command, at any time. This works for @value{GDBN}
1734 commands, @value{GDBN} subcommands, command options, and the names of symbols
1737 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1738 of a word. If there is only one possibility, @value{GDBN} fills in the
1739 word, and waits for you to finish the command (or press @key{RET} to
1740 enter it). For example, if you type
1742 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1743 @c complete accuracy in these examples; space introduced for clarity.
1744 @c If texinfo enhancements make it unnecessary, it would be nice to
1745 @c replace " @key" by "@key" in the following...
1747 (@value{GDBP}) info bre @key{TAB}
1751 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1752 the only @code{info} subcommand beginning with @samp{bre}:
1755 (@value{GDBP}) info breakpoints
1759 You can either press @key{RET} at this point, to run the @code{info
1760 breakpoints} command, or backspace and enter something else, if
1761 @samp{breakpoints} does not look like the command you expected. (If you
1762 were sure you wanted @code{info breakpoints} in the first place, you
1763 might as well just type @key{RET} immediately after @samp{info bre},
1764 to exploit command abbreviations rather than command completion).
1766 If there is more than one possibility for the next word when you press
1767 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1768 characters and try again, or just press @key{TAB} a second time;
1769 @value{GDBN} displays all the possible completions for that word. For
1770 example, you might want to set a breakpoint on a subroutine whose name
1771 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1772 just sounds the bell. Typing @key{TAB} again displays all the
1773 function names in your program that begin with those characters, for
1777 (@value{GDBP}) b make_ @key{TAB}
1778 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1779 make_a_section_from_file make_environ
1780 make_abs_section make_function_type
1781 make_blockvector make_pointer_type
1782 make_cleanup make_reference_type
1783 make_command make_symbol_completion_list
1784 (@value{GDBP}) b make_
1788 After displaying the available possibilities, @value{GDBN} copies your
1789 partial input (@samp{b make_} in the example) so you can finish the
1792 If you just want to see the list of alternatives in the first place, you
1793 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1794 means @kbd{@key{META} ?}. You can type this either by holding down a
1795 key designated as the @key{META} shift on your keyboard (if there is
1796 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1798 If the number of possible completions is large, @value{GDBN} will
1799 print as much of the list as it has collected, as well as a message
1800 indicating that the list may be truncated.
1803 (@value{GDBP}) b m@key{TAB}@key{TAB}
1805 <... the rest of the possible completions ...>
1806 *** List may be truncated, max-completions reached. ***
1811 This behavior can be controlled with the following commands:
1814 @kindex set max-completions
1815 @item set max-completions @var{limit}
1816 @itemx set max-completions unlimited
1817 Set the maximum number of completion candidates. @value{GDBN} will
1818 stop looking for more completions once it collects this many candidates.
1819 This is useful when completing on things like function names as collecting
1820 all the possible candidates can be time consuming.
1821 The default value is 200. A value of zero disables tab-completion.
1822 Note that setting either no limit or a very large limit can make
1824 @kindex show max-completions
1825 @item show max-completions
1826 Show the maximum number of candidates that @value{GDBN} will collect and show
1830 @cindex quotes in commands
1831 @cindex completion of quoted strings
1832 Sometimes the string you need, while logically a ``word'', may contain
1833 parentheses or other characters that @value{GDBN} normally excludes from
1834 its notion of a word. To permit word completion to work in this
1835 situation, you may enclose words in @code{'} (single quote marks) in
1836 @value{GDBN} commands.
1838 A likely situation where you might need this is in typing an
1839 expression that involves a C@t{++} symbol name with template
1840 parameters. This is because when completing expressions, GDB treats
1841 the @samp{<} character as word delimiter, assuming that it's the
1842 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1845 For example, when you want to call a C@t{++} template function
1846 interactively using the @code{print} or @code{call} commands, you may
1847 need to distinguish whether you mean the version of @code{name} that
1848 was specialized for @code{int}, @code{name<int>()}, or the version
1849 that was specialized for @code{float}, @code{name<float>()}. To use
1850 the word-completion facilities in this situation, type a single quote
1851 @code{'} at the beginning of the function name. This alerts
1852 @value{GDBN} that it may need to consider more information than usual
1853 when you press @key{TAB} or @kbd{M-?} to request word completion:
1856 (@value{GDBP}) p 'func< @kbd{M-?}
1857 func<int>() func<float>()
1858 (@value{GDBP}) p 'func<
1861 When setting breakpoints however (@pxref{Specify Location}), you don't
1862 usually need to type a quote before the function name, because
1863 @value{GDBN} understands that you want to set a breakpoint on a
1867 (@value{GDBP}) b func< @kbd{M-?}
1868 func<int>() func<float>()
1869 (@value{GDBP}) b func<
1872 This is true even in the case of typing the name of C@t{++} overloaded
1873 functions (multiple definitions of the same function, distinguished by
1874 argument type). For example, when you want to set a breakpoint you
1875 don't need to distinguish whether you mean the version of @code{name}
1876 that takes an @code{int} parameter, @code{name(int)}, or the version
1877 that takes a @code{float} parameter, @code{name(float)}.
1880 (@value{GDBP}) b bubble( @kbd{M-?}
1881 bubble(int) bubble(double)
1882 (@value{GDBP}) b bubble(dou @kbd{M-?}
1886 See @ref{quoting names} for a description of other scenarios that
1889 For more information about overloaded functions, see @ref{C Plus Plus
1890 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1891 overload-resolution off} to disable overload resolution;
1892 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1894 @cindex completion of structure field names
1895 @cindex structure field name completion
1896 @cindex completion of union field names
1897 @cindex union field name completion
1898 When completing in an expression which looks up a field in a
1899 structure, @value{GDBN} also tries@footnote{The completer can be
1900 confused by certain kinds of invalid expressions. Also, it only
1901 examines the static type of the expression, not the dynamic type.} to
1902 limit completions to the field names available in the type of the
1906 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1907 magic to_fputs to_rewind
1908 to_data to_isatty to_write
1909 to_delete to_put to_write_async_safe
1914 This is because the @code{gdb_stdout} is a variable of the type
1915 @code{struct ui_file} that is defined in @value{GDBN} sources as
1922 ui_file_flush_ftype *to_flush;
1923 ui_file_write_ftype *to_write;
1924 ui_file_write_async_safe_ftype *to_write_async_safe;
1925 ui_file_fputs_ftype *to_fputs;
1926 ui_file_read_ftype *to_read;
1927 ui_file_delete_ftype *to_delete;
1928 ui_file_isatty_ftype *to_isatty;
1929 ui_file_rewind_ftype *to_rewind;
1930 ui_file_put_ftype *to_put;
1935 @node Command Options
1936 @section Command options
1938 @cindex command options
1939 Some commands accept options starting with a leading dash. For
1940 example, @code{print -pretty}. Similarly to command names, you can
1941 abbreviate a @value{GDBN} option to the first few letters of the
1942 option name, if that abbreviation is unambiguous, and you can also use
1943 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
1944 in an option (or to show you the alternatives available, if there is
1945 more than one possibility).
1947 @cindex command options, raw input
1948 Some commands take raw input as argument. For example, the print
1949 command processes arbitrary expressions in any of the languages
1950 supported by @value{GDBN}. With such commands, because raw input may
1951 start with a leading dash that would be confused with an option or any
1952 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
1953 -pretty} or printing negative @code{p}?), if you specify any command
1954 option, then you must use a double-dash (@code{--}) delimiter to
1955 indicate the end of options.
1957 @cindex command options, boolean
1959 Some options are described as accepting an argument which can be
1960 either @code{on} or @code{off}. These are known as @dfn{boolean
1961 options}. Similarly to boolean settings commands---@code{on} and
1962 @code{off} are the typical values, but any of @code{1}, @code{yes} and
1963 @code{enable} can also be used as ``true'' value, and any of @code{0},
1964 @code{no} and @code{disable} can also be used as ``false'' value. You
1965 can also omit a ``true'' value, as it is implied by default.
1967 For example, these are equivalent:
1970 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
1971 (@value{GDBP}) p -o -p 0 -e u -- *myptr
1974 You can discover the set of options some command accepts by completing
1975 on @code{-} after the command name. For example:
1978 (@value{GDBP}) print -@key{TAB}@key{TAB}
1979 -address -max-depth -raw-values -union
1980 -array -null-stop -repeats -vtbl
1981 -array-indexes -object -static-members
1982 -elements -pretty -symbol
1985 Completion will in some cases guide you with a suggestion of what kind
1986 of argument an option expects. For example:
1989 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1993 Here, the option expects a number (e.g., @code{100}), not literal
1994 @code{NUMBER}. Such metasyntactical arguments are always presented in
1997 (For more on using the @code{print} command, see @ref{Data, ,Examining
2001 @section Getting Help
2002 @cindex online documentation
2005 You can always ask @value{GDBN} itself for information on its commands,
2006 using the command @code{help}.
2009 @kindex h @r{(@code{help})}
2012 You can use @code{help} (abbreviated @code{h}) with no arguments to
2013 display a short list of named classes of commands:
2017 List of classes of commands:
2019 aliases -- Aliases of other commands
2020 breakpoints -- Making program stop at certain points
2021 data -- Examining data
2022 files -- Specifying and examining files
2023 internals -- Maintenance commands
2024 obscure -- Obscure features
2025 running -- Running the program
2026 stack -- Examining the stack
2027 status -- Status inquiries
2028 support -- Support facilities
2029 tracepoints -- Tracing of program execution without
2030 stopping the program
2031 user-defined -- User-defined commands
2033 Type "help" followed by a class name for a list of
2034 commands in that class.
2035 Type "help" followed by command name for full
2037 Command name abbreviations are allowed if unambiguous.
2040 @c the above line break eliminates huge line overfull...
2042 @item help @var{class}
2043 Using one of the general help classes as an argument, you can get a
2044 list of the individual commands in that class. For example, here is the
2045 help display for the class @code{status}:
2048 (@value{GDBP}) help status
2053 @c Line break in "show" line falsifies real output, but needed
2054 @c to fit in smallbook page size.
2055 info -- Generic command for showing things
2056 about the program being debugged
2057 show -- Generic command for showing things
2060 Type "help" followed by command name for full
2062 Command name abbreviations are allowed if unambiguous.
2066 @item help @var{command}
2067 With a command name as @code{help} argument, @value{GDBN} displays a
2068 short paragraph on how to use that command.
2071 @item apropos [-v] @var{regexp}
2072 The @code{apropos} command searches through all of the @value{GDBN}
2073 commands, and their documentation, for the regular expression specified in
2074 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2075 which stands for @samp{verbose}, indicates to output the full documentation
2076 of the matching commands and highlight the parts of the documentation
2077 matching @var{regexp}. For example:
2088 alias -- Define a new command that is an alias of an existing command
2089 aliases -- Aliases of other commands
2090 d -- Delete some breakpoints or auto-display expressions
2091 del -- Delete some breakpoints or auto-display expressions
2092 delete -- Delete some breakpoints or auto-display expressions
2100 apropos -v cut.*thread apply
2104 results in the below output, where @samp{cut for 'thread apply}
2105 is highlighted if styling is enabled.
2109 taas -- Apply a command to all threads (ignoring errors
2112 shortcut for 'thread apply all -s COMMAND'
2114 tfaas -- Apply a command to all frames of all threads
2115 (ignoring errors and empty output).
2116 Usage: tfaas COMMAND
2117 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2122 @item complete @var{args}
2123 The @code{complete @var{args}} command lists all the possible completions
2124 for the beginning of a command. Use @var{args} to specify the beginning of the
2125 command you want completed. For example:
2131 @noindent results in:
2142 @noindent This is intended for use by @sc{gnu} Emacs.
2145 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2146 and @code{show} to inquire about the state of your program, or the state
2147 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2148 manual introduces each of them in the appropriate context. The listings
2149 under @code{info} and under @code{show} in the Command, Variable, and
2150 Function Index point to all the sub-commands. @xref{Command and Variable
2156 @kindex i @r{(@code{info})}
2158 This command (abbreviated @code{i}) is for describing the state of your
2159 program. For example, you can show the arguments passed to a function
2160 with @code{info args}, list the registers currently in use with @code{info
2161 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2162 You can get a complete list of the @code{info} sub-commands with
2163 @w{@code{help info}}.
2167 You can assign the result of an expression to an environment variable with
2168 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2169 @code{set prompt $}.
2173 In contrast to @code{info}, @code{show} is for describing the state of
2174 @value{GDBN} itself.
2175 You can change most of the things you can @code{show}, by using the
2176 related command @code{set}; for example, you can control what number
2177 system is used for displays with @code{set radix}, or simply inquire
2178 which is currently in use with @code{show radix}.
2181 To display all the settable parameters and their current
2182 values, you can use @code{show} with no arguments; you may also use
2183 @code{info set}. Both commands produce the same display.
2184 @c FIXME: "info set" violates the rule that "info" is for state of
2185 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2186 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2190 Here are several miscellaneous @code{show} subcommands, all of which are
2191 exceptional in lacking corresponding @code{set} commands:
2194 @kindex show version
2195 @cindex @value{GDBN} version number
2197 Show what version of @value{GDBN} is running. You should include this
2198 information in @value{GDBN} bug-reports. If multiple versions of
2199 @value{GDBN} are in use at your site, you may need to determine which
2200 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2201 commands are introduced, and old ones may wither away. Also, many
2202 system vendors ship variant versions of @value{GDBN}, and there are
2203 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2204 The version number is the same as the one announced when you start
2207 @kindex show copying
2208 @kindex info copying
2209 @cindex display @value{GDBN} copyright
2212 Display information about permission for copying @value{GDBN}.
2214 @kindex show warranty
2215 @kindex info warranty
2217 @itemx info warranty
2218 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2219 if your version of @value{GDBN} comes with one.
2221 @kindex show configuration
2222 @item show configuration
2223 Display detailed information about the way @value{GDBN} was configured
2224 when it was built. This displays the optional arguments passed to the
2225 @file{configure} script and also configuration parameters detected
2226 automatically by @command{configure}. When reporting a @value{GDBN}
2227 bug (@pxref{GDB Bugs}), it is important to include this information in
2233 @chapter Running Programs Under @value{GDBN}
2235 When you run a program under @value{GDBN}, you must first generate
2236 debugging information when you compile it.
2238 You may start @value{GDBN} with its arguments, if any, in an environment
2239 of your choice. If you are doing native debugging, you may redirect
2240 your program's input and output, debug an already running process, or
2241 kill a child process.
2244 * Compilation:: Compiling for debugging
2245 * Starting:: Starting your program
2246 * Arguments:: Your program's arguments
2247 * Environment:: Your program's environment
2249 * Working Directory:: Your program's working directory
2250 * Input/Output:: Your program's input and output
2251 * Attach:: Debugging an already-running process
2252 * Kill Process:: Killing the child process
2253 * Inferiors Connections and Programs:: Debugging multiple inferiors
2254 connections and programs
2255 * Threads:: Debugging programs with multiple threads
2256 * Forks:: Debugging forks
2257 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2261 @section Compiling for Debugging
2263 In order to debug a program effectively, you need to generate
2264 debugging information when you compile it. This debugging information
2265 is stored in the object file; it describes the data type of each
2266 variable or function and the correspondence between source line numbers
2267 and addresses in the executable code.
2269 To request debugging information, specify the @samp{-g} option when you run
2272 Programs that are to be shipped to your customers are compiled with
2273 optimizations, using the @samp{-O} compiler option. However, some
2274 compilers are unable to handle the @samp{-g} and @samp{-O} options
2275 together. Using those compilers, you cannot generate optimized
2276 executables containing debugging information.
2278 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2279 without @samp{-O}, making it possible to debug optimized code. We
2280 recommend that you @emph{always} use @samp{-g} whenever you compile a
2281 program. You may think your program is correct, but there is no sense
2282 in pushing your luck. For more information, see @ref{Optimized Code}.
2284 Older versions of the @sc{gnu} C compiler permitted a variant option
2285 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2286 format; if your @sc{gnu} C compiler has this option, do not use it.
2288 @value{GDBN} knows about preprocessor macros and can show you their
2289 expansion (@pxref{Macros}). Most compilers do not include information
2290 about preprocessor macros in the debugging information if you specify
2291 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2292 the @sc{gnu} C compiler, provides macro information if you are using
2293 the DWARF debugging format, and specify the option @option{-g3}.
2295 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2296 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2297 information on @value{NGCC} options affecting debug information.
2299 You will have the best debugging experience if you use the latest
2300 version of the DWARF debugging format that your compiler supports.
2301 DWARF is currently the most expressive and best supported debugging
2302 format in @value{GDBN}.
2306 @section Starting your Program
2312 @kindex r @r{(@code{run})}
2315 Use the @code{run} command to start your program under @value{GDBN}.
2316 You must first specify the program name with an argument to
2317 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2318 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2319 command (@pxref{Files, ,Commands to Specify Files}).
2323 If you are running your program in an execution environment that
2324 supports processes, @code{run} creates an inferior process and makes
2325 that process run your program. In some environments without processes,
2326 @code{run} jumps to the start of your program. Other targets,
2327 like @samp{remote}, are always running. If you get an error
2328 message like this one:
2331 The "remote" target does not support "run".
2332 Try "help target" or "continue".
2336 then use @code{continue} to run your program. You may need @code{load}
2337 first (@pxref{load}).
2339 The execution of a program is affected by certain information it
2340 receives from its superior. @value{GDBN} provides ways to specify this
2341 information, which you must do @emph{before} starting your program. (You
2342 can change it after starting your program, but such changes only affect
2343 your program the next time you start it.) This information may be
2344 divided into four categories:
2347 @item The @emph{arguments.}
2348 Specify the arguments to give your program as the arguments of the
2349 @code{run} command. If a shell is available on your target, the shell
2350 is used to pass the arguments, so that you may use normal conventions
2351 (such as wildcard expansion or variable substitution) in describing
2353 In Unix systems, you can control which shell is used with the
2354 @code{SHELL} environment variable. If you do not define @code{SHELL},
2355 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2356 use of any shell with the @code{set startup-with-shell} command (see
2359 @item The @emph{environment.}
2360 Your program normally inherits its environment from @value{GDBN}, but you can
2361 use the @value{GDBN} commands @code{set environment} and @code{unset
2362 environment} to change parts of the environment that affect
2363 your program. @xref{Environment, ,Your Program's Environment}.
2365 @item The @emph{working directory.}
2366 You can set your program's working directory with the command
2367 @kbd{set cwd}. If you do not set any working directory with this
2368 command, your program will inherit @value{GDBN}'s working directory if
2369 native debugging, or the remote server's working directory if remote
2370 debugging. @xref{Working Directory, ,Your Program's Working
2373 @item The @emph{standard input and output.}
2374 Your program normally uses the same device for standard input and
2375 standard output as @value{GDBN} is using. You can redirect input and output
2376 in the @code{run} command line, or you can use the @code{tty} command to
2377 set a different device for your program.
2378 @xref{Input/Output, ,Your Program's Input and Output}.
2381 @emph{Warning:} While input and output redirection work, you cannot use
2382 pipes to pass the output of the program you are debugging to another
2383 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2387 When you issue the @code{run} command, your program begins to execute
2388 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2389 of how to arrange for your program to stop. Once your program has
2390 stopped, you may call functions in your program, using the @code{print}
2391 or @code{call} commands. @xref{Data, ,Examining Data}.
2393 If the modification time of your symbol file has changed since the last
2394 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2395 table, and reads it again. When it does this, @value{GDBN} tries to retain
2396 your current breakpoints.
2401 @cindex run to main procedure
2402 The name of the main procedure can vary from language to language.
2403 With C or C@t{++}, the main procedure name is always @code{main}, but
2404 other languages such as Ada do not require a specific name for their
2405 main procedure. The debugger provides a convenient way to start the
2406 execution of the program and to stop at the beginning of the main
2407 procedure, depending on the language used.
2409 The @samp{start} command does the equivalent of setting a temporary
2410 breakpoint at the beginning of the main procedure and then invoking
2411 the @samp{run} command.
2413 @cindex elaboration phase
2414 Some programs contain an @dfn{elaboration} phase where some startup code is
2415 executed before the main procedure is called. This depends on the
2416 languages used to write your program. In C@t{++}, for instance,
2417 constructors for static and global objects are executed before
2418 @code{main} is called. It is therefore possible that the debugger stops
2419 before reaching the main procedure. However, the temporary breakpoint
2420 will remain to halt execution.
2422 Specify the arguments to give to your program as arguments to the
2423 @samp{start} command. These arguments will be given verbatim to the
2424 underlying @samp{run} command. Note that the same arguments will be
2425 reused if no argument is provided during subsequent calls to
2426 @samp{start} or @samp{run}.
2428 It is sometimes necessary to debug the program during elaboration. In
2429 these cases, using the @code{start} command would stop the execution
2430 of your program too late, as the program would have already completed
2431 the elaboration phase. Under these circumstances, either insert
2432 breakpoints in your elaboration code before running your program or
2433 use the @code{starti} command.
2437 @cindex run to first instruction
2438 The @samp{starti} command does the equivalent of setting a temporary
2439 breakpoint at the first instruction of a program's execution and then
2440 invoking the @samp{run} command. For programs containing an
2441 elaboration phase, the @code{starti} command will stop execution at
2442 the start of the elaboration phase.
2444 @anchor{set exec-wrapper}
2445 @kindex set exec-wrapper
2446 @item set exec-wrapper @var{wrapper}
2447 @itemx show exec-wrapper
2448 @itemx unset exec-wrapper
2449 When @samp{exec-wrapper} is set, the specified wrapper is used to
2450 launch programs for debugging. @value{GDBN} starts your program
2451 with a shell command of the form @kbd{exec @var{wrapper}
2452 @var{program}}. Quoting is added to @var{program} and its
2453 arguments, but not to @var{wrapper}, so you should add quotes if
2454 appropriate for your shell. The wrapper runs until it executes
2455 your program, and then @value{GDBN} takes control.
2457 You can use any program that eventually calls @code{execve} with
2458 its arguments as a wrapper. Several standard Unix utilities do
2459 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2460 with @code{exec "$@@"} will also work.
2462 For example, you can use @code{env} to pass an environment variable to
2463 the debugged program, without setting the variable in your shell's
2467 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2471 This command is available when debugging locally on most targets, excluding
2472 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2474 @kindex set startup-with-shell
2475 @anchor{set startup-with-shell}
2476 @item set startup-with-shell
2477 @itemx set startup-with-shell on
2478 @itemx set startup-with-shell off
2479 @itemx show startup-with-shell
2480 On Unix systems, by default, if a shell is available on your target,
2481 @value{GDBN}) uses it to start your program. Arguments of the
2482 @code{run} command are passed to the shell, which does variable
2483 substitution, expands wildcard characters and performs redirection of
2484 I/O. In some circumstances, it may be useful to disable such use of a
2485 shell, for example, when debugging the shell itself or diagnosing
2486 startup failures such as:
2490 Starting program: ./a.out
2491 During startup program terminated with signal SIGSEGV, Segmentation fault.
2495 which indicates the shell or the wrapper specified with
2496 @samp{exec-wrapper} crashed, not your program. Most often, this is
2497 caused by something odd in your shell's non-interactive mode
2498 initialization file---such as @file{.cshrc} for C-shell,
2499 $@file{.zshenv} for the Z shell, or the file specified in the
2500 @samp{BASH_ENV} environment variable for BASH.
2502 @anchor{set auto-connect-native-target}
2503 @kindex set auto-connect-native-target
2504 @item set auto-connect-native-target
2505 @itemx set auto-connect-native-target on
2506 @itemx set auto-connect-native-target off
2507 @itemx show auto-connect-native-target
2509 By default, if the current inferior is not connected to any target yet
2510 (e.g., with @code{target remote}), the @code{run} command starts your
2511 program as a native process under @value{GDBN}, on your local machine.
2512 If you're sure you don't want to debug programs on your local machine,
2513 you can tell @value{GDBN} to not connect to the native target
2514 automatically with the @code{set auto-connect-native-target off}
2517 If @code{on}, which is the default, and if the current inferior is not
2518 connected to a target already, the @code{run} command automaticaly
2519 connects to the native target, if one is available.
2521 If @code{off}, and if the current inferior is not connected to a
2522 target already, the @code{run} command fails with an error:
2526 Don't know how to run. Try "help target".
2529 If the current inferior is already connected to a target, @value{GDBN}
2530 always uses it with the @code{run} command.
2532 In any case, you can explicitly connect to the native target with the
2533 @code{target native} command. For example,
2536 (@value{GDBP}) set auto-connect-native-target off
2538 Don't know how to run. Try "help target".
2539 (@value{GDBP}) target native
2541 Starting program: ./a.out
2542 [Inferior 1 (process 10421) exited normally]
2545 In case you connected explicitly to the @code{native} target,
2546 @value{GDBN} remains connected even if all inferiors exit, ready for
2547 the next @code{run} command. Use the @code{disconnect} command to
2550 Examples of other commands that likewise respect the
2551 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2552 proc}, @code{info os}.
2554 @kindex set disable-randomization
2555 @item set disable-randomization
2556 @itemx set disable-randomization on
2557 This option (enabled by default in @value{GDBN}) will turn off the native
2558 randomization of the virtual address space of the started program. This option
2559 is useful for multiple debugging sessions to make the execution better
2560 reproducible and memory addresses reusable across debugging sessions.
2562 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2563 On @sc{gnu}/Linux you can get the same behavior using
2566 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2569 @item set disable-randomization off
2570 Leave the behavior of the started executable unchanged. Some bugs rear their
2571 ugly heads only when the program is loaded at certain addresses. If your bug
2572 disappears when you run the program under @value{GDBN}, that might be because
2573 @value{GDBN} by default disables the address randomization on platforms, such
2574 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2575 disable-randomization off} to try to reproduce such elusive bugs.
2577 On targets where it is available, virtual address space randomization
2578 protects the programs against certain kinds of security attacks. In these
2579 cases the attacker needs to know the exact location of a concrete executable
2580 code. Randomizing its location makes it impossible to inject jumps misusing
2581 a code at its expected addresses.
2583 Prelinking shared libraries provides a startup performance advantage but it
2584 makes addresses in these libraries predictable for privileged processes by
2585 having just unprivileged access at the target system. Reading the shared
2586 library binary gives enough information for assembling the malicious code
2587 misusing it. Still even a prelinked shared library can get loaded at a new
2588 random address just requiring the regular relocation process during the
2589 startup. Shared libraries not already prelinked are always loaded at
2590 a randomly chosen address.
2592 Position independent executables (PIE) contain position independent code
2593 similar to the shared libraries and therefore such executables get loaded at
2594 a randomly chosen address upon startup. PIE executables always load even
2595 already prelinked shared libraries at a random address. You can build such
2596 executable using @command{gcc -fPIE -pie}.
2598 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2599 (as long as the randomization is enabled).
2601 @item show disable-randomization
2602 Show the current setting of the explicit disable of the native randomization of
2603 the virtual address space of the started program.
2608 @section Your Program's Arguments
2610 @cindex arguments (to your program)
2611 The arguments to your program can be specified by the arguments of the
2613 They are passed to a shell, which expands wildcard characters and
2614 performs redirection of I/O, and thence to your program. Your
2615 @code{SHELL} environment variable (if it exists) specifies what shell
2616 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2617 the default shell (@file{/bin/sh} on Unix).
2619 On non-Unix systems, the program is usually invoked directly by
2620 @value{GDBN}, which emulates I/O redirection via the appropriate system
2621 calls, and the wildcard characters are expanded by the startup code of
2622 the program, not by the shell.
2624 @code{run} with no arguments uses the same arguments used by the previous
2625 @code{run}, or those set by the @code{set args} command.
2630 Specify the arguments to be used the next time your program is run. If
2631 @code{set args} has no arguments, @code{run} executes your program
2632 with no arguments. Once you have run your program with arguments,
2633 using @code{set args} before the next @code{run} is the only way to run
2634 it again without arguments.
2638 Show the arguments to give your program when it is started.
2642 @section Your Program's Environment
2644 @cindex environment (of your program)
2645 The @dfn{environment} consists of a set of environment variables and
2646 their values. Environment variables conventionally record such things as
2647 your user name, your home directory, your terminal type, and your search
2648 path for programs to run. Usually you set up environment variables with
2649 the shell and they are inherited by all the other programs you run. When
2650 debugging, it can be useful to try running your program with a modified
2651 environment without having to start @value{GDBN} over again.
2655 @item path @var{directory}
2656 Add @var{directory} to the front of the @code{PATH} environment variable
2657 (the search path for executables) that will be passed to your program.
2658 The value of @code{PATH} used by @value{GDBN} does not change.
2659 You may specify several directory names, separated by whitespace or by a
2660 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2661 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2662 is moved to the front, so it is searched sooner.
2664 You can use the string @samp{$cwd} to refer to whatever is the current
2665 working directory at the time @value{GDBN} searches the path. If you
2666 use @samp{.} instead, it refers to the directory where you executed the
2667 @code{path} command. @value{GDBN} replaces @samp{.} in the
2668 @var{directory} argument (with the current path) before adding
2669 @var{directory} to the search path.
2670 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2671 @c document that, since repeating it would be a no-op.
2675 Display the list of search paths for executables (the @code{PATH}
2676 environment variable).
2678 @kindex show environment
2679 @item show environment @r{[}@var{varname}@r{]}
2680 Print the value of environment variable @var{varname} to be given to
2681 your program when it starts. If you do not supply @var{varname},
2682 print the names and values of all environment variables to be given to
2683 your program. You can abbreviate @code{environment} as @code{env}.
2685 @kindex set environment
2686 @anchor{set environment}
2687 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2688 Set environment variable @var{varname} to @var{value}. The value
2689 changes for your program (and the shell @value{GDBN} uses to launch
2690 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2691 values of environment variables are just strings, and any
2692 interpretation is supplied by your program itself. The @var{value}
2693 parameter is optional; if it is eliminated, the variable is set to a
2695 @c "any string" here does not include leading, trailing
2696 @c blanks. Gnu asks: does anyone care?
2698 For example, this command:
2705 tells the debugged program, when subsequently run, that its user is named
2706 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2707 are not actually required.)
2709 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2710 which also inherits the environment set with @code{set environment}.
2711 If necessary, you can avoid that by using the @samp{env} program as a
2712 wrapper instead of using @code{set environment}. @xref{set
2713 exec-wrapper}, for an example doing just that.
2715 Environment variables that are set by the user are also transmitted to
2716 @command{gdbserver} to be used when starting the remote inferior.
2717 @pxref{QEnvironmentHexEncoded}.
2719 @kindex unset environment
2720 @anchor{unset environment}
2721 @item unset environment @var{varname}
2722 Remove variable @var{varname} from the environment to be passed to your
2723 program. This is different from @samp{set env @var{varname} =};
2724 @code{unset environment} removes the variable from the environment,
2725 rather than assigning it an empty value.
2727 Environment variables that are unset by the user are also unset on
2728 @command{gdbserver} when starting the remote inferior.
2729 @pxref{QEnvironmentUnset}.
2732 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2733 the shell indicated by your @code{SHELL} environment variable if it
2734 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2735 names a shell that runs an initialization file when started
2736 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2737 for the Z shell, or the file specified in the @samp{BASH_ENV}
2738 environment variable for BASH---any variables you set in that file
2739 affect your program. You may wish to move setting of environment
2740 variables to files that are only run when you sign on, such as
2741 @file{.login} or @file{.profile}.
2743 @node Working Directory
2744 @section Your Program's Working Directory
2746 @cindex working directory (of your program)
2747 Each time you start your program with @code{run}, the inferior will be
2748 initialized with the current working directory specified by the
2749 @kbd{set cwd} command. If no directory has been specified by this
2750 command, then the inferior will inherit @value{GDBN}'s current working
2751 directory as its working directory if native debugging, or it will
2752 inherit the remote server's current working directory if remote
2757 @cindex change inferior's working directory
2758 @anchor{set cwd command}
2759 @item set cwd @r{[}@var{directory}@r{]}
2760 Set the inferior's working directory to @var{directory}, which will be
2761 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2762 argument has been specified, the command clears the setting and resets
2763 it to an empty state. This setting has no effect on @value{GDBN}'s
2764 working directory, and it only takes effect the next time you start
2765 the inferior. The @file{~} in @var{directory} is a short for the
2766 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2767 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2768 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2771 You can also change @value{GDBN}'s current working directory by using
2772 the @code{cd} command.
2776 @cindex show inferior's working directory
2778 Show the inferior's working directory. If no directory has been
2779 specified by @kbd{set cwd}, then the default inferior's working
2780 directory is the same as @value{GDBN}'s working directory.
2783 @cindex change @value{GDBN}'s working directory
2785 @item cd @r{[}@var{directory}@r{]}
2786 Set the @value{GDBN} working directory to @var{directory}. If not
2787 given, @var{directory} uses @file{'~'}.
2789 The @value{GDBN} working directory serves as a default for the
2790 commands that specify files for @value{GDBN} to operate on.
2791 @xref{Files, ,Commands to Specify Files}.
2792 @xref{set cwd command}.
2796 Print the @value{GDBN} working directory.
2799 It is generally impossible to find the current working directory of
2800 the process being debugged (since a program can change its directory
2801 during its run). If you work on a system where @value{GDBN} supports
2802 the @code{info proc} command (@pxref{Process Information}), you can
2803 use the @code{info proc} command to find out the
2804 current working directory of the debuggee.
2807 @section Your Program's Input and Output
2812 By default, the program you run under @value{GDBN} does input and output to
2813 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2814 to its own terminal modes to interact with you, but it records the terminal
2815 modes your program was using and switches back to them when you continue
2816 running your program.
2819 @kindex info terminal
2821 Displays information recorded by @value{GDBN} about the terminal modes your
2825 You can redirect your program's input and/or output using shell
2826 redirection with the @code{run} command. For example,
2833 starts your program, diverting its output to the file @file{outfile}.
2836 @cindex controlling terminal
2837 Another way to specify where your program should do input and output is
2838 with the @code{tty} command. This command accepts a file name as
2839 argument, and causes this file to be the default for future @code{run}
2840 commands. It also resets the controlling terminal for the child
2841 process, for future @code{run} commands. For example,
2848 directs that processes started with subsequent @code{run} commands
2849 default to do input and output on the terminal @file{/dev/ttyb} and have
2850 that as their controlling terminal.
2852 An explicit redirection in @code{run} overrides the @code{tty} command's
2853 effect on the input/output device, but not its effect on the controlling
2856 When you use the @code{tty} command or redirect input in the @code{run}
2857 command, only the input @emph{for your program} is affected. The input
2858 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2859 for @code{set inferior-tty}.
2861 @cindex inferior tty
2862 @cindex set inferior controlling terminal
2863 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2864 display the name of the terminal that will be used for future runs of your
2868 @item set inferior-tty [ @var{tty} ]
2869 @kindex set inferior-tty
2870 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2871 restores the default behavior, which is to use the same terminal as
2874 @item show inferior-tty
2875 @kindex show inferior-tty
2876 Show the current tty for the program being debugged.
2880 @section Debugging an Already-running Process
2885 @item attach @var{process-id}
2886 This command attaches to a running process---one that was started
2887 outside @value{GDBN}. (@code{info files} shows your active
2888 targets.) The command takes as argument a process ID. The usual way to
2889 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2890 or with the @samp{jobs -l} shell command.
2892 @code{attach} does not repeat if you press @key{RET} a second time after
2893 executing the command.
2896 To use @code{attach}, your program must be running in an environment
2897 which supports processes; for example, @code{attach} does not work for
2898 programs on bare-board targets that lack an operating system. You must
2899 also have permission to send the process a signal.
2901 When you use @code{attach}, the debugger finds the program running in
2902 the process first by looking in the current working directory, then (if
2903 the program is not found) by using the source file search path
2904 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2905 the @code{file} command to load the program. @xref{Files, ,Commands to
2908 @anchor{set exec-file-mismatch}
2909 If the debugger can determine the name of the executable file running
2910 in the process it is attaching to, and this file name does not match
2911 the name of the current exec-file loaded by @value{GDBN}, the option
2912 @code{exec-file-mismatch} specifies how to handle the mismatch.
2915 @kindex exec-file-mismatch
2916 @cindex set exec-file-mismatch
2917 @item set exec-file-mismatch @samp{ask|warn|off}
2919 Whether to detect mismatch between the name of the current executable
2920 file loaded by @value{GDBN} and the name of the executable file used to
2921 start the process. If @samp{ask}, the default, display a warning
2922 and ask the user whether to load the process executable file; if
2923 @samp{warn}, just display a warning; if @samp{off}, don't attempt to
2926 @cindex show exec-file-mismatch
2927 @item show exec-file-mismatch
2928 Show the current value of @code{exec-file-mismatch}.
2932 The first thing @value{GDBN} does after arranging to debug the specified
2933 process is to stop it. You can examine and modify an attached process
2934 with all the @value{GDBN} commands that are ordinarily available when
2935 you start processes with @code{run}. You can insert breakpoints; you
2936 can step and continue; you can modify storage. If you would rather the
2937 process continue running, you may use the @code{continue} command after
2938 attaching @value{GDBN} to the process.
2943 When you have finished debugging the attached process, you can use the
2944 @code{detach} command to release it from @value{GDBN} control. Detaching
2945 the process continues its execution. After the @code{detach} command,
2946 that process and @value{GDBN} become completely independent once more, and you
2947 are ready to @code{attach} another process or start one with @code{run}.
2948 @code{detach} does not repeat if you press @key{RET} again after
2949 executing the command.
2952 If you exit @value{GDBN} while you have an attached process, you detach
2953 that process. If you use the @code{run} command, you kill that process.
2954 By default, @value{GDBN} asks for confirmation if you try to do either of these
2955 things; you can control whether or not you need to confirm by using the
2956 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2960 @section Killing the Child Process
2965 Kill the child process in which your program is running under @value{GDBN}.
2968 This command is useful if you wish to debug a core dump instead of a
2969 running process. @value{GDBN} ignores any core dump file while your program
2972 On some operating systems, a program cannot be executed outside @value{GDBN}
2973 while you have breakpoints set on it inside @value{GDBN}. You can use the
2974 @code{kill} command in this situation to permit running your program
2975 outside the debugger.
2977 The @code{kill} command is also useful if you wish to recompile and
2978 relink your program, since on many systems it is impossible to modify an
2979 executable file while it is running in a process. In this case, when you
2980 next type @code{run}, @value{GDBN} notices that the file has changed, and
2981 reads the symbol table again (while trying to preserve your current
2982 breakpoint settings).
2984 @node Inferiors Connections and Programs
2985 @section Debugging Multiple Inferiors Connections and Programs
2987 @value{GDBN} lets you run and debug multiple programs in a single
2988 session. In addition, @value{GDBN} on some systems may let you run
2989 several programs simultaneously (otherwise you have to exit from one
2990 before starting another). On some systems @value{GDBN} may even let
2991 you debug several programs simultaneously on different remote systems.
2992 In the most general case, you can have multiple threads of execution
2993 in each of multiple processes, launched from multiple executables,
2994 running on different machines.
2997 @value{GDBN} represents the state of each program execution with an
2998 object called an @dfn{inferior}. An inferior typically corresponds to
2999 a process, but is more general and applies also to targets that do not
3000 have processes. Inferiors may be created before a process runs, and
3001 may be retained after a process exits. Inferiors have unique
3002 identifiers that are different from process ids. Usually each
3003 inferior will also have its own distinct address space, although some
3004 embedded targets may have several inferiors running in different parts
3005 of a single address space. Each inferior may in turn have multiple
3006 threads running in it.
3008 To find out what inferiors exist at any moment, use @w{@code{info
3012 @kindex info inferiors [ @var{id}@dots{} ]
3013 @item info inferiors
3014 Print a list of all inferiors currently being managed by @value{GDBN}.
3015 By default all inferiors are printed, but the argument @var{id}@dots{}
3016 -- a space separated list of inferior numbers -- can be used to limit
3017 the display to just the requested inferiors.
3019 @value{GDBN} displays for each inferior (in this order):
3023 the inferior number assigned by @value{GDBN}
3026 the target system's inferior identifier
3029 the target connection the inferior is bound to, including the unique
3030 connection number assigned by @value{GDBN}, and the protocol used by
3034 the name of the executable the inferior is running.
3039 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3040 indicates the current inferior.
3044 @c end table here to get a little more width for example
3047 (@value{GDBP}) info inferiors
3048 Num Description Connection Executable
3049 * 1 process 3401 1 (native) goodbye
3050 2 process 2307 2 (extended-remote host:10000) hello
3053 To find out what open target connections exist at any moment, use
3054 @w{@code{info connections}}:
3057 @kindex info connections [ @var{id}@dots{} ]
3058 @item info connections
3059 Print a list of all open target connections currently being managed by
3060 @value{GDBN}. By default all connections are printed, but the
3061 argument @var{id}@dots{} -- a space separated list of connections
3062 numbers -- can be used to limit the display to just the requested
3065 @value{GDBN} displays for each connection (in this order):
3069 the connection number assigned by @value{GDBN}.
3072 the protocol used by the connection.
3075 a textual description of the protocol used by the connection.
3080 An asterisk @samp{*} preceding the connection number indicates the
3081 connection of the current inferior.
3085 @c end table here to get a little more width for example
3088 (@value{GDBP}) info connections
3089 Num What Description
3090 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3091 2 native Native process
3092 3 core Local core dump file
3095 To switch focus between inferiors, use the @code{inferior} command:
3098 @kindex inferior @var{infno}
3099 @item inferior @var{infno}
3100 Make inferior number @var{infno} the current inferior. The argument
3101 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3102 in the first field of the @samp{info inferiors} display.
3105 @vindex $_inferior@r{, convenience variable}
3106 The debugger convenience variable @samp{$_inferior} contains the
3107 number of the current inferior. You may find this useful in writing
3108 breakpoint conditional expressions, command scripts, and so forth.
3109 @xref{Convenience Vars,, Convenience Variables}, for general
3110 information on convenience variables.
3112 You can get multiple executables into a debugging session via the
3113 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3114 systems @value{GDBN} can add inferiors to the debug session
3115 automatically by following calls to @code{fork} and @code{exec}. To
3116 remove inferiors from the debugging session use the
3117 @w{@code{remove-inferiors}} command.
3120 @kindex add-inferior
3121 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3122 Adds @var{n} inferiors to be run using @var{executable} as the
3123 executable; @var{n} defaults to 1. If no executable is specified,
3124 the inferiors begins empty, with no program. You can still assign or
3125 change the program assigned to the inferior at any time by using the
3126 @code{file} command with the executable name as its argument.
3128 By default, the new inferior begins connected to the same target
3129 connection as the current inferior. For example, if the current
3130 inferior was connected to @code{gdbserver} with @code{target remote},
3131 then the new inferior will be connected to the same @code{gdbserver}
3132 instance. The @samp{-no-connection} option starts the new inferior
3133 with no connection yet. You can then for example use the @code{target
3134 remote} command to connect to some other @code{gdbserver} instance,
3135 use @code{run} to spawn a local program, etc.
3137 @kindex clone-inferior
3138 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3139 Adds @var{n} inferiors ready to execute the same program as inferior
3140 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3141 number of the current inferior. This is a convenient command when you
3142 want to run another instance of the inferior you are debugging.
3145 (@value{GDBP}) info inferiors
3146 Num Description Connection Executable
3147 * 1 process 29964 1 (native) helloworld
3148 (@value{GDBP}) clone-inferior
3151 (@value{GDBP}) info inferiors
3152 Num Description Connection Executable
3153 * 1 process 29964 1 (native) helloworld
3154 2 <null> 1 (native) helloworld
3157 You can now simply switch focus to inferior 2 and run it.
3159 @kindex remove-inferiors
3160 @item remove-inferiors @var{infno}@dots{}
3161 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3162 possible to remove an inferior that is running with this command. For
3163 those, use the @code{kill} or @code{detach} command first.
3167 To quit debugging one of the running inferiors that is not the current
3168 inferior, you can either detach from it by using the @w{@code{detach
3169 inferior}} command (allowing it to run independently), or kill it
3170 using the @w{@code{kill inferiors}} command:
3173 @kindex detach inferiors @var{infno}@dots{}
3174 @item detach inferior @var{infno}@dots{}
3175 Detach from the inferior or inferiors identified by @value{GDBN}
3176 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3177 still stays on the list of inferiors shown by @code{info inferiors},
3178 but its Description will show @samp{<null>}.
3180 @kindex kill inferiors @var{infno}@dots{}
3181 @item kill inferiors @var{infno}@dots{}
3182 Kill the inferior or inferiors identified by @value{GDBN} inferior
3183 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3184 stays on the list of inferiors shown by @code{info inferiors}, but its
3185 Description will show @samp{<null>}.
3188 After the successful completion of a command such as @code{detach},
3189 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3190 a normal process exit, the inferior is still valid and listed with
3191 @code{info inferiors}, ready to be restarted.
3194 To be notified when inferiors are started or exit under @value{GDBN}'s
3195 control use @w{@code{set print inferior-events}}:
3198 @kindex set print inferior-events
3199 @cindex print messages on inferior start and exit
3200 @item set print inferior-events
3201 @itemx set print inferior-events on
3202 @itemx set print inferior-events off
3203 The @code{set print inferior-events} command allows you to enable or
3204 disable printing of messages when @value{GDBN} notices that new
3205 inferiors have started or that inferiors have exited or have been
3206 detached. By default, these messages will not be printed.
3208 @kindex show print inferior-events
3209 @item show print inferior-events
3210 Show whether messages will be printed when @value{GDBN} detects that
3211 inferiors have started, exited or have been detached.
3214 Many commands will work the same with multiple programs as with a
3215 single program: e.g., @code{print myglobal} will simply display the
3216 value of @code{myglobal} in the current inferior.
3219 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3220 get more info about the relationship of inferiors, programs, address
3221 spaces in a debug session. You can do that with the @w{@code{maint
3222 info program-spaces}} command.
3225 @kindex maint info program-spaces
3226 @item maint info program-spaces
3227 Print a list of all program spaces currently being managed by
3230 @value{GDBN} displays for each program space (in this order):
3234 the program space number assigned by @value{GDBN}
3237 the name of the executable loaded into the program space, with e.g.,
3238 the @code{file} command.
3243 An asterisk @samp{*} preceding the @value{GDBN} program space number
3244 indicates the current program space.
3246 In addition, below each program space line, @value{GDBN} prints extra
3247 information that isn't suitable to display in tabular form. For
3248 example, the list of inferiors bound to the program space.
3251 (@value{GDBP}) maint info program-spaces
3255 Bound inferiors: ID 1 (process 21561)
3258 Here we can see that no inferior is running the program @code{hello},
3259 while @code{process 21561} is running the program @code{goodbye}. On
3260 some targets, it is possible that multiple inferiors are bound to the
3261 same program space. The most common example is that of debugging both
3262 the parent and child processes of a @code{vfork} call. For example,
3265 (@value{GDBP}) maint info program-spaces
3268 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3271 Here, both inferior 2 and inferior 1 are running in the same program
3272 space as a result of inferior 1 having executed a @code{vfork} call.
3276 @section Debugging Programs with Multiple Threads
3278 @cindex threads of execution
3279 @cindex multiple threads
3280 @cindex switching threads
3281 In some operating systems, such as GNU/Linux and Solaris, a single program
3282 may have more than one @dfn{thread} of execution. The precise semantics
3283 of threads differ from one operating system to another, but in general
3284 the threads of a single program are akin to multiple processes---except
3285 that they share one address space (that is, they can all examine and
3286 modify the same variables). On the other hand, each thread has its own
3287 registers and execution stack, and perhaps private memory.
3289 @value{GDBN} provides these facilities for debugging multi-thread
3293 @item automatic notification of new threads
3294 @item @samp{thread @var{thread-id}}, a command to switch among threads
3295 @item @samp{info threads}, a command to inquire about existing threads
3296 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3297 a command to apply a command to a list of threads
3298 @item thread-specific breakpoints
3299 @item @samp{set print thread-events}, which controls printing of
3300 messages on thread start and exit.
3301 @item @samp{set libthread-db-search-path @var{path}}, which lets
3302 the user specify which @code{libthread_db} to use if the default choice
3303 isn't compatible with the program.
3306 @cindex focus of debugging
3307 @cindex current thread
3308 The @value{GDBN} thread debugging facility allows you to observe all
3309 threads while your program runs---but whenever @value{GDBN} takes
3310 control, one thread in particular is always the focus of debugging.
3311 This thread is called the @dfn{current thread}. Debugging commands show
3312 program information from the perspective of the current thread.
3314 @cindex @code{New} @var{systag} message
3315 @cindex thread identifier (system)
3316 @c FIXME-implementors!! It would be more helpful if the [New...] message
3317 @c included GDB's numeric thread handle, so you could just go to that
3318 @c thread without first checking `info threads'.
3319 Whenever @value{GDBN} detects a new thread in your program, it displays
3320 the target system's identification for the thread with a message in the
3321 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3322 whose form varies depending on the particular system. For example, on
3323 @sc{gnu}/Linux, you might see
3326 [New Thread 0x41e02940 (LWP 25582)]
3330 when @value{GDBN} notices a new thread. In contrast, on other systems,
3331 the @var{systag} is simply something like @samp{process 368}, with no
3334 @c FIXME!! (1) Does the [New...] message appear even for the very first
3335 @c thread of a program, or does it only appear for the
3336 @c second---i.e.@: when it becomes obvious we have a multithread
3338 @c (2) *Is* there necessarily a first thread always? Or do some
3339 @c multithread systems permit starting a program with multiple
3340 @c threads ab initio?
3342 @anchor{thread numbers}
3343 @cindex thread number, per inferior
3344 @cindex thread identifier (GDB)
3345 For debugging purposes, @value{GDBN} associates its own thread number
3346 ---always a single integer---with each thread of an inferior. This
3347 number is unique between all threads of an inferior, but not unique
3348 between threads of different inferiors.
3350 @cindex qualified thread ID
3351 You can refer to a given thread in an inferior using the qualified
3352 @var{inferior-num}.@var{thread-num} syntax, also known as
3353 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3354 number and @var{thread-num} being the thread number of the given
3355 inferior. For example, thread @code{2.3} refers to thread number 3 of
3356 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3357 then @value{GDBN} infers you're referring to a thread of the current
3360 Until you create a second inferior, @value{GDBN} does not show the
3361 @var{inferior-num} part of thread IDs, even though you can always use
3362 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3363 of inferior 1, the initial inferior.
3365 @anchor{thread ID lists}
3366 @cindex thread ID lists
3367 Some commands accept a space-separated @dfn{thread ID list} as
3368 argument. A list element can be:
3372 A thread ID as shown in the first field of the @samp{info threads}
3373 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3377 A range of thread numbers, again with or without an inferior
3378 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3379 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3382 All threads of an inferior, specified with a star wildcard, with or
3383 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3384 @samp{1.*}) or @code{*}. The former refers to all threads of the
3385 given inferior, and the latter form without an inferior qualifier
3386 refers to all threads of the current inferior.
3390 For example, if the current inferior is 1, and inferior 7 has one
3391 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3392 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3393 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3394 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3398 @anchor{global thread numbers}
3399 @cindex global thread number
3400 @cindex global thread identifier (GDB)
3401 In addition to a @emph{per-inferior} number, each thread is also
3402 assigned a unique @emph{global} number, also known as @dfn{global
3403 thread ID}, a single integer. Unlike the thread number component of
3404 the thread ID, no two threads have the same global ID, even when
3405 you're debugging multiple inferiors.
3407 From @value{GDBN}'s perspective, a process always has at least one
3408 thread. In other words, @value{GDBN} assigns a thread number to the
3409 program's ``main thread'' even if the program is not multi-threaded.
3411 @vindex $_thread@r{, convenience variable}
3412 @vindex $_gthread@r{, convenience variable}
3413 The debugger convenience variables @samp{$_thread} and
3414 @samp{$_gthread} contain, respectively, the per-inferior thread number
3415 and the global thread number of the current thread. You may find this
3416 useful in writing breakpoint conditional expressions, command scripts,
3417 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3418 general information on convenience variables.
3420 If @value{GDBN} detects the program is multi-threaded, it augments the
3421 usual message about stopping at a breakpoint with the ID and name of
3422 the thread that hit the breakpoint.
3425 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3428 Likewise when the program receives a signal:
3431 Thread 1 "main" received signal SIGINT, Interrupt.
3435 @kindex info threads
3436 @item info threads @r{[}@var{thread-id-list}@r{]}
3438 Display information about one or more threads. With no arguments
3439 displays information about all threads. You can specify the list of
3440 threads that you want to display using the thread ID list syntax
3441 (@pxref{thread ID lists}).
3443 @value{GDBN} displays for each thread (in this order):
3447 the per-inferior thread number assigned by @value{GDBN}
3450 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3451 option was specified
3454 the target system's thread identifier (@var{systag})
3457 the thread's name, if one is known. A thread can either be named by
3458 the user (see @code{thread name}, below), or, in some cases, by the
3462 the current stack frame summary for that thread
3466 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3467 indicates the current thread.
3471 @c end table here to get a little more width for example
3474 (@value{GDBP}) info threads
3476 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3477 2 process 35 thread 23 0x34e5 in sigpause ()
3478 3 process 35 thread 27 0x34e5 in sigpause ()
3482 If you're debugging multiple inferiors, @value{GDBN} displays thread
3483 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3484 Otherwise, only @var{thread-num} is shown.
3486 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3487 indicating each thread's global thread ID:
3490 (@value{GDBP}) info threads
3491 Id GId Target Id Frame
3492 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3493 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3494 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3495 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3498 On Solaris, you can display more information about user threads with a
3499 Solaris-specific command:
3502 @item maint info sol-threads
3503 @kindex maint info sol-threads
3504 @cindex thread info (Solaris)
3505 Display info on Solaris user threads.
3509 @kindex thread @var{thread-id}
3510 @item thread @var{thread-id}
3511 Make thread ID @var{thread-id} the current thread. The command
3512 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3513 the first field of the @samp{info threads} display, with or without an
3514 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3516 @value{GDBN} responds by displaying the system identifier of the
3517 thread you selected, and its current stack frame summary:
3520 (@value{GDBP}) thread 2
3521 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3522 #0 some_function (ignore=0x0) at example.c:8
3523 8 printf ("hello\n");
3527 As with the @samp{[New @dots{}]} message, the form of the text after
3528 @samp{Switching to} depends on your system's conventions for identifying
3531 @anchor{thread apply all}
3532 @kindex thread apply
3533 @cindex apply command to several threads
3534 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3535 The @code{thread apply} command allows you to apply the named
3536 @var{command} to one or more threads. Specify the threads that you
3537 want affected using the thread ID list syntax (@pxref{thread ID
3538 lists}), or specify @code{all} to apply to all threads. To apply a
3539 command to all threads in descending order, type @kbd{thread apply all
3540 @var{command}}. To apply a command to all threads in ascending order,
3541 type @kbd{thread apply all -ascending @var{command}}.
3543 The @var{flag} arguments control what output to produce and how to handle
3544 errors raised when applying @var{command} to a thread. @var{flag}
3545 must start with a @code{-} directly followed by one letter in
3546 @code{qcs}. If several flags are provided, they must be given
3547 individually, such as @code{-c -q}.
3549 By default, @value{GDBN} displays some thread information before the
3550 output produced by @var{command}, and an error raised during the
3551 execution of a @var{command} will abort @code{thread apply}. The
3552 following flags can be used to fine-tune this behavior:
3556 The flag @code{-c}, which stands for @samp{continue}, causes any
3557 errors in @var{command} to be displayed, and the execution of
3558 @code{thread apply} then continues.
3560 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3561 or empty output produced by a @var{command} to be silently ignored.
3562 That is, the execution continues, but the thread information and errors
3565 The flag @code{-q} (@samp{quiet}) disables printing the thread
3569 Flags @code{-c} and @code{-s} cannot be used together.
3572 @cindex apply command to all threads (ignoring errors and empty output)
3573 @item taas [@var{option}]@dots{} @var{command}
3574 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3575 Applies @var{command} on all threads, ignoring errors and empty output.
3577 The @code{taas} command accepts the same options as the @code{thread
3578 apply all} command. @xref{thread apply all}.
3581 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3582 @item tfaas [@var{option}]@dots{} @var{command}
3583 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3584 Applies @var{command} on all frames of all threads, ignoring errors
3585 and empty output. Note that the flag @code{-s} is specified twice:
3586 The first @code{-s} ensures that @code{thread apply} only shows the thread
3587 information of the threads for which @code{frame apply} produces
3588 some output. The second @code{-s} is needed to ensure that @code{frame
3589 apply} shows the frame information of a frame only if the
3590 @var{command} successfully produced some output.
3592 It can for example be used to print a local variable or a function
3593 argument without knowing the thread or frame where this variable or argument
3596 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3599 The @code{tfaas} command accepts the same options as the @code{frame
3600 apply} command. @xref{frame apply}.
3603 @cindex name a thread
3604 @item thread name [@var{name}]
3605 This command assigns a name to the current thread. If no argument is
3606 given, any existing user-specified name is removed. The thread name
3607 appears in the @samp{info threads} display.
3609 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3610 determine the name of the thread as given by the OS. On these
3611 systems, a name specified with @samp{thread name} will override the
3612 system-give name, and removing the user-specified name will cause
3613 @value{GDBN} to once again display the system-specified name.
3616 @cindex search for a thread
3617 @item thread find [@var{regexp}]
3618 Search for and display thread ids whose name or @var{systag}
3619 matches the supplied regular expression.
3621 As well as being the complement to the @samp{thread name} command,
3622 this command also allows you to identify a thread by its target
3623 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3627 (@value{GDBN}) thread find 26688
3628 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3629 (@value{GDBN}) info thread 4
3631 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3634 @kindex set print thread-events
3635 @cindex print messages on thread start and exit
3636 @item set print thread-events
3637 @itemx set print thread-events on
3638 @itemx set print thread-events off
3639 The @code{set print thread-events} command allows you to enable or
3640 disable printing of messages when @value{GDBN} notices that new threads have
3641 started or that threads have exited. By default, these messages will
3642 be printed if detection of these events is supported by the target.
3643 Note that these messages cannot be disabled on all targets.
3645 @kindex show print thread-events
3646 @item show print thread-events
3647 Show whether messages will be printed when @value{GDBN} detects that threads
3648 have started and exited.
3651 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3652 more information about how @value{GDBN} behaves when you stop and start
3653 programs with multiple threads.
3655 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3656 watchpoints in programs with multiple threads.
3658 @anchor{set libthread-db-search-path}
3660 @kindex set libthread-db-search-path
3661 @cindex search path for @code{libthread_db}
3662 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3663 If this variable is set, @var{path} is a colon-separated list of
3664 directories @value{GDBN} will use to search for @code{libthread_db}.
3665 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3666 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3667 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3670 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3671 @code{libthread_db} library to obtain information about threads in the
3672 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3673 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3674 specific thread debugging library loading is enabled
3675 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3677 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3678 refers to the default system directories that are
3679 normally searched for loading shared libraries. The @samp{$sdir} entry
3680 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3681 (@pxref{libthread_db.so.1 file}).
3683 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3684 refers to the directory from which @code{libpthread}
3685 was loaded in the inferior process.
3687 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3688 @value{GDBN} attempts to initialize it with the current inferior process.
3689 If this initialization fails (which could happen because of a version
3690 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3691 will unload @code{libthread_db}, and continue with the next directory.
3692 If none of @code{libthread_db} libraries initialize successfully,
3693 @value{GDBN} will issue a warning and thread debugging will be disabled.
3695 Setting @code{libthread-db-search-path} is currently implemented
3696 only on some platforms.
3698 @kindex show libthread-db-search-path
3699 @item show libthread-db-search-path
3700 Display current libthread_db search path.
3702 @kindex set debug libthread-db
3703 @kindex show debug libthread-db
3704 @cindex debugging @code{libthread_db}
3705 @item set debug libthread-db
3706 @itemx show debug libthread-db
3707 Turns on or off display of @code{libthread_db}-related events.
3708 Use @code{1} to enable, @code{0} to disable.
3712 @section Debugging Forks
3714 @cindex fork, debugging programs which call
3715 @cindex multiple processes
3716 @cindex processes, multiple
3717 On most systems, @value{GDBN} has no special support for debugging
3718 programs which create additional processes using the @code{fork}
3719 function. When a program forks, @value{GDBN} will continue to debug the
3720 parent process and the child process will run unimpeded. If you have
3721 set a breakpoint in any code which the child then executes, the child
3722 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3723 will cause it to terminate.
3725 However, if you want to debug the child process there is a workaround
3726 which isn't too painful. Put a call to @code{sleep} in the code which
3727 the child process executes after the fork. It may be useful to sleep
3728 only if a certain environment variable is set, or a certain file exists,
3729 so that the delay need not occur when you don't want to run @value{GDBN}
3730 on the child. While the child is sleeping, use the @code{ps} program to
3731 get its process ID. Then tell @value{GDBN} (a new invocation of
3732 @value{GDBN} if you are also debugging the parent process) to attach to
3733 the child process (@pxref{Attach}). From that point on you can debug
3734 the child process just like any other process which you attached to.
3736 On some systems, @value{GDBN} provides support for debugging programs
3737 that create additional processes using the @code{fork} or @code{vfork}
3738 functions. On @sc{gnu}/Linux platforms, this feature is supported
3739 with kernel version 2.5.46 and later.
3741 The fork debugging commands are supported in native mode and when
3742 connected to @code{gdbserver} in either @code{target remote} mode or
3743 @code{target extended-remote} mode.
3745 By default, when a program forks, @value{GDBN} will continue to debug
3746 the parent process and the child process will run unimpeded.
3748 If you want to follow the child process instead of the parent process,
3749 use the command @w{@code{set follow-fork-mode}}.
3752 @kindex set follow-fork-mode
3753 @item set follow-fork-mode @var{mode}
3754 Set the debugger response to a program call of @code{fork} or
3755 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3756 process. The @var{mode} argument can be:
3760 The original process is debugged after a fork. The child process runs
3761 unimpeded. This is the default.
3764 The new process is debugged after a fork. The parent process runs
3769 @kindex show follow-fork-mode
3770 @item show follow-fork-mode
3771 Display the current debugger response to a @code{fork} or @code{vfork} call.
3774 @cindex debugging multiple processes
3775 On Linux, if you want to debug both the parent and child processes, use the
3776 command @w{@code{set detach-on-fork}}.
3779 @kindex set detach-on-fork
3780 @item set detach-on-fork @var{mode}
3781 Tells gdb whether to detach one of the processes after a fork, or
3782 retain debugger control over them both.
3786 The child process (or parent process, depending on the value of
3787 @code{follow-fork-mode}) will be detached and allowed to run
3788 independently. This is the default.
3791 Both processes will be held under the control of @value{GDBN}.
3792 One process (child or parent, depending on the value of
3793 @code{follow-fork-mode}) is debugged as usual, while the other
3798 @kindex show detach-on-fork
3799 @item show detach-on-fork
3800 Show whether detach-on-fork mode is on/off.
3803 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3804 will retain control of all forked processes (including nested forks).
3805 You can list the forked processes under the control of @value{GDBN} by
3806 using the @w{@code{info inferiors}} command, and switch from one fork
3807 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
3808 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
3810 To quit debugging one of the forked processes, you can either detach
3811 from it by using the @w{@code{detach inferiors}} command (allowing it
3812 to run independently), or kill it using the @w{@code{kill inferiors}}
3813 command. @xref{Inferiors Connections and Programs, ,Debugging
3814 Multiple Inferiors Connections and Programs}.
3816 If you ask to debug a child process and a @code{vfork} is followed by an
3817 @code{exec}, @value{GDBN} executes the new target up to the first
3818 breakpoint in the new target. If you have a breakpoint set on
3819 @code{main} in your original program, the breakpoint will also be set on
3820 the child process's @code{main}.
3822 On some systems, when a child process is spawned by @code{vfork}, you
3823 cannot debug the child or parent until an @code{exec} call completes.
3825 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3826 call executes, the new target restarts. To restart the parent
3827 process, use the @code{file} command with the parent executable name
3828 as its argument. By default, after an @code{exec} call executes,
3829 @value{GDBN} discards the symbols of the previous executable image.
3830 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3834 @kindex set follow-exec-mode
3835 @item set follow-exec-mode @var{mode}
3837 Set debugger response to a program call of @code{exec}. An
3838 @code{exec} call replaces the program image of a process.
3840 @code{follow-exec-mode} can be:
3844 @value{GDBN} creates a new inferior and rebinds the process to this
3845 new inferior. The program the process was running before the
3846 @code{exec} call can be restarted afterwards by restarting the
3852 (@value{GDBP}) info inferiors
3854 Id Description Executable
3857 process 12020 is executing new program: prog2
3858 Program exited normally.
3859 (@value{GDBP}) info inferiors
3860 Id Description Executable
3866 @value{GDBN} keeps the process bound to the same inferior. The new
3867 executable image replaces the previous executable loaded in the
3868 inferior. Restarting the inferior after the @code{exec} call, with
3869 e.g., the @code{run} command, restarts the executable the process was
3870 running after the @code{exec} call. This is the default mode.
3875 (@value{GDBP}) info inferiors
3876 Id Description Executable
3879 process 12020 is executing new program: prog2
3880 Program exited normally.
3881 (@value{GDBP}) info inferiors
3882 Id Description Executable
3889 @code{follow-exec-mode} is supported in native mode and
3890 @code{target extended-remote} mode.
3892 You can use the @code{catch} command to make @value{GDBN} stop whenever
3893 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3894 Catchpoints, ,Setting Catchpoints}.
3896 @node Checkpoint/Restart
3897 @section Setting a @emph{Bookmark} to Return to Later
3902 @cindex snapshot of a process
3903 @cindex rewind program state
3905 On certain operating systems@footnote{Currently, only
3906 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3907 program's state, called a @dfn{checkpoint}, and come back to it
3910 Returning to a checkpoint effectively undoes everything that has
3911 happened in the program since the @code{checkpoint} was saved. This
3912 includes changes in memory, registers, and even (within some limits)
3913 system state. Effectively, it is like going back in time to the
3914 moment when the checkpoint was saved.
3916 Thus, if you're stepping thru a program and you think you're
3917 getting close to the point where things go wrong, you can save
3918 a checkpoint. Then, if you accidentally go too far and miss
3919 the critical statement, instead of having to restart your program
3920 from the beginning, you can just go back to the checkpoint and
3921 start again from there.
3923 This can be especially useful if it takes a lot of time or
3924 steps to reach the point where you think the bug occurs.
3926 To use the @code{checkpoint}/@code{restart} method of debugging:
3931 Save a snapshot of the debugged program's current execution state.
3932 The @code{checkpoint} command takes no arguments, but each checkpoint
3933 is assigned a small integer id, similar to a breakpoint id.
3935 @kindex info checkpoints
3936 @item info checkpoints
3937 List the checkpoints that have been saved in the current debugging
3938 session. For each checkpoint, the following information will be
3945 @item Source line, or label
3948 @kindex restart @var{checkpoint-id}
3949 @item restart @var{checkpoint-id}
3950 Restore the program state that was saved as checkpoint number
3951 @var{checkpoint-id}. All program variables, registers, stack frames
3952 etc.@: will be returned to the values that they had when the checkpoint
3953 was saved. In essence, gdb will ``wind back the clock'' to the point
3954 in time when the checkpoint was saved.
3956 Note that breakpoints, @value{GDBN} variables, command history etc.
3957 are not affected by restoring a checkpoint. In general, a checkpoint
3958 only restores things that reside in the program being debugged, not in
3961 @kindex delete checkpoint @var{checkpoint-id}
3962 @item delete checkpoint @var{checkpoint-id}
3963 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3967 Returning to a previously saved checkpoint will restore the user state
3968 of the program being debugged, plus a significant subset of the system
3969 (OS) state, including file pointers. It won't ``un-write'' data from
3970 a file, but it will rewind the file pointer to the previous location,
3971 so that the previously written data can be overwritten. For files
3972 opened in read mode, the pointer will also be restored so that the
3973 previously read data can be read again.
3975 Of course, characters that have been sent to a printer (or other
3976 external device) cannot be ``snatched back'', and characters received
3977 from eg.@: a serial device can be removed from internal program buffers,
3978 but they cannot be ``pushed back'' into the serial pipeline, ready to
3979 be received again. Similarly, the actual contents of files that have
3980 been changed cannot be restored (at this time).
3982 However, within those constraints, you actually can ``rewind'' your
3983 program to a previously saved point in time, and begin debugging it
3984 again --- and you can change the course of events so as to debug a
3985 different execution path this time.
3987 @cindex checkpoints and process id
3988 Finally, there is one bit of internal program state that will be
3989 different when you return to a checkpoint --- the program's process
3990 id. Each checkpoint will have a unique process id (or @var{pid}),
3991 and each will be different from the program's original @var{pid}.
3992 If your program has saved a local copy of its process id, this could
3993 potentially pose a problem.
3995 @subsection A Non-obvious Benefit of Using Checkpoints
3997 On some systems such as @sc{gnu}/Linux, address space randomization
3998 is performed on new processes for security reasons. This makes it
3999 difficult or impossible to set a breakpoint, or watchpoint, on an
4000 absolute address if you have to restart the program, since the
4001 absolute location of a symbol will change from one execution to the
4004 A checkpoint, however, is an @emph{identical} copy of a process.
4005 Therefore if you create a checkpoint at (eg.@:) the start of main,
4006 and simply return to that checkpoint instead of restarting the
4007 process, you can avoid the effects of address randomization and
4008 your symbols will all stay in the same place.
4011 @chapter Stopping and Continuing
4013 The principal purposes of using a debugger are so that you can stop your
4014 program before it terminates; or so that, if your program runs into
4015 trouble, you can investigate and find out why.
4017 Inside @value{GDBN}, your program may stop for any of several reasons,
4018 such as a signal, a breakpoint, or reaching a new line after a
4019 @value{GDBN} command such as @code{step}. You may then examine and
4020 change variables, set new breakpoints or remove old ones, and then
4021 continue execution. Usually, the messages shown by @value{GDBN} provide
4022 ample explanation of the status of your program---but you can also
4023 explicitly request this information at any time.
4026 @kindex info program
4028 Display information about the status of your program: whether it is
4029 running or not, what process it is, and why it stopped.
4033 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4034 * Continuing and Stepping:: Resuming execution
4035 * Skipping Over Functions and Files::
4036 Skipping over functions and files
4038 * Thread Stops:: Stopping and starting multi-thread programs
4042 @section Breakpoints, Watchpoints, and Catchpoints
4045 A @dfn{breakpoint} makes your program stop whenever a certain point in
4046 the program is reached. For each breakpoint, you can add conditions to
4047 control in finer detail whether your program stops. You can set
4048 breakpoints with the @code{break} command and its variants (@pxref{Set
4049 Breaks, ,Setting Breakpoints}), to specify the place where your program
4050 should stop by line number, function name or exact address in the
4053 On some systems, you can set breakpoints in shared libraries before
4054 the executable is run.
4057 @cindex data breakpoints
4058 @cindex memory tracing
4059 @cindex breakpoint on memory address
4060 @cindex breakpoint on variable modification
4061 A @dfn{watchpoint} is a special breakpoint that stops your program
4062 when the value of an expression changes. The expression may be a value
4063 of a variable, or it could involve values of one or more variables
4064 combined by operators, such as @samp{a + b}. This is sometimes called
4065 @dfn{data breakpoints}. You must use a different command to set
4066 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4067 from that, you can manage a watchpoint like any other breakpoint: you
4068 enable, disable, and delete both breakpoints and watchpoints using the
4071 You can arrange to have values from your program displayed automatically
4072 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4076 @cindex breakpoint on events
4077 A @dfn{catchpoint} is another special breakpoint that stops your program
4078 when a certain kind of event occurs, such as the throwing of a C@t{++}
4079 exception or the loading of a library. As with watchpoints, you use a
4080 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4081 Catchpoints}), but aside from that, you can manage a catchpoint like any
4082 other breakpoint. (To stop when your program receives a signal, use the
4083 @code{handle} command; see @ref{Signals, ,Signals}.)
4085 @cindex breakpoint numbers
4086 @cindex numbers for breakpoints
4087 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4088 catchpoint when you create it; these numbers are successive integers
4089 starting with one. In many of the commands for controlling various
4090 features of breakpoints you use the breakpoint number to say which
4091 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4092 @dfn{disabled}; if disabled, it has no effect on your program until you
4095 @cindex breakpoint ranges
4096 @cindex breakpoint lists
4097 @cindex ranges of breakpoints
4098 @cindex lists of breakpoints
4099 Some @value{GDBN} commands accept a space-separated list of breakpoints
4100 on which to operate. A list element can be either a single breakpoint number,
4101 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4102 When a breakpoint list is given to a command, all breakpoints in that list
4106 * Set Breaks:: Setting breakpoints
4107 * Set Watchpoints:: Setting watchpoints
4108 * Set Catchpoints:: Setting catchpoints
4109 * Delete Breaks:: Deleting breakpoints
4110 * Disabling:: Disabling breakpoints
4111 * Conditions:: Break conditions
4112 * Break Commands:: Breakpoint command lists
4113 * Dynamic Printf:: Dynamic printf
4114 * Save Breakpoints:: How to save breakpoints in a file
4115 * Static Probe Points:: Listing static probe points
4116 * Error in Breakpoints:: ``Cannot insert breakpoints''
4117 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4121 @subsection Setting Breakpoints
4123 @c FIXME LMB what does GDB do if no code on line of breakpt?
4124 @c consider in particular declaration with/without initialization.
4126 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4129 @kindex b @r{(@code{break})}
4130 @vindex $bpnum@r{, convenience variable}
4131 @cindex latest breakpoint
4132 Breakpoints are set with the @code{break} command (abbreviated
4133 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4134 number of the breakpoint you've set most recently; see @ref{Convenience
4135 Vars,, Convenience Variables}, for a discussion of what you can do with
4136 convenience variables.
4139 @item break @var{location}
4140 Set a breakpoint at the given @var{location}, which can specify a
4141 function name, a line number, or an address of an instruction.
4142 (@xref{Specify Location}, for a list of all the possible ways to
4143 specify a @var{location}.) The breakpoint will stop your program just
4144 before it executes any of the code in the specified @var{location}.
4146 When using source languages that permit overloading of symbols, such as
4147 C@t{++}, a function name may refer to more than one possible place to break.
4148 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4151 It is also possible to insert a breakpoint that will stop the program
4152 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4153 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4156 When called without any arguments, @code{break} sets a breakpoint at
4157 the next instruction to be executed in the selected stack frame
4158 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4159 innermost, this makes your program stop as soon as control
4160 returns to that frame. This is similar to the effect of a
4161 @code{finish} command in the frame inside the selected frame---except
4162 that @code{finish} does not leave an active breakpoint. If you use
4163 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4164 the next time it reaches the current location; this may be useful
4167 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4168 least one instruction has been executed. If it did not do this, you
4169 would be unable to proceed past a breakpoint without first disabling the
4170 breakpoint. This rule applies whether or not the breakpoint already
4171 existed when your program stopped.
4173 @item break @dots{} if @var{cond}
4174 Set a breakpoint with condition @var{cond}; evaluate the expression
4175 @var{cond} each time the breakpoint is reached, and stop only if the
4176 value is nonzero---that is, if @var{cond} evaluates as true.
4177 @samp{@dots{}} stands for one of the possible arguments described
4178 above (or no argument) specifying where to break. @xref{Conditions,
4179 ,Break Conditions}, for more information on breakpoint conditions.
4182 @item tbreak @var{args}
4183 Set a breakpoint enabled only for one stop. The @var{args} are the
4184 same as for the @code{break} command, and the breakpoint is set in the same
4185 way, but the breakpoint is automatically deleted after the first time your
4186 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4189 @cindex hardware breakpoints
4190 @item hbreak @var{args}
4191 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4192 @code{break} command and the breakpoint is set in the same way, but the
4193 breakpoint requires hardware support and some target hardware may not
4194 have this support. The main purpose of this is EPROM/ROM code
4195 debugging, so you can set a breakpoint at an instruction without
4196 changing the instruction. This can be used with the new trap-generation
4197 provided by SPARClite DSU and most x86-based targets. These targets
4198 will generate traps when a program accesses some data or instruction
4199 address that is assigned to the debug registers. However the hardware
4200 breakpoint registers can take a limited number of breakpoints. For
4201 example, on the DSU, only two data breakpoints can be set at a time, and
4202 @value{GDBN} will reject this command if more than two are used. Delete
4203 or disable unused hardware breakpoints before setting new ones
4204 (@pxref{Disabling, ,Disabling Breakpoints}).
4205 @xref{Conditions, ,Break Conditions}.
4206 For remote targets, you can restrict the number of hardware
4207 breakpoints @value{GDBN} will use, see @ref{set remote
4208 hardware-breakpoint-limit}.
4211 @item thbreak @var{args}
4212 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4213 are the same as for the @code{hbreak} command and the breakpoint is set in
4214 the same way. However, like the @code{tbreak} command,
4215 the breakpoint is automatically deleted after the
4216 first time your program stops there. Also, like the @code{hbreak}
4217 command, the breakpoint requires hardware support and some target hardware
4218 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4219 See also @ref{Conditions, ,Break Conditions}.
4222 @cindex regular expression
4223 @cindex breakpoints at functions matching a regexp
4224 @cindex set breakpoints in many functions
4225 @item rbreak @var{regex}
4226 Set breakpoints on all functions matching the regular expression
4227 @var{regex}. This command sets an unconditional breakpoint on all
4228 matches, printing a list of all breakpoints it set. Once these
4229 breakpoints are set, they are treated just like the breakpoints set with
4230 the @code{break} command. You can delete them, disable them, or make
4231 them conditional the same way as any other breakpoint.
4233 In programs using different languages, @value{GDBN} chooses the syntax
4234 to print the list of all breakpoints it sets according to the
4235 @samp{set language} value: using @samp{set language auto}
4236 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4237 language of the breakpoint's function, other values mean to use
4238 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4240 The syntax of the regular expression is the standard one used with tools
4241 like @file{grep}. Note that this is different from the syntax used by
4242 shells, so for instance @code{foo*} matches all functions that include
4243 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4244 @code{.*} leading and trailing the regular expression you supply, so to
4245 match only functions that begin with @code{foo}, use @code{^foo}.
4247 @cindex non-member C@t{++} functions, set breakpoint in
4248 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4249 breakpoints on overloaded functions that are not members of any special
4252 @cindex set breakpoints on all functions
4253 The @code{rbreak} command can be used to set breakpoints in
4254 @strong{all} the functions in a program, like this:
4257 (@value{GDBP}) rbreak .
4260 @item rbreak @var{file}:@var{regex}
4261 If @code{rbreak} is called with a filename qualification, it limits
4262 the search for functions matching the given regular expression to the
4263 specified @var{file}. This can be used, for example, to set breakpoints on
4264 every function in a given file:
4267 (@value{GDBP}) rbreak file.c:.
4270 The colon separating the filename qualifier from the regex may
4271 optionally be surrounded by spaces.
4273 @kindex info breakpoints
4274 @cindex @code{$_} and @code{info breakpoints}
4275 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4276 @itemx info break @r{[}@var{list}@dots{}@r{]}
4277 Print a table of all breakpoints, watchpoints, and catchpoints set and
4278 not deleted. Optional argument @var{n} means print information only
4279 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4280 For each breakpoint, following columns are printed:
4283 @item Breakpoint Numbers
4285 Breakpoint, watchpoint, or catchpoint.
4287 Whether the breakpoint is marked to be disabled or deleted when hit.
4288 @item Enabled or Disabled
4289 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4290 that are not enabled.
4292 Where the breakpoint is in your program, as a memory address. For a
4293 pending breakpoint whose address is not yet known, this field will
4294 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4295 library that has the symbol or line referred by breakpoint is loaded.
4296 See below for details. A breakpoint with several locations will
4297 have @samp{<MULTIPLE>} in this field---see below for details.
4299 Where the breakpoint is in the source for your program, as a file and
4300 line number. For a pending breakpoint, the original string passed to
4301 the breakpoint command will be listed as it cannot be resolved until
4302 the appropriate shared library is loaded in the future.
4306 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4307 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4308 @value{GDBN} on the host's side. If it is ``target'', then the condition
4309 is evaluated by the target. The @code{info break} command shows
4310 the condition on the line following the affected breakpoint, together with
4311 its condition evaluation mode in between parentheses.
4313 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4314 allowed to have a condition specified for it. The condition is not parsed for
4315 validity until a shared library is loaded that allows the pending
4316 breakpoint to resolve to a valid location.
4319 @code{info break} with a breakpoint
4320 number @var{n} as argument lists only that breakpoint. The
4321 convenience variable @code{$_} and the default examining-address for
4322 the @code{x} command are set to the address of the last breakpoint
4323 listed (@pxref{Memory, ,Examining Memory}).
4326 @code{info break} displays a count of the number of times the breakpoint
4327 has been hit. This is especially useful in conjunction with the
4328 @code{ignore} command. You can ignore a large number of breakpoint
4329 hits, look at the breakpoint info to see how many times the breakpoint
4330 was hit, and then run again, ignoring one less than that number. This
4331 will get you quickly to the last hit of that breakpoint.
4334 For a breakpoints with an enable count (xref) greater than 1,
4335 @code{info break} also displays that count.
4339 @value{GDBN} allows you to set any number of breakpoints at the same place in
4340 your program. There is nothing silly or meaningless about this. When
4341 the breakpoints are conditional, this is even useful
4342 (@pxref{Conditions, ,Break Conditions}).
4344 @cindex multiple locations, breakpoints
4345 @cindex breakpoints, multiple locations
4346 It is possible that a breakpoint corresponds to several locations
4347 in your program. Examples of this situation are:
4351 Multiple functions in the program may have the same name.
4354 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4355 instances of the function body, used in different cases.
4358 For a C@t{++} template function, a given line in the function can
4359 correspond to any number of instantiations.
4362 For an inlined function, a given source line can correspond to
4363 several places where that function is inlined.
4366 In all those cases, @value{GDBN} will insert a breakpoint at all
4367 the relevant locations.
4369 A breakpoint with multiple locations is displayed in the breakpoint
4370 table using several rows---one header row, followed by one row for
4371 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4372 address column. The rows for individual locations contain the actual
4373 addresses for locations, and show the functions to which those
4374 locations belong. The number column for a location is of the form
4375 @var{breakpoint-number}.@var{location-number}.
4380 Num Type Disp Enb Address What
4381 1 breakpoint keep y <MULTIPLE>
4383 breakpoint already hit 1 time
4384 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4385 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4388 You cannot delete the individual locations from a breakpoint. However,
4389 each location can be individually enabled or disabled by passing
4390 @var{breakpoint-number}.@var{location-number} as argument to the
4391 @code{enable} and @code{disable} commands. It's also possible to
4392 @code{enable} and @code{disable} a range of @var{location-number}
4393 locations using a @var{breakpoint-number} and two @var{location-number}s,
4394 in increasing order, separated by a hyphen, like
4395 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4396 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4397 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4398 all of the locations that belong to that breakpoint.
4400 @cindex pending breakpoints
4401 It's quite common to have a breakpoint inside a shared library.
4402 Shared libraries can be loaded and unloaded explicitly,
4403 and possibly repeatedly, as the program is executed. To support
4404 this use case, @value{GDBN} updates breakpoint locations whenever
4405 any shared library is loaded or unloaded. Typically, you would
4406 set a breakpoint in a shared library at the beginning of your
4407 debugging session, when the library is not loaded, and when the
4408 symbols from the library are not available. When you try to set
4409 breakpoint, @value{GDBN} will ask you if you want to set
4410 a so called @dfn{pending breakpoint}---breakpoint whose address
4411 is not yet resolved.
4413 After the program is run, whenever a new shared library is loaded,
4414 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4415 shared library contains the symbol or line referred to by some
4416 pending breakpoint, that breakpoint is resolved and becomes an
4417 ordinary breakpoint. When a library is unloaded, all breakpoints
4418 that refer to its symbols or source lines become pending again.
4420 This logic works for breakpoints with multiple locations, too. For
4421 example, if you have a breakpoint in a C@t{++} template function, and
4422 a newly loaded shared library has an instantiation of that template,
4423 a new location is added to the list of locations for the breakpoint.
4425 Except for having unresolved address, pending breakpoints do not
4426 differ from regular breakpoints. You can set conditions or commands,
4427 enable and disable them and perform other breakpoint operations.
4429 @value{GDBN} provides some additional commands for controlling what
4430 happens when the @samp{break} command cannot resolve breakpoint
4431 address specification to an address:
4433 @kindex set breakpoint pending
4434 @kindex show breakpoint pending
4436 @item set breakpoint pending auto
4437 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4438 location, it queries you whether a pending breakpoint should be created.
4440 @item set breakpoint pending on
4441 This indicates that an unrecognized breakpoint location should automatically
4442 result in a pending breakpoint being created.
4444 @item set breakpoint pending off
4445 This indicates that pending breakpoints are not to be created. Any
4446 unrecognized breakpoint location results in an error. This setting does
4447 not affect any pending breakpoints previously created.
4449 @item show breakpoint pending
4450 Show the current behavior setting for creating pending breakpoints.
4453 The settings above only affect the @code{break} command and its
4454 variants. Once breakpoint is set, it will be automatically updated
4455 as shared libraries are loaded and unloaded.
4457 @cindex automatic hardware breakpoints
4458 For some targets, @value{GDBN} can automatically decide if hardware or
4459 software breakpoints should be used, depending on whether the
4460 breakpoint address is read-only or read-write. This applies to
4461 breakpoints set with the @code{break} command as well as to internal
4462 breakpoints set by commands like @code{next} and @code{finish}. For
4463 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4466 You can control this automatic behaviour with the following commands:
4468 @kindex set breakpoint auto-hw
4469 @kindex show breakpoint auto-hw
4471 @item set breakpoint auto-hw on
4472 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4473 will try to use the target memory map to decide if software or hardware
4474 breakpoint must be used.
4476 @item set breakpoint auto-hw off
4477 This indicates @value{GDBN} should not automatically select breakpoint
4478 type. If the target provides a memory map, @value{GDBN} will warn when
4479 trying to set software breakpoint at a read-only address.
4482 @value{GDBN} normally implements breakpoints by replacing the program code
4483 at the breakpoint address with a special instruction, which, when
4484 executed, given control to the debugger. By default, the program
4485 code is so modified only when the program is resumed. As soon as
4486 the program stops, @value{GDBN} restores the original instructions. This
4487 behaviour guards against leaving breakpoints inserted in the
4488 target should gdb abrubptly disconnect. However, with slow remote
4489 targets, inserting and removing breakpoint can reduce the performance.
4490 This behavior can be controlled with the following commands::
4492 @kindex set breakpoint always-inserted
4493 @kindex show breakpoint always-inserted
4495 @item set breakpoint always-inserted off
4496 All breakpoints, including newly added by the user, are inserted in
4497 the target only when the target is resumed. All breakpoints are
4498 removed from the target when it stops. This is the default mode.
4500 @item set breakpoint always-inserted on
4501 Causes all breakpoints to be inserted in the target at all times. If
4502 the user adds a new breakpoint, or changes an existing breakpoint, the
4503 breakpoints in the target are updated immediately. A breakpoint is
4504 removed from the target only when breakpoint itself is deleted.
4507 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4508 when a breakpoint breaks. If the condition is true, then the process being
4509 debugged stops, otherwise the process is resumed.
4511 If the target supports evaluating conditions on its end, @value{GDBN} may
4512 download the breakpoint, together with its conditions, to it.
4514 This feature can be controlled via the following commands:
4516 @kindex set breakpoint condition-evaluation
4517 @kindex show breakpoint condition-evaluation
4519 @item set breakpoint condition-evaluation host
4520 This option commands @value{GDBN} to evaluate the breakpoint
4521 conditions on the host's side. Unconditional breakpoints are sent to
4522 the target which in turn receives the triggers and reports them back to GDB
4523 for condition evaluation. This is the standard evaluation mode.
4525 @item set breakpoint condition-evaluation target
4526 This option commands @value{GDBN} to download breakpoint conditions
4527 to the target at the moment of their insertion. The target
4528 is responsible for evaluating the conditional expression and reporting
4529 breakpoint stop events back to @value{GDBN} whenever the condition
4530 is true. Due to limitations of target-side evaluation, some conditions
4531 cannot be evaluated there, e.g., conditions that depend on local data
4532 that is only known to the host. Examples include
4533 conditional expressions involving convenience variables, complex types
4534 that cannot be handled by the agent expression parser and expressions
4535 that are too long to be sent over to the target, specially when the
4536 target is a remote system. In these cases, the conditions will be
4537 evaluated by @value{GDBN}.
4539 @item set breakpoint condition-evaluation auto
4540 This is the default mode. If the target supports evaluating breakpoint
4541 conditions on its end, @value{GDBN} will download breakpoint conditions to
4542 the target (limitations mentioned previously apply). If the target does
4543 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4544 to evaluating all these conditions on the host's side.
4548 @cindex negative breakpoint numbers
4549 @cindex internal @value{GDBN} breakpoints
4550 @value{GDBN} itself sometimes sets breakpoints in your program for
4551 special purposes, such as proper handling of @code{longjmp} (in C
4552 programs). These internal breakpoints are assigned negative numbers,
4553 starting with @code{-1}; @samp{info breakpoints} does not display them.
4554 You can see these breakpoints with the @value{GDBN} maintenance command
4555 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4558 @node Set Watchpoints
4559 @subsection Setting Watchpoints
4561 @cindex setting watchpoints
4562 You can use a watchpoint to stop execution whenever the value of an
4563 expression changes, without having to predict a particular place where
4564 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4565 The expression may be as simple as the value of a single variable, or
4566 as complex as many variables combined by operators. Examples include:
4570 A reference to the value of a single variable.
4573 An address cast to an appropriate data type. For example,
4574 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4575 address (assuming an @code{int} occupies 4 bytes).
4578 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4579 expression can use any operators valid in the program's native
4580 language (@pxref{Languages}).
4583 You can set a watchpoint on an expression even if the expression can
4584 not be evaluated yet. For instance, you can set a watchpoint on
4585 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4586 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4587 the expression produces a valid value. If the expression becomes
4588 valid in some other way than changing a variable (e.g.@: if the memory
4589 pointed to by @samp{*global_ptr} becomes readable as the result of a
4590 @code{malloc} call), @value{GDBN} may not stop until the next time
4591 the expression changes.
4593 @cindex software watchpoints
4594 @cindex hardware watchpoints
4595 Depending on your system, watchpoints may be implemented in software or
4596 hardware. @value{GDBN} does software watchpointing by single-stepping your
4597 program and testing the variable's value each time, which is hundreds of
4598 times slower than normal execution. (But this may still be worth it, to
4599 catch errors where you have no clue what part of your program is the
4602 On some systems, such as most PowerPC or x86-based targets,
4603 @value{GDBN} includes support for hardware watchpoints, which do not
4604 slow down the running of your program.
4608 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4609 Set a watchpoint for an expression. @value{GDBN} will break when the
4610 expression @var{expr} is written into by the program and its value
4611 changes. The simplest (and the most popular) use of this command is
4612 to watch the value of a single variable:
4615 (@value{GDBP}) watch foo
4618 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4619 argument, @value{GDBN} breaks only when the thread identified by
4620 @var{thread-id} changes the value of @var{expr}. If any other threads
4621 change the value of @var{expr}, @value{GDBN} will not break. Note
4622 that watchpoints restricted to a single thread in this way only work
4623 with Hardware Watchpoints.
4625 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4626 (see below). The @code{-location} argument tells @value{GDBN} to
4627 instead watch the memory referred to by @var{expr}. In this case,
4628 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4629 and watch the memory at that address. The type of the result is used
4630 to determine the size of the watched memory. If the expression's
4631 result does not have an address, then @value{GDBN} will print an
4634 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4635 of masked watchpoints, if the current architecture supports this
4636 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4637 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4638 to an address to watch. The mask specifies that some bits of an address
4639 (the bits which are reset in the mask) should be ignored when matching
4640 the address accessed by the inferior against the watchpoint address.
4641 Thus, a masked watchpoint watches many addresses simultaneously---those
4642 addresses whose unmasked bits are identical to the unmasked bits in the
4643 watchpoint address. The @code{mask} argument implies @code{-location}.
4647 (@value{GDBP}) watch foo mask 0xffff00ff
4648 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4652 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4653 Set a watchpoint that will break when the value of @var{expr} is read
4657 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4658 Set a watchpoint that will break when @var{expr} is either read from
4659 or written into by the program.
4661 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4662 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4663 This command prints a list of watchpoints, using the same format as
4664 @code{info break} (@pxref{Set Breaks}).
4667 If you watch for a change in a numerically entered address you need to
4668 dereference it, as the address itself is just a constant number which will
4669 never change. @value{GDBN} refuses to create a watchpoint that watches
4670 a never-changing value:
4673 (@value{GDBP}) watch 0x600850
4674 Cannot watch constant value 0x600850.
4675 (@value{GDBP}) watch *(int *) 0x600850
4676 Watchpoint 1: *(int *) 6293584
4679 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4680 watchpoints execute very quickly, and the debugger reports a change in
4681 value at the exact instruction where the change occurs. If @value{GDBN}
4682 cannot set a hardware watchpoint, it sets a software watchpoint, which
4683 executes more slowly and reports the change in value at the next
4684 @emph{statement}, not the instruction, after the change occurs.
4686 @cindex use only software watchpoints
4687 You can force @value{GDBN} to use only software watchpoints with the
4688 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4689 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4690 the underlying system supports them. (Note that hardware-assisted
4691 watchpoints that were set @emph{before} setting
4692 @code{can-use-hw-watchpoints} to zero will still use the hardware
4693 mechanism of watching expression values.)
4696 @item set can-use-hw-watchpoints
4697 @kindex set can-use-hw-watchpoints
4698 Set whether or not to use hardware watchpoints.
4700 @item show can-use-hw-watchpoints
4701 @kindex show can-use-hw-watchpoints
4702 Show the current mode of using hardware watchpoints.
4705 For remote targets, you can restrict the number of hardware
4706 watchpoints @value{GDBN} will use, see @ref{set remote
4707 hardware-breakpoint-limit}.
4709 When you issue the @code{watch} command, @value{GDBN} reports
4712 Hardware watchpoint @var{num}: @var{expr}
4716 if it was able to set a hardware watchpoint.
4718 Currently, the @code{awatch} and @code{rwatch} commands can only set
4719 hardware watchpoints, because accesses to data that don't change the
4720 value of the watched expression cannot be detected without examining
4721 every instruction as it is being executed, and @value{GDBN} does not do
4722 that currently. If @value{GDBN} finds that it is unable to set a
4723 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4724 will print a message like this:
4727 Expression cannot be implemented with read/access watchpoint.
4730 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4731 data type of the watched expression is wider than what a hardware
4732 watchpoint on the target machine can handle. For example, some systems
4733 can only watch regions that are up to 4 bytes wide; on such systems you
4734 cannot set hardware watchpoints for an expression that yields a
4735 double-precision floating-point number (which is typically 8 bytes
4736 wide). As a work-around, it might be possible to break the large region
4737 into a series of smaller ones and watch them with separate watchpoints.
4739 If you set too many hardware watchpoints, @value{GDBN} might be unable
4740 to insert all of them when you resume the execution of your program.
4741 Since the precise number of active watchpoints is unknown until such
4742 time as the program is about to be resumed, @value{GDBN} might not be
4743 able to warn you about this when you set the watchpoints, and the
4744 warning will be printed only when the program is resumed:
4747 Hardware watchpoint @var{num}: Could not insert watchpoint
4751 If this happens, delete or disable some of the watchpoints.
4753 Watching complex expressions that reference many variables can also
4754 exhaust the resources available for hardware-assisted watchpoints.
4755 That's because @value{GDBN} needs to watch every variable in the
4756 expression with separately allocated resources.
4758 If you call a function interactively using @code{print} or @code{call},
4759 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4760 kind of breakpoint or the call completes.
4762 @value{GDBN} automatically deletes watchpoints that watch local
4763 (automatic) variables, or expressions that involve such variables, when
4764 they go out of scope, that is, when the execution leaves the block in
4765 which these variables were defined. In particular, when the program
4766 being debugged terminates, @emph{all} local variables go out of scope,
4767 and so only watchpoints that watch global variables remain set. If you
4768 rerun the program, you will need to set all such watchpoints again. One
4769 way of doing that would be to set a code breakpoint at the entry to the
4770 @code{main} function and when it breaks, set all the watchpoints.
4772 @cindex watchpoints and threads
4773 @cindex threads and watchpoints
4774 In multi-threaded programs, watchpoints will detect changes to the
4775 watched expression from every thread.
4778 @emph{Warning:} In multi-threaded programs, software watchpoints
4779 have only limited usefulness. If @value{GDBN} creates a software
4780 watchpoint, it can only watch the value of an expression @emph{in a
4781 single thread}. If you are confident that the expression can only
4782 change due to the current thread's activity (and if you are also
4783 confident that no other thread can become current), then you can use
4784 software watchpoints as usual. However, @value{GDBN} may not notice
4785 when a non-current thread's activity changes the expression. (Hardware
4786 watchpoints, in contrast, watch an expression in all threads.)
4789 @xref{set remote hardware-watchpoint-limit}.
4791 @node Set Catchpoints
4792 @subsection Setting Catchpoints
4793 @cindex catchpoints, setting
4794 @cindex exception handlers
4795 @cindex event handling
4797 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4798 kinds of program events, such as C@t{++} exceptions or the loading of a
4799 shared library. Use the @code{catch} command to set a catchpoint.
4803 @item catch @var{event}
4804 Stop when @var{event} occurs. The @var{event} can be any of the following:
4807 @item throw @r{[}@var{regexp}@r{]}
4808 @itemx rethrow @r{[}@var{regexp}@r{]}
4809 @itemx catch @r{[}@var{regexp}@r{]}
4811 @kindex catch rethrow
4813 @cindex stop on C@t{++} exceptions
4814 The throwing, re-throwing, or catching of a C@t{++} exception.
4816 If @var{regexp} is given, then only exceptions whose type matches the
4817 regular expression will be caught.
4819 @vindex $_exception@r{, convenience variable}
4820 The convenience variable @code{$_exception} is available at an
4821 exception-related catchpoint, on some systems. This holds the
4822 exception being thrown.
4824 There are currently some limitations to C@t{++} exception handling in
4829 The support for these commands is system-dependent. Currently, only
4830 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4834 The regular expression feature and the @code{$_exception} convenience
4835 variable rely on the presence of some SDT probes in @code{libstdc++}.
4836 If these probes are not present, then these features cannot be used.
4837 These probes were first available in the GCC 4.8 release, but whether
4838 or not they are available in your GCC also depends on how it was
4842 The @code{$_exception} convenience variable is only valid at the
4843 instruction at which an exception-related catchpoint is set.
4846 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4847 location in the system library which implements runtime exception
4848 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4849 (@pxref{Selection}) to get to your code.
4852 If you call a function interactively, @value{GDBN} normally returns
4853 control to you when the function has finished executing. If the call
4854 raises an exception, however, the call may bypass the mechanism that
4855 returns control to you and cause your program either to abort or to
4856 simply continue running until it hits a breakpoint, catches a signal
4857 that @value{GDBN} is listening for, or exits. This is the case even if
4858 you set a catchpoint for the exception; catchpoints on exceptions are
4859 disabled within interactive calls. @xref{Calling}, for information on
4860 controlling this with @code{set unwind-on-terminating-exception}.
4863 You cannot raise an exception interactively.
4866 You cannot install an exception handler interactively.
4869 @item exception @r{[}@var{name}@r{]}
4870 @kindex catch exception
4871 @cindex Ada exception catching
4872 @cindex catch Ada exceptions
4873 An Ada exception being raised. If an exception name is specified
4874 at the end of the command (eg @code{catch exception Program_Error}),
4875 the debugger will stop only when this specific exception is raised.
4876 Otherwise, the debugger stops execution when any Ada exception is raised.
4878 When inserting an exception catchpoint on a user-defined exception whose
4879 name is identical to one of the exceptions defined by the language, the
4880 fully qualified name must be used as the exception name. Otherwise,
4881 @value{GDBN} will assume that it should stop on the pre-defined exception
4882 rather than the user-defined one. For instance, assuming an exception
4883 called @code{Constraint_Error} is defined in package @code{Pck}, then
4884 the command to use to catch such exceptions is @kbd{catch exception
4885 Pck.Constraint_Error}.
4887 @vindex $_ada_exception@r{, convenience variable}
4888 The convenience variable @code{$_ada_exception} holds the address of
4889 the exception being thrown. This can be useful when setting a
4890 condition for such a catchpoint.
4892 @item exception unhandled
4893 @kindex catch exception unhandled
4894 An exception that was raised but is not handled by the program. The
4895 convenience variable @code{$_ada_exception} is set as for @code{catch
4898 @item handlers @r{[}@var{name}@r{]}
4899 @kindex catch handlers
4900 @cindex Ada exception handlers catching
4901 @cindex catch Ada exceptions when handled
4902 An Ada exception being handled. If an exception name is
4903 specified at the end of the command
4904 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4905 only when this specific exception is handled.
4906 Otherwise, the debugger stops execution when any Ada exception is handled.
4908 When inserting a handlers catchpoint on a user-defined
4909 exception whose name is identical to one of the exceptions
4910 defined by the language, the fully qualified name must be used
4911 as the exception name. Otherwise, @value{GDBN} will assume that it
4912 should stop on the pre-defined exception rather than the
4913 user-defined one. For instance, assuming an exception called
4914 @code{Constraint_Error} is defined in package @code{Pck}, then the
4915 command to use to catch such exceptions handling is
4916 @kbd{catch handlers Pck.Constraint_Error}.
4918 The convenience variable @code{$_ada_exception} is set as for
4919 @code{catch exception}.
4922 @kindex catch assert
4923 A failed Ada assertion. Note that the convenience variable
4924 @code{$_ada_exception} is @emph{not} set by this catchpoint.
4928 @cindex break on fork/exec
4929 A call to @code{exec}.
4931 @anchor{catch syscall}
4933 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4934 @kindex catch syscall
4935 @cindex break on a system call.
4936 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4937 syscall is a mechanism for application programs to request a service
4938 from the operating system (OS) or one of the OS system services.
4939 @value{GDBN} can catch some or all of the syscalls issued by the
4940 debuggee, and show the related information for each syscall. If no
4941 argument is specified, calls to and returns from all system calls
4944 @var{name} can be any system call name that is valid for the
4945 underlying OS. Just what syscalls are valid depends on the OS. On
4946 GNU and Unix systems, you can find the full list of valid syscall
4947 names on @file{/usr/include/asm/unistd.h}.
4949 @c For MS-Windows, the syscall names and the corresponding numbers
4950 @c can be found, e.g., on this URL:
4951 @c http://www.metasploit.com/users/opcode/syscalls.html
4952 @c but we don't support Windows syscalls yet.
4954 Normally, @value{GDBN} knows in advance which syscalls are valid for
4955 each OS, so you can use the @value{GDBN} command-line completion
4956 facilities (@pxref{Completion,, command completion}) to list the
4959 You may also specify the system call numerically. A syscall's
4960 number is the value passed to the OS's syscall dispatcher to
4961 identify the requested service. When you specify the syscall by its
4962 name, @value{GDBN} uses its database of syscalls to convert the name
4963 into the corresponding numeric code, but using the number directly
4964 may be useful if @value{GDBN}'s database does not have the complete
4965 list of syscalls on your system (e.g., because @value{GDBN} lags
4966 behind the OS upgrades).
4968 You may specify a group of related syscalls to be caught at once using
4969 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4970 instance, on some platforms @value{GDBN} allows you to catch all
4971 network related syscalls, by passing the argument @code{group:network}
4972 to @code{catch syscall}. Note that not all syscall groups are
4973 available in every system. You can use the command completion
4974 facilities (@pxref{Completion,, command completion}) to list the
4975 syscall groups available on your environment.
4977 The example below illustrates how this command works if you don't provide
4981 (@value{GDBP}) catch syscall
4982 Catchpoint 1 (syscall)
4984 Starting program: /tmp/catch-syscall
4986 Catchpoint 1 (call to syscall 'close'), \
4987 0xffffe424 in __kernel_vsyscall ()
4991 Catchpoint 1 (returned from syscall 'close'), \
4992 0xffffe424 in __kernel_vsyscall ()
4996 Here is an example of catching a system call by name:
4999 (@value{GDBP}) catch syscall chroot
5000 Catchpoint 1 (syscall 'chroot' [61])
5002 Starting program: /tmp/catch-syscall
5004 Catchpoint 1 (call to syscall 'chroot'), \
5005 0xffffe424 in __kernel_vsyscall ()
5009 Catchpoint 1 (returned from syscall 'chroot'), \
5010 0xffffe424 in __kernel_vsyscall ()
5014 An example of specifying a system call numerically. In the case
5015 below, the syscall number has a corresponding entry in the XML
5016 file, so @value{GDBN} finds its name and prints it:
5019 (@value{GDBP}) catch syscall 252
5020 Catchpoint 1 (syscall(s) 'exit_group')
5022 Starting program: /tmp/catch-syscall
5024 Catchpoint 1 (call to syscall 'exit_group'), \
5025 0xffffe424 in __kernel_vsyscall ()
5029 Program exited normally.
5033 Here is an example of catching a syscall group:
5036 (@value{GDBP}) catch syscall group:process
5037 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5038 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5039 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5041 Starting program: /tmp/catch-syscall
5043 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5044 from /lib64/ld-linux-x86-64.so.2
5050 However, there can be situations when there is no corresponding name
5051 in XML file for that syscall number. In this case, @value{GDBN} prints
5052 a warning message saying that it was not able to find the syscall name,
5053 but the catchpoint will be set anyway. See the example below:
5056 (@value{GDBP}) catch syscall 764
5057 warning: The number '764' does not represent a known syscall.
5058 Catchpoint 2 (syscall 764)
5062 If you configure @value{GDBN} using the @samp{--without-expat} option,
5063 it will not be able to display syscall names. Also, if your
5064 architecture does not have an XML file describing its system calls,
5065 you will not be able to see the syscall names. It is important to
5066 notice that these two features are used for accessing the syscall
5067 name database. In either case, you will see a warning like this:
5070 (@value{GDBP}) catch syscall
5071 warning: Could not open "syscalls/i386-linux.xml"
5072 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5073 GDB will not be able to display syscall names.
5074 Catchpoint 1 (syscall)
5078 Of course, the file name will change depending on your architecture and system.
5080 Still using the example above, you can also try to catch a syscall by its
5081 number. In this case, you would see something like:
5084 (@value{GDBP}) catch syscall 252
5085 Catchpoint 1 (syscall(s) 252)
5088 Again, in this case @value{GDBN} would not be able to display syscall's names.
5092 A call to @code{fork}.
5096 A call to @code{vfork}.
5098 @item load @r{[}@var{regexp}@r{]}
5099 @itemx unload @r{[}@var{regexp}@r{]}
5101 @kindex catch unload
5102 The loading or unloading of a shared library. If @var{regexp} is
5103 given, then the catchpoint will stop only if the regular expression
5104 matches one of the affected libraries.
5106 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5107 @kindex catch signal
5108 The delivery of a signal.
5110 With no arguments, this catchpoint will catch any signal that is not
5111 used internally by @value{GDBN}, specifically, all signals except
5112 @samp{SIGTRAP} and @samp{SIGINT}.
5114 With the argument @samp{all}, all signals, including those used by
5115 @value{GDBN}, will be caught. This argument cannot be used with other
5118 Otherwise, the arguments are a list of signal names as given to
5119 @code{handle} (@pxref{Signals}). Only signals specified in this list
5122 One reason that @code{catch signal} can be more useful than
5123 @code{handle} is that you can attach commands and conditions to the
5126 When a signal is caught by a catchpoint, the signal's @code{stop} and
5127 @code{print} settings, as specified by @code{handle}, are ignored.
5128 However, whether the signal is still delivered to the inferior depends
5129 on the @code{pass} setting; this can be changed in the catchpoint's
5134 @item tcatch @var{event}
5136 Set a catchpoint that is enabled only for one stop. The catchpoint is
5137 automatically deleted after the first time the event is caught.
5141 Use the @code{info break} command to list the current catchpoints.
5145 @subsection Deleting Breakpoints
5147 @cindex clearing breakpoints, watchpoints, catchpoints
5148 @cindex deleting breakpoints, watchpoints, catchpoints
5149 It is often necessary to eliminate a breakpoint, watchpoint, or
5150 catchpoint once it has done its job and you no longer want your program
5151 to stop there. This is called @dfn{deleting} the breakpoint. A
5152 breakpoint that has been deleted no longer exists; it is forgotten.
5154 With the @code{clear} command you can delete breakpoints according to
5155 where they are in your program. With the @code{delete} command you can
5156 delete individual breakpoints, watchpoints, or catchpoints by specifying
5157 their breakpoint numbers.
5159 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5160 automatically ignores breakpoints on the first instruction to be executed
5161 when you continue execution without changing the execution address.
5166 Delete any breakpoints at the next instruction to be executed in the
5167 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5168 the innermost frame is selected, this is a good way to delete a
5169 breakpoint where your program just stopped.
5171 @item clear @var{location}
5172 Delete any breakpoints set at the specified @var{location}.
5173 @xref{Specify Location}, for the various forms of @var{location}; the
5174 most useful ones are listed below:
5177 @item clear @var{function}
5178 @itemx clear @var{filename}:@var{function}
5179 Delete any breakpoints set at entry to the named @var{function}.
5181 @item clear @var{linenum}
5182 @itemx clear @var{filename}:@var{linenum}
5183 Delete any breakpoints set at or within the code of the specified
5184 @var{linenum} of the specified @var{filename}.
5187 @cindex delete breakpoints
5189 @kindex d @r{(@code{delete})}
5190 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5191 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5192 list specified as argument. If no argument is specified, delete all
5193 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5194 confirm off}). You can abbreviate this command as @code{d}.
5198 @subsection Disabling Breakpoints
5200 @cindex enable/disable a breakpoint
5201 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5202 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5203 it had been deleted, but remembers the information on the breakpoint so
5204 that you can @dfn{enable} it again later.
5206 You disable and enable breakpoints, watchpoints, and catchpoints with
5207 the @code{enable} and @code{disable} commands, optionally specifying
5208 one or more breakpoint numbers as arguments. Use @code{info break} to
5209 print a list of all breakpoints, watchpoints, and catchpoints if you
5210 do not know which numbers to use.
5212 Disabling and enabling a breakpoint that has multiple locations
5213 affects all of its locations.
5215 A breakpoint, watchpoint, or catchpoint can have any of several
5216 different states of enablement:
5220 Enabled. The breakpoint stops your program. A breakpoint set
5221 with the @code{break} command starts out in this state.
5223 Disabled. The breakpoint has no effect on your program.
5225 Enabled once. The breakpoint stops your program, but then becomes
5228 Enabled for a count. The breakpoint stops your program for the next
5229 N times, then becomes disabled.
5231 Enabled for deletion. The breakpoint stops your program, but
5232 immediately after it does so it is deleted permanently. A breakpoint
5233 set with the @code{tbreak} command starts out in this state.
5236 You can use the following commands to enable or disable breakpoints,
5237 watchpoints, and catchpoints:
5241 @kindex dis @r{(@code{disable})}
5242 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5243 Disable the specified breakpoints---or all breakpoints, if none are
5244 listed. A disabled breakpoint has no effect but is not forgotten. All
5245 options such as ignore-counts, conditions and commands are remembered in
5246 case the breakpoint is enabled again later. You may abbreviate
5247 @code{disable} as @code{dis}.
5250 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5251 Enable the specified breakpoints (or all defined breakpoints). They
5252 become effective once again in stopping your program.
5254 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5255 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5256 of these breakpoints immediately after stopping your program.
5258 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5259 Enable the specified breakpoints temporarily. @value{GDBN} records
5260 @var{count} with each of the specified breakpoints, and decrements a
5261 breakpoint's count when it is hit. When any count reaches 0,
5262 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5263 count (@pxref{Conditions, ,Break Conditions}), that will be
5264 decremented to 0 before @var{count} is affected.
5266 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5267 Enable the specified breakpoints to work once, then die. @value{GDBN}
5268 deletes any of these breakpoints as soon as your program stops there.
5269 Breakpoints set by the @code{tbreak} command start out in this state.
5272 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5273 @c confusing: tbreak is also initially enabled.
5274 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5275 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5276 subsequently, they become disabled or enabled only when you use one of
5277 the commands above. (The command @code{until} can set and delete a
5278 breakpoint of its own, but it does not change the state of your other
5279 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5283 @subsection Break Conditions
5284 @cindex conditional breakpoints
5285 @cindex breakpoint conditions
5287 @c FIXME what is scope of break condition expr? Context where wanted?
5288 @c in particular for a watchpoint?
5289 The simplest sort of breakpoint breaks every time your program reaches a
5290 specified place. You can also specify a @dfn{condition} for a
5291 breakpoint. A condition is just a Boolean expression in your
5292 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5293 a condition evaluates the expression each time your program reaches it,
5294 and your program stops only if the condition is @emph{true}.
5296 This is the converse of using assertions for program validation; in that
5297 situation, you want to stop when the assertion is violated---that is,
5298 when the condition is false. In C, if you want to test an assertion expressed
5299 by the condition @var{assert}, you should set the condition
5300 @samp{! @var{assert}} on the appropriate breakpoint.
5302 Conditions are also accepted for watchpoints; you may not need them,
5303 since a watchpoint is inspecting the value of an expression anyhow---but
5304 it might be simpler, say, to just set a watchpoint on a variable name,
5305 and specify a condition that tests whether the new value is an interesting
5308 Break conditions can have side effects, and may even call functions in
5309 your program. This can be useful, for example, to activate functions
5310 that log program progress, or to use your own print functions to
5311 format special data structures. The effects are completely predictable
5312 unless there is another enabled breakpoint at the same address. (In
5313 that case, @value{GDBN} might see the other breakpoint first and stop your
5314 program without checking the condition of this one.) Note that
5315 breakpoint commands are usually more convenient and flexible than break
5317 purpose of performing side effects when a breakpoint is reached
5318 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5320 Breakpoint conditions can also be evaluated on the target's side if
5321 the target supports it. Instead of evaluating the conditions locally,
5322 @value{GDBN} encodes the expression into an agent expression
5323 (@pxref{Agent Expressions}) suitable for execution on the target,
5324 independently of @value{GDBN}. Global variables become raw memory
5325 locations, locals become stack accesses, and so forth.
5327 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5328 when its condition evaluates to true. This mechanism may provide faster
5329 response times depending on the performance characteristics of the target
5330 since it does not need to keep @value{GDBN} informed about
5331 every breakpoint trigger, even those with false conditions.
5333 Break conditions can be specified when a breakpoint is set, by using
5334 @samp{if} in the arguments to the @code{break} command. @xref{Set
5335 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5336 with the @code{condition} command.
5338 You can also use the @code{if} keyword with the @code{watch} command.
5339 The @code{catch} command does not recognize the @code{if} keyword;
5340 @code{condition} is the only way to impose a further condition on a
5345 @item condition @var{bnum} @var{expression}
5346 Specify @var{expression} as the break condition for breakpoint,
5347 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5348 breakpoint @var{bnum} stops your program only if the value of
5349 @var{expression} is true (nonzero, in C). When you use
5350 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5351 syntactic correctness, and to determine whether symbols in it have
5352 referents in the context of your breakpoint. If @var{expression} uses
5353 symbols not referenced in the context of the breakpoint, @value{GDBN}
5354 prints an error message:
5357 No symbol "foo" in current context.
5362 not actually evaluate @var{expression} at the time the @code{condition}
5363 command (or a command that sets a breakpoint with a condition, like
5364 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5366 @item condition @var{bnum}
5367 Remove the condition from breakpoint number @var{bnum}. It becomes
5368 an ordinary unconditional breakpoint.
5371 @cindex ignore count (of breakpoint)
5372 A special case of a breakpoint condition is to stop only when the
5373 breakpoint has been reached a certain number of times. This is so
5374 useful that there is a special way to do it, using the @dfn{ignore
5375 count} of the breakpoint. Every breakpoint has an ignore count, which
5376 is an integer. Most of the time, the ignore count is zero, and
5377 therefore has no effect. But if your program reaches a breakpoint whose
5378 ignore count is positive, then instead of stopping, it just decrements
5379 the ignore count by one and continues. As a result, if the ignore count
5380 value is @var{n}, the breakpoint does not stop the next @var{n} times
5381 your program reaches it.
5385 @item ignore @var{bnum} @var{count}
5386 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5387 The next @var{count} times the breakpoint is reached, your program's
5388 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5391 To make the breakpoint stop the next time it is reached, specify
5394 When you use @code{continue} to resume execution of your program from a
5395 breakpoint, you can specify an ignore count directly as an argument to
5396 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5397 Stepping,,Continuing and Stepping}.
5399 If a breakpoint has a positive ignore count and a condition, the
5400 condition is not checked. Once the ignore count reaches zero,
5401 @value{GDBN} resumes checking the condition.
5403 You could achieve the effect of the ignore count with a condition such
5404 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5405 is decremented each time. @xref{Convenience Vars, ,Convenience
5409 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5412 @node Break Commands
5413 @subsection Breakpoint Command Lists
5415 @cindex breakpoint commands
5416 You can give any breakpoint (or watchpoint or catchpoint) a series of
5417 commands to execute when your program stops due to that breakpoint. For
5418 example, you might want to print the values of certain expressions, or
5419 enable other breakpoints.
5423 @kindex end@r{ (breakpoint commands)}
5424 @item commands @r{[}@var{list}@dots{}@r{]}
5425 @itemx @dots{} @var{command-list} @dots{}
5427 Specify a list of commands for the given breakpoints. The commands
5428 themselves appear on the following lines. Type a line containing just
5429 @code{end} to terminate the commands.
5431 To remove all commands from a breakpoint, type @code{commands} and
5432 follow it immediately with @code{end}; that is, give no commands.
5434 With no argument, @code{commands} refers to the last breakpoint,
5435 watchpoint, or catchpoint set (not to the breakpoint most recently
5436 encountered). If the most recent breakpoints were set with a single
5437 command, then the @code{commands} will apply to all the breakpoints
5438 set by that command. This applies to breakpoints set by
5439 @code{rbreak}, and also applies when a single @code{break} command
5440 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5444 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5445 disabled within a @var{command-list}.
5447 You can use breakpoint commands to start your program up again. Simply
5448 use the @code{continue} command, or @code{step}, or any other command
5449 that resumes execution.
5451 Any other commands in the command list, after a command that resumes
5452 execution, are ignored. This is because any time you resume execution
5453 (even with a simple @code{next} or @code{step}), you may encounter
5454 another breakpoint---which could have its own command list, leading to
5455 ambiguities about which list to execute.
5458 If the first command you specify in a command list is @code{silent}, the
5459 usual message about stopping at a breakpoint is not printed. This may
5460 be desirable for breakpoints that are to print a specific message and
5461 then continue. If none of the remaining commands print anything, you
5462 see no sign that the breakpoint was reached. @code{silent} is
5463 meaningful only at the beginning of a breakpoint command list.
5465 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5466 print precisely controlled output, and are often useful in silent
5467 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5469 For example, here is how you could use breakpoint commands to print the
5470 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5476 printf "x is %d\n",x
5481 One application for breakpoint commands is to compensate for one bug so
5482 you can test for another. Put a breakpoint just after the erroneous line
5483 of code, give it a condition to detect the case in which something
5484 erroneous has been done, and give it commands to assign correct values
5485 to any variables that need them. End with the @code{continue} command
5486 so that your program does not stop, and start with the @code{silent}
5487 command so that no output is produced. Here is an example:
5498 @node Dynamic Printf
5499 @subsection Dynamic Printf
5501 @cindex dynamic printf
5503 The dynamic printf command @code{dprintf} combines a breakpoint with
5504 formatted printing of your program's data to give you the effect of
5505 inserting @code{printf} calls into your program on-the-fly, without
5506 having to recompile it.
5508 In its most basic form, the output goes to the GDB console. However,
5509 you can set the variable @code{dprintf-style} for alternate handling.
5510 For instance, you can ask to format the output by calling your
5511 program's @code{printf} function. This has the advantage that the
5512 characters go to the program's output device, so they can recorded in
5513 redirects to files and so forth.
5515 If you are doing remote debugging with a stub or agent, you can also
5516 ask to have the printf handled by the remote agent. In addition to
5517 ensuring that the output goes to the remote program's device along
5518 with any other output the program might produce, you can also ask that
5519 the dprintf remain active even after disconnecting from the remote
5520 target. Using the stub/agent is also more efficient, as it can do
5521 everything without needing to communicate with @value{GDBN}.
5525 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5526 Whenever execution reaches @var{location}, print the values of one or
5527 more @var{expressions} under the control of the string @var{template}.
5528 To print several values, separate them with commas.
5530 @item set dprintf-style @var{style}
5531 Set the dprintf output to be handled in one of several different
5532 styles enumerated below. A change of style affects all existing
5533 dynamic printfs immediately. (If you need individual control over the
5534 print commands, simply define normal breakpoints with
5535 explicitly-supplied command lists.)
5539 @kindex dprintf-style gdb
5540 Handle the output using the @value{GDBN} @code{printf} command.
5543 @kindex dprintf-style call
5544 Handle the output by calling a function in your program (normally
5548 @kindex dprintf-style agent
5549 Have the remote debugging agent (such as @code{gdbserver}) handle
5550 the output itself. This style is only available for agents that
5551 support running commands on the target.
5554 @item set dprintf-function @var{function}
5555 Set the function to call if the dprintf style is @code{call}. By
5556 default its value is @code{printf}. You may set it to any expression.
5557 that @value{GDBN} can evaluate to a function, as per the @code{call}
5560 @item set dprintf-channel @var{channel}
5561 Set a ``channel'' for dprintf. If set to a non-empty value,
5562 @value{GDBN} will evaluate it as an expression and pass the result as
5563 a first argument to the @code{dprintf-function}, in the manner of
5564 @code{fprintf} and similar functions. Otherwise, the dprintf format
5565 string will be the first argument, in the manner of @code{printf}.
5567 As an example, if you wanted @code{dprintf} output to go to a logfile
5568 that is a standard I/O stream assigned to the variable @code{mylog},
5569 you could do the following:
5572 (gdb) set dprintf-style call
5573 (gdb) set dprintf-function fprintf
5574 (gdb) set dprintf-channel mylog
5575 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5576 Dprintf 1 at 0x123456: file main.c, line 25.
5578 1 dprintf keep y 0x00123456 in main at main.c:25
5579 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5584 Note that the @code{info break} displays the dynamic printf commands
5585 as normal breakpoint commands; you can thus easily see the effect of
5586 the variable settings.
5588 @item set disconnected-dprintf on
5589 @itemx set disconnected-dprintf off
5590 @kindex set disconnected-dprintf
5591 Choose whether @code{dprintf} commands should continue to run if
5592 @value{GDBN} has disconnected from the target. This only applies
5593 if the @code{dprintf-style} is @code{agent}.
5595 @item show disconnected-dprintf off
5596 @kindex show disconnected-dprintf
5597 Show the current choice for disconnected @code{dprintf}.
5601 @value{GDBN} does not check the validity of function and channel,
5602 relying on you to supply values that are meaningful for the contexts
5603 in which they are being used. For instance, the function and channel
5604 may be the values of local variables, but if that is the case, then
5605 all enabled dynamic prints must be at locations within the scope of
5606 those locals. If evaluation fails, @value{GDBN} will report an error.
5608 @node Save Breakpoints
5609 @subsection How to save breakpoints to a file
5611 To save breakpoint definitions to a file use the @w{@code{save
5612 breakpoints}} command.
5615 @kindex save breakpoints
5616 @cindex save breakpoints to a file for future sessions
5617 @item save breakpoints [@var{filename}]
5618 This command saves all current breakpoint definitions together with
5619 their commands and ignore counts, into a file @file{@var{filename}}
5620 suitable for use in a later debugging session. This includes all
5621 types of breakpoints (breakpoints, watchpoints, catchpoints,
5622 tracepoints). To read the saved breakpoint definitions, use the
5623 @code{source} command (@pxref{Command Files}). Note that watchpoints
5624 with expressions involving local variables may fail to be recreated
5625 because it may not be possible to access the context where the
5626 watchpoint is valid anymore. Because the saved breakpoint definitions
5627 are simply a sequence of @value{GDBN} commands that recreate the
5628 breakpoints, you can edit the file in your favorite editing program,
5629 and remove the breakpoint definitions you're not interested in, or
5630 that can no longer be recreated.
5633 @node Static Probe Points
5634 @subsection Static Probe Points
5636 @cindex static probe point, SystemTap
5637 @cindex static probe point, DTrace
5638 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5639 for Statically Defined Tracing, and the probes are designed to have a tiny
5640 runtime code and data footprint, and no dynamic relocations.
5642 Currently, the following types of probes are supported on
5643 ELF-compatible systems:
5647 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5648 @acronym{SDT} probes@footnote{See
5649 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5650 for more information on how to add @code{SystemTap} @acronym{SDT}
5651 probes in your applications.}. @code{SystemTap} probes are usable
5652 from assembly, C and C@t{++} languages@footnote{See
5653 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5654 for a good reference on how the @acronym{SDT} probes are implemented.}.
5656 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5657 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5661 @cindex semaphores on static probe points
5662 Some @code{SystemTap} probes have an associated semaphore variable;
5663 for instance, this happens automatically if you defined your probe
5664 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5665 @value{GDBN} will automatically enable it when you specify a
5666 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5667 breakpoint at a probe's location by some other method (e.g.,
5668 @code{break file:line}), then @value{GDBN} will not automatically set
5669 the semaphore. @code{DTrace} probes do not support semaphores.
5671 You can examine the available static static probes using @code{info
5672 probes}, with optional arguments:
5676 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5677 If given, @var{type} is either @code{stap} for listing
5678 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5679 probes. If omitted all probes are listed regardless of their types.
5681 If given, @var{provider} is a regular expression used to match against provider
5682 names when selecting which probes to list. If omitted, probes by all
5683 probes from all providers are listed.
5685 If given, @var{name} is a regular expression to match against probe names
5686 when selecting which probes to list. If omitted, probe names are not
5687 considered when deciding whether to display them.
5689 If given, @var{objfile} is a regular expression used to select which
5690 object files (executable or shared libraries) to examine. If not
5691 given, all object files are considered.
5693 @item info probes all
5694 List the available static probes, from all types.
5697 @cindex enabling and disabling probes
5698 Some probe points can be enabled and/or disabled. The effect of
5699 enabling or disabling a probe depends on the type of probe being
5700 handled. Some @code{DTrace} probes can be enabled or
5701 disabled, but @code{SystemTap} probes cannot be disabled.
5703 You can enable (or disable) one or more probes using the following
5704 commands, with optional arguments:
5707 @kindex enable probes
5708 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5709 If given, @var{provider} is a regular expression used to match against
5710 provider names when selecting which probes to enable. If omitted,
5711 all probes from all providers are enabled.
5713 If given, @var{name} is a regular expression to match against probe
5714 names when selecting which probes to enable. If omitted, probe names
5715 are not considered when deciding whether to enable them.
5717 If given, @var{objfile} is a regular expression used to select which
5718 object files (executable or shared libraries) to examine. If not
5719 given, all object files are considered.
5721 @kindex disable probes
5722 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5723 See the @code{enable probes} command above for a description of the
5724 optional arguments accepted by this command.
5727 @vindex $_probe_arg@r{, convenience variable}
5728 A probe may specify up to twelve arguments. These are available at the
5729 point at which the probe is defined---that is, when the current PC is
5730 at the probe's location. The arguments are available using the
5731 convenience variables (@pxref{Convenience Vars})
5732 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5733 probes each probe argument is an integer of the appropriate size;
5734 types are not preserved. In @code{DTrace} probes types are preserved
5735 provided that they are recognized as such by @value{GDBN}; otherwise
5736 the value of the probe argument will be a long integer. The
5737 convenience variable @code{$_probe_argc} holds the number of arguments
5738 at the current probe point.
5740 These variables are always available, but attempts to access them at
5741 any location other than a probe point will cause @value{GDBN} to give
5745 @c @ifclear BARETARGET
5746 @node Error in Breakpoints
5747 @subsection ``Cannot insert breakpoints''
5749 If you request too many active hardware-assisted breakpoints and
5750 watchpoints, you will see this error message:
5752 @c FIXME: the precise wording of this message may change; the relevant
5753 @c source change is not committed yet (Sep 3, 1999).
5755 Stopped; cannot insert breakpoints.
5756 You may have requested too many hardware breakpoints and watchpoints.
5760 This message is printed when you attempt to resume the program, since
5761 only then @value{GDBN} knows exactly how many hardware breakpoints and
5762 watchpoints it needs to insert.
5764 When this message is printed, you need to disable or remove some of the
5765 hardware-assisted breakpoints and watchpoints, and then continue.
5767 @node Breakpoint-related Warnings
5768 @subsection ``Breakpoint address adjusted...''
5769 @cindex breakpoint address adjusted
5771 Some processor architectures place constraints on the addresses at
5772 which breakpoints may be placed. For architectures thus constrained,
5773 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5774 with the constraints dictated by the architecture.
5776 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5777 a VLIW architecture in which a number of RISC-like instructions may be
5778 bundled together for parallel execution. The FR-V architecture
5779 constrains the location of a breakpoint instruction within such a
5780 bundle to the instruction with the lowest address. @value{GDBN}
5781 honors this constraint by adjusting a breakpoint's address to the
5782 first in the bundle.
5784 It is not uncommon for optimized code to have bundles which contain
5785 instructions from different source statements, thus it may happen that
5786 a breakpoint's address will be adjusted from one source statement to
5787 another. Since this adjustment may significantly alter @value{GDBN}'s
5788 breakpoint related behavior from what the user expects, a warning is
5789 printed when the breakpoint is first set and also when the breakpoint
5792 A warning like the one below is printed when setting a breakpoint
5793 that's been subject to address adjustment:
5796 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5799 Such warnings are printed both for user settable and @value{GDBN}'s
5800 internal breakpoints. If you see one of these warnings, you should
5801 verify that a breakpoint set at the adjusted address will have the
5802 desired affect. If not, the breakpoint in question may be removed and
5803 other breakpoints may be set which will have the desired behavior.
5804 E.g., it may be sufficient to place the breakpoint at a later
5805 instruction. A conditional breakpoint may also be useful in some
5806 cases to prevent the breakpoint from triggering too often.
5808 @value{GDBN} will also issue a warning when stopping at one of these
5809 adjusted breakpoints:
5812 warning: Breakpoint 1 address previously adjusted from 0x00010414
5816 When this warning is encountered, it may be too late to take remedial
5817 action except in cases where the breakpoint is hit earlier or more
5818 frequently than expected.
5820 @node Continuing and Stepping
5821 @section Continuing and Stepping
5825 @cindex resuming execution
5826 @dfn{Continuing} means resuming program execution until your program
5827 completes normally. In contrast, @dfn{stepping} means executing just
5828 one more ``step'' of your program, where ``step'' may mean either one
5829 line of source code, or one machine instruction (depending on what
5830 particular command you use). Either when continuing or when stepping,
5831 your program may stop even sooner, due to a breakpoint or a signal. (If
5832 it stops due to a signal, you may want to use @code{handle}, or use
5833 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5834 or you may step into the signal's handler (@pxref{stepping and signal
5839 @kindex c @r{(@code{continue})}
5840 @kindex fg @r{(resume foreground execution)}
5841 @item continue @r{[}@var{ignore-count}@r{]}
5842 @itemx c @r{[}@var{ignore-count}@r{]}
5843 @itemx fg @r{[}@var{ignore-count}@r{]}
5844 Resume program execution, at the address where your program last stopped;
5845 any breakpoints set at that address are bypassed. The optional argument
5846 @var{ignore-count} allows you to specify a further number of times to
5847 ignore a breakpoint at this location; its effect is like that of
5848 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5850 The argument @var{ignore-count} is meaningful only when your program
5851 stopped due to a breakpoint. At other times, the argument to
5852 @code{continue} is ignored.
5854 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5855 debugged program is deemed to be the foreground program) are provided
5856 purely for convenience, and have exactly the same behavior as
5860 To resume execution at a different place, you can use @code{return}
5861 (@pxref{Returning, ,Returning from a Function}) to go back to the
5862 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5863 Different Address}) to go to an arbitrary location in your program.
5865 A typical technique for using stepping is to set a breakpoint
5866 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5867 beginning of the function or the section of your program where a problem
5868 is believed to lie, run your program until it stops at that breakpoint,
5869 and then step through the suspect area, examining the variables that are
5870 interesting, until you see the problem happen.
5874 @kindex s @r{(@code{step})}
5876 Continue running your program until control reaches a different source
5877 line, then stop it and return control to @value{GDBN}. This command is
5878 abbreviated @code{s}.
5881 @c "without debugging information" is imprecise; actually "without line
5882 @c numbers in the debugging information". (gcc -g1 has debugging info but
5883 @c not line numbers). But it seems complex to try to make that
5884 @c distinction here.
5885 @emph{Warning:} If you use the @code{step} command while control is
5886 within a function that was compiled without debugging information,
5887 execution proceeds until control reaches a function that does have
5888 debugging information. Likewise, it will not step into a function which
5889 is compiled without debugging information. To step through functions
5890 without debugging information, use the @code{stepi} command, described
5894 The @code{step} command only stops at the first instruction of a source
5895 line. This prevents the multiple stops that could otherwise occur in
5896 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5897 to stop if a function that has debugging information is called within
5898 the line. In other words, @code{step} @emph{steps inside} any functions
5899 called within the line.
5901 Also, the @code{step} command only enters a function if there is line
5902 number information for the function. Otherwise it acts like the
5903 @code{next} command. This avoids problems when using @code{cc -gl}
5904 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5905 was any debugging information about the routine.
5907 @item step @var{count}
5908 Continue running as in @code{step}, but do so @var{count} times. If a
5909 breakpoint is reached, or a signal not related to stepping occurs before
5910 @var{count} steps, stepping stops right away.
5913 @kindex n @r{(@code{next})}
5914 @item next @r{[}@var{count}@r{]}
5915 Continue to the next source line in the current (innermost) stack frame.
5916 This is similar to @code{step}, but function calls that appear within
5917 the line of code are executed without stopping. Execution stops when
5918 control reaches a different line of code at the original stack level
5919 that was executing when you gave the @code{next} command. This command
5920 is abbreviated @code{n}.
5922 An argument @var{count} is a repeat count, as for @code{step}.
5925 @c FIX ME!! Do we delete this, or is there a way it fits in with
5926 @c the following paragraph? --- Vctoria
5928 @c @code{next} within a function that lacks debugging information acts like
5929 @c @code{step}, but any function calls appearing within the code of the
5930 @c function are executed without stopping.
5932 The @code{next} command only stops at the first instruction of a
5933 source line. This prevents multiple stops that could otherwise occur in
5934 @code{switch} statements, @code{for} loops, etc.
5936 @kindex set step-mode
5938 @cindex functions without line info, and stepping
5939 @cindex stepping into functions with no line info
5940 @itemx set step-mode on
5941 The @code{set step-mode on} command causes the @code{step} command to
5942 stop at the first instruction of a function which contains no debug line
5943 information rather than stepping over it.
5945 This is useful in cases where you may be interested in inspecting the
5946 machine instructions of a function which has no symbolic info and do not
5947 want @value{GDBN} to automatically skip over this function.
5949 @item set step-mode off
5950 Causes the @code{step} command to step over any functions which contains no
5951 debug information. This is the default.
5953 @item show step-mode
5954 Show whether @value{GDBN} will stop in or step over functions without
5955 source line debug information.
5958 @kindex fin @r{(@code{finish})}
5960 Continue running until just after function in the selected stack frame
5961 returns. Print the returned value (if any). This command can be
5962 abbreviated as @code{fin}.
5964 Contrast this with the @code{return} command (@pxref{Returning,
5965 ,Returning from a Function}).
5967 @kindex set print finish
5968 @kindex show print finish
5969 @item set print finish @r{[}on|off@r{]}
5970 @itemx show print finish
5971 By default the @code{finish} command will show the value that is
5972 returned by the function. This can be disabled using @code{set print
5973 finish off}. When disabled, the value is still entered into the value
5974 history (@pxref{Value History}), but not displayed.
5977 @kindex u @r{(@code{until})}
5978 @cindex run until specified location
5981 Continue running until a source line past the current line, in the
5982 current stack frame, is reached. This command is used to avoid single
5983 stepping through a loop more than once. It is like the @code{next}
5984 command, except that when @code{until} encounters a jump, it
5985 automatically continues execution until the program counter is greater
5986 than the address of the jump.
5988 This means that when you reach the end of a loop after single stepping
5989 though it, @code{until} makes your program continue execution until it
5990 exits the loop. In contrast, a @code{next} command at the end of a loop
5991 simply steps back to the beginning of the loop, which forces you to step
5992 through the next iteration.
5994 @code{until} always stops your program if it attempts to exit the current
5997 @code{until} may produce somewhat counterintuitive results if the order
5998 of machine code does not match the order of the source lines. For
5999 example, in the following excerpt from a debugging session, the @code{f}
6000 (@code{frame}) command shows that execution is stopped at line
6001 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6005 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6007 (@value{GDBP}) until
6008 195 for ( ; argc > 0; NEXTARG) @{
6011 This happened because, for execution efficiency, the compiler had
6012 generated code for the loop closure test at the end, rather than the
6013 start, of the loop---even though the test in a C @code{for}-loop is
6014 written before the body of the loop. The @code{until} command appeared
6015 to step back to the beginning of the loop when it advanced to this
6016 expression; however, it has not really gone to an earlier
6017 statement---not in terms of the actual machine code.
6019 @code{until} with no argument works by means of single
6020 instruction stepping, and hence is slower than @code{until} with an
6023 @item until @var{location}
6024 @itemx u @var{location}
6025 Continue running your program until either the specified @var{location} is
6026 reached, or the current stack frame returns. The location is any of
6027 the forms described in @ref{Specify Location}.
6028 This form of the command uses temporary breakpoints, and
6029 hence is quicker than @code{until} without an argument. The specified
6030 location is actually reached only if it is in the current frame. This
6031 implies that @code{until} can be used to skip over recursive function
6032 invocations. For instance in the code below, if the current location is
6033 line @code{96}, issuing @code{until 99} will execute the program up to
6034 line @code{99} in the same invocation of factorial, i.e., after the inner
6035 invocations have returned.
6038 94 int factorial (int value)
6040 96 if (value > 1) @{
6041 97 value *= factorial (value - 1);
6048 @kindex advance @var{location}
6049 @item advance @var{location}
6050 Continue running the program up to the given @var{location}. An argument is
6051 required, which should be of one of the forms described in
6052 @ref{Specify Location}.
6053 Execution will also stop upon exit from the current stack
6054 frame. This command is similar to @code{until}, but @code{advance} will
6055 not skip over recursive function calls, and the target location doesn't
6056 have to be in the same frame as the current one.
6060 @kindex si @r{(@code{stepi})}
6062 @itemx stepi @var{arg}
6064 Execute one machine instruction, then stop and return to the debugger.
6066 It is often useful to do @samp{display/i $pc} when stepping by machine
6067 instructions. This makes @value{GDBN} automatically display the next
6068 instruction to be executed, each time your program stops. @xref{Auto
6069 Display,, Automatic Display}.
6071 An argument is a repeat count, as in @code{step}.
6075 @kindex ni @r{(@code{nexti})}
6077 @itemx nexti @var{arg}
6079 Execute one machine instruction, but if it is a function call,
6080 proceed until the function returns.
6082 An argument is a repeat count, as in @code{next}.
6086 @anchor{range stepping}
6087 @cindex range stepping
6088 @cindex target-assisted range stepping
6089 By default, and if available, @value{GDBN} makes use of
6090 target-assisted @dfn{range stepping}. In other words, whenever you
6091 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6092 tells the target to step the corresponding range of instruction
6093 addresses instead of issuing multiple single-steps. This speeds up
6094 line stepping, particularly for remote targets. Ideally, there should
6095 be no reason you would want to turn range stepping off. However, it's
6096 possible that a bug in the debug info, a bug in the remote stub (for
6097 remote targets), or even a bug in @value{GDBN} could make line
6098 stepping behave incorrectly when target-assisted range stepping is
6099 enabled. You can use the following command to turn off range stepping
6103 @kindex set range-stepping
6104 @kindex show range-stepping
6105 @item set range-stepping
6106 @itemx show range-stepping
6107 Control whether range stepping is enabled.
6109 If @code{on}, and the target supports it, @value{GDBN} tells the
6110 target to step a range of addresses itself, instead of issuing
6111 multiple single-steps. If @code{off}, @value{GDBN} always issues
6112 single-steps, even if range stepping is supported by the target. The
6113 default is @code{on}.
6117 @node Skipping Over Functions and Files
6118 @section Skipping Over Functions and Files
6119 @cindex skipping over functions and files
6121 The program you are debugging may contain some functions which are
6122 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6123 skip a function, all functions in a file or a particular function in
6124 a particular file when stepping.
6126 For example, consider the following C function:
6137 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6138 are not interested in stepping through @code{boring}. If you run @code{step}
6139 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6140 step over both @code{foo} and @code{boring}!
6142 One solution is to @code{step} into @code{boring} and use the @code{finish}
6143 command to immediately exit it. But this can become tedious if @code{boring}
6144 is called from many places.
6146 A more flexible solution is to execute @kbd{skip boring}. This instructs
6147 @value{GDBN} never to step into @code{boring}. Now when you execute
6148 @code{step} at line 103, you'll step over @code{boring} and directly into
6151 Functions may be skipped by providing either a function name, linespec
6152 (@pxref{Specify Location}), regular expression that matches the function's
6153 name, file name or a @code{glob}-style pattern that matches the file name.
6155 On Posix systems the form of the regular expression is
6156 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6157 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6158 expression is whatever is provided by the @code{regcomp} function of
6159 the underlying system.
6160 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6161 description of @code{glob}-style patterns.
6165 @item skip @r{[}@var{options}@r{]}
6166 The basic form of the @code{skip} command takes zero or more options
6167 that specify what to skip.
6168 The @var{options} argument is any useful combination of the following:
6171 @item -file @var{file}
6172 @itemx -fi @var{file}
6173 Functions in @var{file} will be skipped over when stepping.
6175 @item -gfile @var{file-glob-pattern}
6176 @itemx -gfi @var{file-glob-pattern}
6177 @cindex skipping over files via glob-style patterns
6178 Functions in files matching @var{file-glob-pattern} will be skipped
6182 (gdb) skip -gfi utils/*.c
6185 @item -function @var{linespec}
6186 @itemx -fu @var{linespec}
6187 Functions named by @var{linespec} or the function containing the line
6188 named by @var{linespec} will be skipped over when stepping.
6189 @xref{Specify Location}.
6191 @item -rfunction @var{regexp}
6192 @itemx -rfu @var{regexp}
6193 @cindex skipping over functions via regular expressions
6194 Functions whose name matches @var{regexp} will be skipped over when stepping.
6196 This form is useful for complex function names.
6197 For example, there is generally no need to step into C@t{++} @code{std::string}
6198 constructors or destructors. Plus with C@t{++} templates it can be hard to
6199 write out the full name of the function, and often it doesn't matter what
6200 the template arguments are. Specifying the function to be skipped as a
6201 regular expression makes this easier.
6204 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6207 If you want to skip every templated C@t{++} constructor and destructor
6208 in the @code{std} namespace you can do:
6211 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6215 If no options are specified, the function you're currently debugging
6218 @kindex skip function
6219 @item skip function @r{[}@var{linespec}@r{]}
6220 After running this command, the function named by @var{linespec} or the
6221 function containing the line named by @var{linespec} will be skipped over when
6222 stepping. @xref{Specify Location}.
6224 If you do not specify @var{linespec}, the function you're currently debugging
6227 (If you have a function called @code{file} that you want to skip, use
6228 @kbd{skip function file}.)
6231 @item skip file @r{[}@var{filename}@r{]}
6232 After running this command, any function whose source lives in @var{filename}
6233 will be skipped over when stepping.
6236 (gdb) skip file boring.c
6237 File boring.c will be skipped when stepping.
6240 If you do not specify @var{filename}, functions whose source lives in the file
6241 you're currently debugging will be skipped.
6244 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6245 These are the commands for managing your list of skips:
6249 @item info skip @r{[}@var{range}@r{]}
6250 Print details about the specified skip(s). If @var{range} is not specified,
6251 print a table with details about all functions and files marked for skipping.
6252 @code{info skip} prints the following information about each skip:
6256 A number identifying this skip.
6257 @item Enabled or Disabled
6258 Enabled skips are marked with @samp{y}.
6259 Disabled skips are marked with @samp{n}.
6261 If the file name is a @samp{glob} pattern this is @samp{y}.
6262 Otherwise it is @samp{n}.
6264 The name or @samp{glob} pattern of the file to be skipped.
6265 If no file is specified this is @samp{<none>}.
6267 If the function name is a @samp{regular expression} this is @samp{y}.
6268 Otherwise it is @samp{n}.
6270 The name or regular expression of the function to skip.
6271 If no function is specified this is @samp{<none>}.
6275 @item skip delete @r{[}@var{range}@r{]}
6276 Delete the specified skip(s). If @var{range} is not specified, delete all
6280 @item skip enable @r{[}@var{range}@r{]}
6281 Enable the specified skip(s). If @var{range} is not specified, enable all
6284 @kindex skip disable
6285 @item skip disable @r{[}@var{range}@r{]}
6286 Disable the specified skip(s). If @var{range} is not specified, disable all
6289 @kindex set debug skip
6290 @item set debug skip @r{[}on|off@r{]}
6291 Set whether to print the debug output about skipping files and functions.
6293 @kindex show debug skip
6294 @item show debug skip
6295 Show whether the debug output about skipping files and functions is printed.
6303 A signal is an asynchronous event that can happen in a program. The
6304 operating system defines the possible kinds of signals, and gives each
6305 kind a name and a number. For example, in Unix @code{SIGINT} is the
6306 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6307 @code{SIGSEGV} is the signal a program gets from referencing a place in
6308 memory far away from all the areas in use; @code{SIGALRM} occurs when
6309 the alarm clock timer goes off (which happens only if your program has
6310 requested an alarm).
6312 @cindex fatal signals
6313 Some signals, including @code{SIGALRM}, are a normal part of the
6314 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6315 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6316 program has not specified in advance some other way to handle the signal.
6317 @code{SIGINT} does not indicate an error in your program, but it is normally
6318 fatal so it can carry out the purpose of the interrupt: to kill the program.
6320 @value{GDBN} has the ability to detect any occurrence of a signal in your
6321 program. You can tell @value{GDBN} in advance what to do for each kind of
6324 @cindex handling signals
6325 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6326 @code{SIGALRM} be silently passed to your program
6327 (so as not to interfere with their role in the program's functioning)
6328 but to stop your program immediately whenever an error signal happens.
6329 You can change these settings with the @code{handle} command.
6332 @kindex info signals
6336 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6337 handle each one. You can use this to see the signal numbers of all
6338 the defined types of signals.
6340 @item info signals @var{sig}
6341 Similar, but print information only about the specified signal number.
6343 @code{info handle} is an alias for @code{info signals}.
6345 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6346 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6347 for details about this command.
6350 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6351 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6352 can be the number of a signal or its name (with or without the
6353 @samp{SIG} at the beginning); a list of signal numbers of the form
6354 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6355 known signals. Optional arguments @var{keywords}, described below,
6356 say what change to make.
6360 The keywords allowed by the @code{handle} command can be abbreviated.
6361 Their full names are:
6365 @value{GDBN} should not stop your program when this signal happens. It may
6366 still print a message telling you that the signal has come in.
6369 @value{GDBN} should stop your program when this signal happens. This implies
6370 the @code{print} keyword as well.
6373 @value{GDBN} should print a message when this signal happens.
6376 @value{GDBN} should not mention the occurrence of the signal at all. This
6377 implies the @code{nostop} keyword as well.
6381 @value{GDBN} should allow your program to see this signal; your program
6382 can handle the signal, or else it may terminate if the signal is fatal
6383 and not handled. @code{pass} and @code{noignore} are synonyms.
6387 @value{GDBN} should not allow your program to see this signal.
6388 @code{nopass} and @code{ignore} are synonyms.
6392 When a signal stops your program, the signal is not visible to the
6394 continue. Your program sees the signal then, if @code{pass} is in
6395 effect for the signal in question @emph{at that time}. In other words,
6396 after @value{GDBN} reports a signal, you can use the @code{handle}
6397 command with @code{pass} or @code{nopass} to control whether your
6398 program sees that signal when you continue.
6400 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6401 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6402 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6405 You can also use the @code{signal} command to prevent your program from
6406 seeing a signal, or cause it to see a signal it normally would not see,
6407 or to give it any signal at any time. For example, if your program stopped
6408 due to some sort of memory reference error, you might store correct
6409 values into the erroneous variables and continue, hoping to see more
6410 execution; but your program would probably terminate immediately as
6411 a result of the fatal signal once it saw the signal. To prevent this,
6412 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6415 @cindex stepping and signal handlers
6416 @anchor{stepping and signal handlers}
6418 @value{GDBN} optimizes for stepping the mainline code. If a signal
6419 that has @code{handle nostop} and @code{handle pass} set arrives while
6420 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6421 in progress, @value{GDBN} lets the signal handler run and then resumes
6422 stepping the mainline code once the signal handler returns. In other
6423 words, @value{GDBN} steps over the signal handler. This prevents
6424 signals that you've specified as not interesting (with @code{handle
6425 nostop}) from changing the focus of debugging unexpectedly. Note that
6426 the signal handler itself may still hit a breakpoint, stop for another
6427 signal that has @code{handle stop} in effect, or for any other event
6428 that normally results in stopping the stepping command sooner. Also
6429 note that @value{GDBN} still informs you that the program received a
6430 signal if @code{handle print} is set.
6432 @anchor{stepping into signal handlers}
6434 If you set @code{handle pass} for a signal, and your program sets up a
6435 handler for it, then issuing a stepping command, such as @code{step}
6436 or @code{stepi}, when your program is stopped due to the signal will
6437 step @emph{into} the signal handler (if the target supports that).
6439 Likewise, if you use the @code{queue-signal} command to queue a signal
6440 to be delivered to the current thread when execution of the thread
6441 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6442 stepping command will step into the signal handler.
6444 Here's an example, using @code{stepi} to step to the first instruction
6445 of @code{SIGUSR1}'s handler:
6448 (@value{GDBP}) handle SIGUSR1
6449 Signal Stop Print Pass to program Description
6450 SIGUSR1 Yes Yes Yes User defined signal 1
6454 Program received signal SIGUSR1, User defined signal 1.
6455 main () sigusr1.c:28
6458 sigusr1_handler () at sigusr1.c:9
6462 The same, but using @code{queue-signal} instead of waiting for the
6463 program to receive the signal first:
6468 (@value{GDBP}) queue-signal SIGUSR1
6470 sigusr1_handler () at sigusr1.c:9
6475 @cindex extra signal information
6476 @anchor{extra signal information}
6478 On some targets, @value{GDBN} can inspect extra signal information
6479 associated with the intercepted signal, before it is actually
6480 delivered to the program being debugged. This information is exported
6481 by the convenience variable @code{$_siginfo}, and consists of data
6482 that is passed by the kernel to the signal handler at the time of the
6483 receipt of a signal. The data type of the information itself is
6484 target dependent. You can see the data type using the @code{ptype
6485 $_siginfo} command. On Unix systems, it typically corresponds to the
6486 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6489 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6490 referenced address that raised a segmentation fault.
6494 (@value{GDBP}) continue
6495 Program received signal SIGSEGV, Segmentation fault.
6496 0x0000000000400766 in main ()
6498 (@value{GDBP}) ptype $_siginfo
6505 struct @{...@} _kill;
6506 struct @{...@} _timer;
6508 struct @{...@} _sigchld;
6509 struct @{...@} _sigfault;
6510 struct @{...@} _sigpoll;
6513 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6517 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6518 $1 = (void *) 0x7ffff7ff7000
6522 Depending on target support, @code{$_siginfo} may also be writable.
6524 @cindex Intel MPX boundary violations
6525 @cindex boundary violations, Intel MPX
6526 On some targets, a @code{SIGSEGV} can be caused by a boundary
6527 violation, i.e., accessing an address outside of the allowed range.
6528 In those cases @value{GDBN} may displays additional information,
6529 depending on how @value{GDBN} has been told to handle the signal.
6530 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6531 kind: "Upper" or "Lower", the memory address accessed and the
6532 bounds, while with @code{handle nostop SIGSEGV} no additional
6533 information is displayed.
6535 The usual output of a segfault is:
6537 Program received signal SIGSEGV, Segmentation fault
6538 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6539 68 value = *(p + len);
6542 While a bound violation is presented as:
6544 Program received signal SIGSEGV, Segmentation fault
6545 Upper bound violation while accessing address 0x7fffffffc3b3
6546 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6547 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6548 68 value = *(p + len);
6552 @section Stopping and Starting Multi-thread Programs
6554 @cindex stopped threads
6555 @cindex threads, stopped
6557 @cindex continuing threads
6558 @cindex threads, continuing
6560 @value{GDBN} supports debugging programs with multiple threads
6561 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6562 are two modes of controlling execution of your program within the
6563 debugger. In the default mode, referred to as @dfn{all-stop mode},
6564 when any thread in your program stops (for example, at a breakpoint
6565 or while being stepped), all other threads in the program are also stopped by
6566 @value{GDBN}. On some targets, @value{GDBN} also supports
6567 @dfn{non-stop mode}, in which other threads can continue to run freely while
6568 you examine the stopped thread in the debugger.
6571 * All-Stop Mode:: All threads stop when GDB takes control
6572 * Non-Stop Mode:: Other threads continue to execute
6573 * Background Execution:: Running your program asynchronously
6574 * Thread-Specific Breakpoints:: Controlling breakpoints
6575 * Interrupted System Calls:: GDB may interfere with system calls
6576 * Observer Mode:: GDB does not alter program behavior
6580 @subsection All-Stop Mode
6582 @cindex all-stop mode
6584 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6585 @emph{all} threads of execution stop, not just the current thread. This
6586 allows you to examine the overall state of the program, including
6587 switching between threads, without worrying that things may change
6590 Conversely, whenever you restart the program, @emph{all} threads start
6591 executing. @emph{This is true even when single-stepping} with commands
6592 like @code{step} or @code{next}.
6594 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6595 Since thread scheduling is up to your debugging target's operating
6596 system (not controlled by @value{GDBN}), other threads may
6597 execute more than one statement while the current thread completes a
6598 single step. Moreover, in general other threads stop in the middle of a
6599 statement, rather than at a clean statement boundary, when the program
6602 You might even find your program stopped in another thread after
6603 continuing or even single-stepping. This happens whenever some other
6604 thread runs into a breakpoint, a signal, or an exception before the
6605 first thread completes whatever you requested.
6607 @cindex automatic thread selection
6608 @cindex switching threads automatically
6609 @cindex threads, automatic switching
6610 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6611 signal, it automatically selects the thread where that breakpoint or
6612 signal happened. @value{GDBN} alerts you to the context switch with a
6613 message such as @samp{[Switching to Thread @var{n}]} to identify the
6616 On some OSes, you can modify @value{GDBN}'s default behavior by
6617 locking the OS scheduler to allow only a single thread to run.
6620 @item set scheduler-locking @var{mode}
6621 @cindex scheduler locking mode
6622 @cindex lock scheduler
6623 Set the scheduler locking mode. It applies to normal execution,
6624 record mode, and replay mode. If it is @code{off}, then there is no
6625 locking and any thread may run at any time. If @code{on}, then only
6626 the current thread may run when the inferior is resumed. The
6627 @code{step} mode optimizes for single-stepping; it prevents other
6628 threads from preempting the current thread while you are stepping, so
6629 that the focus of debugging does not change unexpectedly. Other
6630 threads never get a chance to run when you step, and they are
6631 completely free to run when you use commands like @samp{continue},
6632 @samp{until}, or @samp{finish}. However, unless another thread hits a
6633 breakpoint during its timeslice, @value{GDBN} does not change the
6634 current thread away from the thread that you are debugging. The
6635 @code{replay} mode behaves like @code{off} in record mode and like
6636 @code{on} in replay mode.
6638 @item show scheduler-locking
6639 Display the current scheduler locking mode.
6642 @cindex resume threads of multiple processes simultaneously
6643 By default, when you issue one of the execution commands such as
6644 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6645 threads of the current inferior to run. For example, if @value{GDBN}
6646 is attached to two inferiors, each with two threads, the
6647 @code{continue} command resumes only the two threads of the current
6648 inferior. This is useful, for example, when you debug a program that
6649 forks and you want to hold the parent stopped (so that, for instance,
6650 it doesn't run to exit), while you debug the child. In other
6651 situations, you may not be interested in inspecting the current state
6652 of any of the processes @value{GDBN} is attached to, and you may want
6653 to resume them all until some breakpoint is hit. In the latter case,
6654 you can instruct @value{GDBN} to allow all threads of all the
6655 inferiors to run with the @w{@code{set schedule-multiple}} command.
6658 @kindex set schedule-multiple
6659 @item set schedule-multiple
6660 Set the mode for allowing threads of multiple processes to be resumed
6661 when an execution command is issued. When @code{on}, all threads of
6662 all processes are allowed to run. When @code{off}, only the threads
6663 of the current process are resumed. The default is @code{off}. The
6664 @code{scheduler-locking} mode takes precedence when set to @code{on},
6665 or while you are stepping and set to @code{step}.
6667 @item show schedule-multiple
6668 Display the current mode for resuming the execution of threads of
6673 @subsection Non-Stop Mode
6675 @cindex non-stop mode
6677 @c This section is really only a place-holder, and needs to be expanded
6678 @c with more details.
6680 For some multi-threaded targets, @value{GDBN} supports an optional
6681 mode of operation in which you can examine stopped program threads in
6682 the debugger while other threads continue to execute freely. This
6683 minimizes intrusion when debugging live systems, such as programs
6684 where some threads have real-time constraints or must continue to
6685 respond to external events. This is referred to as @dfn{non-stop} mode.
6687 In non-stop mode, when a thread stops to report a debugging event,
6688 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6689 threads as well, in contrast to the all-stop mode behavior. Additionally,
6690 execution commands such as @code{continue} and @code{step} apply by default
6691 only to the current thread in non-stop mode, rather than all threads as
6692 in all-stop mode. This allows you to control threads explicitly in
6693 ways that are not possible in all-stop mode --- for example, stepping
6694 one thread while allowing others to run freely, stepping
6695 one thread while holding all others stopped, or stepping several threads
6696 independently and simultaneously.
6698 To enter non-stop mode, use this sequence of commands before you run
6699 or attach to your program:
6702 # If using the CLI, pagination breaks non-stop.
6705 # Finally, turn it on!
6709 You can use these commands to manipulate the non-stop mode setting:
6712 @kindex set non-stop
6713 @item set non-stop on
6714 Enable selection of non-stop mode.
6715 @item set non-stop off
6716 Disable selection of non-stop mode.
6717 @kindex show non-stop
6719 Show the current non-stop enablement setting.
6722 Note these commands only reflect whether non-stop mode is enabled,
6723 not whether the currently-executing program is being run in non-stop mode.
6724 In particular, the @code{set non-stop} preference is only consulted when
6725 @value{GDBN} starts or connects to the target program, and it is generally
6726 not possible to switch modes once debugging has started. Furthermore,
6727 since not all targets support non-stop mode, even when you have enabled
6728 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6731 In non-stop mode, all execution commands apply only to the current thread
6732 by default. That is, @code{continue} only continues one thread.
6733 To continue all threads, issue @code{continue -a} or @code{c -a}.
6735 You can use @value{GDBN}'s background execution commands
6736 (@pxref{Background Execution}) to run some threads in the background
6737 while you continue to examine or step others from @value{GDBN}.
6738 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6739 always executed asynchronously in non-stop mode.
6741 Suspending execution is done with the @code{interrupt} command when
6742 running in the background, or @kbd{Ctrl-c} during foreground execution.
6743 In all-stop mode, this stops the whole process;
6744 but in non-stop mode the interrupt applies only to the current thread.
6745 To stop the whole program, use @code{interrupt -a}.
6747 Other execution commands do not currently support the @code{-a} option.
6749 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6750 that thread current, as it does in all-stop mode. This is because the
6751 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6752 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6753 changed to a different thread just as you entered a command to operate on the
6754 previously current thread.
6756 @node Background Execution
6757 @subsection Background Execution
6759 @cindex foreground execution
6760 @cindex background execution
6761 @cindex asynchronous execution
6762 @cindex execution, foreground, background and asynchronous
6764 @value{GDBN}'s execution commands have two variants: the normal
6765 foreground (synchronous) behavior, and a background
6766 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6767 the program to report that some thread has stopped before prompting for
6768 another command. In background execution, @value{GDBN} immediately gives
6769 a command prompt so that you can issue other commands while your program runs.
6771 If the target doesn't support async mode, @value{GDBN} issues an error
6772 message if you attempt to use the background execution commands.
6774 @cindex @code{&}, background execution of commands
6775 To specify background execution, add a @code{&} to the command. For example,
6776 the background form of the @code{continue} command is @code{continue&}, or
6777 just @code{c&}. The execution commands that accept background execution
6783 @xref{Starting, , Starting your Program}.
6787 @xref{Attach, , Debugging an Already-running Process}.
6791 @xref{Continuing and Stepping, step}.
6795 @xref{Continuing and Stepping, stepi}.
6799 @xref{Continuing and Stepping, next}.
6803 @xref{Continuing and Stepping, nexti}.
6807 @xref{Continuing and Stepping, continue}.
6811 @xref{Continuing and Stepping, finish}.
6815 @xref{Continuing and Stepping, until}.
6819 Background execution is especially useful in conjunction with non-stop
6820 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6821 However, you can also use these commands in the normal all-stop mode with
6822 the restriction that you cannot issue another execution command until the
6823 previous one finishes. Examples of commands that are valid in all-stop
6824 mode while the program is running include @code{help} and @code{info break}.
6826 You can interrupt your program while it is running in the background by
6827 using the @code{interrupt} command.
6834 Suspend execution of the running program. In all-stop mode,
6835 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6836 only the current thread. To stop the whole program in non-stop mode,
6837 use @code{interrupt -a}.
6840 @node Thread-Specific Breakpoints
6841 @subsection Thread-Specific Breakpoints
6843 When your program has multiple threads (@pxref{Threads,, Debugging
6844 Programs with Multiple Threads}), you can choose whether to set
6845 breakpoints on all threads, or on a particular thread.
6848 @cindex breakpoints and threads
6849 @cindex thread breakpoints
6850 @kindex break @dots{} thread @var{thread-id}
6851 @item break @var{location} thread @var{thread-id}
6852 @itemx break @var{location} thread @var{thread-id} if @dots{}
6853 @var{location} specifies source lines; there are several ways of
6854 writing them (@pxref{Specify Location}), but the effect is always to
6855 specify some source line.
6857 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6858 to specify that you only want @value{GDBN} to stop the program when a
6859 particular thread reaches this breakpoint. The @var{thread-id} specifier
6860 is one of the thread identifiers assigned by @value{GDBN}, shown
6861 in the first column of the @samp{info threads} display.
6863 If you do not specify @samp{thread @var{thread-id}} when you set a
6864 breakpoint, the breakpoint applies to @emph{all} threads of your
6867 You can use the @code{thread} qualifier on conditional breakpoints as
6868 well; in this case, place @samp{thread @var{thread-id}} before or
6869 after the breakpoint condition, like this:
6872 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6877 Thread-specific breakpoints are automatically deleted when
6878 @value{GDBN} detects the corresponding thread is no longer in the
6879 thread list. For example:
6883 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6886 There are several ways for a thread to disappear, such as a regular
6887 thread exit, but also when you detach from the process with the
6888 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6889 Process}), or if @value{GDBN} loses the remote connection
6890 (@pxref{Remote Debugging}), etc. Note that with some targets,
6891 @value{GDBN} is only able to detect a thread has exited when the user
6892 explictly asks for the thread list with the @code{info threads}
6895 @node Interrupted System Calls
6896 @subsection Interrupted System Calls
6898 @cindex thread breakpoints and system calls
6899 @cindex system calls and thread breakpoints
6900 @cindex premature return from system calls
6901 There is an unfortunate side effect when using @value{GDBN} to debug
6902 multi-threaded programs. If one thread stops for a
6903 breakpoint, or for some other reason, and another thread is blocked in a
6904 system call, then the system call may return prematurely. This is a
6905 consequence of the interaction between multiple threads and the signals
6906 that @value{GDBN} uses to implement breakpoints and other events that
6909 To handle this problem, your program should check the return value of
6910 each system call and react appropriately. This is good programming
6913 For example, do not write code like this:
6919 The call to @code{sleep} will return early if a different thread stops
6920 at a breakpoint or for some other reason.
6922 Instead, write this:
6927 unslept = sleep (unslept);
6930 A system call is allowed to return early, so the system is still
6931 conforming to its specification. But @value{GDBN} does cause your
6932 multi-threaded program to behave differently than it would without
6935 Also, @value{GDBN} uses internal breakpoints in the thread library to
6936 monitor certain events such as thread creation and thread destruction.
6937 When such an event happens, a system call in another thread may return
6938 prematurely, even though your program does not appear to stop.
6941 @subsection Observer Mode
6943 If you want to build on non-stop mode and observe program behavior
6944 without any chance of disruption by @value{GDBN}, you can set
6945 variables to disable all of the debugger's attempts to modify state,
6946 whether by writing memory, inserting breakpoints, etc. These operate
6947 at a low level, intercepting operations from all commands.
6949 When all of these are set to @code{off}, then @value{GDBN} is said to
6950 be @dfn{observer mode}. As a convenience, the variable
6951 @code{observer} can be set to disable these, plus enable non-stop
6954 Note that @value{GDBN} will not prevent you from making nonsensical
6955 combinations of these settings. For instance, if you have enabled
6956 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6957 then breakpoints that work by writing trap instructions into the code
6958 stream will still not be able to be placed.
6963 @item set observer on
6964 @itemx set observer off
6965 When set to @code{on}, this disables all the permission variables
6966 below (except for @code{insert-fast-tracepoints}), plus enables
6967 non-stop debugging. Setting this to @code{off} switches back to
6968 normal debugging, though remaining in non-stop mode.
6971 Show whether observer mode is on or off.
6973 @kindex may-write-registers
6974 @item set may-write-registers on
6975 @itemx set may-write-registers off
6976 This controls whether @value{GDBN} will attempt to alter the values of
6977 registers, such as with assignment expressions in @code{print}, or the
6978 @code{jump} command. It defaults to @code{on}.
6980 @item show may-write-registers
6981 Show the current permission to write registers.
6983 @kindex may-write-memory
6984 @item set may-write-memory on
6985 @itemx set may-write-memory off
6986 This controls whether @value{GDBN} will attempt to alter the contents
6987 of memory, such as with assignment expressions in @code{print}. It
6988 defaults to @code{on}.
6990 @item show may-write-memory
6991 Show the current permission to write memory.
6993 @kindex may-insert-breakpoints
6994 @item set may-insert-breakpoints on
6995 @itemx set may-insert-breakpoints off
6996 This controls whether @value{GDBN} will attempt to insert breakpoints.
6997 This affects all breakpoints, including internal breakpoints defined
6998 by @value{GDBN}. It defaults to @code{on}.
7000 @item show may-insert-breakpoints
7001 Show the current permission to insert breakpoints.
7003 @kindex may-insert-tracepoints
7004 @item set may-insert-tracepoints on
7005 @itemx set may-insert-tracepoints off
7006 This controls whether @value{GDBN} will attempt to insert (regular)
7007 tracepoints at the beginning of a tracing experiment. It affects only
7008 non-fast tracepoints, fast tracepoints being under the control of
7009 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7011 @item show may-insert-tracepoints
7012 Show the current permission to insert tracepoints.
7014 @kindex may-insert-fast-tracepoints
7015 @item set may-insert-fast-tracepoints on
7016 @itemx set may-insert-fast-tracepoints off
7017 This controls whether @value{GDBN} will attempt to insert fast
7018 tracepoints at the beginning of a tracing experiment. It affects only
7019 fast tracepoints, regular (non-fast) tracepoints being under the
7020 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7022 @item show may-insert-fast-tracepoints
7023 Show the current permission to insert fast tracepoints.
7025 @kindex may-interrupt
7026 @item set may-interrupt on
7027 @itemx set may-interrupt off
7028 This controls whether @value{GDBN} will attempt to interrupt or stop
7029 program execution. When this variable is @code{off}, the
7030 @code{interrupt} command will have no effect, nor will
7031 @kbd{Ctrl-c}. It defaults to @code{on}.
7033 @item show may-interrupt
7034 Show the current permission to interrupt or stop the program.
7038 @node Reverse Execution
7039 @chapter Running programs backward
7040 @cindex reverse execution
7041 @cindex running programs backward
7043 When you are debugging a program, it is not unusual to realize that
7044 you have gone too far, and some event of interest has already happened.
7045 If the target environment supports it, @value{GDBN} can allow you to
7046 ``rewind'' the program by running it backward.
7048 A target environment that supports reverse execution should be able
7049 to ``undo'' the changes in machine state that have taken place as the
7050 program was executing normally. Variables, registers etc.@: should
7051 revert to their previous values. Obviously this requires a great
7052 deal of sophistication on the part of the target environment; not
7053 all target environments can support reverse execution.
7055 When a program is executed in reverse, the instructions that
7056 have most recently been executed are ``un-executed'', in reverse
7057 order. The program counter runs backward, following the previous
7058 thread of execution in reverse. As each instruction is ``un-executed'',
7059 the values of memory and/or registers that were changed by that
7060 instruction are reverted to their previous states. After executing
7061 a piece of source code in reverse, all side effects of that code
7062 should be ``undone'', and all variables should be returned to their
7063 prior values@footnote{
7064 Note that some side effects are easier to undo than others. For instance,
7065 memory and registers are relatively easy, but device I/O is hard. Some
7066 targets may be able undo things like device I/O, and some may not.
7068 The contract between @value{GDBN} and the reverse executing target
7069 requires only that the target do something reasonable when
7070 @value{GDBN} tells it to execute backwards, and then report the
7071 results back to @value{GDBN}. Whatever the target reports back to
7072 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7073 assumes that the memory and registers that the target reports are in a
7074 consistent state, but @value{GDBN} accepts whatever it is given.
7077 On some platforms, @value{GDBN} has built-in support for reverse
7078 execution, activated with the @code{record} or @code{record btrace}
7079 commands. @xref{Process Record and Replay}. Some remote targets,
7080 typically full system emulators, support reverse execution directly
7081 without requiring any special command.
7083 If you are debugging in a target environment that supports
7084 reverse execution, @value{GDBN} provides the following commands.
7087 @kindex reverse-continue
7088 @kindex rc @r{(@code{reverse-continue})}
7089 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7090 @itemx rc @r{[}@var{ignore-count}@r{]}
7091 Beginning at the point where your program last stopped, start executing
7092 in reverse. Reverse execution will stop for breakpoints and synchronous
7093 exceptions (signals), just like normal execution. Behavior of
7094 asynchronous signals depends on the target environment.
7096 @kindex reverse-step
7097 @kindex rs @r{(@code{step})}
7098 @item reverse-step @r{[}@var{count}@r{]}
7099 Run the program backward until control reaches the start of a
7100 different source line; then stop it, and return control to @value{GDBN}.
7102 Like the @code{step} command, @code{reverse-step} will only stop
7103 at the beginning of a source line. It ``un-executes'' the previously
7104 executed source line. If the previous source line included calls to
7105 debuggable functions, @code{reverse-step} will step (backward) into
7106 the called function, stopping at the beginning of the @emph{last}
7107 statement in the called function (typically a return statement).
7109 Also, as with the @code{step} command, if non-debuggable functions are
7110 called, @code{reverse-step} will run thru them backward without stopping.
7112 @kindex reverse-stepi
7113 @kindex rsi @r{(@code{reverse-stepi})}
7114 @item reverse-stepi @r{[}@var{count}@r{]}
7115 Reverse-execute one machine instruction. Note that the instruction
7116 to be reverse-executed is @emph{not} the one pointed to by the program
7117 counter, but the instruction executed prior to that one. For instance,
7118 if the last instruction was a jump, @code{reverse-stepi} will take you
7119 back from the destination of the jump to the jump instruction itself.
7121 @kindex reverse-next
7122 @kindex rn @r{(@code{reverse-next})}
7123 @item reverse-next @r{[}@var{count}@r{]}
7124 Run backward to the beginning of the previous line executed in
7125 the current (innermost) stack frame. If the line contains function
7126 calls, they will be ``un-executed'' without stopping. Starting from
7127 the first line of a function, @code{reverse-next} will take you back
7128 to the caller of that function, @emph{before} the function was called,
7129 just as the normal @code{next} command would take you from the last
7130 line of a function back to its return to its caller
7131 @footnote{Unless the code is too heavily optimized.}.
7133 @kindex reverse-nexti
7134 @kindex rni @r{(@code{reverse-nexti})}
7135 @item reverse-nexti @r{[}@var{count}@r{]}
7136 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7137 in reverse, except that called functions are ``un-executed'' atomically.
7138 That is, if the previously executed instruction was a return from
7139 another function, @code{reverse-nexti} will continue to execute
7140 in reverse until the call to that function (from the current stack
7143 @kindex reverse-finish
7144 @item reverse-finish
7145 Just as the @code{finish} command takes you to the point where the
7146 current function returns, @code{reverse-finish} takes you to the point
7147 where it was called. Instead of ending up at the end of the current
7148 function invocation, you end up at the beginning.
7150 @kindex set exec-direction
7151 @item set exec-direction
7152 Set the direction of target execution.
7153 @item set exec-direction reverse
7154 @cindex execute forward or backward in time
7155 @value{GDBN} will perform all execution commands in reverse, until the
7156 exec-direction mode is changed to ``forward''. Affected commands include
7157 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7158 command cannot be used in reverse mode.
7159 @item set exec-direction forward
7160 @value{GDBN} will perform all execution commands in the normal fashion.
7161 This is the default.
7165 @node Process Record and Replay
7166 @chapter Recording Inferior's Execution and Replaying It
7167 @cindex process record and replay
7168 @cindex recording inferior's execution and replaying it
7170 On some platforms, @value{GDBN} provides a special @dfn{process record
7171 and replay} target that can record a log of the process execution, and
7172 replay it later with both forward and reverse execution commands.
7175 When this target is in use, if the execution log includes the record
7176 for the next instruction, @value{GDBN} will debug in @dfn{replay
7177 mode}. In the replay mode, the inferior does not really execute code
7178 instructions. Instead, all the events that normally happen during
7179 code execution are taken from the execution log. While code is not
7180 really executed in replay mode, the values of registers (including the
7181 program counter register) and the memory of the inferior are still
7182 changed as they normally would. Their contents are taken from the
7186 If the record for the next instruction is not in the execution log,
7187 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7188 inferior executes normally, and @value{GDBN} records the execution log
7191 The process record and replay target supports reverse execution
7192 (@pxref{Reverse Execution}), even if the platform on which the
7193 inferior runs does not. However, the reverse execution is limited in
7194 this case by the range of the instructions recorded in the execution
7195 log. In other words, reverse execution on platforms that don't
7196 support it directly can only be done in the replay mode.
7198 When debugging in the reverse direction, @value{GDBN} will work in
7199 replay mode as long as the execution log includes the record for the
7200 previous instruction; otherwise, it will work in record mode, if the
7201 platform supports reverse execution, or stop if not.
7203 Currently, process record and replay is supported on ARM, Aarch64,
7204 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7205 GNU/Linux. Process record and replay can be used both when native
7206 debugging, and when remote debugging via @code{gdbserver}.
7208 For architecture environments that support process record and replay,
7209 @value{GDBN} provides the following commands:
7212 @kindex target record
7213 @kindex target record-full
7214 @kindex target record-btrace
7217 @kindex record btrace
7218 @kindex record btrace bts
7219 @kindex record btrace pt
7225 @kindex rec btrace bts
7226 @kindex rec btrace pt
7229 @item record @var{method}
7230 This command starts the process record and replay target. The
7231 recording method can be specified as parameter. Without a parameter
7232 the command uses the @code{full} recording method. The following
7233 recording methods are available:
7237 Full record/replay recording using @value{GDBN}'s software record and
7238 replay implementation. This method allows replaying and reverse
7241 @item btrace @var{format}
7242 Hardware-supported instruction recording, supported on Intel
7243 processors. This method does not record data. Further, the data is
7244 collected in a ring buffer so old data will be overwritten when the
7245 buffer is full. It allows limited reverse execution. Variables and
7246 registers are not available during reverse execution. In remote
7247 debugging, recording continues on disconnect. Recorded data can be
7248 inspected after reconnecting. The recording may be stopped using
7251 The recording format can be specified as parameter. Without a parameter
7252 the command chooses the recording format. The following recording
7253 formats are available:
7257 @cindex branch trace store
7258 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7259 this format, the processor stores a from/to record for each executed
7260 branch in the btrace ring buffer.
7263 @cindex Intel Processor Trace
7264 Use the @dfn{Intel Processor Trace} recording format. In this
7265 format, the processor stores the execution trace in a compressed form
7266 that is afterwards decoded by @value{GDBN}.
7268 The trace can be recorded with very low overhead. The compressed
7269 trace format also allows small trace buffers to already contain a big
7270 number of instructions compared to @acronym{BTS}.
7272 Decoding the recorded execution trace, on the other hand, is more
7273 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7274 increased number of instructions to process. You should increase the
7275 buffer-size with care.
7278 Not all recording formats may be available on all processors.
7281 The process record and replay target can only debug a process that is
7282 already running. Therefore, you need first to start the process with
7283 the @kbd{run} or @kbd{start} commands, and then start the recording
7284 with the @kbd{record @var{method}} command.
7286 @cindex displaced stepping, and process record and replay
7287 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7288 will be automatically disabled when process record and replay target
7289 is started. That's because the process record and replay target
7290 doesn't support displaced stepping.
7292 @cindex non-stop mode, and process record and replay
7293 @cindex asynchronous execution, and process record and replay
7294 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7295 the asynchronous execution mode (@pxref{Background Execution}), not
7296 all recording methods are available. The @code{full} recording method
7297 does not support these two modes.
7302 Stop the process record and replay target. When process record and
7303 replay target stops, the entire execution log will be deleted and the
7304 inferior will either be terminated, or will remain in its final state.
7306 When you stop the process record and replay target in record mode (at
7307 the end of the execution log), the inferior will be stopped at the
7308 next instruction that would have been recorded. In other words, if
7309 you record for a while and then stop recording, the inferior process
7310 will be left in the same state as if the recording never happened.
7312 On the other hand, if the process record and replay target is stopped
7313 while in replay mode (that is, not at the end of the execution log,
7314 but at some earlier point), the inferior process will become ``live''
7315 at that earlier state, and it will then be possible to continue the
7316 usual ``live'' debugging of the process from that state.
7318 When the inferior process exits, or @value{GDBN} detaches from it,
7319 process record and replay target will automatically stop itself.
7323 Go to a specific location in the execution log. There are several
7324 ways to specify the location to go to:
7327 @item record goto begin
7328 @itemx record goto start
7329 Go to the beginning of the execution log.
7331 @item record goto end
7332 Go to the end of the execution log.
7334 @item record goto @var{n}
7335 Go to instruction number @var{n} in the execution log.
7339 @item record save @var{filename}
7340 Save the execution log to a file @file{@var{filename}}.
7341 Default filename is @file{gdb_record.@var{process_id}}, where
7342 @var{process_id} is the process ID of the inferior.
7344 This command may not be available for all recording methods.
7346 @kindex record restore
7347 @item record restore @var{filename}
7348 Restore the execution log from a file @file{@var{filename}}.
7349 File must have been created with @code{record save}.
7351 @kindex set record full
7352 @item set record full insn-number-max @var{limit}
7353 @itemx set record full insn-number-max unlimited
7354 Set the limit of instructions to be recorded for the @code{full}
7355 recording method. Default value is 200000.
7357 If @var{limit} is a positive number, then @value{GDBN} will start
7358 deleting instructions from the log once the number of the record
7359 instructions becomes greater than @var{limit}. For every new recorded
7360 instruction, @value{GDBN} will delete the earliest recorded
7361 instruction to keep the number of recorded instructions at the limit.
7362 (Since deleting recorded instructions loses information, @value{GDBN}
7363 lets you control what happens when the limit is reached, by means of
7364 the @code{stop-at-limit} option, described below.)
7366 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7367 delete recorded instructions from the execution log. The number of
7368 recorded instructions is limited only by the available memory.
7370 @kindex show record full
7371 @item show record full insn-number-max
7372 Show the limit of instructions to be recorded with the @code{full}
7375 @item set record full stop-at-limit
7376 Control the behavior of the @code{full} recording method when the
7377 number of recorded instructions reaches the limit. If ON (the
7378 default), @value{GDBN} will stop when the limit is reached for the
7379 first time and ask you whether you want to stop the inferior or
7380 continue running it and recording the execution log. If you decide
7381 to continue recording, each new recorded instruction will cause the
7382 oldest one to be deleted.
7384 If this option is OFF, @value{GDBN} will automatically delete the
7385 oldest record to make room for each new one, without asking.
7387 @item show record full stop-at-limit
7388 Show the current setting of @code{stop-at-limit}.
7390 @item set record full memory-query
7391 Control the behavior when @value{GDBN} is unable to record memory
7392 changes caused by an instruction for the @code{full} recording method.
7393 If ON, @value{GDBN} will query whether to stop the inferior in that
7396 If this option is OFF (the default), @value{GDBN} will automatically
7397 ignore the effect of such instructions on memory. Later, when
7398 @value{GDBN} replays this execution log, it will mark the log of this
7399 instruction as not accessible, and it will not affect the replay
7402 @item show record full memory-query
7403 Show the current setting of @code{memory-query}.
7405 @kindex set record btrace
7406 The @code{btrace} record target does not trace data. As a
7407 convenience, when replaying, @value{GDBN} reads read-only memory off
7408 the live program directly, assuming that the addresses of the
7409 read-only areas don't change. This for example makes it possible to
7410 disassemble code while replaying, but not to print variables.
7411 In some cases, being able to inspect variables might be useful.
7412 You can use the following command for that:
7414 @item set record btrace replay-memory-access
7415 Control the behavior of the @code{btrace} recording method when
7416 accessing memory during replay. If @code{read-only} (the default),
7417 @value{GDBN} will only allow accesses to read-only memory.
7418 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7419 and to read-write memory. Beware that the accessed memory corresponds
7420 to the live target and not necessarily to the current replay
7423 @item set record btrace cpu @var{identifier}
7424 Set the processor to be used for enabling workarounds for processor
7425 errata when decoding the trace.
7427 Processor errata are defects in processor operation, caused by its
7428 design or manufacture. They can cause a trace not to match the
7429 specification. This, in turn, may cause trace decode to fail.
7430 @value{GDBN} can detect erroneous trace packets and correct them, thus
7431 avoiding the decoding failures. These corrections are known as
7432 @dfn{errata workarounds}, and are enabled based on the processor on
7433 which the trace was recorded.
7435 By default, @value{GDBN} attempts to detect the processor
7436 automatically, and apply the necessary workarounds for it. However,
7437 you may need to specify the processor if @value{GDBN} does not yet
7438 support it. This command allows you to do that, and also allows to
7439 disable the workarounds.
7441 The argument @var{identifier} identifies the @sc{cpu} and is of the
7442 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7443 there are two special identifiers, @code{none} and @code{auto}
7446 The following vendor identifiers and corresponding processor
7447 identifiers are currently supported:
7449 @multitable @columnfractions .1 .9
7452 @tab @var{family}/@var{model}[/@var{stepping}]
7456 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7457 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7459 If @var{identifier} is @code{auto}, enable errata workarounds for the
7460 processor on which the trace was recorded. If @var{identifier} is
7461 @code{none}, errata workarounds are disabled.
7463 For example, when using an old @value{GDBN} on a new system, decode
7464 may fail because @value{GDBN} does not support the new processor. It
7465 often suffices to specify an older processor that @value{GDBN}
7470 Active record target: record-btrace
7471 Recording format: Intel Processor Trace.
7473 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7474 (gdb) set record btrace cpu intel:6/158
7476 Active record target: record-btrace
7477 Recording format: Intel Processor Trace.
7479 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7482 @kindex show record btrace
7483 @item show record btrace replay-memory-access
7484 Show the current setting of @code{replay-memory-access}.
7486 @item show record btrace cpu
7487 Show the processor to be used for enabling trace decode errata
7490 @kindex set record btrace bts
7491 @item set record btrace bts buffer-size @var{size}
7492 @itemx set record btrace bts buffer-size unlimited
7493 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7494 format. Default is 64KB.
7496 If @var{size} is a positive number, then @value{GDBN} will try to
7497 allocate a buffer of at least @var{size} bytes for each new thread
7498 that uses the btrace recording method and the @acronym{BTS} format.
7499 The actually obtained buffer size may differ from the requested
7500 @var{size}. Use the @code{info record} command to see the actual
7501 buffer size for each thread that uses the btrace recording method and
7502 the @acronym{BTS} format.
7504 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7505 allocate a buffer of 4MB.
7507 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7508 also need longer to process the branch trace data before it can be used.
7510 @item show record btrace bts buffer-size @var{size}
7511 Show the current setting of the requested ring buffer size for branch
7512 tracing in @acronym{BTS} format.
7514 @kindex set record btrace pt
7515 @item set record btrace pt buffer-size @var{size}
7516 @itemx set record btrace pt buffer-size unlimited
7517 Set the requested ring buffer size for branch tracing in Intel
7518 Processor Trace format. Default is 16KB.
7520 If @var{size} is a positive number, then @value{GDBN} will try to
7521 allocate a buffer of at least @var{size} bytes for each new thread
7522 that uses the btrace recording method and the Intel Processor Trace
7523 format. The actually obtained buffer size may differ from the
7524 requested @var{size}. Use the @code{info record} command to see the
7525 actual buffer size for each thread.
7527 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7528 allocate a buffer of 4MB.
7530 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7531 also need longer to process the branch trace data before it can be used.
7533 @item show record btrace pt buffer-size @var{size}
7534 Show the current setting of the requested ring buffer size for branch
7535 tracing in Intel Processor Trace format.
7539 Show various statistics about the recording depending on the recording
7544 For the @code{full} recording method, it shows the state of process
7545 record and its in-memory execution log buffer, including:
7549 Whether in record mode or replay mode.
7551 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7553 Highest recorded instruction number.
7555 Current instruction about to be replayed (if in replay mode).
7557 Number of instructions contained in the execution log.
7559 Maximum number of instructions that may be contained in the execution log.
7563 For the @code{btrace} recording method, it shows:
7569 Number of instructions that have been recorded.
7571 Number of blocks of sequential control-flow formed by the recorded
7574 Whether in record mode or replay mode.
7577 For the @code{bts} recording format, it also shows:
7580 Size of the perf ring buffer.
7583 For the @code{pt} recording format, it also shows:
7586 Size of the perf ring buffer.
7590 @kindex record delete
7593 When record target runs in replay mode (``in the past''), delete the
7594 subsequent execution log and begin to record a new execution log starting
7595 from the current address. This means you will abandon the previously
7596 recorded ``future'' and begin recording a new ``future''.
7598 @kindex record instruction-history
7599 @kindex rec instruction-history
7600 @item record instruction-history
7601 Disassembles instructions from the recorded execution log. By
7602 default, ten instructions are disassembled. This can be changed using
7603 the @code{set record instruction-history-size} command. Instructions
7604 are printed in execution order.
7606 It can also print mixed source+disassembly if you specify the the
7607 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7608 as well as in symbolic form by specifying the @code{/r} modifier.
7610 The current position marker is printed for the instruction at the
7611 current program counter value. This instruction can appear multiple
7612 times in the trace and the current position marker will be printed
7613 every time. To omit the current position marker, specify the
7616 To better align the printed instructions when the trace contains
7617 instructions from more than one function, the function name may be
7618 omitted by specifying the @code{/f} modifier.
7620 Speculatively executed instructions are prefixed with @samp{?}. This
7621 feature is not available for all recording formats.
7623 There are several ways to specify what part of the execution log to
7627 @item record instruction-history @var{insn}
7628 Disassembles ten instructions starting from instruction number
7631 @item record instruction-history @var{insn}, +/-@var{n}
7632 Disassembles @var{n} instructions around instruction number
7633 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7634 @var{n} instructions after instruction number @var{insn}. If
7635 @var{n} is preceded with @code{-}, disassembles @var{n}
7636 instructions before instruction number @var{insn}.
7638 @item record instruction-history
7639 Disassembles ten more instructions after the last disassembly.
7641 @item record instruction-history -
7642 Disassembles ten more instructions before the last disassembly.
7644 @item record instruction-history @var{begin}, @var{end}
7645 Disassembles instructions beginning with instruction number
7646 @var{begin} until instruction number @var{end}. The instruction
7647 number @var{end} is included.
7650 This command may not be available for all recording methods.
7653 @item set record instruction-history-size @var{size}
7654 @itemx set record instruction-history-size unlimited
7655 Define how many instructions to disassemble in the @code{record
7656 instruction-history} command. The default value is 10.
7657 A @var{size} of @code{unlimited} means unlimited instructions.
7660 @item show record instruction-history-size
7661 Show how many instructions to disassemble in the @code{record
7662 instruction-history} command.
7664 @kindex record function-call-history
7665 @kindex rec function-call-history
7666 @item record function-call-history
7667 Prints the execution history at function granularity. It prints one
7668 line for each sequence of instructions that belong to the same
7669 function giving the name of that function, the source lines
7670 for this instruction sequence (if the @code{/l} modifier is
7671 specified), and the instructions numbers that form the sequence (if
7672 the @code{/i} modifier is specified). The function names are indented
7673 to reflect the call stack depth if the @code{/c} modifier is
7674 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7678 (@value{GDBP}) @b{list 1, 10}
7689 (@value{GDBP}) @b{record function-call-history /ilc}
7690 1 bar inst 1,4 at foo.c:6,8
7691 2 foo inst 5,10 at foo.c:2,3
7692 3 bar inst 11,13 at foo.c:9,10
7695 By default, ten lines are printed. This can be changed using the
7696 @code{set record function-call-history-size} command. Functions are
7697 printed in execution order. There are several ways to specify what
7701 @item record function-call-history @var{func}
7702 Prints ten functions starting from function number @var{func}.
7704 @item record function-call-history @var{func}, +/-@var{n}
7705 Prints @var{n} functions around function number @var{func}. If
7706 @var{n} is preceded with @code{+}, prints @var{n} functions after
7707 function number @var{func}. If @var{n} is preceded with @code{-},
7708 prints @var{n} functions before function number @var{func}.
7710 @item record function-call-history
7711 Prints ten more functions after the last ten-line print.
7713 @item record function-call-history -
7714 Prints ten more functions before the last ten-line print.
7716 @item record function-call-history @var{begin}, @var{end}
7717 Prints functions beginning with function number @var{begin} until
7718 function number @var{end}. The function number @var{end} is included.
7721 This command may not be available for all recording methods.
7723 @item set record function-call-history-size @var{size}
7724 @itemx set record function-call-history-size unlimited
7725 Define how many lines to print in the
7726 @code{record function-call-history} command. The default value is 10.
7727 A size of @code{unlimited} means unlimited lines.
7729 @item show record function-call-history-size
7730 Show how many lines to print in the
7731 @code{record function-call-history} command.
7736 @chapter Examining the Stack
7738 When your program has stopped, the first thing you need to know is where it
7739 stopped and how it got there.
7742 Each time your program performs a function call, information about the call
7744 That information includes the location of the call in your program,
7745 the arguments of the call,
7746 and the local variables of the function being called.
7747 The information is saved in a block of data called a @dfn{stack frame}.
7748 The stack frames are allocated in a region of memory called the @dfn{call
7751 When your program stops, the @value{GDBN} commands for examining the
7752 stack allow you to see all of this information.
7754 @cindex selected frame
7755 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7756 @value{GDBN} commands refer implicitly to the selected frame. In
7757 particular, whenever you ask @value{GDBN} for the value of a variable in
7758 your program, the value is found in the selected frame. There are
7759 special @value{GDBN} commands to select whichever frame you are
7760 interested in. @xref{Selection, ,Selecting a Frame}.
7762 When your program stops, @value{GDBN} automatically selects the
7763 currently executing frame and describes it briefly, similar to the
7764 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7767 * Frames:: Stack frames
7768 * Backtrace:: Backtraces
7769 * Selection:: Selecting a frame
7770 * Frame Info:: Information on a frame
7771 * Frame Apply:: Applying a command to several frames
7772 * Frame Filter Management:: Managing frame filters
7777 @section Stack Frames
7779 @cindex frame, definition
7781 The call stack is divided up into contiguous pieces called @dfn{stack
7782 frames}, or @dfn{frames} for short; each frame is the data associated
7783 with one call to one function. The frame contains the arguments given
7784 to the function, the function's local variables, and the address at
7785 which the function is executing.
7787 @cindex initial frame
7788 @cindex outermost frame
7789 @cindex innermost frame
7790 When your program is started, the stack has only one frame, that of the
7791 function @code{main}. This is called the @dfn{initial} frame or the
7792 @dfn{outermost} frame. Each time a function is called, a new frame is
7793 made. Each time a function returns, the frame for that function invocation
7794 is eliminated. If a function is recursive, there can be many frames for
7795 the same function. The frame for the function in which execution is
7796 actually occurring is called the @dfn{innermost} frame. This is the most
7797 recently created of all the stack frames that still exist.
7799 @cindex frame pointer
7800 Inside your program, stack frames are identified by their addresses. A
7801 stack frame consists of many bytes, each of which has its own address; each
7802 kind of computer has a convention for choosing one byte whose
7803 address serves as the address of the frame. Usually this address is kept
7804 in a register called the @dfn{frame pointer register}
7805 (@pxref{Registers, $fp}) while execution is going on in that frame.
7808 @cindex frame number
7809 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7810 number that is zero for the innermost frame, one for the frame that
7811 called it, and so on upward. These level numbers give you a way of
7812 designating stack frames in @value{GDBN} commands. The terms
7813 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7814 describe this number.
7816 @c The -fomit-frame-pointer below perennially causes hbox overflow
7817 @c underflow problems.
7818 @cindex frameless execution
7819 Some compilers provide a way to compile functions so that they operate
7820 without stack frames. (For example, the @value{NGCC} option
7822 @samp{-fomit-frame-pointer}
7824 generates functions without a frame.)
7825 This is occasionally done with heavily used library functions to save
7826 the frame setup time. @value{GDBN} has limited facilities for dealing
7827 with these function invocations. If the innermost function invocation
7828 has no stack frame, @value{GDBN} nevertheless regards it as though
7829 it had a separate frame, which is numbered zero as usual, allowing
7830 correct tracing of the function call chain. However, @value{GDBN} has
7831 no provision for frameless functions elsewhere in the stack.
7837 @cindex call stack traces
7838 A backtrace is a summary of how your program got where it is. It shows one
7839 line per frame, for many frames, starting with the currently executing
7840 frame (frame zero), followed by its caller (frame one), and on up the
7843 @anchor{backtrace-command}
7845 @kindex bt @r{(@code{backtrace})}
7846 To print a backtrace of the entire stack, use the @code{backtrace}
7847 command, or its alias @code{bt}. This command will print one line per
7848 frame for frames in the stack. By default, all stack frames are
7849 printed. You can stop the backtrace at any time by typing the system
7850 interrupt character, normally @kbd{Ctrl-c}.
7853 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7854 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7855 Print the backtrace of the entire stack.
7857 The optional @var{count} can be one of the following:
7862 Print only the innermost @var{n} frames, where @var{n} is a positive
7867 Print only the outermost @var{n} frames, where @var{n} is a positive
7875 Print the values of the local variables also. This can be combined
7876 with the optional @var{count} to limit the number of frames shown.
7879 Do not run Python frame filters on this backtrace. @xref{Frame
7880 Filter API}, for more information. Additionally use @ref{disable
7881 frame-filter all} to turn off all frame filters. This is only
7882 relevant when @value{GDBN} has been configured with @code{Python}
7886 A Python frame filter might decide to ``elide'' some frames. Normally
7887 such elided frames are still printed, but they are indented relative
7888 to the filtered frames that cause them to be elided. The @code{-hide}
7889 option causes elided frames to not be printed at all.
7892 The @code{backtrace} command also supports a number of options that
7893 allow overriding relevant global print settings as set by @code{set
7894 backtrace} and @code{set print} subcommands:
7897 @item -past-main [@code{on}|@code{off}]
7898 Set whether backtraces should continue past @code{main}. Related setting:
7899 @ref{set backtrace past-main}.
7901 @item -past-entry [@code{on}|@code{off}]
7902 Set whether backtraces should continue past the entry point of a program.
7903 Related setting: @ref{set backtrace past-entry}.
7905 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
7906 Set printing of function arguments at function entry.
7907 Related setting: @ref{set print entry-values}.
7909 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
7910 Set printing of non-scalar frame arguments.
7911 Related setting: @ref{set print frame-arguments}.
7913 @item -raw-frame-arguments [@code{on}|@code{off}]
7914 Set whether to print frame arguments in raw form.
7915 Related setting: @ref{set print raw-frame-arguments}.
7917 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
7918 Set printing of frame information.
7919 Related setting: @ref{set print frame-info}.
7922 The optional @var{qualifier} is maintained for backward compatibility.
7923 It can be one of the following:
7927 Equivalent to the @code{-full} option.
7930 Equivalent to the @code{-no-filters} option.
7933 Equivalent to the @code{-hide} option.
7940 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7941 are additional aliases for @code{backtrace}.
7943 @cindex multiple threads, backtrace
7944 In a multi-threaded program, @value{GDBN} by default shows the
7945 backtrace only for the current thread. To display the backtrace for
7946 several or all of the threads, use the command @code{thread apply}
7947 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7948 apply all backtrace}, @value{GDBN} will display the backtrace for all
7949 the threads; this is handy when you debug a core dump of a
7950 multi-threaded program.
7952 Each line in the backtrace shows the frame number and the function name.
7953 The program counter value is also shown---unless you use @code{set
7954 print address off}. The backtrace also shows the source file name and
7955 line number, as well as the arguments to the function. The program
7956 counter value is omitted if it is at the beginning of the code for that
7959 Here is an example of a backtrace. It was made with the command
7960 @samp{bt 3}, so it shows the innermost three frames.
7964 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7966 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7967 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7969 (More stack frames follow...)
7974 The display for frame zero does not begin with a program counter
7975 value, indicating that your program has stopped at the beginning of the
7976 code for line @code{993} of @code{builtin.c}.
7979 The value of parameter @code{data} in frame 1 has been replaced by
7980 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7981 only if it is a scalar (integer, pointer, enumeration, etc). See command
7982 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7983 on how to configure the way function parameter values are printed.
7984 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
7985 what frame information is printed.
7987 @cindex optimized out, in backtrace
7988 @cindex function call arguments, optimized out
7989 If your program was compiled with optimizations, some compilers will
7990 optimize away arguments passed to functions if those arguments are
7991 never used after the call. Such optimizations generate code that
7992 passes arguments through registers, but doesn't store those arguments
7993 in the stack frame. @value{GDBN} has no way of displaying such
7994 arguments in stack frames other than the innermost one. Here's what
7995 such a backtrace might look like:
7999 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8001 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8002 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8004 (More stack frames follow...)
8009 The values of arguments that were not saved in their stack frames are
8010 shown as @samp{<optimized out>}.
8012 If you need to display the values of such optimized-out arguments,
8013 either deduce that from other variables whose values depend on the one
8014 you are interested in, or recompile without optimizations.
8016 @cindex backtrace beyond @code{main} function
8017 @cindex program entry point
8018 @cindex startup code, and backtrace
8019 Most programs have a standard user entry point---a place where system
8020 libraries and startup code transition into user code. For C this is
8021 @code{main}@footnote{
8022 Note that embedded programs (the so-called ``free-standing''
8023 environment) are not required to have a @code{main} function as the
8024 entry point. They could even have multiple entry points.}.
8025 When @value{GDBN} finds the entry function in a backtrace
8026 it will terminate the backtrace, to avoid tracing into highly
8027 system-specific (and generally uninteresting) code.
8029 If you need to examine the startup code, or limit the number of levels
8030 in a backtrace, you can change this behavior:
8033 @item set backtrace past-main
8034 @itemx set backtrace past-main on
8035 @anchor{set backtrace past-main}
8036 @kindex set backtrace
8037 Backtraces will continue past the user entry point.
8039 @item set backtrace past-main off
8040 Backtraces will stop when they encounter the user entry point. This is the
8043 @item show backtrace past-main
8044 @kindex show backtrace
8045 Display the current user entry point backtrace policy.
8047 @item set backtrace past-entry
8048 @itemx set backtrace past-entry on
8049 @anchor{set backtrace past-entry}
8050 Backtraces will continue past the internal entry point of an application.
8051 This entry point is encoded by the linker when the application is built,
8052 and is likely before the user entry point @code{main} (or equivalent) is called.
8054 @item set backtrace past-entry off
8055 Backtraces will stop when they encounter the internal entry point of an
8056 application. This is the default.
8058 @item show backtrace past-entry
8059 Display the current internal entry point backtrace policy.
8061 @item set backtrace limit @var{n}
8062 @itemx set backtrace limit 0
8063 @itemx set backtrace limit unlimited
8064 @anchor{set backtrace limit}
8065 @cindex backtrace limit
8066 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8067 or zero means unlimited levels.
8069 @item show backtrace limit
8070 Display the current limit on backtrace levels.
8073 You can control how file names are displayed.
8076 @item set filename-display
8077 @itemx set filename-display relative
8078 @cindex filename-display
8079 Display file names relative to the compilation directory. This is the default.
8081 @item set filename-display basename
8082 Display only basename of a filename.
8084 @item set filename-display absolute
8085 Display an absolute filename.
8087 @item show filename-display
8088 Show the current way to display filenames.
8092 @section Selecting a Frame
8094 Most commands for examining the stack and other data in your program work on
8095 whichever stack frame is selected at the moment. Here are the commands for
8096 selecting a stack frame; all of them finish by printing a brief description
8097 of the stack frame just selected.
8100 @kindex frame@r{, selecting}
8101 @kindex f @r{(@code{frame})}
8102 @item frame @r{[} @var{frame-selection-spec} @r{]}
8103 @item f @r{[} @var{frame-selection-spec} @r{]}
8104 The @command{frame} command allows different stack frames to be
8105 selected. The @var{frame-selection-spec} can be any of the following:
8110 @item level @var{num}
8111 Select frame level @var{num}. Recall that frame zero is the innermost
8112 (currently executing) frame, frame one is the frame that called the
8113 innermost one, and so on. The highest level frame is usually the one
8116 As this is the most common method of navigating the frame stack, the
8117 string @command{level} can be omitted. For example, the following two
8118 commands are equivalent:
8121 (@value{GDBP}) frame 3
8122 (@value{GDBP}) frame level 3
8125 @kindex frame address
8126 @item address @var{stack-address}
8127 Select the frame with stack address @var{stack-address}. The
8128 @var{stack-address} for a frame can be seen in the output of
8129 @command{info frame}, for example:
8133 Stack level 1, frame at 0x7fffffffda30:
8134 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8135 tail call frame, caller of frame at 0x7fffffffda30
8136 source language c++.
8137 Arglist at unknown address.
8138 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8141 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8142 indicated by the line:
8145 Stack level 1, frame at 0x7fffffffda30:
8148 @kindex frame function
8149 @item function @var{function-name}
8150 Select the stack frame for function @var{function-name}. If there are
8151 multiple stack frames for function @var{function-name} then the inner
8152 most stack frame is selected.
8155 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8156 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8157 viewed has stack address @var{stack-addr}, and optionally, a program
8158 counter address of @var{pc-addr}.
8160 This is useful mainly if the chaining of stack frames has been
8161 damaged by a bug, making it impossible for @value{GDBN} to assign
8162 numbers properly to all frames. In addition, this can be useful
8163 when your program has multiple stacks and switches between them.
8165 When viewing a frame outside the current backtrace using
8166 @command{frame view} then you can always return to the original
8167 stack using one of the previous stack frame selection instructions,
8168 for example @command{frame level 0}.
8174 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8175 numbers @var{n}, this advances toward the outermost frame, to higher
8176 frame numbers, to frames that have existed longer.
8179 @kindex do @r{(@code{down})}
8181 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8182 positive numbers @var{n}, this advances toward the innermost frame, to
8183 lower frame numbers, to frames that were created more recently.
8184 You may abbreviate @code{down} as @code{do}.
8187 All of these commands end by printing two lines of output describing the
8188 frame. The first line shows the frame number, the function name, the
8189 arguments, and the source file and line number of execution in that
8190 frame. The second line shows the text of that source line.
8198 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8200 10 read_input_file (argv[i]);
8204 After such a printout, the @code{list} command with no arguments
8205 prints ten lines centered on the point of execution in the frame.
8206 You can also edit the program at the point of execution with your favorite
8207 editing program by typing @code{edit}.
8208 @xref{List, ,Printing Source Lines},
8212 @kindex select-frame
8213 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8214 The @code{select-frame} command is a variant of @code{frame} that does
8215 not display the new frame after selecting it. This command is
8216 intended primarily for use in @value{GDBN} command scripts, where the
8217 output might be unnecessary and distracting. The
8218 @var{frame-selection-spec} is as for the @command{frame} command
8219 described in @ref{Selection, ,Selecting a Frame}.
8221 @kindex down-silently
8223 @item up-silently @var{n}
8224 @itemx down-silently @var{n}
8225 These two commands are variants of @code{up} and @code{down},
8226 respectively; they differ in that they do their work silently, without
8227 causing display of the new frame. They are intended primarily for use
8228 in @value{GDBN} command scripts, where the output might be unnecessary and
8233 @section Information About a Frame
8235 There are several other commands to print information about the selected
8241 When used without any argument, this command does not change which
8242 frame is selected, but prints a brief description of the currently
8243 selected stack frame. It can be abbreviated @code{f}. With an
8244 argument, this command is used to select a stack frame.
8245 @xref{Selection, ,Selecting a Frame}.
8248 @kindex info f @r{(@code{info frame})}
8251 This command prints a verbose description of the selected stack frame,
8256 the address of the frame
8258 the address of the next frame down (called by this frame)
8260 the address of the next frame up (caller of this frame)
8262 the language in which the source code corresponding to this frame is written
8264 the address of the frame's arguments
8266 the address of the frame's local variables
8268 the program counter saved in it (the address of execution in the caller frame)
8270 which registers were saved in the frame
8273 @noindent The verbose description is useful when
8274 something has gone wrong that has made the stack format fail to fit
8275 the usual conventions.
8277 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8278 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8279 Print a verbose description of the frame selected by
8280 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8281 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8282 a Frame}). The selected frame remains unchanged by this command.
8285 @item info args [-q]
8286 Print the arguments of the selected frame, each on a separate line.
8288 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8289 printing header information and messages explaining why no argument
8292 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8293 Like @kbd{info args}, but only print the arguments selected
8294 with the provided regexp(s).
8296 If @var{regexp} is provided, print only the arguments whose names
8297 match the regular expression @var{regexp}.
8299 If @var{type_regexp} is provided, print only the arguments whose
8300 types, as printed by the @code{whatis} command, match
8301 the regular expression @var{type_regexp}.
8302 If @var{type_regexp} contains space(s), it should be enclosed in
8303 quote characters. If needed, use backslash to escape the meaning
8304 of special characters or quotes.
8306 If both @var{regexp} and @var{type_regexp} are provided, an argument
8307 is printed only if its name matches @var{regexp} and its type matches
8310 @item info locals [-q]
8312 Print the local variables of the selected frame, each on a separate
8313 line. These are all variables (declared either static or automatic)
8314 accessible at the point of execution of the selected frame.
8316 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8317 printing header information and messages explaining why no local variables
8320 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8321 Like @kbd{info locals}, but only print the local variables selected
8322 with the provided regexp(s).
8324 If @var{regexp} is provided, print only the local variables whose names
8325 match the regular expression @var{regexp}.
8327 If @var{type_regexp} is provided, print only the local variables whose
8328 types, as printed by the @code{whatis} command, match
8329 the regular expression @var{type_regexp}.
8330 If @var{type_regexp} contains space(s), it should be enclosed in
8331 quote characters. If needed, use backslash to escape the meaning
8332 of special characters or quotes.
8334 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8335 is printed only if its name matches @var{regexp} and its type matches
8338 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8339 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8340 For example, your program might use Resource Acquisition Is
8341 Initialization types (RAII) such as @code{lock_something_t}: each
8342 local variable of type @code{lock_something_t} automatically places a
8343 lock that is destroyed when the variable goes out of scope. You can
8344 then list all acquired locks in your program by doing
8346 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8349 or the equivalent shorter form
8351 tfaas i lo -q -t lock_something_t
8357 @section Applying a Command to Several Frames.
8358 @anchor{frame apply}
8360 @cindex apply command to several frames
8362 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8363 The @code{frame apply} command allows you to apply the named
8364 @var{command} to one or more frames.
8368 Specify @code{all} to apply @var{command} to all frames.
8371 Use @var{count} to apply @var{command} to the innermost @var{count}
8372 frames, where @var{count} is a positive number.
8375 Use @var{-count} to apply @var{command} to the outermost @var{count}
8376 frames, where @var{count} is a positive number.
8379 Use @code{level} to apply @var{command} to the set of frames identified
8380 by the @var{level} list. @var{level} is a frame level or a range of frame
8381 levels as @var{level1}-@var{level2}. The frame level is the number shown
8382 in the first field of the @samp{backtrace} command output.
8383 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8384 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8388 Note that the frames on which @code{frame apply} applies a command are
8389 also influenced by the @code{set backtrace} settings such as @code{set
8390 backtrace past-main} and @code{set backtrace limit N}.
8391 @xref{Backtrace,,Backtraces}.
8393 The @code{frame apply} command also supports a number of options that
8394 allow overriding relevant @code{set backtrace} settings:
8397 @item -past-main [@code{on}|@code{off}]
8398 Whether backtraces should continue past @code{main}.
8399 Related setting: @ref{set backtrace past-main}.
8401 @item -past-entry [@code{on}|@code{off}]
8402 Whether backtraces should continue past the entry point of a program.
8403 Related setting: @ref{set backtrace past-entry}.
8406 By default, @value{GDBN} displays some frame information before the
8407 output produced by @var{command}, and an error raised during the
8408 execution of a @var{command} will abort @code{frame apply}. The
8409 following options can be used to fine-tune these behaviors:
8413 The flag @code{-c}, which stands for @samp{continue}, causes any
8414 errors in @var{command} to be displayed, and the execution of
8415 @code{frame apply} then continues.
8417 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8418 or empty output produced by a @var{command} to be silently ignored.
8419 That is, the execution continues, but the frame information and errors
8422 The flag @code{-q} (@samp{quiet}) disables printing the frame
8426 The following example shows how the flags @code{-c} and @code{-s} are
8427 working when applying the command @code{p j} to all frames, where
8428 variable @code{j} can only be successfully printed in the outermost
8429 @code{#1 main} frame.
8433 (gdb) frame apply all p j
8434 #0 some_function (i=5) at fun.c:4
8435 No symbol "j" in current context.
8436 (gdb) frame apply all -c p j
8437 #0 some_function (i=5) at fun.c:4
8438 No symbol "j" in current context.
8439 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8441 (gdb) frame apply all -s p j
8442 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8448 By default, @samp{frame apply}, prints the frame location
8449 information before the command output:
8453 (gdb) frame apply all p $sp
8454 #0 some_function (i=5) at fun.c:4
8455 $4 = (void *) 0xffffd1e0
8456 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8457 $5 = (void *) 0xffffd1f0
8462 If the flag @code{-q} is given, no frame information is printed:
8465 (gdb) frame apply all -q p $sp
8466 $12 = (void *) 0xffffd1e0
8467 $13 = (void *) 0xffffd1f0
8477 @cindex apply a command to all frames (ignoring errors and empty output)
8478 @item faas @var{command}
8479 Shortcut for @code{frame apply all -s @var{command}}.
8480 Applies @var{command} on all frames, ignoring errors and empty output.
8482 It can for example be used to print a local variable or a function
8483 argument without knowing the frame where this variable or argument
8486 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8489 The @code{faas} command accepts the same options as the @code{frame
8490 apply} command. @xref{frame apply}.
8492 Note that the command @code{tfaas @var{command}} applies @var{command}
8493 on all frames of all threads. See @xref{Threads,,Threads}.
8497 @node Frame Filter Management
8498 @section Management of Frame Filters.
8499 @cindex managing frame filters
8501 Frame filters are Python based utilities to manage and decorate the
8502 output of frames. @xref{Frame Filter API}, for further information.
8504 Managing frame filters is performed by several commands available
8505 within @value{GDBN}, detailed here.
8508 @kindex info frame-filter
8509 @item info frame-filter
8510 Print a list of installed frame filters from all dictionaries, showing
8511 their name, priority and enabled status.
8513 @kindex disable frame-filter
8514 @anchor{disable frame-filter all}
8515 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8516 Disable a frame filter in the dictionary matching
8517 @var{filter-dictionary} and @var{filter-name}. The
8518 @var{filter-dictionary} may be @code{all}, @code{global},
8519 @code{progspace}, or the name of the object file where the frame filter
8520 dictionary resides. When @code{all} is specified, all frame filters
8521 across all dictionaries are disabled. The @var{filter-name} is the name
8522 of the frame filter and is used when @code{all} is not the option for
8523 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8524 may be enabled again later.
8526 @kindex enable frame-filter
8527 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8528 Enable a frame filter in the dictionary matching
8529 @var{filter-dictionary} and @var{filter-name}. The
8530 @var{filter-dictionary} may be @code{all}, @code{global},
8531 @code{progspace} or the name of the object file where the frame filter
8532 dictionary resides. When @code{all} is specified, all frame filters across
8533 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8534 filter and is used when @code{all} is not the option for
8535 @var{filter-dictionary}.
8540 (gdb) info frame-filter
8542 global frame-filters:
8543 Priority Enabled Name
8544 1000 No PrimaryFunctionFilter
8547 progspace /build/test frame-filters:
8548 Priority Enabled Name
8549 100 Yes ProgspaceFilter
8551 objfile /build/test frame-filters:
8552 Priority Enabled Name
8553 999 Yes BuildProgramFilter
8555 (gdb) disable frame-filter /build/test BuildProgramFilter
8556 (gdb) info frame-filter
8558 global frame-filters:
8559 Priority Enabled Name
8560 1000 No PrimaryFunctionFilter
8563 progspace /build/test frame-filters:
8564 Priority Enabled Name
8565 100 Yes ProgspaceFilter
8567 objfile /build/test frame-filters:
8568 Priority Enabled Name
8569 999 No BuildProgramFilter
8571 (gdb) enable frame-filter global PrimaryFunctionFilter
8572 (gdb) info frame-filter
8574 global frame-filters:
8575 Priority Enabled Name
8576 1000 Yes PrimaryFunctionFilter
8579 progspace /build/test frame-filters:
8580 Priority Enabled Name
8581 100 Yes ProgspaceFilter
8583 objfile /build/test frame-filters:
8584 Priority Enabled Name
8585 999 No BuildProgramFilter
8588 @kindex set frame-filter priority
8589 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8590 Set the @var{priority} of a frame filter in the dictionary matching
8591 @var{filter-dictionary}, and the frame filter name matching
8592 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8593 @code{progspace} or the name of the object file where the frame filter
8594 dictionary resides. The @var{priority} is an integer.
8596 @kindex show frame-filter priority
8597 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8598 Show the @var{priority} of a frame filter in the dictionary matching
8599 @var{filter-dictionary}, and the frame filter name matching
8600 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8601 @code{progspace} or the name of the object file where the frame filter
8607 (gdb) info frame-filter
8609 global frame-filters:
8610 Priority Enabled Name
8611 1000 Yes PrimaryFunctionFilter
8614 progspace /build/test frame-filters:
8615 Priority Enabled Name
8616 100 Yes ProgspaceFilter
8618 objfile /build/test frame-filters:
8619 Priority Enabled Name
8620 999 No BuildProgramFilter
8622 (gdb) set frame-filter priority global Reverse 50
8623 (gdb) info frame-filter
8625 global frame-filters:
8626 Priority Enabled Name
8627 1000 Yes PrimaryFunctionFilter
8630 progspace /build/test frame-filters:
8631 Priority Enabled Name
8632 100 Yes ProgspaceFilter
8634 objfile /build/test frame-filters:
8635 Priority Enabled Name
8636 999 No BuildProgramFilter
8641 @chapter Examining Source Files
8643 @value{GDBN} can print parts of your program's source, since the debugging
8644 information recorded in the program tells @value{GDBN} what source files were
8645 used to build it. When your program stops, @value{GDBN} spontaneously prints
8646 the line where it stopped. Likewise, when you select a stack frame
8647 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8648 execution in that frame has stopped. You can print other portions of
8649 source files by explicit command.
8651 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8652 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8653 @value{GDBN} under @sc{gnu} Emacs}.
8656 * List:: Printing source lines
8657 * Specify Location:: How to specify code locations
8658 * Edit:: Editing source files
8659 * Search:: Searching source files
8660 * Source Path:: Specifying source directories
8661 * Machine Code:: Source and machine code
8665 @section Printing Source Lines
8668 @kindex l @r{(@code{list})}
8669 To print lines from a source file, use the @code{list} command
8670 (abbreviated @code{l}). By default, ten lines are printed.
8671 There are several ways to specify what part of the file you want to
8672 print; see @ref{Specify Location}, for the full list.
8674 Here are the forms of the @code{list} command most commonly used:
8677 @item list @var{linenum}
8678 Print lines centered around line number @var{linenum} in the
8679 current source file.
8681 @item list @var{function}
8682 Print lines centered around the beginning of function
8686 Print more lines. If the last lines printed were printed with a
8687 @code{list} command, this prints lines following the last lines
8688 printed; however, if the last line printed was a solitary line printed
8689 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8690 Stack}), this prints lines centered around that line.
8693 Print lines just before the lines last printed.
8696 @cindex @code{list}, how many lines to display
8697 By default, @value{GDBN} prints ten source lines with any of these forms of
8698 the @code{list} command. You can change this using @code{set listsize}:
8701 @kindex set listsize
8702 @item set listsize @var{count}
8703 @itemx set listsize unlimited
8704 Make the @code{list} command display @var{count} source lines (unless
8705 the @code{list} argument explicitly specifies some other number).
8706 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8708 @kindex show listsize
8710 Display the number of lines that @code{list} prints.
8713 Repeating a @code{list} command with @key{RET} discards the argument,
8714 so it is equivalent to typing just @code{list}. This is more useful
8715 than listing the same lines again. An exception is made for an
8716 argument of @samp{-}; that argument is preserved in repetition so that
8717 each repetition moves up in the source file.
8719 In general, the @code{list} command expects you to supply zero, one or two
8720 @dfn{locations}. Locations specify source lines; there are several ways
8721 of writing them (@pxref{Specify Location}), but the effect is always
8722 to specify some source line.
8724 Here is a complete description of the possible arguments for @code{list}:
8727 @item list @var{location}
8728 Print lines centered around the line specified by @var{location}.
8730 @item list @var{first},@var{last}
8731 Print lines from @var{first} to @var{last}. Both arguments are
8732 locations. When a @code{list} command has two locations, and the
8733 source file of the second location is omitted, this refers to
8734 the same source file as the first location.
8736 @item list ,@var{last}
8737 Print lines ending with @var{last}.
8739 @item list @var{first},
8740 Print lines starting with @var{first}.
8743 Print lines just after the lines last printed.
8746 Print lines just before the lines last printed.
8749 As described in the preceding table.
8752 @node Specify Location
8753 @section Specifying a Location
8754 @cindex specifying location
8756 @cindex source location
8759 * Linespec Locations:: Linespec locations
8760 * Explicit Locations:: Explicit locations
8761 * Address Locations:: Address locations
8764 Several @value{GDBN} commands accept arguments that specify a location
8765 of your program's code. Since @value{GDBN} is a source-level
8766 debugger, a location usually specifies some line in the source code.
8767 Locations may be specified using three different formats:
8768 linespec locations, explicit locations, or address locations.
8770 @node Linespec Locations
8771 @subsection Linespec Locations
8772 @cindex linespec locations
8774 A @dfn{linespec} is a colon-separated list of source location parameters such
8775 as file name, function name, etc. Here are all the different ways of
8776 specifying a linespec:
8780 Specifies the line number @var{linenum} of the current source file.
8783 @itemx +@var{offset}
8784 Specifies the line @var{offset} lines before or after the @dfn{current
8785 line}. For the @code{list} command, the current line is the last one
8786 printed; for the breakpoint commands, this is the line at which
8787 execution stopped in the currently selected @dfn{stack frame}
8788 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8789 used as the second of the two linespecs in a @code{list} command,
8790 this specifies the line @var{offset} lines up or down from the first
8793 @item @var{filename}:@var{linenum}
8794 Specifies the line @var{linenum} in the source file @var{filename}.
8795 If @var{filename} is a relative file name, then it will match any
8796 source file name with the same trailing components. For example, if
8797 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8798 name of @file{/build/trunk/gcc/expr.c}, but not
8799 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8801 @item @var{function}
8802 Specifies the line that begins the body of the function @var{function}.
8803 For example, in C, this is the line with the open brace.
8805 By default, in C@t{++} and Ada, @var{function} is interpreted as
8806 specifying all functions named @var{function} in all scopes. For
8807 C@t{++}, this means in all namespaces and classes. For Ada, this
8808 means in all packages.
8810 For example, assuming a program with C@t{++} symbols named
8811 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8812 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8814 Commands that accept a linespec let you override this with the
8815 @code{-qualified} option. For example, @w{@kbd{break -qualified
8816 func}} sets a breakpoint on a free-function named @code{func} ignoring
8817 any C@t{++} class methods and namespace functions called @code{func}.
8819 @xref{Explicit Locations}.
8821 @item @var{function}:@var{label}
8822 Specifies the line where @var{label} appears in @var{function}.
8824 @item @var{filename}:@var{function}
8825 Specifies the line that begins the body of the function @var{function}
8826 in the file @var{filename}. You only need the file name with a
8827 function name to avoid ambiguity when there are identically named
8828 functions in different source files.
8831 Specifies the line at which the label named @var{label} appears
8832 in the function corresponding to the currently selected stack frame.
8833 If there is no current selected stack frame (for instance, if the inferior
8834 is not running), then @value{GDBN} will not search for a label.
8836 @cindex breakpoint at static probe point
8837 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8838 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8839 applications to embed static probes. @xref{Static Probe Points}, for more
8840 information on finding and using static probes. This form of linespec
8841 specifies the location of such a static probe.
8843 If @var{objfile} is given, only probes coming from that shared library
8844 or executable matching @var{objfile} as a regular expression are considered.
8845 If @var{provider} is given, then only probes from that provider are considered.
8846 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8847 each one of those probes.
8850 @node Explicit Locations
8851 @subsection Explicit Locations
8852 @cindex explicit locations
8854 @dfn{Explicit locations} allow the user to directly specify the source
8855 location's parameters using option-value pairs.
8857 Explicit locations are useful when several functions, labels, or
8858 file names have the same name (base name for files) in the program's
8859 sources. In these cases, explicit locations point to the source
8860 line you meant more accurately and unambiguously. Also, using
8861 explicit locations might be faster in large programs.
8863 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8864 defined in the file named @file{foo} or the label @code{bar} in a function
8865 named @code{foo}. @value{GDBN} must search either the file system or
8866 the symbol table to know.
8868 The list of valid explicit location options is summarized in the
8872 @item -source @var{filename}
8873 The value specifies the source file name. To differentiate between
8874 files with the same base name, prepend as many directories as is necessary
8875 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8876 @value{GDBN} will use the first file it finds with the given base
8877 name. This option requires the use of either @code{-function} or @code{-line}.
8879 @item -function @var{function}
8880 The value specifies the name of a function. Operations
8881 on function locations unmodified by other options (such as @code{-label}
8882 or @code{-line}) refer to the line that begins the body of the function.
8883 In C, for example, this is the line with the open brace.
8885 By default, in C@t{++} and Ada, @var{function} is interpreted as
8886 specifying all functions named @var{function} in all scopes. For
8887 C@t{++}, this means in all namespaces and classes. For Ada, this
8888 means in all packages.
8890 For example, assuming a program with C@t{++} symbols named
8891 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8892 -function func}} and @w{@kbd{break -function B::func}} set a
8893 breakpoint on both symbols.
8895 You can use the @kbd{-qualified} flag to override this (see below).
8899 This flag makes @value{GDBN} interpret a function name specified with
8900 @kbd{-function} as a complete fully-qualified name.
8902 For example, assuming a C@t{++} program with symbols named
8903 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8904 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8906 (Note: the @kbd{-qualified} option can precede a linespec as well
8907 (@pxref{Linespec Locations}), so the particular example above could be
8908 simplified as @w{@kbd{break -qualified B::func}}.)
8910 @item -label @var{label}
8911 The value specifies the name of a label. When the function
8912 name is not specified, the label is searched in the function of the currently
8913 selected stack frame.
8915 @item -line @var{number}
8916 The value specifies a line offset for the location. The offset may either
8917 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8918 the command. When specified without any other options, the line offset is
8919 relative to the current line.
8922 Explicit location options may be abbreviated by omitting any non-unique
8923 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8925 @node Address Locations
8926 @subsection Address Locations
8927 @cindex address locations
8929 @dfn{Address locations} indicate a specific program address. They have
8930 the generalized form *@var{address}.
8932 For line-oriented commands, such as @code{list} and @code{edit}, this
8933 specifies a source line that contains @var{address}. For @code{break} and
8934 other breakpoint-oriented commands, this can be used to set breakpoints in
8935 parts of your program which do not have debugging information or
8938 Here @var{address} may be any expression valid in the current working
8939 language (@pxref{Languages, working language}) that specifies a code
8940 address. In addition, as a convenience, @value{GDBN} extends the
8941 semantics of expressions used in locations to cover several situations
8942 that frequently occur during debugging. Here are the various forms
8946 @item @var{expression}
8947 Any expression valid in the current working language.
8949 @item @var{funcaddr}
8950 An address of a function or procedure derived from its name. In C,
8951 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8952 simply the function's name @var{function} (and actually a special case
8953 of a valid expression). In Pascal and Modula-2, this is
8954 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8955 (although the Pascal form also works).
8957 This form specifies the address of the function's first instruction,
8958 before the stack frame and arguments have been set up.
8960 @item '@var{filename}':@var{funcaddr}
8961 Like @var{funcaddr} above, but also specifies the name of the source
8962 file explicitly. This is useful if the name of the function does not
8963 specify the function unambiguously, e.g., if there are several
8964 functions with identical names in different source files.
8968 @section Editing Source Files
8969 @cindex editing source files
8972 @kindex e @r{(@code{edit})}
8973 To edit the lines in a source file, use the @code{edit} command.
8974 The editing program of your choice
8975 is invoked with the current line set to
8976 the active line in the program.
8977 Alternatively, there are several ways to specify what part of the file you
8978 want to print if you want to see other parts of the program:
8981 @item edit @var{location}
8982 Edit the source file specified by @code{location}. Editing starts at
8983 that @var{location}, e.g., at the specified source line of the
8984 specified file. @xref{Specify Location}, for all the possible forms
8985 of the @var{location} argument; here are the forms of the @code{edit}
8986 command most commonly used:
8989 @item edit @var{number}
8990 Edit the current source file with @var{number} as the active line number.
8992 @item edit @var{function}
8993 Edit the file containing @var{function} at the beginning of its definition.
8998 @subsection Choosing your Editor
8999 You can customize @value{GDBN} to use any editor you want
9001 The only restriction is that your editor (say @code{ex}), recognizes the
9002 following command-line syntax:
9004 ex +@var{number} file
9006 The optional numeric value +@var{number} specifies the number of the line in
9007 the file where to start editing.}.
9008 By default, it is @file{@value{EDITOR}}, but you can change this
9009 by setting the environment variable @code{EDITOR} before using
9010 @value{GDBN}. For example, to configure @value{GDBN} to use the
9011 @code{vi} editor, you could use these commands with the @code{sh} shell:
9017 or in the @code{csh} shell,
9019 setenv EDITOR /usr/bin/vi
9024 @section Searching Source Files
9025 @cindex searching source files
9027 There are two commands for searching through the current source file for a
9032 @kindex forward-search
9033 @kindex fo @r{(@code{forward-search})}
9034 @item forward-search @var{regexp}
9035 @itemx search @var{regexp}
9036 The command @samp{forward-search @var{regexp}} checks each line,
9037 starting with the one following the last line listed, for a match for
9038 @var{regexp}. It lists the line that is found. You can use the
9039 synonym @samp{search @var{regexp}} or abbreviate the command name as
9042 @kindex reverse-search
9043 @item reverse-search @var{regexp}
9044 The command @samp{reverse-search @var{regexp}} checks each line, starting
9045 with the one before the last line listed and going backward, for a match
9046 for @var{regexp}. It lists the line that is found. You can abbreviate
9047 this command as @code{rev}.
9051 @section Specifying Source Directories
9054 @cindex directories for source files
9055 Executable programs sometimes do not record the directories of the source
9056 files from which they were compiled, just the names. Even when they do,
9057 the directories could be moved between the compilation and your debugging
9058 session. @value{GDBN} has a list of directories to search for source files;
9059 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9060 it tries all the directories in the list, in the order they are present
9061 in the list, until it finds a file with the desired name.
9063 For example, suppose an executable references the file
9064 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9065 directory, and the @dfn{source path} is @file{/mnt/cross}.
9066 @value{GDBN} would look for the source file in the following
9071 @item @file{/usr/src/foo-1.0/lib/foo.c}
9072 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9073 @item @file{/mnt/cross/foo.c}
9077 If the source file is not present at any of the above locations then
9078 an error is printed. @value{GDBN} does not look up the parts of the
9079 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9080 Likewise, the subdirectories of the source path are not searched: if
9081 the source path is @file{/mnt/cross}, and the binary refers to
9082 @file{foo.c}, @value{GDBN} would not find it under
9083 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9085 Plain file names, relative file names with leading directories, file
9086 names containing dots, etc.@: are all treated as described above,
9087 except that non-absolute file names are not looked up literally. If
9088 the @dfn{source path} is @file{/mnt/cross}, the source file is
9089 recorded as @file{../lib/foo.c}, and no compilation directory is
9090 recorded, then @value{GDBN} will search in the following locations:
9094 @item @file{/mnt/cross/../lib/foo.c}
9095 @item @file{/mnt/cross/foo.c}
9101 @vindex $cdir@r{, convenience variable}
9102 @vindex $cwd@r{, convenience variable}
9103 @cindex compilation directory
9104 @cindex current directory
9105 @cindex working directory
9106 @cindex directory, current
9107 @cindex directory, compilation
9108 The @dfn{source path} will always include two special entries
9109 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9110 (if one is recorded) and the current working directory respectively.
9112 @samp{$cdir} causes @value{GDBN} to search within the compilation
9113 directory, if one is recorded in the debug information. If no
9114 compilation directory is recorded in the debug information then
9115 @samp{$cdir} is ignored.
9117 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9118 current working directory as it changes during your @value{GDBN}
9119 session, while the latter is immediately expanded to the current
9120 directory at the time you add an entry to the source path.
9122 If a compilation directory is recorded in the debug information, and
9123 @value{GDBN} has not found the source file after the first search
9124 using @dfn{source path}, then @value{GDBN} will combine the
9125 compilation directory and the filename, and then search for the source
9126 file again using the @dfn{source path}.
9128 For example, if the executable records the source file as
9129 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9130 recorded as @file{/project/build}, and the @dfn{source path} is
9131 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9132 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9133 search for the source file in the following locations:
9137 @item @file{/usr/src/foo-1.0/lib/foo.c}
9138 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9139 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9140 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9141 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9142 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9143 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9144 @item @file{/mnt/cross/foo.c}
9145 @item @file{/project/build/foo.c}
9146 @item @file{/home/user/foo.c}
9150 If the file name in the previous example had been recorded in the
9151 executable as a relative path rather than an absolute path, then the
9152 first look up would not have occurred, but all of the remaining steps
9155 When searching for source files on MS-DOS and MS-Windows, where
9156 absolute paths start with a drive letter (e.g.
9157 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9158 from the file name before appending it to a search directory from
9159 @dfn{source path}; for instance if the executable references the
9160 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9161 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9162 locations for the source file:
9166 @item @file{C:/project/foo.c}
9167 @item @file{D:/mnt/cross/project/foo.c}
9168 @item @file{D:/mnt/cross/foo.c}
9172 Note that the executable search path is @emph{not} used to locate the
9175 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9176 any information it has cached about where source files are found and where
9177 each line is in the file.
9181 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9182 and @samp{$cwd}, in that order.
9183 To add other directories, use the @code{directory} command.
9185 The search path is used to find both program source files and @value{GDBN}
9186 script files (read using the @samp{-command} option and @samp{source} command).
9188 In addition to the source path, @value{GDBN} provides a set of commands
9189 that manage a list of source path substitution rules. A @dfn{substitution
9190 rule} specifies how to rewrite source directories stored in the program's
9191 debug information in case the sources were moved to a different
9192 directory between compilation and debugging. A rule is made of
9193 two strings, the first specifying what needs to be rewritten in
9194 the path, and the second specifying how it should be rewritten.
9195 In @ref{set substitute-path}, we name these two parts @var{from} and
9196 @var{to} respectively. @value{GDBN} does a simple string replacement
9197 of @var{from} with @var{to} at the start of the directory part of the
9198 source file name, and uses that result instead of the original file
9199 name to look up the sources.
9201 Using the previous example, suppose the @file{foo-1.0} tree has been
9202 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9203 @value{GDBN} to replace @file{/usr/src} in all source path names with
9204 @file{/mnt/cross}. The first lookup will then be
9205 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9206 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9207 substitution rule, use the @code{set substitute-path} command
9208 (@pxref{set substitute-path}).
9210 To avoid unexpected substitution results, a rule is applied only if the
9211 @var{from} part of the directory name ends at a directory separator.
9212 For instance, a rule substituting @file{/usr/source} into
9213 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9214 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9215 is applied only at the beginning of the directory name, this rule will
9216 not be applied to @file{/root/usr/source/baz.c} either.
9218 In many cases, you can achieve the same result using the @code{directory}
9219 command. However, @code{set substitute-path} can be more efficient in
9220 the case where the sources are organized in a complex tree with multiple
9221 subdirectories. With the @code{directory} command, you need to add each
9222 subdirectory of your project. If you moved the entire tree while
9223 preserving its internal organization, then @code{set substitute-path}
9224 allows you to direct the debugger to all the sources with one single
9227 @code{set substitute-path} is also more than just a shortcut command.
9228 The source path is only used if the file at the original location no
9229 longer exists. On the other hand, @code{set substitute-path} modifies
9230 the debugger behavior to look at the rewritten location instead. So, if
9231 for any reason a source file that is not relevant to your executable is
9232 located at the original location, a substitution rule is the only
9233 method available to point @value{GDBN} at the new location.
9235 @cindex @samp{--with-relocated-sources}
9236 @cindex default source path substitution
9237 You can configure a default source path substitution rule by
9238 configuring @value{GDBN} with the
9239 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9240 should be the name of a directory under @value{GDBN}'s configured
9241 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9242 directory names in debug information under @var{dir} will be adjusted
9243 automatically if the installed @value{GDBN} is moved to a new
9244 location. This is useful if @value{GDBN}, libraries or executables
9245 with debug information and corresponding source code are being moved
9249 @item directory @var{dirname} @dots{}
9250 @item dir @var{dirname} @dots{}
9251 Add directory @var{dirname} to the front of the source path. Several
9252 directory names may be given to this command, separated by @samp{:}
9253 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9254 part of absolute file names) or
9255 whitespace. You may specify a directory that is already in the source
9256 path; this moves it forward, so @value{GDBN} searches it sooner.
9258 The special strings @samp{$cdir} (to refer to the compilation
9259 directory, if one is recorded), and @samp{$cwd} (to refer to the
9260 current working directory) can also be included in the list of
9261 directories @var{dirname}. Though these will already be in the source
9262 path they will be moved forward in the list so @value{GDBN} searches
9266 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9268 @c RET-repeat for @code{directory} is explicitly disabled, but since
9269 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9271 @item set directories @var{path-list}
9272 @kindex set directories
9273 Set the source path to @var{path-list}.
9274 @samp{$cdir:$cwd} are added if missing.
9276 @item show directories
9277 @kindex show directories
9278 Print the source path: show which directories it contains.
9280 @anchor{set substitute-path}
9281 @item set substitute-path @var{from} @var{to}
9282 @kindex set substitute-path
9283 Define a source path substitution rule, and add it at the end of the
9284 current list of existing substitution rules. If a rule with the same
9285 @var{from} was already defined, then the old rule is also deleted.
9287 For example, if the file @file{/foo/bar/baz.c} was moved to
9288 @file{/mnt/cross/baz.c}, then the command
9291 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9295 will tell @value{GDBN} to replace @samp{/foo/bar} with
9296 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9297 @file{baz.c} even though it was moved.
9299 In the case when more than one substitution rule have been defined,
9300 the rules are evaluated one by one in the order where they have been
9301 defined. The first one matching, if any, is selected to perform
9304 For instance, if we had entered the following commands:
9307 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9308 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9312 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9313 @file{/mnt/include/defs.h} by using the first rule. However, it would
9314 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9315 @file{/mnt/src/lib/foo.c}.
9318 @item unset substitute-path [path]
9319 @kindex unset substitute-path
9320 If a path is specified, search the current list of substitution rules
9321 for a rule that would rewrite that path. Delete that rule if found.
9322 A warning is emitted by the debugger if no rule could be found.
9324 If no path is specified, then all substitution rules are deleted.
9326 @item show substitute-path [path]
9327 @kindex show substitute-path
9328 If a path is specified, then print the source path substitution rule
9329 which would rewrite that path, if any.
9331 If no path is specified, then print all existing source path substitution
9336 If your source path is cluttered with directories that are no longer of
9337 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9338 versions of source. You can correct the situation as follows:
9342 Use @code{directory} with no argument to reset the source path to its default value.
9345 Use @code{directory} with suitable arguments to reinstall the
9346 directories you want in the source path. You can add all the
9347 directories in one command.
9351 @section Source and Machine Code
9352 @cindex source line and its code address
9354 You can use the command @code{info line} to map source lines to program
9355 addresses (and vice versa), and the command @code{disassemble} to display
9356 a range of addresses as machine instructions. You can use the command
9357 @code{set disassemble-next-line} to set whether to disassemble next
9358 source line when execution stops. When run under @sc{gnu} Emacs
9359 mode, the @code{info line} command causes the arrow to point to the
9360 line specified. Also, @code{info line} prints addresses in symbolic form as
9366 @itemx info line @var{location}
9367 Print the starting and ending addresses of the compiled code for
9368 source line @var{location}. You can specify source lines in any of
9369 the ways documented in @ref{Specify Location}. With no @var{location}
9370 information about the current source line is printed.
9373 For example, we can use @code{info line} to discover the location of
9374 the object code for the first line of function
9375 @code{m4_changequote}:
9378 (@value{GDBP}) info line m4_changequote
9379 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9380 ends at 0x6350 <m4_changequote+4>.
9384 @cindex code address and its source line
9385 We can also inquire (using @code{*@var{addr}} as the form for
9386 @var{location}) what source line covers a particular address:
9388 (@value{GDBP}) info line *0x63ff
9389 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9390 ends at 0x6404 <m4_changequote+184>.
9393 @cindex @code{$_} and @code{info line}
9394 @cindex @code{x} command, default address
9395 @kindex x@r{(examine), and} info line
9396 After @code{info line}, the default address for the @code{x} command
9397 is changed to the starting address of the line, so that @samp{x/i} is
9398 sufficient to begin examining the machine code (@pxref{Memory,
9399 ,Examining Memory}). Also, this address is saved as the value of the
9400 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9403 @cindex info line, repeated calls
9404 After @code{info line}, using @code{info line} again without
9405 specifying a location will display information about the next source
9410 @cindex assembly instructions
9411 @cindex instructions, assembly
9412 @cindex machine instructions
9413 @cindex listing machine instructions
9415 @itemx disassemble /m
9416 @itemx disassemble /s
9417 @itemx disassemble /r
9418 This specialized command dumps a range of memory as machine
9419 instructions. It can also print mixed source+disassembly by specifying
9420 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9421 as well as in symbolic form by specifying the @code{/r} modifier.
9422 The default memory range is the function surrounding the
9423 program counter of the selected frame. A single argument to this
9424 command is a program counter value; @value{GDBN} dumps the function
9425 surrounding this value. When two arguments are given, they should
9426 be separated by a comma, possibly surrounded by whitespace. The
9427 arguments specify a range of addresses to dump, in one of two forms:
9430 @item @var{start},@var{end}
9431 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9432 @item @var{start},+@var{length}
9433 the addresses from @var{start} (inclusive) to
9434 @code{@var{start}+@var{length}} (exclusive).
9438 When 2 arguments are specified, the name of the function is also
9439 printed (since there could be several functions in the given range).
9441 The argument(s) can be any expression yielding a numeric value, such as
9442 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9444 If the range of memory being disassembled contains current program counter,
9445 the instruction at that location is shown with a @code{=>} marker.
9448 The following example shows the disassembly of a range of addresses of
9449 HP PA-RISC 2.0 code:
9452 (@value{GDBP}) disas 0x32c4, 0x32e4
9453 Dump of assembler code from 0x32c4 to 0x32e4:
9454 0x32c4 <main+204>: addil 0,dp
9455 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9456 0x32cc <main+212>: ldil 0x3000,r31
9457 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9458 0x32d4 <main+220>: ldo 0(r31),rp
9459 0x32d8 <main+224>: addil -0x800,dp
9460 0x32dc <main+228>: ldo 0x588(r1),r26
9461 0x32e0 <main+232>: ldil 0x3000,r31
9462 End of assembler dump.
9465 Here is an example showing mixed source+assembly for Intel x86
9466 with @code{/m} or @code{/s}, when the program is stopped just after
9467 function prologue in a non-optimized function with no inline code.
9470 (@value{GDBP}) disas /m main
9471 Dump of assembler code for function main:
9473 0x08048330 <+0>: push %ebp
9474 0x08048331 <+1>: mov %esp,%ebp
9475 0x08048333 <+3>: sub $0x8,%esp
9476 0x08048336 <+6>: and $0xfffffff0,%esp
9477 0x08048339 <+9>: sub $0x10,%esp
9479 6 printf ("Hello.\n");
9480 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9481 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9485 0x08048348 <+24>: mov $0x0,%eax
9486 0x0804834d <+29>: leave
9487 0x0804834e <+30>: ret
9489 End of assembler dump.
9492 The @code{/m} option is deprecated as its output is not useful when
9493 there is either inlined code or re-ordered code.
9494 The @code{/s} option is the preferred choice.
9495 Here is an example for AMD x86-64 showing the difference between
9496 @code{/m} output and @code{/s} output.
9497 This example has one inline function defined in a header file,
9498 and the code is compiled with @samp{-O2} optimization.
9499 Note how the @code{/m} output is missing the disassembly of
9500 several instructions that are present in the @code{/s} output.
9530 (@value{GDBP}) disas /m main
9531 Dump of assembler code for function main:
9535 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9536 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9540 0x000000000040041d <+29>: xor %eax,%eax
9541 0x000000000040041f <+31>: retq
9542 0x0000000000400420 <+32>: add %eax,%eax
9543 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9545 End of assembler dump.
9546 (@value{GDBP}) disas /s main
9547 Dump of assembler code for function main:
9551 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9555 0x0000000000400406 <+6>: test %eax,%eax
9556 0x0000000000400408 <+8>: js 0x400420 <main+32>
9561 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9562 0x000000000040040d <+13>: test %eax,%eax
9563 0x000000000040040f <+15>: mov $0x1,%eax
9564 0x0000000000400414 <+20>: cmovne %edx,%eax
9568 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9572 0x000000000040041d <+29>: xor %eax,%eax
9573 0x000000000040041f <+31>: retq
9577 0x0000000000400420 <+32>: add %eax,%eax
9578 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9579 End of assembler dump.
9582 Here is another example showing raw instructions in hex for AMD x86-64,
9585 (gdb) disas /r 0x400281,+10
9586 Dump of assembler code from 0x400281 to 0x40028b:
9587 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9588 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9589 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9590 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9591 End of assembler dump.
9594 Addresses cannot be specified as a location (@pxref{Specify Location}).
9595 So, for example, if you want to disassemble function @code{bar}
9596 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9597 and not @samp{disassemble foo.c:bar}.
9599 Some architectures have more than one commonly-used set of instruction
9600 mnemonics or other syntax.
9602 For programs that were dynamically linked and use shared libraries,
9603 instructions that call functions or branch to locations in the shared
9604 libraries might show a seemingly bogus location---it's actually a
9605 location of the relocation table. On some architectures, @value{GDBN}
9606 might be able to resolve these to actual function names.
9609 @kindex set disassembler-options
9610 @cindex disassembler options
9611 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9612 This command controls the passing of target specific information to
9613 the disassembler. For a list of valid options, please refer to the
9614 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9615 manual and/or the output of @kbd{objdump --help}
9616 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9617 The default value is the empty string.
9619 If it is necessary to specify more than one disassembler option, then
9620 multiple options can be placed together into a comma separated list.
9621 Currently this command is only supported on targets ARM, MIPS, PowerPC
9624 @kindex show disassembler-options
9625 @item show disassembler-options
9626 Show the current setting of the disassembler options.
9630 @kindex set disassembly-flavor
9631 @cindex Intel disassembly flavor
9632 @cindex AT&T disassembly flavor
9633 @item set disassembly-flavor @var{instruction-set}
9634 Select the instruction set to use when disassembling the
9635 program via the @code{disassemble} or @code{x/i} commands.
9637 Currently this command is only defined for the Intel x86 family. You
9638 can set @var{instruction-set} to either @code{intel} or @code{att}.
9639 The default is @code{att}, the AT&T flavor used by default by Unix
9640 assemblers for x86-based targets.
9642 @kindex show disassembly-flavor
9643 @item show disassembly-flavor
9644 Show the current setting of the disassembly flavor.
9648 @kindex set disassemble-next-line
9649 @kindex show disassemble-next-line
9650 @item set disassemble-next-line
9651 @itemx show disassemble-next-line
9652 Control whether or not @value{GDBN} will disassemble the next source
9653 line or instruction when execution stops. If ON, @value{GDBN} will
9654 display disassembly of the next source line when execution of the
9655 program being debugged stops. This is @emph{in addition} to
9656 displaying the source line itself, which @value{GDBN} always does if
9657 possible. If the next source line cannot be displayed for some reason
9658 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9659 info in the debug info), @value{GDBN} will display disassembly of the
9660 next @emph{instruction} instead of showing the next source line. If
9661 AUTO, @value{GDBN} will display disassembly of next instruction only
9662 if the source line cannot be displayed. This setting causes
9663 @value{GDBN} to display some feedback when you step through a function
9664 with no line info or whose source file is unavailable. The default is
9665 OFF, which means never display the disassembly of the next line or
9671 @chapter Examining Data
9673 @cindex printing data
9674 @cindex examining data
9677 The usual way to examine data in your program is with the @code{print}
9678 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9679 evaluates and prints the value of an expression of the language your
9680 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9681 Different Languages}). It may also print the expression using a
9682 Python-based pretty-printer (@pxref{Pretty Printing}).
9685 @item print [[@var{options}] --] @var{expr}
9686 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9687 @var{expr} is an expression (in the source language). By default the
9688 value of @var{expr} is printed in a format appropriate to its data type;
9689 you can choose a different format by specifying @samp{/@var{f}}, where
9690 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9693 @anchor{print options}
9694 The @code{print} command supports a number of options that allow
9695 overriding relevant global print settings as set by @code{set print}
9699 @item -address [@code{on}|@code{off}]
9700 Set printing of addresses.
9701 Related setting: @ref{set print address}.
9703 @item -array [@code{on}|@code{off}]
9704 Pretty formatting of arrays.
9705 Related setting: @ref{set print array}.
9707 @item -array-indexes [@code{on}|@code{off}]
9708 Set printing of array indexes.
9709 Related setting: @ref{set print array-indexes}.
9711 @item -elements @var{number-of-elements}|@code{unlimited}
9712 Set limit on string chars or array elements to print. The value
9713 @code{unlimited} causes there to be no limit. Related setting:
9714 @ref{set print elements}.
9716 @item -max-depth @var{depth}|@code{unlimited}
9717 Set the threshold after which nested structures are replaced with
9718 ellipsis. Related setting: @ref{set print max-depth}.
9720 @item -null-stop [@code{on}|@code{off}]
9721 Set printing of char arrays to stop at first null char. Related
9722 setting: @ref{set print null-stop}.
9724 @item -object [@code{on}|@code{off}]
9725 Set printing C@t{++} virtual function tables. Related setting:
9726 @ref{set print object}.
9728 @item -pretty [@code{on}|@code{off}]
9729 Set pretty formatting of structures. Related setting: @ref{set print
9732 @item -raw-values [@code{on}|@code{off}]
9733 Set whether to print values in raw form, bypassing any
9734 pretty-printers for that value. Related setting: @ref{set print
9737 @item -repeats @var{number-of-repeats}|@code{unlimited}
9738 Set threshold for repeated print elements. @code{unlimited} causes
9739 all elements to be individually printed. Related setting: @ref{set
9742 @item -static-members [@code{on}|@code{off}]
9743 Set printing C@t{++} static members. Related setting: @ref{set print
9746 @item -symbol [@code{on}|@code{off}]
9747 Set printing of symbol names when printing pointers. Related setting:
9748 @ref{set print symbol}.
9750 @item -union [@code{on}|@code{off}]
9751 Set printing of unions interior to structures. Related setting:
9752 @ref{set print union}.
9754 @item -vtbl [@code{on}|@code{off}]
9755 Set printing of C++ virtual function tables. Related setting:
9756 @ref{set print vtbl}.
9759 Because the @code{print} command accepts arbitrary expressions which
9760 may look like options (including abbreviations), if you specify any
9761 command option, then you must use a double dash (@code{--}) to mark
9762 the end of option processing.
9764 For example, this prints the value of the @code{-p} expression:
9767 (@value{GDBP}) print -p
9770 While this repeats the last value in the value history (see below)
9771 with the @code{-pretty} option in effect:
9774 (@value{GDBP}) print -p --
9777 Here is an example including both on option and an expression:
9781 (@value{GDBP}) print -pretty -- *myptr
9793 @item print [@var{options}]
9794 @itemx print [@var{options}] /@var{f}
9795 @cindex reprint the last value
9796 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9797 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9798 conveniently inspect the same value in an alternative format.
9801 A more low-level way of examining data is with the @code{x} command.
9802 It examines data in memory at a specified address and prints it in a
9803 specified format. @xref{Memory, ,Examining Memory}.
9805 If you are interested in information about types, or about how the
9806 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9807 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9810 @cindex exploring hierarchical data structures
9812 Another way of examining values of expressions and type information is
9813 through the Python extension command @code{explore} (available only if
9814 the @value{GDBN} build is configured with @code{--with-python}). It
9815 offers an interactive way to start at the highest level (or, the most
9816 abstract level) of the data type of an expression (or, the data type
9817 itself) and explore all the way down to leaf scalar values/fields
9818 embedded in the higher level data types.
9821 @item explore @var{arg}
9822 @var{arg} is either an expression (in the source language), or a type
9823 visible in the current context of the program being debugged.
9826 The working of the @code{explore} command can be illustrated with an
9827 example. If a data type @code{struct ComplexStruct} is defined in your
9837 struct ComplexStruct
9839 struct SimpleStruct *ss_p;
9845 followed by variable declarations as
9848 struct SimpleStruct ss = @{ 10, 1.11 @};
9849 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9853 then, the value of the variable @code{cs} can be explored using the
9854 @code{explore} command as follows.
9858 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9859 the following fields:
9861 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9862 arr = <Enter 1 to explore this field of type `int [10]'>
9864 Enter the field number of choice:
9868 Since the fields of @code{cs} are not scalar values, you are being
9869 prompted to chose the field you want to explore. Let's say you choose
9870 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9871 pointer, you will be asked if it is pointing to a single value. From
9872 the declaration of @code{cs} above, it is indeed pointing to a single
9873 value, hence you enter @code{y}. If you enter @code{n}, then you will
9874 be asked if it were pointing to an array of values, in which case this
9875 field will be explored as if it were an array.
9878 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9879 Continue exploring it as a pointer to a single value [y/n]: y
9880 The value of `*(cs.ss_p)' is a struct/class of type `struct
9881 SimpleStruct' with the following fields:
9883 i = 10 .. (Value of type `int')
9884 d = 1.1100000000000001 .. (Value of type `double')
9886 Press enter to return to parent value:
9890 If the field @code{arr} of @code{cs} was chosen for exploration by
9891 entering @code{1} earlier, then since it is as array, you will be
9892 prompted to enter the index of the element in the array that you want
9896 `cs.arr' is an array of `int'.
9897 Enter the index of the element you want to explore in `cs.arr': 5
9899 `(cs.arr)[5]' is a scalar value of type `int'.
9903 Press enter to return to parent value:
9906 In general, at any stage of exploration, you can go deeper towards the
9907 leaf values by responding to the prompts appropriately, or hit the
9908 return key to return to the enclosing data structure (the @i{higher}
9909 level data structure).
9911 Similar to exploring values, you can use the @code{explore} command to
9912 explore types. Instead of specifying a value (which is typically a
9913 variable name or an expression valid in the current context of the
9914 program being debugged), you specify a type name. If you consider the
9915 same example as above, your can explore the type
9916 @code{struct ComplexStruct} by passing the argument
9917 @code{struct ComplexStruct} to the @code{explore} command.
9920 (gdb) explore struct ComplexStruct
9924 By responding to the prompts appropriately in the subsequent interactive
9925 session, you can explore the type @code{struct ComplexStruct} in a
9926 manner similar to how the value @code{cs} was explored in the above
9929 The @code{explore} command also has two sub-commands,
9930 @code{explore value} and @code{explore type}. The former sub-command is
9931 a way to explicitly specify that value exploration of the argument is
9932 being invoked, while the latter is a way to explicitly specify that type
9933 exploration of the argument is being invoked.
9936 @item explore value @var{expr}
9937 @cindex explore value
9938 This sub-command of @code{explore} explores the value of the
9939 expression @var{expr} (if @var{expr} is an expression valid in the
9940 current context of the program being debugged). The behavior of this
9941 command is identical to that of the behavior of the @code{explore}
9942 command being passed the argument @var{expr}.
9944 @item explore type @var{arg}
9945 @cindex explore type
9946 This sub-command of @code{explore} explores the type of @var{arg} (if
9947 @var{arg} is a type visible in the current context of program being
9948 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9949 is an expression valid in the current context of the program being
9950 debugged). If @var{arg} is a type, then the behavior of this command is
9951 identical to that of the @code{explore} command being passed the
9952 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9953 this command will be identical to that of the @code{explore} command
9954 being passed the type of @var{arg} as the argument.
9958 * Expressions:: Expressions
9959 * Ambiguous Expressions:: Ambiguous Expressions
9960 * Variables:: Program variables
9961 * Arrays:: Artificial arrays
9962 * Output Formats:: Output formats
9963 * Memory:: Examining memory
9964 * Auto Display:: Automatic display
9965 * Print Settings:: Print settings
9966 * Pretty Printing:: Python pretty printing
9967 * Value History:: Value history
9968 * Convenience Vars:: Convenience variables
9969 * Convenience Funs:: Convenience functions
9970 * Registers:: Registers
9971 * Floating Point Hardware:: Floating point hardware
9972 * Vector Unit:: Vector Unit
9973 * OS Information:: Auxiliary data provided by operating system
9974 * Memory Region Attributes:: Memory region attributes
9975 * Dump/Restore Files:: Copy between memory and a file
9976 * Core File Generation:: Cause a program dump its core
9977 * Character Sets:: Debugging programs that use a different
9978 character set than GDB does
9979 * Caching Target Data:: Data caching for targets
9980 * Searching Memory:: Searching memory for a sequence of bytes
9981 * Value Sizes:: Managing memory allocated for values
9985 @section Expressions
9988 @code{print} and many other @value{GDBN} commands accept an expression and
9989 compute its value. Any kind of constant, variable or operator defined
9990 by the programming language you are using is valid in an expression in
9991 @value{GDBN}. This includes conditional expressions, function calls,
9992 casts, and string constants. It also includes preprocessor macros, if
9993 you compiled your program to include this information; see
9996 @cindex arrays in expressions
9997 @value{GDBN} supports array constants in expressions input by
9998 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9999 you can use the command @code{print @{1, 2, 3@}} to create an array
10000 of three integers. If you pass an array to a function or assign it
10001 to a program variable, @value{GDBN} copies the array to memory that
10002 is @code{malloc}ed in the target program.
10004 Because C is so widespread, most of the expressions shown in examples in
10005 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10006 Languages}, for information on how to use expressions in other
10009 In this section, we discuss operators that you can use in @value{GDBN}
10010 expressions regardless of your programming language.
10012 @cindex casts, in expressions
10013 Casts are supported in all languages, not just in C, because it is so
10014 useful to cast a number into a pointer in order to examine a structure
10015 at that address in memory.
10016 @c FIXME: casts supported---Mod2 true?
10018 @value{GDBN} supports these operators, in addition to those common
10019 to programming languages:
10023 @samp{@@} is a binary operator for treating parts of memory as arrays.
10024 @xref{Arrays, ,Artificial Arrays}, for more information.
10027 @samp{::} allows you to specify a variable in terms of the file or
10028 function where it is defined. @xref{Variables, ,Program Variables}.
10030 @cindex @{@var{type}@}
10031 @cindex type casting memory
10032 @cindex memory, viewing as typed object
10033 @cindex casts, to view memory
10034 @item @{@var{type}@} @var{addr}
10035 Refers to an object of type @var{type} stored at address @var{addr} in
10036 memory. The address @var{addr} may be any expression whose value is
10037 an integer or pointer (but parentheses are required around binary
10038 operators, just as in a cast). This construct is allowed regardless
10039 of what kind of data is normally supposed to reside at @var{addr}.
10042 @node Ambiguous Expressions
10043 @section Ambiguous Expressions
10044 @cindex ambiguous expressions
10046 Expressions can sometimes contain some ambiguous elements. For instance,
10047 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10048 a single function name to be defined several times, for application in
10049 different contexts. This is called @dfn{overloading}. Another example
10050 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10051 templates and is typically instantiated several times, resulting in
10052 the same function name being defined in different contexts.
10054 In some cases and depending on the language, it is possible to adjust
10055 the expression to remove the ambiguity. For instance in C@t{++}, you
10056 can specify the signature of the function you want to break on, as in
10057 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10058 qualified name of your function often makes the expression unambiguous
10061 When an ambiguity that needs to be resolved is detected, the debugger
10062 has the capability to display a menu of numbered choices for each
10063 possibility, and then waits for the selection with the prompt @samp{>}.
10064 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10065 aborts the current command. If the command in which the expression was
10066 used allows more than one choice to be selected, the next option in the
10067 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10070 For example, the following session excerpt shows an attempt to set a
10071 breakpoint at the overloaded symbol @code{String::after}.
10072 We choose three particular definitions of that function name:
10074 @c FIXME! This is likely to change to show arg type lists, at least
10077 (@value{GDBP}) b String::after
10080 [2] file:String.cc; line number:867
10081 [3] file:String.cc; line number:860
10082 [4] file:String.cc; line number:875
10083 [5] file:String.cc; line number:853
10084 [6] file:String.cc; line number:846
10085 [7] file:String.cc; line number:735
10087 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10088 Breakpoint 2 at 0xb344: file String.cc, line 875.
10089 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10090 Multiple breakpoints were set.
10091 Use the "delete" command to delete unwanted
10098 @kindex set multiple-symbols
10099 @item set multiple-symbols @var{mode}
10100 @cindex multiple-symbols menu
10102 This option allows you to adjust the debugger behavior when an expression
10105 By default, @var{mode} is set to @code{all}. If the command with which
10106 the expression is used allows more than one choice, then @value{GDBN}
10107 automatically selects all possible choices. For instance, inserting
10108 a breakpoint on a function using an ambiguous name results in a breakpoint
10109 inserted on each possible match. However, if a unique choice must be made,
10110 then @value{GDBN} uses the menu to help you disambiguate the expression.
10111 For instance, printing the address of an overloaded function will result
10112 in the use of the menu.
10114 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10115 when an ambiguity is detected.
10117 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10118 an error due to the ambiguity and the command is aborted.
10120 @kindex show multiple-symbols
10121 @item show multiple-symbols
10122 Show the current value of the @code{multiple-symbols} setting.
10126 @section Program Variables
10128 The most common kind of expression to use is the name of a variable
10131 Variables in expressions are understood in the selected stack frame
10132 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10136 global (or file-static)
10143 visible according to the scope rules of the
10144 programming language from the point of execution in that frame
10147 @noindent This means that in the function
10162 you can examine and use the variable @code{a} whenever your program is
10163 executing within the function @code{foo}, but you can only use or
10164 examine the variable @code{b} while your program is executing inside
10165 the block where @code{b} is declared.
10167 @cindex variable name conflict
10168 There is an exception: you can refer to a variable or function whose
10169 scope is a single source file even if the current execution point is not
10170 in this file. But it is possible to have more than one such variable or
10171 function with the same name (in different source files). If that
10172 happens, referring to that name has unpredictable effects. If you wish,
10173 you can specify a static variable in a particular function or file by
10174 using the colon-colon (@code{::}) notation:
10176 @cindex colon-colon, context for variables/functions
10178 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10179 @cindex @code{::}, context for variables/functions
10182 @var{file}::@var{variable}
10183 @var{function}::@var{variable}
10187 Here @var{file} or @var{function} is the name of the context for the
10188 static @var{variable}. In the case of file names, you can use quotes to
10189 make sure @value{GDBN} parses the file name as a single word---for example,
10190 to print a global value of @code{x} defined in @file{f2.c}:
10193 (@value{GDBP}) p 'f2.c'::x
10196 The @code{::} notation is normally used for referring to
10197 static variables, since you typically disambiguate uses of local variables
10198 in functions by selecting the appropriate frame and using the
10199 simple name of the variable. However, you may also use this notation
10200 to refer to local variables in frames enclosing the selected frame:
10209 process (a); /* Stop here */
10220 For example, if there is a breakpoint at the commented line,
10221 here is what you might see
10222 when the program stops after executing the call @code{bar(0)}:
10227 (@value{GDBP}) p bar::a
10229 (@value{GDBP}) up 2
10230 #2 0x080483d0 in foo (a=5) at foobar.c:12
10233 (@value{GDBP}) p bar::a
10237 @cindex C@t{++} scope resolution
10238 These uses of @samp{::} are very rarely in conflict with the very
10239 similar use of the same notation in C@t{++}. When they are in
10240 conflict, the C@t{++} meaning takes precedence; however, this can be
10241 overridden by quoting the file or function name with single quotes.
10243 For example, suppose the program is stopped in a method of a class
10244 that has a field named @code{includefile}, and there is also an
10245 include file named @file{includefile} that defines a variable,
10246 @code{some_global}.
10249 (@value{GDBP}) p includefile
10251 (@value{GDBP}) p includefile::some_global
10252 A syntax error in expression, near `'.
10253 (@value{GDBP}) p 'includefile'::some_global
10257 @cindex wrong values
10258 @cindex variable values, wrong
10259 @cindex function entry/exit, wrong values of variables
10260 @cindex optimized code, wrong values of variables
10262 @emph{Warning:} Occasionally, a local variable may appear to have the
10263 wrong value at certain points in a function---just after entry to a new
10264 scope, and just before exit.
10266 You may see this problem when you are stepping by machine instructions.
10267 This is because, on most machines, it takes more than one instruction to
10268 set up a stack frame (including local variable definitions); if you are
10269 stepping by machine instructions, variables may appear to have the wrong
10270 values until the stack frame is completely built. On exit, it usually
10271 also takes more than one machine instruction to destroy a stack frame;
10272 after you begin stepping through that group of instructions, local
10273 variable definitions may be gone.
10275 This may also happen when the compiler does significant optimizations.
10276 To be sure of always seeing accurate values, turn off all optimization
10279 @cindex ``No symbol "foo" in current context''
10280 Another possible effect of compiler optimizations is to optimize
10281 unused variables out of existence, or assign variables to registers (as
10282 opposed to memory addresses). Depending on the support for such cases
10283 offered by the debug info format used by the compiler, @value{GDBN}
10284 might not be able to display values for such local variables. If that
10285 happens, @value{GDBN} will print a message like this:
10288 No symbol "foo" in current context.
10291 To solve such problems, either recompile without optimizations, or use a
10292 different debug info format, if the compiler supports several such
10293 formats. @xref{Compilation}, for more information on choosing compiler
10294 options. @xref{C, ,C and C@t{++}}, for more information about debug
10295 info formats that are best suited to C@t{++} programs.
10297 If you ask to print an object whose contents are unknown to
10298 @value{GDBN}, e.g., because its data type is not completely specified
10299 by the debug information, @value{GDBN} will say @samp{<incomplete
10300 type>}. @xref{Symbols, incomplete type}, for more about this.
10302 @cindex no debug info variables
10303 If you try to examine or use the value of a (global) variable for
10304 which @value{GDBN} has no type information, e.g., because the program
10305 includes no debug information, @value{GDBN} displays an error message.
10306 @xref{Symbols, unknown type}, for more about unknown types. If you
10307 cast the variable to its declared type, @value{GDBN} gets the
10308 variable's value using the cast-to type as the variable's type. For
10309 example, in a C program:
10312 (@value{GDBP}) p var
10313 'var' has unknown type; cast it to its declared type
10314 (@value{GDBP}) p (float) var
10318 If you append @kbd{@@entry} string to a function parameter name you get its
10319 value at the time the function got called. If the value is not available an
10320 error message is printed. Entry values are available only with some compilers.
10321 Entry values are normally also printed at the function parameter list according
10322 to @ref{set print entry-values}.
10325 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10331 (gdb) print i@@entry
10335 Strings are identified as arrays of @code{char} values without specified
10336 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10337 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10338 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10339 defines literal string type @code{"char"} as @code{char} without a sign.
10344 signed char var1[] = "A";
10347 You get during debugging
10352 $2 = @{65 'A', 0 '\0'@}
10356 @section Artificial Arrays
10358 @cindex artificial array
10360 @kindex @@@r{, referencing memory as an array}
10361 It is often useful to print out several successive objects of the
10362 same type in memory; a section of an array, or an array of
10363 dynamically determined size for which only a pointer exists in the
10366 You can do this by referring to a contiguous span of memory as an
10367 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10368 operand of @samp{@@} should be the first element of the desired array
10369 and be an individual object. The right operand should be the desired length
10370 of the array. The result is an array value whose elements are all of
10371 the type of the left argument. The first element is actually the left
10372 argument; the second element comes from bytes of memory immediately
10373 following those that hold the first element, and so on. Here is an
10374 example. If a program says
10377 int *array = (int *) malloc (len * sizeof (int));
10381 you can print the contents of @code{array} with
10387 The left operand of @samp{@@} must reside in memory. Array values made
10388 with @samp{@@} in this way behave just like other arrays in terms of
10389 subscripting, and are coerced to pointers when used in expressions.
10390 Artificial arrays most often appear in expressions via the value history
10391 (@pxref{Value History, ,Value History}), after printing one out.
10393 Another way to create an artificial array is to use a cast.
10394 This re-interprets a value as if it were an array.
10395 The value need not be in memory:
10397 (@value{GDBP}) p/x (short[2])0x12345678
10398 $1 = @{0x1234, 0x5678@}
10401 As a convenience, if you leave the array length out (as in
10402 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10403 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10405 (@value{GDBP}) p/x (short[])0x12345678
10406 $2 = @{0x1234, 0x5678@}
10409 Sometimes the artificial array mechanism is not quite enough; in
10410 moderately complex data structures, the elements of interest may not
10411 actually be adjacent---for example, if you are interested in the values
10412 of pointers in an array. One useful work-around in this situation is
10413 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10414 Variables}) as a counter in an expression that prints the first
10415 interesting value, and then repeat that expression via @key{RET}. For
10416 instance, suppose you have an array @code{dtab} of pointers to
10417 structures, and you are interested in the values of a field @code{fv}
10418 in each structure. Here is an example of what you might type:
10428 @node Output Formats
10429 @section Output Formats
10431 @cindex formatted output
10432 @cindex output formats
10433 By default, @value{GDBN} prints a value according to its data type. Sometimes
10434 this is not what you want. For example, you might want to print a number
10435 in hex, or a pointer in decimal. Or you might want to view data in memory
10436 at a certain address as a character string or as an instruction. To do
10437 these things, specify an @dfn{output format} when you print a value.
10439 The simplest use of output formats is to say how to print a value
10440 already computed. This is done by starting the arguments of the
10441 @code{print} command with a slash and a format letter. The format
10442 letters supported are:
10446 Regard the bits of the value as an integer, and print the integer in
10450 Print as integer in signed decimal.
10453 Print as integer in unsigned decimal.
10456 Print as integer in octal.
10459 Print as integer in binary. The letter @samp{t} stands for ``two''.
10460 @footnote{@samp{b} cannot be used because these format letters are also
10461 used with the @code{x} command, where @samp{b} stands for ``byte'';
10462 see @ref{Memory,,Examining Memory}.}
10465 @cindex unknown address, locating
10466 @cindex locate address
10467 Print as an address, both absolute in hexadecimal and as an offset from
10468 the nearest preceding symbol. You can use this format used to discover
10469 where (in what function) an unknown address is located:
10472 (@value{GDBP}) p/a 0x54320
10473 $3 = 0x54320 <_initialize_vx+396>
10477 The command @code{info symbol 0x54320} yields similar results.
10478 @xref{Symbols, info symbol}.
10481 Regard as an integer and print it as a character constant. This
10482 prints both the numerical value and its character representation. The
10483 character representation is replaced with the octal escape @samp{\nnn}
10484 for characters outside the 7-bit @sc{ascii} range.
10486 Without this format, @value{GDBN} displays @code{char},
10487 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10488 constants. Single-byte members of vectors are displayed as integer
10492 Regard the bits of the value as a floating point number and print
10493 using typical floating point syntax.
10496 @cindex printing strings
10497 @cindex printing byte arrays
10498 Regard as a string, if possible. With this format, pointers to single-byte
10499 data are displayed as null-terminated strings and arrays of single-byte data
10500 are displayed as fixed-length strings. Other values are displayed in their
10503 Without this format, @value{GDBN} displays pointers to and arrays of
10504 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10505 strings. Single-byte members of a vector are displayed as an integer
10509 Like @samp{x} formatting, the value is treated as an integer and
10510 printed as hexadecimal, but leading zeros are printed to pad the value
10511 to the size of the integer type.
10514 @cindex raw printing
10515 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10516 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10517 Printing}). This typically results in a higher-level display of the
10518 value's contents. The @samp{r} format bypasses any Python
10519 pretty-printer which might exist.
10522 For example, to print the program counter in hex (@pxref{Registers}), type
10529 Note that no space is required before the slash; this is because command
10530 names in @value{GDBN} cannot contain a slash.
10532 To reprint the last value in the value history with a different format,
10533 you can use the @code{print} command with just a format and no
10534 expression. For example, @samp{p/x} reprints the last value in hex.
10537 @section Examining Memory
10539 You can use the command @code{x} (for ``examine'') to examine memory in
10540 any of several formats, independently of your program's data types.
10542 @cindex examining memory
10544 @kindex x @r{(examine memory)}
10545 @item x/@var{nfu} @var{addr}
10546 @itemx x @var{addr}
10548 Use the @code{x} command to examine memory.
10551 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10552 much memory to display and how to format it; @var{addr} is an
10553 expression giving the address where you want to start displaying memory.
10554 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10555 Several commands set convenient defaults for @var{addr}.
10558 @item @var{n}, the repeat count
10559 The repeat count is a decimal integer; the default is 1. It specifies
10560 how much memory (counting by units @var{u}) to display. If a negative
10561 number is specified, memory is examined backward from @var{addr}.
10562 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10565 @item @var{f}, the display format
10566 The display format is one of the formats used by @code{print}
10567 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10568 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10569 The default is @samp{x} (hexadecimal) initially. The default changes
10570 each time you use either @code{x} or @code{print}.
10572 @item @var{u}, the unit size
10573 The unit size is any of
10579 Halfwords (two bytes).
10581 Words (four bytes). This is the initial default.
10583 Giant words (eight bytes).
10586 Each time you specify a unit size with @code{x}, that size becomes the
10587 default unit the next time you use @code{x}. For the @samp{i} format,
10588 the unit size is ignored and is normally not written. For the @samp{s} format,
10589 the unit size defaults to @samp{b}, unless it is explicitly given.
10590 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10591 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10592 Note that the results depend on the programming language of the
10593 current compilation unit. If the language is C, the @samp{s}
10594 modifier will use the UTF-16 encoding while @samp{w} will use
10595 UTF-32. The encoding is set by the programming language and cannot
10598 @item @var{addr}, starting display address
10599 @var{addr} is the address where you want @value{GDBN} to begin displaying
10600 memory. The expression need not have a pointer value (though it may);
10601 it is always interpreted as an integer address of a byte of memory.
10602 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10603 @var{addr} is usually just after the last address examined---but several
10604 other commands also set the default address: @code{info breakpoints} (to
10605 the address of the last breakpoint listed), @code{info line} (to the
10606 starting address of a line), and @code{print} (if you use it to display
10607 a value from memory).
10610 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10611 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10612 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10613 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10614 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10616 You can also specify a negative repeat count to examine memory backward
10617 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10618 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10620 Since the letters indicating unit sizes are all distinct from the
10621 letters specifying output formats, you do not have to remember whether
10622 unit size or format comes first; either order works. The output
10623 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10624 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10626 Even though the unit size @var{u} is ignored for the formats @samp{s}
10627 and @samp{i}, you might still want to use a count @var{n}; for example,
10628 @samp{3i} specifies that you want to see three machine instructions,
10629 including any operands. For convenience, especially when used with
10630 the @code{display} command, the @samp{i} format also prints branch delay
10631 slot instructions, if any, beyond the count specified, which immediately
10632 follow the last instruction that is within the count. The command
10633 @code{disassemble} gives an alternative way of inspecting machine
10634 instructions; see @ref{Machine Code,,Source and Machine Code}.
10636 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10637 the command displays null-terminated strings or instructions before the given
10638 address as many as the absolute value of the given number. For the @samp{i}
10639 format, we use line number information in the debug info to accurately locate
10640 instruction boundaries while disassembling backward. If line info is not
10641 available, the command stops examining memory with an error message.
10643 All the defaults for the arguments to @code{x} are designed to make it
10644 easy to continue scanning memory with minimal specifications each time
10645 you use @code{x}. For example, after you have inspected three machine
10646 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10647 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10648 the repeat count @var{n} is used again; the other arguments default as
10649 for successive uses of @code{x}.
10651 When examining machine instructions, the instruction at current program
10652 counter is shown with a @code{=>} marker. For example:
10655 (@value{GDBP}) x/5i $pc-6
10656 0x804837f <main+11>: mov %esp,%ebp
10657 0x8048381 <main+13>: push %ecx
10658 0x8048382 <main+14>: sub $0x4,%esp
10659 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10660 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10663 @cindex @code{$_}, @code{$__}, and value history
10664 The addresses and contents printed by the @code{x} command are not saved
10665 in the value history because there is often too much of them and they
10666 would get in the way. Instead, @value{GDBN} makes these values available for
10667 subsequent use in expressions as values of the convenience variables
10668 @code{$_} and @code{$__}. After an @code{x} command, the last address
10669 examined is available for use in expressions in the convenience variable
10670 @code{$_}. The contents of that address, as examined, are available in
10671 the convenience variable @code{$__}.
10673 If the @code{x} command has a repeat count, the address and contents saved
10674 are from the last memory unit printed; this is not the same as the last
10675 address printed if several units were printed on the last line of output.
10677 @anchor{addressable memory unit}
10678 @cindex addressable memory unit
10679 Most targets have an addressable memory unit size of 8 bits. This means
10680 that to each memory address are associated 8 bits of data. Some
10681 targets, however, have other addressable memory unit sizes.
10682 Within @value{GDBN} and this document, the term
10683 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10684 when explicitly referring to a chunk of data of that size. The word
10685 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10686 the addressable memory unit size of the target. For most systems,
10687 addressable memory unit is a synonym of byte.
10689 @cindex remote memory comparison
10690 @cindex target memory comparison
10691 @cindex verify remote memory image
10692 @cindex verify target memory image
10693 When you are debugging a program running on a remote target machine
10694 (@pxref{Remote Debugging}), you may wish to verify the program's image
10695 in the remote machine's memory against the executable file you
10696 downloaded to the target. Or, on any target, you may want to check
10697 whether the program has corrupted its own read-only sections. The
10698 @code{compare-sections} command is provided for such situations.
10701 @kindex compare-sections
10702 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10703 Compare the data of a loadable section @var{section-name} in the
10704 executable file of the program being debugged with the same section in
10705 the target machine's memory, and report any mismatches. With no
10706 arguments, compares all loadable sections. With an argument of
10707 @code{-r}, compares all loadable read-only sections.
10709 Note: for remote targets, this command can be accelerated if the
10710 target supports computing the CRC checksum of a block of memory
10711 (@pxref{qCRC packet}).
10715 @section Automatic Display
10716 @cindex automatic display
10717 @cindex display of expressions
10719 If you find that you want to print the value of an expression frequently
10720 (to see how it changes), you might want to add it to the @dfn{automatic
10721 display list} so that @value{GDBN} prints its value each time your program stops.
10722 Each expression added to the list is given a number to identify it;
10723 to remove an expression from the list, you specify that number.
10724 The automatic display looks like this:
10728 3: bar[5] = (struct hack *) 0x3804
10732 This display shows item numbers, expressions and their current values. As with
10733 displays you request manually using @code{x} or @code{print}, you can
10734 specify the output format you prefer; in fact, @code{display} decides
10735 whether to use @code{print} or @code{x} depending your format
10736 specification---it uses @code{x} if you specify either the @samp{i}
10737 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10741 @item display @var{expr}
10742 Add the expression @var{expr} to the list of expressions to display
10743 each time your program stops. @xref{Expressions, ,Expressions}.
10745 @code{display} does not repeat if you press @key{RET} again after using it.
10747 @item display/@var{fmt} @var{expr}
10748 For @var{fmt} specifying only a display format and not a size or
10749 count, add the expression @var{expr} to the auto-display list but
10750 arrange to display it each time in the specified format @var{fmt}.
10751 @xref{Output Formats,,Output Formats}.
10753 @item display/@var{fmt} @var{addr}
10754 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10755 number of units, add the expression @var{addr} as a memory address to
10756 be examined each time your program stops. Examining means in effect
10757 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10760 For example, @samp{display/i $pc} can be helpful, to see the machine
10761 instruction about to be executed each time execution stops (@samp{$pc}
10762 is a common name for the program counter; @pxref{Registers, ,Registers}).
10765 @kindex delete display
10767 @item undisplay @var{dnums}@dots{}
10768 @itemx delete display @var{dnums}@dots{}
10769 Remove items from the list of expressions to display. Specify the
10770 numbers of the displays that you want affected with the command
10771 argument @var{dnums}. It can be a single display number, one of the
10772 numbers shown in the first field of the @samp{info display} display;
10773 or it could be a range of display numbers, as in @code{2-4}.
10775 @code{undisplay} does not repeat if you press @key{RET} after using it.
10776 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10778 @kindex disable display
10779 @item disable display @var{dnums}@dots{}
10780 Disable the display of item numbers @var{dnums}. A disabled display
10781 item is not printed automatically, but is not forgotten. It may be
10782 enabled again later. Specify the numbers of the displays that you
10783 want affected with the command argument @var{dnums}. It can be a
10784 single display number, one of the numbers shown in the first field of
10785 the @samp{info display} display; or it could be a range of display
10786 numbers, as in @code{2-4}.
10788 @kindex enable display
10789 @item enable display @var{dnums}@dots{}
10790 Enable display of item numbers @var{dnums}. It becomes effective once
10791 again in auto display of its expression, until you specify otherwise.
10792 Specify the numbers of the displays that you want affected with the
10793 command argument @var{dnums}. It can be a single display number, one
10794 of the numbers shown in the first field of the @samp{info display}
10795 display; or it could be a range of display numbers, as in @code{2-4}.
10798 Display the current values of the expressions on the list, just as is
10799 done when your program stops.
10801 @kindex info display
10803 Print the list of expressions previously set up to display
10804 automatically, each one with its item number, but without showing the
10805 values. This includes disabled expressions, which are marked as such.
10806 It also includes expressions which would not be displayed right now
10807 because they refer to automatic variables not currently available.
10810 @cindex display disabled out of scope
10811 If a display expression refers to local variables, then it does not make
10812 sense outside the lexical context for which it was set up. Such an
10813 expression is disabled when execution enters a context where one of its
10814 variables is not defined. For example, if you give the command
10815 @code{display last_char} while inside a function with an argument
10816 @code{last_char}, @value{GDBN} displays this argument while your program
10817 continues to stop inside that function. When it stops elsewhere---where
10818 there is no variable @code{last_char}---the display is disabled
10819 automatically. The next time your program stops where @code{last_char}
10820 is meaningful, you can enable the display expression once again.
10822 @node Print Settings
10823 @section Print Settings
10825 @cindex format options
10826 @cindex print settings
10827 @value{GDBN} provides the following ways to control how arrays, structures,
10828 and symbols are printed.
10831 These settings are useful for debugging programs in any language:
10835 @anchor{set print address}
10836 @item set print address
10837 @itemx set print address on
10838 @cindex print/don't print memory addresses
10839 @value{GDBN} prints memory addresses showing the location of stack
10840 traces, structure values, pointer values, breakpoints, and so forth,
10841 even when it also displays the contents of those addresses. The default
10842 is @code{on}. For example, this is what a stack frame display looks like with
10843 @code{set print address on}:
10848 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10850 530 if (lquote != def_lquote)
10854 @item set print address off
10855 Do not print addresses when displaying their contents. For example,
10856 this is the same stack frame displayed with @code{set print address off}:
10860 (@value{GDBP}) set print addr off
10862 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10863 530 if (lquote != def_lquote)
10867 You can use @samp{set print address off} to eliminate all machine
10868 dependent displays from the @value{GDBN} interface. For example, with
10869 @code{print address off}, you should get the same text for backtraces on
10870 all machines---whether or not they involve pointer arguments.
10873 @item show print address
10874 Show whether or not addresses are to be printed.
10877 When @value{GDBN} prints a symbolic address, it normally prints the
10878 closest earlier symbol plus an offset. If that symbol does not uniquely
10879 identify the address (for example, it is a name whose scope is a single
10880 source file), you may need to clarify. One way to do this is with
10881 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10882 you can set @value{GDBN} to print the source file and line number when
10883 it prints a symbolic address:
10886 @item set print symbol-filename on
10887 @cindex source file and line of a symbol
10888 @cindex symbol, source file and line
10889 Tell @value{GDBN} to print the source file name and line number of a
10890 symbol in the symbolic form of an address.
10892 @item set print symbol-filename off
10893 Do not print source file name and line number of a symbol. This is the
10896 @item show print symbol-filename
10897 Show whether or not @value{GDBN} will print the source file name and
10898 line number of a symbol in the symbolic form of an address.
10901 Another situation where it is helpful to show symbol filenames and line
10902 numbers is when disassembling code; @value{GDBN} shows you the line
10903 number and source file that corresponds to each instruction.
10905 Also, you may wish to see the symbolic form only if the address being
10906 printed is reasonably close to the closest earlier symbol:
10909 @item set print max-symbolic-offset @var{max-offset}
10910 @itemx set print max-symbolic-offset unlimited
10911 @cindex maximum value for offset of closest symbol
10912 Tell @value{GDBN} to only display the symbolic form of an address if the
10913 offset between the closest earlier symbol and the address is less than
10914 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10915 to always print the symbolic form of an address if any symbol precedes
10916 it. Zero is equivalent to @code{unlimited}.
10918 @item show print max-symbolic-offset
10919 Ask how large the maximum offset is that @value{GDBN} prints in a
10923 @cindex wild pointer, interpreting
10924 @cindex pointer, finding referent
10925 If you have a pointer and you are not sure where it points, try
10926 @samp{set print symbol-filename on}. Then you can determine the name
10927 and source file location of the variable where it points, using
10928 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10929 For example, here @value{GDBN} shows that a variable @code{ptt} points
10930 at another variable @code{t}, defined in @file{hi2.c}:
10933 (@value{GDBP}) set print symbol-filename on
10934 (@value{GDBP}) p/a ptt
10935 $4 = 0xe008 <t in hi2.c>
10939 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10940 does not show the symbol name and filename of the referent, even with
10941 the appropriate @code{set print} options turned on.
10944 You can also enable @samp{/a}-like formatting all the time using
10945 @samp{set print symbol on}:
10947 @anchor{set print symbol}
10949 @item set print symbol on
10950 Tell @value{GDBN} to print the symbol corresponding to an address, if
10953 @item set print symbol off
10954 Tell @value{GDBN} not to print the symbol corresponding to an
10955 address. In this mode, @value{GDBN} will still print the symbol
10956 corresponding to pointers to functions. This is the default.
10958 @item show print symbol
10959 Show whether @value{GDBN} will display the symbol corresponding to an
10963 Other settings control how different kinds of objects are printed:
10966 @anchor{set print array}
10967 @item set print array
10968 @itemx set print array on
10969 @cindex pretty print arrays
10970 Pretty print arrays. This format is more convenient to read,
10971 but uses more space. The default is off.
10973 @item set print array off
10974 Return to compressed format for arrays.
10976 @item show print array
10977 Show whether compressed or pretty format is selected for displaying
10980 @cindex print array indexes
10981 @anchor{set print array-indexes}
10982 @item set print array-indexes
10983 @itemx set print array-indexes on
10984 Print the index of each element when displaying arrays. May be more
10985 convenient to locate a given element in the array or quickly find the
10986 index of a given element in that printed array. The default is off.
10988 @item set print array-indexes off
10989 Stop printing element indexes when displaying arrays.
10991 @item show print array-indexes
10992 Show whether the index of each element is printed when displaying
10995 @anchor{set print elements}
10996 @item set print elements @var{number-of-elements}
10997 @itemx set print elements unlimited
10998 @cindex number of array elements to print
10999 @cindex limit on number of printed array elements
11000 Set a limit on how many elements of an array @value{GDBN} will print.
11001 If @value{GDBN} is printing a large array, it stops printing after it has
11002 printed the number of elements set by the @code{set print elements} command.
11003 This limit also applies to the display of strings.
11004 When @value{GDBN} starts, this limit is set to 200.
11005 Setting @var{number-of-elements} to @code{unlimited} or zero means
11006 that the number of elements to print is unlimited.
11008 @item show print elements
11009 Display the number of elements of a large array that @value{GDBN} will print.
11010 If the number is 0, then the printing is unlimited.
11012 @anchor{set print frame-arguments}
11013 @item set print frame-arguments @var{value}
11014 @kindex set print frame-arguments
11015 @cindex printing frame argument values
11016 @cindex print all frame argument values
11017 @cindex print frame argument values for scalars only
11018 @cindex do not print frame arguments
11019 This command allows to control how the values of arguments are printed
11020 when the debugger prints a frame (@pxref{Frames}). The possible
11025 The values of all arguments are printed.
11028 Print the value of an argument only if it is a scalar. The value of more
11029 complex arguments such as arrays, structures, unions, etc, is replaced
11030 by @code{@dots{}}. This is the default. Here is an example where
11031 only scalar arguments are shown:
11034 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11039 None of the argument values are printed. Instead, the value of each argument
11040 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11043 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11048 Only the presence of arguments is indicated by @code{@dots{}}.
11049 The @code{@dots{}} are not printed for function without any arguments.
11050 None of the argument names and values are printed.
11051 In this case, the example above now becomes:
11054 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11059 By default, only scalar arguments are printed. This command can be used
11060 to configure the debugger to print the value of all arguments, regardless
11061 of their type. However, it is often advantageous to not print the value
11062 of more complex parameters. For instance, it reduces the amount of
11063 information printed in each frame, making the backtrace more readable.
11064 Also, it improves performance when displaying Ada frames, because
11065 the computation of large arguments can sometimes be CPU-intensive,
11066 especially in large applications. Setting @code{print frame-arguments}
11067 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11068 this computation, thus speeding up the display of each Ada frame.
11070 @item show print frame-arguments
11071 Show how the value of arguments should be displayed when printing a frame.
11073 @anchor{set print raw-frame-arguments}
11074 @item set print raw-frame-arguments on
11075 Print frame arguments in raw, non pretty-printed, form.
11077 @item set print raw-frame-arguments off
11078 Print frame arguments in pretty-printed form, if there is a pretty-printer
11079 for the value (@pxref{Pretty Printing}),
11080 otherwise print the value in raw form.
11081 This is the default.
11083 @item show print raw-frame-arguments
11084 Show whether to print frame arguments in raw form.
11086 @anchor{set print entry-values}
11087 @item set print entry-values @var{value}
11088 @kindex set print entry-values
11089 Set printing of frame argument values at function entry. In some cases
11090 @value{GDBN} can determine the value of function argument which was passed by
11091 the function caller, even if the value was modified inside the called function
11092 and therefore is different. With optimized code, the current value could be
11093 unavailable, but the entry value may still be known.
11095 The default value is @code{default} (see below for its description). Older
11096 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11097 this feature will behave in the @code{default} setting the same way as with the
11100 This functionality is currently supported only by DWARF 2 debugging format and
11101 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11102 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11105 The @var{value} parameter can be one of the following:
11109 Print only actual parameter values, never print values from function entry
11113 #0 different (val=6)
11114 #0 lost (val=<optimized out>)
11116 #0 invalid (val=<optimized out>)
11120 Print only parameter values from function entry point. The actual parameter
11121 values are never printed.
11123 #0 equal (val@@entry=5)
11124 #0 different (val@@entry=5)
11125 #0 lost (val@@entry=5)
11126 #0 born (val@@entry=<optimized out>)
11127 #0 invalid (val@@entry=<optimized out>)
11131 Print only parameter values from function entry point. If value from function
11132 entry point is not known while the actual value is known, print the actual
11133 value for such parameter.
11135 #0 equal (val@@entry=5)
11136 #0 different (val@@entry=5)
11137 #0 lost (val@@entry=5)
11139 #0 invalid (val@@entry=<optimized out>)
11143 Print actual parameter values. If actual parameter value is not known while
11144 value from function entry point is known, print the entry point value for such
11148 #0 different (val=6)
11149 #0 lost (val@@entry=5)
11151 #0 invalid (val=<optimized out>)
11155 Always print both the actual parameter value and its value from function entry
11156 point, even if values of one or both are not available due to compiler
11159 #0 equal (val=5, val@@entry=5)
11160 #0 different (val=6, val@@entry=5)
11161 #0 lost (val=<optimized out>, val@@entry=5)
11162 #0 born (val=10, val@@entry=<optimized out>)
11163 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11167 Print the actual parameter value if it is known and also its value from
11168 function entry point if it is known. If neither is known, print for the actual
11169 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11170 values are known and identical, print the shortened
11171 @code{param=param@@entry=VALUE} notation.
11173 #0 equal (val=val@@entry=5)
11174 #0 different (val=6, val@@entry=5)
11175 #0 lost (val@@entry=5)
11177 #0 invalid (val=<optimized out>)
11181 Always print the actual parameter value. Print also its value from function
11182 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11183 if both values are known and identical, print the shortened
11184 @code{param=param@@entry=VALUE} notation.
11186 #0 equal (val=val@@entry=5)
11187 #0 different (val=6, val@@entry=5)
11188 #0 lost (val=<optimized out>, val@@entry=5)
11190 #0 invalid (val=<optimized out>)
11194 For analysis messages on possible failures of frame argument values at function
11195 entry resolution see @ref{set debug entry-values}.
11197 @item show print entry-values
11198 Show the method being used for printing of frame argument values at function
11201 @anchor{set print frame-info}
11202 @item set print frame-info @var{value}
11203 @kindex set print frame-info
11204 @cindex printing frame information
11205 @cindex frame information, printing
11206 This command allows to control the information printed when
11207 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11208 for a general explanation about frames and frame information.
11209 Note that some other settings (such as @code{set print frame-arguments}
11210 and @code{set print address}) are also influencing if and how some frame
11211 information is displayed. In particular, the frame program counter is never
11212 printed if @code{set print address} is off.
11214 The possible values for @code{set print frame-info} are:
11216 @item short-location
11217 Print the frame level, the program counter (if not at the
11218 beginning of the location source line), the function, the function
11221 Same as @code{short-location} but also print the source file and source line
11223 @item location-and-address
11224 Same as @code{location} but print the program counter even if located at the
11225 beginning of the location source line.
11227 Print the program counter (if not at the beginning of the location
11228 source line), the line number and the source line.
11229 @item source-and-location
11230 Print what @code{location} and @code{source-line} are printing.
11232 The information printed for a frame is decided automatically
11233 by the @value{GDBN} command that prints a frame.
11234 For example, @code{frame} prints the information printed by
11235 @code{source-and-location} while @code{stepi} will switch between
11236 @code{source-line} and @code{source-and-location} depending on the program
11238 The default value is @code{auto}.
11241 @anchor{set print repeats}
11242 @item set print repeats @var{number-of-repeats}
11243 @itemx set print repeats unlimited
11244 @cindex repeated array elements
11245 Set the threshold for suppressing display of repeated array
11246 elements. When the number of consecutive identical elements of an
11247 array exceeds the threshold, @value{GDBN} prints the string
11248 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11249 identical repetitions, instead of displaying the identical elements
11250 themselves. Setting the threshold to @code{unlimited} or zero will
11251 cause all elements to be individually printed. The default threshold
11254 @item show print repeats
11255 Display the current threshold for printing repeated identical
11258 @anchor{set print max-depth}
11259 @item set print max-depth @var{depth}
11260 @item set print max-depth unlimited
11261 @cindex printing nested structures
11262 Set the threshold after which nested structures are replaced with
11263 ellipsis, this can make visualising deeply nested structures easier.
11265 For example, given this C code
11268 typedef struct s1 @{ int a; @} s1;
11269 typedef struct s2 @{ s1 b; @} s2;
11270 typedef struct s3 @{ s2 c; @} s3;
11271 typedef struct s4 @{ s3 d; @} s4;
11273 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11276 The following table shows how different values of @var{depth} will
11277 effect how @code{var} is printed by @value{GDBN}:
11279 @multitable @columnfractions .3 .7
11280 @headitem @var{depth} setting @tab Result of @samp{p var}
11282 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11284 @tab @code{$1 = @{...@}}
11286 @tab @code{$1 = @{d = @{...@}@}}
11288 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11290 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11292 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11295 To see the contents of structures that have been hidden the user can
11296 either increase the print max-depth, or they can print the elements of
11297 the structure that are visible, for example
11300 (gdb) set print max-depth 2
11302 $1 = @{d = @{c = @{...@}@}@}
11304 $2 = @{c = @{b = @{...@}@}@}
11306 $3 = @{b = @{a = 3@}@}
11309 The pattern used to replace nested structures varies based on
11310 language, for most languages @code{@{...@}} is used, but Fortran uses
11313 @item show print max-depth
11314 Display the current threshold after which nested structures are
11315 replaces with ellipsis.
11317 @anchor{set print null-stop}
11318 @item set print null-stop
11319 @cindex @sc{null} elements in arrays
11320 Cause @value{GDBN} to stop printing the characters of an array when the first
11321 @sc{null} is encountered. This is useful when large arrays actually
11322 contain only short strings.
11323 The default is off.
11325 @item show print null-stop
11326 Show whether @value{GDBN} stops printing an array on the first
11327 @sc{null} character.
11329 @anchor{set print pretty}
11330 @item set print pretty on
11331 @cindex print structures in indented form
11332 @cindex indentation in structure display
11333 Cause @value{GDBN} to print structures in an indented format with one member
11334 per line, like this:
11349 @item set print pretty off
11350 Cause @value{GDBN} to print structures in a compact format, like this:
11354 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11355 meat = 0x54 "Pork"@}
11360 This is the default format.
11362 @item show print pretty
11363 Show which format @value{GDBN} is using to print structures.
11365 @anchor{set print raw-values}
11366 @item set print raw-values on
11367 Print values in raw form, without applying the pretty
11368 printers for the value.
11370 @item set print raw-values off
11371 Print values in pretty-printed form, if there is a pretty-printer
11372 for the value (@pxref{Pretty Printing}),
11373 otherwise print the value in raw form.
11375 The default setting is ``off''.
11377 @item show print raw-values
11378 Show whether to print values in raw form.
11380 @item set print sevenbit-strings on
11381 @cindex eight-bit characters in strings
11382 @cindex octal escapes in strings
11383 Print using only seven-bit characters; if this option is set,
11384 @value{GDBN} displays any eight-bit characters (in strings or
11385 character values) using the notation @code{\}@var{nnn}. This setting is
11386 best if you are working in English (@sc{ascii}) and you use the
11387 high-order bit of characters as a marker or ``meta'' bit.
11389 @item set print sevenbit-strings off
11390 Print full eight-bit characters. This allows the use of more
11391 international character sets, and is the default.
11393 @item show print sevenbit-strings
11394 Show whether or not @value{GDBN} is printing only seven-bit characters.
11396 @anchor{set print union}
11397 @item set print union on
11398 @cindex unions in structures, printing
11399 Tell @value{GDBN} to print unions which are contained in structures
11400 and other unions. This is the default setting.
11402 @item set print union off
11403 Tell @value{GDBN} not to print unions which are contained in
11404 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11407 @item show print union
11408 Ask @value{GDBN} whether or not it will print unions which are contained in
11409 structures and other unions.
11411 For example, given the declarations
11414 typedef enum @{Tree, Bug@} Species;
11415 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11416 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11427 struct thing foo = @{Tree, @{Acorn@}@};
11431 with @code{set print union on} in effect @samp{p foo} would print
11434 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11438 and with @code{set print union off} in effect it would print
11441 $1 = @{it = Tree, form = @{...@}@}
11445 @code{set print union} affects programs written in C-like languages
11451 These settings are of interest when debugging C@t{++} programs:
11454 @cindex demangling C@t{++} names
11455 @item set print demangle
11456 @itemx set print demangle on
11457 Print C@t{++} names in their source form rather than in the encoded
11458 (``mangled'') form passed to the assembler and linker for type-safe
11459 linkage. The default is on.
11461 @item show print demangle
11462 Show whether C@t{++} names are printed in mangled or demangled form.
11464 @item set print asm-demangle
11465 @itemx set print asm-demangle on
11466 Print C@t{++} names in their source form rather than their mangled form, even
11467 in assembler code printouts such as instruction disassemblies.
11468 The default is off.
11470 @item show print asm-demangle
11471 Show whether C@t{++} names in assembly listings are printed in mangled
11474 @cindex C@t{++} symbol decoding style
11475 @cindex symbol decoding style, C@t{++}
11476 @kindex set demangle-style
11477 @item set demangle-style @var{style}
11478 Choose among several encoding schemes used by different compilers to represent
11479 C@t{++} names. If you omit @var{style}, you will see a list of possible
11480 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11481 decoding style by inspecting your program.
11483 @item show demangle-style
11484 Display the encoding style currently in use for decoding C@t{++} symbols.
11486 @anchor{set print object}
11487 @item set print object
11488 @itemx set print object on
11489 @cindex derived type of an object, printing
11490 @cindex display derived types
11491 When displaying a pointer to an object, identify the @emph{actual}
11492 (derived) type of the object rather than the @emph{declared} type, using
11493 the virtual function table. Note that the virtual function table is
11494 required---this feature can only work for objects that have run-time
11495 type identification; a single virtual method in the object's declared
11496 type is sufficient. Note that this setting is also taken into account when
11497 working with variable objects via MI (@pxref{GDB/MI}).
11499 @item set print object off
11500 Display only the declared type of objects, without reference to the
11501 virtual function table. This is the default setting.
11503 @item show print object
11504 Show whether actual, or declared, object types are displayed.
11506 @anchor{set print static-members}
11507 @item set print static-members
11508 @itemx set print static-members on
11509 @cindex static members of C@t{++} objects
11510 Print static members when displaying a C@t{++} object. The default is on.
11512 @item set print static-members off
11513 Do not print static members when displaying a C@t{++} object.
11515 @item show print static-members
11516 Show whether C@t{++} static members are printed or not.
11518 @item set print pascal_static-members
11519 @itemx set print pascal_static-members on
11520 @cindex static members of Pascal objects
11521 @cindex Pascal objects, static members display
11522 Print static members when displaying a Pascal object. The default is on.
11524 @item set print pascal_static-members off
11525 Do not print static members when displaying a Pascal object.
11527 @item show print pascal_static-members
11528 Show whether Pascal static members are printed or not.
11530 @c These don't work with HP ANSI C++ yet.
11531 @anchor{set print vtbl}
11532 @item set print vtbl
11533 @itemx set print vtbl on
11534 @cindex pretty print C@t{++} virtual function tables
11535 @cindex virtual functions (C@t{++}) display
11536 @cindex VTBL display
11537 Pretty print C@t{++} virtual function tables. The default is off.
11538 (The @code{vtbl} commands do not work on programs compiled with the HP
11539 ANSI C@t{++} compiler (@code{aCC}).)
11541 @item set print vtbl off
11542 Do not pretty print C@t{++} virtual function tables.
11544 @item show print vtbl
11545 Show whether C@t{++} virtual function tables are pretty printed, or not.
11548 @node Pretty Printing
11549 @section Pretty Printing
11551 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11552 Python code. It greatly simplifies the display of complex objects. This
11553 mechanism works for both MI and the CLI.
11556 * Pretty-Printer Introduction:: Introduction to pretty-printers
11557 * Pretty-Printer Example:: An example pretty-printer
11558 * Pretty-Printer Commands:: Pretty-printer commands
11561 @node Pretty-Printer Introduction
11562 @subsection Pretty-Printer Introduction
11564 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11565 registered for the value. If there is then @value{GDBN} invokes the
11566 pretty-printer to print the value. Otherwise the value is printed normally.
11568 Pretty-printers are normally named. This makes them easy to manage.
11569 The @samp{info pretty-printer} command will list all the installed
11570 pretty-printers with their names.
11571 If a pretty-printer can handle multiple data types, then its
11572 @dfn{subprinters} are the printers for the individual data types.
11573 Each such subprinter has its own name.
11574 The format of the name is @var{printer-name};@var{subprinter-name}.
11576 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11577 Typically they are automatically loaded and registered when the corresponding
11578 debug information is loaded, thus making them available without having to
11579 do anything special.
11581 There are three places where a pretty-printer can be registered.
11585 Pretty-printers registered globally are available when debugging
11589 Pretty-printers registered with a program space are available only
11590 when debugging that program.
11591 @xref{Progspaces In Python}, for more details on program spaces in Python.
11594 Pretty-printers registered with an objfile are loaded and unloaded
11595 with the corresponding objfile (e.g., shared library).
11596 @xref{Objfiles In Python}, for more details on objfiles in Python.
11599 @xref{Selecting Pretty-Printers}, for further information on how
11600 pretty-printers are selected,
11602 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11605 @node Pretty-Printer Example
11606 @subsection Pretty-Printer Example
11608 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11611 (@value{GDBP}) print s
11613 static npos = 4294967295,
11615 <std::allocator<char>> = @{
11616 <__gnu_cxx::new_allocator<char>> = @{
11617 <No data fields>@}, <No data fields>
11619 members of std::basic_string<char, std::char_traits<char>,
11620 std::allocator<char> >::_Alloc_hider:
11621 _M_p = 0x804a014 "abcd"
11626 With a pretty-printer for @code{std::string} only the contents are printed:
11629 (@value{GDBP}) print s
11633 @node Pretty-Printer Commands
11634 @subsection Pretty-Printer Commands
11635 @cindex pretty-printer commands
11638 @kindex info pretty-printer
11639 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11640 Print the list of installed pretty-printers.
11641 This includes disabled pretty-printers, which are marked as such.
11643 @var{object-regexp} is a regular expression matching the objects
11644 whose pretty-printers to list.
11645 Objects can be @code{global}, the program space's file
11646 (@pxref{Progspaces In Python}),
11647 and the object files within that program space (@pxref{Objfiles In Python}).
11648 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11649 looks up a printer from these three objects.
11651 @var{name-regexp} is a regular expression matching the name of the printers
11654 @kindex disable pretty-printer
11655 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11656 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11657 A disabled pretty-printer is not forgotten, it may be enabled again later.
11659 @kindex enable pretty-printer
11660 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11661 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11666 Suppose we have three pretty-printers installed: one from library1.so
11667 named @code{foo} that prints objects of type @code{foo}, and
11668 another from library2.so named @code{bar} that prints two types of objects,
11669 @code{bar1} and @code{bar2}.
11672 (gdb) info pretty-printer
11679 (gdb) info pretty-printer library2
11684 (gdb) disable pretty-printer library1
11686 2 of 3 printers enabled
11687 (gdb) info pretty-printer
11694 (gdb) disable pretty-printer library2 bar;bar1
11696 1 of 3 printers enabled
11697 (gdb) info pretty-printer library2
11704 (gdb) disable pretty-printer library2 bar
11706 0 of 3 printers enabled
11707 (gdb) info pretty-printer library2
11716 Note that for @code{bar} the entire printer can be disabled,
11717 as can each individual subprinter.
11719 Printing values and frame arguments is done by default using
11720 the enabled pretty printers.
11722 The print option @code{-raw-values} and @value{GDBN} setting
11723 @code{set print raw-values} (@pxref{set print raw-values}) can be
11724 used to print values without applying the enabled pretty printers.
11726 Similarly, the backtrace option @code{-raw-frame-arguments} and
11727 @value{GDBN} setting @code{set print raw-frame-arguments}
11728 (@pxref{set print raw-frame-arguments}) can be used to ignore the
11729 enabled pretty printers when printing frame argument values.
11731 @node Value History
11732 @section Value History
11734 @cindex value history
11735 @cindex history of values printed by @value{GDBN}
11736 Values printed by the @code{print} command are saved in the @value{GDBN}
11737 @dfn{value history}. This allows you to refer to them in other expressions.
11738 Values are kept until the symbol table is re-read or discarded
11739 (for example with the @code{file} or @code{symbol-file} commands).
11740 When the symbol table changes, the value history is discarded,
11741 since the values may contain pointers back to the types defined in the
11746 @cindex history number
11747 The values printed are given @dfn{history numbers} by which you can
11748 refer to them. These are successive integers starting with one.
11749 @code{print} shows you the history number assigned to a value by
11750 printing @samp{$@var{num} = } before the value; here @var{num} is the
11753 To refer to any previous value, use @samp{$} followed by the value's
11754 history number. The way @code{print} labels its output is designed to
11755 remind you of this. Just @code{$} refers to the most recent value in
11756 the history, and @code{$$} refers to the value before that.
11757 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11758 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11759 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11761 For example, suppose you have just printed a pointer to a structure and
11762 want to see the contents of the structure. It suffices to type
11768 If you have a chain of structures where the component @code{next} points
11769 to the next one, you can print the contents of the next one with this:
11776 You can print successive links in the chain by repeating this
11777 command---which you can do by just typing @key{RET}.
11779 Note that the history records values, not expressions. If the value of
11780 @code{x} is 4 and you type these commands:
11788 then the value recorded in the value history by the @code{print} command
11789 remains 4 even though the value of @code{x} has changed.
11792 @kindex show values
11794 Print the last ten values in the value history, with their item numbers.
11795 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11796 values} does not change the history.
11798 @item show values @var{n}
11799 Print ten history values centered on history item number @var{n}.
11801 @item show values +
11802 Print ten history values just after the values last printed. If no more
11803 values are available, @code{show values +} produces no display.
11806 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11807 same effect as @samp{show values +}.
11809 @node Convenience Vars
11810 @section Convenience Variables
11812 @cindex convenience variables
11813 @cindex user-defined variables
11814 @value{GDBN} provides @dfn{convenience variables} that you can use within
11815 @value{GDBN} to hold on to a value and refer to it later. These variables
11816 exist entirely within @value{GDBN}; they are not part of your program, and
11817 setting a convenience variable has no direct effect on further execution
11818 of your program. That is why you can use them freely.
11820 Convenience variables are prefixed with @samp{$}. Any name preceded by
11821 @samp{$} can be used for a convenience variable, unless it is one of
11822 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11823 (Value history references, in contrast, are @emph{numbers} preceded
11824 by @samp{$}. @xref{Value History, ,Value History}.)
11826 You can save a value in a convenience variable with an assignment
11827 expression, just as you would set a variable in your program.
11831 set $foo = *object_ptr
11835 would save in @code{$foo} the value contained in the object pointed to by
11838 Using a convenience variable for the first time creates it, but its
11839 value is @code{void} until you assign a new value. You can alter the
11840 value with another assignment at any time.
11842 Convenience variables have no fixed types. You can assign a convenience
11843 variable any type of value, including structures and arrays, even if
11844 that variable already has a value of a different type. The convenience
11845 variable, when used as an expression, has the type of its current value.
11848 @kindex show convenience
11849 @cindex show all user variables and functions
11850 @item show convenience
11851 Print a list of convenience variables used so far, and their values,
11852 as well as a list of the convenience functions.
11853 Abbreviated @code{show conv}.
11855 @kindex init-if-undefined
11856 @cindex convenience variables, initializing
11857 @item init-if-undefined $@var{variable} = @var{expression}
11858 Set a convenience variable if it has not already been set. This is useful
11859 for user-defined commands that keep some state. It is similar, in concept,
11860 to using local static variables with initializers in C (except that
11861 convenience variables are global). It can also be used to allow users to
11862 override default values used in a command script.
11864 If the variable is already defined then the expression is not evaluated so
11865 any side-effects do not occur.
11868 One of the ways to use a convenience variable is as a counter to be
11869 incremented or a pointer to be advanced. For example, to print
11870 a field from successive elements of an array of structures:
11874 print bar[$i++]->contents
11878 Repeat that command by typing @key{RET}.
11880 Some convenience variables are created automatically by @value{GDBN} and given
11881 values likely to be useful.
11884 @vindex $_@r{, convenience variable}
11886 The variable @code{$_} is automatically set by the @code{x} command to
11887 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11888 commands which provide a default address for @code{x} to examine also
11889 set @code{$_} to that address; these commands include @code{info line}
11890 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11891 except when set by the @code{x} command, in which case it is a pointer
11892 to the type of @code{$__}.
11894 @vindex $__@r{, convenience variable}
11896 The variable @code{$__} is automatically set by the @code{x} command
11897 to the value found in the last address examined. Its type is chosen
11898 to match the format in which the data was printed.
11901 @vindex $_exitcode@r{, convenience variable}
11902 When the program being debugged terminates normally, @value{GDBN}
11903 automatically sets this variable to the exit code of the program, and
11904 resets @code{$_exitsignal} to @code{void}.
11907 @vindex $_exitsignal@r{, convenience variable}
11908 When the program being debugged dies due to an uncaught signal,
11909 @value{GDBN} automatically sets this variable to that signal's number,
11910 and resets @code{$_exitcode} to @code{void}.
11912 To distinguish between whether the program being debugged has exited
11913 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11914 @code{$_exitsignal} is not @code{void}), the convenience function
11915 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11916 Functions}). For example, considering the following source code:
11919 #include <signal.h>
11922 main (int argc, char *argv[])
11929 A valid way of telling whether the program being debugged has exited
11930 or signalled would be:
11933 (@value{GDBP}) define has_exited_or_signalled
11934 Type commands for definition of ``has_exited_or_signalled''.
11935 End with a line saying just ``end''.
11936 >if $_isvoid ($_exitsignal)
11937 >echo The program has exited\n
11939 >echo The program has signalled\n
11945 Program terminated with signal SIGALRM, Alarm clock.
11946 The program no longer exists.
11947 (@value{GDBP}) has_exited_or_signalled
11948 The program has signalled
11951 As can be seen, @value{GDBN} correctly informs that the program being
11952 debugged has signalled, since it calls @code{raise} and raises a
11953 @code{SIGALRM} signal. If the program being debugged had not called
11954 @code{raise}, then @value{GDBN} would report a normal exit:
11957 (@value{GDBP}) has_exited_or_signalled
11958 The program has exited
11962 The variable @code{$_exception} is set to the exception object being
11963 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11965 @item $_ada_exception
11966 The variable @code{$_ada_exception} is set to the address of the
11967 exception being caught or thrown at an Ada exception-related
11968 catchpoint. @xref{Set Catchpoints}.
11971 @itemx $_probe_arg0@dots{}$_probe_arg11
11972 Arguments to a static probe. @xref{Static Probe Points}.
11975 @vindex $_sdata@r{, inspect, convenience variable}
11976 The variable @code{$_sdata} contains extra collected static tracepoint
11977 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11978 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11979 if extra static tracepoint data has not been collected.
11982 @vindex $_siginfo@r{, convenience variable}
11983 The variable @code{$_siginfo} contains extra signal information
11984 (@pxref{extra signal information}). Note that @code{$_siginfo}
11985 could be empty, if the application has not yet received any signals.
11986 For example, it will be empty before you execute the @code{run} command.
11989 @vindex $_tlb@r{, convenience variable}
11990 The variable @code{$_tlb} is automatically set when debugging
11991 applications running on MS-Windows in native mode or connected to
11992 gdbserver that supports the @code{qGetTIBAddr} request.
11993 @xref{General Query Packets}.
11994 This variable contains the address of the thread information block.
11997 The number of the current inferior. @xref{Inferiors Connections and
11998 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12001 The thread number of the current thread. @xref{thread numbers}.
12004 The global number of the current thread. @xref{global thread numbers}.
12008 @vindex $_gdb_major@r{, convenience variable}
12009 @vindex $_gdb_minor@r{, convenience variable}
12010 The major and minor version numbers of the running @value{GDBN}.
12011 Development snapshots and pretest versions have their minor version
12012 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12013 the value 12 for @code{$_gdb_minor}. These variables allow you to
12014 write scripts that work with different versions of @value{GDBN}
12015 without errors caused by features unavailable in some of those
12018 @item $_shell_exitcode
12019 @itemx $_shell_exitsignal
12020 @vindex $_shell_exitcode@r{, convenience variable}
12021 @vindex $_shell_exitsignal@r{, convenience variable}
12022 @cindex shell command, exit code
12023 @cindex shell command, exit signal
12024 @cindex exit status of shell commands
12025 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12026 shell commands. When a launched command terminates, @value{GDBN}
12027 automatically maintains the variables @code{$_shell_exitcode}
12028 and @code{$_shell_exitsignal} according to the exit status of the last
12029 launched command. These variables are set and used similarly to
12030 the variables @code{$_exitcode} and @code{$_exitsignal}.
12034 @node Convenience Funs
12035 @section Convenience Functions
12037 @cindex convenience functions
12038 @value{GDBN} also supplies some @dfn{convenience functions}. These
12039 have a syntax similar to convenience variables. A convenience
12040 function can be used in an expression just like an ordinary function;
12041 however, a convenience function is implemented internally to
12044 These functions do not require @value{GDBN} to be configured with
12045 @code{Python} support, which means that they are always available.
12049 @item $_isvoid (@var{expr})
12050 @findex $_isvoid@r{, convenience function}
12051 Return one if the expression @var{expr} is @code{void}. Otherwise it
12054 A @code{void} expression is an expression where the type of the result
12055 is @code{void}. For example, you can examine a convenience variable
12056 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12060 (@value{GDBP}) print $_exitcode
12062 (@value{GDBP}) print $_isvoid ($_exitcode)
12065 Starting program: ./a.out
12066 [Inferior 1 (process 29572) exited normally]
12067 (@value{GDBP}) print $_exitcode
12069 (@value{GDBP}) print $_isvoid ($_exitcode)
12073 In the example above, we used @code{$_isvoid} to check whether
12074 @code{$_exitcode} is @code{void} before and after the execution of the
12075 program being debugged. Before the execution there is no exit code to
12076 be examined, therefore @code{$_exitcode} is @code{void}. After the
12077 execution the program being debugged returned zero, therefore
12078 @code{$_exitcode} is zero, which means that it is not @code{void}
12081 The @code{void} expression can also be a call of a function from the
12082 program being debugged. For example, given the following function:
12091 The result of calling it inside @value{GDBN} is @code{void}:
12094 (@value{GDBP}) print foo ()
12096 (@value{GDBP}) print $_isvoid (foo ())
12098 (@value{GDBP}) set $v = foo ()
12099 (@value{GDBP}) print $v
12101 (@value{GDBP}) print $_isvoid ($v)
12105 @item $_gdb_setting_str (@var{setting})
12106 @findex $_gdb_setting_str@r{, convenience function}
12107 Return the value of the @value{GDBN} @var{setting} as a string.
12108 @var{setting} is any setting that can be used in a @code{set} or
12109 @code{show} command (@pxref{Controlling GDB}).
12112 (@value{GDBP}) show print frame-arguments
12113 Printing of non-scalar frame arguments is "scalars".
12114 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12116 (@value{GDBP}) p $_gdb_setting_str("height")
12121 @item $_gdb_setting (@var{setting})
12122 @findex $_gdb_setting@r{, convenience function}
12123 Return the value of the @value{GDBN} @var{setting}.
12124 The type of the returned value depends on the setting.
12126 The value type for boolean and auto boolean settings is @code{int}.
12127 The boolean values @code{off} and @code{on} are converted to
12128 the integer values @code{0} and @code{1}. The value @code{auto} is
12129 converted to the value @code{-1}.
12131 The value type for integer settings is either @code{unsigned int}
12132 or @code{int}, depending on the setting.
12134 Some integer settings accept an @code{unlimited} value.
12135 Depending on the setting, the @code{set} command also accepts
12136 the value @code{0} or the value @code{@minus{}1} as a synonym for
12138 For example, @code{set height unlimited} is equivalent to
12139 @code{set height 0}.
12141 Some other settings that accept the @code{unlimited} value
12142 use the value @code{0} to literally mean zero.
12143 For example, @code{set history size 0} indicates to not
12144 record any @value{GDBN} commands in the command history.
12145 For such settings, @code{@minus{}1} is the synonym
12146 for @code{unlimited}.
12148 See the documentation of the corresponding @code{set} command for
12149 the numerical value equivalent to @code{unlimited}.
12151 The @code{$_gdb_setting} function converts the unlimited value
12152 to a @code{0} or a @code{@minus{}1} value according to what the
12153 @code{set} command uses.
12157 (@value{GDBP}) p $_gdb_setting_str("height")
12159 (@value{GDBP}) p $_gdb_setting("height")
12161 (@value{GDBP}) set height unlimited
12162 (@value{GDBP}) p $_gdb_setting_str("height")
12164 (@value{GDBP}) p $_gdb_setting("height")
12168 (@value{GDBP}) p $_gdb_setting_str("history size")
12170 (@value{GDBP}) p $_gdb_setting("history size")
12172 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12174 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12180 Other setting types (enum, filename, optional filename, string, string noescape)
12181 are returned as string values.
12184 @item $_gdb_maint_setting_str (@var{setting})
12185 @findex $_gdb_maint_setting_str@r{, convenience function}
12186 Like the @code{$_gdb_setting_str} function, but works with
12187 @code{maintenance set} variables.
12189 @item $_gdb_maint_setting (@var{setting})
12190 @findex $_gdb_maint_setting@r{, convenience function}
12191 Like the @code{$_gdb_setting} function, but works with
12192 @code{maintenance set} variables.
12196 The following functions require @value{GDBN} to be configured with
12197 @code{Python} support.
12201 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12202 @findex $_memeq@r{, convenience function}
12203 Returns one if the @var{length} bytes at the addresses given by
12204 @var{buf1} and @var{buf2} are equal.
12205 Otherwise it returns zero.
12207 @item $_regex(@var{str}, @var{regex})
12208 @findex $_regex@r{, convenience function}
12209 Returns one if the string @var{str} matches the regular expression
12210 @var{regex}. Otherwise it returns zero.
12211 The syntax of the regular expression is that specified by @code{Python}'s
12212 regular expression support.
12214 @item $_streq(@var{str1}, @var{str2})
12215 @findex $_streq@r{, convenience function}
12216 Returns one if the strings @var{str1} and @var{str2} are equal.
12217 Otherwise it returns zero.
12219 @item $_strlen(@var{str})
12220 @findex $_strlen@r{, convenience function}
12221 Returns the length of string @var{str}.
12223 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12224 @findex $_caller_is@r{, convenience function}
12225 Returns one if the calling function's name is equal to @var{name}.
12226 Otherwise it returns zero.
12228 If the optional argument @var{number_of_frames} is provided,
12229 it is the number of frames up in the stack to look.
12237 at testsuite/gdb.python/py-caller-is.c:21
12238 #1 0x00000000004005a0 in middle_func ()
12239 at testsuite/gdb.python/py-caller-is.c:27
12240 #2 0x00000000004005ab in top_func ()
12241 at testsuite/gdb.python/py-caller-is.c:33
12242 #3 0x00000000004005b6 in main ()
12243 at testsuite/gdb.python/py-caller-is.c:39
12244 (gdb) print $_caller_is ("middle_func")
12246 (gdb) print $_caller_is ("top_func", 2)
12250 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12251 @findex $_caller_matches@r{, convenience function}
12252 Returns one if the calling function's name matches the regular expression
12253 @var{regexp}. Otherwise it returns zero.
12255 If the optional argument @var{number_of_frames} is provided,
12256 it is the number of frames up in the stack to look.
12259 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12260 @findex $_any_caller_is@r{, convenience function}
12261 Returns one if any calling function's name is equal to @var{name}.
12262 Otherwise it returns zero.
12264 If the optional argument @var{number_of_frames} is provided,
12265 it is the number of frames up in the stack to look.
12268 This function differs from @code{$_caller_is} in that this function
12269 checks all stack frames from the immediate caller to the frame specified
12270 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12271 frame specified by @var{number_of_frames}.
12273 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12274 @findex $_any_caller_matches@r{, convenience function}
12275 Returns one if any calling function's name matches the regular expression
12276 @var{regexp}. Otherwise it returns zero.
12278 If the optional argument @var{number_of_frames} is provided,
12279 it is the number of frames up in the stack to look.
12282 This function differs from @code{$_caller_matches} in that this function
12283 checks all stack frames from the immediate caller to the frame specified
12284 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12285 frame specified by @var{number_of_frames}.
12287 @item $_as_string(@var{value})
12288 @findex $_as_string@r{, convenience function}
12289 Return the string representation of @var{value}.
12291 This function is useful to obtain the textual label (enumerator) of an
12292 enumeration value. For example, assuming the variable @var{node} is of
12293 an enumerated type:
12296 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12297 Visiting node of type NODE_INTEGER
12300 @item $_cimag(@var{value})
12301 @itemx $_creal(@var{value})
12302 @findex $_cimag@r{, convenience function}
12303 @findex $_creal@r{, convenience function}
12304 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12305 the complex number @var{value}.
12307 The type of the imaginary or real part depends on the type of the
12308 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12309 will return an imaginary part of type @code{float}.
12313 @value{GDBN} provides the ability to list and get help on
12314 convenience functions.
12317 @item help function
12318 @kindex help function
12319 @cindex show all convenience functions
12320 Print a list of all convenience functions.
12327 You can refer to machine register contents, in expressions, as variables
12328 with names starting with @samp{$}. The names of registers are different
12329 for each machine; use @code{info registers} to see the names used on
12333 @kindex info registers
12334 @item info registers
12335 Print the names and values of all registers except floating-point
12336 and vector registers (in the selected stack frame).
12338 @kindex info all-registers
12339 @cindex floating point registers
12340 @item info all-registers
12341 Print the names and values of all registers, including floating-point
12342 and vector registers (in the selected stack frame).
12344 @item info registers @var{reggroup} @dots{}
12345 Print the name and value of the registers in each of the specified
12346 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12347 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12349 @item info registers @var{regname} @dots{}
12350 Print the @dfn{relativized} value of each specified register @var{regname}.
12351 As discussed in detail below, register values are normally relative to
12352 the selected stack frame. The @var{regname} may be any register name valid on
12353 the machine you are using, with or without the initial @samp{$}.
12356 @anchor{standard registers}
12357 @cindex stack pointer register
12358 @cindex program counter register
12359 @cindex process status register
12360 @cindex frame pointer register
12361 @cindex standard registers
12362 @value{GDBN} has four ``standard'' register names that are available (in
12363 expressions) on most machines---whenever they do not conflict with an
12364 architecture's canonical mnemonics for registers. The register names
12365 @code{$pc} and @code{$sp} are used for the program counter register and
12366 the stack pointer. @code{$fp} is used for a register that contains a
12367 pointer to the current stack frame, and @code{$ps} is used for a
12368 register that contains the processor status. For example,
12369 you could print the program counter in hex with
12376 or print the instruction to be executed next with
12383 or add four to the stack pointer@footnote{This is a way of removing
12384 one word from the stack, on machines where stacks grow downward in
12385 memory (most machines, nowadays). This assumes that the innermost
12386 stack frame is selected; setting @code{$sp} is not allowed when other
12387 stack frames are selected. To pop entire frames off the stack,
12388 regardless of machine architecture, use @code{return};
12389 see @ref{Returning, ,Returning from a Function}.} with
12395 Whenever possible, these four standard register names are available on
12396 your machine even though the machine has different canonical mnemonics,
12397 so long as there is no conflict. The @code{info registers} command
12398 shows the canonical names. For example, on the SPARC, @code{info
12399 registers} displays the processor status register as @code{$psr} but you
12400 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12401 is an alias for the @sc{eflags} register.
12403 @value{GDBN} always considers the contents of an ordinary register as an
12404 integer when the register is examined in this way. Some machines have
12405 special registers which can hold nothing but floating point; these
12406 registers are considered to have floating point values. There is no way
12407 to refer to the contents of an ordinary register as floating point value
12408 (although you can @emph{print} it as a floating point value with
12409 @samp{print/f $@var{regname}}).
12411 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12412 means that the data format in which the register contents are saved by
12413 the operating system is not the same one that your program normally
12414 sees. For example, the registers of the 68881 floating point
12415 coprocessor are always saved in ``extended'' (raw) format, but all C
12416 programs expect to work with ``double'' (virtual) format. In such
12417 cases, @value{GDBN} normally works with the virtual format only (the format
12418 that makes sense for your program), but the @code{info registers} command
12419 prints the data in both formats.
12421 @cindex SSE registers (x86)
12422 @cindex MMX registers (x86)
12423 Some machines have special registers whose contents can be interpreted
12424 in several different ways. For example, modern x86-based machines
12425 have SSE and MMX registers that can hold several values packed
12426 together in several different formats. @value{GDBN} refers to such
12427 registers in @code{struct} notation:
12430 (@value{GDBP}) print $xmm1
12432 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12433 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12434 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12435 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12436 v4_int32 = @{0, 20657912, 11, 13@},
12437 v2_int64 = @{88725056443645952, 55834574859@},
12438 uint128 = 0x0000000d0000000b013b36f800000000
12443 To set values of such registers, you need to tell @value{GDBN} which
12444 view of the register you wish to change, as if you were assigning
12445 value to a @code{struct} member:
12448 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12451 Normally, register values are relative to the selected stack frame
12452 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12453 value that the register would contain if all stack frames farther in
12454 were exited and their saved registers restored. In order to see the
12455 true contents of hardware registers, you must select the innermost
12456 frame (with @samp{frame 0}).
12458 @cindex caller-saved registers
12459 @cindex call-clobbered registers
12460 @cindex volatile registers
12461 @cindex <not saved> values
12462 Usually ABIs reserve some registers as not needed to be saved by the
12463 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12464 registers). It may therefore not be possible for @value{GDBN} to know
12465 the value a register had before the call (in other words, in the outer
12466 frame), if the register value has since been changed by the callee.
12467 @value{GDBN} tries to deduce where the inner frame saved
12468 (``callee-saved'') registers, from the debug info, unwind info, or the
12469 machine code generated by your compiler. If some register is not
12470 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12471 its own knowledge of the ABI, or because the debug/unwind info
12472 explicitly says the register's value is undefined), @value{GDBN}
12473 displays @w{@samp{<not saved>}} as the register's value. With targets
12474 that @value{GDBN} has no knowledge of the register saving convention,
12475 if a register was not saved by the callee, then its value and location
12476 in the outer frame are assumed to be the same of the inner frame.
12477 This is usually harmless, because if the register is call-clobbered,
12478 the caller either does not care what is in the register after the
12479 call, or has code to restore the value that it does care about. Note,
12480 however, that if you change such a register in the outer frame, you
12481 may also be affecting the inner frame. Also, the more ``outer'' the
12482 frame is you're looking at, the more likely a call-clobbered
12483 register's value is to be wrong, in the sense that it doesn't actually
12484 represent the value the register had just before the call.
12486 @node Floating Point Hardware
12487 @section Floating Point Hardware
12488 @cindex floating point
12490 Depending on the configuration, @value{GDBN} may be able to give
12491 you more information about the status of the floating point hardware.
12496 Display hardware-dependent information about the floating
12497 point unit. The exact contents and layout vary depending on the
12498 floating point chip. Currently, @samp{info float} is supported on
12499 the ARM and x86 machines.
12503 @section Vector Unit
12504 @cindex vector unit
12506 Depending on the configuration, @value{GDBN} may be able to give you
12507 more information about the status of the vector unit.
12510 @kindex info vector
12512 Display information about the vector unit. The exact contents and
12513 layout vary depending on the hardware.
12516 @node OS Information
12517 @section Operating System Auxiliary Information
12518 @cindex OS information
12520 @value{GDBN} provides interfaces to useful OS facilities that can help
12521 you debug your program.
12523 @cindex auxiliary vector
12524 @cindex vector, auxiliary
12525 Some operating systems supply an @dfn{auxiliary vector} to programs at
12526 startup. This is akin to the arguments and environment that you
12527 specify for a program, but contains a system-dependent variety of
12528 binary values that tell system libraries important details about the
12529 hardware, operating system, and process. Each value's purpose is
12530 identified by an integer tag; the meanings are well-known but system-specific.
12531 Depending on the configuration and operating system facilities,
12532 @value{GDBN} may be able to show you this information. For remote
12533 targets, this functionality may further depend on the remote stub's
12534 support of the @samp{qXfer:auxv:read} packet, see
12535 @ref{qXfer auxiliary vector read}.
12540 Display the auxiliary vector of the inferior, which can be either a
12541 live process or a core dump file. @value{GDBN} prints each tag value
12542 numerically, and also shows names and text descriptions for recognized
12543 tags. Some values in the vector are numbers, some bit masks, and some
12544 pointers to strings or other data. @value{GDBN} displays each value in the
12545 most appropriate form for a recognized tag, and in hexadecimal for
12546 an unrecognized tag.
12549 On some targets, @value{GDBN} can access operating system-specific
12550 information and show it to you. The types of information available
12551 will differ depending on the type of operating system running on the
12552 target. The mechanism used to fetch the data is described in
12553 @ref{Operating System Information}. For remote targets, this
12554 functionality depends on the remote stub's support of the
12555 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12559 @item info os @var{infotype}
12561 Display OS information of the requested type.
12563 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12565 @anchor{linux info os infotypes}
12567 @kindex info os cpus
12569 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12570 the available fields from /proc/cpuinfo. For each supported architecture
12571 different fields are available. Two common entries are processor which gives
12572 CPU number and bogomips; a system constant that is calculated during
12573 kernel initialization.
12575 @kindex info os files
12577 Display the list of open file descriptors on the target. For each
12578 file descriptor, @value{GDBN} prints the identifier of the process
12579 owning the descriptor, the command of the owning process, the value
12580 of the descriptor, and the target of the descriptor.
12582 @kindex info os modules
12584 Display the list of all loaded kernel modules on the target. For each
12585 module, @value{GDBN} prints the module name, the size of the module in
12586 bytes, the number of times the module is used, the dependencies of the
12587 module, the status of the module, and the address of the loaded module
12590 @kindex info os msg
12592 Display the list of all System V message queues on the target. For each
12593 message queue, @value{GDBN} prints the message queue key, the message
12594 queue identifier, the access permissions, the current number of bytes
12595 on the queue, the current number of messages on the queue, the processes
12596 that last sent and received a message on the queue, the user and group
12597 of the owner and creator of the message queue, the times at which a
12598 message was last sent and received on the queue, and the time at which
12599 the message queue was last changed.
12601 @kindex info os processes
12603 Display the list of processes on the target. For each process,
12604 @value{GDBN} prints the process identifier, the name of the user, the
12605 command corresponding to the process, and the list of processor cores
12606 that the process is currently running on. (To understand what these
12607 properties mean, for this and the following info types, please consult
12608 the general @sc{gnu}/Linux documentation.)
12610 @kindex info os procgroups
12612 Display the list of process groups on the target. For each process,
12613 @value{GDBN} prints the identifier of the process group that it belongs
12614 to, the command corresponding to the process group leader, the process
12615 identifier, and the command line of the process. The list is sorted
12616 first by the process group identifier, then by the process identifier,
12617 so that processes belonging to the same process group are grouped together
12618 and the process group leader is listed first.
12620 @kindex info os semaphores
12622 Display the list of all System V semaphore sets on the target. For each
12623 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12624 set identifier, the access permissions, the number of semaphores in the
12625 set, the user and group of the owner and creator of the semaphore set,
12626 and the times at which the semaphore set was operated upon and changed.
12628 @kindex info os shm
12630 Display the list of all System V shared-memory regions on the target.
12631 For each shared-memory region, @value{GDBN} prints the region key,
12632 the shared-memory identifier, the access permissions, the size of the
12633 region, the process that created the region, the process that last
12634 attached to or detached from the region, the current number of live
12635 attaches to the region, and the times at which the region was last
12636 attached to, detach from, and changed.
12638 @kindex info os sockets
12640 Display the list of Internet-domain sockets on the target. For each
12641 socket, @value{GDBN} prints the address and port of the local and
12642 remote endpoints, the current state of the connection, the creator of
12643 the socket, the IP address family of the socket, and the type of the
12646 @kindex info os threads
12648 Display the list of threads running on the target. For each thread,
12649 @value{GDBN} prints the identifier of the process that the thread
12650 belongs to, the command of the process, the thread identifier, and the
12651 processor core that it is currently running on. The main thread of a
12652 process is not listed.
12656 If @var{infotype} is omitted, then list the possible values for
12657 @var{infotype} and the kind of OS information available for each
12658 @var{infotype}. If the target does not return a list of possible
12659 types, this command will report an error.
12662 @node Memory Region Attributes
12663 @section Memory Region Attributes
12664 @cindex memory region attributes
12666 @dfn{Memory region attributes} allow you to describe special handling
12667 required by regions of your target's memory. @value{GDBN} uses
12668 attributes to determine whether to allow certain types of memory
12669 accesses; whether to use specific width accesses; and whether to cache
12670 target memory. By default the description of memory regions is
12671 fetched from the target (if the current target supports this), but the
12672 user can override the fetched regions.
12674 Defined memory regions can be individually enabled and disabled. When a
12675 memory region is disabled, @value{GDBN} uses the default attributes when
12676 accessing memory in that region. Similarly, if no memory regions have
12677 been defined, @value{GDBN} uses the default attributes when accessing
12680 When a memory region is defined, it is given a number to identify it;
12681 to enable, disable, or remove a memory region, you specify that number.
12685 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12686 Define a memory region bounded by @var{lower} and @var{upper} with
12687 attributes @var{attributes}@dots{}, and add it to the list of regions
12688 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12689 case: it is treated as the target's maximum memory address.
12690 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12693 Discard any user changes to the memory regions and use target-supplied
12694 regions, if available, or no regions if the target does not support.
12697 @item delete mem @var{nums}@dots{}
12698 Remove memory regions @var{nums}@dots{} from the list of regions
12699 monitored by @value{GDBN}.
12701 @kindex disable mem
12702 @item disable mem @var{nums}@dots{}
12703 Disable monitoring of memory regions @var{nums}@dots{}.
12704 A disabled memory region is not forgotten.
12705 It may be enabled again later.
12708 @item enable mem @var{nums}@dots{}
12709 Enable monitoring of memory regions @var{nums}@dots{}.
12713 Print a table of all defined memory regions, with the following columns
12717 @item Memory Region Number
12718 @item Enabled or Disabled.
12719 Enabled memory regions are marked with @samp{y}.
12720 Disabled memory regions are marked with @samp{n}.
12723 The address defining the inclusive lower bound of the memory region.
12726 The address defining the exclusive upper bound of the memory region.
12729 The list of attributes set for this memory region.
12734 @subsection Attributes
12736 @subsubsection Memory Access Mode
12737 The access mode attributes set whether @value{GDBN} may make read or
12738 write accesses to a memory region.
12740 While these attributes prevent @value{GDBN} from performing invalid
12741 memory accesses, they do nothing to prevent the target system, I/O DMA,
12742 etc.@: from accessing memory.
12746 Memory is read only.
12748 Memory is write only.
12750 Memory is read/write. This is the default.
12753 @subsubsection Memory Access Size
12754 The access size attribute tells @value{GDBN} to use specific sized
12755 accesses in the memory region. Often memory mapped device registers
12756 require specific sized accesses. If no access size attribute is
12757 specified, @value{GDBN} may use accesses of any size.
12761 Use 8 bit memory accesses.
12763 Use 16 bit memory accesses.
12765 Use 32 bit memory accesses.
12767 Use 64 bit memory accesses.
12770 @c @subsubsection Hardware/Software Breakpoints
12771 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12772 @c will use hardware or software breakpoints for the internal breakpoints
12773 @c used by the step, next, finish, until, etc. commands.
12777 @c Always use hardware breakpoints
12778 @c @item swbreak (default)
12781 @subsubsection Data Cache
12782 The data cache attributes set whether @value{GDBN} will cache target
12783 memory. While this generally improves performance by reducing debug
12784 protocol overhead, it can lead to incorrect results because @value{GDBN}
12785 does not know about volatile variables or memory mapped device
12790 Enable @value{GDBN} to cache target memory.
12792 Disable @value{GDBN} from caching target memory. This is the default.
12795 @subsection Memory Access Checking
12796 @value{GDBN} can be instructed to refuse accesses to memory that is
12797 not explicitly described. This can be useful if accessing such
12798 regions has undesired effects for a specific target, or to provide
12799 better error checking. The following commands control this behaviour.
12802 @kindex set mem inaccessible-by-default
12803 @item set mem inaccessible-by-default [on|off]
12804 If @code{on} is specified, make @value{GDBN} treat memory not
12805 explicitly described by the memory ranges as non-existent and refuse accesses
12806 to such memory. The checks are only performed if there's at least one
12807 memory range defined. If @code{off} is specified, make @value{GDBN}
12808 treat the memory not explicitly described by the memory ranges as RAM.
12809 The default value is @code{on}.
12810 @kindex show mem inaccessible-by-default
12811 @item show mem inaccessible-by-default
12812 Show the current handling of accesses to unknown memory.
12816 @c @subsubsection Memory Write Verification
12817 @c The memory write verification attributes set whether @value{GDBN}
12818 @c will re-reads data after each write to verify the write was successful.
12822 @c @item noverify (default)
12825 @node Dump/Restore Files
12826 @section Copy Between Memory and a File
12827 @cindex dump/restore files
12828 @cindex append data to a file
12829 @cindex dump data to a file
12830 @cindex restore data from a file
12832 You can use the commands @code{dump}, @code{append}, and
12833 @code{restore} to copy data between target memory and a file. The
12834 @code{dump} and @code{append} commands write data to a file, and the
12835 @code{restore} command reads data from a file back into the inferior's
12836 memory. Files may be in binary, Motorola S-record, Intel hex,
12837 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12838 append to binary files, and cannot read from Verilog Hex files.
12843 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12844 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12845 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12846 or the value of @var{expr}, to @var{filename} in the given format.
12848 The @var{format} parameter may be any one of:
12855 Motorola S-record format.
12857 Tektronix Hex format.
12859 Verilog Hex format.
12862 @value{GDBN} uses the same definitions of these formats as the
12863 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12864 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12868 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12869 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12870 Append the contents of memory from @var{start_addr} to @var{end_addr},
12871 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12872 (@value{GDBN} can only append data to files in raw binary form.)
12875 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12876 Restore the contents of file @var{filename} into memory. The
12877 @code{restore} command can automatically recognize any known @sc{bfd}
12878 file format, except for raw binary. To restore a raw binary file you
12879 must specify the optional keyword @code{binary} after the filename.
12881 If @var{bias} is non-zero, its value will be added to the addresses
12882 contained in the file. Binary files always start at address zero, so
12883 they will be restored at address @var{bias}. Other bfd files have
12884 a built-in location; they will be restored at offset @var{bias}
12885 from that location.
12887 If @var{start} and/or @var{end} are non-zero, then only data between
12888 file offset @var{start} and file offset @var{end} will be restored.
12889 These offsets are relative to the addresses in the file, before
12890 the @var{bias} argument is applied.
12894 @node Core File Generation
12895 @section How to Produce a Core File from Your Program
12896 @cindex dump core from inferior
12898 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12899 image of a running process and its process status (register values
12900 etc.). Its primary use is post-mortem debugging of a program that
12901 crashed while it ran outside a debugger. A program that crashes
12902 automatically produces a core file, unless this feature is disabled by
12903 the user. @xref{Files}, for information on invoking @value{GDBN} in
12904 the post-mortem debugging mode.
12906 Occasionally, you may wish to produce a core file of the program you
12907 are debugging in order to preserve a snapshot of its state.
12908 @value{GDBN} has a special command for that.
12912 @kindex generate-core-file
12913 @item generate-core-file [@var{file}]
12914 @itemx gcore [@var{file}]
12915 Produce a core dump of the inferior process. The optional argument
12916 @var{file} specifies the file name where to put the core dump. If not
12917 specified, the file name defaults to @file{core.@var{pid}}, where
12918 @var{pid} is the inferior process ID.
12920 Note that this command is implemented only for some systems (as of
12921 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12923 On @sc{gnu}/Linux, this command can take into account the value of the
12924 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12925 dump (@pxref{set use-coredump-filter}), and by default honors the
12926 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12927 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12929 @kindex set use-coredump-filter
12930 @anchor{set use-coredump-filter}
12931 @item set use-coredump-filter on
12932 @itemx set use-coredump-filter off
12933 Enable or disable the use of the file
12934 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12935 files. This file is used by the Linux kernel to decide what types of
12936 memory mappings will be dumped or ignored when generating a core dump
12937 file. @var{pid} is the process ID of a currently running process.
12939 To make use of this feature, you have to write in the
12940 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12941 which is a bit mask representing the memory mapping types. If a bit
12942 is set in the bit mask, then the memory mappings of the corresponding
12943 types will be dumped; otherwise, they will be ignored. This
12944 configuration is inherited by child processes. For more information
12945 about the bits that can be set in the
12946 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12947 manpage of @code{core(5)}.
12949 By default, this option is @code{on}. If this option is turned
12950 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12951 and instead uses the same default value as the Linux kernel in order
12952 to decide which pages will be dumped in the core dump file. This
12953 value is currently @code{0x33}, which means that bits @code{0}
12954 (anonymous private mappings), @code{1} (anonymous shared mappings),
12955 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12956 This will cause these memory mappings to be dumped automatically.
12958 @kindex set dump-excluded-mappings
12959 @anchor{set dump-excluded-mappings}
12960 @item set dump-excluded-mappings on
12961 @itemx set dump-excluded-mappings off
12962 If @code{on} is specified, @value{GDBN} will dump memory mappings
12963 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12964 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12966 The default value is @code{off}.
12969 @node Character Sets
12970 @section Character Sets
12971 @cindex character sets
12973 @cindex translating between character sets
12974 @cindex host character set
12975 @cindex target character set
12977 If the program you are debugging uses a different character set to
12978 represent characters and strings than the one @value{GDBN} uses itself,
12979 @value{GDBN} can automatically translate between the character sets for
12980 you. The character set @value{GDBN} uses we call the @dfn{host
12981 character set}; the one the inferior program uses we call the
12982 @dfn{target character set}.
12984 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12985 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12986 remote protocol (@pxref{Remote Debugging}) to debug a program
12987 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12988 then the host character set is Latin-1, and the target character set is
12989 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12990 target-charset EBCDIC-US}, then @value{GDBN} translates between
12991 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12992 character and string literals in expressions.
12994 @value{GDBN} has no way to automatically recognize which character set
12995 the inferior program uses; you must tell it, using the @code{set
12996 target-charset} command, described below.
12998 Here are the commands for controlling @value{GDBN}'s character set
13002 @item set target-charset @var{charset}
13003 @kindex set target-charset
13004 Set the current target character set to @var{charset}. To display the
13005 list of supported target character sets, type
13006 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13008 @item set host-charset @var{charset}
13009 @kindex set host-charset
13010 Set the current host character set to @var{charset}.
13012 By default, @value{GDBN} uses a host character set appropriate to the
13013 system it is running on; you can override that default using the
13014 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13015 automatically determine the appropriate host character set. In this
13016 case, @value{GDBN} uses @samp{UTF-8}.
13018 @value{GDBN} can only use certain character sets as its host character
13019 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13020 @value{GDBN} will list the host character sets it supports.
13022 @item set charset @var{charset}
13023 @kindex set charset
13024 Set the current host and target character sets to @var{charset}. As
13025 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13026 @value{GDBN} will list the names of the character sets that can be used
13027 for both host and target.
13030 @kindex show charset
13031 Show the names of the current host and target character sets.
13033 @item show host-charset
13034 @kindex show host-charset
13035 Show the name of the current host character set.
13037 @item show target-charset
13038 @kindex show target-charset
13039 Show the name of the current target character set.
13041 @item set target-wide-charset @var{charset}
13042 @kindex set target-wide-charset
13043 Set the current target's wide character set to @var{charset}. This is
13044 the character set used by the target's @code{wchar_t} type. To
13045 display the list of supported wide character sets, type
13046 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13048 @item show target-wide-charset
13049 @kindex show target-wide-charset
13050 Show the name of the current target's wide character set.
13053 Here is an example of @value{GDBN}'s character set support in action.
13054 Assume that the following source code has been placed in the file
13055 @file{charset-test.c}:
13061 = @{72, 101, 108, 108, 111, 44, 32, 119,
13062 111, 114, 108, 100, 33, 10, 0@};
13063 char ibm1047_hello[]
13064 = @{200, 133, 147, 147, 150, 107, 64, 166,
13065 150, 153, 147, 132, 90, 37, 0@};
13069 printf ("Hello, world!\n");
13073 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13074 containing the string @samp{Hello, world!} followed by a newline,
13075 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13077 We compile the program, and invoke the debugger on it:
13080 $ gcc -g charset-test.c -o charset-test
13081 $ gdb -nw charset-test
13082 GNU gdb 2001-12-19-cvs
13083 Copyright 2001 Free Software Foundation, Inc.
13088 We can use the @code{show charset} command to see what character sets
13089 @value{GDBN} is currently using to interpret and display characters and
13093 (@value{GDBP}) show charset
13094 The current host and target character set is `ISO-8859-1'.
13098 For the sake of printing this manual, let's use @sc{ascii} as our
13099 initial character set:
13101 (@value{GDBP}) set charset ASCII
13102 (@value{GDBP}) show charset
13103 The current host and target character set is `ASCII'.
13107 Let's assume that @sc{ascii} is indeed the correct character set for our
13108 host system --- in other words, let's assume that if @value{GDBN} prints
13109 characters using the @sc{ascii} character set, our terminal will display
13110 them properly. Since our current target character set is also
13111 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13114 (@value{GDBP}) print ascii_hello
13115 $1 = 0x401698 "Hello, world!\n"
13116 (@value{GDBP}) print ascii_hello[0]
13121 @value{GDBN} uses the target character set for character and string
13122 literals you use in expressions:
13125 (@value{GDBP}) print '+'
13130 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13133 @value{GDBN} relies on the user to tell it which character set the
13134 target program uses. If we print @code{ibm1047_hello} while our target
13135 character set is still @sc{ascii}, we get jibberish:
13138 (@value{GDBP}) print ibm1047_hello
13139 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13140 (@value{GDBP}) print ibm1047_hello[0]
13145 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13146 @value{GDBN} tells us the character sets it supports:
13149 (@value{GDBP}) set target-charset
13150 ASCII EBCDIC-US IBM1047 ISO-8859-1
13151 (@value{GDBP}) set target-charset
13154 We can select @sc{ibm1047} as our target character set, and examine the
13155 program's strings again. Now the @sc{ascii} string is wrong, but
13156 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13157 target character set, @sc{ibm1047}, to the host character set,
13158 @sc{ascii}, and they display correctly:
13161 (@value{GDBP}) set target-charset IBM1047
13162 (@value{GDBP}) show charset
13163 The current host character set is `ASCII'.
13164 The current target character set is `IBM1047'.
13165 (@value{GDBP}) print ascii_hello
13166 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13167 (@value{GDBP}) print ascii_hello[0]
13169 (@value{GDBP}) print ibm1047_hello
13170 $8 = 0x4016a8 "Hello, world!\n"
13171 (@value{GDBP}) print ibm1047_hello[0]
13176 As above, @value{GDBN} uses the target character set for character and
13177 string literals you use in expressions:
13180 (@value{GDBP}) print '+'
13185 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13188 @node Caching Target Data
13189 @section Caching Data of Targets
13190 @cindex caching data of targets
13192 @value{GDBN} caches data exchanged between the debugger and a target.
13193 Each cache is associated with the address space of the inferior.
13194 @xref{Inferiors Connections and Programs}, about inferior and address space.
13195 Such caching generally improves performance in remote debugging
13196 (@pxref{Remote Debugging}), because it reduces the overhead of the
13197 remote protocol by bundling memory reads and writes into large chunks.
13198 Unfortunately, simply caching everything would lead to incorrect results,
13199 since @value{GDBN} does not necessarily know anything about volatile
13200 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13201 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13203 Therefore, by default, @value{GDBN} only caches data
13204 known to be on the stack@footnote{In non-stop mode, it is moderately
13205 rare for a running thread to modify the stack of a stopped thread
13206 in a way that would interfere with a backtrace, and caching of
13207 stack reads provides a significant speed up of remote backtraces.} or
13208 in the code segment.
13209 Other regions of memory can be explicitly marked as
13210 cacheable; @pxref{Memory Region Attributes}.
13213 @kindex set remotecache
13214 @item set remotecache on
13215 @itemx set remotecache off
13216 This option no longer does anything; it exists for compatibility
13219 @kindex show remotecache
13220 @item show remotecache
13221 Show the current state of the obsolete remotecache flag.
13223 @kindex set stack-cache
13224 @item set stack-cache on
13225 @itemx set stack-cache off
13226 Enable or disable caching of stack accesses. When @code{on}, use
13227 caching. By default, this option is @code{on}.
13229 @kindex show stack-cache
13230 @item show stack-cache
13231 Show the current state of data caching for memory accesses.
13233 @kindex set code-cache
13234 @item set code-cache on
13235 @itemx set code-cache off
13236 Enable or disable caching of code segment accesses. When @code{on},
13237 use caching. By default, this option is @code{on}. This improves
13238 performance of disassembly in remote debugging.
13240 @kindex show code-cache
13241 @item show code-cache
13242 Show the current state of target memory cache for code segment
13245 @kindex info dcache
13246 @item info dcache @r{[}line@r{]}
13247 Print the information about the performance of data cache of the
13248 current inferior's address space. The information displayed
13249 includes the dcache width and depth, and for each cache line, its
13250 number, address, and how many times it was referenced. This
13251 command is useful for debugging the data cache operation.
13253 If a line number is specified, the contents of that line will be
13256 @item set dcache size @var{size}
13257 @cindex dcache size
13258 @kindex set dcache size
13259 Set maximum number of entries in dcache (dcache depth above).
13261 @item set dcache line-size @var{line-size}
13262 @cindex dcache line-size
13263 @kindex set dcache line-size
13264 Set number of bytes each dcache entry caches (dcache width above).
13265 Must be a power of 2.
13267 @item show dcache size
13268 @kindex show dcache size
13269 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13271 @item show dcache line-size
13272 @kindex show dcache line-size
13273 Show default size of dcache lines.
13277 @node Searching Memory
13278 @section Search Memory
13279 @cindex searching memory
13281 Memory can be searched for a particular sequence of bytes with the
13282 @code{find} command.
13286 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13287 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13288 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13289 etc. The search begins at address @var{start_addr} and continues for either
13290 @var{len} bytes or through to @var{end_addr} inclusive.
13293 @var{s} and @var{n} are optional parameters.
13294 They may be specified in either order, apart or together.
13297 @item @var{s}, search query size
13298 The size of each search query value.
13304 halfwords (two bytes)
13308 giant words (eight bytes)
13311 All values are interpreted in the current language.
13312 This means, for example, that if the current source language is C/C@t{++}
13313 then searching for the string ``hello'' includes the trailing '\0'.
13314 The null terminator can be removed from searching by using casts,
13315 e.g.: @samp{@{char[5]@}"hello"}.
13317 If the value size is not specified, it is taken from the
13318 value's type in the current language.
13319 This is useful when one wants to specify the search
13320 pattern as a mixture of types.
13321 Note that this means, for example, that in the case of C-like languages
13322 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13323 which is typically four bytes.
13325 @item @var{n}, maximum number of finds
13326 The maximum number of matches to print. The default is to print all finds.
13329 You can use strings as search values. Quote them with double-quotes
13331 The string value is copied into the search pattern byte by byte,
13332 regardless of the endianness of the target and the size specification.
13334 The address of each match found is printed as well as a count of the
13335 number of matches found.
13337 The address of the last value found is stored in convenience variable
13339 A count of the number of matches is stored in @samp{$numfound}.
13341 For example, if stopped at the @code{printf} in this function:
13347 static char hello[] = "hello-hello";
13348 static struct @{ char c; short s; int i; @}
13349 __attribute__ ((packed)) mixed
13350 = @{ 'c', 0x1234, 0x87654321 @};
13351 printf ("%s\n", hello);
13356 you get during debugging:
13359 (gdb) find &hello[0], +sizeof(hello), "hello"
13360 0x804956d <hello.1620+6>
13362 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13363 0x8049567 <hello.1620>
13364 0x804956d <hello.1620+6>
13366 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13367 0x8049567 <hello.1620>
13368 0x804956d <hello.1620+6>
13370 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13371 0x8049567 <hello.1620>
13373 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13374 0x8049560 <mixed.1625>
13376 (gdb) print $numfound
13379 $2 = (void *) 0x8049560
13383 @section Value Sizes
13385 Whenever @value{GDBN} prints a value memory will be allocated within
13386 @value{GDBN} to hold the contents of the value. It is possible in
13387 some languages with dynamic typing systems, that an invalid program
13388 may indicate a value that is incorrectly large, this in turn may cause
13389 @value{GDBN} to try and allocate an overly large amount of memory.
13392 @kindex set max-value-size
13393 @item set max-value-size @var{bytes}
13394 @itemx set max-value-size unlimited
13395 Set the maximum size of memory that @value{GDBN} will allocate for the
13396 contents of a value to @var{bytes}, trying to display a value that
13397 requires more memory than that will result in an error.
13399 Setting this variable does not effect values that have already been
13400 allocated within @value{GDBN}, only future allocations.
13402 There's a minimum size that @code{max-value-size} can be set to in
13403 order that @value{GDBN} can still operate correctly, this minimum is
13404 currently 16 bytes.
13406 The limit applies to the results of some subexpressions as well as to
13407 complete expressions. For example, an expression denoting a simple
13408 integer component, such as @code{x.y.z}, may fail if the size of
13409 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13410 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13411 @var{A} is an array variable with non-constant size, will generally
13412 succeed regardless of the bounds on @var{A}, as long as the component
13413 size is less than @var{bytes}.
13415 The default value of @code{max-value-size} is currently 64k.
13417 @kindex show max-value-size
13418 @item show max-value-size
13419 Show the maximum size of memory, in bytes, that @value{GDBN} will
13420 allocate for the contents of a value.
13423 @node Optimized Code
13424 @chapter Debugging Optimized Code
13425 @cindex optimized code, debugging
13426 @cindex debugging optimized code
13428 Almost all compilers support optimization. With optimization
13429 disabled, the compiler generates assembly code that corresponds
13430 directly to your source code, in a simplistic way. As the compiler
13431 applies more powerful optimizations, the generated assembly code
13432 diverges from your original source code. With help from debugging
13433 information generated by the compiler, @value{GDBN} can map from
13434 the running program back to constructs from your original source.
13436 @value{GDBN} is more accurate with optimization disabled. If you
13437 can recompile without optimization, it is easier to follow the
13438 progress of your program during debugging. But, there are many cases
13439 where you may need to debug an optimized version.
13441 When you debug a program compiled with @samp{-g -O}, remember that the
13442 optimizer has rearranged your code; the debugger shows you what is
13443 really there. Do not be too surprised when the execution path does not
13444 exactly match your source file! An extreme example: if you define a
13445 variable, but never use it, @value{GDBN} never sees that
13446 variable---because the compiler optimizes it out of existence.
13448 Some things do not work as well with @samp{-g -O} as with just
13449 @samp{-g}, particularly on machines with instruction scheduling. If in
13450 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13451 please report it to us as a bug (including a test case!).
13452 @xref{Variables}, for more information about debugging optimized code.
13455 * Inline Functions:: How @value{GDBN} presents inlining
13456 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13459 @node Inline Functions
13460 @section Inline Functions
13461 @cindex inline functions, debugging
13463 @dfn{Inlining} is an optimization that inserts a copy of the function
13464 body directly at each call site, instead of jumping to a shared
13465 routine. @value{GDBN} displays inlined functions just like
13466 non-inlined functions. They appear in backtraces. You can view their
13467 arguments and local variables, step into them with @code{step}, skip
13468 them with @code{next}, and escape from them with @code{finish}.
13469 You can check whether a function was inlined by using the
13470 @code{info frame} command.
13472 For @value{GDBN} to support inlined functions, the compiler must
13473 record information about inlining in the debug information ---
13474 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13475 other compilers do also. @value{GDBN} only supports inlined functions
13476 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13477 do not emit two required attributes (@samp{DW_AT_call_file} and
13478 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13479 function calls with earlier versions of @value{NGCC}. It instead
13480 displays the arguments and local variables of inlined functions as
13481 local variables in the caller.
13483 The body of an inlined function is directly included at its call site;
13484 unlike a non-inlined function, there are no instructions devoted to
13485 the call. @value{GDBN} still pretends that the call site and the
13486 start of the inlined function are different instructions. Stepping to
13487 the call site shows the call site, and then stepping again shows
13488 the first line of the inlined function, even though no additional
13489 instructions are executed.
13491 This makes source-level debugging much clearer; you can see both the
13492 context of the call and then the effect of the call. Only stepping by
13493 a single instruction using @code{stepi} or @code{nexti} does not do
13494 this; single instruction steps always show the inlined body.
13496 There are some ways that @value{GDBN} does not pretend that inlined
13497 function calls are the same as normal calls:
13501 Setting breakpoints at the call site of an inlined function may not
13502 work, because the call site does not contain any code. @value{GDBN}
13503 may incorrectly move the breakpoint to the next line of the enclosing
13504 function, after the call. This limitation will be removed in a future
13505 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13506 or inside the inlined function instead.
13509 @value{GDBN} cannot locate the return value of inlined calls after
13510 using the @code{finish} command. This is a limitation of compiler-generated
13511 debugging information; after @code{finish}, you can step to the next line
13512 and print a variable where your program stored the return value.
13516 @node Tail Call Frames
13517 @section Tail Call Frames
13518 @cindex tail call frames, debugging
13520 Function @code{B} can call function @code{C} in its very last statement. In
13521 unoptimized compilation the call of @code{C} is immediately followed by return
13522 instruction at the end of @code{B} code. Optimizing compiler may replace the
13523 call and return in function @code{B} into one jump to function @code{C}
13524 instead. Such use of a jump instruction is called @dfn{tail call}.
13526 During execution of function @code{C}, there will be no indication in the
13527 function call stack frames that it was tail-called from @code{B}. If function
13528 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13529 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13530 some cases @value{GDBN} can determine that @code{C} was tail-called from
13531 @code{B}, and it will then create fictitious call frame for that, with the
13532 return address set up as if @code{B} called @code{C} normally.
13534 This functionality is currently supported only by DWARF 2 debugging format and
13535 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13536 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13539 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13540 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13544 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13546 Stack level 1, frame at 0x7fffffffda30:
13547 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13548 tail call frame, caller of frame at 0x7fffffffda30
13549 source language c++.
13550 Arglist at unknown address.
13551 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13554 The detection of all the possible code path executions can find them ambiguous.
13555 There is no execution history stored (possible @ref{Reverse Execution} is never
13556 used for this purpose) and the last known caller could have reached the known
13557 callee by multiple different jump sequences. In such case @value{GDBN} still
13558 tries to show at least all the unambiguous top tail callers and all the
13559 unambiguous bottom tail calees, if any.
13562 @anchor{set debug entry-values}
13563 @item set debug entry-values
13564 @kindex set debug entry-values
13565 When set to on, enables printing of analysis messages for both frame argument
13566 values at function entry and tail calls. It will show all the possible valid
13567 tail calls code paths it has considered. It will also print the intersection
13568 of them with the final unambiguous (possibly partial or even empty) code path
13571 @item show debug entry-values
13572 @kindex show debug entry-values
13573 Show the current state of analysis messages printing for both frame argument
13574 values at function entry and tail calls.
13577 The analysis messages for tail calls can for example show why the virtual tail
13578 call frame for function @code{c} has not been recognized (due to the indirect
13579 reference by variable @code{x}):
13582 static void __attribute__((noinline, noclone)) c (void);
13583 void (*x) (void) = c;
13584 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13585 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13586 int main (void) @{ x (); return 0; @}
13588 Breakpoint 1, DW_OP_entry_value resolving cannot find
13589 DW_TAG_call_site 0x40039a in main
13591 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13594 #1 0x000000000040039a in main () at t.c:5
13597 Another possibility is an ambiguous virtual tail call frames resolution:
13601 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13602 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13603 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13604 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13605 static void __attribute__((noinline, noclone)) b (void)
13606 @{ if (i) c (); else e (); @}
13607 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13608 int main (void) @{ a (); return 0; @}
13610 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13611 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13612 tailcall: reduced: 0x4004d2(a) |
13615 #1 0x00000000004004d2 in a () at t.c:8
13616 #2 0x0000000000400395 in main () at t.c:9
13619 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13620 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13622 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13623 @ifset HAVE_MAKEINFO_CLICK
13624 @set ARROW @click{}
13625 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13626 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13628 @ifclear HAVE_MAKEINFO_CLICK
13630 @set CALLSEQ1B @value{CALLSEQ1A}
13631 @set CALLSEQ2B @value{CALLSEQ2A}
13634 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13635 The code can have possible execution paths @value{CALLSEQ1B} or
13636 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13638 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13639 has found. It then finds another possible calling sequence - that one is
13640 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13641 printed as the @code{reduced:} calling sequence. That one could have many
13642 further @code{compare:} and @code{reduced:} statements as long as there remain
13643 any non-ambiguous sequence entries.
13645 For the frame of function @code{b} in both cases there are different possible
13646 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13647 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
13648 therefore this one is displayed to the user while the ambiguous frames are
13651 There can be also reasons why printing of frame argument values at function
13656 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13657 static void __attribute__((noinline, noclone)) a (int i);
13658 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13659 static void __attribute__((noinline, noclone)) a (int i)
13660 @{ if (i) b (i - 1); else c (0); @}
13661 int main (void) @{ a (5); return 0; @}
13664 #0 c (i=i@@entry=0) at t.c:2
13665 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13666 function "a" at 0x400420 can call itself via tail calls
13667 i=<optimized out>) at t.c:6
13668 #2 0x000000000040036e in main () at t.c:7
13671 @value{GDBN} cannot find out from the inferior state if and how many times did
13672 function @code{a} call itself (via function @code{b}) as these calls would be
13673 tail calls. Such tail calls would modify the @code{i} variable, therefore
13674 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13675 prints @code{<optimized out>} instead.
13678 @chapter C Preprocessor Macros
13680 Some languages, such as C and C@t{++}, provide a way to define and invoke
13681 ``preprocessor macros'' which expand into strings of tokens.
13682 @value{GDBN} can evaluate expressions containing macro invocations, show
13683 the result of macro expansion, and show a macro's definition, including
13684 where it was defined.
13686 You may need to compile your program specially to provide @value{GDBN}
13687 with information about preprocessor macros. Most compilers do not
13688 include macros in their debugging information, even when you compile
13689 with the @option{-g} flag. @xref{Compilation}.
13691 A program may define a macro at one point, remove that definition later,
13692 and then provide a different definition after that. Thus, at different
13693 points in the program, a macro may have different definitions, or have
13694 no definition at all. If there is a current stack frame, @value{GDBN}
13695 uses the macros in scope at that frame's source code line. Otherwise,
13696 @value{GDBN} uses the macros in scope at the current listing location;
13699 Whenever @value{GDBN} evaluates an expression, it always expands any
13700 macro invocations present in the expression. @value{GDBN} also provides
13701 the following commands for working with macros explicitly.
13705 @kindex macro expand
13706 @cindex macro expansion, showing the results of preprocessor
13707 @cindex preprocessor macro expansion, showing the results of
13708 @cindex expanding preprocessor macros
13709 @item macro expand @var{expression}
13710 @itemx macro exp @var{expression}
13711 Show the results of expanding all preprocessor macro invocations in
13712 @var{expression}. Since @value{GDBN} simply expands macros, but does
13713 not parse the result, @var{expression} need not be a valid expression;
13714 it can be any string of tokens.
13717 @item macro expand-once @var{expression}
13718 @itemx macro exp1 @var{expression}
13719 @cindex expand macro once
13720 @i{(This command is not yet implemented.)} Show the results of
13721 expanding those preprocessor macro invocations that appear explicitly in
13722 @var{expression}. Macro invocations appearing in that expansion are
13723 left unchanged. This command allows you to see the effect of a
13724 particular macro more clearly, without being confused by further
13725 expansions. Since @value{GDBN} simply expands macros, but does not
13726 parse the result, @var{expression} need not be a valid expression; it
13727 can be any string of tokens.
13730 @cindex macro definition, showing
13731 @cindex definition of a macro, showing
13732 @cindex macros, from debug info
13733 @item info macro [-a|-all] [--] @var{macro}
13734 Show the current definition or all definitions of the named @var{macro},
13735 and describe the source location or compiler command-line where that
13736 definition was established. The optional double dash is to signify the end of
13737 argument processing and the beginning of @var{macro} for non C-like macros where
13738 the macro may begin with a hyphen.
13740 @kindex info macros
13741 @item info macros @var{location}
13742 Show all macro definitions that are in effect at the location specified
13743 by @var{location}, and describe the source location or compiler
13744 command-line where those definitions were established.
13746 @kindex macro define
13747 @cindex user-defined macros
13748 @cindex defining macros interactively
13749 @cindex macros, user-defined
13750 @item macro define @var{macro} @var{replacement-list}
13751 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13752 Introduce a definition for a preprocessor macro named @var{macro},
13753 invocations of which are replaced by the tokens given in
13754 @var{replacement-list}. The first form of this command defines an
13755 ``object-like'' macro, which takes no arguments; the second form
13756 defines a ``function-like'' macro, which takes the arguments given in
13759 A definition introduced by this command is in scope in every
13760 expression evaluated in @value{GDBN}, until it is removed with the
13761 @code{macro undef} command, described below. The definition overrides
13762 all definitions for @var{macro} present in the program being debugged,
13763 as well as any previous user-supplied definition.
13765 @kindex macro undef
13766 @item macro undef @var{macro}
13767 Remove any user-supplied definition for the macro named @var{macro}.
13768 This command only affects definitions provided with the @code{macro
13769 define} command, described above; it cannot remove definitions present
13770 in the program being debugged.
13774 List all the macros defined using the @code{macro define} command.
13777 @cindex macros, example of debugging with
13778 Here is a transcript showing the above commands in action. First, we
13779 show our source files:
13784 #include "sample.h"
13787 #define ADD(x) (M + x)
13792 printf ("Hello, world!\n");
13794 printf ("We're so creative.\n");
13796 printf ("Goodbye, world!\n");
13803 Now, we compile the program using the @sc{gnu} C compiler,
13804 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13805 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13806 and @option{-gdwarf-4}; we recommend always choosing the most recent
13807 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13808 includes information about preprocessor macros in the debugging
13812 $ gcc -gdwarf-2 -g3 sample.c -o sample
13816 Now, we start @value{GDBN} on our sample program:
13820 GNU gdb 2002-05-06-cvs
13821 Copyright 2002 Free Software Foundation, Inc.
13822 GDB is free software, @dots{}
13826 We can expand macros and examine their definitions, even when the
13827 program is not running. @value{GDBN} uses the current listing position
13828 to decide which macro definitions are in scope:
13831 (@value{GDBP}) list main
13834 5 #define ADD(x) (M + x)
13839 10 printf ("Hello, world!\n");
13841 12 printf ("We're so creative.\n");
13842 (@value{GDBP}) info macro ADD
13843 Defined at /home/jimb/gdb/macros/play/sample.c:5
13844 #define ADD(x) (M + x)
13845 (@value{GDBP}) info macro Q
13846 Defined at /home/jimb/gdb/macros/play/sample.h:1
13847 included at /home/jimb/gdb/macros/play/sample.c:2
13849 (@value{GDBP}) macro expand ADD(1)
13850 expands to: (42 + 1)
13851 (@value{GDBP}) macro expand-once ADD(1)
13852 expands to: once (M + 1)
13856 In the example above, note that @code{macro expand-once} expands only
13857 the macro invocation explicit in the original text --- the invocation of
13858 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13859 which was introduced by @code{ADD}.
13861 Once the program is running, @value{GDBN} uses the macro definitions in
13862 force at the source line of the current stack frame:
13865 (@value{GDBP}) break main
13866 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13868 Starting program: /home/jimb/gdb/macros/play/sample
13870 Breakpoint 1, main () at sample.c:10
13871 10 printf ("Hello, world!\n");
13875 At line 10, the definition of the macro @code{N} at line 9 is in force:
13878 (@value{GDBP}) info macro N
13879 Defined at /home/jimb/gdb/macros/play/sample.c:9
13881 (@value{GDBP}) macro expand N Q M
13882 expands to: 28 < 42
13883 (@value{GDBP}) print N Q M
13888 As we step over directives that remove @code{N}'s definition, and then
13889 give it a new definition, @value{GDBN} finds the definition (or lack
13890 thereof) in force at each point:
13893 (@value{GDBP}) next
13895 12 printf ("We're so creative.\n");
13896 (@value{GDBP}) info macro N
13897 The symbol `N' has no definition as a C/C++ preprocessor macro
13898 at /home/jimb/gdb/macros/play/sample.c:12
13899 (@value{GDBP}) next
13901 14 printf ("Goodbye, world!\n");
13902 (@value{GDBP}) info macro N
13903 Defined at /home/jimb/gdb/macros/play/sample.c:13
13905 (@value{GDBP}) macro expand N Q M
13906 expands to: 1729 < 42
13907 (@value{GDBP}) print N Q M
13912 In addition to source files, macros can be defined on the compilation command
13913 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13914 such a way, @value{GDBN} displays the location of their definition as line zero
13915 of the source file submitted to the compiler.
13918 (@value{GDBP}) info macro __STDC__
13919 Defined at /home/jimb/gdb/macros/play/sample.c:0
13926 @chapter Tracepoints
13927 @c This chapter is based on the documentation written by Michael
13928 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13930 @cindex tracepoints
13931 In some applications, it is not feasible for the debugger to interrupt
13932 the program's execution long enough for the developer to learn
13933 anything helpful about its behavior. If the program's correctness
13934 depends on its real-time behavior, delays introduced by a debugger
13935 might cause the program to change its behavior drastically, or perhaps
13936 fail, even when the code itself is correct. It is useful to be able
13937 to observe the program's behavior without interrupting it.
13939 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13940 specify locations in the program, called @dfn{tracepoints}, and
13941 arbitrary expressions to evaluate when those tracepoints are reached.
13942 Later, using the @code{tfind} command, you can examine the values
13943 those expressions had when the program hit the tracepoints. The
13944 expressions may also denote objects in memory---structures or arrays,
13945 for example---whose values @value{GDBN} should record; while visiting
13946 a particular tracepoint, you may inspect those objects as if they were
13947 in memory at that moment. However, because @value{GDBN} records these
13948 values without interacting with you, it can do so quickly and
13949 unobtrusively, hopefully not disturbing the program's behavior.
13951 The tracepoint facility is currently available only for remote
13952 targets. @xref{Targets}. In addition, your remote target must know
13953 how to collect trace data. This functionality is implemented in the
13954 remote stub; however, none of the stubs distributed with @value{GDBN}
13955 support tracepoints as of this writing. The format of the remote
13956 packets used to implement tracepoints are described in @ref{Tracepoint
13959 It is also possible to get trace data from a file, in a manner reminiscent
13960 of corefiles; you specify the filename, and use @code{tfind} to search
13961 through the file. @xref{Trace Files}, for more details.
13963 This chapter describes the tracepoint commands and features.
13966 * Set Tracepoints::
13967 * Analyze Collected Data::
13968 * Tracepoint Variables::
13972 @node Set Tracepoints
13973 @section Commands to Set Tracepoints
13975 Before running such a @dfn{trace experiment}, an arbitrary number of
13976 tracepoints can be set. A tracepoint is actually a special type of
13977 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13978 standard breakpoint commands. For instance, as with breakpoints,
13979 tracepoint numbers are successive integers starting from one, and many
13980 of the commands associated with tracepoints take the tracepoint number
13981 as their argument, to identify which tracepoint to work on.
13983 For each tracepoint, you can specify, in advance, some arbitrary set
13984 of data that you want the target to collect in the trace buffer when
13985 it hits that tracepoint. The collected data can include registers,
13986 local variables, or global data. Later, you can use @value{GDBN}
13987 commands to examine the values these data had at the time the
13988 tracepoint was hit.
13990 Tracepoints do not support every breakpoint feature. Ignore counts on
13991 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13992 commands when they are hit. Tracepoints may not be thread-specific
13995 @cindex fast tracepoints
13996 Some targets may support @dfn{fast tracepoints}, which are inserted in
13997 a different way (such as with a jump instead of a trap), that is
13998 faster but possibly restricted in where they may be installed.
14000 @cindex static tracepoints
14001 @cindex markers, static tracepoints
14002 @cindex probing markers, static tracepoints
14003 Regular and fast tracepoints are dynamic tracing facilities, meaning
14004 that they can be used to insert tracepoints at (almost) any location
14005 in the target. Some targets may also support controlling @dfn{static
14006 tracepoints} from @value{GDBN}. With static tracing, a set of
14007 instrumentation points, also known as @dfn{markers}, are embedded in
14008 the target program, and can be activated or deactivated by name or
14009 address. These are usually placed at locations which facilitate
14010 investigating what the target is actually doing. @value{GDBN}'s
14011 support for static tracing includes being able to list instrumentation
14012 points, and attach them with @value{GDBN} defined high level
14013 tracepoints that expose the whole range of convenience of
14014 @value{GDBN}'s tracepoints support. Namely, support for collecting
14015 registers values and values of global or local (to the instrumentation
14016 point) variables; tracepoint conditions and trace state variables.
14017 The act of installing a @value{GDBN} static tracepoint on an
14018 instrumentation point, or marker, is referred to as @dfn{probing} a
14019 static tracepoint marker.
14021 @code{gdbserver} supports tracepoints on some target systems.
14022 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14024 This section describes commands to set tracepoints and associated
14025 conditions and actions.
14028 * Create and Delete Tracepoints::
14029 * Enable and Disable Tracepoints::
14030 * Tracepoint Passcounts::
14031 * Tracepoint Conditions::
14032 * Trace State Variables::
14033 * Tracepoint Actions::
14034 * Listing Tracepoints::
14035 * Listing Static Tracepoint Markers::
14036 * Starting and Stopping Trace Experiments::
14037 * Tracepoint Restrictions::
14040 @node Create and Delete Tracepoints
14041 @subsection Create and Delete Tracepoints
14044 @cindex set tracepoint
14046 @item trace @var{location}
14047 The @code{trace} command is very similar to the @code{break} command.
14048 Its argument @var{location} can be any valid location.
14049 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14050 which is a point in the target program where the debugger will briefly stop,
14051 collect some data, and then allow the program to continue. Setting a tracepoint
14052 or changing its actions takes effect immediately if the remote stub
14053 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14055 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14056 these changes don't take effect until the next @code{tstart}
14057 command, and once a trace experiment is running, further changes will
14058 not have any effect until the next trace experiment starts. In addition,
14059 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14060 address is not yet resolved. (This is similar to pending breakpoints.)
14061 Pending tracepoints are not downloaded to the target and not installed
14062 until they are resolved. The resolution of pending tracepoints requires
14063 @value{GDBN} support---when debugging with the remote target, and
14064 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14065 tracing}), pending tracepoints can not be resolved (and downloaded to
14066 the remote stub) while @value{GDBN} is disconnected.
14068 Here are some examples of using the @code{trace} command:
14071 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14073 (@value{GDBP}) @b{trace +2} // 2 lines forward
14075 (@value{GDBP}) @b{trace my_function} // first source line of function
14077 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14079 (@value{GDBP}) @b{trace *0x2117c4} // an address
14083 You can abbreviate @code{trace} as @code{tr}.
14085 @item trace @var{location} if @var{cond}
14086 Set a tracepoint with condition @var{cond}; evaluate the expression
14087 @var{cond} each time the tracepoint is reached, and collect data only
14088 if the value is nonzero---that is, if @var{cond} evaluates as true.
14089 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14090 information on tracepoint conditions.
14092 @item ftrace @var{location} [ if @var{cond} ]
14093 @cindex set fast tracepoint
14094 @cindex fast tracepoints, setting
14096 The @code{ftrace} command sets a fast tracepoint. For targets that
14097 support them, fast tracepoints will use a more efficient but possibly
14098 less general technique to trigger data collection, such as a jump
14099 instruction instead of a trap, or some sort of hardware support. It
14100 may not be possible to create a fast tracepoint at the desired
14101 location, in which case the command will exit with an explanatory
14104 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14107 On 32-bit x86-architecture systems, fast tracepoints normally need to
14108 be placed at an instruction that is 5 bytes or longer, but can be
14109 placed at 4-byte instructions if the low 64K of memory of the target
14110 program is available to install trampolines. Some Unix-type systems,
14111 such as @sc{gnu}/Linux, exclude low addresses from the program's
14112 address space; but for instance with the Linux kernel it is possible
14113 to let @value{GDBN} use this area by doing a @command{sysctl} command
14114 to set the @code{mmap_min_addr} kernel parameter, as in
14117 sudo sysctl -w vm.mmap_min_addr=32768
14121 which sets the low address to 32K, which leaves plenty of room for
14122 trampolines. The minimum address should be set to a page boundary.
14124 @item strace @var{location} [ if @var{cond} ]
14125 @cindex set static tracepoint
14126 @cindex static tracepoints, setting
14127 @cindex probe static tracepoint marker
14129 The @code{strace} command sets a static tracepoint. For targets that
14130 support it, setting a static tracepoint probes a static
14131 instrumentation point, or marker, found at @var{location}. It may not
14132 be possible to set a static tracepoint at the desired location, in
14133 which case the command will exit with an explanatory message.
14135 @value{GDBN} handles arguments to @code{strace} exactly as for
14136 @code{trace}, with the addition that the user can also specify
14137 @code{-m @var{marker}} as @var{location}. This probes the marker
14138 identified by the @var{marker} string identifier. This identifier
14139 depends on the static tracepoint backend library your program is
14140 using. You can find all the marker identifiers in the @samp{ID} field
14141 of the @code{info static-tracepoint-markers} command output.
14142 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14143 Markers}. For example, in the following small program using the UST
14149 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14154 the marker id is composed of joining the first two arguments to the
14155 @code{trace_mark} call with a slash, which translates to:
14158 (@value{GDBP}) info static-tracepoint-markers
14159 Cnt Enb ID Address What
14160 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14166 so you may probe the marker above with:
14169 (@value{GDBP}) strace -m ust/bar33
14172 Static tracepoints accept an extra collect action --- @code{collect
14173 $_sdata}. This collects arbitrary user data passed in the probe point
14174 call to the tracing library. In the UST example above, you'll see
14175 that the third argument to @code{trace_mark} is a printf-like format
14176 string. The user data is then the result of running that formatting
14177 string against the following arguments. Note that @code{info
14178 static-tracepoint-markers} command output lists that format string in
14179 the @samp{Data:} field.
14181 You can inspect this data when analyzing the trace buffer, by printing
14182 the $_sdata variable like any other variable available to
14183 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14186 @cindex last tracepoint number
14187 @cindex recent tracepoint number
14188 @cindex tracepoint number
14189 The convenience variable @code{$tpnum} records the tracepoint number
14190 of the most recently set tracepoint.
14192 @kindex delete tracepoint
14193 @cindex tracepoint deletion
14194 @item delete tracepoint @r{[}@var{num}@r{]}
14195 Permanently delete one or more tracepoints. With no argument, the
14196 default is to delete all tracepoints. Note that the regular
14197 @code{delete} command can remove tracepoints also.
14202 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14204 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14208 You can abbreviate this command as @code{del tr}.
14211 @node Enable and Disable Tracepoints
14212 @subsection Enable and Disable Tracepoints
14214 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14217 @kindex disable tracepoint
14218 @item disable tracepoint @r{[}@var{num}@r{]}
14219 Disable tracepoint @var{num}, or all tracepoints if no argument
14220 @var{num} is given. A disabled tracepoint will have no effect during
14221 a trace experiment, but it is not forgotten. You can re-enable
14222 a disabled tracepoint using the @code{enable tracepoint} command.
14223 If the command is issued during a trace experiment and the debug target
14224 has support for disabling tracepoints during a trace experiment, then the
14225 change will be effective immediately. Otherwise, it will be applied to the
14226 next trace experiment.
14228 @kindex enable tracepoint
14229 @item enable tracepoint @r{[}@var{num}@r{]}
14230 Enable tracepoint @var{num}, or all tracepoints. If this command is
14231 issued during a trace experiment and the debug target supports enabling
14232 tracepoints during a trace experiment, then the enabled tracepoints will
14233 become effective immediately. Otherwise, they will become effective the
14234 next time a trace experiment is run.
14237 @node Tracepoint Passcounts
14238 @subsection Tracepoint Passcounts
14242 @cindex tracepoint pass count
14243 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14244 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14245 automatically stop a trace experiment. If a tracepoint's passcount is
14246 @var{n}, then the trace experiment will be automatically stopped on
14247 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14248 @var{num} is not specified, the @code{passcount} command sets the
14249 passcount of the most recently defined tracepoint. If no passcount is
14250 given, the trace experiment will run until stopped explicitly by the
14256 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14257 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14259 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14260 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14261 (@value{GDBP}) @b{trace foo}
14262 (@value{GDBP}) @b{pass 3}
14263 (@value{GDBP}) @b{trace bar}
14264 (@value{GDBP}) @b{pass 2}
14265 (@value{GDBP}) @b{trace baz}
14266 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14267 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14268 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14269 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14273 @node Tracepoint Conditions
14274 @subsection Tracepoint Conditions
14275 @cindex conditional tracepoints
14276 @cindex tracepoint conditions
14278 The simplest sort of tracepoint collects data every time your program
14279 reaches a specified place. You can also specify a @dfn{condition} for
14280 a tracepoint. A condition is just a Boolean expression in your
14281 programming language (@pxref{Expressions, ,Expressions}). A
14282 tracepoint with a condition evaluates the expression each time your
14283 program reaches it, and data collection happens only if the condition
14286 Tracepoint conditions can be specified when a tracepoint is set, by
14287 using @samp{if} in the arguments to the @code{trace} command.
14288 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14289 also be set or changed at any time with the @code{condition} command,
14290 just as with breakpoints.
14292 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14293 the conditional expression itself. Instead, @value{GDBN} encodes the
14294 expression into an agent expression (@pxref{Agent Expressions})
14295 suitable for execution on the target, independently of @value{GDBN}.
14296 Global variables become raw memory locations, locals become stack
14297 accesses, and so forth.
14299 For instance, suppose you have a function that is usually called
14300 frequently, but should not be called after an error has occurred. You
14301 could use the following tracepoint command to collect data about calls
14302 of that function that happen while the error code is propagating
14303 through the program; an unconditional tracepoint could end up
14304 collecting thousands of useless trace frames that you would have to
14308 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14311 @node Trace State Variables
14312 @subsection Trace State Variables
14313 @cindex trace state variables
14315 A @dfn{trace state variable} is a special type of variable that is
14316 created and managed by target-side code. The syntax is the same as
14317 that for GDB's convenience variables (a string prefixed with ``$''),
14318 but they are stored on the target. They must be created explicitly,
14319 using a @code{tvariable} command. They are always 64-bit signed
14322 Trace state variables are remembered by @value{GDBN}, and downloaded
14323 to the target along with tracepoint information when the trace
14324 experiment starts. There are no intrinsic limits on the number of
14325 trace state variables, beyond memory limitations of the target.
14327 @cindex convenience variables, and trace state variables
14328 Although trace state variables are managed by the target, you can use
14329 them in print commands and expressions as if they were convenience
14330 variables; @value{GDBN} will get the current value from the target
14331 while the trace experiment is running. Trace state variables share
14332 the same namespace as other ``$'' variables, which means that you
14333 cannot have trace state variables with names like @code{$23} or
14334 @code{$pc}, nor can you have a trace state variable and a convenience
14335 variable with the same name.
14339 @item tvariable $@var{name} [ = @var{expression} ]
14341 The @code{tvariable} command creates a new trace state variable named
14342 @code{$@var{name}}, and optionally gives it an initial value of
14343 @var{expression}. The @var{expression} is evaluated when this command is
14344 entered; the result will be converted to an integer if possible,
14345 otherwise @value{GDBN} will report an error. A subsequent
14346 @code{tvariable} command specifying the same name does not create a
14347 variable, but instead assigns the supplied initial value to the
14348 existing variable of that name, overwriting any previous initial
14349 value. The default initial value is 0.
14351 @item info tvariables
14352 @kindex info tvariables
14353 List all the trace state variables along with their initial values.
14354 Their current values may also be displayed, if the trace experiment is
14357 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14358 @kindex delete tvariable
14359 Delete the given trace state variables, or all of them if no arguments
14364 @node Tracepoint Actions
14365 @subsection Tracepoint Action Lists
14369 @cindex tracepoint actions
14370 @item actions @r{[}@var{num}@r{]}
14371 This command will prompt for a list of actions to be taken when the
14372 tracepoint is hit. If the tracepoint number @var{num} is not
14373 specified, this command sets the actions for the one that was most
14374 recently defined (so that you can define a tracepoint and then say
14375 @code{actions} without bothering about its number). You specify the
14376 actions themselves on the following lines, one action at a time, and
14377 terminate the actions list with a line containing just @code{end}. So
14378 far, the only defined actions are @code{collect}, @code{teval}, and
14379 @code{while-stepping}.
14381 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14382 Commands, ,Breakpoint Command Lists}), except that only the defined
14383 actions are allowed; any other @value{GDBN} command is rejected.
14385 @cindex remove actions from a tracepoint
14386 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14387 and follow it immediately with @samp{end}.
14390 (@value{GDBP}) @b{collect @var{data}} // collect some data
14392 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14394 (@value{GDBP}) @b{end} // signals the end of actions.
14397 In the following example, the action list begins with @code{collect}
14398 commands indicating the things to be collected when the tracepoint is
14399 hit. Then, in order to single-step and collect additional data
14400 following the tracepoint, a @code{while-stepping} command is used,
14401 followed by the list of things to be collected after each step in a
14402 sequence of single steps. The @code{while-stepping} command is
14403 terminated by its own separate @code{end} command. Lastly, the action
14404 list is terminated by an @code{end} command.
14407 (@value{GDBP}) @b{trace foo}
14408 (@value{GDBP}) @b{actions}
14409 Enter actions for tracepoint 1, one per line:
14412 > while-stepping 12
14413 > collect $pc, arr[i]
14418 @kindex collect @r{(tracepoints)}
14419 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14420 Collect values of the given expressions when the tracepoint is hit.
14421 This command accepts a comma-separated list of any valid expressions.
14422 In addition to global, static, or local variables, the following
14423 special arguments are supported:
14427 Collect all registers.
14430 Collect all function arguments.
14433 Collect all local variables.
14436 Collect the return address. This is helpful if you want to see more
14439 @emph{Note:} The return address location can not always be reliably
14440 determined up front, and the wrong address / registers may end up
14441 collected instead. On some architectures the reliability is higher
14442 for tracepoints at function entry, while on others it's the opposite.
14443 When this happens, backtracing will stop because the return address is
14444 found unavailable (unless another collect rule happened to match it).
14447 Collects the number of arguments from the static probe at which the
14448 tracepoint is located.
14449 @xref{Static Probe Points}.
14451 @item $_probe_arg@var{n}
14452 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14453 from the static probe at which the tracepoint is located.
14454 @xref{Static Probe Points}.
14457 @vindex $_sdata@r{, collect}
14458 Collect static tracepoint marker specific data. Only available for
14459 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14460 Lists}. On the UST static tracepoints library backend, an
14461 instrumentation point resembles a @code{printf} function call. The
14462 tracing library is able to collect user specified data formatted to a
14463 character string using the format provided by the programmer that
14464 instrumented the program. Other backends have similar mechanisms.
14465 Here's an example of a UST marker call:
14468 const char master_name[] = "$your_name";
14469 trace_mark(channel1, marker1, "hello %s", master_name)
14472 In this case, collecting @code{$_sdata} collects the string
14473 @samp{hello $yourname}. When analyzing the trace buffer, you can
14474 inspect @samp{$_sdata} like any other variable available to
14478 You can give several consecutive @code{collect} commands, each one
14479 with a single argument, or one @code{collect} command with several
14480 arguments separated by commas; the effect is the same.
14482 The optional @var{mods} changes the usual handling of the arguments.
14483 @code{s} requests that pointers to chars be handled as strings, in
14484 particular collecting the contents of the memory being pointed at, up
14485 to the first zero. The upper bound is by default the value of the
14486 @code{print elements} variable; if @code{s} is followed by a decimal
14487 number, that is the upper bound instead. So for instance
14488 @samp{collect/s25 mystr} collects as many as 25 characters at
14491 The command @code{info scope} (@pxref{Symbols, info scope}) is
14492 particularly useful for figuring out what data to collect.
14494 @kindex teval @r{(tracepoints)}
14495 @item teval @var{expr1}, @var{expr2}, @dots{}
14496 Evaluate the given expressions when the tracepoint is hit. This
14497 command accepts a comma-separated list of expressions. The results
14498 are discarded, so this is mainly useful for assigning values to trace
14499 state variables (@pxref{Trace State Variables}) without adding those
14500 values to the trace buffer, as would be the case if the @code{collect}
14503 @kindex while-stepping @r{(tracepoints)}
14504 @item while-stepping @var{n}
14505 Perform @var{n} single-step instruction traces after the tracepoint,
14506 collecting new data after each step. The @code{while-stepping}
14507 command is followed by the list of what to collect while stepping
14508 (followed by its own @code{end} command):
14511 > while-stepping 12
14512 > collect $regs, myglobal
14518 Note that @code{$pc} is not automatically collected by
14519 @code{while-stepping}; you need to explicitly collect that register if
14520 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14523 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14524 @kindex set default-collect
14525 @cindex default collection action
14526 This variable is a list of expressions to collect at each tracepoint
14527 hit. It is effectively an additional @code{collect} action prepended
14528 to every tracepoint action list. The expressions are parsed
14529 individually for each tracepoint, so for instance a variable named
14530 @code{xyz} may be interpreted as a global for one tracepoint, and a
14531 local for another, as appropriate to the tracepoint's location.
14533 @item show default-collect
14534 @kindex show default-collect
14535 Show the list of expressions that are collected by default at each
14540 @node Listing Tracepoints
14541 @subsection Listing Tracepoints
14544 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14545 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14546 @cindex information about tracepoints
14547 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14548 Display information about the tracepoint @var{num}. If you don't
14549 specify a tracepoint number, displays information about all the
14550 tracepoints defined so far. The format is similar to that used for
14551 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14552 command, simply restricting itself to tracepoints.
14554 A tracepoint's listing may include additional information specific to
14559 its passcount as given by the @code{passcount @var{n}} command
14562 the state about installed on target of each location
14566 (@value{GDBP}) @b{info trace}
14567 Num Type Disp Enb Address What
14568 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14570 collect globfoo, $regs
14575 2 tracepoint keep y <MULTIPLE>
14577 2.1 y 0x0804859c in func4 at change-loc.h:35
14578 installed on target
14579 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14580 installed on target
14581 2.3 y <PENDING> set_tracepoint
14582 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14583 not installed on target
14588 This command can be abbreviated @code{info tp}.
14591 @node Listing Static Tracepoint Markers
14592 @subsection Listing Static Tracepoint Markers
14595 @kindex info static-tracepoint-markers
14596 @cindex information about static tracepoint markers
14597 @item info static-tracepoint-markers
14598 Display information about all static tracepoint markers defined in the
14601 For each marker, the following columns are printed:
14605 An incrementing counter, output to help readability. This is not a
14608 The marker ID, as reported by the target.
14609 @item Enabled or Disabled
14610 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14611 that are not enabled.
14613 Where the marker is in your program, as a memory address.
14615 Where the marker is in the source for your program, as a file and line
14616 number. If the debug information included in the program does not
14617 allow @value{GDBN} to locate the source of the marker, this column
14618 will be left blank.
14622 In addition, the following information may be printed for each marker:
14626 User data passed to the tracing library by the marker call. In the
14627 UST backend, this is the format string passed as argument to the
14629 @item Static tracepoints probing the marker
14630 The list of static tracepoints attached to the marker.
14634 (@value{GDBP}) info static-tracepoint-markers
14635 Cnt ID Enb Address What
14636 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14637 Data: number1 %d number2 %d
14638 Probed by static tracepoints: #2
14639 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14645 @node Starting and Stopping Trace Experiments
14646 @subsection Starting and Stopping Trace Experiments
14649 @kindex tstart [ @var{notes} ]
14650 @cindex start a new trace experiment
14651 @cindex collected data discarded
14653 This command starts the trace experiment, and begins collecting data.
14654 It has the side effect of discarding all the data collected in the
14655 trace buffer during the previous trace experiment. If any arguments
14656 are supplied, they are taken as a note and stored with the trace
14657 experiment's state. The notes may be arbitrary text, and are
14658 especially useful with disconnected tracing in a multi-user context;
14659 the notes can explain what the trace is doing, supply user contact
14660 information, and so forth.
14662 @kindex tstop [ @var{notes} ]
14663 @cindex stop a running trace experiment
14665 This command stops the trace experiment. If any arguments are
14666 supplied, they are recorded with the experiment as a note. This is
14667 useful if you are stopping a trace started by someone else, for
14668 instance if the trace is interfering with the system's behavior and
14669 needs to be stopped quickly.
14671 @strong{Note}: a trace experiment and data collection may stop
14672 automatically if any tracepoint's passcount is reached
14673 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14676 @cindex status of trace data collection
14677 @cindex trace experiment, status of
14679 This command displays the status of the current trace data
14683 Here is an example of the commands we described so far:
14686 (@value{GDBP}) @b{trace gdb_c_test}
14687 (@value{GDBP}) @b{actions}
14688 Enter actions for tracepoint #1, one per line.
14689 > collect $regs,$locals,$args
14690 > while-stepping 11
14694 (@value{GDBP}) @b{tstart}
14695 [time passes @dots{}]
14696 (@value{GDBP}) @b{tstop}
14699 @anchor{disconnected tracing}
14700 @cindex disconnected tracing
14701 You can choose to continue running the trace experiment even if
14702 @value{GDBN} disconnects from the target, voluntarily or
14703 involuntarily. For commands such as @code{detach}, the debugger will
14704 ask what you want to do with the trace. But for unexpected
14705 terminations (@value{GDBN} crash, network outage), it would be
14706 unfortunate to lose hard-won trace data, so the variable
14707 @code{disconnected-tracing} lets you decide whether the trace should
14708 continue running without @value{GDBN}.
14711 @item set disconnected-tracing on
14712 @itemx set disconnected-tracing off
14713 @kindex set disconnected-tracing
14714 Choose whether a tracing run should continue to run if @value{GDBN}
14715 has disconnected from the target. Note that @code{detach} or
14716 @code{quit} will ask you directly what to do about a running trace no
14717 matter what this variable's setting, so the variable is mainly useful
14718 for handling unexpected situations, such as loss of the network.
14720 @item show disconnected-tracing
14721 @kindex show disconnected-tracing
14722 Show the current choice for disconnected tracing.
14726 When you reconnect to the target, the trace experiment may or may not
14727 still be running; it might have filled the trace buffer in the
14728 meantime, or stopped for one of the other reasons. If it is running,
14729 it will continue after reconnection.
14731 Upon reconnection, the target will upload information about the
14732 tracepoints in effect. @value{GDBN} will then compare that
14733 information to the set of tracepoints currently defined, and attempt
14734 to match them up, allowing for the possibility that the numbers may
14735 have changed due to creation and deletion in the meantime. If one of
14736 the target's tracepoints does not match any in @value{GDBN}, the
14737 debugger will create a new tracepoint, so that you have a number with
14738 which to specify that tracepoint. This matching-up process is
14739 necessarily heuristic, and it may result in useless tracepoints being
14740 created; you may simply delete them if they are of no use.
14742 @cindex circular trace buffer
14743 If your target agent supports a @dfn{circular trace buffer}, then you
14744 can run a trace experiment indefinitely without filling the trace
14745 buffer; when space runs out, the agent deletes already-collected trace
14746 frames, oldest first, until there is enough room to continue
14747 collecting. This is especially useful if your tracepoints are being
14748 hit too often, and your trace gets terminated prematurely because the
14749 buffer is full. To ask for a circular trace buffer, simply set
14750 @samp{circular-trace-buffer} to on. You can set this at any time,
14751 including during tracing; if the agent can do it, it will change
14752 buffer handling on the fly, otherwise it will not take effect until
14756 @item set circular-trace-buffer on
14757 @itemx set circular-trace-buffer off
14758 @kindex set circular-trace-buffer
14759 Choose whether a tracing run should use a linear or circular buffer
14760 for trace data. A linear buffer will not lose any trace data, but may
14761 fill up prematurely, while a circular buffer will discard old trace
14762 data, but it will have always room for the latest tracepoint hits.
14764 @item show circular-trace-buffer
14765 @kindex show circular-trace-buffer
14766 Show the current choice for the trace buffer. Note that this may not
14767 match the agent's current buffer handling, nor is it guaranteed to
14768 match the setting that might have been in effect during a past run,
14769 for instance if you are looking at frames from a trace file.
14774 @item set trace-buffer-size @var{n}
14775 @itemx set trace-buffer-size unlimited
14776 @kindex set trace-buffer-size
14777 Request that the target use a trace buffer of @var{n} bytes. Not all
14778 targets will honor the request; they may have a compiled-in size for
14779 the trace buffer, or some other limitation. Set to a value of
14780 @code{unlimited} or @code{-1} to let the target use whatever size it
14781 likes. This is also the default.
14783 @item show trace-buffer-size
14784 @kindex show trace-buffer-size
14785 Show the current requested size for the trace buffer. Note that this
14786 will only match the actual size if the target supports size-setting,
14787 and was able to handle the requested size. For instance, if the
14788 target can only change buffer size between runs, this variable will
14789 not reflect the change until the next run starts. Use @code{tstatus}
14790 to get a report of the actual buffer size.
14794 @item set trace-user @var{text}
14795 @kindex set trace-user
14797 @item show trace-user
14798 @kindex show trace-user
14800 @item set trace-notes @var{text}
14801 @kindex set trace-notes
14802 Set the trace run's notes.
14804 @item show trace-notes
14805 @kindex show trace-notes
14806 Show the trace run's notes.
14808 @item set trace-stop-notes @var{text}
14809 @kindex set trace-stop-notes
14810 Set the trace run's stop notes. The handling of the note is as for
14811 @code{tstop} arguments; the set command is convenient way to fix a
14812 stop note that is mistaken or incomplete.
14814 @item show trace-stop-notes
14815 @kindex show trace-stop-notes
14816 Show the trace run's stop notes.
14820 @node Tracepoint Restrictions
14821 @subsection Tracepoint Restrictions
14823 @cindex tracepoint restrictions
14824 There are a number of restrictions on the use of tracepoints. As
14825 described above, tracepoint data gathering occurs on the target
14826 without interaction from @value{GDBN}. Thus the full capabilities of
14827 the debugger are not available during data gathering, and then at data
14828 examination time, you will be limited by only having what was
14829 collected. The following items describe some common problems, but it
14830 is not exhaustive, and you may run into additional difficulties not
14836 Tracepoint expressions are intended to gather objects (lvalues). Thus
14837 the full flexibility of GDB's expression evaluator is not available.
14838 You cannot call functions, cast objects to aggregate types, access
14839 convenience variables or modify values (except by assignment to trace
14840 state variables). Some language features may implicitly call
14841 functions (for instance Objective-C fields with accessors), and therefore
14842 cannot be collected either.
14845 Collection of local variables, either individually or in bulk with
14846 @code{$locals} or @code{$args}, during @code{while-stepping} may
14847 behave erratically. The stepping action may enter a new scope (for
14848 instance by stepping into a function), or the location of the variable
14849 may change (for instance it is loaded into a register). The
14850 tracepoint data recorded uses the location information for the
14851 variables that is correct for the tracepoint location. When the
14852 tracepoint is created, it is not possible, in general, to determine
14853 where the steps of a @code{while-stepping} sequence will advance the
14854 program---particularly if a conditional branch is stepped.
14857 Collection of an incompletely-initialized or partially-destroyed object
14858 may result in something that @value{GDBN} cannot display, or displays
14859 in a misleading way.
14862 When @value{GDBN} displays a pointer to character it automatically
14863 dereferences the pointer to also display characters of the string
14864 being pointed to. However, collecting the pointer during tracing does
14865 not automatically collect the string. You need to explicitly
14866 dereference the pointer and provide size information if you want to
14867 collect not only the pointer, but the memory pointed to. For example,
14868 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14872 It is not possible to collect a complete stack backtrace at a
14873 tracepoint. Instead, you may collect the registers and a few hundred
14874 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14875 (adjust to use the name of the actual stack pointer register on your
14876 target architecture, and the amount of stack you wish to capture).
14877 Then the @code{backtrace} command will show a partial backtrace when
14878 using a trace frame. The number of stack frames that can be examined
14879 depends on the sizes of the frames in the collected stack. Note that
14880 if you ask for a block so large that it goes past the bottom of the
14881 stack, the target agent may report an error trying to read from an
14885 If you do not collect registers at a tracepoint, @value{GDBN} can
14886 infer that the value of @code{$pc} must be the same as the address of
14887 the tracepoint and use that when you are looking at a trace frame
14888 for that tracepoint. However, this cannot work if the tracepoint has
14889 multiple locations (for instance if it was set in a function that was
14890 inlined), or if it has a @code{while-stepping} loop. In those cases
14891 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14896 @node Analyze Collected Data
14897 @section Using the Collected Data
14899 After the tracepoint experiment ends, you use @value{GDBN} commands
14900 for examining the trace data. The basic idea is that each tracepoint
14901 collects a trace @dfn{snapshot} every time it is hit and another
14902 snapshot every time it single-steps. All these snapshots are
14903 consecutively numbered from zero and go into a buffer, and you can
14904 examine them later. The way you examine them is to @dfn{focus} on a
14905 specific trace snapshot. When the remote stub is focused on a trace
14906 snapshot, it will respond to all @value{GDBN} requests for memory and
14907 registers by reading from the buffer which belongs to that snapshot,
14908 rather than from @emph{real} memory or registers of the program being
14909 debugged. This means that @strong{all} @value{GDBN} commands
14910 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14911 behave as if we were currently debugging the program state as it was
14912 when the tracepoint occurred. Any requests for data that are not in
14913 the buffer will fail.
14916 * tfind:: How to select a trace snapshot
14917 * tdump:: How to display all data for a snapshot
14918 * save tracepoints:: How to save tracepoints for a future run
14922 @subsection @code{tfind @var{n}}
14925 @cindex select trace snapshot
14926 @cindex find trace snapshot
14927 The basic command for selecting a trace snapshot from the buffer is
14928 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14929 counting from zero. If no argument @var{n} is given, the next
14930 snapshot is selected.
14932 Here are the various forms of using the @code{tfind} command.
14936 Find the first snapshot in the buffer. This is a synonym for
14937 @code{tfind 0} (since 0 is the number of the first snapshot).
14940 Stop debugging trace snapshots, resume @emph{live} debugging.
14943 Same as @samp{tfind none}.
14946 No argument means find the next trace snapshot or find the first
14947 one if no trace snapshot is selected.
14950 Find the previous trace snapshot before the current one. This permits
14951 retracing earlier steps.
14953 @item tfind tracepoint @var{num}
14954 Find the next snapshot associated with tracepoint @var{num}. Search
14955 proceeds forward from the last examined trace snapshot. If no
14956 argument @var{num} is given, it means find the next snapshot collected
14957 for the same tracepoint as the current snapshot.
14959 @item tfind pc @var{addr}
14960 Find the next snapshot associated with the value @var{addr} of the
14961 program counter. Search proceeds forward from the last examined trace
14962 snapshot. If no argument @var{addr} is given, it means find the next
14963 snapshot with the same value of PC as the current snapshot.
14965 @item tfind outside @var{addr1}, @var{addr2}
14966 Find the next snapshot whose PC is outside the given range of
14967 addresses (exclusive).
14969 @item tfind range @var{addr1}, @var{addr2}
14970 Find the next snapshot whose PC is between @var{addr1} and
14971 @var{addr2} (inclusive).
14973 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14974 Find the next snapshot associated with the source line @var{n}. If
14975 the optional argument @var{file} is given, refer to line @var{n} in
14976 that source file. Search proceeds forward from the last examined
14977 trace snapshot. If no argument @var{n} is given, it means find the
14978 next line other than the one currently being examined; thus saying
14979 @code{tfind line} repeatedly can appear to have the same effect as
14980 stepping from line to line in a @emph{live} debugging session.
14983 The default arguments for the @code{tfind} commands are specifically
14984 designed to make it easy to scan through the trace buffer. For
14985 instance, @code{tfind} with no argument selects the next trace
14986 snapshot, and @code{tfind -} with no argument selects the previous
14987 trace snapshot. So, by giving one @code{tfind} command, and then
14988 simply hitting @key{RET} repeatedly you can examine all the trace
14989 snapshots in order. Or, by saying @code{tfind -} and then hitting
14990 @key{RET} repeatedly you can examine the snapshots in reverse order.
14991 The @code{tfind line} command with no argument selects the snapshot
14992 for the next source line executed. The @code{tfind pc} command with
14993 no argument selects the next snapshot with the same program counter
14994 (PC) as the current frame. The @code{tfind tracepoint} command with
14995 no argument selects the next trace snapshot collected by the same
14996 tracepoint as the current one.
14998 In addition to letting you scan through the trace buffer manually,
14999 these commands make it easy to construct @value{GDBN} scripts that
15000 scan through the trace buffer and print out whatever collected data
15001 you are interested in. Thus, if we want to examine the PC, FP, and SP
15002 registers from each trace frame in the buffer, we can say this:
15005 (@value{GDBP}) @b{tfind start}
15006 (@value{GDBP}) @b{while ($trace_frame != -1)}
15007 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15008 $trace_frame, $pc, $sp, $fp
15012 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15013 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15014 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15015 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15016 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15017 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15018 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15019 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15020 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15021 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15022 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15025 Or, if we want to examine the variable @code{X} at each source line in
15029 (@value{GDBP}) @b{tfind start}
15030 (@value{GDBP}) @b{while ($trace_frame != -1)}
15031 > printf "Frame %d, X == %d\n", $trace_frame, X
15041 @subsection @code{tdump}
15043 @cindex dump all data collected at tracepoint
15044 @cindex tracepoint data, display
15046 This command takes no arguments. It prints all the data collected at
15047 the current trace snapshot.
15050 (@value{GDBP}) @b{trace 444}
15051 (@value{GDBP}) @b{actions}
15052 Enter actions for tracepoint #2, one per line:
15053 > collect $regs, $locals, $args, gdb_long_test
15056 (@value{GDBP}) @b{tstart}
15058 (@value{GDBP}) @b{tfind line 444}
15059 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15061 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15063 (@value{GDBP}) @b{tdump}
15064 Data collected at tracepoint 2, trace frame 1:
15065 d0 0xc4aa0085 -995491707
15069 d4 0x71aea3d 119204413
15072 d7 0x380035 3670069
15073 a0 0x19e24a 1696330
15074 a1 0x3000668 50333288
15076 a3 0x322000 3284992
15077 a4 0x3000698 50333336
15078 a5 0x1ad3cc 1758156
15079 fp 0x30bf3c 0x30bf3c
15080 sp 0x30bf34 0x30bf34
15082 pc 0x20b2c8 0x20b2c8
15086 p = 0x20e5b4 "gdb-test"
15093 gdb_long_test = 17 '\021'
15098 @code{tdump} works by scanning the tracepoint's current collection
15099 actions and printing the value of each expression listed. So
15100 @code{tdump} can fail, if after a run, you change the tracepoint's
15101 actions to mention variables that were not collected during the run.
15103 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15104 uses the collected value of @code{$pc} to distinguish between trace
15105 frames that were collected at the tracepoint hit, and frames that were
15106 collected while stepping. This allows it to correctly choose whether
15107 to display the basic list of collections, or the collections from the
15108 body of the while-stepping loop. However, if @code{$pc} was not collected,
15109 then @code{tdump} will always attempt to dump using the basic collection
15110 list, and may fail if a while-stepping frame does not include all the
15111 same data that is collected at the tracepoint hit.
15112 @c This is getting pretty arcane, example would be good.
15114 @node save tracepoints
15115 @subsection @code{save tracepoints @var{filename}}
15116 @kindex save tracepoints
15117 @kindex save-tracepoints
15118 @cindex save tracepoints for future sessions
15120 This command saves all current tracepoint definitions together with
15121 their actions and passcounts, into a file @file{@var{filename}}
15122 suitable for use in a later debugging session. To read the saved
15123 tracepoint definitions, use the @code{source} command (@pxref{Command
15124 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15125 alias for @w{@code{save tracepoints}}
15127 @node Tracepoint Variables
15128 @section Convenience Variables for Tracepoints
15129 @cindex tracepoint variables
15130 @cindex convenience variables for tracepoints
15133 @vindex $trace_frame
15134 @item (int) $trace_frame
15135 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15136 snapshot is selected.
15138 @vindex $tracepoint
15139 @item (int) $tracepoint
15140 The tracepoint for the current trace snapshot.
15142 @vindex $trace_line
15143 @item (int) $trace_line
15144 The line number for the current trace snapshot.
15146 @vindex $trace_file
15147 @item (char []) $trace_file
15148 The source file for the current trace snapshot.
15150 @vindex $trace_func
15151 @item (char []) $trace_func
15152 The name of the function containing @code{$tracepoint}.
15155 Note: @code{$trace_file} is not suitable for use in @code{printf},
15156 use @code{output} instead.
15158 Here's a simple example of using these convenience variables for
15159 stepping through all the trace snapshots and printing some of their
15160 data. Note that these are not the same as trace state variables,
15161 which are managed by the target.
15164 (@value{GDBP}) @b{tfind start}
15166 (@value{GDBP}) @b{while $trace_frame != -1}
15167 > output $trace_file
15168 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15174 @section Using Trace Files
15175 @cindex trace files
15177 In some situations, the target running a trace experiment may no
15178 longer be available; perhaps it crashed, or the hardware was needed
15179 for a different activity. To handle these cases, you can arrange to
15180 dump the trace data into a file, and later use that file as a source
15181 of trace data, via the @code{target tfile} command.
15186 @item tsave [ -r ] @var{filename}
15187 @itemx tsave [-ctf] @var{dirname}
15188 Save the trace data to @var{filename}. By default, this command
15189 assumes that @var{filename} refers to the host filesystem, so if
15190 necessary @value{GDBN} will copy raw trace data up from the target and
15191 then save it. If the target supports it, you can also supply the
15192 optional argument @code{-r} (``remote'') to direct the target to save
15193 the data directly into @var{filename} in its own filesystem, which may be
15194 more efficient if the trace buffer is very large. (Note, however, that
15195 @code{target tfile} can only read from files accessible to the host.)
15196 By default, this command will save trace frame in tfile format.
15197 You can supply the optional argument @code{-ctf} to save data in CTF
15198 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15199 that can be shared by multiple debugging and tracing tools. Please go to
15200 @indicateurl{http://www.efficios.com/ctf} to get more information.
15202 @kindex target tfile
15206 @item target tfile @var{filename}
15207 @itemx target ctf @var{dirname}
15208 Use the file named @var{filename} or directory named @var{dirname} as
15209 a source of trace data. Commands that examine data work as they do with
15210 a live target, but it is not possible to run any new trace experiments.
15211 @code{tstatus} will report the state of the trace run at the moment
15212 the data was saved, as well as the current trace frame you are examining.
15213 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15217 (@value{GDBP}) target ctf ctf.ctf
15218 (@value{GDBP}) tfind
15219 Found trace frame 0, tracepoint 2
15220 39 ++a; /* set tracepoint 1 here */
15221 (@value{GDBP}) tdump
15222 Data collected at tracepoint 2, trace frame 0:
15226 c = @{"123", "456", "789", "123", "456", "789"@}
15227 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15235 @chapter Debugging Programs That Use Overlays
15238 If your program is too large to fit completely in your target system's
15239 memory, you can sometimes use @dfn{overlays} to work around this
15240 problem. @value{GDBN} provides some support for debugging programs that
15244 * How Overlays Work:: A general explanation of overlays.
15245 * Overlay Commands:: Managing overlays in @value{GDBN}.
15246 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15247 mapped by asking the inferior.
15248 * Overlay Sample Program:: A sample program using overlays.
15251 @node How Overlays Work
15252 @section How Overlays Work
15253 @cindex mapped overlays
15254 @cindex unmapped overlays
15255 @cindex load address, overlay's
15256 @cindex mapped address
15257 @cindex overlay area
15259 Suppose you have a computer whose instruction address space is only 64
15260 kilobytes long, but which has much more memory which can be accessed by
15261 other means: special instructions, segment registers, or memory
15262 management hardware, for example. Suppose further that you want to
15263 adapt a program which is larger than 64 kilobytes to run on this system.
15265 One solution is to identify modules of your program which are relatively
15266 independent, and need not call each other directly; call these modules
15267 @dfn{overlays}. Separate the overlays from the main program, and place
15268 their machine code in the larger memory. Place your main program in
15269 instruction memory, but leave at least enough space there to hold the
15270 largest overlay as well.
15272 Now, to call a function located in an overlay, you must first copy that
15273 overlay's machine code from the large memory into the space set aside
15274 for it in the instruction memory, and then jump to its entry point
15277 @c NB: In the below the mapped area's size is greater or equal to the
15278 @c size of all overlays. This is intentional to remind the developer
15279 @c that overlays don't necessarily need to be the same size.
15283 Data Instruction Larger
15284 Address Space Address Space Address Space
15285 +-----------+ +-----------+ +-----------+
15287 +-----------+ +-----------+ +-----------+<-- overlay 1
15288 | program | | main | .----| overlay 1 | load address
15289 | variables | | program | | +-----------+
15290 | and heap | | | | | |
15291 +-----------+ | | | +-----------+<-- overlay 2
15292 | | +-----------+ | | | load address
15293 +-----------+ | | | .-| overlay 2 |
15295 mapped --->+-----------+ | | +-----------+
15296 address | | | | | |
15297 | overlay | <-' | | |
15298 | area | <---' +-----------+<-- overlay 3
15299 | | <---. | | load address
15300 +-----------+ `--| overlay 3 |
15307 @anchor{A code overlay}A code overlay
15311 The diagram (@pxref{A code overlay}) shows a system with separate data
15312 and instruction address spaces. To map an overlay, the program copies
15313 its code from the larger address space to the instruction address space.
15314 Since the overlays shown here all use the same mapped address, only one
15315 may be mapped at a time. For a system with a single address space for
15316 data and instructions, the diagram would be similar, except that the
15317 program variables and heap would share an address space with the main
15318 program and the overlay area.
15320 An overlay loaded into instruction memory and ready for use is called a
15321 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15322 instruction memory. An overlay not present (or only partially present)
15323 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15324 is its address in the larger memory. The mapped address is also called
15325 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15326 called the @dfn{load memory address}, or @dfn{LMA}.
15328 Unfortunately, overlays are not a completely transparent way to adapt a
15329 program to limited instruction memory. They introduce a new set of
15330 global constraints you must keep in mind as you design your program:
15335 Before calling or returning to a function in an overlay, your program
15336 must make sure that overlay is actually mapped. Otherwise, the call or
15337 return will transfer control to the right address, but in the wrong
15338 overlay, and your program will probably crash.
15341 If the process of mapping an overlay is expensive on your system, you
15342 will need to choose your overlays carefully to minimize their effect on
15343 your program's performance.
15346 The executable file you load onto your system must contain each
15347 overlay's instructions, appearing at the overlay's load address, not its
15348 mapped address. However, each overlay's instructions must be relocated
15349 and its symbols defined as if the overlay were at its mapped address.
15350 You can use GNU linker scripts to specify different load and relocation
15351 addresses for pieces of your program; see @ref{Overlay Description,,,
15352 ld.info, Using ld: the GNU linker}.
15355 The procedure for loading executable files onto your system must be able
15356 to load their contents into the larger address space as well as the
15357 instruction and data spaces.
15361 The overlay system described above is rather simple, and could be
15362 improved in many ways:
15367 If your system has suitable bank switch registers or memory management
15368 hardware, you could use those facilities to make an overlay's load area
15369 contents simply appear at their mapped address in instruction space.
15370 This would probably be faster than copying the overlay to its mapped
15371 area in the usual way.
15374 If your overlays are small enough, you could set aside more than one
15375 overlay area, and have more than one overlay mapped at a time.
15378 You can use overlays to manage data, as well as instructions. In
15379 general, data overlays are even less transparent to your design than
15380 code overlays: whereas code overlays only require care when you call or
15381 return to functions, data overlays require care every time you access
15382 the data. Also, if you change the contents of a data overlay, you
15383 must copy its contents back out to its load address before you can copy a
15384 different data overlay into the same mapped area.
15389 @node Overlay Commands
15390 @section Overlay Commands
15392 To use @value{GDBN}'s overlay support, each overlay in your program must
15393 correspond to a separate section of the executable file. The section's
15394 virtual memory address and load memory address must be the overlay's
15395 mapped and load addresses. Identifying overlays with sections allows
15396 @value{GDBN} to determine the appropriate address of a function or
15397 variable, depending on whether the overlay is mapped or not.
15399 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15400 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15405 Disable @value{GDBN}'s overlay support. When overlay support is
15406 disabled, @value{GDBN} assumes that all functions and variables are
15407 always present at their mapped addresses. By default, @value{GDBN}'s
15408 overlay support is disabled.
15410 @item overlay manual
15411 @cindex manual overlay debugging
15412 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15413 relies on you to tell it which overlays are mapped, and which are not,
15414 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15415 commands described below.
15417 @item overlay map-overlay @var{overlay}
15418 @itemx overlay map @var{overlay}
15419 @cindex map an overlay
15420 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15421 be the name of the object file section containing the overlay. When an
15422 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15423 functions and variables at their mapped addresses. @value{GDBN} assumes
15424 that any other overlays whose mapped ranges overlap that of
15425 @var{overlay} are now unmapped.
15427 @item overlay unmap-overlay @var{overlay}
15428 @itemx overlay unmap @var{overlay}
15429 @cindex unmap an overlay
15430 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15431 must be the name of the object file section containing the overlay.
15432 When an overlay is unmapped, @value{GDBN} assumes it can find the
15433 overlay's functions and variables at their load addresses.
15436 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15437 consults a data structure the overlay manager maintains in the inferior
15438 to see which overlays are mapped. For details, see @ref{Automatic
15439 Overlay Debugging}.
15441 @item overlay load-target
15442 @itemx overlay load
15443 @cindex reloading the overlay table
15444 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15445 re-reads the table @value{GDBN} automatically each time the inferior
15446 stops, so this command should only be necessary if you have changed the
15447 overlay mapping yourself using @value{GDBN}. This command is only
15448 useful when using automatic overlay debugging.
15450 @item overlay list-overlays
15451 @itemx overlay list
15452 @cindex listing mapped overlays
15453 Display a list of the overlays currently mapped, along with their mapped
15454 addresses, load addresses, and sizes.
15458 Normally, when @value{GDBN} prints a code address, it includes the name
15459 of the function the address falls in:
15462 (@value{GDBP}) print main
15463 $3 = @{int ()@} 0x11a0 <main>
15466 When overlay debugging is enabled, @value{GDBN} recognizes code in
15467 unmapped overlays, and prints the names of unmapped functions with
15468 asterisks around them. For example, if @code{foo} is a function in an
15469 unmapped overlay, @value{GDBN} prints it this way:
15472 (@value{GDBP}) overlay list
15473 No sections are mapped.
15474 (@value{GDBP}) print foo
15475 $5 = @{int (int)@} 0x100000 <*foo*>
15478 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15482 (@value{GDBP}) overlay list
15483 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15484 mapped at 0x1016 - 0x104a
15485 (@value{GDBP}) print foo
15486 $6 = @{int (int)@} 0x1016 <foo>
15489 When overlay debugging is enabled, @value{GDBN} can find the correct
15490 address for functions and variables in an overlay, whether or not the
15491 overlay is mapped. This allows most @value{GDBN} commands, like
15492 @code{break} and @code{disassemble}, to work normally, even on unmapped
15493 code. However, @value{GDBN}'s breakpoint support has some limitations:
15497 @cindex breakpoints in overlays
15498 @cindex overlays, setting breakpoints in
15499 You can set breakpoints in functions in unmapped overlays, as long as
15500 @value{GDBN} can write to the overlay at its load address.
15502 @value{GDBN} can not set hardware or simulator-based breakpoints in
15503 unmapped overlays. However, if you set a breakpoint at the end of your
15504 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15505 you are using manual overlay management), @value{GDBN} will re-set its
15506 breakpoints properly.
15510 @node Automatic Overlay Debugging
15511 @section Automatic Overlay Debugging
15512 @cindex automatic overlay debugging
15514 @value{GDBN} can automatically track which overlays are mapped and which
15515 are not, given some simple co-operation from the overlay manager in the
15516 inferior. If you enable automatic overlay debugging with the
15517 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15518 looks in the inferior's memory for certain variables describing the
15519 current state of the overlays.
15521 Here are the variables your overlay manager must define to support
15522 @value{GDBN}'s automatic overlay debugging:
15526 @item @code{_ovly_table}:
15527 This variable must be an array of the following structures:
15532 /* The overlay's mapped address. */
15535 /* The size of the overlay, in bytes. */
15536 unsigned long size;
15538 /* The overlay's load address. */
15541 /* Non-zero if the overlay is currently mapped;
15543 unsigned long mapped;
15547 @item @code{_novlys}:
15548 This variable must be a four-byte signed integer, holding the total
15549 number of elements in @code{_ovly_table}.
15553 To decide whether a particular overlay is mapped or not, @value{GDBN}
15554 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15555 @code{lma} members equal the VMA and LMA of the overlay's section in the
15556 executable file. When @value{GDBN} finds a matching entry, it consults
15557 the entry's @code{mapped} member to determine whether the overlay is
15560 In addition, your overlay manager may define a function called
15561 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15562 will silently set a breakpoint there. If the overlay manager then
15563 calls this function whenever it has changed the overlay table, this
15564 will enable @value{GDBN} to accurately keep track of which overlays
15565 are in program memory, and update any breakpoints that may be set
15566 in overlays. This will allow breakpoints to work even if the
15567 overlays are kept in ROM or other non-writable memory while they
15568 are not being executed.
15570 @node Overlay Sample Program
15571 @section Overlay Sample Program
15572 @cindex overlay example program
15574 When linking a program which uses overlays, you must place the overlays
15575 at their load addresses, while relocating them to run at their mapped
15576 addresses. To do this, you must write a linker script (@pxref{Overlay
15577 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15578 since linker scripts are specific to a particular host system, target
15579 architecture, and target memory layout, this manual cannot provide
15580 portable sample code demonstrating @value{GDBN}'s overlay support.
15582 However, the @value{GDBN} source distribution does contain an overlaid
15583 program, with linker scripts for a few systems, as part of its test
15584 suite. The program consists of the following files from
15585 @file{gdb/testsuite/gdb.base}:
15589 The main program file.
15591 A simple overlay manager, used by @file{overlays.c}.
15596 Overlay modules, loaded and used by @file{overlays.c}.
15599 Linker scripts for linking the test program on the @code{d10v-elf}
15600 and @code{m32r-elf} targets.
15603 You can build the test program using the @code{d10v-elf} GCC
15604 cross-compiler like this:
15607 $ d10v-elf-gcc -g -c overlays.c
15608 $ d10v-elf-gcc -g -c ovlymgr.c
15609 $ d10v-elf-gcc -g -c foo.c
15610 $ d10v-elf-gcc -g -c bar.c
15611 $ d10v-elf-gcc -g -c baz.c
15612 $ d10v-elf-gcc -g -c grbx.c
15613 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15614 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15617 The build process is identical for any other architecture, except that
15618 you must substitute the appropriate compiler and linker script for the
15619 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15623 @chapter Using @value{GDBN} with Different Languages
15626 Although programming languages generally have common aspects, they are
15627 rarely expressed in the same manner. For instance, in ANSI C,
15628 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15629 Modula-2, it is accomplished by @code{p^}. Values can also be
15630 represented (and displayed) differently. Hex numbers in C appear as
15631 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15633 @cindex working language
15634 Language-specific information is built into @value{GDBN} for some languages,
15635 allowing you to express operations like the above in your program's
15636 native language, and allowing @value{GDBN} to output values in a manner
15637 consistent with the syntax of your program's native language. The
15638 language you use to build expressions is called the @dfn{working
15642 * Setting:: Switching between source languages
15643 * Show:: Displaying the language
15644 * Checks:: Type and range checks
15645 * Supported Languages:: Supported languages
15646 * Unsupported Languages:: Unsupported languages
15650 @section Switching Between Source Languages
15652 There are two ways to control the working language---either have @value{GDBN}
15653 set it automatically, or select it manually yourself. You can use the
15654 @code{set language} command for either purpose. On startup, @value{GDBN}
15655 defaults to setting the language automatically. The working language is
15656 used to determine how expressions you type are interpreted, how values
15659 In addition to the working language, every source file that
15660 @value{GDBN} knows about has its own working language. For some object
15661 file formats, the compiler might indicate which language a particular
15662 source file is in. However, most of the time @value{GDBN} infers the
15663 language from the name of the file. The language of a source file
15664 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15665 show each frame appropriately for its own language. There is no way to
15666 set the language of a source file from within @value{GDBN}, but you can
15667 set the language associated with a filename extension. @xref{Show, ,
15668 Displaying the Language}.
15670 This is most commonly a problem when you use a program, such
15671 as @code{cfront} or @code{f2c}, that generates C but is written in
15672 another language. In that case, make the
15673 program use @code{#line} directives in its C output; that way
15674 @value{GDBN} will know the correct language of the source code of the original
15675 program, and will display that source code, not the generated C code.
15678 * Filenames:: Filename extensions and languages.
15679 * Manually:: Setting the working language manually
15680 * Automatically:: Having @value{GDBN} infer the source language
15684 @subsection List of Filename Extensions and Languages
15686 If a source file name ends in one of the following extensions, then
15687 @value{GDBN} infers that its language is the one indicated.
15705 C@t{++} source file
15711 Objective-C source file
15715 Fortran source file
15718 Modula-2 source file
15722 Assembler source file. This actually behaves almost like C, but
15723 @value{GDBN} does not skip over function prologues when stepping.
15726 In addition, you may set the language associated with a filename
15727 extension. @xref{Show, , Displaying the Language}.
15730 @subsection Setting the Working Language
15732 If you allow @value{GDBN} to set the language automatically,
15733 expressions are interpreted the same way in your debugging session and
15736 @kindex set language
15737 If you wish, you may set the language manually. To do this, issue the
15738 command @samp{set language @var{lang}}, where @var{lang} is the name of
15739 a language, such as
15740 @code{c} or @code{modula-2}.
15741 For a list of the supported languages, type @samp{set language}.
15743 Setting the language manually prevents @value{GDBN} from updating the working
15744 language automatically. This can lead to confusion if you try
15745 to debug a program when the working language is not the same as the
15746 source language, when an expression is acceptable to both
15747 languages---but means different things. For instance, if the current
15748 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15756 might not have the effect you intended. In C, this means to add
15757 @code{b} and @code{c} and place the result in @code{a}. The result
15758 printed would be the value of @code{a}. In Modula-2, this means to compare
15759 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15761 @node Automatically
15762 @subsection Having @value{GDBN} Infer the Source Language
15764 To have @value{GDBN} set the working language automatically, use
15765 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15766 then infers the working language. That is, when your program stops in a
15767 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15768 working language to the language recorded for the function in that
15769 frame. If the language for a frame is unknown (that is, if the function
15770 or block corresponding to the frame was defined in a source file that
15771 does not have a recognized extension), the current working language is
15772 not changed, and @value{GDBN} issues a warning.
15774 This may not seem necessary for most programs, which are written
15775 entirely in one source language. However, program modules and libraries
15776 written in one source language can be used by a main program written in
15777 a different source language. Using @samp{set language auto} in this
15778 case frees you from having to set the working language manually.
15781 @section Displaying the Language
15783 The following commands help you find out which language is the
15784 working language, and also what language source files were written in.
15787 @item show language
15788 @anchor{show language}
15789 @kindex show language
15790 Display the current working language. This is the
15791 language you can use with commands such as @code{print} to
15792 build and compute expressions that may involve variables in your program.
15795 @kindex info frame@r{, show the source language}
15796 Display the source language for this frame. This language becomes the
15797 working language if you use an identifier from this frame.
15798 @xref{Frame Info, ,Information about a Frame}, to identify the other
15799 information listed here.
15802 @kindex info source@r{, show the source language}
15803 Display the source language of this source file.
15804 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15805 information listed here.
15808 In unusual circumstances, you may have source files with extensions
15809 not in the standard list. You can then set the extension associated
15810 with a language explicitly:
15813 @item set extension-language @var{ext} @var{language}
15814 @kindex set extension-language
15815 Tell @value{GDBN} that source files with extension @var{ext} are to be
15816 assumed as written in the source language @var{language}.
15818 @item info extensions
15819 @kindex info extensions
15820 List all the filename extensions and the associated languages.
15824 @section Type and Range Checking
15826 Some languages are designed to guard you against making seemingly common
15827 errors through a series of compile- and run-time checks. These include
15828 checking the type of arguments to functions and operators and making
15829 sure mathematical overflows are caught at run time. Checks such as
15830 these help to ensure a program's correctness once it has been compiled
15831 by eliminating type mismatches and providing active checks for range
15832 errors when your program is running.
15834 By default @value{GDBN} checks for these errors according to the
15835 rules of the current source language. Although @value{GDBN} does not check
15836 the statements in your program, it can check expressions entered directly
15837 into @value{GDBN} for evaluation via the @code{print} command, for example.
15840 * Type Checking:: An overview of type checking
15841 * Range Checking:: An overview of range checking
15844 @cindex type checking
15845 @cindex checks, type
15846 @node Type Checking
15847 @subsection An Overview of Type Checking
15849 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15850 arguments to operators and functions have to be of the correct type,
15851 otherwise an error occurs. These checks prevent type mismatch
15852 errors from ever causing any run-time problems. For example,
15855 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15857 (@value{GDBP}) print obj.my_method (0)
15860 (@value{GDBP}) print obj.my_method (0x1234)
15861 Cannot resolve method klass::my_method to any overloaded instance
15864 The second example fails because in C@t{++} the integer constant
15865 @samp{0x1234} is not type-compatible with the pointer parameter type.
15867 For the expressions you use in @value{GDBN} commands, you can tell
15868 @value{GDBN} to not enforce strict type checking or
15869 to treat any mismatches as errors and abandon the expression;
15870 When type checking is disabled, @value{GDBN} successfully evaluates
15871 expressions like the second example above.
15873 Even if type checking is off, there may be other reasons
15874 related to type that prevent @value{GDBN} from evaluating an expression.
15875 For instance, @value{GDBN} does not know how to add an @code{int} and
15876 a @code{struct foo}. These particular type errors have nothing to do
15877 with the language in use and usually arise from expressions which make
15878 little sense to evaluate anyway.
15880 @value{GDBN} provides some additional commands for controlling type checking:
15882 @kindex set check type
15883 @kindex show check type
15885 @item set check type on
15886 @itemx set check type off
15887 Set strict type checking on or off. If any type mismatches occur in
15888 evaluating an expression while type checking is on, @value{GDBN} prints a
15889 message and aborts evaluation of the expression.
15891 @item show check type
15892 Show the current setting of type checking and whether @value{GDBN}
15893 is enforcing strict type checking rules.
15896 @cindex range checking
15897 @cindex checks, range
15898 @node Range Checking
15899 @subsection An Overview of Range Checking
15901 In some languages (such as Modula-2), it is an error to exceed the
15902 bounds of a type; this is enforced with run-time checks. Such range
15903 checking is meant to ensure program correctness by making sure
15904 computations do not overflow, or indices on an array element access do
15905 not exceed the bounds of the array.
15907 For expressions you use in @value{GDBN} commands, you can tell
15908 @value{GDBN} to treat range errors in one of three ways: ignore them,
15909 always treat them as errors and abandon the expression, or issue
15910 warnings but evaluate the expression anyway.
15912 A range error can result from numerical overflow, from exceeding an
15913 array index bound, or when you type a constant that is not a member
15914 of any type. Some languages, however, do not treat overflows as an
15915 error. In many implementations of C, mathematical overflow causes the
15916 result to ``wrap around'' to lower values---for example, if @var{m} is
15917 the largest integer value, and @var{s} is the smallest, then
15920 @var{m} + 1 @result{} @var{s}
15923 This, too, is specific to individual languages, and in some cases
15924 specific to individual compilers or machines. @xref{Supported Languages, ,
15925 Supported Languages}, for further details on specific languages.
15927 @value{GDBN} provides some additional commands for controlling the range checker:
15929 @kindex set check range
15930 @kindex show check range
15932 @item set check range auto
15933 Set range checking on or off based on the current working language.
15934 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15937 @item set check range on
15938 @itemx set check range off
15939 Set range checking on or off, overriding the default setting for the
15940 current working language. A warning is issued if the setting does not
15941 match the language default. If a range error occurs and range checking is on,
15942 then a message is printed and evaluation of the expression is aborted.
15944 @item set check range warn
15945 Output messages when the @value{GDBN} range checker detects a range error,
15946 but attempt to evaluate the expression anyway. Evaluating the
15947 expression may still be impossible for other reasons, such as accessing
15948 memory that the process does not own (a typical example from many Unix
15952 Show the current setting of the range checker, and whether or not it is
15953 being set automatically by @value{GDBN}.
15956 @node Supported Languages
15957 @section Supported Languages
15959 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15960 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15961 @c This is false ...
15962 Some @value{GDBN} features may be used in expressions regardless of the
15963 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15964 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15965 ,Expressions}) can be used with the constructs of any supported
15968 The following sections detail to what degree each source language is
15969 supported by @value{GDBN}. These sections are not meant to be language
15970 tutorials or references, but serve only as a reference guide to what the
15971 @value{GDBN} expression parser accepts, and what input and output
15972 formats should look like for different languages. There are many good
15973 books written on each of these languages; please look to these for a
15974 language reference or tutorial.
15977 * C:: C and C@t{++}
15980 * Objective-C:: Objective-C
15981 * OpenCL C:: OpenCL C
15982 * Fortran:: Fortran
15985 * Modula-2:: Modula-2
15990 @subsection C and C@t{++}
15992 @cindex C and C@t{++}
15993 @cindex expressions in C or C@t{++}
15995 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15996 to both languages. Whenever this is the case, we discuss those languages
16000 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16001 @cindex @sc{gnu} C@t{++}
16002 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16003 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16004 effectively, you must compile your C@t{++} programs with a supported
16005 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16006 compiler (@code{aCC}).
16009 * C Operators:: C and C@t{++} operators
16010 * C Constants:: C and C@t{++} constants
16011 * C Plus Plus Expressions:: C@t{++} expressions
16012 * C Defaults:: Default settings for C and C@t{++}
16013 * C Checks:: C and C@t{++} type and range checks
16014 * Debugging C:: @value{GDBN} and C
16015 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16016 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16020 @subsubsection C and C@t{++} Operators
16022 @cindex C and C@t{++} operators
16024 Operators must be defined on values of specific types. For instance,
16025 @code{+} is defined on numbers, but not on structures. Operators are
16026 often defined on groups of types.
16028 For the purposes of C and C@t{++}, the following definitions hold:
16033 @emph{Integral types} include @code{int} with any of its storage-class
16034 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16037 @emph{Floating-point types} include @code{float}, @code{double}, and
16038 @code{long double} (if supported by the target platform).
16041 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16044 @emph{Scalar types} include all of the above.
16049 The following operators are supported. They are listed here
16050 in order of increasing precedence:
16054 The comma or sequencing operator. Expressions in a comma-separated list
16055 are evaluated from left to right, with the result of the entire
16056 expression being the last expression evaluated.
16059 Assignment. The value of an assignment expression is the value
16060 assigned. Defined on scalar types.
16063 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16064 and translated to @w{@code{@var{a} = @var{a op b}}}.
16065 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16066 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16067 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16070 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16071 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16072 should be of an integral type.
16075 Logical @sc{or}. Defined on integral types.
16078 Logical @sc{and}. Defined on integral types.
16081 Bitwise @sc{or}. Defined on integral types.
16084 Bitwise exclusive-@sc{or}. Defined on integral types.
16087 Bitwise @sc{and}. Defined on integral types.
16090 Equality and inequality. Defined on scalar types. The value of these
16091 expressions is 0 for false and non-zero for true.
16093 @item <@r{, }>@r{, }<=@r{, }>=
16094 Less than, greater than, less than or equal, greater than or equal.
16095 Defined on scalar types. The value of these expressions is 0 for false
16096 and non-zero for true.
16099 left shift, and right shift. Defined on integral types.
16102 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16105 Addition and subtraction. Defined on integral types, floating-point types and
16108 @item *@r{, }/@r{, }%
16109 Multiplication, division, and modulus. Multiplication and division are
16110 defined on integral and floating-point types. Modulus is defined on
16114 Increment and decrement. When appearing before a variable, the
16115 operation is performed before the variable is used in an expression;
16116 when appearing after it, the variable's value is used before the
16117 operation takes place.
16120 Pointer dereferencing. Defined on pointer types. Same precedence as
16124 Address operator. Defined on variables. Same precedence as @code{++}.
16126 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16127 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16128 to examine the address
16129 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16133 Negative. Defined on integral and floating-point types. Same
16134 precedence as @code{++}.
16137 Logical negation. Defined on integral types. Same precedence as
16141 Bitwise complement operator. Defined on integral types. Same precedence as
16146 Structure member, and pointer-to-structure member. For convenience,
16147 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16148 pointer based on the stored type information.
16149 Defined on @code{struct} and @code{union} data.
16152 Dereferences of pointers to members.
16155 Array indexing. @code{@var{a}[@var{i}]} is defined as
16156 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16159 Function parameter list. Same precedence as @code{->}.
16162 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16163 and @code{class} types.
16166 Doubled colons also represent the @value{GDBN} scope operator
16167 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16171 If an operator is redefined in the user code, @value{GDBN} usually
16172 attempts to invoke the redefined version instead of using the operator's
16173 predefined meaning.
16176 @subsubsection C and C@t{++} Constants
16178 @cindex C and C@t{++} constants
16180 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16185 Integer constants are a sequence of digits. Octal constants are
16186 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16187 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16188 @samp{l}, specifying that the constant should be treated as a
16192 Floating point constants are a sequence of digits, followed by a decimal
16193 point, followed by a sequence of digits, and optionally followed by an
16194 exponent. An exponent is of the form:
16195 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16196 sequence of digits. The @samp{+} is optional for positive exponents.
16197 A floating-point constant may also end with a letter @samp{f} or
16198 @samp{F}, specifying that the constant should be treated as being of
16199 the @code{float} (as opposed to the default @code{double}) type; or with
16200 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16204 Enumerated constants consist of enumerated identifiers, or their
16205 integral equivalents.
16208 Character constants are a single character surrounded by single quotes
16209 (@code{'}), or a number---the ordinal value of the corresponding character
16210 (usually its @sc{ascii} value). Within quotes, the single character may
16211 be represented by a letter or by @dfn{escape sequences}, which are of
16212 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16213 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16214 @samp{@var{x}} is a predefined special character---for example,
16215 @samp{\n} for newline.
16217 Wide character constants can be written by prefixing a character
16218 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16219 form of @samp{x}. The target wide character set is used when
16220 computing the value of this constant (@pxref{Character Sets}).
16223 String constants are a sequence of character constants surrounded by
16224 double quotes (@code{"}). Any valid character constant (as described
16225 above) may appear. Double quotes within the string must be preceded by
16226 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16229 Wide string constants can be written by prefixing a string constant
16230 with @samp{L}, as in C. The target wide character set is used when
16231 computing the value of this constant (@pxref{Character Sets}).
16234 Pointer constants are an integral value. You can also write pointers
16235 to constants using the C operator @samp{&}.
16238 Array constants are comma-separated lists surrounded by braces @samp{@{}
16239 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16240 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16241 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16244 @node C Plus Plus Expressions
16245 @subsubsection C@t{++} Expressions
16247 @cindex expressions in C@t{++}
16248 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16250 @cindex debugging C@t{++} programs
16251 @cindex C@t{++} compilers
16252 @cindex debug formats and C@t{++}
16253 @cindex @value{NGCC} and C@t{++}
16255 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16256 the proper compiler and the proper debug format. Currently,
16257 @value{GDBN} works best when debugging C@t{++} code that is compiled
16258 with the most recent version of @value{NGCC} possible. The DWARF
16259 debugging format is preferred; @value{NGCC} defaults to this on most
16260 popular platforms. Other compilers and/or debug formats are likely to
16261 work badly or not at all when using @value{GDBN} to debug C@t{++}
16262 code. @xref{Compilation}.
16267 @cindex member functions
16269 Member function calls are allowed; you can use expressions like
16272 count = aml->GetOriginal(x, y)
16275 @vindex this@r{, inside C@t{++} member functions}
16276 @cindex namespace in C@t{++}
16278 While a member function is active (in the selected stack frame), your
16279 expressions have the same namespace available as the member function;
16280 that is, @value{GDBN} allows implicit references to the class instance
16281 pointer @code{this} following the same rules as C@t{++}. @code{using}
16282 declarations in the current scope are also respected by @value{GDBN}.
16284 @cindex call overloaded functions
16285 @cindex overloaded functions, calling
16286 @cindex type conversions in C@t{++}
16288 You can call overloaded functions; @value{GDBN} resolves the function
16289 call to the right definition, with some restrictions. @value{GDBN} does not
16290 perform overload resolution involving user-defined type conversions,
16291 calls to constructors, or instantiations of templates that do not exist
16292 in the program. It also cannot handle ellipsis argument lists or
16295 It does perform integral conversions and promotions, floating-point
16296 promotions, arithmetic conversions, pointer conversions, conversions of
16297 class objects to base classes, and standard conversions such as those of
16298 functions or arrays to pointers; it requires an exact match on the
16299 number of function arguments.
16301 Overload resolution is always performed, unless you have specified
16302 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16303 ,@value{GDBN} Features for C@t{++}}.
16305 You must specify @code{set overload-resolution off} in order to use an
16306 explicit function signature to call an overloaded function, as in
16308 p 'foo(char,int)'('x', 13)
16311 The @value{GDBN} command-completion facility can simplify this;
16312 see @ref{Completion, ,Command Completion}.
16314 @cindex reference declarations
16316 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16317 references; you can use them in expressions just as you do in C@t{++}
16318 source---they are automatically dereferenced.
16320 In the parameter list shown when @value{GDBN} displays a frame, the values of
16321 reference variables are not displayed (unlike other variables); this
16322 avoids clutter, since references are often used for large structures.
16323 The @emph{address} of a reference variable is always shown, unless
16324 you have specified @samp{set print address off}.
16327 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16328 expressions can use it just as expressions in your program do. Since
16329 one scope may be defined in another, you can use @code{::} repeatedly if
16330 necessary, for example in an expression like
16331 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16332 resolving name scope by reference to source files, in both C and C@t{++}
16333 debugging (@pxref{Variables, ,Program Variables}).
16336 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16341 @subsubsection C and C@t{++} Defaults
16343 @cindex C and C@t{++} defaults
16345 If you allow @value{GDBN} to set range checking automatically, it
16346 defaults to @code{off} whenever the working language changes to
16347 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16348 selects the working language.
16350 If you allow @value{GDBN} to set the language automatically, it
16351 recognizes source files whose names end with @file{.c}, @file{.C}, or
16352 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16353 these files, it sets the working language to C or C@t{++}.
16354 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16355 for further details.
16358 @subsubsection C and C@t{++} Type and Range Checks
16360 @cindex C and C@t{++} checks
16362 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16363 checking is used. However, if you turn type checking off, @value{GDBN}
16364 will allow certain non-standard conversions, such as promoting integer
16365 constants to pointers.
16367 Range checking, if turned on, is done on mathematical operations. Array
16368 indices are not checked, since they are often used to index a pointer
16369 that is not itself an array.
16372 @subsubsection @value{GDBN} and C
16374 The @code{set print union} and @code{show print union} commands apply to
16375 the @code{union} type. When set to @samp{on}, any @code{union} that is
16376 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16377 appears as @samp{@{...@}}.
16379 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16380 with pointers and a memory allocation function. @xref{Expressions,
16383 @node Debugging C Plus Plus
16384 @subsubsection @value{GDBN} Features for C@t{++}
16386 @cindex commands for C@t{++}
16388 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16389 designed specifically for use with C@t{++}. Here is a summary:
16392 @cindex break in overloaded functions
16393 @item @r{breakpoint menus}
16394 When you want a breakpoint in a function whose name is overloaded,
16395 @value{GDBN} has the capability to display a menu of possible breakpoint
16396 locations to help you specify which function definition you want.
16397 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16399 @cindex overloading in C@t{++}
16400 @item rbreak @var{regex}
16401 Setting breakpoints using regular expressions is helpful for setting
16402 breakpoints on overloaded functions that are not members of any special
16404 @xref{Set Breaks, ,Setting Breakpoints}.
16406 @cindex C@t{++} exception handling
16408 @itemx catch rethrow
16410 Debug C@t{++} exception handling using these commands. @xref{Set
16411 Catchpoints, , Setting Catchpoints}.
16413 @cindex inheritance
16414 @item ptype @var{typename}
16415 Print inheritance relationships as well as other information for type
16417 @xref{Symbols, ,Examining the Symbol Table}.
16419 @item info vtbl @var{expression}.
16420 The @code{info vtbl} command can be used to display the virtual
16421 method tables of the object computed by @var{expression}. This shows
16422 one entry per virtual table; there may be multiple virtual tables when
16423 multiple inheritance is in use.
16425 @cindex C@t{++} demangling
16426 @item demangle @var{name}
16427 Demangle @var{name}.
16428 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16430 @cindex C@t{++} symbol display
16431 @item set print demangle
16432 @itemx show print demangle
16433 @itemx set print asm-demangle
16434 @itemx show print asm-demangle
16435 Control whether C@t{++} symbols display in their source form, both when
16436 displaying code as C@t{++} source and when displaying disassemblies.
16437 @xref{Print Settings, ,Print Settings}.
16439 @item set print object
16440 @itemx show print object
16441 Choose whether to print derived (actual) or declared types of objects.
16442 @xref{Print Settings, ,Print Settings}.
16444 @item set print vtbl
16445 @itemx show print vtbl
16446 Control the format for printing virtual function tables.
16447 @xref{Print Settings, ,Print Settings}.
16448 (The @code{vtbl} commands do not work on programs compiled with the HP
16449 ANSI C@t{++} compiler (@code{aCC}).)
16451 @kindex set overload-resolution
16452 @cindex overloaded functions, overload resolution
16453 @item set overload-resolution on
16454 Enable overload resolution for C@t{++} expression evaluation. The default
16455 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16456 and searches for a function whose signature matches the argument types,
16457 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16458 Expressions, ,C@t{++} Expressions}, for details).
16459 If it cannot find a match, it emits a message.
16461 @item set overload-resolution off
16462 Disable overload resolution for C@t{++} expression evaluation. For
16463 overloaded functions that are not class member functions, @value{GDBN}
16464 chooses the first function of the specified name that it finds in the
16465 symbol table, whether or not its arguments are of the correct type. For
16466 overloaded functions that are class member functions, @value{GDBN}
16467 searches for a function whose signature @emph{exactly} matches the
16470 @kindex show overload-resolution
16471 @item show overload-resolution
16472 Show the current setting of overload resolution.
16474 @item @r{Overloaded symbol names}
16475 You can specify a particular definition of an overloaded symbol, using
16476 the same notation that is used to declare such symbols in C@t{++}: type
16477 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16478 also use the @value{GDBN} command-line word completion facilities to list the
16479 available choices, or to finish the type list for you.
16480 @xref{Completion,, Command Completion}, for details on how to do this.
16482 @item @r{Breakpoints in functions with ABI tags}
16484 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16485 correspond to changes in the ABI of a type, function, or variable that
16486 would not otherwise be reflected in a mangled name. See
16487 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16490 The ABI tags are visible in C@t{++} demangled names. For example, a
16491 function that returns a std::string:
16494 std::string function(int);
16498 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16499 tag, and @value{GDBN} displays the symbol like this:
16502 function[abi:cxx11](int)
16505 You can set a breakpoint on such functions simply as if they had no
16509 (gdb) b function(int)
16510 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16511 (gdb) info breakpoints
16512 Num Type Disp Enb Address What
16513 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16517 On the rare occasion you need to disambiguate between different ABI
16518 tags, you can do so by simply including the ABI tag in the function
16522 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16526 @node Decimal Floating Point
16527 @subsubsection Decimal Floating Point format
16528 @cindex decimal floating point format
16530 @value{GDBN} can examine, set and perform computations with numbers in
16531 decimal floating point format, which in the C language correspond to the
16532 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16533 specified by the extension to support decimal floating-point arithmetic.
16535 There are two encodings in use, depending on the architecture: BID (Binary
16536 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16537 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16540 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16541 to manipulate decimal floating point numbers, it is not possible to convert
16542 (using a cast, for example) integers wider than 32-bit to decimal float.
16544 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16545 point computations, error checking in decimal float operations ignores
16546 underflow, overflow and divide by zero exceptions.
16548 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16549 to inspect @code{_Decimal128} values stored in floating point registers.
16550 See @ref{PowerPC,,PowerPC} for more details.
16556 @value{GDBN} can be used to debug programs written in D and compiled with
16557 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16558 specific feature --- dynamic arrays.
16563 @cindex Go (programming language)
16564 @value{GDBN} can be used to debug programs written in Go and compiled with
16565 @file{gccgo} or @file{6g} compilers.
16567 Here is a summary of the Go-specific features and restrictions:
16570 @cindex current Go package
16571 @item The current Go package
16572 The name of the current package does not need to be specified when
16573 specifying global variables and functions.
16575 For example, given the program:
16579 var myglob = "Shall we?"
16585 When stopped inside @code{main} either of these work:
16589 (gdb) p main.myglob
16592 @cindex builtin Go types
16593 @item Builtin Go types
16594 The @code{string} type is recognized by @value{GDBN} and is printed
16597 @cindex builtin Go functions
16598 @item Builtin Go functions
16599 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16600 function and handles it internally.
16602 @cindex restrictions on Go expressions
16603 @item Restrictions on Go expressions
16604 All Go operators are supported except @code{&^}.
16605 The Go @code{_} ``blank identifier'' is not supported.
16606 Automatic dereferencing of pointers is not supported.
16610 @subsection Objective-C
16612 @cindex Objective-C
16613 This section provides information about some commands and command
16614 options that are useful for debugging Objective-C code. See also
16615 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16616 few more commands specific to Objective-C support.
16619 * Method Names in Commands::
16620 * The Print Command with Objective-C::
16623 @node Method Names in Commands
16624 @subsubsection Method Names in Commands
16626 The following commands have been extended to accept Objective-C method
16627 names as line specifications:
16629 @kindex clear@r{, and Objective-C}
16630 @kindex break@r{, and Objective-C}
16631 @kindex info line@r{, and Objective-C}
16632 @kindex jump@r{, and Objective-C}
16633 @kindex list@r{, and Objective-C}
16637 @item @code{info line}
16642 A fully qualified Objective-C method name is specified as
16645 -[@var{Class} @var{methodName}]
16648 where the minus sign is used to indicate an instance method and a
16649 plus sign (not shown) is used to indicate a class method. The class
16650 name @var{Class} and method name @var{methodName} are enclosed in
16651 brackets, similar to the way messages are specified in Objective-C
16652 source code. For example, to set a breakpoint at the @code{create}
16653 instance method of class @code{Fruit} in the program currently being
16657 break -[Fruit create]
16660 To list ten program lines around the @code{initialize} class method,
16664 list +[NSText initialize]
16667 In the current version of @value{GDBN}, the plus or minus sign is
16668 required. In future versions of @value{GDBN}, the plus or minus
16669 sign will be optional, but you can use it to narrow the search. It
16670 is also possible to specify just a method name:
16676 You must specify the complete method name, including any colons. If
16677 your program's source files contain more than one @code{create} method,
16678 you'll be presented with a numbered list of classes that implement that
16679 method. Indicate your choice by number, or type @samp{0} to exit if
16682 As another example, to clear a breakpoint established at the
16683 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16686 clear -[NSWindow makeKeyAndOrderFront:]
16689 @node The Print Command with Objective-C
16690 @subsubsection The Print Command With Objective-C
16691 @cindex Objective-C, print objects
16692 @kindex print-object
16693 @kindex po @r{(@code{print-object})}
16695 The print command has also been extended to accept methods. For example:
16698 print -[@var{object} hash]
16701 @cindex print an Objective-C object description
16702 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16704 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16705 and print the result. Also, an additional command has been added,
16706 @code{print-object} or @code{po} for short, which is meant to print
16707 the description of an object. However, this command may only work
16708 with certain Objective-C libraries that have a particular hook
16709 function, @code{_NSPrintForDebugger}, defined.
16712 @subsection OpenCL C
16715 This section provides information about @value{GDBN}s OpenCL C support.
16718 * OpenCL C Datatypes::
16719 * OpenCL C Expressions::
16720 * OpenCL C Operators::
16723 @node OpenCL C Datatypes
16724 @subsubsection OpenCL C Datatypes
16726 @cindex OpenCL C Datatypes
16727 @value{GDBN} supports the builtin scalar and vector datatypes specified
16728 by OpenCL 1.1. In addition the half- and double-precision floating point
16729 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16730 extensions are also known to @value{GDBN}.
16732 @node OpenCL C Expressions
16733 @subsubsection OpenCL C Expressions
16735 @cindex OpenCL C Expressions
16736 @value{GDBN} supports accesses to vector components including the access as
16737 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16738 supported by @value{GDBN} can be used as well.
16740 @node OpenCL C Operators
16741 @subsubsection OpenCL C Operators
16743 @cindex OpenCL C Operators
16744 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16748 @subsection Fortran
16749 @cindex Fortran-specific support in @value{GDBN}
16751 @value{GDBN} can be used to debug programs written in Fortran, but it
16752 currently supports only the features of Fortran 77 language.
16754 @cindex trailing underscore, in Fortran symbols
16755 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16756 among them) append an underscore to the names of variables and
16757 functions. When you debug programs compiled by those compilers, you
16758 will need to refer to variables and functions with a trailing
16762 * Fortran Operators:: Fortran operators and expressions
16763 * Fortran Defaults:: Default settings for Fortran
16764 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16767 @node Fortran Operators
16768 @subsubsection Fortran Operators and Expressions
16770 @cindex Fortran operators and expressions
16772 Operators must be defined on values of specific types. For instance,
16773 @code{+} is defined on numbers, but not on characters or other non-
16774 arithmetic types. Operators are often defined on groups of types.
16778 The exponentiation operator. It raises the first operand to the power
16782 The range operator. Normally used in the form of array(low:high) to
16783 represent a section of array.
16786 The access component operator. Normally used to access elements in derived
16787 types. Also suitable for unions. As unions aren't part of regular Fortran,
16788 this can only happen when accessing a register that uses a gdbarch-defined
16791 The scope operator. Normally used to access variables in modules or
16792 to set breakpoints on subroutines nested in modules or in other
16793 subroutines (internal subroutines).
16796 @node Fortran Defaults
16797 @subsubsection Fortran Defaults
16799 @cindex Fortran Defaults
16801 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16802 default uses case-insensitive matches for Fortran symbols. You can
16803 change that with the @samp{set case-insensitive} command, see
16804 @ref{Symbols}, for the details.
16806 @node Special Fortran Commands
16807 @subsubsection Special Fortran Commands
16809 @cindex Special Fortran commands
16811 @value{GDBN} has some commands to support Fortran-specific features,
16812 such as displaying common blocks.
16815 @cindex @code{COMMON} blocks, Fortran
16816 @kindex info common
16817 @item info common @r{[}@var{common-name}@r{]}
16818 This command prints the values contained in the Fortran @code{COMMON}
16819 block whose name is @var{common-name}. With no argument, the names of
16820 all @code{COMMON} blocks visible at the current program location are
16827 @cindex Pascal support in @value{GDBN}, limitations
16828 Debugging Pascal programs which use sets, subranges, file variables, or
16829 nested functions does not currently work. @value{GDBN} does not support
16830 entering expressions, printing values, or similar features using Pascal
16833 The Pascal-specific command @code{set print pascal_static-members}
16834 controls whether static members of Pascal objects are displayed.
16835 @xref{Print Settings, pascal_static-members}.
16840 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16841 Programming Language}. Type- and value-printing, and expression
16842 parsing, are reasonably complete. However, there are a few
16843 peculiarities and holes to be aware of.
16847 Linespecs (@pxref{Specify Location}) are never relative to the current
16848 crate. Instead, they act as if there were a global namespace of
16849 crates, somewhat similar to the way @code{extern crate} behaves.
16851 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16852 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16853 to set a breakpoint in a function named @samp{f} in a crate named
16856 As a consequence of this approach, linespecs also cannot refer to
16857 items using @samp{self::} or @samp{super::}.
16860 Because @value{GDBN} implements Rust name-lookup semantics in
16861 expressions, it will sometimes prepend the current crate to a name.
16862 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16863 @samp{K}, then @code{print ::x::y} will try to find the symbol
16866 However, since it is useful to be able to refer to other crates when
16867 debugging, @value{GDBN} provides the @code{extern} extension to
16868 circumvent this. To use the extension, just put @code{extern} before
16869 a path expression to refer to the otherwise unavailable ``global''
16872 In the above example, if you wanted to refer to the symbol @samp{y} in
16873 the crate @samp{x}, you would use @code{print extern x::y}.
16876 The Rust expression evaluator does not support ``statement-like''
16877 expressions such as @code{if} or @code{match}, or lambda expressions.
16880 Tuple expressions are not implemented.
16883 The Rust expression evaluator does not currently implement the
16884 @code{Drop} trait. Objects that may be created by the evaluator will
16885 never be destroyed.
16888 @value{GDBN} does not implement type inference for generics. In order
16889 to call generic functions or otherwise refer to generic items, you
16890 will have to specify the type parameters manually.
16893 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16894 cases this does not cause any problems. However, in an expression
16895 context, completing a generic function name will give syntactically
16896 invalid results. This happens because Rust requires the @samp{::}
16897 operator between the function name and its generic arguments. For
16898 example, @value{GDBN} might provide a completion like
16899 @code{crate::f<u32>}, where the parser would require
16900 @code{crate::f::<u32>}.
16903 As of this writing, the Rust compiler (version 1.8) has a few holes in
16904 the debugging information it generates. These holes prevent certain
16905 features from being implemented by @value{GDBN}:
16909 Method calls cannot be made via traits.
16912 Operator overloading is not implemented.
16915 When debugging in a monomorphized function, you cannot use the generic
16919 The type @code{Self} is not available.
16922 @code{use} statements are not available, so some names may not be
16923 available in the crate.
16928 @subsection Modula-2
16930 @cindex Modula-2, @value{GDBN} support
16932 The extensions made to @value{GDBN} to support Modula-2 only support
16933 output from the @sc{gnu} Modula-2 compiler (which is currently being
16934 developed). Other Modula-2 compilers are not currently supported, and
16935 attempting to debug executables produced by them is most likely
16936 to give an error as @value{GDBN} reads in the executable's symbol
16939 @cindex expressions in Modula-2
16941 * M2 Operators:: Built-in operators
16942 * Built-In Func/Proc:: Built-in functions and procedures
16943 * M2 Constants:: Modula-2 constants
16944 * M2 Types:: Modula-2 types
16945 * M2 Defaults:: Default settings for Modula-2
16946 * Deviations:: Deviations from standard Modula-2
16947 * M2 Checks:: Modula-2 type and range checks
16948 * M2 Scope:: The scope operators @code{::} and @code{.}
16949 * GDB/M2:: @value{GDBN} and Modula-2
16953 @subsubsection Operators
16954 @cindex Modula-2 operators
16956 Operators must be defined on values of specific types. For instance,
16957 @code{+} is defined on numbers, but not on structures. Operators are
16958 often defined on groups of types. For the purposes of Modula-2, the
16959 following definitions hold:
16964 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16968 @emph{Character types} consist of @code{CHAR} and its subranges.
16971 @emph{Floating-point types} consist of @code{REAL}.
16974 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16978 @emph{Scalar types} consist of all of the above.
16981 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16984 @emph{Boolean types} consist of @code{BOOLEAN}.
16988 The following operators are supported, and appear in order of
16989 increasing precedence:
16993 Function argument or array index separator.
16996 Assignment. The value of @var{var} @code{:=} @var{value} is
17000 Less than, greater than on integral, floating-point, or enumerated
17004 Less than or equal to, greater than or equal to
17005 on integral, floating-point and enumerated types, or set inclusion on
17006 set types. Same precedence as @code{<}.
17008 @item =@r{, }<>@r{, }#
17009 Equality and two ways of expressing inequality, valid on scalar types.
17010 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17011 available for inequality, since @code{#} conflicts with the script
17015 Set membership. Defined on set types and the types of their members.
17016 Same precedence as @code{<}.
17019 Boolean disjunction. Defined on boolean types.
17022 Boolean conjunction. Defined on boolean types.
17025 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17028 Addition and subtraction on integral and floating-point types, or union
17029 and difference on set types.
17032 Multiplication on integral and floating-point types, or set intersection
17036 Division on floating-point types, or symmetric set difference on set
17037 types. Same precedence as @code{*}.
17040 Integer division and remainder. Defined on integral types. Same
17041 precedence as @code{*}.
17044 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17047 Pointer dereferencing. Defined on pointer types.
17050 Boolean negation. Defined on boolean types. Same precedence as
17054 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17055 precedence as @code{^}.
17058 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17061 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17065 @value{GDBN} and Modula-2 scope operators.
17069 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17070 treats the use of the operator @code{IN}, or the use of operators
17071 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17072 @code{<=}, and @code{>=} on sets as an error.
17076 @node Built-In Func/Proc
17077 @subsubsection Built-in Functions and Procedures
17078 @cindex Modula-2 built-ins
17080 Modula-2 also makes available several built-in procedures and functions.
17081 In describing these, the following metavariables are used:
17086 represents an @code{ARRAY} variable.
17089 represents a @code{CHAR} constant or variable.
17092 represents a variable or constant of integral type.
17095 represents an identifier that belongs to a set. Generally used in the
17096 same function with the metavariable @var{s}. The type of @var{s} should
17097 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17100 represents a variable or constant of integral or floating-point type.
17103 represents a variable or constant of floating-point type.
17109 represents a variable.
17112 represents a variable or constant of one of many types. See the
17113 explanation of the function for details.
17116 All Modula-2 built-in procedures also return a result, described below.
17120 Returns the absolute value of @var{n}.
17123 If @var{c} is a lower case letter, it returns its upper case
17124 equivalent, otherwise it returns its argument.
17127 Returns the character whose ordinal value is @var{i}.
17130 Decrements the value in the variable @var{v} by one. Returns the new value.
17132 @item DEC(@var{v},@var{i})
17133 Decrements the value in the variable @var{v} by @var{i}. Returns the
17136 @item EXCL(@var{m},@var{s})
17137 Removes the element @var{m} from the set @var{s}. Returns the new
17140 @item FLOAT(@var{i})
17141 Returns the floating point equivalent of the integer @var{i}.
17143 @item HIGH(@var{a})
17144 Returns the index of the last member of @var{a}.
17147 Increments the value in the variable @var{v} by one. Returns the new value.
17149 @item INC(@var{v},@var{i})
17150 Increments the value in the variable @var{v} by @var{i}. Returns the
17153 @item INCL(@var{m},@var{s})
17154 Adds the element @var{m} to the set @var{s} if it is not already
17155 there. Returns the new set.
17158 Returns the maximum value of the type @var{t}.
17161 Returns the minimum value of the type @var{t}.
17164 Returns boolean TRUE if @var{i} is an odd number.
17167 Returns the ordinal value of its argument. For example, the ordinal
17168 value of a character is its @sc{ascii} value (on machines supporting
17169 the @sc{ascii} character set). The argument @var{x} must be of an
17170 ordered type, which include integral, character and enumerated types.
17172 @item SIZE(@var{x})
17173 Returns the size of its argument. The argument @var{x} can be a
17174 variable or a type.
17176 @item TRUNC(@var{r})
17177 Returns the integral part of @var{r}.
17179 @item TSIZE(@var{x})
17180 Returns the size of its argument. The argument @var{x} can be a
17181 variable or a type.
17183 @item VAL(@var{t},@var{i})
17184 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17188 @emph{Warning:} Sets and their operations are not yet supported, so
17189 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17193 @cindex Modula-2 constants
17195 @subsubsection Constants
17197 @value{GDBN} allows you to express the constants of Modula-2 in the following
17203 Integer constants are simply a sequence of digits. When used in an
17204 expression, a constant is interpreted to be type-compatible with the
17205 rest of the expression. Hexadecimal integers are specified by a
17206 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17209 Floating point constants appear as a sequence of digits, followed by a
17210 decimal point and another sequence of digits. An optional exponent can
17211 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17212 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17213 digits of the floating point constant must be valid decimal (base 10)
17217 Character constants consist of a single character enclosed by a pair of
17218 like quotes, either single (@code{'}) or double (@code{"}). They may
17219 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17220 followed by a @samp{C}.
17223 String constants consist of a sequence of characters enclosed by a
17224 pair of like quotes, either single (@code{'}) or double (@code{"}).
17225 Escape sequences in the style of C are also allowed. @xref{C
17226 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17230 Enumerated constants consist of an enumerated identifier.
17233 Boolean constants consist of the identifiers @code{TRUE} and
17237 Pointer constants consist of integral values only.
17240 Set constants are not yet supported.
17244 @subsubsection Modula-2 Types
17245 @cindex Modula-2 types
17247 Currently @value{GDBN} can print the following data types in Modula-2
17248 syntax: array types, record types, set types, pointer types, procedure
17249 types, enumerated types, subrange types and base types. You can also
17250 print the contents of variables declared using these type.
17251 This section gives a number of simple source code examples together with
17252 sample @value{GDBN} sessions.
17254 The first example contains the following section of code:
17263 and you can request @value{GDBN} to interrogate the type and value of
17264 @code{r} and @code{s}.
17267 (@value{GDBP}) print s
17269 (@value{GDBP}) ptype s
17271 (@value{GDBP}) print r
17273 (@value{GDBP}) ptype r
17278 Likewise if your source code declares @code{s} as:
17282 s: SET ['A'..'Z'] ;
17286 then you may query the type of @code{s} by:
17289 (@value{GDBP}) ptype s
17290 type = SET ['A'..'Z']
17294 Note that at present you cannot interactively manipulate set
17295 expressions using the debugger.
17297 The following example shows how you might declare an array in Modula-2
17298 and how you can interact with @value{GDBN} to print its type and contents:
17302 s: ARRAY [-10..10] OF CHAR ;
17306 (@value{GDBP}) ptype s
17307 ARRAY [-10..10] OF CHAR
17310 Note that the array handling is not yet complete and although the type
17311 is printed correctly, expression handling still assumes that all
17312 arrays have a lower bound of zero and not @code{-10} as in the example
17315 Here are some more type related Modula-2 examples:
17319 colour = (blue, red, yellow, green) ;
17320 t = [blue..yellow] ;
17328 The @value{GDBN} interaction shows how you can query the data type
17329 and value of a variable.
17332 (@value{GDBP}) print s
17334 (@value{GDBP}) ptype t
17335 type = [blue..yellow]
17339 In this example a Modula-2 array is declared and its contents
17340 displayed. Observe that the contents are written in the same way as
17341 their @code{C} counterparts.
17345 s: ARRAY [1..5] OF CARDINAL ;
17351 (@value{GDBP}) print s
17352 $1 = @{1, 0, 0, 0, 0@}
17353 (@value{GDBP}) ptype s
17354 type = ARRAY [1..5] OF CARDINAL
17357 The Modula-2 language interface to @value{GDBN} also understands
17358 pointer types as shown in this example:
17362 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17369 and you can request that @value{GDBN} describes the type of @code{s}.
17372 (@value{GDBP}) ptype s
17373 type = POINTER TO ARRAY [1..5] OF CARDINAL
17376 @value{GDBN} handles compound types as we can see in this example.
17377 Here we combine array types, record types, pointer types and subrange
17388 myarray = ARRAY myrange OF CARDINAL ;
17389 myrange = [-2..2] ;
17391 s: POINTER TO ARRAY myrange OF foo ;
17395 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17399 (@value{GDBP}) ptype s
17400 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17403 f3 : ARRAY [-2..2] OF CARDINAL;
17408 @subsubsection Modula-2 Defaults
17409 @cindex Modula-2 defaults
17411 If type and range checking are set automatically by @value{GDBN}, they
17412 both default to @code{on} whenever the working language changes to
17413 Modula-2. This happens regardless of whether you or @value{GDBN}
17414 selected the working language.
17416 If you allow @value{GDBN} to set the language automatically, then entering
17417 code compiled from a file whose name ends with @file{.mod} sets the
17418 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17419 Infer the Source Language}, for further details.
17422 @subsubsection Deviations from Standard Modula-2
17423 @cindex Modula-2, deviations from
17425 A few changes have been made to make Modula-2 programs easier to debug.
17426 This is done primarily via loosening its type strictness:
17430 Unlike in standard Modula-2, pointer constants can be formed by
17431 integers. This allows you to modify pointer variables during
17432 debugging. (In standard Modula-2, the actual address contained in a
17433 pointer variable is hidden from you; it can only be modified
17434 through direct assignment to another pointer variable or expression that
17435 returned a pointer.)
17438 C escape sequences can be used in strings and characters to represent
17439 non-printable characters. @value{GDBN} prints out strings with these
17440 escape sequences embedded. Single non-printable characters are
17441 printed using the @samp{CHR(@var{nnn})} format.
17444 The assignment operator (@code{:=}) returns the value of its right-hand
17448 All built-in procedures both modify @emph{and} return their argument.
17452 @subsubsection Modula-2 Type and Range Checks
17453 @cindex Modula-2 checks
17456 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17459 @c FIXME remove warning when type/range checks added
17461 @value{GDBN} considers two Modula-2 variables type equivalent if:
17465 They are of types that have been declared equivalent via a @code{TYPE
17466 @var{t1} = @var{t2}} statement
17469 They have been declared on the same line. (Note: This is true of the
17470 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17473 As long as type checking is enabled, any attempt to combine variables
17474 whose types are not equivalent is an error.
17476 Range checking is done on all mathematical operations, assignment, array
17477 index bounds, and all built-in functions and procedures.
17480 @subsubsection The Scope Operators @code{::} and @code{.}
17482 @cindex @code{.}, Modula-2 scope operator
17483 @cindex colon, doubled as scope operator
17485 @vindex colon-colon@r{, in Modula-2}
17486 @c Info cannot handle :: but TeX can.
17489 @vindex ::@r{, in Modula-2}
17492 There are a few subtle differences between the Modula-2 scope operator
17493 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17498 @var{module} . @var{id}
17499 @var{scope} :: @var{id}
17503 where @var{scope} is the name of a module or a procedure,
17504 @var{module} the name of a module, and @var{id} is any declared
17505 identifier within your program, except another module.
17507 Using the @code{::} operator makes @value{GDBN} search the scope
17508 specified by @var{scope} for the identifier @var{id}. If it is not
17509 found in the specified scope, then @value{GDBN} searches all scopes
17510 enclosing the one specified by @var{scope}.
17512 Using the @code{.} operator makes @value{GDBN} search the current scope for
17513 the identifier specified by @var{id} that was imported from the
17514 definition module specified by @var{module}. With this operator, it is
17515 an error if the identifier @var{id} was not imported from definition
17516 module @var{module}, or if @var{id} is not an identifier in
17520 @subsubsection @value{GDBN} and Modula-2
17522 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17523 Five subcommands of @code{set print} and @code{show print} apply
17524 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17525 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17526 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17527 analogue in Modula-2.
17529 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17530 with any language, is not useful with Modula-2. Its
17531 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17532 created in Modula-2 as they can in C or C@t{++}. However, because an
17533 address can be specified by an integral constant, the construct
17534 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17536 @cindex @code{#} in Modula-2
17537 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17538 interpreted as the beginning of a comment. Use @code{<>} instead.
17544 The extensions made to @value{GDBN} for Ada only support
17545 output from the @sc{gnu} Ada (GNAT) compiler.
17546 Other Ada compilers are not currently supported, and
17547 attempting to debug executables produced by them is most likely
17551 @cindex expressions in Ada
17553 * Ada Mode Intro:: General remarks on the Ada syntax
17554 and semantics supported by Ada mode
17556 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17557 * Additions to Ada:: Extensions of the Ada expression syntax.
17558 * Overloading support for Ada:: Support for expressions involving overloaded
17560 * Stopping Before Main Program:: Debugging the program during elaboration.
17561 * Ada Exceptions:: Ada Exceptions
17562 * Ada Tasks:: Listing and setting breakpoints in tasks.
17563 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17564 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17566 * Ada Settings:: New settable GDB parameters for Ada.
17567 * Ada Glitches:: Known peculiarities of Ada mode.
17570 @node Ada Mode Intro
17571 @subsubsection Introduction
17572 @cindex Ada mode, general
17574 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17575 syntax, with some extensions.
17576 The philosophy behind the design of this subset is
17580 That @value{GDBN} should provide basic literals and access to operations for
17581 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17582 leaving more sophisticated computations to subprograms written into the
17583 program (which therefore may be called from @value{GDBN}).
17586 That type safety and strict adherence to Ada language restrictions
17587 are not particularly important to the @value{GDBN} user.
17590 That brevity is important to the @value{GDBN} user.
17593 Thus, for brevity, the debugger acts as if all names declared in
17594 user-written packages are directly visible, even if they are not visible
17595 according to Ada rules, thus making it unnecessary to fully qualify most
17596 names with their packages, regardless of context. Where this causes
17597 ambiguity, @value{GDBN} asks the user's intent.
17599 The debugger will start in Ada mode if it detects an Ada main program.
17600 As for other languages, it will enter Ada mode when stopped in a program that
17601 was translated from an Ada source file.
17603 While in Ada mode, you may use `@t{--}' for comments. This is useful
17604 mostly for documenting command files. The standard @value{GDBN} comment
17605 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17606 middle (to allow based literals).
17608 @node Omissions from Ada
17609 @subsubsection Omissions from Ada
17610 @cindex Ada, omissions from
17612 Here are the notable omissions from the subset:
17616 Only a subset of the attributes are supported:
17620 @t{'First}, @t{'Last}, and @t{'Length}
17621 on array objects (not on types and subtypes).
17624 @t{'Min} and @t{'Max}.
17627 @t{'Pos} and @t{'Val}.
17633 @t{'Range} on array objects (not subtypes), but only as the right
17634 operand of the membership (@code{in}) operator.
17637 @t{'Access}, @t{'Unchecked_Access}, and
17638 @t{'Unrestricted_Access} (a GNAT extension).
17646 @code{Characters.Latin_1} are not available and
17647 concatenation is not implemented. Thus, escape characters in strings are
17648 not currently available.
17651 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17652 equality of representations. They will generally work correctly
17653 for strings and arrays whose elements have integer or enumeration types.
17654 They may not work correctly for arrays whose element
17655 types have user-defined equality, for arrays of real values
17656 (in particular, IEEE-conformant floating point, because of negative
17657 zeroes and NaNs), and for arrays whose elements contain unused bits with
17658 indeterminate values.
17661 The other component-by-component array operations (@code{and}, @code{or},
17662 @code{xor}, @code{not}, and relational tests other than equality)
17663 are not implemented.
17666 @cindex array aggregates (Ada)
17667 @cindex record aggregates (Ada)
17668 @cindex aggregates (Ada)
17669 There is limited support for array and record aggregates. They are
17670 permitted only on the right sides of assignments, as in these examples:
17673 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17674 (@value{GDBP}) set An_Array := (1, others => 0)
17675 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17676 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17677 (@value{GDBP}) set A_Record := (1, "Peter", True);
17678 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17682 discriminant's value by assigning an aggregate has an
17683 undefined effect if that discriminant is used within the record.
17684 However, you can first modify discriminants by directly assigning to
17685 them (which normally would not be allowed in Ada), and then performing an
17686 aggregate assignment. For example, given a variable @code{A_Rec}
17687 declared to have a type such as:
17690 type Rec (Len : Small_Integer := 0) is record
17692 Vals : IntArray (1 .. Len);
17696 you can assign a value with a different size of @code{Vals} with two
17700 (@value{GDBP}) set A_Rec.Len := 4
17701 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17704 As this example also illustrates, @value{GDBN} is very loose about the usual
17705 rules concerning aggregates. You may leave out some of the
17706 components of an array or record aggregate (such as the @code{Len}
17707 component in the assignment to @code{A_Rec} above); they will retain their
17708 original values upon assignment. You may freely use dynamic values as
17709 indices in component associations. You may even use overlapping or
17710 redundant component associations, although which component values are
17711 assigned in such cases is not defined.
17714 Calls to dispatching subprograms are not implemented.
17717 The overloading algorithm is much more limited (i.e., less selective)
17718 than that of real Ada. It makes only limited use of the context in
17719 which a subexpression appears to resolve its meaning, and it is much
17720 looser in its rules for allowing type matches. As a result, some
17721 function calls will be ambiguous, and the user will be asked to choose
17722 the proper resolution.
17725 The @code{new} operator is not implemented.
17728 Entry calls are not implemented.
17731 Aside from printing, arithmetic operations on the native VAX floating-point
17732 formats are not supported.
17735 It is not possible to slice a packed array.
17738 The names @code{True} and @code{False}, when not part of a qualified name,
17739 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17741 Should your program
17742 redefine these names in a package or procedure (at best a dubious practice),
17743 you will have to use fully qualified names to access their new definitions.
17746 @node Additions to Ada
17747 @subsubsection Additions to Ada
17748 @cindex Ada, deviations from
17750 As it does for other languages, @value{GDBN} makes certain generic
17751 extensions to Ada (@pxref{Expressions}):
17755 If the expression @var{E} is a variable residing in memory (typically
17756 a local variable or array element) and @var{N} is a positive integer,
17757 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17758 @var{N}-1 adjacent variables following it in memory as an array. In
17759 Ada, this operator is generally not necessary, since its prime use is
17760 in displaying parts of an array, and slicing will usually do this in
17761 Ada. However, there are occasional uses when debugging programs in
17762 which certain debugging information has been optimized away.
17765 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17766 appears in function or file @var{B}.'' When @var{B} is a file name,
17767 you must typically surround it in single quotes.
17770 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17771 @var{type} that appears at address @var{addr}.''
17774 A name starting with @samp{$} is a convenience variable
17775 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17778 In addition, @value{GDBN} provides a few other shortcuts and outright
17779 additions specific to Ada:
17783 The assignment statement is allowed as an expression, returning
17784 its right-hand operand as its value. Thus, you may enter
17787 (@value{GDBP}) set x := y + 3
17788 (@value{GDBP}) print A(tmp := y + 1)
17792 The semicolon is allowed as an ``operator,'' returning as its value
17793 the value of its right-hand operand.
17794 This allows, for example,
17795 complex conditional breaks:
17798 (@value{GDBP}) break f
17799 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17803 Rather than use catenation and symbolic character names to introduce special
17804 characters into strings, one may instead use a special bracket notation,
17805 which is also used to print strings. A sequence of characters of the form
17806 @samp{["@var{XX}"]} within a string or character literal denotes the
17807 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17808 sequence of characters @samp{["""]} also denotes a single quotation mark
17809 in strings. For example,
17811 "One line.["0a"]Next line.["0a"]"
17814 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17818 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17819 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17823 (@value{GDBP}) print 'max(x, y)
17827 When printing arrays, @value{GDBN} uses positional notation when the
17828 array has a lower bound of 1, and uses a modified named notation otherwise.
17829 For example, a one-dimensional array of three integers with a lower bound
17830 of 3 might print as
17837 That is, in contrast to valid Ada, only the first component has a @code{=>}
17841 You may abbreviate attributes in expressions with any unique,
17842 multi-character subsequence of
17843 their names (an exact match gets preference).
17844 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17845 in place of @t{a'length}.
17848 @cindex quoting Ada internal identifiers
17849 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17850 to lower case. The GNAT compiler uses upper-case characters for
17851 some of its internal identifiers, which are normally of no interest to users.
17852 For the rare occasions when you actually have to look at them,
17853 enclose them in angle brackets to avoid the lower-case mapping.
17856 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17860 Printing an object of class-wide type or dereferencing an
17861 access-to-class-wide value will display all the components of the object's
17862 specific type (as indicated by its run-time tag). Likewise, component
17863 selection on such a value will operate on the specific type of the
17868 @node Overloading support for Ada
17869 @subsubsection Overloading support for Ada
17870 @cindex overloading, Ada
17872 The debugger supports limited overloading. Given a subprogram call in which
17873 the function symbol has multiple definitions, it will use the number of
17874 actual parameters and some information about their types to attempt to narrow
17875 the set of definitions. It also makes very limited use of context, preferring
17876 procedures to functions in the context of the @code{call} command, and
17877 functions to procedures elsewhere.
17879 If, after narrowing, the set of matching definitions still contains more than
17880 one definition, @value{GDBN} will display a menu to query which one it should
17884 (@value{GDBP}) print f(1)
17885 Multiple matches for f
17887 [1] foo.f (integer) return boolean at foo.adb:23
17888 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17892 In this case, just select one menu entry either to cancel expression evaluation
17893 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17894 instance (type the corresponding number and press @key{RET}).
17896 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17901 @kindex set ada print-signatures
17902 @item set ada print-signatures
17903 Control whether parameter types and return types are displayed in overloads
17904 selection menus. It is @code{on} by default.
17905 @xref{Overloading support for Ada}.
17907 @kindex show ada print-signatures
17908 @item show ada print-signatures
17909 Show the current setting for displaying parameter types and return types in
17910 overloads selection menu.
17911 @xref{Overloading support for Ada}.
17915 @node Stopping Before Main Program
17916 @subsubsection Stopping at the Very Beginning
17918 @cindex breakpointing Ada elaboration code
17919 It is sometimes necessary to debug the program during elaboration, and
17920 before reaching the main procedure.
17921 As defined in the Ada Reference
17922 Manual, the elaboration code is invoked from a procedure called
17923 @code{adainit}. To run your program up to the beginning of
17924 elaboration, simply use the following two commands:
17925 @code{tbreak adainit} and @code{run}.
17927 @node Ada Exceptions
17928 @subsubsection Ada Exceptions
17930 A command is provided to list all Ada exceptions:
17933 @kindex info exceptions
17934 @item info exceptions
17935 @itemx info exceptions @var{regexp}
17936 The @code{info exceptions} command allows you to list all Ada exceptions
17937 defined within the program being debugged, as well as their addresses.
17938 With a regular expression, @var{regexp}, as argument, only those exceptions
17939 whose names match @var{regexp} are listed.
17942 Below is a small example, showing how the command can be used, first
17943 without argument, and next with a regular expression passed as an
17947 (@value{GDBP}) info exceptions
17948 All defined Ada exceptions:
17949 constraint_error: 0x613da0
17950 program_error: 0x613d20
17951 storage_error: 0x613ce0
17952 tasking_error: 0x613ca0
17953 const.aint_global_e: 0x613b00
17954 (@value{GDBP}) info exceptions const.aint
17955 All Ada exceptions matching regular expression "const.aint":
17956 constraint_error: 0x613da0
17957 const.aint_global_e: 0x613b00
17960 It is also possible to ask @value{GDBN} to stop your program's execution
17961 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17964 @subsubsection Extensions for Ada Tasks
17965 @cindex Ada, tasking
17967 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17968 @value{GDBN} provides the following task-related commands:
17973 This command shows a list of current Ada tasks, as in the following example:
17980 (@value{GDBP}) info tasks
17981 ID TID P-ID Pri State Name
17982 1 8088000 0 15 Child Activation Wait main_task
17983 2 80a4000 1 15 Accept Statement b
17984 3 809a800 1 15 Child Activation Wait a
17985 * 4 80ae800 3 15 Runnable c
17990 In this listing, the asterisk before the last task indicates it to be the
17991 task currently being inspected.
17995 Represents @value{GDBN}'s internal task number.
18001 The parent's task ID (@value{GDBN}'s internal task number).
18004 The base priority of the task.
18007 Current state of the task.
18011 The task has been created but has not been activated. It cannot be
18015 The task is not blocked for any reason known to Ada. (It may be waiting
18016 for a mutex, though.) It is conceptually "executing" in normal mode.
18019 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18020 that were waiting on terminate alternatives have been awakened and have
18021 terminated themselves.
18023 @item Child Activation Wait
18024 The task is waiting for created tasks to complete activation.
18026 @item Accept Statement
18027 The task is waiting on an accept or selective wait statement.
18029 @item Waiting on entry call
18030 The task is waiting on an entry call.
18032 @item Async Select Wait
18033 The task is waiting to start the abortable part of an asynchronous
18037 The task is waiting on a select statement with only a delay
18040 @item Child Termination Wait
18041 The task is sleeping having completed a master within itself, and is
18042 waiting for the tasks dependent on that master to become terminated or
18043 waiting on a terminate Phase.
18045 @item Wait Child in Term Alt
18046 The task is sleeping waiting for tasks on terminate alternatives to
18047 finish terminating.
18049 @item Accepting RV with @var{taskno}
18050 The task is accepting a rendez-vous with the task @var{taskno}.
18054 Name of the task in the program.
18058 @kindex info task @var{taskno}
18059 @item info task @var{taskno}
18060 This command shows detailed informations on the specified task, as in
18061 the following example:
18066 (@value{GDBP}) info tasks
18067 ID TID P-ID Pri State Name
18068 1 8077880 0 15 Child Activation Wait main_task
18069 * 2 807c468 1 15 Runnable task_1
18070 (@value{GDBP}) info task 2
18071 Ada Task: 0x807c468
18075 Parent: 1 ("main_task")
18081 @kindex task@r{ (Ada)}
18082 @cindex current Ada task ID
18083 This command prints the ID and name of the current task.
18089 (@value{GDBP}) info tasks
18090 ID TID P-ID Pri State Name
18091 1 8077870 0 15 Child Activation Wait main_task
18092 * 2 807c458 1 15 Runnable some_task
18093 (@value{GDBP}) task
18094 [Current task is 2 "some_task"]
18097 @item task @var{taskno}
18098 @cindex Ada task switching
18099 This command is like the @code{thread @var{thread-id}}
18100 command (@pxref{Threads}). It switches the context of debugging
18101 from the current task to the given task.
18107 (@value{GDBP}) info tasks
18108 ID TID P-ID Pri State Name
18109 1 8077870 0 15 Child Activation Wait main_task
18110 * 2 807c458 1 15 Runnable some_task
18111 (@value{GDBP}) task 1
18112 [Switching to task 1 "main_task"]
18113 #0 0x8067726 in pthread_cond_wait ()
18115 #0 0x8067726 in pthread_cond_wait ()
18116 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18117 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18118 #3 0x806153e in system.tasking.stages.activate_tasks ()
18119 #4 0x804aacc in un () at un.adb:5
18122 @item break @var{location} task @var{taskno}
18123 @itemx break @var{location} task @var{taskno} if @dots{}
18124 @cindex breakpoints and tasks, in Ada
18125 @cindex task breakpoints, in Ada
18126 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18127 These commands are like the @code{break @dots{} thread @dots{}}
18128 command (@pxref{Thread Stops}). The
18129 @var{location} argument specifies source lines, as described
18130 in @ref{Specify Location}.
18132 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18133 to specify that you only want @value{GDBN} to stop the program when a
18134 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18135 numeric task identifiers assigned by @value{GDBN}, shown in the first
18136 column of the @samp{info tasks} display.
18138 If you do not specify @samp{task @var{taskno}} when you set a
18139 breakpoint, the breakpoint applies to @emph{all} tasks of your
18142 You can use the @code{task} qualifier on conditional breakpoints as
18143 well; in this case, place @samp{task @var{taskno}} before the
18144 breakpoint condition (before the @code{if}).
18152 (@value{GDBP}) info tasks
18153 ID TID P-ID Pri State Name
18154 1 140022020 0 15 Child Activation Wait main_task
18155 2 140045060 1 15 Accept/Select Wait t2
18156 3 140044840 1 15 Runnable t1
18157 * 4 140056040 1 15 Runnable t3
18158 (@value{GDBP}) b 15 task 2
18159 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18160 (@value{GDBP}) cont
18165 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18167 (@value{GDBP}) info tasks
18168 ID TID P-ID Pri State Name
18169 1 140022020 0 15 Child Activation Wait main_task
18170 * 2 140045060 1 15 Runnable t2
18171 3 140044840 1 15 Runnable t1
18172 4 140056040 1 15 Delay Sleep t3
18176 @node Ada Tasks and Core Files
18177 @subsubsection Tasking Support when Debugging Core Files
18178 @cindex Ada tasking and core file debugging
18180 When inspecting a core file, as opposed to debugging a live program,
18181 tasking support may be limited or even unavailable, depending on
18182 the platform being used.
18183 For instance, on x86-linux, the list of tasks is available, but task
18184 switching is not supported.
18186 On certain platforms, the debugger needs to perform some
18187 memory writes in order to provide Ada tasking support. When inspecting
18188 a core file, this means that the core file must be opened with read-write
18189 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18190 Under these circumstances, you should make a backup copy of the core
18191 file before inspecting it with @value{GDBN}.
18193 @node Ravenscar Profile
18194 @subsubsection Tasking Support when using the Ravenscar Profile
18195 @cindex Ravenscar Profile
18197 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18198 specifically designed for systems with safety-critical real-time
18202 @kindex set ravenscar task-switching on
18203 @cindex task switching with program using Ravenscar Profile
18204 @item set ravenscar task-switching on
18205 Allows task switching when debugging a program that uses the Ravenscar
18206 Profile. This is the default.
18208 @kindex set ravenscar task-switching off
18209 @item set ravenscar task-switching off
18210 Turn off task switching when debugging a program that uses the Ravenscar
18211 Profile. This is mostly intended to disable the code that adds support
18212 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18213 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18214 To be effective, this command should be run before the program is started.
18216 @kindex show ravenscar task-switching
18217 @item show ravenscar task-switching
18218 Show whether it is possible to switch from task to task in a program
18219 using the Ravenscar Profile.
18224 @subsubsection Ada Settings
18225 @cindex Ada settings
18228 @kindex set varsize-limit
18229 @item set varsize-limit @var{size}
18230 Prevent @value{GDBN} from attempting to evaluate objects whose size
18231 is above the given limit (@var{size}) when those sizes are computed
18232 from run-time quantities. This is typically the case when the object
18233 has a variable size, such as an array whose bounds are not known at
18234 compile time for example. Setting @var{size} to @code{unlimited}
18235 removes the size limitation. By default, the limit is about 65KB.
18237 The purpose of having such a limit is to prevent @value{GDBN} from
18238 trying to grab enormous chunks of virtual memory when asked to evaluate
18239 a quantity whose bounds have been corrupted or have not yet been fully
18240 initialized. The limit applies to the results of some subexpressions
18241 as well as to complete expressions. For example, an expression denoting
18242 a simple integer component, such as @code{x.y.z}, may fail if the size of
18243 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18244 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18245 @code{A} is an array variable with non-constant size, will generally
18246 succeed regardless of the bounds on @code{A}, as long as the component
18247 size is less than @var{size}.
18249 @kindex show varsize-limit
18250 @item show varsize-limit
18251 Show the limit on types whose size is determined by run-time quantities.
18255 @subsubsection Known Peculiarities of Ada Mode
18256 @cindex Ada, problems
18258 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18259 we know of several problems with and limitations of Ada mode in
18261 some of which will be fixed with planned future releases of the debugger
18262 and the GNU Ada compiler.
18266 Static constants that the compiler chooses not to materialize as objects in
18267 storage are invisible to the debugger.
18270 Named parameter associations in function argument lists are ignored (the
18271 argument lists are treated as positional).
18274 Many useful library packages are currently invisible to the debugger.
18277 Fixed-point arithmetic, conversions, input, and output is carried out using
18278 floating-point arithmetic, and may give results that only approximate those on
18282 The GNAT compiler never generates the prefix @code{Standard} for any of
18283 the standard symbols defined by the Ada language. @value{GDBN} knows about
18284 this: it will strip the prefix from names when you use it, and will never
18285 look for a name you have so qualified among local symbols, nor match against
18286 symbols in other packages or subprograms. If you have
18287 defined entities anywhere in your program other than parameters and
18288 local variables whose simple names match names in @code{Standard},
18289 GNAT's lack of qualification here can cause confusion. When this happens,
18290 you can usually resolve the confusion
18291 by qualifying the problematic names with package
18292 @code{Standard} explicitly.
18295 Older versions of the compiler sometimes generate erroneous debugging
18296 information, resulting in the debugger incorrectly printing the value
18297 of affected entities. In some cases, the debugger is able to work
18298 around an issue automatically. In other cases, the debugger is able
18299 to work around the issue, but the work-around has to be specifically
18302 @kindex set ada trust-PAD-over-XVS
18303 @kindex show ada trust-PAD-over-XVS
18306 @item set ada trust-PAD-over-XVS on
18307 Configure GDB to strictly follow the GNAT encoding when computing the
18308 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18309 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18310 a complete description of the encoding used by the GNAT compiler).
18311 This is the default.
18313 @item set ada trust-PAD-over-XVS off
18314 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18315 sometimes prints the wrong value for certain entities, changing @code{ada
18316 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18317 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18318 @code{off}, but this incurs a slight performance penalty, so it is
18319 recommended to leave this setting to @code{on} unless necessary.
18323 @cindex GNAT descriptive types
18324 @cindex GNAT encoding
18325 Internally, the debugger also relies on the compiler following a number
18326 of conventions known as the @samp{GNAT Encoding}, all documented in
18327 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18328 how the debugging information should be generated for certain types.
18329 In particular, this convention makes use of @dfn{descriptive types},
18330 which are artificial types generated purely to help the debugger.
18332 These encodings were defined at a time when the debugging information
18333 format used was not powerful enough to describe some of the more complex
18334 types available in Ada. Since DWARF allows us to express nearly all
18335 Ada features, the long-term goal is to slowly replace these descriptive
18336 types by their pure DWARF equivalent. To facilitate that transition,
18337 a new maintenance option is available to force the debugger to ignore
18338 those descriptive types. It allows the user to quickly evaluate how
18339 well @value{GDBN} works without them.
18343 @kindex maint ada set ignore-descriptive-types
18344 @item maintenance ada set ignore-descriptive-types [on|off]
18345 Control whether the debugger should ignore descriptive types.
18346 The default is not to ignore descriptives types (@code{off}).
18348 @kindex maint ada show ignore-descriptive-types
18349 @item maintenance ada show ignore-descriptive-types
18350 Show if descriptive types are ignored by @value{GDBN}.
18354 @node Unsupported Languages
18355 @section Unsupported Languages
18357 @cindex unsupported languages
18358 @cindex minimal language
18359 In addition to the other fully-supported programming languages,
18360 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18361 It does not represent a real programming language, but provides a set
18362 of capabilities close to what the C or assembly languages provide.
18363 This should allow most simple operations to be performed while debugging
18364 an application that uses a language currently not supported by @value{GDBN}.
18366 If the language is set to @code{auto}, @value{GDBN} will automatically
18367 select this language if the current frame corresponds to an unsupported
18371 @chapter Examining the Symbol Table
18373 The commands described in this chapter allow you to inquire about the
18374 symbols (names of variables, functions and types) defined in your
18375 program. This information is inherent in the text of your program and
18376 does not change as your program executes. @value{GDBN} finds it in your
18377 program's symbol table, in the file indicated when you started @value{GDBN}
18378 (@pxref{File Options, ,Choosing Files}), or by one of the
18379 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18381 @cindex symbol names
18382 @cindex names of symbols
18383 @cindex quoting names
18384 @anchor{quoting names}
18385 Occasionally, you may need to refer to symbols that contain unusual
18386 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18387 most frequent case is in referring to static variables in other
18388 source files (@pxref{Variables,,Program Variables}). File names
18389 are recorded in object files as debugging symbols, but @value{GDBN} would
18390 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18391 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18392 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18399 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18402 @cindex case-insensitive symbol names
18403 @cindex case sensitivity in symbol names
18404 @kindex set case-sensitive
18405 @item set case-sensitive on
18406 @itemx set case-sensitive off
18407 @itemx set case-sensitive auto
18408 Normally, when @value{GDBN} looks up symbols, it matches their names
18409 with case sensitivity determined by the current source language.
18410 Occasionally, you may wish to control that. The command @code{set
18411 case-sensitive} lets you do that by specifying @code{on} for
18412 case-sensitive matches or @code{off} for case-insensitive ones. If
18413 you specify @code{auto}, case sensitivity is reset to the default
18414 suitable for the source language. The default is case-sensitive
18415 matches for all languages except for Fortran, for which the default is
18416 case-insensitive matches.
18418 @kindex show case-sensitive
18419 @item show case-sensitive
18420 This command shows the current setting of case sensitivity for symbols
18423 @kindex set print type methods
18424 @item set print type methods
18425 @itemx set print type methods on
18426 @itemx set print type methods off
18427 Normally, when @value{GDBN} prints a class, it displays any methods
18428 declared in that class. You can control this behavior either by
18429 passing the appropriate flag to @code{ptype}, or using @command{set
18430 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18431 display the methods; this is the default. Specifying @code{off} will
18432 cause @value{GDBN} to omit the methods.
18434 @kindex show print type methods
18435 @item show print type methods
18436 This command shows the current setting of method display when printing
18439 @kindex set print type nested-type-limit
18440 @item set print type nested-type-limit @var{limit}
18441 @itemx set print type nested-type-limit unlimited
18442 Set the limit of displayed nested types that the type printer will
18443 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18444 nested definitions. By default, the type printer will not show any nested
18445 types defined in classes.
18447 @kindex show print type nested-type-limit
18448 @item show print type nested-type-limit
18449 This command shows the current display limit of nested types when
18452 @kindex set print type typedefs
18453 @item set print type typedefs
18454 @itemx set print type typedefs on
18455 @itemx set print type typedefs off
18457 Normally, when @value{GDBN} prints a class, it displays any typedefs
18458 defined in that class. You can control this behavior either by
18459 passing the appropriate flag to @code{ptype}, or using @command{set
18460 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18461 display the typedef definitions; this is the default. Specifying
18462 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18463 Note that this controls whether the typedef definition itself is
18464 printed, not whether typedef names are substituted when printing other
18467 @kindex show print type typedefs
18468 @item show print type typedefs
18469 This command shows the current setting of typedef display when
18472 @kindex info address
18473 @cindex address of a symbol
18474 @item info address @var{symbol}
18475 Describe where the data for @var{symbol} is stored. For a register
18476 variable, this says which register it is kept in. For a non-register
18477 local variable, this prints the stack-frame offset at which the variable
18480 Note the contrast with @samp{print &@var{symbol}}, which does not work
18481 at all for a register variable, and for a stack local variable prints
18482 the exact address of the current instantiation of the variable.
18484 @kindex info symbol
18485 @cindex symbol from address
18486 @cindex closest symbol and offset for an address
18487 @item info symbol @var{addr}
18488 Print the name of a symbol which is stored at the address @var{addr}.
18489 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18490 nearest symbol and an offset from it:
18493 (@value{GDBP}) info symbol 0x54320
18494 _initialize_vx + 396 in section .text
18498 This is the opposite of the @code{info address} command. You can use
18499 it to find out the name of a variable or a function given its address.
18501 For dynamically linked executables, the name of executable or shared
18502 library containing the symbol is also printed:
18505 (@value{GDBP}) info symbol 0x400225
18506 _start + 5 in section .text of /tmp/a.out
18507 (@value{GDBP}) info symbol 0x2aaaac2811cf
18508 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18513 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18514 Demangle @var{name}.
18515 If @var{language} is provided it is the name of the language to demangle
18516 @var{name} in. Otherwise @var{name} is demangled in the current language.
18518 The @samp{--} option specifies the end of options,
18519 and is useful when @var{name} begins with a dash.
18521 The parameter @code{demangle-style} specifies how to interpret the kind
18522 of mangling used. @xref{Print Settings}.
18525 @item whatis[/@var{flags}] [@var{arg}]
18526 Print the data type of @var{arg}, which can be either an expression
18527 or a name of a data type. With no argument, print the data type of
18528 @code{$}, the last value in the value history.
18530 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18531 is not actually evaluated, and any side-effecting operations (such as
18532 assignments or function calls) inside it do not take place.
18534 If @var{arg} is a variable or an expression, @code{whatis} prints its
18535 literal type as it is used in the source code. If the type was
18536 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18537 the data type underlying the @code{typedef}. If the type of the
18538 variable or the expression is a compound data type, such as
18539 @code{struct} or @code{class}, @code{whatis} never prints their
18540 fields or methods. It just prints the @code{struct}/@code{class}
18541 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18542 such a compound data type, use @code{ptype}.
18544 If @var{arg} is a type name that was defined using @code{typedef},
18545 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18546 Unrolling means that @code{whatis} will show the underlying type used
18547 in the @code{typedef} declaration of @var{arg}. However, if that
18548 underlying type is also a @code{typedef}, @code{whatis} will not
18551 For C code, the type names may also have the form @samp{class
18552 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18553 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18555 @var{flags} can be used to modify how the type is displayed.
18556 Available flags are:
18560 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18561 parameters and typedefs defined in a class when printing the class'
18562 members. The @code{/r} flag disables this.
18565 Do not print methods defined in the class.
18568 Print methods defined in the class. This is the default, but the flag
18569 exists in case you change the default with @command{set print type methods}.
18572 Do not print typedefs defined in the class. Note that this controls
18573 whether the typedef definition itself is printed, not whether typedef
18574 names are substituted when printing other types.
18577 Print typedefs defined in the class. This is the default, but the flag
18578 exists in case you change the default with @command{set print type typedefs}.
18581 Print the offsets and sizes of fields in a struct, similar to what the
18582 @command{pahole} tool does. This option implies the @code{/tm} flags.
18584 For example, given the following declarations:
18620 Issuing a @kbd{ptype /o struct tuv} command would print:
18623 (@value{GDBP}) ptype /o struct tuv
18624 /* offset | size */ type = struct tuv @{
18625 /* 0 | 4 */ int a1;
18626 /* XXX 4-byte hole */
18627 /* 8 | 8 */ char *a2;
18628 /* 16 | 4 */ int a3;
18630 /* total size (bytes): 24 */
18634 Notice the format of the first column of comments. There, you can
18635 find two parts separated by the @samp{|} character: the @emph{offset},
18636 which indicates where the field is located inside the struct, in
18637 bytes, and the @emph{size} of the field. Another interesting line is
18638 the marker of a @emph{hole} in the struct, indicating that it may be
18639 possible to pack the struct and make it use less space by reorganizing
18642 It is also possible to print offsets inside an union:
18645 (@value{GDBP}) ptype /o union qwe
18646 /* offset | size */ type = union qwe @{
18647 /* 24 */ struct tuv @{
18648 /* 0 | 4 */ int a1;
18649 /* XXX 4-byte hole */
18650 /* 8 | 8 */ char *a2;
18651 /* 16 | 4 */ int a3;
18653 /* total size (bytes): 24 */
18655 /* 40 */ struct xyz @{
18656 /* 0 | 4 */ int f1;
18657 /* 4 | 1 */ char f2;
18658 /* XXX 3-byte hole */
18659 /* 8 | 8 */ void *f3;
18660 /* 16 | 24 */ struct tuv @{
18661 /* 16 | 4 */ int a1;
18662 /* XXX 4-byte hole */
18663 /* 24 | 8 */ char *a2;
18664 /* 32 | 4 */ int a3;
18666 /* total size (bytes): 24 */
18669 /* total size (bytes): 40 */
18672 /* total size (bytes): 40 */
18676 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18677 same space (because we are dealing with an union), the offset is not
18678 printed for them. However, you can still examine the offset of each
18679 of these structures' fields.
18681 Another useful scenario is printing the offsets of a struct containing
18685 (@value{GDBP}) ptype /o struct tyu
18686 /* offset | size */ type = struct tyu @{
18687 /* 0:31 | 4 */ int a1 : 1;
18688 /* 0:28 | 4 */ int a2 : 3;
18689 /* 0: 5 | 4 */ int a3 : 23;
18690 /* 3: 3 | 1 */ signed char a4 : 2;
18691 /* XXX 3-bit hole */
18692 /* XXX 4-byte hole */
18693 /* 8 | 8 */ int64_t a5;
18694 /* 16: 0 | 4 */ int a6 : 5;
18695 /* 16: 5 | 8 */ int64_t a7 : 3;
18696 "/* XXX 7-byte padding */
18698 /* total size (bytes): 24 */
18702 Note how the offset information is now extended to also include the
18703 first bit of the bitfield.
18707 @item ptype[/@var{flags}] [@var{arg}]
18708 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18709 detailed description of the type, instead of just the name of the type.
18710 @xref{Expressions, ,Expressions}.
18712 Contrary to @code{whatis}, @code{ptype} always unrolls any
18713 @code{typedef}s in its argument declaration, whether the argument is
18714 a variable, expression, or a data type. This means that @code{ptype}
18715 of a variable or an expression will not print literally its type as
18716 present in the source code---use @code{whatis} for that. @code{typedef}s at
18717 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18718 fields, methods and inner @code{class typedef}s of @code{struct}s,
18719 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18721 For example, for this variable declaration:
18724 typedef double real_t;
18725 struct complex @{ real_t real; double imag; @};
18726 typedef struct complex complex_t;
18728 real_t *real_pointer_var;
18732 the two commands give this output:
18736 (@value{GDBP}) whatis var
18738 (@value{GDBP}) ptype var
18739 type = struct complex @{
18743 (@value{GDBP}) whatis complex_t
18744 type = struct complex
18745 (@value{GDBP}) whatis struct complex
18746 type = struct complex
18747 (@value{GDBP}) ptype struct complex
18748 type = struct complex @{
18752 (@value{GDBP}) whatis real_pointer_var
18754 (@value{GDBP}) ptype real_pointer_var
18760 As with @code{whatis}, using @code{ptype} without an argument refers to
18761 the type of @code{$}, the last value in the value history.
18763 @cindex incomplete type
18764 Sometimes, programs use opaque data types or incomplete specifications
18765 of complex data structure. If the debug information included in the
18766 program does not allow @value{GDBN} to display a full declaration of
18767 the data type, it will say @samp{<incomplete type>}. For example,
18768 given these declarations:
18772 struct foo *fooptr;
18776 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18779 (@value{GDBP}) ptype foo
18780 $1 = <incomplete type>
18784 ``Incomplete type'' is C terminology for data types that are not
18785 completely specified.
18787 @cindex unknown type
18788 Othertimes, information about a variable's type is completely absent
18789 from the debug information included in the program. This most often
18790 happens when the program or library where the variable is defined
18791 includes no debug information at all. @value{GDBN} knows the variable
18792 exists from inspecting the linker/loader symbol table (e.g., the ELF
18793 dynamic symbol table), but such symbols do not contain type
18794 information. Inspecting the type of a (global) variable for which
18795 @value{GDBN} has no type information shows:
18798 (@value{GDBP}) ptype var
18799 type = <data variable, no debug info>
18802 @xref{Variables, no debug info variables}, for how to print the values
18806 @item info types [-q] [@var{regexp}]
18807 Print a brief description of all types whose names match the regular
18808 expression @var{regexp} (or all types in your program, if you supply
18809 no argument). Each complete typename is matched as though it were a
18810 complete line; thus, @samp{i type value} gives information on all
18811 types in your program whose names include the string @code{value}, but
18812 @samp{i type ^value$} gives information only on types whose complete
18813 name is @code{value}.
18815 In programs using different languages, @value{GDBN} chooses the syntax
18816 to print the type description according to the
18817 @samp{set language} value: using @samp{set language auto}
18818 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18819 language of the type, other values mean to use
18820 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18822 This command differs from @code{ptype} in two ways: first, like
18823 @code{whatis}, it does not print a detailed description; second, it
18824 lists all source files and line numbers where a type is defined.
18826 The output from @samp{into types} is proceeded with a header line
18827 describing what types are being listed. The optional flag @samp{-q},
18828 which stands for @samp{quiet}, disables printing this header
18831 @kindex info type-printers
18832 @item info type-printers
18833 Versions of @value{GDBN} that ship with Python scripting enabled may
18834 have ``type printers'' available. When using @command{ptype} or
18835 @command{whatis}, these printers are consulted when the name of a type
18836 is needed. @xref{Type Printing API}, for more information on writing
18839 @code{info type-printers} displays all the available type printers.
18841 @kindex enable type-printer
18842 @kindex disable type-printer
18843 @item enable type-printer @var{name}@dots{}
18844 @item disable type-printer @var{name}@dots{}
18845 These commands can be used to enable or disable type printers.
18848 @cindex local variables
18849 @item info scope @var{location}
18850 List all the variables local to a particular scope. This command
18851 accepts a @var{location} argument---a function name, a source line, or
18852 an address preceded by a @samp{*}, and prints all the variables local
18853 to the scope defined by that location. (@xref{Specify Location}, for
18854 details about supported forms of @var{location}.) For example:
18857 (@value{GDBP}) @b{info scope command_line_handler}
18858 Scope for command_line_handler:
18859 Symbol rl is an argument at stack/frame offset 8, length 4.
18860 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18861 Symbol linelength is in static storage at address 0x150a1c, length 4.
18862 Symbol p is a local variable in register $esi, length 4.
18863 Symbol p1 is a local variable in register $ebx, length 4.
18864 Symbol nline is a local variable in register $edx, length 4.
18865 Symbol repeat is a local variable at frame offset -8, length 4.
18869 This command is especially useful for determining what data to collect
18870 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18873 @kindex info source
18875 Show information about the current source file---that is, the source file for
18876 the function containing the current point of execution:
18879 the name of the source file, and the directory containing it,
18881 the directory it was compiled in,
18883 its length, in lines,
18885 which programming language it is written in,
18887 if the debug information provides it, the program that compiled the file
18888 (which may include, e.g., the compiler version and command line arguments),
18890 whether the executable includes debugging information for that file, and
18891 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18893 whether the debugging information includes information about
18894 preprocessor macros.
18898 @kindex info sources
18900 Print the names of all source files in your program for which there is
18901 debugging information, organized into two lists: files whose symbols
18902 have already been read, and files whose symbols will be read when needed.
18904 @item info sources [-dirname | -basename] [--] [@var{regexp}]
18905 Like @samp{info sources}, but only print the names of the files
18906 matching the provided @var{regexp}.
18907 By default, the @var{regexp} is used to match anywhere in the filename.
18908 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
18909 If @code{-basename}, only files having a basename matching @var{regexp}
18911 The matching is case-sensitive, except on operating systems that
18912 have case-insensitive filesystem (e.g., MS-Windows).
18914 @kindex info functions
18915 @item info functions [-q] [-n]
18916 Print the names and data types of all defined functions.
18917 Similarly to @samp{info types}, this command groups its output by source
18918 files and annotates each function definition with its source line
18921 In programs using different languages, @value{GDBN} chooses the syntax
18922 to print the function name and type according to the
18923 @samp{set language} value: using @samp{set language auto}
18924 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18925 language of the function, other values mean to use
18926 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18928 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
18929 results. A non-debugging symbol is a symbol that comes from the
18930 executable's symbol table, not from the debug information (for
18931 example, DWARF) associated with the executable.
18933 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18934 printing header information and messages explaining why no functions
18937 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
18938 Like @samp{info functions}, but only print the names and data types
18939 of the functions selected with the provided regexp(s).
18941 If @var{regexp} is provided, print only the functions whose names
18942 match the regular expression @var{regexp}.
18943 Thus, @samp{info fun step} finds all functions whose
18944 names include @code{step}; @samp{info fun ^step} finds those whose names
18945 start with @code{step}. If a function name contains characters that
18946 conflict with the regular expression language (e.g.@:
18947 @samp{operator*()}), they may be quoted with a backslash.
18949 If @var{type_regexp} is provided, print only the functions whose
18950 types, as printed by the @code{whatis} command, match
18951 the regular expression @var{type_regexp}.
18952 If @var{type_regexp} contains space(s), it should be enclosed in
18953 quote characters. If needed, use backslash to escape the meaning
18954 of special characters or quotes.
18955 Thus, @samp{info fun -t '^int ('} finds the functions that return
18956 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18957 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18958 finds the functions whose names start with @code{step} and that return
18961 If both @var{regexp} and @var{type_regexp} are provided, a function
18962 is printed only if its name matches @var{regexp} and its type matches
18966 @kindex info variables
18967 @item info variables [-q] [-n]
18968 Print the names and data types of all variables that are defined
18969 outside of functions (i.e.@: excluding local variables).
18970 The printed variables are grouped by source files and annotated with
18971 their respective source line numbers.
18973 In programs using different languages, @value{GDBN} chooses the syntax
18974 to print the variable name and type according to the
18975 @samp{set language} value: using @samp{set language auto}
18976 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18977 language of the variable, other values mean to use
18978 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18980 The @samp{-n} flag excludes non-debugging symbols from the results.
18982 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18983 printing header information and messages explaining why no variables
18986 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
18987 Like @kbd{info variables}, but only print the variables selected
18988 with the provided regexp(s).
18990 If @var{regexp} is provided, print only the variables whose names
18991 match the regular expression @var{regexp}.
18993 If @var{type_regexp} is provided, print only the variables whose
18994 types, as printed by the @code{whatis} command, match
18995 the regular expression @var{type_regexp}.
18996 If @var{type_regexp} contains space(s), it should be enclosed in
18997 quote characters. If needed, use backslash to escape the meaning
18998 of special characters or quotes.
19000 If both @var{regexp} and @var{type_regexp} are provided, an argument
19001 is printed only if its name matches @var{regexp} and its type matches
19004 @kindex info modules
19006 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19007 List all Fortran modules in the program, or all modules matching the
19008 optional regular expression @var{regexp}.
19010 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19011 printing header information and messages explaining why no modules
19014 @kindex info module
19015 @cindex Fortran modules, information about
19016 @cindex functions and variables by Fortran module
19017 @cindex module functions and variables
19018 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19019 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19020 List all functions or variables within all Fortran modules. The set
19021 of functions or variables listed can be limited by providing some or
19022 all of the optional regular expressions. If @var{module-regexp} is
19023 provided, then only Fortran modules matching @var{module-regexp} will
19024 be searched. Only functions or variables whose type matches the
19025 optional regular expression @var{type-regexp} will be listed. And
19026 only functions or variables whose name matches the optional regular
19027 expression @var{regexp} will be listed.
19029 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19030 printing header information and messages explaining why no functions
19031 or variables have been printed.
19033 @kindex info classes
19034 @cindex Objective-C, classes and selectors
19036 @itemx info classes @var{regexp}
19037 Display all Objective-C classes in your program, or
19038 (with the @var{regexp} argument) all those matching a particular regular
19041 @kindex info selectors
19042 @item info selectors
19043 @itemx info selectors @var{regexp}
19044 Display all Objective-C selectors in your program, or
19045 (with the @var{regexp} argument) all those matching a particular regular
19049 This was never implemented.
19050 @kindex info methods
19052 @itemx info methods @var{regexp}
19053 The @code{info methods} command permits the user to examine all defined
19054 methods within C@t{++} program, or (with the @var{regexp} argument) a
19055 specific set of methods found in the various C@t{++} classes. Many
19056 C@t{++} classes provide a large number of methods. Thus, the output
19057 from the @code{ptype} command can be overwhelming and hard to use. The
19058 @code{info-methods} command filters the methods, printing only those
19059 which match the regular-expression @var{regexp}.
19062 @cindex opaque data types
19063 @kindex set opaque-type-resolution
19064 @item set opaque-type-resolution on
19065 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19066 declared as a pointer to a @code{struct}, @code{class}, or
19067 @code{union}---for example, @code{struct MyType *}---that is used in one
19068 source file although the full declaration of @code{struct MyType} is in
19069 another source file. The default is on.
19071 A change in the setting of this subcommand will not take effect until
19072 the next time symbols for a file are loaded.
19074 @item set opaque-type-resolution off
19075 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19076 is printed as follows:
19078 @{<no data fields>@}
19081 @kindex show opaque-type-resolution
19082 @item show opaque-type-resolution
19083 Show whether opaque types are resolved or not.
19085 @kindex set print symbol-loading
19086 @cindex print messages when symbols are loaded
19087 @item set print symbol-loading
19088 @itemx set print symbol-loading full
19089 @itemx set print symbol-loading brief
19090 @itemx set print symbol-loading off
19091 The @code{set print symbol-loading} command allows you to control the
19092 printing of messages when @value{GDBN} loads symbol information.
19093 By default a message is printed for the executable and one for each
19094 shared library, and normally this is what you want. However, when
19095 debugging apps with large numbers of shared libraries these messages
19097 When set to @code{brief} a message is printed for each executable,
19098 and when @value{GDBN} loads a collection of shared libraries at once
19099 it will only print one message regardless of the number of shared
19100 libraries. When set to @code{off} no messages are printed.
19102 @kindex show print symbol-loading
19103 @item show print symbol-loading
19104 Show whether messages will be printed when a @value{GDBN} command
19105 entered from the keyboard causes symbol information to be loaded.
19107 @kindex maint print symbols
19108 @cindex symbol dump
19109 @kindex maint print psymbols
19110 @cindex partial symbol dump
19111 @kindex maint print msymbols
19112 @cindex minimal symbol dump
19113 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19114 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19115 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19116 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19117 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19118 Write a dump of debugging symbol data into the file @var{filename} or
19119 the terminal if @var{filename} is unspecified.
19120 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19122 If @code{-pc @var{address}} is specified, only dump symbols for the file
19123 with code at that address. Note that @var{address} may be a symbol like
19125 If @code{-source @var{source}} is specified, only dump symbols for that
19128 These commands are used to debug the @value{GDBN} symbol-reading code.
19129 These commands do not modify internal @value{GDBN} state, therefore
19130 @samp{maint print symbols} will only print symbols for already expanded symbol
19132 You can use the command @code{info sources} to find out which files these are.
19133 If you use @samp{maint print psymbols} instead, the dump shows information
19134 about symbols that @value{GDBN} only knows partially---that is, symbols
19135 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19136 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19139 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19140 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19142 @kindex maint info symtabs
19143 @kindex maint info psymtabs
19144 @cindex listing @value{GDBN}'s internal symbol tables
19145 @cindex symbol tables, listing @value{GDBN}'s internal
19146 @cindex full symbol tables, listing @value{GDBN}'s internal
19147 @cindex partial symbol tables, listing @value{GDBN}'s internal
19148 @item maint info symtabs @r{[} @var{regexp} @r{]}
19149 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19151 List the @code{struct symtab} or @code{struct partial_symtab}
19152 structures whose names match @var{regexp}. If @var{regexp} is not
19153 given, list them all. The output includes expressions which you can
19154 copy into a @value{GDBN} debugging this one to examine a particular
19155 structure in more detail. For example:
19158 (@value{GDBP}) maint info psymtabs dwarf2read
19159 @{ objfile /home/gnu/build/gdb/gdb
19160 ((struct objfile *) 0x82e69d0)
19161 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19162 ((struct partial_symtab *) 0x8474b10)
19165 text addresses 0x814d3c8 -- 0x8158074
19166 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19167 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19168 dependencies (none)
19171 (@value{GDBP}) maint info symtabs
19175 We see that there is one partial symbol table whose filename contains
19176 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19177 and we see that @value{GDBN} has not read in any symtabs yet at all.
19178 If we set a breakpoint on a function, that will cause @value{GDBN} to
19179 read the symtab for the compilation unit containing that function:
19182 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19183 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19185 (@value{GDBP}) maint info symtabs
19186 @{ objfile /home/gnu/build/gdb/gdb
19187 ((struct objfile *) 0x82e69d0)
19188 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19189 ((struct symtab *) 0x86c1f38)
19192 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19193 linetable ((struct linetable *) 0x8370fa0)
19194 debugformat DWARF 2
19200 @kindex maint info line-table
19201 @cindex listing @value{GDBN}'s internal line tables
19202 @cindex line tables, listing @value{GDBN}'s internal
19203 @item maint info line-table @r{[} @var{regexp} @r{]}
19205 List the @code{struct linetable} from all @code{struct symtab}
19206 instances whose name matches @var{regexp}. If @var{regexp} is not
19207 given, list the @code{struct linetable} from all @code{struct symtab}.
19209 @kindex maint set symbol-cache-size
19210 @cindex symbol cache size
19211 @item maint set symbol-cache-size @var{size}
19212 Set the size of the symbol cache to @var{size}.
19213 The default size is intended to be good enough for debugging
19214 most applications. This option exists to allow for experimenting
19215 with different sizes.
19217 @kindex maint show symbol-cache-size
19218 @item maint show symbol-cache-size
19219 Show the size of the symbol cache.
19221 @kindex maint print symbol-cache
19222 @cindex symbol cache, printing its contents
19223 @item maint print symbol-cache
19224 Print the contents of the symbol cache.
19225 This is useful when debugging symbol cache issues.
19227 @kindex maint print symbol-cache-statistics
19228 @cindex symbol cache, printing usage statistics
19229 @item maint print symbol-cache-statistics
19230 Print symbol cache usage statistics.
19231 This helps determine how well the cache is being utilized.
19233 @kindex maint flush-symbol-cache
19234 @cindex symbol cache, flushing
19235 @item maint flush-symbol-cache
19236 Flush the contents of the symbol cache, all entries are removed.
19237 This command is useful when debugging the symbol cache.
19238 It is also useful when collecting performance data.
19243 @chapter Altering Execution
19245 Once you think you have found an error in your program, you might want to
19246 find out for certain whether correcting the apparent error would lead to
19247 correct results in the rest of the run. You can find the answer by
19248 experiment, using the @value{GDBN} features for altering execution of the
19251 For example, you can store new values into variables or memory
19252 locations, give your program a signal, restart it at a different
19253 address, or even return prematurely from a function.
19256 * Assignment:: Assignment to variables
19257 * Jumping:: Continuing at a different address
19258 * Signaling:: Giving your program a signal
19259 * Returning:: Returning from a function
19260 * Calling:: Calling your program's functions
19261 * Patching:: Patching your program
19262 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19266 @section Assignment to Variables
19269 @cindex setting variables
19270 To alter the value of a variable, evaluate an assignment expression.
19271 @xref{Expressions, ,Expressions}. For example,
19278 stores the value 4 into the variable @code{x}, and then prints the
19279 value of the assignment expression (which is 4).
19280 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19281 information on operators in supported languages.
19283 @kindex set variable
19284 @cindex variables, setting
19285 If you are not interested in seeing the value of the assignment, use the
19286 @code{set} command instead of the @code{print} command. @code{set} is
19287 really the same as @code{print} except that the expression's value is
19288 not printed and is not put in the value history (@pxref{Value History,
19289 ,Value History}). The expression is evaluated only for its effects.
19291 If the beginning of the argument string of the @code{set} command
19292 appears identical to a @code{set} subcommand, use the @code{set
19293 variable} command instead of just @code{set}. This command is identical
19294 to @code{set} except for its lack of subcommands. For example, if your
19295 program has a variable @code{width}, you get an error if you try to set
19296 a new value with just @samp{set width=13}, because @value{GDBN} has the
19297 command @code{set width}:
19300 (@value{GDBP}) whatis width
19302 (@value{GDBP}) p width
19304 (@value{GDBP}) set width=47
19305 Invalid syntax in expression.
19309 The invalid expression, of course, is @samp{=47}. In
19310 order to actually set the program's variable @code{width}, use
19313 (@value{GDBP}) set var width=47
19316 Because the @code{set} command has many subcommands that can conflict
19317 with the names of program variables, it is a good idea to use the
19318 @code{set variable} command instead of just @code{set}. For example, if
19319 your program has a variable @code{g}, you run into problems if you try
19320 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19321 the command @code{set gnutarget}, abbreviated @code{set g}:
19325 (@value{GDBP}) whatis g
19329 (@value{GDBP}) set g=4
19333 The program being debugged has been started already.
19334 Start it from the beginning? (y or n) y
19335 Starting program: /home/smith/cc_progs/a.out
19336 "/home/smith/cc_progs/a.out": can't open to read symbols:
19337 Invalid bfd target.
19338 (@value{GDBP}) show g
19339 The current BFD target is "=4".
19344 The program variable @code{g} did not change, and you silently set the
19345 @code{gnutarget} to an invalid value. In order to set the variable
19349 (@value{GDBP}) set var g=4
19352 @value{GDBN} allows more implicit conversions in assignments than C; you can
19353 freely store an integer value into a pointer variable or vice versa,
19354 and you can convert any structure to any other structure that is the
19355 same length or shorter.
19356 @comment FIXME: how do structs align/pad in these conversions?
19357 @comment /doc@cygnus.com 18dec1990
19359 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19360 construct to generate a value of specified type at a specified address
19361 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19362 to memory location @code{0x83040} as an integer (which implies a certain size
19363 and representation in memory), and
19366 set @{int@}0x83040 = 4
19370 stores the value 4 into that memory location.
19373 @section Continuing at a Different Address
19375 Ordinarily, when you continue your program, you do so at the place where
19376 it stopped, with the @code{continue} command. You can instead continue at
19377 an address of your own choosing, with the following commands:
19381 @kindex j @r{(@code{jump})}
19382 @item jump @var{location}
19383 @itemx j @var{location}
19384 Resume execution at @var{location}. Execution stops again immediately
19385 if there is a breakpoint there. @xref{Specify Location}, for a description
19386 of the different forms of @var{location}. It is common
19387 practice to use the @code{tbreak} command in conjunction with
19388 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19390 The @code{jump} command does not change the current stack frame, or
19391 the stack pointer, or the contents of any memory location or any
19392 register other than the program counter. If @var{location} is in
19393 a different function from the one currently executing, the results may
19394 be bizarre if the two functions expect different patterns of arguments or
19395 of local variables. For this reason, the @code{jump} command requests
19396 confirmation if the specified line is not in the function currently
19397 executing. However, even bizarre results are predictable if you are
19398 well acquainted with the machine-language code of your program.
19401 On many systems, you can get much the same effect as the @code{jump}
19402 command by storing a new value into the register @code{$pc}. The
19403 difference is that this does not start your program running; it only
19404 changes the address of where it @emph{will} run when you continue. For
19412 makes the next @code{continue} command or stepping command execute at
19413 address @code{0x485}, rather than at the address where your program stopped.
19414 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19416 The most common occasion to use the @code{jump} command is to back
19417 up---perhaps with more breakpoints set---over a portion of a program
19418 that has already executed, in order to examine its execution in more
19423 @section Giving your Program a Signal
19424 @cindex deliver a signal to a program
19428 @item signal @var{signal}
19429 Resume execution where your program is stopped, but immediately give it the
19430 signal @var{signal}. The @var{signal} can be the name or the number of a
19431 signal. For example, on many systems @code{signal 2} and @code{signal
19432 SIGINT} are both ways of sending an interrupt signal.
19434 Alternatively, if @var{signal} is zero, continue execution without
19435 giving a signal. This is useful when your program stopped on account of
19436 a signal and would ordinarily see the signal when resumed with the
19437 @code{continue} command; @samp{signal 0} causes it to resume without a
19440 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19441 delivered to the currently selected thread, not the thread that last
19442 reported a stop. This includes the situation where a thread was
19443 stopped due to a signal. So if you want to continue execution
19444 suppressing the signal that stopped a thread, you should select that
19445 same thread before issuing the @samp{signal 0} command. If you issue
19446 the @samp{signal 0} command with another thread as the selected one,
19447 @value{GDBN} detects that and asks for confirmation.
19449 Invoking the @code{signal} command is not the same as invoking the
19450 @code{kill} utility from the shell. Sending a signal with @code{kill}
19451 causes @value{GDBN} to decide what to do with the signal depending on
19452 the signal handling tables (@pxref{Signals}). The @code{signal} command
19453 passes the signal directly to your program.
19455 @code{signal} does not repeat when you press @key{RET} a second time
19456 after executing the command.
19458 @kindex queue-signal
19459 @item queue-signal @var{signal}
19460 Queue @var{signal} to be delivered immediately to the current thread
19461 when execution of the thread resumes. The @var{signal} can be the name or
19462 the number of a signal. For example, on many systems @code{signal 2} and
19463 @code{signal SIGINT} are both ways of sending an interrupt signal.
19464 The handling of the signal must be set to pass the signal to the program,
19465 otherwise @value{GDBN} will report an error.
19466 You can control the handling of signals from @value{GDBN} with the
19467 @code{handle} command (@pxref{Signals}).
19469 Alternatively, if @var{signal} is zero, any currently queued signal
19470 for the current thread is discarded and when execution resumes no signal
19471 will be delivered. This is useful when your program stopped on account
19472 of a signal and would ordinarily see the signal when resumed with the
19473 @code{continue} command.
19475 This command differs from the @code{signal} command in that the signal
19476 is just queued, execution is not resumed. And @code{queue-signal} cannot
19477 be used to pass a signal whose handling state has been set to @code{nopass}
19482 @xref{stepping into signal handlers}, for information on how stepping
19483 commands behave when the thread has a signal queued.
19486 @section Returning from a Function
19489 @cindex returning from a function
19492 @itemx return @var{expression}
19493 You can cancel execution of a function call with the @code{return}
19494 command. If you give an
19495 @var{expression} argument, its value is used as the function's return
19499 When you use @code{return}, @value{GDBN} discards the selected stack frame
19500 (and all frames within it). You can think of this as making the
19501 discarded frame return prematurely. If you wish to specify a value to
19502 be returned, give that value as the argument to @code{return}.
19504 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19505 Frame}), and any other frames inside of it, leaving its caller as the
19506 innermost remaining frame. That frame becomes selected. The
19507 specified value is stored in the registers used for returning values
19510 The @code{return} command does not resume execution; it leaves the
19511 program stopped in the state that would exist if the function had just
19512 returned. In contrast, the @code{finish} command (@pxref{Continuing
19513 and Stepping, ,Continuing and Stepping}) resumes execution until the
19514 selected stack frame returns naturally.
19516 @value{GDBN} needs to know how the @var{expression} argument should be set for
19517 the inferior. The concrete registers assignment depends on the OS ABI and the
19518 type being returned by the selected stack frame. For example it is common for
19519 OS ABI to return floating point values in FPU registers while integer values in
19520 CPU registers. Still some ABIs return even floating point values in CPU
19521 registers. Larger integer widths (such as @code{long long int}) also have
19522 specific placement rules. @value{GDBN} already knows the OS ABI from its
19523 current target so it needs to find out also the type being returned to make the
19524 assignment into the right register(s).
19526 Normally, the selected stack frame has debug info. @value{GDBN} will always
19527 use the debug info instead of the implicit type of @var{expression} when the
19528 debug info is available. For example, if you type @kbd{return -1}, and the
19529 function in the current stack frame is declared to return a @code{long long
19530 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19531 into a @code{long long int}:
19534 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19536 (@value{GDBP}) return -1
19537 Make func return now? (y or n) y
19538 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19539 43 printf ("result=%lld\n", func ());
19543 However, if the selected stack frame does not have a debug info, e.g., if the
19544 function was compiled without debug info, @value{GDBN} has to find out the type
19545 to return from user. Specifying a different type by mistake may set the value
19546 in different inferior registers than the caller code expects. For example,
19547 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19548 of a @code{long long int} result for a debug info less function (on 32-bit
19549 architectures). Therefore the user is required to specify the return type by
19550 an appropriate cast explicitly:
19553 Breakpoint 2, 0x0040050b in func ()
19554 (@value{GDBP}) return -1
19555 Return value type not available for selected stack frame.
19556 Please use an explicit cast of the value to return.
19557 (@value{GDBP}) return (long long int) -1
19558 Make selected stack frame return now? (y or n) y
19559 #0 0x00400526 in main ()
19564 @section Calling Program Functions
19567 @cindex calling functions
19568 @cindex inferior functions, calling
19569 @item print @var{expr}
19570 Evaluate the expression @var{expr} and display the resulting value.
19571 The expression may include calls to functions in the program being
19575 @item call @var{expr}
19576 Evaluate the expression @var{expr} without displaying @code{void}
19579 You can use this variant of the @code{print} command if you want to
19580 execute a function from your program that does not return anything
19581 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19582 with @code{void} returned values that @value{GDBN} will otherwise
19583 print. If the result is not void, it is printed and saved in the
19587 It is possible for the function you call via the @code{print} or
19588 @code{call} command to generate a signal (e.g., if there's a bug in
19589 the function, or if you passed it incorrect arguments). What happens
19590 in that case is controlled by the @code{set unwindonsignal} command.
19592 Similarly, with a C@t{++} program it is possible for the function you
19593 call via the @code{print} or @code{call} command to generate an
19594 exception that is not handled due to the constraints of the dummy
19595 frame. In this case, any exception that is raised in the frame, but has
19596 an out-of-frame exception handler will not be found. GDB builds a
19597 dummy-frame for the inferior function call, and the unwinder cannot
19598 seek for exception handlers outside of this dummy-frame. What happens
19599 in that case is controlled by the
19600 @code{set unwind-on-terminating-exception} command.
19603 @item set unwindonsignal
19604 @kindex set unwindonsignal
19605 @cindex unwind stack in called functions
19606 @cindex call dummy stack unwinding
19607 Set unwinding of the stack if a signal is received while in a function
19608 that @value{GDBN} called in the program being debugged. If set to on,
19609 @value{GDBN} unwinds the stack it created for the call and restores
19610 the context to what it was before the call. If set to off (the
19611 default), @value{GDBN} stops in the frame where the signal was
19614 @item show unwindonsignal
19615 @kindex show unwindonsignal
19616 Show the current setting of stack unwinding in the functions called by
19619 @item set unwind-on-terminating-exception
19620 @kindex set unwind-on-terminating-exception
19621 @cindex unwind stack in called functions with unhandled exceptions
19622 @cindex call dummy stack unwinding on unhandled exception.
19623 Set unwinding of the stack if a C@t{++} exception is raised, but left
19624 unhandled while in a function that @value{GDBN} called in the program being
19625 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19626 it created for the call and restores the context to what it was before
19627 the call. If set to off, @value{GDBN} the exception is delivered to
19628 the default C@t{++} exception handler and the inferior terminated.
19630 @item show unwind-on-terminating-exception
19631 @kindex show unwind-on-terminating-exception
19632 Show the current setting of stack unwinding in the functions called by
19635 @item set may-call-functions
19636 @kindex set may-call-functions
19637 @cindex disabling calling functions in the program
19638 @cindex calling functions in the program, disabling
19639 Set permission to call functions in the program.
19640 This controls whether @value{GDBN} will attempt to call functions in
19641 the program, such as with expressions in the @code{print} command. It
19642 defaults to @code{on}.
19644 To call a function in the program, @value{GDBN} has to temporarily
19645 modify the state of the inferior. This has potentially undesired side
19646 effects. Also, having @value{GDBN} call nested functions is likely to
19647 be erroneous and may even crash the program being debugged. You can
19648 avoid such hazards by forbidding @value{GDBN} from calling functions
19649 in the program being debugged. If calling functions in the program
19650 is forbidden, GDB will throw an error when a command (such as printing
19651 an expression) starts a function call in the program.
19653 @item show may-call-functions
19654 @kindex show may-call-functions
19655 Show permission to call functions in the program.
19659 @subsection Calling functions with no debug info
19661 @cindex no debug info functions
19662 Sometimes, a function you wish to call is missing debug information.
19663 In such case, @value{GDBN} does not know the type of the function,
19664 including the types of the function's parameters. To avoid calling
19665 the inferior function incorrectly, which could result in the called
19666 function functioning erroneously and even crash, @value{GDBN} refuses
19667 to call the function unless you tell it the type of the function.
19669 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19670 to do that. The simplest is to cast the call to the function's
19671 declared return type. For example:
19674 (@value{GDBP}) p getenv ("PATH")
19675 'getenv' has unknown return type; cast the call to its declared return type
19676 (@value{GDBP}) p (char *) getenv ("PATH")
19677 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19680 Casting the return type of a no-debug function is equivalent to
19681 casting the function to a pointer to a prototyped function that has a
19682 prototype that matches the types of the passed-in arguments, and
19683 calling that. I.e., the call above is equivalent to:
19686 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19690 and given this prototyped C or C++ function with float parameters:
19693 float multiply (float v1, float v2) @{ return v1 * v2; @}
19697 these calls are equivalent:
19700 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19701 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19704 If the function you wish to call is declared as unprototyped (i.e.@:
19705 old K&R style), you must use the cast-to-function-pointer syntax, so
19706 that @value{GDBN} knows that it needs to apply default argument
19707 promotions (promote float arguments to double). @xref{ABI, float
19708 promotion}. For example, given this unprototyped C function with
19709 float parameters, and no debug info:
19713 multiply_noproto (v1, v2)
19721 you call it like this:
19724 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19728 @section Patching Programs
19730 @cindex patching binaries
19731 @cindex writing into executables
19732 @cindex writing into corefiles
19734 By default, @value{GDBN} opens the file containing your program's
19735 executable code (or the corefile) read-only. This prevents accidental
19736 alterations to machine code; but it also prevents you from intentionally
19737 patching your program's binary.
19739 If you'd like to be able to patch the binary, you can specify that
19740 explicitly with the @code{set write} command. For example, you might
19741 want to turn on internal debugging flags, or even to make emergency
19747 @itemx set write off
19748 If you specify @samp{set write on}, @value{GDBN} opens executable and
19749 core files for both reading and writing; if you specify @kbd{set write
19750 off} (the default), @value{GDBN} opens them read-only.
19752 If you have already loaded a file, you must load it again (using the
19753 @code{exec-file} or @code{core-file} command) after changing @code{set
19754 write}, for your new setting to take effect.
19758 Display whether executable files and core files are opened for writing
19759 as well as reading.
19762 @node Compiling and Injecting Code
19763 @section Compiling and injecting code in @value{GDBN}
19764 @cindex injecting code
19765 @cindex writing into executables
19766 @cindex compiling code
19768 @value{GDBN} supports on-demand compilation and code injection into
19769 programs running under @value{GDBN}. GCC 5.0 or higher built with
19770 @file{libcc1.so} must be installed for this functionality to be enabled.
19771 This functionality is implemented with the following commands.
19774 @kindex compile code
19775 @item compile code @var{source-code}
19776 @itemx compile code -raw @var{--} @var{source-code}
19777 Compile @var{source-code} with the compiler language found as the current
19778 language in @value{GDBN} (@pxref{Languages}). If compilation and
19779 injection is not supported with the current language specified in
19780 @value{GDBN}, or the compiler does not support this feature, an error
19781 message will be printed. If @var{source-code} compiles and links
19782 successfully, @value{GDBN} will load the object-code emitted,
19783 and execute it within the context of the currently selected inferior.
19784 It is important to note that the compiled code is executed immediately.
19785 After execution, the compiled code is removed from @value{GDBN} and any
19786 new types or variables you have defined will be deleted.
19788 The command allows you to specify @var{source-code} in two ways.
19789 The simplest method is to provide a single line of code to the command.
19793 compile code printf ("hello world\n");
19796 If you specify options on the command line as well as source code, they
19797 may conflict. The @samp{--} delimiter can be used to separate options
19798 from actual source code. E.g.:
19801 compile code -r -- printf ("hello world\n");
19804 Alternatively you can enter source code as multiple lines of text. To
19805 enter this mode, invoke the @samp{compile code} command without any text
19806 following the command. This will start the multiple-line editor and
19807 allow you to type as many lines of source code as required. When you
19808 have completed typing, enter @samp{end} on its own line to exit the
19813 >printf ("hello\n");
19814 >printf ("world\n");
19818 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
19819 provided @var{source-code} in a callable scope. In this case, you must
19820 specify the entry point of the code by defining a function named
19821 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
19822 inferior. Using @samp{-raw} option may be needed for example when
19823 @var{source-code} requires @samp{#include} lines which may conflict with
19824 inferior symbols otherwise.
19826 @kindex compile file
19827 @item compile file @var{filename}
19828 @itemx compile file -raw @var{filename}
19829 Like @code{compile code}, but take the source code from @var{filename}.
19832 compile file /home/user/example.c
19837 @item compile print [[@var{options}] --] @var{expr}
19838 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
19839 Compile and execute @var{expr} with the compiler language found as the
19840 current language in @value{GDBN} (@pxref{Languages}). By default the
19841 value of @var{expr} is printed in a format appropriate to its data type;
19842 you can choose a different format by specifying @samp{/@var{f}}, where
19843 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
19844 Formats}. The @code{compile print} command accepts the same options
19845 as the @code{print} command; see @ref{print options}.
19847 @item compile print [[@var{options}] --]
19848 @itemx compile print [[@var{options}] --] /@var{f}
19849 @cindex reprint the last value
19850 Alternatively you can enter the expression (source code producing it) as
19851 multiple lines of text. To enter this mode, invoke the @samp{compile print}
19852 command without any text following the command. This will start the
19853 multiple-line editor.
19857 The process of compiling and injecting the code can be inspected using:
19860 @anchor{set debug compile}
19861 @item set debug compile
19862 @cindex compile command debugging info
19863 Turns on or off display of @value{GDBN} process of compiling and
19864 injecting the code. The default is off.
19866 @item show debug compile
19867 Displays the current state of displaying @value{GDBN} process of
19868 compiling and injecting the code.
19870 @anchor{set debug compile-cplus-types}
19871 @item set debug compile-cplus-types
19872 @cindex compile C@t{++} type conversion
19873 Turns on or off the display of C@t{++} type conversion debugging information.
19874 The default is off.
19876 @item show debug compile-cplus-types
19877 Displays the current state of displaying debugging information for
19878 C@t{++} type conversion.
19881 @subsection Compilation options for the @code{compile} command
19883 @value{GDBN} needs to specify the right compilation options for the code
19884 to be injected, in part to make its ABI compatible with the inferior
19885 and in part to make the injected code compatible with @value{GDBN}'s
19889 The options used, in increasing precedence:
19892 @item target architecture and OS options (@code{gdbarch})
19893 These options depend on target processor type and target operating
19894 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19895 (@code{-m64}) compilation option.
19897 @item compilation options recorded in the target
19898 @value{NGCC} (since version 4.7) stores the options used for compilation
19899 into @code{DW_AT_producer} part of DWARF debugging information according
19900 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19901 explicitly specify @code{-g} during inferior compilation otherwise
19902 @value{NGCC} produces no DWARF. This feature is only relevant for
19903 platforms where @code{-g} produces DWARF by default, otherwise one may
19904 try to enforce DWARF by using @code{-gdwarf-4}.
19906 @item compilation options set by @code{set compile-args}
19910 You can override compilation options using the following command:
19913 @item set compile-args
19914 @cindex compile command options override
19915 Set compilation options used for compiling and injecting code with the
19916 @code{compile} commands. These options override any conflicting ones
19917 from the target architecture and/or options stored during inferior
19920 @item show compile-args
19921 Displays the current state of compilation options override.
19922 This does not show all the options actually used during compilation,
19923 use @ref{set debug compile} for that.
19926 @subsection Caveats when using the @code{compile} command
19928 There are a few caveats to keep in mind when using the @code{compile}
19929 command. As the caveats are different per language, the table below
19930 highlights specific issues on a per language basis.
19933 @item C code examples and caveats
19934 When the language in @value{GDBN} is set to @samp{C}, the compiler will
19935 attempt to compile the source code with a @samp{C} compiler. The source
19936 code provided to the @code{compile} command will have much the same
19937 access to variables and types as it normally would if it were part of
19938 the program currently being debugged in @value{GDBN}.
19940 Below is a sample program that forms the basis of the examples that
19941 follow. This program has been compiled and loaded into @value{GDBN},
19942 much like any other normal debugging session.
19945 void function1 (void)
19948 printf ("function 1\n");
19951 void function2 (void)
19966 For the purposes of the examples in this section, the program above has
19967 been compiled, loaded into @value{GDBN}, stopped at the function
19968 @code{main}, and @value{GDBN} is awaiting input from the user.
19970 To access variables and types for any program in @value{GDBN}, the
19971 program must be compiled and packaged with debug information. The
19972 @code{compile} command is not an exception to this rule. Without debug
19973 information, you can still use the @code{compile} command, but you will
19974 be very limited in what variables and types you can access.
19976 So with that in mind, the example above has been compiled with debug
19977 information enabled. The @code{compile} command will have access to
19978 all variables and types (except those that may have been optimized
19979 out). Currently, as @value{GDBN} has stopped the program in the
19980 @code{main} function, the @code{compile} command would have access to
19981 the variable @code{k}. You could invoke the @code{compile} command
19982 and type some source code to set the value of @code{k}. You can also
19983 read it, or do anything with that variable you would normally do in
19984 @code{C}. Be aware that changes to inferior variables in the
19985 @code{compile} command are persistent. In the following example:
19988 compile code k = 3;
19992 the variable @code{k} is now 3. It will retain that value until
19993 something else in the example program changes it, or another
19994 @code{compile} command changes it.
19996 Normal scope and access rules apply to source code compiled and
19997 injected by the @code{compile} command. In the example, the variables
19998 @code{j} and @code{k} are not accessible yet, because the program is
19999 currently stopped in the @code{main} function, where these variables
20000 are not in scope. Therefore, the following command
20003 compile code j = 3;
20007 will result in a compilation error message.
20009 Once the program is continued, execution will bring these variables in
20010 scope, and they will become accessible; then the code you specify via
20011 the @code{compile} command will be able to access them.
20013 You can create variables and types with the @code{compile} command as
20014 part of your source code. Variables and types that are created as part
20015 of the @code{compile} command are not visible to the rest of the program for
20016 the duration of its run. This example is valid:
20019 compile code int ff = 5; printf ("ff is %d\n", ff);
20022 However, if you were to type the following into @value{GDBN} after that
20023 command has completed:
20026 compile code printf ("ff is %d\n'', ff);
20030 a compiler error would be raised as the variable @code{ff} no longer
20031 exists. Object code generated and injected by the @code{compile}
20032 command is removed when its execution ends. Caution is advised
20033 when assigning to program variables values of variables created by the
20034 code submitted to the @code{compile} command. This example is valid:
20037 compile code int ff = 5; k = ff;
20040 The value of the variable @code{ff} is assigned to @code{k}. The variable
20041 @code{k} does not require the existence of @code{ff} to maintain the value
20042 it has been assigned. However, pointers require particular care in
20043 assignment. If the source code compiled with the @code{compile} command
20044 changed the address of a pointer in the example program, perhaps to a
20045 variable created in the @code{compile} command, that pointer would point
20046 to an invalid location when the command exits. The following example
20047 would likely cause issues with your debugged program:
20050 compile code int ff = 5; p = &ff;
20053 In this example, @code{p} would point to @code{ff} when the
20054 @code{compile} command is executing the source code provided to it.
20055 However, as variables in the (example) program persist with their
20056 assigned values, the variable @code{p} would point to an invalid
20057 location when the command exists. A general rule should be followed
20058 in that you should either assign @code{NULL} to any assigned pointers,
20059 or restore a valid location to the pointer before the command exits.
20061 Similar caution must be exercised with any structs, unions, and typedefs
20062 defined in @code{compile} command. Types defined in the @code{compile}
20063 command will no longer be available in the next @code{compile} command.
20064 Therefore, if you cast a variable to a type defined in the
20065 @code{compile} command, care must be taken to ensure that any future
20066 need to resolve the type can be achieved.
20069 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20070 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20071 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20072 Compilation failed.
20073 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20077 Variables that have been optimized away by the compiler are not
20078 accessible to the code submitted to the @code{compile} command.
20079 Access to those variables will generate a compiler error which @value{GDBN}
20080 will print to the console.
20083 @subsection Compiler search for the @code{compile} command
20085 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20086 which may not be obvious for remote targets of different architecture
20087 than where @value{GDBN} is running. Environment variable @code{PATH} on
20088 @value{GDBN} host is searched for @value{NGCC} binary matching the
20089 target architecture and operating system. This search can be overriden
20090 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
20091 taken from shell that executed @value{GDBN}, it is not the value set by
20092 @value{GDBN} command @code{set environment}). @xref{Environment}.
20095 Specifically @code{PATH} is searched for binaries matching regular expression
20096 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20097 debugged. @var{arch} is processor name --- multiarch is supported, so for
20098 example both @code{i386} and @code{x86_64} targets look for pattern
20099 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20100 for pattern @code{s390x?}. @var{os} is currently supported only for
20101 pattern @code{linux(-gnu)?}.
20103 On Posix hosts the compiler driver @value{GDBN} needs to find also
20104 shared library @file{libcc1.so} from the compiler. It is searched in
20105 default shared library search path (overridable with usual environment
20106 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
20107 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20108 according to the installation of the found compiler --- as possibly
20109 specified by the @code{set compile-gcc} command.
20112 @item set compile-gcc
20113 @cindex compile command driver filename override
20114 Set compilation command used for compiling and injecting code with the
20115 @code{compile} commands. If this option is not set (it is set to
20116 an empty string), the search described above will occur --- that is the
20119 @item show compile-gcc
20120 Displays the current compile command @value{NGCC} driver filename.
20121 If set, it is the main command @command{gcc}, found usually for example
20122 under name @file{x86_64-linux-gnu-gcc}.
20126 @chapter @value{GDBN} Files
20128 @value{GDBN} needs to know the file name of the program to be debugged,
20129 both in order to read its symbol table and in order to start your
20130 program. To debug a core dump of a previous run, you must also tell
20131 @value{GDBN} the name of the core dump file.
20134 * Files:: Commands to specify files
20135 * File Caching:: Information about @value{GDBN}'s file caching
20136 * Separate Debug Files:: Debugging information in separate files
20137 * MiniDebugInfo:: Debugging information in a special section
20138 * Index Files:: Index files speed up GDB
20139 * Symbol Errors:: Errors reading symbol files
20140 * Data Files:: GDB data files
20144 @section Commands to Specify Files
20146 @cindex symbol table
20147 @cindex core dump file
20149 You may want to specify executable and core dump file names. The usual
20150 way to do this is at start-up time, using the arguments to
20151 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20152 Out of @value{GDBN}}).
20154 Occasionally it is necessary to change to a different file during a
20155 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20156 specify a file you want to use. Or you are debugging a remote target
20157 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20158 Program}). In these situations the @value{GDBN} commands to specify
20159 new files are useful.
20162 @cindex executable file
20164 @item file @var{filename}
20165 Use @var{filename} as the program to be debugged. It is read for its
20166 symbols and for the contents of pure memory. It is also the program
20167 executed when you use the @code{run} command. If you do not specify a
20168 directory and the file is not found in the @value{GDBN} working directory,
20169 @value{GDBN} uses the environment variable @code{PATH} as a list of
20170 directories to search, just as the shell does when looking for a program
20171 to run. You can change the value of this variable, for both @value{GDBN}
20172 and your program, using the @code{path} command.
20174 @cindex unlinked object files
20175 @cindex patching object files
20176 You can load unlinked object @file{.o} files into @value{GDBN} using
20177 the @code{file} command. You will not be able to ``run'' an object
20178 file, but you can disassemble functions and inspect variables. Also,
20179 if the underlying BFD functionality supports it, you could use
20180 @kbd{gdb -write} to patch object files using this technique. Note
20181 that @value{GDBN} can neither interpret nor modify relocations in this
20182 case, so branches and some initialized variables will appear to go to
20183 the wrong place. But this feature is still handy from time to time.
20186 @code{file} with no argument makes @value{GDBN} discard any information it
20187 has on both executable file and the symbol table.
20190 @item exec-file @r{[} @var{filename} @r{]}
20191 Specify that the program to be run (but not the symbol table) is found
20192 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
20193 if necessary to locate your program. Omitting @var{filename} means to
20194 discard information on the executable file.
20196 @kindex symbol-file
20197 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20198 Read symbol table information from file @var{filename}. @code{PATH} is
20199 searched when necessary. Use the @code{file} command to get both symbol
20200 table and program to run from the same file.
20202 If an optional @var{offset} is specified, it is added to the start
20203 address of each section in the symbol file. This is useful if the
20204 program is relocated at runtime, such as the Linux kernel with kASLR
20207 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20208 program's symbol table.
20210 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20211 some breakpoints and auto-display expressions. This is because they may
20212 contain pointers to the internal data recording symbols and data types,
20213 which are part of the old symbol table data being discarded inside
20216 @code{symbol-file} does not repeat if you press @key{RET} again after
20219 When @value{GDBN} is configured for a particular environment, it
20220 understands debugging information in whatever format is the standard
20221 generated for that environment; you may use either a @sc{gnu} compiler, or
20222 other compilers that adhere to the local conventions.
20223 Best results are usually obtained from @sc{gnu} compilers; for example,
20224 using @code{@value{NGCC}} you can generate debugging information for
20227 For most kinds of object files, with the exception of old SVR3 systems
20228 using COFF, the @code{symbol-file} command does not normally read the
20229 symbol table in full right away. Instead, it scans the symbol table
20230 quickly to find which source files and which symbols are present. The
20231 details are read later, one source file at a time, as they are needed.
20233 The purpose of this two-stage reading strategy is to make @value{GDBN}
20234 start up faster. For the most part, it is invisible except for
20235 occasional pauses while the symbol table details for a particular source
20236 file are being read. (The @code{set verbose} command can turn these
20237 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20238 Warnings and Messages}.)
20240 We have not implemented the two-stage strategy for COFF yet. When the
20241 symbol table is stored in COFF format, @code{symbol-file} reads the
20242 symbol table data in full right away. Note that ``stabs-in-COFF''
20243 still does the two-stage strategy, since the debug info is actually
20247 @cindex reading symbols immediately
20248 @cindex symbols, reading immediately
20249 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20250 @itemx file @r{[} -readnow @r{]} @var{filename}
20251 You can override the @value{GDBN} two-stage strategy for reading symbol
20252 tables by using the @samp{-readnow} option with any of the commands that
20253 load symbol table information, if you want to be sure @value{GDBN} has the
20254 entire symbol table available.
20256 @cindex @code{-readnever}, option for symbol-file command
20257 @cindex never read symbols
20258 @cindex symbols, never read
20259 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20260 @itemx file @r{[} -readnever @r{]} @var{filename}
20261 You can instruct @value{GDBN} to never read the symbolic information
20262 contained in @var{filename} by using the @samp{-readnever} option.
20263 @xref{--readnever}.
20265 @c FIXME: for now no mention of directories, since this seems to be in
20266 @c flux. 13mar1992 status is that in theory GDB would look either in
20267 @c current dir or in same dir as myprog; but issues like competing
20268 @c GDB's, or clutter in system dirs, mean that in practice right now
20269 @c only current dir is used. FFish says maybe a special GDB hierarchy
20270 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20274 @item core-file @r{[}@var{filename}@r{]}
20276 Specify the whereabouts of a core dump file to be used as the ``contents
20277 of memory''. Traditionally, core files contain only some parts of the
20278 address space of the process that generated them; @value{GDBN} can access the
20279 executable file itself for other parts.
20281 @code{core-file} with no argument specifies that no core file is
20284 Note that the core file is ignored when your program is actually running
20285 under @value{GDBN}. So, if you have been running your program and you
20286 wish to debug a core file instead, you must kill the subprocess in which
20287 the program is running. To do this, use the @code{kill} command
20288 (@pxref{Kill Process, ,Killing the Child Process}).
20290 @kindex add-symbol-file
20291 @cindex dynamic linking
20292 @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{]}
20293 The @code{add-symbol-file} command reads additional symbol table
20294 information from the file @var{filename}. You would use this command
20295 when @var{filename} has been dynamically loaded (by some other means)
20296 into the program that is running. The @var{textaddress} parameter gives
20297 the memory address at which the file's text section has been loaded.
20298 You can additionally specify the base address of other sections using
20299 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20300 If a section is omitted, @value{GDBN} will use its default addresses
20301 as found in @var{filename}. Any @var{address} or @var{textaddress}
20302 can be given as an expression.
20304 If an optional @var{offset} is specified, it is added to the start
20305 address of each section, except those for which the address was
20306 specified explicitly.
20308 The symbol table of the file @var{filename} is added to the symbol table
20309 originally read with the @code{symbol-file} command. You can use the
20310 @code{add-symbol-file} command any number of times; the new symbol data
20311 thus read is kept in addition to the old.
20313 Changes can be reverted using the command @code{remove-symbol-file}.
20315 @cindex relocatable object files, reading symbols from
20316 @cindex object files, relocatable, reading symbols from
20317 @cindex reading symbols from relocatable object files
20318 @cindex symbols, reading from relocatable object files
20319 @cindex @file{.o} files, reading symbols from
20320 Although @var{filename} is typically a shared library file, an
20321 executable file, or some other object file which has been fully
20322 relocated for loading into a process, you can also load symbolic
20323 information from relocatable @file{.o} files, as long as:
20327 the file's symbolic information refers only to linker symbols defined in
20328 that file, not to symbols defined by other object files,
20330 every section the file's symbolic information refers to has actually
20331 been loaded into the inferior, as it appears in the file, and
20333 you can determine the address at which every section was loaded, and
20334 provide these to the @code{add-symbol-file} command.
20338 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20339 relocatable files into an already running program; such systems
20340 typically make the requirements above easy to meet. However, it's
20341 important to recognize that many native systems use complex link
20342 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20343 assembly, for example) that make the requirements difficult to meet. In
20344 general, one cannot assume that using @code{add-symbol-file} to read a
20345 relocatable object file's symbolic information will have the same effect
20346 as linking the relocatable object file into the program in the normal
20349 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20351 @kindex remove-symbol-file
20352 @item remove-symbol-file @var{filename}
20353 @item remove-symbol-file -a @var{address}
20354 Remove a symbol file added via the @code{add-symbol-file} command. The
20355 file to remove can be identified by its @var{filename} or by an @var{address}
20356 that lies within the boundaries of this symbol file in memory. Example:
20359 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20360 add symbol table from file "/home/user/gdb/mylib.so" at
20361 .text_addr = 0x7ffff7ff9480
20363 Reading symbols from /home/user/gdb/mylib.so...done.
20364 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20365 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20370 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20372 @kindex add-symbol-file-from-memory
20373 @cindex @code{syscall DSO}
20374 @cindex load symbols from memory
20375 @item add-symbol-file-from-memory @var{address}
20376 Load symbols from the given @var{address} in a dynamically loaded
20377 object file whose image is mapped directly into the inferior's memory.
20378 For example, the Linux kernel maps a @code{syscall DSO} into each
20379 process's address space; this DSO provides kernel-specific code for
20380 some system calls. The argument can be any expression whose
20381 evaluation yields the address of the file's shared object file header.
20382 For this command to work, you must have used @code{symbol-file} or
20383 @code{exec-file} commands in advance.
20386 @item section @var{section} @var{addr}
20387 The @code{section} command changes the base address of the named
20388 @var{section} of the exec file to @var{addr}. This can be used if the
20389 exec file does not contain section addresses, (such as in the
20390 @code{a.out} format), or when the addresses specified in the file
20391 itself are wrong. Each section must be changed separately. The
20392 @code{info files} command, described below, lists all the sections and
20396 @kindex info target
20399 @code{info files} and @code{info target} are synonymous; both print the
20400 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20401 including the names of the executable and core dump files currently in
20402 use by @value{GDBN}, and the files from which symbols were loaded. The
20403 command @code{help target} lists all possible targets rather than
20406 @kindex maint info sections
20407 @item maint info sections
20408 Another command that can give you extra information about program sections
20409 is @code{maint info sections}. In addition to the section information
20410 displayed by @code{info files}, this command displays the flags and file
20411 offset of each section in the executable and core dump files. In addition,
20412 @code{maint info sections} provides the following command options (which
20413 may be arbitrarily combined):
20417 Display sections for all loaded object files, including shared libraries.
20418 @item @var{sections}
20419 Display info only for named @var{sections}.
20420 @item @var{section-flags}
20421 Display info only for sections for which @var{section-flags} are true.
20422 The section flags that @value{GDBN} currently knows about are:
20425 Section will have space allocated in the process when loaded.
20426 Set for all sections except those containing debug information.
20428 Section will be loaded from the file into the child process memory.
20429 Set for pre-initialized code and data, clear for @code{.bss} sections.
20431 Section needs to be relocated before loading.
20433 Section cannot be modified by the child process.
20435 Section contains executable code only.
20437 Section contains data only (no executable code).
20439 Section will reside in ROM.
20441 Section contains data for constructor/destructor lists.
20443 Section is not empty.
20445 An instruction to the linker to not output the section.
20446 @item COFF_SHARED_LIBRARY
20447 A notification to the linker that the section contains
20448 COFF shared library information.
20450 Section contains common symbols.
20453 @kindex set trust-readonly-sections
20454 @cindex read-only sections
20455 @item set trust-readonly-sections on
20456 Tell @value{GDBN} that readonly sections in your object file
20457 really are read-only (i.e.@: that their contents will not change).
20458 In that case, @value{GDBN} can fetch values from these sections
20459 out of the object file, rather than from the target program.
20460 For some targets (notably embedded ones), this can be a significant
20461 enhancement to debugging performance.
20463 The default is off.
20465 @item set trust-readonly-sections off
20466 Tell @value{GDBN} not to trust readonly sections. This means that
20467 the contents of the section might change while the program is running,
20468 and must therefore be fetched from the target when needed.
20470 @item show trust-readonly-sections
20471 Show the current setting of trusting readonly sections.
20474 All file-specifying commands allow both absolute and relative file names
20475 as arguments. @value{GDBN} always converts the file name to an absolute file
20476 name and remembers it that way.
20478 @cindex shared libraries
20479 @anchor{Shared Libraries}
20480 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20481 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20482 DSBT (TIC6X) shared libraries.
20484 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20485 shared libraries. @xref{Expat}.
20487 @value{GDBN} automatically loads symbol definitions from shared libraries
20488 when you use the @code{run} command, or when you examine a core file.
20489 (Before you issue the @code{run} command, @value{GDBN} does not understand
20490 references to a function in a shared library, however---unless you are
20491 debugging a core file).
20493 @c FIXME: some @value{GDBN} release may permit some refs to undef
20494 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20495 @c FIXME...lib; check this from time to time when updating manual
20497 There are times, however, when you may wish to not automatically load
20498 symbol definitions from shared libraries, such as when they are
20499 particularly large or there are many of them.
20501 To control the automatic loading of shared library symbols, use the
20505 @kindex set auto-solib-add
20506 @item set auto-solib-add @var{mode}
20507 If @var{mode} is @code{on}, symbols from all shared object libraries
20508 will be loaded automatically when the inferior begins execution, you
20509 attach to an independently started inferior, or when the dynamic linker
20510 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20511 is @code{off}, symbols must be loaded manually, using the
20512 @code{sharedlibrary} command. The default value is @code{on}.
20514 @cindex memory used for symbol tables
20515 If your program uses lots of shared libraries with debug info that
20516 takes large amounts of memory, you can decrease the @value{GDBN}
20517 memory footprint by preventing it from automatically loading the
20518 symbols from shared libraries. To that end, type @kbd{set
20519 auto-solib-add off} before running the inferior, then load each
20520 library whose debug symbols you do need with @kbd{sharedlibrary
20521 @var{regexp}}, where @var{regexp} is a regular expression that matches
20522 the libraries whose symbols you want to be loaded.
20524 @kindex show auto-solib-add
20525 @item show auto-solib-add
20526 Display the current autoloading mode.
20529 @cindex load shared library
20530 To explicitly load shared library symbols, use the @code{sharedlibrary}
20534 @kindex info sharedlibrary
20536 @item info share @var{regex}
20537 @itemx info sharedlibrary @var{regex}
20538 Print the names of the shared libraries which are currently loaded
20539 that match @var{regex}. If @var{regex} is omitted then print
20540 all shared libraries that are loaded.
20543 @item info dll @var{regex}
20544 This is an alias of @code{info sharedlibrary}.
20546 @kindex sharedlibrary
20548 @item sharedlibrary @var{regex}
20549 @itemx share @var{regex}
20550 Load shared object library symbols for files matching a
20551 Unix regular expression.
20552 As with files loaded automatically, it only loads shared libraries
20553 required by your program for a core file or after typing @code{run}. If
20554 @var{regex} is omitted all shared libraries required by your program are
20557 @item nosharedlibrary
20558 @kindex nosharedlibrary
20559 @cindex unload symbols from shared libraries
20560 Unload all shared object library symbols. This discards all symbols
20561 that have been loaded from all shared libraries. Symbols from shared
20562 libraries that were loaded by explicit user requests are not
20566 Sometimes you may wish that @value{GDBN} stops and gives you control
20567 when any of shared library events happen. The best way to do this is
20568 to use @code{catch load} and @code{catch unload} (@pxref{Set
20571 @value{GDBN} also supports the the @code{set stop-on-solib-events}
20572 command for this. This command exists for historical reasons. It is
20573 less useful than setting a catchpoint, because it does not allow for
20574 conditions or commands as a catchpoint does.
20577 @item set stop-on-solib-events
20578 @kindex set stop-on-solib-events
20579 This command controls whether @value{GDBN} should give you control
20580 when the dynamic linker notifies it about some shared library event.
20581 The most common event of interest is loading or unloading of a new
20584 @item show stop-on-solib-events
20585 @kindex show stop-on-solib-events
20586 Show whether @value{GDBN} stops and gives you control when shared
20587 library events happen.
20590 Shared libraries are also supported in many cross or remote debugging
20591 configurations. @value{GDBN} needs to have access to the target's libraries;
20592 this can be accomplished either by providing copies of the libraries
20593 on the host system, or by asking @value{GDBN} to automatically retrieve the
20594 libraries from the target. If copies of the target libraries are
20595 provided, they need to be the same as the target libraries, although the
20596 copies on the target can be stripped as long as the copies on the host are
20599 @cindex where to look for shared libraries
20600 For remote debugging, you need to tell @value{GDBN} where the target
20601 libraries are, so that it can load the correct copies---otherwise, it
20602 may try to load the host's libraries. @value{GDBN} has two variables
20603 to specify the search directories for target libraries.
20606 @cindex prefix for executable and shared library file names
20607 @cindex system root, alternate
20608 @kindex set solib-absolute-prefix
20609 @kindex set sysroot
20610 @item set sysroot @var{path}
20611 Use @var{path} as the system root for the program being debugged. Any
20612 absolute shared library paths will be prefixed with @var{path}; many
20613 runtime loaders store the absolute paths to the shared library in the
20614 target program's memory. When starting processes remotely, and when
20615 attaching to already-running processes (local or remote), their
20616 executable filenames will be prefixed with @var{path} if reported to
20617 @value{GDBN} as absolute by the operating system. If you use
20618 @code{set sysroot} to find executables and shared libraries, they need
20619 to be laid out in the same way that they are on the target, with
20620 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20623 If @var{path} starts with the sequence @file{target:} and the target
20624 system is remote then @value{GDBN} will retrieve the target binaries
20625 from the remote system. This is only supported when using a remote
20626 target that supports the @code{remote get} command (@pxref{File
20627 Transfer,,Sending files to a remote system}). The part of @var{path}
20628 following the initial @file{target:} (if present) is used as system
20629 root prefix on the remote file system. If @var{path} starts with the
20630 sequence @file{remote:} this is converted to the sequence
20631 @file{target:} by @code{set sysroot}@footnote{Historically the
20632 functionality to retrieve binaries from the remote system was
20633 provided by prefixing @var{path} with @file{remote:}}. If you want
20634 to specify a local system root using a directory that happens to be
20635 named @file{target:} or @file{remote:}, you need to use some
20636 equivalent variant of the name like @file{./target:}.
20638 For targets with an MS-DOS based filesystem, such as MS-Windows and
20639 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20640 absolute file name with @var{path}. But first, on Unix hosts,
20641 @value{GDBN} converts all backslash directory separators into forward
20642 slashes, because the backslash is not a directory separator on Unix:
20645 c:\foo\bar.dll @result{} c:/foo/bar.dll
20648 Then, @value{GDBN} attempts prefixing the target file name with
20649 @var{path}, and looks for the resulting file name in the host file
20653 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20656 If that does not find the binary, @value{GDBN} tries removing
20657 the @samp{:} character from the drive spec, both for convenience, and,
20658 for the case of the host file system not supporting file names with
20662 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20665 This makes it possible to have a system root that mirrors a target
20666 with more than one drive. E.g., you may want to setup your local
20667 copies of the target system shared libraries like so (note @samp{c} vs
20671 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20672 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20673 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20677 and point the system root at @file{/path/to/sysroot}, so that
20678 @value{GDBN} can find the correct copies of both
20679 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20681 If that still does not find the binary, @value{GDBN} tries
20682 removing the whole drive spec from the target file name:
20685 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20688 This last lookup makes it possible to not care about the drive name,
20689 if you don't want or need to.
20691 The @code{set solib-absolute-prefix} command is an alias for @code{set
20694 @cindex default system root
20695 @cindex @samp{--with-sysroot}
20696 You can set the default system root by using the configure-time
20697 @samp{--with-sysroot} option. If the system root is inside
20698 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20699 @samp{--exec-prefix}), then the default system root will be updated
20700 automatically if the installed @value{GDBN} is moved to a new
20703 @kindex show sysroot
20705 Display the current executable and shared library prefix.
20707 @kindex set solib-search-path
20708 @item set solib-search-path @var{path}
20709 If this variable is set, @var{path} is a colon-separated list of
20710 directories to search for shared libraries. @samp{solib-search-path}
20711 is used after @samp{sysroot} fails to locate the library, or if the
20712 path to the library is relative instead of absolute. If you want to
20713 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20714 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20715 finding your host's libraries. @samp{sysroot} is preferred; setting
20716 it to a nonexistent directory may interfere with automatic loading
20717 of shared library symbols.
20719 @kindex show solib-search-path
20720 @item show solib-search-path
20721 Display the current shared library search path.
20723 @cindex DOS file-name semantics of file names.
20724 @kindex set target-file-system-kind (unix|dos-based|auto)
20725 @kindex show target-file-system-kind
20726 @item set target-file-system-kind @var{kind}
20727 Set assumed file system kind for target reported file names.
20729 Shared library file names as reported by the target system may not
20730 make sense as is on the system @value{GDBN} is running on. For
20731 example, when remote debugging a target that has MS-DOS based file
20732 system semantics, from a Unix host, the target may be reporting to
20733 @value{GDBN} a list of loaded shared libraries with file names such as
20734 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20735 drive letters, so the @samp{c:\} prefix is not normally understood as
20736 indicating an absolute file name, and neither is the backslash
20737 normally considered a directory separator character. In that case,
20738 the native file system would interpret this whole absolute file name
20739 as a relative file name with no directory components. This would make
20740 it impossible to point @value{GDBN} at a copy of the remote target's
20741 shared libraries on the host using @code{set sysroot}, and impractical
20742 with @code{set solib-search-path}. Setting
20743 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20744 to interpret such file names similarly to how the target would, and to
20745 map them to file names valid on @value{GDBN}'s native file system
20746 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20747 to one of the supported file system kinds. In that case, @value{GDBN}
20748 tries to determine the appropriate file system variant based on the
20749 current target's operating system (@pxref{ABI, ,Configuring the
20750 Current ABI}). The supported file system settings are:
20754 Instruct @value{GDBN} to assume the target file system is of Unix
20755 kind. Only file names starting the forward slash (@samp{/}) character
20756 are considered absolute, and the directory separator character is also
20760 Instruct @value{GDBN} to assume the target file system is DOS based.
20761 File names starting with either a forward slash, or a drive letter
20762 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20763 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20764 considered directory separators.
20767 Instruct @value{GDBN} to use the file system kind associated with the
20768 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20769 This is the default.
20773 @cindex file name canonicalization
20774 @cindex base name differences
20775 When processing file names provided by the user, @value{GDBN}
20776 frequently needs to compare them to the file names recorded in the
20777 program's debug info. Normally, @value{GDBN} compares just the
20778 @dfn{base names} of the files as strings, which is reasonably fast
20779 even for very large programs. (The base name of a file is the last
20780 portion of its name, after stripping all the leading directories.)
20781 This shortcut in comparison is based upon the assumption that files
20782 cannot have more than one base name. This is usually true, but
20783 references to files that use symlinks or similar filesystem
20784 facilities violate that assumption. If your program records files
20785 using such facilities, or if you provide file names to @value{GDBN}
20786 using symlinks etc., you can set @code{basenames-may-differ} to
20787 @code{true} to instruct @value{GDBN} to completely canonicalize each
20788 pair of file names it needs to compare. This will make file-name
20789 comparisons accurate, but at a price of a significant slowdown.
20792 @item set basenames-may-differ
20793 @kindex set basenames-may-differ
20794 Set whether a source file may have multiple base names.
20796 @item show basenames-may-differ
20797 @kindex show basenames-may-differ
20798 Show whether a source file may have multiple base names.
20802 @section File Caching
20803 @cindex caching of opened files
20804 @cindex caching of bfd objects
20806 To speed up file loading, and reduce memory usage, @value{GDBN} will
20807 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
20808 BFD, bfd, The Binary File Descriptor Library}. The following commands
20809 allow visibility and control of the caching behavior.
20812 @kindex maint info bfds
20813 @item maint info bfds
20814 This prints information about each @code{bfd} object that is known to
20817 @kindex maint set bfd-sharing
20818 @kindex maint show bfd-sharing
20819 @kindex bfd caching
20820 @item maint set bfd-sharing
20821 @item maint show bfd-sharing
20822 Control whether @code{bfd} objects can be shared. When sharing is
20823 enabled @value{GDBN} reuses already open @code{bfd} objects rather
20824 than reopening the same file. Turning sharing off does not cause
20825 already shared @code{bfd} objects to be unshared, but all future files
20826 that are opened will create a new @code{bfd} object. Similarly,
20827 re-enabling sharing does not cause multiple existing @code{bfd}
20828 objects to be collapsed into a single shared @code{bfd} object.
20830 @kindex set debug bfd-cache @var{level}
20831 @kindex bfd caching
20832 @item set debug bfd-cache @var{level}
20833 Turns on debugging of the bfd cache, setting the level to @var{level}.
20835 @kindex show debug bfd-cache
20836 @kindex bfd caching
20837 @item show debug bfd-cache
20838 Show the current debugging level of the bfd cache.
20841 @node Separate Debug Files
20842 @section Debugging Information in Separate Files
20843 @cindex separate debugging information files
20844 @cindex debugging information in separate files
20845 @cindex @file{.debug} subdirectories
20846 @cindex debugging information directory, global
20847 @cindex global debugging information directories
20848 @cindex build ID, and separate debugging files
20849 @cindex @file{.build-id} directory
20851 @value{GDBN} allows you to put a program's debugging information in a
20852 file separate from the executable itself, in a way that allows
20853 @value{GDBN} to find and load the debugging information automatically.
20854 Since debugging information can be very large---sometimes larger
20855 than the executable code itself---some systems distribute debugging
20856 information for their executables in separate files, which users can
20857 install only when they need to debug a problem.
20859 @value{GDBN} supports two ways of specifying the separate debug info
20864 The executable contains a @dfn{debug link} that specifies the name of
20865 the separate debug info file. The separate debug file's name is
20866 usually @file{@var{executable}.debug}, where @var{executable} is the
20867 name of the corresponding executable file without leading directories
20868 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20869 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20870 checksum for the debug file, which @value{GDBN} uses to validate that
20871 the executable and the debug file came from the same build.
20874 The executable contains a @dfn{build ID}, a unique bit string that is
20875 also present in the corresponding debug info file. (This is supported
20876 only on some operating systems, when using the ELF or PE file formats
20877 for binary files and the @sc{gnu} Binutils.) For more details about
20878 this feature, see the description of the @option{--build-id}
20879 command-line option in @ref{Options, , Command Line Options, ld,
20880 The GNU Linker}. The debug info file's name is not specified
20881 explicitly by the build ID, but can be computed from the build ID, see
20885 Depending on the way the debug info file is specified, @value{GDBN}
20886 uses two different methods of looking for the debug file:
20890 For the ``debug link'' method, @value{GDBN} looks up the named file in
20891 the directory of the executable file, then in a subdirectory of that
20892 directory named @file{.debug}, and finally under each one of the
20893 global debug directories, in a subdirectory whose name is identical to
20894 the leading directories of the executable's absolute file name. (On
20895 MS-Windows/MS-DOS, the drive letter of the executable's leading
20896 directories is converted to a one-letter subdirectory, i.e.@:
20897 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20898 filesystems disallow colons in file names.)
20901 For the ``build ID'' method, @value{GDBN} looks in the
20902 @file{.build-id} subdirectory of each one of the global debug directories for
20903 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20904 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
20905 are the rest of the bit string. (Real build ID strings are 32 or more
20906 hex characters, not 10.)
20909 So, for example, suppose you ask @value{GDBN} to debug
20910 @file{/usr/bin/ls}, which has a debug link that specifies the
20911 file @file{ls.debug}, and a build ID whose value in hex is
20912 @code{abcdef1234}. If the list of the global debug directories includes
20913 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
20914 debug information files, in the indicated order:
20918 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
20920 @file{/usr/bin/ls.debug}
20922 @file{/usr/bin/.debug/ls.debug}
20924 @file{/usr/lib/debug/usr/bin/ls.debug}.
20927 @anchor{debug-file-directory}
20928 Global debugging info directories default to what is set by @value{GDBN}
20929 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
20930 you can also set the global debugging info directories, and view the list
20931 @value{GDBN} is currently using.
20935 @kindex set debug-file-directory
20936 @item set debug-file-directory @var{directories}
20937 Set the directories which @value{GDBN} searches for separate debugging
20938 information files to @var{directory}. Multiple path components can be set
20939 concatenating them by a path separator.
20941 @kindex show debug-file-directory
20942 @item show debug-file-directory
20943 Show the directories @value{GDBN} searches for separate debugging
20948 @cindex @code{.gnu_debuglink} sections
20949 @cindex debug link sections
20950 A debug link is a special section of the executable file named
20951 @code{.gnu_debuglink}. The section must contain:
20955 A filename, with any leading directory components removed, followed by
20958 zero to three bytes of padding, as needed to reach the next four-byte
20959 boundary within the section, and
20961 a four-byte CRC checksum, stored in the same endianness used for the
20962 executable file itself. The checksum is computed on the debugging
20963 information file's full contents by the function given below, passing
20964 zero as the @var{crc} argument.
20967 Any executable file format can carry a debug link, as long as it can
20968 contain a section named @code{.gnu_debuglink} with the contents
20971 @cindex @code{.note.gnu.build-id} sections
20972 @cindex build ID sections
20973 The build ID is a special section in the executable file (and in other
20974 ELF binary files that @value{GDBN} may consider). This section is
20975 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20976 It contains unique identification for the built files---the ID remains
20977 the same across multiple builds of the same build tree. The default
20978 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20979 content for the build ID string. The same section with an identical
20980 value is present in the original built binary with symbols, in its
20981 stripped variant, and in the separate debugging information file.
20983 The debugging information file itself should be an ordinary
20984 executable, containing a full set of linker symbols, sections, and
20985 debugging information. The sections of the debugging information file
20986 should have the same names, addresses, and sizes as the original file,
20987 but they need not contain any data---much like a @code{.bss} section
20988 in an ordinary executable.
20990 The @sc{gnu} binary utilities (Binutils) package includes the
20991 @samp{objcopy} utility that can produce
20992 the separated executable / debugging information file pairs using the
20993 following commands:
20996 @kbd{objcopy --only-keep-debug foo foo.debug}
21001 These commands remove the debugging
21002 information from the executable file @file{foo} and place it in the file
21003 @file{foo.debug}. You can use the first, second or both methods to link the
21008 The debug link method needs the following additional command to also leave
21009 behind a debug link in @file{foo}:
21012 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21015 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21016 a version of the @code{strip} command such that the command @kbd{strip foo -f
21017 foo.debug} has the same functionality as the two @code{objcopy} commands and
21018 the @code{ln -s} command above, together.
21021 Build ID gets embedded into the main executable using @code{ld --build-id} or
21022 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21023 compatibility fixes for debug files separation are present in @sc{gnu} binary
21024 utilities (Binutils) package since version 2.18.
21029 @cindex CRC algorithm definition
21030 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21031 IEEE 802.3 using the polynomial:
21033 @c TexInfo requires naked braces for multi-digit exponents for Tex
21034 @c output, but this causes HTML output to barf. HTML has to be set using
21035 @c raw commands. So we end up having to specify this equation in 2
21040 <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>
21041 + <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
21047 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21048 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21052 The function is computed byte at a time, taking the least
21053 significant bit of each byte first. The initial pattern
21054 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21055 the final result is inverted to ensure trailing zeros also affect the
21058 @emph{Note:} This is the same CRC polynomial as used in handling the
21059 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21060 However in the case of the Remote Serial Protocol, the CRC is computed
21061 @emph{most} significant bit first, and the result is not inverted, so
21062 trailing zeros have no effect on the CRC value.
21064 To complete the description, we show below the code of the function
21065 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21066 initially supplied @code{crc} argument means that an initial call to
21067 this function passing in zero will start computing the CRC using
21070 @kindex gnu_debuglink_crc32
21073 gnu_debuglink_crc32 (unsigned long crc,
21074 unsigned char *buf, size_t len)
21076 static const unsigned long crc32_table[256] =
21078 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21079 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21080 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21081 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21082 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21083 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21084 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21085 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21086 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21087 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21088 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21089 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21090 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21091 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21092 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21093 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21094 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21095 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21096 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21097 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21098 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21099 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21100 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21101 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21102 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21103 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21104 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21105 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21106 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21107 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21108 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21109 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21110 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21111 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21112 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21113 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21114 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21115 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21116 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21117 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21118 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21119 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21120 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21121 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21122 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21123 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21124 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21125 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21126 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21127 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21128 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21131 unsigned char *end;
21133 crc = ~crc & 0xffffffff;
21134 for (end = buf + len; buf < end; ++buf)
21135 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21136 return ~crc & 0xffffffff;
21141 This computation does not apply to the ``build ID'' method.
21143 @node MiniDebugInfo
21144 @section Debugging information in a special section
21145 @cindex separate debug sections
21146 @cindex @samp{.gnu_debugdata} section
21148 Some systems ship pre-built executables and libraries that have a
21149 special @samp{.gnu_debugdata} section. This feature is called
21150 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21151 is used to supply extra symbols for backtraces.
21153 The intent of this section is to provide extra minimal debugging
21154 information for use in simple backtraces. It is not intended to be a
21155 replacement for full separate debugging information (@pxref{Separate
21156 Debug Files}). The example below shows the intended use; however,
21157 @value{GDBN} does not currently put restrictions on what sort of
21158 debugging information might be included in the section.
21160 @value{GDBN} has support for this extension. If the section exists,
21161 then it is used provided that no other source of debugging information
21162 can be found, and that @value{GDBN} was configured with LZMA support.
21164 This section can be easily created using @command{objcopy} and other
21165 standard utilities:
21168 # Extract the dynamic symbols from the main binary, there is no need
21169 # to also have these in the normal symbol table.
21170 nm -D @var{binary} --format=posix --defined-only \
21171 | awk '@{ print $1 @}' | sort > dynsyms
21173 # Extract all the text (i.e. function) symbols from the debuginfo.
21174 # (Note that we actually also accept "D" symbols, for the benefit
21175 # of platforms like PowerPC64 that use function descriptors.)
21176 nm @var{binary} --format=posix --defined-only \
21177 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21180 # Keep all the function symbols not already in the dynamic symbol
21182 comm -13 dynsyms funcsyms > keep_symbols
21184 # Separate full debug info into debug binary.
21185 objcopy --only-keep-debug @var{binary} debug
21187 # Copy the full debuginfo, keeping only a minimal set of symbols and
21188 # removing some unnecessary sections.
21189 objcopy -S --remove-section .gdb_index --remove-section .comment \
21190 --keep-symbols=keep_symbols debug mini_debuginfo
21192 # Drop the full debug info from the original binary.
21193 strip --strip-all -R .comment @var{binary}
21195 # Inject the compressed data into the .gnu_debugdata section of the
21198 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21202 @section Index Files Speed Up @value{GDBN}
21203 @cindex index files
21204 @cindex @samp{.gdb_index} section
21206 When @value{GDBN} finds a symbol file, it scans the symbols in the
21207 file in order to construct an internal symbol table. This lets most
21208 @value{GDBN} operations work quickly---at the cost of a delay early
21209 on. For large programs, this delay can be quite lengthy, so
21210 @value{GDBN} provides a way to build an index, which speeds up
21213 For convenience, @value{GDBN} comes with a program,
21214 @command{gdb-add-index}, which can be used to add the index to a
21215 symbol file. It takes the symbol file as its only argument:
21218 $ gdb-add-index symfile
21221 @xref{gdb-add-index}.
21223 It is also possible to do the work manually. Here is what
21224 @command{gdb-add-index} does behind the curtains.
21226 The index is stored as a section in the symbol file. @value{GDBN} can
21227 write the index to a file, then you can put it into the symbol file
21228 using @command{objcopy}.
21230 To create an index file, use the @code{save gdb-index} command:
21233 @item save gdb-index [-dwarf-5] @var{directory}
21234 @kindex save gdb-index
21235 Create index files for all symbol files currently known by
21236 @value{GDBN}. For each known @var{symbol-file}, this command by
21237 default creates it produces a single file
21238 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21239 the @option{-dwarf-5} option, it produces 2 files:
21240 @file{@var{symbol-file}.debug_names} and
21241 @file{@var{symbol-file}.debug_str}. The files are created in the
21242 given @var{directory}.
21245 Once you have created an index file you can merge it into your symbol
21246 file, here named @file{symfile}, using @command{objcopy}:
21249 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21250 --set-section-flags .gdb_index=readonly symfile symfile
21253 Or for @code{-dwarf-5}:
21256 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21257 $ cat symfile.debug_str >>symfile.debug_str.new
21258 $ objcopy --add-section .debug_names=symfile.gdb-index \
21259 --set-section-flags .debug_names=readonly \
21260 --update-section .debug_str=symfile.debug_str.new symfile symfile
21263 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21264 sections that have been deprecated. Usually they are deprecated because
21265 they are missing a new feature or have performance issues.
21266 To tell @value{GDBN} to use a deprecated index section anyway
21267 specify @code{set use-deprecated-index-sections on}.
21268 The default is @code{off}.
21269 This can speed up startup, but may result in some functionality being lost.
21270 @xref{Index Section Format}.
21272 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21273 must be done before gdb reads the file. The following will not work:
21276 $ gdb -ex "set use-deprecated-index-sections on" <program>
21279 Instead you must do, for example,
21282 $ gdb -iex "set use-deprecated-index-sections on" <program>
21285 There are currently some limitation on indices. They only work when
21286 using DWARF debugging information, not stabs. And, only the
21287 @code{-dwarf-5} index works for programs using Ada.
21289 @subsection Automatic symbol index cache
21291 @cindex automatic symbol index cache
21292 It is possible for @value{GDBN} to automatically save a copy of this index in a
21293 cache on disk and retrieve it from there when loading the same binary in the
21294 future. This feature can be turned on with @kbd{set index-cache on}. The
21295 following commands can be used to tweak the behavior of the index cache.
21299 @kindex set index-cache
21300 @item set index-cache on
21301 @itemx set index-cache off
21302 Enable or disable the use of the symbol index cache.
21304 @item set index-cache directory @var{directory}
21305 @kindex show index-cache
21306 @itemx show index-cache directory
21307 Set/show the directory where index files will be saved.
21309 The default value for this directory depends on the host platform. On
21310 most systems, the index is cached in the @file{gdb} subdirectory of
21311 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21312 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21313 of your home directory. However, on some systems, the default may
21314 differ according to local convention.
21316 There is no limit on the disk space used by index cache. It is perfectly safe
21317 to delete the content of that directory to free up disk space.
21319 @item show index-cache stats
21320 Print the number of cache hits and misses since the launch of @value{GDBN}.
21324 @node Symbol Errors
21325 @section Errors Reading Symbol Files
21327 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21328 such as symbol types it does not recognize, or known bugs in compiler
21329 output. By default, @value{GDBN} does not notify you of such problems, since
21330 they are relatively common and primarily of interest to people
21331 debugging compilers. If you are interested in seeing information
21332 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21333 only one message about each such type of problem, no matter how many
21334 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21335 to see how many times the problems occur, with the @code{set
21336 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21339 The messages currently printed, and their meanings, include:
21342 @item inner block not inside outer block in @var{symbol}
21344 The symbol information shows where symbol scopes begin and end
21345 (such as at the start of a function or a block of statements). This
21346 error indicates that an inner scope block is not fully contained
21347 in its outer scope blocks.
21349 @value{GDBN} circumvents the problem by treating the inner block as if it had
21350 the same scope as the outer block. In the error message, @var{symbol}
21351 may be shown as ``@code{(don't know)}'' if the outer block is not a
21354 @item block at @var{address} out of order
21356 The symbol information for symbol scope blocks should occur in
21357 order of increasing addresses. This error indicates that it does not
21360 @value{GDBN} does not circumvent this problem, and has trouble
21361 locating symbols in the source file whose symbols it is reading. (You
21362 can often determine what source file is affected by specifying
21363 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21366 @item bad block start address patched
21368 The symbol information for a symbol scope block has a start address
21369 smaller than the address of the preceding source line. This is known
21370 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21372 @value{GDBN} circumvents the problem by treating the symbol scope block as
21373 starting on the previous source line.
21375 @item bad string table offset in symbol @var{n}
21378 Symbol number @var{n} contains a pointer into the string table which is
21379 larger than the size of the string table.
21381 @value{GDBN} circumvents the problem by considering the symbol to have the
21382 name @code{foo}, which may cause other problems if many symbols end up
21385 @item unknown symbol type @code{0x@var{nn}}
21387 The symbol information contains new data types that @value{GDBN} does
21388 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21389 uncomprehended information, in hexadecimal.
21391 @value{GDBN} circumvents the error by ignoring this symbol information.
21392 This usually allows you to debug your program, though certain symbols
21393 are not accessible. If you encounter such a problem and feel like
21394 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21395 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21396 and examine @code{*bufp} to see the symbol.
21398 @item stub type has NULL name
21400 @value{GDBN} could not find the full definition for a struct or class.
21402 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21403 The symbol information for a C@t{++} member function is missing some
21404 information that recent versions of the compiler should have output for
21407 @item info mismatch between compiler and debugger
21409 @value{GDBN} could not parse a type specification output by the compiler.
21414 @section GDB Data Files
21416 @cindex prefix for data files
21417 @value{GDBN} will sometimes read an auxiliary data file. These files
21418 are kept in a directory known as the @dfn{data directory}.
21420 You can set the data directory's name, and view the name @value{GDBN}
21421 is currently using.
21424 @kindex set data-directory
21425 @item set data-directory @var{directory}
21426 Set the directory which @value{GDBN} searches for auxiliary data files
21427 to @var{directory}.
21429 @kindex show data-directory
21430 @item show data-directory
21431 Show the directory @value{GDBN} searches for auxiliary data files.
21434 @cindex default data directory
21435 @cindex @samp{--with-gdb-datadir}
21436 You can set the default data directory by using the configure-time
21437 @samp{--with-gdb-datadir} option. If the data directory is inside
21438 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21439 @samp{--exec-prefix}), then the default data directory will be updated
21440 automatically if the installed @value{GDBN} is moved to a new
21443 The data directory may also be specified with the
21444 @code{--data-directory} command line option.
21445 @xref{Mode Options}.
21448 @chapter Specifying a Debugging Target
21450 @cindex debugging target
21451 A @dfn{target} is the execution environment occupied by your program.
21453 Often, @value{GDBN} runs in the same host environment as your program;
21454 in that case, the debugging target is specified as a side effect when
21455 you use the @code{file} or @code{core} commands. When you need more
21456 flexibility---for example, running @value{GDBN} on a physically separate
21457 host, or controlling a standalone system over a serial port or a
21458 realtime system over a TCP/IP connection---you can use the @code{target}
21459 command to specify one of the target types configured for @value{GDBN}
21460 (@pxref{Target Commands, ,Commands for Managing Targets}).
21462 @cindex target architecture
21463 It is possible to build @value{GDBN} for several different @dfn{target
21464 architectures}. When @value{GDBN} is built like that, you can choose
21465 one of the available architectures with the @kbd{set architecture}
21469 @kindex set architecture
21470 @kindex show architecture
21471 @item set architecture @var{arch}
21472 This command sets the current target architecture to @var{arch}. The
21473 value of @var{arch} can be @code{"auto"}, in addition to one of the
21474 supported architectures.
21476 @item show architecture
21477 Show the current target architecture.
21479 @item set processor
21481 @kindex set processor
21482 @kindex show processor
21483 These are alias commands for, respectively, @code{set architecture}
21484 and @code{show architecture}.
21488 * Active Targets:: Active targets
21489 * Target Commands:: Commands for managing targets
21490 * Byte Order:: Choosing target byte order
21493 @node Active Targets
21494 @section Active Targets
21496 @cindex stacking targets
21497 @cindex active targets
21498 @cindex multiple targets
21500 There are multiple classes of targets such as: processes, executable files or
21501 recording sessions. Core files belong to the process class, making core file
21502 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21503 on multiple active targets, one in each class. This allows you to (for
21504 example) start a process and inspect its activity, while still having access to
21505 the executable file after the process finishes. Or if you start process
21506 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21507 presented a virtual layer of the recording target, while the process target
21508 remains stopped at the chronologically last point of the process execution.
21510 Use the @code{core-file} and @code{exec-file} commands to select a new core
21511 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21512 specify as a target a process that is already running, use the @code{attach}
21513 command (@pxref{Attach, ,Debugging an Already-running Process}).
21515 @node Target Commands
21516 @section Commands for Managing Targets
21519 @item target @var{type} @var{parameters}
21520 Connects the @value{GDBN} host environment to a target machine or
21521 process. A target is typically a protocol for talking to debugging
21522 facilities. You use the argument @var{type} to specify the type or
21523 protocol of the target machine.
21525 Further @var{parameters} are interpreted by the target protocol, but
21526 typically include things like device names or host names to connect
21527 with, process numbers, and baud rates.
21529 The @code{target} command does not repeat if you press @key{RET} again
21530 after executing the command.
21532 @kindex help target
21534 Displays the names of all targets available. To display targets
21535 currently selected, use either @code{info target} or @code{info files}
21536 (@pxref{Files, ,Commands to Specify Files}).
21538 @item help target @var{name}
21539 Describe a particular target, including any parameters necessary to
21542 @kindex set gnutarget
21543 @item set gnutarget @var{args}
21544 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21545 knows whether it is reading an @dfn{executable},
21546 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21547 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21548 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21551 @emph{Warning:} To specify a file format with @code{set gnutarget},
21552 you must know the actual BFD name.
21556 @xref{Files, , Commands to Specify Files}.
21558 @kindex show gnutarget
21559 @item show gnutarget
21560 Use the @code{show gnutarget} command to display what file format
21561 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21562 @value{GDBN} will determine the file format for each file automatically,
21563 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21566 @cindex common targets
21567 Here are some common targets (available, or not, depending on the GDB
21572 @item target exec @var{program}
21573 @cindex executable file target
21574 An executable file. @samp{target exec @var{program}} is the same as
21575 @samp{exec-file @var{program}}.
21577 @item target core @var{filename}
21578 @cindex core dump file target
21579 A core dump file. @samp{target core @var{filename}} is the same as
21580 @samp{core-file @var{filename}}.
21582 @item target remote @var{medium}
21583 @cindex remote target
21584 A remote system connected to @value{GDBN} via a serial line or network
21585 connection. This command tells @value{GDBN} to use its own remote
21586 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21588 For example, if you have a board connected to @file{/dev/ttya} on the
21589 machine running @value{GDBN}, you could say:
21592 target remote /dev/ttya
21595 @code{target remote} supports the @code{load} command. This is only
21596 useful if you have some other way of getting the stub to the target
21597 system, and you can put it somewhere in memory where it won't get
21598 clobbered by the download.
21600 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21601 @cindex built-in simulator target
21602 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21610 works; however, you cannot assume that a specific memory map, device
21611 drivers, or even basic I/O is available, although some simulators do
21612 provide these. For info about any processor-specific simulator details,
21613 see the appropriate section in @ref{Embedded Processors, ,Embedded
21616 @item target native
21617 @cindex native target
21618 Setup for local/native process debugging. Useful to make the
21619 @code{run} command spawn native processes (likewise @code{attach},
21620 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21621 (@pxref{set auto-connect-native-target}).
21625 Different targets are available on different configurations of @value{GDBN};
21626 your configuration may have more or fewer targets.
21628 Many remote targets require you to download the executable's code once
21629 you've successfully established a connection. You may wish to control
21630 various aspects of this process.
21635 @kindex set hash@r{, for remote monitors}
21636 @cindex hash mark while downloading
21637 This command controls whether a hash mark @samp{#} is displayed while
21638 downloading a file to the remote monitor. If on, a hash mark is
21639 displayed after each S-record is successfully downloaded to the
21643 @kindex show hash@r{, for remote monitors}
21644 Show the current status of displaying the hash mark.
21646 @item set debug monitor
21647 @kindex set debug monitor
21648 @cindex display remote monitor communications
21649 Enable or disable display of communications messages between
21650 @value{GDBN} and the remote monitor.
21652 @item show debug monitor
21653 @kindex show debug monitor
21654 Show the current status of displaying communications between
21655 @value{GDBN} and the remote monitor.
21660 @kindex load @var{filename} @var{offset}
21661 @item load @var{filename} @var{offset}
21663 Depending on what remote debugging facilities are configured into
21664 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21665 is meant to make @var{filename} (an executable) available for debugging
21666 on the remote system---by downloading, or dynamic linking, for example.
21667 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21668 the @code{add-symbol-file} command.
21670 If your @value{GDBN} does not have a @code{load} command, attempting to
21671 execute it gets the error message ``@code{You can't do that when your
21672 target is @dots{}}''
21674 The file is loaded at whatever address is specified in the executable.
21675 For some object file formats, you can specify the load address when you
21676 link the program; for other formats, like a.out, the object file format
21677 specifies a fixed address.
21678 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21680 It is also possible to tell @value{GDBN} to load the executable file at a
21681 specific offset described by the optional argument @var{offset}. When
21682 @var{offset} is provided, @var{filename} must also be provided.
21684 Depending on the remote side capabilities, @value{GDBN} may be able to
21685 load programs into flash memory.
21687 @code{load} does not repeat if you press @key{RET} again after using it.
21692 @kindex flash-erase
21694 @anchor{flash-erase}
21696 Erases all known flash memory regions on the target.
21701 @section Choosing Target Byte Order
21703 @cindex choosing target byte order
21704 @cindex target byte order
21706 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21707 offer the ability to run either big-endian or little-endian byte
21708 orders. Usually the executable or symbol will include a bit to
21709 designate the endian-ness, and you will not need to worry about
21710 which to use. However, you may still find it useful to adjust
21711 @value{GDBN}'s idea of processor endian-ness manually.
21715 @item set endian big
21716 Instruct @value{GDBN} to assume the target is big-endian.
21718 @item set endian little
21719 Instruct @value{GDBN} to assume the target is little-endian.
21721 @item set endian auto
21722 Instruct @value{GDBN} to use the byte order associated with the
21726 Display @value{GDBN}'s current idea of the target byte order.
21730 If the @code{set endian auto} mode is in effect and no executable has
21731 been selected, then the endianness used is the last one chosen either
21732 by one of the @code{set endian big} and @code{set endian little}
21733 commands or by inferring from the last executable used. If no
21734 endianness has been previously chosen, then the default for this mode
21735 is inferred from the target @value{GDBN} has been built for, and is
21736 @code{little} if the name of the target CPU has an @code{el} suffix
21737 and @code{big} otherwise.
21739 Note that these commands merely adjust interpretation of symbolic
21740 data on the host, and that they have absolutely no effect on the
21744 @node Remote Debugging
21745 @chapter Debugging Remote Programs
21746 @cindex remote debugging
21748 If you are trying to debug a program running on a machine that cannot run
21749 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21750 For example, you might use remote debugging on an operating system kernel,
21751 or on a small system which does not have a general purpose operating system
21752 powerful enough to run a full-featured debugger.
21754 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21755 to make this work with particular debugging targets. In addition,
21756 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21757 but not specific to any particular target system) which you can use if you
21758 write the remote stubs---the code that runs on the remote system to
21759 communicate with @value{GDBN}.
21761 Other remote targets may be available in your
21762 configuration of @value{GDBN}; use @code{help target} to list them.
21765 * Connecting:: Connecting to a remote target
21766 * File Transfer:: Sending files to a remote system
21767 * Server:: Using the gdbserver program
21768 * Remote Configuration:: Remote configuration
21769 * Remote Stub:: Implementing a remote stub
21773 @section Connecting to a Remote Target
21774 @cindex remote debugging, connecting
21775 @cindex @code{gdbserver}, connecting
21776 @cindex remote debugging, types of connections
21777 @cindex @code{gdbserver}, types of connections
21778 @cindex @code{gdbserver}, @code{target remote} mode
21779 @cindex @code{gdbserver}, @code{target extended-remote} mode
21781 This section describes how to connect to a remote target, including the
21782 types of connections and their differences, how to set up executable and
21783 symbol files on the host and target, and the commands used for
21784 connecting to and disconnecting from the remote target.
21786 @subsection Types of Remote Connections
21788 @value{GDBN} supports two types of remote connections, @code{target remote}
21789 mode and @code{target extended-remote} mode. Note that many remote targets
21790 support only @code{target remote} mode. There are several major
21791 differences between the two types of connections, enumerated here:
21795 @cindex remote debugging, detach and program exit
21796 @item Result of detach or program exit
21797 @strong{With target remote mode:} When the debugged program exits or you
21798 detach from it, @value{GDBN} disconnects from the target. When using
21799 @code{gdbserver}, @code{gdbserver} will exit.
21801 @strong{With target extended-remote mode:} When the debugged program exits or
21802 you detach from it, @value{GDBN} remains connected to the target, even
21803 though no program is running. You can rerun the program, attach to a
21804 running program, or use @code{monitor} commands specific to the target.
21806 When using @code{gdbserver} in this case, it does not exit unless it was
21807 invoked using the @option{--once} option. If the @option{--once} option
21808 was not used, you can ask @code{gdbserver} to exit using the
21809 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
21811 @item Specifying the program to debug
21812 For both connection types you use the @code{file} command to specify the
21813 program on the host system. If you are using @code{gdbserver} there are
21814 some differences in how to specify the location of the program on the
21817 @strong{With target remote mode:} You must either specify the program to debug
21818 on the @code{gdbserver} command line or use the @option{--attach} option
21819 (@pxref{Attaching to a program,,Attaching to a Running Program}).
21821 @cindex @option{--multi}, @code{gdbserver} option
21822 @strong{With target extended-remote mode:} You may specify the program to debug
21823 on the @code{gdbserver} command line, or you can load the program or attach
21824 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
21826 @anchor{--multi Option in Types of Remote Connnections}
21827 You can start @code{gdbserver} without supplying an initial command to run
21828 or process ID to attach. To do this, use the @option{--multi} command line
21829 option. Then you can connect using @code{target extended-remote} and start
21830 the program you want to debug (see below for details on using the
21831 @code{run} command in this scenario). Note that the conditions under which
21832 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
21833 (@code{target remote} or @code{target extended-remote}). The
21834 @option{--multi} option to @code{gdbserver} has no influence on that.
21836 @item The @code{run} command
21837 @strong{With target remote mode:} The @code{run} command is not
21838 supported. Once a connection has been established, you can use all
21839 the usual @value{GDBN} commands to examine and change data. The
21840 remote program is already running, so you can use commands like
21841 @kbd{step} and @kbd{continue}.
21843 @strong{With target extended-remote mode:} The @code{run} command is
21844 supported. The @code{run} command uses the value set by
21845 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
21846 the program to run. Command line arguments are supported, except for
21847 wildcard expansion and I/O redirection (@pxref{Arguments}).
21849 If you specify the program to debug on the command line, then the
21850 @code{run} command is not required to start execution, and you can
21851 resume using commands like @kbd{step} and @kbd{continue} as with
21852 @code{target remote} mode.
21854 @anchor{Attaching in Types of Remote Connections}
21856 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
21857 not supported. To attach to a running program using @code{gdbserver}, you
21858 must use the @option{--attach} option (@pxref{Running gdbserver}).
21860 @strong{With target extended-remote mode:} To attach to a running program,
21861 you may use the @code{attach} command after the connection has been
21862 established. If you are using @code{gdbserver}, you may also invoke
21863 @code{gdbserver} using the @option{--attach} option
21864 (@pxref{Running gdbserver}).
21866 Some remote targets allow @value{GDBN} to determine the executable file running
21867 in the process the debugger is attaching to. In such a case, @value{GDBN}
21868 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
21869 between the executable file name running in the process and the name of the
21870 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
21874 @anchor{Host and target files}
21875 @subsection Host and Target Files
21876 @cindex remote debugging, symbol files
21877 @cindex symbol files, remote debugging
21879 @value{GDBN}, running on the host, needs access to symbol and debugging
21880 information for your program running on the target. This requires
21881 access to an unstripped copy of your program, and possibly any associated
21882 symbol files. Note that this section applies equally to both @code{target
21883 remote} mode and @code{target extended-remote} mode.
21885 Some remote targets (@pxref{qXfer executable filename read}, and
21886 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
21887 the same connection used to communicate with @value{GDBN}. With such a
21888 target, if the remote program is unstripped, the only command you need is
21889 @code{target remote} (or @code{target extended-remote}).
21891 If the remote program is stripped, or the target does not support remote
21892 program file access, start up @value{GDBN} using the name of the local
21893 unstripped copy of your program as the first argument, or use the
21894 @code{file} command. Use @code{set sysroot} to specify the location (on
21895 the host) of target libraries (unless your @value{GDBN} was compiled with
21896 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21897 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21900 The symbol file and target libraries must exactly match the executable
21901 and libraries on the target, with one exception: the files on the host
21902 system should not be stripped, even if the files on the target system
21903 are. Mismatched or missing files will lead to confusing results
21904 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21905 files may also prevent @code{gdbserver} from debugging multi-threaded
21908 @subsection Remote Connection Commands
21909 @cindex remote connection commands
21910 @value{GDBN} can communicate with the target over a serial line, a
21911 local Unix domain socket, or
21912 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
21913 each case, @value{GDBN} uses the same protocol for debugging your
21914 program; only the medium carrying the debugging packets varies. The
21915 @code{target remote} and @code{target extended-remote} commands
21916 establish a connection to the target. Both commands accept the same
21917 arguments, which indicate the medium to use:
21921 @item target remote @var{serial-device}
21922 @itemx target extended-remote @var{serial-device}
21923 @cindex serial line, @code{target remote}
21924 Use @var{serial-device} to communicate with the target. For example,
21925 to use a serial line connected to the device named @file{/dev/ttyb}:
21928 target remote /dev/ttyb
21931 If you're using a serial line, you may want to give @value{GDBN} the
21932 @samp{--baud} option, or use the @code{set serial baud} command
21933 (@pxref{Remote Configuration, set serial baud}) before the
21934 @code{target} command.
21936 @item target remote @var{local-socket}
21937 @itemx target extended-remote @var{local-socket}
21938 @cindex local socket, @code{target remote}
21939 @cindex Unix domain socket
21940 Use @var{local-socket} to communicate with the target. For example,
21941 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
21944 target remote /tmp/gdb-socket0
21947 Note that this command has the same form as the command to connect
21948 to a serial line. @value{GDBN} will automatically determine which
21949 kind of file you have specified and will make the appropriate kind
21951 This feature is not available if the host system does not support
21952 Unix domain sockets.
21954 @item target remote @code{@var{host}:@var{port}}
21955 @itemx target remote @code{@var{[host]}:@var{port}}
21956 @itemx target remote @code{tcp:@var{host}:@var{port}}
21957 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21958 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21959 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21960 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21961 @itemx target extended-remote @code{@var{host}:@var{port}}
21962 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21963 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21964 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21965 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21966 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21967 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21968 @cindex @acronym{TCP} port, @code{target remote}
21969 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21970 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21971 address, or a numeric @acronym{IPv6} address (with or without the
21972 square brackets to separate the address from the port); @var{port}
21973 must be a decimal number. The @var{host} could be the target machine
21974 itself, if it is directly connected to the net, or it might be a
21975 terminal server which in turn has a serial line to the target.
21977 For example, to connect to port 2828 on a terminal server named
21981 target remote manyfarms:2828
21984 To connect to port 2828 on a terminal server whose address is
21985 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21986 square bracket syntax:
21989 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21993 or explicitly specify the @acronym{IPv6} protocol:
21996 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21999 This last example may be confusing to the reader, because there is no
22000 visible separation between the hostname and the port number.
22001 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22002 using square brackets for clarity. However, it is important to
22003 mention that for @value{GDBN} there is no ambiguity: the number after
22004 the last colon is considered to be the port number.
22006 If your remote target is actually running on the same machine as your
22007 debugger session (e.g.@: a simulator for your target running on the
22008 same host), you can omit the hostname. For example, to connect to
22009 port 1234 on your local machine:
22012 target remote :1234
22016 Note that the colon is still required here.
22018 @item target remote @code{udp:@var{host}:@var{port}}
22019 @itemx target remote @code{udp:@var{[host]}:@var{port}}
22020 @itemx target remote @code{udp4:@var{host}:@var{port}}
22021 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
22022 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22023 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22024 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
22025 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22026 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22027 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
22028 @cindex @acronym{UDP} port, @code{target remote}
22029 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22030 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22033 target remote udp:manyfarms:2828
22036 When using a @acronym{UDP} connection for remote debugging, you should
22037 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22038 can silently drop packets on busy or unreliable networks, which will
22039 cause havoc with your debugging session.
22041 @item target remote | @var{command}
22042 @itemx target extended-remote | @var{command}
22043 @cindex pipe, @code{target remote} to
22044 Run @var{command} in the background and communicate with it using a
22045 pipe. The @var{command} is a shell command, to be parsed and expanded
22046 by the system's command shell, @code{/bin/sh}; it should expect remote
22047 protocol packets on its standard input, and send replies on its
22048 standard output. You could use this to run a stand-alone simulator
22049 that speaks the remote debugging protocol, to make net connections
22050 using programs like @code{ssh}, or for other similar tricks.
22052 If @var{command} closes its standard output (perhaps by exiting),
22053 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22054 program has already exited, this will have no effect.)
22058 @cindex interrupting remote programs
22059 @cindex remote programs, interrupting
22060 Whenever @value{GDBN} is waiting for the remote program, if you type the
22061 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22062 program. This may or may not succeed, depending in part on the hardware
22063 and the serial drivers the remote system uses. If you type the
22064 interrupt character once again, @value{GDBN} displays this prompt:
22067 Interrupted while waiting for the program.
22068 Give up (and stop debugging it)? (y or n)
22071 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22072 the remote debugging session. (If you decide you want to try again later,
22073 you can use @kbd{target remote} again to connect once more.) If you type
22074 @kbd{n}, @value{GDBN} goes back to waiting.
22076 In @code{target extended-remote} mode, typing @kbd{n} will leave
22077 @value{GDBN} connected to the target.
22080 @kindex detach (remote)
22082 When you have finished debugging the remote program, you can use the
22083 @code{detach} command to release it from @value{GDBN} control.
22084 Detaching from the target normally resumes its execution, but the results
22085 will depend on your particular remote stub. After the @code{detach}
22086 command in @code{target remote} mode, @value{GDBN} is free to connect to
22087 another target. In @code{target extended-remote} mode, @value{GDBN} is
22088 still connected to the target.
22092 The @code{disconnect} command closes the connection to the target, and
22093 the target is generally not resumed. It will wait for @value{GDBN}
22094 (this instance or another one) to connect and continue debugging. After
22095 the @code{disconnect} command, @value{GDBN} is again free to connect to
22098 @cindex send command to remote monitor
22099 @cindex extend @value{GDBN} for remote targets
22100 @cindex add new commands for external monitor
22102 @item monitor @var{cmd}
22103 This command allows you to send arbitrary commands directly to the
22104 remote monitor. Since @value{GDBN} doesn't care about the commands it
22105 sends like this, this command is the way to extend @value{GDBN}---you
22106 can add new commands that only the external monitor will understand
22110 @node File Transfer
22111 @section Sending files to a remote system
22112 @cindex remote target, file transfer
22113 @cindex file transfer
22114 @cindex sending files to remote systems
22116 Some remote targets offer the ability to transfer files over the same
22117 connection used to communicate with @value{GDBN}. This is convenient
22118 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22119 running @code{gdbserver} over a network interface. For other targets,
22120 e.g.@: embedded devices with only a single serial port, this may be
22121 the only way to upload or download files.
22123 Not all remote targets support these commands.
22127 @item remote put @var{hostfile} @var{targetfile}
22128 Copy file @var{hostfile} from the host system (the machine running
22129 @value{GDBN}) to @var{targetfile} on the target system.
22132 @item remote get @var{targetfile} @var{hostfile}
22133 Copy file @var{targetfile} from the target system to @var{hostfile}
22134 on the host system.
22136 @kindex remote delete
22137 @item remote delete @var{targetfile}
22138 Delete @var{targetfile} from the target system.
22143 @section Using the @code{gdbserver} Program
22146 @cindex remote connection without stubs
22147 @code{gdbserver} is a control program for Unix-like systems, which
22148 allows you to connect your program with a remote @value{GDBN} via
22149 @code{target remote} or @code{target extended-remote}---but without
22150 linking in the usual debugging stub.
22152 @code{gdbserver} is not a complete replacement for the debugging stubs,
22153 because it requires essentially the same operating-system facilities
22154 that @value{GDBN} itself does. In fact, a system that can run
22155 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22156 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22157 because it is a much smaller program than @value{GDBN} itself. It is
22158 also easier to port than all of @value{GDBN}, so you may be able to get
22159 started more quickly on a new system by using @code{gdbserver}.
22160 Finally, if you develop code for real-time systems, you may find that
22161 the tradeoffs involved in real-time operation make it more convenient to
22162 do as much development work as possible on another system, for example
22163 by cross-compiling. You can use @code{gdbserver} to make a similar
22164 choice for debugging.
22166 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22167 or a TCP connection, using the standard @value{GDBN} remote serial
22171 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22172 Do not run @code{gdbserver} connected to any public network; a
22173 @value{GDBN} connection to @code{gdbserver} provides access to the
22174 target system with the same privileges as the user running
22178 @anchor{Running gdbserver}
22179 @subsection Running @code{gdbserver}
22180 @cindex arguments, to @code{gdbserver}
22181 @cindex @code{gdbserver}, command-line arguments
22183 Run @code{gdbserver} on the target system. You need a copy of the
22184 program you want to debug, including any libraries it requires.
22185 @code{gdbserver} does not need your program's symbol table, so you can
22186 strip the program if necessary to save space. @value{GDBN} on the host
22187 system does all the symbol handling.
22189 To use the server, you must tell it how to communicate with @value{GDBN};
22190 the name of your program; and the arguments for your program. The usual
22194 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22197 @var{comm} is either a device name (to use a serial line), or a TCP
22198 hostname and portnumber, or @code{-} or @code{stdio} to use
22199 stdin/stdout of @code{gdbserver}.
22200 For example, to debug Emacs with the argument
22201 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22205 target> gdbserver /dev/com1 emacs foo.txt
22208 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22211 To use a TCP connection instead of a serial line:
22214 target> gdbserver host:2345 emacs foo.txt
22217 The only difference from the previous example is the first argument,
22218 specifying that you are communicating with the host @value{GDBN} via
22219 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22220 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22221 (Currently, the @samp{host} part is ignored.) You can choose any number
22222 you want for the port number as long as it does not conflict with any
22223 TCP ports already in use on the target system (for example, @code{23} is
22224 reserved for @code{telnet}).@footnote{If you choose a port number that
22225 conflicts with another service, @code{gdbserver} prints an error message
22226 and exits.} You must use the same port number with the host @value{GDBN}
22227 @code{target remote} command.
22229 The @code{stdio} connection is useful when starting @code{gdbserver}
22233 (gdb) target remote | ssh -T hostname gdbserver - hello
22236 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22237 and we don't want escape-character handling. Ssh does this by default when
22238 a command is provided, the flag is provided to make it explicit.
22239 You could elide it if you want to.
22241 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22242 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22243 display through a pipe connected to gdbserver.
22244 Both @code{stdout} and @code{stderr} use the same pipe.
22246 @anchor{Attaching to a program}
22247 @subsubsection Attaching to a Running Program
22248 @cindex attach to a program, @code{gdbserver}
22249 @cindex @option{--attach}, @code{gdbserver} option
22251 On some targets, @code{gdbserver} can also attach to running programs.
22252 This is accomplished via the @code{--attach} argument. The syntax is:
22255 target> gdbserver --attach @var{comm} @var{pid}
22258 @var{pid} is the process ID of a currently running process. It isn't
22259 necessary to point @code{gdbserver} at a binary for the running process.
22261 In @code{target extended-remote} mode, you can also attach using the
22262 @value{GDBN} attach command
22263 (@pxref{Attaching in Types of Remote Connections}).
22266 You can debug processes by name instead of process ID if your target has the
22267 @code{pidof} utility:
22270 target> gdbserver --attach @var{comm} `pidof @var{program}`
22273 In case more than one copy of @var{program} is running, or @var{program}
22274 has multiple threads, most versions of @code{pidof} support the
22275 @code{-s} option to only return the first process ID.
22277 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22279 This section applies only when @code{gdbserver} is run to listen on a TCP
22282 @code{gdbserver} normally terminates after all of its debugged processes have
22283 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22284 extended-remote}, @code{gdbserver} stays running even with no processes left.
22285 @value{GDBN} normally terminates the spawned debugged process on its exit,
22286 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22287 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22288 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22289 stays running even in the @kbd{target remote} mode.
22291 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22292 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22293 completeness, at most one @value{GDBN} can be connected at a time.
22295 @cindex @option{--once}, @code{gdbserver} option
22296 By default, @code{gdbserver} keeps the listening TCP port open, so that
22297 subsequent connections are possible. However, if you start @code{gdbserver}
22298 with the @option{--once} option, it will stop listening for any further
22299 connection attempts after connecting to the first @value{GDBN} session. This
22300 means no further connections to @code{gdbserver} will be possible after the
22301 first one. It also means @code{gdbserver} will terminate after the first
22302 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22303 connections and even in the @kbd{target extended-remote} mode. The
22304 @option{--once} option allows reusing the same port number for connecting to
22305 multiple instances of @code{gdbserver} running on the same host, since each
22306 instance closes its port after the first connection.
22308 @anchor{Other Command-Line Arguments for gdbserver}
22309 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22311 You can use the @option{--multi} option to start @code{gdbserver} without
22312 specifying a program to debug or a process to attach to. Then you can
22313 attach in @code{target extended-remote} mode and run or attach to a
22314 program. For more information,
22315 @pxref{--multi Option in Types of Remote Connnections}.
22317 @cindex @option{--debug}, @code{gdbserver} option
22318 The @option{--debug} option tells @code{gdbserver} to display extra
22319 status information about the debugging process.
22320 @cindex @option{--remote-debug}, @code{gdbserver} option
22321 The @option{--remote-debug} option tells @code{gdbserver} to display
22322 remote protocol debug output.
22323 @cindex @option{--debug-file}, @code{gdbserver} option
22324 @cindex @code{gdbserver}, send all debug output to a single file
22325 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22326 write any debug output to the given @var{filename}. These options are intended
22327 for @code{gdbserver} development and for bug reports to the developers.
22329 @cindex @option{--debug-format}, @code{gdbserver} option
22330 The @option{--debug-format=option1[,option2,...]} option tells
22331 @code{gdbserver} to include additional information in each output.
22332 Possible options are:
22336 Turn off all extra information in debugging output.
22338 Turn on all extra information in debugging output.
22340 Include a timestamp in each line of debugging output.
22343 Options are processed in order. Thus, for example, if @option{none}
22344 appears last then no additional information is added to debugging output.
22346 @cindex @option{--wrapper}, @code{gdbserver} option
22347 The @option{--wrapper} option specifies a wrapper to launch programs
22348 for debugging. The option should be followed by the name of the
22349 wrapper, then any command-line arguments to pass to the wrapper, then
22350 @kbd{--} indicating the end of the wrapper arguments.
22352 @code{gdbserver} runs the specified wrapper program with a combined
22353 command line including the wrapper arguments, then the name of the
22354 program to debug, then any arguments to the program. The wrapper
22355 runs until it executes your program, and then @value{GDBN} gains control.
22357 You can use any program that eventually calls @code{execve} with
22358 its arguments as a wrapper. Several standard Unix utilities do
22359 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22360 with @code{exec "$@@"} will also work.
22362 For example, you can use @code{env} to pass an environment variable to
22363 the debugged program, without setting the variable in @code{gdbserver}'s
22367 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22370 @cindex @option{--selftest}
22371 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22374 $ gdbserver --selftest
22375 Ran 2 unit tests, 0 failed
22378 These tests are disabled in release.
22379 @subsection Connecting to @code{gdbserver}
22381 The basic procedure for connecting to the remote target is:
22385 Run @value{GDBN} on the host system.
22388 Make sure you have the necessary symbol files
22389 (@pxref{Host and target files}).
22390 Load symbols for your application using the @code{file} command before you
22391 connect. Use @code{set sysroot} to locate target libraries (unless your
22392 @value{GDBN} was compiled with the correct sysroot using
22393 @code{--with-sysroot}).
22396 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22397 For TCP connections, you must start up @code{gdbserver} prior to using
22398 the @code{target} command. Otherwise you may get an error whose
22399 text depends on the host system, but which usually looks something like
22400 @samp{Connection refused}. Don't use the @code{load}
22401 command in @value{GDBN} when using @code{target remote} mode, since the
22402 program is already on the target.
22406 @anchor{Monitor Commands for gdbserver}
22407 @subsection Monitor Commands for @code{gdbserver}
22408 @cindex monitor commands, for @code{gdbserver}
22410 During a @value{GDBN} session using @code{gdbserver}, you can use the
22411 @code{monitor} command to send special requests to @code{gdbserver}.
22412 Here are the available commands.
22416 List the available monitor commands.
22418 @item monitor set debug 0
22419 @itemx monitor set debug 1
22420 Disable or enable general debugging messages.
22422 @item monitor set remote-debug 0
22423 @itemx monitor set remote-debug 1
22424 Disable or enable specific debugging messages associated with the remote
22425 protocol (@pxref{Remote Protocol}).
22427 @item monitor set debug-file filename
22428 @itemx monitor set debug-file
22429 Send any debug output to the given file, or to stderr.
22431 @item monitor set debug-format option1@r{[},option2,...@r{]}
22432 Specify additional text to add to debugging messages.
22433 Possible options are:
22437 Turn off all extra information in debugging output.
22439 Turn on all extra information in debugging output.
22441 Include a timestamp in each line of debugging output.
22444 Options are processed in order. Thus, for example, if @option{none}
22445 appears last then no additional information is added to debugging output.
22447 @item monitor set libthread-db-search-path [PATH]
22448 @cindex gdbserver, search path for @code{libthread_db}
22449 When this command is issued, @var{path} is a colon-separated list of
22450 directories to search for @code{libthread_db} (@pxref{Threads,,set
22451 libthread-db-search-path}). If you omit @var{path},
22452 @samp{libthread-db-search-path} will be reset to its default value.
22454 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22455 not supported in @code{gdbserver}.
22458 Tell gdbserver to exit immediately. This command should be followed by
22459 @code{disconnect} to close the debugging session. @code{gdbserver} will
22460 detach from any attached processes and kill any processes it created.
22461 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22462 of a multi-process mode debug session.
22466 @subsection Tracepoints support in @code{gdbserver}
22467 @cindex tracepoints support in @code{gdbserver}
22469 On some targets, @code{gdbserver} supports tracepoints, fast
22470 tracepoints and static tracepoints.
22472 For fast or static tracepoints to work, a special library called the
22473 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22474 This library is built and distributed as an integral part of
22475 @code{gdbserver}. In addition, support for static tracepoints
22476 requires building the in-process agent library with static tracepoints
22477 support. At present, the UST (LTTng Userspace Tracer,
22478 @url{http://lttng.org/ust}) tracing engine is supported. This support
22479 is automatically available if UST development headers are found in the
22480 standard include path when @code{gdbserver} is built, or if
22481 @code{gdbserver} was explicitly configured using @option{--with-ust}
22482 to point at such headers. You can explicitly disable the support
22483 using @option{--with-ust=no}.
22485 There are several ways to load the in-process agent in your program:
22488 @item Specifying it as dependency at link time
22490 You can link your program dynamically with the in-process agent
22491 library. On most systems, this is accomplished by adding
22492 @code{-linproctrace} to the link command.
22494 @item Using the system's preloading mechanisms
22496 You can force loading the in-process agent at startup time by using
22497 your system's support for preloading shared libraries. Many Unixes
22498 support the concept of preloading user defined libraries. In most
22499 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22500 in the environment. See also the description of @code{gdbserver}'s
22501 @option{--wrapper} command line option.
22503 @item Using @value{GDBN} to force loading the agent at run time
22505 On some systems, you can force the inferior to load a shared library,
22506 by calling a dynamic loader function in the inferior that takes care
22507 of dynamically looking up and loading a shared library. On most Unix
22508 systems, the function is @code{dlopen}. You'll use the @code{call}
22509 command for that. For example:
22512 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22515 Note that on most Unix systems, for the @code{dlopen} function to be
22516 available, the program needs to be linked with @code{-ldl}.
22519 On systems that have a userspace dynamic loader, like most Unix
22520 systems, when you connect to @code{gdbserver} using @code{target
22521 remote}, you'll find that the program is stopped at the dynamic
22522 loader's entry point, and no shared library has been loaded in the
22523 program's address space yet, including the in-process agent. In that
22524 case, before being able to use any of the fast or static tracepoints
22525 features, you need to let the loader run and load the shared
22526 libraries. The simplest way to do that is to run the program to the
22527 main procedure. E.g., if debugging a C or C@t{++} program, start
22528 @code{gdbserver} like so:
22531 $ gdbserver :9999 myprogram
22534 Start GDB and connect to @code{gdbserver} like so, and run to main:
22538 (@value{GDBP}) target remote myhost:9999
22539 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22540 (@value{GDBP}) b main
22541 (@value{GDBP}) continue
22544 The in-process tracing agent library should now be loaded into the
22545 process; you can confirm it with the @code{info sharedlibrary}
22546 command, which will list @file{libinproctrace.so} as loaded in the
22547 process. You are now ready to install fast tracepoints, list static
22548 tracepoint markers, probe static tracepoints markers, and start
22551 @node Remote Configuration
22552 @section Remote Configuration
22555 @kindex show remote
22556 This section documents the configuration options available when
22557 debugging remote programs. For the options related to the File I/O
22558 extensions of the remote protocol, see @ref{system,
22559 system-call-allowed}.
22562 @item set remoteaddresssize @var{bits}
22563 @cindex address size for remote targets
22564 @cindex bits in remote address
22565 Set the maximum size of address in a memory packet to the specified
22566 number of bits. @value{GDBN} will mask off the address bits above
22567 that number, when it passes addresses to the remote target. The
22568 default value is the number of bits in the target's address.
22570 @item show remoteaddresssize
22571 Show the current value of remote address size in bits.
22573 @item set serial baud @var{n}
22574 @cindex baud rate for remote targets
22575 Set the baud rate for the remote serial I/O to @var{n} baud. The
22576 value is used to set the speed of the serial port used for debugging
22579 @item show serial baud
22580 Show the current speed of the remote connection.
22582 @item set serial parity @var{parity}
22583 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22584 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22586 @item show serial parity
22587 Show the current parity of the serial port.
22589 @item set remotebreak
22590 @cindex interrupt remote programs
22591 @cindex BREAK signal instead of Ctrl-C
22592 @anchor{set remotebreak}
22593 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22594 when you type @kbd{Ctrl-c} to interrupt the program running
22595 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22596 character instead. The default is off, since most remote systems
22597 expect to see @samp{Ctrl-C} as the interrupt signal.
22599 @item show remotebreak
22600 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22601 interrupt the remote program.
22603 @item set remoteflow on
22604 @itemx set remoteflow off
22605 @kindex set remoteflow
22606 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22607 on the serial port used to communicate to the remote target.
22609 @item show remoteflow
22610 @kindex show remoteflow
22611 Show the current setting of hardware flow control.
22613 @item set remotelogbase @var{base}
22614 Set the base (a.k.a.@: radix) of logging serial protocol
22615 communications to @var{base}. Supported values of @var{base} are:
22616 @code{ascii}, @code{octal}, and @code{hex}. The default is
22619 @item show remotelogbase
22620 Show the current setting of the radix for logging remote serial
22623 @item set remotelogfile @var{file}
22624 @cindex record serial communications on file
22625 Record remote serial communications on the named @var{file}. The
22626 default is not to record at all.
22628 @item show remotelogfile
22629 Show the current setting of the file name on which to record the
22630 serial communications.
22632 @item set remotetimeout @var{num}
22633 @cindex timeout for serial communications
22634 @cindex remote timeout
22635 Set the timeout limit to wait for the remote target to respond to
22636 @var{num} seconds. The default is 2 seconds.
22638 @item show remotetimeout
22639 Show the current number of seconds to wait for the remote target
22642 @cindex limit hardware breakpoints and watchpoints
22643 @cindex remote target, limit break- and watchpoints
22644 @anchor{set remote hardware-watchpoint-limit}
22645 @anchor{set remote hardware-breakpoint-limit}
22646 @item set remote hardware-watchpoint-limit @var{limit}
22647 @itemx set remote hardware-breakpoint-limit @var{limit}
22648 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22649 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22650 watchpoints or breakpoints, and @code{unlimited} for unlimited
22651 watchpoints or breakpoints.
22653 @item show remote hardware-watchpoint-limit
22654 @itemx show remote hardware-breakpoint-limit
22655 Show the current limit for the number of hardware watchpoints or
22656 breakpoints that @value{GDBN} can use.
22658 @cindex limit hardware watchpoints length
22659 @cindex remote target, limit watchpoints length
22660 @anchor{set remote hardware-watchpoint-length-limit}
22661 @item set remote hardware-watchpoint-length-limit @var{limit}
22662 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22663 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22664 hardware watchpoints and @code{unlimited} allows watchpoints of any
22667 @item show remote hardware-watchpoint-length-limit
22668 Show the current limit (in bytes) of the maximum length of
22669 a remote hardware watchpoint.
22671 @item set remote exec-file @var{filename}
22672 @itemx show remote exec-file
22673 @anchor{set remote exec-file}
22674 @cindex executable file, for remote target
22675 Select the file used for @code{run} with @code{target
22676 extended-remote}. This should be set to a filename valid on the
22677 target system. If it is not set, the target will use a default
22678 filename (e.g.@: the last program run).
22680 @item set remote interrupt-sequence
22681 @cindex interrupt remote programs
22682 @cindex select Ctrl-C, BREAK or BREAK-g
22683 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22684 @samp{BREAK-g} as the
22685 sequence to the remote target in order to interrupt the execution.
22686 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22687 is high level of serial line for some certain time.
22688 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22689 It is @code{BREAK} signal followed by character @code{g}.
22691 @item show interrupt-sequence
22692 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22693 is sent by @value{GDBN} to interrupt the remote program.
22694 @code{BREAK-g} is BREAK signal followed by @code{g} and
22695 also known as Magic SysRq g.
22697 @item set remote interrupt-on-connect
22698 @cindex send interrupt-sequence on start
22699 Specify whether interrupt-sequence is sent to remote target when
22700 @value{GDBN} connects to it. This is mostly needed when you debug
22701 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22702 which is known as Magic SysRq g in order to connect @value{GDBN}.
22704 @item show interrupt-on-connect
22705 Show whether interrupt-sequence is sent
22706 to remote target when @value{GDBN} connects to it.
22710 @item set tcp auto-retry on
22711 @cindex auto-retry, for remote TCP target
22712 Enable auto-retry for remote TCP connections. This is useful if the remote
22713 debugging agent is launched in parallel with @value{GDBN}; there is a race
22714 condition because the agent may not become ready to accept the connection
22715 before @value{GDBN} attempts to connect. When auto-retry is
22716 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22717 to establish the connection using the timeout specified by
22718 @code{set tcp connect-timeout}.
22720 @item set tcp auto-retry off
22721 Do not auto-retry failed TCP connections.
22723 @item show tcp auto-retry
22724 Show the current auto-retry setting.
22726 @item set tcp connect-timeout @var{seconds}
22727 @itemx set tcp connect-timeout unlimited
22728 @cindex connection timeout, for remote TCP target
22729 @cindex timeout, for remote target connection
22730 Set the timeout for establishing a TCP connection to the remote target to
22731 @var{seconds}. The timeout affects both polling to retry failed connections
22732 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22733 that are merely slow to complete, and represents an approximate cumulative
22734 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22735 @value{GDBN} will keep attempting to establish a connection forever,
22736 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22738 @item show tcp connect-timeout
22739 Show the current connection timeout setting.
22742 @cindex remote packets, enabling and disabling
22743 The @value{GDBN} remote protocol autodetects the packets supported by
22744 your debugging stub. If you need to override the autodetection, you
22745 can use these commands to enable or disable individual packets. Each
22746 packet can be set to @samp{on} (the remote target supports this
22747 packet), @samp{off} (the remote target does not support this packet),
22748 or @samp{auto} (detect remote target support for this packet). They
22749 all default to @samp{auto}. For more information about each packet,
22750 see @ref{Remote Protocol}.
22752 During normal use, you should not have to use any of these commands.
22753 If you do, that may be a bug in your remote debugging stub, or a bug
22754 in @value{GDBN}. You may want to report the problem to the
22755 @value{GDBN} developers.
22757 For each packet @var{name}, the command to enable or disable the
22758 packet is @code{set remote @var{name}-packet}. The available settings
22761 @multitable @columnfractions 0.28 0.32 0.25
22764 @tab Related Features
22766 @item @code{fetch-register}
22768 @tab @code{info registers}
22770 @item @code{set-register}
22774 @item @code{binary-download}
22776 @tab @code{load}, @code{set}
22778 @item @code{read-aux-vector}
22779 @tab @code{qXfer:auxv:read}
22780 @tab @code{info auxv}
22782 @item @code{symbol-lookup}
22783 @tab @code{qSymbol}
22784 @tab Detecting multiple threads
22786 @item @code{attach}
22787 @tab @code{vAttach}
22790 @item @code{verbose-resume}
22792 @tab Stepping or resuming multiple threads
22798 @item @code{software-breakpoint}
22802 @item @code{hardware-breakpoint}
22806 @item @code{write-watchpoint}
22810 @item @code{read-watchpoint}
22814 @item @code{access-watchpoint}
22818 @item @code{pid-to-exec-file}
22819 @tab @code{qXfer:exec-file:read}
22820 @tab @code{attach}, @code{run}
22822 @item @code{target-features}
22823 @tab @code{qXfer:features:read}
22824 @tab @code{set architecture}
22826 @item @code{library-info}
22827 @tab @code{qXfer:libraries:read}
22828 @tab @code{info sharedlibrary}
22830 @item @code{memory-map}
22831 @tab @code{qXfer:memory-map:read}
22832 @tab @code{info mem}
22834 @item @code{read-sdata-object}
22835 @tab @code{qXfer:sdata:read}
22836 @tab @code{print $_sdata}
22838 @item @code{read-siginfo-object}
22839 @tab @code{qXfer:siginfo:read}
22840 @tab @code{print $_siginfo}
22842 @item @code{write-siginfo-object}
22843 @tab @code{qXfer:siginfo:write}
22844 @tab @code{set $_siginfo}
22846 @item @code{threads}
22847 @tab @code{qXfer:threads:read}
22848 @tab @code{info threads}
22850 @item @code{get-thread-local-@*storage-address}
22851 @tab @code{qGetTLSAddr}
22852 @tab Displaying @code{__thread} variables
22854 @item @code{get-thread-information-block-address}
22855 @tab @code{qGetTIBAddr}
22856 @tab Display MS-Windows Thread Information Block.
22858 @item @code{search-memory}
22859 @tab @code{qSearch:memory}
22862 @item @code{supported-packets}
22863 @tab @code{qSupported}
22864 @tab Remote communications parameters
22866 @item @code{catch-syscalls}
22867 @tab @code{QCatchSyscalls}
22868 @tab @code{catch syscall}
22870 @item @code{pass-signals}
22871 @tab @code{QPassSignals}
22872 @tab @code{handle @var{signal}}
22874 @item @code{program-signals}
22875 @tab @code{QProgramSignals}
22876 @tab @code{handle @var{signal}}
22878 @item @code{hostio-close-packet}
22879 @tab @code{vFile:close}
22880 @tab @code{remote get}, @code{remote put}
22882 @item @code{hostio-open-packet}
22883 @tab @code{vFile:open}
22884 @tab @code{remote get}, @code{remote put}
22886 @item @code{hostio-pread-packet}
22887 @tab @code{vFile:pread}
22888 @tab @code{remote get}, @code{remote put}
22890 @item @code{hostio-pwrite-packet}
22891 @tab @code{vFile:pwrite}
22892 @tab @code{remote get}, @code{remote put}
22894 @item @code{hostio-unlink-packet}
22895 @tab @code{vFile:unlink}
22896 @tab @code{remote delete}
22898 @item @code{hostio-readlink-packet}
22899 @tab @code{vFile:readlink}
22902 @item @code{hostio-fstat-packet}
22903 @tab @code{vFile:fstat}
22906 @item @code{hostio-setfs-packet}
22907 @tab @code{vFile:setfs}
22910 @item @code{noack-packet}
22911 @tab @code{QStartNoAckMode}
22912 @tab Packet acknowledgment
22914 @item @code{osdata}
22915 @tab @code{qXfer:osdata:read}
22916 @tab @code{info os}
22918 @item @code{query-attached}
22919 @tab @code{qAttached}
22920 @tab Querying remote process attach state.
22922 @item @code{trace-buffer-size}
22923 @tab @code{QTBuffer:size}
22924 @tab @code{set trace-buffer-size}
22926 @item @code{trace-status}
22927 @tab @code{qTStatus}
22928 @tab @code{tstatus}
22930 @item @code{traceframe-info}
22931 @tab @code{qXfer:traceframe-info:read}
22932 @tab Traceframe info
22934 @item @code{install-in-trace}
22935 @tab @code{InstallInTrace}
22936 @tab Install tracepoint in tracing
22938 @item @code{disable-randomization}
22939 @tab @code{QDisableRandomization}
22940 @tab @code{set disable-randomization}
22942 @item @code{startup-with-shell}
22943 @tab @code{QStartupWithShell}
22944 @tab @code{set startup-with-shell}
22946 @item @code{environment-hex-encoded}
22947 @tab @code{QEnvironmentHexEncoded}
22948 @tab @code{set environment}
22950 @item @code{environment-unset}
22951 @tab @code{QEnvironmentUnset}
22952 @tab @code{unset environment}
22954 @item @code{environment-reset}
22955 @tab @code{QEnvironmentReset}
22956 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22958 @item @code{set-working-dir}
22959 @tab @code{QSetWorkingDir}
22960 @tab @code{set cwd}
22962 @item @code{conditional-breakpoints-packet}
22963 @tab @code{Z0 and Z1}
22964 @tab @code{Support for target-side breakpoint condition evaluation}
22966 @item @code{multiprocess-extensions}
22967 @tab @code{multiprocess extensions}
22968 @tab Debug multiple processes and remote process PID awareness
22970 @item @code{swbreak-feature}
22971 @tab @code{swbreak stop reason}
22974 @item @code{hwbreak-feature}
22975 @tab @code{hwbreak stop reason}
22978 @item @code{fork-event-feature}
22979 @tab @code{fork stop reason}
22982 @item @code{vfork-event-feature}
22983 @tab @code{vfork stop reason}
22986 @item @code{exec-event-feature}
22987 @tab @code{exec stop reason}
22990 @item @code{thread-events}
22991 @tab @code{QThreadEvents}
22992 @tab Tracking thread lifetime.
22994 @item @code{no-resumed-stop-reply}
22995 @tab @code{no resumed thread left stop reply}
22996 @tab Tracking thread lifetime.
23001 @section Implementing a Remote Stub
23003 @cindex debugging stub, example
23004 @cindex remote stub, example
23005 @cindex stub example, remote debugging
23006 The stub files provided with @value{GDBN} implement the target side of the
23007 communication protocol, and the @value{GDBN} side is implemented in the
23008 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23009 these subroutines to communicate, and ignore the details. (If you're
23010 implementing your own stub file, you can still ignore the details: start
23011 with one of the existing stub files. @file{sparc-stub.c} is the best
23012 organized, and therefore the easiest to read.)
23014 @cindex remote serial debugging, overview
23015 To debug a program running on another machine (the debugging
23016 @dfn{target} machine), you must first arrange for all the usual
23017 prerequisites for the program to run by itself. For example, for a C
23022 A startup routine to set up the C runtime environment; these usually
23023 have a name like @file{crt0}. The startup routine may be supplied by
23024 your hardware supplier, or you may have to write your own.
23027 A C subroutine library to support your program's
23028 subroutine calls, notably managing input and output.
23031 A way of getting your program to the other machine---for example, a
23032 download program. These are often supplied by the hardware
23033 manufacturer, but you may have to write your own from hardware
23037 The next step is to arrange for your program to use a serial port to
23038 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23039 machine). In general terms, the scheme looks like this:
23043 @value{GDBN} already understands how to use this protocol; when everything
23044 else is set up, you can simply use the @samp{target remote} command
23045 (@pxref{Targets,,Specifying a Debugging Target}).
23047 @item On the target,
23048 you must link with your program a few special-purpose subroutines that
23049 implement the @value{GDBN} remote serial protocol. The file containing these
23050 subroutines is called a @dfn{debugging stub}.
23052 On certain remote targets, you can use an auxiliary program
23053 @code{gdbserver} instead of linking a stub into your program.
23054 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23057 The debugging stub is specific to the architecture of the remote
23058 machine; for example, use @file{sparc-stub.c} to debug programs on
23061 @cindex remote serial stub list
23062 These working remote stubs are distributed with @value{GDBN}:
23067 @cindex @file{i386-stub.c}
23070 For Intel 386 and compatible architectures.
23073 @cindex @file{m68k-stub.c}
23074 @cindex Motorola 680x0
23076 For Motorola 680x0 architectures.
23079 @cindex @file{sh-stub.c}
23082 For Renesas SH architectures.
23085 @cindex @file{sparc-stub.c}
23087 For @sc{sparc} architectures.
23089 @item sparcl-stub.c
23090 @cindex @file{sparcl-stub.c}
23093 For Fujitsu @sc{sparclite} architectures.
23097 The @file{README} file in the @value{GDBN} distribution may list other
23098 recently added stubs.
23101 * Stub Contents:: What the stub can do for you
23102 * Bootstrapping:: What you must do for the stub
23103 * Debug Session:: Putting it all together
23106 @node Stub Contents
23107 @subsection What the Stub Can Do for You
23109 @cindex remote serial stub
23110 The debugging stub for your architecture supplies these three
23114 @item set_debug_traps
23115 @findex set_debug_traps
23116 @cindex remote serial stub, initialization
23117 This routine arranges for @code{handle_exception} to run when your
23118 program stops. You must call this subroutine explicitly in your
23119 program's startup code.
23121 @item handle_exception
23122 @findex handle_exception
23123 @cindex remote serial stub, main routine
23124 This is the central workhorse, but your program never calls it
23125 explicitly---the setup code arranges for @code{handle_exception} to
23126 run when a trap is triggered.
23128 @code{handle_exception} takes control when your program stops during
23129 execution (for example, on a breakpoint), and mediates communications
23130 with @value{GDBN} on the host machine. This is where the communications
23131 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23132 representative on the target machine. It begins by sending summary
23133 information on the state of your program, then continues to execute,
23134 retrieving and transmitting any information @value{GDBN} needs, until you
23135 execute a @value{GDBN} command that makes your program resume; at that point,
23136 @code{handle_exception} returns control to your own code on the target
23140 @cindex @code{breakpoint} subroutine, remote
23141 Use this auxiliary subroutine to make your program contain a
23142 breakpoint. Depending on the particular situation, this may be the only
23143 way for @value{GDBN} to get control. For instance, if your target
23144 machine has some sort of interrupt button, you won't need to call this;
23145 pressing the interrupt button transfers control to
23146 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23147 simply receiving characters on the serial port may also trigger a trap;
23148 again, in that situation, you don't need to call @code{breakpoint} from
23149 your own program---simply running @samp{target remote} from the host
23150 @value{GDBN} session gets control.
23152 Call @code{breakpoint} if none of these is true, or if you simply want
23153 to make certain your program stops at a predetermined point for the
23154 start of your debugging session.
23157 @node Bootstrapping
23158 @subsection What You Must Do for the Stub
23160 @cindex remote stub, support routines
23161 The debugging stubs that come with @value{GDBN} are set up for a particular
23162 chip architecture, but they have no information about the rest of your
23163 debugging target machine.
23165 First of all you need to tell the stub how to communicate with the
23169 @item int getDebugChar()
23170 @findex getDebugChar
23171 Write this subroutine to read a single character from the serial port.
23172 It may be identical to @code{getchar} for your target system; a
23173 different name is used to allow you to distinguish the two if you wish.
23175 @item void putDebugChar(int)
23176 @findex putDebugChar
23177 Write this subroutine to write a single character to the serial port.
23178 It may be identical to @code{putchar} for your target system; a
23179 different name is used to allow you to distinguish the two if you wish.
23182 @cindex control C, and remote debugging
23183 @cindex interrupting remote targets
23184 If you want @value{GDBN} to be able to stop your program while it is
23185 running, you need to use an interrupt-driven serial driver, and arrange
23186 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23187 character). That is the character which @value{GDBN} uses to tell the
23188 remote system to stop.
23190 Getting the debugging target to return the proper status to @value{GDBN}
23191 probably requires changes to the standard stub; one quick and dirty way
23192 is to just execute a breakpoint instruction (the ``dirty'' part is that
23193 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23195 Other routines you need to supply are:
23198 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23199 @findex exceptionHandler
23200 Write this function to install @var{exception_address} in the exception
23201 handling tables. You need to do this because the stub does not have any
23202 way of knowing what the exception handling tables on your target system
23203 are like (for example, the processor's table might be in @sc{rom},
23204 containing entries which point to a table in @sc{ram}).
23205 The @var{exception_number} specifies the exception which should be changed;
23206 its meaning is architecture-dependent (for example, different numbers
23207 might represent divide by zero, misaligned access, etc). When this
23208 exception occurs, control should be transferred directly to
23209 @var{exception_address}, and the processor state (stack, registers,
23210 and so on) should be just as it is when a processor exception occurs. So if
23211 you want to use a jump instruction to reach @var{exception_address}, it
23212 should be a simple jump, not a jump to subroutine.
23214 For the 386, @var{exception_address} should be installed as an interrupt
23215 gate so that interrupts are masked while the handler runs. The gate
23216 should be at privilege level 0 (the most privileged level). The
23217 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23218 help from @code{exceptionHandler}.
23220 @item void flush_i_cache()
23221 @findex flush_i_cache
23222 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23223 instruction cache, if any, on your target machine. If there is no
23224 instruction cache, this subroutine may be a no-op.
23226 On target machines that have instruction caches, @value{GDBN} requires this
23227 function to make certain that the state of your program is stable.
23231 You must also make sure this library routine is available:
23234 @item void *memset(void *, int, int)
23236 This is the standard library function @code{memset} that sets an area of
23237 memory to a known value. If you have one of the free versions of
23238 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23239 either obtain it from your hardware manufacturer, or write your own.
23242 If you do not use the GNU C compiler, you may need other standard
23243 library subroutines as well; this varies from one stub to another,
23244 but in general the stubs are likely to use any of the common library
23245 subroutines which @code{@value{NGCC}} generates as inline code.
23248 @node Debug Session
23249 @subsection Putting it All Together
23251 @cindex remote serial debugging summary
23252 In summary, when your program is ready to debug, you must follow these
23257 Make sure you have defined the supporting low-level routines
23258 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23260 @code{getDebugChar}, @code{putDebugChar},
23261 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23265 Insert these lines in your program's startup code, before the main
23266 procedure is called:
23273 On some machines, when a breakpoint trap is raised, the hardware
23274 automatically makes the PC point to the instruction after the
23275 breakpoint. If your machine doesn't do that, you may need to adjust
23276 @code{handle_exception} to arrange for it to return to the instruction
23277 after the breakpoint on this first invocation, so that your program
23278 doesn't keep hitting the initial breakpoint instead of making
23282 For the 680x0 stub only, you need to provide a variable called
23283 @code{exceptionHook}. Normally you just use:
23286 void (*exceptionHook)() = 0;
23290 but if before calling @code{set_debug_traps}, you set it to point to a
23291 function in your program, that function is called when
23292 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23293 error). The function indicated by @code{exceptionHook} is called with
23294 one parameter: an @code{int} which is the exception number.
23297 Compile and link together: your program, the @value{GDBN} debugging stub for
23298 your target architecture, and the supporting subroutines.
23301 Make sure you have a serial connection between your target machine and
23302 the @value{GDBN} host, and identify the serial port on the host.
23305 @c The "remote" target now provides a `load' command, so we should
23306 @c document that. FIXME.
23307 Download your program to your target machine (or get it there by
23308 whatever means the manufacturer provides), and start it.
23311 Start @value{GDBN} on the host, and connect to the target
23312 (@pxref{Connecting,,Connecting to a Remote Target}).
23316 @node Configurations
23317 @chapter Configuration-Specific Information
23319 While nearly all @value{GDBN} commands are available for all native and
23320 cross versions of the debugger, there are some exceptions. This chapter
23321 describes things that are only available in certain configurations.
23323 There are three major categories of configurations: native
23324 configurations, where the host and target are the same, embedded
23325 operating system configurations, which are usually the same for several
23326 different processor architectures, and bare embedded processors, which
23327 are quite different from each other.
23332 * Embedded Processors::
23339 This section describes details specific to particular native
23343 * BSD libkvm Interface:: Debugging BSD kernel memory images
23344 * Process Information:: Process information
23345 * DJGPP Native:: Features specific to the DJGPP port
23346 * Cygwin Native:: Features specific to the Cygwin port
23347 * Hurd Native:: Features specific to @sc{gnu} Hurd
23348 * Darwin:: Features specific to Darwin
23349 * FreeBSD:: Features specific to FreeBSD
23352 @node BSD libkvm Interface
23353 @subsection BSD libkvm Interface
23356 @cindex kernel memory image
23357 @cindex kernel crash dump
23359 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23360 interface that provides a uniform interface for accessing kernel virtual
23361 memory images, including live systems and crash dumps. @value{GDBN}
23362 uses this interface to allow you to debug live kernels and kernel crash
23363 dumps on many native BSD configurations. This is implemented as a
23364 special @code{kvm} debugging target. For debugging a live system, load
23365 the currently running kernel into @value{GDBN} and connect to the
23369 (@value{GDBP}) @b{target kvm}
23372 For debugging crash dumps, provide the file name of the crash dump as an
23376 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23379 Once connected to the @code{kvm} target, the following commands are
23385 Set current context from the @dfn{Process Control Block} (PCB) address.
23388 Set current context from proc address. This command isn't available on
23389 modern FreeBSD systems.
23392 @node Process Information
23393 @subsection Process Information
23395 @cindex examine process image
23396 @cindex process info via @file{/proc}
23398 Some operating systems provide interfaces to fetch additional
23399 information about running processes beyond memory and per-thread
23400 register state. If @value{GDBN} is configured for an operating system
23401 with a supported interface, the command @code{info proc} is available
23402 to report information about the process running your program, or about
23403 any process running on your system.
23405 One supported interface is a facility called @samp{/proc} that can be
23406 used to examine the image of a running process using file-system
23407 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23410 On FreeBSD systems, system control nodes are used to query process
23413 In addition, some systems may provide additional process information
23414 in core files. Note that a core file may include a subset of the
23415 information available from a live process. Process information is
23416 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23423 @itemx info proc @var{process-id}
23424 Summarize available information about a process. If a
23425 process ID is specified by @var{process-id}, display information about
23426 that process; otherwise display information about the program being
23427 debugged. The summary includes the debugged process ID, the command
23428 line used to invoke it, its current working directory, and its
23429 executable file's absolute file name.
23431 On some systems, @var{process-id} can be of the form
23432 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23433 within a process. If the optional @var{pid} part is missing, it means
23434 a thread from the process being debugged (the leading @samp{/} still
23435 needs to be present, or else @value{GDBN} will interpret the number as
23436 a process ID rather than a thread ID).
23438 @item info proc cmdline
23439 @cindex info proc cmdline
23440 Show the original command line of the process. This command is
23441 supported on @sc{gnu}/Linux and FreeBSD.
23443 @item info proc cwd
23444 @cindex info proc cwd
23445 Show the current working directory of the process. This command is
23446 supported on @sc{gnu}/Linux and FreeBSD.
23448 @item info proc exe
23449 @cindex info proc exe
23450 Show the name of executable of the process. This command is supported
23451 on @sc{gnu}/Linux and FreeBSD.
23453 @item info proc files
23454 @cindex info proc files
23455 Show the file descriptors open by the process. For each open file
23456 descriptor, @value{GDBN} shows its number, type (file, directory,
23457 character device, socket), file pointer offset, and the name of the
23458 resource open on the descriptor. The resource name can be a file name
23459 (for files, directories, and devices) or a protocol followed by socket
23460 address (for network connections). This command is supported on
23463 This example shows the open file descriptors for a process using a
23464 tty for standard input and output as well as two network sockets:
23467 (gdb) info proc files 22136
23471 FD Type Offset Flags Name
23472 text file - r-------- /usr/bin/ssh
23473 ctty chr - rw------- /dev/pts/20
23474 cwd dir - r-------- /usr/home/john
23475 root dir - r-------- /
23476 0 chr 0x32933a4 rw------- /dev/pts/20
23477 1 chr 0x32933a4 rw------- /dev/pts/20
23478 2 chr 0x32933a4 rw------- /dev/pts/20
23479 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23480 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23483 @item info proc mappings
23484 @cindex memory address space mappings
23485 Report the memory address space ranges accessible in a process. On
23486 Solaris and FreeBSD systems, each memory range includes information on
23487 whether the process has read, write, or execute access rights to each
23488 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
23489 includes the object file which is mapped to that range.
23491 @item info proc stat
23492 @itemx info proc status
23493 @cindex process detailed status information
23494 Show additional process-related information, including the user ID and
23495 group ID; virtual memory usage; the signals that are pending, blocked,
23496 and ignored; its TTY; its consumption of system and user time; its
23497 stack size; its @samp{nice} value; etc. These commands are supported
23498 on @sc{gnu}/Linux and FreeBSD.
23500 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23501 information (type @kbd{man 5 proc} from your shell prompt).
23503 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
23506 @item info proc all
23507 Show all the information about the process described under all of the
23508 above @code{info proc} subcommands.
23511 @comment These sub-options of 'info proc' were not included when
23512 @comment procfs.c was re-written. Keep their descriptions around
23513 @comment against the day when someone finds the time to put them back in.
23514 @kindex info proc times
23515 @item info proc times
23516 Starting time, user CPU time, and system CPU time for your program and
23519 @kindex info proc id
23521 Report on the process IDs related to your program: its own process ID,
23522 the ID of its parent, the process group ID, and the session ID.
23525 @item set procfs-trace
23526 @kindex set procfs-trace
23527 @cindex @code{procfs} API calls
23528 This command enables and disables tracing of @code{procfs} API calls.
23530 @item show procfs-trace
23531 @kindex show procfs-trace
23532 Show the current state of @code{procfs} API call tracing.
23534 @item set procfs-file @var{file}
23535 @kindex set procfs-file
23536 Tell @value{GDBN} to write @code{procfs} API trace to the named
23537 @var{file}. @value{GDBN} appends the trace info to the previous
23538 contents of the file. The default is to display the trace on the
23541 @item show procfs-file
23542 @kindex show procfs-file
23543 Show the file to which @code{procfs} API trace is written.
23545 @item proc-trace-entry
23546 @itemx proc-trace-exit
23547 @itemx proc-untrace-entry
23548 @itemx proc-untrace-exit
23549 @kindex proc-trace-entry
23550 @kindex proc-trace-exit
23551 @kindex proc-untrace-entry
23552 @kindex proc-untrace-exit
23553 These commands enable and disable tracing of entries into and exits
23554 from the @code{syscall} interface.
23557 @kindex info pidlist
23558 @cindex process list, QNX Neutrino
23559 For QNX Neutrino only, this command displays the list of all the
23560 processes and all the threads within each process.
23563 @kindex info meminfo
23564 @cindex mapinfo list, QNX Neutrino
23565 For QNX Neutrino only, this command displays the list of all mapinfos.
23569 @subsection Features for Debugging @sc{djgpp} Programs
23570 @cindex @sc{djgpp} debugging
23571 @cindex native @sc{djgpp} debugging
23572 @cindex MS-DOS-specific commands
23575 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23576 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23577 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23578 top of real-mode DOS systems and their emulations.
23580 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23581 defines a few commands specific to the @sc{djgpp} port. This
23582 subsection describes those commands.
23587 This is a prefix of @sc{djgpp}-specific commands which print
23588 information about the target system and important OS structures.
23591 @cindex MS-DOS system info
23592 @cindex free memory information (MS-DOS)
23593 @item info dos sysinfo
23594 This command displays assorted information about the underlying
23595 platform: the CPU type and features, the OS version and flavor, the
23596 DPMI version, and the available conventional and DPMI memory.
23601 @cindex segment descriptor tables
23602 @cindex descriptor tables display
23604 @itemx info dos ldt
23605 @itemx info dos idt
23606 These 3 commands display entries from, respectively, Global, Local,
23607 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23608 tables are data structures which store a descriptor for each segment
23609 that is currently in use. The segment's selector is an index into a
23610 descriptor table; the table entry for that index holds the
23611 descriptor's base address and limit, and its attributes and access
23614 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23615 segment (used for both data and the stack), and a DOS segment (which
23616 allows access to DOS/BIOS data structures and absolute addresses in
23617 conventional memory). However, the DPMI host will usually define
23618 additional segments in order to support the DPMI environment.
23620 @cindex garbled pointers
23621 These commands allow to display entries from the descriptor tables.
23622 Without an argument, all entries from the specified table are
23623 displayed. An argument, which should be an integer expression, means
23624 display a single entry whose index is given by the argument. For
23625 example, here's a convenient way to display information about the
23626 debugged program's data segment:
23629 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23630 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23634 This comes in handy when you want to see whether a pointer is outside
23635 the data segment's limit (i.e.@: @dfn{garbled}).
23637 @cindex page tables display (MS-DOS)
23639 @itemx info dos pte
23640 These two commands display entries from, respectively, the Page
23641 Directory and the Page Tables. Page Directories and Page Tables are
23642 data structures which control how virtual memory addresses are mapped
23643 into physical addresses. A Page Table includes an entry for every
23644 page of memory that is mapped into the program's address space; there
23645 may be several Page Tables, each one holding up to 4096 entries. A
23646 Page Directory has up to 4096 entries, one each for every Page Table
23647 that is currently in use.
23649 Without an argument, @kbd{info dos pde} displays the entire Page
23650 Directory, and @kbd{info dos pte} displays all the entries in all of
23651 the Page Tables. An argument, an integer expression, given to the
23652 @kbd{info dos pde} command means display only that entry from the Page
23653 Directory table. An argument given to the @kbd{info dos pte} command
23654 means display entries from a single Page Table, the one pointed to by
23655 the specified entry in the Page Directory.
23657 @cindex direct memory access (DMA) on MS-DOS
23658 These commands are useful when your program uses @dfn{DMA} (Direct
23659 Memory Access), which needs physical addresses to program the DMA
23662 These commands are supported only with some DPMI servers.
23664 @cindex physical address from linear address
23665 @item info dos address-pte @var{addr}
23666 This command displays the Page Table entry for a specified linear
23667 address. The argument @var{addr} is a linear address which should
23668 already have the appropriate segment's base address added to it,
23669 because this command accepts addresses which may belong to @emph{any}
23670 segment. For example, here's how to display the Page Table entry for
23671 the page where a variable @code{i} is stored:
23674 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23675 @exdent @code{Page Table entry for address 0x11a00d30:}
23676 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23680 This says that @code{i} is stored at offset @code{0xd30} from the page
23681 whose physical base address is @code{0x02698000}, and shows all the
23682 attributes of that page.
23684 Note that you must cast the addresses of variables to a @code{char *},
23685 since otherwise the value of @code{__djgpp_base_address}, the base
23686 address of all variables and functions in a @sc{djgpp} program, will
23687 be added using the rules of C pointer arithmetics: if @code{i} is
23688 declared an @code{int}, @value{GDBN} will add 4 times the value of
23689 @code{__djgpp_base_address} to the address of @code{i}.
23691 Here's another example, it displays the Page Table entry for the
23695 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23696 @exdent @code{Page Table entry for address 0x29110:}
23697 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23701 (The @code{+ 3} offset is because the transfer buffer's address is the
23702 3rd member of the @code{_go32_info_block} structure.) The output
23703 clearly shows that this DPMI server maps the addresses in conventional
23704 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23705 linear (@code{0x29110}) addresses are identical.
23707 This command is supported only with some DPMI servers.
23710 @cindex DOS serial data link, remote debugging
23711 In addition to native debugging, the DJGPP port supports remote
23712 debugging via a serial data link. The following commands are specific
23713 to remote serial debugging in the DJGPP port of @value{GDBN}.
23716 @kindex set com1base
23717 @kindex set com1irq
23718 @kindex set com2base
23719 @kindex set com2irq
23720 @kindex set com3base
23721 @kindex set com3irq
23722 @kindex set com4base
23723 @kindex set com4irq
23724 @item set com1base @var{addr}
23725 This command sets the base I/O port address of the @file{COM1} serial
23728 @item set com1irq @var{irq}
23729 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23730 for the @file{COM1} serial port.
23732 There are similar commands @samp{set com2base}, @samp{set com3irq},
23733 etc.@: for setting the port address and the @code{IRQ} lines for the
23736 @kindex show com1base
23737 @kindex show com1irq
23738 @kindex show com2base
23739 @kindex show com2irq
23740 @kindex show com3base
23741 @kindex show com3irq
23742 @kindex show com4base
23743 @kindex show com4irq
23744 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23745 display the current settings of the base address and the @code{IRQ}
23746 lines used by the COM ports.
23749 @kindex info serial
23750 @cindex DOS serial port status
23751 This command prints the status of the 4 DOS serial ports. For each
23752 port, it prints whether it's active or not, its I/O base address and
23753 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23754 counts of various errors encountered so far.
23758 @node Cygwin Native
23759 @subsection Features for Debugging MS Windows PE Executables
23760 @cindex MS Windows debugging
23761 @cindex native Cygwin debugging
23762 @cindex Cygwin-specific commands
23764 @value{GDBN} supports native debugging of MS Windows programs, including
23765 DLLs with and without symbolic debugging information.
23767 @cindex Ctrl-BREAK, MS-Windows
23768 @cindex interrupt debuggee on MS-Windows
23769 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23770 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23771 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23772 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23773 sequence, which can be used to interrupt the debuggee even if it
23776 There are various additional Cygwin-specific commands, described in
23777 this section. Working with DLLs that have no debugging symbols is
23778 described in @ref{Non-debug DLL Symbols}.
23783 This is a prefix of MS Windows-specific commands which print
23784 information about the target system and important OS structures.
23786 @item info w32 selector
23787 This command displays information returned by
23788 the Win32 API @code{GetThreadSelectorEntry} function.
23789 It takes an optional argument that is evaluated to
23790 a long value to give the information about this given selector.
23791 Without argument, this command displays information
23792 about the six segment registers.
23794 @item info w32 thread-information-block
23795 This command displays thread specific information stored in the
23796 Thread Information Block (readable on the X86 CPU family using @code{$fs}
23797 selector for 32-bit programs and @code{$gs} for 64-bit programs).
23799 @kindex signal-event
23800 @item signal-event @var{id}
23801 This command signals an event with user-provided @var{id}. Used to resume
23802 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
23804 To use it, create or edit the following keys in
23805 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
23806 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
23807 (for x86_64 versions):
23811 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
23812 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
23813 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
23815 The first @code{%ld} will be replaced by the process ID of the
23816 crashing process, the second @code{%ld} will be replaced by the ID of
23817 the event that blocks the crashing process, waiting for @value{GDBN}
23821 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
23822 make the system run debugger specified by the Debugger key
23823 automatically, @code{0} will cause a dialog box with ``OK'' and
23824 ``Cancel'' buttons to appear, which allows the user to either
23825 terminate the crashing process (OK) or debug it (Cancel).
23828 @kindex set cygwin-exceptions
23829 @cindex debugging the Cygwin DLL
23830 @cindex Cygwin DLL, debugging
23831 @item set cygwin-exceptions @var{mode}
23832 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
23833 happen inside the Cygwin DLL. If @var{mode} is @code{off},
23834 @value{GDBN} will delay recognition of exceptions, and may ignore some
23835 exceptions which seem to be caused by internal Cygwin DLL
23836 ``bookkeeping''. This option is meant primarily for debugging the
23837 Cygwin DLL itself; the default value is @code{off} to avoid annoying
23838 @value{GDBN} users with false @code{SIGSEGV} signals.
23840 @kindex show cygwin-exceptions
23841 @item show cygwin-exceptions
23842 Displays whether @value{GDBN} will break on exceptions that happen
23843 inside the Cygwin DLL itself.
23845 @kindex set new-console
23846 @item set new-console @var{mode}
23847 If @var{mode} is @code{on} the debuggee will
23848 be started in a new console on next start.
23849 If @var{mode} is @code{off}, the debuggee will
23850 be started in the same console as the debugger.
23852 @kindex show new-console
23853 @item show new-console
23854 Displays whether a new console is used
23855 when the debuggee is started.
23857 @kindex set new-group
23858 @item set new-group @var{mode}
23859 This boolean value controls whether the debuggee should
23860 start a new group or stay in the same group as the debugger.
23861 This affects the way the Windows OS handles
23864 @kindex show new-group
23865 @item show new-group
23866 Displays current value of new-group boolean.
23868 @kindex set debugevents
23869 @item set debugevents
23870 This boolean value adds debug output concerning kernel events related
23871 to the debuggee seen by the debugger. This includes events that
23872 signal thread and process creation and exit, DLL loading and
23873 unloading, console interrupts, and debugging messages produced by the
23874 Windows @code{OutputDebugString} API call.
23876 @kindex set debugexec
23877 @item set debugexec
23878 This boolean value adds debug output concerning execute events
23879 (such as resume thread) seen by the debugger.
23881 @kindex set debugexceptions
23882 @item set debugexceptions
23883 This boolean value adds debug output concerning exceptions in the
23884 debuggee seen by the debugger.
23886 @kindex set debugmemory
23887 @item set debugmemory
23888 This boolean value adds debug output concerning debuggee memory reads
23889 and writes by the debugger.
23893 This boolean values specifies whether the debuggee is called
23894 via a shell or directly (default value is on).
23898 Displays if the debuggee will be started with a shell.
23903 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23906 @node Non-debug DLL Symbols
23907 @subsubsection Support for DLLs without Debugging Symbols
23908 @cindex DLLs with no debugging symbols
23909 @cindex Minimal symbols and DLLs
23911 Very often on windows, some of the DLLs that your program relies on do
23912 not include symbolic debugging information (for example,
23913 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
23914 symbols in a DLL, it relies on the minimal amount of symbolic
23915 information contained in the DLL's export table. This section
23916 describes working with such symbols, known internally to @value{GDBN} as
23917 ``minimal symbols''.
23919 Note that before the debugged program has started execution, no DLLs
23920 will have been loaded. The easiest way around this problem is simply to
23921 start the program --- either by setting a breakpoint or letting the
23922 program run once to completion.
23924 @subsubsection DLL Name Prefixes
23926 In keeping with the naming conventions used by the Microsoft debugging
23927 tools, DLL export symbols are made available with a prefix based on the
23928 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
23929 also entered into the symbol table, so @code{CreateFileA} is often
23930 sufficient. In some cases there will be name clashes within a program
23931 (particularly if the executable itself includes full debugging symbols)
23932 necessitating the use of the fully qualified name when referring to the
23933 contents of the DLL. Use single-quotes around the name to avoid the
23934 exclamation mark (``!'') being interpreted as a language operator.
23936 Note that the internal name of the DLL may be all upper-case, even
23937 though the file name of the DLL is lower-case, or vice-versa. Since
23938 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
23939 some confusion. If in doubt, try the @code{info functions} and
23940 @code{info variables} commands or even @code{maint print msymbols}
23941 (@pxref{Symbols}). Here's an example:
23944 (@value{GDBP}) info function CreateFileA
23945 All functions matching regular expression "CreateFileA":
23947 Non-debugging symbols:
23948 0x77e885f4 CreateFileA
23949 0x77e885f4 KERNEL32!CreateFileA
23953 (@value{GDBP}) info function !
23954 All functions matching regular expression "!":
23956 Non-debugging symbols:
23957 0x6100114c cygwin1!__assert
23958 0x61004034 cygwin1!_dll_crt0@@0
23959 0x61004240 cygwin1!dll_crt0(per_process *)
23963 @subsubsection Working with Minimal Symbols
23965 Symbols extracted from a DLL's export table do not contain very much
23966 type information. All that @value{GDBN} can do is guess whether a symbol
23967 refers to a function or variable depending on the linker section that
23968 contains the symbol. Also note that the actual contents of the memory
23969 contained in a DLL are not available unless the program is running. This
23970 means that you cannot examine the contents of a variable or disassemble
23971 a function within a DLL without a running program.
23973 Variables are generally treated as pointers and dereferenced
23974 automatically. For this reason, it is often necessary to prefix a
23975 variable name with the address-of operator (``&'') and provide explicit
23976 type information in the command. Here's an example of the type of
23980 (@value{GDBP}) print 'cygwin1!__argv'
23981 'cygwin1!__argv' has unknown type; cast it to its declared type
23985 (@value{GDBP}) x 'cygwin1!__argv'
23986 'cygwin1!__argv' has unknown type; cast it to its declared type
23989 And two possible solutions:
23992 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23993 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23997 (@value{GDBP}) x/2x &'cygwin1!__argv'
23998 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23999 (@value{GDBP}) x/x 0x10021608
24000 0x10021608: 0x0022fd98
24001 (@value{GDBP}) x/s 0x0022fd98
24002 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24005 Setting a break point within a DLL is possible even before the program
24006 starts execution. However, under these circumstances, @value{GDBN} can't
24007 examine the initial instructions of the function in order to skip the
24008 function's frame set-up code. You can work around this by using ``*&''
24009 to set the breakpoint at a raw memory address:
24012 (@value{GDBP}) break *&'python22!PyOS_Readline'
24013 Breakpoint 1 at 0x1e04eff0
24016 The author of these extensions is not entirely convinced that setting a
24017 break point within a shared DLL like @file{kernel32.dll} is completely
24021 @subsection Commands Specific to @sc{gnu} Hurd Systems
24022 @cindex @sc{gnu} Hurd debugging
24024 This subsection describes @value{GDBN} commands specific to the
24025 @sc{gnu} Hurd native debugging.
24030 @kindex set signals@r{, Hurd command}
24031 @kindex set sigs@r{, Hurd command}
24032 This command toggles the state of inferior signal interception by
24033 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24034 affected by this command. @code{sigs} is a shorthand alias for
24039 @kindex show signals@r{, Hurd command}
24040 @kindex show sigs@r{, Hurd command}
24041 Show the current state of intercepting inferior's signals.
24043 @item set signal-thread
24044 @itemx set sigthread
24045 @kindex set signal-thread
24046 @kindex set sigthread
24047 This command tells @value{GDBN} which thread is the @code{libc} signal
24048 thread. That thread is run when a signal is delivered to a running
24049 process. @code{set sigthread} is the shorthand alias of @code{set
24052 @item show signal-thread
24053 @itemx show sigthread
24054 @kindex show signal-thread
24055 @kindex show sigthread
24056 These two commands show which thread will run when the inferior is
24057 delivered a signal.
24060 @kindex set stopped@r{, Hurd command}
24061 This commands tells @value{GDBN} that the inferior process is stopped,
24062 as with the @code{SIGSTOP} signal. The stopped process can be
24063 continued by delivering a signal to it.
24066 @kindex show stopped@r{, Hurd command}
24067 This command shows whether @value{GDBN} thinks the debuggee is
24070 @item set exceptions
24071 @kindex set exceptions@r{, Hurd command}
24072 Use this command to turn off trapping of exceptions in the inferior.
24073 When exception trapping is off, neither breakpoints nor
24074 single-stepping will work. To restore the default, set exception
24077 @item show exceptions
24078 @kindex show exceptions@r{, Hurd command}
24079 Show the current state of trapping exceptions in the inferior.
24081 @item set task pause
24082 @kindex set task@r{, Hurd commands}
24083 @cindex task attributes (@sc{gnu} Hurd)
24084 @cindex pause current task (@sc{gnu} Hurd)
24085 This command toggles task suspension when @value{GDBN} has control.
24086 Setting it to on takes effect immediately, and the task is suspended
24087 whenever @value{GDBN} gets control. Setting it to off will take
24088 effect the next time the inferior is continued. If this option is set
24089 to off, you can use @code{set thread default pause on} or @code{set
24090 thread pause on} (see below) to pause individual threads.
24092 @item show task pause
24093 @kindex show task@r{, Hurd commands}
24094 Show the current state of task suspension.
24096 @item set task detach-suspend-count
24097 @cindex task suspend count
24098 @cindex detach from task, @sc{gnu} Hurd
24099 This command sets the suspend count the task will be left with when
24100 @value{GDBN} detaches from it.
24102 @item show task detach-suspend-count
24103 Show the suspend count the task will be left with when detaching.
24105 @item set task exception-port
24106 @itemx set task excp
24107 @cindex task exception port, @sc{gnu} Hurd
24108 This command sets the task exception port to which @value{GDBN} will
24109 forward exceptions. The argument should be the value of the @dfn{send
24110 rights} of the task. @code{set task excp} is a shorthand alias.
24112 @item set noninvasive
24113 @cindex noninvasive task options
24114 This command switches @value{GDBN} to a mode that is the least
24115 invasive as far as interfering with the inferior is concerned. This
24116 is the same as using @code{set task pause}, @code{set exceptions}, and
24117 @code{set signals} to values opposite to the defaults.
24119 @item info send-rights
24120 @itemx info receive-rights
24121 @itemx info port-rights
24122 @itemx info port-sets
24123 @itemx info dead-names
24126 @cindex send rights, @sc{gnu} Hurd
24127 @cindex receive rights, @sc{gnu} Hurd
24128 @cindex port rights, @sc{gnu} Hurd
24129 @cindex port sets, @sc{gnu} Hurd
24130 @cindex dead names, @sc{gnu} Hurd
24131 These commands display information about, respectively, send rights,
24132 receive rights, port rights, port sets, and dead names of a task.
24133 There are also shorthand aliases: @code{info ports} for @code{info
24134 port-rights} and @code{info psets} for @code{info port-sets}.
24136 @item set thread pause
24137 @kindex set thread@r{, Hurd command}
24138 @cindex thread properties, @sc{gnu} Hurd
24139 @cindex pause current thread (@sc{gnu} Hurd)
24140 This command toggles current thread suspension when @value{GDBN} has
24141 control. Setting it to on takes effect immediately, and the current
24142 thread is suspended whenever @value{GDBN} gets control. Setting it to
24143 off will take effect the next time the inferior is continued.
24144 Normally, this command has no effect, since when @value{GDBN} has
24145 control, the whole task is suspended. However, if you used @code{set
24146 task pause off} (see above), this command comes in handy to suspend
24147 only the current thread.
24149 @item show thread pause
24150 @kindex show thread@r{, Hurd command}
24151 This command shows the state of current thread suspension.
24153 @item set thread run
24154 This command sets whether the current thread is allowed to run.
24156 @item show thread run
24157 Show whether the current thread is allowed to run.
24159 @item set thread detach-suspend-count
24160 @cindex thread suspend count, @sc{gnu} Hurd
24161 @cindex detach from thread, @sc{gnu} Hurd
24162 This command sets the suspend count @value{GDBN} will leave on a
24163 thread when detaching. This number is relative to the suspend count
24164 found by @value{GDBN} when it notices the thread; use @code{set thread
24165 takeover-suspend-count} to force it to an absolute value.
24167 @item show thread detach-suspend-count
24168 Show the suspend count @value{GDBN} will leave on the thread when
24171 @item set thread exception-port
24172 @itemx set thread excp
24173 Set the thread exception port to which to forward exceptions. This
24174 overrides the port set by @code{set task exception-port} (see above).
24175 @code{set thread excp} is the shorthand alias.
24177 @item set thread takeover-suspend-count
24178 Normally, @value{GDBN}'s thread suspend counts are relative to the
24179 value @value{GDBN} finds when it notices each thread. This command
24180 changes the suspend counts to be absolute instead.
24182 @item set thread default
24183 @itemx show thread default
24184 @cindex thread default settings, @sc{gnu} Hurd
24185 Each of the above @code{set thread} commands has a @code{set thread
24186 default} counterpart (e.g., @code{set thread default pause}, @code{set
24187 thread default exception-port}, etc.). The @code{thread default}
24188 variety of commands sets the default thread properties for all
24189 threads; you can then change the properties of individual threads with
24190 the non-default commands.
24197 @value{GDBN} provides the following commands specific to the Darwin target:
24200 @item set debug darwin @var{num}
24201 @kindex set debug darwin
24202 When set to a non zero value, enables debugging messages specific to
24203 the Darwin support. Higher values produce more verbose output.
24205 @item show debug darwin
24206 @kindex show debug darwin
24207 Show the current state of Darwin messages.
24209 @item set debug mach-o @var{num}
24210 @kindex set debug mach-o
24211 When set to a non zero value, enables debugging messages while
24212 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24213 file format used on Darwin for object and executable files.) Higher
24214 values produce more verbose output. This is a command to diagnose
24215 problems internal to @value{GDBN} and should not be needed in normal
24218 @item show debug mach-o
24219 @kindex show debug mach-o
24220 Show the current state of Mach-O file messages.
24222 @item set mach-exceptions on
24223 @itemx set mach-exceptions off
24224 @kindex set mach-exceptions
24225 On Darwin, faults are first reported as a Mach exception and are then
24226 mapped to a Posix signal. Use this command to turn on trapping of
24227 Mach exceptions in the inferior. This might be sometimes useful to
24228 better understand the cause of a fault. The default is off.
24230 @item show mach-exceptions
24231 @kindex show mach-exceptions
24232 Show the current state of exceptions trapping.
24236 @subsection FreeBSD
24239 When the ABI of a system call is changed in the FreeBSD kernel, this
24240 is implemented by leaving a compatibility system call using the old
24241 ABI at the existing number and allocating a new system call number for
24242 the version using the new ABI. As a convenience, when a system call
24243 is caught by name (@pxref{catch syscall}), compatibility system calls
24246 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24247 system call and catching the @code{kevent} system call by name catches
24251 (@value{GDBP}) catch syscall kevent
24252 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24258 @section Embedded Operating Systems
24260 This section describes configurations involving the debugging of
24261 embedded operating systems that are available for several different
24264 @value{GDBN} includes the ability to debug programs running on
24265 various real-time operating systems.
24267 @node Embedded Processors
24268 @section Embedded Processors
24270 This section goes into details specific to particular embedded
24273 @cindex send command to simulator
24274 Whenever a specific embedded processor has a simulator, @value{GDBN}
24275 allows to send an arbitrary command to the simulator.
24278 @item sim @var{command}
24279 @kindex sim@r{, a command}
24280 Send an arbitrary @var{command} string to the simulator. Consult the
24281 documentation for the specific simulator in use for information about
24282 acceptable commands.
24287 * ARC:: Synopsys ARC
24289 * M68K:: Motorola M68K
24290 * MicroBlaze:: Xilinx MicroBlaze
24291 * MIPS Embedded:: MIPS Embedded
24292 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24293 * PowerPC Embedded:: PowerPC Embedded
24296 * Super-H:: Renesas Super-H
24300 @subsection Synopsys ARC
24301 @cindex Synopsys ARC
24302 @cindex ARC specific commands
24308 @value{GDBN} provides the following ARC-specific commands:
24311 @item set debug arc
24312 @kindex set debug arc
24313 Control the level of ARC specific debug messages. Use 0 for no messages (the
24314 default), 1 for debug messages, and 2 for even more debug messages.
24316 @item show debug arc
24317 @kindex show debug arc
24318 Show the level of ARC specific debugging in operation.
24320 @item maint print arc arc-instruction @var{address}
24321 @kindex maint print arc arc-instruction
24322 Print internal disassembler information about instruction at a given address.
24329 @value{GDBN} provides the following ARM-specific commands:
24332 @item set arm disassembler
24334 This commands selects from a list of disassembly styles. The
24335 @code{"std"} style is the standard style.
24337 @item show arm disassembler
24339 Show the current disassembly style.
24341 @item set arm apcs32
24342 @cindex ARM 32-bit mode
24343 This command toggles ARM operation mode between 32-bit and 26-bit.
24345 @item show arm apcs32
24346 Display the current usage of the ARM 32-bit mode.
24348 @item set arm fpu @var{fputype}
24349 This command sets the ARM floating-point unit (FPU) type. The
24350 argument @var{fputype} can be one of these:
24354 Determine the FPU type by querying the OS ABI.
24356 Software FPU, with mixed-endian doubles on little-endian ARM
24359 GCC-compiled FPA co-processor.
24361 Software FPU with pure-endian doubles.
24367 Show the current type of the FPU.
24370 This command forces @value{GDBN} to use the specified ABI.
24373 Show the currently used ABI.
24375 @item set arm fallback-mode (arm|thumb|auto)
24376 @value{GDBN} uses the symbol table, when available, to determine
24377 whether instructions are ARM or Thumb. This command controls
24378 @value{GDBN}'s default behavior when the symbol table is not
24379 available. The default is @samp{auto}, which causes @value{GDBN} to
24380 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24383 @item show arm fallback-mode
24384 Show the current fallback instruction mode.
24386 @item set arm force-mode (arm|thumb|auto)
24387 This command overrides use of the symbol table to determine whether
24388 instructions are ARM or Thumb. The default is @samp{auto}, which
24389 causes @value{GDBN} to use the symbol table and then the setting
24390 of @samp{set arm fallback-mode}.
24392 @item show arm force-mode
24393 Show the current forced instruction mode.
24395 @item set debug arm
24396 Toggle whether to display ARM-specific debugging messages from the ARM
24397 target support subsystem.
24399 @item show debug arm
24400 Show whether ARM-specific debugging messages are enabled.
24404 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24405 The @value{GDBN} ARM simulator accepts the following optional arguments.
24408 @item --swi-support=@var{type}
24409 Tell the simulator which SWI interfaces to support. The argument
24410 @var{type} may be a comma separated list of the following values.
24411 The default value is @code{all}.
24426 The Motorola m68k configuration includes ColdFire support.
24429 @subsection MicroBlaze
24430 @cindex Xilinx MicroBlaze
24431 @cindex XMD, Xilinx Microprocessor Debugger
24433 The MicroBlaze is a soft-core processor supported on various Xilinx
24434 FPGAs, such as Spartan or Virtex series. Boards with these processors
24435 usually have JTAG ports which connect to a host system running the Xilinx
24436 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24437 This host system is used to download the configuration bitstream to
24438 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24439 communicates with the target board using the JTAG interface and
24440 presents a @code{gdbserver} interface to the board. By default
24441 @code{xmd} uses port @code{1234}. (While it is possible to change
24442 this default port, it requires the use of undocumented @code{xmd}
24443 commands. Contact Xilinx support if you need to do this.)
24445 Use these GDB commands to connect to the MicroBlaze target processor.
24448 @item target remote :1234
24449 Use this command to connect to the target if you are running @value{GDBN}
24450 on the same system as @code{xmd}.
24452 @item target remote @var{xmd-host}:1234
24453 Use this command to connect to the target if it is connected to @code{xmd}
24454 running on a different system named @var{xmd-host}.
24457 Use this command to download a program to the MicroBlaze target.
24459 @item set debug microblaze @var{n}
24460 Enable MicroBlaze-specific debugging messages if non-zero.
24462 @item show debug microblaze @var{n}
24463 Show MicroBlaze-specific debugging level.
24466 @node MIPS Embedded
24467 @subsection @acronym{MIPS} Embedded
24470 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24473 @item set mipsfpu double
24474 @itemx set mipsfpu single
24475 @itemx set mipsfpu none
24476 @itemx set mipsfpu auto
24477 @itemx show mipsfpu
24478 @kindex set mipsfpu
24479 @kindex show mipsfpu
24480 @cindex @acronym{MIPS} remote floating point
24481 @cindex floating point, @acronym{MIPS} remote
24482 If your target board does not support the @acronym{MIPS} floating point
24483 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24484 need this, you may wish to put the command in your @value{GDBN} init
24485 file). This tells @value{GDBN} how to find the return value of
24486 functions which return floating point values. It also allows
24487 @value{GDBN} to avoid saving the floating point registers when calling
24488 functions on the board. If you are using a floating point coprocessor
24489 with only single precision floating point support, as on the @sc{r4650}
24490 processor, use the command @samp{set mipsfpu single}. The default
24491 double precision floating point coprocessor may be selected using
24492 @samp{set mipsfpu double}.
24494 In previous versions the only choices were double precision or no
24495 floating point, so @samp{set mipsfpu on} will select double precision
24496 and @samp{set mipsfpu off} will select no floating point.
24498 As usual, you can inquire about the @code{mipsfpu} variable with
24499 @samp{show mipsfpu}.
24502 @node OpenRISC 1000
24503 @subsection OpenRISC 1000
24504 @cindex OpenRISC 1000
24507 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24508 mainly provided as a soft-core which can run on Xilinx, Altera and other
24511 @value{GDBN} for OpenRISC supports the below commands when connecting to
24519 Runs the builtin CPU simulator which can run very basic
24520 programs but does not support most hardware functions like MMU.
24521 For more complex use cases the user is advised to run an external
24522 target, and connect using @samp{target remote}.
24524 Example: @code{target sim}
24526 @item set debug or1k
24527 Toggle whether to display OpenRISC-specific debugging messages from the
24528 OpenRISC target support subsystem.
24530 @item show debug or1k
24531 Show whether OpenRISC-specific debugging messages are enabled.
24534 @node PowerPC Embedded
24535 @subsection PowerPC Embedded
24537 @cindex DVC register
24538 @value{GDBN} supports using the DVC (Data Value Compare) register to
24539 implement in hardware simple hardware watchpoint conditions of the form:
24542 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
24543 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
24546 The DVC register will be automatically used when @value{GDBN} detects
24547 such pattern in a condition expression, and the created watchpoint uses one
24548 debug register (either the @code{exact-watchpoints} option is on and the
24549 variable is scalar, or the variable has a length of one byte). This feature
24550 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24553 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24554 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24555 in which case watchpoints using only one debug register are created when
24556 watching variables of scalar types.
24558 You can create an artificial array to watch an arbitrary memory
24559 region using one of the following commands (@pxref{Expressions}):
24562 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24563 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24566 PowerPC embedded processors support masked watchpoints. See the discussion
24567 about the @code{mask} argument in @ref{Set Watchpoints}.
24569 @cindex ranged breakpoint
24570 PowerPC embedded processors support hardware accelerated
24571 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24572 the inferior whenever it executes an instruction at any address within
24573 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24574 use the @code{break-range} command.
24576 @value{GDBN} provides the following PowerPC-specific commands:
24579 @kindex break-range
24580 @item break-range @var{start-location}, @var{end-location}
24581 Set a breakpoint for an address range given by
24582 @var{start-location} and @var{end-location}, which can specify a function name,
24583 a line number, an offset of lines from the current line or from the start
24584 location, or an address of an instruction (see @ref{Specify Location},
24585 for a list of all the possible ways to specify a @var{location}.)
24586 The breakpoint will stop execution of the inferior whenever it
24587 executes an instruction at any address within the specified range,
24588 (including @var{start-location} and @var{end-location}.)
24590 @kindex set powerpc
24591 @item set powerpc soft-float
24592 @itemx show powerpc soft-float
24593 Force @value{GDBN} to use (or not use) a software floating point calling
24594 convention. By default, @value{GDBN} selects the calling convention based
24595 on the selected architecture and the provided executable file.
24597 @item set powerpc vector-abi
24598 @itemx show powerpc vector-abi
24599 Force @value{GDBN} to use the specified calling convention for vector
24600 arguments and return values. The valid options are @samp{auto};
24601 @samp{generic}, to avoid vector registers even if they are present;
24602 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24603 registers. By default, @value{GDBN} selects the calling convention
24604 based on the selected architecture and the provided executable file.
24606 @item set powerpc exact-watchpoints
24607 @itemx show powerpc exact-watchpoints
24608 Allow @value{GDBN} to use only one debug register when watching a variable
24609 of scalar type, thus assuming that the variable is accessed through the
24610 address of its first byte.
24615 @subsection Atmel AVR
24618 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24619 following AVR-specific commands:
24622 @item info io_registers
24623 @kindex info io_registers@r{, AVR}
24624 @cindex I/O registers (Atmel AVR)
24625 This command displays information about the AVR I/O registers. For
24626 each register, @value{GDBN} prints its number and value.
24633 When configured for debugging CRIS, @value{GDBN} provides the
24634 following CRIS-specific commands:
24637 @item set cris-version @var{ver}
24638 @cindex CRIS version
24639 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24640 The CRIS version affects register names and sizes. This command is useful in
24641 case autodetection of the CRIS version fails.
24643 @item show cris-version
24644 Show the current CRIS version.
24646 @item set cris-dwarf2-cfi
24647 @cindex DWARF-2 CFI and CRIS
24648 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24649 Change to @samp{off} when using @code{gcc-cris} whose version is below
24652 @item show cris-dwarf2-cfi
24653 Show the current state of using DWARF-2 CFI.
24655 @item set cris-mode @var{mode}
24657 Set the current CRIS mode to @var{mode}. It should only be changed when
24658 debugging in guru mode, in which case it should be set to
24659 @samp{guru} (the default is @samp{normal}).
24661 @item show cris-mode
24662 Show the current CRIS mode.
24666 @subsection Renesas Super-H
24669 For the Renesas Super-H processor, @value{GDBN} provides these
24673 @item set sh calling-convention @var{convention}
24674 @kindex set sh calling-convention
24675 Set the calling-convention used when calling functions from @value{GDBN}.
24676 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24677 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24678 convention. If the DWARF-2 information of the called function specifies
24679 that the function follows the Renesas calling convention, the function
24680 is called using the Renesas calling convention. If the calling convention
24681 is set to @samp{renesas}, the Renesas calling convention is always used,
24682 regardless of the DWARF-2 information. This can be used to override the
24683 default of @samp{gcc} if debug information is missing, or the compiler
24684 does not emit the DWARF-2 calling convention entry for a function.
24686 @item show sh calling-convention
24687 @kindex show sh calling-convention
24688 Show the current calling convention setting.
24693 @node Architectures
24694 @section Architectures
24696 This section describes characteristics of architectures that affect
24697 all uses of @value{GDBN} with the architecture, both native and cross.
24704 * HPPA:: HP PA architecture
24712 @subsection AArch64
24713 @cindex AArch64 support
24715 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24716 following special commands:
24719 @item set debug aarch64
24720 @kindex set debug aarch64
24721 This command determines whether AArch64 architecture-specific debugging
24722 messages are to be displayed.
24724 @item show debug aarch64
24725 Show whether AArch64 debugging messages are displayed.
24729 @subsubsection AArch64 SVE.
24730 @cindex AArch64 SVE.
24732 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24733 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24734 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24735 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24736 @code{$vg} will be provided. This is the vector granule for the current thread
24737 and represents the number of 64-bit chunks in an SVE @code{z} register.
24739 If the vector length changes, then the @code{$vg} register will be updated,
24740 but the lengths of the @code{z} and @code{p} registers will not change. This
24741 is a known limitation of @value{GDBN} and does not affect the execution of the
24744 @subsubsection AArch64 Pointer Authentication.
24745 @cindex AArch64 Pointer Authentication.
24747 When @value{GDBN} is debugging the AArch64 architecture, and the program is
24748 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
24749 register @code{$lr} is pointing to an PAC function its value will be masked.
24750 When GDB prints a backtrace, any addresses that required unmasking will be
24751 postfixed with the marker [PAC]. When using the MI, this is printed as part
24752 of the @code{addr_flags} field.
24755 @subsection x86 Architecture-specific Issues
24758 @item set struct-convention @var{mode}
24759 @kindex set struct-convention
24760 @cindex struct return convention
24761 @cindex struct/union returned in registers
24762 Set the convention used by the inferior to return @code{struct}s and
24763 @code{union}s from functions to @var{mode}. Possible values of
24764 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24765 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24766 are returned on the stack, while @code{"reg"} means that a
24767 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24768 be returned in a register.
24770 @item show struct-convention
24771 @kindex show struct-convention
24772 Show the current setting of the convention to return @code{struct}s
24777 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
24778 @cindex Intel Memory Protection Extensions (MPX).
24780 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
24781 @footnote{The register named with capital letters represent the architecture
24782 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
24783 which are the lower bound and upper bound. Bounds are effective addresses or
24784 memory locations. The upper bounds are architecturally represented in 1's
24785 complement form. A bound having lower bound = 0, and upper bound = 0
24786 (1's complement of all bits set) will allow access to the entire address space.
24788 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
24789 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
24790 display the upper bound performing the complement of one operation on the
24791 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
24792 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
24793 can also be noted that the upper bounds are inclusive.
24795 As an example, assume that the register BND0 holds bounds for a pointer having
24796 access allowed for the range between 0x32 and 0x71. The values present on
24797 bnd0raw and bnd registers are presented as follows:
24800 bnd0raw = @{0x32, 0xffffffff8e@}
24801 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
24804 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
24805 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
24806 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
24807 Python, the display includes the memory size, in bits, accessible to
24810 Bounds can also be stored in bounds tables, which are stored in
24811 application memory. These tables store bounds for pointers by specifying
24812 the bounds pointer's value along with its bounds. Evaluating and changing
24813 bounds located in bound tables is therefore interesting while investigating
24814 bugs on MPX context. @value{GDBN} provides commands for this purpose:
24817 @item show mpx bound @var{pointer}
24818 @kindex show mpx bound
24819 Display bounds of the given @var{pointer}.
24821 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
24822 @kindex set mpx bound
24823 Set the bounds of a pointer in the bound table.
24824 This command takes three parameters: @var{pointer} is the pointers
24825 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
24826 for lower and upper bounds respectively.
24829 When you call an inferior function on an Intel MPX enabled program,
24830 GDB sets the inferior's bound registers to the init (disabled) state
24831 before calling the function. As a consequence, bounds checks for the
24832 pointer arguments passed to the function will always pass.
24834 This is necessary because when you call an inferior function, the
24835 program is usually in the middle of the execution of other function.
24836 Since at that point bound registers are in an arbitrary state, not
24837 clearing them would lead to random bound violations in the called
24840 You can still examine the influence of the bound registers on the
24841 execution of the called function by stopping the execution of the
24842 called function at its prologue, setting bound registers, and
24843 continuing the execution. For example:
24847 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
24848 $ print upper (a, b, c, d, 1)
24849 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
24851 @{lbound = 0x0, ubound = ffffffff@} : size -1
24854 At this last step the value of bnd0 can be changed for investigation of bound
24855 violations caused along the execution of the call. In order to know how to
24856 set the bound registers or bound table for the call consult the ABI.
24861 See the following section.
24864 @subsection @acronym{MIPS}
24866 @cindex stack on Alpha
24867 @cindex stack on @acronym{MIPS}
24868 @cindex Alpha stack
24869 @cindex @acronym{MIPS} stack
24870 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
24871 sometimes requires @value{GDBN} to search backward in the object code to
24872 find the beginning of a function.
24874 @cindex response time, @acronym{MIPS} debugging
24875 To improve response time (especially for embedded applications, where
24876 @value{GDBN} may be restricted to a slow serial line for this search)
24877 you may want to limit the size of this search, using one of these
24881 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
24882 @item set heuristic-fence-post @var{limit}
24883 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
24884 search for the beginning of a function. A value of @var{0} (the
24885 default) means there is no limit. However, except for @var{0}, the
24886 larger the limit the more bytes @code{heuristic-fence-post} must search
24887 and therefore the longer it takes to run. You should only need to use
24888 this command when debugging a stripped executable.
24890 @item show heuristic-fence-post
24891 Display the current limit.
24895 These commands are available @emph{only} when @value{GDBN} is configured
24896 for debugging programs on Alpha or @acronym{MIPS} processors.
24898 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24902 @item set mips abi @var{arg}
24903 @kindex set mips abi
24904 @cindex set ABI for @acronym{MIPS}
24905 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24906 values of @var{arg} are:
24910 The default ABI associated with the current binary (this is the
24920 @item show mips abi
24921 @kindex show mips abi
24922 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
24924 @item set mips compression @var{arg}
24925 @kindex set mips compression
24926 @cindex code compression, @acronym{MIPS}
24927 Tell @value{GDBN} which @acronym{MIPS} compressed
24928 @acronym{ISA, Instruction Set Architecture} encoding is used by the
24929 inferior. @value{GDBN} uses this for code disassembly and other
24930 internal interpretation purposes. This setting is only referred to
24931 when no executable has been associated with the debugging session or
24932 the executable does not provide information about the encoding it uses.
24933 Otherwise this setting is automatically updated from information
24934 provided by the executable.
24936 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
24937 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
24938 executables containing @acronym{MIPS16} code frequently are not
24939 identified as such.
24941 This setting is ``sticky''; that is, it retains its value across
24942 debugging sessions until reset either explicitly with this command or
24943 implicitly from an executable.
24945 The compiler and/or assembler typically add symbol table annotations to
24946 identify functions compiled for the @acronym{MIPS16} or
24947 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
24948 are present, @value{GDBN} uses them in preference to the global
24949 compressed @acronym{ISA} encoding setting.
24951 @item show mips compression
24952 @kindex show mips compression
24953 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24954 @value{GDBN} to debug the inferior.
24957 @itemx show mipsfpu
24958 @xref{MIPS Embedded, set mipsfpu}.
24960 @item set mips mask-address @var{arg}
24961 @kindex set mips mask-address
24962 @cindex @acronym{MIPS} addresses, masking
24963 This command determines whether the most-significant 32 bits of 64-bit
24964 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24965 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24966 setting, which lets @value{GDBN} determine the correct value.
24968 @item show mips mask-address
24969 @kindex show mips mask-address
24970 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24973 @item set remote-mips64-transfers-32bit-regs
24974 @kindex set remote-mips64-transfers-32bit-regs
24975 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24976 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24977 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24978 and 64 bits for other registers, set this option to @samp{on}.
24980 @item show remote-mips64-transfers-32bit-regs
24981 @kindex show remote-mips64-transfers-32bit-regs
24982 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24984 @item set debug mips
24985 @kindex set debug mips
24986 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24987 target code in @value{GDBN}.
24989 @item show debug mips
24990 @kindex show debug mips
24991 Show the current setting of @acronym{MIPS} debugging messages.
24997 @cindex HPPA support
24999 When @value{GDBN} is debugging the HP PA architecture, it provides the
25000 following special commands:
25003 @item set debug hppa
25004 @kindex set debug hppa
25005 This command determines whether HPPA architecture-specific debugging
25006 messages are to be displayed.
25008 @item show debug hppa
25009 Show whether HPPA debugging messages are displayed.
25011 @item maint print unwind @var{address}
25012 @kindex maint print unwind@r{, HPPA}
25013 This command displays the contents of the unwind table entry at the
25014 given @var{address}.
25020 @subsection PowerPC
25021 @cindex PowerPC architecture
25023 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25024 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25025 numbers stored in the floating point registers. These values must be stored
25026 in two consecutive registers, always starting at an even register like
25027 @code{f0} or @code{f2}.
25029 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25030 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25031 @code{f2} and @code{f3} for @code{$dl1} and so on.
25033 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25034 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25037 @subsection Nios II
25038 @cindex Nios II architecture
25040 When @value{GDBN} is debugging the Nios II architecture,
25041 it provides the following special commands:
25045 @item set debug nios2
25046 @kindex set debug nios2
25047 This command turns on and off debugging messages for the Nios II
25048 target code in @value{GDBN}.
25050 @item show debug nios2
25051 @kindex show debug nios2
25052 Show the current setting of Nios II debugging messages.
25056 @subsection Sparc64
25057 @cindex Sparc64 support
25058 @cindex Application Data Integrity
25059 @subsubsection ADI Support
25061 The M7 processor supports an Application Data Integrity (ADI) feature that
25062 detects invalid data accesses. When software allocates memory and enables
25063 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25064 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25065 the 4-bit version in every cacheline of that data. Hardware saves the latter
25066 in spare bits in the cache and memory hierarchy. On each load and store,
25067 the processor compares the upper 4 VA (virtual address) bits to the
25068 cacheline's version. If there is a mismatch, the processor generates a
25069 version mismatch trap which can be either precise or disrupting. The trap
25070 is an error condition which the kernel delivers to the process as a SIGSEGV
25073 Note that only 64-bit applications can use ADI and need to be built with
25076 Values of the ADI version tags, which are in granularity of a
25077 cacheline (64 bytes), can be viewed or modified.
25081 @kindex adi examine
25082 @item adi (examine | x) [ / @var{n} ] @var{addr}
25084 The @code{adi examine} command displays the value of one ADI version tag per
25087 @var{n} is a decimal integer specifying the number in bytes; the default
25088 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25089 block size, to display.
25091 @var{addr} is the address in user address space where you want @value{GDBN}
25092 to begin displaying the ADI version tags.
25094 Below is an example of displaying ADI versions of variable "shmaddr".
25097 (@value{GDBP}) adi x/100 shmaddr
25098 0xfff800010002c000: 0 0
25102 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25104 The @code{adi assign} command is used to assign new ADI version tag
25107 @var{n} is a decimal integer specifying the number in bytes;
25108 the default is 1. It specifies how much ADI version information, at the
25109 ratio of 1:ADI block size, to modify.
25111 @var{addr} is the address in user address space where you want @value{GDBN}
25112 to begin modifying the ADI version tags.
25114 @var{tag} is the new ADI version tag.
25116 For example, do the following to modify then verify ADI versions of
25117 variable "shmaddr":
25120 (@value{GDBP}) adi a/100 shmaddr = 7
25121 (@value{GDBP}) adi x/100 shmaddr
25122 0xfff800010002c000: 7 7
25129 @cindex S12Z support
25131 When @value{GDBN} is debugging the S12Z architecture,
25132 it provides the following special command:
25135 @item maint info bdccsr
25136 @kindex maint info bdccsr@r{, S12Z}
25137 This command displays the current value of the microprocessor's
25142 @node Controlling GDB
25143 @chapter Controlling @value{GDBN}
25145 You can alter the way @value{GDBN} interacts with you by using the
25146 @code{set} command. For commands controlling how @value{GDBN} displays
25147 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25152 * Editing:: Command editing
25153 * Command History:: Command history
25154 * Screen Size:: Screen size
25155 * Output Styling:: Output styling
25156 * Numbers:: Numbers
25157 * ABI:: Configuring the current ABI
25158 * Auto-loading:: Automatically loading associated files
25159 * Messages/Warnings:: Optional warnings and messages
25160 * Debugging Output:: Optional messages about internal happenings
25161 * Other Misc Settings:: Other Miscellaneous Settings
25169 @value{GDBN} indicates its readiness to read a command by printing a string
25170 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25171 can change the prompt string with the @code{set prompt} command. For
25172 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25173 the prompt in one of the @value{GDBN} sessions so that you can always tell
25174 which one you are talking to.
25176 @emph{Note:} @code{set prompt} does not add a space for you after the
25177 prompt you set. This allows you to set a prompt which ends in a space
25178 or a prompt that does not.
25182 @item set prompt @var{newprompt}
25183 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25185 @kindex show prompt
25187 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25190 Versions of @value{GDBN} that ship with Python scripting enabled have
25191 prompt extensions. The commands for interacting with these extensions
25195 @kindex set extended-prompt
25196 @item set extended-prompt @var{prompt}
25197 Set an extended prompt that allows for substitutions.
25198 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25199 substitution. Any escape sequences specified as part of the prompt
25200 string are replaced with the corresponding strings each time the prompt
25206 set extended-prompt Current working directory: \w (gdb)
25209 Note that when an extended-prompt is set, it takes control of the
25210 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25212 @kindex show extended-prompt
25213 @item show extended-prompt
25214 Prints the extended prompt. Any escape sequences specified as part of
25215 the prompt string with @code{set extended-prompt}, are replaced with the
25216 corresponding strings each time the prompt is displayed.
25220 @section Command Editing
25222 @cindex command line editing
25224 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25225 @sc{gnu} library provides consistent behavior for programs which provide a
25226 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25227 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25228 substitution, and a storage and recall of command history across
25229 debugging sessions.
25231 You may control the behavior of command line editing in @value{GDBN} with the
25232 command @code{set}.
25235 @kindex set editing
25238 @itemx set editing on
25239 Enable command line editing (enabled by default).
25241 @item set editing off
25242 Disable command line editing.
25244 @kindex show editing
25246 Show whether command line editing is enabled.
25249 @ifset SYSTEM_READLINE
25250 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25252 @ifclear SYSTEM_READLINE
25253 @xref{Command Line Editing},
25255 for more details about the Readline
25256 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25257 encouraged to read that chapter.
25259 @cindex Readline application name
25260 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25261 is useful for conditions in @file{.inputrc}.
25263 @cindex operate-and-get-next
25264 @value{GDBN} defines a bindable Readline command,
25265 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25266 This command accepts the current line for execution and fetches the
25267 next line relative to the current line from the history for editing.
25268 Any argument is ignored.
25270 @node Command History
25271 @section Command History
25272 @cindex command history
25274 @value{GDBN} can keep track of the commands you type during your
25275 debugging sessions, so that you can be certain of precisely what
25276 happened. Use these commands to manage the @value{GDBN} command
25279 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25280 package, to provide the history facility.
25281 @ifset SYSTEM_READLINE
25282 @xref{Using History Interactively, , , history, GNU History Library},
25284 @ifclear SYSTEM_READLINE
25285 @xref{Using History Interactively},
25287 for the detailed description of the History library.
25289 To issue a command to @value{GDBN} without affecting certain aspects of
25290 the state which is seen by users, prefix it with @samp{server }
25291 (@pxref{Server Prefix}). This
25292 means that this command will not affect the command history, nor will it
25293 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25294 pressed on a line by itself.
25296 @cindex @code{server}, command prefix
25297 The server prefix does not affect the recording of values into the value
25298 history; to print a value without recording it into the value history,
25299 use the @code{output} command instead of the @code{print} command.
25301 Here is the description of @value{GDBN} commands related to command
25305 @cindex history substitution
25306 @cindex history file
25307 @kindex set history filename
25308 @cindex @env{GDBHISTFILE}, environment variable
25309 @item set history filename @var{fname}
25310 Set the name of the @value{GDBN} command history file to @var{fname}.
25311 This is the file where @value{GDBN} reads an initial command history
25312 list, and where it writes the command history from this session when it
25313 exits. You can access this list through history expansion or through
25314 the history command editing characters listed below. This file defaults
25315 to the value of the environment variable @code{GDBHISTFILE}, or to
25316 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25319 @cindex save command history
25320 @kindex set history save
25321 @item set history save
25322 @itemx set history save on
25323 Record command history in a file, whose name may be specified with the
25324 @code{set history filename} command. By default, this option is disabled.
25326 @item set history save off
25327 Stop recording command history in a file.
25329 @cindex history size
25330 @kindex set history size
25331 @cindex @env{GDBHISTSIZE}, environment variable
25332 @item set history size @var{size}
25333 @itemx set history size unlimited
25334 Set the number of commands which @value{GDBN} keeps in its history list.
25335 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25336 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25337 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25338 either a negative number or the empty string, then the number of commands
25339 @value{GDBN} keeps in the history list is unlimited.
25341 @cindex remove duplicate history
25342 @kindex set history remove-duplicates
25343 @item set history remove-duplicates @var{count}
25344 @itemx set history remove-duplicates unlimited
25345 Control the removal of duplicate history entries in the command history list.
25346 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25347 history entries and remove the first entry that is a duplicate of the current
25348 entry being added to the command history list. If @var{count} is
25349 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25350 removal of duplicate history entries is disabled.
25352 Only history entries added during the current session are considered for
25353 removal. This option is set to 0 by default.
25357 History expansion assigns special meaning to the character @kbd{!}.
25358 @ifset SYSTEM_READLINE
25359 @xref{Event Designators, , , history, GNU History Library},
25361 @ifclear SYSTEM_READLINE
25362 @xref{Event Designators},
25366 @cindex history expansion, turn on/off
25367 Since @kbd{!} is also the logical not operator in C, history expansion
25368 is off by default. If you decide to enable history expansion with the
25369 @code{set history expansion on} command, you may sometimes need to
25370 follow @kbd{!} (when it is used as logical not, in an expression) with
25371 a space or a tab to prevent it from being expanded. The readline
25372 history facilities do not attempt substitution on the strings
25373 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25375 The commands to control history expansion are:
25378 @item set history expansion on
25379 @itemx set history expansion
25380 @kindex set history expansion
25381 Enable history expansion. History expansion is off by default.
25383 @item set history expansion off
25384 Disable history expansion.
25387 @kindex show history
25389 @itemx show history filename
25390 @itemx show history save
25391 @itemx show history size
25392 @itemx show history expansion
25393 These commands display the state of the @value{GDBN} history parameters.
25394 @code{show history} by itself displays all four states.
25399 @kindex show commands
25400 @cindex show last commands
25401 @cindex display command history
25402 @item show commands
25403 Display the last ten commands in the command history.
25405 @item show commands @var{n}
25406 Print ten commands centered on command number @var{n}.
25408 @item show commands +
25409 Print ten commands just after the commands last printed.
25413 @section Screen Size
25414 @cindex size of screen
25415 @cindex screen size
25418 @cindex pauses in output
25420 Certain commands to @value{GDBN} may produce large amounts of
25421 information output to the screen. To help you read all of it,
25422 @value{GDBN} pauses and asks you for input at the end of each page of
25423 output. Type @key{RET} when you want to see one more page of output,
25424 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25425 without paging for the rest of the current command. Also, the screen
25426 width setting determines when to wrap lines of output. Depending on
25427 what is being printed, @value{GDBN} tries to break the line at a
25428 readable place, rather than simply letting it overflow onto the
25431 Normally @value{GDBN} knows the size of the screen from the terminal
25432 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25433 together with the value of the @code{TERM} environment variable and the
25434 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25435 you can override it with the @code{set height} and @code{set
25442 @kindex show height
25443 @item set height @var{lpp}
25444 @itemx set height unlimited
25446 @itemx set width @var{cpl}
25447 @itemx set width unlimited
25449 These @code{set} commands specify a screen height of @var{lpp} lines and
25450 a screen width of @var{cpl} characters. The associated @code{show}
25451 commands display the current settings.
25453 If you specify a height of either @code{unlimited} or zero lines,
25454 @value{GDBN} does not pause during output no matter how long the
25455 output is. This is useful if output is to a file or to an editor
25458 Likewise, you can specify @samp{set width unlimited} or @samp{set
25459 width 0} to prevent @value{GDBN} from wrapping its output.
25461 @item set pagination on
25462 @itemx set pagination off
25463 @kindex set pagination
25464 Turn the output pagination on or off; the default is on. Turning
25465 pagination off is the alternative to @code{set height unlimited}. Note that
25466 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25467 Options, -batch}) also automatically disables pagination.
25469 @item show pagination
25470 @kindex show pagination
25471 Show the current pagination mode.
25474 @node Output Styling
25475 @section Output Styling
25481 @value{GDBN} can style its output on a capable terminal. This is
25482 enabled by default on most systems, but disabled by default when in
25483 batch mode (@pxref{Mode Options}). Various style settings are available;
25484 and styles can also be disabled entirely.
25487 @item set style enabled @samp{on|off}
25488 Enable or disable all styling. The default is host-dependent, with
25489 most hosts defaulting to @samp{on}.
25491 @item show style enabled
25492 Show the current state of styling.
25494 @item set style sources @samp{on|off}
25495 Enable or disable source code styling. This affects whether source
25496 code, such as the output of the @code{list} command, is styled. Note
25497 that source styling only works if styling in general is enabled, and
25498 if @value{GDBN} was linked with the GNU Source Highlight library. The
25499 default is @samp{on}.
25501 @item show style sources
25502 Show the current state of source code styling.
25505 Subcommands of @code{set style} control specific forms of styling.
25506 These subcommands all follow the same pattern: each style-able object
25507 can be styled with a foreground color, a background color, and an
25510 For example, the style of file names can be controlled using the
25511 @code{set style filename} group of commands:
25514 @item set style filename background @var{color}
25515 Set the background to @var{color}. Valid colors are @samp{none}
25516 (meaning the terminal's default color), @samp{black}, @samp{red},
25517 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25520 @item set style filename foreground @var{color}
25521 Set the foreground to @var{color}. Valid colors are @samp{none}
25522 (meaning the terminal's default color), @samp{black}, @samp{red},
25523 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25526 @item set style filename intensity @var{value}
25527 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25528 (the default), @samp{bold}, and @samp{dim}.
25531 The @code{show style} command and its subcommands are styling
25532 a style name in their output using its own style.
25533 So, use @command{show style} to see the complete list of styles,
25534 their characteristics and the visual aspect of each style.
25536 The style-able objects are:
25539 Control the styling of file names. By default, this style's
25540 foreground color is green.
25543 Control the styling of function names. These are managed with the
25544 @code{set style function} family of commands. By default, this
25545 style's foreground color is yellow.
25548 Control the styling of variable names. These are managed with the
25549 @code{set style variable} family of commands. By default, this style's
25550 foreground color is cyan.
25553 Control the styling of addresses. These are managed with the
25554 @code{set style address} family of commands. By default, this style's
25555 foreground color is blue.
25558 Control the styling of titles. These are managed with the
25559 @code{set style title} family of commands. By default, this style's
25560 intensity is bold. Commands are using the title style to improve
25561 the readability of large output. For example, the commands
25562 @command{apropos} and @command{help} are using the title style
25563 for the command names.
25566 Control the styling of highlightings. These are managed with the
25567 @code{set style highlight} family of commands. By default, this style's
25568 foreground color is red. Commands are using the highlight style to draw
25569 the user attention to some specific parts of their output. For example,
25570 the command @command{apropos -v REGEXP} uses the highlight style to
25571 mark the documentation parts matching @var{regexp}.
25574 Control the styling of the TUI border. Note that, unlike other
25575 styling options, only the color of the border can be controlled via
25576 @code{set style}. This was done for compatibility reasons, as TUI
25577 controls to set the border's intensity predated the addition of
25578 general styling to @value{GDBN}. @xref{TUI Configuration}.
25580 @item tui-active-border
25581 Control the styling of the active TUI border; that is, the TUI window
25582 that has the focus.
25588 @cindex number representation
25589 @cindex entering numbers
25591 You can always enter numbers in octal, decimal, or hexadecimal in
25592 @value{GDBN} by the usual conventions: octal numbers begin with
25593 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25594 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25595 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25596 10; likewise, the default display for numbers---when no particular
25597 format is specified---is base 10. You can change the default base for
25598 both input and output with the commands described below.
25601 @kindex set input-radix
25602 @item set input-radix @var{base}
25603 Set the default base for numeric input. Supported choices
25604 for @var{base} are decimal 8, 10, or 16. The base must itself be
25605 specified either unambiguously or using the current input radix; for
25609 set input-radix 012
25610 set input-radix 10.
25611 set input-radix 0xa
25615 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25616 leaves the input radix unchanged, no matter what it was, since
25617 @samp{10}, being without any leading or trailing signs of its base, is
25618 interpreted in the current radix. Thus, if the current radix is 16,
25619 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25622 @kindex set output-radix
25623 @item set output-radix @var{base}
25624 Set the default base for numeric display. Supported choices
25625 for @var{base} are decimal 8, 10, or 16. The base must itself be
25626 specified either unambiguously or using the current input radix.
25628 @kindex show input-radix
25629 @item show input-radix
25630 Display the current default base for numeric input.
25632 @kindex show output-radix
25633 @item show output-radix
25634 Display the current default base for numeric display.
25636 @item set radix @r{[}@var{base}@r{]}
25640 These commands set and show the default base for both input and output
25641 of numbers. @code{set radix} sets the radix of input and output to
25642 the same base; without an argument, it resets the radix back to its
25643 default value of 10.
25648 @section Configuring the Current ABI
25650 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25651 application automatically. However, sometimes you need to override its
25652 conclusions. Use these commands to manage @value{GDBN}'s view of the
25658 @cindex Newlib OS ABI and its influence on the longjmp handling
25660 One @value{GDBN} configuration can debug binaries for multiple operating
25661 system targets, either via remote debugging or native emulation.
25662 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25663 but you can override its conclusion using the @code{set osabi} command.
25664 One example where this is useful is in debugging of binaries which use
25665 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25666 not have the same identifying marks that the standard C library for your
25669 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25670 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25671 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25672 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25676 Show the OS ABI currently in use.
25679 With no argument, show the list of registered available OS ABI's.
25681 @item set osabi @var{abi}
25682 Set the current OS ABI to @var{abi}.
25685 @cindex float promotion
25687 Generally, the way that an argument of type @code{float} is passed to a
25688 function depends on whether the function is prototyped. For a prototyped
25689 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25690 according to the architecture's convention for @code{float}. For unprototyped
25691 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25692 @code{double} and then passed.
25694 Unfortunately, some forms of debug information do not reliably indicate whether
25695 a function is prototyped. If @value{GDBN} calls a function that is not marked
25696 as prototyped, it consults @kbd{set coerce-float-to-double}.
25699 @kindex set coerce-float-to-double
25700 @item set coerce-float-to-double
25701 @itemx set coerce-float-to-double on
25702 Arguments of type @code{float} will be promoted to @code{double} when passed
25703 to an unprototyped function. This is the default setting.
25705 @item set coerce-float-to-double off
25706 Arguments of type @code{float} will be passed directly to unprototyped
25709 @kindex show coerce-float-to-double
25710 @item show coerce-float-to-double
25711 Show the current setting of promoting @code{float} to @code{double}.
25715 @kindex show cp-abi
25716 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25717 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25718 used to build your application. @value{GDBN} only fully supports
25719 programs with a single C@t{++} ABI; if your program contains code using
25720 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25721 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25722 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25723 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25724 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25725 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25730 Show the C@t{++} ABI currently in use.
25733 With no argument, show the list of supported C@t{++} ABI's.
25735 @item set cp-abi @var{abi}
25736 @itemx set cp-abi auto
25737 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
25741 @section Automatically loading associated files
25742 @cindex auto-loading
25744 @value{GDBN} sometimes reads files with commands and settings automatically,
25745 without being explicitly told so by the user. We call this feature
25746 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
25747 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
25748 results or introduce security risks (e.g., if the file comes from untrusted
25752 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
25753 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
25755 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
25756 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
25759 There are various kinds of files @value{GDBN} can automatically load.
25760 In addition to these files, @value{GDBN} supports auto-loading code written
25761 in various extension languages. @xref{Auto-loading extensions}.
25763 Note that loading of these associated files (including the local @file{.gdbinit}
25764 file) requires accordingly configured @code{auto-load safe-path}
25765 (@pxref{Auto-loading safe path}).
25767 For these reasons, @value{GDBN} includes commands and options to let you
25768 control when to auto-load files and which files should be auto-loaded.
25771 @anchor{set auto-load off}
25772 @kindex set auto-load off
25773 @item set auto-load off
25774 Globally disable loading of all auto-loaded files.
25775 You may want to use this command with the @samp{-iex} option
25776 (@pxref{Option -init-eval-command}) such as:
25778 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
25781 Be aware that system init file (@pxref{System-wide configuration})
25782 and init files from your home directory (@pxref{Home Directory Init File})
25783 still get read (as they come from generally trusted directories).
25784 To prevent @value{GDBN} from auto-loading even those init files, use the
25785 @option{-nx} option (@pxref{Mode Options}), in addition to
25786 @code{set auto-load no}.
25788 @anchor{show auto-load}
25789 @kindex show auto-load
25790 @item show auto-load
25791 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
25795 (gdb) show auto-load
25796 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
25797 libthread-db: Auto-loading of inferior specific libthread_db is on.
25798 local-gdbinit: Auto-loading of .gdbinit script from current directory
25800 python-scripts: Auto-loading of Python scripts is on.
25801 safe-path: List of directories from which it is safe to auto-load files
25802 is $debugdir:$datadir/auto-load.
25803 scripts-directory: List of directories from which to load auto-loaded scripts
25804 is $debugdir:$datadir/auto-load.
25807 @anchor{info auto-load}
25808 @kindex info auto-load
25809 @item info auto-load
25810 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
25814 (gdb) info auto-load
25817 Yes /home/user/gdb/gdb-gdb.gdb
25818 libthread-db: No auto-loaded libthread-db.
25819 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
25823 Yes /home/user/gdb/gdb-gdb.py
25827 These are @value{GDBN} control commands for the auto-loading:
25829 @multitable @columnfractions .5 .5
25830 @item @xref{set auto-load off}.
25831 @tab Disable auto-loading globally.
25832 @item @xref{show auto-load}.
25833 @tab Show setting of all kinds of files.
25834 @item @xref{info auto-load}.
25835 @tab Show state of all kinds of files.
25836 @item @xref{set auto-load gdb-scripts}.
25837 @tab Control for @value{GDBN} command scripts.
25838 @item @xref{show auto-load gdb-scripts}.
25839 @tab Show setting of @value{GDBN} command scripts.
25840 @item @xref{info auto-load gdb-scripts}.
25841 @tab Show state of @value{GDBN} command scripts.
25842 @item @xref{set auto-load python-scripts}.
25843 @tab Control for @value{GDBN} Python scripts.
25844 @item @xref{show auto-load python-scripts}.
25845 @tab Show setting of @value{GDBN} Python scripts.
25846 @item @xref{info auto-load python-scripts}.
25847 @tab Show state of @value{GDBN} Python scripts.
25848 @item @xref{set auto-load guile-scripts}.
25849 @tab Control for @value{GDBN} Guile scripts.
25850 @item @xref{show auto-load guile-scripts}.
25851 @tab Show setting of @value{GDBN} Guile scripts.
25852 @item @xref{info auto-load guile-scripts}.
25853 @tab Show state of @value{GDBN} Guile scripts.
25854 @item @xref{set auto-load scripts-directory}.
25855 @tab Control for @value{GDBN} auto-loaded scripts location.
25856 @item @xref{show auto-load scripts-directory}.
25857 @tab Show @value{GDBN} auto-loaded scripts location.
25858 @item @xref{add-auto-load-scripts-directory}.
25859 @tab Add directory for auto-loaded scripts location list.
25860 @item @xref{set auto-load local-gdbinit}.
25861 @tab Control for init file in the current directory.
25862 @item @xref{show auto-load local-gdbinit}.
25863 @tab Show setting of init file in the current directory.
25864 @item @xref{info auto-load local-gdbinit}.
25865 @tab Show state of init file in the current directory.
25866 @item @xref{set auto-load libthread-db}.
25867 @tab Control for thread debugging library.
25868 @item @xref{show auto-load libthread-db}.
25869 @tab Show setting of thread debugging library.
25870 @item @xref{info auto-load libthread-db}.
25871 @tab Show state of thread debugging library.
25872 @item @xref{set auto-load safe-path}.
25873 @tab Control directories trusted for automatic loading.
25874 @item @xref{show auto-load safe-path}.
25875 @tab Show directories trusted for automatic loading.
25876 @item @xref{add-auto-load-safe-path}.
25877 @tab Add directory trusted for automatic loading.
25880 @node Init File in the Current Directory
25881 @subsection Automatically loading init file in the current directory
25882 @cindex auto-loading init file in the current directory
25884 By default, @value{GDBN} reads and executes the canned sequences of commands
25885 from init file (if any) in the current working directory,
25886 see @ref{Init File in the Current Directory during Startup}.
25888 Note that loading of this local @file{.gdbinit} file also requires accordingly
25889 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25892 @anchor{set auto-load local-gdbinit}
25893 @kindex set auto-load local-gdbinit
25894 @item set auto-load local-gdbinit [on|off]
25895 Enable or disable the auto-loading of canned sequences of commands
25896 (@pxref{Sequences}) found in init file in the current directory.
25898 @anchor{show auto-load local-gdbinit}
25899 @kindex show auto-load local-gdbinit
25900 @item show auto-load local-gdbinit
25901 Show whether auto-loading of canned sequences of commands from init file in the
25902 current directory is enabled or disabled.
25904 @anchor{info auto-load local-gdbinit}
25905 @kindex info auto-load local-gdbinit
25906 @item info auto-load local-gdbinit
25907 Print whether canned sequences of commands from init file in the
25908 current directory have been auto-loaded.
25911 @node libthread_db.so.1 file
25912 @subsection Automatically loading thread debugging library
25913 @cindex auto-loading libthread_db.so.1
25915 This feature is currently present only on @sc{gnu}/Linux native hosts.
25917 @value{GDBN} reads in some cases thread debugging library from places specific
25918 to the inferior (@pxref{set libthread-db-search-path}).
25920 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
25921 without checking this @samp{set auto-load libthread-db} switch as system
25922 libraries have to be trusted in general. In all other cases of
25923 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
25924 auto-load libthread-db} is enabled before trying to open such thread debugging
25927 Note that loading of this debugging library also requires accordingly configured
25928 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25931 @anchor{set auto-load libthread-db}
25932 @kindex set auto-load libthread-db
25933 @item set auto-load libthread-db [on|off]
25934 Enable or disable the auto-loading of inferior specific thread debugging library.
25936 @anchor{show auto-load libthread-db}
25937 @kindex show auto-load libthread-db
25938 @item show auto-load libthread-db
25939 Show whether auto-loading of inferior specific thread debugging library is
25940 enabled or disabled.
25942 @anchor{info auto-load libthread-db}
25943 @kindex info auto-load libthread-db
25944 @item info auto-load libthread-db
25945 Print the list of all loaded inferior specific thread debugging libraries and
25946 for each such library print list of inferior @var{pid}s using it.
25949 @node Auto-loading safe path
25950 @subsection Security restriction for auto-loading
25951 @cindex auto-loading safe-path
25953 As the files of inferior can come from untrusted source (such as submitted by
25954 an application user) @value{GDBN} does not always load any files automatically.
25955 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25956 directories trusted for loading files not explicitly requested by user.
25957 Each directory can also be a shell wildcard pattern.
25959 If the path is not set properly you will see a warning and the file will not
25964 Reading symbols from /home/user/gdb/gdb...done.
25965 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25966 declined by your `auto-load safe-path' set
25967 to "$debugdir:$datadir/auto-load".
25968 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25969 declined by your `auto-load safe-path' set
25970 to "$debugdir:$datadir/auto-load".
25974 To instruct @value{GDBN} to go ahead and use the init files anyway,
25975 invoke @value{GDBN} like this:
25978 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25981 The list of trusted directories is controlled by the following commands:
25984 @anchor{set auto-load safe-path}
25985 @kindex set auto-load safe-path
25986 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25987 Set the list of directories (and their subdirectories) trusted for automatic
25988 loading and execution of scripts. You can also enter a specific trusted file.
25989 Each directory can also be a shell wildcard pattern; wildcards do not match
25990 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25991 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25992 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25993 its default value as specified during @value{GDBN} compilation.
25995 The list of directories uses path separator (@samp{:} on GNU and Unix
25996 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25997 to the @env{PATH} environment variable.
25999 @anchor{show auto-load safe-path}
26000 @kindex show auto-load safe-path
26001 @item show auto-load safe-path
26002 Show the list of directories trusted for automatic loading and execution of
26005 @anchor{add-auto-load-safe-path}
26006 @kindex add-auto-load-safe-path
26007 @item add-auto-load-safe-path
26008 Add an entry (or list of entries) to the list of directories trusted for
26009 automatic loading and execution of scripts. Multiple entries may be delimited
26010 by the host platform path separator in use.
26013 This variable defaults to what @code{--with-auto-load-dir} has been configured
26014 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26015 substitution applies the same as for @ref{set auto-load scripts-directory}.
26016 The default @code{set auto-load safe-path} value can be also overriden by
26017 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26019 Setting this variable to @file{/} disables this security protection,
26020 corresponding @value{GDBN} configuration option is
26021 @option{--without-auto-load-safe-path}.
26022 This variable is supposed to be set to the system directories writable by the
26023 system superuser only. Users can add their source directories in init files in
26024 their home directories (@pxref{Home Directory Init File}). See also deprecated
26025 init file in the current directory
26026 (@pxref{Init File in the Current Directory during Startup}).
26028 To force @value{GDBN} to load the files it declined to load in the previous
26029 example, you could use one of the following ways:
26032 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26033 Specify this trusted directory (or a file) as additional component of the list.
26034 You have to specify also any existing directories displayed by
26035 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26037 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26038 Specify this directory as in the previous case but just for a single
26039 @value{GDBN} session.
26041 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26042 Disable auto-loading safety for a single @value{GDBN} session.
26043 This assumes all the files you debug during this @value{GDBN} session will come
26044 from trusted sources.
26046 @item @kbd{./configure --without-auto-load-safe-path}
26047 During compilation of @value{GDBN} you may disable any auto-loading safety.
26048 This assumes all the files you will ever debug with this @value{GDBN} come from
26052 On the other hand you can also explicitly forbid automatic files loading which
26053 also suppresses any such warning messages:
26056 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26057 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26059 @item @file{~/.gdbinit}: @samp{set auto-load no}
26060 Disable auto-loading globally for the user
26061 (@pxref{Home Directory Init File}). While it is improbable, you could also
26062 use system init file instead (@pxref{System-wide configuration}).
26065 This setting applies to the file names as entered by user. If no entry matches
26066 @value{GDBN} tries as a last resort to also resolve all the file names into
26067 their canonical form (typically resolving symbolic links) and compare the
26068 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26069 own before starting the comparison so a canonical form of directories is
26070 recommended to be entered.
26072 @node Auto-loading verbose mode
26073 @subsection Displaying files tried for auto-load
26074 @cindex auto-loading verbose mode
26076 For better visibility of all the file locations where you can place scripts to
26077 be auto-loaded with inferior --- or to protect yourself against accidental
26078 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26079 all the files attempted to be loaded. Both existing and non-existing files may
26082 For example the list of directories from which it is safe to auto-load files
26083 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26084 may not be too obvious while setting it up.
26087 (gdb) set debug auto-load on
26088 (gdb) file ~/src/t/true
26089 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26090 for objfile "/tmp/true".
26091 auto-load: Updating directories of "/usr:/opt".
26092 auto-load: Using directory "/usr".
26093 auto-load: Using directory "/opt".
26094 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26095 by your `auto-load safe-path' set to "/usr:/opt".
26099 @anchor{set debug auto-load}
26100 @kindex set debug auto-load
26101 @item set debug auto-load [on|off]
26102 Set whether to print the filenames attempted to be auto-loaded.
26104 @anchor{show debug auto-load}
26105 @kindex show debug auto-load
26106 @item show debug auto-load
26107 Show whether printing of the filenames attempted to be auto-loaded is turned
26111 @node Messages/Warnings
26112 @section Optional Warnings and Messages
26114 @cindex verbose operation
26115 @cindex optional warnings
26116 By default, @value{GDBN} is silent about its inner workings. If you are
26117 running on a slow machine, you may want to use the @code{set verbose}
26118 command. This makes @value{GDBN} tell you when it does a lengthy
26119 internal operation, so you will not think it has crashed.
26121 Currently, the messages controlled by @code{set verbose} are those
26122 which announce that the symbol table for a source file is being read;
26123 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26126 @kindex set verbose
26127 @item set verbose on
26128 Enables @value{GDBN} output of certain informational messages.
26130 @item set verbose off
26131 Disables @value{GDBN} output of certain informational messages.
26133 @kindex show verbose
26135 Displays whether @code{set verbose} is on or off.
26138 By default, if @value{GDBN} encounters bugs in the symbol table of an
26139 object file, it is silent; but if you are debugging a compiler, you may
26140 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26145 @kindex set complaints
26146 @item set complaints @var{limit}
26147 Permits @value{GDBN} to output @var{limit} complaints about each type of
26148 unusual symbols before becoming silent about the problem. Set
26149 @var{limit} to zero to suppress all complaints; set it to a large number
26150 to prevent complaints from being suppressed.
26152 @kindex show complaints
26153 @item show complaints
26154 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26158 @anchor{confirmation requests}
26159 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26160 lot of stupid questions to confirm certain commands. For example, if
26161 you try to run a program which is already running:
26165 The program being debugged has been started already.
26166 Start it from the beginning? (y or n)
26169 If you are willing to unflinchingly face the consequences of your own
26170 commands, you can disable this ``feature'':
26174 @kindex set confirm
26176 @cindex confirmation
26177 @cindex stupid questions
26178 @item set confirm off
26179 Disables confirmation requests. Note that running @value{GDBN} with
26180 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26181 automatically disables confirmation requests.
26183 @item set confirm on
26184 Enables confirmation requests (the default).
26186 @kindex show confirm
26188 Displays state of confirmation requests.
26192 @cindex command tracing
26193 If you need to debug user-defined commands or sourced files you may find it
26194 useful to enable @dfn{command tracing}. In this mode each command will be
26195 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26196 quantity denoting the call depth of each command.
26199 @kindex set trace-commands
26200 @cindex command scripts, debugging
26201 @item set trace-commands on
26202 Enable command tracing.
26203 @item set trace-commands off
26204 Disable command tracing.
26205 @item show trace-commands
26206 Display the current state of command tracing.
26209 @node Debugging Output
26210 @section Optional Messages about Internal Happenings
26211 @cindex optional debugging messages
26213 @value{GDBN} has commands that enable optional debugging messages from
26214 various @value{GDBN} subsystems; normally these commands are of
26215 interest to @value{GDBN} maintainers, or when reporting a bug. This
26216 section documents those commands.
26219 @kindex set exec-done-display
26220 @item set exec-done-display
26221 Turns on or off the notification of asynchronous commands'
26222 completion. When on, @value{GDBN} will print a message when an
26223 asynchronous command finishes its execution. The default is off.
26224 @kindex show exec-done-display
26225 @item show exec-done-display
26226 Displays the current setting of asynchronous command completion
26229 @cindex ARM AArch64
26230 @item set debug aarch64
26231 Turns on or off display of debugging messages related to ARM AArch64.
26232 The default is off.
26234 @item show debug aarch64
26235 Displays the current state of displaying debugging messages related to
26237 @cindex gdbarch debugging info
26238 @cindex architecture debugging info
26239 @item set debug arch
26240 Turns on or off display of gdbarch debugging info. The default is off
26241 @item show debug arch
26242 Displays the current state of displaying gdbarch debugging info.
26243 @item set debug aix-solib
26244 @cindex AIX shared library debugging
26245 Control display of debugging messages from the AIX shared library
26246 support module. The default is off.
26247 @item show debug aix-thread
26248 Show the current state of displaying AIX shared library debugging messages.
26249 @item set debug aix-thread
26250 @cindex AIX threads
26251 Display debugging messages about inner workings of the AIX thread
26253 @item show debug aix-thread
26254 Show the current state of AIX thread debugging info display.
26255 @item set debug check-physname
26257 Check the results of the ``physname'' computation. When reading DWARF
26258 debugging information for C@t{++}, @value{GDBN} attempts to compute
26259 each entity's name. @value{GDBN} can do this computation in two
26260 different ways, depending on exactly what information is present.
26261 When enabled, this setting causes @value{GDBN} to compute the names
26262 both ways and display any discrepancies.
26263 @item show debug check-physname
26264 Show the current state of ``physname'' checking.
26265 @item set debug coff-pe-read
26266 @cindex COFF/PE exported symbols
26267 Control display of debugging messages related to reading of COFF/PE
26268 exported symbols. The default is off.
26269 @item show debug coff-pe-read
26270 Displays the current state of displaying debugging messages related to
26271 reading of COFF/PE exported symbols.
26272 @item set debug dwarf-die
26274 Dump DWARF DIEs after they are read in.
26275 The value is the number of nesting levels to print.
26276 A value of zero turns off the display.
26277 @item show debug dwarf-die
26278 Show the current state of DWARF DIE debugging.
26279 @item set debug dwarf-line
26280 @cindex DWARF Line Tables
26281 Turns on or off display of debugging messages related to reading
26282 DWARF line tables. The default is 0 (off).
26283 A value of 1 provides basic information.
26284 A value greater than 1 provides more verbose information.
26285 @item show debug dwarf-line
26286 Show the current state of DWARF line table debugging.
26287 @item set debug dwarf-read
26288 @cindex DWARF Reading
26289 Turns on or off display of debugging messages related to reading
26290 DWARF debug info. The default is 0 (off).
26291 A value of 1 provides basic information.
26292 A value greater than 1 provides more verbose information.
26293 @item show debug dwarf-read
26294 Show the current state of DWARF reader debugging.
26295 @item set debug displaced
26296 @cindex displaced stepping debugging info
26297 Turns on or off display of @value{GDBN} debugging info for the
26298 displaced stepping support. The default is off.
26299 @item show debug displaced
26300 Displays the current state of displaying @value{GDBN} debugging info
26301 related to displaced stepping.
26302 @item set debug event
26303 @cindex event debugging info
26304 Turns on or off display of @value{GDBN} event debugging info. The
26306 @item show debug event
26307 Displays the current state of displaying @value{GDBN} event debugging
26309 @item set debug expression
26310 @cindex expression debugging info
26311 Turns on or off display of debugging info about @value{GDBN}
26312 expression parsing. The default is off.
26313 @item show debug expression
26314 Displays the current state of displaying debugging info about
26315 @value{GDBN} expression parsing.
26316 @item set debug fbsd-lwp
26317 @cindex FreeBSD LWP debug messages
26318 Turns on or off debugging messages from the FreeBSD LWP debug support.
26319 @item show debug fbsd-lwp
26320 Show the current state of FreeBSD LWP debugging messages.
26321 @item set debug fbsd-nat
26322 @cindex FreeBSD native target debug messages
26323 Turns on or off debugging messages from the FreeBSD native target.
26324 @item show debug fbsd-nat
26325 Show the current state of FreeBSD native target debugging messages.
26326 @item set debug frame
26327 @cindex frame debugging info
26328 Turns on or off display of @value{GDBN} frame debugging info. The
26330 @item show debug frame
26331 Displays the current state of displaying @value{GDBN} frame debugging
26333 @item set debug gnu-nat
26334 @cindex @sc{gnu}/Hurd debug messages
26335 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26336 @item show debug gnu-nat
26337 Show the current state of @sc{gnu}/Hurd debugging messages.
26338 @item set debug infrun
26339 @cindex inferior debugging info
26340 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26341 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26342 for implementing operations such as single-stepping the inferior.
26343 @item show debug infrun
26344 Displays the current state of @value{GDBN} inferior debugging.
26345 @item set debug jit
26346 @cindex just-in-time compilation, debugging messages
26347 Turn on or off debugging messages from JIT debug support.
26348 @item show debug jit
26349 Displays the current state of @value{GDBN} JIT debugging.
26350 @item set debug lin-lwp
26351 @cindex @sc{gnu}/Linux LWP debug messages
26352 @cindex Linux lightweight processes
26353 Turn on or off debugging messages from the Linux LWP debug support.
26354 @item show debug lin-lwp
26355 Show the current state of Linux LWP debugging messages.
26356 @item set debug linux-namespaces
26357 @cindex @sc{gnu}/Linux namespaces debug messages
26358 Turn on or off debugging messages from the Linux namespaces debug support.
26359 @item show debug linux-namespaces
26360 Show the current state of Linux namespaces debugging messages.
26361 @item set debug mach-o
26362 @cindex Mach-O symbols processing
26363 Control display of debugging messages related to Mach-O symbols
26364 processing. The default is off.
26365 @item show debug mach-o
26366 Displays the current state of displaying debugging messages related to
26367 reading of COFF/PE exported symbols.
26368 @item set debug notification
26369 @cindex remote async notification debugging info
26370 Turn on or off debugging messages about remote async notification.
26371 The default is off.
26372 @item show debug notification
26373 Displays the current state of remote async notification debugging messages.
26374 @item set debug observer
26375 @cindex observer debugging info
26376 Turns on or off display of @value{GDBN} observer debugging. This
26377 includes info such as the notification of observable events.
26378 @item show debug observer
26379 Displays the current state of observer debugging.
26380 @item set debug overload
26381 @cindex C@t{++} overload debugging info
26382 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26383 info. This includes info such as ranking of functions, etc. The default
26385 @item show debug overload
26386 Displays the current state of displaying @value{GDBN} C@t{++} overload
26388 @cindex expression parser, debugging info
26389 @cindex debug expression parser
26390 @item set debug parser
26391 Turns on or off the display of expression parser debugging output.
26392 Internally, this sets the @code{yydebug} variable in the expression
26393 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26394 details. The default is off.
26395 @item show debug parser
26396 Show the current state of expression parser debugging.
26397 @cindex packets, reporting on stdout
26398 @cindex serial connections, debugging
26399 @cindex debug remote protocol
26400 @cindex remote protocol debugging
26401 @cindex display remote packets
26402 @item set debug remote
26403 Turns on or off display of reports on all packets sent back and forth across
26404 the serial line to the remote machine. The info is printed on the
26405 @value{GDBN} standard output stream. The default is off.
26406 @item show debug remote
26407 Displays the state of display of remote packets.
26409 @item set debug remote-packet-max-chars
26410 Sets the maximum number of characters to display for each remote packet when
26411 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
26412 displaying lengthy remote packets and polluting the console.
26414 The default value is @code{512}, which means @value{GDBN} will truncate each
26415 remote packet after 512 bytes.
26417 Setting this option to @code{unlimited} will disable truncation and will output
26418 the full length of the remote packets.
26419 @item show debug remote-packet-max-chars
26420 Displays the number of bytes to output for remote packet debugging.
26422 @item set debug separate-debug-file
26423 Turns on or off display of debug output about separate debug file search.
26424 @item show debug separate-debug-file
26425 Displays the state of separate debug file search debug output.
26427 @item set debug serial
26428 Turns on or off display of @value{GDBN} serial debugging info. The
26430 @item show debug serial
26431 Displays the current state of displaying @value{GDBN} serial debugging
26433 @item set debug solib-frv
26434 @cindex FR-V shared-library debugging
26435 Turn on or off debugging messages for FR-V shared-library code.
26436 @item show debug solib-frv
26437 Display the current state of FR-V shared-library code debugging
26439 @item set debug symbol-lookup
26440 @cindex symbol lookup
26441 Turns on or off display of debugging messages related to symbol lookup.
26442 The default is 0 (off).
26443 A value of 1 provides basic information.
26444 A value greater than 1 provides more verbose information.
26445 @item show debug symbol-lookup
26446 Show the current state of symbol lookup debugging messages.
26447 @item set debug symfile
26448 @cindex symbol file functions
26449 Turns on or off display of debugging messages related to symbol file functions.
26450 The default is off. @xref{Files}.
26451 @item show debug symfile
26452 Show the current state of symbol file debugging messages.
26453 @item set debug symtab-create
26454 @cindex symbol table creation
26455 Turns on or off display of debugging messages related to symbol table creation.
26456 The default is 0 (off).
26457 A value of 1 provides basic information.
26458 A value greater than 1 provides more verbose information.
26459 @item show debug symtab-create
26460 Show the current state of symbol table creation debugging.
26461 @item set debug target
26462 @cindex target debugging info
26463 Turns on or off display of @value{GDBN} target debugging info. This info
26464 includes what is going on at the target level of GDB, as it happens. The
26465 default is 0. Set it to 1 to track events, and to 2 to also track the
26466 value of large memory transfers.
26467 @item show debug target
26468 Displays the current state of displaying @value{GDBN} target debugging
26470 @item set debug timestamp
26471 @cindex timestamping debugging info
26472 Turns on or off display of timestamps with @value{GDBN} debugging info.
26473 When enabled, seconds and microseconds are displayed before each debugging
26475 @item show debug timestamp
26476 Displays the current state of displaying timestamps with @value{GDBN}
26478 @item set debug varobj
26479 @cindex variable object debugging info
26480 Turns on or off display of @value{GDBN} variable object debugging
26481 info. The default is off.
26482 @item show debug varobj
26483 Displays the current state of displaying @value{GDBN} variable object
26485 @item set debug xml
26486 @cindex XML parser debugging
26487 Turn on or off debugging messages for built-in XML parsers.
26488 @item show debug xml
26489 Displays the current state of XML debugging messages.
26492 @node Other Misc Settings
26493 @section Other Miscellaneous Settings
26494 @cindex miscellaneous settings
26497 @kindex set interactive-mode
26498 @item set interactive-mode
26499 If @code{on}, forces @value{GDBN} to assume that GDB was started
26500 in a terminal. In practice, this means that @value{GDBN} should wait
26501 for the user to answer queries generated by commands entered at
26502 the command prompt. If @code{off}, forces @value{GDBN} to operate
26503 in the opposite mode, and it uses the default answers to all queries.
26504 If @code{auto} (the default), @value{GDBN} tries to determine whether
26505 its standard input is a terminal, and works in interactive-mode if it
26506 is, non-interactively otherwise.
26508 In the vast majority of cases, the debugger should be able to guess
26509 correctly which mode should be used. But this setting can be useful
26510 in certain specific cases, such as running a MinGW @value{GDBN}
26511 inside a cygwin window.
26513 @kindex show interactive-mode
26514 @item show interactive-mode
26515 Displays whether the debugger is operating in interactive mode or not.
26518 @node Extending GDB
26519 @chapter Extending @value{GDBN}
26520 @cindex extending GDB
26522 @value{GDBN} provides several mechanisms for extension.
26523 @value{GDBN} also provides the ability to automatically load
26524 extensions when it reads a file for debugging. This allows the
26525 user to automatically customize @value{GDBN} for the program
26529 * Sequences:: Canned Sequences of @value{GDBN} Commands
26530 * Python:: Extending @value{GDBN} using Python
26531 * Guile:: Extending @value{GDBN} using Guile
26532 * Auto-loading extensions:: Automatically loading extensions
26533 * Multiple Extension Languages:: Working with multiple extension languages
26534 * Aliases:: Creating new spellings of existing commands
26537 To facilitate the use of extension languages, @value{GDBN} is capable
26538 of evaluating the contents of a file. When doing so, @value{GDBN}
26539 can recognize which extension language is being used by looking at
26540 the filename extension. Files with an unrecognized filename extension
26541 are always treated as a @value{GDBN} Command Files.
26542 @xref{Command Files,, Command files}.
26544 You can control how @value{GDBN} evaluates these files with the following
26548 @kindex set script-extension
26549 @kindex show script-extension
26550 @item set script-extension off
26551 All scripts are always evaluated as @value{GDBN} Command Files.
26553 @item set script-extension soft
26554 The debugger determines the scripting language based on filename
26555 extension. If this scripting language is supported, @value{GDBN}
26556 evaluates the script using that language. Otherwise, it evaluates
26557 the file as a @value{GDBN} Command File.
26559 @item set script-extension strict
26560 The debugger determines the scripting language based on filename
26561 extension, and evaluates the script using that language. If the
26562 language is not supported, then the evaluation fails.
26564 @item show script-extension
26565 Display the current value of the @code{script-extension} option.
26569 @ifset SYSTEM_GDBINIT_DIR
26570 This setting is not used for files in the system-wide gdbinit directory.
26571 Files in that directory must have an extension matching their language,
26572 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
26573 commands. @xref{Startup}.
26577 @section Canned Sequences of Commands
26579 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26580 Command Lists}), @value{GDBN} provides two ways to store sequences of
26581 commands for execution as a unit: user-defined commands and command
26585 * Define:: How to define your own commands
26586 * Hooks:: Hooks for user-defined commands
26587 * Command Files:: How to write scripts of commands to be stored in a file
26588 * Output:: Commands for controlled output
26589 * Auto-loading sequences:: Controlling auto-loaded command files
26593 @subsection User-defined Commands
26595 @cindex user-defined command
26596 @cindex arguments, to user-defined commands
26597 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26598 which you assign a new name as a command. This is done with the
26599 @code{define} command. User commands may accept an unlimited number of arguments
26600 separated by whitespace. Arguments are accessed within the user command
26601 via @code{$arg0@dots{}$argN}. A trivial example:
26605 print $arg0 + $arg1 + $arg2
26610 To execute the command use:
26617 This defines the command @code{adder}, which prints the sum of
26618 its three arguments. Note the arguments are text substitutions, so they may
26619 reference variables, use complex expressions, or even perform inferior
26622 @cindex argument count in user-defined commands
26623 @cindex how many arguments (user-defined commands)
26624 In addition, @code{$argc} may be used to find out how many arguments have
26630 print $arg0 + $arg1
26633 print $arg0 + $arg1 + $arg2
26638 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26639 to process a variable number of arguments:
26646 eval "set $sum = $sum + $arg%d", $i
26656 @item define @var{commandname}
26657 Define a command named @var{commandname}. If there is already a command
26658 by that name, you are asked to confirm that you want to redefine it.
26659 The argument @var{commandname} may be a bare command name consisting of letters,
26660 numbers, dashes, dots, and underscores. It may also start with any
26661 predefined or user-defined prefix command.
26662 For example, @samp{define target my-target} creates
26663 a user-defined @samp{target my-target} command.
26665 The definition of the command is made up of other @value{GDBN} command lines,
26666 which are given following the @code{define} command. The end of these
26667 commands is marked by a line containing @code{end}.
26670 @kindex end@r{ (user-defined commands)}
26671 @item document @var{commandname}
26672 Document the user-defined command @var{commandname}, so that it can be
26673 accessed by @code{help}. The command @var{commandname} must already be
26674 defined. This command reads lines of documentation just as @code{define}
26675 reads the lines of the command definition, ending with @code{end}.
26676 After the @code{document} command is finished, @code{help} on command
26677 @var{commandname} displays the documentation you have written.
26679 You may use the @code{document} command again to change the
26680 documentation of a command. Redefining the command with @code{define}
26681 does not change the documentation.
26683 @kindex define-prefix
26684 @item define-prefix @var{commandname}
26685 Define or mark the command @var{commandname} as a user-defined prefix
26686 command. Once marked, @var{commandname} can be used as prefix command
26687 by the @code{define} command.
26688 Note that @code{define-prefix} can be used with a not yet defined
26689 @var{commandname}. In such a case, @var{commandname} is defined as
26690 an empty user-defined command.
26691 In case you redefine a command that was marked as a user-defined
26692 prefix command, the subcommands of the redefined command are kept
26693 (and @value{GDBN} indicates so to the user).
26697 (gdb) define-prefix abc
26698 (gdb) define-prefix abc def
26699 (gdb) define abc def
26700 Type commands for definition of "abc def".
26701 End with a line saying just "end".
26702 >echo command initial def\n
26704 (gdb) define abc def ghi
26705 Type commands for definition of "abc def ghi".
26706 End with a line saying just "end".
26707 >echo command ghi\n
26709 (gdb) define abc def
26710 Keeping subcommands of prefix command "def".
26711 Redefine command "def"? (y or n) y
26712 Type commands for definition of "abc def".
26713 End with a line saying just "end".
26714 >echo command def\n
26723 @kindex dont-repeat
26724 @cindex don't repeat command
26726 Used inside a user-defined command, this tells @value{GDBN} that this
26727 command should not be repeated when the user hits @key{RET}
26728 (@pxref{Command Syntax, repeat last command}).
26730 @kindex help user-defined
26731 @item help user-defined
26732 List all user-defined commands and all python commands defined in class
26733 COMMAND_USER. The first line of the documentation or docstring is
26738 @itemx show user @var{commandname}
26739 Display the @value{GDBN} commands used to define @var{commandname} (but
26740 not its documentation). If no @var{commandname} is given, display the
26741 definitions for all user-defined commands.
26742 This does not work for user-defined python commands.
26744 @cindex infinite recursion in user-defined commands
26745 @kindex show max-user-call-depth
26746 @kindex set max-user-call-depth
26747 @item show max-user-call-depth
26748 @itemx set max-user-call-depth
26749 The value of @code{max-user-call-depth} controls how many recursion
26750 levels are allowed in user-defined commands before @value{GDBN} suspects an
26751 infinite recursion and aborts the command.
26752 This does not apply to user-defined python commands.
26755 In addition to the above commands, user-defined commands frequently
26756 use control flow commands, described in @ref{Command Files}.
26758 When user-defined commands are executed, the
26759 commands of the definition are not printed. An error in any command
26760 stops execution of the user-defined command.
26762 If used interactively, commands that would ask for confirmation proceed
26763 without asking when used inside a user-defined command. Many @value{GDBN}
26764 commands that normally print messages to say what they are doing omit the
26765 messages when used in a user-defined command.
26768 @subsection User-defined Command Hooks
26769 @cindex command hooks
26770 @cindex hooks, for commands
26771 @cindex hooks, pre-command
26774 You may define @dfn{hooks}, which are a special kind of user-defined
26775 command. Whenever you run the command @samp{foo}, if the user-defined
26776 command @samp{hook-foo} exists, it is executed (with no arguments)
26777 before that command.
26779 @cindex hooks, post-command
26781 A hook may also be defined which is run after the command you executed.
26782 Whenever you run the command @samp{foo}, if the user-defined command
26783 @samp{hookpost-foo} exists, it is executed (with no arguments) after
26784 that command. Post-execution hooks may exist simultaneously with
26785 pre-execution hooks, for the same command.
26787 It is valid for a hook to call the command which it hooks. If this
26788 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
26790 @c It would be nice if hookpost could be passed a parameter indicating
26791 @c if the command it hooks executed properly or not. FIXME!
26793 @kindex stop@r{, a pseudo-command}
26794 In addition, a pseudo-command, @samp{stop} exists. Defining
26795 (@samp{hook-stop}) makes the associated commands execute every time
26796 execution stops in your program: before breakpoint commands are run,
26797 displays are printed, or the stack frame is printed.
26799 For example, to ignore @code{SIGALRM} signals while
26800 single-stepping, but treat them normally during normal execution,
26805 handle SIGALRM nopass
26809 handle SIGALRM pass
26812 define hook-continue
26813 handle SIGALRM pass
26817 As a further example, to hook at the beginning and end of the @code{echo}
26818 command, and to add extra text to the beginning and end of the message,
26826 define hookpost-echo
26830 (@value{GDBP}) echo Hello World
26831 <<<---Hello World--->>>
26836 You can define a hook for any single-word command in @value{GDBN}, but
26837 not for command aliases; you should define a hook for the basic command
26838 name, e.g.@: @code{backtrace} rather than @code{bt}.
26839 @c FIXME! So how does Joe User discover whether a command is an alias
26841 You can hook a multi-word command by adding @code{hook-} or
26842 @code{hookpost-} to the last word of the command, e.g.@:
26843 @samp{define target hook-remote} to add a hook to @samp{target remote}.
26845 If an error occurs during the execution of your hook, execution of
26846 @value{GDBN} commands stops and @value{GDBN} issues a prompt
26847 (before the command that you actually typed had a chance to run).
26849 If you try to define a hook which does not match any known command, you
26850 get a warning from the @code{define} command.
26852 @node Command Files
26853 @subsection Command Files
26855 @cindex command files
26856 @cindex scripting commands
26857 A command file for @value{GDBN} is a text file made of lines that are
26858 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
26859 also be included. An empty line in a command file does nothing; it
26860 does not mean to repeat the last command, as it would from the
26863 You can request the execution of a command file with the @code{source}
26864 command. Note that the @code{source} command is also used to evaluate
26865 scripts that are not Command Files. The exact behavior can be configured
26866 using the @code{script-extension} setting.
26867 @xref{Extending GDB,, Extending GDB}.
26871 @cindex execute commands from a file
26872 @item source [-s] [-v] @var{filename}
26873 Execute the command file @var{filename}.
26876 The lines in a command file are generally executed sequentially,
26877 unless the order of execution is changed by one of the
26878 @emph{flow-control commands} described below. The commands are not
26879 printed as they are executed. An error in any command terminates
26880 execution of the command file and control is returned to the console.
26882 @value{GDBN} first searches for @var{filename} in the current directory.
26883 If the file is not found there, and @var{filename} does not specify a
26884 directory, then @value{GDBN} also looks for the file on the source search path
26885 (specified with the @samp{directory} command);
26886 except that @file{$cdir} is not searched because the compilation directory
26887 is not relevant to scripts.
26889 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
26890 on the search path even if @var{filename} specifies a directory.
26891 The search is done by appending @var{filename} to each element of the
26892 search path. So, for example, if @var{filename} is @file{mylib/myscript}
26893 and the search path contains @file{/home/user} then @value{GDBN} will
26894 look for the script @file{/home/user/mylib/myscript}.
26895 The search is also done if @var{filename} is an absolute path.
26896 For example, if @var{filename} is @file{/tmp/myscript} and
26897 the search path contains @file{/home/user} then @value{GDBN} will
26898 look for the script @file{/home/user/tmp/myscript}.
26899 For DOS-like systems, if @var{filename} contains a drive specification,
26900 it is stripped before concatenation. For example, if @var{filename} is
26901 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
26902 will look for the script @file{c:/tmp/myscript}.
26904 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
26905 each command as it is executed. The option must be given before
26906 @var{filename}, and is interpreted as part of the filename anywhere else.
26908 Commands that would ask for confirmation if used interactively proceed
26909 without asking when used in a command file. Many @value{GDBN} commands that
26910 normally print messages to say what they are doing omit the messages
26911 when called from command files.
26913 @value{GDBN} also accepts command input from standard input. In this
26914 mode, normal output goes to standard output and error output goes to
26915 standard error. Errors in a command file supplied on standard input do
26916 not terminate execution of the command file---execution continues with
26920 gdb < cmds > log 2>&1
26923 (The syntax above will vary depending on the shell used.) This example
26924 will execute commands from the file @file{cmds}. All output and errors
26925 would be directed to @file{log}.
26927 Since commands stored on command files tend to be more general than
26928 commands typed interactively, they frequently need to deal with
26929 complicated situations, such as different or unexpected values of
26930 variables and symbols, changes in how the program being debugged is
26931 built, etc. @value{GDBN} provides a set of flow-control commands to
26932 deal with these complexities. Using these commands, you can write
26933 complex scripts that loop over data structures, execute commands
26934 conditionally, etc.
26941 This command allows to include in your script conditionally executed
26942 commands. The @code{if} command takes a single argument, which is an
26943 expression to evaluate. It is followed by a series of commands that
26944 are executed only if the expression is true (its value is nonzero).
26945 There can then optionally be an @code{else} line, followed by a series
26946 of commands that are only executed if the expression was false. The
26947 end of the list is marked by a line containing @code{end}.
26951 This command allows to write loops. Its syntax is similar to
26952 @code{if}: the command takes a single argument, which is an expression
26953 to evaluate, and must be followed by the commands to execute, one per
26954 line, terminated by an @code{end}. These commands are called the
26955 @dfn{body} of the loop. The commands in the body of @code{while} are
26956 executed repeatedly as long as the expression evaluates to true.
26960 This command exits the @code{while} loop in whose body it is included.
26961 Execution of the script continues after that @code{while}s @code{end}
26964 @kindex loop_continue
26965 @item loop_continue
26966 This command skips the execution of the rest of the body of commands
26967 in the @code{while} loop in whose body it is included. Execution
26968 branches to the beginning of the @code{while} loop, where it evaluates
26969 the controlling expression.
26971 @kindex end@r{ (if/else/while commands)}
26973 Terminate the block of commands that are the body of @code{if},
26974 @code{else}, or @code{while} flow-control commands.
26979 @subsection Commands for Controlled Output
26981 During the execution of a command file or a user-defined command, normal
26982 @value{GDBN} output is suppressed; the only output that appears is what is
26983 explicitly printed by the commands in the definition. This section
26984 describes three commands useful for generating exactly the output you
26989 @item echo @var{text}
26990 @c I do not consider backslash-space a standard C escape sequence
26991 @c because it is not in ANSI.
26992 Print @var{text}. Nonprinting characters can be included in
26993 @var{text} using C escape sequences, such as @samp{\n} to print a
26994 newline. @strong{No newline is printed unless you specify one.}
26995 In addition to the standard C escape sequences, a backslash followed
26996 by a space stands for a space. This is useful for displaying a
26997 string with spaces at the beginning or the end, since leading and
26998 trailing spaces are otherwise trimmed from all arguments.
26999 To print @samp{@w{ }and foo =@w{ }}, use the command
27000 @samp{echo \@w{ }and foo = \@w{ }}.
27002 A backslash at the end of @var{text} can be used, as in C, to continue
27003 the command onto subsequent lines. For example,
27006 echo This is some text\n\
27007 which is continued\n\
27008 onto several lines.\n
27011 produces the same output as
27014 echo This is some text\n
27015 echo which is continued\n
27016 echo onto several lines.\n
27020 @item output @var{expression}
27021 Print the value of @var{expression} and nothing but that value: no
27022 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27023 value history either. @xref{Expressions, ,Expressions}, for more information
27026 @item output/@var{fmt} @var{expression}
27027 Print the value of @var{expression} in format @var{fmt}. You can use
27028 the same formats as for @code{print}. @xref{Output Formats,,Output
27029 Formats}, for more information.
27032 @item printf @var{template}, @var{expressions}@dots{}
27033 Print the values of one or more @var{expressions} under the control of
27034 the string @var{template}. To print several values, make
27035 @var{expressions} be a comma-separated list of individual expressions,
27036 which may be either numbers or pointers. Their values are printed as
27037 specified by @var{template}, exactly as a C program would do by
27038 executing the code below:
27041 printf (@var{template}, @var{expressions}@dots{});
27044 As in @code{C} @code{printf}, ordinary characters in @var{template}
27045 are printed verbatim, while @dfn{conversion specification} introduced
27046 by the @samp{%} character cause subsequent @var{expressions} to be
27047 evaluated, their values converted and formatted according to type and
27048 style information encoded in the conversion specifications, and then
27051 For example, you can print two values in hex like this:
27054 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27057 @code{printf} supports all the standard @code{C} conversion
27058 specifications, including the flags and modifiers between the @samp{%}
27059 character and the conversion letter, with the following exceptions:
27063 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27066 The modifier @samp{*} is not supported for specifying precision or
27070 The @samp{'} flag (for separation of digits into groups according to
27071 @code{LC_NUMERIC'}) is not supported.
27074 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27078 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27081 The conversion letters @samp{a} and @samp{A} are not supported.
27085 Note that the @samp{ll} type modifier is supported only if the
27086 underlying @code{C} implementation used to build @value{GDBN} supports
27087 the @code{long long int} type, and the @samp{L} type modifier is
27088 supported only if @code{long double} type is available.
27090 As in @code{C}, @code{printf} supports simple backslash-escape
27091 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27092 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27093 single character. Octal and hexadecimal escape sequences are not
27096 Additionally, @code{printf} supports conversion specifications for DFP
27097 (@dfn{Decimal Floating Point}) types using the following length modifiers
27098 together with a floating point specifier.
27103 @samp{H} for printing @code{Decimal32} types.
27106 @samp{D} for printing @code{Decimal64} types.
27109 @samp{DD} for printing @code{Decimal128} types.
27112 If the underlying @code{C} implementation used to build @value{GDBN} has
27113 support for the three length modifiers for DFP types, other modifiers
27114 such as width and precision will also be available for @value{GDBN} to use.
27116 In case there is no such @code{C} support, no additional modifiers will be
27117 available and the value will be printed in the standard way.
27119 Here's an example of printing DFP types using the above conversion letters:
27121 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27126 @item eval @var{template}, @var{expressions}@dots{}
27127 Convert the values of one or more @var{expressions} under the control of
27128 the string @var{template} to a command line, and call it.
27132 @node Auto-loading sequences
27133 @subsection Controlling auto-loading native @value{GDBN} scripts
27134 @cindex native script auto-loading
27136 When a new object file is read (for example, due to the @code{file}
27137 command, or because the inferior has loaded a shared library),
27138 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27139 @xref{Auto-loading extensions}.
27141 Auto-loading can be enabled or disabled,
27142 and the list of auto-loaded scripts can be printed.
27145 @anchor{set auto-load gdb-scripts}
27146 @kindex set auto-load gdb-scripts
27147 @item set auto-load gdb-scripts [on|off]
27148 Enable or disable the auto-loading of canned sequences of commands scripts.
27150 @anchor{show auto-load gdb-scripts}
27151 @kindex show auto-load gdb-scripts
27152 @item show auto-load gdb-scripts
27153 Show whether auto-loading of canned sequences of commands scripts is enabled or
27156 @anchor{info auto-load gdb-scripts}
27157 @kindex info auto-load gdb-scripts
27158 @cindex print list of auto-loaded canned sequences of commands scripts
27159 @item info auto-load gdb-scripts [@var{regexp}]
27160 Print the list of all canned sequences of commands scripts that @value{GDBN}
27164 If @var{regexp} is supplied only canned sequences of commands scripts with
27165 matching names are printed.
27167 @c Python docs live in a separate file.
27168 @include python.texi
27170 @c Guile docs live in a separate file.
27171 @include guile.texi
27173 @node Auto-loading extensions
27174 @section Auto-loading extensions
27175 @cindex auto-loading extensions
27177 @value{GDBN} provides two mechanisms for automatically loading extensions
27178 when a new object file is read (for example, due to the @code{file}
27179 command, or because the inferior has loaded a shared library):
27180 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27181 section of modern file formats like ELF.
27184 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27185 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27186 * Which flavor to choose?::
27189 The auto-loading feature is useful for supplying application-specific
27190 debugging commands and features.
27192 Auto-loading can be enabled or disabled,
27193 and the list of auto-loaded scripts can be printed.
27194 See the @samp{auto-loading} section of each extension language
27195 for more information.
27196 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27197 For Python files see @ref{Python Auto-loading}.
27199 Note that loading of this script file also requires accordingly configured
27200 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27202 @node objfile-gdbdotext file
27203 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27204 @cindex @file{@var{objfile}-gdb.gdb}
27205 @cindex @file{@var{objfile}-gdb.py}
27206 @cindex @file{@var{objfile}-gdb.scm}
27208 When a new object file is read, @value{GDBN} looks for a file named
27209 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27210 where @var{objfile} is the object file's name and
27211 where @var{ext} is the file extension for the extension language:
27214 @item @file{@var{objfile}-gdb.gdb}
27215 GDB's own command language
27216 @item @file{@var{objfile}-gdb.py}
27218 @item @file{@var{objfile}-gdb.scm}
27222 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27223 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27224 components, and appending the @file{-gdb.@var{ext}} suffix.
27225 If this file exists and is readable, @value{GDBN} will evaluate it as a
27226 script in the specified extension language.
27228 If this file does not exist, then @value{GDBN} will look for
27229 @var{script-name} file in all of the directories as specified below.
27231 Note that loading of these files requires an accordingly configured
27232 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27234 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27235 scripts normally according to its @file{.exe} filename. But if no scripts are
27236 found @value{GDBN} also tries script filenames matching the object file without
27237 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27238 is attempted on any platform. This makes the script filenames compatible
27239 between Unix and MS-Windows hosts.
27242 @anchor{set auto-load scripts-directory}
27243 @kindex set auto-load scripts-directory
27244 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27245 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27246 may be delimited by the host platform path separator in use
27247 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27249 Each entry here needs to be covered also by the security setting
27250 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27252 @anchor{with-auto-load-dir}
27253 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27254 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27255 configuration option @option{--with-auto-load-dir}.
27257 Any reference to @file{$debugdir} will get replaced by
27258 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27259 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27260 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27261 @file{$datadir} must be placed as a directory component --- either alone or
27262 delimited by @file{/} or @file{\} directory separators, depending on the host
27265 The list of directories uses path separator (@samp{:} on GNU and Unix
27266 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27267 to the @env{PATH} environment variable.
27269 @anchor{show auto-load scripts-directory}
27270 @kindex show auto-load scripts-directory
27271 @item show auto-load scripts-directory
27272 Show @value{GDBN} auto-loaded scripts location.
27274 @anchor{add-auto-load-scripts-directory}
27275 @kindex add-auto-load-scripts-directory
27276 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
27277 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
27278 Multiple entries may be delimited by the host platform path separator in use.
27281 @value{GDBN} does not track which files it has already auto-loaded this way.
27282 @value{GDBN} will load the associated script every time the corresponding
27283 @var{objfile} is opened.
27284 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27285 is evaluated more than once.
27287 @node dotdebug_gdb_scripts section
27288 @subsection The @code{.debug_gdb_scripts} section
27289 @cindex @code{.debug_gdb_scripts} section
27291 For systems using file formats like ELF and COFF,
27292 when @value{GDBN} loads a new object file
27293 it will look for a special section named @code{.debug_gdb_scripts}.
27294 If this section exists, its contents is a list of null-terminated entries
27295 specifying scripts to load. Each entry begins with a non-null prefix byte that
27296 specifies the kind of entry, typically the extension language and whether the
27297 script is in a file or inlined in @code{.debug_gdb_scripts}.
27299 The following entries are supported:
27302 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
27303 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
27304 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
27305 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
27308 @subsubsection Script File Entries
27310 If the entry specifies a file, @value{GDBN} will look for the file first
27311 in the current directory and then along the source search path
27312 (@pxref{Source Path, ,Specifying Source Directories}),
27313 except that @file{$cdir} is not searched, since the compilation
27314 directory is not relevant to scripts.
27316 File entries can be placed in section @code{.debug_gdb_scripts} with,
27317 for example, this GCC macro for Python scripts.
27320 /* Note: The "MS" section flags are to remove duplicates. */
27321 #define DEFINE_GDB_PY_SCRIPT(script_name) \
27323 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27324 .byte 1 /* Python */\n\
27325 .asciz \"" script_name "\"\n\
27331 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
27332 Then one can reference the macro in a header or source file like this:
27335 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
27338 The script name may include directories if desired.
27340 Note that loading of this script file also requires accordingly configured
27341 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27343 If the macro invocation is put in a header, any application or library
27344 using this header will get a reference to the specified script,
27345 and with the use of @code{"MS"} attributes on the section, the linker
27346 will remove duplicates.
27348 @subsubsection Script Text Entries
27350 Script text entries allow to put the executable script in the entry
27351 itself instead of loading it from a file.
27352 The first line of the entry, everything after the prefix byte and up to
27353 the first newline (@code{0xa}) character, is the script name, and must not
27354 contain any kind of space character, e.g., spaces or tabs.
27355 The rest of the entry, up to the trailing null byte, is the script to
27356 execute in the specified language. The name needs to be unique among
27357 all script names, as @value{GDBN} executes each script only once based
27360 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
27364 #include "symcat.h"
27365 #include "gdb/section-scripts.h"
27367 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
27368 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
27369 ".ascii \"gdb.inlined-script\\n\"\n"
27370 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
27371 ".ascii \" def __init__ (self):\\n\"\n"
27372 ".ascii \" super (test_cmd, self).__init__ ("
27373 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
27374 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
27375 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
27376 ".ascii \"test_cmd ()\\n\"\n"
27382 Loading of inlined scripts requires a properly configured
27383 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27384 The path to specify in @code{auto-load safe-path} is the path of the file
27385 containing the @code{.debug_gdb_scripts} section.
27387 @node Which flavor to choose?
27388 @subsection Which flavor to choose?
27390 Given the multiple ways of auto-loading extensions, it might not always
27391 be clear which one to choose. This section provides some guidance.
27394 Benefits of the @file{-gdb.@var{ext}} way:
27398 Can be used with file formats that don't support multiple sections.
27401 Ease of finding scripts for public libraries.
27403 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27404 in the source search path.
27405 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27406 isn't a source directory in which to find the script.
27409 Doesn't require source code additions.
27413 Benefits of the @code{.debug_gdb_scripts} way:
27417 Works with static linking.
27419 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
27420 trigger their loading. When an application is statically linked the only
27421 objfile available is the executable, and it is cumbersome to attach all the
27422 scripts from all the input libraries to the executable's
27423 @file{-gdb.@var{ext}} script.
27426 Works with classes that are entirely inlined.
27428 Some classes can be entirely inlined, and thus there may not be an associated
27429 shared library to attach a @file{-gdb.@var{ext}} script to.
27432 Scripts needn't be copied out of the source tree.
27434 In some circumstances, apps can be built out of large collections of internal
27435 libraries, and the build infrastructure necessary to install the
27436 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
27437 cumbersome. It may be easier to specify the scripts in the
27438 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27439 top of the source tree to the source search path.
27442 @node Multiple Extension Languages
27443 @section Multiple Extension Languages
27445 The Guile and Python extension languages do not share any state,
27446 and generally do not interfere with each other.
27447 There are some things to be aware of, however.
27449 @subsection Python comes first
27451 Python was @value{GDBN}'s first extension language, and to avoid breaking
27452 existing behaviour Python comes first. This is generally solved by the
27453 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27454 extension languages, and when it makes a call to an extension language,
27455 (say to pretty-print a value), it tries each in turn until an extension
27456 language indicates it has performed the request (e.g., has returned the
27457 pretty-printed form of a value).
27458 This extends to errors while performing such requests: If an error happens
27459 while, for example, trying to pretty-print an object then the error is
27460 reported and any following extension languages are not tried.
27463 @section Creating new spellings of existing commands
27464 @cindex aliases for commands
27466 It is often useful to define alternate spellings of existing commands.
27467 For example, if a new @value{GDBN} command defined in Python has
27468 a long name to type, it is handy to have an abbreviated version of it
27469 that involves less typing.
27471 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27472 of the @samp{step} command even though it is otherwise an ambiguous
27473 abbreviation of other commands like @samp{set} and @samp{show}.
27475 Aliases are also used to provide shortened or more common versions
27476 of multi-word commands. For example, @value{GDBN} provides the
27477 @samp{tty} alias of the @samp{set inferior-tty} command.
27479 You can define a new alias with the @samp{alias} command.
27484 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27488 @var{ALIAS} specifies the name of the new alias.
27489 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27492 @var{COMMAND} specifies the name of an existing command
27493 that is being aliased.
27495 The @samp{-a} option specifies that the new alias is an abbreviation
27496 of the command. Abbreviations are not shown in command
27497 lists displayed by the @samp{help} command.
27499 The @samp{--} option specifies the end of options,
27500 and is useful when @var{ALIAS} begins with a dash.
27502 Here is a simple example showing how to make an abbreviation
27503 of a command so that there is less to type.
27504 Suppose you were tired of typing @samp{disas}, the current
27505 shortest unambiguous abbreviation of the @samp{disassemble} command
27506 and you wanted an even shorter version named @samp{di}.
27507 The following will accomplish this.
27510 (gdb) alias -a di = disas
27513 Note that aliases are different from user-defined commands.
27514 With a user-defined command, you also need to write documentation
27515 for it with the @samp{document} command.
27516 An alias automatically picks up the documentation of the existing command.
27518 Here is an example where we make @samp{elms} an abbreviation of
27519 @samp{elements} in the @samp{set print elements} command.
27520 This is to show that you can make an abbreviation of any part
27524 (gdb) alias -a set print elms = set print elements
27525 (gdb) alias -a show print elms = show print elements
27526 (gdb) set p elms 20
27528 Limit on string chars or array elements to print is 200.
27531 Note that if you are defining an alias of a @samp{set} command,
27532 and you want to have an alias for the corresponding @samp{show}
27533 command, then you need to define the latter separately.
27535 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27536 @var{ALIAS}, just as they are normally.
27539 (gdb) alias -a set pr elms = set p ele
27542 Finally, here is an example showing the creation of a one word
27543 alias for a more complex command.
27544 This creates alias @samp{spe} of the command @samp{set print elements}.
27547 (gdb) alias spe = set print elements
27552 @chapter Command Interpreters
27553 @cindex command interpreters
27555 @value{GDBN} supports multiple command interpreters, and some command
27556 infrastructure to allow users or user interface writers to switch
27557 between interpreters or run commands in other interpreters.
27559 @value{GDBN} currently supports two command interpreters, the console
27560 interpreter (sometimes called the command-line interpreter or @sc{cli})
27561 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27562 describes both of these interfaces in great detail.
27564 By default, @value{GDBN} will start with the console interpreter.
27565 However, the user may choose to start @value{GDBN} with another
27566 interpreter by specifying the @option{-i} or @option{--interpreter}
27567 startup options. Defined interpreters include:
27571 @cindex console interpreter
27572 The traditional console or command-line interpreter. This is the most often
27573 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27574 @value{GDBN} will use this interpreter.
27577 @cindex mi interpreter
27578 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
27579 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27580 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27584 @cindex mi3 interpreter
27585 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
27588 @cindex mi2 interpreter
27589 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
27592 @cindex mi1 interpreter
27593 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
27597 @cindex invoke another interpreter
27599 @kindex interpreter-exec
27600 You may execute commands in any interpreter from the current
27601 interpreter using the appropriate command. If you are running the
27602 console interpreter, simply use the @code{interpreter-exec} command:
27605 interpreter-exec mi "-data-list-register-names"
27608 @sc{gdb/mi} has a similar command, although it is only available in versions of
27609 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27611 Note that @code{interpreter-exec} only changes the interpreter for the
27612 duration of the specified command. It does not change the interpreter
27615 @cindex start a new independent interpreter
27617 Although you may only choose a single interpreter at startup, it is
27618 possible to run an independent interpreter on a specified input/output
27619 device (usually a tty).
27621 For example, consider a debugger GUI or IDE that wants to provide a
27622 @value{GDBN} console view. It may do so by embedding a terminal
27623 emulator widget in its GUI, starting @value{GDBN} in the traditional
27624 command-line mode with stdin/stdout/stderr redirected to that
27625 terminal, and then creating an MI interpreter running on a specified
27626 input/output device. The console interpreter created by @value{GDBN}
27627 at startup handles commands the user types in the terminal widget,
27628 while the GUI controls and synchronizes state with @value{GDBN} using
27629 the separate MI interpreter.
27631 To start a new secondary @dfn{user interface} running MI, use the
27632 @code{new-ui} command:
27635 @cindex new user interface
27637 new-ui @var{interpreter} @var{tty}
27640 The @var{interpreter} parameter specifies the interpreter to run.
27641 This accepts the same values as the @code{interpreter-exec} command.
27642 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
27643 @var{tty} parameter specifies the name of the bidirectional file the
27644 interpreter uses for input/output, usually the name of a
27645 pseudoterminal slave on Unix systems. For example:
27648 (@value{GDBP}) new-ui mi /dev/pts/9
27652 runs an MI interpreter on @file{/dev/pts/9}.
27655 @chapter @value{GDBN} Text User Interface
27657 @cindex Text User Interface
27660 * TUI Overview:: TUI overview
27661 * TUI Keys:: TUI key bindings
27662 * TUI Single Key Mode:: TUI single key mode
27663 * TUI Commands:: TUI-specific commands
27664 * TUI Configuration:: TUI configuration variables
27667 The @value{GDBN} Text User Interface (TUI) is a terminal
27668 interface which uses the @code{curses} library to show the source
27669 file, the assembly output, the program registers and @value{GDBN}
27670 commands in separate text windows. The TUI mode is supported only
27671 on platforms where a suitable version of the @code{curses} library
27674 The TUI mode is enabled by default when you invoke @value{GDBN} as
27675 @samp{@value{GDBP} -tui}.
27676 You can also switch in and out of TUI mode while @value{GDBN} runs by
27677 using various TUI commands and key bindings, such as @command{tui
27678 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
27679 @ref{TUI Keys, ,TUI Key Bindings}.
27682 @section TUI Overview
27684 In TUI mode, @value{GDBN} can display several text windows:
27688 This window is the @value{GDBN} command window with the @value{GDBN}
27689 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27690 managed using readline.
27693 The source window shows the source file of the program. The current
27694 line and active breakpoints are displayed in this window.
27697 The assembly window shows the disassembly output of the program.
27700 This window shows the processor registers. Registers are highlighted
27701 when their values change.
27704 The source and assembly windows show the current program position
27705 by highlighting the current line and marking it with a @samp{>} marker.
27706 Breakpoints are indicated with two markers. The first marker
27707 indicates the breakpoint type:
27711 Breakpoint which was hit at least once.
27714 Breakpoint which was never hit.
27717 Hardware breakpoint which was hit at least once.
27720 Hardware breakpoint which was never hit.
27723 The second marker indicates whether the breakpoint is enabled or not:
27727 Breakpoint is enabled.
27730 Breakpoint is disabled.
27733 The source, assembly and register windows are updated when the current
27734 thread changes, when the frame changes, or when the program counter
27737 These windows are not all visible at the same time. The command
27738 window is always visible. The others can be arranged in several
27749 source and assembly,
27752 source and registers, or
27755 assembly and registers.
27758 These are the standard layouts, but other layouts can be defined.
27760 A status line above the command window shows the following information:
27764 Indicates the current @value{GDBN} target.
27765 (@pxref{Targets, ,Specifying a Debugging Target}).
27768 Gives the current process or thread number.
27769 When no process is being debugged, this field is set to @code{No process}.
27772 Gives the current function name for the selected frame.
27773 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27774 When there is no symbol corresponding to the current program counter,
27775 the string @code{??} is displayed.
27778 Indicates the current line number for the selected frame.
27779 When the current line number is not known, the string @code{??} is displayed.
27782 Indicates the current program counter address.
27786 @section TUI Key Bindings
27787 @cindex TUI key bindings
27789 The TUI installs several key bindings in the readline keymaps
27790 @ifset SYSTEM_READLINE
27791 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27793 @ifclear SYSTEM_READLINE
27794 (@pxref{Command Line Editing}).
27796 The following key bindings are installed for both TUI mode and the
27797 @value{GDBN} standard mode.
27806 Enter or leave the TUI mode. When leaving the TUI mode,
27807 the curses window management stops and @value{GDBN} operates using
27808 its standard mode, writing on the terminal directly. When reentering
27809 the TUI mode, control is given back to the curses windows.
27810 The screen is then refreshed.
27812 This key binding uses the bindable Readline function
27813 @code{tui-switch-mode}.
27817 Use a TUI layout with only one window. The layout will
27818 either be @samp{source} or @samp{assembly}. When the TUI mode
27819 is not active, it will switch to the TUI mode.
27821 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27823 This key binding uses the bindable Readline function
27824 @code{tui-delete-other-windows}.
27828 Use a TUI layout with at least two windows. When the current
27829 layout already has two windows, the next layout with two windows is used.
27830 When a new layout is chosen, one window will always be common to the
27831 previous layout and the new one.
27833 Think of it as the Emacs @kbd{C-x 2} binding.
27835 This key binding uses the bindable Readline function
27836 @code{tui-change-windows}.
27840 Change the active window. The TUI associates several key bindings
27841 (like scrolling and arrow keys) with the active window. This command
27842 gives the focus to the next TUI window.
27844 Think of it as the Emacs @kbd{C-x o} binding.
27846 This key binding uses the bindable Readline function
27847 @code{tui-other-window}.
27851 Switch in and out of the TUI SingleKey mode that binds single
27852 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27854 This key binding uses the bindable Readline function
27855 @code{next-keymap}.
27858 The following key bindings only work in the TUI mode:
27863 Scroll the active window one page up.
27867 Scroll the active window one page down.
27871 Scroll the active window one line up.
27875 Scroll the active window one line down.
27879 Scroll the active window one column left.
27883 Scroll the active window one column right.
27887 Refresh the screen.
27890 Because the arrow keys scroll the active window in the TUI mode, they
27891 are not available for their normal use by readline unless the command
27892 window has the focus. When another window is active, you must use
27893 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27894 and @kbd{C-f} to control the command window.
27896 @node TUI Single Key Mode
27897 @section TUI Single Key Mode
27898 @cindex TUI single key mode
27900 The TUI also provides a @dfn{SingleKey} mode, which binds several
27901 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27902 switch into this mode, where the following key bindings are used:
27905 @kindex c @r{(SingleKey TUI key)}
27909 @kindex d @r{(SingleKey TUI key)}
27913 @kindex f @r{(SingleKey TUI key)}
27917 @kindex n @r{(SingleKey TUI key)}
27921 @kindex o @r{(SingleKey TUI key)}
27923 nexti. The shortcut letter @samp{o} stands for ``step Over''.
27925 @kindex q @r{(SingleKey TUI key)}
27927 exit the SingleKey mode.
27929 @kindex r @r{(SingleKey TUI key)}
27933 @kindex s @r{(SingleKey TUI key)}
27937 @kindex i @r{(SingleKey TUI key)}
27939 stepi. The shortcut letter @samp{i} stands for ``step Into''.
27941 @kindex u @r{(SingleKey TUI key)}
27945 @kindex v @r{(SingleKey TUI key)}
27949 @kindex w @r{(SingleKey TUI key)}
27954 Other keys temporarily switch to the @value{GDBN} command prompt.
27955 The key that was pressed is inserted in the editing buffer so that
27956 it is possible to type most @value{GDBN} commands without interaction
27957 with the TUI SingleKey mode. Once the command is entered the TUI
27958 SingleKey mode is restored. The only way to permanently leave
27959 this mode is by typing @kbd{q} or @kbd{C-x s}.
27961 @cindex SingleKey keymap name
27962 If @value{GDBN} was built with Readline 8.0 or later, the TUI
27963 SingleKey keymap will be named @samp{SingleKey}. This can be used in
27964 @file{.inputrc} to add additional bindings to this keymap.
27967 @section TUI-specific Commands
27968 @cindex TUI commands
27970 The TUI has specific commands to control the text windows.
27971 These commands are always available, even when @value{GDBN} is not in
27972 the TUI mode. When @value{GDBN} is in the standard mode, most
27973 of these commands will automatically switch to the TUI mode.
27975 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27976 terminal, or @value{GDBN} has been started with the machine interface
27977 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27978 these commands will fail with an error, because it would not be
27979 possible or desirable to enable curses window management.
27984 Activate TUI mode. The last active TUI window layout will be used if
27985 TUI mode has previously been used in the current debugging session,
27986 otherwise a default layout is used.
27989 @kindex tui disable
27990 Disable TUI mode, returning to the console interpreter.
27994 List and give the size of all displayed windows.
27996 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
27997 @kindex tui new-layout
27998 Create a new TUI layout. The new layout will be named @var{name}, and
27999 can be accessed using the @code{layout} command (see below).
28001 Each @var{window} parameter is either the name of a window to display,
28002 or a window description. The windows will be displayed from top to
28003 bottom in the order listed.
28005 The names of the windows are the same as the ones given to the
28006 @code{focus} command (see below); additional, the @code{status}
28007 window can be specified. Note that, because it is of fixed height,
28008 the weight assigned to the status window is of no importance. It is
28009 conventional to use @samp{0} here.
28011 A window description looks a bit like an invocation of @code{tui
28012 new-layout}, and is of the form
28013 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28015 This specifies a sub-layout. If @code{-horizontal} is given, the
28016 windows in this description will be arranged side-by-side, rather than
28019 Each @var{weight} is an integer. It is the weight of this window
28020 relative to all the other windows in the layout. These numbers are
28021 used to calculate how much of the screen is given to each window.
28026 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28029 Here, the new layout is called @samp{example}. It shows the source
28030 and register windows, followed by the status window, and then finally
28031 the command window. The non-status windows all have the same weight,
28032 so the terminal will be split into three roughly equal sections.
28034 Here is a more complex example, showing a horizontal layout:
28037 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28040 This will result in side-by-side source and assembly windows; with the
28041 status and command window being beneath these, filling the entire
28042 width of the terminal. Because they have weight 2, the source and
28043 assembly windows will be twice the height of the command window.
28045 @item layout @var{name}
28047 Changes which TUI windows are displayed. The @var{name} parameter
28048 controls which layout is shown. It can be either one of the built-in
28049 layout names, or the name of a layout defined by the user using
28050 @code{tui new-layout}.
28052 The built-in layouts are as follows:
28056 Display the next layout.
28059 Display the previous layout.
28062 Display the source and command windows.
28065 Display the assembly and command windows.
28068 Display the source, assembly, and command windows.
28071 When in @code{src} layout display the register, source, and command
28072 windows. When in @code{asm} or @code{split} layout display the
28073 register, assembler, and command windows.
28076 @item focus @var{name}
28078 Changes which TUI window is currently active for scrolling. The
28079 @var{name} parameter can be any of the following:
28083 Make the next window active for scrolling.
28086 Make the previous window active for scrolling.
28089 Make the source window active for scrolling.
28092 Make the assembly window active for scrolling.
28095 Make the register window active for scrolling.
28098 Make the command window active for scrolling.
28103 Refresh the screen. This is similar to typing @kbd{C-L}.
28105 @item tui reg @var{group}
28107 Changes the register group displayed in the tui register window to
28108 @var{group}. If the register window is not currently displayed this
28109 command will cause the register window to be displayed. The list of
28110 register groups, as well as their order is target specific. The
28111 following groups are available on most targets:
28114 Repeatedly selecting this group will cause the display to cycle
28115 through all of the available register groups.
28118 Repeatedly selecting this group will cause the display to cycle
28119 through all of the available register groups in the reverse order to
28123 Display the general registers.
28125 Display the floating point registers.
28127 Display the system registers.
28129 Display the vector registers.
28131 Display all registers.
28136 Update the source window and the current execution point.
28138 @item winheight @var{name} +@var{count}
28139 @itemx winheight @var{name} -@var{count}
28141 Change the height of the window @var{name} by @var{count}
28142 lines. Positive counts increase the height, while negative counts
28143 decrease it. The @var{name} parameter can be one of @code{src} (the
28144 source window), @code{cmd} (the command window), @code{asm} (the
28145 disassembly window), or @code{regs} (the register display window).
28148 @node TUI Configuration
28149 @section TUI Configuration Variables
28150 @cindex TUI configuration variables
28152 Several configuration variables control the appearance of TUI windows.
28155 @item set tui border-kind @var{kind}
28156 @kindex set tui border-kind
28157 Select the border appearance for the source, assembly and register windows.
28158 The possible values are the following:
28161 Use a space character to draw the border.
28164 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28167 Use the Alternate Character Set to draw the border. The border is
28168 drawn using character line graphics if the terminal supports them.
28171 @item set tui border-mode @var{mode}
28172 @kindex set tui border-mode
28173 @itemx set tui active-border-mode @var{mode}
28174 @kindex set tui active-border-mode
28175 Select the display attributes for the borders of the inactive windows
28176 or the active window. The @var{mode} can be one of the following:
28179 Use normal attributes to display the border.
28185 Use reverse video mode.
28188 Use half bright mode.
28190 @item half-standout
28191 Use half bright and standout mode.
28194 Use extra bright or bold mode.
28196 @item bold-standout
28197 Use extra bright or bold and standout mode.
28200 @item set tui tab-width @var{nchars}
28201 @kindex set tui tab-width
28203 Set the width of tab stops to be @var{nchars} characters. This
28204 setting affects the display of TAB characters in the source and
28207 @item set tui compact-source @r{[}on@r{|}off@r{]}
28208 @kindex set tui compact-source
28209 Set whether the TUI source window is displayed in ``compact'' form.
28210 The default display uses more space for line numbers and starts the
28211 source text at the next tab stop; the compact display uses only as
28212 much space as is needed for the line numbers in the current file, and
28213 only a single space to separate the line numbers from the source.
28216 Note that the colors of the TUI borders can be controlled using the
28217 appropriate @code{set style} commands. @xref{Output Styling}.
28220 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28223 @cindex @sc{gnu} Emacs
28224 A special interface allows you to use @sc{gnu} Emacs to view (and
28225 edit) the source files for the program you are debugging with
28228 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28229 executable file you want to debug as an argument. This command starts
28230 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28231 created Emacs buffer.
28232 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28234 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28239 All ``terminal'' input and output goes through an Emacs buffer, called
28242 This applies both to @value{GDBN} commands and their output, and to the input
28243 and output done by the program you are debugging.
28245 This is useful because it means that you can copy the text of previous
28246 commands and input them again; you can even use parts of the output
28249 All the facilities of Emacs' Shell mode are available for interacting
28250 with your program. In particular, you can send signals the usual
28251 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28255 @value{GDBN} displays source code through Emacs.
28257 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28258 source file for that frame and puts an arrow (@samp{=>}) at the
28259 left margin of the current line. Emacs uses a separate buffer for
28260 source display, and splits the screen to show both your @value{GDBN} session
28263 Explicit @value{GDBN} @code{list} or search commands still produce output as
28264 usual, but you probably have no reason to use them from Emacs.
28267 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28268 a graphical mode, enabled by default, which provides further buffers
28269 that can control the execution and describe the state of your program.
28270 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28272 If you specify an absolute file name when prompted for the @kbd{M-x
28273 gdb} argument, then Emacs sets your current working directory to where
28274 your program resides. If you only specify the file name, then Emacs
28275 sets your current working directory to the directory associated
28276 with the previous buffer. In this case, @value{GDBN} may find your
28277 program by searching your environment's @code{PATH} variable, but on
28278 some operating systems it might not find the source. So, although the
28279 @value{GDBN} input and output session proceeds normally, the auxiliary
28280 buffer does not display the current source and line of execution.
28282 The initial working directory of @value{GDBN} is printed on the top
28283 line of the GUD buffer and this serves as a default for the commands
28284 that specify files for @value{GDBN} to operate on. @xref{Files,
28285 ,Commands to Specify Files}.
28287 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28288 need to call @value{GDBN} by a different name (for example, if you
28289 keep several configurations around, with different names) you can
28290 customize the Emacs variable @code{gud-gdb-command-name} to run the
28293 In the GUD buffer, you can use these special Emacs commands in
28294 addition to the standard Shell mode commands:
28298 Describe the features of Emacs' GUD Mode.
28301 Execute to another source line, like the @value{GDBN} @code{step} command; also
28302 update the display window to show the current file and location.
28305 Execute to next source line in this function, skipping all function
28306 calls, like the @value{GDBN} @code{next} command. Then update the display window
28307 to show the current file and location.
28310 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28311 display window accordingly.
28314 Execute until exit from the selected stack frame, like the @value{GDBN}
28315 @code{finish} command.
28318 Continue execution of your program, like the @value{GDBN} @code{continue}
28322 Go up the number of frames indicated by the numeric argument
28323 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28324 like the @value{GDBN} @code{up} command.
28327 Go down the number of frames indicated by the numeric argument, like the
28328 @value{GDBN} @code{down} command.
28331 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28332 tells @value{GDBN} to set a breakpoint on the source line point is on.
28334 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28335 separate frame which shows a backtrace when the GUD buffer is current.
28336 Move point to any frame in the stack and type @key{RET} to make it
28337 become the current frame and display the associated source in the
28338 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28339 selected frame become the current one. In graphical mode, the
28340 speedbar displays watch expressions.
28342 If you accidentally delete the source-display buffer, an easy way to get
28343 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28344 request a frame display; when you run under Emacs, this recreates
28345 the source buffer if necessary to show you the context of the current
28348 The source files displayed in Emacs are in ordinary Emacs buffers
28349 which are visiting the source files in the usual way. You can edit
28350 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28351 communicates with Emacs in terms of line numbers. If you add or
28352 delete lines from the text, the line numbers that @value{GDBN} knows cease
28353 to correspond properly with the code.
28355 A more detailed description of Emacs' interaction with @value{GDBN} is
28356 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28360 @chapter The @sc{gdb/mi} Interface
28362 @unnumberedsec Function and Purpose
28364 @cindex @sc{gdb/mi}, its purpose
28365 @sc{gdb/mi} is a line based machine oriented text interface to
28366 @value{GDBN} and is activated by specifying using the
28367 @option{--interpreter} command line option (@pxref{Mode Options}). It
28368 is specifically intended to support the development of systems which
28369 use the debugger as just one small component of a larger system.
28371 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28372 in the form of a reference manual.
28374 Note that @sc{gdb/mi} is still under construction, so some of the
28375 features described below are incomplete and subject to change
28376 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28378 @unnumberedsec Notation and Terminology
28380 @cindex notational conventions, for @sc{gdb/mi}
28381 This chapter uses the following notation:
28385 @code{|} separates two alternatives.
28388 @code{[ @var{something} ]} indicates that @var{something} is optional:
28389 it may or may not be given.
28392 @code{( @var{group} )*} means that @var{group} inside the parentheses
28393 may repeat zero or more times.
28396 @code{( @var{group} )+} means that @var{group} inside the parentheses
28397 may repeat one or more times.
28400 @code{"@var{string}"} means a literal @var{string}.
28404 @heading Dependencies
28408 * GDB/MI General Design::
28409 * GDB/MI Command Syntax::
28410 * GDB/MI Compatibility with CLI::
28411 * GDB/MI Development and Front Ends::
28412 * GDB/MI Output Records::
28413 * GDB/MI Simple Examples::
28414 * GDB/MI Command Description Format::
28415 * GDB/MI Breakpoint Commands::
28416 * GDB/MI Catchpoint Commands::
28417 * GDB/MI Program Context::
28418 * GDB/MI Thread Commands::
28419 * GDB/MI Ada Tasking Commands::
28420 * GDB/MI Program Execution::
28421 * GDB/MI Stack Manipulation::
28422 * GDB/MI Variable Objects::
28423 * GDB/MI Data Manipulation::
28424 * GDB/MI Tracepoint Commands::
28425 * GDB/MI Symbol Query::
28426 * GDB/MI File Commands::
28428 * GDB/MI Kod Commands::
28429 * GDB/MI Memory Overlay Commands::
28430 * GDB/MI Signal Handling Commands::
28432 * GDB/MI Target Manipulation::
28433 * GDB/MI File Transfer Commands::
28434 * GDB/MI Ada Exceptions Commands::
28435 * GDB/MI Support Commands::
28436 * GDB/MI Miscellaneous Commands::
28439 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28440 @node GDB/MI General Design
28441 @section @sc{gdb/mi} General Design
28442 @cindex GDB/MI General Design
28444 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28445 parts---commands sent to @value{GDBN}, responses to those commands
28446 and notifications. Each command results in exactly one response,
28447 indicating either successful completion of the command, or an error.
28448 For the commands that do not resume the target, the response contains the
28449 requested information. For the commands that resume the target, the
28450 response only indicates whether the target was successfully resumed.
28451 Notifications is the mechanism for reporting changes in the state of the
28452 target, or in @value{GDBN} state, that cannot conveniently be associated with
28453 a command and reported as part of that command response.
28455 The important examples of notifications are:
28459 Exec notifications. These are used to report changes in
28460 target state---when a target is resumed, or stopped. It would not
28461 be feasible to include this information in response of resuming
28462 commands, because one resume commands can result in multiple events in
28463 different threads. Also, quite some time may pass before any event
28464 happens in the target, while a frontend needs to know whether the resuming
28465 command itself was successfully executed.
28468 Console output, and status notifications. Console output
28469 notifications are used to report output of CLI commands, as well as
28470 diagnostics for other commands. Status notifications are used to
28471 report the progress of a long-running operation. Naturally, including
28472 this information in command response would mean no output is produced
28473 until the command is finished, which is undesirable.
28476 General notifications. Commands may have various side effects on
28477 the @value{GDBN} or target state beyond their official purpose. For example,
28478 a command may change the selected thread. Although such changes can
28479 be included in command response, using notification allows for more
28480 orthogonal frontend design.
28484 There's no guarantee that whenever an MI command reports an error,
28485 @value{GDBN} or the target are in any specific state, and especially,
28486 the state is not reverted to the state before the MI command was
28487 processed. Therefore, whenever an MI command results in an error,
28488 we recommend that the frontend refreshes all the information shown in
28489 the user interface.
28493 * Context management::
28494 * Asynchronous and non-stop modes::
28498 @node Context management
28499 @subsection Context management
28501 @subsubsection Threads and Frames
28503 In most cases when @value{GDBN} accesses the target, this access is
28504 done in context of a specific thread and frame (@pxref{Frames}).
28505 Often, even when accessing global data, the target requires that a thread
28506 be specified. The CLI interface maintains the selected thread and frame,
28507 and supplies them to target on each command. This is convenient,
28508 because a command line user would not want to specify that information
28509 explicitly on each command, and because user interacts with
28510 @value{GDBN} via a single terminal, so no confusion is possible as
28511 to what thread and frame are the current ones.
28513 In the case of MI, the concept of selected thread and frame is less
28514 useful. First, a frontend can easily remember this information
28515 itself. Second, a graphical frontend can have more than one window,
28516 each one used for debugging a different thread, and the frontend might
28517 want to access additional threads for internal purposes. This
28518 increases the risk that by relying on implicitly selected thread, the
28519 frontend may be operating on a wrong one. Therefore, each MI command
28520 should explicitly specify which thread and frame to operate on. To
28521 make it possible, each MI command accepts the @samp{--thread} and
28522 @samp{--frame} options, the value to each is @value{GDBN} global
28523 identifier for thread and frame to operate on.
28525 Usually, each top-level window in a frontend allows the user to select
28526 a thread and a frame, and remembers the user selection for further
28527 operations. However, in some cases @value{GDBN} may suggest that the
28528 current thread or frame be changed. For example, when stopping on a
28529 breakpoint it is reasonable to switch to the thread where breakpoint is
28530 hit. For another example, if the user issues the CLI @samp{thread} or
28531 @samp{frame} commands via the frontend, it is desirable to change the
28532 frontend's selection to the one specified by user. @value{GDBN}
28533 communicates the suggestion to change current thread and frame using the
28534 @samp{=thread-selected} notification.
28536 Note that historically, MI shares the selected thread with CLI, so
28537 frontends used the @code{-thread-select} to execute commands in the
28538 right context. However, getting this to work right is cumbersome. The
28539 simplest way is for frontend to emit @code{-thread-select} command
28540 before every command. This doubles the number of commands that need
28541 to be sent. The alternative approach is to suppress @code{-thread-select}
28542 if the selected thread in @value{GDBN} is supposed to be identical to the
28543 thread the frontend wants to operate on. However, getting this
28544 optimization right can be tricky. In particular, if the frontend
28545 sends several commands to @value{GDBN}, and one of the commands changes the
28546 selected thread, then the behaviour of subsequent commands will
28547 change. So, a frontend should either wait for response from such
28548 problematic commands, or explicitly add @code{-thread-select} for
28549 all subsequent commands. No frontend is known to do this exactly
28550 right, so it is suggested to just always pass the @samp{--thread} and
28551 @samp{--frame} options.
28553 @subsubsection Language
28555 The execution of several commands depends on which language is selected.
28556 By default, the current language (@pxref{show language}) is used.
28557 But for commands known to be language-sensitive, it is recommended
28558 to use the @samp{--language} option. This option takes one argument,
28559 which is the name of the language to use while executing the command.
28563 -data-evaluate-expression --language c "sizeof (void*)"
28568 The valid language names are the same names accepted by the
28569 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28570 @samp{local} or @samp{unknown}.
28572 @node Asynchronous and non-stop modes
28573 @subsection Asynchronous command execution and non-stop mode
28575 On some targets, @value{GDBN} is capable of processing MI commands
28576 even while the target is running. This is called @dfn{asynchronous
28577 command execution} (@pxref{Background Execution}). The frontend may
28578 specify a preference for asynchronous execution using the
28579 @code{-gdb-set mi-async 1} command, which should be emitted before
28580 either running the executable or attaching to the target. After the
28581 frontend has started the executable or attached to the target, it can
28582 find if asynchronous execution is enabled using the
28583 @code{-list-target-features} command.
28586 @item -gdb-set mi-async on
28587 @item -gdb-set mi-async off
28588 Set whether MI is in asynchronous mode.
28590 When @code{off}, which is the default, MI execution commands (e.g.,
28591 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
28592 for the program to stop before processing further commands.
28594 When @code{on}, MI execution commands are background execution
28595 commands (e.g., @code{-exec-continue} becomes the equivalent of the
28596 @code{c&} CLI command), and so @value{GDBN} is capable of processing
28597 MI commands even while the target is running.
28599 @item -gdb-show mi-async
28600 Show whether MI asynchronous mode is enabled.
28603 Note: In @value{GDBN} version 7.7 and earlier, this option was called
28604 @code{target-async} instead of @code{mi-async}, and it had the effect
28605 of both putting MI in asynchronous mode and making CLI background
28606 commands possible. CLI background commands are now always possible
28607 ``out of the box'' if the target supports them. The old spelling is
28608 kept as a deprecated alias for backwards compatibility.
28610 Even if @value{GDBN} can accept a command while target is running,
28611 many commands that access the target do not work when the target is
28612 running. Therefore, asynchronous command execution is most useful
28613 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28614 it is possible to examine the state of one thread, while other threads
28617 When a given thread is running, MI commands that try to access the
28618 target in the context of that thread may not work, or may work only on
28619 some targets. In particular, commands that try to operate on thread's
28620 stack will not work, on any target. Commands that read memory, or
28621 modify breakpoints, may work or not work, depending on the target. Note
28622 that even commands that operate on global state, such as @code{print},
28623 @code{set}, and breakpoint commands, still access the target in the
28624 context of a specific thread, so frontend should try to find a
28625 stopped thread and perform the operation on that thread (using the
28626 @samp{--thread} option).
28628 Which commands will work in the context of a running thread is
28629 highly target dependent. However, the two commands
28630 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28631 to find the state of a thread, will always work.
28633 @node Thread groups
28634 @subsection Thread groups
28635 @value{GDBN} may be used to debug several processes at the same time.
28636 On some platforms, @value{GDBN} may support debugging of several
28637 hardware systems, each one having several cores with several different
28638 processes running on each core. This section describes the MI
28639 mechanism to support such debugging scenarios.
28641 The key observation is that regardless of the structure of the
28642 target, MI can have a global list of threads, because most commands that
28643 accept the @samp{--thread} option do not need to know what process that
28644 thread belongs to. Therefore, it is not necessary to introduce
28645 neither additional @samp{--process} option, nor an notion of the
28646 current process in the MI interface. The only strictly new feature
28647 that is required is the ability to find how the threads are grouped
28650 To allow the user to discover such grouping, and to support arbitrary
28651 hierarchy of machines/cores/processes, MI introduces the concept of a
28652 @dfn{thread group}. Thread group is a collection of threads and other
28653 thread groups. A thread group always has a string identifier, a type,
28654 and may have additional attributes specific to the type. A new
28655 command, @code{-list-thread-groups}, returns the list of top-level
28656 thread groups, which correspond to processes that @value{GDBN} is
28657 debugging at the moment. By passing an identifier of a thread group
28658 to the @code{-list-thread-groups} command, it is possible to obtain
28659 the members of specific thread group.
28661 To allow the user to easily discover processes, and other objects, he
28662 wishes to debug, a concept of @dfn{available thread group} is
28663 introduced. Available thread group is an thread group that
28664 @value{GDBN} is not debugging, but that can be attached to, using the
28665 @code{-target-attach} command. The list of available top-level thread
28666 groups can be obtained using @samp{-list-thread-groups --available}.
28667 In general, the content of a thread group may be only retrieved only
28668 after attaching to that thread group.
28670 Thread groups are related to inferiors (@pxref{Inferiors Connections and
28671 Programs}). Each inferior corresponds to a thread group of a special
28672 type @samp{process}, and some additional operations are permitted on
28673 such thread groups.
28675 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28676 @node GDB/MI Command Syntax
28677 @section @sc{gdb/mi} Command Syntax
28680 * GDB/MI Input Syntax::
28681 * GDB/MI Output Syntax::
28684 @node GDB/MI Input Syntax
28685 @subsection @sc{gdb/mi} Input Syntax
28687 @cindex input syntax for @sc{gdb/mi}
28688 @cindex @sc{gdb/mi}, input syntax
28690 @item @var{command} @expansion{}
28691 @code{@var{cli-command} | @var{mi-command}}
28693 @item @var{cli-command} @expansion{}
28694 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28695 @var{cli-command} is any existing @value{GDBN} CLI command.
28697 @item @var{mi-command} @expansion{}
28698 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28699 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28701 @item @var{token} @expansion{}
28702 "any sequence of digits"
28704 @item @var{option} @expansion{}
28705 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28707 @item @var{parameter} @expansion{}
28708 @code{@var{non-blank-sequence} | @var{c-string}}
28710 @item @var{operation} @expansion{}
28711 @emph{any of the operations described in this chapter}
28713 @item @var{non-blank-sequence} @expansion{}
28714 @emph{anything, provided it doesn't contain special characters such as
28715 "-", @var{nl}, """ and of course " "}
28717 @item @var{c-string} @expansion{}
28718 @code{""" @var{seven-bit-iso-c-string-content} """}
28720 @item @var{nl} @expansion{}
28729 The CLI commands are still handled by the @sc{mi} interpreter; their
28730 output is described below.
28733 The @code{@var{token}}, when present, is passed back when the command
28737 Some @sc{mi} commands accept optional arguments as part of the parameter
28738 list. Each option is identified by a leading @samp{-} (dash) and may be
28739 followed by an optional argument parameter. Options occur first in the
28740 parameter list and can be delimited from normal parameters using
28741 @samp{--} (this is useful when some parameters begin with a dash).
28748 We want easy access to the existing CLI syntax (for debugging).
28751 We want it to be easy to spot a @sc{mi} operation.
28754 @node GDB/MI Output Syntax
28755 @subsection @sc{gdb/mi} Output Syntax
28757 @cindex output syntax of @sc{gdb/mi}
28758 @cindex @sc{gdb/mi}, output syntax
28759 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28760 followed, optionally, by a single result record. This result record
28761 is for the most recent command. The sequence of output records is
28762 terminated by @samp{(gdb)}.
28764 If an input command was prefixed with a @code{@var{token}} then the
28765 corresponding output for that command will also be prefixed by that same
28769 @item @var{output} @expansion{}
28770 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28772 @item @var{result-record} @expansion{}
28773 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28775 @item @var{out-of-band-record} @expansion{}
28776 @code{@var{async-record} | @var{stream-record}}
28778 @item @var{async-record} @expansion{}
28779 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28781 @item @var{exec-async-output} @expansion{}
28782 @code{[ @var{token} ] "*" @var{async-output nl}}
28784 @item @var{status-async-output} @expansion{}
28785 @code{[ @var{token} ] "+" @var{async-output nl}}
28787 @item @var{notify-async-output} @expansion{}
28788 @code{[ @var{token} ] "=" @var{async-output nl}}
28790 @item @var{async-output} @expansion{}
28791 @code{@var{async-class} ( "," @var{result} )*}
28793 @item @var{result-class} @expansion{}
28794 @code{"done" | "running" | "connected" | "error" | "exit"}
28796 @item @var{async-class} @expansion{}
28797 @code{"stopped" | @var{others}} (where @var{others} will be added
28798 depending on the needs---this is still in development).
28800 @item @var{result} @expansion{}
28801 @code{ @var{variable} "=" @var{value}}
28803 @item @var{variable} @expansion{}
28804 @code{ @var{string} }
28806 @item @var{value} @expansion{}
28807 @code{ @var{const} | @var{tuple} | @var{list} }
28809 @item @var{const} @expansion{}
28810 @code{@var{c-string}}
28812 @item @var{tuple} @expansion{}
28813 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28815 @item @var{list} @expansion{}
28816 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28817 @var{result} ( "," @var{result} )* "]" }
28819 @item @var{stream-record} @expansion{}
28820 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28822 @item @var{console-stream-output} @expansion{}
28823 @code{"~" @var{c-string nl}}
28825 @item @var{target-stream-output} @expansion{}
28826 @code{"@@" @var{c-string nl}}
28828 @item @var{log-stream-output} @expansion{}
28829 @code{"&" @var{c-string nl}}
28831 @item @var{nl} @expansion{}
28834 @item @var{token} @expansion{}
28835 @emph{any sequence of digits}.
28843 All output sequences end in a single line containing a period.
28846 The @code{@var{token}} is from the corresponding request. Note that
28847 for all async output, while the token is allowed by the grammar and
28848 may be output by future versions of @value{GDBN} for select async
28849 output messages, it is generally omitted. Frontends should treat
28850 all async output as reporting general changes in the state of the
28851 target and there should be no need to associate async output to any
28855 @cindex status output in @sc{gdb/mi}
28856 @var{status-async-output} contains on-going status information about the
28857 progress of a slow operation. It can be discarded. All status output is
28858 prefixed by @samp{+}.
28861 @cindex async output in @sc{gdb/mi}
28862 @var{exec-async-output} contains asynchronous state change on the target
28863 (stopped, started, disappeared). All async output is prefixed by
28867 @cindex notify output in @sc{gdb/mi}
28868 @var{notify-async-output} contains supplementary information that the
28869 client should handle (e.g., a new breakpoint information). All notify
28870 output is prefixed by @samp{=}.
28873 @cindex console output in @sc{gdb/mi}
28874 @var{console-stream-output} is output that should be displayed as is in the
28875 console. It is the textual response to a CLI command. All the console
28876 output is prefixed by @samp{~}.
28879 @cindex target output in @sc{gdb/mi}
28880 @var{target-stream-output} is the output produced by the target program.
28881 All the target output is prefixed by @samp{@@}.
28884 @cindex log output in @sc{gdb/mi}
28885 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28886 instance messages that should be displayed as part of an error log. All
28887 the log output is prefixed by @samp{&}.
28890 @cindex list output in @sc{gdb/mi}
28891 New @sc{gdb/mi} commands should only output @var{lists} containing
28897 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28898 details about the various output records.
28900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28901 @node GDB/MI Compatibility with CLI
28902 @section @sc{gdb/mi} Compatibility with CLI
28904 @cindex compatibility, @sc{gdb/mi} and CLI
28905 @cindex @sc{gdb/mi}, compatibility with CLI
28907 For the developers convenience CLI commands can be entered directly,
28908 but there may be some unexpected behaviour. For example, commands
28909 that query the user will behave as if the user replied yes, breakpoint
28910 command lists are not executed and some CLI commands, such as
28911 @code{if}, @code{when} and @code{define}, prompt for further input with
28912 @samp{>}, which is not valid MI output.
28914 This feature may be removed at some stage in the future and it is
28915 recommended that front ends use the @code{-interpreter-exec} command
28916 (@pxref{-interpreter-exec}).
28918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28919 @node GDB/MI Development and Front Ends
28920 @section @sc{gdb/mi} Development and Front Ends
28921 @cindex @sc{gdb/mi} development
28923 The application which takes the MI output and presents the state of the
28924 program being debugged to the user is called a @dfn{front end}.
28926 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
28927 to the MI interface may break existing usage. This section describes how the
28928 protocol changes and how to request previous version of the protocol when it
28931 Some changes in MI need not break a carefully designed front end, and
28932 for these the MI version will remain unchanged. The following is a
28933 list of changes that may occur within one level, so front ends should
28934 parse MI output in a way that can handle them:
28938 New MI commands may be added.
28941 New fields may be added to the output of any MI command.
28944 The range of values for fields with specified values, e.g.,
28945 @code{in_scope} (@pxref{-var-update}) may be extended.
28947 @c The format of field's content e.g type prefix, may change so parse it
28948 @c at your own risk. Yes, in general?
28950 @c The order of fields may change? Shouldn't really matter but it might
28951 @c resolve inconsistencies.
28954 If the changes are likely to break front ends, the MI version level
28955 will be increased by one. The new versions of the MI protocol are not compatible
28956 with the old versions. Old versions of MI remain available, allowing front ends
28957 to keep using them until they are modified to use the latest MI version.
28959 Since @code{--interpreter=mi} always points to the latest MI version, it is
28960 recommended that front ends request a specific version of MI when launching
28961 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
28962 interpreter with the MI version they expect.
28964 The following table gives a summary of the the released versions of the MI
28965 interface: the version number, the version of GDB in which it first appeared
28966 and the breaking changes compared to the previous version.
28968 @multitable @columnfractions .05 .05 .9
28969 @headitem MI version @tab GDB version @tab Breaking changes
28986 The @code{-environment-pwd}, @code{-environment-directory} and
28987 @code{-environment-path} commands now returns values using the MI output
28988 syntax, rather than CLI output syntax.
28991 @code{-var-list-children}'s @code{children} result field is now a list, rather
28995 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29007 The output of information about multi-location breakpoints has changed in the
29008 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29009 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29010 The multiple locations are now placed in a @code{locations} field, whose value
29016 If your front end cannot yet migrate to a more recent version of the
29017 MI protocol, you can nevertheless selectively enable specific features
29018 available in those recent MI versions, using the following commands:
29022 @item -fix-multi-location-breakpoint-output
29023 Use the output for multi-location breakpoints which was introduced by
29024 MI 3, even when using MI versions 2 or 1. This command has no
29025 effect when using MI version 3 or later.
29029 The best way to avoid unexpected changes in MI that might break your front
29030 end is to make your project known to @value{GDBN} developers and
29031 follow development on @email{gdb@@sourceware.org} and
29032 @email{gdb-patches@@sourceware.org}.
29033 @cindex mailing lists
29035 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29036 @node GDB/MI Output Records
29037 @section @sc{gdb/mi} Output Records
29040 * GDB/MI Result Records::
29041 * GDB/MI Stream Records::
29042 * GDB/MI Async Records::
29043 * GDB/MI Breakpoint Information::
29044 * GDB/MI Frame Information::
29045 * GDB/MI Thread Information::
29046 * GDB/MI Ada Exception Information::
29049 @node GDB/MI Result Records
29050 @subsection @sc{gdb/mi} Result Records
29052 @cindex result records in @sc{gdb/mi}
29053 @cindex @sc{gdb/mi}, result records
29054 In addition to a number of out-of-band notifications, the response to a
29055 @sc{gdb/mi} command includes one of the following result indications:
29059 @item "^done" [ "," @var{results} ]
29060 The synchronous operation was successful, @code{@var{results}} are the return
29065 This result record is equivalent to @samp{^done}. Historically, it
29066 was output instead of @samp{^done} if the command has resumed the
29067 target. This behaviour is maintained for backward compatibility, but
29068 all frontends should treat @samp{^done} and @samp{^running}
29069 identically and rely on the @samp{*running} output record to determine
29070 which threads are resumed.
29074 @value{GDBN} has connected to a remote target.
29076 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29078 The operation failed. The @code{msg=@var{c-string}} variable contains
29079 the corresponding error message.
29081 If present, the @code{code=@var{c-string}} variable provides an error
29082 code on which consumers can rely on to detect the corresponding
29083 error condition. At present, only one error code is defined:
29086 @item "undefined-command"
29087 Indicates that the command causing the error does not exist.
29092 @value{GDBN} has terminated.
29096 @node GDB/MI Stream Records
29097 @subsection @sc{gdb/mi} Stream Records
29099 @cindex @sc{gdb/mi}, stream records
29100 @cindex stream records in @sc{gdb/mi}
29101 @value{GDBN} internally maintains a number of output streams: the console, the
29102 target, and the log. The output intended for each of these streams is
29103 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29105 Each stream record begins with a unique @dfn{prefix character} which
29106 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29107 Syntax}). In addition to the prefix, each stream record contains a
29108 @code{@var{string-output}}. This is either raw text (with an implicit new
29109 line) or a quoted C string (which does not contain an implicit newline).
29112 @item "~" @var{string-output}
29113 The console output stream contains text that should be displayed in the
29114 CLI console window. It contains the textual responses to CLI commands.
29116 @item "@@" @var{string-output}
29117 The target output stream contains any textual output from the running
29118 target. This is only present when GDB's event loop is truly
29119 asynchronous, which is currently only the case for remote targets.
29121 @item "&" @var{string-output}
29122 The log stream contains debugging messages being produced by @value{GDBN}'s
29126 @node GDB/MI Async Records
29127 @subsection @sc{gdb/mi} Async Records
29129 @cindex async records in @sc{gdb/mi}
29130 @cindex @sc{gdb/mi}, async records
29131 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29132 additional changes that have occurred. Those changes can either be a
29133 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29134 target activity (e.g., target stopped).
29136 The following is the list of possible async records:
29140 @item *running,thread-id="@var{thread}"
29141 The target is now running. The @var{thread} field can be the global
29142 thread ID of the the thread that is now running, and it can be
29143 @samp{all} if all threads are running. The frontend should assume
29144 that no interaction with a running thread is possible after this
29145 notification is produced. The frontend should not assume that this
29146 notification is output only once for any command. @value{GDBN} may
29147 emit this notification several times, either for different threads,
29148 because it cannot resume all threads together, or even for a single
29149 thread, if the thread must be stepped though some code before letting
29152 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29153 The target has stopped. The @var{reason} field can have one of the
29157 @item breakpoint-hit
29158 A breakpoint was reached.
29159 @item watchpoint-trigger
29160 A watchpoint was triggered.
29161 @item read-watchpoint-trigger
29162 A read watchpoint was triggered.
29163 @item access-watchpoint-trigger
29164 An access watchpoint was triggered.
29165 @item function-finished
29166 An -exec-finish or similar CLI command was accomplished.
29167 @item location-reached
29168 An -exec-until or similar CLI command was accomplished.
29169 @item watchpoint-scope
29170 A watchpoint has gone out of scope.
29171 @item end-stepping-range
29172 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29173 similar CLI command was accomplished.
29174 @item exited-signalled
29175 The inferior exited because of a signal.
29177 The inferior exited.
29178 @item exited-normally
29179 The inferior exited normally.
29180 @item signal-received
29181 A signal was received by the inferior.
29183 The inferior has stopped due to a library being loaded or unloaded.
29184 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29185 set or when a @code{catch load} or @code{catch unload} catchpoint is
29186 in use (@pxref{Set Catchpoints}).
29188 The inferior has forked. This is reported when @code{catch fork}
29189 (@pxref{Set Catchpoints}) has been used.
29191 The inferior has vforked. This is reported in when @code{catch vfork}
29192 (@pxref{Set Catchpoints}) has been used.
29193 @item syscall-entry
29194 The inferior entered a system call. This is reported when @code{catch
29195 syscall} (@pxref{Set Catchpoints}) has been used.
29196 @item syscall-return
29197 The inferior returned from a system call. This is reported when
29198 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29200 The inferior called @code{exec}. This is reported when @code{catch exec}
29201 (@pxref{Set Catchpoints}) has been used.
29204 The @var{id} field identifies the global thread ID of the thread
29205 that directly caused the stop -- for example by hitting a breakpoint.
29206 Depending on whether all-stop
29207 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29208 stop all threads, or only the thread that directly triggered the stop.
29209 If all threads are stopped, the @var{stopped} field will have the
29210 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29211 field will be a list of thread identifiers. Presently, this list will
29212 always include a single thread, but frontend should be prepared to see
29213 several threads in the list. The @var{core} field reports the
29214 processor core on which the stop event has happened. This field may be absent
29215 if such information is not available.
29217 @item =thread-group-added,id="@var{id}"
29218 @itemx =thread-group-removed,id="@var{id}"
29219 A thread group was either added or removed. The @var{id} field
29220 contains the @value{GDBN} identifier of the thread group. When a thread
29221 group is added, it generally might not be associated with a running
29222 process. When a thread group is removed, its id becomes invalid and
29223 cannot be used in any way.
29225 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29226 A thread group became associated with a running program,
29227 either because the program was just started or the thread group
29228 was attached to a program. The @var{id} field contains the
29229 @value{GDBN} identifier of the thread group. The @var{pid} field
29230 contains process identifier, specific to the operating system.
29232 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29233 A thread group is no longer associated with a running program,
29234 either because the program has exited, or because it was detached
29235 from. The @var{id} field contains the @value{GDBN} identifier of the
29236 thread group. The @var{code} field is the exit code of the inferior; it exists
29237 only when the inferior exited with some code.
29239 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29240 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29241 A thread either was created, or has exited. The @var{id} field
29242 contains the global @value{GDBN} identifier of the thread. The @var{gid}
29243 field identifies the thread group this thread belongs to.
29245 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
29246 Informs that the selected thread or frame were changed. This notification
29247 is not emitted as result of the @code{-thread-select} or
29248 @code{-stack-select-frame} commands, but is emitted whenever an MI command
29249 that is not documented to change the selected thread and frame actually
29250 changes them. In particular, invoking, directly or indirectly
29251 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
29252 will generate this notification. Changing the thread or frame from another
29253 user interface (see @ref{Interpreters}) will also generate this notification.
29255 The @var{frame} field is only present if the newly selected thread is
29256 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
29258 We suggest that in response to this notification, front ends
29259 highlight the selected thread and cause subsequent commands to apply to
29262 @item =library-loaded,...
29263 Reports that a new library file was loaded by the program. This
29264 notification has 5 fields---@var{id}, @var{target-name},
29265 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
29266 opaque identifier of the library. For remote debugging case,
29267 @var{target-name} and @var{host-name} fields give the name of the
29268 library file on the target, and on the host respectively. For native
29269 debugging, both those fields have the same value. The
29270 @var{symbols-loaded} field is emitted only for backward compatibility
29271 and should not be relied on to convey any useful information. The
29272 @var{thread-group} field, if present, specifies the id of the thread
29273 group in whose context the library was loaded. If the field is
29274 absent, it means the library was loaded in the context of all present
29275 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
29278 @item =library-unloaded,...
29279 Reports that a library was unloaded by the program. This notification
29280 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29281 the same meaning as for the @code{=library-loaded} notification.
29282 The @var{thread-group} field, if present, specifies the id of the
29283 thread group in whose context the library was unloaded. If the field is
29284 absent, it means the library was unloaded in the context of all present
29287 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29288 @itemx =traceframe-changed,end
29289 Reports that the trace frame was changed and its new number is
29290 @var{tfnum}. The number of the tracepoint associated with this trace
29291 frame is @var{tpnum}.
29293 @item =tsv-created,name=@var{name},initial=@var{initial}
29294 Reports that the new trace state variable @var{name} is created with
29295 initial value @var{initial}.
29297 @item =tsv-deleted,name=@var{name}
29298 @itemx =tsv-deleted
29299 Reports that the trace state variable @var{name} is deleted or all
29300 trace state variables are deleted.
29302 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29303 Reports that the trace state variable @var{name} is modified with
29304 the initial value @var{initial}. The current value @var{current} of
29305 trace state variable is optional and is reported if the current
29306 value of trace state variable is known.
29308 @item =breakpoint-created,bkpt=@{...@}
29309 @itemx =breakpoint-modified,bkpt=@{...@}
29310 @itemx =breakpoint-deleted,id=@var{number}
29311 Reports that a breakpoint was created, modified, or deleted,
29312 respectively. Only user-visible breakpoints are reported to the MI
29315 The @var{bkpt} argument is of the same form as returned by the various
29316 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29317 @var{number} is the ordinal number of the breakpoint.
29319 Note that if a breakpoint is emitted in the result record of a
29320 command, then it will not also be emitted in an async record.
29322 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
29323 @itemx =record-stopped,thread-group="@var{id}"
29324 Execution log recording was either started or stopped on an
29325 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29326 group corresponding to the affected inferior.
29328 The @var{method} field indicates the method used to record execution. If the
29329 method in use supports multiple recording formats, @var{format} will be present
29330 and contain the currently used format. @xref{Process Record and Replay},
29331 for existing method and format values.
29333 @item =cmd-param-changed,param=@var{param},value=@var{value}
29334 Reports that a parameter of the command @code{set @var{param}} is
29335 changed to @var{value}. In the multi-word @code{set} command,
29336 the @var{param} is the whole parameter list to @code{set} command.
29337 For example, In command @code{set check type on}, @var{param}
29338 is @code{check type} and @var{value} is @code{on}.
29340 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29341 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29342 written in an inferior. The @var{id} is the identifier of the
29343 thread group corresponding to the affected inferior. The optional
29344 @code{type="code"} part is reported if the memory written to holds
29348 @node GDB/MI Breakpoint Information
29349 @subsection @sc{gdb/mi} Breakpoint Information
29351 When @value{GDBN} reports information about a breakpoint, a
29352 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29357 The breakpoint number.
29360 The type of the breakpoint. For ordinary breakpoints this will be
29361 @samp{breakpoint}, but many values are possible.
29364 If the type of the breakpoint is @samp{catchpoint}, then this
29365 indicates the exact type of catchpoint.
29368 This is the breakpoint disposition---either @samp{del}, meaning that
29369 the breakpoint will be deleted at the next stop, or @samp{keep},
29370 meaning that the breakpoint will not be deleted.
29373 This indicates whether the breakpoint is enabled, in which case the
29374 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29375 Note that this is not the same as the field @code{enable}.
29378 The address of the breakpoint. This may be a hexidecimal number,
29379 giving the address; or the string @samp{<PENDING>}, for a pending
29380 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29381 multiple locations. This field will not be present if no address can
29382 be determined. For example, a watchpoint does not have an address.
29385 Optional field containing any flags related to the address. These flags are
29386 architecture-dependent; see @ref{Architectures} for their meaning for a
29390 If known, the function in which the breakpoint appears.
29391 If not known, this field is not present.
29394 The name of the source file which contains this function, if known.
29395 If not known, this field is not present.
29398 The full file name of the source file which contains this function, if
29399 known. If not known, this field is not present.
29402 The line number at which this breakpoint appears, if known.
29403 If not known, this field is not present.
29406 If the source file is not known, this field may be provided. If
29407 provided, this holds the address of the breakpoint, possibly followed
29411 If this breakpoint is pending, this field is present and holds the
29412 text used to set the breakpoint, as entered by the user.
29415 Where this breakpoint's condition is evaluated, either @samp{host} or
29419 If this is a thread-specific breakpoint, then this identifies the
29420 thread in which the breakpoint can trigger.
29423 If this breakpoint is restricted to a particular Ada task, then this
29424 field will hold the task identifier.
29427 If the breakpoint is conditional, this is the condition expression.
29430 The ignore count of the breakpoint.
29433 The enable count of the breakpoint.
29435 @item traceframe-usage
29438 @item static-tracepoint-marker-string-id
29439 For a static tracepoint, the name of the static tracepoint marker.
29442 For a masked watchpoint, this is the mask.
29445 A tracepoint's pass count.
29447 @item original-location
29448 The location of the breakpoint as originally specified by the user.
29449 This field is optional.
29452 The number of times the breakpoint has been hit.
29455 This field is only given for tracepoints. This is either @samp{y},
29456 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29460 Some extra data, the exact contents of which are type-dependent.
29463 This field is present if the breakpoint has multiple locations. It is also
29464 exceptionally present if the breakpoint is enabled and has a single, disabled
29467 The value is a list of locations. The format of a location is described below.
29471 A location in a multi-location breakpoint is represented as a tuple with the
29477 The location number as a dotted pair, like @samp{1.2}. The first digit is the
29478 number of the parent breakpoint. The second digit is the number of the
29479 location within that breakpoint.
29482 This indicates whether the location is enabled, in which case the
29483 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29484 Note that this is not the same as the field @code{enable}.
29487 The address of this location as an hexidecimal number.
29490 Optional field containing any flags related to the address. These flags are
29491 architecture-dependent; see @ref{Architectures} for their meaning for a
29495 If known, the function in which the location appears.
29496 If not known, this field is not present.
29499 The name of the source file which contains this location, if known.
29500 If not known, this field is not present.
29503 The full file name of the source file which contains this location, if
29504 known. If not known, this field is not present.
29507 The line number at which this location appears, if known.
29508 If not known, this field is not present.
29510 @item thread-groups
29511 The thread groups this location is in.
29515 For example, here is what the output of @code{-break-insert}
29516 (@pxref{GDB/MI Breakpoint Commands}) might be:
29519 -> -break-insert main
29520 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29521 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29522 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29527 @node GDB/MI Frame Information
29528 @subsection @sc{gdb/mi} Frame Information
29530 Response from many MI commands includes an information about stack
29531 frame. This information is a tuple that may have the following
29536 The level of the stack frame. The innermost frame has the level of
29537 zero. This field is always present.
29540 The name of the function corresponding to the frame. This field may
29541 be absent if @value{GDBN} is unable to determine the function name.
29544 The code address for the frame. This field is always present.
29547 Optional field containing any flags related to the address. These flags are
29548 architecture-dependent; see @ref{Architectures} for their meaning for a
29552 The name of the source files that correspond to the frame's code
29553 address. This field may be absent.
29556 The source line corresponding to the frames' code address. This field
29560 The name of the binary file (either executable or shared library) the
29561 corresponds to the frame's code address. This field may be absent.
29565 @node GDB/MI Thread Information
29566 @subsection @sc{gdb/mi} Thread Information
29568 Whenever @value{GDBN} has to report an information about a thread, it
29569 uses a tuple with the following fields. The fields are always present unless
29574 The global numeric id assigned to the thread by @value{GDBN}.
29577 The target-specific string identifying the thread.
29580 Additional information about the thread provided by the target.
29581 It is supposed to be human-readable and not interpreted by the
29582 frontend. This field is optional.
29585 The name of the thread. If the user specified a name using the
29586 @code{thread name} command, then this name is given. Otherwise, if
29587 @value{GDBN} can extract the thread name from the target, then that
29588 name is given. If @value{GDBN} cannot find the thread name, then this
29592 The execution state of the thread, either @samp{stopped} or @samp{running},
29593 depending on whether the thread is presently running.
29596 The stack frame currently executing in the thread. This field is only present
29597 if the thread is stopped. Its format is documented in
29598 @ref{GDB/MI Frame Information}.
29601 The value of this field is an integer number of the processor core the
29602 thread was last seen on. This field is optional.
29605 @node GDB/MI Ada Exception Information
29606 @subsection @sc{gdb/mi} Ada Exception Information
29608 Whenever a @code{*stopped} record is emitted because the program
29609 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29610 @value{GDBN} provides the name of the exception that was raised via
29611 the @code{exception-name} field. Also, for exceptions that were raised
29612 with an exception message, @value{GDBN} provides that message via
29613 the @code{exception-message} field.
29615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29616 @node GDB/MI Simple Examples
29617 @section Simple Examples of @sc{gdb/mi} Interaction
29618 @cindex @sc{gdb/mi}, simple examples
29620 This subsection presents several simple examples of interaction using
29621 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29622 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29623 the output received from @sc{gdb/mi}.
29625 Note the line breaks shown in the examples are here only for
29626 readability, they don't appear in the real output.
29628 @subheading Setting a Breakpoint
29630 Setting a breakpoint generates synchronous output which contains detailed
29631 information of the breakpoint.
29634 -> -break-insert main
29635 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29636 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29637 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29642 @subheading Program Execution
29644 Program execution generates asynchronous records and MI gives the
29645 reason that execution stopped.
29651 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29652 frame=@{addr="0x08048564",func="main",
29653 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29654 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
29655 arch="i386:x86_64"@}
29660 <- *stopped,reason="exited-normally"
29664 @subheading Quitting @value{GDBN}
29666 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29674 Please note that @samp{^exit} is printed immediately, but it might
29675 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29676 performs necessary cleanups, including killing programs being debugged
29677 or disconnecting from debug hardware, so the frontend should wait till
29678 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29679 fails to exit in reasonable time.
29681 @subheading A Bad Command
29683 Here's what happens if you pass a non-existent command:
29687 <- ^error,msg="Undefined MI command: rubbish"
29692 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29693 @node GDB/MI Command Description Format
29694 @section @sc{gdb/mi} Command Description Format
29696 The remaining sections describe blocks of commands. Each block of
29697 commands is laid out in a fashion similar to this section.
29699 @subheading Motivation
29701 The motivation for this collection of commands.
29703 @subheading Introduction
29705 A brief introduction to this collection of commands as a whole.
29707 @subheading Commands
29709 For each command in the block, the following is described:
29711 @subsubheading Synopsis
29714 -command @var{args}@dots{}
29717 @subsubheading Result
29719 @subsubheading @value{GDBN} Command
29721 The corresponding @value{GDBN} CLI command(s), if any.
29723 @subsubheading Example
29725 Example(s) formatted for readability. Some of the described commands have
29726 not been implemented yet and these are labeled N.A.@: (not available).
29729 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29730 @node GDB/MI Breakpoint Commands
29731 @section @sc{gdb/mi} Breakpoint Commands
29733 @cindex breakpoint commands for @sc{gdb/mi}
29734 @cindex @sc{gdb/mi}, breakpoint commands
29735 This section documents @sc{gdb/mi} commands for manipulating
29738 @subheading The @code{-break-after} Command
29739 @findex -break-after
29741 @subsubheading Synopsis
29744 -break-after @var{number} @var{count}
29747 The breakpoint number @var{number} is not in effect until it has been
29748 hit @var{count} times. To see how this is reflected in the output of
29749 the @samp{-break-list} command, see the description of the
29750 @samp{-break-list} command below.
29752 @subsubheading @value{GDBN} Command
29754 The corresponding @value{GDBN} command is @samp{ignore}.
29756 @subsubheading Example
29761 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29762 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29763 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29771 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29772 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29773 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29774 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29775 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29776 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29777 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29778 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29779 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29780 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29785 @subheading The @code{-break-catch} Command
29786 @findex -break-catch
29789 @subheading The @code{-break-commands} Command
29790 @findex -break-commands
29792 @subsubheading Synopsis
29795 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29798 Specifies the CLI commands that should be executed when breakpoint
29799 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29800 are the commands. If no command is specified, any previously-set
29801 commands are cleared. @xref{Break Commands}. Typical use of this
29802 functionality is tracing a program, that is, printing of values of
29803 some variables whenever breakpoint is hit and then continuing.
29805 @subsubheading @value{GDBN} Command
29807 The corresponding @value{GDBN} command is @samp{commands}.
29809 @subsubheading Example
29814 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29815 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29816 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29819 -break-commands 1 "print v" "continue"
29824 @subheading The @code{-break-condition} Command
29825 @findex -break-condition
29827 @subsubheading Synopsis
29830 -break-condition @var{number} @var{expr}
29833 Breakpoint @var{number} will stop the program only if the condition in
29834 @var{expr} is true. The condition becomes part of the
29835 @samp{-break-list} output (see the description of the @samp{-break-list}
29838 @subsubheading @value{GDBN} Command
29840 The corresponding @value{GDBN} command is @samp{condition}.
29842 @subsubheading Example
29846 -break-condition 1 1
29850 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29851 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29852 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29853 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29854 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29855 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29856 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29857 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29858 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29859 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29863 @subheading The @code{-break-delete} Command
29864 @findex -break-delete
29866 @subsubheading Synopsis
29869 -break-delete ( @var{breakpoint} )+
29872 Delete the breakpoint(s) whose number(s) are specified in the argument
29873 list. This is obviously reflected in the breakpoint list.
29875 @subsubheading @value{GDBN} Command
29877 The corresponding @value{GDBN} command is @samp{delete}.
29879 @subsubheading Example
29887 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29888 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29889 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29890 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29891 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29892 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29893 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29898 @subheading The @code{-break-disable} Command
29899 @findex -break-disable
29901 @subsubheading Synopsis
29904 -break-disable ( @var{breakpoint} )+
29907 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29908 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29910 @subsubheading @value{GDBN} Command
29912 The corresponding @value{GDBN} command is @samp{disable}.
29914 @subsubheading Example
29922 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29929 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29930 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29931 line="5",thread-groups=["i1"],times="0"@}]@}
29935 @subheading The @code{-break-enable} Command
29936 @findex -break-enable
29938 @subsubheading Synopsis
29941 -break-enable ( @var{breakpoint} )+
29944 Enable (previously disabled) @var{breakpoint}(s).
29946 @subsubheading @value{GDBN} Command
29948 The corresponding @value{GDBN} command is @samp{enable}.
29950 @subsubheading Example
29958 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29959 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29960 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29961 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29962 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29963 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29964 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29965 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29966 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29967 line="5",thread-groups=["i1"],times="0"@}]@}
29971 @subheading The @code{-break-info} Command
29972 @findex -break-info
29974 @subsubheading Synopsis
29977 -break-info @var{breakpoint}
29981 Get information about a single breakpoint.
29983 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29984 Information}, for details on the format of each breakpoint in the
29987 @subsubheading @value{GDBN} Command
29989 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29991 @subsubheading Example
29994 @subheading The @code{-break-insert} Command
29995 @findex -break-insert
29996 @anchor{-break-insert}
29998 @subsubheading Synopsis
30001 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30002 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30003 [ -p @var{thread-id} ] [ @var{location} ]
30007 If specified, @var{location}, can be one of:
30010 @item linespec location
30011 A linespec location. @xref{Linespec Locations}.
30013 @item explicit location
30014 An explicit location. @sc{gdb/mi} explicit locations are
30015 analogous to the CLI's explicit locations using the option names
30016 listed below. @xref{Explicit Locations}.
30019 @item --source @var{filename}
30020 The source file name of the location. This option requires the use
30021 of either @samp{--function} or @samp{--line}.
30023 @item --function @var{function}
30024 The name of a function or method.
30026 @item --label @var{label}
30027 The name of a label.
30029 @item --line @var{lineoffset}
30030 An absolute or relative line offset from the start of the location.
30033 @item address location
30034 An address location, *@var{address}. @xref{Address Locations}.
30038 The possible optional parameters of this command are:
30042 Insert a temporary breakpoint.
30044 Insert a hardware breakpoint.
30046 If @var{location} cannot be parsed (for example if it
30047 refers to unknown files or functions), create a pending
30048 breakpoint. Without this flag, @value{GDBN} will report
30049 an error, and won't create a breakpoint, if @var{location}
30052 Create a disabled breakpoint.
30054 Create a tracepoint. @xref{Tracepoints}. When this parameter
30055 is used together with @samp{-h}, a fast tracepoint is created.
30056 @item -c @var{condition}
30057 Make the breakpoint conditional on @var{condition}.
30058 @item -i @var{ignore-count}
30059 Initialize the @var{ignore-count}.
30060 @item -p @var{thread-id}
30061 Restrict the breakpoint to the thread with the specified global
30065 @subsubheading Result
30067 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30068 resulting breakpoint.
30070 Note: this format is open to change.
30071 @c An out-of-band breakpoint instead of part of the result?
30073 @subsubheading @value{GDBN} Command
30075 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30076 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30078 @subsubheading Example
30083 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30084 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30087 -break-insert -t foo
30088 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30089 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30093 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30094 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30095 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30096 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30097 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30098 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30099 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30100 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30101 addr="0x0001072c", func="main",file="recursive2.c",
30102 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30104 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30105 addr="0x00010774",func="foo",file="recursive2.c",
30106 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30109 @c -break-insert -r foo.*
30110 @c ~int foo(int, int);
30111 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30112 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30117 @subheading The @code{-dprintf-insert} Command
30118 @findex -dprintf-insert
30120 @subsubheading Synopsis
30123 -dprintf-insert [ -t ] [ -f ] [ -d ]
30124 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30125 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30130 If supplied, @var{location} may be specified the same way as for
30131 the @code{-break-insert} command. @xref{-break-insert}.
30133 The possible optional parameters of this command are:
30137 Insert a temporary breakpoint.
30139 If @var{location} cannot be parsed (for example, if it
30140 refers to unknown files or functions), create a pending
30141 breakpoint. Without this flag, @value{GDBN} will report
30142 an error, and won't create a breakpoint, if @var{location}
30145 Create a disabled breakpoint.
30146 @item -c @var{condition}
30147 Make the breakpoint conditional on @var{condition}.
30148 @item -i @var{ignore-count}
30149 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30150 to @var{ignore-count}.
30151 @item -p @var{thread-id}
30152 Restrict the breakpoint to the thread with the specified global
30156 @subsubheading Result
30158 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30159 resulting breakpoint.
30161 @c An out-of-band breakpoint instead of part of the result?
30163 @subsubheading @value{GDBN} Command
30165 The corresponding @value{GDBN} command is @samp{dprintf}.
30167 @subsubheading Example
30171 4-dprintf-insert foo "At foo entry\n"
30172 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30173 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30174 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30175 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30176 original-location="foo"@}
30178 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30179 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30180 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30181 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30182 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30183 original-location="mi-dprintf.c:26"@}
30187 @subheading The @code{-break-list} Command
30188 @findex -break-list
30190 @subsubheading Synopsis
30196 Displays the list of inserted breakpoints, showing the following fields:
30200 number of the breakpoint
30202 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30204 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30207 is the breakpoint enabled or no: @samp{y} or @samp{n}
30209 memory location at which the breakpoint is set
30211 logical location of the breakpoint, expressed by function name, file
30213 @item Thread-groups
30214 list of thread groups to which this breakpoint applies
30216 number of times the breakpoint has been hit
30219 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30220 @code{body} field is an empty list.
30222 @subsubheading @value{GDBN} Command
30224 The corresponding @value{GDBN} command is @samp{info break}.
30226 @subsubheading Example
30231 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30232 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30233 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30234 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30235 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30236 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30237 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30238 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30239 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30241 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30242 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30243 line="13",thread-groups=["i1"],times="0"@}]@}
30247 Here's an example of the result when there are no breakpoints:
30252 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30253 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30254 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30255 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30256 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30257 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30258 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30263 @subheading The @code{-break-passcount} Command
30264 @findex -break-passcount
30266 @subsubheading Synopsis
30269 -break-passcount @var{tracepoint-number} @var{passcount}
30272 Set the passcount for tracepoint @var{tracepoint-number} to
30273 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30274 is not a tracepoint, error is emitted. This corresponds to CLI
30275 command @samp{passcount}.
30277 @subheading The @code{-break-watch} Command
30278 @findex -break-watch
30280 @subsubheading Synopsis
30283 -break-watch [ -a | -r ]
30286 Create a watchpoint. With the @samp{-a} option it will create an
30287 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30288 read from or on a write to the memory location. With the @samp{-r}
30289 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30290 trigger only when the memory location is accessed for reading. Without
30291 either of the options, the watchpoint created is a regular watchpoint,
30292 i.e., it will trigger when the memory location is accessed for writing.
30293 @xref{Set Watchpoints, , Setting Watchpoints}.
30295 Note that @samp{-break-list} will report a single list of watchpoints and
30296 breakpoints inserted.
30298 @subsubheading @value{GDBN} Command
30300 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30303 @subsubheading Example
30305 Setting a watchpoint on a variable in the @code{main} function:
30310 ^done,wpt=@{number="2",exp="x"@}
30315 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30316 value=@{old="-268439212",new="55"@},
30317 frame=@{func="main",args=[],file="recursive2.c",
30318 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
30322 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30323 the program execution twice: first for the variable changing value, then
30324 for the watchpoint going out of scope.
30329 ^done,wpt=@{number="5",exp="C"@}
30334 *stopped,reason="watchpoint-trigger",
30335 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30336 frame=@{func="callee4",args=[],
30337 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30338 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30339 arch="i386:x86_64"@}
30344 *stopped,reason="watchpoint-scope",wpnum="5",
30345 frame=@{func="callee3",args=[@{name="strarg",
30346 value="0x11940 \"A string argument.\""@}],
30347 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30348 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30349 arch="i386:x86_64"@}
30353 Listing breakpoints and watchpoints, at different points in the program
30354 execution. Note that once the watchpoint goes out of scope, it is
30360 ^done,wpt=@{number="2",exp="C"@}
30363 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30364 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30365 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30366 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30367 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30368 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30369 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30370 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30371 addr="0x00010734",func="callee4",
30372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30373 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30375 bkpt=@{number="2",type="watchpoint",disp="keep",
30376 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30381 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30382 value=@{old="-276895068",new="3"@},
30383 frame=@{func="callee4",args=[],
30384 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30385 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30386 arch="i386:x86_64"@}
30389 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30390 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30391 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30392 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30393 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30394 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30395 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30396 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30397 addr="0x00010734",func="callee4",
30398 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30399 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30401 bkpt=@{number="2",type="watchpoint",disp="keep",
30402 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30406 ^done,reason="watchpoint-scope",wpnum="2",
30407 frame=@{func="callee3",args=[@{name="strarg",
30408 value="0x11940 \"A string argument.\""@}],
30409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30411 arch="i386:x86_64"@}
30414 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30415 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30416 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30417 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30418 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30419 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30420 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30421 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30422 addr="0x00010734",func="callee4",
30423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30424 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30425 thread-groups=["i1"],times="1"@}]@}
30430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30431 @node GDB/MI Catchpoint Commands
30432 @section @sc{gdb/mi} Catchpoint Commands
30434 This section documents @sc{gdb/mi} commands for manipulating
30438 * Shared Library GDB/MI Catchpoint Commands::
30439 * Ada Exception GDB/MI Catchpoint Commands::
30440 * C++ Exception GDB/MI Catchpoint Commands::
30443 @node Shared Library GDB/MI Catchpoint Commands
30444 @subsection Shared Library @sc{gdb/mi} Catchpoints
30446 @subheading The @code{-catch-load} Command
30447 @findex -catch-load
30449 @subsubheading Synopsis
30452 -catch-load [ -t ] [ -d ] @var{regexp}
30455 Add a catchpoint for library load events. If the @samp{-t} option is used,
30456 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30457 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30458 in a disabled state. The @samp{regexp} argument is a regular
30459 expression used to match the name of the loaded library.
30462 @subsubheading @value{GDBN} Command
30464 The corresponding @value{GDBN} command is @samp{catch load}.
30466 @subsubheading Example
30469 -catch-load -t foo.so
30470 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30471 what="load of library matching foo.so",catch-type="load",times="0"@}
30476 @subheading The @code{-catch-unload} Command
30477 @findex -catch-unload
30479 @subsubheading Synopsis
30482 -catch-unload [ -t ] [ -d ] @var{regexp}
30485 Add a catchpoint for library unload events. If the @samp{-t} option is
30486 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30487 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30488 created in a disabled state. The @samp{regexp} argument is a regular
30489 expression used to match the name of the unloaded library.
30491 @subsubheading @value{GDBN} Command
30493 The corresponding @value{GDBN} command is @samp{catch unload}.
30495 @subsubheading Example
30498 -catch-unload -d bar.so
30499 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30500 what="load of library matching bar.so",catch-type="unload",times="0"@}
30504 @node Ada Exception GDB/MI Catchpoint Commands
30505 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30507 The following @sc{gdb/mi} commands can be used to create catchpoints
30508 that stop the execution when Ada exceptions are being raised.
30510 @subheading The @code{-catch-assert} Command
30511 @findex -catch-assert
30513 @subsubheading Synopsis
30516 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30519 Add a catchpoint for failed Ada assertions.
30521 The possible optional parameters for this command are:
30524 @item -c @var{condition}
30525 Make the catchpoint conditional on @var{condition}.
30527 Create a disabled catchpoint.
30529 Create a temporary catchpoint.
30532 @subsubheading @value{GDBN} Command
30534 The corresponding @value{GDBN} command is @samp{catch assert}.
30536 @subsubheading Example
30540 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30541 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30542 thread-groups=["i1"],times="0",
30543 original-location="__gnat_debug_raise_assert_failure"@}
30547 @subheading The @code{-catch-exception} Command
30548 @findex -catch-exception
30550 @subsubheading Synopsis
30553 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30557 Add a catchpoint stopping when Ada exceptions are raised.
30558 By default, the command stops the program when any Ada exception
30559 gets raised. But it is also possible, by using some of the
30560 optional parameters described below, to create more selective
30563 The possible optional parameters for this command are:
30566 @item -c @var{condition}
30567 Make the catchpoint conditional on @var{condition}.
30569 Create a disabled catchpoint.
30570 @item -e @var{exception-name}
30571 Only stop when @var{exception-name} is raised. This option cannot
30572 be used combined with @samp{-u}.
30574 Create a temporary catchpoint.
30576 Stop only when an unhandled exception gets raised. This option
30577 cannot be used combined with @samp{-e}.
30580 @subsubheading @value{GDBN} Command
30582 The corresponding @value{GDBN} commands are @samp{catch exception}
30583 and @samp{catch exception unhandled}.
30585 @subsubheading Example
30588 -catch-exception -e Program_Error
30589 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30590 enabled="y",addr="0x0000000000404874",
30591 what="`Program_Error' Ada exception", thread-groups=["i1"],
30592 times="0",original-location="__gnat_debug_raise_exception"@}
30596 @subheading The @code{-catch-handlers} Command
30597 @findex -catch-handlers
30599 @subsubheading Synopsis
30602 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30606 Add a catchpoint stopping when Ada exceptions are handled.
30607 By default, the command stops the program when any Ada exception
30608 gets handled. But it is also possible, by using some of the
30609 optional parameters described below, to create more selective
30612 The possible optional parameters for this command are:
30615 @item -c @var{condition}
30616 Make the catchpoint conditional on @var{condition}.
30618 Create a disabled catchpoint.
30619 @item -e @var{exception-name}
30620 Only stop when @var{exception-name} is handled.
30622 Create a temporary catchpoint.
30625 @subsubheading @value{GDBN} Command
30627 The corresponding @value{GDBN} command is @samp{catch handlers}.
30629 @subsubheading Example
30632 -catch-handlers -e Constraint_Error
30633 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30634 enabled="y",addr="0x0000000000402f68",
30635 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
30636 times="0",original-location="__gnat_begin_handler"@}
30640 @node C++ Exception GDB/MI Catchpoint Commands
30641 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
30643 The following @sc{gdb/mi} commands can be used to create catchpoints
30644 that stop the execution when C@t{++} exceptions are being throw, rethrown,
30647 @subheading The @code{-catch-throw} Command
30648 @findex -catch-throw
30650 @subsubheading Synopsis
30653 -catch-throw [ -t ] [ -r @var{regexp}]
30656 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
30657 given, then only exceptions whose type matches the regular expression
30660 If @samp{-t} is given, then the catchpoint is enabled only for one
30661 stop, the catchpoint is automatically deleted after stopping once for
30664 @subsubheading @value{GDBN} Command
30666 The corresponding @value{GDBN} commands are @samp{catch throw}
30667 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
30669 @subsubheading Example
30672 -catch-throw -r exception_type
30673 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30674 what="exception throw",catch-type="throw",
30675 thread-groups=["i1"],
30676 regexp="exception_type",times="0"@}
30682 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
30683 in __cxa_throw () from /lib64/libstdc++.so.6\n"
30684 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30685 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
30686 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30687 thread-id="1",stopped-threads="all",core="6"
30691 @subheading The @code{-catch-rethrow} Command
30692 @findex -catch-rethrow
30694 @subsubheading Synopsis
30697 -catch-rethrow [ -t ] [ -r @var{regexp}]
30700 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
30701 then only exceptions whose type matches the regular expression will be
30704 If @samp{-t} is given, then the catchpoint is enabled only for one
30705 stop, the catchpoint is automatically deleted after the first event is
30708 @subsubheading @value{GDBN} Command
30710 The corresponding @value{GDBN} commands are @samp{catch rethrow}
30711 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
30713 @subsubheading Example
30716 -catch-rethrow -r exception_type
30717 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30718 what="exception rethrow",catch-type="rethrow",
30719 thread-groups=["i1"],
30720 regexp="exception_type",times="0"@}
30726 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
30727 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
30728 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30729 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
30730 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30731 thread-id="1",stopped-threads="all",core="6"
30735 @subheading The @code{-catch-catch} Command
30736 @findex -catch-catch
30738 @subsubheading Synopsis
30741 -catch-catch [ -t ] [ -r @var{regexp}]
30744 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
30745 is given, then only exceptions whose type matches the regular
30746 expression will be caught.
30748 If @samp{-t} is given, then the catchpoint is enabled only for one
30749 stop, the catchpoint is automatically deleted after the first event is
30752 @subsubheading @value{GDBN} Command
30754 The corresponding @value{GDBN} commands are @samp{catch catch}
30755 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
30757 @subsubheading Example
30760 -catch-catch -r exception_type
30761 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30762 what="exception catch",catch-type="catch",
30763 thread-groups=["i1"],
30764 regexp="exception_type",times="0"@}
30770 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
30771 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
30772 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30773 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
30774 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30775 thread-id="1",stopped-threads="all",core="6"
30779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30780 @node GDB/MI Program Context
30781 @section @sc{gdb/mi} Program Context
30783 @subheading The @code{-exec-arguments} Command
30784 @findex -exec-arguments
30787 @subsubheading Synopsis
30790 -exec-arguments @var{args}
30793 Set the inferior program arguments, to be used in the next
30796 @subsubheading @value{GDBN} Command
30798 The corresponding @value{GDBN} command is @samp{set args}.
30800 @subsubheading Example
30804 -exec-arguments -v word
30811 @subheading The @code{-exec-show-arguments} Command
30812 @findex -exec-show-arguments
30814 @subsubheading Synopsis
30817 -exec-show-arguments
30820 Print the arguments of the program.
30822 @subsubheading @value{GDBN} Command
30824 The corresponding @value{GDBN} command is @samp{show args}.
30826 @subsubheading Example
30831 @subheading The @code{-environment-cd} Command
30832 @findex -environment-cd
30834 @subsubheading Synopsis
30837 -environment-cd @var{pathdir}
30840 Set @value{GDBN}'s working directory.
30842 @subsubheading @value{GDBN} Command
30844 The corresponding @value{GDBN} command is @samp{cd}.
30846 @subsubheading Example
30850 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30856 @subheading The @code{-environment-directory} Command
30857 @findex -environment-directory
30859 @subsubheading Synopsis
30862 -environment-directory [ -r ] [ @var{pathdir} ]+
30865 Add directories @var{pathdir} to beginning of search path for source files.
30866 If the @samp{-r} option is used, the search path is reset to the default
30867 search path. If directories @var{pathdir} are supplied in addition to the
30868 @samp{-r} option, the search path is first reset and then addition
30870 Multiple directories may be specified, separated by blanks. Specifying
30871 multiple directories in a single command
30872 results in the directories added to the beginning of the
30873 search path in the same order they were presented in the command.
30874 If blanks are needed as
30875 part of a directory name, double-quotes should be used around
30876 the name. In the command output, the path will show up separated
30877 by the system directory-separator character. The directory-separator
30878 character must not be used
30879 in any directory name.
30880 If no directories are specified, the current search path is displayed.
30882 @subsubheading @value{GDBN} Command
30884 The corresponding @value{GDBN} command is @samp{dir}.
30886 @subsubheading Example
30890 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30891 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30893 -environment-directory ""
30894 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30896 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30897 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30899 -environment-directory -r
30900 ^done,source-path="$cdir:$cwd"
30905 @subheading The @code{-environment-path} Command
30906 @findex -environment-path
30908 @subsubheading Synopsis
30911 -environment-path [ -r ] [ @var{pathdir} ]+
30914 Add directories @var{pathdir} to beginning of search path for object files.
30915 If the @samp{-r} option is used, the search path is reset to the original
30916 search path that existed at gdb start-up. If directories @var{pathdir} are
30917 supplied in addition to the
30918 @samp{-r} option, the search path is first reset and then addition
30920 Multiple directories may be specified, separated by blanks. Specifying
30921 multiple directories in a single command
30922 results in the directories added to the beginning of the
30923 search path in the same order they were presented in the command.
30924 If blanks are needed as
30925 part of a directory name, double-quotes should be used around
30926 the name. In the command output, the path will show up separated
30927 by the system directory-separator character. The directory-separator
30928 character must not be used
30929 in any directory name.
30930 If no directories are specified, the current path is displayed.
30933 @subsubheading @value{GDBN} Command
30935 The corresponding @value{GDBN} command is @samp{path}.
30937 @subsubheading Example
30942 ^done,path="/usr/bin"
30944 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30945 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30947 -environment-path -r /usr/local/bin
30948 ^done,path="/usr/local/bin:/usr/bin"
30953 @subheading The @code{-environment-pwd} Command
30954 @findex -environment-pwd
30956 @subsubheading Synopsis
30962 Show the current working directory.
30964 @subsubheading @value{GDBN} Command
30966 The corresponding @value{GDBN} command is @samp{pwd}.
30968 @subsubheading Example
30973 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30977 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30978 @node GDB/MI Thread Commands
30979 @section @sc{gdb/mi} Thread Commands
30982 @subheading The @code{-thread-info} Command
30983 @findex -thread-info
30985 @subsubheading Synopsis
30988 -thread-info [ @var{thread-id} ]
30991 Reports information about either a specific thread, if the
30992 @var{thread-id} parameter is present, or about all threads.
30993 @var{thread-id} is the thread's global thread ID. When printing
30994 information about all threads, also reports the global ID of the
30997 @subsubheading @value{GDBN} Command
30999 The @samp{info thread} command prints the same information
31002 @subsubheading Result
31004 The result contains the following attributes:
31008 A list of threads. The format of the elements of the list is described in
31009 @ref{GDB/MI Thread Information}.
31011 @item current-thread-id
31012 The global id of the currently selected thread. This field is omitted if there
31013 is no selected thread (for example, when the selected inferior is not running,
31014 and therefore has no threads) or if a @var{thread-id} argument was passed to
31019 @subsubheading Example
31024 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31025 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31026 args=[]@},state="running"@},
31027 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31028 frame=@{level="0",addr="0x0804891f",func="foo",
31029 args=[@{name="i",value="10"@}],
31030 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31031 state="running"@}],
31032 current-thread-id="1"
31036 @subheading The @code{-thread-list-ids} Command
31037 @findex -thread-list-ids
31039 @subsubheading Synopsis
31045 Produces a list of the currently known global @value{GDBN} thread ids.
31046 At the end of the list it also prints the total number of such
31049 This command is retained for historical reasons, the
31050 @code{-thread-info} command should be used instead.
31052 @subsubheading @value{GDBN} Command
31054 Part of @samp{info threads} supplies the same information.
31056 @subsubheading Example
31061 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31062 current-thread-id="1",number-of-threads="3"
31067 @subheading The @code{-thread-select} Command
31068 @findex -thread-select
31070 @subsubheading Synopsis
31073 -thread-select @var{thread-id}
31076 Make thread with global thread number @var{thread-id} the current
31077 thread. It prints the number of the new current thread, and the
31078 topmost frame for that thread.
31080 This command is deprecated in favor of explicitly using the
31081 @samp{--thread} option to each command.
31083 @subsubheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{thread}.
31087 @subsubheading Example
31094 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31095 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31099 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31100 number-of-threads="3"
31103 ^done,new-thread-id="3",
31104 frame=@{level="0",func="vprintf",
31105 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31106 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31111 @node GDB/MI Ada Tasking Commands
31112 @section @sc{gdb/mi} Ada Tasking Commands
31114 @subheading The @code{-ada-task-info} Command
31115 @findex -ada-task-info
31117 @subsubheading Synopsis
31120 -ada-task-info [ @var{task-id} ]
31123 Reports information about either a specific Ada task, if the
31124 @var{task-id} parameter is present, or about all Ada tasks.
31126 @subsubheading @value{GDBN} Command
31128 The @samp{info tasks} command prints the same information
31129 about all Ada tasks (@pxref{Ada Tasks}).
31131 @subsubheading Result
31133 The result is a table of Ada tasks. The following columns are
31134 defined for each Ada task:
31138 This field exists only for the current thread. It has the value @samp{*}.
31141 The identifier that @value{GDBN} uses to refer to the Ada task.
31144 The identifier that the target uses to refer to the Ada task.
31147 The global thread identifier of the thread corresponding to the Ada
31150 This field should always exist, as Ada tasks are always implemented
31151 on top of a thread. But if @value{GDBN} cannot find this corresponding
31152 thread for any reason, the field is omitted.
31155 This field exists only when the task was created by another task.
31156 In this case, it provides the ID of the parent task.
31159 The base priority of the task.
31162 The current state of the task. For a detailed description of the
31163 possible states, see @ref{Ada Tasks}.
31166 The name of the task.
31170 @subsubheading Example
31174 ^done,tasks=@{nr_rows="3",nr_cols="8",
31175 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31176 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31177 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31178 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31179 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31180 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31181 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31182 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31183 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31184 state="Child Termination Wait",name="main_task"@}]@}
31188 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31189 @node GDB/MI Program Execution
31190 @section @sc{gdb/mi} Program Execution
31192 These are the asynchronous commands which generate the out-of-band
31193 record @samp{*stopped}. Currently @value{GDBN} only really executes
31194 asynchronously with remote targets and this interaction is mimicked in
31197 @subheading The @code{-exec-continue} Command
31198 @findex -exec-continue
31200 @subsubheading Synopsis
31203 -exec-continue [--reverse] [--all|--thread-group N]
31206 Resumes the execution of the inferior program, which will continue
31207 to execute until it reaches a debugger stop event. If the
31208 @samp{--reverse} option is specified, execution resumes in reverse until
31209 it reaches a stop event. Stop events may include
31212 breakpoints or watchpoints
31214 signals or exceptions
31216 the end of the process (or its beginning under @samp{--reverse})
31218 the end or beginning of a replay log if one is being used.
31220 In all-stop mode (@pxref{All-Stop
31221 Mode}), may resume only one thread, or all threads, depending on the
31222 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31223 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31224 ignored in all-stop mode. If the @samp{--thread-group} options is
31225 specified, then all threads in that thread group are resumed.
31227 @subsubheading @value{GDBN} Command
31229 The corresponding @value{GDBN} corresponding is @samp{continue}.
31231 @subsubheading Example
31238 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31239 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31240 line="13",arch="i386:x86_64"@}
31245 @subheading The @code{-exec-finish} Command
31246 @findex -exec-finish
31248 @subsubheading Synopsis
31251 -exec-finish [--reverse]
31254 Resumes the execution of the inferior program until the current
31255 function is exited. Displays the results returned by the function.
31256 If the @samp{--reverse} option is specified, resumes the reverse
31257 execution of the inferior program until the point where current
31258 function was called.
31260 @subsubheading @value{GDBN} Command
31262 The corresponding @value{GDBN} command is @samp{finish}.
31264 @subsubheading Example
31266 Function returning @code{void}.
31273 *stopped,reason="function-finished",frame=@{func="main",args=[],
31274 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
31278 Function returning other than @code{void}. The name of the internal
31279 @value{GDBN} variable storing the result is printed, together with the
31286 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31287 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31288 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31289 arch="i386:x86_64"@},
31290 gdb-result-var="$1",return-value="0"
31295 @subheading The @code{-exec-interrupt} Command
31296 @findex -exec-interrupt
31298 @subsubheading Synopsis
31301 -exec-interrupt [--all|--thread-group N]
31304 Interrupts the background execution of the target. Note how the token
31305 associated with the stop message is the one for the execution command
31306 that has been interrupted. The token for the interrupt itself only
31307 appears in the @samp{^done} output. If the user is trying to
31308 interrupt a non-running program, an error message will be printed.
31310 Note that when asynchronous execution is enabled, this command is
31311 asynchronous just like other execution commands. That is, first the
31312 @samp{^done} response will be printed, and the target stop will be
31313 reported after that using the @samp{*stopped} notification.
31315 In non-stop mode, only the context thread is interrupted by default.
31316 All threads (in all inferiors) will be interrupted if the
31317 @samp{--all} option is specified. If the @samp{--thread-group}
31318 option is specified, all threads in that group will be interrupted.
31320 @subsubheading @value{GDBN} Command
31322 The corresponding @value{GDBN} command is @samp{interrupt}.
31324 @subsubheading Example
31335 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31336 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31337 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
31342 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31346 @subheading The @code{-exec-jump} Command
31349 @subsubheading Synopsis
31352 -exec-jump @var{location}
31355 Resumes execution of the inferior program at the location specified by
31356 parameter. @xref{Specify Location}, for a description of the
31357 different forms of @var{location}.
31359 @subsubheading @value{GDBN} Command
31361 The corresponding @value{GDBN} command is @samp{jump}.
31363 @subsubheading Example
31366 -exec-jump foo.c:10
31367 *running,thread-id="all"
31372 @subheading The @code{-exec-next} Command
31375 @subsubheading Synopsis
31378 -exec-next [--reverse]
31381 Resumes execution of the inferior program, stopping when the beginning
31382 of the next source line is reached.
31384 If the @samp{--reverse} option is specified, resumes reverse execution
31385 of the inferior program, stopping at the beginning of the previous
31386 source line. If you issue this command on the first line of a
31387 function, it will take you back to the caller of that function, to the
31388 source line where the function was called.
31391 @subsubheading @value{GDBN} Command
31393 The corresponding @value{GDBN} command is @samp{next}.
31395 @subsubheading Example
31401 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31406 @subheading The @code{-exec-next-instruction} Command
31407 @findex -exec-next-instruction
31409 @subsubheading Synopsis
31412 -exec-next-instruction [--reverse]
31415 Executes one machine instruction. If the instruction is a function
31416 call, continues until the function returns. If the program stops at an
31417 instruction in the middle of a source line, the address will be
31420 If the @samp{--reverse} option is specified, resumes reverse execution
31421 of the inferior program, stopping at the previous instruction. If the
31422 previously executed instruction was a return from another function,
31423 it will continue to execute in reverse until the call to that function
31424 (from the current stack frame) is reached.
31426 @subsubheading @value{GDBN} Command
31428 The corresponding @value{GDBN} command is @samp{nexti}.
31430 @subsubheading Example
31434 -exec-next-instruction
31438 *stopped,reason="end-stepping-range",
31439 addr="0x000100d4",line="5",file="hello.c"
31444 @subheading The @code{-exec-return} Command
31445 @findex -exec-return
31447 @subsubheading Synopsis
31453 Makes current function return immediately. Doesn't execute the inferior.
31454 Displays the new current frame.
31456 @subsubheading @value{GDBN} Command
31458 The corresponding @value{GDBN} command is @samp{return}.
31460 @subsubheading Example
31464 200-break-insert callee4
31465 200^done,bkpt=@{number="1",addr="0x00010734",
31466 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31471 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31472 frame=@{func="callee4",args=[],
31473 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31474 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31475 arch="i386:x86_64"@}
31481 111^done,frame=@{level="0",func="callee3",
31482 args=[@{name="strarg",
31483 value="0x11940 \"A string argument.\""@}],
31484 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31485 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31486 arch="i386:x86_64"@}
31491 @subheading The @code{-exec-run} Command
31494 @subsubheading Synopsis
31497 -exec-run [ --all | --thread-group N ] [ --start ]
31500 Starts execution of the inferior from the beginning. The inferior
31501 executes until either a breakpoint is encountered or the program
31502 exits. In the latter case the output will include an exit code, if
31503 the program has exited exceptionally.
31505 When neither the @samp{--all} nor the @samp{--thread-group} option
31506 is specified, the current inferior is started. If the
31507 @samp{--thread-group} option is specified, it should refer to a thread
31508 group of type @samp{process}, and that thread group will be started.
31509 If the @samp{--all} option is specified, then all inferiors will be started.
31511 Using the @samp{--start} option instructs the debugger to stop
31512 the execution at the start of the inferior's main subprogram,
31513 following the same behavior as the @code{start} command
31514 (@pxref{Starting}).
31516 @subsubheading @value{GDBN} Command
31518 The corresponding @value{GDBN} command is @samp{run}.
31520 @subsubheading Examples
31525 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31530 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31531 frame=@{func="main",args=[],file="recursive2.c",
31532 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
31537 Program exited normally:
31545 *stopped,reason="exited-normally"
31550 Program exited exceptionally:
31558 *stopped,reason="exited",exit-code="01"
31562 Another way the program can terminate is if it receives a signal such as
31563 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31567 *stopped,reason="exited-signalled",signal-name="SIGINT",
31568 signal-meaning="Interrupt"
31572 @c @subheading -exec-signal
31575 @subheading The @code{-exec-step} Command
31578 @subsubheading Synopsis
31581 -exec-step [--reverse]
31584 Resumes execution of the inferior program, stopping when the beginning
31585 of the next source line is reached, if the next source line is not a
31586 function call. If it is, stop at the first instruction of the called
31587 function. If the @samp{--reverse} option is specified, resumes reverse
31588 execution of the inferior program, stopping at the beginning of the
31589 previously executed source line.
31591 @subsubheading @value{GDBN} Command
31593 The corresponding @value{GDBN} command is @samp{step}.
31595 @subsubheading Example
31597 Stepping into a function:
31603 *stopped,reason="end-stepping-range",
31604 frame=@{func="foo",args=[@{name="a",value="10"@},
31605 @{name="b",value="0"@}],file="recursive2.c",
31606 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
31616 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31621 @subheading The @code{-exec-step-instruction} Command
31622 @findex -exec-step-instruction
31624 @subsubheading Synopsis
31627 -exec-step-instruction [--reverse]
31630 Resumes the inferior which executes one machine instruction. If the
31631 @samp{--reverse} option is specified, resumes reverse execution of the
31632 inferior program, stopping at the previously executed instruction.
31633 The output, once @value{GDBN} has stopped, will vary depending on
31634 whether we have stopped in the middle of a source line or not. In the
31635 former case, the address at which the program stopped will be printed
31638 @subsubheading @value{GDBN} Command
31640 The corresponding @value{GDBN} command is @samp{stepi}.
31642 @subsubheading Example
31646 -exec-step-instruction
31650 *stopped,reason="end-stepping-range",
31651 frame=@{func="foo",args=[],file="try.c",
31652 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31654 -exec-step-instruction
31658 *stopped,reason="end-stepping-range",
31659 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31660 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31665 @subheading The @code{-exec-until} Command
31666 @findex -exec-until
31668 @subsubheading Synopsis
31671 -exec-until [ @var{location} ]
31674 Executes the inferior until the @var{location} specified in the
31675 argument is reached. If there is no argument, the inferior executes
31676 until a source line greater than the current one is reached. The
31677 reason for stopping in this case will be @samp{location-reached}.
31679 @subsubheading @value{GDBN} Command
31681 The corresponding @value{GDBN} command is @samp{until}.
31683 @subsubheading Example
31687 -exec-until recursive2.c:6
31691 *stopped,reason="location-reached",frame=@{func="main",args=[],
31692 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
31693 arch="i386:x86_64"@}
31698 @subheading -file-clear
31699 Is this going away????
31702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31703 @node GDB/MI Stack Manipulation
31704 @section @sc{gdb/mi} Stack Manipulation Commands
31706 @subheading The @code{-enable-frame-filters} Command
31707 @findex -enable-frame-filters
31710 -enable-frame-filters
31713 @value{GDBN} allows Python-based frame filters to affect the output of
31714 the MI commands relating to stack traces. As there is no way to
31715 implement this in a fully backward-compatible way, a front end must
31716 request that this functionality be enabled.
31718 Once enabled, this feature cannot be disabled.
31720 Note that if Python support has not been compiled into @value{GDBN},
31721 this command will still succeed (and do nothing).
31723 @subheading The @code{-stack-info-frame} Command
31724 @findex -stack-info-frame
31726 @subsubheading Synopsis
31732 Get info on the selected frame.
31734 @subsubheading @value{GDBN} Command
31736 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31737 (without arguments).
31739 @subsubheading Example
31744 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31745 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31746 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31747 arch="i386:x86_64"@}
31751 @subheading The @code{-stack-info-depth} Command
31752 @findex -stack-info-depth
31754 @subsubheading Synopsis
31757 -stack-info-depth [ @var{max-depth} ]
31760 Return the depth of the stack. If the integer argument @var{max-depth}
31761 is specified, do not count beyond @var{max-depth} frames.
31763 @subsubheading @value{GDBN} Command
31765 There's no equivalent @value{GDBN} command.
31767 @subsubheading Example
31769 For a stack with frame levels 0 through 11:
31776 -stack-info-depth 4
31779 -stack-info-depth 12
31782 -stack-info-depth 11
31785 -stack-info-depth 13
31790 @anchor{-stack-list-arguments}
31791 @subheading The @code{-stack-list-arguments} Command
31792 @findex -stack-list-arguments
31794 @subsubheading Synopsis
31797 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31798 [ @var{low-frame} @var{high-frame} ]
31801 Display a list of the arguments for the frames between @var{low-frame}
31802 and @var{high-frame} (inclusive). If @var{low-frame} and
31803 @var{high-frame} are not provided, list the arguments for the whole
31804 call stack. If the two arguments are equal, show the single frame
31805 at the corresponding level. It is an error if @var{low-frame} is
31806 larger than the actual number of frames. On the other hand,
31807 @var{high-frame} may be larger than the actual number of frames, in
31808 which case only existing frames will be returned.
31810 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31811 the variables; if it is 1 or @code{--all-values}, print also their
31812 values; and if it is 2 or @code{--simple-values}, print the name,
31813 type and value for simple data types, and the name and type for arrays,
31814 structures and unions. If the option @code{--no-frame-filters} is
31815 supplied, then Python frame filters will not be executed.
31817 If the @code{--skip-unavailable} option is specified, arguments that
31818 are not available are not listed. Partially available arguments
31819 are still displayed, however.
31821 Use of this command to obtain arguments in a single frame is
31822 deprecated in favor of the @samp{-stack-list-variables} command.
31824 @subsubheading @value{GDBN} Command
31826 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31827 @samp{gdb_get_args} command which partially overlaps with the
31828 functionality of @samp{-stack-list-arguments}.
31830 @subsubheading Example
31837 frame=@{level="0",addr="0x00010734",func="callee4",
31838 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31839 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31840 arch="i386:x86_64"@},
31841 frame=@{level="1",addr="0x0001076c",func="callee3",
31842 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31843 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31844 arch="i386:x86_64"@},
31845 frame=@{level="2",addr="0x0001078c",func="callee2",
31846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31847 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
31848 arch="i386:x86_64"@},
31849 frame=@{level="3",addr="0x000107b4",func="callee1",
31850 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31851 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
31852 arch="i386:x86_64"@},
31853 frame=@{level="4",addr="0x000107e0",func="main",
31854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
31856 arch="i386:x86_64"@}]
31858 -stack-list-arguments 0
31861 frame=@{level="0",args=[]@},
31862 frame=@{level="1",args=[name="strarg"]@},
31863 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31864 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31865 frame=@{level="4",args=[]@}]
31867 -stack-list-arguments 1
31870 frame=@{level="0",args=[]@},
31872 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31873 frame=@{level="2",args=[
31874 @{name="intarg",value="2"@},
31875 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31876 @{frame=@{level="3",args=[
31877 @{name="intarg",value="2"@},
31878 @{name="strarg",value="0x11940 \"A string argument.\""@},
31879 @{name="fltarg",value="3.5"@}]@},
31880 frame=@{level="4",args=[]@}]
31882 -stack-list-arguments 0 2 2
31883 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31885 -stack-list-arguments 1 2 2
31886 ^done,stack-args=[frame=@{level="2",
31887 args=[@{name="intarg",value="2"@},
31888 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31892 @c @subheading -stack-list-exception-handlers
31895 @anchor{-stack-list-frames}
31896 @subheading The @code{-stack-list-frames} Command
31897 @findex -stack-list-frames
31899 @subsubheading Synopsis
31902 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31905 List the frames currently on the stack. For each frame it displays the
31910 The frame number, 0 being the topmost frame, i.e., the innermost function.
31912 The @code{$pc} value for that frame.
31916 File name of the source file where the function lives.
31917 @item @var{fullname}
31918 The full file name of the source file where the function lives.
31920 Line number corresponding to the @code{$pc}.
31922 The shared library where this function is defined. This is only given
31923 if the frame's function is not known.
31925 Frame's architecture.
31928 If invoked without arguments, this command prints a backtrace for the
31929 whole stack. If given two integer arguments, it shows the frames whose
31930 levels are between the two arguments (inclusive). If the two arguments
31931 are equal, it shows the single frame at the corresponding level. It is
31932 an error if @var{low-frame} is larger than the actual number of
31933 frames. On the other hand, @var{high-frame} may be larger than the
31934 actual number of frames, in which case only existing frames will be
31935 returned. If the option @code{--no-frame-filters} is supplied, then
31936 Python frame filters will not be executed.
31938 @subsubheading @value{GDBN} Command
31940 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31942 @subsubheading Example
31944 Full stack backtrace:
31950 [frame=@{level="0",addr="0x0001076c",func="foo",
31951 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
31952 arch="i386:x86_64"@},
31953 frame=@{level="1",addr="0x000107a4",func="foo",
31954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31955 arch="i386:x86_64"@},
31956 frame=@{level="2",addr="0x000107a4",func="foo",
31957 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31958 arch="i386:x86_64"@},
31959 frame=@{level="3",addr="0x000107a4",func="foo",
31960 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31961 arch="i386:x86_64"@},
31962 frame=@{level="4",addr="0x000107a4",func="foo",
31963 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31964 arch="i386:x86_64"@},
31965 frame=@{level="5",addr="0x000107a4",func="foo",
31966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31967 arch="i386:x86_64"@},
31968 frame=@{level="6",addr="0x000107a4",func="foo",
31969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31970 arch="i386:x86_64"@},
31971 frame=@{level="7",addr="0x000107a4",func="foo",
31972 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31973 arch="i386:x86_64"@},
31974 frame=@{level="8",addr="0x000107a4",func="foo",
31975 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31976 arch="i386:x86_64"@},
31977 frame=@{level="9",addr="0x000107a4",func="foo",
31978 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31979 arch="i386:x86_64"@},
31980 frame=@{level="10",addr="0x000107a4",func="foo",
31981 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31982 arch="i386:x86_64"@},
31983 frame=@{level="11",addr="0x00010738",func="main",
31984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
31985 arch="i386:x86_64"@}]
31989 Show frames between @var{low_frame} and @var{high_frame}:
31993 -stack-list-frames 3 5
31995 [frame=@{level="3",addr="0x000107a4",func="foo",
31996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31997 arch="i386:x86_64"@},
31998 frame=@{level="4",addr="0x000107a4",func="foo",
31999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32000 arch="i386:x86_64"@},
32001 frame=@{level="5",addr="0x000107a4",func="foo",
32002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32003 arch="i386:x86_64"@}]
32007 Show a single frame:
32011 -stack-list-frames 3 3
32013 [frame=@{level="3",addr="0x000107a4",func="foo",
32014 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32015 arch="i386:x86_64"@}]
32020 @subheading The @code{-stack-list-locals} Command
32021 @findex -stack-list-locals
32022 @anchor{-stack-list-locals}
32024 @subsubheading Synopsis
32027 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32030 Display the local variable names for the selected frame. If
32031 @var{print-values} is 0 or @code{--no-values}, print only the names of
32032 the variables; if it is 1 or @code{--all-values}, print also their
32033 values; and if it is 2 or @code{--simple-values}, print the name,
32034 type and value for simple data types, and the name and type for arrays,
32035 structures and unions. In this last case, a frontend can immediately
32036 display the value of simple data types and create variable objects for
32037 other data types when the user wishes to explore their values in
32038 more detail. If the option @code{--no-frame-filters} is supplied, then
32039 Python frame filters will not be executed.
32041 If the @code{--skip-unavailable} option is specified, local variables
32042 that are not available are not listed. Partially available local
32043 variables are still displayed, however.
32045 This command is deprecated in favor of the
32046 @samp{-stack-list-variables} command.
32048 @subsubheading @value{GDBN} Command
32050 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32052 @subsubheading Example
32056 -stack-list-locals 0
32057 ^done,locals=[name="A",name="B",name="C"]
32059 -stack-list-locals --all-values
32060 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32061 @{name="C",value="@{1, 2, 3@}"@}]
32062 -stack-list-locals --simple-values
32063 ^done,locals=[@{name="A",type="int",value="1"@},
32064 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32068 @anchor{-stack-list-variables}
32069 @subheading The @code{-stack-list-variables} Command
32070 @findex -stack-list-variables
32072 @subsubheading Synopsis
32075 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32078 Display the names of local variables and function arguments for the selected frame. If
32079 @var{print-values} is 0 or @code{--no-values}, print only the names of
32080 the variables; if it is 1 or @code{--all-values}, print also their
32081 values; and if it is 2 or @code{--simple-values}, print the name,
32082 type and value for simple data types, and the name and type for arrays,
32083 structures and unions. If the option @code{--no-frame-filters} is
32084 supplied, then Python frame filters will not be executed.
32086 If the @code{--skip-unavailable} option is specified, local variables
32087 and arguments that are not available are not listed. Partially
32088 available arguments and local variables are still displayed, however.
32090 @subsubheading Example
32094 -stack-list-variables --thread 1 --frame 0 --all-values
32095 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32100 @subheading The @code{-stack-select-frame} Command
32101 @findex -stack-select-frame
32103 @subsubheading Synopsis
32106 -stack-select-frame @var{framenum}
32109 Change the selected frame. Select a different frame @var{framenum} on
32112 This command in deprecated in favor of passing the @samp{--frame}
32113 option to every command.
32115 @subsubheading @value{GDBN} Command
32117 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32118 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32120 @subsubheading Example
32124 -stack-select-frame 2
32129 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32130 @node GDB/MI Variable Objects
32131 @section @sc{gdb/mi} Variable Objects
32135 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32137 For the implementation of a variable debugger window (locals, watched
32138 expressions, etc.), we are proposing the adaptation of the existing code
32139 used by @code{Insight}.
32141 The two main reasons for that are:
32145 It has been proven in practice (it is already on its second generation).
32148 It will shorten development time (needless to say how important it is
32152 The original interface was designed to be used by Tcl code, so it was
32153 slightly changed so it could be used through @sc{gdb/mi}. This section
32154 describes the @sc{gdb/mi} operations that will be available and gives some
32155 hints about their use.
32157 @emph{Note}: In addition to the set of operations described here, we
32158 expect the @sc{gui} implementation of a variable window to require, at
32159 least, the following operations:
32162 @item @code{-gdb-show} @code{output-radix}
32163 @item @code{-stack-list-arguments}
32164 @item @code{-stack-list-locals}
32165 @item @code{-stack-select-frame}
32170 @subheading Introduction to Variable Objects
32172 @cindex variable objects in @sc{gdb/mi}
32174 Variable objects are "object-oriented" MI interface for examining and
32175 changing values of expressions. Unlike some other MI interfaces that
32176 work with expressions, variable objects are specifically designed for
32177 simple and efficient presentation in the frontend. A variable object
32178 is identified by string name. When a variable object is created, the
32179 frontend specifies the expression for that variable object. The
32180 expression can be a simple variable, or it can be an arbitrary complex
32181 expression, and can even involve CPU registers. After creating a
32182 variable object, the frontend can invoke other variable object
32183 operations---for example to obtain or change the value of a variable
32184 object, or to change display format.
32186 Variable objects have hierarchical tree structure. Any variable object
32187 that corresponds to a composite type, such as structure in C, has
32188 a number of child variable objects, for example corresponding to each
32189 element of a structure. A child variable object can itself have
32190 children, recursively. Recursion ends when we reach
32191 leaf variable objects, which always have built-in types. Child variable
32192 objects are created only by explicit request, so if a frontend
32193 is not interested in the children of a particular variable object, no
32194 child will be created.
32196 For a leaf variable object it is possible to obtain its value as a
32197 string, or set the value from a string. String value can be also
32198 obtained for a non-leaf variable object, but it's generally a string
32199 that only indicates the type of the object, and does not list its
32200 contents. Assignment to a non-leaf variable object is not allowed.
32202 A frontend does not need to read the values of all variable objects each time
32203 the program stops. Instead, MI provides an update command that lists all
32204 variable objects whose values has changed since the last update
32205 operation. This considerably reduces the amount of data that must
32206 be transferred to the frontend. As noted above, children variable
32207 objects are created on demand, and only leaf variable objects have a
32208 real value. As result, gdb will read target memory only for leaf
32209 variables that frontend has created.
32211 The automatic update is not always desirable. For example, a frontend
32212 might want to keep a value of some expression for future reference,
32213 and never update it. For another example, fetching memory is
32214 relatively slow for embedded targets, so a frontend might want
32215 to disable automatic update for the variables that are either not
32216 visible on the screen, or ``closed''. This is possible using so
32217 called ``frozen variable objects''. Such variable objects are never
32218 implicitly updated.
32220 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32221 fixed variable object, the expression is parsed when the variable
32222 object is created, including associating identifiers to specific
32223 variables. The meaning of expression never changes. For a floating
32224 variable object the values of variables whose names appear in the
32225 expressions are re-evaluated every time in the context of the current
32226 frame. Consider this example:
32231 struct work_state state;
32238 If a fixed variable object for the @code{state} variable is created in
32239 this function, and we enter the recursive call, the variable
32240 object will report the value of @code{state} in the top-level
32241 @code{do_work} invocation. On the other hand, a floating variable
32242 object will report the value of @code{state} in the current frame.
32244 If an expression specified when creating a fixed variable object
32245 refers to a local variable, the variable object becomes bound to the
32246 thread and frame in which the variable object is created. When such
32247 variable object is updated, @value{GDBN} makes sure that the
32248 thread/frame combination the variable object is bound to still exists,
32249 and re-evaluates the variable object in context of that thread/frame.
32251 The following is the complete set of @sc{gdb/mi} operations defined to
32252 access this functionality:
32254 @multitable @columnfractions .4 .6
32255 @item @strong{Operation}
32256 @tab @strong{Description}
32258 @item @code{-enable-pretty-printing}
32259 @tab enable Python-based pretty-printing
32260 @item @code{-var-create}
32261 @tab create a variable object
32262 @item @code{-var-delete}
32263 @tab delete the variable object and/or its children
32264 @item @code{-var-set-format}
32265 @tab set the display format of this variable
32266 @item @code{-var-show-format}
32267 @tab show the display format of this variable
32268 @item @code{-var-info-num-children}
32269 @tab tells how many children this object has
32270 @item @code{-var-list-children}
32271 @tab return a list of the object's children
32272 @item @code{-var-info-type}
32273 @tab show the type of this variable object
32274 @item @code{-var-info-expression}
32275 @tab print parent-relative expression that this variable object represents
32276 @item @code{-var-info-path-expression}
32277 @tab print full expression that this variable object represents
32278 @item @code{-var-show-attributes}
32279 @tab is this variable editable? does it exist here?
32280 @item @code{-var-evaluate-expression}
32281 @tab get the value of this variable
32282 @item @code{-var-assign}
32283 @tab set the value of this variable
32284 @item @code{-var-update}
32285 @tab update the variable and its children
32286 @item @code{-var-set-frozen}
32287 @tab set frozenness attribute
32288 @item @code{-var-set-update-range}
32289 @tab set range of children to display on update
32292 In the next subsection we describe each operation in detail and suggest
32293 how it can be used.
32295 @subheading Description And Use of Operations on Variable Objects
32297 @subheading The @code{-enable-pretty-printing} Command
32298 @findex -enable-pretty-printing
32301 -enable-pretty-printing
32304 @value{GDBN} allows Python-based visualizers to affect the output of the
32305 MI variable object commands. However, because there was no way to
32306 implement this in a fully backward-compatible way, a front end must
32307 request that this functionality be enabled.
32309 Once enabled, this feature cannot be disabled.
32311 Note that if Python support has not been compiled into @value{GDBN},
32312 this command will still succeed (and do nothing).
32314 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32315 may work differently in future versions of @value{GDBN}.
32317 @subheading The @code{-var-create} Command
32318 @findex -var-create
32320 @subsubheading Synopsis
32323 -var-create @{@var{name} | "-"@}
32324 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32327 This operation creates a variable object, which allows the monitoring of
32328 a variable, the result of an expression, a memory cell or a CPU
32331 The @var{name} parameter is the string by which the object can be
32332 referenced. It must be unique. If @samp{-} is specified, the varobj
32333 system will generate a string ``varNNNNNN'' automatically. It will be
32334 unique provided that one does not specify @var{name} of that format.
32335 The command fails if a duplicate name is found.
32337 The frame under which the expression should be evaluated can be
32338 specified by @var{frame-addr}. A @samp{*} indicates that the current
32339 frame should be used. A @samp{@@} indicates that a floating variable
32340 object must be created.
32342 @var{expression} is any expression valid on the current language set (must not
32343 begin with a @samp{*}), or one of the following:
32347 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32350 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32353 @samp{$@var{regname}} --- a CPU register name
32356 @cindex dynamic varobj
32357 A varobj's contents may be provided by a Python-based pretty-printer. In this
32358 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32359 have slightly different semantics in some cases. If the
32360 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32361 will never create a dynamic varobj. This ensures backward
32362 compatibility for existing clients.
32364 @subsubheading Result
32366 This operation returns attributes of the newly-created varobj. These
32371 The name of the varobj.
32374 The number of children of the varobj. This number is not necessarily
32375 reliable for a dynamic varobj. Instead, you must examine the
32376 @samp{has_more} attribute.
32379 The varobj's scalar value. For a varobj whose type is some sort of
32380 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32381 will not be interesting.
32384 The varobj's type. This is a string representation of the type, as
32385 would be printed by the @value{GDBN} CLI. If @samp{print object}
32386 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32387 @emph{actual} (derived) type of the object is shown rather than the
32388 @emph{declared} one.
32391 If a variable object is bound to a specific thread, then this is the
32392 thread's global identifier.
32395 For a dynamic varobj, this indicates whether there appear to be any
32396 children available. For a non-dynamic varobj, this will be 0.
32399 This attribute will be present and have the value @samp{1} if the
32400 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32401 then this attribute will not be present.
32404 A dynamic varobj can supply a display hint to the front end. The
32405 value comes directly from the Python pretty-printer object's
32406 @code{display_hint} method. @xref{Pretty Printing API}.
32409 Typical output will look like this:
32412 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32413 has_more="@var{has_more}"
32417 @subheading The @code{-var-delete} Command
32418 @findex -var-delete
32420 @subsubheading Synopsis
32423 -var-delete [ -c ] @var{name}
32426 Deletes a previously created variable object and all of its children.
32427 With the @samp{-c} option, just deletes the children.
32429 Returns an error if the object @var{name} is not found.
32432 @subheading The @code{-var-set-format} Command
32433 @findex -var-set-format
32435 @subsubheading Synopsis
32438 -var-set-format @var{name} @var{format-spec}
32441 Sets the output format for the value of the object @var{name} to be
32444 @anchor{-var-set-format}
32445 The syntax for the @var{format-spec} is as follows:
32448 @var{format-spec} @expansion{}
32449 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
32452 The natural format is the default format choosen automatically
32453 based on the variable type (like decimal for an @code{int}, hex
32454 for pointers, etc.).
32456 The zero-hexadecimal format has a representation similar to hexadecimal
32457 but with padding zeroes to the left of the value. For example, a 32-bit
32458 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
32459 zero-hexadecimal format.
32461 For a variable with children, the format is set only on the
32462 variable itself, and the children are not affected.
32464 @subheading The @code{-var-show-format} Command
32465 @findex -var-show-format
32467 @subsubheading Synopsis
32470 -var-show-format @var{name}
32473 Returns the format used to display the value of the object @var{name}.
32476 @var{format} @expansion{}
32481 @subheading The @code{-var-info-num-children} Command
32482 @findex -var-info-num-children
32484 @subsubheading Synopsis
32487 -var-info-num-children @var{name}
32490 Returns the number of children of a variable object @var{name}:
32496 Note that this number is not completely reliable for a dynamic varobj.
32497 It will return the current number of children, but more children may
32501 @subheading The @code{-var-list-children} Command
32502 @findex -var-list-children
32504 @subsubheading Synopsis
32507 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32509 @anchor{-var-list-children}
32511 Return a list of the children of the specified variable object and
32512 create variable objects for them, if they do not already exist. With
32513 a single argument or if @var{print-values} has a value of 0 or
32514 @code{--no-values}, print only the names of the variables; if
32515 @var{print-values} is 1 or @code{--all-values}, also print their
32516 values; and if it is 2 or @code{--simple-values} print the name and
32517 value for simple data types and just the name for arrays, structures
32520 @var{from} and @var{to}, if specified, indicate the range of children
32521 to report. If @var{from} or @var{to} is less than zero, the range is
32522 reset and all children will be reported. Otherwise, children starting
32523 at @var{from} (zero-based) and up to and excluding @var{to} will be
32526 If a child range is requested, it will only affect the current call to
32527 @code{-var-list-children}, but not future calls to @code{-var-update}.
32528 For this, you must instead use @code{-var-set-update-range}. The
32529 intent of this approach is to enable a front end to implement any
32530 update approach it likes; for example, scrolling a view may cause the
32531 front end to request more children with @code{-var-list-children}, and
32532 then the front end could call @code{-var-set-update-range} with a
32533 different range to ensure that future updates are restricted to just
32536 For each child the following results are returned:
32541 Name of the variable object created for this child.
32544 The expression to be shown to the user by the front end to designate this child.
32545 For example this may be the name of a structure member.
32547 For a dynamic varobj, this value cannot be used to form an
32548 expression. There is no way to do this at all with a dynamic varobj.
32550 For C/C@t{++} structures there are several pseudo children returned to
32551 designate access qualifiers. For these pseudo children @var{exp} is
32552 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32553 type and value are not present.
32555 A dynamic varobj will not report the access qualifying
32556 pseudo-children, regardless of the language. This information is not
32557 available at all with a dynamic varobj.
32560 Number of children this child has. For a dynamic varobj, this will be
32564 The type of the child. If @samp{print object}
32565 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32566 @emph{actual} (derived) type of the object is shown rather than the
32567 @emph{declared} one.
32570 If values were requested, this is the value.
32573 If this variable object is associated with a thread, this is the
32574 thread's global thread id. Otherwise this result is not present.
32577 If the variable object is frozen, this variable will be present with a value of 1.
32580 A dynamic varobj can supply a display hint to the front end. The
32581 value comes directly from the Python pretty-printer object's
32582 @code{display_hint} method. @xref{Pretty Printing API}.
32585 This attribute will be present and have the value @samp{1} if the
32586 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32587 then this attribute will not be present.
32591 The result may have its own attributes:
32595 A dynamic varobj can supply a display hint to the front end. The
32596 value comes directly from the Python pretty-printer object's
32597 @code{display_hint} method. @xref{Pretty Printing API}.
32600 This is an integer attribute which is nonzero if there are children
32601 remaining after the end of the selected range.
32604 @subsubheading Example
32608 -var-list-children n
32609 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32610 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32612 -var-list-children --all-values n
32613 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32614 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32618 @subheading The @code{-var-info-type} Command
32619 @findex -var-info-type
32621 @subsubheading Synopsis
32624 -var-info-type @var{name}
32627 Returns the type of the specified variable @var{name}. The type is
32628 returned as a string in the same format as it is output by the
32632 type=@var{typename}
32636 @subheading The @code{-var-info-expression} Command
32637 @findex -var-info-expression
32639 @subsubheading Synopsis
32642 -var-info-expression @var{name}
32645 Returns a string that is suitable for presenting this
32646 variable object in user interface. The string is generally
32647 not valid expression in the current language, and cannot be evaluated.
32649 For example, if @code{a} is an array, and variable object
32650 @code{A} was created for @code{a}, then we'll get this output:
32653 (gdb) -var-info-expression A.1
32654 ^done,lang="C",exp="1"
32658 Here, the value of @code{lang} is the language name, which can be
32659 found in @ref{Supported Languages}.
32661 Note that the output of the @code{-var-list-children} command also
32662 includes those expressions, so the @code{-var-info-expression} command
32665 @subheading The @code{-var-info-path-expression} Command
32666 @findex -var-info-path-expression
32668 @subsubheading Synopsis
32671 -var-info-path-expression @var{name}
32674 Returns an expression that can be evaluated in the current
32675 context and will yield the same value that a variable object has.
32676 Compare this with the @code{-var-info-expression} command, which
32677 result can be used only for UI presentation. Typical use of
32678 the @code{-var-info-path-expression} command is creating a
32679 watchpoint from a variable object.
32681 This command is currently not valid for children of a dynamic varobj,
32682 and will give an error when invoked on one.
32684 For example, suppose @code{C} is a C@t{++} class, derived from class
32685 @code{Base}, and that the @code{Base} class has a member called
32686 @code{m_size}. Assume a variable @code{c} is has the type of
32687 @code{C} and a variable object @code{C} was created for variable
32688 @code{c}. Then, we'll get this output:
32690 (gdb) -var-info-path-expression C.Base.public.m_size
32691 ^done,path_expr=((Base)c).m_size)
32694 @subheading The @code{-var-show-attributes} Command
32695 @findex -var-show-attributes
32697 @subsubheading Synopsis
32700 -var-show-attributes @var{name}
32703 List attributes of the specified variable object @var{name}:
32706 status=@var{attr} [ ( ,@var{attr} )* ]
32710 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32712 @subheading The @code{-var-evaluate-expression} Command
32713 @findex -var-evaluate-expression
32715 @subsubheading Synopsis
32718 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32721 Evaluates the expression that is represented by the specified variable
32722 object and returns its value as a string. The format of the string
32723 can be specified with the @samp{-f} option. The possible values of
32724 this option are the same as for @code{-var-set-format}
32725 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32726 the current display format will be used. The current display format
32727 can be changed using the @code{-var-set-format} command.
32733 Note that one must invoke @code{-var-list-children} for a variable
32734 before the value of a child variable can be evaluated.
32736 @subheading The @code{-var-assign} Command
32737 @findex -var-assign
32739 @subsubheading Synopsis
32742 -var-assign @var{name} @var{expression}
32745 Assigns the value of @var{expression} to the variable object specified
32746 by @var{name}. The object must be @samp{editable}. If the variable's
32747 value is altered by the assign, the variable will show up in any
32748 subsequent @code{-var-update} list.
32750 @subsubheading Example
32758 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32762 @subheading The @code{-var-update} Command
32763 @findex -var-update
32765 @subsubheading Synopsis
32768 -var-update [@var{print-values}] @{@var{name} | "*"@}
32771 Reevaluate the expressions corresponding to the variable object
32772 @var{name} and all its direct and indirect children, and return the
32773 list of variable objects whose values have changed; @var{name} must
32774 be a root variable object. Here, ``changed'' means that the result of
32775 @code{-var-evaluate-expression} before and after the
32776 @code{-var-update} is different. If @samp{*} is used as the variable
32777 object names, all existing variable objects are updated, except
32778 for frozen ones (@pxref{-var-set-frozen}). The option
32779 @var{print-values} determines whether both names and values, or just
32780 names are printed. The possible values of this option are the same
32781 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32782 recommended to use the @samp{--all-values} option, to reduce the
32783 number of MI commands needed on each program stop.
32785 With the @samp{*} parameter, if a variable object is bound to a
32786 currently running thread, it will not be updated, without any
32789 If @code{-var-set-update-range} was previously used on a varobj, then
32790 only the selected range of children will be reported.
32792 @code{-var-update} reports all the changed varobjs in a tuple named
32795 Each item in the change list is itself a tuple holding:
32799 The name of the varobj.
32802 If values were requested for this update, then this field will be
32803 present and will hold the value of the varobj.
32806 @anchor{-var-update}
32807 This field is a string which may take one of three values:
32811 The variable object's current value is valid.
32814 The variable object does not currently hold a valid value but it may
32815 hold one in the future if its associated expression comes back into
32819 The variable object no longer holds a valid value.
32820 This can occur when the executable file being debugged has changed,
32821 either through recompilation or by using the @value{GDBN} @code{file}
32822 command. The front end should normally choose to delete these variable
32826 In the future new values may be added to this list so the front should
32827 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32830 This is only present if the varobj is still valid. If the type
32831 changed, then this will be the string @samp{true}; otherwise it will
32834 When a varobj's type changes, its children are also likely to have
32835 become incorrect. Therefore, the varobj's children are automatically
32836 deleted when this attribute is @samp{true}. Also, the varobj's update
32837 range, when set using the @code{-var-set-update-range} command, is
32841 If the varobj's type changed, then this field will be present and will
32844 @item new_num_children
32845 For a dynamic varobj, if the number of children changed, or if the
32846 type changed, this will be the new number of children.
32848 The @samp{numchild} field in other varobj responses is generally not
32849 valid for a dynamic varobj -- it will show the number of children that
32850 @value{GDBN} knows about, but because dynamic varobjs lazily
32851 instantiate their children, this will not reflect the number of
32852 children which may be available.
32854 The @samp{new_num_children} attribute only reports changes to the
32855 number of children known by @value{GDBN}. This is the only way to
32856 detect whether an update has removed children (which necessarily can
32857 only happen at the end of the update range).
32860 The display hint, if any.
32863 This is an integer value, which will be 1 if there are more children
32864 available outside the varobj's update range.
32867 This attribute will be present and have the value @samp{1} if the
32868 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32869 then this attribute will not be present.
32872 If new children were added to a dynamic varobj within the selected
32873 update range (as set by @code{-var-set-update-range}), then they will
32874 be listed in this attribute.
32877 @subsubheading Example
32884 -var-update --all-values var1
32885 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32886 type_changed="false"@}]
32890 @subheading The @code{-var-set-frozen} Command
32891 @findex -var-set-frozen
32892 @anchor{-var-set-frozen}
32894 @subsubheading Synopsis
32897 -var-set-frozen @var{name} @var{flag}
32900 Set the frozenness flag on the variable object @var{name}. The
32901 @var{flag} parameter should be either @samp{1} to make the variable
32902 frozen or @samp{0} to make it unfrozen. If a variable object is
32903 frozen, then neither itself, nor any of its children, are
32904 implicitly updated by @code{-var-update} of
32905 a parent variable or by @code{-var-update *}. Only
32906 @code{-var-update} of the variable itself will update its value and
32907 values of its children. After a variable object is unfrozen, it is
32908 implicitly updated by all subsequent @code{-var-update} operations.
32909 Unfreezing a variable does not update it, only subsequent
32910 @code{-var-update} does.
32912 @subsubheading Example
32916 -var-set-frozen V 1
32921 @subheading The @code{-var-set-update-range} command
32922 @findex -var-set-update-range
32923 @anchor{-var-set-update-range}
32925 @subsubheading Synopsis
32928 -var-set-update-range @var{name} @var{from} @var{to}
32931 Set the range of children to be returned by future invocations of
32932 @code{-var-update}.
32934 @var{from} and @var{to} indicate the range of children to report. If
32935 @var{from} or @var{to} is less than zero, the range is reset and all
32936 children will be reported. Otherwise, children starting at @var{from}
32937 (zero-based) and up to and excluding @var{to} will be reported.
32939 @subsubheading Example
32943 -var-set-update-range V 1 2
32947 @subheading The @code{-var-set-visualizer} command
32948 @findex -var-set-visualizer
32949 @anchor{-var-set-visualizer}
32951 @subsubheading Synopsis
32954 -var-set-visualizer @var{name} @var{visualizer}
32957 Set a visualizer for the variable object @var{name}.
32959 @var{visualizer} is the visualizer to use. The special value
32960 @samp{None} means to disable any visualizer in use.
32962 If not @samp{None}, @var{visualizer} must be a Python expression.
32963 This expression must evaluate to a callable object which accepts a
32964 single argument. @value{GDBN} will call this object with the value of
32965 the varobj @var{name} as an argument (this is done so that the same
32966 Python pretty-printing code can be used for both the CLI and MI).
32967 When called, this object must return an object which conforms to the
32968 pretty-printing interface (@pxref{Pretty Printing API}).
32970 The pre-defined function @code{gdb.default_visualizer} may be used to
32971 select a visualizer by following the built-in process
32972 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32973 a varobj is created, and so ordinarily is not needed.
32975 This feature is only available if Python support is enabled. The MI
32976 command @code{-list-features} (@pxref{GDB/MI Support Commands})
32977 can be used to check this.
32979 @subsubheading Example
32981 Resetting the visualizer:
32985 -var-set-visualizer V None
32989 Reselecting the default (type-based) visualizer:
32993 -var-set-visualizer V gdb.default_visualizer
32997 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32998 can be used to instantiate this class for a varobj:
33002 -var-set-visualizer V "lambda val: SomeClass()"
33006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33007 @node GDB/MI Data Manipulation
33008 @section @sc{gdb/mi} Data Manipulation
33010 @cindex data manipulation, in @sc{gdb/mi}
33011 @cindex @sc{gdb/mi}, data manipulation
33012 This section describes the @sc{gdb/mi} commands that manipulate data:
33013 examine memory and registers, evaluate expressions, etc.
33015 For details about what an addressable memory unit is,
33016 @pxref{addressable memory unit}.
33018 @c REMOVED FROM THE INTERFACE.
33019 @c @subheading -data-assign
33020 @c Change the value of a program variable. Plenty of side effects.
33021 @c @subsubheading GDB Command
33023 @c @subsubheading Example
33026 @subheading The @code{-data-disassemble} Command
33027 @findex -data-disassemble
33029 @subsubheading Synopsis
33033 [ -s @var{start-addr} -e @var{end-addr} ]
33034 | [ -a @var{addr} ]
33035 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33043 @item @var{start-addr}
33044 is the beginning address (or @code{$pc})
33045 @item @var{end-addr}
33048 is an address anywhere within (or the name of) the function to
33049 disassemble. If an address is specified, the whole function
33050 surrounding that address will be disassembled. If a name is
33051 specified, the whole function with that name will be disassembled.
33052 @item @var{filename}
33053 is the name of the file to disassemble
33054 @item @var{linenum}
33055 is the line number to disassemble around
33057 is the number of disassembly lines to be produced. If it is -1,
33058 the whole function will be disassembled, in case no @var{end-addr} is
33059 specified. If @var{end-addr} is specified as a non-zero value, and
33060 @var{lines} is lower than the number of disassembly lines between
33061 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33062 displayed; if @var{lines} is higher than the number of lines between
33063 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33068 @item 0 disassembly only
33069 @item 1 mixed source and disassembly (deprecated)
33070 @item 2 disassembly with raw opcodes
33071 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33072 @item 4 mixed source and disassembly
33073 @item 5 mixed source and disassembly with raw opcodes
33076 Modes 1 and 3 are deprecated. The output is ``source centric''
33077 which hasn't proved useful in practice.
33078 @xref{Machine Code}, for a discussion of the difference between
33079 @code{/m} and @code{/s} output of the @code{disassemble} command.
33082 @subsubheading Result
33084 The result of the @code{-data-disassemble} command will be a list named
33085 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33086 used with the @code{-data-disassemble} command.
33088 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33093 The address at which this instruction was disassembled.
33096 The name of the function this instruction is within.
33099 The decimal offset in bytes from the start of @samp{func-name}.
33102 The text disassembly for this @samp{address}.
33105 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33106 bytes for the @samp{inst} field.
33110 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33111 @samp{src_and_asm_line}, each of which has the following fields:
33115 The line number within @samp{file}.
33118 The file name from the compilation unit. This might be an absolute
33119 file name or a relative file name depending on the compile command
33123 Absolute file name of @samp{file}. It is converted to a canonical form
33124 using the source file search path
33125 (@pxref{Source Path, ,Specifying Source Directories})
33126 and after resolving all the symbolic links.
33128 If the source file is not found this field will contain the path as
33129 present in the debug information.
33131 @item line_asm_insn
33132 This is a list of tuples containing the disassembly for @samp{line} in
33133 @samp{file}. The fields of each tuple are the same as for
33134 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33135 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33140 Note that whatever included in the @samp{inst} field, is not
33141 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33144 @subsubheading @value{GDBN} Command
33146 The corresponding @value{GDBN} command is @samp{disassemble}.
33148 @subsubheading Example
33150 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33154 -data-disassemble -s $pc -e "$pc + 20" -- 0
33157 @{address="0x000107c0",func-name="main",offset="4",
33158 inst="mov 2, %o0"@},
33159 @{address="0x000107c4",func-name="main",offset="8",
33160 inst="sethi %hi(0x11800), %o2"@},
33161 @{address="0x000107c8",func-name="main",offset="12",
33162 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33163 @{address="0x000107cc",func-name="main",offset="16",
33164 inst="sethi %hi(0x11800), %o2"@},
33165 @{address="0x000107d0",func-name="main",offset="20",
33166 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33170 Disassemble the whole @code{main} function. Line 32 is part of
33174 -data-disassemble -f basics.c -l 32 -- 0
33176 @{address="0x000107bc",func-name="main",offset="0",
33177 inst="save %sp, -112, %sp"@},
33178 @{address="0x000107c0",func-name="main",offset="4",
33179 inst="mov 2, %o0"@},
33180 @{address="0x000107c4",func-name="main",offset="8",
33181 inst="sethi %hi(0x11800), %o2"@},
33183 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33184 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33188 Disassemble 3 instructions from the start of @code{main}:
33192 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33194 @{address="0x000107bc",func-name="main",offset="0",
33195 inst="save %sp, -112, %sp"@},
33196 @{address="0x000107c0",func-name="main",offset="4",
33197 inst="mov 2, %o0"@},
33198 @{address="0x000107c4",func-name="main",offset="8",
33199 inst="sethi %hi(0x11800), %o2"@}]
33203 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33207 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33209 src_and_asm_line=@{line="31",
33210 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33211 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33212 line_asm_insn=[@{address="0x000107bc",
33213 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33214 src_and_asm_line=@{line="32",
33215 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33216 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33217 line_asm_insn=[@{address="0x000107c0",
33218 func-name="main",offset="4",inst="mov 2, %o0"@},
33219 @{address="0x000107c4",func-name="main",offset="8",
33220 inst="sethi %hi(0x11800), %o2"@}]@}]
33225 @subheading The @code{-data-evaluate-expression} Command
33226 @findex -data-evaluate-expression
33228 @subsubheading Synopsis
33231 -data-evaluate-expression @var{expr}
33234 Evaluate @var{expr} as an expression. The expression could contain an
33235 inferior function call. The function call will execute synchronously.
33236 If the expression contains spaces, it must be enclosed in double quotes.
33238 @subsubheading @value{GDBN} Command
33240 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33241 @samp{call}. In @code{gdbtk} only, there's a corresponding
33242 @samp{gdb_eval} command.
33244 @subsubheading Example
33246 In the following example, the numbers that precede the commands are the
33247 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33248 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33252 211-data-evaluate-expression A
33255 311-data-evaluate-expression &A
33256 311^done,value="0xefffeb7c"
33258 411-data-evaluate-expression A+3
33261 511-data-evaluate-expression "A + 3"
33267 @subheading The @code{-data-list-changed-registers} Command
33268 @findex -data-list-changed-registers
33270 @subsubheading Synopsis
33273 -data-list-changed-registers
33276 Display a list of the registers that have changed.
33278 @subsubheading @value{GDBN} Command
33280 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33281 has the corresponding command @samp{gdb_changed_register_list}.
33283 @subsubheading Example
33285 On a PPC MBX board:
33293 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33294 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33295 line="5",arch="powerpc"@}
33297 -data-list-changed-registers
33298 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33299 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33300 "24","25","26","27","28","30","31","64","65","66","67","69"]
33305 @subheading The @code{-data-list-register-names} Command
33306 @findex -data-list-register-names
33308 @subsubheading Synopsis
33311 -data-list-register-names [ ( @var{regno} )+ ]
33314 Show a list of register names for the current target. If no arguments
33315 are given, it shows a list of the names of all the registers. If
33316 integer numbers are given as arguments, it will print a list of the
33317 names of the registers corresponding to the arguments. To ensure
33318 consistency between a register name and its number, the output list may
33319 include empty register names.
33321 @subsubheading @value{GDBN} Command
33323 @value{GDBN} does not have a command which corresponds to
33324 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33325 corresponding command @samp{gdb_regnames}.
33327 @subsubheading Example
33329 For the PPC MBX board:
33332 -data-list-register-names
33333 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33334 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33335 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33336 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33337 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33338 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33339 "", "pc","ps","cr","lr","ctr","xer"]
33341 -data-list-register-names 1 2 3
33342 ^done,register-names=["r1","r2","r3"]
33346 @subheading The @code{-data-list-register-values} Command
33347 @findex -data-list-register-values
33349 @subsubheading Synopsis
33352 -data-list-register-values
33353 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33356 Display the registers' contents. The format according to which the
33357 registers' contents are to be returned is given by @var{fmt}, followed
33358 by an optional list of numbers specifying the registers to display. A
33359 missing list of numbers indicates that the contents of all the
33360 registers must be returned. The @code{--skip-unavailable} option
33361 indicates that only the available registers are to be returned.
33363 Allowed formats for @var{fmt} are:
33380 @subsubheading @value{GDBN} Command
33382 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33383 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33385 @subsubheading Example
33387 For a PPC MBX board (note: line breaks are for readability only, they
33388 don't appear in the actual output):
33392 -data-list-register-values r 64 65
33393 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33394 @{number="65",value="0x00029002"@}]
33396 -data-list-register-values x
33397 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33398 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33399 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33400 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33401 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33402 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33403 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33404 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33405 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33406 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33407 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33408 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33409 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33410 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33411 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33412 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33413 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33414 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33415 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33416 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33417 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33418 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33419 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33420 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33421 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33422 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33423 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33424 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33425 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33426 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33427 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33428 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33429 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33430 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33431 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33432 @{number="69",value="0x20002b03"@}]
33437 @subheading The @code{-data-read-memory} Command
33438 @findex -data-read-memory
33440 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33442 @subsubheading Synopsis
33445 -data-read-memory [ -o @var{byte-offset} ]
33446 @var{address} @var{word-format} @var{word-size}
33447 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33454 @item @var{address}
33455 An expression specifying the address of the first memory word to be
33456 read. Complex expressions containing embedded white space should be
33457 quoted using the C convention.
33459 @item @var{word-format}
33460 The format to be used to print the memory words. The notation is the
33461 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33464 @item @var{word-size}
33465 The size of each memory word in bytes.
33467 @item @var{nr-rows}
33468 The number of rows in the output table.
33470 @item @var{nr-cols}
33471 The number of columns in the output table.
33474 If present, indicates that each row should include an @sc{ascii} dump. The
33475 value of @var{aschar} is used as a padding character when a byte is not a
33476 member of the printable @sc{ascii} character set (printable @sc{ascii}
33477 characters are those whose code is between 32 and 126, inclusively).
33479 @item @var{byte-offset}
33480 An offset to add to the @var{address} before fetching memory.
33483 This command displays memory contents as a table of @var{nr-rows} by
33484 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33485 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33486 (returned as @samp{total-bytes}). Should less than the requested number
33487 of bytes be returned by the target, the missing words are identified
33488 using @samp{N/A}. The number of bytes read from the target is returned
33489 in @samp{nr-bytes} and the starting address used to read memory in
33492 The address of the next/previous row or page is available in
33493 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33496 @subsubheading @value{GDBN} Command
33498 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33499 @samp{gdb_get_mem} memory read command.
33501 @subsubheading Example
33503 Read six bytes of memory starting at @code{bytes+6} but then offset by
33504 @code{-6} bytes. Format as three rows of two columns. One byte per
33505 word. Display each word in hex.
33509 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33510 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33511 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33512 prev-page="0x0000138a",memory=[
33513 @{addr="0x00001390",data=["0x00","0x01"]@},
33514 @{addr="0x00001392",data=["0x02","0x03"]@},
33515 @{addr="0x00001394",data=["0x04","0x05"]@}]
33519 Read two bytes of memory starting at address @code{shorts + 64} and
33520 display as a single word formatted in decimal.
33524 5-data-read-memory shorts+64 d 2 1 1
33525 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33526 next-row="0x00001512",prev-row="0x0000150e",
33527 next-page="0x00001512",prev-page="0x0000150e",memory=[
33528 @{addr="0x00001510",data=["128"]@}]
33532 Read thirty two bytes of memory starting at @code{bytes+16} and format
33533 as eight rows of four columns. Include a string encoding with @samp{x}
33534 used as the non-printable character.
33538 4-data-read-memory bytes+16 x 1 8 4 x
33539 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33540 next-row="0x000013c0",prev-row="0x0000139c",
33541 next-page="0x000013c0",prev-page="0x00001380",memory=[
33542 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33543 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33544 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33545 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33546 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33547 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33548 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33549 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33553 @subheading The @code{-data-read-memory-bytes} Command
33554 @findex -data-read-memory-bytes
33556 @subsubheading Synopsis
33559 -data-read-memory-bytes [ -o @var{offset} ]
33560 @var{address} @var{count}
33567 @item @var{address}
33568 An expression specifying the address of the first addressable memory unit
33569 to be read. Complex expressions containing embedded white space should be
33570 quoted using the C convention.
33573 The number of addressable memory units to read. This should be an integer
33577 The offset relative to @var{address} at which to start reading. This
33578 should be an integer literal. This option is provided so that a frontend
33579 is not required to first evaluate address and then perform address
33580 arithmetics itself.
33584 This command attempts to read all accessible memory regions in the
33585 specified range. First, all regions marked as unreadable in the memory
33586 map (if one is defined) will be skipped. @xref{Memory Region
33587 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33588 regions. For each one, if reading full region results in an errors,
33589 @value{GDBN} will try to read a subset of the region.
33591 In general, every single memory unit in the region may be readable or not,
33592 and the only way to read every readable unit is to try a read at
33593 every address, which is not practical. Therefore, @value{GDBN} will
33594 attempt to read all accessible memory units at either beginning or the end
33595 of the region, using a binary division scheme. This heuristic works
33596 well for reading across a memory map boundary. Note that if a region
33597 has a readable range that is neither at the beginning or the end,
33598 @value{GDBN} will not read it.
33600 The result record (@pxref{GDB/MI Result Records}) that is output of
33601 the command includes a field named @samp{memory} whose content is a
33602 list of tuples. Each tuple represent a successfully read memory block
33603 and has the following fields:
33607 The start address of the memory block, as hexadecimal literal.
33610 The end address of the memory block, as hexadecimal literal.
33613 The offset of the memory block, as hexadecimal literal, relative to
33614 the start address passed to @code{-data-read-memory-bytes}.
33617 The contents of the memory block, in hex.
33623 @subsubheading @value{GDBN} Command
33625 The corresponding @value{GDBN} command is @samp{x}.
33627 @subsubheading Example
33631 -data-read-memory-bytes &a 10
33632 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33634 contents="01000000020000000300"@}]
33639 @subheading The @code{-data-write-memory-bytes} Command
33640 @findex -data-write-memory-bytes
33642 @subsubheading Synopsis
33645 -data-write-memory-bytes @var{address} @var{contents}
33646 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33653 @item @var{address}
33654 An expression specifying the address of the first addressable memory unit
33655 to be written. Complex expressions containing embedded white space should
33656 be quoted using the C convention.
33658 @item @var{contents}
33659 The hex-encoded data to write. It is an error if @var{contents} does
33660 not represent an integral number of addressable memory units.
33663 Optional argument indicating the number of addressable memory units to be
33664 written. If @var{count} is greater than @var{contents}' length,
33665 @value{GDBN} will repeatedly write @var{contents} until it fills
33666 @var{count} memory units.
33670 @subsubheading @value{GDBN} Command
33672 There's no corresponding @value{GDBN} command.
33674 @subsubheading Example
33678 -data-write-memory-bytes &a "aabbccdd"
33685 -data-write-memory-bytes &a "aabbccdd" 16e
33690 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33691 @node GDB/MI Tracepoint Commands
33692 @section @sc{gdb/mi} Tracepoint Commands
33694 The commands defined in this section implement MI support for
33695 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33697 @subheading The @code{-trace-find} Command
33698 @findex -trace-find
33700 @subsubheading Synopsis
33703 -trace-find @var{mode} [@var{parameters}@dots{}]
33706 Find a trace frame using criteria defined by @var{mode} and
33707 @var{parameters}. The following table lists permissible
33708 modes and their parameters. For details of operation, see @ref{tfind}.
33713 No parameters are required. Stops examining trace frames.
33716 An integer is required as parameter. Selects tracepoint frame with
33719 @item tracepoint-number
33720 An integer is required as parameter. Finds next
33721 trace frame that corresponds to tracepoint with the specified number.
33724 An address is required as parameter. Finds
33725 next trace frame that corresponds to any tracepoint at the specified
33728 @item pc-inside-range
33729 Two addresses are required as parameters. Finds next trace
33730 frame that corresponds to a tracepoint at an address inside the
33731 specified range. Both bounds are considered to be inside the range.
33733 @item pc-outside-range
33734 Two addresses are required as parameters. Finds
33735 next trace frame that corresponds to a tracepoint at an address outside
33736 the specified range. Both bounds are considered to be inside the range.
33739 Line specification is required as parameter. @xref{Specify Location}.
33740 Finds next trace frame that corresponds to a tracepoint at
33741 the specified location.
33745 If @samp{none} was passed as @var{mode}, the response does not
33746 have fields. Otherwise, the response may have the following fields:
33750 This field has either @samp{0} or @samp{1} as the value, depending
33751 on whether a matching tracepoint was found.
33754 The index of the found traceframe. This field is present iff
33755 the @samp{found} field has value of @samp{1}.
33758 The index of the found tracepoint. This field is present iff
33759 the @samp{found} field has value of @samp{1}.
33762 The information about the frame corresponding to the found trace
33763 frame. This field is present only if a trace frame was found.
33764 @xref{GDB/MI Frame Information}, for description of this field.
33768 @subsubheading @value{GDBN} Command
33770 The corresponding @value{GDBN} command is @samp{tfind}.
33772 @subheading -trace-define-variable
33773 @findex -trace-define-variable
33775 @subsubheading Synopsis
33778 -trace-define-variable @var{name} [ @var{value} ]
33781 Create trace variable @var{name} if it does not exist. If
33782 @var{value} is specified, sets the initial value of the specified
33783 trace variable to that value. Note that the @var{name} should start
33784 with the @samp{$} character.
33786 @subsubheading @value{GDBN} Command
33788 The corresponding @value{GDBN} command is @samp{tvariable}.
33790 @subheading The @code{-trace-frame-collected} Command
33791 @findex -trace-frame-collected
33793 @subsubheading Synopsis
33796 -trace-frame-collected
33797 [--var-print-values @var{var_pval}]
33798 [--comp-print-values @var{comp_pval}]
33799 [--registers-format @var{regformat}]
33800 [--memory-contents]
33803 This command returns the set of collected objects, register names,
33804 trace state variable names, memory ranges and computed expressions
33805 that have been collected at a particular trace frame. The optional
33806 parameters to the command affect the output format in different ways.
33807 See the output description table below for more details.
33809 The reported names can be used in the normal manner to create
33810 varobjs and inspect the objects themselves. The items returned by
33811 this command are categorized so that it is clear which is a variable,
33812 which is a register, which is a trace state variable, which is a
33813 memory range and which is a computed expression.
33815 For instance, if the actions were
33817 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33818 collect *(int*)0xaf02bef0@@40
33822 the object collected in its entirety would be @code{myVar}. The
33823 object @code{myArray} would be partially collected, because only the
33824 element at index @code{myIndex} would be collected. The remaining
33825 objects would be computed expressions.
33827 An example output would be:
33831 -trace-frame-collected
33833 explicit-variables=[@{name="myVar",value="1"@}],
33834 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33835 @{name="myObj.field",value="0"@},
33836 @{name="myPtr->field",value="1"@},
33837 @{name="myCount + 2",value="3"@},
33838 @{name="$tvar1 + 1",value="43970027"@}],
33839 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33840 @{number="1",value="0x0"@},
33841 @{number="2",value="0x4"@},
33843 @{number="125",value="0x0"@}],
33844 tvars=[@{name="$tvar1",current="43970026"@}],
33845 memory=[@{address="0x0000000000602264",length="4"@},
33846 @{address="0x0000000000615bc0",length="4"@}]
33853 @item explicit-variables
33854 The set of objects that have been collected in their entirety (as
33855 opposed to collecting just a few elements of an array or a few struct
33856 members). For each object, its name and value are printed.
33857 The @code{--var-print-values} option affects how or whether the value
33858 field is output. If @var{var_pval} is 0, then print only the names;
33859 if it is 1, print also their values; and if it is 2, print the name,
33860 type and value for simple data types, and the name and type for
33861 arrays, structures and unions.
33863 @item computed-expressions
33864 The set of computed expressions that have been collected at the
33865 current trace frame. The @code{--comp-print-values} option affects
33866 this set like the @code{--var-print-values} option affects the
33867 @code{explicit-variables} set. See above.
33870 The registers that have been collected at the current trace frame.
33871 For each register collected, the name and current value are returned.
33872 The value is formatted according to the @code{--registers-format}
33873 option. See the @command{-data-list-register-values} command for a
33874 list of the allowed formats. The default is @samp{x}.
33877 The trace state variables that have been collected at the current
33878 trace frame. For each trace state variable collected, the name and
33879 current value are returned.
33882 The set of memory ranges that have been collected at the current trace
33883 frame. Its content is a list of tuples. Each tuple represents a
33884 collected memory range and has the following fields:
33888 The start address of the memory range, as hexadecimal literal.
33891 The length of the memory range, as decimal literal.
33894 The contents of the memory block, in hex. This field is only present
33895 if the @code{--memory-contents} option is specified.
33901 @subsubheading @value{GDBN} Command
33903 There is no corresponding @value{GDBN} command.
33905 @subsubheading Example
33907 @subheading -trace-list-variables
33908 @findex -trace-list-variables
33910 @subsubheading Synopsis
33913 -trace-list-variables
33916 Return a table of all defined trace variables. Each element of the
33917 table has the following fields:
33921 The name of the trace variable. This field is always present.
33924 The initial value. This is a 64-bit signed integer. This
33925 field is always present.
33928 The value the trace variable has at the moment. This is a 64-bit
33929 signed integer. This field is absent iff current value is
33930 not defined, for example if the trace was never run, or is
33935 @subsubheading @value{GDBN} Command
33937 The corresponding @value{GDBN} command is @samp{tvariables}.
33939 @subsubheading Example
33943 -trace-list-variables
33944 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33945 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33946 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33947 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33948 body=[variable=@{name="$trace_timestamp",initial="0"@}
33949 variable=@{name="$foo",initial="10",current="15"@}]@}
33953 @subheading -trace-save
33954 @findex -trace-save
33956 @subsubheading Synopsis
33959 -trace-save [ -r ] [ -ctf ] @var{filename}
33962 Saves the collected trace data to @var{filename}. Without the
33963 @samp{-r} option, the data is downloaded from the target and saved
33964 in a local file. With the @samp{-r} option the target is asked
33965 to perform the save.
33967 By default, this command will save the trace in the tfile format. You can
33968 supply the optional @samp{-ctf} argument to save it the CTF format. See
33969 @ref{Trace Files} for more information about CTF.
33971 @subsubheading @value{GDBN} Command
33973 The corresponding @value{GDBN} command is @samp{tsave}.
33976 @subheading -trace-start
33977 @findex -trace-start
33979 @subsubheading Synopsis
33985 Starts a tracing experiment. The result of this command does not
33988 @subsubheading @value{GDBN} Command
33990 The corresponding @value{GDBN} command is @samp{tstart}.
33992 @subheading -trace-status
33993 @findex -trace-status
33995 @subsubheading Synopsis
34001 Obtains the status of a tracing experiment. The result may include
34002 the following fields:
34007 May have a value of either @samp{0}, when no tracing operations are
34008 supported, @samp{1}, when all tracing operations are supported, or
34009 @samp{file} when examining trace file. In the latter case, examining
34010 of trace frame is possible but new tracing experiement cannot be
34011 started. This field is always present.
34014 May have a value of either @samp{0} or @samp{1} depending on whether
34015 tracing experiement is in progress on target. This field is present
34016 if @samp{supported} field is not @samp{0}.
34019 Report the reason why the tracing was stopped last time. This field
34020 may be absent iff tracing was never stopped on target yet. The
34021 value of @samp{request} means the tracing was stopped as result of
34022 the @code{-trace-stop} command. The value of @samp{overflow} means
34023 the tracing buffer is full. The value of @samp{disconnection} means
34024 tracing was automatically stopped when @value{GDBN} has disconnected.
34025 The value of @samp{passcount} means tracing was stopped when a
34026 tracepoint was passed a maximal number of times for that tracepoint.
34027 This field is present if @samp{supported} field is not @samp{0}.
34029 @item stopping-tracepoint
34030 The number of tracepoint whose passcount as exceeded. This field is
34031 present iff the @samp{stop-reason} field has the value of
34035 @itemx frames-created
34036 The @samp{frames} field is a count of the total number of trace frames
34037 in the trace buffer, while @samp{frames-created} is the total created
34038 during the run, including ones that were discarded, such as when a
34039 circular trace buffer filled up. Both fields are optional.
34043 These fields tell the current size of the tracing buffer and the
34044 remaining space. These fields are optional.
34047 The value of the circular trace buffer flag. @code{1} means that the
34048 trace buffer is circular and old trace frames will be discarded if
34049 necessary to make room, @code{0} means that the trace buffer is linear
34053 The value of the disconnected tracing flag. @code{1} means that
34054 tracing will continue after @value{GDBN} disconnects, @code{0} means
34055 that the trace run will stop.
34058 The filename of the trace file being examined. This field is
34059 optional, and only present when examining a trace file.
34063 @subsubheading @value{GDBN} Command
34065 The corresponding @value{GDBN} command is @samp{tstatus}.
34067 @subheading -trace-stop
34068 @findex -trace-stop
34070 @subsubheading Synopsis
34076 Stops a tracing experiment. The result of this command has the same
34077 fields as @code{-trace-status}, except that the @samp{supported} and
34078 @samp{running} fields are not output.
34080 @subsubheading @value{GDBN} Command
34082 The corresponding @value{GDBN} command is @samp{tstop}.
34085 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34086 @node GDB/MI Symbol Query
34087 @section @sc{gdb/mi} Symbol Query Commands
34091 @subheading The @code{-symbol-info-address} Command
34092 @findex -symbol-info-address
34094 @subsubheading Synopsis
34097 -symbol-info-address @var{symbol}
34100 Describe where @var{symbol} is stored.
34102 @subsubheading @value{GDBN} Command
34104 The corresponding @value{GDBN} command is @samp{info address}.
34106 @subsubheading Example
34110 @subheading The @code{-symbol-info-file} Command
34111 @findex -symbol-info-file
34113 @subsubheading Synopsis
34119 Show the file for the symbol.
34121 @subsubheading @value{GDBN} Command
34123 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34124 @samp{gdb_find_file}.
34126 @subsubheading Example
34130 @subheading The @code{-symbol-info-functions} Command
34131 @findex -symbol-info-functions
34132 @anchor{-symbol-info-functions}
34134 @subsubheading Synopsis
34137 -symbol-info-functions [--include-nondebug]
34138 [--type @var{type_regexp}]
34139 [--name @var{name_regexp}]
34140 [--max-results @var{limit}]
34144 Return a list containing the names and types for all global functions
34145 taken from the debug information. The functions are grouped by source
34146 file, and shown with the line number on which each function is
34149 The @code{--include-nondebug} option causes the output to include
34150 code symbols from the symbol table.
34152 The options @code{--type} and @code{--name} allow the symbols returned
34153 to be filtered based on either the name of the function, or the type
34154 signature of the function.
34156 The option @code{--max-results} restricts the command to return no
34157 more than @var{limit} results. If exactly @var{limit} results are
34158 returned then there might be additional results available if a higher
34161 @subsubheading @value{GDBN} Command
34163 The corresponding @value{GDBN} command is @samp{info functions}.
34165 @subsubheading Example
34169 -symbol-info-functions
34172 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34173 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34174 symbols=[@{line="36", name="f4", type="void (int *)",
34175 description="void f4(int *);"@},
34176 @{line="42", name="main", type="int ()",
34177 description="int main();"@},
34178 @{line="30", name="f1", type="my_int_t (int, int)",
34179 description="static my_int_t f1(int, int);"@}]@},
34180 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34181 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34182 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34183 description="float f2(another_float_t);"@},
34184 @{line="39", name="f3", type="int (another_int_t)",
34185 description="int f3(another_int_t);"@},
34186 @{line="27", name="f1", type="another_float_t (int)",
34187 description="static another_float_t f1(int);"@}]@}]@}
34191 -symbol-info-functions --name f1
34194 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34195 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34196 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
34197 description="static my_int_t f1(int, int);"@}]@},
34198 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34199 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34200 symbols=[@{line="27", name="f1", type="another_float_t (int)",
34201 description="static another_float_t f1(int);"@}]@}]@}
34205 -symbol-info-functions --type void
34208 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34209 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34210 symbols=[@{line="36", name="f4", type="void (int *)",
34211 description="void f4(int *);"@}]@}]@}
34215 -symbol-info-functions --include-nondebug
34218 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34219 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34220 symbols=[@{line="36", name="f4", type="void (int *)",
34221 description="void f4(int *);"@},
34222 @{line="42", name="main", type="int ()",
34223 description="int main();"@},
34224 @{line="30", name="f1", type="my_int_t (int, int)",
34225 description="static my_int_t f1(int, int);"@}]@},
34226 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34227 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34228 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34229 description="float f2(another_float_t);"@},
34230 @{line="39", name="f3", type="int (another_int_t)",
34231 description="int f3(another_int_t);"@},
34232 @{line="27", name="f1", type="another_float_t (int)",
34233 description="static another_float_t f1(int);"@}]@}],
34235 [@{address="0x0000000000400398",name="_init"@},
34236 @{address="0x00000000004003b0",name="_start"@},
34242 @subheading The @code{-symbol-info-module-functions} Command
34243 @findex -symbol-info-module-functions
34244 @anchor{-symbol-info-module-functions}
34246 @subsubheading Synopsis
34249 -symbol-info-module-functions [--module @var{module_regexp}]
34250 [--name @var{name_regexp}]
34251 [--type @var{type_regexp}]
34255 Return a list containing the names of all known functions within all
34256 know Fortran modules. The functions are grouped by source file and
34257 containing module, and shown with the line number on which each
34258 function is defined.
34260 The option @code{--module} only returns results for modules matching
34261 @var{module_regexp}. The option @code{--name} only returns functions
34262 whose name matches @var{name_regexp}, and @code{--type} only returns
34263 functions whose type matches @var{type_regexp}.
34265 @subsubheading @value{GDBN} Command
34267 The corresponding @value{GDBN} command is @samp{info module functions}.
34269 @subsubheading Example
34274 -symbol-info-module-functions
34277 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34278 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34279 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
34280 description="void mod1::check_all(void);"@}]@}]@},
34282 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34283 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34284 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
34285 description="void mod2::check_var_i(void);"@}]@}]@},
34287 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34288 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34289 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
34290 description="void mod3::check_all(void);"@},
34291 @{line="27",name="mod3::check_mod2",type="void (void)",
34292 description="void mod3::check_mod2(void);"@}]@}]@},
34293 @{module="modmany",
34294 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34295 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34296 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
34297 description="void modmany::check_some(void);"@}]@}]@},
34299 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34300 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34301 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
34302 description="void moduse::check_all(void);"@},
34303 @{line="49",name="moduse::check_var_x",type="void (void)",
34304 description="void moduse::check_var_x(void);"@}]@}]@}]
34308 @subheading The @code{-symbol-info-module-variables} Command
34309 @findex -symbol-info-module-variables
34310 @anchor{-symbol-info-module-variables}
34312 @subsubheading Synopsis
34315 -symbol-info-module-variables [--module @var{module_regexp}]
34316 [--name @var{name_regexp}]
34317 [--type @var{type_regexp}]
34321 Return a list containing the names of all known variables within all
34322 know Fortran modules. The variables are grouped by source file and
34323 containing module, and shown with the line number on which each
34324 variable is defined.
34326 The option @code{--module} only returns results for modules matching
34327 @var{module_regexp}. The option @code{--name} only returns variables
34328 whose name matches @var{name_regexp}, and @code{--type} only returns
34329 variables whose type matches @var{type_regexp}.
34331 @subsubheading @value{GDBN} Command
34333 The corresponding @value{GDBN} command is @samp{info module variables}.
34335 @subsubheading Example
34340 -symbol-info-module-variables
34343 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34344 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34345 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
34346 description="integer(kind=4) mod1::var_const;"@},
34347 @{line="17",name="mod1::var_i",type="integer(kind=4)",
34348 description="integer(kind=4) mod1::var_i;"@}]@}]@},
34350 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34351 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34352 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
34353 description="integer(kind=4) mod2::var_i;"@}]@}]@},
34355 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34356 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34357 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
34358 description="integer(kind=4) mod3::mod1;"@},
34359 @{line="17",name="mod3::mod2",type="integer(kind=4)",
34360 description="integer(kind=4) mod3::mod2;"@},
34361 @{line="19",name="mod3::var_i",type="integer(kind=4)",
34362 description="integer(kind=4) mod3::var_i;"@}]@}]@},
34363 @{module="modmany",
34364 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34365 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34366 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
34367 description="integer(kind=4) modmany::var_a;"@},
34368 @{line="33",name="modmany::var_b",type="integer(kind=4)",
34369 description="integer(kind=4) modmany::var_b;"@},
34370 @{line="33",name="modmany::var_c",type="integer(kind=4)",
34371 description="integer(kind=4) modmany::var_c;"@},
34372 @{line="33",name="modmany::var_i",type="integer(kind=4)",
34373 description="integer(kind=4) modmany::var_i;"@}]@}]@},
34375 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34376 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34377 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
34378 description="integer(kind=4) moduse::var_x;"@},
34379 @{line="42",name="moduse::var_y",type="integer(kind=4)",
34380 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
34384 @subheading The @code{-symbol-info-modules} Command
34385 @findex -symbol-info-modules
34386 @anchor{-symbol-info-modules}
34388 @subsubheading Synopsis
34391 -symbol-info-modules [--name @var{name_regexp}]
34392 [--max-results @var{limit}]
34397 Return a list containing the names of all known Fortran modules. The
34398 modules are grouped by source file, and shown with the line number on
34399 which each modules is defined.
34401 The option @code{--name} allows the modules returned to be filtered
34402 based the name of the module.
34404 The option @code{--max-results} restricts the command to return no
34405 more than @var{limit} results. If exactly @var{limit} results are
34406 returned then there might be additional results available if a higher
34409 @subsubheading @value{GDBN} Command
34411 The corresponding @value{GDBN} command is @samp{info modules}.
34413 @subsubheading Example
34417 -symbol-info-modules
34420 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34421 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34422 symbols=[@{line="16",name="mod1"@},
34423 @{line="22",name="mod2"@}]@},
34424 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34425 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34426 symbols=[@{line="16",name="mod3"@},
34427 @{line="22",name="modmany"@},
34428 @{line="26",name="moduse"@}]@}]@}
34432 -symbol-info-modules --name mod[123]
34435 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34436 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34437 symbols=[@{line="16",name="mod1"@},
34438 @{line="22",name="mod2"@}]@},
34439 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34440 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34441 symbols=[@{line="16",name="mod3"@}]@}]@}
34445 @subheading The @code{-symbol-info-types} Command
34446 @findex -symbol-info-types
34447 @anchor{-symbol-info-types}
34449 @subsubheading Synopsis
34452 -symbol-info-types [--name @var{name_regexp}]
34453 [--max-results @var{limit}]
34458 Return a list of all defined types. The types are grouped by source
34459 file, and shown with the line number on which each user defined type
34460 is defined. Some base types are not defined in the source code but
34461 are added to the debug information by the compiler, for example
34462 @code{int}, @code{float}, etc.; these types do not have an associated
34465 The option @code{--name} allows the list of types returned to be
34468 The option @code{--max-results} restricts the command to return no
34469 more than @var{limit} results. If exactly @var{limit} results are
34470 returned then there might be additional results available if a higher
34473 @subsubheading @value{GDBN} Command
34475 The corresponding @value{GDBN} command is @samp{info types}.
34477 @subsubheading Example
34484 [@{filename="gdb.mi/mi-sym-info-1.c",
34485 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34486 symbols=[@{name="float"@},
34488 @{line="27",name="typedef int my_int_t;"@}]@},
34489 @{filename="gdb.mi/mi-sym-info-2.c",
34490 fullname="/project/gdb.mi/mi-sym-info-2.c",
34491 symbols=[@{line="24",name="typedef float another_float_t;"@},
34492 @{line="23",name="typedef int another_int_t;"@},
34494 @{name="int"@}]@}]@}
34498 -symbol-info-types --name _int_
34501 [@{filename="gdb.mi/mi-sym-info-1.c",
34502 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34503 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
34504 @{filename="gdb.mi/mi-sym-info-2.c",
34505 fullname="/project/gdb.mi/mi-sym-info-2.c",
34506 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
34510 @subheading The @code{-symbol-info-variables} Command
34511 @findex -symbol-info-variables
34512 @anchor{-symbol-info-variables}
34514 @subsubheading Synopsis
34517 -symbol-info-variables [--include-nondebug]
34518 [--type @var{type_regexp}]
34519 [--name @var{name_regexp}]
34520 [--max-results @var{limit}]
34525 Return a list containing the names and types for all global variables
34526 taken from the debug information. The variables are grouped by source
34527 file, and shown with the line number on which each variable is
34530 The @code{--include-nondebug} option causes the output to include
34531 data symbols from the symbol table.
34533 The options @code{--type} and @code{--name} allow the symbols returned
34534 to be filtered based on either the name of the variable, or the type
34537 The option @code{--max-results} restricts the command to return no
34538 more than @var{limit} results. If exactly @var{limit} results are
34539 returned then there might be additional results available if a higher
34542 @subsubheading @value{GDBN} Command
34544 The corresponding @value{GDBN} command is @samp{info variables}.
34546 @subsubheading Example
34550 -symbol-info-variables
34553 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34554 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34555 symbols=[@{line="25",name="global_f1",type="float",
34556 description="static float global_f1;"@},
34557 @{line="24",name="global_i1",type="int",
34558 description="static int global_i1;"@}]@},
34559 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34560 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34561 symbols=[@{line="21",name="global_f2",type="int",
34562 description="int global_f2;"@},
34563 @{line="20",name="global_i2",type="int",
34564 description="int global_i2;"@},
34565 @{line="19",name="global_f1",type="float",
34566 description="static float global_f1;"@},
34567 @{line="18",name="global_i1",type="int",
34568 description="static int global_i1;"@}]@}]@}
34572 -symbol-info-variables --name f1
34575 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34576 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34577 symbols=[@{line="25",name="global_f1",type="float",
34578 description="static float global_f1;"@}]@},
34579 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34580 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34581 symbols=[@{line="19",name="global_f1",type="float",
34582 description="static float global_f1;"@}]@}]@}
34586 -symbol-info-variables --type float
34589 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34590 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34591 symbols=[@{line="25",name="global_f1",type="float",
34592 description="static float global_f1;"@}]@},
34593 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34594 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34595 symbols=[@{line="19",name="global_f1",type="float",
34596 description="static float global_f1;"@}]@}]@}
34600 -symbol-info-variables --include-nondebug
34603 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34604 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34605 symbols=[@{line="25",name="global_f1",type="float",
34606 description="static float global_f1;"@},
34607 @{line="24",name="global_i1",type="int",
34608 description="static int global_i1;"@}]@},
34609 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34610 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34611 symbols=[@{line="21",name="global_f2",type="int",
34612 description="int global_f2;"@},
34613 @{line="20",name="global_i2",type="int",
34614 description="int global_i2;"@},
34615 @{line="19",name="global_f1",type="float",
34616 description="static float global_f1;"@},
34617 @{line="18",name="global_i1",type="int",
34618 description="static int global_i1;"@}]@}],
34620 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
34621 @{address="0x00000000004005d8",name="__dso_handle"@}
34628 @subheading The @code{-symbol-info-line} Command
34629 @findex -symbol-info-line
34631 @subsubheading Synopsis
34637 Show the core addresses of the code for a source line.
34639 @subsubheading @value{GDBN} Command
34641 The corresponding @value{GDBN} command is @samp{info line}.
34642 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34644 @subsubheading Example
34648 @subheading The @code{-symbol-info-symbol} Command
34649 @findex -symbol-info-symbol
34651 @subsubheading Synopsis
34654 -symbol-info-symbol @var{addr}
34657 Describe what symbol is at location @var{addr}.
34659 @subsubheading @value{GDBN} Command
34661 The corresponding @value{GDBN} command is @samp{info symbol}.
34663 @subsubheading Example
34667 @subheading The @code{-symbol-list-functions} Command
34668 @findex -symbol-list-functions
34670 @subsubheading Synopsis
34673 -symbol-list-functions
34676 List the functions in the executable.
34678 @subsubheading @value{GDBN} Command
34680 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34681 @samp{gdb_search} in @code{gdbtk}.
34683 @subsubheading Example
34688 @subheading The @code{-symbol-list-lines} Command
34689 @findex -symbol-list-lines
34691 @subsubheading Synopsis
34694 -symbol-list-lines @var{filename}
34697 Print the list of lines that contain code and their associated program
34698 addresses for the given source filename. The entries are sorted in
34699 ascending PC order.
34701 @subsubheading @value{GDBN} Command
34703 There is no corresponding @value{GDBN} command.
34705 @subsubheading Example
34708 -symbol-list-lines basics.c
34709 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34715 @subheading The @code{-symbol-list-types} Command
34716 @findex -symbol-list-types
34718 @subsubheading Synopsis
34724 List all the type names.
34726 @subsubheading @value{GDBN} Command
34728 The corresponding commands are @samp{info types} in @value{GDBN},
34729 @samp{gdb_search} in @code{gdbtk}.
34731 @subsubheading Example
34735 @subheading The @code{-symbol-list-variables} Command
34736 @findex -symbol-list-variables
34738 @subsubheading Synopsis
34741 -symbol-list-variables
34744 List all the global and static variable names.
34746 @subsubheading @value{GDBN} Command
34748 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34750 @subsubheading Example
34754 @subheading The @code{-symbol-locate} Command
34755 @findex -symbol-locate
34757 @subsubheading Synopsis
34763 @subsubheading @value{GDBN} Command
34765 @samp{gdb_loc} in @code{gdbtk}.
34767 @subsubheading Example
34771 @subheading The @code{-symbol-type} Command
34772 @findex -symbol-type
34774 @subsubheading Synopsis
34777 -symbol-type @var{variable}
34780 Show type of @var{variable}.
34782 @subsubheading @value{GDBN} Command
34784 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34785 @samp{gdb_obj_variable}.
34787 @subsubheading Example
34792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34793 @node GDB/MI File Commands
34794 @section @sc{gdb/mi} File Commands
34796 This section describes the GDB/MI commands to specify executable file names
34797 and to read in and obtain symbol table information.
34799 @subheading The @code{-file-exec-and-symbols} Command
34800 @findex -file-exec-and-symbols
34802 @subsubheading Synopsis
34805 -file-exec-and-symbols @var{file}
34808 Specify the executable file to be debugged. This file is the one from
34809 which the symbol table is also read. If no file is specified, the
34810 command clears the executable and symbol information. If breakpoints
34811 are set when using this command with no arguments, @value{GDBN} will produce
34812 error messages. Otherwise, no output is produced, except a completion
34815 @subsubheading @value{GDBN} Command
34817 The corresponding @value{GDBN} command is @samp{file}.
34819 @subsubheading Example
34823 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34829 @subheading The @code{-file-exec-file} Command
34830 @findex -file-exec-file
34832 @subsubheading Synopsis
34835 -file-exec-file @var{file}
34838 Specify the executable file to be debugged. Unlike
34839 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34840 from this file. If used without argument, @value{GDBN} clears the information
34841 about the executable file. No output is produced, except a completion
34844 @subsubheading @value{GDBN} Command
34846 The corresponding @value{GDBN} command is @samp{exec-file}.
34848 @subsubheading Example
34852 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34859 @subheading The @code{-file-list-exec-sections} Command
34860 @findex -file-list-exec-sections
34862 @subsubheading Synopsis
34865 -file-list-exec-sections
34868 List the sections of the current executable file.
34870 @subsubheading @value{GDBN} Command
34872 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34873 information as this command. @code{gdbtk} has a corresponding command
34874 @samp{gdb_load_info}.
34876 @subsubheading Example
34881 @subheading The @code{-file-list-exec-source-file} Command
34882 @findex -file-list-exec-source-file
34884 @subsubheading Synopsis
34887 -file-list-exec-source-file
34890 List the line number, the current source file, and the absolute path
34891 to the current source file for the current executable. The macro
34892 information field has a value of @samp{1} or @samp{0} depending on
34893 whether or not the file includes preprocessor macro information.
34895 @subsubheading @value{GDBN} Command
34897 The @value{GDBN} equivalent is @samp{info source}
34899 @subsubheading Example
34903 123-file-list-exec-source-file
34904 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34909 @subheading The @code{-file-list-exec-source-files} Command
34910 @findex -file-list-exec-source-files
34912 @subsubheading Synopsis
34915 -file-list-exec-source-files
34918 List the source files for the current executable.
34920 It will always output both the filename and fullname (absolute file
34921 name) of a source file.
34923 @subsubheading @value{GDBN} Command
34925 The @value{GDBN} equivalent is @samp{info sources}.
34926 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34928 @subsubheading Example
34931 -file-list-exec-source-files
34933 @{file=foo.c,fullname=/home/foo.c@},
34934 @{file=/home/bar.c,fullname=/home/bar.c@},
34935 @{file=gdb_could_not_find_fullpath.c@}]
34939 @subheading The @code{-file-list-shared-libraries} Command
34940 @findex -file-list-shared-libraries
34942 @subsubheading Synopsis
34945 -file-list-shared-libraries [ @var{regexp} ]
34948 List the shared libraries in the program.
34949 With a regular expression @var{regexp}, only those libraries whose
34950 names match @var{regexp} are listed.
34952 @subsubheading @value{GDBN} Command
34954 The corresponding @value{GDBN} command is @samp{info shared}. The fields
34955 have a similar meaning to the @code{=library-loaded} notification.
34956 The @code{ranges} field specifies the multiple segments belonging to this
34957 library. Each range has the following fields:
34961 The address defining the inclusive lower bound of the segment.
34963 The address defining the exclusive upper bound of the segment.
34966 @subsubheading Example
34969 -file-list-exec-source-files
34970 ^done,shared-libraries=[
34971 @{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"@}]@},
34972 @{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"@}]@}]
34978 @subheading The @code{-file-list-symbol-files} Command
34979 @findex -file-list-symbol-files
34981 @subsubheading Synopsis
34984 -file-list-symbol-files
34989 @subsubheading @value{GDBN} Command
34991 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34993 @subsubheading Example
34998 @subheading The @code{-file-symbol-file} Command
34999 @findex -file-symbol-file
35001 @subsubheading Synopsis
35004 -file-symbol-file @var{file}
35007 Read symbol table info from the specified @var{file} argument. When
35008 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35009 produced, except for a completion notification.
35011 @subsubheading @value{GDBN} Command
35013 The corresponding @value{GDBN} command is @samp{symbol-file}.
35015 @subsubheading Example
35019 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35026 @node GDB/MI Memory Overlay Commands
35027 @section @sc{gdb/mi} Memory Overlay Commands
35029 The memory overlay commands are not implemented.
35031 @c @subheading -overlay-auto
35033 @c @subheading -overlay-list-mapping-state
35035 @c @subheading -overlay-list-overlays
35037 @c @subheading -overlay-map
35039 @c @subheading -overlay-off
35041 @c @subheading -overlay-on
35043 @c @subheading -overlay-unmap
35045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35046 @node GDB/MI Signal Handling Commands
35047 @section @sc{gdb/mi} Signal Handling Commands
35049 Signal handling commands are not implemented.
35051 @c @subheading -signal-handle
35053 @c @subheading -signal-list-handle-actions
35055 @c @subheading -signal-list-signal-types
35059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35060 @node GDB/MI Target Manipulation
35061 @section @sc{gdb/mi} Target Manipulation Commands
35064 @subheading The @code{-target-attach} Command
35065 @findex -target-attach
35067 @subsubheading Synopsis
35070 -target-attach @var{pid} | @var{gid} | @var{file}
35073 Attach to a process @var{pid} or a file @var{file} outside of
35074 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
35075 group, the id previously returned by
35076 @samp{-list-thread-groups --available} must be used.
35078 @subsubheading @value{GDBN} Command
35080 The corresponding @value{GDBN} command is @samp{attach}.
35082 @subsubheading Example
35086 =thread-created,id="1"
35087 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
35093 @subheading The @code{-target-compare-sections} Command
35094 @findex -target-compare-sections
35096 @subsubheading Synopsis
35099 -target-compare-sections [ @var{section} ]
35102 Compare data of section @var{section} on target to the exec file.
35103 Without the argument, all sections are compared.
35105 @subsubheading @value{GDBN} Command
35107 The @value{GDBN} equivalent is @samp{compare-sections}.
35109 @subsubheading Example
35114 @subheading The @code{-target-detach} Command
35115 @findex -target-detach
35117 @subsubheading Synopsis
35120 -target-detach [ @var{pid} | @var{gid} ]
35123 Detach from the remote target which normally resumes its execution.
35124 If either @var{pid} or @var{gid} is specified, detaches from either
35125 the specified process, or specified thread group. There's no output.
35127 @subsubheading @value{GDBN} Command
35129 The corresponding @value{GDBN} command is @samp{detach}.
35131 @subsubheading Example
35141 @subheading The @code{-target-disconnect} Command
35142 @findex -target-disconnect
35144 @subsubheading Synopsis
35150 Disconnect from the remote target. There's no output and the target is
35151 generally not resumed.
35153 @subsubheading @value{GDBN} Command
35155 The corresponding @value{GDBN} command is @samp{disconnect}.
35157 @subsubheading Example
35167 @subheading The @code{-target-download} Command
35168 @findex -target-download
35170 @subsubheading Synopsis
35176 Loads the executable onto the remote target.
35177 It prints out an update message every half second, which includes the fields:
35181 The name of the section.
35183 The size of what has been sent so far for that section.
35185 The size of the section.
35187 The total size of what was sent so far (the current and the previous sections).
35189 The size of the overall executable to download.
35193 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
35194 @sc{gdb/mi} Output Syntax}).
35196 In addition, it prints the name and size of the sections, as they are
35197 downloaded. These messages include the following fields:
35201 The name of the section.
35203 The size of the section.
35205 The size of the overall executable to download.
35209 At the end, a summary is printed.
35211 @subsubheading @value{GDBN} Command
35213 The corresponding @value{GDBN} command is @samp{load}.
35215 @subsubheading Example
35217 Note: each status message appears on a single line. Here the messages
35218 have been broken down so that they can fit onto a page.
35223 +download,@{section=".text",section-size="6668",total-size="9880"@}
35224 +download,@{section=".text",section-sent="512",section-size="6668",
35225 total-sent="512",total-size="9880"@}
35226 +download,@{section=".text",section-sent="1024",section-size="6668",
35227 total-sent="1024",total-size="9880"@}
35228 +download,@{section=".text",section-sent="1536",section-size="6668",
35229 total-sent="1536",total-size="9880"@}
35230 +download,@{section=".text",section-sent="2048",section-size="6668",
35231 total-sent="2048",total-size="9880"@}
35232 +download,@{section=".text",section-sent="2560",section-size="6668",
35233 total-sent="2560",total-size="9880"@}
35234 +download,@{section=".text",section-sent="3072",section-size="6668",
35235 total-sent="3072",total-size="9880"@}
35236 +download,@{section=".text",section-sent="3584",section-size="6668",
35237 total-sent="3584",total-size="9880"@}
35238 +download,@{section=".text",section-sent="4096",section-size="6668",
35239 total-sent="4096",total-size="9880"@}
35240 +download,@{section=".text",section-sent="4608",section-size="6668",
35241 total-sent="4608",total-size="9880"@}
35242 +download,@{section=".text",section-sent="5120",section-size="6668",
35243 total-sent="5120",total-size="9880"@}
35244 +download,@{section=".text",section-sent="5632",section-size="6668",
35245 total-sent="5632",total-size="9880"@}
35246 +download,@{section=".text",section-sent="6144",section-size="6668",
35247 total-sent="6144",total-size="9880"@}
35248 +download,@{section=".text",section-sent="6656",section-size="6668",
35249 total-sent="6656",total-size="9880"@}
35250 +download,@{section=".init",section-size="28",total-size="9880"@}
35251 +download,@{section=".fini",section-size="28",total-size="9880"@}
35252 +download,@{section=".data",section-size="3156",total-size="9880"@}
35253 +download,@{section=".data",section-sent="512",section-size="3156",
35254 total-sent="7236",total-size="9880"@}
35255 +download,@{section=".data",section-sent="1024",section-size="3156",
35256 total-sent="7748",total-size="9880"@}
35257 +download,@{section=".data",section-sent="1536",section-size="3156",
35258 total-sent="8260",total-size="9880"@}
35259 +download,@{section=".data",section-sent="2048",section-size="3156",
35260 total-sent="8772",total-size="9880"@}
35261 +download,@{section=".data",section-sent="2560",section-size="3156",
35262 total-sent="9284",total-size="9880"@}
35263 +download,@{section=".data",section-sent="3072",section-size="3156",
35264 total-sent="9796",total-size="9880"@}
35265 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
35272 @subheading The @code{-target-exec-status} Command
35273 @findex -target-exec-status
35275 @subsubheading Synopsis
35278 -target-exec-status
35281 Provide information on the state of the target (whether it is running or
35282 not, for instance).
35284 @subsubheading @value{GDBN} Command
35286 There's no equivalent @value{GDBN} command.
35288 @subsubheading Example
35292 @subheading The @code{-target-list-available-targets} Command
35293 @findex -target-list-available-targets
35295 @subsubheading Synopsis
35298 -target-list-available-targets
35301 List the possible targets to connect to.
35303 @subsubheading @value{GDBN} Command
35305 The corresponding @value{GDBN} command is @samp{help target}.
35307 @subsubheading Example
35311 @subheading The @code{-target-list-current-targets} Command
35312 @findex -target-list-current-targets
35314 @subsubheading Synopsis
35317 -target-list-current-targets
35320 Describe the current target.
35322 @subsubheading @value{GDBN} Command
35324 The corresponding information is printed by @samp{info file} (among
35327 @subsubheading Example
35331 @subheading The @code{-target-list-parameters} Command
35332 @findex -target-list-parameters
35334 @subsubheading Synopsis
35337 -target-list-parameters
35343 @subsubheading @value{GDBN} Command
35347 @subsubheading Example
35350 @subheading The @code{-target-flash-erase} Command
35351 @findex -target-flash-erase
35353 @subsubheading Synopsis
35356 -target-flash-erase
35359 Erases all known flash memory regions on the target.
35361 The corresponding @value{GDBN} command is @samp{flash-erase}.
35363 The output is a list of flash regions that have been erased, with starting
35364 addresses and memory region sizes.
35368 -target-flash-erase
35369 ^done,erased-regions=@{address="0x0",size="0x40000"@}
35373 @subheading The @code{-target-select} Command
35374 @findex -target-select
35376 @subsubheading Synopsis
35379 -target-select @var{type} @var{parameters @dots{}}
35382 Connect @value{GDBN} to the remote target. This command takes two args:
35386 The type of target, for instance @samp{remote}, etc.
35387 @item @var{parameters}
35388 Device names, host names and the like. @xref{Target Commands, ,
35389 Commands for Managing Targets}, for more details.
35392 The output is a connection notification, followed by the address at
35393 which the target program is, in the following form:
35396 ^connected,addr="@var{address}",func="@var{function name}",
35397 args=[@var{arg list}]
35400 @subsubheading @value{GDBN} Command
35402 The corresponding @value{GDBN} command is @samp{target}.
35404 @subsubheading Example
35408 -target-select remote /dev/ttya
35409 ^connected,addr="0xfe00a300",func="??",args=[]
35413 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35414 @node GDB/MI File Transfer Commands
35415 @section @sc{gdb/mi} File Transfer Commands
35418 @subheading The @code{-target-file-put} Command
35419 @findex -target-file-put
35421 @subsubheading Synopsis
35424 -target-file-put @var{hostfile} @var{targetfile}
35427 Copy file @var{hostfile} from the host system (the machine running
35428 @value{GDBN}) to @var{targetfile} on the target system.
35430 @subsubheading @value{GDBN} Command
35432 The corresponding @value{GDBN} command is @samp{remote put}.
35434 @subsubheading Example
35438 -target-file-put localfile remotefile
35444 @subheading The @code{-target-file-get} Command
35445 @findex -target-file-get
35447 @subsubheading Synopsis
35450 -target-file-get @var{targetfile} @var{hostfile}
35453 Copy file @var{targetfile} from the target system to @var{hostfile}
35454 on the host system.
35456 @subsubheading @value{GDBN} Command
35458 The corresponding @value{GDBN} command is @samp{remote get}.
35460 @subsubheading Example
35464 -target-file-get remotefile localfile
35470 @subheading The @code{-target-file-delete} Command
35471 @findex -target-file-delete
35473 @subsubheading Synopsis
35476 -target-file-delete @var{targetfile}
35479 Delete @var{targetfile} from the target system.
35481 @subsubheading @value{GDBN} Command
35483 The corresponding @value{GDBN} command is @samp{remote delete}.
35485 @subsubheading Example
35489 -target-file-delete remotefile
35495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35496 @node GDB/MI Ada Exceptions Commands
35497 @section Ada Exceptions @sc{gdb/mi} Commands
35499 @subheading The @code{-info-ada-exceptions} Command
35500 @findex -info-ada-exceptions
35502 @subsubheading Synopsis
35505 -info-ada-exceptions [ @var{regexp}]
35508 List all Ada exceptions defined within the program being debugged.
35509 With a regular expression @var{regexp}, only those exceptions whose
35510 names match @var{regexp} are listed.
35512 @subsubheading @value{GDBN} Command
35514 The corresponding @value{GDBN} command is @samp{info exceptions}.
35516 @subsubheading Result
35518 The result is a table of Ada exceptions. The following columns are
35519 defined for each exception:
35523 The name of the exception.
35526 The address of the exception.
35530 @subsubheading Example
35533 -info-ada-exceptions aint
35534 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35535 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35536 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35537 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35538 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35541 @subheading Catching Ada Exceptions
35543 The commands describing how to ask @value{GDBN} to stop when a program
35544 raises an exception are described at @ref{Ada Exception GDB/MI
35545 Catchpoint Commands}.
35548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35549 @node GDB/MI Support Commands
35550 @section @sc{gdb/mi} Support Commands
35552 Since new commands and features get regularly added to @sc{gdb/mi},
35553 some commands are available to help front-ends query the debugger
35554 about support for these capabilities. Similarly, it is also possible
35555 to query @value{GDBN} about target support of certain features.
35557 @subheading The @code{-info-gdb-mi-command} Command
35558 @cindex @code{-info-gdb-mi-command}
35559 @findex -info-gdb-mi-command
35561 @subsubheading Synopsis
35564 -info-gdb-mi-command @var{cmd_name}
35567 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35569 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35570 is technically not part of the command name (@pxref{GDB/MI Input
35571 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35572 for ease of use, this command also accepts the form with the leading
35575 @subsubheading @value{GDBN} Command
35577 There is no corresponding @value{GDBN} command.
35579 @subsubheading Result
35581 The result is a tuple. There is currently only one field:
35585 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35586 @code{"false"} otherwise.
35590 @subsubheading Example
35592 Here is an example where the @sc{gdb/mi} command does not exist:
35595 -info-gdb-mi-command unsupported-command
35596 ^done,command=@{exists="false"@}
35600 And here is an example where the @sc{gdb/mi} command is known
35604 -info-gdb-mi-command symbol-list-lines
35605 ^done,command=@{exists="true"@}
35608 @subheading The @code{-list-features} Command
35609 @findex -list-features
35610 @cindex supported @sc{gdb/mi} features, list
35612 Returns a list of particular features of the MI protocol that
35613 this version of gdb implements. A feature can be a command,
35614 or a new field in an output of some command, or even an
35615 important bugfix. While a frontend can sometimes detect presence
35616 of a feature at runtime, it is easier to perform detection at debugger
35619 The command returns a list of strings, with each string naming an
35620 available feature. Each returned string is just a name, it does not
35621 have any internal structure. The list of possible feature names
35627 (gdb) -list-features
35628 ^done,result=["feature1","feature2"]
35631 The current list of features is:
35634 @item frozen-varobjs
35635 Indicates support for the @code{-var-set-frozen} command, as well
35636 as possible presence of the @code{frozen} field in the output
35637 of @code{-varobj-create}.
35638 @item pending-breakpoints
35639 Indicates support for the @option{-f} option to the @code{-break-insert}
35642 Indicates Python scripting support, Python-based
35643 pretty-printing commands, and possible presence of the
35644 @samp{display_hint} field in the output of @code{-var-list-children}
35646 Indicates support for the @code{-thread-info} command.
35647 @item data-read-memory-bytes
35648 Indicates support for the @code{-data-read-memory-bytes} and the
35649 @code{-data-write-memory-bytes} commands.
35650 @item breakpoint-notifications
35651 Indicates that changes to breakpoints and breakpoints created via the
35652 CLI will be announced via async records.
35653 @item ada-task-info
35654 Indicates support for the @code{-ada-task-info} command.
35655 @item language-option
35656 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35657 option (@pxref{Context management}).
35658 @item info-gdb-mi-command
35659 Indicates support for the @code{-info-gdb-mi-command} command.
35660 @item undefined-command-error-code
35661 Indicates support for the "undefined-command" error code in error result
35662 records, produced when trying to execute an undefined @sc{gdb/mi} command
35663 (@pxref{GDB/MI Result Records}).
35664 @item exec-run-start-option
35665 Indicates that the @code{-exec-run} command supports the @option{--start}
35666 option (@pxref{GDB/MI Program Execution}).
35667 @item data-disassemble-a-option
35668 Indicates that the @code{-data-disassemble} command supports the @option{-a}
35669 option (@pxref{GDB/MI Data Manipulation}).
35672 @subheading The @code{-list-target-features} Command
35673 @findex -list-target-features
35675 Returns a list of particular features that are supported by the
35676 target. Those features affect the permitted MI commands, but
35677 unlike the features reported by the @code{-list-features} command, the
35678 features depend on which target GDB is using at the moment. Whenever
35679 a target can change, due to commands such as @code{-target-select},
35680 @code{-target-attach} or @code{-exec-run}, the list of target features
35681 may change, and the frontend should obtain it again.
35685 (gdb) -list-target-features
35686 ^done,result=["async"]
35689 The current list of features is:
35693 Indicates that the target is capable of asynchronous command
35694 execution, which means that @value{GDBN} will accept further commands
35695 while the target is running.
35698 Indicates that the target is capable of reverse execution.
35699 @xref{Reverse Execution}, for more information.
35703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35704 @node GDB/MI Miscellaneous Commands
35705 @section Miscellaneous @sc{gdb/mi} Commands
35707 @c @subheading -gdb-complete
35709 @subheading The @code{-gdb-exit} Command
35712 @subsubheading Synopsis
35718 Exit @value{GDBN} immediately.
35720 @subsubheading @value{GDBN} Command
35722 Approximately corresponds to @samp{quit}.
35724 @subsubheading Example
35734 @subheading The @code{-exec-abort} Command
35735 @findex -exec-abort
35737 @subsubheading Synopsis
35743 Kill the inferior running program.
35745 @subsubheading @value{GDBN} Command
35747 The corresponding @value{GDBN} command is @samp{kill}.
35749 @subsubheading Example
35754 @subheading The @code{-gdb-set} Command
35757 @subsubheading Synopsis
35763 Set an internal @value{GDBN} variable.
35764 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35766 @subsubheading @value{GDBN} Command
35768 The corresponding @value{GDBN} command is @samp{set}.
35770 @subsubheading Example
35780 @subheading The @code{-gdb-show} Command
35783 @subsubheading Synopsis
35789 Show the current value of a @value{GDBN} variable.
35791 @subsubheading @value{GDBN} Command
35793 The corresponding @value{GDBN} command is @samp{show}.
35795 @subsubheading Example
35804 @c @subheading -gdb-source
35807 @subheading The @code{-gdb-version} Command
35808 @findex -gdb-version
35810 @subsubheading Synopsis
35816 Show version information for @value{GDBN}. Used mostly in testing.
35818 @subsubheading @value{GDBN} Command
35820 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35821 default shows this information when you start an interactive session.
35823 @subsubheading Example
35825 @c This example modifies the actual output from GDB to avoid overfull
35831 ~Copyright 2000 Free Software Foundation, Inc.
35832 ~GDB is free software, covered by the GNU General Public License, and
35833 ~you are welcome to change it and/or distribute copies of it under
35834 ~ certain conditions.
35835 ~Type "show copying" to see the conditions.
35836 ~There is absolutely no warranty for GDB. Type "show warranty" for
35838 ~This GDB was configured as
35839 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35844 @subheading The @code{-list-thread-groups} Command
35845 @findex -list-thread-groups
35847 @subheading Synopsis
35850 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35853 Lists thread groups (@pxref{Thread groups}). When a single thread
35854 group is passed as the argument, lists the children of that group.
35855 When several thread group are passed, lists information about those
35856 thread groups. Without any parameters, lists information about all
35857 top-level thread groups.
35859 Normally, thread groups that are being debugged are reported.
35860 With the @samp{--available} option, @value{GDBN} reports thread groups
35861 available on the target.
35863 The output of this command may have either a @samp{threads} result or
35864 a @samp{groups} result. The @samp{thread} result has a list of tuples
35865 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35866 Information}). The @samp{groups} result has a list of tuples as value,
35867 each tuple describing a thread group. If top-level groups are
35868 requested (that is, no parameter is passed), or when several groups
35869 are passed, the output always has a @samp{groups} result. The format
35870 of the @samp{group} result is described below.
35872 To reduce the number of roundtrips it's possible to list thread groups
35873 together with their children, by passing the @samp{--recurse} option
35874 and the recursion depth. Presently, only recursion depth of 1 is
35875 permitted. If this option is present, then every reported thread group
35876 will also include its children, either as @samp{group} or
35877 @samp{threads} field.
35879 In general, any combination of option and parameters is permitted, with
35880 the following caveats:
35884 When a single thread group is passed, the output will typically
35885 be the @samp{threads} result. Because threads may not contain
35886 anything, the @samp{recurse} option will be ignored.
35889 When the @samp{--available} option is passed, limited information may
35890 be available. In particular, the list of threads of a process might
35891 be inaccessible. Further, specifying specific thread groups might
35892 not give any performance advantage over listing all thread groups.
35893 The frontend should assume that @samp{-list-thread-groups --available}
35894 is always an expensive operation and cache the results.
35898 The @samp{groups} result is a list of tuples, where each tuple may
35899 have the following fields:
35903 Identifier of the thread group. This field is always present.
35904 The identifier is an opaque string; frontends should not try to
35905 convert it to an integer, even though it might look like one.
35908 The type of the thread group. At present, only @samp{process} is a
35912 The target-specific process identifier. This field is only present
35913 for thread groups of type @samp{process} and only if the process exists.
35916 The exit code of this group's last exited thread, formatted in octal.
35917 This field is only present for thread groups of type @samp{process} and
35918 only if the process is not running.
35921 The number of children this thread group has. This field may be
35922 absent for an available thread group.
35925 This field has a list of tuples as value, each tuple describing a
35926 thread. It may be present if the @samp{--recurse} option is
35927 specified, and it's actually possible to obtain the threads.
35930 This field is a list of integers, each identifying a core that one
35931 thread of the group is running on. This field may be absent if
35932 such information is not available.
35935 The name of the executable file that corresponds to this thread group.
35936 The field is only present for thread groups of type @samp{process},
35937 and only if there is a corresponding executable file.
35941 @subheading Example
35945 -list-thread-groups
35946 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35947 -list-thread-groups 17
35948 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35949 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35950 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35951 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35952 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
35953 -list-thread-groups --available
35954 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35955 -list-thread-groups --available --recurse 1
35956 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35957 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35958 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35959 -list-thread-groups --available --recurse 1 17 18
35960 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35961 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35962 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35965 @subheading The @code{-info-os} Command
35968 @subsubheading Synopsis
35971 -info-os [ @var{type} ]
35974 If no argument is supplied, the command returns a table of available
35975 operating-system-specific information types. If one of these types is
35976 supplied as an argument @var{type}, then the command returns a table
35977 of data of that type.
35979 The types of information available depend on the target operating
35982 @subsubheading @value{GDBN} Command
35984 The corresponding @value{GDBN} command is @samp{info os}.
35986 @subsubheading Example
35988 When run on a @sc{gnu}/Linux system, the output will look something
35994 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
35995 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35996 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35997 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35998 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36000 item=@{col0="files",col1="Listing of all file descriptors",
36001 col2="File descriptors"@},
36002 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36003 col2="Kernel modules"@},
36004 item=@{col0="msg",col1="Listing of all message queues",
36005 col2="Message queues"@},
36006 item=@{col0="processes",col1="Listing of all processes",
36007 col2="Processes"@},
36008 item=@{col0="procgroups",col1="Listing of all process groups",
36009 col2="Process groups"@},
36010 item=@{col0="semaphores",col1="Listing of all semaphores",
36011 col2="Semaphores"@},
36012 item=@{col0="shm",col1="Listing of all shared-memory regions",
36013 col2="Shared-memory regions"@},
36014 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36016 item=@{col0="threads",col1="Listing of all threads",
36020 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36021 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36022 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36023 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36024 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36025 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36026 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36027 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36029 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36030 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36034 (Note that the MI output here includes a @code{"Title"} column that
36035 does not appear in command-line @code{info os}; this column is useful
36036 for MI clients that want to enumerate the types of data, such as in a
36037 popup menu, but is needless clutter on the command line, and
36038 @code{info os} omits it.)
36040 @subheading The @code{-add-inferior} Command
36041 @findex -add-inferior
36043 @subheading Synopsis
36049 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36050 inferior is not associated with any executable. Such association may
36051 be established with the @samp{-file-exec-and-symbols} command
36052 (@pxref{GDB/MI File Commands}). The command response has a single
36053 field, @samp{inferior}, whose value is the identifier of the
36054 thread group corresponding to the new inferior.
36056 @subheading Example
36061 ^done,inferior="i3"
36064 @subheading The @code{-interpreter-exec} Command
36065 @findex -interpreter-exec
36067 @subheading Synopsis
36070 -interpreter-exec @var{interpreter} @var{command}
36072 @anchor{-interpreter-exec}
36074 Execute the specified @var{command} in the given @var{interpreter}.
36076 @subheading @value{GDBN} Command
36078 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
36080 @subheading Example
36084 -interpreter-exec console "break main"
36085 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
36086 &"During symbol reading, bad structure-type format.\n"
36087 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
36092 @subheading The @code{-inferior-tty-set} Command
36093 @findex -inferior-tty-set
36095 @subheading Synopsis
36098 -inferior-tty-set /dev/pts/1
36101 Set terminal for future runs of the program being debugged.
36103 @subheading @value{GDBN} Command
36105 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
36107 @subheading Example
36111 -inferior-tty-set /dev/pts/1
36116 @subheading The @code{-inferior-tty-show} Command
36117 @findex -inferior-tty-show
36119 @subheading Synopsis
36125 Show terminal for future runs of program being debugged.
36127 @subheading @value{GDBN} Command
36129 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
36131 @subheading Example
36135 -inferior-tty-set /dev/pts/1
36139 ^done,inferior_tty_terminal="/dev/pts/1"
36143 @subheading The @code{-enable-timings} Command
36144 @findex -enable-timings
36146 @subheading Synopsis
36149 -enable-timings [yes | no]
36152 Toggle the printing of the wallclock, user and system times for an MI
36153 command as a field in its output. This command is to help frontend
36154 developers optimize the performance of their code. No argument is
36155 equivalent to @samp{yes}.
36157 @subheading @value{GDBN} Command
36161 @subheading Example
36169 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
36170 addr="0x080484ed",func="main",file="myprog.c",
36171 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
36173 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
36181 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
36182 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
36183 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
36184 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
36188 @subheading The @code{-complete} Command
36191 @subheading Synopsis
36194 -complete @var{command}
36197 Show a list of completions for partially typed CLI @var{command}.
36199 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
36200 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
36201 because @value{GDBN} is used remotely via a SSH connection.
36205 The result consists of two or three fields:
36209 This field contains the completed @var{command}. If @var{command}
36210 has no known completions, this field is omitted.
36213 This field contains a (possibly empty) array of matches. It is always present.
36215 @item max_completions_reached
36216 This field contains @code{1} if number of known completions is above
36217 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
36218 @code{0}. It is always present.
36222 @subheading @value{GDBN} Command
36224 The corresponding @value{GDBN} command is @samp{complete}.
36226 @subheading Example
36231 ^done,completion="break",
36232 matches=["break","break-range"],
36233 max_completions_reached="0"
36236 ^done,completion="b ma",
36237 matches=["b madvise","b main"],max_completions_reached="0"
36239 -complete "b push_b"
36240 ^done,completion="b push_back(",
36242 "b A::push_back(void*)",
36243 "b std::string::push_back(char)",
36244 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
36245 max_completions_reached="0"
36247 -complete "nonexist"
36248 ^done,matches=[],max_completions_reached="0"
36254 @chapter @value{GDBN} Annotations
36256 This chapter describes annotations in @value{GDBN}. Annotations were
36257 designed to interface @value{GDBN} to graphical user interfaces or other
36258 similar programs which want to interact with @value{GDBN} at a
36259 relatively high level.
36261 The annotation mechanism has largely been superseded by @sc{gdb/mi}
36265 This is Edition @value{EDITION}, @value{DATE}.
36269 * Annotations Overview:: What annotations are; the general syntax.
36270 * Server Prefix:: Issuing a command without affecting user state.
36271 * Prompting:: Annotations marking @value{GDBN}'s need for input.
36272 * Errors:: Annotations for error messages.
36273 * Invalidation:: Some annotations describe things now invalid.
36274 * Annotations for Running::
36275 Whether the program is running, how it stopped, etc.
36276 * Source Annotations:: Annotations describing source code.
36279 @node Annotations Overview
36280 @section What is an Annotation?
36281 @cindex annotations
36283 Annotations start with a newline character, two @samp{control-z}
36284 characters, and the name of the annotation. If there is no additional
36285 information associated with this annotation, the name of the annotation
36286 is followed immediately by a newline. If there is additional
36287 information, the name of the annotation is followed by a space, the
36288 additional information, and a newline. The additional information
36289 cannot contain newline characters.
36291 Any output not beginning with a newline and two @samp{control-z}
36292 characters denotes literal output from @value{GDBN}. Currently there is
36293 no need for @value{GDBN} to output a newline followed by two
36294 @samp{control-z} characters, but if there was such a need, the
36295 annotations could be extended with an @samp{escape} annotation which
36296 means those three characters as output.
36298 The annotation @var{level}, which is specified using the
36299 @option{--annotate} command line option (@pxref{Mode Options}), controls
36300 how much information @value{GDBN} prints together with its prompt,
36301 values of expressions, source lines, and other types of output. Level 0
36302 is for no annotations, level 1 is for use when @value{GDBN} is run as a
36303 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
36304 for programs that control @value{GDBN}, and level 2 annotations have
36305 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
36306 Interface, annotate, GDB's Obsolete Annotations}).
36309 @kindex set annotate
36310 @item set annotate @var{level}
36311 The @value{GDBN} command @code{set annotate} sets the level of
36312 annotations to the specified @var{level}.
36314 @item show annotate
36315 @kindex show annotate
36316 Show the current annotation level.
36319 This chapter describes level 3 annotations.
36321 A simple example of starting up @value{GDBN} with annotations is:
36324 $ @kbd{gdb --annotate=3}
36326 Copyright 2003 Free Software Foundation, Inc.
36327 GDB is free software, covered by the GNU General Public License,
36328 and you are welcome to change it and/or distribute copies of it
36329 under certain conditions.
36330 Type "show copying" to see the conditions.
36331 There is absolutely no warranty for GDB. Type "show warranty"
36333 This GDB was configured as "i386-pc-linux-gnu"
36344 Here @samp{quit} is input to @value{GDBN}; the rest is output from
36345 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
36346 denotes a @samp{control-z} character) are annotations; the rest is
36347 output from @value{GDBN}.
36349 @node Server Prefix
36350 @section The Server Prefix
36351 @cindex server prefix
36353 If you prefix a command with @samp{server } then it will not affect
36354 the command history, nor will it affect @value{GDBN}'s notion of which
36355 command to repeat if @key{RET} is pressed on a line by itself. This
36356 means that commands can be run behind a user's back by a front-end in
36357 a transparent manner.
36359 The @code{server } prefix does not affect the recording of values into
36360 the value history; to print a value without recording it into the
36361 value history, use the @code{output} command instead of the
36362 @code{print} command.
36364 Using this prefix also disables confirmation requests
36365 (@pxref{confirmation requests}).
36368 @section Annotation for @value{GDBN} Input
36370 @cindex annotations for prompts
36371 When @value{GDBN} prompts for input, it annotates this fact so it is possible
36372 to know when to send output, when the output from a given command is
36375 Different kinds of input each have a different @dfn{input type}. Each
36376 input type has three annotations: a @code{pre-} annotation, which
36377 denotes the beginning of any prompt which is being output, a plain
36378 annotation, which denotes the end of the prompt, and then a @code{post-}
36379 annotation which denotes the end of any echo which may (or may not) be
36380 associated with the input. For example, the @code{prompt} input type
36381 features the following annotations:
36389 The input types are
36392 @findex pre-prompt annotation
36393 @findex prompt annotation
36394 @findex post-prompt annotation
36396 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
36398 @findex pre-commands annotation
36399 @findex commands annotation
36400 @findex post-commands annotation
36402 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
36403 command. The annotations are repeated for each command which is input.
36405 @findex pre-overload-choice annotation
36406 @findex overload-choice annotation
36407 @findex post-overload-choice annotation
36408 @item overload-choice
36409 When @value{GDBN} wants the user to select between various overloaded functions.
36411 @findex pre-query annotation
36412 @findex query annotation
36413 @findex post-query annotation
36415 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
36417 @findex pre-prompt-for-continue annotation
36418 @findex prompt-for-continue annotation
36419 @findex post-prompt-for-continue annotation
36420 @item prompt-for-continue
36421 When @value{GDBN} is asking the user to press return to continue. Note: Don't
36422 expect this to work well; instead use @code{set height 0} to disable
36423 prompting. This is because the counting of lines is buggy in the
36424 presence of annotations.
36429 @cindex annotations for errors, warnings and interrupts
36431 @findex quit annotation
36436 This annotation occurs right before @value{GDBN} responds to an interrupt.
36438 @findex error annotation
36443 This annotation occurs right before @value{GDBN} responds to an error.
36445 Quit and error annotations indicate that any annotations which @value{GDBN} was
36446 in the middle of may end abruptly. For example, if a
36447 @code{value-history-begin} annotation is followed by a @code{error}, one
36448 cannot expect to receive the matching @code{value-history-end}. One
36449 cannot expect not to receive it either, however; an error annotation
36450 does not necessarily mean that @value{GDBN} is immediately returning all the way
36453 @findex error-begin annotation
36454 A quit or error annotation may be preceded by
36460 Any output between that and the quit or error annotation is the error
36463 Warning messages are not yet annotated.
36464 @c If we want to change that, need to fix warning(), type_error(),
36465 @c range_error(), and possibly other places.
36468 @section Invalidation Notices
36470 @cindex annotations for invalidation messages
36471 The following annotations say that certain pieces of state may have
36475 @findex frames-invalid annotation
36476 @item ^Z^Zframes-invalid
36478 The frames (for example, output from the @code{backtrace} command) may
36481 @findex breakpoints-invalid annotation
36482 @item ^Z^Zbreakpoints-invalid
36484 The breakpoints may have changed. For example, the user just added or
36485 deleted a breakpoint.
36488 @node Annotations for Running
36489 @section Running the Program
36490 @cindex annotations for running programs
36492 @findex starting annotation
36493 @findex stopping annotation
36494 When the program starts executing due to a @value{GDBN} command such as
36495 @code{step} or @code{continue},
36501 is output. When the program stops,
36507 is output. Before the @code{stopped} annotation, a variety of
36508 annotations describe how the program stopped.
36511 @findex exited annotation
36512 @item ^Z^Zexited @var{exit-status}
36513 The program exited, and @var{exit-status} is the exit status (zero for
36514 successful exit, otherwise nonzero).
36516 @findex signalled annotation
36517 @findex signal-name annotation
36518 @findex signal-name-end annotation
36519 @findex signal-string annotation
36520 @findex signal-string-end annotation
36521 @item ^Z^Zsignalled
36522 The program exited with a signal. After the @code{^Z^Zsignalled}, the
36523 annotation continues:
36529 ^Z^Zsignal-name-end
36533 ^Z^Zsignal-string-end
36538 where @var{name} is the name of the signal, such as @code{SIGILL} or
36539 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
36540 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
36541 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
36542 user's benefit and have no particular format.
36544 @findex signal annotation
36546 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36547 just saying that the program received the signal, not that it was
36548 terminated with it.
36550 @findex breakpoint annotation
36551 @item ^Z^Zbreakpoint @var{number}
36552 The program hit breakpoint number @var{number}.
36554 @findex watchpoint annotation
36555 @item ^Z^Zwatchpoint @var{number}
36556 The program hit watchpoint number @var{number}.
36559 @node Source Annotations
36560 @section Displaying Source
36561 @cindex annotations for source display
36563 @findex source annotation
36564 The following annotation is used instead of displaying source code:
36567 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36570 where @var{filename} is an absolute file name indicating which source
36571 file, @var{line} is the line number within that file (where 1 is the
36572 first line in the file), @var{character} is the character position
36573 within the file (where 0 is the first character in the file) (for most
36574 debug formats this will necessarily point to the beginning of a line),
36575 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36576 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36577 @var{addr} is the address in the target program associated with the
36578 source which is being displayed. The @var{addr} is in the form @samp{0x}
36579 followed by one or more lowercase hex digits (note that this does not
36580 depend on the language).
36582 @node JIT Interface
36583 @chapter JIT Compilation Interface
36584 @cindex just-in-time compilation
36585 @cindex JIT compilation interface
36587 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36588 interface. A JIT compiler is a program or library that generates native
36589 executable code at runtime and executes it, usually in order to achieve good
36590 performance while maintaining platform independence.
36592 Programs that use JIT compilation are normally difficult to debug because
36593 portions of their code are generated at runtime, instead of being loaded from
36594 object files, which is where @value{GDBN} normally finds the program's symbols
36595 and debug information. In order to debug programs that use JIT compilation,
36596 @value{GDBN} has an interface that allows the program to register in-memory
36597 symbol files with @value{GDBN} at runtime.
36599 If you are using @value{GDBN} to debug a program that uses this interface, then
36600 it should work transparently so long as you have not stripped the binary. If
36601 you are developing a JIT compiler, then the interface is documented in the rest
36602 of this chapter. At this time, the only known client of this interface is the
36605 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36606 JIT compiler communicates with @value{GDBN} by writing data into a global
36607 variable and calling a function at a well-known symbol. When @value{GDBN}
36608 attaches, it reads a linked list of symbol files from the global variable to
36609 find existing code, and puts a breakpoint in the function so that it can find
36610 out about additional code.
36613 * Declarations:: Relevant C struct declarations
36614 * Registering Code:: Steps to register code
36615 * Unregistering Code:: Steps to unregister code
36616 * Custom Debug Info:: Emit debug information in a custom format
36620 @section JIT Declarations
36622 These are the relevant struct declarations that a C program should include to
36623 implement the interface:
36633 struct jit_code_entry
36635 struct jit_code_entry *next_entry;
36636 struct jit_code_entry *prev_entry;
36637 const char *symfile_addr;
36638 uint64_t symfile_size;
36641 struct jit_descriptor
36644 /* This type should be jit_actions_t, but we use uint32_t
36645 to be explicit about the bitwidth. */
36646 uint32_t action_flag;
36647 struct jit_code_entry *relevant_entry;
36648 struct jit_code_entry *first_entry;
36651 /* GDB puts a breakpoint in this function. */
36652 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36654 /* Make sure to specify the version statically, because the
36655 debugger may check the version before we can set it. */
36656 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36659 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36660 modifications to this global data properly, which can easily be done by putting
36661 a global mutex around modifications to these structures.
36663 @node Registering Code
36664 @section Registering Code
36666 To register code with @value{GDBN}, the JIT should follow this protocol:
36670 Generate an object file in memory with symbols and other desired debug
36671 information. The file must include the virtual addresses of the sections.
36674 Create a code entry for the file, which gives the start and size of the symbol
36678 Add it to the linked list in the JIT descriptor.
36681 Point the relevant_entry field of the descriptor at the entry.
36684 Set @code{action_flag} to @code{JIT_REGISTER} and call
36685 @code{__jit_debug_register_code}.
36688 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36689 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36690 new code. However, the linked list must still be maintained in order to allow
36691 @value{GDBN} to attach to a running process and still find the symbol files.
36693 @node Unregistering Code
36694 @section Unregistering Code
36696 If code is freed, then the JIT should use the following protocol:
36700 Remove the code entry corresponding to the code from the linked list.
36703 Point the @code{relevant_entry} field of the descriptor at the code entry.
36706 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36707 @code{__jit_debug_register_code}.
36710 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36711 and the JIT will leak the memory used for the associated symbol files.
36713 @node Custom Debug Info
36714 @section Custom Debug Info
36715 @cindex custom JIT debug info
36716 @cindex JIT debug info reader
36718 Generating debug information in platform-native file formats (like ELF
36719 or COFF) may be an overkill for JIT compilers; especially if all the
36720 debug info is used for is displaying a meaningful backtrace. The
36721 issue can be resolved by having the JIT writers decide on a debug info
36722 format and also provide a reader that parses the debug info generated
36723 by the JIT compiler. This section gives a brief overview on writing
36724 such a parser. More specific details can be found in the source file
36725 @file{gdb/jit-reader.in}, which is also installed as a header at
36726 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36728 The reader is implemented as a shared object (so this functionality is
36729 not available on platforms which don't allow loading shared objects at
36730 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36731 @code{jit-reader-unload} are provided, to be used to load and unload
36732 the readers from a preconfigured directory. Once loaded, the shared
36733 object is used the parse the debug information emitted by the JIT
36737 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36738 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36741 @node Using JIT Debug Info Readers
36742 @subsection Using JIT Debug Info Readers
36743 @kindex jit-reader-load
36744 @kindex jit-reader-unload
36746 Readers can be loaded and unloaded using the @code{jit-reader-load}
36747 and @code{jit-reader-unload} commands.
36750 @item jit-reader-load @var{reader}
36751 Load the JIT reader named @var{reader}, which is a shared
36752 object specified as either an absolute or a relative file name. In
36753 the latter case, @value{GDBN} will try to load the reader from a
36754 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36755 system (here @var{libdir} is the system library directory, often
36756 @file{/usr/local/lib}).
36758 Only one reader can be active at a time; trying to load a second
36759 reader when one is already loaded will result in @value{GDBN}
36760 reporting an error. A new JIT reader can be loaded by first unloading
36761 the current one using @code{jit-reader-unload} and then invoking
36762 @code{jit-reader-load}.
36764 @item jit-reader-unload
36765 Unload the currently loaded JIT reader.
36769 @node Writing JIT Debug Info Readers
36770 @subsection Writing JIT Debug Info Readers
36771 @cindex writing JIT debug info readers
36773 As mentioned, a reader is essentially a shared object conforming to a
36774 certain ABI. This ABI is described in @file{jit-reader.h}.
36776 @file{jit-reader.h} defines the structures, macros and functions
36777 required to write a reader. It is installed (along with
36778 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36779 the system include directory.
36781 Readers need to be released under a GPL compatible license. A reader
36782 can be declared as released under such a license by placing the macro
36783 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36785 The entry point for readers is the symbol @code{gdb_init_reader},
36786 which is expected to be a function with the prototype
36788 @findex gdb_init_reader
36790 extern struct gdb_reader_funcs *gdb_init_reader (void);
36793 @cindex @code{struct gdb_reader_funcs}
36795 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36796 functions. These functions are executed to read the debug info
36797 generated by the JIT compiler (@code{read}), to unwind stack frames
36798 (@code{unwind}) and to create canonical frame IDs
36799 (@code{get_frame_id}). It also has a callback that is called when the
36800 reader is being unloaded (@code{destroy}). The struct looks like this
36803 struct gdb_reader_funcs
36805 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36806 int reader_version;
36808 /* For use by the reader. */
36811 gdb_read_debug_info *read;
36812 gdb_unwind_frame *unwind;
36813 gdb_get_frame_id *get_frame_id;
36814 gdb_destroy_reader *destroy;
36818 @cindex @code{struct gdb_symbol_callbacks}
36819 @cindex @code{struct gdb_unwind_callbacks}
36821 The callbacks are provided with another set of callbacks by
36822 @value{GDBN} to do their job. For @code{read}, these callbacks are
36823 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36824 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36825 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36826 files and new symbol tables inside those object files. @code{struct
36827 gdb_unwind_callbacks} has callbacks to read registers off the current
36828 frame and to write out the values of the registers in the previous
36829 frame. Both have a callback (@code{target_read}) to read bytes off the
36830 target's address space.
36832 @node In-Process Agent
36833 @chapter In-Process Agent
36834 @cindex debugging agent
36835 The traditional debugging model is conceptually low-speed, but works fine,
36836 because most bugs can be reproduced in debugging-mode execution. However,
36837 as multi-core or many-core processors are becoming mainstream, and
36838 multi-threaded programs become more and more popular, there should be more
36839 and more bugs that only manifest themselves at normal-mode execution, for
36840 example, thread races, because debugger's interference with the program's
36841 timing may conceal the bugs. On the other hand, in some applications,
36842 it is not feasible for the debugger to interrupt the program's execution
36843 long enough for the developer to learn anything helpful about its behavior.
36844 If the program's correctness depends on its real-time behavior, delays
36845 introduced by a debugger might cause the program to fail, even when the
36846 code itself is correct. It is useful to be able to observe the program's
36847 behavior without interrupting it.
36849 Therefore, traditional debugging model is too intrusive to reproduce
36850 some bugs. In order to reduce the interference with the program, we can
36851 reduce the number of operations performed by debugger. The
36852 @dfn{In-Process Agent}, a shared library, is running within the same
36853 process with inferior, and is able to perform some debugging operations
36854 itself. As a result, debugger is only involved when necessary, and
36855 performance of debugging can be improved accordingly. Note that
36856 interference with program can be reduced but can't be removed completely,
36857 because the in-process agent will still stop or slow down the program.
36859 The in-process agent can interpret and execute Agent Expressions
36860 (@pxref{Agent Expressions}) during performing debugging operations. The
36861 agent expressions can be used for different purposes, such as collecting
36862 data in tracepoints, and condition evaluation in breakpoints.
36864 @anchor{Control Agent}
36865 You can control whether the in-process agent is used as an aid for
36866 debugging with the following commands:
36869 @kindex set agent on
36871 Causes the in-process agent to perform some operations on behalf of the
36872 debugger. Just which operations requested by the user will be done
36873 by the in-process agent depends on the its capabilities. For example,
36874 if you request to evaluate breakpoint conditions in the in-process agent,
36875 and the in-process agent has such capability as well, then breakpoint
36876 conditions will be evaluated in the in-process agent.
36878 @kindex set agent off
36879 @item set agent off
36880 Disables execution of debugging operations by the in-process agent. All
36881 of the operations will be performed by @value{GDBN}.
36885 Display the current setting of execution of debugging operations by
36886 the in-process agent.
36890 * In-Process Agent Protocol::
36893 @node In-Process Agent Protocol
36894 @section In-Process Agent Protocol
36895 @cindex in-process agent protocol
36897 The in-process agent is able to communicate with both @value{GDBN} and
36898 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36899 used for communications between @value{GDBN} or GDBserver and the IPA.
36900 In general, @value{GDBN} or GDBserver sends commands
36901 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36902 in-process agent replies back with the return result of the command, or
36903 some other information. The data sent to in-process agent is composed
36904 of primitive data types, such as 4-byte or 8-byte type, and composite
36905 types, which are called objects (@pxref{IPA Protocol Objects}).
36908 * IPA Protocol Objects::
36909 * IPA Protocol Commands::
36912 @node IPA Protocol Objects
36913 @subsection IPA Protocol Objects
36914 @cindex ipa protocol objects
36916 The commands sent to and results received from agent may contain some
36917 complex data types called @dfn{objects}.
36919 The in-process agent is running on the same machine with @value{GDBN}
36920 or GDBserver, so it doesn't have to handle as much differences between
36921 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36922 However, there are still some differences of two ends in two processes:
36926 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36927 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36929 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36930 GDBserver is compiled with one, and in-process agent is compiled with
36934 Here are the IPA Protocol Objects:
36938 agent expression object. It represents an agent expression
36939 (@pxref{Agent Expressions}).
36940 @anchor{agent expression object}
36942 tracepoint action object. It represents a tracepoint action
36943 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36944 memory, static trace data and to evaluate expression.
36945 @anchor{tracepoint action object}
36947 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36948 @anchor{tracepoint object}
36952 The following table describes important attributes of each IPA protocol
36955 @multitable @columnfractions .30 .20 .50
36956 @headitem Name @tab Size @tab Description
36957 @item @emph{agent expression object} @tab @tab
36958 @item length @tab 4 @tab length of bytes code
36959 @item byte code @tab @var{length} @tab contents of byte code
36960 @item @emph{tracepoint action for collecting memory} @tab @tab
36961 @item 'M' @tab 1 @tab type of tracepoint action
36962 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36963 address of the lowest byte to collect, otherwise @var{addr} is the offset
36964 of @var{basereg} for memory collecting.
36965 @item len @tab 8 @tab length of memory for collecting
36966 @item basereg @tab 4 @tab the register number containing the starting
36967 memory address for collecting.
36968 @item @emph{tracepoint action for collecting registers} @tab @tab
36969 @item 'R' @tab 1 @tab type of tracepoint action
36970 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36971 @item 'L' @tab 1 @tab type of tracepoint action
36972 @item @emph{tracepoint action for expression evaluation} @tab @tab
36973 @item 'X' @tab 1 @tab type of tracepoint action
36974 @item agent expression @tab length of @tab @ref{agent expression object}
36975 @item @emph{tracepoint object} @tab @tab
36976 @item number @tab 4 @tab number of tracepoint
36977 @item address @tab 8 @tab address of tracepoint inserted on
36978 @item type @tab 4 @tab type of tracepoint
36979 @item enabled @tab 1 @tab enable or disable of tracepoint
36980 @item step_count @tab 8 @tab step
36981 @item pass_count @tab 8 @tab pass
36982 @item numactions @tab 4 @tab number of tracepoint actions
36983 @item hit count @tab 8 @tab hit count
36984 @item trace frame usage @tab 8 @tab trace frame usage
36985 @item compiled_cond @tab 8 @tab compiled condition
36986 @item orig_size @tab 8 @tab orig size
36987 @item condition @tab 4 if condition is NULL otherwise length of
36988 @ref{agent expression object}
36989 @tab zero if condition is NULL, otherwise is
36990 @ref{agent expression object}
36991 @item actions @tab variable
36992 @tab numactions number of @ref{tracepoint action object}
36995 @node IPA Protocol Commands
36996 @subsection IPA Protocol Commands
36997 @cindex ipa protocol commands
36999 The spaces in each command are delimiters to ease reading this commands
37000 specification. They don't exist in real commands.
37004 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37005 Installs a new fast tracepoint described by @var{tracepoint_object}
37006 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37007 head of @dfn{jumppad}, which is used to jump to data collection routine
37012 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37013 @var{target_address} is address of tracepoint in the inferior.
37014 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37015 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37016 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37017 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37024 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37025 is about to kill inferiors.
37033 @item probe_marker_at:@var{address}
37034 Asks in-process agent to probe the marker at @var{address}.
37041 @item unprobe_marker_at:@var{address}
37042 Asks in-process agent to unprobe the marker at @var{address}.
37046 @chapter Reporting Bugs in @value{GDBN}
37047 @cindex bugs in @value{GDBN}
37048 @cindex reporting bugs in @value{GDBN}
37050 Your bug reports play an essential role in making @value{GDBN} reliable.
37052 Reporting a bug may help you by bringing a solution to your problem, or it
37053 may not. But in any case the principal function of a bug report is to help
37054 the entire community by making the next version of @value{GDBN} work better. Bug
37055 reports are your contribution to the maintenance of @value{GDBN}.
37057 In order for a bug report to serve its purpose, you must include the
37058 information that enables us to fix the bug.
37061 * Bug Criteria:: Have you found a bug?
37062 * Bug Reporting:: How to report bugs
37066 @section Have You Found a Bug?
37067 @cindex bug criteria
37069 If you are not sure whether you have found a bug, here are some guidelines:
37072 @cindex fatal signal
37073 @cindex debugger crash
37074 @cindex crash of debugger
37076 If the debugger gets a fatal signal, for any input whatever, that is a
37077 @value{GDBN} bug. Reliable debuggers never crash.
37079 @cindex error on valid input
37081 If @value{GDBN} produces an error message for valid input, that is a
37082 bug. (Note that if you're cross debugging, the problem may also be
37083 somewhere in the connection to the target.)
37085 @cindex invalid input
37087 If @value{GDBN} does not produce an error message for invalid input,
37088 that is a bug. However, you should note that your idea of
37089 ``invalid input'' might be our idea of ``an extension'' or ``support
37090 for traditional practice''.
37093 If you are an experienced user of debugging tools, your suggestions
37094 for improvement of @value{GDBN} are welcome in any case.
37097 @node Bug Reporting
37098 @section How to Report Bugs
37099 @cindex bug reports
37100 @cindex @value{GDBN} bugs, reporting
37102 A number of companies and individuals offer support for @sc{gnu} products.
37103 If you obtained @value{GDBN} from a support organization, we recommend you
37104 contact that organization first.
37106 You can find contact information for many support companies and
37107 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
37109 @c should add a web page ref...
37112 @ifset BUGURL_DEFAULT
37113 In any event, we also recommend that you submit bug reports for
37114 @value{GDBN}. The preferred method is to submit them directly using
37115 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
37116 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
37119 @strong{Do not send bug reports to @samp{info-gdb}, or to
37120 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
37121 not want to receive bug reports. Those that do have arranged to receive
37124 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
37125 serves as a repeater. The mailing list and the newsgroup carry exactly
37126 the same messages. Often people think of posting bug reports to the
37127 newsgroup instead of mailing them. This appears to work, but it has one
37128 problem which can be crucial: a newsgroup posting often lacks a mail
37129 path back to the sender. Thus, if we need to ask for more information,
37130 we may be unable to reach you. For this reason, it is better to send
37131 bug reports to the mailing list.
37133 @ifclear BUGURL_DEFAULT
37134 In any event, we also recommend that you submit bug reports for
37135 @value{GDBN} to @value{BUGURL}.
37139 The fundamental principle of reporting bugs usefully is this:
37140 @strong{report all the facts}. If you are not sure whether to state a
37141 fact or leave it out, state it!
37143 Often people omit facts because they think they know what causes the
37144 problem and assume that some details do not matter. Thus, you might
37145 assume that the name of the variable you use in an example does not matter.
37146 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
37147 stray memory reference which happens to fetch from the location where that
37148 name is stored in memory; perhaps, if the name were different, the contents
37149 of that location would fool the debugger into doing the right thing despite
37150 the bug. Play it safe and give a specific, complete example. That is the
37151 easiest thing for you to do, and the most helpful.
37153 Keep in mind that the purpose of a bug report is to enable us to fix the
37154 bug. It may be that the bug has been reported previously, but neither
37155 you nor we can know that unless your bug report is complete and
37158 Sometimes people give a few sketchy facts and ask, ``Does this ring a
37159 bell?'' Those bug reports are useless, and we urge everyone to
37160 @emph{refuse to respond to them} except to chide the sender to report
37163 To enable us to fix the bug, you should include all these things:
37167 The version of @value{GDBN}. @value{GDBN} announces it if you start
37168 with no arguments; you can also print it at any time using @code{show
37171 Without this, we will not know whether there is any point in looking for
37172 the bug in the current version of @value{GDBN}.
37175 The type of machine you are using, and the operating system name and
37179 The details of the @value{GDBN} build-time configuration.
37180 @value{GDBN} shows these details if you invoke it with the
37181 @option{--configuration} command-line option, or if you type
37182 @code{show configuration} at @value{GDBN}'s prompt.
37185 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
37186 ``@value{GCC}--2.8.1''.
37189 What compiler (and its version) was used to compile the program you are
37190 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
37191 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
37192 to get this information; for other compilers, see the documentation for
37196 The command arguments you gave the compiler to compile your example and
37197 observe the bug. For example, did you use @samp{-O}? To guarantee
37198 you will not omit something important, list them all. A copy of the
37199 Makefile (or the output from make) is sufficient.
37201 If we were to try to guess the arguments, we would probably guess wrong
37202 and then we might not encounter the bug.
37205 A complete input script, and all necessary source files, that will
37209 A description of what behavior you observe that you believe is
37210 incorrect. For example, ``It gets a fatal signal.''
37212 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
37213 will certainly notice it. But if the bug is incorrect output, we might
37214 not notice unless it is glaringly wrong. You might as well not give us
37215 a chance to make a mistake.
37217 Even if the problem you experience is a fatal signal, you should still
37218 say so explicitly. Suppose something strange is going on, such as, your
37219 copy of @value{GDBN} is out of synch, or you have encountered a bug in
37220 the C library on your system. (This has happened!) Your copy might
37221 crash and ours would not. If you told us to expect a crash, then when
37222 ours fails to crash, we would know that the bug was not happening for
37223 us. If you had not told us to expect a crash, then we would not be able
37224 to draw any conclusion from our observations.
37227 @cindex recording a session script
37228 To collect all this information, you can use a session recording program
37229 such as @command{script}, which is available on many Unix systems.
37230 Just run your @value{GDBN} session inside @command{script} and then
37231 include the @file{typescript} file with your bug report.
37233 Another way to record a @value{GDBN} session is to run @value{GDBN}
37234 inside Emacs and then save the entire buffer to a file.
37237 If you wish to suggest changes to the @value{GDBN} source, send us context
37238 diffs. If you even discuss something in the @value{GDBN} source, refer to
37239 it by context, not by line number.
37241 The line numbers in our development sources will not match those in your
37242 sources. Your line numbers would convey no useful information to us.
37246 Here are some things that are not necessary:
37250 A description of the envelope of the bug.
37252 Often people who encounter a bug spend a lot of time investigating
37253 which changes to the input file will make the bug go away and which
37254 changes will not affect it.
37256 This is often time consuming and not very useful, because the way we
37257 will find the bug is by running a single example under the debugger
37258 with breakpoints, not by pure deduction from a series of examples.
37259 We recommend that you save your time for something else.
37261 Of course, if you can find a simpler example to report @emph{instead}
37262 of the original one, that is a convenience for us. Errors in the
37263 output will be easier to spot, running under the debugger will take
37264 less time, and so on.
37266 However, simplification is not vital; if you do not want to do this,
37267 report the bug anyway and send us the entire test case you used.
37270 A patch for the bug.
37272 A patch for the bug does help us if it is a good one. But do not omit
37273 the necessary information, such as the test case, on the assumption that
37274 a patch is all we need. We might see problems with your patch and decide
37275 to fix the problem another way, or we might not understand it at all.
37277 Sometimes with a program as complicated as @value{GDBN} it is very hard to
37278 construct an example that will make the program follow a certain path
37279 through the code. If you do not send us the example, we will not be able
37280 to construct one, so we will not be able to verify that the bug is fixed.
37282 And if we cannot understand what bug you are trying to fix, or why your
37283 patch should be an improvement, we will not install it. A test case will
37284 help us to understand.
37287 A guess about what the bug is or what it depends on.
37289 Such guesses are usually wrong. Even we cannot guess right about such
37290 things without first using the debugger to find the facts.
37293 @c The readline documentation is distributed with the readline code
37294 @c and consists of the two following files:
37297 @c Use -I with makeinfo to point to the appropriate directory,
37298 @c environment var TEXINPUTS with TeX.
37299 @ifclear SYSTEM_READLINE
37300 @include rluser.texi
37301 @include hsuser.texi
37305 @appendix In Memoriam
37307 The @value{GDBN} project mourns the loss of the following long-time
37312 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
37313 to Free Software in general. Outside of @value{GDBN}, he was known in
37314 the Amiga world for his series of Fish Disks, and the GeekGadget project.
37316 @item Michael Snyder
37317 Michael was one of the Global Maintainers of the @value{GDBN} project,
37318 with contributions recorded as early as 1996, until 2011. In addition
37319 to his day to day participation, he was a large driving force behind
37320 adding Reverse Debugging to @value{GDBN}.
37323 Beyond their technical contributions to the project, they were also
37324 enjoyable members of the Free Software Community. We will miss them.
37326 @node Formatting Documentation
37327 @appendix Formatting Documentation
37329 @cindex @value{GDBN} reference card
37330 @cindex reference card
37331 The @value{GDBN} 4 release includes an already-formatted reference card, ready
37332 for printing with PostScript or Ghostscript, in the @file{gdb}
37333 subdirectory of the main source directory@footnote{In
37334 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
37335 release.}. If you can use PostScript or Ghostscript with your printer,
37336 you can print the reference card immediately with @file{refcard.ps}.
37338 The release also includes the source for the reference card. You
37339 can format it, using @TeX{}, by typing:
37345 The @value{GDBN} reference card is designed to print in @dfn{landscape}
37346 mode on US ``letter'' size paper;
37347 that is, on a sheet 11 inches wide by 8.5 inches
37348 high. You will need to specify this form of printing as an option to
37349 your @sc{dvi} output program.
37351 @cindex documentation
37353 All the documentation for @value{GDBN} comes as part of the machine-readable
37354 distribution. The documentation is written in Texinfo format, which is
37355 a documentation system that uses a single source file to produce both
37356 on-line information and a printed manual. You can use one of the Info
37357 formatting commands to create the on-line version of the documentation
37358 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
37360 @value{GDBN} includes an already formatted copy of the on-line Info
37361 version of this manual in the @file{gdb} subdirectory. The main Info
37362 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
37363 subordinate files matching @samp{gdb.info*} in the same directory. If
37364 necessary, you can print out these files, or read them with any editor;
37365 but they are easier to read using the @code{info} subsystem in @sc{gnu}
37366 Emacs or the standalone @code{info} program, available as part of the
37367 @sc{gnu} Texinfo distribution.
37369 If you want to format these Info files yourself, you need one of the
37370 Info formatting programs, such as @code{texinfo-format-buffer} or
37373 If you have @code{makeinfo} installed, and are in the top level
37374 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
37375 version @value{GDBVN}), you can make the Info file by typing:
37382 If you want to typeset and print copies of this manual, you need @TeX{},
37383 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
37384 Texinfo definitions file.
37386 @TeX{} is a typesetting program; it does not print files directly, but
37387 produces output files called @sc{dvi} files. To print a typeset
37388 document, you need a program to print @sc{dvi} files. If your system
37389 has @TeX{} installed, chances are it has such a program. The precise
37390 command to use depends on your system; @kbd{lpr -d} is common; another
37391 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
37392 require a file name without any extension or a @samp{.dvi} extension.
37394 @TeX{} also requires a macro definitions file called
37395 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
37396 written in Texinfo format. On its own, @TeX{} cannot either read or
37397 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
37398 and is located in the @file{gdb-@var{version-number}/texinfo}
37401 If you have @TeX{} and a @sc{dvi} printer program installed, you can
37402 typeset and print this manual. First switch to the @file{gdb}
37403 subdirectory of the main source directory (for example, to
37404 @file{gdb-@value{GDBVN}/gdb}) and type:
37410 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
37412 @node Installing GDB
37413 @appendix Installing @value{GDBN}
37414 @cindex installation
37417 * Requirements:: Requirements for building @value{GDBN}
37418 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
37419 * Separate Objdir:: Compiling @value{GDBN} in another directory
37420 * Config Names:: Specifying names for hosts and targets
37421 * Configure Options:: Summary of options for configure
37422 * System-wide configuration:: Having a system-wide init file
37426 @section Requirements for Building @value{GDBN}
37427 @cindex building @value{GDBN}, requirements for
37429 Building @value{GDBN} requires various tools and packages to be available.
37430 Other packages will be used only if they are found.
37432 @heading Tools/Packages Necessary for Building @value{GDBN}
37434 @item C@t{++}11 compiler
37435 @value{GDBN} is written in C@t{++}11. It should be buildable with any
37436 recent C@t{++}11 compiler, e.g.@: GCC.
37439 @value{GDBN}'s build system relies on features only found in the GNU
37440 make program. Other variants of @code{make} will not work.
37443 @heading Tools/Packages Optional for Building @value{GDBN}
37447 @value{GDBN} can use the Expat XML parsing library. This library may be
37448 included with your operating system distribution; if it is not, you
37449 can get the latest version from @url{http://expat.sourceforge.net}.
37450 The @file{configure} script will search for this library in several
37451 standard locations; if it is installed in an unusual path, you can
37452 use the @option{--with-libexpat-prefix} option to specify its location.
37458 Remote protocol memory maps (@pxref{Memory Map Format})
37460 Target descriptions (@pxref{Target Descriptions})
37462 Remote shared library lists (@xref{Library List Format},
37463 or alternatively @pxref{Library List Format for SVR4 Targets})
37465 MS-Windows shared libraries (@pxref{Shared Libraries})
37467 Traceframe info (@pxref{Traceframe Info Format})
37469 Branch trace (@pxref{Branch Trace Format},
37470 @pxref{Branch Trace Configuration Format})
37474 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
37475 default, @value{GDBN} will be compiled if the Guile libraries are
37476 installed and are found by @file{configure}. You can use the
37477 @code{--with-guile} option to request Guile, and pass either the Guile
37478 version number or the file name of the relevant @code{pkg-config}
37479 program to choose a particular version of Guile.
37482 @value{GDBN}'s features related to character sets (@pxref{Character
37483 Sets}) require a functioning @code{iconv} implementation. If you are
37484 on a GNU system, then this is provided by the GNU C Library. Some
37485 other systems also provide a working @code{iconv}.
37487 If @value{GDBN} is using the @code{iconv} program which is installed
37488 in a non-standard place, you will need to tell @value{GDBN} where to
37489 find it. This is done with @option{--with-iconv-bin} which specifies
37490 the directory that contains the @code{iconv} program. This program is
37491 run in order to make a list of the available character sets.
37493 On systems without @code{iconv}, you can install GNU Libiconv. If
37494 Libiconv is installed in a standard place, @value{GDBN} will
37495 automatically use it if it is needed. If you have previously
37496 installed Libiconv in a non-standard place, you can use the
37497 @option{--with-libiconv-prefix} option to @file{configure}.
37499 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
37500 arrange to build Libiconv if a directory named @file{libiconv} appears
37501 in the top-most source directory. If Libiconv is built this way, and
37502 if the operating system does not provide a suitable @code{iconv}
37503 implementation, then the just-built library will automatically be used
37504 by @value{GDBN}. One easy way to set this up is to download GNU
37505 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
37506 source tree, and then rename the directory holding the Libiconv source
37507 code to @samp{libiconv}.
37510 @value{GDBN} can support debugging sections that are compressed with
37511 the LZMA library. @xref{MiniDebugInfo}. If this library is not
37512 included with your operating system, you can find it in the xz package
37513 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
37514 the usual place, then the @file{configure} script will use it
37515 automatically. If it is installed in an unusual path, you can use the
37516 @option{--with-lzma-prefix} option to specify its location.
37520 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
37521 library. This library may be included with your operating system
37522 distribution; if it is not, you can get the latest version from
37523 @url{http://www.mpfr.org}. The @file{configure} script will search
37524 for this library in several standard locations; if it is installed
37525 in an unusual path, you can use the @option{--with-libmpfr-prefix}
37526 option to specify its location.
37528 GNU MPFR is used to emulate target floating-point arithmetic during
37529 expression evaluation when the target uses different floating-point
37530 formats than the host. If GNU MPFR it is not available, @value{GDBN}
37531 will fall back to using host floating-point arithmetic.
37534 @value{GDBN} can be scripted using Python language. @xref{Python}.
37535 By default, @value{GDBN} will be compiled if the Python libraries are
37536 installed and are found by @file{configure}. You can use the
37537 @code{--with-python} option to request Python, and pass either the
37538 file name of the relevant @code{python} executable, or the name of the
37539 directory in which Python is installed, to choose a particular
37540 installation of Python.
37543 @cindex compressed debug sections
37544 @value{GDBN} will use the @samp{zlib} library, if available, to read
37545 compressed debug sections. Some linkers, such as GNU gold, are capable
37546 of producing binaries with compressed debug sections. If @value{GDBN}
37547 is compiled with @samp{zlib}, it will be able to read the debug
37548 information in such binaries.
37550 The @samp{zlib} library is likely included with your operating system
37551 distribution; if it is not, you can get the latest version from
37552 @url{http://zlib.net}.
37555 @node Running Configure
37556 @section Invoking the @value{GDBN} @file{configure} Script
37557 @cindex configuring @value{GDBN}
37558 @value{GDBN} comes with a @file{configure} script that automates the process
37559 of preparing @value{GDBN} for installation; you can then use @code{make} to
37560 build the @code{gdb} program.
37562 @c irrelevant in info file; it's as current as the code it lives with.
37563 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
37564 look at the @file{README} file in the sources; we may have improved the
37565 installation procedures since publishing this manual.}
37568 The @value{GDBN} distribution includes all the source code you need for
37569 @value{GDBN} in a single directory, whose name is usually composed by
37570 appending the version number to @samp{gdb}.
37572 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
37573 @file{gdb-@value{GDBVN}} directory. That directory contains:
37576 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
37577 script for configuring @value{GDBN} and all its supporting libraries
37579 @item gdb-@value{GDBVN}/gdb
37580 the source specific to @value{GDBN} itself
37582 @item gdb-@value{GDBVN}/bfd
37583 source for the Binary File Descriptor library
37585 @item gdb-@value{GDBVN}/include
37586 @sc{gnu} include files
37588 @item gdb-@value{GDBVN}/libiberty
37589 source for the @samp{-liberty} free software library
37591 @item gdb-@value{GDBVN}/opcodes
37592 source for the library of opcode tables and disassemblers
37594 @item gdb-@value{GDBVN}/readline
37595 source for the @sc{gnu} command-line interface
37598 There may be other subdirectories as well.
37600 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37601 from the @file{gdb-@var{version-number}} source directory, which in
37602 this example is the @file{gdb-@value{GDBVN}} directory.
37604 First switch to the @file{gdb-@var{version-number}} source directory
37605 if you are not already in it; then run @file{configure}. Pass the
37606 identifier for the platform on which @value{GDBN} will run as an
37612 cd gdb-@value{GDBVN}
37617 Running @samp{configure} and then running @code{make} builds the
37618 included supporting libraries, then @code{gdb} itself. The configured
37619 source files, and the binaries, are left in the corresponding source
37623 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37624 system does not recognize this automatically when you run a different
37625 shell, you may need to run @code{sh} on it explicitly:
37631 You should run the @file{configure} script from the top directory in the
37632 source tree, the @file{gdb-@var{version-number}} directory. If you run
37633 @file{configure} from one of the subdirectories, you will configure only
37634 that subdirectory. That is usually not what you want. In particular,
37635 if you run the first @file{configure} from the @file{gdb} subdirectory
37636 of the @file{gdb-@var{version-number}} directory, you will omit the
37637 configuration of @file{bfd}, @file{readline}, and other sibling
37638 directories of the @file{gdb} subdirectory. This leads to build errors
37639 about missing include files such as @file{bfd/bfd.h}.
37641 You can install @code{@value{GDBN}} anywhere. The best way to do this
37642 is to pass the @code{--prefix} option to @code{configure}, and then
37643 install it with @code{make install}.
37645 @node Separate Objdir
37646 @section Compiling @value{GDBN} in Another Directory
37648 If you want to run @value{GDBN} versions for several host or target machines,
37649 you need a different @code{gdb} compiled for each combination of
37650 host and target. @file{configure} is designed to make this easy by
37651 allowing you to generate each configuration in a separate subdirectory,
37652 rather than in the source directory. If your @code{make} program
37653 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37654 @code{make} in each of these directories builds the @code{gdb}
37655 program specified there.
37657 To build @code{gdb} in a separate directory, run @file{configure}
37658 with the @samp{--srcdir} option to specify where to find the source.
37659 (You also need to specify a path to find @file{configure}
37660 itself from your working directory. If the path to @file{configure}
37661 would be the same as the argument to @samp{--srcdir}, you can leave out
37662 the @samp{--srcdir} option; it is assumed.)
37664 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37665 separate directory for a Sun 4 like this:
37669 cd gdb-@value{GDBVN}
37672 ../gdb-@value{GDBVN}/configure
37677 When @file{configure} builds a configuration using a remote source
37678 directory, it creates a tree for the binaries with the same structure
37679 (and using the same names) as the tree under the source directory. In
37680 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37681 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37682 @file{gdb-sun4/gdb}.
37684 Make sure that your path to the @file{configure} script has just one
37685 instance of @file{gdb} in it. If your path to @file{configure} looks
37686 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37687 one subdirectory of @value{GDBN}, not the whole package. This leads to
37688 build errors about missing include files such as @file{bfd/bfd.h}.
37690 One popular reason to build several @value{GDBN} configurations in separate
37691 directories is to configure @value{GDBN} for cross-compiling (where
37692 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37693 programs that run on another machine---the @dfn{target}).
37694 You specify a cross-debugging target by
37695 giving the @samp{--target=@var{target}} option to @file{configure}.
37697 When you run @code{make} to build a program or library, you must run
37698 it in a configured directory---whatever directory you were in when you
37699 called @file{configure} (or one of its subdirectories).
37701 The @code{Makefile} that @file{configure} generates in each source
37702 directory also runs recursively. If you type @code{make} in a source
37703 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37704 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37705 will build all the required libraries, and then build GDB.
37707 When you have multiple hosts or targets configured in separate
37708 directories, you can run @code{make} on them in parallel (for example,
37709 if they are NFS-mounted on each of the hosts); they will not interfere
37713 @section Specifying Names for Hosts and Targets
37715 The specifications used for hosts and targets in the @file{configure}
37716 script are based on a three-part naming scheme, but some short predefined
37717 aliases are also supported. The full naming scheme encodes three pieces
37718 of information in the following pattern:
37721 @var{architecture}-@var{vendor}-@var{os}
37724 For example, you can use the alias @code{sun4} as a @var{host} argument,
37725 or as the value for @var{target} in a @code{--target=@var{target}}
37726 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37728 The @file{configure} script accompanying @value{GDBN} does not provide
37729 any query facility to list all supported host and target names or
37730 aliases. @file{configure} calls the Bourne shell script
37731 @code{config.sub} to map abbreviations to full names; you can read the
37732 script, if you wish, or you can use it to test your guesses on
37733 abbreviations---for example:
37736 % sh config.sub i386-linux
37738 % sh config.sub alpha-linux
37739 alpha-unknown-linux-gnu
37740 % sh config.sub hp9k700
37742 % sh config.sub sun4
37743 sparc-sun-sunos4.1.1
37744 % sh config.sub sun3
37745 m68k-sun-sunos4.1.1
37746 % sh config.sub i986v
37747 Invalid configuration `i986v': machine `i986v' not recognized
37751 @code{config.sub} is also distributed in the @value{GDBN} source
37752 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37754 @node Configure Options
37755 @section @file{configure} Options
37757 Here is a summary of the @file{configure} options and arguments that
37758 are most often useful for building @value{GDBN}. @file{configure}
37759 also has several other options not listed here. @inforef{Running
37760 configure scripts,,autoconf.info}, for a full
37761 explanation of @file{configure}.
37764 configure @r{[}--help@r{]}
37765 @r{[}--prefix=@var{dir}@r{]}
37766 @r{[}--exec-prefix=@var{dir}@r{]}
37767 @r{[}--srcdir=@var{dirname}@r{]}
37768 @r{[}--target=@var{target}@r{]}
37772 You may introduce options with a single @samp{-} rather than
37773 @samp{--} if you prefer; but you may abbreviate option names if you use
37778 Display a quick summary of how to invoke @file{configure}.
37780 @item --prefix=@var{dir}
37781 Configure the source to install programs and files under directory
37784 @item --exec-prefix=@var{dir}
37785 Configure the source to install programs under directory
37788 @c avoid splitting the warning from the explanation:
37790 @item --srcdir=@var{dirname}
37791 Use this option to make configurations in directories separate from the
37792 @value{GDBN} source directories. Among other things, you can use this to
37793 build (or maintain) several configurations simultaneously, in separate
37794 directories. @file{configure} writes configuration-specific files in
37795 the current directory, but arranges for them to use the source in the
37796 directory @var{dirname}. @file{configure} creates directories under
37797 the working directory in parallel to the source directories below
37800 @item --target=@var{target}
37801 Configure @value{GDBN} for cross-debugging programs running on the specified
37802 @var{target}. Without this option, @value{GDBN} is configured to debug
37803 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37805 There is no convenient way to generate a list of all available
37806 targets. Also see the @code{--enable-targets} option, below.
37809 There are many other options that are specific to @value{GDBN}. This
37810 lists just the most common ones; there are some very specialized
37811 options not described here.
37814 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
37815 @itemx --enable-targets=all
37816 Configure @value{GDBN} for cross-debugging programs running on the
37817 specified list of targets. The special value @samp{all} configures
37818 @value{GDBN} for debugging programs running on any target it supports.
37820 @item --with-gdb-datadir=@var{path}
37821 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
37822 here for certain supporting files or scripts. This defaults to the
37823 @file{gdb} subdirectory of @samp{datadir} (which can be set using
37826 @item --with-relocated-sources=@var{dir}
37827 Sets up the default source path substitution rule so that directory
37828 names recorded in debug information will be automatically adjusted for
37829 any directory under @var{dir}. @var{dir} should be a subdirectory of
37830 @value{GDBN}'s configured prefix, the one mentioned in the
37831 @code{--prefix} or @code{--exec-prefix} options to configure. This
37832 option is useful if GDB is supposed to be moved to a different place
37835 @item --enable-64-bit-bfd
37836 Enable 64-bit support in BFD on 32-bit hosts.
37838 @item --disable-gdbmi
37839 Build @value{GDBN} without the GDB/MI machine interface
37843 Build @value{GDBN} with the text-mode full-screen user interface
37844 (TUI). Requires a curses library (ncurses and cursesX are also
37847 @item --with-curses
37848 Use the curses library instead of the termcap library, for text-mode
37849 terminal operations.
37851 @item --with-libunwind-ia64
37852 Use the libunwind library for unwinding function call stack on ia64
37853 target platforms. See http://www.nongnu.org/libunwind/index.html for
37856 @item --with-system-readline
37857 Use the readline library installed on the host, rather than the
37858 library supplied as part of @value{GDBN}. Readline 7 or newer is
37859 required; this is enforced by the build system.
37861 @item --with-system-zlib
37862 Use the zlib library installed on the host, rather than the library
37863 supplied as part of @value{GDBN}.
37866 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
37867 default if libexpat is installed and found at configure time.) This
37868 library is used to read XML files supplied with @value{GDBN}. If it
37869 is unavailable, some features, such as remote protocol memory maps,
37870 target descriptions, and shared library lists, that are based on XML
37871 files, will not be available in @value{GDBN}. If your host does not
37872 have libexpat installed, you can get the latest version from
37873 `http://expat.sourceforge.net'.
37875 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
37877 Build @value{GDBN} with GNU libiconv, a character set encoding
37878 conversion library. This is not done by default, as on GNU systems
37879 the @code{iconv} that is built in to the C library is sufficient. If
37880 your host does not have a working @code{iconv}, you can get the latest
37881 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
37883 @value{GDBN}'s build system also supports building GNU libiconv as
37884 part of the overall build. @xref{Requirements}.
37887 Build @value{GDBN} with LZMA, a compression library. (Done by default
37888 if liblzma is installed and found at configure time.) LZMA is used by
37889 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
37890 platforms using the ELF object file format. If your host does not
37891 have liblzma installed, you can get the latest version from
37892 `https://tukaani.org/xz/'.
37895 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
37896 floating-point computation with correct rounding. (Done by default if
37897 GNU MPFR is installed and found at configure time.) This library is
37898 used to emulate target floating-point arithmetic during expression
37899 evaluation when the target uses different floating-point formats than
37900 the host. If GNU MPFR is not available, @value{GDBN} will fall back
37901 to using host floating-point arithmetic. If your host does not have
37902 GNU MPFR installed, you can get the latest version from
37903 `http://www.mpfr.org'.
37905 @item --with-python@r{[}=@var{python}@r{]}
37906 Build @value{GDBN} with Python scripting support. (Done by default if
37907 libpython is present and found at configure time.) Python makes
37908 @value{GDBN} scripting much more powerful than the restricted CLI
37909 scripting language. If your host does not have Python installed, you
37910 can find it on `http://www.python.org/download/'. The oldest version
37911 of Python supported by GDB is 2.6. The optional argument @var{python}
37912 is used to find the Python headers and libraries. It can be either
37913 the name of a Python executable, or the name of the directory in which
37914 Python is installed.
37916 @item --with-guile[=GUILE]'
37917 Build @value{GDBN} with GNU Guile scripting support. (Done by default
37918 if libguile is present and found at configure time.) If your host
37919 does not have Guile installed, you can find it at
37920 `https://www.gnu.org/software/guile/'. The optional argument GUILE
37921 can be a version number, which will cause @code{configure} to try to
37922 use that version of Guile; or the file name of a @code{pkg-config}
37923 executable, which will be queried to find the information needed to
37924 compile and link against Guile.
37926 @item --without-included-regex
37927 Don't use the regex library included with @value{GDBN} (as part of the
37928 libiberty library). This is the default on hosts with version 2 of
37931 @item --with-sysroot=@var{dir}
37932 Use @var{dir} as the default system root directory for libraries whose
37933 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
37934 @var{dir} can be modified at run time by using the @command{set
37935 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
37936 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
37937 default system root will be automatically adjusted if and when
37938 @value{GDBN} is moved to a different location.
37940 @item --with-system-gdbinit=@var{file}
37941 Configure @value{GDBN} to automatically load a system-wide init file.
37942 @var{file} should be an absolute file name. If @var{file} is in a
37943 directory under the configured prefix, and @value{GDBN} is moved to
37944 another location after being built, the location of the system-wide
37945 init file will be adjusted accordingly.
37947 @item --with-system-gdbinit-dir=@var{directory}
37948 Configure @value{GDBN} to automatically load init files from a
37949 system-wide directory. @var{directory} should be an absolute directory
37950 name. If @var{directory} is in a directory under the configured
37951 prefix, and @value{GDBN} is moved to another location after being
37952 built, the location of the system-wide init directory will be
37953 adjusted accordingly.
37955 @item --enable-build-warnings
37956 When building the @value{GDBN} sources, ask the compiler to warn about
37957 any code which looks even vaguely suspicious. It passes many
37958 different warning flags, depending on the exact version of the
37959 compiler you are using.
37961 @item --enable-werror
37962 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
37963 to the compiler, which will fail the compilation if the compiler
37964 outputs any warning messages.
37966 @item --enable-ubsan
37967 Enable the GCC undefined behavior sanitizer. This is disabled by
37968 default, but passing @code{--enable-ubsan=yes} or
37969 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
37970 undefined behavior sanitizer checks for C@t{++} undefined behavior.
37971 It has a performance cost, so if you are looking at @value{GDBN}'s
37972 performance, you should disable it. The undefined behavior sanitizer
37973 was first introduced in GCC 4.9.
37976 @node System-wide configuration
37977 @section System-wide configuration and settings
37978 @cindex system-wide init file
37980 @value{GDBN} can be configured to have a system-wide init file and a
37981 system-wide init file directory; this file and files in that directory
37982 (if they have a recognized file extension) will be read and executed at
37983 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
37985 Here are the corresponding configure options:
37988 @item --with-system-gdbinit=@var{file}
37989 Specify that the default location of the system-wide init file is
37991 @item --with-system-gdbinit-dir=@var{directory}
37992 Specify that the default location of the system-wide init file directory
37993 is @var{directory}.
37996 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37997 they may be subject to relocation. Two possible cases:
38001 If the default location of this init file/directory contains @file{$prefix},
38002 it will be subject to relocation. Suppose that the configure options
38003 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38004 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38005 init file is looked for as @file{$install/etc/gdbinit} instead of
38006 @file{$prefix/etc/gdbinit}.
38009 By contrast, if the default location does not contain the prefix,
38010 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38011 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38012 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38013 wherever @value{GDBN} is installed.
38016 If the configured location of the system-wide init file (as given by the
38017 @option{--with-system-gdbinit} option at configure time) is in the
38018 data-directory (as specified by @option{--with-gdb-datadir} at configure
38019 time) or in one of its subdirectories, then @value{GDBN} will look for the
38020 system-wide init file in the directory specified by the
38021 @option{--data-directory} command-line option.
38022 Note that the system-wide init file is only read once, during @value{GDBN}
38023 initialization. If the data-directory is changed after @value{GDBN} has
38024 started with the @code{set data-directory} command, the file will not be
38027 This applies similarly to the system-wide directory specified in
38028 @option{--with-system-gdbinit-dir}.
38030 Any supported scripting language can be used for these init files, as long
38031 as the file extension matches the scripting language. To be interpreted
38032 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
38036 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
38039 @node System-wide Configuration Scripts
38040 @subsection Installed System-wide Configuration Scripts
38041 @cindex system-wide configuration scripts
38043 The @file{system-gdbinit} directory, located inside the data-directory
38044 (as specified by @option{--with-gdb-datadir} at configure time) contains
38045 a number of scripts which can be used as system-wide init files. To
38046 automatically source those scripts at startup, @value{GDBN} should be
38047 configured with @option{--with-system-gdbinit}. Otherwise, any user
38048 should be able to source them by hand as needed.
38050 The following scripts are currently available:
38053 @item @file{elinos.py}
38055 @cindex ELinOS system-wide configuration script
38056 This script is useful when debugging a program on an ELinOS target.
38057 It takes advantage of the environment variables defined in a standard
38058 ELinOS environment in order to determine the location of the system
38059 shared libraries, and then sets the @samp{solib-absolute-prefix}
38060 and @samp{solib-search-path} variables appropriately.
38062 @item @file{wrs-linux.py}
38063 @pindex wrs-linux.py
38064 @cindex Wind River Linux system-wide configuration script
38065 This script is useful when debugging a program on a target running
38066 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
38067 the host-side sysroot used by the target system.
38071 @node Maintenance Commands
38072 @appendix Maintenance Commands
38073 @cindex maintenance commands
38074 @cindex internal commands
38076 In addition to commands intended for @value{GDBN} users, @value{GDBN}
38077 includes a number of commands intended for @value{GDBN} developers,
38078 that are not documented elsewhere in this manual. These commands are
38079 provided here for reference. (For commands that turn on debugging
38080 messages, see @ref{Debugging Output}.)
38083 @kindex maint agent
38084 @kindex maint agent-eval
38085 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38086 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38087 Translate the given @var{expression} into remote agent bytecodes.
38088 This command is useful for debugging the Agent Expression mechanism
38089 (@pxref{Agent Expressions}). The @samp{agent} version produces an
38090 expression useful for data collection, such as by tracepoints, while
38091 @samp{maint agent-eval} produces an expression that evaluates directly
38092 to a result. For instance, a collection expression for @code{globa +
38093 globb} will include bytecodes to record four bytes of memory at each
38094 of the addresses of @code{globa} and @code{globb}, while discarding
38095 the result of the addition, while an evaluation expression will do the
38096 addition and return the sum.
38097 If @code{-at} is given, generate remote agent bytecode for @var{location}.
38098 If not, generate remote agent bytecode for current frame PC address.
38100 @kindex maint agent-printf
38101 @item maint agent-printf @var{format},@var{expr},...
38102 Translate the given format string and list of argument expressions
38103 into remote agent bytecodes and display them as a disassembled list.
38104 This command is useful for debugging the agent version of dynamic
38105 printf (@pxref{Dynamic Printf}).
38107 @kindex maint info breakpoints
38108 @item @anchor{maint info breakpoints}maint info breakpoints
38109 Using the same format as @samp{info breakpoints}, display both the
38110 breakpoints you've set explicitly, and those @value{GDBN} is using for
38111 internal purposes. Internal breakpoints are shown with negative
38112 breakpoint numbers. The type column identifies what kind of breakpoint
38117 Normal, explicitly set breakpoint.
38120 Normal, explicitly set watchpoint.
38123 Internal breakpoint, used to handle correctly stepping through
38124 @code{longjmp} calls.
38126 @item longjmp resume
38127 Internal breakpoint at the target of a @code{longjmp}.
38130 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
38133 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
38136 Shared library events.
38140 @kindex maint info btrace
38141 @item maint info btrace
38142 Pint information about raw branch tracing data.
38144 @kindex maint btrace packet-history
38145 @item maint btrace packet-history
38146 Print the raw branch trace packets that are used to compute the
38147 execution history for the @samp{record btrace} command. Both the
38148 information and the format in which it is printed depend on the btrace
38153 For the BTS recording format, print a list of blocks of sequential
38154 code. For each block, the following information is printed:
38158 Newer blocks have higher numbers. The oldest block has number zero.
38159 @item Lowest @samp{PC}
38160 @item Highest @samp{PC}
38164 For the Intel Processor Trace recording format, print a list of
38165 Intel Processor Trace packets. For each packet, the following
38166 information is printed:
38169 @item Packet number
38170 Newer packets have higher numbers. The oldest packet has number zero.
38172 The packet's offset in the trace stream.
38173 @item Packet opcode and payload
38177 @kindex maint btrace clear-packet-history
38178 @item maint btrace clear-packet-history
38179 Discards the cached packet history printed by the @samp{maint btrace
38180 packet-history} command. The history will be computed again when
38183 @kindex maint btrace clear
38184 @item maint btrace clear
38185 Discard the branch trace data. The data will be fetched anew and the
38186 branch trace will be recomputed when needed.
38188 This implicitly truncates the branch trace to a single branch trace
38189 buffer. When updating branch trace incrementally, the branch trace
38190 available to @value{GDBN} may be bigger than a single branch trace
38193 @kindex maint set btrace pt skip-pad
38194 @item maint set btrace pt skip-pad
38195 @kindex maint show btrace pt skip-pad
38196 @item maint show btrace pt skip-pad
38197 Control whether @value{GDBN} will skip PAD packets when computing the
38200 @kindex set displaced-stepping
38201 @kindex show displaced-stepping
38202 @cindex displaced stepping support
38203 @cindex out-of-line single-stepping
38204 @item set displaced-stepping
38205 @itemx show displaced-stepping
38206 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
38207 if the target supports it. Displaced stepping is a way to single-step
38208 over breakpoints without removing them from the inferior, by executing
38209 an out-of-line copy of the instruction that was originally at the
38210 breakpoint location. It is also known as out-of-line single-stepping.
38213 @item set displaced-stepping on
38214 If the target architecture supports it, @value{GDBN} will use
38215 displaced stepping to step over breakpoints.
38217 @item set displaced-stepping off
38218 @value{GDBN} will not use displaced stepping to step over breakpoints,
38219 even if such is supported by the target architecture.
38221 @cindex non-stop mode, and @samp{set displaced-stepping}
38222 @item set displaced-stepping auto
38223 This is the default mode. @value{GDBN} will use displaced stepping
38224 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
38225 architecture supports displaced stepping.
38228 @kindex maint check-psymtabs
38229 @item maint check-psymtabs
38230 Check the consistency of currently expanded psymtabs versus symtabs.
38231 Use this to check, for example, whether a symbol is in one but not the other.
38233 @kindex maint check-symtabs
38234 @item maint check-symtabs
38235 Check the consistency of currently expanded symtabs.
38237 @kindex maint expand-symtabs
38238 @item maint expand-symtabs [@var{regexp}]
38239 Expand symbol tables.
38240 If @var{regexp} is specified, only expand symbol tables for file
38241 names matching @var{regexp}.
38243 @kindex maint set catch-demangler-crashes
38244 @kindex maint show catch-demangler-crashes
38245 @cindex demangler crashes
38246 @item maint set catch-demangler-crashes [on|off]
38247 @itemx maint show catch-demangler-crashes
38248 Control whether @value{GDBN} should attempt to catch crashes in the
38249 symbol name demangler. The default is to attempt to catch crashes.
38250 If enabled, the first time a crash is caught, a core file is created,
38251 the offending symbol is displayed and the user is presented with the
38252 option to terminate the current session.
38254 @kindex maint cplus first_component
38255 @item maint cplus first_component @var{name}
38256 Print the first C@t{++} class/namespace component of @var{name}.
38258 @kindex maint cplus namespace
38259 @item maint cplus namespace
38260 Print the list of possible C@t{++} namespaces.
38262 @kindex maint deprecate
38263 @kindex maint undeprecate
38264 @cindex deprecated commands
38265 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
38266 @itemx maint undeprecate @var{command}
38267 Deprecate or undeprecate the named @var{command}. Deprecated commands
38268 cause @value{GDBN} to issue a warning when you use them. The optional
38269 argument @var{replacement} says which newer command should be used in
38270 favor of the deprecated one; if it is given, @value{GDBN} will mention
38271 the replacement as part of the warning.
38273 @kindex maint dump-me
38274 @item maint dump-me
38275 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
38276 Cause a fatal signal in the debugger and force it to dump its core.
38277 This is supported only on systems which support aborting a program
38278 with the @code{SIGQUIT} signal.
38280 @kindex maint internal-error
38281 @kindex maint internal-warning
38282 @kindex maint demangler-warning
38283 @cindex demangler crashes
38284 @item maint internal-error @r{[}@var{message-text}@r{]}
38285 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
38286 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
38288 Cause @value{GDBN} to call the internal function @code{internal_error},
38289 @code{internal_warning} or @code{demangler_warning} and hence behave
38290 as though an internal problem has been detected. In addition to
38291 reporting the internal problem, these functions give the user the
38292 opportunity to either quit @value{GDBN} or (for @code{internal_error}
38293 and @code{internal_warning}) create a core file of the current
38294 @value{GDBN} session.
38296 These commands take an optional parameter @var{message-text} that is
38297 used as the text of the error or warning message.
38299 Here's an example of using @code{internal-error}:
38302 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
38303 @dots{}/maint.c:121: internal-error: testing, 1, 2
38304 A problem internal to GDB has been detected. Further
38305 debugging may prove unreliable.
38306 Quit this debugging session? (y or n) @kbd{n}
38307 Create a core file? (y or n) @kbd{n}
38311 @cindex @value{GDBN} internal error
38312 @cindex internal errors, control of @value{GDBN} behavior
38313 @cindex demangler crashes
38315 @kindex maint set internal-error
38316 @kindex maint show internal-error
38317 @kindex maint set internal-warning
38318 @kindex maint show internal-warning
38319 @kindex maint set demangler-warning
38320 @kindex maint show demangler-warning
38321 @item maint set internal-error @var{action} [ask|yes|no]
38322 @itemx maint show internal-error @var{action}
38323 @itemx maint set internal-warning @var{action} [ask|yes|no]
38324 @itemx maint show internal-warning @var{action}
38325 @itemx maint set demangler-warning @var{action} [ask|yes|no]
38326 @itemx maint show demangler-warning @var{action}
38327 When @value{GDBN} reports an internal problem (error or warning) it
38328 gives the user the opportunity to both quit @value{GDBN} and create a
38329 core file of the current @value{GDBN} session. These commands let you
38330 override the default behaviour for each particular @var{action},
38331 described in the table below.
38335 You can specify that @value{GDBN} should always (yes) or never (no)
38336 quit. The default is to ask the user what to do.
38339 You can specify that @value{GDBN} should always (yes) or never (no)
38340 create a core file. The default is to ask the user what to do. Note
38341 that there is no @code{corefile} option for @code{demangler-warning}:
38342 demangler warnings always create a core file and this cannot be
38346 @kindex maint packet
38347 @item maint packet @var{text}
38348 If @value{GDBN} is talking to an inferior via the serial protocol,
38349 then this command sends the string @var{text} to the inferior, and
38350 displays the response packet. @value{GDBN} supplies the initial
38351 @samp{$} character, the terminating @samp{#} character, and the
38354 @kindex maint print architecture
38355 @item maint print architecture @r{[}@var{file}@r{]}
38356 Print the entire architecture configuration. The optional argument
38357 @var{file} names the file where the output goes.
38359 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
38360 @item maint print c-tdesc
38361 Print the target description (@pxref{Target Descriptions}) as
38362 a C source file. By default, the target description is for the current
38363 target, but if the optional argument @var{file} is provided, that file
38364 is used to produce the description. The @var{file} should be an XML
38365 document, of the form described in @ref{Target Description Format}.
38366 The created source file is built into @value{GDBN} when @value{GDBN} is
38367 built again. This command is used by developers after they add or
38368 modify XML target descriptions.
38370 @kindex maint check xml-descriptions
38371 @item maint check xml-descriptions @var{dir}
38372 Check that the target descriptions dynamically created by @value{GDBN}
38373 equal the descriptions created from XML files found in @var{dir}.
38375 @anchor{maint check libthread-db}
38376 @kindex maint check libthread-db
38377 @item maint check libthread-db
38378 Run integrity checks on the current inferior's thread debugging
38379 library. This exercises all @code{libthread_db} functionality used by
38380 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
38381 @code{proc_service} functions provided by @value{GDBN} that
38382 @code{libthread_db} uses. Note that parts of the test may be skipped
38383 on some platforms when debugging core files.
38385 @kindex maint print dummy-frames
38386 @item maint print dummy-frames
38387 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
38390 (@value{GDBP}) @kbd{b add}
38392 (@value{GDBP}) @kbd{print add(2,3)}
38393 Breakpoint 2, add (a=2, b=3) at @dots{}
38395 The program being debugged stopped while in a function called from GDB.
38397 (@value{GDBP}) @kbd{maint print dummy-frames}
38398 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
38402 Takes an optional file parameter.
38404 @kindex maint print registers
38405 @kindex maint print raw-registers
38406 @kindex maint print cooked-registers
38407 @kindex maint print register-groups
38408 @kindex maint print remote-registers
38409 @item maint print registers @r{[}@var{file}@r{]}
38410 @itemx maint print raw-registers @r{[}@var{file}@r{]}
38411 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
38412 @itemx maint print register-groups @r{[}@var{file}@r{]}
38413 @itemx maint print remote-registers @r{[}@var{file}@r{]}
38414 Print @value{GDBN}'s internal register data structures.
38416 The command @code{maint print raw-registers} includes the contents of
38417 the raw register cache; the command @code{maint print
38418 cooked-registers} includes the (cooked) value of all registers,
38419 including registers which aren't available on the target nor visible
38420 to user; the command @code{maint print register-groups} includes the
38421 groups that each register is a member of; and the command @code{maint
38422 print remote-registers} includes the remote target's register numbers
38423 and offsets in the `G' packets.
38425 These commands take an optional parameter, a file name to which to
38426 write the information.
38428 @kindex maint print reggroups
38429 @item maint print reggroups @r{[}@var{file}@r{]}
38430 Print @value{GDBN}'s internal register group data structures. The
38431 optional argument @var{file} tells to what file to write the
38434 The register groups info looks like this:
38437 (@value{GDBP}) @kbd{maint print reggroups}
38450 This command forces @value{GDBN} to flush its internal register cache.
38452 @kindex maint print objfiles
38453 @cindex info for known object files
38454 @item maint print objfiles @r{[}@var{regexp}@r{]}
38455 Print a dump of all known object files.
38456 If @var{regexp} is specified, only print object files whose names
38457 match @var{regexp}. For each object file, this command prints its name,
38458 address in memory, and all of its psymtabs and symtabs.
38460 @kindex maint print user-registers
38461 @cindex user registers
38462 @item maint print user-registers
38463 List all currently available @dfn{user registers}. User registers
38464 typically provide alternate names for actual hardware registers. They
38465 include the four ``standard'' registers @code{$fp}, @code{$pc},
38466 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
38467 registers can be used in expressions in the same way as the canonical
38468 register names, but only the latter are listed by the @code{info
38469 registers} and @code{maint print registers} commands.
38471 @kindex maint print section-scripts
38472 @cindex info for known .debug_gdb_scripts-loaded scripts
38473 @item maint print section-scripts [@var{regexp}]
38474 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
38475 If @var{regexp} is specified, only print scripts loaded by object files
38476 matching @var{regexp}.
38477 For each script, this command prints its name as specified in the objfile,
38478 and the full path if known.
38479 @xref{dotdebug_gdb_scripts section}.
38481 @kindex maint print statistics
38482 @cindex bcache statistics
38483 @item maint print statistics
38484 This command prints, for each object file in the program, various data
38485 about that object file followed by the byte cache (@dfn{bcache})
38486 statistics for the object file. The objfile data includes the number
38487 of minimal, partial, full, and stabs symbols, the number of types
38488 defined by the objfile, the number of as yet unexpanded psym tables,
38489 the number of line tables and string tables, and the amount of memory
38490 used by the various tables. The bcache statistics include the counts,
38491 sizes, and counts of duplicates of all and unique objects, max,
38492 average, and median entry size, total memory used and its overhead and
38493 savings, and various measures of the hash table size and chain
38496 @kindex maint print target-stack
38497 @cindex target stack description
38498 @item maint print target-stack
38499 A @dfn{target} is an interface between the debugger and a particular
38500 kind of file or process. Targets can be stacked in @dfn{strata},
38501 so that more than one target can potentially respond to a request.
38502 In particular, memory accesses will walk down the stack of targets
38503 until they find a target that is interested in handling that particular
38506 This command prints a short description of each layer that was pushed on
38507 the @dfn{target stack}, starting from the top layer down to the bottom one.
38509 @kindex maint print type
38510 @cindex type chain of a data type
38511 @item maint print type @var{expr}
38512 Print the type chain for a type specified by @var{expr}. The argument
38513 can be either a type name or a symbol. If it is a symbol, the type of
38514 that symbol is described. The type chain produced by this command is
38515 a recursive definition of the data type as stored in @value{GDBN}'s
38516 data structures, including its flags and contained types.
38518 @kindex maint selftest
38520 @item maint selftest @r{[}@var{filter}@r{]}
38521 Run any self tests that were compiled in to @value{GDBN}. This will
38522 print a message showing how many tests were run, and how many failed.
38523 If a @var{filter} is passed, only the tests with @var{filter} in their
38526 @kindex maint info selftests
38528 @item maint info selftests
38529 List the selftests compiled in to @value{GDBN}.
38531 @kindex maint set dwarf always-disassemble
38532 @kindex maint show dwarf always-disassemble
38533 @item maint set dwarf always-disassemble
38534 @item maint show dwarf always-disassemble
38535 Control the behavior of @code{info address} when using DWARF debugging
38538 The default is @code{off}, which means that @value{GDBN} should try to
38539 describe a variable's location in an easily readable format. When
38540 @code{on}, @value{GDBN} will instead display the DWARF location
38541 expression in an assembly-like format. Note that some locations are
38542 too complex for @value{GDBN} to describe simply; in this case you will
38543 always see the disassembly form.
38545 Here is an example of the resulting disassembly:
38548 (gdb) info addr argc
38549 Symbol "argc" is a complex DWARF expression:
38553 For more information on these expressions, see
38554 @uref{http://www.dwarfstd.org/, the DWARF standard}.
38556 @kindex maint set dwarf max-cache-age
38557 @kindex maint show dwarf max-cache-age
38558 @item maint set dwarf max-cache-age
38559 @itemx maint show dwarf max-cache-age
38560 Control the DWARF compilation unit cache.
38562 @cindex DWARF compilation units cache
38563 In object files with inter-compilation-unit references, such as those
38564 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
38565 reader needs to frequently refer to previously read compilation units.
38566 This setting controls how long a compilation unit will remain in the
38567 cache if it is not referenced. A higher limit means that cached
38568 compilation units will be stored in memory longer, and more total
38569 memory will be used. Setting it to zero disables caching, which will
38570 slow down @value{GDBN} startup, but reduce memory consumption.
38572 @kindex maint set dwarf unwinders
38573 @kindex maint show dwarf unwinders
38574 @item maint set dwarf unwinders
38575 @itemx maint show dwarf unwinders
38576 Control use of the DWARF frame unwinders.
38578 @cindex DWARF frame unwinders
38579 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
38580 frame unwinders to build the backtrace. Many of these targets will
38581 also have a second mechanism for building the backtrace for use in
38582 cases where DWARF information is not available, this second mechanism
38583 is often an analysis of a function's prologue.
38585 In order to extend testing coverage of the second level stack
38586 unwinding mechanisms it is helpful to be able to disable the DWARF
38587 stack unwinders, this can be done with this switch.
38589 In normal use of @value{GDBN} disabling the DWARF unwinders is not
38590 advisable, there are cases that are better handled through DWARF than
38591 prologue analysis, and the debug experience is likely to be better
38592 with the DWARF frame unwinders enabled.
38594 If DWARF frame unwinders are not supported for a particular target
38595 architecture, then enabling this flag does not cause them to be used.
38597 @kindex maint set worker-threads
38598 @kindex maint show worker-threads
38599 @item maint set worker-threads
38600 @item maint show worker-threads
38601 Control the number of worker threads that may be used by @value{GDBN}.
38602 On capable hosts, @value{GDBN} may use multiple threads to speed up
38603 certain CPU-intensive operations, such as demangling symbol names.
38604 While the number of threads used by @value{GDBN} may vary, this
38605 command can be used to set an upper bound on this number. The default
38606 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
38607 number. Note that this only controls worker threads started by
38608 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
38611 @kindex maint set profile
38612 @kindex maint show profile
38613 @cindex profiling GDB
38614 @item maint set profile
38615 @itemx maint show profile
38616 Control profiling of @value{GDBN}.
38618 Profiling will be disabled until you use the @samp{maint set profile}
38619 command to enable it. When you enable profiling, the system will begin
38620 collecting timing and execution count data; when you disable profiling or
38621 exit @value{GDBN}, the results will be written to a log file. Remember that
38622 if you use profiling, @value{GDBN} will overwrite the profiling log file
38623 (often called @file{gmon.out}). If you have a record of important profiling
38624 data in a @file{gmon.out} file, be sure to move it to a safe location.
38626 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
38627 compiled with the @samp{-pg} compiler option.
38629 @kindex maint set show-debug-regs
38630 @kindex maint show show-debug-regs
38631 @cindex hardware debug registers
38632 @item maint set show-debug-regs
38633 @itemx maint show show-debug-regs
38634 Control whether to show variables that mirror the hardware debug
38635 registers. Use @code{on} to enable, @code{off} to disable. If
38636 enabled, the debug registers values are shown when @value{GDBN} inserts or
38637 removes a hardware breakpoint or watchpoint, and when the inferior
38638 triggers a hardware-assisted breakpoint or watchpoint.
38640 @kindex maint set show-all-tib
38641 @kindex maint show show-all-tib
38642 @item maint set show-all-tib
38643 @itemx maint show show-all-tib
38644 Control whether to show all non zero areas within a 1k block starting
38645 at thread local base, when using the @samp{info w32 thread-information-block}
38648 @kindex maint set target-async
38649 @kindex maint show target-async
38650 @item maint set target-async
38651 @itemx maint show target-async
38652 This controls whether @value{GDBN} targets operate in synchronous or
38653 asynchronous mode (@pxref{Background Execution}). Normally the
38654 default is asynchronous, if it is available; but this can be changed
38655 to more easily debug problems occurring only in synchronous mode.
38657 @kindex maint set target-non-stop @var{mode} [on|off|auto]
38658 @kindex maint show target-non-stop
38659 @item maint set target-non-stop
38660 @itemx maint show target-non-stop
38662 This controls whether @value{GDBN} targets always operate in non-stop
38663 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
38664 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
38665 if supported by the target.
38668 @item maint set target-non-stop auto
38669 This is the default mode. @value{GDBN} controls the target in
38670 non-stop mode if the target supports it.
38672 @item maint set target-non-stop on
38673 @value{GDBN} controls the target in non-stop mode even if the target
38674 does not indicate support.
38676 @item maint set target-non-stop off
38677 @value{GDBN} does not control the target in non-stop mode even if the
38678 target supports it.
38681 @kindex maint set tui-resize-message
38682 @kindex maint show tui-resize-message
38683 @item maint set tui-resize-message
38684 @item maint show tui-resize-message
38685 Control whether @value{GDBN} displays a message each time the terminal
38686 is resized when in TUI mode. The default is @code{off}, which means
38687 that @value{GDBN} is silent during resizes. When @code{on},
38688 @value{GDBN} will display a message after a resize is completed; the
38689 message will include a number indicating how many times the terminal
38690 has been resized. This setting is intended for use by the test suite,
38691 where it would otherwise be difficult to determine when a resize and
38692 refresh has been completed.
38694 @kindex maint set per-command
38695 @kindex maint show per-command
38696 @item maint set per-command
38697 @itemx maint show per-command
38698 @cindex resources used by commands
38700 @value{GDBN} can display the resources used by each command.
38701 This is useful in debugging performance problems.
38704 @item maint set per-command space [on|off]
38705 @itemx maint show per-command space
38706 Enable or disable the printing of the memory used by GDB for each command.
38707 If enabled, @value{GDBN} will display how much memory each command
38708 took, following the command's own output.
38709 This can also be requested by invoking @value{GDBN} with the
38710 @option{--statistics} command-line switch (@pxref{Mode Options}).
38712 @item maint set per-command time [on|off]
38713 @itemx maint show per-command time
38714 Enable or disable the printing of the execution time of @value{GDBN}
38716 If enabled, @value{GDBN} will display how much time it
38717 took to execute each command, following the command's own output.
38718 Both CPU time and wallclock time are printed.
38719 Printing both is useful when trying to determine whether the cost is
38720 CPU or, e.g., disk/network latency.
38721 Note that the CPU time printed is for @value{GDBN} only, it does not include
38722 the execution time of the inferior because there's no mechanism currently
38723 to compute how much time was spent by @value{GDBN} and how much time was
38724 spent by the program been debugged.
38725 This can also be requested by invoking @value{GDBN} with the
38726 @option{--statistics} command-line switch (@pxref{Mode Options}).
38728 @item maint set per-command symtab [on|off]
38729 @itemx maint show per-command symtab
38730 Enable or disable the printing of basic symbol table statistics
38732 If enabled, @value{GDBN} will display the following information:
38736 number of symbol tables
38738 number of primary symbol tables
38740 number of blocks in the blockvector
38744 @kindex maint set check-libthread-db
38745 @kindex maint show check-libthread-db
38746 @item maint set check-libthread-db [on|off]
38747 @itemx maint show check-libthread-db
38748 Control whether @value{GDBN} should run integrity checks on inferior
38749 specific thread debugging libraries as they are loaded. The default
38750 is not to perform such checks. If any check fails @value{GDBN} will
38751 unload the library and continue searching for a suitable candidate as
38752 described in @ref{set libthread-db-search-path}. For more information
38753 about the tests, see @ref{maint check libthread-db}.
38755 @kindex maint space
38756 @cindex memory used by commands
38757 @item maint space @var{value}
38758 An alias for @code{maint set per-command space}.
38759 A non-zero value enables it, zero disables it.
38762 @cindex time of command execution
38763 @item maint time @var{value}
38764 An alias for @code{maint set per-command time}.
38765 A non-zero value enables it, zero disables it.
38767 @kindex maint translate-address
38768 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
38769 Find the symbol stored at the location specified by the address
38770 @var{addr} and an optional section name @var{section}. If found,
38771 @value{GDBN} prints the name of the closest symbol and an offset from
38772 the symbol's location to the specified address. This is similar to
38773 the @code{info address} command (@pxref{Symbols}), except that this
38774 command also allows to find symbols in other sections.
38776 If section was not specified, the section in which the symbol was found
38777 is also printed. For dynamically linked executables, the name of
38778 executable or shared library containing the symbol is printed as well.
38780 @kindex maint test-options
38781 @item maint test-options require-delimiter
38782 @itemx maint test-options unknown-is-error
38783 @itemx maint test-options unknown-is-operand
38784 These commands are used by the testsuite to validate the command
38785 options framework. The @code{require-delimiter} variant requires a
38786 double-dash delimiter to indicate end of options. The
38787 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
38788 @code{unknown-is-error} variant throws an error on unknown option,
38789 while @code{unknown-is-operand} treats unknown options as the start of
38790 the command's operands. When run, the commands output the result of
38791 the processed options. When completed, the commands store the
38792 internal result of completion in a variable exposed by the @code{maint
38793 show test-options-completion-result} command.
38795 @kindex maint show test-options-completion-result
38796 @item maint show test-options-completion-result
38797 Shows the result of completing the @code{maint test-options}
38798 subcommands. This is used by the testsuite to validate completion
38799 support in the command options framework.
38801 @kindex maint set test-settings
38802 @kindex maint show test-settings
38803 @item maint set test-settings @var{kind}
38804 @itemx maint show test-settings @var{kind}
38805 These are representative commands for each @var{kind} of setting type
38806 @value{GDBN} supports. They are used by the testsuite for exercising
38807 the settings infrastructure.
38810 @item maint with @var{setting} [@var{value}] [-- @var{command}]
38811 Like the @code{with} command, but works with @code{maintenance set}
38812 variables. This is used by the testsuite to exercise the @code{with}
38813 command's infrastructure.
38817 The following command is useful for non-interactive invocations of
38818 @value{GDBN}, such as in the test suite.
38821 @item set watchdog @var{nsec}
38822 @kindex set watchdog
38823 @cindex watchdog timer
38824 @cindex timeout for commands
38825 Set the maximum number of seconds @value{GDBN} will wait for the
38826 target operation to finish. If this time expires, @value{GDBN}
38827 reports and error and the command is aborted.
38829 @item show watchdog
38830 Show the current setting of the target wait timeout.
38833 @node Remote Protocol
38834 @appendix @value{GDBN} Remote Serial Protocol
38839 * Stop Reply Packets::
38840 * General Query Packets::
38841 * Architecture-Specific Protocol Details::
38842 * Tracepoint Packets::
38843 * Host I/O Packets::
38845 * Notification Packets::
38846 * Remote Non-Stop::
38847 * Packet Acknowledgment::
38849 * File-I/O Remote Protocol Extension::
38850 * Library List Format::
38851 * Library List Format for SVR4 Targets::
38852 * Memory Map Format::
38853 * Thread List Format::
38854 * Traceframe Info Format::
38855 * Branch Trace Format::
38856 * Branch Trace Configuration Format::
38862 There may be occasions when you need to know something about the
38863 protocol---for example, if there is only one serial port to your target
38864 machine, you might want your program to do something special if it
38865 recognizes a packet meant for @value{GDBN}.
38867 In the examples below, @samp{->} and @samp{<-} are used to indicate
38868 transmitted and received data, respectively.
38870 @cindex protocol, @value{GDBN} remote serial
38871 @cindex serial protocol, @value{GDBN} remote
38872 @cindex remote serial protocol
38873 All @value{GDBN} commands and responses (other than acknowledgments
38874 and notifications, see @ref{Notification Packets}) are sent as a
38875 @var{packet}. A @var{packet} is introduced with the character
38876 @samp{$}, the actual @var{packet-data}, and the terminating character
38877 @samp{#} followed by a two-digit @var{checksum}:
38880 @code{$}@var{packet-data}@code{#}@var{checksum}
38884 @cindex checksum, for @value{GDBN} remote
38886 The two-digit @var{checksum} is computed as the modulo 256 sum of all
38887 characters between the leading @samp{$} and the trailing @samp{#} (an
38888 eight bit unsigned checksum).
38890 Implementors should note that prior to @value{GDBN} 5.0 the protocol
38891 specification also included an optional two-digit @var{sequence-id}:
38894 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
38897 @cindex sequence-id, for @value{GDBN} remote
38899 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
38900 has never output @var{sequence-id}s. Stubs that handle packets added
38901 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
38903 When either the host or the target machine receives a packet, the first
38904 response expected is an acknowledgment: either @samp{+} (to indicate
38905 the package was received correctly) or @samp{-} (to request
38909 -> @code{$}@var{packet-data}@code{#}@var{checksum}
38914 The @samp{+}/@samp{-} acknowledgments can be disabled
38915 once a connection is established.
38916 @xref{Packet Acknowledgment}, for details.
38918 The host (@value{GDBN}) sends @var{command}s, and the target (the
38919 debugging stub incorporated in your program) sends a @var{response}. In
38920 the case of step and continue @var{command}s, the response is only sent
38921 when the operation has completed, and the target has again stopped all
38922 threads in all attached processes. This is the default all-stop mode
38923 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
38924 execution mode; see @ref{Remote Non-Stop}, for details.
38926 @var{packet-data} consists of a sequence of characters with the
38927 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
38930 @cindex remote protocol, field separator
38931 Fields within the packet should be separated using @samp{,} @samp{;} or
38932 @samp{:}. Except where otherwise noted all numbers are represented in
38933 @sc{hex} with leading zeros suppressed.
38935 Implementors should note that prior to @value{GDBN} 5.0, the character
38936 @samp{:} could not appear as the third character in a packet (as it
38937 would potentially conflict with the @var{sequence-id}).
38939 @cindex remote protocol, binary data
38940 @anchor{Binary Data}
38941 Binary data in most packets is encoded either as two hexadecimal
38942 digits per byte of binary data. This allowed the traditional remote
38943 protocol to work over connections which were only seven-bit clean.
38944 Some packets designed more recently assume an eight-bit clean
38945 connection, and use a more efficient encoding to send and receive
38948 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
38949 as an escape character. Any escaped byte is transmitted as the escape
38950 character followed by the original character XORed with @code{0x20}.
38951 For example, the byte @code{0x7d} would be transmitted as the two
38952 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
38953 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
38954 @samp{@}}) must always be escaped. Responses sent by the stub
38955 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
38956 is not interpreted as the start of a run-length encoded sequence
38959 Response @var{data} can be run-length encoded to save space.
38960 Run-length encoding replaces runs of identical characters with one
38961 instance of the repeated character, followed by a @samp{*} and a
38962 repeat count. The repeat count is itself sent encoded, to avoid
38963 binary characters in @var{data}: a value of @var{n} is sent as
38964 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
38965 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
38966 code 32) for a repeat count of 3. (This is because run-length
38967 encoding starts to win for counts 3 or more.) Thus, for example,
38968 @samp{0* } is a run-length encoding of ``0000'': the space character
38969 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
38972 The printable characters @samp{#} and @samp{$} or with a numeric value
38973 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
38974 seven repeats (@samp{$}) can be expanded using a repeat count of only
38975 five (@samp{"}). For example, @samp{00000000} can be encoded as
38978 The error response returned for some packets includes a two character
38979 error number. That number is not well defined.
38981 @cindex empty response, for unsupported packets
38982 For any @var{command} not supported by the stub, an empty response
38983 (@samp{$#00}) should be returned. That way it is possible to extend the
38984 protocol. A newer @value{GDBN} can tell if a packet is supported based
38987 At a minimum, a stub is required to support the @samp{g} and @samp{G}
38988 commands for register access, and the @samp{m} and @samp{M} commands
38989 for memory access. Stubs that only control single-threaded targets
38990 can implement run control with the @samp{c} (continue), and @samp{s}
38991 (step) commands. Stubs that support multi-threading targets should
38992 support the @samp{vCont} command. All other commands are optional.
38997 The following table provides a complete list of all currently defined
38998 @var{command}s and their corresponding response @var{data}.
38999 @xref{File-I/O Remote Protocol Extension}, for details about the File
39000 I/O extension of the remote protocol.
39002 Each packet's description has a template showing the packet's overall
39003 syntax, followed by an explanation of the packet's meaning. We
39004 include spaces in some of the templates for clarity; these are not
39005 part of the packet's syntax. No @value{GDBN} packet uses spaces to
39006 separate its components. For example, a template like @samp{foo
39007 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
39008 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
39009 @var{baz}. @value{GDBN} does not transmit a space character between the
39010 @samp{foo} and the @var{bar}, or between the @var{bar} and the
39013 @cindex @var{thread-id}, in remote protocol
39014 @anchor{thread-id syntax}
39015 Several packets and replies include a @var{thread-id} field to identify
39016 a thread. Normally these are positive numbers with a target-specific
39017 interpretation, formatted as big-endian hex strings. A @var{thread-id}
39018 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
39021 In addition, the remote protocol supports a multiprocess feature in
39022 which the @var{thread-id} syntax is extended to optionally include both
39023 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
39024 The @var{pid} (process) and @var{tid} (thread) components each have the
39025 format described above: a positive number with target-specific
39026 interpretation formatted as a big-endian hex string, literal @samp{-1}
39027 to indicate all processes or threads (respectively), or @samp{0} to
39028 indicate an arbitrary process or thread. Specifying just a process, as
39029 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
39030 error to specify all processes but a specific thread, such as
39031 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
39032 for those packets and replies explicitly documented to include a process
39033 ID, rather than a @var{thread-id}.
39035 The multiprocess @var{thread-id} syntax extensions are only used if both
39036 @value{GDBN} and the stub report support for the @samp{multiprocess}
39037 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
39040 Note that all packet forms beginning with an upper- or lower-case
39041 letter, other than those described here, are reserved for future use.
39043 Here are the packet descriptions.
39048 @cindex @samp{!} packet
39049 @anchor{extended mode}
39050 Enable extended mode. In extended mode, the remote server is made
39051 persistent. The @samp{R} packet is used to restart the program being
39057 The remote target both supports and has enabled extended mode.
39061 @cindex @samp{?} packet
39063 Indicate the reason the target halted. The reply is the same as for
39064 step and continue. This packet has a special interpretation when the
39065 target is in non-stop mode; see @ref{Remote Non-Stop}.
39068 @xref{Stop Reply Packets}, for the reply specifications.
39070 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
39071 @cindex @samp{A} packet
39072 Initialized @code{argv[]} array passed into program. @var{arglen}
39073 specifies the number of bytes in the hex encoded byte stream
39074 @var{arg}. See @code{gdbserver} for more details.
39079 The arguments were set.
39085 @cindex @samp{b} packet
39086 (Don't use this packet; its behavior is not well-defined.)
39087 Change the serial line speed to @var{baud}.
39089 JTC: @emph{When does the transport layer state change? When it's
39090 received, or after the ACK is transmitted. In either case, there are
39091 problems if the command or the acknowledgment packet is dropped.}
39093 Stan: @emph{If people really wanted to add something like this, and get
39094 it working for the first time, they ought to modify ser-unix.c to send
39095 some kind of out-of-band message to a specially-setup stub and have the
39096 switch happen "in between" packets, so that from remote protocol's point
39097 of view, nothing actually happened.}
39099 @item B @var{addr},@var{mode}
39100 @cindex @samp{B} packet
39101 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
39102 breakpoint at @var{addr}.
39104 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
39105 (@pxref{insert breakpoint or watchpoint packet}).
39107 @cindex @samp{bc} packet
39110 Backward continue. Execute the target system in reverse. No parameter.
39111 @xref{Reverse Execution}, for more information.
39114 @xref{Stop Reply Packets}, for the reply specifications.
39116 @cindex @samp{bs} packet
39119 Backward single step. Execute one instruction in reverse. No parameter.
39120 @xref{Reverse Execution}, for more information.
39123 @xref{Stop Reply Packets}, for the reply specifications.
39125 @item c @r{[}@var{addr}@r{]}
39126 @cindex @samp{c} packet
39127 Continue at @var{addr}, which is the address to resume. If @var{addr}
39128 is omitted, resume at current address.
39130 This packet is deprecated for multi-threading support. @xref{vCont
39134 @xref{Stop Reply Packets}, for the reply specifications.
39136 @item C @var{sig}@r{[};@var{addr}@r{]}
39137 @cindex @samp{C} packet
39138 Continue with signal @var{sig} (hex signal number). If
39139 @samp{;@var{addr}} is omitted, resume at same address.
39141 This packet is deprecated for multi-threading support. @xref{vCont
39145 @xref{Stop Reply Packets}, for the reply specifications.
39148 @cindex @samp{d} packet
39151 Don't use this packet; instead, define a general set packet
39152 (@pxref{General Query Packets}).
39156 @cindex @samp{D} packet
39157 The first form of the packet is used to detach @value{GDBN} from the
39158 remote system. It is sent to the remote target
39159 before @value{GDBN} disconnects via the @code{detach} command.
39161 The second form, including a process ID, is used when multiprocess
39162 protocol extensions are enabled (@pxref{multiprocess extensions}), to
39163 detach only a specific process. The @var{pid} is specified as a
39164 big-endian hex string.
39174 @item F @var{RC},@var{EE},@var{CF};@var{XX}
39175 @cindex @samp{F} packet
39176 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
39177 This is part of the File-I/O protocol extension. @xref{File-I/O
39178 Remote Protocol Extension}, for the specification.
39181 @anchor{read registers packet}
39182 @cindex @samp{g} packet
39183 Read general registers.
39187 @item @var{XX@dots{}}
39188 Each byte of register data is described by two hex digits. The bytes
39189 with the register are transmitted in target byte order. The size of
39190 each register and their position within the @samp{g} packet are
39191 determined by the @value{GDBN} internal gdbarch functions
39192 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
39194 When reading registers from a trace frame (@pxref{Analyze Collected
39195 Data,,Using the Collected Data}), the stub may also return a string of
39196 literal @samp{x}'s in place of the register data digits, to indicate
39197 that the corresponding register has not been collected, thus its value
39198 is unavailable. For example, for an architecture with 4 registers of
39199 4 bytes each, the following reply indicates to @value{GDBN} that
39200 registers 0 and 2 have not been collected, while registers 1 and 3
39201 have been collected, and both have zero value:
39205 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
39212 @item G @var{XX@dots{}}
39213 @cindex @samp{G} packet
39214 Write general registers. @xref{read registers packet}, for a
39215 description of the @var{XX@dots{}} data.
39225 @item H @var{op} @var{thread-id}
39226 @cindex @samp{H} packet
39227 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
39228 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
39229 should be @samp{c} for step and continue operations (note that this
39230 is deprecated, supporting the @samp{vCont} command is a better
39231 option), and @samp{g} for other operations. The thread designator
39232 @var{thread-id} has the format and interpretation described in
39233 @ref{thread-id syntax}.
39244 @c 'H': How restrictive (or permissive) is the thread model. If a
39245 @c thread is selected and stopped, are other threads allowed
39246 @c to continue to execute? As I mentioned above, I think the
39247 @c semantics of each command when a thread is selected must be
39248 @c described. For example:
39250 @c 'g': If the stub supports threads and a specific thread is
39251 @c selected, returns the register block from that thread;
39252 @c otherwise returns current registers.
39254 @c 'G' If the stub supports threads and a specific thread is
39255 @c selected, sets the registers of the register block of
39256 @c that thread; otherwise sets current registers.
39258 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
39259 @anchor{cycle step packet}
39260 @cindex @samp{i} packet
39261 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
39262 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
39263 step starting at that address.
39266 @cindex @samp{I} packet
39267 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
39271 @cindex @samp{k} packet
39274 The exact effect of this packet is not specified.
39276 For a bare-metal target, it may power cycle or reset the target
39277 system. For that reason, the @samp{k} packet has no reply.
39279 For a single-process target, it may kill that process if possible.
39281 A multiple-process target may choose to kill just one process, or all
39282 that are under @value{GDBN}'s control. For more precise control, use
39283 the vKill packet (@pxref{vKill packet}).
39285 If the target system immediately closes the connection in response to
39286 @samp{k}, @value{GDBN} does not consider the lack of packet
39287 acknowledgment to be an error, and assumes the kill was successful.
39289 If connected using @kbd{target extended-remote}, and the target does
39290 not close the connection in response to a kill request, @value{GDBN}
39291 probes the target state as if a new connection was opened
39292 (@pxref{? packet}).
39294 @item m @var{addr},@var{length}
39295 @cindex @samp{m} packet
39296 Read @var{length} addressable memory units starting at address @var{addr}
39297 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
39298 any particular boundary.
39300 The stub need not use any particular size or alignment when gathering
39301 data from memory for the response; even if @var{addr} is word-aligned
39302 and @var{length} is a multiple of the word size, the stub is free to
39303 use byte accesses, or not. For this reason, this packet may not be
39304 suitable for accessing memory-mapped I/O devices.
39305 @cindex alignment of remote memory accesses
39306 @cindex size of remote memory accesses
39307 @cindex memory, alignment and size of remote accesses
39311 @item @var{XX@dots{}}
39312 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
39313 The reply may contain fewer addressable memory units than requested if the
39314 server was able to read only part of the region of memory.
39319 @item M @var{addr},@var{length}:@var{XX@dots{}}
39320 @cindex @samp{M} packet
39321 Write @var{length} addressable memory units starting at address @var{addr}
39322 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
39323 byte is transmitted as a two-digit hexadecimal number.
39330 for an error (this includes the case where only part of the data was
39335 @cindex @samp{p} packet
39336 Read the value of register @var{n}; @var{n} is in hex.
39337 @xref{read registers packet}, for a description of how the returned
39338 register value is encoded.
39342 @item @var{XX@dots{}}
39343 the register's value
39347 Indicating an unrecognized @var{query}.
39350 @item P @var{n@dots{}}=@var{r@dots{}}
39351 @anchor{write register packet}
39352 @cindex @samp{P} packet
39353 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
39354 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
39355 digits for each byte in the register (target byte order).
39365 @item q @var{name} @var{params}@dots{}
39366 @itemx Q @var{name} @var{params}@dots{}
39367 @cindex @samp{q} packet
39368 @cindex @samp{Q} packet
39369 General query (@samp{q}) and set (@samp{Q}). These packets are
39370 described fully in @ref{General Query Packets}.
39373 @cindex @samp{r} packet
39374 Reset the entire system.
39376 Don't use this packet; use the @samp{R} packet instead.
39379 @cindex @samp{R} packet
39380 Restart the program being debugged. The @var{XX}, while needed, is ignored.
39381 This packet is only available in extended mode (@pxref{extended mode}).
39383 The @samp{R} packet has no reply.
39385 @item s @r{[}@var{addr}@r{]}
39386 @cindex @samp{s} packet
39387 Single step, resuming at @var{addr}. If
39388 @var{addr} is omitted, resume at same address.
39390 This packet is deprecated for multi-threading support. @xref{vCont
39394 @xref{Stop Reply Packets}, for the reply specifications.
39396 @item S @var{sig}@r{[};@var{addr}@r{]}
39397 @anchor{step with signal packet}
39398 @cindex @samp{S} packet
39399 Step with signal. This is analogous to the @samp{C} packet, but
39400 requests a single-step, rather than a normal resumption of execution.
39402 This packet is deprecated for multi-threading support. @xref{vCont
39406 @xref{Stop Reply Packets}, for the reply specifications.
39408 @item t @var{addr}:@var{PP},@var{MM}
39409 @cindex @samp{t} packet
39410 Search backwards starting at address @var{addr} for a match with pattern
39411 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
39412 There must be at least 3 digits in @var{addr}.
39414 @item T @var{thread-id}
39415 @cindex @samp{T} packet
39416 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
39421 thread is still alive
39427 Packets starting with @samp{v} are identified by a multi-letter name,
39428 up to the first @samp{;} or @samp{?} (or the end of the packet).
39430 @item vAttach;@var{pid}
39431 @cindex @samp{vAttach} packet
39432 Attach to a new process with the specified process ID @var{pid}.
39433 The process ID is a
39434 hexadecimal integer identifying the process. In all-stop mode, all
39435 threads in the attached process are stopped; in non-stop mode, it may be
39436 attached without being stopped if that is supported by the target.
39438 @c In non-stop mode, on a successful vAttach, the stub should set the
39439 @c current thread to a thread of the newly-attached process. After
39440 @c attaching, GDB queries for the attached process's thread ID with qC.
39441 @c Also note that, from a user perspective, whether or not the
39442 @c target is stopped on attach in non-stop mode depends on whether you
39443 @c use the foreground or background version of the attach command, not
39444 @c on what vAttach does; GDB does the right thing with respect to either
39445 @c stopping or restarting threads.
39447 This packet is only available in extended mode (@pxref{extended mode}).
39453 @item @r{Any stop packet}
39454 for success in all-stop mode (@pxref{Stop Reply Packets})
39456 for success in non-stop mode (@pxref{Remote Non-Stop})
39459 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
39460 @cindex @samp{vCont} packet
39461 @anchor{vCont packet}
39462 Resume the inferior, specifying different actions for each thread.
39464 For each inferior thread, the leftmost action with a matching
39465 @var{thread-id} is applied. Threads that don't match any action
39466 remain in their current state. Thread IDs are specified using the
39467 syntax described in @ref{thread-id syntax}. If multiprocess
39468 extensions (@pxref{multiprocess extensions}) are supported, actions
39469 can be specified to match all threads in a process by using the
39470 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
39471 @var{thread-id} matches all threads. Specifying no actions is an
39474 Currently supported actions are:
39480 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
39484 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
39487 @item r @var{start},@var{end}
39488 Step once, and then keep stepping as long as the thread stops at
39489 addresses between @var{start} (inclusive) and @var{end} (exclusive).
39490 The remote stub reports a stop reply when either the thread goes out
39491 of the range or is stopped due to an unrelated reason, such as hitting
39492 a breakpoint. @xref{range stepping}.
39494 If the range is empty (@var{start} == @var{end}), then the action
39495 becomes equivalent to the @samp{s} action. In other words,
39496 single-step once, and report the stop (even if the stepped instruction
39497 jumps to @var{start}).
39499 (A stop reply may be sent at any point even if the PC is still within
39500 the stepping range; for example, it is valid to implement this packet
39501 in a degenerate way as a single instruction step operation.)
39505 The optional argument @var{addr} normally associated with the
39506 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
39507 not supported in @samp{vCont}.
39509 The @samp{t} action is only relevant in non-stop mode
39510 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
39511 A stop reply should be generated for any affected thread not already stopped.
39512 When a thread is stopped by means of a @samp{t} action,
39513 the corresponding stop reply should indicate that the thread has stopped with
39514 signal @samp{0}, regardless of whether the target uses some other signal
39515 as an implementation detail.
39517 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
39518 @samp{r} actions for threads that are already running. Conversely,
39519 the server must ignore @samp{t} actions for threads that are already
39522 @emph{Note:} In non-stop mode, a thread is considered running until
39523 @value{GDBN} acknowledges an asynchronous stop notification for it with
39524 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
39526 The stub must support @samp{vCont} if it reports support for
39527 multiprocess extensions (@pxref{multiprocess extensions}).
39530 @xref{Stop Reply Packets}, for the reply specifications.
39533 @cindex @samp{vCont?} packet
39534 Request a list of actions supported by the @samp{vCont} packet.
39538 @item vCont@r{[};@var{action}@dots{}@r{]}
39539 The @samp{vCont} packet is supported. Each @var{action} is a supported
39540 command in the @samp{vCont} packet.
39542 The @samp{vCont} packet is not supported.
39545 @anchor{vCtrlC packet}
39547 @cindex @samp{vCtrlC} packet
39548 Interrupt remote target as if a control-C was pressed on the remote
39549 terminal. This is the equivalent to reacting to the @code{^C}
39550 (@samp{\003}, the control-C character) character in all-stop mode
39551 while the target is running, except this works in non-stop mode.
39552 @xref{interrupting remote targets}, for more info on the all-stop
39563 @item vFile:@var{operation}:@var{parameter}@dots{}
39564 @cindex @samp{vFile} packet
39565 Perform a file operation on the target system. For details,
39566 see @ref{Host I/O Packets}.
39568 @item vFlashErase:@var{addr},@var{length}
39569 @cindex @samp{vFlashErase} packet
39570 Direct the stub to erase @var{length} bytes of flash starting at
39571 @var{addr}. The region may enclose any number of flash blocks, but
39572 its start and end must fall on block boundaries, as indicated by the
39573 flash block size appearing in the memory map (@pxref{Memory Map
39574 Format}). @value{GDBN} groups flash memory programming operations
39575 together, and sends a @samp{vFlashDone} request after each group; the
39576 stub is allowed to delay erase operation until the @samp{vFlashDone}
39577 packet is received.
39587 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
39588 @cindex @samp{vFlashWrite} packet
39589 Direct the stub to write data to flash address @var{addr}. The data
39590 is passed in binary form using the same encoding as for the @samp{X}
39591 packet (@pxref{Binary Data}). The memory ranges specified by
39592 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
39593 not overlap, and must appear in order of increasing addresses
39594 (although @samp{vFlashErase} packets for higher addresses may already
39595 have been received; the ordering is guaranteed only between
39596 @samp{vFlashWrite} packets). If a packet writes to an address that was
39597 neither erased by a preceding @samp{vFlashErase} packet nor by some other
39598 target-specific method, the results are unpredictable.
39606 for vFlashWrite addressing non-flash memory
39612 @cindex @samp{vFlashDone} packet
39613 Indicate to the stub that flash programming operation is finished.
39614 The stub is permitted to delay or batch the effects of a group of
39615 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
39616 @samp{vFlashDone} packet is received. The contents of the affected
39617 regions of flash memory are unpredictable until the @samp{vFlashDone}
39618 request is completed.
39620 @item vKill;@var{pid}
39621 @cindex @samp{vKill} packet
39622 @anchor{vKill packet}
39623 Kill the process with the specified process ID @var{pid}, which is a
39624 hexadecimal integer identifying the process. This packet is used in
39625 preference to @samp{k} when multiprocess protocol extensions are
39626 supported; see @ref{multiprocess extensions}.
39636 @item vMustReplyEmpty
39637 @cindex @samp{vMustReplyEmpty} packet
39638 The correct reply to an unknown @samp{v} packet is to return the empty
39639 string, however, some older versions of @command{gdbserver} would
39640 incorrectly return @samp{OK} for unknown @samp{v} packets.
39642 The @samp{vMustReplyEmpty} is used as a feature test to check how
39643 @command{gdbserver} handles unknown packets, it is important that this
39644 packet be handled in the same way as other unknown @samp{v} packets.
39645 If this packet is handled differently to other unknown @samp{v}
39646 packets then it is possible that @value{GDBN} may run into problems in
39647 other areas, specifically around use of @samp{vFile:setfs:}.
39649 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
39650 @cindex @samp{vRun} packet
39651 Run the program @var{filename}, passing it each @var{argument} on its
39652 command line. The file and arguments are hex-encoded strings. If
39653 @var{filename} is an empty string, the stub may use a default program
39654 (e.g.@: the last program run). The program is created in the stopped
39657 @c FIXME: What about non-stop mode?
39659 This packet is only available in extended mode (@pxref{extended mode}).
39665 @item @r{Any stop packet}
39666 for success (@pxref{Stop Reply Packets})
39670 @cindex @samp{vStopped} packet
39671 @xref{Notification Packets}.
39673 @item X @var{addr},@var{length}:@var{XX@dots{}}
39675 @cindex @samp{X} packet
39676 Write data to memory, where the data is transmitted in binary.
39677 Memory is specified by its address @var{addr} and number of addressable memory
39678 units @var{length} (@pxref{addressable memory unit});
39679 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
39689 @item z @var{type},@var{addr},@var{kind}
39690 @itemx Z @var{type},@var{addr},@var{kind}
39691 @anchor{insert breakpoint or watchpoint packet}
39692 @cindex @samp{z} packet
39693 @cindex @samp{Z} packets
39694 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
39695 watchpoint starting at address @var{address} of kind @var{kind}.
39697 Each breakpoint and watchpoint packet @var{type} is documented
39700 @emph{Implementation notes: A remote target shall return an empty string
39701 for an unrecognized breakpoint or watchpoint packet @var{type}. A
39702 remote target shall support either both or neither of a given
39703 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
39704 avoid potential problems with duplicate packets, the operations should
39705 be implemented in an idempotent way.}
39707 @item z0,@var{addr},@var{kind}
39708 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
39709 @cindex @samp{z0} packet
39710 @cindex @samp{Z0} packet
39711 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
39712 @var{addr} of type @var{kind}.
39714 A software breakpoint is implemented by replacing the instruction at
39715 @var{addr} with a software breakpoint or trap instruction. The
39716 @var{kind} is target-specific and typically indicates the size of the
39717 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
39718 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
39719 architectures have additional meanings for @var{kind}
39720 (@pxref{Architecture-Specific Protocol Details}); if no
39721 architecture-specific value is being used, it should be @samp{0}.
39722 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
39723 conditional expressions in bytecode form that should be evaluated on
39724 the target's side. These are the conditions that should be taken into
39725 consideration when deciding if the breakpoint trigger should be
39726 reported back to @value{GDBN}.
39728 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
39729 for how to best report a software breakpoint event to @value{GDBN}.
39731 The @var{cond_list} parameter is comprised of a series of expressions,
39732 concatenated without separators. Each expression has the following form:
39736 @item X @var{len},@var{expr}
39737 @var{len} is the length of the bytecode expression and @var{expr} is the
39738 actual conditional expression in bytecode form.
39742 The optional @var{cmd_list} parameter introduces commands that may be
39743 run on the target, rather than being reported back to @value{GDBN}.
39744 The parameter starts with a numeric flag @var{persist}; if the flag is
39745 nonzero, then the breakpoint may remain active and the commands
39746 continue to be run even when @value{GDBN} disconnects from the target.
39747 Following this flag is a series of expressions concatenated with no
39748 separators. Each expression has the following form:
39752 @item X @var{len},@var{expr}
39753 @var{len} is the length of the bytecode expression and @var{expr} is the
39754 actual commands expression in bytecode form.
39758 @emph{Implementation note: It is possible for a target to copy or move
39759 code that contains software breakpoints (e.g., when implementing
39760 overlays). The behavior of this packet, in the presence of such a
39761 target, is not defined.}
39773 @item z1,@var{addr},@var{kind}
39774 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
39775 @cindex @samp{z1} packet
39776 @cindex @samp{Z1} packet
39777 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
39778 address @var{addr}.
39780 A hardware breakpoint is implemented using a mechanism that is not
39781 dependent on being able to modify the target's memory. The
39782 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
39783 same meaning as in @samp{Z0} packets.
39785 @emph{Implementation note: A hardware breakpoint is not affected by code
39798 @item z2,@var{addr},@var{kind}
39799 @itemx Z2,@var{addr},@var{kind}
39800 @cindex @samp{z2} packet
39801 @cindex @samp{Z2} packet
39802 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
39803 The number of bytes to watch is specified by @var{kind}.
39815 @item z3,@var{addr},@var{kind}
39816 @itemx Z3,@var{addr},@var{kind}
39817 @cindex @samp{z3} packet
39818 @cindex @samp{Z3} packet
39819 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
39820 The number of bytes to watch is specified by @var{kind}.
39832 @item z4,@var{addr},@var{kind}
39833 @itemx Z4,@var{addr},@var{kind}
39834 @cindex @samp{z4} packet
39835 @cindex @samp{Z4} packet
39836 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
39837 The number of bytes to watch is specified by @var{kind}.
39851 @node Stop Reply Packets
39852 @section Stop Reply Packets
39853 @cindex stop reply packets
39855 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
39856 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
39857 receive any of the below as a reply. Except for @samp{?}
39858 and @samp{vStopped}, that reply is only returned
39859 when the target halts. In the below the exact meaning of @dfn{signal
39860 number} is defined by the header @file{include/gdb/signals.h} in the
39861 @value{GDBN} source code.
39863 In non-stop mode, the server will simply reply @samp{OK} to commands
39864 such as @samp{vCont}; any stop will be the subject of a future
39865 notification. @xref{Remote Non-Stop}.
39867 As in the description of request packets, we include spaces in the
39868 reply templates for clarity; these are not part of the reply packet's
39869 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
39875 The program received signal number @var{AA} (a two-digit hexadecimal
39876 number). This is equivalent to a @samp{T} response with no
39877 @var{n}:@var{r} pairs.
39879 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
39880 @cindex @samp{T} packet reply
39881 The program received signal number @var{AA} (a two-digit hexadecimal
39882 number). This is equivalent to an @samp{S} response, except that the
39883 @samp{@var{n}:@var{r}} pairs can carry values of important registers
39884 and other information directly in the stop reply packet, reducing
39885 round-trip latency. Single-step and breakpoint traps are reported
39886 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
39890 If @var{n} is a hexadecimal number, it is a register number, and the
39891 corresponding @var{r} gives that register's value. The data @var{r} is a
39892 series of bytes in target byte order, with each byte given by a
39893 two-digit hex number.
39896 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
39897 the stopped thread, as specified in @ref{thread-id syntax}.
39900 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
39901 the core on which the stop event was detected.
39904 If @var{n} is a recognized @dfn{stop reason}, it describes a more
39905 specific event that stopped the target. The currently defined stop
39906 reasons are listed below. The @var{aa} should be @samp{05}, the trap
39907 signal. At most one stop reason should be present.
39910 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
39911 and go on to the next; this allows us to extend the protocol in the
39915 The currently defined stop reasons are:
39921 The packet indicates a watchpoint hit, and @var{r} is the data address, in
39924 @item syscall_entry
39925 @itemx syscall_return
39926 The packet indicates a syscall entry or return, and @var{r} is the
39927 syscall number, in hex.
39929 @cindex shared library events, remote reply
39931 The packet indicates that the loaded libraries have changed.
39932 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
39933 list of loaded libraries. The @var{r} part is ignored.
39935 @cindex replay log events, remote reply
39937 The packet indicates that the target cannot continue replaying
39938 logged execution events, because it has reached the end (or the
39939 beginning when executing backward) of the log. The value of @var{r}
39940 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
39941 for more information.
39944 @anchor{swbreak stop reason}
39945 The packet indicates a software breakpoint instruction was executed,
39946 irrespective of whether it was @value{GDBN} that planted the
39947 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
39948 part must be left empty.
39950 On some architectures, such as x86, at the architecture level, when a
39951 breakpoint instruction executes the program counter points at the
39952 breakpoint address plus an offset. On such targets, the stub is
39953 responsible for adjusting the PC to point back at the breakpoint
39956 This packet should not be sent by default; older @value{GDBN} versions
39957 did not support it. @value{GDBN} requests it, by supplying an
39958 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39959 remote stub must also supply the appropriate @samp{qSupported} feature
39960 indicating support.
39962 This packet is required for correct non-stop mode operation.
39965 The packet indicates the target stopped for a hardware breakpoint.
39966 The @var{r} part must be left empty.
39968 The same remarks about @samp{qSupported} and non-stop mode above
39971 @cindex fork events, remote reply
39973 The packet indicates that @code{fork} was called, and @var{r}
39974 is the thread ID of the new child process. Refer to
39975 @ref{thread-id syntax} for the format of the @var{thread-id}
39976 field. This packet is only applicable to targets that support
39979 This packet should not be sent by default; older @value{GDBN} versions
39980 did not support it. @value{GDBN} requests it, by supplying an
39981 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39982 remote stub must also supply the appropriate @samp{qSupported} feature
39983 indicating support.
39985 @cindex vfork events, remote reply
39987 The packet indicates that @code{vfork} was called, and @var{r}
39988 is the thread ID of the new child process. Refer to
39989 @ref{thread-id syntax} for the format of the @var{thread-id}
39990 field. This packet is only applicable to targets that support
39993 This packet should not be sent by default; older @value{GDBN} versions
39994 did not support it. @value{GDBN} requests it, by supplying an
39995 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
39996 remote stub must also supply the appropriate @samp{qSupported} feature
39997 indicating support.
39999 @cindex vforkdone events, remote reply
40001 The packet indicates that a child process created by a vfork
40002 has either called @code{exec} or terminated, so that the
40003 address spaces of the parent and child process are no longer
40004 shared. The @var{r} part is ignored. This packet is only
40005 applicable to targets that support vforkdone events.
40007 This packet should not be sent by default; older @value{GDBN} versions
40008 did not support it. @value{GDBN} requests it, by supplying an
40009 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40010 remote stub must also supply the appropriate @samp{qSupported} feature
40011 indicating support.
40013 @cindex exec events, remote reply
40015 The packet indicates that @code{execve} was called, and @var{r}
40016 is the absolute pathname of the file that was executed, in hex.
40017 This packet is only applicable to targets that support exec events.
40019 This packet should not be sent by default; older @value{GDBN} versions
40020 did not support it. @value{GDBN} requests it, by supplying an
40021 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40022 remote stub must also supply the appropriate @samp{qSupported} feature
40023 indicating support.
40025 @cindex thread create event, remote reply
40026 @anchor{thread create event}
40028 The packet indicates that the thread was just created. The new thread
40029 is stopped until @value{GDBN} sets it running with a resumption packet
40030 (@pxref{vCont packet}). This packet should not be sent by default;
40031 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
40032 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
40033 @var{r} part is ignored.
40038 @itemx W @var{AA} ; process:@var{pid}
40039 The process exited, and @var{AA} is the exit status. This is only
40040 applicable to certain targets.
40042 The second form of the response, including the process ID of the
40043 exited process, can be used only when @value{GDBN} has reported
40044 support for multiprocess protocol extensions; see @ref{multiprocess
40045 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40049 @itemx X @var{AA} ; process:@var{pid}
40050 The process terminated with signal @var{AA}.
40052 The second form of the response, including the process ID of the
40053 terminated process, can be used only when @value{GDBN} has reported
40054 support for multiprocess protocol extensions; see @ref{multiprocess
40055 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40058 @anchor{thread exit event}
40059 @cindex thread exit event, remote reply
40060 @item w @var{AA} ; @var{tid}
40062 The thread exited, and @var{AA} is the exit status. This response
40063 should not be sent by default; @value{GDBN} requests it with the
40064 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
40065 @var{AA} is formatted as a big-endian hex string.
40068 There are no resumed threads left in the target. In other words, even
40069 though the process is alive, the last resumed thread has exited. For
40070 example, say the target process has two threads: thread 1 and thread
40071 2. The client leaves thread 1 stopped, and resumes thread 2, which
40072 subsequently exits. At this point, even though the process is still
40073 alive, and thus no @samp{W} stop reply is sent, no thread is actually
40074 executing either. The @samp{N} stop reply thus informs the client
40075 that it can stop waiting for stop replies. This packet should not be
40076 sent by default; older @value{GDBN} versions did not support it.
40077 @value{GDBN} requests it, by supplying an appropriate
40078 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
40079 also supply the appropriate @samp{qSupported} feature indicating
40082 @item O @var{XX}@dots{}
40083 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
40084 written as the program's console output. This can happen at any time
40085 while the program is running and the debugger should continue to wait
40086 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
40088 @item F @var{call-id},@var{parameter}@dots{}
40089 @var{call-id} is the identifier which says which host system call should
40090 be called. This is just the name of the function. Translation into the
40091 correct system call is only applicable as it's defined in @value{GDBN}.
40092 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
40095 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
40096 this very system call.
40098 The target replies with this packet when it expects @value{GDBN} to
40099 call a host system call on behalf of the target. @value{GDBN} replies
40100 with an appropriate @samp{F} packet and keeps up waiting for the next
40101 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
40102 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
40103 Protocol Extension}, for more details.
40107 @node General Query Packets
40108 @section General Query Packets
40109 @cindex remote query requests
40111 Packets starting with @samp{q} are @dfn{general query packets};
40112 packets starting with @samp{Q} are @dfn{general set packets}. General
40113 query and set packets are a semi-unified form for retrieving and
40114 sending information to and from the stub.
40116 The initial letter of a query or set packet is followed by a name
40117 indicating what sort of thing the packet applies to. For example,
40118 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
40119 definitions with the stub. These packet names follow some
40124 The name must not contain commas, colons or semicolons.
40126 Most @value{GDBN} query and set packets have a leading upper case
40129 The names of custom vendor packets should use a company prefix, in
40130 lower case, followed by a period. For example, packets designed at
40131 the Acme Corporation might begin with @samp{qacme.foo} (for querying
40132 foos) or @samp{Qacme.bar} (for setting bars).
40135 The name of a query or set packet should be separated from any
40136 parameters by a @samp{:}; the parameters themselves should be
40137 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
40138 full packet name, and check for a separator or the end of the packet,
40139 in case two packet names share a common prefix. New packets should not begin
40140 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
40141 packets predate these conventions, and have arguments without any terminator
40142 for the packet name; we suspect they are in widespread use in places that
40143 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
40144 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
40147 Like the descriptions of the other packets, each description here
40148 has a template showing the packet's overall syntax, followed by an
40149 explanation of the packet's meaning. We include spaces in some of the
40150 templates for clarity; these are not part of the packet's syntax. No
40151 @value{GDBN} packet uses spaces to separate its components.
40153 Here are the currently defined query and set packets:
40159 Turn on or off the agent as a helper to perform some debugging operations
40160 delegated from @value{GDBN} (@pxref{Control Agent}).
40162 @item QAllow:@var{op}:@var{val}@dots{}
40163 @cindex @samp{QAllow} packet
40164 Specify which operations @value{GDBN} expects to request of the
40165 target, as a semicolon-separated list of operation name and value
40166 pairs. Possible values for @var{op} include @samp{WriteReg},
40167 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
40168 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
40169 indicating that @value{GDBN} will not request the operation, or 1,
40170 indicating that it may. (The target can then use this to set up its
40171 own internals optimally, for instance if the debugger never expects to
40172 insert breakpoints, it may not need to install its own trap handler.)
40175 @cindex current thread, remote request
40176 @cindex @samp{qC} packet
40177 Return the current thread ID.
40181 @item QC @var{thread-id}
40182 Where @var{thread-id} is a thread ID as documented in
40183 @ref{thread-id syntax}.
40184 @item @r{(anything else)}
40185 Any other reply implies the old thread ID.
40188 @item qCRC:@var{addr},@var{length}
40189 @cindex CRC of memory block, remote request
40190 @cindex @samp{qCRC} packet
40191 @anchor{qCRC packet}
40192 Compute the CRC checksum of a block of memory using CRC-32 defined in
40193 IEEE 802.3. The CRC is computed byte at a time, taking the most
40194 significant bit of each byte first. The initial pattern code
40195 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
40197 @emph{Note:} This is the same CRC used in validating separate debug
40198 files (@pxref{Separate Debug Files, , Debugging Information in Separate
40199 Files}). However the algorithm is slightly different. When validating
40200 separate debug files, the CRC is computed taking the @emph{least}
40201 significant bit of each byte first, and the final result is inverted to
40202 detect trailing zeros.
40207 An error (such as memory fault)
40208 @item C @var{crc32}
40209 The specified memory region's checksum is @var{crc32}.
40212 @item QDisableRandomization:@var{value}
40213 @cindex disable address space randomization, remote request
40214 @cindex @samp{QDisableRandomization} packet
40215 Some target operating systems will randomize the virtual address space
40216 of the inferior process as a security feature, but provide a feature
40217 to disable such randomization, e.g.@: to allow for a more deterministic
40218 debugging experience. On such systems, this packet with a @var{value}
40219 of 1 directs the target to disable address space randomization for
40220 processes subsequently started via @samp{vRun} packets, while a packet
40221 with a @var{value} of 0 tells the target to enable address space
40224 This packet is only available in extended mode (@pxref{extended mode}).
40229 The request succeeded.
40232 An error occurred. The error number @var{nn} is given as hex digits.
40235 An empty reply indicates that @samp{QDisableRandomization} is not supported
40239 This packet is not probed by default; the remote stub must request it,
40240 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40241 This should only be done on targets that actually support disabling
40242 address space randomization.
40244 @item QStartupWithShell:@var{value}
40245 @cindex startup with shell, remote request
40246 @cindex @samp{QStartupWithShell} packet
40247 On UNIX-like targets, it is possible to start the inferior using a
40248 shell program. This is the default behavior on both @value{GDBN} and
40249 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
40250 used to inform @command{gdbserver} whether it should start the
40251 inferior using a shell or not.
40253 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
40254 to start the inferior. If @var{value} is @samp{1},
40255 @command{gdbserver} will use a shell to start the inferior. All other
40256 values are considered an error.
40258 This packet is only available in extended mode (@pxref{extended
40264 The request succeeded.
40267 An error occurred. The error number @var{nn} is given as hex digits.
40270 This packet is not probed by default; the remote stub must request it,
40271 by supplying an appropriate @samp{qSupported} response
40272 (@pxref{qSupported}). This should only be done on targets that
40273 actually support starting the inferior using a shell.
40275 Use of this packet is controlled by the @code{set startup-with-shell}
40276 command; @pxref{set startup-with-shell}.
40278 @item QEnvironmentHexEncoded:@var{hex-value}
40279 @anchor{QEnvironmentHexEncoded}
40280 @cindex set environment variable, remote request
40281 @cindex @samp{QEnvironmentHexEncoded} packet
40282 On UNIX-like targets, it is possible to set environment variables that
40283 will be passed to the inferior during the startup process. This
40284 packet is used to inform @command{gdbserver} of an environment
40285 variable that has been defined by the user on @value{GDBN} (@pxref{set
40288 The packet is composed by @var{hex-value}, an hex encoded
40289 representation of the @var{name=value} format representing an
40290 environment variable. The name of the environment variable is
40291 represented by @var{name}, and the value to be assigned to the
40292 environment variable is represented by @var{value}. If the variable
40293 has no value (i.e., the value is @code{null}), then @var{value} will
40296 This packet is only available in extended mode (@pxref{extended
40302 The request succeeded.
40305 This packet is not probed by default; the remote stub must request it,
40306 by supplying an appropriate @samp{qSupported} response
40307 (@pxref{qSupported}). This should only be done on targets that
40308 actually support passing environment variables to the starting
40311 This packet is related to the @code{set environment} command;
40312 @pxref{set environment}.
40314 @item QEnvironmentUnset:@var{hex-value}
40315 @anchor{QEnvironmentUnset}
40316 @cindex unset environment variable, remote request
40317 @cindex @samp{QEnvironmentUnset} packet
40318 On UNIX-like targets, it is possible to unset environment variables
40319 before starting the inferior in the remote target. This packet is
40320 used to inform @command{gdbserver} of an environment variable that has
40321 been unset by the user on @value{GDBN} (@pxref{unset environment}).
40323 The packet is composed by @var{hex-value}, an hex encoded
40324 representation of the name of the environment variable to be unset.
40326 This packet is only available in extended mode (@pxref{extended
40332 The request succeeded.
40335 This packet is not probed by default; the remote stub must request it,
40336 by supplying an appropriate @samp{qSupported} response
40337 (@pxref{qSupported}). This should only be done on targets that
40338 actually support passing environment variables to the starting
40341 This packet is related to the @code{unset environment} command;
40342 @pxref{unset environment}.
40344 @item QEnvironmentReset
40345 @anchor{QEnvironmentReset}
40346 @cindex reset environment, remote request
40347 @cindex @samp{QEnvironmentReset} packet
40348 On UNIX-like targets, this packet is used to reset the state of
40349 environment variables in the remote target before starting the
40350 inferior. In this context, reset means unsetting all environment
40351 variables that were previously set by the user (i.e., were not
40352 initially present in the environment). It is sent to
40353 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
40354 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
40355 (@pxref{QEnvironmentUnset}) packets.
40357 This packet is only available in extended mode (@pxref{extended
40363 The request succeeded.
40366 This packet is not probed by default; the remote stub must request it,
40367 by supplying an appropriate @samp{qSupported} response
40368 (@pxref{qSupported}). This should only be done on targets that
40369 actually support passing environment variables to the starting
40372 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
40373 @anchor{QSetWorkingDir packet}
40374 @cindex set working directory, remote request
40375 @cindex @samp{QSetWorkingDir} packet
40376 This packet is used to inform the remote server of the intended
40377 current working directory for programs that are going to be executed.
40379 The packet is composed by @var{directory}, an hex encoded
40380 representation of the directory that the remote inferior will use as
40381 its current working directory. If @var{directory} is an empty string,
40382 the remote server should reset the inferior's current working
40383 directory to its original, empty value.
40385 This packet is only available in extended mode (@pxref{extended
40391 The request succeeded.
40395 @itemx qsThreadInfo
40396 @cindex list active threads, remote request
40397 @cindex @samp{qfThreadInfo} packet
40398 @cindex @samp{qsThreadInfo} packet
40399 Obtain a list of all active thread IDs from the target (OS). Since there
40400 may be too many active threads to fit into one reply packet, this query
40401 works iteratively: it may require more than one query/reply sequence to
40402 obtain the entire list of threads. The first query of the sequence will
40403 be the @samp{qfThreadInfo} query; subsequent queries in the
40404 sequence will be the @samp{qsThreadInfo} query.
40406 NOTE: This packet replaces the @samp{qL} query (see below).
40410 @item m @var{thread-id}
40412 @item m @var{thread-id},@var{thread-id}@dots{}
40413 a comma-separated list of thread IDs
40415 (lower case letter @samp{L}) denotes end of list.
40418 In response to each query, the target will reply with a list of one or
40419 more thread IDs, separated by commas.
40420 @value{GDBN} will respond to each reply with a request for more thread
40421 ids (using the @samp{qs} form of the query), until the target responds
40422 with @samp{l} (lower-case ell, for @dfn{last}).
40423 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
40426 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
40427 initial connection with the remote target, and the very first thread ID
40428 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
40429 message. Therefore, the stub should ensure that the first thread ID in
40430 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
40432 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
40433 @cindex get thread-local storage address, remote request
40434 @cindex @samp{qGetTLSAddr} packet
40435 Fetch the address associated with thread local storage specified
40436 by @var{thread-id}, @var{offset}, and @var{lm}.
40438 @var{thread-id} is the thread ID associated with the
40439 thread for which to fetch the TLS address. @xref{thread-id syntax}.
40441 @var{offset} is the (big endian, hex encoded) offset associated with the
40442 thread local variable. (This offset is obtained from the debug
40443 information associated with the variable.)
40445 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
40446 load module associated with the thread local storage. For example,
40447 a @sc{gnu}/Linux system will pass the link map address of the shared
40448 object associated with the thread local storage under consideration.
40449 Other operating environments may choose to represent the load module
40450 differently, so the precise meaning of this parameter will vary.
40454 @item @var{XX}@dots{}
40455 Hex encoded (big endian) bytes representing the address of the thread
40456 local storage requested.
40459 An error occurred. The error number @var{nn} is given as hex digits.
40462 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
40465 @item qGetTIBAddr:@var{thread-id}
40466 @cindex get thread information block address
40467 @cindex @samp{qGetTIBAddr} packet
40468 Fetch address of the Windows OS specific Thread Information Block.
40470 @var{thread-id} is the thread ID associated with the thread.
40474 @item @var{XX}@dots{}
40475 Hex encoded (big endian) bytes representing the linear address of the
40476 thread information block.
40479 An error occured. This means that either the thread was not found, or the
40480 address could not be retrieved.
40483 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
40486 @item qL @var{startflag} @var{threadcount} @var{nextthread}
40487 Obtain thread information from RTOS. Where: @var{startflag} (one hex
40488 digit) is one to indicate the first query and zero to indicate a
40489 subsequent query; @var{threadcount} (two hex digits) is the maximum
40490 number of threads the response packet can contain; and @var{nextthread}
40491 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
40492 returned in the response as @var{argthread}.
40494 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
40498 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
40499 Where: @var{count} (two hex digits) is the number of threads being
40500 returned; @var{done} (one hex digit) is zero to indicate more threads
40501 and one indicates no further threads; @var{argthreadid} (eight hex
40502 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
40503 is a sequence of thread IDs, @var{threadid} (eight hex
40504 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
40508 @cindex section offsets, remote request
40509 @cindex @samp{qOffsets} packet
40510 Get section offsets that the target used when relocating the downloaded
40515 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
40516 Relocate the @code{Text} section by @var{xxx} from its original address.
40517 Relocate the @code{Data} section by @var{yyy} from its original address.
40518 If the object file format provides segment information (e.g.@: @sc{elf}
40519 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
40520 segments by the supplied offsets.
40522 @emph{Note: while a @code{Bss} offset may be included in the response,
40523 @value{GDBN} ignores this and instead applies the @code{Data} offset
40524 to the @code{Bss} section.}
40526 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
40527 Relocate the first segment of the object file, which conventionally
40528 contains program code, to a starting address of @var{xxx}. If
40529 @samp{DataSeg} is specified, relocate the second segment, which
40530 conventionally contains modifiable data, to a starting address of
40531 @var{yyy}. @value{GDBN} will report an error if the object file
40532 does not contain segment information, or does not contain at least
40533 as many segments as mentioned in the reply. Extra segments are
40534 kept at fixed offsets relative to the last relocated segment.
40537 @item qP @var{mode} @var{thread-id}
40538 @cindex thread information, remote request
40539 @cindex @samp{qP} packet
40540 Returns information on @var{thread-id}. Where: @var{mode} is a hex
40541 encoded 32 bit mode; @var{thread-id} is a thread ID
40542 (@pxref{thread-id syntax}).
40544 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
40547 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
40551 @cindex non-stop mode, remote request
40552 @cindex @samp{QNonStop} packet
40554 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
40555 @xref{Remote Non-Stop}, for more information.
40560 The request succeeded.
40563 An error occurred. The error number @var{nn} is given as hex digits.
40566 An empty reply indicates that @samp{QNonStop} is not supported by
40570 This packet is not probed by default; the remote stub must request it,
40571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40572 Use of this packet is controlled by the @code{set non-stop} command;
40573 @pxref{Non-Stop Mode}.
40575 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
40576 @itemx QCatchSyscalls:0
40577 @cindex catch syscalls from inferior, remote request
40578 @cindex @samp{QCatchSyscalls} packet
40579 @anchor{QCatchSyscalls}
40580 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
40581 catching syscalls from the inferior process.
40583 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
40584 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
40585 is listed, every system call should be reported.
40587 Note that if a syscall not in the list is reported, @value{GDBN} will
40588 still filter the event according to its own list from all corresponding
40589 @code{catch syscall} commands. However, it is more efficient to only
40590 report the requested syscalls.
40592 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
40593 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
40595 If the inferior process execs, the state of @samp{QCatchSyscalls} is
40596 kept for the new process too. On targets where exec may affect syscall
40597 numbers, for example with exec between 32 and 64-bit processes, the
40598 client should send a new packet with the new syscall list.
40603 The request succeeded.
40606 An error occurred. @var{nn} are hex digits.
40609 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
40613 Use of this packet is controlled by the @code{set remote catch-syscalls}
40614 command (@pxref{Remote Configuration, set remote catch-syscalls}).
40615 This packet is not probed by default; the remote stub must request it,
40616 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40618 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40619 @cindex pass signals to inferior, remote request
40620 @cindex @samp{QPassSignals} packet
40621 @anchor{QPassSignals}
40622 Each listed @var{signal} should be passed directly to the inferior process.
40623 Signals are numbered identically to continue packets and stop replies
40624 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40625 strictly greater than the previous item. These signals do not need to stop
40626 the inferior, or be reported to @value{GDBN}. All other signals should be
40627 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
40628 combine; any earlier @samp{QPassSignals} list is completely replaced by the
40629 new list. This packet improves performance when using @samp{handle
40630 @var{signal} nostop noprint pass}.
40635 The request succeeded.
40638 An error occurred. The error number @var{nn} is given as hex digits.
40641 An empty reply indicates that @samp{QPassSignals} is not supported by
40645 Use of this packet is controlled by the @code{set remote pass-signals}
40646 command (@pxref{Remote Configuration, set remote pass-signals}).
40647 This packet is not probed by default; the remote stub must request it,
40648 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40650 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40651 @cindex signals the inferior may see, remote request
40652 @cindex @samp{QProgramSignals} packet
40653 @anchor{QProgramSignals}
40654 Each listed @var{signal} may be delivered to the inferior process.
40655 Others should be silently discarded.
40657 In some cases, the remote stub may need to decide whether to deliver a
40658 signal to the program or not without @value{GDBN} involvement. One
40659 example of that is while detaching --- the program's threads may have
40660 stopped for signals that haven't yet had a chance of being reported to
40661 @value{GDBN}, and so the remote stub can use the signal list specified
40662 by this packet to know whether to deliver or ignore those pending
40665 This does not influence whether to deliver a signal as requested by a
40666 resumption packet (@pxref{vCont packet}).
40668 Signals are numbered identically to continue packets and stop replies
40669 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40670 strictly greater than the previous item. Multiple
40671 @samp{QProgramSignals} packets do not combine; any earlier
40672 @samp{QProgramSignals} list is completely replaced by the new list.
40677 The request succeeded.
40680 An error occurred. The error number @var{nn} is given as hex digits.
40683 An empty reply indicates that @samp{QProgramSignals} is not supported
40687 Use of this packet is controlled by the @code{set remote program-signals}
40688 command (@pxref{Remote Configuration, set remote program-signals}).
40689 This packet is not probed by default; the remote stub must request it,
40690 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40692 @anchor{QThreadEvents}
40693 @item QThreadEvents:1
40694 @itemx QThreadEvents:0
40695 @cindex thread create/exit events, remote request
40696 @cindex @samp{QThreadEvents} packet
40698 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
40699 reporting of thread create and exit events. @xref{thread create
40700 event}, for the reply specifications. For example, this is used in
40701 non-stop mode when @value{GDBN} stops a set of threads and
40702 synchronously waits for the their corresponding stop replies. Without
40703 exit events, if one of the threads exits, @value{GDBN} would hang
40704 forever not knowing that it should no longer expect a stop for that
40705 same thread. @value{GDBN} does not enable this feature unless the
40706 stub reports that it supports it by including @samp{QThreadEvents+} in
40707 its @samp{qSupported} reply.
40712 The request succeeded.
40715 An error occurred. The error number @var{nn} is given as hex digits.
40718 An empty reply indicates that @samp{QThreadEvents} is not supported by
40722 Use of this packet is controlled by the @code{set remote thread-events}
40723 command (@pxref{Remote Configuration, set remote thread-events}).
40725 @item qRcmd,@var{command}
40726 @cindex execute remote command, remote request
40727 @cindex @samp{qRcmd} packet
40728 @var{command} (hex encoded) is passed to the local interpreter for
40729 execution. Invalid commands should be reported using the output
40730 string. Before the final result packet, the target may also respond
40731 with a number of intermediate @samp{O@var{output}} console output
40732 packets. @emph{Implementors should note that providing access to a
40733 stubs's interpreter may have security implications}.
40738 A command response with no output.
40740 A command response with the hex encoded output string @var{OUTPUT}.
40742 Indicate a badly formed request.
40744 An empty reply indicates that @samp{qRcmd} is not recognized.
40747 (Note that the @code{qRcmd} packet's name is separated from the
40748 command by a @samp{,}, not a @samp{:}, contrary to the naming
40749 conventions above. Please don't use this packet as a model for new
40752 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
40753 @cindex searching memory, in remote debugging
40755 @cindex @samp{qSearch:memory} packet
40757 @cindex @samp{qSearch memory} packet
40758 @anchor{qSearch memory}
40759 Search @var{length} bytes at @var{address} for @var{search-pattern}.
40760 Both @var{address} and @var{length} are encoded in hex;
40761 @var{search-pattern} is a sequence of bytes, also hex encoded.
40766 The pattern was not found.
40768 The pattern was found at @var{address}.
40770 A badly formed request or an error was encountered while searching memory.
40772 An empty reply indicates that @samp{qSearch:memory} is not recognized.
40775 @item QStartNoAckMode
40776 @cindex @samp{QStartNoAckMode} packet
40777 @anchor{QStartNoAckMode}
40778 Request that the remote stub disable the normal @samp{+}/@samp{-}
40779 protocol acknowledgments (@pxref{Packet Acknowledgment}).
40784 The stub has switched to no-acknowledgment mode.
40785 @value{GDBN} acknowledges this response,
40786 but neither the stub nor @value{GDBN} shall send or expect further
40787 @samp{+}/@samp{-} acknowledgments in the current connection.
40789 An empty reply indicates that the stub does not support no-acknowledgment mode.
40792 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
40793 @cindex supported packets, remote query
40794 @cindex features of the remote protocol
40795 @cindex @samp{qSupported} packet
40796 @anchor{qSupported}
40797 Tell the remote stub about features supported by @value{GDBN}, and
40798 query the stub for features it supports. This packet allows
40799 @value{GDBN} and the remote stub to take advantage of each others'
40800 features. @samp{qSupported} also consolidates multiple feature probes
40801 at startup, to improve @value{GDBN} performance---a single larger
40802 packet performs better than multiple smaller probe packets on
40803 high-latency links. Some features may enable behavior which must not
40804 be on by default, e.g.@: because it would confuse older clients or
40805 stubs. Other features may describe packets which could be
40806 automatically probed for, but are not. These features must be
40807 reported before @value{GDBN} will use them. This ``default
40808 unsupported'' behavior is not appropriate for all packets, but it
40809 helps to keep the initial connection time under control with new
40810 versions of @value{GDBN} which support increasing numbers of packets.
40814 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
40815 The stub supports or does not support each returned @var{stubfeature},
40816 depending on the form of each @var{stubfeature} (see below for the
40819 An empty reply indicates that @samp{qSupported} is not recognized,
40820 or that no features needed to be reported to @value{GDBN}.
40823 The allowed forms for each feature (either a @var{gdbfeature} in the
40824 @samp{qSupported} packet, or a @var{stubfeature} in the response)
40828 @item @var{name}=@var{value}
40829 The remote protocol feature @var{name} is supported, and associated
40830 with the specified @var{value}. The format of @var{value} depends
40831 on the feature, but it must not include a semicolon.
40833 The remote protocol feature @var{name} is supported, and does not
40834 need an associated value.
40836 The remote protocol feature @var{name} is not supported.
40838 The remote protocol feature @var{name} may be supported, and
40839 @value{GDBN} should auto-detect support in some other way when it is
40840 needed. This form will not be used for @var{gdbfeature} notifications,
40841 but may be used for @var{stubfeature} responses.
40844 Whenever the stub receives a @samp{qSupported} request, the
40845 supplied set of @value{GDBN} features should override any previous
40846 request. This allows @value{GDBN} to put the stub in a known
40847 state, even if the stub had previously been communicating with
40848 a different version of @value{GDBN}.
40850 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
40855 This feature indicates whether @value{GDBN} supports multiprocess
40856 extensions to the remote protocol. @value{GDBN} does not use such
40857 extensions unless the stub also reports that it supports them by
40858 including @samp{multiprocess+} in its @samp{qSupported} reply.
40859 @xref{multiprocess extensions}, for details.
40862 This feature indicates that @value{GDBN} supports the XML target
40863 description. If the stub sees @samp{xmlRegisters=} with target
40864 specific strings separated by a comma, it will report register
40868 This feature indicates whether @value{GDBN} supports the
40869 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
40870 instruction reply packet}).
40873 This feature indicates whether @value{GDBN} supports the swbreak stop
40874 reason in stop replies. @xref{swbreak stop reason}, for details.
40877 This feature indicates whether @value{GDBN} supports the hwbreak stop
40878 reason in stop replies. @xref{swbreak stop reason}, for details.
40881 This feature indicates whether @value{GDBN} supports fork event
40882 extensions to the remote protocol. @value{GDBN} does not use such
40883 extensions unless the stub also reports that it supports them by
40884 including @samp{fork-events+} in its @samp{qSupported} reply.
40887 This feature indicates whether @value{GDBN} supports vfork event
40888 extensions to the remote protocol. @value{GDBN} does not use such
40889 extensions unless the stub also reports that it supports them by
40890 including @samp{vfork-events+} in its @samp{qSupported} reply.
40893 This feature indicates whether @value{GDBN} supports exec event
40894 extensions to the remote protocol. @value{GDBN} does not use such
40895 extensions unless the stub also reports that it supports them by
40896 including @samp{exec-events+} in its @samp{qSupported} reply.
40898 @item vContSupported
40899 This feature indicates whether @value{GDBN} wants to know the
40900 supported actions in the reply to @samp{vCont?} packet.
40903 Stubs should ignore any unknown values for
40904 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
40905 packet supports receiving packets of unlimited length (earlier
40906 versions of @value{GDBN} may reject overly long responses). Additional values
40907 for @var{gdbfeature} may be defined in the future to let the stub take
40908 advantage of new features in @value{GDBN}, e.g.@: incompatible
40909 improvements in the remote protocol---the @samp{multiprocess} feature is
40910 an example of such a feature. The stub's reply should be independent
40911 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
40912 describes all the features it supports, and then the stub replies with
40913 all the features it supports.
40915 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
40916 responses, as long as each response uses one of the standard forms.
40918 Some features are flags. A stub which supports a flag feature
40919 should respond with a @samp{+} form response. Other features
40920 require values, and the stub should respond with an @samp{=}
40923 Each feature has a default value, which @value{GDBN} will use if
40924 @samp{qSupported} is not available or if the feature is not mentioned
40925 in the @samp{qSupported} response. The default values are fixed; a
40926 stub is free to omit any feature responses that match the defaults.
40928 Not all features can be probed, but for those which can, the probing
40929 mechanism is useful: in some cases, a stub's internal
40930 architecture may not allow the protocol layer to know some information
40931 about the underlying target in advance. This is especially common in
40932 stubs which may be configured for multiple targets.
40934 These are the currently defined stub features and their properties:
40936 @multitable @columnfractions 0.35 0.2 0.12 0.2
40937 @c NOTE: The first row should be @headitem, but we do not yet require
40938 @c a new enough version of Texinfo (4.7) to use @headitem.
40940 @tab Value Required
40944 @item @samp{PacketSize}
40949 @item @samp{qXfer:auxv:read}
40954 @item @samp{qXfer:btrace:read}
40959 @item @samp{qXfer:btrace-conf:read}
40964 @item @samp{qXfer:exec-file:read}
40969 @item @samp{qXfer:features:read}
40974 @item @samp{qXfer:libraries:read}
40979 @item @samp{qXfer:libraries-svr4:read}
40984 @item @samp{augmented-libraries-svr4-read}
40989 @item @samp{qXfer:memory-map:read}
40994 @item @samp{qXfer:sdata:read}
40999 @item @samp{qXfer:siginfo:read}
41004 @item @samp{qXfer:siginfo:write}
41009 @item @samp{qXfer:threads:read}
41014 @item @samp{qXfer:traceframe-info:read}
41019 @item @samp{qXfer:uib:read}
41024 @item @samp{qXfer:fdpic:read}
41029 @item @samp{Qbtrace:off}
41034 @item @samp{Qbtrace:bts}
41039 @item @samp{Qbtrace:pt}
41044 @item @samp{Qbtrace-conf:bts:size}
41049 @item @samp{Qbtrace-conf:pt:size}
41054 @item @samp{QNonStop}
41059 @item @samp{QCatchSyscalls}
41064 @item @samp{QPassSignals}
41069 @item @samp{QStartNoAckMode}
41074 @item @samp{multiprocess}
41079 @item @samp{ConditionalBreakpoints}
41084 @item @samp{ConditionalTracepoints}
41089 @item @samp{ReverseContinue}
41094 @item @samp{ReverseStep}
41099 @item @samp{TracepointSource}
41104 @item @samp{QAgent}
41109 @item @samp{QAllow}
41114 @item @samp{QDisableRandomization}
41119 @item @samp{EnableDisableTracepoints}
41124 @item @samp{QTBuffer:size}
41129 @item @samp{tracenz}
41134 @item @samp{BreakpointCommands}
41139 @item @samp{swbreak}
41144 @item @samp{hwbreak}
41149 @item @samp{fork-events}
41154 @item @samp{vfork-events}
41159 @item @samp{exec-events}
41164 @item @samp{QThreadEvents}
41169 @item @samp{no-resumed}
41176 These are the currently defined stub features, in more detail:
41179 @cindex packet size, remote protocol
41180 @item PacketSize=@var{bytes}
41181 The remote stub can accept packets up to at least @var{bytes} in
41182 length. @value{GDBN} will send packets up to this size for bulk
41183 transfers, and will never send larger packets. This is a limit on the
41184 data characters in the packet, including the frame and checksum.
41185 There is no trailing NUL byte in a remote protocol packet; if the stub
41186 stores packets in a NUL-terminated format, it should allow an extra
41187 byte in its buffer for the NUL. If this stub feature is not supported,
41188 @value{GDBN} guesses based on the size of the @samp{g} packet response.
41190 @item qXfer:auxv:read
41191 The remote stub understands the @samp{qXfer:auxv:read} packet
41192 (@pxref{qXfer auxiliary vector read}).
41194 @item qXfer:btrace:read
41195 The remote stub understands the @samp{qXfer:btrace:read}
41196 packet (@pxref{qXfer btrace read}).
41198 @item qXfer:btrace-conf:read
41199 The remote stub understands the @samp{qXfer:btrace-conf:read}
41200 packet (@pxref{qXfer btrace-conf read}).
41202 @item qXfer:exec-file:read
41203 The remote stub understands the @samp{qXfer:exec-file:read} packet
41204 (@pxref{qXfer executable filename read}).
41206 @item qXfer:features:read
41207 The remote stub understands the @samp{qXfer:features:read} packet
41208 (@pxref{qXfer target description read}).
41210 @item qXfer:libraries:read
41211 The remote stub understands the @samp{qXfer:libraries:read} packet
41212 (@pxref{qXfer library list read}).
41214 @item qXfer:libraries-svr4:read
41215 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
41216 (@pxref{qXfer svr4 library list read}).
41218 @item augmented-libraries-svr4-read
41219 The remote stub understands the augmented form of the
41220 @samp{qXfer:libraries-svr4:read} packet
41221 (@pxref{qXfer svr4 library list read}).
41223 @item qXfer:memory-map:read
41224 The remote stub understands the @samp{qXfer:memory-map:read} packet
41225 (@pxref{qXfer memory map read}).
41227 @item qXfer:sdata:read
41228 The remote stub understands the @samp{qXfer:sdata:read} packet
41229 (@pxref{qXfer sdata read}).
41231 @item qXfer:siginfo:read
41232 The remote stub understands the @samp{qXfer:siginfo:read} packet
41233 (@pxref{qXfer siginfo read}).
41235 @item qXfer:siginfo:write
41236 The remote stub understands the @samp{qXfer:siginfo:write} packet
41237 (@pxref{qXfer siginfo write}).
41239 @item qXfer:threads:read
41240 The remote stub understands the @samp{qXfer:threads:read} packet
41241 (@pxref{qXfer threads read}).
41243 @item qXfer:traceframe-info:read
41244 The remote stub understands the @samp{qXfer:traceframe-info:read}
41245 packet (@pxref{qXfer traceframe info read}).
41247 @item qXfer:uib:read
41248 The remote stub understands the @samp{qXfer:uib:read}
41249 packet (@pxref{qXfer unwind info block}).
41251 @item qXfer:fdpic:read
41252 The remote stub understands the @samp{qXfer:fdpic:read}
41253 packet (@pxref{qXfer fdpic loadmap read}).
41256 The remote stub understands the @samp{QNonStop} packet
41257 (@pxref{QNonStop}).
41259 @item QCatchSyscalls
41260 The remote stub understands the @samp{QCatchSyscalls} packet
41261 (@pxref{QCatchSyscalls}).
41264 The remote stub understands the @samp{QPassSignals} packet
41265 (@pxref{QPassSignals}).
41267 @item QStartNoAckMode
41268 The remote stub understands the @samp{QStartNoAckMode} packet and
41269 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
41272 @anchor{multiprocess extensions}
41273 @cindex multiprocess extensions, in remote protocol
41274 The remote stub understands the multiprocess extensions to the remote
41275 protocol syntax. The multiprocess extensions affect the syntax of
41276 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
41277 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
41278 replies. Note that reporting this feature indicates support for the
41279 syntactic extensions only, not that the stub necessarily supports
41280 debugging of more than one process at a time. The stub must not use
41281 multiprocess extensions in packet replies unless @value{GDBN} has also
41282 indicated it supports them in its @samp{qSupported} request.
41284 @item qXfer:osdata:read
41285 The remote stub understands the @samp{qXfer:osdata:read} packet
41286 ((@pxref{qXfer osdata read}).
41288 @item ConditionalBreakpoints
41289 The target accepts and implements evaluation of conditional expressions
41290 defined for breakpoints. The target will only report breakpoint triggers
41291 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
41293 @item ConditionalTracepoints
41294 The remote stub accepts and implements conditional expressions defined
41295 for tracepoints (@pxref{Tracepoint Conditions}).
41297 @item ReverseContinue
41298 The remote stub accepts and implements the reverse continue packet
41302 The remote stub accepts and implements the reverse step packet
41305 @item TracepointSource
41306 The remote stub understands the @samp{QTDPsrc} packet that supplies
41307 the source form of tracepoint definitions.
41310 The remote stub understands the @samp{QAgent} packet.
41313 The remote stub understands the @samp{QAllow} packet.
41315 @item QDisableRandomization
41316 The remote stub understands the @samp{QDisableRandomization} packet.
41318 @item StaticTracepoint
41319 @cindex static tracepoints, in remote protocol
41320 The remote stub supports static tracepoints.
41322 @item InstallInTrace
41323 @anchor{install tracepoint in tracing}
41324 The remote stub supports installing tracepoint in tracing.
41326 @item EnableDisableTracepoints
41327 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
41328 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
41329 to be enabled and disabled while a trace experiment is running.
41331 @item QTBuffer:size
41332 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
41333 packet that allows to change the size of the trace buffer.
41336 @cindex string tracing, in remote protocol
41337 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
41338 See @ref{Bytecode Descriptions} for details about the bytecode.
41340 @item BreakpointCommands
41341 @cindex breakpoint commands, in remote protocol
41342 The remote stub supports running a breakpoint's command list itself,
41343 rather than reporting the hit to @value{GDBN}.
41346 The remote stub understands the @samp{Qbtrace:off} packet.
41349 The remote stub understands the @samp{Qbtrace:bts} packet.
41352 The remote stub understands the @samp{Qbtrace:pt} packet.
41354 @item Qbtrace-conf:bts:size
41355 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
41357 @item Qbtrace-conf:pt:size
41358 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
41361 The remote stub reports the @samp{swbreak} stop reason for memory
41365 The remote stub reports the @samp{hwbreak} stop reason for hardware
41369 The remote stub reports the @samp{fork} stop reason for fork events.
41372 The remote stub reports the @samp{vfork} stop reason for vfork events
41373 and vforkdone events.
41376 The remote stub reports the @samp{exec} stop reason for exec events.
41378 @item vContSupported
41379 The remote stub reports the supported actions in the reply to
41380 @samp{vCont?} packet.
41382 @item QThreadEvents
41383 The remote stub understands the @samp{QThreadEvents} packet.
41386 The remote stub reports the @samp{N} stop reply.
41391 @cindex symbol lookup, remote request
41392 @cindex @samp{qSymbol} packet
41393 Notify the target that @value{GDBN} is prepared to serve symbol lookup
41394 requests. Accept requests from the target for the values of symbols.
41399 The target does not need to look up any (more) symbols.
41400 @item qSymbol:@var{sym_name}
41401 The target requests the value of symbol @var{sym_name} (hex encoded).
41402 @value{GDBN} may provide the value by using the
41403 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
41407 @item qSymbol:@var{sym_value}:@var{sym_name}
41408 Set the value of @var{sym_name} to @var{sym_value}.
41410 @var{sym_name} (hex encoded) is the name of a symbol whose value the
41411 target has previously requested.
41413 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
41414 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
41420 The target does not need to look up any (more) symbols.
41421 @item qSymbol:@var{sym_name}
41422 The target requests the value of a new symbol @var{sym_name} (hex
41423 encoded). @value{GDBN} will continue to supply the values of symbols
41424 (if available), until the target ceases to request them.
41429 @itemx QTDisconnected
41436 @itemx qTMinFTPILen
41438 @xref{Tracepoint Packets}.
41440 @item qThreadExtraInfo,@var{thread-id}
41441 @cindex thread attributes info, remote request
41442 @cindex @samp{qThreadExtraInfo} packet
41443 Obtain from the target OS a printable string description of thread
41444 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
41445 for the forms of @var{thread-id}. This
41446 string may contain anything that the target OS thinks is interesting
41447 for @value{GDBN} to tell the user about the thread. The string is
41448 displayed in @value{GDBN}'s @code{info threads} display. Some
41449 examples of possible thread extra info strings are @samp{Runnable}, or
41450 @samp{Blocked on Mutex}.
41454 @item @var{XX}@dots{}
41455 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
41456 comprising the printable string containing the extra information about
41457 the thread's attributes.
41460 (Note that the @code{qThreadExtraInfo} packet's name is separated from
41461 the command by a @samp{,}, not a @samp{:}, contrary to the naming
41462 conventions above. Please don't use this packet as a model for new
41481 @xref{Tracepoint Packets}.
41483 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
41484 @cindex read special object, remote request
41485 @cindex @samp{qXfer} packet
41486 @anchor{qXfer read}
41487 Read uninterpreted bytes from the target's special data area
41488 identified by the keyword @var{object}. Request @var{length} bytes
41489 starting at @var{offset} bytes into the data. The content and
41490 encoding of @var{annex} is specific to @var{object}; it can supply
41491 additional details about what data to access.
41496 Data @var{data} (@pxref{Binary Data}) has been read from the
41497 target. There may be more data at a higher address (although
41498 it is permitted to return @samp{m} even for the last valid
41499 block of data, as long as at least one byte of data was read).
41500 It is possible for @var{data} to have fewer bytes than the @var{length} in the
41504 Data @var{data} (@pxref{Binary Data}) has been read from the target.
41505 There is no more data to be read. It is possible for @var{data} to
41506 have fewer bytes than the @var{length} in the request.
41509 The @var{offset} in the request is at the end of the data.
41510 There is no more data to be read.
41513 The request was malformed, or @var{annex} was invalid.
41516 The offset was invalid, or there was an error encountered reading the data.
41517 The @var{nn} part is a hex-encoded @code{errno} value.
41520 An empty reply indicates the @var{object} string was not recognized by
41521 the stub, or that the object does not support reading.
41524 Here are the specific requests of this form defined so far. All the
41525 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
41526 formats, listed above.
41529 @item qXfer:auxv:read::@var{offset},@var{length}
41530 @anchor{qXfer auxiliary vector read}
41531 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
41532 auxiliary vector}. Note @var{annex} must be empty.
41534 This packet is not probed by default; the remote stub must request it,
41535 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41537 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
41538 @anchor{qXfer btrace read}
41540 Return a description of the current branch trace.
41541 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
41542 packet may have one of the following values:
41546 Returns all available branch trace.
41549 Returns all available branch trace if the branch trace changed since
41550 the last read request.
41553 Returns the new branch trace since the last read request. Adds a new
41554 block to the end of the trace that begins at zero and ends at the source
41555 location of the first branch in the trace buffer. This extra block is
41556 used to stitch traces together.
41558 If the trace buffer overflowed, returns an error indicating the overflow.
41561 This packet is not probed by default; the remote stub must request it
41562 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41564 @item qXfer:btrace-conf:read::@var{offset},@var{length}
41565 @anchor{qXfer btrace-conf read}
41567 Return a description of the current branch trace configuration.
41568 @xref{Branch Trace Configuration Format}.
41570 This packet is not probed by default; the remote stub must request it
41571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41573 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
41574 @anchor{qXfer executable filename read}
41575 Return the full absolute name of the file that was executed to create
41576 a process running on the remote system. The annex specifies the
41577 numeric process ID of the process to query, encoded as a hexadecimal
41578 number. If the annex part is empty the remote stub should return the
41579 filename corresponding to the currently executing process.
41581 This packet is not probed by default; the remote stub must request it,
41582 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41584 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
41585 @anchor{qXfer target description read}
41586 Access the @dfn{target description}. @xref{Target Descriptions}. The
41587 annex specifies which XML document to access. The main description is
41588 always loaded from the @samp{target.xml} annex.
41590 This packet is not probed by default; the remote stub must request it,
41591 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41593 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
41594 @anchor{qXfer library list read}
41595 Access the target's list of loaded libraries. @xref{Library List Format}.
41596 The annex part of the generic @samp{qXfer} packet must be empty
41597 (@pxref{qXfer read}).
41599 Targets which maintain a list of libraries in the program's memory do
41600 not need to implement this packet; it is designed for platforms where
41601 the operating system manages the list of loaded libraries.
41603 This packet is not probed by default; the remote stub must request it,
41604 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41606 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
41607 @anchor{qXfer svr4 library list read}
41608 Access the target's list of loaded libraries when the target is an SVR4
41609 platform. @xref{Library List Format for SVR4 Targets}. The annex part
41610 of the generic @samp{qXfer} packet must be empty unless the remote
41611 stub indicated it supports the augmented form of this packet
41612 by supplying an appropriate @samp{qSupported} response
41613 (@pxref{qXfer read}, @ref{qSupported}).
41615 This packet is optional for better performance on SVR4 targets.
41616 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
41618 This packet is not probed by default; the remote stub must request it,
41619 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41621 If the remote stub indicates it supports the augmented form of this
41622 packet then the annex part of the generic @samp{qXfer} packet may
41623 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
41624 arguments. The currently supported arguments are:
41627 @item start=@var{address}
41628 A hexadecimal number specifying the address of the @samp{struct
41629 link_map} to start reading the library list from. If unset or zero
41630 then the first @samp{struct link_map} in the library list will be
41631 chosen as the starting point.
41633 @item prev=@var{address}
41634 A hexadecimal number specifying the address of the @samp{struct
41635 link_map} immediately preceding the @samp{struct link_map}
41636 specified by the @samp{start} argument. If unset or zero then
41637 the remote stub will expect that no @samp{struct link_map}
41638 exists prior to the starting point.
41642 Arguments that are not understood by the remote stub will be silently
41645 @item qXfer:memory-map:read::@var{offset},@var{length}
41646 @anchor{qXfer memory map read}
41647 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
41648 annex part of the generic @samp{qXfer} packet must be empty
41649 (@pxref{qXfer read}).
41651 This packet is not probed by default; the remote stub must request it,
41652 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41654 @item qXfer:sdata:read::@var{offset},@var{length}
41655 @anchor{qXfer sdata read}
41657 Read contents of the extra collected static tracepoint marker
41658 information. The annex part of the generic @samp{qXfer} packet must
41659 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
41662 This packet is not probed by default; the remote stub must request it,
41663 by supplying an appropriate @samp{qSupported} response
41664 (@pxref{qSupported}).
41666 @item qXfer:siginfo:read::@var{offset},@var{length}
41667 @anchor{qXfer siginfo read}
41668 Read contents of the extra signal information on the target
41669 system. The annex part of the generic @samp{qXfer} packet must be
41670 empty (@pxref{qXfer read}).
41672 This packet is not probed by default; the remote stub must request it,
41673 by supplying an appropriate @samp{qSupported} response
41674 (@pxref{qSupported}).
41676 @item qXfer:threads:read::@var{offset},@var{length}
41677 @anchor{qXfer threads read}
41678 Access the list of threads on target. @xref{Thread List Format}. The
41679 annex part of the generic @samp{qXfer} packet must be empty
41680 (@pxref{qXfer read}).
41682 This packet is not probed by default; the remote stub must request it,
41683 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41685 @item qXfer:traceframe-info:read::@var{offset},@var{length}
41686 @anchor{qXfer traceframe info read}
41688 Return a description of the current traceframe's contents.
41689 @xref{Traceframe Info Format}. The annex part of the generic
41690 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
41692 This packet is not probed by default; the remote stub must request it,
41693 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41695 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
41696 @anchor{qXfer unwind info block}
41698 Return the unwind information block for @var{pc}. This packet is used
41699 on OpenVMS/ia64 to ask the kernel unwind information.
41701 This packet is not probed by default.
41703 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
41704 @anchor{qXfer fdpic loadmap read}
41705 Read contents of @code{loadmap}s on the target system. The
41706 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
41707 executable @code{loadmap} or interpreter @code{loadmap} to read.
41709 This packet is not probed by default; the remote stub must request it,
41710 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41712 @item qXfer:osdata:read::@var{offset},@var{length}
41713 @anchor{qXfer osdata read}
41714 Access the target's @dfn{operating system information}.
41715 @xref{Operating System Information}.
41719 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
41720 @cindex write data into object, remote request
41721 @anchor{qXfer write}
41722 Write uninterpreted bytes into the target's special data area
41723 identified by the keyword @var{object}, starting at @var{offset} bytes
41724 into the data. The binary-encoded data (@pxref{Binary Data}) to be
41725 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
41726 is specific to @var{object}; it can supply additional details about what data
41732 @var{nn} (hex encoded) is the number of bytes written.
41733 This may be fewer bytes than supplied in the request.
41736 The request was malformed, or @var{annex} was invalid.
41739 The offset was invalid, or there was an error encountered writing the data.
41740 The @var{nn} part is a hex-encoded @code{errno} value.
41743 An empty reply indicates the @var{object} string was not
41744 recognized by the stub, or that the object does not support writing.
41747 Here are the specific requests of this form defined so far. All the
41748 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
41749 formats, listed above.
41752 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
41753 @anchor{qXfer siginfo write}
41754 Write @var{data} to the extra signal information on the target system.
41755 The annex part of the generic @samp{qXfer} packet must be
41756 empty (@pxref{qXfer write}).
41758 This packet is not probed by default; the remote stub must request it,
41759 by supplying an appropriate @samp{qSupported} response
41760 (@pxref{qSupported}).
41763 @item qXfer:@var{object}:@var{operation}:@dots{}
41764 Requests of this form may be added in the future. When a stub does
41765 not recognize the @var{object} keyword, or its support for
41766 @var{object} does not recognize the @var{operation} keyword, the stub
41767 must respond with an empty packet.
41769 @item qAttached:@var{pid}
41770 @cindex query attached, remote request
41771 @cindex @samp{qAttached} packet
41772 Return an indication of whether the remote server attached to an
41773 existing process or created a new process. When the multiprocess
41774 protocol extensions are supported (@pxref{multiprocess extensions}),
41775 @var{pid} is an integer in hexadecimal format identifying the target
41776 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
41777 the query packet will be simplified as @samp{qAttached}.
41779 This query is used, for example, to know whether the remote process
41780 should be detached or killed when a @value{GDBN} session is ended with
41781 the @code{quit} command.
41786 The remote server attached to an existing process.
41788 The remote server created a new process.
41790 A badly formed request or an error was encountered.
41794 Enable branch tracing for the current thread using Branch Trace Store.
41799 Branch tracing has been enabled.
41801 A badly formed request or an error was encountered.
41805 Enable branch tracing for the current thread using Intel Processor Trace.
41810 Branch tracing has been enabled.
41812 A badly formed request or an error was encountered.
41816 Disable branch tracing for the current thread.
41821 Branch tracing has been disabled.
41823 A badly formed request or an error was encountered.
41826 @item Qbtrace-conf:bts:size=@var{value}
41827 Set the requested ring buffer size for new threads that use the
41828 btrace recording method in bts format.
41833 The ring buffer size has been set.
41835 A badly formed request or an error was encountered.
41838 @item Qbtrace-conf:pt:size=@var{value}
41839 Set the requested ring buffer size for new threads that use the
41840 btrace recording method in pt format.
41845 The ring buffer size has been set.
41847 A badly formed request or an error was encountered.
41852 @node Architecture-Specific Protocol Details
41853 @section Architecture-Specific Protocol Details
41855 This section describes how the remote protocol is applied to specific
41856 target architectures. Also see @ref{Standard Target Features}, for
41857 details of XML target descriptions for each architecture.
41860 * ARM-Specific Protocol Details::
41861 * MIPS-Specific Protocol Details::
41864 @node ARM-Specific Protocol Details
41865 @subsection @acronym{ARM}-specific Protocol Details
41868 * ARM Breakpoint Kinds::
41871 @node ARM Breakpoint Kinds
41872 @subsubsection @acronym{ARM} Breakpoint Kinds
41873 @cindex breakpoint kinds, @acronym{ARM}
41875 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
41880 16-bit Thumb mode breakpoint.
41883 32-bit Thumb mode (Thumb-2) breakpoint.
41886 32-bit @acronym{ARM} mode breakpoint.
41890 @node MIPS-Specific Protocol Details
41891 @subsection @acronym{MIPS}-specific Protocol Details
41894 * MIPS Register packet Format::
41895 * MIPS Breakpoint Kinds::
41898 @node MIPS Register packet Format
41899 @subsubsection @acronym{MIPS} Register Packet Format
41900 @cindex register packet format, @acronym{MIPS}
41902 The following @code{g}/@code{G} packets have previously been defined.
41903 In the below, some thirty-two bit registers are transferred as
41904 sixty-four bits. Those registers should be zero/sign extended (which?)
41905 to fill the space allocated. Register bytes are transferred in target
41906 byte order. The two nibbles within a register byte are transferred
41907 most-significant -- least-significant.
41912 All registers are transferred as thirty-two bit quantities in the order:
41913 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
41914 registers; fsr; fir; fp.
41917 All registers are transferred as sixty-four bit quantities (including
41918 thirty-two bit registers such as @code{sr}). The ordering is the same
41923 @node MIPS Breakpoint Kinds
41924 @subsubsection @acronym{MIPS} Breakpoint Kinds
41925 @cindex breakpoint kinds, @acronym{MIPS}
41927 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
41932 16-bit @acronym{MIPS16} mode breakpoint.
41935 16-bit @acronym{microMIPS} mode breakpoint.
41938 32-bit standard @acronym{MIPS} mode breakpoint.
41941 32-bit @acronym{microMIPS} mode breakpoint.
41945 @node Tracepoint Packets
41946 @section Tracepoint Packets
41947 @cindex tracepoint packets
41948 @cindex packets, tracepoint
41950 Here we describe the packets @value{GDBN} uses to implement
41951 tracepoints (@pxref{Tracepoints}).
41955 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
41956 @cindex @samp{QTDP} packet
41957 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
41958 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
41959 the tracepoint is disabled. The @var{step} gives the tracepoint's step
41960 count, and @var{pass} gives its pass count. If an @samp{F} is present,
41961 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
41962 the number of bytes that the target should copy elsewhere to make room
41963 for the tracepoint. If an @samp{X} is present, it introduces a
41964 tracepoint condition, which consists of a hexadecimal length, followed
41965 by a comma and hex-encoded bytes, in a manner similar to action
41966 encodings as described below. If the trailing @samp{-} is present,
41967 further @samp{QTDP} packets will follow to specify this tracepoint's
41973 The packet was understood and carried out.
41975 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
41977 The packet was not recognized.
41980 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
41981 Define actions to be taken when a tracepoint is hit. The @var{n} and
41982 @var{addr} must be the same as in the initial @samp{QTDP} packet for
41983 this tracepoint. This packet may only be sent immediately after
41984 another @samp{QTDP} packet that ended with a @samp{-}. If the
41985 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
41986 specifying more actions for this tracepoint.
41988 In the series of action packets for a given tracepoint, at most one
41989 can have an @samp{S} before its first @var{action}. If such a packet
41990 is sent, it and the following packets define ``while-stepping''
41991 actions. Any prior packets define ordinary actions --- that is, those
41992 taken when the tracepoint is first hit. If no action packet has an
41993 @samp{S}, then all the packets in the series specify ordinary
41994 tracepoint actions.
41996 The @samp{@var{action}@dots{}} portion of the packet is a series of
41997 actions, concatenated without separators. Each action has one of the
42003 Collect the registers whose bits are set in @var{mask},
42004 a hexadecimal number whose @var{i}'th bit is set if register number
42005 @var{i} should be collected. (The least significant bit is numbered
42006 zero.) Note that @var{mask} may be any number of digits long; it may
42007 not fit in a 32-bit word.
42009 @item M @var{basereg},@var{offset},@var{len}
42010 Collect @var{len} bytes of memory starting at the address in register
42011 number @var{basereg}, plus @var{offset}. If @var{basereg} is
42012 @samp{-1}, then the range has a fixed address: @var{offset} is the
42013 address of the lowest byte to collect. The @var{basereg},
42014 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
42015 values (the @samp{-1} value for @var{basereg} is a special case).
42017 @item X @var{len},@var{expr}
42018 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
42019 it directs. The agent expression @var{expr} is as described in
42020 @ref{Agent Expressions}. Each byte of the expression is encoded as a
42021 two-digit hex number in the packet; @var{len} is the number of bytes
42022 in the expression (and thus one-half the number of hex digits in the
42027 Any number of actions may be packed together in a single @samp{QTDP}
42028 packet, as long as the packet does not exceed the maximum packet
42029 length (400 bytes, for many stubs). There may be only one @samp{R}
42030 action per tracepoint, and it must precede any @samp{M} or @samp{X}
42031 actions. Any registers referred to by @samp{M} and @samp{X} actions
42032 must be collected by a preceding @samp{R} action. (The
42033 ``while-stepping'' actions are treated as if they were attached to a
42034 separate tracepoint, as far as these restrictions are concerned.)
42039 The packet was understood and carried out.
42041 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42043 The packet was not recognized.
42046 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
42047 @cindex @samp{QTDPsrc} packet
42048 Specify a source string of tracepoint @var{n} at address @var{addr}.
42049 This is useful to get accurate reproduction of the tracepoints
42050 originally downloaded at the beginning of the trace run. The @var{type}
42051 is the name of the tracepoint part, such as @samp{cond} for the
42052 tracepoint's conditional expression (see below for a list of types), while
42053 @var{bytes} is the string, encoded in hexadecimal.
42055 @var{start} is the offset of the @var{bytes} within the overall source
42056 string, while @var{slen} is the total length of the source string.
42057 This is intended for handling source strings that are longer than will
42058 fit in a single packet.
42059 @c Add detailed example when this info is moved into a dedicated
42060 @c tracepoint descriptions section.
42062 The available string types are @samp{at} for the location,
42063 @samp{cond} for the conditional, and @samp{cmd} for an action command.
42064 @value{GDBN} sends a separate packet for each command in the action
42065 list, in the same order in which the commands are stored in the list.
42067 The target does not need to do anything with source strings except
42068 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
42071 Although this packet is optional, and @value{GDBN} will only send it
42072 if the target replies with @samp{TracepointSource} @xref{General
42073 Query Packets}, it makes both disconnected tracing and trace files
42074 much easier to use. Otherwise the user must be careful that the
42075 tracepoints in effect while looking at trace frames are identical to
42076 the ones in effect during the trace run; even a small discrepancy
42077 could cause @samp{tdump} not to work, or a particular trace frame not
42080 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
42081 @cindex define trace state variable, remote request
42082 @cindex @samp{QTDV} packet
42083 Create a new trace state variable, number @var{n}, with an initial
42084 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
42085 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
42086 the option of not using this packet for initial values of zero; the
42087 target should simply create the trace state variables as they are
42088 mentioned in expressions. The value @var{builtin} should be 1 (one)
42089 if the trace state variable is builtin and 0 (zero) if it is not builtin.
42090 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
42091 @samp{qTsV} packet had it set. The contents of @var{name} is the
42092 hex-encoded name (without the leading @samp{$}) of the trace state
42095 @item QTFrame:@var{n}
42096 @cindex @samp{QTFrame} packet
42097 Select the @var{n}'th tracepoint frame from the buffer, and use the
42098 register and memory contents recorded there to answer subsequent
42099 request packets from @value{GDBN}.
42101 A successful reply from the stub indicates that the stub has found the
42102 requested frame. The response is a series of parts, concatenated
42103 without separators, describing the frame we selected. Each part has
42104 one of the following forms:
42108 The selected frame is number @var{n} in the trace frame buffer;
42109 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
42110 was no frame matching the criteria in the request packet.
42113 The selected trace frame records a hit of tracepoint number @var{t};
42114 @var{t} is a hexadecimal number.
42118 @item QTFrame:pc:@var{addr}
42119 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42120 currently selected frame whose PC is @var{addr};
42121 @var{addr} is a hexadecimal number.
42123 @item QTFrame:tdp:@var{t}
42124 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42125 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
42126 is a hexadecimal number.
42128 @item QTFrame:range:@var{start}:@var{end}
42129 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42130 currently selected frame whose PC is between @var{start} (inclusive)
42131 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
42134 @item QTFrame:outside:@var{start}:@var{end}
42135 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
42136 frame @emph{outside} the given range of addresses (exclusive).
42139 @cindex @samp{qTMinFTPILen} packet
42140 This packet requests the minimum length of instruction at which a fast
42141 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
42142 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
42143 it depends on the target system being able to create trampolines in
42144 the first 64K of memory, which might or might not be possible for that
42145 system. So the reply to this packet will be 4 if it is able to
42152 The minimum instruction length is currently unknown.
42154 The minimum instruction length is @var{length}, where @var{length}
42155 is a hexadecimal number greater or equal to 1. A reply
42156 of 1 means that a fast tracepoint may be placed on any instruction
42157 regardless of size.
42159 An error has occurred.
42161 An empty reply indicates that the request is not supported by the stub.
42165 @cindex @samp{QTStart} packet
42166 Begin the tracepoint experiment. Begin collecting data from
42167 tracepoint hits in the trace frame buffer. This packet supports the
42168 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
42169 instruction reply packet}).
42172 @cindex @samp{QTStop} packet
42173 End the tracepoint experiment. Stop collecting trace frames.
42175 @item QTEnable:@var{n}:@var{addr}
42177 @cindex @samp{QTEnable} packet
42178 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
42179 experiment. If the tracepoint was previously disabled, then collection
42180 of data from it will resume.
42182 @item QTDisable:@var{n}:@var{addr}
42184 @cindex @samp{QTDisable} packet
42185 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
42186 experiment. No more data will be collected from the tracepoint unless
42187 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
42190 @cindex @samp{QTinit} packet
42191 Clear the table of tracepoints, and empty the trace frame buffer.
42193 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
42194 @cindex @samp{QTro} packet
42195 Establish the given ranges of memory as ``transparent''. The stub
42196 will answer requests for these ranges from memory's current contents,
42197 if they were not collected as part of the tracepoint hit.
42199 @value{GDBN} uses this to mark read-only regions of memory, like those
42200 containing program code. Since these areas never change, they should
42201 still have the same contents they did when the tracepoint was hit, so
42202 there's no reason for the stub to refuse to provide their contents.
42204 @item QTDisconnected:@var{value}
42205 @cindex @samp{QTDisconnected} packet
42206 Set the choice to what to do with the tracing run when @value{GDBN}
42207 disconnects from the target. A @var{value} of 1 directs the target to
42208 continue the tracing run, while 0 tells the target to stop tracing if
42209 @value{GDBN} is no longer in the picture.
42212 @cindex @samp{qTStatus} packet
42213 Ask the stub if there is a trace experiment running right now.
42215 The reply has the form:
42219 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
42220 @var{running} is a single digit @code{1} if the trace is presently
42221 running, or @code{0} if not. It is followed by semicolon-separated
42222 optional fields that an agent may use to report additional status.
42226 If the trace is not running, the agent may report any of several
42227 explanations as one of the optional fields:
42232 No trace has been run yet.
42234 @item tstop[:@var{text}]:0
42235 The trace was stopped by a user-originated stop command. The optional
42236 @var{text} field is a user-supplied string supplied as part of the
42237 stop command (for instance, an explanation of why the trace was
42238 stopped manually). It is hex-encoded.
42241 The trace stopped because the trace buffer filled up.
42243 @item tdisconnected:0
42244 The trace stopped because @value{GDBN} disconnected from the target.
42246 @item tpasscount:@var{tpnum}
42247 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
42249 @item terror:@var{text}:@var{tpnum}
42250 The trace stopped because tracepoint @var{tpnum} had an error. The
42251 string @var{text} is available to describe the nature of the error
42252 (for instance, a divide by zero in the condition expression); it
42256 The trace stopped for some other reason.
42260 Additional optional fields supply statistical and other information.
42261 Although not required, they are extremely useful for users monitoring
42262 the progress of a trace run. If a trace has stopped, and these
42263 numbers are reported, they must reflect the state of the just-stopped
42268 @item tframes:@var{n}
42269 The number of trace frames in the buffer.
42271 @item tcreated:@var{n}
42272 The total number of trace frames created during the run. This may
42273 be larger than the trace frame count, if the buffer is circular.
42275 @item tsize:@var{n}
42276 The total size of the trace buffer, in bytes.
42278 @item tfree:@var{n}
42279 The number of bytes still unused in the buffer.
42281 @item circular:@var{n}
42282 The value of the circular trace buffer flag. @code{1} means that the
42283 trace buffer is circular and old trace frames will be discarded if
42284 necessary to make room, @code{0} means that the trace buffer is linear
42287 @item disconn:@var{n}
42288 The value of the disconnected tracing flag. @code{1} means that
42289 tracing will continue after @value{GDBN} disconnects, @code{0} means
42290 that the trace run will stop.
42294 @item qTP:@var{tp}:@var{addr}
42295 @cindex tracepoint status, remote request
42296 @cindex @samp{qTP} packet
42297 Ask the stub for the current state of tracepoint number @var{tp} at
42298 address @var{addr}.
42302 @item V@var{hits}:@var{usage}
42303 The tracepoint has been hit @var{hits} times so far during the trace
42304 run, and accounts for @var{usage} in the trace buffer. Note that
42305 @code{while-stepping} steps are not counted as separate hits, but the
42306 steps' space consumption is added into the usage number.
42310 @item qTV:@var{var}
42311 @cindex trace state variable value, remote request
42312 @cindex @samp{qTV} packet
42313 Ask the stub for the value of the trace state variable number @var{var}.
42318 The value of the variable is @var{value}. This will be the current
42319 value of the variable if the user is examining a running target, or a
42320 saved value if the variable was collected in the trace frame that the
42321 user is looking at. Note that multiple requests may result in
42322 different reply values, such as when requesting values while the
42323 program is running.
42326 The value of the variable is unknown. This would occur, for example,
42327 if the user is examining a trace frame in which the requested variable
42332 @cindex @samp{qTfP} packet
42334 @cindex @samp{qTsP} packet
42335 These packets request data about tracepoints that are being used by
42336 the target. @value{GDBN} sends @code{qTfP} to get the first piece
42337 of data, and multiple @code{qTsP} to get additional pieces. Replies
42338 to these packets generally take the form of the @code{QTDP} packets
42339 that define tracepoints. (FIXME add detailed syntax)
42342 @cindex @samp{qTfV} packet
42344 @cindex @samp{qTsV} packet
42345 These packets request data about trace state variables that are on the
42346 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
42347 and multiple @code{qTsV} to get additional variables. Replies to
42348 these packets follow the syntax of the @code{QTDV} packets that define
42349 trace state variables.
42355 @cindex @samp{qTfSTM} packet
42356 @cindex @samp{qTsSTM} packet
42357 These packets request data about static tracepoint markers that exist
42358 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
42359 first piece of data, and multiple @code{qTsSTM} to get additional
42360 pieces. Replies to these packets take the following form:
42364 @item m @var{address}:@var{id}:@var{extra}
42366 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
42367 a comma-separated list of markers
42369 (lower case letter @samp{L}) denotes end of list.
42371 An error occurred. The error number @var{nn} is given as hex digits.
42373 An empty reply indicates that the request is not supported by the
42377 The @var{address} is encoded in hex;
42378 @var{id} and @var{extra} are strings encoded in hex.
42380 In response to each query, the target will reply with a list of one or
42381 more markers, separated by commas. @value{GDBN} will respond to each
42382 reply with a request for more markers (using the @samp{qs} form of the
42383 query), until the target responds with @samp{l} (lower-case ell, for
42386 @item qTSTMat:@var{address}
42388 @cindex @samp{qTSTMat} packet
42389 This packets requests data about static tracepoint markers in the
42390 target program at @var{address}. Replies to this packet follow the
42391 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
42392 tracepoint markers.
42394 @item QTSave:@var{filename}
42395 @cindex @samp{QTSave} packet
42396 This packet directs the target to save trace data to the file name
42397 @var{filename} in the target's filesystem. The @var{filename} is encoded
42398 as a hex string; the interpretation of the file name (relative vs
42399 absolute, wild cards, etc) is up to the target.
42401 @item qTBuffer:@var{offset},@var{len}
42402 @cindex @samp{qTBuffer} packet
42403 Return up to @var{len} bytes of the current contents of trace buffer,
42404 starting at @var{offset}. The trace buffer is treated as if it were
42405 a contiguous collection of traceframes, as per the trace file format.
42406 The reply consists as many hex-encoded bytes as the target can deliver
42407 in a packet; it is not an error to return fewer than were asked for.
42408 A reply consisting of just @code{l} indicates that no bytes are
42411 @item QTBuffer:circular:@var{value}
42412 This packet directs the target to use a circular trace buffer if
42413 @var{value} is 1, or a linear buffer if the value is 0.
42415 @item QTBuffer:size:@var{size}
42416 @anchor{QTBuffer-size}
42417 @cindex @samp{QTBuffer size} packet
42418 This packet directs the target to make the trace buffer be of size
42419 @var{size} if possible. A value of @code{-1} tells the target to
42420 use whatever size it prefers.
42422 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
42423 @cindex @samp{QTNotes} packet
42424 This packet adds optional textual notes to the trace run. Allowable
42425 types include @code{user}, @code{notes}, and @code{tstop}, the
42426 @var{text} fields are arbitrary strings, hex-encoded.
42430 @subsection Relocate instruction reply packet
42431 When installing fast tracepoints in memory, the target may need to
42432 relocate the instruction currently at the tracepoint address to a
42433 different address in memory. For most instructions, a simple copy is
42434 enough, but, for example, call instructions that implicitly push the
42435 return address on the stack, and relative branches or other
42436 PC-relative instructions require offset adjustment, so that the effect
42437 of executing the instruction at a different address is the same as if
42438 it had executed in the original location.
42440 In response to several of the tracepoint packets, the target may also
42441 respond with a number of intermediate @samp{qRelocInsn} request
42442 packets before the final result packet, to have @value{GDBN} handle
42443 this relocation operation. If a packet supports this mechanism, its
42444 documentation will explicitly say so. See for example the above
42445 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
42446 format of the request is:
42449 @item qRelocInsn:@var{from};@var{to}
42451 This requests @value{GDBN} to copy instruction at address @var{from}
42452 to address @var{to}, possibly adjusted so that executing the
42453 instruction at @var{to} has the same effect as executing it at
42454 @var{from}. @value{GDBN} writes the adjusted instruction to target
42455 memory starting at @var{to}.
42460 @item qRelocInsn:@var{adjusted_size}
42461 Informs the stub the relocation is complete. The @var{adjusted_size} is
42462 the length in bytes of resulting relocated instruction sequence.
42464 A badly formed request was detected, or an error was encountered while
42465 relocating the instruction.
42468 @node Host I/O Packets
42469 @section Host I/O Packets
42470 @cindex Host I/O, remote protocol
42471 @cindex file transfer, remote protocol
42473 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
42474 operations on the far side of a remote link. For example, Host I/O is
42475 used to upload and download files to a remote target with its own
42476 filesystem. Host I/O uses the same constant values and data structure
42477 layout as the target-initiated File-I/O protocol. However, the
42478 Host I/O packets are structured differently. The target-initiated
42479 protocol relies on target memory to store parameters and buffers.
42480 Host I/O requests are initiated by @value{GDBN}, and the
42481 target's memory is not involved. @xref{File-I/O Remote Protocol
42482 Extension}, for more details on the target-initiated protocol.
42484 The Host I/O request packets all encode a single operation along with
42485 its arguments. They have this format:
42489 @item vFile:@var{operation}: @var{parameter}@dots{}
42490 @var{operation} is the name of the particular request; the target
42491 should compare the entire packet name up to the second colon when checking
42492 for a supported operation. The format of @var{parameter} depends on
42493 the operation. Numbers are always passed in hexadecimal. Negative
42494 numbers have an explicit minus sign (i.e.@: two's complement is not
42495 used). Strings (e.g.@: filenames) are encoded as a series of
42496 hexadecimal bytes. The last argument to a system call may be a
42497 buffer of escaped binary data (@pxref{Binary Data}).
42501 The valid responses to Host I/O packets are:
42505 @item F @var{result} [, @var{errno}] [; @var{attachment}]
42506 @var{result} is the integer value returned by this operation, usually
42507 non-negative for success and -1 for errors. If an error has occured,
42508 @var{errno} will be included in the result specifying a
42509 value defined by the File-I/O protocol (@pxref{Errno Values}). For
42510 operations which return data, @var{attachment} supplies the data as a
42511 binary buffer. Binary buffers in response packets are escaped in the
42512 normal way (@pxref{Binary Data}). See the individual packet
42513 documentation for the interpretation of @var{result} and
42517 An empty response indicates that this operation is not recognized.
42521 These are the supported Host I/O operations:
42524 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
42525 Open a file at @var{filename} and return a file descriptor for it, or
42526 return -1 if an error occurs. The @var{filename} is a string,
42527 @var{flags} is an integer indicating a mask of open flags
42528 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
42529 of mode bits to use if the file is created (@pxref{mode_t Values}).
42530 @xref{open}, for details of the open flags and mode values.
42532 @item vFile:close: @var{fd}
42533 Close the open file corresponding to @var{fd} and return 0, or
42534 -1 if an error occurs.
42536 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
42537 Read data from the open file corresponding to @var{fd}. Up to
42538 @var{count} bytes will be read from the file, starting at @var{offset}
42539 relative to the start of the file. The target may read fewer bytes;
42540 common reasons include packet size limits and an end-of-file
42541 condition. The number of bytes read is returned. Zero should only be
42542 returned for a successful read at the end of the file, or if
42543 @var{count} was zero.
42545 The data read should be returned as a binary attachment on success.
42546 If zero bytes were read, the response should include an empty binary
42547 attachment (i.e.@: a trailing semicolon). The return value is the
42548 number of target bytes read; the binary attachment may be longer if
42549 some characters were escaped.
42551 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
42552 Write @var{data} (a binary buffer) to the open file corresponding
42553 to @var{fd}. Start the write at @var{offset} from the start of the
42554 file. Unlike many @code{write} system calls, there is no
42555 separate @var{count} argument; the length of @var{data} in the
42556 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
42557 which may be shorter than the length of @var{data}, or -1 if an
42560 @item vFile:fstat: @var{fd}
42561 Get information about the open file corresponding to @var{fd}.
42562 On success the information is returned as a binary attachment
42563 and the return value is the size of this attachment in bytes.
42564 If an error occurs the return value is -1. The format of the
42565 returned binary attachment is as described in @ref{struct stat}.
42567 @item vFile:unlink: @var{filename}
42568 Delete the file at @var{filename} on the target. Return 0,
42569 or -1 if an error occurs. The @var{filename} is a string.
42571 @item vFile:readlink: @var{filename}
42572 Read value of symbolic link @var{filename} on the target. Return
42573 the number of bytes read, or -1 if an error occurs.
42575 The data read should be returned as a binary attachment on success.
42576 If zero bytes were read, the response should include an empty binary
42577 attachment (i.e.@: a trailing semicolon). The return value is the
42578 number of target bytes read; the binary attachment may be longer if
42579 some characters were escaped.
42581 @item vFile:setfs: @var{pid}
42582 Select the filesystem on which @code{vFile} operations with
42583 @var{filename} arguments will operate. This is required for
42584 @value{GDBN} to be able to access files on remote targets where
42585 the remote stub does not share a common filesystem with the
42588 If @var{pid} is nonzero, select the filesystem as seen by process
42589 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
42590 the remote stub. Return 0 on success, or -1 if an error occurs.
42591 If @code{vFile:setfs:} indicates success, the selected filesystem
42592 remains selected until the next successful @code{vFile:setfs:}
42598 @section Interrupts
42599 @cindex interrupts (remote protocol)
42600 @anchor{interrupting remote targets}
42602 In all-stop mode, when a program on the remote target is running,
42603 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
42604 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
42605 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
42607 The precise meaning of @code{BREAK} is defined by the transport
42608 mechanism and may, in fact, be undefined. @value{GDBN} does not
42609 currently define a @code{BREAK} mechanism for any of the network
42610 interfaces except for TCP, in which case @value{GDBN} sends the
42611 @code{telnet} BREAK sequence.
42613 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
42614 transport mechanisms. It is represented by sending the single byte
42615 @code{0x03} without any of the usual packet overhead described in
42616 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
42617 transmitted as part of a packet, it is considered to be packet data
42618 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
42619 (@pxref{X packet}), used for binary downloads, may include an unescaped
42620 @code{0x03} as part of its packet.
42622 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
42623 When Linux kernel receives this sequence from serial port,
42624 it stops execution and connects to gdb.
42626 In non-stop mode, because packet resumptions are asynchronous
42627 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
42628 command to the remote stub, even when the target is running. For that
42629 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
42630 packet}) with the usual packet framing instead of the single byte
42633 Stubs are not required to recognize these interrupt mechanisms and the
42634 precise meaning associated with receipt of the interrupt is
42635 implementation defined. If the target supports debugging of multiple
42636 threads and/or processes, it should attempt to interrupt all
42637 currently-executing threads and processes.
42638 If the stub is successful at interrupting the
42639 running program, it should send one of the stop
42640 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
42641 of successfully stopping the program in all-stop mode, and a stop reply
42642 for each stopped thread in non-stop mode.
42643 Interrupts received while the
42644 program is stopped are queued and the program will be interrupted when
42645 it is resumed next time.
42647 @node Notification Packets
42648 @section Notification Packets
42649 @cindex notification packets
42650 @cindex packets, notification
42652 The @value{GDBN} remote serial protocol includes @dfn{notifications},
42653 packets that require no acknowledgment. Both the GDB and the stub
42654 may send notifications (although the only notifications defined at
42655 present are sent by the stub). Notifications carry information
42656 without incurring the round-trip latency of an acknowledgment, and so
42657 are useful for low-impact communications where occasional packet loss
42660 A notification packet has the form @samp{% @var{data} #
42661 @var{checksum}}, where @var{data} is the content of the notification,
42662 and @var{checksum} is a checksum of @var{data}, computed and formatted
42663 as for ordinary @value{GDBN} packets. A notification's @var{data}
42664 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
42665 receiving a notification, the recipient sends no @samp{+} or @samp{-}
42666 to acknowledge the notification's receipt or to report its corruption.
42668 Every notification's @var{data} begins with a name, which contains no
42669 colon characters, followed by a colon character.
42671 Recipients should silently ignore corrupted notifications and
42672 notifications they do not understand. Recipients should restart
42673 timeout periods on receipt of a well-formed notification, whether or
42674 not they understand it.
42676 Senders should only send the notifications described here when this
42677 protocol description specifies that they are permitted. In the
42678 future, we may extend the protocol to permit existing notifications in
42679 new contexts; this rule helps older senders avoid confusing newer
42682 (Older versions of @value{GDBN} ignore bytes received until they see
42683 the @samp{$} byte that begins an ordinary packet, so new stubs may
42684 transmit notifications without fear of confusing older clients. There
42685 are no notifications defined for @value{GDBN} to send at the moment, but we
42686 assume that most older stubs would ignore them, as well.)
42688 Each notification is comprised of three parts:
42690 @item @var{name}:@var{event}
42691 The notification packet is sent by the side that initiates the
42692 exchange (currently, only the stub does that), with @var{event}
42693 carrying the specific information about the notification, and
42694 @var{name} specifying the name of the notification.
42696 The acknowledge sent by the other side, usually @value{GDBN}, to
42697 acknowledge the exchange and request the event.
42700 The purpose of an asynchronous notification mechanism is to report to
42701 @value{GDBN} that something interesting happened in the remote stub.
42703 The remote stub may send notification @var{name}:@var{event}
42704 at any time, but @value{GDBN} acknowledges the notification when
42705 appropriate. The notification event is pending before @value{GDBN}
42706 acknowledges. Only one notification at a time may be pending; if
42707 additional events occur before @value{GDBN} has acknowledged the
42708 previous notification, they must be queued by the stub for later
42709 synchronous transmission in response to @var{ack} packets from
42710 @value{GDBN}. Because the notification mechanism is unreliable,
42711 the stub is permitted to resend a notification if it believes
42712 @value{GDBN} may not have received it.
42714 Specifically, notifications may appear when @value{GDBN} is not
42715 otherwise reading input from the stub, or when @value{GDBN} is
42716 expecting to read a normal synchronous response or a
42717 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
42718 Notification packets are distinct from any other communication from
42719 the stub so there is no ambiguity.
42721 After receiving a notification, @value{GDBN} shall acknowledge it by
42722 sending a @var{ack} packet as a regular, synchronous request to the
42723 stub. Such acknowledgment is not required to happen immediately, as
42724 @value{GDBN} is permitted to send other, unrelated packets to the
42725 stub first, which the stub should process normally.
42727 Upon receiving a @var{ack} packet, if the stub has other queued
42728 events to report to @value{GDBN}, it shall respond by sending a
42729 normal @var{event}. @value{GDBN} shall then send another @var{ack}
42730 packet to solicit further responses; again, it is permitted to send
42731 other, unrelated packets as well which the stub should process
42734 If the stub receives a @var{ack} packet and there are no additional
42735 @var{event} to report, the stub shall return an @samp{OK} response.
42736 At this point, @value{GDBN} has finished processing a notification
42737 and the stub has completed sending any queued events. @value{GDBN}
42738 won't accept any new notifications until the final @samp{OK} is
42739 received . If further notification events occur, the stub shall send
42740 a new notification, @value{GDBN} shall accept the notification, and
42741 the process shall be repeated.
42743 The process of asynchronous notification can be illustrated by the
42746 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
42749 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
42751 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
42756 The following notifications are defined:
42757 @multitable @columnfractions 0.12 0.12 0.38 0.38
42766 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
42767 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
42768 for information on how these notifications are acknowledged by
42770 @tab Report an asynchronous stop event in non-stop mode.
42774 @node Remote Non-Stop
42775 @section Remote Protocol Support for Non-Stop Mode
42777 @value{GDBN}'s remote protocol supports non-stop debugging of
42778 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
42779 supports non-stop mode, it should report that to @value{GDBN} by including
42780 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
42782 @value{GDBN} typically sends a @samp{QNonStop} packet only when
42783 establishing a new connection with the stub. Entering non-stop mode
42784 does not alter the state of any currently-running threads, but targets
42785 must stop all threads in any already-attached processes when entering
42786 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
42787 probe the target state after a mode change.
42789 In non-stop mode, when an attached process encounters an event that
42790 would otherwise be reported with a stop reply, it uses the
42791 asynchronous notification mechanism (@pxref{Notification Packets}) to
42792 inform @value{GDBN}. In contrast to all-stop mode, where all threads
42793 in all processes are stopped when a stop reply is sent, in non-stop
42794 mode only the thread reporting the stop event is stopped. That is,
42795 when reporting a @samp{S} or @samp{T} response to indicate completion
42796 of a step operation, hitting a breakpoint, or a fault, only the
42797 affected thread is stopped; any other still-running threads continue
42798 to run. When reporting a @samp{W} or @samp{X} response, all running
42799 threads belonging to other attached processes continue to run.
42801 In non-stop mode, the target shall respond to the @samp{?} packet as
42802 follows. First, any incomplete stop reply notification/@samp{vStopped}
42803 sequence in progress is abandoned. The target must begin a new
42804 sequence reporting stop events for all stopped threads, whether or not
42805 it has previously reported those events to @value{GDBN}. The first
42806 stop reply is sent as a synchronous reply to the @samp{?} packet, and
42807 subsequent stop replies are sent as responses to @samp{vStopped} packets
42808 using the mechanism described above. The target must not send
42809 asynchronous stop reply notifications until the sequence is complete.
42810 If all threads are running when the target receives the @samp{?} packet,
42811 or if the target is not attached to any process, it shall respond
42814 If the stub supports non-stop mode, it should also support the
42815 @samp{swbreak} stop reason if software breakpoints are supported, and
42816 the @samp{hwbreak} stop reason if hardware breakpoints are supported
42817 (@pxref{swbreak stop reason}). This is because given the asynchronous
42818 nature of non-stop mode, between the time a thread hits a breakpoint
42819 and the time the event is finally processed by @value{GDBN}, the
42820 breakpoint may have already been removed from the target. Due to
42821 this, @value{GDBN} needs to be able to tell whether a trap stop was
42822 caused by a delayed breakpoint event, which should be ignored, as
42823 opposed to a random trap signal, which should be reported to the user.
42824 Note the @samp{swbreak} feature implies that the target is responsible
42825 for adjusting the PC when a software breakpoint triggers, if
42826 necessary, such as on the x86 architecture.
42828 @node Packet Acknowledgment
42829 @section Packet Acknowledgment
42831 @cindex acknowledgment, for @value{GDBN} remote
42832 @cindex packet acknowledgment, for @value{GDBN} remote
42833 By default, when either the host or the target machine receives a packet,
42834 the first response expected is an acknowledgment: either @samp{+} (to indicate
42835 the package was received correctly) or @samp{-} (to request retransmission).
42836 This mechanism allows the @value{GDBN} remote protocol to operate over
42837 unreliable transport mechanisms, such as a serial line.
42839 In cases where the transport mechanism is itself reliable (such as a pipe or
42840 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
42841 It may be desirable to disable them in that case to reduce communication
42842 overhead, or for other reasons. This can be accomplished by means of the
42843 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
42845 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
42846 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
42847 and response format still includes the normal checksum, as described in
42848 @ref{Overview}, but the checksum may be ignored by the receiver.
42850 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
42851 no-acknowledgment mode, it should report that to @value{GDBN}
42852 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
42853 @pxref{qSupported}.
42854 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
42855 disabled via the @code{set remote noack-packet off} command
42856 (@pxref{Remote Configuration}),
42857 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
42858 Only then may the stub actually turn off packet acknowledgments.
42859 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
42860 response, which can be safely ignored by the stub.
42862 Note that @code{set remote noack-packet} command only affects negotiation
42863 between @value{GDBN} and the stub when subsequent connections are made;
42864 it does not affect the protocol acknowledgment state for any current
42866 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
42867 new connection is established,
42868 there is also no protocol request to re-enable the acknowledgments
42869 for the current connection, once disabled.
42874 Example sequence of a target being re-started. Notice how the restart
42875 does not get any direct output:
42880 @emph{target restarts}
42883 <- @code{T001:1234123412341234}
42887 Example sequence of a target being stepped by a single instruction:
42890 -> @code{G1445@dots{}}
42895 <- @code{T001:1234123412341234}
42899 <- @code{1455@dots{}}
42903 @node File-I/O Remote Protocol Extension
42904 @section File-I/O Remote Protocol Extension
42905 @cindex File-I/O remote protocol extension
42908 * File-I/O Overview::
42909 * Protocol Basics::
42910 * The F Request Packet::
42911 * The F Reply Packet::
42912 * The Ctrl-C Message::
42914 * List of Supported Calls::
42915 * Protocol-specific Representation of Datatypes::
42917 * File-I/O Examples::
42920 @node File-I/O Overview
42921 @subsection File-I/O Overview
42922 @cindex file-i/o overview
42924 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
42925 target to use the host's file system and console I/O to perform various
42926 system calls. System calls on the target system are translated into a
42927 remote protocol packet to the host system, which then performs the needed
42928 actions and returns a response packet to the target system.
42929 This simulates file system operations even on targets that lack file systems.
42931 The protocol is defined to be independent of both the host and target systems.
42932 It uses its own internal representation of datatypes and values. Both
42933 @value{GDBN} and the target's @value{GDBN} stub are responsible for
42934 translating the system-dependent value representations into the internal
42935 protocol representations when data is transmitted.
42937 The communication is synchronous. A system call is possible only when
42938 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
42939 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
42940 the target is stopped to allow deterministic access to the target's
42941 memory. Therefore File-I/O is not interruptible by target signals. On
42942 the other hand, it is possible to interrupt File-I/O by a user interrupt
42943 (@samp{Ctrl-C}) within @value{GDBN}.
42945 The target's request to perform a host system call does not finish
42946 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
42947 after finishing the system call, the target returns to continuing the
42948 previous activity (continue, step). No additional continue or step
42949 request from @value{GDBN} is required.
42952 (@value{GDBP}) continue
42953 <- target requests 'system call X'
42954 target is stopped, @value{GDBN} executes system call
42955 -> @value{GDBN} returns result
42956 ... target continues, @value{GDBN} returns to wait for the target
42957 <- target hits breakpoint and sends a Txx packet
42960 The protocol only supports I/O on the console and to regular files on
42961 the host file system. Character or block special devices, pipes,
42962 named pipes, sockets or any other communication method on the host
42963 system are not supported by this protocol.
42965 File I/O is not supported in non-stop mode.
42967 @node Protocol Basics
42968 @subsection Protocol Basics
42969 @cindex protocol basics, file-i/o
42971 The File-I/O protocol uses the @code{F} packet as the request as well
42972 as reply packet. Since a File-I/O system call can only occur when
42973 @value{GDBN} is waiting for a response from the continuing or stepping target,
42974 the File-I/O request is a reply that @value{GDBN} has to expect as a result
42975 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
42976 This @code{F} packet contains all information needed to allow @value{GDBN}
42977 to call the appropriate host system call:
42981 A unique identifier for the requested system call.
42984 All parameters to the system call. Pointers are given as addresses
42985 in the target memory address space. Pointers to strings are given as
42986 pointer/length pair. Numerical values are given as they are.
42987 Numerical control flags are given in a protocol-specific representation.
42991 At this point, @value{GDBN} has to perform the following actions.
42995 If the parameters include pointer values to data needed as input to a
42996 system call, @value{GDBN} requests this data from the target with a
42997 standard @code{m} packet request. This additional communication has to be
42998 expected by the target implementation and is handled as any other @code{m}
43002 @value{GDBN} translates all value from protocol representation to host
43003 representation as needed. Datatypes are coerced into the host types.
43006 @value{GDBN} calls the system call.
43009 It then coerces datatypes back to protocol representation.
43012 If the system call is expected to return data in buffer space specified
43013 by pointer parameters to the call, the data is transmitted to the
43014 target using a @code{M} or @code{X} packet. This packet has to be expected
43015 by the target implementation and is handled as any other @code{M} or @code{X}
43020 Eventually @value{GDBN} replies with another @code{F} packet which contains all
43021 necessary information for the target to continue. This at least contains
43028 @code{errno}, if has been changed by the system call.
43035 After having done the needed type and value coercion, the target continues
43036 the latest continue or step action.
43038 @node The F Request Packet
43039 @subsection The @code{F} Request Packet
43040 @cindex file-i/o request packet
43041 @cindex @code{F} request packet
43043 The @code{F} request packet has the following format:
43046 @item F@var{call-id},@var{parameter@dots{}}
43048 @var{call-id} is the identifier to indicate the host system call to be called.
43049 This is just the name of the function.
43051 @var{parameter@dots{}} are the parameters to the system call.
43052 Parameters are hexadecimal integer values, either the actual values in case
43053 of scalar datatypes, pointers to target buffer space in case of compound
43054 datatypes and unspecified memory areas, or pointer/length pairs in case
43055 of string parameters. These are appended to the @var{call-id} as a
43056 comma-delimited list. All values are transmitted in ASCII
43057 string representation, pointer/length pairs separated by a slash.
43063 @node The F Reply Packet
43064 @subsection The @code{F} Reply Packet
43065 @cindex file-i/o reply packet
43066 @cindex @code{F} reply packet
43068 The @code{F} reply packet has the following format:
43072 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
43074 @var{retcode} is the return code of the system call as hexadecimal value.
43076 @var{errno} is the @code{errno} set by the call, in protocol-specific
43078 This parameter can be omitted if the call was successful.
43080 @var{Ctrl-C flag} is only sent if the user requested a break. In this
43081 case, @var{errno} must be sent as well, even if the call was successful.
43082 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
43089 or, if the call was interrupted before the host call has been performed:
43096 assuming 4 is the protocol-specific representation of @code{EINTR}.
43101 @node The Ctrl-C Message
43102 @subsection The @samp{Ctrl-C} Message
43103 @cindex ctrl-c message, in file-i/o protocol
43105 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
43106 reply packet (@pxref{The F Reply Packet}),
43107 the target should behave as if it had
43108 gotten a break message. The meaning for the target is ``system call
43109 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
43110 (as with a break message) and return to @value{GDBN} with a @code{T02}
43113 It's important for the target to know in which
43114 state the system call was interrupted. There are two possible cases:
43118 The system call hasn't been performed on the host yet.
43121 The system call on the host has been finished.
43125 These two states can be distinguished by the target by the value of the
43126 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
43127 call hasn't been performed. This is equivalent to the @code{EINTR} handling
43128 on POSIX systems. In any other case, the target may presume that the
43129 system call has been finished --- successfully or not --- and should behave
43130 as if the break message arrived right after the system call.
43132 @value{GDBN} must behave reliably. If the system call has not been called
43133 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
43134 @code{errno} in the packet. If the system call on the host has been finished
43135 before the user requests a break, the full action must be finished by
43136 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
43137 The @code{F} packet may only be sent when either nothing has happened
43138 or the full action has been completed.
43141 @subsection Console I/O
43142 @cindex console i/o as part of file-i/o
43144 By default and if not explicitly closed by the target system, the file
43145 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
43146 on the @value{GDBN} console is handled as any other file output operation
43147 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
43148 by @value{GDBN} so that after the target read request from file descriptor
43149 0 all following typing is buffered until either one of the following
43154 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
43156 system call is treated as finished.
43159 The user presses @key{RET}. This is treated as end of input with a trailing
43163 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
43164 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
43168 If the user has typed more characters than fit in the buffer given to
43169 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
43170 either another @code{read(0, @dots{})} is requested by the target, or debugging
43171 is stopped at the user's request.
43174 @node List of Supported Calls
43175 @subsection List of Supported Calls
43176 @cindex list of supported file-i/o calls
43193 @unnumberedsubsubsec open
43194 @cindex open, file-i/o system call
43199 int open(const char *pathname, int flags);
43200 int open(const char *pathname, int flags, mode_t mode);
43204 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
43207 @var{flags} is the bitwise @code{OR} of the following values:
43211 If the file does not exist it will be created. The host
43212 rules apply as far as file ownership and time stamps
43216 When used with @code{O_CREAT}, if the file already exists it is
43217 an error and open() fails.
43220 If the file already exists and the open mode allows
43221 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
43222 truncated to zero length.
43225 The file is opened in append mode.
43228 The file is opened for reading only.
43231 The file is opened for writing only.
43234 The file is opened for reading and writing.
43238 Other bits are silently ignored.
43242 @var{mode} is the bitwise @code{OR} of the following values:
43246 User has read permission.
43249 User has write permission.
43252 Group has read permission.
43255 Group has write permission.
43258 Others have read permission.
43261 Others have write permission.
43265 Other bits are silently ignored.
43268 @item Return value:
43269 @code{open} returns the new file descriptor or -1 if an error
43276 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
43279 @var{pathname} refers to a directory.
43282 The requested access is not allowed.
43285 @var{pathname} was too long.
43288 A directory component in @var{pathname} does not exist.
43291 @var{pathname} refers to a device, pipe, named pipe or socket.
43294 @var{pathname} refers to a file on a read-only filesystem and
43295 write access was requested.
43298 @var{pathname} is an invalid pointer value.
43301 No space on device to create the file.
43304 The process already has the maximum number of files open.
43307 The limit on the total number of files open on the system
43311 The call was interrupted by the user.
43317 @unnumberedsubsubsec close
43318 @cindex close, file-i/o system call
43327 @samp{Fclose,@var{fd}}
43329 @item Return value:
43330 @code{close} returns zero on success, or -1 if an error occurred.
43336 @var{fd} isn't a valid open file descriptor.
43339 The call was interrupted by the user.
43345 @unnumberedsubsubsec read
43346 @cindex read, file-i/o system call
43351 int read(int fd, void *buf, unsigned int count);
43355 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
43357 @item Return value:
43358 On success, the number of bytes read is returned.
43359 Zero indicates end of file. If count is zero, read
43360 returns zero as well. On error, -1 is returned.
43366 @var{fd} is not a valid file descriptor or is not open for
43370 @var{bufptr} is an invalid pointer value.
43373 The call was interrupted by the user.
43379 @unnumberedsubsubsec write
43380 @cindex write, file-i/o system call
43385 int write(int fd, const void *buf, unsigned int count);
43389 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
43391 @item Return value:
43392 On success, the number of bytes written are returned.
43393 Zero indicates nothing was written. On error, -1
43400 @var{fd} is not a valid file descriptor or is not open for
43404 @var{bufptr} is an invalid pointer value.
43407 An attempt was made to write a file that exceeds the
43408 host-specific maximum file size allowed.
43411 No space on device to write the data.
43414 The call was interrupted by the user.
43420 @unnumberedsubsubsec lseek
43421 @cindex lseek, file-i/o system call
43426 long lseek (int fd, long offset, int flag);
43430 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
43432 @var{flag} is one of:
43436 The offset is set to @var{offset} bytes.
43439 The offset is set to its current location plus @var{offset}
43443 The offset is set to the size of the file plus @var{offset}
43447 @item Return value:
43448 On success, the resulting unsigned offset in bytes from
43449 the beginning of the file is returned. Otherwise, a
43450 value of -1 is returned.
43456 @var{fd} is not a valid open file descriptor.
43459 @var{fd} is associated with the @value{GDBN} console.
43462 @var{flag} is not a proper value.
43465 The call was interrupted by the user.
43471 @unnumberedsubsubsec rename
43472 @cindex rename, file-i/o system call
43477 int rename(const char *oldpath, const char *newpath);
43481 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
43483 @item Return value:
43484 On success, zero is returned. On error, -1 is returned.
43490 @var{newpath} is an existing directory, but @var{oldpath} is not a
43494 @var{newpath} is a non-empty directory.
43497 @var{oldpath} or @var{newpath} is a directory that is in use by some
43501 An attempt was made to make a directory a subdirectory
43505 A component used as a directory in @var{oldpath} or new
43506 path is not a directory. Or @var{oldpath} is a directory
43507 and @var{newpath} exists but is not a directory.
43510 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
43513 No access to the file or the path of the file.
43517 @var{oldpath} or @var{newpath} was too long.
43520 A directory component in @var{oldpath} or @var{newpath} does not exist.
43523 The file is on a read-only filesystem.
43526 The device containing the file has no room for the new
43530 The call was interrupted by the user.
43536 @unnumberedsubsubsec unlink
43537 @cindex unlink, file-i/o system call
43542 int unlink(const char *pathname);
43546 @samp{Funlink,@var{pathnameptr}/@var{len}}
43548 @item Return value:
43549 On success, zero is returned. On error, -1 is returned.
43555 No access to the file or the path of the file.
43558 The system does not allow unlinking of directories.
43561 The file @var{pathname} cannot be unlinked because it's
43562 being used by another process.
43565 @var{pathnameptr} is an invalid pointer value.
43568 @var{pathname} was too long.
43571 A directory component in @var{pathname} does not exist.
43574 A component of the path is not a directory.
43577 The file is on a read-only filesystem.
43580 The call was interrupted by the user.
43586 @unnumberedsubsubsec stat/fstat
43587 @cindex fstat, file-i/o system call
43588 @cindex stat, file-i/o system call
43593 int stat(const char *pathname, struct stat *buf);
43594 int fstat(int fd, struct stat *buf);
43598 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
43599 @samp{Ffstat,@var{fd},@var{bufptr}}
43601 @item Return value:
43602 On success, zero is returned. On error, -1 is returned.
43608 @var{fd} is not a valid open file.
43611 A directory component in @var{pathname} does not exist or the
43612 path is an empty string.
43615 A component of the path is not a directory.
43618 @var{pathnameptr} is an invalid pointer value.
43621 No access to the file or the path of the file.
43624 @var{pathname} was too long.
43627 The call was interrupted by the user.
43633 @unnumberedsubsubsec gettimeofday
43634 @cindex gettimeofday, file-i/o system call
43639 int gettimeofday(struct timeval *tv, void *tz);
43643 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
43645 @item Return value:
43646 On success, 0 is returned, -1 otherwise.
43652 @var{tz} is a non-NULL pointer.
43655 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
43661 @unnumberedsubsubsec isatty
43662 @cindex isatty, file-i/o system call
43667 int isatty(int fd);
43671 @samp{Fisatty,@var{fd}}
43673 @item Return value:
43674 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
43680 The call was interrupted by the user.
43685 Note that the @code{isatty} call is treated as a special case: it returns
43686 1 to the target if the file descriptor is attached
43687 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
43688 would require implementing @code{ioctl} and would be more complex than
43693 @unnumberedsubsubsec system
43694 @cindex system, file-i/o system call
43699 int system(const char *command);
43703 @samp{Fsystem,@var{commandptr}/@var{len}}
43705 @item Return value:
43706 If @var{len} is zero, the return value indicates whether a shell is
43707 available. A zero return value indicates a shell is not available.
43708 For non-zero @var{len}, the value returned is -1 on error and the
43709 return status of the command otherwise. Only the exit status of the
43710 command is returned, which is extracted from the host's @code{system}
43711 return value by calling @code{WEXITSTATUS(retval)}. In case
43712 @file{/bin/sh} could not be executed, 127 is returned.
43718 The call was interrupted by the user.
43723 @value{GDBN} takes over the full task of calling the necessary host calls
43724 to perform the @code{system} call. The return value of @code{system} on
43725 the host is simplified before it's returned
43726 to the target. Any termination signal information from the child process
43727 is discarded, and the return value consists
43728 entirely of the exit status of the called command.
43730 Due to security concerns, the @code{system} call is by default refused
43731 by @value{GDBN}. The user has to allow this call explicitly with the
43732 @code{set remote system-call-allowed 1} command.
43735 @item set remote system-call-allowed
43736 @kindex set remote system-call-allowed
43737 Control whether to allow the @code{system} calls in the File I/O
43738 protocol for the remote target. The default is zero (disabled).
43740 @item show remote system-call-allowed
43741 @kindex show remote system-call-allowed
43742 Show whether the @code{system} calls are allowed in the File I/O
43746 @node Protocol-specific Representation of Datatypes
43747 @subsection Protocol-specific Representation of Datatypes
43748 @cindex protocol-specific representation of datatypes, in file-i/o protocol
43751 * Integral Datatypes::
43753 * Memory Transfer::
43758 @node Integral Datatypes
43759 @unnumberedsubsubsec Integral Datatypes
43760 @cindex integral datatypes, in file-i/o protocol
43762 The integral datatypes used in the system calls are @code{int},
43763 @code{unsigned int}, @code{long}, @code{unsigned long},
43764 @code{mode_t}, and @code{time_t}.
43766 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
43767 implemented as 32 bit values in this protocol.
43769 @code{long} and @code{unsigned long} are implemented as 64 bit types.
43771 @xref{Limits}, for corresponding MIN and MAX values (similar to those
43772 in @file{limits.h}) to allow range checking on host and target.
43774 @code{time_t} datatypes are defined as seconds since the Epoch.
43776 All integral datatypes transferred as part of a memory read or write of a
43777 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
43780 @node Pointer Values
43781 @unnumberedsubsubsec Pointer Values
43782 @cindex pointer values, in file-i/o protocol
43784 Pointers to target data are transmitted as they are. An exception
43785 is made for pointers to buffers for which the length isn't
43786 transmitted as part of the function call, namely strings. Strings
43787 are transmitted as a pointer/length pair, both as hex values, e.g.@:
43794 which is a pointer to data of length 18 bytes at position 0x1aaf.
43795 The length is defined as the full string length in bytes, including
43796 the trailing null byte. For example, the string @code{"hello world"}
43797 at address 0x123456 is transmitted as
43803 @node Memory Transfer
43804 @unnumberedsubsubsec Memory Transfer
43805 @cindex memory transfer, in file-i/o protocol
43807 Structured data which is transferred using a memory read or write (for
43808 example, a @code{struct stat}) is expected to be in a protocol-specific format
43809 with all scalar multibyte datatypes being big endian. Translation to
43810 this representation needs to be done both by the target before the @code{F}
43811 packet is sent, and by @value{GDBN} before
43812 it transfers memory to the target. Transferred pointers to structured
43813 data should point to the already-coerced data at any time.
43817 @unnumberedsubsubsec struct stat
43818 @cindex struct stat, in file-i/o protocol
43820 The buffer of type @code{struct stat} used by the target and @value{GDBN}
43821 is defined as follows:
43825 unsigned int st_dev; /* device */
43826 unsigned int st_ino; /* inode */
43827 mode_t st_mode; /* protection */
43828 unsigned int st_nlink; /* number of hard links */
43829 unsigned int st_uid; /* user ID of owner */
43830 unsigned int st_gid; /* group ID of owner */
43831 unsigned int st_rdev; /* device type (if inode device) */
43832 unsigned long st_size; /* total size, in bytes */
43833 unsigned long st_blksize; /* blocksize for filesystem I/O */
43834 unsigned long st_blocks; /* number of blocks allocated */
43835 time_t st_atime; /* time of last access */
43836 time_t st_mtime; /* time of last modification */
43837 time_t st_ctime; /* time of last change */
43841 The integral datatypes conform to the definitions given in the
43842 appropriate section (see @ref{Integral Datatypes}, for details) so this
43843 structure is of size 64 bytes.
43845 The values of several fields have a restricted meaning and/or
43851 A value of 0 represents a file, 1 the console.
43854 No valid meaning for the target. Transmitted unchanged.
43857 Valid mode bits are described in @ref{Constants}. Any other
43858 bits have currently no meaning for the target.
43863 No valid meaning for the target. Transmitted unchanged.
43868 These values have a host and file system dependent
43869 accuracy. Especially on Windows hosts, the file system may not
43870 support exact timing values.
43873 The target gets a @code{struct stat} of the above representation and is
43874 responsible for coercing it to the target representation before
43877 Note that due to size differences between the host, target, and protocol
43878 representations of @code{struct stat} members, these members could eventually
43879 get truncated on the target.
43881 @node struct timeval
43882 @unnumberedsubsubsec struct timeval
43883 @cindex struct timeval, in file-i/o protocol
43885 The buffer of type @code{struct timeval} used by the File-I/O protocol
43886 is defined as follows:
43890 time_t tv_sec; /* second */
43891 long tv_usec; /* microsecond */
43895 The integral datatypes conform to the definitions given in the
43896 appropriate section (see @ref{Integral Datatypes}, for details) so this
43897 structure is of size 8 bytes.
43900 @subsection Constants
43901 @cindex constants, in file-i/o protocol
43903 The following values are used for the constants inside of the
43904 protocol. @value{GDBN} and target are responsible for translating these
43905 values before and after the call as needed.
43916 @unnumberedsubsubsec Open Flags
43917 @cindex open flags, in file-i/o protocol
43919 All values are given in hexadecimal representation.
43931 @node mode_t Values
43932 @unnumberedsubsubsec mode_t Values
43933 @cindex mode_t values, in file-i/o protocol
43935 All values are given in octal representation.
43952 @unnumberedsubsubsec Errno Values
43953 @cindex errno values, in file-i/o protocol
43955 All values are given in decimal representation.
43980 @code{EUNKNOWN} is used as a fallback error value if a host system returns
43981 any error value not in the list of supported error numbers.
43984 @unnumberedsubsubsec Lseek Flags
43985 @cindex lseek flags, in file-i/o protocol
43994 @unnumberedsubsubsec Limits
43995 @cindex limits, in file-i/o protocol
43997 All values are given in decimal representation.
44000 INT_MIN -2147483648
44002 UINT_MAX 4294967295
44003 LONG_MIN -9223372036854775808
44004 LONG_MAX 9223372036854775807
44005 ULONG_MAX 18446744073709551615
44008 @node File-I/O Examples
44009 @subsection File-I/O Examples
44010 @cindex file-i/o examples
44012 Example sequence of a write call, file descriptor 3, buffer is at target
44013 address 0x1234, 6 bytes should be written:
44016 <- @code{Fwrite,3,1234,6}
44017 @emph{request memory read from target}
44020 @emph{return "6 bytes written"}
44024 Example sequence of a read call, file descriptor 3, buffer is at target
44025 address 0x1234, 6 bytes should be read:
44028 <- @code{Fread,3,1234,6}
44029 @emph{request memory write to target}
44030 -> @code{X1234,6:XXXXXX}
44031 @emph{return "6 bytes read"}
44035 Example sequence of a read call, call fails on the host due to invalid
44036 file descriptor (@code{EBADF}):
44039 <- @code{Fread,3,1234,6}
44043 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
44047 <- @code{Fread,3,1234,6}
44052 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
44056 <- @code{Fread,3,1234,6}
44057 -> @code{X1234,6:XXXXXX}
44061 @node Library List Format
44062 @section Library List Format
44063 @cindex library list format, remote protocol
44065 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
44066 same process as your application to manage libraries. In this case,
44067 @value{GDBN} can use the loader's symbol table and normal memory
44068 operations to maintain a list of shared libraries. On other
44069 platforms, the operating system manages loaded libraries.
44070 @value{GDBN} can not retrieve the list of currently loaded libraries
44071 through memory operations, so it uses the @samp{qXfer:libraries:read}
44072 packet (@pxref{qXfer library list read}) instead. The remote stub
44073 queries the target's operating system and reports which libraries
44076 The @samp{qXfer:libraries:read} packet returns an XML document which
44077 lists loaded libraries and their offsets. Each library has an
44078 associated name and one or more segment or section base addresses,
44079 which report where the library was loaded in memory.
44081 For the common case of libraries that are fully linked binaries, the
44082 library should have a list of segments. If the target supports
44083 dynamic linking of a relocatable object file, its library XML element
44084 should instead include a list of allocated sections. The segment or
44085 section bases are start addresses, not relocation offsets; they do not
44086 depend on the library's link-time base addresses.
44088 @value{GDBN} must be linked with the Expat library to support XML
44089 library lists. @xref{Expat}.
44091 A simple memory map, with one loaded library relocated by a single
44092 offset, looks like this:
44096 <library name="/lib/libc.so.6">
44097 <segment address="0x10000000"/>
44102 Another simple memory map, with one loaded library with three
44103 allocated sections (.text, .data, .bss), looks like this:
44107 <library name="sharedlib.o">
44108 <section address="0x10000000"/>
44109 <section address="0x20000000"/>
44110 <section address="0x30000000"/>
44115 The format of a library list is described by this DTD:
44118 <!-- library-list: Root element with versioning -->
44119 <!ELEMENT library-list (library)*>
44120 <!ATTLIST library-list version CDATA #FIXED "1.0">
44121 <!ELEMENT library (segment*, section*)>
44122 <!ATTLIST library name CDATA #REQUIRED>
44123 <!ELEMENT segment EMPTY>
44124 <!ATTLIST segment address CDATA #REQUIRED>
44125 <!ELEMENT section EMPTY>
44126 <!ATTLIST section address CDATA #REQUIRED>
44129 In addition, segments and section descriptors cannot be mixed within a
44130 single library element, and you must supply at least one segment or
44131 section for each library.
44133 @node Library List Format for SVR4 Targets
44134 @section Library List Format for SVR4 Targets
44135 @cindex library list format, remote protocol
44137 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
44138 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
44139 shared libraries. Still a special library list provided by this packet is
44140 more efficient for the @value{GDBN} remote protocol.
44142 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
44143 loaded libraries and their SVR4 linker parameters. For each library on SVR4
44144 target, the following parameters are reported:
44148 @code{name}, the absolute file name from the @code{l_name} field of
44149 @code{struct link_map}.
44151 @code{lm} with address of @code{struct link_map} used for TLS
44152 (Thread Local Storage) access.
44154 @code{l_addr}, the displacement as read from the field @code{l_addr} of
44155 @code{struct link_map}. For prelinked libraries this is not an absolute
44156 memory address. It is a displacement of absolute memory address against
44157 address the file was prelinked to during the library load.
44159 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
44162 Additionally the single @code{main-lm} attribute specifies address of
44163 @code{struct link_map} used for the main executable. This parameter is used
44164 for TLS access and its presence is optional.
44166 @value{GDBN} must be linked with the Expat library to support XML
44167 SVR4 library lists. @xref{Expat}.
44169 A simple memory map, with two loaded libraries (which do not use prelink),
44173 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
44174 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
44176 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
44178 </library-list-svr>
44181 The format of an SVR4 library list is described by this DTD:
44184 <!-- library-list-svr4: Root element with versioning -->
44185 <!ELEMENT library-list-svr4 (library)*>
44186 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
44187 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
44188 <!ELEMENT library EMPTY>
44189 <!ATTLIST library name CDATA #REQUIRED>
44190 <!ATTLIST library lm CDATA #REQUIRED>
44191 <!ATTLIST library l_addr CDATA #REQUIRED>
44192 <!ATTLIST library l_ld CDATA #REQUIRED>
44195 @node Memory Map Format
44196 @section Memory Map Format
44197 @cindex memory map format
44199 To be able to write into flash memory, @value{GDBN} needs to obtain a
44200 memory map from the target. This section describes the format of the
44203 The memory map is obtained using the @samp{qXfer:memory-map:read}
44204 (@pxref{qXfer memory map read}) packet and is an XML document that
44205 lists memory regions.
44207 @value{GDBN} must be linked with the Expat library to support XML
44208 memory maps. @xref{Expat}.
44210 The top-level structure of the document is shown below:
44213 <?xml version="1.0"?>
44214 <!DOCTYPE memory-map
44215 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44216 "http://sourceware.org/gdb/gdb-memory-map.dtd">
44222 Each region can be either:
44227 A region of RAM starting at @var{addr} and extending for @var{length}
44231 <memory type="ram" start="@var{addr}" length="@var{length}"/>
44236 A region of read-only memory:
44239 <memory type="rom" start="@var{addr}" length="@var{length}"/>
44244 A region of flash memory, with erasure blocks @var{blocksize}
44248 <memory type="flash" start="@var{addr}" length="@var{length}">
44249 <property name="blocksize">@var{blocksize}</property>
44255 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
44256 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
44257 packets to write to addresses in such ranges.
44259 The formal DTD for memory map format is given below:
44262 <!-- ................................................... -->
44263 <!-- Memory Map XML DTD ................................ -->
44264 <!-- File: memory-map.dtd .............................. -->
44265 <!-- .................................... .............. -->
44266 <!-- memory-map.dtd -->
44267 <!-- memory-map: Root element with versioning -->
44268 <!ELEMENT memory-map (memory)*>
44269 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
44270 <!ELEMENT memory (property)*>
44271 <!-- memory: Specifies a memory region,
44272 and its type, or device. -->
44273 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
44274 start CDATA #REQUIRED
44275 length CDATA #REQUIRED>
44276 <!-- property: Generic attribute tag -->
44277 <!ELEMENT property (#PCDATA | property)*>
44278 <!ATTLIST property name (blocksize) #REQUIRED>
44281 @node Thread List Format
44282 @section Thread List Format
44283 @cindex thread list format
44285 To efficiently update the list of threads and their attributes,
44286 @value{GDBN} issues the @samp{qXfer:threads:read} packet
44287 (@pxref{qXfer threads read}) and obtains the XML document with
44288 the following structure:
44291 <?xml version="1.0"?>
44293 <thread id="id" core="0" name="name">
44294 ... description ...
44299 Each @samp{thread} element must have the @samp{id} attribute that
44300 identifies the thread (@pxref{thread-id syntax}). The
44301 @samp{core} attribute, if present, specifies which processor core
44302 the thread was last executing on. The @samp{name} attribute, if
44303 present, specifies the human-readable name of the thread. The content
44304 of the of @samp{thread} element is interpreted as human-readable
44305 auxiliary information. The @samp{handle} attribute, if present,
44306 is a hex encoded representation of the thread handle.
44309 @node Traceframe Info Format
44310 @section Traceframe Info Format
44311 @cindex traceframe info format
44313 To be able to know which objects in the inferior can be examined when
44314 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
44315 memory ranges, registers and trace state variables that have been
44316 collected in a traceframe.
44318 This list is obtained using the @samp{qXfer:traceframe-info:read}
44319 (@pxref{qXfer traceframe info read}) packet and is an XML document.
44321 @value{GDBN} must be linked with the Expat library to support XML
44322 traceframe info discovery. @xref{Expat}.
44324 The top-level structure of the document is shown below:
44327 <?xml version="1.0"?>
44328 <!DOCTYPE traceframe-info
44329 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44330 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
44336 Each traceframe block can be either:
44341 A region of collected memory starting at @var{addr} and extending for
44342 @var{length} bytes from there:
44345 <memory start="@var{addr}" length="@var{length}"/>
44349 A block indicating trace state variable numbered @var{number} has been
44353 <tvar id="@var{number}"/>
44358 The formal DTD for the traceframe info format is given below:
44361 <!ELEMENT traceframe-info (memory | tvar)* >
44362 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
44364 <!ELEMENT memory EMPTY>
44365 <!ATTLIST memory start CDATA #REQUIRED
44366 length CDATA #REQUIRED>
44368 <!ATTLIST tvar id CDATA #REQUIRED>
44371 @node Branch Trace Format
44372 @section Branch Trace Format
44373 @cindex branch trace format
44375 In order to display the branch trace of an inferior thread,
44376 @value{GDBN} needs to obtain the list of branches. This list is
44377 represented as list of sequential code blocks that are connected via
44378 branches. The code in each block has been executed sequentially.
44380 This list is obtained using the @samp{qXfer:btrace:read}
44381 (@pxref{qXfer btrace read}) packet and is an XML document.
44383 @value{GDBN} must be linked with the Expat library to support XML
44384 traceframe info discovery. @xref{Expat}.
44386 The top-level structure of the document is shown below:
44389 <?xml version="1.0"?>
44391 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
44392 "http://sourceware.org/gdb/gdb-btrace.dtd">
44401 A block of sequentially executed instructions starting at @var{begin}
44402 and ending at @var{end}:
44405 <block begin="@var{begin}" end="@var{end}"/>
44410 The formal DTD for the branch trace format is given below:
44413 <!ELEMENT btrace (block* | pt) >
44414 <!ATTLIST btrace version CDATA #FIXED "1.0">
44416 <!ELEMENT block EMPTY>
44417 <!ATTLIST block begin CDATA #REQUIRED
44418 end CDATA #REQUIRED>
44420 <!ELEMENT pt (pt-config?, raw?)>
44422 <!ELEMENT pt-config (cpu?)>
44424 <!ELEMENT cpu EMPTY>
44425 <!ATTLIST cpu vendor CDATA #REQUIRED
44426 family CDATA #REQUIRED
44427 model CDATA #REQUIRED
44428 stepping CDATA #REQUIRED>
44430 <!ELEMENT raw (#PCDATA)>
44433 @node Branch Trace Configuration Format
44434 @section Branch Trace Configuration Format
44435 @cindex branch trace configuration format
44437 For each inferior thread, @value{GDBN} can obtain the branch trace
44438 configuration using the @samp{qXfer:btrace-conf:read}
44439 (@pxref{qXfer btrace-conf read}) packet.
44441 The configuration describes the branch trace format and configuration
44442 settings for that format. The following information is described:
44446 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
44449 The size of the @acronym{BTS} ring buffer in bytes.
44452 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
44456 The size of the @acronym{Intel PT} ring buffer in bytes.
44460 @value{GDBN} must be linked with the Expat library to support XML
44461 branch trace configuration discovery. @xref{Expat}.
44463 The formal DTD for the branch trace configuration format is given below:
44466 <!ELEMENT btrace-conf (bts?, pt?)>
44467 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
44469 <!ELEMENT bts EMPTY>
44470 <!ATTLIST bts size CDATA #IMPLIED>
44472 <!ELEMENT pt EMPTY>
44473 <!ATTLIST pt size CDATA #IMPLIED>
44476 @include agentexpr.texi
44478 @node Target Descriptions
44479 @appendix Target Descriptions
44480 @cindex target descriptions
44482 One of the challenges of using @value{GDBN} to debug embedded systems
44483 is that there are so many minor variants of each processor
44484 architecture in use. It is common practice for vendors to start with
44485 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
44486 and then make changes to adapt it to a particular market niche. Some
44487 architectures have hundreds of variants, available from dozens of
44488 vendors. This leads to a number of problems:
44492 With so many different customized processors, it is difficult for
44493 the @value{GDBN} maintainers to keep up with the changes.
44495 Since individual variants may have short lifetimes or limited
44496 audiences, it may not be worthwhile to carry information about every
44497 variant in the @value{GDBN} source tree.
44499 When @value{GDBN} does support the architecture of the embedded system
44500 at hand, the task of finding the correct architecture name to give the
44501 @command{set architecture} command can be error-prone.
44504 To address these problems, the @value{GDBN} remote protocol allows a
44505 target system to not only identify itself to @value{GDBN}, but to
44506 actually describe its own features. This lets @value{GDBN} support
44507 processor variants it has never seen before --- to the extent that the
44508 descriptions are accurate, and that @value{GDBN} understands them.
44510 @value{GDBN} must be linked with the Expat library to support XML
44511 target descriptions. @xref{Expat}.
44514 * Retrieving Descriptions:: How descriptions are fetched from a target.
44515 * Target Description Format:: The contents of a target description.
44516 * Predefined Target Types:: Standard types available for target
44518 * Enum Target Types:: How to define enum target types.
44519 * Standard Target Features:: Features @value{GDBN} knows about.
44522 @node Retrieving Descriptions
44523 @section Retrieving Descriptions
44525 Target descriptions can be read from the target automatically, or
44526 specified by the user manually. The default behavior is to read the
44527 description from the target. @value{GDBN} retrieves it via the remote
44528 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
44529 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
44530 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
44531 XML document, of the form described in @ref{Target Description
44534 Alternatively, you can specify a file to read for the target description.
44535 If a file is set, the target will not be queried. The commands to
44536 specify a file are:
44539 @cindex set tdesc filename
44540 @item set tdesc filename @var{path}
44541 Read the target description from @var{path}.
44543 @cindex unset tdesc filename
44544 @item unset tdesc filename
44545 Do not read the XML target description from a file. @value{GDBN}
44546 will use the description supplied by the current target.
44548 @cindex show tdesc filename
44549 @item show tdesc filename
44550 Show the filename to read for a target description, if any.
44554 @node Target Description Format
44555 @section Target Description Format
44556 @cindex target descriptions, XML format
44558 A target description annex is an @uref{http://www.w3.org/XML/, XML}
44559 document which complies with the Document Type Definition provided in
44560 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
44561 means you can use generally available tools like @command{xmllint} to
44562 check that your feature descriptions are well-formed and valid.
44563 However, to help people unfamiliar with XML write descriptions for
44564 their targets, we also describe the grammar here.
44566 Target descriptions can identify the architecture of the remote target
44567 and (for some architectures) provide information about custom register
44568 sets. They can also identify the OS ABI of the remote target.
44569 @value{GDBN} can use this information to autoconfigure for your
44570 target, or to warn you if you connect to an unsupported target.
44572 Here is a simple target description:
44575 <target version="1.0">
44576 <architecture>i386:x86-64</architecture>
44581 This minimal description only says that the target uses
44582 the x86-64 architecture.
44584 A target description has the following overall form, with [ ] marking
44585 optional elements and @dots{} marking repeatable elements. The elements
44586 are explained further below.
44589 <?xml version="1.0"?>
44590 <!DOCTYPE target SYSTEM "gdb-target.dtd">
44591 <target version="1.0">
44592 @r{[}@var{architecture}@r{]}
44593 @r{[}@var{osabi}@r{]}
44594 @r{[}@var{compatible}@r{]}
44595 @r{[}@var{feature}@dots{}@r{]}
44600 The description is generally insensitive to whitespace and line
44601 breaks, under the usual common-sense rules. The XML version
44602 declaration and document type declaration can generally be omitted
44603 (@value{GDBN} does not require them), but specifying them may be
44604 useful for XML validation tools. The @samp{version} attribute for
44605 @samp{<target>} may also be omitted, but we recommend
44606 including it; if future versions of @value{GDBN} use an incompatible
44607 revision of @file{gdb-target.dtd}, they will detect and report
44608 the version mismatch.
44610 @subsection Inclusion
44611 @cindex target descriptions, inclusion
44614 @cindex <xi:include>
44617 It can sometimes be valuable to split a target description up into
44618 several different annexes, either for organizational purposes, or to
44619 share files between different possible target descriptions. You can
44620 divide a description into multiple files by replacing any element of
44621 the target description with an inclusion directive of the form:
44624 <xi:include href="@var{document}"/>
44628 When @value{GDBN} encounters an element of this form, it will retrieve
44629 the named XML @var{document}, and replace the inclusion directive with
44630 the contents of that document. If the current description was read
44631 using @samp{qXfer}, then so will be the included document;
44632 @var{document} will be interpreted as the name of an annex. If the
44633 current description was read from a file, @value{GDBN} will look for
44634 @var{document} as a file in the same directory where it found the
44635 original description.
44637 @subsection Architecture
44638 @cindex <architecture>
44640 An @samp{<architecture>} element has this form:
44643 <architecture>@var{arch}</architecture>
44646 @var{arch} is one of the architectures from the set accepted by
44647 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44650 @cindex @code{<osabi>}
44652 This optional field was introduced in @value{GDBN} version 7.0.
44653 Previous versions of @value{GDBN} ignore it.
44655 An @samp{<osabi>} element has this form:
44658 <osabi>@var{abi-name}</osabi>
44661 @var{abi-name} is an OS ABI name from the same selection accepted by
44662 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
44664 @subsection Compatible Architecture
44665 @cindex @code{<compatible>}
44667 This optional field was introduced in @value{GDBN} version 7.0.
44668 Previous versions of @value{GDBN} ignore it.
44670 A @samp{<compatible>} element has this form:
44673 <compatible>@var{arch}</compatible>
44676 @var{arch} is one of the architectures from the set accepted by
44677 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44679 A @samp{<compatible>} element is used to specify that the target
44680 is able to run binaries in some other than the main target architecture
44681 given by the @samp{<architecture>} element. For example, on the
44682 Cell Broadband Engine, the main architecture is @code{powerpc:common}
44683 or @code{powerpc:common64}, but the system is able to run binaries
44684 in the @code{spu} architecture as well. The way to describe this
44685 capability with @samp{<compatible>} is as follows:
44688 <architecture>powerpc:common</architecture>
44689 <compatible>spu</compatible>
44692 @subsection Features
44695 Each @samp{<feature>} describes some logical portion of the target
44696 system. Features are currently used to describe available CPU
44697 registers and the types of their contents. A @samp{<feature>} element
44701 <feature name="@var{name}">
44702 @r{[}@var{type}@dots{}@r{]}
44708 Each feature's name should be unique within the description. The name
44709 of a feature does not matter unless @value{GDBN} has some special
44710 knowledge of the contents of that feature; if it does, the feature
44711 should have its standard name. @xref{Standard Target Features}.
44715 Any register's value is a collection of bits which @value{GDBN} must
44716 interpret. The default interpretation is a two's complement integer,
44717 but other types can be requested by name in the register description.
44718 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
44719 Target Types}), and the description can define additional composite
44722 Each type element must have an @samp{id} attribute, which gives
44723 a unique (within the containing @samp{<feature>}) name to the type.
44724 Types must be defined before they are used.
44727 Some targets offer vector registers, which can be treated as arrays
44728 of scalar elements. These types are written as @samp{<vector>} elements,
44729 specifying the array element type, @var{type}, and the number of elements,
44733 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
44737 If a register's value is usefully viewed in multiple ways, define it
44738 with a union type containing the useful representations. The
44739 @samp{<union>} element contains one or more @samp{<field>} elements,
44740 each of which has a @var{name} and a @var{type}:
44743 <union id="@var{id}">
44744 <field name="@var{name}" type="@var{type}"/>
44751 If a register's value is composed from several separate values, define
44752 it with either a structure type or a flags type.
44753 A flags type may only contain bitfields.
44754 A structure type may either contain only bitfields or contain no bitfields.
44755 If the value contains only bitfields, its total size in bytes must be
44758 Non-bitfield values have a @var{name} and @var{type}.
44761 <struct id="@var{id}">
44762 <field name="@var{name}" type="@var{type}"/>
44767 Both @var{name} and @var{type} values are required.
44768 No implicit padding is added.
44770 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
44773 <struct id="@var{id}" size="@var{size}">
44774 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
44780 <flags id="@var{id}" size="@var{size}">
44781 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
44786 The @var{name} value is required.
44787 Bitfield values may be named with the empty string, @samp{""},
44788 in which case the field is ``filler'' and its value is not printed.
44789 Not all bits need to be specified, so ``filler'' fields are optional.
44791 The @var{start} and @var{end} values are required, and @var{type}
44793 The field's @var{start} must be less than or equal to its @var{end},
44794 and zero represents the least significant bit.
44796 The default value of @var{type} is @code{bool} for single bit fields,
44797 and an unsigned integer otherwise.
44799 Which to choose? Structures or flags?
44801 Registers defined with @samp{flags} have these advantages over
44802 defining them with @samp{struct}:
44806 Arithmetic may be performed on them as if they were integers.
44808 They are printed in a more readable fashion.
44811 Registers defined with @samp{struct} have one advantage over
44812 defining them with @samp{flags}:
44816 One can fetch individual fields like in @samp{C}.
44819 (gdb) print $my_struct_reg.field3
44825 @subsection Registers
44828 Each register is represented as an element with this form:
44831 <reg name="@var{name}"
44832 bitsize="@var{size}"
44833 @r{[}regnum="@var{num}"@r{]}
44834 @r{[}save-restore="@var{save-restore}"@r{]}
44835 @r{[}type="@var{type}"@r{]}
44836 @r{[}group="@var{group}"@r{]}/>
44840 The components are as follows:
44845 The register's name; it must be unique within the target description.
44848 The register's size, in bits.
44851 The register's number. If omitted, a register's number is one greater
44852 than that of the previous register (either in the current feature or in
44853 a preceding feature); the first register in the target description
44854 defaults to zero. This register number is used to read or write
44855 the register; e.g.@: it is used in the remote @code{p} and @code{P}
44856 packets, and registers appear in the @code{g} and @code{G} packets
44857 in order of increasing register number.
44860 Whether the register should be preserved across inferior function
44861 calls; this must be either @code{yes} or @code{no}. The default is
44862 @code{yes}, which is appropriate for most registers except for
44863 some system control registers; this is not related to the target's
44867 The type of the register. It may be a predefined type, a type
44868 defined in the current feature, or one of the special types @code{int}
44869 and @code{float}. @code{int} is an integer type of the correct size
44870 for @var{bitsize}, and @code{float} is a floating point type (in the
44871 architecture's normal floating point format) of the correct size for
44872 @var{bitsize}. The default is @code{int}.
44875 The register group to which this register belongs. It can be one of the
44876 standard register groups @code{general}, @code{float}, @code{vector} or an
44877 arbitrary string. Group names should be limited to alphanumeric characters.
44878 If a group name is made up of multiple words the words may be separated by
44879 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
44880 @var{group} is specified, @value{GDBN} will not display the register in
44881 @code{info registers}.
44885 @node Predefined Target Types
44886 @section Predefined Target Types
44887 @cindex target descriptions, predefined types
44889 Type definitions in the self-description can build up composite types
44890 from basic building blocks, but can not define fundamental types. Instead,
44891 standard identifiers are provided by @value{GDBN} for the fundamental
44892 types. The currently supported types are:
44897 Boolean type, occupying a single bit.
44905 Signed integer types holding the specified number of bits.
44913 Unsigned integer types holding the specified number of bits.
44917 Pointers to unspecified code and data. The program counter and
44918 any dedicated return address register may be marked as code
44919 pointers; printing a code pointer converts it into a symbolic
44920 address. The stack pointer and any dedicated address registers
44921 may be marked as data pointers.
44924 Single precision IEEE floating point.
44927 Double precision IEEE floating point.
44930 The 12-byte extended precision format used by ARM FPA registers.
44933 The 10-byte extended precision format used by x87 registers.
44936 32bit @sc{eflags} register used by x86.
44939 32bit @sc{mxcsr} register used by x86.
44943 @node Enum Target Types
44944 @section Enum Target Types
44945 @cindex target descriptions, enum types
44947 Enum target types are useful in @samp{struct} and @samp{flags}
44948 register descriptions. @xref{Target Description Format}.
44950 Enum types have a name, size and a list of name/value pairs.
44953 <enum id="@var{id}" size="@var{size}">
44954 <evalue name="@var{name}" value="@var{value}"/>
44959 Enums must be defined before they are used.
44962 <enum id="levels_type" size="4">
44963 <evalue name="low" value="0"/>
44964 <evalue name="high" value="1"/>
44966 <flags id="flags_type" size="4">
44967 <field name="X" start="0"/>
44968 <field name="LEVEL" start="1" end="1" type="levels_type"/>
44970 <reg name="flags" bitsize="32" type="flags_type"/>
44973 Given that description, a value of 3 for the @samp{flags} register
44974 would be printed as:
44977 (gdb) info register flags
44978 flags 0x3 [ X LEVEL=high ]
44981 @node Standard Target Features
44982 @section Standard Target Features
44983 @cindex target descriptions, standard features
44985 A target description must contain either no registers or all the
44986 target's registers. If the description contains no registers, then
44987 @value{GDBN} will assume a default register layout, selected based on
44988 the architecture. If the description contains any registers, the
44989 default layout will not be used; the standard registers must be
44990 described in the target description, in such a way that @value{GDBN}
44991 can recognize them.
44993 This is accomplished by giving specific names to feature elements
44994 which contain standard registers. @value{GDBN} will look for features
44995 with those names and verify that they contain the expected registers;
44996 if any known feature is missing required registers, or if any required
44997 feature is missing, @value{GDBN} will reject the target
44998 description. You can add additional registers to any of the
44999 standard features --- @value{GDBN} will display them just as if
45000 they were added to an unrecognized feature.
45002 This section lists the known features and their expected contents.
45003 Sample XML documents for these features are included in the
45004 @value{GDBN} source tree, in the directory @file{gdb/features}.
45006 Names recognized by @value{GDBN} should include the name of the
45007 company or organization which selected the name, and the overall
45008 architecture to which the feature applies; so e.g.@: the feature
45009 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
45011 The names of registers are not case sensitive for the purpose
45012 of recognizing standard features, but @value{GDBN} will only display
45013 registers using the capitalization used in the description.
45016 * AArch64 Features::
45020 * MicroBlaze Features::
45024 * Nios II Features::
45025 * OpenRISC 1000 Features::
45026 * PowerPC Features::
45027 * RISC-V Features::
45029 * S/390 and System z Features::
45035 @node AArch64 Features
45036 @subsection AArch64 Features
45037 @cindex target descriptions, AArch64 features
45039 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
45040 targets. It should contain registers @samp{x0} through @samp{x30},
45041 @samp{sp}, @samp{pc}, and @samp{cpsr}.
45043 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
45044 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
45047 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
45048 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
45049 through @samp{p15}, @samp{ffr} and @samp{vg}.
45051 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
45052 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
45055 @subsection ARC Features
45056 @cindex target descriptions, ARC Features
45058 ARC processors are highly configurable, so even core registers and their number
45059 are not completely predetermined. In addition flags and PC registers which are
45060 important to @value{GDBN} are not ``core'' registers in ARC. It is required
45061 that one of the core registers features is present.
45062 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
45064 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
45065 targets with a normal register file. It should contain registers @samp{r0}
45066 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
45067 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
45068 and any of extension core registers @samp{r32} through @samp{r59/acch}.
45069 @samp{ilink} and extension core registers are not available to read/write, when
45070 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
45072 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
45073 ARC HS targets with a reduced register file. It should contain registers
45074 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
45075 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
45076 This feature may contain register @samp{ilink} and any of extension core
45077 registers @samp{r32} through @samp{r59/acch}.
45079 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
45080 targets with a normal register file. It should contain registers @samp{r0}
45081 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
45082 @samp{lp_count} and @samp{pcl}. This feature may contain registers
45083 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
45084 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
45085 registers are not available when debugging GNU/Linux applications. The only
45086 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
45087 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
45088 ARC v2, but @samp{ilink2} is optional on ARCompact.
45090 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
45091 targets. It should contain registers @samp{pc} and @samp{status32}.
45094 @subsection ARM Features
45095 @cindex target descriptions, ARM features
45097 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
45099 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
45100 @samp{lr}, @samp{pc}, and @samp{cpsr}.
45102 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
45103 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
45104 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
45107 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
45108 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
45110 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
45111 it should contain at least registers @samp{wR0} through @samp{wR15} and
45112 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
45113 @samp{wCSSF}, and @samp{wCASF} registers are optional.
45115 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
45116 should contain at least registers @samp{d0} through @samp{d15}. If
45117 they are present, @samp{d16} through @samp{d31} should also be included.
45118 @value{GDBN} will synthesize the single-precision registers from
45119 halves of the double-precision registers.
45121 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
45122 need to contain registers; it instructs @value{GDBN} to display the
45123 VFP double-precision registers as vectors and to synthesize the
45124 quad-precision registers from pairs of double-precision registers.
45125 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
45126 be present and include 32 double-precision registers.
45128 @node i386 Features
45129 @subsection i386 Features
45130 @cindex target descriptions, i386 features
45132 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
45133 targets. It should describe the following registers:
45137 @samp{eax} through @samp{edi} plus @samp{eip} for i386
45139 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
45141 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
45142 @samp{fs}, @samp{gs}
45144 @samp{st0} through @samp{st7}
45146 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
45147 @samp{foseg}, @samp{fooff} and @samp{fop}
45150 The register sets may be different, depending on the target.
45152 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
45153 describe registers:
45157 @samp{xmm0} through @samp{xmm7} for i386
45159 @samp{xmm0} through @samp{xmm15} for amd64
45164 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
45165 @samp{org.gnu.gdb.i386.sse} feature. It should
45166 describe the upper 128 bits of @sc{ymm} registers:
45170 @samp{ymm0h} through @samp{ymm7h} for i386
45172 @samp{ymm0h} through @samp{ymm15h} for amd64
45175 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
45176 Memory Protection Extension (MPX). It should describe the following registers:
45180 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
45182 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
45185 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
45186 describe a single register, @samp{orig_eax}.
45188 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
45189 describe two system registers: @samp{fs_base} and @samp{gs_base}.
45191 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
45192 @samp{org.gnu.gdb.i386.avx} feature. It should
45193 describe additional @sc{xmm} registers:
45197 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
45200 It should describe the upper 128 bits of additional @sc{ymm} registers:
45204 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
45208 describe the upper 256 bits of @sc{zmm} registers:
45212 @samp{zmm0h} through @samp{zmm7h} for i386.
45214 @samp{zmm0h} through @samp{zmm15h} for amd64.
45218 describe the additional @sc{zmm} registers:
45222 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
45225 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
45226 describe a single register, @samp{pkru}. It is a 32-bit register
45227 valid for i386 and amd64.
45229 @node MicroBlaze Features
45230 @subsection MicroBlaze Features
45231 @cindex target descriptions, MicroBlaze features
45233 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
45234 targets. It should contain registers @samp{r0} through @samp{r31},
45235 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
45236 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
45237 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
45239 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
45240 If present, it should contain registers @samp{rshr} and @samp{rslr}
45242 @node MIPS Features
45243 @subsection @acronym{MIPS} Features
45244 @cindex target descriptions, @acronym{MIPS} features
45246 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
45247 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
45248 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
45251 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
45252 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
45253 registers. They may be 32-bit or 64-bit depending on the target.
45255 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
45256 it may be optional in a future version of @value{GDBN}. It should
45257 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
45258 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
45260 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
45261 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
45262 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
45263 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
45265 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
45266 contain a single register, @samp{restart}, which is used by the
45267 Linux kernel to control restartable syscalls.
45269 @node M68K Features
45270 @subsection M68K Features
45271 @cindex target descriptions, M68K features
45274 @item @samp{org.gnu.gdb.m68k.core}
45275 @itemx @samp{org.gnu.gdb.coldfire.core}
45276 @itemx @samp{org.gnu.gdb.fido.core}
45277 One of those features must be always present.
45278 The feature that is present determines which flavor of m68k is
45279 used. The feature that is present should contain registers
45280 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
45281 @samp{sp}, @samp{ps} and @samp{pc}.
45283 @item @samp{org.gnu.gdb.coldfire.fp}
45284 This feature is optional. If present, it should contain registers
45285 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
45288 Note that, despite the fact that this feature's name says
45289 @samp{coldfire}, it is used to describe any floating point registers.
45290 The size of the registers must match the main m68k flavor; so, for
45291 example, if the primary feature is reported as @samp{coldfire}, then
45292 64-bit floating point registers are required.
45295 @node NDS32 Features
45296 @subsection NDS32 Features
45297 @cindex target descriptions, NDS32 features
45299 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
45300 targets. It should contain at least registers @samp{r0} through
45301 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
45304 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
45305 it should contain 64-bit double-precision floating-point registers
45306 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
45307 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
45309 @emph{Note:} The first sixteen 64-bit double-precision floating-point
45310 registers are overlapped with the thirty-two 32-bit single-precision
45311 floating-point registers. The 32-bit single-precision registers, if
45312 not being listed explicitly, will be synthesized from halves of the
45313 overlapping 64-bit double-precision registers. Listing 32-bit
45314 single-precision registers explicitly is deprecated, and the
45315 support to it could be totally removed some day.
45317 @node Nios II Features
45318 @subsection Nios II Features
45319 @cindex target descriptions, Nios II features
45321 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
45322 targets. It should contain the 32 core registers (@samp{zero},
45323 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
45324 @samp{pc}, and the 16 control registers (@samp{status} through
45327 @node OpenRISC 1000 Features
45328 @subsection Openrisc 1000 Features
45329 @cindex target descriptions, OpenRISC 1000 features
45331 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
45332 targets. It should contain the 32 general purpose registers (@samp{r0}
45333 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
45335 @node PowerPC Features
45336 @subsection PowerPC Features
45337 @cindex target descriptions, PowerPC features
45339 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
45340 targets. It should contain registers @samp{r0} through @samp{r31},
45341 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
45342 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
45344 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
45345 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
45347 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
45348 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
45349 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
45350 through @samp{v31} as aliases for the corresponding @samp{vrX}
45353 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
45354 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
45355 combine these registers with the floating point registers (@samp{f0}
45356 through @samp{f31}) and the altivec registers (@samp{vr0} through
45357 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
45358 @samp{vs63}, the set of vector-scalar registers for POWER7.
45359 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
45360 @samp{org.gnu.gdb.power.altivec}.
45362 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
45363 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
45364 @samp{spefscr}. SPE targets should provide 32-bit registers in
45365 @samp{org.gnu.gdb.power.core} and provide the upper halves in
45366 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
45367 these to present registers @samp{ev0} through @samp{ev31} to the
45370 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
45371 contain the 64-bit register @samp{ppr}.
45373 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
45374 contain the 64-bit register @samp{dscr}.
45376 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
45377 contain the 64-bit register @samp{tar}.
45379 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
45380 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
45383 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
45384 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
45385 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
45386 server PMU registers provided by @sc{gnu}/Linux.
45388 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
45389 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
45392 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
45393 contain the checkpointed general-purpose registers @samp{cr0} through
45394 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
45395 @samp{cctr}. These registers may all be either 32-bit or 64-bit
45396 depending on the target. It should also contain the checkpointed
45397 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
45400 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
45401 contain the checkpointed 64-bit floating-point registers @samp{cf0}
45402 through @samp{cf31}, as well as the checkpointed 64-bit register
45405 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
45406 should contain the checkpointed altivec registers @samp{cvr0} through
45407 @samp{cvr31}, all 128-bit wide. It should also contain the
45408 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
45411 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
45412 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
45413 will combine these registers with the checkpointed floating point
45414 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
45415 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
45416 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
45417 @samp{cvs63}. Therefore, this feature requires both
45418 @samp{org.gnu.gdb.power.htm.altivec} and
45419 @samp{org.gnu.gdb.power.htm.fpu}.
45421 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
45422 contain the 64-bit checkpointed register @samp{cppr}.
45424 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
45425 contain the 64-bit checkpointed register @samp{cdscr}.
45427 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
45428 contain the 64-bit checkpointed register @samp{ctar}.
45431 @node RISC-V Features
45432 @subsection RISC-V Features
45433 @cindex target descriptions, RISC-V Features
45435 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
45436 targets. It should contain the registers @samp{x0} through
45437 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
45438 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
45441 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
45442 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
45443 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
45444 architectural register names, or the ABI names can be used.
45446 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
45447 it should contain registers that are not backed by real registers on
45448 the target, but are instead virtual, where the register value is
45449 derived from other target state. In many ways these are like
45450 @value{GDBN}s pseudo-registers, except implemented by the target.
45451 Currently the only register expected in this set is the one byte
45452 @samp{priv} register that contains the target's privilege level in the
45453 least significant two bits.
45455 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
45456 should contain all of the target's standard CSRs. Standard CSRs are
45457 those defined in the RISC-V specification documents. There is some
45458 overlap between this feature and the fpu feature; the @samp{fflags},
45459 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
45460 expectation is that these registers will be in the fpu feature if the
45461 target has floating point hardware, but can be moved into the csr
45462 feature if the target has the floating point control registers, but no
45463 other floating point hardware.
45466 @subsection RX Features
45467 @cindex target descriptions, RX Features
45469 The @samp{org.gnu.gdb.rx.core} feature is required for RX
45470 targets. It should contain the registers @samp{r0} through
45471 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
45472 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
45474 @node S/390 and System z Features
45475 @subsection S/390 and System z Features
45476 @cindex target descriptions, S/390 features
45477 @cindex target descriptions, System z features
45479 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
45480 System z targets. It should contain the PSW and the 16 general
45481 registers. In particular, System z targets should provide the 64-bit
45482 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
45483 S/390 targets should provide the 32-bit versions of these registers.
45484 A System z target that runs in 31-bit addressing mode should provide
45485 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
45486 register's upper halves @samp{r0h} through @samp{r15h}, and their
45487 lower halves @samp{r0l} through @samp{r15l}.
45489 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
45490 contain the 64-bit registers @samp{f0} through @samp{f15}, and
45493 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
45494 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
45496 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
45497 contain the register @samp{orig_r2}, which is 64-bit wide on System z
45498 targets and 32-bit otherwise. In addition, the feature may contain
45499 the @samp{last_break} register, whose width depends on the addressing
45500 mode, as well as the @samp{system_call} register, which is always
45503 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
45504 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
45505 @samp{atia}, and @samp{tr0} through @samp{tr15}.
45507 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
45508 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
45509 combined by @value{GDBN} with the floating point registers @samp{f0}
45510 through @samp{f15} to present the 128-bit wide vector registers
45511 @samp{v0} through @samp{v15}. In addition, this feature should
45512 contain the 128-bit wide vector registers @samp{v16} through
45515 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
45516 the 64-bit wide guarded-storage-control registers @samp{gsd},
45517 @samp{gssm}, and @samp{gsepla}.
45519 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
45520 the 64-bit wide guarded-storage broadcast control registers
45521 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
45523 @node Sparc Features
45524 @subsection Sparc Features
45525 @cindex target descriptions, sparc32 features
45526 @cindex target descriptions, sparc64 features
45527 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
45528 targets. It should describe the following registers:
45532 @samp{g0} through @samp{g7}
45534 @samp{o0} through @samp{o7}
45536 @samp{l0} through @samp{l7}
45538 @samp{i0} through @samp{i7}
45541 They may be 32-bit or 64-bit depending on the target.
45543 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
45544 targets. It should describe the following registers:
45548 @samp{f0} through @samp{f31}
45550 @samp{f32} through @samp{f62} for sparc64
45553 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
45554 targets. It should describe the following registers:
45558 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
45559 @samp{fsr}, and @samp{csr} for sparc32
45561 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
45565 @node TIC6x Features
45566 @subsection TMS320C6x Features
45567 @cindex target descriptions, TIC6x features
45568 @cindex target descriptions, TMS320C6x features
45569 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
45570 targets. It should contain registers @samp{A0} through @samp{A15},
45571 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
45573 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
45574 contain registers @samp{A16} through @samp{A31} and @samp{B16}
45575 through @samp{B31}.
45577 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
45578 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
45580 @node Operating System Information
45581 @appendix Operating System Information
45582 @cindex operating system information
45588 Users of @value{GDBN} often wish to obtain information about the state of
45589 the operating system running on the target---for example the list of
45590 processes, or the list of open files. This section describes the
45591 mechanism that makes it possible. This mechanism is similar to the
45592 target features mechanism (@pxref{Target Descriptions}), but focuses
45593 on a different aspect of target.
45595 Operating system information is retrieved from the target via the
45596 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
45597 read}). The object name in the request should be @samp{osdata}, and
45598 the @var{annex} identifies the data to be fetched.
45601 @appendixsection Process list
45602 @cindex operating system information, process list
45604 When requesting the process list, the @var{annex} field in the
45605 @samp{qXfer} request should be @samp{processes}. The returned data is
45606 an XML document. The formal syntax of this document is defined in
45607 @file{gdb/features/osdata.dtd}.
45609 An example document is:
45612 <?xml version="1.0"?>
45613 <!DOCTYPE target SYSTEM "osdata.dtd">
45614 <osdata type="processes">
45616 <column name="pid">1</column>
45617 <column name="user">root</column>
45618 <column name="command">/sbin/init</column>
45619 <column name="cores">1,2,3</column>
45624 Each item should include a column whose name is @samp{pid}. The value
45625 of that column should identify the process on the target. The
45626 @samp{user} and @samp{command} columns are optional, and will be
45627 displayed by @value{GDBN}. The @samp{cores} column, if present,
45628 should contain a comma-separated list of cores that this process
45629 is running on. Target may provide additional columns,
45630 which @value{GDBN} currently ignores.
45632 @node Trace File Format
45633 @appendix Trace File Format
45634 @cindex trace file format
45636 The trace file comes in three parts: a header, a textual description
45637 section, and a trace frame section with binary data.
45639 The header has the form @code{\x7fTRACE0\n}. The first byte is
45640 @code{0x7f} so as to indicate that the file contains binary data,
45641 while the @code{0} is a version number that may have different values
45644 The description section consists of multiple lines of @sc{ascii} text
45645 separated by newline characters (@code{0xa}). The lines may include a
45646 variety of optional descriptive or context-setting information, such
45647 as tracepoint definitions or register set size. @value{GDBN} will
45648 ignore any line that it does not recognize. An empty line marks the end
45653 Specifies the size of a register block in bytes. This is equal to the
45654 size of a @code{g} packet payload in the remote protocol. @var{size}
45655 is an ascii decimal number. There should be only one such line in
45656 a single trace file.
45658 @item status @var{status}
45659 Trace status. @var{status} has the same format as a @code{qTStatus}
45660 remote packet reply. There should be only one such line in a single trace
45663 @item tp @var{payload}
45664 Tracepoint definition. The @var{payload} has the same format as
45665 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
45666 may take multiple lines of definition, corresponding to the multiple
45669 @item tsv @var{payload}
45670 Trace state variable definition. The @var{payload} has the same format as
45671 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
45672 may take multiple lines of definition, corresponding to the multiple
45675 @item tdesc @var{payload}
45676 Target description in XML format. The @var{payload} is a single line of
45677 the XML file. All such lines should be concatenated together to get
45678 the original XML file. This file is in the same format as @code{qXfer}
45679 @code{features} payload, and corresponds to the main @code{target.xml}
45680 file. Includes are not allowed.
45684 The trace frame section consists of a number of consecutive frames.
45685 Each frame begins with a two-byte tracepoint number, followed by a
45686 four-byte size giving the amount of data in the frame. The data in
45687 the frame consists of a number of blocks, each introduced by a
45688 character indicating its type (at least register, memory, and trace
45689 state variable). The data in this section is raw binary, not a
45690 hexadecimal or other encoding; its endianness matches the target's
45693 @c FIXME bi-arch may require endianness/arch info in description section
45696 @item R @var{bytes}
45697 Register block. The number and ordering of bytes matches that of a
45698 @code{g} packet in the remote protocol. Note that these are the
45699 actual bytes, in target order, not a hexadecimal encoding.
45701 @item M @var{address} @var{length} @var{bytes}...
45702 Memory block. This is a contiguous block of memory, at the 8-byte
45703 address @var{address}, with a 2-byte length @var{length}, followed by
45704 @var{length} bytes.
45706 @item V @var{number} @var{value}
45707 Trace state variable block. This records the 8-byte signed value
45708 @var{value} of trace state variable numbered @var{number}.
45712 Future enhancements of the trace file format may include additional types
45715 @node Index Section Format
45716 @appendix @code{.gdb_index} section format
45717 @cindex .gdb_index section format
45718 @cindex index section format
45720 This section documents the index section that is created by @code{save
45721 gdb-index} (@pxref{Index Files}). The index section is
45722 DWARF-specific; some knowledge of DWARF is assumed in this
45725 The mapped index file format is designed to be directly
45726 @code{mmap}able on any architecture. In most cases, a datum is
45727 represented using a little-endian 32-bit integer value, called an
45728 @code{offset_type}. Big endian machines must byte-swap the values
45729 before using them. Exceptions to this rule are noted. The data is
45730 laid out such that alignment is always respected.
45732 A mapped index consists of several areas, laid out in order.
45736 The file header. This is a sequence of values, of @code{offset_type}
45737 unless otherwise noted:
45741 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
45742 Version 4 uses a different hashing function from versions 5 and 6.
45743 Version 6 includes symbols for inlined functions, whereas versions 4
45744 and 5 do not. Version 7 adds attributes to the CU indices in the
45745 symbol table. Version 8 specifies that symbols from DWARF type units
45746 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
45747 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
45749 @value{GDBN} will only read version 4, 5, or 6 indices
45750 by specifying @code{set use-deprecated-index-sections on}.
45751 GDB has a workaround for potentially broken version 7 indices so it is
45752 currently not flagged as deprecated.
45755 The offset, from the start of the file, of the CU list.
45758 The offset, from the start of the file, of the types CU list. Note
45759 that this area can be empty, in which case this offset will be equal
45760 to the next offset.
45763 The offset, from the start of the file, of the address area.
45766 The offset, from the start of the file, of the symbol table.
45769 The offset, from the start of the file, of the constant pool.
45773 The CU list. This is a sequence of pairs of 64-bit little-endian
45774 values, sorted by the CU offset. The first element in each pair is
45775 the offset of a CU in the @code{.debug_info} section. The second
45776 element in each pair is the length of that CU. References to a CU
45777 elsewhere in the map are done using a CU index, which is just the
45778 0-based index into this table. Note that if there are type CUs, then
45779 conceptually CUs and type CUs form a single list for the purposes of
45783 The types CU list. This is a sequence of triplets of 64-bit
45784 little-endian values. In a triplet, the first value is the CU offset,
45785 the second value is the type offset in the CU, and the third value is
45786 the type signature. The types CU list is not sorted.
45789 The address area. The address area consists of a sequence of address
45790 entries. Each address entry has three elements:
45794 The low address. This is a 64-bit little-endian value.
45797 The high address. This is a 64-bit little-endian value. Like
45798 @code{DW_AT_high_pc}, the value is one byte beyond the end.
45801 The CU index. This is an @code{offset_type} value.
45805 The symbol table. This is an open-addressed hash table. The size of
45806 the hash table is always a power of 2.
45808 Each slot in the hash table consists of a pair of @code{offset_type}
45809 values. The first value is the offset of the symbol's name in the
45810 constant pool. The second value is the offset of the CU vector in the
45813 If both values are 0, then this slot in the hash table is empty. This
45814 is ok because while 0 is a valid constant pool index, it cannot be a
45815 valid index for both a string and a CU vector.
45817 The hash value for a table entry is computed by applying an
45818 iterative hash function to the symbol's name. Starting with an
45819 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
45820 the string is incorporated into the hash using the formula depending on the
45825 The formula is @code{r = r * 67 + c - 113}.
45827 @item Versions 5 to 7
45828 The formula is @code{r = r * 67 + tolower (c) - 113}.
45831 The terminating @samp{\0} is not incorporated into the hash.
45833 The step size used in the hash table is computed via
45834 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
45835 value, and @samp{size} is the size of the hash table. The step size
45836 is used to find the next candidate slot when handling a hash
45839 The names of C@t{++} symbols in the hash table are canonicalized. We
45840 don't currently have a simple description of the canonicalization
45841 algorithm; if you intend to create new index sections, you must read
45845 The constant pool. This is simply a bunch of bytes. It is organized
45846 so that alignment is correct: CU vectors are stored first, followed by
45849 A CU vector in the constant pool is a sequence of @code{offset_type}
45850 values. The first value is the number of CU indices in the vector.
45851 Each subsequent value is the index and symbol attributes of a CU in
45852 the CU list. This element in the hash table is used to indicate which
45853 CUs define the symbol and how the symbol is used.
45854 See below for the format of each CU index+attributes entry.
45856 A string in the constant pool is zero-terminated.
45859 Attributes were added to CU index values in @code{.gdb_index} version 7.
45860 If a symbol has multiple uses within a CU then there is one
45861 CU index+attributes value for each use.
45863 The format of each CU index+attributes entry is as follows
45869 This is the index of the CU in the CU list.
45871 These bits are reserved for future purposes and must be zero.
45873 The kind of the symbol in the CU.
45877 This value is reserved and should not be used.
45878 By reserving zero the full @code{offset_type} value is backwards compatible
45879 with previous versions of the index.
45881 The symbol is a type.
45883 The symbol is a variable or an enum value.
45885 The symbol is a function.
45887 Any other kind of symbol.
45889 These values are reserved.
45893 This bit is zero if the value is global and one if it is static.
45895 The determination of whether a symbol is global or static is complicated.
45896 The authorative reference is the file @file{dwarf2read.c} in
45897 @value{GDBN} sources.
45901 This pseudo-code describes the computation of a symbol's kind and
45902 global/static attributes in the index.
45905 is_external = get_attribute (die, DW_AT_external);
45906 language = get_attribute (cu_die, DW_AT_language);
45909 case DW_TAG_typedef:
45910 case DW_TAG_base_type:
45911 case DW_TAG_subrange_type:
45915 case DW_TAG_enumerator:
45917 is_static = language != CPLUS;
45919 case DW_TAG_subprogram:
45921 is_static = ! (is_external || language == ADA);
45923 case DW_TAG_constant:
45925 is_static = ! is_external;
45927 case DW_TAG_variable:
45929 is_static = ! is_external;
45931 case DW_TAG_namespace:
45935 case DW_TAG_class_type:
45936 case DW_TAG_interface_type:
45937 case DW_TAG_structure_type:
45938 case DW_TAG_union_type:
45939 case DW_TAG_enumeration_type:
45941 is_static = language != CPLUS;
45949 @appendix Manual pages
45953 * gdb man:: The GNU Debugger man page
45954 * gdbserver man:: Remote Server for the GNU Debugger man page
45955 * gcore man:: Generate a core file of a running program
45956 * gdbinit man:: gdbinit scripts
45957 * gdb-add-index man:: Add index files to speed up GDB
45963 @c man title gdb The GNU Debugger
45965 @c man begin SYNOPSIS gdb
45966 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
45967 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
45968 [@option{-b}@w{ }@var{bps}]
45969 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
45970 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
45971 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
45972 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
45973 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
45976 @c man begin DESCRIPTION gdb
45977 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
45978 going on ``inside'' another program while it executes -- or what another
45979 program was doing at the moment it crashed.
45981 @value{GDBN} can do four main kinds of things (plus other things in support of
45982 these) to help you catch bugs in the act:
45986 Start your program, specifying anything that might affect its behavior.
45989 Make your program stop on specified conditions.
45992 Examine what has happened, when your program has stopped.
45995 Change things in your program, so you can experiment with correcting the
45996 effects of one bug and go on to learn about another.
45999 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
46002 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
46003 commands from the terminal until you tell it to exit with the @value{GDBN}
46004 command @code{quit}. You can get online help from @value{GDBN} itself
46005 by using the command @code{help}.
46007 You can run @code{gdb} with no arguments or options; but the most
46008 usual way to start @value{GDBN} is with one argument or two, specifying an
46009 executable program as the argument:
46015 You can also start with both an executable program and a core file specified:
46021 You can, instead, specify a process ID as a second argument or use option
46022 @code{-p}, if you want to debug a running process:
46030 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
46031 can omit the @var{program} filename.
46033 Here are some of the most frequently needed @value{GDBN} commands:
46035 @c pod2man highlights the right hand side of the @item lines.
46037 @item break [@var{file}:]@var{function}
46038 Set a breakpoint at @var{function} (in @var{file}).
46040 @item run [@var{arglist}]
46041 Start your program (with @var{arglist}, if specified).
46044 Backtrace: display the program stack.
46046 @item print @var{expr}
46047 Display the value of an expression.
46050 Continue running your program (after stopping, e.g. at a breakpoint).
46053 Execute next program line (after stopping); step @emph{over} any
46054 function calls in the line.
46056 @item edit [@var{file}:]@var{function}
46057 look at the program line where it is presently stopped.
46059 @item list [@var{file}:]@var{function}
46060 type the text of the program in the vicinity of where it is presently stopped.
46063 Execute next program line (after stopping); step @emph{into} any
46064 function calls in the line.
46066 @item help [@var{name}]
46067 Show information about @value{GDBN} command @var{name}, or general information
46068 about using @value{GDBN}.
46071 Exit from @value{GDBN}.
46075 For full details on @value{GDBN},
46076 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46077 by Richard M. Stallman and Roland H. Pesch. The same text is available online
46078 as the @code{gdb} entry in the @code{info} program.
46082 @c man begin OPTIONS gdb
46083 Any arguments other than options specify an executable
46084 file and core file (or process ID); that is, the first argument
46085 encountered with no
46086 associated option flag is equivalent to a @option{-se} option, and the second,
46087 if any, is equivalent to a @option{-c} option if it's the name of a file.
46089 both long and short forms; both are shown here. The long forms are also
46090 recognized if you truncate them, so long as enough of the option is
46091 present to be unambiguous. (If you prefer, you can flag option
46092 arguments with @option{+} rather than @option{-}, though we illustrate the
46093 more usual convention.)
46095 All the options and command line arguments you give are processed
46096 in sequential order. The order makes a difference when the @option{-x}
46102 List all options, with brief explanations.
46104 @item -symbols=@var{file}
46105 @itemx -s @var{file}
46106 Read symbol table from file @var{file}.
46109 Enable writing into executable and core files.
46111 @item -exec=@var{file}
46112 @itemx -e @var{file}
46113 Use file @var{file} as the executable file to execute when
46114 appropriate, and for examining pure data in conjunction with a core
46117 @item -se=@var{file}
46118 Read symbol table from file @var{file} and use it as the executable
46121 @item -core=@var{file}
46122 @itemx -c @var{file}
46123 Use file @var{file} as a core dump to examine.
46125 @item -command=@var{file}
46126 @itemx -x @var{file}
46127 Execute @value{GDBN} commands from file @var{file}.
46129 @item -ex @var{command}
46130 Execute given @value{GDBN} @var{command}.
46132 @item -directory=@var{directory}
46133 @itemx -d @var{directory}
46134 Add @var{directory} to the path to search for source files.
46137 Do not execute commands from @file{~/.gdbinit}.
46141 Do not execute commands from any @file{.gdbinit} initialization files.
46145 ``Quiet''. Do not print the introductory and copyright messages. These
46146 messages are also suppressed in batch mode.
46149 Run in batch mode. Exit with status @code{0} after processing all the command
46150 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
46151 Exit with nonzero status if an error occurs in executing the @value{GDBN}
46152 commands in the command files.
46154 Batch mode may be useful for running @value{GDBN} as a filter, for example to
46155 download and run a program on another computer; in order to make this
46156 more useful, the message
46159 Program exited normally.
46163 (which is ordinarily issued whenever a program running under @value{GDBN} control
46164 terminates) is not issued when running in batch mode.
46166 @item -cd=@var{directory}
46167 Run @value{GDBN} using @var{directory} as its working directory,
46168 instead of the current directory.
46172 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
46173 @value{GDBN} to output the full file name and line number in a standard,
46174 recognizable fashion each time a stack frame is displayed (which
46175 includes each time the program stops). This recognizable format looks
46176 like two @samp{\032} characters, followed by the file name, line number
46177 and character position separated by colons, and a newline. The
46178 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
46179 characters as a signal to display the source code for the frame.
46182 Set the line speed (baud rate or bits per second) of any serial
46183 interface used by @value{GDBN} for remote debugging.
46185 @item -tty=@var{device}
46186 Run using @var{device} for your program's standard input and output.
46190 @c man begin SEEALSO gdb
46192 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46193 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46194 documentation are properly installed at your site, the command
46201 should give you access to the complete manual.
46203 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46204 Richard M. Stallman and Roland H. Pesch, July 1991.
46208 @node gdbserver man
46209 @heading gdbserver man
46211 @c man title gdbserver Remote Server for the GNU Debugger
46213 @c man begin SYNOPSIS gdbserver
46214 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46216 gdbserver --attach @var{comm} @var{pid}
46218 gdbserver --multi @var{comm}
46222 @c man begin DESCRIPTION gdbserver
46223 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
46224 than the one which is running the program being debugged.
46227 @subheading Usage (server (target) side)
46230 Usage (server (target) side):
46233 First, you need to have a copy of the program you want to debug put onto
46234 the target system. The program can be stripped to save space if needed, as
46235 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
46236 the @value{GDBN} running on the host system.
46238 To use the server, you log on to the target system, and run the @command{gdbserver}
46239 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
46240 your program, and (c) its arguments. The general syntax is:
46243 target> gdbserver @var{comm} @var{program} [@var{args} ...]
46246 For example, using a serial port, you might say:
46250 @c @file would wrap it as F</dev/com1>.
46251 target> gdbserver /dev/com1 emacs foo.txt
46254 target> gdbserver @file{/dev/com1} emacs foo.txt
46258 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
46259 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
46260 waits patiently for the host @value{GDBN} to communicate with it.
46262 To use a TCP connection, you could say:
46265 target> gdbserver host:2345 emacs foo.txt
46268 This says pretty much the same thing as the last example, except that we are
46269 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
46270 that we are expecting to see a TCP connection from @code{host} to local TCP port
46271 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
46272 want for the port number as long as it does not conflict with any existing TCP
46273 ports on the target system. This same port number must be used in the host
46274 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
46275 you chose a port number that conflicts with another service, @command{gdbserver} will
46276 print an error message and exit.
46278 @command{gdbserver} can also attach to running programs.
46279 This is accomplished via the @option{--attach} argument. The syntax is:
46282 target> gdbserver --attach @var{comm} @var{pid}
46285 @var{pid} is the process ID of a currently running process. It isn't
46286 necessary to point @command{gdbserver} at a binary for the running process.
46288 To start @code{gdbserver} without supplying an initial command to run
46289 or process ID to attach, use the @option{--multi} command line option.
46290 In such case you should connect using @kbd{target extended-remote} to start
46291 the program you want to debug.
46294 target> gdbserver --multi @var{comm}
46298 @subheading Usage (host side)
46304 You need an unstripped copy of the target program on your host system, since
46305 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
46306 would, with the target program as the first argument. (You may need to use the
46307 @option{--baud} option if the serial line is running at anything except 9600 baud.)
46308 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
46309 new command you need to know about is @code{target remote}
46310 (or @code{target extended-remote}). Its argument is either
46311 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
46312 descriptor. For example:
46316 @c @file would wrap it as F</dev/ttyb>.
46317 (gdb) target remote /dev/ttyb
46320 (gdb) target remote @file{/dev/ttyb}
46325 communicates with the server via serial line @file{/dev/ttyb}, and:
46328 (gdb) target remote the-target:2345
46332 communicates via a TCP connection to port 2345 on host `the-target', where
46333 you previously started up @command{gdbserver} with the same port number. Note that for
46334 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
46335 command, otherwise you may get an error that looks something like
46336 `Connection refused'.
46338 @command{gdbserver} can also debug multiple inferiors at once,
46341 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
46342 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
46345 @ref{Inferiors Connections and Programs}.
46347 In such case use the @code{extended-remote} @value{GDBN} command variant:
46350 (gdb) target extended-remote the-target:2345
46353 The @command{gdbserver} option @option{--multi} may or may not be used in such
46357 @c man begin OPTIONS gdbserver
46358 There are three different modes for invoking @command{gdbserver}:
46363 Debug a specific program specified by its program name:
46366 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46369 The @var{comm} parameter specifies how should the server communicate
46370 with @value{GDBN}; it is either a device name (to use a serial line),
46371 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
46372 stdin/stdout of @code{gdbserver}. Specify the name of the program to
46373 debug in @var{prog}. Any remaining arguments will be passed to the
46374 program verbatim. When the program exits, @value{GDBN} will close the
46375 connection, and @code{gdbserver} will exit.
46378 Debug a specific program by specifying the process ID of a running
46382 gdbserver --attach @var{comm} @var{pid}
46385 The @var{comm} parameter is as described above. Supply the process ID
46386 of a running program in @var{pid}; @value{GDBN} will do everything
46387 else. Like with the previous mode, when the process @var{pid} exits,
46388 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
46391 Multi-process mode -- debug more than one program/process:
46394 gdbserver --multi @var{comm}
46397 In this mode, @value{GDBN} can instruct @command{gdbserver} which
46398 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
46399 close the connection when a process being debugged exits, so you can
46400 debug several processes in the same session.
46403 In each of the modes you may specify these options:
46408 List all options, with brief explanations.
46411 This option causes @command{gdbserver} to print its version number and exit.
46414 @command{gdbserver} will attach to a running program. The syntax is:
46417 target> gdbserver --attach @var{comm} @var{pid}
46420 @var{pid} is the process ID of a currently running process. It isn't
46421 necessary to point @command{gdbserver} at a binary for the running process.
46424 To start @code{gdbserver} without supplying an initial command to run
46425 or process ID to attach, use this command line option.
46426 Then you can connect using @kbd{target extended-remote} and start
46427 the program you want to debug. The syntax is:
46430 target> gdbserver --multi @var{comm}
46434 Instruct @code{gdbserver} to display extra status information about the debugging
46436 This option is intended for @code{gdbserver} development and for bug reports to
46439 @item --remote-debug
46440 Instruct @code{gdbserver} to display remote protocol debug output.
46441 This option is intended for @code{gdbserver} development and for bug reports to
46444 @item --debug-file=@var{filename}
46445 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
46446 This option is intended for @code{gdbserver} development and for bug reports to
46449 @item --debug-format=option1@r{[},option2,...@r{]}
46450 Instruct @code{gdbserver} to include extra information in each line
46451 of debugging output.
46452 @xref{Other Command-Line Arguments for gdbserver}.
46455 Specify a wrapper to launch programs
46456 for debugging. The option should be followed by the name of the
46457 wrapper, then any command-line arguments to pass to the wrapper, then
46458 @kbd{--} indicating the end of the wrapper arguments.
46461 By default, @command{gdbserver} keeps the listening TCP port open, so that
46462 additional connections are possible. However, if you start @code{gdbserver}
46463 with the @option{--once} option, it will stop listening for any further
46464 connection attempts after connecting to the first @value{GDBN} session.
46466 @c --disable-packet is not documented for users.
46468 @c --disable-randomization and --no-disable-randomization are superseded by
46469 @c QDisableRandomization.
46474 @c man begin SEEALSO gdbserver
46476 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46477 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46478 documentation are properly installed at your site, the command
46484 should give you access to the complete manual.
46486 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46487 Richard M. Stallman and Roland H. Pesch, July 1991.
46494 @c man title gcore Generate a core file of a running program
46497 @c man begin SYNOPSIS gcore
46498 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
46502 @c man begin DESCRIPTION gcore
46503 Generate core dumps of one or more running programs with process IDs
46504 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
46505 is equivalent to one produced by the kernel when the process crashes
46506 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
46507 limit). However, unlike after a crash, after @command{gcore} finishes
46508 its job the program remains running without any change.
46511 @c man begin OPTIONS gcore
46514 Dump all memory mappings. The actual effect of this option depends on
46515 the Operating System. On @sc{gnu}/Linux, it will disable
46516 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
46517 enable @code{dump-excluded-mappings} (@pxref{set
46518 dump-excluded-mappings}).
46520 @item -o @var{prefix}
46521 The optional argument @var{prefix} specifies the prefix to be used
46522 when composing the file names of the core dumps. The file name is
46523 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
46524 process ID of the running program being analyzed by @command{gcore}.
46525 If not specified, @var{prefix} defaults to @var{gcore}.
46529 @c man begin SEEALSO gcore
46531 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46532 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46533 documentation are properly installed at your site, the command
46540 should give you access to the complete manual.
46542 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46543 Richard M. Stallman and Roland H. Pesch, July 1991.
46550 @c man title gdbinit GDB initialization scripts
46553 @c man begin SYNOPSIS gdbinit
46554 @ifset SYSTEM_GDBINIT
46555 @value{SYSTEM_GDBINIT}
46558 @ifset SYSTEM_GDBINIT_DIR
46559 @value{SYSTEM_GDBINIT_DIR}/*
46568 @c man begin DESCRIPTION gdbinit
46569 These files contain @value{GDBN} commands to automatically execute during
46570 @value{GDBN} startup. The lines of contents are canned sequences of commands,
46573 the @value{GDBN} manual in node @code{Sequences}
46574 -- shell command @code{info -f gdb -n Sequences}.
46580 Please read more in
46582 the @value{GDBN} manual in node @code{Startup}
46583 -- shell command @code{info -f gdb -n Startup}.
46590 @ifset SYSTEM_GDBINIT
46591 @item @value{SYSTEM_GDBINIT}
46593 @ifclear SYSTEM_GDBINIT
46594 @item (not enabled with @code{--with-system-gdbinit} during compilation)
46596 System-wide initialization file. It is executed unless user specified
46597 @value{GDBN} option @code{-nx} or @code{-n}.
46600 the @value{GDBN} manual in node @code{System-wide configuration}
46601 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46603 @ifset SYSTEM_GDBINIT_DIR
46604 @item @value{SYSTEM_GDBINIT_DIR}
46606 @ifclear SYSTEM_GDBINIT_DIR
46607 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
46609 System-wide initialization directory. All files in this directory are
46610 executed on startup unless user specified @value{GDBN} option @code{-nx} or
46611 @code{-n}, as long as they have a recognized file extension.
46614 the @value{GDBN} manual in node @code{System-wide configuration}
46615 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46618 @ref{System-wide configuration}.
46622 User initialization file. It is executed unless user specified
46623 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
46626 Initialization file for current directory. It may need to be enabled with
46627 @value{GDBN} security command @code{set auto-load local-gdbinit}.
46630 the @value{GDBN} manual in node @code{Init File in the Current Directory}
46631 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
46634 @ref{Init File in the Current Directory}.
46639 @c man begin SEEALSO gdbinit
46641 gdb(1), @code{info -f gdb -n Startup}
46643 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46644 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46645 documentation are properly installed at your site, the command
46651 should give you access to the complete manual.
46653 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46654 Richard M. Stallman and Roland H. Pesch, July 1991.
46658 @node gdb-add-index man
46659 @heading gdb-add-index
46660 @pindex gdb-add-index
46661 @anchor{gdb-add-index}
46663 @c man title gdb-add-index Add index files to speed up GDB
46665 @c man begin SYNOPSIS gdb-add-index
46666 gdb-add-index @var{filename}
46669 @c man begin DESCRIPTION gdb-add-index
46670 When @value{GDBN} finds a symbol file, it scans the symbols in the
46671 file in order to construct an internal symbol table. This lets most
46672 @value{GDBN} operations work quickly--at the cost of a delay early on.
46673 For large programs, this delay can be quite lengthy, so @value{GDBN}
46674 provides a way to build an index, which speeds up startup.
46676 To determine whether a file contains such an index, use the command
46677 @kbd{readelf -S filename}: the index is stored in a section named
46678 @code{.gdb_index}. The index file can only be produced on systems
46679 which use ELF binaries and DWARF debug information (i.e., sections
46680 named @code{.debug_*}).
46682 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
46683 in the @env{PATH} environment variable. If you want to use different
46684 versions of these programs, you can specify them through the
46685 @env{GDB} and @env{OBJDUMP} environment variables.
46689 the @value{GDBN} manual in node @code{Index Files}
46690 -- shell command @kbd{info -f gdb -n "Index Files"}.
46697 @c man begin SEEALSO gdb-add-index
46699 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46700 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46701 documentation are properly installed at your site, the command
46707 should give you access to the complete manual.
46709 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46710 Richard M. Stallman and Roland H. Pesch, July 1991.
46716 @node GNU Free Documentation License
46717 @appendix GNU Free Documentation License
46720 @node Concept Index
46721 @unnumbered Concept Index
46725 @node Command and Variable Index
46726 @unnumbered Command, Variable, and Function Index
46731 % I think something like @@colophon should be in texinfo. In the
46733 \long\def\colophon{\hbox to0pt{}\vfill
46734 \centerline{The body of this manual is set in}
46735 \centerline{\fontname\tenrm,}
46736 \centerline{with headings in {\bf\fontname\tenbf}}
46737 \centerline{and examples in {\tt\fontname\tentt}.}
46738 \centerline{{\it\fontname\tenit\/},}
46739 \centerline{{\bf\fontname\tenbf}, and}
46740 \centerline{{\sl\fontname\tensl\/}}
46741 \centerline{are used for emphasis.}\vfill}
46743 % Blame: doc@@cygnus.com, 1991.