1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2019 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2019 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2019 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument, if you want
878 to debug a running process:
881 @value{GDBP} @var{program} 1234
885 would attach @value{GDBN} to process @code{1234} (unless you also have a file
886 named @file{1234}; @value{GDBN} does check for a core file first).
888 Taking advantage of the second command-line argument requires a fairly
889 complete operating system; when you use @value{GDBN} as a remote
890 debugger attached to a bare board, there may not be any notion of
891 ``process'', and there is often no way to get a core dump. @value{GDBN}
892 will warn you if it is unable to attach or to read core dumps.
894 You can optionally have @code{@value{GDBP}} pass any arguments after the
895 executable file to the inferior using @code{--args}. This option stops
898 @value{GDBP} --args gcc -O2 -c foo.c
900 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
901 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
903 You can run @code{@value{GDBP}} without printing the front material, which describes
904 @value{GDBN}'s non-warranty, by specifying @code{--silent}
905 (or @code{-q}/@code{--quiet}):
908 @value{GDBP} --silent
912 You can further control how @value{GDBN} starts up by using command-line
913 options. @value{GDBN} itself can remind you of the options available.
923 to display all available options and briefly describe their use
924 (@samp{@value{GDBP} -h} is a shorter equivalent).
926 All options and command line arguments you give are processed
927 in sequential order. The order makes a difference when the
928 @samp{-x} option is used.
932 * File Options:: Choosing files
933 * Mode Options:: Choosing modes
934 * Startup:: What @value{GDBN} does during startup
938 @subsection Choosing Files
940 When @value{GDBN} starts, it reads any arguments other than options as
941 specifying an executable file and core file (or process ID). This is
942 the same as if the arguments were specified by the @samp{-se} and
943 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
944 first argument that does not have an associated option flag as
945 equivalent to the @samp{-se} option followed by that argument; and the
946 second argument that does not have an associated option flag, if any, as
947 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
948 If the second argument begins with a decimal digit, @value{GDBN} will
949 first attempt to attach to it as a process, and if that fails, attempt
950 to open it as a corefile. If you have a corefile whose name begins with
951 a digit, you can prevent @value{GDBN} from treating it as a pid by
952 prefixing it with @file{./}, e.g.@: @file{./12345}.
954 If @value{GDBN} has not been configured to included core file support,
955 such as for most embedded targets, then it will complain about a second
956 argument and ignore it.
958 Many options have both long and short forms; both are shown in the
959 following list. @value{GDBN} also recognizes the long forms if you truncate
960 them, so long as enough of the option is present to be unambiguous.
961 (If you prefer, you can flag option arguments with @samp{--} rather
962 than @samp{-}, though we illustrate the more usual convention.)
964 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
965 @c way, both those who look for -foo and --foo in the index, will find
969 @item -symbols @var{file}
971 @cindex @code{--symbols}
973 Read symbol table from file @var{file}.
975 @item -exec @var{file}
977 @cindex @code{--exec}
979 Use file @var{file} as the executable file to execute when appropriate,
980 and for examining pure data in conjunction with a core dump.
984 Read symbol table from file @var{file} and use it as the executable
987 @item -core @var{file}
989 @cindex @code{--core}
991 Use file @var{file} as a core dump to examine.
993 @item -pid @var{number}
994 @itemx -p @var{number}
997 Connect to process ID @var{number}, as with the @code{attach} command.
999 @item -command @var{file}
1000 @itemx -x @var{file}
1001 @cindex @code{--command}
1003 Execute commands from file @var{file}. The contents of this file is
1004 evaluated exactly as the @code{source} command would.
1005 @xref{Command Files,, Command files}.
1007 @item -eval-command @var{command}
1008 @itemx -ex @var{command}
1009 @cindex @code{--eval-command}
1011 Execute a single @value{GDBN} command.
1013 This option may be used multiple times to call multiple commands. It may
1014 also be interleaved with @samp{-command} as required.
1017 @value{GDBP} -ex 'target sim' -ex 'load' \
1018 -x setbreakpoints -ex 'run' a.out
1021 @item -init-command @var{file}
1022 @itemx -ix @var{file}
1023 @cindex @code{--init-command}
1025 Execute commands from file @var{file} before loading the inferior (but
1026 after loading gdbinit files).
1029 @item -init-eval-command @var{command}
1030 @itemx -iex @var{command}
1031 @cindex @code{--init-eval-command}
1033 Execute a single @value{GDBN} command before loading the inferior (but
1034 after loading gdbinit files).
1037 @item -directory @var{directory}
1038 @itemx -d @var{directory}
1039 @cindex @code{--directory}
1041 Add @var{directory} to the path to search for source and script files.
1045 @cindex @code{--readnow}
1047 Read each symbol file's entire symbol table immediately, rather than
1048 the default, which is to read it incrementally as it is needed.
1049 This makes startup slower, but makes future operations faster.
1052 @anchor{--readnever}
1053 @cindex @code{--readnever}, command-line option
1054 Do not read each symbol file's symbolic debug information. This makes
1055 startup faster but at the expense of not being able to perform
1056 symbolic debugging. DWARF unwind information is also not read,
1057 meaning backtraces may become incomplete or inaccurate. One use of
1058 this is when a user simply wants to do the following sequence: attach,
1059 dump core, detach. Loading the debugging information in this case is
1060 an unnecessary cause of delay.
1064 @subsection Choosing Modes
1066 You can run @value{GDBN} in various alternative modes---for example, in
1067 batch mode or quiet mode.
1075 Do not execute commands found in any initialization file.
1076 There are three init files, loaded in the following order:
1079 @item @file{system.gdbinit}
1080 This is the system-wide init file.
1081 Its location is specified with the @code{--with-system-gdbinit}
1082 configure option (@pxref{System-wide configuration}).
1083 It is loaded first when @value{GDBN} starts, before command line options
1084 have been processed.
1085 @item @file{~/.gdbinit}
1086 This is the init file in your home directory.
1087 It is loaded next, after @file{system.gdbinit}, and before
1088 command options have been processed.
1089 @item @file{./.gdbinit}
1090 This is the init file in the current directory.
1091 It is loaded last, after command line options other than @code{-x} and
1092 @code{-ex} have been processed. Command line options @code{-x} and
1093 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1096 For further documentation on startup processing, @xref{Startup}.
1097 For documentation on how to write command files,
1098 @xref{Command Files,,Command Files}.
1103 Do not execute commands found in @file{~/.gdbinit}, the init file
1104 in your home directory.
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1117 @cindex @code{--batch}
1118 Run in batch mode. Exit with status @code{0} after processing all the
1119 command files specified with @samp{-x} (and all commands from
1120 initialization files, if not inhibited with @samp{-n}). Exit with
1121 nonzero status if an error occurs in executing the @value{GDBN} commands
1122 in the command files. Batch mode also disables pagination, sets unlimited
1123 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1124 off} were in effect (@pxref{Messages/Warnings}).
1126 Batch mode may be useful for running @value{GDBN} as a filter, for
1127 example to download and run a program on another computer; in order to
1128 make this more useful, the message
1131 Program exited normally.
1135 (which is ordinarily issued whenever a program running under
1136 @value{GDBN} control terminates) is not issued when running in batch
1140 @cindex @code{--batch-silent}
1141 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1142 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1143 unaffected). This is much quieter than @samp{-silent} and would be useless
1144 for an interactive session.
1146 This is particularly useful when using targets that give @samp{Loading section}
1147 messages, for example.
1149 Note that targets that give their output via @value{GDBN}, as opposed to
1150 writing directly to @code{stdout}, will also be made silent.
1152 @item -return-child-result
1153 @cindex @code{--return-child-result}
1154 The return code from @value{GDBN} will be the return code from the child
1155 process (the process being debugged), with the following exceptions:
1159 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1160 internal error. In this case the exit code is the same as it would have been
1161 without @samp{-return-child-result}.
1163 The user quits with an explicit value. E.g., @samp{quit 1}.
1165 The child process never runs, or is not allowed to terminate, in which case
1166 the exit code will be -1.
1169 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1170 when @value{GDBN} is being used as a remote program loader or simulator
1175 @cindex @code{--nowindows}
1177 ``No windows''. If @value{GDBN} comes with a graphical user interface
1178 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1179 interface. If no GUI is available, this option has no effect.
1183 @cindex @code{--windows}
1185 If @value{GDBN} includes a GUI, then this option requires it to be
1188 @item -cd @var{directory}
1190 Run @value{GDBN} using @var{directory} as its working directory,
1191 instead of the current directory.
1193 @item -data-directory @var{directory}
1194 @itemx -D @var{directory}
1195 @cindex @code{--data-directory}
1197 Run @value{GDBN} using @var{directory} as its data directory.
1198 The data directory is where @value{GDBN} searches for its
1199 auxiliary files. @xref{Data Files}.
1203 @cindex @code{--fullname}
1205 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1206 subprocess. It tells @value{GDBN} to output the full file name and line
1207 number in a standard, recognizable fashion each time a stack frame is
1208 displayed (which includes each time your program stops). This
1209 recognizable format looks like two @samp{\032} characters, followed by
1210 the file name, line number and character position separated by colons,
1211 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1212 @samp{\032} characters as a signal to display the source code for the
1215 @item -annotate @var{level}
1216 @cindex @code{--annotate}
1217 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1218 effect is identical to using @samp{set annotate @var{level}}
1219 (@pxref{Annotations}). The annotation @var{level} controls how much
1220 information @value{GDBN} prints together with its prompt, values of
1221 expressions, source lines, and other types of output. Level 0 is the
1222 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1223 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1224 that control @value{GDBN}, and level 2 has been deprecated.
1226 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1230 @cindex @code{--args}
1231 Change interpretation of command line so that arguments following the
1232 executable file are passed as command line arguments to the inferior.
1233 This option stops option processing.
1235 @item -baud @var{bps}
1237 @cindex @code{--baud}
1239 Set the line speed (baud rate or bits per second) of any serial
1240 interface used by @value{GDBN} for remote debugging.
1242 @item -l @var{timeout}
1244 Set the timeout (in seconds) of any communication used by @value{GDBN}
1245 for remote debugging.
1247 @item -tty @var{device}
1248 @itemx -t @var{device}
1249 @cindex @code{--tty}
1251 Run using @var{device} for your program's standard input and output.
1252 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1254 @c resolve the situation of these eventually
1256 @cindex @code{--tui}
1257 Activate the @dfn{Text User Interface} when starting. The Text User
1258 Interface manages several text windows on the terminal, showing
1259 source, assembly, registers and @value{GDBN} command outputs
1260 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1261 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1262 Using @value{GDBN} under @sc{gnu} Emacs}).
1264 @item -interpreter @var{interp}
1265 @cindex @code{--interpreter}
1266 Use the interpreter @var{interp} for interface with the controlling
1267 program or device. This option is meant to be set by programs which
1268 communicate with @value{GDBN} using it as a back end.
1269 @xref{Interpreters, , Command Interpreters}.
1271 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1274 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1275 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1276 interfaces are no longer supported.
1279 @cindex @code{--write}
1280 Open the executable and core files for both reading and writing. This
1281 is equivalent to the @samp{set write on} command inside @value{GDBN}
1285 @cindex @code{--statistics}
1286 This option causes @value{GDBN} to print statistics about time and
1287 memory usage after it completes each command and returns to the prompt.
1290 @cindex @code{--version}
1291 This option causes @value{GDBN} to print its version number and
1292 no-warranty blurb, and exit.
1294 @item -configuration
1295 @cindex @code{--configuration}
1296 This option causes @value{GDBN} to print details about its build-time
1297 configuration parameters, and then exit. These details can be
1298 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1303 @subsection What @value{GDBN} Does During Startup
1304 @cindex @value{GDBN} startup
1306 Here's the description of what @value{GDBN} does during session startup:
1310 Sets up the command interpreter as specified by the command line
1311 (@pxref{Mode Options, interpreter}).
1315 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1316 used when building @value{GDBN}; @pxref{System-wide configuration,
1317 ,System-wide configuration and settings}) and executes all the commands in
1320 @anchor{Home Directory Init File}
1322 Reads the init file (if any) in your home directory@footnote{On
1323 DOS/Windows systems, the home directory is the one pointed to by the
1324 @code{HOME} environment variable.} and executes all the commands in
1327 @anchor{Option -init-eval-command}
1329 Executes commands and command files specified by the @samp{-iex} and
1330 @samp{-ix} options in their specified order. Usually you should use the
1331 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1332 settings before @value{GDBN} init files get executed and before inferior
1336 Processes command line options and operands.
1338 @anchor{Init File in the Current Directory during Startup}
1340 Reads and executes the commands from init file (if any) in the current
1341 working directory as long as @samp{set auto-load local-gdbinit} is set to
1342 @samp{on} (@pxref{Init File in the Current Directory}).
1343 This is only done if the current directory is
1344 different from your home directory. Thus, you can have more than one
1345 init file, one generic in your home directory, and another, specific
1346 to the program you are debugging, in the directory where you invoke
1350 If the command line specified a program to debug, or a process to
1351 attach to, or a core file, @value{GDBN} loads any auto-loaded
1352 scripts provided for the program or for its loaded shared libraries.
1353 @xref{Auto-loading}.
1355 If you wish to disable the auto-loading during startup,
1356 you must do something like the following:
1359 $ gdb -iex "set auto-load python-scripts off" myprogram
1362 Option @samp{-ex} does not work because the auto-loading is then turned
1366 Executes commands and command files specified by the @samp{-ex} and
1367 @samp{-x} options in their specified order. @xref{Command Files}, for
1368 more details about @value{GDBN} command files.
1371 Reads the command history recorded in the @dfn{history file}.
1372 @xref{Command History}, for more details about the command history and the
1373 files where @value{GDBN} records it.
1376 Init files use the same syntax as @dfn{command files} (@pxref{Command
1377 Files}) and are processed by @value{GDBN} in the same way. The init
1378 file in your home directory can set options (such as @samp{set
1379 complaints}) that affect subsequent processing of command line options
1380 and operands. Init files are not executed if you use the @samp{-nx}
1381 option (@pxref{Mode Options, ,Choosing Modes}).
1383 To display the list of init files loaded by gdb at startup, you
1384 can use @kbd{gdb --help}.
1386 @cindex init file name
1387 @cindex @file{.gdbinit}
1388 @cindex @file{gdb.ini}
1389 The @value{GDBN} init files are normally called @file{.gdbinit}.
1390 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1391 the limitations of file names imposed by DOS filesystems. The Windows
1392 port of @value{GDBN} uses the standard name, but if it finds a
1393 @file{gdb.ini} file in your home directory, it warns you about that
1394 and suggests to rename the file to the standard name.
1398 @section Quitting @value{GDBN}
1399 @cindex exiting @value{GDBN}
1400 @cindex leaving @value{GDBN}
1403 @kindex quit @r{[}@var{expression}@r{]}
1404 @kindex q @r{(@code{quit})}
1405 @item quit @r{[}@var{expression}@r{]}
1407 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1408 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1409 do not supply @var{expression}, @value{GDBN} will terminate normally;
1410 otherwise it will terminate using the result of @var{expression} as the
1415 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1416 terminates the action of any @value{GDBN} command that is in progress and
1417 returns to @value{GDBN} command level. It is safe to type the interrupt
1418 character at any time because @value{GDBN} does not allow it to take effect
1419 until a time when it is safe.
1421 If you have been using @value{GDBN} to control an attached process or
1422 device, you can release it with the @code{detach} command
1423 (@pxref{Attach, ,Debugging an Already-running Process}).
1425 @node Shell Commands
1426 @section Shell Commands
1428 If you need to execute occasional shell commands during your
1429 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1430 just use the @code{shell} command.
1435 @cindex shell escape
1436 @item shell @var{command-string}
1437 @itemx !@var{command-string}
1438 Invoke a standard shell to execute @var{command-string}.
1439 Note that no space is needed between @code{!} and @var{command-string}.
1440 If it exists, the environment variable @code{SHELL} determines which
1441 shell to run. Otherwise @value{GDBN} uses the default shell
1442 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1445 The utility @code{make} is often needed in development environments.
1446 You do not have to use the @code{shell} command for this purpose in
1451 @cindex calling make
1452 @item make @var{make-args}
1453 Execute the @code{make} program with the specified
1454 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1457 @node Logging Output
1458 @section Logging Output
1459 @cindex logging @value{GDBN} output
1460 @cindex save @value{GDBN} output to a file
1462 You may want to save the output of @value{GDBN} commands to a file.
1463 There are several commands to control @value{GDBN}'s logging.
1467 @item set logging on
1469 @item set logging off
1471 @cindex logging file name
1472 @item set logging file @var{file}
1473 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1474 @item set logging overwrite [on|off]
1475 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1476 you want @code{set logging on} to overwrite the logfile instead.
1477 @item set logging redirect [on|off]
1478 By default, @value{GDBN} output will go to both the terminal and the logfile.
1479 Set @code{redirect} if you want output to go only to the log file.
1480 @kindex show logging
1482 Show the current values of the logging settings.
1486 @chapter @value{GDBN} Commands
1488 You can abbreviate a @value{GDBN} command to the first few letters of the command
1489 name, if that abbreviation is unambiguous; and you can repeat certain
1490 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1491 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1492 show you the alternatives available, if there is more than one possibility).
1495 * Command Syntax:: How to give commands to @value{GDBN}
1496 * Completion:: Command completion
1497 * Help:: How to ask @value{GDBN} for help
1500 @node Command Syntax
1501 @section Command Syntax
1503 A @value{GDBN} command is a single line of input. There is no limit on
1504 how long it can be. It starts with a command name, which is followed by
1505 arguments whose meaning depends on the command name. For example, the
1506 command @code{step} accepts an argument which is the number of times to
1507 step, as in @samp{step 5}. You can also use the @code{step} command
1508 with no arguments. Some commands do not allow any arguments.
1510 @cindex abbreviation
1511 @value{GDBN} command names may always be truncated if that abbreviation is
1512 unambiguous. Other possible command abbreviations are listed in the
1513 documentation for individual commands. In some cases, even ambiguous
1514 abbreviations are allowed; for example, @code{s} is specially defined as
1515 equivalent to @code{step} even though there are other commands whose
1516 names start with @code{s}. You can test abbreviations by using them as
1517 arguments to the @code{help} command.
1519 @cindex repeating commands
1520 @kindex RET @r{(repeat last command)}
1521 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1522 repeat the previous command. Certain commands (for example, @code{run})
1523 will not repeat this way; these are commands whose unintentional
1524 repetition might cause trouble and which you are unlikely to want to
1525 repeat. User-defined commands can disable this feature; see
1526 @ref{Define, dont-repeat}.
1528 The @code{list} and @code{x} commands, when you repeat them with
1529 @key{RET}, construct new arguments rather than repeating
1530 exactly as typed. This permits easy scanning of source or memory.
1532 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1533 output, in a way similar to the common utility @code{more}
1534 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1535 @key{RET} too many in this situation, @value{GDBN} disables command
1536 repetition after any command that generates this sort of display.
1538 @kindex # @r{(a comment)}
1540 Any text from a @kbd{#} to the end of the line is a comment; it does
1541 nothing. This is useful mainly in command files (@pxref{Command
1542 Files,,Command Files}).
1544 @cindex repeating command sequences
1545 @kindex Ctrl-o @r{(operate-and-get-next)}
1546 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1547 commands. This command accepts the current line, like @key{RET}, and
1548 then fetches the next line relative to the current line from the history
1552 @section Command Completion
1555 @cindex word completion
1556 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1557 only one possibility; it can also show you what the valid possibilities
1558 are for the next word in a command, at any time. This works for @value{GDBN}
1559 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1561 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1562 of a word. If there is only one possibility, @value{GDBN} fills in the
1563 word, and waits for you to finish the command (or press @key{RET} to
1564 enter it). For example, if you type
1566 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1567 @c complete accuracy in these examples; space introduced for clarity.
1568 @c If texinfo enhancements make it unnecessary, it would be nice to
1569 @c replace " @key" by "@key" in the following...
1571 (@value{GDBP}) info bre @key{TAB}
1575 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1576 the only @code{info} subcommand beginning with @samp{bre}:
1579 (@value{GDBP}) info breakpoints
1583 You can either press @key{RET} at this point, to run the @code{info
1584 breakpoints} command, or backspace and enter something else, if
1585 @samp{breakpoints} does not look like the command you expected. (If you
1586 were sure you wanted @code{info breakpoints} in the first place, you
1587 might as well just type @key{RET} immediately after @samp{info bre},
1588 to exploit command abbreviations rather than command completion).
1590 If there is more than one possibility for the next word when you press
1591 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1592 characters and try again, or just press @key{TAB} a second time;
1593 @value{GDBN} displays all the possible completions for that word. For
1594 example, you might want to set a breakpoint on a subroutine whose name
1595 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1596 just sounds the bell. Typing @key{TAB} again displays all the
1597 function names in your program that begin with those characters, for
1601 (@value{GDBP}) b make_ @key{TAB}
1602 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1603 make_a_section_from_file make_environ
1604 make_abs_section make_function_type
1605 make_blockvector make_pointer_type
1606 make_cleanup make_reference_type
1607 make_command make_symbol_completion_list
1608 (@value{GDBP}) b make_
1612 After displaying the available possibilities, @value{GDBN} copies your
1613 partial input (@samp{b make_} in the example) so you can finish the
1616 If you just want to see the list of alternatives in the first place, you
1617 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1618 means @kbd{@key{META} ?}. You can type this either by holding down a
1619 key designated as the @key{META} shift on your keyboard (if there is
1620 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1622 If the number of possible completions is large, @value{GDBN} will
1623 print as much of the list as it has collected, as well as a message
1624 indicating that the list may be truncated.
1627 (@value{GDBP}) b m@key{TAB}@key{TAB}
1629 <... the rest of the possible completions ...>
1630 *** List may be truncated, max-completions reached. ***
1635 This behavior can be controlled with the following commands:
1638 @kindex set max-completions
1639 @item set max-completions @var{limit}
1640 @itemx set max-completions unlimited
1641 Set the maximum number of completion candidates. @value{GDBN} will
1642 stop looking for more completions once it collects this many candidates.
1643 This is useful when completing on things like function names as collecting
1644 all the possible candidates can be time consuming.
1645 The default value is 200. A value of zero disables tab-completion.
1646 Note that setting either no limit or a very large limit can make
1648 @kindex show max-completions
1649 @item show max-completions
1650 Show the maximum number of candidates that @value{GDBN} will collect and show
1654 @cindex quotes in commands
1655 @cindex completion of quoted strings
1656 Sometimes the string you need, while logically a ``word'', may contain
1657 parentheses or other characters that @value{GDBN} normally excludes from
1658 its notion of a word. To permit word completion to work in this
1659 situation, you may enclose words in @code{'} (single quote marks) in
1660 @value{GDBN} commands.
1662 A likely situation where you might need this is in typing an
1663 expression that involves a C@t{++} symbol name with template
1664 parameters. This is because when completing expressions, GDB treats
1665 the @samp{<} character as word delimiter, assuming that it's the
1666 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1669 For example, when you want to call a C@t{++} template function
1670 interactively using the @code{print} or @code{call} commands, you may
1671 need to distinguish whether you mean the version of @code{name} that
1672 was specialized for @code{int}, @code{name<int>()}, or the version
1673 that was specialized for @code{float}, @code{name<float>()}. To use
1674 the word-completion facilities in this situation, type a single quote
1675 @code{'} at the beginning of the function name. This alerts
1676 @value{GDBN} that it may need to consider more information than usual
1677 when you press @key{TAB} or @kbd{M-?} to request word completion:
1680 (@value{GDBP}) p 'func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) p 'func<
1685 When setting breakpoints however (@pxref{Specify Location}), you don't
1686 usually need to type a quote before the function name, because
1687 @value{GDBN} understands that you want to set a breakpoint on a
1691 (@value{GDBP}) b func< @kbd{M-?}
1692 func<int>() func<float>()
1693 (@value{GDBP}) b func<
1696 This is true even in the case of typing the name of C@t{++} overloaded
1697 functions (multiple definitions of the same function, distinguished by
1698 argument type). For example, when you want to set a breakpoint you
1699 don't need to distinguish whether you mean the version of @code{name}
1700 that takes an @code{int} parameter, @code{name(int)}, or the version
1701 that takes a @code{float} parameter, @code{name(float)}.
1704 (@value{GDBP}) b bubble( @kbd{M-?}
1705 bubble(int) bubble(double)
1706 (@value{GDBP}) b bubble(dou @kbd{M-?}
1710 See @ref{quoting names} for a description of other scenarios that
1713 For more information about overloaded functions, see @ref{C Plus Plus
1714 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1715 overload-resolution off} to disable overload resolution;
1716 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1718 @cindex completion of structure field names
1719 @cindex structure field name completion
1720 @cindex completion of union field names
1721 @cindex union field name completion
1722 When completing in an expression which looks up a field in a
1723 structure, @value{GDBN} also tries@footnote{The completer can be
1724 confused by certain kinds of invalid expressions. Also, it only
1725 examines the static type of the expression, not the dynamic type.} to
1726 limit completions to the field names available in the type of the
1730 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1731 magic to_fputs to_rewind
1732 to_data to_isatty to_write
1733 to_delete to_put to_write_async_safe
1738 This is because the @code{gdb_stdout} is a variable of the type
1739 @code{struct ui_file} that is defined in @value{GDBN} sources as
1746 ui_file_flush_ftype *to_flush;
1747 ui_file_write_ftype *to_write;
1748 ui_file_write_async_safe_ftype *to_write_async_safe;
1749 ui_file_fputs_ftype *to_fputs;
1750 ui_file_read_ftype *to_read;
1751 ui_file_delete_ftype *to_delete;
1752 ui_file_isatty_ftype *to_isatty;
1753 ui_file_rewind_ftype *to_rewind;
1754 ui_file_put_ftype *to_put;
1761 @section Getting Help
1762 @cindex online documentation
1765 You can always ask @value{GDBN} itself for information on its commands,
1766 using the command @code{help}.
1769 @kindex h @r{(@code{help})}
1772 You can use @code{help} (abbreviated @code{h}) with no arguments to
1773 display a short list of named classes of commands:
1777 List of classes of commands:
1779 aliases -- Aliases of other commands
1780 breakpoints -- Making program stop at certain points
1781 data -- Examining data
1782 files -- Specifying and examining files
1783 internals -- Maintenance commands
1784 obscure -- Obscure features
1785 running -- Running the program
1786 stack -- Examining the stack
1787 status -- Status inquiries
1788 support -- Support facilities
1789 tracepoints -- Tracing of program execution without
1790 stopping the program
1791 user-defined -- User-defined commands
1793 Type "help" followed by a class name for a list of
1794 commands in that class.
1795 Type "help" followed by command name for full
1797 Command name abbreviations are allowed if unambiguous.
1800 @c the above line break eliminates huge line overfull...
1802 @item help @var{class}
1803 Using one of the general help classes as an argument, you can get a
1804 list of the individual commands in that class. For example, here is the
1805 help display for the class @code{status}:
1808 (@value{GDBP}) help status
1813 @c Line break in "show" line falsifies real output, but needed
1814 @c to fit in smallbook page size.
1815 info -- Generic command for showing things
1816 about the program being debugged
1817 show -- Generic command for showing things
1820 Type "help" followed by command name for full
1822 Command name abbreviations are allowed if unambiguous.
1826 @item help @var{command}
1827 With a command name as @code{help} argument, @value{GDBN} displays a
1828 short paragraph on how to use that command.
1831 @item apropos @var{args}
1832 The @code{apropos} command searches through all of the @value{GDBN}
1833 commands, and their documentation, for the regular expression specified in
1834 @var{args}. It prints out all matches found. For example:
1845 alias -- Define a new command that is an alias of an existing command
1846 aliases -- Aliases of other commands
1847 d -- Delete some breakpoints or auto-display expressions
1848 del -- Delete some breakpoints or auto-display expressions
1849 delete -- Delete some breakpoints or auto-display expressions
1854 @item complete @var{args}
1855 The @code{complete @var{args}} command lists all the possible completions
1856 for the beginning of a command. Use @var{args} to specify the beginning of the
1857 command you want completed. For example:
1863 @noindent results in:
1874 @noindent This is intended for use by @sc{gnu} Emacs.
1877 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1878 and @code{show} to inquire about the state of your program, or the state
1879 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1880 manual introduces each of them in the appropriate context. The listings
1881 under @code{info} and under @code{show} in the Command, Variable, and
1882 Function Index point to all the sub-commands. @xref{Command and Variable
1888 @kindex i @r{(@code{info})}
1890 This command (abbreviated @code{i}) is for describing the state of your
1891 program. For example, you can show the arguments passed to a function
1892 with @code{info args}, list the registers currently in use with @code{info
1893 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1894 You can get a complete list of the @code{info} sub-commands with
1895 @w{@code{help info}}.
1899 You can assign the result of an expression to an environment variable with
1900 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1901 @code{set prompt $}.
1905 In contrast to @code{info}, @code{show} is for describing the state of
1906 @value{GDBN} itself.
1907 You can change most of the things you can @code{show}, by using the
1908 related command @code{set}; for example, you can control what number
1909 system is used for displays with @code{set radix}, or simply inquire
1910 which is currently in use with @code{show radix}.
1913 To display all the settable parameters and their current
1914 values, you can use @code{show} with no arguments; you may also use
1915 @code{info set}. Both commands produce the same display.
1916 @c FIXME: "info set" violates the rule that "info" is for state of
1917 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1918 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1922 Here are several miscellaneous @code{show} subcommands, all of which are
1923 exceptional in lacking corresponding @code{set} commands:
1926 @kindex show version
1927 @cindex @value{GDBN} version number
1929 Show what version of @value{GDBN} is running. You should include this
1930 information in @value{GDBN} bug-reports. If multiple versions of
1931 @value{GDBN} are in use at your site, you may need to determine which
1932 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1933 commands are introduced, and old ones may wither away. Also, many
1934 system vendors ship variant versions of @value{GDBN}, and there are
1935 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1936 The version number is the same as the one announced when you start
1939 @kindex show copying
1940 @kindex info copying
1941 @cindex display @value{GDBN} copyright
1944 Display information about permission for copying @value{GDBN}.
1946 @kindex show warranty
1947 @kindex info warranty
1949 @itemx info warranty
1950 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1951 if your version of @value{GDBN} comes with one.
1953 @kindex show configuration
1954 @item show configuration
1955 Display detailed information about the way @value{GDBN} was configured
1956 when it was built. This displays the optional arguments passed to the
1957 @file{configure} script and also configuration parameters detected
1958 automatically by @command{configure}. When reporting a @value{GDBN}
1959 bug (@pxref{GDB Bugs}), it is important to include this information in
1965 @chapter Running Programs Under @value{GDBN}
1967 When you run a program under @value{GDBN}, you must first generate
1968 debugging information when you compile it.
1970 You may start @value{GDBN} with its arguments, if any, in an environment
1971 of your choice. If you are doing native debugging, you may redirect
1972 your program's input and output, debug an already running process, or
1973 kill a child process.
1976 * Compilation:: Compiling for debugging
1977 * Starting:: Starting your program
1978 * Arguments:: Your program's arguments
1979 * Environment:: Your program's environment
1981 * Working Directory:: Your program's working directory
1982 * Input/Output:: Your program's input and output
1983 * Attach:: Debugging an already-running process
1984 * Kill Process:: Killing the child process
1986 * Inferiors and Programs:: Debugging multiple inferiors and programs
1987 * Threads:: Debugging programs with multiple threads
1988 * Forks:: Debugging forks
1989 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1993 @section Compiling for Debugging
1995 In order to debug a program effectively, you need to generate
1996 debugging information when you compile it. This debugging information
1997 is stored in the object file; it describes the data type of each
1998 variable or function and the correspondence between source line numbers
1999 and addresses in the executable code.
2001 To request debugging information, specify the @samp{-g} option when you run
2004 Programs that are to be shipped to your customers are compiled with
2005 optimizations, using the @samp{-O} compiler option. However, some
2006 compilers are unable to handle the @samp{-g} and @samp{-O} options
2007 together. Using those compilers, you cannot generate optimized
2008 executables containing debugging information.
2010 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2011 without @samp{-O}, making it possible to debug optimized code. We
2012 recommend that you @emph{always} use @samp{-g} whenever you compile a
2013 program. You may think your program is correct, but there is no sense
2014 in pushing your luck. For more information, see @ref{Optimized Code}.
2016 Older versions of the @sc{gnu} C compiler permitted a variant option
2017 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2018 format; if your @sc{gnu} C compiler has this option, do not use it.
2020 @value{GDBN} knows about preprocessor macros and can show you their
2021 expansion (@pxref{Macros}). Most compilers do not include information
2022 about preprocessor macros in the debugging information if you specify
2023 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2024 the @sc{gnu} C compiler, provides macro information if you are using
2025 the DWARF debugging format, and specify the option @option{-g3}.
2027 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2028 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2029 information on @value{NGCC} options affecting debug information.
2031 You will have the best debugging experience if you use the latest
2032 version of the DWARF debugging format that your compiler supports.
2033 DWARF is currently the most expressive and best supported debugging
2034 format in @value{GDBN}.
2038 @section Starting your Program
2044 @kindex r @r{(@code{run})}
2047 Use the @code{run} command to start your program under @value{GDBN}.
2048 You must first specify the program name with an argument to
2049 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2050 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2051 command (@pxref{Files, ,Commands to Specify Files}).
2055 If you are running your program in an execution environment that
2056 supports processes, @code{run} creates an inferior process and makes
2057 that process run your program. In some environments without processes,
2058 @code{run} jumps to the start of your program. Other targets,
2059 like @samp{remote}, are always running. If you get an error
2060 message like this one:
2063 The "remote" target does not support "run".
2064 Try "help target" or "continue".
2068 then use @code{continue} to run your program. You may need @code{load}
2069 first (@pxref{load}).
2071 The execution of a program is affected by certain information it
2072 receives from its superior. @value{GDBN} provides ways to specify this
2073 information, which you must do @emph{before} starting your program. (You
2074 can change it after starting your program, but such changes only affect
2075 your program the next time you start it.) This information may be
2076 divided into four categories:
2079 @item The @emph{arguments.}
2080 Specify the arguments to give your program as the arguments of the
2081 @code{run} command. If a shell is available on your target, the shell
2082 is used to pass the arguments, so that you may use normal conventions
2083 (such as wildcard expansion or variable substitution) in describing
2085 In Unix systems, you can control which shell is used with the
2086 @code{SHELL} environment variable. If you do not define @code{SHELL},
2087 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2088 use of any shell with the @code{set startup-with-shell} command (see
2091 @item The @emph{environment.}
2092 Your program normally inherits its environment from @value{GDBN}, but you can
2093 use the @value{GDBN} commands @code{set environment} and @code{unset
2094 environment} to change parts of the environment that affect
2095 your program. @xref{Environment, ,Your Program's Environment}.
2097 @item The @emph{working directory.}
2098 You can set your program's working directory with the command
2099 @kbd{set cwd}. If you do not set any working directory with this
2100 command, your program will inherit @value{GDBN}'s working directory if
2101 native debugging, or the remote server's working directory if remote
2102 debugging. @xref{Working Directory, ,Your Program's Working
2105 @item The @emph{standard input and output.}
2106 Your program normally uses the same device for standard input and
2107 standard output as @value{GDBN} is using. You can redirect input and output
2108 in the @code{run} command line, or you can use the @code{tty} command to
2109 set a different device for your program.
2110 @xref{Input/Output, ,Your Program's Input and Output}.
2113 @emph{Warning:} While input and output redirection work, you cannot use
2114 pipes to pass the output of the program you are debugging to another
2115 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2119 When you issue the @code{run} command, your program begins to execute
2120 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2121 of how to arrange for your program to stop. Once your program has
2122 stopped, you may call functions in your program, using the @code{print}
2123 or @code{call} commands. @xref{Data, ,Examining Data}.
2125 If the modification time of your symbol file has changed since the last
2126 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2127 table, and reads it again. When it does this, @value{GDBN} tries to retain
2128 your current breakpoints.
2133 @cindex run to main procedure
2134 The name of the main procedure can vary from language to language.
2135 With C or C@t{++}, the main procedure name is always @code{main}, but
2136 other languages such as Ada do not require a specific name for their
2137 main procedure. The debugger provides a convenient way to start the
2138 execution of the program and to stop at the beginning of the main
2139 procedure, depending on the language used.
2141 The @samp{start} command does the equivalent of setting a temporary
2142 breakpoint at the beginning of the main procedure and then invoking
2143 the @samp{run} command.
2145 @cindex elaboration phase
2146 Some programs contain an @dfn{elaboration} phase where some startup code is
2147 executed before the main procedure is called. This depends on the
2148 languages used to write your program. In C@t{++}, for instance,
2149 constructors for static and global objects are executed before
2150 @code{main} is called. It is therefore possible that the debugger stops
2151 before reaching the main procedure. However, the temporary breakpoint
2152 will remain to halt execution.
2154 Specify the arguments to give to your program as arguments to the
2155 @samp{start} command. These arguments will be given verbatim to the
2156 underlying @samp{run} command. Note that the same arguments will be
2157 reused if no argument is provided during subsequent calls to
2158 @samp{start} or @samp{run}.
2160 It is sometimes necessary to debug the program during elaboration. In
2161 these cases, using the @code{start} command would stop the execution
2162 of your program too late, as the program would have already completed
2163 the elaboration phase. Under these circumstances, either insert
2164 breakpoints in your elaboration code before running your program or
2165 use the @code{starti} command.
2169 @cindex run to first instruction
2170 The @samp{starti} command does the equivalent of setting a temporary
2171 breakpoint at the first instruction of a program's execution and then
2172 invoking the @samp{run} command. For programs containing an
2173 elaboration phase, the @code{starti} command will stop execution at
2174 the start of the elaboration phase.
2176 @anchor{set exec-wrapper}
2177 @kindex set exec-wrapper
2178 @item set exec-wrapper @var{wrapper}
2179 @itemx show exec-wrapper
2180 @itemx unset exec-wrapper
2181 When @samp{exec-wrapper} is set, the specified wrapper is used to
2182 launch programs for debugging. @value{GDBN} starts your program
2183 with a shell command of the form @kbd{exec @var{wrapper}
2184 @var{program}}. Quoting is added to @var{program} and its
2185 arguments, but not to @var{wrapper}, so you should add quotes if
2186 appropriate for your shell. The wrapper runs until it executes
2187 your program, and then @value{GDBN} takes control.
2189 You can use any program that eventually calls @code{execve} with
2190 its arguments as a wrapper. Several standard Unix utilities do
2191 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2192 with @code{exec "$@@"} will also work.
2194 For example, you can use @code{env} to pass an environment variable to
2195 the debugged program, without setting the variable in your shell's
2199 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2203 This command is available when debugging locally on most targets, excluding
2204 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2206 @kindex set startup-with-shell
2207 @anchor{set startup-with-shell}
2208 @item set startup-with-shell
2209 @itemx set startup-with-shell on
2210 @itemx set startup-with-shell off
2211 @itemx show startup-with-shell
2212 On Unix systems, by default, if a shell is available on your target,
2213 @value{GDBN}) uses it to start your program. Arguments of the
2214 @code{run} command are passed to the shell, which does variable
2215 substitution, expands wildcard characters and performs redirection of
2216 I/O. In some circumstances, it may be useful to disable such use of a
2217 shell, for example, when debugging the shell itself or diagnosing
2218 startup failures such as:
2222 Starting program: ./a.out
2223 During startup program terminated with signal SIGSEGV, Segmentation fault.
2227 which indicates the shell or the wrapper specified with
2228 @samp{exec-wrapper} crashed, not your program. Most often, this is
2229 caused by something odd in your shell's non-interactive mode
2230 initialization file---such as @file{.cshrc} for C-shell,
2231 $@file{.zshenv} for the Z shell, or the file specified in the
2232 @samp{BASH_ENV} environment variable for BASH.
2234 @anchor{set auto-connect-native-target}
2235 @kindex set auto-connect-native-target
2236 @item set auto-connect-native-target
2237 @itemx set auto-connect-native-target on
2238 @itemx set auto-connect-native-target off
2239 @itemx show auto-connect-native-target
2241 By default, if not connected to any target yet (e.g., with
2242 @code{target remote}), the @code{run} command starts your program as a
2243 native process under @value{GDBN}, on your local machine. If you're
2244 sure you don't want to debug programs on your local machine, you can
2245 tell @value{GDBN} to not connect to the native target automatically
2246 with the @code{set auto-connect-native-target off} command.
2248 If @code{on}, which is the default, and if @value{GDBN} is not
2249 connected to a target already, the @code{run} command automaticaly
2250 connects to the native target, if one is available.
2252 If @code{off}, and if @value{GDBN} is not connected to a target
2253 already, the @code{run} command fails with an error:
2257 Don't know how to run. Try "help target".
2260 If @value{GDBN} is already connected to a target, @value{GDBN} always
2261 uses it with the @code{run} command.
2263 In any case, you can explicitly connect to the native target with the
2264 @code{target native} command. For example,
2267 (@value{GDBP}) set auto-connect-native-target off
2269 Don't know how to run. Try "help target".
2270 (@value{GDBP}) target native
2272 Starting program: ./a.out
2273 [Inferior 1 (process 10421) exited normally]
2276 In case you connected explicitly to the @code{native} target,
2277 @value{GDBN} remains connected even if all inferiors exit, ready for
2278 the next @code{run} command. Use the @code{disconnect} command to
2281 Examples of other commands that likewise respect the
2282 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2283 proc}, @code{info os}.
2285 @kindex set disable-randomization
2286 @item set disable-randomization
2287 @itemx set disable-randomization on
2288 This option (enabled by default in @value{GDBN}) will turn off the native
2289 randomization of the virtual address space of the started program. This option
2290 is useful for multiple debugging sessions to make the execution better
2291 reproducible and memory addresses reusable across debugging sessions.
2293 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2294 On @sc{gnu}/Linux you can get the same behavior using
2297 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2300 @item set disable-randomization off
2301 Leave the behavior of the started executable unchanged. Some bugs rear their
2302 ugly heads only when the program is loaded at certain addresses. If your bug
2303 disappears when you run the program under @value{GDBN}, that might be because
2304 @value{GDBN} by default disables the address randomization on platforms, such
2305 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2306 disable-randomization off} to try to reproduce such elusive bugs.
2308 On targets where it is available, virtual address space randomization
2309 protects the programs against certain kinds of security attacks. In these
2310 cases the attacker needs to know the exact location of a concrete executable
2311 code. Randomizing its location makes it impossible to inject jumps misusing
2312 a code at its expected addresses.
2314 Prelinking shared libraries provides a startup performance advantage but it
2315 makes addresses in these libraries predictable for privileged processes by
2316 having just unprivileged access at the target system. Reading the shared
2317 library binary gives enough information for assembling the malicious code
2318 misusing it. Still even a prelinked shared library can get loaded at a new
2319 random address just requiring the regular relocation process during the
2320 startup. Shared libraries not already prelinked are always loaded at
2321 a randomly chosen address.
2323 Position independent executables (PIE) contain position independent code
2324 similar to the shared libraries and therefore such executables get loaded at
2325 a randomly chosen address upon startup. PIE executables always load even
2326 already prelinked shared libraries at a random address. You can build such
2327 executable using @command{gcc -fPIE -pie}.
2329 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2330 (as long as the randomization is enabled).
2332 @item show disable-randomization
2333 Show the current setting of the explicit disable of the native randomization of
2334 the virtual address space of the started program.
2339 @section Your Program's Arguments
2341 @cindex arguments (to your program)
2342 The arguments to your program can be specified by the arguments of the
2344 They are passed to a shell, which expands wildcard characters and
2345 performs redirection of I/O, and thence to your program. Your
2346 @code{SHELL} environment variable (if it exists) specifies what shell
2347 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2348 the default shell (@file{/bin/sh} on Unix).
2350 On non-Unix systems, the program is usually invoked directly by
2351 @value{GDBN}, which emulates I/O redirection via the appropriate system
2352 calls, and the wildcard characters are expanded by the startup code of
2353 the program, not by the shell.
2355 @code{run} with no arguments uses the same arguments used by the previous
2356 @code{run}, or those set by the @code{set args} command.
2361 Specify the arguments to be used the next time your program is run. If
2362 @code{set args} has no arguments, @code{run} executes your program
2363 with no arguments. Once you have run your program with arguments,
2364 using @code{set args} before the next @code{run} is the only way to run
2365 it again without arguments.
2369 Show the arguments to give your program when it is started.
2373 @section Your Program's Environment
2375 @cindex environment (of your program)
2376 The @dfn{environment} consists of a set of environment variables and
2377 their values. Environment variables conventionally record such things as
2378 your user name, your home directory, your terminal type, and your search
2379 path for programs to run. Usually you set up environment variables with
2380 the shell and they are inherited by all the other programs you run. When
2381 debugging, it can be useful to try running your program with a modified
2382 environment without having to start @value{GDBN} over again.
2386 @item path @var{directory}
2387 Add @var{directory} to the front of the @code{PATH} environment variable
2388 (the search path for executables) that will be passed to your program.
2389 The value of @code{PATH} used by @value{GDBN} does not change.
2390 You may specify several directory names, separated by whitespace or by a
2391 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2392 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2393 is moved to the front, so it is searched sooner.
2395 You can use the string @samp{$cwd} to refer to whatever is the current
2396 working directory at the time @value{GDBN} searches the path. If you
2397 use @samp{.} instead, it refers to the directory where you executed the
2398 @code{path} command. @value{GDBN} replaces @samp{.} in the
2399 @var{directory} argument (with the current path) before adding
2400 @var{directory} to the search path.
2401 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2402 @c document that, since repeating it would be a no-op.
2406 Display the list of search paths for executables (the @code{PATH}
2407 environment variable).
2409 @kindex show environment
2410 @item show environment @r{[}@var{varname}@r{]}
2411 Print the value of environment variable @var{varname} to be given to
2412 your program when it starts. If you do not supply @var{varname},
2413 print the names and values of all environment variables to be given to
2414 your program. You can abbreviate @code{environment} as @code{env}.
2416 @kindex set environment
2417 @anchor{set environment}
2418 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2419 Set environment variable @var{varname} to @var{value}. The value
2420 changes for your program (and the shell @value{GDBN} uses to launch
2421 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2422 values of environment variables are just strings, and any
2423 interpretation is supplied by your program itself. The @var{value}
2424 parameter is optional; if it is eliminated, the variable is set to a
2426 @c "any string" here does not include leading, trailing
2427 @c blanks. Gnu asks: does anyone care?
2429 For example, this command:
2436 tells the debugged program, when subsequently run, that its user is named
2437 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2438 are not actually required.)
2440 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2441 which also inherits the environment set with @code{set environment}.
2442 If necessary, you can avoid that by using the @samp{env} program as a
2443 wrapper instead of using @code{set environment}. @xref{set
2444 exec-wrapper}, for an example doing just that.
2446 Environment variables that are set by the user are also transmitted to
2447 @command{gdbserver} to be used when starting the remote inferior.
2448 @pxref{QEnvironmentHexEncoded}.
2450 @kindex unset environment
2451 @anchor{unset environment}
2452 @item unset environment @var{varname}
2453 Remove variable @var{varname} from the environment to be passed to your
2454 program. This is different from @samp{set env @var{varname} =};
2455 @code{unset environment} removes the variable from the environment,
2456 rather than assigning it an empty value.
2458 Environment variables that are unset by the user are also unset on
2459 @command{gdbserver} when starting the remote inferior.
2460 @pxref{QEnvironmentUnset}.
2463 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2464 the shell indicated by your @code{SHELL} environment variable if it
2465 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2466 names a shell that runs an initialization file when started
2467 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2468 for the Z shell, or the file specified in the @samp{BASH_ENV}
2469 environment variable for BASH---any variables you set in that file
2470 affect your program. You may wish to move setting of environment
2471 variables to files that are only run when you sign on, such as
2472 @file{.login} or @file{.profile}.
2474 @node Working Directory
2475 @section Your Program's Working Directory
2477 @cindex working directory (of your program)
2478 Each time you start your program with @code{run}, the inferior will be
2479 initialized with the current working directory specified by the
2480 @kbd{set cwd} command. If no directory has been specified by this
2481 command, then the inferior will inherit @value{GDBN}'s current working
2482 directory as its working directory if native debugging, or it will
2483 inherit the remote server's current working directory if remote
2488 @cindex change inferior's working directory
2489 @anchor{set cwd command}
2490 @item set cwd @r{[}@var{directory}@r{]}
2491 Set the inferior's working directory to @var{directory}, which will be
2492 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2493 argument has been specified, the command clears the setting and resets
2494 it to an empty state. This setting has no effect on @value{GDBN}'s
2495 working directory, and it only takes effect the next time you start
2496 the inferior. The @file{~} in @var{directory} is a short for the
2497 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2498 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2499 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2502 You can also change @value{GDBN}'s current working directory by using
2503 the @code{cd} command.
2507 @cindex show inferior's working directory
2509 Show the inferior's working directory. If no directory has been
2510 specified by @kbd{set cwd}, then the default inferior's working
2511 directory is the same as @value{GDBN}'s working directory.
2514 @cindex change @value{GDBN}'s working directory
2516 @item cd @r{[}@var{directory}@r{]}
2517 Set the @value{GDBN} working directory to @var{directory}. If not
2518 given, @var{directory} uses @file{'~'}.
2520 The @value{GDBN} working directory serves as a default for the
2521 commands that specify files for @value{GDBN} to operate on.
2522 @xref{Files, ,Commands to Specify Files}.
2523 @xref{set cwd command}.
2527 Print the @value{GDBN} working directory.
2530 It is generally impossible to find the current working directory of
2531 the process being debugged (since a program can change its directory
2532 during its run). If you work on a system where @value{GDBN} supports
2533 the @code{info proc} command (@pxref{Process Information}), you can
2534 use the @code{info proc} command to find out the
2535 current working directory of the debuggee.
2538 @section Your Program's Input and Output
2543 By default, the program you run under @value{GDBN} does input and output to
2544 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2545 to its own terminal modes to interact with you, but it records the terminal
2546 modes your program was using and switches back to them when you continue
2547 running your program.
2550 @kindex info terminal
2552 Displays information recorded by @value{GDBN} about the terminal modes your
2556 You can redirect your program's input and/or output using shell
2557 redirection with the @code{run} command. For example,
2564 starts your program, diverting its output to the file @file{outfile}.
2567 @cindex controlling terminal
2568 Another way to specify where your program should do input and output is
2569 with the @code{tty} command. This command accepts a file name as
2570 argument, and causes this file to be the default for future @code{run}
2571 commands. It also resets the controlling terminal for the child
2572 process, for future @code{run} commands. For example,
2579 directs that processes started with subsequent @code{run} commands
2580 default to do input and output on the terminal @file{/dev/ttyb} and have
2581 that as their controlling terminal.
2583 An explicit redirection in @code{run} overrides the @code{tty} command's
2584 effect on the input/output device, but not its effect on the controlling
2587 When you use the @code{tty} command or redirect input in the @code{run}
2588 command, only the input @emph{for your program} is affected. The input
2589 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2590 for @code{set inferior-tty}.
2592 @cindex inferior tty
2593 @cindex set inferior controlling terminal
2594 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2595 display the name of the terminal that will be used for future runs of your
2599 @item set inferior-tty [ @var{tty} ]
2600 @kindex set inferior-tty
2601 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2602 restores the default behavior, which is to use the same terminal as
2605 @item show inferior-tty
2606 @kindex show inferior-tty
2607 Show the current tty for the program being debugged.
2611 @section Debugging an Already-running Process
2616 @item attach @var{process-id}
2617 This command attaches to a running process---one that was started
2618 outside @value{GDBN}. (@code{info files} shows your active
2619 targets.) The command takes as argument a process ID. The usual way to
2620 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2621 or with the @samp{jobs -l} shell command.
2623 @code{attach} does not repeat if you press @key{RET} a second time after
2624 executing the command.
2627 To use @code{attach}, your program must be running in an environment
2628 which supports processes; for example, @code{attach} does not work for
2629 programs on bare-board targets that lack an operating system. You must
2630 also have permission to send the process a signal.
2632 When you use @code{attach}, the debugger finds the program running in
2633 the process first by looking in the current working directory, then (if
2634 the program is not found) by using the source file search path
2635 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2636 the @code{file} command to load the program. @xref{Files, ,Commands to
2639 The first thing @value{GDBN} does after arranging to debug the specified
2640 process is to stop it. You can examine and modify an attached process
2641 with all the @value{GDBN} commands that are ordinarily available when
2642 you start processes with @code{run}. You can insert breakpoints; you
2643 can step and continue; you can modify storage. If you would rather the
2644 process continue running, you may use the @code{continue} command after
2645 attaching @value{GDBN} to the process.
2650 When you have finished debugging the attached process, you can use the
2651 @code{detach} command to release it from @value{GDBN} control. Detaching
2652 the process continues its execution. After the @code{detach} command,
2653 that process and @value{GDBN} become completely independent once more, and you
2654 are ready to @code{attach} another process or start one with @code{run}.
2655 @code{detach} does not repeat if you press @key{RET} again after
2656 executing the command.
2659 If you exit @value{GDBN} while you have an attached process, you detach
2660 that process. If you use the @code{run} command, you kill that process.
2661 By default, @value{GDBN} asks for confirmation if you try to do either of these
2662 things; you can control whether or not you need to confirm by using the
2663 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2667 @section Killing the Child Process
2672 Kill the child process in which your program is running under @value{GDBN}.
2675 This command is useful if you wish to debug a core dump instead of a
2676 running process. @value{GDBN} ignores any core dump file while your program
2679 On some operating systems, a program cannot be executed outside @value{GDBN}
2680 while you have breakpoints set on it inside @value{GDBN}. You can use the
2681 @code{kill} command in this situation to permit running your program
2682 outside the debugger.
2684 The @code{kill} command is also useful if you wish to recompile and
2685 relink your program, since on many systems it is impossible to modify an
2686 executable file while it is running in a process. In this case, when you
2687 next type @code{run}, @value{GDBN} notices that the file has changed, and
2688 reads the symbol table again (while trying to preserve your current
2689 breakpoint settings).
2691 @node Inferiors and Programs
2692 @section Debugging Multiple Inferiors and Programs
2694 @value{GDBN} lets you run and debug multiple programs in a single
2695 session. In addition, @value{GDBN} on some systems may let you run
2696 several programs simultaneously (otherwise you have to exit from one
2697 before starting another). In the most general case, you can have
2698 multiple threads of execution in each of multiple processes, launched
2699 from multiple executables.
2702 @value{GDBN} represents the state of each program execution with an
2703 object called an @dfn{inferior}. An inferior typically corresponds to
2704 a process, but is more general and applies also to targets that do not
2705 have processes. Inferiors may be created before a process runs, and
2706 may be retained after a process exits. Inferiors have unique
2707 identifiers that are different from process ids. Usually each
2708 inferior will also have its own distinct address space, although some
2709 embedded targets may have several inferiors running in different parts
2710 of a single address space. Each inferior may in turn have multiple
2711 threads running in it.
2713 To find out what inferiors exist at any moment, use @w{@code{info
2717 @kindex info inferiors [ @var{id}@dots{} ]
2718 @item info inferiors
2719 Print a list of all inferiors currently being managed by @value{GDBN}.
2720 By default all inferiors are printed, but the argument @var{id}@dots{}
2721 -- a space separated list of inferior numbers -- can be used to limit
2722 the display to just the requested inferiors.
2724 @value{GDBN} displays for each inferior (in this order):
2728 the inferior number assigned by @value{GDBN}
2731 the target system's inferior identifier
2734 the name of the executable the inferior is running.
2739 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2740 indicates the current inferior.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info inferiors
2748 Num Description Executable
2749 2 process 2307 hello
2750 * 1 process 3401 goodbye
2753 To switch focus between inferiors, use the @code{inferior} command:
2756 @kindex inferior @var{infno}
2757 @item inferior @var{infno}
2758 Make inferior number @var{infno} the current inferior. The argument
2759 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2760 in the first field of the @samp{info inferiors} display.
2763 @vindex $_inferior@r{, convenience variable}
2764 The debugger convenience variable @samp{$_inferior} contains the
2765 number of the current inferior. You may find this useful in writing
2766 breakpoint conditional expressions, command scripts, and so forth.
2767 @xref{Convenience Vars,, Convenience Variables}, for general
2768 information on convenience variables.
2770 You can get multiple executables into a debugging session via the
2771 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2772 systems @value{GDBN} can add inferiors to the debug session
2773 automatically by following calls to @code{fork} and @code{exec}. To
2774 remove inferiors from the debugging session use the
2775 @w{@code{remove-inferiors}} command.
2778 @kindex add-inferior
2779 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2780 Adds @var{n} inferiors to be run using @var{executable} as the
2781 executable; @var{n} defaults to 1. If no executable is specified,
2782 the inferiors begins empty, with no program. You can still assign or
2783 change the program assigned to the inferior at any time by using the
2784 @code{file} command with the executable name as its argument.
2786 @kindex clone-inferior
2787 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2788 Adds @var{n} inferiors ready to execute the same program as inferior
2789 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2790 number of the current inferior. This is a convenient command when you
2791 want to run another instance of the inferior you are debugging.
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2796 * 1 process 29964 helloworld
2797 (@value{GDBP}) clone-inferior
2800 (@value{GDBP}) info inferiors
2801 Num Description Executable
2803 * 1 process 29964 helloworld
2806 You can now simply switch focus to inferior 2 and run it.
2808 @kindex remove-inferiors
2809 @item remove-inferiors @var{infno}@dots{}
2810 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2811 possible to remove an inferior that is running with this command. For
2812 those, use the @code{kill} or @code{detach} command first.
2816 To quit debugging one of the running inferiors that is not the current
2817 inferior, you can either detach from it by using the @w{@code{detach
2818 inferior}} command (allowing it to run independently), or kill it
2819 using the @w{@code{kill inferiors}} command:
2822 @kindex detach inferiors @var{infno}@dots{}
2823 @item detach inferior @var{infno}@dots{}
2824 Detach from the inferior or inferiors identified by @value{GDBN}
2825 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2826 still stays on the list of inferiors shown by @code{info inferiors},
2827 but its Description will show @samp{<null>}.
2829 @kindex kill inferiors @var{infno}@dots{}
2830 @item kill inferiors @var{infno}@dots{}
2831 Kill the inferior or inferiors identified by @value{GDBN} inferior
2832 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2833 stays on the list of inferiors shown by @code{info inferiors}, but its
2834 Description will show @samp{<null>}.
2837 After the successful completion of a command such as @code{detach},
2838 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2839 a normal process exit, the inferior is still valid and listed with
2840 @code{info inferiors}, ready to be restarted.
2843 To be notified when inferiors are started or exit under @value{GDBN}'s
2844 control use @w{@code{set print inferior-events}}:
2847 @kindex set print inferior-events
2848 @cindex print messages on inferior start and exit
2849 @item set print inferior-events
2850 @itemx set print inferior-events on
2851 @itemx set print inferior-events off
2852 The @code{set print inferior-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new
2854 inferiors have started or that inferiors have exited or have been
2855 detached. By default, these messages will not be printed.
2857 @kindex show print inferior-events
2858 @item show print inferior-events
2859 Show whether messages will be printed when @value{GDBN} detects that
2860 inferiors have started, exited or have been detached.
2863 Many commands will work the same with multiple programs as with a
2864 single program: e.g., @code{print myglobal} will simply display the
2865 value of @code{myglobal} in the current inferior.
2868 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2869 get more info about the relationship of inferiors, programs, address
2870 spaces in a debug session. You can do that with the @w{@code{maint
2871 info program-spaces}} command.
2874 @kindex maint info program-spaces
2875 @item maint info program-spaces
2876 Print a list of all program spaces currently being managed by
2879 @value{GDBN} displays for each program space (in this order):
2883 the program space number assigned by @value{GDBN}
2886 the name of the executable loaded into the program space, with e.g.,
2887 the @code{file} command.
2892 An asterisk @samp{*} preceding the @value{GDBN} program space number
2893 indicates the current program space.
2895 In addition, below each program space line, @value{GDBN} prints extra
2896 information that isn't suitable to display in tabular form. For
2897 example, the list of inferiors bound to the program space.
2900 (@value{GDBP}) maint info program-spaces
2904 Bound inferiors: ID 1 (process 21561)
2907 Here we can see that no inferior is running the program @code{hello},
2908 while @code{process 21561} is running the program @code{goodbye}. On
2909 some targets, it is possible that multiple inferiors are bound to the
2910 same program space. The most common example is that of debugging both
2911 the parent and child processes of a @code{vfork} call. For example,
2914 (@value{GDBP}) maint info program-spaces
2917 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2920 Here, both inferior 2 and inferior 1 are running in the same program
2921 space as a result of inferior 1 having executed a @code{vfork} call.
2925 @section Debugging Programs with Multiple Threads
2927 @cindex threads of execution
2928 @cindex multiple threads
2929 @cindex switching threads
2930 In some operating systems, such as GNU/Linux and Solaris, a single program
2931 may have more than one @dfn{thread} of execution. The precise semantics
2932 of threads differ from one operating system to another, but in general
2933 the threads of a single program are akin to multiple processes---except
2934 that they share one address space (that is, they can all examine and
2935 modify the same variables). On the other hand, each thread has its own
2936 registers and execution stack, and perhaps private memory.
2938 @value{GDBN} provides these facilities for debugging multi-thread
2942 @item automatic notification of new threads
2943 @item @samp{thread @var{thread-id}}, a command to switch among threads
2944 @item @samp{info threads}, a command to inquire about existing threads
2945 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2946 a command to apply a command to a list of threads
2947 @item thread-specific breakpoints
2948 @item @samp{set print thread-events}, which controls printing of
2949 messages on thread start and exit.
2950 @item @samp{set libthread-db-search-path @var{path}}, which lets
2951 the user specify which @code{libthread_db} to use if the default choice
2952 isn't compatible with the program.
2955 @cindex focus of debugging
2956 @cindex current thread
2957 The @value{GDBN} thread debugging facility allows you to observe all
2958 threads while your program runs---but whenever @value{GDBN} takes
2959 control, one thread in particular is always the focus of debugging.
2960 This thread is called the @dfn{current thread}. Debugging commands show
2961 program information from the perspective of the current thread.
2963 @cindex @code{New} @var{systag} message
2964 @cindex thread identifier (system)
2965 @c FIXME-implementors!! It would be more helpful if the [New...] message
2966 @c included GDB's numeric thread handle, so you could just go to that
2967 @c thread without first checking `info threads'.
2968 Whenever @value{GDBN} detects a new thread in your program, it displays
2969 the target system's identification for the thread with a message in the
2970 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2971 whose form varies depending on the particular system. For example, on
2972 @sc{gnu}/Linux, you might see
2975 [New Thread 0x41e02940 (LWP 25582)]
2979 when @value{GDBN} notices a new thread. In contrast, on other systems,
2980 the @var{systag} is simply something like @samp{process 368}, with no
2983 @c FIXME!! (1) Does the [New...] message appear even for the very first
2984 @c thread of a program, or does it only appear for the
2985 @c second---i.e.@: when it becomes obvious we have a multithread
2987 @c (2) *Is* there necessarily a first thread always? Or do some
2988 @c multithread systems permit starting a program with multiple
2989 @c threads ab initio?
2991 @anchor{thread numbers}
2992 @cindex thread number, per inferior
2993 @cindex thread identifier (GDB)
2994 For debugging purposes, @value{GDBN} associates its own thread number
2995 ---always a single integer---with each thread of an inferior. This
2996 number is unique between all threads of an inferior, but not unique
2997 between threads of different inferiors.
2999 @cindex qualified thread ID
3000 You can refer to a given thread in an inferior using the qualified
3001 @var{inferior-num}.@var{thread-num} syntax, also known as
3002 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3003 number and @var{thread-num} being the thread number of the given
3004 inferior. For example, thread @code{2.3} refers to thread number 3 of
3005 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3006 then @value{GDBN} infers you're referring to a thread of the current
3009 Until you create a second inferior, @value{GDBN} does not show the
3010 @var{inferior-num} part of thread IDs, even though you can always use
3011 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3012 of inferior 1, the initial inferior.
3014 @anchor{thread ID lists}
3015 @cindex thread ID lists
3016 Some commands accept a space-separated @dfn{thread ID list} as
3017 argument. A list element can be:
3021 A thread ID as shown in the first field of the @samp{info threads}
3022 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3026 A range of thread numbers, again with or without an inferior
3027 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3028 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3031 All threads of an inferior, specified with a star wildcard, with or
3032 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3033 @samp{1.*}) or @code{*}. The former refers to all threads of the
3034 given inferior, and the latter form without an inferior qualifier
3035 refers to all threads of the current inferior.
3039 For example, if the current inferior is 1, and inferior 7 has one
3040 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3041 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3042 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3043 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3047 @anchor{global thread numbers}
3048 @cindex global thread number
3049 @cindex global thread identifier (GDB)
3050 In addition to a @emph{per-inferior} number, each thread is also
3051 assigned a unique @emph{global} number, also known as @dfn{global
3052 thread ID}, a single integer. Unlike the thread number component of
3053 the thread ID, no two threads have the same global ID, even when
3054 you're debugging multiple inferiors.
3056 From @value{GDBN}'s perspective, a process always has at least one
3057 thread. In other words, @value{GDBN} assigns a thread number to the
3058 program's ``main thread'' even if the program is not multi-threaded.
3060 @vindex $_thread@r{, convenience variable}
3061 @vindex $_gthread@r{, convenience variable}
3062 The debugger convenience variables @samp{$_thread} and
3063 @samp{$_gthread} contain, respectively, the per-inferior thread number
3064 and the global thread number of the current thread. You may find this
3065 useful in writing breakpoint conditional expressions, command scripts,
3066 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3067 general information on convenience variables.
3069 If @value{GDBN} detects the program is multi-threaded, it augments the
3070 usual message about stopping at a breakpoint with the ID and name of
3071 the thread that hit the breakpoint.
3074 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3077 Likewise when the program receives a signal:
3080 Thread 1 "main" received signal SIGINT, Interrupt.
3084 @kindex info threads
3085 @item info threads @r{[}@var{thread-id-list}@r{]}
3087 Display information about one or more threads. With no arguments
3088 displays information about all threads. You can specify the list of
3089 threads that you want to display using the thread ID list syntax
3090 (@pxref{thread ID lists}).
3092 @value{GDBN} displays for each thread (in this order):
3096 the per-inferior thread number assigned by @value{GDBN}
3099 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3100 option was specified
3103 the target system's thread identifier (@var{systag})
3106 the thread's name, if one is known. A thread can either be named by
3107 the user (see @code{thread name}, below), or, in some cases, by the
3111 the current stack frame summary for that thread
3115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3116 indicates the current thread.
3120 @c end table here to get a little more width for example
3123 (@value{GDBP}) info threads
3125 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3126 2 process 35 thread 23 0x34e5 in sigpause ()
3127 3 process 35 thread 27 0x34e5 in sigpause ()
3131 If you're debugging multiple inferiors, @value{GDBN} displays thread
3132 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3133 Otherwise, only @var{thread-num} is shown.
3135 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3136 indicating each thread's global thread ID:
3139 (@value{GDBP}) info threads
3140 Id GId Target Id Frame
3141 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3142 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3143 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3144 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3147 On Solaris, you can display more information about user threads with a
3148 Solaris-specific command:
3151 @item maint info sol-threads
3152 @kindex maint info sol-threads
3153 @cindex thread info (Solaris)
3154 Display info on Solaris user threads.
3158 @kindex thread @var{thread-id}
3159 @item thread @var{thread-id}
3160 Make thread ID @var{thread-id} the current thread. The command
3161 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3162 the first field of the @samp{info threads} display, with or without an
3163 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3165 @value{GDBN} responds by displaying the system identifier of the
3166 thread you selected, and its current stack frame summary:
3169 (@value{GDBP}) thread 2
3170 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3171 #0 some_function (ignore=0x0) at example.c:8
3172 8 printf ("hello\n");
3176 As with the @samp{[New @dots{}]} message, the form of the text after
3177 @samp{Switching to} depends on your system's conventions for identifying
3180 @kindex thread apply
3181 @cindex apply command to several threads
3182 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3183 The @code{thread apply} command allows you to apply the named
3184 @var{command} to one or more threads. Specify the threads that you
3185 want affected using the thread ID list syntax (@pxref{thread ID
3186 lists}), or specify @code{all} to apply to all threads. To apply a
3187 command to all threads in descending order, type @kbd{thread apply all
3188 @var{command}}. To apply a command to all threads in ascending order,
3189 type @kbd{thread apply all -ascending @var{command}}.
3191 The @var{flag} arguments control what output to produce and how to handle
3192 errors raised when applying @var{command} to a thread. @var{flag}
3193 must start with a @code{-} directly followed by one letter in
3194 @code{qcs}. If several flags are provided, they must be given
3195 individually, such as @code{-c -q}.
3197 By default, @value{GDBN} displays some thread information before the
3198 output produced by @var{command}, and an error raised during the
3199 execution of a @var{command} will abort @code{thread apply}. The
3200 following flags can be used to fine-tune this behavior:
3204 The flag @code{-c}, which stands for @samp{continue}, causes any
3205 errors in @var{command} to be displayed, and the execution of
3206 @code{thread apply} then continues.
3208 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3209 or empty output produced by a @var{command} to be silently ignored.
3210 That is, the execution continues, but the thread information and errors
3213 The flag @code{-q} (@samp{quiet}) disables printing the thread
3217 Flags @code{-c} and @code{-s} cannot be used together.
3220 @cindex apply command to all threads (ignoring errors and empty output)
3221 @item taas @var{command}
3222 Shortcut for @code{thread apply all -s @var{command}}.
3223 Applies @var{command} on all threads, ignoring errors and empty output.
3226 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3227 @item tfaas @var{command}
3228 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3229 Applies @var{command} on all frames of all threads, ignoring errors
3230 and empty output. Note that the flag @code{-s} is specified twice:
3231 The first @code{-s} ensures that @code{thread apply} only shows the thread
3232 information of the threads for which @code{frame apply} produces
3233 some output. The second @code{-s} is needed to ensure that @code{frame
3234 apply} shows the frame information of a frame only if the
3235 @var{command} successfully produced some output.
3237 It can for example be used to print a local variable or a function
3238 argument without knowing the thread or frame where this variable or argument
3241 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3246 @cindex name a thread
3247 @item thread name [@var{name}]
3248 This command assigns a name to the current thread. If no argument is
3249 given, any existing user-specified name is removed. The thread name
3250 appears in the @samp{info threads} display.
3252 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3253 determine the name of the thread as given by the OS. On these
3254 systems, a name specified with @samp{thread name} will override the
3255 system-give name, and removing the user-specified name will cause
3256 @value{GDBN} to once again display the system-specified name.
3259 @cindex search for a thread
3260 @item thread find [@var{regexp}]
3261 Search for and display thread ids whose name or @var{systag}
3262 matches the supplied regular expression.
3264 As well as being the complement to the @samp{thread name} command,
3265 this command also allows you to identify a thread by its target
3266 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3270 (@value{GDBN}) thread find 26688
3271 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3272 (@value{GDBN}) info thread 4
3274 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3277 @kindex set print thread-events
3278 @cindex print messages on thread start and exit
3279 @item set print thread-events
3280 @itemx set print thread-events on
3281 @itemx set print thread-events off
3282 The @code{set print thread-events} command allows you to enable or
3283 disable printing of messages when @value{GDBN} notices that new threads have
3284 started or that threads have exited. By default, these messages will
3285 be printed if detection of these events is supported by the target.
3286 Note that these messages cannot be disabled on all targets.
3288 @kindex show print thread-events
3289 @item show print thread-events
3290 Show whether messages will be printed when @value{GDBN} detects that threads
3291 have started and exited.
3294 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3295 more information about how @value{GDBN} behaves when you stop and start
3296 programs with multiple threads.
3298 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3299 watchpoints in programs with multiple threads.
3301 @anchor{set libthread-db-search-path}
3303 @kindex set libthread-db-search-path
3304 @cindex search path for @code{libthread_db}
3305 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3306 If this variable is set, @var{path} is a colon-separated list of
3307 directories @value{GDBN} will use to search for @code{libthread_db}.
3308 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3309 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3310 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3313 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3314 @code{libthread_db} library to obtain information about threads in the
3315 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3316 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3317 specific thread debugging library loading is enabled
3318 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3321 refers to the default system directories that are
3322 normally searched for loading shared libraries. The @samp{$sdir} entry
3323 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3324 (@pxref{libthread_db.so.1 file}).
3326 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3327 refers to the directory from which @code{libpthread}
3328 was loaded in the inferior process.
3330 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3331 @value{GDBN} attempts to initialize it with the current inferior process.
3332 If this initialization fails (which could happen because of a version
3333 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3334 will unload @code{libthread_db}, and continue with the next directory.
3335 If none of @code{libthread_db} libraries initialize successfully,
3336 @value{GDBN} will issue a warning and thread debugging will be disabled.
3338 Setting @code{libthread-db-search-path} is currently implemented
3339 only on some platforms.
3341 @kindex show libthread-db-search-path
3342 @item show libthread-db-search-path
3343 Display current libthread_db search path.
3345 @kindex set debug libthread-db
3346 @kindex show debug libthread-db
3347 @cindex debugging @code{libthread_db}
3348 @item set debug libthread-db
3349 @itemx show debug libthread-db
3350 Turns on or off display of @code{libthread_db}-related events.
3351 Use @code{1} to enable, @code{0} to disable.
3355 @section Debugging Forks
3357 @cindex fork, debugging programs which call
3358 @cindex multiple processes
3359 @cindex processes, multiple
3360 On most systems, @value{GDBN} has no special support for debugging
3361 programs which create additional processes using the @code{fork}
3362 function. When a program forks, @value{GDBN} will continue to debug the
3363 parent process and the child process will run unimpeded. If you have
3364 set a breakpoint in any code which the child then executes, the child
3365 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3366 will cause it to terminate.
3368 However, if you want to debug the child process there is a workaround
3369 which isn't too painful. Put a call to @code{sleep} in the code which
3370 the child process executes after the fork. It may be useful to sleep
3371 only if a certain environment variable is set, or a certain file exists,
3372 so that the delay need not occur when you don't want to run @value{GDBN}
3373 on the child. While the child is sleeping, use the @code{ps} program to
3374 get its process ID. Then tell @value{GDBN} (a new invocation of
3375 @value{GDBN} if you are also debugging the parent process) to attach to
3376 the child process (@pxref{Attach}). From that point on you can debug
3377 the child process just like any other process which you attached to.
3379 On some systems, @value{GDBN} provides support for debugging programs
3380 that create additional processes using the @code{fork} or @code{vfork}
3381 functions. On @sc{gnu}/Linux platforms, this feature is supported
3382 with kernel version 2.5.46 and later.
3384 The fork debugging commands are supported in native mode and when
3385 connected to @code{gdbserver} in either @code{target remote} mode or
3386 @code{target extended-remote} mode.
3388 By default, when a program forks, @value{GDBN} will continue to debug
3389 the parent process and the child process will run unimpeded.
3391 If you want to follow the child process instead of the parent process,
3392 use the command @w{@code{set follow-fork-mode}}.
3395 @kindex set follow-fork-mode
3396 @item set follow-fork-mode @var{mode}
3397 Set the debugger response to a program call of @code{fork} or
3398 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3399 process. The @var{mode} argument can be:
3403 The original process is debugged after a fork. The child process runs
3404 unimpeded. This is the default.
3407 The new process is debugged after a fork. The parent process runs
3412 @kindex show follow-fork-mode
3413 @item show follow-fork-mode
3414 Display the current debugger response to a @code{fork} or @code{vfork} call.
3417 @cindex debugging multiple processes
3418 On Linux, if you want to debug both the parent and child processes, use the
3419 command @w{@code{set detach-on-fork}}.
3422 @kindex set detach-on-fork
3423 @item set detach-on-fork @var{mode}
3424 Tells gdb whether to detach one of the processes after a fork, or
3425 retain debugger control over them both.
3429 The child process (or parent process, depending on the value of
3430 @code{follow-fork-mode}) will be detached and allowed to run
3431 independently. This is the default.
3434 Both processes will be held under the control of @value{GDBN}.
3435 One process (child or parent, depending on the value of
3436 @code{follow-fork-mode}) is debugged as usual, while the other
3441 @kindex show detach-on-fork
3442 @item show detach-on-fork
3443 Show whether detach-on-fork mode is on/off.
3446 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3447 will retain control of all forked processes (including nested forks).
3448 You can list the forked processes under the control of @value{GDBN} by
3449 using the @w{@code{info inferiors}} command, and switch from one fork
3450 to another by using the @code{inferior} command (@pxref{Inferiors and
3451 Programs, ,Debugging Multiple Inferiors and Programs}).
3453 To quit debugging one of the forked processes, you can either detach
3454 from it by using the @w{@code{detach inferiors}} command (allowing it
3455 to run independently), or kill it using the @w{@code{kill inferiors}}
3456 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3459 If you ask to debug a child process and a @code{vfork} is followed by an
3460 @code{exec}, @value{GDBN} executes the new target up to the first
3461 breakpoint in the new target. If you have a breakpoint set on
3462 @code{main} in your original program, the breakpoint will also be set on
3463 the child process's @code{main}.
3465 On some systems, when a child process is spawned by @code{vfork}, you
3466 cannot debug the child or parent until an @code{exec} call completes.
3468 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3469 call executes, the new target restarts. To restart the parent
3470 process, use the @code{file} command with the parent executable name
3471 as its argument. By default, after an @code{exec} call executes,
3472 @value{GDBN} discards the symbols of the previous executable image.
3473 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3477 @kindex set follow-exec-mode
3478 @item set follow-exec-mode @var{mode}
3480 Set debugger response to a program call of @code{exec}. An
3481 @code{exec} call replaces the program image of a process.
3483 @code{follow-exec-mode} can be:
3487 @value{GDBN} creates a new inferior and rebinds the process to this
3488 new inferior. The program the process was running before the
3489 @code{exec} call can be restarted afterwards by restarting the
3495 (@value{GDBP}) info inferiors
3497 Id Description Executable
3500 process 12020 is executing new program: prog2
3501 Program exited normally.
3502 (@value{GDBP}) info inferiors
3503 Id Description Executable
3509 @value{GDBN} keeps the process bound to the same inferior. The new
3510 executable image replaces the previous executable loaded in the
3511 inferior. Restarting the inferior after the @code{exec} call, with
3512 e.g., the @code{run} command, restarts the executable the process was
3513 running after the @code{exec} call. This is the default mode.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3522 process 12020 is executing new program: prog2
3523 Program exited normally.
3524 (@value{GDBP}) info inferiors
3525 Id Description Executable
3532 @code{follow-exec-mode} is supported in native mode and
3533 @code{target extended-remote} mode.
3535 You can use the @code{catch} command to make @value{GDBN} stop whenever
3536 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3537 Catchpoints, ,Setting Catchpoints}.
3539 @node Checkpoint/Restart
3540 @section Setting a @emph{Bookmark} to Return to Later
3545 @cindex snapshot of a process
3546 @cindex rewind program state
3548 On certain operating systems@footnote{Currently, only
3549 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3550 program's state, called a @dfn{checkpoint}, and come back to it
3553 Returning to a checkpoint effectively undoes everything that has
3554 happened in the program since the @code{checkpoint} was saved. This
3555 includes changes in memory, registers, and even (within some limits)
3556 system state. Effectively, it is like going back in time to the
3557 moment when the checkpoint was saved.
3559 Thus, if you're stepping thru a program and you think you're
3560 getting close to the point where things go wrong, you can save
3561 a checkpoint. Then, if you accidentally go too far and miss
3562 the critical statement, instead of having to restart your program
3563 from the beginning, you can just go back to the checkpoint and
3564 start again from there.
3566 This can be especially useful if it takes a lot of time or
3567 steps to reach the point where you think the bug occurs.
3569 To use the @code{checkpoint}/@code{restart} method of debugging:
3574 Save a snapshot of the debugged program's current execution state.
3575 The @code{checkpoint} command takes no arguments, but each checkpoint
3576 is assigned a small integer id, similar to a breakpoint id.
3578 @kindex info checkpoints
3579 @item info checkpoints
3580 List the checkpoints that have been saved in the current debugging
3581 session. For each checkpoint, the following information will be
3588 @item Source line, or label
3591 @kindex restart @var{checkpoint-id}
3592 @item restart @var{checkpoint-id}
3593 Restore the program state that was saved as checkpoint number
3594 @var{checkpoint-id}. All program variables, registers, stack frames
3595 etc.@: will be returned to the values that they had when the checkpoint
3596 was saved. In essence, gdb will ``wind back the clock'' to the point
3597 in time when the checkpoint was saved.
3599 Note that breakpoints, @value{GDBN} variables, command history etc.
3600 are not affected by restoring a checkpoint. In general, a checkpoint
3601 only restores things that reside in the program being debugged, not in
3604 @kindex delete checkpoint @var{checkpoint-id}
3605 @item delete checkpoint @var{checkpoint-id}
3606 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3610 Returning to a previously saved checkpoint will restore the user state
3611 of the program being debugged, plus a significant subset of the system
3612 (OS) state, including file pointers. It won't ``un-write'' data from
3613 a file, but it will rewind the file pointer to the previous location,
3614 so that the previously written data can be overwritten. For files
3615 opened in read mode, the pointer will also be restored so that the
3616 previously read data can be read again.
3618 Of course, characters that have been sent to a printer (or other
3619 external device) cannot be ``snatched back'', and characters received
3620 from eg.@: a serial device can be removed from internal program buffers,
3621 but they cannot be ``pushed back'' into the serial pipeline, ready to
3622 be received again. Similarly, the actual contents of files that have
3623 been changed cannot be restored (at this time).
3625 However, within those constraints, you actually can ``rewind'' your
3626 program to a previously saved point in time, and begin debugging it
3627 again --- and you can change the course of events so as to debug a
3628 different execution path this time.
3630 @cindex checkpoints and process id
3631 Finally, there is one bit of internal program state that will be
3632 different when you return to a checkpoint --- the program's process
3633 id. Each checkpoint will have a unique process id (or @var{pid}),
3634 and each will be different from the program's original @var{pid}.
3635 If your program has saved a local copy of its process id, this could
3636 potentially pose a problem.
3638 @subsection A Non-obvious Benefit of Using Checkpoints
3640 On some systems such as @sc{gnu}/Linux, address space randomization
3641 is performed on new processes for security reasons. This makes it
3642 difficult or impossible to set a breakpoint, or watchpoint, on an
3643 absolute address if you have to restart the program, since the
3644 absolute location of a symbol will change from one execution to the
3647 A checkpoint, however, is an @emph{identical} copy of a process.
3648 Therefore if you create a checkpoint at (eg.@:) the start of main,
3649 and simply return to that checkpoint instead of restarting the
3650 process, you can avoid the effects of address randomization and
3651 your symbols will all stay in the same place.
3654 @chapter Stopping and Continuing
3656 The principal purposes of using a debugger are so that you can stop your
3657 program before it terminates; or so that, if your program runs into
3658 trouble, you can investigate and find out why.
3660 Inside @value{GDBN}, your program may stop for any of several reasons,
3661 such as a signal, a breakpoint, or reaching a new line after a
3662 @value{GDBN} command such as @code{step}. You may then examine and
3663 change variables, set new breakpoints or remove old ones, and then
3664 continue execution. Usually, the messages shown by @value{GDBN} provide
3665 ample explanation of the status of your program---but you can also
3666 explicitly request this information at any time.
3669 @kindex info program
3671 Display information about the status of your program: whether it is
3672 running or not, what process it is, and why it stopped.
3676 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3677 * Continuing and Stepping:: Resuming execution
3678 * Skipping Over Functions and Files::
3679 Skipping over functions and files
3681 * Thread Stops:: Stopping and starting multi-thread programs
3685 @section Breakpoints, Watchpoints, and Catchpoints
3688 A @dfn{breakpoint} makes your program stop whenever a certain point in
3689 the program is reached. For each breakpoint, you can add conditions to
3690 control in finer detail whether your program stops. You can set
3691 breakpoints with the @code{break} command and its variants (@pxref{Set
3692 Breaks, ,Setting Breakpoints}), to specify the place where your program
3693 should stop by line number, function name or exact address in the
3696 On some systems, you can set breakpoints in shared libraries before
3697 the executable is run.
3700 @cindex data breakpoints
3701 @cindex memory tracing
3702 @cindex breakpoint on memory address
3703 @cindex breakpoint on variable modification
3704 A @dfn{watchpoint} is a special breakpoint that stops your program
3705 when the value of an expression changes. The expression may be a value
3706 of a variable, or it could involve values of one or more variables
3707 combined by operators, such as @samp{a + b}. This is sometimes called
3708 @dfn{data breakpoints}. You must use a different command to set
3709 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3710 from that, you can manage a watchpoint like any other breakpoint: you
3711 enable, disable, and delete both breakpoints and watchpoints using the
3714 You can arrange to have values from your program displayed automatically
3715 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3719 @cindex breakpoint on events
3720 A @dfn{catchpoint} is another special breakpoint that stops your program
3721 when a certain kind of event occurs, such as the throwing of a C@t{++}
3722 exception or the loading of a library. As with watchpoints, you use a
3723 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3724 Catchpoints}), but aside from that, you can manage a catchpoint like any
3725 other breakpoint. (To stop when your program receives a signal, use the
3726 @code{handle} command; see @ref{Signals, ,Signals}.)
3728 @cindex breakpoint numbers
3729 @cindex numbers for breakpoints
3730 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3731 catchpoint when you create it; these numbers are successive integers
3732 starting with one. In many of the commands for controlling various
3733 features of breakpoints you use the breakpoint number to say which
3734 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3735 @dfn{disabled}; if disabled, it has no effect on your program until you
3738 @cindex breakpoint ranges
3739 @cindex breakpoint lists
3740 @cindex ranges of breakpoints
3741 @cindex lists of breakpoints
3742 Some @value{GDBN} commands accept a space-separated list of breakpoints
3743 on which to operate. A list element can be either a single breakpoint number,
3744 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3745 When a breakpoint list is given to a command, all breakpoints in that list
3749 * Set Breaks:: Setting breakpoints
3750 * Set Watchpoints:: Setting watchpoints
3751 * Set Catchpoints:: Setting catchpoints
3752 * Delete Breaks:: Deleting breakpoints
3753 * Disabling:: Disabling breakpoints
3754 * Conditions:: Break conditions
3755 * Break Commands:: Breakpoint command lists
3756 * Dynamic Printf:: Dynamic printf
3757 * Save Breakpoints:: How to save breakpoints in a file
3758 * Static Probe Points:: Listing static probe points
3759 * Error in Breakpoints:: ``Cannot insert breakpoints''
3760 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3764 @subsection Setting Breakpoints
3766 @c FIXME LMB what does GDB do if no code on line of breakpt?
3767 @c consider in particular declaration with/without initialization.
3769 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3772 @kindex b @r{(@code{break})}
3773 @vindex $bpnum@r{, convenience variable}
3774 @cindex latest breakpoint
3775 Breakpoints are set with the @code{break} command (abbreviated
3776 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3777 number of the breakpoint you've set most recently; see @ref{Convenience
3778 Vars,, Convenience Variables}, for a discussion of what you can do with
3779 convenience variables.
3782 @item break @var{location}
3783 Set a breakpoint at the given @var{location}, which can specify a
3784 function name, a line number, or an address of an instruction.
3785 (@xref{Specify Location}, for a list of all the possible ways to
3786 specify a @var{location}.) The breakpoint will stop your program just
3787 before it executes any of the code in the specified @var{location}.
3789 When using source languages that permit overloading of symbols, such as
3790 C@t{++}, a function name may refer to more than one possible place to break.
3791 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3794 It is also possible to insert a breakpoint that will stop the program
3795 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3796 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3799 When called without any arguments, @code{break} sets a breakpoint at
3800 the next instruction to be executed in the selected stack frame
3801 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3802 innermost, this makes your program stop as soon as control
3803 returns to that frame. This is similar to the effect of a
3804 @code{finish} command in the frame inside the selected frame---except
3805 that @code{finish} does not leave an active breakpoint. If you use
3806 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3807 the next time it reaches the current location; this may be useful
3810 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3811 least one instruction has been executed. If it did not do this, you
3812 would be unable to proceed past a breakpoint without first disabling the
3813 breakpoint. This rule applies whether or not the breakpoint already
3814 existed when your program stopped.
3816 @item break @dots{} if @var{cond}
3817 Set a breakpoint with condition @var{cond}; evaluate the expression
3818 @var{cond} each time the breakpoint is reached, and stop only if the
3819 value is nonzero---that is, if @var{cond} evaluates as true.
3820 @samp{@dots{}} stands for one of the possible arguments described
3821 above (or no argument) specifying where to break. @xref{Conditions,
3822 ,Break Conditions}, for more information on breakpoint conditions.
3825 @item tbreak @var{args}
3826 Set a breakpoint enabled only for one stop. The @var{args} are the
3827 same as for the @code{break} command, and the breakpoint is set in the same
3828 way, but the breakpoint is automatically deleted after the first time your
3829 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3832 @cindex hardware breakpoints
3833 @item hbreak @var{args}
3834 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3835 @code{break} command and the breakpoint is set in the same way, but the
3836 breakpoint requires hardware support and some target hardware may not
3837 have this support. The main purpose of this is EPROM/ROM code
3838 debugging, so you can set a breakpoint at an instruction without
3839 changing the instruction. This can be used with the new trap-generation
3840 provided by SPARClite DSU and most x86-based targets. These targets
3841 will generate traps when a program accesses some data or instruction
3842 address that is assigned to the debug registers. However the hardware
3843 breakpoint registers can take a limited number of breakpoints. For
3844 example, on the DSU, only two data breakpoints can be set at a time, and
3845 @value{GDBN} will reject this command if more than two are used. Delete
3846 or disable unused hardware breakpoints before setting new ones
3847 (@pxref{Disabling, ,Disabling Breakpoints}).
3848 @xref{Conditions, ,Break Conditions}.
3849 For remote targets, you can restrict the number of hardware
3850 breakpoints @value{GDBN} will use, see @ref{set remote
3851 hardware-breakpoint-limit}.
3854 @item thbreak @var{args}
3855 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3856 are the same as for the @code{hbreak} command and the breakpoint is set in
3857 the same way. However, like the @code{tbreak} command,
3858 the breakpoint is automatically deleted after the
3859 first time your program stops there. Also, like the @code{hbreak}
3860 command, the breakpoint requires hardware support and some target hardware
3861 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3862 See also @ref{Conditions, ,Break Conditions}.
3865 @cindex regular expression
3866 @cindex breakpoints at functions matching a regexp
3867 @cindex set breakpoints in many functions
3868 @item rbreak @var{regex}
3869 Set breakpoints on all functions matching the regular expression
3870 @var{regex}. This command sets an unconditional breakpoint on all
3871 matches, printing a list of all breakpoints it set. Once these
3872 breakpoints are set, they are treated just like the breakpoints set with
3873 the @code{break} command. You can delete them, disable them, or make
3874 them conditional the same way as any other breakpoint.
3876 In programs using different languages, @value{GDBN} chooses the syntax
3877 to print the list of all breakpoints it sets according to the
3878 @samp{set language} value: using @samp{set language auto}
3879 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3880 language of the breakpoint's function, other values mean to use
3881 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3883 The syntax of the regular expression is the standard one used with tools
3884 like @file{grep}. Note that this is different from the syntax used by
3885 shells, so for instance @code{foo*} matches all functions that include
3886 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3887 @code{.*} leading and trailing the regular expression you supply, so to
3888 match only functions that begin with @code{foo}, use @code{^foo}.
3890 @cindex non-member C@t{++} functions, set breakpoint in
3891 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3892 breakpoints on overloaded functions that are not members of any special
3895 @cindex set breakpoints on all functions
3896 The @code{rbreak} command can be used to set breakpoints in
3897 @strong{all} the functions in a program, like this:
3900 (@value{GDBP}) rbreak .
3903 @item rbreak @var{file}:@var{regex}
3904 If @code{rbreak} is called with a filename qualification, it limits
3905 the search for functions matching the given regular expression to the
3906 specified @var{file}. This can be used, for example, to set breakpoints on
3907 every function in a given file:
3910 (@value{GDBP}) rbreak file.c:.
3913 The colon separating the filename qualifier from the regex may
3914 optionally be surrounded by spaces.
3916 @kindex info breakpoints
3917 @cindex @code{$_} and @code{info breakpoints}
3918 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3919 @itemx info break @r{[}@var{list}@dots{}@r{]}
3920 Print a table of all breakpoints, watchpoints, and catchpoints set and
3921 not deleted. Optional argument @var{n} means print information only
3922 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3923 For each breakpoint, following columns are printed:
3926 @item Breakpoint Numbers
3928 Breakpoint, watchpoint, or catchpoint.
3930 Whether the breakpoint is marked to be disabled or deleted when hit.
3931 @item Enabled or Disabled
3932 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3933 that are not enabled.
3935 Where the breakpoint is in your program, as a memory address. For a
3936 pending breakpoint whose address is not yet known, this field will
3937 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3938 library that has the symbol or line referred by breakpoint is loaded.
3939 See below for details. A breakpoint with several locations will
3940 have @samp{<MULTIPLE>} in this field---see below for details.
3942 Where the breakpoint is in the source for your program, as a file and
3943 line number. For a pending breakpoint, the original string passed to
3944 the breakpoint command will be listed as it cannot be resolved until
3945 the appropriate shared library is loaded in the future.
3949 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3950 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3951 @value{GDBN} on the host's side. If it is ``target'', then the condition
3952 is evaluated by the target. The @code{info break} command shows
3953 the condition on the line following the affected breakpoint, together with
3954 its condition evaluation mode in between parentheses.
3956 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3957 allowed to have a condition specified for it. The condition is not parsed for
3958 validity until a shared library is loaded that allows the pending
3959 breakpoint to resolve to a valid location.
3962 @code{info break} with a breakpoint
3963 number @var{n} as argument lists only that breakpoint. The
3964 convenience variable @code{$_} and the default examining-address for
3965 the @code{x} command are set to the address of the last breakpoint
3966 listed (@pxref{Memory, ,Examining Memory}).
3969 @code{info break} displays a count of the number of times the breakpoint
3970 has been hit. This is especially useful in conjunction with the
3971 @code{ignore} command. You can ignore a large number of breakpoint
3972 hits, look at the breakpoint info to see how many times the breakpoint
3973 was hit, and then run again, ignoring one less than that number. This
3974 will get you quickly to the last hit of that breakpoint.
3977 For a breakpoints with an enable count (xref) greater than 1,
3978 @code{info break} also displays that count.
3982 @value{GDBN} allows you to set any number of breakpoints at the same place in
3983 your program. There is nothing silly or meaningless about this. When
3984 the breakpoints are conditional, this is even useful
3985 (@pxref{Conditions, ,Break Conditions}).
3987 @cindex multiple locations, breakpoints
3988 @cindex breakpoints, multiple locations
3989 It is possible that a breakpoint corresponds to several locations
3990 in your program. Examples of this situation are:
3994 Multiple functions in the program may have the same name.
3997 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3998 instances of the function body, used in different cases.
4001 For a C@t{++} template function, a given line in the function can
4002 correspond to any number of instantiations.
4005 For an inlined function, a given source line can correspond to
4006 several places where that function is inlined.
4009 In all those cases, @value{GDBN} will insert a breakpoint at all
4010 the relevant locations.
4012 A breakpoint with multiple locations is displayed in the breakpoint
4013 table using several rows---one header row, followed by one row for
4014 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4015 address column. The rows for individual locations contain the actual
4016 addresses for locations, and show the functions to which those
4017 locations belong. The number column for a location is of the form
4018 @var{breakpoint-number}.@var{location-number}.
4023 Num Type Disp Enb Address What
4024 1 breakpoint keep y <MULTIPLE>
4026 breakpoint already hit 1 time
4027 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4028 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4031 You cannot delete the individual locations from a breakpoint. However,
4032 each location can be individually enabled or disabled by passing
4033 @var{breakpoint-number}.@var{location-number} as argument to the
4034 @code{enable} and @code{disable} commands. It's also possible to
4035 @code{enable} and @code{disable} a range of @var{location-number}
4036 locations using a @var{breakpoint-number} and two @var{location-number}s,
4037 in increasing order, separated by a hyphen, like
4038 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4039 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4040 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4041 all of the locations that belong to that breakpoint.
4043 @cindex pending breakpoints
4044 It's quite common to have a breakpoint inside a shared library.
4045 Shared libraries can be loaded and unloaded explicitly,
4046 and possibly repeatedly, as the program is executed. To support
4047 this use case, @value{GDBN} updates breakpoint locations whenever
4048 any shared library is loaded or unloaded. Typically, you would
4049 set a breakpoint in a shared library at the beginning of your
4050 debugging session, when the library is not loaded, and when the
4051 symbols from the library are not available. When you try to set
4052 breakpoint, @value{GDBN} will ask you if you want to set
4053 a so called @dfn{pending breakpoint}---breakpoint whose address
4054 is not yet resolved.
4056 After the program is run, whenever a new shared library is loaded,
4057 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4058 shared library contains the symbol or line referred to by some
4059 pending breakpoint, that breakpoint is resolved and becomes an
4060 ordinary breakpoint. When a library is unloaded, all breakpoints
4061 that refer to its symbols or source lines become pending again.
4063 This logic works for breakpoints with multiple locations, too. For
4064 example, if you have a breakpoint in a C@t{++} template function, and
4065 a newly loaded shared library has an instantiation of that template,
4066 a new location is added to the list of locations for the breakpoint.
4068 Except for having unresolved address, pending breakpoints do not
4069 differ from regular breakpoints. You can set conditions or commands,
4070 enable and disable them and perform other breakpoint operations.
4072 @value{GDBN} provides some additional commands for controlling what
4073 happens when the @samp{break} command cannot resolve breakpoint
4074 address specification to an address:
4076 @kindex set breakpoint pending
4077 @kindex show breakpoint pending
4079 @item set breakpoint pending auto
4080 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4081 location, it queries you whether a pending breakpoint should be created.
4083 @item set breakpoint pending on
4084 This indicates that an unrecognized breakpoint location should automatically
4085 result in a pending breakpoint being created.
4087 @item set breakpoint pending off
4088 This indicates that pending breakpoints are not to be created. Any
4089 unrecognized breakpoint location results in an error. This setting does
4090 not affect any pending breakpoints previously created.
4092 @item show breakpoint pending
4093 Show the current behavior setting for creating pending breakpoints.
4096 The settings above only affect the @code{break} command and its
4097 variants. Once breakpoint is set, it will be automatically updated
4098 as shared libraries are loaded and unloaded.
4100 @cindex automatic hardware breakpoints
4101 For some targets, @value{GDBN} can automatically decide if hardware or
4102 software breakpoints should be used, depending on whether the
4103 breakpoint address is read-only or read-write. This applies to
4104 breakpoints set with the @code{break} command as well as to internal
4105 breakpoints set by commands like @code{next} and @code{finish}. For
4106 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4109 You can control this automatic behaviour with the following commands:
4111 @kindex set breakpoint auto-hw
4112 @kindex show breakpoint auto-hw
4114 @item set breakpoint auto-hw on
4115 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4116 will try to use the target memory map to decide if software or hardware
4117 breakpoint must be used.
4119 @item set breakpoint auto-hw off
4120 This indicates @value{GDBN} should not automatically select breakpoint
4121 type. If the target provides a memory map, @value{GDBN} will warn when
4122 trying to set software breakpoint at a read-only address.
4125 @value{GDBN} normally implements breakpoints by replacing the program code
4126 at the breakpoint address with a special instruction, which, when
4127 executed, given control to the debugger. By default, the program
4128 code is so modified only when the program is resumed. As soon as
4129 the program stops, @value{GDBN} restores the original instructions. This
4130 behaviour guards against leaving breakpoints inserted in the
4131 target should gdb abrubptly disconnect. However, with slow remote
4132 targets, inserting and removing breakpoint can reduce the performance.
4133 This behavior can be controlled with the following commands::
4135 @kindex set breakpoint always-inserted
4136 @kindex show breakpoint always-inserted
4138 @item set breakpoint always-inserted off
4139 All breakpoints, including newly added by the user, are inserted in
4140 the target only when the target is resumed. All breakpoints are
4141 removed from the target when it stops. This is the default mode.
4143 @item set breakpoint always-inserted on
4144 Causes all breakpoints to be inserted in the target at all times. If
4145 the user adds a new breakpoint, or changes an existing breakpoint, the
4146 breakpoints in the target are updated immediately. A breakpoint is
4147 removed from the target only when breakpoint itself is deleted.
4150 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4151 when a breakpoint breaks. If the condition is true, then the process being
4152 debugged stops, otherwise the process is resumed.
4154 If the target supports evaluating conditions on its end, @value{GDBN} may
4155 download the breakpoint, together with its conditions, to it.
4157 This feature can be controlled via the following commands:
4159 @kindex set breakpoint condition-evaluation
4160 @kindex show breakpoint condition-evaluation
4162 @item set breakpoint condition-evaluation host
4163 This option commands @value{GDBN} to evaluate the breakpoint
4164 conditions on the host's side. Unconditional breakpoints are sent to
4165 the target which in turn receives the triggers and reports them back to GDB
4166 for condition evaluation. This is the standard evaluation mode.
4168 @item set breakpoint condition-evaluation target
4169 This option commands @value{GDBN} to download breakpoint conditions
4170 to the target at the moment of their insertion. The target
4171 is responsible for evaluating the conditional expression and reporting
4172 breakpoint stop events back to @value{GDBN} whenever the condition
4173 is true. Due to limitations of target-side evaluation, some conditions
4174 cannot be evaluated there, e.g., conditions that depend on local data
4175 that is only known to the host. Examples include
4176 conditional expressions involving convenience variables, complex types
4177 that cannot be handled by the agent expression parser and expressions
4178 that are too long to be sent over to the target, specially when the
4179 target is a remote system. In these cases, the conditions will be
4180 evaluated by @value{GDBN}.
4182 @item set breakpoint condition-evaluation auto
4183 This is the default mode. If the target supports evaluating breakpoint
4184 conditions on its end, @value{GDBN} will download breakpoint conditions to
4185 the target (limitations mentioned previously apply). If the target does
4186 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4187 to evaluating all these conditions on the host's side.
4191 @cindex negative breakpoint numbers
4192 @cindex internal @value{GDBN} breakpoints
4193 @value{GDBN} itself sometimes sets breakpoints in your program for
4194 special purposes, such as proper handling of @code{longjmp} (in C
4195 programs). These internal breakpoints are assigned negative numbers,
4196 starting with @code{-1}; @samp{info breakpoints} does not display them.
4197 You can see these breakpoints with the @value{GDBN} maintenance command
4198 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4201 @node Set Watchpoints
4202 @subsection Setting Watchpoints
4204 @cindex setting watchpoints
4205 You can use a watchpoint to stop execution whenever the value of an
4206 expression changes, without having to predict a particular place where
4207 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4208 The expression may be as simple as the value of a single variable, or
4209 as complex as many variables combined by operators. Examples include:
4213 A reference to the value of a single variable.
4216 An address cast to an appropriate data type. For example,
4217 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4218 address (assuming an @code{int} occupies 4 bytes).
4221 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4222 expression can use any operators valid in the program's native
4223 language (@pxref{Languages}).
4226 You can set a watchpoint on an expression even if the expression can
4227 not be evaluated yet. For instance, you can set a watchpoint on
4228 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4229 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4230 the expression produces a valid value. If the expression becomes
4231 valid in some other way than changing a variable (e.g.@: if the memory
4232 pointed to by @samp{*global_ptr} becomes readable as the result of a
4233 @code{malloc} call), @value{GDBN} may not stop until the next time
4234 the expression changes.
4236 @cindex software watchpoints
4237 @cindex hardware watchpoints
4238 Depending on your system, watchpoints may be implemented in software or
4239 hardware. @value{GDBN} does software watchpointing by single-stepping your
4240 program and testing the variable's value each time, which is hundreds of
4241 times slower than normal execution. (But this may still be worth it, to
4242 catch errors where you have no clue what part of your program is the
4245 On some systems, such as most PowerPC or x86-based targets,
4246 @value{GDBN} includes support for hardware watchpoints, which do not
4247 slow down the running of your program.
4251 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4252 Set a watchpoint for an expression. @value{GDBN} will break when the
4253 expression @var{expr} is written into by the program and its value
4254 changes. The simplest (and the most popular) use of this command is
4255 to watch the value of a single variable:
4258 (@value{GDBP}) watch foo
4261 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4262 argument, @value{GDBN} breaks only when the thread identified by
4263 @var{thread-id} changes the value of @var{expr}. If any other threads
4264 change the value of @var{expr}, @value{GDBN} will not break. Note
4265 that watchpoints restricted to a single thread in this way only work
4266 with Hardware Watchpoints.
4268 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4269 (see below). The @code{-location} argument tells @value{GDBN} to
4270 instead watch the memory referred to by @var{expr}. In this case,
4271 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4272 and watch the memory at that address. The type of the result is used
4273 to determine the size of the watched memory. If the expression's
4274 result does not have an address, then @value{GDBN} will print an
4277 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4278 of masked watchpoints, if the current architecture supports this
4279 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4280 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4281 to an address to watch. The mask specifies that some bits of an address
4282 (the bits which are reset in the mask) should be ignored when matching
4283 the address accessed by the inferior against the watchpoint address.
4284 Thus, a masked watchpoint watches many addresses simultaneously---those
4285 addresses whose unmasked bits are identical to the unmasked bits in the
4286 watchpoint address. The @code{mask} argument implies @code{-location}.
4290 (@value{GDBP}) watch foo mask 0xffff00ff
4291 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4295 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4296 Set a watchpoint that will break when the value of @var{expr} is read
4300 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4301 Set a watchpoint that will break when @var{expr} is either read from
4302 or written into by the program.
4304 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4305 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4306 This command prints a list of watchpoints, using the same format as
4307 @code{info break} (@pxref{Set Breaks}).
4310 If you watch for a change in a numerically entered address you need to
4311 dereference it, as the address itself is just a constant number which will
4312 never change. @value{GDBN} refuses to create a watchpoint that watches
4313 a never-changing value:
4316 (@value{GDBP}) watch 0x600850
4317 Cannot watch constant value 0x600850.
4318 (@value{GDBP}) watch *(int *) 0x600850
4319 Watchpoint 1: *(int *) 6293584
4322 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4323 watchpoints execute very quickly, and the debugger reports a change in
4324 value at the exact instruction where the change occurs. If @value{GDBN}
4325 cannot set a hardware watchpoint, it sets a software watchpoint, which
4326 executes more slowly and reports the change in value at the next
4327 @emph{statement}, not the instruction, after the change occurs.
4329 @cindex use only software watchpoints
4330 You can force @value{GDBN} to use only software watchpoints with the
4331 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4332 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4333 the underlying system supports them. (Note that hardware-assisted
4334 watchpoints that were set @emph{before} setting
4335 @code{can-use-hw-watchpoints} to zero will still use the hardware
4336 mechanism of watching expression values.)
4339 @item set can-use-hw-watchpoints
4340 @kindex set can-use-hw-watchpoints
4341 Set whether or not to use hardware watchpoints.
4343 @item show can-use-hw-watchpoints
4344 @kindex show can-use-hw-watchpoints
4345 Show the current mode of using hardware watchpoints.
4348 For remote targets, you can restrict the number of hardware
4349 watchpoints @value{GDBN} will use, see @ref{set remote
4350 hardware-breakpoint-limit}.
4352 When you issue the @code{watch} command, @value{GDBN} reports
4355 Hardware watchpoint @var{num}: @var{expr}
4359 if it was able to set a hardware watchpoint.
4361 Currently, the @code{awatch} and @code{rwatch} commands can only set
4362 hardware watchpoints, because accesses to data that don't change the
4363 value of the watched expression cannot be detected without examining
4364 every instruction as it is being executed, and @value{GDBN} does not do
4365 that currently. If @value{GDBN} finds that it is unable to set a
4366 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4367 will print a message like this:
4370 Expression cannot be implemented with read/access watchpoint.
4373 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4374 data type of the watched expression is wider than what a hardware
4375 watchpoint on the target machine can handle. For example, some systems
4376 can only watch regions that are up to 4 bytes wide; on such systems you
4377 cannot set hardware watchpoints for an expression that yields a
4378 double-precision floating-point number (which is typically 8 bytes
4379 wide). As a work-around, it might be possible to break the large region
4380 into a series of smaller ones and watch them with separate watchpoints.
4382 If you set too many hardware watchpoints, @value{GDBN} might be unable
4383 to insert all of them when you resume the execution of your program.
4384 Since the precise number of active watchpoints is unknown until such
4385 time as the program is about to be resumed, @value{GDBN} might not be
4386 able to warn you about this when you set the watchpoints, and the
4387 warning will be printed only when the program is resumed:
4390 Hardware watchpoint @var{num}: Could not insert watchpoint
4394 If this happens, delete or disable some of the watchpoints.
4396 Watching complex expressions that reference many variables can also
4397 exhaust the resources available for hardware-assisted watchpoints.
4398 That's because @value{GDBN} needs to watch every variable in the
4399 expression with separately allocated resources.
4401 If you call a function interactively using @code{print} or @code{call},
4402 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4403 kind of breakpoint or the call completes.
4405 @value{GDBN} automatically deletes watchpoints that watch local
4406 (automatic) variables, or expressions that involve such variables, when
4407 they go out of scope, that is, when the execution leaves the block in
4408 which these variables were defined. In particular, when the program
4409 being debugged terminates, @emph{all} local variables go out of scope,
4410 and so only watchpoints that watch global variables remain set. If you
4411 rerun the program, you will need to set all such watchpoints again. One
4412 way of doing that would be to set a code breakpoint at the entry to the
4413 @code{main} function and when it breaks, set all the watchpoints.
4415 @cindex watchpoints and threads
4416 @cindex threads and watchpoints
4417 In multi-threaded programs, watchpoints will detect changes to the
4418 watched expression from every thread.
4421 @emph{Warning:} In multi-threaded programs, software watchpoints
4422 have only limited usefulness. If @value{GDBN} creates a software
4423 watchpoint, it can only watch the value of an expression @emph{in a
4424 single thread}. If you are confident that the expression can only
4425 change due to the current thread's activity (and if you are also
4426 confident that no other thread can become current), then you can use
4427 software watchpoints as usual. However, @value{GDBN} may not notice
4428 when a non-current thread's activity changes the expression. (Hardware
4429 watchpoints, in contrast, watch an expression in all threads.)
4432 @xref{set remote hardware-watchpoint-limit}.
4434 @node Set Catchpoints
4435 @subsection Setting Catchpoints
4436 @cindex catchpoints, setting
4437 @cindex exception handlers
4438 @cindex event handling
4440 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4441 kinds of program events, such as C@t{++} exceptions or the loading of a
4442 shared library. Use the @code{catch} command to set a catchpoint.
4446 @item catch @var{event}
4447 Stop when @var{event} occurs. The @var{event} can be any of the following:
4450 @item throw @r{[}@var{regexp}@r{]}
4451 @itemx rethrow @r{[}@var{regexp}@r{]}
4452 @itemx catch @r{[}@var{regexp}@r{]}
4454 @kindex catch rethrow
4456 @cindex stop on C@t{++} exceptions
4457 The throwing, re-throwing, or catching of a C@t{++} exception.
4459 If @var{regexp} is given, then only exceptions whose type matches the
4460 regular expression will be caught.
4462 @vindex $_exception@r{, convenience variable}
4463 The convenience variable @code{$_exception} is available at an
4464 exception-related catchpoint, on some systems. This holds the
4465 exception being thrown.
4467 There are currently some limitations to C@t{++} exception handling in
4472 The support for these commands is system-dependent. Currently, only
4473 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4477 The regular expression feature and the @code{$_exception} convenience
4478 variable rely on the presence of some SDT probes in @code{libstdc++}.
4479 If these probes are not present, then these features cannot be used.
4480 These probes were first available in the GCC 4.8 release, but whether
4481 or not they are available in your GCC also depends on how it was
4485 The @code{$_exception} convenience variable is only valid at the
4486 instruction at which an exception-related catchpoint is set.
4489 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4490 location in the system library which implements runtime exception
4491 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4492 (@pxref{Selection}) to get to your code.
4495 If you call a function interactively, @value{GDBN} normally returns
4496 control to you when the function has finished executing. If the call
4497 raises an exception, however, the call may bypass the mechanism that
4498 returns control to you and cause your program either to abort or to
4499 simply continue running until it hits a breakpoint, catches a signal
4500 that @value{GDBN} is listening for, or exits. This is the case even if
4501 you set a catchpoint for the exception; catchpoints on exceptions are
4502 disabled within interactive calls. @xref{Calling}, for information on
4503 controlling this with @code{set unwind-on-terminating-exception}.
4506 You cannot raise an exception interactively.
4509 You cannot install an exception handler interactively.
4513 @kindex catch exception
4514 @cindex Ada exception catching
4515 @cindex catch Ada exceptions
4516 An Ada exception being raised. If an exception name is specified
4517 at the end of the command (eg @code{catch exception Program_Error}),
4518 the debugger will stop only when this specific exception is raised.
4519 Otherwise, the debugger stops execution when any Ada exception is raised.
4521 When inserting an exception catchpoint on a user-defined exception whose
4522 name is identical to one of the exceptions defined by the language, the
4523 fully qualified name must be used as the exception name. Otherwise,
4524 @value{GDBN} will assume that it should stop on the pre-defined exception
4525 rather than the user-defined one. For instance, assuming an exception
4526 called @code{Constraint_Error} is defined in package @code{Pck}, then
4527 the command to use to catch such exceptions is @kbd{catch exception
4528 Pck.Constraint_Error}.
4531 @kindex catch handlers
4532 @cindex Ada exception handlers catching
4533 @cindex catch Ada exceptions when handled
4534 An Ada exception being handled. If an exception name is
4535 specified at the end of the command
4536 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4537 only when this specific exception is handled.
4538 Otherwise, the debugger stops execution when any Ada exception is handled.
4540 When inserting a handlers catchpoint on a user-defined
4541 exception whose name is identical to one of the exceptions
4542 defined by the language, the fully qualified name must be used
4543 as the exception name. Otherwise, @value{GDBN} will assume that it
4544 should stop on the pre-defined exception rather than the
4545 user-defined one. For instance, assuming an exception called
4546 @code{Constraint_Error} is defined in package @code{Pck}, then the
4547 command to use to catch such exceptions handling is
4548 @kbd{catch handlers Pck.Constraint_Error}.
4550 @item exception unhandled
4551 @kindex catch exception unhandled
4552 An exception that was raised but is not handled by the program.
4555 @kindex catch assert
4556 A failed Ada assertion.
4560 @cindex break on fork/exec
4561 A call to @code{exec}.
4563 @anchor{catch syscall}
4565 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4566 @kindex catch syscall
4567 @cindex break on a system call.
4568 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4569 syscall is a mechanism for application programs to request a service
4570 from the operating system (OS) or one of the OS system services.
4571 @value{GDBN} can catch some or all of the syscalls issued by the
4572 debuggee, and show the related information for each syscall. If no
4573 argument is specified, calls to and returns from all system calls
4576 @var{name} can be any system call name that is valid for the
4577 underlying OS. Just what syscalls are valid depends on the OS. On
4578 GNU and Unix systems, you can find the full list of valid syscall
4579 names on @file{/usr/include/asm/unistd.h}.
4581 @c For MS-Windows, the syscall names and the corresponding numbers
4582 @c can be found, e.g., on this URL:
4583 @c http://www.metasploit.com/users/opcode/syscalls.html
4584 @c but we don't support Windows syscalls yet.
4586 Normally, @value{GDBN} knows in advance which syscalls are valid for
4587 each OS, so you can use the @value{GDBN} command-line completion
4588 facilities (@pxref{Completion,, command completion}) to list the
4591 You may also specify the system call numerically. A syscall's
4592 number is the value passed to the OS's syscall dispatcher to
4593 identify the requested service. When you specify the syscall by its
4594 name, @value{GDBN} uses its database of syscalls to convert the name
4595 into the corresponding numeric code, but using the number directly
4596 may be useful if @value{GDBN}'s database does not have the complete
4597 list of syscalls on your system (e.g., because @value{GDBN} lags
4598 behind the OS upgrades).
4600 You may specify a group of related syscalls to be caught at once using
4601 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4602 instance, on some platforms @value{GDBN} allows you to catch all
4603 network related syscalls, by passing the argument @code{group:network}
4604 to @code{catch syscall}. Note that not all syscall groups are
4605 available in every system. You can use the command completion
4606 facilities (@pxref{Completion,, command completion}) to list the
4607 syscall groups available on your environment.
4609 The example below illustrates how this command works if you don't provide
4613 (@value{GDBP}) catch syscall
4614 Catchpoint 1 (syscall)
4616 Starting program: /tmp/catch-syscall
4618 Catchpoint 1 (call to syscall 'close'), \
4619 0xffffe424 in __kernel_vsyscall ()
4623 Catchpoint 1 (returned from syscall 'close'), \
4624 0xffffe424 in __kernel_vsyscall ()
4628 Here is an example of catching a system call by name:
4631 (@value{GDBP}) catch syscall chroot
4632 Catchpoint 1 (syscall 'chroot' [61])
4634 Starting program: /tmp/catch-syscall
4636 Catchpoint 1 (call to syscall 'chroot'), \
4637 0xffffe424 in __kernel_vsyscall ()
4641 Catchpoint 1 (returned from syscall 'chroot'), \
4642 0xffffe424 in __kernel_vsyscall ()
4646 An example of specifying a system call numerically. In the case
4647 below, the syscall number has a corresponding entry in the XML
4648 file, so @value{GDBN} finds its name and prints it:
4651 (@value{GDBP}) catch syscall 252
4652 Catchpoint 1 (syscall(s) 'exit_group')
4654 Starting program: /tmp/catch-syscall
4656 Catchpoint 1 (call to syscall 'exit_group'), \
4657 0xffffe424 in __kernel_vsyscall ()
4661 Program exited normally.
4665 Here is an example of catching a syscall group:
4668 (@value{GDBP}) catch syscall group:process
4669 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4670 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4671 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4673 Starting program: /tmp/catch-syscall
4675 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4676 from /lib64/ld-linux-x86-64.so.2
4682 However, there can be situations when there is no corresponding name
4683 in XML file for that syscall number. In this case, @value{GDBN} prints
4684 a warning message saying that it was not able to find the syscall name,
4685 but the catchpoint will be set anyway. See the example below:
4688 (@value{GDBP}) catch syscall 764
4689 warning: The number '764' does not represent a known syscall.
4690 Catchpoint 2 (syscall 764)
4694 If you configure @value{GDBN} using the @samp{--without-expat} option,
4695 it will not be able to display syscall names. Also, if your
4696 architecture does not have an XML file describing its system calls,
4697 you will not be able to see the syscall names. It is important to
4698 notice that these two features are used for accessing the syscall
4699 name database. In either case, you will see a warning like this:
4702 (@value{GDBP}) catch syscall
4703 warning: Could not open "syscalls/i386-linux.xml"
4704 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4705 GDB will not be able to display syscall names.
4706 Catchpoint 1 (syscall)
4710 Of course, the file name will change depending on your architecture and system.
4712 Still using the example above, you can also try to catch a syscall by its
4713 number. In this case, you would see something like:
4716 (@value{GDBP}) catch syscall 252
4717 Catchpoint 1 (syscall(s) 252)
4720 Again, in this case @value{GDBN} would not be able to display syscall's names.
4724 A call to @code{fork}.
4728 A call to @code{vfork}.
4730 @item load @r{[}regexp@r{]}
4731 @itemx unload @r{[}regexp@r{]}
4733 @kindex catch unload
4734 The loading or unloading of a shared library. If @var{regexp} is
4735 given, then the catchpoint will stop only if the regular expression
4736 matches one of the affected libraries.
4738 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4739 @kindex catch signal
4740 The delivery of a signal.
4742 With no arguments, this catchpoint will catch any signal that is not
4743 used internally by @value{GDBN}, specifically, all signals except
4744 @samp{SIGTRAP} and @samp{SIGINT}.
4746 With the argument @samp{all}, all signals, including those used by
4747 @value{GDBN}, will be caught. This argument cannot be used with other
4750 Otherwise, the arguments are a list of signal names as given to
4751 @code{handle} (@pxref{Signals}). Only signals specified in this list
4754 One reason that @code{catch signal} can be more useful than
4755 @code{handle} is that you can attach commands and conditions to the
4758 When a signal is caught by a catchpoint, the signal's @code{stop} and
4759 @code{print} settings, as specified by @code{handle}, are ignored.
4760 However, whether the signal is still delivered to the inferior depends
4761 on the @code{pass} setting; this can be changed in the catchpoint's
4766 @item tcatch @var{event}
4768 Set a catchpoint that is enabled only for one stop. The catchpoint is
4769 automatically deleted after the first time the event is caught.
4773 Use the @code{info break} command to list the current catchpoints.
4777 @subsection Deleting Breakpoints
4779 @cindex clearing breakpoints, watchpoints, catchpoints
4780 @cindex deleting breakpoints, watchpoints, catchpoints
4781 It is often necessary to eliminate a breakpoint, watchpoint, or
4782 catchpoint once it has done its job and you no longer want your program
4783 to stop there. This is called @dfn{deleting} the breakpoint. A
4784 breakpoint that has been deleted no longer exists; it is forgotten.
4786 With the @code{clear} command you can delete breakpoints according to
4787 where they are in your program. With the @code{delete} command you can
4788 delete individual breakpoints, watchpoints, or catchpoints by specifying
4789 their breakpoint numbers.
4791 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4792 automatically ignores breakpoints on the first instruction to be executed
4793 when you continue execution without changing the execution address.
4798 Delete any breakpoints at the next instruction to be executed in the
4799 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4800 the innermost frame is selected, this is a good way to delete a
4801 breakpoint where your program just stopped.
4803 @item clear @var{location}
4804 Delete any breakpoints set at the specified @var{location}.
4805 @xref{Specify Location}, for the various forms of @var{location}; the
4806 most useful ones are listed below:
4809 @item clear @var{function}
4810 @itemx clear @var{filename}:@var{function}
4811 Delete any breakpoints set at entry to the named @var{function}.
4813 @item clear @var{linenum}
4814 @itemx clear @var{filename}:@var{linenum}
4815 Delete any breakpoints set at or within the code of the specified
4816 @var{linenum} of the specified @var{filename}.
4819 @cindex delete breakpoints
4821 @kindex d @r{(@code{delete})}
4822 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4823 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4824 list specified as argument. If no argument is specified, delete all
4825 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4826 confirm off}). You can abbreviate this command as @code{d}.
4830 @subsection Disabling Breakpoints
4832 @cindex enable/disable a breakpoint
4833 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4834 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4835 it had been deleted, but remembers the information on the breakpoint so
4836 that you can @dfn{enable} it again later.
4838 You disable and enable breakpoints, watchpoints, and catchpoints with
4839 the @code{enable} and @code{disable} commands, optionally specifying
4840 one or more breakpoint numbers as arguments. Use @code{info break} to
4841 print a list of all breakpoints, watchpoints, and catchpoints if you
4842 do not know which numbers to use.
4844 Disabling and enabling a breakpoint that has multiple locations
4845 affects all of its locations.
4847 A breakpoint, watchpoint, or catchpoint can have any of several
4848 different states of enablement:
4852 Enabled. The breakpoint stops your program. A breakpoint set
4853 with the @code{break} command starts out in this state.
4855 Disabled. The breakpoint has no effect on your program.
4857 Enabled once. The breakpoint stops your program, but then becomes
4860 Enabled for a count. The breakpoint stops your program for the next
4861 N times, then becomes disabled.
4863 Enabled for deletion. The breakpoint stops your program, but
4864 immediately after it does so it is deleted permanently. A breakpoint
4865 set with the @code{tbreak} command starts out in this state.
4868 You can use the following commands to enable or disable breakpoints,
4869 watchpoints, and catchpoints:
4873 @kindex dis @r{(@code{disable})}
4874 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Disable the specified breakpoints---or all breakpoints, if none are
4876 listed. A disabled breakpoint has no effect but is not forgotten. All
4877 options such as ignore-counts, conditions and commands are remembered in
4878 case the breakpoint is enabled again later. You may abbreviate
4879 @code{disable} as @code{dis}.
4882 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4883 Enable the specified breakpoints (or all defined breakpoints). They
4884 become effective once again in stopping your program.
4886 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4887 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4888 of these breakpoints immediately after stopping your program.
4890 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4891 Enable the specified breakpoints temporarily. @value{GDBN} records
4892 @var{count} with each of the specified breakpoints, and decrements a
4893 breakpoint's count when it is hit. When any count reaches 0,
4894 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4895 count (@pxref{Conditions, ,Break Conditions}), that will be
4896 decremented to 0 before @var{count} is affected.
4898 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4899 Enable the specified breakpoints to work once, then die. @value{GDBN}
4900 deletes any of these breakpoints as soon as your program stops there.
4901 Breakpoints set by the @code{tbreak} command start out in this state.
4904 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4905 @c confusing: tbreak is also initially enabled.
4906 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4907 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4908 subsequently, they become disabled or enabled only when you use one of
4909 the commands above. (The command @code{until} can set and delete a
4910 breakpoint of its own, but it does not change the state of your other
4911 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4915 @subsection Break Conditions
4916 @cindex conditional breakpoints
4917 @cindex breakpoint conditions
4919 @c FIXME what is scope of break condition expr? Context where wanted?
4920 @c in particular for a watchpoint?
4921 The simplest sort of breakpoint breaks every time your program reaches a
4922 specified place. You can also specify a @dfn{condition} for a
4923 breakpoint. A condition is just a Boolean expression in your
4924 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4925 a condition evaluates the expression each time your program reaches it,
4926 and your program stops only if the condition is @emph{true}.
4928 This is the converse of using assertions for program validation; in that
4929 situation, you want to stop when the assertion is violated---that is,
4930 when the condition is false. In C, if you want to test an assertion expressed
4931 by the condition @var{assert}, you should set the condition
4932 @samp{! @var{assert}} on the appropriate breakpoint.
4934 Conditions are also accepted for watchpoints; you may not need them,
4935 since a watchpoint is inspecting the value of an expression anyhow---but
4936 it might be simpler, say, to just set a watchpoint on a variable name,
4937 and specify a condition that tests whether the new value is an interesting
4940 Break conditions can have side effects, and may even call functions in
4941 your program. This can be useful, for example, to activate functions
4942 that log program progress, or to use your own print functions to
4943 format special data structures. The effects are completely predictable
4944 unless there is another enabled breakpoint at the same address. (In
4945 that case, @value{GDBN} might see the other breakpoint first and stop your
4946 program without checking the condition of this one.) Note that
4947 breakpoint commands are usually more convenient and flexible than break
4949 purpose of performing side effects when a breakpoint is reached
4950 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4952 Breakpoint conditions can also be evaluated on the target's side if
4953 the target supports it. Instead of evaluating the conditions locally,
4954 @value{GDBN} encodes the expression into an agent expression
4955 (@pxref{Agent Expressions}) suitable for execution on the target,
4956 independently of @value{GDBN}. Global variables become raw memory
4957 locations, locals become stack accesses, and so forth.
4959 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4960 when its condition evaluates to true. This mechanism may provide faster
4961 response times depending on the performance characteristics of the target
4962 since it does not need to keep @value{GDBN} informed about
4963 every breakpoint trigger, even those with false conditions.
4965 Break conditions can be specified when a breakpoint is set, by using
4966 @samp{if} in the arguments to the @code{break} command. @xref{Set
4967 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4968 with the @code{condition} command.
4970 You can also use the @code{if} keyword with the @code{watch} command.
4971 The @code{catch} command does not recognize the @code{if} keyword;
4972 @code{condition} is the only way to impose a further condition on a
4977 @item condition @var{bnum} @var{expression}
4978 Specify @var{expression} as the break condition for breakpoint,
4979 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4980 breakpoint @var{bnum} stops your program only if the value of
4981 @var{expression} is true (nonzero, in C). When you use
4982 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4983 syntactic correctness, and to determine whether symbols in it have
4984 referents in the context of your breakpoint. If @var{expression} uses
4985 symbols not referenced in the context of the breakpoint, @value{GDBN}
4986 prints an error message:
4989 No symbol "foo" in current context.
4994 not actually evaluate @var{expression} at the time the @code{condition}
4995 command (or a command that sets a breakpoint with a condition, like
4996 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4998 @item condition @var{bnum}
4999 Remove the condition from breakpoint number @var{bnum}. It becomes
5000 an ordinary unconditional breakpoint.
5003 @cindex ignore count (of breakpoint)
5004 A special case of a breakpoint condition is to stop only when the
5005 breakpoint has been reached a certain number of times. This is so
5006 useful that there is a special way to do it, using the @dfn{ignore
5007 count} of the breakpoint. Every breakpoint has an ignore count, which
5008 is an integer. Most of the time, the ignore count is zero, and
5009 therefore has no effect. But if your program reaches a breakpoint whose
5010 ignore count is positive, then instead of stopping, it just decrements
5011 the ignore count by one and continues. As a result, if the ignore count
5012 value is @var{n}, the breakpoint does not stop the next @var{n} times
5013 your program reaches it.
5017 @item ignore @var{bnum} @var{count}
5018 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5019 The next @var{count} times the breakpoint is reached, your program's
5020 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5023 To make the breakpoint stop the next time it is reached, specify
5026 When you use @code{continue} to resume execution of your program from a
5027 breakpoint, you can specify an ignore count directly as an argument to
5028 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5029 Stepping,,Continuing and Stepping}.
5031 If a breakpoint has a positive ignore count and a condition, the
5032 condition is not checked. Once the ignore count reaches zero,
5033 @value{GDBN} resumes checking the condition.
5035 You could achieve the effect of the ignore count with a condition such
5036 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5037 is decremented each time. @xref{Convenience Vars, ,Convenience
5041 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5044 @node Break Commands
5045 @subsection Breakpoint Command Lists
5047 @cindex breakpoint commands
5048 You can give any breakpoint (or watchpoint or catchpoint) a series of
5049 commands to execute when your program stops due to that breakpoint. For
5050 example, you might want to print the values of certain expressions, or
5051 enable other breakpoints.
5055 @kindex end@r{ (breakpoint commands)}
5056 @item commands @r{[}@var{list}@dots{}@r{]}
5057 @itemx @dots{} @var{command-list} @dots{}
5059 Specify a list of commands for the given breakpoints. The commands
5060 themselves appear on the following lines. Type a line containing just
5061 @code{end} to terminate the commands.
5063 To remove all commands from a breakpoint, type @code{commands} and
5064 follow it immediately with @code{end}; that is, give no commands.
5066 With no argument, @code{commands} refers to the last breakpoint,
5067 watchpoint, or catchpoint set (not to the breakpoint most recently
5068 encountered). If the most recent breakpoints were set with a single
5069 command, then the @code{commands} will apply to all the breakpoints
5070 set by that command. This applies to breakpoints set by
5071 @code{rbreak}, and also applies when a single @code{break} command
5072 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5076 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5077 disabled within a @var{command-list}.
5079 You can use breakpoint commands to start your program up again. Simply
5080 use the @code{continue} command, or @code{step}, or any other command
5081 that resumes execution.
5083 Any other commands in the command list, after a command that resumes
5084 execution, are ignored. This is because any time you resume execution
5085 (even with a simple @code{next} or @code{step}), you may encounter
5086 another breakpoint---which could have its own command list, leading to
5087 ambiguities about which list to execute.
5090 If the first command you specify in a command list is @code{silent}, the
5091 usual message about stopping at a breakpoint is not printed. This may
5092 be desirable for breakpoints that are to print a specific message and
5093 then continue. If none of the remaining commands print anything, you
5094 see no sign that the breakpoint was reached. @code{silent} is
5095 meaningful only at the beginning of a breakpoint command list.
5097 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5098 print precisely controlled output, and are often useful in silent
5099 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5101 For example, here is how you could use breakpoint commands to print the
5102 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5108 printf "x is %d\n",x
5113 One application for breakpoint commands is to compensate for one bug so
5114 you can test for another. Put a breakpoint just after the erroneous line
5115 of code, give it a condition to detect the case in which something
5116 erroneous has been done, and give it commands to assign correct values
5117 to any variables that need them. End with the @code{continue} command
5118 so that your program does not stop, and start with the @code{silent}
5119 command so that no output is produced. Here is an example:
5130 @node Dynamic Printf
5131 @subsection Dynamic Printf
5133 @cindex dynamic printf
5135 The dynamic printf command @code{dprintf} combines a breakpoint with
5136 formatted printing of your program's data to give you the effect of
5137 inserting @code{printf} calls into your program on-the-fly, without
5138 having to recompile it.
5140 In its most basic form, the output goes to the GDB console. However,
5141 you can set the variable @code{dprintf-style} for alternate handling.
5142 For instance, you can ask to format the output by calling your
5143 program's @code{printf} function. This has the advantage that the
5144 characters go to the program's output device, so they can recorded in
5145 redirects to files and so forth.
5147 If you are doing remote debugging with a stub or agent, you can also
5148 ask to have the printf handled by the remote agent. In addition to
5149 ensuring that the output goes to the remote program's device along
5150 with any other output the program might produce, you can also ask that
5151 the dprintf remain active even after disconnecting from the remote
5152 target. Using the stub/agent is also more efficient, as it can do
5153 everything without needing to communicate with @value{GDBN}.
5157 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5158 Whenever execution reaches @var{location}, print the values of one or
5159 more @var{expressions} under the control of the string @var{template}.
5160 To print several values, separate them with commas.
5162 @item set dprintf-style @var{style}
5163 Set the dprintf output to be handled in one of several different
5164 styles enumerated below. A change of style affects all existing
5165 dynamic printfs immediately. (If you need individual control over the
5166 print commands, simply define normal breakpoints with
5167 explicitly-supplied command lists.)
5171 @kindex dprintf-style gdb
5172 Handle the output using the @value{GDBN} @code{printf} command.
5175 @kindex dprintf-style call
5176 Handle the output by calling a function in your program (normally
5180 @kindex dprintf-style agent
5181 Have the remote debugging agent (such as @code{gdbserver}) handle
5182 the output itself. This style is only available for agents that
5183 support running commands on the target.
5186 @item set dprintf-function @var{function}
5187 Set the function to call if the dprintf style is @code{call}. By
5188 default its value is @code{printf}. You may set it to any expression.
5189 that @value{GDBN} can evaluate to a function, as per the @code{call}
5192 @item set dprintf-channel @var{channel}
5193 Set a ``channel'' for dprintf. If set to a non-empty value,
5194 @value{GDBN} will evaluate it as an expression and pass the result as
5195 a first argument to the @code{dprintf-function}, in the manner of
5196 @code{fprintf} and similar functions. Otherwise, the dprintf format
5197 string will be the first argument, in the manner of @code{printf}.
5199 As an example, if you wanted @code{dprintf} output to go to a logfile
5200 that is a standard I/O stream assigned to the variable @code{mylog},
5201 you could do the following:
5204 (gdb) set dprintf-style call
5205 (gdb) set dprintf-function fprintf
5206 (gdb) set dprintf-channel mylog
5207 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5208 Dprintf 1 at 0x123456: file main.c, line 25.
5210 1 dprintf keep y 0x00123456 in main at main.c:25
5211 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5216 Note that the @code{info break} displays the dynamic printf commands
5217 as normal breakpoint commands; you can thus easily see the effect of
5218 the variable settings.
5220 @item set disconnected-dprintf on
5221 @itemx set disconnected-dprintf off
5222 @kindex set disconnected-dprintf
5223 Choose whether @code{dprintf} commands should continue to run if
5224 @value{GDBN} has disconnected from the target. This only applies
5225 if the @code{dprintf-style} is @code{agent}.
5227 @item show disconnected-dprintf off
5228 @kindex show disconnected-dprintf
5229 Show the current choice for disconnected @code{dprintf}.
5233 @value{GDBN} does not check the validity of function and channel,
5234 relying on you to supply values that are meaningful for the contexts
5235 in which they are being used. For instance, the function and channel
5236 may be the values of local variables, but if that is the case, then
5237 all enabled dynamic prints must be at locations within the scope of
5238 those locals. If evaluation fails, @value{GDBN} will report an error.
5240 @node Save Breakpoints
5241 @subsection How to save breakpoints to a file
5243 To save breakpoint definitions to a file use the @w{@code{save
5244 breakpoints}} command.
5247 @kindex save breakpoints
5248 @cindex save breakpoints to a file for future sessions
5249 @item save breakpoints [@var{filename}]
5250 This command saves all current breakpoint definitions together with
5251 their commands and ignore counts, into a file @file{@var{filename}}
5252 suitable for use in a later debugging session. This includes all
5253 types of breakpoints (breakpoints, watchpoints, catchpoints,
5254 tracepoints). To read the saved breakpoint definitions, use the
5255 @code{source} command (@pxref{Command Files}). Note that watchpoints
5256 with expressions involving local variables may fail to be recreated
5257 because it may not be possible to access the context where the
5258 watchpoint is valid anymore. Because the saved breakpoint definitions
5259 are simply a sequence of @value{GDBN} commands that recreate the
5260 breakpoints, you can edit the file in your favorite editing program,
5261 and remove the breakpoint definitions you're not interested in, or
5262 that can no longer be recreated.
5265 @node Static Probe Points
5266 @subsection Static Probe Points
5268 @cindex static probe point, SystemTap
5269 @cindex static probe point, DTrace
5270 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5271 for Statically Defined Tracing, and the probes are designed to have a tiny
5272 runtime code and data footprint, and no dynamic relocations.
5274 Currently, the following types of probes are supported on
5275 ELF-compatible systems:
5279 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5280 @acronym{SDT} probes@footnote{See
5281 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5282 for more information on how to add @code{SystemTap} @acronym{SDT}
5283 probes in your applications.}. @code{SystemTap} probes are usable
5284 from assembly, C and C@t{++} languages@footnote{See
5285 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5286 for a good reference on how the @acronym{SDT} probes are implemented.}.
5288 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5289 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5293 @cindex semaphores on static probe points
5294 Some @code{SystemTap} probes have an associated semaphore variable;
5295 for instance, this happens automatically if you defined your probe
5296 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5297 @value{GDBN} will automatically enable it when you specify a
5298 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5299 breakpoint at a probe's location by some other method (e.g.,
5300 @code{break file:line}), then @value{GDBN} will not automatically set
5301 the semaphore. @code{DTrace} probes do not support semaphores.
5303 You can examine the available static static probes using @code{info
5304 probes}, with optional arguments:
5308 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5309 If given, @var{type} is either @code{stap} for listing
5310 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5311 probes. If omitted all probes are listed regardless of their types.
5313 If given, @var{provider} is a regular expression used to match against provider
5314 names when selecting which probes to list. If omitted, probes by all
5315 probes from all providers are listed.
5317 If given, @var{name} is a regular expression to match against probe names
5318 when selecting which probes to list. If omitted, probe names are not
5319 considered when deciding whether to display them.
5321 If given, @var{objfile} is a regular expression used to select which
5322 object files (executable or shared libraries) to examine. If not
5323 given, all object files are considered.
5325 @item info probes all
5326 List the available static probes, from all types.
5329 @cindex enabling and disabling probes
5330 Some probe points can be enabled and/or disabled. The effect of
5331 enabling or disabling a probe depends on the type of probe being
5332 handled. Some @code{DTrace} probes can be enabled or
5333 disabled, but @code{SystemTap} probes cannot be disabled.
5335 You can enable (or disable) one or more probes using the following
5336 commands, with optional arguments:
5339 @kindex enable probes
5340 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5341 If given, @var{provider} is a regular expression used to match against
5342 provider names when selecting which probes to enable. If omitted,
5343 all probes from all providers are enabled.
5345 If given, @var{name} is a regular expression to match against probe
5346 names when selecting which probes to enable. If omitted, probe names
5347 are not considered when deciding whether to enable them.
5349 If given, @var{objfile} is a regular expression used to select which
5350 object files (executable or shared libraries) to examine. If not
5351 given, all object files are considered.
5353 @kindex disable probes
5354 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5355 See the @code{enable probes} command above for a description of the
5356 optional arguments accepted by this command.
5359 @vindex $_probe_arg@r{, convenience variable}
5360 A probe may specify up to twelve arguments. These are available at the
5361 point at which the probe is defined---that is, when the current PC is
5362 at the probe's location. The arguments are available using the
5363 convenience variables (@pxref{Convenience Vars})
5364 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5365 probes each probe argument is an integer of the appropriate size;
5366 types are not preserved. In @code{DTrace} probes types are preserved
5367 provided that they are recognized as such by @value{GDBN}; otherwise
5368 the value of the probe argument will be a long integer. The
5369 convenience variable @code{$_probe_argc} holds the number of arguments
5370 at the current probe point.
5372 These variables are always available, but attempts to access them at
5373 any location other than a probe point will cause @value{GDBN} to give
5377 @c @ifclear BARETARGET
5378 @node Error in Breakpoints
5379 @subsection ``Cannot insert breakpoints''
5381 If you request too many active hardware-assisted breakpoints and
5382 watchpoints, you will see this error message:
5384 @c FIXME: the precise wording of this message may change; the relevant
5385 @c source change is not committed yet (Sep 3, 1999).
5387 Stopped; cannot insert breakpoints.
5388 You may have requested too many hardware breakpoints and watchpoints.
5392 This message is printed when you attempt to resume the program, since
5393 only then @value{GDBN} knows exactly how many hardware breakpoints and
5394 watchpoints it needs to insert.
5396 When this message is printed, you need to disable or remove some of the
5397 hardware-assisted breakpoints and watchpoints, and then continue.
5399 @node Breakpoint-related Warnings
5400 @subsection ``Breakpoint address adjusted...''
5401 @cindex breakpoint address adjusted
5403 Some processor architectures place constraints on the addresses at
5404 which breakpoints may be placed. For architectures thus constrained,
5405 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5406 with the constraints dictated by the architecture.
5408 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5409 a VLIW architecture in which a number of RISC-like instructions may be
5410 bundled together for parallel execution. The FR-V architecture
5411 constrains the location of a breakpoint instruction within such a
5412 bundle to the instruction with the lowest address. @value{GDBN}
5413 honors this constraint by adjusting a breakpoint's address to the
5414 first in the bundle.
5416 It is not uncommon for optimized code to have bundles which contain
5417 instructions from different source statements, thus it may happen that
5418 a breakpoint's address will be adjusted from one source statement to
5419 another. Since this adjustment may significantly alter @value{GDBN}'s
5420 breakpoint related behavior from what the user expects, a warning is
5421 printed when the breakpoint is first set and also when the breakpoint
5424 A warning like the one below is printed when setting a breakpoint
5425 that's been subject to address adjustment:
5428 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5431 Such warnings are printed both for user settable and @value{GDBN}'s
5432 internal breakpoints. If you see one of these warnings, you should
5433 verify that a breakpoint set at the adjusted address will have the
5434 desired affect. If not, the breakpoint in question may be removed and
5435 other breakpoints may be set which will have the desired behavior.
5436 E.g., it may be sufficient to place the breakpoint at a later
5437 instruction. A conditional breakpoint may also be useful in some
5438 cases to prevent the breakpoint from triggering too often.
5440 @value{GDBN} will also issue a warning when stopping at one of these
5441 adjusted breakpoints:
5444 warning: Breakpoint 1 address previously adjusted from 0x00010414
5448 When this warning is encountered, it may be too late to take remedial
5449 action except in cases where the breakpoint is hit earlier or more
5450 frequently than expected.
5452 @node Continuing and Stepping
5453 @section Continuing and Stepping
5457 @cindex resuming execution
5458 @dfn{Continuing} means resuming program execution until your program
5459 completes normally. In contrast, @dfn{stepping} means executing just
5460 one more ``step'' of your program, where ``step'' may mean either one
5461 line of source code, or one machine instruction (depending on what
5462 particular command you use). Either when continuing or when stepping,
5463 your program may stop even sooner, due to a breakpoint or a signal. (If
5464 it stops due to a signal, you may want to use @code{handle}, or use
5465 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5466 or you may step into the signal's handler (@pxref{stepping and signal
5471 @kindex c @r{(@code{continue})}
5472 @kindex fg @r{(resume foreground execution)}
5473 @item continue @r{[}@var{ignore-count}@r{]}
5474 @itemx c @r{[}@var{ignore-count}@r{]}
5475 @itemx fg @r{[}@var{ignore-count}@r{]}
5476 Resume program execution, at the address where your program last stopped;
5477 any breakpoints set at that address are bypassed. The optional argument
5478 @var{ignore-count} allows you to specify a further number of times to
5479 ignore a breakpoint at this location; its effect is like that of
5480 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5482 The argument @var{ignore-count} is meaningful only when your program
5483 stopped due to a breakpoint. At other times, the argument to
5484 @code{continue} is ignored.
5486 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5487 debugged program is deemed to be the foreground program) are provided
5488 purely for convenience, and have exactly the same behavior as
5492 To resume execution at a different place, you can use @code{return}
5493 (@pxref{Returning, ,Returning from a Function}) to go back to the
5494 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5495 Different Address}) to go to an arbitrary location in your program.
5497 A typical technique for using stepping is to set a breakpoint
5498 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5499 beginning of the function or the section of your program where a problem
5500 is believed to lie, run your program until it stops at that breakpoint,
5501 and then step through the suspect area, examining the variables that are
5502 interesting, until you see the problem happen.
5506 @kindex s @r{(@code{step})}
5508 Continue running your program until control reaches a different source
5509 line, then stop it and return control to @value{GDBN}. This command is
5510 abbreviated @code{s}.
5513 @c "without debugging information" is imprecise; actually "without line
5514 @c numbers in the debugging information". (gcc -g1 has debugging info but
5515 @c not line numbers). But it seems complex to try to make that
5516 @c distinction here.
5517 @emph{Warning:} If you use the @code{step} command while control is
5518 within a function that was compiled without debugging information,
5519 execution proceeds until control reaches a function that does have
5520 debugging information. Likewise, it will not step into a function which
5521 is compiled without debugging information. To step through functions
5522 without debugging information, use the @code{stepi} command, described
5526 The @code{step} command only stops at the first instruction of a source
5527 line. This prevents the multiple stops that could otherwise occur in
5528 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5529 to stop if a function that has debugging information is called within
5530 the line. In other words, @code{step} @emph{steps inside} any functions
5531 called within the line.
5533 Also, the @code{step} command only enters a function if there is line
5534 number information for the function. Otherwise it acts like the
5535 @code{next} command. This avoids problems when using @code{cc -gl}
5536 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5537 was any debugging information about the routine.
5539 @item step @var{count}
5540 Continue running as in @code{step}, but do so @var{count} times. If a
5541 breakpoint is reached, or a signal not related to stepping occurs before
5542 @var{count} steps, stepping stops right away.
5545 @kindex n @r{(@code{next})}
5546 @item next @r{[}@var{count}@r{]}
5547 Continue to the next source line in the current (innermost) stack frame.
5548 This is similar to @code{step}, but function calls that appear within
5549 the line of code are executed without stopping. Execution stops when
5550 control reaches a different line of code at the original stack level
5551 that was executing when you gave the @code{next} command. This command
5552 is abbreviated @code{n}.
5554 An argument @var{count} is a repeat count, as for @code{step}.
5557 @c FIX ME!! Do we delete this, or is there a way it fits in with
5558 @c the following paragraph? --- Vctoria
5560 @c @code{next} within a function that lacks debugging information acts like
5561 @c @code{step}, but any function calls appearing within the code of the
5562 @c function are executed without stopping.
5564 The @code{next} command only stops at the first instruction of a
5565 source line. This prevents multiple stops that could otherwise occur in
5566 @code{switch} statements, @code{for} loops, etc.
5568 @kindex set step-mode
5570 @cindex functions without line info, and stepping
5571 @cindex stepping into functions with no line info
5572 @itemx set step-mode on
5573 The @code{set step-mode on} command causes the @code{step} command to
5574 stop at the first instruction of a function which contains no debug line
5575 information rather than stepping over it.
5577 This is useful in cases where you may be interested in inspecting the
5578 machine instructions of a function which has no symbolic info and do not
5579 want @value{GDBN} to automatically skip over this function.
5581 @item set step-mode off
5582 Causes the @code{step} command to step over any functions which contains no
5583 debug information. This is the default.
5585 @item show step-mode
5586 Show whether @value{GDBN} will stop in or step over functions without
5587 source line debug information.
5590 @kindex fin @r{(@code{finish})}
5592 Continue running until just after function in the selected stack frame
5593 returns. Print the returned value (if any). This command can be
5594 abbreviated as @code{fin}.
5596 Contrast this with the @code{return} command (@pxref{Returning,
5597 ,Returning from a Function}).
5600 @kindex u @r{(@code{until})}
5601 @cindex run until specified location
5604 Continue running until a source line past the current line, in the
5605 current stack frame, is reached. This command is used to avoid single
5606 stepping through a loop more than once. It is like the @code{next}
5607 command, except that when @code{until} encounters a jump, it
5608 automatically continues execution until the program counter is greater
5609 than the address of the jump.
5611 This means that when you reach the end of a loop after single stepping
5612 though it, @code{until} makes your program continue execution until it
5613 exits the loop. In contrast, a @code{next} command at the end of a loop
5614 simply steps back to the beginning of the loop, which forces you to step
5615 through the next iteration.
5617 @code{until} always stops your program if it attempts to exit the current
5620 @code{until} may produce somewhat counterintuitive results if the order
5621 of machine code does not match the order of the source lines. For
5622 example, in the following excerpt from a debugging session, the @code{f}
5623 (@code{frame}) command shows that execution is stopped at line
5624 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5628 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5630 (@value{GDBP}) until
5631 195 for ( ; argc > 0; NEXTARG) @{
5634 This happened because, for execution efficiency, the compiler had
5635 generated code for the loop closure test at the end, rather than the
5636 start, of the loop---even though the test in a C @code{for}-loop is
5637 written before the body of the loop. The @code{until} command appeared
5638 to step back to the beginning of the loop when it advanced to this
5639 expression; however, it has not really gone to an earlier
5640 statement---not in terms of the actual machine code.
5642 @code{until} with no argument works by means of single
5643 instruction stepping, and hence is slower than @code{until} with an
5646 @item until @var{location}
5647 @itemx u @var{location}
5648 Continue running your program until either the specified @var{location} is
5649 reached, or the current stack frame returns. The location is any of
5650 the forms described in @ref{Specify Location}.
5651 This form of the command uses temporary breakpoints, and
5652 hence is quicker than @code{until} without an argument. The specified
5653 location is actually reached only if it is in the current frame. This
5654 implies that @code{until} can be used to skip over recursive function
5655 invocations. For instance in the code below, if the current location is
5656 line @code{96}, issuing @code{until 99} will execute the program up to
5657 line @code{99} in the same invocation of factorial, i.e., after the inner
5658 invocations have returned.
5661 94 int factorial (int value)
5663 96 if (value > 1) @{
5664 97 value *= factorial (value - 1);
5671 @kindex advance @var{location}
5672 @item advance @var{location}
5673 Continue running the program up to the given @var{location}. An argument is
5674 required, which should be of one of the forms described in
5675 @ref{Specify Location}.
5676 Execution will also stop upon exit from the current stack
5677 frame. This command is similar to @code{until}, but @code{advance} will
5678 not skip over recursive function calls, and the target location doesn't
5679 have to be in the same frame as the current one.
5683 @kindex si @r{(@code{stepi})}
5685 @itemx stepi @var{arg}
5687 Execute one machine instruction, then stop and return to the debugger.
5689 It is often useful to do @samp{display/i $pc} when stepping by machine
5690 instructions. This makes @value{GDBN} automatically display the next
5691 instruction to be executed, each time your program stops. @xref{Auto
5692 Display,, Automatic Display}.
5694 An argument is a repeat count, as in @code{step}.
5698 @kindex ni @r{(@code{nexti})}
5700 @itemx nexti @var{arg}
5702 Execute one machine instruction, but if it is a function call,
5703 proceed until the function returns.
5705 An argument is a repeat count, as in @code{next}.
5709 @anchor{range stepping}
5710 @cindex range stepping
5711 @cindex target-assisted range stepping
5712 By default, and if available, @value{GDBN} makes use of
5713 target-assisted @dfn{range stepping}. In other words, whenever you
5714 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5715 tells the target to step the corresponding range of instruction
5716 addresses instead of issuing multiple single-steps. This speeds up
5717 line stepping, particularly for remote targets. Ideally, there should
5718 be no reason you would want to turn range stepping off. However, it's
5719 possible that a bug in the debug info, a bug in the remote stub (for
5720 remote targets), or even a bug in @value{GDBN} could make line
5721 stepping behave incorrectly when target-assisted range stepping is
5722 enabled. You can use the following command to turn off range stepping
5726 @kindex set range-stepping
5727 @kindex show range-stepping
5728 @item set range-stepping
5729 @itemx show range-stepping
5730 Control whether range stepping is enabled.
5732 If @code{on}, and the target supports it, @value{GDBN} tells the
5733 target to step a range of addresses itself, instead of issuing
5734 multiple single-steps. If @code{off}, @value{GDBN} always issues
5735 single-steps, even if range stepping is supported by the target. The
5736 default is @code{on}.
5740 @node Skipping Over Functions and Files
5741 @section Skipping Over Functions and Files
5742 @cindex skipping over functions and files
5744 The program you are debugging may contain some functions which are
5745 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5746 skip a function, all functions in a file or a particular function in
5747 a particular file when stepping.
5749 For example, consider the following C function:
5760 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5761 are not interested in stepping through @code{boring}. If you run @code{step}
5762 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5763 step over both @code{foo} and @code{boring}!
5765 One solution is to @code{step} into @code{boring} and use the @code{finish}
5766 command to immediately exit it. But this can become tedious if @code{boring}
5767 is called from many places.
5769 A more flexible solution is to execute @kbd{skip boring}. This instructs
5770 @value{GDBN} never to step into @code{boring}. Now when you execute
5771 @code{step} at line 103, you'll step over @code{boring} and directly into
5774 Functions may be skipped by providing either a function name, linespec
5775 (@pxref{Specify Location}), regular expression that matches the function's
5776 name, file name or a @code{glob}-style pattern that matches the file name.
5778 On Posix systems the form of the regular expression is
5779 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5780 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5781 expression is whatever is provided by the @code{regcomp} function of
5782 the underlying system.
5783 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5784 description of @code{glob}-style patterns.
5788 @item skip @r{[}@var{options}@r{]}
5789 The basic form of the @code{skip} command takes zero or more options
5790 that specify what to skip.
5791 The @var{options} argument is any useful combination of the following:
5794 @item -file @var{file}
5795 @itemx -fi @var{file}
5796 Functions in @var{file} will be skipped over when stepping.
5798 @item -gfile @var{file-glob-pattern}
5799 @itemx -gfi @var{file-glob-pattern}
5800 @cindex skipping over files via glob-style patterns
5801 Functions in files matching @var{file-glob-pattern} will be skipped
5805 (gdb) skip -gfi utils/*.c
5808 @item -function @var{linespec}
5809 @itemx -fu @var{linespec}
5810 Functions named by @var{linespec} or the function containing the line
5811 named by @var{linespec} will be skipped over when stepping.
5812 @xref{Specify Location}.
5814 @item -rfunction @var{regexp}
5815 @itemx -rfu @var{regexp}
5816 @cindex skipping over functions via regular expressions
5817 Functions whose name matches @var{regexp} will be skipped over when stepping.
5819 This form is useful for complex function names.
5820 For example, there is generally no need to step into C@t{++} @code{std::string}
5821 constructors or destructors. Plus with C@t{++} templates it can be hard to
5822 write out the full name of the function, and often it doesn't matter what
5823 the template arguments are. Specifying the function to be skipped as a
5824 regular expression makes this easier.
5827 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5830 If you want to skip every templated C@t{++} constructor and destructor
5831 in the @code{std} namespace you can do:
5834 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5838 If no options are specified, the function you're currently debugging
5841 @kindex skip function
5842 @item skip function @r{[}@var{linespec}@r{]}
5843 After running this command, the function named by @var{linespec} or the
5844 function containing the line named by @var{linespec} will be skipped over when
5845 stepping. @xref{Specify Location}.
5847 If you do not specify @var{linespec}, the function you're currently debugging
5850 (If you have a function called @code{file} that you want to skip, use
5851 @kbd{skip function file}.)
5854 @item skip file @r{[}@var{filename}@r{]}
5855 After running this command, any function whose source lives in @var{filename}
5856 will be skipped over when stepping.
5859 (gdb) skip file boring.c
5860 File boring.c will be skipped when stepping.
5863 If you do not specify @var{filename}, functions whose source lives in the file
5864 you're currently debugging will be skipped.
5867 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5868 These are the commands for managing your list of skips:
5872 @item info skip @r{[}@var{range}@r{]}
5873 Print details about the specified skip(s). If @var{range} is not specified,
5874 print a table with details about all functions and files marked for skipping.
5875 @code{info skip} prints the following information about each skip:
5879 A number identifying this skip.
5880 @item Enabled or Disabled
5881 Enabled skips are marked with @samp{y}.
5882 Disabled skips are marked with @samp{n}.
5884 If the file name is a @samp{glob} pattern this is @samp{y}.
5885 Otherwise it is @samp{n}.
5887 The name or @samp{glob} pattern of the file to be skipped.
5888 If no file is specified this is @samp{<none>}.
5890 If the function name is a @samp{regular expression} this is @samp{y}.
5891 Otherwise it is @samp{n}.
5893 The name or regular expression of the function to skip.
5894 If no function is specified this is @samp{<none>}.
5898 @item skip delete @r{[}@var{range}@r{]}
5899 Delete the specified skip(s). If @var{range} is not specified, delete all
5903 @item skip enable @r{[}@var{range}@r{]}
5904 Enable the specified skip(s). If @var{range} is not specified, enable all
5907 @kindex skip disable
5908 @item skip disable @r{[}@var{range}@r{]}
5909 Disable the specified skip(s). If @var{range} is not specified, disable all
5912 @kindex set debug skip
5913 @item set debug skip @r{[}on|off@r{]}
5914 Set whether to print the debug output about skipping files and functions.
5916 @kindex show debug skip
5917 @item show debug skip
5918 Show whether the debug output about skipping files and functions is printed.
5926 A signal is an asynchronous event that can happen in a program. The
5927 operating system defines the possible kinds of signals, and gives each
5928 kind a name and a number. For example, in Unix @code{SIGINT} is the
5929 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5930 @code{SIGSEGV} is the signal a program gets from referencing a place in
5931 memory far away from all the areas in use; @code{SIGALRM} occurs when
5932 the alarm clock timer goes off (which happens only if your program has
5933 requested an alarm).
5935 @cindex fatal signals
5936 Some signals, including @code{SIGALRM}, are a normal part of the
5937 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5938 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5939 program has not specified in advance some other way to handle the signal.
5940 @code{SIGINT} does not indicate an error in your program, but it is normally
5941 fatal so it can carry out the purpose of the interrupt: to kill the program.
5943 @value{GDBN} has the ability to detect any occurrence of a signal in your
5944 program. You can tell @value{GDBN} in advance what to do for each kind of
5947 @cindex handling signals
5948 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5949 @code{SIGALRM} be silently passed to your program
5950 (so as not to interfere with their role in the program's functioning)
5951 but to stop your program immediately whenever an error signal happens.
5952 You can change these settings with the @code{handle} command.
5955 @kindex info signals
5959 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5960 handle each one. You can use this to see the signal numbers of all
5961 the defined types of signals.
5963 @item info signals @var{sig}
5964 Similar, but print information only about the specified signal number.
5966 @code{info handle} is an alias for @code{info signals}.
5968 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5969 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5970 for details about this command.
5973 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5974 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5975 can be the number of a signal or its name (with or without the
5976 @samp{SIG} at the beginning); a list of signal numbers of the form
5977 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5978 known signals. Optional arguments @var{keywords}, described below,
5979 say what change to make.
5983 The keywords allowed by the @code{handle} command can be abbreviated.
5984 Their full names are:
5988 @value{GDBN} should not stop your program when this signal happens. It may
5989 still print a message telling you that the signal has come in.
5992 @value{GDBN} should stop your program when this signal happens. This implies
5993 the @code{print} keyword as well.
5996 @value{GDBN} should print a message when this signal happens.
5999 @value{GDBN} should not mention the occurrence of the signal at all. This
6000 implies the @code{nostop} keyword as well.
6004 @value{GDBN} should allow your program to see this signal; your program
6005 can handle the signal, or else it may terminate if the signal is fatal
6006 and not handled. @code{pass} and @code{noignore} are synonyms.
6010 @value{GDBN} should not allow your program to see this signal.
6011 @code{nopass} and @code{ignore} are synonyms.
6015 When a signal stops your program, the signal is not visible to the
6017 continue. Your program sees the signal then, if @code{pass} is in
6018 effect for the signal in question @emph{at that time}. In other words,
6019 after @value{GDBN} reports a signal, you can use the @code{handle}
6020 command with @code{pass} or @code{nopass} to control whether your
6021 program sees that signal when you continue.
6023 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6024 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6025 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6028 You can also use the @code{signal} command to prevent your program from
6029 seeing a signal, or cause it to see a signal it normally would not see,
6030 or to give it any signal at any time. For example, if your program stopped
6031 due to some sort of memory reference error, you might store correct
6032 values into the erroneous variables and continue, hoping to see more
6033 execution; but your program would probably terminate immediately as
6034 a result of the fatal signal once it saw the signal. To prevent this,
6035 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6038 @cindex stepping and signal handlers
6039 @anchor{stepping and signal handlers}
6041 @value{GDBN} optimizes for stepping the mainline code. If a signal
6042 that has @code{handle nostop} and @code{handle pass} set arrives while
6043 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6044 in progress, @value{GDBN} lets the signal handler run and then resumes
6045 stepping the mainline code once the signal handler returns. In other
6046 words, @value{GDBN} steps over the signal handler. This prevents
6047 signals that you've specified as not interesting (with @code{handle
6048 nostop}) from changing the focus of debugging unexpectedly. Note that
6049 the signal handler itself may still hit a breakpoint, stop for another
6050 signal that has @code{handle stop} in effect, or for any other event
6051 that normally results in stopping the stepping command sooner. Also
6052 note that @value{GDBN} still informs you that the program received a
6053 signal if @code{handle print} is set.
6055 @anchor{stepping into signal handlers}
6057 If you set @code{handle pass} for a signal, and your program sets up a
6058 handler for it, then issuing a stepping command, such as @code{step}
6059 or @code{stepi}, when your program is stopped due to the signal will
6060 step @emph{into} the signal handler (if the target supports that).
6062 Likewise, if you use the @code{queue-signal} command to queue a signal
6063 to be delivered to the current thread when execution of the thread
6064 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6065 stepping command will step into the signal handler.
6067 Here's an example, using @code{stepi} to step to the first instruction
6068 of @code{SIGUSR1}'s handler:
6071 (@value{GDBP}) handle SIGUSR1
6072 Signal Stop Print Pass to program Description
6073 SIGUSR1 Yes Yes Yes User defined signal 1
6077 Program received signal SIGUSR1, User defined signal 1.
6078 main () sigusr1.c:28
6081 sigusr1_handler () at sigusr1.c:9
6085 The same, but using @code{queue-signal} instead of waiting for the
6086 program to receive the signal first:
6091 (@value{GDBP}) queue-signal SIGUSR1
6093 sigusr1_handler () at sigusr1.c:9
6098 @cindex extra signal information
6099 @anchor{extra signal information}
6101 On some targets, @value{GDBN} can inspect extra signal information
6102 associated with the intercepted signal, before it is actually
6103 delivered to the program being debugged. This information is exported
6104 by the convenience variable @code{$_siginfo}, and consists of data
6105 that is passed by the kernel to the signal handler at the time of the
6106 receipt of a signal. The data type of the information itself is
6107 target dependent. You can see the data type using the @code{ptype
6108 $_siginfo} command. On Unix systems, it typically corresponds to the
6109 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6112 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6113 referenced address that raised a segmentation fault.
6117 (@value{GDBP}) continue
6118 Program received signal SIGSEGV, Segmentation fault.
6119 0x0000000000400766 in main ()
6121 (@value{GDBP}) ptype $_siginfo
6128 struct @{...@} _kill;
6129 struct @{...@} _timer;
6131 struct @{...@} _sigchld;
6132 struct @{...@} _sigfault;
6133 struct @{...@} _sigpoll;
6136 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6140 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6141 $1 = (void *) 0x7ffff7ff7000
6145 Depending on target support, @code{$_siginfo} may also be writable.
6147 @cindex Intel MPX boundary violations
6148 @cindex boundary violations, Intel MPX
6149 On some targets, a @code{SIGSEGV} can be caused by a boundary
6150 violation, i.e., accessing an address outside of the allowed range.
6151 In those cases @value{GDBN} may displays additional information,
6152 depending on how @value{GDBN} has been told to handle the signal.
6153 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6154 kind: "Upper" or "Lower", the memory address accessed and the
6155 bounds, while with @code{handle nostop SIGSEGV} no additional
6156 information is displayed.
6158 The usual output of a segfault is:
6160 Program received signal SIGSEGV, Segmentation fault
6161 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6162 68 value = *(p + len);
6165 While a bound violation is presented as:
6167 Program received signal SIGSEGV, Segmentation fault
6168 Upper bound violation while accessing address 0x7fffffffc3b3
6169 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6170 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6171 68 value = *(p + len);
6175 @section Stopping and Starting Multi-thread Programs
6177 @cindex stopped threads
6178 @cindex threads, stopped
6180 @cindex continuing threads
6181 @cindex threads, continuing
6183 @value{GDBN} supports debugging programs with multiple threads
6184 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6185 are two modes of controlling execution of your program within the
6186 debugger. In the default mode, referred to as @dfn{all-stop mode},
6187 when any thread in your program stops (for example, at a breakpoint
6188 or while being stepped), all other threads in the program are also stopped by
6189 @value{GDBN}. On some targets, @value{GDBN} also supports
6190 @dfn{non-stop mode}, in which other threads can continue to run freely while
6191 you examine the stopped thread in the debugger.
6194 * All-Stop Mode:: All threads stop when GDB takes control
6195 * Non-Stop Mode:: Other threads continue to execute
6196 * Background Execution:: Running your program asynchronously
6197 * Thread-Specific Breakpoints:: Controlling breakpoints
6198 * Interrupted System Calls:: GDB may interfere with system calls
6199 * Observer Mode:: GDB does not alter program behavior
6203 @subsection All-Stop Mode
6205 @cindex all-stop mode
6207 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6208 @emph{all} threads of execution stop, not just the current thread. This
6209 allows you to examine the overall state of the program, including
6210 switching between threads, without worrying that things may change
6213 Conversely, whenever you restart the program, @emph{all} threads start
6214 executing. @emph{This is true even when single-stepping} with commands
6215 like @code{step} or @code{next}.
6217 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6218 Since thread scheduling is up to your debugging target's operating
6219 system (not controlled by @value{GDBN}), other threads may
6220 execute more than one statement while the current thread completes a
6221 single step. Moreover, in general other threads stop in the middle of a
6222 statement, rather than at a clean statement boundary, when the program
6225 You might even find your program stopped in another thread after
6226 continuing or even single-stepping. This happens whenever some other
6227 thread runs into a breakpoint, a signal, or an exception before the
6228 first thread completes whatever you requested.
6230 @cindex automatic thread selection
6231 @cindex switching threads automatically
6232 @cindex threads, automatic switching
6233 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6234 signal, it automatically selects the thread where that breakpoint or
6235 signal happened. @value{GDBN} alerts you to the context switch with a
6236 message such as @samp{[Switching to Thread @var{n}]} to identify the
6239 On some OSes, you can modify @value{GDBN}'s default behavior by
6240 locking the OS scheduler to allow only a single thread to run.
6243 @item set scheduler-locking @var{mode}
6244 @cindex scheduler locking mode
6245 @cindex lock scheduler
6246 Set the scheduler locking mode. It applies to normal execution,
6247 record mode, and replay mode. If it is @code{off}, then there is no
6248 locking and any thread may run at any time. If @code{on}, then only
6249 the current thread may run when the inferior is resumed. The
6250 @code{step} mode optimizes for single-stepping; it prevents other
6251 threads from preempting the current thread while you are stepping, so
6252 that the focus of debugging does not change unexpectedly. Other
6253 threads never get a chance to run when you step, and they are
6254 completely free to run when you use commands like @samp{continue},
6255 @samp{until}, or @samp{finish}. However, unless another thread hits a
6256 breakpoint during its timeslice, @value{GDBN} does not change the
6257 current thread away from the thread that you are debugging. The
6258 @code{replay} mode behaves like @code{off} in record mode and like
6259 @code{on} in replay mode.
6261 @item show scheduler-locking
6262 Display the current scheduler locking mode.
6265 @cindex resume threads of multiple processes simultaneously
6266 By default, when you issue one of the execution commands such as
6267 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6268 threads of the current inferior to run. For example, if @value{GDBN}
6269 is attached to two inferiors, each with two threads, the
6270 @code{continue} command resumes only the two threads of the current
6271 inferior. This is useful, for example, when you debug a program that
6272 forks and you want to hold the parent stopped (so that, for instance,
6273 it doesn't run to exit), while you debug the child. In other
6274 situations, you may not be interested in inspecting the current state
6275 of any of the processes @value{GDBN} is attached to, and you may want
6276 to resume them all until some breakpoint is hit. In the latter case,
6277 you can instruct @value{GDBN} to allow all threads of all the
6278 inferiors to run with the @w{@code{set schedule-multiple}} command.
6281 @kindex set schedule-multiple
6282 @item set schedule-multiple
6283 Set the mode for allowing threads of multiple processes to be resumed
6284 when an execution command is issued. When @code{on}, all threads of
6285 all processes are allowed to run. When @code{off}, only the threads
6286 of the current process are resumed. The default is @code{off}. The
6287 @code{scheduler-locking} mode takes precedence when set to @code{on},
6288 or while you are stepping and set to @code{step}.
6290 @item show schedule-multiple
6291 Display the current mode for resuming the execution of threads of
6296 @subsection Non-Stop Mode
6298 @cindex non-stop mode
6300 @c This section is really only a place-holder, and needs to be expanded
6301 @c with more details.
6303 For some multi-threaded targets, @value{GDBN} supports an optional
6304 mode of operation in which you can examine stopped program threads in
6305 the debugger while other threads continue to execute freely. This
6306 minimizes intrusion when debugging live systems, such as programs
6307 where some threads have real-time constraints or must continue to
6308 respond to external events. This is referred to as @dfn{non-stop} mode.
6310 In non-stop mode, when a thread stops to report a debugging event,
6311 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6312 threads as well, in contrast to the all-stop mode behavior. Additionally,
6313 execution commands such as @code{continue} and @code{step} apply by default
6314 only to the current thread in non-stop mode, rather than all threads as
6315 in all-stop mode. This allows you to control threads explicitly in
6316 ways that are not possible in all-stop mode --- for example, stepping
6317 one thread while allowing others to run freely, stepping
6318 one thread while holding all others stopped, or stepping several threads
6319 independently and simultaneously.
6321 To enter non-stop mode, use this sequence of commands before you run
6322 or attach to your program:
6325 # If using the CLI, pagination breaks non-stop.
6328 # Finally, turn it on!
6332 You can use these commands to manipulate the non-stop mode setting:
6335 @kindex set non-stop
6336 @item set non-stop on
6337 Enable selection of non-stop mode.
6338 @item set non-stop off
6339 Disable selection of non-stop mode.
6340 @kindex show non-stop
6342 Show the current non-stop enablement setting.
6345 Note these commands only reflect whether non-stop mode is enabled,
6346 not whether the currently-executing program is being run in non-stop mode.
6347 In particular, the @code{set non-stop} preference is only consulted when
6348 @value{GDBN} starts or connects to the target program, and it is generally
6349 not possible to switch modes once debugging has started. Furthermore,
6350 since not all targets support non-stop mode, even when you have enabled
6351 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6354 In non-stop mode, all execution commands apply only to the current thread
6355 by default. That is, @code{continue} only continues one thread.
6356 To continue all threads, issue @code{continue -a} or @code{c -a}.
6358 You can use @value{GDBN}'s background execution commands
6359 (@pxref{Background Execution}) to run some threads in the background
6360 while you continue to examine or step others from @value{GDBN}.
6361 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6362 always executed asynchronously in non-stop mode.
6364 Suspending execution is done with the @code{interrupt} command when
6365 running in the background, or @kbd{Ctrl-c} during foreground execution.
6366 In all-stop mode, this stops the whole process;
6367 but in non-stop mode the interrupt applies only to the current thread.
6368 To stop the whole program, use @code{interrupt -a}.
6370 Other execution commands do not currently support the @code{-a} option.
6372 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6373 that thread current, as it does in all-stop mode. This is because the
6374 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6375 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6376 changed to a different thread just as you entered a command to operate on the
6377 previously current thread.
6379 @node Background Execution
6380 @subsection Background Execution
6382 @cindex foreground execution
6383 @cindex background execution
6384 @cindex asynchronous execution
6385 @cindex execution, foreground, background and asynchronous
6387 @value{GDBN}'s execution commands have two variants: the normal
6388 foreground (synchronous) behavior, and a background
6389 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6390 the program to report that some thread has stopped before prompting for
6391 another command. In background execution, @value{GDBN} immediately gives
6392 a command prompt so that you can issue other commands while your program runs.
6394 If the target doesn't support async mode, @value{GDBN} issues an error
6395 message if you attempt to use the background execution commands.
6397 @cindex @code{&}, background execution of commands
6398 To specify background execution, add a @code{&} to the command. For example,
6399 the background form of the @code{continue} command is @code{continue&}, or
6400 just @code{c&}. The execution commands that accept background execution
6406 @xref{Starting, , Starting your Program}.
6410 @xref{Attach, , Debugging an Already-running Process}.
6414 @xref{Continuing and Stepping, step}.
6418 @xref{Continuing and Stepping, stepi}.
6422 @xref{Continuing and Stepping, next}.
6426 @xref{Continuing and Stepping, nexti}.
6430 @xref{Continuing and Stepping, continue}.
6434 @xref{Continuing and Stepping, finish}.
6438 @xref{Continuing and Stepping, until}.
6442 Background execution is especially useful in conjunction with non-stop
6443 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6444 However, you can also use these commands in the normal all-stop mode with
6445 the restriction that you cannot issue another execution command until the
6446 previous one finishes. Examples of commands that are valid in all-stop
6447 mode while the program is running include @code{help} and @code{info break}.
6449 You can interrupt your program while it is running in the background by
6450 using the @code{interrupt} command.
6457 Suspend execution of the running program. In all-stop mode,
6458 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6459 only the current thread. To stop the whole program in non-stop mode,
6460 use @code{interrupt -a}.
6463 @node Thread-Specific Breakpoints
6464 @subsection Thread-Specific Breakpoints
6466 When your program has multiple threads (@pxref{Threads,, Debugging
6467 Programs with Multiple Threads}), you can choose whether to set
6468 breakpoints on all threads, or on a particular thread.
6471 @cindex breakpoints and threads
6472 @cindex thread breakpoints
6473 @kindex break @dots{} thread @var{thread-id}
6474 @item break @var{location} thread @var{thread-id}
6475 @itemx break @var{location} thread @var{thread-id} if @dots{}
6476 @var{location} specifies source lines; there are several ways of
6477 writing them (@pxref{Specify Location}), but the effect is always to
6478 specify some source line.
6480 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6481 to specify that you only want @value{GDBN} to stop the program when a
6482 particular thread reaches this breakpoint. The @var{thread-id} specifier
6483 is one of the thread identifiers assigned by @value{GDBN}, shown
6484 in the first column of the @samp{info threads} display.
6486 If you do not specify @samp{thread @var{thread-id}} when you set a
6487 breakpoint, the breakpoint applies to @emph{all} threads of your
6490 You can use the @code{thread} qualifier on conditional breakpoints as
6491 well; in this case, place @samp{thread @var{thread-id}} before or
6492 after the breakpoint condition, like this:
6495 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6500 Thread-specific breakpoints are automatically deleted when
6501 @value{GDBN} detects the corresponding thread is no longer in the
6502 thread list. For example:
6506 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6509 There are several ways for a thread to disappear, such as a regular
6510 thread exit, but also when you detach from the process with the
6511 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6512 Process}), or if @value{GDBN} loses the remote connection
6513 (@pxref{Remote Debugging}), etc. Note that with some targets,
6514 @value{GDBN} is only able to detect a thread has exited when the user
6515 explictly asks for the thread list with the @code{info threads}
6518 @node Interrupted System Calls
6519 @subsection Interrupted System Calls
6521 @cindex thread breakpoints and system calls
6522 @cindex system calls and thread breakpoints
6523 @cindex premature return from system calls
6524 There is an unfortunate side effect when using @value{GDBN} to debug
6525 multi-threaded programs. If one thread stops for a
6526 breakpoint, or for some other reason, and another thread is blocked in a
6527 system call, then the system call may return prematurely. This is a
6528 consequence of the interaction between multiple threads and the signals
6529 that @value{GDBN} uses to implement breakpoints and other events that
6532 To handle this problem, your program should check the return value of
6533 each system call and react appropriately. This is good programming
6536 For example, do not write code like this:
6542 The call to @code{sleep} will return early if a different thread stops
6543 at a breakpoint or for some other reason.
6545 Instead, write this:
6550 unslept = sleep (unslept);
6553 A system call is allowed to return early, so the system is still
6554 conforming to its specification. But @value{GDBN} does cause your
6555 multi-threaded program to behave differently than it would without
6558 Also, @value{GDBN} uses internal breakpoints in the thread library to
6559 monitor certain events such as thread creation and thread destruction.
6560 When such an event happens, a system call in another thread may return
6561 prematurely, even though your program does not appear to stop.
6564 @subsection Observer Mode
6566 If you want to build on non-stop mode and observe program behavior
6567 without any chance of disruption by @value{GDBN}, you can set
6568 variables to disable all of the debugger's attempts to modify state,
6569 whether by writing memory, inserting breakpoints, etc. These operate
6570 at a low level, intercepting operations from all commands.
6572 When all of these are set to @code{off}, then @value{GDBN} is said to
6573 be @dfn{observer mode}. As a convenience, the variable
6574 @code{observer} can be set to disable these, plus enable non-stop
6577 Note that @value{GDBN} will not prevent you from making nonsensical
6578 combinations of these settings. For instance, if you have enabled
6579 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6580 then breakpoints that work by writing trap instructions into the code
6581 stream will still not be able to be placed.
6586 @item set observer on
6587 @itemx set observer off
6588 When set to @code{on}, this disables all the permission variables
6589 below (except for @code{insert-fast-tracepoints}), plus enables
6590 non-stop debugging. Setting this to @code{off} switches back to
6591 normal debugging, though remaining in non-stop mode.
6594 Show whether observer mode is on or off.
6596 @kindex may-write-registers
6597 @item set may-write-registers on
6598 @itemx set may-write-registers off
6599 This controls whether @value{GDBN} will attempt to alter the values of
6600 registers, such as with assignment expressions in @code{print}, or the
6601 @code{jump} command. It defaults to @code{on}.
6603 @item show may-write-registers
6604 Show the current permission to write registers.
6606 @kindex may-write-memory
6607 @item set may-write-memory on
6608 @itemx set may-write-memory off
6609 This controls whether @value{GDBN} will attempt to alter the contents
6610 of memory, such as with assignment expressions in @code{print}. It
6611 defaults to @code{on}.
6613 @item show may-write-memory
6614 Show the current permission to write memory.
6616 @kindex may-insert-breakpoints
6617 @item set may-insert-breakpoints on
6618 @itemx set may-insert-breakpoints off
6619 This controls whether @value{GDBN} will attempt to insert breakpoints.
6620 This affects all breakpoints, including internal breakpoints defined
6621 by @value{GDBN}. It defaults to @code{on}.
6623 @item show may-insert-breakpoints
6624 Show the current permission to insert breakpoints.
6626 @kindex may-insert-tracepoints
6627 @item set may-insert-tracepoints on
6628 @itemx set may-insert-tracepoints off
6629 This controls whether @value{GDBN} will attempt to insert (regular)
6630 tracepoints at the beginning of a tracing experiment. It affects only
6631 non-fast tracepoints, fast tracepoints being under the control of
6632 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6634 @item show may-insert-tracepoints
6635 Show the current permission to insert tracepoints.
6637 @kindex may-insert-fast-tracepoints
6638 @item set may-insert-fast-tracepoints on
6639 @itemx set may-insert-fast-tracepoints off
6640 This controls whether @value{GDBN} will attempt to insert fast
6641 tracepoints at the beginning of a tracing experiment. It affects only
6642 fast tracepoints, regular (non-fast) tracepoints being under the
6643 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6645 @item show may-insert-fast-tracepoints
6646 Show the current permission to insert fast tracepoints.
6648 @kindex may-interrupt
6649 @item set may-interrupt on
6650 @itemx set may-interrupt off
6651 This controls whether @value{GDBN} will attempt to interrupt or stop
6652 program execution. When this variable is @code{off}, the
6653 @code{interrupt} command will have no effect, nor will
6654 @kbd{Ctrl-c}. It defaults to @code{on}.
6656 @item show may-interrupt
6657 Show the current permission to interrupt or stop the program.
6661 @node Reverse Execution
6662 @chapter Running programs backward
6663 @cindex reverse execution
6664 @cindex running programs backward
6666 When you are debugging a program, it is not unusual to realize that
6667 you have gone too far, and some event of interest has already happened.
6668 If the target environment supports it, @value{GDBN} can allow you to
6669 ``rewind'' the program by running it backward.
6671 A target environment that supports reverse execution should be able
6672 to ``undo'' the changes in machine state that have taken place as the
6673 program was executing normally. Variables, registers etc.@: should
6674 revert to their previous values. Obviously this requires a great
6675 deal of sophistication on the part of the target environment; not
6676 all target environments can support reverse execution.
6678 When a program is executed in reverse, the instructions that
6679 have most recently been executed are ``un-executed'', in reverse
6680 order. The program counter runs backward, following the previous
6681 thread of execution in reverse. As each instruction is ``un-executed'',
6682 the values of memory and/or registers that were changed by that
6683 instruction are reverted to their previous states. After executing
6684 a piece of source code in reverse, all side effects of that code
6685 should be ``undone'', and all variables should be returned to their
6686 prior values@footnote{
6687 Note that some side effects are easier to undo than others. For instance,
6688 memory and registers are relatively easy, but device I/O is hard. Some
6689 targets may be able undo things like device I/O, and some may not.
6691 The contract between @value{GDBN} and the reverse executing target
6692 requires only that the target do something reasonable when
6693 @value{GDBN} tells it to execute backwards, and then report the
6694 results back to @value{GDBN}. Whatever the target reports back to
6695 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6696 assumes that the memory and registers that the target reports are in a
6697 consistant state, but @value{GDBN} accepts whatever it is given.
6700 On some platforms, @value{GDBN} has built-in support for reverse
6701 execution, activated with the @code{record} or @code{record btrace}
6702 commands. @xref{Process Record and Replay}. Some remote targets,
6703 typically full system emulators, support reverse execution directly
6704 without requiring any special command.
6706 If you are debugging in a target environment that supports
6707 reverse execution, @value{GDBN} provides the following commands.
6710 @kindex reverse-continue
6711 @kindex rc @r{(@code{reverse-continue})}
6712 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6713 @itemx rc @r{[}@var{ignore-count}@r{]}
6714 Beginning at the point where your program last stopped, start executing
6715 in reverse. Reverse execution will stop for breakpoints and synchronous
6716 exceptions (signals), just like normal execution. Behavior of
6717 asynchronous signals depends on the target environment.
6719 @kindex reverse-step
6720 @kindex rs @r{(@code{step})}
6721 @item reverse-step @r{[}@var{count}@r{]}
6722 Run the program backward until control reaches the start of a
6723 different source line; then stop it, and return control to @value{GDBN}.
6725 Like the @code{step} command, @code{reverse-step} will only stop
6726 at the beginning of a source line. It ``un-executes'' the previously
6727 executed source line. If the previous source line included calls to
6728 debuggable functions, @code{reverse-step} will step (backward) into
6729 the called function, stopping at the beginning of the @emph{last}
6730 statement in the called function (typically a return statement).
6732 Also, as with the @code{step} command, if non-debuggable functions are
6733 called, @code{reverse-step} will run thru them backward without stopping.
6735 @kindex reverse-stepi
6736 @kindex rsi @r{(@code{reverse-stepi})}
6737 @item reverse-stepi @r{[}@var{count}@r{]}
6738 Reverse-execute one machine instruction. Note that the instruction
6739 to be reverse-executed is @emph{not} the one pointed to by the program
6740 counter, but the instruction executed prior to that one. For instance,
6741 if the last instruction was a jump, @code{reverse-stepi} will take you
6742 back from the destination of the jump to the jump instruction itself.
6744 @kindex reverse-next
6745 @kindex rn @r{(@code{reverse-next})}
6746 @item reverse-next @r{[}@var{count}@r{]}
6747 Run backward to the beginning of the previous line executed in
6748 the current (innermost) stack frame. If the line contains function
6749 calls, they will be ``un-executed'' without stopping. Starting from
6750 the first line of a function, @code{reverse-next} will take you back
6751 to the caller of that function, @emph{before} the function was called,
6752 just as the normal @code{next} command would take you from the last
6753 line of a function back to its return to its caller
6754 @footnote{Unless the code is too heavily optimized.}.
6756 @kindex reverse-nexti
6757 @kindex rni @r{(@code{reverse-nexti})}
6758 @item reverse-nexti @r{[}@var{count}@r{]}
6759 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6760 in reverse, except that called functions are ``un-executed'' atomically.
6761 That is, if the previously executed instruction was a return from
6762 another function, @code{reverse-nexti} will continue to execute
6763 in reverse until the call to that function (from the current stack
6766 @kindex reverse-finish
6767 @item reverse-finish
6768 Just as the @code{finish} command takes you to the point where the
6769 current function returns, @code{reverse-finish} takes you to the point
6770 where it was called. Instead of ending up at the end of the current
6771 function invocation, you end up at the beginning.
6773 @kindex set exec-direction
6774 @item set exec-direction
6775 Set the direction of target execution.
6776 @item set exec-direction reverse
6777 @cindex execute forward or backward in time
6778 @value{GDBN} will perform all execution commands in reverse, until the
6779 exec-direction mode is changed to ``forward''. Affected commands include
6780 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6781 command cannot be used in reverse mode.
6782 @item set exec-direction forward
6783 @value{GDBN} will perform all execution commands in the normal fashion.
6784 This is the default.
6788 @node Process Record and Replay
6789 @chapter Recording Inferior's Execution and Replaying It
6790 @cindex process record and replay
6791 @cindex recording inferior's execution and replaying it
6793 On some platforms, @value{GDBN} provides a special @dfn{process record
6794 and replay} target that can record a log of the process execution, and
6795 replay it later with both forward and reverse execution commands.
6798 When this target is in use, if the execution log includes the record
6799 for the next instruction, @value{GDBN} will debug in @dfn{replay
6800 mode}. In the replay mode, the inferior does not really execute code
6801 instructions. Instead, all the events that normally happen during
6802 code execution are taken from the execution log. While code is not
6803 really executed in replay mode, the values of registers (including the
6804 program counter register) and the memory of the inferior are still
6805 changed as they normally would. Their contents are taken from the
6809 If the record for the next instruction is not in the execution log,
6810 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6811 inferior executes normally, and @value{GDBN} records the execution log
6814 The process record and replay target supports reverse execution
6815 (@pxref{Reverse Execution}), even if the platform on which the
6816 inferior runs does not. However, the reverse execution is limited in
6817 this case by the range of the instructions recorded in the execution
6818 log. In other words, reverse execution on platforms that don't
6819 support it directly can only be done in the replay mode.
6821 When debugging in the reverse direction, @value{GDBN} will work in
6822 replay mode as long as the execution log includes the record for the
6823 previous instruction; otherwise, it will work in record mode, if the
6824 platform supports reverse execution, or stop if not.
6826 Currently, process record and replay is supported on ARM, Aarch64,
6827 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
6828 GNU/Linux. Process record and replay can be used both when native
6829 debugging, and when remote debugging via @code{gdbserver}.
6831 For architecture environments that support process record and replay,
6832 @value{GDBN} provides the following commands:
6835 @kindex target record
6836 @kindex target record-full
6837 @kindex target record-btrace
6840 @kindex record btrace
6841 @kindex record btrace bts
6842 @kindex record btrace pt
6848 @kindex rec btrace bts
6849 @kindex rec btrace pt
6852 @item record @var{method}
6853 This command starts the process record and replay target. The
6854 recording method can be specified as parameter. Without a parameter
6855 the command uses the @code{full} recording method. The following
6856 recording methods are available:
6860 Full record/replay recording using @value{GDBN}'s software record and
6861 replay implementation. This method allows replaying and reverse
6864 @item btrace @var{format}
6865 Hardware-supported instruction recording, supported on Intel
6866 processors. This method does not record data. Further, the data is
6867 collected in a ring buffer so old data will be overwritten when the
6868 buffer is full. It allows limited reverse execution. Variables and
6869 registers are not available during reverse execution. In remote
6870 debugging, recording continues on disconnect. Recorded data can be
6871 inspected after reconnecting. The recording may be stopped using
6874 The recording format can be specified as parameter. Without a parameter
6875 the command chooses the recording format. The following recording
6876 formats are available:
6880 @cindex branch trace store
6881 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6882 this format, the processor stores a from/to record for each executed
6883 branch in the btrace ring buffer.
6886 @cindex Intel Processor Trace
6887 Use the @dfn{Intel Processor Trace} recording format. In this
6888 format, the processor stores the execution trace in a compressed form
6889 that is afterwards decoded by @value{GDBN}.
6891 The trace can be recorded with very low overhead. The compressed
6892 trace format also allows small trace buffers to already contain a big
6893 number of instructions compared to @acronym{BTS}.
6895 Decoding the recorded execution trace, on the other hand, is more
6896 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6897 increased number of instructions to process. You should increase the
6898 buffer-size with care.
6901 Not all recording formats may be available on all processors.
6904 The process record and replay target can only debug a process that is
6905 already running. Therefore, you need first to start the process with
6906 the @kbd{run} or @kbd{start} commands, and then start the recording
6907 with the @kbd{record @var{method}} command.
6909 @cindex displaced stepping, and process record and replay
6910 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6911 will be automatically disabled when process record and replay target
6912 is started. That's because the process record and replay target
6913 doesn't support displaced stepping.
6915 @cindex non-stop mode, and process record and replay
6916 @cindex asynchronous execution, and process record and replay
6917 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6918 the asynchronous execution mode (@pxref{Background Execution}), not
6919 all recording methods are available. The @code{full} recording method
6920 does not support these two modes.
6925 Stop the process record and replay target. When process record and
6926 replay target stops, the entire execution log will be deleted and the
6927 inferior will either be terminated, or will remain in its final state.
6929 When you stop the process record and replay target in record mode (at
6930 the end of the execution log), the inferior will be stopped at the
6931 next instruction that would have been recorded. In other words, if
6932 you record for a while and then stop recording, the inferior process
6933 will be left in the same state as if the recording never happened.
6935 On the other hand, if the process record and replay target is stopped
6936 while in replay mode (that is, not at the end of the execution log,
6937 but at some earlier point), the inferior process will become ``live''
6938 at that earlier state, and it will then be possible to continue the
6939 usual ``live'' debugging of the process from that state.
6941 When the inferior process exits, or @value{GDBN} detaches from it,
6942 process record and replay target will automatically stop itself.
6946 Go to a specific location in the execution log. There are several
6947 ways to specify the location to go to:
6950 @item record goto begin
6951 @itemx record goto start
6952 Go to the beginning of the execution log.
6954 @item record goto end
6955 Go to the end of the execution log.
6957 @item record goto @var{n}
6958 Go to instruction number @var{n} in the execution log.
6962 @item record save @var{filename}
6963 Save the execution log to a file @file{@var{filename}}.
6964 Default filename is @file{gdb_record.@var{process_id}}, where
6965 @var{process_id} is the process ID of the inferior.
6967 This command may not be available for all recording methods.
6969 @kindex record restore
6970 @item record restore @var{filename}
6971 Restore the execution log from a file @file{@var{filename}}.
6972 File must have been created with @code{record save}.
6974 @kindex set record full
6975 @item set record full insn-number-max @var{limit}
6976 @itemx set record full insn-number-max unlimited
6977 Set the limit of instructions to be recorded for the @code{full}
6978 recording method. Default value is 200000.
6980 If @var{limit} is a positive number, then @value{GDBN} will start
6981 deleting instructions from the log once the number of the record
6982 instructions becomes greater than @var{limit}. For every new recorded
6983 instruction, @value{GDBN} will delete the earliest recorded
6984 instruction to keep the number of recorded instructions at the limit.
6985 (Since deleting recorded instructions loses information, @value{GDBN}
6986 lets you control what happens when the limit is reached, by means of
6987 the @code{stop-at-limit} option, described below.)
6989 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6990 delete recorded instructions from the execution log. The number of
6991 recorded instructions is limited only by the available memory.
6993 @kindex show record full
6994 @item show record full insn-number-max
6995 Show the limit of instructions to be recorded with the @code{full}
6998 @item set record full stop-at-limit
6999 Control the behavior of the @code{full} recording method when the
7000 number of recorded instructions reaches the limit. If ON (the
7001 default), @value{GDBN} will stop when the limit is reached for the
7002 first time and ask you whether you want to stop the inferior or
7003 continue running it and recording the execution log. If you decide
7004 to continue recording, each new recorded instruction will cause the
7005 oldest one to be deleted.
7007 If this option is OFF, @value{GDBN} will automatically delete the
7008 oldest record to make room for each new one, without asking.
7010 @item show record full stop-at-limit
7011 Show the current setting of @code{stop-at-limit}.
7013 @item set record full memory-query
7014 Control the behavior when @value{GDBN} is unable to record memory
7015 changes caused by an instruction for the @code{full} recording method.
7016 If ON, @value{GDBN} will query whether to stop the inferior in that
7019 If this option is OFF (the default), @value{GDBN} will automatically
7020 ignore the effect of such instructions on memory. Later, when
7021 @value{GDBN} replays this execution log, it will mark the log of this
7022 instruction as not accessible, and it will not affect the replay
7025 @item show record full memory-query
7026 Show the current setting of @code{memory-query}.
7028 @kindex set record btrace
7029 The @code{btrace} record target does not trace data. As a
7030 convenience, when replaying, @value{GDBN} reads read-only memory off
7031 the live program directly, assuming that the addresses of the
7032 read-only areas don't change. This for example makes it possible to
7033 disassemble code while replaying, but not to print variables.
7034 In some cases, being able to inspect variables might be useful.
7035 You can use the following command for that:
7037 @item set record btrace replay-memory-access
7038 Control the behavior of the @code{btrace} recording method when
7039 accessing memory during replay. If @code{read-only} (the default),
7040 @value{GDBN} will only allow accesses to read-only memory.
7041 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7042 and to read-write memory. Beware that the accessed memory corresponds
7043 to the live target and not necessarily to the current replay
7046 @item set record btrace cpu @var{identifier}
7047 Set the processor to be used for enabling workarounds for processor
7048 errata when decoding the trace.
7050 Processor errata are defects in processor operation, caused by its
7051 design or manufacture. They can cause a trace not to match the
7052 specification. This, in turn, may cause trace decode to fail.
7053 @value{GDBN} can detect erroneous trace packets and correct them, thus
7054 avoiding the decoding failures. These corrections are known as
7055 @dfn{errata workarounds}, and are enabled based on the processor on
7056 which the trace was recorded.
7058 By default, @value{GDBN} attempts to detect the processor
7059 automatically, and apply the necessary workarounds for it. However,
7060 you may need to specify the processor if @value{GDBN} does not yet
7061 support it. This command allows you to do that, and also allows to
7062 disable the workarounds.
7064 The argument @var{identifier} identifies the @sc{cpu} and is of the
7065 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7066 there are two special identifiers, @code{none} and @code{auto}
7069 The following vendor identifiers and corresponding processor
7070 identifiers are currently supported:
7072 @multitable @columnfractions .1 .9
7075 @tab @var{family}/@var{model}[/@var{stepping}]
7079 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7080 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7082 If @var{identifier} is @code{auto}, enable errata workarounds for the
7083 processor on which the trace was recorded. If @var{identifier} is
7084 @code{none}, errata workarounds are disabled.
7086 For example, when using an old @value{GDBN} on a new system, decode
7087 may fail because @value{GDBN} does not support the new processor. It
7088 often suffices to specify an older processor that @value{GDBN}
7093 Active record target: record-btrace
7094 Recording format: Intel Processor Trace.
7096 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7097 (gdb) set record btrace cpu intel:6/158
7099 Active record target: record-btrace
7100 Recording format: Intel Processor Trace.
7102 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7105 @kindex show record btrace
7106 @item show record btrace replay-memory-access
7107 Show the current setting of @code{replay-memory-access}.
7109 @item show record btrace cpu
7110 Show the processor to be used for enabling trace decode errata
7113 @kindex set record btrace bts
7114 @item set record btrace bts buffer-size @var{size}
7115 @itemx set record btrace bts buffer-size unlimited
7116 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7117 format. Default is 64KB.
7119 If @var{size} is a positive number, then @value{GDBN} will try to
7120 allocate a buffer of at least @var{size} bytes for each new thread
7121 that uses the btrace recording method and the @acronym{BTS} format.
7122 The actually obtained buffer size may differ from the requested
7123 @var{size}. Use the @code{info record} command to see the actual
7124 buffer size for each thread that uses the btrace recording method and
7125 the @acronym{BTS} format.
7127 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7128 allocate a buffer of 4MB.
7130 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7131 also need longer to process the branch trace data before it can be used.
7133 @item show record btrace bts buffer-size @var{size}
7134 Show the current setting of the requested ring buffer size for branch
7135 tracing in @acronym{BTS} format.
7137 @kindex set record btrace pt
7138 @item set record btrace pt buffer-size @var{size}
7139 @itemx set record btrace pt buffer-size unlimited
7140 Set the requested ring buffer size for branch tracing in Intel
7141 Processor Trace format. Default is 16KB.
7143 If @var{size} is a positive number, then @value{GDBN} will try to
7144 allocate a buffer of at least @var{size} bytes for each new thread
7145 that uses the btrace recording method and the Intel Processor Trace
7146 format. The actually obtained buffer size may differ from the
7147 requested @var{size}. Use the @code{info record} command to see the
7148 actual buffer size for each thread.
7150 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7151 allocate a buffer of 4MB.
7153 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7154 also need longer to process the branch trace data before it can be used.
7156 @item show record btrace pt buffer-size @var{size}
7157 Show the current setting of the requested ring buffer size for branch
7158 tracing in Intel Processor Trace format.
7162 Show various statistics about the recording depending on the recording
7167 For the @code{full} recording method, it shows the state of process
7168 record and its in-memory execution log buffer, including:
7172 Whether in record mode or replay mode.
7174 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7176 Highest recorded instruction number.
7178 Current instruction about to be replayed (if in replay mode).
7180 Number of instructions contained in the execution log.
7182 Maximum number of instructions that may be contained in the execution log.
7186 For the @code{btrace} recording method, it shows:
7192 Number of instructions that have been recorded.
7194 Number of blocks of sequential control-flow formed by the recorded
7197 Whether in record mode or replay mode.
7200 For the @code{bts} recording format, it also shows:
7203 Size of the perf ring buffer.
7206 For the @code{pt} recording format, it also shows:
7209 Size of the perf ring buffer.
7213 @kindex record delete
7216 When record target runs in replay mode (``in the past''), delete the
7217 subsequent execution log and begin to record a new execution log starting
7218 from the current address. This means you will abandon the previously
7219 recorded ``future'' and begin recording a new ``future''.
7221 @kindex record instruction-history
7222 @kindex rec instruction-history
7223 @item record instruction-history
7224 Disassembles instructions from the recorded execution log. By
7225 default, ten instructions are disassembled. This can be changed using
7226 the @code{set record instruction-history-size} command. Instructions
7227 are printed in execution order.
7229 It can also print mixed source+disassembly if you specify the the
7230 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7231 as well as in symbolic form by specifying the @code{/r} modifier.
7233 The current position marker is printed for the instruction at the
7234 current program counter value. This instruction can appear multiple
7235 times in the trace and the current position marker will be printed
7236 every time. To omit the current position marker, specify the
7239 To better align the printed instructions when the trace contains
7240 instructions from more than one function, the function name may be
7241 omitted by specifying the @code{/f} modifier.
7243 Speculatively executed instructions are prefixed with @samp{?}. This
7244 feature is not available for all recording formats.
7246 There are several ways to specify what part of the execution log to
7250 @item record instruction-history @var{insn}
7251 Disassembles ten instructions starting from instruction number
7254 @item record instruction-history @var{insn}, +/-@var{n}
7255 Disassembles @var{n} instructions around instruction number
7256 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7257 @var{n} instructions after instruction number @var{insn}. If
7258 @var{n} is preceded with @code{-}, disassembles @var{n}
7259 instructions before instruction number @var{insn}.
7261 @item record instruction-history
7262 Disassembles ten more instructions after the last disassembly.
7264 @item record instruction-history -
7265 Disassembles ten more instructions before the last disassembly.
7267 @item record instruction-history @var{begin}, @var{end}
7268 Disassembles instructions beginning with instruction number
7269 @var{begin} until instruction number @var{end}. The instruction
7270 number @var{end} is included.
7273 This command may not be available for all recording methods.
7276 @item set record instruction-history-size @var{size}
7277 @itemx set record instruction-history-size unlimited
7278 Define how many instructions to disassemble in the @code{record
7279 instruction-history} command. The default value is 10.
7280 A @var{size} of @code{unlimited} means unlimited instructions.
7283 @item show record instruction-history-size
7284 Show how many instructions to disassemble in the @code{record
7285 instruction-history} command.
7287 @kindex record function-call-history
7288 @kindex rec function-call-history
7289 @item record function-call-history
7290 Prints the execution history at function granularity. It prints one
7291 line for each sequence of instructions that belong to the same
7292 function giving the name of that function, the source lines
7293 for this instruction sequence (if the @code{/l} modifier is
7294 specified), and the instructions numbers that form the sequence (if
7295 the @code{/i} modifier is specified). The function names are indented
7296 to reflect the call stack depth if the @code{/c} modifier is
7297 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7301 (@value{GDBP}) @b{list 1, 10}
7312 (@value{GDBP}) @b{record function-call-history /ilc}
7313 1 bar inst 1,4 at foo.c:6,8
7314 2 foo inst 5,10 at foo.c:2,3
7315 3 bar inst 11,13 at foo.c:9,10
7318 By default, ten lines are printed. This can be changed using the
7319 @code{set record function-call-history-size} command. Functions are
7320 printed in execution order. There are several ways to specify what
7324 @item record function-call-history @var{func}
7325 Prints ten functions starting from function number @var{func}.
7327 @item record function-call-history @var{func}, +/-@var{n}
7328 Prints @var{n} functions around function number @var{func}. If
7329 @var{n} is preceded with @code{+}, prints @var{n} functions after
7330 function number @var{func}. If @var{n} is preceded with @code{-},
7331 prints @var{n} functions before function number @var{func}.
7333 @item record function-call-history
7334 Prints ten more functions after the last ten-line print.
7336 @item record function-call-history -
7337 Prints ten more functions before the last ten-line print.
7339 @item record function-call-history @var{begin}, @var{end}
7340 Prints functions beginning with function number @var{begin} until
7341 function number @var{end}. The function number @var{end} is included.
7344 This command may not be available for all recording methods.
7346 @item set record function-call-history-size @var{size}
7347 @itemx set record function-call-history-size unlimited
7348 Define how many lines to print in the
7349 @code{record function-call-history} command. The default value is 10.
7350 A size of @code{unlimited} means unlimited lines.
7352 @item show record function-call-history-size
7353 Show how many lines to print in the
7354 @code{record function-call-history} command.
7359 @chapter Examining the Stack
7361 When your program has stopped, the first thing you need to know is where it
7362 stopped and how it got there.
7365 Each time your program performs a function call, information about the call
7367 That information includes the location of the call in your program,
7368 the arguments of the call,
7369 and the local variables of the function being called.
7370 The information is saved in a block of data called a @dfn{stack frame}.
7371 The stack frames are allocated in a region of memory called the @dfn{call
7374 When your program stops, the @value{GDBN} commands for examining the
7375 stack allow you to see all of this information.
7377 @cindex selected frame
7378 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7379 @value{GDBN} commands refer implicitly to the selected frame. In
7380 particular, whenever you ask @value{GDBN} for the value of a variable in
7381 your program, the value is found in the selected frame. There are
7382 special @value{GDBN} commands to select whichever frame you are
7383 interested in. @xref{Selection, ,Selecting a Frame}.
7385 When your program stops, @value{GDBN} automatically selects the
7386 currently executing frame and describes it briefly, similar to the
7387 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7390 * Frames:: Stack frames
7391 * Backtrace:: Backtraces
7392 * Selection:: Selecting a frame
7393 * Frame Info:: Information on a frame
7394 * Frame Apply:: Applying a command to several frames
7395 * Frame Filter Management:: Managing frame filters
7400 @section Stack Frames
7402 @cindex frame, definition
7404 The call stack is divided up into contiguous pieces called @dfn{stack
7405 frames}, or @dfn{frames} for short; each frame is the data associated
7406 with one call to one function. The frame contains the arguments given
7407 to the function, the function's local variables, and the address at
7408 which the function is executing.
7410 @cindex initial frame
7411 @cindex outermost frame
7412 @cindex innermost frame
7413 When your program is started, the stack has only one frame, that of the
7414 function @code{main}. This is called the @dfn{initial} frame or the
7415 @dfn{outermost} frame. Each time a function is called, a new frame is
7416 made. Each time a function returns, the frame for that function invocation
7417 is eliminated. If a function is recursive, there can be many frames for
7418 the same function. The frame for the function in which execution is
7419 actually occurring is called the @dfn{innermost} frame. This is the most
7420 recently created of all the stack frames that still exist.
7422 @cindex frame pointer
7423 Inside your program, stack frames are identified by their addresses. A
7424 stack frame consists of many bytes, each of which has its own address; each
7425 kind of computer has a convention for choosing one byte whose
7426 address serves as the address of the frame. Usually this address is kept
7427 in a register called the @dfn{frame pointer register}
7428 (@pxref{Registers, $fp}) while execution is going on in that frame.
7431 @cindex frame number
7432 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7433 number that is zero for the innermost frame, one for the frame that
7434 called it, and so on upward. These level numbers give you a way of
7435 designating stack frames in @value{GDBN} commands. The terms
7436 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7437 describe this number.
7439 @c The -fomit-frame-pointer below perennially causes hbox overflow
7440 @c underflow problems.
7441 @cindex frameless execution
7442 Some compilers provide a way to compile functions so that they operate
7443 without stack frames. (For example, the @value{NGCC} option
7445 @samp{-fomit-frame-pointer}
7447 generates functions without a frame.)
7448 This is occasionally done with heavily used library functions to save
7449 the frame setup time. @value{GDBN} has limited facilities for dealing
7450 with these function invocations. If the innermost function invocation
7451 has no stack frame, @value{GDBN} nevertheless regards it as though
7452 it had a separate frame, which is numbered zero as usual, allowing
7453 correct tracing of the function call chain. However, @value{GDBN} has
7454 no provision for frameless functions elsewhere in the stack.
7460 @cindex call stack traces
7461 A backtrace is a summary of how your program got where it is. It shows one
7462 line per frame, for many frames, starting with the currently executing
7463 frame (frame zero), followed by its caller (frame one), and on up the
7466 @anchor{backtrace-command}
7468 @kindex bt @r{(@code{backtrace})}
7469 To print a backtrace of the entire stack, use the @code{backtrace}
7470 command, or its alias @code{bt}. This command will print one line per
7471 frame for frames in the stack. By default, all stack frames are
7472 printed. You can stop the backtrace at any time by typing the system
7473 interrupt character, normally @kbd{Ctrl-c}.
7476 @item backtrace [@var{args}@dots{}]
7477 @itemx bt [@var{args}@dots{}]
7478 Print the backtrace of the entire stack. The optional @var{args} can
7479 be one of the following:
7484 Print only the innermost @var{n} frames, where @var{n} is a positive
7489 Print only the outermost @var{n} frames, where @var{n} is a positive
7493 Print the values of the local variables also. This can be combined
7494 with a number to limit the number of frames shown.
7497 Do not run Python frame filters on this backtrace. @xref{Frame
7498 Filter API}, for more information. Additionally use @ref{disable
7499 frame-filter all} to turn off all frame filters. This is only
7500 relevant when @value{GDBN} has been configured with @code{Python}
7504 A Python frame filter might decide to ``elide'' some frames. Normally
7505 such elided frames are still printed, but they are indented relative
7506 to the filtered frames that cause them to be elided. The @code{hide}
7507 option causes elided frames to not be printed at all.
7513 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7514 are additional aliases for @code{backtrace}.
7516 @cindex multiple threads, backtrace
7517 In a multi-threaded program, @value{GDBN} by default shows the
7518 backtrace only for the current thread. To display the backtrace for
7519 several or all of the threads, use the command @code{thread apply}
7520 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7521 apply all backtrace}, @value{GDBN} will display the backtrace for all
7522 the threads; this is handy when you debug a core dump of a
7523 multi-threaded program.
7525 Each line in the backtrace shows the frame number and the function name.
7526 The program counter value is also shown---unless you use @code{set
7527 print address off}. The backtrace also shows the source file name and
7528 line number, as well as the arguments to the function. The program
7529 counter value is omitted if it is at the beginning of the code for that
7532 Here is an example of a backtrace. It was made with the command
7533 @samp{bt 3}, so it shows the innermost three frames.
7537 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7539 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7540 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7542 (More stack frames follow...)
7547 The display for frame zero does not begin with a program counter
7548 value, indicating that your program has stopped at the beginning of the
7549 code for line @code{993} of @code{builtin.c}.
7552 The value of parameter @code{data} in frame 1 has been replaced by
7553 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7554 only if it is a scalar (integer, pointer, enumeration, etc). See command
7555 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7556 on how to configure the way function parameter values are printed.
7558 @cindex optimized out, in backtrace
7559 @cindex function call arguments, optimized out
7560 If your program was compiled with optimizations, some compilers will
7561 optimize away arguments passed to functions if those arguments are
7562 never used after the call. Such optimizations generate code that
7563 passes arguments through registers, but doesn't store those arguments
7564 in the stack frame. @value{GDBN} has no way of displaying such
7565 arguments in stack frames other than the innermost one. Here's what
7566 such a backtrace might look like:
7570 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7572 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7573 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7575 (More stack frames follow...)
7580 The values of arguments that were not saved in their stack frames are
7581 shown as @samp{<optimized out>}.
7583 If you need to display the values of such optimized-out arguments,
7584 either deduce that from other variables whose values depend on the one
7585 you are interested in, or recompile without optimizations.
7587 @cindex backtrace beyond @code{main} function
7588 @cindex program entry point
7589 @cindex startup code, and backtrace
7590 Most programs have a standard user entry point---a place where system
7591 libraries and startup code transition into user code. For C this is
7592 @code{main}@footnote{
7593 Note that embedded programs (the so-called ``free-standing''
7594 environment) are not required to have a @code{main} function as the
7595 entry point. They could even have multiple entry points.}.
7596 When @value{GDBN} finds the entry function in a backtrace
7597 it will terminate the backtrace, to avoid tracing into highly
7598 system-specific (and generally uninteresting) code.
7600 If you need to examine the startup code, or limit the number of levels
7601 in a backtrace, you can change this behavior:
7604 @item set backtrace past-main
7605 @itemx set backtrace past-main on
7606 @kindex set backtrace
7607 Backtraces will continue past the user entry point.
7609 @item set backtrace past-main off
7610 Backtraces will stop when they encounter the user entry point. This is the
7613 @item show backtrace past-main
7614 @kindex show backtrace
7615 Display the current user entry point backtrace policy.
7617 @item set backtrace past-entry
7618 @itemx set backtrace past-entry on
7619 Backtraces will continue past the internal entry point of an application.
7620 This entry point is encoded by the linker when the application is built,
7621 and is likely before the user entry point @code{main} (or equivalent) is called.
7623 @item set backtrace past-entry off
7624 Backtraces will stop when they encounter the internal entry point of an
7625 application. This is the default.
7627 @item show backtrace past-entry
7628 Display the current internal entry point backtrace policy.
7630 @item set backtrace limit @var{n}
7631 @itemx set backtrace limit 0
7632 @itemx set backtrace limit unlimited
7633 @cindex backtrace limit
7634 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7635 or zero means unlimited levels.
7637 @item show backtrace limit
7638 Display the current limit on backtrace levels.
7641 You can control how file names are displayed.
7644 @item set filename-display
7645 @itemx set filename-display relative
7646 @cindex filename-display
7647 Display file names relative to the compilation directory. This is the default.
7649 @item set filename-display basename
7650 Display only basename of a filename.
7652 @item set filename-display absolute
7653 Display an absolute filename.
7655 @item show filename-display
7656 Show the current way to display filenames.
7660 @section Selecting a Frame
7662 Most commands for examining the stack and other data in your program work on
7663 whichever stack frame is selected at the moment. Here are the commands for
7664 selecting a stack frame; all of them finish by printing a brief description
7665 of the stack frame just selected.
7668 @kindex frame@r{, selecting}
7669 @kindex f @r{(@code{frame})}
7670 @item frame @r{[} @var{frame-selection-spec} @r{]}
7671 @item f @r{[} @var{frame-selection-spec} @r{]}
7672 The @command{frame} command allows different stack frames to be
7673 selected. The @var{frame-selection-spec} can be any of the following:
7678 @item level @var{num}
7679 Select frame level @var{num}. Recall that frame zero is the innermost
7680 (currently executing) frame, frame one is the frame that called the
7681 innermost one, and so on. The highest level frame is usually the one
7684 As this is the most common method of navigating the frame stack, the
7685 string @command{level} can be omitted. For example, the following two
7686 commands are equivalent:
7689 (@value{GDBP}) frame 3
7690 (@value{GDBP}) frame level 3
7693 @kindex frame address
7694 @item address @var{stack-address}
7695 Select the frame with stack address @var{stack-address}. The
7696 @var{stack-address} for a frame can be seen in the output of
7697 @command{info frame}, for example:
7701 Stack level 1, frame at 0x7fffffffda30:
7702 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7703 tail call frame, caller of frame at 0x7fffffffda30
7704 source language c++.
7705 Arglist at unknown address.
7706 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7709 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7710 indicated by the line:
7713 Stack level 1, frame at 0x7fffffffda30:
7716 @kindex frame function
7717 @item function @var{function-name}
7718 Select the stack frame for function @var{function-name}. If there are
7719 multiple stack frames for function @var{function-name} then the inner
7720 most stack frame is selected.
7723 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7724 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7725 viewed has stack address @var{stack-addr}, and optionally, a program
7726 counter address of @var{pc-addr}.
7728 This is useful mainly if the chaining of stack frames has been
7729 damaged by a bug, making it impossible for @value{GDBN} to assign
7730 numbers properly to all frames. In addition, this can be useful
7731 when your program has multiple stacks and switches between them.
7733 When viewing a frame outside the current backtrace using
7734 @command{frame view} then you can always return to the original
7735 stack using one of the previous stack frame selection instructions,
7736 for example @command{frame level 0}.
7742 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7743 numbers @var{n}, this advances toward the outermost frame, to higher
7744 frame numbers, to frames that have existed longer.
7747 @kindex do @r{(@code{down})}
7749 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7750 positive numbers @var{n}, this advances toward the innermost frame, to
7751 lower frame numbers, to frames that were created more recently.
7752 You may abbreviate @code{down} as @code{do}.
7755 All of these commands end by printing two lines of output describing the
7756 frame. The first line shows the frame number, the function name, the
7757 arguments, and the source file and line number of execution in that
7758 frame. The second line shows the text of that source line.
7766 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7768 10 read_input_file (argv[i]);
7772 After such a printout, the @code{list} command with no arguments
7773 prints ten lines centered on the point of execution in the frame.
7774 You can also edit the program at the point of execution with your favorite
7775 editing program by typing @code{edit}.
7776 @xref{List, ,Printing Source Lines},
7780 @kindex select-frame
7781 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7782 The @code{select-frame} command is a variant of @code{frame} that does
7783 not display the new frame after selecting it. This command is
7784 intended primarily for use in @value{GDBN} command scripts, where the
7785 output might be unnecessary and distracting. The
7786 @var{frame-selection-spec} is as for the @command{frame} command
7787 described in @ref{Selection, ,Selecting a Frame}.
7789 @kindex down-silently
7791 @item up-silently @var{n}
7792 @itemx down-silently @var{n}
7793 These two commands are variants of @code{up} and @code{down},
7794 respectively; they differ in that they do their work silently, without
7795 causing display of the new frame. They are intended primarily for use
7796 in @value{GDBN} command scripts, where the output might be unnecessary and
7801 @section Information About a Frame
7803 There are several other commands to print information about the selected
7809 When used without any argument, this command does not change which
7810 frame is selected, but prints a brief description of the currently
7811 selected stack frame. It can be abbreviated @code{f}. With an
7812 argument, this command is used to select a stack frame.
7813 @xref{Selection, ,Selecting a Frame}.
7816 @kindex info f @r{(@code{info frame})}
7819 This command prints a verbose description of the selected stack frame,
7824 the address of the frame
7826 the address of the next frame down (called by this frame)
7828 the address of the next frame up (caller of this frame)
7830 the language in which the source code corresponding to this frame is written
7832 the address of the frame's arguments
7834 the address of the frame's local variables
7836 the program counter saved in it (the address of execution in the caller frame)
7838 which registers were saved in the frame
7841 @noindent The verbose description is useful when
7842 something has gone wrong that has made the stack format fail to fit
7843 the usual conventions.
7845 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7846 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7847 Print a verbose description of the frame selected by
7848 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7849 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7850 a Frame}). The selected frame remains unchanged by this command.
7853 @item info args [-q]
7854 Print the arguments of the selected frame, each on a separate line.
7856 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7857 printing header information and messages explaining why no argument
7860 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7861 Like @kbd{info args}, but only print the arguments selected
7862 with the provided regexp(s).
7864 If @var{regexp} is provided, print only the arguments whose names
7865 match the regular expression @var{regexp}.
7867 If @var{type_regexp} is provided, print only the arguments whose
7868 types, as printed by the @code{whatis} command, match
7869 the regular expression @var{type_regexp}.
7870 If @var{type_regexp} contains space(s), it should be enclosed in
7871 quote characters. If needed, use backslash to escape the meaning
7872 of special characters or quotes.
7874 If both @var{regexp} and @var{type_regexp} are provided, an argument
7875 is printed only if its name matches @var{regexp} and its type matches
7878 @item info locals [-q]
7880 Print the local variables of the selected frame, each on a separate
7881 line. These are all variables (declared either static or automatic)
7882 accessible at the point of execution of the selected frame.
7884 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7885 printing header information and messages explaining why no local variables
7888 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7889 Like @kbd{info locals}, but only print the local variables selected
7890 with the provided regexp(s).
7892 If @var{regexp} is provided, print only the local variables whose names
7893 match the regular expression @var{regexp}.
7895 If @var{type_regexp} is provided, print only the local variables whose
7896 types, as printed by the @code{whatis} command, match
7897 the regular expression @var{type_regexp}.
7898 If @var{type_regexp} contains space(s), it should be enclosed in
7899 quote characters. If needed, use backslash to escape the meaning
7900 of special characters or quotes.
7902 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7903 is printed only if its name matches @var{regexp} and its type matches
7906 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7907 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7908 For example, your program might use Resource Acquisition Is
7909 Initialization types (RAII) such as @code{lock_something_t}: each
7910 local variable of type @code{lock_something_t} automatically places a
7911 lock that is destroyed when the variable goes out of scope. You can
7912 then list all acquired locks in your program by doing
7914 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7917 or the equivalent shorter form
7919 tfaas i lo -q -t lock_something_t
7925 @section Applying a Command to Several Frames.
7927 @cindex apply command to several frames
7929 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7930 The @code{frame apply} command allows you to apply the named
7931 @var{command} to one or more frames.
7935 Specify @code{all} to apply @var{command} to all frames.
7938 Use @var{count} to apply @var{command} to the innermost @var{count}
7939 frames, where @var{count} is a positive number.
7942 Use @var{-count} to apply @var{command} to the outermost @var{count}
7943 frames, where @var{count} is a positive number.
7946 Use @code{level} to apply @var{command} to the set of frames identified
7947 by the @var{level} list. @var{level} is a frame level or a range of frame
7948 levels as @var{level1}-@var{level2}. The frame level is the number shown
7949 in the first field of the @samp{backtrace} command output.
7950 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7951 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7957 Note that the frames on which @code{frame apply} applies a command are
7958 also influenced by the @code{set backtrace} settings such as @code{set
7959 backtrace past-main} and @code{set backtrace limit N}. See
7960 @xref{Backtrace,,Backtraces}.
7962 The @var{flag} arguments control what output to produce and how to handle
7963 errors raised when applying @var{command} to a frame. @var{flag}
7964 must start with a @code{-} directly followed by one letter in
7965 @code{qcs}. If several flags are provided, they must be given
7966 individually, such as @code{-c -q}.
7968 By default, @value{GDBN} displays some frame information before the
7969 output produced by @var{command}, and an error raised during the
7970 execution of a @var{command} will abort @code{frame apply}. The
7971 following flags can be used to fine-tune this behavior:
7975 The flag @code{-c}, which stands for @samp{continue}, causes any
7976 errors in @var{command} to be displayed, and the execution of
7977 @code{frame apply} then continues.
7979 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7980 or empty output produced by a @var{command} to be silently ignored.
7981 That is, the execution continues, but the frame information and errors
7984 The flag @code{-q} (@samp{quiet}) disables printing the frame
7988 The following example shows how the flags @code{-c} and @code{-s} are
7989 working when applying the command @code{p j} to all frames, where
7990 variable @code{j} can only be successfully printed in the outermost
7991 @code{#1 main} frame.
7995 (gdb) frame apply all p j
7996 #0 some_function (i=5) at fun.c:4
7997 No symbol "j" in current context.
7998 (gdb) frame apply all -c p j
7999 #0 some_function (i=5) at fun.c:4
8000 No symbol "j" in current context.
8001 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8003 (gdb) frame apply all -s p j
8004 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8010 By default, @samp{frame apply}, prints the frame location
8011 information before the command output:
8015 (gdb) frame apply all p $sp
8016 #0 some_function (i=5) at fun.c:4
8017 $4 = (void *) 0xffffd1e0
8018 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8019 $5 = (void *) 0xffffd1f0
8024 If flag @code{-q} is given, no frame information is printed:
8027 (gdb) frame apply all -q p $sp
8028 $12 = (void *) 0xffffd1e0
8029 $13 = (void *) 0xffffd1f0
8037 @cindex apply a command to all frames (ignoring errors and empty output)
8038 @item faas @var{command}
8039 Shortcut for @code{frame apply all -s @var{command}}.
8040 Applies @var{command} on all frames, ignoring errors and empty output.
8042 It can for example be used to print a local variable or a function
8043 argument without knowing the frame where this variable or argument
8046 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8049 Note that the command @code{tfaas @var{command}} applies @var{command}
8050 on all frames of all threads. See @xref{Threads,,Threads}.
8054 @node Frame Filter Management
8055 @section Management of Frame Filters.
8056 @cindex managing frame filters
8058 Frame filters are Python based utilities to manage and decorate the
8059 output of frames. @xref{Frame Filter API}, for further information.
8061 Managing frame filters is performed by several commands available
8062 within @value{GDBN}, detailed here.
8065 @kindex info frame-filter
8066 @item info frame-filter
8067 Print a list of installed frame filters from all dictionaries, showing
8068 their name, priority and enabled status.
8070 @kindex disable frame-filter
8071 @anchor{disable frame-filter all}
8072 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8073 Disable a frame filter in the dictionary matching
8074 @var{filter-dictionary} and @var{filter-name}. The
8075 @var{filter-dictionary} may be @code{all}, @code{global},
8076 @code{progspace}, or the name of the object file where the frame filter
8077 dictionary resides. When @code{all} is specified, all frame filters
8078 across all dictionaries are disabled. The @var{filter-name} is the name
8079 of the frame filter and is used when @code{all} is not the option for
8080 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8081 may be enabled again later.
8083 @kindex enable frame-filter
8084 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8085 Enable a frame filter in the dictionary matching
8086 @var{filter-dictionary} and @var{filter-name}. The
8087 @var{filter-dictionary} may be @code{all}, @code{global},
8088 @code{progspace} or the name of the object file where the frame filter
8089 dictionary resides. When @code{all} is specified, all frame filters across
8090 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8091 filter and is used when @code{all} is not the option for
8092 @var{filter-dictionary}.
8097 (gdb) info frame-filter
8099 global frame-filters:
8100 Priority Enabled Name
8101 1000 No PrimaryFunctionFilter
8104 progspace /build/test frame-filters:
8105 Priority Enabled Name
8106 100 Yes ProgspaceFilter
8108 objfile /build/test frame-filters:
8109 Priority Enabled Name
8110 999 Yes BuildProgra Filter
8112 (gdb) disable frame-filter /build/test BuildProgramFilter
8113 (gdb) info frame-filter
8115 global frame-filters:
8116 Priority Enabled Name
8117 1000 No PrimaryFunctionFilter
8120 progspace /build/test frame-filters:
8121 Priority Enabled Name
8122 100 Yes ProgspaceFilter
8124 objfile /build/test frame-filters:
8125 Priority Enabled Name
8126 999 No BuildProgramFilter
8128 (gdb) enable frame-filter global PrimaryFunctionFilter
8129 (gdb) info frame-filter
8131 global frame-filters:
8132 Priority Enabled Name
8133 1000 Yes PrimaryFunctionFilter
8136 progspace /build/test frame-filters:
8137 Priority Enabled Name
8138 100 Yes ProgspaceFilter
8140 objfile /build/test frame-filters:
8141 Priority Enabled Name
8142 999 No BuildProgramFilter
8145 @kindex set frame-filter priority
8146 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8147 Set the @var{priority} of a frame filter in the dictionary matching
8148 @var{filter-dictionary}, and the frame filter name matching
8149 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8150 @code{progspace} or the name of the object file where the frame filter
8151 dictionary resides. The @var{priority} is an integer.
8153 @kindex show frame-filter priority
8154 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8155 Show the @var{priority} of a frame filter in the dictionary matching
8156 @var{filter-dictionary}, and the frame filter name matching
8157 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8158 @code{progspace} or the name of the object file where the frame filter
8164 (gdb) info frame-filter
8166 global frame-filters:
8167 Priority Enabled Name
8168 1000 Yes PrimaryFunctionFilter
8171 progspace /build/test frame-filters:
8172 Priority Enabled Name
8173 100 Yes ProgspaceFilter
8175 objfile /build/test frame-filters:
8176 Priority Enabled Name
8177 999 No BuildProgramFilter
8179 (gdb) set frame-filter priority global Reverse 50
8180 (gdb) info frame-filter
8182 global frame-filters:
8183 Priority Enabled Name
8184 1000 Yes PrimaryFunctionFilter
8187 progspace /build/test frame-filters:
8188 Priority Enabled Name
8189 100 Yes ProgspaceFilter
8191 objfile /build/test frame-filters:
8192 Priority Enabled Name
8193 999 No BuildProgramFilter
8198 @chapter Examining Source Files
8200 @value{GDBN} can print parts of your program's source, since the debugging
8201 information recorded in the program tells @value{GDBN} what source files were
8202 used to build it. When your program stops, @value{GDBN} spontaneously prints
8203 the line where it stopped. Likewise, when you select a stack frame
8204 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8205 execution in that frame has stopped. You can print other portions of
8206 source files by explicit command.
8208 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8209 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8210 @value{GDBN} under @sc{gnu} Emacs}.
8213 * List:: Printing source lines
8214 * Specify Location:: How to specify code locations
8215 * Edit:: Editing source files
8216 * Search:: Searching source files
8217 * Source Path:: Specifying source directories
8218 * Machine Code:: Source and machine code
8222 @section Printing Source Lines
8225 @kindex l @r{(@code{list})}
8226 To print lines from a source file, use the @code{list} command
8227 (abbreviated @code{l}). By default, ten lines are printed.
8228 There are several ways to specify what part of the file you want to
8229 print; see @ref{Specify Location}, for the full list.
8231 Here are the forms of the @code{list} command most commonly used:
8234 @item list @var{linenum}
8235 Print lines centered around line number @var{linenum} in the
8236 current source file.
8238 @item list @var{function}
8239 Print lines centered around the beginning of function
8243 Print more lines. If the last lines printed were printed with a
8244 @code{list} command, this prints lines following the last lines
8245 printed; however, if the last line printed was a solitary line printed
8246 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8247 Stack}), this prints lines centered around that line.
8250 Print lines just before the lines last printed.
8253 @cindex @code{list}, how many lines to display
8254 By default, @value{GDBN} prints ten source lines with any of these forms of
8255 the @code{list} command. You can change this using @code{set listsize}:
8258 @kindex set listsize
8259 @item set listsize @var{count}
8260 @itemx set listsize unlimited
8261 Make the @code{list} command display @var{count} source lines (unless
8262 the @code{list} argument explicitly specifies some other number).
8263 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8265 @kindex show listsize
8267 Display the number of lines that @code{list} prints.
8270 Repeating a @code{list} command with @key{RET} discards the argument,
8271 so it is equivalent to typing just @code{list}. This is more useful
8272 than listing the same lines again. An exception is made for an
8273 argument of @samp{-}; that argument is preserved in repetition so that
8274 each repetition moves up in the source file.
8276 In general, the @code{list} command expects you to supply zero, one or two
8277 @dfn{locations}. Locations specify source lines; there are several ways
8278 of writing them (@pxref{Specify Location}), but the effect is always
8279 to specify some source line.
8281 Here is a complete description of the possible arguments for @code{list}:
8284 @item list @var{location}
8285 Print lines centered around the line specified by @var{location}.
8287 @item list @var{first},@var{last}
8288 Print lines from @var{first} to @var{last}. Both arguments are
8289 locations. When a @code{list} command has two locations, and the
8290 source file of the second location is omitted, this refers to
8291 the same source file as the first location.
8293 @item list ,@var{last}
8294 Print lines ending with @var{last}.
8296 @item list @var{first},
8297 Print lines starting with @var{first}.
8300 Print lines just after the lines last printed.
8303 Print lines just before the lines last printed.
8306 As described in the preceding table.
8309 @node Specify Location
8310 @section Specifying a Location
8311 @cindex specifying location
8313 @cindex source location
8316 * Linespec Locations:: Linespec locations
8317 * Explicit Locations:: Explicit locations
8318 * Address Locations:: Address locations
8321 Several @value{GDBN} commands accept arguments that specify a location
8322 of your program's code. Since @value{GDBN} is a source-level
8323 debugger, a location usually specifies some line in the source code.
8324 Locations may be specified using three different formats:
8325 linespec locations, explicit locations, or address locations.
8327 @node Linespec Locations
8328 @subsection Linespec Locations
8329 @cindex linespec locations
8331 A @dfn{linespec} is a colon-separated list of source location parameters such
8332 as file name, function name, etc. Here are all the different ways of
8333 specifying a linespec:
8337 Specifies the line number @var{linenum} of the current source file.
8340 @itemx +@var{offset}
8341 Specifies the line @var{offset} lines before or after the @dfn{current
8342 line}. For the @code{list} command, the current line is the last one
8343 printed; for the breakpoint commands, this is the line at which
8344 execution stopped in the currently selected @dfn{stack frame}
8345 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8346 used as the second of the two linespecs in a @code{list} command,
8347 this specifies the line @var{offset} lines up or down from the first
8350 @item @var{filename}:@var{linenum}
8351 Specifies the line @var{linenum} in the source file @var{filename}.
8352 If @var{filename} is a relative file name, then it will match any
8353 source file name with the same trailing components. For example, if
8354 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8355 name of @file{/build/trunk/gcc/expr.c}, but not
8356 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8358 @item @var{function}
8359 Specifies the line that begins the body of the function @var{function}.
8360 For example, in C, this is the line with the open brace.
8362 By default, in C@t{++} and Ada, @var{function} is interpreted as
8363 specifying all functions named @var{function} in all scopes. For
8364 C@t{++}, this means in all namespaces and classes. For Ada, this
8365 means in all packages.
8367 For example, assuming a program with C@t{++} symbols named
8368 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8369 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8371 Commands that accept a linespec let you override this with the
8372 @code{-qualified} option. For example, @w{@kbd{break -qualified
8373 func}} sets a breakpoint on a free-function named @code{func} ignoring
8374 any C@t{++} class methods and namespace functions called @code{func}.
8376 @xref{Explicit Locations}.
8378 @item @var{function}:@var{label}
8379 Specifies the line where @var{label} appears in @var{function}.
8381 @item @var{filename}:@var{function}
8382 Specifies the line that begins the body of the function @var{function}
8383 in the file @var{filename}. You only need the file name with a
8384 function name to avoid ambiguity when there are identically named
8385 functions in different source files.
8388 Specifies the line at which the label named @var{label} appears
8389 in the function corresponding to the currently selected stack frame.
8390 If there is no current selected stack frame (for instance, if the inferior
8391 is not running), then @value{GDBN} will not search for a label.
8393 @cindex breakpoint at static probe point
8394 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8395 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8396 applications to embed static probes. @xref{Static Probe Points}, for more
8397 information on finding and using static probes. This form of linespec
8398 specifies the location of such a static probe.
8400 If @var{objfile} is given, only probes coming from that shared library
8401 or executable matching @var{objfile} as a regular expression are considered.
8402 If @var{provider} is given, then only probes from that provider are considered.
8403 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8404 each one of those probes.
8407 @node Explicit Locations
8408 @subsection Explicit Locations
8409 @cindex explicit locations
8411 @dfn{Explicit locations} allow the user to directly specify the source
8412 location's parameters using option-value pairs.
8414 Explicit locations are useful when several functions, labels, or
8415 file names have the same name (base name for files) in the program's
8416 sources. In these cases, explicit locations point to the source
8417 line you meant more accurately and unambiguously. Also, using
8418 explicit locations might be faster in large programs.
8420 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8421 defined in the file named @file{foo} or the label @code{bar} in a function
8422 named @code{foo}. @value{GDBN} must search either the file system or
8423 the symbol table to know.
8425 The list of valid explicit location options is summarized in the
8429 @item -source @var{filename}
8430 The value specifies the source file name. To differentiate between
8431 files with the same base name, prepend as many directories as is necessary
8432 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8433 @value{GDBN} will use the first file it finds with the given base
8434 name. This option requires the use of either @code{-function} or @code{-line}.
8436 @item -function @var{function}
8437 The value specifies the name of a function. Operations
8438 on function locations unmodified by other options (such as @code{-label}
8439 or @code{-line}) refer to the line that begins the body of the function.
8440 In C, for example, this is the line with the open brace.
8442 By default, in C@t{++} and Ada, @var{function} is interpreted as
8443 specifying all functions named @var{function} in all scopes. For
8444 C@t{++}, this means in all namespaces and classes. For Ada, this
8445 means in all packages.
8447 For example, assuming a program with C@t{++} symbols named
8448 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8449 -function func}} and @w{@kbd{break -function B::func}} set a
8450 breakpoint on both symbols.
8452 You can use the @kbd{-qualified} flag to override this (see below).
8456 This flag makes @value{GDBN} interpret a function name specified with
8457 @kbd{-function} as a complete fully-qualified name.
8459 For example, assuming a C@t{++} program with symbols named
8460 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8461 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8463 (Note: the @kbd{-qualified} option can precede a linespec as well
8464 (@pxref{Linespec Locations}), so the particular example above could be
8465 simplified as @w{@kbd{break -qualified B::func}}.)
8467 @item -label @var{label}
8468 The value specifies the name of a label. When the function
8469 name is not specified, the label is searched in the function of the currently
8470 selected stack frame.
8472 @item -line @var{number}
8473 The value specifies a line offset for the location. The offset may either
8474 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8475 the command. When specified without any other options, the line offset is
8476 relative to the current line.
8479 Explicit location options may be abbreviated by omitting any non-unique
8480 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8482 @node Address Locations
8483 @subsection Address Locations
8484 @cindex address locations
8486 @dfn{Address locations} indicate a specific program address. They have
8487 the generalized form *@var{address}.
8489 For line-oriented commands, such as @code{list} and @code{edit}, this
8490 specifies a source line that contains @var{address}. For @code{break} and
8491 other breakpoint-oriented commands, this can be used to set breakpoints in
8492 parts of your program which do not have debugging information or
8495 Here @var{address} may be any expression valid in the current working
8496 language (@pxref{Languages, working language}) that specifies a code
8497 address. In addition, as a convenience, @value{GDBN} extends the
8498 semantics of expressions used in locations to cover several situations
8499 that frequently occur during debugging. Here are the various forms
8503 @item @var{expression}
8504 Any expression valid in the current working language.
8506 @item @var{funcaddr}
8507 An address of a function or procedure derived from its name. In C,
8508 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8509 simply the function's name @var{function} (and actually a special case
8510 of a valid expression). In Pascal and Modula-2, this is
8511 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8512 (although the Pascal form also works).
8514 This form specifies the address of the function's first instruction,
8515 before the stack frame and arguments have been set up.
8517 @item '@var{filename}':@var{funcaddr}
8518 Like @var{funcaddr} above, but also specifies the name of the source
8519 file explicitly. This is useful if the name of the function does not
8520 specify the function unambiguously, e.g., if there are several
8521 functions with identical names in different source files.
8525 @section Editing Source Files
8526 @cindex editing source files
8529 @kindex e @r{(@code{edit})}
8530 To edit the lines in a source file, use the @code{edit} command.
8531 The editing program of your choice
8532 is invoked with the current line set to
8533 the active line in the program.
8534 Alternatively, there are several ways to specify what part of the file you
8535 want to print if you want to see other parts of the program:
8538 @item edit @var{location}
8539 Edit the source file specified by @code{location}. Editing starts at
8540 that @var{location}, e.g., at the specified source line of the
8541 specified file. @xref{Specify Location}, for all the possible forms
8542 of the @var{location} argument; here are the forms of the @code{edit}
8543 command most commonly used:
8546 @item edit @var{number}
8547 Edit the current source file with @var{number} as the active line number.
8549 @item edit @var{function}
8550 Edit the file containing @var{function} at the beginning of its definition.
8555 @subsection Choosing your Editor
8556 You can customize @value{GDBN} to use any editor you want
8558 The only restriction is that your editor (say @code{ex}), recognizes the
8559 following command-line syntax:
8561 ex +@var{number} file
8563 The optional numeric value +@var{number} specifies the number of the line in
8564 the file where to start editing.}.
8565 By default, it is @file{@value{EDITOR}}, but you can change this
8566 by setting the environment variable @code{EDITOR} before using
8567 @value{GDBN}. For example, to configure @value{GDBN} to use the
8568 @code{vi} editor, you could use these commands with the @code{sh} shell:
8574 or in the @code{csh} shell,
8576 setenv EDITOR /usr/bin/vi
8581 @section Searching Source Files
8582 @cindex searching source files
8584 There are two commands for searching through the current source file for a
8589 @kindex forward-search
8590 @kindex fo @r{(@code{forward-search})}
8591 @item forward-search @var{regexp}
8592 @itemx search @var{regexp}
8593 The command @samp{forward-search @var{regexp}} checks each line,
8594 starting with the one following the last line listed, for a match for
8595 @var{regexp}. It lists the line that is found. You can use the
8596 synonym @samp{search @var{regexp}} or abbreviate the command name as
8599 @kindex reverse-search
8600 @item reverse-search @var{regexp}
8601 The command @samp{reverse-search @var{regexp}} checks each line, starting
8602 with the one before the last line listed and going backward, for a match
8603 for @var{regexp}. It lists the line that is found. You can abbreviate
8604 this command as @code{rev}.
8608 @section Specifying Source Directories
8611 @cindex directories for source files
8612 Executable programs sometimes do not record the directories of the source
8613 files from which they were compiled, just the names. Even when they do,
8614 the directories could be moved between the compilation and your debugging
8615 session. @value{GDBN} has a list of directories to search for source files;
8616 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8617 it tries all the directories in the list, in the order they are present
8618 in the list, until it finds a file with the desired name.
8620 For example, suppose an executable references the file
8621 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8622 @file{/mnt/cross}. The file is first looked up literally; if this
8623 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8624 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8625 message is printed. @value{GDBN} does not look up the parts of the
8626 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8627 Likewise, the subdirectories of the source path are not searched: if
8628 the source path is @file{/mnt/cross}, and the binary refers to
8629 @file{foo.c}, @value{GDBN} would not find it under
8630 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8632 Plain file names, relative file names with leading directories, file
8633 names containing dots, etc.@: are all treated as described above; for
8634 instance, if the source path is @file{/mnt/cross}, and the source file
8635 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8636 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8637 that---@file{/mnt/cross/foo.c}.
8639 Note that the executable search path is @emph{not} used to locate the
8642 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8643 any information it has cached about where source files are found and where
8644 each line is in the file.
8648 When you start @value{GDBN}, its source path includes only @samp{cdir}
8649 and @samp{cwd}, in that order.
8650 To add other directories, use the @code{directory} command.
8652 The search path is used to find both program source files and @value{GDBN}
8653 script files (read using the @samp{-command} option and @samp{source} command).
8655 In addition to the source path, @value{GDBN} provides a set of commands
8656 that manage a list of source path substitution rules. A @dfn{substitution
8657 rule} specifies how to rewrite source directories stored in the program's
8658 debug information in case the sources were moved to a different
8659 directory between compilation and debugging. A rule is made of
8660 two strings, the first specifying what needs to be rewritten in
8661 the path, and the second specifying how it should be rewritten.
8662 In @ref{set substitute-path}, we name these two parts @var{from} and
8663 @var{to} respectively. @value{GDBN} does a simple string replacement
8664 of @var{from} with @var{to} at the start of the directory part of the
8665 source file name, and uses that result instead of the original file
8666 name to look up the sources.
8668 Using the previous example, suppose the @file{foo-1.0} tree has been
8669 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8670 @value{GDBN} to replace @file{/usr/src} in all source path names with
8671 @file{/mnt/cross}. The first lookup will then be
8672 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8673 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8674 substitution rule, use the @code{set substitute-path} command
8675 (@pxref{set substitute-path}).
8677 To avoid unexpected substitution results, a rule is applied only if the
8678 @var{from} part of the directory name ends at a directory separator.
8679 For instance, a rule substituting @file{/usr/source} into
8680 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8681 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8682 is applied only at the beginning of the directory name, this rule will
8683 not be applied to @file{/root/usr/source/baz.c} either.
8685 In many cases, you can achieve the same result using the @code{directory}
8686 command. However, @code{set substitute-path} can be more efficient in
8687 the case where the sources are organized in a complex tree with multiple
8688 subdirectories. With the @code{directory} command, you need to add each
8689 subdirectory of your project. If you moved the entire tree while
8690 preserving its internal organization, then @code{set substitute-path}
8691 allows you to direct the debugger to all the sources with one single
8694 @code{set substitute-path} is also more than just a shortcut command.
8695 The source path is only used if the file at the original location no
8696 longer exists. On the other hand, @code{set substitute-path} modifies
8697 the debugger behavior to look at the rewritten location instead. So, if
8698 for any reason a source file that is not relevant to your executable is
8699 located at the original location, a substitution rule is the only
8700 method available to point @value{GDBN} at the new location.
8702 @cindex @samp{--with-relocated-sources}
8703 @cindex default source path substitution
8704 You can configure a default source path substitution rule by
8705 configuring @value{GDBN} with the
8706 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8707 should be the name of a directory under @value{GDBN}'s configured
8708 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8709 directory names in debug information under @var{dir} will be adjusted
8710 automatically if the installed @value{GDBN} is moved to a new
8711 location. This is useful if @value{GDBN}, libraries or executables
8712 with debug information and corresponding source code are being moved
8716 @item directory @var{dirname} @dots{}
8717 @item dir @var{dirname} @dots{}
8718 Add directory @var{dirname} to the front of the source path. Several
8719 directory names may be given to this command, separated by @samp{:}
8720 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8721 part of absolute file names) or
8722 whitespace. You may specify a directory that is already in the source
8723 path; this moves it forward, so @value{GDBN} searches it sooner.
8727 @vindex $cdir@r{, convenience variable}
8728 @vindex $cwd@r{, convenience variable}
8729 @cindex compilation directory
8730 @cindex current directory
8731 @cindex working directory
8732 @cindex directory, current
8733 @cindex directory, compilation
8734 You can use the string @samp{$cdir} to refer to the compilation
8735 directory (if one is recorded), and @samp{$cwd} to refer to the current
8736 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8737 tracks the current working directory as it changes during your @value{GDBN}
8738 session, while the latter is immediately expanded to the current
8739 directory at the time you add an entry to the source path.
8742 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8744 @c RET-repeat for @code{directory} is explicitly disabled, but since
8745 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8747 @item set directories @var{path-list}
8748 @kindex set directories
8749 Set the source path to @var{path-list}.
8750 @samp{$cdir:$cwd} are added if missing.
8752 @item show directories
8753 @kindex show directories
8754 Print the source path: show which directories it contains.
8756 @anchor{set substitute-path}
8757 @item set substitute-path @var{from} @var{to}
8758 @kindex set substitute-path
8759 Define a source path substitution rule, and add it at the end of the
8760 current list of existing substitution rules. If a rule with the same
8761 @var{from} was already defined, then the old rule is also deleted.
8763 For example, if the file @file{/foo/bar/baz.c} was moved to
8764 @file{/mnt/cross/baz.c}, then the command
8767 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8771 will tell @value{GDBN} to replace @samp{/foo/bar} with
8772 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8773 @file{baz.c} even though it was moved.
8775 In the case when more than one substitution rule have been defined,
8776 the rules are evaluated one by one in the order where they have been
8777 defined. The first one matching, if any, is selected to perform
8780 For instance, if we had entered the following commands:
8783 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8784 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8788 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8789 @file{/mnt/include/defs.h} by using the first rule. However, it would
8790 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8791 @file{/mnt/src/lib/foo.c}.
8794 @item unset substitute-path [path]
8795 @kindex unset substitute-path
8796 If a path is specified, search the current list of substitution rules
8797 for a rule that would rewrite that path. Delete that rule if found.
8798 A warning is emitted by the debugger if no rule could be found.
8800 If no path is specified, then all substitution rules are deleted.
8802 @item show substitute-path [path]
8803 @kindex show substitute-path
8804 If a path is specified, then print the source path substitution rule
8805 which would rewrite that path, if any.
8807 If no path is specified, then print all existing source path substitution
8812 If your source path is cluttered with directories that are no longer of
8813 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8814 versions of source. You can correct the situation as follows:
8818 Use @code{directory} with no argument to reset the source path to its default value.
8821 Use @code{directory} with suitable arguments to reinstall the
8822 directories you want in the source path. You can add all the
8823 directories in one command.
8827 @section Source and Machine Code
8828 @cindex source line and its code address
8830 You can use the command @code{info line} to map source lines to program
8831 addresses (and vice versa), and the command @code{disassemble} to display
8832 a range of addresses as machine instructions. You can use the command
8833 @code{set disassemble-next-line} to set whether to disassemble next
8834 source line when execution stops. When run under @sc{gnu} Emacs
8835 mode, the @code{info line} command causes the arrow to point to the
8836 line specified. Also, @code{info line} prints addresses in symbolic form as
8842 @itemx info line @var{location}
8843 Print the starting and ending addresses of the compiled code for
8844 source line @var{location}. You can specify source lines in any of
8845 the ways documented in @ref{Specify Location}. With no @var{location}
8846 information about the current source line is printed.
8849 For example, we can use @code{info line} to discover the location of
8850 the object code for the first line of function
8851 @code{m4_changequote}:
8854 (@value{GDBP}) info line m4_changequote
8855 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8856 ends at 0x6350 <m4_changequote+4>.
8860 @cindex code address and its source line
8861 We can also inquire (using @code{*@var{addr}} as the form for
8862 @var{location}) what source line covers a particular address:
8864 (@value{GDBP}) info line *0x63ff
8865 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8866 ends at 0x6404 <m4_changequote+184>.
8869 @cindex @code{$_} and @code{info line}
8870 @cindex @code{x} command, default address
8871 @kindex x@r{(examine), and} info line
8872 After @code{info line}, the default address for the @code{x} command
8873 is changed to the starting address of the line, so that @samp{x/i} is
8874 sufficient to begin examining the machine code (@pxref{Memory,
8875 ,Examining Memory}). Also, this address is saved as the value of the
8876 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8879 @cindex info line, repeated calls
8880 After @code{info line}, using @code{info line} again without
8881 specifying a location will display information about the next source
8886 @cindex assembly instructions
8887 @cindex instructions, assembly
8888 @cindex machine instructions
8889 @cindex listing machine instructions
8891 @itemx disassemble /m
8892 @itemx disassemble /s
8893 @itemx disassemble /r
8894 This specialized command dumps a range of memory as machine
8895 instructions. It can also print mixed source+disassembly by specifying
8896 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8897 as well as in symbolic form by specifying the @code{/r} modifier.
8898 The default memory range is the function surrounding the
8899 program counter of the selected frame. A single argument to this
8900 command is a program counter value; @value{GDBN} dumps the function
8901 surrounding this value. When two arguments are given, they should
8902 be separated by a comma, possibly surrounded by whitespace. The
8903 arguments specify a range of addresses to dump, in one of two forms:
8906 @item @var{start},@var{end}
8907 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8908 @item @var{start},+@var{length}
8909 the addresses from @var{start} (inclusive) to
8910 @code{@var{start}+@var{length}} (exclusive).
8914 When 2 arguments are specified, the name of the function is also
8915 printed (since there could be several functions in the given range).
8917 The argument(s) can be any expression yielding a numeric value, such as
8918 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8920 If the range of memory being disassembled contains current program counter,
8921 the instruction at that location is shown with a @code{=>} marker.
8924 The following example shows the disassembly of a range of addresses of
8925 HP PA-RISC 2.0 code:
8928 (@value{GDBP}) disas 0x32c4, 0x32e4
8929 Dump of assembler code from 0x32c4 to 0x32e4:
8930 0x32c4 <main+204>: addil 0,dp
8931 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8932 0x32cc <main+212>: ldil 0x3000,r31
8933 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8934 0x32d4 <main+220>: ldo 0(r31),rp
8935 0x32d8 <main+224>: addil -0x800,dp
8936 0x32dc <main+228>: ldo 0x588(r1),r26
8937 0x32e0 <main+232>: ldil 0x3000,r31
8938 End of assembler dump.
8941 Here is an example showing mixed source+assembly for Intel x86
8942 with @code{/m} or @code{/s}, when the program is stopped just after
8943 function prologue in a non-optimized function with no inline code.
8946 (@value{GDBP}) disas /m main
8947 Dump of assembler code for function main:
8949 0x08048330 <+0>: push %ebp
8950 0x08048331 <+1>: mov %esp,%ebp
8951 0x08048333 <+3>: sub $0x8,%esp
8952 0x08048336 <+6>: and $0xfffffff0,%esp
8953 0x08048339 <+9>: sub $0x10,%esp
8955 6 printf ("Hello.\n");
8956 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8957 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8961 0x08048348 <+24>: mov $0x0,%eax
8962 0x0804834d <+29>: leave
8963 0x0804834e <+30>: ret
8965 End of assembler dump.
8968 The @code{/m} option is deprecated as its output is not useful when
8969 there is either inlined code or re-ordered code.
8970 The @code{/s} option is the preferred choice.
8971 Here is an example for AMD x86-64 showing the difference between
8972 @code{/m} output and @code{/s} output.
8973 This example has one inline function defined in a header file,
8974 and the code is compiled with @samp{-O2} optimization.
8975 Note how the @code{/m} output is missing the disassembly of
8976 several instructions that are present in the @code{/s} output.
9006 (@value{GDBP}) disas /m main
9007 Dump of assembler code for function main:
9011 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9012 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9016 0x000000000040041d <+29>: xor %eax,%eax
9017 0x000000000040041f <+31>: retq
9018 0x0000000000400420 <+32>: add %eax,%eax
9019 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9021 End of assembler dump.
9022 (@value{GDBP}) disas /s main
9023 Dump of assembler code for function main:
9027 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9031 0x0000000000400406 <+6>: test %eax,%eax
9032 0x0000000000400408 <+8>: js 0x400420 <main+32>
9037 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9038 0x000000000040040d <+13>: test %eax,%eax
9039 0x000000000040040f <+15>: mov $0x1,%eax
9040 0x0000000000400414 <+20>: cmovne %edx,%eax
9044 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9048 0x000000000040041d <+29>: xor %eax,%eax
9049 0x000000000040041f <+31>: retq
9053 0x0000000000400420 <+32>: add %eax,%eax
9054 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9055 End of assembler dump.
9058 Here is another example showing raw instructions in hex for AMD x86-64,
9061 (gdb) disas /r 0x400281,+10
9062 Dump of assembler code from 0x400281 to 0x40028b:
9063 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9064 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9065 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9066 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9067 End of assembler dump.
9070 Addresses cannot be specified as a location (@pxref{Specify Location}).
9071 So, for example, if you want to disassemble function @code{bar}
9072 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9073 and not @samp{disassemble foo.c:bar}.
9075 Some architectures have more than one commonly-used set of instruction
9076 mnemonics or other syntax.
9078 For programs that were dynamically linked and use shared libraries,
9079 instructions that call functions or branch to locations in the shared
9080 libraries might show a seemingly bogus location---it's actually a
9081 location of the relocation table. On some architectures, @value{GDBN}
9082 might be able to resolve these to actual function names.
9085 @kindex set disassembler-options
9086 @cindex disassembler options
9087 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9088 This command controls the passing of target specific information to
9089 the disassembler. For a list of valid options, please refer to the
9090 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9091 manual and/or the output of @kbd{objdump --help}
9092 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9093 The default value is the empty string.
9095 If it is necessary to specify more than one disassembler option, then
9096 multiple options can be placed together into a comma separated list.
9097 Currently this command is only supported on targets ARM, MIPS, PowerPC
9100 @kindex show disassembler-options
9101 @item show disassembler-options
9102 Show the current setting of the disassembler options.
9106 @kindex set disassembly-flavor
9107 @cindex Intel disassembly flavor
9108 @cindex AT&T disassembly flavor
9109 @item set disassembly-flavor @var{instruction-set}
9110 Select the instruction set to use when disassembling the
9111 program via the @code{disassemble} or @code{x/i} commands.
9113 Currently this command is only defined for the Intel x86 family. You
9114 can set @var{instruction-set} to either @code{intel} or @code{att}.
9115 The default is @code{att}, the AT&T flavor used by default by Unix
9116 assemblers for x86-based targets.
9118 @kindex show disassembly-flavor
9119 @item show disassembly-flavor
9120 Show the current setting of the disassembly flavor.
9124 @kindex set disassemble-next-line
9125 @kindex show disassemble-next-line
9126 @item set disassemble-next-line
9127 @itemx show disassemble-next-line
9128 Control whether or not @value{GDBN} will disassemble the next source
9129 line or instruction when execution stops. If ON, @value{GDBN} will
9130 display disassembly of the next source line when execution of the
9131 program being debugged stops. This is @emph{in addition} to
9132 displaying the source line itself, which @value{GDBN} always does if
9133 possible. If the next source line cannot be displayed for some reason
9134 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9135 info in the debug info), @value{GDBN} will display disassembly of the
9136 next @emph{instruction} instead of showing the next source line. If
9137 AUTO, @value{GDBN} will display disassembly of next instruction only
9138 if the source line cannot be displayed. This setting causes
9139 @value{GDBN} to display some feedback when you step through a function
9140 with no line info or whose source file is unavailable. The default is
9141 OFF, which means never display the disassembly of the next line or
9147 @chapter Examining Data
9149 @cindex printing data
9150 @cindex examining data
9153 The usual way to examine data in your program is with the @code{print}
9154 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9155 evaluates and prints the value of an expression of the language your
9156 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9157 Different Languages}). It may also print the expression using a
9158 Python-based pretty-printer (@pxref{Pretty Printing}).
9161 @item print @var{expr}
9162 @itemx print /@var{f} @var{expr}
9163 @var{expr} is an expression (in the source language). By default the
9164 value of @var{expr} is printed in a format appropriate to its data type;
9165 you can choose a different format by specifying @samp{/@var{f}}, where
9166 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9170 @itemx print /@var{f}
9171 @cindex reprint the last value
9172 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9173 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9174 conveniently inspect the same value in an alternative format.
9177 A more low-level way of examining data is with the @code{x} command.
9178 It examines data in memory at a specified address and prints it in a
9179 specified format. @xref{Memory, ,Examining Memory}.
9181 If you are interested in information about types, or about how the
9182 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9183 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9186 @cindex exploring hierarchical data structures
9188 Another way of examining values of expressions and type information is
9189 through the Python extension command @code{explore} (available only if
9190 the @value{GDBN} build is configured with @code{--with-python}). It
9191 offers an interactive way to start at the highest level (or, the most
9192 abstract level) of the data type of an expression (or, the data type
9193 itself) and explore all the way down to leaf scalar values/fields
9194 embedded in the higher level data types.
9197 @item explore @var{arg}
9198 @var{arg} is either an expression (in the source language), or a type
9199 visible in the current context of the program being debugged.
9202 The working of the @code{explore} command can be illustrated with an
9203 example. If a data type @code{struct ComplexStruct} is defined in your
9213 struct ComplexStruct
9215 struct SimpleStruct *ss_p;
9221 followed by variable declarations as
9224 struct SimpleStruct ss = @{ 10, 1.11 @};
9225 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9229 then, the value of the variable @code{cs} can be explored using the
9230 @code{explore} command as follows.
9234 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9235 the following fields:
9237 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9238 arr = <Enter 1 to explore this field of type `int [10]'>
9240 Enter the field number of choice:
9244 Since the fields of @code{cs} are not scalar values, you are being
9245 prompted to chose the field you want to explore. Let's say you choose
9246 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9247 pointer, you will be asked if it is pointing to a single value. From
9248 the declaration of @code{cs} above, it is indeed pointing to a single
9249 value, hence you enter @code{y}. If you enter @code{n}, then you will
9250 be asked if it were pointing to an array of values, in which case this
9251 field will be explored as if it were an array.
9254 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9255 Continue exploring it as a pointer to a single value [y/n]: y
9256 The value of `*(cs.ss_p)' is a struct/class of type `struct
9257 SimpleStruct' with the following fields:
9259 i = 10 .. (Value of type `int')
9260 d = 1.1100000000000001 .. (Value of type `double')
9262 Press enter to return to parent value:
9266 If the field @code{arr} of @code{cs} was chosen for exploration by
9267 entering @code{1} earlier, then since it is as array, you will be
9268 prompted to enter the index of the element in the array that you want
9272 `cs.arr' is an array of `int'.
9273 Enter the index of the element you want to explore in `cs.arr': 5
9275 `(cs.arr)[5]' is a scalar value of type `int'.
9279 Press enter to return to parent value:
9282 In general, at any stage of exploration, you can go deeper towards the
9283 leaf values by responding to the prompts appropriately, or hit the
9284 return key to return to the enclosing data structure (the @i{higher}
9285 level data structure).
9287 Similar to exploring values, you can use the @code{explore} command to
9288 explore types. Instead of specifying a value (which is typically a
9289 variable name or an expression valid in the current context of the
9290 program being debugged), you specify a type name. If you consider the
9291 same example as above, your can explore the type
9292 @code{struct ComplexStruct} by passing the argument
9293 @code{struct ComplexStruct} to the @code{explore} command.
9296 (gdb) explore struct ComplexStruct
9300 By responding to the prompts appropriately in the subsequent interactive
9301 session, you can explore the type @code{struct ComplexStruct} in a
9302 manner similar to how the value @code{cs} was explored in the above
9305 The @code{explore} command also has two sub-commands,
9306 @code{explore value} and @code{explore type}. The former sub-command is
9307 a way to explicitly specify that value exploration of the argument is
9308 being invoked, while the latter is a way to explicitly specify that type
9309 exploration of the argument is being invoked.
9312 @item explore value @var{expr}
9313 @cindex explore value
9314 This sub-command of @code{explore} explores the value of the
9315 expression @var{expr} (if @var{expr} is an expression valid in the
9316 current context of the program being debugged). The behavior of this
9317 command is identical to that of the behavior of the @code{explore}
9318 command being passed the argument @var{expr}.
9320 @item explore type @var{arg}
9321 @cindex explore type
9322 This sub-command of @code{explore} explores the type of @var{arg} (if
9323 @var{arg} is a type visible in the current context of program being
9324 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9325 is an expression valid in the current context of the program being
9326 debugged). If @var{arg} is a type, then the behavior of this command is
9327 identical to that of the @code{explore} command being passed the
9328 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9329 this command will be identical to that of the @code{explore} command
9330 being passed the type of @var{arg} as the argument.
9334 * Expressions:: Expressions
9335 * Ambiguous Expressions:: Ambiguous Expressions
9336 * Variables:: Program variables
9337 * Arrays:: Artificial arrays
9338 * Output Formats:: Output formats
9339 * Memory:: Examining memory
9340 * Auto Display:: Automatic display
9341 * Print Settings:: Print settings
9342 * Pretty Printing:: Python pretty printing
9343 * Value History:: Value history
9344 * Convenience Vars:: Convenience variables
9345 * Convenience Funs:: Convenience functions
9346 * Registers:: Registers
9347 * Floating Point Hardware:: Floating point hardware
9348 * Vector Unit:: Vector Unit
9349 * OS Information:: Auxiliary data provided by operating system
9350 * Memory Region Attributes:: Memory region attributes
9351 * Dump/Restore Files:: Copy between memory and a file
9352 * Core File Generation:: Cause a program dump its core
9353 * Character Sets:: Debugging programs that use a different
9354 character set than GDB does
9355 * Caching Target Data:: Data caching for targets
9356 * Searching Memory:: Searching memory for a sequence of bytes
9357 * Value Sizes:: Managing memory allocated for values
9361 @section Expressions
9364 @code{print} and many other @value{GDBN} commands accept an expression and
9365 compute its value. Any kind of constant, variable or operator defined
9366 by the programming language you are using is valid in an expression in
9367 @value{GDBN}. This includes conditional expressions, function calls,
9368 casts, and string constants. It also includes preprocessor macros, if
9369 you compiled your program to include this information; see
9372 @cindex arrays in expressions
9373 @value{GDBN} supports array constants in expressions input by
9374 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9375 you can use the command @code{print @{1, 2, 3@}} to create an array
9376 of three integers. If you pass an array to a function or assign it
9377 to a program variable, @value{GDBN} copies the array to memory that
9378 is @code{malloc}ed in the target program.
9380 Because C is so widespread, most of the expressions shown in examples in
9381 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9382 Languages}, for information on how to use expressions in other
9385 In this section, we discuss operators that you can use in @value{GDBN}
9386 expressions regardless of your programming language.
9388 @cindex casts, in expressions
9389 Casts are supported in all languages, not just in C, because it is so
9390 useful to cast a number into a pointer in order to examine a structure
9391 at that address in memory.
9392 @c FIXME: casts supported---Mod2 true?
9394 @value{GDBN} supports these operators, in addition to those common
9395 to programming languages:
9399 @samp{@@} is a binary operator for treating parts of memory as arrays.
9400 @xref{Arrays, ,Artificial Arrays}, for more information.
9403 @samp{::} allows you to specify a variable in terms of the file or
9404 function where it is defined. @xref{Variables, ,Program Variables}.
9406 @cindex @{@var{type}@}
9407 @cindex type casting memory
9408 @cindex memory, viewing as typed object
9409 @cindex casts, to view memory
9410 @item @{@var{type}@} @var{addr}
9411 Refers to an object of type @var{type} stored at address @var{addr} in
9412 memory. The address @var{addr} may be any expression whose value is
9413 an integer or pointer (but parentheses are required around binary
9414 operators, just as in a cast). This construct is allowed regardless
9415 of what kind of data is normally supposed to reside at @var{addr}.
9418 @node Ambiguous Expressions
9419 @section Ambiguous Expressions
9420 @cindex ambiguous expressions
9422 Expressions can sometimes contain some ambiguous elements. For instance,
9423 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9424 a single function name to be defined several times, for application in
9425 different contexts. This is called @dfn{overloading}. Another example
9426 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9427 templates and is typically instantiated several times, resulting in
9428 the same function name being defined in different contexts.
9430 In some cases and depending on the language, it is possible to adjust
9431 the expression to remove the ambiguity. For instance in C@t{++}, you
9432 can specify the signature of the function you want to break on, as in
9433 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9434 qualified name of your function often makes the expression unambiguous
9437 When an ambiguity that needs to be resolved is detected, the debugger
9438 has the capability to display a menu of numbered choices for each
9439 possibility, and then waits for the selection with the prompt @samp{>}.
9440 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9441 aborts the current command. If the command in which the expression was
9442 used allows more than one choice to be selected, the next option in the
9443 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9446 For example, the following session excerpt shows an attempt to set a
9447 breakpoint at the overloaded symbol @code{String::after}.
9448 We choose three particular definitions of that function name:
9450 @c FIXME! This is likely to change to show arg type lists, at least
9453 (@value{GDBP}) b String::after
9456 [2] file:String.cc; line number:867
9457 [3] file:String.cc; line number:860
9458 [4] file:String.cc; line number:875
9459 [5] file:String.cc; line number:853
9460 [6] file:String.cc; line number:846
9461 [7] file:String.cc; line number:735
9463 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9464 Breakpoint 2 at 0xb344: file String.cc, line 875.
9465 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9466 Multiple breakpoints were set.
9467 Use the "delete" command to delete unwanted
9474 @kindex set multiple-symbols
9475 @item set multiple-symbols @var{mode}
9476 @cindex multiple-symbols menu
9478 This option allows you to adjust the debugger behavior when an expression
9481 By default, @var{mode} is set to @code{all}. If the command with which
9482 the expression is used allows more than one choice, then @value{GDBN}
9483 automatically selects all possible choices. For instance, inserting
9484 a breakpoint on a function using an ambiguous name results in a breakpoint
9485 inserted on each possible match. However, if a unique choice must be made,
9486 then @value{GDBN} uses the menu to help you disambiguate the expression.
9487 For instance, printing the address of an overloaded function will result
9488 in the use of the menu.
9490 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9491 when an ambiguity is detected.
9493 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9494 an error due to the ambiguity and the command is aborted.
9496 @kindex show multiple-symbols
9497 @item show multiple-symbols
9498 Show the current value of the @code{multiple-symbols} setting.
9502 @section Program Variables
9504 The most common kind of expression to use is the name of a variable
9507 Variables in expressions are understood in the selected stack frame
9508 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9512 global (or file-static)
9519 visible according to the scope rules of the
9520 programming language from the point of execution in that frame
9523 @noindent This means that in the function
9538 you can examine and use the variable @code{a} whenever your program is
9539 executing within the function @code{foo}, but you can only use or
9540 examine the variable @code{b} while your program is executing inside
9541 the block where @code{b} is declared.
9543 @cindex variable name conflict
9544 There is an exception: you can refer to a variable or function whose
9545 scope is a single source file even if the current execution point is not
9546 in this file. But it is possible to have more than one such variable or
9547 function with the same name (in different source files). If that
9548 happens, referring to that name has unpredictable effects. If you wish,
9549 you can specify a static variable in a particular function or file by
9550 using the colon-colon (@code{::}) notation:
9552 @cindex colon-colon, context for variables/functions
9554 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9555 @cindex @code{::}, context for variables/functions
9558 @var{file}::@var{variable}
9559 @var{function}::@var{variable}
9563 Here @var{file} or @var{function} is the name of the context for the
9564 static @var{variable}. In the case of file names, you can use quotes to
9565 make sure @value{GDBN} parses the file name as a single word---for example,
9566 to print a global value of @code{x} defined in @file{f2.c}:
9569 (@value{GDBP}) p 'f2.c'::x
9572 The @code{::} notation is normally used for referring to
9573 static variables, since you typically disambiguate uses of local variables
9574 in functions by selecting the appropriate frame and using the
9575 simple name of the variable. However, you may also use this notation
9576 to refer to local variables in frames enclosing the selected frame:
9585 process (a); /* Stop here */
9596 For example, if there is a breakpoint at the commented line,
9597 here is what you might see
9598 when the program stops after executing the call @code{bar(0)}:
9603 (@value{GDBP}) p bar::a
9606 #2 0x080483d0 in foo (a=5) at foobar.c:12
9609 (@value{GDBP}) p bar::a
9613 @cindex C@t{++} scope resolution
9614 These uses of @samp{::} are very rarely in conflict with the very
9615 similar use of the same notation in C@t{++}. When they are in
9616 conflict, the C@t{++} meaning takes precedence; however, this can be
9617 overridden by quoting the file or function name with single quotes.
9619 For example, suppose the program is stopped in a method of a class
9620 that has a field named @code{includefile}, and there is also an
9621 include file named @file{includefile} that defines a variable,
9625 (@value{GDBP}) p includefile
9627 (@value{GDBP}) p includefile::some_global
9628 A syntax error in expression, near `'.
9629 (@value{GDBP}) p 'includefile'::some_global
9633 @cindex wrong values
9634 @cindex variable values, wrong
9635 @cindex function entry/exit, wrong values of variables
9636 @cindex optimized code, wrong values of variables
9638 @emph{Warning:} Occasionally, a local variable may appear to have the
9639 wrong value at certain points in a function---just after entry to a new
9640 scope, and just before exit.
9642 You may see this problem when you are stepping by machine instructions.
9643 This is because, on most machines, it takes more than one instruction to
9644 set up a stack frame (including local variable definitions); if you are
9645 stepping by machine instructions, variables may appear to have the wrong
9646 values until the stack frame is completely built. On exit, it usually
9647 also takes more than one machine instruction to destroy a stack frame;
9648 after you begin stepping through that group of instructions, local
9649 variable definitions may be gone.
9651 This may also happen when the compiler does significant optimizations.
9652 To be sure of always seeing accurate values, turn off all optimization
9655 @cindex ``No symbol "foo" in current context''
9656 Another possible effect of compiler optimizations is to optimize
9657 unused variables out of existence, or assign variables to registers (as
9658 opposed to memory addresses). Depending on the support for such cases
9659 offered by the debug info format used by the compiler, @value{GDBN}
9660 might not be able to display values for such local variables. If that
9661 happens, @value{GDBN} will print a message like this:
9664 No symbol "foo" in current context.
9667 To solve such problems, either recompile without optimizations, or use a
9668 different debug info format, if the compiler supports several such
9669 formats. @xref{Compilation}, for more information on choosing compiler
9670 options. @xref{C, ,C and C@t{++}}, for more information about debug
9671 info formats that are best suited to C@t{++} programs.
9673 If you ask to print an object whose contents are unknown to
9674 @value{GDBN}, e.g., because its data type is not completely specified
9675 by the debug information, @value{GDBN} will say @samp{<incomplete
9676 type>}. @xref{Symbols, incomplete type}, for more about this.
9678 @cindex no debug info variables
9679 If you try to examine or use the value of a (global) variable for
9680 which @value{GDBN} has no type information, e.g., because the program
9681 includes no debug information, @value{GDBN} displays an error message.
9682 @xref{Symbols, unknown type}, for more about unknown types. If you
9683 cast the variable to its declared type, @value{GDBN} gets the
9684 variable's value using the cast-to type as the variable's type. For
9685 example, in a C program:
9688 (@value{GDBP}) p var
9689 'var' has unknown type; cast it to its declared type
9690 (@value{GDBP}) p (float) var
9694 If you append @kbd{@@entry} string to a function parameter name you get its
9695 value at the time the function got called. If the value is not available an
9696 error message is printed. Entry values are available only with some compilers.
9697 Entry values are normally also printed at the function parameter list according
9698 to @ref{set print entry-values}.
9701 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9707 (gdb) print i@@entry
9711 Strings are identified as arrays of @code{char} values without specified
9712 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9713 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9714 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9715 defines literal string type @code{"char"} as @code{char} without a sign.
9720 signed char var1[] = "A";
9723 You get during debugging
9728 $2 = @{65 'A', 0 '\0'@}
9732 @section Artificial Arrays
9734 @cindex artificial array
9736 @kindex @@@r{, referencing memory as an array}
9737 It is often useful to print out several successive objects of the
9738 same type in memory; a section of an array, or an array of
9739 dynamically determined size for which only a pointer exists in the
9742 You can do this by referring to a contiguous span of memory as an
9743 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9744 operand of @samp{@@} should be the first element of the desired array
9745 and be an individual object. The right operand should be the desired length
9746 of the array. The result is an array value whose elements are all of
9747 the type of the left argument. The first element is actually the left
9748 argument; the second element comes from bytes of memory immediately
9749 following those that hold the first element, and so on. Here is an
9750 example. If a program says
9753 int *array = (int *) malloc (len * sizeof (int));
9757 you can print the contents of @code{array} with
9763 The left operand of @samp{@@} must reside in memory. Array values made
9764 with @samp{@@} in this way behave just like other arrays in terms of
9765 subscripting, and are coerced to pointers when used in expressions.
9766 Artificial arrays most often appear in expressions via the value history
9767 (@pxref{Value History, ,Value History}), after printing one out.
9769 Another way to create an artificial array is to use a cast.
9770 This re-interprets a value as if it were an array.
9771 The value need not be in memory:
9773 (@value{GDBP}) p/x (short[2])0x12345678
9774 $1 = @{0x1234, 0x5678@}
9777 As a convenience, if you leave the array length out (as in
9778 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9779 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9781 (@value{GDBP}) p/x (short[])0x12345678
9782 $2 = @{0x1234, 0x5678@}
9785 Sometimes the artificial array mechanism is not quite enough; in
9786 moderately complex data structures, the elements of interest may not
9787 actually be adjacent---for example, if you are interested in the values
9788 of pointers in an array. One useful work-around in this situation is
9789 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9790 Variables}) as a counter in an expression that prints the first
9791 interesting value, and then repeat that expression via @key{RET}. For
9792 instance, suppose you have an array @code{dtab} of pointers to
9793 structures, and you are interested in the values of a field @code{fv}
9794 in each structure. Here is an example of what you might type:
9804 @node Output Formats
9805 @section Output Formats
9807 @cindex formatted output
9808 @cindex output formats
9809 By default, @value{GDBN} prints a value according to its data type. Sometimes
9810 this is not what you want. For example, you might want to print a number
9811 in hex, or a pointer in decimal. Or you might want to view data in memory
9812 at a certain address as a character string or as an instruction. To do
9813 these things, specify an @dfn{output format} when you print a value.
9815 The simplest use of output formats is to say how to print a value
9816 already computed. This is done by starting the arguments of the
9817 @code{print} command with a slash and a format letter. The format
9818 letters supported are:
9822 Regard the bits of the value as an integer, and print the integer in
9826 Print as integer in signed decimal.
9829 Print as integer in unsigned decimal.
9832 Print as integer in octal.
9835 Print as integer in binary. The letter @samp{t} stands for ``two''.
9836 @footnote{@samp{b} cannot be used because these format letters are also
9837 used with the @code{x} command, where @samp{b} stands for ``byte'';
9838 see @ref{Memory,,Examining Memory}.}
9841 @cindex unknown address, locating
9842 @cindex locate address
9843 Print as an address, both absolute in hexadecimal and as an offset from
9844 the nearest preceding symbol. You can use this format used to discover
9845 where (in what function) an unknown address is located:
9848 (@value{GDBP}) p/a 0x54320
9849 $3 = 0x54320 <_initialize_vx+396>
9853 The command @code{info symbol 0x54320} yields similar results.
9854 @xref{Symbols, info symbol}.
9857 Regard as an integer and print it as a character constant. This
9858 prints both the numerical value and its character representation. The
9859 character representation is replaced with the octal escape @samp{\nnn}
9860 for characters outside the 7-bit @sc{ascii} range.
9862 Without this format, @value{GDBN} displays @code{char},
9863 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9864 constants. Single-byte members of vectors are displayed as integer
9868 Regard the bits of the value as a floating point number and print
9869 using typical floating point syntax.
9872 @cindex printing strings
9873 @cindex printing byte arrays
9874 Regard as a string, if possible. With this format, pointers to single-byte
9875 data are displayed as null-terminated strings and arrays of single-byte data
9876 are displayed as fixed-length strings. Other values are displayed in their
9879 Without this format, @value{GDBN} displays pointers to and arrays of
9880 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9881 strings. Single-byte members of a vector are displayed as an integer
9885 Like @samp{x} formatting, the value is treated as an integer and
9886 printed as hexadecimal, but leading zeros are printed to pad the value
9887 to the size of the integer type.
9890 @cindex raw printing
9891 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9892 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9893 Printing}). This typically results in a higher-level display of the
9894 value's contents. The @samp{r} format bypasses any Python
9895 pretty-printer which might exist.
9898 For example, to print the program counter in hex (@pxref{Registers}), type
9905 Note that no space is required before the slash; this is because command
9906 names in @value{GDBN} cannot contain a slash.
9908 To reprint the last value in the value history with a different format,
9909 you can use the @code{print} command with just a format and no
9910 expression. For example, @samp{p/x} reprints the last value in hex.
9913 @section Examining Memory
9915 You can use the command @code{x} (for ``examine'') to examine memory in
9916 any of several formats, independently of your program's data types.
9918 @cindex examining memory
9920 @kindex x @r{(examine memory)}
9921 @item x/@var{nfu} @var{addr}
9924 Use the @code{x} command to examine memory.
9927 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9928 much memory to display and how to format it; @var{addr} is an
9929 expression giving the address where you want to start displaying memory.
9930 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9931 Several commands set convenient defaults for @var{addr}.
9934 @item @var{n}, the repeat count
9935 The repeat count is a decimal integer; the default is 1. It specifies
9936 how much memory (counting by units @var{u}) to display. If a negative
9937 number is specified, memory is examined backward from @var{addr}.
9938 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9941 @item @var{f}, the display format
9942 The display format is one of the formats used by @code{print}
9943 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9944 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9945 The default is @samp{x} (hexadecimal) initially. The default changes
9946 each time you use either @code{x} or @code{print}.
9948 @item @var{u}, the unit size
9949 The unit size is any of
9955 Halfwords (two bytes).
9957 Words (four bytes). This is the initial default.
9959 Giant words (eight bytes).
9962 Each time you specify a unit size with @code{x}, that size becomes the
9963 default unit the next time you use @code{x}. For the @samp{i} format,
9964 the unit size is ignored and is normally not written. For the @samp{s} format,
9965 the unit size defaults to @samp{b}, unless it is explicitly given.
9966 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9967 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9968 Note that the results depend on the programming language of the
9969 current compilation unit. If the language is C, the @samp{s}
9970 modifier will use the UTF-16 encoding while @samp{w} will use
9971 UTF-32. The encoding is set by the programming language and cannot
9974 @item @var{addr}, starting display address
9975 @var{addr} is the address where you want @value{GDBN} to begin displaying
9976 memory. The expression need not have a pointer value (though it may);
9977 it is always interpreted as an integer address of a byte of memory.
9978 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9979 @var{addr} is usually just after the last address examined---but several
9980 other commands also set the default address: @code{info breakpoints} (to
9981 the address of the last breakpoint listed), @code{info line} (to the
9982 starting address of a line), and @code{print} (if you use it to display
9983 a value from memory).
9986 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9987 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9988 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9989 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9990 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9992 You can also specify a negative repeat count to examine memory backward
9993 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9994 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9996 Since the letters indicating unit sizes are all distinct from the
9997 letters specifying output formats, you do not have to remember whether
9998 unit size or format comes first; either order works. The output
9999 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10000 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10002 Even though the unit size @var{u} is ignored for the formats @samp{s}
10003 and @samp{i}, you might still want to use a count @var{n}; for example,
10004 @samp{3i} specifies that you want to see three machine instructions,
10005 including any operands. For convenience, especially when used with
10006 the @code{display} command, the @samp{i} format also prints branch delay
10007 slot instructions, if any, beyond the count specified, which immediately
10008 follow the last instruction that is within the count. The command
10009 @code{disassemble} gives an alternative way of inspecting machine
10010 instructions; see @ref{Machine Code,,Source and Machine Code}.
10012 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10013 the command displays null-terminated strings or instructions before the given
10014 address as many as the absolute value of the given number. For the @samp{i}
10015 format, we use line number information in the debug info to accurately locate
10016 instruction boundaries while disassembling backward. If line info is not
10017 available, the command stops examining memory with an error message.
10019 All the defaults for the arguments to @code{x} are designed to make it
10020 easy to continue scanning memory with minimal specifications each time
10021 you use @code{x}. For example, after you have inspected three machine
10022 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10023 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10024 the repeat count @var{n} is used again; the other arguments default as
10025 for successive uses of @code{x}.
10027 When examining machine instructions, the instruction at current program
10028 counter is shown with a @code{=>} marker. For example:
10031 (@value{GDBP}) x/5i $pc-6
10032 0x804837f <main+11>: mov %esp,%ebp
10033 0x8048381 <main+13>: push %ecx
10034 0x8048382 <main+14>: sub $0x4,%esp
10035 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10036 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10039 @cindex @code{$_}, @code{$__}, and value history
10040 The addresses and contents printed by the @code{x} command are not saved
10041 in the value history because there is often too much of them and they
10042 would get in the way. Instead, @value{GDBN} makes these values available for
10043 subsequent use in expressions as values of the convenience variables
10044 @code{$_} and @code{$__}. After an @code{x} command, the last address
10045 examined is available for use in expressions in the convenience variable
10046 @code{$_}. The contents of that address, as examined, are available in
10047 the convenience variable @code{$__}.
10049 If the @code{x} command has a repeat count, the address and contents saved
10050 are from the last memory unit printed; this is not the same as the last
10051 address printed if several units were printed on the last line of output.
10053 @anchor{addressable memory unit}
10054 @cindex addressable memory unit
10055 Most targets have an addressable memory unit size of 8 bits. This means
10056 that to each memory address are associated 8 bits of data. Some
10057 targets, however, have other addressable memory unit sizes.
10058 Within @value{GDBN} and this document, the term
10059 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10060 when explicitly referring to a chunk of data of that size. The word
10061 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10062 the addressable memory unit size of the target. For most systems,
10063 addressable memory unit is a synonym of byte.
10065 @cindex remote memory comparison
10066 @cindex target memory comparison
10067 @cindex verify remote memory image
10068 @cindex verify target memory image
10069 When you are debugging a program running on a remote target machine
10070 (@pxref{Remote Debugging}), you may wish to verify the program's image
10071 in the remote machine's memory against the executable file you
10072 downloaded to the target. Or, on any target, you may want to check
10073 whether the program has corrupted its own read-only sections. The
10074 @code{compare-sections} command is provided for such situations.
10077 @kindex compare-sections
10078 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10079 Compare the data of a loadable section @var{section-name} in the
10080 executable file of the program being debugged with the same section in
10081 the target machine's memory, and report any mismatches. With no
10082 arguments, compares all loadable sections. With an argument of
10083 @code{-r}, compares all loadable read-only sections.
10085 Note: for remote targets, this command can be accelerated if the
10086 target supports computing the CRC checksum of a block of memory
10087 (@pxref{qCRC packet}).
10091 @section Automatic Display
10092 @cindex automatic display
10093 @cindex display of expressions
10095 If you find that you want to print the value of an expression frequently
10096 (to see how it changes), you might want to add it to the @dfn{automatic
10097 display list} so that @value{GDBN} prints its value each time your program stops.
10098 Each expression added to the list is given a number to identify it;
10099 to remove an expression from the list, you specify that number.
10100 The automatic display looks like this:
10104 3: bar[5] = (struct hack *) 0x3804
10108 This display shows item numbers, expressions and their current values. As with
10109 displays you request manually using @code{x} or @code{print}, you can
10110 specify the output format you prefer; in fact, @code{display} decides
10111 whether to use @code{print} or @code{x} depending your format
10112 specification---it uses @code{x} if you specify either the @samp{i}
10113 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10117 @item display @var{expr}
10118 Add the expression @var{expr} to the list of expressions to display
10119 each time your program stops. @xref{Expressions, ,Expressions}.
10121 @code{display} does not repeat if you press @key{RET} again after using it.
10123 @item display/@var{fmt} @var{expr}
10124 For @var{fmt} specifying only a display format and not a size or
10125 count, add the expression @var{expr} to the auto-display list but
10126 arrange to display it each time in the specified format @var{fmt}.
10127 @xref{Output Formats,,Output Formats}.
10129 @item display/@var{fmt} @var{addr}
10130 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10131 number of units, add the expression @var{addr} as a memory address to
10132 be examined each time your program stops. Examining means in effect
10133 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10136 For example, @samp{display/i $pc} can be helpful, to see the machine
10137 instruction about to be executed each time execution stops (@samp{$pc}
10138 is a common name for the program counter; @pxref{Registers, ,Registers}).
10141 @kindex delete display
10143 @item undisplay @var{dnums}@dots{}
10144 @itemx delete display @var{dnums}@dots{}
10145 Remove items from the list of expressions to display. Specify the
10146 numbers of the displays that you want affected with the command
10147 argument @var{dnums}. It can be a single display number, one of the
10148 numbers shown in the first field of the @samp{info display} display;
10149 or it could be a range of display numbers, as in @code{2-4}.
10151 @code{undisplay} does not repeat if you press @key{RET} after using it.
10152 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10154 @kindex disable display
10155 @item disable display @var{dnums}@dots{}
10156 Disable the display of item numbers @var{dnums}. A disabled display
10157 item is not printed automatically, but is not forgotten. It may be
10158 enabled again later. Specify the numbers of the displays that you
10159 want affected with the command argument @var{dnums}. It can be a
10160 single display number, one of the numbers shown in the first field of
10161 the @samp{info display} display; or it could be a range of display
10162 numbers, as in @code{2-4}.
10164 @kindex enable display
10165 @item enable display @var{dnums}@dots{}
10166 Enable display of item numbers @var{dnums}. It becomes effective once
10167 again in auto display of its expression, until you specify otherwise.
10168 Specify the numbers of the displays that you want affected with the
10169 command argument @var{dnums}. It can be a single display number, one
10170 of the numbers shown in the first field of the @samp{info display}
10171 display; or it could be a range of display numbers, as in @code{2-4}.
10174 Display the current values of the expressions on the list, just as is
10175 done when your program stops.
10177 @kindex info display
10179 Print the list of expressions previously set up to display
10180 automatically, each one with its item number, but without showing the
10181 values. This includes disabled expressions, which are marked as such.
10182 It also includes expressions which would not be displayed right now
10183 because they refer to automatic variables not currently available.
10186 @cindex display disabled out of scope
10187 If a display expression refers to local variables, then it does not make
10188 sense outside the lexical context for which it was set up. Such an
10189 expression is disabled when execution enters a context where one of its
10190 variables is not defined. For example, if you give the command
10191 @code{display last_char} while inside a function with an argument
10192 @code{last_char}, @value{GDBN} displays this argument while your program
10193 continues to stop inside that function. When it stops elsewhere---where
10194 there is no variable @code{last_char}---the display is disabled
10195 automatically. The next time your program stops where @code{last_char}
10196 is meaningful, you can enable the display expression once again.
10198 @node Print Settings
10199 @section Print Settings
10201 @cindex format options
10202 @cindex print settings
10203 @value{GDBN} provides the following ways to control how arrays, structures,
10204 and symbols are printed.
10207 These settings are useful for debugging programs in any language:
10211 @item set print address
10212 @itemx set print address on
10213 @cindex print/don't print memory addresses
10214 @value{GDBN} prints memory addresses showing the location of stack
10215 traces, structure values, pointer values, breakpoints, and so forth,
10216 even when it also displays the contents of those addresses. The default
10217 is @code{on}. For example, this is what a stack frame display looks like with
10218 @code{set print address on}:
10223 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10225 530 if (lquote != def_lquote)
10229 @item set print address off
10230 Do not print addresses when displaying their contents. For example,
10231 this is the same stack frame displayed with @code{set print address off}:
10235 (@value{GDBP}) set print addr off
10237 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10238 530 if (lquote != def_lquote)
10242 You can use @samp{set print address off} to eliminate all machine
10243 dependent displays from the @value{GDBN} interface. For example, with
10244 @code{print address off}, you should get the same text for backtraces on
10245 all machines---whether or not they involve pointer arguments.
10248 @item show print address
10249 Show whether or not addresses are to be printed.
10252 When @value{GDBN} prints a symbolic address, it normally prints the
10253 closest earlier symbol plus an offset. If that symbol does not uniquely
10254 identify the address (for example, it is a name whose scope is a single
10255 source file), you may need to clarify. One way to do this is with
10256 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10257 you can set @value{GDBN} to print the source file and line number when
10258 it prints a symbolic address:
10261 @item set print symbol-filename on
10262 @cindex source file and line of a symbol
10263 @cindex symbol, source file and line
10264 Tell @value{GDBN} to print the source file name and line number of a
10265 symbol in the symbolic form of an address.
10267 @item set print symbol-filename off
10268 Do not print source file name and line number of a symbol. This is the
10271 @item show print symbol-filename
10272 Show whether or not @value{GDBN} will print the source file name and
10273 line number of a symbol in the symbolic form of an address.
10276 Another situation where it is helpful to show symbol filenames and line
10277 numbers is when disassembling code; @value{GDBN} shows you the line
10278 number and source file that corresponds to each instruction.
10280 Also, you may wish to see the symbolic form only if the address being
10281 printed is reasonably close to the closest earlier symbol:
10284 @item set print max-symbolic-offset @var{max-offset}
10285 @itemx set print max-symbolic-offset unlimited
10286 @cindex maximum value for offset of closest symbol
10287 Tell @value{GDBN} to only display the symbolic form of an address if the
10288 offset between the closest earlier symbol and the address is less than
10289 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10290 to always print the symbolic form of an address if any symbol precedes
10291 it. Zero is equivalent to @code{unlimited}.
10293 @item show print max-symbolic-offset
10294 Ask how large the maximum offset is that @value{GDBN} prints in a
10298 @cindex wild pointer, interpreting
10299 @cindex pointer, finding referent
10300 If you have a pointer and you are not sure where it points, try
10301 @samp{set print symbol-filename on}. Then you can determine the name
10302 and source file location of the variable where it points, using
10303 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10304 For example, here @value{GDBN} shows that a variable @code{ptt} points
10305 at another variable @code{t}, defined in @file{hi2.c}:
10308 (@value{GDBP}) set print symbol-filename on
10309 (@value{GDBP}) p/a ptt
10310 $4 = 0xe008 <t in hi2.c>
10314 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10315 does not show the symbol name and filename of the referent, even with
10316 the appropriate @code{set print} options turned on.
10319 You can also enable @samp{/a}-like formatting all the time using
10320 @samp{set print symbol on}:
10323 @item set print symbol on
10324 Tell @value{GDBN} to print the symbol corresponding to an address, if
10327 @item set print symbol off
10328 Tell @value{GDBN} not to print the symbol corresponding to an
10329 address. In this mode, @value{GDBN} will still print the symbol
10330 corresponding to pointers to functions. This is the default.
10332 @item show print symbol
10333 Show whether @value{GDBN} will display the symbol corresponding to an
10337 Other settings control how different kinds of objects are printed:
10340 @item set print array
10341 @itemx set print array on
10342 @cindex pretty print arrays
10343 Pretty print arrays. This format is more convenient to read,
10344 but uses more space. The default is off.
10346 @item set print array off
10347 Return to compressed format for arrays.
10349 @item show print array
10350 Show whether compressed or pretty format is selected for displaying
10353 @cindex print array indexes
10354 @item set print array-indexes
10355 @itemx set print array-indexes on
10356 Print the index of each element when displaying arrays. May be more
10357 convenient to locate a given element in the array or quickly find the
10358 index of a given element in that printed array. The default is off.
10360 @item set print array-indexes off
10361 Stop printing element indexes when displaying arrays.
10363 @item show print array-indexes
10364 Show whether the index of each element is printed when displaying
10367 @item set print elements @var{number-of-elements}
10368 @itemx set print elements unlimited
10369 @cindex number of array elements to print
10370 @cindex limit on number of printed array elements
10371 Set a limit on how many elements of an array @value{GDBN} will print.
10372 If @value{GDBN} is printing a large array, it stops printing after it has
10373 printed the number of elements set by the @code{set print elements} command.
10374 This limit also applies to the display of strings.
10375 When @value{GDBN} starts, this limit is set to 200.
10376 Setting @var{number-of-elements} to @code{unlimited} or zero means
10377 that the number of elements to print is unlimited.
10379 @item show print elements
10380 Display the number of elements of a large array that @value{GDBN} will print.
10381 If the number is 0, then the printing is unlimited.
10383 @item set print frame-arguments @var{value}
10384 @kindex set print frame-arguments
10385 @cindex printing frame argument values
10386 @cindex print all frame argument values
10387 @cindex print frame argument values for scalars only
10388 @cindex do not print frame argument values
10389 This command allows to control how the values of arguments are printed
10390 when the debugger prints a frame (@pxref{Frames}). The possible
10395 The values of all arguments are printed.
10398 Print the value of an argument only if it is a scalar. The value of more
10399 complex arguments such as arrays, structures, unions, etc, is replaced
10400 by @code{@dots{}}. This is the default. Here is an example where
10401 only scalar arguments are shown:
10404 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10409 None of the argument values are printed. Instead, the value of each argument
10410 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10413 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10418 By default, only scalar arguments are printed. This command can be used
10419 to configure the debugger to print the value of all arguments, regardless
10420 of their type. However, it is often advantageous to not print the value
10421 of more complex parameters. For instance, it reduces the amount of
10422 information printed in each frame, making the backtrace more readable.
10423 Also, it improves performance when displaying Ada frames, because
10424 the computation of large arguments can sometimes be CPU-intensive,
10425 especially in large applications. Setting @code{print frame-arguments}
10426 to @code{scalars} (the default) or @code{none} avoids this computation,
10427 thus speeding up the display of each Ada frame.
10429 @item show print frame-arguments
10430 Show how the value of arguments should be displayed when printing a frame.
10432 @item set print raw frame-arguments on
10433 Print frame arguments in raw, non pretty-printed, form.
10435 @item set print raw frame-arguments off
10436 Print frame arguments in pretty-printed form, if there is a pretty-printer
10437 for the value (@pxref{Pretty Printing}),
10438 otherwise print the value in raw form.
10439 This is the default.
10441 @item show print raw frame-arguments
10442 Show whether to print frame arguments in raw form.
10444 @anchor{set print entry-values}
10445 @item set print entry-values @var{value}
10446 @kindex set print entry-values
10447 Set printing of frame argument values at function entry. In some cases
10448 @value{GDBN} can determine the value of function argument which was passed by
10449 the function caller, even if the value was modified inside the called function
10450 and therefore is different. With optimized code, the current value could be
10451 unavailable, but the entry value may still be known.
10453 The default value is @code{default} (see below for its description). Older
10454 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10455 this feature will behave in the @code{default} setting the same way as with the
10458 This functionality is currently supported only by DWARF 2 debugging format and
10459 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10460 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10463 The @var{value} parameter can be one of the following:
10467 Print only actual parameter values, never print values from function entry
10471 #0 different (val=6)
10472 #0 lost (val=<optimized out>)
10474 #0 invalid (val=<optimized out>)
10478 Print only parameter values from function entry point. The actual parameter
10479 values are never printed.
10481 #0 equal (val@@entry=5)
10482 #0 different (val@@entry=5)
10483 #0 lost (val@@entry=5)
10484 #0 born (val@@entry=<optimized out>)
10485 #0 invalid (val@@entry=<optimized out>)
10489 Print only parameter values from function entry point. If value from function
10490 entry point is not known while the actual value is known, print the actual
10491 value for such parameter.
10493 #0 equal (val@@entry=5)
10494 #0 different (val@@entry=5)
10495 #0 lost (val@@entry=5)
10497 #0 invalid (val@@entry=<optimized out>)
10501 Print actual parameter values. If actual parameter value is not known while
10502 value from function entry point is known, print the entry point value for such
10506 #0 different (val=6)
10507 #0 lost (val@@entry=5)
10509 #0 invalid (val=<optimized out>)
10513 Always print both the actual parameter value and its value from function entry
10514 point, even if values of one or both are not available due to compiler
10517 #0 equal (val=5, val@@entry=5)
10518 #0 different (val=6, val@@entry=5)
10519 #0 lost (val=<optimized out>, val@@entry=5)
10520 #0 born (val=10, val@@entry=<optimized out>)
10521 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10525 Print the actual parameter value if it is known and also its value from
10526 function entry point if it is known. If neither is known, print for the actual
10527 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10528 values are known and identical, print the shortened
10529 @code{param=param@@entry=VALUE} notation.
10531 #0 equal (val=val@@entry=5)
10532 #0 different (val=6, val@@entry=5)
10533 #0 lost (val@@entry=5)
10535 #0 invalid (val=<optimized out>)
10539 Always print the actual parameter value. Print also its value from function
10540 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10541 if both values are known and identical, print the shortened
10542 @code{param=param@@entry=VALUE} notation.
10544 #0 equal (val=val@@entry=5)
10545 #0 different (val=6, val@@entry=5)
10546 #0 lost (val=<optimized out>, val@@entry=5)
10548 #0 invalid (val=<optimized out>)
10552 For analysis messages on possible failures of frame argument values at function
10553 entry resolution see @ref{set debug entry-values}.
10555 @item show print entry-values
10556 Show the method being used for printing of frame argument values at function
10559 @item set print repeats @var{number-of-repeats}
10560 @itemx set print repeats unlimited
10561 @cindex repeated array elements
10562 Set the threshold for suppressing display of repeated array
10563 elements. When the number of consecutive identical elements of an
10564 array exceeds the threshold, @value{GDBN} prints the string
10565 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10566 identical repetitions, instead of displaying the identical elements
10567 themselves. Setting the threshold to @code{unlimited} or zero will
10568 cause all elements to be individually printed. The default threshold
10571 @item show print repeats
10572 Display the current threshold for printing repeated identical
10575 @item set print null-stop
10576 @cindex @sc{null} elements in arrays
10577 Cause @value{GDBN} to stop printing the characters of an array when the first
10578 @sc{null} is encountered. This is useful when large arrays actually
10579 contain only short strings.
10580 The default is off.
10582 @item show print null-stop
10583 Show whether @value{GDBN} stops printing an array on the first
10584 @sc{null} character.
10586 @item set print pretty on
10587 @cindex print structures in indented form
10588 @cindex indentation in structure display
10589 Cause @value{GDBN} to print structures in an indented format with one member
10590 per line, like this:
10605 @item set print pretty off
10606 Cause @value{GDBN} to print structures in a compact format, like this:
10610 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10611 meat = 0x54 "Pork"@}
10616 This is the default format.
10618 @item show print pretty
10619 Show which format @value{GDBN} is using to print structures.
10621 @item set print sevenbit-strings on
10622 @cindex eight-bit characters in strings
10623 @cindex octal escapes in strings
10624 Print using only seven-bit characters; if this option is set,
10625 @value{GDBN} displays any eight-bit characters (in strings or
10626 character values) using the notation @code{\}@var{nnn}. This setting is
10627 best if you are working in English (@sc{ascii}) and you use the
10628 high-order bit of characters as a marker or ``meta'' bit.
10630 @item set print sevenbit-strings off
10631 Print full eight-bit characters. This allows the use of more
10632 international character sets, and is the default.
10634 @item show print sevenbit-strings
10635 Show whether or not @value{GDBN} is printing only seven-bit characters.
10637 @item set print union on
10638 @cindex unions in structures, printing
10639 Tell @value{GDBN} to print unions which are contained in structures
10640 and other unions. This is the default setting.
10642 @item set print union off
10643 Tell @value{GDBN} not to print unions which are contained in
10644 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10647 @item show print union
10648 Ask @value{GDBN} whether or not it will print unions which are contained in
10649 structures and other unions.
10651 For example, given the declarations
10654 typedef enum @{Tree, Bug@} Species;
10655 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10656 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10667 struct thing foo = @{Tree, @{Acorn@}@};
10671 with @code{set print union on} in effect @samp{p foo} would print
10674 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10678 and with @code{set print union off} in effect it would print
10681 $1 = @{it = Tree, form = @{...@}@}
10685 @code{set print union} affects programs written in C-like languages
10691 These settings are of interest when debugging C@t{++} programs:
10694 @cindex demangling C@t{++} names
10695 @item set print demangle
10696 @itemx set print demangle on
10697 Print C@t{++} names in their source form rather than in the encoded
10698 (``mangled'') form passed to the assembler and linker for type-safe
10699 linkage. The default is on.
10701 @item show print demangle
10702 Show whether C@t{++} names are printed in mangled or demangled form.
10704 @item set print asm-demangle
10705 @itemx set print asm-demangle on
10706 Print C@t{++} names in their source form rather than their mangled form, even
10707 in assembler code printouts such as instruction disassemblies.
10708 The default is off.
10710 @item show print asm-demangle
10711 Show whether C@t{++} names in assembly listings are printed in mangled
10714 @cindex C@t{++} symbol decoding style
10715 @cindex symbol decoding style, C@t{++}
10716 @kindex set demangle-style
10717 @item set demangle-style @var{style}
10718 Choose among several encoding schemes used by different compilers to represent
10719 C@t{++} names. If you omit @var{style}, you will see a list of possible
10720 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10721 decoding style by inspecting your program.
10723 @item show demangle-style
10724 Display the encoding style currently in use for decoding C@t{++} symbols.
10726 @item set print object
10727 @itemx set print object on
10728 @cindex derived type of an object, printing
10729 @cindex display derived types
10730 When displaying a pointer to an object, identify the @emph{actual}
10731 (derived) type of the object rather than the @emph{declared} type, using
10732 the virtual function table. Note that the virtual function table is
10733 required---this feature can only work for objects that have run-time
10734 type identification; a single virtual method in the object's declared
10735 type is sufficient. Note that this setting is also taken into account when
10736 working with variable objects via MI (@pxref{GDB/MI}).
10738 @item set print object off
10739 Display only the declared type of objects, without reference to the
10740 virtual function table. This is the default setting.
10742 @item show print object
10743 Show whether actual, or declared, object types are displayed.
10745 @item set print static-members
10746 @itemx set print static-members on
10747 @cindex static members of C@t{++} objects
10748 Print static members when displaying a C@t{++} object. The default is on.
10750 @item set print static-members off
10751 Do not print static members when displaying a C@t{++} object.
10753 @item show print static-members
10754 Show whether C@t{++} static members are printed or not.
10756 @item set print pascal_static-members
10757 @itemx set print pascal_static-members on
10758 @cindex static members of Pascal objects
10759 @cindex Pascal objects, static members display
10760 Print static members when displaying a Pascal object. The default is on.
10762 @item set print pascal_static-members off
10763 Do not print static members when displaying a Pascal object.
10765 @item show print pascal_static-members
10766 Show whether Pascal static members are printed or not.
10768 @c These don't work with HP ANSI C++ yet.
10769 @item set print vtbl
10770 @itemx set print vtbl on
10771 @cindex pretty print C@t{++} virtual function tables
10772 @cindex virtual functions (C@t{++}) display
10773 @cindex VTBL display
10774 Pretty print C@t{++} virtual function tables. The default is off.
10775 (The @code{vtbl} commands do not work on programs compiled with the HP
10776 ANSI C@t{++} compiler (@code{aCC}).)
10778 @item set print vtbl off
10779 Do not pretty print C@t{++} virtual function tables.
10781 @item show print vtbl
10782 Show whether C@t{++} virtual function tables are pretty printed, or not.
10785 @node Pretty Printing
10786 @section Pretty Printing
10788 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10789 Python code. It greatly simplifies the display of complex objects. This
10790 mechanism works for both MI and the CLI.
10793 * Pretty-Printer Introduction:: Introduction to pretty-printers
10794 * Pretty-Printer Example:: An example pretty-printer
10795 * Pretty-Printer Commands:: Pretty-printer commands
10798 @node Pretty-Printer Introduction
10799 @subsection Pretty-Printer Introduction
10801 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10802 registered for the value. If there is then @value{GDBN} invokes the
10803 pretty-printer to print the value. Otherwise the value is printed normally.
10805 Pretty-printers are normally named. This makes them easy to manage.
10806 The @samp{info pretty-printer} command will list all the installed
10807 pretty-printers with their names.
10808 If a pretty-printer can handle multiple data types, then its
10809 @dfn{subprinters} are the printers for the individual data types.
10810 Each such subprinter has its own name.
10811 The format of the name is @var{printer-name};@var{subprinter-name}.
10813 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10814 Typically they are automatically loaded and registered when the corresponding
10815 debug information is loaded, thus making them available without having to
10816 do anything special.
10818 There are three places where a pretty-printer can be registered.
10822 Pretty-printers registered globally are available when debugging
10826 Pretty-printers registered with a program space are available only
10827 when debugging that program.
10828 @xref{Progspaces In Python}, for more details on program spaces in Python.
10831 Pretty-printers registered with an objfile are loaded and unloaded
10832 with the corresponding objfile (e.g., shared library).
10833 @xref{Objfiles In Python}, for more details on objfiles in Python.
10836 @xref{Selecting Pretty-Printers}, for further information on how
10837 pretty-printers are selected,
10839 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10842 @node Pretty-Printer Example
10843 @subsection Pretty-Printer Example
10845 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10848 (@value{GDBP}) print s
10850 static npos = 4294967295,
10852 <std::allocator<char>> = @{
10853 <__gnu_cxx::new_allocator<char>> = @{
10854 <No data fields>@}, <No data fields>
10856 members of std::basic_string<char, std::char_traits<char>,
10857 std::allocator<char> >::_Alloc_hider:
10858 _M_p = 0x804a014 "abcd"
10863 With a pretty-printer for @code{std::string} only the contents are printed:
10866 (@value{GDBP}) print s
10870 @node Pretty-Printer Commands
10871 @subsection Pretty-Printer Commands
10872 @cindex pretty-printer commands
10875 @kindex info pretty-printer
10876 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10877 Print the list of installed pretty-printers.
10878 This includes disabled pretty-printers, which are marked as such.
10880 @var{object-regexp} is a regular expression matching the objects
10881 whose pretty-printers to list.
10882 Objects can be @code{global}, the program space's file
10883 (@pxref{Progspaces In Python}),
10884 and the object files within that program space (@pxref{Objfiles In Python}).
10885 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10886 looks up a printer from these three objects.
10888 @var{name-regexp} is a regular expression matching the name of the printers
10891 @kindex disable pretty-printer
10892 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10893 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10894 A disabled pretty-printer is not forgotten, it may be enabled again later.
10896 @kindex enable pretty-printer
10897 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10898 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10903 Suppose we have three pretty-printers installed: one from library1.so
10904 named @code{foo} that prints objects of type @code{foo}, and
10905 another from library2.so named @code{bar} that prints two types of objects,
10906 @code{bar1} and @code{bar2}.
10909 (gdb) info pretty-printer
10916 (gdb) info pretty-printer library2
10921 (gdb) disable pretty-printer library1
10923 2 of 3 printers enabled
10924 (gdb) info pretty-printer
10931 (gdb) disable pretty-printer library2 bar;bar1
10933 1 of 3 printers enabled
10934 (gdb) info pretty-printer library2
10941 (gdb) disable pretty-printer library2 bar
10943 0 of 3 printers enabled
10944 (gdb) info pretty-printer library2
10953 Note that for @code{bar} the entire printer can be disabled,
10954 as can each individual subprinter.
10956 @node Value History
10957 @section Value History
10959 @cindex value history
10960 @cindex history of values printed by @value{GDBN}
10961 Values printed by the @code{print} command are saved in the @value{GDBN}
10962 @dfn{value history}. This allows you to refer to them in other expressions.
10963 Values are kept until the symbol table is re-read or discarded
10964 (for example with the @code{file} or @code{symbol-file} commands).
10965 When the symbol table changes, the value history is discarded,
10966 since the values may contain pointers back to the types defined in the
10971 @cindex history number
10972 The values printed are given @dfn{history numbers} by which you can
10973 refer to them. These are successive integers starting with one.
10974 @code{print} shows you the history number assigned to a value by
10975 printing @samp{$@var{num} = } before the value; here @var{num} is the
10978 To refer to any previous value, use @samp{$} followed by the value's
10979 history number. The way @code{print} labels its output is designed to
10980 remind you of this. Just @code{$} refers to the most recent value in
10981 the history, and @code{$$} refers to the value before that.
10982 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10983 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10984 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10986 For example, suppose you have just printed a pointer to a structure and
10987 want to see the contents of the structure. It suffices to type
10993 If you have a chain of structures where the component @code{next} points
10994 to the next one, you can print the contents of the next one with this:
11001 You can print successive links in the chain by repeating this
11002 command---which you can do by just typing @key{RET}.
11004 Note that the history records values, not expressions. If the value of
11005 @code{x} is 4 and you type these commands:
11013 then the value recorded in the value history by the @code{print} command
11014 remains 4 even though the value of @code{x} has changed.
11017 @kindex show values
11019 Print the last ten values in the value history, with their item numbers.
11020 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11021 values} does not change the history.
11023 @item show values @var{n}
11024 Print ten history values centered on history item number @var{n}.
11026 @item show values +
11027 Print ten history values just after the values last printed. If no more
11028 values are available, @code{show values +} produces no display.
11031 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11032 same effect as @samp{show values +}.
11034 @node Convenience Vars
11035 @section Convenience Variables
11037 @cindex convenience variables
11038 @cindex user-defined variables
11039 @value{GDBN} provides @dfn{convenience variables} that you can use within
11040 @value{GDBN} to hold on to a value and refer to it later. These variables
11041 exist entirely within @value{GDBN}; they are not part of your program, and
11042 setting a convenience variable has no direct effect on further execution
11043 of your program. That is why you can use them freely.
11045 Convenience variables are prefixed with @samp{$}. Any name preceded by
11046 @samp{$} can be used for a convenience variable, unless it is one of
11047 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11048 (Value history references, in contrast, are @emph{numbers} preceded
11049 by @samp{$}. @xref{Value History, ,Value History}.)
11051 You can save a value in a convenience variable with an assignment
11052 expression, just as you would set a variable in your program.
11056 set $foo = *object_ptr
11060 would save in @code{$foo} the value contained in the object pointed to by
11063 Using a convenience variable for the first time creates it, but its
11064 value is @code{void} until you assign a new value. You can alter the
11065 value with another assignment at any time.
11067 Convenience variables have no fixed types. You can assign a convenience
11068 variable any type of value, including structures and arrays, even if
11069 that variable already has a value of a different type. The convenience
11070 variable, when used as an expression, has the type of its current value.
11073 @kindex show convenience
11074 @cindex show all user variables and functions
11075 @item show convenience
11076 Print a list of convenience variables used so far, and their values,
11077 as well as a list of the convenience functions.
11078 Abbreviated @code{show conv}.
11080 @kindex init-if-undefined
11081 @cindex convenience variables, initializing
11082 @item init-if-undefined $@var{variable} = @var{expression}
11083 Set a convenience variable if it has not already been set. This is useful
11084 for user-defined commands that keep some state. It is similar, in concept,
11085 to using local static variables with initializers in C (except that
11086 convenience variables are global). It can also be used to allow users to
11087 override default values used in a command script.
11089 If the variable is already defined then the expression is not evaluated so
11090 any side-effects do not occur.
11093 One of the ways to use a convenience variable is as a counter to be
11094 incremented or a pointer to be advanced. For example, to print
11095 a field from successive elements of an array of structures:
11099 print bar[$i++]->contents
11103 Repeat that command by typing @key{RET}.
11105 Some convenience variables are created automatically by @value{GDBN} and given
11106 values likely to be useful.
11109 @vindex $_@r{, convenience variable}
11111 The variable @code{$_} is automatically set by the @code{x} command to
11112 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11113 commands which provide a default address for @code{x} to examine also
11114 set @code{$_} to that address; these commands include @code{info line}
11115 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11116 except when set by the @code{x} command, in which case it is a pointer
11117 to the type of @code{$__}.
11119 @vindex $__@r{, convenience variable}
11121 The variable @code{$__} is automatically set by the @code{x} command
11122 to the value found in the last address examined. Its type is chosen
11123 to match the format in which the data was printed.
11126 @vindex $_exitcode@r{, convenience variable}
11127 When the program being debugged terminates normally, @value{GDBN}
11128 automatically sets this variable to the exit code of the program, and
11129 resets @code{$_exitsignal} to @code{void}.
11132 @vindex $_exitsignal@r{, convenience variable}
11133 When the program being debugged dies due to an uncaught signal,
11134 @value{GDBN} automatically sets this variable to that signal's number,
11135 and resets @code{$_exitcode} to @code{void}.
11137 To distinguish between whether the program being debugged has exited
11138 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11139 @code{$_exitsignal} is not @code{void}), the convenience function
11140 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11141 Functions}). For example, considering the following source code:
11144 #include <signal.h>
11147 main (int argc, char *argv[])
11154 A valid way of telling whether the program being debugged has exited
11155 or signalled would be:
11158 (@value{GDBP}) define has_exited_or_signalled
11159 Type commands for definition of ``has_exited_or_signalled''.
11160 End with a line saying just ``end''.
11161 >if $_isvoid ($_exitsignal)
11162 >echo The program has exited\n
11164 >echo The program has signalled\n
11170 Program terminated with signal SIGALRM, Alarm clock.
11171 The program no longer exists.
11172 (@value{GDBP}) has_exited_or_signalled
11173 The program has signalled
11176 As can be seen, @value{GDBN} correctly informs that the program being
11177 debugged has signalled, since it calls @code{raise} and raises a
11178 @code{SIGALRM} signal. If the program being debugged had not called
11179 @code{raise}, then @value{GDBN} would report a normal exit:
11182 (@value{GDBP}) has_exited_or_signalled
11183 The program has exited
11187 The variable @code{$_exception} is set to the exception object being
11188 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11191 @itemx $_probe_arg0@dots{}$_probe_arg11
11192 Arguments to a static probe. @xref{Static Probe Points}.
11195 @vindex $_sdata@r{, inspect, convenience variable}
11196 The variable @code{$_sdata} contains extra collected static tracepoint
11197 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11198 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11199 if extra static tracepoint data has not been collected.
11202 @vindex $_siginfo@r{, convenience variable}
11203 The variable @code{$_siginfo} contains extra signal information
11204 (@pxref{extra signal information}). Note that @code{$_siginfo}
11205 could be empty, if the application has not yet received any signals.
11206 For example, it will be empty before you execute the @code{run} command.
11209 @vindex $_tlb@r{, convenience variable}
11210 The variable @code{$_tlb} is automatically set when debugging
11211 applications running on MS-Windows in native mode or connected to
11212 gdbserver that supports the @code{qGetTIBAddr} request.
11213 @xref{General Query Packets}.
11214 This variable contains the address of the thread information block.
11217 The number of the current inferior. @xref{Inferiors and
11218 Programs, ,Debugging Multiple Inferiors and Programs}.
11221 The thread number of the current thread. @xref{thread numbers}.
11224 The global number of the current thread. @xref{global thread numbers}.
11228 @vindex $_gdb_major@r{, convenience variable}
11229 @vindex $_gdb_minor@r{, convenience variable}
11230 The major and minor version numbers of the running @value{GDBN}.
11231 Development snapshots and pretest versions have their minor version
11232 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11233 the value 12 for @code{$_gdb_minor}. These variables allow you to
11234 write scripts that work with different versions of @value{GDBN}
11235 without errors caused by features unavailable in some of those
11239 @node Convenience Funs
11240 @section Convenience Functions
11242 @cindex convenience functions
11243 @value{GDBN} also supplies some @dfn{convenience functions}. These
11244 have a syntax similar to convenience variables. A convenience
11245 function can be used in an expression just like an ordinary function;
11246 however, a convenience function is implemented internally to
11249 These functions do not require @value{GDBN} to be configured with
11250 @code{Python} support, which means that they are always available.
11254 @item $_isvoid (@var{expr})
11255 @findex $_isvoid@r{, convenience function}
11256 Return one if the expression @var{expr} is @code{void}. Otherwise it
11259 A @code{void} expression is an expression where the type of the result
11260 is @code{void}. For example, you can examine a convenience variable
11261 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11265 (@value{GDBP}) print $_exitcode
11267 (@value{GDBP}) print $_isvoid ($_exitcode)
11270 Starting program: ./a.out
11271 [Inferior 1 (process 29572) exited normally]
11272 (@value{GDBP}) print $_exitcode
11274 (@value{GDBP}) print $_isvoid ($_exitcode)
11278 In the example above, we used @code{$_isvoid} to check whether
11279 @code{$_exitcode} is @code{void} before and after the execution of the
11280 program being debugged. Before the execution there is no exit code to
11281 be examined, therefore @code{$_exitcode} is @code{void}. After the
11282 execution the program being debugged returned zero, therefore
11283 @code{$_exitcode} is zero, which means that it is not @code{void}
11286 The @code{void} expression can also be a call of a function from the
11287 program being debugged. For example, given the following function:
11296 The result of calling it inside @value{GDBN} is @code{void}:
11299 (@value{GDBP}) print foo ()
11301 (@value{GDBP}) print $_isvoid (foo ())
11303 (@value{GDBP}) set $v = foo ()
11304 (@value{GDBP}) print $v
11306 (@value{GDBP}) print $_isvoid ($v)
11312 These functions require @value{GDBN} to be configured with
11313 @code{Python} support.
11317 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11318 @findex $_memeq@r{, convenience function}
11319 Returns one if the @var{length} bytes at the addresses given by
11320 @var{buf1} and @var{buf2} are equal.
11321 Otherwise it returns zero.
11323 @item $_regex(@var{str}, @var{regex})
11324 @findex $_regex@r{, convenience function}
11325 Returns one if the string @var{str} matches the regular expression
11326 @var{regex}. Otherwise it returns zero.
11327 The syntax of the regular expression is that specified by @code{Python}'s
11328 regular expression support.
11330 @item $_streq(@var{str1}, @var{str2})
11331 @findex $_streq@r{, convenience function}
11332 Returns one if the strings @var{str1} and @var{str2} are equal.
11333 Otherwise it returns zero.
11335 @item $_strlen(@var{str})
11336 @findex $_strlen@r{, convenience function}
11337 Returns the length of string @var{str}.
11339 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11340 @findex $_caller_is@r{, convenience function}
11341 Returns one if the calling function's name is equal to @var{name}.
11342 Otherwise it returns zero.
11344 If the optional argument @var{number_of_frames} is provided,
11345 it is the number of frames up in the stack to look.
11353 at testsuite/gdb.python/py-caller-is.c:21
11354 #1 0x00000000004005a0 in middle_func ()
11355 at testsuite/gdb.python/py-caller-is.c:27
11356 #2 0x00000000004005ab in top_func ()
11357 at testsuite/gdb.python/py-caller-is.c:33
11358 #3 0x00000000004005b6 in main ()
11359 at testsuite/gdb.python/py-caller-is.c:39
11360 (gdb) print $_caller_is ("middle_func")
11362 (gdb) print $_caller_is ("top_func", 2)
11366 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11367 @findex $_caller_matches@r{, convenience function}
11368 Returns one if the calling function's name matches the regular expression
11369 @var{regexp}. Otherwise it returns zero.
11371 If the optional argument @var{number_of_frames} is provided,
11372 it is the number of frames up in the stack to look.
11375 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11376 @findex $_any_caller_is@r{, convenience function}
11377 Returns one if any calling function's name is equal to @var{name}.
11378 Otherwise it returns zero.
11380 If the optional argument @var{number_of_frames} is provided,
11381 it is the number of frames up in the stack to look.
11384 This function differs from @code{$_caller_is} in that this function
11385 checks all stack frames from the immediate caller to the frame specified
11386 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11387 frame specified by @var{number_of_frames}.
11389 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11390 @findex $_any_caller_matches@r{, convenience function}
11391 Returns one if any calling function's name matches the regular expression
11392 @var{regexp}. Otherwise it returns zero.
11394 If the optional argument @var{number_of_frames} is provided,
11395 it is the number of frames up in the stack to look.
11398 This function differs from @code{$_caller_matches} in that this function
11399 checks all stack frames from the immediate caller to the frame specified
11400 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11401 frame specified by @var{number_of_frames}.
11403 @item $_as_string(@var{value})
11404 @findex $_as_string@r{, convenience function}
11405 Return the string representation of @var{value}.
11407 This function is useful to obtain the textual label (enumerator) of an
11408 enumeration value. For example, assuming the variable @var{node} is of
11409 an enumerated type:
11412 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11413 Visiting node of type NODE_INTEGER
11416 @item $_cimag(@var{value})
11417 @itemx $_creal(@var{value})
11418 @findex $_cimag@r{, convenience function}
11419 @findex $_creal@r{, convenience function}
11420 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11421 the complex number @var{value}.
11423 The type of the imaginary or real part depends on the type of the
11424 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11425 will return an imaginary part of type @code{float}.
11429 @value{GDBN} provides the ability to list and get help on
11430 convenience functions.
11433 @item help function
11434 @kindex help function
11435 @cindex show all convenience functions
11436 Print a list of all convenience functions.
11443 You can refer to machine register contents, in expressions, as variables
11444 with names starting with @samp{$}. The names of registers are different
11445 for each machine; use @code{info registers} to see the names used on
11449 @kindex info registers
11450 @item info registers
11451 Print the names and values of all registers except floating-point
11452 and vector registers (in the selected stack frame).
11454 @kindex info all-registers
11455 @cindex floating point registers
11456 @item info all-registers
11457 Print the names and values of all registers, including floating-point
11458 and vector registers (in the selected stack frame).
11460 @item info registers @var{reggroup} @dots{}
11461 Print the name and value of the registers in each of the specified
11462 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11463 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11465 @item info registers @var{regname} @dots{}
11466 Print the @dfn{relativized} value of each specified register @var{regname}.
11467 As discussed in detail below, register values are normally relative to
11468 the selected stack frame. The @var{regname} may be any register name valid on
11469 the machine you are using, with or without the initial @samp{$}.
11472 @anchor{standard registers}
11473 @cindex stack pointer register
11474 @cindex program counter register
11475 @cindex process status register
11476 @cindex frame pointer register
11477 @cindex standard registers
11478 @value{GDBN} has four ``standard'' register names that are available (in
11479 expressions) on most machines---whenever they do not conflict with an
11480 architecture's canonical mnemonics for registers. The register names
11481 @code{$pc} and @code{$sp} are used for the program counter register and
11482 the stack pointer. @code{$fp} is used for a register that contains a
11483 pointer to the current stack frame, and @code{$ps} is used for a
11484 register that contains the processor status. For example,
11485 you could print the program counter in hex with
11492 or print the instruction to be executed next with
11499 or add four to the stack pointer@footnote{This is a way of removing
11500 one word from the stack, on machines where stacks grow downward in
11501 memory (most machines, nowadays). This assumes that the innermost
11502 stack frame is selected; setting @code{$sp} is not allowed when other
11503 stack frames are selected. To pop entire frames off the stack,
11504 regardless of machine architecture, use @code{return};
11505 see @ref{Returning, ,Returning from a Function}.} with
11511 Whenever possible, these four standard register names are available on
11512 your machine even though the machine has different canonical mnemonics,
11513 so long as there is no conflict. The @code{info registers} command
11514 shows the canonical names. For example, on the SPARC, @code{info
11515 registers} displays the processor status register as @code{$psr} but you
11516 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11517 is an alias for the @sc{eflags} register.
11519 @value{GDBN} always considers the contents of an ordinary register as an
11520 integer when the register is examined in this way. Some machines have
11521 special registers which can hold nothing but floating point; these
11522 registers are considered to have floating point values. There is no way
11523 to refer to the contents of an ordinary register as floating point value
11524 (although you can @emph{print} it as a floating point value with
11525 @samp{print/f $@var{regname}}).
11527 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11528 means that the data format in which the register contents are saved by
11529 the operating system is not the same one that your program normally
11530 sees. For example, the registers of the 68881 floating point
11531 coprocessor are always saved in ``extended'' (raw) format, but all C
11532 programs expect to work with ``double'' (virtual) format. In such
11533 cases, @value{GDBN} normally works with the virtual format only (the format
11534 that makes sense for your program), but the @code{info registers} command
11535 prints the data in both formats.
11537 @cindex SSE registers (x86)
11538 @cindex MMX registers (x86)
11539 Some machines have special registers whose contents can be interpreted
11540 in several different ways. For example, modern x86-based machines
11541 have SSE and MMX registers that can hold several values packed
11542 together in several different formats. @value{GDBN} refers to such
11543 registers in @code{struct} notation:
11546 (@value{GDBP}) print $xmm1
11548 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11549 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11550 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11551 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11552 v4_int32 = @{0, 20657912, 11, 13@},
11553 v2_int64 = @{88725056443645952, 55834574859@},
11554 uint128 = 0x0000000d0000000b013b36f800000000
11559 To set values of such registers, you need to tell @value{GDBN} which
11560 view of the register you wish to change, as if you were assigning
11561 value to a @code{struct} member:
11564 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11567 Normally, register values are relative to the selected stack frame
11568 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11569 value that the register would contain if all stack frames farther in
11570 were exited and their saved registers restored. In order to see the
11571 true contents of hardware registers, you must select the innermost
11572 frame (with @samp{frame 0}).
11574 @cindex caller-saved registers
11575 @cindex call-clobbered registers
11576 @cindex volatile registers
11577 @cindex <not saved> values
11578 Usually ABIs reserve some registers as not needed to be saved by the
11579 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11580 registers). It may therefore not be possible for @value{GDBN} to know
11581 the value a register had before the call (in other words, in the outer
11582 frame), if the register value has since been changed by the callee.
11583 @value{GDBN} tries to deduce where the inner frame saved
11584 (``callee-saved'') registers, from the debug info, unwind info, or the
11585 machine code generated by your compiler. If some register is not
11586 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11587 its own knowledge of the ABI, or because the debug/unwind info
11588 explicitly says the register's value is undefined), @value{GDBN}
11589 displays @w{@samp{<not saved>}} as the register's value. With targets
11590 that @value{GDBN} has no knowledge of the register saving convention,
11591 if a register was not saved by the callee, then its value and location
11592 in the outer frame are assumed to be the same of the inner frame.
11593 This is usually harmless, because if the register is call-clobbered,
11594 the caller either does not care what is in the register after the
11595 call, or has code to restore the value that it does care about. Note,
11596 however, that if you change such a register in the outer frame, you
11597 may also be affecting the inner frame. Also, the more ``outer'' the
11598 frame is you're looking at, the more likely a call-clobbered
11599 register's value is to be wrong, in the sense that it doesn't actually
11600 represent the value the register had just before the call.
11602 @node Floating Point Hardware
11603 @section Floating Point Hardware
11604 @cindex floating point
11606 Depending on the configuration, @value{GDBN} may be able to give
11607 you more information about the status of the floating point hardware.
11612 Display hardware-dependent information about the floating
11613 point unit. The exact contents and layout vary depending on the
11614 floating point chip. Currently, @samp{info float} is supported on
11615 the ARM and x86 machines.
11619 @section Vector Unit
11620 @cindex vector unit
11622 Depending on the configuration, @value{GDBN} may be able to give you
11623 more information about the status of the vector unit.
11626 @kindex info vector
11628 Display information about the vector unit. The exact contents and
11629 layout vary depending on the hardware.
11632 @node OS Information
11633 @section Operating System Auxiliary Information
11634 @cindex OS information
11636 @value{GDBN} provides interfaces to useful OS facilities that can help
11637 you debug your program.
11639 @cindex auxiliary vector
11640 @cindex vector, auxiliary
11641 Some operating systems supply an @dfn{auxiliary vector} to programs at
11642 startup. This is akin to the arguments and environment that you
11643 specify for a program, but contains a system-dependent variety of
11644 binary values that tell system libraries important details about the
11645 hardware, operating system, and process. Each value's purpose is
11646 identified by an integer tag; the meanings are well-known but system-specific.
11647 Depending on the configuration and operating system facilities,
11648 @value{GDBN} may be able to show you this information. For remote
11649 targets, this functionality may further depend on the remote stub's
11650 support of the @samp{qXfer:auxv:read} packet, see
11651 @ref{qXfer auxiliary vector read}.
11656 Display the auxiliary vector of the inferior, which can be either a
11657 live process or a core dump file. @value{GDBN} prints each tag value
11658 numerically, and also shows names and text descriptions for recognized
11659 tags. Some values in the vector are numbers, some bit masks, and some
11660 pointers to strings or other data. @value{GDBN} displays each value in the
11661 most appropriate form for a recognized tag, and in hexadecimal for
11662 an unrecognized tag.
11665 On some targets, @value{GDBN} can access operating system-specific
11666 information and show it to you. The types of information available
11667 will differ depending on the type of operating system running on the
11668 target. The mechanism used to fetch the data is described in
11669 @ref{Operating System Information}. For remote targets, this
11670 functionality depends on the remote stub's support of the
11671 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11675 @item info os @var{infotype}
11677 Display OS information of the requested type.
11679 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11681 @anchor{linux info os infotypes}
11683 @kindex info os cpus
11685 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11686 the available fields from /proc/cpuinfo. For each supported architecture
11687 different fields are available. Two common entries are processor which gives
11688 CPU number and bogomips; a system constant that is calculated during
11689 kernel initialization.
11691 @kindex info os files
11693 Display the list of open file descriptors on the target. For each
11694 file descriptor, @value{GDBN} prints the identifier of the process
11695 owning the descriptor, the command of the owning process, the value
11696 of the descriptor, and the target of the descriptor.
11698 @kindex info os modules
11700 Display the list of all loaded kernel modules on the target. For each
11701 module, @value{GDBN} prints the module name, the size of the module in
11702 bytes, the number of times the module is used, the dependencies of the
11703 module, the status of the module, and the address of the loaded module
11706 @kindex info os msg
11708 Display the list of all System V message queues on the target. For each
11709 message queue, @value{GDBN} prints the message queue key, the message
11710 queue identifier, the access permissions, the current number of bytes
11711 on the queue, the current number of messages on the queue, the processes
11712 that last sent and received a message on the queue, the user and group
11713 of the owner and creator of the message queue, the times at which a
11714 message was last sent and received on the queue, and the time at which
11715 the message queue was last changed.
11717 @kindex info os processes
11719 Display the list of processes on the target. For each process,
11720 @value{GDBN} prints the process identifier, the name of the user, the
11721 command corresponding to the process, and the list of processor cores
11722 that the process is currently running on. (To understand what these
11723 properties mean, for this and the following info types, please consult
11724 the general @sc{gnu}/Linux documentation.)
11726 @kindex info os procgroups
11728 Display the list of process groups on the target. For each process,
11729 @value{GDBN} prints the identifier of the process group that it belongs
11730 to, the command corresponding to the process group leader, the process
11731 identifier, and the command line of the process. The list is sorted
11732 first by the process group identifier, then by the process identifier,
11733 so that processes belonging to the same process group are grouped together
11734 and the process group leader is listed first.
11736 @kindex info os semaphores
11738 Display the list of all System V semaphore sets on the target. For each
11739 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11740 set identifier, the access permissions, the number of semaphores in the
11741 set, the user and group of the owner and creator of the semaphore set,
11742 and the times at which the semaphore set was operated upon and changed.
11744 @kindex info os shm
11746 Display the list of all System V shared-memory regions on the target.
11747 For each shared-memory region, @value{GDBN} prints the region key,
11748 the shared-memory identifier, the access permissions, the size of the
11749 region, the process that created the region, the process that last
11750 attached to or detached from the region, the current number of live
11751 attaches to the region, and the times at which the region was last
11752 attached to, detach from, and changed.
11754 @kindex info os sockets
11756 Display the list of Internet-domain sockets on the target. For each
11757 socket, @value{GDBN} prints the address and port of the local and
11758 remote endpoints, the current state of the connection, the creator of
11759 the socket, the IP address family of the socket, and the type of the
11762 @kindex info os threads
11764 Display the list of threads running on the target. For each thread,
11765 @value{GDBN} prints the identifier of the process that the thread
11766 belongs to, the command of the process, the thread identifier, and the
11767 processor core that it is currently running on. The main thread of a
11768 process is not listed.
11772 If @var{infotype} is omitted, then list the possible values for
11773 @var{infotype} and the kind of OS information available for each
11774 @var{infotype}. If the target does not return a list of possible
11775 types, this command will report an error.
11778 @node Memory Region Attributes
11779 @section Memory Region Attributes
11780 @cindex memory region attributes
11782 @dfn{Memory region attributes} allow you to describe special handling
11783 required by regions of your target's memory. @value{GDBN} uses
11784 attributes to determine whether to allow certain types of memory
11785 accesses; whether to use specific width accesses; and whether to cache
11786 target memory. By default the description of memory regions is
11787 fetched from the target (if the current target supports this), but the
11788 user can override the fetched regions.
11790 Defined memory regions can be individually enabled and disabled. When a
11791 memory region is disabled, @value{GDBN} uses the default attributes when
11792 accessing memory in that region. Similarly, if no memory regions have
11793 been defined, @value{GDBN} uses the default attributes when accessing
11796 When a memory region is defined, it is given a number to identify it;
11797 to enable, disable, or remove a memory region, you specify that number.
11801 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11802 Define a memory region bounded by @var{lower} and @var{upper} with
11803 attributes @var{attributes}@dots{}, and add it to the list of regions
11804 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11805 case: it is treated as the target's maximum memory address.
11806 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11809 Discard any user changes to the memory regions and use target-supplied
11810 regions, if available, or no regions if the target does not support.
11813 @item delete mem @var{nums}@dots{}
11814 Remove memory regions @var{nums}@dots{} from the list of regions
11815 monitored by @value{GDBN}.
11817 @kindex disable mem
11818 @item disable mem @var{nums}@dots{}
11819 Disable monitoring of memory regions @var{nums}@dots{}.
11820 A disabled memory region is not forgotten.
11821 It may be enabled again later.
11824 @item enable mem @var{nums}@dots{}
11825 Enable monitoring of memory regions @var{nums}@dots{}.
11829 Print a table of all defined memory regions, with the following columns
11833 @item Memory Region Number
11834 @item Enabled or Disabled.
11835 Enabled memory regions are marked with @samp{y}.
11836 Disabled memory regions are marked with @samp{n}.
11839 The address defining the inclusive lower bound of the memory region.
11842 The address defining the exclusive upper bound of the memory region.
11845 The list of attributes set for this memory region.
11850 @subsection Attributes
11852 @subsubsection Memory Access Mode
11853 The access mode attributes set whether @value{GDBN} may make read or
11854 write accesses to a memory region.
11856 While these attributes prevent @value{GDBN} from performing invalid
11857 memory accesses, they do nothing to prevent the target system, I/O DMA,
11858 etc.@: from accessing memory.
11862 Memory is read only.
11864 Memory is write only.
11866 Memory is read/write. This is the default.
11869 @subsubsection Memory Access Size
11870 The access size attribute tells @value{GDBN} to use specific sized
11871 accesses in the memory region. Often memory mapped device registers
11872 require specific sized accesses. If no access size attribute is
11873 specified, @value{GDBN} may use accesses of any size.
11877 Use 8 bit memory accesses.
11879 Use 16 bit memory accesses.
11881 Use 32 bit memory accesses.
11883 Use 64 bit memory accesses.
11886 @c @subsubsection Hardware/Software Breakpoints
11887 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11888 @c will use hardware or software breakpoints for the internal breakpoints
11889 @c used by the step, next, finish, until, etc. commands.
11893 @c Always use hardware breakpoints
11894 @c @item swbreak (default)
11897 @subsubsection Data Cache
11898 The data cache attributes set whether @value{GDBN} will cache target
11899 memory. While this generally improves performance by reducing debug
11900 protocol overhead, it can lead to incorrect results because @value{GDBN}
11901 does not know about volatile variables or memory mapped device
11906 Enable @value{GDBN} to cache target memory.
11908 Disable @value{GDBN} from caching target memory. This is the default.
11911 @subsection Memory Access Checking
11912 @value{GDBN} can be instructed to refuse accesses to memory that is
11913 not explicitly described. This can be useful if accessing such
11914 regions has undesired effects for a specific target, or to provide
11915 better error checking. The following commands control this behaviour.
11918 @kindex set mem inaccessible-by-default
11919 @item set mem inaccessible-by-default [on|off]
11920 If @code{on} is specified, make @value{GDBN} treat memory not
11921 explicitly described by the memory ranges as non-existent and refuse accesses
11922 to such memory. The checks are only performed if there's at least one
11923 memory range defined. If @code{off} is specified, make @value{GDBN}
11924 treat the memory not explicitly described by the memory ranges as RAM.
11925 The default value is @code{on}.
11926 @kindex show mem inaccessible-by-default
11927 @item show mem inaccessible-by-default
11928 Show the current handling of accesses to unknown memory.
11932 @c @subsubsection Memory Write Verification
11933 @c The memory write verification attributes set whether @value{GDBN}
11934 @c will re-reads data after each write to verify the write was successful.
11938 @c @item noverify (default)
11941 @node Dump/Restore Files
11942 @section Copy Between Memory and a File
11943 @cindex dump/restore files
11944 @cindex append data to a file
11945 @cindex dump data to a file
11946 @cindex restore data from a file
11948 You can use the commands @code{dump}, @code{append}, and
11949 @code{restore} to copy data between target memory and a file. The
11950 @code{dump} and @code{append} commands write data to a file, and the
11951 @code{restore} command reads data from a file back into the inferior's
11952 memory. Files may be in binary, Motorola S-record, Intel hex,
11953 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11954 append to binary files, and cannot read from Verilog Hex files.
11959 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11960 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11961 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11962 or the value of @var{expr}, to @var{filename} in the given format.
11964 The @var{format} parameter may be any one of:
11971 Motorola S-record format.
11973 Tektronix Hex format.
11975 Verilog Hex format.
11978 @value{GDBN} uses the same definitions of these formats as the
11979 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11980 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11984 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11985 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11986 Append the contents of memory from @var{start_addr} to @var{end_addr},
11987 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11988 (@value{GDBN} can only append data to files in raw binary form.)
11991 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11992 Restore the contents of file @var{filename} into memory. The
11993 @code{restore} command can automatically recognize any known @sc{bfd}
11994 file format, except for raw binary. To restore a raw binary file you
11995 must specify the optional keyword @code{binary} after the filename.
11997 If @var{bias} is non-zero, its value will be added to the addresses
11998 contained in the file. Binary files always start at address zero, so
11999 they will be restored at address @var{bias}. Other bfd files have
12000 a built-in location; they will be restored at offset @var{bias}
12001 from that location.
12003 If @var{start} and/or @var{end} are non-zero, then only data between
12004 file offset @var{start} and file offset @var{end} will be restored.
12005 These offsets are relative to the addresses in the file, before
12006 the @var{bias} argument is applied.
12010 @node Core File Generation
12011 @section How to Produce a Core File from Your Program
12012 @cindex dump core from inferior
12014 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12015 image of a running process and its process status (register values
12016 etc.). Its primary use is post-mortem debugging of a program that
12017 crashed while it ran outside a debugger. A program that crashes
12018 automatically produces a core file, unless this feature is disabled by
12019 the user. @xref{Files}, for information on invoking @value{GDBN} in
12020 the post-mortem debugging mode.
12022 Occasionally, you may wish to produce a core file of the program you
12023 are debugging in order to preserve a snapshot of its state.
12024 @value{GDBN} has a special command for that.
12028 @kindex generate-core-file
12029 @item generate-core-file [@var{file}]
12030 @itemx gcore [@var{file}]
12031 Produce a core dump of the inferior process. The optional argument
12032 @var{file} specifies the file name where to put the core dump. If not
12033 specified, the file name defaults to @file{core.@var{pid}}, where
12034 @var{pid} is the inferior process ID.
12036 Note that this command is implemented only for some systems (as of
12037 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12039 On @sc{gnu}/Linux, this command can take into account the value of the
12040 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12041 dump (@pxref{set use-coredump-filter}), and by default honors the
12042 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12043 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12045 @kindex set use-coredump-filter
12046 @anchor{set use-coredump-filter}
12047 @item set use-coredump-filter on
12048 @itemx set use-coredump-filter off
12049 Enable or disable the use of the file
12050 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12051 files. This file is used by the Linux kernel to decide what types of
12052 memory mappings will be dumped or ignored when generating a core dump
12053 file. @var{pid} is the process ID of a currently running process.
12055 To make use of this feature, you have to write in the
12056 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12057 which is a bit mask representing the memory mapping types. If a bit
12058 is set in the bit mask, then the memory mappings of the corresponding
12059 types will be dumped; otherwise, they will be ignored. This
12060 configuration is inherited by child processes. For more information
12061 about the bits that can be set in the
12062 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12063 manpage of @code{core(5)}.
12065 By default, this option is @code{on}. If this option is turned
12066 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12067 and instead uses the same default value as the Linux kernel in order
12068 to decide which pages will be dumped in the core dump file. This
12069 value is currently @code{0x33}, which means that bits @code{0}
12070 (anonymous private mappings), @code{1} (anonymous shared mappings),
12071 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12072 This will cause these memory mappings to be dumped automatically.
12074 @kindex set dump-excluded-mappings
12075 @anchor{set dump-excluded-mappings}
12076 @item set dump-excluded-mappings on
12077 @itemx set dump-excluded-mappings off
12078 If @code{on} is specified, @value{GDBN} will dump memory mappings
12079 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12080 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12082 The default value is @code{off}.
12085 @node Character Sets
12086 @section Character Sets
12087 @cindex character sets
12089 @cindex translating between character sets
12090 @cindex host character set
12091 @cindex target character set
12093 If the program you are debugging uses a different character set to
12094 represent characters and strings than the one @value{GDBN} uses itself,
12095 @value{GDBN} can automatically translate between the character sets for
12096 you. The character set @value{GDBN} uses we call the @dfn{host
12097 character set}; the one the inferior program uses we call the
12098 @dfn{target character set}.
12100 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12101 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12102 remote protocol (@pxref{Remote Debugging}) to debug a program
12103 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12104 then the host character set is Latin-1, and the target character set is
12105 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12106 target-charset EBCDIC-US}, then @value{GDBN} translates between
12107 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12108 character and string literals in expressions.
12110 @value{GDBN} has no way to automatically recognize which character set
12111 the inferior program uses; you must tell it, using the @code{set
12112 target-charset} command, described below.
12114 Here are the commands for controlling @value{GDBN}'s character set
12118 @item set target-charset @var{charset}
12119 @kindex set target-charset
12120 Set the current target character set to @var{charset}. To display the
12121 list of supported target character sets, type
12122 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12124 @item set host-charset @var{charset}
12125 @kindex set host-charset
12126 Set the current host character set to @var{charset}.
12128 By default, @value{GDBN} uses a host character set appropriate to the
12129 system it is running on; you can override that default using the
12130 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12131 automatically determine the appropriate host character set. In this
12132 case, @value{GDBN} uses @samp{UTF-8}.
12134 @value{GDBN} can only use certain character sets as its host character
12135 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12136 @value{GDBN} will list the host character sets it supports.
12138 @item set charset @var{charset}
12139 @kindex set charset
12140 Set the current host and target character sets to @var{charset}. As
12141 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12142 @value{GDBN} will list the names of the character sets that can be used
12143 for both host and target.
12146 @kindex show charset
12147 Show the names of the current host and target character sets.
12149 @item show host-charset
12150 @kindex show host-charset
12151 Show the name of the current host character set.
12153 @item show target-charset
12154 @kindex show target-charset
12155 Show the name of the current target character set.
12157 @item set target-wide-charset @var{charset}
12158 @kindex set target-wide-charset
12159 Set the current target's wide character set to @var{charset}. This is
12160 the character set used by the target's @code{wchar_t} type. To
12161 display the list of supported wide character sets, type
12162 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12164 @item show target-wide-charset
12165 @kindex show target-wide-charset
12166 Show the name of the current target's wide character set.
12169 Here is an example of @value{GDBN}'s character set support in action.
12170 Assume that the following source code has been placed in the file
12171 @file{charset-test.c}:
12177 = @{72, 101, 108, 108, 111, 44, 32, 119,
12178 111, 114, 108, 100, 33, 10, 0@};
12179 char ibm1047_hello[]
12180 = @{200, 133, 147, 147, 150, 107, 64, 166,
12181 150, 153, 147, 132, 90, 37, 0@};
12185 printf ("Hello, world!\n");
12189 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12190 containing the string @samp{Hello, world!} followed by a newline,
12191 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12193 We compile the program, and invoke the debugger on it:
12196 $ gcc -g charset-test.c -o charset-test
12197 $ gdb -nw charset-test
12198 GNU gdb 2001-12-19-cvs
12199 Copyright 2001 Free Software Foundation, Inc.
12204 We can use the @code{show charset} command to see what character sets
12205 @value{GDBN} is currently using to interpret and display characters and
12209 (@value{GDBP}) show charset
12210 The current host and target character set is `ISO-8859-1'.
12214 For the sake of printing this manual, let's use @sc{ascii} as our
12215 initial character set:
12217 (@value{GDBP}) set charset ASCII
12218 (@value{GDBP}) show charset
12219 The current host and target character set is `ASCII'.
12223 Let's assume that @sc{ascii} is indeed the correct character set for our
12224 host system --- in other words, let's assume that if @value{GDBN} prints
12225 characters using the @sc{ascii} character set, our terminal will display
12226 them properly. Since our current target character set is also
12227 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12230 (@value{GDBP}) print ascii_hello
12231 $1 = 0x401698 "Hello, world!\n"
12232 (@value{GDBP}) print ascii_hello[0]
12237 @value{GDBN} uses the target character set for character and string
12238 literals you use in expressions:
12241 (@value{GDBP}) print '+'
12246 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12249 @value{GDBN} relies on the user to tell it which character set the
12250 target program uses. If we print @code{ibm1047_hello} while our target
12251 character set is still @sc{ascii}, we get jibberish:
12254 (@value{GDBP}) print ibm1047_hello
12255 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12256 (@value{GDBP}) print ibm1047_hello[0]
12261 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12262 @value{GDBN} tells us the character sets it supports:
12265 (@value{GDBP}) set target-charset
12266 ASCII EBCDIC-US IBM1047 ISO-8859-1
12267 (@value{GDBP}) set target-charset
12270 We can select @sc{ibm1047} as our target character set, and examine the
12271 program's strings again. Now the @sc{ascii} string is wrong, but
12272 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12273 target character set, @sc{ibm1047}, to the host character set,
12274 @sc{ascii}, and they display correctly:
12277 (@value{GDBP}) set target-charset IBM1047
12278 (@value{GDBP}) show charset
12279 The current host character set is `ASCII'.
12280 The current target character set is `IBM1047'.
12281 (@value{GDBP}) print ascii_hello
12282 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12283 (@value{GDBP}) print ascii_hello[0]
12285 (@value{GDBP}) print ibm1047_hello
12286 $8 = 0x4016a8 "Hello, world!\n"
12287 (@value{GDBP}) print ibm1047_hello[0]
12292 As above, @value{GDBN} uses the target character set for character and
12293 string literals you use in expressions:
12296 (@value{GDBP}) print '+'
12301 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12304 @node Caching Target Data
12305 @section Caching Data of Targets
12306 @cindex caching data of targets
12308 @value{GDBN} caches data exchanged between the debugger and a target.
12309 Each cache is associated with the address space of the inferior.
12310 @xref{Inferiors and Programs}, about inferior and address space.
12311 Such caching generally improves performance in remote debugging
12312 (@pxref{Remote Debugging}), because it reduces the overhead of the
12313 remote protocol by bundling memory reads and writes into large chunks.
12314 Unfortunately, simply caching everything would lead to incorrect results,
12315 since @value{GDBN} does not necessarily know anything about volatile
12316 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12317 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12319 Therefore, by default, @value{GDBN} only caches data
12320 known to be on the stack@footnote{In non-stop mode, it is moderately
12321 rare for a running thread to modify the stack of a stopped thread
12322 in a way that would interfere with a backtrace, and caching of
12323 stack reads provides a significant speed up of remote backtraces.} or
12324 in the code segment.
12325 Other regions of memory can be explicitly marked as
12326 cacheable; @pxref{Memory Region Attributes}.
12329 @kindex set remotecache
12330 @item set remotecache on
12331 @itemx set remotecache off
12332 This option no longer does anything; it exists for compatibility
12335 @kindex show remotecache
12336 @item show remotecache
12337 Show the current state of the obsolete remotecache flag.
12339 @kindex set stack-cache
12340 @item set stack-cache on
12341 @itemx set stack-cache off
12342 Enable or disable caching of stack accesses. When @code{on}, use
12343 caching. By default, this option is @code{on}.
12345 @kindex show stack-cache
12346 @item show stack-cache
12347 Show the current state of data caching for memory accesses.
12349 @kindex set code-cache
12350 @item set code-cache on
12351 @itemx set code-cache off
12352 Enable or disable caching of code segment accesses. When @code{on},
12353 use caching. By default, this option is @code{on}. This improves
12354 performance of disassembly in remote debugging.
12356 @kindex show code-cache
12357 @item show code-cache
12358 Show the current state of target memory cache for code segment
12361 @kindex info dcache
12362 @item info dcache @r{[}line@r{]}
12363 Print the information about the performance of data cache of the
12364 current inferior's address space. The information displayed
12365 includes the dcache width and depth, and for each cache line, its
12366 number, address, and how many times it was referenced. This
12367 command is useful for debugging the data cache operation.
12369 If a line number is specified, the contents of that line will be
12372 @item set dcache size @var{size}
12373 @cindex dcache size
12374 @kindex set dcache size
12375 Set maximum number of entries in dcache (dcache depth above).
12377 @item set dcache line-size @var{line-size}
12378 @cindex dcache line-size
12379 @kindex set dcache line-size
12380 Set number of bytes each dcache entry caches (dcache width above).
12381 Must be a power of 2.
12383 @item show dcache size
12384 @kindex show dcache size
12385 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12387 @item show dcache line-size
12388 @kindex show dcache line-size
12389 Show default size of dcache lines.
12393 @node Searching Memory
12394 @section Search Memory
12395 @cindex searching memory
12397 Memory can be searched for a particular sequence of bytes with the
12398 @code{find} command.
12402 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12403 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12404 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12405 etc. The search begins at address @var{start_addr} and continues for either
12406 @var{len} bytes or through to @var{end_addr} inclusive.
12409 @var{s} and @var{n} are optional parameters.
12410 They may be specified in either order, apart or together.
12413 @item @var{s}, search query size
12414 The size of each search query value.
12420 halfwords (two bytes)
12424 giant words (eight bytes)
12427 All values are interpreted in the current language.
12428 This means, for example, that if the current source language is C/C@t{++}
12429 then searching for the string ``hello'' includes the trailing '\0'.
12430 The null terminator can be removed from searching by using casts,
12431 e.g.: @samp{@{char[5]@}"hello"}.
12433 If the value size is not specified, it is taken from the
12434 value's type in the current language.
12435 This is useful when one wants to specify the search
12436 pattern as a mixture of types.
12437 Note that this means, for example, that in the case of C-like languages
12438 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12439 which is typically four bytes.
12441 @item @var{n}, maximum number of finds
12442 The maximum number of matches to print. The default is to print all finds.
12445 You can use strings as search values. Quote them with double-quotes
12447 The string value is copied into the search pattern byte by byte,
12448 regardless of the endianness of the target and the size specification.
12450 The address of each match found is printed as well as a count of the
12451 number of matches found.
12453 The address of the last value found is stored in convenience variable
12455 A count of the number of matches is stored in @samp{$numfound}.
12457 For example, if stopped at the @code{printf} in this function:
12463 static char hello[] = "hello-hello";
12464 static struct @{ char c; short s; int i; @}
12465 __attribute__ ((packed)) mixed
12466 = @{ 'c', 0x1234, 0x87654321 @};
12467 printf ("%s\n", hello);
12472 you get during debugging:
12475 (gdb) find &hello[0], +sizeof(hello), "hello"
12476 0x804956d <hello.1620+6>
12478 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12479 0x8049567 <hello.1620>
12480 0x804956d <hello.1620+6>
12482 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12483 0x8049567 <hello.1620>
12484 0x804956d <hello.1620+6>
12486 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12487 0x8049567 <hello.1620>
12489 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12490 0x8049560 <mixed.1625>
12492 (gdb) print $numfound
12495 $2 = (void *) 0x8049560
12499 @section Value Sizes
12501 Whenever @value{GDBN} prints a value memory will be allocated within
12502 @value{GDBN} to hold the contents of the value. It is possible in
12503 some languages with dynamic typing systems, that an invalid program
12504 may indicate a value that is incorrectly large, this in turn may cause
12505 @value{GDBN} to try and allocate an overly large ammount of memory.
12508 @kindex set max-value-size
12509 @item set max-value-size @var{bytes}
12510 @itemx set max-value-size unlimited
12511 Set the maximum size of memory that @value{GDBN} will allocate for the
12512 contents of a value to @var{bytes}, trying to display a value that
12513 requires more memory than that will result in an error.
12515 Setting this variable does not effect values that have already been
12516 allocated within @value{GDBN}, only future allocations.
12518 There's a minimum size that @code{max-value-size} can be set to in
12519 order that @value{GDBN} can still operate correctly, this minimum is
12520 currently 16 bytes.
12522 The limit applies to the results of some subexpressions as well as to
12523 complete expressions. For example, an expression denoting a simple
12524 integer component, such as @code{x.y.z}, may fail if the size of
12525 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12526 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12527 @var{A} is an array variable with non-constant size, will generally
12528 succeed regardless of the bounds on @var{A}, as long as the component
12529 size is less than @var{bytes}.
12531 The default value of @code{max-value-size} is currently 64k.
12533 @kindex show max-value-size
12534 @item show max-value-size
12535 Show the maximum size of memory, in bytes, that @value{GDBN} will
12536 allocate for the contents of a value.
12539 @node Optimized Code
12540 @chapter Debugging Optimized Code
12541 @cindex optimized code, debugging
12542 @cindex debugging optimized code
12544 Almost all compilers support optimization. With optimization
12545 disabled, the compiler generates assembly code that corresponds
12546 directly to your source code, in a simplistic way. As the compiler
12547 applies more powerful optimizations, the generated assembly code
12548 diverges from your original source code. With help from debugging
12549 information generated by the compiler, @value{GDBN} can map from
12550 the running program back to constructs from your original source.
12552 @value{GDBN} is more accurate with optimization disabled. If you
12553 can recompile without optimization, it is easier to follow the
12554 progress of your program during debugging. But, there are many cases
12555 where you may need to debug an optimized version.
12557 When you debug a program compiled with @samp{-g -O}, remember that the
12558 optimizer has rearranged your code; the debugger shows you what is
12559 really there. Do not be too surprised when the execution path does not
12560 exactly match your source file! An extreme example: if you define a
12561 variable, but never use it, @value{GDBN} never sees that
12562 variable---because the compiler optimizes it out of existence.
12564 Some things do not work as well with @samp{-g -O} as with just
12565 @samp{-g}, particularly on machines with instruction scheduling. If in
12566 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12567 please report it to us as a bug (including a test case!).
12568 @xref{Variables}, for more information about debugging optimized code.
12571 * Inline Functions:: How @value{GDBN} presents inlining
12572 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12575 @node Inline Functions
12576 @section Inline Functions
12577 @cindex inline functions, debugging
12579 @dfn{Inlining} is an optimization that inserts a copy of the function
12580 body directly at each call site, instead of jumping to a shared
12581 routine. @value{GDBN} displays inlined functions just like
12582 non-inlined functions. They appear in backtraces. You can view their
12583 arguments and local variables, step into them with @code{step}, skip
12584 them with @code{next}, and escape from them with @code{finish}.
12585 You can check whether a function was inlined by using the
12586 @code{info frame} command.
12588 For @value{GDBN} to support inlined functions, the compiler must
12589 record information about inlining in the debug information ---
12590 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12591 other compilers do also. @value{GDBN} only supports inlined functions
12592 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12593 do not emit two required attributes (@samp{DW_AT_call_file} and
12594 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12595 function calls with earlier versions of @value{NGCC}. It instead
12596 displays the arguments and local variables of inlined functions as
12597 local variables in the caller.
12599 The body of an inlined function is directly included at its call site;
12600 unlike a non-inlined function, there are no instructions devoted to
12601 the call. @value{GDBN} still pretends that the call site and the
12602 start of the inlined function are different instructions. Stepping to
12603 the call site shows the call site, and then stepping again shows
12604 the first line of the inlined function, even though no additional
12605 instructions are executed.
12607 This makes source-level debugging much clearer; you can see both the
12608 context of the call and then the effect of the call. Only stepping by
12609 a single instruction using @code{stepi} or @code{nexti} does not do
12610 this; single instruction steps always show the inlined body.
12612 There are some ways that @value{GDBN} does not pretend that inlined
12613 function calls are the same as normal calls:
12617 Setting breakpoints at the call site of an inlined function may not
12618 work, because the call site does not contain any code. @value{GDBN}
12619 may incorrectly move the breakpoint to the next line of the enclosing
12620 function, after the call. This limitation will be removed in a future
12621 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12622 or inside the inlined function instead.
12625 @value{GDBN} cannot locate the return value of inlined calls after
12626 using the @code{finish} command. This is a limitation of compiler-generated
12627 debugging information; after @code{finish}, you can step to the next line
12628 and print a variable where your program stored the return value.
12632 @node Tail Call Frames
12633 @section Tail Call Frames
12634 @cindex tail call frames, debugging
12636 Function @code{B} can call function @code{C} in its very last statement. In
12637 unoptimized compilation the call of @code{C} is immediately followed by return
12638 instruction at the end of @code{B} code. Optimizing compiler may replace the
12639 call and return in function @code{B} into one jump to function @code{C}
12640 instead. Such use of a jump instruction is called @dfn{tail call}.
12642 During execution of function @code{C}, there will be no indication in the
12643 function call stack frames that it was tail-called from @code{B}. If function
12644 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12645 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12646 some cases @value{GDBN} can determine that @code{C} was tail-called from
12647 @code{B}, and it will then create fictitious call frame for that, with the
12648 return address set up as if @code{B} called @code{C} normally.
12650 This functionality is currently supported only by DWARF 2 debugging format and
12651 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12652 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12655 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12656 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12660 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12662 Stack level 1, frame at 0x7fffffffda30:
12663 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12664 tail call frame, caller of frame at 0x7fffffffda30
12665 source language c++.
12666 Arglist at unknown address.
12667 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12670 The detection of all the possible code path executions can find them ambiguous.
12671 There is no execution history stored (possible @ref{Reverse Execution} is never
12672 used for this purpose) and the last known caller could have reached the known
12673 callee by multiple different jump sequences. In such case @value{GDBN} still
12674 tries to show at least all the unambiguous top tail callers and all the
12675 unambiguous bottom tail calees, if any.
12678 @anchor{set debug entry-values}
12679 @item set debug entry-values
12680 @kindex set debug entry-values
12681 When set to on, enables printing of analysis messages for both frame argument
12682 values at function entry and tail calls. It will show all the possible valid
12683 tail calls code paths it has considered. It will also print the intersection
12684 of them with the final unambiguous (possibly partial or even empty) code path
12687 @item show debug entry-values
12688 @kindex show debug entry-values
12689 Show the current state of analysis messages printing for both frame argument
12690 values at function entry and tail calls.
12693 The analysis messages for tail calls can for example show why the virtual tail
12694 call frame for function @code{c} has not been recognized (due to the indirect
12695 reference by variable @code{x}):
12698 static void __attribute__((noinline, noclone)) c (void);
12699 void (*x) (void) = c;
12700 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12701 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12702 int main (void) @{ x (); return 0; @}
12704 Breakpoint 1, DW_OP_entry_value resolving cannot find
12705 DW_TAG_call_site 0x40039a in main
12707 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12710 #1 0x000000000040039a in main () at t.c:5
12713 Another possibility is an ambiguous virtual tail call frames resolution:
12717 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12718 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12719 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12720 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12721 static void __attribute__((noinline, noclone)) b (void)
12722 @{ if (i) c (); else e (); @}
12723 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12724 int main (void) @{ a (); return 0; @}
12726 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12727 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12728 tailcall: reduced: 0x4004d2(a) |
12731 #1 0x00000000004004d2 in a () at t.c:8
12732 #2 0x0000000000400395 in main () at t.c:9
12735 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12736 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12738 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12739 @ifset HAVE_MAKEINFO_CLICK
12740 @set ARROW @click{}
12741 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12742 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12744 @ifclear HAVE_MAKEINFO_CLICK
12746 @set CALLSEQ1B @value{CALLSEQ1A}
12747 @set CALLSEQ2B @value{CALLSEQ2A}
12750 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12751 The code can have possible execution paths @value{CALLSEQ1B} or
12752 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12754 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12755 has found. It then finds another possible calling sequcen - that one is
12756 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12757 printed as the @code{reduced:} calling sequence. That one could have many
12758 futher @code{compare:} and @code{reduced:} statements as long as there remain
12759 any non-ambiguous sequence entries.
12761 For the frame of function @code{b} in both cases there are different possible
12762 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12763 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12764 therefore this one is displayed to the user while the ambiguous frames are
12767 There can be also reasons why printing of frame argument values at function
12772 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12773 static void __attribute__((noinline, noclone)) a (int i);
12774 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12775 static void __attribute__((noinline, noclone)) a (int i)
12776 @{ if (i) b (i - 1); else c (0); @}
12777 int main (void) @{ a (5); return 0; @}
12780 #0 c (i=i@@entry=0) at t.c:2
12781 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12782 function "a" at 0x400420 can call itself via tail calls
12783 i=<optimized out>) at t.c:6
12784 #2 0x000000000040036e in main () at t.c:7
12787 @value{GDBN} cannot find out from the inferior state if and how many times did
12788 function @code{a} call itself (via function @code{b}) as these calls would be
12789 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12790 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12791 prints @code{<optimized out>} instead.
12794 @chapter C Preprocessor Macros
12796 Some languages, such as C and C@t{++}, provide a way to define and invoke
12797 ``preprocessor macros'' which expand into strings of tokens.
12798 @value{GDBN} can evaluate expressions containing macro invocations, show
12799 the result of macro expansion, and show a macro's definition, including
12800 where it was defined.
12802 You may need to compile your program specially to provide @value{GDBN}
12803 with information about preprocessor macros. Most compilers do not
12804 include macros in their debugging information, even when you compile
12805 with the @option{-g} flag. @xref{Compilation}.
12807 A program may define a macro at one point, remove that definition later,
12808 and then provide a different definition after that. Thus, at different
12809 points in the program, a macro may have different definitions, or have
12810 no definition at all. If there is a current stack frame, @value{GDBN}
12811 uses the macros in scope at that frame's source code line. Otherwise,
12812 @value{GDBN} uses the macros in scope at the current listing location;
12815 Whenever @value{GDBN} evaluates an expression, it always expands any
12816 macro invocations present in the expression. @value{GDBN} also provides
12817 the following commands for working with macros explicitly.
12821 @kindex macro expand
12822 @cindex macro expansion, showing the results of preprocessor
12823 @cindex preprocessor macro expansion, showing the results of
12824 @cindex expanding preprocessor macros
12825 @item macro expand @var{expression}
12826 @itemx macro exp @var{expression}
12827 Show the results of expanding all preprocessor macro invocations in
12828 @var{expression}. Since @value{GDBN} simply expands macros, but does
12829 not parse the result, @var{expression} need not be a valid expression;
12830 it can be any string of tokens.
12833 @item macro expand-once @var{expression}
12834 @itemx macro exp1 @var{expression}
12835 @cindex expand macro once
12836 @i{(This command is not yet implemented.)} Show the results of
12837 expanding those preprocessor macro invocations that appear explicitly in
12838 @var{expression}. Macro invocations appearing in that expansion are
12839 left unchanged. This command allows you to see the effect of a
12840 particular macro more clearly, without being confused by further
12841 expansions. Since @value{GDBN} simply expands macros, but does not
12842 parse the result, @var{expression} need not be a valid expression; it
12843 can be any string of tokens.
12846 @cindex macro definition, showing
12847 @cindex definition of a macro, showing
12848 @cindex macros, from debug info
12849 @item info macro [-a|-all] [--] @var{macro}
12850 Show the current definition or all definitions of the named @var{macro},
12851 and describe the source location or compiler command-line where that
12852 definition was established. The optional double dash is to signify the end of
12853 argument processing and the beginning of @var{macro} for non C-like macros where
12854 the macro may begin with a hyphen.
12856 @kindex info macros
12857 @item info macros @var{location}
12858 Show all macro definitions that are in effect at the location specified
12859 by @var{location}, and describe the source location or compiler
12860 command-line where those definitions were established.
12862 @kindex macro define
12863 @cindex user-defined macros
12864 @cindex defining macros interactively
12865 @cindex macros, user-defined
12866 @item macro define @var{macro} @var{replacement-list}
12867 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12868 Introduce a definition for a preprocessor macro named @var{macro},
12869 invocations of which are replaced by the tokens given in
12870 @var{replacement-list}. The first form of this command defines an
12871 ``object-like'' macro, which takes no arguments; the second form
12872 defines a ``function-like'' macro, which takes the arguments given in
12875 A definition introduced by this command is in scope in every
12876 expression evaluated in @value{GDBN}, until it is removed with the
12877 @code{macro undef} command, described below. The definition overrides
12878 all definitions for @var{macro} present in the program being debugged,
12879 as well as any previous user-supplied definition.
12881 @kindex macro undef
12882 @item macro undef @var{macro}
12883 Remove any user-supplied definition for the macro named @var{macro}.
12884 This command only affects definitions provided with the @code{macro
12885 define} command, described above; it cannot remove definitions present
12886 in the program being debugged.
12890 List all the macros defined using the @code{macro define} command.
12893 @cindex macros, example of debugging with
12894 Here is a transcript showing the above commands in action. First, we
12895 show our source files:
12900 #include "sample.h"
12903 #define ADD(x) (M + x)
12908 printf ("Hello, world!\n");
12910 printf ("We're so creative.\n");
12912 printf ("Goodbye, world!\n");
12919 Now, we compile the program using the @sc{gnu} C compiler,
12920 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12921 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12922 and @option{-gdwarf-4}; we recommend always choosing the most recent
12923 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12924 includes information about preprocessor macros in the debugging
12928 $ gcc -gdwarf-2 -g3 sample.c -o sample
12932 Now, we start @value{GDBN} on our sample program:
12936 GNU gdb 2002-05-06-cvs
12937 Copyright 2002 Free Software Foundation, Inc.
12938 GDB is free software, @dots{}
12942 We can expand macros and examine their definitions, even when the
12943 program is not running. @value{GDBN} uses the current listing position
12944 to decide which macro definitions are in scope:
12947 (@value{GDBP}) list main
12950 5 #define ADD(x) (M + x)
12955 10 printf ("Hello, world!\n");
12957 12 printf ("We're so creative.\n");
12958 (@value{GDBP}) info macro ADD
12959 Defined at /home/jimb/gdb/macros/play/sample.c:5
12960 #define ADD(x) (M + x)
12961 (@value{GDBP}) info macro Q
12962 Defined at /home/jimb/gdb/macros/play/sample.h:1
12963 included at /home/jimb/gdb/macros/play/sample.c:2
12965 (@value{GDBP}) macro expand ADD(1)
12966 expands to: (42 + 1)
12967 (@value{GDBP}) macro expand-once ADD(1)
12968 expands to: once (M + 1)
12972 In the example above, note that @code{macro expand-once} expands only
12973 the macro invocation explicit in the original text --- the invocation of
12974 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12975 which was introduced by @code{ADD}.
12977 Once the program is running, @value{GDBN} uses the macro definitions in
12978 force at the source line of the current stack frame:
12981 (@value{GDBP}) break main
12982 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12984 Starting program: /home/jimb/gdb/macros/play/sample
12986 Breakpoint 1, main () at sample.c:10
12987 10 printf ("Hello, world!\n");
12991 At line 10, the definition of the macro @code{N} at line 9 is in force:
12994 (@value{GDBP}) info macro N
12995 Defined at /home/jimb/gdb/macros/play/sample.c:9
12997 (@value{GDBP}) macro expand N Q M
12998 expands to: 28 < 42
12999 (@value{GDBP}) print N Q M
13004 As we step over directives that remove @code{N}'s definition, and then
13005 give it a new definition, @value{GDBN} finds the definition (or lack
13006 thereof) in force at each point:
13009 (@value{GDBP}) next
13011 12 printf ("We're so creative.\n");
13012 (@value{GDBP}) info macro N
13013 The symbol `N' has no definition as a C/C++ preprocessor macro
13014 at /home/jimb/gdb/macros/play/sample.c:12
13015 (@value{GDBP}) next
13017 14 printf ("Goodbye, world!\n");
13018 (@value{GDBP}) info macro N
13019 Defined at /home/jimb/gdb/macros/play/sample.c:13
13021 (@value{GDBP}) macro expand N Q M
13022 expands to: 1729 < 42
13023 (@value{GDBP}) print N Q M
13028 In addition to source files, macros can be defined on the compilation command
13029 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13030 such a way, @value{GDBN} displays the location of their definition as line zero
13031 of the source file submitted to the compiler.
13034 (@value{GDBP}) info macro __STDC__
13035 Defined at /home/jimb/gdb/macros/play/sample.c:0
13042 @chapter Tracepoints
13043 @c This chapter is based on the documentation written by Michael
13044 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13046 @cindex tracepoints
13047 In some applications, it is not feasible for the debugger to interrupt
13048 the program's execution long enough for the developer to learn
13049 anything helpful about its behavior. If the program's correctness
13050 depends on its real-time behavior, delays introduced by a debugger
13051 might cause the program to change its behavior drastically, or perhaps
13052 fail, even when the code itself is correct. It is useful to be able
13053 to observe the program's behavior without interrupting it.
13055 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13056 specify locations in the program, called @dfn{tracepoints}, and
13057 arbitrary expressions to evaluate when those tracepoints are reached.
13058 Later, using the @code{tfind} command, you can examine the values
13059 those expressions had when the program hit the tracepoints. The
13060 expressions may also denote objects in memory---structures or arrays,
13061 for example---whose values @value{GDBN} should record; while visiting
13062 a particular tracepoint, you may inspect those objects as if they were
13063 in memory at that moment. However, because @value{GDBN} records these
13064 values without interacting with you, it can do so quickly and
13065 unobtrusively, hopefully not disturbing the program's behavior.
13067 The tracepoint facility is currently available only for remote
13068 targets. @xref{Targets}. In addition, your remote target must know
13069 how to collect trace data. This functionality is implemented in the
13070 remote stub; however, none of the stubs distributed with @value{GDBN}
13071 support tracepoints as of this writing. The format of the remote
13072 packets used to implement tracepoints are described in @ref{Tracepoint
13075 It is also possible to get trace data from a file, in a manner reminiscent
13076 of corefiles; you specify the filename, and use @code{tfind} to search
13077 through the file. @xref{Trace Files}, for more details.
13079 This chapter describes the tracepoint commands and features.
13082 * Set Tracepoints::
13083 * Analyze Collected Data::
13084 * Tracepoint Variables::
13088 @node Set Tracepoints
13089 @section Commands to Set Tracepoints
13091 Before running such a @dfn{trace experiment}, an arbitrary number of
13092 tracepoints can be set. A tracepoint is actually a special type of
13093 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13094 standard breakpoint commands. For instance, as with breakpoints,
13095 tracepoint numbers are successive integers starting from one, and many
13096 of the commands associated with tracepoints take the tracepoint number
13097 as their argument, to identify which tracepoint to work on.
13099 For each tracepoint, you can specify, in advance, some arbitrary set
13100 of data that you want the target to collect in the trace buffer when
13101 it hits that tracepoint. The collected data can include registers,
13102 local variables, or global data. Later, you can use @value{GDBN}
13103 commands to examine the values these data had at the time the
13104 tracepoint was hit.
13106 Tracepoints do not support every breakpoint feature. Ignore counts on
13107 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13108 commands when they are hit. Tracepoints may not be thread-specific
13111 @cindex fast tracepoints
13112 Some targets may support @dfn{fast tracepoints}, which are inserted in
13113 a different way (such as with a jump instead of a trap), that is
13114 faster but possibly restricted in where they may be installed.
13116 @cindex static tracepoints
13117 @cindex markers, static tracepoints
13118 @cindex probing markers, static tracepoints
13119 Regular and fast tracepoints are dynamic tracing facilities, meaning
13120 that they can be used to insert tracepoints at (almost) any location
13121 in the target. Some targets may also support controlling @dfn{static
13122 tracepoints} from @value{GDBN}. With static tracing, a set of
13123 instrumentation points, also known as @dfn{markers}, are embedded in
13124 the target program, and can be activated or deactivated by name or
13125 address. These are usually placed at locations which facilitate
13126 investigating what the target is actually doing. @value{GDBN}'s
13127 support for static tracing includes being able to list instrumentation
13128 points, and attach them with @value{GDBN} defined high level
13129 tracepoints that expose the whole range of convenience of
13130 @value{GDBN}'s tracepoints support. Namely, support for collecting
13131 registers values and values of global or local (to the instrumentation
13132 point) variables; tracepoint conditions and trace state variables.
13133 The act of installing a @value{GDBN} static tracepoint on an
13134 instrumentation point, or marker, is referred to as @dfn{probing} a
13135 static tracepoint marker.
13137 @code{gdbserver} supports tracepoints on some target systems.
13138 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13140 This section describes commands to set tracepoints and associated
13141 conditions and actions.
13144 * Create and Delete Tracepoints::
13145 * Enable and Disable Tracepoints::
13146 * Tracepoint Passcounts::
13147 * Tracepoint Conditions::
13148 * Trace State Variables::
13149 * Tracepoint Actions::
13150 * Listing Tracepoints::
13151 * Listing Static Tracepoint Markers::
13152 * Starting and Stopping Trace Experiments::
13153 * Tracepoint Restrictions::
13156 @node Create and Delete Tracepoints
13157 @subsection Create and Delete Tracepoints
13160 @cindex set tracepoint
13162 @item trace @var{location}
13163 The @code{trace} command is very similar to the @code{break} command.
13164 Its argument @var{location} can be any valid location.
13165 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13166 which is a point in the target program where the debugger will briefly stop,
13167 collect some data, and then allow the program to continue. Setting a tracepoint
13168 or changing its actions takes effect immediately if the remote stub
13169 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13171 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13172 these changes don't take effect until the next @code{tstart}
13173 command, and once a trace experiment is running, further changes will
13174 not have any effect until the next trace experiment starts. In addition,
13175 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13176 address is not yet resolved. (This is similar to pending breakpoints.)
13177 Pending tracepoints are not downloaded to the target and not installed
13178 until they are resolved. The resolution of pending tracepoints requires
13179 @value{GDBN} support---when debugging with the remote target, and
13180 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13181 tracing}), pending tracepoints can not be resolved (and downloaded to
13182 the remote stub) while @value{GDBN} is disconnected.
13184 Here are some examples of using the @code{trace} command:
13187 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13189 (@value{GDBP}) @b{trace +2} // 2 lines forward
13191 (@value{GDBP}) @b{trace my_function} // first source line of function
13193 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13195 (@value{GDBP}) @b{trace *0x2117c4} // an address
13199 You can abbreviate @code{trace} as @code{tr}.
13201 @item trace @var{location} if @var{cond}
13202 Set a tracepoint with condition @var{cond}; evaluate the expression
13203 @var{cond} each time the tracepoint is reached, and collect data only
13204 if the value is nonzero---that is, if @var{cond} evaluates as true.
13205 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13206 information on tracepoint conditions.
13208 @item ftrace @var{location} [ if @var{cond} ]
13209 @cindex set fast tracepoint
13210 @cindex fast tracepoints, setting
13212 The @code{ftrace} command sets a fast tracepoint. For targets that
13213 support them, fast tracepoints will use a more efficient but possibly
13214 less general technique to trigger data collection, such as a jump
13215 instruction instead of a trap, or some sort of hardware support. It
13216 may not be possible to create a fast tracepoint at the desired
13217 location, in which case the command will exit with an explanatory
13220 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13223 On 32-bit x86-architecture systems, fast tracepoints normally need to
13224 be placed at an instruction that is 5 bytes or longer, but can be
13225 placed at 4-byte instructions if the low 64K of memory of the target
13226 program is available to install trampolines. Some Unix-type systems,
13227 such as @sc{gnu}/Linux, exclude low addresses from the program's
13228 address space; but for instance with the Linux kernel it is possible
13229 to let @value{GDBN} use this area by doing a @command{sysctl} command
13230 to set the @code{mmap_min_addr} kernel parameter, as in
13233 sudo sysctl -w vm.mmap_min_addr=32768
13237 which sets the low address to 32K, which leaves plenty of room for
13238 trampolines. The minimum address should be set to a page boundary.
13240 @item strace @var{location} [ if @var{cond} ]
13241 @cindex set static tracepoint
13242 @cindex static tracepoints, setting
13243 @cindex probe static tracepoint marker
13245 The @code{strace} command sets a static tracepoint. For targets that
13246 support it, setting a static tracepoint probes a static
13247 instrumentation point, or marker, found at @var{location}. It may not
13248 be possible to set a static tracepoint at the desired location, in
13249 which case the command will exit with an explanatory message.
13251 @value{GDBN} handles arguments to @code{strace} exactly as for
13252 @code{trace}, with the addition that the user can also specify
13253 @code{-m @var{marker}} as @var{location}. This probes the marker
13254 identified by the @var{marker} string identifier. This identifier
13255 depends on the static tracepoint backend library your program is
13256 using. You can find all the marker identifiers in the @samp{ID} field
13257 of the @code{info static-tracepoint-markers} command output.
13258 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13259 Markers}. For example, in the following small program using the UST
13265 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13270 the marker id is composed of joining the first two arguments to the
13271 @code{trace_mark} call with a slash, which translates to:
13274 (@value{GDBP}) info static-tracepoint-markers
13275 Cnt Enb ID Address What
13276 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13282 so you may probe the marker above with:
13285 (@value{GDBP}) strace -m ust/bar33
13288 Static tracepoints accept an extra collect action --- @code{collect
13289 $_sdata}. This collects arbitrary user data passed in the probe point
13290 call to the tracing library. In the UST example above, you'll see
13291 that the third argument to @code{trace_mark} is a printf-like format
13292 string. The user data is then the result of running that formating
13293 string against the following arguments. Note that @code{info
13294 static-tracepoint-markers} command output lists that format string in
13295 the @samp{Data:} field.
13297 You can inspect this data when analyzing the trace buffer, by printing
13298 the $_sdata variable like any other variable available to
13299 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13302 @cindex last tracepoint number
13303 @cindex recent tracepoint number
13304 @cindex tracepoint number
13305 The convenience variable @code{$tpnum} records the tracepoint number
13306 of the most recently set tracepoint.
13308 @kindex delete tracepoint
13309 @cindex tracepoint deletion
13310 @item delete tracepoint @r{[}@var{num}@r{]}
13311 Permanently delete one or more tracepoints. With no argument, the
13312 default is to delete all tracepoints. Note that the regular
13313 @code{delete} command can remove tracepoints also.
13318 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13320 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13324 You can abbreviate this command as @code{del tr}.
13327 @node Enable and Disable Tracepoints
13328 @subsection Enable and Disable Tracepoints
13330 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13333 @kindex disable tracepoint
13334 @item disable tracepoint @r{[}@var{num}@r{]}
13335 Disable tracepoint @var{num}, or all tracepoints if no argument
13336 @var{num} is given. A disabled tracepoint will have no effect during
13337 a trace experiment, but it is not forgotten. You can re-enable
13338 a disabled tracepoint using the @code{enable tracepoint} command.
13339 If the command is issued during a trace experiment and the debug target
13340 has support for disabling tracepoints during a trace experiment, then the
13341 change will be effective immediately. Otherwise, it will be applied to the
13342 next trace experiment.
13344 @kindex enable tracepoint
13345 @item enable tracepoint @r{[}@var{num}@r{]}
13346 Enable tracepoint @var{num}, or all tracepoints. If this command is
13347 issued during a trace experiment and the debug target supports enabling
13348 tracepoints during a trace experiment, then the enabled tracepoints will
13349 become effective immediately. Otherwise, they will become effective the
13350 next time a trace experiment is run.
13353 @node Tracepoint Passcounts
13354 @subsection Tracepoint Passcounts
13358 @cindex tracepoint pass count
13359 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13360 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13361 automatically stop a trace experiment. If a tracepoint's passcount is
13362 @var{n}, then the trace experiment will be automatically stopped on
13363 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13364 @var{num} is not specified, the @code{passcount} command sets the
13365 passcount of the most recently defined tracepoint. If no passcount is
13366 given, the trace experiment will run until stopped explicitly by the
13372 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13373 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13375 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13376 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13377 (@value{GDBP}) @b{trace foo}
13378 (@value{GDBP}) @b{pass 3}
13379 (@value{GDBP}) @b{trace bar}
13380 (@value{GDBP}) @b{pass 2}
13381 (@value{GDBP}) @b{trace baz}
13382 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13383 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13384 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13385 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13389 @node Tracepoint Conditions
13390 @subsection Tracepoint Conditions
13391 @cindex conditional tracepoints
13392 @cindex tracepoint conditions
13394 The simplest sort of tracepoint collects data every time your program
13395 reaches a specified place. You can also specify a @dfn{condition} for
13396 a tracepoint. A condition is just a Boolean expression in your
13397 programming language (@pxref{Expressions, ,Expressions}). A
13398 tracepoint with a condition evaluates the expression each time your
13399 program reaches it, and data collection happens only if the condition
13402 Tracepoint conditions can be specified when a tracepoint is set, by
13403 using @samp{if} in the arguments to the @code{trace} command.
13404 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13405 also be set or changed at any time with the @code{condition} command,
13406 just as with breakpoints.
13408 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13409 the conditional expression itself. Instead, @value{GDBN} encodes the
13410 expression into an agent expression (@pxref{Agent Expressions})
13411 suitable for execution on the target, independently of @value{GDBN}.
13412 Global variables become raw memory locations, locals become stack
13413 accesses, and so forth.
13415 For instance, suppose you have a function that is usually called
13416 frequently, but should not be called after an error has occurred. You
13417 could use the following tracepoint command to collect data about calls
13418 of that function that happen while the error code is propagating
13419 through the program; an unconditional tracepoint could end up
13420 collecting thousands of useless trace frames that you would have to
13424 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13427 @node Trace State Variables
13428 @subsection Trace State Variables
13429 @cindex trace state variables
13431 A @dfn{trace state variable} is a special type of variable that is
13432 created and managed by target-side code. The syntax is the same as
13433 that for GDB's convenience variables (a string prefixed with ``$''),
13434 but they are stored on the target. They must be created explicitly,
13435 using a @code{tvariable} command. They are always 64-bit signed
13438 Trace state variables are remembered by @value{GDBN}, and downloaded
13439 to the target along with tracepoint information when the trace
13440 experiment starts. There are no intrinsic limits on the number of
13441 trace state variables, beyond memory limitations of the target.
13443 @cindex convenience variables, and trace state variables
13444 Although trace state variables are managed by the target, you can use
13445 them in print commands and expressions as if they were convenience
13446 variables; @value{GDBN} will get the current value from the target
13447 while the trace experiment is running. Trace state variables share
13448 the same namespace as other ``$'' variables, which means that you
13449 cannot have trace state variables with names like @code{$23} or
13450 @code{$pc}, nor can you have a trace state variable and a convenience
13451 variable with the same name.
13455 @item tvariable $@var{name} [ = @var{expression} ]
13457 The @code{tvariable} command creates a new trace state variable named
13458 @code{$@var{name}}, and optionally gives it an initial value of
13459 @var{expression}. The @var{expression} is evaluated when this command is
13460 entered; the result will be converted to an integer if possible,
13461 otherwise @value{GDBN} will report an error. A subsequent
13462 @code{tvariable} command specifying the same name does not create a
13463 variable, but instead assigns the supplied initial value to the
13464 existing variable of that name, overwriting any previous initial
13465 value. The default initial value is 0.
13467 @item info tvariables
13468 @kindex info tvariables
13469 List all the trace state variables along with their initial values.
13470 Their current values may also be displayed, if the trace experiment is
13473 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13474 @kindex delete tvariable
13475 Delete the given trace state variables, or all of them if no arguments
13480 @node Tracepoint Actions
13481 @subsection Tracepoint Action Lists
13485 @cindex tracepoint actions
13486 @item actions @r{[}@var{num}@r{]}
13487 This command will prompt for a list of actions to be taken when the
13488 tracepoint is hit. If the tracepoint number @var{num} is not
13489 specified, this command sets the actions for the one that was most
13490 recently defined (so that you can define a tracepoint and then say
13491 @code{actions} without bothering about its number). You specify the
13492 actions themselves on the following lines, one action at a time, and
13493 terminate the actions list with a line containing just @code{end}. So
13494 far, the only defined actions are @code{collect}, @code{teval}, and
13495 @code{while-stepping}.
13497 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13498 Commands, ,Breakpoint Command Lists}), except that only the defined
13499 actions are allowed; any other @value{GDBN} command is rejected.
13501 @cindex remove actions from a tracepoint
13502 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13503 and follow it immediately with @samp{end}.
13506 (@value{GDBP}) @b{collect @var{data}} // collect some data
13508 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13510 (@value{GDBP}) @b{end} // signals the end of actions.
13513 In the following example, the action list begins with @code{collect}
13514 commands indicating the things to be collected when the tracepoint is
13515 hit. Then, in order to single-step and collect additional data
13516 following the tracepoint, a @code{while-stepping} command is used,
13517 followed by the list of things to be collected after each step in a
13518 sequence of single steps. The @code{while-stepping} command is
13519 terminated by its own separate @code{end} command. Lastly, the action
13520 list is terminated by an @code{end} command.
13523 (@value{GDBP}) @b{trace foo}
13524 (@value{GDBP}) @b{actions}
13525 Enter actions for tracepoint 1, one per line:
13528 > while-stepping 12
13529 > collect $pc, arr[i]
13534 @kindex collect @r{(tracepoints)}
13535 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13536 Collect values of the given expressions when the tracepoint is hit.
13537 This command accepts a comma-separated list of any valid expressions.
13538 In addition to global, static, or local variables, the following
13539 special arguments are supported:
13543 Collect all registers.
13546 Collect all function arguments.
13549 Collect all local variables.
13552 Collect the return address. This is helpful if you want to see more
13555 @emph{Note:} The return address location can not always be reliably
13556 determined up front, and the wrong address / registers may end up
13557 collected instead. On some architectures the reliability is higher
13558 for tracepoints at function entry, while on others it's the opposite.
13559 When this happens, backtracing will stop because the return address is
13560 found unavailable (unless another collect rule happened to match it).
13563 Collects the number of arguments from the static probe at which the
13564 tracepoint is located.
13565 @xref{Static Probe Points}.
13567 @item $_probe_arg@var{n}
13568 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13569 from the static probe at which the tracepoint is located.
13570 @xref{Static Probe Points}.
13573 @vindex $_sdata@r{, collect}
13574 Collect static tracepoint marker specific data. Only available for
13575 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13576 Lists}. On the UST static tracepoints library backend, an
13577 instrumentation point resembles a @code{printf} function call. The
13578 tracing library is able to collect user specified data formatted to a
13579 character string using the format provided by the programmer that
13580 instrumented the program. Other backends have similar mechanisms.
13581 Here's an example of a UST marker call:
13584 const char master_name[] = "$your_name";
13585 trace_mark(channel1, marker1, "hello %s", master_name)
13588 In this case, collecting @code{$_sdata} collects the string
13589 @samp{hello $yourname}. When analyzing the trace buffer, you can
13590 inspect @samp{$_sdata} like any other variable available to
13594 You can give several consecutive @code{collect} commands, each one
13595 with a single argument, or one @code{collect} command with several
13596 arguments separated by commas; the effect is the same.
13598 The optional @var{mods} changes the usual handling of the arguments.
13599 @code{s} requests that pointers to chars be handled as strings, in
13600 particular collecting the contents of the memory being pointed at, up
13601 to the first zero. The upper bound is by default the value of the
13602 @code{print elements} variable; if @code{s} is followed by a decimal
13603 number, that is the upper bound instead. So for instance
13604 @samp{collect/s25 mystr} collects as many as 25 characters at
13607 The command @code{info scope} (@pxref{Symbols, info scope}) is
13608 particularly useful for figuring out what data to collect.
13610 @kindex teval @r{(tracepoints)}
13611 @item teval @var{expr1}, @var{expr2}, @dots{}
13612 Evaluate the given expressions when the tracepoint is hit. This
13613 command accepts a comma-separated list of expressions. The results
13614 are discarded, so this is mainly useful for assigning values to trace
13615 state variables (@pxref{Trace State Variables}) without adding those
13616 values to the trace buffer, as would be the case if the @code{collect}
13619 @kindex while-stepping @r{(tracepoints)}
13620 @item while-stepping @var{n}
13621 Perform @var{n} single-step instruction traces after the tracepoint,
13622 collecting new data after each step. The @code{while-stepping}
13623 command is followed by the list of what to collect while stepping
13624 (followed by its own @code{end} command):
13627 > while-stepping 12
13628 > collect $regs, myglobal
13634 Note that @code{$pc} is not automatically collected by
13635 @code{while-stepping}; you need to explicitly collect that register if
13636 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13639 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13640 @kindex set default-collect
13641 @cindex default collection action
13642 This variable is a list of expressions to collect at each tracepoint
13643 hit. It is effectively an additional @code{collect} action prepended
13644 to every tracepoint action list. The expressions are parsed
13645 individually for each tracepoint, so for instance a variable named
13646 @code{xyz} may be interpreted as a global for one tracepoint, and a
13647 local for another, as appropriate to the tracepoint's location.
13649 @item show default-collect
13650 @kindex show default-collect
13651 Show the list of expressions that are collected by default at each
13656 @node Listing Tracepoints
13657 @subsection Listing Tracepoints
13660 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13661 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13662 @cindex information about tracepoints
13663 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13664 Display information about the tracepoint @var{num}. If you don't
13665 specify a tracepoint number, displays information about all the
13666 tracepoints defined so far. The format is similar to that used for
13667 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13668 command, simply restricting itself to tracepoints.
13670 A tracepoint's listing may include additional information specific to
13675 its passcount as given by the @code{passcount @var{n}} command
13678 the state about installed on target of each location
13682 (@value{GDBP}) @b{info trace}
13683 Num Type Disp Enb Address What
13684 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13686 collect globfoo, $regs
13691 2 tracepoint keep y <MULTIPLE>
13693 2.1 y 0x0804859c in func4 at change-loc.h:35
13694 installed on target
13695 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13696 installed on target
13697 2.3 y <PENDING> set_tracepoint
13698 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13699 not installed on target
13704 This command can be abbreviated @code{info tp}.
13707 @node Listing Static Tracepoint Markers
13708 @subsection Listing Static Tracepoint Markers
13711 @kindex info static-tracepoint-markers
13712 @cindex information about static tracepoint markers
13713 @item info static-tracepoint-markers
13714 Display information about all static tracepoint markers defined in the
13717 For each marker, the following columns are printed:
13721 An incrementing counter, output to help readability. This is not a
13724 The marker ID, as reported by the target.
13725 @item Enabled or Disabled
13726 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13727 that are not enabled.
13729 Where the marker is in your program, as a memory address.
13731 Where the marker is in the source for your program, as a file and line
13732 number. If the debug information included in the program does not
13733 allow @value{GDBN} to locate the source of the marker, this column
13734 will be left blank.
13738 In addition, the following information may be printed for each marker:
13742 User data passed to the tracing library by the marker call. In the
13743 UST backend, this is the format string passed as argument to the
13745 @item Static tracepoints probing the marker
13746 The list of static tracepoints attached to the marker.
13750 (@value{GDBP}) info static-tracepoint-markers
13751 Cnt ID Enb Address What
13752 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13753 Data: number1 %d number2 %d
13754 Probed by static tracepoints: #2
13755 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13761 @node Starting and Stopping Trace Experiments
13762 @subsection Starting and Stopping Trace Experiments
13765 @kindex tstart [ @var{notes} ]
13766 @cindex start a new trace experiment
13767 @cindex collected data discarded
13769 This command starts the trace experiment, and begins collecting data.
13770 It has the side effect of discarding all the data collected in the
13771 trace buffer during the previous trace experiment. If any arguments
13772 are supplied, they are taken as a note and stored with the trace
13773 experiment's state. The notes may be arbitrary text, and are
13774 especially useful with disconnected tracing in a multi-user context;
13775 the notes can explain what the trace is doing, supply user contact
13776 information, and so forth.
13778 @kindex tstop [ @var{notes} ]
13779 @cindex stop a running trace experiment
13781 This command stops the trace experiment. If any arguments are
13782 supplied, they are recorded with the experiment as a note. This is
13783 useful if you are stopping a trace started by someone else, for
13784 instance if the trace is interfering with the system's behavior and
13785 needs to be stopped quickly.
13787 @strong{Note}: a trace experiment and data collection may stop
13788 automatically if any tracepoint's passcount is reached
13789 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13792 @cindex status of trace data collection
13793 @cindex trace experiment, status of
13795 This command displays the status of the current trace data
13799 Here is an example of the commands we described so far:
13802 (@value{GDBP}) @b{trace gdb_c_test}
13803 (@value{GDBP}) @b{actions}
13804 Enter actions for tracepoint #1, one per line.
13805 > collect $regs,$locals,$args
13806 > while-stepping 11
13810 (@value{GDBP}) @b{tstart}
13811 [time passes @dots{}]
13812 (@value{GDBP}) @b{tstop}
13815 @anchor{disconnected tracing}
13816 @cindex disconnected tracing
13817 You can choose to continue running the trace experiment even if
13818 @value{GDBN} disconnects from the target, voluntarily or
13819 involuntarily. For commands such as @code{detach}, the debugger will
13820 ask what you want to do with the trace. But for unexpected
13821 terminations (@value{GDBN} crash, network outage), it would be
13822 unfortunate to lose hard-won trace data, so the variable
13823 @code{disconnected-tracing} lets you decide whether the trace should
13824 continue running without @value{GDBN}.
13827 @item set disconnected-tracing on
13828 @itemx set disconnected-tracing off
13829 @kindex set disconnected-tracing
13830 Choose whether a tracing run should continue to run if @value{GDBN}
13831 has disconnected from the target. Note that @code{detach} or
13832 @code{quit} will ask you directly what to do about a running trace no
13833 matter what this variable's setting, so the variable is mainly useful
13834 for handling unexpected situations, such as loss of the network.
13836 @item show disconnected-tracing
13837 @kindex show disconnected-tracing
13838 Show the current choice for disconnected tracing.
13842 When you reconnect to the target, the trace experiment may or may not
13843 still be running; it might have filled the trace buffer in the
13844 meantime, or stopped for one of the other reasons. If it is running,
13845 it will continue after reconnection.
13847 Upon reconnection, the target will upload information about the
13848 tracepoints in effect. @value{GDBN} will then compare that
13849 information to the set of tracepoints currently defined, and attempt
13850 to match them up, allowing for the possibility that the numbers may
13851 have changed due to creation and deletion in the meantime. If one of
13852 the target's tracepoints does not match any in @value{GDBN}, the
13853 debugger will create a new tracepoint, so that you have a number with
13854 which to specify that tracepoint. This matching-up process is
13855 necessarily heuristic, and it may result in useless tracepoints being
13856 created; you may simply delete them if they are of no use.
13858 @cindex circular trace buffer
13859 If your target agent supports a @dfn{circular trace buffer}, then you
13860 can run a trace experiment indefinitely without filling the trace
13861 buffer; when space runs out, the agent deletes already-collected trace
13862 frames, oldest first, until there is enough room to continue
13863 collecting. This is especially useful if your tracepoints are being
13864 hit too often, and your trace gets terminated prematurely because the
13865 buffer is full. To ask for a circular trace buffer, simply set
13866 @samp{circular-trace-buffer} to on. You can set this at any time,
13867 including during tracing; if the agent can do it, it will change
13868 buffer handling on the fly, otherwise it will not take effect until
13872 @item set circular-trace-buffer on
13873 @itemx set circular-trace-buffer off
13874 @kindex set circular-trace-buffer
13875 Choose whether a tracing run should use a linear or circular buffer
13876 for trace data. A linear buffer will not lose any trace data, but may
13877 fill up prematurely, while a circular buffer will discard old trace
13878 data, but it will have always room for the latest tracepoint hits.
13880 @item show circular-trace-buffer
13881 @kindex show circular-trace-buffer
13882 Show the current choice for the trace buffer. Note that this may not
13883 match the agent's current buffer handling, nor is it guaranteed to
13884 match the setting that might have been in effect during a past run,
13885 for instance if you are looking at frames from a trace file.
13890 @item set trace-buffer-size @var{n}
13891 @itemx set trace-buffer-size unlimited
13892 @kindex set trace-buffer-size
13893 Request that the target use a trace buffer of @var{n} bytes. Not all
13894 targets will honor the request; they may have a compiled-in size for
13895 the trace buffer, or some other limitation. Set to a value of
13896 @code{unlimited} or @code{-1} to let the target use whatever size it
13897 likes. This is also the default.
13899 @item show trace-buffer-size
13900 @kindex show trace-buffer-size
13901 Show the current requested size for the trace buffer. Note that this
13902 will only match the actual size if the target supports size-setting,
13903 and was able to handle the requested size. For instance, if the
13904 target can only change buffer size between runs, this variable will
13905 not reflect the change until the next run starts. Use @code{tstatus}
13906 to get a report of the actual buffer size.
13910 @item set trace-user @var{text}
13911 @kindex set trace-user
13913 @item show trace-user
13914 @kindex show trace-user
13916 @item set trace-notes @var{text}
13917 @kindex set trace-notes
13918 Set the trace run's notes.
13920 @item show trace-notes
13921 @kindex show trace-notes
13922 Show the trace run's notes.
13924 @item set trace-stop-notes @var{text}
13925 @kindex set trace-stop-notes
13926 Set the trace run's stop notes. The handling of the note is as for
13927 @code{tstop} arguments; the set command is convenient way to fix a
13928 stop note that is mistaken or incomplete.
13930 @item show trace-stop-notes
13931 @kindex show trace-stop-notes
13932 Show the trace run's stop notes.
13936 @node Tracepoint Restrictions
13937 @subsection Tracepoint Restrictions
13939 @cindex tracepoint restrictions
13940 There are a number of restrictions on the use of tracepoints. As
13941 described above, tracepoint data gathering occurs on the target
13942 without interaction from @value{GDBN}. Thus the full capabilities of
13943 the debugger are not available during data gathering, and then at data
13944 examination time, you will be limited by only having what was
13945 collected. The following items describe some common problems, but it
13946 is not exhaustive, and you may run into additional difficulties not
13952 Tracepoint expressions are intended to gather objects (lvalues). Thus
13953 the full flexibility of GDB's expression evaluator is not available.
13954 You cannot call functions, cast objects to aggregate types, access
13955 convenience variables or modify values (except by assignment to trace
13956 state variables). Some language features may implicitly call
13957 functions (for instance Objective-C fields with accessors), and therefore
13958 cannot be collected either.
13961 Collection of local variables, either individually or in bulk with
13962 @code{$locals} or @code{$args}, during @code{while-stepping} may
13963 behave erratically. The stepping action may enter a new scope (for
13964 instance by stepping into a function), or the location of the variable
13965 may change (for instance it is loaded into a register). The
13966 tracepoint data recorded uses the location information for the
13967 variables that is correct for the tracepoint location. When the
13968 tracepoint is created, it is not possible, in general, to determine
13969 where the steps of a @code{while-stepping} sequence will advance the
13970 program---particularly if a conditional branch is stepped.
13973 Collection of an incompletely-initialized or partially-destroyed object
13974 may result in something that @value{GDBN} cannot display, or displays
13975 in a misleading way.
13978 When @value{GDBN} displays a pointer to character it automatically
13979 dereferences the pointer to also display characters of the string
13980 being pointed to. However, collecting the pointer during tracing does
13981 not automatically collect the string. You need to explicitly
13982 dereference the pointer and provide size information if you want to
13983 collect not only the pointer, but the memory pointed to. For example,
13984 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13988 It is not possible to collect a complete stack backtrace at a
13989 tracepoint. Instead, you may collect the registers and a few hundred
13990 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13991 (adjust to use the name of the actual stack pointer register on your
13992 target architecture, and the amount of stack you wish to capture).
13993 Then the @code{backtrace} command will show a partial backtrace when
13994 using a trace frame. The number of stack frames that can be examined
13995 depends on the sizes of the frames in the collected stack. Note that
13996 if you ask for a block so large that it goes past the bottom of the
13997 stack, the target agent may report an error trying to read from an
14001 If you do not collect registers at a tracepoint, @value{GDBN} can
14002 infer that the value of @code{$pc} must be the same as the address of
14003 the tracepoint and use that when you are looking at a trace frame
14004 for that tracepoint. However, this cannot work if the tracepoint has
14005 multiple locations (for instance if it was set in a function that was
14006 inlined), or if it has a @code{while-stepping} loop. In those cases
14007 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14012 @node Analyze Collected Data
14013 @section Using the Collected Data
14015 After the tracepoint experiment ends, you use @value{GDBN} commands
14016 for examining the trace data. The basic idea is that each tracepoint
14017 collects a trace @dfn{snapshot} every time it is hit and another
14018 snapshot every time it single-steps. All these snapshots are
14019 consecutively numbered from zero and go into a buffer, and you can
14020 examine them later. The way you examine them is to @dfn{focus} on a
14021 specific trace snapshot. When the remote stub is focused on a trace
14022 snapshot, it will respond to all @value{GDBN} requests for memory and
14023 registers by reading from the buffer which belongs to that snapshot,
14024 rather than from @emph{real} memory or registers of the program being
14025 debugged. This means that @strong{all} @value{GDBN} commands
14026 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14027 behave as if we were currently debugging the program state as it was
14028 when the tracepoint occurred. Any requests for data that are not in
14029 the buffer will fail.
14032 * tfind:: How to select a trace snapshot
14033 * tdump:: How to display all data for a snapshot
14034 * save tracepoints:: How to save tracepoints for a future run
14038 @subsection @code{tfind @var{n}}
14041 @cindex select trace snapshot
14042 @cindex find trace snapshot
14043 The basic command for selecting a trace snapshot from the buffer is
14044 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14045 counting from zero. If no argument @var{n} is given, the next
14046 snapshot is selected.
14048 Here are the various forms of using the @code{tfind} command.
14052 Find the first snapshot in the buffer. This is a synonym for
14053 @code{tfind 0} (since 0 is the number of the first snapshot).
14056 Stop debugging trace snapshots, resume @emph{live} debugging.
14059 Same as @samp{tfind none}.
14062 No argument means find the next trace snapshot or find the first
14063 one if no trace snapshot is selected.
14066 Find the previous trace snapshot before the current one. This permits
14067 retracing earlier steps.
14069 @item tfind tracepoint @var{num}
14070 Find the next snapshot associated with tracepoint @var{num}. Search
14071 proceeds forward from the last examined trace snapshot. If no
14072 argument @var{num} is given, it means find the next snapshot collected
14073 for the same tracepoint as the current snapshot.
14075 @item tfind pc @var{addr}
14076 Find the next snapshot associated with the value @var{addr} of the
14077 program counter. Search proceeds forward from the last examined trace
14078 snapshot. If no argument @var{addr} is given, it means find the next
14079 snapshot with the same value of PC as the current snapshot.
14081 @item tfind outside @var{addr1}, @var{addr2}
14082 Find the next snapshot whose PC is outside the given range of
14083 addresses (exclusive).
14085 @item tfind range @var{addr1}, @var{addr2}
14086 Find the next snapshot whose PC is between @var{addr1} and
14087 @var{addr2} (inclusive).
14089 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14090 Find the next snapshot associated with the source line @var{n}. If
14091 the optional argument @var{file} is given, refer to line @var{n} in
14092 that source file. Search proceeds forward from the last examined
14093 trace snapshot. If no argument @var{n} is given, it means find the
14094 next line other than the one currently being examined; thus saying
14095 @code{tfind line} repeatedly can appear to have the same effect as
14096 stepping from line to line in a @emph{live} debugging session.
14099 The default arguments for the @code{tfind} commands are specifically
14100 designed to make it easy to scan through the trace buffer. For
14101 instance, @code{tfind} with no argument selects the next trace
14102 snapshot, and @code{tfind -} with no argument selects the previous
14103 trace snapshot. So, by giving one @code{tfind} command, and then
14104 simply hitting @key{RET} repeatedly you can examine all the trace
14105 snapshots in order. Or, by saying @code{tfind -} and then hitting
14106 @key{RET} repeatedly you can examine the snapshots in reverse order.
14107 The @code{tfind line} command with no argument selects the snapshot
14108 for the next source line executed. The @code{tfind pc} command with
14109 no argument selects the next snapshot with the same program counter
14110 (PC) as the current frame. The @code{tfind tracepoint} command with
14111 no argument selects the next trace snapshot collected by the same
14112 tracepoint as the current one.
14114 In addition to letting you scan through the trace buffer manually,
14115 these commands make it easy to construct @value{GDBN} scripts that
14116 scan through the trace buffer and print out whatever collected data
14117 you are interested in. Thus, if we want to examine the PC, FP, and SP
14118 registers from each trace frame in the buffer, we can say this:
14121 (@value{GDBP}) @b{tfind start}
14122 (@value{GDBP}) @b{while ($trace_frame != -1)}
14123 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14124 $trace_frame, $pc, $sp, $fp
14128 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14129 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14130 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14131 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14132 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14133 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14134 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14135 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14136 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14137 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14138 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14141 Or, if we want to examine the variable @code{X} at each source line in
14145 (@value{GDBP}) @b{tfind start}
14146 (@value{GDBP}) @b{while ($trace_frame != -1)}
14147 > printf "Frame %d, X == %d\n", $trace_frame, X
14157 @subsection @code{tdump}
14159 @cindex dump all data collected at tracepoint
14160 @cindex tracepoint data, display
14162 This command takes no arguments. It prints all the data collected at
14163 the current trace snapshot.
14166 (@value{GDBP}) @b{trace 444}
14167 (@value{GDBP}) @b{actions}
14168 Enter actions for tracepoint #2, one per line:
14169 > collect $regs, $locals, $args, gdb_long_test
14172 (@value{GDBP}) @b{tstart}
14174 (@value{GDBP}) @b{tfind line 444}
14175 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14177 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14179 (@value{GDBP}) @b{tdump}
14180 Data collected at tracepoint 2, trace frame 1:
14181 d0 0xc4aa0085 -995491707
14185 d4 0x71aea3d 119204413
14188 d7 0x380035 3670069
14189 a0 0x19e24a 1696330
14190 a1 0x3000668 50333288
14192 a3 0x322000 3284992
14193 a4 0x3000698 50333336
14194 a5 0x1ad3cc 1758156
14195 fp 0x30bf3c 0x30bf3c
14196 sp 0x30bf34 0x30bf34
14198 pc 0x20b2c8 0x20b2c8
14202 p = 0x20e5b4 "gdb-test"
14209 gdb_long_test = 17 '\021'
14214 @code{tdump} works by scanning the tracepoint's current collection
14215 actions and printing the value of each expression listed. So
14216 @code{tdump} can fail, if after a run, you change the tracepoint's
14217 actions to mention variables that were not collected during the run.
14219 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14220 uses the collected value of @code{$pc} to distinguish between trace
14221 frames that were collected at the tracepoint hit, and frames that were
14222 collected while stepping. This allows it to correctly choose whether
14223 to display the basic list of collections, or the collections from the
14224 body of the while-stepping loop. However, if @code{$pc} was not collected,
14225 then @code{tdump} will always attempt to dump using the basic collection
14226 list, and may fail if a while-stepping frame does not include all the
14227 same data that is collected at the tracepoint hit.
14228 @c This is getting pretty arcane, example would be good.
14230 @node save tracepoints
14231 @subsection @code{save tracepoints @var{filename}}
14232 @kindex save tracepoints
14233 @kindex save-tracepoints
14234 @cindex save tracepoints for future sessions
14236 This command saves all current tracepoint definitions together with
14237 their actions and passcounts, into a file @file{@var{filename}}
14238 suitable for use in a later debugging session. To read the saved
14239 tracepoint definitions, use the @code{source} command (@pxref{Command
14240 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14241 alias for @w{@code{save tracepoints}}
14243 @node Tracepoint Variables
14244 @section Convenience Variables for Tracepoints
14245 @cindex tracepoint variables
14246 @cindex convenience variables for tracepoints
14249 @vindex $trace_frame
14250 @item (int) $trace_frame
14251 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14252 snapshot is selected.
14254 @vindex $tracepoint
14255 @item (int) $tracepoint
14256 The tracepoint for the current trace snapshot.
14258 @vindex $trace_line
14259 @item (int) $trace_line
14260 The line number for the current trace snapshot.
14262 @vindex $trace_file
14263 @item (char []) $trace_file
14264 The source file for the current trace snapshot.
14266 @vindex $trace_func
14267 @item (char []) $trace_func
14268 The name of the function containing @code{$tracepoint}.
14271 Note: @code{$trace_file} is not suitable for use in @code{printf},
14272 use @code{output} instead.
14274 Here's a simple example of using these convenience variables for
14275 stepping through all the trace snapshots and printing some of their
14276 data. Note that these are not the same as trace state variables,
14277 which are managed by the target.
14280 (@value{GDBP}) @b{tfind start}
14282 (@value{GDBP}) @b{while $trace_frame != -1}
14283 > output $trace_file
14284 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14290 @section Using Trace Files
14291 @cindex trace files
14293 In some situations, the target running a trace experiment may no
14294 longer be available; perhaps it crashed, or the hardware was needed
14295 for a different activity. To handle these cases, you can arrange to
14296 dump the trace data into a file, and later use that file as a source
14297 of trace data, via the @code{target tfile} command.
14302 @item tsave [ -r ] @var{filename}
14303 @itemx tsave [-ctf] @var{dirname}
14304 Save the trace data to @var{filename}. By default, this command
14305 assumes that @var{filename} refers to the host filesystem, so if
14306 necessary @value{GDBN} will copy raw trace data up from the target and
14307 then save it. If the target supports it, you can also supply the
14308 optional argument @code{-r} (``remote'') to direct the target to save
14309 the data directly into @var{filename} in its own filesystem, which may be
14310 more efficient if the trace buffer is very large. (Note, however, that
14311 @code{target tfile} can only read from files accessible to the host.)
14312 By default, this command will save trace frame in tfile format.
14313 You can supply the optional argument @code{-ctf} to save data in CTF
14314 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14315 that can be shared by multiple debugging and tracing tools. Please go to
14316 @indicateurl{http://www.efficios.com/ctf} to get more information.
14318 @kindex target tfile
14322 @item target tfile @var{filename}
14323 @itemx target ctf @var{dirname}
14324 Use the file named @var{filename} or directory named @var{dirname} as
14325 a source of trace data. Commands that examine data work as they do with
14326 a live target, but it is not possible to run any new trace experiments.
14327 @code{tstatus} will report the state of the trace run at the moment
14328 the data was saved, as well as the current trace frame you are examining.
14329 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14333 (@value{GDBP}) target ctf ctf.ctf
14334 (@value{GDBP}) tfind
14335 Found trace frame 0, tracepoint 2
14336 39 ++a; /* set tracepoint 1 here */
14337 (@value{GDBP}) tdump
14338 Data collected at tracepoint 2, trace frame 0:
14342 c = @{"123", "456", "789", "123", "456", "789"@}
14343 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14351 @chapter Debugging Programs That Use Overlays
14354 If your program is too large to fit completely in your target system's
14355 memory, you can sometimes use @dfn{overlays} to work around this
14356 problem. @value{GDBN} provides some support for debugging programs that
14360 * How Overlays Work:: A general explanation of overlays.
14361 * Overlay Commands:: Managing overlays in @value{GDBN}.
14362 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14363 mapped by asking the inferior.
14364 * Overlay Sample Program:: A sample program using overlays.
14367 @node How Overlays Work
14368 @section How Overlays Work
14369 @cindex mapped overlays
14370 @cindex unmapped overlays
14371 @cindex load address, overlay's
14372 @cindex mapped address
14373 @cindex overlay area
14375 Suppose you have a computer whose instruction address space is only 64
14376 kilobytes long, but which has much more memory which can be accessed by
14377 other means: special instructions, segment registers, or memory
14378 management hardware, for example. Suppose further that you want to
14379 adapt a program which is larger than 64 kilobytes to run on this system.
14381 One solution is to identify modules of your program which are relatively
14382 independent, and need not call each other directly; call these modules
14383 @dfn{overlays}. Separate the overlays from the main program, and place
14384 their machine code in the larger memory. Place your main program in
14385 instruction memory, but leave at least enough space there to hold the
14386 largest overlay as well.
14388 Now, to call a function located in an overlay, you must first copy that
14389 overlay's machine code from the large memory into the space set aside
14390 for it in the instruction memory, and then jump to its entry point
14393 @c NB: In the below the mapped area's size is greater or equal to the
14394 @c size of all overlays. This is intentional to remind the developer
14395 @c that overlays don't necessarily need to be the same size.
14399 Data Instruction Larger
14400 Address Space Address Space Address Space
14401 +-----------+ +-----------+ +-----------+
14403 +-----------+ +-----------+ +-----------+<-- overlay 1
14404 | program | | main | .----| overlay 1 | load address
14405 | variables | | program | | +-----------+
14406 | and heap | | | | | |
14407 +-----------+ | | | +-----------+<-- overlay 2
14408 | | +-----------+ | | | load address
14409 +-----------+ | | | .-| overlay 2 |
14411 mapped --->+-----------+ | | +-----------+
14412 address | | | | | |
14413 | overlay | <-' | | |
14414 | area | <---' +-----------+<-- overlay 3
14415 | | <---. | | load address
14416 +-----------+ `--| overlay 3 |
14423 @anchor{A code overlay}A code overlay
14427 The diagram (@pxref{A code overlay}) shows a system with separate data
14428 and instruction address spaces. To map an overlay, the program copies
14429 its code from the larger address space to the instruction address space.
14430 Since the overlays shown here all use the same mapped address, only one
14431 may be mapped at a time. For a system with a single address space for
14432 data and instructions, the diagram would be similar, except that the
14433 program variables and heap would share an address space with the main
14434 program and the overlay area.
14436 An overlay loaded into instruction memory and ready for use is called a
14437 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14438 instruction memory. An overlay not present (or only partially present)
14439 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14440 is its address in the larger memory. The mapped address is also called
14441 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14442 called the @dfn{load memory address}, or @dfn{LMA}.
14444 Unfortunately, overlays are not a completely transparent way to adapt a
14445 program to limited instruction memory. They introduce a new set of
14446 global constraints you must keep in mind as you design your program:
14451 Before calling or returning to a function in an overlay, your program
14452 must make sure that overlay is actually mapped. Otherwise, the call or
14453 return will transfer control to the right address, but in the wrong
14454 overlay, and your program will probably crash.
14457 If the process of mapping an overlay is expensive on your system, you
14458 will need to choose your overlays carefully to minimize their effect on
14459 your program's performance.
14462 The executable file you load onto your system must contain each
14463 overlay's instructions, appearing at the overlay's load address, not its
14464 mapped address. However, each overlay's instructions must be relocated
14465 and its symbols defined as if the overlay were at its mapped address.
14466 You can use GNU linker scripts to specify different load and relocation
14467 addresses for pieces of your program; see @ref{Overlay Description,,,
14468 ld.info, Using ld: the GNU linker}.
14471 The procedure for loading executable files onto your system must be able
14472 to load their contents into the larger address space as well as the
14473 instruction and data spaces.
14477 The overlay system described above is rather simple, and could be
14478 improved in many ways:
14483 If your system has suitable bank switch registers or memory management
14484 hardware, you could use those facilities to make an overlay's load area
14485 contents simply appear at their mapped address in instruction space.
14486 This would probably be faster than copying the overlay to its mapped
14487 area in the usual way.
14490 If your overlays are small enough, you could set aside more than one
14491 overlay area, and have more than one overlay mapped at a time.
14494 You can use overlays to manage data, as well as instructions. In
14495 general, data overlays are even less transparent to your design than
14496 code overlays: whereas code overlays only require care when you call or
14497 return to functions, data overlays require care every time you access
14498 the data. Also, if you change the contents of a data overlay, you
14499 must copy its contents back out to its load address before you can copy a
14500 different data overlay into the same mapped area.
14505 @node Overlay Commands
14506 @section Overlay Commands
14508 To use @value{GDBN}'s overlay support, each overlay in your program must
14509 correspond to a separate section of the executable file. The section's
14510 virtual memory address and load memory address must be the overlay's
14511 mapped and load addresses. Identifying overlays with sections allows
14512 @value{GDBN} to determine the appropriate address of a function or
14513 variable, depending on whether the overlay is mapped or not.
14515 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14516 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14521 Disable @value{GDBN}'s overlay support. When overlay support is
14522 disabled, @value{GDBN} assumes that all functions and variables are
14523 always present at their mapped addresses. By default, @value{GDBN}'s
14524 overlay support is disabled.
14526 @item overlay manual
14527 @cindex manual overlay debugging
14528 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14529 relies on you to tell it which overlays are mapped, and which are not,
14530 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14531 commands described below.
14533 @item overlay map-overlay @var{overlay}
14534 @itemx overlay map @var{overlay}
14535 @cindex map an overlay
14536 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14537 be the name of the object file section containing the overlay. When an
14538 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14539 functions and variables at their mapped addresses. @value{GDBN} assumes
14540 that any other overlays whose mapped ranges overlap that of
14541 @var{overlay} are now unmapped.
14543 @item overlay unmap-overlay @var{overlay}
14544 @itemx overlay unmap @var{overlay}
14545 @cindex unmap an overlay
14546 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14547 must be the name of the object file section containing the overlay.
14548 When an overlay is unmapped, @value{GDBN} assumes it can find the
14549 overlay's functions and variables at their load addresses.
14552 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14553 consults a data structure the overlay manager maintains in the inferior
14554 to see which overlays are mapped. For details, see @ref{Automatic
14555 Overlay Debugging}.
14557 @item overlay load-target
14558 @itemx overlay load
14559 @cindex reloading the overlay table
14560 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14561 re-reads the table @value{GDBN} automatically each time the inferior
14562 stops, so this command should only be necessary if you have changed the
14563 overlay mapping yourself using @value{GDBN}. This command is only
14564 useful when using automatic overlay debugging.
14566 @item overlay list-overlays
14567 @itemx overlay list
14568 @cindex listing mapped overlays
14569 Display a list of the overlays currently mapped, along with their mapped
14570 addresses, load addresses, and sizes.
14574 Normally, when @value{GDBN} prints a code address, it includes the name
14575 of the function the address falls in:
14578 (@value{GDBP}) print main
14579 $3 = @{int ()@} 0x11a0 <main>
14582 When overlay debugging is enabled, @value{GDBN} recognizes code in
14583 unmapped overlays, and prints the names of unmapped functions with
14584 asterisks around them. For example, if @code{foo} is a function in an
14585 unmapped overlay, @value{GDBN} prints it this way:
14588 (@value{GDBP}) overlay list
14589 No sections are mapped.
14590 (@value{GDBP}) print foo
14591 $5 = @{int (int)@} 0x100000 <*foo*>
14594 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14598 (@value{GDBP}) overlay list
14599 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14600 mapped at 0x1016 - 0x104a
14601 (@value{GDBP}) print foo
14602 $6 = @{int (int)@} 0x1016 <foo>
14605 When overlay debugging is enabled, @value{GDBN} can find the correct
14606 address for functions and variables in an overlay, whether or not the
14607 overlay is mapped. This allows most @value{GDBN} commands, like
14608 @code{break} and @code{disassemble}, to work normally, even on unmapped
14609 code. However, @value{GDBN}'s breakpoint support has some limitations:
14613 @cindex breakpoints in overlays
14614 @cindex overlays, setting breakpoints in
14615 You can set breakpoints in functions in unmapped overlays, as long as
14616 @value{GDBN} can write to the overlay at its load address.
14618 @value{GDBN} can not set hardware or simulator-based breakpoints in
14619 unmapped overlays. However, if you set a breakpoint at the end of your
14620 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14621 you are using manual overlay management), @value{GDBN} will re-set its
14622 breakpoints properly.
14626 @node Automatic Overlay Debugging
14627 @section Automatic Overlay Debugging
14628 @cindex automatic overlay debugging
14630 @value{GDBN} can automatically track which overlays are mapped and which
14631 are not, given some simple co-operation from the overlay manager in the
14632 inferior. If you enable automatic overlay debugging with the
14633 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14634 looks in the inferior's memory for certain variables describing the
14635 current state of the overlays.
14637 Here are the variables your overlay manager must define to support
14638 @value{GDBN}'s automatic overlay debugging:
14642 @item @code{_ovly_table}:
14643 This variable must be an array of the following structures:
14648 /* The overlay's mapped address. */
14651 /* The size of the overlay, in bytes. */
14652 unsigned long size;
14654 /* The overlay's load address. */
14657 /* Non-zero if the overlay is currently mapped;
14659 unsigned long mapped;
14663 @item @code{_novlys}:
14664 This variable must be a four-byte signed integer, holding the total
14665 number of elements in @code{_ovly_table}.
14669 To decide whether a particular overlay is mapped or not, @value{GDBN}
14670 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14671 @code{lma} members equal the VMA and LMA of the overlay's section in the
14672 executable file. When @value{GDBN} finds a matching entry, it consults
14673 the entry's @code{mapped} member to determine whether the overlay is
14676 In addition, your overlay manager may define a function called
14677 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14678 will silently set a breakpoint there. If the overlay manager then
14679 calls this function whenever it has changed the overlay table, this
14680 will enable @value{GDBN} to accurately keep track of which overlays
14681 are in program memory, and update any breakpoints that may be set
14682 in overlays. This will allow breakpoints to work even if the
14683 overlays are kept in ROM or other non-writable memory while they
14684 are not being executed.
14686 @node Overlay Sample Program
14687 @section Overlay Sample Program
14688 @cindex overlay example program
14690 When linking a program which uses overlays, you must place the overlays
14691 at their load addresses, while relocating them to run at their mapped
14692 addresses. To do this, you must write a linker script (@pxref{Overlay
14693 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14694 since linker scripts are specific to a particular host system, target
14695 architecture, and target memory layout, this manual cannot provide
14696 portable sample code demonstrating @value{GDBN}'s overlay support.
14698 However, the @value{GDBN} source distribution does contain an overlaid
14699 program, with linker scripts for a few systems, as part of its test
14700 suite. The program consists of the following files from
14701 @file{gdb/testsuite/gdb.base}:
14705 The main program file.
14707 A simple overlay manager, used by @file{overlays.c}.
14712 Overlay modules, loaded and used by @file{overlays.c}.
14715 Linker scripts for linking the test program on the @code{d10v-elf}
14716 and @code{m32r-elf} targets.
14719 You can build the test program using the @code{d10v-elf} GCC
14720 cross-compiler like this:
14723 $ d10v-elf-gcc -g -c overlays.c
14724 $ d10v-elf-gcc -g -c ovlymgr.c
14725 $ d10v-elf-gcc -g -c foo.c
14726 $ d10v-elf-gcc -g -c bar.c
14727 $ d10v-elf-gcc -g -c baz.c
14728 $ d10v-elf-gcc -g -c grbx.c
14729 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14730 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14733 The build process is identical for any other architecture, except that
14734 you must substitute the appropriate compiler and linker script for the
14735 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14739 @chapter Using @value{GDBN} with Different Languages
14742 Although programming languages generally have common aspects, they are
14743 rarely expressed in the same manner. For instance, in ANSI C,
14744 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14745 Modula-2, it is accomplished by @code{p^}. Values can also be
14746 represented (and displayed) differently. Hex numbers in C appear as
14747 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14749 @cindex working language
14750 Language-specific information is built into @value{GDBN} for some languages,
14751 allowing you to express operations like the above in your program's
14752 native language, and allowing @value{GDBN} to output values in a manner
14753 consistent with the syntax of your program's native language. The
14754 language you use to build expressions is called the @dfn{working
14758 * Setting:: Switching between source languages
14759 * Show:: Displaying the language
14760 * Checks:: Type and range checks
14761 * Supported Languages:: Supported languages
14762 * Unsupported Languages:: Unsupported languages
14766 @section Switching Between Source Languages
14768 There are two ways to control the working language---either have @value{GDBN}
14769 set it automatically, or select it manually yourself. You can use the
14770 @code{set language} command for either purpose. On startup, @value{GDBN}
14771 defaults to setting the language automatically. The working language is
14772 used to determine how expressions you type are interpreted, how values
14775 In addition to the working language, every source file that
14776 @value{GDBN} knows about has its own working language. For some object
14777 file formats, the compiler might indicate which language a particular
14778 source file is in. However, most of the time @value{GDBN} infers the
14779 language from the name of the file. The language of a source file
14780 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14781 show each frame appropriately for its own language. There is no way to
14782 set the language of a source file from within @value{GDBN}, but you can
14783 set the language associated with a filename extension. @xref{Show, ,
14784 Displaying the Language}.
14786 This is most commonly a problem when you use a program, such
14787 as @code{cfront} or @code{f2c}, that generates C but is written in
14788 another language. In that case, make the
14789 program use @code{#line} directives in its C output; that way
14790 @value{GDBN} will know the correct language of the source code of the original
14791 program, and will display that source code, not the generated C code.
14794 * Filenames:: Filename extensions and languages.
14795 * Manually:: Setting the working language manually
14796 * Automatically:: Having @value{GDBN} infer the source language
14800 @subsection List of Filename Extensions and Languages
14802 If a source file name ends in one of the following extensions, then
14803 @value{GDBN} infers that its language is the one indicated.
14821 C@t{++} source file
14827 Objective-C source file
14831 Fortran source file
14834 Modula-2 source file
14838 Assembler source file. This actually behaves almost like C, but
14839 @value{GDBN} does not skip over function prologues when stepping.
14842 In addition, you may set the language associated with a filename
14843 extension. @xref{Show, , Displaying the Language}.
14846 @subsection Setting the Working Language
14848 If you allow @value{GDBN} to set the language automatically,
14849 expressions are interpreted the same way in your debugging session and
14852 @kindex set language
14853 If you wish, you may set the language manually. To do this, issue the
14854 command @samp{set language @var{lang}}, where @var{lang} is the name of
14855 a language, such as
14856 @code{c} or @code{modula-2}.
14857 For a list of the supported languages, type @samp{set language}.
14859 Setting the language manually prevents @value{GDBN} from updating the working
14860 language automatically. This can lead to confusion if you try
14861 to debug a program when the working language is not the same as the
14862 source language, when an expression is acceptable to both
14863 languages---but means different things. For instance, if the current
14864 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14872 might not have the effect you intended. In C, this means to add
14873 @code{b} and @code{c} and place the result in @code{a}. The result
14874 printed would be the value of @code{a}. In Modula-2, this means to compare
14875 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14877 @node Automatically
14878 @subsection Having @value{GDBN} Infer the Source Language
14880 To have @value{GDBN} set the working language automatically, use
14881 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14882 then infers the working language. That is, when your program stops in a
14883 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14884 working language to the language recorded for the function in that
14885 frame. If the language for a frame is unknown (that is, if the function
14886 or block corresponding to the frame was defined in a source file that
14887 does not have a recognized extension), the current working language is
14888 not changed, and @value{GDBN} issues a warning.
14890 This may not seem necessary for most programs, which are written
14891 entirely in one source language. However, program modules and libraries
14892 written in one source language can be used by a main program written in
14893 a different source language. Using @samp{set language auto} in this
14894 case frees you from having to set the working language manually.
14897 @section Displaying the Language
14899 The following commands help you find out which language is the
14900 working language, and also what language source files were written in.
14903 @item show language
14904 @anchor{show language}
14905 @kindex show language
14906 Display the current working language. This is the
14907 language you can use with commands such as @code{print} to
14908 build and compute expressions that may involve variables in your program.
14911 @kindex info frame@r{, show the source language}
14912 Display the source language for this frame. This language becomes the
14913 working language if you use an identifier from this frame.
14914 @xref{Frame Info, ,Information about a Frame}, to identify the other
14915 information listed here.
14918 @kindex info source@r{, show the source language}
14919 Display the source language of this source file.
14920 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14921 information listed here.
14924 In unusual circumstances, you may have source files with extensions
14925 not in the standard list. You can then set the extension associated
14926 with a language explicitly:
14929 @item set extension-language @var{ext} @var{language}
14930 @kindex set extension-language
14931 Tell @value{GDBN} that source files with extension @var{ext} are to be
14932 assumed as written in the source language @var{language}.
14934 @item info extensions
14935 @kindex info extensions
14936 List all the filename extensions and the associated languages.
14940 @section Type and Range Checking
14942 Some languages are designed to guard you against making seemingly common
14943 errors through a series of compile- and run-time checks. These include
14944 checking the type of arguments to functions and operators and making
14945 sure mathematical overflows are caught at run time. Checks such as
14946 these help to ensure a program's correctness once it has been compiled
14947 by eliminating type mismatches and providing active checks for range
14948 errors when your program is running.
14950 By default @value{GDBN} checks for these errors according to the
14951 rules of the current source language. Although @value{GDBN} does not check
14952 the statements in your program, it can check expressions entered directly
14953 into @value{GDBN} for evaluation via the @code{print} command, for example.
14956 * Type Checking:: An overview of type checking
14957 * Range Checking:: An overview of range checking
14960 @cindex type checking
14961 @cindex checks, type
14962 @node Type Checking
14963 @subsection An Overview of Type Checking
14965 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14966 arguments to operators and functions have to be of the correct type,
14967 otherwise an error occurs. These checks prevent type mismatch
14968 errors from ever causing any run-time problems. For example,
14971 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14973 (@value{GDBP}) print obj.my_method (0)
14976 (@value{GDBP}) print obj.my_method (0x1234)
14977 Cannot resolve method klass::my_method to any overloaded instance
14980 The second example fails because in C@t{++} the integer constant
14981 @samp{0x1234} is not type-compatible with the pointer parameter type.
14983 For the expressions you use in @value{GDBN} commands, you can tell
14984 @value{GDBN} to not enforce strict type checking or
14985 to treat any mismatches as errors and abandon the expression;
14986 When type checking is disabled, @value{GDBN} successfully evaluates
14987 expressions like the second example above.
14989 Even if type checking is off, there may be other reasons
14990 related to type that prevent @value{GDBN} from evaluating an expression.
14991 For instance, @value{GDBN} does not know how to add an @code{int} and
14992 a @code{struct foo}. These particular type errors have nothing to do
14993 with the language in use and usually arise from expressions which make
14994 little sense to evaluate anyway.
14996 @value{GDBN} provides some additional commands for controlling type checking:
14998 @kindex set check type
14999 @kindex show check type
15001 @item set check type on
15002 @itemx set check type off
15003 Set strict type checking on or off. If any type mismatches occur in
15004 evaluating an expression while type checking is on, @value{GDBN} prints a
15005 message and aborts evaluation of the expression.
15007 @item show check type
15008 Show the current setting of type checking and whether @value{GDBN}
15009 is enforcing strict type checking rules.
15012 @cindex range checking
15013 @cindex checks, range
15014 @node Range Checking
15015 @subsection An Overview of Range Checking
15017 In some languages (such as Modula-2), it is an error to exceed the
15018 bounds of a type; this is enforced with run-time checks. Such range
15019 checking is meant to ensure program correctness by making sure
15020 computations do not overflow, or indices on an array element access do
15021 not exceed the bounds of the array.
15023 For expressions you use in @value{GDBN} commands, you can tell
15024 @value{GDBN} to treat range errors in one of three ways: ignore them,
15025 always treat them as errors and abandon the expression, or issue
15026 warnings but evaluate the expression anyway.
15028 A range error can result from numerical overflow, from exceeding an
15029 array index bound, or when you type a constant that is not a member
15030 of any type. Some languages, however, do not treat overflows as an
15031 error. In many implementations of C, mathematical overflow causes the
15032 result to ``wrap around'' to lower values---for example, if @var{m} is
15033 the largest integer value, and @var{s} is the smallest, then
15036 @var{m} + 1 @result{} @var{s}
15039 This, too, is specific to individual languages, and in some cases
15040 specific to individual compilers or machines. @xref{Supported Languages, ,
15041 Supported Languages}, for further details on specific languages.
15043 @value{GDBN} provides some additional commands for controlling the range checker:
15045 @kindex set check range
15046 @kindex show check range
15048 @item set check range auto
15049 Set range checking on or off based on the current working language.
15050 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15053 @item set check range on
15054 @itemx set check range off
15055 Set range checking on or off, overriding the default setting for the
15056 current working language. A warning is issued if the setting does not
15057 match the language default. If a range error occurs and range checking is on,
15058 then a message is printed and evaluation of the expression is aborted.
15060 @item set check range warn
15061 Output messages when the @value{GDBN} range checker detects a range error,
15062 but attempt to evaluate the expression anyway. Evaluating the
15063 expression may still be impossible for other reasons, such as accessing
15064 memory that the process does not own (a typical example from many Unix
15068 Show the current setting of the range checker, and whether or not it is
15069 being set automatically by @value{GDBN}.
15072 @node Supported Languages
15073 @section Supported Languages
15075 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15076 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15077 @c This is false ...
15078 Some @value{GDBN} features may be used in expressions regardless of the
15079 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15080 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15081 ,Expressions}) can be used with the constructs of any supported
15084 The following sections detail to what degree each source language is
15085 supported by @value{GDBN}. These sections are not meant to be language
15086 tutorials or references, but serve only as a reference guide to what the
15087 @value{GDBN} expression parser accepts, and what input and output
15088 formats should look like for different languages. There are many good
15089 books written on each of these languages; please look to these for a
15090 language reference or tutorial.
15093 * C:: C and C@t{++}
15096 * Objective-C:: Objective-C
15097 * OpenCL C:: OpenCL C
15098 * Fortran:: Fortran
15101 * Modula-2:: Modula-2
15106 @subsection C and C@t{++}
15108 @cindex C and C@t{++}
15109 @cindex expressions in C or C@t{++}
15111 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15112 to both languages. Whenever this is the case, we discuss those languages
15116 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15117 @cindex @sc{gnu} C@t{++}
15118 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15119 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15120 effectively, you must compile your C@t{++} programs with a supported
15121 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15122 compiler (@code{aCC}).
15125 * C Operators:: C and C@t{++} operators
15126 * C Constants:: C and C@t{++} constants
15127 * C Plus Plus Expressions:: C@t{++} expressions
15128 * C Defaults:: Default settings for C and C@t{++}
15129 * C Checks:: C and C@t{++} type and range checks
15130 * Debugging C:: @value{GDBN} and C
15131 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15132 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15136 @subsubsection C and C@t{++} Operators
15138 @cindex C and C@t{++} operators
15140 Operators must be defined on values of specific types. For instance,
15141 @code{+} is defined on numbers, but not on structures. Operators are
15142 often defined on groups of types.
15144 For the purposes of C and C@t{++}, the following definitions hold:
15149 @emph{Integral types} include @code{int} with any of its storage-class
15150 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15153 @emph{Floating-point types} include @code{float}, @code{double}, and
15154 @code{long double} (if supported by the target platform).
15157 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15160 @emph{Scalar types} include all of the above.
15165 The following operators are supported. They are listed here
15166 in order of increasing precedence:
15170 The comma or sequencing operator. Expressions in a comma-separated list
15171 are evaluated from left to right, with the result of the entire
15172 expression being the last expression evaluated.
15175 Assignment. The value of an assignment expression is the value
15176 assigned. Defined on scalar types.
15179 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15180 and translated to @w{@code{@var{a} = @var{a op b}}}.
15181 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15182 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15183 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15186 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15187 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15188 should be of an integral type.
15191 Logical @sc{or}. Defined on integral types.
15194 Logical @sc{and}. Defined on integral types.
15197 Bitwise @sc{or}. Defined on integral types.
15200 Bitwise exclusive-@sc{or}. Defined on integral types.
15203 Bitwise @sc{and}. Defined on integral types.
15206 Equality and inequality. Defined on scalar types. The value of these
15207 expressions is 0 for false and non-zero for true.
15209 @item <@r{, }>@r{, }<=@r{, }>=
15210 Less than, greater than, less than or equal, greater than or equal.
15211 Defined on scalar types. The value of these expressions is 0 for false
15212 and non-zero for true.
15215 left shift, and right shift. Defined on integral types.
15218 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15221 Addition and subtraction. Defined on integral types, floating-point types and
15224 @item *@r{, }/@r{, }%
15225 Multiplication, division, and modulus. Multiplication and division are
15226 defined on integral and floating-point types. Modulus is defined on
15230 Increment and decrement. When appearing before a variable, the
15231 operation is performed before the variable is used in an expression;
15232 when appearing after it, the variable's value is used before the
15233 operation takes place.
15236 Pointer dereferencing. Defined on pointer types. Same precedence as
15240 Address operator. Defined on variables. Same precedence as @code{++}.
15242 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15243 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15244 to examine the address
15245 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15249 Negative. Defined on integral and floating-point types. Same
15250 precedence as @code{++}.
15253 Logical negation. Defined on integral types. Same precedence as
15257 Bitwise complement operator. Defined on integral types. Same precedence as
15262 Structure member, and pointer-to-structure member. For convenience,
15263 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15264 pointer based on the stored type information.
15265 Defined on @code{struct} and @code{union} data.
15268 Dereferences of pointers to members.
15271 Array indexing. @code{@var{a}[@var{i}]} is defined as
15272 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15275 Function parameter list. Same precedence as @code{->}.
15278 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15279 and @code{class} types.
15282 Doubled colons also represent the @value{GDBN} scope operator
15283 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15287 If an operator is redefined in the user code, @value{GDBN} usually
15288 attempts to invoke the redefined version instead of using the operator's
15289 predefined meaning.
15292 @subsubsection C and C@t{++} Constants
15294 @cindex C and C@t{++} constants
15296 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15301 Integer constants are a sequence of digits. Octal constants are
15302 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15303 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15304 @samp{l}, specifying that the constant should be treated as a
15308 Floating point constants are a sequence of digits, followed by a decimal
15309 point, followed by a sequence of digits, and optionally followed by an
15310 exponent. An exponent is of the form:
15311 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15312 sequence of digits. The @samp{+} is optional for positive exponents.
15313 A floating-point constant may also end with a letter @samp{f} or
15314 @samp{F}, specifying that the constant should be treated as being of
15315 the @code{float} (as opposed to the default @code{double}) type; or with
15316 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15320 Enumerated constants consist of enumerated identifiers, or their
15321 integral equivalents.
15324 Character constants are a single character surrounded by single quotes
15325 (@code{'}), or a number---the ordinal value of the corresponding character
15326 (usually its @sc{ascii} value). Within quotes, the single character may
15327 be represented by a letter or by @dfn{escape sequences}, which are of
15328 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15329 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15330 @samp{@var{x}} is a predefined special character---for example,
15331 @samp{\n} for newline.
15333 Wide character constants can be written by prefixing a character
15334 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15335 form of @samp{x}. The target wide character set is used when
15336 computing the value of this constant (@pxref{Character Sets}).
15339 String constants are a sequence of character constants surrounded by
15340 double quotes (@code{"}). Any valid character constant (as described
15341 above) may appear. Double quotes within the string must be preceded by
15342 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15345 Wide string constants can be written by prefixing a string constant
15346 with @samp{L}, as in C. The target wide character set is used when
15347 computing the value of this constant (@pxref{Character Sets}).
15350 Pointer constants are an integral value. You can also write pointers
15351 to constants using the C operator @samp{&}.
15354 Array constants are comma-separated lists surrounded by braces @samp{@{}
15355 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15356 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15357 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15360 @node C Plus Plus Expressions
15361 @subsubsection C@t{++} Expressions
15363 @cindex expressions in C@t{++}
15364 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15366 @cindex debugging C@t{++} programs
15367 @cindex C@t{++} compilers
15368 @cindex debug formats and C@t{++}
15369 @cindex @value{NGCC} and C@t{++}
15371 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15372 the proper compiler and the proper debug format. Currently,
15373 @value{GDBN} works best when debugging C@t{++} code that is compiled
15374 with the most recent version of @value{NGCC} possible. The DWARF
15375 debugging format is preferred; @value{NGCC} defaults to this on most
15376 popular platforms. Other compilers and/or debug formats are likely to
15377 work badly or not at all when using @value{GDBN} to debug C@t{++}
15378 code. @xref{Compilation}.
15383 @cindex member functions
15385 Member function calls are allowed; you can use expressions like
15388 count = aml->GetOriginal(x, y)
15391 @vindex this@r{, inside C@t{++} member functions}
15392 @cindex namespace in C@t{++}
15394 While a member function is active (in the selected stack frame), your
15395 expressions have the same namespace available as the member function;
15396 that is, @value{GDBN} allows implicit references to the class instance
15397 pointer @code{this} following the same rules as C@t{++}. @code{using}
15398 declarations in the current scope are also respected by @value{GDBN}.
15400 @cindex call overloaded functions
15401 @cindex overloaded functions, calling
15402 @cindex type conversions in C@t{++}
15404 You can call overloaded functions; @value{GDBN} resolves the function
15405 call to the right definition, with some restrictions. @value{GDBN} does not
15406 perform overload resolution involving user-defined type conversions,
15407 calls to constructors, or instantiations of templates that do not exist
15408 in the program. It also cannot handle ellipsis argument lists or
15411 It does perform integral conversions and promotions, floating-point
15412 promotions, arithmetic conversions, pointer conversions, conversions of
15413 class objects to base classes, and standard conversions such as those of
15414 functions or arrays to pointers; it requires an exact match on the
15415 number of function arguments.
15417 Overload resolution is always performed, unless you have specified
15418 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15419 ,@value{GDBN} Features for C@t{++}}.
15421 You must specify @code{set overload-resolution off} in order to use an
15422 explicit function signature to call an overloaded function, as in
15424 p 'foo(char,int)'('x', 13)
15427 The @value{GDBN} command-completion facility can simplify this;
15428 see @ref{Completion, ,Command Completion}.
15430 @cindex reference declarations
15432 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15433 references; you can use them in expressions just as you do in C@t{++}
15434 source---they are automatically dereferenced.
15436 In the parameter list shown when @value{GDBN} displays a frame, the values of
15437 reference variables are not displayed (unlike other variables); this
15438 avoids clutter, since references are often used for large structures.
15439 The @emph{address} of a reference variable is always shown, unless
15440 you have specified @samp{set print address off}.
15443 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15444 expressions can use it just as expressions in your program do. Since
15445 one scope may be defined in another, you can use @code{::} repeatedly if
15446 necessary, for example in an expression like
15447 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15448 resolving name scope by reference to source files, in both C and C@t{++}
15449 debugging (@pxref{Variables, ,Program Variables}).
15452 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15457 @subsubsection C and C@t{++} Defaults
15459 @cindex C and C@t{++} defaults
15461 If you allow @value{GDBN} to set range checking automatically, it
15462 defaults to @code{off} whenever the working language changes to
15463 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15464 selects the working language.
15466 If you allow @value{GDBN} to set the language automatically, it
15467 recognizes source files whose names end with @file{.c}, @file{.C}, or
15468 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15469 these files, it sets the working language to C or C@t{++}.
15470 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15471 for further details.
15474 @subsubsection C and C@t{++} Type and Range Checks
15476 @cindex C and C@t{++} checks
15478 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15479 checking is used. However, if you turn type checking off, @value{GDBN}
15480 will allow certain non-standard conversions, such as promoting integer
15481 constants to pointers.
15483 Range checking, if turned on, is done on mathematical operations. Array
15484 indices are not checked, since they are often used to index a pointer
15485 that is not itself an array.
15488 @subsubsection @value{GDBN} and C
15490 The @code{set print union} and @code{show print union} commands apply to
15491 the @code{union} type. When set to @samp{on}, any @code{union} that is
15492 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15493 appears as @samp{@{...@}}.
15495 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15496 with pointers and a memory allocation function. @xref{Expressions,
15499 @node Debugging C Plus Plus
15500 @subsubsection @value{GDBN} Features for C@t{++}
15502 @cindex commands for C@t{++}
15504 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15505 designed specifically for use with C@t{++}. Here is a summary:
15508 @cindex break in overloaded functions
15509 @item @r{breakpoint menus}
15510 When you want a breakpoint in a function whose name is overloaded,
15511 @value{GDBN} has the capability to display a menu of possible breakpoint
15512 locations to help you specify which function definition you want.
15513 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15515 @cindex overloading in C@t{++}
15516 @item rbreak @var{regex}
15517 Setting breakpoints using regular expressions is helpful for setting
15518 breakpoints on overloaded functions that are not members of any special
15520 @xref{Set Breaks, ,Setting Breakpoints}.
15522 @cindex C@t{++} exception handling
15524 @itemx catch rethrow
15526 Debug C@t{++} exception handling using these commands. @xref{Set
15527 Catchpoints, , Setting Catchpoints}.
15529 @cindex inheritance
15530 @item ptype @var{typename}
15531 Print inheritance relationships as well as other information for type
15533 @xref{Symbols, ,Examining the Symbol Table}.
15535 @item info vtbl @var{expression}.
15536 The @code{info vtbl} command can be used to display the virtual
15537 method tables of the object computed by @var{expression}. This shows
15538 one entry per virtual table; there may be multiple virtual tables when
15539 multiple inheritance is in use.
15541 @cindex C@t{++} demangling
15542 @item demangle @var{name}
15543 Demangle @var{name}.
15544 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15546 @cindex C@t{++} symbol display
15547 @item set print demangle
15548 @itemx show print demangle
15549 @itemx set print asm-demangle
15550 @itemx show print asm-demangle
15551 Control whether C@t{++} symbols display in their source form, both when
15552 displaying code as C@t{++} source and when displaying disassemblies.
15553 @xref{Print Settings, ,Print Settings}.
15555 @item set print object
15556 @itemx show print object
15557 Choose whether to print derived (actual) or declared types of objects.
15558 @xref{Print Settings, ,Print Settings}.
15560 @item set print vtbl
15561 @itemx show print vtbl
15562 Control the format for printing virtual function tables.
15563 @xref{Print Settings, ,Print Settings}.
15564 (The @code{vtbl} commands do not work on programs compiled with the HP
15565 ANSI C@t{++} compiler (@code{aCC}).)
15567 @kindex set overload-resolution
15568 @cindex overloaded functions, overload resolution
15569 @item set overload-resolution on
15570 Enable overload resolution for C@t{++} expression evaluation. The default
15571 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15572 and searches for a function whose signature matches the argument types,
15573 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15574 Expressions, ,C@t{++} Expressions}, for details).
15575 If it cannot find a match, it emits a message.
15577 @item set overload-resolution off
15578 Disable overload resolution for C@t{++} expression evaluation. For
15579 overloaded functions that are not class member functions, @value{GDBN}
15580 chooses the first function of the specified name that it finds in the
15581 symbol table, whether or not its arguments are of the correct type. For
15582 overloaded functions that are class member functions, @value{GDBN}
15583 searches for a function whose signature @emph{exactly} matches the
15586 @kindex show overload-resolution
15587 @item show overload-resolution
15588 Show the current setting of overload resolution.
15590 @item @r{Overloaded symbol names}
15591 You can specify a particular definition of an overloaded symbol, using
15592 the same notation that is used to declare such symbols in C@t{++}: type
15593 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15594 also use the @value{GDBN} command-line word completion facilities to list the
15595 available choices, or to finish the type list for you.
15596 @xref{Completion,, Command Completion}, for details on how to do this.
15598 @item @r{Breakpoints in functions with ABI tags}
15600 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15601 correspond to changes in the ABI of a type, function, or variable that
15602 would not otherwise be reflected in a mangled name. See
15603 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15606 The ABI tags are visible in C@t{++} demangled names. For example, a
15607 function that returns a std::string:
15610 std::string function(int);
15614 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15615 tag, and @value{GDBN} displays the symbol like this:
15618 function[abi:cxx11](int)
15621 You can set a breakpoint on such functions simply as if they had no
15625 (gdb) b function(int)
15626 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15627 (gdb) info breakpoints
15628 Num Type Disp Enb Address What
15629 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15633 On the rare occasion you need to disambiguate between different ABI
15634 tags, you can do so by simply including the ABI tag in the function
15638 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15642 @node Decimal Floating Point
15643 @subsubsection Decimal Floating Point format
15644 @cindex decimal floating point format
15646 @value{GDBN} can examine, set and perform computations with numbers in
15647 decimal floating point format, which in the C language correspond to the
15648 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15649 specified by the extension to support decimal floating-point arithmetic.
15651 There are two encodings in use, depending on the architecture: BID (Binary
15652 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15653 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15656 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15657 to manipulate decimal floating point numbers, it is not possible to convert
15658 (using a cast, for example) integers wider than 32-bit to decimal float.
15660 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15661 point computations, error checking in decimal float operations ignores
15662 underflow, overflow and divide by zero exceptions.
15664 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15665 to inspect @code{_Decimal128} values stored in floating point registers.
15666 See @ref{PowerPC,,PowerPC} for more details.
15672 @value{GDBN} can be used to debug programs written in D and compiled with
15673 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15674 specific feature --- dynamic arrays.
15679 @cindex Go (programming language)
15680 @value{GDBN} can be used to debug programs written in Go and compiled with
15681 @file{gccgo} or @file{6g} compilers.
15683 Here is a summary of the Go-specific features and restrictions:
15686 @cindex current Go package
15687 @item The current Go package
15688 The name of the current package does not need to be specified when
15689 specifying global variables and functions.
15691 For example, given the program:
15695 var myglob = "Shall we?"
15701 When stopped inside @code{main} either of these work:
15705 (gdb) p main.myglob
15708 @cindex builtin Go types
15709 @item Builtin Go types
15710 The @code{string} type is recognized by @value{GDBN} and is printed
15713 @cindex builtin Go functions
15714 @item Builtin Go functions
15715 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15716 function and handles it internally.
15718 @cindex restrictions on Go expressions
15719 @item Restrictions on Go expressions
15720 All Go operators are supported except @code{&^}.
15721 The Go @code{_} ``blank identifier'' is not supported.
15722 Automatic dereferencing of pointers is not supported.
15726 @subsection Objective-C
15728 @cindex Objective-C
15729 This section provides information about some commands and command
15730 options that are useful for debugging Objective-C code. See also
15731 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15732 few more commands specific to Objective-C support.
15735 * Method Names in Commands::
15736 * The Print Command with Objective-C::
15739 @node Method Names in Commands
15740 @subsubsection Method Names in Commands
15742 The following commands have been extended to accept Objective-C method
15743 names as line specifications:
15745 @kindex clear@r{, and Objective-C}
15746 @kindex break@r{, and Objective-C}
15747 @kindex info line@r{, and Objective-C}
15748 @kindex jump@r{, and Objective-C}
15749 @kindex list@r{, and Objective-C}
15753 @item @code{info line}
15758 A fully qualified Objective-C method name is specified as
15761 -[@var{Class} @var{methodName}]
15764 where the minus sign is used to indicate an instance method and a
15765 plus sign (not shown) is used to indicate a class method. The class
15766 name @var{Class} and method name @var{methodName} are enclosed in
15767 brackets, similar to the way messages are specified in Objective-C
15768 source code. For example, to set a breakpoint at the @code{create}
15769 instance method of class @code{Fruit} in the program currently being
15773 break -[Fruit create]
15776 To list ten program lines around the @code{initialize} class method,
15780 list +[NSText initialize]
15783 In the current version of @value{GDBN}, the plus or minus sign is
15784 required. In future versions of @value{GDBN}, the plus or minus
15785 sign will be optional, but you can use it to narrow the search. It
15786 is also possible to specify just a method name:
15792 You must specify the complete method name, including any colons. If
15793 your program's source files contain more than one @code{create} method,
15794 you'll be presented with a numbered list of classes that implement that
15795 method. Indicate your choice by number, or type @samp{0} to exit if
15798 As another example, to clear a breakpoint established at the
15799 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15802 clear -[NSWindow makeKeyAndOrderFront:]
15805 @node The Print Command with Objective-C
15806 @subsubsection The Print Command With Objective-C
15807 @cindex Objective-C, print objects
15808 @kindex print-object
15809 @kindex po @r{(@code{print-object})}
15811 The print command has also been extended to accept methods. For example:
15814 print -[@var{object} hash]
15817 @cindex print an Objective-C object description
15818 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15820 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15821 and print the result. Also, an additional command has been added,
15822 @code{print-object} or @code{po} for short, which is meant to print
15823 the description of an object. However, this command may only work
15824 with certain Objective-C libraries that have a particular hook
15825 function, @code{_NSPrintForDebugger}, defined.
15828 @subsection OpenCL C
15831 This section provides information about @value{GDBN}s OpenCL C support.
15834 * OpenCL C Datatypes::
15835 * OpenCL C Expressions::
15836 * OpenCL C Operators::
15839 @node OpenCL C Datatypes
15840 @subsubsection OpenCL C Datatypes
15842 @cindex OpenCL C Datatypes
15843 @value{GDBN} supports the builtin scalar and vector datatypes specified
15844 by OpenCL 1.1. In addition the half- and double-precision floating point
15845 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15846 extensions are also known to @value{GDBN}.
15848 @node OpenCL C Expressions
15849 @subsubsection OpenCL C Expressions
15851 @cindex OpenCL C Expressions
15852 @value{GDBN} supports accesses to vector components including the access as
15853 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15854 supported by @value{GDBN} can be used as well.
15856 @node OpenCL C Operators
15857 @subsubsection OpenCL C Operators
15859 @cindex OpenCL C Operators
15860 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15864 @subsection Fortran
15865 @cindex Fortran-specific support in @value{GDBN}
15867 @value{GDBN} can be used to debug programs written in Fortran, but it
15868 currently supports only the features of Fortran 77 language.
15870 @cindex trailing underscore, in Fortran symbols
15871 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15872 among them) append an underscore to the names of variables and
15873 functions. When you debug programs compiled by those compilers, you
15874 will need to refer to variables and functions with a trailing
15878 * Fortran Operators:: Fortran operators and expressions
15879 * Fortran Defaults:: Default settings for Fortran
15880 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15883 @node Fortran Operators
15884 @subsubsection Fortran Operators and Expressions
15886 @cindex Fortran operators and expressions
15888 Operators must be defined on values of specific types. For instance,
15889 @code{+} is defined on numbers, but not on characters or other non-
15890 arithmetic types. Operators are often defined on groups of types.
15894 The exponentiation operator. It raises the first operand to the power
15898 The range operator. Normally used in the form of array(low:high) to
15899 represent a section of array.
15902 The access component operator. Normally used to access elements in derived
15903 types. Also suitable for unions. As unions aren't part of regular Fortran,
15904 this can only happen when accessing a register that uses a gdbarch-defined
15908 @node Fortran Defaults
15909 @subsubsection Fortran Defaults
15911 @cindex Fortran Defaults
15913 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15914 default uses case-insensitive matches for Fortran symbols. You can
15915 change that with the @samp{set case-insensitive} command, see
15916 @ref{Symbols}, for the details.
15918 @node Special Fortran Commands
15919 @subsubsection Special Fortran Commands
15921 @cindex Special Fortran commands
15923 @value{GDBN} has some commands to support Fortran-specific features,
15924 such as displaying common blocks.
15927 @cindex @code{COMMON} blocks, Fortran
15928 @kindex info common
15929 @item info common @r{[}@var{common-name}@r{]}
15930 This command prints the values contained in the Fortran @code{COMMON}
15931 block whose name is @var{common-name}. With no argument, the names of
15932 all @code{COMMON} blocks visible at the current program location are
15939 @cindex Pascal support in @value{GDBN}, limitations
15940 Debugging Pascal programs which use sets, subranges, file variables, or
15941 nested functions does not currently work. @value{GDBN} does not support
15942 entering expressions, printing values, or similar features using Pascal
15945 The Pascal-specific command @code{set print pascal_static-members}
15946 controls whether static members of Pascal objects are displayed.
15947 @xref{Print Settings, pascal_static-members}.
15952 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15953 Programming Language}. Type- and value-printing, and expression
15954 parsing, are reasonably complete. However, there are a few
15955 peculiarities and holes to be aware of.
15959 Linespecs (@pxref{Specify Location}) are never relative to the current
15960 crate. Instead, they act as if there were a global namespace of
15961 crates, somewhat similar to the way @code{extern crate} behaves.
15963 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15964 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15965 to set a breakpoint in a function named @samp{f} in a crate named
15968 As a consequence of this approach, linespecs also cannot refer to
15969 items using @samp{self::} or @samp{super::}.
15972 Because @value{GDBN} implements Rust name-lookup semantics in
15973 expressions, it will sometimes prepend the current crate to a name.
15974 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15975 @samp{K}, then @code{print ::x::y} will try to find the symbol
15978 However, since it is useful to be able to refer to other crates when
15979 debugging, @value{GDBN} provides the @code{extern} extension to
15980 circumvent this. To use the extension, just put @code{extern} before
15981 a path expression to refer to the otherwise unavailable ``global''
15984 In the above example, if you wanted to refer to the symbol @samp{y} in
15985 the crate @samp{x}, you would use @code{print extern x::y}.
15988 The Rust expression evaluator does not support ``statement-like''
15989 expressions such as @code{if} or @code{match}, or lambda expressions.
15992 Tuple expressions are not implemented.
15995 The Rust expression evaluator does not currently implement the
15996 @code{Drop} trait. Objects that may be created by the evaluator will
15997 never be destroyed.
16000 @value{GDBN} does not implement type inference for generics. In order
16001 to call generic functions or otherwise refer to generic items, you
16002 will have to specify the type parameters manually.
16005 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16006 cases this does not cause any problems. However, in an expression
16007 context, completing a generic function name will give syntactically
16008 invalid results. This happens because Rust requires the @samp{::}
16009 operator between the function name and its generic arguments. For
16010 example, @value{GDBN} might provide a completion like
16011 @code{crate::f<u32>}, where the parser would require
16012 @code{crate::f::<u32>}.
16015 As of this writing, the Rust compiler (version 1.8) has a few holes in
16016 the debugging information it generates. These holes prevent certain
16017 features from being implemented by @value{GDBN}:
16021 Method calls cannot be made via traits.
16024 Operator overloading is not implemented.
16027 When debugging in a monomorphized function, you cannot use the generic
16031 The type @code{Self} is not available.
16034 @code{use} statements are not available, so some names may not be
16035 available in the crate.
16040 @subsection Modula-2
16042 @cindex Modula-2, @value{GDBN} support
16044 The extensions made to @value{GDBN} to support Modula-2 only support
16045 output from the @sc{gnu} Modula-2 compiler (which is currently being
16046 developed). Other Modula-2 compilers are not currently supported, and
16047 attempting to debug executables produced by them is most likely
16048 to give an error as @value{GDBN} reads in the executable's symbol
16051 @cindex expressions in Modula-2
16053 * M2 Operators:: Built-in operators
16054 * Built-In Func/Proc:: Built-in functions and procedures
16055 * M2 Constants:: Modula-2 constants
16056 * M2 Types:: Modula-2 types
16057 * M2 Defaults:: Default settings for Modula-2
16058 * Deviations:: Deviations from standard Modula-2
16059 * M2 Checks:: Modula-2 type and range checks
16060 * M2 Scope:: The scope operators @code{::} and @code{.}
16061 * GDB/M2:: @value{GDBN} and Modula-2
16065 @subsubsection Operators
16066 @cindex Modula-2 operators
16068 Operators must be defined on values of specific types. For instance,
16069 @code{+} is defined on numbers, but not on structures. Operators are
16070 often defined on groups of types. For the purposes of Modula-2, the
16071 following definitions hold:
16076 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16080 @emph{Character types} consist of @code{CHAR} and its subranges.
16083 @emph{Floating-point types} consist of @code{REAL}.
16086 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16090 @emph{Scalar types} consist of all of the above.
16093 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16096 @emph{Boolean types} consist of @code{BOOLEAN}.
16100 The following operators are supported, and appear in order of
16101 increasing precedence:
16105 Function argument or array index separator.
16108 Assignment. The value of @var{var} @code{:=} @var{value} is
16112 Less than, greater than on integral, floating-point, or enumerated
16116 Less than or equal to, greater than or equal to
16117 on integral, floating-point and enumerated types, or set inclusion on
16118 set types. Same precedence as @code{<}.
16120 @item =@r{, }<>@r{, }#
16121 Equality and two ways of expressing inequality, valid on scalar types.
16122 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16123 available for inequality, since @code{#} conflicts with the script
16127 Set membership. Defined on set types and the types of their members.
16128 Same precedence as @code{<}.
16131 Boolean disjunction. Defined on boolean types.
16134 Boolean conjunction. Defined on boolean types.
16137 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16140 Addition and subtraction on integral and floating-point types, or union
16141 and difference on set types.
16144 Multiplication on integral and floating-point types, or set intersection
16148 Division on floating-point types, or symmetric set difference on set
16149 types. Same precedence as @code{*}.
16152 Integer division and remainder. Defined on integral types. Same
16153 precedence as @code{*}.
16156 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16159 Pointer dereferencing. Defined on pointer types.
16162 Boolean negation. Defined on boolean types. Same precedence as
16166 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16167 precedence as @code{^}.
16170 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16173 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16177 @value{GDBN} and Modula-2 scope operators.
16181 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16182 treats the use of the operator @code{IN}, or the use of operators
16183 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16184 @code{<=}, and @code{>=} on sets as an error.
16188 @node Built-In Func/Proc
16189 @subsubsection Built-in Functions and Procedures
16190 @cindex Modula-2 built-ins
16192 Modula-2 also makes available several built-in procedures and functions.
16193 In describing these, the following metavariables are used:
16198 represents an @code{ARRAY} variable.
16201 represents a @code{CHAR} constant or variable.
16204 represents a variable or constant of integral type.
16207 represents an identifier that belongs to a set. Generally used in the
16208 same function with the metavariable @var{s}. The type of @var{s} should
16209 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16212 represents a variable or constant of integral or floating-point type.
16215 represents a variable or constant of floating-point type.
16221 represents a variable.
16224 represents a variable or constant of one of many types. See the
16225 explanation of the function for details.
16228 All Modula-2 built-in procedures also return a result, described below.
16232 Returns the absolute value of @var{n}.
16235 If @var{c} is a lower case letter, it returns its upper case
16236 equivalent, otherwise it returns its argument.
16239 Returns the character whose ordinal value is @var{i}.
16242 Decrements the value in the variable @var{v} by one. Returns the new value.
16244 @item DEC(@var{v},@var{i})
16245 Decrements the value in the variable @var{v} by @var{i}. Returns the
16248 @item EXCL(@var{m},@var{s})
16249 Removes the element @var{m} from the set @var{s}. Returns the new
16252 @item FLOAT(@var{i})
16253 Returns the floating point equivalent of the integer @var{i}.
16255 @item HIGH(@var{a})
16256 Returns the index of the last member of @var{a}.
16259 Increments the value in the variable @var{v} by one. Returns the new value.
16261 @item INC(@var{v},@var{i})
16262 Increments the value in the variable @var{v} by @var{i}. Returns the
16265 @item INCL(@var{m},@var{s})
16266 Adds the element @var{m} to the set @var{s} if it is not already
16267 there. Returns the new set.
16270 Returns the maximum value of the type @var{t}.
16273 Returns the minimum value of the type @var{t}.
16276 Returns boolean TRUE if @var{i} is an odd number.
16279 Returns the ordinal value of its argument. For example, the ordinal
16280 value of a character is its @sc{ascii} value (on machines supporting
16281 the @sc{ascii} character set). The argument @var{x} must be of an
16282 ordered type, which include integral, character and enumerated types.
16284 @item SIZE(@var{x})
16285 Returns the size of its argument. The argument @var{x} can be a
16286 variable or a type.
16288 @item TRUNC(@var{r})
16289 Returns the integral part of @var{r}.
16291 @item TSIZE(@var{x})
16292 Returns the size of its argument. The argument @var{x} can be a
16293 variable or a type.
16295 @item VAL(@var{t},@var{i})
16296 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16300 @emph{Warning:} Sets and their operations are not yet supported, so
16301 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16305 @cindex Modula-2 constants
16307 @subsubsection Constants
16309 @value{GDBN} allows you to express the constants of Modula-2 in the following
16315 Integer constants are simply a sequence of digits. When used in an
16316 expression, a constant is interpreted to be type-compatible with the
16317 rest of the expression. Hexadecimal integers are specified by a
16318 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16321 Floating point constants appear as a sequence of digits, followed by a
16322 decimal point and another sequence of digits. An optional exponent can
16323 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16324 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16325 digits of the floating point constant must be valid decimal (base 10)
16329 Character constants consist of a single character enclosed by a pair of
16330 like quotes, either single (@code{'}) or double (@code{"}). They may
16331 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16332 followed by a @samp{C}.
16335 String constants consist of a sequence of characters enclosed by a
16336 pair of like quotes, either single (@code{'}) or double (@code{"}).
16337 Escape sequences in the style of C are also allowed. @xref{C
16338 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16342 Enumerated constants consist of an enumerated identifier.
16345 Boolean constants consist of the identifiers @code{TRUE} and
16349 Pointer constants consist of integral values only.
16352 Set constants are not yet supported.
16356 @subsubsection Modula-2 Types
16357 @cindex Modula-2 types
16359 Currently @value{GDBN} can print the following data types in Modula-2
16360 syntax: array types, record types, set types, pointer types, procedure
16361 types, enumerated types, subrange types and base types. You can also
16362 print the contents of variables declared using these type.
16363 This section gives a number of simple source code examples together with
16364 sample @value{GDBN} sessions.
16366 The first example contains the following section of code:
16375 and you can request @value{GDBN} to interrogate the type and value of
16376 @code{r} and @code{s}.
16379 (@value{GDBP}) print s
16381 (@value{GDBP}) ptype s
16383 (@value{GDBP}) print r
16385 (@value{GDBP}) ptype r
16390 Likewise if your source code declares @code{s} as:
16394 s: SET ['A'..'Z'] ;
16398 then you may query the type of @code{s} by:
16401 (@value{GDBP}) ptype s
16402 type = SET ['A'..'Z']
16406 Note that at present you cannot interactively manipulate set
16407 expressions using the debugger.
16409 The following example shows how you might declare an array in Modula-2
16410 and how you can interact with @value{GDBN} to print its type and contents:
16414 s: ARRAY [-10..10] OF CHAR ;
16418 (@value{GDBP}) ptype s
16419 ARRAY [-10..10] OF CHAR
16422 Note that the array handling is not yet complete and although the type
16423 is printed correctly, expression handling still assumes that all
16424 arrays have a lower bound of zero and not @code{-10} as in the example
16427 Here are some more type related Modula-2 examples:
16431 colour = (blue, red, yellow, green) ;
16432 t = [blue..yellow] ;
16440 The @value{GDBN} interaction shows how you can query the data type
16441 and value of a variable.
16444 (@value{GDBP}) print s
16446 (@value{GDBP}) ptype t
16447 type = [blue..yellow]
16451 In this example a Modula-2 array is declared and its contents
16452 displayed. Observe that the contents are written in the same way as
16453 their @code{C} counterparts.
16457 s: ARRAY [1..5] OF CARDINAL ;
16463 (@value{GDBP}) print s
16464 $1 = @{1, 0, 0, 0, 0@}
16465 (@value{GDBP}) ptype s
16466 type = ARRAY [1..5] OF CARDINAL
16469 The Modula-2 language interface to @value{GDBN} also understands
16470 pointer types as shown in this example:
16474 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16481 and you can request that @value{GDBN} describes the type of @code{s}.
16484 (@value{GDBP}) ptype s
16485 type = POINTER TO ARRAY [1..5] OF CARDINAL
16488 @value{GDBN} handles compound types as we can see in this example.
16489 Here we combine array types, record types, pointer types and subrange
16500 myarray = ARRAY myrange OF CARDINAL ;
16501 myrange = [-2..2] ;
16503 s: POINTER TO ARRAY myrange OF foo ;
16507 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16511 (@value{GDBP}) ptype s
16512 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16515 f3 : ARRAY [-2..2] OF CARDINAL;
16520 @subsubsection Modula-2 Defaults
16521 @cindex Modula-2 defaults
16523 If type and range checking are set automatically by @value{GDBN}, they
16524 both default to @code{on} whenever the working language changes to
16525 Modula-2. This happens regardless of whether you or @value{GDBN}
16526 selected the working language.
16528 If you allow @value{GDBN} to set the language automatically, then entering
16529 code compiled from a file whose name ends with @file{.mod} sets the
16530 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16531 Infer the Source Language}, for further details.
16534 @subsubsection Deviations from Standard Modula-2
16535 @cindex Modula-2, deviations from
16537 A few changes have been made to make Modula-2 programs easier to debug.
16538 This is done primarily via loosening its type strictness:
16542 Unlike in standard Modula-2, pointer constants can be formed by
16543 integers. This allows you to modify pointer variables during
16544 debugging. (In standard Modula-2, the actual address contained in a
16545 pointer variable is hidden from you; it can only be modified
16546 through direct assignment to another pointer variable or expression that
16547 returned a pointer.)
16550 C escape sequences can be used in strings and characters to represent
16551 non-printable characters. @value{GDBN} prints out strings with these
16552 escape sequences embedded. Single non-printable characters are
16553 printed using the @samp{CHR(@var{nnn})} format.
16556 The assignment operator (@code{:=}) returns the value of its right-hand
16560 All built-in procedures both modify @emph{and} return their argument.
16564 @subsubsection Modula-2 Type and Range Checks
16565 @cindex Modula-2 checks
16568 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16571 @c FIXME remove warning when type/range checks added
16573 @value{GDBN} considers two Modula-2 variables type equivalent if:
16577 They are of types that have been declared equivalent via a @code{TYPE
16578 @var{t1} = @var{t2}} statement
16581 They have been declared on the same line. (Note: This is true of the
16582 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16585 As long as type checking is enabled, any attempt to combine variables
16586 whose types are not equivalent is an error.
16588 Range checking is done on all mathematical operations, assignment, array
16589 index bounds, and all built-in functions and procedures.
16592 @subsubsection The Scope Operators @code{::} and @code{.}
16594 @cindex @code{.}, Modula-2 scope operator
16595 @cindex colon, doubled as scope operator
16597 @vindex colon-colon@r{, in Modula-2}
16598 @c Info cannot handle :: but TeX can.
16601 @vindex ::@r{, in Modula-2}
16604 There are a few subtle differences between the Modula-2 scope operator
16605 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16610 @var{module} . @var{id}
16611 @var{scope} :: @var{id}
16615 where @var{scope} is the name of a module or a procedure,
16616 @var{module} the name of a module, and @var{id} is any declared
16617 identifier within your program, except another module.
16619 Using the @code{::} operator makes @value{GDBN} search the scope
16620 specified by @var{scope} for the identifier @var{id}. If it is not
16621 found in the specified scope, then @value{GDBN} searches all scopes
16622 enclosing the one specified by @var{scope}.
16624 Using the @code{.} operator makes @value{GDBN} search the current scope for
16625 the identifier specified by @var{id} that was imported from the
16626 definition module specified by @var{module}. With this operator, it is
16627 an error if the identifier @var{id} was not imported from definition
16628 module @var{module}, or if @var{id} is not an identifier in
16632 @subsubsection @value{GDBN} and Modula-2
16634 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16635 Five subcommands of @code{set print} and @code{show print} apply
16636 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16637 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16638 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16639 analogue in Modula-2.
16641 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16642 with any language, is not useful with Modula-2. Its
16643 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16644 created in Modula-2 as they can in C or C@t{++}. However, because an
16645 address can be specified by an integral constant, the construct
16646 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16648 @cindex @code{#} in Modula-2
16649 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16650 interpreted as the beginning of a comment. Use @code{<>} instead.
16656 The extensions made to @value{GDBN} for Ada only support
16657 output from the @sc{gnu} Ada (GNAT) compiler.
16658 Other Ada compilers are not currently supported, and
16659 attempting to debug executables produced by them is most likely
16663 @cindex expressions in Ada
16665 * Ada Mode Intro:: General remarks on the Ada syntax
16666 and semantics supported by Ada mode
16668 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16669 * Additions to Ada:: Extensions of the Ada expression syntax.
16670 * Overloading support for Ada:: Support for expressions involving overloaded
16672 * Stopping Before Main Program:: Debugging the program during elaboration.
16673 * Ada Exceptions:: Ada Exceptions
16674 * Ada Tasks:: Listing and setting breakpoints in tasks.
16675 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16676 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16678 * Ada Settings:: New settable GDB parameters for Ada.
16679 * Ada Glitches:: Known peculiarities of Ada mode.
16682 @node Ada Mode Intro
16683 @subsubsection Introduction
16684 @cindex Ada mode, general
16686 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16687 syntax, with some extensions.
16688 The philosophy behind the design of this subset is
16692 That @value{GDBN} should provide basic literals and access to operations for
16693 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16694 leaving more sophisticated computations to subprograms written into the
16695 program (which therefore may be called from @value{GDBN}).
16698 That type safety and strict adherence to Ada language restrictions
16699 are not particularly important to the @value{GDBN} user.
16702 That brevity is important to the @value{GDBN} user.
16705 Thus, for brevity, the debugger acts as if all names declared in
16706 user-written packages are directly visible, even if they are not visible
16707 according to Ada rules, thus making it unnecessary to fully qualify most
16708 names with their packages, regardless of context. Where this causes
16709 ambiguity, @value{GDBN} asks the user's intent.
16711 The debugger will start in Ada mode if it detects an Ada main program.
16712 As for other languages, it will enter Ada mode when stopped in a program that
16713 was translated from an Ada source file.
16715 While in Ada mode, you may use `@t{--}' for comments. This is useful
16716 mostly for documenting command files. The standard @value{GDBN} comment
16717 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16718 middle (to allow based literals).
16720 @node Omissions from Ada
16721 @subsubsection Omissions from Ada
16722 @cindex Ada, omissions from
16724 Here are the notable omissions from the subset:
16728 Only a subset of the attributes are supported:
16732 @t{'First}, @t{'Last}, and @t{'Length}
16733 on array objects (not on types and subtypes).
16736 @t{'Min} and @t{'Max}.
16739 @t{'Pos} and @t{'Val}.
16745 @t{'Range} on array objects (not subtypes), but only as the right
16746 operand of the membership (@code{in}) operator.
16749 @t{'Access}, @t{'Unchecked_Access}, and
16750 @t{'Unrestricted_Access} (a GNAT extension).
16758 @code{Characters.Latin_1} are not available and
16759 concatenation is not implemented. Thus, escape characters in strings are
16760 not currently available.
16763 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16764 equality of representations. They will generally work correctly
16765 for strings and arrays whose elements have integer or enumeration types.
16766 They may not work correctly for arrays whose element
16767 types have user-defined equality, for arrays of real values
16768 (in particular, IEEE-conformant floating point, because of negative
16769 zeroes and NaNs), and for arrays whose elements contain unused bits with
16770 indeterminate values.
16773 The other component-by-component array operations (@code{and}, @code{or},
16774 @code{xor}, @code{not}, and relational tests other than equality)
16775 are not implemented.
16778 @cindex array aggregates (Ada)
16779 @cindex record aggregates (Ada)
16780 @cindex aggregates (Ada)
16781 There is limited support for array and record aggregates. They are
16782 permitted only on the right sides of assignments, as in these examples:
16785 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16786 (@value{GDBP}) set An_Array := (1, others => 0)
16787 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16788 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16789 (@value{GDBP}) set A_Record := (1, "Peter", True);
16790 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16794 discriminant's value by assigning an aggregate has an
16795 undefined effect if that discriminant is used within the record.
16796 However, you can first modify discriminants by directly assigning to
16797 them (which normally would not be allowed in Ada), and then performing an
16798 aggregate assignment. For example, given a variable @code{A_Rec}
16799 declared to have a type such as:
16802 type Rec (Len : Small_Integer := 0) is record
16804 Vals : IntArray (1 .. Len);
16808 you can assign a value with a different size of @code{Vals} with two
16812 (@value{GDBP}) set A_Rec.Len := 4
16813 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16816 As this example also illustrates, @value{GDBN} is very loose about the usual
16817 rules concerning aggregates. You may leave out some of the
16818 components of an array or record aggregate (such as the @code{Len}
16819 component in the assignment to @code{A_Rec} above); they will retain their
16820 original values upon assignment. You may freely use dynamic values as
16821 indices in component associations. You may even use overlapping or
16822 redundant component associations, although which component values are
16823 assigned in such cases is not defined.
16826 Calls to dispatching subprograms are not implemented.
16829 The overloading algorithm is much more limited (i.e., less selective)
16830 than that of real Ada. It makes only limited use of the context in
16831 which a subexpression appears to resolve its meaning, and it is much
16832 looser in its rules for allowing type matches. As a result, some
16833 function calls will be ambiguous, and the user will be asked to choose
16834 the proper resolution.
16837 The @code{new} operator is not implemented.
16840 Entry calls are not implemented.
16843 Aside from printing, arithmetic operations on the native VAX floating-point
16844 formats are not supported.
16847 It is not possible to slice a packed array.
16850 The names @code{True} and @code{False}, when not part of a qualified name,
16851 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16853 Should your program
16854 redefine these names in a package or procedure (at best a dubious practice),
16855 you will have to use fully qualified names to access their new definitions.
16858 @node Additions to Ada
16859 @subsubsection Additions to Ada
16860 @cindex Ada, deviations from
16862 As it does for other languages, @value{GDBN} makes certain generic
16863 extensions to Ada (@pxref{Expressions}):
16867 If the expression @var{E} is a variable residing in memory (typically
16868 a local variable or array element) and @var{N} is a positive integer,
16869 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16870 @var{N}-1 adjacent variables following it in memory as an array. In
16871 Ada, this operator is generally not necessary, since its prime use is
16872 in displaying parts of an array, and slicing will usually do this in
16873 Ada. However, there are occasional uses when debugging programs in
16874 which certain debugging information has been optimized away.
16877 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16878 appears in function or file @var{B}.'' When @var{B} is a file name,
16879 you must typically surround it in single quotes.
16882 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16883 @var{type} that appears at address @var{addr}.''
16886 A name starting with @samp{$} is a convenience variable
16887 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16890 In addition, @value{GDBN} provides a few other shortcuts and outright
16891 additions specific to Ada:
16895 The assignment statement is allowed as an expression, returning
16896 its right-hand operand as its value. Thus, you may enter
16899 (@value{GDBP}) set x := y + 3
16900 (@value{GDBP}) print A(tmp := y + 1)
16904 The semicolon is allowed as an ``operator,'' returning as its value
16905 the value of its right-hand operand.
16906 This allows, for example,
16907 complex conditional breaks:
16910 (@value{GDBP}) break f
16911 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16915 Rather than use catenation and symbolic character names to introduce special
16916 characters into strings, one may instead use a special bracket notation,
16917 which is also used to print strings. A sequence of characters of the form
16918 @samp{["@var{XX}"]} within a string or character literal denotes the
16919 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16920 sequence of characters @samp{["""]} also denotes a single quotation mark
16921 in strings. For example,
16923 "One line.["0a"]Next line.["0a"]"
16926 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16930 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16931 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16935 (@value{GDBP}) print 'max(x, y)
16939 When printing arrays, @value{GDBN} uses positional notation when the
16940 array has a lower bound of 1, and uses a modified named notation otherwise.
16941 For example, a one-dimensional array of three integers with a lower bound
16942 of 3 might print as
16949 That is, in contrast to valid Ada, only the first component has a @code{=>}
16953 You may abbreviate attributes in expressions with any unique,
16954 multi-character subsequence of
16955 their names (an exact match gets preference).
16956 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16957 in place of @t{a'length}.
16960 @cindex quoting Ada internal identifiers
16961 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16962 to lower case. The GNAT compiler uses upper-case characters for
16963 some of its internal identifiers, which are normally of no interest to users.
16964 For the rare occasions when you actually have to look at them,
16965 enclose them in angle brackets to avoid the lower-case mapping.
16968 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16972 Printing an object of class-wide type or dereferencing an
16973 access-to-class-wide value will display all the components of the object's
16974 specific type (as indicated by its run-time tag). Likewise, component
16975 selection on such a value will operate on the specific type of the
16980 @node Overloading support for Ada
16981 @subsubsection Overloading support for Ada
16982 @cindex overloading, Ada
16984 The debugger supports limited overloading. Given a subprogram call in which
16985 the function symbol has multiple definitions, it will use the number of
16986 actual parameters and some information about their types to attempt to narrow
16987 the set of definitions. It also makes very limited use of context, preferring
16988 procedures to functions in the context of the @code{call} command, and
16989 functions to procedures elsewhere.
16991 If, after narrowing, the set of matching definitions still contains more than
16992 one definition, @value{GDBN} will display a menu to query which one it should
16996 (@value{GDBP}) print f(1)
16997 Multiple matches for f
16999 [1] foo.f (integer) return boolean at foo.adb:23
17000 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17004 In this case, just select one menu entry either to cancel expression evaluation
17005 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17006 instance (type the corresponding number and press @key{RET}).
17008 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17013 @kindex set ada print-signatures
17014 @item set ada print-signatures
17015 Control whether parameter types and return types are displayed in overloads
17016 selection menus. It is @code{on} by default.
17017 @xref{Overloading support for Ada}.
17019 @kindex show ada print-signatures
17020 @item show ada print-signatures
17021 Show the current setting for displaying parameter types and return types in
17022 overloads selection menu.
17023 @xref{Overloading support for Ada}.
17027 @node Stopping Before Main Program
17028 @subsubsection Stopping at the Very Beginning
17030 @cindex breakpointing Ada elaboration code
17031 It is sometimes necessary to debug the program during elaboration, and
17032 before reaching the main procedure.
17033 As defined in the Ada Reference
17034 Manual, the elaboration code is invoked from a procedure called
17035 @code{adainit}. To run your program up to the beginning of
17036 elaboration, simply use the following two commands:
17037 @code{tbreak adainit} and @code{run}.
17039 @node Ada Exceptions
17040 @subsubsection Ada Exceptions
17042 A command is provided to list all Ada exceptions:
17045 @kindex info exceptions
17046 @item info exceptions
17047 @itemx info exceptions @var{regexp}
17048 The @code{info exceptions} command allows you to list all Ada exceptions
17049 defined within the program being debugged, as well as their addresses.
17050 With a regular expression, @var{regexp}, as argument, only those exceptions
17051 whose names match @var{regexp} are listed.
17054 Below is a small example, showing how the command can be used, first
17055 without argument, and next with a regular expression passed as an
17059 (@value{GDBP}) info exceptions
17060 All defined Ada exceptions:
17061 constraint_error: 0x613da0
17062 program_error: 0x613d20
17063 storage_error: 0x613ce0
17064 tasking_error: 0x613ca0
17065 const.aint_global_e: 0x613b00
17066 (@value{GDBP}) info exceptions const.aint
17067 All Ada exceptions matching regular expression "const.aint":
17068 constraint_error: 0x613da0
17069 const.aint_global_e: 0x613b00
17072 It is also possible to ask @value{GDBN} to stop your program's execution
17073 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17076 @subsubsection Extensions for Ada Tasks
17077 @cindex Ada, tasking
17079 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17080 @value{GDBN} provides the following task-related commands:
17085 This command shows a list of current Ada tasks, as in the following example:
17092 (@value{GDBP}) info tasks
17093 ID TID P-ID Pri State Name
17094 1 8088000 0 15 Child Activation Wait main_task
17095 2 80a4000 1 15 Accept Statement b
17096 3 809a800 1 15 Child Activation Wait a
17097 * 4 80ae800 3 15 Runnable c
17102 In this listing, the asterisk before the last task indicates it to be the
17103 task currently being inspected.
17107 Represents @value{GDBN}'s internal task number.
17113 The parent's task ID (@value{GDBN}'s internal task number).
17116 The base priority of the task.
17119 Current state of the task.
17123 The task has been created but has not been activated. It cannot be
17127 The task is not blocked for any reason known to Ada. (It may be waiting
17128 for a mutex, though.) It is conceptually "executing" in normal mode.
17131 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17132 that were waiting on terminate alternatives have been awakened and have
17133 terminated themselves.
17135 @item Child Activation Wait
17136 The task is waiting for created tasks to complete activation.
17138 @item Accept Statement
17139 The task is waiting on an accept or selective wait statement.
17141 @item Waiting on entry call
17142 The task is waiting on an entry call.
17144 @item Async Select Wait
17145 The task is waiting to start the abortable part of an asynchronous
17149 The task is waiting on a select statement with only a delay
17152 @item Child Termination Wait
17153 The task is sleeping having completed a master within itself, and is
17154 waiting for the tasks dependent on that master to become terminated or
17155 waiting on a terminate Phase.
17157 @item Wait Child in Term Alt
17158 The task is sleeping waiting for tasks on terminate alternatives to
17159 finish terminating.
17161 @item Accepting RV with @var{taskno}
17162 The task is accepting a rendez-vous with the task @var{taskno}.
17166 Name of the task in the program.
17170 @kindex info task @var{taskno}
17171 @item info task @var{taskno}
17172 This command shows detailled informations on the specified task, as in
17173 the following example:
17178 (@value{GDBP}) info tasks
17179 ID TID P-ID Pri State Name
17180 1 8077880 0 15 Child Activation Wait main_task
17181 * 2 807c468 1 15 Runnable task_1
17182 (@value{GDBP}) info task 2
17183 Ada Task: 0x807c468
17187 Parent: 1 (main_task)
17193 @kindex task@r{ (Ada)}
17194 @cindex current Ada task ID
17195 This command prints the ID of the current task.
17201 (@value{GDBP}) info tasks
17202 ID TID P-ID Pri State Name
17203 1 8077870 0 15 Child Activation Wait main_task
17204 * 2 807c458 1 15 Runnable t
17205 (@value{GDBP}) task
17206 [Current task is 2]
17209 @item task @var{taskno}
17210 @cindex Ada task switching
17211 This command is like the @code{thread @var{thread-id}}
17212 command (@pxref{Threads}). It switches the context of debugging
17213 from the current task to the given task.
17219 (@value{GDBP}) info tasks
17220 ID TID P-ID Pri State Name
17221 1 8077870 0 15 Child Activation Wait main_task
17222 * 2 807c458 1 15 Runnable t
17223 (@value{GDBP}) task 1
17224 [Switching to task 1]
17225 #0 0x8067726 in pthread_cond_wait ()
17227 #0 0x8067726 in pthread_cond_wait ()
17228 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17229 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17230 #3 0x806153e in system.tasking.stages.activate_tasks ()
17231 #4 0x804aacc in un () at un.adb:5
17234 @item break @var{location} task @var{taskno}
17235 @itemx break @var{location} task @var{taskno} if @dots{}
17236 @cindex breakpoints and tasks, in Ada
17237 @cindex task breakpoints, in Ada
17238 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17239 These commands are like the @code{break @dots{} thread @dots{}}
17240 command (@pxref{Thread Stops}). The
17241 @var{location} argument specifies source lines, as described
17242 in @ref{Specify Location}.
17244 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17245 to specify that you only want @value{GDBN} to stop the program when a
17246 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17247 numeric task identifiers assigned by @value{GDBN}, shown in the first
17248 column of the @samp{info tasks} display.
17250 If you do not specify @samp{task @var{taskno}} when you set a
17251 breakpoint, the breakpoint applies to @emph{all} tasks of your
17254 You can use the @code{task} qualifier on conditional breakpoints as
17255 well; in this case, place @samp{task @var{taskno}} before the
17256 breakpoint condition (before the @code{if}).
17264 (@value{GDBP}) info tasks
17265 ID TID P-ID Pri State Name
17266 1 140022020 0 15 Child Activation Wait main_task
17267 2 140045060 1 15 Accept/Select Wait t2
17268 3 140044840 1 15 Runnable t1
17269 * 4 140056040 1 15 Runnable t3
17270 (@value{GDBP}) b 15 task 2
17271 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17272 (@value{GDBP}) cont
17277 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17279 (@value{GDBP}) info tasks
17280 ID TID P-ID Pri State Name
17281 1 140022020 0 15 Child Activation Wait main_task
17282 * 2 140045060 1 15 Runnable t2
17283 3 140044840 1 15 Runnable t1
17284 4 140056040 1 15 Delay Sleep t3
17288 @node Ada Tasks and Core Files
17289 @subsubsection Tasking Support when Debugging Core Files
17290 @cindex Ada tasking and core file debugging
17292 When inspecting a core file, as opposed to debugging a live program,
17293 tasking support may be limited or even unavailable, depending on
17294 the platform being used.
17295 For instance, on x86-linux, the list of tasks is available, but task
17296 switching is not supported.
17298 On certain platforms, the debugger needs to perform some
17299 memory writes in order to provide Ada tasking support. When inspecting
17300 a core file, this means that the core file must be opened with read-write
17301 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17302 Under these circumstances, you should make a backup copy of the core
17303 file before inspecting it with @value{GDBN}.
17305 @node Ravenscar Profile
17306 @subsubsection Tasking Support when using the Ravenscar Profile
17307 @cindex Ravenscar Profile
17309 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17310 specifically designed for systems with safety-critical real-time
17314 @kindex set ravenscar task-switching on
17315 @cindex task switching with program using Ravenscar Profile
17316 @item set ravenscar task-switching on
17317 Allows task switching when debugging a program that uses the Ravenscar
17318 Profile. This is the default.
17320 @kindex set ravenscar task-switching off
17321 @item set ravenscar task-switching off
17322 Turn off task switching when debugging a program that uses the Ravenscar
17323 Profile. This is mostly intended to disable the code that adds support
17324 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17325 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17326 To be effective, this command should be run before the program is started.
17328 @kindex show ravenscar task-switching
17329 @item show ravenscar task-switching
17330 Show whether it is possible to switch from task to task in a program
17331 using the Ravenscar Profile.
17336 @subsubsection Ada Settings
17337 @cindex Ada settings
17340 @kindex set varsize-limit
17341 @item set varsize-limit @var{size}
17342 Prevent @value{GDBN} from attempting to evaluate objects whose size
17343 is above the given limit (@var{size}) when those sizes are computed
17344 from run-time quantities. This is typically the case when the object
17345 has a variable size, such as an array whose bounds are not known at
17346 compile time for example. Setting @var{size} to @code{unlimited}
17347 removes the size limitation. By default, the limit is about 65KB.
17349 The purpose of having such a limit is to prevent @value{GDBN} from
17350 trying to grab enormous chunks of virtual memory when asked to evaluate
17351 a quantity whose bounds have been corrupted or have not yet been fully
17352 initialized. The limit applies to the results of some subexpressions
17353 as well as to complete expressions. For example, an expression denoting
17354 a simple integer component, such as @code{x.y.z}, may fail if the size of
17355 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17356 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17357 @code{A} is an array variable with non-constant size, will generally
17358 succeed regardless of the bounds on @code{A}, as long as the component
17359 size is less than @var{size}.
17361 @kindex show varsize-limit
17362 @item show varsize-limit
17363 Show the limit on types whose size is determined by run-time quantities.
17367 @subsubsection Known Peculiarities of Ada Mode
17368 @cindex Ada, problems
17370 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17371 we know of several problems with and limitations of Ada mode in
17373 some of which will be fixed with planned future releases of the debugger
17374 and the GNU Ada compiler.
17378 Static constants that the compiler chooses not to materialize as objects in
17379 storage are invisible to the debugger.
17382 Named parameter associations in function argument lists are ignored (the
17383 argument lists are treated as positional).
17386 Many useful library packages are currently invisible to the debugger.
17389 Fixed-point arithmetic, conversions, input, and output is carried out using
17390 floating-point arithmetic, and may give results that only approximate those on
17394 The GNAT compiler never generates the prefix @code{Standard} for any of
17395 the standard symbols defined by the Ada language. @value{GDBN} knows about
17396 this: it will strip the prefix from names when you use it, and will never
17397 look for a name you have so qualified among local symbols, nor match against
17398 symbols in other packages or subprograms. If you have
17399 defined entities anywhere in your program other than parameters and
17400 local variables whose simple names match names in @code{Standard},
17401 GNAT's lack of qualification here can cause confusion. When this happens,
17402 you can usually resolve the confusion
17403 by qualifying the problematic names with package
17404 @code{Standard} explicitly.
17407 Older versions of the compiler sometimes generate erroneous debugging
17408 information, resulting in the debugger incorrectly printing the value
17409 of affected entities. In some cases, the debugger is able to work
17410 around an issue automatically. In other cases, the debugger is able
17411 to work around the issue, but the work-around has to be specifically
17414 @kindex set ada trust-PAD-over-XVS
17415 @kindex show ada trust-PAD-over-XVS
17418 @item set ada trust-PAD-over-XVS on
17419 Configure GDB to strictly follow the GNAT encoding when computing the
17420 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17421 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17422 a complete description of the encoding used by the GNAT compiler).
17423 This is the default.
17425 @item set ada trust-PAD-over-XVS off
17426 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17427 sometimes prints the wrong value for certain entities, changing @code{ada
17428 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17429 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17430 @code{off}, but this incurs a slight performance penalty, so it is
17431 recommended to leave this setting to @code{on} unless necessary.
17435 @cindex GNAT descriptive types
17436 @cindex GNAT encoding
17437 Internally, the debugger also relies on the compiler following a number
17438 of conventions known as the @samp{GNAT Encoding}, all documented in
17439 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17440 how the debugging information should be generated for certain types.
17441 In particular, this convention makes use of @dfn{descriptive types},
17442 which are artificial types generated purely to help the debugger.
17444 These encodings were defined at a time when the debugging information
17445 format used was not powerful enough to describe some of the more complex
17446 types available in Ada. Since DWARF allows us to express nearly all
17447 Ada features, the long-term goal is to slowly replace these descriptive
17448 types by their pure DWARF equivalent. To facilitate that transition,
17449 a new maintenance option is available to force the debugger to ignore
17450 those descriptive types. It allows the user to quickly evaluate how
17451 well @value{GDBN} works without them.
17455 @kindex maint ada set ignore-descriptive-types
17456 @item maintenance ada set ignore-descriptive-types [on|off]
17457 Control whether the debugger should ignore descriptive types.
17458 The default is not to ignore descriptives types (@code{off}).
17460 @kindex maint ada show ignore-descriptive-types
17461 @item maintenance ada show ignore-descriptive-types
17462 Show if descriptive types are ignored by @value{GDBN}.
17466 @node Unsupported Languages
17467 @section Unsupported Languages
17469 @cindex unsupported languages
17470 @cindex minimal language
17471 In addition to the other fully-supported programming languages,
17472 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17473 It does not represent a real programming language, but provides a set
17474 of capabilities close to what the C or assembly languages provide.
17475 This should allow most simple operations to be performed while debugging
17476 an application that uses a language currently not supported by @value{GDBN}.
17478 If the language is set to @code{auto}, @value{GDBN} will automatically
17479 select this language if the current frame corresponds to an unsupported
17483 @chapter Examining the Symbol Table
17485 The commands described in this chapter allow you to inquire about the
17486 symbols (names of variables, functions and types) defined in your
17487 program. This information is inherent in the text of your program and
17488 does not change as your program executes. @value{GDBN} finds it in your
17489 program's symbol table, in the file indicated when you started @value{GDBN}
17490 (@pxref{File Options, ,Choosing Files}), or by one of the
17491 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17493 @cindex symbol names
17494 @cindex names of symbols
17495 @cindex quoting names
17496 @anchor{quoting names}
17497 Occasionally, you may need to refer to symbols that contain unusual
17498 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17499 most frequent case is in referring to static variables in other
17500 source files (@pxref{Variables,,Program Variables}). File names
17501 are recorded in object files as debugging symbols, but @value{GDBN} would
17502 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17503 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17504 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17511 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17514 @cindex case-insensitive symbol names
17515 @cindex case sensitivity in symbol names
17516 @kindex set case-sensitive
17517 @item set case-sensitive on
17518 @itemx set case-sensitive off
17519 @itemx set case-sensitive auto
17520 Normally, when @value{GDBN} looks up symbols, it matches their names
17521 with case sensitivity determined by the current source language.
17522 Occasionally, you may wish to control that. The command @code{set
17523 case-sensitive} lets you do that by specifying @code{on} for
17524 case-sensitive matches or @code{off} for case-insensitive ones. If
17525 you specify @code{auto}, case sensitivity is reset to the default
17526 suitable for the source language. The default is case-sensitive
17527 matches for all languages except for Fortran, for which the default is
17528 case-insensitive matches.
17530 @kindex show case-sensitive
17531 @item show case-sensitive
17532 This command shows the current setting of case sensitivity for symbols
17535 @kindex set print type methods
17536 @item set print type methods
17537 @itemx set print type methods on
17538 @itemx set print type methods off
17539 Normally, when @value{GDBN} prints a class, it displays any methods
17540 declared in that class. You can control this behavior either by
17541 passing the appropriate flag to @code{ptype}, or using @command{set
17542 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17543 display the methods; this is the default. Specifying @code{off} will
17544 cause @value{GDBN} to omit the methods.
17546 @kindex show print type methods
17547 @item show print type methods
17548 This command shows the current setting of method display when printing
17551 @kindex set print type nested-type-limit
17552 @item set print type nested-type-limit @var{limit}
17553 @itemx set print type nested-type-limit unlimited
17554 Set the limit of displayed nested types that the type printer will
17555 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17556 nested definitions. By default, the type printer will not show any nested
17557 types defined in classes.
17559 @kindex show print type nested-type-limit
17560 @item show print type nested-type-limit
17561 This command shows the current display limit of nested types when
17564 @kindex set print type typedefs
17565 @item set print type typedefs
17566 @itemx set print type typedefs on
17567 @itemx set print type typedefs off
17569 Normally, when @value{GDBN} prints a class, it displays any typedefs
17570 defined in that class. You can control this behavior either by
17571 passing the appropriate flag to @code{ptype}, or using @command{set
17572 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17573 display the typedef definitions; this is the default. Specifying
17574 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17575 Note that this controls whether the typedef definition itself is
17576 printed, not whether typedef names are substituted when printing other
17579 @kindex show print type typedefs
17580 @item show print type typedefs
17581 This command shows the current setting of typedef display when
17584 @kindex info address
17585 @cindex address of a symbol
17586 @item info address @var{symbol}
17587 Describe where the data for @var{symbol} is stored. For a register
17588 variable, this says which register it is kept in. For a non-register
17589 local variable, this prints the stack-frame offset at which the variable
17592 Note the contrast with @samp{print &@var{symbol}}, which does not work
17593 at all for a register variable, and for a stack local variable prints
17594 the exact address of the current instantiation of the variable.
17596 @kindex info symbol
17597 @cindex symbol from address
17598 @cindex closest symbol and offset for an address
17599 @item info symbol @var{addr}
17600 Print the name of a symbol which is stored at the address @var{addr}.
17601 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17602 nearest symbol and an offset from it:
17605 (@value{GDBP}) info symbol 0x54320
17606 _initialize_vx + 396 in section .text
17610 This is the opposite of the @code{info address} command. You can use
17611 it to find out the name of a variable or a function given its address.
17613 For dynamically linked executables, the name of executable or shared
17614 library containing the symbol is also printed:
17617 (@value{GDBP}) info symbol 0x400225
17618 _start + 5 in section .text of /tmp/a.out
17619 (@value{GDBP}) info symbol 0x2aaaac2811cf
17620 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17625 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17626 Demangle @var{name}.
17627 If @var{language} is provided it is the name of the language to demangle
17628 @var{name} in. Otherwise @var{name} is demangled in the current language.
17630 The @samp{--} option specifies the end of options,
17631 and is useful when @var{name} begins with a dash.
17633 The parameter @code{demangle-style} specifies how to interpret the kind
17634 of mangling used. @xref{Print Settings}.
17637 @item whatis[/@var{flags}] [@var{arg}]
17638 Print the data type of @var{arg}, which can be either an expression
17639 or a name of a data type. With no argument, print the data type of
17640 @code{$}, the last value in the value history.
17642 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17643 is not actually evaluated, and any side-effecting operations (such as
17644 assignments or function calls) inside it do not take place.
17646 If @var{arg} is a variable or an expression, @code{whatis} prints its
17647 literal type as it is used in the source code. If the type was
17648 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17649 the data type underlying the @code{typedef}. If the type of the
17650 variable or the expression is a compound data type, such as
17651 @code{struct} or @code{class}, @code{whatis} never prints their
17652 fields or methods. It just prints the @code{struct}/@code{class}
17653 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17654 such a compound data type, use @code{ptype}.
17656 If @var{arg} is a type name that was defined using @code{typedef},
17657 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17658 Unrolling means that @code{whatis} will show the underlying type used
17659 in the @code{typedef} declaration of @var{arg}. However, if that
17660 underlying type is also a @code{typedef}, @code{whatis} will not
17663 For C code, the type names may also have the form @samp{class
17664 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17665 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17667 @var{flags} can be used to modify how the type is displayed.
17668 Available flags are:
17672 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17673 parameters and typedefs defined in a class when printing the class'
17674 members. The @code{/r} flag disables this.
17677 Do not print methods defined in the class.
17680 Print methods defined in the class. This is the default, but the flag
17681 exists in case you change the default with @command{set print type methods}.
17684 Do not print typedefs defined in the class. Note that this controls
17685 whether the typedef definition itself is printed, not whether typedef
17686 names are substituted when printing other types.
17689 Print typedefs defined in the class. This is the default, but the flag
17690 exists in case you change the default with @command{set print type typedefs}.
17693 Print the offsets and sizes of fields in a struct, similar to what the
17694 @command{pahole} tool does. This option implies the @code{/tm} flags.
17696 For example, given the following declarations:
17732 Issuing a @kbd{ptype /o struct tuv} command would print:
17735 (@value{GDBP}) ptype /o struct tuv
17736 /* offset | size */ type = struct tuv @{
17737 /* 0 | 4 */ int a1;
17738 /* XXX 4-byte hole */
17739 /* 8 | 8 */ char *a2;
17740 /* 16 | 4 */ int a3;
17742 /* total size (bytes): 24 */
17746 Notice the format of the first column of comments. There, you can
17747 find two parts separated by the @samp{|} character: the @emph{offset},
17748 which indicates where the field is located inside the struct, in
17749 bytes, and the @emph{size} of the field. Another interesting line is
17750 the marker of a @emph{hole} in the struct, indicating that it may be
17751 possible to pack the struct and make it use less space by reorganizing
17754 It is also possible to print offsets inside an union:
17757 (@value{GDBP}) ptype /o union qwe
17758 /* offset | size */ type = union qwe @{
17759 /* 24 */ struct tuv @{
17760 /* 0 | 4 */ int a1;
17761 /* XXX 4-byte hole */
17762 /* 8 | 8 */ char *a2;
17763 /* 16 | 4 */ int a3;
17765 /* total size (bytes): 24 */
17767 /* 40 */ struct xyz @{
17768 /* 0 | 4 */ int f1;
17769 /* 4 | 1 */ char f2;
17770 /* XXX 3-byte hole */
17771 /* 8 | 8 */ void *f3;
17772 /* 16 | 24 */ struct tuv @{
17773 /* 16 | 4 */ int a1;
17774 /* XXX 4-byte hole */
17775 /* 24 | 8 */ char *a2;
17776 /* 32 | 4 */ int a3;
17778 /* total size (bytes): 24 */
17781 /* total size (bytes): 40 */
17784 /* total size (bytes): 40 */
17788 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17789 same space (because we are dealing with an union), the offset is not
17790 printed for them. However, you can still examine the offset of each
17791 of these structures' fields.
17793 Another useful scenario is printing the offsets of a struct containing
17797 (@value{GDBP}) ptype /o struct tyu
17798 /* offset | size */ type = struct tyu @{
17799 /* 0:31 | 4 */ int a1 : 1;
17800 /* 0:28 | 4 */ int a2 : 3;
17801 /* 0: 5 | 4 */ int a3 : 23;
17802 /* 3: 3 | 1 */ signed char a4 : 2;
17803 /* XXX 3-bit hole */
17804 /* XXX 4-byte hole */
17805 /* 8 | 8 */ int64_t a5;
17806 /* 16:27 | 4 */ int a6 : 5;
17807 /* 16:56 | 8 */ int64_t a7 : 3;
17809 /* total size (bytes): 24 */
17813 Note how the offset information is now extended to also include how
17814 many bits are left to be used in each bitfield.
17818 @item ptype[/@var{flags}] [@var{arg}]
17819 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17820 detailed description of the type, instead of just the name of the type.
17821 @xref{Expressions, ,Expressions}.
17823 Contrary to @code{whatis}, @code{ptype} always unrolls any
17824 @code{typedef}s in its argument declaration, whether the argument is
17825 a variable, expression, or a data type. This means that @code{ptype}
17826 of a variable or an expression will not print literally its type as
17827 present in the source code---use @code{whatis} for that. @code{typedef}s at
17828 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17829 fields, methods and inner @code{class typedef}s of @code{struct}s,
17830 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17832 For example, for this variable declaration:
17835 typedef double real_t;
17836 struct complex @{ real_t real; double imag; @};
17837 typedef struct complex complex_t;
17839 real_t *real_pointer_var;
17843 the two commands give this output:
17847 (@value{GDBP}) whatis var
17849 (@value{GDBP}) ptype var
17850 type = struct complex @{
17854 (@value{GDBP}) whatis complex_t
17855 type = struct complex
17856 (@value{GDBP}) whatis struct complex
17857 type = struct complex
17858 (@value{GDBP}) ptype struct complex
17859 type = struct complex @{
17863 (@value{GDBP}) whatis real_pointer_var
17865 (@value{GDBP}) ptype real_pointer_var
17871 As with @code{whatis}, using @code{ptype} without an argument refers to
17872 the type of @code{$}, the last value in the value history.
17874 @cindex incomplete type
17875 Sometimes, programs use opaque data types or incomplete specifications
17876 of complex data structure. If the debug information included in the
17877 program does not allow @value{GDBN} to display a full declaration of
17878 the data type, it will say @samp{<incomplete type>}. For example,
17879 given these declarations:
17883 struct foo *fooptr;
17887 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17890 (@value{GDBP}) ptype foo
17891 $1 = <incomplete type>
17895 ``Incomplete type'' is C terminology for data types that are not
17896 completely specified.
17898 @cindex unknown type
17899 Othertimes, information about a variable's type is completely absent
17900 from the debug information included in the program. This most often
17901 happens when the program or library where the variable is defined
17902 includes no debug information at all. @value{GDBN} knows the variable
17903 exists from inspecting the linker/loader symbol table (e.g., the ELF
17904 dynamic symbol table), but such symbols do not contain type
17905 information. Inspecting the type of a (global) variable for which
17906 @value{GDBN} has no type information shows:
17909 (@value{GDBP}) ptype var
17910 type = <data variable, no debug info>
17913 @xref{Variables, no debug info variables}, for how to print the values
17917 @item info types @var{regexp}
17919 Print a brief description of all types whose names match the regular
17920 expression @var{regexp} (or all types in your program, if you supply
17921 no argument). Each complete typename is matched as though it were a
17922 complete line; thus, @samp{i type value} gives information on all
17923 types in your program whose names include the string @code{value}, but
17924 @samp{i type ^value$} gives information only on types whose complete
17925 name is @code{value}.
17927 In programs using different languages, @value{GDBN} chooses the syntax
17928 to print the type description according to the
17929 @samp{set language} value: using @samp{set language auto}
17930 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17931 language of the type, other values mean to use
17932 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17934 This command differs from @code{ptype} in two ways: first, like
17935 @code{whatis}, it does not print a detailed description; second, it
17936 lists all source files and line numbers where a type is defined.
17938 @kindex info type-printers
17939 @item info type-printers
17940 Versions of @value{GDBN} that ship with Python scripting enabled may
17941 have ``type printers'' available. When using @command{ptype} or
17942 @command{whatis}, these printers are consulted when the name of a type
17943 is needed. @xref{Type Printing API}, for more information on writing
17946 @code{info type-printers} displays all the available type printers.
17948 @kindex enable type-printer
17949 @kindex disable type-printer
17950 @item enable type-printer @var{name}@dots{}
17951 @item disable type-printer @var{name}@dots{}
17952 These commands can be used to enable or disable type printers.
17955 @cindex local variables
17956 @item info scope @var{location}
17957 List all the variables local to a particular scope. This command
17958 accepts a @var{location} argument---a function name, a source line, or
17959 an address preceded by a @samp{*}, and prints all the variables local
17960 to the scope defined by that location. (@xref{Specify Location}, for
17961 details about supported forms of @var{location}.) For example:
17964 (@value{GDBP}) @b{info scope command_line_handler}
17965 Scope for command_line_handler:
17966 Symbol rl is an argument at stack/frame offset 8, length 4.
17967 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17968 Symbol linelength is in static storage at address 0x150a1c, length 4.
17969 Symbol p is a local variable in register $esi, length 4.
17970 Symbol p1 is a local variable in register $ebx, length 4.
17971 Symbol nline is a local variable in register $edx, length 4.
17972 Symbol repeat is a local variable at frame offset -8, length 4.
17976 This command is especially useful for determining what data to collect
17977 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17980 @kindex info source
17982 Show information about the current source file---that is, the source file for
17983 the function containing the current point of execution:
17986 the name of the source file, and the directory containing it,
17988 the directory it was compiled in,
17990 its length, in lines,
17992 which programming language it is written in,
17994 if the debug information provides it, the program that compiled the file
17995 (which may include, e.g., the compiler version and command line arguments),
17997 whether the executable includes debugging information for that file, and
17998 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18000 whether the debugging information includes information about
18001 preprocessor macros.
18005 @kindex info sources
18007 Print the names of all source files in your program for which there is
18008 debugging information, organized into two lists: files whose symbols
18009 have already been read, and files whose symbols will be read when needed.
18011 @kindex info functions
18012 @item info functions [-q]
18013 Print the names and data types of all defined functions.
18014 Similarly to @samp{info types}, this command groups its output by source
18015 files and annotates each function definition with its source line
18018 In programs using different languages, @value{GDBN} chooses the syntax
18019 to print the function name and type according to the
18020 @samp{set language} value: using @samp{set language auto}
18021 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18022 language of the function, other values mean to use
18023 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18025 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18026 printing header information and messages explaining why no functions
18029 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18030 Like @samp{info functions}, but only print the names and data types
18031 of the functions selected with the provided regexp(s).
18033 If @var{regexp} is provided, print only the functions whose names
18034 match the regular expression @var{regexp}.
18035 Thus, @samp{info fun step} finds all functions whose
18036 names include @code{step}; @samp{info fun ^step} finds those whose names
18037 start with @code{step}. If a function name contains characters that
18038 conflict with the regular expression language (e.g.@:
18039 @samp{operator*()}), they may be quoted with a backslash.
18041 If @var{type_regexp} is provided, print only the functions whose
18042 types, as printed by the @code{whatis} command, match
18043 the regular expression @var{type_regexp}.
18044 If @var{type_regexp} contains space(s), it should be enclosed in
18045 quote characters. If needed, use backslash to escape the meaning
18046 of special characters or quotes.
18047 Thus, @samp{info fun -t '^int ('} finds the functions that return
18048 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18049 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18050 finds the functions whose names start with @code{step} and that return
18053 If both @var{regexp} and @var{type_regexp} are provided, a function
18054 is printed only if its name matches @var{regexp} and its type matches
18058 @kindex info variables
18059 @item info variables [-q]
18060 Print the names and data types of all variables that are defined
18061 outside of functions (i.e.@: excluding local variables).
18062 The printed variables are grouped by source files and annotated with
18063 their respective source line numbers.
18065 In programs using different languages, @value{GDBN} chooses the syntax
18066 to print the variable name and type according to the
18067 @samp{set language} value: using @samp{set language auto}
18068 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18069 language of the variable, other values mean to use
18070 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18072 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18073 printing header information and messages explaining why no variables
18076 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18077 Like @kbd{info variables}, but only print the variables selected
18078 with the provided regexp(s).
18080 If @var{regexp} is provided, print only the variables whose names
18081 match the regular expression @var{regexp}.
18083 If @var{type_regexp} is provided, print only the variables whose
18084 types, as printed by the @code{whatis} command, match
18085 the regular expression @var{type_regexp}.
18086 If @var{type_regexp} contains space(s), it should be enclosed in
18087 quote characters. If needed, use backslash to escape the meaning
18088 of special characters or quotes.
18090 If both @var{regexp} and @var{type_regexp} are provided, an argument
18091 is printed only if its name matches @var{regexp} and its type matches
18094 @kindex info classes
18095 @cindex Objective-C, classes and selectors
18097 @itemx info classes @var{regexp}
18098 Display all Objective-C classes in your program, or
18099 (with the @var{regexp} argument) all those matching a particular regular
18102 @kindex info selectors
18103 @item info selectors
18104 @itemx info selectors @var{regexp}
18105 Display all Objective-C selectors in your program, or
18106 (with the @var{regexp} argument) all those matching a particular regular
18110 This was never implemented.
18111 @kindex info methods
18113 @itemx info methods @var{regexp}
18114 The @code{info methods} command permits the user to examine all defined
18115 methods within C@t{++} program, or (with the @var{regexp} argument) a
18116 specific set of methods found in the various C@t{++} classes. Many
18117 C@t{++} classes provide a large number of methods. Thus, the output
18118 from the @code{ptype} command can be overwhelming and hard to use. The
18119 @code{info-methods} command filters the methods, printing only those
18120 which match the regular-expression @var{regexp}.
18123 @cindex opaque data types
18124 @kindex set opaque-type-resolution
18125 @item set opaque-type-resolution on
18126 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18127 declared as a pointer to a @code{struct}, @code{class}, or
18128 @code{union}---for example, @code{struct MyType *}---that is used in one
18129 source file although the full declaration of @code{struct MyType} is in
18130 another source file. The default is on.
18132 A change in the setting of this subcommand will not take effect until
18133 the next time symbols for a file are loaded.
18135 @item set opaque-type-resolution off
18136 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18137 is printed as follows:
18139 @{<no data fields>@}
18142 @kindex show opaque-type-resolution
18143 @item show opaque-type-resolution
18144 Show whether opaque types are resolved or not.
18146 @kindex set print symbol-loading
18147 @cindex print messages when symbols are loaded
18148 @item set print symbol-loading
18149 @itemx set print symbol-loading full
18150 @itemx set print symbol-loading brief
18151 @itemx set print symbol-loading off
18152 The @code{set print symbol-loading} command allows you to control the
18153 printing of messages when @value{GDBN} loads symbol information.
18154 By default a message is printed for the executable and one for each
18155 shared library, and normally this is what you want. However, when
18156 debugging apps with large numbers of shared libraries these messages
18158 When set to @code{brief} a message is printed for each executable,
18159 and when @value{GDBN} loads a collection of shared libraries at once
18160 it will only print one message regardless of the number of shared
18161 libraries. When set to @code{off} no messages are printed.
18163 @kindex show print symbol-loading
18164 @item show print symbol-loading
18165 Show whether messages will be printed when a @value{GDBN} command
18166 entered from the keyboard causes symbol information to be loaded.
18168 @kindex maint print symbols
18169 @cindex symbol dump
18170 @kindex maint print psymbols
18171 @cindex partial symbol dump
18172 @kindex maint print msymbols
18173 @cindex minimal symbol dump
18174 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18175 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18176 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18177 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18178 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18179 Write a dump of debugging symbol data into the file @var{filename} or
18180 the terminal if @var{filename} is unspecified.
18181 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18183 If @code{-pc @var{address}} is specified, only dump symbols for the file
18184 with code at that address. Note that @var{address} may be a symbol like
18186 If @code{-source @var{source}} is specified, only dump symbols for that
18189 These commands are used to debug the @value{GDBN} symbol-reading code.
18190 These commands do not modify internal @value{GDBN} state, therefore
18191 @samp{maint print symbols} will only print symbols for already expanded symbol
18193 You can use the command @code{info sources} to find out which files these are.
18194 If you use @samp{maint print psymbols} instead, the dump shows information
18195 about symbols that @value{GDBN} only knows partially---that is, symbols
18196 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18197 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18200 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18201 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18203 @kindex maint info symtabs
18204 @kindex maint info psymtabs
18205 @cindex listing @value{GDBN}'s internal symbol tables
18206 @cindex symbol tables, listing @value{GDBN}'s internal
18207 @cindex full symbol tables, listing @value{GDBN}'s internal
18208 @cindex partial symbol tables, listing @value{GDBN}'s internal
18209 @item maint info symtabs @r{[} @var{regexp} @r{]}
18210 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18212 List the @code{struct symtab} or @code{struct partial_symtab}
18213 structures whose names match @var{regexp}. If @var{regexp} is not
18214 given, list them all. The output includes expressions which you can
18215 copy into a @value{GDBN} debugging this one to examine a particular
18216 structure in more detail. For example:
18219 (@value{GDBP}) maint info psymtabs dwarf2read
18220 @{ objfile /home/gnu/build/gdb/gdb
18221 ((struct objfile *) 0x82e69d0)
18222 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18223 ((struct partial_symtab *) 0x8474b10)
18226 text addresses 0x814d3c8 -- 0x8158074
18227 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18228 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18229 dependencies (none)
18232 (@value{GDBP}) maint info symtabs
18236 We see that there is one partial symbol table whose filename contains
18237 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18238 and we see that @value{GDBN} has not read in any symtabs yet at all.
18239 If we set a breakpoint on a function, that will cause @value{GDBN} to
18240 read the symtab for the compilation unit containing that function:
18243 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18244 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18246 (@value{GDBP}) maint info symtabs
18247 @{ objfile /home/gnu/build/gdb/gdb
18248 ((struct objfile *) 0x82e69d0)
18249 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18250 ((struct symtab *) 0x86c1f38)
18253 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18254 linetable ((struct linetable *) 0x8370fa0)
18255 debugformat DWARF 2
18261 @kindex maint info line-table
18262 @cindex listing @value{GDBN}'s internal line tables
18263 @cindex line tables, listing @value{GDBN}'s internal
18264 @item maint info line-table @r{[} @var{regexp} @r{]}
18266 List the @code{struct linetable} from all @code{struct symtab}
18267 instances whose name matches @var{regexp}. If @var{regexp} is not
18268 given, list the @code{struct linetable} from all @code{struct symtab}.
18270 @kindex maint set symbol-cache-size
18271 @cindex symbol cache size
18272 @item maint set symbol-cache-size @var{size}
18273 Set the size of the symbol cache to @var{size}.
18274 The default size is intended to be good enough for debugging
18275 most applications. This option exists to allow for experimenting
18276 with different sizes.
18278 @kindex maint show symbol-cache-size
18279 @item maint show symbol-cache-size
18280 Show the size of the symbol cache.
18282 @kindex maint print symbol-cache
18283 @cindex symbol cache, printing its contents
18284 @item maint print symbol-cache
18285 Print the contents of the symbol cache.
18286 This is useful when debugging symbol cache issues.
18288 @kindex maint print symbol-cache-statistics
18289 @cindex symbol cache, printing usage statistics
18290 @item maint print symbol-cache-statistics
18291 Print symbol cache usage statistics.
18292 This helps determine how well the cache is being utilized.
18294 @kindex maint flush-symbol-cache
18295 @cindex symbol cache, flushing
18296 @item maint flush-symbol-cache
18297 Flush the contents of the symbol cache, all entries are removed.
18298 This command is useful when debugging the symbol cache.
18299 It is also useful when collecting performance data.
18304 @chapter Altering Execution
18306 Once you think you have found an error in your program, you might want to
18307 find out for certain whether correcting the apparent error would lead to
18308 correct results in the rest of the run. You can find the answer by
18309 experiment, using the @value{GDBN} features for altering execution of the
18312 For example, you can store new values into variables or memory
18313 locations, give your program a signal, restart it at a different
18314 address, or even return prematurely from a function.
18317 * Assignment:: Assignment to variables
18318 * Jumping:: Continuing at a different address
18319 * Signaling:: Giving your program a signal
18320 * Returning:: Returning from a function
18321 * Calling:: Calling your program's functions
18322 * Patching:: Patching your program
18323 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18327 @section Assignment to Variables
18330 @cindex setting variables
18331 To alter the value of a variable, evaluate an assignment expression.
18332 @xref{Expressions, ,Expressions}. For example,
18339 stores the value 4 into the variable @code{x}, and then prints the
18340 value of the assignment expression (which is 4).
18341 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18342 information on operators in supported languages.
18344 @kindex set variable
18345 @cindex variables, setting
18346 If you are not interested in seeing the value of the assignment, use the
18347 @code{set} command instead of the @code{print} command. @code{set} is
18348 really the same as @code{print} except that the expression's value is
18349 not printed and is not put in the value history (@pxref{Value History,
18350 ,Value History}). The expression is evaluated only for its effects.
18352 If the beginning of the argument string of the @code{set} command
18353 appears identical to a @code{set} subcommand, use the @code{set
18354 variable} command instead of just @code{set}. This command is identical
18355 to @code{set} except for its lack of subcommands. For example, if your
18356 program has a variable @code{width}, you get an error if you try to set
18357 a new value with just @samp{set width=13}, because @value{GDBN} has the
18358 command @code{set width}:
18361 (@value{GDBP}) whatis width
18363 (@value{GDBP}) p width
18365 (@value{GDBP}) set width=47
18366 Invalid syntax in expression.
18370 The invalid expression, of course, is @samp{=47}. In
18371 order to actually set the program's variable @code{width}, use
18374 (@value{GDBP}) set var width=47
18377 Because the @code{set} command has many subcommands that can conflict
18378 with the names of program variables, it is a good idea to use the
18379 @code{set variable} command instead of just @code{set}. For example, if
18380 your program has a variable @code{g}, you run into problems if you try
18381 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18382 the command @code{set gnutarget}, abbreviated @code{set g}:
18386 (@value{GDBP}) whatis g
18390 (@value{GDBP}) set g=4
18394 The program being debugged has been started already.
18395 Start it from the beginning? (y or n) y
18396 Starting program: /home/smith/cc_progs/a.out
18397 "/home/smith/cc_progs/a.out": can't open to read symbols:
18398 Invalid bfd target.
18399 (@value{GDBP}) show g
18400 The current BFD target is "=4".
18405 The program variable @code{g} did not change, and you silently set the
18406 @code{gnutarget} to an invalid value. In order to set the variable
18410 (@value{GDBP}) set var g=4
18413 @value{GDBN} allows more implicit conversions in assignments than C; you can
18414 freely store an integer value into a pointer variable or vice versa,
18415 and you can convert any structure to any other structure that is the
18416 same length or shorter.
18417 @comment FIXME: how do structs align/pad in these conversions?
18418 @comment /doc@cygnus.com 18dec1990
18420 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18421 construct to generate a value of specified type at a specified address
18422 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18423 to memory location @code{0x83040} as an integer (which implies a certain size
18424 and representation in memory), and
18427 set @{int@}0x83040 = 4
18431 stores the value 4 into that memory location.
18434 @section Continuing at a Different Address
18436 Ordinarily, when you continue your program, you do so at the place where
18437 it stopped, with the @code{continue} command. You can instead continue at
18438 an address of your own choosing, with the following commands:
18442 @kindex j @r{(@code{jump})}
18443 @item jump @var{location}
18444 @itemx j @var{location}
18445 Resume execution at @var{location}. Execution stops again immediately
18446 if there is a breakpoint there. @xref{Specify Location}, for a description
18447 of the different forms of @var{location}. It is common
18448 practice to use the @code{tbreak} command in conjunction with
18449 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18451 The @code{jump} command does not change the current stack frame, or
18452 the stack pointer, or the contents of any memory location or any
18453 register other than the program counter. If @var{location} is in
18454 a different function from the one currently executing, the results may
18455 be bizarre if the two functions expect different patterns of arguments or
18456 of local variables. For this reason, the @code{jump} command requests
18457 confirmation if the specified line is not in the function currently
18458 executing. However, even bizarre results are predictable if you are
18459 well acquainted with the machine-language code of your program.
18462 On many systems, you can get much the same effect as the @code{jump}
18463 command by storing a new value into the register @code{$pc}. The
18464 difference is that this does not start your program running; it only
18465 changes the address of where it @emph{will} run when you continue. For
18473 makes the next @code{continue} command or stepping command execute at
18474 address @code{0x485}, rather than at the address where your program stopped.
18475 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18477 The most common occasion to use the @code{jump} command is to back
18478 up---perhaps with more breakpoints set---over a portion of a program
18479 that has already executed, in order to examine its execution in more
18484 @section Giving your Program a Signal
18485 @cindex deliver a signal to a program
18489 @item signal @var{signal}
18490 Resume execution where your program is stopped, but immediately give it the
18491 signal @var{signal}. The @var{signal} can be the name or the number of a
18492 signal. For example, on many systems @code{signal 2} and @code{signal
18493 SIGINT} are both ways of sending an interrupt signal.
18495 Alternatively, if @var{signal} is zero, continue execution without
18496 giving a signal. This is useful when your program stopped on account of
18497 a signal and would ordinarily see the signal when resumed with the
18498 @code{continue} command; @samp{signal 0} causes it to resume without a
18501 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18502 delivered to the currently selected thread, not the thread that last
18503 reported a stop. This includes the situation where a thread was
18504 stopped due to a signal. So if you want to continue execution
18505 suppressing the signal that stopped a thread, you should select that
18506 same thread before issuing the @samp{signal 0} command. If you issue
18507 the @samp{signal 0} command with another thread as the selected one,
18508 @value{GDBN} detects that and asks for confirmation.
18510 Invoking the @code{signal} command is not the same as invoking the
18511 @code{kill} utility from the shell. Sending a signal with @code{kill}
18512 causes @value{GDBN} to decide what to do with the signal depending on
18513 the signal handling tables (@pxref{Signals}). The @code{signal} command
18514 passes the signal directly to your program.
18516 @code{signal} does not repeat when you press @key{RET} a second time
18517 after executing the command.
18519 @kindex queue-signal
18520 @item queue-signal @var{signal}
18521 Queue @var{signal} to be delivered immediately to the current thread
18522 when execution of the thread resumes. The @var{signal} can be the name or
18523 the number of a signal. For example, on many systems @code{signal 2} and
18524 @code{signal SIGINT} are both ways of sending an interrupt signal.
18525 The handling of the signal must be set to pass the signal to the program,
18526 otherwise @value{GDBN} will report an error.
18527 You can control the handling of signals from @value{GDBN} with the
18528 @code{handle} command (@pxref{Signals}).
18530 Alternatively, if @var{signal} is zero, any currently queued signal
18531 for the current thread is discarded and when execution resumes no signal
18532 will be delivered. This is useful when your program stopped on account
18533 of a signal and would ordinarily see the signal when resumed with the
18534 @code{continue} command.
18536 This command differs from the @code{signal} command in that the signal
18537 is just queued, execution is not resumed. And @code{queue-signal} cannot
18538 be used to pass a signal whose handling state has been set to @code{nopass}
18543 @xref{stepping into signal handlers}, for information on how stepping
18544 commands behave when the thread has a signal queued.
18547 @section Returning from a Function
18550 @cindex returning from a function
18553 @itemx return @var{expression}
18554 You can cancel execution of a function call with the @code{return}
18555 command. If you give an
18556 @var{expression} argument, its value is used as the function's return
18560 When you use @code{return}, @value{GDBN} discards the selected stack frame
18561 (and all frames within it). You can think of this as making the
18562 discarded frame return prematurely. If you wish to specify a value to
18563 be returned, give that value as the argument to @code{return}.
18565 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18566 Frame}), and any other frames inside of it, leaving its caller as the
18567 innermost remaining frame. That frame becomes selected. The
18568 specified value is stored in the registers used for returning values
18571 The @code{return} command does not resume execution; it leaves the
18572 program stopped in the state that would exist if the function had just
18573 returned. In contrast, the @code{finish} command (@pxref{Continuing
18574 and Stepping, ,Continuing and Stepping}) resumes execution until the
18575 selected stack frame returns naturally.
18577 @value{GDBN} needs to know how the @var{expression} argument should be set for
18578 the inferior. The concrete registers assignment depends on the OS ABI and the
18579 type being returned by the selected stack frame. For example it is common for
18580 OS ABI to return floating point values in FPU registers while integer values in
18581 CPU registers. Still some ABIs return even floating point values in CPU
18582 registers. Larger integer widths (such as @code{long long int}) also have
18583 specific placement rules. @value{GDBN} already knows the OS ABI from its
18584 current target so it needs to find out also the type being returned to make the
18585 assignment into the right register(s).
18587 Normally, the selected stack frame has debug info. @value{GDBN} will always
18588 use the debug info instead of the implicit type of @var{expression} when the
18589 debug info is available. For example, if you type @kbd{return -1}, and the
18590 function in the current stack frame is declared to return a @code{long long
18591 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18592 into a @code{long long int}:
18595 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18597 (@value{GDBP}) return -1
18598 Make func return now? (y or n) y
18599 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18600 43 printf ("result=%lld\n", func ());
18604 However, if the selected stack frame does not have a debug info, e.g., if the
18605 function was compiled without debug info, @value{GDBN} has to find out the type
18606 to return from user. Specifying a different type by mistake may set the value
18607 in different inferior registers than the caller code expects. For example,
18608 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18609 of a @code{long long int} result for a debug info less function (on 32-bit
18610 architectures). Therefore the user is required to specify the return type by
18611 an appropriate cast explicitly:
18614 Breakpoint 2, 0x0040050b in func ()
18615 (@value{GDBP}) return -1
18616 Return value type not available for selected stack frame.
18617 Please use an explicit cast of the value to return.
18618 (@value{GDBP}) return (long long int) -1
18619 Make selected stack frame return now? (y or n) y
18620 #0 0x00400526 in main ()
18625 @section Calling Program Functions
18628 @cindex calling functions
18629 @cindex inferior functions, calling
18630 @item print @var{expr}
18631 Evaluate the expression @var{expr} and display the resulting value.
18632 The expression may include calls to functions in the program being
18636 @item call @var{expr}
18637 Evaluate the expression @var{expr} without displaying @code{void}
18640 You can use this variant of the @code{print} command if you want to
18641 execute a function from your program that does not return anything
18642 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18643 with @code{void} returned values that @value{GDBN} will otherwise
18644 print. If the result is not void, it is printed and saved in the
18648 It is possible for the function you call via the @code{print} or
18649 @code{call} command to generate a signal (e.g., if there's a bug in
18650 the function, or if you passed it incorrect arguments). What happens
18651 in that case is controlled by the @code{set unwindonsignal} command.
18653 Similarly, with a C@t{++} program it is possible for the function you
18654 call via the @code{print} or @code{call} command to generate an
18655 exception that is not handled due to the constraints of the dummy
18656 frame. In this case, any exception that is raised in the frame, but has
18657 an out-of-frame exception handler will not be found. GDB builds a
18658 dummy-frame for the inferior function call, and the unwinder cannot
18659 seek for exception handlers outside of this dummy-frame. What happens
18660 in that case is controlled by the
18661 @code{set unwind-on-terminating-exception} command.
18664 @item set unwindonsignal
18665 @kindex set unwindonsignal
18666 @cindex unwind stack in called functions
18667 @cindex call dummy stack unwinding
18668 Set unwinding of the stack if a signal is received while in a function
18669 that @value{GDBN} called in the program being debugged. If set to on,
18670 @value{GDBN} unwinds the stack it created for the call and restores
18671 the context to what it was before the call. If set to off (the
18672 default), @value{GDBN} stops in the frame where the signal was
18675 @item show unwindonsignal
18676 @kindex show unwindonsignal
18677 Show the current setting of stack unwinding in the functions called by
18680 @item set unwind-on-terminating-exception
18681 @kindex set unwind-on-terminating-exception
18682 @cindex unwind stack in called functions with unhandled exceptions
18683 @cindex call dummy stack unwinding on unhandled exception.
18684 Set unwinding of the stack if a C@t{++} exception is raised, but left
18685 unhandled while in a function that @value{GDBN} called in the program being
18686 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18687 it created for the call and restores the context to what it was before
18688 the call. If set to off, @value{GDBN} the exception is delivered to
18689 the default C@t{++} exception handler and the inferior terminated.
18691 @item show unwind-on-terminating-exception
18692 @kindex show unwind-on-terminating-exception
18693 Show the current setting of stack unwinding in the functions called by
18698 @subsection Calling functions with no debug info
18700 @cindex no debug info functions
18701 Sometimes, a function you wish to call is missing debug information.
18702 In such case, @value{GDBN} does not know the type of the function,
18703 including the types of the function's parameters. To avoid calling
18704 the inferior function incorrectly, which could result in the called
18705 function functioning erroneously and even crash, @value{GDBN} refuses
18706 to call the function unless you tell it the type of the function.
18708 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18709 to do that. The simplest is to cast the call to the function's
18710 declared return type. For example:
18713 (@value{GDBP}) p getenv ("PATH")
18714 'getenv' has unknown return type; cast the call to its declared return type
18715 (@value{GDBP}) p (char *) getenv ("PATH")
18716 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18719 Casting the return type of a no-debug function is equivalent to
18720 casting the function to a pointer to a prototyped function that has a
18721 prototype that matches the types of the passed-in arguments, and
18722 calling that. I.e., the call above is equivalent to:
18725 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18729 and given this prototyped C or C++ function with float parameters:
18732 float multiply (float v1, float v2) @{ return v1 * v2; @}
18736 these calls are equivalent:
18739 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18740 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18743 If the function you wish to call is declared as unprototyped (i.e.@:
18744 old K&R style), you must use the cast-to-function-pointer syntax, so
18745 that @value{GDBN} knows that it needs to apply default argument
18746 promotions (promote float arguments to double). @xref{ABI, float
18747 promotion}. For example, given this unprototyped C function with
18748 float parameters, and no debug info:
18752 multiply_noproto (v1, v2)
18760 you call it like this:
18763 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18767 @section Patching Programs
18769 @cindex patching binaries
18770 @cindex writing into executables
18771 @cindex writing into corefiles
18773 By default, @value{GDBN} opens the file containing your program's
18774 executable code (or the corefile) read-only. This prevents accidental
18775 alterations to machine code; but it also prevents you from intentionally
18776 patching your program's binary.
18778 If you'd like to be able to patch the binary, you can specify that
18779 explicitly with the @code{set write} command. For example, you might
18780 want to turn on internal debugging flags, or even to make emergency
18786 @itemx set write off
18787 If you specify @samp{set write on}, @value{GDBN} opens executable and
18788 core files for both reading and writing; if you specify @kbd{set write
18789 off} (the default), @value{GDBN} opens them read-only.
18791 If you have already loaded a file, you must load it again (using the
18792 @code{exec-file} or @code{core-file} command) after changing @code{set
18793 write}, for your new setting to take effect.
18797 Display whether executable files and core files are opened for writing
18798 as well as reading.
18801 @node Compiling and Injecting Code
18802 @section Compiling and injecting code in @value{GDBN}
18803 @cindex injecting code
18804 @cindex writing into executables
18805 @cindex compiling code
18807 @value{GDBN} supports on-demand compilation and code injection into
18808 programs running under @value{GDBN}. GCC 5.0 or higher built with
18809 @file{libcc1.so} must be installed for this functionality to be enabled.
18810 This functionality is implemented with the following commands.
18813 @kindex compile code
18814 @item compile code @var{source-code}
18815 @itemx compile code -raw @var{--} @var{source-code}
18816 Compile @var{source-code} with the compiler language found as the current
18817 language in @value{GDBN} (@pxref{Languages}). If compilation and
18818 injection is not supported with the current language specified in
18819 @value{GDBN}, or the compiler does not support this feature, an error
18820 message will be printed. If @var{source-code} compiles and links
18821 successfully, @value{GDBN} will load the object-code emitted,
18822 and execute it within the context of the currently selected inferior.
18823 It is important to note that the compiled code is executed immediately.
18824 After execution, the compiled code is removed from @value{GDBN} and any
18825 new types or variables you have defined will be deleted.
18827 The command allows you to specify @var{source-code} in two ways.
18828 The simplest method is to provide a single line of code to the command.
18832 compile code printf ("hello world\n");
18835 If you specify options on the command line as well as source code, they
18836 may conflict. The @samp{--} delimiter can be used to separate options
18837 from actual source code. E.g.:
18840 compile code -r -- printf ("hello world\n");
18843 Alternatively you can enter source code as multiple lines of text. To
18844 enter this mode, invoke the @samp{compile code} command without any text
18845 following the command. This will start the multiple-line editor and
18846 allow you to type as many lines of source code as required. When you
18847 have completed typing, enter @samp{end} on its own line to exit the
18852 >printf ("hello\n");
18853 >printf ("world\n");
18857 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18858 provided @var{source-code} in a callable scope. In this case, you must
18859 specify the entry point of the code by defining a function named
18860 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18861 inferior. Using @samp{-raw} option may be needed for example when
18862 @var{source-code} requires @samp{#include} lines which may conflict with
18863 inferior symbols otherwise.
18865 @kindex compile file
18866 @item compile file @var{filename}
18867 @itemx compile file -raw @var{filename}
18868 Like @code{compile code}, but take the source code from @var{filename}.
18871 compile file /home/user/example.c
18876 @item compile print @var{expr}
18877 @itemx compile print /@var{f} @var{expr}
18878 Compile and execute @var{expr} with the compiler language found as the
18879 current language in @value{GDBN} (@pxref{Languages}). By default the
18880 value of @var{expr} is printed in a format appropriate to its data type;
18881 you can choose a different format by specifying @samp{/@var{f}}, where
18882 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18885 @item compile print
18886 @itemx compile print /@var{f}
18887 @cindex reprint the last value
18888 Alternatively you can enter the expression (source code producing it) as
18889 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18890 command without any text following the command. This will start the
18891 multiple-line editor.
18895 The process of compiling and injecting the code can be inspected using:
18898 @anchor{set debug compile}
18899 @item set debug compile
18900 @cindex compile command debugging info
18901 Turns on or off display of @value{GDBN} process of compiling and
18902 injecting the code. The default is off.
18904 @item show debug compile
18905 Displays the current state of displaying @value{GDBN} process of
18906 compiling and injecting the code.
18908 @anchor{set debug compile-cplus-types}
18909 @item set debug compile-cplus-types
18910 @cindex compile C@t{++} type conversion
18911 Turns on or off the display of C@t{++} type conversion debugging information.
18912 The default is off.
18914 @item show debug compile-cplus-types
18915 Displays the current state of displaying debugging information for
18916 C@t{++} type conversion.
18919 @subsection Compilation options for the @code{compile} command
18921 @value{GDBN} needs to specify the right compilation options for the code
18922 to be injected, in part to make its ABI compatible with the inferior
18923 and in part to make the injected code compatible with @value{GDBN}'s
18927 The options used, in increasing precedence:
18930 @item target architecture and OS options (@code{gdbarch})
18931 These options depend on target processor type and target operating
18932 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18933 (@code{-m64}) compilation option.
18935 @item compilation options recorded in the target
18936 @value{NGCC} (since version 4.7) stores the options used for compilation
18937 into @code{DW_AT_producer} part of DWARF debugging information according
18938 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18939 explicitly specify @code{-g} during inferior compilation otherwise
18940 @value{NGCC} produces no DWARF. This feature is only relevant for
18941 platforms where @code{-g} produces DWARF by default, otherwise one may
18942 try to enforce DWARF by using @code{-gdwarf-4}.
18944 @item compilation options set by @code{set compile-args}
18948 You can override compilation options using the following command:
18951 @item set compile-args
18952 @cindex compile command options override
18953 Set compilation options used for compiling and injecting code with the
18954 @code{compile} commands. These options override any conflicting ones
18955 from the target architecture and/or options stored during inferior
18958 @item show compile-args
18959 Displays the current state of compilation options override.
18960 This does not show all the options actually used during compilation,
18961 use @ref{set debug compile} for that.
18964 @subsection Caveats when using the @code{compile} command
18966 There are a few caveats to keep in mind when using the @code{compile}
18967 command. As the caveats are different per language, the table below
18968 highlights specific issues on a per language basis.
18971 @item C code examples and caveats
18972 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18973 attempt to compile the source code with a @samp{C} compiler. The source
18974 code provided to the @code{compile} command will have much the same
18975 access to variables and types as it normally would if it were part of
18976 the program currently being debugged in @value{GDBN}.
18978 Below is a sample program that forms the basis of the examples that
18979 follow. This program has been compiled and loaded into @value{GDBN},
18980 much like any other normal debugging session.
18983 void function1 (void)
18986 printf ("function 1\n");
18989 void function2 (void)
19004 For the purposes of the examples in this section, the program above has
19005 been compiled, loaded into @value{GDBN}, stopped at the function
19006 @code{main}, and @value{GDBN} is awaiting input from the user.
19008 To access variables and types for any program in @value{GDBN}, the
19009 program must be compiled and packaged with debug information. The
19010 @code{compile} command is not an exception to this rule. Without debug
19011 information, you can still use the @code{compile} command, but you will
19012 be very limited in what variables and types you can access.
19014 So with that in mind, the example above has been compiled with debug
19015 information enabled. The @code{compile} command will have access to
19016 all variables and types (except those that may have been optimized
19017 out). Currently, as @value{GDBN} has stopped the program in the
19018 @code{main} function, the @code{compile} command would have access to
19019 the variable @code{k}. You could invoke the @code{compile} command
19020 and type some source code to set the value of @code{k}. You can also
19021 read it, or do anything with that variable you would normally do in
19022 @code{C}. Be aware that changes to inferior variables in the
19023 @code{compile} command are persistent. In the following example:
19026 compile code k = 3;
19030 the variable @code{k} is now 3. It will retain that value until
19031 something else in the example program changes it, or another
19032 @code{compile} command changes it.
19034 Normal scope and access rules apply to source code compiled and
19035 injected by the @code{compile} command. In the example, the variables
19036 @code{j} and @code{k} are not accessible yet, because the program is
19037 currently stopped in the @code{main} function, where these variables
19038 are not in scope. Therefore, the following command
19041 compile code j = 3;
19045 will result in a compilation error message.
19047 Once the program is continued, execution will bring these variables in
19048 scope, and they will become accessible; then the code you specify via
19049 the @code{compile} command will be able to access them.
19051 You can create variables and types with the @code{compile} command as
19052 part of your source code. Variables and types that are created as part
19053 of the @code{compile} command are not visible to the rest of the program for
19054 the duration of its run. This example is valid:
19057 compile code int ff = 5; printf ("ff is %d\n", ff);
19060 However, if you were to type the following into @value{GDBN} after that
19061 command has completed:
19064 compile code printf ("ff is %d\n'', ff);
19068 a compiler error would be raised as the variable @code{ff} no longer
19069 exists. Object code generated and injected by the @code{compile}
19070 command is removed when its execution ends. Caution is advised
19071 when assigning to program variables values of variables created by the
19072 code submitted to the @code{compile} command. This example is valid:
19075 compile code int ff = 5; k = ff;
19078 The value of the variable @code{ff} is assigned to @code{k}. The variable
19079 @code{k} does not require the existence of @code{ff} to maintain the value
19080 it has been assigned. However, pointers require particular care in
19081 assignment. If the source code compiled with the @code{compile} command
19082 changed the address of a pointer in the example program, perhaps to a
19083 variable created in the @code{compile} command, that pointer would point
19084 to an invalid location when the command exits. The following example
19085 would likely cause issues with your debugged program:
19088 compile code int ff = 5; p = &ff;
19091 In this example, @code{p} would point to @code{ff} when the
19092 @code{compile} command is executing the source code provided to it.
19093 However, as variables in the (example) program persist with their
19094 assigned values, the variable @code{p} would point to an invalid
19095 location when the command exists. A general rule should be followed
19096 in that you should either assign @code{NULL} to any assigned pointers,
19097 or restore a valid location to the pointer before the command exits.
19099 Similar caution must be exercised with any structs, unions, and typedefs
19100 defined in @code{compile} command. Types defined in the @code{compile}
19101 command will no longer be available in the next @code{compile} command.
19102 Therefore, if you cast a variable to a type defined in the
19103 @code{compile} command, care must be taken to ensure that any future
19104 need to resolve the type can be achieved.
19107 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19108 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19109 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19110 Compilation failed.
19111 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19115 Variables that have been optimized away by the compiler are not
19116 accessible to the code submitted to the @code{compile} command.
19117 Access to those variables will generate a compiler error which @value{GDBN}
19118 will print to the console.
19121 @subsection Compiler search for the @code{compile} command
19123 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19124 which may not be obvious for remote targets of different architecture
19125 than where @value{GDBN} is running. Environment variable @code{PATH} on
19126 @value{GDBN} host is searched for @value{NGCC} binary matching the
19127 target architecture and operating system. This search can be overriden
19128 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19129 taken from shell that executed @value{GDBN}, it is not the value set by
19130 @value{GDBN} command @code{set environment}). @xref{Environment}.
19133 Specifically @code{PATH} is searched for binaries matching regular expression
19134 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19135 debugged. @var{arch} is processor name --- multiarch is supported, so for
19136 example both @code{i386} and @code{x86_64} targets look for pattern
19137 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19138 for pattern @code{s390x?}. @var{os} is currently supported only for
19139 pattern @code{linux(-gnu)?}.
19141 On Posix hosts the compiler driver @value{GDBN} needs to find also
19142 shared library @file{libcc1.so} from the compiler. It is searched in
19143 default shared library search path (overridable with usual environment
19144 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19145 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19146 according to the installation of the found compiler --- as possibly
19147 specified by the @code{set compile-gcc} command.
19150 @item set compile-gcc
19151 @cindex compile command driver filename override
19152 Set compilation command used for compiling and injecting code with the
19153 @code{compile} commands. If this option is not set (it is set to
19154 an empty string), the search described above will occur --- that is the
19157 @item show compile-gcc
19158 Displays the current compile command @value{NGCC} driver filename.
19159 If set, it is the main command @command{gcc}, found usually for example
19160 under name @file{x86_64-linux-gnu-gcc}.
19164 @chapter @value{GDBN} Files
19166 @value{GDBN} needs to know the file name of the program to be debugged,
19167 both in order to read its symbol table and in order to start your
19168 program. To debug a core dump of a previous run, you must also tell
19169 @value{GDBN} the name of the core dump file.
19172 * Files:: Commands to specify files
19173 * File Caching:: Information about @value{GDBN}'s file caching
19174 * Separate Debug Files:: Debugging information in separate files
19175 * MiniDebugInfo:: Debugging information in a special section
19176 * Index Files:: Index files speed up GDB
19177 * Symbol Errors:: Errors reading symbol files
19178 * Data Files:: GDB data files
19182 @section Commands to Specify Files
19184 @cindex symbol table
19185 @cindex core dump file
19187 You may want to specify executable and core dump file names. The usual
19188 way to do this is at start-up time, using the arguments to
19189 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19190 Out of @value{GDBN}}).
19192 Occasionally it is necessary to change to a different file during a
19193 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19194 specify a file you want to use. Or you are debugging a remote target
19195 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19196 Program}). In these situations the @value{GDBN} commands to specify
19197 new files are useful.
19200 @cindex executable file
19202 @item file @var{filename}
19203 Use @var{filename} as the program to be debugged. It is read for its
19204 symbols and for the contents of pure memory. It is also the program
19205 executed when you use the @code{run} command. If you do not specify a
19206 directory and the file is not found in the @value{GDBN} working directory,
19207 @value{GDBN} uses the environment variable @code{PATH} as a list of
19208 directories to search, just as the shell does when looking for a program
19209 to run. You can change the value of this variable, for both @value{GDBN}
19210 and your program, using the @code{path} command.
19212 @cindex unlinked object files
19213 @cindex patching object files
19214 You can load unlinked object @file{.o} files into @value{GDBN} using
19215 the @code{file} command. You will not be able to ``run'' an object
19216 file, but you can disassemble functions and inspect variables. Also,
19217 if the underlying BFD functionality supports it, you could use
19218 @kbd{gdb -write} to patch object files using this technique. Note
19219 that @value{GDBN} can neither interpret nor modify relocations in this
19220 case, so branches and some initialized variables will appear to go to
19221 the wrong place. But this feature is still handy from time to time.
19224 @code{file} with no argument makes @value{GDBN} discard any information it
19225 has on both executable file and the symbol table.
19228 @item exec-file @r{[} @var{filename} @r{]}
19229 Specify that the program to be run (but not the symbol table) is found
19230 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19231 if necessary to locate your program. Omitting @var{filename} means to
19232 discard information on the executable file.
19234 @kindex symbol-file
19235 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19236 Read symbol table information from file @var{filename}. @code{PATH} is
19237 searched when necessary. Use the @code{file} command to get both symbol
19238 table and program to run from the same file.
19240 If an optional @var{offset} is specified, it is added to the start
19241 address of each section in the symbol file. This is useful if the
19242 program is relocated at runtime, such as the Linux kernel with kASLR
19245 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19246 program's symbol table.
19248 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19249 some breakpoints and auto-display expressions. This is because they may
19250 contain pointers to the internal data recording symbols and data types,
19251 which are part of the old symbol table data being discarded inside
19254 @code{symbol-file} does not repeat if you press @key{RET} again after
19257 When @value{GDBN} is configured for a particular environment, it
19258 understands debugging information in whatever format is the standard
19259 generated for that environment; you may use either a @sc{gnu} compiler, or
19260 other compilers that adhere to the local conventions.
19261 Best results are usually obtained from @sc{gnu} compilers; for example,
19262 using @code{@value{NGCC}} you can generate debugging information for
19265 For most kinds of object files, with the exception of old SVR3 systems
19266 using COFF, the @code{symbol-file} command does not normally read the
19267 symbol table in full right away. Instead, it scans the symbol table
19268 quickly to find which source files and which symbols are present. The
19269 details are read later, one source file at a time, as they are needed.
19271 The purpose of this two-stage reading strategy is to make @value{GDBN}
19272 start up faster. For the most part, it is invisible except for
19273 occasional pauses while the symbol table details for a particular source
19274 file are being read. (The @code{set verbose} command can turn these
19275 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19276 Warnings and Messages}.)
19278 We have not implemented the two-stage strategy for COFF yet. When the
19279 symbol table is stored in COFF format, @code{symbol-file} reads the
19280 symbol table data in full right away. Note that ``stabs-in-COFF''
19281 still does the two-stage strategy, since the debug info is actually
19285 @cindex reading symbols immediately
19286 @cindex symbols, reading immediately
19287 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19288 @itemx file @r{[} -readnow @r{]} @var{filename}
19289 You can override the @value{GDBN} two-stage strategy for reading symbol
19290 tables by using the @samp{-readnow} option with any of the commands that
19291 load symbol table information, if you want to be sure @value{GDBN} has the
19292 entire symbol table available.
19294 @cindex @code{-readnever}, option for symbol-file command
19295 @cindex never read symbols
19296 @cindex symbols, never read
19297 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19298 @itemx file @r{[} -readnever @r{]} @var{filename}
19299 You can instruct @value{GDBN} to never read the symbolic information
19300 contained in @var{filename} by using the @samp{-readnever} option.
19301 @xref{--readnever}.
19303 @c FIXME: for now no mention of directories, since this seems to be in
19304 @c flux. 13mar1992 status is that in theory GDB would look either in
19305 @c current dir or in same dir as myprog; but issues like competing
19306 @c GDB's, or clutter in system dirs, mean that in practice right now
19307 @c only current dir is used. FFish says maybe a special GDB hierarchy
19308 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19312 @item core-file @r{[}@var{filename}@r{]}
19314 Specify the whereabouts of a core dump file to be used as the ``contents
19315 of memory''. Traditionally, core files contain only some parts of the
19316 address space of the process that generated them; @value{GDBN} can access the
19317 executable file itself for other parts.
19319 @code{core-file} with no argument specifies that no core file is
19322 Note that the core file is ignored when your program is actually running
19323 under @value{GDBN}. So, if you have been running your program and you
19324 wish to debug a core file instead, you must kill the subprocess in which
19325 the program is running. To do this, use the @code{kill} command
19326 (@pxref{Kill Process, ,Killing the Child Process}).
19328 @kindex add-symbol-file
19329 @cindex dynamic linking
19330 @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{]}
19331 The @code{add-symbol-file} command reads additional symbol table
19332 information from the file @var{filename}. You would use this command
19333 when @var{filename} has been dynamically loaded (by some other means)
19334 into the program that is running. The @var{textaddress} parameter gives
19335 the memory address at which the file's text section has been loaded.
19336 You can additionally specify the base address of other sections using
19337 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19338 If a section is omitted, @value{GDBN} will use its default addresses
19339 as found in @var{filename}. Any @var{address} or @var{textaddress}
19340 can be given as an expression.
19342 If an optional @var{offset} is specified, it is added to the start
19343 address of each section, except those for which the address was
19344 specified explicitly.
19346 The symbol table of the file @var{filename} is added to the symbol table
19347 originally read with the @code{symbol-file} command. You can use the
19348 @code{add-symbol-file} command any number of times; the new symbol data
19349 thus read is kept in addition to the old.
19351 Changes can be reverted using the command @code{remove-symbol-file}.
19353 @cindex relocatable object files, reading symbols from
19354 @cindex object files, relocatable, reading symbols from
19355 @cindex reading symbols from relocatable object files
19356 @cindex symbols, reading from relocatable object files
19357 @cindex @file{.o} files, reading symbols from
19358 Although @var{filename} is typically a shared library file, an
19359 executable file, or some other object file which has been fully
19360 relocated for loading into a process, you can also load symbolic
19361 information from relocatable @file{.o} files, as long as:
19365 the file's symbolic information refers only to linker symbols defined in
19366 that file, not to symbols defined by other object files,
19368 every section the file's symbolic information refers to has actually
19369 been loaded into the inferior, as it appears in the file, and
19371 you can determine the address at which every section was loaded, and
19372 provide these to the @code{add-symbol-file} command.
19376 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19377 relocatable files into an already running program; such systems
19378 typically make the requirements above easy to meet. However, it's
19379 important to recognize that many native systems use complex link
19380 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19381 assembly, for example) that make the requirements difficult to meet. In
19382 general, one cannot assume that using @code{add-symbol-file} to read a
19383 relocatable object file's symbolic information will have the same effect
19384 as linking the relocatable object file into the program in the normal
19387 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19389 @kindex remove-symbol-file
19390 @item remove-symbol-file @var{filename}
19391 @item remove-symbol-file -a @var{address}
19392 Remove a symbol file added via the @code{add-symbol-file} command. The
19393 file to remove can be identified by its @var{filename} or by an @var{address}
19394 that lies within the boundaries of this symbol file in memory. Example:
19397 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19398 add symbol table from file "/home/user/gdb/mylib.so" at
19399 .text_addr = 0x7ffff7ff9480
19401 Reading symbols from /home/user/gdb/mylib.so...done.
19402 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19403 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19408 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19410 @kindex add-symbol-file-from-memory
19411 @cindex @code{syscall DSO}
19412 @cindex load symbols from memory
19413 @item add-symbol-file-from-memory @var{address}
19414 Load symbols from the given @var{address} in a dynamically loaded
19415 object file whose image is mapped directly into the inferior's memory.
19416 For example, the Linux kernel maps a @code{syscall DSO} into each
19417 process's address space; this DSO provides kernel-specific code for
19418 some system calls. The argument can be any expression whose
19419 evaluation yields the address of the file's shared object file header.
19420 For this command to work, you must have used @code{symbol-file} or
19421 @code{exec-file} commands in advance.
19424 @item section @var{section} @var{addr}
19425 The @code{section} command changes the base address of the named
19426 @var{section} of the exec file to @var{addr}. This can be used if the
19427 exec file does not contain section addresses, (such as in the
19428 @code{a.out} format), or when the addresses specified in the file
19429 itself are wrong. Each section must be changed separately. The
19430 @code{info files} command, described below, lists all the sections and
19434 @kindex info target
19437 @code{info files} and @code{info target} are synonymous; both print the
19438 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19439 including the names of the executable and core dump files currently in
19440 use by @value{GDBN}, and the files from which symbols were loaded. The
19441 command @code{help target} lists all possible targets rather than
19444 @kindex maint info sections
19445 @item maint info sections
19446 Another command that can give you extra information about program sections
19447 is @code{maint info sections}. In addition to the section information
19448 displayed by @code{info files}, this command displays the flags and file
19449 offset of each section in the executable and core dump files. In addition,
19450 @code{maint info sections} provides the following command options (which
19451 may be arbitrarily combined):
19455 Display sections for all loaded object files, including shared libraries.
19456 @item @var{sections}
19457 Display info only for named @var{sections}.
19458 @item @var{section-flags}
19459 Display info only for sections for which @var{section-flags} are true.
19460 The section flags that @value{GDBN} currently knows about are:
19463 Section will have space allocated in the process when loaded.
19464 Set for all sections except those containing debug information.
19466 Section will be loaded from the file into the child process memory.
19467 Set for pre-initialized code and data, clear for @code{.bss} sections.
19469 Section needs to be relocated before loading.
19471 Section cannot be modified by the child process.
19473 Section contains executable code only.
19475 Section contains data only (no executable code).
19477 Section will reside in ROM.
19479 Section contains data for constructor/destructor lists.
19481 Section is not empty.
19483 An instruction to the linker to not output the section.
19484 @item COFF_SHARED_LIBRARY
19485 A notification to the linker that the section contains
19486 COFF shared library information.
19488 Section contains common symbols.
19491 @kindex set trust-readonly-sections
19492 @cindex read-only sections
19493 @item set trust-readonly-sections on
19494 Tell @value{GDBN} that readonly sections in your object file
19495 really are read-only (i.e.@: that their contents will not change).
19496 In that case, @value{GDBN} can fetch values from these sections
19497 out of the object file, rather than from the target program.
19498 For some targets (notably embedded ones), this can be a significant
19499 enhancement to debugging performance.
19501 The default is off.
19503 @item set trust-readonly-sections off
19504 Tell @value{GDBN} not to trust readonly sections. This means that
19505 the contents of the section might change while the program is running,
19506 and must therefore be fetched from the target when needed.
19508 @item show trust-readonly-sections
19509 Show the current setting of trusting readonly sections.
19512 All file-specifying commands allow both absolute and relative file names
19513 as arguments. @value{GDBN} always converts the file name to an absolute file
19514 name and remembers it that way.
19516 @cindex shared libraries
19517 @anchor{Shared Libraries}
19518 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19519 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19520 DSBT (TIC6X) shared libraries.
19522 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19523 shared libraries. @xref{Expat}.
19525 @value{GDBN} automatically loads symbol definitions from shared libraries
19526 when you use the @code{run} command, or when you examine a core file.
19527 (Before you issue the @code{run} command, @value{GDBN} does not understand
19528 references to a function in a shared library, however---unless you are
19529 debugging a core file).
19531 @c FIXME: some @value{GDBN} release may permit some refs to undef
19532 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19533 @c FIXME...lib; check this from time to time when updating manual
19535 There are times, however, when you may wish to not automatically load
19536 symbol definitions from shared libraries, such as when they are
19537 particularly large or there are many of them.
19539 To control the automatic loading of shared library symbols, use the
19543 @kindex set auto-solib-add
19544 @item set auto-solib-add @var{mode}
19545 If @var{mode} is @code{on}, symbols from all shared object libraries
19546 will be loaded automatically when the inferior begins execution, you
19547 attach to an independently started inferior, or when the dynamic linker
19548 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19549 is @code{off}, symbols must be loaded manually, using the
19550 @code{sharedlibrary} command. The default value is @code{on}.
19552 @cindex memory used for symbol tables
19553 If your program uses lots of shared libraries with debug info that
19554 takes large amounts of memory, you can decrease the @value{GDBN}
19555 memory footprint by preventing it from automatically loading the
19556 symbols from shared libraries. To that end, type @kbd{set
19557 auto-solib-add off} before running the inferior, then load each
19558 library whose debug symbols you do need with @kbd{sharedlibrary
19559 @var{regexp}}, where @var{regexp} is a regular expression that matches
19560 the libraries whose symbols you want to be loaded.
19562 @kindex show auto-solib-add
19563 @item show auto-solib-add
19564 Display the current autoloading mode.
19567 @cindex load shared library
19568 To explicitly load shared library symbols, use the @code{sharedlibrary}
19572 @kindex info sharedlibrary
19574 @item info share @var{regex}
19575 @itemx info sharedlibrary @var{regex}
19576 Print the names of the shared libraries which are currently loaded
19577 that match @var{regex}. If @var{regex} is omitted then print
19578 all shared libraries that are loaded.
19581 @item info dll @var{regex}
19582 This is an alias of @code{info sharedlibrary}.
19584 @kindex sharedlibrary
19586 @item sharedlibrary @var{regex}
19587 @itemx share @var{regex}
19588 Load shared object library symbols for files matching a
19589 Unix regular expression.
19590 As with files loaded automatically, it only loads shared libraries
19591 required by your program for a core file or after typing @code{run}. If
19592 @var{regex} is omitted all shared libraries required by your program are
19595 @item nosharedlibrary
19596 @kindex nosharedlibrary
19597 @cindex unload symbols from shared libraries
19598 Unload all shared object library symbols. This discards all symbols
19599 that have been loaded from all shared libraries. Symbols from shared
19600 libraries that were loaded by explicit user requests are not
19604 Sometimes you may wish that @value{GDBN} stops and gives you control
19605 when any of shared library events happen. The best way to do this is
19606 to use @code{catch load} and @code{catch unload} (@pxref{Set
19609 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19610 command for this. This command exists for historical reasons. It is
19611 less useful than setting a catchpoint, because it does not allow for
19612 conditions or commands as a catchpoint does.
19615 @item set stop-on-solib-events
19616 @kindex set stop-on-solib-events
19617 This command controls whether @value{GDBN} should give you control
19618 when the dynamic linker notifies it about some shared library event.
19619 The most common event of interest is loading or unloading of a new
19622 @item show stop-on-solib-events
19623 @kindex show stop-on-solib-events
19624 Show whether @value{GDBN} stops and gives you control when shared
19625 library events happen.
19628 Shared libraries are also supported in many cross or remote debugging
19629 configurations. @value{GDBN} needs to have access to the target's libraries;
19630 this can be accomplished either by providing copies of the libraries
19631 on the host system, or by asking @value{GDBN} to automatically retrieve the
19632 libraries from the target. If copies of the target libraries are
19633 provided, they need to be the same as the target libraries, although the
19634 copies on the target can be stripped as long as the copies on the host are
19637 @cindex where to look for shared libraries
19638 For remote debugging, you need to tell @value{GDBN} where the target
19639 libraries are, so that it can load the correct copies---otherwise, it
19640 may try to load the host's libraries. @value{GDBN} has two variables
19641 to specify the search directories for target libraries.
19644 @cindex prefix for executable and shared library file names
19645 @cindex system root, alternate
19646 @kindex set solib-absolute-prefix
19647 @kindex set sysroot
19648 @item set sysroot @var{path}
19649 Use @var{path} as the system root for the program being debugged. Any
19650 absolute shared library paths will be prefixed with @var{path}; many
19651 runtime loaders store the absolute paths to the shared library in the
19652 target program's memory. When starting processes remotely, and when
19653 attaching to already-running processes (local or remote), their
19654 executable filenames will be prefixed with @var{path} if reported to
19655 @value{GDBN} as absolute by the operating system. If you use
19656 @code{set sysroot} to find executables and shared libraries, they need
19657 to be laid out in the same way that they are on the target, with
19658 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19661 If @var{path} starts with the sequence @file{target:} and the target
19662 system is remote then @value{GDBN} will retrieve the target binaries
19663 from the remote system. This is only supported when using a remote
19664 target that supports the @code{remote get} command (@pxref{File
19665 Transfer,,Sending files to a remote system}). The part of @var{path}
19666 following the initial @file{target:} (if present) is used as system
19667 root prefix on the remote file system. If @var{path} starts with the
19668 sequence @file{remote:} this is converted to the sequence
19669 @file{target:} by @code{set sysroot}@footnote{Historically the
19670 functionality to retrieve binaries from the remote system was
19671 provided by prefixing @var{path} with @file{remote:}}. If you want
19672 to specify a local system root using a directory that happens to be
19673 named @file{target:} or @file{remote:}, you need to use some
19674 equivalent variant of the name like @file{./target:}.
19676 For targets with an MS-DOS based filesystem, such as MS-Windows and
19677 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19678 absolute file name with @var{path}. But first, on Unix hosts,
19679 @value{GDBN} converts all backslash directory separators into forward
19680 slashes, because the backslash is not a directory separator on Unix:
19683 c:\foo\bar.dll @result{} c:/foo/bar.dll
19686 Then, @value{GDBN} attempts prefixing the target file name with
19687 @var{path}, and looks for the resulting file name in the host file
19691 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19694 If that does not find the binary, @value{GDBN} tries removing
19695 the @samp{:} character from the drive spec, both for convenience, and,
19696 for the case of the host file system not supporting file names with
19700 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19703 This makes it possible to have a system root that mirrors a target
19704 with more than one drive. E.g., you may want to setup your local
19705 copies of the target system shared libraries like so (note @samp{c} vs
19709 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19710 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19711 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19715 and point the system root at @file{/path/to/sysroot}, so that
19716 @value{GDBN} can find the correct copies of both
19717 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19719 If that still does not find the binary, @value{GDBN} tries
19720 removing the whole drive spec from the target file name:
19723 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19726 This last lookup makes it possible to not care about the drive name,
19727 if you don't want or need to.
19729 The @code{set solib-absolute-prefix} command is an alias for @code{set
19732 @cindex default system root
19733 @cindex @samp{--with-sysroot}
19734 You can set the default system root by using the configure-time
19735 @samp{--with-sysroot} option. If the system root is inside
19736 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19737 @samp{--exec-prefix}), then the default system root will be updated
19738 automatically if the installed @value{GDBN} is moved to a new
19741 @kindex show sysroot
19743 Display the current executable and shared library prefix.
19745 @kindex set solib-search-path
19746 @item set solib-search-path @var{path}
19747 If this variable is set, @var{path} is a colon-separated list of
19748 directories to search for shared libraries. @samp{solib-search-path}
19749 is used after @samp{sysroot} fails to locate the library, or if the
19750 path to the library is relative instead of absolute. If you want to
19751 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19752 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19753 finding your host's libraries. @samp{sysroot} is preferred; setting
19754 it to a nonexistent directory may interfere with automatic loading
19755 of shared library symbols.
19757 @kindex show solib-search-path
19758 @item show solib-search-path
19759 Display the current shared library search path.
19761 @cindex DOS file-name semantics of file names.
19762 @kindex set target-file-system-kind (unix|dos-based|auto)
19763 @kindex show target-file-system-kind
19764 @item set target-file-system-kind @var{kind}
19765 Set assumed file system kind for target reported file names.
19767 Shared library file names as reported by the target system may not
19768 make sense as is on the system @value{GDBN} is running on. For
19769 example, when remote debugging a target that has MS-DOS based file
19770 system semantics, from a Unix host, the target may be reporting to
19771 @value{GDBN} a list of loaded shared libraries with file names such as
19772 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19773 drive letters, so the @samp{c:\} prefix is not normally understood as
19774 indicating an absolute file name, and neither is the backslash
19775 normally considered a directory separator character. In that case,
19776 the native file system would interpret this whole absolute file name
19777 as a relative file name with no directory components. This would make
19778 it impossible to point @value{GDBN} at a copy of the remote target's
19779 shared libraries on the host using @code{set sysroot}, and impractical
19780 with @code{set solib-search-path}. Setting
19781 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19782 to interpret such file names similarly to how the target would, and to
19783 map them to file names valid on @value{GDBN}'s native file system
19784 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19785 to one of the supported file system kinds. In that case, @value{GDBN}
19786 tries to determine the appropriate file system variant based on the
19787 current target's operating system (@pxref{ABI, ,Configuring the
19788 Current ABI}). The supported file system settings are:
19792 Instruct @value{GDBN} to assume the target file system is of Unix
19793 kind. Only file names starting the forward slash (@samp{/}) character
19794 are considered absolute, and the directory separator character is also
19798 Instruct @value{GDBN} to assume the target file system is DOS based.
19799 File names starting with either a forward slash, or a drive letter
19800 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19801 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19802 considered directory separators.
19805 Instruct @value{GDBN} to use the file system kind associated with the
19806 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19807 This is the default.
19811 @cindex file name canonicalization
19812 @cindex base name differences
19813 When processing file names provided by the user, @value{GDBN}
19814 frequently needs to compare them to the file names recorded in the
19815 program's debug info. Normally, @value{GDBN} compares just the
19816 @dfn{base names} of the files as strings, which is reasonably fast
19817 even for very large programs. (The base name of a file is the last
19818 portion of its name, after stripping all the leading directories.)
19819 This shortcut in comparison is based upon the assumption that files
19820 cannot have more than one base name. This is usually true, but
19821 references to files that use symlinks or similar filesystem
19822 facilities violate that assumption. If your program records files
19823 using such facilities, or if you provide file names to @value{GDBN}
19824 using symlinks etc., you can set @code{basenames-may-differ} to
19825 @code{true} to instruct @value{GDBN} to completely canonicalize each
19826 pair of file names it needs to compare. This will make file-name
19827 comparisons accurate, but at a price of a significant slowdown.
19830 @item set basenames-may-differ
19831 @kindex set basenames-may-differ
19832 Set whether a source file may have multiple base names.
19834 @item show basenames-may-differ
19835 @kindex show basenames-may-differ
19836 Show whether a source file may have multiple base names.
19840 @section File Caching
19841 @cindex caching of opened files
19842 @cindex caching of bfd objects
19844 To speed up file loading, and reduce memory usage, @value{GDBN} will
19845 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19846 BFD, bfd, The Binary File Descriptor Library}. The following commands
19847 allow visibility and control of the caching behavior.
19850 @kindex maint info bfds
19851 @item maint info bfds
19852 This prints information about each @code{bfd} object that is known to
19855 @kindex maint set bfd-sharing
19856 @kindex maint show bfd-sharing
19857 @kindex bfd caching
19858 @item maint set bfd-sharing
19859 @item maint show bfd-sharing
19860 Control whether @code{bfd} objects can be shared. When sharing is
19861 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19862 than reopening the same file. Turning sharing off does not cause
19863 already shared @code{bfd} objects to be unshared, but all future files
19864 that are opened will create a new @code{bfd} object. Similarly,
19865 re-enabling sharing does not cause multiple existing @code{bfd}
19866 objects to be collapsed into a single shared @code{bfd} object.
19868 @kindex set debug bfd-cache @var{level}
19869 @kindex bfd caching
19870 @item set debug bfd-cache @var{level}
19871 Turns on debugging of the bfd cache, setting the level to @var{level}.
19873 @kindex show debug bfd-cache
19874 @kindex bfd caching
19875 @item show debug bfd-cache
19876 Show the current debugging level of the bfd cache.
19879 @node Separate Debug Files
19880 @section Debugging Information in Separate Files
19881 @cindex separate debugging information files
19882 @cindex debugging information in separate files
19883 @cindex @file{.debug} subdirectories
19884 @cindex debugging information directory, global
19885 @cindex global debugging information directories
19886 @cindex build ID, and separate debugging files
19887 @cindex @file{.build-id} directory
19889 @value{GDBN} allows you to put a program's debugging information in a
19890 file separate from the executable itself, in a way that allows
19891 @value{GDBN} to find and load the debugging information automatically.
19892 Since debugging information can be very large---sometimes larger
19893 than the executable code itself---some systems distribute debugging
19894 information for their executables in separate files, which users can
19895 install only when they need to debug a problem.
19897 @value{GDBN} supports two ways of specifying the separate debug info
19902 The executable contains a @dfn{debug link} that specifies the name of
19903 the separate debug info file. The separate debug file's name is
19904 usually @file{@var{executable}.debug}, where @var{executable} is the
19905 name of the corresponding executable file without leading directories
19906 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19907 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19908 checksum for the debug file, which @value{GDBN} uses to validate that
19909 the executable and the debug file came from the same build.
19912 The executable contains a @dfn{build ID}, a unique bit string that is
19913 also present in the corresponding debug info file. (This is supported
19914 only on some operating systems, when using the ELF or PE file formats
19915 for binary files and the @sc{gnu} Binutils.) For more details about
19916 this feature, see the description of the @option{--build-id}
19917 command-line option in @ref{Options, , Command Line Options, ld,
19918 The GNU Linker}. The debug info file's name is not specified
19919 explicitly by the build ID, but can be computed from the build ID, see
19923 Depending on the way the debug info file is specified, @value{GDBN}
19924 uses two different methods of looking for the debug file:
19928 For the ``debug link'' method, @value{GDBN} looks up the named file in
19929 the directory of the executable file, then in a subdirectory of that
19930 directory named @file{.debug}, and finally under each one of the global debug
19931 directories, in a subdirectory whose name is identical to the leading
19932 directories of the executable's absolute file name.
19935 For the ``build ID'' method, @value{GDBN} looks in the
19936 @file{.build-id} subdirectory of each one of the global debug directories for
19937 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19938 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19939 are the rest of the bit string. (Real build ID strings are 32 or more
19940 hex characters, not 10.)
19943 So, for example, suppose you ask @value{GDBN} to debug
19944 @file{/usr/bin/ls}, which has a debug link that specifies the
19945 file @file{ls.debug}, and a build ID whose value in hex is
19946 @code{abcdef1234}. If the list of the global debug directories includes
19947 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19948 debug information files, in the indicated order:
19952 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19954 @file{/usr/bin/ls.debug}
19956 @file{/usr/bin/.debug/ls.debug}
19958 @file{/usr/lib/debug/usr/bin/ls.debug}.
19961 @anchor{debug-file-directory}
19962 Global debugging info directories default to what is set by @value{GDBN}
19963 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19964 you can also set the global debugging info directories, and view the list
19965 @value{GDBN} is currently using.
19969 @kindex set debug-file-directory
19970 @item set debug-file-directory @var{directories}
19971 Set the directories which @value{GDBN} searches for separate debugging
19972 information files to @var{directory}. Multiple path components can be set
19973 concatenating them by a path separator.
19975 @kindex show debug-file-directory
19976 @item show debug-file-directory
19977 Show the directories @value{GDBN} searches for separate debugging
19982 @cindex @code{.gnu_debuglink} sections
19983 @cindex debug link sections
19984 A debug link is a special section of the executable file named
19985 @code{.gnu_debuglink}. The section must contain:
19989 A filename, with any leading directory components removed, followed by
19992 zero to three bytes of padding, as needed to reach the next four-byte
19993 boundary within the section, and
19995 a four-byte CRC checksum, stored in the same endianness used for the
19996 executable file itself. The checksum is computed on the debugging
19997 information file's full contents by the function given below, passing
19998 zero as the @var{crc} argument.
20001 Any executable file format can carry a debug link, as long as it can
20002 contain a section named @code{.gnu_debuglink} with the contents
20005 @cindex @code{.note.gnu.build-id} sections
20006 @cindex build ID sections
20007 The build ID is a special section in the executable file (and in other
20008 ELF binary files that @value{GDBN} may consider). This section is
20009 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20010 It contains unique identification for the built files---the ID remains
20011 the same across multiple builds of the same build tree. The default
20012 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20013 content for the build ID string. The same section with an identical
20014 value is present in the original built binary with symbols, in its
20015 stripped variant, and in the separate debugging information file.
20017 The debugging information file itself should be an ordinary
20018 executable, containing a full set of linker symbols, sections, and
20019 debugging information. The sections of the debugging information file
20020 should have the same names, addresses, and sizes as the original file,
20021 but they need not contain any data---much like a @code{.bss} section
20022 in an ordinary executable.
20024 The @sc{gnu} binary utilities (Binutils) package includes the
20025 @samp{objcopy} utility that can produce
20026 the separated executable / debugging information file pairs using the
20027 following commands:
20030 @kbd{objcopy --only-keep-debug foo foo.debug}
20035 These commands remove the debugging
20036 information from the executable file @file{foo} and place it in the file
20037 @file{foo.debug}. You can use the first, second or both methods to link the
20042 The debug link method needs the following additional command to also leave
20043 behind a debug link in @file{foo}:
20046 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20049 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20050 a version of the @code{strip} command such that the command @kbd{strip foo -f
20051 foo.debug} has the same functionality as the two @code{objcopy} commands and
20052 the @code{ln -s} command above, together.
20055 Build ID gets embedded into the main executable using @code{ld --build-id} or
20056 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20057 compatibility fixes for debug files separation are present in @sc{gnu} binary
20058 utilities (Binutils) package since version 2.18.
20063 @cindex CRC algorithm definition
20064 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20065 IEEE 802.3 using the polynomial:
20067 @c TexInfo requires naked braces for multi-digit exponents for Tex
20068 @c output, but this causes HTML output to barf. HTML has to be set using
20069 @c raw commands. So we end up having to specify this equation in 2
20074 <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>
20075 + <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
20081 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20082 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20086 The function is computed byte at a time, taking the least
20087 significant bit of each byte first. The initial pattern
20088 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20089 the final result is inverted to ensure trailing zeros also affect the
20092 @emph{Note:} This is the same CRC polynomial as used in handling the
20093 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20094 However in the case of the Remote Serial Protocol, the CRC is computed
20095 @emph{most} significant bit first, and the result is not inverted, so
20096 trailing zeros have no effect on the CRC value.
20098 To complete the description, we show below the code of the function
20099 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20100 initially supplied @code{crc} argument means that an initial call to
20101 this function passing in zero will start computing the CRC using
20104 @kindex gnu_debuglink_crc32
20107 gnu_debuglink_crc32 (unsigned long crc,
20108 unsigned char *buf, size_t len)
20110 static const unsigned long crc32_table[256] =
20112 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20113 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20114 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20115 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20116 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20117 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20118 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20119 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20120 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20121 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20122 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20123 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20124 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20125 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20126 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20127 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20128 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20129 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20130 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20131 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20132 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20133 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20134 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20135 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20136 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20137 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20138 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20139 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20140 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20141 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20142 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20143 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20144 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20145 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20146 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20147 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20148 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20149 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20150 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20151 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20152 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20153 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20154 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20155 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20156 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20157 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20158 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20159 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20160 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20161 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20162 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20165 unsigned char *end;
20167 crc = ~crc & 0xffffffff;
20168 for (end = buf + len; buf < end; ++buf)
20169 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20170 return ~crc & 0xffffffff;
20175 This computation does not apply to the ``build ID'' method.
20177 @node MiniDebugInfo
20178 @section Debugging information in a special section
20179 @cindex separate debug sections
20180 @cindex @samp{.gnu_debugdata} section
20182 Some systems ship pre-built executables and libraries that have a
20183 special @samp{.gnu_debugdata} section. This feature is called
20184 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20185 is used to supply extra symbols for backtraces.
20187 The intent of this section is to provide extra minimal debugging
20188 information for use in simple backtraces. It is not intended to be a
20189 replacement for full separate debugging information (@pxref{Separate
20190 Debug Files}). The example below shows the intended use; however,
20191 @value{GDBN} does not currently put restrictions on what sort of
20192 debugging information might be included in the section.
20194 @value{GDBN} has support for this extension. If the section exists,
20195 then it is used provided that no other source of debugging information
20196 can be found, and that @value{GDBN} was configured with LZMA support.
20198 This section can be easily created using @command{objcopy} and other
20199 standard utilities:
20202 # Extract the dynamic symbols from the main binary, there is no need
20203 # to also have these in the normal symbol table.
20204 nm -D @var{binary} --format=posix --defined-only \
20205 | awk '@{ print $1 @}' | sort > dynsyms
20207 # Extract all the text (i.e. function) symbols from the debuginfo.
20208 # (Note that we actually also accept "D" symbols, for the benefit
20209 # of platforms like PowerPC64 that use function descriptors.)
20210 nm @var{binary} --format=posix --defined-only \
20211 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20214 # Keep all the function symbols not already in the dynamic symbol
20216 comm -13 dynsyms funcsyms > keep_symbols
20218 # Separate full debug info into debug binary.
20219 objcopy --only-keep-debug @var{binary} debug
20221 # Copy the full debuginfo, keeping only a minimal set of symbols and
20222 # removing some unnecessary sections.
20223 objcopy -S --remove-section .gdb_index --remove-section .comment \
20224 --keep-symbols=keep_symbols debug mini_debuginfo
20226 # Drop the full debug info from the original binary.
20227 strip --strip-all -R .comment @var{binary}
20229 # Inject the compressed data into the .gnu_debugdata section of the
20232 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20236 @section Index Files Speed Up @value{GDBN}
20237 @cindex index files
20238 @cindex @samp{.gdb_index} section
20240 When @value{GDBN} finds a symbol file, it scans the symbols in the
20241 file in order to construct an internal symbol table. This lets most
20242 @value{GDBN} operations work quickly---at the cost of a delay early
20243 on. For large programs, this delay can be quite lengthy, so
20244 @value{GDBN} provides a way to build an index, which speeds up
20247 For convenience, @value{GDBN} comes with a program,
20248 @command{gdb-add-index}, which can be used to add the index to a
20249 symbol file. It takes the symbol file as its only argument:
20252 $ gdb-add-index symfile
20255 @xref{gdb-add-index}.
20257 It is also possible to do the work manually. Here is what
20258 @command{gdb-add-index} does behind the curtains.
20260 The index is stored as a section in the symbol file. @value{GDBN} can
20261 write the index to a file, then you can put it into the symbol file
20262 using @command{objcopy}.
20264 To create an index file, use the @code{save gdb-index} command:
20267 @item save gdb-index [-dwarf-5] @var{directory}
20268 @kindex save gdb-index
20269 Create index files for all symbol files currently known by
20270 @value{GDBN}. For each known @var{symbol-file}, this command by
20271 default creates it produces a single file
20272 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20273 the @option{-dwarf-5} option, it produces 2 files:
20274 @file{@var{symbol-file}.debug_names} and
20275 @file{@var{symbol-file}.debug_str}. The files are created in the
20276 given @var{directory}.
20279 Once you have created an index file you can merge it into your symbol
20280 file, here named @file{symfile}, using @command{objcopy}:
20283 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20284 --set-section-flags .gdb_index=readonly symfile symfile
20287 Or for @code{-dwarf-5}:
20290 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20291 $ cat symfile.debug_str >>symfile.debug_str.new
20292 $ objcopy --add-section .debug_names=symfile.gdb-index \
20293 --set-section-flags .debug_names=readonly \
20294 --update-section .debug_str=symfile.debug_str.new symfile symfile
20297 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20298 sections that have been deprecated. Usually they are deprecated because
20299 they are missing a new feature or have performance issues.
20300 To tell @value{GDBN} to use a deprecated index section anyway
20301 specify @code{set use-deprecated-index-sections on}.
20302 The default is @code{off}.
20303 This can speed up startup, but may result in some functionality being lost.
20304 @xref{Index Section Format}.
20306 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20307 must be done before gdb reads the file. The following will not work:
20310 $ gdb -ex "set use-deprecated-index-sections on" <program>
20313 Instead you must do, for example,
20316 $ gdb -iex "set use-deprecated-index-sections on" <program>
20319 There are currently some limitation on indices. They only work when
20320 for DWARF debugging information, not stabs. And, they do not
20321 currently work for programs using Ada.
20323 @subsection Automatic symbol index cache
20325 It is possible for @value{GDBN} to automatically save a copy of this index in a
20326 cache on disk and retrieve it from there when loading the same binary in the
20327 future. This feature can be turned on with @kbd{set index-cache on}. The
20328 following commands can be used to tweak the behavior of the index cache.
20332 @item set index-cache on
20333 @itemx set index-cache off
20334 Enable or disable the use of the symbol index cache.
20336 @item set index-cache directory @var{directory}
20337 @itemx show index-cache directory
20338 Set/show the directory where index files will be saved.
20340 The default value for this directory depends on the host platform. On
20341 most systems, the index is cached in the @file{gdb} subdirectory of
20342 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20343 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20344 of your home directory. However, on some systems, the default may
20345 differ according to local convention.
20347 There is no limit on the disk space used by index cache. It is perfectly safe
20348 to delete the content of that directory to free up disk space.
20350 @item show index-cache stats
20351 Print the number of cache hits and misses since the launch of @value{GDBN}.
20355 @node Symbol Errors
20356 @section Errors Reading Symbol Files
20358 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20359 such as symbol types it does not recognize, or known bugs in compiler
20360 output. By default, @value{GDBN} does not notify you of such problems, since
20361 they are relatively common and primarily of interest to people
20362 debugging compilers. If you are interested in seeing information
20363 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20364 only one message about each such type of problem, no matter how many
20365 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20366 to see how many times the problems occur, with the @code{set
20367 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20370 The messages currently printed, and their meanings, include:
20373 @item inner block not inside outer block in @var{symbol}
20375 The symbol information shows where symbol scopes begin and end
20376 (such as at the start of a function or a block of statements). This
20377 error indicates that an inner scope block is not fully contained
20378 in its outer scope blocks.
20380 @value{GDBN} circumvents the problem by treating the inner block as if it had
20381 the same scope as the outer block. In the error message, @var{symbol}
20382 may be shown as ``@code{(don't know)}'' if the outer block is not a
20385 @item block at @var{address} out of order
20387 The symbol information for symbol scope blocks should occur in
20388 order of increasing addresses. This error indicates that it does not
20391 @value{GDBN} does not circumvent this problem, and has trouble
20392 locating symbols in the source file whose symbols it is reading. (You
20393 can often determine what source file is affected by specifying
20394 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20397 @item bad block start address patched
20399 The symbol information for a symbol scope block has a start address
20400 smaller than the address of the preceding source line. This is known
20401 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20403 @value{GDBN} circumvents the problem by treating the symbol scope block as
20404 starting on the previous source line.
20406 @item bad string table offset in symbol @var{n}
20409 Symbol number @var{n} contains a pointer into the string table which is
20410 larger than the size of the string table.
20412 @value{GDBN} circumvents the problem by considering the symbol to have the
20413 name @code{foo}, which may cause other problems if many symbols end up
20416 @item unknown symbol type @code{0x@var{nn}}
20418 The symbol information contains new data types that @value{GDBN} does
20419 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20420 uncomprehended information, in hexadecimal.
20422 @value{GDBN} circumvents the error by ignoring this symbol information.
20423 This usually allows you to debug your program, though certain symbols
20424 are not accessible. If you encounter such a problem and feel like
20425 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20426 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20427 and examine @code{*bufp} to see the symbol.
20429 @item stub type has NULL name
20431 @value{GDBN} could not find the full definition for a struct or class.
20433 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20434 The symbol information for a C@t{++} member function is missing some
20435 information that recent versions of the compiler should have output for
20438 @item info mismatch between compiler and debugger
20440 @value{GDBN} could not parse a type specification output by the compiler.
20445 @section GDB Data Files
20447 @cindex prefix for data files
20448 @value{GDBN} will sometimes read an auxiliary data file. These files
20449 are kept in a directory known as the @dfn{data directory}.
20451 You can set the data directory's name, and view the name @value{GDBN}
20452 is currently using.
20455 @kindex set data-directory
20456 @item set data-directory @var{directory}
20457 Set the directory which @value{GDBN} searches for auxiliary data files
20458 to @var{directory}.
20460 @kindex show data-directory
20461 @item show data-directory
20462 Show the directory @value{GDBN} searches for auxiliary data files.
20465 @cindex default data directory
20466 @cindex @samp{--with-gdb-datadir}
20467 You can set the default data directory by using the configure-time
20468 @samp{--with-gdb-datadir} option. If the data directory is inside
20469 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20470 @samp{--exec-prefix}), then the default data directory will be updated
20471 automatically if the installed @value{GDBN} is moved to a new
20474 The data directory may also be specified with the
20475 @code{--data-directory} command line option.
20476 @xref{Mode Options}.
20479 @chapter Specifying a Debugging Target
20481 @cindex debugging target
20482 A @dfn{target} is the execution environment occupied by your program.
20484 Often, @value{GDBN} runs in the same host environment as your program;
20485 in that case, the debugging target is specified as a side effect when
20486 you use the @code{file} or @code{core} commands. When you need more
20487 flexibility---for example, running @value{GDBN} on a physically separate
20488 host, or controlling a standalone system over a serial port or a
20489 realtime system over a TCP/IP connection---you can use the @code{target}
20490 command to specify one of the target types configured for @value{GDBN}
20491 (@pxref{Target Commands, ,Commands for Managing Targets}).
20493 @cindex target architecture
20494 It is possible to build @value{GDBN} for several different @dfn{target
20495 architectures}. When @value{GDBN} is built like that, you can choose
20496 one of the available architectures with the @kbd{set architecture}
20500 @kindex set architecture
20501 @kindex show architecture
20502 @item set architecture @var{arch}
20503 This command sets the current target architecture to @var{arch}. The
20504 value of @var{arch} can be @code{"auto"}, in addition to one of the
20505 supported architectures.
20507 @item show architecture
20508 Show the current target architecture.
20510 @item set processor
20512 @kindex set processor
20513 @kindex show processor
20514 These are alias commands for, respectively, @code{set architecture}
20515 and @code{show architecture}.
20519 * Active Targets:: Active targets
20520 * Target Commands:: Commands for managing targets
20521 * Byte Order:: Choosing target byte order
20524 @node Active Targets
20525 @section Active Targets
20527 @cindex stacking targets
20528 @cindex active targets
20529 @cindex multiple targets
20531 There are multiple classes of targets such as: processes, executable files or
20532 recording sessions. Core files belong to the process class, making core file
20533 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20534 on multiple active targets, one in each class. This allows you to (for
20535 example) start a process and inspect its activity, while still having access to
20536 the executable file after the process finishes. Or if you start process
20537 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20538 presented a virtual layer of the recording target, while the process target
20539 remains stopped at the chronologically last point of the process execution.
20541 Use the @code{core-file} and @code{exec-file} commands to select a new core
20542 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20543 specify as a target a process that is already running, use the @code{attach}
20544 command (@pxref{Attach, ,Debugging an Already-running Process}).
20546 @node Target Commands
20547 @section Commands for Managing Targets
20550 @item target @var{type} @var{parameters}
20551 Connects the @value{GDBN} host environment to a target machine or
20552 process. A target is typically a protocol for talking to debugging
20553 facilities. You use the argument @var{type} to specify the type or
20554 protocol of the target machine.
20556 Further @var{parameters} are interpreted by the target protocol, but
20557 typically include things like device names or host names to connect
20558 with, process numbers, and baud rates.
20560 The @code{target} command does not repeat if you press @key{RET} again
20561 after executing the command.
20563 @kindex help target
20565 Displays the names of all targets available. To display targets
20566 currently selected, use either @code{info target} or @code{info files}
20567 (@pxref{Files, ,Commands to Specify Files}).
20569 @item help target @var{name}
20570 Describe a particular target, including any parameters necessary to
20573 @kindex set gnutarget
20574 @item set gnutarget @var{args}
20575 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20576 knows whether it is reading an @dfn{executable},
20577 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20578 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20579 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20582 @emph{Warning:} To specify a file format with @code{set gnutarget},
20583 you must know the actual BFD name.
20587 @xref{Files, , Commands to Specify Files}.
20589 @kindex show gnutarget
20590 @item show gnutarget
20591 Use the @code{show gnutarget} command to display what file format
20592 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20593 @value{GDBN} will determine the file format for each file automatically,
20594 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20597 @cindex common targets
20598 Here are some common targets (available, or not, depending on the GDB
20603 @item target exec @var{program}
20604 @cindex executable file target
20605 An executable file. @samp{target exec @var{program}} is the same as
20606 @samp{exec-file @var{program}}.
20608 @item target core @var{filename}
20609 @cindex core dump file target
20610 A core dump file. @samp{target core @var{filename}} is the same as
20611 @samp{core-file @var{filename}}.
20613 @item target remote @var{medium}
20614 @cindex remote target
20615 A remote system connected to @value{GDBN} via a serial line or network
20616 connection. This command tells @value{GDBN} to use its own remote
20617 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20619 For example, if you have a board connected to @file{/dev/ttya} on the
20620 machine running @value{GDBN}, you could say:
20623 target remote /dev/ttya
20626 @code{target remote} supports the @code{load} command. This is only
20627 useful if you have some other way of getting the stub to the target
20628 system, and you can put it somewhere in memory where it won't get
20629 clobbered by the download.
20631 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20632 @cindex built-in simulator target
20633 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20641 works; however, you cannot assume that a specific memory map, device
20642 drivers, or even basic I/O is available, although some simulators do
20643 provide these. For info about any processor-specific simulator details,
20644 see the appropriate section in @ref{Embedded Processors, ,Embedded
20647 @item target native
20648 @cindex native target
20649 Setup for local/native process debugging. Useful to make the
20650 @code{run} command spawn native processes (likewise @code{attach},
20651 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20652 (@pxref{set auto-connect-native-target}).
20656 Different targets are available on different configurations of @value{GDBN};
20657 your configuration may have more or fewer targets.
20659 Many remote targets require you to download the executable's code once
20660 you've successfully established a connection. You may wish to control
20661 various aspects of this process.
20666 @kindex set hash@r{, for remote monitors}
20667 @cindex hash mark while downloading
20668 This command controls whether a hash mark @samp{#} is displayed while
20669 downloading a file to the remote monitor. If on, a hash mark is
20670 displayed after each S-record is successfully downloaded to the
20674 @kindex show hash@r{, for remote monitors}
20675 Show the current status of displaying the hash mark.
20677 @item set debug monitor
20678 @kindex set debug monitor
20679 @cindex display remote monitor communications
20680 Enable or disable display of communications messages between
20681 @value{GDBN} and the remote monitor.
20683 @item show debug monitor
20684 @kindex show debug monitor
20685 Show the current status of displaying communications between
20686 @value{GDBN} and the remote monitor.
20691 @kindex load @var{filename} @var{offset}
20692 @item load @var{filename} @var{offset}
20694 Depending on what remote debugging facilities are configured into
20695 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20696 is meant to make @var{filename} (an executable) available for debugging
20697 on the remote system---by downloading, or dynamic linking, for example.
20698 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20699 the @code{add-symbol-file} command.
20701 If your @value{GDBN} does not have a @code{load} command, attempting to
20702 execute it gets the error message ``@code{You can't do that when your
20703 target is @dots{}}''
20705 The file is loaded at whatever address is specified in the executable.
20706 For some object file formats, you can specify the load address when you
20707 link the program; for other formats, like a.out, the object file format
20708 specifies a fixed address.
20709 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20711 It is also possible to tell @value{GDBN} to load the executable file at a
20712 specific offset described by the optional argument @var{offset}. When
20713 @var{offset} is provided, @var{filename} must also be provided.
20715 Depending on the remote side capabilities, @value{GDBN} may be able to
20716 load programs into flash memory.
20718 @code{load} does not repeat if you press @key{RET} again after using it.
20723 @kindex flash-erase
20725 @anchor{flash-erase}
20727 Erases all known flash memory regions on the target.
20732 @section Choosing Target Byte Order
20734 @cindex choosing target byte order
20735 @cindex target byte order
20737 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20738 offer the ability to run either big-endian or little-endian byte
20739 orders. Usually the executable or symbol will include a bit to
20740 designate the endian-ness, and you will not need to worry about
20741 which to use. However, you may still find it useful to adjust
20742 @value{GDBN}'s idea of processor endian-ness manually.
20746 @item set endian big
20747 Instruct @value{GDBN} to assume the target is big-endian.
20749 @item set endian little
20750 Instruct @value{GDBN} to assume the target is little-endian.
20752 @item set endian auto
20753 Instruct @value{GDBN} to use the byte order associated with the
20757 Display @value{GDBN}'s current idea of the target byte order.
20761 If the @code{set endian auto} mode is in effect and no executable has
20762 been selected, then the endianness used is the last one chosen either
20763 by one of the @code{set endian big} and @code{set endian little}
20764 commands or by inferring from the last executable used. If no
20765 endianness has been previously chosen, then the default for this mode
20766 is inferred from the target @value{GDBN} has been built for, and is
20767 @code{little} if the name of the target CPU has an @code{el} suffix
20768 and @code{big} otherwise.
20770 Note that these commands merely adjust interpretation of symbolic
20771 data on the host, and that they have absolutely no effect on the
20775 @node Remote Debugging
20776 @chapter Debugging Remote Programs
20777 @cindex remote debugging
20779 If you are trying to debug a program running on a machine that cannot run
20780 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20781 For example, you might use remote debugging on an operating system kernel,
20782 or on a small system which does not have a general purpose operating system
20783 powerful enough to run a full-featured debugger.
20785 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20786 to make this work with particular debugging targets. In addition,
20787 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20788 but not specific to any particular target system) which you can use if you
20789 write the remote stubs---the code that runs on the remote system to
20790 communicate with @value{GDBN}.
20792 Other remote targets may be available in your
20793 configuration of @value{GDBN}; use @code{help target} to list them.
20796 * Connecting:: Connecting to a remote target
20797 * File Transfer:: Sending files to a remote system
20798 * Server:: Using the gdbserver program
20799 * Remote Configuration:: Remote configuration
20800 * Remote Stub:: Implementing a remote stub
20804 @section Connecting to a Remote Target
20805 @cindex remote debugging, connecting
20806 @cindex @code{gdbserver}, connecting
20807 @cindex remote debugging, types of connections
20808 @cindex @code{gdbserver}, types of connections
20809 @cindex @code{gdbserver}, @code{target remote} mode
20810 @cindex @code{gdbserver}, @code{target extended-remote} mode
20812 This section describes how to connect to a remote target, including the
20813 types of connections and their differences, how to set up executable and
20814 symbol files on the host and target, and the commands used for
20815 connecting to and disconnecting from the remote target.
20817 @subsection Types of Remote Connections
20819 @value{GDBN} supports two types of remote connections, @code{target remote}
20820 mode and @code{target extended-remote} mode. Note that many remote targets
20821 support only @code{target remote} mode. There are several major
20822 differences between the two types of connections, enumerated here:
20826 @cindex remote debugging, detach and program exit
20827 @item Result of detach or program exit
20828 @strong{With target remote mode:} When the debugged program exits or you
20829 detach from it, @value{GDBN} disconnects from the target. When using
20830 @code{gdbserver}, @code{gdbserver} will exit.
20832 @strong{With target extended-remote mode:} When the debugged program exits or
20833 you detach from it, @value{GDBN} remains connected to the target, even
20834 though no program is running. You can rerun the program, attach to a
20835 running program, or use @code{monitor} commands specific to the target.
20837 When using @code{gdbserver} in this case, it does not exit unless it was
20838 invoked using the @option{--once} option. If the @option{--once} option
20839 was not used, you can ask @code{gdbserver} to exit using the
20840 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20842 @item Specifying the program to debug
20843 For both connection types you use the @code{file} command to specify the
20844 program on the host system. If you are using @code{gdbserver} there are
20845 some differences in how to specify the location of the program on the
20848 @strong{With target remote mode:} You must either specify the program to debug
20849 on the @code{gdbserver} command line or use the @option{--attach} option
20850 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20852 @cindex @option{--multi}, @code{gdbserver} option
20853 @strong{With target extended-remote mode:} You may specify the program to debug
20854 on the @code{gdbserver} command line, or you can load the program or attach
20855 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20857 @anchor{--multi Option in Types of Remote Connnections}
20858 You can start @code{gdbserver} without supplying an initial command to run
20859 or process ID to attach. To do this, use the @option{--multi} command line
20860 option. Then you can connect using @code{target extended-remote} and start
20861 the program you want to debug (see below for details on using the
20862 @code{run} command in this scenario). Note that the conditions under which
20863 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20864 (@code{target remote} or @code{target extended-remote}). The
20865 @option{--multi} option to @code{gdbserver} has no influence on that.
20867 @item The @code{run} command
20868 @strong{With target remote mode:} The @code{run} command is not
20869 supported. Once a connection has been established, you can use all
20870 the usual @value{GDBN} commands to examine and change data. The
20871 remote program is already running, so you can use commands like
20872 @kbd{step} and @kbd{continue}.
20874 @strong{With target extended-remote mode:} The @code{run} command is
20875 supported. The @code{run} command uses the value set by
20876 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20877 the program to run. Command line arguments are supported, except for
20878 wildcard expansion and I/O redirection (@pxref{Arguments}).
20880 If you specify the program to debug on the command line, then the
20881 @code{run} command is not required to start execution, and you can
20882 resume using commands like @kbd{step} and @kbd{continue} as with
20883 @code{target remote} mode.
20885 @anchor{Attaching in Types of Remote Connections}
20887 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20888 not supported. To attach to a running program using @code{gdbserver}, you
20889 must use the @option{--attach} option (@pxref{Running gdbserver}).
20891 @strong{With target extended-remote mode:} To attach to a running program,
20892 you may use the @code{attach} command after the connection has been
20893 established. If you are using @code{gdbserver}, you may also invoke
20894 @code{gdbserver} using the @option{--attach} option
20895 (@pxref{Running gdbserver}).
20899 @anchor{Host and target files}
20900 @subsection Host and Target Files
20901 @cindex remote debugging, symbol files
20902 @cindex symbol files, remote debugging
20904 @value{GDBN}, running on the host, needs access to symbol and debugging
20905 information for your program running on the target. This requires
20906 access to an unstripped copy of your program, and possibly any associated
20907 symbol files. Note that this section applies equally to both @code{target
20908 remote} mode and @code{target extended-remote} mode.
20910 Some remote targets (@pxref{qXfer executable filename read}, and
20911 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20912 the same connection used to communicate with @value{GDBN}. With such a
20913 target, if the remote program is unstripped, the only command you need is
20914 @code{target remote} (or @code{target extended-remote}).
20916 If the remote program is stripped, or the target does not support remote
20917 program file access, start up @value{GDBN} using the name of the local
20918 unstripped copy of your program as the first argument, or use the
20919 @code{file} command. Use @code{set sysroot} to specify the location (on
20920 the host) of target libraries (unless your @value{GDBN} was compiled with
20921 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20922 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20925 The symbol file and target libraries must exactly match the executable
20926 and libraries on the target, with one exception: the files on the host
20927 system should not be stripped, even if the files on the target system
20928 are. Mismatched or missing files will lead to confusing results
20929 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20930 files may also prevent @code{gdbserver} from debugging multi-threaded
20933 @subsection Remote Connection Commands
20934 @cindex remote connection commands
20935 @value{GDBN} can communicate with the target over a serial line, a
20936 local Unix domain socket, or
20937 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20938 each case, @value{GDBN} uses the same protocol for debugging your
20939 program; only the medium carrying the debugging packets varies. The
20940 @code{target remote} and @code{target extended-remote} commands
20941 establish a connection to the target. Both commands accept the same
20942 arguments, which indicate the medium to use:
20946 @item target remote @var{serial-device}
20947 @itemx target extended-remote @var{serial-device}
20948 @cindex serial line, @code{target remote}
20949 Use @var{serial-device} to communicate with the target. For example,
20950 to use a serial line connected to the device named @file{/dev/ttyb}:
20953 target remote /dev/ttyb
20956 If you're using a serial line, you may want to give @value{GDBN} the
20957 @samp{--baud} option, or use the @code{set serial baud} command
20958 (@pxref{Remote Configuration, set serial baud}) before the
20959 @code{target} command.
20961 @item target remote @var{local-socket}
20962 @itemx target extended-remote @var{local-socket}
20963 @cindex local socket, @code{target remote}
20964 @cindex Unix domain socket
20965 Use @var{local-socket} to communicate with the target. For example,
20966 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20969 target remote /tmp/gdb-socket0
20972 Note that this command has the same form as the command to connect
20973 to a serial line. @value{GDBN} will automatically determine which
20974 kind of file you have specified and will make the appropriate kind
20976 This feature is not available if the host system does not support
20977 Unix domain sockets.
20979 @item target remote @code{@var{host}:@var{port}}
20980 @itemx target remote @code{@var{[host]}:@var{port}}
20981 @itemx target remote @code{tcp:@var{host}:@var{port}}
20982 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20983 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20984 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20985 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20986 @itemx target extended-remote @code{@var{host}:@var{port}}
20987 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20988 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20989 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20990 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20991 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20992 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20993 @cindex @acronym{TCP} port, @code{target remote}
20994 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20995 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20996 address, or a numeric @acronym{IPv6} address (with or without the
20997 square brackets to separate the address from the port); @var{port}
20998 must be a decimal number. The @var{host} could be the target machine
20999 itself, if it is directly connected to the net, or it might be a
21000 terminal server which in turn has a serial line to the target.
21002 For example, to connect to port 2828 on a terminal server named
21006 target remote manyfarms:2828
21009 To connect to port 2828 on a terminal server whose address is
21010 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21011 square bracket syntax:
21014 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21018 or explicitly specify the @acronym{IPv6} protocol:
21021 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21024 This last example may be confusing to the reader, because there is no
21025 visible separation between the hostname and the port number.
21026 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21027 using square brackets for clarity. However, it is important to
21028 mention that for @value{GDBN} there is no ambiguity: the number after
21029 the last colon is considered to be the port number.
21031 If your remote target is actually running on the same machine as your
21032 debugger session (e.g.@: a simulator for your target running on the
21033 same host), you can omit the hostname. For example, to connect to
21034 port 1234 on your local machine:
21037 target remote :1234
21041 Note that the colon is still required here.
21043 @item target remote @code{udp:@var{host}:@var{port}}
21044 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21045 @itemx target remote @code{udp4:@var{host}:@var{port}}
21046 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21047 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21048 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21049 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21050 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21051 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21052 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21053 @cindex @acronym{UDP} port, @code{target remote}
21054 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21055 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21058 target remote udp:manyfarms:2828
21061 When using a @acronym{UDP} connection for remote debugging, you should
21062 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21063 can silently drop packets on busy or unreliable networks, which will
21064 cause havoc with your debugging session.
21066 @item target remote | @var{command}
21067 @itemx target extended-remote | @var{command}
21068 @cindex pipe, @code{target remote} to
21069 Run @var{command} in the background and communicate with it using a
21070 pipe. The @var{command} is a shell command, to be parsed and expanded
21071 by the system's command shell, @code{/bin/sh}; it should expect remote
21072 protocol packets on its standard input, and send replies on its
21073 standard output. You could use this to run a stand-alone simulator
21074 that speaks the remote debugging protocol, to make net connections
21075 using programs like @code{ssh}, or for other similar tricks.
21077 If @var{command} closes its standard output (perhaps by exiting),
21078 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21079 program has already exited, this will have no effect.)
21083 @cindex interrupting remote programs
21084 @cindex remote programs, interrupting
21085 Whenever @value{GDBN} is waiting for the remote program, if you type the
21086 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21087 program. This may or may not succeed, depending in part on the hardware
21088 and the serial drivers the remote system uses. If you type the
21089 interrupt character once again, @value{GDBN} displays this prompt:
21092 Interrupted while waiting for the program.
21093 Give up (and stop debugging it)? (y or n)
21096 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21097 the remote debugging session. (If you decide you want to try again later,
21098 you can use @kbd{target remote} again to connect once more.) If you type
21099 @kbd{n}, @value{GDBN} goes back to waiting.
21101 In @code{target extended-remote} mode, typing @kbd{n} will leave
21102 @value{GDBN} connected to the target.
21105 @kindex detach (remote)
21107 When you have finished debugging the remote program, you can use the
21108 @code{detach} command to release it from @value{GDBN} control.
21109 Detaching from the target normally resumes its execution, but the results
21110 will depend on your particular remote stub. After the @code{detach}
21111 command in @code{target remote} mode, @value{GDBN} is free to connect to
21112 another target. In @code{target extended-remote} mode, @value{GDBN} is
21113 still connected to the target.
21117 The @code{disconnect} command closes the connection to the target, and
21118 the target is generally not resumed. It will wait for @value{GDBN}
21119 (this instance or another one) to connect and continue debugging. After
21120 the @code{disconnect} command, @value{GDBN} is again free to connect to
21123 @cindex send command to remote monitor
21124 @cindex extend @value{GDBN} for remote targets
21125 @cindex add new commands for external monitor
21127 @item monitor @var{cmd}
21128 This command allows you to send arbitrary commands directly to the
21129 remote monitor. Since @value{GDBN} doesn't care about the commands it
21130 sends like this, this command is the way to extend @value{GDBN}---you
21131 can add new commands that only the external monitor will understand
21135 @node File Transfer
21136 @section Sending files to a remote system
21137 @cindex remote target, file transfer
21138 @cindex file transfer
21139 @cindex sending files to remote systems
21141 Some remote targets offer the ability to transfer files over the same
21142 connection used to communicate with @value{GDBN}. This is convenient
21143 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21144 running @code{gdbserver} over a network interface. For other targets,
21145 e.g.@: embedded devices with only a single serial port, this may be
21146 the only way to upload or download files.
21148 Not all remote targets support these commands.
21152 @item remote put @var{hostfile} @var{targetfile}
21153 Copy file @var{hostfile} from the host system (the machine running
21154 @value{GDBN}) to @var{targetfile} on the target system.
21157 @item remote get @var{targetfile} @var{hostfile}
21158 Copy file @var{targetfile} from the target system to @var{hostfile}
21159 on the host system.
21161 @kindex remote delete
21162 @item remote delete @var{targetfile}
21163 Delete @var{targetfile} from the target system.
21168 @section Using the @code{gdbserver} Program
21171 @cindex remote connection without stubs
21172 @code{gdbserver} is a control program for Unix-like systems, which
21173 allows you to connect your program with a remote @value{GDBN} via
21174 @code{target remote} or @code{target extended-remote}---but without
21175 linking in the usual debugging stub.
21177 @code{gdbserver} is not a complete replacement for the debugging stubs,
21178 because it requires essentially the same operating-system facilities
21179 that @value{GDBN} itself does. In fact, a system that can run
21180 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21181 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21182 because it is a much smaller program than @value{GDBN} itself. It is
21183 also easier to port than all of @value{GDBN}, so you may be able to get
21184 started more quickly on a new system by using @code{gdbserver}.
21185 Finally, if you develop code for real-time systems, you may find that
21186 the tradeoffs involved in real-time operation make it more convenient to
21187 do as much development work as possible on another system, for example
21188 by cross-compiling. You can use @code{gdbserver} to make a similar
21189 choice for debugging.
21191 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21192 or a TCP connection, using the standard @value{GDBN} remote serial
21196 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21197 Do not run @code{gdbserver} connected to any public network; a
21198 @value{GDBN} connection to @code{gdbserver} provides access to the
21199 target system with the same privileges as the user running
21203 @anchor{Running gdbserver}
21204 @subsection Running @code{gdbserver}
21205 @cindex arguments, to @code{gdbserver}
21206 @cindex @code{gdbserver}, command-line arguments
21208 Run @code{gdbserver} on the target system. You need a copy of the
21209 program you want to debug, including any libraries it requires.
21210 @code{gdbserver} does not need your program's symbol table, so you can
21211 strip the program if necessary to save space. @value{GDBN} on the host
21212 system does all the symbol handling.
21214 To use the server, you must tell it how to communicate with @value{GDBN};
21215 the name of your program; and the arguments for your program. The usual
21219 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21222 @var{comm} is either a device name (to use a serial line), or a TCP
21223 hostname and portnumber, or @code{-} or @code{stdio} to use
21224 stdin/stdout of @code{gdbserver}.
21225 For example, to debug Emacs with the argument
21226 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21230 target> gdbserver /dev/com1 emacs foo.txt
21233 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21236 To use a TCP connection instead of a serial line:
21239 target> gdbserver host:2345 emacs foo.txt
21242 The only difference from the previous example is the first argument,
21243 specifying that you are communicating with the host @value{GDBN} via
21244 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21245 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21246 (Currently, the @samp{host} part is ignored.) You can choose any number
21247 you want for the port number as long as it does not conflict with any
21248 TCP ports already in use on the target system (for example, @code{23} is
21249 reserved for @code{telnet}).@footnote{If you choose a port number that
21250 conflicts with another service, @code{gdbserver} prints an error message
21251 and exits.} You must use the same port number with the host @value{GDBN}
21252 @code{target remote} command.
21254 The @code{stdio} connection is useful when starting @code{gdbserver}
21258 (gdb) target remote | ssh -T hostname gdbserver - hello
21261 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21262 and we don't want escape-character handling. Ssh does this by default when
21263 a command is provided, the flag is provided to make it explicit.
21264 You could elide it if you want to.
21266 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21267 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21268 display through a pipe connected to gdbserver.
21269 Both @code{stdout} and @code{stderr} use the same pipe.
21271 @anchor{Attaching to a program}
21272 @subsubsection Attaching to a Running Program
21273 @cindex attach to a program, @code{gdbserver}
21274 @cindex @option{--attach}, @code{gdbserver} option
21276 On some targets, @code{gdbserver} can also attach to running programs.
21277 This is accomplished via the @code{--attach} argument. The syntax is:
21280 target> gdbserver --attach @var{comm} @var{pid}
21283 @var{pid} is the process ID of a currently running process. It isn't
21284 necessary to point @code{gdbserver} at a binary for the running process.
21286 In @code{target extended-remote} mode, you can also attach using the
21287 @value{GDBN} attach command
21288 (@pxref{Attaching in Types of Remote Connections}).
21291 You can debug processes by name instead of process ID if your target has the
21292 @code{pidof} utility:
21295 target> gdbserver --attach @var{comm} `pidof @var{program}`
21298 In case more than one copy of @var{program} is running, or @var{program}
21299 has multiple threads, most versions of @code{pidof} support the
21300 @code{-s} option to only return the first process ID.
21302 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21304 This section applies only when @code{gdbserver} is run to listen on a TCP
21307 @code{gdbserver} normally terminates after all of its debugged processes have
21308 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21309 extended-remote}, @code{gdbserver} stays running even with no processes left.
21310 @value{GDBN} normally terminates the spawned debugged process on its exit,
21311 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21312 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21313 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21314 stays running even in the @kbd{target remote} mode.
21316 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21317 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21318 completeness, at most one @value{GDBN} can be connected at a time.
21320 @cindex @option{--once}, @code{gdbserver} option
21321 By default, @code{gdbserver} keeps the listening TCP port open, so that
21322 subsequent connections are possible. However, if you start @code{gdbserver}
21323 with the @option{--once} option, it will stop listening for any further
21324 connection attempts after connecting to the first @value{GDBN} session. This
21325 means no further connections to @code{gdbserver} will be possible after the
21326 first one. It also means @code{gdbserver} will terminate after the first
21327 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21328 connections and even in the @kbd{target extended-remote} mode. The
21329 @option{--once} option allows reusing the same port number for connecting to
21330 multiple instances of @code{gdbserver} running on the same host, since each
21331 instance closes its port after the first connection.
21333 @anchor{Other Command-Line Arguments for gdbserver}
21334 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21336 You can use the @option{--multi} option to start @code{gdbserver} without
21337 specifying a program to debug or a process to attach to. Then you can
21338 attach in @code{target extended-remote} mode and run or attach to a
21339 program. For more information,
21340 @pxref{--multi Option in Types of Remote Connnections}.
21342 @cindex @option{--debug}, @code{gdbserver} option
21343 The @option{--debug} option tells @code{gdbserver} to display extra
21344 status information about the debugging process.
21345 @cindex @option{--remote-debug}, @code{gdbserver} option
21346 The @option{--remote-debug} option tells @code{gdbserver} to display
21347 remote protocol debug output.
21348 @cindex @option{--debug-file}, @code{gdbserver} option
21349 @cindex @code{gdbserver}, send all debug output to a single file
21350 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
21351 write any debug output to the given @var{filename}. These options are intended
21352 for @code{gdbserver} development and for bug reports to the developers.
21354 @cindex @option{--debug-format}, @code{gdbserver} option
21355 The @option{--debug-format=option1[,option2,...]} option tells
21356 @code{gdbserver} to include additional information in each output.
21357 Possible options are:
21361 Turn off all extra information in debugging output.
21363 Turn on all extra information in debugging output.
21365 Include a timestamp in each line of debugging output.
21368 Options are processed in order. Thus, for example, if @option{none}
21369 appears last then no additional information is added to debugging output.
21371 @cindex @option{--wrapper}, @code{gdbserver} option
21372 The @option{--wrapper} option specifies a wrapper to launch programs
21373 for debugging. The option should be followed by the name of the
21374 wrapper, then any command-line arguments to pass to the wrapper, then
21375 @kbd{--} indicating the end of the wrapper arguments.
21377 @code{gdbserver} runs the specified wrapper program with a combined
21378 command line including the wrapper arguments, then the name of the
21379 program to debug, then any arguments to the program. The wrapper
21380 runs until it executes your program, and then @value{GDBN} gains control.
21382 You can use any program that eventually calls @code{execve} with
21383 its arguments as a wrapper. Several standard Unix utilities do
21384 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21385 with @code{exec "$@@"} will also work.
21387 For example, you can use @code{env} to pass an environment variable to
21388 the debugged program, without setting the variable in @code{gdbserver}'s
21392 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21395 @cindex @option{--selftest}
21396 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21399 $ gdbserver --selftest
21400 Ran 2 unit tests, 0 failed
21403 These tests are disabled in release.
21404 @subsection Connecting to @code{gdbserver}
21406 The basic procedure for connecting to the remote target is:
21410 Run @value{GDBN} on the host system.
21413 Make sure you have the necessary symbol files
21414 (@pxref{Host and target files}).
21415 Load symbols for your application using the @code{file} command before you
21416 connect. Use @code{set sysroot} to locate target libraries (unless your
21417 @value{GDBN} was compiled with the correct sysroot using
21418 @code{--with-sysroot}).
21421 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21422 For TCP connections, you must start up @code{gdbserver} prior to using
21423 the @code{target} command. Otherwise you may get an error whose
21424 text depends on the host system, but which usually looks something like
21425 @samp{Connection refused}. Don't use the @code{load}
21426 command in @value{GDBN} when using @code{target remote} mode, since the
21427 program is already on the target.
21431 @anchor{Monitor Commands for gdbserver}
21432 @subsection Monitor Commands for @code{gdbserver}
21433 @cindex monitor commands, for @code{gdbserver}
21435 During a @value{GDBN} session using @code{gdbserver}, you can use the
21436 @code{monitor} command to send special requests to @code{gdbserver}.
21437 Here are the available commands.
21441 List the available monitor commands.
21443 @item monitor set debug 0
21444 @itemx monitor set debug 1
21445 Disable or enable general debugging messages.
21447 @item monitor set remote-debug 0
21448 @itemx monitor set remote-debug 1
21449 Disable or enable specific debugging messages associated with the remote
21450 protocol (@pxref{Remote Protocol}).
21452 @item monitor set debug-file filename
21453 @itemx monitor set debug-file
21454 Send any debug output to the given file, or to stderr.
21456 @item monitor set debug-format option1@r{[},option2,...@r{]}
21457 Specify additional text to add to debugging messages.
21458 Possible options are:
21462 Turn off all extra information in debugging output.
21464 Turn on all extra information in debugging output.
21466 Include a timestamp in each line of debugging output.
21469 Options are processed in order. Thus, for example, if @option{none}
21470 appears last then no additional information is added to debugging output.
21472 @item monitor set libthread-db-search-path [PATH]
21473 @cindex gdbserver, search path for @code{libthread_db}
21474 When this command is issued, @var{path} is a colon-separated list of
21475 directories to search for @code{libthread_db} (@pxref{Threads,,set
21476 libthread-db-search-path}). If you omit @var{path},
21477 @samp{libthread-db-search-path} will be reset to its default value.
21479 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21480 not supported in @code{gdbserver}.
21483 Tell gdbserver to exit immediately. This command should be followed by
21484 @code{disconnect} to close the debugging session. @code{gdbserver} will
21485 detach from any attached processes and kill any processes it created.
21486 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21487 of a multi-process mode debug session.
21491 @subsection Tracepoints support in @code{gdbserver}
21492 @cindex tracepoints support in @code{gdbserver}
21494 On some targets, @code{gdbserver} supports tracepoints, fast
21495 tracepoints and static tracepoints.
21497 For fast or static tracepoints to work, a special library called the
21498 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21499 This library is built and distributed as an integral part of
21500 @code{gdbserver}. In addition, support for static tracepoints
21501 requires building the in-process agent library with static tracepoints
21502 support. At present, the UST (LTTng Userspace Tracer,
21503 @url{http://lttng.org/ust}) tracing engine is supported. This support
21504 is automatically available if UST development headers are found in the
21505 standard include path when @code{gdbserver} is built, or if
21506 @code{gdbserver} was explicitly configured using @option{--with-ust}
21507 to point at such headers. You can explicitly disable the support
21508 using @option{--with-ust=no}.
21510 There are several ways to load the in-process agent in your program:
21513 @item Specifying it as dependency at link time
21515 You can link your program dynamically with the in-process agent
21516 library. On most systems, this is accomplished by adding
21517 @code{-linproctrace} to the link command.
21519 @item Using the system's preloading mechanisms
21521 You can force loading the in-process agent at startup time by using
21522 your system's support for preloading shared libraries. Many Unixes
21523 support the concept of preloading user defined libraries. In most
21524 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21525 in the environment. See also the description of @code{gdbserver}'s
21526 @option{--wrapper} command line option.
21528 @item Using @value{GDBN} to force loading the agent at run time
21530 On some systems, you can force the inferior to load a shared library,
21531 by calling a dynamic loader function in the inferior that takes care
21532 of dynamically looking up and loading a shared library. On most Unix
21533 systems, the function is @code{dlopen}. You'll use the @code{call}
21534 command for that. For example:
21537 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21540 Note that on most Unix systems, for the @code{dlopen} function to be
21541 available, the program needs to be linked with @code{-ldl}.
21544 On systems that have a userspace dynamic loader, like most Unix
21545 systems, when you connect to @code{gdbserver} using @code{target
21546 remote}, you'll find that the program is stopped at the dynamic
21547 loader's entry point, and no shared library has been loaded in the
21548 program's address space yet, including the in-process agent. In that
21549 case, before being able to use any of the fast or static tracepoints
21550 features, you need to let the loader run and load the shared
21551 libraries. The simplest way to do that is to run the program to the
21552 main procedure. E.g., if debugging a C or C@t{++} program, start
21553 @code{gdbserver} like so:
21556 $ gdbserver :9999 myprogram
21559 Start GDB and connect to @code{gdbserver} like so, and run to main:
21563 (@value{GDBP}) target remote myhost:9999
21564 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21565 (@value{GDBP}) b main
21566 (@value{GDBP}) continue
21569 The in-process tracing agent library should now be loaded into the
21570 process; you can confirm it with the @code{info sharedlibrary}
21571 command, which will list @file{libinproctrace.so} as loaded in the
21572 process. You are now ready to install fast tracepoints, list static
21573 tracepoint markers, probe static tracepoints markers, and start
21576 @node Remote Configuration
21577 @section Remote Configuration
21580 @kindex show remote
21581 This section documents the configuration options available when
21582 debugging remote programs. For the options related to the File I/O
21583 extensions of the remote protocol, see @ref{system,
21584 system-call-allowed}.
21587 @item set remoteaddresssize @var{bits}
21588 @cindex address size for remote targets
21589 @cindex bits in remote address
21590 Set the maximum size of address in a memory packet to the specified
21591 number of bits. @value{GDBN} will mask off the address bits above
21592 that number, when it passes addresses to the remote target. The
21593 default value is the number of bits in the target's address.
21595 @item show remoteaddresssize
21596 Show the current value of remote address size in bits.
21598 @item set serial baud @var{n}
21599 @cindex baud rate for remote targets
21600 Set the baud rate for the remote serial I/O to @var{n} baud. The
21601 value is used to set the speed of the serial port used for debugging
21604 @item show serial baud
21605 Show the current speed of the remote connection.
21607 @item set serial parity @var{parity}
21608 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21609 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21611 @item show serial parity
21612 Show the current parity of the serial port.
21614 @item set remotebreak
21615 @cindex interrupt remote programs
21616 @cindex BREAK signal instead of Ctrl-C
21617 @anchor{set remotebreak}
21618 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21619 when you type @kbd{Ctrl-c} to interrupt the program running
21620 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21621 character instead. The default is off, since most remote systems
21622 expect to see @samp{Ctrl-C} as the interrupt signal.
21624 @item show remotebreak
21625 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21626 interrupt the remote program.
21628 @item set remoteflow on
21629 @itemx set remoteflow off
21630 @kindex set remoteflow
21631 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21632 on the serial port used to communicate to the remote target.
21634 @item show remoteflow
21635 @kindex show remoteflow
21636 Show the current setting of hardware flow control.
21638 @item set remotelogbase @var{base}
21639 Set the base (a.k.a.@: radix) of logging serial protocol
21640 communications to @var{base}. Supported values of @var{base} are:
21641 @code{ascii}, @code{octal}, and @code{hex}. The default is
21644 @item show remotelogbase
21645 Show the current setting of the radix for logging remote serial
21648 @item set remotelogfile @var{file}
21649 @cindex record serial communications on file
21650 Record remote serial communications on the named @var{file}. The
21651 default is not to record at all.
21653 @item show remotelogfile
21654 Show the current setting of the file name on which to record the
21655 serial communications.
21657 @item set remotetimeout @var{num}
21658 @cindex timeout for serial communications
21659 @cindex remote timeout
21660 Set the timeout limit to wait for the remote target to respond to
21661 @var{num} seconds. The default is 2 seconds.
21663 @item show remotetimeout
21664 Show the current number of seconds to wait for the remote target
21667 @cindex limit hardware breakpoints and watchpoints
21668 @cindex remote target, limit break- and watchpoints
21669 @anchor{set remote hardware-watchpoint-limit}
21670 @anchor{set remote hardware-breakpoint-limit}
21671 @item set remote hardware-watchpoint-limit @var{limit}
21672 @itemx set remote hardware-breakpoint-limit @var{limit}
21673 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21674 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21675 watchpoints or breakpoints, and @code{unlimited} for unlimited
21676 watchpoints or breakpoints.
21678 @item show remote hardware-watchpoint-limit
21679 @itemx show remote hardware-breakpoint-limit
21680 Show the current limit for the number of hardware watchpoints or
21681 breakpoints that @value{GDBN} can use.
21683 @cindex limit hardware watchpoints length
21684 @cindex remote target, limit watchpoints length
21685 @anchor{set remote hardware-watchpoint-length-limit}
21686 @item set remote hardware-watchpoint-length-limit @var{limit}
21687 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21688 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21689 hardware watchpoints and @code{unlimited} allows watchpoints of any
21692 @item show remote hardware-watchpoint-length-limit
21693 Show the current limit (in bytes) of the maximum length of
21694 a remote hardware watchpoint.
21696 @item set remote exec-file @var{filename}
21697 @itemx show remote exec-file
21698 @anchor{set remote exec-file}
21699 @cindex executable file, for remote target
21700 Select the file used for @code{run} with @code{target
21701 extended-remote}. This should be set to a filename valid on the
21702 target system. If it is not set, the target will use a default
21703 filename (e.g.@: the last program run).
21705 @item set remote interrupt-sequence
21706 @cindex interrupt remote programs
21707 @cindex select Ctrl-C, BREAK or BREAK-g
21708 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21709 @samp{BREAK-g} as the
21710 sequence to the remote target in order to interrupt the execution.
21711 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21712 is high level of serial line for some certain time.
21713 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21714 It is @code{BREAK} signal followed by character @code{g}.
21716 @item show interrupt-sequence
21717 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21718 is sent by @value{GDBN} to interrupt the remote program.
21719 @code{BREAK-g} is BREAK signal followed by @code{g} and
21720 also known as Magic SysRq g.
21722 @item set remote interrupt-on-connect
21723 @cindex send interrupt-sequence on start
21724 Specify whether interrupt-sequence is sent to remote target when
21725 @value{GDBN} connects to it. This is mostly needed when you debug
21726 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21727 which is known as Magic SysRq g in order to connect @value{GDBN}.
21729 @item show interrupt-on-connect
21730 Show whether interrupt-sequence is sent
21731 to remote target when @value{GDBN} connects to it.
21735 @item set tcp auto-retry on
21736 @cindex auto-retry, for remote TCP target
21737 Enable auto-retry for remote TCP connections. This is useful if the remote
21738 debugging agent is launched in parallel with @value{GDBN}; there is a race
21739 condition because the agent may not become ready to accept the connection
21740 before @value{GDBN} attempts to connect. When auto-retry is
21741 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21742 to establish the connection using the timeout specified by
21743 @code{set tcp connect-timeout}.
21745 @item set tcp auto-retry off
21746 Do not auto-retry failed TCP connections.
21748 @item show tcp auto-retry
21749 Show the current auto-retry setting.
21751 @item set tcp connect-timeout @var{seconds}
21752 @itemx set tcp connect-timeout unlimited
21753 @cindex connection timeout, for remote TCP target
21754 @cindex timeout, for remote target connection
21755 Set the timeout for establishing a TCP connection to the remote target to
21756 @var{seconds}. The timeout affects both polling to retry failed connections
21757 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21758 that are merely slow to complete, and represents an approximate cumulative
21759 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21760 @value{GDBN} will keep attempting to establish a connection forever,
21761 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21763 @item show tcp connect-timeout
21764 Show the current connection timeout setting.
21767 @cindex remote packets, enabling and disabling
21768 The @value{GDBN} remote protocol autodetects the packets supported by
21769 your debugging stub. If you need to override the autodetection, you
21770 can use these commands to enable or disable individual packets. Each
21771 packet can be set to @samp{on} (the remote target supports this
21772 packet), @samp{off} (the remote target does not support this packet),
21773 or @samp{auto} (detect remote target support for this packet). They
21774 all default to @samp{auto}. For more information about each packet,
21775 see @ref{Remote Protocol}.
21777 During normal use, you should not have to use any of these commands.
21778 If you do, that may be a bug in your remote debugging stub, or a bug
21779 in @value{GDBN}. You may want to report the problem to the
21780 @value{GDBN} developers.
21782 For each packet @var{name}, the command to enable or disable the
21783 packet is @code{set remote @var{name}-packet}. The available settings
21786 @multitable @columnfractions 0.28 0.32 0.25
21789 @tab Related Features
21791 @item @code{fetch-register}
21793 @tab @code{info registers}
21795 @item @code{set-register}
21799 @item @code{binary-download}
21801 @tab @code{load}, @code{set}
21803 @item @code{read-aux-vector}
21804 @tab @code{qXfer:auxv:read}
21805 @tab @code{info auxv}
21807 @item @code{symbol-lookup}
21808 @tab @code{qSymbol}
21809 @tab Detecting multiple threads
21811 @item @code{attach}
21812 @tab @code{vAttach}
21815 @item @code{verbose-resume}
21817 @tab Stepping or resuming multiple threads
21823 @item @code{software-breakpoint}
21827 @item @code{hardware-breakpoint}
21831 @item @code{write-watchpoint}
21835 @item @code{read-watchpoint}
21839 @item @code{access-watchpoint}
21843 @item @code{pid-to-exec-file}
21844 @tab @code{qXfer:exec-file:read}
21845 @tab @code{attach}, @code{run}
21847 @item @code{target-features}
21848 @tab @code{qXfer:features:read}
21849 @tab @code{set architecture}
21851 @item @code{library-info}
21852 @tab @code{qXfer:libraries:read}
21853 @tab @code{info sharedlibrary}
21855 @item @code{memory-map}
21856 @tab @code{qXfer:memory-map:read}
21857 @tab @code{info mem}
21859 @item @code{read-sdata-object}
21860 @tab @code{qXfer:sdata:read}
21861 @tab @code{print $_sdata}
21863 @item @code{read-spu-object}
21864 @tab @code{qXfer:spu:read}
21865 @tab @code{info spu}
21867 @item @code{write-spu-object}
21868 @tab @code{qXfer:spu:write}
21869 @tab @code{info spu}
21871 @item @code{read-siginfo-object}
21872 @tab @code{qXfer:siginfo:read}
21873 @tab @code{print $_siginfo}
21875 @item @code{write-siginfo-object}
21876 @tab @code{qXfer:siginfo:write}
21877 @tab @code{set $_siginfo}
21879 @item @code{threads}
21880 @tab @code{qXfer:threads:read}
21881 @tab @code{info threads}
21883 @item @code{get-thread-local-@*storage-address}
21884 @tab @code{qGetTLSAddr}
21885 @tab Displaying @code{__thread} variables
21887 @item @code{get-thread-information-block-address}
21888 @tab @code{qGetTIBAddr}
21889 @tab Display MS-Windows Thread Information Block.
21891 @item @code{search-memory}
21892 @tab @code{qSearch:memory}
21895 @item @code{supported-packets}
21896 @tab @code{qSupported}
21897 @tab Remote communications parameters
21899 @item @code{catch-syscalls}
21900 @tab @code{QCatchSyscalls}
21901 @tab @code{catch syscall}
21903 @item @code{pass-signals}
21904 @tab @code{QPassSignals}
21905 @tab @code{handle @var{signal}}
21907 @item @code{program-signals}
21908 @tab @code{QProgramSignals}
21909 @tab @code{handle @var{signal}}
21911 @item @code{hostio-close-packet}
21912 @tab @code{vFile:close}
21913 @tab @code{remote get}, @code{remote put}
21915 @item @code{hostio-open-packet}
21916 @tab @code{vFile:open}
21917 @tab @code{remote get}, @code{remote put}
21919 @item @code{hostio-pread-packet}
21920 @tab @code{vFile:pread}
21921 @tab @code{remote get}, @code{remote put}
21923 @item @code{hostio-pwrite-packet}
21924 @tab @code{vFile:pwrite}
21925 @tab @code{remote get}, @code{remote put}
21927 @item @code{hostio-unlink-packet}
21928 @tab @code{vFile:unlink}
21929 @tab @code{remote delete}
21931 @item @code{hostio-readlink-packet}
21932 @tab @code{vFile:readlink}
21935 @item @code{hostio-fstat-packet}
21936 @tab @code{vFile:fstat}
21939 @item @code{hostio-setfs-packet}
21940 @tab @code{vFile:setfs}
21943 @item @code{noack-packet}
21944 @tab @code{QStartNoAckMode}
21945 @tab Packet acknowledgment
21947 @item @code{osdata}
21948 @tab @code{qXfer:osdata:read}
21949 @tab @code{info os}
21951 @item @code{query-attached}
21952 @tab @code{qAttached}
21953 @tab Querying remote process attach state.
21955 @item @code{trace-buffer-size}
21956 @tab @code{QTBuffer:size}
21957 @tab @code{set trace-buffer-size}
21959 @item @code{trace-status}
21960 @tab @code{qTStatus}
21961 @tab @code{tstatus}
21963 @item @code{traceframe-info}
21964 @tab @code{qXfer:traceframe-info:read}
21965 @tab Traceframe info
21967 @item @code{install-in-trace}
21968 @tab @code{InstallInTrace}
21969 @tab Install tracepoint in tracing
21971 @item @code{disable-randomization}
21972 @tab @code{QDisableRandomization}
21973 @tab @code{set disable-randomization}
21975 @item @code{startup-with-shell}
21976 @tab @code{QStartupWithShell}
21977 @tab @code{set startup-with-shell}
21979 @item @code{environment-hex-encoded}
21980 @tab @code{QEnvironmentHexEncoded}
21981 @tab @code{set environment}
21983 @item @code{environment-unset}
21984 @tab @code{QEnvironmentUnset}
21985 @tab @code{unset environment}
21987 @item @code{environment-reset}
21988 @tab @code{QEnvironmentReset}
21989 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21991 @item @code{set-working-dir}
21992 @tab @code{QSetWorkingDir}
21993 @tab @code{set cwd}
21995 @item @code{conditional-breakpoints-packet}
21996 @tab @code{Z0 and Z1}
21997 @tab @code{Support for target-side breakpoint condition evaluation}
21999 @item @code{multiprocess-extensions}
22000 @tab @code{multiprocess extensions}
22001 @tab Debug multiple processes and remote process PID awareness
22003 @item @code{swbreak-feature}
22004 @tab @code{swbreak stop reason}
22007 @item @code{hwbreak-feature}
22008 @tab @code{hwbreak stop reason}
22011 @item @code{fork-event-feature}
22012 @tab @code{fork stop reason}
22015 @item @code{vfork-event-feature}
22016 @tab @code{vfork stop reason}
22019 @item @code{exec-event-feature}
22020 @tab @code{exec stop reason}
22023 @item @code{thread-events}
22024 @tab @code{QThreadEvents}
22025 @tab Tracking thread lifetime.
22027 @item @code{no-resumed-stop-reply}
22028 @tab @code{no resumed thread left stop reply}
22029 @tab Tracking thread lifetime.
22034 @section Implementing a Remote Stub
22036 @cindex debugging stub, example
22037 @cindex remote stub, example
22038 @cindex stub example, remote debugging
22039 The stub files provided with @value{GDBN} implement the target side of the
22040 communication protocol, and the @value{GDBN} side is implemented in the
22041 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22042 these subroutines to communicate, and ignore the details. (If you're
22043 implementing your own stub file, you can still ignore the details: start
22044 with one of the existing stub files. @file{sparc-stub.c} is the best
22045 organized, and therefore the easiest to read.)
22047 @cindex remote serial debugging, overview
22048 To debug a program running on another machine (the debugging
22049 @dfn{target} machine), you must first arrange for all the usual
22050 prerequisites for the program to run by itself. For example, for a C
22055 A startup routine to set up the C runtime environment; these usually
22056 have a name like @file{crt0}. The startup routine may be supplied by
22057 your hardware supplier, or you may have to write your own.
22060 A C subroutine library to support your program's
22061 subroutine calls, notably managing input and output.
22064 A way of getting your program to the other machine---for example, a
22065 download program. These are often supplied by the hardware
22066 manufacturer, but you may have to write your own from hardware
22070 The next step is to arrange for your program to use a serial port to
22071 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22072 machine). In general terms, the scheme looks like this:
22076 @value{GDBN} already understands how to use this protocol; when everything
22077 else is set up, you can simply use the @samp{target remote} command
22078 (@pxref{Targets,,Specifying a Debugging Target}).
22080 @item On the target,
22081 you must link with your program a few special-purpose subroutines that
22082 implement the @value{GDBN} remote serial protocol. The file containing these
22083 subroutines is called a @dfn{debugging stub}.
22085 On certain remote targets, you can use an auxiliary program
22086 @code{gdbserver} instead of linking a stub into your program.
22087 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22090 The debugging stub is specific to the architecture of the remote
22091 machine; for example, use @file{sparc-stub.c} to debug programs on
22094 @cindex remote serial stub list
22095 These working remote stubs are distributed with @value{GDBN}:
22100 @cindex @file{i386-stub.c}
22103 For Intel 386 and compatible architectures.
22106 @cindex @file{m68k-stub.c}
22107 @cindex Motorola 680x0
22109 For Motorola 680x0 architectures.
22112 @cindex @file{sh-stub.c}
22115 For Renesas SH architectures.
22118 @cindex @file{sparc-stub.c}
22120 For @sc{sparc} architectures.
22122 @item sparcl-stub.c
22123 @cindex @file{sparcl-stub.c}
22126 For Fujitsu @sc{sparclite} architectures.
22130 The @file{README} file in the @value{GDBN} distribution may list other
22131 recently added stubs.
22134 * Stub Contents:: What the stub can do for you
22135 * Bootstrapping:: What you must do for the stub
22136 * Debug Session:: Putting it all together
22139 @node Stub Contents
22140 @subsection What the Stub Can Do for You
22142 @cindex remote serial stub
22143 The debugging stub for your architecture supplies these three
22147 @item set_debug_traps
22148 @findex set_debug_traps
22149 @cindex remote serial stub, initialization
22150 This routine arranges for @code{handle_exception} to run when your
22151 program stops. You must call this subroutine explicitly in your
22152 program's startup code.
22154 @item handle_exception
22155 @findex handle_exception
22156 @cindex remote serial stub, main routine
22157 This is the central workhorse, but your program never calls it
22158 explicitly---the setup code arranges for @code{handle_exception} to
22159 run when a trap is triggered.
22161 @code{handle_exception} takes control when your program stops during
22162 execution (for example, on a breakpoint), and mediates communications
22163 with @value{GDBN} on the host machine. This is where the communications
22164 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22165 representative on the target machine. It begins by sending summary
22166 information on the state of your program, then continues to execute,
22167 retrieving and transmitting any information @value{GDBN} needs, until you
22168 execute a @value{GDBN} command that makes your program resume; at that point,
22169 @code{handle_exception} returns control to your own code on the target
22173 @cindex @code{breakpoint} subroutine, remote
22174 Use this auxiliary subroutine to make your program contain a
22175 breakpoint. Depending on the particular situation, this may be the only
22176 way for @value{GDBN} to get control. For instance, if your target
22177 machine has some sort of interrupt button, you won't need to call this;
22178 pressing the interrupt button transfers control to
22179 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22180 simply receiving characters on the serial port may also trigger a trap;
22181 again, in that situation, you don't need to call @code{breakpoint} from
22182 your own program---simply running @samp{target remote} from the host
22183 @value{GDBN} session gets control.
22185 Call @code{breakpoint} if none of these is true, or if you simply want
22186 to make certain your program stops at a predetermined point for the
22187 start of your debugging session.
22190 @node Bootstrapping
22191 @subsection What You Must Do for the Stub
22193 @cindex remote stub, support routines
22194 The debugging stubs that come with @value{GDBN} are set up for a particular
22195 chip architecture, but they have no information about the rest of your
22196 debugging target machine.
22198 First of all you need to tell the stub how to communicate with the
22202 @item int getDebugChar()
22203 @findex getDebugChar
22204 Write this subroutine to read a single character from the serial port.
22205 It may be identical to @code{getchar} for your target system; a
22206 different name is used to allow you to distinguish the two if you wish.
22208 @item void putDebugChar(int)
22209 @findex putDebugChar
22210 Write this subroutine to write a single character to the serial port.
22211 It may be identical to @code{putchar} for your target system; a
22212 different name is used to allow you to distinguish the two if you wish.
22215 @cindex control C, and remote debugging
22216 @cindex interrupting remote targets
22217 If you want @value{GDBN} to be able to stop your program while it is
22218 running, you need to use an interrupt-driven serial driver, and arrange
22219 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22220 character). That is the character which @value{GDBN} uses to tell the
22221 remote system to stop.
22223 Getting the debugging target to return the proper status to @value{GDBN}
22224 probably requires changes to the standard stub; one quick and dirty way
22225 is to just execute a breakpoint instruction (the ``dirty'' part is that
22226 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22228 Other routines you need to supply are:
22231 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22232 @findex exceptionHandler
22233 Write this function to install @var{exception_address} in the exception
22234 handling tables. You need to do this because the stub does not have any
22235 way of knowing what the exception handling tables on your target system
22236 are like (for example, the processor's table might be in @sc{rom},
22237 containing entries which point to a table in @sc{ram}).
22238 The @var{exception_number} specifies the exception which should be changed;
22239 its meaning is architecture-dependent (for example, different numbers
22240 might represent divide by zero, misaligned access, etc). When this
22241 exception occurs, control should be transferred directly to
22242 @var{exception_address}, and the processor state (stack, registers,
22243 and so on) should be just as it is when a processor exception occurs. So if
22244 you want to use a jump instruction to reach @var{exception_address}, it
22245 should be a simple jump, not a jump to subroutine.
22247 For the 386, @var{exception_address} should be installed as an interrupt
22248 gate so that interrupts are masked while the handler runs. The gate
22249 should be at privilege level 0 (the most privileged level). The
22250 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22251 help from @code{exceptionHandler}.
22253 @item void flush_i_cache()
22254 @findex flush_i_cache
22255 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22256 instruction cache, if any, on your target machine. If there is no
22257 instruction cache, this subroutine may be a no-op.
22259 On target machines that have instruction caches, @value{GDBN} requires this
22260 function to make certain that the state of your program is stable.
22264 You must also make sure this library routine is available:
22267 @item void *memset(void *, int, int)
22269 This is the standard library function @code{memset} that sets an area of
22270 memory to a known value. If you have one of the free versions of
22271 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22272 either obtain it from your hardware manufacturer, or write your own.
22275 If you do not use the GNU C compiler, you may need other standard
22276 library subroutines as well; this varies from one stub to another,
22277 but in general the stubs are likely to use any of the common library
22278 subroutines which @code{@value{NGCC}} generates as inline code.
22281 @node Debug Session
22282 @subsection Putting it All Together
22284 @cindex remote serial debugging summary
22285 In summary, when your program is ready to debug, you must follow these
22290 Make sure you have defined the supporting low-level routines
22291 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22293 @code{getDebugChar}, @code{putDebugChar},
22294 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22298 Insert these lines in your program's startup code, before the main
22299 procedure is called:
22306 On some machines, when a breakpoint trap is raised, the hardware
22307 automatically makes the PC point to the instruction after the
22308 breakpoint. If your machine doesn't do that, you may need to adjust
22309 @code{handle_exception} to arrange for it to return to the instruction
22310 after the breakpoint on this first invocation, so that your program
22311 doesn't keep hitting the initial breakpoint instead of making
22315 For the 680x0 stub only, you need to provide a variable called
22316 @code{exceptionHook}. Normally you just use:
22319 void (*exceptionHook)() = 0;
22323 but if before calling @code{set_debug_traps}, you set it to point to a
22324 function in your program, that function is called when
22325 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22326 error). The function indicated by @code{exceptionHook} is called with
22327 one parameter: an @code{int} which is the exception number.
22330 Compile and link together: your program, the @value{GDBN} debugging stub for
22331 your target architecture, and the supporting subroutines.
22334 Make sure you have a serial connection between your target machine and
22335 the @value{GDBN} host, and identify the serial port on the host.
22338 @c The "remote" target now provides a `load' command, so we should
22339 @c document that. FIXME.
22340 Download your program to your target machine (or get it there by
22341 whatever means the manufacturer provides), and start it.
22344 Start @value{GDBN} on the host, and connect to the target
22345 (@pxref{Connecting,,Connecting to a Remote Target}).
22349 @node Configurations
22350 @chapter Configuration-Specific Information
22352 While nearly all @value{GDBN} commands are available for all native and
22353 cross versions of the debugger, there are some exceptions. This chapter
22354 describes things that are only available in certain configurations.
22356 There are three major categories of configurations: native
22357 configurations, where the host and target are the same, embedded
22358 operating system configurations, which are usually the same for several
22359 different processor architectures, and bare embedded processors, which
22360 are quite different from each other.
22365 * Embedded Processors::
22372 This section describes details specific to particular native
22376 * BSD libkvm Interface:: Debugging BSD kernel memory images
22377 * Process Information:: Process information
22378 * DJGPP Native:: Features specific to the DJGPP port
22379 * Cygwin Native:: Features specific to the Cygwin port
22380 * Hurd Native:: Features specific to @sc{gnu} Hurd
22381 * Darwin:: Features specific to Darwin
22382 * FreeBSD:: Features specific to FreeBSD
22385 @node BSD libkvm Interface
22386 @subsection BSD libkvm Interface
22389 @cindex kernel memory image
22390 @cindex kernel crash dump
22392 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22393 interface that provides a uniform interface for accessing kernel virtual
22394 memory images, including live systems and crash dumps. @value{GDBN}
22395 uses this interface to allow you to debug live kernels and kernel crash
22396 dumps on many native BSD configurations. This is implemented as a
22397 special @code{kvm} debugging target. For debugging a live system, load
22398 the currently running kernel into @value{GDBN} and connect to the
22402 (@value{GDBP}) @b{target kvm}
22405 For debugging crash dumps, provide the file name of the crash dump as an
22409 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22412 Once connected to the @code{kvm} target, the following commands are
22418 Set current context from the @dfn{Process Control Block} (PCB) address.
22421 Set current context from proc address. This command isn't available on
22422 modern FreeBSD systems.
22425 @node Process Information
22426 @subsection Process Information
22428 @cindex examine process image
22429 @cindex process info via @file{/proc}
22431 Some operating systems provide interfaces to fetch additional
22432 information about running processes beyond memory and per-thread
22433 register state. If @value{GDBN} is configured for an operating system
22434 with a supported interface, the command @code{info proc} is available
22435 to report information about the process running your program, or about
22436 any process running on your system.
22438 One supported interface is a facility called @samp{/proc} that can be
22439 used to examine the image of a running process using file-system
22440 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22443 On FreeBSD systems, system control nodes are used to query process
22446 In addition, some systems may provide additional process information
22447 in core files. Note that a core file may include a subset of the
22448 information available from a live process. Process information is
22449 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22456 @itemx info proc @var{process-id}
22457 Summarize available information about a process. If a
22458 process ID is specified by @var{process-id}, display information about
22459 that process; otherwise display information about the program being
22460 debugged. The summary includes the debugged process ID, the command
22461 line used to invoke it, its current working directory, and its
22462 executable file's absolute file name.
22464 On some systems, @var{process-id} can be of the form
22465 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22466 within a process. If the optional @var{pid} part is missing, it means
22467 a thread from the process being debugged (the leading @samp{/} still
22468 needs to be present, or else @value{GDBN} will interpret the number as
22469 a process ID rather than a thread ID).
22471 @item info proc cmdline
22472 @cindex info proc cmdline
22473 Show the original command line of the process. This command is
22474 supported on @sc{gnu}/Linux and FreeBSD.
22476 @item info proc cwd
22477 @cindex info proc cwd
22478 Show the current working directory of the process. This command is
22479 supported on @sc{gnu}/Linux and FreeBSD.
22481 @item info proc exe
22482 @cindex info proc exe
22483 Show the name of executable of the process. This command is supported
22484 on @sc{gnu}/Linux and FreeBSD.
22486 @item info proc files
22487 @cindex info proc files
22488 Show the file descriptors open by the process. For each open file
22489 descriptor, @value{GDBN} shows its number, type (file, directory,
22490 character device, socket), file pointer offset, and the name of the
22491 resource open on the descriptor. The resource name can be a file name
22492 (for files, directories, and devices) or a protocol followed by socket
22493 address (for network connections). This command is supported on
22496 This example shows the open file descriptors for a process using a
22497 tty for standard input and output as well as two network sockets:
22500 (gdb) info proc files 22136
22504 FD Type Offset Flags Name
22505 text file - r-------- /usr/bin/ssh
22506 ctty chr - rw------- /dev/pts/20
22507 cwd dir - r-------- /usr/home/john
22508 root dir - r-------- /
22509 0 chr 0x32933a4 rw------- /dev/pts/20
22510 1 chr 0x32933a4 rw------- /dev/pts/20
22511 2 chr 0x32933a4 rw------- /dev/pts/20
22512 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22513 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22516 @item info proc mappings
22517 @cindex memory address space mappings
22518 Report the memory address space ranges accessible in a process. On
22519 Solaris and FreeBSD systems, each memory range includes information on
22520 whether the process has read, write, or execute access rights to each
22521 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22522 includes the object file which is mapped to that range.
22524 @item info proc stat
22525 @itemx info proc status
22526 @cindex process detailed status information
22527 Show additional process-related information, including the user ID and
22528 group ID; virtual memory usage; the signals that are pending, blocked,
22529 and ignored; its TTY; its consumption of system and user time; its
22530 stack size; its @samp{nice} value; etc. These commands are supported
22531 on @sc{gnu}/Linux and FreeBSD.
22533 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22534 information (type @kbd{man 5 proc} from your shell prompt).
22536 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22539 @item info proc all
22540 Show all the information about the process described under all of the
22541 above @code{info proc} subcommands.
22544 @comment These sub-options of 'info proc' were not included when
22545 @comment procfs.c was re-written. Keep their descriptions around
22546 @comment against the day when someone finds the time to put them back in.
22547 @kindex info proc times
22548 @item info proc times
22549 Starting time, user CPU time, and system CPU time for your program and
22552 @kindex info proc id
22554 Report on the process IDs related to your program: its own process ID,
22555 the ID of its parent, the process group ID, and the session ID.
22558 @item set procfs-trace
22559 @kindex set procfs-trace
22560 @cindex @code{procfs} API calls
22561 This command enables and disables tracing of @code{procfs} API calls.
22563 @item show procfs-trace
22564 @kindex show procfs-trace
22565 Show the current state of @code{procfs} API call tracing.
22567 @item set procfs-file @var{file}
22568 @kindex set procfs-file
22569 Tell @value{GDBN} to write @code{procfs} API trace to the named
22570 @var{file}. @value{GDBN} appends the trace info to the previous
22571 contents of the file. The default is to display the trace on the
22574 @item show procfs-file
22575 @kindex show procfs-file
22576 Show the file to which @code{procfs} API trace is written.
22578 @item proc-trace-entry
22579 @itemx proc-trace-exit
22580 @itemx proc-untrace-entry
22581 @itemx proc-untrace-exit
22582 @kindex proc-trace-entry
22583 @kindex proc-trace-exit
22584 @kindex proc-untrace-entry
22585 @kindex proc-untrace-exit
22586 These commands enable and disable tracing of entries into and exits
22587 from the @code{syscall} interface.
22590 @kindex info pidlist
22591 @cindex process list, QNX Neutrino
22592 For QNX Neutrino only, this command displays the list of all the
22593 processes and all the threads within each process.
22596 @kindex info meminfo
22597 @cindex mapinfo list, QNX Neutrino
22598 For QNX Neutrino only, this command displays the list of all mapinfos.
22602 @subsection Features for Debugging @sc{djgpp} Programs
22603 @cindex @sc{djgpp} debugging
22604 @cindex native @sc{djgpp} debugging
22605 @cindex MS-DOS-specific commands
22608 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22609 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22610 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22611 top of real-mode DOS systems and their emulations.
22613 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22614 defines a few commands specific to the @sc{djgpp} port. This
22615 subsection describes those commands.
22620 This is a prefix of @sc{djgpp}-specific commands which print
22621 information about the target system and important OS structures.
22624 @cindex MS-DOS system info
22625 @cindex free memory information (MS-DOS)
22626 @item info dos sysinfo
22627 This command displays assorted information about the underlying
22628 platform: the CPU type and features, the OS version and flavor, the
22629 DPMI version, and the available conventional and DPMI memory.
22634 @cindex segment descriptor tables
22635 @cindex descriptor tables display
22637 @itemx info dos ldt
22638 @itemx info dos idt
22639 These 3 commands display entries from, respectively, Global, Local,
22640 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22641 tables are data structures which store a descriptor for each segment
22642 that is currently in use. The segment's selector is an index into a
22643 descriptor table; the table entry for that index holds the
22644 descriptor's base address and limit, and its attributes and access
22647 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22648 segment (used for both data and the stack), and a DOS segment (which
22649 allows access to DOS/BIOS data structures and absolute addresses in
22650 conventional memory). However, the DPMI host will usually define
22651 additional segments in order to support the DPMI environment.
22653 @cindex garbled pointers
22654 These commands allow to display entries from the descriptor tables.
22655 Without an argument, all entries from the specified table are
22656 displayed. An argument, which should be an integer expression, means
22657 display a single entry whose index is given by the argument. For
22658 example, here's a convenient way to display information about the
22659 debugged program's data segment:
22662 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22663 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22667 This comes in handy when you want to see whether a pointer is outside
22668 the data segment's limit (i.e.@: @dfn{garbled}).
22670 @cindex page tables display (MS-DOS)
22672 @itemx info dos pte
22673 These two commands display entries from, respectively, the Page
22674 Directory and the Page Tables. Page Directories and Page Tables are
22675 data structures which control how virtual memory addresses are mapped
22676 into physical addresses. A Page Table includes an entry for every
22677 page of memory that is mapped into the program's address space; there
22678 may be several Page Tables, each one holding up to 4096 entries. A
22679 Page Directory has up to 4096 entries, one each for every Page Table
22680 that is currently in use.
22682 Without an argument, @kbd{info dos pde} displays the entire Page
22683 Directory, and @kbd{info dos pte} displays all the entries in all of
22684 the Page Tables. An argument, an integer expression, given to the
22685 @kbd{info dos pde} command means display only that entry from the Page
22686 Directory table. An argument given to the @kbd{info dos pte} command
22687 means display entries from a single Page Table, the one pointed to by
22688 the specified entry in the Page Directory.
22690 @cindex direct memory access (DMA) on MS-DOS
22691 These commands are useful when your program uses @dfn{DMA} (Direct
22692 Memory Access), which needs physical addresses to program the DMA
22695 These commands are supported only with some DPMI servers.
22697 @cindex physical address from linear address
22698 @item info dos address-pte @var{addr}
22699 This command displays the Page Table entry for a specified linear
22700 address. The argument @var{addr} is a linear address which should
22701 already have the appropriate segment's base address added to it,
22702 because this command accepts addresses which may belong to @emph{any}
22703 segment. For example, here's how to display the Page Table entry for
22704 the page where a variable @code{i} is stored:
22707 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22708 @exdent @code{Page Table entry for address 0x11a00d30:}
22709 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22713 This says that @code{i} is stored at offset @code{0xd30} from the page
22714 whose physical base address is @code{0x02698000}, and shows all the
22715 attributes of that page.
22717 Note that you must cast the addresses of variables to a @code{char *},
22718 since otherwise the value of @code{__djgpp_base_address}, the base
22719 address of all variables and functions in a @sc{djgpp} program, will
22720 be added using the rules of C pointer arithmetics: if @code{i} is
22721 declared an @code{int}, @value{GDBN} will add 4 times the value of
22722 @code{__djgpp_base_address} to the address of @code{i}.
22724 Here's another example, it displays the Page Table entry for the
22728 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22729 @exdent @code{Page Table entry for address 0x29110:}
22730 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22734 (The @code{+ 3} offset is because the transfer buffer's address is the
22735 3rd member of the @code{_go32_info_block} structure.) The output
22736 clearly shows that this DPMI server maps the addresses in conventional
22737 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22738 linear (@code{0x29110}) addresses are identical.
22740 This command is supported only with some DPMI servers.
22743 @cindex DOS serial data link, remote debugging
22744 In addition to native debugging, the DJGPP port supports remote
22745 debugging via a serial data link. The following commands are specific
22746 to remote serial debugging in the DJGPP port of @value{GDBN}.
22749 @kindex set com1base
22750 @kindex set com1irq
22751 @kindex set com2base
22752 @kindex set com2irq
22753 @kindex set com3base
22754 @kindex set com3irq
22755 @kindex set com4base
22756 @kindex set com4irq
22757 @item set com1base @var{addr}
22758 This command sets the base I/O port address of the @file{COM1} serial
22761 @item set com1irq @var{irq}
22762 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22763 for the @file{COM1} serial port.
22765 There are similar commands @samp{set com2base}, @samp{set com3irq},
22766 etc.@: for setting the port address and the @code{IRQ} lines for the
22769 @kindex show com1base
22770 @kindex show com1irq
22771 @kindex show com2base
22772 @kindex show com2irq
22773 @kindex show com3base
22774 @kindex show com3irq
22775 @kindex show com4base
22776 @kindex show com4irq
22777 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22778 display the current settings of the base address and the @code{IRQ}
22779 lines used by the COM ports.
22782 @kindex info serial
22783 @cindex DOS serial port status
22784 This command prints the status of the 4 DOS serial ports. For each
22785 port, it prints whether it's active or not, its I/O base address and
22786 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22787 counts of various errors encountered so far.
22791 @node Cygwin Native
22792 @subsection Features for Debugging MS Windows PE Executables
22793 @cindex MS Windows debugging
22794 @cindex native Cygwin debugging
22795 @cindex Cygwin-specific commands
22797 @value{GDBN} supports native debugging of MS Windows programs, including
22798 DLLs with and without symbolic debugging information.
22800 @cindex Ctrl-BREAK, MS-Windows
22801 @cindex interrupt debuggee on MS-Windows
22802 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22803 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22804 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22805 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22806 sequence, which can be used to interrupt the debuggee even if it
22809 There are various additional Cygwin-specific commands, described in
22810 this section. Working with DLLs that have no debugging symbols is
22811 described in @ref{Non-debug DLL Symbols}.
22816 This is a prefix of MS Windows-specific commands which print
22817 information about the target system and important OS structures.
22819 @item info w32 selector
22820 This command displays information returned by
22821 the Win32 API @code{GetThreadSelectorEntry} function.
22822 It takes an optional argument that is evaluated to
22823 a long value to give the information about this given selector.
22824 Without argument, this command displays information
22825 about the six segment registers.
22827 @item info w32 thread-information-block
22828 This command displays thread specific information stored in the
22829 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22830 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22832 @kindex signal-event
22833 @item signal-event @var{id}
22834 This command signals an event with user-provided @var{id}. Used to resume
22835 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22837 To use it, create or edit the following keys in
22838 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22839 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22840 (for x86_64 versions):
22844 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22845 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22846 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22848 The first @code{%ld} will be replaced by the process ID of the
22849 crashing process, the second @code{%ld} will be replaced by the ID of
22850 the event that blocks the crashing process, waiting for @value{GDBN}
22854 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22855 make the system run debugger specified by the Debugger key
22856 automatically, @code{0} will cause a dialog box with ``OK'' and
22857 ``Cancel'' buttons to appear, which allows the user to either
22858 terminate the crashing process (OK) or debug it (Cancel).
22861 @kindex set cygwin-exceptions
22862 @cindex debugging the Cygwin DLL
22863 @cindex Cygwin DLL, debugging
22864 @item set cygwin-exceptions @var{mode}
22865 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22866 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22867 @value{GDBN} will delay recognition of exceptions, and may ignore some
22868 exceptions which seem to be caused by internal Cygwin DLL
22869 ``bookkeeping''. This option is meant primarily for debugging the
22870 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22871 @value{GDBN} users with false @code{SIGSEGV} signals.
22873 @kindex show cygwin-exceptions
22874 @item show cygwin-exceptions
22875 Displays whether @value{GDBN} will break on exceptions that happen
22876 inside the Cygwin DLL itself.
22878 @kindex set new-console
22879 @item set new-console @var{mode}
22880 If @var{mode} is @code{on} the debuggee will
22881 be started in a new console on next start.
22882 If @var{mode} is @code{off}, the debuggee will
22883 be started in the same console as the debugger.
22885 @kindex show new-console
22886 @item show new-console
22887 Displays whether a new console is used
22888 when the debuggee is started.
22890 @kindex set new-group
22891 @item set new-group @var{mode}
22892 This boolean value controls whether the debuggee should
22893 start a new group or stay in the same group as the debugger.
22894 This affects the way the Windows OS handles
22897 @kindex show new-group
22898 @item show new-group
22899 Displays current value of new-group boolean.
22901 @kindex set debugevents
22902 @item set debugevents
22903 This boolean value adds debug output concerning kernel events related
22904 to the debuggee seen by the debugger. This includes events that
22905 signal thread and process creation and exit, DLL loading and
22906 unloading, console interrupts, and debugging messages produced by the
22907 Windows @code{OutputDebugString} API call.
22909 @kindex set debugexec
22910 @item set debugexec
22911 This boolean value adds debug output concerning execute events
22912 (such as resume thread) seen by the debugger.
22914 @kindex set debugexceptions
22915 @item set debugexceptions
22916 This boolean value adds debug output concerning exceptions in the
22917 debuggee seen by the debugger.
22919 @kindex set debugmemory
22920 @item set debugmemory
22921 This boolean value adds debug output concerning debuggee memory reads
22922 and writes by the debugger.
22926 This boolean values specifies whether the debuggee is called
22927 via a shell or directly (default value is on).
22931 Displays if the debuggee will be started with a shell.
22936 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22939 @node Non-debug DLL Symbols
22940 @subsubsection Support for DLLs without Debugging Symbols
22941 @cindex DLLs with no debugging symbols
22942 @cindex Minimal symbols and DLLs
22944 Very often on windows, some of the DLLs that your program relies on do
22945 not include symbolic debugging information (for example,
22946 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22947 symbols in a DLL, it relies on the minimal amount of symbolic
22948 information contained in the DLL's export table. This section
22949 describes working with such symbols, known internally to @value{GDBN} as
22950 ``minimal symbols''.
22952 Note that before the debugged program has started execution, no DLLs
22953 will have been loaded. The easiest way around this problem is simply to
22954 start the program --- either by setting a breakpoint or letting the
22955 program run once to completion.
22957 @subsubsection DLL Name Prefixes
22959 In keeping with the naming conventions used by the Microsoft debugging
22960 tools, DLL export symbols are made available with a prefix based on the
22961 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22962 also entered into the symbol table, so @code{CreateFileA} is often
22963 sufficient. In some cases there will be name clashes within a program
22964 (particularly if the executable itself includes full debugging symbols)
22965 necessitating the use of the fully qualified name when referring to the
22966 contents of the DLL. Use single-quotes around the name to avoid the
22967 exclamation mark (``!'') being interpreted as a language operator.
22969 Note that the internal name of the DLL may be all upper-case, even
22970 though the file name of the DLL is lower-case, or vice-versa. Since
22971 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22972 some confusion. If in doubt, try the @code{info functions} and
22973 @code{info variables} commands or even @code{maint print msymbols}
22974 (@pxref{Symbols}). Here's an example:
22977 (@value{GDBP}) info function CreateFileA
22978 All functions matching regular expression "CreateFileA":
22980 Non-debugging symbols:
22981 0x77e885f4 CreateFileA
22982 0x77e885f4 KERNEL32!CreateFileA
22986 (@value{GDBP}) info function !
22987 All functions matching regular expression "!":
22989 Non-debugging symbols:
22990 0x6100114c cygwin1!__assert
22991 0x61004034 cygwin1!_dll_crt0@@0
22992 0x61004240 cygwin1!dll_crt0(per_process *)
22996 @subsubsection Working with Minimal Symbols
22998 Symbols extracted from a DLL's export table do not contain very much
22999 type information. All that @value{GDBN} can do is guess whether a symbol
23000 refers to a function or variable depending on the linker section that
23001 contains the symbol. Also note that the actual contents of the memory
23002 contained in a DLL are not available unless the program is running. This
23003 means that you cannot examine the contents of a variable or disassemble
23004 a function within a DLL without a running program.
23006 Variables are generally treated as pointers and dereferenced
23007 automatically. For this reason, it is often necessary to prefix a
23008 variable name with the address-of operator (``&'') and provide explicit
23009 type information in the command. Here's an example of the type of
23013 (@value{GDBP}) print 'cygwin1!__argv'
23014 'cygwin1!__argv' has unknown type; cast it to its declared type
23018 (@value{GDBP}) x 'cygwin1!__argv'
23019 'cygwin1!__argv' has unknown type; cast it to its declared type
23022 And two possible solutions:
23025 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23026 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23030 (@value{GDBP}) x/2x &'cygwin1!__argv'
23031 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23032 (@value{GDBP}) x/x 0x10021608
23033 0x10021608: 0x0022fd98
23034 (@value{GDBP}) x/s 0x0022fd98
23035 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23038 Setting a break point within a DLL is possible even before the program
23039 starts execution. However, under these circumstances, @value{GDBN} can't
23040 examine the initial instructions of the function in order to skip the
23041 function's frame set-up code. You can work around this by using ``*&''
23042 to set the breakpoint at a raw memory address:
23045 (@value{GDBP}) break *&'python22!PyOS_Readline'
23046 Breakpoint 1 at 0x1e04eff0
23049 The author of these extensions is not entirely convinced that setting a
23050 break point within a shared DLL like @file{kernel32.dll} is completely
23054 @subsection Commands Specific to @sc{gnu} Hurd Systems
23055 @cindex @sc{gnu} Hurd debugging
23057 This subsection describes @value{GDBN} commands specific to the
23058 @sc{gnu} Hurd native debugging.
23063 @kindex set signals@r{, Hurd command}
23064 @kindex set sigs@r{, Hurd command}
23065 This command toggles the state of inferior signal interception by
23066 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23067 affected by this command. @code{sigs} is a shorthand alias for
23072 @kindex show signals@r{, Hurd command}
23073 @kindex show sigs@r{, Hurd command}
23074 Show the current state of intercepting inferior's signals.
23076 @item set signal-thread
23077 @itemx set sigthread
23078 @kindex set signal-thread
23079 @kindex set sigthread
23080 This command tells @value{GDBN} which thread is the @code{libc} signal
23081 thread. That thread is run when a signal is delivered to a running
23082 process. @code{set sigthread} is the shorthand alias of @code{set
23085 @item show signal-thread
23086 @itemx show sigthread
23087 @kindex show signal-thread
23088 @kindex show sigthread
23089 These two commands show which thread will run when the inferior is
23090 delivered a signal.
23093 @kindex set stopped@r{, Hurd command}
23094 This commands tells @value{GDBN} that the inferior process is stopped,
23095 as with the @code{SIGSTOP} signal. The stopped process can be
23096 continued by delivering a signal to it.
23099 @kindex show stopped@r{, Hurd command}
23100 This command shows whether @value{GDBN} thinks the debuggee is
23103 @item set exceptions
23104 @kindex set exceptions@r{, Hurd command}
23105 Use this command to turn off trapping of exceptions in the inferior.
23106 When exception trapping is off, neither breakpoints nor
23107 single-stepping will work. To restore the default, set exception
23110 @item show exceptions
23111 @kindex show exceptions@r{, Hurd command}
23112 Show the current state of trapping exceptions in the inferior.
23114 @item set task pause
23115 @kindex set task@r{, Hurd commands}
23116 @cindex task attributes (@sc{gnu} Hurd)
23117 @cindex pause current task (@sc{gnu} Hurd)
23118 This command toggles task suspension when @value{GDBN} has control.
23119 Setting it to on takes effect immediately, and the task is suspended
23120 whenever @value{GDBN} gets control. Setting it to off will take
23121 effect the next time the inferior is continued. If this option is set
23122 to off, you can use @code{set thread default pause on} or @code{set
23123 thread pause on} (see below) to pause individual threads.
23125 @item show task pause
23126 @kindex show task@r{, Hurd commands}
23127 Show the current state of task suspension.
23129 @item set task detach-suspend-count
23130 @cindex task suspend count
23131 @cindex detach from task, @sc{gnu} Hurd
23132 This command sets the suspend count the task will be left with when
23133 @value{GDBN} detaches from it.
23135 @item show task detach-suspend-count
23136 Show the suspend count the task will be left with when detaching.
23138 @item set task exception-port
23139 @itemx set task excp
23140 @cindex task exception port, @sc{gnu} Hurd
23141 This command sets the task exception port to which @value{GDBN} will
23142 forward exceptions. The argument should be the value of the @dfn{send
23143 rights} of the task. @code{set task excp} is a shorthand alias.
23145 @item set noninvasive
23146 @cindex noninvasive task options
23147 This command switches @value{GDBN} to a mode that is the least
23148 invasive as far as interfering with the inferior is concerned. This
23149 is the same as using @code{set task pause}, @code{set exceptions}, and
23150 @code{set signals} to values opposite to the defaults.
23152 @item info send-rights
23153 @itemx info receive-rights
23154 @itemx info port-rights
23155 @itemx info port-sets
23156 @itemx info dead-names
23159 @cindex send rights, @sc{gnu} Hurd
23160 @cindex receive rights, @sc{gnu} Hurd
23161 @cindex port rights, @sc{gnu} Hurd
23162 @cindex port sets, @sc{gnu} Hurd
23163 @cindex dead names, @sc{gnu} Hurd
23164 These commands display information about, respectively, send rights,
23165 receive rights, port rights, port sets, and dead names of a task.
23166 There are also shorthand aliases: @code{info ports} for @code{info
23167 port-rights} and @code{info psets} for @code{info port-sets}.
23169 @item set thread pause
23170 @kindex set thread@r{, Hurd command}
23171 @cindex thread properties, @sc{gnu} Hurd
23172 @cindex pause current thread (@sc{gnu} Hurd)
23173 This command toggles current thread suspension when @value{GDBN} has
23174 control. Setting it to on takes effect immediately, and the current
23175 thread is suspended whenever @value{GDBN} gets control. Setting it to
23176 off will take effect the next time the inferior is continued.
23177 Normally, this command has no effect, since when @value{GDBN} has
23178 control, the whole task is suspended. However, if you used @code{set
23179 task pause off} (see above), this command comes in handy to suspend
23180 only the current thread.
23182 @item show thread pause
23183 @kindex show thread@r{, Hurd command}
23184 This command shows the state of current thread suspension.
23186 @item set thread run
23187 This command sets whether the current thread is allowed to run.
23189 @item show thread run
23190 Show whether the current thread is allowed to run.
23192 @item set thread detach-suspend-count
23193 @cindex thread suspend count, @sc{gnu} Hurd
23194 @cindex detach from thread, @sc{gnu} Hurd
23195 This command sets the suspend count @value{GDBN} will leave on a
23196 thread when detaching. This number is relative to the suspend count
23197 found by @value{GDBN} when it notices the thread; use @code{set thread
23198 takeover-suspend-count} to force it to an absolute value.
23200 @item show thread detach-suspend-count
23201 Show the suspend count @value{GDBN} will leave on the thread when
23204 @item set thread exception-port
23205 @itemx set thread excp
23206 Set the thread exception port to which to forward exceptions. This
23207 overrides the port set by @code{set task exception-port} (see above).
23208 @code{set thread excp} is the shorthand alias.
23210 @item set thread takeover-suspend-count
23211 Normally, @value{GDBN}'s thread suspend counts are relative to the
23212 value @value{GDBN} finds when it notices each thread. This command
23213 changes the suspend counts to be absolute instead.
23215 @item set thread default
23216 @itemx show thread default
23217 @cindex thread default settings, @sc{gnu} Hurd
23218 Each of the above @code{set thread} commands has a @code{set thread
23219 default} counterpart (e.g., @code{set thread default pause}, @code{set
23220 thread default exception-port}, etc.). The @code{thread default}
23221 variety of commands sets the default thread properties for all
23222 threads; you can then change the properties of individual threads with
23223 the non-default commands.
23230 @value{GDBN} provides the following commands specific to the Darwin target:
23233 @item set debug darwin @var{num}
23234 @kindex set debug darwin
23235 When set to a non zero value, enables debugging messages specific to
23236 the Darwin support. Higher values produce more verbose output.
23238 @item show debug darwin
23239 @kindex show debug darwin
23240 Show the current state of Darwin messages.
23242 @item set debug mach-o @var{num}
23243 @kindex set debug mach-o
23244 When set to a non zero value, enables debugging messages while
23245 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23246 file format used on Darwin for object and executable files.) Higher
23247 values produce more verbose output. This is a command to diagnose
23248 problems internal to @value{GDBN} and should not be needed in normal
23251 @item show debug mach-o
23252 @kindex show debug mach-o
23253 Show the current state of Mach-O file messages.
23255 @item set mach-exceptions on
23256 @itemx set mach-exceptions off
23257 @kindex set mach-exceptions
23258 On Darwin, faults are first reported as a Mach exception and are then
23259 mapped to a Posix signal. Use this command to turn on trapping of
23260 Mach exceptions in the inferior. This might be sometimes useful to
23261 better understand the cause of a fault. The default is off.
23263 @item show mach-exceptions
23264 @kindex show mach-exceptions
23265 Show the current state of exceptions trapping.
23269 @subsection FreeBSD
23272 When the ABI of a system call is changed in the FreeBSD kernel, this
23273 is implemented by leaving a compatibility system call using the old
23274 ABI at the existing number and allocating a new system call number for
23275 the version using the new ABI. As a convenience, when a system call
23276 is caught by name (@pxref{catch syscall}), compatibility system calls
23279 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23280 system call and catching the @code{kevent} system call by name catches
23284 (@value{GDBP}) catch syscall kevent
23285 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23291 @section Embedded Operating Systems
23293 This section describes configurations involving the debugging of
23294 embedded operating systems that are available for several different
23297 @value{GDBN} includes the ability to debug programs running on
23298 various real-time operating systems.
23300 @node Embedded Processors
23301 @section Embedded Processors
23303 This section goes into details specific to particular embedded
23306 @cindex send command to simulator
23307 Whenever a specific embedded processor has a simulator, @value{GDBN}
23308 allows to send an arbitrary command to the simulator.
23311 @item sim @var{command}
23312 @kindex sim@r{, a command}
23313 Send an arbitrary @var{command} string to the simulator. Consult the
23314 documentation for the specific simulator in use for information about
23315 acceptable commands.
23320 * ARC:: Synopsys ARC
23322 * M68K:: Motorola M68K
23323 * MicroBlaze:: Xilinx MicroBlaze
23324 * MIPS Embedded:: MIPS Embedded
23325 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23326 * PowerPC Embedded:: PowerPC Embedded
23329 * Super-H:: Renesas Super-H
23333 @subsection Synopsys ARC
23334 @cindex Synopsys ARC
23335 @cindex ARC specific commands
23341 @value{GDBN} provides the following ARC-specific commands:
23344 @item set debug arc
23345 @kindex set debug arc
23346 Control the level of ARC specific debug messages. Use 0 for no messages (the
23347 default), 1 for debug messages, and 2 for even more debug messages.
23349 @item show debug arc
23350 @kindex show debug arc
23351 Show the level of ARC specific debugging in operation.
23353 @item maint print arc arc-instruction @var{address}
23354 @kindex maint print arc arc-instruction
23355 Print internal disassembler information about instruction at a given address.
23362 @value{GDBN} provides the following ARM-specific commands:
23365 @item set arm disassembler
23367 This commands selects from a list of disassembly styles. The
23368 @code{"std"} style is the standard style.
23370 @item show arm disassembler
23372 Show the current disassembly style.
23374 @item set arm apcs32
23375 @cindex ARM 32-bit mode
23376 This command toggles ARM operation mode between 32-bit and 26-bit.
23378 @item show arm apcs32
23379 Display the current usage of the ARM 32-bit mode.
23381 @item set arm fpu @var{fputype}
23382 This command sets the ARM floating-point unit (FPU) type. The
23383 argument @var{fputype} can be one of these:
23387 Determine the FPU type by querying the OS ABI.
23389 Software FPU, with mixed-endian doubles on little-endian ARM
23392 GCC-compiled FPA co-processor.
23394 Software FPU with pure-endian doubles.
23400 Show the current type of the FPU.
23403 This command forces @value{GDBN} to use the specified ABI.
23406 Show the currently used ABI.
23408 @item set arm fallback-mode (arm|thumb|auto)
23409 @value{GDBN} uses the symbol table, when available, to determine
23410 whether instructions are ARM or Thumb. This command controls
23411 @value{GDBN}'s default behavior when the symbol table is not
23412 available. The default is @samp{auto}, which causes @value{GDBN} to
23413 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23416 @item show arm fallback-mode
23417 Show the current fallback instruction mode.
23419 @item set arm force-mode (arm|thumb|auto)
23420 This command overrides use of the symbol table to determine whether
23421 instructions are ARM or Thumb. The default is @samp{auto}, which
23422 causes @value{GDBN} to use the symbol table and then the setting
23423 of @samp{set arm fallback-mode}.
23425 @item show arm force-mode
23426 Show the current forced instruction mode.
23428 @item set debug arm
23429 Toggle whether to display ARM-specific debugging messages from the ARM
23430 target support subsystem.
23432 @item show debug arm
23433 Show whether ARM-specific debugging messages are enabled.
23437 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23438 The @value{GDBN} ARM simulator accepts the following optional arguments.
23441 @item --swi-support=@var{type}
23442 Tell the simulator which SWI interfaces to support. The argument
23443 @var{type} may be a comma separated list of the following values.
23444 The default value is @code{all}.
23459 The Motorola m68k configuration includes ColdFire support.
23462 @subsection MicroBlaze
23463 @cindex Xilinx MicroBlaze
23464 @cindex XMD, Xilinx Microprocessor Debugger
23466 The MicroBlaze is a soft-core processor supported on various Xilinx
23467 FPGAs, such as Spartan or Virtex series. Boards with these processors
23468 usually have JTAG ports which connect to a host system running the Xilinx
23469 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23470 This host system is used to download the configuration bitstream to
23471 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23472 communicates with the target board using the JTAG interface and
23473 presents a @code{gdbserver} interface to the board. By default
23474 @code{xmd} uses port @code{1234}. (While it is possible to change
23475 this default port, it requires the use of undocumented @code{xmd}
23476 commands. Contact Xilinx support if you need to do this.)
23478 Use these GDB commands to connect to the MicroBlaze target processor.
23481 @item target remote :1234
23482 Use this command to connect to the target if you are running @value{GDBN}
23483 on the same system as @code{xmd}.
23485 @item target remote @var{xmd-host}:1234
23486 Use this command to connect to the target if it is connected to @code{xmd}
23487 running on a different system named @var{xmd-host}.
23490 Use this command to download a program to the MicroBlaze target.
23492 @item set debug microblaze @var{n}
23493 Enable MicroBlaze-specific debugging messages if non-zero.
23495 @item show debug microblaze @var{n}
23496 Show MicroBlaze-specific debugging level.
23499 @node MIPS Embedded
23500 @subsection @acronym{MIPS} Embedded
23503 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23506 @item set mipsfpu double
23507 @itemx set mipsfpu single
23508 @itemx set mipsfpu none
23509 @itemx set mipsfpu auto
23510 @itemx show mipsfpu
23511 @kindex set mipsfpu
23512 @kindex show mipsfpu
23513 @cindex @acronym{MIPS} remote floating point
23514 @cindex floating point, @acronym{MIPS} remote
23515 If your target board does not support the @acronym{MIPS} floating point
23516 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23517 need this, you may wish to put the command in your @value{GDBN} init
23518 file). This tells @value{GDBN} how to find the return value of
23519 functions which return floating point values. It also allows
23520 @value{GDBN} to avoid saving the floating point registers when calling
23521 functions on the board. If you are using a floating point coprocessor
23522 with only single precision floating point support, as on the @sc{r4650}
23523 processor, use the command @samp{set mipsfpu single}. The default
23524 double precision floating point coprocessor may be selected using
23525 @samp{set mipsfpu double}.
23527 In previous versions the only choices were double precision or no
23528 floating point, so @samp{set mipsfpu on} will select double precision
23529 and @samp{set mipsfpu off} will select no floating point.
23531 As usual, you can inquire about the @code{mipsfpu} variable with
23532 @samp{show mipsfpu}.
23535 @node OpenRISC 1000
23536 @subsection OpenRISC 1000
23537 @cindex OpenRISC 1000
23540 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23541 mainly provided as a soft-core which can run on Xilinx, Altera and other
23544 @value{GDBN} for OpenRISC supports the below commands when connecting to
23552 Runs the builtin CPU simulator which can run very basic
23553 programs but does not support most hardware functions like MMU.
23554 For more complex use cases the user is advised to run an external
23555 target, and connect using @samp{target remote}.
23557 Example: @code{target sim}
23559 @item set debug or1k
23560 Toggle whether to display OpenRISC-specific debugging messages from the
23561 OpenRISC target support subsystem.
23563 @item show debug or1k
23564 Show whether OpenRISC-specific debugging messages are enabled.
23567 @node PowerPC Embedded
23568 @subsection PowerPC Embedded
23570 @cindex DVC register
23571 @value{GDBN} supports using the DVC (Data Value Compare) register to
23572 implement in hardware simple hardware watchpoint conditions of the form:
23575 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23576 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23579 The DVC register will be automatically used when @value{GDBN} detects
23580 such pattern in a condition expression, and the created watchpoint uses one
23581 debug register (either the @code{exact-watchpoints} option is on and the
23582 variable is scalar, or the variable has a length of one byte). This feature
23583 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23586 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23587 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23588 in which case watchpoints using only one debug register are created when
23589 watching variables of scalar types.
23591 You can create an artificial array to watch an arbitrary memory
23592 region using one of the following commands (@pxref{Expressions}):
23595 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23596 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23599 PowerPC embedded processors support masked watchpoints. See the discussion
23600 about the @code{mask} argument in @ref{Set Watchpoints}.
23602 @cindex ranged breakpoint
23603 PowerPC embedded processors support hardware accelerated
23604 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23605 the inferior whenever it executes an instruction at any address within
23606 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23607 use the @code{break-range} command.
23609 @value{GDBN} provides the following PowerPC-specific commands:
23612 @kindex break-range
23613 @item break-range @var{start-location}, @var{end-location}
23614 Set a breakpoint for an address range given by
23615 @var{start-location} and @var{end-location}, which can specify a function name,
23616 a line number, an offset of lines from the current line or from the start
23617 location, or an address of an instruction (see @ref{Specify Location},
23618 for a list of all the possible ways to specify a @var{location}.)
23619 The breakpoint will stop execution of the inferior whenever it
23620 executes an instruction at any address within the specified range,
23621 (including @var{start-location} and @var{end-location}.)
23623 @kindex set powerpc
23624 @item set powerpc soft-float
23625 @itemx show powerpc soft-float
23626 Force @value{GDBN} to use (or not use) a software floating point calling
23627 convention. By default, @value{GDBN} selects the calling convention based
23628 on the selected architecture and the provided executable file.
23630 @item set powerpc vector-abi
23631 @itemx show powerpc vector-abi
23632 Force @value{GDBN} to use the specified calling convention for vector
23633 arguments and return values. The valid options are @samp{auto};
23634 @samp{generic}, to avoid vector registers even if they are present;
23635 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23636 registers. By default, @value{GDBN} selects the calling convention
23637 based on the selected architecture and the provided executable file.
23639 @item set powerpc exact-watchpoints
23640 @itemx show powerpc exact-watchpoints
23641 Allow @value{GDBN} to use only one debug register when watching a variable
23642 of scalar type, thus assuming that the variable is accessed through the
23643 address of its first byte.
23648 @subsection Atmel AVR
23651 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23652 following AVR-specific commands:
23655 @item info io_registers
23656 @kindex info io_registers@r{, AVR}
23657 @cindex I/O registers (Atmel AVR)
23658 This command displays information about the AVR I/O registers. For
23659 each register, @value{GDBN} prints its number and value.
23666 When configured for debugging CRIS, @value{GDBN} provides the
23667 following CRIS-specific commands:
23670 @item set cris-version @var{ver}
23671 @cindex CRIS version
23672 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23673 The CRIS version affects register names and sizes. This command is useful in
23674 case autodetection of the CRIS version fails.
23676 @item show cris-version
23677 Show the current CRIS version.
23679 @item set cris-dwarf2-cfi
23680 @cindex DWARF-2 CFI and CRIS
23681 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23682 Change to @samp{off} when using @code{gcc-cris} whose version is below
23685 @item show cris-dwarf2-cfi
23686 Show the current state of using DWARF-2 CFI.
23688 @item set cris-mode @var{mode}
23690 Set the current CRIS mode to @var{mode}. It should only be changed when
23691 debugging in guru mode, in which case it should be set to
23692 @samp{guru} (the default is @samp{normal}).
23694 @item show cris-mode
23695 Show the current CRIS mode.
23699 @subsection Renesas Super-H
23702 For the Renesas Super-H processor, @value{GDBN} provides these
23706 @item set sh calling-convention @var{convention}
23707 @kindex set sh calling-convention
23708 Set the calling-convention used when calling functions from @value{GDBN}.
23709 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23710 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23711 convention. If the DWARF-2 information of the called function specifies
23712 that the function follows the Renesas calling convention, the function
23713 is called using the Renesas calling convention. If the calling convention
23714 is set to @samp{renesas}, the Renesas calling convention is always used,
23715 regardless of the DWARF-2 information. This can be used to override the
23716 default of @samp{gcc} if debug information is missing, or the compiler
23717 does not emit the DWARF-2 calling convention entry for a function.
23719 @item show sh calling-convention
23720 @kindex show sh calling-convention
23721 Show the current calling convention setting.
23726 @node Architectures
23727 @section Architectures
23729 This section describes characteristics of architectures that affect
23730 all uses of @value{GDBN} with the architecture, both native and cross.
23737 * HPPA:: HP PA architecture
23738 * SPU:: Cell Broadband Engine SPU architecture
23746 @subsection AArch64
23747 @cindex AArch64 support
23749 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23750 following special commands:
23753 @item set debug aarch64
23754 @kindex set debug aarch64
23755 This command determines whether AArch64 architecture-specific debugging
23756 messages are to be displayed.
23758 @item show debug aarch64
23759 Show whether AArch64 debugging messages are displayed.
23763 @subsubsection AArch64 SVE.
23764 @cindex AArch64 SVE.
23766 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23767 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23768 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23769 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23770 @code{$vg} will be provided. This is the vector granule for the current thread
23771 and represents the number of 64-bit chunks in an SVE @code{z} register.
23773 If the vector length changes, then the @code{$vg} register will be updated,
23774 but the lengths of the @code{z} and @code{p} registers will not change. This
23775 is a known limitation of @value{GDBN} and does not affect the execution of the
23780 @subsection x86 Architecture-specific Issues
23783 @item set struct-convention @var{mode}
23784 @kindex set struct-convention
23785 @cindex struct return convention
23786 @cindex struct/union returned in registers
23787 Set the convention used by the inferior to return @code{struct}s and
23788 @code{union}s from functions to @var{mode}. Possible values of
23789 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23790 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23791 are returned on the stack, while @code{"reg"} means that a
23792 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23793 be returned in a register.
23795 @item show struct-convention
23796 @kindex show struct-convention
23797 Show the current setting of the convention to return @code{struct}s
23802 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23803 @cindex Intel Memory Protection Extensions (MPX).
23805 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23806 @footnote{The register named with capital letters represent the architecture
23807 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23808 which are the lower bound and upper bound. Bounds are effective addresses or
23809 memory locations. The upper bounds are architecturally represented in 1's
23810 complement form. A bound having lower bound = 0, and upper bound = 0
23811 (1's complement of all bits set) will allow access to the entire address space.
23813 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23814 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23815 display the upper bound performing the complement of one operation on the
23816 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23817 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23818 can also be noted that the upper bounds are inclusive.
23820 As an example, assume that the register BND0 holds bounds for a pointer having
23821 access allowed for the range between 0x32 and 0x71. The values present on
23822 bnd0raw and bnd registers are presented as follows:
23825 bnd0raw = @{0x32, 0xffffffff8e@}
23826 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23829 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23830 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23831 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23832 Python, the display includes the memory size, in bits, accessible to
23835 Bounds can also be stored in bounds tables, which are stored in
23836 application memory. These tables store bounds for pointers by specifying
23837 the bounds pointer's value along with its bounds. Evaluating and changing
23838 bounds located in bound tables is therefore interesting while investigating
23839 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23842 @item show mpx bound @var{pointer}
23843 @kindex show mpx bound
23844 Display bounds of the given @var{pointer}.
23846 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23847 @kindex set mpx bound
23848 Set the bounds of a pointer in the bound table.
23849 This command takes three parameters: @var{pointer} is the pointers
23850 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23851 for lower and upper bounds respectively.
23854 When you call an inferior function on an Intel MPX enabled program,
23855 GDB sets the inferior's bound registers to the init (disabled) state
23856 before calling the function. As a consequence, bounds checks for the
23857 pointer arguments passed to the function will always pass.
23859 This is necessary because when you call an inferior function, the
23860 program is usually in the middle of the execution of other function.
23861 Since at that point bound registers are in an arbitrary state, not
23862 clearing them would lead to random bound violations in the called
23865 You can still examine the influence of the bound registers on the
23866 execution of the called function by stopping the execution of the
23867 called function at its prologue, setting bound registers, and
23868 continuing the execution. For example:
23872 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23873 $ print upper (a, b, c, d, 1)
23874 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23876 @{lbound = 0x0, ubound = ffffffff@} : size -1
23879 At this last step the value of bnd0 can be changed for investigation of bound
23880 violations caused along the execution of the call. In order to know how to
23881 set the bound registers or bound table for the call consult the ABI.
23886 See the following section.
23889 @subsection @acronym{MIPS}
23891 @cindex stack on Alpha
23892 @cindex stack on @acronym{MIPS}
23893 @cindex Alpha stack
23894 @cindex @acronym{MIPS} stack
23895 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23896 sometimes requires @value{GDBN} to search backward in the object code to
23897 find the beginning of a function.
23899 @cindex response time, @acronym{MIPS} debugging
23900 To improve response time (especially for embedded applications, where
23901 @value{GDBN} may be restricted to a slow serial line for this search)
23902 you may want to limit the size of this search, using one of these
23906 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23907 @item set heuristic-fence-post @var{limit}
23908 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23909 search for the beginning of a function. A value of @var{0} (the
23910 default) means there is no limit. However, except for @var{0}, the
23911 larger the limit the more bytes @code{heuristic-fence-post} must search
23912 and therefore the longer it takes to run. You should only need to use
23913 this command when debugging a stripped executable.
23915 @item show heuristic-fence-post
23916 Display the current limit.
23920 These commands are available @emph{only} when @value{GDBN} is configured
23921 for debugging programs on Alpha or @acronym{MIPS} processors.
23923 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23927 @item set mips abi @var{arg}
23928 @kindex set mips abi
23929 @cindex set ABI for @acronym{MIPS}
23930 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23931 values of @var{arg} are:
23935 The default ABI associated with the current binary (this is the
23945 @item show mips abi
23946 @kindex show mips abi
23947 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23949 @item set mips compression @var{arg}
23950 @kindex set mips compression
23951 @cindex code compression, @acronym{MIPS}
23952 Tell @value{GDBN} which @acronym{MIPS} compressed
23953 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23954 inferior. @value{GDBN} uses this for code disassembly and other
23955 internal interpretation purposes. This setting is only referred to
23956 when no executable has been associated with the debugging session or
23957 the executable does not provide information about the encoding it uses.
23958 Otherwise this setting is automatically updated from information
23959 provided by the executable.
23961 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23962 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23963 executables containing @acronym{MIPS16} code frequently are not
23964 identified as such.
23966 This setting is ``sticky''; that is, it retains its value across
23967 debugging sessions until reset either explicitly with this command or
23968 implicitly from an executable.
23970 The compiler and/or assembler typically add symbol table annotations to
23971 identify functions compiled for the @acronym{MIPS16} or
23972 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23973 are present, @value{GDBN} uses them in preference to the global
23974 compressed @acronym{ISA} encoding setting.
23976 @item show mips compression
23977 @kindex show mips compression
23978 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23979 @value{GDBN} to debug the inferior.
23982 @itemx show mipsfpu
23983 @xref{MIPS Embedded, set mipsfpu}.
23985 @item set mips mask-address @var{arg}
23986 @kindex set mips mask-address
23987 @cindex @acronym{MIPS} addresses, masking
23988 This command determines whether the most-significant 32 bits of 64-bit
23989 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23990 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23991 setting, which lets @value{GDBN} determine the correct value.
23993 @item show mips mask-address
23994 @kindex show mips mask-address
23995 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23998 @item set remote-mips64-transfers-32bit-regs
23999 @kindex set remote-mips64-transfers-32bit-regs
24000 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24001 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24002 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24003 and 64 bits for other registers, set this option to @samp{on}.
24005 @item show remote-mips64-transfers-32bit-regs
24006 @kindex show remote-mips64-transfers-32bit-regs
24007 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24009 @item set debug mips
24010 @kindex set debug mips
24011 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24012 target code in @value{GDBN}.
24014 @item show debug mips
24015 @kindex show debug mips
24016 Show the current setting of @acronym{MIPS} debugging messages.
24022 @cindex HPPA support
24024 When @value{GDBN} is debugging the HP PA architecture, it provides the
24025 following special commands:
24028 @item set debug hppa
24029 @kindex set debug hppa
24030 This command determines whether HPPA architecture-specific debugging
24031 messages are to be displayed.
24033 @item show debug hppa
24034 Show whether HPPA debugging messages are displayed.
24036 @item maint print unwind @var{address}
24037 @kindex maint print unwind@r{, HPPA}
24038 This command displays the contents of the unwind table entry at the
24039 given @var{address}.
24045 @subsection Cell Broadband Engine SPU architecture
24046 @cindex Cell Broadband Engine
24049 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24050 it provides the following special commands:
24053 @item info spu event
24055 Display SPU event facility status. Shows current event mask
24056 and pending event status.
24058 @item info spu signal
24059 Display SPU signal notification facility status. Shows pending
24060 signal-control word and signal notification mode of both signal
24061 notification channels.
24063 @item info spu mailbox
24064 Display SPU mailbox facility status. Shows all pending entries,
24065 in order of processing, in each of the SPU Write Outbound,
24066 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24069 Display MFC DMA status. Shows all pending commands in the MFC
24070 DMA queue. For each entry, opcode, tag, class IDs, effective
24071 and local store addresses and transfer size are shown.
24073 @item info spu proxydma
24074 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24075 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24076 and local store addresses and transfer size are shown.
24080 When @value{GDBN} is debugging a combined PowerPC/SPU application
24081 on the Cell Broadband Engine, it provides in addition the following
24085 @item set spu stop-on-load @var{arg}
24087 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24088 will give control to the user when a new SPE thread enters its @code{main}
24089 function. The default is @code{off}.
24091 @item show spu stop-on-load
24093 Show whether to stop for new SPE threads.
24095 @item set spu auto-flush-cache @var{arg}
24096 Set whether to automatically flush the software-managed cache. When set to
24097 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24098 cache to be flushed whenever SPE execution stops. This provides a consistent
24099 view of PowerPC memory that is accessed via the cache. If an application
24100 does not use the software-managed cache, this option has no effect.
24102 @item show spu auto-flush-cache
24103 Show whether to automatically flush the software-managed cache.
24108 @subsection PowerPC
24109 @cindex PowerPC architecture
24111 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24112 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24113 numbers stored in the floating point registers. These values must be stored
24114 in two consecutive registers, always starting at an even register like
24115 @code{f0} or @code{f2}.
24117 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24118 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24119 @code{f2} and @code{f3} for @code{$dl1} and so on.
24121 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24122 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24125 @subsection Nios II
24126 @cindex Nios II architecture
24128 When @value{GDBN} is debugging the Nios II architecture,
24129 it provides the following special commands:
24133 @item set debug nios2
24134 @kindex set debug nios2
24135 This command turns on and off debugging messages for the Nios II
24136 target code in @value{GDBN}.
24138 @item show debug nios2
24139 @kindex show debug nios2
24140 Show the current setting of Nios II debugging messages.
24144 @subsection Sparc64
24145 @cindex Sparc64 support
24146 @cindex Application Data Integrity
24147 @subsubsection ADI Support
24149 The M7 processor supports an Application Data Integrity (ADI) feature that
24150 detects invalid data accesses. When software allocates memory and enables
24151 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24152 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24153 the 4-bit version in every cacheline of that data. Hardware saves the latter
24154 in spare bits in the cache and memory hierarchy. On each load and store,
24155 the processor compares the upper 4 VA (virtual address) bits to the
24156 cacheline's version. If there is a mismatch, the processor generates a
24157 version mismatch trap which can be either precise or disrupting. The trap
24158 is an error condition which the kernel delivers to the process as a SIGSEGV
24161 Note that only 64-bit applications can use ADI and need to be built with
24164 Values of the ADI version tags, which are in granularity of a
24165 cacheline (64 bytes), can be viewed or modified.
24169 @kindex adi examine
24170 @item adi (examine | x) [ / @var{n} ] @var{addr}
24172 The @code{adi examine} command displays the value of one ADI version tag per
24175 @var{n} is a decimal integer specifying the number in bytes; the default
24176 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24177 block size, to display.
24179 @var{addr} is the address in user address space where you want @value{GDBN}
24180 to begin displaying the ADI version tags.
24182 Below is an example of displaying ADI versions of variable "shmaddr".
24185 (@value{GDBP}) adi x/100 shmaddr
24186 0xfff800010002c000: 0 0
24190 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24192 The @code{adi assign} command is used to assign new ADI version tag
24195 @var{n} is a decimal integer specifying the number in bytes;
24196 the default is 1. It specifies how much ADI version information, at the
24197 ratio of 1:ADI block size, to modify.
24199 @var{addr} is the address in user address space where you want @value{GDBN}
24200 to begin modifying the ADI version tags.
24202 @var{tag} is the new ADI version tag.
24204 For example, do the following to modify then verify ADI versions of
24205 variable "shmaddr":
24208 (@value{GDBP}) adi a/100 shmaddr = 7
24209 (@value{GDBP}) adi x/100 shmaddr
24210 0xfff800010002c000: 7 7
24217 @cindex S12Z support
24219 When @value{GDBN} is debugging the S12Z architecture,
24220 it provides the following special command:
24223 @item maint info bdccsr
24224 @kindex maint info bdccsr@r{, S12Z}
24225 This command displays the current value of the microprocessor's
24230 @node Controlling GDB
24231 @chapter Controlling @value{GDBN}
24233 You can alter the way @value{GDBN} interacts with you by using the
24234 @code{set} command. For commands controlling how @value{GDBN} displays
24235 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24240 * Editing:: Command editing
24241 * Command History:: Command history
24242 * Screen Size:: Screen size
24243 * Output Styling:: Output styling
24244 * Numbers:: Numbers
24245 * ABI:: Configuring the current ABI
24246 * Auto-loading:: Automatically loading associated files
24247 * Messages/Warnings:: Optional warnings and messages
24248 * Debugging Output:: Optional messages about internal happenings
24249 * Other Misc Settings:: Other Miscellaneous Settings
24257 @value{GDBN} indicates its readiness to read a command by printing a string
24258 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24259 can change the prompt string with the @code{set prompt} command. For
24260 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24261 the prompt in one of the @value{GDBN} sessions so that you can always tell
24262 which one you are talking to.
24264 @emph{Note:} @code{set prompt} does not add a space for you after the
24265 prompt you set. This allows you to set a prompt which ends in a space
24266 or a prompt that does not.
24270 @item set prompt @var{newprompt}
24271 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24273 @kindex show prompt
24275 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24278 Versions of @value{GDBN} that ship with Python scripting enabled have
24279 prompt extensions. The commands for interacting with these extensions
24283 @kindex set extended-prompt
24284 @item set extended-prompt @var{prompt}
24285 Set an extended prompt that allows for substitutions.
24286 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24287 substitution. Any escape sequences specified as part of the prompt
24288 string are replaced with the corresponding strings each time the prompt
24294 set extended-prompt Current working directory: \w (gdb)
24297 Note that when an extended-prompt is set, it takes control of the
24298 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24300 @kindex show extended-prompt
24301 @item show extended-prompt
24302 Prints the extended prompt. Any escape sequences specified as part of
24303 the prompt string with @code{set extended-prompt}, are replaced with the
24304 corresponding strings each time the prompt is displayed.
24308 @section Command Editing
24310 @cindex command line editing
24312 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24313 @sc{gnu} library provides consistent behavior for programs which provide a
24314 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24315 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24316 substitution, and a storage and recall of command history across
24317 debugging sessions.
24319 You may control the behavior of command line editing in @value{GDBN} with the
24320 command @code{set}.
24323 @kindex set editing
24326 @itemx set editing on
24327 Enable command line editing (enabled by default).
24329 @item set editing off
24330 Disable command line editing.
24332 @kindex show editing
24334 Show whether command line editing is enabled.
24337 @ifset SYSTEM_READLINE
24338 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24340 @ifclear SYSTEM_READLINE
24341 @xref{Command Line Editing},
24343 for more details about the Readline
24344 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24345 encouraged to read that chapter.
24347 @node Command History
24348 @section Command History
24349 @cindex command history
24351 @value{GDBN} can keep track of the commands you type during your
24352 debugging sessions, so that you can be certain of precisely what
24353 happened. Use these commands to manage the @value{GDBN} command
24356 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24357 package, to provide the history facility.
24358 @ifset SYSTEM_READLINE
24359 @xref{Using History Interactively, , , history, GNU History Library},
24361 @ifclear SYSTEM_READLINE
24362 @xref{Using History Interactively},
24364 for the detailed description of the History library.
24366 To issue a command to @value{GDBN} without affecting certain aspects of
24367 the state which is seen by users, prefix it with @samp{server }
24368 (@pxref{Server Prefix}). This
24369 means that this command will not affect the command history, nor will it
24370 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24371 pressed on a line by itself.
24373 @cindex @code{server}, command prefix
24374 The server prefix does not affect the recording of values into the value
24375 history; to print a value without recording it into the value history,
24376 use the @code{output} command instead of the @code{print} command.
24378 Here is the description of @value{GDBN} commands related to command
24382 @cindex history substitution
24383 @cindex history file
24384 @kindex set history filename
24385 @cindex @env{GDBHISTFILE}, environment variable
24386 @item set history filename @var{fname}
24387 Set the name of the @value{GDBN} command history file to @var{fname}.
24388 This is the file where @value{GDBN} reads an initial command history
24389 list, and where it writes the command history from this session when it
24390 exits. You can access this list through history expansion or through
24391 the history command editing characters listed below. This file defaults
24392 to the value of the environment variable @code{GDBHISTFILE}, or to
24393 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24396 @cindex save command history
24397 @kindex set history save
24398 @item set history save
24399 @itemx set history save on
24400 Record command history in a file, whose name may be specified with the
24401 @code{set history filename} command. By default, this option is disabled.
24403 @item set history save off
24404 Stop recording command history in a file.
24406 @cindex history size
24407 @kindex set history size
24408 @cindex @env{GDBHISTSIZE}, environment variable
24409 @item set history size @var{size}
24410 @itemx set history size unlimited
24411 Set the number of commands which @value{GDBN} keeps in its history list.
24412 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24413 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24414 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24415 either a negative number or the empty string, then the number of commands
24416 @value{GDBN} keeps in the history list is unlimited.
24418 @cindex remove duplicate history
24419 @kindex set history remove-duplicates
24420 @item set history remove-duplicates @var{count}
24421 @itemx set history remove-duplicates unlimited
24422 Control the removal of duplicate history entries in the command history list.
24423 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24424 history entries and remove the first entry that is a duplicate of the current
24425 entry being added to the command history list. If @var{count} is
24426 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24427 removal of duplicate history entries is disabled.
24429 Only history entries added during the current session are considered for
24430 removal. This option is set to 0 by default.
24434 History expansion assigns special meaning to the character @kbd{!}.
24435 @ifset SYSTEM_READLINE
24436 @xref{Event Designators, , , history, GNU History Library},
24438 @ifclear SYSTEM_READLINE
24439 @xref{Event Designators},
24443 @cindex history expansion, turn on/off
24444 Since @kbd{!} is also the logical not operator in C, history expansion
24445 is off by default. If you decide to enable history expansion with the
24446 @code{set history expansion on} command, you may sometimes need to
24447 follow @kbd{!} (when it is used as logical not, in an expression) with
24448 a space or a tab to prevent it from being expanded. The readline
24449 history facilities do not attempt substitution on the strings
24450 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24452 The commands to control history expansion are:
24455 @item set history expansion on
24456 @itemx set history expansion
24457 @kindex set history expansion
24458 Enable history expansion. History expansion is off by default.
24460 @item set history expansion off
24461 Disable history expansion.
24464 @kindex show history
24466 @itemx show history filename
24467 @itemx show history save
24468 @itemx show history size
24469 @itemx show history expansion
24470 These commands display the state of the @value{GDBN} history parameters.
24471 @code{show history} by itself displays all four states.
24476 @kindex show commands
24477 @cindex show last commands
24478 @cindex display command history
24479 @item show commands
24480 Display the last ten commands in the command history.
24482 @item show commands @var{n}
24483 Print ten commands centered on command number @var{n}.
24485 @item show commands +
24486 Print ten commands just after the commands last printed.
24490 @section Screen Size
24491 @cindex size of screen
24492 @cindex screen size
24495 @cindex pauses in output
24497 Certain commands to @value{GDBN} may produce large amounts of
24498 information output to the screen. To help you read all of it,
24499 @value{GDBN} pauses and asks you for input at the end of each page of
24500 output. Type @key{RET} when you want to see one more page of output,
24501 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24502 without paging for the rest of the current command. Also, the screen
24503 width setting determines when to wrap lines of output. Depending on
24504 what is being printed, @value{GDBN} tries to break the line at a
24505 readable place, rather than simply letting it overflow onto the
24508 Normally @value{GDBN} knows the size of the screen from the terminal
24509 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24510 together with the value of the @code{TERM} environment variable and the
24511 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24512 you can override it with the @code{set height} and @code{set
24519 @kindex show height
24520 @item set height @var{lpp}
24521 @itemx set height unlimited
24523 @itemx set width @var{cpl}
24524 @itemx set width unlimited
24526 These @code{set} commands specify a screen height of @var{lpp} lines and
24527 a screen width of @var{cpl} characters. The associated @code{show}
24528 commands display the current settings.
24530 If you specify a height of either @code{unlimited} or zero lines,
24531 @value{GDBN} does not pause during output no matter how long the
24532 output is. This is useful if output is to a file or to an editor
24535 Likewise, you can specify @samp{set width unlimited} or @samp{set
24536 width 0} to prevent @value{GDBN} from wrapping its output.
24538 @item set pagination on
24539 @itemx set pagination off
24540 @kindex set pagination
24541 Turn the output pagination on or off; the default is on. Turning
24542 pagination off is the alternative to @code{set height unlimited}. Note that
24543 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24544 Options, -batch}) also automatically disables pagination.
24546 @item show pagination
24547 @kindex show pagination
24548 Show the current pagination mode.
24551 @node Output Styling
24552 @section Output Styling
24558 @value{GDBN} can style its output on a capable terminal. This is
24559 enabled by default on most systems, but disabled by default when in
24560 batch mode (@pxref{Mode Options}). Various style settings are available;
24561 and styles can also be disabled entirely.
24564 @item set style enabled @samp{on|off}
24565 Enable or disable all styling. The default is host-dependent, with
24566 most hosts defaulting to @samp{on}.
24568 @item show style enabled
24569 Show the current state of styling.
24571 @item set style sources @samp{on|off}
24572 Enable or disable source code styling. This affects whether source
24573 code, such as the output of the @code{list} command, is styled. Note
24574 that source styling only works if styling in general is enabled, and
24575 if @value{GDBN} was linked with the GNU Source Highlight library. The
24576 default is @samp{on}.
24578 @item show style sources
24579 Show the current state of source code styling.
24582 Subcommands of @code{set style} control specific forms of styling.
24583 These subcommands all follow the same pattern: each style-able object
24584 can be styled with a foreground color, a background color, and an
24587 For example, the style of file names can be controlled using the
24588 @code{set style filename} group of commands:
24591 @item set style filename background @var{color}
24592 Set the background to @var{color}. Valid colors are @samp{none}
24593 (meaning the terminal's default color), @samp{black}, @samp{red},
24594 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24597 @item set style filename foreground @var{color}
24598 Set the foreground to @var{color}. Valid colors are @samp{none}
24599 (meaning the terminal's default color), @samp{black}, @samp{red},
24600 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24603 @item set style filename intensity @var{value}
24604 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24605 (the default), @samp{bold}, and @samp{dim}.
24608 The style-able objects are:
24611 Control the styling of file names. By default, this style's
24612 foreground color is green.
24615 Control the styling of function names. These are managed with the
24616 @code{set style function} family of commands. By default, this
24617 style's foreground color is yellow.
24620 Control the styling of variable names. These are managed with the
24621 @code{set style variable} family of commands. By default, this style's
24622 foreground color is cyan.
24625 Control the styling of addresses. These are managed with the
24626 @code{set style address} family of commands. By default, this style's
24627 foreground color is blue.
24632 @cindex number representation
24633 @cindex entering numbers
24635 You can always enter numbers in octal, decimal, or hexadecimal in
24636 @value{GDBN} by the usual conventions: octal numbers begin with
24637 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24638 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24639 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24640 10; likewise, the default display for numbers---when no particular
24641 format is specified---is base 10. You can change the default base for
24642 both input and output with the commands described below.
24645 @kindex set input-radix
24646 @item set input-radix @var{base}
24647 Set the default base for numeric input. Supported choices
24648 for @var{base} are decimal 8, 10, or 16. The base must itself be
24649 specified either unambiguously or using the current input radix; for
24653 set input-radix 012
24654 set input-radix 10.
24655 set input-radix 0xa
24659 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24660 leaves the input radix unchanged, no matter what it was, since
24661 @samp{10}, being without any leading or trailing signs of its base, is
24662 interpreted in the current radix. Thus, if the current radix is 16,
24663 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24666 @kindex set output-radix
24667 @item set output-radix @var{base}
24668 Set the default base for numeric display. Supported choices
24669 for @var{base} are decimal 8, 10, or 16. The base must itself be
24670 specified either unambiguously or using the current input radix.
24672 @kindex show input-radix
24673 @item show input-radix
24674 Display the current default base for numeric input.
24676 @kindex show output-radix
24677 @item show output-radix
24678 Display the current default base for numeric display.
24680 @item set radix @r{[}@var{base}@r{]}
24684 These commands set and show the default base for both input and output
24685 of numbers. @code{set radix} sets the radix of input and output to
24686 the same base; without an argument, it resets the radix back to its
24687 default value of 10.
24692 @section Configuring the Current ABI
24694 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24695 application automatically. However, sometimes you need to override its
24696 conclusions. Use these commands to manage @value{GDBN}'s view of the
24702 @cindex Newlib OS ABI and its influence on the longjmp handling
24704 One @value{GDBN} configuration can debug binaries for multiple operating
24705 system targets, either via remote debugging or native emulation.
24706 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24707 but you can override its conclusion using the @code{set osabi} command.
24708 One example where this is useful is in debugging of binaries which use
24709 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24710 not have the same identifying marks that the standard C library for your
24713 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24714 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24715 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24716 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24720 Show the OS ABI currently in use.
24723 With no argument, show the list of registered available OS ABI's.
24725 @item set osabi @var{abi}
24726 Set the current OS ABI to @var{abi}.
24729 @cindex float promotion
24731 Generally, the way that an argument of type @code{float} is passed to a
24732 function depends on whether the function is prototyped. For a prototyped
24733 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24734 according to the architecture's convention for @code{float}. For unprototyped
24735 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24736 @code{double} and then passed.
24738 Unfortunately, some forms of debug information do not reliably indicate whether
24739 a function is prototyped. If @value{GDBN} calls a function that is not marked
24740 as prototyped, it consults @kbd{set coerce-float-to-double}.
24743 @kindex set coerce-float-to-double
24744 @item set coerce-float-to-double
24745 @itemx set coerce-float-to-double on
24746 Arguments of type @code{float} will be promoted to @code{double} when passed
24747 to an unprototyped function. This is the default setting.
24749 @item set coerce-float-to-double off
24750 Arguments of type @code{float} will be passed directly to unprototyped
24753 @kindex show coerce-float-to-double
24754 @item show coerce-float-to-double
24755 Show the current setting of promoting @code{float} to @code{double}.
24759 @kindex show cp-abi
24760 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24761 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24762 used to build your application. @value{GDBN} only fully supports
24763 programs with a single C@t{++} ABI; if your program contains code using
24764 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24765 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24766 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24767 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24768 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24769 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24774 Show the C@t{++} ABI currently in use.
24777 With no argument, show the list of supported C@t{++} ABI's.
24779 @item set cp-abi @var{abi}
24780 @itemx set cp-abi auto
24781 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24785 @section Automatically loading associated files
24786 @cindex auto-loading
24788 @value{GDBN} sometimes reads files with commands and settings automatically,
24789 without being explicitly told so by the user. We call this feature
24790 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24791 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24792 results or introduce security risks (e.g., if the file comes from untrusted
24796 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24797 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24799 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24800 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24803 There are various kinds of files @value{GDBN} can automatically load.
24804 In addition to these files, @value{GDBN} supports auto-loading code written
24805 in various extension languages. @xref{Auto-loading extensions}.
24807 Note that loading of these associated files (including the local @file{.gdbinit}
24808 file) requires accordingly configured @code{auto-load safe-path}
24809 (@pxref{Auto-loading safe path}).
24811 For these reasons, @value{GDBN} includes commands and options to let you
24812 control when to auto-load files and which files should be auto-loaded.
24815 @anchor{set auto-load off}
24816 @kindex set auto-load off
24817 @item set auto-load off
24818 Globally disable loading of all auto-loaded files.
24819 You may want to use this command with the @samp{-iex} option
24820 (@pxref{Option -init-eval-command}) such as:
24822 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24825 Be aware that system init file (@pxref{System-wide configuration})
24826 and init files from your home directory (@pxref{Home Directory Init File})
24827 still get read (as they come from generally trusted directories).
24828 To prevent @value{GDBN} from auto-loading even those init files, use the
24829 @option{-nx} option (@pxref{Mode Options}), in addition to
24830 @code{set auto-load no}.
24832 @anchor{show auto-load}
24833 @kindex show auto-load
24834 @item show auto-load
24835 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24839 (gdb) show auto-load
24840 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24841 libthread-db: Auto-loading of inferior specific libthread_db is on.
24842 local-gdbinit: Auto-loading of .gdbinit script from current directory
24844 python-scripts: Auto-loading of Python scripts is on.
24845 safe-path: List of directories from which it is safe to auto-load files
24846 is $debugdir:$datadir/auto-load.
24847 scripts-directory: List of directories from which to load auto-loaded scripts
24848 is $debugdir:$datadir/auto-load.
24851 @anchor{info auto-load}
24852 @kindex info auto-load
24853 @item info auto-load
24854 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24858 (gdb) info auto-load
24861 Yes /home/user/gdb/gdb-gdb.gdb
24862 libthread-db: No auto-loaded libthread-db.
24863 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24867 Yes /home/user/gdb/gdb-gdb.py
24871 These are @value{GDBN} control commands for the auto-loading:
24873 @multitable @columnfractions .5 .5
24874 @item @xref{set auto-load off}.
24875 @tab Disable auto-loading globally.
24876 @item @xref{show auto-load}.
24877 @tab Show setting of all kinds of files.
24878 @item @xref{info auto-load}.
24879 @tab Show state of all kinds of files.
24880 @item @xref{set auto-load gdb-scripts}.
24881 @tab Control for @value{GDBN} command scripts.
24882 @item @xref{show auto-load gdb-scripts}.
24883 @tab Show setting of @value{GDBN} command scripts.
24884 @item @xref{info auto-load gdb-scripts}.
24885 @tab Show state of @value{GDBN} command scripts.
24886 @item @xref{set auto-load python-scripts}.
24887 @tab Control for @value{GDBN} Python scripts.
24888 @item @xref{show auto-load python-scripts}.
24889 @tab Show setting of @value{GDBN} Python scripts.
24890 @item @xref{info auto-load python-scripts}.
24891 @tab Show state of @value{GDBN} Python scripts.
24892 @item @xref{set auto-load guile-scripts}.
24893 @tab Control for @value{GDBN} Guile scripts.
24894 @item @xref{show auto-load guile-scripts}.
24895 @tab Show setting of @value{GDBN} Guile scripts.
24896 @item @xref{info auto-load guile-scripts}.
24897 @tab Show state of @value{GDBN} Guile scripts.
24898 @item @xref{set auto-load scripts-directory}.
24899 @tab Control for @value{GDBN} auto-loaded scripts location.
24900 @item @xref{show auto-load scripts-directory}.
24901 @tab Show @value{GDBN} auto-loaded scripts location.
24902 @item @xref{add-auto-load-scripts-directory}.
24903 @tab Add directory for auto-loaded scripts location list.
24904 @item @xref{set auto-load local-gdbinit}.
24905 @tab Control for init file in the current directory.
24906 @item @xref{show auto-load local-gdbinit}.
24907 @tab Show setting of init file in the current directory.
24908 @item @xref{info auto-load local-gdbinit}.
24909 @tab Show state of init file in the current directory.
24910 @item @xref{set auto-load libthread-db}.
24911 @tab Control for thread debugging library.
24912 @item @xref{show auto-load libthread-db}.
24913 @tab Show setting of thread debugging library.
24914 @item @xref{info auto-load libthread-db}.
24915 @tab Show state of thread debugging library.
24916 @item @xref{set auto-load safe-path}.
24917 @tab Control directories trusted for automatic loading.
24918 @item @xref{show auto-load safe-path}.
24919 @tab Show directories trusted for automatic loading.
24920 @item @xref{add-auto-load-safe-path}.
24921 @tab Add directory trusted for automatic loading.
24924 @node Init File in the Current Directory
24925 @subsection Automatically loading init file in the current directory
24926 @cindex auto-loading init file in the current directory
24928 By default, @value{GDBN} reads and executes the canned sequences of commands
24929 from init file (if any) in the current working directory,
24930 see @ref{Init File in the Current Directory during Startup}.
24932 Note that loading of this local @file{.gdbinit} file also requires accordingly
24933 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24936 @anchor{set auto-load local-gdbinit}
24937 @kindex set auto-load local-gdbinit
24938 @item set auto-load local-gdbinit [on|off]
24939 Enable or disable the auto-loading of canned sequences of commands
24940 (@pxref{Sequences}) found in init file in the current directory.
24942 @anchor{show auto-load local-gdbinit}
24943 @kindex show auto-load local-gdbinit
24944 @item show auto-load local-gdbinit
24945 Show whether auto-loading of canned sequences of commands from init file in the
24946 current directory is enabled or disabled.
24948 @anchor{info auto-load local-gdbinit}
24949 @kindex info auto-load local-gdbinit
24950 @item info auto-load local-gdbinit
24951 Print whether canned sequences of commands from init file in the
24952 current directory have been auto-loaded.
24955 @node libthread_db.so.1 file
24956 @subsection Automatically loading thread debugging library
24957 @cindex auto-loading libthread_db.so.1
24959 This feature is currently present only on @sc{gnu}/Linux native hosts.
24961 @value{GDBN} reads in some cases thread debugging library from places specific
24962 to the inferior (@pxref{set libthread-db-search-path}).
24964 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24965 without checking this @samp{set auto-load libthread-db} switch as system
24966 libraries have to be trusted in general. In all other cases of
24967 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24968 auto-load libthread-db} is enabled before trying to open such thread debugging
24971 Note that loading of this debugging library also requires accordingly configured
24972 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24975 @anchor{set auto-load libthread-db}
24976 @kindex set auto-load libthread-db
24977 @item set auto-load libthread-db [on|off]
24978 Enable or disable the auto-loading of inferior specific thread debugging library.
24980 @anchor{show auto-load libthread-db}
24981 @kindex show auto-load libthread-db
24982 @item show auto-load libthread-db
24983 Show whether auto-loading of inferior specific thread debugging library is
24984 enabled or disabled.
24986 @anchor{info auto-load libthread-db}
24987 @kindex info auto-load libthread-db
24988 @item info auto-load libthread-db
24989 Print the list of all loaded inferior specific thread debugging libraries and
24990 for each such library print list of inferior @var{pid}s using it.
24993 @node Auto-loading safe path
24994 @subsection Security restriction for auto-loading
24995 @cindex auto-loading safe-path
24997 As the files of inferior can come from untrusted source (such as submitted by
24998 an application user) @value{GDBN} does not always load any files automatically.
24999 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25000 directories trusted for loading files not explicitly requested by user.
25001 Each directory can also be a shell wildcard pattern.
25003 If the path is not set properly you will see a warning and the file will not
25008 Reading symbols from /home/user/gdb/gdb...done.
25009 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25010 declined by your `auto-load safe-path' set
25011 to "$debugdir:$datadir/auto-load".
25012 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25013 declined by your `auto-load safe-path' set
25014 to "$debugdir:$datadir/auto-load".
25018 To instruct @value{GDBN} to go ahead and use the init files anyway,
25019 invoke @value{GDBN} like this:
25022 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25025 The list of trusted directories is controlled by the following commands:
25028 @anchor{set auto-load safe-path}
25029 @kindex set auto-load safe-path
25030 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25031 Set the list of directories (and their subdirectories) trusted for automatic
25032 loading and execution of scripts. You can also enter a specific trusted file.
25033 Each directory can also be a shell wildcard pattern; wildcards do not match
25034 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25035 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25036 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25037 its default value as specified during @value{GDBN} compilation.
25039 The list of directories uses path separator (@samp{:} on GNU and Unix
25040 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25041 to the @env{PATH} environment variable.
25043 @anchor{show auto-load safe-path}
25044 @kindex show auto-load safe-path
25045 @item show auto-load safe-path
25046 Show the list of directories trusted for automatic loading and execution of
25049 @anchor{add-auto-load-safe-path}
25050 @kindex add-auto-load-safe-path
25051 @item add-auto-load-safe-path
25052 Add an entry (or list of entries) to the list of directories trusted for
25053 automatic loading and execution of scripts. Multiple entries may be delimited
25054 by the host platform path separator in use.
25057 This variable defaults to what @code{--with-auto-load-dir} has been configured
25058 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25059 substitution applies the same as for @ref{set auto-load scripts-directory}.
25060 The default @code{set auto-load safe-path} value can be also overriden by
25061 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25063 Setting this variable to @file{/} disables this security protection,
25064 corresponding @value{GDBN} configuration option is
25065 @option{--without-auto-load-safe-path}.
25066 This variable is supposed to be set to the system directories writable by the
25067 system superuser only. Users can add their source directories in init files in
25068 their home directories (@pxref{Home Directory Init File}). See also deprecated
25069 init file in the current directory
25070 (@pxref{Init File in the Current Directory during Startup}).
25072 To force @value{GDBN} to load the files it declined to load in the previous
25073 example, you could use one of the following ways:
25076 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25077 Specify this trusted directory (or a file) as additional component of the list.
25078 You have to specify also any existing directories displayed by
25079 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25081 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25082 Specify this directory as in the previous case but just for a single
25083 @value{GDBN} session.
25085 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25086 Disable auto-loading safety for a single @value{GDBN} session.
25087 This assumes all the files you debug during this @value{GDBN} session will come
25088 from trusted sources.
25090 @item @kbd{./configure --without-auto-load-safe-path}
25091 During compilation of @value{GDBN} you may disable any auto-loading safety.
25092 This assumes all the files you will ever debug with this @value{GDBN} come from
25096 On the other hand you can also explicitly forbid automatic files loading which
25097 also suppresses any such warning messages:
25100 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25101 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25103 @item @file{~/.gdbinit}: @samp{set auto-load no}
25104 Disable auto-loading globally for the user
25105 (@pxref{Home Directory Init File}). While it is improbable, you could also
25106 use system init file instead (@pxref{System-wide configuration}).
25109 This setting applies to the file names as entered by user. If no entry matches
25110 @value{GDBN} tries as a last resort to also resolve all the file names into
25111 their canonical form (typically resolving symbolic links) and compare the
25112 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25113 own before starting the comparison so a canonical form of directories is
25114 recommended to be entered.
25116 @node Auto-loading verbose mode
25117 @subsection Displaying files tried for auto-load
25118 @cindex auto-loading verbose mode
25120 For better visibility of all the file locations where you can place scripts to
25121 be auto-loaded with inferior --- or to protect yourself against accidental
25122 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25123 all the files attempted to be loaded. Both existing and non-existing files may
25126 For example the list of directories from which it is safe to auto-load files
25127 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25128 may not be too obvious while setting it up.
25131 (gdb) set debug auto-load on
25132 (gdb) file ~/src/t/true
25133 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25134 for objfile "/tmp/true".
25135 auto-load: Updating directories of "/usr:/opt".
25136 auto-load: Using directory "/usr".
25137 auto-load: Using directory "/opt".
25138 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25139 by your `auto-load safe-path' set to "/usr:/opt".
25143 @anchor{set debug auto-load}
25144 @kindex set debug auto-load
25145 @item set debug auto-load [on|off]
25146 Set whether to print the filenames attempted to be auto-loaded.
25148 @anchor{show debug auto-load}
25149 @kindex show debug auto-load
25150 @item show debug auto-load
25151 Show whether printing of the filenames attempted to be auto-loaded is turned
25155 @node Messages/Warnings
25156 @section Optional Warnings and Messages
25158 @cindex verbose operation
25159 @cindex optional warnings
25160 By default, @value{GDBN} is silent about its inner workings. If you are
25161 running on a slow machine, you may want to use the @code{set verbose}
25162 command. This makes @value{GDBN} tell you when it does a lengthy
25163 internal operation, so you will not think it has crashed.
25165 Currently, the messages controlled by @code{set verbose} are those
25166 which announce that the symbol table for a source file is being read;
25167 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25170 @kindex set verbose
25171 @item set verbose on
25172 Enables @value{GDBN} output of certain informational messages.
25174 @item set verbose off
25175 Disables @value{GDBN} output of certain informational messages.
25177 @kindex show verbose
25179 Displays whether @code{set verbose} is on or off.
25182 By default, if @value{GDBN} encounters bugs in the symbol table of an
25183 object file, it is silent; but if you are debugging a compiler, you may
25184 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25189 @kindex set complaints
25190 @item set complaints @var{limit}
25191 Permits @value{GDBN} to output @var{limit} complaints about each type of
25192 unusual symbols before becoming silent about the problem. Set
25193 @var{limit} to zero to suppress all complaints; set it to a large number
25194 to prevent complaints from being suppressed.
25196 @kindex show complaints
25197 @item show complaints
25198 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25202 @anchor{confirmation requests}
25203 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25204 lot of stupid questions to confirm certain commands. For example, if
25205 you try to run a program which is already running:
25209 The program being debugged has been started already.
25210 Start it from the beginning? (y or n)
25213 If you are willing to unflinchingly face the consequences of your own
25214 commands, you can disable this ``feature'':
25218 @kindex set confirm
25220 @cindex confirmation
25221 @cindex stupid questions
25222 @item set confirm off
25223 Disables confirmation requests. Note that running @value{GDBN} with
25224 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25225 automatically disables confirmation requests.
25227 @item set confirm on
25228 Enables confirmation requests (the default).
25230 @kindex show confirm
25232 Displays state of confirmation requests.
25236 @cindex command tracing
25237 If you need to debug user-defined commands or sourced files you may find it
25238 useful to enable @dfn{command tracing}. In this mode each command will be
25239 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25240 quantity denoting the call depth of each command.
25243 @kindex set trace-commands
25244 @cindex command scripts, debugging
25245 @item set trace-commands on
25246 Enable command tracing.
25247 @item set trace-commands off
25248 Disable command tracing.
25249 @item show trace-commands
25250 Display the current state of command tracing.
25253 @node Debugging Output
25254 @section Optional Messages about Internal Happenings
25255 @cindex optional debugging messages
25257 @value{GDBN} has commands that enable optional debugging messages from
25258 various @value{GDBN} subsystems; normally these commands are of
25259 interest to @value{GDBN} maintainers, or when reporting a bug. This
25260 section documents those commands.
25263 @kindex set exec-done-display
25264 @item set exec-done-display
25265 Turns on or off the notification of asynchronous commands'
25266 completion. When on, @value{GDBN} will print a message when an
25267 asynchronous command finishes its execution. The default is off.
25268 @kindex show exec-done-display
25269 @item show exec-done-display
25270 Displays the current setting of asynchronous command completion
25273 @cindex ARM AArch64
25274 @item set debug aarch64
25275 Turns on or off display of debugging messages related to ARM AArch64.
25276 The default is off.
25278 @item show debug aarch64
25279 Displays the current state of displaying debugging messages related to
25281 @cindex gdbarch debugging info
25282 @cindex architecture debugging info
25283 @item set debug arch
25284 Turns on or off display of gdbarch debugging info. The default is off
25285 @item show debug arch
25286 Displays the current state of displaying gdbarch debugging info.
25287 @item set debug aix-solib
25288 @cindex AIX shared library debugging
25289 Control display of debugging messages from the AIX shared library
25290 support module. The default is off.
25291 @item show debug aix-thread
25292 Show the current state of displaying AIX shared library debugging messages.
25293 @item set debug aix-thread
25294 @cindex AIX threads
25295 Display debugging messages about inner workings of the AIX thread
25297 @item show debug aix-thread
25298 Show the current state of AIX thread debugging info display.
25299 @item set debug check-physname
25301 Check the results of the ``physname'' computation. When reading DWARF
25302 debugging information for C@t{++}, @value{GDBN} attempts to compute
25303 each entity's name. @value{GDBN} can do this computation in two
25304 different ways, depending on exactly what information is present.
25305 When enabled, this setting causes @value{GDBN} to compute the names
25306 both ways and display any discrepancies.
25307 @item show debug check-physname
25308 Show the current state of ``physname'' checking.
25309 @item set debug coff-pe-read
25310 @cindex COFF/PE exported symbols
25311 Control display of debugging messages related to reading of COFF/PE
25312 exported symbols. The default is off.
25313 @item show debug coff-pe-read
25314 Displays the current state of displaying debugging messages related to
25315 reading of COFF/PE exported symbols.
25316 @item set debug dwarf-die
25318 Dump DWARF DIEs after they are read in.
25319 The value is the number of nesting levels to print.
25320 A value of zero turns off the display.
25321 @item show debug dwarf-die
25322 Show the current state of DWARF DIE debugging.
25323 @item set debug dwarf-line
25324 @cindex DWARF Line Tables
25325 Turns on or off display of debugging messages related to reading
25326 DWARF line tables. The default is 0 (off).
25327 A value of 1 provides basic information.
25328 A value greater than 1 provides more verbose information.
25329 @item show debug dwarf-line
25330 Show the current state of DWARF line table debugging.
25331 @item set debug dwarf-read
25332 @cindex DWARF Reading
25333 Turns on or off display of debugging messages related to reading
25334 DWARF debug info. The default is 0 (off).
25335 A value of 1 provides basic information.
25336 A value greater than 1 provides more verbose information.
25337 @item show debug dwarf-read
25338 Show the current state of DWARF reader debugging.
25339 @item set debug displaced
25340 @cindex displaced stepping debugging info
25341 Turns on or off display of @value{GDBN} debugging info for the
25342 displaced stepping support. The default is off.
25343 @item show debug displaced
25344 Displays the current state of displaying @value{GDBN} debugging info
25345 related to displaced stepping.
25346 @item set debug event
25347 @cindex event debugging info
25348 Turns on or off display of @value{GDBN} event debugging info. The
25350 @item show debug event
25351 Displays the current state of displaying @value{GDBN} event debugging
25353 @item set debug expression
25354 @cindex expression debugging info
25355 Turns on or off display of debugging info about @value{GDBN}
25356 expression parsing. The default is off.
25357 @item show debug expression
25358 Displays the current state of displaying debugging info about
25359 @value{GDBN} expression parsing.
25360 @item set debug fbsd-lwp
25361 @cindex FreeBSD LWP debug messages
25362 Turns on or off debugging messages from the FreeBSD LWP debug support.
25363 @item show debug fbsd-lwp
25364 Show the current state of FreeBSD LWP debugging messages.
25365 @item set debug fbsd-nat
25366 @cindex FreeBSD native target debug messages
25367 Turns on or off debugging messages from the FreeBSD native target.
25368 @item show debug fbsd-nat
25369 Show the current state of FreeBSD native target debugging messages.
25370 @item set debug frame
25371 @cindex frame debugging info
25372 Turns on or off display of @value{GDBN} frame debugging info. The
25374 @item show debug frame
25375 Displays the current state of displaying @value{GDBN} frame debugging
25377 @item set debug gnu-nat
25378 @cindex @sc{gnu}/Hurd debug messages
25379 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25380 @item show debug gnu-nat
25381 Show the current state of @sc{gnu}/Hurd debugging messages.
25382 @item set debug infrun
25383 @cindex inferior debugging info
25384 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25385 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25386 for implementing operations such as single-stepping the inferior.
25387 @item show debug infrun
25388 Displays the current state of @value{GDBN} inferior debugging.
25389 @item set debug jit
25390 @cindex just-in-time compilation, debugging messages
25391 Turn on or off debugging messages from JIT debug support.
25392 @item show debug jit
25393 Displays the current state of @value{GDBN} JIT debugging.
25394 @item set debug lin-lwp
25395 @cindex @sc{gnu}/Linux LWP debug messages
25396 @cindex Linux lightweight processes
25397 Turn on or off debugging messages from the Linux LWP debug support.
25398 @item show debug lin-lwp
25399 Show the current state of Linux LWP debugging messages.
25400 @item set debug linux-namespaces
25401 @cindex @sc{gnu}/Linux namespaces debug messages
25402 Turn on or off debugging messages from the Linux namespaces debug support.
25403 @item show debug linux-namespaces
25404 Show the current state of Linux namespaces debugging messages.
25405 @item set debug mach-o
25406 @cindex Mach-O symbols processing
25407 Control display of debugging messages related to Mach-O symbols
25408 processing. The default is off.
25409 @item show debug mach-o
25410 Displays the current state of displaying debugging messages related to
25411 reading of COFF/PE exported symbols.
25412 @item set debug notification
25413 @cindex remote async notification debugging info
25414 Turn on or off debugging messages about remote async notification.
25415 The default is off.
25416 @item show debug notification
25417 Displays the current state of remote async notification debugging messages.
25418 @item set debug observer
25419 @cindex observer debugging info
25420 Turns on or off display of @value{GDBN} observer debugging. This
25421 includes info such as the notification of observable events.
25422 @item show debug observer
25423 Displays the current state of observer debugging.
25424 @item set debug overload
25425 @cindex C@t{++} overload debugging info
25426 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25427 info. This includes info such as ranking of functions, etc. The default
25429 @item show debug overload
25430 Displays the current state of displaying @value{GDBN} C@t{++} overload
25432 @cindex expression parser, debugging info
25433 @cindex debug expression parser
25434 @item set debug parser
25435 Turns on or off the display of expression parser debugging output.
25436 Internally, this sets the @code{yydebug} variable in the expression
25437 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25438 details. The default is off.
25439 @item show debug parser
25440 Show the current state of expression parser debugging.
25441 @cindex packets, reporting on stdout
25442 @cindex serial connections, debugging
25443 @cindex debug remote protocol
25444 @cindex remote protocol debugging
25445 @cindex display remote packets
25446 @item set debug remote
25447 Turns on or off display of reports on all packets sent back and forth across
25448 the serial line to the remote machine. The info is printed on the
25449 @value{GDBN} standard output stream. The default is off.
25450 @item show debug remote
25451 Displays the state of display of remote packets.
25453 @item set debug separate-debug-file
25454 Turns on or off display of debug output about separate debug file search.
25455 @item show debug separate-debug-file
25456 Displays the state of separate debug file search debug output.
25458 @item set debug serial
25459 Turns on or off display of @value{GDBN} serial debugging info. The
25461 @item show debug serial
25462 Displays the current state of displaying @value{GDBN} serial debugging
25464 @item set debug solib-frv
25465 @cindex FR-V shared-library debugging
25466 Turn on or off debugging messages for FR-V shared-library code.
25467 @item show debug solib-frv
25468 Display the current state of FR-V shared-library code debugging
25470 @item set debug symbol-lookup
25471 @cindex symbol lookup
25472 Turns on or off display of debugging messages related to symbol lookup.
25473 The default is 0 (off).
25474 A value of 1 provides basic information.
25475 A value greater than 1 provides more verbose information.
25476 @item show debug symbol-lookup
25477 Show the current state of symbol lookup debugging messages.
25478 @item set debug symfile
25479 @cindex symbol file functions
25480 Turns on or off display of debugging messages related to symbol file functions.
25481 The default is off. @xref{Files}.
25482 @item show debug symfile
25483 Show the current state of symbol file debugging messages.
25484 @item set debug symtab-create
25485 @cindex symbol table creation
25486 Turns on or off display of debugging messages related to symbol table creation.
25487 The default is 0 (off).
25488 A value of 1 provides basic information.
25489 A value greater than 1 provides more verbose information.
25490 @item show debug symtab-create
25491 Show the current state of symbol table creation debugging.
25492 @item set debug target
25493 @cindex target debugging info
25494 Turns on or off display of @value{GDBN} target debugging info. This info
25495 includes what is going on at the target level of GDB, as it happens. The
25496 default is 0. Set it to 1 to track events, and to 2 to also track the
25497 value of large memory transfers.
25498 @item show debug target
25499 Displays the current state of displaying @value{GDBN} target debugging
25501 @item set debug timestamp
25502 @cindex timestampping debugging info
25503 Turns on or off display of timestamps with @value{GDBN} debugging info.
25504 When enabled, seconds and microseconds are displayed before each debugging
25506 @item show debug timestamp
25507 Displays the current state of displaying timestamps with @value{GDBN}
25509 @item set debug varobj
25510 @cindex variable object debugging info
25511 Turns on or off display of @value{GDBN} variable object debugging
25512 info. The default is off.
25513 @item show debug varobj
25514 Displays the current state of displaying @value{GDBN} variable object
25516 @item set debug xml
25517 @cindex XML parser debugging
25518 Turn on or off debugging messages for built-in XML parsers.
25519 @item show debug xml
25520 Displays the current state of XML debugging messages.
25523 @node Other Misc Settings
25524 @section Other Miscellaneous Settings
25525 @cindex miscellaneous settings
25528 @kindex set interactive-mode
25529 @item set interactive-mode
25530 If @code{on}, forces @value{GDBN} to assume that GDB was started
25531 in a terminal. In practice, this means that @value{GDBN} should wait
25532 for the user to answer queries generated by commands entered at
25533 the command prompt. If @code{off}, forces @value{GDBN} to operate
25534 in the opposite mode, and it uses the default answers to all queries.
25535 If @code{auto} (the default), @value{GDBN} tries to determine whether
25536 its standard input is a terminal, and works in interactive-mode if it
25537 is, non-interactively otherwise.
25539 In the vast majority of cases, the debugger should be able to guess
25540 correctly which mode should be used. But this setting can be useful
25541 in certain specific cases, such as running a MinGW @value{GDBN}
25542 inside a cygwin window.
25544 @kindex show interactive-mode
25545 @item show interactive-mode
25546 Displays whether the debugger is operating in interactive mode or not.
25549 @node Extending GDB
25550 @chapter Extending @value{GDBN}
25551 @cindex extending GDB
25553 @value{GDBN} provides several mechanisms for extension.
25554 @value{GDBN} also provides the ability to automatically load
25555 extensions when it reads a file for debugging. This allows the
25556 user to automatically customize @value{GDBN} for the program
25560 * Sequences:: Canned Sequences of @value{GDBN} Commands
25561 * Python:: Extending @value{GDBN} using Python
25562 * Guile:: Extending @value{GDBN} using Guile
25563 * Auto-loading extensions:: Automatically loading extensions
25564 * Multiple Extension Languages:: Working with multiple extension languages
25565 * Aliases:: Creating new spellings of existing commands
25568 To facilitate the use of extension languages, @value{GDBN} is capable
25569 of evaluating the contents of a file. When doing so, @value{GDBN}
25570 can recognize which extension language is being used by looking at
25571 the filename extension. Files with an unrecognized filename extension
25572 are always treated as a @value{GDBN} Command Files.
25573 @xref{Command Files,, Command files}.
25575 You can control how @value{GDBN} evaluates these files with the following
25579 @kindex set script-extension
25580 @kindex show script-extension
25581 @item set script-extension off
25582 All scripts are always evaluated as @value{GDBN} Command Files.
25584 @item set script-extension soft
25585 The debugger determines the scripting language based on filename
25586 extension. If this scripting language is supported, @value{GDBN}
25587 evaluates the script using that language. Otherwise, it evaluates
25588 the file as a @value{GDBN} Command File.
25590 @item set script-extension strict
25591 The debugger determines the scripting language based on filename
25592 extension, and evaluates the script using that language. If the
25593 language is not supported, then the evaluation fails.
25595 @item show script-extension
25596 Display the current value of the @code{script-extension} option.
25601 @section Canned Sequences of Commands
25603 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25604 Command Lists}), @value{GDBN} provides two ways to store sequences of
25605 commands for execution as a unit: user-defined commands and command
25609 * Define:: How to define your own commands
25610 * Hooks:: Hooks for user-defined commands
25611 * Command Files:: How to write scripts of commands to be stored in a file
25612 * Output:: Commands for controlled output
25613 * Auto-loading sequences:: Controlling auto-loaded command files
25617 @subsection User-defined Commands
25619 @cindex user-defined command
25620 @cindex arguments, to user-defined commands
25621 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25622 which you assign a new name as a command. This is done with the
25623 @code{define} command. User commands may accept an unlimited number of arguments
25624 separated by whitespace. Arguments are accessed within the user command
25625 via @code{$arg0@dots{}$argN}. A trivial example:
25629 print $arg0 + $arg1 + $arg2
25634 To execute the command use:
25641 This defines the command @code{adder}, which prints the sum of
25642 its three arguments. Note the arguments are text substitutions, so they may
25643 reference variables, use complex expressions, or even perform inferior
25646 @cindex argument count in user-defined commands
25647 @cindex how many arguments (user-defined commands)
25648 In addition, @code{$argc} may be used to find out how many arguments have
25654 print $arg0 + $arg1
25657 print $arg0 + $arg1 + $arg2
25662 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25663 to process a variable number of arguments:
25670 eval "set $sum = $sum + $arg%d", $i
25680 @item define @var{commandname}
25681 Define a command named @var{commandname}. If there is already a command
25682 by that name, you are asked to confirm that you want to redefine it.
25683 The argument @var{commandname} may be a bare command name consisting of letters,
25684 numbers, dashes, and underscores. It may also start with any predefined
25685 prefix command. For example, @samp{define target my-target} creates
25686 a user-defined @samp{target my-target} command.
25688 The definition of the command is made up of other @value{GDBN} command lines,
25689 which are given following the @code{define} command. The end of these
25690 commands is marked by a line containing @code{end}.
25693 @kindex end@r{ (user-defined commands)}
25694 @item document @var{commandname}
25695 Document the user-defined command @var{commandname}, so that it can be
25696 accessed by @code{help}. The command @var{commandname} must already be
25697 defined. This command reads lines of documentation just as @code{define}
25698 reads the lines of the command definition, ending with @code{end}.
25699 After the @code{document} command is finished, @code{help} on command
25700 @var{commandname} displays the documentation you have written.
25702 You may use the @code{document} command again to change the
25703 documentation of a command. Redefining the command with @code{define}
25704 does not change the documentation.
25706 @kindex dont-repeat
25707 @cindex don't repeat command
25709 Used inside a user-defined command, this tells @value{GDBN} that this
25710 command should not be repeated when the user hits @key{RET}
25711 (@pxref{Command Syntax, repeat last command}).
25713 @kindex help user-defined
25714 @item help user-defined
25715 List all user-defined commands and all python commands defined in class
25716 COMAND_USER. The first line of the documentation or docstring is
25721 @itemx show user @var{commandname}
25722 Display the @value{GDBN} commands used to define @var{commandname} (but
25723 not its documentation). If no @var{commandname} is given, display the
25724 definitions for all user-defined commands.
25725 This does not work for user-defined python commands.
25727 @cindex infinite recursion in user-defined commands
25728 @kindex show max-user-call-depth
25729 @kindex set max-user-call-depth
25730 @item show max-user-call-depth
25731 @itemx set max-user-call-depth
25732 The value of @code{max-user-call-depth} controls how many recursion
25733 levels are allowed in user-defined commands before @value{GDBN} suspects an
25734 infinite recursion and aborts the command.
25735 This does not apply to user-defined python commands.
25738 In addition to the above commands, user-defined commands frequently
25739 use control flow commands, described in @ref{Command Files}.
25741 When user-defined commands are executed, the
25742 commands of the definition are not printed. An error in any command
25743 stops execution of the user-defined command.
25745 If used interactively, commands that would ask for confirmation proceed
25746 without asking when used inside a user-defined command. Many @value{GDBN}
25747 commands that normally print messages to say what they are doing omit the
25748 messages when used in a user-defined command.
25751 @subsection User-defined Command Hooks
25752 @cindex command hooks
25753 @cindex hooks, for commands
25754 @cindex hooks, pre-command
25757 You may define @dfn{hooks}, which are a special kind of user-defined
25758 command. Whenever you run the command @samp{foo}, if the user-defined
25759 command @samp{hook-foo} exists, it is executed (with no arguments)
25760 before that command.
25762 @cindex hooks, post-command
25764 A hook may also be defined which is run after the command you executed.
25765 Whenever you run the command @samp{foo}, if the user-defined command
25766 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25767 that command. Post-execution hooks may exist simultaneously with
25768 pre-execution hooks, for the same command.
25770 It is valid for a hook to call the command which it hooks. If this
25771 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25773 @c It would be nice if hookpost could be passed a parameter indicating
25774 @c if the command it hooks executed properly or not. FIXME!
25776 @kindex stop@r{, a pseudo-command}
25777 In addition, a pseudo-command, @samp{stop} exists. Defining
25778 (@samp{hook-stop}) makes the associated commands execute every time
25779 execution stops in your program: before breakpoint commands are run,
25780 displays are printed, or the stack frame is printed.
25782 For example, to ignore @code{SIGALRM} signals while
25783 single-stepping, but treat them normally during normal execution,
25788 handle SIGALRM nopass
25792 handle SIGALRM pass
25795 define hook-continue
25796 handle SIGALRM pass
25800 As a further example, to hook at the beginning and end of the @code{echo}
25801 command, and to add extra text to the beginning and end of the message,
25809 define hookpost-echo
25813 (@value{GDBP}) echo Hello World
25814 <<<---Hello World--->>>
25819 You can define a hook for any single-word command in @value{GDBN}, but
25820 not for command aliases; you should define a hook for the basic command
25821 name, e.g.@: @code{backtrace} rather than @code{bt}.
25822 @c FIXME! So how does Joe User discover whether a command is an alias
25824 You can hook a multi-word command by adding @code{hook-} or
25825 @code{hookpost-} to the last word of the command, e.g.@:
25826 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25828 If an error occurs during the execution of your hook, execution of
25829 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25830 (before the command that you actually typed had a chance to run).
25832 If you try to define a hook which does not match any known command, you
25833 get a warning from the @code{define} command.
25835 @node Command Files
25836 @subsection Command Files
25838 @cindex command files
25839 @cindex scripting commands
25840 A command file for @value{GDBN} is a text file made of lines that are
25841 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25842 also be included. An empty line in a command file does nothing; it
25843 does not mean to repeat the last command, as it would from the
25846 You can request the execution of a command file with the @code{source}
25847 command. Note that the @code{source} command is also used to evaluate
25848 scripts that are not Command Files. The exact behavior can be configured
25849 using the @code{script-extension} setting.
25850 @xref{Extending GDB,, Extending GDB}.
25854 @cindex execute commands from a file
25855 @item source [-s] [-v] @var{filename}
25856 Execute the command file @var{filename}.
25859 The lines in a command file are generally executed sequentially,
25860 unless the order of execution is changed by one of the
25861 @emph{flow-control commands} described below. The commands are not
25862 printed as they are executed. An error in any command terminates
25863 execution of the command file and control is returned to the console.
25865 @value{GDBN} first searches for @var{filename} in the current directory.
25866 If the file is not found there, and @var{filename} does not specify a
25867 directory, then @value{GDBN} also looks for the file on the source search path
25868 (specified with the @samp{directory} command);
25869 except that @file{$cdir} is not searched because the compilation directory
25870 is not relevant to scripts.
25872 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25873 on the search path even if @var{filename} specifies a directory.
25874 The search is done by appending @var{filename} to each element of the
25875 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25876 and the search path contains @file{/home/user} then @value{GDBN} will
25877 look for the script @file{/home/user/mylib/myscript}.
25878 The search is also done if @var{filename} is an absolute path.
25879 For example, if @var{filename} is @file{/tmp/myscript} and
25880 the search path contains @file{/home/user} then @value{GDBN} will
25881 look for the script @file{/home/user/tmp/myscript}.
25882 For DOS-like systems, if @var{filename} contains a drive specification,
25883 it is stripped before concatenation. For example, if @var{filename} is
25884 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25885 will look for the script @file{c:/tmp/myscript}.
25887 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25888 each command as it is executed. The option must be given before
25889 @var{filename}, and is interpreted as part of the filename anywhere else.
25891 Commands that would ask for confirmation if used interactively proceed
25892 without asking when used in a command file. Many @value{GDBN} commands that
25893 normally print messages to say what they are doing omit the messages
25894 when called from command files.
25896 @value{GDBN} also accepts command input from standard input. In this
25897 mode, normal output goes to standard output and error output goes to
25898 standard error. Errors in a command file supplied on standard input do
25899 not terminate execution of the command file---execution continues with
25903 gdb < cmds > log 2>&1
25906 (The syntax above will vary depending on the shell used.) This example
25907 will execute commands from the file @file{cmds}. All output and errors
25908 would be directed to @file{log}.
25910 Since commands stored on command files tend to be more general than
25911 commands typed interactively, they frequently need to deal with
25912 complicated situations, such as different or unexpected values of
25913 variables and symbols, changes in how the program being debugged is
25914 built, etc. @value{GDBN} provides a set of flow-control commands to
25915 deal with these complexities. Using these commands, you can write
25916 complex scripts that loop over data structures, execute commands
25917 conditionally, etc.
25924 This command allows to include in your script conditionally executed
25925 commands. The @code{if} command takes a single argument, which is an
25926 expression to evaluate. It is followed by a series of commands that
25927 are executed only if the expression is true (its value is nonzero).
25928 There can then optionally be an @code{else} line, followed by a series
25929 of commands that are only executed if the expression was false. The
25930 end of the list is marked by a line containing @code{end}.
25934 This command allows to write loops. Its syntax is similar to
25935 @code{if}: the command takes a single argument, which is an expression
25936 to evaluate, and must be followed by the commands to execute, one per
25937 line, terminated by an @code{end}. These commands are called the
25938 @dfn{body} of the loop. The commands in the body of @code{while} are
25939 executed repeatedly as long as the expression evaluates to true.
25943 This command exits the @code{while} loop in whose body it is included.
25944 Execution of the script continues after that @code{while}s @code{end}
25947 @kindex loop_continue
25948 @item loop_continue
25949 This command skips the execution of the rest of the body of commands
25950 in the @code{while} loop in whose body it is included. Execution
25951 branches to the beginning of the @code{while} loop, where it evaluates
25952 the controlling expression.
25954 @kindex end@r{ (if/else/while commands)}
25956 Terminate the block of commands that are the body of @code{if},
25957 @code{else}, or @code{while} flow-control commands.
25962 @subsection Commands for Controlled Output
25964 During the execution of a command file or a user-defined command, normal
25965 @value{GDBN} output is suppressed; the only output that appears is what is
25966 explicitly printed by the commands in the definition. This section
25967 describes three commands useful for generating exactly the output you
25972 @item echo @var{text}
25973 @c I do not consider backslash-space a standard C escape sequence
25974 @c because it is not in ANSI.
25975 Print @var{text}. Nonprinting characters can be included in
25976 @var{text} using C escape sequences, such as @samp{\n} to print a
25977 newline. @strong{No newline is printed unless you specify one.}
25978 In addition to the standard C escape sequences, a backslash followed
25979 by a space stands for a space. This is useful for displaying a
25980 string with spaces at the beginning or the end, since leading and
25981 trailing spaces are otherwise trimmed from all arguments.
25982 To print @samp{@w{ }and foo =@w{ }}, use the command
25983 @samp{echo \@w{ }and foo = \@w{ }}.
25985 A backslash at the end of @var{text} can be used, as in C, to continue
25986 the command onto subsequent lines. For example,
25989 echo This is some text\n\
25990 which is continued\n\
25991 onto several lines.\n
25994 produces the same output as
25997 echo This is some text\n
25998 echo which is continued\n
25999 echo onto several lines.\n
26003 @item output @var{expression}
26004 Print the value of @var{expression} and nothing but that value: no
26005 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26006 value history either. @xref{Expressions, ,Expressions}, for more information
26009 @item output/@var{fmt} @var{expression}
26010 Print the value of @var{expression} in format @var{fmt}. You can use
26011 the same formats as for @code{print}. @xref{Output Formats,,Output
26012 Formats}, for more information.
26015 @item printf @var{template}, @var{expressions}@dots{}
26016 Print the values of one or more @var{expressions} under the control of
26017 the string @var{template}. To print several values, make
26018 @var{expressions} be a comma-separated list of individual expressions,
26019 which may be either numbers or pointers. Their values are printed as
26020 specified by @var{template}, exactly as a C program would do by
26021 executing the code below:
26024 printf (@var{template}, @var{expressions}@dots{});
26027 As in @code{C} @code{printf}, ordinary characters in @var{template}
26028 are printed verbatim, while @dfn{conversion specification} introduced
26029 by the @samp{%} character cause subsequent @var{expressions} to be
26030 evaluated, their values converted and formatted according to type and
26031 style information encoded in the conversion specifications, and then
26034 For example, you can print two values in hex like this:
26037 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26040 @code{printf} supports all the standard @code{C} conversion
26041 specifications, including the flags and modifiers between the @samp{%}
26042 character and the conversion letter, with the following exceptions:
26046 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26049 The modifier @samp{*} is not supported for specifying precision or
26053 The @samp{'} flag (for separation of digits into groups according to
26054 @code{LC_NUMERIC'}) is not supported.
26057 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26061 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26064 The conversion letters @samp{a} and @samp{A} are not supported.
26068 Note that the @samp{ll} type modifier is supported only if the
26069 underlying @code{C} implementation used to build @value{GDBN} supports
26070 the @code{long long int} type, and the @samp{L} type modifier is
26071 supported only if @code{long double} type is available.
26073 As in @code{C}, @code{printf} supports simple backslash-escape
26074 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26075 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26076 single character. Octal and hexadecimal escape sequences are not
26079 Additionally, @code{printf} supports conversion specifications for DFP
26080 (@dfn{Decimal Floating Point}) types using the following length modifiers
26081 together with a floating point specifier.
26086 @samp{H} for printing @code{Decimal32} types.
26089 @samp{D} for printing @code{Decimal64} types.
26092 @samp{DD} for printing @code{Decimal128} types.
26095 If the underlying @code{C} implementation used to build @value{GDBN} has
26096 support for the three length modifiers for DFP types, other modifiers
26097 such as width and precision will also be available for @value{GDBN} to use.
26099 In case there is no such @code{C} support, no additional modifiers will be
26100 available and the value will be printed in the standard way.
26102 Here's an example of printing DFP types using the above conversion letters:
26104 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26109 @item eval @var{template}, @var{expressions}@dots{}
26110 Convert the values of one or more @var{expressions} under the control of
26111 the string @var{template} to a command line, and call it.
26115 @node Auto-loading sequences
26116 @subsection Controlling auto-loading native @value{GDBN} scripts
26117 @cindex native script auto-loading
26119 When a new object file is read (for example, due to the @code{file}
26120 command, or because the inferior has loaded a shared library),
26121 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26122 @xref{Auto-loading extensions}.
26124 Auto-loading can be enabled or disabled,
26125 and the list of auto-loaded scripts can be printed.
26128 @anchor{set auto-load gdb-scripts}
26129 @kindex set auto-load gdb-scripts
26130 @item set auto-load gdb-scripts [on|off]
26131 Enable or disable the auto-loading of canned sequences of commands scripts.
26133 @anchor{show auto-load gdb-scripts}
26134 @kindex show auto-load gdb-scripts
26135 @item show auto-load gdb-scripts
26136 Show whether auto-loading of canned sequences of commands scripts is enabled or
26139 @anchor{info auto-load gdb-scripts}
26140 @kindex info auto-load gdb-scripts
26141 @cindex print list of auto-loaded canned sequences of commands scripts
26142 @item info auto-load gdb-scripts [@var{regexp}]
26143 Print the list of all canned sequences of commands scripts that @value{GDBN}
26147 If @var{regexp} is supplied only canned sequences of commands scripts with
26148 matching names are printed.
26150 @c Python docs live in a separate file.
26151 @include python.texi
26153 @c Guile docs live in a separate file.
26154 @include guile.texi
26156 @node Auto-loading extensions
26157 @section Auto-loading extensions
26158 @cindex auto-loading extensions
26160 @value{GDBN} provides two mechanisms for automatically loading extensions
26161 when a new object file is read (for example, due to the @code{file}
26162 command, or because the inferior has loaded a shared library):
26163 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26164 section of modern file formats like ELF.
26167 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26168 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26169 * Which flavor to choose?::
26172 The auto-loading feature is useful for supplying application-specific
26173 debugging commands and features.
26175 Auto-loading can be enabled or disabled,
26176 and the list of auto-loaded scripts can be printed.
26177 See the @samp{auto-loading} section of each extension language
26178 for more information.
26179 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26180 For Python files see @ref{Python Auto-loading}.
26182 Note that loading of this script file also requires accordingly configured
26183 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26185 @node objfile-gdbdotext file
26186 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26187 @cindex @file{@var{objfile}-gdb.gdb}
26188 @cindex @file{@var{objfile}-gdb.py}
26189 @cindex @file{@var{objfile}-gdb.scm}
26191 When a new object file is read, @value{GDBN} looks for a file named
26192 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26193 where @var{objfile} is the object file's name and
26194 where @var{ext} is the file extension for the extension language:
26197 @item @file{@var{objfile}-gdb.gdb}
26198 GDB's own command language
26199 @item @file{@var{objfile}-gdb.py}
26201 @item @file{@var{objfile}-gdb.scm}
26205 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26206 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26207 components, and appending the @file{-gdb.@var{ext}} suffix.
26208 If this file exists and is readable, @value{GDBN} will evaluate it as a
26209 script in the specified extension language.
26211 If this file does not exist, then @value{GDBN} will look for
26212 @var{script-name} file in all of the directories as specified below.
26214 Note that loading of these files requires an accordingly configured
26215 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26217 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26218 scripts normally according to its @file{.exe} filename. But if no scripts are
26219 found @value{GDBN} also tries script filenames matching the object file without
26220 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26221 is attempted on any platform. This makes the script filenames compatible
26222 between Unix and MS-Windows hosts.
26225 @anchor{set auto-load scripts-directory}
26226 @kindex set auto-load scripts-directory
26227 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26228 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26229 may be delimited by the host platform path separator in use
26230 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26232 Each entry here needs to be covered also by the security setting
26233 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26235 @anchor{with-auto-load-dir}
26236 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26237 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26238 configuration option @option{--with-auto-load-dir}.
26240 Any reference to @file{$debugdir} will get replaced by
26241 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26242 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26243 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26244 @file{$datadir} must be placed as a directory component --- either alone or
26245 delimited by @file{/} or @file{\} directory separators, depending on the host
26248 The list of directories uses path separator (@samp{:} on GNU and Unix
26249 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26250 to the @env{PATH} environment variable.
26252 @anchor{show auto-load scripts-directory}
26253 @kindex show auto-load scripts-directory
26254 @item show auto-load scripts-directory
26255 Show @value{GDBN} auto-loaded scripts location.
26257 @anchor{add-auto-load-scripts-directory}
26258 @kindex add-auto-load-scripts-directory
26259 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26260 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26261 Multiple entries may be delimited by the host platform path separator in use.
26264 @value{GDBN} does not track which files it has already auto-loaded this way.
26265 @value{GDBN} will load the associated script every time the corresponding
26266 @var{objfile} is opened.
26267 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26268 is evaluated more than once.
26270 @node dotdebug_gdb_scripts section
26271 @subsection The @code{.debug_gdb_scripts} section
26272 @cindex @code{.debug_gdb_scripts} section
26274 For systems using file formats like ELF and COFF,
26275 when @value{GDBN} loads a new object file
26276 it will look for a special section named @code{.debug_gdb_scripts}.
26277 If this section exists, its contents is a list of null-terminated entries
26278 specifying scripts to load. Each entry begins with a non-null prefix byte that
26279 specifies the kind of entry, typically the extension language and whether the
26280 script is in a file or inlined in @code{.debug_gdb_scripts}.
26282 The following entries are supported:
26285 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26286 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26287 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26288 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26291 @subsubsection Script File Entries
26293 If the entry specifies a file, @value{GDBN} will look for the file first
26294 in the current directory and then along the source search path
26295 (@pxref{Source Path, ,Specifying Source Directories}),
26296 except that @file{$cdir} is not searched, since the compilation
26297 directory is not relevant to scripts.
26299 File entries can be placed in section @code{.debug_gdb_scripts} with,
26300 for example, this GCC macro for Python scripts.
26303 /* Note: The "MS" section flags are to remove duplicates. */
26304 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26306 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26307 .byte 1 /* Python */\n\
26308 .asciz \"" script_name "\"\n\
26314 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26315 Then one can reference the macro in a header or source file like this:
26318 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26321 The script name may include directories if desired.
26323 Note that loading of this script file also requires accordingly configured
26324 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26326 If the macro invocation is put in a header, any application or library
26327 using this header will get a reference to the specified script,
26328 and with the use of @code{"MS"} attributes on the section, the linker
26329 will remove duplicates.
26331 @subsubsection Script Text Entries
26333 Script text entries allow to put the executable script in the entry
26334 itself instead of loading it from a file.
26335 The first line of the entry, everything after the prefix byte and up to
26336 the first newline (@code{0xa}) character, is the script name, and must not
26337 contain any kind of space character, e.g., spaces or tabs.
26338 The rest of the entry, up to the trailing null byte, is the script to
26339 execute in the specified language. The name needs to be unique among
26340 all script names, as @value{GDBN} executes each script only once based
26343 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26347 #include "symcat.h"
26348 #include "gdb/section-scripts.h"
26350 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26351 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26352 ".ascii \"gdb.inlined-script\\n\"\n"
26353 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26354 ".ascii \" def __init__ (self):\\n\"\n"
26355 ".ascii \" super (test_cmd, self).__init__ ("
26356 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26357 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26358 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26359 ".ascii \"test_cmd ()\\n\"\n"
26365 Loading of inlined scripts requires a properly configured
26366 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26367 The path to specify in @code{auto-load safe-path} is the path of the file
26368 containing the @code{.debug_gdb_scripts} section.
26370 @node Which flavor to choose?
26371 @subsection Which flavor to choose?
26373 Given the multiple ways of auto-loading extensions, it might not always
26374 be clear which one to choose. This section provides some guidance.
26377 Benefits of the @file{-gdb.@var{ext}} way:
26381 Can be used with file formats that don't support multiple sections.
26384 Ease of finding scripts for public libraries.
26386 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26387 in the source search path.
26388 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26389 isn't a source directory in which to find the script.
26392 Doesn't require source code additions.
26396 Benefits of the @code{.debug_gdb_scripts} way:
26400 Works with static linking.
26402 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26403 trigger their loading. When an application is statically linked the only
26404 objfile available is the executable, and it is cumbersome to attach all the
26405 scripts from all the input libraries to the executable's
26406 @file{-gdb.@var{ext}} script.
26409 Works with classes that are entirely inlined.
26411 Some classes can be entirely inlined, and thus there may not be an associated
26412 shared library to attach a @file{-gdb.@var{ext}} script to.
26415 Scripts needn't be copied out of the source tree.
26417 In some circumstances, apps can be built out of large collections of internal
26418 libraries, and the build infrastructure necessary to install the
26419 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26420 cumbersome. It may be easier to specify the scripts in the
26421 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26422 top of the source tree to the source search path.
26425 @node Multiple Extension Languages
26426 @section Multiple Extension Languages
26428 The Guile and Python extension languages do not share any state,
26429 and generally do not interfere with each other.
26430 There are some things to be aware of, however.
26432 @subsection Python comes first
26434 Python was @value{GDBN}'s first extension language, and to avoid breaking
26435 existing behaviour Python comes first. This is generally solved by the
26436 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26437 extension languages, and when it makes a call to an extension language,
26438 (say to pretty-print a value), it tries each in turn until an extension
26439 language indicates it has performed the request (e.g., has returned the
26440 pretty-printed form of a value).
26441 This extends to errors while performing such requests: If an error happens
26442 while, for example, trying to pretty-print an object then the error is
26443 reported and any following extension languages are not tried.
26446 @section Creating new spellings of existing commands
26447 @cindex aliases for commands
26449 It is often useful to define alternate spellings of existing commands.
26450 For example, if a new @value{GDBN} command defined in Python has
26451 a long name to type, it is handy to have an abbreviated version of it
26452 that involves less typing.
26454 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26455 of the @samp{step} command even though it is otherwise an ambiguous
26456 abbreviation of other commands like @samp{set} and @samp{show}.
26458 Aliases are also used to provide shortened or more common versions
26459 of multi-word commands. For example, @value{GDBN} provides the
26460 @samp{tty} alias of the @samp{set inferior-tty} command.
26462 You can define a new alias with the @samp{alias} command.
26467 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26471 @var{ALIAS} specifies the name of the new alias.
26472 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26475 @var{COMMAND} specifies the name of an existing command
26476 that is being aliased.
26478 The @samp{-a} option specifies that the new alias is an abbreviation
26479 of the command. Abbreviations are not shown in command
26480 lists displayed by the @samp{help} command.
26482 The @samp{--} option specifies the end of options,
26483 and is useful when @var{ALIAS} begins with a dash.
26485 Here is a simple example showing how to make an abbreviation
26486 of a command so that there is less to type.
26487 Suppose you were tired of typing @samp{disas}, the current
26488 shortest unambiguous abbreviation of the @samp{disassemble} command
26489 and you wanted an even shorter version named @samp{di}.
26490 The following will accomplish this.
26493 (gdb) alias -a di = disas
26496 Note that aliases are different from user-defined commands.
26497 With a user-defined command, you also need to write documentation
26498 for it with the @samp{document} command.
26499 An alias automatically picks up the documentation of the existing command.
26501 Here is an example where we make @samp{elms} an abbreviation of
26502 @samp{elements} in the @samp{set print elements} command.
26503 This is to show that you can make an abbreviation of any part
26507 (gdb) alias -a set print elms = set print elements
26508 (gdb) alias -a show print elms = show print elements
26509 (gdb) set p elms 20
26511 Limit on string chars or array elements to print is 200.
26514 Note that if you are defining an alias of a @samp{set} command,
26515 and you want to have an alias for the corresponding @samp{show}
26516 command, then you need to define the latter separately.
26518 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26519 @var{ALIAS}, just as they are normally.
26522 (gdb) alias -a set pr elms = set p ele
26525 Finally, here is an example showing the creation of a one word
26526 alias for a more complex command.
26527 This creates alias @samp{spe} of the command @samp{set print elements}.
26530 (gdb) alias spe = set print elements
26535 @chapter Command Interpreters
26536 @cindex command interpreters
26538 @value{GDBN} supports multiple command interpreters, and some command
26539 infrastructure to allow users or user interface writers to switch
26540 between interpreters or run commands in other interpreters.
26542 @value{GDBN} currently supports two command interpreters, the console
26543 interpreter (sometimes called the command-line interpreter or @sc{cli})
26544 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26545 describes both of these interfaces in great detail.
26547 By default, @value{GDBN} will start with the console interpreter.
26548 However, the user may choose to start @value{GDBN} with another
26549 interpreter by specifying the @option{-i} or @option{--interpreter}
26550 startup options. Defined interpreters include:
26554 @cindex console interpreter
26555 The traditional console or command-line interpreter. This is the most often
26556 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26557 @value{GDBN} will use this interpreter.
26560 @cindex mi interpreter
26561 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26562 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26563 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26567 @cindex mi3 interpreter
26568 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26571 @cindex mi2 interpreter
26572 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26575 @cindex mi1 interpreter
26576 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26580 @cindex invoke another interpreter
26582 @kindex interpreter-exec
26583 You may execute commands in any interpreter from the current
26584 interpreter using the appropriate command. If you are running the
26585 console interpreter, simply use the @code{interpreter-exec} command:
26588 interpreter-exec mi "-data-list-register-names"
26591 @sc{gdb/mi} has a similar command, although it is only available in versions of
26592 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26594 Note that @code{interpreter-exec} only changes the interpreter for the
26595 duration of the specified command. It does not change the interpreter
26598 @cindex start a new independent interpreter
26600 Although you may only choose a single interpreter at startup, it is
26601 possible to run an independent interpreter on a specified input/output
26602 device (usually a tty).
26604 For example, consider a debugger GUI or IDE that wants to provide a
26605 @value{GDBN} console view. It may do so by embedding a terminal
26606 emulator widget in its GUI, starting @value{GDBN} in the traditional
26607 command-line mode with stdin/stdout/stderr redirected to that
26608 terminal, and then creating an MI interpreter running on a specified
26609 input/output device. The console interpreter created by @value{GDBN}
26610 at startup handles commands the user types in the terminal widget,
26611 while the GUI controls and synchronizes state with @value{GDBN} using
26612 the separate MI interpreter.
26614 To start a new secondary @dfn{user interface} running MI, use the
26615 @code{new-ui} command:
26618 @cindex new user interface
26620 new-ui @var{interpreter} @var{tty}
26623 The @var{interpreter} parameter specifies the interpreter to run.
26624 This accepts the same values as the @code{interpreter-exec} command.
26625 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26626 @var{tty} parameter specifies the name of the bidirectional file the
26627 interpreter uses for input/output, usually the name of a
26628 pseudoterminal slave on Unix systems. For example:
26631 (@value{GDBP}) new-ui mi /dev/pts/9
26635 runs an MI interpreter on @file{/dev/pts/9}.
26638 @chapter @value{GDBN} Text User Interface
26640 @cindex Text User Interface
26643 * TUI Overview:: TUI overview
26644 * TUI Keys:: TUI key bindings
26645 * TUI Single Key Mode:: TUI single key mode
26646 * TUI Commands:: TUI-specific commands
26647 * TUI Configuration:: TUI configuration variables
26650 The @value{GDBN} Text User Interface (TUI) is a terminal
26651 interface which uses the @code{curses} library to show the source
26652 file, the assembly output, the program registers and @value{GDBN}
26653 commands in separate text windows. The TUI mode is supported only
26654 on platforms where a suitable version of the @code{curses} library
26657 The TUI mode is enabled by default when you invoke @value{GDBN} as
26658 @samp{@value{GDBP} -tui}.
26659 You can also switch in and out of TUI mode while @value{GDBN} runs by
26660 using various TUI commands and key bindings, such as @command{tui
26661 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26662 @ref{TUI Keys, ,TUI Key Bindings}.
26665 @section TUI Overview
26667 In TUI mode, @value{GDBN} can display several text windows:
26671 This window is the @value{GDBN} command window with the @value{GDBN}
26672 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26673 managed using readline.
26676 The source window shows the source file of the program. The current
26677 line and active breakpoints are displayed in this window.
26680 The assembly window shows the disassembly output of the program.
26683 This window shows the processor registers. Registers are highlighted
26684 when their values change.
26687 The source and assembly windows show the current program position
26688 by highlighting the current line and marking it with a @samp{>} marker.
26689 Breakpoints are indicated with two markers. The first marker
26690 indicates the breakpoint type:
26694 Breakpoint which was hit at least once.
26697 Breakpoint which was never hit.
26700 Hardware breakpoint which was hit at least once.
26703 Hardware breakpoint which was never hit.
26706 The second marker indicates whether the breakpoint is enabled or not:
26710 Breakpoint is enabled.
26713 Breakpoint is disabled.
26716 The source, assembly and register windows are updated when the current
26717 thread changes, when the frame changes, or when the program counter
26720 These windows are not all visible at the same time. The command
26721 window is always visible. The others can be arranged in several
26732 source and assembly,
26735 source and registers, or
26738 assembly and registers.
26741 A status line above the command window shows the following information:
26745 Indicates the current @value{GDBN} target.
26746 (@pxref{Targets, ,Specifying a Debugging Target}).
26749 Gives the current process or thread number.
26750 When no process is being debugged, this field is set to @code{No process}.
26753 Gives the current function name for the selected frame.
26754 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26755 When there is no symbol corresponding to the current program counter,
26756 the string @code{??} is displayed.
26759 Indicates the current line number for the selected frame.
26760 When the current line number is not known, the string @code{??} is displayed.
26763 Indicates the current program counter address.
26767 @section TUI Key Bindings
26768 @cindex TUI key bindings
26770 The TUI installs several key bindings in the readline keymaps
26771 @ifset SYSTEM_READLINE
26772 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26774 @ifclear SYSTEM_READLINE
26775 (@pxref{Command Line Editing}).
26777 The following key bindings are installed for both TUI mode and the
26778 @value{GDBN} standard mode.
26787 Enter or leave the TUI mode. When leaving the TUI mode,
26788 the curses window management stops and @value{GDBN} operates using
26789 its standard mode, writing on the terminal directly. When reentering
26790 the TUI mode, control is given back to the curses windows.
26791 The screen is then refreshed.
26795 Use a TUI layout with only one window. The layout will
26796 either be @samp{source} or @samp{assembly}. When the TUI mode
26797 is not active, it will switch to the TUI mode.
26799 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26803 Use a TUI layout with at least two windows. When the current
26804 layout already has two windows, the next layout with two windows is used.
26805 When a new layout is chosen, one window will always be common to the
26806 previous layout and the new one.
26808 Think of it as the Emacs @kbd{C-x 2} binding.
26812 Change the active window. The TUI associates several key bindings
26813 (like scrolling and arrow keys) with the active window. This command
26814 gives the focus to the next TUI window.
26816 Think of it as the Emacs @kbd{C-x o} binding.
26820 Switch in and out of the TUI SingleKey mode that binds single
26821 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26824 The following key bindings only work in the TUI mode:
26829 Scroll the active window one page up.
26833 Scroll the active window one page down.
26837 Scroll the active window one line up.
26841 Scroll the active window one line down.
26845 Scroll the active window one column left.
26849 Scroll the active window one column right.
26853 Refresh the screen.
26856 Because the arrow keys scroll the active window in the TUI mode, they
26857 are not available for their normal use by readline unless the command
26858 window has the focus. When another window is active, you must use
26859 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26860 and @kbd{C-f} to control the command window.
26862 @node TUI Single Key Mode
26863 @section TUI Single Key Mode
26864 @cindex TUI single key mode
26866 The TUI also provides a @dfn{SingleKey} mode, which binds several
26867 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26868 switch into this mode, where the following key bindings are used:
26871 @kindex c @r{(SingleKey TUI key)}
26875 @kindex d @r{(SingleKey TUI key)}
26879 @kindex f @r{(SingleKey TUI key)}
26883 @kindex n @r{(SingleKey TUI key)}
26887 @kindex o @r{(SingleKey TUI key)}
26889 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26891 @kindex q @r{(SingleKey TUI key)}
26893 exit the SingleKey mode.
26895 @kindex r @r{(SingleKey TUI key)}
26899 @kindex s @r{(SingleKey TUI key)}
26903 @kindex i @r{(SingleKey TUI key)}
26905 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26907 @kindex u @r{(SingleKey TUI key)}
26911 @kindex v @r{(SingleKey TUI key)}
26915 @kindex w @r{(SingleKey TUI key)}
26920 Other keys temporarily switch to the @value{GDBN} command prompt.
26921 The key that was pressed is inserted in the editing buffer so that
26922 it is possible to type most @value{GDBN} commands without interaction
26923 with the TUI SingleKey mode. Once the command is entered the TUI
26924 SingleKey mode is restored. The only way to permanently leave
26925 this mode is by typing @kbd{q} or @kbd{C-x s}.
26929 @section TUI-specific Commands
26930 @cindex TUI commands
26932 The TUI has specific commands to control the text windows.
26933 These commands are always available, even when @value{GDBN} is not in
26934 the TUI mode. When @value{GDBN} is in the standard mode, most
26935 of these commands will automatically switch to the TUI mode.
26937 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26938 terminal, or @value{GDBN} has been started with the machine interface
26939 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26940 these commands will fail with an error, because it would not be
26941 possible or desirable to enable curses window management.
26946 Activate TUI mode. The last active TUI window layout will be used if
26947 TUI mode has prevsiouly been used in the current debugging session,
26948 otherwise a default layout is used.
26951 @kindex tui disable
26952 Disable TUI mode, returning to the console interpreter.
26956 List and give the size of all displayed windows.
26958 @item layout @var{name}
26960 Changes which TUI windows are displayed. In each layout the command
26961 window is always displayed, the @var{name} parameter controls which
26962 additional windows are displayed, and can be any of the following:
26966 Display the next layout.
26969 Display the previous layout.
26972 Display the source and command windows.
26975 Display the assembly and command windows.
26978 Display the source, assembly, and command windows.
26981 When in @code{src} layout display the register, source, and command
26982 windows. When in @code{asm} or @code{split} layout display the
26983 register, assembler, and command windows.
26986 @item focus @var{name}
26988 Changes which TUI window is currently active for scrolling. The
26989 @var{name} parameter can be any of the following:
26993 Make the next window active for scrolling.
26996 Make the previous window active for scrolling.
26999 Make the source window active for scrolling.
27002 Make the assembly window active for scrolling.
27005 Make the register window active for scrolling.
27008 Make the command window active for scrolling.
27013 Refresh the screen. This is similar to typing @kbd{C-L}.
27015 @item tui reg @var{group}
27017 Changes the register group displayed in the tui register window to
27018 @var{group}. If the register window is not currently displayed this
27019 command will cause the register window to be displayed. The list of
27020 register groups, as well as their order is target specific. The
27021 following groups are available on most targets:
27024 Repeatedly selecting this group will cause the display to cycle
27025 through all of the available register groups.
27028 Repeatedly selecting this group will cause the display to cycle
27029 through all of the available register groups in the reverse order to
27033 Display the general registers.
27035 Display the floating point registers.
27037 Display the system registers.
27039 Display the vector registers.
27041 Display all registers.
27046 Update the source window and the current execution point.
27048 @item winheight @var{name} +@var{count}
27049 @itemx winheight @var{name} -@var{count}
27051 Change the height of the window @var{name} by @var{count}
27052 lines. Positive counts increase the height, while negative counts
27053 decrease it. The @var{name} parameter can be one of @code{src} (the
27054 source window), @code{cmd} (the command window), @code{asm} (the
27055 disassembly window), or @code{regs} (the register display window).
27058 @node TUI Configuration
27059 @section TUI Configuration Variables
27060 @cindex TUI configuration variables
27062 Several configuration variables control the appearance of TUI windows.
27065 @item set tui border-kind @var{kind}
27066 @kindex set tui border-kind
27067 Select the border appearance for the source, assembly and register windows.
27068 The possible values are the following:
27071 Use a space character to draw the border.
27074 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27077 Use the Alternate Character Set to draw the border. The border is
27078 drawn using character line graphics if the terminal supports them.
27081 @item set tui border-mode @var{mode}
27082 @kindex set tui border-mode
27083 @itemx set tui active-border-mode @var{mode}
27084 @kindex set tui active-border-mode
27085 Select the display attributes for the borders of the inactive windows
27086 or the active window. The @var{mode} can be one of the following:
27089 Use normal attributes to display the border.
27095 Use reverse video mode.
27098 Use half bright mode.
27100 @item half-standout
27101 Use half bright and standout mode.
27104 Use extra bright or bold mode.
27106 @item bold-standout
27107 Use extra bright or bold and standout mode.
27110 @item set tui tab-width @var{nchars}
27111 @kindex set tui tab-width
27113 Set the width of tab stops to be @var{nchars} characters. This
27114 setting affects the display of TAB characters in the source and
27119 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27122 @cindex @sc{gnu} Emacs
27123 A special interface allows you to use @sc{gnu} Emacs to view (and
27124 edit) the source files for the program you are debugging with
27127 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27128 executable file you want to debug as an argument. This command starts
27129 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27130 created Emacs buffer.
27131 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27133 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27138 All ``terminal'' input and output goes through an Emacs buffer, called
27141 This applies both to @value{GDBN} commands and their output, and to the input
27142 and output done by the program you are debugging.
27144 This is useful because it means that you can copy the text of previous
27145 commands and input them again; you can even use parts of the output
27148 All the facilities of Emacs' Shell mode are available for interacting
27149 with your program. In particular, you can send signals the usual
27150 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27154 @value{GDBN} displays source code through Emacs.
27156 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27157 source file for that frame and puts an arrow (@samp{=>}) at the
27158 left margin of the current line. Emacs uses a separate buffer for
27159 source display, and splits the screen to show both your @value{GDBN} session
27162 Explicit @value{GDBN} @code{list} or search commands still produce output as
27163 usual, but you probably have no reason to use them from Emacs.
27166 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27167 a graphical mode, enabled by default, which provides further buffers
27168 that can control the execution and describe the state of your program.
27169 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27171 If you specify an absolute file name when prompted for the @kbd{M-x
27172 gdb} argument, then Emacs sets your current working directory to where
27173 your program resides. If you only specify the file name, then Emacs
27174 sets your current working directory to the directory associated
27175 with the previous buffer. In this case, @value{GDBN} may find your
27176 program by searching your environment's @code{PATH} variable, but on
27177 some operating systems it might not find the source. So, although the
27178 @value{GDBN} input and output session proceeds normally, the auxiliary
27179 buffer does not display the current source and line of execution.
27181 The initial working directory of @value{GDBN} is printed on the top
27182 line of the GUD buffer and this serves as a default for the commands
27183 that specify files for @value{GDBN} to operate on. @xref{Files,
27184 ,Commands to Specify Files}.
27186 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27187 need to call @value{GDBN} by a different name (for example, if you
27188 keep several configurations around, with different names) you can
27189 customize the Emacs variable @code{gud-gdb-command-name} to run the
27192 In the GUD buffer, you can use these special Emacs commands in
27193 addition to the standard Shell mode commands:
27197 Describe the features of Emacs' GUD Mode.
27200 Execute to another source line, like the @value{GDBN} @code{step} command; also
27201 update the display window to show the current file and location.
27204 Execute to next source line in this function, skipping all function
27205 calls, like the @value{GDBN} @code{next} command. Then update the display window
27206 to show the current file and location.
27209 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27210 display window accordingly.
27213 Execute until exit from the selected stack frame, like the @value{GDBN}
27214 @code{finish} command.
27217 Continue execution of your program, like the @value{GDBN} @code{continue}
27221 Go up the number of frames indicated by the numeric argument
27222 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27223 like the @value{GDBN} @code{up} command.
27226 Go down the number of frames indicated by the numeric argument, like the
27227 @value{GDBN} @code{down} command.
27230 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27231 tells @value{GDBN} to set a breakpoint on the source line point is on.
27233 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27234 separate frame which shows a backtrace when the GUD buffer is current.
27235 Move point to any frame in the stack and type @key{RET} to make it
27236 become the current frame and display the associated source in the
27237 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27238 selected frame become the current one. In graphical mode, the
27239 speedbar displays watch expressions.
27241 If you accidentally delete the source-display buffer, an easy way to get
27242 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27243 request a frame display; when you run under Emacs, this recreates
27244 the source buffer if necessary to show you the context of the current
27247 The source files displayed in Emacs are in ordinary Emacs buffers
27248 which are visiting the source files in the usual way. You can edit
27249 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27250 communicates with Emacs in terms of line numbers. If you add or
27251 delete lines from the text, the line numbers that @value{GDBN} knows cease
27252 to correspond properly with the code.
27254 A more detailed description of Emacs' interaction with @value{GDBN} is
27255 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27259 @chapter The @sc{gdb/mi} Interface
27261 @unnumberedsec Function and Purpose
27263 @cindex @sc{gdb/mi}, its purpose
27264 @sc{gdb/mi} is a line based machine oriented text interface to
27265 @value{GDBN} and is activated by specifying using the
27266 @option{--interpreter} command line option (@pxref{Mode Options}). It
27267 is specifically intended to support the development of systems which
27268 use the debugger as just one small component of a larger system.
27270 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27271 in the form of a reference manual.
27273 Note that @sc{gdb/mi} is still under construction, so some of the
27274 features described below are incomplete and subject to change
27275 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27277 @unnumberedsec Notation and Terminology
27279 @cindex notational conventions, for @sc{gdb/mi}
27280 This chapter uses the following notation:
27284 @code{|} separates two alternatives.
27287 @code{[ @var{something} ]} indicates that @var{something} is optional:
27288 it may or may not be given.
27291 @code{( @var{group} )*} means that @var{group} inside the parentheses
27292 may repeat zero or more times.
27295 @code{( @var{group} )+} means that @var{group} inside the parentheses
27296 may repeat one or more times.
27299 @code{"@var{string}"} means a literal @var{string}.
27303 @heading Dependencies
27307 * GDB/MI General Design::
27308 * GDB/MI Command Syntax::
27309 * GDB/MI Compatibility with CLI::
27310 * GDB/MI Development and Front Ends::
27311 * GDB/MI Output Records::
27312 * GDB/MI Simple Examples::
27313 * GDB/MI Command Description Format::
27314 * GDB/MI Breakpoint Commands::
27315 * GDB/MI Catchpoint Commands::
27316 * GDB/MI Program Context::
27317 * GDB/MI Thread Commands::
27318 * GDB/MI Ada Tasking Commands::
27319 * GDB/MI Program Execution::
27320 * GDB/MI Stack Manipulation::
27321 * GDB/MI Variable Objects::
27322 * GDB/MI Data Manipulation::
27323 * GDB/MI Tracepoint Commands::
27324 * GDB/MI Symbol Query::
27325 * GDB/MI File Commands::
27327 * GDB/MI Kod Commands::
27328 * GDB/MI Memory Overlay Commands::
27329 * GDB/MI Signal Handling Commands::
27331 * GDB/MI Target Manipulation::
27332 * GDB/MI File Transfer Commands::
27333 * GDB/MI Ada Exceptions Commands::
27334 * GDB/MI Support Commands::
27335 * GDB/MI Miscellaneous Commands::
27338 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27339 @node GDB/MI General Design
27340 @section @sc{gdb/mi} General Design
27341 @cindex GDB/MI General Design
27343 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27344 parts---commands sent to @value{GDBN}, responses to those commands
27345 and notifications. Each command results in exactly one response,
27346 indicating either successful completion of the command, or an error.
27347 For the commands that do not resume the target, the response contains the
27348 requested information. For the commands that resume the target, the
27349 response only indicates whether the target was successfully resumed.
27350 Notifications is the mechanism for reporting changes in the state of the
27351 target, or in @value{GDBN} state, that cannot conveniently be associated with
27352 a command and reported as part of that command response.
27354 The important examples of notifications are:
27358 Exec notifications. These are used to report changes in
27359 target state---when a target is resumed, or stopped. It would not
27360 be feasible to include this information in response of resuming
27361 commands, because one resume commands can result in multiple events in
27362 different threads. Also, quite some time may pass before any event
27363 happens in the target, while a frontend needs to know whether the resuming
27364 command itself was successfully executed.
27367 Console output, and status notifications. Console output
27368 notifications are used to report output of CLI commands, as well as
27369 diagnostics for other commands. Status notifications are used to
27370 report the progress of a long-running operation. Naturally, including
27371 this information in command response would mean no output is produced
27372 until the command is finished, which is undesirable.
27375 General notifications. Commands may have various side effects on
27376 the @value{GDBN} or target state beyond their official purpose. For example,
27377 a command may change the selected thread. Although such changes can
27378 be included in command response, using notification allows for more
27379 orthogonal frontend design.
27383 There's no guarantee that whenever an MI command reports an error,
27384 @value{GDBN} or the target are in any specific state, and especially,
27385 the state is not reverted to the state before the MI command was
27386 processed. Therefore, whenever an MI command results in an error,
27387 we recommend that the frontend refreshes all the information shown in
27388 the user interface.
27392 * Context management::
27393 * Asynchronous and non-stop modes::
27397 @node Context management
27398 @subsection Context management
27400 @subsubsection Threads and Frames
27402 In most cases when @value{GDBN} accesses the target, this access is
27403 done in context of a specific thread and frame (@pxref{Frames}).
27404 Often, even when accessing global data, the target requires that a thread
27405 be specified. The CLI interface maintains the selected thread and frame,
27406 and supplies them to target on each command. This is convenient,
27407 because a command line user would not want to specify that information
27408 explicitly on each command, and because user interacts with
27409 @value{GDBN} via a single terminal, so no confusion is possible as
27410 to what thread and frame are the current ones.
27412 In the case of MI, the concept of selected thread and frame is less
27413 useful. First, a frontend can easily remember this information
27414 itself. Second, a graphical frontend can have more than one window,
27415 each one used for debugging a different thread, and the frontend might
27416 want to access additional threads for internal purposes. This
27417 increases the risk that by relying on implicitly selected thread, the
27418 frontend may be operating on a wrong one. Therefore, each MI command
27419 should explicitly specify which thread and frame to operate on. To
27420 make it possible, each MI command accepts the @samp{--thread} and
27421 @samp{--frame} options, the value to each is @value{GDBN} global
27422 identifier for thread and frame to operate on.
27424 Usually, each top-level window in a frontend allows the user to select
27425 a thread and a frame, and remembers the user selection for further
27426 operations. However, in some cases @value{GDBN} may suggest that the
27427 current thread or frame be changed. For example, when stopping on a
27428 breakpoint it is reasonable to switch to the thread where breakpoint is
27429 hit. For another example, if the user issues the CLI @samp{thread} or
27430 @samp{frame} commands via the frontend, it is desirable to change the
27431 frontend's selection to the one specified by user. @value{GDBN}
27432 communicates the suggestion to change current thread and frame using the
27433 @samp{=thread-selected} notification.
27435 Note that historically, MI shares the selected thread with CLI, so
27436 frontends used the @code{-thread-select} to execute commands in the
27437 right context. However, getting this to work right is cumbersome. The
27438 simplest way is for frontend to emit @code{-thread-select} command
27439 before every command. This doubles the number of commands that need
27440 to be sent. The alternative approach is to suppress @code{-thread-select}
27441 if the selected thread in @value{GDBN} is supposed to be identical to the
27442 thread the frontend wants to operate on. However, getting this
27443 optimization right can be tricky. In particular, if the frontend
27444 sends several commands to @value{GDBN}, and one of the commands changes the
27445 selected thread, then the behaviour of subsequent commands will
27446 change. So, a frontend should either wait for response from such
27447 problematic commands, or explicitly add @code{-thread-select} for
27448 all subsequent commands. No frontend is known to do this exactly
27449 right, so it is suggested to just always pass the @samp{--thread} and
27450 @samp{--frame} options.
27452 @subsubsection Language
27454 The execution of several commands depends on which language is selected.
27455 By default, the current language (@pxref{show language}) is used.
27456 But for commands known to be language-sensitive, it is recommended
27457 to use the @samp{--language} option. This option takes one argument,
27458 which is the name of the language to use while executing the command.
27462 -data-evaluate-expression --language c "sizeof (void*)"
27467 The valid language names are the same names accepted by the
27468 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27469 @samp{local} or @samp{unknown}.
27471 @node Asynchronous and non-stop modes
27472 @subsection Asynchronous command execution and non-stop mode
27474 On some targets, @value{GDBN} is capable of processing MI commands
27475 even while the target is running. This is called @dfn{asynchronous
27476 command execution} (@pxref{Background Execution}). The frontend may
27477 specify a preferrence for asynchronous execution using the
27478 @code{-gdb-set mi-async 1} command, which should be emitted before
27479 either running the executable or attaching to the target. After the
27480 frontend has started the executable or attached to the target, it can
27481 find if asynchronous execution is enabled using the
27482 @code{-list-target-features} command.
27485 @item -gdb-set mi-async on
27486 @item -gdb-set mi-async off
27487 Set whether MI is in asynchronous mode.
27489 When @code{off}, which is the default, MI execution commands (e.g.,
27490 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27491 for the program to stop before processing further commands.
27493 When @code{on}, MI execution commands are background execution
27494 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27495 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27496 MI commands even while the target is running.
27498 @item -gdb-show mi-async
27499 Show whether MI asynchronous mode is enabled.
27502 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27503 @code{target-async} instead of @code{mi-async}, and it had the effect
27504 of both putting MI in asynchronous mode and making CLI background
27505 commands possible. CLI background commands are now always possible
27506 ``out of the box'' if the target supports them. The old spelling is
27507 kept as a deprecated alias for backwards compatibility.
27509 Even if @value{GDBN} can accept a command while target is running,
27510 many commands that access the target do not work when the target is
27511 running. Therefore, asynchronous command execution is most useful
27512 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27513 it is possible to examine the state of one thread, while other threads
27516 When a given thread is running, MI commands that try to access the
27517 target in the context of that thread may not work, or may work only on
27518 some targets. In particular, commands that try to operate on thread's
27519 stack will not work, on any target. Commands that read memory, or
27520 modify breakpoints, may work or not work, depending on the target. Note
27521 that even commands that operate on global state, such as @code{print},
27522 @code{set}, and breakpoint commands, still access the target in the
27523 context of a specific thread, so frontend should try to find a
27524 stopped thread and perform the operation on that thread (using the
27525 @samp{--thread} option).
27527 Which commands will work in the context of a running thread is
27528 highly target dependent. However, the two commands
27529 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27530 to find the state of a thread, will always work.
27532 @node Thread groups
27533 @subsection Thread groups
27534 @value{GDBN} may be used to debug several processes at the same time.
27535 On some platfroms, @value{GDBN} may support debugging of several
27536 hardware systems, each one having several cores with several different
27537 processes running on each core. This section describes the MI
27538 mechanism to support such debugging scenarios.
27540 The key observation is that regardless of the structure of the
27541 target, MI can have a global list of threads, because most commands that
27542 accept the @samp{--thread} option do not need to know what process that
27543 thread belongs to. Therefore, it is not necessary to introduce
27544 neither additional @samp{--process} option, nor an notion of the
27545 current process in the MI interface. The only strictly new feature
27546 that is required is the ability to find how the threads are grouped
27549 To allow the user to discover such grouping, and to support arbitrary
27550 hierarchy of machines/cores/processes, MI introduces the concept of a
27551 @dfn{thread group}. Thread group is a collection of threads and other
27552 thread groups. A thread group always has a string identifier, a type,
27553 and may have additional attributes specific to the type. A new
27554 command, @code{-list-thread-groups}, returns the list of top-level
27555 thread groups, which correspond to processes that @value{GDBN} is
27556 debugging at the moment. By passing an identifier of a thread group
27557 to the @code{-list-thread-groups} command, it is possible to obtain
27558 the members of specific thread group.
27560 To allow the user to easily discover processes, and other objects, he
27561 wishes to debug, a concept of @dfn{available thread group} is
27562 introduced. Available thread group is an thread group that
27563 @value{GDBN} is not debugging, but that can be attached to, using the
27564 @code{-target-attach} command. The list of available top-level thread
27565 groups can be obtained using @samp{-list-thread-groups --available}.
27566 In general, the content of a thread group may be only retrieved only
27567 after attaching to that thread group.
27569 Thread groups are related to inferiors (@pxref{Inferiors and
27570 Programs}). Each inferior corresponds to a thread group of a special
27571 type @samp{process}, and some additional operations are permitted on
27572 such thread groups.
27574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27575 @node GDB/MI Command Syntax
27576 @section @sc{gdb/mi} Command Syntax
27579 * GDB/MI Input Syntax::
27580 * GDB/MI Output Syntax::
27583 @node GDB/MI Input Syntax
27584 @subsection @sc{gdb/mi} Input Syntax
27586 @cindex input syntax for @sc{gdb/mi}
27587 @cindex @sc{gdb/mi}, input syntax
27589 @item @var{command} @expansion{}
27590 @code{@var{cli-command} | @var{mi-command}}
27592 @item @var{cli-command} @expansion{}
27593 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27594 @var{cli-command} is any existing @value{GDBN} CLI command.
27596 @item @var{mi-command} @expansion{}
27597 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27598 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27600 @item @var{token} @expansion{}
27601 "any sequence of digits"
27603 @item @var{option} @expansion{}
27604 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27606 @item @var{parameter} @expansion{}
27607 @code{@var{non-blank-sequence} | @var{c-string}}
27609 @item @var{operation} @expansion{}
27610 @emph{any of the operations described in this chapter}
27612 @item @var{non-blank-sequence} @expansion{}
27613 @emph{anything, provided it doesn't contain special characters such as
27614 "-", @var{nl}, """ and of course " "}
27616 @item @var{c-string} @expansion{}
27617 @code{""" @var{seven-bit-iso-c-string-content} """}
27619 @item @var{nl} @expansion{}
27628 The CLI commands are still handled by the @sc{mi} interpreter; their
27629 output is described below.
27632 The @code{@var{token}}, when present, is passed back when the command
27636 Some @sc{mi} commands accept optional arguments as part of the parameter
27637 list. Each option is identified by a leading @samp{-} (dash) and may be
27638 followed by an optional argument parameter. Options occur first in the
27639 parameter list and can be delimited from normal parameters using
27640 @samp{--} (this is useful when some parameters begin with a dash).
27647 We want easy access to the existing CLI syntax (for debugging).
27650 We want it to be easy to spot a @sc{mi} operation.
27653 @node GDB/MI Output Syntax
27654 @subsection @sc{gdb/mi} Output Syntax
27656 @cindex output syntax of @sc{gdb/mi}
27657 @cindex @sc{gdb/mi}, output syntax
27658 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27659 followed, optionally, by a single result record. This result record
27660 is for the most recent command. The sequence of output records is
27661 terminated by @samp{(gdb)}.
27663 If an input command was prefixed with a @code{@var{token}} then the
27664 corresponding output for that command will also be prefixed by that same
27668 @item @var{output} @expansion{}
27669 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27671 @item @var{result-record} @expansion{}
27672 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27674 @item @var{out-of-band-record} @expansion{}
27675 @code{@var{async-record} | @var{stream-record}}
27677 @item @var{async-record} @expansion{}
27678 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27680 @item @var{exec-async-output} @expansion{}
27681 @code{[ @var{token} ] "*" @var{async-output nl}}
27683 @item @var{status-async-output} @expansion{}
27684 @code{[ @var{token} ] "+" @var{async-output nl}}
27686 @item @var{notify-async-output} @expansion{}
27687 @code{[ @var{token} ] "=" @var{async-output nl}}
27689 @item @var{async-output} @expansion{}
27690 @code{@var{async-class} ( "," @var{result} )*}
27692 @item @var{result-class} @expansion{}
27693 @code{"done" | "running" | "connected" | "error" | "exit"}
27695 @item @var{async-class} @expansion{}
27696 @code{"stopped" | @var{others}} (where @var{others} will be added
27697 depending on the needs---this is still in development).
27699 @item @var{result} @expansion{}
27700 @code{ @var{variable} "=" @var{value}}
27702 @item @var{variable} @expansion{}
27703 @code{ @var{string} }
27705 @item @var{value} @expansion{}
27706 @code{ @var{const} | @var{tuple} | @var{list} }
27708 @item @var{const} @expansion{}
27709 @code{@var{c-string}}
27711 @item @var{tuple} @expansion{}
27712 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27714 @item @var{list} @expansion{}
27715 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27716 @var{result} ( "," @var{result} )* "]" }
27718 @item @var{stream-record} @expansion{}
27719 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27721 @item @var{console-stream-output} @expansion{}
27722 @code{"~" @var{c-string nl}}
27724 @item @var{target-stream-output} @expansion{}
27725 @code{"@@" @var{c-string nl}}
27727 @item @var{log-stream-output} @expansion{}
27728 @code{"&" @var{c-string nl}}
27730 @item @var{nl} @expansion{}
27733 @item @var{token} @expansion{}
27734 @emph{any sequence of digits}.
27742 All output sequences end in a single line containing a period.
27745 The @code{@var{token}} is from the corresponding request. Note that
27746 for all async output, while the token is allowed by the grammar and
27747 may be output by future versions of @value{GDBN} for select async
27748 output messages, it is generally omitted. Frontends should treat
27749 all async output as reporting general changes in the state of the
27750 target and there should be no need to associate async output to any
27754 @cindex status output in @sc{gdb/mi}
27755 @var{status-async-output} contains on-going status information about the
27756 progress of a slow operation. It can be discarded. All status output is
27757 prefixed by @samp{+}.
27760 @cindex async output in @sc{gdb/mi}
27761 @var{exec-async-output} contains asynchronous state change on the target
27762 (stopped, started, disappeared). All async output is prefixed by
27766 @cindex notify output in @sc{gdb/mi}
27767 @var{notify-async-output} contains supplementary information that the
27768 client should handle (e.g., a new breakpoint information). All notify
27769 output is prefixed by @samp{=}.
27772 @cindex console output in @sc{gdb/mi}
27773 @var{console-stream-output} is output that should be displayed as is in the
27774 console. It is the textual response to a CLI command. All the console
27775 output is prefixed by @samp{~}.
27778 @cindex target output in @sc{gdb/mi}
27779 @var{target-stream-output} is the output produced by the target program.
27780 All the target output is prefixed by @samp{@@}.
27783 @cindex log output in @sc{gdb/mi}
27784 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27785 instance messages that should be displayed as part of an error log. All
27786 the log output is prefixed by @samp{&}.
27789 @cindex list output in @sc{gdb/mi}
27790 New @sc{gdb/mi} commands should only output @var{lists} containing
27796 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27797 details about the various output records.
27799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27800 @node GDB/MI Compatibility with CLI
27801 @section @sc{gdb/mi} Compatibility with CLI
27803 @cindex compatibility, @sc{gdb/mi} and CLI
27804 @cindex @sc{gdb/mi}, compatibility with CLI
27806 For the developers convenience CLI commands can be entered directly,
27807 but there may be some unexpected behaviour. For example, commands
27808 that query the user will behave as if the user replied yes, breakpoint
27809 command lists are not executed and some CLI commands, such as
27810 @code{if}, @code{when} and @code{define}, prompt for further input with
27811 @samp{>}, which is not valid MI output.
27813 This feature may be removed at some stage in the future and it is
27814 recommended that front ends use the @code{-interpreter-exec} command
27815 (@pxref{-interpreter-exec}).
27817 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27818 @node GDB/MI Development and Front Ends
27819 @section @sc{gdb/mi} Development and Front Ends
27820 @cindex @sc{gdb/mi} development
27822 The application which takes the MI output and presents the state of the
27823 program being debugged to the user is called a @dfn{front end}.
27825 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27826 to the MI interface may break existing usage. This section describes how the
27827 protocol changes and how to request previous version of the protocol when it
27830 Some changes in MI need not break a carefully designed front end, and
27831 for these the MI version will remain unchanged. The following is a
27832 list of changes that may occur within one level, so front ends should
27833 parse MI output in a way that can handle them:
27837 New MI commands may be added.
27840 New fields may be added to the output of any MI command.
27843 The range of values for fields with specified values, e.g.,
27844 @code{in_scope} (@pxref{-var-update}) may be extended.
27846 @c The format of field's content e.g type prefix, may change so parse it
27847 @c at your own risk. Yes, in general?
27849 @c The order of fields may change? Shouldn't really matter but it might
27850 @c resolve inconsistencies.
27853 If the changes are likely to break front ends, the MI version level
27854 will be increased by one. The new versions of the MI protocol are not compatible
27855 with the old versions. Old versions of MI remain available, allowing front ends
27856 to keep using them until they are modified to use the latest MI version.
27858 Since @code{--interpreter=mi} always points to the latest MI version, it is
27859 recommended that front ends request a specific version of MI when launching
27860 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27861 interpreter with the MI version they expect.
27863 The following table gives a summary of the the released versions of the MI
27864 interface: the version number, the version of GDB in which it first appeared
27865 and the breaking changes compared to the previous version.
27867 @multitable @columnfractions .05 .05 .9
27868 @headitem MI version @tab GDB version @tab Breaking changes
27885 The @code{-environment-pwd}, @code{-environment-directory} and
27886 @code{-environment-path} commands now returns values using the MI output
27887 syntax, rather than CLI output syntax.
27890 @code{-var-list-children}'s @code{children} result field is now a list, rather
27894 @code{-var-update}'s @code{changelist} result field is now a list, rather than
27906 The output of information about multi-location breakpoints has changed in the
27907 responses to the @code{-break-insert} and @code{-break-info} commands, as well
27908 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
27909 The multiple locations are now placed in a @code{locations} field, whose value
27915 If your front end cannot yet migrate to a more recent version of the
27916 MI protocol, you can nevertheless selectively enable specific features
27917 available in those recent MI versions, using the following commands:
27921 @item -fix-multi-location-breakpoint-output
27922 Use the output for multi-location breakpoints which was introduced by
27923 MI 3, even when using MI versions 2 or 1. This command has no
27924 effect when using MI version 3 or later.
27928 The best way to avoid unexpected changes in MI that might break your front
27929 end is to make your project known to @value{GDBN} developers and
27930 follow development on @email{gdb@@sourceware.org} and
27931 @email{gdb-patches@@sourceware.org}.
27932 @cindex mailing lists
27934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27935 @node GDB/MI Output Records
27936 @section @sc{gdb/mi} Output Records
27939 * GDB/MI Result Records::
27940 * GDB/MI Stream Records::
27941 * GDB/MI Async Records::
27942 * GDB/MI Breakpoint Information::
27943 * GDB/MI Frame Information::
27944 * GDB/MI Thread Information::
27945 * GDB/MI Ada Exception Information::
27948 @node GDB/MI Result Records
27949 @subsection @sc{gdb/mi} Result Records
27951 @cindex result records in @sc{gdb/mi}
27952 @cindex @sc{gdb/mi}, result records
27953 In addition to a number of out-of-band notifications, the response to a
27954 @sc{gdb/mi} command includes one of the following result indications:
27958 @item "^done" [ "," @var{results} ]
27959 The synchronous operation was successful, @code{@var{results}} are the return
27964 This result record is equivalent to @samp{^done}. Historically, it
27965 was output instead of @samp{^done} if the command has resumed the
27966 target. This behaviour is maintained for backward compatibility, but
27967 all frontends should treat @samp{^done} and @samp{^running}
27968 identically and rely on the @samp{*running} output record to determine
27969 which threads are resumed.
27973 @value{GDBN} has connected to a remote target.
27975 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27977 The operation failed. The @code{msg=@var{c-string}} variable contains
27978 the corresponding error message.
27980 If present, the @code{code=@var{c-string}} variable provides an error
27981 code on which consumers can rely on to detect the corresponding
27982 error condition. At present, only one error code is defined:
27985 @item "undefined-command"
27986 Indicates that the command causing the error does not exist.
27991 @value{GDBN} has terminated.
27995 @node GDB/MI Stream Records
27996 @subsection @sc{gdb/mi} Stream Records
27998 @cindex @sc{gdb/mi}, stream records
27999 @cindex stream records in @sc{gdb/mi}
28000 @value{GDBN} internally maintains a number of output streams: the console, the
28001 target, and the log. The output intended for each of these streams is
28002 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28004 Each stream record begins with a unique @dfn{prefix character} which
28005 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28006 Syntax}). In addition to the prefix, each stream record contains a
28007 @code{@var{string-output}}. This is either raw text (with an implicit new
28008 line) or a quoted C string (which does not contain an implicit newline).
28011 @item "~" @var{string-output}
28012 The console output stream contains text that should be displayed in the
28013 CLI console window. It contains the textual responses to CLI commands.
28015 @item "@@" @var{string-output}
28016 The target output stream contains any textual output from the running
28017 target. This is only present when GDB's event loop is truly
28018 asynchronous, which is currently only the case for remote targets.
28020 @item "&" @var{string-output}
28021 The log stream contains debugging messages being produced by @value{GDBN}'s
28025 @node GDB/MI Async Records
28026 @subsection @sc{gdb/mi} Async Records
28028 @cindex async records in @sc{gdb/mi}
28029 @cindex @sc{gdb/mi}, async records
28030 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28031 additional changes that have occurred. Those changes can either be a
28032 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28033 target activity (e.g., target stopped).
28035 The following is the list of possible async records:
28039 @item *running,thread-id="@var{thread}"
28040 The target is now running. The @var{thread} field can be the global
28041 thread ID of the the thread that is now running, and it can be
28042 @samp{all} if all threads are running. The frontend should assume
28043 that no interaction with a running thread is possible after this
28044 notification is produced. The frontend should not assume that this
28045 notification is output only once for any command. @value{GDBN} may
28046 emit this notification several times, either for different threads,
28047 because it cannot resume all threads together, or even for a single
28048 thread, if the thread must be stepped though some code before letting
28051 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28052 The target has stopped. The @var{reason} field can have one of the
28056 @item breakpoint-hit
28057 A breakpoint was reached.
28058 @item watchpoint-trigger
28059 A watchpoint was triggered.
28060 @item read-watchpoint-trigger
28061 A read watchpoint was triggered.
28062 @item access-watchpoint-trigger
28063 An access watchpoint was triggered.
28064 @item function-finished
28065 An -exec-finish or similar CLI command was accomplished.
28066 @item location-reached
28067 An -exec-until or similar CLI command was accomplished.
28068 @item watchpoint-scope
28069 A watchpoint has gone out of scope.
28070 @item end-stepping-range
28071 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28072 similar CLI command was accomplished.
28073 @item exited-signalled
28074 The inferior exited because of a signal.
28076 The inferior exited.
28077 @item exited-normally
28078 The inferior exited normally.
28079 @item signal-received
28080 A signal was received by the inferior.
28082 The inferior has stopped due to a library being loaded or unloaded.
28083 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28084 set or when a @code{catch load} or @code{catch unload} catchpoint is
28085 in use (@pxref{Set Catchpoints}).
28087 The inferior has forked. This is reported when @code{catch fork}
28088 (@pxref{Set Catchpoints}) has been used.
28090 The inferior has vforked. This is reported in when @code{catch vfork}
28091 (@pxref{Set Catchpoints}) has been used.
28092 @item syscall-entry
28093 The inferior entered a system call. This is reported when @code{catch
28094 syscall} (@pxref{Set Catchpoints}) has been used.
28095 @item syscall-return
28096 The inferior returned from a system call. This is reported when
28097 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28099 The inferior called @code{exec}. This is reported when @code{catch exec}
28100 (@pxref{Set Catchpoints}) has been used.
28103 The @var{id} field identifies the global thread ID of the thread
28104 that directly caused the stop -- for example by hitting a breakpoint.
28105 Depending on whether all-stop
28106 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28107 stop all threads, or only the thread that directly triggered the stop.
28108 If all threads are stopped, the @var{stopped} field will have the
28109 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28110 field will be a list of thread identifiers. Presently, this list will
28111 always include a single thread, but frontend should be prepared to see
28112 several threads in the list. The @var{core} field reports the
28113 processor core on which the stop event has happened. This field may be absent
28114 if such information is not available.
28116 @item =thread-group-added,id="@var{id}"
28117 @itemx =thread-group-removed,id="@var{id}"
28118 A thread group was either added or removed. The @var{id} field
28119 contains the @value{GDBN} identifier of the thread group. When a thread
28120 group is added, it generally might not be associated with a running
28121 process. When a thread group is removed, its id becomes invalid and
28122 cannot be used in any way.
28124 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28125 A thread group became associated with a running program,
28126 either because the program was just started or the thread group
28127 was attached to a program. The @var{id} field contains the
28128 @value{GDBN} identifier of the thread group. The @var{pid} field
28129 contains process identifier, specific to the operating system.
28131 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28132 A thread group is no longer associated with a running program,
28133 either because the program has exited, or because it was detached
28134 from. The @var{id} field contains the @value{GDBN} identifier of the
28135 thread group. The @var{code} field is the exit code of the inferior; it exists
28136 only when the inferior exited with some code.
28138 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28139 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28140 A thread either was created, or has exited. The @var{id} field
28141 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28142 field identifies the thread group this thread belongs to.
28144 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28145 Informs that the selected thread or frame were changed. This notification
28146 is not emitted as result of the @code{-thread-select} or
28147 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28148 that is not documented to change the selected thread and frame actually
28149 changes them. In particular, invoking, directly or indirectly
28150 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28151 will generate this notification. Changing the thread or frame from another
28152 user interface (see @ref{Interpreters}) will also generate this notification.
28154 The @var{frame} field is only present if the newly selected thread is
28155 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28157 We suggest that in response to this notification, front ends
28158 highlight the selected thread and cause subsequent commands to apply to
28161 @item =library-loaded,...
28162 Reports that a new library file was loaded by the program. This
28163 notification has 5 fields---@var{id}, @var{target-name},
28164 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28165 opaque identifier of the library. For remote debugging case,
28166 @var{target-name} and @var{host-name} fields give the name of the
28167 library file on the target, and on the host respectively. For native
28168 debugging, both those fields have the same value. The
28169 @var{symbols-loaded} field is emitted only for backward compatibility
28170 and should not be relied on to convey any useful information. The
28171 @var{thread-group} field, if present, specifies the id of the thread
28172 group in whose context the library was loaded. If the field is
28173 absent, it means the library was loaded in the context of all present
28174 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28177 @item =library-unloaded,...
28178 Reports that a library was unloaded by the program. This notification
28179 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28180 the same meaning as for the @code{=library-loaded} notification.
28181 The @var{thread-group} field, if present, specifies the id of the
28182 thread group in whose context the library was unloaded. If the field is
28183 absent, it means the library was unloaded in the context of all present
28186 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28187 @itemx =traceframe-changed,end
28188 Reports that the trace frame was changed and its new number is
28189 @var{tfnum}. The number of the tracepoint associated with this trace
28190 frame is @var{tpnum}.
28192 @item =tsv-created,name=@var{name},initial=@var{initial}
28193 Reports that the new trace state variable @var{name} is created with
28194 initial value @var{initial}.
28196 @item =tsv-deleted,name=@var{name}
28197 @itemx =tsv-deleted
28198 Reports that the trace state variable @var{name} is deleted or all
28199 trace state variables are deleted.
28201 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28202 Reports that the trace state variable @var{name} is modified with
28203 the initial value @var{initial}. The current value @var{current} of
28204 trace state variable is optional and is reported if the current
28205 value of trace state variable is known.
28207 @item =breakpoint-created,bkpt=@{...@}
28208 @itemx =breakpoint-modified,bkpt=@{...@}
28209 @itemx =breakpoint-deleted,id=@var{number}
28210 Reports that a breakpoint was created, modified, or deleted,
28211 respectively. Only user-visible breakpoints are reported to the MI
28214 The @var{bkpt} argument is of the same form as returned by the various
28215 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28216 @var{number} is the ordinal number of the breakpoint.
28218 Note that if a breakpoint is emitted in the result record of a
28219 command, then it will not also be emitted in an async record.
28221 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28222 @itemx =record-stopped,thread-group="@var{id}"
28223 Execution log recording was either started or stopped on an
28224 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28225 group corresponding to the affected inferior.
28227 The @var{method} field indicates the method used to record execution. If the
28228 method in use supports multiple recording formats, @var{format} will be present
28229 and contain the currently used format. @xref{Process Record and Replay},
28230 for existing method and format values.
28232 @item =cmd-param-changed,param=@var{param},value=@var{value}
28233 Reports that a parameter of the command @code{set @var{param}} is
28234 changed to @var{value}. In the multi-word @code{set} command,
28235 the @var{param} is the whole parameter list to @code{set} command.
28236 For example, In command @code{set check type on}, @var{param}
28237 is @code{check type} and @var{value} is @code{on}.
28239 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28240 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28241 written in an inferior. The @var{id} is the identifier of the
28242 thread group corresponding to the affected inferior. The optional
28243 @code{type="code"} part is reported if the memory written to holds
28247 @node GDB/MI Breakpoint Information
28248 @subsection @sc{gdb/mi} Breakpoint Information
28250 When @value{GDBN} reports information about a breakpoint, a
28251 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28256 The breakpoint number.
28259 The type of the breakpoint. For ordinary breakpoints this will be
28260 @samp{breakpoint}, but many values are possible.
28263 If the type of the breakpoint is @samp{catchpoint}, then this
28264 indicates the exact type of catchpoint.
28267 This is the breakpoint disposition---either @samp{del}, meaning that
28268 the breakpoint will be deleted at the next stop, or @samp{keep},
28269 meaning that the breakpoint will not be deleted.
28272 This indicates whether the breakpoint is enabled, in which case the
28273 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28274 Note that this is not the same as the field @code{enable}.
28277 The address of the breakpoint. This may be a hexidecimal number,
28278 giving the address; or the string @samp{<PENDING>}, for a pending
28279 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28280 multiple locations. This field will not be present if no address can
28281 be determined. For example, a watchpoint does not have an address.
28284 If known, the function in which the breakpoint appears.
28285 If not known, this field is not present.
28288 The name of the source file which contains this function, if known.
28289 If not known, this field is not present.
28292 The full file name of the source file which contains this function, if
28293 known. If not known, this field is not present.
28296 The line number at which this breakpoint appears, if known.
28297 If not known, this field is not present.
28300 If the source file is not known, this field may be provided. If
28301 provided, this holds the address of the breakpoint, possibly followed
28305 If this breakpoint is pending, this field is present and holds the
28306 text used to set the breakpoint, as entered by the user.
28309 Where this breakpoint's condition is evaluated, either @samp{host} or
28313 If this is a thread-specific breakpoint, then this identifies the
28314 thread in which the breakpoint can trigger.
28317 If this breakpoint is restricted to a particular Ada task, then this
28318 field will hold the task identifier.
28321 If the breakpoint is conditional, this is the condition expression.
28324 The ignore count of the breakpoint.
28327 The enable count of the breakpoint.
28329 @item traceframe-usage
28332 @item static-tracepoint-marker-string-id
28333 For a static tracepoint, the name of the static tracepoint marker.
28336 For a masked watchpoint, this is the mask.
28339 A tracepoint's pass count.
28341 @item original-location
28342 The location of the breakpoint as originally specified by the user.
28343 This field is optional.
28346 The number of times the breakpoint has been hit.
28349 This field is only given for tracepoints. This is either @samp{y},
28350 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28354 Some extra data, the exact contents of which are type-dependent.
28357 This field is present if the breakpoint has multiple locations. It is also
28358 exceptionally present if the breakpoint is enabled and has a single, disabled
28361 The value is a list of locations. The format of a location is decribed below.
28365 A location in a multi-location breakpoint is represented as a tuple with the
28371 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28372 number of the parent breakpoint. The second digit is the number of the
28373 location within that breakpoint.
28376 This indicates whether the location is enabled, in which case the
28377 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28378 Note that this is not the same as the field @code{enable}.
28381 The address of this location as an hexidecimal number.
28384 If known, the function in which the location appears.
28385 If not known, this field is not present.
28388 The name of the source file which contains this location, if known.
28389 If not known, this field is not present.
28392 The full file name of the source file which contains this location, if
28393 known. If not known, this field is not present.
28396 The line number at which this location appears, if known.
28397 If not known, this field is not present.
28399 @item thread-groups
28400 The thread groups this location is in.
28404 For example, here is what the output of @code{-break-insert}
28405 (@pxref{GDB/MI Breakpoint Commands}) might be:
28408 -> -break-insert main
28409 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28410 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28411 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28416 @node GDB/MI Frame Information
28417 @subsection @sc{gdb/mi} Frame Information
28419 Response from many MI commands includes an information about stack
28420 frame. This information is a tuple that may have the following
28425 The level of the stack frame. The innermost frame has the level of
28426 zero. This field is always present.
28429 The name of the function corresponding to the frame. This field may
28430 be absent if @value{GDBN} is unable to determine the function name.
28433 The code address for the frame. This field is always present.
28436 The name of the source files that correspond to the frame's code
28437 address. This field may be absent.
28440 The source line corresponding to the frames' code address. This field
28444 The name of the binary file (either executable or shared library) the
28445 corresponds to the frame's code address. This field may be absent.
28449 @node GDB/MI Thread Information
28450 @subsection @sc{gdb/mi} Thread Information
28452 Whenever @value{GDBN} has to report an information about a thread, it
28453 uses a tuple with the following fields. The fields are always present unless
28458 The global numeric id assigned to the thread by @value{GDBN}.
28461 The target-specific string identifying the thread.
28464 Additional information about the thread provided by the target.
28465 It is supposed to be human-readable and not interpreted by the
28466 frontend. This field is optional.
28469 The name of the thread. If the user specified a name using the
28470 @code{thread name} command, then this name is given. Otherwise, if
28471 @value{GDBN} can extract the thread name from the target, then that
28472 name is given. If @value{GDBN} cannot find the thread name, then this
28476 The execution state of the thread, either @samp{stopped} or @samp{running},
28477 depending on whether the thread is presently running.
28480 The stack frame currently executing in the thread. This field is only present
28481 if the thread is stopped. Its format is documented in
28482 @ref{GDB/MI Frame Information}.
28485 The value of this field is an integer number of the processor core the
28486 thread was last seen on. This field is optional.
28489 @node GDB/MI Ada Exception Information
28490 @subsection @sc{gdb/mi} Ada Exception Information
28492 Whenever a @code{*stopped} record is emitted because the program
28493 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28494 @value{GDBN} provides the name of the exception that was raised via
28495 the @code{exception-name} field. Also, for exceptions that were raised
28496 with an exception message, @value{GDBN} provides that message via
28497 the @code{exception-message} field.
28499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28500 @node GDB/MI Simple Examples
28501 @section Simple Examples of @sc{gdb/mi} Interaction
28502 @cindex @sc{gdb/mi}, simple examples
28504 This subsection presents several simple examples of interaction using
28505 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28506 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28507 the output received from @sc{gdb/mi}.
28509 Note the line breaks shown in the examples are here only for
28510 readability, they don't appear in the real output.
28512 @subheading Setting a Breakpoint
28514 Setting a breakpoint generates synchronous output which contains detailed
28515 information of the breakpoint.
28518 -> -break-insert main
28519 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28520 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28521 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28526 @subheading Program Execution
28528 Program execution generates asynchronous records and MI gives the
28529 reason that execution stopped.
28535 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28536 frame=@{addr="0x08048564",func="main",
28537 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28538 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28539 arch="i386:x86_64"@}
28544 <- *stopped,reason="exited-normally"
28548 @subheading Quitting @value{GDBN}
28550 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28558 Please note that @samp{^exit} is printed immediately, but it might
28559 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28560 performs necessary cleanups, including killing programs being debugged
28561 or disconnecting from debug hardware, so the frontend should wait till
28562 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28563 fails to exit in reasonable time.
28565 @subheading A Bad Command
28567 Here's what happens if you pass a non-existent command:
28571 <- ^error,msg="Undefined MI command: rubbish"
28576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28577 @node GDB/MI Command Description Format
28578 @section @sc{gdb/mi} Command Description Format
28580 The remaining sections describe blocks of commands. Each block of
28581 commands is laid out in a fashion similar to this section.
28583 @subheading Motivation
28585 The motivation for this collection of commands.
28587 @subheading Introduction
28589 A brief introduction to this collection of commands as a whole.
28591 @subheading Commands
28593 For each command in the block, the following is described:
28595 @subsubheading Synopsis
28598 -command @var{args}@dots{}
28601 @subsubheading Result
28603 @subsubheading @value{GDBN} Command
28605 The corresponding @value{GDBN} CLI command(s), if any.
28607 @subsubheading Example
28609 Example(s) formatted for readability. Some of the described commands have
28610 not been implemented yet and these are labeled N.A.@: (not available).
28613 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28614 @node GDB/MI Breakpoint Commands
28615 @section @sc{gdb/mi} Breakpoint Commands
28617 @cindex breakpoint commands for @sc{gdb/mi}
28618 @cindex @sc{gdb/mi}, breakpoint commands
28619 This section documents @sc{gdb/mi} commands for manipulating
28622 @subheading The @code{-break-after} Command
28623 @findex -break-after
28625 @subsubheading Synopsis
28628 -break-after @var{number} @var{count}
28631 The breakpoint number @var{number} is not in effect until it has been
28632 hit @var{count} times. To see how this is reflected in the output of
28633 the @samp{-break-list} command, see the description of the
28634 @samp{-break-list} command below.
28636 @subsubheading @value{GDBN} Command
28638 The corresponding @value{GDBN} command is @samp{ignore}.
28640 @subsubheading Example
28645 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28646 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28647 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28655 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28656 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28657 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28658 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28659 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28660 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28661 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28662 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28663 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28664 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28669 @subheading The @code{-break-catch} Command
28670 @findex -break-catch
28673 @subheading The @code{-break-commands} Command
28674 @findex -break-commands
28676 @subsubheading Synopsis
28679 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28682 Specifies the CLI commands that should be executed when breakpoint
28683 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28684 are the commands. If no command is specified, any previously-set
28685 commands are cleared. @xref{Break Commands}. Typical use of this
28686 functionality is tracing a program, that is, printing of values of
28687 some variables whenever breakpoint is hit and then continuing.
28689 @subsubheading @value{GDBN} Command
28691 The corresponding @value{GDBN} command is @samp{commands}.
28693 @subsubheading Example
28698 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28699 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28700 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28703 -break-commands 1 "print v" "continue"
28708 @subheading The @code{-break-condition} Command
28709 @findex -break-condition
28711 @subsubheading Synopsis
28714 -break-condition @var{number} @var{expr}
28717 Breakpoint @var{number} will stop the program only if the condition in
28718 @var{expr} is true. The condition becomes part of the
28719 @samp{-break-list} output (see the description of the @samp{-break-list}
28722 @subsubheading @value{GDBN} Command
28724 The corresponding @value{GDBN} command is @samp{condition}.
28726 @subsubheading Example
28730 -break-condition 1 1
28734 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28735 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28736 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28737 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28738 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28739 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28740 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28741 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28742 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28743 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28747 @subheading The @code{-break-delete} Command
28748 @findex -break-delete
28750 @subsubheading Synopsis
28753 -break-delete ( @var{breakpoint} )+
28756 Delete the breakpoint(s) whose number(s) are specified in the argument
28757 list. This is obviously reflected in the breakpoint list.
28759 @subsubheading @value{GDBN} Command
28761 The corresponding @value{GDBN} command is @samp{delete}.
28763 @subsubheading Example
28771 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28772 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28773 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28774 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28775 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28776 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28777 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28782 @subheading The @code{-break-disable} Command
28783 @findex -break-disable
28785 @subsubheading Synopsis
28788 -break-disable ( @var{breakpoint} )+
28791 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28792 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28794 @subsubheading @value{GDBN} Command
28796 The corresponding @value{GDBN} command is @samp{disable}.
28798 @subsubheading Example
28806 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28807 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28808 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28809 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28810 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28811 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28812 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28813 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28814 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28815 line="5",thread-groups=["i1"],times="0"@}]@}
28819 @subheading The @code{-break-enable} Command
28820 @findex -break-enable
28822 @subsubheading Synopsis
28825 -break-enable ( @var{breakpoint} )+
28828 Enable (previously disabled) @var{breakpoint}(s).
28830 @subsubheading @value{GDBN} Command
28832 The corresponding @value{GDBN} command is @samp{enable}.
28834 @subsubheading Example
28842 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28843 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28844 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28845 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28846 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28847 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28848 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28849 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28850 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28851 line="5",thread-groups=["i1"],times="0"@}]@}
28855 @subheading The @code{-break-info} Command
28856 @findex -break-info
28858 @subsubheading Synopsis
28861 -break-info @var{breakpoint}
28865 Get information about a single breakpoint.
28867 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28868 Information}, for details on the format of each breakpoint in the
28871 @subsubheading @value{GDBN} Command
28873 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28875 @subsubheading Example
28878 @subheading The @code{-break-insert} Command
28879 @findex -break-insert
28880 @anchor{-break-insert}
28882 @subsubheading Synopsis
28885 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28886 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28887 [ -p @var{thread-id} ] [ @var{location} ]
28891 If specified, @var{location}, can be one of:
28894 @item linespec location
28895 A linespec location. @xref{Linespec Locations}.
28897 @item explicit location
28898 An explicit location. @sc{gdb/mi} explicit locations are
28899 analogous to the CLI's explicit locations using the option names
28900 listed below. @xref{Explicit Locations}.
28903 @item --source @var{filename}
28904 The source file name of the location. This option requires the use
28905 of either @samp{--function} or @samp{--line}.
28907 @item --function @var{function}
28908 The name of a function or method.
28910 @item --label @var{label}
28911 The name of a label.
28913 @item --line @var{lineoffset}
28914 An absolute or relative line offset from the start of the location.
28917 @item address location
28918 An address location, *@var{address}. @xref{Address Locations}.
28922 The possible optional parameters of this command are:
28926 Insert a temporary breakpoint.
28928 Insert a hardware breakpoint.
28930 If @var{location} cannot be parsed (for example if it
28931 refers to unknown files or functions), create a pending
28932 breakpoint. Without this flag, @value{GDBN} will report
28933 an error, and won't create a breakpoint, if @var{location}
28936 Create a disabled breakpoint.
28938 Create a tracepoint. @xref{Tracepoints}. When this parameter
28939 is used together with @samp{-h}, a fast tracepoint is created.
28940 @item -c @var{condition}
28941 Make the breakpoint conditional on @var{condition}.
28942 @item -i @var{ignore-count}
28943 Initialize the @var{ignore-count}.
28944 @item -p @var{thread-id}
28945 Restrict the breakpoint to the thread with the specified global
28949 @subsubheading Result
28951 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28952 resulting breakpoint.
28954 Note: this format is open to change.
28955 @c An out-of-band breakpoint instead of part of the result?
28957 @subsubheading @value{GDBN} Command
28959 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28960 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28962 @subsubheading Example
28967 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28968 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28971 -break-insert -t foo
28972 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28973 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28977 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28984 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28985 addr="0x0001072c", func="main",file="recursive2.c",
28986 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28988 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28989 addr="0x00010774",func="foo",file="recursive2.c",
28990 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28993 @c -break-insert -r foo.*
28994 @c ~int foo(int, int);
28995 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28996 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29001 @subheading The @code{-dprintf-insert} Command
29002 @findex -dprintf-insert
29004 @subsubheading Synopsis
29007 -dprintf-insert [ -t ] [ -f ] [ -d ]
29008 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29009 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29014 If supplied, @var{location} may be specified the same way as for
29015 the @code{-break-insert} command. @xref{-break-insert}.
29017 The possible optional parameters of this command are:
29021 Insert a temporary breakpoint.
29023 If @var{location} cannot be parsed (for example, if it
29024 refers to unknown files or functions), create a pending
29025 breakpoint. Without this flag, @value{GDBN} will report
29026 an error, and won't create a breakpoint, if @var{location}
29029 Create a disabled breakpoint.
29030 @item -c @var{condition}
29031 Make the breakpoint conditional on @var{condition}.
29032 @item -i @var{ignore-count}
29033 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29034 to @var{ignore-count}.
29035 @item -p @var{thread-id}
29036 Restrict the breakpoint to the thread with the specified global
29040 @subsubheading Result
29042 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29043 resulting breakpoint.
29045 @c An out-of-band breakpoint instead of part of the result?
29047 @subsubheading @value{GDBN} Command
29049 The corresponding @value{GDBN} command is @samp{dprintf}.
29051 @subsubheading Example
29055 4-dprintf-insert foo "At foo entry\n"
29056 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29057 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29058 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29059 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29060 original-location="foo"@}
29062 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29063 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29064 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29065 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29066 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29067 original-location="mi-dprintf.c:26"@}
29071 @subheading The @code{-break-list} Command
29072 @findex -break-list
29074 @subsubheading Synopsis
29080 Displays the list of inserted breakpoints, showing the following fields:
29084 number of the breakpoint
29086 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29088 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29091 is the breakpoint enabled or no: @samp{y} or @samp{n}
29093 memory location at which the breakpoint is set
29095 logical location of the breakpoint, expressed by function name, file
29097 @item Thread-groups
29098 list of thread groups to which this breakpoint applies
29100 number of times the breakpoint has been hit
29103 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29104 @code{body} field is an empty list.
29106 @subsubheading @value{GDBN} Command
29108 The corresponding @value{GDBN} command is @samp{info break}.
29110 @subsubheading Example
29115 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29116 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29117 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29118 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29119 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29120 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29121 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29122 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29123 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29125 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29126 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29127 line="13",thread-groups=["i1"],times="0"@}]@}
29131 Here's an example of the result when there are no breakpoints:
29136 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29137 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29138 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29139 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29140 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29141 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29142 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29147 @subheading The @code{-break-passcount} Command
29148 @findex -break-passcount
29150 @subsubheading Synopsis
29153 -break-passcount @var{tracepoint-number} @var{passcount}
29156 Set the passcount for tracepoint @var{tracepoint-number} to
29157 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29158 is not a tracepoint, error is emitted. This corresponds to CLI
29159 command @samp{passcount}.
29161 @subheading The @code{-break-watch} Command
29162 @findex -break-watch
29164 @subsubheading Synopsis
29167 -break-watch [ -a | -r ]
29170 Create a watchpoint. With the @samp{-a} option it will create an
29171 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29172 read from or on a write to the memory location. With the @samp{-r}
29173 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29174 trigger only when the memory location is accessed for reading. Without
29175 either of the options, the watchpoint created is a regular watchpoint,
29176 i.e., it will trigger when the memory location is accessed for writing.
29177 @xref{Set Watchpoints, , Setting Watchpoints}.
29179 Note that @samp{-break-list} will report a single list of watchpoints and
29180 breakpoints inserted.
29182 @subsubheading @value{GDBN} Command
29184 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29187 @subsubheading Example
29189 Setting a watchpoint on a variable in the @code{main} function:
29194 ^done,wpt=@{number="2",exp="x"@}
29199 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29200 value=@{old="-268439212",new="55"@},
29201 frame=@{func="main",args=[],file="recursive2.c",
29202 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29206 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29207 the program execution twice: first for the variable changing value, then
29208 for the watchpoint going out of scope.
29213 ^done,wpt=@{number="5",exp="C"@}
29218 *stopped,reason="watchpoint-trigger",
29219 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29220 frame=@{func="callee4",args=[],
29221 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29222 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29223 arch="i386:x86_64"@}
29228 *stopped,reason="watchpoint-scope",wpnum="5",
29229 frame=@{func="callee3",args=[@{name="strarg",
29230 value="0x11940 \"A string argument.\""@}],
29231 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29232 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29233 arch="i386:x86_64"@}
29237 Listing breakpoints and watchpoints, at different points in the program
29238 execution. Note that once the watchpoint goes out of scope, it is
29244 ^done,wpt=@{number="2",exp="C"@}
29247 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29248 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29249 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29250 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29251 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29252 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29253 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29254 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29255 addr="0x00010734",func="callee4",
29256 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29257 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29259 bkpt=@{number="2",type="watchpoint",disp="keep",
29260 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29265 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29266 value=@{old="-276895068",new="3"@},
29267 frame=@{func="callee4",args=[],
29268 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29269 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29270 arch="i386:x86_64"@}
29273 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29274 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29275 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29276 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29277 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29278 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29279 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29280 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29281 addr="0x00010734",func="callee4",
29282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29283 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29285 bkpt=@{number="2",type="watchpoint",disp="keep",
29286 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29290 ^done,reason="watchpoint-scope",wpnum="2",
29291 frame=@{func="callee3",args=[@{name="strarg",
29292 value="0x11940 \"A string argument.\""@}],
29293 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29294 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29295 arch="i386:x86_64"@}
29298 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29299 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29300 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29301 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29302 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29303 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29304 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29305 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29306 addr="0x00010734",func="callee4",
29307 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29308 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29309 thread-groups=["i1"],times="1"@}]@}
29314 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29315 @node GDB/MI Catchpoint Commands
29316 @section @sc{gdb/mi} Catchpoint Commands
29318 This section documents @sc{gdb/mi} commands for manipulating
29322 * Shared Library GDB/MI Catchpoint Commands::
29323 * Ada Exception GDB/MI Catchpoint Commands::
29326 @node Shared Library GDB/MI Catchpoint Commands
29327 @subsection Shared Library @sc{gdb/mi} Catchpoints
29329 @subheading The @code{-catch-load} Command
29330 @findex -catch-load
29332 @subsubheading Synopsis
29335 -catch-load [ -t ] [ -d ] @var{regexp}
29338 Add a catchpoint for library load events. If the @samp{-t} option is used,
29339 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29340 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29341 in a disabled state. The @samp{regexp} argument is a regular
29342 expression used to match the name of the loaded library.
29345 @subsubheading @value{GDBN} Command
29347 The corresponding @value{GDBN} command is @samp{catch load}.
29349 @subsubheading Example
29352 -catch-load -t foo.so
29353 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29354 what="load of library matching foo.so",catch-type="load",times="0"@}
29359 @subheading The @code{-catch-unload} Command
29360 @findex -catch-unload
29362 @subsubheading Synopsis
29365 -catch-unload [ -t ] [ -d ] @var{regexp}
29368 Add a catchpoint for library unload events. If the @samp{-t} option is
29369 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29370 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29371 created in a disabled state. The @samp{regexp} argument is a regular
29372 expression used to match the name of the unloaded library.
29374 @subsubheading @value{GDBN} Command
29376 The corresponding @value{GDBN} command is @samp{catch unload}.
29378 @subsubheading Example
29381 -catch-unload -d bar.so
29382 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29383 what="load of library matching bar.so",catch-type="unload",times="0"@}
29387 @node Ada Exception GDB/MI Catchpoint Commands
29388 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29390 The following @sc{gdb/mi} commands can be used to create catchpoints
29391 that stop the execution when Ada exceptions are being raised.
29393 @subheading The @code{-catch-assert} Command
29394 @findex -catch-assert
29396 @subsubheading Synopsis
29399 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29402 Add a catchpoint for failed Ada assertions.
29404 The possible optional parameters for this command are:
29407 @item -c @var{condition}
29408 Make the catchpoint conditional on @var{condition}.
29410 Create a disabled catchpoint.
29412 Create a temporary catchpoint.
29415 @subsubheading @value{GDBN} Command
29417 The corresponding @value{GDBN} command is @samp{catch assert}.
29419 @subsubheading Example
29423 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29424 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29425 thread-groups=["i1"],times="0",
29426 original-location="__gnat_debug_raise_assert_failure"@}
29430 @subheading The @code{-catch-exception} Command
29431 @findex -catch-exception
29433 @subsubheading Synopsis
29436 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29440 Add a catchpoint stopping when Ada exceptions are raised.
29441 By default, the command stops the program when any Ada exception
29442 gets raised. But it is also possible, by using some of the
29443 optional parameters described below, to create more selective
29446 The possible optional parameters for this command are:
29449 @item -c @var{condition}
29450 Make the catchpoint conditional on @var{condition}.
29452 Create a disabled catchpoint.
29453 @item -e @var{exception-name}
29454 Only stop when @var{exception-name} is raised. This option cannot
29455 be used combined with @samp{-u}.
29457 Create a temporary catchpoint.
29459 Stop only when an unhandled exception gets raised. This option
29460 cannot be used combined with @samp{-e}.
29463 @subsubheading @value{GDBN} Command
29465 The corresponding @value{GDBN} commands are @samp{catch exception}
29466 and @samp{catch exception unhandled}.
29468 @subsubheading Example
29471 -catch-exception -e Program_Error
29472 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29473 enabled="y",addr="0x0000000000404874",
29474 what="`Program_Error' Ada exception", thread-groups=["i1"],
29475 times="0",original-location="__gnat_debug_raise_exception"@}
29479 @subheading The @code{-catch-handlers} Command
29480 @findex -catch-handlers
29482 @subsubheading Synopsis
29485 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29489 Add a catchpoint stopping when Ada exceptions are handled.
29490 By default, the command stops the program when any Ada exception
29491 gets handled. But it is also possible, by using some of the
29492 optional parameters described below, to create more selective
29495 The possible optional parameters for this command are:
29498 @item -c @var{condition}
29499 Make the catchpoint conditional on @var{condition}.
29501 Create a disabled catchpoint.
29502 @item -e @var{exception-name}
29503 Only stop when @var{exception-name} is handled.
29505 Create a temporary catchpoint.
29508 @subsubheading @value{GDBN} Command
29510 The corresponding @value{GDBN} command is @samp{catch handlers}.
29512 @subsubheading Example
29515 -catch-handlers -e Constraint_Error
29516 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29517 enabled="y",addr="0x0000000000402f68",
29518 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29519 times="0",original-location="__gnat_begin_handler"@}
29523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29524 @node GDB/MI Program Context
29525 @section @sc{gdb/mi} Program Context
29527 @subheading The @code{-exec-arguments} Command
29528 @findex -exec-arguments
29531 @subsubheading Synopsis
29534 -exec-arguments @var{args}
29537 Set the inferior program arguments, to be used in the next
29540 @subsubheading @value{GDBN} Command
29542 The corresponding @value{GDBN} command is @samp{set args}.
29544 @subsubheading Example
29548 -exec-arguments -v word
29555 @subheading The @code{-exec-show-arguments} Command
29556 @findex -exec-show-arguments
29558 @subsubheading Synopsis
29561 -exec-show-arguments
29564 Print the arguments of the program.
29566 @subsubheading @value{GDBN} Command
29568 The corresponding @value{GDBN} command is @samp{show args}.
29570 @subsubheading Example
29575 @subheading The @code{-environment-cd} Command
29576 @findex -environment-cd
29578 @subsubheading Synopsis
29581 -environment-cd @var{pathdir}
29584 Set @value{GDBN}'s working directory.
29586 @subsubheading @value{GDBN} Command
29588 The corresponding @value{GDBN} command is @samp{cd}.
29590 @subsubheading Example
29594 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29600 @subheading The @code{-environment-directory} Command
29601 @findex -environment-directory
29603 @subsubheading Synopsis
29606 -environment-directory [ -r ] [ @var{pathdir} ]+
29609 Add directories @var{pathdir} to beginning of search path for source files.
29610 If the @samp{-r} option is used, the search path is reset to the default
29611 search path. If directories @var{pathdir} are supplied in addition to the
29612 @samp{-r} option, the search path is first reset and then addition
29614 Multiple directories may be specified, separated by blanks. Specifying
29615 multiple directories in a single command
29616 results in the directories added to the beginning of the
29617 search path in the same order they were presented in the command.
29618 If blanks are needed as
29619 part of a directory name, double-quotes should be used around
29620 the name. In the command output, the path will show up separated
29621 by the system directory-separator character. The directory-separator
29622 character must not be used
29623 in any directory name.
29624 If no directories are specified, the current search path is displayed.
29626 @subsubheading @value{GDBN} Command
29628 The corresponding @value{GDBN} command is @samp{dir}.
29630 @subsubheading Example
29634 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29635 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29637 -environment-directory ""
29638 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29640 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29641 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29643 -environment-directory -r
29644 ^done,source-path="$cdir:$cwd"
29649 @subheading The @code{-environment-path} Command
29650 @findex -environment-path
29652 @subsubheading Synopsis
29655 -environment-path [ -r ] [ @var{pathdir} ]+
29658 Add directories @var{pathdir} to beginning of search path for object files.
29659 If the @samp{-r} option is used, the search path is reset to the original
29660 search path that existed at gdb start-up. If directories @var{pathdir} are
29661 supplied in addition to the
29662 @samp{-r} option, the search path is first reset and then addition
29664 Multiple directories may be specified, separated by blanks. Specifying
29665 multiple directories in a single command
29666 results in the directories added to the beginning of the
29667 search path in the same order they were presented in the command.
29668 If blanks are needed as
29669 part of a directory name, double-quotes should be used around
29670 the name. In the command output, the path will show up separated
29671 by the system directory-separator character. The directory-separator
29672 character must not be used
29673 in any directory name.
29674 If no directories are specified, the current path is displayed.
29677 @subsubheading @value{GDBN} Command
29679 The corresponding @value{GDBN} command is @samp{path}.
29681 @subsubheading Example
29686 ^done,path="/usr/bin"
29688 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29689 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29691 -environment-path -r /usr/local/bin
29692 ^done,path="/usr/local/bin:/usr/bin"
29697 @subheading The @code{-environment-pwd} Command
29698 @findex -environment-pwd
29700 @subsubheading Synopsis
29706 Show the current working directory.
29708 @subsubheading @value{GDBN} Command
29710 The corresponding @value{GDBN} command is @samp{pwd}.
29712 @subsubheading Example
29717 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29722 @node GDB/MI Thread Commands
29723 @section @sc{gdb/mi} Thread Commands
29726 @subheading The @code{-thread-info} Command
29727 @findex -thread-info
29729 @subsubheading Synopsis
29732 -thread-info [ @var{thread-id} ]
29735 Reports information about either a specific thread, if the
29736 @var{thread-id} parameter is present, or about all threads.
29737 @var{thread-id} is the thread's global thread ID. When printing
29738 information about all threads, also reports the global ID of the
29741 @subsubheading @value{GDBN} Command
29743 The @samp{info thread} command prints the same information
29746 @subsubheading Result
29748 The result contains the following attributes:
29752 A list of threads. The format of the elements of the list is described in
29753 @ref{GDB/MI Thread Information}.
29755 @item current-thread-id
29756 The global id of the currently selected thread. This field is omitted if there
29757 is no selected thread (for example, when the selected inferior is not running,
29758 and therefore has no threads) or if a @var{thread-id} argument was passed to
29763 @subsubheading Example
29768 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29769 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29770 args=[]@},state="running"@},
29771 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29772 frame=@{level="0",addr="0x0804891f",func="foo",
29773 args=[@{name="i",value="10"@}],
29774 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29775 state="running"@}],
29776 current-thread-id="1"
29780 @subheading The @code{-thread-list-ids} Command
29781 @findex -thread-list-ids
29783 @subsubheading Synopsis
29789 Produces a list of the currently known global @value{GDBN} thread ids.
29790 At the end of the list it also prints the total number of such
29793 This command is retained for historical reasons, the
29794 @code{-thread-info} command should be used instead.
29796 @subsubheading @value{GDBN} Command
29798 Part of @samp{info threads} supplies the same information.
29800 @subsubheading Example
29805 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29806 current-thread-id="1",number-of-threads="3"
29811 @subheading The @code{-thread-select} Command
29812 @findex -thread-select
29814 @subsubheading Synopsis
29817 -thread-select @var{thread-id}
29820 Make thread with global thread number @var{thread-id} the current
29821 thread. It prints the number of the new current thread, and the
29822 topmost frame for that thread.
29824 This command is deprecated in favor of explicitly using the
29825 @samp{--thread} option to each command.
29827 @subsubheading @value{GDBN} Command
29829 The corresponding @value{GDBN} command is @samp{thread}.
29831 @subsubheading Example
29838 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29839 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29843 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29844 number-of-threads="3"
29847 ^done,new-thread-id="3",
29848 frame=@{level="0",func="vprintf",
29849 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29850 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29855 @node GDB/MI Ada Tasking Commands
29856 @section @sc{gdb/mi} Ada Tasking Commands
29858 @subheading The @code{-ada-task-info} Command
29859 @findex -ada-task-info
29861 @subsubheading Synopsis
29864 -ada-task-info [ @var{task-id} ]
29867 Reports information about either a specific Ada task, if the
29868 @var{task-id} parameter is present, or about all Ada tasks.
29870 @subsubheading @value{GDBN} Command
29872 The @samp{info tasks} command prints the same information
29873 about all Ada tasks (@pxref{Ada Tasks}).
29875 @subsubheading Result
29877 The result is a table of Ada tasks. The following columns are
29878 defined for each Ada task:
29882 This field exists only for the current thread. It has the value @samp{*}.
29885 The identifier that @value{GDBN} uses to refer to the Ada task.
29888 The identifier that the target uses to refer to the Ada task.
29891 The global thread identifier of the thread corresponding to the Ada
29894 This field should always exist, as Ada tasks are always implemented
29895 on top of a thread. But if @value{GDBN} cannot find this corresponding
29896 thread for any reason, the field is omitted.
29899 This field exists only when the task was created by another task.
29900 In this case, it provides the ID of the parent task.
29903 The base priority of the task.
29906 The current state of the task. For a detailed description of the
29907 possible states, see @ref{Ada Tasks}.
29910 The name of the task.
29914 @subsubheading Example
29918 ^done,tasks=@{nr_rows="3",nr_cols="8",
29919 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29920 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29921 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29922 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29923 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29924 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29925 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29926 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29927 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29928 state="Child Termination Wait",name="main_task"@}]@}
29932 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29933 @node GDB/MI Program Execution
29934 @section @sc{gdb/mi} Program Execution
29936 These are the asynchronous commands which generate the out-of-band
29937 record @samp{*stopped}. Currently @value{GDBN} only really executes
29938 asynchronously with remote targets and this interaction is mimicked in
29941 @subheading The @code{-exec-continue} Command
29942 @findex -exec-continue
29944 @subsubheading Synopsis
29947 -exec-continue [--reverse] [--all|--thread-group N]
29950 Resumes the execution of the inferior program, which will continue
29951 to execute until it reaches a debugger stop event. If the
29952 @samp{--reverse} option is specified, execution resumes in reverse until
29953 it reaches a stop event. Stop events may include
29956 breakpoints or watchpoints
29958 signals or exceptions
29960 the end of the process (or its beginning under @samp{--reverse})
29962 the end or beginning of a replay log if one is being used.
29964 In all-stop mode (@pxref{All-Stop
29965 Mode}), may resume only one thread, or all threads, depending on the
29966 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29967 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29968 ignored in all-stop mode. If the @samp{--thread-group} options is
29969 specified, then all threads in that thread group are resumed.
29971 @subsubheading @value{GDBN} Command
29973 The corresponding @value{GDBN} corresponding is @samp{continue}.
29975 @subsubheading Example
29982 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29983 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29984 line="13",arch="i386:x86_64"@}
29989 @subheading The @code{-exec-finish} Command
29990 @findex -exec-finish
29992 @subsubheading Synopsis
29995 -exec-finish [--reverse]
29998 Resumes the execution of the inferior program until the current
29999 function is exited. Displays the results returned by the function.
30000 If the @samp{--reverse} option is specified, resumes the reverse
30001 execution of the inferior program until the point where current
30002 function was called.
30004 @subsubheading @value{GDBN} Command
30006 The corresponding @value{GDBN} command is @samp{finish}.
30008 @subsubheading Example
30010 Function returning @code{void}.
30017 *stopped,reason="function-finished",frame=@{func="main",args=[],
30018 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30022 Function returning other than @code{void}. The name of the internal
30023 @value{GDBN} variable storing the result is printed, together with the
30030 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30031 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30032 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30033 arch="i386:x86_64"@},
30034 gdb-result-var="$1",return-value="0"
30039 @subheading The @code{-exec-interrupt} Command
30040 @findex -exec-interrupt
30042 @subsubheading Synopsis
30045 -exec-interrupt [--all|--thread-group N]
30048 Interrupts the background execution of the target. Note how the token
30049 associated with the stop message is the one for the execution command
30050 that has been interrupted. The token for the interrupt itself only
30051 appears in the @samp{^done} output. If the user is trying to
30052 interrupt a non-running program, an error message will be printed.
30054 Note that when asynchronous execution is enabled, this command is
30055 asynchronous just like other execution commands. That is, first the
30056 @samp{^done} response will be printed, and the target stop will be
30057 reported after that using the @samp{*stopped} notification.
30059 In non-stop mode, only the context thread is interrupted by default.
30060 All threads (in all inferiors) will be interrupted if the
30061 @samp{--all} option is specified. If the @samp{--thread-group}
30062 option is specified, all threads in that group will be interrupted.
30064 @subsubheading @value{GDBN} Command
30066 The corresponding @value{GDBN} command is @samp{interrupt}.
30068 @subsubheading Example
30079 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30080 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30081 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30086 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30090 @subheading The @code{-exec-jump} Command
30093 @subsubheading Synopsis
30096 -exec-jump @var{location}
30099 Resumes execution of the inferior program at the location specified by
30100 parameter. @xref{Specify Location}, for a description of the
30101 different forms of @var{location}.
30103 @subsubheading @value{GDBN} Command
30105 The corresponding @value{GDBN} command is @samp{jump}.
30107 @subsubheading Example
30110 -exec-jump foo.c:10
30111 *running,thread-id="all"
30116 @subheading The @code{-exec-next} Command
30119 @subsubheading Synopsis
30122 -exec-next [--reverse]
30125 Resumes execution of the inferior program, stopping when the beginning
30126 of the next source line is reached.
30128 If the @samp{--reverse} option is specified, resumes reverse execution
30129 of the inferior program, stopping at the beginning of the previous
30130 source line. If you issue this command on the first line of a
30131 function, it will take you back to the caller of that function, to the
30132 source line where the function was called.
30135 @subsubheading @value{GDBN} Command
30137 The corresponding @value{GDBN} command is @samp{next}.
30139 @subsubheading Example
30145 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30150 @subheading The @code{-exec-next-instruction} Command
30151 @findex -exec-next-instruction
30153 @subsubheading Synopsis
30156 -exec-next-instruction [--reverse]
30159 Executes one machine instruction. If the instruction is a function
30160 call, continues until the function returns. If the program stops at an
30161 instruction in the middle of a source line, the address will be
30164 If the @samp{--reverse} option is specified, resumes reverse execution
30165 of the inferior program, stopping at the previous instruction. If the
30166 previously executed instruction was a return from another function,
30167 it will continue to execute in reverse until the call to that function
30168 (from the current stack frame) is reached.
30170 @subsubheading @value{GDBN} Command
30172 The corresponding @value{GDBN} command is @samp{nexti}.
30174 @subsubheading Example
30178 -exec-next-instruction
30182 *stopped,reason="end-stepping-range",
30183 addr="0x000100d4",line="5",file="hello.c"
30188 @subheading The @code{-exec-return} Command
30189 @findex -exec-return
30191 @subsubheading Synopsis
30197 Makes current function return immediately. Doesn't execute the inferior.
30198 Displays the new current frame.
30200 @subsubheading @value{GDBN} Command
30202 The corresponding @value{GDBN} command is @samp{return}.
30204 @subsubheading Example
30208 200-break-insert callee4
30209 200^done,bkpt=@{number="1",addr="0x00010734",
30210 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30215 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30216 frame=@{func="callee4",args=[],
30217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30218 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30219 arch="i386:x86_64"@}
30225 111^done,frame=@{level="0",func="callee3",
30226 args=[@{name="strarg",
30227 value="0x11940 \"A string argument.\""@}],
30228 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30229 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30230 arch="i386:x86_64"@}
30235 @subheading The @code{-exec-run} Command
30238 @subsubheading Synopsis
30241 -exec-run [ --all | --thread-group N ] [ --start ]
30244 Starts execution of the inferior from the beginning. The inferior
30245 executes until either a breakpoint is encountered or the program
30246 exits. In the latter case the output will include an exit code, if
30247 the program has exited exceptionally.
30249 When neither the @samp{--all} nor the @samp{--thread-group} option
30250 is specified, the current inferior is started. If the
30251 @samp{--thread-group} option is specified, it should refer to a thread
30252 group of type @samp{process}, and that thread group will be started.
30253 If the @samp{--all} option is specified, then all inferiors will be started.
30255 Using the @samp{--start} option instructs the debugger to stop
30256 the execution at the start of the inferior's main subprogram,
30257 following the same behavior as the @code{start} command
30258 (@pxref{Starting}).
30260 @subsubheading @value{GDBN} Command
30262 The corresponding @value{GDBN} command is @samp{run}.
30264 @subsubheading Examples
30269 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30274 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30275 frame=@{func="main",args=[],file="recursive2.c",
30276 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30281 Program exited normally:
30289 *stopped,reason="exited-normally"
30294 Program exited exceptionally:
30302 *stopped,reason="exited",exit-code="01"
30306 Another way the program can terminate is if it receives a signal such as
30307 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30311 *stopped,reason="exited-signalled",signal-name="SIGINT",
30312 signal-meaning="Interrupt"
30316 @c @subheading -exec-signal
30319 @subheading The @code{-exec-step} Command
30322 @subsubheading Synopsis
30325 -exec-step [--reverse]
30328 Resumes execution of the inferior program, stopping when the beginning
30329 of the next source line is reached, if the next source line is not a
30330 function call. If it is, stop at the first instruction of the called
30331 function. If the @samp{--reverse} option is specified, resumes reverse
30332 execution of the inferior program, stopping at the beginning of the
30333 previously executed source line.
30335 @subsubheading @value{GDBN} Command
30337 The corresponding @value{GDBN} command is @samp{step}.
30339 @subsubheading Example
30341 Stepping into a function:
30347 *stopped,reason="end-stepping-range",
30348 frame=@{func="foo",args=[@{name="a",value="10"@},
30349 @{name="b",value="0"@}],file="recursive2.c",
30350 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30360 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30365 @subheading The @code{-exec-step-instruction} Command
30366 @findex -exec-step-instruction
30368 @subsubheading Synopsis
30371 -exec-step-instruction [--reverse]
30374 Resumes the inferior which executes one machine instruction. If the
30375 @samp{--reverse} option is specified, resumes reverse execution of the
30376 inferior program, stopping at the previously executed instruction.
30377 The output, once @value{GDBN} has stopped, will vary depending on
30378 whether we have stopped in the middle of a source line or not. In the
30379 former case, the address at which the program stopped will be printed
30382 @subsubheading @value{GDBN} Command
30384 The corresponding @value{GDBN} command is @samp{stepi}.
30386 @subsubheading Example
30390 -exec-step-instruction
30394 *stopped,reason="end-stepping-range",
30395 frame=@{func="foo",args=[],file="try.c",
30396 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30398 -exec-step-instruction
30402 *stopped,reason="end-stepping-range",
30403 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30404 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30409 @subheading The @code{-exec-until} Command
30410 @findex -exec-until
30412 @subsubheading Synopsis
30415 -exec-until [ @var{location} ]
30418 Executes the inferior until the @var{location} specified in the
30419 argument is reached. If there is no argument, the inferior executes
30420 until a source line greater than the current one is reached. The
30421 reason for stopping in this case will be @samp{location-reached}.
30423 @subsubheading @value{GDBN} Command
30425 The corresponding @value{GDBN} command is @samp{until}.
30427 @subsubheading Example
30431 -exec-until recursive2.c:6
30435 *stopped,reason="location-reached",frame=@{func="main",args=[],
30436 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30437 arch="i386:x86_64"@}
30442 @subheading -file-clear
30443 Is this going away????
30446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30447 @node GDB/MI Stack Manipulation
30448 @section @sc{gdb/mi} Stack Manipulation Commands
30450 @subheading The @code{-enable-frame-filters} Command
30451 @findex -enable-frame-filters
30454 -enable-frame-filters
30457 @value{GDBN} allows Python-based frame filters to affect the output of
30458 the MI commands relating to stack traces. As there is no way to
30459 implement this in a fully backward-compatible way, a front end must
30460 request that this functionality be enabled.
30462 Once enabled, this feature cannot be disabled.
30464 Note that if Python support has not been compiled into @value{GDBN},
30465 this command will still succeed (and do nothing).
30467 @subheading The @code{-stack-info-frame} Command
30468 @findex -stack-info-frame
30470 @subsubheading Synopsis
30476 Get info on the selected frame.
30478 @subsubheading @value{GDBN} Command
30480 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30481 (without arguments).
30483 @subsubheading Example
30488 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30489 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30490 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30491 arch="i386:x86_64"@}
30495 @subheading The @code{-stack-info-depth} Command
30496 @findex -stack-info-depth
30498 @subsubheading Synopsis
30501 -stack-info-depth [ @var{max-depth} ]
30504 Return the depth of the stack. If the integer argument @var{max-depth}
30505 is specified, do not count beyond @var{max-depth} frames.
30507 @subsubheading @value{GDBN} Command
30509 There's no equivalent @value{GDBN} command.
30511 @subsubheading Example
30513 For a stack with frame levels 0 through 11:
30520 -stack-info-depth 4
30523 -stack-info-depth 12
30526 -stack-info-depth 11
30529 -stack-info-depth 13
30534 @anchor{-stack-list-arguments}
30535 @subheading The @code{-stack-list-arguments} Command
30536 @findex -stack-list-arguments
30538 @subsubheading Synopsis
30541 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30542 [ @var{low-frame} @var{high-frame} ]
30545 Display a list of the arguments for the frames between @var{low-frame}
30546 and @var{high-frame} (inclusive). If @var{low-frame} and
30547 @var{high-frame} are not provided, list the arguments for the whole
30548 call stack. If the two arguments are equal, show the single frame
30549 at the corresponding level. It is an error if @var{low-frame} is
30550 larger than the actual number of frames. On the other hand,
30551 @var{high-frame} may be larger than the actual number of frames, in
30552 which case only existing frames will be returned.
30554 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30555 the variables; if it is 1 or @code{--all-values}, print also their
30556 values; and if it is 2 or @code{--simple-values}, print the name,
30557 type and value for simple data types, and the name and type for arrays,
30558 structures and unions. If the option @code{--no-frame-filters} is
30559 supplied, then Python frame filters will not be executed.
30561 If the @code{--skip-unavailable} option is specified, arguments that
30562 are not available are not listed. Partially available arguments
30563 are still displayed, however.
30565 Use of this command to obtain arguments in a single frame is
30566 deprecated in favor of the @samp{-stack-list-variables} command.
30568 @subsubheading @value{GDBN} Command
30570 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30571 @samp{gdb_get_args} command which partially overlaps with the
30572 functionality of @samp{-stack-list-arguments}.
30574 @subsubheading Example
30581 frame=@{level="0",addr="0x00010734",func="callee4",
30582 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30583 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30584 arch="i386:x86_64"@},
30585 frame=@{level="1",addr="0x0001076c",func="callee3",
30586 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30587 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30588 arch="i386:x86_64"@},
30589 frame=@{level="2",addr="0x0001078c",func="callee2",
30590 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30591 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30592 arch="i386:x86_64"@},
30593 frame=@{level="3",addr="0x000107b4",func="callee1",
30594 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30595 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30596 arch="i386:x86_64"@},
30597 frame=@{level="4",addr="0x000107e0",func="main",
30598 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30599 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30600 arch="i386:x86_64"@}]
30602 -stack-list-arguments 0
30605 frame=@{level="0",args=[]@},
30606 frame=@{level="1",args=[name="strarg"]@},
30607 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30608 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30609 frame=@{level="4",args=[]@}]
30611 -stack-list-arguments 1
30614 frame=@{level="0",args=[]@},
30616 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30617 frame=@{level="2",args=[
30618 @{name="intarg",value="2"@},
30619 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30620 @{frame=@{level="3",args=[
30621 @{name="intarg",value="2"@},
30622 @{name="strarg",value="0x11940 \"A string argument.\""@},
30623 @{name="fltarg",value="3.5"@}]@},
30624 frame=@{level="4",args=[]@}]
30626 -stack-list-arguments 0 2 2
30627 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30629 -stack-list-arguments 1 2 2
30630 ^done,stack-args=[frame=@{level="2",
30631 args=[@{name="intarg",value="2"@},
30632 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30636 @c @subheading -stack-list-exception-handlers
30639 @anchor{-stack-list-frames}
30640 @subheading The @code{-stack-list-frames} Command
30641 @findex -stack-list-frames
30643 @subsubheading Synopsis
30646 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30649 List the frames currently on the stack. For each frame it displays the
30654 The frame number, 0 being the topmost frame, i.e., the innermost function.
30656 The @code{$pc} value for that frame.
30660 File name of the source file where the function lives.
30661 @item @var{fullname}
30662 The full file name of the source file where the function lives.
30664 Line number corresponding to the @code{$pc}.
30666 The shared library where this function is defined. This is only given
30667 if the frame's function is not known.
30669 Frame's architecture.
30672 If invoked without arguments, this command prints a backtrace for the
30673 whole stack. If given two integer arguments, it shows the frames whose
30674 levels are between the two arguments (inclusive). If the two arguments
30675 are equal, it shows the single frame at the corresponding level. It is
30676 an error if @var{low-frame} is larger than the actual number of
30677 frames. On the other hand, @var{high-frame} may be larger than the
30678 actual number of frames, in which case only existing frames will be
30679 returned. If the option @code{--no-frame-filters} is supplied, then
30680 Python frame filters will not be executed.
30682 @subsubheading @value{GDBN} Command
30684 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30686 @subsubheading Example
30688 Full stack backtrace:
30694 [frame=@{level="0",addr="0x0001076c",func="foo",
30695 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30696 arch="i386:x86_64"@},
30697 frame=@{level="1",addr="0x000107a4",func="foo",
30698 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30699 arch="i386:x86_64"@},
30700 frame=@{level="2",addr="0x000107a4",func="foo",
30701 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30702 arch="i386:x86_64"@},
30703 frame=@{level="3",addr="0x000107a4",func="foo",
30704 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30705 arch="i386:x86_64"@},
30706 frame=@{level="4",addr="0x000107a4",func="foo",
30707 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30708 arch="i386:x86_64"@},
30709 frame=@{level="5",addr="0x000107a4",func="foo",
30710 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30711 arch="i386:x86_64"@},
30712 frame=@{level="6",addr="0x000107a4",func="foo",
30713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30714 arch="i386:x86_64"@},
30715 frame=@{level="7",addr="0x000107a4",func="foo",
30716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30717 arch="i386:x86_64"@},
30718 frame=@{level="8",addr="0x000107a4",func="foo",
30719 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30720 arch="i386:x86_64"@},
30721 frame=@{level="9",addr="0x000107a4",func="foo",
30722 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30723 arch="i386:x86_64"@},
30724 frame=@{level="10",addr="0x000107a4",func="foo",
30725 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30726 arch="i386:x86_64"@},
30727 frame=@{level="11",addr="0x00010738",func="main",
30728 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30729 arch="i386:x86_64"@}]
30733 Show frames between @var{low_frame} and @var{high_frame}:
30737 -stack-list-frames 3 5
30739 [frame=@{level="3",addr="0x000107a4",func="foo",
30740 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30741 arch="i386:x86_64"@},
30742 frame=@{level="4",addr="0x000107a4",func="foo",
30743 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30744 arch="i386:x86_64"@},
30745 frame=@{level="5",addr="0x000107a4",func="foo",
30746 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30747 arch="i386:x86_64"@}]
30751 Show a single frame:
30755 -stack-list-frames 3 3
30757 [frame=@{level="3",addr="0x000107a4",func="foo",
30758 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30759 arch="i386:x86_64"@}]
30764 @subheading The @code{-stack-list-locals} Command
30765 @findex -stack-list-locals
30766 @anchor{-stack-list-locals}
30768 @subsubheading Synopsis
30771 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30774 Display the local variable names for the selected frame. If
30775 @var{print-values} is 0 or @code{--no-values}, print only the names of
30776 the variables; if it is 1 or @code{--all-values}, print also their
30777 values; and if it is 2 or @code{--simple-values}, print the name,
30778 type and value for simple data types, and the name and type for arrays,
30779 structures and unions. In this last case, a frontend can immediately
30780 display the value of simple data types and create variable objects for
30781 other data types when the user wishes to explore their values in
30782 more detail. If the option @code{--no-frame-filters} is supplied, then
30783 Python frame filters will not be executed.
30785 If the @code{--skip-unavailable} option is specified, local variables
30786 that are not available are not listed. Partially available local
30787 variables are still displayed, however.
30789 This command is deprecated in favor of the
30790 @samp{-stack-list-variables} command.
30792 @subsubheading @value{GDBN} Command
30794 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30796 @subsubheading Example
30800 -stack-list-locals 0
30801 ^done,locals=[name="A",name="B",name="C"]
30803 -stack-list-locals --all-values
30804 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30805 @{name="C",value="@{1, 2, 3@}"@}]
30806 -stack-list-locals --simple-values
30807 ^done,locals=[@{name="A",type="int",value="1"@},
30808 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30812 @anchor{-stack-list-variables}
30813 @subheading The @code{-stack-list-variables} Command
30814 @findex -stack-list-variables
30816 @subsubheading Synopsis
30819 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30822 Display the names of local variables and function arguments for the selected frame. If
30823 @var{print-values} is 0 or @code{--no-values}, print only the names of
30824 the variables; if it is 1 or @code{--all-values}, print also their
30825 values; and if it is 2 or @code{--simple-values}, print the name,
30826 type and value for simple data types, and the name and type for arrays,
30827 structures and unions. If the option @code{--no-frame-filters} is
30828 supplied, then Python frame filters will not be executed.
30830 If the @code{--skip-unavailable} option is specified, local variables
30831 and arguments that are not available are not listed. Partially
30832 available arguments and local variables are still displayed, however.
30834 @subsubheading Example
30838 -stack-list-variables --thread 1 --frame 0 --all-values
30839 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30844 @subheading The @code{-stack-select-frame} Command
30845 @findex -stack-select-frame
30847 @subsubheading Synopsis
30850 -stack-select-frame @var{framenum}
30853 Change the selected frame. Select a different frame @var{framenum} on
30856 This command in deprecated in favor of passing the @samp{--frame}
30857 option to every command.
30859 @subsubheading @value{GDBN} Command
30861 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30862 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30864 @subsubheading Example
30868 -stack-select-frame 2
30873 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30874 @node GDB/MI Variable Objects
30875 @section @sc{gdb/mi} Variable Objects
30879 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30881 For the implementation of a variable debugger window (locals, watched
30882 expressions, etc.), we are proposing the adaptation of the existing code
30883 used by @code{Insight}.
30885 The two main reasons for that are:
30889 It has been proven in practice (it is already on its second generation).
30892 It will shorten development time (needless to say how important it is
30896 The original interface was designed to be used by Tcl code, so it was
30897 slightly changed so it could be used through @sc{gdb/mi}. This section
30898 describes the @sc{gdb/mi} operations that will be available and gives some
30899 hints about their use.
30901 @emph{Note}: In addition to the set of operations described here, we
30902 expect the @sc{gui} implementation of a variable window to require, at
30903 least, the following operations:
30906 @item @code{-gdb-show} @code{output-radix}
30907 @item @code{-stack-list-arguments}
30908 @item @code{-stack-list-locals}
30909 @item @code{-stack-select-frame}
30914 @subheading Introduction to Variable Objects
30916 @cindex variable objects in @sc{gdb/mi}
30918 Variable objects are "object-oriented" MI interface for examining and
30919 changing values of expressions. Unlike some other MI interfaces that
30920 work with expressions, variable objects are specifically designed for
30921 simple and efficient presentation in the frontend. A variable object
30922 is identified by string name. When a variable object is created, the
30923 frontend specifies the expression for that variable object. The
30924 expression can be a simple variable, or it can be an arbitrary complex
30925 expression, and can even involve CPU registers. After creating a
30926 variable object, the frontend can invoke other variable object
30927 operations---for example to obtain or change the value of a variable
30928 object, or to change display format.
30930 Variable objects have hierarchical tree structure. Any variable object
30931 that corresponds to a composite type, such as structure in C, has
30932 a number of child variable objects, for example corresponding to each
30933 element of a structure. A child variable object can itself have
30934 children, recursively. Recursion ends when we reach
30935 leaf variable objects, which always have built-in types. Child variable
30936 objects are created only by explicit request, so if a frontend
30937 is not interested in the children of a particular variable object, no
30938 child will be created.
30940 For a leaf variable object it is possible to obtain its value as a
30941 string, or set the value from a string. String value can be also
30942 obtained for a non-leaf variable object, but it's generally a string
30943 that only indicates the type of the object, and does not list its
30944 contents. Assignment to a non-leaf variable object is not allowed.
30946 A frontend does not need to read the values of all variable objects each time
30947 the program stops. Instead, MI provides an update command that lists all
30948 variable objects whose values has changed since the last update
30949 operation. This considerably reduces the amount of data that must
30950 be transferred to the frontend. As noted above, children variable
30951 objects are created on demand, and only leaf variable objects have a
30952 real value. As result, gdb will read target memory only for leaf
30953 variables that frontend has created.
30955 The automatic update is not always desirable. For example, a frontend
30956 might want to keep a value of some expression for future reference,
30957 and never update it. For another example, fetching memory is
30958 relatively slow for embedded targets, so a frontend might want
30959 to disable automatic update for the variables that are either not
30960 visible on the screen, or ``closed''. This is possible using so
30961 called ``frozen variable objects''. Such variable objects are never
30962 implicitly updated.
30964 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30965 fixed variable object, the expression is parsed when the variable
30966 object is created, including associating identifiers to specific
30967 variables. The meaning of expression never changes. For a floating
30968 variable object the values of variables whose names appear in the
30969 expressions are re-evaluated every time in the context of the current
30970 frame. Consider this example:
30975 struct work_state state;
30982 If a fixed variable object for the @code{state} variable is created in
30983 this function, and we enter the recursive call, the variable
30984 object will report the value of @code{state} in the top-level
30985 @code{do_work} invocation. On the other hand, a floating variable
30986 object will report the value of @code{state} in the current frame.
30988 If an expression specified when creating a fixed variable object
30989 refers to a local variable, the variable object becomes bound to the
30990 thread and frame in which the variable object is created. When such
30991 variable object is updated, @value{GDBN} makes sure that the
30992 thread/frame combination the variable object is bound to still exists,
30993 and re-evaluates the variable object in context of that thread/frame.
30995 The following is the complete set of @sc{gdb/mi} operations defined to
30996 access this functionality:
30998 @multitable @columnfractions .4 .6
30999 @item @strong{Operation}
31000 @tab @strong{Description}
31002 @item @code{-enable-pretty-printing}
31003 @tab enable Python-based pretty-printing
31004 @item @code{-var-create}
31005 @tab create a variable object
31006 @item @code{-var-delete}
31007 @tab delete the variable object and/or its children
31008 @item @code{-var-set-format}
31009 @tab set the display format of this variable
31010 @item @code{-var-show-format}
31011 @tab show the display format of this variable
31012 @item @code{-var-info-num-children}
31013 @tab tells how many children this object has
31014 @item @code{-var-list-children}
31015 @tab return a list of the object's children
31016 @item @code{-var-info-type}
31017 @tab show the type of this variable object
31018 @item @code{-var-info-expression}
31019 @tab print parent-relative expression that this variable object represents
31020 @item @code{-var-info-path-expression}
31021 @tab print full expression that this variable object represents
31022 @item @code{-var-show-attributes}
31023 @tab is this variable editable? does it exist here?
31024 @item @code{-var-evaluate-expression}
31025 @tab get the value of this variable
31026 @item @code{-var-assign}
31027 @tab set the value of this variable
31028 @item @code{-var-update}
31029 @tab update the variable and its children
31030 @item @code{-var-set-frozen}
31031 @tab set frozeness attribute
31032 @item @code{-var-set-update-range}
31033 @tab set range of children to display on update
31036 In the next subsection we describe each operation in detail and suggest
31037 how it can be used.
31039 @subheading Description And Use of Operations on Variable Objects
31041 @subheading The @code{-enable-pretty-printing} Command
31042 @findex -enable-pretty-printing
31045 -enable-pretty-printing
31048 @value{GDBN} allows Python-based visualizers to affect the output of the
31049 MI variable object commands. However, because there was no way to
31050 implement this in a fully backward-compatible way, a front end must
31051 request that this functionality be enabled.
31053 Once enabled, this feature cannot be disabled.
31055 Note that if Python support has not been compiled into @value{GDBN},
31056 this command will still succeed (and do nothing).
31058 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31059 may work differently in future versions of @value{GDBN}.
31061 @subheading The @code{-var-create} Command
31062 @findex -var-create
31064 @subsubheading Synopsis
31067 -var-create @{@var{name} | "-"@}
31068 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31071 This operation creates a variable object, which allows the monitoring of
31072 a variable, the result of an expression, a memory cell or a CPU
31075 The @var{name} parameter is the string by which the object can be
31076 referenced. It must be unique. If @samp{-} is specified, the varobj
31077 system will generate a string ``varNNNNNN'' automatically. It will be
31078 unique provided that one does not specify @var{name} of that format.
31079 The command fails if a duplicate name is found.
31081 The frame under which the expression should be evaluated can be
31082 specified by @var{frame-addr}. A @samp{*} indicates that the current
31083 frame should be used. A @samp{@@} indicates that a floating variable
31084 object must be created.
31086 @var{expression} is any expression valid on the current language set (must not
31087 begin with a @samp{*}), or one of the following:
31091 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31094 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31097 @samp{$@var{regname}} --- a CPU register name
31100 @cindex dynamic varobj
31101 A varobj's contents may be provided by a Python-based pretty-printer. In this
31102 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31103 have slightly different semantics in some cases. If the
31104 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31105 will never create a dynamic varobj. This ensures backward
31106 compatibility for existing clients.
31108 @subsubheading Result
31110 This operation returns attributes of the newly-created varobj. These
31115 The name of the varobj.
31118 The number of children of the varobj. This number is not necessarily
31119 reliable for a dynamic varobj. Instead, you must examine the
31120 @samp{has_more} attribute.
31123 The varobj's scalar value. For a varobj whose type is some sort of
31124 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31125 will not be interesting.
31128 The varobj's type. This is a string representation of the type, as
31129 would be printed by the @value{GDBN} CLI. If @samp{print object}
31130 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31131 @emph{actual} (derived) type of the object is shown rather than the
31132 @emph{declared} one.
31135 If a variable object is bound to a specific thread, then this is the
31136 thread's global identifier.
31139 For a dynamic varobj, this indicates whether there appear to be any
31140 children available. For a non-dynamic varobj, this will be 0.
31143 This attribute will be present and have the value @samp{1} if the
31144 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31145 then this attribute will not be present.
31148 A dynamic varobj can supply a display hint to the front end. The
31149 value comes directly from the Python pretty-printer object's
31150 @code{display_hint} method. @xref{Pretty Printing API}.
31153 Typical output will look like this:
31156 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31157 has_more="@var{has_more}"
31161 @subheading The @code{-var-delete} Command
31162 @findex -var-delete
31164 @subsubheading Synopsis
31167 -var-delete [ -c ] @var{name}
31170 Deletes a previously created variable object and all of its children.
31171 With the @samp{-c} option, just deletes the children.
31173 Returns an error if the object @var{name} is not found.
31176 @subheading The @code{-var-set-format} Command
31177 @findex -var-set-format
31179 @subsubheading Synopsis
31182 -var-set-format @var{name} @var{format-spec}
31185 Sets the output format for the value of the object @var{name} to be
31188 @anchor{-var-set-format}
31189 The syntax for the @var{format-spec} is as follows:
31192 @var{format-spec} @expansion{}
31193 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31196 The natural format is the default format choosen automatically
31197 based on the variable type (like decimal for an @code{int}, hex
31198 for pointers, etc.).
31200 The zero-hexadecimal format has a representation similar to hexadecimal
31201 but with padding zeroes to the left of the value. For example, a 32-bit
31202 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31203 zero-hexadecimal format.
31205 For a variable with children, the format is set only on the
31206 variable itself, and the children are not affected.
31208 @subheading The @code{-var-show-format} Command
31209 @findex -var-show-format
31211 @subsubheading Synopsis
31214 -var-show-format @var{name}
31217 Returns the format used to display the value of the object @var{name}.
31220 @var{format} @expansion{}
31225 @subheading The @code{-var-info-num-children} Command
31226 @findex -var-info-num-children
31228 @subsubheading Synopsis
31231 -var-info-num-children @var{name}
31234 Returns the number of children of a variable object @var{name}:
31240 Note that this number is not completely reliable for a dynamic varobj.
31241 It will return the current number of children, but more children may
31245 @subheading The @code{-var-list-children} Command
31246 @findex -var-list-children
31248 @subsubheading Synopsis
31251 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31253 @anchor{-var-list-children}
31255 Return a list of the children of the specified variable object and
31256 create variable objects for them, if they do not already exist. With
31257 a single argument or if @var{print-values} has a value of 0 or
31258 @code{--no-values}, print only the names of the variables; if
31259 @var{print-values} is 1 or @code{--all-values}, also print their
31260 values; and if it is 2 or @code{--simple-values} print the name and
31261 value for simple data types and just the name for arrays, structures
31264 @var{from} and @var{to}, if specified, indicate the range of children
31265 to report. If @var{from} or @var{to} is less than zero, the range is
31266 reset and all children will be reported. Otherwise, children starting
31267 at @var{from} (zero-based) and up to and excluding @var{to} will be
31270 If a child range is requested, it will only affect the current call to
31271 @code{-var-list-children}, but not future calls to @code{-var-update}.
31272 For this, you must instead use @code{-var-set-update-range}. The
31273 intent of this approach is to enable a front end to implement any
31274 update approach it likes; for example, scrolling a view may cause the
31275 front end to request more children with @code{-var-list-children}, and
31276 then the front end could call @code{-var-set-update-range} with a
31277 different range to ensure that future updates are restricted to just
31280 For each child the following results are returned:
31285 Name of the variable object created for this child.
31288 The expression to be shown to the user by the front end to designate this child.
31289 For example this may be the name of a structure member.
31291 For a dynamic varobj, this value cannot be used to form an
31292 expression. There is no way to do this at all with a dynamic varobj.
31294 For C/C@t{++} structures there are several pseudo children returned to
31295 designate access qualifiers. For these pseudo children @var{exp} is
31296 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31297 type and value are not present.
31299 A dynamic varobj will not report the access qualifying
31300 pseudo-children, regardless of the language. This information is not
31301 available at all with a dynamic varobj.
31304 Number of children this child has. For a dynamic varobj, this will be
31308 The type of the child. If @samp{print object}
31309 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31310 @emph{actual} (derived) type of the object is shown rather than the
31311 @emph{declared} one.
31314 If values were requested, this is the value.
31317 If this variable object is associated with a thread, this is the
31318 thread's global thread id. Otherwise this result is not present.
31321 If the variable object is frozen, this variable will be present with a value of 1.
31324 A dynamic varobj can supply a display hint to the front end. The
31325 value comes directly from the Python pretty-printer object's
31326 @code{display_hint} method. @xref{Pretty Printing API}.
31329 This attribute will be present and have the value @samp{1} if the
31330 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31331 then this attribute will not be present.
31335 The result may have its own attributes:
31339 A dynamic varobj can supply a display hint to the front end. The
31340 value comes directly from the Python pretty-printer object's
31341 @code{display_hint} method. @xref{Pretty Printing API}.
31344 This is an integer attribute which is nonzero if there are children
31345 remaining after the end of the selected range.
31348 @subsubheading Example
31352 -var-list-children n
31353 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31354 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31356 -var-list-children --all-values n
31357 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31358 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31362 @subheading The @code{-var-info-type} Command
31363 @findex -var-info-type
31365 @subsubheading Synopsis
31368 -var-info-type @var{name}
31371 Returns the type of the specified variable @var{name}. The type is
31372 returned as a string in the same format as it is output by the
31376 type=@var{typename}
31380 @subheading The @code{-var-info-expression} Command
31381 @findex -var-info-expression
31383 @subsubheading Synopsis
31386 -var-info-expression @var{name}
31389 Returns a string that is suitable for presenting this
31390 variable object in user interface. The string is generally
31391 not valid expression in the current language, and cannot be evaluated.
31393 For example, if @code{a} is an array, and variable object
31394 @code{A} was created for @code{a}, then we'll get this output:
31397 (gdb) -var-info-expression A.1
31398 ^done,lang="C",exp="1"
31402 Here, the value of @code{lang} is the language name, which can be
31403 found in @ref{Supported Languages}.
31405 Note that the output of the @code{-var-list-children} command also
31406 includes those expressions, so the @code{-var-info-expression} command
31409 @subheading The @code{-var-info-path-expression} Command
31410 @findex -var-info-path-expression
31412 @subsubheading Synopsis
31415 -var-info-path-expression @var{name}
31418 Returns an expression that can be evaluated in the current
31419 context and will yield the same value that a variable object has.
31420 Compare this with the @code{-var-info-expression} command, which
31421 result can be used only for UI presentation. Typical use of
31422 the @code{-var-info-path-expression} command is creating a
31423 watchpoint from a variable object.
31425 This command is currently not valid for children of a dynamic varobj,
31426 and will give an error when invoked on one.
31428 For example, suppose @code{C} is a C@t{++} class, derived from class
31429 @code{Base}, and that the @code{Base} class has a member called
31430 @code{m_size}. Assume a variable @code{c} is has the type of
31431 @code{C} and a variable object @code{C} was created for variable
31432 @code{c}. Then, we'll get this output:
31434 (gdb) -var-info-path-expression C.Base.public.m_size
31435 ^done,path_expr=((Base)c).m_size)
31438 @subheading The @code{-var-show-attributes} Command
31439 @findex -var-show-attributes
31441 @subsubheading Synopsis
31444 -var-show-attributes @var{name}
31447 List attributes of the specified variable object @var{name}:
31450 status=@var{attr} [ ( ,@var{attr} )* ]
31454 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31456 @subheading The @code{-var-evaluate-expression} Command
31457 @findex -var-evaluate-expression
31459 @subsubheading Synopsis
31462 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31465 Evaluates the expression that is represented by the specified variable
31466 object and returns its value as a string. The format of the string
31467 can be specified with the @samp{-f} option. The possible values of
31468 this option are the same as for @code{-var-set-format}
31469 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31470 the current display format will be used. The current display format
31471 can be changed using the @code{-var-set-format} command.
31477 Note that one must invoke @code{-var-list-children} for a variable
31478 before the value of a child variable can be evaluated.
31480 @subheading The @code{-var-assign} Command
31481 @findex -var-assign
31483 @subsubheading Synopsis
31486 -var-assign @var{name} @var{expression}
31489 Assigns the value of @var{expression} to the variable object specified
31490 by @var{name}. The object must be @samp{editable}. If the variable's
31491 value is altered by the assign, the variable will show up in any
31492 subsequent @code{-var-update} list.
31494 @subsubheading Example
31502 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31506 @subheading The @code{-var-update} Command
31507 @findex -var-update
31509 @subsubheading Synopsis
31512 -var-update [@var{print-values}] @{@var{name} | "*"@}
31515 Reevaluate the expressions corresponding to the variable object
31516 @var{name} and all its direct and indirect children, and return the
31517 list of variable objects whose values have changed; @var{name} must
31518 be a root variable object. Here, ``changed'' means that the result of
31519 @code{-var-evaluate-expression} before and after the
31520 @code{-var-update} is different. If @samp{*} is used as the variable
31521 object names, all existing variable objects are updated, except
31522 for frozen ones (@pxref{-var-set-frozen}). The option
31523 @var{print-values} determines whether both names and values, or just
31524 names are printed. The possible values of this option are the same
31525 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31526 recommended to use the @samp{--all-values} option, to reduce the
31527 number of MI commands needed on each program stop.
31529 With the @samp{*} parameter, if a variable object is bound to a
31530 currently running thread, it will not be updated, without any
31533 If @code{-var-set-update-range} was previously used on a varobj, then
31534 only the selected range of children will be reported.
31536 @code{-var-update} reports all the changed varobjs in a tuple named
31539 Each item in the change list is itself a tuple holding:
31543 The name of the varobj.
31546 If values were requested for this update, then this field will be
31547 present and will hold the value of the varobj.
31550 @anchor{-var-update}
31551 This field is a string which may take one of three values:
31555 The variable object's current value is valid.
31558 The variable object does not currently hold a valid value but it may
31559 hold one in the future if its associated expression comes back into
31563 The variable object no longer holds a valid value.
31564 This can occur when the executable file being debugged has changed,
31565 either through recompilation or by using the @value{GDBN} @code{file}
31566 command. The front end should normally choose to delete these variable
31570 In the future new values may be added to this list so the front should
31571 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31574 This is only present if the varobj is still valid. If the type
31575 changed, then this will be the string @samp{true}; otherwise it will
31578 When a varobj's type changes, its children are also likely to have
31579 become incorrect. Therefore, the varobj's children are automatically
31580 deleted when this attribute is @samp{true}. Also, the varobj's update
31581 range, when set using the @code{-var-set-update-range} command, is
31585 If the varobj's type changed, then this field will be present and will
31588 @item new_num_children
31589 For a dynamic varobj, if the number of children changed, or if the
31590 type changed, this will be the new number of children.
31592 The @samp{numchild} field in other varobj responses is generally not
31593 valid for a dynamic varobj -- it will show the number of children that
31594 @value{GDBN} knows about, but because dynamic varobjs lazily
31595 instantiate their children, this will not reflect the number of
31596 children which may be available.
31598 The @samp{new_num_children} attribute only reports changes to the
31599 number of children known by @value{GDBN}. This is the only way to
31600 detect whether an update has removed children (which necessarily can
31601 only happen at the end of the update range).
31604 The display hint, if any.
31607 This is an integer value, which will be 1 if there are more children
31608 available outside the varobj's update range.
31611 This attribute will be present and have the value @samp{1} if the
31612 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31613 then this attribute will not be present.
31616 If new children were added to a dynamic varobj within the selected
31617 update range (as set by @code{-var-set-update-range}), then they will
31618 be listed in this attribute.
31621 @subsubheading Example
31628 -var-update --all-values var1
31629 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31630 type_changed="false"@}]
31634 @subheading The @code{-var-set-frozen} Command
31635 @findex -var-set-frozen
31636 @anchor{-var-set-frozen}
31638 @subsubheading Synopsis
31641 -var-set-frozen @var{name} @var{flag}
31644 Set the frozenness flag on the variable object @var{name}. The
31645 @var{flag} parameter should be either @samp{1} to make the variable
31646 frozen or @samp{0} to make it unfrozen. If a variable object is
31647 frozen, then neither itself, nor any of its children, are
31648 implicitly updated by @code{-var-update} of
31649 a parent variable or by @code{-var-update *}. Only
31650 @code{-var-update} of the variable itself will update its value and
31651 values of its children. After a variable object is unfrozen, it is
31652 implicitly updated by all subsequent @code{-var-update} operations.
31653 Unfreezing a variable does not update it, only subsequent
31654 @code{-var-update} does.
31656 @subsubheading Example
31660 -var-set-frozen V 1
31665 @subheading The @code{-var-set-update-range} command
31666 @findex -var-set-update-range
31667 @anchor{-var-set-update-range}
31669 @subsubheading Synopsis
31672 -var-set-update-range @var{name} @var{from} @var{to}
31675 Set the range of children to be returned by future invocations of
31676 @code{-var-update}.
31678 @var{from} and @var{to} indicate the range of children to report. If
31679 @var{from} or @var{to} is less than zero, the range is reset and all
31680 children will be reported. Otherwise, children starting at @var{from}
31681 (zero-based) and up to and excluding @var{to} will be reported.
31683 @subsubheading Example
31687 -var-set-update-range V 1 2
31691 @subheading The @code{-var-set-visualizer} command
31692 @findex -var-set-visualizer
31693 @anchor{-var-set-visualizer}
31695 @subsubheading Synopsis
31698 -var-set-visualizer @var{name} @var{visualizer}
31701 Set a visualizer for the variable object @var{name}.
31703 @var{visualizer} is the visualizer to use. The special value
31704 @samp{None} means to disable any visualizer in use.
31706 If not @samp{None}, @var{visualizer} must be a Python expression.
31707 This expression must evaluate to a callable object which accepts a
31708 single argument. @value{GDBN} will call this object with the value of
31709 the varobj @var{name} as an argument (this is done so that the same
31710 Python pretty-printing code can be used for both the CLI and MI).
31711 When called, this object must return an object which conforms to the
31712 pretty-printing interface (@pxref{Pretty Printing API}).
31714 The pre-defined function @code{gdb.default_visualizer} may be used to
31715 select a visualizer by following the built-in process
31716 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31717 a varobj is created, and so ordinarily is not needed.
31719 This feature is only available if Python support is enabled. The MI
31720 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31721 can be used to check this.
31723 @subsubheading Example
31725 Resetting the visualizer:
31729 -var-set-visualizer V None
31733 Reselecting the default (type-based) visualizer:
31737 -var-set-visualizer V gdb.default_visualizer
31741 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31742 can be used to instantiate this class for a varobj:
31746 -var-set-visualizer V "lambda val: SomeClass()"
31750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31751 @node GDB/MI Data Manipulation
31752 @section @sc{gdb/mi} Data Manipulation
31754 @cindex data manipulation, in @sc{gdb/mi}
31755 @cindex @sc{gdb/mi}, data manipulation
31756 This section describes the @sc{gdb/mi} commands that manipulate data:
31757 examine memory and registers, evaluate expressions, etc.
31759 For details about what an addressable memory unit is,
31760 @pxref{addressable memory unit}.
31762 @c REMOVED FROM THE INTERFACE.
31763 @c @subheading -data-assign
31764 @c Change the value of a program variable. Plenty of side effects.
31765 @c @subsubheading GDB Command
31767 @c @subsubheading Example
31770 @subheading The @code{-data-disassemble} Command
31771 @findex -data-disassemble
31773 @subsubheading Synopsis
31777 [ -s @var{start-addr} -e @var{end-addr} ]
31778 | [ -a @var{addr} ]
31779 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31787 @item @var{start-addr}
31788 is the beginning address (or @code{$pc})
31789 @item @var{end-addr}
31792 is an address anywhere within (or the name of) the function to
31793 disassemble. If an address is specified, the whole function
31794 surrounding that address will be disassembled. If a name is
31795 specified, the whole function with that name will be disassembled.
31796 @item @var{filename}
31797 is the name of the file to disassemble
31798 @item @var{linenum}
31799 is the line number to disassemble around
31801 is the number of disassembly lines to be produced. If it is -1,
31802 the whole function will be disassembled, in case no @var{end-addr} is
31803 specified. If @var{end-addr} is specified as a non-zero value, and
31804 @var{lines} is lower than the number of disassembly lines between
31805 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31806 displayed; if @var{lines} is higher than the number of lines between
31807 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31812 @item 0 disassembly only
31813 @item 1 mixed source and disassembly (deprecated)
31814 @item 2 disassembly with raw opcodes
31815 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31816 @item 4 mixed source and disassembly
31817 @item 5 mixed source and disassembly with raw opcodes
31820 Modes 1 and 3 are deprecated. The output is ``source centric''
31821 which hasn't proved useful in practice.
31822 @xref{Machine Code}, for a discussion of the difference between
31823 @code{/m} and @code{/s} output of the @code{disassemble} command.
31826 @subsubheading Result
31828 The result of the @code{-data-disassemble} command will be a list named
31829 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31830 used with the @code{-data-disassemble} command.
31832 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31837 The address at which this instruction was disassembled.
31840 The name of the function this instruction is within.
31843 The decimal offset in bytes from the start of @samp{func-name}.
31846 The text disassembly for this @samp{address}.
31849 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31850 bytes for the @samp{inst} field.
31854 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31855 @samp{src_and_asm_line}, each of which has the following fields:
31859 The line number within @samp{file}.
31862 The file name from the compilation unit. This might be an absolute
31863 file name or a relative file name depending on the compile command
31867 Absolute file name of @samp{file}. It is converted to a canonical form
31868 using the source file search path
31869 (@pxref{Source Path, ,Specifying Source Directories})
31870 and after resolving all the symbolic links.
31872 If the source file is not found this field will contain the path as
31873 present in the debug information.
31875 @item line_asm_insn
31876 This is a list of tuples containing the disassembly for @samp{line} in
31877 @samp{file}. The fields of each tuple are the same as for
31878 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31879 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31884 Note that whatever included in the @samp{inst} field, is not
31885 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31888 @subsubheading @value{GDBN} Command
31890 The corresponding @value{GDBN} command is @samp{disassemble}.
31892 @subsubheading Example
31894 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31898 -data-disassemble -s $pc -e "$pc + 20" -- 0
31901 @{address="0x000107c0",func-name="main",offset="4",
31902 inst="mov 2, %o0"@},
31903 @{address="0x000107c4",func-name="main",offset="8",
31904 inst="sethi %hi(0x11800), %o2"@},
31905 @{address="0x000107c8",func-name="main",offset="12",
31906 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31907 @{address="0x000107cc",func-name="main",offset="16",
31908 inst="sethi %hi(0x11800), %o2"@},
31909 @{address="0x000107d0",func-name="main",offset="20",
31910 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31914 Disassemble the whole @code{main} function. Line 32 is part of
31918 -data-disassemble -f basics.c -l 32 -- 0
31920 @{address="0x000107bc",func-name="main",offset="0",
31921 inst="save %sp, -112, %sp"@},
31922 @{address="0x000107c0",func-name="main",offset="4",
31923 inst="mov 2, %o0"@},
31924 @{address="0x000107c4",func-name="main",offset="8",
31925 inst="sethi %hi(0x11800), %o2"@},
31927 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31928 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31932 Disassemble 3 instructions from the start of @code{main}:
31936 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31938 @{address="0x000107bc",func-name="main",offset="0",
31939 inst="save %sp, -112, %sp"@},
31940 @{address="0x000107c0",func-name="main",offset="4",
31941 inst="mov 2, %o0"@},
31942 @{address="0x000107c4",func-name="main",offset="8",
31943 inst="sethi %hi(0x11800), %o2"@}]
31947 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31951 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31953 src_and_asm_line=@{line="31",
31954 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31955 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31956 line_asm_insn=[@{address="0x000107bc",
31957 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31958 src_and_asm_line=@{line="32",
31959 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31960 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31961 line_asm_insn=[@{address="0x000107c0",
31962 func-name="main",offset="4",inst="mov 2, %o0"@},
31963 @{address="0x000107c4",func-name="main",offset="8",
31964 inst="sethi %hi(0x11800), %o2"@}]@}]
31969 @subheading The @code{-data-evaluate-expression} Command
31970 @findex -data-evaluate-expression
31972 @subsubheading Synopsis
31975 -data-evaluate-expression @var{expr}
31978 Evaluate @var{expr} as an expression. The expression could contain an
31979 inferior function call. The function call will execute synchronously.
31980 If the expression contains spaces, it must be enclosed in double quotes.
31982 @subsubheading @value{GDBN} Command
31984 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31985 @samp{call}. In @code{gdbtk} only, there's a corresponding
31986 @samp{gdb_eval} command.
31988 @subsubheading Example
31990 In the following example, the numbers that precede the commands are the
31991 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31992 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31996 211-data-evaluate-expression A
31999 311-data-evaluate-expression &A
32000 311^done,value="0xefffeb7c"
32002 411-data-evaluate-expression A+3
32005 511-data-evaluate-expression "A + 3"
32011 @subheading The @code{-data-list-changed-registers} Command
32012 @findex -data-list-changed-registers
32014 @subsubheading Synopsis
32017 -data-list-changed-registers
32020 Display a list of the registers that have changed.
32022 @subsubheading @value{GDBN} Command
32024 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32025 has the corresponding command @samp{gdb_changed_register_list}.
32027 @subsubheading Example
32029 On a PPC MBX board:
32037 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32038 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32039 line="5",arch="powerpc"@}
32041 -data-list-changed-registers
32042 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32043 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32044 "24","25","26","27","28","30","31","64","65","66","67","69"]
32049 @subheading The @code{-data-list-register-names} Command
32050 @findex -data-list-register-names
32052 @subsubheading Synopsis
32055 -data-list-register-names [ ( @var{regno} )+ ]
32058 Show a list of register names for the current target. If no arguments
32059 are given, it shows a list of the names of all the registers. If
32060 integer numbers are given as arguments, it will print a list of the
32061 names of the registers corresponding to the arguments. To ensure
32062 consistency between a register name and its number, the output list may
32063 include empty register names.
32065 @subsubheading @value{GDBN} Command
32067 @value{GDBN} does not have a command which corresponds to
32068 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32069 corresponding command @samp{gdb_regnames}.
32071 @subsubheading Example
32073 For the PPC MBX board:
32076 -data-list-register-names
32077 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32078 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32079 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32080 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32081 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32082 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32083 "", "pc","ps","cr","lr","ctr","xer"]
32085 -data-list-register-names 1 2 3
32086 ^done,register-names=["r1","r2","r3"]
32090 @subheading The @code{-data-list-register-values} Command
32091 @findex -data-list-register-values
32093 @subsubheading Synopsis
32096 -data-list-register-values
32097 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32100 Display the registers' contents. The format according to which the
32101 registers' contents are to be returned is given by @var{fmt}, followed
32102 by an optional list of numbers specifying the registers to display. A
32103 missing list of numbers indicates that the contents of all the
32104 registers must be returned. The @code{--skip-unavailable} option
32105 indicates that only the available registers are to be returned.
32107 Allowed formats for @var{fmt} are:
32124 @subsubheading @value{GDBN} Command
32126 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32127 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32129 @subsubheading Example
32131 For a PPC MBX board (note: line breaks are for readability only, they
32132 don't appear in the actual output):
32136 -data-list-register-values r 64 65
32137 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32138 @{number="65",value="0x00029002"@}]
32140 -data-list-register-values x
32141 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32142 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32143 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32144 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32145 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32146 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32147 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32148 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32149 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32150 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32151 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32152 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32153 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32154 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32155 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32156 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32157 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32158 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32159 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32160 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32161 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32162 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32163 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32164 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32165 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32166 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32167 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32168 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32169 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32170 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32171 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32172 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32173 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32174 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32175 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32176 @{number="69",value="0x20002b03"@}]
32181 @subheading The @code{-data-read-memory} Command
32182 @findex -data-read-memory
32184 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32186 @subsubheading Synopsis
32189 -data-read-memory [ -o @var{byte-offset} ]
32190 @var{address} @var{word-format} @var{word-size}
32191 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32198 @item @var{address}
32199 An expression specifying the address of the first memory word to be
32200 read. Complex expressions containing embedded white space should be
32201 quoted using the C convention.
32203 @item @var{word-format}
32204 The format to be used to print the memory words. The notation is the
32205 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32208 @item @var{word-size}
32209 The size of each memory word in bytes.
32211 @item @var{nr-rows}
32212 The number of rows in the output table.
32214 @item @var{nr-cols}
32215 The number of columns in the output table.
32218 If present, indicates that each row should include an @sc{ascii} dump. The
32219 value of @var{aschar} is used as a padding character when a byte is not a
32220 member of the printable @sc{ascii} character set (printable @sc{ascii}
32221 characters are those whose code is between 32 and 126, inclusively).
32223 @item @var{byte-offset}
32224 An offset to add to the @var{address} before fetching memory.
32227 This command displays memory contents as a table of @var{nr-rows} by
32228 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32229 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32230 (returned as @samp{total-bytes}). Should less than the requested number
32231 of bytes be returned by the target, the missing words are identified
32232 using @samp{N/A}. The number of bytes read from the target is returned
32233 in @samp{nr-bytes} and the starting address used to read memory in
32236 The address of the next/previous row or page is available in
32237 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32240 @subsubheading @value{GDBN} Command
32242 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32243 @samp{gdb_get_mem} memory read command.
32245 @subsubheading Example
32247 Read six bytes of memory starting at @code{bytes+6} but then offset by
32248 @code{-6} bytes. Format as three rows of two columns. One byte per
32249 word. Display each word in hex.
32253 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32254 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32255 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32256 prev-page="0x0000138a",memory=[
32257 @{addr="0x00001390",data=["0x00","0x01"]@},
32258 @{addr="0x00001392",data=["0x02","0x03"]@},
32259 @{addr="0x00001394",data=["0x04","0x05"]@}]
32263 Read two bytes of memory starting at address @code{shorts + 64} and
32264 display as a single word formatted in decimal.
32268 5-data-read-memory shorts+64 d 2 1 1
32269 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32270 next-row="0x00001512",prev-row="0x0000150e",
32271 next-page="0x00001512",prev-page="0x0000150e",memory=[
32272 @{addr="0x00001510",data=["128"]@}]
32276 Read thirty two bytes of memory starting at @code{bytes+16} and format
32277 as eight rows of four columns. Include a string encoding with @samp{x}
32278 used as the non-printable character.
32282 4-data-read-memory bytes+16 x 1 8 4 x
32283 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32284 next-row="0x000013c0",prev-row="0x0000139c",
32285 next-page="0x000013c0",prev-page="0x00001380",memory=[
32286 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32287 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32288 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32289 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32290 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32291 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32292 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32293 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32297 @subheading The @code{-data-read-memory-bytes} Command
32298 @findex -data-read-memory-bytes
32300 @subsubheading Synopsis
32303 -data-read-memory-bytes [ -o @var{offset} ]
32304 @var{address} @var{count}
32311 @item @var{address}
32312 An expression specifying the address of the first addressable memory unit
32313 to be read. Complex expressions containing embedded white space should be
32314 quoted using the C convention.
32317 The number of addressable memory units to read. This should be an integer
32321 The offset relative to @var{address} at which to start reading. This
32322 should be an integer literal. This option is provided so that a frontend
32323 is not required to first evaluate address and then perform address
32324 arithmetics itself.
32328 This command attempts to read all accessible memory regions in the
32329 specified range. First, all regions marked as unreadable in the memory
32330 map (if one is defined) will be skipped. @xref{Memory Region
32331 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32332 regions. For each one, if reading full region results in an errors,
32333 @value{GDBN} will try to read a subset of the region.
32335 In general, every single memory unit in the region may be readable or not,
32336 and the only way to read every readable unit is to try a read at
32337 every address, which is not practical. Therefore, @value{GDBN} will
32338 attempt to read all accessible memory units at either beginning or the end
32339 of the region, using a binary division scheme. This heuristic works
32340 well for reading accross a memory map boundary. Note that if a region
32341 has a readable range that is neither at the beginning or the end,
32342 @value{GDBN} will not read it.
32344 The result record (@pxref{GDB/MI Result Records}) that is output of
32345 the command includes a field named @samp{memory} whose content is a
32346 list of tuples. Each tuple represent a successfully read memory block
32347 and has the following fields:
32351 The start address of the memory block, as hexadecimal literal.
32354 The end address of the memory block, as hexadecimal literal.
32357 The offset of the memory block, as hexadecimal literal, relative to
32358 the start address passed to @code{-data-read-memory-bytes}.
32361 The contents of the memory block, in hex.
32367 @subsubheading @value{GDBN} Command
32369 The corresponding @value{GDBN} command is @samp{x}.
32371 @subsubheading Example
32375 -data-read-memory-bytes &a 10
32376 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32378 contents="01000000020000000300"@}]
32383 @subheading The @code{-data-write-memory-bytes} Command
32384 @findex -data-write-memory-bytes
32386 @subsubheading Synopsis
32389 -data-write-memory-bytes @var{address} @var{contents}
32390 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32397 @item @var{address}
32398 An expression specifying the address of the first addressable memory unit
32399 to be written. Complex expressions containing embedded white space should
32400 be quoted using the C convention.
32402 @item @var{contents}
32403 The hex-encoded data to write. It is an error if @var{contents} does
32404 not represent an integral number of addressable memory units.
32407 Optional argument indicating the number of addressable memory units to be
32408 written. If @var{count} is greater than @var{contents}' length,
32409 @value{GDBN} will repeatedly write @var{contents} until it fills
32410 @var{count} memory units.
32414 @subsubheading @value{GDBN} Command
32416 There's no corresponding @value{GDBN} command.
32418 @subsubheading Example
32422 -data-write-memory-bytes &a "aabbccdd"
32429 -data-write-memory-bytes &a "aabbccdd" 16e
32434 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32435 @node GDB/MI Tracepoint Commands
32436 @section @sc{gdb/mi} Tracepoint Commands
32438 The commands defined in this section implement MI support for
32439 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32441 @subheading The @code{-trace-find} Command
32442 @findex -trace-find
32444 @subsubheading Synopsis
32447 -trace-find @var{mode} [@var{parameters}@dots{}]
32450 Find a trace frame using criteria defined by @var{mode} and
32451 @var{parameters}. The following table lists permissible
32452 modes and their parameters. For details of operation, see @ref{tfind}.
32457 No parameters are required. Stops examining trace frames.
32460 An integer is required as parameter. Selects tracepoint frame with
32463 @item tracepoint-number
32464 An integer is required as parameter. Finds next
32465 trace frame that corresponds to tracepoint with the specified number.
32468 An address is required as parameter. Finds
32469 next trace frame that corresponds to any tracepoint at the specified
32472 @item pc-inside-range
32473 Two addresses are required as parameters. Finds next trace
32474 frame that corresponds to a tracepoint at an address inside the
32475 specified range. Both bounds are considered to be inside the range.
32477 @item pc-outside-range
32478 Two addresses are required as parameters. Finds
32479 next trace frame that corresponds to a tracepoint at an address outside
32480 the specified range. Both bounds are considered to be inside the range.
32483 Line specification is required as parameter. @xref{Specify Location}.
32484 Finds next trace frame that corresponds to a tracepoint at
32485 the specified location.
32489 If @samp{none} was passed as @var{mode}, the response does not
32490 have fields. Otherwise, the response may have the following fields:
32494 This field has either @samp{0} or @samp{1} as the value, depending
32495 on whether a matching tracepoint was found.
32498 The index of the found traceframe. This field is present iff
32499 the @samp{found} field has value of @samp{1}.
32502 The index of the found tracepoint. This field is present iff
32503 the @samp{found} field has value of @samp{1}.
32506 The information about the frame corresponding to the found trace
32507 frame. This field is present only if a trace frame was found.
32508 @xref{GDB/MI Frame Information}, for description of this field.
32512 @subsubheading @value{GDBN} Command
32514 The corresponding @value{GDBN} command is @samp{tfind}.
32516 @subheading -trace-define-variable
32517 @findex -trace-define-variable
32519 @subsubheading Synopsis
32522 -trace-define-variable @var{name} [ @var{value} ]
32525 Create trace variable @var{name} if it does not exist. If
32526 @var{value} is specified, sets the initial value of the specified
32527 trace variable to that value. Note that the @var{name} should start
32528 with the @samp{$} character.
32530 @subsubheading @value{GDBN} Command
32532 The corresponding @value{GDBN} command is @samp{tvariable}.
32534 @subheading The @code{-trace-frame-collected} Command
32535 @findex -trace-frame-collected
32537 @subsubheading Synopsis
32540 -trace-frame-collected
32541 [--var-print-values @var{var_pval}]
32542 [--comp-print-values @var{comp_pval}]
32543 [--registers-format @var{regformat}]
32544 [--memory-contents]
32547 This command returns the set of collected objects, register names,
32548 trace state variable names, memory ranges and computed expressions
32549 that have been collected at a particular trace frame. The optional
32550 parameters to the command affect the output format in different ways.
32551 See the output description table below for more details.
32553 The reported names can be used in the normal manner to create
32554 varobjs and inspect the objects themselves. The items returned by
32555 this command are categorized so that it is clear which is a variable,
32556 which is a register, which is a trace state variable, which is a
32557 memory range and which is a computed expression.
32559 For instance, if the actions were
32561 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32562 collect *(int*)0xaf02bef0@@40
32566 the object collected in its entirety would be @code{myVar}. The
32567 object @code{myArray} would be partially collected, because only the
32568 element at index @code{myIndex} would be collected. The remaining
32569 objects would be computed expressions.
32571 An example output would be:
32575 -trace-frame-collected
32577 explicit-variables=[@{name="myVar",value="1"@}],
32578 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32579 @{name="myObj.field",value="0"@},
32580 @{name="myPtr->field",value="1"@},
32581 @{name="myCount + 2",value="3"@},
32582 @{name="$tvar1 + 1",value="43970027"@}],
32583 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32584 @{number="1",value="0x0"@},
32585 @{number="2",value="0x4"@},
32587 @{number="125",value="0x0"@}],
32588 tvars=[@{name="$tvar1",current="43970026"@}],
32589 memory=[@{address="0x0000000000602264",length="4"@},
32590 @{address="0x0000000000615bc0",length="4"@}]
32597 @item explicit-variables
32598 The set of objects that have been collected in their entirety (as
32599 opposed to collecting just a few elements of an array or a few struct
32600 members). For each object, its name and value are printed.
32601 The @code{--var-print-values} option affects how or whether the value
32602 field is output. If @var{var_pval} is 0, then print only the names;
32603 if it is 1, print also their values; and if it is 2, print the name,
32604 type and value for simple data types, and the name and type for
32605 arrays, structures and unions.
32607 @item computed-expressions
32608 The set of computed expressions that have been collected at the
32609 current trace frame. The @code{--comp-print-values} option affects
32610 this set like the @code{--var-print-values} option affects the
32611 @code{explicit-variables} set. See above.
32614 The registers that have been collected at the current trace frame.
32615 For each register collected, the name and current value are returned.
32616 The value is formatted according to the @code{--registers-format}
32617 option. See the @command{-data-list-register-values} command for a
32618 list of the allowed formats. The default is @samp{x}.
32621 The trace state variables that have been collected at the current
32622 trace frame. For each trace state variable collected, the name and
32623 current value are returned.
32626 The set of memory ranges that have been collected at the current trace
32627 frame. Its content is a list of tuples. Each tuple represents a
32628 collected memory range and has the following fields:
32632 The start address of the memory range, as hexadecimal literal.
32635 The length of the memory range, as decimal literal.
32638 The contents of the memory block, in hex. This field is only present
32639 if the @code{--memory-contents} option is specified.
32645 @subsubheading @value{GDBN} Command
32647 There is no corresponding @value{GDBN} command.
32649 @subsubheading Example
32651 @subheading -trace-list-variables
32652 @findex -trace-list-variables
32654 @subsubheading Synopsis
32657 -trace-list-variables
32660 Return a table of all defined trace variables. Each element of the
32661 table has the following fields:
32665 The name of the trace variable. This field is always present.
32668 The initial value. This is a 64-bit signed integer. This
32669 field is always present.
32672 The value the trace variable has at the moment. This is a 64-bit
32673 signed integer. This field is absent iff current value is
32674 not defined, for example if the trace was never run, or is
32679 @subsubheading @value{GDBN} Command
32681 The corresponding @value{GDBN} command is @samp{tvariables}.
32683 @subsubheading Example
32687 -trace-list-variables
32688 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32689 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32690 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32691 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32692 body=[variable=@{name="$trace_timestamp",initial="0"@}
32693 variable=@{name="$foo",initial="10",current="15"@}]@}
32697 @subheading -trace-save
32698 @findex -trace-save
32700 @subsubheading Synopsis
32703 -trace-save [ -r ] [ -ctf ] @var{filename}
32706 Saves the collected trace data to @var{filename}. Without the
32707 @samp{-r} option, the data is downloaded from the target and saved
32708 in a local file. With the @samp{-r} option the target is asked
32709 to perform the save.
32711 By default, this command will save the trace in the tfile format. You can
32712 supply the optional @samp{-ctf} argument to save it the CTF format. See
32713 @ref{Trace Files} for more information about CTF.
32715 @subsubheading @value{GDBN} Command
32717 The corresponding @value{GDBN} command is @samp{tsave}.
32720 @subheading -trace-start
32721 @findex -trace-start
32723 @subsubheading Synopsis
32729 Starts a tracing experiment. The result of this command does not
32732 @subsubheading @value{GDBN} Command
32734 The corresponding @value{GDBN} command is @samp{tstart}.
32736 @subheading -trace-status
32737 @findex -trace-status
32739 @subsubheading Synopsis
32745 Obtains the status of a tracing experiment. The result may include
32746 the following fields:
32751 May have a value of either @samp{0}, when no tracing operations are
32752 supported, @samp{1}, when all tracing operations are supported, or
32753 @samp{file} when examining trace file. In the latter case, examining
32754 of trace frame is possible but new tracing experiement cannot be
32755 started. This field is always present.
32758 May have a value of either @samp{0} or @samp{1} depending on whether
32759 tracing experiement is in progress on target. This field is present
32760 if @samp{supported} field is not @samp{0}.
32763 Report the reason why the tracing was stopped last time. This field
32764 may be absent iff tracing was never stopped on target yet. The
32765 value of @samp{request} means the tracing was stopped as result of
32766 the @code{-trace-stop} command. The value of @samp{overflow} means
32767 the tracing buffer is full. The value of @samp{disconnection} means
32768 tracing was automatically stopped when @value{GDBN} has disconnected.
32769 The value of @samp{passcount} means tracing was stopped when a
32770 tracepoint was passed a maximal number of times for that tracepoint.
32771 This field is present if @samp{supported} field is not @samp{0}.
32773 @item stopping-tracepoint
32774 The number of tracepoint whose passcount as exceeded. This field is
32775 present iff the @samp{stop-reason} field has the value of
32779 @itemx frames-created
32780 The @samp{frames} field is a count of the total number of trace frames
32781 in the trace buffer, while @samp{frames-created} is the total created
32782 during the run, including ones that were discarded, such as when a
32783 circular trace buffer filled up. Both fields are optional.
32787 These fields tell the current size of the tracing buffer and the
32788 remaining space. These fields are optional.
32791 The value of the circular trace buffer flag. @code{1} means that the
32792 trace buffer is circular and old trace frames will be discarded if
32793 necessary to make room, @code{0} means that the trace buffer is linear
32797 The value of the disconnected tracing flag. @code{1} means that
32798 tracing will continue after @value{GDBN} disconnects, @code{0} means
32799 that the trace run will stop.
32802 The filename of the trace file being examined. This field is
32803 optional, and only present when examining a trace file.
32807 @subsubheading @value{GDBN} Command
32809 The corresponding @value{GDBN} command is @samp{tstatus}.
32811 @subheading -trace-stop
32812 @findex -trace-stop
32814 @subsubheading Synopsis
32820 Stops a tracing experiment. The result of this command has the same
32821 fields as @code{-trace-status}, except that the @samp{supported} and
32822 @samp{running} fields are not output.
32824 @subsubheading @value{GDBN} Command
32826 The corresponding @value{GDBN} command is @samp{tstop}.
32829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32830 @node GDB/MI Symbol Query
32831 @section @sc{gdb/mi} Symbol Query Commands
32835 @subheading The @code{-symbol-info-address} Command
32836 @findex -symbol-info-address
32838 @subsubheading Synopsis
32841 -symbol-info-address @var{symbol}
32844 Describe where @var{symbol} is stored.
32846 @subsubheading @value{GDBN} Command
32848 The corresponding @value{GDBN} command is @samp{info address}.
32850 @subsubheading Example
32854 @subheading The @code{-symbol-info-file} Command
32855 @findex -symbol-info-file
32857 @subsubheading Synopsis
32863 Show the file for the symbol.
32865 @subsubheading @value{GDBN} Command
32867 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32868 @samp{gdb_find_file}.
32870 @subsubheading Example
32874 @subheading The @code{-symbol-info-function} Command
32875 @findex -symbol-info-function
32877 @subsubheading Synopsis
32880 -symbol-info-function
32883 Show which function the symbol lives in.
32885 @subsubheading @value{GDBN} Command
32887 @samp{gdb_get_function} in @code{gdbtk}.
32889 @subsubheading Example
32893 @subheading The @code{-symbol-info-line} Command
32894 @findex -symbol-info-line
32896 @subsubheading Synopsis
32902 Show the core addresses of the code for a source line.
32904 @subsubheading @value{GDBN} Command
32906 The corresponding @value{GDBN} command is @samp{info line}.
32907 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32909 @subsubheading Example
32913 @subheading The @code{-symbol-info-symbol} Command
32914 @findex -symbol-info-symbol
32916 @subsubheading Synopsis
32919 -symbol-info-symbol @var{addr}
32922 Describe what symbol is at location @var{addr}.
32924 @subsubheading @value{GDBN} Command
32926 The corresponding @value{GDBN} command is @samp{info symbol}.
32928 @subsubheading Example
32932 @subheading The @code{-symbol-list-functions} Command
32933 @findex -symbol-list-functions
32935 @subsubheading Synopsis
32938 -symbol-list-functions
32941 List the functions in the executable.
32943 @subsubheading @value{GDBN} Command
32945 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32946 @samp{gdb_search} in @code{gdbtk}.
32948 @subsubheading Example
32953 @subheading The @code{-symbol-list-lines} Command
32954 @findex -symbol-list-lines
32956 @subsubheading Synopsis
32959 -symbol-list-lines @var{filename}
32962 Print the list of lines that contain code and their associated program
32963 addresses for the given source filename. The entries are sorted in
32964 ascending PC order.
32966 @subsubheading @value{GDBN} Command
32968 There is no corresponding @value{GDBN} command.
32970 @subsubheading Example
32973 -symbol-list-lines basics.c
32974 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32980 @subheading The @code{-symbol-list-types} Command
32981 @findex -symbol-list-types
32983 @subsubheading Synopsis
32989 List all the type names.
32991 @subsubheading @value{GDBN} Command
32993 The corresponding commands are @samp{info types} in @value{GDBN},
32994 @samp{gdb_search} in @code{gdbtk}.
32996 @subsubheading Example
33000 @subheading The @code{-symbol-list-variables} Command
33001 @findex -symbol-list-variables
33003 @subsubheading Synopsis
33006 -symbol-list-variables
33009 List all the global and static variable names.
33011 @subsubheading @value{GDBN} Command
33013 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33015 @subsubheading Example
33019 @subheading The @code{-symbol-locate} Command
33020 @findex -symbol-locate
33022 @subsubheading Synopsis
33028 @subsubheading @value{GDBN} Command
33030 @samp{gdb_loc} in @code{gdbtk}.
33032 @subsubheading Example
33036 @subheading The @code{-symbol-type} Command
33037 @findex -symbol-type
33039 @subsubheading Synopsis
33042 -symbol-type @var{variable}
33045 Show type of @var{variable}.
33047 @subsubheading @value{GDBN} Command
33049 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33050 @samp{gdb_obj_variable}.
33052 @subsubheading Example
33057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33058 @node GDB/MI File Commands
33059 @section @sc{gdb/mi} File Commands
33061 This section describes the GDB/MI commands to specify executable file names
33062 and to read in and obtain symbol table information.
33064 @subheading The @code{-file-exec-and-symbols} Command
33065 @findex -file-exec-and-symbols
33067 @subsubheading Synopsis
33070 -file-exec-and-symbols @var{file}
33073 Specify the executable file to be debugged. This file is the one from
33074 which the symbol table is also read. If no file is specified, the
33075 command clears the executable and symbol information. If breakpoints
33076 are set when using this command with no arguments, @value{GDBN} will produce
33077 error messages. Otherwise, no output is produced, except a completion
33080 @subsubheading @value{GDBN} Command
33082 The corresponding @value{GDBN} command is @samp{file}.
33084 @subsubheading Example
33088 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33094 @subheading The @code{-file-exec-file} Command
33095 @findex -file-exec-file
33097 @subsubheading Synopsis
33100 -file-exec-file @var{file}
33103 Specify the executable file to be debugged. Unlike
33104 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33105 from this file. If used without argument, @value{GDBN} clears the information
33106 about the executable file. No output is produced, except a completion
33109 @subsubheading @value{GDBN} Command
33111 The corresponding @value{GDBN} command is @samp{exec-file}.
33113 @subsubheading Example
33117 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33124 @subheading The @code{-file-list-exec-sections} Command
33125 @findex -file-list-exec-sections
33127 @subsubheading Synopsis
33130 -file-list-exec-sections
33133 List the sections of the current executable file.
33135 @subsubheading @value{GDBN} Command
33137 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33138 information as this command. @code{gdbtk} has a corresponding command
33139 @samp{gdb_load_info}.
33141 @subsubheading Example
33146 @subheading The @code{-file-list-exec-source-file} Command
33147 @findex -file-list-exec-source-file
33149 @subsubheading Synopsis
33152 -file-list-exec-source-file
33155 List the line number, the current source file, and the absolute path
33156 to the current source file for the current executable. The macro
33157 information field has a value of @samp{1} or @samp{0} depending on
33158 whether or not the file includes preprocessor macro information.
33160 @subsubheading @value{GDBN} Command
33162 The @value{GDBN} equivalent is @samp{info source}
33164 @subsubheading Example
33168 123-file-list-exec-source-file
33169 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33174 @subheading The @code{-file-list-exec-source-files} Command
33175 @findex -file-list-exec-source-files
33177 @subsubheading Synopsis
33180 -file-list-exec-source-files
33183 List the source files for the current executable.
33185 It will always output both the filename and fullname (absolute file
33186 name) of a source file.
33188 @subsubheading @value{GDBN} Command
33190 The @value{GDBN} equivalent is @samp{info sources}.
33191 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33193 @subsubheading Example
33196 -file-list-exec-source-files
33198 @{file=foo.c,fullname=/home/foo.c@},
33199 @{file=/home/bar.c,fullname=/home/bar.c@},
33200 @{file=gdb_could_not_find_fullpath.c@}]
33204 @subheading The @code{-file-list-shared-libraries} Command
33205 @findex -file-list-shared-libraries
33207 @subsubheading Synopsis
33210 -file-list-shared-libraries [ @var{regexp} ]
33213 List the shared libraries in the program.
33214 With a regular expression @var{regexp}, only those libraries whose
33215 names match @var{regexp} are listed.
33217 @subsubheading @value{GDBN} Command
33219 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33220 have a similar meaning to the @code{=library-loaded} notification.
33221 The @code{ranges} field specifies the multiple segments belonging to this
33222 library. Each range has the following fields:
33226 The address defining the inclusive lower bound of the segment.
33228 The address defining the exclusive upper bound of the segment.
33231 @subsubheading Example
33234 -file-list-exec-source-files
33235 ^done,shared-libraries=[
33236 @{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"@}]@},
33237 @{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"@}]@}]
33243 @subheading The @code{-file-list-symbol-files} Command
33244 @findex -file-list-symbol-files
33246 @subsubheading Synopsis
33249 -file-list-symbol-files
33254 @subsubheading @value{GDBN} Command
33256 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33258 @subsubheading Example
33263 @subheading The @code{-file-symbol-file} Command
33264 @findex -file-symbol-file
33266 @subsubheading Synopsis
33269 -file-symbol-file @var{file}
33272 Read symbol table info from the specified @var{file} argument. When
33273 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33274 produced, except for a completion notification.
33276 @subsubheading @value{GDBN} Command
33278 The corresponding @value{GDBN} command is @samp{symbol-file}.
33280 @subsubheading Example
33284 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33291 @node GDB/MI Memory Overlay Commands
33292 @section @sc{gdb/mi} Memory Overlay Commands
33294 The memory overlay commands are not implemented.
33296 @c @subheading -overlay-auto
33298 @c @subheading -overlay-list-mapping-state
33300 @c @subheading -overlay-list-overlays
33302 @c @subheading -overlay-map
33304 @c @subheading -overlay-off
33306 @c @subheading -overlay-on
33308 @c @subheading -overlay-unmap
33310 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33311 @node GDB/MI Signal Handling Commands
33312 @section @sc{gdb/mi} Signal Handling Commands
33314 Signal handling commands are not implemented.
33316 @c @subheading -signal-handle
33318 @c @subheading -signal-list-handle-actions
33320 @c @subheading -signal-list-signal-types
33324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33325 @node GDB/MI Target Manipulation
33326 @section @sc{gdb/mi} Target Manipulation Commands
33329 @subheading The @code{-target-attach} Command
33330 @findex -target-attach
33332 @subsubheading Synopsis
33335 -target-attach @var{pid} | @var{gid} | @var{file}
33338 Attach to a process @var{pid} or a file @var{file} outside of
33339 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33340 group, the id previously returned by
33341 @samp{-list-thread-groups --available} must be used.
33343 @subsubheading @value{GDBN} Command
33345 The corresponding @value{GDBN} command is @samp{attach}.
33347 @subsubheading Example
33351 =thread-created,id="1"
33352 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33358 @subheading The @code{-target-compare-sections} Command
33359 @findex -target-compare-sections
33361 @subsubheading Synopsis
33364 -target-compare-sections [ @var{section} ]
33367 Compare data of section @var{section} on target to the exec file.
33368 Without the argument, all sections are compared.
33370 @subsubheading @value{GDBN} Command
33372 The @value{GDBN} equivalent is @samp{compare-sections}.
33374 @subsubheading Example
33379 @subheading The @code{-target-detach} Command
33380 @findex -target-detach
33382 @subsubheading Synopsis
33385 -target-detach [ @var{pid} | @var{gid} ]
33388 Detach from the remote target which normally resumes its execution.
33389 If either @var{pid} or @var{gid} is specified, detaches from either
33390 the specified process, or specified thread group. There's no output.
33392 @subsubheading @value{GDBN} Command
33394 The corresponding @value{GDBN} command is @samp{detach}.
33396 @subsubheading Example
33406 @subheading The @code{-target-disconnect} Command
33407 @findex -target-disconnect
33409 @subsubheading Synopsis
33415 Disconnect from the remote target. There's no output and the target is
33416 generally not resumed.
33418 @subsubheading @value{GDBN} Command
33420 The corresponding @value{GDBN} command is @samp{disconnect}.
33422 @subsubheading Example
33432 @subheading The @code{-target-download} Command
33433 @findex -target-download
33435 @subsubheading Synopsis
33441 Loads the executable onto the remote target.
33442 It prints out an update message every half second, which includes the fields:
33446 The name of the section.
33448 The size of what has been sent so far for that section.
33450 The size of the section.
33452 The total size of what was sent so far (the current and the previous sections).
33454 The size of the overall executable to download.
33458 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33459 @sc{gdb/mi} Output Syntax}).
33461 In addition, it prints the name and size of the sections, as they are
33462 downloaded. These messages include the following fields:
33466 The name of the section.
33468 The size of the section.
33470 The size of the overall executable to download.
33474 At the end, a summary is printed.
33476 @subsubheading @value{GDBN} Command
33478 The corresponding @value{GDBN} command is @samp{load}.
33480 @subsubheading Example
33482 Note: each status message appears on a single line. Here the messages
33483 have been broken down so that they can fit onto a page.
33488 +download,@{section=".text",section-size="6668",total-size="9880"@}
33489 +download,@{section=".text",section-sent="512",section-size="6668",
33490 total-sent="512",total-size="9880"@}
33491 +download,@{section=".text",section-sent="1024",section-size="6668",
33492 total-sent="1024",total-size="9880"@}
33493 +download,@{section=".text",section-sent="1536",section-size="6668",
33494 total-sent="1536",total-size="9880"@}
33495 +download,@{section=".text",section-sent="2048",section-size="6668",
33496 total-sent="2048",total-size="9880"@}
33497 +download,@{section=".text",section-sent="2560",section-size="6668",
33498 total-sent="2560",total-size="9880"@}
33499 +download,@{section=".text",section-sent="3072",section-size="6668",
33500 total-sent="3072",total-size="9880"@}
33501 +download,@{section=".text",section-sent="3584",section-size="6668",
33502 total-sent="3584",total-size="9880"@}
33503 +download,@{section=".text",section-sent="4096",section-size="6668",
33504 total-sent="4096",total-size="9880"@}
33505 +download,@{section=".text",section-sent="4608",section-size="6668",
33506 total-sent="4608",total-size="9880"@}
33507 +download,@{section=".text",section-sent="5120",section-size="6668",
33508 total-sent="5120",total-size="9880"@}
33509 +download,@{section=".text",section-sent="5632",section-size="6668",
33510 total-sent="5632",total-size="9880"@}
33511 +download,@{section=".text",section-sent="6144",section-size="6668",
33512 total-sent="6144",total-size="9880"@}
33513 +download,@{section=".text",section-sent="6656",section-size="6668",
33514 total-sent="6656",total-size="9880"@}
33515 +download,@{section=".init",section-size="28",total-size="9880"@}
33516 +download,@{section=".fini",section-size="28",total-size="9880"@}
33517 +download,@{section=".data",section-size="3156",total-size="9880"@}
33518 +download,@{section=".data",section-sent="512",section-size="3156",
33519 total-sent="7236",total-size="9880"@}
33520 +download,@{section=".data",section-sent="1024",section-size="3156",
33521 total-sent="7748",total-size="9880"@}
33522 +download,@{section=".data",section-sent="1536",section-size="3156",
33523 total-sent="8260",total-size="9880"@}
33524 +download,@{section=".data",section-sent="2048",section-size="3156",
33525 total-sent="8772",total-size="9880"@}
33526 +download,@{section=".data",section-sent="2560",section-size="3156",
33527 total-sent="9284",total-size="9880"@}
33528 +download,@{section=".data",section-sent="3072",section-size="3156",
33529 total-sent="9796",total-size="9880"@}
33530 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33537 @subheading The @code{-target-exec-status} Command
33538 @findex -target-exec-status
33540 @subsubheading Synopsis
33543 -target-exec-status
33546 Provide information on the state of the target (whether it is running or
33547 not, for instance).
33549 @subsubheading @value{GDBN} Command
33551 There's no equivalent @value{GDBN} command.
33553 @subsubheading Example
33557 @subheading The @code{-target-list-available-targets} Command
33558 @findex -target-list-available-targets
33560 @subsubheading Synopsis
33563 -target-list-available-targets
33566 List the possible targets to connect to.
33568 @subsubheading @value{GDBN} Command
33570 The corresponding @value{GDBN} command is @samp{help target}.
33572 @subsubheading Example
33576 @subheading The @code{-target-list-current-targets} Command
33577 @findex -target-list-current-targets
33579 @subsubheading Synopsis
33582 -target-list-current-targets
33585 Describe the current target.
33587 @subsubheading @value{GDBN} Command
33589 The corresponding information is printed by @samp{info file} (among
33592 @subsubheading Example
33596 @subheading The @code{-target-list-parameters} Command
33597 @findex -target-list-parameters
33599 @subsubheading Synopsis
33602 -target-list-parameters
33608 @subsubheading @value{GDBN} Command
33612 @subsubheading Example
33615 @subheading The @code{-target-flash-erase} Command
33616 @findex -target-flash-erase
33618 @subsubheading Synopsis
33621 -target-flash-erase
33624 Erases all known flash memory regions on the target.
33626 The corresponding @value{GDBN} command is @samp{flash-erase}.
33628 The output is a list of flash regions that have been erased, with starting
33629 addresses and memory region sizes.
33633 -target-flash-erase
33634 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33638 @subheading The @code{-target-select} Command
33639 @findex -target-select
33641 @subsubheading Synopsis
33644 -target-select @var{type} @var{parameters @dots{}}
33647 Connect @value{GDBN} to the remote target. This command takes two args:
33651 The type of target, for instance @samp{remote}, etc.
33652 @item @var{parameters}
33653 Device names, host names and the like. @xref{Target Commands, ,
33654 Commands for Managing Targets}, for more details.
33657 The output is a connection notification, followed by the address at
33658 which the target program is, in the following form:
33661 ^connected,addr="@var{address}",func="@var{function name}",
33662 args=[@var{arg list}]
33665 @subsubheading @value{GDBN} Command
33667 The corresponding @value{GDBN} command is @samp{target}.
33669 @subsubheading Example
33673 -target-select remote /dev/ttya
33674 ^connected,addr="0xfe00a300",func="??",args=[]
33678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33679 @node GDB/MI File Transfer Commands
33680 @section @sc{gdb/mi} File Transfer Commands
33683 @subheading The @code{-target-file-put} Command
33684 @findex -target-file-put
33686 @subsubheading Synopsis
33689 -target-file-put @var{hostfile} @var{targetfile}
33692 Copy file @var{hostfile} from the host system (the machine running
33693 @value{GDBN}) to @var{targetfile} on the target system.
33695 @subsubheading @value{GDBN} Command
33697 The corresponding @value{GDBN} command is @samp{remote put}.
33699 @subsubheading Example
33703 -target-file-put localfile remotefile
33709 @subheading The @code{-target-file-get} Command
33710 @findex -target-file-get
33712 @subsubheading Synopsis
33715 -target-file-get @var{targetfile} @var{hostfile}
33718 Copy file @var{targetfile} from the target system to @var{hostfile}
33719 on the host system.
33721 @subsubheading @value{GDBN} Command
33723 The corresponding @value{GDBN} command is @samp{remote get}.
33725 @subsubheading Example
33729 -target-file-get remotefile localfile
33735 @subheading The @code{-target-file-delete} Command
33736 @findex -target-file-delete
33738 @subsubheading Synopsis
33741 -target-file-delete @var{targetfile}
33744 Delete @var{targetfile} from the target system.
33746 @subsubheading @value{GDBN} Command
33748 The corresponding @value{GDBN} command is @samp{remote delete}.
33750 @subsubheading Example
33754 -target-file-delete remotefile
33760 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33761 @node GDB/MI Ada Exceptions Commands
33762 @section Ada Exceptions @sc{gdb/mi} Commands
33764 @subheading The @code{-info-ada-exceptions} Command
33765 @findex -info-ada-exceptions
33767 @subsubheading Synopsis
33770 -info-ada-exceptions [ @var{regexp}]
33773 List all Ada exceptions defined within the program being debugged.
33774 With a regular expression @var{regexp}, only those exceptions whose
33775 names match @var{regexp} are listed.
33777 @subsubheading @value{GDBN} Command
33779 The corresponding @value{GDBN} command is @samp{info exceptions}.
33781 @subsubheading Result
33783 The result is a table of Ada exceptions. The following columns are
33784 defined for each exception:
33788 The name of the exception.
33791 The address of the exception.
33795 @subsubheading Example
33798 -info-ada-exceptions aint
33799 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33800 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33801 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33802 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33803 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33806 @subheading Catching Ada Exceptions
33808 The commands describing how to ask @value{GDBN} to stop when a program
33809 raises an exception are described at @ref{Ada Exception GDB/MI
33810 Catchpoint Commands}.
33813 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33814 @node GDB/MI Support Commands
33815 @section @sc{gdb/mi} Support Commands
33817 Since new commands and features get regularly added to @sc{gdb/mi},
33818 some commands are available to help front-ends query the debugger
33819 about support for these capabilities. Similarly, it is also possible
33820 to query @value{GDBN} about target support of certain features.
33822 @subheading The @code{-info-gdb-mi-command} Command
33823 @cindex @code{-info-gdb-mi-command}
33824 @findex -info-gdb-mi-command
33826 @subsubheading Synopsis
33829 -info-gdb-mi-command @var{cmd_name}
33832 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33834 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33835 is technically not part of the command name (@pxref{GDB/MI Input
33836 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33837 for ease of use, this command also accepts the form with the leading
33840 @subsubheading @value{GDBN} Command
33842 There is no corresponding @value{GDBN} command.
33844 @subsubheading Result
33846 The result is a tuple. There is currently only one field:
33850 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33851 @code{"false"} otherwise.
33855 @subsubheading Example
33857 Here is an example where the @sc{gdb/mi} command does not exist:
33860 -info-gdb-mi-command unsupported-command
33861 ^done,command=@{exists="false"@}
33865 And here is an example where the @sc{gdb/mi} command is known
33869 -info-gdb-mi-command symbol-list-lines
33870 ^done,command=@{exists="true"@}
33873 @subheading The @code{-list-features} Command
33874 @findex -list-features
33875 @cindex supported @sc{gdb/mi} features, list
33877 Returns a list of particular features of the MI protocol that
33878 this version of gdb implements. A feature can be a command,
33879 or a new field in an output of some command, or even an
33880 important bugfix. While a frontend can sometimes detect presence
33881 of a feature at runtime, it is easier to perform detection at debugger
33884 The command returns a list of strings, with each string naming an
33885 available feature. Each returned string is just a name, it does not
33886 have any internal structure. The list of possible feature names
33892 (gdb) -list-features
33893 ^done,result=["feature1","feature2"]
33896 The current list of features is:
33899 @item frozen-varobjs
33900 Indicates support for the @code{-var-set-frozen} command, as well
33901 as possible presense of the @code{frozen} field in the output
33902 of @code{-varobj-create}.
33903 @item pending-breakpoints
33904 Indicates support for the @option{-f} option to the @code{-break-insert}
33907 Indicates Python scripting support, Python-based
33908 pretty-printing commands, and possible presence of the
33909 @samp{display_hint} field in the output of @code{-var-list-children}
33911 Indicates support for the @code{-thread-info} command.
33912 @item data-read-memory-bytes
33913 Indicates support for the @code{-data-read-memory-bytes} and the
33914 @code{-data-write-memory-bytes} commands.
33915 @item breakpoint-notifications
33916 Indicates that changes to breakpoints and breakpoints created via the
33917 CLI will be announced via async records.
33918 @item ada-task-info
33919 Indicates support for the @code{-ada-task-info} command.
33920 @item language-option
33921 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33922 option (@pxref{Context management}).
33923 @item info-gdb-mi-command
33924 Indicates support for the @code{-info-gdb-mi-command} command.
33925 @item undefined-command-error-code
33926 Indicates support for the "undefined-command" error code in error result
33927 records, produced when trying to execute an undefined @sc{gdb/mi} command
33928 (@pxref{GDB/MI Result Records}).
33929 @item exec-run-start-option
33930 Indicates that the @code{-exec-run} command supports the @option{--start}
33931 option (@pxref{GDB/MI Program Execution}).
33932 @item data-disassemble-a-option
33933 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33934 option (@pxref{GDB/MI Data Manipulation}).
33937 @subheading The @code{-list-target-features} Command
33938 @findex -list-target-features
33940 Returns a list of particular features that are supported by the
33941 target. Those features affect the permitted MI commands, but
33942 unlike the features reported by the @code{-list-features} command, the
33943 features depend on which target GDB is using at the moment. Whenever
33944 a target can change, due to commands such as @code{-target-select},
33945 @code{-target-attach} or @code{-exec-run}, the list of target features
33946 may change, and the frontend should obtain it again.
33950 (gdb) -list-target-features
33951 ^done,result=["async"]
33954 The current list of features is:
33958 Indicates that the target is capable of asynchronous command
33959 execution, which means that @value{GDBN} will accept further commands
33960 while the target is running.
33963 Indicates that the target is capable of reverse execution.
33964 @xref{Reverse Execution}, for more information.
33968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33969 @node GDB/MI Miscellaneous Commands
33970 @section Miscellaneous @sc{gdb/mi} Commands
33972 @c @subheading -gdb-complete
33974 @subheading The @code{-gdb-exit} Command
33977 @subsubheading Synopsis
33983 Exit @value{GDBN} immediately.
33985 @subsubheading @value{GDBN} Command
33987 Approximately corresponds to @samp{quit}.
33989 @subsubheading Example
33999 @subheading The @code{-exec-abort} Command
34000 @findex -exec-abort
34002 @subsubheading Synopsis
34008 Kill the inferior running program.
34010 @subsubheading @value{GDBN} Command
34012 The corresponding @value{GDBN} command is @samp{kill}.
34014 @subsubheading Example
34019 @subheading The @code{-gdb-set} Command
34022 @subsubheading Synopsis
34028 Set an internal @value{GDBN} variable.
34029 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34031 @subsubheading @value{GDBN} Command
34033 The corresponding @value{GDBN} command is @samp{set}.
34035 @subsubheading Example
34045 @subheading The @code{-gdb-show} Command
34048 @subsubheading Synopsis
34054 Show the current value of a @value{GDBN} variable.
34056 @subsubheading @value{GDBN} Command
34058 The corresponding @value{GDBN} command is @samp{show}.
34060 @subsubheading Example
34069 @c @subheading -gdb-source
34072 @subheading The @code{-gdb-version} Command
34073 @findex -gdb-version
34075 @subsubheading Synopsis
34081 Show version information for @value{GDBN}. Used mostly in testing.
34083 @subsubheading @value{GDBN} Command
34085 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34086 default shows this information when you start an interactive session.
34088 @subsubheading Example
34090 @c This example modifies the actual output from GDB to avoid overfull
34096 ~Copyright 2000 Free Software Foundation, Inc.
34097 ~GDB is free software, covered by the GNU General Public License, and
34098 ~you are welcome to change it and/or distribute copies of it under
34099 ~ certain conditions.
34100 ~Type "show copying" to see the conditions.
34101 ~There is absolutely no warranty for GDB. Type "show warranty" for
34103 ~This GDB was configured as
34104 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34109 @subheading The @code{-list-thread-groups} Command
34110 @findex -list-thread-groups
34112 @subheading Synopsis
34115 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34118 Lists thread groups (@pxref{Thread groups}). When a single thread
34119 group is passed as the argument, lists the children of that group.
34120 When several thread group are passed, lists information about those
34121 thread groups. Without any parameters, lists information about all
34122 top-level thread groups.
34124 Normally, thread groups that are being debugged are reported.
34125 With the @samp{--available} option, @value{GDBN} reports thread groups
34126 available on the target.
34128 The output of this command may have either a @samp{threads} result or
34129 a @samp{groups} result. The @samp{thread} result has a list of tuples
34130 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34131 Information}). The @samp{groups} result has a list of tuples as value,
34132 each tuple describing a thread group. If top-level groups are
34133 requested (that is, no parameter is passed), or when several groups
34134 are passed, the output always has a @samp{groups} result. The format
34135 of the @samp{group} result is described below.
34137 To reduce the number of roundtrips it's possible to list thread groups
34138 together with their children, by passing the @samp{--recurse} option
34139 and the recursion depth. Presently, only recursion depth of 1 is
34140 permitted. If this option is present, then every reported thread group
34141 will also include its children, either as @samp{group} or
34142 @samp{threads} field.
34144 In general, any combination of option and parameters is permitted, with
34145 the following caveats:
34149 When a single thread group is passed, the output will typically
34150 be the @samp{threads} result. Because threads may not contain
34151 anything, the @samp{recurse} option will be ignored.
34154 When the @samp{--available} option is passed, limited information may
34155 be available. In particular, the list of threads of a process might
34156 be inaccessible. Further, specifying specific thread groups might
34157 not give any performance advantage over listing all thread groups.
34158 The frontend should assume that @samp{-list-thread-groups --available}
34159 is always an expensive operation and cache the results.
34163 The @samp{groups} result is a list of tuples, where each tuple may
34164 have the following fields:
34168 Identifier of the thread group. This field is always present.
34169 The identifier is an opaque string; frontends should not try to
34170 convert it to an integer, even though it might look like one.
34173 The type of the thread group. At present, only @samp{process} is a
34177 The target-specific process identifier. This field is only present
34178 for thread groups of type @samp{process} and only if the process exists.
34181 The exit code of this group's last exited thread, formatted in octal.
34182 This field is only present for thread groups of type @samp{process} and
34183 only if the process is not running.
34186 The number of children this thread group has. This field may be
34187 absent for an available thread group.
34190 This field has a list of tuples as value, each tuple describing a
34191 thread. It may be present if the @samp{--recurse} option is
34192 specified, and it's actually possible to obtain the threads.
34195 This field is a list of integers, each identifying a core that one
34196 thread of the group is running on. This field may be absent if
34197 such information is not available.
34200 The name of the executable file that corresponds to this thread group.
34201 The field is only present for thread groups of type @samp{process},
34202 and only if there is a corresponding executable file.
34206 @subheading Example
34210 -list-thread-groups
34211 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34212 -list-thread-groups 17
34213 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34214 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34215 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34216 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34217 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34218 -list-thread-groups --available
34219 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34220 -list-thread-groups --available --recurse 1
34221 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34222 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34223 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34224 -list-thread-groups --available --recurse 1 17 18
34225 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34226 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34227 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34230 @subheading The @code{-info-os} Command
34233 @subsubheading Synopsis
34236 -info-os [ @var{type} ]
34239 If no argument is supplied, the command returns a table of available
34240 operating-system-specific information types. If one of these types is
34241 supplied as an argument @var{type}, then the command returns a table
34242 of data of that type.
34244 The types of information available depend on the target operating
34247 @subsubheading @value{GDBN} Command
34249 The corresponding @value{GDBN} command is @samp{info os}.
34251 @subsubheading Example
34253 When run on a @sc{gnu}/Linux system, the output will look something
34259 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34260 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34261 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34262 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34263 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34265 item=@{col0="files",col1="Listing of all file descriptors",
34266 col2="File descriptors"@},
34267 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34268 col2="Kernel modules"@},
34269 item=@{col0="msg",col1="Listing of all message queues",
34270 col2="Message queues"@},
34271 item=@{col0="processes",col1="Listing of all processes",
34272 col2="Processes"@},
34273 item=@{col0="procgroups",col1="Listing of all process groups",
34274 col2="Process groups"@},
34275 item=@{col0="semaphores",col1="Listing of all semaphores",
34276 col2="Semaphores"@},
34277 item=@{col0="shm",col1="Listing of all shared-memory regions",
34278 col2="Shared-memory regions"@},
34279 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34281 item=@{col0="threads",col1="Listing of all threads",
34285 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34286 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34287 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34288 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34289 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34290 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34291 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34292 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34294 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34295 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34299 (Note that the MI output here includes a @code{"Title"} column that
34300 does not appear in command-line @code{info os}; this column is useful
34301 for MI clients that want to enumerate the types of data, such as in a
34302 popup menu, but is needless clutter on the command line, and
34303 @code{info os} omits it.)
34305 @subheading The @code{-add-inferior} Command
34306 @findex -add-inferior
34308 @subheading Synopsis
34314 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34315 inferior is not associated with any executable. Such association may
34316 be established with the @samp{-file-exec-and-symbols} command
34317 (@pxref{GDB/MI File Commands}). The command response has a single
34318 field, @samp{inferior}, whose value is the identifier of the
34319 thread group corresponding to the new inferior.
34321 @subheading Example
34326 ^done,inferior="i3"
34329 @subheading The @code{-interpreter-exec} Command
34330 @findex -interpreter-exec
34332 @subheading Synopsis
34335 -interpreter-exec @var{interpreter} @var{command}
34337 @anchor{-interpreter-exec}
34339 Execute the specified @var{command} in the given @var{interpreter}.
34341 @subheading @value{GDBN} Command
34343 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34345 @subheading Example
34349 -interpreter-exec console "break main"
34350 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34351 &"During symbol reading, bad structure-type format.\n"
34352 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34357 @subheading The @code{-inferior-tty-set} Command
34358 @findex -inferior-tty-set
34360 @subheading Synopsis
34363 -inferior-tty-set /dev/pts/1
34366 Set terminal for future runs of the program being debugged.
34368 @subheading @value{GDBN} Command
34370 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34372 @subheading Example
34376 -inferior-tty-set /dev/pts/1
34381 @subheading The @code{-inferior-tty-show} Command
34382 @findex -inferior-tty-show
34384 @subheading Synopsis
34390 Show terminal for future runs of program being debugged.
34392 @subheading @value{GDBN} Command
34394 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34396 @subheading Example
34400 -inferior-tty-set /dev/pts/1
34404 ^done,inferior_tty_terminal="/dev/pts/1"
34408 @subheading The @code{-enable-timings} Command
34409 @findex -enable-timings
34411 @subheading Synopsis
34414 -enable-timings [yes | no]
34417 Toggle the printing of the wallclock, user and system times for an MI
34418 command as a field in its output. This command is to help frontend
34419 developers optimize the performance of their code. No argument is
34420 equivalent to @samp{yes}.
34422 @subheading @value{GDBN} Command
34426 @subheading Example
34434 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34435 addr="0x080484ed",func="main",file="myprog.c",
34436 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34438 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34446 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34447 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34448 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34449 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34454 @chapter @value{GDBN} Annotations
34456 This chapter describes annotations in @value{GDBN}. Annotations were
34457 designed to interface @value{GDBN} to graphical user interfaces or other
34458 similar programs which want to interact with @value{GDBN} at a
34459 relatively high level.
34461 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34465 This is Edition @value{EDITION}, @value{DATE}.
34469 * Annotations Overview:: What annotations are; the general syntax.
34470 * Server Prefix:: Issuing a command without affecting user state.
34471 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34472 * Errors:: Annotations for error messages.
34473 * Invalidation:: Some annotations describe things now invalid.
34474 * Annotations for Running::
34475 Whether the program is running, how it stopped, etc.
34476 * Source Annotations:: Annotations describing source code.
34479 @node Annotations Overview
34480 @section What is an Annotation?
34481 @cindex annotations
34483 Annotations start with a newline character, two @samp{control-z}
34484 characters, and the name of the annotation. If there is no additional
34485 information associated with this annotation, the name of the annotation
34486 is followed immediately by a newline. If there is additional
34487 information, the name of the annotation is followed by a space, the
34488 additional information, and a newline. The additional information
34489 cannot contain newline characters.
34491 Any output not beginning with a newline and two @samp{control-z}
34492 characters denotes literal output from @value{GDBN}. Currently there is
34493 no need for @value{GDBN} to output a newline followed by two
34494 @samp{control-z} characters, but if there was such a need, the
34495 annotations could be extended with an @samp{escape} annotation which
34496 means those three characters as output.
34498 The annotation @var{level}, which is specified using the
34499 @option{--annotate} command line option (@pxref{Mode Options}), controls
34500 how much information @value{GDBN} prints together with its prompt,
34501 values of expressions, source lines, and other types of output. Level 0
34502 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34503 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34504 for programs that control @value{GDBN}, and level 2 annotations have
34505 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34506 Interface, annotate, GDB's Obsolete Annotations}).
34509 @kindex set annotate
34510 @item set annotate @var{level}
34511 The @value{GDBN} command @code{set annotate} sets the level of
34512 annotations to the specified @var{level}.
34514 @item show annotate
34515 @kindex show annotate
34516 Show the current annotation level.
34519 This chapter describes level 3 annotations.
34521 A simple example of starting up @value{GDBN} with annotations is:
34524 $ @kbd{gdb --annotate=3}
34526 Copyright 2003 Free Software Foundation, Inc.
34527 GDB is free software, covered by the GNU General Public License,
34528 and you are welcome to change it and/or distribute copies of it
34529 under certain conditions.
34530 Type "show copying" to see the conditions.
34531 There is absolutely no warranty for GDB. Type "show warranty"
34533 This GDB was configured as "i386-pc-linux-gnu"
34544 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34545 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34546 denotes a @samp{control-z} character) are annotations; the rest is
34547 output from @value{GDBN}.
34549 @node Server Prefix
34550 @section The Server Prefix
34551 @cindex server prefix
34553 If you prefix a command with @samp{server } then it will not affect
34554 the command history, nor will it affect @value{GDBN}'s notion of which
34555 command to repeat if @key{RET} is pressed on a line by itself. This
34556 means that commands can be run behind a user's back by a front-end in
34557 a transparent manner.
34559 The @code{server } prefix does not affect the recording of values into
34560 the value history; to print a value without recording it into the
34561 value history, use the @code{output} command instead of the
34562 @code{print} command.
34564 Using this prefix also disables confirmation requests
34565 (@pxref{confirmation requests}).
34568 @section Annotation for @value{GDBN} Input
34570 @cindex annotations for prompts
34571 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34572 to know when to send output, when the output from a given command is
34575 Different kinds of input each have a different @dfn{input type}. Each
34576 input type has three annotations: a @code{pre-} annotation, which
34577 denotes the beginning of any prompt which is being output, a plain
34578 annotation, which denotes the end of the prompt, and then a @code{post-}
34579 annotation which denotes the end of any echo which may (or may not) be
34580 associated with the input. For example, the @code{prompt} input type
34581 features the following annotations:
34589 The input types are
34592 @findex pre-prompt annotation
34593 @findex prompt annotation
34594 @findex post-prompt annotation
34596 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34598 @findex pre-commands annotation
34599 @findex commands annotation
34600 @findex post-commands annotation
34602 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34603 command. The annotations are repeated for each command which is input.
34605 @findex pre-overload-choice annotation
34606 @findex overload-choice annotation
34607 @findex post-overload-choice annotation
34608 @item overload-choice
34609 When @value{GDBN} wants the user to select between various overloaded functions.
34611 @findex pre-query annotation
34612 @findex query annotation
34613 @findex post-query annotation
34615 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34617 @findex pre-prompt-for-continue annotation
34618 @findex prompt-for-continue annotation
34619 @findex post-prompt-for-continue annotation
34620 @item prompt-for-continue
34621 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34622 expect this to work well; instead use @code{set height 0} to disable
34623 prompting. This is because the counting of lines is buggy in the
34624 presence of annotations.
34629 @cindex annotations for errors, warnings and interrupts
34631 @findex quit annotation
34636 This annotation occurs right before @value{GDBN} responds to an interrupt.
34638 @findex error annotation
34643 This annotation occurs right before @value{GDBN} responds to an error.
34645 Quit and error annotations indicate that any annotations which @value{GDBN} was
34646 in the middle of may end abruptly. For example, if a
34647 @code{value-history-begin} annotation is followed by a @code{error}, one
34648 cannot expect to receive the matching @code{value-history-end}. One
34649 cannot expect not to receive it either, however; an error annotation
34650 does not necessarily mean that @value{GDBN} is immediately returning all the way
34653 @findex error-begin annotation
34654 A quit or error annotation may be preceded by
34660 Any output between that and the quit or error annotation is the error
34663 Warning messages are not yet annotated.
34664 @c If we want to change that, need to fix warning(), type_error(),
34665 @c range_error(), and possibly other places.
34668 @section Invalidation Notices
34670 @cindex annotations for invalidation messages
34671 The following annotations say that certain pieces of state may have
34675 @findex frames-invalid annotation
34676 @item ^Z^Zframes-invalid
34678 The frames (for example, output from the @code{backtrace} command) may
34681 @findex breakpoints-invalid annotation
34682 @item ^Z^Zbreakpoints-invalid
34684 The breakpoints may have changed. For example, the user just added or
34685 deleted a breakpoint.
34688 @node Annotations for Running
34689 @section Running the Program
34690 @cindex annotations for running programs
34692 @findex starting annotation
34693 @findex stopping annotation
34694 When the program starts executing due to a @value{GDBN} command such as
34695 @code{step} or @code{continue},
34701 is output. When the program stops,
34707 is output. Before the @code{stopped} annotation, a variety of
34708 annotations describe how the program stopped.
34711 @findex exited annotation
34712 @item ^Z^Zexited @var{exit-status}
34713 The program exited, and @var{exit-status} is the exit status (zero for
34714 successful exit, otherwise nonzero).
34716 @findex signalled annotation
34717 @findex signal-name annotation
34718 @findex signal-name-end annotation
34719 @findex signal-string annotation
34720 @findex signal-string-end annotation
34721 @item ^Z^Zsignalled
34722 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34723 annotation continues:
34729 ^Z^Zsignal-name-end
34733 ^Z^Zsignal-string-end
34738 where @var{name} is the name of the signal, such as @code{SIGILL} or
34739 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34740 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34741 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34742 user's benefit and have no particular format.
34744 @findex signal annotation
34746 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34747 just saying that the program received the signal, not that it was
34748 terminated with it.
34750 @findex breakpoint annotation
34751 @item ^Z^Zbreakpoint @var{number}
34752 The program hit breakpoint number @var{number}.
34754 @findex watchpoint annotation
34755 @item ^Z^Zwatchpoint @var{number}
34756 The program hit watchpoint number @var{number}.
34759 @node Source Annotations
34760 @section Displaying Source
34761 @cindex annotations for source display
34763 @findex source annotation
34764 The following annotation is used instead of displaying source code:
34767 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34770 where @var{filename} is an absolute file name indicating which source
34771 file, @var{line} is the line number within that file (where 1 is the
34772 first line in the file), @var{character} is the character position
34773 within the file (where 0 is the first character in the file) (for most
34774 debug formats this will necessarily point to the beginning of a line),
34775 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34776 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34777 @var{addr} is the address in the target program associated with the
34778 source which is being displayed. The @var{addr} is in the form @samp{0x}
34779 followed by one or more lowercase hex digits (note that this does not
34780 depend on the language).
34782 @node JIT Interface
34783 @chapter JIT Compilation Interface
34784 @cindex just-in-time compilation
34785 @cindex JIT compilation interface
34787 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34788 interface. A JIT compiler is a program or library that generates native
34789 executable code at runtime and executes it, usually in order to achieve good
34790 performance while maintaining platform independence.
34792 Programs that use JIT compilation are normally difficult to debug because
34793 portions of their code are generated at runtime, instead of being loaded from
34794 object files, which is where @value{GDBN} normally finds the program's symbols
34795 and debug information. In order to debug programs that use JIT compilation,
34796 @value{GDBN} has an interface that allows the program to register in-memory
34797 symbol files with @value{GDBN} at runtime.
34799 If you are using @value{GDBN} to debug a program that uses this interface, then
34800 it should work transparently so long as you have not stripped the binary. If
34801 you are developing a JIT compiler, then the interface is documented in the rest
34802 of this chapter. At this time, the only known client of this interface is the
34805 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34806 JIT compiler communicates with @value{GDBN} by writing data into a global
34807 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34808 attaches, it reads a linked list of symbol files from the global variable to
34809 find existing code, and puts a breakpoint in the function so that it can find
34810 out about additional code.
34813 * Declarations:: Relevant C struct declarations
34814 * Registering Code:: Steps to register code
34815 * Unregistering Code:: Steps to unregister code
34816 * Custom Debug Info:: Emit debug information in a custom format
34820 @section JIT Declarations
34822 These are the relevant struct declarations that a C program should include to
34823 implement the interface:
34833 struct jit_code_entry
34835 struct jit_code_entry *next_entry;
34836 struct jit_code_entry *prev_entry;
34837 const char *symfile_addr;
34838 uint64_t symfile_size;
34841 struct jit_descriptor
34844 /* This type should be jit_actions_t, but we use uint32_t
34845 to be explicit about the bitwidth. */
34846 uint32_t action_flag;
34847 struct jit_code_entry *relevant_entry;
34848 struct jit_code_entry *first_entry;
34851 /* GDB puts a breakpoint in this function. */
34852 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34854 /* Make sure to specify the version statically, because the
34855 debugger may check the version before we can set it. */
34856 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34859 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34860 modifications to this global data properly, which can easily be done by putting
34861 a global mutex around modifications to these structures.
34863 @node Registering Code
34864 @section Registering Code
34866 To register code with @value{GDBN}, the JIT should follow this protocol:
34870 Generate an object file in memory with symbols and other desired debug
34871 information. The file must include the virtual addresses of the sections.
34874 Create a code entry for the file, which gives the start and size of the symbol
34878 Add it to the linked list in the JIT descriptor.
34881 Point the relevant_entry field of the descriptor at the entry.
34884 Set @code{action_flag} to @code{JIT_REGISTER} and call
34885 @code{__jit_debug_register_code}.
34888 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34889 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34890 new code. However, the linked list must still be maintained in order to allow
34891 @value{GDBN} to attach to a running process and still find the symbol files.
34893 @node Unregistering Code
34894 @section Unregistering Code
34896 If code is freed, then the JIT should use the following protocol:
34900 Remove the code entry corresponding to the code from the linked list.
34903 Point the @code{relevant_entry} field of the descriptor at the code entry.
34906 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34907 @code{__jit_debug_register_code}.
34910 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34911 and the JIT will leak the memory used for the associated symbol files.
34913 @node Custom Debug Info
34914 @section Custom Debug Info
34915 @cindex custom JIT debug info
34916 @cindex JIT debug info reader
34918 Generating debug information in platform-native file formats (like ELF
34919 or COFF) may be an overkill for JIT compilers; especially if all the
34920 debug info is used for is displaying a meaningful backtrace. The
34921 issue can be resolved by having the JIT writers decide on a debug info
34922 format and also provide a reader that parses the debug info generated
34923 by the JIT compiler. This section gives a brief overview on writing
34924 such a parser. More specific details can be found in the source file
34925 @file{gdb/jit-reader.in}, which is also installed as a header at
34926 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34928 The reader is implemented as a shared object (so this functionality is
34929 not available on platforms which don't allow loading shared objects at
34930 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34931 @code{jit-reader-unload} are provided, to be used to load and unload
34932 the readers from a preconfigured directory. Once loaded, the shared
34933 object is used the parse the debug information emitted by the JIT
34937 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34938 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34941 @node Using JIT Debug Info Readers
34942 @subsection Using JIT Debug Info Readers
34943 @kindex jit-reader-load
34944 @kindex jit-reader-unload
34946 Readers can be loaded and unloaded using the @code{jit-reader-load}
34947 and @code{jit-reader-unload} commands.
34950 @item jit-reader-load @var{reader}
34951 Load the JIT reader named @var{reader}, which is a shared
34952 object specified as either an absolute or a relative file name. In
34953 the latter case, @value{GDBN} will try to load the reader from a
34954 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34955 system (here @var{libdir} is the system library directory, often
34956 @file{/usr/local/lib}).
34958 Only one reader can be active at a time; trying to load a second
34959 reader when one is already loaded will result in @value{GDBN}
34960 reporting an error. A new JIT reader can be loaded by first unloading
34961 the current one using @code{jit-reader-unload} and then invoking
34962 @code{jit-reader-load}.
34964 @item jit-reader-unload
34965 Unload the currently loaded JIT reader.
34969 @node Writing JIT Debug Info Readers
34970 @subsection Writing JIT Debug Info Readers
34971 @cindex writing JIT debug info readers
34973 As mentioned, a reader is essentially a shared object conforming to a
34974 certain ABI. This ABI is described in @file{jit-reader.h}.
34976 @file{jit-reader.h} defines the structures, macros and functions
34977 required to write a reader. It is installed (along with
34978 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34979 the system include directory.
34981 Readers need to be released under a GPL compatible license. A reader
34982 can be declared as released under such a license by placing the macro
34983 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34985 The entry point for readers is the symbol @code{gdb_init_reader},
34986 which is expected to be a function with the prototype
34988 @findex gdb_init_reader
34990 extern struct gdb_reader_funcs *gdb_init_reader (void);
34993 @cindex @code{struct gdb_reader_funcs}
34995 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34996 functions. These functions are executed to read the debug info
34997 generated by the JIT compiler (@code{read}), to unwind stack frames
34998 (@code{unwind}) and to create canonical frame IDs
34999 (@code{get_Frame_id}). It also has a callback that is called when the
35000 reader is being unloaded (@code{destroy}). The struct looks like this
35003 struct gdb_reader_funcs
35005 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35006 int reader_version;
35008 /* For use by the reader. */
35011 gdb_read_debug_info *read;
35012 gdb_unwind_frame *unwind;
35013 gdb_get_frame_id *get_frame_id;
35014 gdb_destroy_reader *destroy;
35018 @cindex @code{struct gdb_symbol_callbacks}
35019 @cindex @code{struct gdb_unwind_callbacks}
35021 The callbacks are provided with another set of callbacks by
35022 @value{GDBN} to do their job. For @code{read}, these callbacks are
35023 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35024 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35025 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35026 files and new symbol tables inside those object files. @code{struct
35027 gdb_unwind_callbacks} has callbacks to read registers off the current
35028 frame and to write out the values of the registers in the previous
35029 frame. Both have a callback (@code{target_read}) to read bytes off the
35030 target's address space.
35032 @node In-Process Agent
35033 @chapter In-Process Agent
35034 @cindex debugging agent
35035 The traditional debugging model is conceptually low-speed, but works fine,
35036 because most bugs can be reproduced in debugging-mode execution. However,
35037 as multi-core or many-core processors are becoming mainstream, and
35038 multi-threaded programs become more and more popular, there should be more
35039 and more bugs that only manifest themselves at normal-mode execution, for
35040 example, thread races, because debugger's interference with the program's
35041 timing may conceal the bugs. On the other hand, in some applications,
35042 it is not feasible for the debugger to interrupt the program's execution
35043 long enough for the developer to learn anything helpful about its behavior.
35044 If the program's correctness depends on its real-time behavior, delays
35045 introduced by a debugger might cause the program to fail, even when the
35046 code itself is correct. It is useful to be able to observe the program's
35047 behavior without interrupting it.
35049 Therefore, traditional debugging model is too intrusive to reproduce
35050 some bugs. In order to reduce the interference with the program, we can
35051 reduce the number of operations performed by debugger. The
35052 @dfn{In-Process Agent}, a shared library, is running within the same
35053 process with inferior, and is able to perform some debugging operations
35054 itself. As a result, debugger is only involved when necessary, and
35055 performance of debugging can be improved accordingly. Note that
35056 interference with program can be reduced but can't be removed completely,
35057 because the in-process agent will still stop or slow down the program.
35059 The in-process agent can interpret and execute Agent Expressions
35060 (@pxref{Agent Expressions}) during performing debugging operations. The
35061 agent expressions can be used for different purposes, such as collecting
35062 data in tracepoints, and condition evaluation in breakpoints.
35064 @anchor{Control Agent}
35065 You can control whether the in-process agent is used as an aid for
35066 debugging with the following commands:
35069 @kindex set agent on
35071 Causes the in-process agent to perform some operations on behalf of the
35072 debugger. Just which operations requested by the user will be done
35073 by the in-process agent depends on the its capabilities. For example,
35074 if you request to evaluate breakpoint conditions in the in-process agent,
35075 and the in-process agent has such capability as well, then breakpoint
35076 conditions will be evaluated in the in-process agent.
35078 @kindex set agent off
35079 @item set agent off
35080 Disables execution of debugging operations by the in-process agent. All
35081 of the operations will be performed by @value{GDBN}.
35085 Display the current setting of execution of debugging operations by
35086 the in-process agent.
35090 * In-Process Agent Protocol::
35093 @node In-Process Agent Protocol
35094 @section In-Process Agent Protocol
35095 @cindex in-process agent protocol
35097 The in-process agent is able to communicate with both @value{GDBN} and
35098 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35099 used for communications between @value{GDBN} or GDBserver and the IPA.
35100 In general, @value{GDBN} or GDBserver sends commands
35101 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35102 in-process agent replies back with the return result of the command, or
35103 some other information. The data sent to in-process agent is composed
35104 of primitive data types, such as 4-byte or 8-byte type, and composite
35105 types, which are called objects (@pxref{IPA Protocol Objects}).
35108 * IPA Protocol Objects::
35109 * IPA Protocol Commands::
35112 @node IPA Protocol Objects
35113 @subsection IPA Protocol Objects
35114 @cindex ipa protocol objects
35116 The commands sent to and results received from agent may contain some
35117 complex data types called @dfn{objects}.
35119 The in-process agent is running on the same machine with @value{GDBN}
35120 or GDBserver, so it doesn't have to handle as much differences between
35121 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35122 However, there are still some differences of two ends in two processes:
35126 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35127 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35129 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35130 GDBserver is compiled with one, and in-process agent is compiled with
35134 Here are the IPA Protocol Objects:
35138 agent expression object. It represents an agent expression
35139 (@pxref{Agent Expressions}).
35140 @anchor{agent expression object}
35142 tracepoint action object. It represents a tracepoint action
35143 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35144 memory, static trace data and to evaluate expression.
35145 @anchor{tracepoint action object}
35147 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35148 @anchor{tracepoint object}
35152 The following table describes important attributes of each IPA protocol
35155 @multitable @columnfractions .30 .20 .50
35156 @headitem Name @tab Size @tab Description
35157 @item @emph{agent expression object} @tab @tab
35158 @item length @tab 4 @tab length of bytes code
35159 @item byte code @tab @var{length} @tab contents of byte code
35160 @item @emph{tracepoint action for collecting memory} @tab @tab
35161 @item 'M' @tab 1 @tab type of tracepoint action
35162 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35163 address of the lowest byte to collect, otherwise @var{addr} is the offset
35164 of @var{basereg} for memory collecting.
35165 @item len @tab 8 @tab length of memory for collecting
35166 @item basereg @tab 4 @tab the register number containing the starting
35167 memory address for collecting.
35168 @item @emph{tracepoint action for collecting registers} @tab @tab
35169 @item 'R' @tab 1 @tab type of tracepoint action
35170 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35171 @item 'L' @tab 1 @tab type of tracepoint action
35172 @item @emph{tracepoint action for expression evaluation} @tab @tab
35173 @item 'X' @tab 1 @tab type of tracepoint action
35174 @item agent expression @tab length of @tab @ref{agent expression object}
35175 @item @emph{tracepoint object} @tab @tab
35176 @item number @tab 4 @tab number of tracepoint
35177 @item address @tab 8 @tab address of tracepoint inserted on
35178 @item type @tab 4 @tab type of tracepoint
35179 @item enabled @tab 1 @tab enable or disable of tracepoint
35180 @item step_count @tab 8 @tab step
35181 @item pass_count @tab 8 @tab pass
35182 @item numactions @tab 4 @tab number of tracepoint actions
35183 @item hit count @tab 8 @tab hit count
35184 @item trace frame usage @tab 8 @tab trace frame usage
35185 @item compiled_cond @tab 8 @tab compiled condition
35186 @item orig_size @tab 8 @tab orig size
35187 @item condition @tab 4 if condition is NULL otherwise length of
35188 @ref{agent expression object}
35189 @tab zero if condition is NULL, otherwise is
35190 @ref{agent expression object}
35191 @item actions @tab variable
35192 @tab numactions number of @ref{tracepoint action object}
35195 @node IPA Protocol Commands
35196 @subsection IPA Protocol Commands
35197 @cindex ipa protocol commands
35199 The spaces in each command are delimiters to ease reading this commands
35200 specification. They don't exist in real commands.
35204 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35205 Installs a new fast tracepoint described by @var{tracepoint_object}
35206 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35207 head of @dfn{jumppad}, which is used to jump to data collection routine
35212 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35213 @var{target_address} is address of tracepoint in the inferior.
35214 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35215 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35216 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35217 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35224 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35225 is about to kill inferiors.
35233 @item probe_marker_at:@var{address}
35234 Asks in-process agent to probe the marker at @var{address}.
35241 @item unprobe_marker_at:@var{address}
35242 Asks in-process agent to unprobe the marker at @var{address}.
35246 @chapter Reporting Bugs in @value{GDBN}
35247 @cindex bugs in @value{GDBN}
35248 @cindex reporting bugs in @value{GDBN}
35250 Your bug reports play an essential role in making @value{GDBN} reliable.
35252 Reporting a bug may help you by bringing a solution to your problem, or it
35253 may not. But in any case the principal function of a bug report is to help
35254 the entire community by making the next version of @value{GDBN} work better. Bug
35255 reports are your contribution to the maintenance of @value{GDBN}.
35257 In order for a bug report to serve its purpose, you must include the
35258 information that enables us to fix the bug.
35261 * Bug Criteria:: Have you found a bug?
35262 * Bug Reporting:: How to report bugs
35266 @section Have You Found a Bug?
35267 @cindex bug criteria
35269 If you are not sure whether you have found a bug, here are some guidelines:
35272 @cindex fatal signal
35273 @cindex debugger crash
35274 @cindex crash of debugger
35276 If the debugger gets a fatal signal, for any input whatever, that is a
35277 @value{GDBN} bug. Reliable debuggers never crash.
35279 @cindex error on valid input
35281 If @value{GDBN} produces an error message for valid input, that is a
35282 bug. (Note that if you're cross debugging, the problem may also be
35283 somewhere in the connection to the target.)
35285 @cindex invalid input
35287 If @value{GDBN} does not produce an error message for invalid input,
35288 that is a bug. However, you should note that your idea of
35289 ``invalid input'' might be our idea of ``an extension'' or ``support
35290 for traditional practice''.
35293 If you are an experienced user of debugging tools, your suggestions
35294 for improvement of @value{GDBN} are welcome in any case.
35297 @node Bug Reporting
35298 @section How to Report Bugs
35299 @cindex bug reports
35300 @cindex @value{GDBN} bugs, reporting
35302 A number of companies and individuals offer support for @sc{gnu} products.
35303 If you obtained @value{GDBN} from a support organization, we recommend you
35304 contact that organization first.
35306 You can find contact information for many support companies and
35307 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35309 @c should add a web page ref...
35312 @ifset BUGURL_DEFAULT
35313 In any event, we also recommend that you submit bug reports for
35314 @value{GDBN}. The preferred method is to submit them directly using
35315 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35316 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35319 @strong{Do not send bug reports to @samp{info-gdb}, or to
35320 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35321 not want to receive bug reports. Those that do have arranged to receive
35324 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35325 serves as a repeater. The mailing list and the newsgroup carry exactly
35326 the same messages. Often people think of posting bug reports to the
35327 newsgroup instead of mailing them. This appears to work, but it has one
35328 problem which can be crucial: a newsgroup posting often lacks a mail
35329 path back to the sender. Thus, if we need to ask for more information,
35330 we may be unable to reach you. For this reason, it is better to send
35331 bug reports to the mailing list.
35333 @ifclear BUGURL_DEFAULT
35334 In any event, we also recommend that you submit bug reports for
35335 @value{GDBN} to @value{BUGURL}.
35339 The fundamental principle of reporting bugs usefully is this:
35340 @strong{report all the facts}. If you are not sure whether to state a
35341 fact or leave it out, state it!
35343 Often people omit facts because they think they know what causes the
35344 problem and assume that some details do not matter. Thus, you might
35345 assume that the name of the variable you use in an example does not matter.
35346 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35347 stray memory reference which happens to fetch from the location where that
35348 name is stored in memory; perhaps, if the name were different, the contents
35349 of that location would fool the debugger into doing the right thing despite
35350 the bug. Play it safe and give a specific, complete example. That is the
35351 easiest thing for you to do, and the most helpful.
35353 Keep in mind that the purpose of a bug report is to enable us to fix the
35354 bug. It may be that the bug has been reported previously, but neither
35355 you nor we can know that unless your bug report is complete and
35358 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35359 bell?'' Those bug reports are useless, and we urge everyone to
35360 @emph{refuse to respond to them} except to chide the sender to report
35363 To enable us to fix the bug, you should include all these things:
35367 The version of @value{GDBN}. @value{GDBN} announces it if you start
35368 with no arguments; you can also print it at any time using @code{show
35371 Without this, we will not know whether there is any point in looking for
35372 the bug in the current version of @value{GDBN}.
35375 The type of machine you are using, and the operating system name and
35379 The details of the @value{GDBN} build-time configuration.
35380 @value{GDBN} shows these details if you invoke it with the
35381 @option{--configuration} command-line option, or if you type
35382 @code{show configuration} at @value{GDBN}'s prompt.
35385 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35386 ``@value{GCC}--2.8.1''.
35389 What compiler (and its version) was used to compile the program you are
35390 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35391 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35392 to get this information; for other compilers, see the documentation for
35396 The command arguments you gave the compiler to compile your example and
35397 observe the bug. For example, did you use @samp{-O}? To guarantee
35398 you will not omit something important, list them all. A copy of the
35399 Makefile (or the output from make) is sufficient.
35401 If we were to try to guess the arguments, we would probably guess wrong
35402 and then we might not encounter the bug.
35405 A complete input script, and all necessary source files, that will
35409 A description of what behavior you observe that you believe is
35410 incorrect. For example, ``It gets a fatal signal.''
35412 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35413 will certainly notice it. But if the bug is incorrect output, we might
35414 not notice unless it is glaringly wrong. You might as well not give us
35415 a chance to make a mistake.
35417 Even if the problem you experience is a fatal signal, you should still
35418 say so explicitly. Suppose something strange is going on, such as, your
35419 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35420 the C library on your system. (This has happened!) Your copy might
35421 crash and ours would not. If you told us to expect a crash, then when
35422 ours fails to crash, we would know that the bug was not happening for
35423 us. If you had not told us to expect a crash, then we would not be able
35424 to draw any conclusion from our observations.
35427 @cindex recording a session script
35428 To collect all this information, you can use a session recording program
35429 such as @command{script}, which is available on many Unix systems.
35430 Just run your @value{GDBN} session inside @command{script} and then
35431 include the @file{typescript} file with your bug report.
35433 Another way to record a @value{GDBN} session is to run @value{GDBN}
35434 inside Emacs and then save the entire buffer to a file.
35437 If you wish to suggest changes to the @value{GDBN} source, send us context
35438 diffs. If you even discuss something in the @value{GDBN} source, refer to
35439 it by context, not by line number.
35441 The line numbers in our development sources will not match those in your
35442 sources. Your line numbers would convey no useful information to us.
35446 Here are some things that are not necessary:
35450 A description of the envelope of the bug.
35452 Often people who encounter a bug spend a lot of time investigating
35453 which changes to the input file will make the bug go away and which
35454 changes will not affect it.
35456 This is often time consuming and not very useful, because the way we
35457 will find the bug is by running a single example under the debugger
35458 with breakpoints, not by pure deduction from a series of examples.
35459 We recommend that you save your time for something else.
35461 Of course, if you can find a simpler example to report @emph{instead}
35462 of the original one, that is a convenience for us. Errors in the
35463 output will be easier to spot, running under the debugger will take
35464 less time, and so on.
35466 However, simplification is not vital; if you do not want to do this,
35467 report the bug anyway and send us the entire test case you used.
35470 A patch for the bug.
35472 A patch for the bug does help us if it is a good one. But do not omit
35473 the necessary information, such as the test case, on the assumption that
35474 a patch is all we need. We might see problems with your patch and decide
35475 to fix the problem another way, or we might not understand it at all.
35477 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35478 construct an example that will make the program follow a certain path
35479 through the code. If you do not send us the example, we will not be able
35480 to construct one, so we will not be able to verify that the bug is fixed.
35482 And if we cannot understand what bug you are trying to fix, or why your
35483 patch should be an improvement, we will not install it. A test case will
35484 help us to understand.
35487 A guess about what the bug is or what it depends on.
35489 Such guesses are usually wrong. Even we cannot guess right about such
35490 things without first using the debugger to find the facts.
35493 @c The readline documentation is distributed with the readline code
35494 @c and consists of the two following files:
35497 @c Use -I with makeinfo to point to the appropriate directory,
35498 @c environment var TEXINPUTS with TeX.
35499 @ifclear SYSTEM_READLINE
35500 @include rluser.texi
35501 @include hsuser.texi
35505 @appendix In Memoriam
35507 The @value{GDBN} project mourns the loss of the following long-time
35512 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35513 to Free Software in general. Outside of @value{GDBN}, he was known in
35514 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35516 @item Michael Snyder
35517 Michael was one of the Global Maintainers of the @value{GDBN} project,
35518 with contributions recorded as early as 1996, until 2011. In addition
35519 to his day to day participation, he was a large driving force behind
35520 adding Reverse Debugging to @value{GDBN}.
35523 Beyond their technical contributions to the project, they were also
35524 enjoyable members of the Free Software Community. We will miss them.
35526 @node Formatting Documentation
35527 @appendix Formatting Documentation
35529 @cindex @value{GDBN} reference card
35530 @cindex reference card
35531 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35532 for printing with PostScript or Ghostscript, in the @file{gdb}
35533 subdirectory of the main source directory@footnote{In
35534 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35535 release.}. If you can use PostScript or Ghostscript with your printer,
35536 you can print the reference card immediately with @file{refcard.ps}.
35538 The release also includes the source for the reference card. You
35539 can format it, using @TeX{}, by typing:
35545 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35546 mode on US ``letter'' size paper;
35547 that is, on a sheet 11 inches wide by 8.5 inches
35548 high. You will need to specify this form of printing as an option to
35549 your @sc{dvi} output program.
35551 @cindex documentation
35553 All the documentation for @value{GDBN} comes as part of the machine-readable
35554 distribution. The documentation is written in Texinfo format, which is
35555 a documentation system that uses a single source file to produce both
35556 on-line information and a printed manual. You can use one of the Info
35557 formatting commands to create the on-line version of the documentation
35558 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35560 @value{GDBN} includes an already formatted copy of the on-line Info
35561 version of this manual in the @file{gdb} subdirectory. The main Info
35562 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35563 subordinate files matching @samp{gdb.info*} in the same directory. If
35564 necessary, you can print out these files, or read them with any editor;
35565 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35566 Emacs or the standalone @code{info} program, available as part of the
35567 @sc{gnu} Texinfo distribution.
35569 If you want to format these Info files yourself, you need one of the
35570 Info formatting programs, such as @code{texinfo-format-buffer} or
35573 If you have @code{makeinfo} installed, and are in the top level
35574 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35575 version @value{GDBVN}), you can make the Info file by typing:
35582 If you want to typeset and print copies of this manual, you need @TeX{},
35583 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35584 Texinfo definitions file.
35586 @TeX{} is a typesetting program; it does not print files directly, but
35587 produces output files called @sc{dvi} files. To print a typeset
35588 document, you need a program to print @sc{dvi} files. If your system
35589 has @TeX{} installed, chances are it has such a program. The precise
35590 command to use depends on your system; @kbd{lpr -d} is common; another
35591 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35592 require a file name without any extension or a @samp{.dvi} extension.
35594 @TeX{} also requires a macro definitions file called
35595 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35596 written in Texinfo format. On its own, @TeX{} cannot either read or
35597 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35598 and is located in the @file{gdb-@var{version-number}/texinfo}
35601 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35602 typeset and print this manual. First switch to the @file{gdb}
35603 subdirectory of the main source directory (for example, to
35604 @file{gdb-@value{GDBVN}/gdb}) and type:
35610 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35612 @node Installing GDB
35613 @appendix Installing @value{GDBN}
35614 @cindex installation
35617 * Requirements:: Requirements for building @value{GDBN}
35618 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35619 * Separate Objdir:: Compiling @value{GDBN} in another directory
35620 * Config Names:: Specifying names for hosts and targets
35621 * Configure Options:: Summary of options for configure
35622 * System-wide configuration:: Having a system-wide init file
35626 @section Requirements for Building @value{GDBN}
35627 @cindex building @value{GDBN}, requirements for
35629 Building @value{GDBN} requires various tools and packages to be available.
35630 Other packages will be used only if they are found.
35632 @heading Tools/Packages Necessary for Building @value{GDBN}
35634 @item C@t{++}11 compiler
35635 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35636 recent C@t{++}11 compiler, e.g.@: GCC.
35639 @value{GDBN}'s build system relies on features only found in the GNU
35640 make program. Other variants of @code{make} will not work.
35643 @heading Tools/Packages Optional for Building @value{GDBN}
35647 @value{GDBN} can use the Expat XML parsing library. This library may be
35648 included with your operating system distribution; if it is not, you
35649 can get the latest version from @url{http://expat.sourceforge.net}.
35650 The @file{configure} script will search for this library in several
35651 standard locations; if it is installed in an unusual path, you can
35652 use the @option{--with-libexpat-prefix} option to specify its location.
35658 Remote protocol memory maps (@pxref{Memory Map Format})
35660 Target descriptions (@pxref{Target Descriptions})
35662 Remote shared library lists (@xref{Library List Format},
35663 or alternatively @pxref{Library List Format for SVR4 Targets})
35665 MS-Windows shared libraries (@pxref{Shared Libraries})
35667 Traceframe info (@pxref{Traceframe Info Format})
35669 Branch trace (@pxref{Branch Trace Format},
35670 @pxref{Branch Trace Configuration Format})
35674 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35675 default, @value{GDBN} will be compiled if the Guile libraries are
35676 installed and are found by @file{configure}. You can use the
35677 @code{--with-guile} option to request Guile, and pass either the Guile
35678 version number or the file name of the relevant @code{pkg-config}
35679 program to choose a particular version of Guile.
35682 @value{GDBN}'s features related to character sets (@pxref{Character
35683 Sets}) require a functioning @code{iconv} implementation. If you are
35684 on a GNU system, then this is provided by the GNU C Library. Some
35685 other systems also provide a working @code{iconv}.
35687 If @value{GDBN} is using the @code{iconv} program which is installed
35688 in a non-standard place, you will need to tell @value{GDBN} where to
35689 find it. This is done with @option{--with-iconv-bin} which specifies
35690 the directory that contains the @code{iconv} program. This program is
35691 run in order to make a list of the available character sets.
35693 On systems without @code{iconv}, you can install GNU Libiconv. If
35694 Libiconv is installed in a standard place, @value{GDBN} will
35695 automatically use it if it is needed. If you have previously
35696 installed Libiconv in a non-standard place, you can use the
35697 @option{--with-libiconv-prefix} option to @file{configure}.
35699 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35700 arrange to build Libiconv if a directory named @file{libiconv} appears
35701 in the top-most source directory. If Libiconv is built this way, and
35702 if the operating system does not provide a suitable @code{iconv}
35703 implementation, then the just-built library will automatically be used
35704 by @value{GDBN}. One easy way to set this up is to download GNU
35705 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35706 source tree, and then rename the directory holding the Libiconv source
35707 code to @samp{libiconv}.
35710 @value{GDBN} can support debugging sections that are compressed with
35711 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35712 included with your operating system, you can find it in the xz package
35713 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35714 the usual place, then the @file{configure} script will use it
35715 automatically. If it is installed in an unusual path, you can use the
35716 @option{--with-lzma-prefix} option to specify its location.
35720 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35721 library. This library may be included with your operating system
35722 distribution; if it is not, you can get the latest version from
35723 @url{http://www.mpfr.org}. The @file{configure} script will search
35724 for this library in several standard locations; if it is installed
35725 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35726 option to specify its location.
35728 GNU MPFR is used to emulate target floating-point arithmetic during
35729 expression evaluation when the target uses different floating-point
35730 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35731 will fall back to using host floating-point arithmetic.
35734 @value{GDBN} can be scripted using Python language. @xref{Python}.
35735 By default, @value{GDBN} will be compiled if the Python libraries are
35736 installed and are found by @file{configure}. You can use the
35737 @code{--with-python} option to request Python, and pass either the
35738 file name of the relevant @code{python} executable, or the name of the
35739 directory in which Python is installed, to choose a particular
35740 installation of Python.
35743 @cindex compressed debug sections
35744 @value{GDBN} will use the @samp{zlib} library, if available, to read
35745 compressed debug sections. Some linkers, such as GNU gold, are capable
35746 of producing binaries with compressed debug sections. If @value{GDBN}
35747 is compiled with @samp{zlib}, it will be able to read the debug
35748 information in such binaries.
35750 The @samp{zlib} library is likely included with your operating system
35751 distribution; if it is not, you can get the latest version from
35752 @url{http://zlib.net}.
35755 @node Running Configure
35756 @section Invoking the @value{GDBN} @file{configure} Script
35757 @cindex configuring @value{GDBN}
35758 @value{GDBN} comes with a @file{configure} script that automates the process
35759 of preparing @value{GDBN} for installation; you can then use @code{make} to
35760 build the @code{gdb} program.
35762 @c irrelevant in info file; it's as current as the code it lives with.
35763 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35764 look at the @file{README} file in the sources; we may have improved the
35765 installation procedures since publishing this manual.}
35768 The @value{GDBN} distribution includes all the source code you need for
35769 @value{GDBN} in a single directory, whose name is usually composed by
35770 appending the version number to @samp{gdb}.
35772 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35773 @file{gdb-@value{GDBVN}} directory. That directory contains:
35776 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35777 script for configuring @value{GDBN} and all its supporting libraries
35779 @item gdb-@value{GDBVN}/gdb
35780 the source specific to @value{GDBN} itself
35782 @item gdb-@value{GDBVN}/bfd
35783 source for the Binary File Descriptor library
35785 @item gdb-@value{GDBVN}/include
35786 @sc{gnu} include files
35788 @item gdb-@value{GDBVN}/libiberty
35789 source for the @samp{-liberty} free software library
35791 @item gdb-@value{GDBVN}/opcodes
35792 source for the library of opcode tables and disassemblers
35794 @item gdb-@value{GDBVN}/readline
35795 source for the @sc{gnu} command-line interface
35798 There may be other subdirectories as well.
35800 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35801 from the @file{gdb-@var{version-number}} source directory, which in
35802 this example is the @file{gdb-@value{GDBVN}} directory.
35804 First switch to the @file{gdb-@var{version-number}} source directory
35805 if you are not already in it; then run @file{configure}. Pass the
35806 identifier for the platform on which @value{GDBN} will run as an
35812 cd gdb-@value{GDBVN}
35817 Running @samp{configure} and then running @code{make} builds the
35818 included supporting libraries, then @code{gdb} itself. The configured
35819 source files, and the binaries, are left in the corresponding source
35823 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35824 system does not recognize this automatically when you run a different
35825 shell, you may need to run @code{sh} on it explicitly:
35831 You should run the @file{configure} script from the top directory in the
35832 source tree, the @file{gdb-@var{version-number}} directory. If you run
35833 @file{configure} from one of the subdirectories, you will configure only
35834 that subdirectory. That is usually not what you want. In particular,
35835 if you run the first @file{configure} from the @file{gdb} subdirectory
35836 of the @file{gdb-@var{version-number}} directory, you will omit the
35837 configuration of @file{bfd}, @file{readline}, and other sibling
35838 directories of the @file{gdb} subdirectory. This leads to build errors
35839 about missing include files such as @file{bfd/bfd.h}.
35841 You can install @code{@value{GDBN}} anywhere. The best way to do this
35842 is to pass the @code{--prefix} option to @code{configure}, and then
35843 install it with @code{make install}.
35845 @node Separate Objdir
35846 @section Compiling @value{GDBN} in Another Directory
35848 If you want to run @value{GDBN} versions for several host or target machines,
35849 you need a different @code{gdb} compiled for each combination of
35850 host and target. @file{configure} is designed to make this easy by
35851 allowing you to generate each configuration in a separate subdirectory,
35852 rather than in the source directory. If your @code{make} program
35853 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35854 @code{make} in each of these directories builds the @code{gdb}
35855 program specified there.
35857 To build @code{gdb} in a separate directory, run @file{configure}
35858 with the @samp{--srcdir} option to specify where to find the source.
35859 (You also need to specify a path to find @file{configure}
35860 itself from your working directory. If the path to @file{configure}
35861 would be the same as the argument to @samp{--srcdir}, you can leave out
35862 the @samp{--srcdir} option; it is assumed.)
35864 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35865 separate directory for a Sun 4 like this:
35869 cd gdb-@value{GDBVN}
35872 ../gdb-@value{GDBVN}/configure
35877 When @file{configure} builds a configuration using a remote source
35878 directory, it creates a tree for the binaries with the same structure
35879 (and using the same names) as the tree under the source directory. In
35880 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35881 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35882 @file{gdb-sun4/gdb}.
35884 Make sure that your path to the @file{configure} script has just one
35885 instance of @file{gdb} in it. If your path to @file{configure} looks
35886 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35887 one subdirectory of @value{GDBN}, not the whole package. This leads to
35888 build errors about missing include files such as @file{bfd/bfd.h}.
35890 One popular reason to build several @value{GDBN} configurations in separate
35891 directories is to configure @value{GDBN} for cross-compiling (where
35892 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35893 programs that run on another machine---the @dfn{target}).
35894 You specify a cross-debugging target by
35895 giving the @samp{--target=@var{target}} option to @file{configure}.
35897 When you run @code{make} to build a program or library, you must run
35898 it in a configured directory---whatever directory you were in when you
35899 called @file{configure} (or one of its subdirectories).
35901 The @code{Makefile} that @file{configure} generates in each source
35902 directory also runs recursively. If you type @code{make} in a source
35903 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35904 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35905 will build all the required libraries, and then build GDB.
35907 When you have multiple hosts or targets configured in separate
35908 directories, you can run @code{make} on them in parallel (for example,
35909 if they are NFS-mounted on each of the hosts); they will not interfere
35913 @section Specifying Names for Hosts and Targets
35915 The specifications used for hosts and targets in the @file{configure}
35916 script are based on a three-part naming scheme, but some short predefined
35917 aliases are also supported. The full naming scheme encodes three pieces
35918 of information in the following pattern:
35921 @var{architecture}-@var{vendor}-@var{os}
35924 For example, you can use the alias @code{sun4} as a @var{host} argument,
35925 or as the value for @var{target} in a @code{--target=@var{target}}
35926 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35928 The @file{configure} script accompanying @value{GDBN} does not provide
35929 any query facility to list all supported host and target names or
35930 aliases. @file{configure} calls the Bourne shell script
35931 @code{config.sub} to map abbreviations to full names; you can read the
35932 script, if you wish, or you can use it to test your guesses on
35933 abbreviations---for example:
35936 % sh config.sub i386-linux
35938 % sh config.sub alpha-linux
35939 alpha-unknown-linux-gnu
35940 % sh config.sub hp9k700
35942 % sh config.sub sun4
35943 sparc-sun-sunos4.1.1
35944 % sh config.sub sun3
35945 m68k-sun-sunos4.1.1
35946 % sh config.sub i986v
35947 Invalid configuration `i986v': machine `i986v' not recognized
35951 @code{config.sub} is also distributed in the @value{GDBN} source
35952 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35954 @node Configure Options
35955 @section @file{configure} Options
35957 Here is a summary of the @file{configure} options and arguments that
35958 are most often useful for building @value{GDBN}. @file{configure}
35959 also has several other options not listed here. @inforef{Running
35960 configure scripts,,autoconf.info}, for a full
35961 explanation of @file{configure}.
35964 configure @r{[}--help@r{]}
35965 @r{[}--prefix=@var{dir}@r{]}
35966 @r{[}--exec-prefix=@var{dir}@r{]}
35967 @r{[}--srcdir=@var{dirname}@r{]}
35968 @r{[}--target=@var{target}@r{]}
35972 You may introduce options with a single @samp{-} rather than
35973 @samp{--} if you prefer; but you may abbreviate option names if you use
35978 Display a quick summary of how to invoke @file{configure}.
35980 @item --prefix=@var{dir}
35981 Configure the source to install programs and files under directory
35984 @item --exec-prefix=@var{dir}
35985 Configure the source to install programs under directory
35988 @c avoid splitting the warning from the explanation:
35990 @item --srcdir=@var{dirname}
35991 Use this option to make configurations in directories separate from the
35992 @value{GDBN} source directories. Among other things, you can use this to
35993 build (or maintain) several configurations simultaneously, in separate
35994 directories. @file{configure} writes configuration-specific files in
35995 the current directory, but arranges for them to use the source in the
35996 directory @var{dirname}. @file{configure} creates directories under
35997 the working directory in parallel to the source directories below
36000 @item --target=@var{target}
36001 Configure @value{GDBN} for cross-debugging programs running on the specified
36002 @var{target}. Without this option, @value{GDBN} is configured to debug
36003 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36005 There is no convenient way to generate a list of all available
36006 targets. Also see the @code{--enable-targets} option, below.
36009 There are many other options that are specific to @value{GDBN}. This
36010 lists just the most common ones; there are some very specialized
36011 options not described here.
36014 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36015 @itemx --enable-targets=all
36016 Configure @value{GDBN} for cross-debugging programs running on the
36017 specified list of targets. The special value @samp{all} configures
36018 @value{GDBN} for debugging programs running on any target it supports.
36020 @item --with-gdb-datadir=@var{path}
36021 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36022 here for certain supporting files or scripts. This defaults to the
36023 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36026 @item --with-relocated-sources=@var{dir}
36027 Sets up the default source path substitution rule so that directory
36028 names recorded in debug information will be automatically adjusted for
36029 any directory under @var{dir}. @var{dir} should be a subdirectory of
36030 @value{GDBN}'s configured prefix, the one mentioned in the
36031 @code{--prefix} or @code{--exec-prefix} options to configure. This
36032 option is useful if GDB is supposed to be moved to a different place
36035 @item --enable-64-bit-bfd
36036 Enable 64-bit support in BFD on 32-bit hosts.
36038 @item --disable-gdbmi
36039 Build @value{GDBN} without the GDB/MI machine interface
36043 Build @value{GDBN} with the text-mode full-screen user interface
36044 (TUI). Requires a curses library (ncurses and cursesX are also
36047 @item --with-curses
36048 Use the curses library instead of the termcap library, for text-mode
36049 terminal operations.
36051 @item --with-libunwind-ia64
36052 Use the libunwind library for unwinding function call stack on ia64
36053 target platforms. See http://www.nongnu.org/libunwind/index.html for
36056 @item --with-system-readline
36057 Use the readline library installed on the host, rather than the
36058 library supplied as part of @value{GDBN}.
36060 @item --with-system-zlib
36061 Use the zlib library installed on the host, rather than the library
36062 supplied as part of @value{GDBN}.
36065 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36066 default if libexpat is installed and found at configure time.) This
36067 library is used to read XML files supplied with @value{GDBN}. If it
36068 is unavailable, some features, such as remote protocol memory maps,
36069 target descriptions, and shared library lists, that are based on XML
36070 files, will not be available in @value{GDBN}. If your host does not
36071 have libexpat installed, you can get the latest version from
36072 `http://expat.sourceforge.net'.
36074 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36076 Build @value{GDBN} with GNU libiconv, a character set encoding
36077 conversion library. This is not done by default, as on GNU systems
36078 the @code{iconv} that is built in to the C library is sufficient. If
36079 your host does not have a working @code{iconv}, you can get the latest
36080 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36082 @value{GDBN}'s build system also supports building GNU libiconv as
36083 part of the overall build. @xref{Requirements}.
36086 Build @value{GDBN} with LZMA, a compression library. (Done by default
36087 if liblzma is installed and found at configure time.) LZMA is used by
36088 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36089 platforms using the ELF object file format. If your host does not
36090 have liblzma installed, you can get the latest version from
36091 `https://tukaani.org/xz/'.
36094 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36095 floating-point computation with correct rounding. (Done by default if
36096 GNU MPFR is installed and found at configure time.) This library is
36097 used to emulate target floating-point arithmetic during expression
36098 evaluation when the target uses different floating-point formats than
36099 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36100 to using host floating-point arithmetic. If your host does not have
36101 GNU MPFR installed, you can get the latest version from
36102 `http://www.mpfr.org'.
36104 @item --with-python@r{[}=@var{python}@r{]}
36105 Build @value{GDBN} with Python scripting support. (Done by default if
36106 libpython is present and found at configure time.) Python makes
36107 @value{GDBN} scripting much more powerful than the restricted CLI
36108 scripting language. If your host does not have Python installed, you
36109 can find it on `http://www.python.org/download/'. The oldest version
36110 of Python supported by GDB is 2.6. The optional argument @var{python}
36111 is used to find the Python headers and libraries. It can be either
36112 the name of a Python executable, or the name of the directory in which
36113 Python is installed.
36115 @item --with-guile[=GUILE]'
36116 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36117 if libguile is present and found at configure time.) If your host
36118 does not have Guile installed, you can find it at
36119 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36120 can be a version number, which will cause @code{configure} to try to
36121 use that version of Guile; or the file name of a @code{pkg-config}
36122 executable, which will be queried to find the information needed to
36123 compile and link against Guile.
36125 @item --without-included-regex
36126 Don't use the regex library included with @value{GDBN} (as part of the
36127 libiberty library). This is the default on hosts with version 2 of
36130 @item --with-sysroot=@var{dir}
36131 Use @var{dir} as the default system root directory for libraries whose
36132 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36133 @var{dir} can be modified at run time by using the @command{set
36134 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36135 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36136 default system root will be automatically adjusted if and when
36137 @value{GDBN} is moved to a different location.
36139 @item --with-system-gdbinit=@var{file}
36140 Configure @value{GDBN} to automatically load a system-wide init file.
36141 @var{file} should be an absolute file name. If @var{file} is in a
36142 directory under the configured prefix, and @value{GDBN} is moved to
36143 another location after being built, the location of the system-wide
36144 init file will be adjusted accordingly.
36146 @item --enable-build-warnings
36147 When building the @value{GDBN} sources, ask the compiler to warn about
36148 any code which looks even vaguely suspicious. It passes many
36149 different warning flags, depending on the exact version of the
36150 compiler you are using.
36152 @item --enable-werror
36153 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36154 to the compiler, which will fail the compilation if the compiler
36155 outputs any warning messages.
36157 @item --enable-ubsan
36158 Enable the GCC undefined behavior sanitizer. This is disabled by
36159 default, but passing @code{--enable-ubsan=yes} or
36160 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36161 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36162 It has a performance cost, so if you are looking at @value{GDBN}'s
36163 performance, you should disable it. The undefined behavior sanitizer
36164 was first introduced in GCC 4.9.
36167 @node System-wide configuration
36168 @section System-wide configuration and settings
36169 @cindex system-wide init file
36171 @value{GDBN} can be configured to have a system-wide init file;
36172 this file will be read and executed at startup (@pxref{Startup, , What
36173 @value{GDBN} does during startup}).
36175 Here is the corresponding configure option:
36178 @item --with-system-gdbinit=@var{file}
36179 Specify that the default location of the system-wide init file is
36183 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36184 it may be subject to relocation. Two possible cases:
36188 If the default location of this init file contains @file{$prefix},
36189 it will be subject to relocation. Suppose that the configure options
36190 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36191 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36192 init file is looked for as @file{$install/etc/gdbinit} instead of
36193 @file{$prefix/etc/gdbinit}.
36196 By contrast, if the default location does not contain the prefix,
36197 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36198 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36199 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36200 wherever @value{GDBN} is installed.
36203 If the configured location of the system-wide init file (as given by the
36204 @option{--with-system-gdbinit} option at configure time) is in the
36205 data-directory (as specified by @option{--with-gdb-datadir} at configure
36206 time) or in one of its subdirectories, then @value{GDBN} will look for the
36207 system-wide init file in the directory specified by the
36208 @option{--data-directory} command-line option.
36209 Note that the system-wide init file is only read once, during @value{GDBN}
36210 initialization. If the data-directory is changed after @value{GDBN} has
36211 started with the @code{set data-directory} command, the file will not be
36215 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36218 @node System-wide Configuration Scripts
36219 @subsection Installed System-wide Configuration Scripts
36220 @cindex system-wide configuration scripts
36222 The @file{system-gdbinit} directory, located inside the data-directory
36223 (as specified by @option{--with-gdb-datadir} at configure time) contains
36224 a number of scripts which can be used as system-wide init files. To
36225 automatically source those scripts at startup, @value{GDBN} should be
36226 configured with @option{--with-system-gdbinit}. Otherwise, any user
36227 should be able to source them by hand as needed.
36229 The following scripts are currently available:
36232 @item @file{elinos.py}
36234 @cindex ELinOS system-wide configuration script
36235 This script is useful when debugging a program on an ELinOS target.
36236 It takes advantage of the environment variables defined in a standard
36237 ELinOS environment in order to determine the location of the system
36238 shared libraries, and then sets the @samp{solib-absolute-prefix}
36239 and @samp{solib-search-path} variables appropriately.
36241 @item @file{wrs-linux.py}
36242 @pindex wrs-linux.py
36243 @cindex Wind River Linux system-wide configuration script
36244 This script is useful when debugging a program on a target running
36245 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36246 the host-side sysroot used by the target system.
36250 @node Maintenance Commands
36251 @appendix Maintenance Commands
36252 @cindex maintenance commands
36253 @cindex internal commands
36255 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36256 includes a number of commands intended for @value{GDBN} developers,
36257 that are not documented elsewhere in this manual. These commands are
36258 provided here for reference. (For commands that turn on debugging
36259 messages, see @ref{Debugging Output}.)
36262 @kindex maint agent
36263 @kindex maint agent-eval
36264 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36265 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36266 Translate the given @var{expression} into remote agent bytecodes.
36267 This command is useful for debugging the Agent Expression mechanism
36268 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36269 expression useful for data collection, such as by tracepoints, while
36270 @samp{maint agent-eval} produces an expression that evaluates directly
36271 to a result. For instance, a collection expression for @code{globa +
36272 globb} will include bytecodes to record four bytes of memory at each
36273 of the addresses of @code{globa} and @code{globb}, while discarding
36274 the result of the addition, while an evaluation expression will do the
36275 addition and return the sum.
36276 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36277 If not, generate remote agent bytecode for current frame PC address.
36279 @kindex maint agent-printf
36280 @item maint agent-printf @var{format},@var{expr},...
36281 Translate the given format string and list of argument expressions
36282 into remote agent bytecodes and display them as a disassembled list.
36283 This command is useful for debugging the agent version of dynamic
36284 printf (@pxref{Dynamic Printf}).
36286 @kindex maint info breakpoints
36287 @item @anchor{maint info breakpoints}maint info breakpoints
36288 Using the same format as @samp{info breakpoints}, display both the
36289 breakpoints you've set explicitly, and those @value{GDBN} is using for
36290 internal purposes. Internal breakpoints are shown with negative
36291 breakpoint numbers. The type column identifies what kind of breakpoint
36296 Normal, explicitly set breakpoint.
36299 Normal, explicitly set watchpoint.
36302 Internal breakpoint, used to handle correctly stepping through
36303 @code{longjmp} calls.
36305 @item longjmp resume
36306 Internal breakpoint at the target of a @code{longjmp}.
36309 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36312 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36315 Shared library events.
36319 @kindex maint info btrace
36320 @item maint info btrace
36321 Pint information about raw branch tracing data.
36323 @kindex maint btrace packet-history
36324 @item maint btrace packet-history
36325 Print the raw branch trace packets that are used to compute the
36326 execution history for the @samp{record btrace} command. Both the
36327 information and the format in which it is printed depend on the btrace
36332 For the BTS recording format, print a list of blocks of sequential
36333 code. For each block, the following information is printed:
36337 Newer blocks have higher numbers. The oldest block has number zero.
36338 @item Lowest @samp{PC}
36339 @item Highest @samp{PC}
36343 For the Intel Processor Trace recording format, print a list of
36344 Intel Processor Trace packets. For each packet, the following
36345 information is printed:
36348 @item Packet number
36349 Newer packets have higher numbers. The oldest packet has number zero.
36351 The packet's offset in the trace stream.
36352 @item Packet opcode and payload
36356 @kindex maint btrace clear-packet-history
36357 @item maint btrace clear-packet-history
36358 Discards the cached packet history printed by the @samp{maint btrace
36359 packet-history} command. The history will be computed again when
36362 @kindex maint btrace clear
36363 @item maint btrace clear
36364 Discard the branch trace data. The data will be fetched anew and the
36365 branch trace will be recomputed when needed.
36367 This implicitly truncates the branch trace to a single branch trace
36368 buffer. When updating branch trace incrementally, the branch trace
36369 available to @value{GDBN} may be bigger than a single branch trace
36372 @kindex maint set btrace pt skip-pad
36373 @item maint set btrace pt skip-pad
36374 @kindex maint show btrace pt skip-pad
36375 @item maint show btrace pt skip-pad
36376 Control whether @value{GDBN} will skip PAD packets when computing the
36379 @kindex set displaced-stepping
36380 @kindex show displaced-stepping
36381 @cindex displaced stepping support
36382 @cindex out-of-line single-stepping
36383 @item set displaced-stepping
36384 @itemx show displaced-stepping
36385 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36386 if the target supports it. Displaced stepping is a way to single-step
36387 over breakpoints without removing them from the inferior, by executing
36388 an out-of-line copy of the instruction that was originally at the
36389 breakpoint location. It is also known as out-of-line single-stepping.
36392 @item set displaced-stepping on
36393 If the target architecture supports it, @value{GDBN} will use
36394 displaced stepping to step over breakpoints.
36396 @item set displaced-stepping off
36397 @value{GDBN} will not use displaced stepping to step over breakpoints,
36398 even if such is supported by the target architecture.
36400 @cindex non-stop mode, and @samp{set displaced-stepping}
36401 @item set displaced-stepping auto
36402 This is the default mode. @value{GDBN} will use displaced stepping
36403 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36404 architecture supports displaced stepping.
36407 @kindex maint check-psymtabs
36408 @item maint check-psymtabs
36409 Check the consistency of currently expanded psymtabs versus symtabs.
36410 Use this to check, for example, whether a symbol is in one but not the other.
36412 @kindex maint check-symtabs
36413 @item maint check-symtabs
36414 Check the consistency of currently expanded symtabs.
36416 @kindex maint expand-symtabs
36417 @item maint expand-symtabs [@var{regexp}]
36418 Expand symbol tables.
36419 If @var{regexp} is specified, only expand symbol tables for file
36420 names matching @var{regexp}.
36422 @kindex maint set catch-demangler-crashes
36423 @kindex maint show catch-demangler-crashes
36424 @cindex demangler crashes
36425 @item maint set catch-demangler-crashes [on|off]
36426 @itemx maint show catch-demangler-crashes
36427 Control whether @value{GDBN} should attempt to catch crashes in the
36428 symbol name demangler. The default is to attempt to catch crashes.
36429 If enabled, the first time a crash is caught, a core file is created,
36430 the offending symbol is displayed and the user is presented with the
36431 option to terminate the current session.
36433 @kindex maint cplus first_component
36434 @item maint cplus first_component @var{name}
36435 Print the first C@t{++} class/namespace component of @var{name}.
36437 @kindex maint cplus namespace
36438 @item maint cplus namespace
36439 Print the list of possible C@t{++} namespaces.
36441 @kindex maint deprecate
36442 @kindex maint undeprecate
36443 @cindex deprecated commands
36444 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36445 @itemx maint undeprecate @var{command}
36446 Deprecate or undeprecate the named @var{command}. Deprecated commands
36447 cause @value{GDBN} to issue a warning when you use them. The optional
36448 argument @var{replacement} says which newer command should be used in
36449 favor of the deprecated one; if it is given, @value{GDBN} will mention
36450 the replacement as part of the warning.
36452 @kindex maint dump-me
36453 @item maint dump-me
36454 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36455 Cause a fatal signal in the debugger and force it to dump its core.
36456 This is supported only on systems which support aborting a program
36457 with the @code{SIGQUIT} signal.
36459 @kindex maint internal-error
36460 @kindex maint internal-warning
36461 @kindex maint demangler-warning
36462 @cindex demangler crashes
36463 @item maint internal-error @r{[}@var{message-text}@r{]}
36464 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36465 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36467 Cause @value{GDBN} to call the internal function @code{internal_error},
36468 @code{internal_warning} or @code{demangler_warning} and hence behave
36469 as though an internal problem has been detected. In addition to
36470 reporting the internal problem, these functions give the user the
36471 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36472 and @code{internal_warning}) create a core file of the current
36473 @value{GDBN} session.
36475 These commands take an optional parameter @var{message-text} that is
36476 used as the text of the error or warning message.
36478 Here's an example of using @code{internal-error}:
36481 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36482 @dots{}/maint.c:121: internal-error: testing, 1, 2
36483 A problem internal to GDB has been detected. Further
36484 debugging may prove unreliable.
36485 Quit this debugging session? (y or n) @kbd{n}
36486 Create a core file? (y or n) @kbd{n}
36490 @cindex @value{GDBN} internal error
36491 @cindex internal errors, control of @value{GDBN} behavior
36492 @cindex demangler crashes
36494 @kindex maint set internal-error
36495 @kindex maint show internal-error
36496 @kindex maint set internal-warning
36497 @kindex maint show internal-warning
36498 @kindex maint set demangler-warning
36499 @kindex maint show demangler-warning
36500 @item maint set internal-error @var{action} [ask|yes|no]
36501 @itemx maint show internal-error @var{action}
36502 @itemx maint set internal-warning @var{action} [ask|yes|no]
36503 @itemx maint show internal-warning @var{action}
36504 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36505 @itemx maint show demangler-warning @var{action}
36506 When @value{GDBN} reports an internal problem (error or warning) it
36507 gives the user the opportunity to both quit @value{GDBN} and create a
36508 core file of the current @value{GDBN} session. These commands let you
36509 override the default behaviour for each particular @var{action},
36510 described in the table below.
36514 You can specify that @value{GDBN} should always (yes) or never (no)
36515 quit. The default is to ask the user what to do.
36518 You can specify that @value{GDBN} should always (yes) or never (no)
36519 create a core file. The default is to ask the user what to do. Note
36520 that there is no @code{corefile} option for @code{demangler-warning}:
36521 demangler warnings always create a core file and this cannot be
36525 @kindex maint packet
36526 @item maint packet @var{text}
36527 If @value{GDBN} is talking to an inferior via the serial protocol,
36528 then this command sends the string @var{text} to the inferior, and
36529 displays the response packet. @value{GDBN} supplies the initial
36530 @samp{$} character, the terminating @samp{#} character, and the
36533 @kindex maint print architecture
36534 @item maint print architecture @r{[}@var{file}@r{]}
36535 Print the entire architecture configuration. The optional argument
36536 @var{file} names the file where the output goes.
36538 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36539 @item maint print c-tdesc
36540 Print the target description (@pxref{Target Descriptions}) as
36541 a C source file. By default, the target description is for the current
36542 target, but if the optional argument @var{file} is provided, that file
36543 is used to produce the description. The @var{file} should be an XML
36544 document, of the form described in @ref{Target Description Format}.
36545 The created source file is built into @value{GDBN} when @value{GDBN} is
36546 built again. This command is used by developers after they add or
36547 modify XML target descriptions.
36549 @kindex maint check xml-descriptions
36550 @item maint check xml-descriptions @var{dir}
36551 Check that the target descriptions dynamically created by @value{GDBN}
36552 equal the descriptions created from XML files found in @var{dir}.
36554 @anchor{maint check libthread-db}
36555 @kindex maint check libthread-db
36556 @item maint check libthread-db
36557 Run integrity checks on the current inferior's thread debugging
36558 library. This exercises all @code{libthread_db} functionality used by
36559 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36560 @code{proc_service} functions provided by @value{GDBN} that
36561 @code{libthread_db} uses. Note that parts of the test may be skipped
36562 on some platforms when debugging core files.
36564 @kindex maint print dummy-frames
36565 @item maint print dummy-frames
36566 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36569 (@value{GDBP}) @kbd{b add}
36571 (@value{GDBP}) @kbd{print add(2,3)}
36572 Breakpoint 2, add (a=2, b=3) at @dots{}
36574 The program being debugged stopped while in a function called from GDB.
36576 (@value{GDBP}) @kbd{maint print dummy-frames}
36577 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36581 Takes an optional file parameter.
36583 @kindex maint print registers
36584 @kindex maint print raw-registers
36585 @kindex maint print cooked-registers
36586 @kindex maint print register-groups
36587 @kindex maint print remote-registers
36588 @item maint print registers @r{[}@var{file}@r{]}
36589 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36590 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36591 @itemx maint print register-groups @r{[}@var{file}@r{]}
36592 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36593 Print @value{GDBN}'s internal register data structures.
36595 The command @code{maint print raw-registers} includes the contents of
36596 the raw register cache; the command @code{maint print
36597 cooked-registers} includes the (cooked) value of all registers,
36598 including registers which aren't available on the target nor visible
36599 to user; the command @code{maint print register-groups} includes the
36600 groups that each register is a member of; and the command @code{maint
36601 print remote-registers} includes the remote target's register numbers
36602 and offsets in the `G' packets.
36604 These commands take an optional parameter, a file name to which to
36605 write the information.
36607 @kindex maint print reggroups
36608 @item maint print reggroups @r{[}@var{file}@r{]}
36609 Print @value{GDBN}'s internal register group data structures. The
36610 optional argument @var{file} tells to what file to write the
36613 The register groups info looks like this:
36616 (@value{GDBP}) @kbd{maint print reggroups}
36629 This command forces @value{GDBN} to flush its internal register cache.
36631 @kindex maint print objfiles
36632 @cindex info for known object files
36633 @item maint print objfiles @r{[}@var{regexp}@r{]}
36634 Print a dump of all known object files.
36635 If @var{regexp} is specified, only print object files whose names
36636 match @var{regexp}. For each object file, this command prints its name,
36637 address in memory, and all of its psymtabs and symtabs.
36639 @kindex maint print user-registers
36640 @cindex user registers
36641 @item maint print user-registers
36642 List all currently available @dfn{user registers}. User registers
36643 typically provide alternate names for actual hardware registers. They
36644 include the four ``standard'' registers @code{$fp}, @code{$pc},
36645 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36646 registers can be used in expressions in the same way as the canonical
36647 register names, but only the latter are listed by the @code{info
36648 registers} and @code{maint print registers} commands.
36650 @kindex maint print section-scripts
36651 @cindex info for known .debug_gdb_scripts-loaded scripts
36652 @item maint print section-scripts [@var{regexp}]
36653 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36654 If @var{regexp} is specified, only print scripts loaded by object files
36655 matching @var{regexp}.
36656 For each script, this command prints its name as specified in the objfile,
36657 and the full path if known.
36658 @xref{dotdebug_gdb_scripts section}.
36660 @kindex maint print statistics
36661 @cindex bcache statistics
36662 @item maint print statistics
36663 This command prints, for each object file in the program, various data
36664 about that object file followed by the byte cache (@dfn{bcache})
36665 statistics for the object file. The objfile data includes the number
36666 of minimal, partial, full, and stabs symbols, the number of types
36667 defined by the objfile, the number of as yet unexpanded psym tables,
36668 the number of line tables and string tables, and the amount of memory
36669 used by the various tables. The bcache statistics include the counts,
36670 sizes, and counts of duplicates of all and unique objects, max,
36671 average, and median entry size, total memory used and its overhead and
36672 savings, and various measures of the hash table size and chain
36675 @kindex maint print target-stack
36676 @cindex target stack description
36677 @item maint print target-stack
36678 A @dfn{target} is an interface between the debugger and a particular
36679 kind of file or process. Targets can be stacked in @dfn{strata},
36680 so that more than one target can potentially respond to a request.
36681 In particular, memory accesses will walk down the stack of targets
36682 until they find a target that is interested in handling that particular
36685 This command prints a short description of each layer that was pushed on
36686 the @dfn{target stack}, starting from the top layer down to the bottom one.
36688 @kindex maint print type
36689 @cindex type chain of a data type
36690 @item maint print type @var{expr}
36691 Print the type chain for a type specified by @var{expr}. The argument
36692 can be either a type name or a symbol. If it is a symbol, the type of
36693 that symbol is described. The type chain produced by this command is
36694 a recursive definition of the data type as stored in @value{GDBN}'s
36695 data structures, including its flags and contained types.
36697 @kindex maint selftest
36699 @item maint selftest @r{[}@var{filter}@r{]}
36700 Run any self tests that were compiled in to @value{GDBN}. This will
36701 print a message showing how many tests were run, and how many failed.
36702 If a @var{filter} is passed, only the tests with @var{filter} in their
36705 @kindex "maint info selftests"
36707 @item maint info selftests
36708 List the selftests compiled in to @value{GDBN}.
36710 @kindex maint set dwarf always-disassemble
36711 @kindex maint show dwarf always-disassemble
36712 @item maint set dwarf always-disassemble
36713 @item maint show dwarf always-disassemble
36714 Control the behavior of @code{info address} when using DWARF debugging
36717 The default is @code{off}, which means that @value{GDBN} should try to
36718 describe a variable's location in an easily readable format. When
36719 @code{on}, @value{GDBN} will instead display the DWARF location
36720 expression in an assembly-like format. Note that some locations are
36721 too complex for @value{GDBN} to describe simply; in this case you will
36722 always see the disassembly form.
36724 Here is an example of the resulting disassembly:
36727 (gdb) info addr argc
36728 Symbol "argc" is a complex DWARF expression:
36732 For more information on these expressions, see
36733 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36735 @kindex maint set dwarf max-cache-age
36736 @kindex maint show dwarf max-cache-age
36737 @item maint set dwarf max-cache-age
36738 @itemx maint show dwarf max-cache-age
36739 Control the DWARF compilation unit cache.
36741 @cindex DWARF compilation units cache
36742 In object files with inter-compilation-unit references, such as those
36743 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36744 reader needs to frequently refer to previously read compilation units.
36745 This setting controls how long a compilation unit will remain in the
36746 cache if it is not referenced. A higher limit means that cached
36747 compilation units will be stored in memory longer, and more total
36748 memory will be used. Setting it to zero disables caching, which will
36749 slow down @value{GDBN} startup, but reduce memory consumption.
36751 @kindex maint set dwarf unwinders
36752 @kindex maint show dwarf unwinders
36753 @item maint set dwarf unwinders
36754 @itemx maint show dwarf unwinders
36755 Control use of the DWARF frame unwinders.
36757 @cindex DWARF frame unwinders
36758 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36759 frame unwinders to build the backtrace. Many of these targets will
36760 also have a second mechanism for building the backtrace for use in
36761 cases where DWARF information is not available, this second mechanism
36762 is often an analysis of a function's prologue.
36764 In order to extend testing coverage of the second level stack
36765 unwinding mechanisms it is helpful to be able to disable the DWARF
36766 stack unwinders, this can be done with this switch.
36768 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36769 advisable, there are cases that are better handled through DWARF than
36770 prologue analysis, and the debug experience is likely to be better
36771 with the DWARF frame unwinders enabled.
36773 If DWARF frame unwinders are not supported for a particular target
36774 architecture, then enabling this flag does not cause them to be used.
36775 @kindex maint set profile
36776 @kindex maint show profile
36777 @cindex profiling GDB
36778 @item maint set profile
36779 @itemx maint show profile
36780 Control profiling of @value{GDBN}.
36782 Profiling will be disabled until you use the @samp{maint set profile}
36783 command to enable it. When you enable profiling, the system will begin
36784 collecting timing and execution count data; when you disable profiling or
36785 exit @value{GDBN}, the results will be written to a log file. Remember that
36786 if you use profiling, @value{GDBN} will overwrite the profiling log file
36787 (often called @file{gmon.out}). If you have a record of important profiling
36788 data in a @file{gmon.out} file, be sure to move it to a safe location.
36790 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36791 compiled with the @samp{-pg} compiler option.
36793 @kindex maint set show-debug-regs
36794 @kindex maint show show-debug-regs
36795 @cindex hardware debug registers
36796 @item maint set show-debug-regs
36797 @itemx maint show show-debug-regs
36798 Control whether to show variables that mirror the hardware debug
36799 registers. Use @code{on} to enable, @code{off} to disable. If
36800 enabled, the debug registers values are shown when @value{GDBN} inserts or
36801 removes a hardware breakpoint or watchpoint, and when the inferior
36802 triggers a hardware-assisted breakpoint or watchpoint.
36804 @kindex maint set show-all-tib
36805 @kindex maint show show-all-tib
36806 @item maint set show-all-tib
36807 @itemx maint show show-all-tib
36808 Control whether to show all non zero areas within a 1k block starting
36809 at thread local base, when using the @samp{info w32 thread-information-block}
36812 @kindex maint set target-async
36813 @kindex maint show target-async
36814 @item maint set target-async
36815 @itemx maint show target-async
36816 This controls whether @value{GDBN} targets operate in synchronous or
36817 asynchronous mode (@pxref{Background Execution}). Normally the
36818 default is asynchronous, if it is available; but this can be changed
36819 to more easily debug problems occurring only in synchronous mode.
36821 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36822 @kindex maint show target-non-stop
36823 @item maint set target-non-stop
36824 @itemx maint show target-non-stop
36826 This controls whether @value{GDBN} targets always operate in non-stop
36827 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36828 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36829 if supported by the target.
36832 @item maint set target-non-stop auto
36833 This is the default mode. @value{GDBN} controls the target in
36834 non-stop mode if the target supports it.
36836 @item maint set target-non-stop on
36837 @value{GDBN} controls the target in non-stop mode even if the target
36838 does not indicate support.
36840 @item maint set target-non-stop off
36841 @value{GDBN} does not control the target in non-stop mode even if the
36842 target supports it.
36845 @kindex maint set per-command
36846 @kindex maint show per-command
36847 @item maint set per-command
36848 @itemx maint show per-command
36849 @cindex resources used by commands
36851 @value{GDBN} can display the resources used by each command.
36852 This is useful in debugging performance problems.
36855 @item maint set per-command space [on|off]
36856 @itemx maint show per-command space
36857 Enable or disable the printing of the memory used by GDB for each command.
36858 If enabled, @value{GDBN} will display how much memory each command
36859 took, following the command's own output.
36860 This can also be requested by invoking @value{GDBN} with the
36861 @option{--statistics} command-line switch (@pxref{Mode Options}).
36863 @item maint set per-command time [on|off]
36864 @itemx maint show per-command time
36865 Enable or disable the printing of the execution time of @value{GDBN}
36867 If enabled, @value{GDBN} will display how much time it
36868 took to execute each command, following the command's own output.
36869 Both CPU time and wallclock time are printed.
36870 Printing both is useful when trying to determine whether the cost is
36871 CPU or, e.g., disk/network latency.
36872 Note that the CPU time printed is for @value{GDBN} only, it does not include
36873 the execution time of the inferior because there's no mechanism currently
36874 to compute how much time was spent by @value{GDBN} and how much time was
36875 spent by the program been debugged.
36876 This can also be requested by invoking @value{GDBN} with the
36877 @option{--statistics} command-line switch (@pxref{Mode Options}).
36879 @item maint set per-command symtab [on|off]
36880 @itemx maint show per-command symtab
36881 Enable or disable the printing of basic symbol table statistics
36883 If enabled, @value{GDBN} will display the following information:
36887 number of symbol tables
36889 number of primary symbol tables
36891 number of blocks in the blockvector
36895 @kindex maint set check-libthread-db
36896 @kindex maint show check-libthread-db
36897 @item maint set check-libthread-db [on|off]
36898 @itemx maint show check-libthread-db
36899 Control whether @value{GDBN} should run integrity checks on inferior
36900 specific thread debugging libraries as they are loaded. The default
36901 is not to perform such checks. If any check fails @value{GDBN} will
36902 unload the library and continue searching for a suitable candidate as
36903 described in @ref{set libthread-db-search-path}. For more information
36904 about the tests, see @ref{maint check libthread-db}.
36906 @kindex maint space
36907 @cindex memory used by commands
36908 @item maint space @var{value}
36909 An alias for @code{maint set per-command space}.
36910 A non-zero value enables it, zero disables it.
36913 @cindex time of command execution
36914 @item maint time @var{value}
36915 An alias for @code{maint set per-command time}.
36916 A non-zero value enables it, zero disables it.
36918 @kindex maint translate-address
36919 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36920 Find the symbol stored at the location specified by the address
36921 @var{addr} and an optional section name @var{section}. If found,
36922 @value{GDBN} prints the name of the closest symbol and an offset from
36923 the symbol's location to the specified address. This is similar to
36924 the @code{info address} command (@pxref{Symbols}), except that this
36925 command also allows to find symbols in other sections.
36927 If section was not specified, the section in which the symbol was found
36928 is also printed. For dynamically linked executables, the name of
36929 executable or shared library containing the symbol is printed as well.
36933 The following command is useful for non-interactive invocations of
36934 @value{GDBN}, such as in the test suite.
36937 @item set watchdog @var{nsec}
36938 @kindex set watchdog
36939 @cindex watchdog timer
36940 @cindex timeout for commands
36941 Set the maximum number of seconds @value{GDBN} will wait for the
36942 target operation to finish. If this time expires, @value{GDBN}
36943 reports and error and the command is aborted.
36945 @item show watchdog
36946 Show the current setting of the target wait timeout.
36949 @node Remote Protocol
36950 @appendix @value{GDBN} Remote Serial Protocol
36955 * Stop Reply Packets::
36956 * General Query Packets::
36957 * Architecture-Specific Protocol Details::
36958 * Tracepoint Packets::
36959 * Host I/O Packets::
36961 * Notification Packets::
36962 * Remote Non-Stop::
36963 * Packet Acknowledgment::
36965 * File-I/O Remote Protocol Extension::
36966 * Library List Format::
36967 * Library List Format for SVR4 Targets::
36968 * Memory Map Format::
36969 * Thread List Format::
36970 * Traceframe Info Format::
36971 * Branch Trace Format::
36972 * Branch Trace Configuration Format::
36978 There may be occasions when you need to know something about the
36979 protocol---for example, if there is only one serial port to your target
36980 machine, you might want your program to do something special if it
36981 recognizes a packet meant for @value{GDBN}.
36983 In the examples below, @samp{->} and @samp{<-} are used to indicate
36984 transmitted and received data, respectively.
36986 @cindex protocol, @value{GDBN} remote serial
36987 @cindex serial protocol, @value{GDBN} remote
36988 @cindex remote serial protocol
36989 All @value{GDBN} commands and responses (other than acknowledgments
36990 and notifications, see @ref{Notification Packets}) are sent as a
36991 @var{packet}. A @var{packet} is introduced with the character
36992 @samp{$}, the actual @var{packet-data}, and the terminating character
36993 @samp{#} followed by a two-digit @var{checksum}:
36996 @code{$}@var{packet-data}@code{#}@var{checksum}
37000 @cindex checksum, for @value{GDBN} remote
37002 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37003 characters between the leading @samp{$} and the trailing @samp{#} (an
37004 eight bit unsigned checksum).
37006 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37007 specification also included an optional two-digit @var{sequence-id}:
37010 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37013 @cindex sequence-id, for @value{GDBN} remote
37015 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37016 has never output @var{sequence-id}s. Stubs that handle packets added
37017 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37019 When either the host or the target machine receives a packet, the first
37020 response expected is an acknowledgment: either @samp{+} (to indicate
37021 the package was received correctly) or @samp{-} (to request
37025 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37030 The @samp{+}/@samp{-} acknowledgments can be disabled
37031 once a connection is established.
37032 @xref{Packet Acknowledgment}, for details.
37034 The host (@value{GDBN}) sends @var{command}s, and the target (the
37035 debugging stub incorporated in your program) sends a @var{response}. In
37036 the case of step and continue @var{command}s, the response is only sent
37037 when the operation has completed, and the target has again stopped all
37038 threads in all attached processes. This is the default all-stop mode
37039 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37040 execution mode; see @ref{Remote Non-Stop}, for details.
37042 @var{packet-data} consists of a sequence of characters with the
37043 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37046 @cindex remote protocol, field separator
37047 Fields within the packet should be separated using @samp{,} @samp{;} or
37048 @samp{:}. Except where otherwise noted all numbers are represented in
37049 @sc{hex} with leading zeros suppressed.
37051 Implementors should note that prior to @value{GDBN} 5.0, the character
37052 @samp{:} could not appear as the third character in a packet (as it
37053 would potentially conflict with the @var{sequence-id}).
37055 @cindex remote protocol, binary data
37056 @anchor{Binary Data}
37057 Binary data in most packets is encoded either as two hexadecimal
37058 digits per byte of binary data. This allowed the traditional remote
37059 protocol to work over connections which were only seven-bit clean.
37060 Some packets designed more recently assume an eight-bit clean
37061 connection, and use a more efficient encoding to send and receive
37064 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37065 as an escape character. Any escaped byte is transmitted as the escape
37066 character followed by the original character XORed with @code{0x20}.
37067 For example, the byte @code{0x7d} would be transmitted as the two
37068 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37069 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37070 @samp{@}}) must always be escaped. Responses sent by the stub
37071 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37072 is not interpreted as the start of a run-length encoded sequence
37075 Response @var{data} can be run-length encoded to save space.
37076 Run-length encoding replaces runs of identical characters with one
37077 instance of the repeated character, followed by a @samp{*} and a
37078 repeat count. The repeat count is itself sent encoded, to avoid
37079 binary characters in @var{data}: a value of @var{n} is sent as
37080 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37081 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37082 code 32) for a repeat count of 3. (This is because run-length
37083 encoding starts to win for counts 3 or more.) Thus, for example,
37084 @samp{0* } is a run-length encoding of ``0000'': the space character
37085 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37088 The printable characters @samp{#} and @samp{$} or with a numeric value
37089 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37090 seven repeats (@samp{$}) can be expanded using a repeat count of only
37091 five (@samp{"}). For example, @samp{00000000} can be encoded as
37094 The error response returned for some packets includes a two character
37095 error number. That number is not well defined.
37097 @cindex empty response, for unsupported packets
37098 For any @var{command} not supported by the stub, an empty response
37099 (@samp{$#00}) should be returned. That way it is possible to extend the
37100 protocol. A newer @value{GDBN} can tell if a packet is supported based
37103 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37104 commands for register access, and the @samp{m} and @samp{M} commands
37105 for memory access. Stubs that only control single-threaded targets
37106 can implement run control with the @samp{c} (continue), and @samp{s}
37107 (step) commands. Stubs that support multi-threading targets should
37108 support the @samp{vCont} command. All other commands are optional.
37113 The following table provides a complete list of all currently defined
37114 @var{command}s and their corresponding response @var{data}.
37115 @xref{File-I/O Remote Protocol Extension}, for details about the File
37116 I/O extension of the remote protocol.
37118 Each packet's description has a template showing the packet's overall
37119 syntax, followed by an explanation of the packet's meaning. We
37120 include spaces in some of the templates for clarity; these are not
37121 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37122 separate its components. For example, a template like @samp{foo
37123 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37124 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37125 @var{baz}. @value{GDBN} does not transmit a space character between the
37126 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37129 @cindex @var{thread-id}, in remote protocol
37130 @anchor{thread-id syntax}
37131 Several packets and replies include a @var{thread-id} field to identify
37132 a thread. Normally these are positive numbers with a target-specific
37133 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37134 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37137 In addition, the remote protocol supports a multiprocess feature in
37138 which the @var{thread-id} syntax is extended to optionally include both
37139 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37140 The @var{pid} (process) and @var{tid} (thread) components each have the
37141 format described above: a positive number with target-specific
37142 interpretation formatted as a big-endian hex string, literal @samp{-1}
37143 to indicate all processes or threads (respectively), or @samp{0} to
37144 indicate an arbitrary process or thread. Specifying just a process, as
37145 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37146 error to specify all processes but a specific thread, such as
37147 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37148 for those packets and replies explicitly documented to include a process
37149 ID, rather than a @var{thread-id}.
37151 The multiprocess @var{thread-id} syntax extensions are only used if both
37152 @value{GDBN} and the stub report support for the @samp{multiprocess}
37153 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37156 Note that all packet forms beginning with an upper- or lower-case
37157 letter, other than those described here, are reserved for future use.
37159 Here are the packet descriptions.
37164 @cindex @samp{!} packet
37165 @anchor{extended mode}
37166 Enable extended mode. In extended mode, the remote server is made
37167 persistent. The @samp{R} packet is used to restart the program being
37173 The remote target both supports and has enabled extended mode.
37177 @cindex @samp{?} packet
37179 Indicate the reason the target halted. The reply is the same as for
37180 step and continue. This packet has a special interpretation when the
37181 target is in non-stop mode; see @ref{Remote Non-Stop}.
37184 @xref{Stop Reply Packets}, for the reply specifications.
37186 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37187 @cindex @samp{A} packet
37188 Initialized @code{argv[]} array passed into program. @var{arglen}
37189 specifies the number of bytes in the hex encoded byte stream
37190 @var{arg}. See @code{gdbserver} for more details.
37195 The arguments were set.
37201 @cindex @samp{b} packet
37202 (Don't use this packet; its behavior is not well-defined.)
37203 Change the serial line speed to @var{baud}.
37205 JTC: @emph{When does the transport layer state change? When it's
37206 received, or after the ACK is transmitted. In either case, there are
37207 problems if the command or the acknowledgment packet is dropped.}
37209 Stan: @emph{If people really wanted to add something like this, and get
37210 it working for the first time, they ought to modify ser-unix.c to send
37211 some kind of out-of-band message to a specially-setup stub and have the
37212 switch happen "in between" packets, so that from remote protocol's point
37213 of view, nothing actually happened.}
37215 @item B @var{addr},@var{mode}
37216 @cindex @samp{B} packet
37217 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37218 breakpoint at @var{addr}.
37220 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37221 (@pxref{insert breakpoint or watchpoint packet}).
37223 @cindex @samp{bc} packet
37226 Backward continue. Execute the target system in reverse. No parameter.
37227 @xref{Reverse Execution}, for more information.
37230 @xref{Stop Reply Packets}, for the reply specifications.
37232 @cindex @samp{bs} packet
37235 Backward single step. Execute one instruction in reverse. No parameter.
37236 @xref{Reverse Execution}, for more information.
37239 @xref{Stop Reply Packets}, for the reply specifications.
37241 @item c @r{[}@var{addr}@r{]}
37242 @cindex @samp{c} packet
37243 Continue at @var{addr}, which is the address to resume. If @var{addr}
37244 is omitted, resume at current address.
37246 This packet is deprecated for multi-threading support. @xref{vCont
37250 @xref{Stop Reply Packets}, for the reply specifications.
37252 @item C @var{sig}@r{[};@var{addr}@r{]}
37253 @cindex @samp{C} packet
37254 Continue with signal @var{sig} (hex signal number). If
37255 @samp{;@var{addr}} is omitted, resume at same address.
37257 This packet is deprecated for multi-threading support. @xref{vCont
37261 @xref{Stop Reply Packets}, for the reply specifications.
37264 @cindex @samp{d} packet
37267 Don't use this packet; instead, define a general set packet
37268 (@pxref{General Query Packets}).
37272 @cindex @samp{D} packet
37273 The first form of the packet is used to detach @value{GDBN} from the
37274 remote system. It is sent to the remote target
37275 before @value{GDBN} disconnects via the @code{detach} command.
37277 The second form, including a process ID, is used when multiprocess
37278 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37279 detach only a specific process. The @var{pid} is specified as a
37280 big-endian hex string.
37290 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37291 @cindex @samp{F} packet
37292 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37293 This is part of the File-I/O protocol extension. @xref{File-I/O
37294 Remote Protocol Extension}, for the specification.
37297 @anchor{read registers packet}
37298 @cindex @samp{g} packet
37299 Read general registers.
37303 @item @var{XX@dots{}}
37304 Each byte of register data is described by two hex digits. The bytes
37305 with the register are transmitted in target byte order. The size of
37306 each register and their position within the @samp{g} packet are
37307 determined by the @value{GDBN} internal gdbarch functions
37308 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37310 When reading registers from a trace frame (@pxref{Analyze Collected
37311 Data,,Using the Collected Data}), the stub may also return a string of
37312 literal @samp{x}'s in place of the register data digits, to indicate
37313 that the corresponding register has not been collected, thus its value
37314 is unavailable. For example, for an architecture with 4 registers of
37315 4 bytes each, the following reply indicates to @value{GDBN} that
37316 registers 0 and 2 have not been collected, while registers 1 and 3
37317 have been collected, and both have zero value:
37321 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37328 @item G @var{XX@dots{}}
37329 @cindex @samp{G} packet
37330 Write general registers. @xref{read registers packet}, for a
37331 description of the @var{XX@dots{}} data.
37341 @item H @var{op} @var{thread-id}
37342 @cindex @samp{H} packet
37343 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37344 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37345 should be @samp{c} for step and continue operations (note that this
37346 is deprecated, supporting the @samp{vCont} command is a better
37347 option), and @samp{g} for other operations. The thread designator
37348 @var{thread-id} has the format and interpretation described in
37349 @ref{thread-id syntax}.
37360 @c 'H': How restrictive (or permissive) is the thread model. If a
37361 @c thread is selected and stopped, are other threads allowed
37362 @c to continue to execute? As I mentioned above, I think the
37363 @c semantics of each command when a thread is selected must be
37364 @c described. For example:
37366 @c 'g': If the stub supports threads and a specific thread is
37367 @c selected, returns the register block from that thread;
37368 @c otherwise returns current registers.
37370 @c 'G' If the stub supports threads and a specific thread is
37371 @c selected, sets the registers of the register block of
37372 @c that thread; otherwise sets current registers.
37374 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37375 @anchor{cycle step packet}
37376 @cindex @samp{i} packet
37377 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37378 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37379 step starting at that address.
37382 @cindex @samp{I} packet
37383 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37387 @cindex @samp{k} packet
37390 The exact effect of this packet is not specified.
37392 For a bare-metal target, it may power cycle or reset the target
37393 system. For that reason, the @samp{k} packet has no reply.
37395 For a single-process target, it may kill that process if possible.
37397 A multiple-process target may choose to kill just one process, or all
37398 that are under @value{GDBN}'s control. For more precise control, use
37399 the vKill packet (@pxref{vKill packet}).
37401 If the target system immediately closes the connection in response to
37402 @samp{k}, @value{GDBN} does not consider the lack of packet
37403 acknowledgment to be an error, and assumes the kill was successful.
37405 If connected using @kbd{target extended-remote}, and the target does
37406 not close the connection in response to a kill request, @value{GDBN}
37407 probes the target state as if a new connection was opened
37408 (@pxref{? packet}).
37410 @item m @var{addr},@var{length}
37411 @cindex @samp{m} packet
37412 Read @var{length} addressable memory units starting at address @var{addr}
37413 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37414 any particular boundary.
37416 The stub need not use any particular size or alignment when gathering
37417 data from memory for the response; even if @var{addr} is word-aligned
37418 and @var{length} is a multiple of the word size, the stub is free to
37419 use byte accesses, or not. For this reason, this packet may not be
37420 suitable for accessing memory-mapped I/O devices.
37421 @cindex alignment of remote memory accesses
37422 @cindex size of remote memory accesses
37423 @cindex memory, alignment and size of remote accesses
37427 @item @var{XX@dots{}}
37428 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37429 The reply may contain fewer addressable memory units than requested if the
37430 server was able to read only part of the region of memory.
37435 @item M @var{addr},@var{length}:@var{XX@dots{}}
37436 @cindex @samp{M} packet
37437 Write @var{length} addressable memory units starting at address @var{addr}
37438 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37439 byte is transmitted as a two-digit hexadecimal number.
37446 for an error (this includes the case where only part of the data was
37451 @cindex @samp{p} packet
37452 Read the value of register @var{n}; @var{n} is in hex.
37453 @xref{read registers packet}, for a description of how the returned
37454 register value is encoded.
37458 @item @var{XX@dots{}}
37459 the register's value
37463 Indicating an unrecognized @var{query}.
37466 @item P @var{n@dots{}}=@var{r@dots{}}
37467 @anchor{write register packet}
37468 @cindex @samp{P} packet
37469 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37470 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37471 digits for each byte in the register (target byte order).
37481 @item q @var{name} @var{params}@dots{}
37482 @itemx Q @var{name} @var{params}@dots{}
37483 @cindex @samp{q} packet
37484 @cindex @samp{Q} packet
37485 General query (@samp{q}) and set (@samp{Q}). These packets are
37486 described fully in @ref{General Query Packets}.
37489 @cindex @samp{r} packet
37490 Reset the entire system.
37492 Don't use this packet; use the @samp{R} packet instead.
37495 @cindex @samp{R} packet
37496 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37497 This packet is only available in extended mode (@pxref{extended mode}).
37499 The @samp{R} packet has no reply.
37501 @item s @r{[}@var{addr}@r{]}
37502 @cindex @samp{s} packet
37503 Single step, resuming at @var{addr}. If
37504 @var{addr} is omitted, resume at same address.
37506 This packet is deprecated for multi-threading support. @xref{vCont
37510 @xref{Stop Reply Packets}, for the reply specifications.
37512 @item S @var{sig}@r{[};@var{addr}@r{]}
37513 @anchor{step with signal packet}
37514 @cindex @samp{S} packet
37515 Step with signal. This is analogous to the @samp{C} packet, but
37516 requests a single-step, rather than a normal resumption of execution.
37518 This packet is deprecated for multi-threading support. @xref{vCont
37522 @xref{Stop Reply Packets}, for the reply specifications.
37524 @item t @var{addr}:@var{PP},@var{MM}
37525 @cindex @samp{t} packet
37526 Search backwards starting at address @var{addr} for a match with pattern
37527 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37528 There must be at least 3 digits in @var{addr}.
37530 @item T @var{thread-id}
37531 @cindex @samp{T} packet
37532 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37537 thread is still alive
37543 Packets starting with @samp{v} are identified by a multi-letter name,
37544 up to the first @samp{;} or @samp{?} (or the end of the packet).
37546 @item vAttach;@var{pid}
37547 @cindex @samp{vAttach} packet
37548 Attach to a new process with the specified process ID @var{pid}.
37549 The process ID is a
37550 hexadecimal integer identifying the process. In all-stop mode, all
37551 threads in the attached process are stopped; in non-stop mode, it may be
37552 attached without being stopped if that is supported by the target.
37554 @c In non-stop mode, on a successful vAttach, the stub should set the
37555 @c current thread to a thread of the newly-attached process. After
37556 @c attaching, GDB queries for the attached process's thread ID with qC.
37557 @c Also note that, from a user perspective, whether or not the
37558 @c target is stopped on attach in non-stop mode depends on whether you
37559 @c use the foreground or background version of the attach command, not
37560 @c on what vAttach does; GDB does the right thing with respect to either
37561 @c stopping or restarting threads.
37563 This packet is only available in extended mode (@pxref{extended mode}).
37569 @item @r{Any stop packet}
37570 for success in all-stop mode (@pxref{Stop Reply Packets})
37572 for success in non-stop mode (@pxref{Remote Non-Stop})
37575 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37576 @cindex @samp{vCont} packet
37577 @anchor{vCont packet}
37578 Resume the inferior, specifying different actions for each thread.
37580 For each inferior thread, the leftmost action with a matching
37581 @var{thread-id} is applied. Threads that don't match any action
37582 remain in their current state. Thread IDs are specified using the
37583 syntax described in @ref{thread-id syntax}. If multiprocess
37584 extensions (@pxref{multiprocess extensions}) are supported, actions
37585 can be specified to match all threads in a process by using the
37586 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37587 @var{thread-id} matches all threads. Specifying no actions is an
37590 Currently supported actions are:
37596 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37600 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37603 @item r @var{start},@var{end}
37604 Step once, and then keep stepping as long as the thread stops at
37605 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37606 The remote stub reports a stop reply when either the thread goes out
37607 of the range or is stopped due to an unrelated reason, such as hitting
37608 a breakpoint. @xref{range stepping}.
37610 If the range is empty (@var{start} == @var{end}), then the action
37611 becomes equivalent to the @samp{s} action. In other words,
37612 single-step once, and report the stop (even if the stepped instruction
37613 jumps to @var{start}).
37615 (A stop reply may be sent at any point even if the PC is still within
37616 the stepping range; for example, it is valid to implement this packet
37617 in a degenerate way as a single instruction step operation.)
37621 The optional argument @var{addr} normally associated with the
37622 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37623 not supported in @samp{vCont}.
37625 The @samp{t} action is only relevant in non-stop mode
37626 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37627 A stop reply should be generated for any affected thread not already stopped.
37628 When a thread is stopped by means of a @samp{t} action,
37629 the corresponding stop reply should indicate that the thread has stopped with
37630 signal @samp{0}, regardless of whether the target uses some other signal
37631 as an implementation detail.
37633 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37634 @samp{r} actions for threads that are already running. Conversely,
37635 the server must ignore @samp{t} actions for threads that are already
37638 @emph{Note:} In non-stop mode, a thread is considered running until
37639 @value{GDBN} acknowleges an asynchronous stop notification for it with
37640 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37642 The stub must support @samp{vCont} if it reports support for
37643 multiprocess extensions (@pxref{multiprocess extensions}).
37646 @xref{Stop Reply Packets}, for the reply specifications.
37649 @cindex @samp{vCont?} packet
37650 Request a list of actions supported by the @samp{vCont} packet.
37654 @item vCont@r{[};@var{action}@dots{}@r{]}
37655 The @samp{vCont} packet is supported. Each @var{action} is a supported
37656 command in the @samp{vCont} packet.
37658 The @samp{vCont} packet is not supported.
37661 @anchor{vCtrlC packet}
37663 @cindex @samp{vCtrlC} packet
37664 Interrupt remote target as if a control-C was pressed on the remote
37665 terminal. This is the equivalent to reacting to the @code{^C}
37666 (@samp{\003}, the control-C character) character in all-stop mode
37667 while the target is running, except this works in non-stop mode.
37668 @xref{interrupting remote targets}, for more info on the all-stop
37679 @item vFile:@var{operation}:@var{parameter}@dots{}
37680 @cindex @samp{vFile} packet
37681 Perform a file operation on the target system. For details,
37682 see @ref{Host I/O Packets}.
37684 @item vFlashErase:@var{addr},@var{length}
37685 @cindex @samp{vFlashErase} packet
37686 Direct the stub to erase @var{length} bytes of flash starting at
37687 @var{addr}. The region may enclose any number of flash blocks, but
37688 its start and end must fall on block boundaries, as indicated by the
37689 flash block size appearing in the memory map (@pxref{Memory Map
37690 Format}). @value{GDBN} groups flash memory programming operations
37691 together, and sends a @samp{vFlashDone} request after each group; the
37692 stub is allowed to delay erase operation until the @samp{vFlashDone}
37693 packet is received.
37703 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37704 @cindex @samp{vFlashWrite} packet
37705 Direct the stub to write data to flash address @var{addr}. The data
37706 is passed in binary form using the same encoding as for the @samp{X}
37707 packet (@pxref{Binary Data}). The memory ranges specified by
37708 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37709 not overlap, and must appear in order of increasing addresses
37710 (although @samp{vFlashErase} packets for higher addresses may already
37711 have been received; the ordering is guaranteed only between
37712 @samp{vFlashWrite} packets). If a packet writes to an address that was
37713 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37714 target-specific method, the results are unpredictable.
37722 for vFlashWrite addressing non-flash memory
37728 @cindex @samp{vFlashDone} packet
37729 Indicate to the stub that flash programming operation is finished.
37730 The stub is permitted to delay or batch the effects of a group of
37731 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37732 @samp{vFlashDone} packet is received. The contents of the affected
37733 regions of flash memory are unpredictable until the @samp{vFlashDone}
37734 request is completed.
37736 @item vKill;@var{pid}
37737 @cindex @samp{vKill} packet
37738 @anchor{vKill packet}
37739 Kill the process with the specified process ID @var{pid}, which is a
37740 hexadecimal integer identifying the process. This packet is used in
37741 preference to @samp{k} when multiprocess protocol extensions are
37742 supported; see @ref{multiprocess extensions}.
37752 @item vMustReplyEmpty
37753 @cindex @samp{vMustReplyEmpty} packet
37754 The correct reply to an unknown @samp{v} packet is to return the empty
37755 string, however, some older versions of @command{gdbserver} would
37756 incorrectly return @samp{OK} for unknown @samp{v} packets.
37758 The @samp{vMustReplyEmpty} is used as a feature test to check how
37759 @command{gdbserver} handles unknown packets, it is important that this
37760 packet be handled in the same way as other unknown @samp{v} packets.
37761 If this packet is handled differently to other unknown @samp{v}
37762 packets then it is possile that @value{GDBN} may run into problems in
37763 other areas, specifically around use of @samp{vFile:setfs:}.
37765 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37766 @cindex @samp{vRun} packet
37767 Run the program @var{filename}, passing it each @var{argument} on its
37768 command line. The file and arguments are hex-encoded strings. If
37769 @var{filename} is an empty string, the stub may use a default program
37770 (e.g.@: the last program run). The program is created in the stopped
37773 @c FIXME: What about non-stop mode?
37775 This packet is only available in extended mode (@pxref{extended mode}).
37781 @item @r{Any stop packet}
37782 for success (@pxref{Stop Reply Packets})
37786 @cindex @samp{vStopped} packet
37787 @xref{Notification Packets}.
37789 @item X @var{addr},@var{length}:@var{XX@dots{}}
37791 @cindex @samp{X} packet
37792 Write data to memory, where the data is transmitted in binary.
37793 Memory is specified by its address @var{addr} and number of addressable memory
37794 units @var{length} (@pxref{addressable memory unit});
37795 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37805 @item z @var{type},@var{addr},@var{kind}
37806 @itemx Z @var{type},@var{addr},@var{kind}
37807 @anchor{insert breakpoint or watchpoint packet}
37808 @cindex @samp{z} packet
37809 @cindex @samp{Z} packets
37810 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37811 watchpoint starting at address @var{address} of kind @var{kind}.
37813 Each breakpoint and watchpoint packet @var{type} is documented
37816 @emph{Implementation notes: A remote target shall return an empty string
37817 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37818 remote target shall support either both or neither of a given
37819 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37820 avoid potential problems with duplicate packets, the operations should
37821 be implemented in an idempotent way.}
37823 @item z0,@var{addr},@var{kind}
37824 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37825 @cindex @samp{z0} packet
37826 @cindex @samp{Z0} packet
37827 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37828 @var{addr} of type @var{kind}.
37830 A software breakpoint is implemented by replacing the instruction at
37831 @var{addr} with a software breakpoint or trap instruction. The
37832 @var{kind} is target-specific and typically indicates the size of the
37833 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37834 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37835 architectures have additional meanings for @var{kind}
37836 (@pxref{Architecture-Specific Protocol Details}); if no
37837 architecture-specific value is being used, it should be @samp{0}.
37838 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37839 conditional expressions in bytecode form that should be evaluated on
37840 the target's side. These are the conditions that should be taken into
37841 consideration when deciding if the breakpoint trigger should be
37842 reported back to @value{GDBN}.
37844 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37845 for how to best report a software breakpoint event to @value{GDBN}.
37847 The @var{cond_list} parameter is comprised of a series of expressions,
37848 concatenated without separators. Each expression has the following form:
37852 @item X @var{len},@var{expr}
37853 @var{len} is the length of the bytecode expression and @var{expr} is the
37854 actual conditional expression in bytecode form.
37858 The optional @var{cmd_list} parameter introduces commands that may be
37859 run on the target, rather than being reported back to @value{GDBN}.
37860 The parameter starts with a numeric flag @var{persist}; if the flag is
37861 nonzero, then the breakpoint may remain active and the commands
37862 continue to be run even when @value{GDBN} disconnects from the target.
37863 Following this flag is a series of expressions concatenated with no
37864 separators. Each expression has the following form:
37868 @item X @var{len},@var{expr}
37869 @var{len} is the length of the bytecode expression and @var{expr} is the
37870 actual commands expression in bytecode form.
37874 @emph{Implementation note: It is possible for a target to copy or move
37875 code that contains software breakpoints (e.g., when implementing
37876 overlays). The behavior of this packet, in the presence of such a
37877 target, is not defined.}
37889 @item z1,@var{addr},@var{kind}
37890 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37891 @cindex @samp{z1} packet
37892 @cindex @samp{Z1} packet
37893 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37894 address @var{addr}.
37896 A hardware breakpoint is implemented using a mechanism that is not
37897 dependent on being able to modify the target's memory. The
37898 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37899 same meaning as in @samp{Z0} packets.
37901 @emph{Implementation note: A hardware breakpoint is not affected by code
37914 @item z2,@var{addr},@var{kind}
37915 @itemx Z2,@var{addr},@var{kind}
37916 @cindex @samp{z2} packet
37917 @cindex @samp{Z2} packet
37918 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37919 The number of bytes to watch is specified by @var{kind}.
37931 @item z3,@var{addr},@var{kind}
37932 @itemx Z3,@var{addr},@var{kind}
37933 @cindex @samp{z3} packet
37934 @cindex @samp{Z3} packet
37935 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37936 The number of bytes to watch is specified by @var{kind}.
37948 @item z4,@var{addr},@var{kind}
37949 @itemx Z4,@var{addr},@var{kind}
37950 @cindex @samp{z4} packet
37951 @cindex @samp{Z4} packet
37952 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37953 The number of bytes to watch is specified by @var{kind}.
37967 @node Stop Reply Packets
37968 @section Stop Reply Packets
37969 @cindex stop reply packets
37971 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37972 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37973 receive any of the below as a reply. Except for @samp{?}
37974 and @samp{vStopped}, that reply is only returned
37975 when the target halts. In the below the exact meaning of @dfn{signal
37976 number} is defined by the header @file{include/gdb/signals.h} in the
37977 @value{GDBN} source code.
37979 In non-stop mode, the server will simply reply @samp{OK} to commands
37980 such as @samp{vCont}; any stop will be the subject of a future
37981 notification. @xref{Remote Non-Stop}.
37983 As in the description of request packets, we include spaces in the
37984 reply templates for clarity; these are not part of the reply packet's
37985 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37991 The program received signal number @var{AA} (a two-digit hexadecimal
37992 number). This is equivalent to a @samp{T} response with no
37993 @var{n}:@var{r} pairs.
37995 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37996 @cindex @samp{T} packet reply
37997 The program received signal number @var{AA} (a two-digit hexadecimal
37998 number). This is equivalent to an @samp{S} response, except that the
37999 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38000 and other information directly in the stop reply packet, reducing
38001 round-trip latency. Single-step and breakpoint traps are reported
38002 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38006 If @var{n} is a hexadecimal number, it is a register number, and the
38007 corresponding @var{r} gives that register's value. The data @var{r} is a
38008 series of bytes in target byte order, with each byte given by a
38009 two-digit hex number.
38012 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38013 the stopped thread, as specified in @ref{thread-id syntax}.
38016 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38017 the core on which the stop event was detected.
38020 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38021 specific event that stopped the target. The currently defined stop
38022 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38023 signal. At most one stop reason should be present.
38026 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38027 and go on to the next; this allows us to extend the protocol in the
38031 The currently defined stop reasons are:
38037 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38040 @item syscall_entry
38041 @itemx syscall_return
38042 The packet indicates a syscall entry or return, and @var{r} is the
38043 syscall number, in hex.
38045 @cindex shared library events, remote reply
38047 The packet indicates that the loaded libraries have changed.
38048 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38049 list of loaded libraries. The @var{r} part is ignored.
38051 @cindex replay log events, remote reply
38053 The packet indicates that the target cannot continue replaying
38054 logged execution events, because it has reached the end (or the
38055 beginning when executing backward) of the log. The value of @var{r}
38056 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38057 for more information.
38060 @anchor{swbreak stop reason}
38061 The packet indicates a software breakpoint instruction was executed,
38062 irrespective of whether it was @value{GDBN} that planted the
38063 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38064 part must be left empty.
38066 On some architectures, such as x86, at the architecture level, when a
38067 breakpoint instruction executes the program counter points at the
38068 breakpoint address plus an offset. On such targets, the stub is
38069 responsible for adjusting the PC to point back at the breakpoint
38072 This packet should not be sent by default; older @value{GDBN} versions
38073 did not support it. @value{GDBN} requests it, by supplying an
38074 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38075 remote stub must also supply the appropriate @samp{qSupported} feature
38076 indicating support.
38078 This packet is required for correct non-stop mode operation.
38081 The packet indicates the target stopped for a hardware breakpoint.
38082 The @var{r} part must be left empty.
38084 The same remarks about @samp{qSupported} and non-stop mode above
38087 @cindex fork events, remote reply
38089 The packet indicates that @code{fork} was called, and @var{r}
38090 is the thread ID of the new child process. Refer to
38091 @ref{thread-id syntax} for the format of the @var{thread-id}
38092 field. This packet is only applicable to targets that support
38095 This packet should not be sent by default; older @value{GDBN} versions
38096 did not support it. @value{GDBN} requests it, by supplying an
38097 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38098 remote stub must also supply the appropriate @samp{qSupported} feature
38099 indicating support.
38101 @cindex vfork events, remote reply
38103 The packet indicates that @code{vfork} was called, and @var{r}
38104 is the thread ID of the new child process. Refer to
38105 @ref{thread-id syntax} for the format of the @var{thread-id}
38106 field. This packet is only applicable to targets that support
38109 This packet should not be sent by default; older @value{GDBN} versions
38110 did not support it. @value{GDBN} requests it, by supplying an
38111 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38112 remote stub must also supply the appropriate @samp{qSupported} feature
38113 indicating support.
38115 @cindex vforkdone events, remote reply
38117 The packet indicates that a child process created by a vfork
38118 has either called @code{exec} or terminated, so that the
38119 address spaces of the parent and child process are no longer
38120 shared. The @var{r} part is ignored. This packet is only
38121 applicable to targets that support vforkdone events.
38123 This packet should not be sent by default; older @value{GDBN} versions
38124 did not support it. @value{GDBN} requests it, by supplying an
38125 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38126 remote stub must also supply the appropriate @samp{qSupported} feature
38127 indicating support.
38129 @cindex exec events, remote reply
38131 The packet indicates that @code{execve} was called, and @var{r}
38132 is the absolute pathname of the file that was executed, in hex.
38133 This packet is only applicable to targets that support exec events.
38135 This packet should not be sent by default; older @value{GDBN} versions
38136 did not support it. @value{GDBN} requests it, by supplying an
38137 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38138 remote stub must also supply the appropriate @samp{qSupported} feature
38139 indicating support.
38141 @cindex thread create event, remote reply
38142 @anchor{thread create event}
38144 The packet indicates that the thread was just created. The new thread
38145 is stopped until @value{GDBN} sets it running with a resumption packet
38146 (@pxref{vCont packet}). This packet should not be sent by default;
38147 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38148 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38149 @var{r} part is ignored.
38154 @itemx W @var{AA} ; process:@var{pid}
38155 The process exited, and @var{AA} is the exit status. This is only
38156 applicable to certain targets.
38158 The second form of the response, including the process ID of the
38159 exited process, can be used only when @value{GDBN} has reported
38160 support for multiprocess protocol extensions; see @ref{multiprocess
38161 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38165 @itemx X @var{AA} ; process:@var{pid}
38166 The process terminated with signal @var{AA}.
38168 The second form of the response, including the process ID of the
38169 terminated process, can be used only when @value{GDBN} has reported
38170 support for multiprocess protocol extensions; see @ref{multiprocess
38171 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38174 @anchor{thread exit event}
38175 @cindex thread exit event, remote reply
38176 @item w @var{AA} ; @var{tid}
38178 The thread exited, and @var{AA} is the exit status. This response
38179 should not be sent by default; @value{GDBN} requests it with the
38180 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38181 @var{AA} is formatted as a big-endian hex string.
38184 There are no resumed threads left in the target. In other words, even
38185 though the process is alive, the last resumed thread has exited. For
38186 example, say the target process has two threads: thread 1 and thread
38187 2. The client leaves thread 1 stopped, and resumes thread 2, which
38188 subsequently exits. At this point, even though the process is still
38189 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38190 executing either. The @samp{N} stop reply thus informs the client
38191 that it can stop waiting for stop replies. This packet should not be
38192 sent by default; older @value{GDBN} versions did not support it.
38193 @value{GDBN} requests it, by supplying an appropriate
38194 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38195 also supply the appropriate @samp{qSupported} feature indicating
38198 @item O @var{XX}@dots{}
38199 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38200 written as the program's console output. This can happen at any time
38201 while the program is running and the debugger should continue to wait
38202 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38204 @item F @var{call-id},@var{parameter}@dots{}
38205 @var{call-id} is the identifier which says which host system call should
38206 be called. This is just the name of the function. Translation into the
38207 correct system call is only applicable as it's defined in @value{GDBN}.
38208 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38211 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38212 this very system call.
38214 The target replies with this packet when it expects @value{GDBN} to
38215 call a host system call on behalf of the target. @value{GDBN} replies
38216 with an appropriate @samp{F} packet and keeps up waiting for the next
38217 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38218 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38219 Protocol Extension}, for more details.
38223 @node General Query Packets
38224 @section General Query Packets
38225 @cindex remote query requests
38227 Packets starting with @samp{q} are @dfn{general query packets};
38228 packets starting with @samp{Q} are @dfn{general set packets}. General
38229 query and set packets are a semi-unified form for retrieving and
38230 sending information to and from the stub.
38232 The initial letter of a query or set packet is followed by a name
38233 indicating what sort of thing the packet applies to. For example,
38234 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38235 definitions with the stub. These packet names follow some
38240 The name must not contain commas, colons or semicolons.
38242 Most @value{GDBN} query and set packets have a leading upper case
38245 The names of custom vendor packets should use a company prefix, in
38246 lower case, followed by a period. For example, packets designed at
38247 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38248 foos) or @samp{Qacme.bar} (for setting bars).
38251 The name of a query or set packet should be separated from any
38252 parameters by a @samp{:}; the parameters themselves should be
38253 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38254 full packet name, and check for a separator or the end of the packet,
38255 in case two packet names share a common prefix. New packets should not begin
38256 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38257 packets predate these conventions, and have arguments without any terminator
38258 for the packet name; we suspect they are in widespread use in places that
38259 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38260 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38263 Like the descriptions of the other packets, each description here
38264 has a template showing the packet's overall syntax, followed by an
38265 explanation of the packet's meaning. We include spaces in some of the
38266 templates for clarity; these are not part of the packet's syntax. No
38267 @value{GDBN} packet uses spaces to separate its components.
38269 Here are the currently defined query and set packets:
38275 Turn on or off the agent as a helper to perform some debugging operations
38276 delegated from @value{GDBN} (@pxref{Control Agent}).
38278 @item QAllow:@var{op}:@var{val}@dots{}
38279 @cindex @samp{QAllow} packet
38280 Specify which operations @value{GDBN} expects to request of the
38281 target, as a semicolon-separated list of operation name and value
38282 pairs. Possible values for @var{op} include @samp{WriteReg},
38283 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38284 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38285 indicating that @value{GDBN} will not request the operation, or 1,
38286 indicating that it may. (The target can then use this to set up its
38287 own internals optimally, for instance if the debugger never expects to
38288 insert breakpoints, it may not need to install its own trap handler.)
38291 @cindex current thread, remote request
38292 @cindex @samp{qC} packet
38293 Return the current thread ID.
38297 @item QC @var{thread-id}
38298 Where @var{thread-id} is a thread ID as documented in
38299 @ref{thread-id syntax}.
38300 @item @r{(anything else)}
38301 Any other reply implies the old thread ID.
38304 @item qCRC:@var{addr},@var{length}
38305 @cindex CRC of memory block, remote request
38306 @cindex @samp{qCRC} packet
38307 @anchor{qCRC packet}
38308 Compute the CRC checksum of a block of memory using CRC-32 defined in
38309 IEEE 802.3. The CRC is computed byte at a time, taking the most
38310 significant bit of each byte first. The initial pattern code
38311 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38313 @emph{Note:} This is the same CRC used in validating separate debug
38314 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38315 Files}). However the algorithm is slightly different. When validating
38316 separate debug files, the CRC is computed taking the @emph{least}
38317 significant bit of each byte first, and the final result is inverted to
38318 detect trailing zeros.
38323 An error (such as memory fault)
38324 @item C @var{crc32}
38325 The specified memory region's checksum is @var{crc32}.
38328 @item QDisableRandomization:@var{value}
38329 @cindex disable address space randomization, remote request
38330 @cindex @samp{QDisableRandomization} packet
38331 Some target operating systems will randomize the virtual address space
38332 of the inferior process as a security feature, but provide a feature
38333 to disable such randomization, e.g.@: to allow for a more deterministic
38334 debugging experience. On such systems, this packet with a @var{value}
38335 of 1 directs the target to disable address space randomization for
38336 processes subsequently started via @samp{vRun} packets, while a packet
38337 with a @var{value} of 0 tells the target to enable address space
38340 This packet is only available in extended mode (@pxref{extended mode}).
38345 The request succeeded.
38348 An error occurred. The error number @var{nn} is given as hex digits.
38351 An empty reply indicates that @samp{QDisableRandomization} is not supported
38355 This packet is not probed by default; the remote stub must request it,
38356 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38357 This should only be done on targets that actually support disabling
38358 address space randomization.
38360 @item QStartupWithShell:@var{value}
38361 @cindex startup with shell, remote request
38362 @cindex @samp{QStartupWithShell} packet
38363 On UNIX-like targets, it is possible to start the inferior using a
38364 shell program. This is the default behavior on both @value{GDBN} and
38365 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38366 used to inform @command{gdbserver} whether it should start the
38367 inferior using a shell or not.
38369 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38370 to start the inferior. If @var{value} is @samp{1},
38371 @command{gdbserver} will use a shell to start the inferior. All other
38372 values are considered an error.
38374 This packet is only available in extended mode (@pxref{extended
38380 The request succeeded.
38383 An error occurred. The error number @var{nn} is given as hex digits.
38386 This packet is not probed by default; the remote stub must request it,
38387 by supplying an appropriate @samp{qSupported} response
38388 (@pxref{qSupported}). This should only be done on targets that
38389 actually support starting the inferior using a shell.
38391 Use of this packet is controlled by the @code{set startup-with-shell}
38392 command; @pxref{set startup-with-shell}.
38394 @item QEnvironmentHexEncoded:@var{hex-value}
38395 @anchor{QEnvironmentHexEncoded}
38396 @cindex set environment variable, remote request
38397 @cindex @samp{QEnvironmentHexEncoded} packet
38398 On UNIX-like targets, it is possible to set environment variables that
38399 will be passed to the inferior during the startup process. This
38400 packet is used to inform @command{gdbserver} of an environment
38401 variable that has been defined by the user on @value{GDBN} (@pxref{set
38404 The packet is composed by @var{hex-value}, an hex encoded
38405 representation of the @var{name=value} format representing an
38406 environment variable. The name of the environment variable is
38407 represented by @var{name}, and the value to be assigned to the
38408 environment variable is represented by @var{value}. If the variable
38409 has no value (i.e., the value is @code{null}), then @var{value} will
38412 This packet is only available in extended mode (@pxref{extended
38418 The request succeeded.
38421 This packet is not probed by default; the remote stub must request it,
38422 by supplying an appropriate @samp{qSupported} response
38423 (@pxref{qSupported}). This should only be done on targets that
38424 actually support passing environment variables to the starting
38427 This packet is related to the @code{set environment} command;
38428 @pxref{set environment}.
38430 @item QEnvironmentUnset:@var{hex-value}
38431 @anchor{QEnvironmentUnset}
38432 @cindex unset environment variable, remote request
38433 @cindex @samp{QEnvironmentUnset} packet
38434 On UNIX-like targets, it is possible to unset environment variables
38435 before starting the inferior in the remote target. This packet is
38436 used to inform @command{gdbserver} of an environment variable that has
38437 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38439 The packet is composed by @var{hex-value}, an hex encoded
38440 representation of the name of the environment variable to be unset.
38442 This packet is only available in extended mode (@pxref{extended
38448 The request succeeded.
38451 This packet is not probed by default; the remote stub must request it,
38452 by supplying an appropriate @samp{qSupported} response
38453 (@pxref{qSupported}). This should only be done on targets that
38454 actually support passing environment variables to the starting
38457 This packet is related to the @code{unset environment} command;
38458 @pxref{unset environment}.
38460 @item QEnvironmentReset
38461 @anchor{QEnvironmentReset}
38462 @cindex reset environment, remote request
38463 @cindex @samp{QEnvironmentReset} packet
38464 On UNIX-like targets, this packet is used to reset the state of
38465 environment variables in the remote target before starting the
38466 inferior. In this context, reset means unsetting all environment
38467 variables that were previously set by the user (i.e., were not
38468 initially present in the environment). It is sent to
38469 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38470 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38471 (@pxref{QEnvironmentUnset}) packets.
38473 This packet is only available in extended mode (@pxref{extended
38479 The request succeeded.
38482 This packet is not probed by default; the remote stub must request it,
38483 by supplying an appropriate @samp{qSupported} response
38484 (@pxref{qSupported}). This should only be done on targets that
38485 actually support passing environment variables to the starting
38488 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38489 @anchor{QSetWorkingDir packet}
38490 @cindex set working directory, remote request
38491 @cindex @samp{QSetWorkingDir} packet
38492 This packet is used to inform the remote server of the intended
38493 current working directory for programs that are going to be executed.
38495 The packet is composed by @var{directory}, an hex encoded
38496 representation of the directory that the remote inferior will use as
38497 its current working directory. If @var{directory} is an empty string,
38498 the remote server should reset the inferior's current working
38499 directory to its original, empty value.
38501 This packet is only available in extended mode (@pxref{extended
38507 The request succeeded.
38511 @itemx qsThreadInfo
38512 @cindex list active threads, remote request
38513 @cindex @samp{qfThreadInfo} packet
38514 @cindex @samp{qsThreadInfo} packet
38515 Obtain a list of all active thread IDs from the target (OS). Since there
38516 may be too many active threads to fit into one reply packet, this query
38517 works iteratively: it may require more than one query/reply sequence to
38518 obtain the entire list of threads. The first query of the sequence will
38519 be the @samp{qfThreadInfo} query; subsequent queries in the
38520 sequence will be the @samp{qsThreadInfo} query.
38522 NOTE: This packet replaces the @samp{qL} query (see below).
38526 @item m @var{thread-id}
38528 @item m @var{thread-id},@var{thread-id}@dots{}
38529 a comma-separated list of thread IDs
38531 (lower case letter @samp{L}) denotes end of list.
38534 In response to each query, the target will reply with a list of one or
38535 more thread IDs, separated by commas.
38536 @value{GDBN} will respond to each reply with a request for more thread
38537 ids (using the @samp{qs} form of the query), until the target responds
38538 with @samp{l} (lower-case ell, for @dfn{last}).
38539 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38542 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38543 initial connection with the remote target, and the very first thread ID
38544 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38545 message. Therefore, the stub should ensure that the first thread ID in
38546 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38548 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38549 @cindex get thread-local storage address, remote request
38550 @cindex @samp{qGetTLSAddr} packet
38551 Fetch the address associated with thread local storage specified
38552 by @var{thread-id}, @var{offset}, and @var{lm}.
38554 @var{thread-id} is the thread ID associated with the
38555 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38557 @var{offset} is the (big endian, hex encoded) offset associated with the
38558 thread local variable. (This offset is obtained from the debug
38559 information associated with the variable.)
38561 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38562 load module associated with the thread local storage. For example,
38563 a @sc{gnu}/Linux system will pass the link map address of the shared
38564 object associated with the thread local storage under consideration.
38565 Other operating environments may choose to represent the load module
38566 differently, so the precise meaning of this parameter will vary.
38570 @item @var{XX}@dots{}
38571 Hex encoded (big endian) bytes representing the address of the thread
38572 local storage requested.
38575 An error occurred. The error number @var{nn} is given as hex digits.
38578 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38581 @item qGetTIBAddr:@var{thread-id}
38582 @cindex get thread information block address
38583 @cindex @samp{qGetTIBAddr} packet
38584 Fetch address of the Windows OS specific Thread Information Block.
38586 @var{thread-id} is the thread ID associated with the thread.
38590 @item @var{XX}@dots{}
38591 Hex encoded (big endian) bytes representing the linear address of the
38592 thread information block.
38595 An error occured. This means that either the thread was not found, or the
38596 address could not be retrieved.
38599 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38602 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38603 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38604 digit) is one to indicate the first query and zero to indicate a
38605 subsequent query; @var{threadcount} (two hex digits) is the maximum
38606 number of threads the response packet can contain; and @var{nextthread}
38607 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38608 returned in the response as @var{argthread}.
38610 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38614 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38615 Where: @var{count} (two hex digits) is the number of threads being
38616 returned; @var{done} (one hex digit) is zero to indicate more threads
38617 and one indicates no further threads; @var{argthreadid} (eight hex
38618 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38619 is a sequence of thread IDs, @var{threadid} (eight hex
38620 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38624 @cindex section offsets, remote request
38625 @cindex @samp{qOffsets} packet
38626 Get section offsets that the target used when relocating the downloaded
38631 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38632 Relocate the @code{Text} section by @var{xxx} from its original address.
38633 Relocate the @code{Data} section by @var{yyy} from its original address.
38634 If the object file format provides segment information (e.g.@: @sc{elf}
38635 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38636 segments by the supplied offsets.
38638 @emph{Note: while a @code{Bss} offset may be included in the response,
38639 @value{GDBN} ignores this and instead applies the @code{Data} offset
38640 to the @code{Bss} section.}
38642 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38643 Relocate the first segment of the object file, which conventionally
38644 contains program code, to a starting address of @var{xxx}. If
38645 @samp{DataSeg} is specified, relocate the second segment, which
38646 conventionally contains modifiable data, to a starting address of
38647 @var{yyy}. @value{GDBN} will report an error if the object file
38648 does not contain segment information, or does not contain at least
38649 as many segments as mentioned in the reply. Extra segments are
38650 kept at fixed offsets relative to the last relocated segment.
38653 @item qP @var{mode} @var{thread-id}
38654 @cindex thread information, remote request
38655 @cindex @samp{qP} packet
38656 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38657 encoded 32 bit mode; @var{thread-id} is a thread ID
38658 (@pxref{thread-id syntax}).
38660 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38663 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38667 @cindex non-stop mode, remote request
38668 @cindex @samp{QNonStop} packet
38670 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38671 @xref{Remote Non-Stop}, for more information.
38676 The request succeeded.
38679 An error occurred. The error number @var{nn} is given as hex digits.
38682 An empty reply indicates that @samp{QNonStop} is not supported by
38686 This packet is not probed by default; the remote stub must request it,
38687 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38688 Use of this packet is controlled by the @code{set non-stop} command;
38689 @pxref{Non-Stop Mode}.
38691 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38692 @itemx QCatchSyscalls:0
38693 @cindex catch syscalls from inferior, remote request
38694 @cindex @samp{QCatchSyscalls} packet
38695 @anchor{QCatchSyscalls}
38696 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38697 catching syscalls from the inferior process.
38699 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38700 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38701 is listed, every system call should be reported.
38703 Note that if a syscall not in the list is reported, @value{GDBN} will
38704 still filter the event according to its own list from all corresponding
38705 @code{catch syscall} commands. However, it is more efficient to only
38706 report the requested syscalls.
38708 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38709 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38711 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38712 kept for the new process too. On targets where exec may affect syscall
38713 numbers, for example with exec between 32 and 64-bit processes, the
38714 client should send a new packet with the new syscall list.
38719 The request succeeded.
38722 An error occurred. @var{nn} are hex digits.
38725 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38729 Use of this packet is controlled by the @code{set remote catch-syscalls}
38730 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38731 This packet is not probed by default; the remote stub must request it,
38732 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38734 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38735 @cindex pass signals to inferior, remote request
38736 @cindex @samp{QPassSignals} packet
38737 @anchor{QPassSignals}
38738 Each listed @var{signal} should be passed directly to the inferior process.
38739 Signals are numbered identically to continue packets and stop replies
38740 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38741 strictly greater than the previous item. These signals do not need to stop
38742 the inferior, or be reported to @value{GDBN}. All other signals should be
38743 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38744 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38745 new list. This packet improves performance when using @samp{handle
38746 @var{signal} nostop noprint pass}.
38751 The request succeeded.
38754 An error occurred. The error number @var{nn} is given as hex digits.
38757 An empty reply indicates that @samp{QPassSignals} is not supported by
38761 Use of this packet is controlled by the @code{set remote pass-signals}
38762 command (@pxref{Remote Configuration, set remote pass-signals}).
38763 This packet is not probed by default; the remote stub must request it,
38764 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38766 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38767 @cindex signals the inferior may see, remote request
38768 @cindex @samp{QProgramSignals} packet
38769 @anchor{QProgramSignals}
38770 Each listed @var{signal} may be delivered to the inferior process.
38771 Others should be silently discarded.
38773 In some cases, the remote stub may need to decide whether to deliver a
38774 signal to the program or not without @value{GDBN} involvement. One
38775 example of that is while detaching --- the program's threads may have
38776 stopped for signals that haven't yet had a chance of being reported to
38777 @value{GDBN}, and so the remote stub can use the signal list specified
38778 by this packet to know whether to deliver or ignore those pending
38781 This does not influence whether to deliver a signal as requested by a
38782 resumption packet (@pxref{vCont packet}).
38784 Signals are numbered identically to continue packets and stop replies
38785 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38786 strictly greater than the previous item. Multiple
38787 @samp{QProgramSignals} packets do not combine; any earlier
38788 @samp{QProgramSignals} list is completely replaced by the new list.
38793 The request succeeded.
38796 An error occurred. The error number @var{nn} is given as hex digits.
38799 An empty reply indicates that @samp{QProgramSignals} is not supported
38803 Use of this packet is controlled by the @code{set remote program-signals}
38804 command (@pxref{Remote Configuration, set remote program-signals}).
38805 This packet is not probed by default; the remote stub must request it,
38806 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38808 @anchor{QThreadEvents}
38809 @item QThreadEvents:1
38810 @itemx QThreadEvents:0
38811 @cindex thread create/exit events, remote request
38812 @cindex @samp{QThreadEvents} packet
38814 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38815 reporting of thread create and exit events. @xref{thread create
38816 event}, for the reply specifications. For example, this is used in
38817 non-stop mode when @value{GDBN} stops a set of threads and
38818 synchronously waits for the their corresponding stop replies. Without
38819 exit events, if one of the threads exits, @value{GDBN} would hang
38820 forever not knowing that it should no longer expect a stop for that
38821 same thread. @value{GDBN} does not enable this feature unless the
38822 stub reports that it supports it by including @samp{QThreadEvents+} in
38823 its @samp{qSupported} reply.
38828 The request succeeded.
38831 An error occurred. The error number @var{nn} is given as hex digits.
38834 An empty reply indicates that @samp{QThreadEvents} is not supported by
38838 Use of this packet is controlled by the @code{set remote thread-events}
38839 command (@pxref{Remote Configuration, set remote thread-events}).
38841 @item qRcmd,@var{command}
38842 @cindex execute remote command, remote request
38843 @cindex @samp{qRcmd} packet
38844 @var{command} (hex encoded) is passed to the local interpreter for
38845 execution. Invalid commands should be reported using the output
38846 string. Before the final result packet, the target may also respond
38847 with a number of intermediate @samp{O@var{output}} console output
38848 packets. @emph{Implementors should note that providing access to a
38849 stubs's interpreter may have security implications}.
38854 A command response with no output.
38856 A command response with the hex encoded output string @var{OUTPUT}.
38858 Indicate a badly formed request.
38860 An empty reply indicates that @samp{qRcmd} is not recognized.
38863 (Note that the @code{qRcmd} packet's name is separated from the
38864 command by a @samp{,}, not a @samp{:}, contrary to the naming
38865 conventions above. Please don't use this packet as a model for new
38868 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38869 @cindex searching memory, in remote debugging
38871 @cindex @samp{qSearch:memory} packet
38873 @cindex @samp{qSearch memory} packet
38874 @anchor{qSearch memory}
38875 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38876 Both @var{address} and @var{length} are encoded in hex;
38877 @var{search-pattern} is a sequence of bytes, also hex encoded.
38882 The pattern was not found.
38884 The pattern was found at @var{address}.
38886 A badly formed request or an error was encountered while searching memory.
38888 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38891 @item QStartNoAckMode
38892 @cindex @samp{QStartNoAckMode} packet
38893 @anchor{QStartNoAckMode}
38894 Request that the remote stub disable the normal @samp{+}/@samp{-}
38895 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38900 The stub has switched to no-acknowledgment mode.
38901 @value{GDBN} acknowledges this reponse,
38902 but neither the stub nor @value{GDBN} shall send or expect further
38903 @samp{+}/@samp{-} acknowledgments in the current connection.
38905 An empty reply indicates that the stub does not support no-acknowledgment mode.
38908 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38909 @cindex supported packets, remote query
38910 @cindex features of the remote protocol
38911 @cindex @samp{qSupported} packet
38912 @anchor{qSupported}
38913 Tell the remote stub about features supported by @value{GDBN}, and
38914 query the stub for features it supports. This packet allows
38915 @value{GDBN} and the remote stub to take advantage of each others'
38916 features. @samp{qSupported} also consolidates multiple feature probes
38917 at startup, to improve @value{GDBN} performance---a single larger
38918 packet performs better than multiple smaller probe packets on
38919 high-latency links. Some features may enable behavior which must not
38920 be on by default, e.g.@: because it would confuse older clients or
38921 stubs. Other features may describe packets which could be
38922 automatically probed for, but are not. These features must be
38923 reported before @value{GDBN} will use them. This ``default
38924 unsupported'' behavior is not appropriate for all packets, but it
38925 helps to keep the initial connection time under control with new
38926 versions of @value{GDBN} which support increasing numbers of packets.
38930 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38931 The stub supports or does not support each returned @var{stubfeature},
38932 depending on the form of each @var{stubfeature} (see below for the
38935 An empty reply indicates that @samp{qSupported} is not recognized,
38936 or that no features needed to be reported to @value{GDBN}.
38939 The allowed forms for each feature (either a @var{gdbfeature} in the
38940 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38944 @item @var{name}=@var{value}
38945 The remote protocol feature @var{name} is supported, and associated
38946 with the specified @var{value}. The format of @var{value} depends
38947 on the feature, but it must not include a semicolon.
38949 The remote protocol feature @var{name} is supported, and does not
38950 need an associated value.
38952 The remote protocol feature @var{name} is not supported.
38954 The remote protocol feature @var{name} may be supported, and
38955 @value{GDBN} should auto-detect support in some other way when it is
38956 needed. This form will not be used for @var{gdbfeature} notifications,
38957 but may be used for @var{stubfeature} responses.
38960 Whenever the stub receives a @samp{qSupported} request, the
38961 supplied set of @value{GDBN} features should override any previous
38962 request. This allows @value{GDBN} to put the stub in a known
38963 state, even if the stub had previously been communicating with
38964 a different version of @value{GDBN}.
38966 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38971 This feature indicates whether @value{GDBN} supports multiprocess
38972 extensions to the remote protocol. @value{GDBN} does not use such
38973 extensions unless the stub also reports that it supports them by
38974 including @samp{multiprocess+} in its @samp{qSupported} reply.
38975 @xref{multiprocess extensions}, for details.
38978 This feature indicates that @value{GDBN} supports the XML target
38979 description. If the stub sees @samp{xmlRegisters=} with target
38980 specific strings separated by a comma, it will report register
38984 This feature indicates whether @value{GDBN} supports the
38985 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38986 instruction reply packet}).
38989 This feature indicates whether @value{GDBN} supports the swbreak stop
38990 reason in stop replies. @xref{swbreak stop reason}, for details.
38993 This feature indicates whether @value{GDBN} supports the hwbreak stop
38994 reason in stop replies. @xref{swbreak stop reason}, for details.
38997 This feature indicates whether @value{GDBN} supports fork event
38998 extensions to the remote protocol. @value{GDBN} does not use such
38999 extensions unless the stub also reports that it supports them by
39000 including @samp{fork-events+} in its @samp{qSupported} reply.
39003 This feature indicates whether @value{GDBN} supports vfork event
39004 extensions to the remote protocol. @value{GDBN} does not use such
39005 extensions unless the stub also reports that it supports them by
39006 including @samp{vfork-events+} in its @samp{qSupported} reply.
39009 This feature indicates whether @value{GDBN} supports exec event
39010 extensions to the remote protocol. @value{GDBN} does not use such
39011 extensions unless the stub also reports that it supports them by
39012 including @samp{exec-events+} in its @samp{qSupported} reply.
39014 @item vContSupported
39015 This feature indicates whether @value{GDBN} wants to know the
39016 supported actions in the reply to @samp{vCont?} packet.
39019 Stubs should ignore any unknown values for
39020 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39021 packet supports receiving packets of unlimited length (earlier
39022 versions of @value{GDBN} may reject overly long responses). Additional values
39023 for @var{gdbfeature} may be defined in the future to let the stub take
39024 advantage of new features in @value{GDBN}, e.g.@: incompatible
39025 improvements in the remote protocol---the @samp{multiprocess} feature is
39026 an example of such a feature. The stub's reply should be independent
39027 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39028 describes all the features it supports, and then the stub replies with
39029 all the features it supports.
39031 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39032 responses, as long as each response uses one of the standard forms.
39034 Some features are flags. A stub which supports a flag feature
39035 should respond with a @samp{+} form response. Other features
39036 require values, and the stub should respond with an @samp{=}
39039 Each feature has a default value, which @value{GDBN} will use if
39040 @samp{qSupported} is not available or if the feature is not mentioned
39041 in the @samp{qSupported} response. The default values are fixed; a
39042 stub is free to omit any feature responses that match the defaults.
39044 Not all features can be probed, but for those which can, the probing
39045 mechanism is useful: in some cases, a stub's internal
39046 architecture may not allow the protocol layer to know some information
39047 about the underlying target in advance. This is especially common in
39048 stubs which may be configured for multiple targets.
39050 These are the currently defined stub features and their properties:
39052 @multitable @columnfractions 0.35 0.2 0.12 0.2
39053 @c NOTE: The first row should be @headitem, but we do not yet require
39054 @c a new enough version of Texinfo (4.7) to use @headitem.
39056 @tab Value Required
39060 @item @samp{PacketSize}
39065 @item @samp{qXfer:auxv:read}
39070 @item @samp{qXfer:btrace:read}
39075 @item @samp{qXfer:btrace-conf:read}
39080 @item @samp{qXfer:exec-file:read}
39085 @item @samp{qXfer:features:read}
39090 @item @samp{qXfer:libraries:read}
39095 @item @samp{qXfer:libraries-svr4:read}
39100 @item @samp{augmented-libraries-svr4-read}
39105 @item @samp{qXfer:memory-map:read}
39110 @item @samp{qXfer:sdata:read}
39115 @item @samp{qXfer:spu:read}
39120 @item @samp{qXfer:spu:write}
39125 @item @samp{qXfer:siginfo:read}
39130 @item @samp{qXfer:siginfo:write}
39135 @item @samp{qXfer:threads:read}
39140 @item @samp{qXfer:traceframe-info:read}
39145 @item @samp{qXfer:uib:read}
39150 @item @samp{qXfer:fdpic:read}
39155 @item @samp{Qbtrace:off}
39160 @item @samp{Qbtrace:bts}
39165 @item @samp{Qbtrace:pt}
39170 @item @samp{Qbtrace-conf:bts:size}
39175 @item @samp{Qbtrace-conf:pt:size}
39180 @item @samp{QNonStop}
39185 @item @samp{QCatchSyscalls}
39190 @item @samp{QPassSignals}
39195 @item @samp{QStartNoAckMode}
39200 @item @samp{multiprocess}
39205 @item @samp{ConditionalBreakpoints}
39210 @item @samp{ConditionalTracepoints}
39215 @item @samp{ReverseContinue}
39220 @item @samp{ReverseStep}
39225 @item @samp{TracepointSource}
39230 @item @samp{QAgent}
39235 @item @samp{QAllow}
39240 @item @samp{QDisableRandomization}
39245 @item @samp{EnableDisableTracepoints}
39250 @item @samp{QTBuffer:size}
39255 @item @samp{tracenz}
39260 @item @samp{BreakpointCommands}
39265 @item @samp{swbreak}
39270 @item @samp{hwbreak}
39275 @item @samp{fork-events}
39280 @item @samp{vfork-events}
39285 @item @samp{exec-events}
39290 @item @samp{QThreadEvents}
39295 @item @samp{no-resumed}
39302 These are the currently defined stub features, in more detail:
39305 @cindex packet size, remote protocol
39306 @item PacketSize=@var{bytes}
39307 The remote stub can accept packets up to at least @var{bytes} in
39308 length. @value{GDBN} will send packets up to this size for bulk
39309 transfers, and will never send larger packets. This is a limit on the
39310 data characters in the packet, including the frame and checksum.
39311 There is no trailing NUL byte in a remote protocol packet; if the stub
39312 stores packets in a NUL-terminated format, it should allow an extra
39313 byte in its buffer for the NUL. If this stub feature is not supported,
39314 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39316 @item qXfer:auxv:read
39317 The remote stub understands the @samp{qXfer:auxv:read} packet
39318 (@pxref{qXfer auxiliary vector read}).
39320 @item qXfer:btrace:read
39321 The remote stub understands the @samp{qXfer:btrace:read}
39322 packet (@pxref{qXfer btrace read}).
39324 @item qXfer:btrace-conf:read
39325 The remote stub understands the @samp{qXfer:btrace-conf:read}
39326 packet (@pxref{qXfer btrace-conf read}).
39328 @item qXfer:exec-file:read
39329 The remote stub understands the @samp{qXfer:exec-file:read} packet
39330 (@pxref{qXfer executable filename read}).
39332 @item qXfer:features:read
39333 The remote stub understands the @samp{qXfer:features:read} packet
39334 (@pxref{qXfer target description read}).
39336 @item qXfer:libraries:read
39337 The remote stub understands the @samp{qXfer:libraries:read} packet
39338 (@pxref{qXfer library list read}).
39340 @item qXfer:libraries-svr4:read
39341 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39342 (@pxref{qXfer svr4 library list read}).
39344 @item augmented-libraries-svr4-read
39345 The remote stub understands the augmented form of the
39346 @samp{qXfer:libraries-svr4:read} packet
39347 (@pxref{qXfer svr4 library list read}).
39349 @item qXfer:memory-map:read
39350 The remote stub understands the @samp{qXfer:memory-map:read} packet
39351 (@pxref{qXfer memory map read}).
39353 @item qXfer:sdata:read
39354 The remote stub understands the @samp{qXfer:sdata:read} packet
39355 (@pxref{qXfer sdata read}).
39357 @item qXfer:spu:read
39358 The remote stub understands the @samp{qXfer:spu:read} packet
39359 (@pxref{qXfer spu read}).
39361 @item qXfer:spu:write
39362 The remote stub understands the @samp{qXfer:spu:write} packet
39363 (@pxref{qXfer spu write}).
39365 @item qXfer:siginfo:read
39366 The remote stub understands the @samp{qXfer:siginfo:read} packet
39367 (@pxref{qXfer siginfo read}).
39369 @item qXfer:siginfo:write
39370 The remote stub understands the @samp{qXfer:siginfo:write} packet
39371 (@pxref{qXfer siginfo write}).
39373 @item qXfer:threads:read
39374 The remote stub understands the @samp{qXfer:threads:read} packet
39375 (@pxref{qXfer threads read}).
39377 @item qXfer:traceframe-info:read
39378 The remote stub understands the @samp{qXfer:traceframe-info:read}
39379 packet (@pxref{qXfer traceframe info read}).
39381 @item qXfer:uib:read
39382 The remote stub understands the @samp{qXfer:uib:read}
39383 packet (@pxref{qXfer unwind info block}).
39385 @item qXfer:fdpic:read
39386 The remote stub understands the @samp{qXfer:fdpic:read}
39387 packet (@pxref{qXfer fdpic loadmap read}).
39390 The remote stub understands the @samp{QNonStop} packet
39391 (@pxref{QNonStop}).
39393 @item QCatchSyscalls
39394 The remote stub understands the @samp{QCatchSyscalls} packet
39395 (@pxref{QCatchSyscalls}).
39398 The remote stub understands the @samp{QPassSignals} packet
39399 (@pxref{QPassSignals}).
39401 @item QStartNoAckMode
39402 The remote stub understands the @samp{QStartNoAckMode} packet and
39403 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39406 @anchor{multiprocess extensions}
39407 @cindex multiprocess extensions, in remote protocol
39408 The remote stub understands the multiprocess extensions to the remote
39409 protocol syntax. The multiprocess extensions affect the syntax of
39410 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39411 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39412 replies. Note that reporting this feature indicates support for the
39413 syntactic extensions only, not that the stub necessarily supports
39414 debugging of more than one process at a time. The stub must not use
39415 multiprocess extensions in packet replies unless @value{GDBN} has also
39416 indicated it supports them in its @samp{qSupported} request.
39418 @item qXfer:osdata:read
39419 The remote stub understands the @samp{qXfer:osdata:read} packet
39420 ((@pxref{qXfer osdata read}).
39422 @item ConditionalBreakpoints
39423 The target accepts and implements evaluation of conditional expressions
39424 defined for breakpoints. The target will only report breakpoint triggers
39425 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39427 @item ConditionalTracepoints
39428 The remote stub accepts and implements conditional expressions defined
39429 for tracepoints (@pxref{Tracepoint Conditions}).
39431 @item ReverseContinue
39432 The remote stub accepts and implements the reverse continue packet
39436 The remote stub accepts and implements the reverse step packet
39439 @item TracepointSource
39440 The remote stub understands the @samp{QTDPsrc} packet that supplies
39441 the source form of tracepoint definitions.
39444 The remote stub understands the @samp{QAgent} packet.
39447 The remote stub understands the @samp{QAllow} packet.
39449 @item QDisableRandomization
39450 The remote stub understands the @samp{QDisableRandomization} packet.
39452 @item StaticTracepoint
39453 @cindex static tracepoints, in remote protocol
39454 The remote stub supports static tracepoints.
39456 @item InstallInTrace
39457 @anchor{install tracepoint in tracing}
39458 The remote stub supports installing tracepoint in tracing.
39460 @item EnableDisableTracepoints
39461 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39462 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39463 to be enabled and disabled while a trace experiment is running.
39465 @item QTBuffer:size
39466 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39467 packet that allows to change the size of the trace buffer.
39470 @cindex string tracing, in remote protocol
39471 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39472 See @ref{Bytecode Descriptions} for details about the bytecode.
39474 @item BreakpointCommands
39475 @cindex breakpoint commands, in remote protocol
39476 The remote stub supports running a breakpoint's command list itself,
39477 rather than reporting the hit to @value{GDBN}.
39480 The remote stub understands the @samp{Qbtrace:off} packet.
39483 The remote stub understands the @samp{Qbtrace:bts} packet.
39486 The remote stub understands the @samp{Qbtrace:pt} packet.
39488 @item Qbtrace-conf:bts:size
39489 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39491 @item Qbtrace-conf:pt:size
39492 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39495 The remote stub reports the @samp{swbreak} stop reason for memory
39499 The remote stub reports the @samp{hwbreak} stop reason for hardware
39503 The remote stub reports the @samp{fork} stop reason for fork events.
39506 The remote stub reports the @samp{vfork} stop reason for vfork events
39507 and vforkdone events.
39510 The remote stub reports the @samp{exec} stop reason for exec events.
39512 @item vContSupported
39513 The remote stub reports the supported actions in the reply to
39514 @samp{vCont?} packet.
39516 @item QThreadEvents
39517 The remote stub understands the @samp{QThreadEvents} packet.
39520 The remote stub reports the @samp{N} stop reply.
39525 @cindex symbol lookup, remote request
39526 @cindex @samp{qSymbol} packet
39527 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39528 requests. Accept requests from the target for the values of symbols.
39533 The target does not need to look up any (more) symbols.
39534 @item qSymbol:@var{sym_name}
39535 The target requests the value of symbol @var{sym_name} (hex encoded).
39536 @value{GDBN} may provide the value by using the
39537 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39541 @item qSymbol:@var{sym_value}:@var{sym_name}
39542 Set the value of @var{sym_name} to @var{sym_value}.
39544 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39545 target has previously requested.
39547 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39548 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39554 The target does not need to look up any (more) symbols.
39555 @item qSymbol:@var{sym_name}
39556 The target requests the value of a new symbol @var{sym_name} (hex
39557 encoded). @value{GDBN} will continue to supply the values of symbols
39558 (if available), until the target ceases to request them.
39563 @itemx QTDisconnected
39570 @itemx qTMinFTPILen
39572 @xref{Tracepoint Packets}.
39574 @item qThreadExtraInfo,@var{thread-id}
39575 @cindex thread attributes info, remote request
39576 @cindex @samp{qThreadExtraInfo} packet
39577 Obtain from the target OS a printable string description of thread
39578 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39579 for the forms of @var{thread-id}. This
39580 string may contain anything that the target OS thinks is interesting
39581 for @value{GDBN} to tell the user about the thread. The string is
39582 displayed in @value{GDBN}'s @code{info threads} display. Some
39583 examples of possible thread extra info strings are @samp{Runnable}, or
39584 @samp{Blocked on Mutex}.
39588 @item @var{XX}@dots{}
39589 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39590 comprising the printable string containing the extra information about
39591 the thread's attributes.
39594 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39595 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39596 conventions above. Please don't use this packet as a model for new
39615 @xref{Tracepoint Packets}.
39617 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39618 @cindex read special object, remote request
39619 @cindex @samp{qXfer} packet
39620 @anchor{qXfer read}
39621 Read uninterpreted bytes from the target's special data area
39622 identified by the keyword @var{object}. Request @var{length} bytes
39623 starting at @var{offset} bytes into the data. The content and
39624 encoding of @var{annex} is specific to @var{object}; it can supply
39625 additional details about what data to access.
39630 Data @var{data} (@pxref{Binary Data}) has been read from the
39631 target. There may be more data at a higher address (although
39632 it is permitted to return @samp{m} even for the last valid
39633 block of data, as long as at least one byte of data was read).
39634 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39638 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39639 There is no more data to be read. It is possible for @var{data} to
39640 have fewer bytes than the @var{length} in the request.
39643 The @var{offset} in the request is at the end of the data.
39644 There is no more data to be read.
39647 The request was malformed, or @var{annex} was invalid.
39650 The offset was invalid, or there was an error encountered reading the data.
39651 The @var{nn} part is a hex-encoded @code{errno} value.
39654 An empty reply indicates the @var{object} string was not recognized by
39655 the stub, or that the object does not support reading.
39658 Here are the specific requests of this form defined so far. All the
39659 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39660 formats, listed above.
39663 @item qXfer:auxv:read::@var{offset},@var{length}
39664 @anchor{qXfer auxiliary vector read}
39665 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39666 auxiliary vector}. Note @var{annex} must be empty.
39668 This packet is not probed by default; the remote stub must request it,
39669 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39671 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39672 @anchor{qXfer btrace read}
39674 Return a description of the current branch trace.
39675 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39676 packet may have one of the following values:
39680 Returns all available branch trace.
39683 Returns all available branch trace if the branch trace changed since
39684 the last read request.
39687 Returns the new branch trace since the last read request. Adds a new
39688 block to the end of the trace that begins at zero and ends at the source
39689 location of the first branch in the trace buffer. This extra block is
39690 used to stitch traces together.
39692 If the trace buffer overflowed, returns an error indicating the overflow.
39695 This packet is not probed by default; the remote stub must request it
39696 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39698 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39699 @anchor{qXfer btrace-conf read}
39701 Return a description of the current branch trace configuration.
39702 @xref{Branch Trace Configuration Format}.
39704 This packet is not probed by default; the remote stub must request it
39705 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39707 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39708 @anchor{qXfer executable filename read}
39709 Return the full absolute name of the file that was executed to create
39710 a process running on the remote system. The annex specifies the
39711 numeric process ID of the process to query, encoded as a hexadecimal
39712 number. If the annex part is empty the remote stub should return the
39713 filename corresponding to the currently executing process.
39715 This packet is not probed by default; the remote stub must request it,
39716 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39718 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39719 @anchor{qXfer target description read}
39720 Access the @dfn{target description}. @xref{Target Descriptions}. The
39721 annex specifies which XML document to access. The main description is
39722 always loaded from the @samp{target.xml} annex.
39724 This packet is not probed by default; the remote stub must request it,
39725 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39727 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39728 @anchor{qXfer library list read}
39729 Access the target's list of loaded libraries. @xref{Library List Format}.
39730 The annex part of the generic @samp{qXfer} packet must be empty
39731 (@pxref{qXfer read}).
39733 Targets which maintain a list of libraries in the program's memory do
39734 not need to implement this packet; it is designed for platforms where
39735 the operating system manages the list of loaded libraries.
39737 This packet is not probed by default; the remote stub must request it,
39738 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39740 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39741 @anchor{qXfer svr4 library list read}
39742 Access the target's list of loaded libraries when the target is an SVR4
39743 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39744 of the generic @samp{qXfer} packet must be empty unless the remote
39745 stub indicated it supports the augmented form of this packet
39746 by supplying an appropriate @samp{qSupported} response
39747 (@pxref{qXfer read}, @ref{qSupported}).
39749 This packet is optional for better performance on SVR4 targets.
39750 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39752 This packet is not probed by default; the remote stub must request it,
39753 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39755 If the remote stub indicates it supports the augmented form of this
39756 packet then the annex part of the generic @samp{qXfer} packet may
39757 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39758 arguments. The currently supported arguments are:
39761 @item start=@var{address}
39762 A hexadecimal number specifying the address of the @samp{struct
39763 link_map} to start reading the library list from. If unset or zero
39764 then the first @samp{struct link_map} in the library list will be
39765 chosen as the starting point.
39767 @item prev=@var{address}
39768 A hexadecimal number specifying the address of the @samp{struct
39769 link_map} immediately preceding the @samp{struct link_map}
39770 specified by the @samp{start} argument. If unset or zero then
39771 the remote stub will expect that no @samp{struct link_map}
39772 exists prior to the starting point.
39776 Arguments that are not understood by the remote stub will be silently
39779 @item qXfer:memory-map:read::@var{offset},@var{length}
39780 @anchor{qXfer memory map read}
39781 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39782 annex part of the generic @samp{qXfer} packet must be empty
39783 (@pxref{qXfer read}).
39785 This packet is not probed by default; the remote stub must request it,
39786 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39788 @item qXfer:sdata:read::@var{offset},@var{length}
39789 @anchor{qXfer sdata read}
39791 Read contents of the extra collected static tracepoint marker
39792 information. The annex part of the generic @samp{qXfer} packet must
39793 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39796 This packet is not probed by default; the remote stub must request it,
39797 by supplying an appropriate @samp{qSupported} response
39798 (@pxref{qSupported}).
39800 @item qXfer:siginfo:read::@var{offset},@var{length}
39801 @anchor{qXfer siginfo read}
39802 Read contents of the extra signal information on the target
39803 system. The annex part of the generic @samp{qXfer} packet must be
39804 empty (@pxref{qXfer read}).
39806 This packet is not probed by default; the remote stub must request it,
39807 by supplying an appropriate @samp{qSupported} response
39808 (@pxref{qSupported}).
39810 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39811 @anchor{qXfer spu read}
39812 Read contents of an @code{spufs} file on the target system. The
39813 annex specifies which file to read; it must be of the form
39814 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39815 in the target process, and @var{name} identifes the @code{spufs} file
39816 in that context to be accessed.
39818 This packet is not probed by default; the remote stub must request it,
39819 by supplying an appropriate @samp{qSupported} response
39820 (@pxref{qSupported}).
39822 @item qXfer:threads:read::@var{offset},@var{length}
39823 @anchor{qXfer threads read}
39824 Access the list of threads on target. @xref{Thread List Format}. The
39825 annex part of the generic @samp{qXfer} packet must be empty
39826 (@pxref{qXfer read}).
39828 This packet is not probed by default; the remote stub must request it,
39829 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39831 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39832 @anchor{qXfer traceframe info read}
39834 Return a description of the current traceframe's contents.
39835 @xref{Traceframe Info Format}. The annex part of the generic
39836 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39838 This packet is not probed by default; the remote stub must request it,
39839 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39841 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39842 @anchor{qXfer unwind info block}
39844 Return the unwind information block for @var{pc}. This packet is used
39845 on OpenVMS/ia64 to ask the kernel unwind information.
39847 This packet is not probed by default.
39849 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39850 @anchor{qXfer fdpic loadmap read}
39851 Read contents of @code{loadmap}s on the target system. The
39852 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39853 executable @code{loadmap} or interpreter @code{loadmap} to read.
39855 This packet is not probed by default; the remote stub must request it,
39856 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39858 @item qXfer:osdata:read::@var{offset},@var{length}
39859 @anchor{qXfer osdata read}
39860 Access the target's @dfn{operating system information}.
39861 @xref{Operating System Information}.
39865 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39866 @cindex write data into object, remote request
39867 @anchor{qXfer write}
39868 Write uninterpreted bytes into the target's special data area
39869 identified by the keyword @var{object}, starting at @var{offset} bytes
39870 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39871 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39872 is specific to @var{object}; it can supply additional details about what data
39878 @var{nn} (hex encoded) is the number of bytes written.
39879 This may be fewer bytes than supplied in the request.
39882 The request was malformed, or @var{annex} was invalid.
39885 The offset was invalid, or there was an error encountered writing the data.
39886 The @var{nn} part is a hex-encoded @code{errno} value.
39889 An empty reply indicates the @var{object} string was not
39890 recognized by the stub, or that the object does not support writing.
39893 Here are the specific requests of this form defined so far. All the
39894 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39895 formats, listed above.
39898 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39899 @anchor{qXfer siginfo write}
39900 Write @var{data} to the extra signal information on the target system.
39901 The annex part of the generic @samp{qXfer} packet must be
39902 empty (@pxref{qXfer write}).
39904 This packet is not probed by default; the remote stub must request it,
39905 by supplying an appropriate @samp{qSupported} response
39906 (@pxref{qSupported}).
39908 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39909 @anchor{qXfer spu write}
39910 Write @var{data} to an @code{spufs} file on the target system. The
39911 annex specifies which file to write; it must be of the form
39912 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39913 in the target process, and @var{name} identifes the @code{spufs} file
39914 in that context to be accessed.
39916 This packet is not probed by default; the remote stub must request it,
39917 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39920 @item qXfer:@var{object}:@var{operation}:@dots{}
39921 Requests of this form may be added in the future. When a stub does
39922 not recognize the @var{object} keyword, or its support for
39923 @var{object} does not recognize the @var{operation} keyword, the stub
39924 must respond with an empty packet.
39926 @item qAttached:@var{pid}
39927 @cindex query attached, remote request
39928 @cindex @samp{qAttached} packet
39929 Return an indication of whether the remote server attached to an
39930 existing process or created a new process. When the multiprocess
39931 protocol extensions are supported (@pxref{multiprocess extensions}),
39932 @var{pid} is an integer in hexadecimal format identifying the target
39933 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39934 the query packet will be simplified as @samp{qAttached}.
39936 This query is used, for example, to know whether the remote process
39937 should be detached or killed when a @value{GDBN} session is ended with
39938 the @code{quit} command.
39943 The remote server attached to an existing process.
39945 The remote server created a new process.
39947 A badly formed request or an error was encountered.
39951 Enable branch tracing for the current thread using Branch Trace Store.
39956 Branch tracing has been enabled.
39958 A badly formed request or an error was encountered.
39962 Enable branch tracing for the current thread using Intel Processor Trace.
39967 Branch tracing has been enabled.
39969 A badly formed request or an error was encountered.
39973 Disable branch tracing for the current thread.
39978 Branch tracing has been disabled.
39980 A badly formed request or an error was encountered.
39983 @item Qbtrace-conf:bts:size=@var{value}
39984 Set the requested ring buffer size for new threads that use the
39985 btrace recording method in bts format.
39990 The ring buffer size has been set.
39992 A badly formed request or an error was encountered.
39995 @item Qbtrace-conf:pt:size=@var{value}
39996 Set the requested ring buffer size for new threads that use the
39997 btrace recording method in pt format.
40002 The ring buffer size has been set.
40004 A badly formed request or an error was encountered.
40009 @node Architecture-Specific Protocol Details
40010 @section Architecture-Specific Protocol Details
40012 This section describes how the remote protocol is applied to specific
40013 target architectures. Also see @ref{Standard Target Features}, for
40014 details of XML target descriptions for each architecture.
40017 * ARM-Specific Protocol Details::
40018 * MIPS-Specific Protocol Details::
40021 @node ARM-Specific Protocol Details
40022 @subsection @acronym{ARM}-specific Protocol Details
40025 * ARM Breakpoint Kinds::
40028 @node ARM Breakpoint Kinds
40029 @subsubsection @acronym{ARM} Breakpoint Kinds
40030 @cindex breakpoint kinds, @acronym{ARM}
40032 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40037 16-bit Thumb mode breakpoint.
40040 32-bit Thumb mode (Thumb-2) breakpoint.
40043 32-bit @acronym{ARM} mode breakpoint.
40047 @node MIPS-Specific Protocol Details
40048 @subsection @acronym{MIPS}-specific Protocol Details
40051 * MIPS Register packet Format::
40052 * MIPS Breakpoint Kinds::
40055 @node MIPS Register packet Format
40056 @subsubsection @acronym{MIPS} Register Packet Format
40057 @cindex register packet format, @acronym{MIPS}
40059 The following @code{g}/@code{G} packets have previously been defined.
40060 In the below, some thirty-two bit registers are transferred as
40061 sixty-four bits. Those registers should be zero/sign extended (which?)
40062 to fill the space allocated. Register bytes are transferred in target
40063 byte order. The two nibbles within a register byte are transferred
40064 most-significant -- least-significant.
40069 All registers are transferred as thirty-two bit quantities in the order:
40070 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40071 registers; fsr; fir; fp.
40074 All registers are transferred as sixty-four bit quantities (including
40075 thirty-two bit registers such as @code{sr}). The ordering is the same
40080 @node MIPS Breakpoint Kinds
40081 @subsubsection @acronym{MIPS} Breakpoint Kinds
40082 @cindex breakpoint kinds, @acronym{MIPS}
40084 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40089 16-bit @acronym{MIPS16} mode breakpoint.
40092 16-bit @acronym{microMIPS} mode breakpoint.
40095 32-bit standard @acronym{MIPS} mode breakpoint.
40098 32-bit @acronym{microMIPS} mode breakpoint.
40102 @node Tracepoint Packets
40103 @section Tracepoint Packets
40104 @cindex tracepoint packets
40105 @cindex packets, tracepoint
40107 Here we describe the packets @value{GDBN} uses to implement
40108 tracepoints (@pxref{Tracepoints}).
40112 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40113 @cindex @samp{QTDP} packet
40114 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40115 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40116 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40117 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40118 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40119 the number of bytes that the target should copy elsewhere to make room
40120 for the tracepoint. If an @samp{X} is present, it introduces a
40121 tracepoint condition, which consists of a hexadecimal length, followed
40122 by a comma and hex-encoded bytes, in a manner similar to action
40123 encodings as described below. If the trailing @samp{-} is present,
40124 further @samp{QTDP} packets will follow to specify this tracepoint's
40130 The packet was understood and carried out.
40132 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40134 The packet was not recognized.
40137 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40138 Define actions to be taken when a tracepoint is hit. The @var{n} and
40139 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40140 this tracepoint. This packet may only be sent immediately after
40141 another @samp{QTDP} packet that ended with a @samp{-}. If the
40142 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40143 specifying more actions for this tracepoint.
40145 In the series of action packets for a given tracepoint, at most one
40146 can have an @samp{S} before its first @var{action}. If such a packet
40147 is sent, it and the following packets define ``while-stepping''
40148 actions. Any prior packets define ordinary actions --- that is, those
40149 taken when the tracepoint is first hit. If no action packet has an
40150 @samp{S}, then all the packets in the series specify ordinary
40151 tracepoint actions.
40153 The @samp{@var{action}@dots{}} portion of the packet is a series of
40154 actions, concatenated without separators. Each action has one of the
40160 Collect the registers whose bits are set in @var{mask},
40161 a hexadecimal number whose @var{i}'th bit is set if register number
40162 @var{i} should be collected. (The least significant bit is numbered
40163 zero.) Note that @var{mask} may be any number of digits long; it may
40164 not fit in a 32-bit word.
40166 @item M @var{basereg},@var{offset},@var{len}
40167 Collect @var{len} bytes of memory starting at the address in register
40168 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40169 @samp{-1}, then the range has a fixed address: @var{offset} is the
40170 address of the lowest byte to collect. The @var{basereg},
40171 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40172 values (the @samp{-1} value for @var{basereg} is a special case).
40174 @item X @var{len},@var{expr}
40175 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40176 it directs. The agent expression @var{expr} is as described in
40177 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40178 two-digit hex number in the packet; @var{len} is the number of bytes
40179 in the expression (and thus one-half the number of hex digits in the
40184 Any number of actions may be packed together in a single @samp{QTDP}
40185 packet, as long as the packet does not exceed the maximum packet
40186 length (400 bytes, for many stubs). There may be only one @samp{R}
40187 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40188 actions. Any registers referred to by @samp{M} and @samp{X} actions
40189 must be collected by a preceding @samp{R} action. (The
40190 ``while-stepping'' actions are treated as if they were attached to a
40191 separate tracepoint, as far as these restrictions are concerned.)
40196 The packet was understood and carried out.
40198 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40200 The packet was not recognized.
40203 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40204 @cindex @samp{QTDPsrc} packet
40205 Specify a source string of tracepoint @var{n} at address @var{addr}.
40206 This is useful to get accurate reproduction of the tracepoints
40207 originally downloaded at the beginning of the trace run. The @var{type}
40208 is the name of the tracepoint part, such as @samp{cond} for the
40209 tracepoint's conditional expression (see below for a list of types), while
40210 @var{bytes} is the string, encoded in hexadecimal.
40212 @var{start} is the offset of the @var{bytes} within the overall source
40213 string, while @var{slen} is the total length of the source string.
40214 This is intended for handling source strings that are longer than will
40215 fit in a single packet.
40216 @c Add detailed example when this info is moved into a dedicated
40217 @c tracepoint descriptions section.
40219 The available string types are @samp{at} for the location,
40220 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40221 @value{GDBN} sends a separate packet for each command in the action
40222 list, in the same order in which the commands are stored in the list.
40224 The target does not need to do anything with source strings except
40225 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40228 Although this packet is optional, and @value{GDBN} will only send it
40229 if the target replies with @samp{TracepointSource} @xref{General
40230 Query Packets}, it makes both disconnected tracing and trace files
40231 much easier to use. Otherwise the user must be careful that the
40232 tracepoints in effect while looking at trace frames are identical to
40233 the ones in effect during the trace run; even a small discrepancy
40234 could cause @samp{tdump} not to work, or a particular trace frame not
40237 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40238 @cindex define trace state variable, remote request
40239 @cindex @samp{QTDV} packet
40240 Create a new trace state variable, number @var{n}, with an initial
40241 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40242 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40243 the option of not using this packet for initial values of zero; the
40244 target should simply create the trace state variables as they are
40245 mentioned in expressions. The value @var{builtin} should be 1 (one)
40246 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40247 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40248 @samp{qTsV} packet had it set. The contents of @var{name} is the
40249 hex-encoded name (without the leading @samp{$}) of the trace state
40252 @item QTFrame:@var{n}
40253 @cindex @samp{QTFrame} packet
40254 Select the @var{n}'th tracepoint frame from the buffer, and use the
40255 register and memory contents recorded there to answer subsequent
40256 request packets from @value{GDBN}.
40258 A successful reply from the stub indicates that the stub has found the
40259 requested frame. The response is a series of parts, concatenated
40260 without separators, describing the frame we selected. Each part has
40261 one of the following forms:
40265 The selected frame is number @var{n} in the trace frame buffer;
40266 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40267 was no frame matching the criteria in the request packet.
40270 The selected trace frame records a hit of tracepoint number @var{t};
40271 @var{t} is a hexadecimal number.
40275 @item QTFrame:pc:@var{addr}
40276 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40277 currently selected frame whose PC is @var{addr};
40278 @var{addr} is a hexadecimal number.
40280 @item QTFrame:tdp:@var{t}
40281 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40282 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40283 is a hexadecimal number.
40285 @item QTFrame:range:@var{start}:@var{end}
40286 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40287 currently selected frame whose PC is between @var{start} (inclusive)
40288 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40291 @item QTFrame:outside:@var{start}:@var{end}
40292 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40293 frame @emph{outside} the given range of addresses (exclusive).
40296 @cindex @samp{qTMinFTPILen} packet
40297 This packet requests the minimum length of instruction at which a fast
40298 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40299 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40300 it depends on the target system being able to create trampolines in
40301 the first 64K of memory, which might or might not be possible for that
40302 system. So the reply to this packet will be 4 if it is able to
40309 The minimum instruction length is currently unknown.
40311 The minimum instruction length is @var{length}, where @var{length}
40312 is a hexadecimal number greater or equal to 1. A reply
40313 of 1 means that a fast tracepoint may be placed on any instruction
40314 regardless of size.
40316 An error has occurred.
40318 An empty reply indicates that the request is not supported by the stub.
40322 @cindex @samp{QTStart} packet
40323 Begin the tracepoint experiment. Begin collecting data from
40324 tracepoint hits in the trace frame buffer. This packet supports the
40325 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40326 instruction reply packet}).
40329 @cindex @samp{QTStop} packet
40330 End the tracepoint experiment. Stop collecting trace frames.
40332 @item QTEnable:@var{n}:@var{addr}
40334 @cindex @samp{QTEnable} packet
40335 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40336 experiment. If the tracepoint was previously disabled, then collection
40337 of data from it will resume.
40339 @item QTDisable:@var{n}:@var{addr}
40341 @cindex @samp{QTDisable} packet
40342 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40343 experiment. No more data will be collected from the tracepoint unless
40344 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40347 @cindex @samp{QTinit} packet
40348 Clear the table of tracepoints, and empty the trace frame buffer.
40350 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40351 @cindex @samp{QTro} packet
40352 Establish the given ranges of memory as ``transparent''. The stub
40353 will answer requests for these ranges from memory's current contents,
40354 if they were not collected as part of the tracepoint hit.
40356 @value{GDBN} uses this to mark read-only regions of memory, like those
40357 containing program code. Since these areas never change, they should
40358 still have the same contents they did when the tracepoint was hit, so
40359 there's no reason for the stub to refuse to provide their contents.
40361 @item QTDisconnected:@var{value}
40362 @cindex @samp{QTDisconnected} packet
40363 Set the choice to what to do with the tracing run when @value{GDBN}
40364 disconnects from the target. A @var{value} of 1 directs the target to
40365 continue the tracing run, while 0 tells the target to stop tracing if
40366 @value{GDBN} is no longer in the picture.
40369 @cindex @samp{qTStatus} packet
40370 Ask the stub if there is a trace experiment running right now.
40372 The reply has the form:
40376 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40377 @var{running} is a single digit @code{1} if the trace is presently
40378 running, or @code{0} if not. It is followed by semicolon-separated
40379 optional fields that an agent may use to report additional status.
40383 If the trace is not running, the agent may report any of several
40384 explanations as one of the optional fields:
40389 No trace has been run yet.
40391 @item tstop[:@var{text}]:0
40392 The trace was stopped by a user-originated stop command. The optional
40393 @var{text} field is a user-supplied string supplied as part of the
40394 stop command (for instance, an explanation of why the trace was
40395 stopped manually). It is hex-encoded.
40398 The trace stopped because the trace buffer filled up.
40400 @item tdisconnected:0
40401 The trace stopped because @value{GDBN} disconnected from the target.
40403 @item tpasscount:@var{tpnum}
40404 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40406 @item terror:@var{text}:@var{tpnum}
40407 The trace stopped because tracepoint @var{tpnum} had an error. The
40408 string @var{text} is available to describe the nature of the error
40409 (for instance, a divide by zero in the condition expression); it
40413 The trace stopped for some other reason.
40417 Additional optional fields supply statistical and other information.
40418 Although not required, they are extremely useful for users monitoring
40419 the progress of a trace run. If a trace has stopped, and these
40420 numbers are reported, they must reflect the state of the just-stopped
40425 @item tframes:@var{n}
40426 The number of trace frames in the buffer.
40428 @item tcreated:@var{n}
40429 The total number of trace frames created during the run. This may
40430 be larger than the trace frame count, if the buffer is circular.
40432 @item tsize:@var{n}
40433 The total size of the trace buffer, in bytes.
40435 @item tfree:@var{n}
40436 The number of bytes still unused in the buffer.
40438 @item circular:@var{n}
40439 The value of the circular trace buffer flag. @code{1} means that the
40440 trace buffer is circular and old trace frames will be discarded if
40441 necessary to make room, @code{0} means that the trace buffer is linear
40444 @item disconn:@var{n}
40445 The value of the disconnected tracing flag. @code{1} means that
40446 tracing will continue after @value{GDBN} disconnects, @code{0} means
40447 that the trace run will stop.
40451 @item qTP:@var{tp}:@var{addr}
40452 @cindex tracepoint status, remote request
40453 @cindex @samp{qTP} packet
40454 Ask the stub for the current state of tracepoint number @var{tp} at
40455 address @var{addr}.
40459 @item V@var{hits}:@var{usage}
40460 The tracepoint has been hit @var{hits} times so far during the trace
40461 run, and accounts for @var{usage} in the trace buffer. Note that
40462 @code{while-stepping} steps are not counted as separate hits, but the
40463 steps' space consumption is added into the usage number.
40467 @item qTV:@var{var}
40468 @cindex trace state variable value, remote request
40469 @cindex @samp{qTV} packet
40470 Ask the stub for the value of the trace state variable number @var{var}.
40475 The value of the variable is @var{value}. This will be the current
40476 value of the variable if the user is examining a running target, or a
40477 saved value if the variable was collected in the trace frame that the
40478 user is looking at. Note that multiple requests may result in
40479 different reply values, such as when requesting values while the
40480 program is running.
40483 The value of the variable is unknown. This would occur, for example,
40484 if the user is examining a trace frame in which the requested variable
40489 @cindex @samp{qTfP} packet
40491 @cindex @samp{qTsP} packet
40492 These packets request data about tracepoints that are being used by
40493 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40494 of data, and multiple @code{qTsP} to get additional pieces. Replies
40495 to these packets generally take the form of the @code{QTDP} packets
40496 that define tracepoints. (FIXME add detailed syntax)
40499 @cindex @samp{qTfV} packet
40501 @cindex @samp{qTsV} packet
40502 These packets request data about trace state variables that are on the
40503 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40504 and multiple @code{qTsV} to get additional variables. Replies to
40505 these packets follow the syntax of the @code{QTDV} packets that define
40506 trace state variables.
40512 @cindex @samp{qTfSTM} packet
40513 @cindex @samp{qTsSTM} packet
40514 These packets request data about static tracepoint markers that exist
40515 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40516 first piece of data, and multiple @code{qTsSTM} to get additional
40517 pieces. Replies to these packets take the following form:
40521 @item m @var{address}:@var{id}:@var{extra}
40523 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40524 a comma-separated list of markers
40526 (lower case letter @samp{L}) denotes end of list.
40528 An error occurred. The error number @var{nn} is given as hex digits.
40530 An empty reply indicates that the request is not supported by the
40534 The @var{address} is encoded in hex;
40535 @var{id} and @var{extra} are strings encoded in hex.
40537 In response to each query, the target will reply with a list of one or
40538 more markers, separated by commas. @value{GDBN} will respond to each
40539 reply with a request for more markers (using the @samp{qs} form of the
40540 query), until the target responds with @samp{l} (lower-case ell, for
40543 @item qTSTMat:@var{address}
40545 @cindex @samp{qTSTMat} packet
40546 This packets requests data about static tracepoint markers in the
40547 target program at @var{address}. Replies to this packet follow the
40548 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40549 tracepoint markers.
40551 @item QTSave:@var{filename}
40552 @cindex @samp{QTSave} packet
40553 This packet directs the target to save trace data to the file name
40554 @var{filename} in the target's filesystem. The @var{filename} is encoded
40555 as a hex string; the interpretation of the file name (relative vs
40556 absolute, wild cards, etc) is up to the target.
40558 @item qTBuffer:@var{offset},@var{len}
40559 @cindex @samp{qTBuffer} packet
40560 Return up to @var{len} bytes of the current contents of trace buffer,
40561 starting at @var{offset}. The trace buffer is treated as if it were
40562 a contiguous collection of traceframes, as per the trace file format.
40563 The reply consists as many hex-encoded bytes as the target can deliver
40564 in a packet; it is not an error to return fewer than were asked for.
40565 A reply consisting of just @code{l} indicates that no bytes are
40568 @item QTBuffer:circular:@var{value}
40569 This packet directs the target to use a circular trace buffer if
40570 @var{value} is 1, or a linear buffer if the value is 0.
40572 @item QTBuffer:size:@var{size}
40573 @anchor{QTBuffer-size}
40574 @cindex @samp{QTBuffer size} packet
40575 This packet directs the target to make the trace buffer be of size
40576 @var{size} if possible. A value of @code{-1} tells the target to
40577 use whatever size it prefers.
40579 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40580 @cindex @samp{QTNotes} packet
40581 This packet adds optional textual notes to the trace run. Allowable
40582 types include @code{user}, @code{notes}, and @code{tstop}, the
40583 @var{text} fields are arbitrary strings, hex-encoded.
40587 @subsection Relocate instruction reply packet
40588 When installing fast tracepoints in memory, the target may need to
40589 relocate the instruction currently at the tracepoint address to a
40590 different address in memory. For most instructions, a simple copy is
40591 enough, but, for example, call instructions that implicitly push the
40592 return address on the stack, and relative branches or other
40593 PC-relative instructions require offset adjustment, so that the effect
40594 of executing the instruction at a different address is the same as if
40595 it had executed in the original location.
40597 In response to several of the tracepoint packets, the target may also
40598 respond with a number of intermediate @samp{qRelocInsn} request
40599 packets before the final result packet, to have @value{GDBN} handle
40600 this relocation operation. If a packet supports this mechanism, its
40601 documentation will explicitly say so. See for example the above
40602 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40603 format of the request is:
40606 @item qRelocInsn:@var{from};@var{to}
40608 This requests @value{GDBN} to copy instruction at address @var{from}
40609 to address @var{to}, possibly adjusted so that executing the
40610 instruction at @var{to} has the same effect as executing it at
40611 @var{from}. @value{GDBN} writes the adjusted instruction to target
40612 memory starting at @var{to}.
40617 @item qRelocInsn:@var{adjusted_size}
40618 Informs the stub the relocation is complete. The @var{adjusted_size} is
40619 the length in bytes of resulting relocated instruction sequence.
40621 A badly formed request was detected, or an error was encountered while
40622 relocating the instruction.
40625 @node Host I/O Packets
40626 @section Host I/O Packets
40627 @cindex Host I/O, remote protocol
40628 @cindex file transfer, remote protocol
40630 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40631 operations on the far side of a remote link. For example, Host I/O is
40632 used to upload and download files to a remote target with its own
40633 filesystem. Host I/O uses the same constant values and data structure
40634 layout as the target-initiated File-I/O protocol. However, the
40635 Host I/O packets are structured differently. The target-initiated
40636 protocol relies on target memory to store parameters and buffers.
40637 Host I/O requests are initiated by @value{GDBN}, and the
40638 target's memory is not involved. @xref{File-I/O Remote Protocol
40639 Extension}, for more details on the target-initiated protocol.
40641 The Host I/O request packets all encode a single operation along with
40642 its arguments. They have this format:
40646 @item vFile:@var{operation}: @var{parameter}@dots{}
40647 @var{operation} is the name of the particular request; the target
40648 should compare the entire packet name up to the second colon when checking
40649 for a supported operation. The format of @var{parameter} depends on
40650 the operation. Numbers are always passed in hexadecimal. Negative
40651 numbers have an explicit minus sign (i.e.@: two's complement is not
40652 used). Strings (e.g.@: filenames) are encoded as a series of
40653 hexadecimal bytes. The last argument to a system call may be a
40654 buffer of escaped binary data (@pxref{Binary Data}).
40658 The valid responses to Host I/O packets are:
40662 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40663 @var{result} is the integer value returned by this operation, usually
40664 non-negative for success and -1 for errors. If an error has occured,
40665 @var{errno} will be included in the result specifying a
40666 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40667 operations which return data, @var{attachment} supplies the data as a
40668 binary buffer. Binary buffers in response packets are escaped in the
40669 normal way (@pxref{Binary Data}). See the individual packet
40670 documentation for the interpretation of @var{result} and
40674 An empty response indicates that this operation is not recognized.
40678 These are the supported Host I/O operations:
40681 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40682 Open a file at @var{filename} and return a file descriptor for it, or
40683 return -1 if an error occurs. The @var{filename} is a string,
40684 @var{flags} is an integer indicating a mask of open flags
40685 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40686 of mode bits to use if the file is created (@pxref{mode_t Values}).
40687 @xref{open}, for details of the open flags and mode values.
40689 @item vFile:close: @var{fd}
40690 Close the open file corresponding to @var{fd} and return 0, or
40691 -1 if an error occurs.
40693 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40694 Read data from the open file corresponding to @var{fd}. Up to
40695 @var{count} bytes will be read from the file, starting at @var{offset}
40696 relative to the start of the file. The target may read fewer bytes;
40697 common reasons include packet size limits and an end-of-file
40698 condition. The number of bytes read is returned. Zero should only be
40699 returned for a successful read at the end of the file, or if
40700 @var{count} was zero.
40702 The data read should be returned as a binary attachment on success.
40703 If zero bytes were read, the response should include an empty binary
40704 attachment (i.e.@: a trailing semicolon). The return value is the
40705 number of target bytes read; the binary attachment may be longer if
40706 some characters were escaped.
40708 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40709 Write @var{data} (a binary buffer) to the open file corresponding
40710 to @var{fd}. Start the write at @var{offset} from the start of the
40711 file. Unlike many @code{write} system calls, there is no
40712 separate @var{count} argument; the length of @var{data} in the
40713 packet is used. @samp{vFile:write} returns the number of bytes written,
40714 which may be shorter than the length of @var{data}, or -1 if an
40717 @item vFile:fstat: @var{fd}
40718 Get information about the open file corresponding to @var{fd}.
40719 On success the information is returned as a binary attachment
40720 and the return value is the size of this attachment in bytes.
40721 If an error occurs the return value is -1. The format of the
40722 returned binary attachment is as described in @ref{struct stat}.
40724 @item vFile:unlink: @var{filename}
40725 Delete the file at @var{filename} on the target. Return 0,
40726 or -1 if an error occurs. The @var{filename} is a string.
40728 @item vFile:readlink: @var{filename}
40729 Read value of symbolic link @var{filename} on the target. Return
40730 the number of bytes read, or -1 if an error occurs.
40732 The data read should be returned as a binary attachment on success.
40733 If zero bytes were read, the response should include an empty binary
40734 attachment (i.e.@: a trailing semicolon). The return value is the
40735 number of target bytes read; the binary attachment may be longer if
40736 some characters were escaped.
40738 @item vFile:setfs: @var{pid}
40739 Select the filesystem on which @code{vFile} operations with
40740 @var{filename} arguments will operate. This is required for
40741 @value{GDBN} to be able to access files on remote targets where
40742 the remote stub does not share a common filesystem with the
40745 If @var{pid} is nonzero, select the filesystem as seen by process
40746 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40747 the remote stub. Return 0 on success, or -1 if an error occurs.
40748 If @code{vFile:setfs:} indicates success, the selected filesystem
40749 remains selected until the next successful @code{vFile:setfs:}
40755 @section Interrupts
40756 @cindex interrupts (remote protocol)
40757 @anchor{interrupting remote targets}
40759 In all-stop mode, when a program on the remote target is running,
40760 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40761 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40762 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40764 The precise meaning of @code{BREAK} is defined by the transport
40765 mechanism and may, in fact, be undefined. @value{GDBN} does not
40766 currently define a @code{BREAK} mechanism for any of the network
40767 interfaces except for TCP, in which case @value{GDBN} sends the
40768 @code{telnet} BREAK sequence.
40770 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40771 transport mechanisms. It is represented by sending the single byte
40772 @code{0x03} without any of the usual packet overhead described in
40773 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40774 transmitted as part of a packet, it is considered to be packet data
40775 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40776 (@pxref{X packet}), used for binary downloads, may include an unescaped
40777 @code{0x03} as part of its packet.
40779 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40780 When Linux kernel receives this sequence from serial port,
40781 it stops execution and connects to gdb.
40783 In non-stop mode, because packet resumptions are asynchronous
40784 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40785 command to the remote stub, even when the target is running. For that
40786 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40787 packet}) with the usual packet framing instead of the single byte
40790 Stubs are not required to recognize these interrupt mechanisms and the
40791 precise meaning associated with receipt of the interrupt is
40792 implementation defined. If the target supports debugging of multiple
40793 threads and/or processes, it should attempt to interrupt all
40794 currently-executing threads and processes.
40795 If the stub is successful at interrupting the
40796 running program, it should send one of the stop
40797 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40798 of successfully stopping the program in all-stop mode, and a stop reply
40799 for each stopped thread in non-stop mode.
40800 Interrupts received while the
40801 program is stopped are queued and the program will be interrupted when
40802 it is resumed next time.
40804 @node Notification Packets
40805 @section Notification Packets
40806 @cindex notification packets
40807 @cindex packets, notification
40809 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40810 packets that require no acknowledgment. Both the GDB and the stub
40811 may send notifications (although the only notifications defined at
40812 present are sent by the stub). Notifications carry information
40813 without incurring the round-trip latency of an acknowledgment, and so
40814 are useful for low-impact communications where occasional packet loss
40817 A notification packet has the form @samp{% @var{data} #
40818 @var{checksum}}, where @var{data} is the content of the notification,
40819 and @var{checksum} is a checksum of @var{data}, computed and formatted
40820 as for ordinary @value{GDBN} packets. A notification's @var{data}
40821 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40822 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40823 to acknowledge the notification's receipt or to report its corruption.
40825 Every notification's @var{data} begins with a name, which contains no
40826 colon characters, followed by a colon character.
40828 Recipients should silently ignore corrupted notifications and
40829 notifications they do not understand. Recipients should restart
40830 timeout periods on receipt of a well-formed notification, whether or
40831 not they understand it.
40833 Senders should only send the notifications described here when this
40834 protocol description specifies that they are permitted. In the
40835 future, we may extend the protocol to permit existing notifications in
40836 new contexts; this rule helps older senders avoid confusing newer
40839 (Older versions of @value{GDBN} ignore bytes received until they see
40840 the @samp{$} byte that begins an ordinary packet, so new stubs may
40841 transmit notifications without fear of confusing older clients. There
40842 are no notifications defined for @value{GDBN} to send at the moment, but we
40843 assume that most older stubs would ignore them, as well.)
40845 Each notification is comprised of three parts:
40847 @item @var{name}:@var{event}
40848 The notification packet is sent by the side that initiates the
40849 exchange (currently, only the stub does that), with @var{event}
40850 carrying the specific information about the notification, and
40851 @var{name} specifying the name of the notification.
40853 The acknowledge sent by the other side, usually @value{GDBN}, to
40854 acknowledge the exchange and request the event.
40857 The purpose of an asynchronous notification mechanism is to report to
40858 @value{GDBN} that something interesting happened in the remote stub.
40860 The remote stub may send notification @var{name}:@var{event}
40861 at any time, but @value{GDBN} acknowledges the notification when
40862 appropriate. The notification event is pending before @value{GDBN}
40863 acknowledges. Only one notification at a time may be pending; if
40864 additional events occur before @value{GDBN} has acknowledged the
40865 previous notification, they must be queued by the stub for later
40866 synchronous transmission in response to @var{ack} packets from
40867 @value{GDBN}. Because the notification mechanism is unreliable,
40868 the stub is permitted to resend a notification if it believes
40869 @value{GDBN} may not have received it.
40871 Specifically, notifications may appear when @value{GDBN} is not
40872 otherwise reading input from the stub, or when @value{GDBN} is
40873 expecting to read a normal synchronous response or a
40874 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40875 Notification packets are distinct from any other communication from
40876 the stub so there is no ambiguity.
40878 After receiving a notification, @value{GDBN} shall acknowledge it by
40879 sending a @var{ack} packet as a regular, synchronous request to the
40880 stub. Such acknowledgment is not required to happen immediately, as
40881 @value{GDBN} is permitted to send other, unrelated packets to the
40882 stub first, which the stub should process normally.
40884 Upon receiving a @var{ack} packet, if the stub has other queued
40885 events to report to @value{GDBN}, it shall respond by sending a
40886 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40887 packet to solicit further responses; again, it is permitted to send
40888 other, unrelated packets as well which the stub should process
40891 If the stub receives a @var{ack} packet and there are no additional
40892 @var{event} to report, the stub shall return an @samp{OK} response.
40893 At this point, @value{GDBN} has finished processing a notification
40894 and the stub has completed sending any queued events. @value{GDBN}
40895 won't accept any new notifications until the final @samp{OK} is
40896 received . If further notification events occur, the stub shall send
40897 a new notification, @value{GDBN} shall accept the notification, and
40898 the process shall be repeated.
40900 The process of asynchronous notification can be illustrated by the
40903 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40906 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40908 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40913 The following notifications are defined:
40914 @multitable @columnfractions 0.12 0.12 0.38 0.38
40923 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40924 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40925 for information on how these notifications are acknowledged by
40927 @tab Report an asynchronous stop event in non-stop mode.
40931 @node Remote Non-Stop
40932 @section Remote Protocol Support for Non-Stop Mode
40934 @value{GDBN}'s remote protocol supports non-stop debugging of
40935 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40936 supports non-stop mode, it should report that to @value{GDBN} by including
40937 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40939 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40940 establishing a new connection with the stub. Entering non-stop mode
40941 does not alter the state of any currently-running threads, but targets
40942 must stop all threads in any already-attached processes when entering
40943 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40944 probe the target state after a mode change.
40946 In non-stop mode, when an attached process encounters an event that
40947 would otherwise be reported with a stop reply, it uses the
40948 asynchronous notification mechanism (@pxref{Notification Packets}) to
40949 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40950 in all processes are stopped when a stop reply is sent, in non-stop
40951 mode only the thread reporting the stop event is stopped. That is,
40952 when reporting a @samp{S} or @samp{T} response to indicate completion
40953 of a step operation, hitting a breakpoint, or a fault, only the
40954 affected thread is stopped; any other still-running threads continue
40955 to run. When reporting a @samp{W} or @samp{X} response, all running
40956 threads belonging to other attached processes continue to run.
40958 In non-stop mode, the target shall respond to the @samp{?} packet as
40959 follows. First, any incomplete stop reply notification/@samp{vStopped}
40960 sequence in progress is abandoned. The target must begin a new
40961 sequence reporting stop events for all stopped threads, whether or not
40962 it has previously reported those events to @value{GDBN}. The first
40963 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40964 subsequent stop replies are sent as responses to @samp{vStopped} packets
40965 using the mechanism described above. The target must not send
40966 asynchronous stop reply notifications until the sequence is complete.
40967 If all threads are running when the target receives the @samp{?} packet,
40968 or if the target is not attached to any process, it shall respond
40971 If the stub supports non-stop mode, it should also support the
40972 @samp{swbreak} stop reason if software breakpoints are supported, and
40973 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40974 (@pxref{swbreak stop reason}). This is because given the asynchronous
40975 nature of non-stop mode, between the time a thread hits a breakpoint
40976 and the time the event is finally processed by @value{GDBN}, the
40977 breakpoint may have already been removed from the target. Due to
40978 this, @value{GDBN} needs to be able to tell whether a trap stop was
40979 caused by a delayed breakpoint event, which should be ignored, as
40980 opposed to a random trap signal, which should be reported to the user.
40981 Note the @samp{swbreak} feature implies that the target is responsible
40982 for adjusting the PC when a software breakpoint triggers, if
40983 necessary, such as on the x86 architecture.
40985 @node Packet Acknowledgment
40986 @section Packet Acknowledgment
40988 @cindex acknowledgment, for @value{GDBN} remote
40989 @cindex packet acknowledgment, for @value{GDBN} remote
40990 By default, when either the host or the target machine receives a packet,
40991 the first response expected is an acknowledgment: either @samp{+} (to indicate
40992 the package was received correctly) or @samp{-} (to request retransmission).
40993 This mechanism allows the @value{GDBN} remote protocol to operate over
40994 unreliable transport mechanisms, such as a serial line.
40996 In cases where the transport mechanism is itself reliable (such as a pipe or
40997 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40998 It may be desirable to disable them in that case to reduce communication
40999 overhead, or for other reasons. This can be accomplished by means of the
41000 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41002 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41003 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41004 and response format still includes the normal checksum, as described in
41005 @ref{Overview}, but the checksum may be ignored by the receiver.
41007 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41008 no-acknowledgment mode, it should report that to @value{GDBN}
41009 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41010 @pxref{qSupported}.
41011 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41012 disabled via the @code{set remote noack-packet off} command
41013 (@pxref{Remote Configuration}),
41014 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41015 Only then may the stub actually turn off packet acknowledgments.
41016 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41017 response, which can be safely ignored by the stub.
41019 Note that @code{set remote noack-packet} command only affects negotiation
41020 between @value{GDBN} and the stub when subsequent connections are made;
41021 it does not affect the protocol acknowledgment state for any current
41023 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41024 new connection is established,
41025 there is also no protocol request to re-enable the acknowledgments
41026 for the current connection, once disabled.
41031 Example sequence of a target being re-started. Notice how the restart
41032 does not get any direct output:
41037 @emph{target restarts}
41040 <- @code{T001:1234123412341234}
41044 Example sequence of a target being stepped by a single instruction:
41047 -> @code{G1445@dots{}}
41052 <- @code{T001:1234123412341234}
41056 <- @code{1455@dots{}}
41060 @node File-I/O Remote Protocol Extension
41061 @section File-I/O Remote Protocol Extension
41062 @cindex File-I/O remote protocol extension
41065 * File-I/O Overview::
41066 * Protocol Basics::
41067 * The F Request Packet::
41068 * The F Reply Packet::
41069 * The Ctrl-C Message::
41071 * List of Supported Calls::
41072 * Protocol-specific Representation of Datatypes::
41074 * File-I/O Examples::
41077 @node File-I/O Overview
41078 @subsection File-I/O Overview
41079 @cindex file-i/o overview
41081 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41082 target to use the host's file system and console I/O to perform various
41083 system calls. System calls on the target system are translated into a
41084 remote protocol packet to the host system, which then performs the needed
41085 actions and returns a response packet to the target system.
41086 This simulates file system operations even on targets that lack file systems.
41088 The protocol is defined to be independent of both the host and target systems.
41089 It uses its own internal representation of datatypes and values. Both
41090 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41091 translating the system-dependent value representations into the internal
41092 protocol representations when data is transmitted.
41094 The communication is synchronous. A system call is possible only when
41095 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41096 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41097 the target is stopped to allow deterministic access to the target's
41098 memory. Therefore File-I/O is not interruptible by target signals. On
41099 the other hand, it is possible to interrupt File-I/O by a user interrupt
41100 (@samp{Ctrl-C}) within @value{GDBN}.
41102 The target's request to perform a host system call does not finish
41103 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41104 after finishing the system call, the target returns to continuing the
41105 previous activity (continue, step). No additional continue or step
41106 request from @value{GDBN} is required.
41109 (@value{GDBP}) continue
41110 <- target requests 'system call X'
41111 target is stopped, @value{GDBN} executes system call
41112 -> @value{GDBN} returns result
41113 ... target continues, @value{GDBN} returns to wait for the target
41114 <- target hits breakpoint and sends a Txx packet
41117 The protocol only supports I/O on the console and to regular files on
41118 the host file system. Character or block special devices, pipes,
41119 named pipes, sockets or any other communication method on the host
41120 system are not supported by this protocol.
41122 File I/O is not supported in non-stop mode.
41124 @node Protocol Basics
41125 @subsection Protocol Basics
41126 @cindex protocol basics, file-i/o
41128 The File-I/O protocol uses the @code{F} packet as the request as well
41129 as reply packet. Since a File-I/O system call can only occur when
41130 @value{GDBN} is waiting for a response from the continuing or stepping target,
41131 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41132 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41133 This @code{F} packet contains all information needed to allow @value{GDBN}
41134 to call the appropriate host system call:
41138 A unique identifier for the requested system call.
41141 All parameters to the system call. Pointers are given as addresses
41142 in the target memory address space. Pointers to strings are given as
41143 pointer/length pair. Numerical values are given as they are.
41144 Numerical control flags are given in a protocol-specific representation.
41148 At this point, @value{GDBN} has to perform the following actions.
41152 If the parameters include pointer values to data needed as input to a
41153 system call, @value{GDBN} requests this data from the target with a
41154 standard @code{m} packet request. This additional communication has to be
41155 expected by the target implementation and is handled as any other @code{m}
41159 @value{GDBN} translates all value from protocol representation to host
41160 representation as needed. Datatypes are coerced into the host types.
41163 @value{GDBN} calls the system call.
41166 It then coerces datatypes back to protocol representation.
41169 If the system call is expected to return data in buffer space specified
41170 by pointer parameters to the call, the data is transmitted to the
41171 target using a @code{M} or @code{X} packet. This packet has to be expected
41172 by the target implementation and is handled as any other @code{M} or @code{X}
41177 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41178 necessary information for the target to continue. This at least contains
41185 @code{errno}, if has been changed by the system call.
41192 After having done the needed type and value coercion, the target continues
41193 the latest continue or step action.
41195 @node The F Request Packet
41196 @subsection The @code{F} Request Packet
41197 @cindex file-i/o request packet
41198 @cindex @code{F} request packet
41200 The @code{F} request packet has the following format:
41203 @item F@var{call-id},@var{parameter@dots{}}
41205 @var{call-id} is the identifier to indicate the host system call to be called.
41206 This is just the name of the function.
41208 @var{parameter@dots{}} are the parameters to the system call.
41209 Parameters are hexadecimal integer values, either the actual values in case
41210 of scalar datatypes, pointers to target buffer space in case of compound
41211 datatypes and unspecified memory areas, or pointer/length pairs in case
41212 of string parameters. These are appended to the @var{call-id} as a
41213 comma-delimited list. All values are transmitted in ASCII
41214 string representation, pointer/length pairs separated by a slash.
41220 @node The F Reply Packet
41221 @subsection The @code{F} Reply Packet
41222 @cindex file-i/o reply packet
41223 @cindex @code{F} reply packet
41225 The @code{F} reply packet has the following format:
41229 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41231 @var{retcode} is the return code of the system call as hexadecimal value.
41233 @var{errno} is the @code{errno} set by the call, in protocol-specific
41235 This parameter can be omitted if the call was successful.
41237 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41238 case, @var{errno} must be sent as well, even if the call was successful.
41239 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41246 or, if the call was interrupted before the host call has been performed:
41253 assuming 4 is the protocol-specific representation of @code{EINTR}.
41258 @node The Ctrl-C Message
41259 @subsection The @samp{Ctrl-C} Message
41260 @cindex ctrl-c message, in file-i/o protocol
41262 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41263 reply packet (@pxref{The F Reply Packet}),
41264 the target should behave as if it had
41265 gotten a break message. The meaning for the target is ``system call
41266 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41267 (as with a break message) and return to @value{GDBN} with a @code{T02}
41270 It's important for the target to know in which
41271 state the system call was interrupted. There are two possible cases:
41275 The system call hasn't been performed on the host yet.
41278 The system call on the host has been finished.
41282 These two states can be distinguished by the target by the value of the
41283 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41284 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41285 on POSIX systems. In any other case, the target may presume that the
41286 system call has been finished --- successfully or not --- and should behave
41287 as if the break message arrived right after the system call.
41289 @value{GDBN} must behave reliably. If the system call has not been called
41290 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41291 @code{errno} in the packet. If the system call on the host has been finished
41292 before the user requests a break, the full action must be finished by
41293 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41294 The @code{F} packet may only be sent when either nothing has happened
41295 or the full action has been completed.
41298 @subsection Console I/O
41299 @cindex console i/o as part of file-i/o
41301 By default and if not explicitly closed by the target system, the file
41302 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41303 on the @value{GDBN} console is handled as any other file output operation
41304 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41305 by @value{GDBN} so that after the target read request from file descriptor
41306 0 all following typing is buffered until either one of the following
41311 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41313 system call is treated as finished.
41316 The user presses @key{RET}. This is treated as end of input with a trailing
41320 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41321 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41325 If the user has typed more characters than fit in the buffer given to
41326 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41327 either another @code{read(0, @dots{})} is requested by the target, or debugging
41328 is stopped at the user's request.
41331 @node List of Supported Calls
41332 @subsection List of Supported Calls
41333 @cindex list of supported file-i/o calls
41350 @unnumberedsubsubsec open
41351 @cindex open, file-i/o system call
41356 int open(const char *pathname, int flags);
41357 int open(const char *pathname, int flags, mode_t mode);
41361 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41364 @var{flags} is the bitwise @code{OR} of the following values:
41368 If the file does not exist it will be created. The host
41369 rules apply as far as file ownership and time stamps
41373 When used with @code{O_CREAT}, if the file already exists it is
41374 an error and open() fails.
41377 If the file already exists and the open mode allows
41378 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41379 truncated to zero length.
41382 The file is opened in append mode.
41385 The file is opened for reading only.
41388 The file is opened for writing only.
41391 The file is opened for reading and writing.
41395 Other bits are silently ignored.
41399 @var{mode} is the bitwise @code{OR} of the following values:
41403 User has read permission.
41406 User has write permission.
41409 Group has read permission.
41412 Group has write permission.
41415 Others have read permission.
41418 Others have write permission.
41422 Other bits are silently ignored.
41425 @item Return value:
41426 @code{open} returns the new file descriptor or -1 if an error
41433 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41436 @var{pathname} refers to a directory.
41439 The requested access is not allowed.
41442 @var{pathname} was too long.
41445 A directory component in @var{pathname} does not exist.
41448 @var{pathname} refers to a device, pipe, named pipe or socket.
41451 @var{pathname} refers to a file on a read-only filesystem and
41452 write access was requested.
41455 @var{pathname} is an invalid pointer value.
41458 No space on device to create the file.
41461 The process already has the maximum number of files open.
41464 The limit on the total number of files open on the system
41468 The call was interrupted by the user.
41474 @unnumberedsubsubsec close
41475 @cindex close, file-i/o system call
41484 @samp{Fclose,@var{fd}}
41486 @item Return value:
41487 @code{close} returns zero on success, or -1 if an error occurred.
41493 @var{fd} isn't a valid open file descriptor.
41496 The call was interrupted by the user.
41502 @unnumberedsubsubsec read
41503 @cindex read, file-i/o system call
41508 int read(int fd, void *buf, unsigned int count);
41512 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41514 @item Return value:
41515 On success, the number of bytes read is returned.
41516 Zero indicates end of file. If count is zero, read
41517 returns zero as well. On error, -1 is returned.
41523 @var{fd} is not a valid file descriptor or is not open for
41527 @var{bufptr} is an invalid pointer value.
41530 The call was interrupted by the user.
41536 @unnumberedsubsubsec write
41537 @cindex write, file-i/o system call
41542 int write(int fd, const void *buf, unsigned int count);
41546 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41548 @item Return value:
41549 On success, the number of bytes written are returned.
41550 Zero indicates nothing was written. On error, -1
41557 @var{fd} is not a valid file descriptor or is not open for
41561 @var{bufptr} is an invalid pointer value.
41564 An attempt was made to write a file that exceeds the
41565 host-specific maximum file size allowed.
41568 No space on device to write the data.
41571 The call was interrupted by the user.
41577 @unnumberedsubsubsec lseek
41578 @cindex lseek, file-i/o system call
41583 long lseek (int fd, long offset, int flag);
41587 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41589 @var{flag} is one of:
41593 The offset is set to @var{offset} bytes.
41596 The offset is set to its current location plus @var{offset}
41600 The offset is set to the size of the file plus @var{offset}
41604 @item Return value:
41605 On success, the resulting unsigned offset in bytes from
41606 the beginning of the file is returned. Otherwise, a
41607 value of -1 is returned.
41613 @var{fd} is not a valid open file descriptor.
41616 @var{fd} is associated with the @value{GDBN} console.
41619 @var{flag} is not a proper value.
41622 The call was interrupted by the user.
41628 @unnumberedsubsubsec rename
41629 @cindex rename, file-i/o system call
41634 int rename(const char *oldpath, const char *newpath);
41638 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41640 @item Return value:
41641 On success, zero is returned. On error, -1 is returned.
41647 @var{newpath} is an existing directory, but @var{oldpath} is not a
41651 @var{newpath} is a non-empty directory.
41654 @var{oldpath} or @var{newpath} is a directory that is in use by some
41658 An attempt was made to make a directory a subdirectory
41662 A component used as a directory in @var{oldpath} or new
41663 path is not a directory. Or @var{oldpath} is a directory
41664 and @var{newpath} exists but is not a directory.
41667 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41670 No access to the file or the path of the file.
41674 @var{oldpath} or @var{newpath} was too long.
41677 A directory component in @var{oldpath} or @var{newpath} does not exist.
41680 The file is on a read-only filesystem.
41683 The device containing the file has no room for the new
41687 The call was interrupted by the user.
41693 @unnumberedsubsubsec unlink
41694 @cindex unlink, file-i/o system call
41699 int unlink(const char *pathname);
41703 @samp{Funlink,@var{pathnameptr}/@var{len}}
41705 @item Return value:
41706 On success, zero is returned. On error, -1 is returned.
41712 No access to the file or the path of the file.
41715 The system does not allow unlinking of directories.
41718 The file @var{pathname} cannot be unlinked because it's
41719 being used by another process.
41722 @var{pathnameptr} is an invalid pointer value.
41725 @var{pathname} was too long.
41728 A directory component in @var{pathname} does not exist.
41731 A component of the path is not a directory.
41734 The file is on a read-only filesystem.
41737 The call was interrupted by the user.
41743 @unnumberedsubsubsec stat/fstat
41744 @cindex fstat, file-i/o system call
41745 @cindex stat, file-i/o system call
41750 int stat(const char *pathname, struct stat *buf);
41751 int fstat(int fd, struct stat *buf);
41755 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41756 @samp{Ffstat,@var{fd},@var{bufptr}}
41758 @item Return value:
41759 On success, zero is returned. On error, -1 is returned.
41765 @var{fd} is not a valid open file.
41768 A directory component in @var{pathname} does not exist or the
41769 path is an empty string.
41772 A component of the path is not a directory.
41775 @var{pathnameptr} is an invalid pointer value.
41778 No access to the file or the path of the file.
41781 @var{pathname} was too long.
41784 The call was interrupted by the user.
41790 @unnumberedsubsubsec gettimeofday
41791 @cindex gettimeofday, file-i/o system call
41796 int gettimeofday(struct timeval *tv, void *tz);
41800 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41802 @item Return value:
41803 On success, 0 is returned, -1 otherwise.
41809 @var{tz} is a non-NULL pointer.
41812 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41818 @unnumberedsubsubsec isatty
41819 @cindex isatty, file-i/o system call
41824 int isatty(int fd);
41828 @samp{Fisatty,@var{fd}}
41830 @item Return value:
41831 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41837 The call was interrupted by the user.
41842 Note that the @code{isatty} call is treated as a special case: it returns
41843 1 to the target if the file descriptor is attached
41844 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41845 would require implementing @code{ioctl} and would be more complex than
41850 @unnumberedsubsubsec system
41851 @cindex system, file-i/o system call
41856 int system(const char *command);
41860 @samp{Fsystem,@var{commandptr}/@var{len}}
41862 @item Return value:
41863 If @var{len} is zero, the return value indicates whether a shell is
41864 available. A zero return value indicates a shell is not available.
41865 For non-zero @var{len}, the value returned is -1 on error and the
41866 return status of the command otherwise. Only the exit status of the
41867 command is returned, which is extracted from the host's @code{system}
41868 return value by calling @code{WEXITSTATUS(retval)}. In case
41869 @file{/bin/sh} could not be executed, 127 is returned.
41875 The call was interrupted by the user.
41880 @value{GDBN} takes over the full task of calling the necessary host calls
41881 to perform the @code{system} call. The return value of @code{system} on
41882 the host is simplified before it's returned
41883 to the target. Any termination signal information from the child process
41884 is discarded, and the return value consists
41885 entirely of the exit status of the called command.
41887 Due to security concerns, the @code{system} call is by default refused
41888 by @value{GDBN}. The user has to allow this call explicitly with the
41889 @code{set remote system-call-allowed 1} command.
41892 @item set remote system-call-allowed
41893 @kindex set remote system-call-allowed
41894 Control whether to allow the @code{system} calls in the File I/O
41895 protocol for the remote target. The default is zero (disabled).
41897 @item show remote system-call-allowed
41898 @kindex show remote system-call-allowed
41899 Show whether the @code{system} calls are allowed in the File I/O
41903 @node Protocol-specific Representation of Datatypes
41904 @subsection Protocol-specific Representation of Datatypes
41905 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41908 * Integral Datatypes::
41910 * Memory Transfer::
41915 @node Integral Datatypes
41916 @unnumberedsubsubsec Integral Datatypes
41917 @cindex integral datatypes, in file-i/o protocol
41919 The integral datatypes used in the system calls are @code{int},
41920 @code{unsigned int}, @code{long}, @code{unsigned long},
41921 @code{mode_t}, and @code{time_t}.
41923 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41924 implemented as 32 bit values in this protocol.
41926 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41928 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41929 in @file{limits.h}) to allow range checking on host and target.
41931 @code{time_t} datatypes are defined as seconds since the Epoch.
41933 All integral datatypes transferred as part of a memory read or write of a
41934 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41937 @node Pointer Values
41938 @unnumberedsubsubsec Pointer Values
41939 @cindex pointer values, in file-i/o protocol
41941 Pointers to target data are transmitted as they are. An exception
41942 is made for pointers to buffers for which the length isn't
41943 transmitted as part of the function call, namely strings. Strings
41944 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41951 which is a pointer to data of length 18 bytes at position 0x1aaf.
41952 The length is defined as the full string length in bytes, including
41953 the trailing null byte. For example, the string @code{"hello world"}
41954 at address 0x123456 is transmitted as
41960 @node Memory Transfer
41961 @unnumberedsubsubsec Memory Transfer
41962 @cindex memory transfer, in file-i/o protocol
41964 Structured data which is transferred using a memory read or write (for
41965 example, a @code{struct stat}) is expected to be in a protocol-specific format
41966 with all scalar multibyte datatypes being big endian. Translation to
41967 this representation needs to be done both by the target before the @code{F}
41968 packet is sent, and by @value{GDBN} before
41969 it transfers memory to the target. Transferred pointers to structured
41970 data should point to the already-coerced data at any time.
41974 @unnumberedsubsubsec struct stat
41975 @cindex struct stat, in file-i/o protocol
41977 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41978 is defined as follows:
41982 unsigned int st_dev; /* device */
41983 unsigned int st_ino; /* inode */
41984 mode_t st_mode; /* protection */
41985 unsigned int st_nlink; /* number of hard links */
41986 unsigned int st_uid; /* user ID of owner */
41987 unsigned int st_gid; /* group ID of owner */
41988 unsigned int st_rdev; /* device type (if inode device) */
41989 unsigned long st_size; /* total size, in bytes */
41990 unsigned long st_blksize; /* blocksize for filesystem I/O */
41991 unsigned long st_blocks; /* number of blocks allocated */
41992 time_t st_atime; /* time of last access */
41993 time_t st_mtime; /* time of last modification */
41994 time_t st_ctime; /* time of last change */
41998 The integral datatypes conform to the definitions given in the
41999 appropriate section (see @ref{Integral Datatypes}, for details) so this
42000 structure is of size 64 bytes.
42002 The values of several fields have a restricted meaning and/or
42008 A value of 0 represents a file, 1 the console.
42011 No valid meaning for the target. Transmitted unchanged.
42014 Valid mode bits are described in @ref{Constants}. Any other
42015 bits have currently no meaning for the target.
42020 No valid meaning for the target. Transmitted unchanged.
42025 These values have a host and file system dependent
42026 accuracy. Especially on Windows hosts, the file system may not
42027 support exact timing values.
42030 The target gets a @code{struct stat} of the above representation and is
42031 responsible for coercing it to the target representation before
42034 Note that due to size differences between the host, target, and protocol
42035 representations of @code{struct stat} members, these members could eventually
42036 get truncated on the target.
42038 @node struct timeval
42039 @unnumberedsubsubsec struct timeval
42040 @cindex struct timeval, in file-i/o protocol
42042 The buffer of type @code{struct timeval} used by the File-I/O protocol
42043 is defined as follows:
42047 time_t tv_sec; /* second */
42048 long tv_usec; /* microsecond */
42052 The integral datatypes conform to the definitions given in the
42053 appropriate section (see @ref{Integral Datatypes}, for details) so this
42054 structure is of size 8 bytes.
42057 @subsection Constants
42058 @cindex constants, in file-i/o protocol
42060 The following values are used for the constants inside of the
42061 protocol. @value{GDBN} and target are responsible for translating these
42062 values before and after the call as needed.
42073 @unnumberedsubsubsec Open Flags
42074 @cindex open flags, in file-i/o protocol
42076 All values are given in hexadecimal representation.
42088 @node mode_t Values
42089 @unnumberedsubsubsec mode_t Values
42090 @cindex mode_t values, in file-i/o protocol
42092 All values are given in octal representation.
42109 @unnumberedsubsubsec Errno Values
42110 @cindex errno values, in file-i/o protocol
42112 All values are given in decimal representation.
42137 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42138 any error value not in the list of supported error numbers.
42141 @unnumberedsubsubsec Lseek Flags
42142 @cindex lseek flags, in file-i/o protocol
42151 @unnumberedsubsubsec Limits
42152 @cindex limits, in file-i/o protocol
42154 All values are given in decimal representation.
42157 INT_MIN -2147483648
42159 UINT_MAX 4294967295
42160 LONG_MIN -9223372036854775808
42161 LONG_MAX 9223372036854775807
42162 ULONG_MAX 18446744073709551615
42165 @node File-I/O Examples
42166 @subsection File-I/O Examples
42167 @cindex file-i/o examples
42169 Example sequence of a write call, file descriptor 3, buffer is at target
42170 address 0x1234, 6 bytes should be written:
42173 <- @code{Fwrite,3,1234,6}
42174 @emph{request memory read from target}
42177 @emph{return "6 bytes written"}
42181 Example sequence of a read call, file descriptor 3, buffer is at target
42182 address 0x1234, 6 bytes should be read:
42185 <- @code{Fread,3,1234,6}
42186 @emph{request memory write to target}
42187 -> @code{X1234,6:XXXXXX}
42188 @emph{return "6 bytes read"}
42192 Example sequence of a read call, call fails on the host due to invalid
42193 file descriptor (@code{EBADF}):
42196 <- @code{Fread,3,1234,6}
42200 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42204 <- @code{Fread,3,1234,6}
42209 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42213 <- @code{Fread,3,1234,6}
42214 -> @code{X1234,6:XXXXXX}
42218 @node Library List Format
42219 @section Library List Format
42220 @cindex library list format, remote protocol
42222 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42223 same process as your application to manage libraries. In this case,
42224 @value{GDBN} can use the loader's symbol table and normal memory
42225 operations to maintain a list of shared libraries. On other
42226 platforms, the operating system manages loaded libraries.
42227 @value{GDBN} can not retrieve the list of currently loaded libraries
42228 through memory operations, so it uses the @samp{qXfer:libraries:read}
42229 packet (@pxref{qXfer library list read}) instead. The remote stub
42230 queries the target's operating system and reports which libraries
42233 The @samp{qXfer:libraries:read} packet returns an XML document which
42234 lists loaded libraries and their offsets. Each library has an
42235 associated name and one or more segment or section base addresses,
42236 which report where the library was loaded in memory.
42238 For the common case of libraries that are fully linked binaries, the
42239 library should have a list of segments. If the target supports
42240 dynamic linking of a relocatable object file, its library XML element
42241 should instead include a list of allocated sections. The segment or
42242 section bases are start addresses, not relocation offsets; they do not
42243 depend on the library's link-time base addresses.
42245 @value{GDBN} must be linked with the Expat library to support XML
42246 library lists. @xref{Expat}.
42248 A simple memory map, with one loaded library relocated by a single
42249 offset, looks like this:
42253 <library name="/lib/libc.so.6">
42254 <segment address="0x10000000"/>
42259 Another simple memory map, with one loaded library with three
42260 allocated sections (.text, .data, .bss), looks like this:
42264 <library name="sharedlib.o">
42265 <section address="0x10000000"/>
42266 <section address="0x20000000"/>
42267 <section address="0x30000000"/>
42272 The format of a library list is described by this DTD:
42275 <!-- library-list: Root element with versioning -->
42276 <!ELEMENT library-list (library)*>
42277 <!ATTLIST library-list version CDATA #FIXED "1.0">
42278 <!ELEMENT library (segment*, section*)>
42279 <!ATTLIST library name CDATA #REQUIRED>
42280 <!ELEMENT segment EMPTY>
42281 <!ATTLIST segment address CDATA #REQUIRED>
42282 <!ELEMENT section EMPTY>
42283 <!ATTLIST section address CDATA #REQUIRED>
42286 In addition, segments and section descriptors cannot be mixed within a
42287 single library element, and you must supply at least one segment or
42288 section for each library.
42290 @node Library List Format for SVR4 Targets
42291 @section Library List Format for SVR4 Targets
42292 @cindex library list format, remote protocol
42294 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42295 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42296 shared libraries. Still a special library list provided by this packet is
42297 more efficient for the @value{GDBN} remote protocol.
42299 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42300 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42301 target, the following parameters are reported:
42305 @code{name}, the absolute file name from the @code{l_name} field of
42306 @code{struct link_map}.
42308 @code{lm} with address of @code{struct link_map} used for TLS
42309 (Thread Local Storage) access.
42311 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42312 @code{struct link_map}. For prelinked libraries this is not an absolute
42313 memory address. It is a displacement of absolute memory address against
42314 address the file was prelinked to during the library load.
42316 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42319 Additionally the single @code{main-lm} attribute specifies address of
42320 @code{struct link_map} used for the main executable. This parameter is used
42321 for TLS access and its presence is optional.
42323 @value{GDBN} must be linked with the Expat library to support XML
42324 SVR4 library lists. @xref{Expat}.
42326 A simple memory map, with two loaded libraries (which do not use prelink),
42330 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42331 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42333 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42335 </library-list-svr>
42338 The format of an SVR4 library list is described by this DTD:
42341 <!-- library-list-svr4: Root element with versioning -->
42342 <!ELEMENT library-list-svr4 (library)*>
42343 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42344 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42345 <!ELEMENT library EMPTY>
42346 <!ATTLIST library name CDATA #REQUIRED>
42347 <!ATTLIST library lm CDATA #REQUIRED>
42348 <!ATTLIST library l_addr CDATA #REQUIRED>
42349 <!ATTLIST library l_ld CDATA #REQUIRED>
42352 @node Memory Map Format
42353 @section Memory Map Format
42354 @cindex memory map format
42356 To be able to write into flash memory, @value{GDBN} needs to obtain a
42357 memory map from the target. This section describes the format of the
42360 The memory map is obtained using the @samp{qXfer:memory-map:read}
42361 (@pxref{qXfer memory map read}) packet and is an XML document that
42362 lists memory regions.
42364 @value{GDBN} must be linked with the Expat library to support XML
42365 memory maps. @xref{Expat}.
42367 The top-level structure of the document is shown below:
42370 <?xml version="1.0"?>
42371 <!DOCTYPE memory-map
42372 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42373 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42379 Each region can be either:
42384 A region of RAM starting at @var{addr} and extending for @var{length}
42388 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42393 A region of read-only memory:
42396 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42401 A region of flash memory, with erasure blocks @var{blocksize}
42405 <memory type="flash" start="@var{addr}" length="@var{length}">
42406 <property name="blocksize">@var{blocksize}</property>
42412 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42413 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42414 packets to write to addresses in such ranges.
42416 The formal DTD for memory map format is given below:
42419 <!-- ................................................... -->
42420 <!-- Memory Map XML DTD ................................ -->
42421 <!-- File: memory-map.dtd .............................. -->
42422 <!-- .................................... .............. -->
42423 <!-- memory-map.dtd -->
42424 <!-- memory-map: Root element with versioning -->
42425 <!ELEMENT memory-map (memory)*>
42426 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42427 <!ELEMENT memory (property)*>
42428 <!-- memory: Specifies a memory region,
42429 and its type, or device. -->
42430 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42431 start CDATA #REQUIRED
42432 length CDATA #REQUIRED>
42433 <!-- property: Generic attribute tag -->
42434 <!ELEMENT property (#PCDATA | property)*>
42435 <!ATTLIST property name (blocksize) #REQUIRED>
42438 @node Thread List Format
42439 @section Thread List Format
42440 @cindex thread list format
42442 To efficiently update the list of threads and their attributes,
42443 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42444 (@pxref{qXfer threads read}) and obtains the XML document with
42445 the following structure:
42448 <?xml version="1.0"?>
42450 <thread id="id" core="0" name="name">
42451 ... description ...
42456 Each @samp{thread} element must have the @samp{id} attribute that
42457 identifies the thread (@pxref{thread-id syntax}). The
42458 @samp{core} attribute, if present, specifies which processor core
42459 the thread was last executing on. The @samp{name} attribute, if
42460 present, specifies the human-readable name of the thread. The content
42461 of the of @samp{thread} element is interpreted as human-readable
42462 auxiliary information. The @samp{handle} attribute, if present,
42463 is a hex encoded representation of the thread handle.
42466 @node Traceframe Info Format
42467 @section Traceframe Info Format
42468 @cindex traceframe info format
42470 To be able to know which objects in the inferior can be examined when
42471 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42472 memory ranges, registers and trace state variables that have been
42473 collected in a traceframe.
42475 This list is obtained using the @samp{qXfer:traceframe-info:read}
42476 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42478 @value{GDBN} must be linked with the Expat library to support XML
42479 traceframe info discovery. @xref{Expat}.
42481 The top-level structure of the document is shown below:
42484 <?xml version="1.0"?>
42485 <!DOCTYPE traceframe-info
42486 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42487 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42493 Each traceframe block can be either:
42498 A region of collected memory starting at @var{addr} and extending for
42499 @var{length} bytes from there:
42502 <memory start="@var{addr}" length="@var{length}"/>
42506 A block indicating trace state variable numbered @var{number} has been
42510 <tvar id="@var{number}"/>
42515 The formal DTD for the traceframe info format is given below:
42518 <!ELEMENT traceframe-info (memory | tvar)* >
42519 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42521 <!ELEMENT memory EMPTY>
42522 <!ATTLIST memory start CDATA #REQUIRED
42523 length CDATA #REQUIRED>
42525 <!ATTLIST tvar id CDATA #REQUIRED>
42528 @node Branch Trace Format
42529 @section Branch Trace Format
42530 @cindex branch trace format
42532 In order to display the branch trace of an inferior thread,
42533 @value{GDBN} needs to obtain the list of branches. This list is
42534 represented as list of sequential code blocks that are connected via
42535 branches. The code in each block has been executed sequentially.
42537 This list is obtained using the @samp{qXfer:btrace:read}
42538 (@pxref{qXfer btrace read}) packet and is an XML document.
42540 @value{GDBN} must be linked with the Expat library to support XML
42541 traceframe info discovery. @xref{Expat}.
42543 The top-level structure of the document is shown below:
42546 <?xml version="1.0"?>
42548 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42549 "http://sourceware.org/gdb/gdb-btrace.dtd">
42558 A block of sequentially executed instructions starting at @var{begin}
42559 and ending at @var{end}:
42562 <block begin="@var{begin}" end="@var{end}"/>
42567 The formal DTD for the branch trace format is given below:
42570 <!ELEMENT btrace (block* | pt) >
42571 <!ATTLIST btrace version CDATA #FIXED "1.0">
42573 <!ELEMENT block EMPTY>
42574 <!ATTLIST block begin CDATA #REQUIRED
42575 end CDATA #REQUIRED>
42577 <!ELEMENT pt (pt-config?, raw?)>
42579 <!ELEMENT pt-config (cpu?)>
42581 <!ELEMENT cpu EMPTY>
42582 <!ATTLIST cpu vendor CDATA #REQUIRED
42583 family CDATA #REQUIRED
42584 model CDATA #REQUIRED
42585 stepping CDATA #REQUIRED>
42587 <!ELEMENT raw (#PCDATA)>
42590 @node Branch Trace Configuration Format
42591 @section Branch Trace Configuration Format
42592 @cindex branch trace configuration format
42594 For each inferior thread, @value{GDBN} can obtain the branch trace
42595 configuration using the @samp{qXfer:btrace-conf:read}
42596 (@pxref{qXfer btrace-conf read}) packet.
42598 The configuration describes the branch trace format and configuration
42599 settings for that format. The following information is described:
42603 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42606 The size of the @acronym{BTS} ring buffer in bytes.
42609 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42613 The size of the @acronym{Intel PT} ring buffer in bytes.
42617 @value{GDBN} must be linked with the Expat library to support XML
42618 branch trace configuration discovery. @xref{Expat}.
42620 The formal DTD for the branch trace configuration format is given below:
42623 <!ELEMENT btrace-conf (bts?, pt?)>
42624 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42626 <!ELEMENT bts EMPTY>
42627 <!ATTLIST bts size CDATA #IMPLIED>
42629 <!ELEMENT pt EMPTY>
42630 <!ATTLIST pt size CDATA #IMPLIED>
42633 @include agentexpr.texi
42635 @node Target Descriptions
42636 @appendix Target Descriptions
42637 @cindex target descriptions
42639 One of the challenges of using @value{GDBN} to debug embedded systems
42640 is that there are so many minor variants of each processor
42641 architecture in use. It is common practice for vendors to start with
42642 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42643 and then make changes to adapt it to a particular market niche. Some
42644 architectures have hundreds of variants, available from dozens of
42645 vendors. This leads to a number of problems:
42649 With so many different customized processors, it is difficult for
42650 the @value{GDBN} maintainers to keep up with the changes.
42652 Since individual variants may have short lifetimes or limited
42653 audiences, it may not be worthwhile to carry information about every
42654 variant in the @value{GDBN} source tree.
42656 When @value{GDBN} does support the architecture of the embedded system
42657 at hand, the task of finding the correct architecture name to give the
42658 @command{set architecture} command can be error-prone.
42661 To address these problems, the @value{GDBN} remote protocol allows a
42662 target system to not only identify itself to @value{GDBN}, but to
42663 actually describe its own features. This lets @value{GDBN} support
42664 processor variants it has never seen before --- to the extent that the
42665 descriptions are accurate, and that @value{GDBN} understands them.
42667 @value{GDBN} must be linked with the Expat library to support XML
42668 target descriptions. @xref{Expat}.
42671 * Retrieving Descriptions:: How descriptions are fetched from a target.
42672 * Target Description Format:: The contents of a target description.
42673 * Predefined Target Types:: Standard types available for target
42675 * Enum Target Types:: How to define enum target types.
42676 * Standard Target Features:: Features @value{GDBN} knows about.
42679 @node Retrieving Descriptions
42680 @section Retrieving Descriptions
42682 Target descriptions can be read from the target automatically, or
42683 specified by the user manually. The default behavior is to read the
42684 description from the target. @value{GDBN} retrieves it via the remote
42685 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42686 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42687 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42688 XML document, of the form described in @ref{Target Description
42691 Alternatively, you can specify a file to read for the target description.
42692 If a file is set, the target will not be queried. The commands to
42693 specify a file are:
42696 @cindex set tdesc filename
42697 @item set tdesc filename @var{path}
42698 Read the target description from @var{path}.
42700 @cindex unset tdesc filename
42701 @item unset tdesc filename
42702 Do not read the XML target description from a file. @value{GDBN}
42703 will use the description supplied by the current target.
42705 @cindex show tdesc filename
42706 @item show tdesc filename
42707 Show the filename to read for a target description, if any.
42711 @node Target Description Format
42712 @section Target Description Format
42713 @cindex target descriptions, XML format
42715 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42716 document which complies with the Document Type Definition provided in
42717 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42718 means you can use generally available tools like @command{xmllint} to
42719 check that your feature descriptions are well-formed and valid.
42720 However, to help people unfamiliar with XML write descriptions for
42721 their targets, we also describe the grammar here.
42723 Target descriptions can identify the architecture of the remote target
42724 and (for some architectures) provide information about custom register
42725 sets. They can also identify the OS ABI of the remote target.
42726 @value{GDBN} can use this information to autoconfigure for your
42727 target, or to warn you if you connect to an unsupported target.
42729 Here is a simple target description:
42732 <target version="1.0">
42733 <architecture>i386:x86-64</architecture>
42738 This minimal description only says that the target uses
42739 the x86-64 architecture.
42741 A target description has the following overall form, with [ ] marking
42742 optional elements and @dots{} marking repeatable elements. The elements
42743 are explained further below.
42746 <?xml version="1.0"?>
42747 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42748 <target version="1.0">
42749 @r{[}@var{architecture}@r{]}
42750 @r{[}@var{osabi}@r{]}
42751 @r{[}@var{compatible}@r{]}
42752 @r{[}@var{feature}@dots{}@r{]}
42757 The description is generally insensitive to whitespace and line
42758 breaks, under the usual common-sense rules. The XML version
42759 declaration and document type declaration can generally be omitted
42760 (@value{GDBN} does not require them), but specifying them may be
42761 useful for XML validation tools. The @samp{version} attribute for
42762 @samp{<target>} may also be omitted, but we recommend
42763 including it; if future versions of @value{GDBN} use an incompatible
42764 revision of @file{gdb-target.dtd}, they will detect and report
42765 the version mismatch.
42767 @subsection Inclusion
42768 @cindex target descriptions, inclusion
42771 @cindex <xi:include>
42774 It can sometimes be valuable to split a target description up into
42775 several different annexes, either for organizational purposes, or to
42776 share files between different possible target descriptions. You can
42777 divide a description into multiple files by replacing any element of
42778 the target description with an inclusion directive of the form:
42781 <xi:include href="@var{document}"/>
42785 When @value{GDBN} encounters an element of this form, it will retrieve
42786 the named XML @var{document}, and replace the inclusion directive with
42787 the contents of that document. If the current description was read
42788 using @samp{qXfer}, then so will be the included document;
42789 @var{document} will be interpreted as the name of an annex. If the
42790 current description was read from a file, @value{GDBN} will look for
42791 @var{document} as a file in the same directory where it found the
42792 original description.
42794 @subsection Architecture
42795 @cindex <architecture>
42797 An @samp{<architecture>} element has this form:
42800 <architecture>@var{arch}</architecture>
42803 @var{arch} is one of the architectures from the set accepted by
42804 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42807 @cindex @code{<osabi>}
42809 This optional field was introduced in @value{GDBN} version 7.0.
42810 Previous versions of @value{GDBN} ignore it.
42812 An @samp{<osabi>} element has this form:
42815 <osabi>@var{abi-name}</osabi>
42818 @var{abi-name} is an OS ABI name from the same selection accepted by
42819 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42821 @subsection Compatible Architecture
42822 @cindex @code{<compatible>}
42824 This optional field was introduced in @value{GDBN} version 7.0.
42825 Previous versions of @value{GDBN} ignore it.
42827 A @samp{<compatible>} element has this form:
42830 <compatible>@var{arch}</compatible>
42833 @var{arch} is one of the architectures from the set accepted by
42834 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42836 A @samp{<compatible>} element is used to specify that the target
42837 is able to run binaries in some other than the main target architecture
42838 given by the @samp{<architecture>} element. For example, on the
42839 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42840 or @code{powerpc:common64}, but the system is able to run binaries
42841 in the @code{spu} architecture as well. The way to describe this
42842 capability with @samp{<compatible>} is as follows:
42845 <architecture>powerpc:common</architecture>
42846 <compatible>spu</compatible>
42849 @subsection Features
42852 Each @samp{<feature>} describes some logical portion of the target
42853 system. Features are currently used to describe available CPU
42854 registers and the types of their contents. A @samp{<feature>} element
42858 <feature name="@var{name}">
42859 @r{[}@var{type}@dots{}@r{]}
42865 Each feature's name should be unique within the description. The name
42866 of a feature does not matter unless @value{GDBN} has some special
42867 knowledge of the contents of that feature; if it does, the feature
42868 should have its standard name. @xref{Standard Target Features}.
42872 Any register's value is a collection of bits which @value{GDBN} must
42873 interpret. The default interpretation is a two's complement integer,
42874 but other types can be requested by name in the register description.
42875 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42876 Target Types}), and the description can define additional composite
42879 Each type element must have an @samp{id} attribute, which gives
42880 a unique (within the containing @samp{<feature>}) name to the type.
42881 Types must be defined before they are used.
42884 Some targets offer vector registers, which can be treated as arrays
42885 of scalar elements. These types are written as @samp{<vector>} elements,
42886 specifying the array element type, @var{type}, and the number of elements,
42890 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42894 If a register's value is usefully viewed in multiple ways, define it
42895 with a union type containing the useful representations. The
42896 @samp{<union>} element contains one or more @samp{<field>} elements,
42897 each of which has a @var{name} and a @var{type}:
42900 <union id="@var{id}">
42901 <field name="@var{name}" type="@var{type}"/>
42908 If a register's value is composed from several separate values, define
42909 it with either a structure type or a flags type.
42910 A flags type may only contain bitfields.
42911 A structure type may either contain only bitfields or contain no bitfields.
42912 If the value contains only bitfields, its total size in bytes must be
42915 Non-bitfield values have a @var{name} and @var{type}.
42918 <struct id="@var{id}">
42919 <field name="@var{name}" type="@var{type}"/>
42924 Both @var{name} and @var{type} values are required.
42925 No implicit padding is added.
42927 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42930 <struct id="@var{id}" size="@var{size}">
42931 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42937 <flags id="@var{id}" size="@var{size}">
42938 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42943 The @var{name} value is required.
42944 Bitfield values may be named with the empty string, @samp{""},
42945 in which case the field is ``filler'' and its value is not printed.
42946 Not all bits need to be specified, so ``filler'' fields are optional.
42948 The @var{start} and @var{end} values are required, and @var{type}
42950 The field's @var{start} must be less than or equal to its @var{end},
42951 and zero represents the least significant bit.
42953 The default value of @var{type} is @code{bool} for single bit fields,
42954 and an unsigned integer otherwise.
42956 Which to choose? Structures or flags?
42958 Registers defined with @samp{flags} have these advantages over
42959 defining them with @samp{struct}:
42963 Arithmetic may be performed on them as if they were integers.
42965 They are printed in a more readable fashion.
42968 Registers defined with @samp{struct} have one advantage over
42969 defining them with @samp{flags}:
42973 One can fetch individual fields like in @samp{C}.
42976 (gdb) print $my_struct_reg.field3
42982 @subsection Registers
42985 Each register is represented as an element with this form:
42988 <reg name="@var{name}"
42989 bitsize="@var{size}"
42990 @r{[}regnum="@var{num}"@r{]}
42991 @r{[}save-restore="@var{save-restore}"@r{]}
42992 @r{[}type="@var{type}"@r{]}
42993 @r{[}group="@var{group}"@r{]}/>
42997 The components are as follows:
43002 The register's name; it must be unique within the target description.
43005 The register's size, in bits.
43008 The register's number. If omitted, a register's number is one greater
43009 than that of the previous register (either in the current feature or in
43010 a preceding feature); the first register in the target description
43011 defaults to zero. This register number is used to read or write
43012 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43013 packets, and registers appear in the @code{g} and @code{G} packets
43014 in order of increasing register number.
43017 Whether the register should be preserved across inferior function
43018 calls; this must be either @code{yes} or @code{no}. The default is
43019 @code{yes}, which is appropriate for most registers except for
43020 some system control registers; this is not related to the target's
43024 The type of the register. It may be a predefined type, a type
43025 defined in the current feature, or one of the special types @code{int}
43026 and @code{float}. @code{int} is an integer type of the correct size
43027 for @var{bitsize}, and @code{float} is a floating point type (in the
43028 architecture's normal floating point format) of the correct size for
43029 @var{bitsize}. The default is @code{int}.
43032 The register group to which this register belongs. It can be one of the
43033 standard register groups @code{general}, @code{float}, @code{vector} or an
43034 arbitrary string. Group names should be limited to alphanumeric characters.
43035 If a group name is made up of multiple words the words may be separated by
43036 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43037 @var{group} is specified, @value{GDBN} will not display the register in
43038 @code{info registers}.
43042 @node Predefined Target Types
43043 @section Predefined Target Types
43044 @cindex target descriptions, predefined types
43046 Type definitions in the self-description can build up composite types
43047 from basic building blocks, but can not define fundamental types. Instead,
43048 standard identifiers are provided by @value{GDBN} for the fundamental
43049 types. The currently supported types are:
43054 Boolean type, occupying a single bit.
43062 Signed integer types holding the specified number of bits.
43070 Unsigned integer types holding the specified number of bits.
43074 Pointers to unspecified code and data. The program counter and
43075 any dedicated return address register may be marked as code
43076 pointers; printing a code pointer converts it into a symbolic
43077 address. The stack pointer and any dedicated address registers
43078 may be marked as data pointers.
43081 Single precision IEEE floating point.
43084 Double precision IEEE floating point.
43087 The 12-byte extended precision format used by ARM FPA registers.
43090 The 10-byte extended precision format used by x87 registers.
43093 32bit @sc{eflags} register used by x86.
43096 32bit @sc{mxcsr} register used by x86.
43100 @node Enum Target Types
43101 @section Enum Target Types
43102 @cindex target descriptions, enum types
43104 Enum target types are useful in @samp{struct} and @samp{flags}
43105 register descriptions. @xref{Target Description Format}.
43107 Enum types have a name, size and a list of name/value pairs.
43110 <enum id="@var{id}" size="@var{size}">
43111 <evalue name="@var{name}" value="@var{value}"/>
43116 Enums must be defined before they are used.
43119 <enum id="levels_type" size="4">
43120 <evalue name="low" value="0"/>
43121 <evalue name="high" value="1"/>
43123 <flags id="flags_type" size="4">
43124 <field name="X" start="0"/>
43125 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43127 <reg name="flags" bitsize="32" type="flags_type"/>
43130 Given that description, a value of 3 for the @samp{flags} register
43131 would be printed as:
43134 (gdb) info register flags
43135 flags 0x3 [ X LEVEL=high ]
43138 @node Standard Target Features
43139 @section Standard Target Features
43140 @cindex target descriptions, standard features
43142 A target description must contain either no registers or all the
43143 target's registers. If the description contains no registers, then
43144 @value{GDBN} will assume a default register layout, selected based on
43145 the architecture. If the description contains any registers, the
43146 default layout will not be used; the standard registers must be
43147 described in the target description, in such a way that @value{GDBN}
43148 can recognize them.
43150 This is accomplished by giving specific names to feature elements
43151 which contain standard registers. @value{GDBN} will look for features
43152 with those names and verify that they contain the expected registers;
43153 if any known feature is missing required registers, or if any required
43154 feature is missing, @value{GDBN} will reject the target
43155 description. You can add additional registers to any of the
43156 standard features --- @value{GDBN} will display them just as if
43157 they were added to an unrecognized feature.
43159 This section lists the known features and their expected contents.
43160 Sample XML documents for these features are included in the
43161 @value{GDBN} source tree, in the directory @file{gdb/features}.
43163 Names recognized by @value{GDBN} should include the name of the
43164 company or organization which selected the name, and the overall
43165 architecture to which the feature applies; so e.g.@: the feature
43166 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43168 The names of registers are not case sensitive for the purpose
43169 of recognizing standard features, but @value{GDBN} will only display
43170 registers using the capitalization used in the description.
43173 * AArch64 Features::
43177 * MicroBlaze Features::
43181 * Nios II Features::
43182 * OpenRISC 1000 Features::
43183 * PowerPC Features::
43184 * RISC-V Features::
43185 * S/390 and System z Features::
43191 @node AArch64 Features
43192 @subsection AArch64 Features
43193 @cindex target descriptions, AArch64 features
43195 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43196 targets. It should contain registers @samp{x0} through @samp{x30},
43197 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43199 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43200 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43203 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43204 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43205 through @samp{p15}, @samp{ffr} and @samp{vg}.
43207 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43208 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43211 @subsection ARC Features
43212 @cindex target descriptions, ARC Features
43214 ARC processors are highly configurable, so even core registers and their number
43215 are not completely predetermined. In addition flags and PC registers which are
43216 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43217 that one of the core registers features is present.
43218 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43220 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43221 targets with a normal register file. It should contain registers @samp{r0}
43222 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43223 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43224 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43225 @samp{ilink} and extension core registers are not available to read/write, when
43226 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43228 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43229 ARC HS targets with a reduced register file. It should contain registers
43230 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43231 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43232 This feature may contain register @samp{ilink} and any of extension core
43233 registers @samp{r32} through @samp{r59/acch}.
43235 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43236 targets with a normal register file. It should contain registers @samp{r0}
43237 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43238 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43239 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43240 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43241 registers are not available when debugging GNU/Linux applications. The only
43242 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43243 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43244 ARC v2, but @samp{ilink2} is optional on ARCompact.
43246 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43247 targets. It should contain registers @samp{pc} and @samp{status32}.
43250 @subsection ARM Features
43251 @cindex target descriptions, ARM features
43253 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43255 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43256 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43258 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43259 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43260 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43263 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43264 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43266 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43267 it should contain at least registers @samp{wR0} through @samp{wR15} and
43268 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43269 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43271 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43272 should contain at least registers @samp{d0} through @samp{d15}. If
43273 they are present, @samp{d16} through @samp{d31} should also be included.
43274 @value{GDBN} will synthesize the single-precision registers from
43275 halves of the double-precision registers.
43277 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43278 need to contain registers; it instructs @value{GDBN} to display the
43279 VFP double-precision registers as vectors and to synthesize the
43280 quad-precision registers from pairs of double-precision registers.
43281 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43282 be present and include 32 double-precision registers.
43284 @node i386 Features
43285 @subsection i386 Features
43286 @cindex target descriptions, i386 features
43288 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43289 targets. It should describe the following registers:
43293 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43295 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43297 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43298 @samp{fs}, @samp{gs}
43300 @samp{st0} through @samp{st7}
43302 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43303 @samp{foseg}, @samp{fooff} and @samp{fop}
43306 The register sets may be different, depending on the target.
43308 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43309 describe registers:
43313 @samp{xmm0} through @samp{xmm7} for i386
43315 @samp{xmm0} through @samp{xmm15} for amd64
43320 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43321 @samp{org.gnu.gdb.i386.sse} feature. It should
43322 describe the upper 128 bits of @sc{ymm} registers:
43326 @samp{ymm0h} through @samp{ymm7h} for i386
43328 @samp{ymm0h} through @samp{ymm15h} for amd64
43331 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43332 Memory Protection Extension (MPX). It should describe the following registers:
43336 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43338 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43341 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43342 describe a single register, @samp{orig_eax}.
43344 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43345 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43347 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43348 @samp{org.gnu.gdb.i386.avx} feature. It should
43349 describe additional @sc{xmm} registers:
43353 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43356 It should describe the upper 128 bits of additional @sc{ymm} registers:
43360 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43364 describe the upper 256 bits of @sc{zmm} registers:
43368 @samp{zmm0h} through @samp{zmm7h} for i386.
43370 @samp{zmm0h} through @samp{zmm15h} for amd64.
43374 describe the additional @sc{zmm} registers:
43378 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43381 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43382 describe a single register, @samp{pkru}. It is a 32-bit register
43383 valid for i386 and amd64.
43385 @node MicroBlaze Features
43386 @subsection MicroBlaze Features
43387 @cindex target descriptions, MicroBlaze features
43389 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43390 targets. It should contain registers @samp{r0} through @samp{r31},
43391 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43392 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43393 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43395 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43396 If present, it should contain registers @samp{rshr} and @samp{rslr}
43398 @node MIPS Features
43399 @subsection @acronym{MIPS} Features
43400 @cindex target descriptions, @acronym{MIPS} features
43402 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43403 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43404 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43407 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43408 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43409 registers. They may be 32-bit or 64-bit depending on the target.
43411 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43412 it may be optional in a future version of @value{GDBN}. It should
43413 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43414 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43416 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43417 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43418 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43419 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43421 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43422 contain a single register, @samp{restart}, which is used by the
43423 Linux kernel to control restartable syscalls.
43425 @node M68K Features
43426 @subsection M68K Features
43427 @cindex target descriptions, M68K features
43430 @item @samp{org.gnu.gdb.m68k.core}
43431 @itemx @samp{org.gnu.gdb.coldfire.core}
43432 @itemx @samp{org.gnu.gdb.fido.core}
43433 One of those features must be always present.
43434 The feature that is present determines which flavor of m68k is
43435 used. The feature that is present should contain registers
43436 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43437 @samp{sp}, @samp{ps} and @samp{pc}.
43439 @item @samp{org.gnu.gdb.coldfire.fp}
43440 This feature is optional. If present, it should contain registers
43441 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43445 @node NDS32 Features
43446 @subsection NDS32 Features
43447 @cindex target descriptions, NDS32 features
43449 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43450 targets. It should contain at least registers @samp{r0} through
43451 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43454 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43455 it should contain 64-bit double-precision floating-point registers
43456 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43457 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43459 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43460 registers are overlapped with the thirty-two 32-bit single-precision
43461 floating-point registers. The 32-bit single-precision registers, if
43462 not being listed explicitly, will be synthesized from halves of the
43463 overlapping 64-bit double-precision registers. Listing 32-bit
43464 single-precision registers explicitly is deprecated, and the
43465 support to it could be totally removed some day.
43467 @node Nios II Features
43468 @subsection Nios II Features
43469 @cindex target descriptions, Nios II features
43471 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43472 targets. It should contain the 32 core registers (@samp{zero},
43473 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43474 @samp{pc}, and the 16 control registers (@samp{status} through
43477 @node OpenRISC 1000 Features
43478 @subsection Openrisc 1000 Features
43479 @cindex target descriptions, OpenRISC 1000 features
43481 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43482 targets. It should contain the 32 general purpose registers (@samp{r0}
43483 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43485 @node PowerPC Features
43486 @subsection PowerPC Features
43487 @cindex target descriptions, PowerPC features
43489 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43490 targets. It should contain registers @samp{r0} through @samp{r31},
43491 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43492 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43494 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43495 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43497 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43498 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43499 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43500 through @samp{v31} as aliases for the corresponding @samp{vrX}
43503 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43504 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43505 combine these registers with the floating point registers (@samp{f0}
43506 through @samp{f31}) and the altivec registers (@samp{vr0} through
43507 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43508 @samp{vs63}, the set of vector-scalar registers for POWER7.
43509 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43510 @samp{org.gnu.gdb.power.altivec}.
43512 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43513 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43514 @samp{spefscr}. SPE targets should provide 32-bit registers in
43515 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43516 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43517 these to present registers @samp{ev0} through @samp{ev31} to the
43520 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43521 contain the 64-bit register @samp{ppr}.
43523 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43524 contain the 64-bit register @samp{dscr}.
43526 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43527 contain the 64-bit register @samp{tar}.
43529 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43530 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43533 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43534 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43535 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43536 server PMU registers provided by @sc{gnu}/Linux.
43538 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43539 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43542 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43543 contain the checkpointed general-purpose registers @samp{cr0} through
43544 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43545 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43546 depending on the target. It should also contain the checkpointed
43547 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43550 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43551 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43552 through @samp{cf31}, as well as the checkpointed 64-bit register
43555 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43556 should contain the checkpointed altivec registers @samp{cvr0} through
43557 @samp{cvr31}, all 128-bit wide. It should also contain the
43558 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43561 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43562 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43563 will combine these registers with the checkpointed floating point
43564 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43565 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43566 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43567 @samp{cvs63}. Therefore, this feature requires both
43568 @samp{org.gnu.gdb.power.htm.altivec} and
43569 @samp{org.gnu.gdb.power.htm.fpu}.
43571 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43572 contain the 64-bit checkpointed register @samp{cppr}.
43574 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43575 contain the 64-bit checkpointed register @samp{cdscr}.
43577 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43578 contain the 64-bit checkpointed register @samp{ctar}.
43581 @node RISC-V Features
43582 @subsection RISC-V Features
43583 @cindex target descriptions, RISC-V Features
43585 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43586 targets. It should contain the registers @samp{x0} through
43587 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43588 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43591 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43592 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43593 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43594 architectural register names, or the ABI names can be used.
43596 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43597 it should contain registers that are not backed by real registers on
43598 the target, but are instead virtual, where the register value is
43599 derived from other target state. In many ways these are like
43600 @value{GDBN}s pseudo-registers, except implemented by the target.
43601 Currently the only register expected in this set is the one byte
43602 @samp{priv} register that contains the target's privilege level in the
43603 least significant two bits.
43605 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43606 should contain all of the target's standard CSRs. Standard CSRs are
43607 those defined in the RISC-V specification documents. There is some
43608 overlap between this feature and the fpu feature; the @samp{fflags},
43609 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43610 expectation is that these registers will be in the fpu feature if the
43611 target has floating point hardware, but can be moved into the csr
43612 feature if the target has the floating point control registers, but no
43613 other floating point hardware.
43615 @node S/390 and System z Features
43616 @subsection S/390 and System z Features
43617 @cindex target descriptions, S/390 features
43618 @cindex target descriptions, System z features
43620 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43621 System z targets. It should contain the PSW and the 16 general
43622 registers. In particular, System z targets should provide the 64-bit
43623 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43624 S/390 targets should provide the 32-bit versions of these registers.
43625 A System z target that runs in 31-bit addressing mode should provide
43626 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43627 register's upper halves @samp{r0h} through @samp{r15h}, and their
43628 lower halves @samp{r0l} through @samp{r15l}.
43630 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43631 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43634 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43635 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43637 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43638 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43639 targets and 32-bit otherwise. In addition, the feature may contain
43640 the @samp{last_break} register, whose width depends on the addressing
43641 mode, as well as the @samp{system_call} register, which is always
43644 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43645 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43646 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43648 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43649 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43650 combined by @value{GDBN} with the floating point registers @samp{f0}
43651 through @samp{f15} to present the 128-bit wide vector registers
43652 @samp{v0} through @samp{v15}. In addition, this feature should
43653 contain the 128-bit wide vector registers @samp{v16} through
43656 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43657 the 64-bit wide guarded-storage-control registers @samp{gsd},
43658 @samp{gssm}, and @samp{gsepla}.
43660 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43661 the 64-bit wide guarded-storage broadcast control registers
43662 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43664 @node Sparc Features
43665 @subsection Sparc Features
43666 @cindex target descriptions, sparc32 features
43667 @cindex target descriptions, sparc64 features
43668 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43669 targets. It should describe the following registers:
43673 @samp{g0} through @samp{g7}
43675 @samp{o0} through @samp{o7}
43677 @samp{l0} through @samp{l7}
43679 @samp{i0} through @samp{i7}
43682 They may be 32-bit or 64-bit depending on the target.
43684 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43685 targets. It should describe the following registers:
43689 @samp{f0} through @samp{f31}
43691 @samp{f32} through @samp{f62} for sparc64
43694 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43695 targets. It should describe the following registers:
43699 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43700 @samp{fsr}, and @samp{csr} for sparc32
43702 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43706 @node TIC6x Features
43707 @subsection TMS320C6x Features
43708 @cindex target descriptions, TIC6x features
43709 @cindex target descriptions, TMS320C6x features
43710 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43711 targets. It should contain registers @samp{A0} through @samp{A15},
43712 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43714 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43715 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43716 through @samp{B31}.
43718 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43719 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43721 @node Operating System Information
43722 @appendix Operating System Information
43723 @cindex operating system information
43729 Users of @value{GDBN} often wish to obtain information about the state of
43730 the operating system running on the target---for example the list of
43731 processes, or the list of open files. This section describes the
43732 mechanism that makes it possible. This mechanism is similar to the
43733 target features mechanism (@pxref{Target Descriptions}), but focuses
43734 on a different aspect of target.
43736 Operating system information is retrived from the target via the
43737 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43738 read}). The object name in the request should be @samp{osdata}, and
43739 the @var{annex} identifies the data to be fetched.
43742 @appendixsection Process list
43743 @cindex operating system information, process list
43745 When requesting the process list, the @var{annex} field in the
43746 @samp{qXfer} request should be @samp{processes}. The returned data is
43747 an XML document. The formal syntax of this document is defined in
43748 @file{gdb/features/osdata.dtd}.
43750 An example document is:
43753 <?xml version="1.0"?>
43754 <!DOCTYPE target SYSTEM "osdata.dtd">
43755 <osdata type="processes">
43757 <column name="pid">1</column>
43758 <column name="user">root</column>
43759 <column name="command">/sbin/init</column>
43760 <column name="cores">1,2,3</column>
43765 Each item should include a column whose name is @samp{pid}. The value
43766 of that column should identify the process on the target. The
43767 @samp{user} and @samp{command} columns are optional, and will be
43768 displayed by @value{GDBN}. The @samp{cores} column, if present,
43769 should contain a comma-separated list of cores that this process
43770 is running on. Target may provide additional columns,
43771 which @value{GDBN} currently ignores.
43773 @node Trace File Format
43774 @appendix Trace File Format
43775 @cindex trace file format
43777 The trace file comes in three parts: a header, a textual description
43778 section, and a trace frame section with binary data.
43780 The header has the form @code{\x7fTRACE0\n}. The first byte is
43781 @code{0x7f} so as to indicate that the file contains binary data,
43782 while the @code{0} is a version number that may have different values
43785 The description section consists of multiple lines of @sc{ascii} text
43786 separated by newline characters (@code{0xa}). The lines may include a
43787 variety of optional descriptive or context-setting information, such
43788 as tracepoint definitions or register set size. @value{GDBN} will
43789 ignore any line that it does not recognize. An empty line marks the end
43794 Specifies the size of a register block in bytes. This is equal to the
43795 size of a @code{g} packet payload in the remote protocol. @var{size}
43796 is an ascii decimal number. There should be only one such line in
43797 a single trace file.
43799 @item status @var{status}
43800 Trace status. @var{status} has the same format as a @code{qTStatus}
43801 remote packet reply. There should be only one such line in a single trace
43804 @item tp @var{payload}
43805 Tracepoint definition. The @var{payload} has the same format as
43806 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43807 may take multiple lines of definition, corresponding to the multiple
43810 @item tsv @var{payload}
43811 Trace state variable definition. The @var{payload} has the same format as
43812 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43813 may take multiple lines of definition, corresponding to the multiple
43816 @item tdesc @var{payload}
43817 Target description in XML format. The @var{payload} is a single line of
43818 the XML file. All such lines should be concatenated together to get
43819 the original XML file. This file is in the same format as @code{qXfer}
43820 @code{features} payload, and corresponds to the main @code{target.xml}
43821 file. Includes are not allowed.
43825 The trace frame section consists of a number of consecutive frames.
43826 Each frame begins with a two-byte tracepoint number, followed by a
43827 four-byte size giving the amount of data in the frame. The data in
43828 the frame consists of a number of blocks, each introduced by a
43829 character indicating its type (at least register, memory, and trace
43830 state variable). The data in this section is raw binary, not a
43831 hexadecimal or other encoding; its endianness matches the target's
43834 @c FIXME bi-arch may require endianness/arch info in description section
43837 @item R @var{bytes}
43838 Register block. The number and ordering of bytes matches that of a
43839 @code{g} packet in the remote protocol. Note that these are the
43840 actual bytes, in target order, not a hexadecimal encoding.
43842 @item M @var{address} @var{length} @var{bytes}...
43843 Memory block. This is a contiguous block of memory, at the 8-byte
43844 address @var{address}, with a 2-byte length @var{length}, followed by
43845 @var{length} bytes.
43847 @item V @var{number} @var{value}
43848 Trace state variable block. This records the 8-byte signed value
43849 @var{value} of trace state variable numbered @var{number}.
43853 Future enhancements of the trace file format may include additional types
43856 @node Index Section Format
43857 @appendix @code{.gdb_index} section format
43858 @cindex .gdb_index section format
43859 @cindex index section format
43861 This section documents the index section that is created by @code{save
43862 gdb-index} (@pxref{Index Files}). The index section is
43863 DWARF-specific; some knowledge of DWARF is assumed in this
43866 The mapped index file format is designed to be directly
43867 @code{mmap}able on any architecture. In most cases, a datum is
43868 represented using a little-endian 32-bit integer value, called an
43869 @code{offset_type}. Big endian machines must byte-swap the values
43870 before using them. Exceptions to this rule are noted. The data is
43871 laid out such that alignment is always respected.
43873 A mapped index consists of several areas, laid out in order.
43877 The file header. This is a sequence of values, of @code{offset_type}
43878 unless otherwise noted:
43882 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43883 Version 4 uses a different hashing function from versions 5 and 6.
43884 Version 6 includes symbols for inlined functions, whereas versions 4
43885 and 5 do not. Version 7 adds attributes to the CU indices in the
43886 symbol table. Version 8 specifies that symbols from DWARF type units
43887 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43888 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43890 @value{GDBN} will only read version 4, 5, or 6 indices
43891 by specifying @code{set use-deprecated-index-sections on}.
43892 GDB has a workaround for potentially broken version 7 indices so it is
43893 currently not flagged as deprecated.
43896 The offset, from the start of the file, of the CU list.
43899 The offset, from the start of the file, of the types CU list. Note
43900 that this area can be empty, in which case this offset will be equal
43901 to the next offset.
43904 The offset, from the start of the file, of the address area.
43907 The offset, from the start of the file, of the symbol table.
43910 The offset, from the start of the file, of the constant pool.
43914 The CU list. This is a sequence of pairs of 64-bit little-endian
43915 values, sorted by the CU offset. The first element in each pair is
43916 the offset of a CU in the @code{.debug_info} section. The second
43917 element in each pair is the length of that CU. References to a CU
43918 elsewhere in the map are done using a CU index, which is just the
43919 0-based index into this table. Note that if there are type CUs, then
43920 conceptually CUs and type CUs form a single list for the purposes of
43924 The types CU list. This is a sequence of triplets of 64-bit
43925 little-endian values. In a triplet, the first value is the CU offset,
43926 the second value is the type offset in the CU, and the third value is
43927 the type signature. The types CU list is not sorted.
43930 The address area. The address area consists of a sequence of address
43931 entries. Each address entry has three elements:
43935 The low address. This is a 64-bit little-endian value.
43938 The high address. This is a 64-bit little-endian value. Like
43939 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43942 The CU index. This is an @code{offset_type} value.
43946 The symbol table. This is an open-addressed hash table. The size of
43947 the hash table is always a power of 2.
43949 Each slot in the hash table consists of a pair of @code{offset_type}
43950 values. The first value is the offset of the symbol's name in the
43951 constant pool. The second value is the offset of the CU vector in the
43954 If both values are 0, then this slot in the hash table is empty. This
43955 is ok because while 0 is a valid constant pool index, it cannot be a
43956 valid index for both a string and a CU vector.
43958 The hash value for a table entry is computed by applying an
43959 iterative hash function to the symbol's name. Starting with an
43960 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43961 the string is incorporated into the hash using the formula depending on the
43966 The formula is @code{r = r * 67 + c - 113}.
43968 @item Versions 5 to 7
43969 The formula is @code{r = r * 67 + tolower (c) - 113}.
43972 The terminating @samp{\0} is not incorporated into the hash.
43974 The step size used in the hash table is computed via
43975 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43976 value, and @samp{size} is the size of the hash table. The step size
43977 is used to find the next candidate slot when handling a hash
43980 The names of C@t{++} symbols in the hash table are canonicalized. We
43981 don't currently have a simple description of the canonicalization
43982 algorithm; if you intend to create new index sections, you must read
43986 The constant pool. This is simply a bunch of bytes. It is organized
43987 so that alignment is correct: CU vectors are stored first, followed by
43990 A CU vector in the constant pool is a sequence of @code{offset_type}
43991 values. The first value is the number of CU indices in the vector.
43992 Each subsequent value is the index and symbol attributes of a CU in
43993 the CU list. This element in the hash table is used to indicate which
43994 CUs define the symbol and how the symbol is used.
43995 See below for the format of each CU index+attributes entry.
43997 A string in the constant pool is zero-terminated.
44000 Attributes were added to CU index values in @code{.gdb_index} version 7.
44001 If a symbol has multiple uses within a CU then there is one
44002 CU index+attributes value for each use.
44004 The format of each CU index+attributes entry is as follows
44010 This is the index of the CU in the CU list.
44012 These bits are reserved for future purposes and must be zero.
44014 The kind of the symbol in the CU.
44018 This value is reserved and should not be used.
44019 By reserving zero the full @code{offset_type} value is backwards compatible
44020 with previous versions of the index.
44022 The symbol is a type.
44024 The symbol is a variable or an enum value.
44026 The symbol is a function.
44028 Any other kind of symbol.
44030 These values are reserved.
44034 This bit is zero if the value is global and one if it is static.
44036 The determination of whether a symbol is global or static is complicated.
44037 The authorative reference is the file @file{dwarf2read.c} in
44038 @value{GDBN} sources.
44042 This pseudo-code describes the computation of a symbol's kind and
44043 global/static attributes in the index.
44046 is_external = get_attribute (die, DW_AT_external);
44047 language = get_attribute (cu_die, DW_AT_language);
44050 case DW_TAG_typedef:
44051 case DW_TAG_base_type:
44052 case DW_TAG_subrange_type:
44056 case DW_TAG_enumerator:
44058 is_static = language != CPLUS;
44060 case DW_TAG_subprogram:
44062 is_static = ! (is_external || language == ADA);
44064 case DW_TAG_constant:
44066 is_static = ! is_external;
44068 case DW_TAG_variable:
44070 is_static = ! is_external;
44072 case DW_TAG_namespace:
44076 case DW_TAG_class_type:
44077 case DW_TAG_interface_type:
44078 case DW_TAG_structure_type:
44079 case DW_TAG_union_type:
44080 case DW_TAG_enumeration_type:
44082 is_static = language != CPLUS;
44090 @appendix Manual pages
44094 * gdb man:: The GNU Debugger man page
44095 * gdbserver man:: Remote Server for the GNU Debugger man page
44096 * gcore man:: Generate a core file of a running program
44097 * gdbinit man:: gdbinit scripts
44098 * gdb-add-index man:: Add index files to speed up GDB
44104 @c man title gdb The GNU Debugger
44106 @c man begin SYNOPSIS gdb
44107 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44108 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44109 [@option{-b}@w{ }@var{bps}]
44110 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44111 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44112 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44113 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44114 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44117 @c man begin DESCRIPTION gdb
44118 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44119 going on ``inside'' another program while it executes -- or what another
44120 program was doing at the moment it crashed.
44122 @value{GDBN} can do four main kinds of things (plus other things in support of
44123 these) to help you catch bugs in the act:
44127 Start your program, specifying anything that might affect its behavior.
44130 Make your program stop on specified conditions.
44133 Examine what has happened, when your program has stopped.
44136 Change things in your program, so you can experiment with correcting the
44137 effects of one bug and go on to learn about another.
44140 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44143 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44144 commands from the terminal until you tell it to exit with the @value{GDBN}
44145 command @code{quit}. You can get online help from @value{GDBN} itself
44146 by using the command @code{help}.
44148 You can run @code{gdb} with no arguments or options; but the most
44149 usual way to start @value{GDBN} is with one argument or two, specifying an
44150 executable program as the argument:
44156 You can also start with both an executable program and a core file specified:
44162 You can, instead, specify a process ID as a second argument, if you want
44163 to debug a running process:
44171 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44172 named @file{1234}; @value{GDBN} does check for a core file first).
44173 With option @option{-p} you can omit the @var{program} filename.
44175 Here are some of the most frequently needed @value{GDBN} commands:
44177 @c pod2man highlights the right hand side of the @item lines.
44179 @item break [@var{file}:]@var{function}
44180 Set a breakpoint at @var{function} (in @var{file}).
44182 @item run [@var{arglist}]
44183 Start your program (with @var{arglist}, if specified).
44186 Backtrace: display the program stack.
44188 @item print @var{expr}
44189 Display the value of an expression.
44192 Continue running your program (after stopping, e.g. at a breakpoint).
44195 Execute next program line (after stopping); step @emph{over} any
44196 function calls in the line.
44198 @item edit [@var{file}:]@var{function}
44199 look at the program line where it is presently stopped.
44201 @item list [@var{file}:]@var{function}
44202 type the text of the program in the vicinity of where it is presently stopped.
44205 Execute next program line (after stopping); step @emph{into} any
44206 function calls in the line.
44208 @item help [@var{name}]
44209 Show information about @value{GDBN} command @var{name}, or general information
44210 about using @value{GDBN}.
44213 Exit from @value{GDBN}.
44217 For full details on @value{GDBN},
44218 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44219 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44220 as the @code{gdb} entry in the @code{info} program.
44224 @c man begin OPTIONS gdb
44225 Any arguments other than options specify an executable
44226 file and core file (or process ID); that is, the first argument
44227 encountered with no
44228 associated option flag is equivalent to a @option{-se} option, and the second,
44229 if any, is equivalent to a @option{-c} option if it's the name of a file.
44231 both long and short forms; both are shown here. The long forms are also
44232 recognized if you truncate them, so long as enough of the option is
44233 present to be unambiguous. (If you prefer, you can flag option
44234 arguments with @option{+} rather than @option{-}, though we illustrate the
44235 more usual convention.)
44237 All the options and command line arguments you give are processed
44238 in sequential order. The order makes a difference when the @option{-x}
44244 List all options, with brief explanations.
44246 @item -symbols=@var{file}
44247 @itemx -s @var{file}
44248 Read symbol table from file @var{file}.
44251 Enable writing into executable and core files.
44253 @item -exec=@var{file}
44254 @itemx -e @var{file}
44255 Use file @var{file} as the executable file to execute when
44256 appropriate, and for examining pure data in conjunction with a core
44259 @item -se=@var{file}
44260 Read symbol table from file @var{file} and use it as the executable
44263 @item -core=@var{file}
44264 @itemx -c @var{file}
44265 Use file @var{file} as a core dump to examine.
44267 @item -command=@var{file}
44268 @itemx -x @var{file}
44269 Execute @value{GDBN} commands from file @var{file}.
44271 @item -ex @var{command}
44272 Execute given @value{GDBN} @var{command}.
44274 @item -directory=@var{directory}
44275 @itemx -d @var{directory}
44276 Add @var{directory} to the path to search for source files.
44279 Do not execute commands from @file{~/.gdbinit}.
44283 Do not execute commands from any @file{.gdbinit} initialization files.
44287 ``Quiet''. Do not print the introductory and copyright messages. These
44288 messages are also suppressed in batch mode.
44291 Run in batch mode. Exit with status @code{0} after processing all the command
44292 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44293 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44294 commands in the command files.
44296 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44297 download and run a program on another computer; in order to make this
44298 more useful, the message
44301 Program exited normally.
44305 (which is ordinarily issued whenever a program running under @value{GDBN} control
44306 terminates) is not issued when running in batch mode.
44308 @item -cd=@var{directory}
44309 Run @value{GDBN} using @var{directory} as its working directory,
44310 instead of the current directory.
44314 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44315 @value{GDBN} to output the full file name and line number in a standard,
44316 recognizable fashion each time a stack frame is displayed (which
44317 includes each time the program stops). This recognizable format looks
44318 like two @samp{\032} characters, followed by the file name, line number
44319 and character position separated by colons, and a newline. The
44320 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44321 characters as a signal to display the source code for the frame.
44324 Set the line speed (baud rate or bits per second) of any serial
44325 interface used by @value{GDBN} for remote debugging.
44327 @item -tty=@var{device}
44328 Run using @var{device} for your program's standard input and output.
44332 @c man begin SEEALSO gdb
44334 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44335 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44336 documentation are properly installed at your site, the command
44343 should give you access to the complete manual.
44345 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44346 Richard M. Stallman and Roland H. Pesch, July 1991.
44350 @node gdbserver man
44351 @heading gdbserver man
44353 @c man title gdbserver Remote Server for the GNU Debugger
44355 @c man begin SYNOPSIS gdbserver
44356 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44358 gdbserver --attach @var{comm} @var{pid}
44360 gdbserver --multi @var{comm}
44364 @c man begin DESCRIPTION gdbserver
44365 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44366 than the one which is running the program being debugged.
44369 @subheading Usage (server (target) side)
44372 Usage (server (target) side):
44375 First, you need to have a copy of the program you want to debug put onto
44376 the target system. The program can be stripped to save space if needed, as
44377 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44378 the @value{GDBN} running on the host system.
44380 To use the server, you log on to the target system, and run the @command{gdbserver}
44381 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44382 your program, and (c) its arguments. The general syntax is:
44385 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44388 For example, using a serial port, you might say:
44392 @c @file would wrap it as F</dev/com1>.
44393 target> gdbserver /dev/com1 emacs foo.txt
44396 target> gdbserver @file{/dev/com1} emacs foo.txt
44400 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44401 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44402 waits patiently for the host @value{GDBN} to communicate with it.
44404 To use a TCP connection, you could say:
44407 target> gdbserver host:2345 emacs foo.txt
44410 This says pretty much the same thing as the last example, except that we are
44411 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44412 that we are expecting to see a TCP connection from @code{host} to local TCP port
44413 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44414 want for the port number as long as it does not conflict with any existing TCP
44415 ports on the target system. This same port number must be used in the host
44416 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44417 you chose a port number that conflicts with another service, @command{gdbserver} will
44418 print an error message and exit.
44420 @command{gdbserver} can also attach to running programs.
44421 This is accomplished via the @option{--attach} argument. The syntax is:
44424 target> gdbserver --attach @var{comm} @var{pid}
44427 @var{pid} is the process ID of a currently running process. It isn't
44428 necessary to point @command{gdbserver} at a binary for the running process.
44430 To start @code{gdbserver} without supplying an initial command to run
44431 or process ID to attach, use the @option{--multi} command line option.
44432 In such case you should connect using @kbd{target extended-remote} to start
44433 the program you want to debug.
44436 target> gdbserver --multi @var{comm}
44440 @subheading Usage (host side)
44446 You need an unstripped copy of the target program on your host system, since
44447 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44448 would, with the target program as the first argument. (You may need to use the
44449 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44450 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44451 new command you need to know about is @code{target remote}
44452 (or @code{target extended-remote}). Its argument is either
44453 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44454 descriptor. For example:
44458 @c @file would wrap it as F</dev/ttyb>.
44459 (gdb) target remote /dev/ttyb
44462 (gdb) target remote @file{/dev/ttyb}
44467 communicates with the server via serial line @file{/dev/ttyb}, and:
44470 (gdb) target remote the-target:2345
44474 communicates via a TCP connection to port 2345 on host `the-target', where
44475 you previously started up @command{gdbserver} with the same port number. Note that for
44476 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44477 command, otherwise you may get an error that looks something like
44478 `Connection refused'.
44480 @command{gdbserver} can also debug multiple inferiors at once,
44483 the @value{GDBN} manual in node @code{Inferiors and Programs}
44484 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44487 @ref{Inferiors and Programs}.
44489 In such case use the @code{extended-remote} @value{GDBN} command variant:
44492 (gdb) target extended-remote the-target:2345
44495 The @command{gdbserver} option @option{--multi} may or may not be used in such
44499 @c man begin OPTIONS gdbserver
44500 There are three different modes for invoking @command{gdbserver}:
44505 Debug a specific program specified by its program name:
44508 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44511 The @var{comm} parameter specifies how should the server communicate
44512 with @value{GDBN}; it is either a device name (to use a serial line),
44513 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44514 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44515 debug in @var{prog}. Any remaining arguments will be passed to the
44516 program verbatim. When the program exits, @value{GDBN} will close the
44517 connection, and @code{gdbserver} will exit.
44520 Debug a specific program by specifying the process ID of a running
44524 gdbserver --attach @var{comm} @var{pid}
44527 The @var{comm} parameter is as described above. Supply the process ID
44528 of a running program in @var{pid}; @value{GDBN} will do everything
44529 else. Like with the previous mode, when the process @var{pid} exits,
44530 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44533 Multi-process mode -- debug more than one program/process:
44536 gdbserver --multi @var{comm}
44539 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44540 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44541 close the connection when a process being debugged exits, so you can
44542 debug several processes in the same session.
44545 In each of the modes you may specify these options:
44550 List all options, with brief explanations.
44553 This option causes @command{gdbserver} to print its version number and exit.
44556 @command{gdbserver} will attach to a running program. The syntax is:
44559 target> gdbserver --attach @var{comm} @var{pid}
44562 @var{pid} is the process ID of a currently running process. It isn't
44563 necessary to point @command{gdbserver} at a binary for the running process.
44566 To start @code{gdbserver} without supplying an initial command to run
44567 or process ID to attach, use this command line option.
44568 Then you can connect using @kbd{target extended-remote} and start
44569 the program you want to debug. The syntax is:
44572 target> gdbserver --multi @var{comm}
44576 Instruct @code{gdbserver} to display extra status information about the debugging
44578 This option is intended for @code{gdbserver} development and for bug reports to
44581 @item --remote-debug
44582 Instruct @code{gdbserver} to display remote protocol debug output.
44583 This option is intended for @code{gdbserver} development and for bug reports to
44586 @item --debug-file=@var{filename}
44587 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
44588 This option is intended for @code{gdbserver} development and for bug reports to
44591 @item --debug-format=option1@r{[},option2,...@r{]}
44592 Instruct @code{gdbserver} to include extra information in each line
44593 of debugging output.
44594 @xref{Other Command-Line Arguments for gdbserver}.
44597 Specify a wrapper to launch programs
44598 for debugging. The option should be followed by the name of the
44599 wrapper, then any command-line arguments to pass to the wrapper, then
44600 @kbd{--} indicating the end of the wrapper arguments.
44603 By default, @command{gdbserver} keeps the listening TCP port open, so that
44604 additional connections are possible. However, if you start @code{gdbserver}
44605 with the @option{--once} option, it will stop listening for any further
44606 connection attempts after connecting to the first @value{GDBN} session.
44608 @c --disable-packet is not documented for users.
44610 @c --disable-randomization and --no-disable-randomization are superseded by
44611 @c QDisableRandomization.
44616 @c man begin SEEALSO gdbserver
44618 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44619 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44620 documentation are properly installed at your site, the command
44626 should give you access to the complete manual.
44628 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44629 Richard M. Stallman and Roland H. Pesch, July 1991.
44636 @c man title gcore Generate a core file of a running program
44639 @c man begin SYNOPSIS gcore
44640 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44644 @c man begin DESCRIPTION gcore
44645 Generate core dumps of one or more running programs with process IDs
44646 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44647 is equivalent to one produced by the kernel when the process crashes
44648 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44649 limit). However, unlike after a crash, after @command{gcore} finishes
44650 its job the program remains running without any change.
44653 @c man begin OPTIONS gcore
44656 Dump all memory mappings. The actual effect of this option depends on
44657 the Operating System. On @sc{gnu}/Linux, it will disable
44658 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44659 enable @code{dump-excluded-mappings} (@pxref{set
44660 dump-excluded-mappings}).
44662 @item -o @var{prefix}
44663 The optional argument @var{prefix} specifies the prefix to be used
44664 when composing the file names of the core dumps. The file name is
44665 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44666 process ID of the running program being analyzed by @command{gcore}.
44667 If not specified, @var{prefix} defaults to @var{gcore}.
44671 @c man begin SEEALSO gcore
44673 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44674 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44675 documentation are properly installed at your site, the command
44682 should give you access to the complete manual.
44684 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44685 Richard M. Stallman and Roland H. Pesch, July 1991.
44692 @c man title gdbinit GDB initialization scripts
44695 @c man begin SYNOPSIS gdbinit
44696 @ifset SYSTEM_GDBINIT
44697 @value{SYSTEM_GDBINIT}
44706 @c man begin DESCRIPTION gdbinit
44707 These files contain @value{GDBN} commands to automatically execute during
44708 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44711 the @value{GDBN} manual in node @code{Sequences}
44712 -- shell command @code{info -f gdb -n Sequences}.
44718 Please read more in
44720 the @value{GDBN} manual in node @code{Startup}
44721 -- shell command @code{info -f gdb -n Startup}.
44728 @ifset SYSTEM_GDBINIT
44729 @item @value{SYSTEM_GDBINIT}
44731 @ifclear SYSTEM_GDBINIT
44732 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44734 System-wide initialization file. It is executed unless user specified
44735 @value{GDBN} option @code{-nx} or @code{-n}.
44738 the @value{GDBN} manual in node @code{System-wide configuration}
44739 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44742 @ref{System-wide configuration}.
44746 User initialization file. It is executed unless user specified
44747 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44750 Initialization file for current directory. It may need to be enabled with
44751 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44754 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44755 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44758 @ref{Init File in the Current Directory}.
44763 @c man begin SEEALSO gdbinit
44765 gdb(1), @code{info -f gdb -n Startup}
44767 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44768 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44769 documentation are properly installed at your site, the command
44775 should give you access to the complete manual.
44777 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44778 Richard M. Stallman and Roland H. Pesch, July 1991.
44782 @node gdb-add-index man
44783 @heading gdb-add-index
44784 @pindex gdb-add-index
44785 @anchor{gdb-add-index}
44787 @c man title gdb-add-index Add index files to speed up GDB
44789 @c man begin SYNOPSIS gdb-add-index
44790 gdb-add-index @var{filename}
44793 @c man begin DESCRIPTION gdb-add-index
44794 When @value{GDBN} finds a symbol file, it scans the symbols in the
44795 file in order to construct an internal symbol table. This lets most
44796 @value{GDBN} operations work quickly--at the cost of a delay early on.
44797 For large programs, this delay can be quite lengthy, so @value{GDBN}
44798 provides a way to build an index, which speeds up startup.
44800 To determine whether a file contains such an index, use the command
44801 @kbd{readelf -S filename}: the index is stored in a section named
44802 @code{.gdb_index}. The index file can only be produced on systems
44803 which use ELF binaries and DWARF debug information (i.e., sections
44804 named @code{.debug_*}).
44806 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44807 in the @env{PATH} environment variable. If you want to use different
44808 versions of these programs, you can specify them through the
44809 @env{GDB} and @env{OBJDUMP} environment variables.
44813 the @value{GDBN} manual in node @code{Index Files}
44814 -- shell command @kbd{info -f gdb -n "Index Files"}.
44821 @c man begin SEEALSO gdb-add-index
44823 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44824 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44825 documentation are properly installed at your site, the command
44831 should give you access to the complete manual.
44833 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44834 Richard M. Stallman and Roland H. Pesch, July 1991.
44840 @node GNU Free Documentation License
44841 @appendix GNU Free Documentation License
44844 @node Concept Index
44845 @unnumbered Concept Index
44849 @node Command and Variable Index
44850 @unnumbered Command, Variable, and Function Index
44855 % I think something like @@colophon should be in texinfo. In the
44857 \long\def\colophon{\hbox to0pt{}\vfill
44858 \centerline{The body of this manual is set in}
44859 \centerline{\fontname\tenrm,}
44860 \centerline{with headings in {\bf\fontname\tenbf}}
44861 \centerline{and examples in {\tt\fontname\tentt}.}
44862 \centerline{{\it\fontname\tenit\/},}
44863 \centerline{{\bf\fontname\tenbf}, and}
44864 \centerline{{\sl\fontname\tensl\/}}
44865 \centerline{are used for emphasis.}\vfill}
44867 % Blame: doc@@cygnus.com, 1991.