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 @item set logging debugredirect [on|off]
1481 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1482 Set @code{debugredirect} if you want debug output to go only to the log file.
1483 @kindex show logging
1485 Show the current values of the logging settings.
1489 @chapter @value{GDBN} Commands
1491 You can abbreviate a @value{GDBN} command to the first few letters of the command
1492 name, if that abbreviation is unambiguous; and you can repeat certain
1493 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1494 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1495 show you the alternatives available, if there is more than one possibility).
1498 * Command Syntax:: How to give commands to @value{GDBN}
1499 * Completion:: Command completion
1500 * Help:: How to ask @value{GDBN} for help
1503 @node Command Syntax
1504 @section Command Syntax
1506 A @value{GDBN} command is a single line of input. There is no limit on
1507 how long it can be. It starts with a command name, which is followed by
1508 arguments whose meaning depends on the command name. For example, the
1509 command @code{step} accepts an argument which is the number of times to
1510 step, as in @samp{step 5}. You can also use the @code{step} command
1511 with no arguments. Some commands do not allow any arguments.
1513 @cindex abbreviation
1514 @value{GDBN} command names may always be truncated if that abbreviation is
1515 unambiguous. Other possible command abbreviations are listed in the
1516 documentation for individual commands. In some cases, even ambiguous
1517 abbreviations are allowed; for example, @code{s} is specially defined as
1518 equivalent to @code{step} even though there are other commands whose
1519 names start with @code{s}. You can test abbreviations by using them as
1520 arguments to the @code{help} command.
1522 @cindex repeating commands
1523 @kindex RET @r{(repeat last command)}
1524 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1525 repeat the previous command. Certain commands (for example, @code{run})
1526 will not repeat this way; these are commands whose unintentional
1527 repetition might cause trouble and which you are unlikely to want to
1528 repeat. User-defined commands can disable this feature; see
1529 @ref{Define, dont-repeat}.
1531 The @code{list} and @code{x} commands, when you repeat them with
1532 @key{RET}, construct new arguments rather than repeating
1533 exactly as typed. This permits easy scanning of source or memory.
1535 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1536 output, in a way similar to the common utility @code{more}
1537 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1538 @key{RET} too many in this situation, @value{GDBN} disables command
1539 repetition after any command that generates this sort of display.
1541 @kindex # @r{(a comment)}
1543 Any text from a @kbd{#} to the end of the line is a comment; it does
1544 nothing. This is useful mainly in command files (@pxref{Command
1545 Files,,Command Files}).
1547 @cindex repeating command sequences
1548 @kindex Ctrl-o @r{(operate-and-get-next)}
1549 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1550 commands. This command accepts the current line, like @key{RET}, and
1551 then fetches the next line relative to the current line from the history
1555 @section Command Completion
1558 @cindex word completion
1559 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1560 only one possibility; it can also show you what the valid possibilities
1561 are for the next word in a command, at any time. This works for @value{GDBN}
1562 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1564 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1565 of a word. If there is only one possibility, @value{GDBN} fills in the
1566 word, and waits for you to finish the command (or press @key{RET} to
1567 enter it). For example, if you type
1569 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1570 @c complete accuracy in these examples; space introduced for clarity.
1571 @c If texinfo enhancements make it unnecessary, it would be nice to
1572 @c replace " @key" by "@key" in the following...
1574 (@value{GDBP}) info bre @key{TAB}
1578 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1579 the only @code{info} subcommand beginning with @samp{bre}:
1582 (@value{GDBP}) info breakpoints
1586 You can either press @key{RET} at this point, to run the @code{info
1587 breakpoints} command, or backspace and enter something else, if
1588 @samp{breakpoints} does not look like the command you expected. (If you
1589 were sure you wanted @code{info breakpoints} in the first place, you
1590 might as well just type @key{RET} immediately after @samp{info bre},
1591 to exploit command abbreviations rather than command completion).
1593 If there is more than one possibility for the next word when you press
1594 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1595 characters and try again, or just press @key{TAB} a second time;
1596 @value{GDBN} displays all the possible completions for that word. For
1597 example, you might want to set a breakpoint on a subroutine whose name
1598 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1599 just sounds the bell. Typing @key{TAB} again displays all the
1600 function names in your program that begin with those characters, for
1604 (@value{GDBP}) b make_ @key{TAB}
1605 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1606 make_a_section_from_file make_environ
1607 make_abs_section make_function_type
1608 make_blockvector make_pointer_type
1609 make_cleanup make_reference_type
1610 make_command make_symbol_completion_list
1611 (@value{GDBP}) b make_
1615 After displaying the available possibilities, @value{GDBN} copies your
1616 partial input (@samp{b make_} in the example) so you can finish the
1619 If you just want to see the list of alternatives in the first place, you
1620 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1621 means @kbd{@key{META} ?}. You can type this either by holding down a
1622 key designated as the @key{META} shift on your keyboard (if there is
1623 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1625 If the number of possible completions is large, @value{GDBN} will
1626 print as much of the list as it has collected, as well as a message
1627 indicating that the list may be truncated.
1630 (@value{GDBP}) b m@key{TAB}@key{TAB}
1632 <... the rest of the possible completions ...>
1633 *** List may be truncated, max-completions reached. ***
1638 This behavior can be controlled with the following commands:
1641 @kindex set max-completions
1642 @item set max-completions @var{limit}
1643 @itemx set max-completions unlimited
1644 Set the maximum number of completion candidates. @value{GDBN} will
1645 stop looking for more completions once it collects this many candidates.
1646 This is useful when completing on things like function names as collecting
1647 all the possible candidates can be time consuming.
1648 The default value is 200. A value of zero disables tab-completion.
1649 Note that setting either no limit or a very large limit can make
1651 @kindex show max-completions
1652 @item show max-completions
1653 Show the maximum number of candidates that @value{GDBN} will collect and show
1657 @cindex quotes in commands
1658 @cindex completion of quoted strings
1659 Sometimes the string you need, while logically a ``word'', may contain
1660 parentheses or other characters that @value{GDBN} normally excludes from
1661 its notion of a word. To permit word completion to work in this
1662 situation, you may enclose words in @code{'} (single quote marks) in
1663 @value{GDBN} commands.
1665 A likely situation where you might need this is in typing an
1666 expression that involves a C@t{++} symbol name with template
1667 parameters. This is because when completing expressions, GDB treats
1668 the @samp{<} character as word delimiter, assuming that it's the
1669 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1672 For example, when you want to call a C@t{++} template function
1673 interactively using the @code{print} or @code{call} commands, you may
1674 need to distinguish whether you mean the version of @code{name} that
1675 was specialized for @code{int}, @code{name<int>()}, or the version
1676 that was specialized for @code{float}, @code{name<float>()}. To use
1677 the word-completion facilities in this situation, type a single quote
1678 @code{'} at the beginning of the function name. This alerts
1679 @value{GDBN} that it may need to consider more information than usual
1680 when you press @key{TAB} or @kbd{M-?} to request word completion:
1683 (@value{GDBP}) p 'func< @kbd{M-?}
1684 func<int>() func<float>()
1685 (@value{GDBP}) p 'func<
1688 When setting breakpoints however (@pxref{Specify Location}), you don't
1689 usually need to type a quote before the function name, because
1690 @value{GDBN} understands that you want to set a breakpoint on a
1694 (@value{GDBP}) b func< @kbd{M-?}
1695 func<int>() func<float>()
1696 (@value{GDBP}) b func<
1699 This is true even in the case of typing the name of C@t{++} overloaded
1700 functions (multiple definitions of the same function, distinguished by
1701 argument type). For example, when you want to set a breakpoint you
1702 don't need to distinguish whether you mean the version of @code{name}
1703 that takes an @code{int} parameter, @code{name(int)}, or the version
1704 that takes a @code{float} parameter, @code{name(float)}.
1707 (@value{GDBP}) b bubble( @kbd{M-?}
1708 bubble(int) bubble(double)
1709 (@value{GDBP}) b bubble(dou @kbd{M-?}
1713 See @ref{quoting names} for a description of other scenarios that
1716 For more information about overloaded functions, see @ref{C Plus Plus
1717 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1718 overload-resolution off} to disable overload resolution;
1719 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1721 @cindex completion of structure field names
1722 @cindex structure field name completion
1723 @cindex completion of union field names
1724 @cindex union field name completion
1725 When completing in an expression which looks up a field in a
1726 structure, @value{GDBN} also tries@footnote{The completer can be
1727 confused by certain kinds of invalid expressions. Also, it only
1728 examines the static type of the expression, not the dynamic type.} to
1729 limit completions to the field names available in the type of the
1733 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1734 magic to_fputs to_rewind
1735 to_data to_isatty to_write
1736 to_delete to_put to_write_async_safe
1741 This is because the @code{gdb_stdout} is a variable of the type
1742 @code{struct ui_file} that is defined in @value{GDBN} sources as
1749 ui_file_flush_ftype *to_flush;
1750 ui_file_write_ftype *to_write;
1751 ui_file_write_async_safe_ftype *to_write_async_safe;
1752 ui_file_fputs_ftype *to_fputs;
1753 ui_file_read_ftype *to_read;
1754 ui_file_delete_ftype *to_delete;
1755 ui_file_isatty_ftype *to_isatty;
1756 ui_file_rewind_ftype *to_rewind;
1757 ui_file_put_ftype *to_put;
1764 @section Getting Help
1765 @cindex online documentation
1768 You can always ask @value{GDBN} itself for information on its commands,
1769 using the command @code{help}.
1772 @kindex h @r{(@code{help})}
1775 You can use @code{help} (abbreviated @code{h}) with no arguments to
1776 display a short list of named classes of commands:
1780 List of classes of commands:
1782 aliases -- Aliases of other commands
1783 breakpoints -- Making program stop at certain points
1784 data -- Examining data
1785 files -- Specifying and examining files
1786 internals -- Maintenance commands
1787 obscure -- Obscure features
1788 running -- Running the program
1789 stack -- Examining the stack
1790 status -- Status inquiries
1791 support -- Support facilities
1792 tracepoints -- Tracing of program execution without
1793 stopping the program
1794 user-defined -- User-defined commands
1796 Type "help" followed by a class name for a list of
1797 commands in that class.
1798 Type "help" followed by command name for full
1800 Command name abbreviations are allowed if unambiguous.
1803 @c the above line break eliminates huge line overfull...
1805 @item help @var{class}
1806 Using one of the general help classes as an argument, you can get a
1807 list of the individual commands in that class. For example, here is the
1808 help display for the class @code{status}:
1811 (@value{GDBP}) help status
1816 @c Line break in "show" line falsifies real output, but needed
1817 @c to fit in smallbook page size.
1818 info -- Generic command for showing things
1819 about the program being debugged
1820 show -- Generic command for showing things
1823 Type "help" followed by command name for full
1825 Command name abbreviations are allowed if unambiguous.
1829 @item help @var{command}
1830 With a command name as @code{help} argument, @value{GDBN} displays a
1831 short paragraph on how to use that command.
1834 @item apropos @var{args}
1835 The @code{apropos} command searches through all of the @value{GDBN}
1836 commands, and their documentation, for the regular expression specified in
1837 @var{args}. It prints out all matches found. For example:
1848 alias -- Define a new command that is an alias of an existing command
1849 aliases -- Aliases of other commands
1850 d -- Delete some breakpoints or auto-display expressions
1851 del -- Delete some breakpoints or auto-display expressions
1852 delete -- Delete some breakpoints or auto-display expressions
1857 @item complete @var{args}
1858 The @code{complete @var{args}} command lists all the possible completions
1859 for the beginning of a command. Use @var{args} to specify the beginning of the
1860 command you want completed. For example:
1866 @noindent results in:
1877 @noindent This is intended for use by @sc{gnu} Emacs.
1880 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1881 and @code{show} to inquire about the state of your program, or the state
1882 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1883 manual introduces each of them in the appropriate context. The listings
1884 under @code{info} and under @code{show} in the Command, Variable, and
1885 Function Index point to all the sub-commands. @xref{Command and Variable
1891 @kindex i @r{(@code{info})}
1893 This command (abbreviated @code{i}) is for describing the state of your
1894 program. For example, you can show the arguments passed to a function
1895 with @code{info args}, list the registers currently in use with @code{info
1896 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1897 You can get a complete list of the @code{info} sub-commands with
1898 @w{@code{help info}}.
1902 You can assign the result of an expression to an environment variable with
1903 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1904 @code{set prompt $}.
1908 In contrast to @code{info}, @code{show} is for describing the state of
1909 @value{GDBN} itself.
1910 You can change most of the things you can @code{show}, by using the
1911 related command @code{set}; for example, you can control what number
1912 system is used for displays with @code{set radix}, or simply inquire
1913 which is currently in use with @code{show radix}.
1916 To display all the settable parameters and their current
1917 values, you can use @code{show} with no arguments; you may also use
1918 @code{info set}. Both commands produce the same display.
1919 @c FIXME: "info set" violates the rule that "info" is for state of
1920 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1921 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1925 Here are several miscellaneous @code{show} subcommands, all of which are
1926 exceptional in lacking corresponding @code{set} commands:
1929 @kindex show version
1930 @cindex @value{GDBN} version number
1932 Show what version of @value{GDBN} is running. You should include this
1933 information in @value{GDBN} bug-reports. If multiple versions of
1934 @value{GDBN} are in use at your site, you may need to determine which
1935 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1936 commands are introduced, and old ones may wither away. Also, many
1937 system vendors ship variant versions of @value{GDBN}, and there are
1938 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1939 The version number is the same as the one announced when you start
1942 @kindex show copying
1943 @kindex info copying
1944 @cindex display @value{GDBN} copyright
1947 Display information about permission for copying @value{GDBN}.
1949 @kindex show warranty
1950 @kindex info warranty
1952 @itemx info warranty
1953 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1954 if your version of @value{GDBN} comes with one.
1956 @kindex show configuration
1957 @item show configuration
1958 Display detailed information about the way @value{GDBN} was configured
1959 when it was built. This displays the optional arguments passed to the
1960 @file{configure} script and also configuration parameters detected
1961 automatically by @command{configure}. When reporting a @value{GDBN}
1962 bug (@pxref{GDB Bugs}), it is important to include this information in
1968 @chapter Running Programs Under @value{GDBN}
1970 When you run a program under @value{GDBN}, you must first generate
1971 debugging information when you compile it.
1973 You may start @value{GDBN} with its arguments, if any, in an environment
1974 of your choice. If you are doing native debugging, you may redirect
1975 your program's input and output, debug an already running process, or
1976 kill a child process.
1979 * Compilation:: Compiling for debugging
1980 * Starting:: Starting your program
1981 * Arguments:: Your program's arguments
1982 * Environment:: Your program's environment
1984 * Working Directory:: Your program's working directory
1985 * Input/Output:: Your program's input and output
1986 * Attach:: Debugging an already-running process
1987 * Kill Process:: Killing the child process
1989 * Inferiors and Programs:: Debugging multiple inferiors and programs
1990 * Threads:: Debugging programs with multiple threads
1991 * Forks:: Debugging forks
1992 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1996 @section Compiling for Debugging
1998 In order to debug a program effectively, you need to generate
1999 debugging information when you compile it. This debugging information
2000 is stored in the object file; it describes the data type of each
2001 variable or function and the correspondence between source line numbers
2002 and addresses in the executable code.
2004 To request debugging information, specify the @samp{-g} option when you run
2007 Programs that are to be shipped to your customers are compiled with
2008 optimizations, using the @samp{-O} compiler option. However, some
2009 compilers are unable to handle the @samp{-g} and @samp{-O} options
2010 together. Using those compilers, you cannot generate optimized
2011 executables containing debugging information.
2013 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2014 without @samp{-O}, making it possible to debug optimized code. We
2015 recommend that you @emph{always} use @samp{-g} whenever you compile a
2016 program. You may think your program is correct, but there is no sense
2017 in pushing your luck. For more information, see @ref{Optimized Code}.
2019 Older versions of the @sc{gnu} C compiler permitted a variant option
2020 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2021 format; if your @sc{gnu} C compiler has this option, do not use it.
2023 @value{GDBN} knows about preprocessor macros and can show you their
2024 expansion (@pxref{Macros}). Most compilers do not include information
2025 about preprocessor macros in the debugging information if you specify
2026 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2027 the @sc{gnu} C compiler, provides macro information if you are using
2028 the DWARF debugging format, and specify the option @option{-g3}.
2030 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2031 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2032 information on @value{NGCC} options affecting debug information.
2034 You will have the best debugging experience if you use the latest
2035 version of the DWARF debugging format that your compiler supports.
2036 DWARF is currently the most expressive and best supported debugging
2037 format in @value{GDBN}.
2041 @section Starting your Program
2047 @kindex r @r{(@code{run})}
2050 Use the @code{run} command to start your program under @value{GDBN}.
2051 You must first specify the program name with an argument to
2052 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2053 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2054 command (@pxref{Files, ,Commands to Specify Files}).
2058 If you are running your program in an execution environment that
2059 supports processes, @code{run} creates an inferior process and makes
2060 that process run your program. In some environments without processes,
2061 @code{run} jumps to the start of your program. Other targets,
2062 like @samp{remote}, are always running. If you get an error
2063 message like this one:
2066 The "remote" target does not support "run".
2067 Try "help target" or "continue".
2071 then use @code{continue} to run your program. You may need @code{load}
2072 first (@pxref{load}).
2074 The execution of a program is affected by certain information it
2075 receives from its superior. @value{GDBN} provides ways to specify this
2076 information, which you must do @emph{before} starting your program. (You
2077 can change it after starting your program, but such changes only affect
2078 your program the next time you start it.) This information may be
2079 divided into four categories:
2082 @item The @emph{arguments.}
2083 Specify the arguments to give your program as the arguments of the
2084 @code{run} command. If a shell is available on your target, the shell
2085 is used to pass the arguments, so that you may use normal conventions
2086 (such as wildcard expansion or variable substitution) in describing
2088 In Unix systems, you can control which shell is used with the
2089 @code{SHELL} environment variable. If you do not define @code{SHELL},
2090 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2091 use of any shell with the @code{set startup-with-shell} command (see
2094 @item The @emph{environment.}
2095 Your program normally inherits its environment from @value{GDBN}, but you can
2096 use the @value{GDBN} commands @code{set environment} and @code{unset
2097 environment} to change parts of the environment that affect
2098 your program. @xref{Environment, ,Your Program's Environment}.
2100 @item The @emph{working directory.}
2101 You can set your program's working directory with the command
2102 @kbd{set cwd}. If you do not set any working directory with this
2103 command, your program will inherit @value{GDBN}'s working directory if
2104 native debugging, or the remote server's working directory if remote
2105 debugging. @xref{Working Directory, ,Your Program's Working
2108 @item The @emph{standard input and output.}
2109 Your program normally uses the same device for standard input and
2110 standard output as @value{GDBN} is using. You can redirect input and output
2111 in the @code{run} command line, or you can use the @code{tty} command to
2112 set a different device for your program.
2113 @xref{Input/Output, ,Your Program's Input and Output}.
2116 @emph{Warning:} While input and output redirection work, you cannot use
2117 pipes to pass the output of the program you are debugging to another
2118 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2122 When you issue the @code{run} command, your program begins to execute
2123 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2124 of how to arrange for your program to stop. Once your program has
2125 stopped, you may call functions in your program, using the @code{print}
2126 or @code{call} commands. @xref{Data, ,Examining Data}.
2128 If the modification time of your symbol file has changed since the last
2129 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2130 table, and reads it again. When it does this, @value{GDBN} tries to retain
2131 your current breakpoints.
2136 @cindex run to main procedure
2137 The name of the main procedure can vary from language to language.
2138 With C or C@t{++}, the main procedure name is always @code{main}, but
2139 other languages such as Ada do not require a specific name for their
2140 main procedure. The debugger provides a convenient way to start the
2141 execution of the program and to stop at the beginning of the main
2142 procedure, depending on the language used.
2144 The @samp{start} command does the equivalent of setting a temporary
2145 breakpoint at the beginning of the main procedure and then invoking
2146 the @samp{run} command.
2148 @cindex elaboration phase
2149 Some programs contain an @dfn{elaboration} phase where some startup code is
2150 executed before the main procedure is called. This depends on the
2151 languages used to write your program. In C@t{++}, for instance,
2152 constructors for static and global objects are executed before
2153 @code{main} is called. It is therefore possible that the debugger stops
2154 before reaching the main procedure. However, the temporary breakpoint
2155 will remain to halt execution.
2157 Specify the arguments to give to your program as arguments to the
2158 @samp{start} command. These arguments will be given verbatim to the
2159 underlying @samp{run} command. Note that the same arguments will be
2160 reused if no argument is provided during subsequent calls to
2161 @samp{start} or @samp{run}.
2163 It is sometimes necessary to debug the program during elaboration. In
2164 these cases, using the @code{start} command would stop the execution
2165 of your program too late, as the program would have already completed
2166 the elaboration phase. Under these circumstances, either insert
2167 breakpoints in your elaboration code before running your program or
2168 use the @code{starti} command.
2172 @cindex run to first instruction
2173 The @samp{starti} command does the equivalent of setting a temporary
2174 breakpoint at the first instruction of a program's execution and then
2175 invoking the @samp{run} command. For programs containing an
2176 elaboration phase, the @code{starti} command will stop execution at
2177 the start of the elaboration phase.
2179 @anchor{set exec-wrapper}
2180 @kindex set exec-wrapper
2181 @item set exec-wrapper @var{wrapper}
2182 @itemx show exec-wrapper
2183 @itemx unset exec-wrapper
2184 When @samp{exec-wrapper} is set, the specified wrapper is used to
2185 launch programs for debugging. @value{GDBN} starts your program
2186 with a shell command of the form @kbd{exec @var{wrapper}
2187 @var{program}}. Quoting is added to @var{program} and its
2188 arguments, but not to @var{wrapper}, so you should add quotes if
2189 appropriate for your shell. The wrapper runs until it executes
2190 your program, and then @value{GDBN} takes control.
2192 You can use any program that eventually calls @code{execve} with
2193 its arguments as a wrapper. Several standard Unix utilities do
2194 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2195 with @code{exec "$@@"} will also work.
2197 For example, you can use @code{env} to pass an environment variable to
2198 the debugged program, without setting the variable in your shell's
2202 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2206 This command is available when debugging locally on most targets, excluding
2207 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2209 @kindex set startup-with-shell
2210 @anchor{set startup-with-shell}
2211 @item set startup-with-shell
2212 @itemx set startup-with-shell on
2213 @itemx set startup-with-shell off
2214 @itemx show startup-with-shell
2215 On Unix systems, by default, if a shell is available on your target,
2216 @value{GDBN}) uses it to start your program. Arguments of the
2217 @code{run} command are passed to the shell, which does variable
2218 substitution, expands wildcard characters and performs redirection of
2219 I/O. In some circumstances, it may be useful to disable such use of a
2220 shell, for example, when debugging the shell itself or diagnosing
2221 startup failures such as:
2225 Starting program: ./a.out
2226 During startup program terminated with signal SIGSEGV, Segmentation fault.
2230 which indicates the shell or the wrapper specified with
2231 @samp{exec-wrapper} crashed, not your program. Most often, this is
2232 caused by something odd in your shell's non-interactive mode
2233 initialization file---such as @file{.cshrc} for C-shell,
2234 $@file{.zshenv} for the Z shell, or the file specified in the
2235 @samp{BASH_ENV} environment variable for BASH.
2237 @anchor{set auto-connect-native-target}
2238 @kindex set auto-connect-native-target
2239 @item set auto-connect-native-target
2240 @itemx set auto-connect-native-target on
2241 @itemx set auto-connect-native-target off
2242 @itemx show auto-connect-native-target
2244 By default, if not connected to any target yet (e.g., with
2245 @code{target remote}), the @code{run} command starts your program as a
2246 native process under @value{GDBN}, on your local machine. If you're
2247 sure you don't want to debug programs on your local machine, you can
2248 tell @value{GDBN} to not connect to the native target automatically
2249 with the @code{set auto-connect-native-target off} command.
2251 If @code{on}, which is the default, and if @value{GDBN} is not
2252 connected to a target already, the @code{run} command automaticaly
2253 connects to the native target, if one is available.
2255 If @code{off}, and if @value{GDBN} is not connected to a target
2256 already, the @code{run} command fails with an error:
2260 Don't know how to run. Try "help target".
2263 If @value{GDBN} is already connected to a target, @value{GDBN} always
2264 uses it with the @code{run} command.
2266 In any case, you can explicitly connect to the native target with the
2267 @code{target native} command. For example,
2270 (@value{GDBP}) set auto-connect-native-target off
2272 Don't know how to run. Try "help target".
2273 (@value{GDBP}) target native
2275 Starting program: ./a.out
2276 [Inferior 1 (process 10421) exited normally]
2279 In case you connected explicitly to the @code{native} target,
2280 @value{GDBN} remains connected even if all inferiors exit, ready for
2281 the next @code{run} command. Use the @code{disconnect} command to
2284 Examples of other commands that likewise respect the
2285 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2286 proc}, @code{info os}.
2288 @kindex set disable-randomization
2289 @item set disable-randomization
2290 @itemx set disable-randomization on
2291 This option (enabled by default in @value{GDBN}) will turn off the native
2292 randomization of the virtual address space of the started program. This option
2293 is useful for multiple debugging sessions to make the execution better
2294 reproducible and memory addresses reusable across debugging sessions.
2296 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2297 On @sc{gnu}/Linux you can get the same behavior using
2300 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2303 @item set disable-randomization off
2304 Leave the behavior of the started executable unchanged. Some bugs rear their
2305 ugly heads only when the program is loaded at certain addresses. If your bug
2306 disappears when you run the program under @value{GDBN}, that might be because
2307 @value{GDBN} by default disables the address randomization on platforms, such
2308 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2309 disable-randomization off} to try to reproduce such elusive bugs.
2311 On targets where it is available, virtual address space randomization
2312 protects the programs against certain kinds of security attacks. In these
2313 cases the attacker needs to know the exact location of a concrete executable
2314 code. Randomizing its location makes it impossible to inject jumps misusing
2315 a code at its expected addresses.
2317 Prelinking shared libraries provides a startup performance advantage but it
2318 makes addresses in these libraries predictable for privileged processes by
2319 having just unprivileged access at the target system. Reading the shared
2320 library binary gives enough information for assembling the malicious code
2321 misusing it. Still even a prelinked shared library can get loaded at a new
2322 random address just requiring the regular relocation process during the
2323 startup. Shared libraries not already prelinked are always loaded at
2324 a randomly chosen address.
2326 Position independent executables (PIE) contain position independent code
2327 similar to the shared libraries and therefore such executables get loaded at
2328 a randomly chosen address upon startup. PIE executables always load even
2329 already prelinked shared libraries at a random address. You can build such
2330 executable using @command{gcc -fPIE -pie}.
2332 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2333 (as long as the randomization is enabled).
2335 @item show disable-randomization
2336 Show the current setting of the explicit disable of the native randomization of
2337 the virtual address space of the started program.
2342 @section Your Program's Arguments
2344 @cindex arguments (to your program)
2345 The arguments to your program can be specified by the arguments of the
2347 They are passed to a shell, which expands wildcard characters and
2348 performs redirection of I/O, and thence to your program. Your
2349 @code{SHELL} environment variable (if it exists) specifies what shell
2350 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2351 the default shell (@file{/bin/sh} on Unix).
2353 On non-Unix systems, the program is usually invoked directly by
2354 @value{GDBN}, which emulates I/O redirection via the appropriate system
2355 calls, and the wildcard characters are expanded by the startup code of
2356 the program, not by the shell.
2358 @code{run} with no arguments uses the same arguments used by the previous
2359 @code{run}, or those set by the @code{set args} command.
2364 Specify the arguments to be used the next time your program is run. If
2365 @code{set args} has no arguments, @code{run} executes your program
2366 with no arguments. Once you have run your program with arguments,
2367 using @code{set args} before the next @code{run} is the only way to run
2368 it again without arguments.
2372 Show the arguments to give your program when it is started.
2376 @section Your Program's Environment
2378 @cindex environment (of your program)
2379 The @dfn{environment} consists of a set of environment variables and
2380 their values. Environment variables conventionally record such things as
2381 your user name, your home directory, your terminal type, and your search
2382 path for programs to run. Usually you set up environment variables with
2383 the shell and they are inherited by all the other programs you run. When
2384 debugging, it can be useful to try running your program with a modified
2385 environment without having to start @value{GDBN} over again.
2389 @item path @var{directory}
2390 Add @var{directory} to the front of the @code{PATH} environment variable
2391 (the search path for executables) that will be passed to your program.
2392 The value of @code{PATH} used by @value{GDBN} does not change.
2393 You may specify several directory names, separated by whitespace or by a
2394 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2395 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2396 is moved to the front, so it is searched sooner.
2398 You can use the string @samp{$cwd} to refer to whatever is the current
2399 working directory at the time @value{GDBN} searches the path. If you
2400 use @samp{.} instead, it refers to the directory where you executed the
2401 @code{path} command. @value{GDBN} replaces @samp{.} in the
2402 @var{directory} argument (with the current path) before adding
2403 @var{directory} to the search path.
2404 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2405 @c document that, since repeating it would be a no-op.
2409 Display the list of search paths for executables (the @code{PATH}
2410 environment variable).
2412 @kindex show environment
2413 @item show environment @r{[}@var{varname}@r{]}
2414 Print the value of environment variable @var{varname} to be given to
2415 your program when it starts. If you do not supply @var{varname},
2416 print the names and values of all environment variables to be given to
2417 your program. You can abbreviate @code{environment} as @code{env}.
2419 @kindex set environment
2420 @anchor{set environment}
2421 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2422 Set environment variable @var{varname} to @var{value}. The value
2423 changes for your program (and the shell @value{GDBN} uses to launch
2424 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2425 values of environment variables are just strings, and any
2426 interpretation is supplied by your program itself. The @var{value}
2427 parameter is optional; if it is eliminated, the variable is set to a
2429 @c "any string" here does not include leading, trailing
2430 @c blanks. Gnu asks: does anyone care?
2432 For example, this command:
2439 tells the debugged program, when subsequently run, that its user is named
2440 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2441 are not actually required.)
2443 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2444 which also inherits the environment set with @code{set environment}.
2445 If necessary, you can avoid that by using the @samp{env} program as a
2446 wrapper instead of using @code{set environment}. @xref{set
2447 exec-wrapper}, for an example doing just that.
2449 Environment variables that are set by the user are also transmitted to
2450 @command{gdbserver} to be used when starting the remote inferior.
2451 @pxref{QEnvironmentHexEncoded}.
2453 @kindex unset environment
2454 @anchor{unset environment}
2455 @item unset environment @var{varname}
2456 Remove variable @var{varname} from the environment to be passed to your
2457 program. This is different from @samp{set env @var{varname} =};
2458 @code{unset environment} removes the variable from the environment,
2459 rather than assigning it an empty value.
2461 Environment variables that are unset by the user are also unset on
2462 @command{gdbserver} when starting the remote inferior.
2463 @pxref{QEnvironmentUnset}.
2466 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2467 the shell indicated by your @code{SHELL} environment variable if it
2468 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2469 names a shell that runs an initialization file when started
2470 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2471 for the Z shell, or the file specified in the @samp{BASH_ENV}
2472 environment variable for BASH---any variables you set in that file
2473 affect your program. You may wish to move setting of environment
2474 variables to files that are only run when you sign on, such as
2475 @file{.login} or @file{.profile}.
2477 @node Working Directory
2478 @section Your Program's Working Directory
2480 @cindex working directory (of your program)
2481 Each time you start your program with @code{run}, the inferior will be
2482 initialized with the current working directory specified by the
2483 @kbd{set cwd} command. If no directory has been specified by this
2484 command, then the inferior will inherit @value{GDBN}'s current working
2485 directory as its working directory if native debugging, or it will
2486 inherit the remote server's current working directory if remote
2491 @cindex change inferior's working directory
2492 @anchor{set cwd command}
2493 @item set cwd @r{[}@var{directory}@r{]}
2494 Set the inferior's working directory to @var{directory}, which will be
2495 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2496 argument has been specified, the command clears the setting and resets
2497 it to an empty state. This setting has no effect on @value{GDBN}'s
2498 working directory, and it only takes effect the next time you start
2499 the inferior. The @file{~} in @var{directory} is a short for the
2500 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2501 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2502 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2505 You can also change @value{GDBN}'s current working directory by using
2506 the @code{cd} command.
2510 @cindex show inferior's working directory
2512 Show the inferior's working directory. If no directory has been
2513 specified by @kbd{set cwd}, then the default inferior's working
2514 directory is the same as @value{GDBN}'s working directory.
2517 @cindex change @value{GDBN}'s working directory
2519 @item cd @r{[}@var{directory}@r{]}
2520 Set the @value{GDBN} working directory to @var{directory}. If not
2521 given, @var{directory} uses @file{'~'}.
2523 The @value{GDBN} working directory serves as a default for the
2524 commands that specify files for @value{GDBN} to operate on.
2525 @xref{Files, ,Commands to Specify Files}.
2526 @xref{set cwd command}.
2530 Print the @value{GDBN} working directory.
2533 It is generally impossible to find the current working directory of
2534 the process being debugged (since a program can change its directory
2535 during its run). If you work on a system where @value{GDBN} supports
2536 the @code{info proc} command (@pxref{Process Information}), you can
2537 use the @code{info proc} command to find out the
2538 current working directory of the debuggee.
2541 @section Your Program's Input and Output
2546 By default, the program you run under @value{GDBN} does input and output to
2547 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2548 to its own terminal modes to interact with you, but it records the terminal
2549 modes your program was using and switches back to them when you continue
2550 running your program.
2553 @kindex info terminal
2555 Displays information recorded by @value{GDBN} about the terminal modes your
2559 You can redirect your program's input and/or output using shell
2560 redirection with the @code{run} command. For example,
2567 starts your program, diverting its output to the file @file{outfile}.
2570 @cindex controlling terminal
2571 Another way to specify where your program should do input and output is
2572 with the @code{tty} command. This command accepts a file name as
2573 argument, and causes this file to be the default for future @code{run}
2574 commands. It also resets the controlling terminal for the child
2575 process, for future @code{run} commands. For example,
2582 directs that processes started with subsequent @code{run} commands
2583 default to do input and output on the terminal @file{/dev/ttyb} and have
2584 that as their controlling terminal.
2586 An explicit redirection in @code{run} overrides the @code{tty} command's
2587 effect on the input/output device, but not its effect on the controlling
2590 When you use the @code{tty} command or redirect input in the @code{run}
2591 command, only the input @emph{for your program} is affected. The input
2592 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2593 for @code{set inferior-tty}.
2595 @cindex inferior tty
2596 @cindex set inferior controlling terminal
2597 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2598 display the name of the terminal that will be used for future runs of your
2602 @item set inferior-tty [ @var{tty} ]
2603 @kindex set inferior-tty
2604 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2605 restores the default behavior, which is to use the same terminal as
2608 @item show inferior-tty
2609 @kindex show inferior-tty
2610 Show the current tty for the program being debugged.
2614 @section Debugging an Already-running Process
2619 @item attach @var{process-id}
2620 This command attaches to a running process---one that was started
2621 outside @value{GDBN}. (@code{info files} shows your active
2622 targets.) The command takes as argument a process ID. The usual way to
2623 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2624 or with the @samp{jobs -l} shell command.
2626 @code{attach} does not repeat if you press @key{RET} a second time after
2627 executing the command.
2630 To use @code{attach}, your program must be running in an environment
2631 which supports processes; for example, @code{attach} does not work for
2632 programs on bare-board targets that lack an operating system. You must
2633 also have permission to send the process a signal.
2635 When you use @code{attach}, the debugger finds the program running in
2636 the process first by looking in the current working directory, then (if
2637 the program is not found) by using the source file search path
2638 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2639 the @code{file} command to load the program. @xref{Files, ,Commands to
2642 The first thing @value{GDBN} does after arranging to debug the specified
2643 process is to stop it. You can examine and modify an attached process
2644 with all the @value{GDBN} commands that are ordinarily available when
2645 you start processes with @code{run}. You can insert breakpoints; you
2646 can step and continue; you can modify storage. If you would rather the
2647 process continue running, you may use the @code{continue} command after
2648 attaching @value{GDBN} to the process.
2653 When you have finished debugging the attached process, you can use the
2654 @code{detach} command to release it from @value{GDBN} control. Detaching
2655 the process continues its execution. After the @code{detach} command,
2656 that process and @value{GDBN} become completely independent once more, and you
2657 are ready to @code{attach} another process or start one with @code{run}.
2658 @code{detach} does not repeat if you press @key{RET} again after
2659 executing the command.
2662 If you exit @value{GDBN} while you have an attached process, you detach
2663 that process. If you use the @code{run} command, you kill that process.
2664 By default, @value{GDBN} asks for confirmation if you try to do either of these
2665 things; you can control whether or not you need to confirm by using the
2666 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2670 @section Killing the Child Process
2675 Kill the child process in which your program is running under @value{GDBN}.
2678 This command is useful if you wish to debug a core dump instead of a
2679 running process. @value{GDBN} ignores any core dump file while your program
2682 On some operating systems, a program cannot be executed outside @value{GDBN}
2683 while you have breakpoints set on it inside @value{GDBN}. You can use the
2684 @code{kill} command in this situation to permit running your program
2685 outside the debugger.
2687 The @code{kill} command is also useful if you wish to recompile and
2688 relink your program, since on many systems it is impossible to modify an
2689 executable file while it is running in a process. In this case, when you
2690 next type @code{run}, @value{GDBN} notices that the file has changed, and
2691 reads the symbol table again (while trying to preserve your current
2692 breakpoint settings).
2694 @node Inferiors and Programs
2695 @section Debugging Multiple Inferiors and Programs
2697 @value{GDBN} lets you run and debug multiple programs in a single
2698 session. In addition, @value{GDBN} on some systems may let you run
2699 several programs simultaneously (otherwise you have to exit from one
2700 before starting another). In the most general case, you can have
2701 multiple threads of execution in each of multiple processes, launched
2702 from multiple executables.
2705 @value{GDBN} represents the state of each program execution with an
2706 object called an @dfn{inferior}. An inferior typically corresponds to
2707 a process, but is more general and applies also to targets that do not
2708 have processes. Inferiors may be created before a process runs, and
2709 may be retained after a process exits. Inferiors have unique
2710 identifiers that are different from process ids. Usually each
2711 inferior will also have its own distinct address space, although some
2712 embedded targets may have several inferiors running in different parts
2713 of a single address space. Each inferior may in turn have multiple
2714 threads running in it.
2716 To find out what inferiors exist at any moment, use @w{@code{info
2720 @kindex info inferiors [ @var{id}@dots{} ]
2721 @item info inferiors
2722 Print a list of all inferiors currently being managed by @value{GDBN}.
2723 By default all inferiors are printed, but the argument @var{id}@dots{}
2724 -- a space separated list of inferior numbers -- can be used to limit
2725 the display to just the requested inferiors.
2727 @value{GDBN} displays for each inferior (in this order):
2731 the inferior number assigned by @value{GDBN}
2734 the target system's inferior identifier
2737 the name of the executable the inferior is running.
2742 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2743 indicates the current inferior.
2747 @c end table here to get a little more width for example
2750 (@value{GDBP}) info inferiors
2751 Num Description Executable
2752 2 process 2307 hello
2753 * 1 process 3401 goodbye
2756 To switch focus between inferiors, use the @code{inferior} command:
2759 @kindex inferior @var{infno}
2760 @item inferior @var{infno}
2761 Make inferior number @var{infno} the current inferior. The argument
2762 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2763 in the first field of the @samp{info inferiors} display.
2766 @vindex $_inferior@r{, convenience variable}
2767 The debugger convenience variable @samp{$_inferior} contains the
2768 number of the current inferior. You may find this useful in writing
2769 breakpoint conditional expressions, command scripts, and so forth.
2770 @xref{Convenience Vars,, Convenience Variables}, for general
2771 information on convenience variables.
2773 You can get multiple executables into a debugging session via the
2774 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2775 systems @value{GDBN} can add inferiors to the debug session
2776 automatically by following calls to @code{fork} and @code{exec}. To
2777 remove inferiors from the debugging session use the
2778 @w{@code{remove-inferiors}} command.
2781 @kindex add-inferior
2782 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2783 Adds @var{n} inferiors to be run using @var{executable} as the
2784 executable; @var{n} defaults to 1. If no executable is specified,
2785 the inferiors begins empty, with no program. You can still assign or
2786 change the program assigned to the inferior at any time by using the
2787 @code{file} command with the executable name as its argument.
2789 @kindex clone-inferior
2790 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2791 Adds @var{n} inferiors ready to execute the same program as inferior
2792 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2793 number of the current inferior. This is a convenient command when you
2794 want to run another instance of the inferior you are debugging.
2797 (@value{GDBP}) info inferiors
2798 Num Description Executable
2799 * 1 process 29964 helloworld
2800 (@value{GDBP}) clone-inferior
2803 (@value{GDBP}) info inferiors
2804 Num Description Executable
2806 * 1 process 29964 helloworld
2809 You can now simply switch focus to inferior 2 and run it.
2811 @kindex remove-inferiors
2812 @item remove-inferiors @var{infno}@dots{}
2813 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2814 possible to remove an inferior that is running with this command. For
2815 those, use the @code{kill} or @code{detach} command first.
2819 To quit debugging one of the running inferiors that is not the current
2820 inferior, you can either detach from it by using the @w{@code{detach
2821 inferior}} command (allowing it to run independently), or kill it
2822 using the @w{@code{kill inferiors}} command:
2825 @kindex detach inferiors @var{infno}@dots{}
2826 @item detach inferior @var{infno}@dots{}
2827 Detach from the inferior or inferiors identified by @value{GDBN}
2828 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2829 still stays on the list of inferiors shown by @code{info inferiors},
2830 but its Description will show @samp{<null>}.
2832 @kindex kill inferiors @var{infno}@dots{}
2833 @item kill inferiors @var{infno}@dots{}
2834 Kill the inferior or inferiors identified by @value{GDBN} inferior
2835 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2836 stays on the list of inferiors shown by @code{info inferiors}, but its
2837 Description will show @samp{<null>}.
2840 After the successful completion of a command such as @code{detach},
2841 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2842 a normal process exit, the inferior is still valid and listed with
2843 @code{info inferiors}, ready to be restarted.
2846 To be notified when inferiors are started or exit under @value{GDBN}'s
2847 control use @w{@code{set print inferior-events}}:
2850 @kindex set print inferior-events
2851 @cindex print messages on inferior start and exit
2852 @item set print inferior-events
2853 @itemx set print inferior-events on
2854 @itemx set print inferior-events off
2855 The @code{set print inferior-events} command allows you to enable or
2856 disable printing of messages when @value{GDBN} notices that new
2857 inferiors have started or that inferiors have exited or have been
2858 detached. By default, these messages will not be printed.
2860 @kindex show print inferior-events
2861 @item show print inferior-events
2862 Show whether messages will be printed when @value{GDBN} detects that
2863 inferiors have started, exited or have been detached.
2866 Many commands will work the same with multiple programs as with a
2867 single program: e.g., @code{print myglobal} will simply display the
2868 value of @code{myglobal} in the current inferior.
2871 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2872 get more info about the relationship of inferiors, programs, address
2873 spaces in a debug session. You can do that with the @w{@code{maint
2874 info program-spaces}} command.
2877 @kindex maint info program-spaces
2878 @item maint info program-spaces
2879 Print a list of all program spaces currently being managed by
2882 @value{GDBN} displays for each program space (in this order):
2886 the program space number assigned by @value{GDBN}
2889 the name of the executable loaded into the program space, with e.g.,
2890 the @code{file} command.
2895 An asterisk @samp{*} preceding the @value{GDBN} program space number
2896 indicates the current program space.
2898 In addition, below each program space line, @value{GDBN} prints extra
2899 information that isn't suitable to display in tabular form. For
2900 example, the list of inferiors bound to the program space.
2903 (@value{GDBP}) maint info program-spaces
2907 Bound inferiors: ID 1 (process 21561)
2910 Here we can see that no inferior is running the program @code{hello},
2911 while @code{process 21561} is running the program @code{goodbye}. On
2912 some targets, it is possible that multiple inferiors are bound to the
2913 same program space. The most common example is that of debugging both
2914 the parent and child processes of a @code{vfork} call. For example,
2917 (@value{GDBP}) maint info program-spaces
2920 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2923 Here, both inferior 2 and inferior 1 are running in the same program
2924 space as a result of inferior 1 having executed a @code{vfork} call.
2928 @section Debugging Programs with Multiple Threads
2930 @cindex threads of execution
2931 @cindex multiple threads
2932 @cindex switching threads
2933 In some operating systems, such as GNU/Linux and Solaris, a single program
2934 may have more than one @dfn{thread} of execution. The precise semantics
2935 of threads differ from one operating system to another, but in general
2936 the threads of a single program are akin to multiple processes---except
2937 that they share one address space (that is, they can all examine and
2938 modify the same variables). On the other hand, each thread has its own
2939 registers and execution stack, and perhaps private memory.
2941 @value{GDBN} provides these facilities for debugging multi-thread
2945 @item automatic notification of new threads
2946 @item @samp{thread @var{thread-id}}, a command to switch among threads
2947 @item @samp{info threads}, a command to inquire about existing threads
2948 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2949 a command to apply a command to a list of threads
2950 @item thread-specific breakpoints
2951 @item @samp{set print thread-events}, which controls printing of
2952 messages on thread start and exit.
2953 @item @samp{set libthread-db-search-path @var{path}}, which lets
2954 the user specify which @code{libthread_db} to use if the default choice
2955 isn't compatible with the program.
2958 @cindex focus of debugging
2959 @cindex current thread
2960 The @value{GDBN} thread debugging facility allows you to observe all
2961 threads while your program runs---but whenever @value{GDBN} takes
2962 control, one thread in particular is always the focus of debugging.
2963 This thread is called the @dfn{current thread}. Debugging commands show
2964 program information from the perspective of the current thread.
2966 @cindex @code{New} @var{systag} message
2967 @cindex thread identifier (system)
2968 @c FIXME-implementors!! It would be more helpful if the [New...] message
2969 @c included GDB's numeric thread handle, so you could just go to that
2970 @c thread without first checking `info threads'.
2971 Whenever @value{GDBN} detects a new thread in your program, it displays
2972 the target system's identification for the thread with a message in the
2973 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2974 whose form varies depending on the particular system. For example, on
2975 @sc{gnu}/Linux, you might see
2978 [New Thread 0x41e02940 (LWP 25582)]
2982 when @value{GDBN} notices a new thread. In contrast, on other systems,
2983 the @var{systag} is simply something like @samp{process 368}, with no
2986 @c FIXME!! (1) Does the [New...] message appear even for the very first
2987 @c thread of a program, or does it only appear for the
2988 @c second---i.e.@: when it becomes obvious we have a multithread
2990 @c (2) *Is* there necessarily a first thread always? Or do some
2991 @c multithread systems permit starting a program with multiple
2992 @c threads ab initio?
2994 @anchor{thread numbers}
2995 @cindex thread number, per inferior
2996 @cindex thread identifier (GDB)
2997 For debugging purposes, @value{GDBN} associates its own thread number
2998 ---always a single integer---with each thread of an inferior. This
2999 number is unique between all threads of an inferior, but not unique
3000 between threads of different inferiors.
3002 @cindex qualified thread ID
3003 You can refer to a given thread in an inferior using the qualified
3004 @var{inferior-num}.@var{thread-num} syntax, also known as
3005 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3006 number and @var{thread-num} being the thread number of the given
3007 inferior. For example, thread @code{2.3} refers to thread number 3 of
3008 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3009 then @value{GDBN} infers you're referring to a thread of the current
3012 Until you create a second inferior, @value{GDBN} does not show the
3013 @var{inferior-num} part of thread IDs, even though you can always use
3014 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3015 of inferior 1, the initial inferior.
3017 @anchor{thread ID lists}
3018 @cindex thread ID lists
3019 Some commands accept a space-separated @dfn{thread ID list} as
3020 argument. A list element can be:
3024 A thread ID as shown in the first field of the @samp{info threads}
3025 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3029 A range of thread numbers, again with or without an inferior
3030 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3031 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3034 All threads of an inferior, specified with a star wildcard, with or
3035 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3036 @samp{1.*}) or @code{*}. The former refers to all threads of the
3037 given inferior, and the latter form without an inferior qualifier
3038 refers to all threads of the current inferior.
3042 For example, if the current inferior is 1, and inferior 7 has one
3043 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3044 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3045 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3046 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3050 @anchor{global thread numbers}
3051 @cindex global thread number
3052 @cindex global thread identifier (GDB)
3053 In addition to a @emph{per-inferior} number, each thread is also
3054 assigned a unique @emph{global} number, also known as @dfn{global
3055 thread ID}, a single integer. Unlike the thread number component of
3056 the thread ID, no two threads have the same global ID, even when
3057 you're debugging multiple inferiors.
3059 From @value{GDBN}'s perspective, a process always has at least one
3060 thread. In other words, @value{GDBN} assigns a thread number to the
3061 program's ``main thread'' even if the program is not multi-threaded.
3063 @vindex $_thread@r{, convenience variable}
3064 @vindex $_gthread@r{, convenience variable}
3065 The debugger convenience variables @samp{$_thread} and
3066 @samp{$_gthread} contain, respectively, the per-inferior thread number
3067 and the global thread number of the current thread. You may find this
3068 useful in writing breakpoint conditional expressions, command scripts,
3069 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3070 general information on convenience variables.
3072 If @value{GDBN} detects the program is multi-threaded, it augments the
3073 usual message about stopping at a breakpoint with the ID and name of
3074 the thread that hit the breakpoint.
3077 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3080 Likewise when the program receives a signal:
3083 Thread 1 "main" received signal SIGINT, Interrupt.
3087 @kindex info threads
3088 @item info threads @r{[}@var{thread-id-list}@r{]}
3090 Display information about one or more threads. With no arguments
3091 displays information about all threads. You can specify the list of
3092 threads that you want to display using the thread ID list syntax
3093 (@pxref{thread ID lists}).
3095 @value{GDBN} displays for each thread (in this order):
3099 the per-inferior thread number assigned by @value{GDBN}
3102 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3103 option was specified
3106 the target system's thread identifier (@var{systag})
3109 the thread's name, if one is known. A thread can either be named by
3110 the user (see @code{thread name}, below), or, in some cases, by the
3114 the current stack frame summary for that thread
3118 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3119 indicates the current thread.
3123 @c end table here to get a little more width for example
3126 (@value{GDBP}) info threads
3128 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3129 2 process 35 thread 23 0x34e5 in sigpause ()
3130 3 process 35 thread 27 0x34e5 in sigpause ()
3134 If you're debugging multiple inferiors, @value{GDBN} displays thread
3135 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3136 Otherwise, only @var{thread-num} is shown.
3138 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3139 indicating each thread's global thread ID:
3142 (@value{GDBP}) info threads
3143 Id GId Target Id Frame
3144 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3145 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3146 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3147 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3150 On Solaris, you can display more information about user threads with a
3151 Solaris-specific command:
3154 @item maint info sol-threads
3155 @kindex maint info sol-threads
3156 @cindex thread info (Solaris)
3157 Display info on Solaris user threads.
3161 @kindex thread @var{thread-id}
3162 @item thread @var{thread-id}
3163 Make thread ID @var{thread-id} the current thread. The command
3164 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3165 the first field of the @samp{info threads} display, with or without an
3166 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3168 @value{GDBN} responds by displaying the system identifier of the
3169 thread you selected, and its current stack frame summary:
3172 (@value{GDBP}) thread 2
3173 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3174 #0 some_function (ignore=0x0) at example.c:8
3175 8 printf ("hello\n");
3179 As with the @samp{[New @dots{}]} message, the form of the text after
3180 @samp{Switching to} depends on your system's conventions for identifying
3183 @kindex thread apply
3184 @cindex apply command to several threads
3185 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3186 The @code{thread apply} command allows you to apply the named
3187 @var{command} to one or more threads. Specify the threads that you
3188 want affected using the thread ID list syntax (@pxref{thread ID
3189 lists}), or specify @code{all} to apply to all threads. To apply a
3190 command to all threads in descending order, type @kbd{thread apply all
3191 @var{command}}. To apply a command to all threads in ascending order,
3192 type @kbd{thread apply all -ascending @var{command}}.
3194 The @var{flag} arguments control what output to produce and how to handle
3195 errors raised when applying @var{command} to a thread. @var{flag}
3196 must start with a @code{-} directly followed by one letter in
3197 @code{qcs}. If several flags are provided, they must be given
3198 individually, such as @code{-c -q}.
3200 By default, @value{GDBN} displays some thread information before the
3201 output produced by @var{command}, and an error raised during the
3202 execution of a @var{command} will abort @code{thread apply}. The
3203 following flags can be used to fine-tune this behavior:
3207 The flag @code{-c}, which stands for @samp{continue}, causes any
3208 errors in @var{command} to be displayed, and the execution of
3209 @code{thread apply} then continues.
3211 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3212 or empty output produced by a @var{command} to be silently ignored.
3213 That is, the execution continues, but the thread information and errors
3216 The flag @code{-q} (@samp{quiet}) disables printing the thread
3220 Flags @code{-c} and @code{-s} cannot be used together.
3223 @cindex apply command to all threads (ignoring errors and empty output)
3224 @item taas @var{command}
3225 Shortcut for @code{thread apply all -s @var{command}}.
3226 Applies @var{command} on all threads, ignoring errors and empty output.
3229 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3230 @item tfaas @var{command}
3231 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3232 Applies @var{command} on all frames of all threads, ignoring errors
3233 and empty output. Note that the flag @code{-s} is specified twice:
3234 The first @code{-s} ensures that @code{thread apply} only shows the thread
3235 information of the threads for which @code{frame apply} produces
3236 some output. The second @code{-s} is needed to ensure that @code{frame
3237 apply} shows the frame information of a frame only if the
3238 @var{command} successfully produced some output.
3240 It can for example be used to print a local variable or a function
3241 argument without knowing the thread or frame where this variable or argument
3244 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3249 @cindex name a thread
3250 @item thread name [@var{name}]
3251 This command assigns a name to the current thread. If no argument is
3252 given, any existing user-specified name is removed. The thread name
3253 appears in the @samp{info threads} display.
3255 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3256 determine the name of the thread as given by the OS. On these
3257 systems, a name specified with @samp{thread name} will override the
3258 system-give name, and removing the user-specified name will cause
3259 @value{GDBN} to once again display the system-specified name.
3262 @cindex search for a thread
3263 @item thread find [@var{regexp}]
3264 Search for and display thread ids whose name or @var{systag}
3265 matches the supplied regular expression.
3267 As well as being the complement to the @samp{thread name} command,
3268 this command also allows you to identify a thread by its target
3269 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3273 (@value{GDBN}) thread find 26688
3274 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3275 (@value{GDBN}) info thread 4
3277 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3280 @kindex set print thread-events
3281 @cindex print messages on thread start and exit
3282 @item set print thread-events
3283 @itemx set print thread-events on
3284 @itemx set print thread-events off
3285 The @code{set print thread-events} command allows you to enable or
3286 disable printing of messages when @value{GDBN} notices that new threads have
3287 started or that threads have exited. By default, these messages will
3288 be printed if detection of these events is supported by the target.
3289 Note that these messages cannot be disabled on all targets.
3291 @kindex show print thread-events
3292 @item show print thread-events
3293 Show whether messages will be printed when @value{GDBN} detects that threads
3294 have started and exited.
3297 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3298 more information about how @value{GDBN} behaves when you stop and start
3299 programs with multiple threads.
3301 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3302 watchpoints in programs with multiple threads.
3304 @anchor{set libthread-db-search-path}
3306 @kindex set libthread-db-search-path
3307 @cindex search path for @code{libthread_db}
3308 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3309 If this variable is set, @var{path} is a colon-separated list of
3310 directories @value{GDBN} will use to search for @code{libthread_db}.
3311 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3312 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3313 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3316 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3317 @code{libthread_db} library to obtain information about threads in the
3318 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3319 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3320 specific thread debugging library loading is enabled
3321 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3323 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3324 refers to the default system directories that are
3325 normally searched for loading shared libraries. The @samp{$sdir} entry
3326 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3327 (@pxref{libthread_db.so.1 file}).
3329 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3330 refers to the directory from which @code{libpthread}
3331 was loaded in the inferior process.
3333 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3334 @value{GDBN} attempts to initialize it with the current inferior process.
3335 If this initialization fails (which could happen because of a version
3336 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3337 will unload @code{libthread_db}, and continue with the next directory.
3338 If none of @code{libthread_db} libraries initialize successfully,
3339 @value{GDBN} will issue a warning and thread debugging will be disabled.
3341 Setting @code{libthread-db-search-path} is currently implemented
3342 only on some platforms.
3344 @kindex show libthread-db-search-path
3345 @item show libthread-db-search-path
3346 Display current libthread_db search path.
3348 @kindex set debug libthread-db
3349 @kindex show debug libthread-db
3350 @cindex debugging @code{libthread_db}
3351 @item set debug libthread-db
3352 @itemx show debug libthread-db
3353 Turns on or off display of @code{libthread_db}-related events.
3354 Use @code{1} to enable, @code{0} to disable.
3358 @section Debugging Forks
3360 @cindex fork, debugging programs which call
3361 @cindex multiple processes
3362 @cindex processes, multiple
3363 On most systems, @value{GDBN} has no special support for debugging
3364 programs which create additional processes using the @code{fork}
3365 function. When a program forks, @value{GDBN} will continue to debug the
3366 parent process and the child process will run unimpeded. If you have
3367 set a breakpoint in any code which the child then executes, the child
3368 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3369 will cause it to terminate.
3371 However, if you want to debug the child process there is a workaround
3372 which isn't too painful. Put a call to @code{sleep} in the code which
3373 the child process executes after the fork. It may be useful to sleep
3374 only if a certain environment variable is set, or a certain file exists,
3375 so that the delay need not occur when you don't want to run @value{GDBN}
3376 on the child. While the child is sleeping, use the @code{ps} program to
3377 get its process ID. Then tell @value{GDBN} (a new invocation of
3378 @value{GDBN} if you are also debugging the parent process) to attach to
3379 the child process (@pxref{Attach}). From that point on you can debug
3380 the child process just like any other process which you attached to.
3382 On some systems, @value{GDBN} provides support for debugging programs
3383 that create additional processes using the @code{fork} or @code{vfork}
3384 functions. On @sc{gnu}/Linux platforms, this feature is supported
3385 with kernel version 2.5.46 and later.
3387 The fork debugging commands are supported in native mode and when
3388 connected to @code{gdbserver} in either @code{target remote} mode or
3389 @code{target extended-remote} mode.
3391 By default, when a program forks, @value{GDBN} will continue to debug
3392 the parent process and the child process will run unimpeded.
3394 If you want to follow the child process instead of the parent process,
3395 use the command @w{@code{set follow-fork-mode}}.
3398 @kindex set follow-fork-mode
3399 @item set follow-fork-mode @var{mode}
3400 Set the debugger response to a program call of @code{fork} or
3401 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3402 process. The @var{mode} argument can be:
3406 The original process is debugged after a fork. The child process runs
3407 unimpeded. This is the default.
3410 The new process is debugged after a fork. The parent process runs
3415 @kindex show follow-fork-mode
3416 @item show follow-fork-mode
3417 Display the current debugger response to a @code{fork} or @code{vfork} call.
3420 @cindex debugging multiple processes
3421 On Linux, if you want to debug both the parent and child processes, use the
3422 command @w{@code{set detach-on-fork}}.
3425 @kindex set detach-on-fork
3426 @item set detach-on-fork @var{mode}
3427 Tells gdb whether to detach one of the processes after a fork, or
3428 retain debugger control over them both.
3432 The child process (or parent process, depending on the value of
3433 @code{follow-fork-mode}) will be detached and allowed to run
3434 independently. This is the default.
3437 Both processes will be held under the control of @value{GDBN}.
3438 One process (child or parent, depending on the value of
3439 @code{follow-fork-mode}) is debugged as usual, while the other
3444 @kindex show detach-on-fork
3445 @item show detach-on-fork
3446 Show whether detach-on-fork mode is on/off.
3449 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3450 will retain control of all forked processes (including nested forks).
3451 You can list the forked processes under the control of @value{GDBN} by
3452 using the @w{@code{info inferiors}} command, and switch from one fork
3453 to another by using the @code{inferior} command (@pxref{Inferiors and
3454 Programs, ,Debugging Multiple Inferiors and Programs}).
3456 To quit debugging one of the forked processes, you can either detach
3457 from it by using the @w{@code{detach inferiors}} command (allowing it
3458 to run independently), or kill it using the @w{@code{kill inferiors}}
3459 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3462 If you ask to debug a child process and a @code{vfork} is followed by an
3463 @code{exec}, @value{GDBN} executes the new target up to the first
3464 breakpoint in the new target. If you have a breakpoint set on
3465 @code{main} in your original program, the breakpoint will also be set on
3466 the child process's @code{main}.
3468 On some systems, when a child process is spawned by @code{vfork}, you
3469 cannot debug the child or parent until an @code{exec} call completes.
3471 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3472 call executes, the new target restarts. To restart the parent
3473 process, use the @code{file} command with the parent executable name
3474 as its argument. By default, after an @code{exec} call executes,
3475 @value{GDBN} discards the symbols of the previous executable image.
3476 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3480 @kindex set follow-exec-mode
3481 @item set follow-exec-mode @var{mode}
3483 Set debugger response to a program call of @code{exec}. An
3484 @code{exec} call replaces the program image of a process.
3486 @code{follow-exec-mode} can be:
3490 @value{GDBN} creates a new inferior and rebinds the process to this
3491 new inferior. The program the process was running before the
3492 @code{exec} call can be restarted afterwards by restarting the
3498 (@value{GDBP}) info inferiors
3500 Id Description Executable
3503 process 12020 is executing new program: prog2
3504 Program exited normally.
3505 (@value{GDBP}) info inferiors
3506 Id Description Executable
3512 @value{GDBN} keeps the process bound to the same inferior. The new
3513 executable image replaces the previous executable loaded in the
3514 inferior. Restarting the inferior after the @code{exec} call, with
3515 e.g., the @code{run} command, restarts the executable the process was
3516 running after the @code{exec} call. This is the default mode.
3521 (@value{GDBP}) info inferiors
3522 Id Description Executable
3525 process 12020 is executing new program: prog2
3526 Program exited normally.
3527 (@value{GDBP}) info inferiors
3528 Id Description Executable
3535 @code{follow-exec-mode} is supported in native mode and
3536 @code{target extended-remote} mode.
3538 You can use the @code{catch} command to make @value{GDBN} stop whenever
3539 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3540 Catchpoints, ,Setting Catchpoints}.
3542 @node Checkpoint/Restart
3543 @section Setting a @emph{Bookmark} to Return to Later
3548 @cindex snapshot of a process
3549 @cindex rewind program state
3551 On certain operating systems@footnote{Currently, only
3552 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3553 program's state, called a @dfn{checkpoint}, and come back to it
3556 Returning to a checkpoint effectively undoes everything that has
3557 happened in the program since the @code{checkpoint} was saved. This
3558 includes changes in memory, registers, and even (within some limits)
3559 system state. Effectively, it is like going back in time to the
3560 moment when the checkpoint was saved.
3562 Thus, if you're stepping thru a program and you think you're
3563 getting close to the point where things go wrong, you can save
3564 a checkpoint. Then, if you accidentally go too far and miss
3565 the critical statement, instead of having to restart your program
3566 from the beginning, you can just go back to the checkpoint and
3567 start again from there.
3569 This can be especially useful if it takes a lot of time or
3570 steps to reach the point where you think the bug occurs.
3572 To use the @code{checkpoint}/@code{restart} method of debugging:
3577 Save a snapshot of the debugged program's current execution state.
3578 The @code{checkpoint} command takes no arguments, but each checkpoint
3579 is assigned a small integer id, similar to a breakpoint id.
3581 @kindex info checkpoints
3582 @item info checkpoints
3583 List the checkpoints that have been saved in the current debugging
3584 session. For each checkpoint, the following information will be
3591 @item Source line, or label
3594 @kindex restart @var{checkpoint-id}
3595 @item restart @var{checkpoint-id}
3596 Restore the program state that was saved as checkpoint number
3597 @var{checkpoint-id}. All program variables, registers, stack frames
3598 etc.@: will be returned to the values that they had when the checkpoint
3599 was saved. In essence, gdb will ``wind back the clock'' to the point
3600 in time when the checkpoint was saved.
3602 Note that breakpoints, @value{GDBN} variables, command history etc.
3603 are not affected by restoring a checkpoint. In general, a checkpoint
3604 only restores things that reside in the program being debugged, not in
3607 @kindex delete checkpoint @var{checkpoint-id}
3608 @item delete checkpoint @var{checkpoint-id}
3609 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3613 Returning to a previously saved checkpoint will restore the user state
3614 of the program being debugged, plus a significant subset of the system
3615 (OS) state, including file pointers. It won't ``un-write'' data from
3616 a file, but it will rewind the file pointer to the previous location,
3617 so that the previously written data can be overwritten. For files
3618 opened in read mode, the pointer will also be restored so that the
3619 previously read data can be read again.
3621 Of course, characters that have been sent to a printer (or other
3622 external device) cannot be ``snatched back'', and characters received
3623 from eg.@: a serial device can be removed from internal program buffers,
3624 but they cannot be ``pushed back'' into the serial pipeline, ready to
3625 be received again. Similarly, the actual contents of files that have
3626 been changed cannot be restored (at this time).
3628 However, within those constraints, you actually can ``rewind'' your
3629 program to a previously saved point in time, and begin debugging it
3630 again --- and you can change the course of events so as to debug a
3631 different execution path this time.
3633 @cindex checkpoints and process id
3634 Finally, there is one bit of internal program state that will be
3635 different when you return to a checkpoint --- the program's process
3636 id. Each checkpoint will have a unique process id (or @var{pid}),
3637 and each will be different from the program's original @var{pid}.
3638 If your program has saved a local copy of its process id, this could
3639 potentially pose a problem.
3641 @subsection A Non-obvious Benefit of Using Checkpoints
3643 On some systems such as @sc{gnu}/Linux, address space randomization
3644 is performed on new processes for security reasons. This makes it
3645 difficult or impossible to set a breakpoint, or watchpoint, on an
3646 absolute address if you have to restart the program, since the
3647 absolute location of a symbol will change from one execution to the
3650 A checkpoint, however, is an @emph{identical} copy of a process.
3651 Therefore if you create a checkpoint at (eg.@:) the start of main,
3652 and simply return to that checkpoint instead of restarting the
3653 process, you can avoid the effects of address randomization and
3654 your symbols will all stay in the same place.
3657 @chapter Stopping and Continuing
3659 The principal purposes of using a debugger are so that you can stop your
3660 program before it terminates; or so that, if your program runs into
3661 trouble, you can investigate and find out why.
3663 Inside @value{GDBN}, your program may stop for any of several reasons,
3664 such as a signal, a breakpoint, or reaching a new line after a
3665 @value{GDBN} command such as @code{step}. You may then examine and
3666 change variables, set new breakpoints or remove old ones, and then
3667 continue execution. Usually, the messages shown by @value{GDBN} provide
3668 ample explanation of the status of your program---but you can also
3669 explicitly request this information at any time.
3672 @kindex info program
3674 Display information about the status of your program: whether it is
3675 running or not, what process it is, and why it stopped.
3679 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3680 * Continuing and Stepping:: Resuming execution
3681 * Skipping Over Functions and Files::
3682 Skipping over functions and files
3684 * Thread Stops:: Stopping and starting multi-thread programs
3688 @section Breakpoints, Watchpoints, and Catchpoints
3691 A @dfn{breakpoint} makes your program stop whenever a certain point in
3692 the program is reached. For each breakpoint, you can add conditions to
3693 control in finer detail whether your program stops. You can set
3694 breakpoints with the @code{break} command and its variants (@pxref{Set
3695 Breaks, ,Setting Breakpoints}), to specify the place where your program
3696 should stop by line number, function name or exact address in the
3699 On some systems, you can set breakpoints in shared libraries before
3700 the executable is run.
3703 @cindex data breakpoints
3704 @cindex memory tracing
3705 @cindex breakpoint on memory address
3706 @cindex breakpoint on variable modification
3707 A @dfn{watchpoint} is a special breakpoint that stops your program
3708 when the value of an expression changes. The expression may be a value
3709 of a variable, or it could involve values of one or more variables
3710 combined by operators, such as @samp{a + b}. This is sometimes called
3711 @dfn{data breakpoints}. You must use a different command to set
3712 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3713 from that, you can manage a watchpoint like any other breakpoint: you
3714 enable, disable, and delete both breakpoints and watchpoints using the
3717 You can arrange to have values from your program displayed automatically
3718 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3722 @cindex breakpoint on events
3723 A @dfn{catchpoint} is another special breakpoint that stops your program
3724 when a certain kind of event occurs, such as the throwing of a C@t{++}
3725 exception or the loading of a library. As with watchpoints, you use a
3726 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3727 Catchpoints}), but aside from that, you can manage a catchpoint like any
3728 other breakpoint. (To stop when your program receives a signal, use the
3729 @code{handle} command; see @ref{Signals, ,Signals}.)
3731 @cindex breakpoint numbers
3732 @cindex numbers for breakpoints
3733 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3734 catchpoint when you create it; these numbers are successive integers
3735 starting with one. In many of the commands for controlling various
3736 features of breakpoints you use the breakpoint number to say which
3737 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3738 @dfn{disabled}; if disabled, it has no effect on your program until you
3741 @cindex breakpoint ranges
3742 @cindex breakpoint lists
3743 @cindex ranges of breakpoints
3744 @cindex lists of breakpoints
3745 Some @value{GDBN} commands accept a space-separated list of breakpoints
3746 on which to operate. A list element can be either a single breakpoint number,
3747 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3748 When a breakpoint list is given to a command, all breakpoints in that list
3752 * Set Breaks:: Setting breakpoints
3753 * Set Watchpoints:: Setting watchpoints
3754 * Set Catchpoints:: Setting catchpoints
3755 * Delete Breaks:: Deleting breakpoints
3756 * Disabling:: Disabling breakpoints
3757 * Conditions:: Break conditions
3758 * Break Commands:: Breakpoint command lists
3759 * Dynamic Printf:: Dynamic printf
3760 * Save Breakpoints:: How to save breakpoints in a file
3761 * Static Probe Points:: Listing static probe points
3762 * Error in Breakpoints:: ``Cannot insert breakpoints''
3763 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3767 @subsection Setting Breakpoints
3769 @c FIXME LMB what does GDB do if no code on line of breakpt?
3770 @c consider in particular declaration with/without initialization.
3772 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3775 @kindex b @r{(@code{break})}
3776 @vindex $bpnum@r{, convenience variable}
3777 @cindex latest breakpoint
3778 Breakpoints are set with the @code{break} command (abbreviated
3779 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3780 number of the breakpoint you've set most recently; see @ref{Convenience
3781 Vars,, Convenience Variables}, for a discussion of what you can do with
3782 convenience variables.
3785 @item break @var{location}
3786 Set a breakpoint at the given @var{location}, which can specify a
3787 function name, a line number, or an address of an instruction.
3788 (@xref{Specify Location}, for a list of all the possible ways to
3789 specify a @var{location}.) The breakpoint will stop your program just
3790 before it executes any of the code in the specified @var{location}.
3792 When using source languages that permit overloading of symbols, such as
3793 C@t{++}, a function name may refer to more than one possible place to break.
3794 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3797 It is also possible to insert a breakpoint that will stop the program
3798 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3799 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3802 When called without any arguments, @code{break} sets a breakpoint at
3803 the next instruction to be executed in the selected stack frame
3804 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3805 innermost, this makes your program stop as soon as control
3806 returns to that frame. This is similar to the effect of a
3807 @code{finish} command in the frame inside the selected frame---except
3808 that @code{finish} does not leave an active breakpoint. If you use
3809 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3810 the next time it reaches the current location; this may be useful
3813 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3814 least one instruction has been executed. If it did not do this, you
3815 would be unable to proceed past a breakpoint without first disabling the
3816 breakpoint. This rule applies whether or not the breakpoint already
3817 existed when your program stopped.
3819 @item break @dots{} if @var{cond}
3820 Set a breakpoint with condition @var{cond}; evaluate the expression
3821 @var{cond} each time the breakpoint is reached, and stop only if the
3822 value is nonzero---that is, if @var{cond} evaluates as true.
3823 @samp{@dots{}} stands for one of the possible arguments described
3824 above (or no argument) specifying where to break. @xref{Conditions,
3825 ,Break Conditions}, for more information on breakpoint conditions.
3828 @item tbreak @var{args}
3829 Set a breakpoint enabled only for one stop. The @var{args} are the
3830 same as for the @code{break} command, and the breakpoint is set in the same
3831 way, but the breakpoint is automatically deleted after the first time your
3832 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3835 @cindex hardware breakpoints
3836 @item hbreak @var{args}
3837 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3838 @code{break} command and the breakpoint is set in the same way, but the
3839 breakpoint requires hardware support and some target hardware may not
3840 have this support. The main purpose of this is EPROM/ROM code
3841 debugging, so you can set a breakpoint at an instruction without
3842 changing the instruction. This can be used with the new trap-generation
3843 provided by SPARClite DSU and most x86-based targets. These targets
3844 will generate traps when a program accesses some data or instruction
3845 address that is assigned to the debug registers. However the hardware
3846 breakpoint registers can take a limited number of breakpoints. For
3847 example, on the DSU, only two data breakpoints can be set at a time, and
3848 @value{GDBN} will reject this command if more than two are used. Delete
3849 or disable unused hardware breakpoints before setting new ones
3850 (@pxref{Disabling, ,Disabling Breakpoints}).
3851 @xref{Conditions, ,Break Conditions}.
3852 For remote targets, you can restrict the number of hardware
3853 breakpoints @value{GDBN} will use, see @ref{set remote
3854 hardware-breakpoint-limit}.
3857 @item thbreak @var{args}
3858 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3859 are the same as for the @code{hbreak} command and the breakpoint is set in
3860 the same way. However, like the @code{tbreak} command,
3861 the breakpoint is automatically deleted after the
3862 first time your program stops there. Also, like the @code{hbreak}
3863 command, the breakpoint requires hardware support and some target hardware
3864 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3865 See also @ref{Conditions, ,Break Conditions}.
3868 @cindex regular expression
3869 @cindex breakpoints at functions matching a regexp
3870 @cindex set breakpoints in many functions
3871 @item rbreak @var{regex}
3872 Set breakpoints on all functions matching the regular expression
3873 @var{regex}. This command sets an unconditional breakpoint on all
3874 matches, printing a list of all breakpoints it set. Once these
3875 breakpoints are set, they are treated just like the breakpoints set with
3876 the @code{break} command. You can delete them, disable them, or make
3877 them conditional the same way as any other breakpoint.
3879 In programs using different languages, @value{GDBN} chooses the syntax
3880 to print the list of all breakpoints it sets according to the
3881 @samp{set language} value: using @samp{set language auto}
3882 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3883 language of the breakpoint's function, other values mean to use
3884 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3886 The syntax of the regular expression is the standard one used with tools
3887 like @file{grep}. Note that this is different from the syntax used by
3888 shells, so for instance @code{foo*} matches all functions that include
3889 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3890 @code{.*} leading and trailing the regular expression you supply, so to
3891 match only functions that begin with @code{foo}, use @code{^foo}.
3893 @cindex non-member C@t{++} functions, set breakpoint in
3894 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3895 breakpoints on overloaded functions that are not members of any special
3898 @cindex set breakpoints on all functions
3899 The @code{rbreak} command can be used to set breakpoints in
3900 @strong{all} the functions in a program, like this:
3903 (@value{GDBP}) rbreak .
3906 @item rbreak @var{file}:@var{regex}
3907 If @code{rbreak} is called with a filename qualification, it limits
3908 the search for functions matching the given regular expression to the
3909 specified @var{file}. This can be used, for example, to set breakpoints on
3910 every function in a given file:
3913 (@value{GDBP}) rbreak file.c:.
3916 The colon separating the filename qualifier from the regex may
3917 optionally be surrounded by spaces.
3919 @kindex info breakpoints
3920 @cindex @code{$_} and @code{info breakpoints}
3921 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3922 @itemx info break @r{[}@var{list}@dots{}@r{]}
3923 Print a table of all breakpoints, watchpoints, and catchpoints set and
3924 not deleted. Optional argument @var{n} means print information only
3925 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3926 For each breakpoint, following columns are printed:
3929 @item Breakpoint Numbers
3931 Breakpoint, watchpoint, or catchpoint.
3933 Whether the breakpoint is marked to be disabled or deleted when hit.
3934 @item Enabled or Disabled
3935 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3936 that are not enabled.
3938 Where the breakpoint is in your program, as a memory address. For a
3939 pending breakpoint whose address is not yet known, this field will
3940 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3941 library that has the symbol or line referred by breakpoint is loaded.
3942 See below for details. A breakpoint with several locations will
3943 have @samp{<MULTIPLE>} in this field---see below for details.
3945 Where the breakpoint is in the source for your program, as a file and
3946 line number. For a pending breakpoint, the original string passed to
3947 the breakpoint command will be listed as it cannot be resolved until
3948 the appropriate shared library is loaded in the future.
3952 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3953 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3954 @value{GDBN} on the host's side. If it is ``target'', then the condition
3955 is evaluated by the target. The @code{info break} command shows
3956 the condition on the line following the affected breakpoint, together with
3957 its condition evaluation mode in between parentheses.
3959 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3960 allowed to have a condition specified for it. The condition is not parsed for
3961 validity until a shared library is loaded that allows the pending
3962 breakpoint to resolve to a valid location.
3965 @code{info break} with a breakpoint
3966 number @var{n} as argument lists only that breakpoint. The
3967 convenience variable @code{$_} and the default examining-address for
3968 the @code{x} command are set to the address of the last breakpoint
3969 listed (@pxref{Memory, ,Examining Memory}).
3972 @code{info break} displays a count of the number of times the breakpoint
3973 has been hit. This is especially useful in conjunction with the
3974 @code{ignore} command. You can ignore a large number of breakpoint
3975 hits, look at the breakpoint info to see how many times the breakpoint
3976 was hit, and then run again, ignoring one less than that number. This
3977 will get you quickly to the last hit of that breakpoint.
3980 For a breakpoints with an enable count (xref) greater than 1,
3981 @code{info break} also displays that count.
3985 @value{GDBN} allows you to set any number of breakpoints at the same place in
3986 your program. There is nothing silly or meaningless about this. When
3987 the breakpoints are conditional, this is even useful
3988 (@pxref{Conditions, ,Break Conditions}).
3990 @cindex multiple locations, breakpoints
3991 @cindex breakpoints, multiple locations
3992 It is possible that a breakpoint corresponds to several locations
3993 in your program. Examples of this situation are:
3997 Multiple functions in the program may have the same name.
4000 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4001 instances of the function body, used in different cases.
4004 For a C@t{++} template function, a given line in the function can
4005 correspond to any number of instantiations.
4008 For an inlined function, a given source line can correspond to
4009 several places where that function is inlined.
4012 In all those cases, @value{GDBN} will insert a breakpoint at all
4013 the relevant locations.
4015 A breakpoint with multiple locations is displayed in the breakpoint
4016 table using several rows---one header row, followed by one row for
4017 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4018 address column. The rows for individual locations contain the actual
4019 addresses for locations, and show the functions to which those
4020 locations belong. The number column for a location is of the form
4021 @var{breakpoint-number}.@var{location-number}.
4026 Num Type Disp Enb Address What
4027 1 breakpoint keep y <MULTIPLE>
4029 breakpoint already hit 1 time
4030 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4031 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4034 You cannot delete the individual locations from a breakpoint. However,
4035 each location can be individually enabled or disabled by passing
4036 @var{breakpoint-number}.@var{location-number} as argument to the
4037 @code{enable} and @code{disable} commands. It's also possible to
4038 @code{enable} and @code{disable} a range of @var{location-number}
4039 locations using a @var{breakpoint-number} and two @var{location-number}s,
4040 in increasing order, separated by a hyphen, like
4041 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4042 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4043 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4044 all of the locations that belong to that breakpoint.
4046 @cindex pending breakpoints
4047 It's quite common to have a breakpoint inside a shared library.
4048 Shared libraries can be loaded and unloaded explicitly,
4049 and possibly repeatedly, as the program is executed. To support
4050 this use case, @value{GDBN} updates breakpoint locations whenever
4051 any shared library is loaded or unloaded. Typically, you would
4052 set a breakpoint in a shared library at the beginning of your
4053 debugging session, when the library is not loaded, and when the
4054 symbols from the library are not available. When you try to set
4055 breakpoint, @value{GDBN} will ask you if you want to set
4056 a so called @dfn{pending breakpoint}---breakpoint whose address
4057 is not yet resolved.
4059 After the program is run, whenever a new shared library is loaded,
4060 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4061 shared library contains the symbol or line referred to by some
4062 pending breakpoint, that breakpoint is resolved and becomes an
4063 ordinary breakpoint. When a library is unloaded, all breakpoints
4064 that refer to its symbols or source lines become pending again.
4066 This logic works for breakpoints with multiple locations, too. For
4067 example, if you have a breakpoint in a C@t{++} template function, and
4068 a newly loaded shared library has an instantiation of that template,
4069 a new location is added to the list of locations for the breakpoint.
4071 Except for having unresolved address, pending breakpoints do not
4072 differ from regular breakpoints. You can set conditions or commands,
4073 enable and disable them and perform other breakpoint operations.
4075 @value{GDBN} provides some additional commands for controlling what
4076 happens when the @samp{break} command cannot resolve breakpoint
4077 address specification to an address:
4079 @kindex set breakpoint pending
4080 @kindex show breakpoint pending
4082 @item set breakpoint pending auto
4083 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4084 location, it queries you whether a pending breakpoint should be created.
4086 @item set breakpoint pending on
4087 This indicates that an unrecognized breakpoint location should automatically
4088 result in a pending breakpoint being created.
4090 @item set breakpoint pending off
4091 This indicates that pending breakpoints are not to be created. Any
4092 unrecognized breakpoint location results in an error. This setting does
4093 not affect any pending breakpoints previously created.
4095 @item show breakpoint pending
4096 Show the current behavior setting for creating pending breakpoints.
4099 The settings above only affect the @code{break} command and its
4100 variants. Once breakpoint is set, it will be automatically updated
4101 as shared libraries are loaded and unloaded.
4103 @cindex automatic hardware breakpoints
4104 For some targets, @value{GDBN} can automatically decide if hardware or
4105 software breakpoints should be used, depending on whether the
4106 breakpoint address is read-only or read-write. This applies to
4107 breakpoints set with the @code{break} command as well as to internal
4108 breakpoints set by commands like @code{next} and @code{finish}. For
4109 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4112 You can control this automatic behaviour with the following commands:
4114 @kindex set breakpoint auto-hw
4115 @kindex show breakpoint auto-hw
4117 @item set breakpoint auto-hw on
4118 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4119 will try to use the target memory map to decide if software or hardware
4120 breakpoint must be used.
4122 @item set breakpoint auto-hw off
4123 This indicates @value{GDBN} should not automatically select breakpoint
4124 type. If the target provides a memory map, @value{GDBN} will warn when
4125 trying to set software breakpoint at a read-only address.
4128 @value{GDBN} normally implements breakpoints by replacing the program code
4129 at the breakpoint address with a special instruction, which, when
4130 executed, given control to the debugger. By default, the program
4131 code is so modified only when the program is resumed. As soon as
4132 the program stops, @value{GDBN} restores the original instructions. This
4133 behaviour guards against leaving breakpoints inserted in the
4134 target should gdb abrubptly disconnect. However, with slow remote
4135 targets, inserting and removing breakpoint can reduce the performance.
4136 This behavior can be controlled with the following commands::
4138 @kindex set breakpoint always-inserted
4139 @kindex show breakpoint always-inserted
4141 @item set breakpoint always-inserted off
4142 All breakpoints, including newly added by the user, are inserted in
4143 the target only when the target is resumed. All breakpoints are
4144 removed from the target when it stops. This is the default mode.
4146 @item set breakpoint always-inserted on
4147 Causes all breakpoints to be inserted in the target at all times. If
4148 the user adds a new breakpoint, or changes an existing breakpoint, the
4149 breakpoints in the target are updated immediately. A breakpoint is
4150 removed from the target only when breakpoint itself is deleted.
4153 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4154 when a breakpoint breaks. If the condition is true, then the process being
4155 debugged stops, otherwise the process is resumed.
4157 If the target supports evaluating conditions on its end, @value{GDBN} may
4158 download the breakpoint, together with its conditions, to it.
4160 This feature can be controlled via the following commands:
4162 @kindex set breakpoint condition-evaluation
4163 @kindex show breakpoint condition-evaluation
4165 @item set breakpoint condition-evaluation host
4166 This option commands @value{GDBN} to evaluate the breakpoint
4167 conditions on the host's side. Unconditional breakpoints are sent to
4168 the target which in turn receives the triggers and reports them back to GDB
4169 for condition evaluation. This is the standard evaluation mode.
4171 @item set breakpoint condition-evaluation target
4172 This option commands @value{GDBN} to download breakpoint conditions
4173 to the target at the moment of their insertion. The target
4174 is responsible for evaluating the conditional expression and reporting
4175 breakpoint stop events back to @value{GDBN} whenever the condition
4176 is true. Due to limitations of target-side evaluation, some conditions
4177 cannot be evaluated there, e.g., conditions that depend on local data
4178 that is only known to the host. Examples include
4179 conditional expressions involving convenience variables, complex types
4180 that cannot be handled by the agent expression parser and expressions
4181 that are too long to be sent over to the target, specially when the
4182 target is a remote system. In these cases, the conditions will be
4183 evaluated by @value{GDBN}.
4185 @item set breakpoint condition-evaluation auto
4186 This is the default mode. If the target supports evaluating breakpoint
4187 conditions on its end, @value{GDBN} will download breakpoint conditions to
4188 the target (limitations mentioned previously apply). If the target does
4189 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4190 to evaluating all these conditions on the host's side.
4194 @cindex negative breakpoint numbers
4195 @cindex internal @value{GDBN} breakpoints
4196 @value{GDBN} itself sometimes sets breakpoints in your program for
4197 special purposes, such as proper handling of @code{longjmp} (in C
4198 programs). These internal breakpoints are assigned negative numbers,
4199 starting with @code{-1}; @samp{info breakpoints} does not display them.
4200 You can see these breakpoints with the @value{GDBN} maintenance command
4201 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4204 @node Set Watchpoints
4205 @subsection Setting Watchpoints
4207 @cindex setting watchpoints
4208 You can use a watchpoint to stop execution whenever the value of an
4209 expression changes, without having to predict a particular place where
4210 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4211 The expression may be as simple as the value of a single variable, or
4212 as complex as many variables combined by operators. Examples include:
4216 A reference to the value of a single variable.
4219 An address cast to an appropriate data type. For example,
4220 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4221 address (assuming an @code{int} occupies 4 bytes).
4224 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4225 expression can use any operators valid in the program's native
4226 language (@pxref{Languages}).
4229 You can set a watchpoint on an expression even if the expression can
4230 not be evaluated yet. For instance, you can set a watchpoint on
4231 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4232 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4233 the expression produces a valid value. If the expression becomes
4234 valid in some other way than changing a variable (e.g.@: if the memory
4235 pointed to by @samp{*global_ptr} becomes readable as the result of a
4236 @code{malloc} call), @value{GDBN} may not stop until the next time
4237 the expression changes.
4239 @cindex software watchpoints
4240 @cindex hardware watchpoints
4241 Depending on your system, watchpoints may be implemented in software or
4242 hardware. @value{GDBN} does software watchpointing by single-stepping your
4243 program and testing the variable's value each time, which is hundreds of
4244 times slower than normal execution. (But this may still be worth it, to
4245 catch errors where you have no clue what part of your program is the
4248 On some systems, such as most PowerPC or x86-based targets,
4249 @value{GDBN} includes support for hardware watchpoints, which do not
4250 slow down the running of your program.
4254 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4255 Set a watchpoint for an expression. @value{GDBN} will break when the
4256 expression @var{expr} is written into by the program and its value
4257 changes. The simplest (and the most popular) use of this command is
4258 to watch the value of a single variable:
4261 (@value{GDBP}) watch foo
4264 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4265 argument, @value{GDBN} breaks only when the thread identified by
4266 @var{thread-id} changes the value of @var{expr}. If any other threads
4267 change the value of @var{expr}, @value{GDBN} will not break. Note
4268 that watchpoints restricted to a single thread in this way only work
4269 with Hardware Watchpoints.
4271 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4272 (see below). The @code{-location} argument tells @value{GDBN} to
4273 instead watch the memory referred to by @var{expr}. In this case,
4274 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4275 and watch the memory at that address. The type of the result is used
4276 to determine the size of the watched memory. If the expression's
4277 result does not have an address, then @value{GDBN} will print an
4280 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4281 of masked watchpoints, if the current architecture supports this
4282 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4283 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4284 to an address to watch. The mask specifies that some bits of an address
4285 (the bits which are reset in the mask) should be ignored when matching
4286 the address accessed by the inferior against the watchpoint address.
4287 Thus, a masked watchpoint watches many addresses simultaneously---those
4288 addresses whose unmasked bits are identical to the unmasked bits in the
4289 watchpoint address. The @code{mask} argument implies @code{-location}.
4293 (@value{GDBP}) watch foo mask 0xffff00ff
4294 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4298 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4299 Set a watchpoint that will break when the value of @var{expr} is read
4303 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4304 Set a watchpoint that will break when @var{expr} is either read from
4305 or written into by the program.
4307 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4308 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4309 This command prints a list of watchpoints, using the same format as
4310 @code{info break} (@pxref{Set Breaks}).
4313 If you watch for a change in a numerically entered address you need to
4314 dereference it, as the address itself is just a constant number which will
4315 never change. @value{GDBN} refuses to create a watchpoint that watches
4316 a never-changing value:
4319 (@value{GDBP}) watch 0x600850
4320 Cannot watch constant value 0x600850.
4321 (@value{GDBP}) watch *(int *) 0x600850
4322 Watchpoint 1: *(int *) 6293584
4325 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4326 watchpoints execute very quickly, and the debugger reports a change in
4327 value at the exact instruction where the change occurs. If @value{GDBN}
4328 cannot set a hardware watchpoint, it sets a software watchpoint, which
4329 executes more slowly and reports the change in value at the next
4330 @emph{statement}, not the instruction, after the change occurs.
4332 @cindex use only software watchpoints
4333 You can force @value{GDBN} to use only software watchpoints with the
4334 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4335 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4336 the underlying system supports them. (Note that hardware-assisted
4337 watchpoints that were set @emph{before} setting
4338 @code{can-use-hw-watchpoints} to zero will still use the hardware
4339 mechanism of watching expression values.)
4342 @item set can-use-hw-watchpoints
4343 @kindex set can-use-hw-watchpoints
4344 Set whether or not to use hardware watchpoints.
4346 @item show can-use-hw-watchpoints
4347 @kindex show can-use-hw-watchpoints
4348 Show the current mode of using hardware watchpoints.
4351 For remote targets, you can restrict the number of hardware
4352 watchpoints @value{GDBN} will use, see @ref{set remote
4353 hardware-breakpoint-limit}.
4355 When you issue the @code{watch} command, @value{GDBN} reports
4358 Hardware watchpoint @var{num}: @var{expr}
4362 if it was able to set a hardware watchpoint.
4364 Currently, the @code{awatch} and @code{rwatch} commands can only set
4365 hardware watchpoints, because accesses to data that don't change the
4366 value of the watched expression cannot be detected without examining
4367 every instruction as it is being executed, and @value{GDBN} does not do
4368 that currently. If @value{GDBN} finds that it is unable to set a
4369 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4370 will print a message like this:
4373 Expression cannot be implemented with read/access watchpoint.
4376 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4377 data type of the watched expression is wider than what a hardware
4378 watchpoint on the target machine can handle. For example, some systems
4379 can only watch regions that are up to 4 bytes wide; on such systems you
4380 cannot set hardware watchpoints for an expression that yields a
4381 double-precision floating-point number (which is typically 8 bytes
4382 wide). As a work-around, it might be possible to break the large region
4383 into a series of smaller ones and watch them with separate watchpoints.
4385 If you set too many hardware watchpoints, @value{GDBN} might be unable
4386 to insert all of them when you resume the execution of your program.
4387 Since the precise number of active watchpoints is unknown until such
4388 time as the program is about to be resumed, @value{GDBN} might not be
4389 able to warn you about this when you set the watchpoints, and the
4390 warning will be printed only when the program is resumed:
4393 Hardware watchpoint @var{num}: Could not insert watchpoint
4397 If this happens, delete or disable some of the watchpoints.
4399 Watching complex expressions that reference many variables can also
4400 exhaust the resources available for hardware-assisted watchpoints.
4401 That's because @value{GDBN} needs to watch every variable in the
4402 expression with separately allocated resources.
4404 If you call a function interactively using @code{print} or @code{call},
4405 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4406 kind of breakpoint or the call completes.
4408 @value{GDBN} automatically deletes watchpoints that watch local
4409 (automatic) variables, or expressions that involve such variables, when
4410 they go out of scope, that is, when the execution leaves the block in
4411 which these variables were defined. In particular, when the program
4412 being debugged terminates, @emph{all} local variables go out of scope,
4413 and so only watchpoints that watch global variables remain set. If you
4414 rerun the program, you will need to set all such watchpoints again. One
4415 way of doing that would be to set a code breakpoint at the entry to the
4416 @code{main} function and when it breaks, set all the watchpoints.
4418 @cindex watchpoints and threads
4419 @cindex threads and watchpoints
4420 In multi-threaded programs, watchpoints will detect changes to the
4421 watched expression from every thread.
4424 @emph{Warning:} In multi-threaded programs, software watchpoints
4425 have only limited usefulness. If @value{GDBN} creates a software
4426 watchpoint, it can only watch the value of an expression @emph{in a
4427 single thread}. If you are confident that the expression can only
4428 change due to the current thread's activity (and if you are also
4429 confident that no other thread can become current), then you can use
4430 software watchpoints as usual. However, @value{GDBN} may not notice
4431 when a non-current thread's activity changes the expression. (Hardware
4432 watchpoints, in contrast, watch an expression in all threads.)
4435 @xref{set remote hardware-watchpoint-limit}.
4437 @node Set Catchpoints
4438 @subsection Setting Catchpoints
4439 @cindex catchpoints, setting
4440 @cindex exception handlers
4441 @cindex event handling
4443 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4444 kinds of program events, such as C@t{++} exceptions or the loading of a
4445 shared library. Use the @code{catch} command to set a catchpoint.
4449 @item catch @var{event}
4450 Stop when @var{event} occurs. The @var{event} can be any of the following:
4453 @item throw @r{[}@var{regexp}@r{]}
4454 @itemx rethrow @r{[}@var{regexp}@r{]}
4455 @itemx catch @r{[}@var{regexp}@r{]}
4457 @kindex catch rethrow
4459 @cindex stop on C@t{++} exceptions
4460 The throwing, re-throwing, or catching of a C@t{++} exception.
4462 If @var{regexp} is given, then only exceptions whose type matches the
4463 regular expression will be caught.
4465 @vindex $_exception@r{, convenience variable}
4466 The convenience variable @code{$_exception} is available at an
4467 exception-related catchpoint, on some systems. This holds the
4468 exception being thrown.
4470 There are currently some limitations to C@t{++} exception handling in
4475 The support for these commands is system-dependent. Currently, only
4476 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4480 The regular expression feature and the @code{$_exception} convenience
4481 variable rely on the presence of some SDT probes in @code{libstdc++}.
4482 If these probes are not present, then these features cannot be used.
4483 These probes were first available in the GCC 4.8 release, but whether
4484 or not they are available in your GCC also depends on how it was
4488 The @code{$_exception} convenience variable is only valid at the
4489 instruction at which an exception-related catchpoint is set.
4492 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4493 location in the system library which implements runtime exception
4494 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4495 (@pxref{Selection}) to get to your code.
4498 If you call a function interactively, @value{GDBN} normally returns
4499 control to you when the function has finished executing. If the call
4500 raises an exception, however, the call may bypass the mechanism that
4501 returns control to you and cause your program either to abort or to
4502 simply continue running until it hits a breakpoint, catches a signal
4503 that @value{GDBN} is listening for, or exits. This is the case even if
4504 you set a catchpoint for the exception; catchpoints on exceptions are
4505 disabled within interactive calls. @xref{Calling}, for information on
4506 controlling this with @code{set unwind-on-terminating-exception}.
4509 You cannot raise an exception interactively.
4512 You cannot install an exception handler interactively.
4515 @item exception @r{[}@var{name}@r{]}
4516 @kindex catch exception
4517 @cindex Ada exception catching
4518 @cindex catch Ada exceptions
4519 An Ada exception being raised. If an exception name is specified
4520 at the end of the command (eg @code{catch exception Program_Error}),
4521 the debugger will stop only when this specific exception is raised.
4522 Otherwise, the debugger stops execution when any Ada exception is raised.
4524 When inserting an exception catchpoint on a user-defined exception whose
4525 name is identical to one of the exceptions defined by the language, the
4526 fully qualified name must be used as the exception name. Otherwise,
4527 @value{GDBN} will assume that it should stop on the pre-defined exception
4528 rather than the user-defined one. For instance, assuming an exception
4529 called @code{Constraint_Error} is defined in package @code{Pck}, then
4530 the command to use to catch such exceptions is @kbd{catch exception
4531 Pck.Constraint_Error}.
4533 @item exception unhandled
4534 @kindex catch exception unhandled
4535 An exception that was raised but is not handled by the program.
4537 @item handlers @r{[}@var{name}@r{]}
4538 @kindex catch handlers
4539 @cindex Ada exception handlers catching
4540 @cindex catch Ada exceptions when handled
4541 An Ada exception being handled. If an exception name is
4542 specified at the end of the command
4543 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4544 only when this specific exception is handled.
4545 Otherwise, the debugger stops execution when any Ada exception is handled.
4547 When inserting a handlers catchpoint on a user-defined
4548 exception whose name is identical to one of the exceptions
4549 defined by the language, the fully qualified name must be used
4550 as the exception name. Otherwise, @value{GDBN} will assume that it
4551 should stop on the pre-defined exception rather than the
4552 user-defined one. For instance, assuming an exception called
4553 @code{Constraint_Error} is defined in package @code{Pck}, then the
4554 command to use to catch such exceptions handling is
4555 @kbd{catch handlers Pck.Constraint_Error}.
4558 @kindex catch assert
4559 A failed Ada assertion.
4563 @cindex break on fork/exec
4564 A call to @code{exec}.
4566 @anchor{catch syscall}
4568 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4569 @kindex catch syscall
4570 @cindex break on a system call.
4571 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4572 syscall is a mechanism for application programs to request a service
4573 from the operating system (OS) or one of the OS system services.
4574 @value{GDBN} can catch some or all of the syscalls issued by the
4575 debuggee, and show the related information for each syscall. If no
4576 argument is specified, calls to and returns from all system calls
4579 @var{name} can be any system call name that is valid for the
4580 underlying OS. Just what syscalls are valid depends on the OS. On
4581 GNU and Unix systems, you can find the full list of valid syscall
4582 names on @file{/usr/include/asm/unistd.h}.
4584 @c For MS-Windows, the syscall names and the corresponding numbers
4585 @c can be found, e.g., on this URL:
4586 @c http://www.metasploit.com/users/opcode/syscalls.html
4587 @c but we don't support Windows syscalls yet.
4589 Normally, @value{GDBN} knows in advance which syscalls are valid for
4590 each OS, so you can use the @value{GDBN} command-line completion
4591 facilities (@pxref{Completion,, command completion}) to list the
4594 You may also specify the system call numerically. A syscall's
4595 number is the value passed to the OS's syscall dispatcher to
4596 identify the requested service. When you specify the syscall by its
4597 name, @value{GDBN} uses its database of syscalls to convert the name
4598 into the corresponding numeric code, but using the number directly
4599 may be useful if @value{GDBN}'s database does not have the complete
4600 list of syscalls on your system (e.g., because @value{GDBN} lags
4601 behind the OS upgrades).
4603 You may specify a group of related syscalls to be caught at once using
4604 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4605 instance, on some platforms @value{GDBN} allows you to catch all
4606 network related syscalls, by passing the argument @code{group:network}
4607 to @code{catch syscall}. Note that not all syscall groups are
4608 available in every system. You can use the command completion
4609 facilities (@pxref{Completion,, command completion}) to list the
4610 syscall groups available on your environment.
4612 The example below illustrates how this command works if you don't provide
4616 (@value{GDBP}) catch syscall
4617 Catchpoint 1 (syscall)
4619 Starting program: /tmp/catch-syscall
4621 Catchpoint 1 (call to syscall 'close'), \
4622 0xffffe424 in __kernel_vsyscall ()
4626 Catchpoint 1 (returned from syscall 'close'), \
4627 0xffffe424 in __kernel_vsyscall ()
4631 Here is an example of catching a system call by name:
4634 (@value{GDBP}) catch syscall chroot
4635 Catchpoint 1 (syscall 'chroot' [61])
4637 Starting program: /tmp/catch-syscall
4639 Catchpoint 1 (call to syscall 'chroot'), \
4640 0xffffe424 in __kernel_vsyscall ()
4644 Catchpoint 1 (returned from syscall 'chroot'), \
4645 0xffffe424 in __kernel_vsyscall ()
4649 An example of specifying a system call numerically. In the case
4650 below, the syscall number has a corresponding entry in the XML
4651 file, so @value{GDBN} finds its name and prints it:
4654 (@value{GDBP}) catch syscall 252
4655 Catchpoint 1 (syscall(s) 'exit_group')
4657 Starting program: /tmp/catch-syscall
4659 Catchpoint 1 (call to syscall 'exit_group'), \
4660 0xffffe424 in __kernel_vsyscall ()
4664 Program exited normally.
4668 Here is an example of catching a syscall group:
4671 (@value{GDBP}) catch syscall group:process
4672 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4673 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4674 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4676 Starting program: /tmp/catch-syscall
4678 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4679 from /lib64/ld-linux-x86-64.so.2
4685 However, there can be situations when there is no corresponding name
4686 in XML file for that syscall number. In this case, @value{GDBN} prints
4687 a warning message saying that it was not able to find the syscall name,
4688 but the catchpoint will be set anyway. See the example below:
4691 (@value{GDBP}) catch syscall 764
4692 warning: The number '764' does not represent a known syscall.
4693 Catchpoint 2 (syscall 764)
4697 If you configure @value{GDBN} using the @samp{--without-expat} option,
4698 it will not be able to display syscall names. Also, if your
4699 architecture does not have an XML file describing its system calls,
4700 you will not be able to see the syscall names. It is important to
4701 notice that these two features are used for accessing the syscall
4702 name database. In either case, you will see a warning like this:
4705 (@value{GDBP}) catch syscall
4706 warning: Could not open "syscalls/i386-linux.xml"
4707 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4708 GDB will not be able to display syscall names.
4709 Catchpoint 1 (syscall)
4713 Of course, the file name will change depending on your architecture and system.
4715 Still using the example above, you can also try to catch a syscall by its
4716 number. In this case, you would see something like:
4719 (@value{GDBP}) catch syscall 252
4720 Catchpoint 1 (syscall(s) 252)
4723 Again, in this case @value{GDBN} would not be able to display syscall's names.
4727 A call to @code{fork}.
4731 A call to @code{vfork}.
4733 @item load @r{[}@var{regexp}@r{]}
4734 @itemx unload @r{[}@var{regexp}@r{]}
4736 @kindex catch unload
4737 The loading or unloading of a shared library. If @var{regexp} is
4738 given, then the catchpoint will stop only if the regular expression
4739 matches one of the affected libraries.
4741 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4742 @kindex catch signal
4743 The delivery of a signal.
4745 With no arguments, this catchpoint will catch any signal that is not
4746 used internally by @value{GDBN}, specifically, all signals except
4747 @samp{SIGTRAP} and @samp{SIGINT}.
4749 With the argument @samp{all}, all signals, including those used by
4750 @value{GDBN}, will be caught. This argument cannot be used with other
4753 Otherwise, the arguments are a list of signal names as given to
4754 @code{handle} (@pxref{Signals}). Only signals specified in this list
4757 One reason that @code{catch signal} can be more useful than
4758 @code{handle} is that you can attach commands and conditions to the
4761 When a signal is caught by a catchpoint, the signal's @code{stop} and
4762 @code{print} settings, as specified by @code{handle}, are ignored.
4763 However, whether the signal is still delivered to the inferior depends
4764 on the @code{pass} setting; this can be changed in the catchpoint's
4769 @item tcatch @var{event}
4771 Set a catchpoint that is enabled only for one stop. The catchpoint is
4772 automatically deleted after the first time the event is caught.
4776 Use the @code{info break} command to list the current catchpoints.
4780 @subsection Deleting Breakpoints
4782 @cindex clearing breakpoints, watchpoints, catchpoints
4783 @cindex deleting breakpoints, watchpoints, catchpoints
4784 It is often necessary to eliminate a breakpoint, watchpoint, or
4785 catchpoint once it has done its job and you no longer want your program
4786 to stop there. This is called @dfn{deleting} the breakpoint. A
4787 breakpoint that has been deleted no longer exists; it is forgotten.
4789 With the @code{clear} command you can delete breakpoints according to
4790 where they are in your program. With the @code{delete} command you can
4791 delete individual breakpoints, watchpoints, or catchpoints by specifying
4792 their breakpoint numbers.
4794 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4795 automatically ignores breakpoints on the first instruction to be executed
4796 when you continue execution without changing the execution address.
4801 Delete any breakpoints at the next instruction to be executed in the
4802 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4803 the innermost frame is selected, this is a good way to delete a
4804 breakpoint where your program just stopped.
4806 @item clear @var{location}
4807 Delete any breakpoints set at the specified @var{location}.
4808 @xref{Specify Location}, for the various forms of @var{location}; the
4809 most useful ones are listed below:
4812 @item clear @var{function}
4813 @itemx clear @var{filename}:@var{function}
4814 Delete any breakpoints set at entry to the named @var{function}.
4816 @item clear @var{linenum}
4817 @itemx clear @var{filename}:@var{linenum}
4818 Delete any breakpoints set at or within the code of the specified
4819 @var{linenum} of the specified @var{filename}.
4822 @cindex delete breakpoints
4824 @kindex d @r{(@code{delete})}
4825 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4826 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4827 list specified as argument. If no argument is specified, delete all
4828 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4829 confirm off}). You can abbreviate this command as @code{d}.
4833 @subsection Disabling Breakpoints
4835 @cindex enable/disable a breakpoint
4836 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4837 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4838 it had been deleted, but remembers the information on the breakpoint so
4839 that you can @dfn{enable} it again later.
4841 You disable and enable breakpoints, watchpoints, and catchpoints with
4842 the @code{enable} and @code{disable} commands, optionally specifying
4843 one or more breakpoint numbers as arguments. Use @code{info break} to
4844 print a list of all breakpoints, watchpoints, and catchpoints if you
4845 do not know which numbers to use.
4847 Disabling and enabling a breakpoint that has multiple locations
4848 affects all of its locations.
4850 A breakpoint, watchpoint, or catchpoint can have any of several
4851 different states of enablement:
4855 Enabled. The breakpoint stops your program. A breakpoint set
4856 with the @code{break} command starts out in this state.
4858 Disabled. The breakpoint has no effect on your program.
4860 Enabled once. The breakpoint stops your program, but then becomes
4863 Enabled for a count. The breakpoint stops your program for the next
4864 N times, then becomes disabled.
4866 Enabled for deletion. The breakpoint stops your program, but
4867 immediately after it does so it is deleted permanently. A breakpoint
4868 set with the @code{tbreak} command starts out in this state.
4871 You can use the following commands to enable or disable breakpoints,
4872 watchpoints, and catchpoints:
4876 @kindex dis @r{(@code{disable})}
4877 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4878 Disable the specified breakpoints---or all breakpoints, if none are
4879 listed. A disabled breakpoint has no effect but is not forgotten. All
4880 options such as ignore-counts, conditions and commands are remembered in
4881 case the breakpoint is enabled again later. You may abbreviate
4882 @code{disable} as @code{dis}.
4885 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4886 Enable the specified breakpoints (or all defined breakpoints). They
4887 become effective once again in stopping your program.
4889 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4890 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4891 of these breakpoints immediately after stopping your program.
4893 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4894 Enable the specified breakpoints temporarily. @value{GDBN} records
4895 @var{count} with each of the specified breakpoints, and decrements a
4896 breakpoint's count when it is hit. When any count reaches 0,
4897 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4898 count (@pxref{Conditions, ,Break Conditions}), that will be
4899 decremented to 0 before @var{count} is affected.
4901 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4902 Enable the specified breakpoints to work once, then die. @value{GDBN}
4903 deletes any of these breakpoints as soon as your program stops there.
4904 Breakpoints set by the @code{tbreak} command start out in this state.
4907 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4908 @c confusing: tbreak is also initially enabled.
4909 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4910 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4911 subsequently, they become disabled or enabled only when you use one of
4912 the commands above. (The command @code{until} can set and delete a
4913 breakpoint of its own, but it does not change the state of your other
4914 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4918 @subsection Break Conditions
4919 @cindex conditional breakpoints
4920 @cindex breakpoint conditions
4922 @c FIXME what is scope of break condition expr? Context where wanted?
4923 @c in particular for a watchpoint?
4924 The simplest sort of breakpoint breaks every time your program reaches a
4925 specified place. You can also specify a @dfn{condition} for a
4926 breakpoint. A condition is just a Boolean expression in your
4927 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4928 a condition evaluates the expression each time your program reaches it,
4929 and your program stops only if the condition is @emph{true}.
4931 This is the converse of using assertions for program validation; in that
4932 situation, you want to stop when the assertion is violated---that is,
4933 when the condition is false. In C, if you want to test an assertion expressed
4934 by the condition @var{assert}, you should set the condition
4935 @samp{! @var{assert}} on the appropriate breakpoint.
4937 Conditions are also accepted for watchpoints; you may not need them,
4938 since a watchpoint is inspecting the value of an expression anyhow---but
4939 it might be simpler, say, to just set a watchpoint on a variable name,
4940 and specify a condition that tests whether the new value is an interesting
4943 Break conditions can have side effects, and may even call functions in
4944 your program. This can be useful, for example, to activate functions
4945 that log program progress, or to use your own print functions to
4946 format special data structures. The effects are completely predictable
4947 unless there is another enabled breakpoint at the same address. (In
4948 that case, @value{GDBN} might see the other breakpoint first and stop your
4949 program without checking the condition of this one.) Note that
4950 breakpoint commands are usually more convenient and flexible than break
4952 purpose of performing side effects when a breakpoint is reached
4953 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4955 Breakpoint conditions can also be evaluated on the target's side if
4956 the target supports it. Instead of evaluating the conditions locally,
4957 @value{GDBN} encodes the expression into an agent expression
4958 (@pxref{Agent Expressions}) suitable for execution on the target,
4959 independently of @value{GDBN}. Global variables become raw memory
4960 locations, locals become stack accesses, and so forth.
4962 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4963 when its condition evaluates to true. This mechanism may provide faster
4964 response times depending on the performance characteristics of the target
4965 since it does not need to keep @value{GDBN} informed about
4966 every breakpoint trigger, even those with false conditions.
4968 Break conditions can be specified when a breakpoint is set, by using
4969 @samp{if} in the arguments to the @code{break} command. @xref{Set
4970 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4971 with the @code{condition} command.
4973 You can also use the @code{if} keyword with the @code{watch} command.
4974 The @code{catch} command does not recognize the @code{if} keyword;
4975 @code{condition} is the only way to impose a further condition on a
4980 @item condition @var{bnum} @var{expression}
4981 Specify @var{expression} as the break condition for breakpoint,
4982 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4983 breakpoint @var{bnum} stops your program only if the value of
4984 @var{expression} is true (nonzero, in C). When you use
4985 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4986 syntactic correctness, and to determine whether symbols in it have
4987 referents in the context of your breakpoint. If @var{expression} uses
4988 symbols not referenced in the context of the breakpoint, @value{GDBN}
4989 prints an error message:
4992 No symbol "foo" in current context.
4997 not actually evaluate @var{expression} at the time the @code{condition}
4998 command (or a command that sets a breakpoint with a condition, like
4999 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5001 @item condition @var{bnum}
5002 Remove the condition from breakpoint number @var{bnum}. It becomes
5003 an ordinary unconditional breakpoint.
5006 @cindex ignore count (of breakpoint)
5007 A special case of a breakpoint condition is to stop only when the
5008 breakpoint has been reached a certain number of times. This is so
5009 useful that there is a special way to do it, using the @dfn{ignore
5010 count} of the breakpoint. Every breakpoint has an ignore count, which
5011 is an integer. Most of the time, the ignore count is zero, and
5012 therefore has no effect. But if your program reaches a breakpoint whose
5013 ignore count is positive, then instead of stopping, it just decrements
5014 the ignore count by one and continues. As a result, if the ignore count
5015 value is @var{n}, the breakpoint does not stop the next @var{n} times
5016 your program reaches it.
5020 @item ignore @var{bnum} @var{count}
5021 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5022 The next @var{count} times the breakpoint is reached, your program's
5023 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5026 To make the breakpoint stop the next time it is reached, specify
5029 When you use @code{continue} to resume execution of your program from a
5030 breakpoint, you can specify an ignore count directly as an argument to
5031 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5032 Stepping,,Continuing and Stepping}.
5034 If a breakpoint has a positive ignore count and a condition, the
5035 condition is not checked. Once the ignore count reaches zero,
5036 @value{GDBN} resumes checking the condition.
5038 You could achieve the effect of the ignore count with a condition such
5039 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5040 is decremented each time. @xref{Convenience Vars, ,Convenience
5044 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5047 @node Break Commands
5048 @subsection Breakpoint Command Lists
5050 @cindex breakpoint commands
5051 You can give any breakpoint (or watchpoint or catchpoint) a series of
5052 commands to execute when your program stops due to that breakpoint. For
5053 example, you might want to print the values of certain expressions, or
5054 enable other breakpoints.
5058 @kindex end@r{ (breakpoint commands)}
5059 @item commands @r{[}@var{list}@dots{}@r{]}
5060 @itemx @dots{} @var{command-list} @dots{}
5062 Specify a list of commands for the given breakpoints. The commands
5063 themselves appear on the following lines. Type a line containing just
5064 @code{end} to terminate the commands.
5066 To remove all commands from a breakpoint, type @code{commands} and
5067 follow it immediately with @code{end}; that is, give no commands.
5069 With no argument, @code{commands} refers to the last breakpoint,
5070 watchpoint, or catchpoint set (not to the breakpoint most recently
5071 encountered). If the most recent breakpoints were set with a single
5072 command, then the @code{commands} will apply to all the breakpoints
5073 set by that command. This applies to breakpoints set by
5074 @code{rbreak}, and also applies when a single @code{break} command
5075 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5079 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5080 disabled within a @var{command-list}.
5082 You can use breakpoint commands to start your program up again. Simply
5083 use the @code{continue} command, or @code{step}, or any other command
5084 that resumes execution.
5086 Any other commands in the command list, after a command that resumes
5087 execution, are ignored. This is because any time you resume execution
5088 (even with a simple @code{next} or @code{step}), you may encounter
5089 another breakpoint---which could have its own command list, leading to
5090 ambiguities about which list to execute.
5093 If the first command you specify in a command list is @code{silent}, the
5094 usual message about stopping at a breakpoint is not printed. This may
5095 be desirable for breakpoints that are to print a specific message and
5096 then continue. If none of the remaining commands print anything, you
5097 see no sign that the breakpoint was reached. @code{silent} is
5098 meaningful only at the beginning of a breakpoint command list.
5100 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5101 print precisely controlled output, and are often useful in silent
5102 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5104 For example, here is how you could use breakpoint commands to print the
5105 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5111 printf "x is %d\n",x
5116 One application for breakpoint commands is to compensate for one bug so
5117 you can test for another. Put a breakpoint just after the erroneous line
5118 of code, give it a condition to detect the case in which something
5119 erroneous has been done, and give it commands to assign correct values
5120 to any variables that need them. End with the @code{continue} command
5121 so that your program does not stop, and start with the @code{silent}
5122 command so that no output is produced. Here is an example:
5133 @node Dynamic Printf
5134 @subsection Dynamic Printf
5136 @cindex dynamic printf
5138 The dynamic printf command @code{dprintf} combines a breakpoint with
5139 formatted printing of your program's data to give you the effect of
5140 inserting @code{printf} calls into your program on-the-fly, without
5141 having to recompile it.
5143 In its most basic form, the output goes to the GDB console. However,
5144 you can set the variable @code{dprintf-style} for alternate handling.
5145 For instance, you can ask to format the output by calling your
5146 program's @code{printf} function. This has the advantage that the
5147 characters go to the program's output device, so they can recorded in
5148 redirects to files and so forth.
5150 If you are doing remote debugging with a stub or agent, you can also
5151 ask to have the printf handled by the remote agent. In addition to
5152 ensuring that the output goes to the remote program's device along
5153 with any other output the program might produce, you can also ask that
5154 the dprintf remain active even after disconnecting from the remote
5155 target. Using the stub/agent is also more efficient, as it can do
5156 everything without needing to communicate with @value{GDBN}.
5160 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5161 Whenever execution reaches @var{location}, print the values of one or
5162 more @var{expressions} under the control of the string @var{template}.
5163 To print several values, separate them with commas.
5165 @item set dprintf-style @var{style}
5166 Set the dprintf output to be handled in one of several different
5167 styles enumerated below. A change of style affects all existing
5168 dynamic printfs immediately. (If you need individual control over the
5169 print commands, simply define normal breakpoints with
5170 explicitly-supplied command lists.)
5174 @kindex dprintf-style gdb
5175 Handle the output using the @value{GDBN} @code{printf} command.
5178 @kindex dprintf-style call
5179 Handle the output by calling a function in your program (normally
5183 @kindex dprintf-style agent
5184 Have the remote debugging agent (such as @code{gdbserver}) handle
5185 the output itself. This style is only available for agents that
5186 support running commands on the target.
5189 @item set dprintf-function @var{function}
5190 Set the function to call if the dprintf style is @code{call}. By
5191 default its value is @code{printf}. You may set it to any expression.
5192 that @value{GDBN} can evaluate to a function, as per the @code{call}
5195 @item set dprintf-channel @var{channel}
5196 Set a ``channel'' for dprintf. If set to a non-empty value,
5197 @value{GDBN} will evaluate it as an expression and pass the result as
5198 a first argument to the @code{dprintf-function}, in the manner of
5199 @code{fprintf} and similar functions. Otherwise, the dprintf format
5200 string will be the first argument, in the manner of @code{printf}.
5202 As an example, if you wanted @code{dprintf} output to go to a logfile
5203 that is a standard I/O stream assigned to the variable @code{mylog},
5204 you could do the following:
5207 (gdb) set dprintf-style call
5208 (gdb) set dprintf-function fprintf
5209 (gdb) set dprintf-channel mylog
5210 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5211 Dprintf 1 at 0x123456: file main.c, line 25.
5213 1 dprintf keep y 0x00123456 in main at main.c:25
5214 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5219 Note that the @code{info break} displays the dynamic printf commands
5220 as normal breakpoint commands; you can thus easily see the effect of
5221 the variable settings.
5223 @item set disconnected-dprintf on
5224 @itemx set disconnected-dprintf off
5225 @kindex set disconnected-dprintf
5226 Choose whether @code{dprintf} commands should continue to run if
5227 @value{GDBN} has disconnected from the target. This only applies
5228 if the @code{dprintf-style} is @code{agent}.
5230 @item show disconnected-dprintf off
5231 @kindex show disconnected-dprintf
5232 Show the current choice for disconnected @code{dprintf}.
5236 @value{GDBN} does not check the validity of function and channel,
5237 relying on you to supply values that are meaningful for the contexts
5238 in which they are being used. For instance, the function and channel
5239 may be the values of local variables, but if that is the case, then
5240 all enabled dynamic prints must be at locations within the scope of
5241 those locals. If evaluation fails, @value{GDBN} will report an error.
5243 @node Save Breakpoints
5244 @subsection How to save breakpoints to a file
5246 To save breakpoint definitions to a file use the @w{@code{save
5247 breakpoints}} command.
5250 @kindex save breakpoints
5251 @cindex save breakpoints to a file for future sessions
5252 @item save breakpoints [@var{filename}]
5253 This command saves all current breakpoint definitions together with
5254 their commands and ignore counts, into a file @file{@var{filename}}
5255 suitable for use in a later debugging session. This includes all
5256 types of breakpoints (breakpoints, watchpoints, catchpoints,
5257 tracepoints). To read the saved breakpoint definitions, use the
5258 @code{source} command (@pxref{Command Files}). Note that watchpoints
5259 with expressions involving local variables may fail to be recreated
5260 because it may not be possible to access the context where the
5261 watchpoint is valid anymore. Because the saved breakpoint definitions
5262 are simply a sequence of @value{GDBN} commands that recreate the
5263 breakpoints, you can edit the file in your favorite editing program,
5264 and remove the breakpoint definitions you're not interested in, or
5265 that can no longer be recreated.
5268 @node Static Probe Points
5269 @subsection Static Probe Points
5271 @cindex static probe point, SystemTap
5272 @cindex static probe point, DTrace
5273 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5274 for Statically Defined Tracing, and the probes are designed to have a tiny
5275 runtime code and data footprint, and no dynamic relocations.
5277 Currently, the following types of probes are supported on
5278 ELF-compatible systems:
5282 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5283 @acronym{SDT} probes@footnote{See
5284 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5285 for more information on how to add @code{SystemTap} @acronym{SDT}
5286 probes in your applications.}. @code{SystemTap} probes are usable
5287 from assembly, C and C@t{++} languages@footnote{See
5288 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5289 for a good reference on how the @acronym{SDT} probes are implemented.}.
5291 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5292 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5296 @cindex semaphores on static probe points
5297 Some @code{SystemTap} probes have an associated semaphore variable;
5298 for instance, this happens automatically if you defined your probe
5299 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5300 @value{GDBN} will automatically enable it when you specify a
5301 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5302 breakpoint at a probe's location by some other method (e.g.,
5303 @code{break file:line}), then @value{GDBN} will not automatically set
5304 the semaphore. @code{DTrace} probes do not support semaphores.
5306 You can examine the available static static probes using @code{info
5307 probes}, with optional arguments:
5311 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5312 If given, @var{type} is either @code{stap} for listing
5313 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5314 probes. If omitted all probes are listed regardless of their types.
5316 If given, @var{provider} is a regular expression used to match against provider
5317 names when selecting which probes to list. If omitted, probes by all
5318 probes from all providers are listed.
5320 If given, @var{name} is a regular expression to match against probe names
5321 when selecting which probes to list. If omitted, probe names are not
5322 considered when deciding whether to display them.
5324 If given, @var{objfile} is a regular expression used to select which
5325 object files (executable or shared libraries) to examine. If not
5326 given, all object files are considered.
5328 @item info probes all
5329 List the available static probes, from all types.
5332 @cindex enabling and disabling probes
5333 Some probe points can be enabled and/or disabled. The effect of
5334 enabling or disabling a probe depends on the type of probe being
5335 handled. Some @code{DTrace} probes can be enabled or
5336 disabled, but @code{SystemTap} probes cannot be disabled.
5338 You can enable (or disable) one or more probes using the following
5339 commands, with optional arguments:
5342 @kindex enable probes
5343 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5344 If given, @var{provider} is a regular expression used to match against
5345 provider names when selecting which probes to enable. If omitted,
5346 all probes from all providers are enabled.
5348 If given, @var{name} is a regular expression to match against probe
5349 names when selecting which probes to enable. If omitted, probe names
5350 are not considered when deciding whether to enable them.
5352 If given, @var{objfile} is a regular expression used to select which
5353 object files (executable or shared libraries) to examine. If not
5354 given, all object files are considered.
5356 @kindex disable probes
5357 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5358 See the @code{enable probes} command above for a description of the
5359 optional arguments accepted by this command.
5362 @vindex $_probe_arg@r{, convenience variable}
5363 A probe may specify up to twelve arguments. These are available at the
5364 point at which the probe is defined---that is, when the current PC is
5365 at the probe's location. The arguments are available using the
5366 convenience variables (@pxref{Convenience Vars})
5367 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5368 probes each probe argument is an integer of the appropriate size;
5369 types are not preserved. In @code{DTrace} probes types are preserved
5370 provided that they are recognized as such by @value{GDBN}; otherwise
5371 the value of the probe argument will be a long integer. The
5372 convenience variable @code{$_probe_argc} holds the number of arguments
5373 at the current probe point.
5375 These variables are always available, but attempts to access them at
5376 any location other than a probe point will cause @value{GDBN} to give
5380 @c @ifclear BARETARGET
5381 @node Error in Breakpoints
5382 @subsection ``Cannot insert breakpoints''
5384 If you request too many active hardware-assisted breakpoints and
5385 watchpoints, you will see this error message:
5387 @c FIXME: the precise wording of this message may change; the relevant
5388 @c source change is not committed yet (Sep 3, 1999).
5390 Stopped; cannot insert breakpoints.
5391 You may have requested too many hardware breakpoints and watchpoints.
5395 This message is printed when you attempt to resume the program, since
5396 only then @value{GDBN} knows exactly how many hardware breakpoints and
5397 watchpoints it needs to insert.
5399 When this message is printed, you need to disable or remove some of the
5400 hardware-assisted breakpoints and watchpoints, and then continue.
5402 @node Breakpoint-related Warnings
5403 @subsection ``Breakpoint address adjusted...''
5404 @cindex breakpoint address adjusted
5406 Some processor architectures place constraints on the addresses at
5407 which breakpoints may be placed. For architectures thus constrained,
5408 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5409 with the constraints dictated by the architecture.
5411 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5412 a VLIW architecture in which a number of RISC-like instructions may be
5413 bundled together for parallel execution. The FR-V architecture
5414 constrains the location of a breakpoint instruction within such a
5415 bundle to the instruction with the lowest address. @value{GDBN}
5416 honors this constraint by adjusting a breakpoint's address to the
5417 first in the bundle.
5419 It is not uncommon for optimized code to have bundles which contain
5420 instructions from different source statements, thus it may happen that
5421 a breakpoint's address will be adjusted from one source statement to
5422 another. Since this adjustment may significantly alter @value{GDBN}'s
5423 breakpoint related behavior from what the user expects, a warning is
5424 printed when the breakpoint is first set and also when the breakpoint
5427 A warning like the one below is printed when setting a breakpoint
5428 that's been subject to address adjustment:
5431 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5434 Such warnings are printed both for user settable and @value{GDBN}'s
5435 internal breakpoints. If you see one of these warnings, you should
5436 verify that a breakpoint set at the adjusted address will have the
5437 desired affect. If not, the breakpoint in question may be removed and
5438 other breakpoints may be set which will have the desired behavior.
5439 E.g., it may be sufficient to place the breakpoint at a later
5440 instruction. A conditional breakpoint may also be useful in some
5441 cases to prevent the breakpoint from triggering too often.
5443 @value{GDBN} will also issue a warning when stopping at one of these
5444 adjusted breakpoints:
5447 warning: Breakpoint 1 address previously adjusted from 0x00010414
5451 When this warning is encountered, it may be too late to take remedial
5452 action except in cases where the breakpoint is hit earlier or more
5453 frequently than expected.
5455 @node Continuing and Stepping
5456 @section Continuing and Stepping
5460 @cindex resuming execution
5461 @dfn{Continuing} means resuming program execution until your program
5462 completes normally. In contrast, @dfn{stepping} means executing just
5463 one more ``step'' of your program, where ``step'' may mean either one
5464 line of source code, or one machine instruction (depending on what
5465 particular command you use). Either when continuing or when stepping,
5466 your program may stop even sooner, due to a breakpoint or a signal. (If
5467 it stops due to a signal, you may want to use @code{handle}, or use
5468 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5469 or you may step into the signal's handler (@pxref{stepping and signal
5474 @kindex c @r{(@code{continue})}
5475 @kindex fg @r{(resume foreground execution)}
5476 @item continue @r{[}@var{ignore-count}@r{]}
5477 @itemx c @r{[}@var{ignore-count}@r{]}
5478 @itemx fg @r{[}@var{ignore-count}@r{]}
5479 Resume program execution, at the address where your program last stopped;
5480 any breakpoints set at that address are bypassed. The optional argument
5481 @var{ignore-count} allows you to specify a further number of times to
5482 ignore a breakpoint at this location; its effect is like that of
5483 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5485 The argument @var{ignore-count} is meaningful only when your program
5486 stopped due to a breakpoint. At other times, the argument to
5487 @code{continue} is ignored.
5489 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5490 debugged program is deemed to be the foreground program) are provided
5491 purely for convenience, and have exactly the same behavior as
5495 To resume execution at a different place, you can use @code{return}
5496 (@pxref{Returning, ,Returning from a Function}) to go back to the
5497 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5498 Different Address}) to go to an arbitrary location in your program.
5500 A typical technique for using stepping is to set a breakpoint
5501 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5502 beginning of the function or the section of your program where a problem
5503 is believed to lie, run your program until it stops at that breakpoint,
5504 and then step through the suspect area, examining the variables that are
5505 interesting, until you see the problem happen.
5509 @kindex s @r{(@code{step})}
5511 Continue running your program until control reaches a different source
5512 line, then stop it and return control to @value{GDBN}. This command is
5513 abbreviated @code{s}.
5516 @c "without debugging information" is imprecise; actually "without line
5517 @c numbers in the debugging information". (gcc -g1 has debugging info but
5518 @c not line numbers). But it seems complex to try to make that
5519 @c distinction here.
5520 @emph{Warning:} If you use the @code{step} command while control is
5521 within a function that was compiled without debugging information,
5522 execution proceeds until control reaches a function that does have
5523 debugging information. Likewise, it will not step into a function which
5524 is compiled without debugging information. To step through functions
5525 without debugging information, use the @code{stepi} command, described
5529 The @code{step} command only stops at the first instruction of a source
5530 line. This prevents the multiple stops that could otherwise occur in
5531 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5532 to stop if a function that has debugging information is called within
5533 the line. In other words, @code{step} @emph{steps inside} any functions
5534 called within the line.
5536 Also, the @code{step} command only enters a function if there is line
5537 number information for the function. Otherwise it acts like the
5538 @code{next} command. This avoids problems when using @code{cc -gl}
5539 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5540 was any debugging information about the routine.
5542 @item step @var{count}
5543 Continue running as in @code{step}, but do so @var{count} times. If a
5544 breakpoint is reached, or a signal not related to stepping occurs before
5545 @var{count} steps, stepping stops right away.
5548 @kindex n @r{(@code{next})}
5549 @item next @r{[}@var{count}@r{]}
5550 Continue to the next source line in the current (innermost) stack frame.
5551 This is similar to @code{step}, but function calls that appear within
5552 the line of code are executed without stopping. Execution stops when
5553 control reaches a different line of code at the original stack level
5554 that was executing when you gave the @code{next} command. This command
5555 is abbreviated @code{n}.
5557 An argument @var{count} is a repeat count, as for @code{step}.
5560 @c FIX ME!! Do we delete this, or is there a way it fits in with
5561 @c the following paragraph? --- Vctoria
5563 @c @code{next} within a function that lacks debugging information acts like
5564 @c @code{step}, but any function calls appearing within the code of the
5565 @c function are executed without stopping.
5567 The @code{next} command only stops at the first instruction of a
5568 source line. This prevents multiple stops that could otherwise occur in
5569 @code{switch} statements, @code{for} loops, etc.
5571 @kindex set step-mode
5573 @cindex functions without line info, and stepping
5574 @cindex stepping into functions with no line info
5575 @itemx set step-mode on
5576 The @code{set step-mode on} command causes the @code{step} command to
5577 stop at the first instruction of a function which contains no debug line
5578 information rather than stepping over it.
5580 This is useful in cases where you may be interested in inspecting the
5581 machine instructions of a function which has no symbolic info and do not
5582 want @value{GDBN} to automatically skip over this function.
5584 @item set step-mode off
5585 Causes the @code{step} command to step over any functions which contains no
5586 debug information. This is the default.
5588 @item show step-mode
5589 Show whether @value{GDBN} will stop in or step over functions without
5590 source line debug information.
5593 @kindex fin @r{(@code{finish})}
5595 Continue running until just after function in the selected stack frame
5596 returns. Print the returned value (if any). This command can be
5597 abbreviated as @code{fin}.
5599 Contrast this with the @code{return} command (@pxref{Returning,
5600 ,Returning from a Function}).
5602 @kindex set print finish
5603 @kindex show print finish
5604 @item set print finish @r{[}on|off@r{]}
5605 @itemx show print finish
5606 By default the @code{finish} command will show the value that is
5607 returned by the function. This can be disabled using @code{set print
5608 finish off}. When disabled, the value is still entered into the value
5609 history (@pxref{Value History}), but not displayed.
5612 @kindex u @r{(@code{until})}
5613 @cindex run until specified location
5616 Continue running until a source line past the current line, in the
5617 current stack frame, is reached. This command is used to avoid single
5618 stepping through a loop more than once. It is like the @code{next}
5619 command, except that when @code{until} encounters a jump, it
5620 automatically continues execution until the program counter is greater
5621 than the address of the jump.
5623 This means that when you reach the end of a loop after single stepping
5624 though it, @code{until} makes your program continue execution until it
5625 exits the loop. In contrast, a @code{next} command at the end of a loop
5626 simply steps back to the beginning of the loop, which forces you to step
5627 through the next iteration.
5629 @code{until} always stops your program if it attempts to exit the current
5632 @code{until} may produce somewhat counterintuitive results if the order
5633 of machine code does not match the order of the source lines. For
5634 example, in the following excerpt from a debugging session, the @code{f}
5635 (@code{frame}) command shows that execution is stopped at line
5636 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5640 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5642 (@value{GDBP}) until
5643 195 for ( ; argc > 0; NEXTARG) @{
5646 This happened because, for execution efficiency, the compiler had
5647 generated code for the loop closure test at the end, rather than the
5648 start, of the loop---even though the test in a C @code{for}-loop is
5649 written before the body of the loop. The @code{until} command appeared
5650 to step back to the beginning of the loop when it advanced to this
5651 expression; however, it has not really gone to an earlier
5652 statement---not in terms of the actual machine code.
5654 @code{until} with no argument works by means of single
5655 instruction stepping, and hence is slower than @code{until} with an
5658 @item until @var{location}
5659 @itemx u @var{location}
5660 Continue running your program until either the specified @var{location} is
5661 reached, or the current stack frame returns. The location is any of
5662 the forms described in @ref{Specify Location}.
5663 This form of the command uses temporary breakpoints, and
5664 hence is quicker than @code{until} without an argument. The specified
5665 location is actually reached only if it is in the current frame. This
5666 implies that @code{until} can be used to skip over recursive function
5667 invocations. For instance in the code below, if the current location is
5668 line @code{96}, issuing @code{until 99} will execute the program up to
5669 line @code{99} in the same invocation of factorial, i.e., after the inner
5670 invocations have returned.
5673 94 int factorial (int value)
5675 96 if (value > 1) @{
5676 97 value *= factorial (value - 1);
5683 @kindex advance @var{location}
5684 @item advance @var{location}
5685 Continue running the program up to the given @var{location}. An argument is
5686 required, which should be of one of the forms described in
5687 @ref{Specify Location}.
5688 Execution will also stop upon exit from the current stack
5689 frame. This command is similar to @code{until}, but @code{advance} will
5690 not skip over recursive function calls, and the target location doesn't
5691 have to be in the same frame as the current one.
5695 @kindex si @r{(@code{stepi})}
5697 @itemx stepi @var{arg}
5699 Execute one machine instruction, then stop and return to the debugger.
5701 It is often useful to do @samp{display/i $pc} when stepping by machine
5702 instructions. This makes @value{GDBN} automatically display the next
5703 instruction to be executed, each time your program stops. @xref{Auto
5704 Display,, Automatic Display}.
5706 An argument is a repeat count, as in @code{step}.
5710 @kindex ni @r{(@code{nexti})}
5712 @itemx nexti @var{arg}
5714 Execute one machine instruction, but if it is a function call,
5715 proceed until the function returns.
5717 An argument is a repeat count, as in @code{next}.
5721 @anchor{range stepping}
5722 @cindex range stepping
5723 @cindex target-assisted range stepping
5724 By default, and if available, @value{GDBN} makes use of
5725 target-assisted @dfn{range stepping}. In other words, whenever you
5726 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5727 tells the target to step the corresponding range of instruction
5728 addresses instead of issuing multiple single-steps. This speeds up
5729 line stepping, particularly for remote targets. Ideally, there should
5730 be no reason you would want to turn range stepping off. However, it's
5731 possible that a bug in the debug info, a bug in the remote stub (for
5732 remote targets), or even a bug in @value{GDBN} could make line
5733 stepping behave incorrectly when target-assisted range stepping is
5734 enabled. You can use the following command to turn off range stepping
5738 @kindex set range-stepping
5739 @kindex show range-stepping
5740 @item set range-stepping
5741 @itemx show range-stepping
5742 Control whether range stepping is enabled.
5744 If @code{on}, and the target supports it, @value{GDBN} tells the
5745 target to step a range of addresses itself, instead of issuing
5746 multiple single-steps. If @code{off}, @value{GDBN} always issues
5747 single-steps, even if range stepping is supported by the target. The
5748 default is @code{on}.
5752 @node Skipping Over Functions and Files
5753 @section Skipping Over Functions and Files
5754 @cindex skipping over functions and files
5756 The program you are debugging may contain some functions which are
5757 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5758 skip a function, all functions in a file or a particular function in
5759 a particular file when stepping.
5761 For example, consider the following C function:
5772 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5773 are not interested in stepping through @code{boring}. If you run @code{step}
5774 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5775 step over both @code{foo} and @code{boring}!
5777 One solution is to @code{step} into @code{boring} and use the @code{finish}
5778 command to immediately exit it. But this can become tedious if @code{boring}
5779 is called from many places.
5781 A more flexible solution is to execute @kbd{skip boring}. This instructs
5782 @value{GDBN} never to step into @code{boring}. Now when you execute
5783 @code{step} at line 103, you'll step over @code{boring} and directly into
5786 Functions may be skipped by providing either a function name, linespec
5787 (@pxref{Specify Location}), regular expression that matches the function's
5788 name, file name or a @code{glob}-style pattern that matches the file name.
5790 On Posix systems the form of the regular expression is
5791 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5792 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5793 expression is whatever is provided by the @code{regcomp} function of
5794 the underlying system.
5795 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5796 description of @code{glob}-style patterns.
5800 @item skip @r{[}@var{options}@r{]}
5801 The basic form of the @code{skip} command takes zero or more options
5802 that specify what to skip.
5803 The @var{options} argument is any useful combination of the following:
5806 @item -file @var{file}
5807 @itemx -fi @var{file}
5808 Functions in @var{file} will be skipped over when stepping.
5810 @item -gfile @var{file-glob-pattern}
5811 @itemx -gfi @var{file-glob-pattern}
5812 @cindex skipping over files via glob-style patterns
5813 Functions in files matching @var{file-glob-pattern} will be skipped
5817 (gdb) skip -gfi utils/*.c
5820 @item -function @var{linespec}
5821 @itemx -fu @var{linespec}
5822 Functions named by @var{linespec} or the function containing the line
5823 named by @var{linespec} will be skipped over when stepping.
5824 @xref{Specify Location}.
5826 @item -rfunction @var{regexp}
5827 @itemx -rfu @var{regexp}
5828 @cindex skipping over functions via regular expressions
5829 Functions whose name matches @var{regexp} will be skipped over when stepping.
5831 This form is useful for complex function names.
5832 For example, there is generally no need to step into C@t{++} @code{std::string}
5833 constructors or destructors. Plus with C@t{++} templates it can be hard to
5834 write out the full name of the function, and often it doesn't matter what
5835 the template arguments are. Specifying the function to be skipped as a
5836 regular expression makes this easier.
5839 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5842 If you want to skip every templated C@t{++} constructor and destructor
5843 in the @code{std} namespace you can do:
5846 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5850 If no options are specified, the function you're currently debugging
5853 @kindex skip function
5854 @item skip function @r{[}@var{linespec}@r{]}
5855 After running this command, the function named by @var{linespec} or the
5856 function containing the line named by @var{linespec} will be skipped over when
5857 stepping. @xref{Specify Location}.
5859 If you do not specify @var{linespec}, the function you're currently debugging
5862 (If you have a function called @code{file} that you want to skip, use
5863 @kbd{skip function file}.)
5866 @item skip file @r{[}@var{filename}@r{]}
5867 After running this command, any function whose source lives in @var{filename}
5868 will be skipped over when stepping.
5871 (gdb) skip file boring.c
5872 File boring.c will be skipped when stepping.
5875 If you do not specify @var{filename}, functions whose source lives in the file
5876 you're currently debugging will be skipped.
5879 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5880 These are the commands for managing your list of skips:
5884 @item info skip @r{[}@var{range}@r{]}
5885 Print details about the specified skip(s). If @var{range} is not specified,
5886 print a table with details about all functions and files marked for skipping.
5887 @code{info skip} prints the following information about each skip:
5891 A number identifying this skip.
5892 @item Enabled or Disabled
5893 Enabled skips are marked with @samp{y}.
5894 Disabled skips are marked with @samp{n}.
5896 If the file name is a @samp{glob} pattern this is @samp{y}.
5897 Otherwise it is @samp{n}.
5899 The name or @samp{glob} pattern of the file to be skipped.
5900 If no file is specified this is @samp{<none>}.
5902 If the function name is a @samp{regular expression} this is @samp{y}.
5903 Otherwise it is @samp{n}.
5905 The name or regular expression of the function to skip.
5906 If no function is specified this is @samp{<none>}.
5910 @item skip delete @r{[}@var{range}@r{]}
5911 Delete the specified skip(s). If @var{range} is not specified, delete all
5915 @item skip enable @r{[}@var{range}@r{]}
5916 Enable the specified skip(s). If @var{range} is not specified, enable all
5919 @kindex skip disable
5920 @item skip disable @r{[}@var{range}@r{]}
5921 Disable the specified skip(s). If @var{range} is not specified, disable all
5924 @kindex set debug skip
5925 @item set debug skip @r{[}on|off@r{]}
5926 Set whether to print the debug output about skipping files and functions.
5928 @kindex show debug skip
5929 @item show debug skip
5930 Show whether the debug output about skipping files and functions is printed.
5938 A signal is an asynchronous event that can happen in a program. The
5939 operating system defines the possible kinds of signals, and gives each
5940 kind a name and a number. For example, in Unix @code{SIGINT} is the
5941 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5942 @code{SIGSEGV} is the signal a program gets from referencing a place in
5943 memory far away from all the areas in use; @code{SIGALRM} occurs when
5944 the alarm clock timer goes off (which happens only if your program has
5945 requested an alarm).
5947 @cindex fatal signals
5948 Some signals, including @code{SIGALRM}, are a normal part of the
5949 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5950 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5951 program has not specified in advance some other way to handle the signal.
5952 @code{SIGINT} does not indicate an error in your program, but it is normally
5953 fatal so it can carry out the purpose of the interrupt: to kill the program.
5955 @value{GDBN} has the ability to detect any occurrence of a signal in your
5956 program. You can tell @value{GDBN} in advance what to do for each kind of
5959 @cindex handling signals
5960 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5961 @code{SIGALRM} be silently passed to your program
5962 (so as not to interfere with their role in the program's functioning)
5963 but to stop your program immediately whenever an error signal happens.
5964 You can change these settings with the @code{handle} command.
5967 @kindex info signals
5971 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5972 handle each one. You can use this to see the signal numbers of all
5973 the defined types of signals.
5975 @item info signals @var{sig}
5976 Similar, but print information only about the specified signal number.
5978 @code{info handle} is an alias for @code{info signals}.
5980 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5981 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5982 for details about this command.
5985 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5986 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5987 can be the number of a signal or its name (with or without the
5988 @samp{SIG} at the beginning); a list of signal numbers of the form
5989 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5990 known signals. Optional arguments @var{keywords}, described below,
5991 say what change to make.
5995 The keywords allowed by the @code{handle} command can be abbreviated.
5996 Their full names are:
6000 @value{GDBN} should not stop your program when this signal happens. It may
6001 still print a message telling you that the signal has come in.
6004 @value{GDBN} should stop your program when this signal happens. This implies
6005 the @code{print} keyword as well.
6008 @value{GDBN} should print a message when this signal happens.
6011 @value{GDBN} should not mention the occurrence of the signal at all. This
6012 implies the @code{nostop} keyword as well.
6016 @value{GDBN} should allow your program to see this signal; your program
6017 can handle the signal, or else it may terminate if the signal is fatal
6018 and not handled. @code{pass} and @code{noignore} are synonyms.
6022 @value{GDBN} should not allow your program to see this signal.
6023 @code{nopass} and @code{ignore} are synonyms.
6027 When a signal stops your program, the signal is not visible to the
6029 continue. Your program sees the signal then, if @code{pass} is in
6030 effect for the signal in question @emph{at that time}. In other words,
6031 after @value{GDBN} reports a signal, you can use the @code{handle}
6032 command with @code{pass} or @code{nopass} to control whether your
6033 program sees that signal when you continue.
6035 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6036 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6037 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6040 You can also use the @code{signal} command to prevent your program from
6041 seeing a signal, or cause it to see a signal it normally would not see,
6042 or to give it any signal at any time. For example, if your program stopped
6043 due to some sort of memory reference error, you might store correct
6044 values into the erroneous variables and continue, hoping to see more
6045 execution; but your program would probably terminate immediately as
6046 a result of the fatal signal once it saw the signal. To prevent this,
6047 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6050 @cindex stepping and signal handlers
6051 @anchor{stepping and signal handlers}
6053 @value{GDBN} optimizes for stepping the mainline code. If a signal
6054 that has @code{handle nostop} and @code{handle pass} set arrives while
6055 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6056 in progress, @value{GDBN} lets the signal handler run and then resumes
6057 stepping the mainline code once the signal handler returns. In other
6058 words, @value{GDBN} steps over the signal handler. This prevents
6059 signals that you've specified as not interesting (with @code{handle
6060 nostop}) from changing the focus of debugging unexpectedly. Note that
6061 the signal handler itself may still hit a breakpoint, stop for another
6062 signal that has @code{handle stop} in effect, or for any other event
6063 that normally results in stopping the stepping command sooner. Also
6064 note that @value{GDBN} still informs you that the program received a
6065 signal if @code{handle print} is set.
6067 @anchor{stepping into signal handlers}
6069 If you set @code{handle pass} for a signal, and your program sets up a
6070 handler for it, then issuing a stepping command, such as @code{step}
6071 or @code{stepi}, when your program is stopped due to the signal will
6072 step @emph{into} the signal handler (if the target supports that).
6074 Likewise, if you use the @code{queue-signal} command to queue a signal
6075 to be delivered to the current thread when execution of the thread
6076 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6077 stepping command will step into the signal handler.
6079 Here's an example, using @code{stepi} to step to the first instruction
6080 of @code{SIGUSR1}'s handler:
6083 (@value{GDBP}) handle SIGUSR1
6084 Signal Stop Print Pass to program Description
6085 SIGUSR1 Yes Yes Yes User defined signal 1
6089 Program received signal SIGUSR1, User defined signal 1.
6090 main () sigusr1.c:28
6093 sigusr1_handler () at sigusr1.c:9
6097 The same, but using @code{queue-signal} instead of waiting for the
6098 program to receive the signal first:
6103 (@value{GDBP}) queue-signal SIGUSR1
6105 sigusr1_handler () at sigusr1.c:9
6110 @cindex extra signal information
6111 @anchor{extra signal information}
6113 On some targets, @value{GDBN} can inspect extra signal information
6114 associated with the intercepted signal, before it is actually
6115 delivered to the program being debugged. This information is exported
6116 by the convenience variable @code{$_siginfo}, and consists of data
6117 that is passed by the kernel to the signal handler at the time of the
6118 receipt of a signal. The data type of the information itself is
6119 target dependent. You can see the data type using the @code{ptype
6120 $_siginfo} command. On Unix systems, it typically corresponds to the
6121 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6124 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6125 referenced address that raised a segmentation fault.
6129 (@value{GDBP}) continue
6130 Program received signal SIGSEGV, Segmentation fault.
6131 0x0000000000400766 in main ()
6133 (@value{GDBP}) ptype $_siginfo
6140 struct @{...@} _kill;
6141 struct @{...@} _timer;
6143 struct @{...@} _sigchld;
6144 struct @{...@} _sigfault;
6145 struct @{...@} _sigpoll;
6148 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6152 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6153 $1 = (void *) 0x7ffff7ff7000
6157 Depending on target support, @code{$_siginfo} may also be writable.
6159 @cindex Intel MPX boundary violations
6160 @cindex boundary violations, Intel MPX
6161 On some targets, a @code{SIGSEGV} can be caused by a boundary
6162 violation, i.e., accessing an address outside of the allowed range.
6163 In those cases @value{GDBN} may displays additional information,
6164 depending on how @value{GDBN} has been told to handle the signal.
6165 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6166 kind: "Upper" or "Lower", the memory address accessed and the
6167 bounds, while with @code{handle nostop SIGSEGV} no additional
6168 information is displayed.
6170 The usual output of a segfault is:
6172 Program received signal SIGSEGV, Segmentation fault
6173 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6174 68 value = *(p + len);
6177 While a bound violation is presented as:
6179 Program received signal SIGSEGV, Segmentation fault
6180 Upper bound violation while accessing address 0x7fffffffc3b3
6181 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6182 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6183 68 value = *(p + len);
6187 @section Stopping and Starting Multi-thread Programs
6189 @cindex stopped threads
6190 @cindex threads, stopped
6192 @cindex continuing threads
6193 @cindex threads, continuing
6195 @value{GDBN} supports debugging programs with multiple threads
6196 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6197 are two modes of controlling execution of your program within the
6198 debugger. In the default mode, referred to as @dfn{all-stop mode},
6199 when any thread in your program stops (for example, at a breakpoint
6200 or while being stepped), all other threads in the program are also stopped by
6201 @value{GDBN}. On some targets, @value{GDBN} also supports
6202 @dfn{non-stop mode}, in which other threads can continue to run freely while
6203 you examine the stopped thread in the debugger.
6206 * All-Stop Mode:: All threads stop when GDB takes control
6207 * Non-Stop Mode:: Other threads continue to execute
6208 * Background Execution:: Running your program asynchronously
6209 * Thread-Specific Breakpoints:: Controlling breakpoints
6210 * Interrupted System Calls:: GDB may interfere with system calls
6211 * Observer Mode:: GDB does not alter program behavior
6215 @subsection All-Stop Mode
6217 @cindex all-stop mode
6219 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6220 @emph{all} threads of execution stop, not just the current thread. This
6221 allows you to examine the overall state of the program, including
6222 switching between threads, without worrying that things may change
6225 Conversely, whenever you restart the program, @emph{all} threads start
6226 executing. @emph{This is true even when single-stepping} with commands
6227 like @code{step} or @code{next}.
6229 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6230 Since thread scheduling is up to your debugging target's operating
6231 system (not controlled by @value{GDBN}), other threads may
6232 execute more than one statement while the current thread completes a
6233 single step. Moreover, in general other threads stop in the middle of a
6234 statement, rather than at a clean statement boundary, when the program
6237 You might even find your program stopped in another thread after
6238 continuing or even single-stepping. This happens whenever some other
6239 thread runs into a breakpoint, a signal, or an exception before the
6240 first thread completes whatever you requested.
6242 @cindex automatic thread selection
6243 @cindex switching threads automatically
6244 @cindex threads, automatic switching
6245 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6246 signal, it automatically selects the thread where that breakpoint or
6247 signal happened. @value{GDBN} alerts you to the context switch with a
6248 message such as @samp{[Switching to Thread @var{n}]} to identify the
6251 On some OSes, you can modify @value{GDBN}'s default behavior by
6252 locking the OS scheduler to allow only a single thread to run.
6255 @item set scheduler-locking @var{mode}
6256 @cindex scheduler locking mode
6257 @cindex lock scheduler
6258 Set the scheduler locking mode. It applies to normal execution,
6259 record mode, and replay mode. If it is @code{off}, then there is no
6260 locking and any thread may run at any time. If @code{on}, then only
6261 the current thread may run when the inferior is resumed. The
6262 @code{step} mode optimizes for single-stepping; it prevents other
6263 threads from preempting the current thread while you are stepping, so
6264 that the focus of debugging does not change unexpectedly. Other
6265 threads never get a chance to run when you step, and they are
6266 completely free to run when you use commands like @samp{continue},
6267 @samp{until}, or @samp{finish}. However, unless another thread hits a
6268 breakpoint during its timeslice, @value{GDBN} does not change the
6269 current thread away from the thread that you are debugging. The
6270 @code{replay} mode behaves like @code{off} in record mode and like
6271 @code{on} in replay mode.
6273 @item show scheduler-locking
6274 Display the current scheduler locking mode.
6277 @cindex resume threads of multiple processes simultaneously
6278 By default, when you issue one of the execution commands such as
6279 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6280 threads of the current inferior to run. For example, if @value{GDBN}
6281 is attached to two inferiors, each with two threads, the
6282 @code{continue} command resumes only the two threads of the current
6283 inferior. This is useful, for example, when you debug a program that
6284 forks and you want to hold the parent stopped (so that, for instance,
6285 it doesn't run to exit), while you debug the child. In other
6286 situations, you may not be interested in inspecting the current state
6287 of any of the processes @value{GDBN} is attached to, and you may want
6288 to resume them all until some breakpoint is hit. In the latter case,
6289 you can instruct @value{GDBN} to allow all threads of all the
6290 inferiors to run with the @w{@code{set schedule-multiple}} command.
6293 @kindex set schedule-multiple
6294 @item set schedule-multiple
6295 Set the mode for allowing threads of multiple processes to be resumed
6296 when an execution command is issued. When @code{on}, all threads of
6297 all processes are allowed to run. When @code{off}, only the threads
6298 of the current process are resumed. The default is @code{off}. The
6299 @code{scheduler-locking} mode takes precedence when set to @code{on},
6300 or while you are stepping and set to @code{step}.
6302 @item show schedule-multiple
6303 Display the current mode for resuming the execution of threads of
6308 @subsection Non-Stop Mode
6310 @cindex non-stop mode
6312 @c This section is really only a place-holder, and needs to be expanded
6313 @c with more details.
6315 For some multi-threaded targets, @value{GDBN} supports an optional
6316 mode of operation in which you can examine stopped program threads in
6317 the debugger while other threads continue to execute freely. This
6318 minimizes intrusion when debugging live systems, such as programs
6319 where some threads have real-time constraints or must continue to
6320 respond to external events. This is referred to as @dfn{non-stop} mode.
6322 In non-stop mode, when a thread stops to report a debugging event,
6323 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6324 threads as well, in contrast to the all-stop mode behavior. Additionally,
6325 execution commands such as @code{continue} and @code{step} apply by default
6326 only to the current thread in non-stop mode, rather than all threads as
6327 in all-stop mode. This allows you to control threads explicitly in
6328 ways that are not possible in all-stop mode --- for example, stepping
6329 one thread while allowing others to run freely, stepping
6330 one thread while holding all others stopped, or stepping several threads
6331 independently and simultaneously.
6333 To enter non-stop mode, use this sequence of commands before you run
6334 or attach to your program:
6337 # If using the CLI, pagination breaks non-stop.
6340 # Finally, turn it on!
6344 You can use these commands to manipulate the non-stop mode setting:
6347 @kindex set non-stop
6348 @item set non-stop on
6349 Enable selection of non-stop mode.
6350 @item set non-stop off
6351 Disable selection of non-stop mode.
6352 @kindex show non-stop
6354 Show the current non-stop enablement setting.
6357 Note these commands only reflect whether non-stop mode is enabled,
6358 not whether the currently-executing program is being run in non-stop mode.
6359 In particular, the @code{set non-stop} preference is only consulted when
6360 @value{GDBN} starts or connects to the target program, and it is generally
6361 not possible to switch modes once debugging has started. Furthermore,
6362 since not all targets support non-stop mode, even when you have enabled
6363 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6366 In non-stop mode, all execution commands apply only to the current thread
6367 by default. That is, @code{continue} only continues one thread.
6368 To continue all threads, issue @code{continue -a} or @code{c -a}.
6370 You can use @value{GDBN}'s background execution commands
6371 (@pxref{Background Execution}) to run some threads in the background
6372 while you continue to examine or step others from @value{GDBN}.
6373 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6374 always executed asynchronously in non-stop mode.
6376 Suspending execution is done with the @code{interrupt} command when
6377 running in the background, or @kbd{Ctrl-c} during foreground execution.
6378 In all-stop mode, this stops the whole process;
6379 but in non-stop mode the interrupt applies only to the current thread.
6380 To stop the whole program, use @code{interrupt -a}.
6382 Other execution commands do not currently support the @code{-a} option.
6384 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6385 that thread current, as it does in all-stop mode. This is because the
6386 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6387 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6388 changed to a different thread just as you entered a command to operate on the
6389 previously current thread.
6391 @node Background Execution
6392 @subsection Background Execution
6394 @cindex foreground execution
6395 @cindex background execution
6396 @cindex asynchronous execution
6397 @cindex execution, foreground, background and asynchronous
6399 @value{GDBN}'s execution commands have two variants: the normal
6400 foreground (synchronous) behavior, and a background
6401 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6402 the program to report that some thread has stopped before prompting for
6403 another command. In background execution, @value{GDBN} immediately gives
6404 a command prompt so that you can issue other commands while your program runs.
6406 If the target doesn't support async mode, @value{GDBN} issues an error
6407 message if you attempt to use the background execution commands.
6409 @cindex @code{&}, background execution of commands
6410 To specify background execution, add a @code{&} to the command. For example,
6411 the background form of the @code{continue} command is @code{continue&}, or
6412 just @code{c&}. The execution commands that accept background execution
6418 @xref{Starting, , Starting your Program}.
6422 @xref{Attach, , Debugging an Already-running Process}.
6426 @xref{Continuing and Stepping, step}.
6430 @xref{Continuing and Stepping, stepi}.
6434 @xref{Continuing and Stepping, next}.
6438 @xref{Continuing and Stepping, nexti}.
6442 @xref{Continuing and Stepping, continue}.
6446 @xref{Continuing and Stepping, finish}.
6450 @xref{Continuing and Stepping, until}.
6454 Background execution is especially useful in conjunction with non-stop
6455 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6456 However, you can also use these commands in the normal all-stop mode with
6457 the restriction that you cannot issue another execution command until the
6458 previous one finishes. Examples of commands that are valid in all-stop
6459 mode while the program is running include @code{help} and @code{info break}.
6461 You can interrupt your program while it is running in the background by
6462 using the @code{interrupt} command.
6469 Suspend execution of the running program. In all-stop mode,
6470 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6471 only the current thread. To stop the whole program in non-stop mode,
6472 use @code{interrupt -a}.
6475 @node Thread-Specific Breakpoints
6476 @subsection Thread-Specific Breakpoints
6478 When your program has multiple threads (@pxref{Threads,, Debugging
6479 Programs with Multiple Threads}), you can choose whether to set
6480 breakpoints on all threads, or on a particular thread.
6483 @cindex breakpoints and threads
6484 @cindex thread breakpoints
6485 @kindex break @dots{} thread @var{thread-id}
6486 @item break @var{location} thread @var{thread-id}
6487 @itemx break @var{location} thread @var{thread-id} if @dots{}
6488 @var{location} specifies source lines; there are several ways of
6489 writing them (@pxref{Specify Location}), but the effect is always to
6490 specify some source line.
6492 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6493 to specify that you only want @value{GDBN} to stop the program when a
6494 particular thread reaches this breakpoint. The @var{thread-id} specifier
6495 is one of the thread identifiers assigned by @value{GDBN}, shown
6496 in the first column of the @samp{info threads} display.
6498 If you do not specify @samp{thread @var{thread-id}} when you set a
6499 breakpoint, the breakpoint applies to @emph{all} threads of your
6502 You can use the @code{thread} qualifier on conditional breakpoints as
6503 well; in this case, place @samp{thread @var{thread-id}} before or
6504 after the breakpoint condition, like this:
6507 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6512 Thread-specific breakpoints are automatically deleted when
6513 @value{GDBN} detects the corresponding thread is no longer in the
6514 thread list. For example:
6518 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6521 There are several ways for a thread to disappear, such as a regular
6522 thread exit, but also when you detach from the process with the
6523 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6524 Process}), or if @value{GDBN} loses the remote connection
6525 (@pxref{Remote Debugging}), etc. Note that with some targets,
6526 @value{GDBN} is only able to detect a thread has exited when the user
6527 explictly asks for the thread list with the @code{info threads}
6530 @node Interrupted System Calls
6531 @subsection Interrupted System Calls
6533 @cindex thread breakpoints and system calls
6534 @cindex system calls and thread breakpoints
6535 @cindex premature return from system calls
6536 There is an unfortunate side effect when using @value{GDBN} to debug
6537 multi-threaded programs. If one thread stops for a
6538 breakpoint, or for some other reason, and another thread is blocked in a
6539 system call, then the system call may return prematurely. This is a
6540 consequence of the interaction between multiple threads and the signals
6541 that @value{GDBN} uses to implement breakpoints and other events that
6544 To handle this problem, your program should check the return value of
6545 each system call and react appropriately. This is good programming
6548 For example, do not write code like this:
6554 The call to @code{sleep} will return early if a different thread stops
6555 at a breakpoint or for some other reason.
6557 Instead, write this:
6562 unslept = sleep (unslept);
6565 A system call is allowed to return early, so the system is still
6566 conforming to its specification. But @value{GDBN} does cause your
6567 multi-threaded program to behave differently than it would without
6570 Also, @value{GDBN} uses internal breakpoints in the thread library to
6571 monitor certain events such as thread creation and thread destruction.
6572 When such an event happens, a system call in another thread may return
6573 prematurely, even though your program does not appear to stop.
6576 @subsection Observer Mode
6578 If you want to build on non-stop mode and observe program behavior
6579 without any chance of disruption by @value{GDBN}, you can set
6580 variables to disable all of the debugger's attempts to modify state,
6581 whether by writing memory, inserting breakpoints, etc. These operate
6582 at a low level, intercepting operations from all commands.
6584 When all of these are set to @code{off}, then @value{GDBN} is said to
6585 be @dfn{observer mode}. As a convenience, the variable
6586 @code{observer} can be set to disable these, plus enable non-stop
6589 Note that @value{GDBN} will not prevent you from making nonsensical
6590 combinations of these settings. For instance, if you have enabled
6591 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6592 then breakpoints that work by writing trap instructions into the code
6593 stream will still not be able to be placed.
6598 @item set observer on
6599 @itemx set observer off
6600 When set to @code{on}, this disables all the permission variables
6601 below (except for @code{insert-fast-tracepoints}), plus enables
6602 non-stop debugging. Setting this to @code{off} switches back to
6603 normal debugging, though remaining in non-stop mode.
6606 Show whether observer mode is on or off.
6608 @kindex may-write-registers
6609 @item set may-write-registers on
6610 @itemx set may-write-registers off
6611 This controls whether @value{GDBN} will attempt to alter the values of
6612 registers, such as with assignment expressions in @code{print}, or the
6613 @code{jump} command. It defaults to @code{on}.
6615 @item show may-write-registers
6616 Show the current permission to write registers.
6618 @kindex may-write-memory
6619 @item set may-write-memory on
6620 @itemx set may-write-memory off
6621 This controls whether @value{GDBN} will attempt to alter the contents
6622 of memory, such as with assignment expressions in @code{print}. It
6623 defaults to @code{on}.
6625 @item show may-write-memory
6626 Show the current permission to write memory.
6628 @kindex may-insert-breakpoints
6629 @item set may-insert-breakpoints on
6630 @itemx set may-insert-breakpoints off
6631 This controls whether @value{GDBN} will attempt to insert breakpoints.
6632 This affects all breakpoints, including internal breakpoints defined
6633 by @value{GDBN}. It defaults to @code{on}.
6635 @item show may-insert-breakpoints
6636 Show the current permission to insert breakpoints.
6638 @kindex may-insert-tracepoints
6639 @item set may-insert-tracepoints on
6640 @itemx set may-insert-tracepoints off
6641 This controls whether @value{GDBN} will attempt to insert (regular)
6642 tracepoints at the beginning of a tracing experiment. It affects only
6643 non-fast tracepoints, fast tracepoints being under the control of
6644 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6646 @item show may-insert-tracepoints
6647 Show the current permission to insert tracepoints.
6649 @kindex may-insert-fast-tracepoints
6650 @item set may-insert-fast-tracepoints on
6651 @itemx set may-insert-fast-tracepoints off
6652 This controls whether @value{GDBN} will attempt to insert fast
6653 tracepoints at the beginning of a tracing experiment. It affects only
6654 fast tracepoints, regular (non-fast) tracepoints being under the
6655 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6657 @item show may-insert-fast-tracepoints
6658 Show the current permission to insert fast tracepoints.
6660 @kindex may-interrupt
6661 @item set may-interrupt on
6662 @itemx set may-interrupt off
6663 This controls whether @value{GDBN} will attempt to interrupt or stop
6664 program execution. When this variable is @code{off}, the
6665 @code{interrupt} command will have no effect, nor will
6666 @kbd{Ctrl-c}. It defaults to @code{on}.
6668 @item show may-interrupt
6669 Show the current permission to interrupt or stop the program.
6673 @node Reverse Execution
6674 @chapter Running programs backward
6675 @cindex reverse execution
6676 @cindex running programs backward
6678 When you are debugging a program, it is not unusual to realize that
6679 you have gone too far, and some event of interest has already happened.
6680 If the target environment supports it, @value{GDBN} can allow you to
6681 ``rewind'' the program by running it backward.
6683 A target environment that supports reverse execution should be able
6684 to ``undo'' the changes in machine state that have taken place as the
6685 program was executing normally. Variables, registers etc.@: should
6686 revert to their previous values. Obviously this requires a great
6687 deal of sophistication on the part of the target environment; not
6688 all target environments can support reverse execution.
6690 When a program is executed in reverse, the instructions that
6691 have most recently been executed are ``un-executed'', in reverse
6692 order. The program counter runs backward, following the previous
6693 thread of execution in reverse. As each instruction is ``un-executed'',
6694 the values of memory and/or registers that were changed by that
6695 instruction are reverted to their previous states. After executing
6696 a piece of source code in reverse, all side effects of that code
6697 should be ``undone'', and all variables should be returned to their
6698 prior values@footnote{
6699 Note that some side effects are easier to undo than others. For instance,
6700 memory and registers are relatively easy, but device I/O is hard. Some
6701 targets may be able undo things like device I/O, and some may not.
6703 The contract between @value{GDBN} and the reverse executing target
6704 requires only that the target do something reasonable when
6705 @value{GDBN} tells it to execute backwards, and then report the
6706 results back to @value{GDBN}. Whatever the target reports back to
6707 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6708 assumes that the memory and registers that the target reports are in a
6709 consistant state, but @value{GDBN} accepts whatever it is given.
6712 On some platforms, @value{GDBN} has built-in support for reverse
6713 execution, activated with the @code{record} or @code{record btrace}
6714 commands. @xref{Process Record and Replay}. Some remote targets,
6715 typically full system emulators, support reverse execution directly
6716 without requiring any special command.
6718 If you are debugging in a target environment that supports
6719 reverse execution, @value{GDBN} provides the following commands.
6722 @kindex reverse-continue
6723 @kindex rc @r{(@code{reverse-continue})}
6724 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6725 @itemx rc @r{[}@var{ignore-count}@r{]}
6726 Beginning at the point where your program last stopped, start executing
6727 in reverse. Reverse execution will stop for breakpoints and synchronous
6728 exceptions (signals), just like normal execution. Behavior of
6729 asynchronous signals depends on the target environment.
6731 @kindex reverse-step
6732 @kindex rs @r{(@code{step})}
6733 @item reverse-step @r{[}@var{count}@r{]}
6734 Run the program backward until control reaches the start of a
6735 different source line; then stop it, and return control to @value{GDBN}.
6737 Like the @code{step} command, @code{reverse-step} will only stop
6738 at the beginning of a source line. It ``un-executes'' the previously
6739 executed source line. If the previous source line included calls to
6740 debuggable functions, @code{reverse-step} will step (backward) into
6741 the called function, stopping at the beginning of the @emph{last}
6742 statement in the called function (typically a return statement).
6744 Also, as with the @code{step} command, if non-debuggable functions are
6745 called, @code{reverse-step} will run thru them backward without stopping.
6747 @kindex reverse-stepi
6748 @kindex rsi @r{(@code{reverse-stepi})}
6749 @item reverse-stepi @r{[}@var{count}@r{]}
6750 Reverse-execute one machine instruction. Note that the instruction
6751 to be reverse-executed is @emph{not} the one pointed to by the program
6752 counter, but the instruction executed prior to that one. For instance,
6753 if the last instruction was a jump, @code{reverse-stepi} will take you
6754 back from the destination of the jump to the jump instruction itself.
6756 @kindex reverse-next
6757 @kindex rn @r{(@code{reverse-next})}
6758 @item reverse-next @r{[}@var{count}@r{]}
6759 Run backward to the beginning of the previous line executed in
6760 the current (innermost) stack frame. If the line contains function
6761 calls, they will be ``un-executed'' without stopping. Starting from
6762 the first line of a function, @code{reverse-next} will take you back
6763 to the caller of that function, @emph{before} the function was called,
6764 just as the normal @code{next} command would take you from the last
6765 line of a function back to its return to its caller
6766 @footnote{Unless the code is too heavily optimized.}.
6768 @kindex reverse-nexti
6769 @kindex rni @r{(@code{reverse-nexti})}
6770 @item reverse-nexti @r{[}@var{count}@r{]}
6771 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6772 in reverse, except that called functions are ``un-executed'' atomically.
6773 That is, if the previously executed instruction was a return from
6774 another function, @code{reverse-nexti} will continue to execute
6775 in reverse until the call to that function (from the current stack
6778 @kindex reverse-finish
6779 @item reverse-finish
6780 Just as the @code{finish} command takes you to the point where the
6781 current function returns, @code{reverse-finish} takes you to the point
6782 where it was called. Instead of ending up at the end of the current
6783 function invocation, you end up at the beginning.
6785 @kindex set exec-direction
6786 @item set exec-direction
6787 Set the direction of target execution.
6788 @item set exec-direction reverse
6789 @cindex execute forward or backward in time
6790 @value{GDBN} will perform all execution commands in reverse, until the
6791 exec-direction mode is changed to ``forward''. Affected commands include
6792 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6793 command cannot be used in reverse mode.
6794 @item set exec-direction forward
6795 @value{GDBN} will perform all execution commands in the normal fashion.
6796 This is the default.
6800 @node Process Record and Replay
6801 @chapter Recording Inferior's Execution and Replaying It
6802 @cindex process record and replay
6803 @cindex recording inferior's execution and replaying it
6805 On some platforms, @value{GDBN} provides a special @dfn{process record
6806 and replay} target that can record a log of the process execution, and
6807 replay it later with both forward and reverse execution commands.
6810 When this target is in use, if the execution log includes the record
6811 for the next instruction, @value{GDBN} will debug in @dfn{replay
6812 mode}. In the replay mode, the inferior does not really execute code
6813 instructions. Instead, all the events that normally happen during
6814 code execution are taken from the execution log. While code is not
6815 really executed in replay mode, the values of registers (including the
6816 program counter register) and the memory of the inferior are still
6817 changed as they normally would. Their contents are taken from the
6821 If the record for the next instruction is not in the execution log,
6822 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6823 inferior executes normally, and @value{GDBN} records the execution log
6826 The process record and replay target supports reverse execution
6827 (@pxref{Reverse Execution}), even if the platform on which the
6828 inferior runs does not. However, the reverse execution is limited in
6829 this case by the range of the instructions recorded in the execution
6830 log. In other words, reverse execution on platforms that don't
6831 support it directly can only be done in the replay mode.
6833 When debugging in the reverse direction, @value{GDBN} will work in
6834 replay mode as long as the execution log includes the record for the
6835 previous instruction; otherwise, it will work in record mode, if the
6836 platform supports reverse execution, or stop if not.
6838 Currently, process record and replay is supported on ARM, Aarch64,
6839 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
6840 GNU/Linux. Process record and replay can be used both when native
6841 debugging, and when remote debugging via @code{gdbserver}.
6843 For architecture environments that support process record and replay,
6844 @value{GDBN} provides the following commands:
6847 @kindex target record
6848 @kindex target record-full
6849 @kindex target record-btrace
6852 @kindex record btrace
6853 @kindex record btrace bts
6854 @kindex record btrace pt
6860 @kindex rec btrace bts
6861 @kindex rec btrace pt
6864 @item record @var{method}
6865 This command starts the process record and replay target. The
6866 recording method can be specified as parameter. Without a parameter
6867 the command uses the @code{full} recording method. The following
6868 recording methods are available:
6872 Full record/replay recording using @value{GDBN}'s software record and
6873 replay implementation. This method allows replaying and reverse
6876 @item btrace @var{format}
6877 Hardware-supported instruction recording, supported on Intel
6878 processors. This method does not record data. Further, the data is
6879 collected in a ring buffer so old data will be overwritten when the
6880 buffer is full. It allows limited reverse execution. Variables and
6881 registers are not available during reverse execution. In remote
6882 debugging, recording continues on disconnect. Recorded data can be
6883 inspected after reconnecting. The recording may be stopped using
6886 The recording format can be specified as parameter. Without a parameter
6887 the command chooses the recording format. The following recording
6888 formats are available:
6892 @cindex branch trace store
6893 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6894 this format, the processor stores a from/to record for each executed
6895 branch in the btrace ring buffer.
6898 @cindex Intel Processor Trace
6899 Use the @dfn{Intel Processor Trace} recording format. In this
6900 format, the processor stores the execution trace in a compressed form
6901 that is afterwards decoded by @value{GDBN}.
6903 The trace can be recorded with very low overhead. The compressed
6904 trace format also allows small trace buffers to already contain a big
6905 number of instructions compared to @acronym{BTS}.
6907 Decoding the recorded execution trace, on the other hand, is more
6908 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6909 increased number of instructions to process. You should increase the
6910 buffer-size with care.
6913 Not all recording formats may be available on all processors.
6916 The process record and replay target can only debug a process that is
6917 already running. Therefore, you need first to start the process with
6918 the @kbd{run} or @kbd{start} commands, and then start the recording
6919 with the @kbd{record @var{method}} command.
6921 @cindex displaced stepping, and process record and replay
6922 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6923 will be automatically disabled when process record and replay target
6924 is started. That's because the process record and replay target
6925 doesn't support displaced stepping.
6927 @cindex non-stop mode, and process record and replay
6928 @cindex asynchronous execution, and process record and replay
6929 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6930 the asynchronous execution mode (@pxref{Background Execution}), not
6931 all recording methods are available. The @code{full} recording method
6932 does not support these two modes.
6937 Stop the process record and replay target. When process record and
6938 replay target stops, the entire execution log will be deleted and the
6939 inferior will either be terminated, or will remain in its final state.
6941 When you stop the process record and replay target in record mode (at
6942 the end of the execution log), the inferior will be stopped at the
6943 next instruction that would have been recorded. In other words, if
6944 you record for a while and then stop recording, the inferior process
6945 will be left in the same state as if the recording never happened.
6947 On the other hand, if the process record and replay target is stopped
6948 while in replay mode (that is, not at the end of the execution log,
6949 but at some earlier point), the inferior process will become ``live''
6950 at that earlier state, and it will then be possible to continue the
6951 usual ``live'' debugging of the process from that state.
6953 When the inferior process exits, or @value{GDBN} detaches from it,
6954 process record and replay target will automatically stop itself.
6958 Go to a specific location in the execution log. There are several
6959 ways to specify the location to go to:
6962 @item record goto begin
6963 @itemx record goto start
6964 Go to the beginning of the execution log.
6966 @item record goto end
6967 Go to the end of the execution log.
6969 @item record goto @var{n}
6970 Go to instruction number @var{n} in the execution log.
6974 @item record save @var{filename}
6975 Save the execution log to a file @file{@var{filename}}.
6976 Default filename is @file{gdb_record.@var{process_id}}, where
6977 @var{process_id} is the process ID of the inferior.
6979 This command may not be available for all recording methods.
6981 @kindex record restore
6982 @item record restore @var{filename}
6983 Restore the execution log from a file @file{@var{filename}}.
6984 File must have been created with @code{record save}.
6986 @kindex set record full
6987 @item set record full insn-number-max @var{limit}
6988 @itemx set record full insn-number-max unlimited
6989 Set the limit of instructions to be recorded for the @code{full}
6990 recording method. Default value is 200000.
6992 If @var{limit} is a positive number, then @value{GDBN} will start
6993 deleting instructions from the log once the number of the record
6994 instructions becomes greater than @var{limit}. For every new recorded
6995 instruction, @value{GDBN} will delete the earliest recorded
6996 instruction to keep the number of recorded instructions at the limit.
6997 (Since deleting recorded instructions loses information, @value{GDBN}
6998 lets you control what happens when the limit is reached, by means of
6999 the @code{stop-at-limit} option, described below.)
7001 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7002 delete recorded instructions from the execution log. The number of
7003 recorded instructions is limited only by the available memory.
7005 @kindex show record full
7006 @item show record full insn-number-max
7007 Show the limit of instructions to be recorded with the @code{full}
7010 @item set record full stop-at-limit
7011 Control the behavior of the @code{full} recording method when the
7012 number of recorded instructions reaches the limit. If ON (the
7013 default), @value{GDBN} will stop when the limit is reached for the
7014 first time and ask you whether you want to stop the inferior or
7015 continue running it and recording the execution log. If you decide
7016 to continue recording, each new recorded instruction will cause the
7017 oldest one to be deleted.
7019 If this option is OFF, @value{GDBN} will automatically delete the
7020 oldest record to make room for each new one, without asking.
7022 @item show record full stop-at-limit
7023 Show the current setting of @code{stop-at-limit}.
7025 @item set record full memory-query
7026 Control the behavior when @value{GDBN} is unable to record memory
7027 changes caused by an instruction for the @code{full} recording method.
7028 If ON, @value{GDBN} will query whether to stop the inferior in that
7031 If this option is OFF (the default), @value{GDBN} will automatically
7032 ignore the effect of such instructions on memory. Later, when
7033 @value{GDBN} replays this execution log, it will mark the log of this
7034 instruction as not accessible, and it will not affect the replay
7037 @item show record full memory-query
7038 Show the current setting of @code{memory-query}.
7040 @kindex set record btrace
7041 The @code{btrace} record target does not trace data. As a
7042 convenience, when replaying, @value{GDBN} reads read-only memory off
7043 the live program directly, assuming that the addresses of the
7044 read-only areas don't change. This for example makes it possible to
7045 disassemble code while replaying, but not to print variables.
7046 In some cases, being able to inspect variables might be useful.
7047 You can use the following command for that:
7049 @item set record btrace replay-memory-access
7050 Control the behavior of the @code{btrace} recording method when
7051 accessing memory during replay. If @code{read-only} (the default),
7052 @value{GDBN} will only allow accesses to read-only memory.
7053 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7054 and to read-write memory. Beware that the accessed memory corresponds
7055 to the live target and not necessarily to the current replay
7058 @item set record btrace cpu @var{identifier}
7059 Set the processor to be used for enabling workarounds for processor
7060 errata when decoding the trace.
7062 Processor errata are defects in processor operation, caused by its
7063 design or manufacture. They can cause a trace not to match the
7064 specification. This, in turn, may cause trace decode to fail.
7065 @value{GDBN} can detect erroneous trace packets and correct them, thus
7066 avoiding the decoding failures. These corrections are known as
7067 @dfn{errata workarounds}, and are enabled based on the processor on
7068 which the trace was recorded.
7070 By default, @value{GDBN} attempts to detect the processor
7071 automatically, and apply the necessary workarounds for it. However,
7072 you may need to specify the processor if @value{GDBN} does not yet
7073 support it. This command allows you to do that, and also allows to
7074 disable the workarounds.
7076 The argument @var{identifier} identifies the @sc{cpu} and is of the
7077 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7078 there are two special identifiers, @code{none} and @code{auto}
7081 The following vendor identifiers and corresponding processor
7082 identifiers are currently supported:
7084 @multitable @columnfractions .1 .9
7087 @tab @var{family}/@var{model}[/@var{stepping}]
7091 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7092 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7094 If @var{identifier} is @code{auto}, enable errata workarounds for the
7095 processor on which the trace was recorded. If @var{identifier} is
7096 @code{none}, errata workarounds are disabled.
7098 For example, when using an old @value{GDBN} on a new system, decode
7099 may fail because @value{GDBN} does not support the new processor. It
7100 often suffices to specify an older processor that @value{GDBN}
7105 Active record target: record-btrace
7106 Recording format: Intel Processor Trace.
7108 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7109 (gdb) set record btrace cpu intel:6/158
7111 Active record target: record-btrace
7112 Recording format: Intel Processor Trace.
7114 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7117 @kindex show record btrace
7118 @item show record btrace replay-memory-access
7119 Show the current setting of @code{replay-memory-access}.
7121 @item show record btrace cpu
7122 Show the processor to be used for enabling trace decode errata
7125 @kindex set record btrace bts
7126 @item set record btrace bts buffer-size @var{size}
7127 @itemx set record btrace bts buffer-size unlimited
7128 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7129 format. Default is 64KB.
7131 If @var{size} is a positive number, then @value{GDBN} will try to
7132 allocate a buffer of at least @var{size} bytes for each new thread
7133 that uses the btrace recording method and the @acronym{BTS} format.
7134 The actually obtained buffer size may differ from the requested
7135 @var{size}. Use the @code{info record} command to see the actual
7136 buffer size for each thread that uses the btrace recording method and
7137 the @acronym{BTS} format.
7139 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7140 allocate a buffer of 4MB.
7142 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7143 also need longer to process the branch trace data before it can be used.
7145 @item show record btrace bts buffer-size @var{size}
7146 Show the current setting of the requested ring buffer size for branch
7147 tracing in @acronym{BTS} format.
7149 @kindex set record btrace pt
7150 @item set record btrace pt buffer-size @var{size}
7151 @itemx set record btrace pt buffer-size unlimited
7152 Set the requested ring buffer size for branch tracing in Intel
7153 Processor Trace format. Default is 16KB.
7155 If @var{size} is a positive number, then @value{GDBN} will try to
7156 allocate a buffer of at least @var{size} bytes for each new thread
7157 that uses the btrace recording method and the Intel Processor Trace
7158 format. The actually obtained buffer size may differ from the
7159 requested @var{size}. Use the @code{info record} command to see the
7160 actual buffer size for each thread.
7162 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7163 allocate a buffer of 4MB.
7165 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7166 also need longer to process the branch trace data before it can be used.
7168 @item show record btrace pt buffer-size @var{size}
7169 Show the current setting of the requested ring buffer size for branch
7170 tracing in Intel Processor Trace format.
7174 Show various statistics about the recording depending on the recording
7179 For the @code{full} recording method, it shows the state of process
7180 record and its in-memory execution log buffer, including:
7184 Whether in record mode or replay mode.
7186 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7188 Highest recorded instruction number.
7190 Current instruction about to be replayed (if in replay mode).
7192 Number of instructions contained in the execution log.
7194 Maximum number of instructions that may be contained in the execution log.
7198 For the @code{btrace} recording method, it shows:
7204 Number of instructions that have been recorded.
7206 Number of blocks of sequential control-flow formed by the recorded
7209 Whether in record mode or replay mode.
7212 For the @code{bts} recording format, it also shows:
7215 Size of the perf ring buffer.
7218 For the @code{pt} recording format, it also shows:
7221 Size of the perf ring buffer.
7225 @kindex record delete
7228 When record target runs in replay mode (``in the past''), delete the
7229 subsequent execution log and begin to record a new execution log starting
7230 from the current address. This means you will abandon the previously
7231 recorded ``future'' and begin recording a new ``future''.
7233 @kindex record instruction-history
7234 @kindex rec instruction-history
7235 @item record instruction-history
7236 Disassembles instructions from the recorded execution log. By
7237 default, ten instructions are disassembled. This can be changed using
7238 the @code{set record instruction-history-size} command. Instructions
7239 are printed in execution order.
7241 It can also print mixed source+disassembly if you specify the the
7242 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7243 as well as in symbolic form by specifying the @code{/r} modifier.
7245 The current position marker is printed for the instruction at the
7246 current program counter value. This instruction can appear multiple
7247 times in the trace and the current position marker will be printed
7248 every time. To omit the current position marker, specify the
7251 To better align the printed instructions when the trace contains
7252 instructions from more than one function, the function name may be
7253 omitted by specifying the @code{/f} modifier.
7255 Speculatively executed instructions are prefixed with @samp{?}. This
7256 feature is not available for all recording formats.
7258 There are several ways to specify what part of the execution log to
7262 @item record instruction-history @var{insn}
7263 Disassembles ten instructions starting from instruction number
7266 @item record instruction-history @var{insn}, +/-@var{n}
7267 Disassembles @var{n} instructions around instruction number
7268 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7269 @var{n} instructions after instruction number @var{insn}. If
7270 @var{n} is preceded with @code{-}, disassembles @var{n}
7271 instructions before instruction number @var{insn}.
7273 @item record instruction-history
7274 Disassembles ten more instructions after the last disassembly.
7276 @item record instruction-history -
7277 Disassembles ten more instructions before the last disassembly.
7279 @item record instruction-history @var{begin}, @var{end}
7280 Disassembles instructions beginning with instruction number
7281 @var{begin} until instruction number @var{end}. The instruction
7282 number @var{end} is included.
7285 This command may not be available for all recording methods.
7288 @item set record instruction-history-size @var{size}
7289 @itemx set record instruction-history-size unlimited
7290 Define how many instructions to disassemble in the @code{record
7291 instruction-history} command. The default value is 10.
7292 A @var{size} of @code{unlimited} means unlimited instructions.
7295 @item show record instruction-history-size
7296 Show how many instructions to disassemble in the @code{record
7297 instruction-history} command.
7299 @kindex record function-call-history
7300 @kindex rec function-call-history
7301 @item record function-call-history
7302 Prints the execution history at function granularity. It prints one
7303 line for each sequence of instructions that belong to the same
7304 function giving the name of that function, the source lines
7305 for this instruction sequence (if the @code{/l} modifier is
7306 specified), and the instructions numbers that form the sequence (if
7307 the @code{/i} modifier is specified). The function names are indented
7308 to reflect the call stack depth if the @code{/c} modifier is
7309 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7313 (@value{GDBP}) @b{list 1, 10}
7324 (@value{GDBP}) @b{record function-call-history /ilc}
7325 1 bar inst 1,4 at foo.c:6,8
7326 2 foo inst 5,10 at foo.c:2,3
7327 3 bar inst 11,13 at foo.c:9,10
7330 By default, ten lines are printed. This can be changed using the
7331 @code{set record function-call-history-size} command. Functions are
7332 printed in execution order. There are several ways to specify what
7336 @item record function-call-history @var{func}
7337 Prints ten functions starting from function number @var{func}.
7339 @item record function-call-history @var{func}, +/-@var{n}
7340 Prints @var{n} functions around function number @var{func}. If
7341 @var{n} is preceded with @code{+}, prints @var{n} functions after
7342 function number @var{func}. If @var{n} is preceded with @code{-},
7343 prints @var{n} functions before function number @var{func}.
7345 @item record function-call-history
7346 Prints ten more functions after the last ten-line print.
7348 @item record function-call-history -
7349 Prints ten more functions before the last ten-line print.
7351 @item record function-call-history @var{begin}, @var{end}
7352 Prints functions beginning with function number @var{begin} until
7353 function number @var{end}. The function number @var{end} is included.
7356 This command may not be available for all recording methods.
7358 @item set record function-call-history-size @var{size}
7359 @itemx set record function-call-history-size unlimited
7360 Define how many lines to print in the
7361 @code{record function-call-history} command. The default value is 10.
7362 A size of @code{unlimited} means unlimited lines.
7364 @item show record function-call-history-size
7365 Show how many lines to print in the
7366 @code{record function-call-history} command.
7371 @chapter Examining the Stack
7373 When your program has stopped, the first thing you need to know is where it
7374 stopped and how it got there.
7377 Each time your program performs a function call, information about the call
7379 That information includes the location of the call in your program,
7380 the arguments of the call,
7381 and the local variables of the function being called.
7382 The information is saved in a block of data called a @dfn{stack frame}.
7383 The stack frames are allocated in a region of memory called the @dfn{call
7386 When your program stops, the @value{GDBN} commands for examining the
7387 stack allow you to see all of this information.
7389 @cindex selected frame
7390 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7391 @value{GDBN} commands refer implicitly to the selected frame. In
7392 particular, whenever you ask @value{GDBN} for the value of a variable in
7393 your program, the value is found in the selected frame. There are
7394 special @value{GDBN} commands to select whichever frame you are
7395 interested in. @xref{Selection, ,Selecting a Frame}.
7397 When your program stops, @value{GDBN} automatically selects the
7398 currently executing frame and describes it briefly, similar to the
7399 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7402 * Frames:: Stack frames
7403 * Backtrace:: Backtraces
7404 * Selection:: Selecting a frame
7405 * Frame Info:: Information on a frame
7406 * Frame Apply:: Applying a command to several frames
7407 * Frame Filter Management:: Managing frame filters
7412 @section Stack Frames
7414 @cindex frame, definition
7416 The call stack is divided up into contiguous pieces called @dfn{stack
7417 frames}, or @dfn{frames} for short; each frame is the data associated
7418 with one call to one function. The frame contains the arguments given
7419 to the function, the function's local variables, and the address at
7420 which the function is executing.
7422 @cindex initial frame
7423 @cindex outermost frame
7424 @cindex innermost frame
7425 When your program is started, the stack has only one frame, that of the
7426 function @code{main}. This is called the @dfn{initial} frame or the
7427 @dfn{outermost} frame. Each time a function is called, a new frame is
7428 made. Each time a function returns, the frame for that function invocation
7429 is eliminated. If a function is recursive, there can be many frames for
7430 the same function. The frame for the function in which execution is
7431 actually occurring is called the @dfn{innermost} frame. This is the most
7432 recently created of all the stack frames that still exist.
7434 @cindex frame pointer
7435 Inside your program, stack frames are identified by their addresses. A
7436 stack frame consists of many bytes, each of which has its own address; each
7437 kind of computer has a convention for choosing one byte whose
7438 address serves as the address of the frame. Usually this address is kept
7439 in a register called the @dfn{frame pointer register}
7440 (@pxref{Registers, $fp}) while execution is going on in that frame.
7443 @cindex frame number
7444 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7445 number that is zero for the innermost frame, one for the frame that
7446 called it, and so on upward. These level numbers give you a way of
7447 designating stack frames in @value{GDBN} commands. The terms
7448 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7449 describe this number.
7451 @c The -fomit-frame-pointer below perennially causes hbox overflow
7452 @c underflow problems.
7453 @cindex frameless execution
7454 Some compilers provide a way to compile functions so that they operate
7455 without stack frames. (For example, the @value{NGCC} option
7457 @samp{-fomit-frame-pointer}
7459 generates functions without a frame.)
7460 This is occasionally done with heavily used library functions to save
7461 the frame setup time. @value{GDBN} has limited facilities for dealing
7462 with these function invocations. If the innermost function invocation
7463 has no stack frame, @value{GDBN} nevertheless regards it as though
7464 it had a separate frame, which is numbered zero as usual, allowing
7465 correct tracing of the function call chain. However, @value{GDBN} has
7466 no provision for frameless functions elsewhere in the stack.
7472 @cindex call stack traces
7473 A backtrace is a summary of how your program got where it is. It shows one
7474 line per frame, for many frames, starting with the currently executing
7475 frame (frame zero), followed by its caller (frame one), and on up the
7478 @anchor{backtrace-command}
7480 @kindex bt @r{(@code{backtrace})}
7481 To print a backtrace of the entire stack, use the @code{backtrace}
7482 command, or its alias @code{bt}. This command will print one line per
7483 frame for frames in the stack. By default, all stack frames are
7484 printed. You can stop the backtrace at any time by typing the system
7485 interrupt character, normally @kbd{Ctrl-c}.
7488 @item backtrace [@var{args}@dots{}]
7489 @itemx bt [@var{args}@dots{}]
7490 Print the backtrace of the entire stack. The optional @var{args} can
7491 be one of the following:
7496 Print only the innermost @var{n} frames, where @var{n} is a positive
7501 Print only the outermost @var{n} frames, where @var{n} is a positive
7505 Print the values of the local variables also. This can be combined
7506 with a number to limit the number of frames shown.
7509 Do not run Python frame filters on this backtrace. @xref{Frame
7510 Filter API}, for more information. Additionally use @ref{disable
7511 frame-filter all} to turn off all frame filters. This is only
7512 relevant when @value{GDBN} has been configured with @code{Python}
7516 A Python frame filter might decide to ``elide'' some frames. Normally
7517 such elided frames are still printed, but they are indented relative
7518 to the filtered frames that cause them to be elided. The @code{hide}
7519 option causes elided frames to not be printed at all.
7525 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7526 are additional aliases for @code{backtrace}.
7528 @cindex multiple threads, backtrace
7529 In a multi-threaded program, @value{GDBN} by default shows the
7530 backtrace only for the current thread. To display the backtrace for
7531 several or all of the threads, use the command @code{thread apply}
7532 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7533 apply all backtrace}, @value{GDBN} will display the backtrace for all
7534 the threads; this is handy when you debug a core dump of a
7535 multi-threaded program.
7537 Each line in the backtrace shows the frame number and the function name.
7538 The program counter value is also shown---unless you use @code{set
7539 print address off}. The backtrace also shows the source file name and
7540 line number, as well as the arguments to the function. The program
7541 counter value is omitted if it is at the beginning of the code for that
7544 Here is an example of a backtrace. It was made with the command
7545 @samp{bt 3}, so it shows the innermost three frames.
7549 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7551 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7552 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7554 (More stack frames follow...)
7559 The display for frame zero does not begin with a program counter
7560 value, indicating that your program has stopped at the beginning of the
7561 code for line @code{993} of @code{builtin.c}.
7564 The value of parameter @code{data} in frame 1 has been replaced by
7565 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7566 only if it is a scalar (integer, pointer, enumeration, etc). See command
7567 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7568 on how to configure the way function parameter values are printed.
7570 @cindex optimized out, in backtrace
7571 @cindex function call arguments, optimized out
7572 If your program was compiled with optimizations, some compilers will
7573 optimize away arguments passed to functions if those arguments are
7574 never used after the call. Such optimizations generate code that
7575 passes arguments through registers, but doesn't store those arguments
7576 in the stack frame. @value{GDBN} has no way of displaying such
7577 arguments in stack frames other than the innermost one. Here's what
7578 such a backtrace might look like:
7582 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7584 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7585 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7587 (More stack frames follow...)
7592 The values of arguments that were not saved in their stack frames are
7593 shown as @samp{<optimized out>}.
7595 If you need to display the values of such optimized-out arguments,
7596 either deduce that from other variables whose values depend on the one
7597 you are interested in, or recompile without optimizations.
7599 @cindex backtrace beyond @code{main} function
7600 @cindex program entry point
7601 @cindex startup code, and backtrace
7602 Most programs have a standard user entry point---a place where system
7603 libraries and startup code transition into user code. For C this is
7604 @code{main}@footnote{
7605 Note that embedded programs (the so-called ``free-standing''
7606 environment) are not required to have a @code{main} function as the
7607 entry point. They could even have multiple entry points.}.
7608 When @value{GDBN} finds the entry function in a backtrace
7609 it will terminate the backtrace, to avoid tracing into highly
7610 system-specific (and generally uninteresting) code.
7612 If you need to examine the startup code, or limit the number of levels
7613 in a backtrace, you can change this behavior:
7616 @item set backtrace past-main
7617 @itemx set backtrace past-main on
7618 @kindex set backtrace
7619 Backtraces will continue past the user entry point.
7621 @item set backtrace past-main off
7622 Backtraces will stop when they encounter the user entry point. This is the
7625 @item show backtrace past-main
7626 @kindex show backtrace
7627 Display the current user entry point backtrace policy.
7629 @item set backtrace past-entry
7630 @itemx set backtrace past-entry on
7631 Backtraces will continue past the internal entry point of an application.
7632 This entry point is encoded by the linker when the application is built,
7633 and is likely before the user entry point @code{main} (or equivalent) is called.
7635 @item set backtrace past-entry off
7636 Backtraces will stop when they encounter the internal entry point of an
7637 application. This is the default.
7639 @item show backtrace past-entry
7640 Display the current internal entry point backtrace policy.
7642 @item set backtrace limit @var{n}
7643 @itemx set backtrace limit 0
7644 @itemx set backtrace limit unlimited
7645 @cindex backtrace limit
7646 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7647 or zero means unlimited levels.
7649 @item show backtrace limit
7650 Display the current limit on backtrace levels.
7653 You can control how file names are displayed.
7656 @item set filename-display
7657 @itemx set filename-display relative
7658 @cindex filename-display
7659 Display file names relative to the compilation directory. This is the default.
7661 @item set filename-display basename
7662 Display only basename of a filename.
7664 @item set filename-display absolute
7665 Display an absolute filename.
7667 @item show filename-display
7668 Show the current way to display filenames.
7672 @section Selecting a Frame
7674 Most commands for examining the stack and other data in your program work on
7675 whichever stack frame is selected at the moment. Here are the commands for
7676 selecting a stack frame; all of them finish by printing a brief description
7677 of the stack frame just selected.
7680 @kindex frame@r{, selecting}
7681 @kindex f @r{(@code{frame})}
7682 @item frame @r{[} @var{frame-selection-spec} @r{]}
7683 @item f @r{[} @var{frame-selection-spec} @r{]}
7684 The @command{frame} command allows different stack frames to be
7685 selected. The @var{frame-selection-spec} can be any of the following:
7690 @item level @var{num}
7691 Select frame level @var{num}. Recall that frame zero is the innermost
7692 (currently executing) frame, frame one is the frame that called the
7693 innermost one, and so on. The highest level frame is usually the one
7696 As this is the most common method of navigating the frame stack, the
7697 string @command{level} can be omitted. For example, the following two
7698 commands are equivalent:
7701 (@value{GDBP}) frame 3
7702 (@value{GDBP}) frame level 3
7705 @kindex frame address
7706 @item address @var{stack-address}
7707 Select the frame with stack address @var{stack-address}. The
7708 @var{stack-address} for a frame can be seen in the output of
7709 @command{info frame}, for example:
7713 Stack level 1, frame at 0x7fffffffda30:
7714 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7715 tail call frame, caller of frame at 0x7fffffffda30
7716 source language c++.
7717 Arglist at unknown address.
7718 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7721 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7722 indicated by the line:
7725 Stack level 1, frame at 0x7fffffffda30:
7728 @kindex frame function
7729 @item function @var{function-name}
7730 Select the stack frame for function @var{function-name}. If there are
7731 multiple stack frames for function @var{function-name} then the inner
7732 most stack frame is selected.
7735 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7736 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7737 viewed has stack address @var{stack-addr}, and optionally, a program
7738 counter address of @var{pc-addr}.
7740 This is useful mainly if the chaining of stack frames has been
7741 damaged by a bug, making it impossible for @value{GDBN} to assign
7742 numbers properly to all frames. In addition, this can be useful
7743 when your program has multiple stacks and switches between them.
7745 When viewing a frame outside the current backtrace using
7746 @command{frame view} then you can always return to the original
7747 stack using one of the previous stack frame selection instructions,
7748 for example @command{frame level 0}.
7754 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7755 numbers @var{n}, this advances toward the outermost frame, to higher
7756 frame numbers, to frames that have existed longer.
7759 @kindex do @r{(@code{down})}
7761 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7762 positive numbers @var{n}, this advances toward the innermost frame, to
7763 lower frame numbers, to frames that were created more recently.
7764 You may abbreviate @code{down} as @code{do}.
7767 All of these commands end by printing two lines of output describing the
7768 frame. The first line shows the frame number, the function name, the
7769 arguments, and the source file and line number of execution in that
7770 frame. The second line shows the text of that source line.
7778 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7780 10 read_input_file (argv[i]);
7784 After such a printout, the @code{list} command with no arguments
7785 prints ten lines centered on the point of execution in the frame.
7786 You can also edit the program at the point of execution with your favorite
7787 editing program by typing @code{edit}.
7788 @xref{List, ,Printing Source Lines},
7792 @kindex select-frame
7793 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7794 The @code{select-frame} command is a variant of @code{frame} that does
7795 not display the new frame after selecting it. This command is
7796 intended primarily for use in @value{GDBN} command scripts, where the
7797 output might be unnecessary and distracting. The
7798 @var{frame-selection-spec} is as for the @command{frame} command
7799 described in @ref{Selection, ,Selecting a Frame}.
7801 @kindex down-silently
7803 @item up-silently @var{n}
7804 @itemx down-silently @var{n}
7805 These two commands are variants of @code{up} and @code{down},
7806 respectively; they differ in that they do their work silently, without
7807 causing display of the new frame. They are intended primarily for use
7808 in @value{GDBN} command scripts, where the output might be unnecessary and
7813 @section Information About a Frame
7815 There are several other commands to print information about the selected
7821 When used without any argument, this command does not change which
7822 frame is selected, but prints a brief description of the currently
7823 selected stack frame. It can be abbreviated @code{f}. With an
7824 argument, this command is used to select a stack frame.
7825 @xref{Selection, ,Selecting a Frame}.
7828 @kindex info f @r{(@code{info frame})}
7831 This command prints a verbose description of the selected stack frame,
7836 the address of the frame
7838 the address of the next frame down (called by this frame)
7840 the address of the next frame up (caller of this frame)
7842 the language in which the source code corresponding to this frame is written
7844 the address of the frame's arguments
7846 the address of the frame's local variables
7848 the program counter saved in it (the address of execution in the caller frame)
7850 which registers were saved in the frame
7853 @noindent The verbose description is useful when
7854 something has gone wrong that has made the stack format fail to fit
7855 the usual conventions.
7857 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7858 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7859 Print a verbose description of the frame selected by
7860 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7861 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7862 a Frame}). The selected frame remains unchanged by this command.
7865 @item info args [-q]
7866 Print the arguments of the selected frame, each on a separate line.
7868 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7869 printing header information and messages explaining why no argument
7872 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7873 Like @kbd{info args}, but only print the arguments selected
7874 with the provided regexp(s).
7876 If @var{regexp} is provided, print only the arguments whose names
7877 match the regular expression @var{regexp}.
7879 If @var{type_regexp} is provided, print only the arguments whose
7880 types, as printed by the @code{whatis} command, match
7881 the regular expression @var{type_regexp}.
7882 If @var{type_regexp} contains space(s), it should be enclosed in
7883 quote characters. If needed, use backslash to escape the meaning
7884 of special characters or quotes.
7886 If both @var{regexp} and @var{type_regexp} are provided, an argument
7887 is printed only if its name matches @var{regexp} and its type matches
7890 @item info locals [-q]
7892 Print the local variables of the selected frame, each on a separate
7893 line. These are all variables (declared either static or automatic)
7894 accessible at the point of execution of the selected frame.
7896 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7897 printing header information and messages explaining why no local variables
7900 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7901 Like @kbd{info locals}, but only print the local variables selected
7902 with the provided regexp(s).
7904 If @var{regexp} is provided, print only the local variables whose names
7905 match the regular expression @var{regexp}.
7907 If @var{type_regexp} is provided, print only the local variables whose
7908 types, as printed by the @code{whatis} command, match
7909 the regular expression @var{type_regexp}.
7910 If @var{type_regexp} contains space(s), it should be enclosed in
7911 quote characters. If needed, use backslash to escape the meaning
7912 of special characters or quotes.
7914 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7915 is printed only if its name matches @var{regexp} and its type matches
7918 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7919 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7920 For example, your program might use Resource Acquisition Is
7921 Initialization types (RAII) such as @code{lock_something_t}: each
7922 local variable of type @code{lock_something_t} automatically places a
7923 lock that is destroyed when the variable goes out of scope. You can
7924 then list all acquired locks in your program by doing
7926 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7929 or the equivalent shorter form
7931 tfaas i lo -q -t lock_something_t
7937 @section Applying a Command to Several Frames.
7939 @cindex apply command to several frames
7941 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7942 The @code{frame apply} command allows you to apply the named
7943 @var{command} to one or more frames.
7947 Specify @code{all} to apply @var{command} to all frames.
7950 Use @var{count} to apply @var{command} to the innermost @var{count}
7951 frames, where @var{count} is a positive number.
7954 Use @var{-count} to apply @var{command} to the outermost @var{count}
7955 frames, where @var{count} is a positive number.
7958 Use @code{level} to apply @var{command} to the set of frames identified
7959 by the @var{level} list. @var{level} is a frame level or a range of frame
7960 levels as @var{level1}-@var{level2}. The frame level is the number shown
7961 in the first field of the @samp{backtrace} command output.
7962 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7963 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7969 Note that the frames on which @code{frame apply} applies a command are
7970 also influenced by the @code{set backtrace} settings such as @code{set
7971 backtrace past-main} and @code{set backtrace limit N}. See
7972 @xref{Backtrace,,Backtraces}.
7974 The @var{flag} arguments control what output to produce and how to handle
7975 errors raised when applying @var{command} to a frame. @var{flag}
7976 must start with a @code{-} directly followed by one letter in
7977 @code{qcs}. If several flags are provided, they must be given
7978 individually, such as @code{-c -q}.
7980 By default, @value{GDBN} displays some frame information before the
7981 output produced by @var{command}, and an error raised during the
7982 execution of a @var{command} will abort @code{frame apply}. The
7983 following flags can be used to fine-tune this behavior:
7987 The flag @code{-c}, which stands for @samp{continue}, causes any
7988 errors in @var{command} to be displayed, and the execution of
7989 @code{frame apply} then continues.
7991 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7992 or empty output produced by a @var{command} to be silently ignored.
7993 That is, the execution continues, but the frame information and errors
7996 The flag @code{-q} (@samp{quiet}) disables printing the frame
8000 The following example shows how the flags @code{-c} and @code{-s} are
8001 working when applying the command @code{p j} to all frames, where
8002 variable @code{j} can only be successfully printed in the outermost
8003 @code{#1 main} frame.
8007 (gdb) frame apply all p j
8008 #0 some_function (i=5) at fun.c:4
8009 No symbol "j" in current context.
8010 (gdb) frame apply all -c p j
8011 #0 some_function (i=5) at fun.c:4
8012 No symbol "j" in current context.
8013 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8015 (gdb) frame apply all -s p j
8016 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8022 By default, @samp{frame apply}, prints the frame location
8023 information before the command output:
8027 (gdb) frame apply all p $sp
8028 #0 some_function (i=5) at fun.c:4
8029 $4 = (void *) 0xffffd1e0
8030 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8031 $5 = (void *) 0xffffd1f0
8036 If flag @code{-q} is given, no frame information is printed:
8039 (gdb) frame apply all -q p $sp
8040 $12 = (void *) 0xffffd1e0
8041 $13 = (void *) 0xffffd1f0
8049 @cindex apply a command to all frames (ignoring errors and empty output)
8050 @item faas @var{command}
8051 Shortcut for @code{frame apply all -s @var{command}}.
8052 Applies @var{command} on all frames, ignoring errors and empty output.
8054 It can for example be used to print a local variable or a function
8055 argument without knowing the frame where this variable or argument
8058 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8061 Note that the command @code{tfaas @var{command}} applies @var{command}
8062 on all frames of all threads. See @xref{Threads,,Threads}.
8066 @node Frame Filter Management
8067 @section Management of Frame Filters.
8068 @cindex managing frame filters
8070 Frame filters are Python based utilities to manage and decorate the
8071 output of frames. @xref{Frame Filter API}, for further information.
8073 Managing frame filters is performed by several commands available
8074 within @value{GDBN}, detailed here.
8077 @kindex info frame-filter
8078 @item info frame-filter
8079 Print a list of installed frame filters from all dictionaries, showing
8080 their name, priority and enabled status.
8082 @kindex disable frame-filter
8083 @anchor{disable frame-filter all}
8084 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8085 Disable 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
8090 across all dictionaries are disabled. The @var{filter-name} is the name
8091 of the frame filter and is used when @code{all} is not the option for
8092 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8093 may be enabled again later.
8095 @kindex enable frame-filter
8096 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8097 Enable a frame filter in the dictionary matching
8098 @var{filter-dictionary} and @var{filter-name}. The
8099 @var{filter-dictionary} may be @code{all}, @code{global},
8100 @code{progspace} or the name of the object file where the frame filter
8101 dictionary resides. When @code{all} is specified, all frame filters across
8102 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8103 filter and is used when @code{all} is not the option for
8104 @var{filter-dictionary}.
8109 (gdb) info frame-filter
8111 global frame-filters:
8112 Priority Enabled Name
8113 1000 No PrimaryFunctionFilter
8116 progspace /build/test frame-filters:
8117 Priority Enabled Name
8118 100 Yes ProgspaceFilter
8120 objfile /build/test frame-filters:
8121 Priority Enabled Name
8122 999 Yes BuildProgra Filter
8124 (gdb) disable frame-filter /build/test BuildProgramFilter
8125 (gdb) info frame-filter
8127 global frame-filters:
8128 Priority Enabled Name
8129 1000 No PrimaryFunctionFilter
8132 progspace /build/test frame-filters:
8133 Priority Enabled Name
8134 100 Yes ProgspaceFilter
8136 objfile /build/test frame-filters:
8137 Priority Enabled Name
8138 999 No BuildProgramFilter
8140 (gdb) enable frame-filter global PrimaryFunctionFilter
8141 (gdb) info frame-filter
8143 global frame-filters:
8144 Priority Enabled Name
8145 1000 Yes PrimaryFunctionFilter
8148 progspace /build/test frame-filters:
8149 Priority Enabled Name
8150 100 Yes ProgspaceFilter
8152 objfile /build/test frame-filters:
8153 Priority Enabled Name
8154 999 No BuildProgramFilter
8157 @kindex set frame-filter priority
8158 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8159 Set the @var{priority} of a frame filter in the dictionary matching
8160 @var{filter-dictionary}, and the frame filter name matching
8161 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8162 @code{progspace} or the name of the object file where the frame filter
8163 dictionary resides. The @var{priority} is an integer.
8165 @kindex show frame-filter priority
8166 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8167 Show the @var{priority} of a frame filter in the dictionary matching
8168 @var{filter-dictionary}, and the frame filter name matching
8169 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8170 @code{progspace} or the name of the object file where the frame filter
8176 (gdb) info frame-filter
8178 global frame-filters:
8179 Priority Enabled Name
8180 1000 Yes PrimaryFunctionFilter
8183 progspace /build/test frame-filters:
8184 Priority Enabled Name
8185 100 Yes ProgspaceFilter
8187 objfile /build/test frame-filters:
8188 Priority Enabled Name
8189 999 No BuildProgramFilter
8191 (gdb) set frame-filter priority global Reverse 50
8192 (gdb) info frame-filter
8194 global frame-filters:
8195 Priority Enabled Name
8196 1000 Yes PrimaryFunctionFilter
8199 progspace /build/test frame-filters:
8200 Priority Enabled Name
8201 100 Yes ProgspaceFilter
8203 objfile /build/test frame-filters:
8204 Priority Enabled Name
8205 999 No BuildProgramFilter
8210 @chapter Examining Source Files
8212 @value{GDBN} can print parts of your program's source, since the debugging
8213 information recorded in the program tells @value{GDBN} what source files were
8214 used to build it. When your program stops, @value{GDBN} spontaneously prints
8215 the line where it stopped. Likewise, when you select a stack frame
8216 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8217 execution in that frame has stopped. You can print other portions of
8218 source files by explicit command.
8220 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8221 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8222 @value{GDBN} under @sc{gnu} Emacs}.
8225 * List:: Printing source lines
8226 * Specify Location:: How to specify code locations
8227 * Edit:: Editing source files
8228 * Search:: Searching source files
8229 * Source Path:: Specifying source directories
8230 * Machine Code:: Source and machine code
8234 @section Printing Source Lines
8237 @kindex l @r{(@code{list})}
8238 To print lines from a source file, use the @code{list} command
8239 (abbreviated @code{l}). By default, ten lines are printed.
8240 There are several ways to specify what part of the file you want to
8241 print; see @ref{Specify Location}, for the full list.
8243 Here are the forms of the @code{list} command most commonly used:
8246 @item list @var{linenum}
8247 Print lines centered around line number @var{linenum} in the
8248 current source file.
8250 @item list @var{function}
8251 Print lines centered around the beginning of function
8255 Print more lines. If the last lines printed were printed with a
8256 @code{list} command, this prints lines following the last lines
8257 printed; however, if the last line printed was a solitary line printed
8258 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8259 Stack}), this prints lines centered around that line.
8262 Print lines just before the lines last printed.
8265 @cindex @code{list}, how many lines to display
8266 By default, @value{GDBN} prints ten source lines with any of these forms of
8267 the @code{list} command. You can change this using @code{set listsize}:
8270 @kindex set listsize
8271 @item set listsize @var{count}
8272 @itemx set listsize unlimited
8273 Make the @code{list} command display @var{count} source lines (unless
8274 the @code{list} argument explicitly specifies some other number).
8275 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8277 @kindex show listsize
8279 Display the number of lines that @code{list} prints.
8282 Repeating a @code{list} command with @key{RET} discards the argument,
8283 so it is equivalent to typing just @code{list}. This is more useful
8284 than listing the same lines again. An exception is made for an
8285 argument of @samp{-}; that argument is preserved in repetition so that
8286 each repetition moves up in the source file.
8288 In general, the @code{list} command expects you to supply zero, one or two
8289 @dfn{locations}. Locations specify source lines; there are several ways
8290 of writing them (@pxref{Specify Location}), but the effect is always
8291 to specify some source line.
8293 Here is a complete description of the possible arguments for @code{list}:
8296 @item list @var{location}
8297 Print lines centered around the line specified by @var{location}.
8299 @item list @var{first},@var{last}
8300 Print lines from @var{first} to @var{last}. Both arguments are
8301 locations. When a @code{list} command has two locations, and the
8302 source file of the second location is omitted, this refers to
8303 the same source file as the first location.
8305 @item list ,@var{last}
8306 Print lines ending with @var{last}.
8308 @item list @var{first},
8309 Print lines starting with @var{first}.
8312 Print lines just after the lines last printed.
8315 Print lines just before the lines last printed.
8318 As described in the preceding table.
8321 @node Specify Location
8322 @section Specifying a Location
8323 @cindex specifying location
8325 @cindex source location
8328 * Linespec Locations:: Linespec locations
8329 * Explicit Locations:: Explicit locations
8330 * Address Locations:: Address locations
8333 Several @value{GDBN} commands accept arguments that specify a location
8334 of your program's code. Since @value{GDBN} is a source-level
8335 debugger, a location usually specifies some line in the source code.
8336 Locations may be specified using three different formats:
8337 linespec locations, explicit locations, or address locations.
8339 @node Linespec Locations
8340 @subsection Linespec Locations
8341 @cindex linespec locations
8343 A @dfn{linespec} is a colon-separated list of source location parameters such
8344 as file name, function name, etc. Here are all the different ways of
8345 specifying a linespec:
8349 Specifies the line number @var{linenum} of the current source file.
8352 @itemx +@var{offset}
8353 Specifies the line @var{offset} lines before or after the @dfn{current
8354 line}. For the @code{list} command, the current line is the last one
8355 printed; for the breakpoint commands, this is the line at which
8356 execution stopped in the currently selected @dfn{stack frame}
8357 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8358 used as the second of the two linespecs in a @code{list} command,
8359 this specifies the line @var{offset} lines up or down from the first
8362 @item @var{filename}:@var{linenum}
8363 Specifies the line @var{linenum} in the source file @var{filename}.
8364 If @var{filename} is a relative file name, then it will match any
8365 source file name with the same trailing components. For example, if
8366 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8367 name of @file{/build/trunk/gcc/expr.c}, but not
8368 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8370 @item @var{function}
8371 Specifies the line that begins the body of the function @var{function}.
8372 For example, in C, this is the line with the open brace.
8374 By default, in C@t{++} and Ada, @var{function} is interpreted as
8375 specifying all functions named @var{function} in all scopes. For
8376 C@t{++}, this means in all namespaces and classes. For Ada, this
8377 means in all packages.
8379 For example, assuming a program with C@t{++} symbols named
8380 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8381 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8383 Commands that accept a linespec let you override this with the
8384 @code{-qualified} option. For example, @w{@kbd{break -qualified
8385 func}} sets a breakpoint on a free-function named @code{func} ignoring
8386 any C@t{++} class methods and namespace functions called @code{func}.
8388 @xref{Explicit Locations}.
8390 @item @var{function}:@var{label}
8391 Specifies the line where @var{label} appears in @var{function}.
8393 @item @var{filename}:@var{function}
8394 Specifies the line that begins the body of the function @var{function}
8395 in the file @var{filename}. You only need the file name with a
8396 function name to avoid ambiguity when there are identically named
8397 functions in different source files.
8400 Specifies the line at which the label named @var{label} appears
8401 in the function corresponding to the currently selected stack frame.
8402 If there is no current selected stack frame (for instance, if the inferior
8403 is not running), then @value{GDBN} will not search for a label.
8405 @cindex breakpoint at static probe point
8406 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8407 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8408 applications to embed static probes. @xref{Static Probe Points}, for more
8409 information on finding and using static probes. This form of linespec
8410 specifies the location of such a static probe.
8412 If @var{objfile} is given, only probes coming from that shared library
8413 or executable matching @var{objfile} as a regular expression are considered.
8414 If @var{provider} is given, then only probes from that provider are considered.
8415 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8416 each one of those probes.
8419 @node Explicit Locations
8420 @subsection Explicit Locations
8421 @cindex explicit locations
8423 @dfn{Explicit locations} allow the user to directly specify the source
8424 location's parameters using option-value pairs.
8426 Explicit locations are useful when several functions, labels, or
8427 file names have the same name (base name for files) in the program's
8428 sources. In these cases, explicit locations point to the source
8429 line you meant more accurately and unambiguously. Also, using
8430 explicit locations might be faster in large programs.
8432 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8433 defined in the file named @file{foo} or the label @code{bar} in a function
8434 named @code{foo}. @value{GDBN} must search either the file system or
8435 the symbol table to know.
8437 The list of valid explicit location options is summarized in the
8441 @item -source @var{filename}
8442 The value specifies the source file name. To differentiate between
8443 files with the same base name, prepend as many directories as is necessary
8444 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8445 @value{GDBN} will use the first file it finds with the given base
8446 name. This option requires the use of either @code{-function} or @code{-line}.
8448 @item -function @var{function}
8449 The value specifies the name of a function. Operations
8450 on function locations unmodified by other options (such as @code{-label}
8451 or @code{-line}) refer to the line that begins the body of the function.
8452 In C, for example, this is the line with the open brace.
8454 By default, in C@t{++} and Ada, @var{function} is interpreted as
8455 specifying all functions named @var{function} in all scopes. For
8456 C@t{++}, this means in all namespaces and classes. For Ada, this
8457 means in all packages.
8459 For example, assuming a program with C@t{++} symbols named
8460 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8461 -function func}} and @w{@kbd{break -function B::func}} set a
8462 breakpoint on both symbols.
8464 You can use the @kbd{-qualified} flag to override this (see below).
8468 This flag makes @value{GDBN} interpret a function name specified with
8469 @kbd{-function} as a complete fully-qualified name.
8471 For example, assuming a C@t{++} program with symbols named
8472 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8473 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8475 (Note: the @kbd{-qualified} option can precede a linespec as well
8476 (@pxref{Linespec Locations}), so the particular example above could be
8477 simplified as @w{@kbd{break -qualified B::func}}.)
8479 @item -label @var{label}
8480 The value specifies the name of a label. When the function
8481 name is not specified, the label is searched in the function of the currently
8482 selected stack frame.
8484 @item -line @var{number}
8485 The value specifies a line offset for the location. The offset may either
8486 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8487 the command. When specified without any other options, the line offset is
8488 relative to the current line.
8491 Explicit location options may be abbreviated by omitting any non-unique
8492 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8494 @node Address Locations
8495 @subsection Address Locations
8496 @cindex address locations
8498 @dfn{Address locations} indicate a specific program address. They have
8499 the generalized form *@var{address}.
8501 For line-oriented commands, such as @code{list} and @code{edit}, this
8502 specifies a source line that contains @var{address}. For @code{break} and
8503 other breakpoint-oriented commands, this can be used to set breakpoints in
8504 parts of your program which do not have debugging information or
8507 Here @var{address} may be any expression valid in the current working
8508 language (@pxref{Languages, working language}) that specifies a code
8509 address. In addition, as a convenience, @value{GDBN} extends the
8510 semantics of expressions used in locations to cover several situations
8511 that frequently occur during debugging. Here are the various forms
8515 @item @var{expression}
8516 Any expression valid in the current working language.
8518 @item @var{funcaddr}
8519 An address of a function or procedure derived from its name. In C,
8520 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8521 simply the function's name @var{function} (and actually a special case
8522 of a valid expression). In Pascal and Modula-2, this is
8523 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8524 (although the Pascal form also works).
8526 This form specifies the address of the function's first instruction,
8527 before the stack frame and arguments have been set up.
8529 @item '@var{filename}':@var{funcaddr}
8530 Like @var{funcaddr} above, but also specifies the name of the source
8531 file explicitly. This is useful if the name of the function does not
8532 specify the function unambiguously, e.g., if there are several
8533 functions with identical names in different source files.
8537 @section Editing Source Files
8538 @cindex editing source files
8541 @kindex e @r{(@code{edit})}
8542 To edit the lines in a source file, use the @code{edit} command.
8543 The editing program of your choice
8544 is invoked with the current line set to
8545 the active line in the program.
8546 Alternatively, there are several ways to specify what part of the file you
8547 want to print if you want to see other parts of the program:
8550 @item edit @var{location}
8551 Edit the source file specified by @code{location}. Editing starts at
8552 that @var{location}, e.g., at the specified source line of the
8553 specified file. @xref{Specify Location}, for all the possible forms
8554 of the @var{location} argument; here are the forms of the @code{edit}
8555 command most commonly used:
8558 @item edit @var{number}
8559 Edit the current source file with @var{number} as the active line number.
8561 @item edit @var{function}
8562 Edit the file containing @var{function} at the beginning of its definition.
8567 @subsection Choosing your Editor
8568 You can customize @value{GDBN} to use any editor you want
8570 The only restriction is that your editor (say @code{ex}), recognizes the
8571 following command-line syntax:
8573 ex +@var{number} file
8575 The optional numeric value +@var{number} specifies the number of the line in
8576 the file where to start editing.}.
8577 By default, it is @file{@value{EDITOR}}, but you can change this
8578 by setting the environment variable @code{EDITOR} before using
8579 @value{GDBN}. For example, to configure @value{GDBN} to use the
8580 @code{vi} editor, you could use these commands with the @code{sh} shell:
8586 or in the @code{csh} shell,
8588 setenv EDITOR /usr/bin/vi
8593 @section Searching Source Files
8594 @cindex searching source files
8596 There are two commands for searching through the current source file for a
8601 @kindex forward-search
8602 @kindex fo @r{(@code{forward-search})}
8603 @item forward-search @var{regexp}
8604 @itemx search @var{regexp}
8605 The command @samp{forward-search @var{regexp}} checks each line,
8606 starting with the one following the last line listed, for a match for
8607 @var{regexp}. It lists the line that is found. You can use the
8608 synonym @samp{search @var{regexp}} or abbreviate the command name as
8611 @kindex reverse-search
8612 @item reverse-search @var{regexp}
8613 The command @samp{reverse-search @var{regexp}} checks each line, starting
8614 with the one before the last line listed and going backward, for a match
8615 for @var{regexp}. It lists the line that is found. You can abbreviate
8616 this command as @code{rev}.
8620 @section Specifying Source Directories
8623 @cindex directories for source files
8624 Executable programs sometimes do not record the directories of the source
8625 files from which they were compiled, just the names. Even when they do,
8626 the directories could be moved between the compilation and your debugging
8627 session. @value{GDBN} has a list of directories to search for source files;
8628 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8629 it tries all the directories in the list, in the order they are present
8630 in the list, until it finds a file with the desired name.
8632 For example, suppose an executable references the file
8633 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8634 @file{/mnt/cross}. The file is first looked up literally; if this
8635 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8636 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8637 message is printed. @value{GDBN} does not look up the parts of the
8638 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8639 Likewise, the subdirectories of the source path are not searched: if
8640 the source path is @file{/mnt/cross}, and the binary refers to
8641 @file{foo.c}, @value{GDBN} would not find it under
8642 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8644 Plain file names, relative file names with leading directories, file
8645 names containing dots, etc.@: are all treated as described above; for
8646 instance, if the source path is @file{/mnt/cross}, and the source file
8647 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8648 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8649 that---@file{/mnt/cross/foo.c}.
8651 Note that the executable search path is @emph{not} used to locate the
8654 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8655 any information it has cached about where source files are found and where
8656 each line is in the file.
8660 When you start @value{GDBN}, its source path includes only @samp{cdir}
8661 and @samp{cwd}, in that order.
8662 To add other directories, use the @code{directory} command.
8664 The search path is used to find both program source files and @value{GDBN}
8665 script files (read using the @samp{-command} option and @samp{source} command).
8667 In addition to the source path, @value{GDBN} provides a set of commands
8668 that manage a list of source path substitution rules. A @dfn{substitution
8669 rule} specifies how to rewrite source directories stored in the program's
8670 debug information in case the sources were moved to a different
8671 directory between compilation and debugging. A rule is made of
8672 two strings, the first specifying what needs to be rewritten in
8673 the path, and the second specifying how it should be rewritten.
8674 In @ref{set substitute-path}, we name these two parts @var{from} and
8675 @var{to} respectively. @value{GDBN} does a simple string replacement
8676 of @var{from} with @var{to} at the start of the directory part of the
8677 source file name, and uses that result instead of the original file
8678 name to look up the sources.
8680 Using the previous example, suppose the @file{foo-1.0} tree has been
8681 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8682 @value{GDBN} to replace @file{/usr/src} in all source path names with
8683 @file{/mnt/cross}. The first lookup will then be
8684 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8685 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8686 substitution rule, use the @code{set substitute-path} command
8687 (@pxref{set substitute-path}).
8689 To avoid unexpected substitution results, a rule is applied only if the
8690 @var{from} part of the directory name ends at a directory separator.
8691 For instance, a rule substituting @file{/usr/source} into
8692 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8693 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8694 is applied only at the beginning of the directory name, this rule will
8695 not be applied to @file{/root/usr/source/baz.c} either.
8697 In many cases, you can achieve the same result using the @code{directory}
8698 command. However, @code{set substitute-path} can be more efficient in
8699 the case where the sources are organized in a complex tree with multiple
8700 subdirectories. With the @code{directory} command, you need to add each
8701 subdirectory of your project. If you moved the entire tree while
8702 preserving its internal organization, then @code{set substitute-path}
8703 allows you to direct the debugger to all the sources with one single
8706 @code{set substitute-path} is also more than just a shortcut command.
8707 The source path is only used if the file at the original location no
8708 longer exists. On the other hand, @code{set substitute-path} modifies
8709 the debugger behavior to look at the rewritten location instead. So, if
8710 for any reason a source file that is not relevant to your executable is
8711 located at the original location, a substitution rule is the only
8712 method available to point @value{GDBN} at the new location.
8714 @cindex @samp{--with-relocated-sources}
8715 @cindex default source path substitution
8716 You can configure a default source path substitution rule by
8717 configuring @value{GDBN} with the
8718 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8719 should be the name of a directory under @value{GDBN}'s configured
8720 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8721 directory names in debug information under @var{dir} will be adjusted
8722 automatically if the installed @value{GDBN} is moved to a new
8723 location. This is useful if @value{GDBN}, libraries or executables
8724 with debug information and corresponding source code are being moved
8728 @item directory @var{dirname} @dots{}
8729 @item dir @var{dirname} @dots{}
8730 Add directory @var{dirname} to the front of the source path. Several
8731 directory names may be given to this command, separated by @samp{:}
8732 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8733 part of absolute file names) or
8734 whitespace. You may specify a directory that is already in the source
8735 path; this moves it forward, so @value{GDBN} searches it sooner.
8739 @vindex $cdir@r{, convenience variable}
8740 @vindex $cwd@r{, convenience variable}
8741 @cindex compilation directory
8742 @cindex current directory
8743 @cindex working directory
8744 @cindex directory, current
8745 @cindex directory, compilation
8746 You can use the string @samp{$cdir} to refer to the compilation
8747 directory (if one is recorded), and @samp{$cwd} to refer to the current
8748 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8749 tracks the current working directory as it changes during your @value{GDBN}
8750 session, while the latter is immediately expanded to the current
8751 directory at the time you add an entry to the source path.
8754 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8756 @c RET-repeat for @code{directory} is explicitly disabled, but since
8757 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8759 @item set directories @var{path-list}
8760 @kindex set directories
8761 Set the source path to @var{path-list}.
8762 @samp{$cdir:$cwd} are added if missing.
8764 @item show directories
8765 @kindex show directories
8766 Print the source path: show which directories it contains.
8768 @anchor{set substitute-path}
8769 @item set substitute-path @var{from} @var{to}
8770 @kindex set substitute-path
8771 Define a source path substitution rule, and add it at the end of the
8772 current list of existing substitution rules. If a rule with the same
8773 @var{from} was already defined, then the old rule is also deleted.
8775 For example, if the file @file{/foo/bar/baz.c} was moved to
8776 @file{/mnt/cross/baz.c}, then the command
8779 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8783 will tell @value{GDBN} to replace @samp{/foo/bar} with
8784 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8785 @file{baz.c} even though it was moved.
8787 In the case when more than one substitution rule have been defined,
8788 the rules are evaluated one by one in the order where they have been
8789 defined. The first one matching, if any, is selected to perform
8792 For instance, if we had entered the following commands:
8795 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8796 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8800 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8801 @file{/mnt/include/defs.h} by using the first rule. However, it would
8802 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8803 @file{/mnt/src/lib/foo.c}.
8806 @item unset substitute-path [path]
8807 @kindex unset substitute-path
8808 If a path is specified, search the current list of substitution rules
8809 for a rule that would rewrite that path. Delete that rule if found.
8810 A warning is emitted by the debugger if no rule could be found.
8812 If no path is specified, then all substitution rules are deleted.
8814 @item show substitute-path [path]
8815 @kindex show substitute-path
8816 If a path is specified, then print the source path substitution rule
8817 which would rewrite that path, if any.
8819 If no path is specified, then print all existing source path substitution
8824 If your source path is cluttered with directories that are no longer of
8825 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8826 versions of source. You can correct the situation as follows:
8830 Use @code{directory} with no argument to reset the source path to its default value.
8833 Use @code{directory} with suitable arguments to reinstall the
8834 directories you want in the source path. You can add all the
8835 directories in one command.
8839 @section Source and Machine Code
8840 @cindex source line and its code address
8842 You can use the command @code{info line} to map source lines to program
8843 addresses (and vice versa), and the command @code{disassemble} to display
8844 a range of addresses as machine instructions. You can use the command
8845 @code{set disassemble-next-line} to set whether to disassemble next
8846 source line when execution stops. When run under @sc{gnu} Emacs
8847 mode, the @code{info line} command causes the arrow to point to the
8848 line specified. Also, @code{info line} prints addresses in symbolic form as
8854 @itemx info line @var{location}
8855 Print the starting and ending addresses of the compiled code for
8856 source line @var{location}. You can specify source lines in any of
8857 the ways documented in @ref{Specify Location}. With no @var{location}
8858 information about the current source line is printed.
8861 For example, we can use @code{info line} to discover the location of
8862 the object code for the first line of function
8863 @code{m4_changequote}:
8866 (@value{GDBP}) info line m4_changequote
8867 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8868 ends at 0x6350 <m4_changequote+4>.
8872 @cindex code address and its source line
8873 We can also inquire (using @code{*@var{addr}} as the form for
8874 @var{location}) what source line covers a particular address:
8876 (@value{GDBP}) info line *0x63ff
8877 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8878 ends at 0x6404 <m4_changequote+184>.
8881 @cindex @code{$_} and @code{info line}
8882 @cindex @code{x} command, default address
8883 @kindex x@r{(examine), and} info line
8884 After @code{info line}, the default address for the @code{x} command
8885 is changed to the starting address of the line, so that @samp{x/i} is
8886 sufficient to begin examining the machine code (@pxref{Memory,
8887 ,Examining Memory}). Also, this address is saved as the value of the
8888 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8891 @cindex info line, repeated calls
8892 After @code{info line}, using @code{info line} again without
8893 specifying a location will display information about the next source
8898 @cindex assembly instructions
8899 @cindex instructions, assembly
8900 @cindex machine instructions
8901 @cindex listing machine instructions
8903 @itemx disassemble /m
8904 @itemx disassemble /s
8905 @itemx disassemble /r
8906 This specialized command dumps a range of memory as machine
8907 instructions. It can also print mixed source+disassembly by specifying
8908 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8909 as well as in symbolic form by specifying the @code{/r} modifier.
8910 The default memory range is the function surrounding the
8911 program counter of the selected frame. A single argument to this
8912 command is a program counter value; @value{GDBN} dumps the function
8913 surrounding this value. When two arguments are given, they should
8914 be separated by a comma, possibly surrounded by whitespace. The
8915 arguments specify a range of addresses to dump, in one of two forms:
8918 @item @var{start},@var{end}
8919 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8920 @item @var{start},+@var{length}
8921 the addresses from @var{start} (inclusive) to
8922 @code{@var{start}+@var{length}} (exclusive).
8926 When 2 arguments are specified, the name of the function is also
8927 printed (since there could be several functions in the given range).
8929 The argument(s) can be any expression yielding a numeric value, such as
8930 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8932 If the range of memory being disassembled contains current program counter,
8933 the instruction at that location is shown with a @code{=>} marker.
8936 The following example shows the disassembly of a range of addresses of
8937 HP PA-RISC 2.0 code:
8940 (@value{GDBP}) disas 0x32c4, 0x32e4
8941 Dump of assembler code from 0x32c4 to 0x32e4:
8942 0x32c4 <main+204>: addil 0,dp
8943 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8944 0x32cc <main+212>: ldil 0x3000,r31
8945 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8946 0x32d4 <main+220>: ldo 0(r31),rp
8947 0x32d8 <main+224>: addil -0x800,dp
8948 0x32dc <main+228>: ldo 0x588(r1),r26
8949 0x32e0 <main+232>: ldil 0x3000,r31
8950 End of assembler dump.
8953 Here is an example showing mixed source+assembly for Intel x86
8954 with @code{/m} or @code{/s}, when the program is stopped just after
8955 function prologue in a non-optimized function with no inline code.
8958 (@value{GDBP}) disas /m main
8959 Dump of assembler code for function main:
8961 0x08048330 <+0>: push %ebp
8962 0x08048331 <+1>: mov %esp,%ebp
8963 0x08048333 <+3>: sub $0x8,%esp
8964 0x08048336 <+6>: and $0xfffffff0,%esp
8965 0x08048339 <+9>: sub $0x10,%esp
8967 6 printf ("Hello.\n");
8968 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8969 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8973 0x08048348 <+24>: mov $0x0,%eax
8974 0x0804834d <+29>: leave
8975 0x0804834e <+30>: ret
8977 End of assembler dump.
8980 The @code{/m} option is deprecated as its output is not useful when
8981 there is either inlined code or re-ordered code.
8982 The @code{/s} option is the preferred choice.
8983 Here is an example for AMD x86-64 showing the difference between
8984 @code{/m} output and @code{/s} output.
8985 This example has one inline function defined in a header file,
8986 and the code is compiled with @samp{-O2} optimization.
8987 Note how the @code{/m} output is missing the disassembly of
8988 several instructions that are present in the @code{/s} output.
9018 (@value{GDBP}) disas /m main
9019 Dump of assembler code for function main:
9023 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9024 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9028 0x000000000040041d <+29>: xor %eax,%eax
9029 0x000000000040041f <+31>: retq
9030 0x0000000000400420 <+32>: add %eax,%eax
9031 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9033 End of assembler dump.
9034 (@value{GDBP}) disas /s main
9035 Dump of assembler code for function main:
9039 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9043 0x0000000000400406 <+6>: test %eax,%eax
9044 0x0000000000400408 <+8>: js 0x400420 <main+32>
9049 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9050 0x000000000040040d <+13>: test %eax,%eax
9051 0x000000000040040f <+15>: mov $0x1,%eax
9052 0x0000000000400414 <+20>: cmovne %edx,%eax
9056 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9060 0x000000000040041d <+29>: xor %eax,%eax
9061 0x000000000040041f <+31>: retq
9065 0x0000000000400420 <+32>: add %eax,%eax
9066 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9067 End of assembler dump.
9070 Here is another example showing raw instructions in hex for AMD x86-64,
9073 (gdb) disas /r 0x400281,+10
9074 Dump of assembler code from 0x400281 to 0x40028b:
9075 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9076 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9077 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9078 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9079 End of assembler dump.
9082 Addresses cannot be specified as a location (@pxref{Specify Location}).
9083 So, for example, if you want to disassemble function @code{bar}
9084 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9085 and not @samp{disassemble foo.c:bar}.
9087 Some architectures have more than one commonly-used set of instruction
9088 mnemonics or other syntax.
9090 For programs that were dynamically linked and use shared libraries,
9091 instructions that call functions or branch to locations in the shared
9092 libraries might show a seemingly bogus location---it's actually a
9093 location of the relocation table. On some architectures, @value{GDBN}
9094 might be able to resolve these to actual function names.
9097 @kindex set disassembler-options
9098 @cindex disassembler options
9099 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9100 This command controls the passing of target specific information to
9101 the disassembler. For a list of valid options, please refer to the
9102 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9103 manual and/or the output of @kbd{objdump --help}
9104 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9105 The default value is the empty string.
9107 If it is necessary to specify more than one disassembler option, then
9108 multiple options can be placed together into a comma separated list.
9109 Currently this command is only supported on targets ARM, MIPS, PowerPC
9112 @kindex show disassembler-options
9113 @item show disassembler-options
9114 Show the current setting of the disassembler options.
9118 @kindex set disassembly-flavor
9119 @cindex Intel disassembly flavor
9120 @cindex AT&T disassembly flavor
9121 @item set disassembly-flavor @var{instruction-set}
9122 Select the instruction set to use when disassembling the
9123 program via the @code{disassemble} or @code{x/i} commands.
9125 Currently this command is only defined for the Intel x86 family. You
9126 can set @var{instruction-set} to either @code{intel} or @code{att}.
9127 The default is @code{att}, the AT&T flavor used by default by Unix
9128 assemblers for x86-based targets.
9130 @kindex show disassembly-flavor
9131 @item show disassembly-flavor
9132 Show the current setting of the disassembly flavor.
9136 @kindex set disassemble-next-line
9137 @kindex show disassemble-next-line
9138 @item set disassemble-next-line
9139 @itemx show disassemble-next-line
9140 Control whether or not @value{GDBN} will disassemble the next source
9141 line or instruction when execution stops. If ON, @value{GDBN} will
9142 display disassembly of the next source line when execution of the
9143 program being debugged stops. This is @emph{in addition} to
9144 displaying the source line itself, which @value{GDBN} always does if
9145 possible. If the next source line cannot be displayed for some reason
9146 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9147 info in the debug info), @value{GDBN} will display disassembly of the
9148 next @emph{instruction} instead of showing the next source line. If
9149 AUTO, @value{GDBN} will display disassembly of next instruction only
9150 if the source line cannot be displayed. This setting causes
9151 @value{GDBN} to display some feedback when you step through a function
9152 with no line info or whose source file is unavailable. The default is
9153 OFF, which means never display the disassembly of the next line or
9159 @chapter Examining Data
9161 @cindex printing data
9162 @cindex examining data
9165 The usual way to examine data in your program is with the @code{print}
9166 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9167 evaluates and prints the value of an expression of the language your
9168 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9169 Different Languages}). It may also print the expression using a
9170 Python-based pretty-printer (@pxref{Pretty Printing}).
9173 @item print @var{expr}
9174 @itemx print /@var{f} @var{expr}
9175 @var{expr} is an expression (in the source language). By default the
9176 value of @var{expr} is printed in a format appropriate to its data type;
9177 you can choose a different format by specifying @samp{/@var{f}}, where
9178 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9182 @itemx print /@var{f}
9183 @cindex reprint the last value
9184 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9185 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9186 conveniently inspect the same value in an alternative format.
9189 A more low-level way of examining data is with the @code{x} command.
9190 It examines data in memory at a specified address and prints it in a
9191 specified format. @xref{Memory, ,Examining Memory}.
9193 If you are interested in information about types, or about how the
9194 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9195 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9198 @cindex exploring hierarchical data structures
9200 Another way of examining values of expressions and type information is
9201 through the Python extension command @code{explore} (available only if
9202 the @value{GDBN} build is configured with @code{--with-python}). It
9203 offers an interactive way to start at the highest level (or, the most
9204 abstract level) of the data type of an expression (or, the data type
9205 itself) and explore all the way down to leaf scalar values/fields
9206 embedded in the higher level data types.
9209 @item explore @var{arg}
9210 @var{arg} is either an expression (in the source language), or a type
9211 visible in the current context of the program being debugged.
9214 The working of the @code{explore} command can be illustrated with an
9215 example. If a data type @code{struct ComplexStruct} is defined in your
9225 struct ComplexStruct
9227 struct SimpleStruct *ss_p;
9233 followed by variable declarations as
9236 struct SimpleStruct ss = @{ 10, 1.11 @};
9237 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9241 then, the value of the variable @code{cs} can be explored using the
9242 @code{explore} command as follows.
9246 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9247 the following fields:
9249 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9250 arr = <Enter 1 to explore this field of type `int [10]'>
9252 Enter the field number of choice:
9256 Since the fields of @code{cs} are not scalar values, you are being
9257 prompted to chose the field you want to explore. Let's say you choose
9258 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9259 pointer, you will be asked if it is pointing to a single value. From
9260 the declaration of @code{cs} above, it is indeed pointing to a single
9261 value, hence you enter @code{y}. If you enter @code{n}, then you will
9262 be asked if it were pointing to an array of values, in which case this
9263 field will be explored as if it were an array.
9266 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9267 Continue exploring it as a pointer to a single value [y/n]: y
9268 The value of `*(cs.ss_p)' is a struct/class of type `struct
9269 SimpleStruct' with the following fields:
9271 i = 10 .. (Value of type `int')
9272 d = 1.1100000000000001 .. (Value of type `double')
9274 Press enter to return to parent value:
9278 If the field @code{arr} of @code{cs} was chosen for exploration by
9279 entering @code{1} earlier, then since it is as array, you will be
9280 prompted to enter the index of the element in the array that you want
9284 `cs.arr' is an array of `int'.
9285 Enter the index of the element you want to explore in `cs.arr': 5
9287 `(cs.arr)[5]' is a scalar value of type `int'.
9291 Press enter to return to parent value:
9294 In general, at any stage of exploration, you can go deeper towards the
9295 leaf values by responding to the prompts appropriately, or hit the
9296 return key to return to the enclosing data structure (the @i{higher}
9297 level data structure).
9299 Similar to exploring values, you can use the @code{explore} command to
9300 explore types. Instead of specifying a value (which is typically a
9301 variable name or an expression valid in the current context of the
9302 program being debugged), you specify a type name. If you consider the
9303 same example as above, your can explore the type
9304 @code{struct ComplexStruct} by passing the argument
9305 @code{struct ComplexStruct} to the @code{explore} command.
9308 (gdb) explore struct ComplexStruct
9312 By responding to the prompts appropriately in the subsequent interactive
9313 session, you can explore the type @code{struct ComplexStruct} in a
9314 manner similar to how the value @code{cs} was explored in the above
9317 The @code{explore} command also has two sub-commands,
9318 @code{explore value} and @code{explore type}. The former sub-command is
9319 a way to explicitly specify that value exploration of the argument is
9320 being invoked, while the latter is a way to explicitly specify that type
9321 exploration of the argument is being invoked.
9324 @item explore value @var{expr}
9325 @cindex explore value
9326 This sub-command of @code{explore} explores the value of the
9327 expression @var{expr} (if @var{expr} is an expression valid in the
9328 current context of the program being debugged). The behavior of this
9329 command is identical to that of the behavior of the @code{explore}
9330 command being passed the argument @var{expr}.
9332 @item explore type @var{arg}
9333 @cindex explore type
9334 This sub-command of @code{explore} explores the type of @var{arg} (if
9335 @var{arg} is a type visible in the current context of program being
9336 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9337 is an expression valid in the current context of the program being
9338 debugged). If @var{arg} is a type, then the behavior of this command is
9339 identical to that of the @code{explore} command being passed the
9340 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9341 this command will be identical to that of the @code{explore} command
9342 being passed the type of @var{arg} as the argument.
9346 * Expressions:: Expressions
9347 * Ambiguous Expressions:: Ambiguous Expressions
9348 * Variables:: Program variables
9349 * Arrays:: Artificial arrays
9350 * Output Formats:: Output formats
9351 * Memory:: Examining memory
9352 * Auto Display:: Automatic display
9353 * Print Settings:: Print settings
9354 * Pretty Printing:: Python pretty printing
9355 * Value History:: Value history
9356 * Convenience Vars:: Convenience variables
9357 * Convenience Funs:: Convenience functions
9358 * Registers:: Registers
9359 * Floating Point Hardware:: Floating point hardware
9360 * Vector Unit:: Vector Unit
9361 * OS Information:: Auxiliary data provided by operating system
9362 * Memory Region Attributes:: Memory region attributes
9363 * Dump/Restore Files:: Copy between memory and a file
9364 * Core File Generation:: Cause a program dump its core
9365 * Character Sets:: Debugging programs that use a different
9366 character set than GDB does
9367 * Caching Target Data:: Data caching for targets
9368 * Searching Memory:: Searching memory for a sequence of bytes
9369 * Value Sizes:: Managing memory allocated for values
9373 @section Expressions
9376 @code{print} and many other @value{GDBN} commands accept an expression and
9377 compute its value. Any kind of constant, variable or operator defined
9378 by the programming language you are using is valid in an expression in
9379 @value{GDBN}. This includes conditional expressions, function calls,
9380 casts, and string constants. It also includes preprocessor macros, if
9381 you compiled your program to include this information; see
9384 @cindex arrays in expressions
9385 @value{GDBN} supports array constants in expressions input by
9386 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9387 you can use the command @code{print @{1, 2, 3@}} to create an array
9388 of three integers. If you pass an array to a function or assign it
9389 to a program variable, @value{GDBN} copies the array to memory that
9390 is @code{malloc}ed in the target program.
9392 Because C is so widespread, most of the expressions shown in examples in
9393 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9394 Languages}, for information on how to use expressions in other
9397 In this section, we discuss operators that you can use in @value{GDBN}
9398 expressions regardless of your programming language.
9400 @cindex casts, in expressions
9401 Casts are supported in all languages, not just in C, because it is so
9402 useful to cast a number into a pointer in order to examine a structure
9403 at that address in memory.
9404 @c FIXME: casts supported---Mod2 true?
9406 @value{GDBN} supports these operators, in addition to those common
9407 to programming languages:
9411 @samp{@@} is a binary operator for treating parts of memory as arrays.
9412 @xref{Arrays, ,Artificial Arrays}, for more information.
9415 @samp{::} allows you to specify a variable in terms of the file or
9416 function where it is defined. @xref{Variables, ,Program Variables}.
9418 @cindex @{@var{type}@}
9419 @cindex type casting memory
9420 @cindex memory, viewing as typed object
9421 @cindex casts, to view memory
9422 @item @{@var{type}@} @var{addr}
9423 Refers to an object of type @var{type} stored at address @var{addr} in
9424 memory. The address @var{addr} may be any expression whose value is
9425 an integer or pointer (but parentheses are required around binary
9426 operators, just as in a cast). This construct is allowed regardless
9427 of what kind of data is normally supposed to reside at @var{addr}.
9430 @node Ambiguous Expressions
9431 @section Ambiguous Expressions
9432 @cindex ambiguous expressions
9434 Expressions can sometimes contain some ambiguous elements. For instance,
9435 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9436 a single function name to be defined several times, for application in
9437 different contexts. This is called @dfn{overloading}. Another example
9438 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9439 templates and is typically instantiated several times, resulting in
9440 the same function name being defined in different contexts.
9442 In some cases and depending on the language, it is possible to adjust
9443 the expression to remove the ambiguity. For instance in C@t{++}, you
9444 can specify the signature of the function you want to break on, as in
9445 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9446 qualified name of your function often makes the expression unambiguous
9449 When an ambiguity that needs to be resolved is detected, the debugger
9450 has the capability to display a menu of numbered choices for each
9451 possibility, and then waits for the selection with the prompt @samp{>}.
9452 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9453 aborts the current command. If the command in which the expression was
9454 used allows more than one choice to be selected, the next option in the
9455 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9458 For example, the following session excerpt shows an attempt to set a
9459 breakpoint at the overloaded symbol @code{String::after}.
9460 We choose three particular definitions of that function name:
9462 @c FIXME! This is likely to change to show arg type lists, at least
9465 (@value{GDBP}) b String::after
9468 [2] file:String.cc; line number:867
9469 [3] file:String.cc; line number:860
9470 [4] file:String.cc; line number:875
9471 [5] file:String.cc; line number:853
9472 [6] file:String.cc; line number:846
9473 [7] file:String.cc; line number:735
9475 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9476 Breakpoint 2 at 0xb344: file String.cc, line 875.
9477 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9478 Multiple breakpoints were set.
9479 Use the "delete" command to delete unwanted
9486 @kindex set multiple-symbols
9487 @item set multiple-symbols @var{mode}
9488 @cindex multiple-symbols menu
9490 This option allows you to adjust the debugger behavior when an expression
9493 By default, @var{mode} is set to @code{all}. If the command with which
9494 the expression is used allows more than one choice, then @value{GDBN}
9495 automatically selects all possible choices. For instance, inserting
9496 a breakpoint on a function using an ambiguous name results in a breakpoint
9497 inserted on each possible match. However, if a unique choice must be made,
9498 then @value{GDBN} uses the menu to help you disambiguate the expression.
9499 For instance, printing the address of an overloaded function will result
9500 in the use of the menu.
9502 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9503 when an ambiguity is detected.
9505 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9506 an error due to the ambiguity and the command is aborted.
9508 @kindex show multiple-symbols
9509 @item show multiple-symbols
9510 Show the current value of the @code{multiple-symbols} setting.
9514 @section Program Variables
9516 The most common kind of expression to use is the name of a variable
9519 Variables in expressions are understood in the selected stack frame
9520 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9524 global (or file-static)
9531 visible according to the scope rules of the
9532 programming language from the point of execution in that frame
9535 @noindent This means that in the function
9550 you can examine and use the variable @code{a} whenever your program is
9551 executing within the function @code{foo}, but you can only use or
9552 examine the variable @code{b} while your program is executing inside
9553 the block where @code{b} is declared.
9555 @cindex variable name conflict
9556 There is an exception: you can refer to a variable or function whose
9557 scope is a single source file even if the current execution point is not
9558 in this file. But it is possible to have more than one such variable or
9559 function with the same name (in different source files). If that
9560 happens, referring to that name has unpredictable effects. If you wish,
9561 you can specify a static variable in a particular function or file by
9562 using the colon-colon (@code{::}) notation:
9564 @cindex colon-colon, context for variables/functions
9566 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9567 @cindex @code{::}, context for variables/functions
9570 @var{file}::@var{variable}
9571 @var{function}::@var{variable}
9575 Here @var{file} or @var{function} is the name of the context for the
9576 static @var{variable}. In the case of file names, you can use quotes to
9577 make sure @value{GDBN} parses the file name as a single word---for example,
9578 to print a global value of @code{x} defined in @file{f2.c}:
9581 (@value{GDBP}) p 'f2.c'::x
9584 The @code{::} notation is normally used for referring to
9585 static variables, since you typically disambiguate uses of local variables
9586 in functions by selecting the appropriate frame and using the
9587 simple name of the variable. However, you may also use this notation
9588 to refer to local variables in frames enclosing the selected frame:
9597 process (a); /* Stop here */
9608 For example, if there is a breakpoint at the commented line,
9609 here is what you might see
9610 when the program stops after executing the call @code{bar(0)}:
9615 (@value{GDBP}) p bar::a
9618 #2 0x080483d0 in foo (a=5) at foobar.c:12
9621 (@value{GDBP}) p bar::a
9625 @cindex C@t{++} scope resolution
9626 These uses of @samp{::} are very rarely in conflict with the very
9627 similar use of the same notation in C@t{++}. When they are in
9628 conflict, the C@t{++} meaning takes precedence; however, this can be
9629 overridden by quoting the file or function name with single quotes.
9631 For example, suppose the program is stopped in a method of a class
9632 that has a field named @code{includefile}, and there is also an
9633 include file named @file{includefile} that defines a variable,
9637 (@value{GDBP}) p includefile
9639 (@value{GDBP}) p includefile::some_global
9640 A syntax error in expression, near `'.
9641 (@value{GDBP}) p 'includefile'::some_global
9645 @cindex wrong values
9646 @cindex variable values, wrong
9647 @cindex function entry/exit, wrong values of variables
9648 @cindex optimized code, wrong values of variables
9650 @emph{Warning:} Occasionally, a local variable may appear to have the
9651 wrong value at certain points in a function---just after entry to a new
9652 scope, and just before exit.
9654 You may see this problem when you are stepping by machine instructions.
9655 This is because, on most machines, it takes more than one instruction to
9656 set up a stack frame (including local variable definitions); if you are
9657 stepping by machine instructions, variables may appear to have the wrong
9658 values until the stack frame is completely built. On exit, it usually
9659 also takes more than one machine instruction to destroy a stack frame;
9660 after you begin stepping through that group of instructions, local
9661 variable definitions may be gone.
9663 This may also happen when the compiler does significant optimizations.
9664 To be sure of always seeing accurate values, turn off all optimization
9667 @cindex ``No symbol "foo" in current context''
9668 Another possible effect of compiler optimizations is to optimize
9669 unused variables out of existence, or assign variables to registers (as
9670 opposed to memory addresses). Depending on the support for such cases
9671 offered by the debug info format used by the compiler, @value{GDBN}
9672 might not be able to display values for such local variables. If that
9673 happens, @value{GDBN} will print a message like this:
9676 No symbol "foo" in current context.
9679 To solve such problems, either recompile without optimizations, or use a
9680 different debug info format, if the compiler supports several such
9681 formats. @xref{Compilation}, for more information on choosing compiler
9682 options. @xref{C, ,C and C@t{++}}, for more information about debug
9683 info formats that are best suited to C@t{++} programs.
9685 If you ask to print an object whose contents are unknown to
9686 @value{GDBN}, e.g., because its data type is not completely specified
9687 by the debug information, @value{GDBN} will say @samp{<incomplete
9688 type>}. @xref{Symbols, incomplete type}, for more about this.
9690 @cindex no debug info variables
9691 If you try to examine or use the value of a (global) variable for
9692 which @value{GDBN} has no type information, e.g., because the program
9693 includes no debug information, @value{GDBN} displays an error message.
9694 @xref{Symbols, unknown type}, for more about unknown types. If you
9695 cast the variable to its declared type, @value{GDBN} gets the
9696 variable's value using the cast-to type as the variable's type. For
9697 example, in a C program:
9700 (@value{GDBP}) p var
9701 'var' has unknown type; cast it to its declared type
9702 (@value{GDBP}) p (float) var
9706 If you append @kbd{@@entry} string to a function parameter name you get its
9707 value at the time the function got called. If the value is not available an
9708 error message is printed. Entry values are available only with some compilers.
9709 Entry values are normally also printed at the function parameter list according
9710 to @ref{set print entry-values}.
9713 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9719 (gdb) print i@@entry
9723 Strings are identified as arrays of @code{char} values without specified
9724 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9725 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9726 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9727 defines literal string type @code{"char"} as @code{char} without a sign.
9732 signed char var1[] = "A";
9735 You get during debugging
9740 $2 = @{65 'A', 0 '\0'@}
9744 @section Artificial Arrays
9746 @cindex artificial array
9748 @kindex @@@r{, referencing memory as an array}
9749 It is often useful to print out several successive objects of the
9750 same type in memory; a section of an array, or an array of
9751 dynamically determined size for which only a pointer exists in the
9754 You can do this by referring to a contiguous span of memory as an
9755 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9756 operand of @samp{@@} should be the first element of the desired array
9757 and be an individual object. The right operand should be the desired length
9758 of the array. The result is an array value whose elements are all of
9759 the type of the left argument. The first element is actually the left
9760 argument; the second element comes from bytes of memory immediately
9761 following those that hold the first element, and so on. Here is an
9762 example. If a program says
9765 int *array = (int *) malloc (len * sizeof (int));
9769 you can print the contents of @code{array} with
9775 The left operand of @samp{@@} must reside in memory. Array values made
9776 with @samp{@@} in this way behave just like other arrays in terms of
9777 subscripting, and are coerced to pointers when used in expressions.
9778 Artificial arrays most often appear in expressions via the value history
9779 (@pxref{Value History, ,Value History}), after printing one out.
9781 Another way to create an artificial array is to use a cast.
9782 This re-interprets a value as if it were an array.
9783 The value need not be in memory:
9785 (@value{GDBP}) p/x (short[2])0x12345678
9786 $1 = @{0x1234, 0x5678@}
9789 As a convenience, if you leave the array length out (as in
9790 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9791 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9793 (@value{GDBP}) p/x (short[])0x12345678
9794 $2 = @{0x1234, 0x5678@}
9797 Sometimes the artificial array mechanism is not quite enough; in
9798 moderately complex data structures, the elements of interest may not
9799 actually be adjacent---for example, if you are interested in the values
9800 of pointers in an array. One useful work-around in this situation is
9801 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9802 Variables}) as a counter in an expression that prints the first
9803 interesting value, and then repeat that expression via @key{RET}. For
9804 instance, suppose you have an array @code{dtab} of pointers to
9805 structures, and you are interested in the values of a field @code{fv}
9806 in each structure. Here is an example of what you might type:
9816 @node Output Formats
9817 @section Output Formats
9819 @cindex formatted output
9820 @cindex output formats
9821 By default, @value{GDBN} prints a value according to its data type. Sometimes
9822 this is not what you want. For example, you might want to print a number
9823 in hex, or a pointer in decimal. Or you might want to view data in memory
9824 at a certain address as a character string or as an instruction. To do
9825 these things, specify an @dfn{output format} when you print a value.
9827 The simplest use of output formats is to say how to print a value
9828 already computed. This is done by starting the arguments of the
9829 @code{print} command with a slash and a format letter. The format
9830 letters supported are:
9834 Regard the bits of the value as an integer, and print the integer in
9838 Print as integer in signed decimal.
9841 Print as integer in unsigned decimal.
9844 Print as integer in octal.
9847 Print as integer in binary. The letter @samp{t} stands for ``two''.
9848 @footnote{@samp{b} cannot be used because these format letters are also
9849 used with the @code{x} command, where @samp{b} stands for ``byte'';
9850 see @ref{Memory,,Examining Memory}.}
9853 @cindex unknown address, locating
9854 @cindex locate address
9855 Print as an address, both absolute in hexadecimal and as an offset from
9856 the nearest preceding symbol. You can use this format used to discover
9857 where (in what function) an unknown address is located:
9860 (@value{GDBP}) p/a 0x54320
9861 $3 = 0x54320 <_initialize_vx+396>
9865 The command @code{info symbol 0x54320} yields similar results.
9866 @xref{Symbols, info symbol}.
9869 Regard as an integer and print it as a character constant. This
9870 prints both the numerical value and its character representation. The
9871 character representation is replaced with the octal escape @samp{\nnn}
9872 for characters outside the 7-bit @sc{ascii} range.
9874 Without this format, @value{GDBN} displays @code{char},
9875 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9876 constants. Single-byte members of vectors are displayed as integer
9880 Regard the bits of the value as a floating point number and print
9881 using typical floating point syntax.
9884 @cindex printing strings
9885 @cindex printing byte arrays
9886 Regard as a string, if possible. With this format, pointers to single-byte
9887 data are displayed as null-terminated strings and arrays of single-byte data
9888 are displayed as fixed-length strings. Other values are displayed in their
9891 Without this format, @value{GDBN} displays pointers to and arrays of
9892 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9893 strings. Single-byte members of a vector are displayed as an integer
9897 Like @samp{x} formatting, the value is treated as an integer and
9898 printed as hexadecimal, but leading zeros are printed to pad the value
9899 to the size of the integer type.
9902 @cindex raw printing
9903 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9904 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9905 Printing}). This typically results in a higher-level display of the
9906 value's contents. The @samp{r} format bypasses any Python
9907 pretty-printer which might exist.
9910 For example, to print the program counter in hex (@pxref{Registers}), type
9917 Note that no space is required before the slash; this is because command
9918 names in @value{GDBN} cannot contain a slash.
9920 To reprint the last value in the value history with a different format,
9921 you can use the @code{print} command with just a format and no
9922 expression. For example, @samp{p/x} reprints the last value in hex.
9925 @section Examining Memory
9927 You can use the command @code{x} (for ``examine'') to examine memory in
9928 any of several formats, independently of your program's data types.
9930 @cindex examining memory
9932 @kindex x @r{(examine memory)}
9933 @item x/@var{nfu} @var{addr}
9936 Use the @code{x} command to examine memory.
9939 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9940 much memory to display and how to format it; @var{addr} is an
9941 expression giving the address where you want to start displaying memory.
9942 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9943 Several commands set convenient defaults for @var{addr}.
9946 @item @var{n}, the repeat count
9947 The repeat count is a decimal integer; the default is 1. It specifies
9948 how much memory (counting by units @var{u}) to display. If a negative
9949 number is specified, memory is examined backward from @var{addr}.
9950 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9953 @item @var{f}, the display format
9954 The display format is one of the formats used by @code{print}
9955 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9956 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9957 The default is @samp{x} (hexadecimal) initially. The default changes
9958 each time you use either @code{x} or @code{print}.
9960 @item @var{u}, the unit size
9961 The unit size is any of
9967 Halfwords (two bytes).
9969 Words (four bytes). This is the initial default.
9971 Giant words (eight bytes).
9974 Each time you specify a unit size with @code{x}, that size becomes the
9975 default unit the next time you use @code{x}. For the @samp{i} format,
9976 the unit size is ignored and is normally not written. For the @samp{s} format,
9977 the unit size defaults to @samp{b}, unless it is explicitly given.
9978 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9979 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9980 Note that the results depend on the programming language of the
9981 current compilation unit. If the language is C, the @samp{s}
9982 modifier will use the UTF-16 encoding while @samp{w} will use
9983 UTF-32. The encoding is set by the programming language and cannot
9986 @item @var{addr}, starting display address
9987 @var{addr} is the address where you want @value{GDBN} to begin displaying
9988 memory. The expression need not have a pointer value (though it may);
9989 it is always interpreted as an integer address of a byte of memory.
9990 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9991 @var{addr} is usually just after the last address examined---but several
9992 other commands also set the default address: @code{info breakpoints} (to
9993 the address of the last breakpoint listed), @code{info line} (to the
9994 starting address of a line), and @code{print} (if you use it to display
9995 a value from memory).
9998 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9999 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10000 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10001 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10002 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10004 You can also specify a negative repeat count to examine memory backward
10005 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10006 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10008 Since the letters indicating unit sizes are all distinct from the
10009 letters specifying output formats, you do not have to remember whether
10010 unit size or format comes first; either order works. The output
10011 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10012 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10014 Even though the unit size @var{u} is ignored for the formats @samp{s}
10015 and @samp{i}, you might still want to use a count @var{n}; for example,
10016 @samp{3i} specifies that you want to see three machine instructions,
10017 including any operands. For convenience, especially when used with
10018 the @code{display} command, the @samp{i} format also prints branch delay
10019 slot instructions, if any, beyond the count specified, which immediately
10020 follow the last instruction that is within the count. The command
10021 @code{disassemble} gives an alternative way of inspecting machine
10022 instructions; see @ref{Machine Code,,Source and Machine Code}.
10024 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10025 the command displays null-terminated strings or instructions before the given
10026 address as many as the absolute value of the given number. For the @samp{i}
10027 format, we use line number information in the debug info to accurately locate
10028 instruction boundaries while disassembling backward. If line info is not
10029 available, the command stops examining memory with an error message.
10031 All the defaults for the arguments to @code{x} are designed to make it
10032 easy to continue scanning memory with minimal specifications each time
10033 you use @code{x}. For example, after you have inspected three machine
10034 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10035 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10036 the repeat count @var{n} is used again; the other arguments default as
10037 for successive uses of @code{x}.
10039 When examining machine instructions, the instruction at current program
10040 counter is shown with a @code{=>} marker. For example:
10043 (@value{GDBP}) x/5i $pc-6
10044 0x804837f <main+11>: mov %esp,%ebp
10045 0x8048381 <main+13>: push %ecx
10046 0x8048382 <main+14>: sub $0x4,%esp
10047 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10048 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10051 @cindex @code{$_}, @code{$__}, and value history
10052 The addresses and contents printed by the @code{x} command are not saved
10053 in the value history because there is often too much of them and they
10054 would get in the way. Instead, @value{GDBN} makes these values available for
10055 subsequent use in expressions as values of the convenience variables
10056 @code{$_} and @code{$__}. After an @code{x} command, the last address
10057 examined is available for use in expressions in the convenience variable
10058 @code{$_}. The contents of that address, as examined, are available in
10059 the convenience variable @code{$__}.
10061 If the @code{x} command has a repeat count, the address and contents saved
10062 are from the last memory unit printed; this is not the same as the last
10063 address printed if several units were printed on the last line of output.
10065 @anchor{addressable memory unit}
10066 @cindex addressable memory unit
10067 Most targets have an addressable memory unit size of 8 bits. This means
10068 that to each memory address are associated 8 bits of data. Some
10069 targets, however, have other addressable memory unit sizes.
10070 Within @value{GDBN} and this document, the term
10071 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10072 when explicitly referring to a chunk of data of that size. The word
10073 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10074 the addressable memory unit size of the target. For most systems,
10075 addressable memory unit is a synonym of byte.
10077 @cindex remote memory comparison
10078 @cindex target memory comparison
10079 @cindex verify remote memory image
10080 @cindex verify target memory image
10081 When you are debugging a program running on a remote target machine
10082 (@pxref{Remote Debugging}), you may wish to verify the program's image
10083 in the remote machine's memory against the executable file you
10084 downloaded to the target. Or, on any target, you may want to check
10085 whether the program has corrupted its own read-only sections. The
10086 @code{compare-sections} command is provided for such situations.
10089 @kindex compare-sections
10090 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10091 Compare the data of a loadable section @var{section-name} in the
10092 executable file of the program being debugged with the same section in
10093 the target machine's memory, and report any mismatches. With no
10094 arguments, compares all loadable sections. With an argument of
10095 @code{-r}, compares all loadable read-only sections.
10097 Note: for remote targets, this command can be accelerated if the
10098 target supports computing the CRC checksum of a block of memory
10099 (@pxref{qCRC packet}).
10103 @section Automatic Display
10104 @cindex automatic display
10105 @cindex display of expressions
10107 If you find that you want to print the value of an expression frequently
10108 (to see how it changes), you might want to add it to the @dfn{automatic
10109 display list} so that @value{GDBN} prints its value each time your program stops.
10110 Each expression added to the list is given a number to identify it;
10111 to remove an expression from the list, you specify that number.
10112 The automatic display looks like this:
10116 3: bar[5] = (struct hack *) 0x3804
10120 This display shows item numbers, expressions and their current values. As with
10121 displays you request manually using @code{x} or @code{print}, you can
10122 specify the output format you prefer; in fact, @code{display} decides
10123 whether to use @code{print} or @code{x} depending your format
10124 specification---it uses @code{x} if you specify either the @samp{i}
10125 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10129 @item display @var{expr}
10130 Add the expression @var{expr} to the list of expressions to display
10131 each time your program stops. @xref{Expressions, ,Expressions}.
10133 @code{display} does not repeat if you press @key{RET} again after using it.
10135 @item display/@var{fmt} @var{expr}
10136 For @var{fmt} specifying only a display format and not a size or
10137 count, add the expression @var{expr} to the auto-display list but
10138 arrange to display it each time in the specified format @var{fmt}.
10139 @xref{Output Formats,,Output Formats}.
10141 @item display/@var{fmt} @var{addr}
10142 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10143 number of units, add the expression @var{addr} as a memory address to
10144 be examined each time your program stops. Examining means in effect
10145 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10148 For example, @samp{display/i $pc} can be helpful, to see the machine
10149 instruction about to be executed each time execution stops (@samp{$pc}
10150 is a common name for the program counter; @pxref{Registers, ,Registers}).
10153 @kindex delete display
10155 @item undisplay @var{dnums}@dots{}
10156 @itemx delete display @var{dnums}@dots{}
10157 Remove items from the list of expressions to display. Specify the
10158 numbers of the displays that you want affected with the command
10159 argument @var{dnums}. It can be a single display number, one of the
10160 numbers shown in the first field of the @samp{info display} display;
10161 or it could be a range of display numbers, as in @code{2-4}.
10163 @code{undisplay} does not repeat if you press @key{RET} after using it.
10164 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10166 @kindex disable display
10167 @item disable display @var{dnums}@dots{}
10168 Disable the display of item numbers @var{dnums}. A disabled display
10169 item is not printed automatically, but is not forgotten. It may be
10170 enabled again later. Specify the numbers of the displays that you
10171 want affected with the command argument @var{dnums}. It can be a
10172 single display number, one of the numbers shown in the first field of
10173 the @samp{info display} display; or it could be a range of display
10174 numbers, as in @code{2-4}.
10176 @kindex enable display
10177 @item enable display @var{dnums}@dots{}
10178 Enable display of item numbers @var{dnums}. It becomes effective once
10179 again in auto display of its expression, until you specify otherwise.
10180 Specify the numbers of the displays that you want affected with the
10181 command argument @var{dnums}. It can be a single display number, one
10182 of the numbers shown in the first field of the @samp{info display}
10183 display; or it could be a range of display numbers, as in @code{2-4}.
10186 Display the current values of the expressions on the list, just as is
10187 done when your program stops.
10189 @kindex info display
10191 Print the list of expressions previously set up to display
10192 automatically, each one with its item number, but without showing the
10193 values. This includes disabled expressions, which are marked as such.
10194 It also includes expressions which would not be displayed right now
10195 because they refer to automatic variables not currently available.
10198 @cindex display disabled out of scope
10199 If a display expression refers to local variables, then it does not make
10200 sense outside the lexical context for which it was set up. Such an
10201 expression is disabled when execution enters a context where one of its
10202 variables is not defined. For example, if you give the command
10203 @code{display last_char} while inside a function with an argument
10204 @code{last_char}, @value{GDBN} displays this argument while your program
10205 continues to stop inside that function. When it stops elsewhere---where
10206 there is no variable @code{last_char}---the display is disabled
10207 automatically. The next time your program stops where @code{last_char}
10208 is meaningful, you can enable the display expression once again.
10210 @node Print Settings
10211 @section Print Settings
10213 @cindex format options
10214 @cindex print settings
10215 @value{GDBN} provides the following ways to control how arrays, structures,
10216 and symbols are printed.
10219 These settings are useful for debugging programs in any language:
10223 @item set print address
10224 @itemx set print address on
10225 @cindex print/don't print memory addresses
10226 @value{GDBN} prints memory addresses showing the location of stack
10227 traces, structure values, pointer values, breakpoints, and so forth,
10228 even when it also displays the contents of those addresses. The default
10229 is @code{on}. For example, this is what a stack frame display looks like with
10230 @code{set print address on}:
10235 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10237 530 if (lquote != def_lquote)
10241 @item set print address off
10242 Do not print addresses when displaying their contents. For example,
10243 this is the same stack frame displayed with @code{set print address off}:
10247 (@value{GDBP}) set print addr off
10249 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10250 530 if (lquote != def_lquote)
10254 You can use @samp{set print address off} to eliminate all machine
10255 dependent displays from the @value{GDBN} interface. For example, with
10256 @code{print address off}, you should get the same text for backtraces on
10257 all machines---whether or not they involve pointer arguments.
10260 @item show print address
10261 Show whether or not addresses are to be printed.
10264 When @value{GDBN} prints a symbolic address, it normally prints the
10265 closest earlier symbol plus an offset. If that symbol does not uniquely
10266 identify the address (for example, it is a name whose scope is a single
10267 source file), you may need to clarify. One way to do this is with
10268 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10269 you can set @value{GDBN} to print the source file and line number when
10270 it prints a symbolic address:
10273 @item set print symbol-filename on
10274 @cindex source file and line of a symbol
10275 @cindex symbol, source file and line
10276 Tell @value{GDBN} to print the source file name and line number of a
10277 symbol in the symbolic form of an address.
10279 @item set print symbol-filename off
10280 Do not print source file name and line number of a symbol. This is the
10283 @item show print symbol-filename
10284 Show whether or not @value{GDBN} will print the source file name and
10285 line number of a symbol in the symbolic form of an address.
10288 Another situation where it is helpful to show symbol filenames and line
10289 numbers is when disassembling code; @value{GDBN} shows you the line
10290 number and source file that corresponds to each instruction.
10292 Also, you may wish to see the symbolic form only if the address being
10293 printed is reasonably close to the closest earlier symbol:
10296 @item set print max-symbolic-offset @var{max-offset}
10297 @itemx set print max-symbolic-offset unlimited
10298 @cindex maximum value for offset of closest symbol
10299 Tell @value{GDBN} to only display the symbolic form of an address if the
10300 offset between the closest earlier symbol and the address is less than
10301 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10302 to always print the symbolic form of an address if any symbol precedes
10303 it. Zero is equivalent to @code{unlimited}.
10305 @item show print max-symbolic-offset
10306 Ask how large the maximum offset is that @value{GDBN} prints in a
10310 @cindex wild pointer, interpreting
10311 @cindex pointer, finding referent
10312 If you have a pointer and you are not sure where it points, try
10313 @samp{set print symbol-filename on}. Then you can determine the name
10314 and source file location of the variable where it points, using
10315 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10316 For example, here @value{GDBN} shows that a variable @code{ptt} points
10317 at another variable @code{t}, defined in @file{hi2.c}:
10320 (@value{GDBP}) set print symbol-filename on
10321 (@value{GDBP}) p/a ptt
10322 $4 = 0xe008 <t in hi2.c>
10326 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10327 does not show the symbol name and filename of the referent, even with
10328 the appropriate @code{set print} options turned on.
10331 You can also enable @samp{/a}-like formatting all the time using
10332 @samp{set print symbol on}:
10335 @item set print symbol on
10336 Tell @value{GDBN} to print the symbol corresponding to an address, if
10339 @item set print symbol off
10340 Tell @value{GDBN} not to print the symbol corresponding to an
10341 address. In this mode, @value{GDBN} will still print the symbol
10342 corresponding to pointers to functions. This is the default.
10344 @item show print symbol
10345 Show whether @value{GDBN} will display the symbol corresponding to an
10349 Other settings control how different kinds of objects are printed:
10352 @item set print array
10353 @itemx set print array on
10354 @cindex pretty print arrays
10355 Pretty print arrays. This format is more convenient to read,
10356 but uses more space. The default is off.
10358 @item set print array off
10359 Return to compressed format for arrays.
10361 @item show print array
10362 Show whether compressed or pretty format is selected for displaying
10365 @cindex print array indexes
10366 @item set print array-indexes
10367 @itemx set print array-indexes on
10368 Print the index of each element when displaying arrays. May be more
10369 convenient to locate a given element in the array or quickly find the
10370 index of a given element in that printed array. The default is off.
10372 @item set print array-indexes off
10373 Stop printing element indexes when displaying arrays.
10375 @item show print array-indexes
10376 Show whether the index of each element is printed when displaying
10379 @item set print elements @var{number-of-elements}
10380 @itemx set print elements unlimited
10381 @cindex number of array elements to print
10382 @cindex limit on number of printed array elements
10383 Set a limit on how many elements of an array @value{GDBN} will print.
10384 If @value{GDBN} is printing a large array, it stops printing after it has
10385 printed the number of elements set by the @code{set print elements} command.
10386 This limit also applies to the display of strings.
10387 When @value{GDBN} starts, this limit is set to 200.
10388 Setting @var{number-of-elements} to @code{unlimited} or zero means
10389 that the number of elements to print is unlimited.
10391 @item show print elements
10392 Display the number of elements of a large array that @value{GDBN} will print.
10393 If the number is 0, then the printing is unlimited.
10395 @item set print frame-arguments @var{value}
10396 @kindex set print frame-arguments
10397 @cindex printing frame argument values
10398 @cindex print all frame argument values
10399 @cindex print frame argument values for scalars only
10400 @cindex do not print frame argument values
10401 This command allows to control how the values of arguments are printed
10402 when the debugger prints a frame (@pxref{Frames}). The possible
10407 The values of all arguments are printed.
10410 Print the value of an argument only if it is a scalar. The value of more
10411 complex arguments such as arrays, structures, unions, etc, is replaced
10412 by @code{@dots{}}. This is the default. Here is an example where
10413 only scalar arguments are shown:
10416 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10421 None of the argument values are printed. Instead, the value of each argument
10422 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10425 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10430 By default, only scalar arguments are printed. This command can be used
10431 to configure the debugger to print the value of all arguments, regardless
10432 of their type. However, it is often advantageous to not print the value
10433 of more complex parameters. For instance, it reduces the amount of
10434 information printed in each frame, making the backtrace more readable.
10435 Also, it improves performance when displaying Ada frames, because
10436 the computation of large arguments can sometimes be CPU-intensive,
10437 especially in large applications. Setting @code{print frame-arguments}
10438 to @code{scalars} (the default) or @code{none} avoids this computation,
10439 thus speeding up the display of each Ada frame.
10441 @item show print frame-arguments
10442 Show how the value of arguments should be displayed when printing a frame.
10444 @item set print raw frame-arguments on
10445 Print frame arguments in raw, non pretty-printed, form.
10447 @item set print raw frame-arguments off
10448 Print frame arguments in pretty-printed form, if there is a pretty-printer
10449 for the value (@pxref{Pretty Printing}),
10450 otherwise print the value in raw form.
10451 This is the default.
10453 @item show print raw frame-arguments
10454 Show whether to print frame arguments in raw form.
10456 @anchor{set print entry-values}
10457 @item set print entry-values @var{value}
10458 @kindex set print entry-values
10459 Set printing of frame argument values at function entry. In some cases
10460 @value{GDBN} can determine the value of function argument which was passed by
10461 the function caller, even if the value was modified inside the called function
10462 and therefore is different. With optimized code, the current value could be
10463 unavailable, but the entry value may still be known.
10465 The default value is @code{default} (see below for its description). Older
10466 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10467 this feature will behave in the @code{default} setting the same way as with the
10470 This functionality is currently supported only by DWARF 2 debugging format and
10471 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10472 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10475 The @var{value} parameter can be one of the following:
10479 Print only actual parameter values, never print values from function entry
10483 #0 different (val=6)
10484 #0 lost (val=<optimized out>)
10486 #0 invalid (val=<optimized out>)
10490 Print only parameter values from function entry point. The actual parameter
10491 values are never printed.
10493 #0 equal (val@@entry=5)
10494 #0 different (val@@entry=5)
10495 #0 lost (val@@entry=5)
10496 #0 born (val@@entry=<optimized out>)
10497 #0 invalid (val@@entry=<optimized out>)
10501 Print only parameter values from function entry point. If value from function
10502 entry point is not known while the actual value is known, print the actual
10503 value for such parameter.
10505 #0 equal (val@@entry=5)
10506 #0 different (val@@entry=5)
10507 #0 lost (val@@entry=5)
10509 #0 invalid (val@@entry=<optimized out>)
10513 Print actual parameter values. If actual parameter value is not known while
10514 value from function entry point is known, print the entry point value for such
10518 #0 different (val=6)
10519 #0 lost (val@@entry=5)
10521 #0 invalid (val=<optimized out>)
10525 Always print both the actual parameter value and its value from function entry
10526 point, even if values of one or both are not available due to compiler
10529 #0 equal (val=5, val@@entry=5)
10530 #0 different (val=6, val@@entry=5)
10531 #0 lost (val=<optimized out>, val@@entry=5)
10532 #0 born (val=10, val@@entry=<optimized out>)
10533 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10537 Print the actual parameter value if it is known and also its value from
10538 function entry point if it is known. If neither is known, print for the actual
10539 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10540 values are known and identical, print the shortened
10541 @code{param=param@@entry=VALUE} notation.
10543 #0 equal (val=val@@entry=5)
10544 #0 different (val=6, val@@entry=5)
10545 #0 lost (val@@entry=5)
10547 #0 invalid (val=<optimized out>)
10551 Always print the actual parameter value. Print also its value from function
10552 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10553 if both values are known and identical, print the shortened
10554 @code{param=param@@entry=VALUE} notation.
10556 #0 equal (val=val@@entry=5)
10557 #0 different (val=6, val@@entry=5)
10558 #0 lost (val=<optimized out>, val@@entry=5)
10560 #0 invalid (val=<optimized out>)
10564 For analysis messages on possible failures of frame argument values at function
10565 entry resolution see @ref{set debug entry-values}.
10567 @item show print entry-values
10568 Show the method being used for printing of frame argument values at function
10571 @item set print repeats @var{number-of-repeats}
10572 @itemx set print repeats unlimited
10573 @cindex repeated array elements
10574 Set the threshold for suppressing display of repeated array
10575 elements. When the number of consecutive identical elements of an
10576 array exceeds the threshold, @value{GDBN} prints the string
10577 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10578 identical repetitions, instead of displaying the identical elements
10579 themselves. Setting the threshold to @code{unlimited} or zero will
10580 cause all elements to be individually printed. The default threshold
10583 @item show print repeats
10584 Display the current threshold for printing repeated identical
10587 @item set print max-depth @var{depth}
10588 @item set print max-depth unlimited
10589 @cindex printing nested structures
10590 Set the threshold after which nested structures are replaced with
10591 ellipsis, this can make visualising deeply nested structures easier.
10593 For example, given this C code
10596 typedef struct s1 @{ int a; @} s1;
10597 typedef struct s2 @{ s1 b; @} s2;
10598 typedef struct s3 @{ s2 c; @} s3;
10599 typedef struct s4 @{ s3 d; @} s4;
10601 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
10604 The following table shows how different values of @var{depth} will
10605 effect how @code{var} is printed by @value{GDBN}:
10607 @multitable @columnfractions .3 .7
10608 @headitem @var{depth} setting @tab Result of @samp{p var}
10610 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
10612 @tab @code{$1 = @{...@}}
10614 @tab @code{$1 = @{d = @{...@}@}}
10616 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
10618 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
10620 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
10623 To see the contents of structures that have been hidden the user can
10624 either increase the print max-depth, or they can print the elements of
10625 the structure that are visible, for example
10628 (gdb) set print max-depth 2
10630 $1 = @{d = @{c = @{...@}@}@}
10632 $2 = @{c = @{b = @{...@}@}@}
10634 $3 = @{b = @{a = 3@}@}
10637 The pattern used to replace nested structures varies based on
10638 language, for most languages @code{@{...@}} is used, but Fortran uses
10641 @item show print max-depth
10642 Display the current threshold after which nested structures are
10643 replaces with ellipsis.
10645 @item set print null-stop
10646 @cindex @sc{null} elements in arrays
10647 Cause @value{GDBN} to stop printing the characters of an array when the first
10648 @sc{null} is encountered. This is useful when large arrays actually
10649 contain only short strings.
10650 The default is off.
10652 @item show print null-stop
10653 Show whether @value{GDBN} stops printing an array on the first
10654 @sc{null} character.
10656 @item set print pretty on
10657 @cindex print structures in indented form
10658 @cindex indentation in structure display
10659 Cause @value{GDBN} to print structures in an indented format with one member
10660 per line, like this:
10675 @item set print pretty off
10676 Cause @value{GDBN} to print structures in a compact format, like this:
10680 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10681 meat = 0x54 "Pork"@}
10686 This is the default format.
10688 @item show print pretty
10689 Show which format @value{GDBN} is using to print structures.
10691 @item set print sevenbit-strings on
10692 @cindex eight-bit characters in strings
10693 @cindex octal escapes in strings
10694 Print using only seven-bit characters; if this option is set,
10695 @value{GDBN} displays any eight-bit characters (in strings or
10696 character values) using the notation @code{\}@var{nnn}. This setting is
10697 best if you are working in English (@sc{ascii}) and you use the
10698 high-order bit of characters as a marker or ``meta'' bit.
10700 @item set print sevenbit-strings off
10701 Print full eight-bit characters. This allows the use of more
10702 international character sets, and is the default.
10704 @item show print sevenbit-strings
10705 Show whether or not @value{GDBN} is printing only seven-bit characters.
10707 @item set print union on
10708 @cindex unions in structures, printing
10709 Tell @value{GDBN} to print unions which are contained in structures
10710 and other unions. This is the default setting.
10712 @item set print union off
10713 Tell @value{GDBN} not to print unions which are contained in
10714 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10717 @item show print union
10718 Ask @value{GDBN} whether or not it will print unions which are contained in
10719 structures and other unions.
10721 For example, given the declarations
10724 typedef enum @{Tree, Bug@} Species;
10725 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10726 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10737 struct thing foo = @{Tree, @{Acorn@}@};
10741 with @code{set print union on} in effect @samp{p foo} would print
10744 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10748 and with @code{set print union off} in effect it would print
10751 $1 = @{it = Tree, form = @{...@}@}
10755 @code{set print union} affects programs written in C-like languages
10761 These settings are of interest when debugging C@t{++} programs:
10764 @cindex demangling C@t{++} names
10765 @item set print demangle
10766 @itemx set print demangle on
10767 Print C@t{++} names in their source form rather than in the encoded
10768 (``mangled'') form passed to the assembler and linker for type-safe
10769 linkage. The default is on.
10771 @item show print demangle
10772 Show whether C@t{++} names are printed in mangled or demangled form.
10774 @item set print asm-demangle
10775 @itemx set print asm-demangle on
10776 Print C@t{++} names in their source form rather than their mangled form, even
10777 in assembler code printouts such as instruction disassemblies.
10778 The default is off.
10780 @item show print asm-demangle
10781 Show whether C@t{++} names in assembly listings are printed in mangled
10784 @cindex C@t{++} symbol decoding style
10785 @cindex symbol decoding style, C@t{++}
10786 @kindex set demangle-style
10787 @item set demangle-style @var{style}
10788 Choose among several encoding schemes used by different compilers to represent
10789 C@t{++} names. If you omit @var{style}, you will see a list of possible
10790 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10791 decoding style by inspecting your program.
10793 @item show demangle-style
10794 Display the encoding style currently in use for decoding C@t{++} symbols.
10796 @item set print object
10797 @itemx set print object on
10798 @cindex derived type of an object, printing
10799 @cindex display derived types
10800 When displaying a pointer to an object, identify the @emph{actual}
10801 (derived) type of the object rather than the @emph{declared} type, using
10802 the virtual function table. Note that the virtual function table is
10803 required---this feature can only work for objects that have run-time
10804 type identification; a single virtual method in the object's declared
10805 type is sufficient. Note that this setting is also taken into account when
10806 working with variable objects via MI (@pxref{GDB/MI}).
10808 @item set print object off
10809 Display only the declared type of objects, without reference to the
10810 virtual function table. This is the default setting.
10812 @item show print object
10813 Show whether actual, or declared, object types are displayed.
10815 @item set print static-members
10816 @itemx set print static-members on
10817 @cindex static members of C@t{++} objects
10818 Print static members when displaying a C@t{++} object. The default is on.
10820 @item set print static-members off
10821 Do not print static members when displaying a C@t{++} object.
10823 @item show print static-members
10824 Show whether C@t{++} static members are printed or not.
10826 @item set print pascal_static-members
10827 @itemx set print pascal_static-members on
10828 @cindex static members of Pascal objects
10829 @cindex Pascal objects, static members display
10830 Print static members when displaying a Pascal object. The default is on.
10832 @item set print pascal_static-members off
10833 Do not print static members when displaying a Pascal object.
10835 @item show print pascal_static-members
10836 Show whether Pascal static members are printed or not.
10838 @c These don't work with HP ANSI C++ yet.
10839 @item set print vtbl
10840 @itemx set print vtbl on
10841 @cindex pretty print C@t{++} virtual function tables
10842 @cindex virtual functions (C@t{++}) display
10843 @cindex VTBL display
10844 Pretty print C@t{++} virtual function tables. The default is off.
10845 (The @code{vtbl} commands do not work on programs compiled with the HP
10846 ANSI C@t{++} compiler (@code{aCC}).)
10848 @item set print vtbl off
10849 Do not pretty print C@t{++} virtual function tables.
10851 @item show print vtbl
10852 Show whether C@t{++} virtual function tables are pretty printed, or not.
10855 @node Pretty Printing
10856 @section Pretty Printing
10858 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10859 Python code. It greatly simplifies the display of complex objects. This
10860 mechanism works for both MI and the CLI.
10863 * Pretty-Printer Introduction:: Introduction to pretty-printers
10864 * Pretty-Printer Example:: An example pretty-printer
10865 * Pretty-Printer Commands:: Pretty-printer commands
10868 @node Pretty-Printer Introduction
10869 @subsection Pretty-Printer Introduction
10871 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10872 registered for the value. If there is then @value{GDBN} invokes the
10873 pretty-printer to print the value. Otherwise the value is printed normally.
10875 Pretty-printers are normally named. This makes them easy to manage.
10876 The @samp{info pretty-printer} command will list all the installed
10877 pretty-printers with their names.
10878 If a pretty-printer can handle multiple data types, then its
10879 @dfn{subprinters} are the printers for the individual data types.
10880 Each such subprinter has its own name.
10881 The format of the name is @var{printer-name};@var{subprinter-name}.
10883 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10884 Typically they are automatically loaded and registered when the corresponding
10885 debug information is loaded, thus making them available without having to
10886 do anything special.
10888 There are three places where a pretty-printer can be registered.
10892 Pretty-printers registered globally are available when debugging
10896 Pretty-printers registered with a program space are available only
10897 when debugging that program.
10898 @xref{Progspaces In Python}, for more details on program spaces in Python.
10901 Pretty-printers registered with an objfile are loaded and unloaded
10902 with the corresponding objfile (e.g., shared library).
10903 @xref{Objfiles In Python}, for more details on objfiles in Python.
10906 @xref{Selecting Pretty-Printers}, for further information on how
10907 pretty-printers are selected,
10909 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10912 @node Pretty-Printer Example
10913 @subsection Pretty-Printer Example
10915 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10918 (@value{GDBP}) print s
10920 static npos = 4294967295,
10922 <std::allocator<char>> = @{
10923 <__gnu_cxx::new_allocator<char>> = @{
10924 <No data fields>@}, <No data fields>
10926 members of std::basic_string<char, std::char_traits<char>,
10927 std::allocator<char> >::_Alloc_hider:
10928 _M_p = 0x804a014 "abcd"
10933 With a pretty-printer for @code{std::string} only the contents are printed:
10936 (@value{GDBP}) print s
10940 @node Pretty-Printer Commands
10941 @subsection Pretty-Printer Commands
10942 @cindex pretty-printer commands
10945 @kindex info pretty-printer
10946 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10947 Print the list of installed pretty-printers.
10948 This includes disabled pretty-printers, which are marked as such.
10950 @var{object-regexp} is a regular expression matching the objects
10951 whose pretty-printers to list.
10952 Objects can be @code{global}, the program space's file
10953 (@pxref{Progspaces In Python}),
10954 and the object files within that program space (@pxref{Objfiles In Python}).
10955 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10956 looks up a printer from these three objects.
10958 @var{name-regexp} is a regular expression matching the name of the printers
10961 @kindex disable pretty-printer
10962 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10963 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10964 A disabled pretty-printer is not forgotten, it may be enabled again later.
10966 @kindex enable pretty-printer
10967 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10968 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10973 Suppose we have three pretty-printers installed: one from library1.so
10974 named @code{foo} that prints objects of type @code{foo}, and
10975 another from library2.so named @code{bar} that prints two types of objects,
10976 @code{bar1} and @code{bar2}.
10979 (gdb) info pretty-printer
10986 (gdb) info pretty-printer library2
10991 (gdb) disable pretty-printer library1
10993 2 of 3 printers enabled
10994 (gdb) info pretty-printer
11001 (gdb) disable pretty-printer library2 bar;bar1
11003 1 of 3 printers enabled
11004 (gdb) info pretty-printer library2
11011 (gdb) disable pretty-printer library2 bar
11013 0 of 3 printers enabled
11014 (gdb) info pretty-printer library2
11023 Note that for @code{bar} the entire printer can be disabled,
11024 as can each individual subprinter.
11026 @node Value History
11027 @section Value History
11029 @cindex value history
11030 @cindex history of values printed by @value{GDBN}
11031 Values printed by the @code{print} command are saved in the @value{GDBN}
11032 @dfn{value history}. This allows you to refer to them in other expressions.
11033 Values are kept until the symbol table is re-read or discarded
11034 (for example with the @code{file} or @code{symbol-file} commands).
11035 When the symbol table changes, the value history is discarded,
11036 since the values may contain pointers back to the types defined in the
11041 @cindex history number
11042 The values printed are given @dfn{history numbers} by which you can
11043 refer to them. These are successive integers starting with one.
11044 @code{print} shows you the history number assigned to a value by
11045 printing @samp{$@var{num} = } before the value; here @var{num} is the
11048 To refer to any previous value, use @samp{$} followed by the value's
11049 history number. The way @code{print} labels its output is designed to
11050 remind you of this. Just @code{$} refers to the most recent value in
11051 the history, and @code{$$} refers to the value before that.
11052 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11053 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11054 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11056 For example, suppose you have just printed a pointer to a structure and
11057 want to see the contents of the structure. It suffices to type
11063 If you have a chain of structures where the component @code{next} points
11064 to the next one, you can print the contents of the next one with this:
11071 You can print successive links in the chain by repeating this
11072 command---which you can do by just typing @key{RET}.
11074 Note that the history records values, not expressions. If the value of
11075 @code{x} is 4 and you type these commands:
11083 then the value recorded in the value history by the @code{print} command
11084 remains 4 even though the value of @code{x} has changed.
11087 @kindex show values
11089 Print the last ten values in the value history, with their item numbers.
11090 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11091 values} does not change the history.
11093 @item show values @var{n}
11094 Print ten history values centered on history item number @var{n}.
11096 @item show values +
11097 Print ten history values just after the values last printed. If no more
11098 values are available, @code{show values +} produces no display.
11101 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11102 same effect as @samp{show values +}.
11104 @node Convenience Vars
11105 @section Convenience Variables
11107 @cindex convenience variables
11108 @cindex user-defined variables
11109 @value{GDBN} provides @dfn{convenience variables} that you can use within
11110 @value{GDBN} to hold on to a value and refer to it later. These variables
11111 exist entirely within @value{GDBN}; they are not part of your program, and
11112 setting a convenience variable has no direct effect on further execution
11113 of your program. That is why you can use them freely.
11115 Convenience variables are prefixed with @samp{$}. Any name preceded by
11116 @samp{$} can be used for a convenience variable, unless it is one of
11117 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11118 (Value history references, in contrast, are @emph{numbers} preceded
11119 by @samp{$}. @xref{Value History, ,Value History}.)
11121 You can save a value in a convenience variable with an assignment
11122 expression, just as you would set a variable in your program.
11126 set $foo = *object_ptr
11130 would save in @code{$foo} the value contained in the object pointed to by
11133 Using a convenience variable for the first time creates it, but its
11134 value is @code{void} until you assign a new value. You can alter the
11135 value with another assignment at any time.
11137 Convenience variables have no fixed types. You can assign a convenience
11138 variable any type of value, including structures and arrays, even if
11139 that variable already has a value of a different type. The convenience
11140 variable, when used as an expression, has the type of its current value.
11143 @kindex show convenience
11144 @cindex show all user variables and functions
11145 @item show convenience
11146 Print a list of convenience variables used so far, and their values,
11147 as well as a list of the convenience functions.
11148 Abbreviated @code{show conv}.
11150 @kindex init-if-undefined
11151 @cindex convenience variables, initializing
11152 @item init-if-undefined $@var{variable} = @var{expression}
11153 Set a convenience variable if it has not already been set. This is useful
11154 for user-defined commands that keep some state. It is similar, in concept,
11155 to using local static variables with initializers in C (except that
11156 convenience variables are global). It can also be used to allow users to
11157 override default values used in a command script.
11159 If the variable is already defined then the expression is not evaluated so
11160 any side-effects do not occur.
11163 One of the ways to use a convenience variable is as a counter to be
11164 incremented or a pointer to be advanced. For example, to print
11165 a field from successive elements of an array of structures:
11169 print bar[$i++]->contents
11173 Repeat that command by typing @key{RET}.
11175 Some convenience variables are created automatically by @value{GDBN} and given
11176 values likely to be useful.
11179 @vindex $_@r{, convenience variable}
11181 The variable @code{$_} is automatically set by the @code{x} command to
11182 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11183 commands which provide a default address for @code{x} to examine also
11184 set @code{$_} to that address; these commands include @code{info line}
11185 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11186 except when set by the @code{x} command, in which case it is a pointer
11187 to the type of @code{$__}.
11189 @vindex $__@r{, convenience variable}
11191 The variable @code{$__} is automatically set by the @code{x} command
11192 to the value found in the last address examined. Its type is chosen
11193 to match the format in which the data was printed.
11196 @vindex $_exitcode@r{, convenience variable}
11197 When the program being debugged terminates normally, @value{GDBN}
11198 automatically sets this variable to the exit code of the program, and
11199 resets @code{$_exitsignal} to @code{void}.
11202 @vindex $_exitsignal@r{, convenience variable}
11203 When the program being debugged dies due to an uncaught signal,
11204 @value{GDBN} automatically sets this variable to that signal's number,
11205 and resets @code{$_exitcode} to @code{void}.
11207 To distinguish between whether the program being debugged has exited
11208 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11209 @code{$_exitsignal} is not @code{void}), the convenience function
11210 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11211 Functions}). For example, considering the following source code:
11214 #include <signal.h>
11217 main (int argc, char *argv[])
11224 A valid way of telling whether the program being debugged has exited
11225 or signalled would be:
11228 (@value{GDBP}) define has_exited_or_signalled
11229 Type commands for definition of ``has_exited_or_signalled''.
11230 End with a line saying just ``end''.
11231 >if $_isvoid ($_exitsignal)
11232 >echo The program has exited\n
11234 >echo The program has signalled\n
11240 Program terminated with signal SIGALRM, Alarm clock.
11241 The program no longer exists.
11242 (@value{GDBP}) has_exited_or_signalled
11243 The program has signalled
11246 As can be seen, @value{GDBN} correctly informs that the program being
11247 debugged has signalled, since it calls @code{raise} and raises a
11248 @code{SIGALRM} signal. If the program being debugged had not called
11249 @code{raise}, then @value{GDBN} would report a normal exit:
11252 (@value{GDBP}) has_exited_or_signalled
11253 The program has exited
11257 The variable @code{$_exception} is set to the exception object being
11258 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11261 @itemx $_probe_arg0@dots{}$_probe_arg11
11262 Arguments to a static probe. @xref{Static Probe Points}.
11265 @vindex $_sdata@r{, inspect, convenience variable}
11266 The variable @code{$_sdata} contains extra collected static tracepoint
11267 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11268 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11269 if extra static tracepoint data has not been collected.
11272 @vindex $_siginfo@r{, convenience variable}
11273 The variable @code{$_siginfo} contains extra signal information
11274 (@pxref{extra signal information}). Note that @code{$_siginfo}
11275 could be empty, if the application has not yet received any signals.
11276 For example, it will be empty before you execute the @code{run} command.
11279 @vindex $_tlb@r{, convenience variable}
11280 The variable @code{$_tlb} is automatically set when debugging
11281 applications running on MS-Windows in native mode or connected to
11282 gdbserver that supports the @code{qGetTIBAddr} request.
11283 @xref{General Query Packets}.
11284 This variable contains the address of the thread information block.
11287 The number of the current inferior. @xref{Inferiors and
11288 Programs, ,Debugging Multiple Inferiors and Programs}.
11291 The thread number of the current thread. @xref{thread numbers}.
11294 The global number of the current thread. @xref{global thread numbers}.
11298 @vindex $_gdb_major@r{, convenience variable}
11299 @vindex $_gdb_minor@r{, convenience variable}
11300 The major and minor version numbers of the running @value{GDBN}.
11301 Development snapshots and pretest versions have their minor version
11302 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11303 the value 12 for @code{$_gdb_minor}. These variables allow you to
11304 write scripts that work with different versions of @value{GDBN}
11305 without errors caused by features unavailable in some of those
11309 @node Convenience Funs
11310 @section Convenience Functions
11312 @cindex convenience functions
11313 @value{GDBN} also supplies some @dfn{convenience functions}. These
11314 have a syntax similar to convenience variables. A convenience
11315 function can be used in an expression just like an ordinary function;
11316 however, a convenience function is implemented internally to
11319 These functions do not require @value{GDBN} to be configured with
11320 @code{Python} support, which means that they are always available.
11324 @item $_isvoid (@var{expr})
11325 @findex $_isvoid@r{, convenience function}
11326 Return one if the expression @var{expr} is @code{void}. Otherwise it
11329 A @code{void} expression is an expression where the type of the result
11330 is @code{void}. For example, you can examine a convenience variable
11331 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11335 (@value{GDBP}) print $_exitcode
11337 (@value{GDBP}) print $_isvoid ($_exitcode)
11340 Starting program: ./a.out
11341 [Inferior 1 (process 29572) exited normally]
11342 (@value{GDBP}) print $_exitcode
11344 (@value{GDBP}) print $_isvoid ($_exitcode)
11348 In the example above, we used @code{$_isvoid} to check whether
11349 @code{$_exitcode} is @code{void} before and after the execution of the
11350 program being debugged. Before the execution there is no exit code to
11351 be examined, therefore @code{$_exitcode} is @code{void}. After the
11352 execution the program being debugged returned zero, therefore
11353 @code{$_exitcode} is zero, which means that it is not @code{void}
11356 The @code{void} expression can also be a call of a function from the
11357 program being debugged. For example, given the following function:
11366 The result of calling it inside @value{GDBN} is @code{void}:
11369 (@value{GDBP}) print foo ()
11371 (@value{GDBP}) print $_isvoid (foo ())
11373 (@value{GDBP}) set $v = foo ()
11374 (@value{GDBP}) print $v
11376 (@value{GDBP}) print $_isvoid ($v)
11382 These functions require @value{GDBN} to be configured with
11383 @code{Python} support.
11387 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11388 @findex $_memeq@r{, convenience function}
11389 Returns one if the @var{length} bytes at the addresses given by
11390 @var{buf1} and @var{buf2} are equal.
11391 Otherwise it returns zero.
11393 @item $_regex(@var{str}, @var{regex})
11394 @findex $_regex@r{, convenience function}
11395 Returns one if the string @var{str} matches the regular expression
11396 @var{regex}. Otherwise it returns zero.
11397 The syntax of the regular expression is that specified by @code{Python}'s
11398 regular expression support.
11400 @item $_streq(@var{str1}, @var{str2})
11401 @findex $_streq@r{, convenience function}
11402 Returns one if the strings @var{str1} and @var{str2} are equal.
11403 Otherwise it returns zero.
11405 @item $_strlen(@var{str})
11406 @findex $_strlen@r{, convenience function}
11407 Returns the length of string @var{str}.
11409 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11410 @findex $_caller_is@r{, convenience function}
11411 Returns one if the calling function's name is equal to @var{name}.
11412 Otherwise it returns zero.
11414 If the optional argument @var{number_of_frames} is provided,
11415 it is the number of frames up in the stack to look.
11423 at testsuite/gdb.python/py-caller-is.c:21
11424 #1 0x00000000004005a0 in middle_func ()
11425 at testsuite/gdb.python/py-caller-is.c:27
11426 #2 0x00000000004005ab in top_func ()
11427 at testsuite/gdb.python/py-caller-is.c:33
11428 #3 0x00000000004005b6 in main ()
11429 at testsuite/gdb.python/py-caller-is.c:39
11430 (gdb) print $_caller_is ("middle_func")
11432 (gdb) print $_caller_is ("top_func", 2)
11436 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11437 @findex $_caller_matches@r{, convenience function}
11438 Returns one if the calling function's name matches the regular expression
11439 @var{regexp}. Otherwise it returns zero.
11441 If the optional argument @var{number_of_frames} is provided,
11442 it is the number of frames up in the stack to look.
11445 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11446 @findex $_any_caller_is@r{, convenience function}
11447 Returns one if any calling function's name is equal to @var{name}.
11448 Otherwise it returns zero.
11450 If the optional argument @var{number_of_frames} is provided,
11451 it is the number of frames up in the stack to look.
11454 This function differs from @code{$_caller_is} in that this function
11455 checks all stack frames from the immediate caller to the frame specified
11456 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11457 frame specified by @var{number_of_frames}.
11459 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11460 @findex $_any_caller_matches@r{, convenience function}
11461 Returns one if any calling function's name matches the regular expression
11462 @var{regexp}. Otherwise it returns zero.
11464 If the optional argument @var{number_of_frames} is provided,
11465 it is the number of frames up in the stack to look.
11468 This function differs from @code{$_caller_matches} in that this function
11469 checks all stack frames from the immediate caller to the frame specified
11470 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11471 frame specified by @var{number_of_frames}.
11473 @item $_as_string(@var{value})
11474 @findex $_as_string@r{, convenience function}
11475 Return the string representation of @var{value}.
11477 This function is useful to obtain the textual label (enumerator) of an
11478 enumeration value. For example, assuming the variable @var{node} is of
11479 an enumerated type:
11482 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11483 Visiting node of type NODE_INTEGER
11486 @item $_cimag(@var{value})
11487 @itemx $_creal(@var{value})
11488 @findex $_cimag@r{, convenience function}
11489 @findex $_creal@r{, convenience function}
11490 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11491 the complex number @var{value}.
11493 The type of the imaginary or real part depends on the type of the
11494 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11495 will return an imaginary part of type @code{float}.
11499 @value{GDBN} provides the ability to list and get help on
11500 convenience functions.
11503 @item help function
11504 @kindex help function
11505 @cindex show all convenience functions
11506 Print a list of all convenience functions.
11513 You can refer to machine register contents, in expressions, as variables
11514 with names starting with @samp{$}. The names of registers are different
11515 for each machine; use @code{info registers} to see the names used on
11519 @kindex info registers
11520 @item info registers
11521 Print the names and values of all registers except floating-point
11522 and vector registers (in the selected stack frame).
11524 @kindex info all-registers
11525 @cindex floating point registers
11526 @item info all-registers
11527 Print the names and values of all registers, including floating-point
11528 and vector registers (in the selected stack frame).
11530 @item info registers @var{reggroup} @dots{}
11531 Print the name and value of the registers in each of the specified
11532 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11533 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11535 @item info registers @var{regname} @dots{}
11536 Print the @dfn{relativized} value of each specified register @var{regname}.
11537 As discussed in detail below, register values are normally relative to
11538 the selected stack frame. The @var{regname} may be any register name valid on
11539 the machine you are using, with or without the initial @samp{$}.
11542 @anchor{standard registers}
11543 @cindex stack pointer register
11544 @cindex program counter register
11545 @cindex process status register
11546 @cindex frame pointer register
11547 @cindex standard registers
11548 @value{GDBN} has four ``standard'' register names that are available (in
11549 expressions) on most machines---whenever they do not conflict with an
11550 architecture's canonical mnemonics for registers. The register names
11551 @code{$pc} and @code{$sp} are used for the program counter register and
11552 the stack pointer. @code{$fp} is used for a register that contains a
11553 pointer to the current stack frame, and @code{$ps} is used for a
11554 register that contains the processor status. For example,
11555 you could print the program counter in hex with
11562 or print the instruction to be executed next with
11569 or add four to the stack pointer@footnote{This is a way of removing
11570 one word from the stack, on machines where stacks grow downward in
11571 memory (most machines, nowadays). This assumes that the innermost
11572 stack frame is selected; setting @code{$sp} is not allowed when other
11573 stack frames are selected. To pop entire frames off the stack,
11574 regardless of machine architecture, use @code{return};
11575 see @ref{Returning, ,Returning from a Function}.} with
11581 Whenever possible, these four standard register names are available on
11582 your machine even though the machine has different canonical mnemonics,
11583 so long as there is no conflict. The @code{info registers} command
11584 shows the canonical names. For example, on the SPARC, @code{info
11585 registers} displays the processor status register as @code{$psr} but you
11586 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11587 is an alias for the @sc{eflags} register.
11589 @value{GDBN} always considers the contents of an ordinary register as an
11590 integer when the register is examined in this way. Some machines have
11591 special registers which can hold nothing but floating point; these
11592 registers are considered to have floating point values. There is no way
11593 to refer to the contents of an ordinary register as floating point value
11594 (although you can @emph{print} it as a floating point value with
11595 @samp{print/f $@var{regname}}).
11597 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11598 means that the data format in which the register contents are saved by
11599 the operating system is not the same one that your program normally
11600 sees. For example, the registers of the 68881 floating point
11601 coprocessor are always saved in ``extended'' (raw) format, but all C
11602 programs expect to work with ``double'' (virtual) format. In such
11603 cases, @value{GDBN} normally works with the virtual format only (the format
11604 that makes sense for your program), but the @code{info registers} command
11605 prints the data in both formats.
11607 @cindex SSE registers (x86)
11608 @cindex MMX registers (x86)
11609 Some machines have special registers whose contents can be interpreted
11610 in several different ways. For example, modern x86-based machines
11611 have SSE and MMX registers that can hold several values packed
11612 together in several different formats. @value{GDBN} refers to such
11613 registers in @code{struct} notation:
11616 (@value{GDBP}) print $xmm1
11618 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11619 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11620 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11621 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11622 v4_int32 = @{0, 20657912, 11, 13@},
11623 v2_int64 = @{88725056443645952, 55834574859@},
11624 uint128 = 0x0000000d0000000b013b36f800000000
11629 To set values of such registers, you need to tell @value{GDBN} which
11630 view of the register you wish to change, as if you were assigning
11631 value to a @code{struct} member:
11634 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11637 Normally, register values are relative to the selected stack frame
11638 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11639 value that the register would contain if all stack frames farther in
11640 were exited and their saved registers restored. In order to see the
11641 true contents of hardware registers, you must select the innermost
11642 frame (with @samp{frame 0}).
11644 @cindex caller-saved registers
11645 @cindex call-clobbered registers
11646 @cindex volatile registers
11647 @cindex <not saved> values
11648 Usually ABIs reserve some registers as not needed to be saved by the
11649 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11650 registers). It may therefore not be possible for @value{GDBN} to know
11651 the value a register had before the call (in other words, in the outer
11652 frame), if the register value has since been changed by the callee.
11653 @value{GDBN} tries to deduce where the inner frame saved
11654 (``callee-saved'') registers, from the debug info, unwind info, or the
11655 machine code generated by your compiler. If some register is not
11656 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11657 its own knowledge of the ABI, or because the debug/unwind info
11658 explicitly says the register's value is undefined), @value{GDBN}
11659 displays @w{@samp{<not saved>}} as the register's value. With targets
11660 that @value{GDBN} has no knowledge of the register saving convention,
11661 if a register was not saved by the callee, then its value and location
11662 in the outer frame are assumed to be the same of the inner frame.
11663 This is usually harmless, because if the register is call-clobbered,
11664 the caller either does not care what is in the register after the
11665 call, or has code to restore the value that it does care about. Note,
11666 however, that if you change such a register in the outer frame, you
11667 may also be affecting the inner frame. Also, the more ``outer'' the
11668 frame is you're looking at, the more likely a call-clobbered
11669 register's value is to be wrong, in the sense that it doesn't actually
11670 represent the value the register had just before the call.
11672 @node Floating Point Hardware
11673 @section Floating Point Hardware
11674 @cindex floating point
11676 Depending on the configuration, @value{GDBN} may be able to give
11677 you more information about the status of the floating point hardware.
11682 Display hardware-dependent information about the floating
11683 point unit. The exact contents and layout vary depending on the
11684 floating point chip. Currently, @samp{info float} is supported on
11685 the ARM and x86 machines.
11689 @section Vector Unit
11690 @cindex vector unit
11692 Depending on the configuration, @value{GDBN} may be able to give you
11693 more information about the status of the vector unit.
11696 @kindex info vector
11698 Display information about the vector unit. The exact contents and
11699 layout vary depending on the hardware.
11702 @node OS Information
11703 @section Operating System Auxiliary Information
11704 @cindex OS information
11706 @value{GDBN} provides interfaces to useful OS facilities that can help
11707 you debug your program.
11709 @cindex auxiliary vector
11710 @cindex vector, auxiliary
11711 Some operating systems supply an @dfn{auxiliary vector} to programs at
11712 startup. This is akin to the arguments and environment that you
11713 specify for a program, but contains a system-dependent variety of
11714 binary values that tell system libraries important details about the
11715 hardware, operating system, and process. Each value's purpose is
11716 identified by an integer tag; the meanings are well-known but system-specific.
11717 Depending on the configuration and operating system facilities,
11718 @value{GDBN} may be able to show you this information. For remote
11719 targets, this functionality may further depend on the remote stub's
11720 support of the @samp{qXfer:auxv:read} packet, see
11721 @ref{qXfer auxiliary vector read}.
11726 Display the auxiliary vector of the inferior, which can be either a
11727 live process or a core dump file. @value{GDBN} prints each tag value
11728 numerically, and also shows names and text descriptions for recognized
11729 tags. Some values in the vector are numbers, some bit masks, and some
11730 pointers to strings or other data. @value{GDBN} displays each value in the
11731 most appropriate form for a recognized tag, and in hexadecimal for
11732 an unrecognized tag.
11735 On some targets, @value{GDBN} can access operating system-specific
11736 information and show it to you. The types of information available
11737 will differ depending on the type of operating system running on the
11738 target. The mechanism used to fetch the data is described in
11739 @ref{Operating System Information}. For remote targets, this
11740 functionality depends on the remote stub's support of the
11741 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11745 @item info os @var{infotype}
11747 Display OS information of the requested type.
11749 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11751 @anchor{linux info os infotypes}
11753 @kindex info os cpus
11755 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11756 the available fields from /proc/cpuinfo. For each supported architecture
11757 different fields are available. Two common entries are processor which gives
11758 CPU number and bogomips; a system constant that is calculated during
11759 kernel initialization.
11761 @kindex info os files
11763 Display the list of open file descriptors on the target. For each
11764 file descriptor, @value{GDBN} prints the identifier of the process
11765 owning the descriptor, the command of the owning process, the value
11766 of the descriptor, and the target of the descriptor.
11768 @kindex info os modules
11770 Display the list of all loaded kernel modules on the target. For each
11771 module, @value{GDBN} prints the module name, the size of the module in
11772 bytes, the number of times the module is used, the dependencies of the
11773 module, the status of the module, and the address of the loaded module
11776 @kindex info os msg
11778 Display the list of all System V message queues on the target. For each
11779 message queue, @value{GDBN} prints the message queue key, the message
11780 queue identifier, the access permissions, the current number of bytes
11781 on the queue, the current number of messages on the queue, the processes
11782 that last sent and received a message on the queue, the user and group
11783 of the owner and creator of the message queue, the times at which a
11784 message was last sent and received on the queue, and the time at which
11785 the message queue was last changed.
11787 @kindex info os processes
11789 Display the list of processes on the target. For each process,
11790 @value{GDBN} prints the process identifier, the name of the user, the
11791 command corresponding to the process, and the list of processor cores
11792 that the process is currently running on. (To understand what these
11793 properties mean, for this and the following info types, please consult
11794 the general @sc{gnu}/Linux documentation.)
11796 @kindex info os procgroups
11798 Display the list of process groups on the target. For each process,
11799 @value{GDBN} prints the identifier of the process group that it belongs
11800 to, the command corresponding to the process group leader, the process
11801 identifier, and the command line of the process. The list is sorted
11802 first by the process group identifier, then by the process identifier,
11803 so that processes belonging to the same process group are grouped together
11804 and the process group leader is listed first.
11806 @kindex info os semaphores
11808 Display the list of all System V semaphore sets on the target. For each
11809 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11810 set identifier, the access permissions, the number of semaphores in the
11811 set, the user and group of the owner and creator of the semaphore set,
11812 and the times at which the semaphore set was operated upon and changed.
11814 @kindex info os shm
11816 Display the list of all System V shared-memory regions on the target.
11817 For each shared-memory region, @value{GDBN} prints the region key,
11818 the shared-memory identifier, the access permissions, the size of the
11819 region, the process that created the region, the process that last
11820 attached to or detached from the region, the current number of live
11821 attaches to the region, and the times at which the region was last
11822 attached to, detach from, and changed.
11824 @kindex info os sockets
11826 Display the list of Internet-domain sockets on the target. For each
11827 socket, @value{GDBN} prints the address and port of the local and
11828 remote endpoints, the current state of the connection, the creator of
11829 the socket, the IP address family of the socket, and the type of the
11832 @kindex info os threads
11834 Display the list of threads running on the target. For each thread,
11835 @value{GDBN} prints the identifier of the process that the thread
11836 belongs to, the command of the process, the thread identifier, and the
11837 processor core that it is currently running on. The main thread of a
11838 process is not listed.
11842 If @var{infotype} is omitted, then list the possible values for
11843 @var{infotype} and the kind of OS information available for each
11844 @var{infotype}. If the target does not return a list of possible
11845 types, this command will report an error.
11848 @node Memory Region Attributes
11849 @section Memory Region Attributes
11850 @cindex memory region attributes
11852 @dfn{Memory region attributes} allow you to describe special handling
11853 required by regions of your target's memory. @value{GDBN} uses
11854 attributes to determine whether to allow certain types of memory
11855 accesses; whether to use specific width accesses; and whether to cache
11856 target memory. By default the description of memory regions is
11857 fetched from the target (if the current target supports this), but the
11858 user can override the fetched regions.
11860 Defined memory regions can be individually enabled and disabled. When a
11861 memory region is disabled, @value{GDBN} uses the default attributes when
11862 accessing memory in that region. Similarly, if no memory regions have
11863 been defined, @value{GDBN} uses the default attributes when accessing
11866 When a memory region is defined, it is given a number to identify it;
11867 to enable, disable, or remove a memory region, you specify that number.
11871 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11872 Define a memory region bounded by @var{lower} and @var{upper} with
11873 attributes @var{attributes}@dots{}, and add it to the list of regions
11874 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11875 case: it is treated as the target's maximum memory address.
11876 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11879 Discard any user changes to the memory regions and use target-supplied
11880 regions, if available, or no regions if the target does not support.
11883 @item delete mem @var{nums}@dots{}
11884 Remove memory regions @var{nums}@dots{} from the list of regions
11885 monitored by @value{GDBN}.
11887 @kindex disable mem
11888 @item disable mem @var{nums}@dots{}
11889 Disable monitoring of memory regions @var{nums}@dots{}.
11890 A disabled memory region is not forgotten.
11891 It may be enabled again later.
11894 @item enable mem @var{nums}@dots{}
11895 Enable monitoring of memory regions @var{nums}@dots{}.
11899 Print a table of all defined memory regions, with the following columns
11903 @item Memory Region Number
11904 @item Enabled or Disabled.
11905 Enabled memory regions are marked with @samp{y}.
11906 Disabled memory regions are marked with @samp{n}.
11909 The address defining the inclusive lower bound of the memory region.
11912 The address defining the exclusive upper bound of the memory region.
11915 The list of attributes set for this memory region.
11920 @subsection Attributes
11922 @subsubsection Memory Access Mode
11923 The access mode attributes set whether @value{GDBN} may make read or
11924 write accesses to a memory region.
11926 While these attributes prevent @value{GDBN} from performing invalid
11927 memory accesses, they do nothing to prevent the target system, I/O DMA,
11928 etc.@: from accessing memory.
11932 Memory is read only.
11934 Memory is write only.
11936 Memory is read/write. This is the default.
11939 @subsubsection Memory Access Size
11940 The access size attribute tells @value{GDBN} to use specific sized
11941 accesses in the memory region. Often memory mapped device registers
11942 require specific sized accesses. If no access size attribute is
11943 specified, @value{GDBN} may use accesses of any size.
11947 Use 8 bit memory accesses.
11949 Use 16 bit memory accesses.
11951 Use 32 bit memory accesses.
11953 Use 64 bit memory accesses.
11956 @c @subsubsection Hardware/Software Breakpoints
11957 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11958 @c will use hardware or software breakpoints for the internal breakpoints
11959 @c used by the step, next, finish, until, etc. commands.
11963 @c Always use hardware breakpoints
11964 @c @item swbreak (default)
11967 @subsubsection Data Cache
11968 The data cache attributes set whether @value{GDBN} will cache target
11969 memory. While this generally improves performance by reducing debug
11970 protocol overhead, it can lead to incorrect results because @value{GDBN}
11971 does not know about volatile variables or memory mapped device
11976 Enable @value{GDBN} to cache target memory.
11978 Disable @value{GDBN} from caching target memory. This is the default.
11981 @subsection Memory Access Checking
11982 @value{GDBN} can be instructed to refuse accesses to memory that is
11983 not explicitly described. This can be useful if accessing such
11984 regions has undesired effects for a specific target, or to provide
11985 better error checking. The following commands control this behaviour.
11988 @kindex set mem inaccessible-by-default
11989 @item set mem inaccessible-by-default [on|off]
11990 If @code{on} is specified, make @value{GDBN} treat memory not
11991 explicitly described by the memory ranges as non-existent and refuse accesses
11992 to such memory. The checks are only performed if there's at least one
11993 memory range defined. If @code{off} is specified, make @value{GDBN}
11994 treat the memory not explicitly described by the memory ranges as RAM.
11995 The default value is @code{on}.
11996 @kindex show mem inaccessible-by-default
11997 @item show mem inaccessible-by-default
11998 Show the current handling of accesses to unknown memory.
12002 @c @subsubsection Memory Write Verification
12003 @c The memory write verification attributes set whether @value{GDBN}
12004 @c will re-reads data after each write to verify the write was successful.
12008 @c @item noverify (default)
12011 @node Dump/Restore Files
12012 @section Copy Between Memory and a File
12013 @cindex dump/restore files
12014 @cindex append data to a file
12015 @cindex dump data to a file
12016 @cindex restore data from a file
12018 You can use the commands @code{dump}, @code{append}, and
12019 @code{restore} to copy data between target memory and a file. The
12020 @code{dump} and @code{append} commands write data to a file, and the
12021 @code{restore} command reads data from a file back into the inferior's
12022 memory. Files may be in binary, Motorola S-record, Intel hex,
12023 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12024 append to binary files, and cannot read from Verilog Hex files.
12029 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12030 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12031 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12032 or the value of @var{expr}, to @var{filename} in the given format.
12034 The @var{format} parameter may be any one of:
12041 Motorola S-record format.
12043 Tektronix Hex format.
12045 Verilog Hex format.
12048 @value{GDBN} uses the same definitions of these formats as the
12049 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12050 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12054 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12055 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12056 Append the contents of memory from @var{start_addr} to @var{end_addr},
12057 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12058 (@value{GDBN} can only append data to files in raw binary form.)
12061 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12062 Restore the contents of file @var{filename} into memory. The
12063 @code{restore} command can automatically recognize any known @sc{bfd}
12064 file format, except for raw binary. To restore a raw binary file you
12065 must specify the optional keyword @code{binary} after the filename.
12067 If @var{bias} is non-zero, its value will be added to the addresses
12068 contained in the file. Binary files always start at address zero, so
12069 they will be restored at address @var{bias}. Other bfd files have
12070 a built-in location; they will be restored at offset @var{bias}
12071 from that location.
12073 If @var{start} and/or @var{end} are non-zero, then only data between
12074 file offset @var{start} and file offset @var{end} will be restored.
12075 These offsets are relative to the addresses in the file, before
12076 the @var{bias} argument is applied.
12080 @node Core File Generation
12081 @section How to Produce a Core File from Your Program
12082 @cindex dump core from inferior
12084 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12085 image of a running process and its process status (register values
12086 etc.). Its primary use is post-mortem debugging of a program that
12087 crashed while it ran outside a debugger. A program that crashes
12088 automatically produces a core file, unless this feature is disabled by
12089 the user. @xref{Files}, for information on invoking @value{GDBN} in
12090 the post-mortem debugging mode.
12092 Occasionally, you may wish to produce a core file of the program you
12093 are debugging in order to preserve a snapshot of its state.
12094 @value{GDBN} has a special command for that.
12098 @kindex generate-core-file
12099 @item generate-core-file [@var{file}]
12100 @itemx gcore [@var{file}]
12101 Produce a core dump of the inferior process. The optional argument
12102 @var{file} specifies the file name where to put the core dump. If not
12103 specified, the file name defaults to @file{core.@var{pid}}, where
12104 @var{pid} is the inferior process ID.
12106 Note that this command is implemented only for some systems (as of
12107 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12109 On @sc{gnu}/Linux, this command can take into account the value of the
12110 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12111 dump (@pxref{set use-coredump-filter}), and by default honors the
12112 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12113 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12115 @kindex set use-coredump-filter
12116 @anchor{set use-coredump-filter}
12117 @item set use-coredump-filter on
12118 @itemx set use-coredump-filter off
12119 Enable or disable the use of the file
12120 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12121 files. This file is used by the Linux kernel to decide what types of
12122 memory mappings will be dumped or ignored when generating a core dump
12123 file. @var{pid} is the process ID of a currently running process.
12125 To make use of this feature, you have to write in the
12126 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12127 which is a bit mask representing the memory mapping types. If a bit
12128 is set in the bit mask, then the memory mappings of the corresponding
12129 types will be dumped; otherwise, they will be ignored. This
12130 configuration is inherited by child processes. For more information
12131 about the bits that can be set in the
12132 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12133 manpage of @code{core(5)}.
12135 By default, this option is @code{on}. If this option is turned
12136 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12137 and instead uses the same default value as the Linux kernel in order
12138 to decide which pages will be dumped in the core dump file. This
12139 value is currently @code{0x33}, which means that bits @code{0}
12140 (anonymous private mappings), @code{1} (anonymous shared mappings),
12141 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12142 This will cause these memory mappings to be dumped automatically.
12144 @kindex set dump-excluded-mappings
12145 @anchor{set dump-excluded-mappings}
12146 @item set dump-excluded-mappings on
12147 @itemx set dump-excluded-mappings off
12148 If @code{on} is specified, @value{GDBN} will dump memory mappings
12149 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12150 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12152 The default value is @code{off}.
12155 @node Character Sets
12156 @section Character Sets
12157 @cindex character sets
12159 @cindex translating between character sets
12160 @cindex host character set
12161 @cindex target character set
12163 If the program you are debugging uses a different character set to
12164 represent characters and strings than the one @value{GDBN} uses itself,
12165 @value{GDBN} can automatically translate between the character sets for
12166 you. The character set @value{GDBN} uses we call the @dfn{host
12167 character set}; the one the inferior program uses we call the
12168 @dfn{target character set}.
12170 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12171 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12172 remote protocol (@pxref{Remote Debugging}) to debug a program
12173 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12174 then the host character set is Latin-1, and the target character set is
12175 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12176 target-charset EBCDIC-US}, then @value{GDBN} translates between
12177 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12178 character and string literals in expressions.
12180 @value{GDBN} has no way to automatically recognize which character set
12181 the inferior program uses; you must tell it, using the @code{set
12182 target-charset} command, described below.
12184 Here are the commands for controlling @value{GDBN}'s character set
12188 @item set target-charset @var{charset}
12189 @kindex set target-charset
12190 Set the current target character set to @var{charset}. To display the
12191 list of supported target character sets, type
12192 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12194 @item set host-charset @var{charset}
12195 @kindex set host-charset
12196 Set the current host character set to @var{charset}.
12198 By default, @value{GDBN} uses a host character set appropriate to the
12199 system it is running on; you can override that default using the
12200 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12201 automatically determine the appropriate host character set. In this
12202 case, @value{GDBN} uses @samp{UTF-8}.
12204 @value{GDBN} can only use certain character sets as its host character
12205 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12206 @value{GDBN} will list the host character sets it supports.
12208 @item set charset @var{charset}
12209 @kindex set charset
12210 Set the current host and target character sets to @var{charset}. As
12211 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12212 @value{GDBN} will list the names of the character sets that can be used
12213 for both host and target.
12216 @kindex show charset
12217 Show the names of the current host and target character sets.
12219 @item show host-charset
12220 @kindex show host-charset
12221 Show the name of the current host character set.
12223 @item show target-charset
12224 @kindex show target-charset
12225 Show the name of the current target character set.
12227 @item set target-wide-charset @var{charset}
12228 @kindex set target-wide-charset
12229 Set the current target's wide character set to @var{charset}. This is
12230 the character set used by the target's @code{wchar_t} type. To
12231 display the list of supported wide character sets, type
12232 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12234 @item show target-wide-charset
12235 @kindex show target-wide-charset
12236 Show the name of the current target's wide character set.
12239 Here is an example of @value{GDBN}'s character set support in action.
12240 Assume that the following source code has been placed in the file
12241 @file{charset-test.c}:
12247 = @{72, 101, 108, 108, 111, 44, 32, 119,
12248 111, 114, 108, 100, 33, 10, 0@};
12249 char ibm1047_hello[]
12250 = @{200, 133, 147, 147, 150, 107, 64, 166,
12251 150, 153, 147, 132, 90, 37, 0@};
12255 printf ("Hello, world!\n");
12259 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12260 containing the string @samp{Hello, world!} followed by a newline,
12261 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12263 We compile the program, and invoke the debugger on it:
12266 $ gcc -g charset-test.c -o charset-test
12267 $ gdb -nw charset-test
12268 GNU gdb 2001-12-19-cvs
12269 Copyright 2001 Free Software Foundation, Inc.
12274 We can use the @code{show charset} command to see what character sets
12275 @value{GDBN} is currently using to interpret and display characters and
12279 (@value{GDBP}) show charset
12280 The current host and target character set is `ISO-8859-1'.
12284 For the sake of printing this manual, let's use @sc{ascii} as our
12285 initial character set:
12287 (@value{GDBP}) set charset ASCII
12288 (@value{GDBP}) show charset
12289 The current host and target character set is `ASCII'.
12293 Let's assume that @sc{ascii} is indeed the correct character set for our
12294 host system --- in other words, let's assume that if @value{GDBN} prints
12295 characters using the @sc{ascii} character set, our terminal will display
12296 them properly. Since our current target character set is also
12297 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12300 (@value{GDBP}) print ascii_hello
12301 $1 = 0x401698 "Hello, world!\n"
12302 (@value{GDBP}) print ascii_hello[0]
12307 @value{GDBN} uses the target character set for character and string
12308 literals you use in expressions:
12311 (@value{GDBP}) print '+'
12316 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12319 @value{GDBN} relies on the user to tell it which character set the
12320 target program uses. If we print @code{ibm1047_hello} while our target
12321 character set is still @sc{ascii}, we get jibberish:
12324 (@value{GDBP}) print ibm1047_hello
12325 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12326 (@value{GDBP}) print ibm1047_hello[0]
12331 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12332 @value{GDBN} tells us the character sets it supports:
12335 (@value{GDBP}) set target-charset
12336 ASCII EBCDIC-US IBM1047 ISO-8859-1
12337 (@value{GDBP}) set target-charset
12340 We can select @sc{ibm1047} as our target character set, and examine the
12341 program's strings again. Now the @sc{ascii} string is wrong, but
12342 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12343 target character set, @sc{ibm1047}, to the host character set,
12344 @sc{ascii}, and they display correctly:
12347 (@value{GDBP}) set target-charset IBM1047
12348 (@value{GDBP}) show charset
12349 The current host character set is `ASCII'.
12350 The current target character set is `IBM1047'.
12351 (@value{GDBP}) print ascii_hello
12352 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12353 (@value{GDBP}) print ascii_hello[0]
12355 (@value{GDBP}) print ibm1047_hello
12356 $8 = 0x4016a8 "Hello, world!\n"
12357 (@value{GDBP}) print ibm1047_hello[0]
12362 As above, @value{GDBN} uses the target character set for character and
12363 string literals you use in expressions:
12366 (@value{GDBP}) print '+'
12371 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12374 @node Caching Target Data
12375 @section Caching Data of Targets
12376 @cindex caching data of targets
12378 @value{GDBN} caches data exchanged between the debugger and a target.
12379 Each cache is associated with the address space of the inferior.
12380 @xref{Inferiors and Programs}, about inferior and address space.
12381 Such caching generally improves performance in remote debugging
12382 (@pxref{Remote Debugging}), because it reduces the overhead of the
12383 remote protocol by bundling memory reads and writes into large chunks.
12384 Unfortunately, simply caching everything would lead to incorrect results,
12385 since @value{GDBN} does not necessarily know anything about volatile
12386 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12387 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12389 Therefore, by default, @value{GDBN} only caches data
12390 known to be on the stack@footnote{In non-stop mode, it is moderately
12391 rare for a running thread to modify the stack of a stopped thread
12392 in a way that would interfere with a backtrace, and caching of
12393 stack reads provides a significant speed up of remote backtraces.} or
12394 in the code segment.
12395 Other regions of memory can be explicitly marked as
12396 cacheable; @pxref{Memory Region Attributes}.
12399 @kindex set remotecache
12400 @item set remotecache on
12401 @itemx set remotecache off
12402 This option no longer does anything; it exists for compatibility
12405 @kindex show remotecache
12406 @item show remotecache
12407 Show the current state of the obsolete remotecache flag.
12409 @kindex set stack-cache
12410 @item set stack-cache on
12411 @itemx set stack-cache off
12412 Enable or disable caching of stack accesses. When @code{on}, use
12413 caching. By default, this option is @code{on}.
12415 @kindex show stack-cache
12416 @item show stack-cache
12417 Show the current state of data caching for memory accesses.
12419 @kindex set code-cache
12420 @item set code-cache on
12421 @itemx set code-cache off
12422 Enable or disable caching of code segment accesses. When @code{on},
12423 use caching. By default, this option is @code{on}. This improves
12424 performance of disassembly in remote debugging.
12426 @kindex show code-cache
12427 @item show code-cache
12428 Show the current state of target memory cache for code segment
12431 @kindex info dcache
12432 @item info dcache @r{[}line@r{]}
12433 Print the information about the performance of data cache of the
12434 current inferior's address space. The information displayed
12435 includes the dcache width and depth, and for each cache line, its
12436 number, address, and how many times it was referenced. This
12437 command is useful for debugging the data cache operation.
12439 If a line number is specified, the contents of that line will be
12442 @item set dcache size @var{size}
12443 @cindex dcache size
12444 @kindex set dcache size
12445 Set maximum number of entries in dcache (dcache depth above).
12447 @item set dcache line-size @var{line-size}
12448 @cindex dcache line-size
12449 @kindex set dcache line-size
12450 Set number of bytes each dcache entry caches (dcache width above).
12451 Must be a power of 2.
12453 @item show dcache size
12454 @kindex show dcache size
12455 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12457 @item show dcache line-size
12458 @kindex show dcache line-size
12459 Show default size of dcache lines.
12463 @node Searching Memory
12464 @section Search Memory
12465 @cindex searching memory
12467 Memory can be searched for a particular sequence of bytes with the
12468 @code{find} command.
12472 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12473 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12474 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12475 etc. The search begins at address @var{start_addr} and continues for either
12476 @var{len} bytes or through to @var{end_addr} inclusive.
12479 @var{s} and @var{n} are optional parameters.
12480 They may be specified in either order, apart or together.
12483 @item @var{s}, search query size
12484 The size of each search query value.
12490 halfwords (two bytes)
12494 giant words (eight bytes)
12497 All values are interpreted in the current language.
12498 This means, for example, that if the current source language is C/C@t{++}
12499 then searching for the string ``hello'' includes the trailing '\0'.
12500 The null terminator can be removed from searching by using casts,
12501 e.g.: @samp{@{char[5]@}"hello"}.
12503 If the value size is not specified, it is taken from the
12504 value's type in the current language.
12505 This is useful when one wants to specify the search
12506 pattern as a mixture of types.
12507 Note that this means, for example, that in the case of C-like languages
12508 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12509 which is typically four bytes.
12511 @item @var{n}, maximum number of finds
12512 The maximum number of matches to print. The default is to print all finds.
12515 You can use strings as search values. Quote them with double-quotes
12517 The string value is copied into the search pattern byte by byte,
12518 regardless of the endianness of the target and the size specification.
12520 The address of each match found is printed as well as a count of the
12521 number of matches found.
12523 The address of the last value found is stored in convenience variable
12525 A count of the number of matches is stored in @samp{$numfound}.
12527 For example, if stopped at the @code{printf} in this function:
12533 static char hello[] = "hello-hello";
12534 static struct @{ char c; short s; int i; @}
12535 __attribute__ ((packed)) mixed
12536 = @{ 'c', 0x1234, 0x87654321 @};
12537 printf ("%s\n", hello);
12542 you get during debugging:
12545 (gdb) find &hello[0], +sizeof(hello), "hello"
12546 0x804956d <hello.1620+6>
12548 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12549 0x8049567 <hello.1620>
12550 0x804956d <hello.1620+6>
12552 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12553 0x8049567 <hello.1620>
12554 0x804956d <hello.1620+6>
12556 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12557 0x8049567 <hello.1620>
12559 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12560 0x8049560 <mixed.1625>
12562 (gdb) print $numfound
12565 $2 = (void *) 0x8049560
12569 @section Value Sizes
12571 Whenever @value{GDBN} prints a value memory will be allocated within
12572 @value{GDBN} to hold the contents of the value. It is possible in
12573 some languages with dynamic typing systems, that an invalid program
12574 may indicate a value that is incorrectly large, this in turn may cause
12575 @value{GDBN} to try and allocate an overly large ammount of memory.
12578 @kindex set max-value-size
12579 @item set max-value-size @var{bytes}
12580 @itemx set max-value-size unlimited
12581 Set the maximum size of memory that @value{GDBN} will allocate for the
12582 contents of a value to @var{bytes}, trying to display a value that
12583 requires more memory than that will result in an error.
12585 Setting this variable does not effect values that have already been
12586 allocated within @value{GDBN}, only future allocations.
12588 There's a minimum size that @code{max-value-size} can be set to in
12589 order that @value{GDBN} can still operate correctly, this minimum is
12590 currently 16 bytes.
12592 The limit applies to the results of some subexpressions as well as to
12593 complete expressions. For example, an expression denoting a simple
12594 integer component, such as @code{x.y.z}, may fail if the size of
12595 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12596 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12597 @var{A} is an array variable with non-constant size, will generally
12598 succeed regardless of the bounds on @var{A}, as long as the component
12599 size is less than @var{bytes}.
12601 The default value of @code{max-value-size} is currently 64k.
12603 @kindex show max-value-size
12604 @item show max-value-size
12605 Show the maximum size of memory, in bytes, that @value{GDBN} will
12606 allocate for the contents of a value.
12609 @node Optimized Code
12610 @chapter Debugging Optimized Code
12611 @cindex optimized code, debugging
12612 @cindex debugging optimized code
12614 Almost all compilers support optimization. With optimization
12615 disabled, the compiler generates assembly code that corresponds
12616 directly to your source code, in a simplistic way. As the compiler
12617 applies more powerful optimizations, the generated assembly code
12618 diverges from your original source code. With help from debugging
12619 information generated by the compiler, @value{GDBN} can map from
12620 the running program back to constructs from your original source.
12622 @value{GDBN} is more accurate with optimization disabled. If you
12623 can recompile without optimization, it is easier to follow the
12624 progress of your program during debugging. But, there are many cases
12625 where you may need to debug an optimized version.
12627 When you debug a program compiled with @samp{-g -O}, remember that the
12628 optimizer has rearranged your code; the debugger shows you what is
12629 really there. Do not be too surprised when the execution path does not
12630 exactly match your source file! An extreme example: if you define a
12631 variable, but never use it, @value{GDBN} never sees that
12632 variable---because the compiler optimizes it out of existence.
12634 Some things do not work as well with @samp{-g -O} as with just
12635 @samp{-g}, particularly on machines with instruction scheduling. If in
12636 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12637 please report it to us as a bug (including a test case!).
12638 @xref{Variables}, for more information about debugging optimized code.
12641 * Inline Functions:: How @value{GDBN} presents inlining
12642 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12645 @node Inline Functions
12646 @section Inline Functions
12647 @cindex inline functions, debugging
12649 @dfn{Inlining} is an optimization that inserts a copy of the function
12650 body directly at each call site, instead of jumping to a shared
12651 routine. @value{GDBN} displays inlined functions just like
12652 non-inlined functions. They appear in backtraces. You can view their
12653 arguments and local variables, step into them with @code{step}, skip
12654 them with @code{next}, and escape from them with @code{finish}.
12655 You can check whether a function was inlined by using the
12656 @code{info frame} command.
12658 For @value{GDBN} to support inlined functions, the compiler must
12659 record information about inlining in the debug information ---
12660 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12661 other compilers do also. @value{GDBN} only supports inlined functions
12662 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12663 do not emit two required attributes (@samp{DW_AT_call_file} and
12664 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12665 function calls with earlier versions of @value{NGCC}. It instead
12666 displays the arguments and local variables of inlined functions as
12667 local variables in the caller.
12669 The body of an inlined function is directly included at its call site;
12670 unlike a non-inlined function, there are no instructions devoted to
12671 the call. @value{GDBN} still pretends that the call site and the
12672 start of the inlined function are different instructions. Stepping to
12673 the call site shows the call site, and then stepping again shows
12674 the first line of the inlined function, even though no additional
12675 instructions are executed.
12677 This makes source-level debugging much clearer; you can see both the
12678 context of the call and then the effect of the call. Only stepping by
12679 a single instruction using @code{stepi} or @code{nexti} does not do
12680 this; single instruction steps always show the inlined body.
12682 There are some ways that @value{GDBN} does not pretend that inlined
12683 function calls are the same as normal calls:
12687 Setting breakpoints at the call site of an inlined function may not
12688 work, because the call site does not contain any code. @value{GDBN}
12689 may incorrectly move the breakpoint to the next line of the enclosing
12690 function, after the call. This limitation will be removed in a future
12691 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12692 or inside the inlined function instead.
12695 @value{GDBN} cannot locate the return value of inlined calls after
12696 using the @code{finish} command. This is a limitation of compiler-generated
12697 debugging information; after @code{finish}, you can step to the next line
12698 and print a variable where your program stored the return value.
12702 @node Tail Call Frames
12703 @section Tail Call Frames
12704 @cindex tail call frames, debugging
12706 Function @code{B} can call function @code{C} in its very last statement. In
12707 unoptimized compilation the call of @code{C} is immediately followed by return
12708 instruction at the end of @code{B} code. Optimizing compiler may replace the
12709 call and return in function @code{B} into one jump to function @code{C}
12710 instead. Such use of a jump instruction is called @dfn{tail call}.
12712 During execution of function @code{C}, there will be no indication in the
12713 function call stack frames that it was tail-called from @code{B}. If function
12714 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12715 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12716 some cases @value{GDBN} can determine that @code{C} was tail-called from
12717 @code{B}, and it will then create fictitious call frame for that, with the
12718 return address set up as if @code{B} called @code{C} normally.
12720 This functionality is currently supported only by DWARF 2 debugging format and
12721 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12722 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12725 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12726 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12730 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12732 Stack level 1, frame at 0x7fffffffda30:
12733 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12734 tail call frame, caller of frame at 0x7fffffffda30
12735 source language c++.
12736 Arglist at unknown address.
12737 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12740 The detection of all the possible code path executions can find them ambiguous.
12741 There is no execution history stored (possible @ref{Reverse Execution} is never
12742 used for this purpose) and the last known caller could have reached the known
12743 callee by multiple different jump sequences. In such case @value{GDBN} still
12744 tries to show at least all the unambiguous top tail callers and all the
12745 unambiguous bottom tail calees, if any.
12748 @anchor{set debug entry-values}
12749 @item set debug entry-values
12750 @kindex set debug entry-values
12751 When set to on, enables printing of analysis messages for both frame argument
12752 values at function entry and tail calls. It will show all the possible valid
12753 tail calls code paths it has considered. It will also print the intersection
12754 of them with the final unambiguous (possibly partial or even empty) code path
12757 @item show debug entry-values
12758 @kindex show debug entry-values
12759 Show the current state of analysis messages printing for both frame argument
12760 values at function entry and tail calls.
12763 The analysis messages for tail calls can for example show why the virtual tail
12764 call frame for function @code{c} has not been recognized (due to the indirect
12765 reference by variable @code{x}):
12768 static void __attribute__((noinline, noclone)) c (void);
12769 void (*x) (void) = c;
12770 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12771 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12772 int main (void) @{ x (); return 0; @}
12774 Breakpoint 1, DW_OP_entry_value resolving cannot find
12775 DW_TAG_call_site 0x40039a in main
12777 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12780 #1 0x000000000040039a in main () at t.c:5
12783 Another possibility is an ambiguous virtual tail call frames resolution:
12787 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12788 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12789 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12790 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12791 static void __attribute__((noinline, noclone)) b (void)
12792 @{ if (i) c (); else e (); @}
12793 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12794 int main (void) @{ a (); return 0; @}
12796 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12797 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12798 tailcall: reduced: 0x4004d2(a) |
12801 #1 0x00000000004004d2 in a () at t.c:8
12802 #2 0x0000000000400395 in main () at t.c:9
12805 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12806 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12808 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12809 @ifset HAVE_MAKEINFO_CLICK
12810 @set ARROW @click{}
12811 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12812 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12814 @ifclear HAVE_MAKEINFO_CLICK
12816 @set CALLSEQ1B @value{CALLSEQ1A}
12817 @set CALLSEQ2B @value{CALLSEQ2A}
12820 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12821 The code can have possible execution paths @value{CALLSEQ1B} or
12822 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12824 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12825 has found. It then finds another possible calling sequcen - that one is
12826 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12827 printed as the @code{reduced:} calling sequence. That one could have many
12828 futher @code{compare:} and @code{reduced:} statements as long as there remain
12829 any non-ambiguous sequence entries.
12831 For the frame of function @code{b} in both cases there are different possible
12832 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12833 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12834 therefore this one is displayed to the user while the ambiguous frames are
12837 There can be also reasons why printing of frame argument values at function
12842 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12843 static void __attribute__((noinline, noclone)) a (int i);
12844 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12845 static void __attribute__((noinline, noclone)) a (int i)
12846 @{ if (i) b (i - 1); else c (0); @}
12847 int main (void) @{ a (5); return 0; @}
12850 #0 c (i=i@@entry=0) at t.c:2
12851 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12852 function "a" at 0x400420 can call itself via tail calls
12853 i=<optimized out>) at t.c:6
12854 #2 0x000000000040036e in main () at t.c:7
12857 @value{GDBN} cannot find out from the inferior state if and how many times did
12858 function @code{a} call itself (via function @code{b}) as these calls would be
12859 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12860 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12861 prints @code{<optimized out>} instead.
12864 @chapter C Preprocessor Macros
12866 Some languages, such as C and C@t{++}, provide a way to define and invoke
12867 ``preprocessor macros'' which expand into strings of tokens.
12868 @value{GDBN} can evaluate expressions containing macro invocations, show
12869 the result of macro expansion, and show a macro's definition, including
12870 where it was defined.
12872 You may need to compile your program specially to provide @value{GDBN}
12873 with information about preprocessor macros. Most compilers do not
12874 include macros in their debugging information, even when you compile
12875 with the @option{-g} flag. @xref{Compilation}.
12877 A program may define a macro at one point, remove that definition later,
12878 and then provide a different definition after that. Thus, at different
12879 points in the program, a macro may have different definitions, or have
12880 no definition at all. If there is a current stack frame, @value{GDBN}
12881 uses the macros in scope at that frame's source code line. Otherwise,
12882 @value{GDBN} uses the macros in scope at the current listing location;
12885 Whenever @value{GDBN} evaluates an expression, it always expands any
12886 macro invocations present in the expression. @value{GDBN} also provides
12887 the following commands for working with macros explicitly.
12891 @kindex macro expand
12892 @cindex macro expansion, showing the results of preprocessor
12893 @cindex preprocessor macro expansion, showing the results of
12894 @cindex expanding preprocessor macros
12895 @item macro expand @var{expression}
12896 @itemx macro exp @var{expression}
12897 Show the results of expanding all preprocessor macro invocations in
12898 @var{expression}. Since @value{GDBN} simply expands macros, but does
12899 not parse the result, @var{expression} need not be a valid expression;
12900 it can be any string of tokens.
12903 @item macro expand-once @var{expression}
12904 @itemx macro exp1 @var{expression}
12905 @cindex expand macro once
12906 @i{(This command is not yet implemented.)} Show the results of
12907 expanding those preprocessor macro invocations that appear explicitly in
12908 @var{expression}. Macro invocations appearing in that expansion are
12909 left unchanged. This command allows you to see the effect of a
12910 particular macro more clearly, without being confused by further
12911 expansions. Since @value{GDBN} simply expands macros, but does not
12912 parse the result, @var{expression} need not be a valid expression; it
12913 can be any string of tokens.
12916 @cindex macro definition, showing
12917 @cindex definition of a macro, showing
12918 @cindex macros, from debug info
12919 @item info macro [-a|-all] [--] @var{macro}
12920 Show the current definition or all definitions of the named @var{macro},
12921 and describe the source location or compiler command-line where that
12922 definition was established. The optional double dash is to signify the end of
12923 argument processing and the beginning of @var{macro} for non C-like macros where
12924 the macro may begin with a hyphen.
12926 @kindex info macros
12927 @item info macros @var{location}
12928 Show all macro definitions that are in effect at the location specified
12929 by @var{location}, and describe the source location or compiler
12930 command-line where those definitions were established.
12932 @kindex macro define
12933 @cindex user-defined macros
12934 @cindex defining macros interactively
12935 @cindex macros, user-defined
12936 @item macro define @var{macro} @var{replacement-list}
12937 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12938 Introduce a definition for a preprocessor macro named @var{macro},
12939 invocations of which are replaced by the tokens given in
12940 @var{replacement-list}. The first form of this command defines an
12941 ``object-like'' macro, which takes no arguments; the second form
12942 defines a ``function-like'' macro, which takes the arguments given in
12945 A definition introduced by this command is in scope in every
12946 expression evaluated in @value{GDBN}, until it is removed with the
12947 @code{macro undef} command, described below. The definition overrides
12948 all definitions for @var{macro} present in the program being debugged,
12949 as well as any previous user-supplied definition.
12951 @kindex macro undef
12952 @item macro undef @var{macro}
12953 Remove any user-supplied definition for the macro named @var{macro}.
12954 This command only affects definitions provided with the @code{macro
12955 define} command, described above; it cannot remove definitions present
12956 in the program being debugged.
12960 List all the macros defined using the @code{macro define} command.
12963 @cindex macros, example of debugging with
12964 Here is a transcript showing the above commands in action. First, we
12965 show our source files:
12970 #include "sample.h"
12973 #define ADD(x) (M + x)
12978 printf ("Hello, world!\n");
12980 printf ("We're so creative.\n");
12982 printf ("Goodbye, world!\n");
12989 Now, we compile the program using the @sc{gnu} C compiler,
12990 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12991 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12992 and @option{-gdwarf-4}; we recommend always choosing the most recent
12993 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12994 includes information about preprocessor macros in the debugging
12998 $ gcc -gdwarf-2 -g3 sample.c -o sample
13002 Now, we start @value{GDBN} on our sample program:
13006 GNU gdb 2002-05-06-cvs
13007 Copyright 2002 Free Software Foundation, Inc.
13008 GDB is free software, @dots{}
13012 We can expand macros and examine their definitions, even when the
13013 program is not running. @value{GDBN} uses the current listing position
13014 to decide which macro definitions are in scope:
13017 (@value{GDBP}) list main
13020 5 #define ADD(x) (M + x)
13025 10 printf ("Hello, world!\n");
13027 12 printf ("We're so creative.\n");
13028 (@value{GDBP}) info macro ADD
13029 Defined at /home/jimb/gdb/macros/play/sample.c:5
13030 #define ADD(x) (M + x)
13031 (@value{GDBP}) info macro Q
13032 Defined at /home/jimb/gdb/macros/play/sample.h:1
13033 included at /home/jimb/gdb/macros/play/sample.c:2
13035 (@value{GDBP}) macro expand ADD(1)
13036 expands to: (42 + 1)
13037 (@value{GDBP}) macro expand-once ADD(1)
13038 expands to: once (M + 1)
13042 In the example above, note that @code{macro expand-once} expands only
13043 the macro invocation explicit in the original text --- the invocation of
13044 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13045 which was introduced by @code{ADD}.
13047 Once the program is running, @value{GDBN} uses the macro definitions in
13048 force at the source line of the current stack frame:
13051 (@value{GDBP}) break main
13052 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13054 Starting program: /home/jimb/gdb/macros/play/sample
13056 Breakpoint 1, main () at sample.c:10
13057 10 printf ("Hello, world!\n");
13061 At line 10, the definition of the macro @code{N} at line 9 is in force:
13064 (@value{GDBP}) info macro N
13065 Defined at /home/jimb/gdb/macros/play/sample.c:9
13067 (@value{GDBP}) macro expand N Q M
13068 expands to: 28 < 42
13069 (@value{GDBP}) print N Q M
13074 As we step over directives that remove @code{N}'s definition, and then
13075 give it a new definition, @value{GDBN} finds the definition (or lack
13076 thereof) in force at each point:
13079 (@value{GDBP}) next
13081 12 printf ("We're so creative.\n");
13082 (@value{GDBP}) info macro N
13083 The symbol `N' has no definition as a C/C++ preprocessor macro
13084 at /home/jimb/gdb/macros/play/sample.c:12
13085 (@value{GDBP}) next
13087 14 printf ("Goodbye, world!\n");
13088 (@value{GDBP}) info macro N
13089 Defined at /home/jimb/gdb/macros/play/sample.c:13
13091 (@value{GDBP}) macro expand N Q M
13092 expands to: 1729 < 42
13093 (@value{GDBP}) print N Q M
13098 In addition to source files, macros can be defined on the compilation command
13099 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13100 such a way, @value{GDBN} displays the location of their definition as line zero
13101 of the source file submitted to the compiler.
13104 (@value{GDBP}) info macro __STDC__
13105 Defined at /home/jimb/gdb/macros/play/sample.c:0
13112 @chapter Tracepoints
13113 @c This chapter is based on the documentation written by Michael
13114 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13116 @cindex tracepoints
13117 In some applications, it is not feasible for the debugger to interrupt
13118 the program's execution long enough for the developer to learn
13119 anything helpful about its behavior. If the program's correctness
13120 depends on its real-time behavior, delays introduced by a debugger
13121 might cause the program to change its behavior drastically, or perhaps
13122 fail, even when the code itself is correct. It is useful to be able
13123 to observe the program's behavior without interrupting it.
13125 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13126 specify locations in the program, called @dfn{tracepoints}, and
13127 arbitrary expressions to evaluate when those tracepoints are reached.
13128 Later, using the @code{tfind} command, you can examine the values
13129 those expressions had when the program hit the tracepoints. The
13130 expressions may also denote objects in memory---structures or arrays,
13131 for example---whose values @value{GDBN} should record; while visiting
13132 a particular tracepoint, you may inspect those objects as if they were
13133 in memory at that moment. However, because @value{GDBN} records these
13134 values without interacting with you, it can do so quickly and
13135 unobtrusively, hopefully not disturbing the program's behavior.
13137 The tracepoint facility is currently available only for remote
13138 targets. @xref{Targets}. In addition, your remote target must know
13139 how to collect trace data. This functionality is implemented in the
13140 remote stub; however, none of the stubs distributed with @value{GDBN}
13141 support tracepoints as of this writing. The format of the remote
13142 packets used to implement tracepoints are described in @ref{Tracepoint
13145 It is also possible to get trace data from a file, in a manner reminiscent
13146 of corefiles; you specify the filename, and use @code{tfind} to search
13147 through the file. @xref{Trace Files}, for more details.
13149 This chapter describes the tracepoint commands and features.
13152 * Set Tracepoints::
13153 * Analyze Collected Data::
13154 * Tracepoint Variables::
13158 @node Set Tracepoints
13159 @section Commands to Set Tracepoints
13161 Before running such a @dfn{trace experiment}, an arbitrary number of
13162 tracepoints can be set. A tracepoint is actually a special type of
13163 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13164 standard breakpoint commands. For instance, as with breakpoints,
13165 tracepoint numbers are successive integers starting from one, and many
13166 of the commands associated with tracepoints take the tracepoint number
13167 as their argument, to identify which tracepoint to work on.
13169 For each tracepoint, you can specify, in advance, some arbitrary set
13170 of data that you want the target to collect in the trace buffer when
13171 it hits that tracepoint. The collected data can include registers,
13172 local variables, or global data. Later, you can use @value{GDBN}
13173 commands to examine the values these data had at the time the
13174 tracepoint was hit.
13176 Tracepoints do not support every breakpoint feature. Ignore counts on
13177 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13178 commands when they are hit. Tracepoints may not be thread-specific
13181 @cindex fast tracepoints
13182 Some targets may support @dfn{fast tracepoints}, which are inserted in
13183 a different way (such as with a jump instead of a trap), that is
13184 faster but possibly restricted in where they may be installed.
13186 @cindex static tracepoints
13187 @cindex markers, static tracepoints
13188 @cindex probing markers, static tracepoints
13189 Regular and fast tracepoints are dynamic tracing facilities, meaning
13190 that they can be used to insert tracepoints at (almost) any location
13191 in the target. Some targets may also support controlling @dfn{static
13192 tracepoints} from @value{GDBN}. With static tracing, a set of
13193 instrumentation points, also known as @dfn{markers}, are embedded in
13194 the target program, and can be activated or deactivated by name or
13195 address. These are usually placed at locations which facilitate
13196 investigating what the target is actually doing. @value{GDBN}'s
13197 support for static tracing includes being able to list instrumentation
13198 points, and attach them with @value{GDBN} defined high level
13199 tracepoints that expose the whole range of convenience of
13200 @value{GDBN}'s tracepoints support. Namely, support for collecting
13201 registers values and values of global or local (to the instrumentation
13202 point) variables; tracepoint conditions and trace state variables.
13203 The act of installing a @value{GDBN} static tracepoint on an
13204 instrumentation point, or marker, is referred to as @dfn{probing} a
13205 static tracepoint marker.
13207 @code{gdbserver} supports tracepoints on some target systems.
13208 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13210 This section describes commands to set tracepoints and associated
13211 conditions and actions.
13214 * Create and Delete Tracepoints::
13215 * Enable and Disable Tracepoints::
13216 * Tracepoint Passcounts::
13217 * Tracepoint Conditions::
13218 * Trace State Variables::
13219 * Tracepoint Actions::
13220 * Listing Tracepoints::
13221 * Listing Static Tracepoint Markers::
13222 * Starting and Stopping Trace Experiments::
13223 * Tracepoint Restrictions::
13226 @node Create and Delete Tracepoints
13227 @subsection Create and Delete Tracepoints
13230 @cindex set tracepoint
13232 @item trace @var{location}
13233 The @code{trace} command is very similar to the @code{break} command.
13234 Its argument @var{location} can be any valid location.
13235 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13236 which is a point in the target program where the debugger will briefly stop,
13237 collect some data, and then allow the program to continue. Setting a tracepoint
13238 or changing its actions takes effect immediately if the remote stub
13239 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13241 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13242 these changes don't take effect until the next @code{tstart}
13243 command, and once a trace experiment is running, further changes will
13244 not have any effect until the next trace experiment starts. In addition,
13245 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13246 address is not yet resolved. (This is similar to pending breakpoints.)
13247 Pending tracepoints are not downloaded to the target and not installed
13248 until they are resolved. The resolution of pending tracepoints requires
13249 @value{GDBN} support---when debugging with the remote target, and
13250 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13251 tracing}), pending tracepoints can not be resolved (and downloaded to
13252 the remote stub) while @value{GDBN} is disconnected.
13254 Here are some examples of using the @code{trace} command:
13257 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13259 (@value{GDBP}) @b{trace +2} // 2 lines forward
13261 (@value{GDBP}) @b{trace my_function} // first source line of function
13263 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13265 (@value{GDBP}) @b{trace *0x2117c4} // an address
13269 You can abbreviate @code{trace} as @code{tr}.
13271 @item trace @var{location} if @var{cond}
13272 Set a tracepoint with condition @var{cond}; evaluate the expression
13273 @var{cond} each time the tracepoint is reached, and collect data only
13274 if the value is nonzero---that is, if @var{cond} evaluates as true.
13275 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13276 information on tracepoint conditions.
13278 @item ftrace @var{location} [ if @var{cond} ]
13279 @cindex set fast tracepoint
13280 @cindex fast tracepoints, setting
13282 The @code{ftrace} command sets a fast tracepoint. For targets that
13283 support them, fast tracepoints will use a more efficient but possibly
13284 less general technique to trigger data collection, such as a jump
13285 instruction instead of a trap, or some sort of hardware support. It
13286 may not be possible to create a fast tracepoint at the desired
13287 location, in which case the command will exit with an explanatory
13290 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13293 On 32-bit x86-architecture systems, fast tracepoints normally need to
13294 be placed at an instruction that is 5 bytes or longer, but can be
13295 placed at 4-byte instructions if the low 64K of memory of the target
13296 program is available to install trampolines. Some Unix-type systems,
13297 such as @sc{gnu}/Linux, exclude low addresses from the program's
13298 address space; but for instance with the Linux kernel it is possible
13299 to let @value{GDBN} use this area by doing a @command{sysctl} command
13300 to set the @code{mmap_min_addr} kernel parameter, as in
13303 sudo sysctl -w vm.mmap_min_addr=32768
13307 which sets the low address to 32K, which leaves plenty of room for
13308 trampolines. The minimum address should be set to a page boundary.
13310 @item strace @var{location} [ if @var{cond} ]
13311 @cindex set static tracepoint
13312 @cindex static tracepoints, setting
13313 @cindex probe static tracepoint marker
13315 The @code{strace} command sets a static tracepoint. For targets that
13316 support it, setting a static tracepoint probes a static
13317 instrumentation point, or marker, found at @var{location}. It may not
13318 be possible to set a static tracepoint at the desired location, in
13319 which case the command will exit with an explanatory message.
13321 @value{GDBN} handles arguments to @code{strace} exactly as for
13322 @code{trace}, with the addition that the user can also specify
13323 @code{-m @var{marker}} as @var{location}. This probes the marker
13324 identified by the @var{marker} string identifier. This identifier
13325 depends on the static tracepoint backend library your program is
13326 using. You can find all the marker identifiers in the @samp{ID} field
13327 of the @code{info static-tracepoint-markers} command output.
13328 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13329 Markers}. For example, in the following small program using the UST
13335 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13340 the marker id is composed of joining the first two arguments to the
13341 @code{trace_mark} call with a slash, which translates to:
13344 (@value{GDBP}) info static-tracepoint-markers
13345 Cnt Enb ID Address What
13346 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13352 so you may probe the marker above with:
13355 (@value{GDBP}) strace -m ust/bar33
13358 Static tracepoints accept an extra collect action --- @code{collect
13359 $_sdata}. This collects arbitrary user data passed in the probe point
13360 call to the tracing library. In the UST example above, you'll see
13361 that the third argument to @code{trace_mark} is a printf-like format
13362 string. The user data is then the result of running that formating
13363 string against the following arguments. Note that @code{info
13364 static-tracepoint-markers} command output lists that format string in
13365 the @samp{Data:} field.
13367 You can inspect this data when analyzing the trace buffer, by printing
13368 the $_sdata variable like any other variable available to
13369 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13372 @cindex last tracepoint number
13373 @cindex recent tracepoint number
13374 @cindex tracepoint number
13375 The convenience variable @code{$tpnum} records the tracepoint number
13376 of the most recently set tracepoint.
13378 @kindex delete tracepoint
13379 @cindex tracepoint deletion
13380 @item delete tracepoint @r{[}@var{num}@r{]}
13381 Permanently delete one or more tracepoints. With no argument, the
13382 default is to delete all tracepoints. Note that the regular
13383 @code{delete} command can remove tracepoints also.
13388 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13390 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13394 You can abbreviate this command as @code{del tr}.
13397 @node Enable and Disable Tracepoints
13398 @subsection Enable and Disable Tracepoints
13400 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13403 @kindex disable tracepoint
13404 @item disable tracepoint @r{[}@var{num}@r{]}
13405 Disable tracepoint @var{num}, or all tracepoints if no argument
13406 @var{num} is given. A disabled tracepoint will have no effect during
13407 a trace experiment, but it is not forgotten. You can re-enable
13408 a disabled tracepoint using the @code{enable tracepoint} command.
13409 If the command is issued during a trace experiment and the debug target
13410 has support for disabling tracepoints during a trace experiment, then the
13411 change will be effective immediately. Otherwise, it will be applied to the
13412 next trace experiment.
13414 @kindex enable tracepoint
13415 @item enable tracepoint @r{[}@var{num}@r{]}
13416 Enable tracepoint @var{num}, or all tracepoints. If this command is
13417 issued during a trace experiment and the debug target supports enabling
13418 tracepoints during a trace experiment, then the enabled tracepoints will
13419 become effective immediately. Otherwise, they will become effective the
13420 next time a trace experiment is run.
13423 @node Tracepoint Passcounts
13424 @subsection Tracepoint Passcounts
13428 @cindex tracepoint pass count
13429 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13430 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13431 automatically stop a trace experiment. If a tracepoint's passcount is
13432 @var{n}, then the trace experiment will be automatically stopped on
13433 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13434 @var{num} is not specified, the @code{passcount} command sets the
13435 passcount of the most recently defined tracepoint. If no passcount is
13436 given, the trace experiment will run until stopped explicitly by the
13442 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13443 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13445 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13446 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13447 (@value{GDBP}) @b{trace foo}
13448 (@value{GDBP}) @b{pass 3}
13449 (@value{GDBP}) @b{trace bar}
13450 (@value{GDBP}) @b{pass 2}
13451 (@value{GDBP}) @b{trace baz}
13452 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13453 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13454 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13455 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13459 @node Tracepoint Conditions
13460 @subsection Tracepoint Conditions
13461 @cindex conditional tracepoints
13462 @cindex tracepoint conditions
13464 The simplest sort of tracepoint collects data every time your program
13465 reaches a specified place. You can also specify a @dfn{condition} for
13466 a tracepoint. A condition is just a Boolean expression in your
13467 programming language (@pxref{Expressions, ,Expressions}). A
13468 tracepoint with a condition evaluates the expression each time your
13469 program reaches it, and data collection happens only if the condition
13472 Tracepoint conditions can be specified when a tracepoint is set, by
13473 using @samp{if} in the arguments to the @code{trace} command.
13474 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13475 also be set or changed at any time with the @code{condition} command,
13476 just as with breakpoints.
13478 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13479 the conditional expression itself. Instead, @value{GDBN} encodes the
13480 expression into an agent expression (@pxref{Agent Expressions})
13481 suitable for execution on the target, independently of @value{GDBN}.
13482 Global variables become raw memory locations, locals become stack
13483 accesses, and so forth.
13485 For instance, suppose you have a function that is usually called
13486 frequently, but should not be called after an error has occurred. You
13487 could use the following tracepoint command to collect data about calls
13488 of that function that happen while the error code is propagating
13489 through the program; an unconditional tracepoint could end up
13490 collecting thousands of useless trace frames that you would have to
13494 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13497 @node Trace State Variables
13498 @subsection Trace State Variables
13499 @cindex trace state variables
13501 A @dfn{trace state variable} is a special type of variable that is
13502 created and managed by target-side code. The syntax is the same as
13503 that for GDB's convenience variables (a string prefixed with ``$''),
13504 but they are stored on the target. They must be created explicitly,
13505 using a @code{tvariable} command. They are always 64-bit signed
13508 Trace state variables are remembered by @value{GDBN}, and downloaded
13509 to the target along with tracepoint information when the trace
13510 experiment starts. There are no intrinsic limits on the number of
13511 trace state variables, beyond memory limitations of the target.
13513 @cindex convenience variables, and trace state variables
13514 Although trace state variables are managed by the target, you can use
13515 them in print commands and expressions as if they were convenience
13516 variables; @value{GDBN} will get the current value from the target
13517 while the trace experiment is running. Trace state variables share
13518 the same namespace as other ``$'' variables, which means that you
13519 cannot have trace state variables with names like @code{$23} or
13520 @code{$pc}, nor can you have a trace state variable and a convenience
13521 variable with the same name.
13525 @item tvariable $@var{name} [ = @var{expression} ]
13527 The @code{tvariable} command creates a new trace state variable named
13528 @code{$@var{name}}, and optionally gives it an initial value of
13529 @var{expression}. The @var{expression} is evaluated when this command is
13530 entered; the result will be converted to an integer if possible,
13531 otherwise @value{GDBN} will report an error. A subsequent
13532 @code{tvariable} command specifying the same name does not create a
13533 variable, but instead assigns the supplied initial value to the
13534 existing variable of that name, overwriting any previous initial
13535 value. The default initial value is 0.
13537 @item info tvariables
13538 @kindex info tvariables
13539 List all the trace state variables along with their initial values.
13540 Their current values may also be displayed, if the trace experiment is
13543 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13544 @kindex delete tvariable
13545 Delete the given trace state variables, or all of them if no arguments
13550 @node Tracepoint Actions
13551 @subsection Tracepoint Action Lists
13555 @cindex tracepoint actions
13556 @item actions @r{[}@var{num}@r{]}
13557 This command will prompt for a list of actions to be taken when the
13558 tracepoint is hit. If the tracepoint number @var{num} is not
13559 specified, this command sets the actions for the one that was most
13560 recently defined (so that you can define a tracepoint and then say
13561 @code{actions} without bothering about its number). You specify the
13562 actions themselves on the following lines, one action at a time, and
13563 terminate the actions list with a line containing just @code{end}. So
13564 far, the only defined actions are @code{collect}, @code{teval}, and
13565 @code{while-stepping}.
13567 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13568 Commands, ,Breakpoint Command Lists}), except that only the defined
13569 actions are allowed; any other @value{GDBN} command is rejected.
13571 @cindex remove actions from a tracepoint
13572 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13573 and follow it immediately with @samp{end}.
13576 (@value{GDBP}) @b{collect @var{data}} // collect some data
13578 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13580 (@value{GDBP}) @b{end} // signals the end of actions.
13583 In the following example, the action list begins with @code{collect}
13584 commands indicating the things to be collected when the tracepoint is
13585 hit. Then, in order to single-step and collect additional data
13586 following the tracepoint, a @code{while-stepping} command is used,
13587 followed by the list of things to be collected after each step in a
13588 sequence of single steps. The @code{while-stepping} command is
13589 terminated by its own separate @code{end} command. Lastly, the action
13590 list is terminated by an @code{end} command.
13593 (@value{GDBP}) @b{trace foo}
13594 (@value{GDBP}) @b{actions}
13595 Enter actions for tracepoint 1, one per line:
13598 > while-stepping 12
13599 > collect $pc, arr[i]
13604 @kindex collect @r{(tracepoints)}
13605 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13606 Collect values of the given expressions when the tracepoint is hit.
13607 This command accepts a comma-separated list of any valid expressions.
13608 In addition to global, static, or local variables, the following
13609 special arguments are supported:
13613 Collect all registers.
13616 Collect all function arguments.
13619 Collect all local variables.
13622 Collect the return address. This is helpful if you want to see more
13625 @emph{Note:} The return address location can not always be reliably
13626 determined up front, and the wrong address / registers may end up
13627 collected instead. On some architectures the reliability is higher
13628 for tracepoints at function entry, while on others it's the opposite.
13629 When this happens, backtracing will stop because the return address is
13630 found unavailable (unless another collect rule happened to match it).
13633 Collects the number of arguments from the static probe at which the
13634 tracepoint is located.
13635 @xref{Static Probe Points}.
13637 @item $_probe_arg@var{n}
13638 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13639 from the static probe at which the tracepoint is located.
13640 @xref{Static Probe Points}.
13643 @vindex $_sdata@r{, collect}
13644 Collect static tracepoint marker specific data. Only available for
13645 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13646 Lists}. On the UST static tracepoints library backend, an
13647 instrumentation point resembles a @code{printf} function call. The
13648 tracing library is able to collect user specified data formatted to a
13649 character string using the format provided by the programmer that
13650 instrumented the program. Other backends have similar mechanisms.
13651 Here's an example of a UST marker call:
13654 const char master_name[] = "$your_name";
13655 trace_mark(channel1, marker1, "hello %s", master_name)
13658 In this case, collecting @code{$_sdata} collects the string
13659 @samp{hello $yourname}. When analyzing the trace buffer, you can
13660 inspect @samp{$_sdata} like any other variable available to
13664 You can give several consecutive @code{collect} commands, each one
13665 with a single argument, or one @code{collect} command with several
13666 arguments separated by commas; the effect is the same.
13668 The optional @var{mods} changes the usual handling of the arguments.
13669 @code{s} requests that pointers to chars be handled as strings, in
13670 particular collecting the contents of the memory being pointed at, up
13671 to the first zero. The upper bound is by default the value of the
13672 @code{print elements} variable; if @code{s} is followed by a decimal
13673 number, that is the upper bound instead. So for instance
13674 @samp{collect/s25 mystr} collects as many as 25 characters at
13677 The command @code{info scope} (@pxref{Symbols, info scope}) is
13678 particularly useful for figuring out what data to collect.
13680 @kindex teval @r{(tracepoints)}
13681 @item teval @var{expr1}, @var{expr2}, @dots{}
13682 Evaluate the given expressions when the tracepoint is hit. This
13683 command accepts a comma-separated list of expressions. The results
13684 are discarded, so this is mainly useful for assigning values to trace
13685 state variables (@pxref{Trace State Variables}) without adding those
13686 values to the trace buffer, as would be the case if the @code{collect}
13689 @kindex while-stepping @r{(tracepoints)}
13690 @item while-stepping @var{n}
13691 Perform @var{n} single-step instruction traces after the tracepoint,
13692 collecting new data after each step. The @code{while-stepping}
13693 command is followed by the list of what to collect while stepping
13694 (followed by its own @code{end} command):
13697 > while-stepping 12
13698 > collect $regs, myglobal
13704 Note that @code{$pc} is not automatically collected by
13705 @code{while-stepping}; you need to explicitly collect that register if
13706 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13709 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13710 @kindex set default-collect
13711 @cindex default collection action
13712 This variable is a list of expressions to collect at each tracepoint
13713 hit. It is effectively an additional @code{collect} action prepended
13714 to every tracepoint action list. The expressions are parsed
13715 individually for each tracepoint, so for instance a variable named
13716 @code{xyz} may be interpreted as a global for one tracepoint, and a
13717 local for another, as appropriate to the tracepoint's location.
13719 @item show default-collect
13720 @kindex show default-collect
13721 Show the list of expressions that are collected by default at each
13726 @node Listing Tracepoints
13727 @subsection Listing Tracepoints
13730 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13731 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13732 @cindex information about tracepoints
13733 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13734 Display information about the tracepoint @var{num}. If you don't
13735 specify a tracepoint number, displays information about all the
13736 tracepoints defined so far. The format is similar to that used for
13737 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13738 command, simply restricting itself to tracepoints.
13740 A tracepoint's listing may include additional information specific to
13745 its passcount as given by the @code{passcount @var{n}} command
13748 the state about installed on target of each location
13752 (@value{GDBP}) @b{info trace}
13753 Num Type Disp Enb Address What
13754 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13756 collect globfoo, $regs
13761 2 tracepoint keep y <MULTIPLE>
13763 2.1 y 0x0804859c in func4 at change-loc.h:35
13764 installed on target
13765 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13766 installed on target
13767 2.3 y <PENDING> set_tracepoint
13768 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13769 not installed on target
13774 This command can be abbreviated @code{info tp}.
13777 @node Listing Static Tracepoint Markers
13778 @subsection Listing Static Tracepoint Markers
13781 @kindex info static-tracepoint-markers
13782 @cindex information about static tracepoint markers
13783 @item info static-tracepoint-markers
13784 Display information about all static tracepoint markers defined in the
13787 For each marker, the following columns are printed:
13791 An incrementing counter, output to help readability. This is not a
13794 The marker ID, as reported by the target.
13795 @item Enabled or Disabled
13796 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13797 that are not enabled.
13799 Where the marker is in your program, as a memory address.
13801 Where the marker is in the source for your program, as a file and line
13802 number. If the debug information included in the program does not
13803 allow @value{GDBN} to locate the source of the marker, this column
13804 will be left blank.
13808 In addition, the following information may be printed for each marker:
13812 User data passed to the tracing library by the marker call. In the
13813 UST backend, this is the format string passed as argument to the
13815 @item Static tracepoints probing the marker
13816 The list of static tracepoints attached to the marker.
13820 (@value{GDBP}) info static-tracepoint-markers
13821 Cnt ID Enb Address What
13822 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13823 Data: number1 %d number2 %d
13824 Probed by static tracepoints: #2
13825 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13831 @node Starting and Stopping Trace Experiments
13832 @subsection Starting and Stopping Trace Experiments
13835 @kindex tstart [ @var{notes} ]
13836 @cindex start a new trace experiment
13837 @cindex collected data discarded
13839 This command starts the trace experiment, and begins collecting data.
13840 It has the side effect of discarding all the data collected in the
13841 trace buffer during the previous trace experiment. If any arguments
13842 are supplied, they are taken as a note and stored with the trace
13843 experiment's state. The notes may be arbitrary text, and are
13844 especially useful with disconnected tracing in a multi-user context;
13845 the notes can explain what the trace is doing, supply user contact
13846 information, and so forth.
13848 @kindex tstop [ @var{notes} ]
13849 @cindex stop a running trace experiment
13851 This command stops the trace experiment. If any arguments are
13852 supplied, they are recorded with the experiment as a note. This is
13853 useful if you are stopping a trace started by someone else, for
13854 instance if the trace is interfering with the system's behavior and
13855 needs to be stopped quickly.
13857 @strong{Note}: a trace experiment and data collection may stop
13858 automatically if any tracepoint's passcount is reached
13859 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13862 @cindex status of trace data collection
13863 @cindex trace experiment, status of
13865 This command displays the status of the current trace data
13869 Here is an example of the commands we described so far:
13872 (@value{GDBP}) @b{trace gdb_c_test}
13873 (@value{GDBP}) @b{actions}
13874 Enter actions for tracepoint #1, one per line.
13875 > collect $regs,$locals,$args
13876 > while-stepping 11
13880 (@value{GDBP}) @b{tstart}
13881 [time passes @dots{}]
13882 (@value{GDBP}) @b{tstop}
13885 @anchor{disconnected tracing}
13886 @cindex disconnected tracing
13887 You can choose to continue running the trace experiment even if
13888 @value{GDBN} disconnects from the target, voluntarily or
13889 involuntarily. For commands such as @code{detach}, the debugger will
13890 ask what you want to do with the trace. But for unexpected
13891 terminations (@value{GDBN} crash, network outage), it would be
13892 unfortunate to lose hard-won trace data, so the variable
13893 @code{disconnected-tracing} lets you decide whether the trace should
13894 continue running without @value{GDBN}.
13897 @item set disconnected-tracing on
13898 @itemx set disconnected-tracing off
13899 @kindex set disconnected-tracing
13900 Choose whether a tracing run should continue to run if @value{GDBN}
13901 has disconnected from the target. Note that @code{detach} or
13902 @code{quit} will ask you directly what to do about a running trace no
13903 matter what this variable's setting, so the variable is mainly useful
13904 for handling unexpected situations, such as loss of the network.
13906 @item show disconnected-tracing
13907 @kindex show disconnected-tracing
13908 Show the current choice for disconnected tracing.
13912 When you reconnect to the target, the trace experiment may or may not
13913 still be running; it might have filled the trace buffer in the
13914 meantime, or stopped for one of the other reasons. If it is running,
13915 it will continue after reconnection.
13917 Upon reconnection, the target will upload information about the
13918 tracepoints in effect. @value{GDBN} will then compare that
13919 information to the set of tracepoints currently defined, and attempt
13920 to match them up, allowing for the possibility that the numbers may
13921 have changed due to creation and deletion in the meantime. If one of
13922 the target's tracepoints does not match any in @value{GDBN}, the
13923 debugger will create a new tracepoint, so that you have a number with
13924 which to specify that tracepoint. This matching-up process is
13925 necessarily heuristic, and it may result in useless tracepoints being
13926 created; you may simply delete them if they are of no use.
13928 @cindex circular trace buffer
13929 If your target agent supports a @dfn{circular trace buffer}, then you
13930 can run a trace experiment indefinitely without filling the trace
13931 buffer; when space runs out, the agent deletes already-collected trace
13932 frames, oldest first, until there is enough room to continue
13933 collecting. This is especially useful if your tracepoints are being
13934 hit too often, and your trace gets terminated prematurely because the
13935 buffer is full. To ask for a circular trace buffer, simply set
13936 @samp{circular-trace-buffer} to on. You can set this at any time,
13937 including during tracing; if the agent can do it, it will change
13938 buffer handling on the fly, otherwise it will not take effect until
13942 @item set circular-trace-buffer on
13943 @itemx set circular-trace-buffer off
13944 @kindex set circular-trace-buffer
13945 Choose whether a tracing run should use a linear or circular buffer
13946 for trace data. A linear buffer will not lose any trace data, but may
13947 fill up prematurely, while a circular buffer will discard old trace
13948 data, but it will have always room for the latest tracepoint hits.
13950 @item show circular-trace-buffer
13951 @kindex show circular-trace-buffer
13952 Show the current choice for the trace buffer. Note that this may not
13953 match the agent's current buffer handling, nor is it guaranteed to
13954 match the setting that might have been in effect during a past run,
13955 for instance if you are looking at frames from a trace file.
13960 @item set trace-buffer-size @var{n}
13961 @itemx set trace-buffer-size unlimited
13962 @kindex set trace-buffer-size
13963 Request that the target use a trace buffer of @var{n} bytes. Not all
13964 targets will honor the request; they may have a compiled-in size for
13965 the trace buffer, or some other limitation. Set to a value of
13966 @code{unlimited} or @code{-1} to let the target use whatever size it
13967 likes. This is also the default.
13969 @item show trace-buffer-size
13970 @kindex show trace-buffer-size
13971 Show the current requested size for the trace buffer. Note that this
13972 will only match the actual size if the target supports size-setting,
13973 and was able to handle the requested size. For instance, if the
13974 target can only change buffer size between runs, this variable will
13975 not reflect the change until the next run starts. Use @code{tstatus}
13976 to get a report of the actual buffer size.
13980 @item set trace-user @var{text}
13981 @kindex set trace-user
13983 @item show trace-user
13984 @kindex show trace-user
13986 @item set trace-notes @var{text}
13987 @kindex set trace-notes
13988 Set the trace run's notes.
13990 @item show trace-notes
13991 @kindex show trace-notes
13992 Show the trace run's notes.
13994 @item set trace-stop-notes @var{text}
13995 @kindex set trace-stop-notes
13996 Set the trace run's stop notes. The handling of the note is as for
13997 @code{tstop} arguments; the set command is convenient way to fix a
13998 stop note that is mistaken or incomplete.
14000 @item show trace-stop-notes
14001 @kindex show trace-stop-notes
14002 Show the trace run's stop notes.
14006 @node Tracepoint Restrictions
14007 @subsection Tracepoint Restrictions
14009 @cindex tracepoint restrictions
14010 There are a number of restrictions on the use of tracepoints. As
14011 described above, tracepoint data gathering occurs on the target
14012 without interaction from @value{GDBN}. Thus the full capabilities of
14013 the debugger are not available during data gathering, and then at data
14014 examination time, you will be limited by only having what was
14015 collected. The following items describe some common problems, but it
14016 is not exhaustive, and you may run into additional difficulties not
14022 Tracepoint expressions are intended to gather objects (lvalues). Thus
14023 the full flexibility of GDB's expression evaluator is not available.
14024 You cannot call functions, cast objects to aggregate types, access
14025 convenience variables or modify values (except by assignment to trace
14026 state variables). Some language features may implicitly call
14027 functions (for instance Objective-C fields with accessors), and therefore
14028 cannot be collected either.
14031 Collection of local variables, either individually or in bulk with
14032 @code{$locals} or @code{$args}, during @code{while-stepping} may
14033 behave erratically. The stepping action may enter a new scope (for
14034 instance by stepping into a function), or the location of the variable
14035 may change (for instance it is loaded into a register). The
14036 tracepoint data recorded uses the location information for the
14037 variables that is correct for the tracepoint location. When the
14038 tracepoint is created, it is not possible, in general, to determine
14039 where the steps of a @code{while-stepping} sequence will advance the
14040 program---particularly if a conditional branch is stepped.
14043 Collection of an incompletely-initialized or partially-destroyed object
14044 may result in something that @value{GDBN} cannot display, or displays
14045 in a misleading way.
14048 When @value{GDBN} displays a pointer to character it automatically
14049 dereferences the pointer to also display characters of the string
14050 being pointed to. However, collecting the pointer during tracing does
14051 not automatically collect the string. You need to explicitly
14052 dereference the pointer and provide size information if you want to
14053 collect not only the pointer, but the memory pointed to. For example,
14054 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14058 It is not possible to collect a complete stack backtrace at a
14059 tracepoint. Instead, you may collect the registers and a few hundred
14060 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14061 (adjust to use the name of the actual stack pointer register on your
14062 target architecture, and the amount of stack you wish to capture).
14063 Then the @code{backtrace} command will show a partial backtrace when
14064 using a trace frame. The number of stack frames that can be examined
14065 depends on the sizes of the frames in the collected stack. Note that
14066 if you ask for a block so large that it goes past the bottom of the
14067 stack, the target agent may report an error trying to read from an
14071 If you do not collect registers at a tracepoint, @value{GDBN} can
14072 infer that the value of @code{$pc} must be the same as the address of
14073 the tracepoint and use that when you are looking at a trace frame
14074 for that tracepoint. However, this cannot work if the tracepoint has
14075 multiple locations (for instance if it was set in a function that was
14076 inlined), or if it has a @code{while-stepping} loop. In those cases
14077 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14082 @node Analyze Collected Data
14083 @section Using the Collected Data
14085 After the tracepoint experiment ends, you use @value{GDBN} commands
14086 for examining the trace data. The basic idea is that each tracepoint
14087 collects a trace @dfn{snapshot} every time it is hit and another
14088 snapshot every time it single-steps. All these snapshots are
14089 consecutively numbered from zero and go into a buffer, and you can
14090 examine them later. The way you examine them is to @dfn{focus} on a
14091 specific trace snapshot. When the remote stub is focused on a trace
14092 snapshot, it will respond to all @value{GDBN} requests for memory and
14093 registers by reading from the buffer which belongs to that snapshot,
14094 rather than from @emph{real} memory or registers of the program being
14095 debugged. This means that @strong{all} @value{GDBN} commands
14096 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14097 behave as if we were currently debugging the program state as it was
14098 when the tracepoint occurred. Any requests for data that are not in
14099 the buffer will fail.
14102 * tfind:: How to select a trace snapshot
14103 * tdump:: How to display all data for a snapshot
14104 * save tracepoints:: How to save tracepoints for a future run
14108 @subsection @code{tfind @var{n}}
14111 @cindex select trace snapshot
14112 @cindex find trace snapshot
14113 The basic command for selecting a trace snapshot from the buffer is
14114 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14115 counting from zero. If no argument @var{n} is given, the next
14116 snapshot is selected.
14118 Here are the various forms of using the @code{tfind} command.
14122 Find the first snapshot in the buffer. This is a synonym for
14123 @code{tfind 0} (since 0 is the number of the first snapshot).
14126 Stop debugging trace snapshots, resume @emph{live} debugging.
14129 Same as @samp{tfind none}.
14132 No argument means find the next trace snapshot or find the first
14133 one if no trace snapshot is selected.
14136 Find the previous trace snapshot before the current one. This permits
14137 retracing earlier steps.
14139 @item tfind tracepoint @var{num}
14140 Find the next snapshot associated with tracepoint @var{num}. Search
14141 proceeds forward from the last examined trace snapshot. If no
14142 argument @var{num} is given, it means find the next snapshot collected
14143 for the same tracepoint as the current snapshot.
14145 @item tfind pc @var{addr}
14146 Find the next snapshot associated with the value @var{addr} of the
14147 program counter. Search proceeds forward from the last examined trace
14148 snapshot. If no argument @var{addr} is given, it means find the next
14149 snapshot with the same value of PC as the current snapshot.
14151 @item tfind outside @var{addr1}, @var{addr2}
14152 Find the next snapshot whose PC is outside the given range of
14153 addresses (exclusive).
14155 @item tfind range @var{addr1}, @var{addr2}
14156 Find the next snapshot whose PC is between @var{addr1} and
14157 @var{addr2} (inclusive).
14159 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14160 Find the next snapshot associated with the source line @var{n}. If
14161 the optional argument @var{file} is given, refer to line @var{n} in
14162 that source file. Search proceeds forward from the last examined
14163 trace snapshot. If no argument @var{n} is given, it means find the
14164 next line other than the one currently being examined; thus saying
14165 @code{tfind line} repeatedly can appear to have the same effect as
14166 stepping from line to line in a @emph{live} debugging session.
14169 The default arguments for the @code{tfind} commands are specifically
14170 designed to make it easy to scan through the trace buffer. For
14171 instance, @code{tfind} with no argument selects the next trace
14172 snapshot, and @code{tfind -} with no argument selects the previous
14173 trace snapshot. So, by giving one @code{tfind} command, and then
14174 simply hitting @key{RET} repeatedly you can examine all the trace
14175 snapshots in order. Or, by saying @code{tfind -} and then hitting
14176 @key{RET} repeatedly you can examine the snapshots in reverse order.
14177 The @code{tfind line} command with no argument selects the snapshot
14178 for the next source line executed. The @code{tfind pc} command with
14179 no argument selects the next snapshot with the same program counter
14180 (PC) as the current frame. The @code{tfind tracepoint} command with
14181 no argument selects the next trace snapshot collected by the same
14182 tracepoint as the current one.
14184 In addition to letting you scan through the trace buffer manually,
14185 these commands make it easy to construct @value{GDBN} scripts that
14186 scan through the trace buffer and print out whatever collected data
14187 you are interested in. Thus, if we want to examine the PC, FP, and SP
14188 registers from each trace frame in the buffer, we can say this:
14191 (@value{GDBP}) @b{tfind start}
14192 (@value{GDBP}) @b{while ($trace_frame != -1)}
14193 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14194 $trace_frame, $pc, $sp, $fp
14198 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14199 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14200 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14201 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14202 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14203 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14204 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14205 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14206 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14207 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14208 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14211 Or, if we want to examine the variable @code{X} at each source line in
14215 (@value{GDBP}) @b{tfind start}
14216 (@value{GDBP}) @b{while ($trace_frame != -1)}
14217 > printf "Frame %d, X == %d\n", $trace_frame, X
14227 @subsection @code{tdump}
14229 @cindex dump all data collected at tracepoint
14230 @cindex tracepoint data, display
14232 This command takes no arguments. It prints all the data collected at
14233 the current trace snapshot.
14236 (@value{GDBP}) @b{trace 444}
14237 (@value{GDBP}) @b{actions}
14238 Enter actions for tracepoint #2, one per line:
14239 > collect $regs, $locals, $args, gdb_long_test
14242 (@value{GDBP}) @b{tstart}
14244 (@value{GDBP}) @b{tfind line 444}
14245 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14247 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14249 (@value{GDBP}) @b{tdump}
14250 Data collected at tracepoint 2, trace frame 1:
14251 d0 0xc4aa0085 -995491707
14255 d4 0x71aea3d 119204413
14258 d7 0x380035 3670069
14259 a0 0x19e24a 1696330
14260 a1 0x3000668 50333288
14262 a3 0x322000 3284992
14263 a4 0x3000698 50333336
14264 a5 0x1ad3cc 1758156
14265 fp 0x30bf3c 0x30bf3c
14266 sp 0x30bf34 0x30bf34
14268 pc 0x20b2c8 0x20b2c8
14272 p = 0x20e5b4 "gdb-test"
14279 gdb_long_test = 17 '\021'
14284 @code{tdump} works by scanning the tracepoint's current collection
14285 actions and printing the value of each expression listed. So
14286 @code{tdump} can fail, if after a run, you change the tracepoint's
14287 actions to mention variables that were not collected during the run.
14289 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14290 uses the collected value of @code{$pc} to distinguish between trace
14291 frames that were collected at the tracepoint hit, and frames that were
14292 collected while stepping. This allows it to correctly choose whether
14293 to display the basic list of collections, or the collections from the
14294 body of the while-stepping loop. However, if @code{$pc} was not collected,
14295 then @code{tdump} will always attempt to dump using the basic collection
14296 list, and may fail if a while-stepping frame does not include all the
14297 same data that is collected at the tracepoint hit.
14298 @c This is getting pretty arcane, example would be good.
14300 @node save tracepoints
14301 @subsection @code{save tracepoints @var{filename}}
14302 @kindex save tracepoints
14303 @kindex save-tracepoints
14304 @cindex save tracepoints for future sessions
14306 This command saves all current tracepoint definitions together with
14307 their actions and passcounts, into a file @file{@var{filename}}
14308 suitable for use in a later debugging session. To read the saved
14309 tracepoint definitions, use the @code{source} command (@pxref{Command
14310 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14311 alias for @w{@code{save tracepoints}}
14313 @node Tracepoint Variables
14314 @section Convenience Variables for Tracepoints
14315 @cindex tracepoint variables
14316 @cindex convenience variables for tracepoints
14319 @vindex $trace_frame
14320 @item (int) $trace_frame
14321 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14322 snapshot is selected.
14324 @vindex $tracepoint
14325 @item (int) $tracepoint
14326 The tracepoint for the current trace snapshot.
14328 @vindex $trace_line
14329 @item (int) $trace_line
14330 The line number for the current trace snapshot.
14332 @vindex $trace_file
14333 @item (char []) $trace_file
14334 The source file for the current trace snapshot.
14336 @vindex $trace_func
14337 @item (char []) $trace_func
14338 The name of the function containing @code{$tracepoint}.
14341 Note: @code{$trace_file} is not suitable for use in @code{printf},
14342 use @code{output} instead.
14344 Here's a simple example of using these convenience variables for
14345 stepping through all the trace snapshots and printing some of their
14346 data. Note that these are not the same as trace state variables,
14347 which are managed by the target.
14350 (@value{GDBP}) @b{tfind start}
14352 (@value{GDBP}) @b{while $trace_frame != -1}
14353 > output $trace_file
14354 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14360 @section Using Trace Files
14361 @cindex trace files
14363 In some situations, the target running a trace experiment may no
14364 longer be available; perhaps it crashed, or the hardware was needed
14365 for a different activity. To handle these cases, you can arrange to
14366 dump the trace data into a file, and later use that file as a source
14367 of trace data, via the @code{target tfile} command.
14372 @item tsave [ -r ] @var{filename}
14373 @itemx tsave [-ctf] @var{dirname}
14374 Save the trace data to @var{filename}. By default, this command
14375 assumes that @var{filename} refers to the host filesystem, so if
14376 necessary @value{GDBN} will copy raw trace data up from the target and
14377 then save it. If the target supports it, you can also supply the
14378 optional argument @code{-r} (``remote'') to direct the target to save
14379 the data directly into @var{filename} in its own filesystem, which may be
14380 more efficient if the trace buffer is very large. (Note, however, that
14381 @code{target tfile} can only read from files accessible to the host.)
14382 By default, this command will save trace frame in tfile format.
14383 You can supply the optional argument @code{-ctf} to save data in CTF
14384 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14385 that can be shared by multiple debugging and tracing tools. Please go to
14386 @indicateurl{http://www.efficios.com/ctf} to get more information.
14388 @kindex target tfile
14392 @item target tfile @var{filename}
14393 @itemx target ctf @var{dirname}
14394 Use the file named @var{filename} or directory named @var{dirname} as
14395 a source of trace data. Commands that examine data work as they do with
14396 a live target, but it is not possible to run any new trace experiments.
14397 @code{tstatus} will report the state of the trace run at the moment
14398 the data was saved, as well as the current trace frame you are examining.
14399 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14403 (@value{GDBP}) target ctf ctf.ctf
14404 (@value{GDBP}) tfind
14405 Found trace frame 0, tracepoint 2
14406 39 ++a; /* set tracepoint 1 here */
14407 (@value{GDBP}) tdump
14408 Data collected at tracepoint 2, trace frame 0:
14412 c = @{"123", "456", "789", "123", "456", "789"@}
14413 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14421 @chapter Debugging Programs That Use Overlays
14424 If your program is too large to fit completely in your target system's
14425 memory, you can sometimes use @dfn{overlays} to work around this
14426 problem. @value{GDBN} provides some support for debugging programs that
14430 * How Overlays Work:: A general explanation of overlays.
14431 * Overlay Commands:: Managing overlays in @value{GDBN}.
14432 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14433 mapped by asking the inferior.
14434 * Overlay Sample Program:: A sample program using overlays.
14437 @node How Overlays Work
14438 @section How Overlays Work
14439 @cindex mapped overlays
14440 @cindex unmapped overlays
14441 @cindex load address, overlay's
14442 @cindex mapped address
14443 @cindex overlay area
14445 Suppose you have a computer whose instruction address space is only 64
14446 kilobytes long, but which has much more memory which can be accessed by
14447 other means: special instructions, segment registers, or memory
14448 management hardware, for example. Suppose further that you want to
14449 adapt a program which is larger than 64 kilobytes to run on this system.
14451 One solution is to identify modules of your program which are relatively
14452 independent, and need not call each other directly; call these modules
14453 @dfn{overlays}. Separate the overlays from the main program, and place
14454 their machine code in the larger memory. Place your main program in
14455 instruction memory, but leave at least enough space there to hold the
14456 largest overlay as well.
14458 Now, to call a function located in an overlay, you must first copy that
14459 overlay's machine code from the large memory into the space set aside
14460 for it in the instruction memory, and then jump to its entry point
14463 @c NB: In the below the mapped area's size is greater or equal to the
14464 @c size of all overlays. This is intentional to remind the developer
14465 @c that overlays don't necessarily need to be the same size.
14469 Data Instruction Larger
14470 Address Space Address Space Address Space
14471 +-----------+ +-----------+ +-----------+
14473 +-----------+ +-----------+ +-----------+<-- overlay 1
14474 | program | | main | .----| overlay 1 | load address
14475 | variables | | program | | +-----------+
14476 | and heap | | | | | |
14477 +-----------+ | | | +-----------+<-- overlay 2
14478 | | +-----------+ | | | load address
14479 +-----------+ | | | .-| overlay 2 |
14481 mapped --->+-----------+ | | +-----------+
14482 address | | | | | |
14483 | overlay | <-' | | |
14484 | area | <---' +-----------+<-- overlay 3
14485 | | <---. | | load address
14486 +-----------+ `--| overlay 3 |
14493 @anchor{A code overlay}A code overlay
14497 The diagram (@pxref{A code overlay}) shows a system with separate data
14498 and instruction address spaces. To map an overlay, the program copies
14499 its code from the larger address space to the instruction address space.
14500 Since the overlays shown here all use the same mapped address, only one
14501 may be mapped at a time. For a system with a single address space for
14502 data and instructions, the diagram would be similar, except that the
14503 program variables and heap would share an address space with the main
14504 program and the overlay area.
14506 An overlay loaded into instruction memory and ready for use is called a
14507 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14508 instruction memory. An overlay not present (or only partially present)
14509 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14510 is its address in the larger memory. The mapped address is also called
14511 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14512 called the @dfn{load memory address}, or @dfn{LMA}.
14514 Unfortunately, overlays are not a completely transparent way to adapt a
14515 program to limited instruction memory. They introduce a new set of
14516 global constraints you must keep in mind as you design your program:
14521 Before calling or returning to a function in an overlay, your program
14522 must make sure that overlay is actually mapped. Otherwise, the call or
14523 return will transfer control to the right address, but in the wrong
14524 overlay, and your program will probably crash.
14527 If the process of mapping an overlay is expensive on your system, you
14528 will need to choose your overlays carefully to minimize their effect on
14529 your program's performance.
14532 The executable file you load onto your system must contain each
14533 overlay's instructions, appearing at the overlay's load address, not its
14534 mapped address. However, each overlay's instructions must be relocated
14535 and its symbols defined as if the overlay were at its mapped address.
14536 You can use GNU linker scripts to specify different load and relocation
14537 addresses for pieces of your program; see @ref{Overlay Description,,,
14538 ld.info, Using ld: the GNU linker}.
14541 The procedure for loading executable files onto your system must be able
14542 to load their contents into the larger address space as well as the
14543 instruction and data spaces.
14547 The overlay system described above is rather simple, and could be
14548 improved in many ways:
14553 If your system has suitable bank switch registers or memory management
14554 hardware, you could use those facilities to make an overlay's load area
14555 contents simply appear at their mapped address in instruction space.
14556 This would probably be faster than copying the overlay to its mapped
14557 area in the usual way.
14560 If your overlays are small enough, you could set aside more than one
14561 overlay area, and have more than one overlay mapped at a time.
14564 You can use overlays to manage data, as well as instructions. In
14565 general, data overlays are even less transparent to your design than
14566 code overlays: whereas code overlays only require care when you call or
14567 return to functions, data overlays require care every time you access
14568 the data. Also, if you change the contents of a data overlay, you
14569 must copy its contents back out to its load address before you can copy a
14570 different data overlay into the same mapped area.
14575 @node Overlay Commands
14576 @section Overlay Commands
14578 To use @value{GDBN}'s overlay support, each overlay in your program must
14579 correspond to a separate section of the executable file. The section's
14580 virtual memory address and load memory address must be the overlay's
14581 mapped and load addresses. Identifying overlays with sections allows
14582 @value{GDBN} to determine the appropriate address of a function or
14583 variable, depending on whether the overlay is mapped or not.
14585 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14586 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14591 Disable @value{GDBN}'s overlay support. When overlay support is
14592 disabled, @value{GDBN} assumes that all functions and variables are
14593 always present at their mapped addresses. By default, @value{GDBN}'s
14594 overlay support is disabled.
14596 @item overlay manual
14597 @cindex manual overlay debugging
14598 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14599 relies on you to tell it which overlays are mapped, and which are not,
14600 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14601 commands described below.
14603 @item overlay map-overlay @var{overlay}
14604 @itemx overlay map @var{overlay}
14605 @cindex map an overlay
14606 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14607 be the name of the object file section containing the overlay. When an
14608 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14609 functions and variables at their mapped addresses. @value{GDBN} assumes
14610 that any other overlays whose mapped ranges overlap that of
14611 @var{overlay} are now unmapped.
14613 @item overlay unmap-overlay @var{overlay}
14614 @itemx overlay unmap @var{overlay}
14615 @cindex unmap an overlay
14616 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14617 must be the name of the object file section containing the overlay.
14618 When an overlay is unmapped, @value{GDBN} assumes it can find the
14619 overlay's functions and variables at their load addresses.
14622 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14623 consults a data structure the overlay manager maintains in the inferior
14624 to see which overlays are mapped. For details, see @ref{Automatic
14625 Overlay Debugging}.
14627 @item overlay load-target
14628 @itemx overlay load
14629 @cindex reloading the overlay table
14630 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14631 re-reads the table @value{GDBN} automatically each time the inferior
14632 stops, so this command should only be necessary if you have changed the
14633 overlay mapping yourself using @value{GDBN}. This command is only
14634 useful when using automatic overlay debugging.
14636 @item overlay list-overlays
14637 @itemx overlay list
14638 @cindex listing mapped overlays
14639 Display a list of the overlays currently mapped, along with their mapped
14640 addresses, load addresses, and sizes.
14644 Normally, when @value{GDBN} prints a code address, it includes the name
14645 of the function the address falls in:
14648 (@value{GDBP}) print main
14649 $3 = @{int ()@} 0x11a0 <main>
14652 When overlay debugging is enabled, @value{GDBN} recognizes code in
14653 unmapped overlays, and prints the names of unmapped functions with
14654 asterisks around them. For example, if @code{foo} is a function in an
14655 unmapped overlay, @value{GDBN} prints it this way:
14658 (@value{GDBP}) overlay list
14659 No sections are mapped.
14660 (@value{GDBP}) print foo
14661 $5 = @{int (int)@} 0x100000 <*foo*>
14664 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14668 (@value{GDBP}) overlay list
14669 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14670 mapped at 0x1016 - 0x104a
14671 (@value{GDBP}) print foo
14672 $6 = @{int (int)@} 0x1016 <foo>
14675 When overlay debugging is enabled, @value{GDBN} can find the correct
14676 address for functions and variables in an overlay, whether or not the
14677 overlay is mapped. This allows most @value{GDBN} commands, like
14678 @code{break} and @code{disassemble}, to work normally, even on unmapped
14679 code. However, @value{GDBN}'s breakpoint support has some limitations:
14683 @cindex breakpoints in overlays
14684 @cindex overlays, setting breakpoints in
14685 You can set breakpoints in functions in unmapped overlays, as long as
14686 @value{GDBN} can write to the overlay at its load address.
14688 @value{GDBN} can not set hardware or simulator-based breakpoints in
14689 unmapped overlays. However, if you set a breakpoint at the end of your
14690 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14691 you are using manual overlay management), @value{GDBN} will re-set its
14692 breakpoints properly.
14696 @node Automatic Overlay Debugging
14697 @section Automatic Overlay Debugging
14698 @cindex automatic overlay debugging
14700 @value{GDBN} can automatically track which overlays are mapped and which
14701 are not, given some simple co-operation from the overlay manager in the
14702 inferior. If you enable automatic overlay debugging with the
14703 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14704 looks in the inferior's memory for certain variables describing the
14705 current state of the overlays.
14707 Here are the variables your overlay manager must define to support
14708 @value{GDBN}'s automatic overlay debugging:
14712 @item @code{_ovly_table}:
14713 This variable must be an array of the following structures:
14718 /* The overlay's mapped address. */
14721 /* The size of the overlay, in bytes. */
14722 unsigned long size;
14724 /* The overlay's load address. */
14727 /* Non-zero if the overlay is currently mapped;
14729 unsigned long mapped;
14733 @item @code{_novlys}:
14734 This variable must be a four-byte signed integer, holding the total
14735 number of elements in @code{_ovly_table}.
14739 To decide whether a particular overlay is mapped or not, @value{GDBN}
14740 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14741 @code{lma} members equal the VMA and LMA of the overlay's section in the
14742 executable file. When @value{GDBN} finds a matching entry, it consults
14743 the entry's @code{mapped} member to determine whether the overlay is
14746 In addition, your overlay manager may define a function called
14747 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14748 will silently set a breakpoint there. If the overlay manager then
14749 calls this function whenever it has changed the overlay table, this
14750 will enable @value{GDBN} to accurately keep track of which overlays
14751 are in program memory, and update any breakpoints that may be set
14752 in overlays. This will allow breakpoints to work even if the
14753 overlays are kept in ROM or other non-writable memory while they
14754 are not being executed.
14756 @node Overlay Sample Program
14757 @section Overlay Sample Program
14758 @cindex overlay example program
14760 When linking a program which uses overlays, you must place the overlays
14761 at their load addresses, while relocating them to run at their mapped
14762 addresses. To do this, you must write a linker script (@pxref{Overlay
14763 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14764 since linker scripts are specific to a particular host system, target
14765 architecture, and target memory layout, this manual cannot provide
14766 portable sample code demonstrating @value{GDBN}'s overlay support.
14768 However, the @value{GDBN} source distribution does contain an overlaid
14769 program, with linker scripts for a few systems, as part of its test
14770 suite. The program consists of the following files from
14771 @file{gdb/testsuite/gdb.base}:
14775 The main program file.
14777 A simple overlay manager, used by @file{overlays.c}.
14782 Overlay modules, loaded and used by @file{overlays.c}.
14785 Linker scripts for linking the test program on the @code{d10v-elf}
14786 and @code{m32r-elf} targets.
14789 You can build the test program using the @code{d10v-elf} GCC
14790 cross-compiler like this:
14793 $ d10v-elf-gcc -g -c overlays.c
14794 $ d10v-elf-gcc -g -c ovlymgr.c
14795 $ d10v-elf-gcc -g -c foo.c
14796 $ d10v-elf-gcc -g -c bar.c
14797 $ d10v-elf-gcc -g -c baz.c
14798 $ d10v-elf-gcc -g -c grbx.c
14799 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14800 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14803 The build process is identical for any other architecture, except that
14804 you must substitute the appropriate compiler and linker script for the
14805 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14809 @chapter Using @value{GDBN} with Different Languages
14812 Although programming languages generally have common aspects, they are
14813 rarely expressed in the same manner. For instance, in ANSI C,
14814 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14815 Modula-2, it is accomplished by @code{p^}. Values can also be
14816 represented (and displayed) differently. Hex numbers in C appear as
14817 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14819 @cindex working language
14820 Language-specific information is built into @value{GDBN} for some languages,
14821 allowing you to express operations like the above in your program's
14822 native language, and allowing @value{GDBN} to output values in a manner
14823 consistent with the syntax of your program's native language. The
14824 language you use to build expressions is called the @dfn{working
14828 * Setting:: Switching between source languages
14829 * Show:: Displaying the language
14830 * Checks:: Type and range checks
14831 * Supported Languages:: Supported languages
14832 * Unsupported Languages:: Unsupported languages
14836 @section Switching Between Source Languages
14838 There are two ways to control the working language---either have @value{GDBN}
14839 set it automatically, or select it manually yourself. You can use the
14840 @code{set language} command for either purpose. On startup, @value{GDBN}
14841 defaults to setting the language automatically. The working language is
14842 used to determine how expressions you type are interpreted, how values
14845 In addition to the working language, every source file that
14846 @value{GDBN} knows about has its own working language. For some object
14847 file formats, the compiler might indicate which language a particular
14848 source file is in. However, most of the time @value{GDBN} infers the
14849 language from the name of the file. The language of a source file
14850 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14851 show each frame appropriately for its own language. There is no way to
14852 set the language of a source file from within @value{GDBN}, but you can
14853 set the language associated with a filename extension. @xref{Show, ,
14854 Displaying the Language}.
14856 This is most commonly a problem when you use a program, such
14857 as @code{cfront} or @code{f2c}, that generates C but is written in
14858 another language. In that case, make the
14859 program use @code{#line} directives in its C output; that way
14860 @value{GDBN} will know the correct language of the source code of the original
14861 program, and will display that source code, not the generated C code.
14864 * Filenames:: Filename extensions and languages.
14865 * Manually:: Setting the working language manually
14866 * Automatically:: Having @value{GDBN} infer the source language
14870 @subsection List of Filename Extensions and Languages
14872 If a source file name ends in one of the following extensions, then
14873 @value{GDBN} infers that its language is the one indicated.
14891 C@t{++} source file
14897 Objective-C source file
14901 Fortran source file
14904 Modula-2 source file
14908 Assembler source file. This actually behaves almost like C, but
14909 @value{GDBN} does not skip over function prologues when stepping.
14912 In addition, you may set the language associated with a filename
14913 extension. @xref{Show, , Displaying the Language}.
14916 @subsection Setting the Working Language
14918 If you allow @value{GDBN} to set the language automatically,
14919 expressions are interpreted the same way in your debugging session and
14922 @kindex set language
14923 If you wish, you may set the language manually. To do this, issue the
14924 command @samp{set language @var{lang}}, where @var{lang} is the name of
14925 a language, such as
14926 @code{c} or @code{modula-2}.
14927 For a list of the supported languages, type @samp{set language}.
14929 Setting the language manually prevents @value{GDBN} from updating the working
14930 language automatically. This can lead to confusion if you try
14931 to debug a program when the working language is not the same as the
14932 source language, when an expression is acceptable to both
14933 languages---but means different things. For instance, if the current
14934 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14942 might not have the effect you intended. In C, this means to add
14943 @code{b} and @code{c} and place the result in @code{a}. The result
14944 printed would be the value of @code{a}. In Modula-2, this means to compare
14945 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14947 @node Automatically
14948 @subsection Having @value{GDBN} Infer the Source Language
14950 To have @value{GDBN} set the working language automatically, use
14951 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14952 then infers the working language. That is, when your program stops in a
14953 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14954 working language to the language recorded for the function in that
14955 frame. If the language for a frame is unknown (that is, if the function
14956 or block corresponding to the frame was defined in a source file that
14957 does not have a recognized extension), the current working language is
14958 not changed, and @value{GDBN} issues a warning.
14960 This may not seem necessary for most programs, which are written
14961 entirely in one source language. However, program modules and libraries
14962 written in one source language can be used by a main program written in
14963 a different source language. Using @samp{set language auto} in this
14964 case frees you from having to set the working language manually.
14967 @section Displaying the Language
14969 The following commands help you find out which language is the
14970 working language, and also what language source files were written in.
14973 @item show language
14974 @anchor{show language}
14975 @kindex show language
14976 Display the current working language. This is the
14977 language you can use with commands such as @code{print} to
14978 build and compute expressions that may involve variables in your program.
14981 @kindex info frame@r{, show the source language}
14982 Display the source language for this frame. This language becomes the
14983 working language if you use an identifier from this frame.
14984 @xref{Frame Info, ,Information about a Frame}, to identify the other
14985 information listed here.
14988 @kindex info source@r{, show the source language}
14989 Display the source language of this source file.
14990 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14991 information listed here.
14994 In unusual circumstances, you may have source files with extensions
14995 not in the standard list. You can then set the extension associated
14996 with a language explicitly:
14999 @item set extension-language @var{ext} @var{language}
15000 @kindex set extension-language
15001 Tell @value{GDBN} that source files with extension @var{ext} are to be
15002 assumed as written in the source language @var{language}.
15004 @item info extensions
15005 @kindex info extensions
15006 List all the filename extensions and the associated languages.
15010 @section Type and Range Checking
15012 Some languages are designed to guard you against making seemingly common
15013 errors through a series of compile- and run-time checks. These include
15014 checking the type of arguments to functions and operators and making
15015 sure mathematical overflows are caught at run time. Checks such as
15016 these help to ensure a program's correctness once it has been compiled
15017 by eliminating type mismatches and providing active checks for range
15018 errors when your program is running.
15020 By default @value{GDBN} checks for these errors according to the
15021 rules of the current source language. Although @value{GDBN} does not check
15022 the statements in your program, it can check expressions entered directly
15023 into @value{GDBN} for evaluation via the @code{print} command, for example.
15026 * Type Checking:: An overview of type checking
15027 * Range Checking:: An overview of range checking
15030 @cindex type checking
15031 @cindex checks, type
15032 @node Type Checking
15033 @subsection An Overview of Type Checking
15035 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15036 arguments to operators and functions have to be of the correct type,
15037 otherwise an error occurs. These checks prevent type mismatch
15038 errors from ever causing any run-time problems. For example,
15041 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15043 (@value{GDBP}) print obj.my_method (0)
15046 (@value{GDBP}) print obj.my_method (0x1234)
15047 Cannot resolve method klass::my_method to any overloaded instance
15050 The second example fails because in C@t{++} the integer constant
15051 @samp{0x1234} is not type-compatible with the pointer parameter type.
15053 For the expressions you use in @value{GDBN} commands, you can tell
15054 @value{GDBN} to not enforce strict type checking or
15055 to treat any mismatches as errors and abandon the expression;
15056 When type checking is disabled, @value{GDBN} successfully evaluates
15057 expressions like the second example above.
15059 Even if type checking is off, there may be other reasons
15060 related to type that prevent @value{GDBN} from evaluating an expression.
15061 For instance, @value{GDBN} does not know how to add an @code{int} and
15062 a @code{struct foo}. These particular type errors have nothing to do
15063 with the language in use and usually arise from expressions which make
15064 little sense to evaluate anyway.
15066 @value{GDBN} provides some additional commands for controlling type checking:
15068 @kindex set check type
15069 @kindex show check type
15071 @item set check type on
15072 @itemx set check type off
15073 Set strict type checking on or off. If any type mismatches occur in
15074 evaluating an expression while type checking is on, @value{GDBN} prints a
15075 message and aborts evaluation of the expression.
15077 @item show check type
15078 Show the current setting of type checking and whether @value{GDBN}
15079 is enforcing strict type checking rules.
15082 @cindex range checking
15083 @cindex checks, range
15084 @node Range Checking
15085 @subsection An Overview of Range Checking
15087 In some languages (such as Modula-2), it is an error to exceed the
15088 bounds of a type; this is enforced with run-time checks. Such range
15089 checking is meant to ensure program correctness by making sure
15090 computations do not overflow, or indices on an array element access do
15091 not exceed the bounds of the array.
15093 For expressions you use in @value{GDBN} commands, you can tell
15094 @value{GDBN} to treat range errors in one of three ways: ignore them,
15095 always treat them as errors and abandon the expression, or issue
15096 warnings but evaluate the expression anyway.
15098 A range error can result from numerical overflow, from exceeding an
15099 array index bound, or when you type a constant that is not a member
15100 of any type. Some languages, however, do not treat overflows as an
15101 error. In many implementations of C, mathematical overflow causes the
15102 result to ``wrap around'' to lower values---for example, if @var{m} is
15103 the largest integer value, and @var{s} is the smallest, then
15106 @var{m} + 1 @result{} @var{s}
15109 This, too, is specific to individual languages, and in some cases
15110 specific to individual compilers or machines. @xref{Supported Languages, ,
15111 Supported Languages}, for further details on specific languages.
15113 @value{GDBN} provides some additional commands for controlling the range checker:
15115 @kindex set check range
15116 @kindex show check range
15118 @item set check range auto
15119 Set range checking on or off based on the current working language.
15120 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15123 @item set check range on
15124 @itemx set check range off
15125 Set range checking on or off, overriding the default setting for the
15126 current working language. A warning is issued if the setting does not
15127 match the language default. If a range error occurs and range checking is on,
15128 then a message is printed and evaluation of the expression is aborted.
15130 @item set check range warn
15131 Output messages when the @value{GDBN} range checker detects a range error,
15132 but attempt to evaluate the expression anyway. Evaluating the
15133 expression may still be impossible for other reasons, such as accessing
15134 memory that the process does not own (a typical example from many Unix
15138 Show the current setting of the range checker, and whether or not it is
15139 being set automatically by @value{GDBN}.
15142 @node Supported Languages
15143 @section Supported Languages
15145 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15146 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15147 @c This is false ...
15148 Some @value{GDBN} features may be used in expressions regardless of the
15149 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15150 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15151 ,Expressions}) can be used with the constructs of any supported
15154 The following sections detail to what degree each source language is
15155 supported by @value{GDBN}. These sections are not meant to be language
15156 tutorials or references, but serve only as a reference guide to what the
15157 @value{GDBN} expression parser accepts, and what input and output
15158 formats should look like for different languages. There are many good
15159 books written on each of these languages; please look to these for a
15160 language reference or tutorial.
15163 * C:: C and C@t{++}
15166 * Objective-C:: Objective-C
15167 * OpenCL C:: OpenCL C
15168 * Fortran:: Fortran
15171 * Modula-2:: Modula-2
15176 @subsection C and C@t{++}
15178 @cindex C and C@t{++}
15179 @cindex expressions in C or C@t{++}
15181 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15182 to both languages. Whenever this is the case, we discuss those languages
15186 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15187 @cindex @sc{gnu} C@t{++}
15188 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15189 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15190 effectively, you must compile your C@t{++} programs with a supported
15191 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15192 compiler (@code{aCC}).
15195 * C Operators:: C and C@t{++} operators
15196 * C Constants:: C and C@t{++} constants
15197 * C Plus Plus Expressions:: C@t{++} expressions
15198 * C Defaults:: Default settings for C and C@t{++}
15199 * C Checks:: C and C@t{++} type and range checks
15200 * Debugging C:: @value{GDBN} and C
15201 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15202 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15206 @subsubsection C and C@t{++} Operators
15208 @cindex C and C@t{++} operators
15210 Operators must be defined on values of specific types. For instance,
15211 @code{+} is defined on numbers, but not on structures. Operators are
15212 often defined on groups of types.
15214 For the purposes of C and C@t{++}, the following definitions hold:
15219 @emph{Integral types} include @code{int} with any of its storage-class
15220 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15223 @emph{Floating-point types} include @code{float}, @code{double}, and
15224 @code{long double} (if supported by the target platform).
15227 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15230 @emph{Scalar types} include all of the above.
15235 The following operators are supported. They are listed here
15236 in order of increasing precedence:
15240 The comma or sequencing operator. Expressions in a comma-separated list
15241 are evaluated from left to right, with the result of the entire
15242 expression being the last expression evaluated.
15245 Assignment. The value of an assignment expression is the value
15246 assigned. Defined on scalar types.
15249 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15250 and translated to @w{@code{@var{a} = @var{a op b}}}.
15251 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15252 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15253 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15256 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15257 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15258 should be of an integral type.
15261 Logical @sc{or}. Defined on integral types.
15264 Logical @sc{and}. Defined on integral types.
15267 Bitwise @sc{or}. Defined on integral types.
15270 Bitwise exclusive-@sc{or}. Defined on integral types.
15273 Bitwise @sc{and}. Defined on integral types.
15276 Equality and inequality. Defined on scalar types. The value of these
15277 expressions is 0 for false and non-zero for true.
15279 @item <@r{, }>@r{, }<=@r{, }>=
15280 Less than, greater than, less than or equal, greater than or equal.
15281 Defined on scalar types. The value of these expressions is 0 for false
15282 and non-zero for true.
15285 left shift, and right shift. Defined on integral types.
15288 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15291 Addition and subtraction. Defined on integral types, floating-point types and
15294 @item *@r{, }/@r{, }%
15295 Multiplication, division, and modulus. Multiplication and division are
15296 defined on integral and floating-point types. Modulus is defined on
15300 Increment and decrement. When appearing before a variable, the
15301 operation is performed before the variable is used in an expression;
15302 when appearing after it, the variable's value is used before the
15303 operation takes place.
15306 Pointer dereferencing. Defined on pointer types. Same precedence as
15310 Address operator. Defined on variables. Same precedence as @code{++}.
15312 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15313 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15314 to examine the address
15315 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15319 Negative. Defined on integral and floating-point types. Same
15320 precedence as @code{++}.
15323 Logical negation. Defined on integral types. Same precedence as
15327 Bitwise complement operator. Defined on integral types. Same precedence as
15332 Structure member, and pointer-to-structure member. For convenience,
15333 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15334 pointer based on the stored type information.
15335 Defined on @code{struct} and @code{union} data.
15338 Dereferences of pointers to members.
15341 Array indexing. @code{@var{a}[@var{i}]} is defined as
15342 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15345 Function parameter list. Same precedence as @code{->}.
15348 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15349 and @code{class} types.
15352 Doubled colons also represent the @value{GDBN} scope operator
15353 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15357 If an operator is redefined in the user code, @value{GDBN} usually
15358 attempts to invoke the redefined version instead of using the operator's
15359 predefined meaning.
15362 @subsubsection C and C@t{++} Constants
15364 @cindex C and C@t{++} constants
15366 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15371 Integer constants are a sequence of digits. Octal constants are
15372 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15373 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15374 @samp{l}, specifying that the constant should be treated as a
15378 Floating point constants are a sequence of digits, followed by a decimal
15379 point, followed by a sequence of digits, and optionally followed by an
15380 exponent. An exponent is of the form:
15381 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15382 sequence of digits. The @samp{+} is optional for positive exponents.
15383 A floating-point constant may also end with a letter @samp{f} or
15384 @samp{F}, specifying that the constant should be treated as being of
15385 the @code{float} (as opposed to the default @code{double}) type; or with
15386 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15390 Enumerated constants consist of enumerated identifiers, or their
15391 integral equivalents.
15394 Character constants are a single character surrounded by single quotes
15395 (@code{'}), or a number---the ordinal value of the corresponding character
15396 (usually its @sc{ascii} value). Within quotes, the single character may
15397 be represented by a letter or by @dfn{escape sequences}, which are of
15398 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15399 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15400 @samp{@var{x}} is a predefined special character---for example,
15401 @samp{\n} for newline.
15403 Wide character constants can be written by prefixing a character
15404 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15405 form of @samp{x}. The target wide character set is used when
15406 computing the value of this constant (@pxref{Character Sets}).
15409 String constants are a sequence of character constants surrounded by
15410 double quotes (@code{"}). Any valid character constant (as described
15411 above) may appear. Double quotes within the string must be preceded by
15412 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15415 Wide string constants can be written by prefixing a string constant
15416 with @samp{L}, as in C. The target wide character set is used when
15417 computing the value of this constant (@pxref{Character Sets}).
15420 Pointer constants are an integral value. You can also write pointers
15421 to constants using the C operator @samp{&}.
15424 Array constants are comma-separated lists surrounded by braces @samp{@{}
15425 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15426 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15427 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15430 @node C Plus Plus Expressions
15431 @subsubsection C@t{++} Expressions
15433 @cindex expressions in C@t{++}
15434 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15436 @cindex debugging C@t{++} programs
15437 @cindex C@t{++} compilers
15438 @cindex debug formats and C@t{++}
15439 @cindex @value{NGCC} and C@t{++}
15441 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15442 the proper compiler and the proper debug format. Currently,
15443 @value{GDBN} works best when debugging C@t{++} code that is compiled
15444 with the most recent version of @value{NGCC} possible. The DWARF
15445 debugging format is preferred; @value{NGCC} defaults to this on most
15446 popular platforms. Other compilers and/or debug formats are likely to
15447 work badly or not at all when using @value{GDBN} to debug C@t{++}
15448 code. @xref{Compilation}.
15453 @cindex member functions
15455 Member function calls are allowed; you can use expressions like
15458 count = aml->GetOriginal(x, y)
15461 @vindex this@r{, inside C@t{++} member functions}
15462 @cindex namespace in C@t{++}
15464 While a member function is active (in the selected stack frame), your
15465 expressions have the same namespace available as the member function;
15466 that is, @value{GDBN} allows implicit references to the class instance
15467 pointer @code{this} following the same rules as C@t{++}. @code{using}
15468 declarations in the current scope are also respected by @value{GDBN}.
15470 @cindex call overloaded functions
15471 @cindex overloaded functions, calling
15472 @cindex type conversions in C@t{++}
15474 You can call overloaded functions; @value{GDBN} resolves the function
15475 call to the right definition, with some restrictions. @value{GDBN} does not
15476 perform overload resolution involving user-defined type conversions,
15477 calls to constructors, or instantiations of templates that do not exist
15478 in the program. It also cannot handle ellipsis argument lists or
15481 It does perform integral conversions and promotions, floating-point
15482 promotions, arithmetic conversions, pointer conversions, conversions of
15483 class objects to base classes, and standard conversions such as those of
15484 functions or arrays to pointers; it requires an exact match on the
15485 number of function arguments.
15487 Overload resolution is always performed, unless you have specified
15488 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15489 ,@value{GDBN} Features for C@t{++}}.
15491 You must specify @code{set overload-resolution off} in order to use an
15492 explicit function signature to call an overloaded function, as in
15494 p 'foo(char,int)'('x', 13)
15497 The @value{GDBN} command-completion facility can simplify this;
15498 see @ref{Completion, ,Command Completion}.
15500 @cindex reference declarations
15502 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15503 references; you can use them in expressions just as you do in C@t{++}
15504 source---they are automatically dereferenced.
15506 In the parameter list shown when @value{GDBN} displays a frame, the values of
15507 reference variables are not displayed (unlike other variables); this
15508 avoids clutter, since references are often used for large structures.
15509 The @emph{address} of a reference variable is always shown, unless
15510 you have specified @samp{set print address off}.
15513 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15514 expressions can use it just as expressions in your program do. Since
15515 one scope may be defined in another, you can use @code{::} repeatedly if
15516 necessary, for example in an expression like
15517 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15518 resolving name scope by reference to source files, in both C and C@t{++}
15519 debugging (@pxref{Variables, ,Program Variables}).
15522 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15527 @subsubsection C and C@t{++} Defaults
15529 @cindex C and C@t{++} defaults
15531 If you allow @value{GDBN} to set range checking automatically, it
15532 defaults to @code{off} whenever the working language changes to
15533 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15534 selects the working language.
15536 If you allow @value{GDBN} to set the language automatically, it
15537 recognizes source files whose names end with @file{.c}, @file{.C}, or
15538 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15539 these files, it sets the working language to C or C@t{++}.
15540 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15541 for further details.
15544 @subsubsection C and C@t{++} Type and Range Checks
15546 @cindex C and C@t{++} checks
15548 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15549 checking is used. However, if you turn type checking off, @value{GDBN}
15550 will allow certain non-standard conversions, such as promoting integer
15551 constants to pointers.
15553 Range checking, if turned on, is done on mathematical operations. Array
15554 indices are not checked, since they are often used to index a pointer
15555 that is not itself an array.
15558 @subsubsection @value{GDBN} and C
15560 The @code{set print union} and @code{show print union} commands apply to
15561 the @code{union} type. When set to @samp{on}, any @code{union} that is
15562 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15563 appears as @samp{@{...@}}.
15565 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15566 with pointers and a memory allocation function. @xref{Expressions,
15569 @node Debugging C Plus Plus
15570 @subsubsection @value{GDBN} Features for C@t{++}
15572 @cindex commands for C@t{++}
15574 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15575 designed specifically for use with C@t{++}. Here is a summary:
15578 @cindex break in overloaded functions
15579 @item @r{breakpoint menus}
15580 When you want a breakpoint in a function whose name is overloaded,
15581 @value{GDBN} has the capability to display a menu of possible breakpoint
15582 locations to help you specify which function definition you want.
15583 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15585 @cindex overloading in C@t{++}
15586 @item rbreak @var{regex}
15587 Setting breakpoints using regular expressions is helpful for setting
15588 breakpoints on overloaded functions that are not members of any special
15590 @xref{Set Breaks, ,Setting Breakpoints}.
15592 @cindex C@t{++} exception handling
15594 @itemx catch rethrow
15596 Debug C@t{++} exception handling using these commands. @xref{Set
15597 Catchpoints, , Setting Catchpoints}.
15599 @cindex inheritance
15600 @item ptype @var{typename}
15601 Print inheritance relationships as well as other information for type
15603 @xref{Symbols, ,Examining the Symbol Table}.
15605 @item info vtbl @var{expression}.
15606 The @code{info vtbl} command can be used to display the virtual
15607 method tables of the object computed by @var{expression}. This shows
15608 one entry per virtual table; there may be multiple virtual tables when
15609 multiple inheritance is in use.
15611 @cindex C@t{++} demangling
15612 @item demangle @var{name}
15613 Demangle @var{name}.
15614 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15616 @cindex C@t{++} symbol display
15617 @item set print demangle
15618 @itemx show print demangle
15619 @itemx set print asm-demangle
15620 @itemx show print asm-demangle
15621 Control whether C@t{++} symbols display in their source form, both when
15622 displaying code as C@t{++} source and when displaying disassemblies.
15623 @xref{Print Settings, ,Print Settings}.
15625 @item set print object
15626 @itemx show print object
15627 Choose whether to print derived (actual) or declared types of objects.
15628 @xref{Print Settings, ,Print Settings}.
15630 @item set print vtbl
15631 @itemx show print vtbl
15632 Control the format for printing virtual function tables.
15633 @xref{Print Settings, ,Print Settings}.
15634 (The @code{vtbl} commands do not work on programs compiled with the HP
15635 ANSI C@t{++} compiler (@code{aCC}).)
15637 @kindex set overload-resolution
15638 @cindex overloaded functions, overload resolution
15639 @item set overload-resolution on
15640 Enable overload resolution for C@t{++} expression evaluation. The default
15641 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15642 and searches for a function whose signature matches the argument types,
15643 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15644 Expressions, ,C@t{++} Expressions}, for details).
15645 If it cannot find a match, it emits a message.
15647 @item set overload-resolution off
15648 Disable overload resolution for C@t{++} expression evaluation. For
15649 overloaded functions that are not class member functions, @value{GDBN}
15650 chooses the first function of the specified name that it finds in the
15651 symbol table, whether or not its arguments are of the correct type. For
15652 overloaded functions that are class member functions, @value{GDBN}
15653 searches for a function whose signature @emph{exactly} matches the
15656 @kindex show overload-resolution
15657 @item show overload-resolution
15658 Show the current setting of overload resolution.
15660 @item @r{Overloaded symbol names}
15661 You can specify a particular definition of an overloaded symbol, using
15662 the same notation that is used to declare such symbols in C@t{++}: type
15663 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15664 also use the @value{GDBN} command-line word completion facilities to list the
15665 available choices, or to finish the type list for you.
15666 @xref{Completion,, Command Completion}, for details on how to do this.
15668 @item @r{Breakpoints in functions with ABI tags}
15670 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15671 correspond to changes in the ABI of a type, function, or variable that
15672 would not otherwise be reflected in a mangled name. See
15673 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15676 The ABI tags are visible in C@t{++} demangled names. For example, a
15677 function that returns a std::string:
15680 std::string function(int);
15684 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15685 tag, and @value{GDBN} displays the symbol like this:
15688 function[abi:cxx11](int)
15691 You can set a breakpoint on such functions simply as if they had no
15695 (gdb) b function(int)
15696 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15697 (gdb) info breakpoints
15698 Num Type Disp Enb Address What
15699 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15703 On the rare occasion you need to disambiguate between different ABI
15704 tags, you can do so by simply including the ABI tag in the function
15708 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15712 @node Decimal Floating Point
15713 @subsubsection Decimal Floating Point format
15714 @cindex decimal floating point format
15716 @value{GDBN} can examine, set and perform computations with numbers in
15717 decimal floating point format, which in the C language correspond to the
15718 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15719 specified by the extension to support decimal floating-point arithmetic.
15721 There are two encodings in use, depending on the architecture: BID (Binary
15722 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15723 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15726 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15727 to manipulate decimal floating point numbers, it is not possible to convert
15728 (using a cast, for example) integers wider than 32-bit to decimal float.
15730 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15731 point computations, error checking in decimal float operations ignores
15732 underflow, overflow and divide by zero exceptions.
15734 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15735 to inspect @code{_Decimal128} values stored in floating point registers.
15736 See @ref{PowerPC,,PowerPC} for more details.
15742 @value{GDBN} can be used to debug programs written in D and compiled with
15743 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15744 specific feature --- dynamic arrays.
15749 @cindex Go (programming language)
15750 @value{GDBN} can be used to debug programs written in Go and compiled with
15751 @file{gccgo} or @file{6g} compilers.
15753 Here is a summary of the Go-specific features and restrictions:
15756 @cindex current Go package
15757 @item The current Go package
15758 The name of the current package does not need to be specified when
15759 specifying global variables and functions.
15761 For example, given the program:
15765 var myglob = "Shall we?"
15771 When stopped inside @code{main} either of these work:
15775 (gdb) p main.myglob
15778 @cindex builtin Go types
15779 @item Builtin Go types
15780 The @code{string} type is recognized by @value{GDBN} and is printed
15783 @cindex builtin Go functions
15784 @item Builtin Go functions
15785 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15786 function and handles it internally.
15788 @cindex restrictions on Go expressions
15789 @item Restrictions on Go expressions
15790 All Go operators are supported except @code{&^}.
15791 The Go @code{_} ``blank identifier'' is not supported.
15792 Automatic dereferencing of pointers is not supported.
15796 @subsection Objective-C
15798 @cindex Objective-C
15799 This section provides information about some commands and command
15800 options that are useful for debugging Objective-C code. See also
15801 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15802 few more commands specific to Objective-C support.
15805 * Method Names in Commands::
15806 * The Print Command with Objective-C::
15809 @node Method Names in Commands
15810 @subsubsection Method Names in Commands
15812 The following commands have been extended to accept Objective-C method
15813 names as line specifications:
15815 @kindex clear@r{, and Objective-C}
15816 @kindex break@r{, and Objective-C}
15817 @kindex info line@r{, and Objective-C}
15818 @kindex jump@r{, and Objective-C}
15819 @kindex list@r{, and Objective-C}
15823 @item @code{info line}
15828 A fully qualified Objective-C method name is specified as
15831 -[@var{Class} @var{methodName}]
15834 where the minus sign is used to indicate an instance method and a
15835 plus sign (not shown) is used to indicate a class method. The class
15836 name @var{Class} and method name @var{methodName} are enclosed in
15837 brackets, similar to the way messages are specified in Objective-C
15838 source code. For example, to set a breakpoint at the @code{create}
15839 instance method of class @code{Fruit} in the program currently being
15843 break -[Fruit create]
15846 To list ten program lines around the @code{initialize} class method,
15850 list +[NSText initialize]
15853 In the current version of @value{GDBN}, the plus or minus sign is
15854 required. In future versions of @value{GDBN}, the plus or minus
15855 sign will be optional, but you can use it to narrow the search. It
15856 is also possible to specify just a method name:
15862 You must specify the complete method name, including any colons. If
15863 your program's source files contain more than one @code{create} method,
15864 you'll be presented with a numbered list of classes that implement that
15865 method. Indicate your choice by number, or type @samp{0} to exit if
15868 As another example, to clear a breakpoint established at the
15869 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15872 clear -[NSWindow makeKeyAndOrderFront:]
15875 @node The Print Command with Objective-C
15876 @subsubsection The Print Command With Objective-C
15877 @cindex Objective-C, print objects
15878 @kindex print-object
15879 @kindex po @r{(@code{print-object})}
15881 The print command has also been extended to accept methods. For example:
15884 print -[@var{object} hash]
15887 @cindex print an Objective-C object description
15888 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15890 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15891 and print the result. Also, an additional command has been added,
15892 @code{print-object} or @code{po} for short, which is meant to print
15893 the description of an object. However, this command may only work
15894 with certain Objective-C libraries that have a particular hook
15895 function, @code{_NSPrintForDebugger}, defined.
15898 @subsection OpenCL C
15901 This section provides information about @value{GDBN}s OpenCL C support.
15904 * OpenCL C Datatypes::
15905 * OpenCL C Expressions::
15906 * OpenCL C Operators::
15909 @node OpenCL C Datatypes
15910 @subsubsection OpenCL C Datatypes
15912 @cindex OpenCL C Datatypes
15913 @value{GDBN} supports the builtin scalar and vector datatypes specified
15914 by OpenCL 1.1. In addition the half- and double-precision floating point
15915 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15916 extensions are also known to @value{GDBN}.
15918 @node OpenCL C Expressions
15919 @subsubsection OpenCL C Expressions
15921 @cindex OpenCL C Expressions
15922 @value{GDBN} supports accesses to vector components including the access as
15923 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15924 supported by @value{GDBN} can be used as well.
15926 @node OpenCL C Operators
15927 @subsubsection OpenCL C Operators
15929 @cindex OpenCL C Operators
15930 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15934 @subsection Fortran
15935 @cindex Fortran-specific support in @value{GDBN}
15937 @value{GDBN} can be used to debug programs written in Fortran, but it
15938 currently supports only the features of Fortran 77 language.
15940 @cindex trailing underscore, in Fortran symbols
15941 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15942 among them) append an underscore to the names of variables and
15943 functions. When you debug programs compiled by those compilers, you
15944 will need to refer to variables and functions with a trailing
15948 * Fortran Operators:: Fortran operators and expressions
15949 * Fortran Defaults:: Default settings for Fortran
15950 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15953 @node Fortran Operators
15954 @subsubsection Fortran Operators and Expressions
15956 @cindex Fortran operators and expressions
15958 Operators must be defined on values of specific types. For instance,
15959 @code{+} is defined on numbers, but not on characters or other non-
15960 arithmetic types. Operators are often defined on groups of types.
15964 The exponentiation operator. It raises the first operand to the power
15968 The range operator. Normally used in the form of array(low:high) to
15969 represent a section of array.
15972 The access component operator. Normally used to access elements in derived
15973 types. Also suitable for unions. As unions aren't part of regular Fortran,
15974 this can only happen when accessing a register that uses a gdbarch-defined
15978 @node Fortran Defaults
15979 @subsubsection Fortran Defaults
15981 @cindex Fortran Defaults
15983 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15984 default uses case-insensitive matches for Fortran symbols. You can
15985 change that with the @samp{set case-insensitive} command, see
15986 @ref{Symbols}, for the details.
15988 @node Special Fortran Commands
15989 @subsubsection Special Fortran Commands
15991 @cindex Special Fortran commands
15993 @value{GDBN} has some commands to support Fortran-specific features,
15994 such as displaying common blocks.
15997 @cindex @code{COMMON} blocks, Fortran
15998 @kindex info common
15999 @item info common @r{[}@var{common-name}@r{]}
16000 This command prints the values contained in the Fortran @code{COMMON}
16001 block whose name is @var{common-name}. With no argument, the names of
16002 all @code{COMMON} blocks visible at the current program location are
16009 @cindex Pascal support in @value{GDBN}, limitations
16010 Debugging Pascal programs which use sets, subranges, file variables, or
16011 nested functions does not currently work. @value{GDBN} does not support
16012 entering expressions, printing values, or similar features using Pascal
16015 The Pascal-specific command @code{set print pascal_static-members}
16016 controls whether static members of Pascal objects are displayed.
16017 @xref{Print Settings, pascal_static-members}.
16022 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16023 Programming Language}. Type- and value-printing, and expression
16024 parsing, are reasonably complete. However, there are a few
16025 peculiarities and holes to be aware of.
16029 Linespecs (@pxref{Specify Location}) are never relative to the current
16030 crate. Instead, they act as if there were a global namespace of
16031 crates, somewhat similar to the way @code{extern crate} behaves.
16033 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16034 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16035 to set a breakpoint in a function named @samp{f} in a crate named
16038 As a consequence of this approach, linespecs also cannot refer to
16039 items using @samp{self::} or @samp{super::}.
16042 Because @value{GDBN} implements Rust name-lookup semantics in
16043 expressions, it will sometimes prepend the current crate to a name.
16044 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16045 @samp{K}, then @code{print ::x::y} will try to find the symbol
16048 However, since it is useful to be able to refer to other crates when
16049 debugging, @value{GDBN} provides the @code{extern} extension to
16050 circumvent this. To use the extension, just put @code{extern} before
16051 a path expression to refer to the otherwise unavailable ``global''
16054 In the above example, if you wanted to refer to the symbol @samp{y} in
16055 the crate @samp{x}, you would use @code{print extern x::y}.
16058 The Rust expression evaluator does not support ``statement-like''
16059 expressions such as @code{if} or @code{match}, or lambda expressions.
16062 Tuple expressions are not implemented.
16065 The Rust expression evaluator does not currently implement the
16066 @code{Drop} trait. Objects that may be created by the evaluator will
16067 never be destroyed.
16070 @value{GDBN} does not implement type inference for generics. In order
16071 to call generic functions or otherwise refer to generic items, you
16072 will have to specify the type parameters manually.
16075 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16076 cases this does not cause any problems. However, in an expression
16077 context, completing a generic function name will give syntactically
16078 invalid results. This happens because Rust requires the @samp{::}
16079 operator between the function name and its generic arguments. For
16080 example, @value{GDBN} might provide a completion like
16081 @code{crate::f<u32>}, where the parser would require
16082 @code{crate::f::<u32>}.
16085 As of this writing, the Rust compiler (version 1.8) has a few holes in
16086 the debugging information it generates. These holes prevent certain
16087 features from being implemented by @value{GDBN}:
16091 Method calls cannot be made via traits.
16094 Operator overloading is not implemented.
16097 When debugging in a monomorphized function, you cannot use the generic
16101 The type @code{Self} is not available.
16104 @code{use} statements are not available, so some names may not be
16105 available in the crate.
16110 @subsection Modula-2
16112 @cindex Modula-2, @value{GDBN} support
16114 The extensions made to @value{GDBN} to support Modula-2 only support
16115 output from the @sc{gnu} Modula-2 compiler (which is currently being
16116 developed). Other Modula-2 compilers are not currently supported, and
16117 attempting to debug executables produced by them is most likely
16118 to give an error as @value{GDBN} reads in the executable's symbol
16121 @cindex expressions in Modula-2
16123 * M2 Operators:: Built-in operators
16124 * Built-In Func/Proc:: Built-in functions and procedures
16125 * M2 Constants:: Modula-2 constants
16126 * M2 Types:: Modula-2 types
16127 * M2 Defaults:: Default settings for Modula-2
16128 * Deviations:: Deviations from standard Modula-2
16129 * M2 Checks:: Modula-2 type and range checks
16130 * M2 Scope:: The scope operators @code{::} and @code{.}
16131 * GDB/M2:: @value{GDBN} and Modula-2
16135 @subsubsection Operators
16136 @cindex Modula-2 operators
16138 Operators must be defined on values of specific types. For instance,
16139 @code{+} is defined on numbers, but not on structures. Operators are
16140 often defined on groups of types. For the purposes of Modula-2, the
16141 following definitions hold:
16146 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16150 @emph{Character types} consist of @code{CHAR} and its subranges.
16153 @emph{Floating-point types} consist of @code{REAL}.
16156 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16160 @emph{Scalar types} consist of all of the above.
16163 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16166 @emph{Boolean types} consist of @code{BOOLEAN}.
16170 The following operators are supported, and appear in order of
16171 increasing precedence:
16175 Function argument or array index separator.
16178 Assignment. The value of @var{var} @code{:=} @var{value} is
16182 Less than, greater than on integral, floating-point, or enumerated
16186 Less than or equal to, greater than or equal to
16187 on integral, floating-point and enumerated types, or set inclusion on
16188 set types. Same precedence as @code{<}.
16190 @item =@r{, }<>@r{, }#
16191 Equality and two ways of expressing inequality, valid on scalar types.
16192 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16193 available for inequality, since @code{#} conflicts with the script
16197 Set membership. Defined on set types and the types of their members.
16198 Same precedence as @code{<}.
16201 Boolean disjunction. Defined on boolean types.
16204 Boolean conjunction. Defined on boolean types.
16207 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16210 Addition and subtraction on integral and floating-point types, or union
16211 and difference on set types.
16214 Multiplication on integral and floating-point types, or set intersection
16218 Division on floating-point types, or symmetric set difference on set
16219 types. Same precedence as @code{*}.
16222 Integer division and remainder. Defined on integral types. Same
16223 precedence as @code{*}.
16226 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16229 Pointer dereferencing. Defined on pointer types.
16232 Boolean negation. Defined on boolean types. Same precedence as
16236 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16237 precedence as @code{^}.
16240 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16243 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16247 @value{GDBN} and Modula-2 scope operators.
16251 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16252 treats the use of the operator @code{IN}, or the use of operators
16253 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16254 @code{<=}, and @code{>=} on sets as an error.
16258 @node Built-In Func/Proc
16259 @subsubsection Built-in Functions and Procedures
16260 @cindex Modula-2 built-ins
16262 Modula-2 also makes available several built-in procedures and functions.
16263 In describing these, the following metavariables are used:
16268 represents an @code{ARRAY} variable.
16271 represents a @code{CHAR} constant or variable.
16274 represents a variable or constant of integral type.
16277 represents an identifier that belongs to a set. Generally used in the
16278 same function with the metavariable @var{s}. The type of @var{s} should
16279 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16282 represents a variable or constant of integral or floating-point type.
16285 represents a variable or constant of floating-point type.
16291 represents a variable.
16294 represents a variable or constant of one of many types. See the
16295 explanation of the function for details.
16298 All Modula-2 built-in procedures also return a result, described below.
16302 Returns the absolute value of @var{n}.
16305 If @var{c} is a lower case letter, it returns its upper case
16306 equivalent, otherwise it returns its argument.
16309 Returns the character whose ordinal value is @var{i}.
16312 Decrements the value in the variable @var{v} by one. Returns the new value.
16314 @item DEC(@var{v},@var{i})
16315 Decrements the value in the variable @var{v} by @var{i}. Returns the
16318 @item EXCL(@var{m},@var{s})
16319 Removes the element @var{m} from the set @var{s}. Returns the new
16322 @item FLOAT(@var{i})
16323 Returns the floating point equivalent of the integer @var{i}.
16325 @item HIGH(@var{a})
16326 Returns the index of the last member of @var{a}.
16329 Increments the value in the variable @var{v} by one. Returns the new value.
16331 @item INC(@var{v},@var{i})
16332 Increments the value in the variable @var{v} by @var{i}. Returns the
16335 @item INCL(@var{m},@var{s})
16336 Adds the element @var{m} to the set @var{s} if it is not already
16337 there. Returns the new set.
16340 Returns the maximum value of the type @var{t}.
16343 Returns the minimum value of the type @var{t}.
16346 Returns boolean TRUE if @var{i} is an odd number.
16349 Returns the ordinal value of its argument. For example, the ordinal
16350 value of a character is its @sc{ascii} value (on machines supporting
16351 the @sc{ascii} character set). The argument @var{x} must be of an
16352 ordered type, which include integral, character and enumerated types.
16354 @item SIZE(@var{x})
16355 Returns the size of its argument. The argument @var{x} can be a
16356 variable or a type.
16358 @item TRUNC(@var{r})
16359 Returns the integral part of @var{r}.
16361 @item TSIZE(@var{x})
16362 Returns the size of its argument. The argument @var{x} can be a
16363 variable or a type.
16365 @item VAL(@var{t},@var{i})
16366 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16370 @emph{Warning:} Sets and their operations are not yet supported, so
16371 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16375 @cindex Modula-2 constants
16377 @subsubsection Constants
16379 @value{GDBN} allows you to express the constants of Modula-2 in the following
16385 Integer constants are simply a sequence of digits. When used in an
16386 expression, a constant is interpreted to be type-compatible with the
16387 rest of the expression. Hexadecimal integers are specified by a
16388 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16391 Floating point constants appear as a sequence of digits, followed by a
16392 decimal point and another sequence of digits. An optional exponent can
16393 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16394 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16395 digits of the floating point constant must be valid decimal (base 10)
16399 Character constants consist of a single character enclosed by a pair of
16400 like quotes, either single (@code{'}) or double (@code{"}). They may
16401 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16402 followed by a @samp{C}.
16405 String constants consist of a sequence of characters enclosed by a
16406 pair of like quotes, either single (@code{'}) or double (@code{"}).
16407 Escape sequences in the style of C are also allowed. @xref{C
16408 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16412 Enumerated constants consist of an enumerated identifier.
16415 Boolean constants consist of the identifiers @code{TRUE} and
16419 Pointer constants consist of integral values only.
16422 Set constants are not yet supported.
16426 @subsubsection Modula-2 Types
16427 @cindex Modula-2 types
16429 Currently @value{GDBN} can print the following data types in Modula-2
16430 syntax: array types, record types, set types, pointer types, procedure
16431 types, enumerated types, subrange types and base types. You can also
16432 print the contents of variables declared using these type.
16433 This section gives a number of simple source code examples together with
16434 sample @value{GDBN} sessions.
16436 The first example contains the following section of code:
16445 and you can request @value{GDBN} to interrogate the type and value of
16446 @code{r} and @code{s}.
16449 (@value{GDBP}) print s
16451 (@value{GDBP}) ptype s
16453 (@value{GDBP}) print r
16455 (@value{GDBP}) ptype r
16460 Likewise if your source code declares @code{s} as:
16464 s: SET ['A'..'Z'] ;
16468 then you may query the type of @code{s} by:
16471 (@value{GDBP}) ptype s
16472 type = SET ['A'..'Z']
16476 Note that at present you cannot interactively manipulate set
16477 expressions using the debugger.
16479 The following example shows how you might declare an array in Modula-2
16480 and how you can interact with @value{GDBN} to print its type and contents:
16484 s: ARRAY [-10..10] OF CHAR ;
16488 (@value{GDBP}) ptype s
16489 ARRAY [-10..10] OF CHAR
16492 Note that the array handling is not yet complete and although the type
16493 is printed correctly, expression handling still assumes that all
16494 arrays have a lower bound of zero and not @code{-10} as in the example
16497 Here are some more type related Modula-2 examples:
16501 colour = (blue, red, yellow, green) ;
16502 t = [blue..yellow] ;
16510 The @value{GDBN} interaction shows how you can query the data type
16511 and value of a variable.
16514 (@value{GDBP}) print s
16516 (@value{GDBP}) ptype t
16517 type = [blue..yellow]
16521 In this example a Modula-2 array is declared and its contents
16522 displayed. Observe that the contents are written in the same way as
16523 their @code{C} counterparts.
16527 s: ARRAY [1..5] OF CARDINAL ;
16533 (@value{GDBP}) print s
16534 $1 = @{1, 0, 0, 0, 0@}
16535 (@value{GDBP}) ptype s
16536 type = ARRAY [1..5] OF CARDINAL
16539 The Modula-2 language interface to @value{GDBN} also understands
16540 pointer types as shown in this example:
16544 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16551 and you can request that @value{GDBN} describes the type of @code{s}.
16554 (@value{GDBP}) ptype s
16555 type = POINTER TO ARRAY [1..5] OF CARDINAL
16558 @value{GDBN} handles compound types as we can see in this example.
16559 Here we combine array types, record types, pointer types and subrange
16570 myarray = ARRAY myrange OF CARDINAL ;
16571 myrange = [-2..2] ;
16573 s: POINTER TO ARRAY myrange OF foo ;
16577 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16581 (@value{GDBP}) ptype s
16582 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16585 f3 : ARRAY [-2..2] OF CARDINAL;
16590 @subsubsection Modula-2 Defaults
16591 @cindex Modula-2 defaults
16593 If type and range checking are set automatically by @value{GDBN}, they
16594 both default to @code{on} whenever the working language changes to
16595 Modula-2. This happens regardless of whether you or @value{GDBN}
16596 selected the working language.
16598 If you allow @value{GDBN} to set the language automatically, then entering
16599 code compiled from a file whose name ends with @file{.mod} sets the
16600 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16601 Infer the Source Language}, for further details.
16604 @subsubsection Deviations from Standard Modula-2
16605 @cindex Modula-2, deviations from
16607 A few changes have been made to make Modula-2 programs easier to debug.
16608 This is done primarily via loosening its type strictness:
16612 Unlike in standard Modula-2, pointer constants can be formed by
16613 integers. This allows you to modify pointer variables during
16614 debugging. (In standard Modula-2, the actual address contained in a
16615 pointer variable is hidden from you; it can only be modified
16616 through direct assignment to another pointer variable or expression that
16617 returned a pointer.)
16620 C escape sequences can be used in strings and characters to represent
16621 non-printable characters. @value{GDBN} prints out strings with these
16622 escape sequences embedded. Single non-printable characters are
16623 printed using the @samp{CHR(@var{nnn})} format.
16626 The assignment operator (@code{:=}) returns the value of its right-hand
16630 All built-in procedures both modify @emph{and} return their argument.
16634 @subsubsection Modula-2 Type and Range Checks
16635 @cindex Modula-2 checks
16638 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16641 @c FIXME remove warning when type/range checks added
16643 @value{GDBN} considers two Modula-2 variables type equivalent if:
16647 They are of types that have been declared equivalent via a @code{TYPE
16648 @var{t1} = @var{t2}} statement
16651 They have been declared on the same line. (Note: This is true of the
16652 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16655 As long as type checking is enabled, any attempt to combine variables
16656 whose types are not equivalent is an error.
16658 Range checking is done on all mathematical operations, assignment, array
16659 index bounds, and all built-in functions and procedures.
16662 @subsubsection The Scope Operators @code{::} and @code{.}
16664 @cindex @code{.}, Modula-2 scope operator
16665 @cindex colon, doubled as scope operator
16667 @vindex colon-colon@r{, in Modula-2}
16668 @c Info cannot handle :: but TeX can.
16671 @vindex ::@r{, in Modula-2}
16674 There are a few subtle differences between the Modula-2 scope operator
16675 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16680 @var{module} . @var{id}
16681 @var{scope} :: @var{id}
16685 where @var{scope} is the name of a module or a procedure,
16686 @var{module} the name of a module, and @var{id} is any declared
16687 identifier within your program, except another module.
16689 Using the @code{::} operator makes @value{GDBN} search the scope
16690 specified by @var{scope} for the identifier @var{id}. If it is not
16691 found in the specified scope, then @value{GDBN} searches all scopes
16692 enclosing the one specified by @var{scope}.
16694 Using the @code{.} operator makes @value{GDBN} search the current scope for
16695 the identifier specified by @var{id} that was imported from the
16696 definition module specified by @var{module}. With this operator, it is
16697 an error if the identifier @var{id} was not imported from definition
16698 module @var{module}, or if @var{id} is not an identifier in
16702 @subsubsection @value{GDBN} and Modula-2
16704 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16705 Five subcommands of @code{set print} and @code{show print} apply
16706 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16707 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16708 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16709 analogue in Modula-2.
16711 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16712 with any language, is not useful with Modula-2. Its
16713 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16714 created in Modula-2 as they can in C or C@t{++}. However, because an
16715 address can be specified by an integral constant, the construct
16716 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16718 @cindex @code{#} in Modula-2
16719 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16720 interpreted as the beginning of a comment. Use @code{<>} instead.
16726 The extensions made to @value{GDBN} for Ada only support
16727 output from the @sc{gnu} Ada (GNAT) compiler.
16728 Other Ada compilers are not currently supported, and
16729 attempting to debug executables produced by them is most likely
16733 @cindex expressions in Ada
16735 * Ada Mode Intro:: General remarks on the Ada syntax
16736 and semantics supported by Ada mode
16738 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16739 * Additions to Ada:: Extensions of the Ada expression syntax.
16740 * Overloading support for Ada:: Support for expressions involving overloaded
16742 * Stopping Before Main Program:: Debugging the program during elaboration.
16743 * Ada Exceptions:: Ada Exceptions
16744 * Ada Tasks:: Listing and setting breakpoints in tasks.
16745 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16746 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16748 * Ada Settings:: New settable GDB parameters for Ada.
16749 * Ada Glitches:: Known peculiarities of Ada mode.
16752 @node Ada Mode Intro
16753 @subsubsection Introduction
16754 @cindex Ada mode, general
16756 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16757 syntax, with some extensions.
16758 The philosophy behind the design of this subset is
16762 That @value{GDBN} should provide basic literals and access to operations for
16763 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16764 leaving more sophisticated computations to subprograms written into the
16765 program (which therefore may be called from @value{GDBN}).
16768 That type safety and strict adherence to Ada language restrictions
16769 are not particularly important to the @value{GDBN} user.
16772 That brevity is important to the @value{GDBN} user.
16775 Thus, for brevity, the debugger acts as if all names declared in
16776 user-written packages are directly visible, even if they are not visible
16777 according to Ada rules, thus making it unnecessary to fully qualify most
16778 names with their packages, regardless of context. Where this causes
16779 ambiguity, @value{GDBN} asks the user's intent.
16781 The debugger will start in Ada mode if it detects an Ada main program.
16782 As for other languages, it will enter Ada mode when stopped in a program that
16783 was translated from an Ada source file.
16785 While in Ada mode, you may use `@t{--}' for comments. This is useful
16786 mostly for documenting command files. The standard @value{GDBN} comment
16787 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16788 middle (to allow based literals).
16790 @node Omissions from Ada
16791 @subsubsection Omissions from Ada
16792 @cindex Ada, omissions from
16794 Here are the notable omissions from the subset:
16798 Only a subset of the attributes are supported:
16802 @t{'First}, @t{'Last}, and @t{'Length}
16803 on array objects (not on types and subtypes).
16806 @t{'Min} and @t{'Max}.
16809 @t{'Pos} and @t{'Val}.
16815 @t{'Range} on array objects (not subtypes), but only as the right
16816 operand of the membership (@code{in}) operator.
16819 @t{'Access}, @t{'Unchecked_Access}, and
16820 @t{'Unrestricted_Access} (a GNAT extension).
16828 @code{Characters.Latin_1} are not available and
16829 concatenation is not implemented. Thus, escape characters in strings are
16830 not currently available.
16833 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16834 equality of representations. They will generally work correctly
16835 for strings and arrays whose elements have integer or enumeration types.
16836 They may not work correctly for arrays whose element
16837 types have user-defined equality, for arrays of real values
16838 (in particular, IEEE-conformant floating point, because of negative
16839 zeroes and NaNs), and for arrays whose elements contain unused bits with
16840 indeterminate values.
16843 The other component-by-component array operations (@code{and}, @code{or},
16844 @code{xor}, @code{not}, and relational tests other than equality)
16845 are not implemented.
16848 @cindex array aggregates (Ada)
16849 @cindex record aggregates (Ada)
16850 @cindex aggregates (Ada)
16851 There is limited support for array and record aggregates. They are
16852 permitted only on the right sides of assignments, as in these examples:
16855 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16856 (@value{GDBP}) set An_Array := (1, others => 0)
16857 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16858 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16859 (@value{GDBP}) set A_Record := (1, "Peter", True);
16860 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16864 discriminant's value by assigning an aggregate has an
16865 undefined effect if that discriminant is used within the record.
16866 However, you can first modify discriminants by directly assigning to
16867 them (which normally would not be allowed in Ada), and then performing an
16868 aggregate assignment. For example, given a variable @code{A_Rec}
16869 declared to have a type such as:
16872 type Rec (Len : Small_Integer := 0) is record
16874 Vals : IntArray (1 .. Len);
16878 you can assign a value with a different size of @code{Vals} with two
16882 (@value{GDBP}) set A_Rec.Len := 4
16883 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16886 As this example also illustrates, @value{GDBN} is very loose about the usual
16887 rules concerning aggregates. You may leave out some of the
16888 components of an array or record aggregate (such as the @code{Len}
16889 component in the assignment to @code{A_Rec} above); they will retain their
16890 original values upon assignment. You may freely use dynamic values as
16891 indices in component associations. You may even use overlapping or
16892 redundant component associations, although which component values are
16893 assigned in such cases is not defined.
16896 Calls to dispatching subprograms are not implemented.
16899 The overloading algorithm is much more limited (i.e., less selective)
16900 than that of real Ada. It makes only limited use of the context in
16901 which a subexpression appears to resolve its meaning, and it is much
16902 looser in its rules for allowing type matches. As a result, some
16903 function calls will be ambiguous, and the user will be asked to choose
16904 the proper resolution.
16907 The @code{new} operator is not implemented.
16910 Entry calls are not implemented.
16913 Aside from printing, arithmetic operations on the native VAX floating-point
16914 formats are not supported.
16917 It is not possible to slice a packed array.
16920 The names @code{True} and @code{False}, when not part of a qualified name,
16921 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16923 Should your program
16924 redefine these names in a package or procedure (at best a dubious practice),
16925 you will have to use fully qualified names to access their new definitions.
16928 @node Additions to Ada
16929 @subsubsection Additions to Ada
16930 @cindex Ada, deviations from
16932 As it does for other languages, @value{GDBN} makes certain generic
16933 extensions to Ada (@pxref{Expressions}):
16937 If the expression @var{E} is a variable residing in memory (typically
16938 a local variable or array element) and @var{N} is a positive integer,
16939 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16940 @var{N}-1 adjacent variables following it in memory as an array. In
16941 Ada, this operator is generally not necessary, since its prime use is
16942 in displaying parts of an array, and slicing will usually do this in
16943 Ada. However, there are occasional uses when debugging programs in
16944 which certain debugging information has been optimized away.
16947 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16948 appears in function or file @var{B}.'' When @var{B} is a file name,
16949 you must typically surround it in single quotes.
16952 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16953 @var{type} that appears at address @var{addr}.''
16956 A name starting with @samp{$} is a convenience variable
16957 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16960 In addition, @value{GDBN} provides a few other shortcuts and outright
16961 additions specific to Ada:
16965 The assignment statement is allowed as an expression, returning
16966 its right-hand operand as its value. Thus, you may enter
16969 (@value{GDBP}) set x := y + 3
16970 (@value{GDBP}) print A(tmp := y + 1)
16974 The semicolon is allowed as an ``operator,'' returning as its value
16975 the value of its right-hand operand.
16976 This allows, for example,
16977 complex conditional breaks:
16980 (@value{GDBP}) break f
16981 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16985 Rather than use catenation and symbolic character names to introduce special
16986 characters into strings, one may instead use a special bracket notation,
16987 which is also used to print strings. A sequence of characters of the form
16988 @samp{["@var{XX}"]} within a string or character literal denotes the
16989 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16990 sequence of characters @samp{["""]} also denotes a single quotation mark
16991 in strings. For example,
16993 "One line.["0a"]Next line.["0a"]"
16996 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17000 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17001 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17005 (@value{GDBP}) print 'max(x, y)
17009 When printing arrays, @value{GDBN} uses positional notation when the
17010 array has a lower bound of 1, and uses a modified named notation otherwise.
17011 For example, a one-dimensional array of three integers with a lower bound
17012 of 3 might print as
17019 That is, in contrast to valid Ada, only the first component has a @code{=>}
17023 You may abbreviate attributes in expressions with any unique,
17024 multi-character subsequence of
17025 their names (an exact match gets preference).
17026 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17027 in place of @t{a'length}.
17030 @cindex quoting Ada internal identifiers
17031 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17032 to lower case. The GNAT compiler uses upper-case characters for
17033 some of its internal identifiers, which are normally of no interest to users.
17034 For the rare occasions when you actually have to look at them,
17035 enclose them in angle brackets to avoid the lower-case mapping.
17038 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17042 Printing an object of class-wide type or dereferencing an
17043 access-to-class-wide value will display all the components of the object's
17044 specific type (as indicated by its run-time tag). Likewise, component
17045 selection on such a value will operate on the specific type of the
17050 @node Overloading support for Ada
17051 @subsubsection Overloading support for Ada
17052 @cindex overloading, Ada
17054 The debugger supports limited overloading. Given a subprogram call in which
17055 the function symbol has multiple definitions, it will use the number of
17056 actual parameters and some information about their types to attempt to narrow
17057 the set of definitions. It also makes very limited use of context, preferring
17058 procedures to functions in the context of the @code{call} command, and
17059 functions to procedures elsewhere.
17061 If, after narrowing, the set of matching definitions still contains more than
17062 one definition, @value{GDBN} will display a menu to query which one it should
17066 (@value{GDBP}) print f(1)
17067 Multiple matches for f
17069 [1] foo.f (integer) return boolean at foo.adb:23
17070 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17074 In this case, just select one menu entry either to cancel expression evaluation
17075 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17076 instance (type the corresponding number and press @key{RET}).
17078 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17083 @kindex set ada print-signatures
17084 @item set ada print-signatures
17085 Control whether parameter types and return types are displayed in overloads
17086 selection menus. It is @code{on} by default.
17087 @xref{Overloading support for Ada}.
17089 @kindex show ada print-signatures
17090 @item show ada print-signatures
17091 Show the current setting for displaying parameter types and return types in
17092 overloads selection menu.
17093 @xref{Overloading support for Ada}.
17097 @node Stopping Before Main Program
17098 @subsubsection Stopping at the Very Beginning
17100 @cindex breakpointing Ada elaboration code
17101 It is sometimes necessary to debug the program during elaboration, and
17102 before reaching the main procedure.
17103 As defined in the Ada Reference
17104 Manual, the elaboration code is invoked from a procedure called
17105 @code{adainit}. To run your program up to the beginning of
17106 elaboration, simply use the following two commands:
17107 @code{tbreak adainit} and @code{run}.
17109 @node Ada Exceptions
17110 @subsubsection Ada Exceptions
17112 A command is provided to list all Ada exceptions:
17115 @kindex info exceptions
17116 @item info exceptions
17117 @itemx info exceptions @var{regexp}
17118 The @code{info exceptions} command allows you to list all Ada exceptions
17119 defined within the program being debugged, as well as their addresses.
17120 With a regular expression, @var{regexp}, as argument, only those exceptions
17121 whose names match @var{regexp} are listed.
17124 Below is a small example, showing how the command can be used, first
17125 without argument, and next with a regular expression passed as an
17129 (@value{GDBP}) info exceptions
17130 All defined Ada exceptions:
17131 constraint_error: 0x613da0
17132 program_error: 0x613d20
17133 storage_error: 0x613ce0
17134 tasking_error: 0x613ca0
17135 const.aint_global_e: 0x613b00
17136 (@value{GDBP}) info exceptions const.aint
17137 All Ada exceptions matching regular expression "const.aint":
17138 constraint_error: 0x613da0
17139 const.aint_global_e: 0x613b00
17142 It is also possible to ask @value{GDBN} to stop your program's execution
17143 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17146 @subsubsection Extensions for Ada Tasks
17147 @cindex Ada, tasking
17149 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17150 @value{GDBN} provides the following task-related commands:
17155 This command shows a list of current Ada tasks, as in the following example:
17162 (@value{GDBP}) info tasks
17163 ID TID P-ID Pri State Name
17164 1 8088000 0 15 Child Activation Wait main_task
17165 2 80a4000 1 15 Accept Statement b
17166 3 809a800 1 15 Child Activation Wait a
17167 * 4 80ae800 3 15 Runnable c
17172 In this listing, the asterisk before the last task indicates it to be the
17173 task currently being inspected.
17177 Represents @value{GDBN}'s internal task number.
17183 The parent's task ID (@value{GDBN}'s internal task number).
17186 The base priority of the task.
17189 Current state of the task.
17193 The task has been created but has not been activated. It cannot be
17197 The task is not blocked for any reason known to Ada. (It may be waiting
17198 for a mutex, though.) It is conceptually "executing" in normal mode.
17201 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17202 that were waiting on terminate alternatives have been awakened and have
17203 terminated themselves.
17205 @item Child Activation Wait
17206 The task is waiting for created tasks to complete activation.
17208 @item Accept Statement
17209 The task is waiting on an accept or selective wait statement.
17211 @item Waiting on entry call
17212 The task is waiting on an entry call.
17214 @item Async Select Wait
17215 The task is waiting to start the abortable part of an asynchronous
17219 The task is waiting on a select statement with only a delay
17222 @item Child Termination Wait
17223 The task is sleeping having completed a master within itself, and is
17224 waiting for the tasks dependent on that master to become terminated or
17225 waiting on a terminate Phase.
17227 @item Wait Child in Term Alt
17228 The task is sleeping waiting for tasks on terminate alternatives to
17229 finish terminating.
17231 @item Accepting RV with @var{taskno}
17232 The task is accepting a rendez-vous with the task @var{taskno}.
17236 Name of the task in the program.
17240 @kindex info task @var{taskno}
17241 @item info task @var{taskno}
17242 This command shows detailled informations on the specified task, as in
17243 the following example:
17248 (@value{GDBP}) info tasks
17249 ID TID P-ID Pri State Name
17250 1 8077880 0 15 Child Activation Wait main_task
17251 * 2 807c468 1 15 Runnable task_1
17252 (@value{GDBP}) info task 2
17253 Ada Task: 0x807c468
17257 Parent: 1 (main_task)
17263 @kindex task@r{ (Ada)}
17264 @cindex current Ada task ID
17265 This command prints the ID of the current task.
17271 (@value{GDBP}) info tasks
17272 ID TID P-ID Pri State Name
17273 1 8077870 0 15 Child Activation Wait main_task
17274 * 2 807c458 1 15 Runnable t
17275 (@value{GDBP}) task
17276 [Current task is 2]
17279 @item task @var{taskno}
17280 @cindex Ada task switching
17281 This command is like the @code{thread @var{thread-id}}
17282 command (@pxref{Threads}). It switches the context of debugging
17283 from the current task to the given task.
17289 (@value{GDBP}) info tasks
17290 ID TID P-ID Pri State Name
17291 1 8077870 0 15 Child Activation Wait main_task
17292 * 2 807c458 1 15 Runnable t
17293 (@value{GDBP}) task 1
17294 [Switching to task 1]
17295 #0 0x8067726 in pthread_cond_wait ()
17297 #0 0x8067726 in pthread_cond_wait ()
17298 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17299 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17300 #3 0x806153e in system.tasking.stages.activate_tasks ()
17301 #4 0x804aacc in un () at un.adb:5
17304 @item break @var{location} task @var{taskno}
17305 @itemx break @var{location} task @var{taskno} if @dots{}
17306 @cindex breakpoints and tasks, in Ada
17307 @cindex task breakpoints, in Ada
17308 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17309 These commands are like the @code{break @dots{} thread @dots{}}
17310 command (@pxref{Thread Stops}). The
17311 @var{location} argument specifies source lines, as described
17312 in @ref{Specify Location}.
17314 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17315 to specify that you only want @value{GDBN} to stop the program when a
17316 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17317 numeric task identifiers assigned by @value{GDBN}, shown in the first
17318 column of the @samp{info tasks} display.
17320 If you do not specify @samp{task @var{taskno}} when you set a
17321 breakpoint, the breakpoint applies to @emph{all} tasks of your
17324 You can use the @code{task} qualifier on conditional breakpoints as
17325 well; in this case, place @samp{task @var{taskno}} before the
17326 breakpoint condition (before the @code{if}).
17334 (@value{GDBP}) info tasks
17335 ID TID P-ID Pri State Name
17336 1 140022020 0 15 Child Activation Wait main_task
17337 2 140045060 1 15 Accept/Select Wait t2
17338 3 140044840 1 15 Runnable t1
17339 * 4 140056040 1 15 Runnable t3
17340 (@value{GDBP}) b 15 task 2
17341 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17342 (@value{GDBP}) cont
17347 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17349 (@value{GDBP}) info tasks
17350 ID TID P-ID Pri State Name
17351 1 140022020 0 15 Child Activation Wait main_task
17352 * 2 140045060 1 15 Runnable t2
17353 3 140044840 1 15 Runnable t1
17354 4 140056040 1 15 Delay Sleep t3
17358 @node Ada Tasks and Core Files
17359 @subsubsection Tasking Support when Debugging Core Files
17360 @cindex Ada tasking and core file debugging
17362 When inspecting a core file, as opposed to debugging a live program,
17363 tasking support may be limited or even unavailable, depending on
17364 the platform being used.
17365 For instance, on x86-linux, the list of tasks is available, but task
17366 switching is not supported.
17368 On certain platforms, the debugger needs to perform some
17369 memory writes in order to provide Ada tasking support. When inspecting
17370 a core file, this means that the core file must be opened with read-write
17371 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17372 Under these circumstances, you should make a backup copy of the core
17373 file before inspecting it with @value{GDBN}.
17375 @node Ravenscar Profile
17376 @subsubsection Tasking Support when using the Ravenscar Profile
17377 @cindex Ravenscar Profile
17379 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17380 specifically designed for systems with safety-critical real-time
17384 @kindex set ravenscar task-switching on
17385 @cindex task switching with program using Ravenscar Profile
17386 @item set ravenscar task-switching on
17387 Allows task switching when debugging a program that uses the Ravenscar
17388 Profile. This is the default.
17390 @kindex set ravenscar task-switching off
17391 @item set ravenscar task-switching off
17392 Turn off task switching when debugging a program that uses the Ravenscar
17393 Profile. This is mostly intended to disable the code that adds support
17394 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17395 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17396 To be effective, this command should be run before the program is started.
17398 @kindex show ravenscar task-switching
17399 @item show ravenscar task-switching
17400 Show whether it is possible to switch from task to task in a program
17401 using the Ravenscar Profile.
17406 @subsubsection Ada Settings
17407 @cindex Ada settings
17410 @kindex set varsize-limit
17411 @item set varsize-limit @var{size}
17412 Prevent @value{GDBN} from attempting to evaluate objects whose size
17413 is above the given limit (@var{size}) when those sizes are computed
17414 from run-time quantities. This is typically the case when the object
17415 has a variable size, such as an array whose bounds are not known at
17416 compile time for example. Setting @var{size} to @code{unlimited}
17417 removes the size limitation. By default, the limit is about 65KB.
17419 The purpose of having such a limit is to prevent @value{GDBN} from
17420 trying to grab enormous chunks of virtual memory when asked to evaluate
17421 a quantity whose bounds have been corrupted or have not yet been fully
17422 initialized. The limit applies to the results of some subexpressions
17423 as well as to complete expressions. For example, an expression denoting
17424 a simple integer component, such as @code{x.y.z}, may fail if the size of
17425 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17426 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17427 @code{A} is an array variable with non-constant size, will generally
17428 succeed regardless of the bounds on @code{A}, as long as the component
17429 size is less than @var{size}.
17431 @kindex show varsize-limit
17432 @item show varsize-limit
17433 Show the limit on types whose size is determined by run-time quantities.
17437 @subsubsection Known Peculiarities of Ada Mode
17438 @cindex Ada, problems
17440 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17441 we know of several problems with and limitations of Ada mode in
17443 some of which will be fixed with planned future releases of the debugger
17444 and the GNU Ada compiler.
17448 Static constants that the compiler chooses not to materialize as objects in
17449 storage are invisible to the debugger.
17452 Named parameter associations in function argument lists are ignored (the
17453 argument lists are treated as positional).
17456 Many useful library packages are currently invisible to the debugger.
17459 Fixed-point arithmetic, conversions, input, and output is carried out using
17460 floating-point arithmetic, and may give results that only approximate those on
17464 The GNAT compiler never generates the prefix @code{Standard} for any of
17465 the standard symbols defined by the Ada language. @value{GDBN} knows about
17466 this: it will strip the prefix from names when you use it, and will never
17467 look for a name you have so qualified among local symbols, nor match against
17468 symbols in other packages or subprograms. If you have
17469 defined entities anywhere in your program other than parameters and
17470 local variables whose simple names match names in @code{Standard},
17471 GNAT's lack of qualification here can cause confusion. When this happens,
17472 you can usually resolve the confusion
17473 by qualifying the problematic names with package
17474 @code{Standard} explicitly.
17477 Older versions of the compiler sometimes generate erroneous debugging
17478 information, resulting in the debugger incorrectly printing the value
17479 of affected entities. In some cases, the debugger is able to work
17480 around an issue automatically. In other cases, the debugger is able
17481 to work around the issue, but the work-around has to be specifically
17484 @kindex set ada trust-PAD-over-XVS
17485 @kindex show ada trust-PAD-over-XVS
17488 @item set ada trust-PAD-over-XVS on
17489 Configure GDB to strictly follow the GNAT encoding when computing the
17490 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17491 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17492 a complete description of the encoding used by the GNAT compiler).
17493 This is the default.
17495 @item set ada trust-PAD-over-XVS off
17496 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17497 sometimes prints the wrong value for certain entities, changing @code{ada
17498 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17499 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17500 @code{off}, but this incurs a slight performance penalty, so it is
17501 recommended to leave this setting to @code{on} unless necessary.
17505 @cindex GNAT descriptive types
17506 @cindex GNAT encoding
17507 Internally, the debugger also relies on the compiler following a number
17508 of conventions known as the @samp{GNAT Encoding}, all documented in
17509 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17510 how the debugging information should be generated for certain types.
17511 In particular, this convention makes use of @dfn{descriptive types},
17512 which are artificial types generated purely to help the debugger.
17514 These encodings were defined at a time when the debugging information
17515 format used was not powerful enough to describe some of the more complex
17516 types available in Ada. Since DWARF allows us to express nearly all
17517 Ada features, the long-term goal is to slowly replace these descriptive
17518 types by their pure DWARF equivalent. To facilitate that transition,
17519 a new maintenance option is available to force the debugger to ignore
17520 those descriptive types. It allows the user to quickly evaluate how
17521 well @value{GDBN} works without them.
17525 @kindex maint ada set ignore-descriptive-types
17526 @item maintenance ada set ignore-descriptive-types [on|off]
17527 Control whether the debugger should ignore descriptive types.
17528 The default is not to ignore descriptives types (@code{off}).
17530 @kindex maint ada show ignore-descriptive-types
17531 @item maintenance ada show ignore-descriptive-types
17532 Show if descriptive types are ignored by @value{GDBN}.
17536 @node Unsupported Languages
17537 @section Unsupported Languages
17539 @cindex unsupported languages
17540 @cindex minimal language
17541 In addition to the other fully-supported programming languages,
17542 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17543 It does not represent a real programming language, but provides a set
17544 of capabilities close to what the C or assembly languages provide.
17545 This should allow most simple operations to be performed while debugging
17546 an application that uses a language currently not supported by @value{GDBN}.
17548 If the language is set to @code{auto}, @value{GDBN} will automatically
17549 select this language if the current frame corresponds to an unsupported
17553 @chapter Examining the Symbol Table
17555 The commands described in this chapter allow you to inquire about the
17556 symbols (names of variables, functions and types) defined in your
17557 program. This information is inherent in the text of your program and
17558 does not change as your program executes. @value{GDBN} finds it in your
17559 program's symbol table, in the file indicated when you started @value{GDBN}
17560 (@pxref{File Options, ,Choosing Files}), or by one of the
17561 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17563 @cindex symbol names
17564 @cindex names of symbols
17565 @cindex quoting names
17566 @anchor{quoting names}
17567 Occasionally, you may need to refer to symbols that contain unusual
17568 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17569 most frequent case is in referring to static variables in other
17570 source files (@pxref{Variables,,Program Variables}). File names
17571 are recorded in object files as debugging symbols, but @value{GDBN} would
17572 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17573 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17574 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17581 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17584 @cindex case-insensitive symbol names
17585 @cindex case sensitivity in symbol names
17586 @kindex set case-sensitive
17587 @item set case-sensitive on
17588 @itemx set case-sensitive off
17589 @itemx set case-sensitive auto
17590 Normally, when @value{GDBN} looks up symbols, it matches their names
17591 with case sensitivity determined by the current source language.
17592 Occasionally, you may wish to control that. The command @code{set
17593 case-sensitive} lets you do that by specifying @code{on} for
17594 case-sensitive matches or @code{off} for case-insensitive ones. If
17595 you specify @code{auto}, case sensitivity is reset to the default
17596 suitable for the source language. The default is case-sensitive
17597 matches for all languages except for Fortran, for which the default is
17598 case-insensitive matches.
17600 @kindex show case-sensitive
17601 @item show case-sensitive
17602 This command shows the current setting of case sensitivity for symbols
17605 @kindex set print type methods
17606 @item set print type methods
17607 @itemx set print type methods on
17608 @itemx set print type methods off
17609 Normally, when @value{GDBN} prints a class, it displays any methods
17610 declared in that class. You can control this behavior either by
17611 passing the appropriate flag to @code{ptype}, or using @command{set
17612 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17613 display the methods; this is the default. Specifying @code{off} will
17614 cause @value{GDBN} to omit the methods.
17616 @kindex show print type methods
17617 @item show print type methods
17618 This command shows the current setting of method display when printing
17621 @kindex set print type nested-type-limit
17622 @item set print type nested-type-limit @var{limit}
17623 @itemx set print type nested-type-limit unlimited
17624 Set the limit of displayed nested types that the type printer will
17625 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17626 nested definitions. By default, the type printer will not show any nested
17627 types defined in classes.
17629 @kindex show print type nested-type-limit
17630 @item show print type nested-type-limit
17631 This command shows the current display limit of nested types when
17634 @kindex set print type typedefs
17635 @item set print type typedefs
17636 @itemx set print type typedefs on
17637 @itemx set print type typedefs off
17639 Normally, when @value{GDBN} prints a class, it displays any typedefs
17640 defined in that class. You can control this behavior either by
17641 passing the appropriate flag to @code{ptype}, or using @command{set
17642 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17643 display the typedef definitions; this is the default. Specifying
17644 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17645 Note that this controls whether the typedef definition itself is
17646 printed, not whether typedef names are substituted when printing other
17649 @kindex show print type typedefs
17650 @item show print type typedefs
17651 This command shows the current setting of typedef display when
17654 @kindex info address
17655 @cindex address of a symbol
17656 @item info address @var{symbol}
17657 Describe where the data for @var{symbol} is stored. For a register
17658 variable, this says which register it is kept in. For a non-register
17659 local variable, this prints the stack-frame offset at which the variable
17662 Note the contrast with @samp{print &@var{symbol}}, which does not work
17663 at all for a register variable, and for a stack local variable prints
17664 the exact address of the current instantiation of the variable.
17666 @kindex info symbol
17667 @cindex symbol from address
17668 @cindex closest symbol and offset for an address
17669 @item info symbol @var{addr}
17670 Print the name of a symbol which is stored at the address @var{addr}.
17671 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17672 nearest symbol and an offset from it:
17675 (@value{GDBP}) info symbol 0x54320
17676 _initialize_vx + 396 in section .text
17680 This is the opposite of the @code{info address} command. You can use
17681 it to find out the name of a variable or a function given its address.
17683 For dynamically linked executables, the name of executable or shared
17684 library containing the symbol is also printed:
17687 (@value{GDBP}) info symbol 0x400225
17688 _start + 5 in section .text of /tmp/a.out
17689 (@value{GDBP}) info symbol 0x2aaaac2811cf
17690 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17695 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17696 Demangle @var{name}.
17697 If @var{language} is provided it is the name of the language to demangle
17698 @var{name} in. Otherwise @var{name} is demangled in the current language.
17700 The @samp{--} option specifies the end of options,
17701 and is useful when @var{name} begins with a dash.
17703 The parameter @code{demangle-style} specifies how to interpret the kind
17704 of mangling used. @xref{Print Settings}.
17707 @item whatis[/@var{flags}] [@var{arg}]
17708 Print the data type of @var{arg}, which can be either an expression
17709 or a name of a data type. With no argument, print the data type of
17710 @code{$}, the last value in the value history.
17712 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17713 is not actually evaluated, and any side-effecting operations (such as
17714 assignments or function calls) inside it do not take place.
17716 If @var{arg} is a variable or an expression, @code{whatis} prints its
17717 literal type as it is used in the source code. If the type was
17718 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17719 the data type underlying the @code{typedef}. If the type of the
17720 variable or the expression is a compound data type, such as
17721 @code{struct} or @code{class}, @code{whatis} never prints their
17722 fields or methods. It just prints the @code{struct}/@code{class}
17723 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17724 such a compound data type, use @code{ptype}.
17726 If @var{arg} is a type name that was defined using @code{typedef},
17727 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17728 Unrolling means that @code{whatis} will show the underlying type used
17729 in the @code{typedef} declaration of @var{arg}. However, if that
17730 underlying type is also a @code{typedef}, @code{whatis} will not
17733 For C code, the type names may also have the form @samp{class
17734 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17735 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17737 @var{flags} can be used to modify how the type is displayed.
17738 Available flags are:
17742 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17743 parameters and typedefs defined in a class when printing the class'
17744 members. The @code{/r} flag disables this.
17747 Do not print methods defined in the class.
17750 Print methods defined in the class. This is the default, but the flag
17751 exists in case you change the default with @command{set print type methods}.
17754 Do not print typedefs defined in the class. Note that this controls
17755 whether the typedef definition itself is printed, not whether typedef
17756 names are substituted when printing other types.
17759 Print typedefs defined in the class. This is the default, but the flag
17760 exists in case you change the default with @command{set print type typedefs}.
17763 Print the offsets and sizes of fields in a struct, similar to what the
17764 @command{pahole} tool does. This option implies the @code{/tm} flags.
17766 For example, given the following declarations:
17802 Issuing a @kbd{ptype /o struct tuv} command would print:
17805 (@value{GDBP}) ptype /o struct tuv
17806 /* offset | size */ type = struct tuv @{
17807 /* 0 | 4 */ int a1;
17808 /* XXX 4-byte hole */
17809 /* 8 | 8 */ char *a2;
17810 /* 16 | 4 */ int a3;
17812 /* total size (bytes): 24 */
17816 Notice the format of the first column of comments. There, you can
17817 find two parts separated by the @samp{|} character: the @emph{offset},
17818 which indicates where the field is located inside the struct, in
17819 bytes, and the @emph{size} of the field. Another interesting line is
17820 the marker of a @emph{hole} in the struct, indicating that it may be
17821 possible to pack the struct and make it use less space by reorganizing
17824 It is also possible to print offsets inside an union:
17827 (@value{GDBP}) ptype /o union qwe
17828 /* offset | size */ type = union qwe @{
17829 /* 24 */ struct tuv @{
17830 /* 0 | 4 */ int a1;
17831 /* XXX 4-byte hole */
17832 /* 8 | 8 */ char *a2;
17833 /* 16 | 4 */ int a3;
17835 /* total size (bytes): 24 */
17837 /* 40 */ struct xyz @{
17838 /* 0 | 4 */ int f1;
17839 /* 4 | 1 */ char f2;
17840 /* XXX 3-byte hole */
17841 /* 8 | 8 */ void *f3;
17842 /* 16 | 24 */ struct tuv @{
17843 /* 16 | 4 */ int a1;
17844 /* XXX 4-byte hole */
17845 /* 24 | 8 */ char *a2;
17846 /* 32 | 4 */ int a3;
17848 /* total size (bytes): 24 */
17851 /* total size (bytes): 40 */
17854 /* total size (bytes): 40 */
17858 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17859 same space (because we are dealing with an union), the offset is not
17860 printed for them. However, you can still examine the offset of each
17861 of these structures' fields.
17863 Another useful scenario is printing the offsets of a struct containing
17867 (@value{GDBP}) ptype /o struct tyu
17868 /* offset | size */ type = struct tyu @{
17869 /* 0:31 | 4 */ int a1 : 1;
17870 /* 0:28 | 4 */ int a2 : 3;
17871 /* 0: 5 | 4 */ int a3 : 23;
17872 /* 3: 3 | 1 */ signed char a4 : 2;
17873 /* XXX 3-bit hole */
17874 /* XXX 4-byte hole */
17875 /* 8 | 8 */ int64_t a5;
17876 /* 16: 0 | 4 */ int a6 : 5;
17877 /* 16: 5 | 8 */ int64_t a7 : 3;
17878 "/* XXX 7-byte padding */
17880 /* total size (bytes): 24 */
17884 Note how the offset information is now extended to also include the
17885 first bit of the bitfield.
17889 @item ptype[/@var{flags}] [@var{arg}]
17890 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17891 detailed description of the type, instead of just the name of the type.
17892 @xref{Expressions, ,Expressions}.
17894 Contrary to @code{whatis}, @code{ptype} always unrolls any
17895 @code{typedef}s in its argument declaration, whether the argument is
17896 a variable, expression, or a data type. This means that @code{ptype}
17897 of a variable or an expression will not print literally its type as
17898 present in the source code---use @code{whatis} for that. @code{typedef}s at
17899 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17900 fields, methods and inner @code{class typedef}s of @code{struct}s,
17901 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17903 For example, for this variable declaration:
17906 typedef double real_t;
17907 struct complex @{ real_t real; double imag; @};
17908 typedef struct complex complex_t;
17910 real_t *real_pointer_var;
17914 the two commands give this output:
17918 (@value{GDBP}) whatis var
17920 (@value{GDBP}) ptype var
17921 type = struct complex @{
17925 (@value{GDBP}) whatis complex_t
17926 type = struct complex
17927 (@value{GDBP}) whatis struct complex
17928 type = struct complex
17929 (@value{GDBP}) ptype struct complex
17930 type = struct complex @{
17934 (@value{GDBP}) whatis real_pointer_var
17936 (@value{GDBP}) ptype real_pointer_var
17942 As with @code{whatis}, using @code{ptype} without an argument refers to
17943 the type of @code{$}, the last value in the value history.
17945 @cindex incomplete type
17946 Sometimes, programs use opaque data types or incomplete specifications
17947 of complex data structure. If the debug information included in the
17948 program does not allow @value{GDBN} to display a full declaration of
17949 the data type, it will say @samp{<incomplete type>}. For example,
17950 given these declarations:
17954 struct foo *fooptr;
17958 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17961 (@value{GDBP}) ptype foo
17962 $1 = <incomplete type>
17966 ``Incomplete type'' is C terminology for data types that are not
17967 completely specified.
17969 @cindex unknown type
17970 Othertimes, information about a variable's type is completely absent
17971 from the debug information included in the program. This most often
17972 happens when the program or library where the variable is defined
17973 includes no debug information at all. @value{GDBN} knows the variable
17974 exists from inspecting the linker/loader symbol table (e.g., the ELF
17975 dynamic symbol table), but such symbols do not contain type
17976 information. Inspecting the type of a (global) variable for which
17977 @value{GDBN} has no type information shows:
17980 (@value{GDBP}) ptype var
17981 type = <data variable, no debug info>
17984 @xref{Variables, no debug info variables}, for how to print the values
17988 @item info types @var{regexp}
17990 Print a brief description of all types whose names match the regular
17991 expression @var{regexp} (or all types in your program, if you supply
17992 no argument). Each complete typename is matched as though it were a
17993 complete line; thus, @samp{i type value} gives information on all
17994 types in your program whose names include the string @code{value}, but
17995 @samp{i type ^value$} gives information only on types whose complete
17996 name is @code{value}.
17998 In programs using different languages, @value{GDBN} chooses the syntax
17999 to print the type description according to the
18000 @samp{set language} value: using @samp{set language auto}
18001 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18002 language of the type, other values mean to use
18003 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18005 This command differs from @code{ptype} in two ways: first, like
18006 @code{whatis}, it does not print a detailed description; second, it
18007 lists all source files and line numbers where a type is defined.
18009 @kindex info type-printers
18010 @item info type-printers
18011 Versions of @value{GDBN} that ship with Python scripting enabled may
18012 have ``type printers'' available. When using @command{ptype} or
18013 @command{whatis}, these printers are consulted when the name of a type
18014 is needed. @xref{Type Printing API}, for more information on writing
18017 @code{info type-printers} displays all the available type printers.
18019 @kindex enable type-printer
18020 @kindex disable type-printer
18021 @item enable type-printer @var{name}@dots{}
18022 @item disable type-printer @var{name}@dots{}
18023 These commands can be used to enable or disable type printers.
18026 @cindex local variables
18027 @item info scope @var{location}
18028 List all the variables local to a particular scope. This command
18029 accepts a @var{location} argument---a function name, a source line, or
18030 an address preceded by a @samp{*}, and prints all the variables local
18031 to the scope defined by that location. (@xref{Specify Location}, for
18032 details about supported forms of @var{location}.) For example:
18035 (@value{GDBP}) @b{info scope command_line_handler}
18036 Scope for command_line_handler:
18037 Symbol rl is an argument at stack/frame offset 8, length 4.
18038 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18039 Symbol linelength is in static storage at address 0x150a1c, length 4.
18040 Symbol p is a local variable in register $esi, length 4.
18041 Symbol p1 is a local variable in register $ebx, length 4.
18042 Symbol nline is a local variable in register $edx, length 4.
18043 Symbol repeat is a local variable at frame offset -8, length 4.
18047 This command is especially useful for determining what data to collect
18048 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18051 @kindex info source
18053 Show information about the current source file---that is, the source file for
18054 the function containing the current point of execution:
18057 the name of the source file, and the directory containing it,
18059 the directory it was compiled in,
18061 its length, in lines,
18063 which programming language it is written in,
18065 if the debug information provides it, the program that compiled the file
18066 (which may include, e.g., the compiler version and command line arguments),
18068 whether the executable includes debugging information for that file, and
18069 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18071 whether the debugging information includes information about
18072 preprocessor macros.
18076 @kindex info sources
18078 Print the names of all source files in your program for which there is
18079 debugging information, organized into two lists: files whose symbols
18080 have already been read, and files whose symbols will be read when needed.
18082 @kindex info functions
18083 @item info functions [-q]
18084 Print the names and data types of all defined functions.
18085 Similarly to @samp{info types}, this command groups its output by source
18086 files and annotates each function definition with its source line
18089 In programs using different languages, @value{GDBN} chooses the syntax
18090 to print the function name and type according to the
18091 @samp{set language} value: using @samp{set language auto}
18092 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18093 language of the function, other values mean to use
18094 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18096 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18097 printing header information and messages explaining why no functions
18100 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18101 Like @samp{info functions}, but only print the names and data types
18102 of the functions selected with the provided regexp(s).
18104 If @var{regexp} is provided, print only the functions whose names
18105 match the regular expression @var{regexp}.
18106 Thus, @samp{info fun step} finds all functions whose
18107 names include @code{step}; @samp{info fun ^step} finds those whose names
18108 start with @code{step}. If a function name contains characters that
18109 conflict with the regular expression language (e.g.@:
18110 @samp{operator*()}), they may be quoted with a backslash.
18112 If @var{type_regexp} is provided, print only the functions whose
18113 types, as printed by the @code{whatis} command, match
18114 the regular expression @var{type_regexp}.
18115 If @var{type_regexp} contains space(s), it should be enclosed in
18116 quote characters. If needed, use backslash to escape the meaning
18117 of special characters or quotes.
18118 Thus, @samp{info fun -t '^int ('} finds the functions that return
18119 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18120 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18121 finds the functions whose names start with @code{step} and that return
18124 If both @var{regexp} and @var{type_regexp} are provided, a function
18125 is printed only if its name matches @var{regexp} and its type matches
18129 @kindex info variables
18130 @item info variables [-q]
18131 Print the names and data types of all variables that are defined
18132 outside of functions (i.e.@: excluding local variables).
18133 The printed variables are grouped by source files and annotated with
18134 their respective source line numbers.
18136 In programs using different languages, @value{GDBN} chooses the syntax
18137 to print the variable name and type according to the
18138 @samp{set language} value: using @samp{set language auto}
18139 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18140 language of the variable, other values mean to use
18141 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18143 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18144 printing header information and messages explaining why no variables
18147 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18148 Like @kbd{info variables}, but only print the variables selected
18149 with the provided regexp(s).
18151 If @var{regexp} is provided, print only the variables whose names
18152 match the regular expression @var{regexp}.
18154 If @var{type_regexp} is provided, print only the variables whose
18155 types, as printed by the @code{whatis} command, match
18156 the regular expression @var{type_regexp}.
18157 If @var{type_regexp} contains space(s), it should be enclosed in
18158 quote characters. If needed, use backslash to escape the meaning
18159 of special characters or quotes.
18161 If both @var{regexp} and @var{type_regexp} are provided, an argument
18162 is printed only if its name matches @var{regexp} and its type matches
18165 @kindex info classes
18166 @cindex Objective-C, classes and selectors
18168 @itemx info classes @var{regexp}
18169 Display all Objective-C classes in your program, or
18170 (with the @var{regexp} argument) all those matching a particular regular
18173 @kindex info selectors
18174 @item info selectors
18175 @itemx info selectors @var{regexp}
18176 Display all Objective-C selectors in your program, or
18177 (with the @var{regexp} argument) all those matching a particular regular
18181 This was never implemented.
18182 @kindex info methods
18184 @itemx info methods @var{regexp}
18185 The @code{info methods} command permits the user to examine all defined
18186 methods within C@t{++} program, or (with the @var{regexp} argument) a
18187 specific set of methods found in the various C@t{++} classes. Many
18188 C@t{++} classes provide a large number of methods. Thus, the output
18189 from the @code{ptype} command can be overwhelming and hard to use. The
18190 @code{info-methods} command filters the methods, printing only those
18191 which match the regular-expression @var{regexp}.
18194 @cindex opaque data types
18195 @kindex set opaque-type-resolution
18196 @item set opaque-type-resolution on
18197 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18198 declared as a pointer to a @code{struct}, @code{class}, or
18199 @code{union}---for example, @code{struct MyType *}---that is used in one
18200 source file although the full declaration of @code{struct MyType} is in
18201 another source file. The default is on.
18203 A change in the setting of this subcommand will not take effect until
18204 the next time symbols for a file are loaded.
18206 @item set opaque-type-resolution off
18207 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18208 is printed as follows:
18210 @{<no data fields>@}
18213 @kindex show opaque-type-resolution
18214 @item show opaque-type-resolution
18215 Show whether opaque types are resolved or not.
18217 @kindex set print symbol-loading
18218 @cindex print messages when symbols are loaded
18219 @item set print symbol-loading
18220 @itemx set print symbol-loading full
18221 @itemx set print symbol-loading brief
18222 @itemx set print symbol-loading off
18223 The @code{set print symbol-loading} command allows you to control the
18224 printing of messages when @value{GDBN} loads symbol information.
18225 By default a message is printed for the executable and one for each
18226 shared library, and normally this is what you want. However, when
18227 debugging apps with large numbers of shared libraries these messages
18229 When set to @code{brief} a message is printed for each executable,
18230 and when @value{GDBN} loads a collection of shared libraries at once
18231 it will only print one message regardless of the number of shared
18232 libraries. When set to @code{off} no messages are printed.
18234 @kindex show print symbol-loading
18235 @item show print symbol-loading
18236 Show whether messages will be printed when a @value{GDBN} command
18237 entered from the keyboard causes symbol information to be loaded.
18239 @kindex maint print symbols
18240 @cindex symbol dump
18241 @kindex maint print psymbols
18242 @cindex partial symbol dump
18243 @kindex maint print msymbols
18244 @cindex minimal symbol dump
18245 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18246 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18247 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18248 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18249 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18250 Write a dump of debugging symbol data into the file @var{filename} or
18251 the terminal if @var{filename} is unspecified.
18252 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18254 If @code{-pc @var{address}} is specified, only dump symbols for the file
18255 with code at that address. Note that @var{address} may be a symbol like
18257 If @code{-source @var{source}} is specified, only dump symbols for that
18260 These commands are used to debug the @value{GDBN} symbol-reading code.
18261 These commands do not modify internal @value{GDBN} state, therefore
18262 @samp{maint print symbols} will only print symbols for already expanded symbol
18264 You can use the command @code{info sources} to find out which files these are.
18265 If you use @samp{maint print psymbols} instead, the dump shows information
18266 about symbols that @value{GDBN} only knows partially---that is, symbols
18267 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18268 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18271 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18272 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18274 @kindex maint info symtabs
18275 @kindex maint info psymtabs
18276 @cindex listing @value{GDBN}'s internal symbol tables
18277 @cindex symbol tables, listing @value{GDBN}'s internal
18278 @cindex full symbol tables, listing @value{GDBN}'s internal
18279 @cindex partial symbol tables, listing @value{GDBN}'s internal
18280 @item maint info symtabs @r{[} @var{regexp} @r{]}
18281 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18283 List the @code{struct symtab} or @code{struct partial_symtab}
18284 structures whose names match @var{regexp}. If @var{regexp} is not
18285 given, list them all. The output includes expressions which you can
18286 copy into a @value{GDBN} debugging this one to examine a particular
18287 structure in more detail. For example:
18290 (@value{GDBP}) maint info psymtabs dwarf2read
18291 @{ objfile /home/gnu/build/gdb/gdb
18292 ((struct objfile *) 0x82e69d0)
18293 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18294 ((struct partial_symtab *) 0x8474b10)
18297 text addresses 0x814d3c8 -- 0x8158074
18298 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18299 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18300 dependencies (none)
18303 (@value{GDBP}) maint info symtabs
18307 We see that there is one partial symbol table whose filename contains
18308 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18309 and we see that @value{GDBN} has not read in any symtabs yet at all.
18310 If we set a breakpoint on a function, that will cause @value{GDBN} to
18311 read the symtab for the compilation unit containing that function:
18314 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18315 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18317 (@value{GDBP}) maint info symtabs
18318 @{ objfile /home/gnu/build/gdb/gdb
18319 ((struct objfile *) 0x82e69d0)
18320 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18321 ((struct symtab *) 0x86c1f38)
18324 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18325 linetable ((struct linetable *) 0x8370fa0)
18326 debugformat DWARF 2
18332 @kindex maint info line-table
18333 @cindex listing @value{GDBN}'s internal line tables
18334 @cindex line tables, listing @value{GDBN}'s internal
18335 @item maint info line-table @r{[} @var{regexp} @r{]}
18337 List the @code{struct linetable} from all @code{struct symtab}
18338 instances whose name matches @var{regexp}. If @var{regexp} is not
18339 given, list the @code{struct linetable} from all @code{struct symtab}.
18341 @kindex maint set symbol-cache-size
18342 @cindex symbol cache size
18343 @item maint set symbol-cache-size @var{size}
18344 Set the size of the symbol cache to @var{size}.
18345 The default size is intended to be good enough for debugging
18346 most applications. This option exists to allow for experimenting
18347 with different sizes.
18349 @kindex maint show symbol-cache-size
18350 @item maint show symbol-cache-size
18351 Show the size of the symbol cache.
18353 @kindex maint print symbol-cache
18354 @cindex symbol cache, printing its contents
18355 @item maint print symbol-cache
18356 Print the contents of the symbol cache.
18357 This is useful when debugging symbol cache issues.
18359 @kindex maint print symbol-cache-statistics
18360 @cindex symbol cache, printing usage statistics
18361 @item maint print symbol-cache-statistics
18362 Print symbol cache usage statistics.
18363 This helps determine how well the cache is being utilized.
18365 @kindex maint flush-symbol-cache
18366 @cindex symbol cache, flushing
18367 @item maint flush-symbol-cache
18368 Flush the contents of the symbol cache, all entries are removed.
18369 This command is useful when debugging the symbol cache.
18370 It is also useful when collecting performance data.
18375 @chapter Altering Execution
18377 Once you think you have found an error in your program, you might want to
18378 find out for certain whether correcting the apparent error would lead to
18379 correct results in the rest of the run. You can find the answer by
18380 experiment, using the @value{GDBN} features for altering execution of the
18383 For example, you can store new values into variables or memory
18384 locations, give your program a signal, restart it at a different
18385 address, or even return prematurely from a function.
18388 * Assignment:: Assignment to variables
18389 * Jumping:: Continuing at a different address
18390 * Signaling:: Giving your program a signal
18391 * Returning:: Returning from a function
18392 * Calling:: Calling your program's functions
18393 * Patching:: Patching your program
18394 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18398 @section Assignment to Variables
18401 @cindex setting variables
18402 To alter the value of a variable, evaluate an assignment expression.
18403 @xref{Expressions, ,Expressions}. For example,
18410 stores the value 4 into the variable @code{x}, and then prints the
18411 value of the assignment expression (which is 4).
18412 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18413 information on operators in supported languages.
18415 @kindex set variable
18416 @cindex variables, setting
18417 If you are not interested in seeing the value of the assignment, use the
18418 @code{set} command instead of the @code{print} command. @code{set} is
18419 really the same as @code{print} except that the expression's value is
18420 not printed and is not put in the value history (@pxref{Value History,
18421 ,Value History}). The expression is evaluated only for its effects.
18423 If the beginning of the argument string of the @code{set} command
18424 appears identical to a @code{set} subcommand, use the @code{set
18425 variable} command instead of just @code{set}. This command is identical
18426 to @code{set} except for its lack of subcommands. For example, if your
18427 program has a variable @code{width}, you get an error if you try to set
18428 a new value with just @samp{set width=13}, because @value{GDBN} has the
18429 command @code{set width}:
18432 (@value{GDBP}) whatis width
18434 (@value{GDBP}) p width
18436 (@value{GDBP}) set width=47
18437 Invalid syntax in expression.
18441 The invalid expression, of course, is @samp{=47}. In
18442 order to actually set the program's variable @code{width}, use
18445 (@value{GDBP}) set var width=47
18448 Because the @code{set} command has many subcommands that can conflict
18449 with the names of program variables, it is a good idea to use the
18450 @code{set variable} command instead of just @code{set}. For example, if
18451 your program has a variable @code{g}, you run into problems if you try
18452 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18453 the command @code{set gnutarget}, abbreviated @code{set g}:
18457 (@value{GDBP}) whatis g
18461 (@value{GDBP}) set g=4
18465 The program being debugged has been started already.
18466 Start it from the beginning? (y or n) y
18467 Starting program: /home/smith/cc_progs/a.out
18468 "/home/smith/cc_progs/a.out": can't open to read symbols:
18469 Invalid bfd target.
18470 (@value{GDBP}) show g
18471 The current BFD target is "=4".
18476 The program variable @code{g} did not change, and you silently set the
18477 @code{gnutarget} to an invalid value. In order to set the variable
18481 (@value{GDBP}) set var g=4
18484 @value{GDBN} allows more implicit conversions in assignments than C; you can
18485 freely store an integer value into a pointer variable or vice versa,
18486 and you can convert any structure to any other structure that is the
18487 same length or shorter.
18488 @comment FIXME: how do structs align/pad in these conversions?
18489 @comment /doc@cygnus.com 18dec1990
18491 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18492 construct to generate a value of specified type at a specified address
18493 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18494 to memory location @code{0x83040} as an integer (which implies a certain size
18495 and representation in memory), and
18498 set @{int@}0x83040 = 4
18502 stores the value 4 into that memory location.
18505 @section Continuing at a Different Address
18507 Ordinarily, when you continue your program, you do so at the place where
18508 it stopped, with the @code{continue} command. You can instead continue at
18509 an address of your own choosing, with the following commands:
18513 @kindex j @r{(@code{jump})}
18514 @item jump @var{location}
18515 @itemx j @var{location}
18516 Resume execution at @var{location}. Execution stops again immediately
18517 if there is a breakpoint there. @xref{Specify Location}, for a description
18518 of the different forms of @var{location}. It is common
18519 practice to use the @code{tbreak} command in conjunction with
18520 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18522 The @code{jump} command does not change the current stack frame, or
18523 the stack pointer, or the contents of any memory location or any
18524 register other than the program counter. If @var{location} is in
18525 a different function from the one currently executing, the results may
18526 be bizarre if the two functions expect different patterns of arguments or
18527 of local variables. For this reason, the @code{jump} command requests
18528 confirmation if the specified line is not in the function currently
18529 executing. However, even bizarre results are predictable if you are
18530 well acquainted with the machine-language code of your program.
18533 On many systems, you can get much the same effect as the @code{jump}
18534 command by storing a new value into the register @code{$pc}. The
18535 difference is that this does not start your program running; it only
18536 changes the address of where it @emph{will} run when you continue. For
18544 makes the next @code{continue} command or stepping command execute at
18545 address @code{0x485}, rather than at the address where your program stopped.
18546 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18548 The most common occasion to use the @code{jump} command is to back
18549 up---perhaps with more breakpoints set---over a portion of a program
18550 that has already executed, in order to examine its execution in more
18555 @section Giving your Program a Signal
18556 @cindex deliver a signal to a program
18560 @item signal @var{signal}
18561 Resume execution where your program is stopped, but immediately give it the
18562 signal @var{signal}. The @var{signal} can be the name or the number of a
18563 signal. For example, on many systems @code{signal 2} and @code{signal
18564 SIGINT} are both ways of sending an interrupt signal.
18566 Alternatively, if @var{signal} is zero, continue execution without
18567 giving a signal. This is useful when your program stopped on account of
18568 a signal and would ordinarily see the signal when resumed with the
18569 @code{continue} command; @samp{signal 0} causes it to resume without a
18572 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18573 delivered to the currently selected thread, not the thread that last
18574 reported a stop. This includes the situation where a thread was
18575 stopped due to a signal. So if you want to continue execution
18576 suppressing the signal that stopped a thread, you should select that
18577 same thread before issuing the @samp{signal 0} command. If you issue
18578 the @samp{signal 0} command with another thread as the selected one,
18579 @value{GDBN} detects that and asks for confirmation.
18581 Invoking the @code{signal} command is not the same as invoking the
18582 @code{kill} utility from the shell. Sending a signal with @code{kill}
18583 causes @value{GDBN} to decide what to do with the signal depending on
18584 the signal handling tables (@pxref{Signals}). The @code{signal} command
18585 passes the signal directly to your program.
18587 @code{signal} does not repeat when you press @key{RET} a second time
18588 after executing the command.
18590 @kindex queue-signal
18591 @item queue-signal @var{signal}
18592 Queue @var{signal} to be delivered immediately to the current thread
18593 when execution of the thread resumes. The @var{signal} can be the name or
18594 the number of a signal. For example, on many systems @code{signal 2} and
18595 @code{signal SIGINT} are both ways of sending an interrupt signal.
18596 The handling of the signal must be set to pass the signal to the program,
18597 otherwise @value{GDBN} will report an error.
18598 You can control the handling of signals from @value{GDBN} with the
18599 @code{handle} command (@pxref{Signals}).
18601 Alternatively, if @var{signal} is zero, any currently queued signal
18602 for the current thread is discarded and when execution resumes no signal
18603 will be delivered. This is useful when your program stopped on account
18604 of a signal and would ordinarily see the signal when resumed with the
18605 @code{continue} command.
18607 This command differs from the @code{signal} command in that the signal
18608 is just queued, execution is not resumed. And @code{queue-signal} cannot
18609 be used to pass a signal whose handling state has been set to @code{nopass}
18614 @xref{stepping into signal handlers}, for information on how stepping
18615 commands behave when the thread has a signal queued.
18618 @section Returning from a Function
18621 @cindex returning from a function
18624 @itemx return @var{expression}
18625 You can cancel execution of a function call with the @code{return}
18626 command. If you give an
18627 @var{expression} argument, its value is used as the function's return
18631 When you use @code{return}, @value{GDBN} discards the selected stack frame
18632 (and all frames within it). You can think of this as making the
18633 discarded frame return prematurely. If you wish to specify a value to
18634 be returned, give that value as the argument to @code{return}.
18636 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18637 Frame}), and any other frames inside of it, leaving its caller as the
18638 innermost remaining frame. That frame becomes selected. The
18639 specified value is stored in the registers used for returning values
18642 The @code{return} command does not resume execution; it leaves the
18643 program stopped in the state that would exist if the function had just
18644 returned. In contrast, the @code{finish} command (@pxref{Continuing
18645 and Stepping, ,Continuing and Stepping}) resumes execution until the
18646 selected stack frame returns naturally.
18648 @value{GDBN} needs to know how the @var{expression} argument should be set for
18649 the inferior. The concrete registers assignment depends on the OS ABI and the
18650 type being returned by the selected stack frame. For example it is common for
18651 OS ABI to return floating point values in FPU registers while integer values in
18652 CPU registers. Still some ABIs return even floating point values in CPU
18653 registers. Larger integer widths (such as @code{long long int}) also have
18654 specific placement rules. @value{GDBN} already knows the OS ABI from its
18655 current target so it needs to find out also the type being returned to make the
18656 assignment into the right register(s).
18658 Normally, the selected stack frame has debug info. @value{GDBN} will always
18659 use the debug info instead of the implicit type of @var{expression} when the
18660 debug info is available. For example, if you type @kbd{return -1}, and the
18661 function in the current stack frame is declared to return a @code{long long
18662 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18663 into a @code{long long int}:
18666 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18668 (@value{GDBP}) return -1
18669 Make func return now? (y or n) y
18670 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18671 43 printf ("result=%lld\n", func ());
18675 However, if the selected stack frame does not have a debug info, e.g., if the
18676 function was compiled without debug info, @value{GDBN} has to find out the type
18677 to return from user. Specifying a different type by mistake may set the value
18678 in different inferior registers than the caller code expects. For example,
18679 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18680 of a @code{long long int} result for a debug info less function (on 32-bit
18681 architectures). Therefore the user is required to specify the return type by
18682 an appropriate cast explicitly:
18685 Breakpoint 2, 0x0040050b in func ()
18686 (@value{GDBP}) return -1
18687 Return value type not available for selected stack frame.
18688 Please use an explicit cast of the value to return.
18689 (@value{GDBP}) return (long long int) -1
18690 Make selected stack frame return now? (y or n) y
18691 #0 0x00400526 in main ()
18696 @section Calling Program Functions
18699 @cindex calling functions
18700 @cindex inferior functions, calling
18701 @item print @var{expr}
18702 Evaluate the expression @var{expr} and display the resulting value.
18703 The expression may include calls to functions in the program being
18707 @item call @var{expr}
18708 Evaluate the expression @var{expr} without displaying @code{void}
18711 You can use this variant of the @code{print} command if you want to
18712 execute a function from your program that does not return anything
18713 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18714 with @code{void} returned values that @value{GDBN} will otherwise
18715 print. If the result is not void, it is printed and saved in the
18719 It is possible for the function you call via the @code{print} or
18720 @code{call} command to generate a signal (e.g., if there's a bug in
18721 the function, or if you passed it incorrect arguments). What happens
18722 in that case is controlled by the @code{set unwindonsignal} command.
18724 Similarly, with a C@t{++} program it is possible for the function you
18725 call via the @code{print} or @code{call} command to generate an
18726 exception that is not handled due to the constraints of the dummy
18727 frame. In this case, any exception that is raised in the frame, but has
18728 an out-of-frame exception handler will not be found. GDB builds a
18729 dummy-frame for the inferior function call, and the unwinder cannot
18730 seek for exception handlers outside of this dummy-frame. What happens
18731 in that case is controlled by the
18732 @code{set unwind-on-terminating-exception} command.
18735 @item set unwindonsignal
18736 @kindex set unwindonsignal
18737 @cindex unwind stack in called functions
18738 @cindex call dummy stack unwinding
18739 Set unwinding of the stack if a signal is received while in a function
18740 that @value{GDBN} called in the program being debugged. If set to on,
18741 @value{GDBN} unwinds the stack it created for the call and restores
18742 the context to what it was before the call. If set to off (the
18743 default), @value{GDBN} stops in the frame where the signal was
18746 @item show unwindonsignal
18747 @kindex show unwindonsignal
18748 Show the current setting of stack unwinding in the functions called by
18751 @item set unwind-on-terminating-exception
18752 @kindex set unwind-on-terminating-exception
18753 @cindex unwind stack in called functions with unhandled exceptions
18754 @cindex call dummy stack unwinding on unhandled exception.
18755 Set unwinding of the stack if a C@t{++} exception is raised, but left
18756 unhandled while in a function that @value{GDBN} called in the program being
18757 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18758 it created for the call and restores the context to what it was before
18759 the call. If set to off, @value{GDBN} the exception is delivered to
18760 the default C@t{++} exception handler and the inferior terminated.
18762 @item show unwind-on-terminating-exception
18763 @kindex show unwind-on-terminating-exception
18764 Show the current setting of stack unwinding in the functions called by
18767 @item set may-call-functions
18768 @kindex set may-call-functions
18769 @cindex disabling calling functions in the program
18770 @cindex calling functions in the program, disabling
18771 Set permission to call functions in the program.
18772 This controls whether @value{GDBN} will attempt to call functions in
18773 the program, such as with expressions in the @code{print} command. It
18774 defaults to @code{on}.
18776 To call a function in the program, @value{GDBN} has to temporarily
18777 modify the state of the inferior. This has potentially undesired side
18778 effects. Also, having @value{GDBN} call nested functions is likely to
18779 be erroneous and may even crash the program being debugged. You can
18780 avoid such hazards by forbidding @value{GDBN} from calling functions
18781 in the program being debugged. If calling functions in the program
18782 is forbidden, GDB will throw an error when a command (such as printing
18783 an expression) starts a function call in the program.
18785 @item show may-call-functions
18786 @kindex show may-call-functions
18787 Show permission to call functions in the program.
18791 @subsection Calling functions with no debug info
18793 @cindex no debug info functions
18794 Sometimes, a function you wish to call is missing debug information.
18795 In such case, @value{GDBN} does not know the type of the function,
18796 including the types of the function's parameters. To avoid calling
18797 the inferior function incorrectly, which could result in the called
18798 function functioning erroneously and even crash, @value{GDBN} refuses
18799 to call the function unless you tell it the type of the function.
18801 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18802 to do that. The simplest is to cast the call to the function's
18803 declared return type. For example:
18806 (@value{GDBP}) p getenv ("PATH")
18807 'getenv' has unknown return type; cast the call to its declared return type
18808 (@value{GDBP}) p (char *) getenv ("PATH")
18809 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18812 Casting the return type of a no-debug function is equivalent to
18813 casting the function to a pointer to a prototyped function that has a
18814 prototype that matches the types of the passed-in arguments, and
18815 calling that. I.e., the call above is equivalent to:
18818 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18822 and given this prototyped C or C++ function with float parameters:
18825 float multiply (float v1, float v2) @{ return v1 * v2; @}
18829 these calls are equivalent:
18832 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18833 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18836 If the function you wish to call is declared as unprototyped (i.e.@:
18837 old K&R style), you must use the cast-to-function-pointer syntax, so
18838 that @value{GDBN} knows that it needs to apply default argument
18839 promotions (promote float arguments to double). @xref{ABI, float
18840 promotion}. For example, given this unprototyped C function with
18841 float parameters, and no debug info:
18845 multiply_noproto (v1, v2)
18853 you call it like this:
18856 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18860 @section Patching Programs
18862 @cindex patching binaries
18863 @cindex writing into executables
18864 @cindex writing into corefiles
18866 By default, @value{GDBN} opens the file containing your program's
18867 executable code (or the corefile) read-only. This prevents accidental
18868 alterations to machine code; but it also prevents you from intentionally
18869 patching your program's binary.
18871 If you'd like to be able to patch the binary, you can specify that
18872 explicitly with the @code{set write} command. For example, you might
18873 want to turn on internal debugging flags, or even to make emergency
18879 @itemx set write off
18880 If you specify @samp{set write on}, @value{GDBN} opens executable and
18881 core files for both reading and writing; if you specify @kbd{set write
18882 off} (the default), @value{GDBN} opens them read-only.
18884 If you have already loaded a file, you must load it again (using the
18885 @code{exec-file} or @code{core-file} command) after changing @code{set
18886 write}, for your new setting to take effect.
18890 Display whether executable files and core files are opened for writing
18891 as well as reading.
18894 @node Compiling and Injecting Code
18895 @section Compiling and injecting code in @value{GDBN}
18896 @cindex injecting code
18897 @cindex writing into executables
18898 @cindex compiling code
18900 @value{GDBN} supports on-demand compilation and code injection into
18901 programs running under @value{GDBN}. GCC 5.0 or higher built with
18902 @file{libcc1.so} must be installed for this functionality to be enabled.
18903 This functionality is implemented with the following commands.
18906 @kindex compile code
18907 @item compile code @var{source-code}
18908 @itemx compile code -raw @var{--} @var{source-code}
18909 Compile @var{source-code} with the compiler language found as the current
18910 language in @value{GDBN} (@pxref{Languages}). If compilation and
18911 injection is not supported with the current language specified in
18912 @value{GDBN}, or the compiler does not support this feature, an error
18913 message will be printed. If @var{source-code} compiles and links
18914 successfully, @value{GDBN} will load the object-code emitted,
18915 and execute it within the context of the currently selected inferior.
18916 It is important to note that the compiled code is executed immediately.
18917 After execution, the compiled code is removed from @value{GDBN} and any
18918 new types or variables you have defined will be deleted.
18920 The command allows you to specify @var{source-code} in two ways.
18921 The simplest method is to provide a single line of code to the command.
18925 compile code printf ("hello world\n");
18928 If you specify options on the command line as well as source code, they
18929 may conflict. The @samp{--} delimiter can be used to separate options
18930 from actual source code. E.g.:
18933 compile code -r -- printf ("hello world\n");
18936 Alternatively you can enter source code as multiple lines of text. To
18937 enter this mode, invoke the @samp{compile code} command without any text
18938 following the command. This will start the multiple-line editor and
18939 allow you to type as many lines of source code as required. When you
18940 have completed typing, enter @samp{end} on its own line to exit the
18945 >printf ("hello\n");
18946 >printf ("world\n");
18950 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18951 provided @var{source-code} in a callable scope. In this case, you must
18952 specify the entry point of the code by defining a function named
18953 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18954 inferior. Using @samp{-raw} option may be needed for example when
18955 @var{source-code} requires @samp{#include} lines which may conflict with
18956 inferior symbols otherwise.
18958 @kindex compile file
18959 @item compile file @var{filename}
18960 @itemx compile file -raw @var{filename}
18961 Like @code{compile code}, but take the source code from @var{filename}.
18964 compile file /home/user/example.c
18969 @item compile print @var{expr}
18970 @itemx compile print /@var{f} @var{expr}
18971 Compile and execute @var{expr} with the compiler language found as the
18972 current language in @value{GDBN} (@pxref{Languages}). By default the
18973 value of @var{expr} is printed in a format appropriate to its data type;
18974 you can choose a different format by specifying @samp{/@var{f}}, where
18975 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18978 @item compile print
18979 @itemx compile print /@var{f}
18980 @cindex reprint the last value
18981 Alternatively you can enter the expression (source code producing it) as
18982 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18983 command without any text following the command. This will start the
18984 multiple-line editor.
18988 The process of compiling and injecting the code can be inspected using:
18991 @anchor{set debug compile}
18992 @item set debug compile
18993 @cindex compile command debugging info
18994 Turns on or off display of @value{GDBN} process of compiling and
18995 injecting the code. The default is off.
18997 @item show debug compile
18998 Displays the current state of displaying @value{GDBN} process of
18999 compiling and injecting the code.
19001 @anchor{set debug compile-cplus-types}
19002 @item set debug compile-cplus-types
19003 @cindex compile C@t{++} type conversion
19004 Turns on or off the display of C@t{++} type conversion debugging information.
19005 The default is off.
19007 @item show debug compile-cplus-types
19008 Displays the current state of displaying debugging information for
19009 C@t{++} type conversion.
19012 @subsection Compilation options for the @code{compile} command
19014 @value{GDBN} needs to specify the right compilation options for the code
19015 to be injected, in part to make its ABI compatible with the inferior
19016 and in part to make the injected code compatible with @value{GDBN}'s
19020 The options used, in increasing precedence:
19023 @item target architecture and OS options (@code{gdbarch})
19024 These options depend on target processor type and target operating
19025 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19026 (@code{-m64}) compilation option.
19028 @item compilation options recorded in the target
19029 @value{NGCC} (since version 4.7) stores the options used for compilation
19030 into @code{DW_AT_producer} part of DWARF debugging information according
19031 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19032 explicitly specify @code{-g} during inferior compilation otherwise
19033 @value{NGCC} produces no DWARF. This feature is only relevant for
19034 platforms where @code{-g} produces DWARF by default, otherwise one may
19035 try to enforce DWARF by using @code{-gdwarf-4}.
19037 @item compilation options set by @code{set compile-args}
19041 You can override compilation options using the following command:
19044 @item set compile-args
19045 @cindex compile command options override
19046 Set compilation options used for compiling and injecting code with the
19047 @code{compile} commands. These options override any conflicting ones
19048 from the target architecture and/or options stored during inferior
19051 @item show compile-args
19052 Displays the current state of compilation options override.
19053 This does not show all the options actually used during compilation,
19054 use @ref{set debug compile} for that.
19057 @subsection Caveats when using the @code{compile} command
19059 There are a few caveats to keep in mind when using the @code{compile}
19060 command. As the caveats are different per language, the table below
19061 highlights specific issues on a per language basis.
19064 @item C code examples and caveats
19065 When the language in @value{GDBN} is set to @samp{C}, the compiler will
19066 attempt to compile the source code with a @samp{C} compiler. The source
19067 code provided to the @code{compile} command will have much the same
19068 access to variables and types as it normally would if it were part of
19069 the program currently being debugged in @value{GDBN}.
19071 Below is a sample program that forms the basis of the examples that
19072 follow. This program has been compiled and loaded into @value{GDBN},
19073 much like any other normal debugging session.
19076 void function1 (void)
19079 printf ("function 1\n");
19082 void function2 (void)
19097 For the purposes of the examples in this section, the program above has
19098 been compiled, loaded into @value{GDBN}, stopped at the function
19099 @code{main}, and @value{GDBN} is awaiting input from the user.
19101 To access variables and types for any program in @value{GDBN}, the
19102 program must be compiled and packaged with debug information. The
19103 @code{compile} command is not an exception to this rule. Without debug
19104 information, you can still use the @code{compile} command, but you will
19105 be very limited in what variables and types you can access.
19107 So with that in mind, the example above has been compiled with debug
19108 information enabled. The @code{compile} command will have access to
19109 all variables and types (except those that may have been optimized
19110 out). Currently, as @value{GDBN} has stopped the program in the
19111 @code{main} function, the @code{compile} command would have access to
19112 the variable @code{k}. You could invoke the @code{compile} command
19113 and type some source code to set the value of @code{k}. You can also
19114 read it, or do anything with that variable you would normally do in
19115 @code{C}. Be aware that changes to inferior variables in the
19116 @code{compile} command are persistent. In the following example:
19119 compile code k = 3;
19123 the variable @code{k} is now 3. It will retain that value until
19124 something else in the example program changes it, or another
19125 @code{compile} command changes it.
19127 Normal scope and access rules apply to source code compiled and
19128 injected by the @code{compile} command. In the example, the variables
19129 @code{j} and @code{k} are not accessible yet, because the program is
19130 currently stopped in the @code{main} function, where these variables
19131 are not in scope. Therefore, the following command
19134 compile code j = 3;
19138 will result in a compilation error message.
19140 Once the program is continued, execution will bring these variables in
19141 scope, and they will become accessible; then the code you specify via
19142 the @code{compile} command will be able to access them.
19144 You can create variables and types with the @code{compile} command as
19145 part of your source code. Variables and types that are created as part
19146 of the @code{compile} command are not visible to the rest of the program for
19147 the duration of its run. This example is valid:
19150 compile code int ff = 5; printf ("ff is %d\n", ff);
19153 However, if you were to type the following into @value{GDBN} after that
19154 command has completed:
19157 compile code printf ("ff is %d\n'', ff);
19161 a compiler error would be raised as the variable @code{ff} no longer
19162 exists. Object code generated and injected by the @code{compile}
19163 command is removed when its execution ends. Caution is advised
19164 when assigning to program variables values of variables created by the
19165 code submitted to the @code{compile} command. This example is valid:
19168 compile code int ff = 5; k = ff;
19171 The value of the variable @code{ff} is assigned to @code{k}. The variable
19172 @code{k} does not require the existence of @code{ff} to maintain the value
19173 it has been assigned. However, pointers require particular care in
19174 assignment. If the source code compiled with the @code{compile} command
19175 changed the address of a pointer in the example program, perhaps to a
19176 variable created in the @code{compile} command, that pointer would point
19177 to an invalid location when the command exits. The following example
19178 would likely cause issues with your debugged program:
19181 compile code int ff = 5; p = &ff;
19184 In this example, @code{p} would point to @code{ff} when the
19185 @code{compile} command is executing the source code provided to it.
19186 However, as variables in the (example) program persist with their
19187 assigned values, the variable @code{p} would point to an invalid
19188 location when the command exists. A general rule should be followed
19189 in that you should either assign @code{NULL} to any assigned pointers,
19190 or restore a valid location to the pointer before the command exits.
19192 Similar caution must be exercised with any structs, unions, and typedefs
19193 defined in @code{compile} command. Types defined in the @code{compile}
19194 command will no longer be available in the next @code{compile} command.
19195 Therefore, if you cast a variable to a type defined in the
19196 @code{compile} command, care must be taken to ensure that any future
19197 need to resolve the type can be achieved.
19200 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19201 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19202 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19203 Compilation failed.
19204 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19208 Variables that have been optimized away by the compiler are not
19209 accessible to the code submitted to the @code{compile} command.
19210 Access to those variables will generate a compiler error which @value{GDBN}
19211 will print to the console.
19214 @subsection Compiler search for the @code{compile} command
19216 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19217 which may not be obvious for remote targets of different architecture
19218 than where @value{GDBN} is running. Environment variable @code{PATH} on
19219 @value{GDBN} host is searched for @value{NGCC} binary matching the
19220 target architecture and operating system. This search can be overriden
19221 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19222 taken from shell that executed @value{GDBN}, it is not the value set by
19223 @value{GDBN} command @code{set environment}). @xref{Environment}.
19226 Specifically @code{PATH} is searched for binaries matching regular expression
19227 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19228 debugged. @var{arch} is processor name --- multiarch is supported, so for
19229 example both @code{i386} and @code{x86_64} targets look for pattern
19230 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19231 for pattern @code{s390x?}. @var{os} is currently supported only for
19232 pattern @code{linux(-gnu)?}.
19234 On Posix hosts the compiler driver @value{GDBN} needs to find also
19235 shared library @file{libcc1.so} from the compiler. It is searched in
19236 default shared library search path (overridable with usual environment
19237 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19238 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19239 according to the installation of the found compiler --- as possibly
19240 specified by the @code{set compile-gcc} command.
19243 @item set compile-gcc
19244 @cindex compile command driver filename override
19245 Set compilation command used for compiling and injecting code with the
19246 @code{compile} commands. If this option is not set (it is set to
19247 an empty string), the search described above will occur --- that is the
19250 @item show compile-gcc
19251 Displays the current compile command @value{NGCC} driver filename.
19252 If set, it is the main command @command{gcc}, found usually for example
19253 under name @file{x86_64-linux-gnu-gcc}.
19257 @chapter @value{GDBN} Files
19259 @value{GDBN} needs to know the file name of the program to be debugged,
19260 both in order to read its symbol table and in order to start your
19261 program. To debug a core dump of a previous run, you must also tell
19262 @value{GDBN} the name of the core dump file.
19265 * Files:: Commands to specify files
19266 * File Caching:: Information about @value{GDBN}'s file caching
19267 * Separate Debug Files:: Debugging information in separate files
19268 * MiniDebugInfo:: Debugging information in a special section
19269 * Index Files:: Index files speed up GDB
19270 * Symbol Errors:: Errors reading symbol files
19271 * Data Files:: GDB data files
19275 @section Commands to Specify Files
19277 @cindex symbol table
19278 @cindex core dump file
19280 You may want to specify executable and core dump file names. The usual
19281 way to do this is at start-up time, using the arguments to
19282 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19283 Out of @value{GDBN}}).
19285 Occasionally it is necessary to change to a different file during a
19286 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19287 specify a file you want to use. Or you are debugging a remote target
19288 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19289 Program}). In these situations the @value{GDBN} commands to specify
19290 new files are useful.
19293 @cindex executable file
19295 @item file @var{filename}
19296 Use @var{filename} as the program to be debugged. It is read for its
19297 symbols and for the contents of pure memory. It is also the program
19298 executed when you use the @code{run} command. If you do not specify a
19299 directory and the file is not found in the @value{GDBN} working directory,
19300 @value{GDBN} uses the environment variable @code{PATH} as a list of
19301 directories to search, just as the shell does when looking for a program
19302 to run. You can change the value of this variable, for both @value{GDBN}
19303 and your program, using the @code{path} command.
19305 @cindex unlinked object files
19306 @cindex patching object files
19307 You can load unlinked object @file{.o} files into @value{GDBN} using
19308 the @code{file} command. You will not be able to ``run'' an object
19309 file, but you can disassemble functions and inspect variables. Also,
19310 if the underlying BFD functionality supports it, you could use
19311 @kbd{gdb -write} to patch object files using this technique. Note
19312 that @value{GDBN} can neither interpret nor modify relocations in this
19313 case, so branches and some initialized variables will appear to go to
19314 the wrong place. But this feature is still handy from time to time.
19317 @code{file} with no argument makes @value{GDBN} discard any information it
19318 has on both executable file and the symbol table.
19321 @item exec-file @r{[} @var{filename} @r{]}
19322 Specify that the program to be run (but not the symbol table) is found
19323 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19324 if necessary to locate your program. Omitting @var{filename} means to
19325 discard information on the executable file.
19327 @kindex symbol-file
19328 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19329 Read symbol table information from file @var{filename}. @code{PATH} is
19330 searched when necessary. Use the @code{file} command to get both symbol
19331 table and program to run from the same file.
19333 If an optional @var{offset} is specified, it is added to the start
19334 address of each section in the symbol file. This is useful if the
19335 program is relocated at runtime, such as the Linux kernel with kASLR
19338 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19339 program's symbol table.
19341 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19342 some breakpoints and auto-display expressions. This is because they may
19343 contain pointers to the internal data recording symbols and data types,
19344 which are part of the old symbol table data being discarded inside
19347 @code{symbol-file} does not repeat if you press @key{RET} again after
19350 When @value{GDBN} is configured for a particular environment, it
19351 understands debugging information in whatever format is the standard
19352 generated for that environment; you may use either a @sc{gnu} compiler, or
19353 other compilers that adhere to the local conventions.
19354 Best results are usually obtained from @sc{gnu} compilers; for example,
19355 using @code{@value{NGCC}} you can generate debugging information for
19358 For most kinds of object files, with the exception of old SVR3 systems
19359 using COFF, the @code{symbol-file} command does not normally read the
19360 symbol table in full right away. Instead, it scans the symbol table
19361 quickly to find which source files and which symbols are present. The
19362 details are read later, one source file at a time, as they are needed.
19364 The purpose of this two-stage reading strategy is to make @value{GDBN}
19365 start up faster. For the most part, it is invisible except for
19366 occasional pauses while the symbol table details for a particular source
19367 file are being read. (The @code{set verbose} command can turn these
19368 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19369 Warnings and Messages}.)
19371 We have not implemented the two-stage strategy for COFF yet. When the
19372 symbol table is stored in COFF format, @code{symbol-file} reads the
19373 symbol table data in full right away. Note that ``stabs-in-COFF''
19374 still does the two-stage strategy, since the debug info is actually
19378 @cindex reading symbols immediately
19379 @cindex symbols, reading immediately
19380 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19381 @itemx file @r{[} -readnow @r{]} @var{filename}
19382 You can override the @value{GDBN} two-stage strategy for reading symbol
19383 tables by using the @samp{-readnow} option with any of the commands that
19384 load symbol table information, if you want to be sure @value{GDBN} has the
19385 entire symbol table available.
19387 @cindex @code{-readnever}, option for symbol-file command
19388 @cindex never read symbols
19389 @cindex symbols, never read
19390 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19391 @itemx file @r{[} -readnever @r{]} @var{filename}
19392 You can instruct @value{GDBN} to never read the symbolic information
19393 contained in @var{filename} by using the @samp{-readnever} option.
19394 @xref{--readnever}.
19396 @c FIXME: for now no mention of directories, since this seems to be in
19397 @c flux. 13mar1992 status is that in theory GDB would look either in
19398 @c current dir or in same dir as myprog; but issues like competing
19399 @c GDB's, or clutter in system dirs, mean that in practice right now
19400 @c only current dir is used. FFish says maybe a special GDB hierarchy
19401 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19405 @item core-file @r{[}@var{filename}@r{]}
19407 Specify the whereabouts of a core dump file to be used as the ``contents
19408 of memory''. Traditionally, core files contain only some parts of the
19409 address space of the process that generated them; @value{GDBN} can access the
19410 executable file itself for other parts.
19412 @code{core-file} with no argument specifies that no core file is
19415 Note that the core file is ignored when your program is actually running
19416 under @value{GDBN}. So, if you have been running your program and you
19417 wish to debug a core file instead, you must kill the subprocess in which
19418 the program is running. To do this, use the @code{kill} command
19419 (@pxref{Kill Process, ,Killing the Child Process}).
19421 @kindex add-symbol-file
19422 @cindex dynamic linking
19423 @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{]}
19424 The @code{add-symbol-file} command reads additional symbol table
19425 information from the file @var{filename}. You would use this command
19426 when @var{filename} has been dynamically loaded (by some other means)
19427 into the program that is running. The @var{textaddress} parameter gives
19428 the memory address at which the file's text section has been loaded.
19429 You can additionally specify the base address of other sections using
19430 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19431 If a section is omitted, @value{GDBN} will use its default addresses
19432 as found in @var{filename}. Any @var{address} or @var{textaddress}
19433 can be given as an expression.
19435 If an optional @var{offset} is specified, it is added to the start
19436 address of each section, except those for which the address was
19437 specified explicitly.
19439 The symbol table of the file @var{filename} is added to the symbol table
19440 originally read with the @code{symbol-file} command. You can use the
19441 @code{add-symbol-file} command any number of times; the new symbol data
19442 thus read is kept in addition to the old.
19444 Changes can be reverted using the command @code{remove-symbol-file}.
19446 @cindex relocatable object files, reading symbols from
19447 @cindex object files, relocatable, reading symbols from
19448 @cindex reading symbols from relocatable object files
19449 @cindex symbols, reading from relocatable object files
19450 @cindex @file{.o} files, reading symbols from
19451 Although @var{filename} is typically a shared library file, an
19452 executable file, or some other object file which has been fully
19453 relocated for loading into a process, you can also load symbolic
19454 information from relocatable @file{.o} files, as long as:
19458 the file's symbolic information refers only to linker symbols defined in
19459 that file, not to symbols defined by other object files,
19461 every section the file's symbolic information refers to has actually
19462 been loaded into the inferior, as it appears in the file, and
19464 you can determine the address at which every section was loaded, and
19465 provide these to the @code{add-symbol-file} command.
19469 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19470 relocatable files into an already running program; such systems
19471 typically make the requirements above easy to meet. However, it's
19472 important to recognize that many native systems use complex link
19473 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19474 assembly, for example) that make the requirements difficult to meet. In
19475 general, one cannot assume that using @code{add-symbol-file} to read a
19476 relocatable object file's symbolic information will have the same effect
19477 as linking the relocatable object file into the program in the normal
19480 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19482 @kindex remove-symbol-file
19483 @item remove-symbol-file @var{filename}
19484 @item remove-symbol-file -a @var{address}
19485 Remove a symbol file added via the @code{add-symbol-file} command. The
19486 file to remove can be identified by its @var{filename} or by an @var{address}
19487 that lies within the boundaries of this symbol file in memory. Example:
19490 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19491 add symbol table from file "/home/user/gdb/mylib.so" at
19492 .text_addr = 0x7ffff7ff9480
19494 Reading symbols from /home/user/gdb/mylib.so...done.
19495 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19496 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19501 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19503 @kindex add-symbol-file-from-memory
19504 @cindex @code{syscall DSO}
19505 @cindex load symbols from memory
19506 @item add-symbol-file-from-memory @var{address}
19507 Load symbols from the given @var{address} in a dynamically loaded
19508 object file whose image is mapped directly into the inferior's memory.
19509 For example, the Linux kernel maps a @code{syscall DSO} into each
19510 process's address space; this DSO provides kernel-specific code for
19511 some system calls. The argument can be any expression whose
19512 evaluation yields the address of the file's shared object file header.
19513 For this command to work, you must have used @code{symbol-file} or
19514 @code{exec-file} commands in advance.
19517 @item section @var{section} @var{addr}
19518 The @code{section} command changes the base address of the named
19519 @var{section} of the exec file to @var{addr}. This can be used if the
19520 exec file does not contain section addresses, (such as in the
19521 @code{a.out} format), or when the addresses specified in the file
19522 itself are wrong. Each section must be changed separately. The
19523 @code{info files} command, described below, lists all the sections and
19527 @kindex info target
19530 @code{info files} and @code{info target} are synonymous; both print the
19531 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19532 including the names of the executable and core dump files currently in
19533 use by @value{GDBN}, and the files from which symbols were loaded. The
19534 command @code{help target} lists all possible targets rather than
19537 @kindex maint info sections
19538 @item maint info sections
19539 Another command that can give you extra information about program sections
19540 is @code{maint info sections}. In addition to the section information
19541 displayed by @code{info files}, this command displays the flags and file
19542 offset of each section in the executable and core dump files. In addition,
19543 @code{maint info sections} provides the following command options (which
19544 may be arbitrarily combined):
19548 Display sections for all loaded object files, including shared libraries.
19549 @item @var{sections}
19550 Display info only for named @var{sections}.
19551 @item @var{section-flags}
19552 Display info only for sections for which @var{section-flags} are true.
19553 The section flags that @value{GDBN} currently knows about are:
19556 Section will have space allocated in the process when loaded.
19557 Set for all sections except those containing debug information.
19559 Section will be loaded from the file into the child process memory.
19560 Set for pre-initialized code and data, clear for @code{.bss} sections.
19562 Section needs to be relocated before loading.
19564 Section cannot be modified by the child process.
19566 Section contains executable code only.
19568 Section contains data only (no executable code).
19570 Section will reside in ROM.
19572 Section contains data for constructor/destructor lists.
19574 Section is not empty.
19576 An instruction to the linker to not output the section.
19577 @item COFF_SHARED_LIBRARY
19578 A notification to the linker that the section contains
19579 COFF shared library information.
19581 Section contains common symbols.
19584 @kindex set trust-readonly-sections
19585 @cindex read-only sections
19586 @item set trust-readonly-sections on
19587 Tell @value{GDBN} that readonly sections in your object file
19588 really are read-only (i.e.@: that their contents will not change).
19589 In that case, @value{GDBN} can fetch values from these sections
19590 out of the object file, rather than from the target program.
19591 For some targets (notably embedded ones), this can be a significant
19592 enhancement to debugging performance.
19594 The default is off.
19596 @item set trust-readonly-sections off
19597 Tell @value{GDBN} not to trust readonly sections. This means that
19598 the contents of the section might change while the program is running,
19599 and must therefore be fetched from the target when needed.
19601 @item show trust-readonly-sections
19602 Show the current setting of trusting readonly sections.
19605 All file-specifying commands allow both absolute and relative file names
19606 as arguments. @value{GDBN} always converts the file name to an absolute file
19607 name and remembers it that way.
19609 @cindex shared libraries
19610 @anchor{Shared Libraries}
19611 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19612 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19613 DSBT (TIC6X) shared libraries.
19615 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19616 shared libraries. @xref{Expat}.
19618 @value{GDBN} automatically loads symbol definitions from shared libraries
19619 when you use the @code{run} command, or when you examine a core file.
19620 (Before you issue the @code{run} command, @value{GDBN} does not understand
19621 references to a function in a shared library, however---unless you are
19622 debugging a core file).
19624 @c FIXME: some @value{GDBN} release may permit some refs to undef
19625 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19626 @c FIXME...lib; check this from time to time when updating manual
19628 There are times, however, when you may wish to not automatically load
19629 symbol definitions from shared libraries, such as when they are
19630 particularly large or there are many of them.
19632 To control the automatic loading of shared library symbols, use the
19636 @kindex set auto-solib-add
19637 @item set auto-solib-add @var{mode}
19638 If @var{mode} is @code{on}, symbols from all shared object libraries
19639 will be loaded automatically when the inferior begins execution, you
19640 attach to an independently started inferior, or when the dynamic linker
19641 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19642 is @code{off}, symbols must be loaded manually, using the
19643 @code{sharedlibrary} command. The default value is @code{on}.
19645 @cindex memory used for symbol tables
19646 If your program uses lots of shared libraries with debug info that
19647 takes large amounts of memory, you can decrease the @value{GDBN}
19648 memory footprint by preventing it from automatically loading the
19649 symbols from shared libraries. To that end, type @kbd{set
19650 auto-solib-add off} before running the inferior, then load each
19651 library whose debug symbols you do need with @kbd{sharedlibrary
19652 @var{regexp}}, where @var{regexp} is a regular expression that matches
19653 the libraries whose symbols you want to be loaded.
19655 @kindex show auto-solib-add
19656 @item show auto-solib-add
19657 Display the current autoloading mode.
19660 @cindex load shared library
19661 To explicitly load shared library symbols, use the @code{sharedlibrary}
19665 @kindex info sharedlibrary
19667 @item info share @var{regex}
19668 @itemx info sharedlibrary @var{regex}
19669 Print the names of the shared libraries which are currently loaded
19670 that match @var{regex}. If @var{regex} is omitted then print
19671 all shared libraries that are loaded.
19674 @item info dll @var{regex}
19675 This is an alias of @code{info sharedlibrary}.
19677 @kindex sharedlibrary
19679 @item sharedlibrary @var{regex}
19680 @itemx share @var{regex}
19681 Load shared object library symbols for files matching a
19682 Unix regular expression.
19683 As with files loaded automatically, it only loads shared libraries
19684 required by your program for a core file or after typing @code{run}. If
19685 @var{regex} is omitted all shared libraries required by your program are
19688 @item nosharedlibrary
19689 @kindex nosharedlibrary
19690 @cindex unload symbols from shared libraries
19691 Unload all shared object library symbols. This discards all symbols
19692 that have been loaded from all shared libraries. Symbols from shared
19693 libraries that were loaded by explicit user requests are not
19697 Sometimes you may wish that @value{GDBN} stops and gives you control
19698 when any of shared library events happen. The best way to do this is
19699 to use @code{catch load} and @code{catch unload} (@pxref{Set
19702 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19703 command for this. This command exists for historical reasons. It is
19704 less useful than setting a catchpoint, because it does not allow for
19705 conditions or commands as a catchpoint does.
19708 @item set stop-on-solib-events
19709 @kindex set stop-on-solib-events
19710 This command controls whether @value{GDBN} should give you control
19711 when the dynamic linker notifies it about some shared library event.
19712 The most common event of interest is loading or unloading of a new
19715 @item show stop-on-solib-events
19716 @kindex show stop-on-solib-events
19717 Show whether @value{GDBN} stops and gives you control when shared
19718 library events happen.
19721 Shared libraries are also supported in many cross or remote debugging
19722 configurations. @value{GDBN} needs to have access to the target's libraries;
19723 this can be accomplished either by providing copies of the libraries
19724 on the host system, or by asking @value{GDBN} to automatically retrieve the
19725 libraries from the target. If copies of the target libraries are
19726 provided, they need to be the same as the target libraries, although the
19727 copies on the target can be stripped as long as the copies on the host are
19730 @cindex where to look for shared libraries
19731 For remote debugging, you need to tell @value{GDBN} where the target
19732 libraries are, so that it can load the correct copies---otherwise, it
19733 may try to load the host's libraries. @value{GDBN} has two variables
19734 to specify the search directories for target libraries.
19737 @cindex prefix for executable and shared library file names
19738 @cindex system root, alternate
19739 @kindex set solib-absolute-prefix
19740 @kindex set sysroot
19741 @item set sysroot @var{path}
19742 Use @var{path} as the system root for the program being debugged. Any
19743 absolute shared library paths will be prefixed with @var{path}; many
19744 runtime loaders store the absolute paths to the shared library in the
19745 target program's memory. When starting processes remotely, and when
19746 attaching to already-running processes (local or remote), their
19747 executable filenames will be prefixed with @var{path} if reported to
19748 @value{GDBN} as absolute by the operating system. If you use
19749 @code{set sysroot} to find executables and shared libraries, they need
19750 to be laid out in the same way that they are on the target, with
19751 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19754 If @var{path} starts with the sequence @file{target:} and the target
19755 system is remote then @value{GDBN} will retrieve the target binaries
19756 from the remote system. This is only supported when using a remote
19757 target that supports the @code{remote get} command (@pxref{File
19758 Transfer,,Sending files to a remote system}). The part of @var{path}
19759 following the initial @file{target:} (if present) is used as system
19760 root prefix on the remote file system. If @var{path} starts with the
19761 sequence @file{remote:} this is converted to the sequence
19762 @file{target:} by @code{set sysroot}@footnote{Historically the
19763 functionality to retrieve binaries from the remote system was
19764 provided by prefixing @var{path} with @file{remote:}}. If you want
19765 to specify a local system root using a directory that happens to be
19766 named @file{target:} or @file{remote:}, you need to use some
19767 equivalent variant of the name like @file{./target:}.
19769 For targets with an MS-DOS based filesystem, such as MS-Windows and
19770 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19771 absolute file name with @var{path}. But first, on Unix hosts,
19772 @value{GDBN} converts all backslash directory separators into forward
19773 slashes, because the backslash is not a directory separator on Unix:
19776 c:\foo\bar.dll @result{} c:/foo/bar.dll
19779 Then, @value{GDBN} attempts prefixing the target file name with
19780 @var{path}, and looks for the resulting file name in the host file
19784 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19787 If that does not find the binary, @value{GDBN} tries removing
19788 the @samp{:} character from the drive spec, both for convenience, and,
19789 for the case of the host file system not supporting file names with
19793 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19796 This makes it possible to have a system root that mirrors a target
19797 with more than one drive. E.g., you may want to setup your local
19798 copies of the target system shared libraries like so (note @samp{c} vs
19802 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19803 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19804 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19808 and point the system root at @file{/path/to/sysroot}, so that
19809 @value{GDBN} can find the correct copies of both
19810 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19812 If that still does not find the binary, @value{GDBN} tries
19813 removing the whole drive spec from the target file name:
19816 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19819 This last lookup makes it possible to not care about the drive name,
19820 if you don't want or need to.
19822 The @code{set solib-absolute-prefix} command is an alias for @code{set
19825 @cindex default system root
19826 @cindex @samp{--with-sysroot}
19827 You can set the default system root by using the configure-time
19828 @samp{--with-sysroot} option. If the system root is inside
19829 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19830 @samp{--exec-prefix}), then the default system root will be updated
19831 automatically if the installed @value{GDBN} is moved to a new
19834 @kindex show sysroot
19836 Display the current executable and shared library prefix.
19838 @kindex set solib-search-path
19839 @item set solib-search-path @var{path}
19840 If this variable is set, @var{path} is a colon-separated list of
19841 directories to search for shared libraries. @samp{solib-search-path}
19842 is used after @samp{sysroot} fails to locate the library, or if the
19843 path to the library is relative instead of absolute. If you want to
19844 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19845 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19846 finding your host's libraries. @samp{sysroot} is preferred; setting
19847 it to a nonexistent directory may interfere with automatic loading
19848 of shared library symbols.
19850 @kindex show solib-search-path
19851 @item show solib-search-path
19852 Display the current shared library search path.
19854 @cindex DOS file-name semantics of file names.
19855 @kindex set target-file-system-kind (unix|dos-based|auto)
19856 @kindex show target-file-system-kind
19857 @item set target-file-system-kind @var{kind}
19858 Set assumed file system kind for target reported file names.
19860 Shared library file names as reported by the target system may not
19861 make sense as is on the system @value{GDBN} is running on. For
19862 example, when remote debugging a target that has MS-DOS based file
19863 system semantics, from a Unix host, the target may be reporting to
19864 @value{GDBN} a list of loaded shared libraries with file names such as
19865 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19866 drive letters, so the @samp{c:\} prefix is not normally understood as
19867 indicating an absolute file name, and neither is the backslash
19868 normally considered a directory separator character. In that case,
19869 the native file system would interpret this whole absolute file name
19870 as a relative file name with no directory components. This would make
19871 it impossible to point @value{GDBN} at a copy of the remote target's
19872 shared libraries on the host using @code{set sysroot}, and impractical
19873 with @code{set solib-search-path}. Setting
19874 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19875 to interpret such file names similarly to how the target would, and to
19876 map them to file names valid on @value{GDBN}'s native file system
19877 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19878 to one of the supported file system kinds. In that case, @value{GDBN}
19879 tries to determine the appropriate file system variant based on the
19880 current target's operating system (@pxref{ABI, ,Configuring the
19881 Current ABI}). The supported file system settings are:
19885 Instruct @value{GDBN} to assume the target file system is of Unix
19886 kind. Only file names starting the forward slash (@samp{/}) character
19887 are considered absolute, and the directory separator character is also
19891 Instruct @value{GDBN} to assume the target file system is DOS based.
19892 File names starting with either a forward slash, or a drive letter
19893 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19894 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19895 considered directory separators.
19898 Instruct @value{GDBN} to use the file system kind associated with the
19899 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19900 This is the default.
19904 @cindex file name canonicalization
19905 @cindex base name differences
19906 When processing file names provided by the user, @value{GDBN}
19907 frequently needs to compare them to the file names recorded in the
19908 program's debug info. Normally, @value{GDBN} compares just the
19909 @dfn{base names} of the files as strings, which is reasonably fast
19910 even for very large programs. (The base name of a file is the last
19911 portion of its name, after stripping all the leading directories.)
19912 This shortcut in comparison is based upon the assumption that files
19913 cannot have more than one base name. This is usually true, but
19914 references to files that use symlinks or similar filesystem
19915 facilities violate that assumption. If your program records files
19916 using such facilities, or if you provide file names to @value{GDBN}
19917 using symlinks etc., you can set @code{basenames-may-differ} to
19918 @code{true} to instruct @value{GDBN} to completely canonicalize each
19919 pair of file names it needs to compare. This will make file-name
19920 comparisons accurate, but at a price of a significant slowdown.
19923 @item set basenames-may-differ
19924 @kindex set basenames-may-differ
19925 Set whether a source file may have multiple base names.
19927 @item show basenames-may-differ
19928 @kindex show basenames-may-differ
19929 Show whether a source file may have multiple base names.
19933 @section File Caching
19934 @cindex caching of opened files
19935 @cindex caching of bfd objects
19937 To speed up file loading, and reduce memory usage, @value{GDBN} will
19938 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19939 BFD, bfd, The Binary File Descriptor Library}. The following commands
19940 allow visibility and control of the caching behavior.
19943 @kindex maint info bfds
19944 @item maint info bfds
19945 This prints information about each @code{bfd} object that is known to
19948 @kindex maint set bfd-sharing
19949 @kindex maint show bfd-sharing
19950 @kindex bfd caching
19951 @item maint set bfd-sharing
19952 @item maint show bfd-sharing
19953 Control whether @code{bfd} objects can be shared. When sharing is
19954 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19955 than reopening the same file. Turning sharing off does not cause
19956 already shared @code{bfd} objects to be unshared, but all future files
19957 that are opened will create a new @code{bfd} object. Similarly,
19958 re-enabling sharing does not cause multiple existing @code{bfd}
19959 objects to be collapsed into a single shared @code{bfd} object.
19961 @kindex set debug bfd-cache @var{level}
19962 @kindex bfd caching
19963 @item set debug bfd-cache @var{level}
19964 Turns on debugging of the bfd cache, setting the level to @var{level}.
19966 @kindex show debug bfd-cache
19967 @kindex bfd caching
19968 @item show debug bfd-cache
19969 Show the current debugging level of the bfd cache.
19972 @node Separate Debug Files
19973 @section Debugging Information in Separate Files
19974 @cindex separate debugging information files
19975 @cindex debugging information in separate files
19976 @cindex @file{.debug} subdirectories
19977 @cindex debugging information directory, global
19978 @cindex global debugging information directories
19979 @cindex build ID, and separate debugging files
19980 @cindex @file{.build-id} directory
19982 @value{GDBN} allows you to put a program's debugging information in a
19983 file separate from the executable itself, in a way that allows
19984 @value{GDBN} to find and load the debugging information automatically.
19985 Since debugging information can be very large---sometimes larger
19986 than the executable code itself---some systems distribute debugging
19987 information for their executables in separate files, which users can
19988 install only when they need to debug a problem.
19990 @value{GDBN} supports two ways of specifying the separate debug info
19995 The executable contains a @dfn{debug link} that specifies the name of
19996 the separate debug info file. The separate debug file's name is
19997 usually @file{@var{executable}.debug}, where @var{executable} is the
19998 name of the corresponding executable file without leading directories
19999 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20000 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20001 checksum for the debug file, which @value{GDBN} uses to validate that
20002 the executable and the debug file came from the same build.
20005 The executable contains a @dfn{build ID}, a unique bit string that is
20006 also present in the corresponding debug info file. (This is supported
20007 only on some operating systems, when using the ELF or PE file formats
20008 for binary files and the @sc{gnu} Binutils.) For more details about
20009 this feature, see the description of the @option{--build-id}
20010 command-line option in @ref{Options, , Command Line Options, ld,
20011 The GNU Linker}. The debug info file's name is not specified
20012 explicitly by the build ID, but can be computed from the build ID, see
20016 Depending on the way the debug info file is specified, @value{GDBN}
20017 uses two different methods of looking for the debug file:
20021 For the ``debug link'' method, @value{GDBN} looks up the named file in
20022 the directory of the executable file, then in a subdirectory of that
20023 directory named @file{.debug}, and finally under each one of the
20024 global debug directories, in a subdirectory whose name is identical to
20025 the leading directories of the executable's absolute file name. (On
20026 MS-Windows/MS-DOS, the drive letter of the executable's leading
20027 directories is converted to a one-letter subdirectory, i.e.@:
20028 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20029 filesystems disallow colons in file names.)
20032 For the ``build ID'' method, @value{GDBN} looks in the
20033 @file{.build-id} subdirectory of each one of the global debug directories for
20034 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20035 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
20036 are the rest of the bit string. (Real build ID strings are 32 or more
20037 hex characters, not 10.)
20040 So, for example, suppose you ask @value{GDBN} to debug
20041 @file{/usr/bin/ls}, which has a debug link that specifies the
20042 file @file{ls.debug}, and a build ID whose value in hex is
20043 @code{abcdef1234}. If the list of the global debug directories includes
20044 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
20045 debug information files, in the indicated order:
20049 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
20051 @file{/usr/bin/ls.debug}
20053 @file{/usr/bin/.debug/ls.debug}
20055 @file{/usr/lib/debug/usr/bin/ls.debug}.
20058 @anchor{debug-file-directory}
20059 Global debugging info directories default to what is set by @value{GDBN}
20060 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
20061 you can also set the global debugging info directories, and view the list
20062 @value{GDBN} is currently using.
20066 @kindex set debug-file-directory
20067 @item set debug-file-directory @var{directories}
20068 Set the directories which @value{GDBN} searches for separate debugging
20069 information files to @var{directory}. Multiple path components can be set
20070 concatenating them by a path separator.
20072 @kindex show debug-file-directory
20073 @item show debug-file-directory
20074 Show the directories @value{GDBN} searches for separate debugging
20079 @cindex @code{.gnu_debuglink} sections
20080 @cindex debug link sections
20081 A debug link is a special section of the executable file named
20082 @code{.gnu_debuglink}. The section must contain:
20086 A filename, with any leading directory components removed, followed by
20089 zero to three bytes of padding, as needed to reach the next four-byte
20090 boundary within the section, and
20092 a four-byte CRC checksum, stored in the same endianness used for the
20093 executable file itself. The checksum is computed on the debugging
20094 information file's full contents by the function given below, passing
20095 zero as the @var{crc} argument.
20098 Any executable file format can carry a debug link, as long as it can
20099 contain a section named @code{.gnu_debuglink} with the contents
20102 @cindex @code{.note.gnu.build-id} sections
20103 @cindex build ID sections
20104 The build ID is a special section in the executable file (and in other
20105 ELF binary files that @value{GDBN} may consider). This section is
20106 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20107 It contains unique identification for the built files---the ID remains
20108 the same across multiple builds of the same build tree. The default
20109 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20110 content for the build ID string. The same section with an identical
20111 value is present in the original built binary with symbols, in its
20112 stripped variant, and in the separate debugging information file.
20114 The debugging information file itself should be an ordinary
20115 executable, containing a full set of linker symbols, sections, and
20116 debugging information. The sections of the debugging information file
20117 should have the same names, addresses, and sizes as the original file,
20118 but they need not contain any data---much like a @code{.bss} section
20119 in an ordinary executable.
20121 The @sc{gnu} binary utilities (Binutils) package includes the
20122 @samp{objcopy} utility that can produce
20123 the separated executable / debugging information file pairs using the
20124 following commands:
20127 @kbd{objcopy --only-keep-debug foo foo.debug}
20132 These commands remove the debugging
20133 information from the executable file @file{foo} and place it in the file
20134 @file{foo.debug}. You can use the first, second or both methods to link the
20139 The debug link method needs the following additional command to also leave
20140 behind a debug link in @file{foo}:
20143 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20146 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20147 a version of the @code{strip} command such that the command @kbd{strip foo -f
20148 foo.debug} has the same functionality as the two @code{objcopy} commands and
20149 the @code{ln -s} command above, together.
20152 Build ID gets embedded into the main executable using @code{ld --build-id} or
20153 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20154 compatibility fixes for debug files separation are present in @sc{gnu} binary
20155 utilities (Binutils) package since version 2.18.
20160 @cindex CRC algorithm definition
20161 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20162 IEEE 802.3 using the polynomial:
20164 @c TexInfo requires naked braces for multi-digit exponents for Tex
20165 @c output, but this causes HTML output to barf. HTML has to be set using
20166 @c raw commands. So we end up having to specify this equation in 2
20171 <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>
20172 + <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
20178 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20179 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20183 The function is computed byte at a time, taking the least
20184 significant bit of each byte first. The initial pattern
20185 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20186 the final result is inverted to ensure trailing zeros also affect the
20189 @emph{Note:} This is the same CRC polynomial as used in handling the
20190 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20191 However in the case of the Remote Serial Protocol, the CRC is computed
20192 @emph{most} significant bit first, and the result is not inverted, so
20193 trailing zeros have no effect on the CRC value.
20195 To complete the description, we show below the code of the function
20196 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20197 initially supplied @code{crc} argument means that an initial call to
20198 this function passing in zero will start computing the CRC using
20201 @kindex gnu_debuglink_crc32
20204 gnu_debuglink_crc32 (unsigned long crc,
20205 unsigned char *buf, size_t len)
20207 static const unsigned long crc32_table[256] =
20209 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20210 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20211 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20212 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20213 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20214 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20215 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20216 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20217 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20218 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20219 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20220 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20221 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20222 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20223 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20224 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20225 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20226 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20227 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20228 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20229 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20230 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20231 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20232 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20233 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20234 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20235 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20236 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20237 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20238 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20239 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20240 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20241 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20242 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20243 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20244 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20245 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20246 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20247 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20248 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20249 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20250 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20251 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20252 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20253 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20254 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20255 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20256 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20257 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20258 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20259 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20262 unsigned char *end;
20264 crc = ~crc & 0xffffffff;
20265 for (end = buf + len; buf < end; ++buf)
20266 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20267 return ~crc & 0xffffffff;
20272 This computation does not apply to the ``build ID'' method.
20274 @node MiniDebugInfo
20275 @section Debugging information in a special section
20276 @cindex separate debug sections
20277 @cindex @samp{.gnu_debugdata} section
20279 Some systems ship pre-built executables and libraries that have a
20280 special @samp{.gnu_debugdata} section. This feature is called
20281 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20282 is used to supply extra symbols for backtraces.
20284 The intent of this section is to provide extra minimal debugging
20285 information for use in simple backtraces. It is not intended to be a
20286 replacement for full separate debugging information (@pxref{Separate
20287 Debug Files}). The example below shows the intended use; however,
20288 @value{GDBN} does not currently put restrictions on what sort of
20289 debugging information might be included in the section.
20291 @value{GDBN} has support for this extension. If the section exists,
20292 then it is used provided that no other source of debugging information
20293 can be found, and that @value{GDBN} was configured with LZMA support.
20295 This section can be easily created using @command{objcopy} and other
20296 standard utilities:
20299 # Extract the dynamic symbols from the main binary, there is no need
20300 # to also have these in the normal symbol table.
20301 nm -D @var{binary} --format=posix --defined-only \
20302 | awk '@{ print $1 @}' | sort > dynsyms
20304 # Extract all the text (i.e. function) symbols from the debuginfo.
20305 # (Note that we actually also accept "D" symbols, for the benefit
20306 # of platforms like PowerPC64 that use function descriptors.)
20307 nm @var{binary} --format=posix --defined-only \
20308 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20311 # Keep all the function symbols not already in the dynamic symbol
20313 comm -13 dynsyms funcsyms > keep_symbols
20315 # Separate full debug info into debug binary.
20316 objcopy --only-keep-debug @var{binary} debug
20318 # Copy the full debuginfo, keeping only a minimal set of symbols and
20319 # removing some unnecessary sections.
20320 objcopy -S --remove-section .gdb_index --remove-section .comment \
20321 --keep-symbols=keep_symbols debug mini_debuginfo
20323 # Drop the full debug info from the original binary.
20324 strip --strip-all -R .comment @var{binary}
20326 # Inject the compressed data into the .gnu_debugdata section of the
20329 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20333 @section Index Files Speed Up @value{GDBN}
20334 @cindex index files
20335 @cindex @samp{.gdb_index} section
20337 When @value{GDBN} finds a symbol file, it scans the symbols in the
20338 file in order to construct an internal symbol table. This lets most
20339 @value{GDBN} operations work quickly---at the cost of a delay early
20340 on. For large programs, this delay can be quite lengthy, so
20341 @value{GDBN} provides a way to build an index, which speeds up
20344 For convenience, @value{GDBN} comes with a program,
20345 @command{gdb-add-index}, which can be used to add the index to a
20346 symbol file. It takes the symbol file as its only argument:
20349 $ gdb-add-index symfile
20352 @xref{gdb-add-index}.
20354 It is also possible to do the work manually. Here is what
20355 @command{gdb-add-index} does behind the curtains.
20357 The index is stored as a section in the symbol file. @value{GDBN} can
20358 write the index to a file, then you can put it into the symbol file
20359 using @command{objcopy}.
20361 To create an index file, use the @code{save gdb-index} command:
20364 @item save gdb-index [-dwarf-5] @var{directory}
20365 @kindex save gdb-index
20366 Create index files for all symbol files currently known by
20367 @value{GDBN}. For each known @var{symbol-file}, this command by
20368 default creates it produces a single file
20369 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20370 the @option{-dwarf-5} option, it produces 2 files:
20371 @file{@var{symbol-file}.debug_names} and
20372 @file{@var{symbol-file}.debug_str}. The files are created in the
20373 given @var{directory}.
20376 Once you have created an index file you can merge it into your symbol
20377 file, here named @file{symfile}, using @command{objcopy}:
20380 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20381 --set-section-flags .gdb_index=readonly symfile symfile
20384 Or for @code{-dwarf-5}:
20387 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20388 $ cat symfile.debug_str >>symfile.debug_str.new
20389 $ objcopy --add-section .debug_names=symfile.gdb-index \
20390 --set-section-flags .debug_names=readonly \
20391 --update-section .debug_str=symfile.debug_str.new symfile symfile
20394 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20395 sections that have been deprecated. Usually they are deprecated because
20396 they are missing a new feature or have performance issues.
20397 To tell @value{GDBN} to use a deprecated index section anyway
20398 specify @code{set use-deprecated-index-sections on}.
20399 The default is @code{off}.
20400 This can speed up startup, but may result in some functionality being lost.
20401 @xref{Index Section Format}.
20403 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20404 must be done before gdb reads the file. The following will not work:
20407 $ gdb -ex "set use-deprecated-index-sections on" <program>
20410 Instead you must do, for example,
20413 $ gdb -iex "set use-deprecated-index-sections on" <program>
20416 There are currently some limitation on indices. They only work when
20417 for DWARF debugging information, not stabs. And, they do not
20418 currently work for programs using Ada.
20420 @subsection Automatic symbol index cache
20422 @cindex automatic symbol index cache
20423 It is possible for @value{GDBN} to automatically save a copy of this index in a
20424 cache on disk and retrieve it from there when loading the same binary in the
20425 future. This feature can be turned on with @kbd{set index-cache on}. The
20426 following commands can be used to tweak the behavior of the index cache.
20430 @kindex set index-cache
20431 @item set index-cache on
20432 @itemx set index-cache off
20433 Enable or disable the use of the symbol index cache.
20435 @item set index-cache directory @var{directory}
20436 @kindex show index-cache
20437 @itemx show index-cache directory
20438 Set/show the directory where index files will be saved.
20440 The default value for this directory depends on the host platform. On
20441 most systems, the index is cached in the @file{gdb} subdirectory of
20442 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20443 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20444 of your home directory. However, on some systems, the default may
20445 differ according to local convention.
20447 There is no limit on the disk space used by index cache. It is perfectly safe
20448 to delete the content of that directory to free up disk space.
20450 @item show index-cache stats
20451 Print the number of cache hits and misses since the launch of @value{GDBN}.
20455 @node Symbol Errors
20456 @section Errors Reading Symbol Files
20458 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20459 such as symbol types it does not recognize, or known bugs in compiler
20460 output. By default, @value{GDBN} does not notify you of such problems, since
20461 they are relatively common and primarily of interest to people
20462 debugging compilers. If you are interested in seeing information
20463 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20464 only one message about each such type of problem, no matter how many
20465 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20466 to see how many times the problems occur, with the @code{set
20467 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20470 The messages currently printed, and their meanings, include:
20473 @item inner block not inside outer block in @var{symbol}
20475 The symbol information shows where symbol scopes begin and end
20476 (such as at the start of a function or a block of statements). This
20477 error indicates that an inner scope block is not fully contained
20478 in its outer scope blocks.
20480 @value{GDBN} circumvents the problem by treating the inner block as if it had
20481 the same scope as the outer block. In the error message, @var{symbol}
20482 may be shown as ``@code{(don't know)}'' if the outer block is not a
20485 @item block at @var{address} out of order
20487 The symbol information for symbol scope blocks should occur in
20488 order of increasing addresses. This error indicates that it does not
20491 @value{GDBN} does not circumvent this problem, and has trouble
20492 locating symbols in the source file whose symbols it is reading. (You
20493 can often determine what source file is affected by specifying
20494 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20497 @item bad block start address patched
20499 The symbol information for a symbol scope block has a start address
20500 smaller than the address of the preceding source line. This is known
20501 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20503 @value{GDBN} circumvents the problem by treating the symbol scope block as
20504 starting on the previous source line.
20506 @item bad string table offset in symbol @var{n}
20509 Symbol number @var{n} contains a pointer into the string table which is
20510 larger than the size of the string table.
20512 @value{GDBN} circumvents the problem by considering the symbol to have the
20513 name @code{foo}, which may cause other problems if many symbols end up
20516 @item unknown symbol type @code{0x@var{nn}}
20518 The symbol information contains new data types that @value{GDBN} does
20519 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20520 uncomprehended information, in hexadecimal.
20522 @value{GDBN} circumvents the error by ignoring this symbol information.
20523 This usually allows you to debug your program, though certain symbols
20524 are not accessible. If you encounter such a problem and feel like
20525 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20526 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20527 and examine @code{*bufp} to see the symbol.
20529 @item stub type has NULL name
20531 @value{GDBN} could not find the full definition for a struct or class.
20533 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20534 The symbol information for a C@t{++} member function is missing some
20535 information that recent versions of the compiler should have output for
20538 @item info mismatch between compiler and debugger
20540 @value{GDBN} could not parse a type specification output by the compiler.
20545 @section GDB Data Files
20547 @cindex prefix for data files
20548 @value{GDBN} will sometimes read an auxiliary data file. These files
20549 are kept in a directory known as the @dfn{data directory}.
20551 You can set the data directory's name, and view the name @value{GDBN}
20552 is currently using.
20555 @kindex set data-directory
20556 @item set data-directory @var{directory}
20557 Set the directory which @value{GDBN} searches for auxiliary data files
20558 to @var{directory}.
20560 @kindex show data-directory
20561 @item show data-directory
20562 Show the directory @value{GDBN} searches for auxiliary data files.
20565 @cindex default data directory
20566 @cindex @samp{--with-gdb-datadir}
20567 You can set the default data directory by using the configure-time
20568 @samp{--with-gdb-datadir} option. If the data directory is inside
20569 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20570 @samp{--exec-prefix}), then the default data directory will be updated
20571 automatically if the installed @value{GDBN} is moved to a new
20574 The data directory may also be specified with the
20575 @code{--data-directory} command line option.
20576 @xref{Mode Options}.
20579 @chapter Specifying a Debugging Target
20581 @cindex debugging target
20582 A @dfn{target} is the execution environment occupied by your program.
20584 Often, @value{GDBN} runs in the same host environment as your program;
20585 in that case, the debugging target is specified as a side effect when
20586 you use the @code{file} or @code{core} commands. When you need more
20587 flexibility---for example, running @value{GDBN} on a physically separate
20588 host, or controlling a standalone system over a serial port or a
20589 realtime system over a TCP/IP connection---you can use the @code{target}
20590 command to specify one of the target types configured for @value{GDBN}
20591 (@pxref{Target Commands, ,Commands for Managing Targets}).
20593 @cindex target architecture
20594 It is possible to build @value{GDBN} for several different @dfn{target
20595 architectures}. When @value{GDBN} is built like that, you can choose
20596 one of the available architectures with the @kbd{set architecture}
20600 @kindex set architecture
20601 @kindex show architecture
20602 @item set architecture @var{arch}
20603 This command sets the current target architecture to @var{arch}. The
20604 value of @var{arch} can be @code{"auto"}, in addition to one of the
20605 supported architectures.
20607 @item show architecture
20608 Show the current target architecture.
20610 @item set processor
20612 @kindex set processor
20613 @kindex show processor
20614 These are alias commands for, respectively, @code{set architecture}
20615 and @code{show architecture}.
20619 * Active Targets:: Active targets
20620 * Target Commands:: Commands for managing targets
20621 * Byte Order:: Choosing target byte order
20624 @node Active Targets
20625 @section Active Targets
20627 @cindex stacking targets
20628 @cindex active targets
20629 @cindex multiple targets
20631 There are multiple classes of targets such as: processes, executable files or
20632 recording sessions. Core files belong to the process class, making core file
20633 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20634 on multiple active targets, one in each class. This allows you to (for
20635 example) start a process and inspect its activity, while still having access to
20636 the executable file after the process finishes. Or if you start process
20637 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20638 presented a virtual layer of the recording target, while the process target
20639 remains stopped at the chronologically last point of the process execution.
20641 Use the @code{core-file} and @code{exec-file} commands to select a new core
20642 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20643 specify as a target a process that is already running, use the @code{attach}
20644 command (@pxref{Attach, ,Debugging an Already-running Process}).
20646 @node Target Commands
20647 @section Commands for Managing Targets
20650 @item target @var{type} @var{parameters}
20651 Connects the @value{GDBN} host environment to a target machine or
20652 process. A target is typically a protocol for talking to debugging
20653 facilities. You use the argument @var{type} to specify the type or
20654 protocol of the target machine.
20656 Further @var{parameters} are interpreted by the target protocol, but
20657 typically include things like device names or host names to connect
20658 with, process numbers, and baud rates.
20660 The @code{target} command does not repeat if you press @key{RET} again
20661 after executing the command.
20663 @kindex help target
20665 Displays the names of all targets available. To display targets
20666 currently selected, use either @code{info target} or @code{info files}
20667 (@pxref{Files, ,Commands to Specify Files}).
20669 @item help target @var{name}
20670 Describe a particular target, including any parameters necessary to
20673 @kindex set gnutarget
20674 @item set gnutarget @var{args}
20675 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20676 knows whether it is reading an @dfn{executable},
20677 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20678 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20679 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20682 @emph{Warning:} To specify a file format with @code{set gnutarget},
20683 you must know the actual BFD name.
20687 @xref{Files, , Commands to Specify Files}.
20689 @kindex show gnutarget
20690 @item show gnutarget
20691 Use the @code{show gnutarget} command to display what file format
20692 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20693 @value{GDBN} will determine the file format for each file automatically,
20694 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20697 @cindex common targets
20698 Here are some common targets (available, or not, depending on the GDB
20703 @item target exec @var{program}
20704 @cindex executable file target
20705 An executable file. @samp{target exec @var{program}} is the same as
20706 @samp{exec-file @var{program}}.
20708 @item target core @var{filename}
20709 @cindex core dump file target
20710 A core dump file. @samp{target core @var{filename}} is the same as
20711 @samp{core-file @var{filename}}.
20713 @item target remote @var{medium}
20714 @cindex remote target
20715 A remote system connected to @value{GDBN} via a serial line or network
20716 connection. This command tells @value{GDBN} to use its own remote
20717 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20719 For example, if you have a board connected to @file{/dev/ttya} on the
20720 machine running @value{GDBN}, you could say:
20723 target remote /dev/ttya
20726 @code{target remote} supports the @code{load} command. This is only
20727 useful if you have some other way of getting the stub to the target
20728 system, and you can put it somewhere in memory where it won't get
20729 clobbered by the download.
20731 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20732 @cindex built-in simulator target
20733 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20741 works; however, you cannot assume that a specific memory map, device
20742 drivers, or even basic I/O is available, although some simulators do
20743 provide these. For info about any processor-specific simulator details,
20744 see the appropriate section in @ref{Embedded Processors, ,Embedded
20747 @item target native
20748 @cindex native target
20749 Setup for local/native process debugging. Useful to make the
20750 @code{run} command spawn native processes (likewise @code{attach},
20751 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20752 (@pxref{set auto-connect-native-target}).
20756 Different targets are available on different configurations of @value{GDBN};
20757 your configuration may have more or fewer targets.
20759 Many remote targets require you to download the executable's code once
20760 you've successfully established a connection. You may wish to control
20761 various aspects of this process.
20766 @kindex set hash@r{, for remote monitors}
20767 @cindex hash mark while downloading
20768 This command controls whether a hash mark @samp{#} is displayed while
20769 downloading a file to the remote monitor. If on, a hash mark is
20770 displayed after each S-record is successfully downloaded to the
20774 @kindex show hash@r{, for remote monitors}
20775 Show the current status of displaying the hash mark.
20777 @item set debug monitor
20778 @kindex set debug monitor
20779 @cindex display remote monitor communications
20780 Enable or disable display of communications messages between
20781 @value{GDBN} and the remote monitor.
20783 @item show debug monitor
20784 @kindex show debug monitor
20785 Show the current status of displaying communications between
20786 @value{GDBN} and the remote monitor.
20791 @kindex load @var{filename} @var{offset}
20792 @item load @var{filename} @var{offset}
20794 Depending on what remote debugging facilities are configured into
20795 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20796 is meant to make @var{filename} (an executable) available for debugging
20797 on the remote system---by downloading, or dynamic linking, for example.
20798 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20799 the @code{add-symbol-file} command.
20801 If your @value{GDBN} does not have a @code{load} command, attempting to
20802 execute it gets the error message ``@code{You can't do that when your
20803 target is @dots{}}''
20805 The file is loaded at whatever address is specified in the executable.
20806 For some object file formats, you can specify the load address when you
20807 link the program; for other formats, like a.out, the object file format
20808 specifies a fixed address.
20809 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20811 It is also possible to tell @value{GDBN} to load the executable file at a
20812 specific offset described by the optional argument @var{offset}. When
20813 @var{offset} is provided, @var{filename} must also be provided.
20815 Depending on the remote side capabilities, @value{GDBN} may be able to
20816 load programs into flash memory.
20818 @code{load} does not repeat if you press @key{RET} again after using it.
20823 @kindex flash-erase
20825 @anchor{flash-erase}
20827 Erases all known flash memory regions on the target.
20832 @section Choosing Target Byte Order
20834 @cindex choosing target byte order
20835 @cindex target byte order
20837 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20838 offer the ability to run either big-endian or little-endian byte
20839 orders. Usually the executable or symbol will include a bit to
20840 designate the endian-ness, and you will not need to worry about
20841 which to use. However, you may still find it useful to adjust
20842 @value{GDBN}'s idea of processor endian-ness manually.
20846 @item set endian big
20847 Instruct @value{GDBN} to assume the target is big-endian.
20849 @item set endian little
20850 Instruct @value{GDBN} to assume the target is little-endian.
20852 @item set endian auto
20853 Instruct @value{GDBN} to use the byte order associated with the
20857 Display @value{GDBN}'s current idea of the target byte order.
20861 If the @code{set endian auto} mode is in effect and no executable has
20862 been selected, then the endianness used is the last one chosen either
20863 by one of the @code{set endian big} and @code{set endian little}
20864 commands or by inferring from the last executable used. If no
20865 endianness has been previously chosen, then the default for this mode
20866 is inferred from the target @value{GDBN} has been built for, and is
20867 @code{little} if the name of the target CPU has an @code{el} suffix
20868 and @code{big} otherwise.
20870 Note that these commands merely adjust interpretation of symbolic
20871 data on the host, and that they have absolutely no effect on the
20875 @node Remote Debugging
20876 @chapter Debugging Remote Programs
20877 @cindex remote debugging
20879 If you are trying to debug a program running on a machine that cannot run
20880 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20881 For example, you might use remote debugging on an operating system kernel,
20882 or on a small system which does not have a general purpose operating system
20883 powerful enough to run a full-featured debugger.
20885 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20886 to make this work with particular debugging targets. In addition,
20887 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20888 but not specific to any particular target system) which you can use if you
20889 write the remote stubs---the code that runs on the remote system to
20890 communicate with @value{GDBN}.
20892 Other remote targets may be available in your
20893 configuration of @value{GDBN}; use @code{help target} to list them.
20896 * Connecting:: Connecting to a remote target
20897 * File Transfer:: Sending files to a remote system
20898 * Server:: Using the gdbserver program
20899 * Remote Configuration:: Remote configuration
20900 * Remote Stub:: Implementing a remote stub
20904 @section Connecting to a Remote Target
20905 @cindex remote debugging, connecting
20906 @cindex @code{gdbserver}, connecting
20907 @cindex remote debugging, types of connections
20908 @cindex @code{gdbserver}, types of connections
20909 @cindex @code{gdbserver}, @code{target remote} mode
20910 @cindex @code{gdbserver}, @code{target extended-remote} mode
20912 This section describes how to connect to a remote target, including the
20913 types of connections and their differences, how to set up executable and
20914 symbol files on the host and target, and the commands used for
20915 connecting to and disconnecting from the remote target.
20917 @subsection Types of Remote Connections
20919 @value{GDBN} supports two types of remote connections, @code{target remote}
20920 mode and @code{target extended-remote} mode. Note that many remote targets
20921 support only @code{target remote} mode. There are several major
20922 differences between the two types of connections, enumerated here:
20926 @cindex remote debugging, detach and program exit
20927 @item Result of detach or program exit
20928 @strong{With target remote mode:} When the debugged program exits or you
20929 detach from it, @value{GDBN} disconnects from the target. When using
20930 @code{gdbserver}, @code{gdbserver} will exit.
20932 @strong{With target extended-remote mode:} When the debugged program exits or
20933 you detach from it, @value{GDBN} remains connected to the target, even
20934 though no program is running. You can rerun the program, attach to a
20935 running program, or use @code{monitor} commands specific to the target.
20937 When using @code{gdbserver} in this case, it does not exit unless it was
20938 invoked using the @option{--once} option. If the @option{--once} option
20939 was not used, you can ask @code{gdbserver} to exit using the
20940 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20942 @item Specifying the program to debug
20943 For both connection types you use the @code{file} command to specify the
20944 program on the host system. If you are using @code{gdbserver} there are
20945 some differences in how to specify the location of the program on the
20948 @strong{With target remote mode:} You must either specify the program to debug
20949 on the @code{gdbserver} command line or use the @option{--attach} option
20950 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20952 @cindex @option{--multi}, @code{gdbserver} option
20953 @strong{With target extended-remote mode:} You may specify the program to debug
20954 on the @code{gdbserver} command line, or you can load the program or attach
20955 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20957 @anchor{--multi Option in Types of Remote Connnections}
20958 You can start @code{gdbserver} without supplying an initial command to run
20959 or process ID to attach. To do this, use the @option{--multi} command line
20960 option. Then you can connect using @code{target extended-remote} and start
20961 the program you want to debug (see below for details on using the
20962 @code{run} command in this scenario). Note that the conditions under which
20963 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20964 (@code{target remote} or @code{target extended-remote}). The
20965 @option{--multi} option to @code{gdbserver} has no influence on that.
20967 @item The @code{run} command
20968 @strong{With target remote mode:} The @code{run} command is not
20969 supported. Once a connection has been established, you can use all
20970 the usual @value{GDBN} commands to examine and change data. The
20971 remote program is already running, so you can use commands like
20972 @kbd{step} and @kbd{continue}.
20974 @strong{With target extended-remote mode:} The @code{run} command is
20975 supported. The @code{run} command uses the value set by
20976 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20977 the program to run. Command line arguments are supported, except for
20978 wildcard expansion and I/O redirection (@pxref{Arguments}).
20980 If you specify the program to debug on the command line, then the
20981 @code{run} command is not required to start execution, and you can
20982 resume using commands like @kbd{step} and @kbd{continue} as with
20983 @code{target remote} mode.
20985 @anchor{Attaching in Types of Remote Connections}
20987 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20988 not supported. To attach to a running program using @code{gdbserver}, you
20989 must use the @option{--attach} option (@pxref{Running gdbserver}).
20991 @strong{With target extended-remote mode:} To attach to a running program,
20992 you may use the @code{attach} command after the connection has been
20993 established. If you are using @code{gdbserver}, you may also invoke
20994 @code{gdbserver} using the @option{--attach} option
20995 (@pxref{Running gdbserver}).
20999 @anchor{Host and target files}
21000 @subsection Host and Target Files
21001 @cindex remote debugging, symbol files
21002 @cindex symbol files, remote debugging
21004 @value{GDBN}, running on the host, needs access to symbol and debugging
21005 information for your program running on the target. This requires
21006 access to an unstripped copy of your program, and possibly any associated
21007 symbol files. Note that this section applies equally to both @code{target
21008 remote} mode and @code{target extended-remote} mode.
21010 Some remote targets (@pxref{qXfer executable filename read}, and
21011 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
21012 the same connection used to communicate with @value{GDBN}. With such a
21013 target, if the remote program is unstripped, the only command you need is
21014 @code{target remote} (or @code{target extended-remote}).
21016 If the remote program is stripped, or the target does not support remote
21017 program file access, start up @value{GDBN} using the name of the local
21018 unstripped copy of your program as the first argument, or use the
21019 @code{file} command. Use @code{set sysroot} to specify the location (on
21020 the host) of target libraries (unless your @value{GDBN} was compiled with
21021 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21022 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21025 The symbol file and target libraries must exactly match the executable
21026 and libraries on the target, with one exception: the files on the host
21027 system should not be stripped, even if the files on the target system
21028 are. Mismatched or missing files will lead to confusing results
21029 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21030 files may also prevent @code{gdbserver} from debugging multi-threaded
21033 @subsection Remote Connection Commands
21034 @cindex remote connection commands
21035 @value{GDBN} can communicate with the target over a serial line, a
21036 local Unix domain socket, or
21037 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
21038 each case, @value{GDBN} uses the same protocol for debugging your
21039 program; only the medium carrying the debugging packets varies. The
21040 @code{target remote} and @code{target extended-remote} commands
21041 establish a connection to the target. Both commands accept the same
21042 arguments, which indicate the medium to use:
21046 @item target remote @var{serial-device}
21047 @itemx target extended-remote @var{serial-device}
21048 @cindex serial line, @code{target remote}
21049 Use @var{serial-device} to communicate with the target. For example,
21050 to use a serial line connected to the device named @file{/dev/ttyb}:
21053 target remote /dev/ttyb
21056 If you're using a serial line, you may want to give @value{GDBN} the
21057 @samp{--baud} option, or use the @code{set serial baud} command
21058 (@pxref{Remote Configuration, set serial baud}) before the
21059 @code{target} command.
21061 @item target remote @var{local-socket}
21062 @itemx target extended-remote @var{local-socket}
21063 @cindex local socket, @code{target remote}
21064 @cindex Unix domain socket
21065 Use @var{local-socket} to communicate with the target. For example,
21066 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
21069 target remote /tmp/gdb-socket0
21072 Note that this command has the same form as the command to connect
21073 to a serial line. @value{GDBN} will automatically determine which
21074 kind of file you have specified and will make the appropriate kind
21076 This feature is not available if the host system does not support
21077 Unix domain sockets.
21079 @item target remote @code{@var{host}:@var{port}}
21080 @itemx target remote @code{@var{[host]}:@var{port}}
21081 @itemx target remote @code{tcp:@var{host}:@var{port}}
21082 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21083 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21084 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21085 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21086 @itemx target extended-remote @code{@var{host}:@var{port}}
21087 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21088 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21089 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21090 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21091 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21092 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21093 @cindex @acronym{TCP} port, @code{target remote}
21094 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21095 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21096 address, or a numeric @acronym{IPv6} address (with or without the
21097 square brackets to separate the address from the port); @var{port}
21098 must be a decimal number. The @var{host} could be the target machine
21099 itself, if it is directly connected to the net, or it might be a
21100 terminal server which in turn has a serial line to the target.
21102 For example, to connect to port 2828 on a terminal server named
21106 target remote manyfarms:2828
21109 To connect to port 2828 on a terminal server whose address is
21110 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21111 square bracket syntax:
21114 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21118 or explicitly specify the @acronym{IPv6} protocol:
21121 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21124 This last example may be confusing to the reader, because there is no
21125 visible separation between the hostname and the port number.
21126 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21127 using square brackets for clarity. However, it is important to
21128 mention that for @value{GDBN} there is no ambiguity: the number after
21129 the last colon is considered to be the port number.
21131 If your remote target is actually running on the same machine as your
21132 debugger session (e.g.@: a simulator for your target running on the
21133 same host), you can omit the hostname. For example, to connect to
21134 port 1234 on your local machine:
21137 target remote :1234
21141 Note that the colon is still required here.
21143 @item target remote @code{udp:@var{host}:@var{port}}
21144 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21145 @itemx target remote @code{udp4:@var{host}:@var{port}}
21146 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21147 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21148 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21149 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21150 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21151 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21152 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21153 @cindex @acronym{UDP} port, @code{target remote}
21154 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21155 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21158 target remote udp:manyfarms:2828
21161 When using a @acronym{UDP} connection for remote debugging, you should
21162 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21163 can silently drop packets on busy or unreliable networks, which will
21164 cause havoc with your debugging session.
21166 @item target remote | @var{command}
21167 @itemx target extended-remote | @var{command}
21168 @cindex pipe, @code{target remote} to
21169 Run @var{command} in the background and communicate with it using a
21170 pipe. The @var{command} is a shell command, to be parsed and expanded
21171 by the system's command shell, @code{/bin/sh}; it should expect remote
21172 protocol packets on its standard input, and send replies on its
21173 standard output. You could use this to run a stand-alone simulator
21174 that speaks the remote debugging protocol, to make net connections
21175 using programs like @code{ssh}, or for other similar tricks.
21177 If @var{command} closes its standard output (perhaps by exiting),
21178 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21179 program has already exited, this will have no effect.)
21183 @cindex interrupting remote programs
21184 @cindex remote programs, interrupting
21185 Whenever @value{GDBN} is waiting for the remote program, if you type the
21186 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21187 program. This may or may not succeed, depending in part on the hardware
21188 and the serial drivers the remote system uses. If you type the
21189 interrupt character once again, @value{GDBN} displays this prompt:
21192 Interrupted while waiting for the program.
21193 Give up (and stop debugging it)? (y or n)
21196 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21197 the remote debugging session. (If you decide you want to try again later,
21198 you can use @kbd{target remote} again to connect once more.) If you type
21199 @kbd{n}, @value{GDBN} goes back to waiting.
21201 In @code{target extended-remote} mode, typing @kbd{n} will leave
21202 @value{GDBN} connected to the target.
21205 @kindex detach (remote)
21207 When you have finished debugging the remote program, you can use the
21208 @code{detach} command to release it from @value{GDBN} control.
21209 Detaching from the target normally resumes its execution, but the results
21210 will depend on your particular remote stub. After the @code{detach}
21211 command in @code{target remote} mode, @value{GDBN} is free to connect to
21212 another target. In @code{target extended-remote} mode, @value{GDBN} is
21213 still connected to the target.
21217 The @code{disconnect} command closes the connection to the target, and
21218 the target is generally not resumed. It will wait for @value{GDBN}
21219 (this instance or another one) to connect and continue debugging. After
21220 the @code{disconnect} command, @value{GDBN} is again free to connect to
21223 @cindex send command to remote monitor
21224 @cindex extend @value{GDBN} for remote targets
21225 @cindex add new commands for external monitor
21227 @item monitor @var{cmd}
21228 This command allows you to send arbitrary commands directly to the
21229 remote monitor. Since @value{GDBN} doesn't care about the commands it
21230 sends like this, this command is the way to extend @value{GDBN}---you
21231 can add new commands that only the external monitor will understand
21235 @node File Transfer
21236 @section Sending files to a remote system
21237 @cindex remote target, file transfer
21238 @cindex file transfer
21239 @cindex sending files to remote systems
21241 Some remote targets offer the ability to transfer files over the same
21242 connection used to communicate with @value{GDBN}. This is convenient
21243 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21244 running @code{gdbserver} over a network interface. For other targets,
21245 e.g.@: embedded devices with only a single serial port, this may be
21246 the only way to upload or download files.
21248 Not all remote targets support these commands.
21252 @item remote put @var{hostfile} @var{targetfile}
21253 Copy file @var{hostfile} from the host system (the machine running
21254 @value{GDBN}) to @var{targetfile} on the target system.
21257 @item remote get @var{targetfile} @var{hostfile}
21258 Copy file @var{targetfile} from the target system to @var{hostfile}
21259 on the host system.
21261 @kindex remote delete
21262 @item remote delete @var{targetfile}
21263 Delete @var{targetfile} from the target system.
21268 @section Using the @code{gdbserver} Program
21271 @cindex remote connection without stubs
21272 @code{gdbserver} is a control program for Unix-like systems, which
21273 allows you to connect your program with a remote @value{GDBN} via
21274 @code{target remote} or @code{target extended-remote}---but without
21275 linking in the usual debugging stub.
21277 @code{gdbserver} is not a complete replacement for the debugging stubs,
21278 because it requires essentially the same operating-system facilities
21279 that @value{GDBN} itself does. In fact, a system that can run
21280 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21281 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21282 because it is a much smaller program than @value{GDBN} itself. It is
21283 also easier to port than all of @value{GDBN}, so you may be able to get
21284 started more quickly on a new system by using @code{gdbserver}.
21285 Finally, if you develop code for real-time systems, you may find that
21286 the tradeoffs involved in real-time operation make it more convenient to
21287 do as much development work as possible on another system, for example
21288 by cross-compiling. You can use @code{gdbserver} to make a similar
21289 choice for debugging.
21291 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21292 or a TCP connection, using the standard @value{GDBN} remote serial
21296 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21297 Do not run @code{gdbserver} connected to any public network; a
21298 @value{GDBN} connection to @code{gdbserver} provides access to the
21299 target system with the same privileges as the user running
21303 @anchor{Running gdbserver}
21304 @subsection Running @code{gdbserver}
21305 @cindex arguments, to @code{gdbserver}
21306 @cindex @code{gdbserver}, command-line arguments
21308 Run @code{gdbserver} on the target system. You need a copy of the
21309 program you want to debug, including any libraries it requires.
21310 @code{gdbserver} does not need your program's symbol table, so you can
21311 strip the program if necessary to save space. @value{GDBN} on the host
21312 system does all the symbol handling.
21314 To use the server, you must tell it how to communicate with @value{GDBN};
21315 the name of your program; and the arguments for your program. The usual
21319 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21322 @var{comm} is either a device name (to use a serial line), or a TCP
21323 hostname and portnumber, or @code{-} or @code{stdio} to use
21324 stdin/stdout of @code{gdbserver}.
21325 For example, to debug Emacs with the argument
21326 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21330 target> gdbserver /dev/com1 emacs foo.txt
21333 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21336 To use a TCP connection instead of a serial line:
21339 target> gdbserver host:2345 emacs foo.txt
21342 The only difference from the previous example is the first argument,
21343 specifying that you are communicating with the host @value{GDBN} via
21344 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21345 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21346 (Currently, the @samp{host} part is ignored.) You can choose any number
21347 you want for the port number as long as it does not conflict with any
21348 TCP ports already in use on the target system (for example, @code{23} is
21349 reserved for @code{telnet}).@footnote{If you choose a port number that
21350 conflicts with another service, @code{gdbserver} prints an error message
21351 and exits.} You must use the same port number with the host @value{GDBN}
21352 @code{target remote} command.
21354 The @code{stdio} connection is useful when starting @code{gdbserver}
21358 (gdb) target remote | ssh -T hostname gdbserver - hello
21361 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21362 and we don't want escape-character handling. Ssh does this by default when
21363 a command is provided, the flag is provided to make it explicit.
21364 You could elide it if you want to.
21366 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21367 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21368 display through a pipe connected to gdbserver.
21369 Both @code{stdout} and @code{stderr} use the same pipe.
21371 @anchor{Attaching to a program}
21372 @subsubsection Attaching to a Running Program
21373 @cindex attach to a program, @code{gdbserver}
21374 @cindex @option{--attach}, @code{gdbserver} option
21376 On some targets, @code{gdbserver} can also attach to running programs.
21377 This is accomplished via the @code{--attach} argument. The syntax is:
21380 target> gdbserver --attach @var{comm} @var{pid}
21383 @var{pid} is the process ID of a currently running process. It isn't
21384 necessary to point @code{gdbserver} at a binary for the running process.
21386 In @code{target extended-remote} mode, you can also attach using the
21387 @value{GDBN} attach command
21388 (@pxref{Attaching in Types of Remote Connections}).
21391 You can debug processes by name instead of process ID if your target has the
21392 @code{pidof} utility:
21395 target> gdbserver --attach @var{comm} `pidof @var{program}`
21398 In case more than one copy of @var{program} is running, or @var{program}
21399 has multiple threads, most versions of @code{pidof} support the
21400 @code{-s} option to only return the first process ID.
21402 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21404 This section applies only when @code{gdbserver} is run to listen on a TCP
21407 @code{gdbserver} normally terminates after all of its debugged processes have
21408 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21409 extended-remote}, @code{gdbserver} stays running even with no processes left.
21410 @value{GDBN} normally terminates the spawned debugged process on its exit,
21411 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21412 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21413 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21414 stays running even in the @kbd{target remote} mode.
21416 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21417 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21418 completeness, at most one @value{GDBN} can be connected at a time.
21420 @cindex @option{--once}, @code{gdbserver} option
21421 By default, @code{gdbserver} keeps the listening TCP port open, so that
21422 subsequent connections are possible. However, if you start @code{gdbserver}
21423 with the @option{--once} option, it will stop listening for any further
21424 connection attempts after connecting to the first @value{GDBN} session. This
21425 means no further connections to @code{gdbserver} will be possible after the
21426 first one. It also means @code{gdbserver} will terminate after the first
21427 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21428 connections and even in the @kbd{target extended-remote} mode. The
21429 @option{--once} option allows reusing the same port number for connecting to
21430 multiple instances of @code{gdbserver} running on the same host, since each
21431 instance closes its port after the first connection.
21433 @anchor{Other Command-Line Arguments for gdbserver}
21434 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21436 You can use the @option{--multi} option to start @code{gdbserver} without
21437 specifying a program to debug or a process to attach to. Then you can
21438 attach in @code{target extended-remote} mode and run or attach to a
21439 program. For more information,
21440 @pxref{--multi Option in Types of Remote Connnections}.
21442 @cindex @option{--debug}, @code{gdbserver} option
21443 The @option{--debug} option tells @code{gdbserver} to display extra
21444 status information about the debugging process.
21445 @cindex @option{--remote-debug}, @code{gdbserver} option
21446 The @option{--remote-debug} option tells @code{gdbserver} to display
21447 remote protocol debug output.
21448 @cindex @option{--debug-file}, @code{gdbserver} option
21449 @cindex @code{gdbserver}, send all debug output to a single file
21450 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
21451 write any debug output to the given @var{filename}. These options are intended
21452 for @code{gdbserver} development and for bug reports to the developers.
21454 @cindex @option{--debug-format}, @code{gdbserver} option
21455 The @option{--debug-format=option1[,option2,...]} option tells
21456 @code{gdbserver} to include additional information in each output.
21457 Possible options are:
21461 Turn off all extra information in debugging output.
21463 Turn on all extra information in debugging output.
21465 Include a timestamp in each line of debugging output.
21468 Options are processed in order. Thus, for example, if @option{none}
21469 appears last then no additional information is added to debugging output.
21471 @cindex @option{--wrapper}, @code{gdbserver} option
21472 The @option{--wrapper} option specifies a wrapper to launch programs
21473 for debugging. The option should be followed by the name of the
21474 wrapper, then any command-line arguments to pass to the wrapper, then
21475 @kbd{--} indicating the end of the wrapper arguments.
21477 @code{gdbserver} runs the specified wrapper program with a combined
21478 command line including the wrapper arguments, then the name of the
21479 program to debug, then any arguments to the program. The wrapper
21480 runs until it executes your program, and then @value{GDBN} gains control.
21482 You can use any program that eventually calls @code{execve} with
21483 its arguments as a wrapper. Several standard Unix utilities do
21484 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21485 with @code{exec "$@@"} will also work.
21487 For example, you can use @code{env} to pass an environment variable to
21488 the debugged program, without setting the variable in @code{gdbserver}'s
21492 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21495 @cindex @option{--selftest}
21496 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21499 $ gdbserver --selftest
21500 Ran 2 unit tests, 0 failed
21503 These tests are disabled in release.
21504 @subsection Connecting to @code{gdbserver}
21506 The basic procedure for connecting to the remote target is:
21510 Run @value{GDBN} on the host system.
21513 Make sure you have the necessary symbol files
21514 (@pxref{Host and target files}).
21515 Load symbols for your application using the @code{file} command before you
21516 connect. Use @code{set sysroot} to locate target libraries (unless your
21517 @value{GDBN} was compiled with the correct sysroot using
21518 @code{--with-sysroot}).
21521 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21522 For TCP connections, you must start up @code{gdbserver} prior to using
21523 the @code{target} command. Otherwise you may get an error whose
21524 text depends on the host system, but which usually looks something like
21525 @samp{Connection refused}. Don't use the @code{load}
21526 command in @value{GDBN} when using @code{target remote} mode, since the
21527 program is already on the target.
21531 @anchor{Monitor Commands for gdbserver}
21532 @subsection Monitor Commands for @code{gdbserver}
21533 @cindex monitor commands, for @code{gdbserver}
21535 During a @value{GDBN} session using @code{gdbserver}, you can use the
21536 @code{monitor} command to send special requests to @code{gdbserver}.
21537 Here are the available commands.
21541 List the available monitor commands.
21543 @item monitor set debug 0
21544 @itemx monitor set debug 1
21545 Disable or enable general debugging messages.
21547 @item monitor set remote-debug 0
21548 @itemx monitor set remote-debug 1
21549 Disable or enable specific debugging messages associated with the remote
21550 protocol (@pxref{Remote Protocol}).
21552 @item monitor set debug-file filename
21553 @itemx monitor set debug-file
21554 Send any debug output to the given file, or to stderr.
21556 @item monitor set debug-format option1@r{[},option2,...@r{]}
21557 Specify additional text to add to debugging messages.
21558 Possible options are:
21562 Turn off all extra information in debugging output.
21564 Turn on all extra information in debugging output.
21566 Include a timestamp in each line of debugging output.
21569 Options are processed in order. Thus, for example, if @option{none}
21570 appears last then no additional information is added to debugging output.
21572 @item monitor set libthread-db-search-path [PATH]
21573 @cindex gdbserver, search path for @code{libthread_db}
21574 When this command is issued, @var{path} is a colon-separated list of
21575 directories to search for @code{libthread_db} (@pxref{Threads,,set
21576 libthread-db-search-path}). If you omit @var{path},
21577 @samp{libthread-db-search-path} will be reset to its default value.
21579 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21580 not supported in @code{gdbserver}.
21583 Tell gdbserver to exit immediately. This command should be followed by
21584 @code{disconnect} to close the debugging session. @code{gdbserver} will
21585 detach from any attached processes and kill any processes it created.
21586 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21587 of a multi-process mode debug session.
21591 @subsection Tracepoints support in @code{gdbserver}
21592 @cindex tracepoints support in @code{gdbserver}
21594 On some targets, @code{gdbserver} supports tracepoints, fast
21595 tracepoints and static tracepoints.
21597 For fast or static tracepoints to work, a special library called the
21598 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21599 This library is built and distributed as an integral part of
21600 @code{gdbserver}. In addition, support for static tracepoints
21601 requires building the in-process agent library with static tracepoints
21602 support. At present, the UST (LTTng Userspace Tracer,
21603 @url{http://lttng.org/ust}) tracing engine is supported. This support
21604 is automatically available if UST development headers are found in the
21605 standard include path when @code{gdbserver} is built, or if
21606 @code{gdbserver} was explicitly configured using @option{--with-ust}
21607 to point at such headers. You can explicitly disable the support
21608 using @option{--with-ust=no}.
21610 There are several ways to load the in-process agent in your program:
21613 @item Specifying it as dependency at link time
21615 You can link your program dynamically with the in-process agent
21616 library. On most systems, this is accomplished by adding
21617 @code{-linproctrace} to the link command.
21619 @item Using the system's preloading mechanisms
21621 You can force loading the in-process agent at startup time by using
21622 your system's support for preloading shared libraries. Many Unixes
21623 support the concept of preloading user defined libraries. In most
21624 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21625 in the environment. See also the description of @code{gdbserver}'s
21626 @option{--wrapper} command line option.
21628 @item Using @value{GDBN} to force loading the agent at run time
21630 On some systems, you can force the inferior to load a shared library,
21631 by calling a dynamic loader function in the inferior that takes care
21632 of dynamically looking up and loading a shared library. On most Unix
21633 systems, the function is @code{dlopen}. You'll use the @code{call}
21634 command for that. For example:
21637 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21640 Note that on most Unix systems, for the @code{dlopen} function to be
21641 available, the program needs to be linked with @code{-ldl}.
21644 On systems that have a userspace dynamic loader, like most Unix
21645 systems, when you connect to @code{gdbserver} using @code{target
21646 remote}, you'll find that the program is stopped at the dynamic
21647 loader's entry point, and no shared library has been loaded in the
21648 program's address space yet, including the in-process agent. In that
21649 case, before being able to use any of the fast or static tracepoints
21650 features, you need to let the loader run and load the shared
21651 libraries. The simplest way to do that is to run the program to the
21652 main procedure. E.g., if debugging a C or C@t{++} program, start
21653 @code{gdbserver} like so:
21656 $ gdbserver :9999 myprogram
21659 Start GDB and connect to @code{gdbserver} like so, and run to main:
21663 (@value{GDBP}) target remote myhost:9999
21664 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21665 (@value{GDBP}) b main
21666 (@value{GDBP}) continue
21669 The in-process tracing agent library should now be loaded into the
21670 process; you can confirm it with the @code{info sharedlibrary}
21671 command, which will list @file{libinproctrace.so} as loaded in the
21672 process. You are now ready to install fast tracepoints, list static
21673 tracepoint markers, probe static tracepoints markers, and start
21676 @node Remote Configuration
21677 @section Remote Configuration
21680 @kindex show remote
21681 This section documents the configuration options available when
21682 debugging remote programs. For the options related to the File I/O
21683 extensions of the remote protocol, see @ref{system,
21684 system-call-allowed}.
21687 @item set remoteaddresssize @var{bits}
21688 @cindex address size for remote targets
21689 @cindex bits in remote address
21690 Set the maximum size of address in a memory packet to the specified
21691 number of bits. @value{GDBN} will mask off the address bits above
21692 that number, when it passes addresses to the remote target. The
21693 default value is the number of bits in the target's address.
21695 @item show remoteaddresssize
21696 Show the current value of remote address size in bits.
21698 @item set serial baud @var{n}
21699 @cindex baud rate for remote targets
21700 Set the baud rate for the remote serial I/O to @var{n} baud. The
21701 value is used to set the speed of the serial port used for debugging
21704 @item show serial baud
21705 Show the current speed of the remote connection.
21707 @item set serial parity @var{parity}
21708 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21709 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21711 @item show serial parity
21712 Show the current parity of the serial port.
21714 @item set remotebreak
21715 @cindex interrupt remote programs
21716 @cindex BREAK signal instead of Ctrl-C
21717 @anchor{set remotebreak}
21718 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21719 when you type @kbd{Ctrl-c} to interrupt the program running
21720 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21721 character instead. The default is off, since most remote systems
21722 expect to see @samp{Ctrl-C} as the interrupt signal.
21724 @item show remotebreak
21725 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21726 interrupt the remote program.
21728 @item set remoteflow on
21729 @itemx set remoteflow off
21730 @kindex set remoteflow
21731 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21732 on the serial port used to communicate to the remote target.
21734 @item show remoteflow
21735 @kindex show remoteflow
21736 Show the current setting of hardware flow control.
21738 @item set remotelogbase @var{base}
21739 Set the base (a.k.a.@: radix) of logging serial protocol
21740 communications to @var{base}. Supported values of @var{base} are:
21741 @code{ascii}, @code{octal}, and @code{hex}. The default is
21744 @item show remotelogbase
21745 Show the current setting of the radix for logging remote serial
21748 @item set remotelogfile @var{file}
21749 @cindex record serial communications on file
21750 Record remote serial communications on the named @var{file}. The
21751 default is not to record at all.
21753 @item show remotelogfile
21754 Show the current setting of the file name on which to record the
21755 serial communications.
21757 @item set remotetimeout @var{num}
21758 @cindex timeout for serial communications
21759 @cindex remote timeout
21760 Set the timeout limit to wait for the remote target to respond to
21761 @var{num} seconds. The default is 2 seconds.
21763 @item show remotetimeout
21764 Show the current number of seconds to wait for the remote target
21767 @cindex limit hardware breakpoints and watchpoints
21768 @cindex remote target, limit break- and watchpoints
21769 @anchor{set remote hardware-watchpoint-limit}
21770 @anchor{set remote hardware-breakpoint-limit}
21771 @item set remote hardware-watchpoint-limit @var{limit}
21772 @itemx set remote hardware-breakpoint-limit @var{limit}
21773 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21774 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21775 watchpoints or breakpoints, and @code{unlimited} for unlimited
21776 watchpoints or breakpoints.
21778 @item show remote hardware-watchpoint-limit
21779 @itemx show remote hardware-breakpoint-limit
21780 Show the current limit for the number of hardware watchpoints or
21781 breakpoints that @value{GDBN} can use.
21783 @cindex limit hardware watchpoints length
21784 @cindex remote target, limit watchpoints length
21785 @anchor{set remote hardware-watchpoint-length-limit}
21786 @item set remote hardware-watchpoint-length-limit @var{limit}
21787 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21788 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21789 hardware watchpoints and @code{unlimited} allows watchpoints of any
21792 @item show remote hardware-watchpoint-length-limit
21793 Show the current limit (in bytes) of the maximum length of
21794 a remote hardware watchpoint.
21796 @item set remote exec-file @var{filename}
21797 @itemx show remote exec-file
21798 @anchor{set remote exec-file}
21799 @cindex executable file, for remote target
21800 Select the file used for @code{run} with @code{target
21801 extended-remote}. This should be set to a filename valid on the
21802 target system. If it is not set, the target will use a default
21803 filename (e.g.@: the last program run).
21805 @item set remote interrupt-sequence
21806 @cindex interrupt remote programs
21807 @cindex select Ctrl-C, BREAK or BREAK-g
21808 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21809 @samp{BREAK-g} as the
21810 sequence to the remote target in order to interrupt the execution.
21811 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21812 is high level of serial line for some certain time.
21813 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21814 It is @code{BREAK} signal followed by character @code{g}.
21816 @item show interrupt-sequence
21817 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21818 is sent by @value{GDBN} to interrupt the remote program.
21819 @code{BREAK-g} is BREAK signal followed by @code{g} and
21820 also known as Magic SysRq g.
21822 @item set remote interrupt-on-connect
21823 @cindex send interrupt-sequence on start
21824 Specify whether interrupt-sequence is sent to remote target when
21825 @value{GDBN} connects to it. This is mostly needed when you debug
21826 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21827 which is known as Magic SysRq g in order to connect @value{GDBN}.
21829 @item show interrupt-on-connect
21830 Show whether interrupt-sequence is sent
21831 to remote target when @value{GDBN} connects to it.
21835 @item set tcp auto-retry on
21836 @cindex auto-retry, for remote TCP target
21837 Enable auto-retry for remote TCP connections. This is useful if the remote
21838 debugging agent is launched in parallel with @value{GDBN}; there is a race
21839 condition because the agent may not become ready to accept the connection
21840 before @value{GDBN} attempts to connect. When auto-retry is
21841 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21842 to establish the connection using the timeout specified by
21843 @code{set tcp connect-timeout}.
21845 @item set tcp auto-retry off
21846 Do not auto-retry failed TCP connections.
21848 @item show tcp auto-retry
21849 Show the current auto-retry setting.
21851 @item set tcp connect-timeout @var{seconds}
21852 @itemx set tcp connect-timeout unlimited
21853 @cindex connection timeout, for remote TCP target
21854 @cindex timeout, for remote target connection
21855 Set the timeout for establishing a TCP connection to the remote target to
21856 @var{seconds}. The timeout affects both polling to retry failed connections
21857 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21858 that are merely slow to complete, and represents an approximate cumulative
21859 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21860 @value{GDBN} will keep attempting to establish a connection forever,
21861 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21863 @item show tcp connect-timeout
21864 Show the current connection timeout setting.
21867 @cindex remote packets, enabling and disabling
21868 The @value{GDBN} remote protocol autodetects the packets supported by
21869 your debugging stub. If you need to override the autodetection, you
21870 can use these commands to enable or disable individual packets. Each
21871 packet can be set to @samp{on} (the remote target supports this
21872 packet), @samp{off} (the remote target does not support this packet),
21873 or @samp{auto} (detect remote target support for this packet). They
21874 all default to @samp{auto}. For more information about each packet,
21875 see @ref{Remote Protocol}.
21877 During normal use, you should not have to use any of these commands.
21878 If you do, that may be a bug in your remote debugging stub, or a bug
21879 in @value{GDBN}. You may want to report the problem to the
21880 @value{GDBN} developers.
21882 For each packet @var{name}, the command to enable or disable the
21883 packet is @code{set remote @var{name}-packet}. The available settings
21886 @multitable @columnfractions 0.28 0.32 0.25
21889 @tab Related Features
21891 @item @code{fetch-register}
21893 @tab @code{info registers}
21895 @item @code{set-register}
21899 @item @code{binary-download}
21901 @tab @code{load}, @code{set}
21903 @item @code{read-aux-vector}
21904 @tab @code{qXfer:auxv:read}
21905 @tab @code{info auxv}
21907 @item @code{symbol-lookup}
21908 @tab @code{qSymbol}
21909 @tab Detecting multiple threads
21911 @item @code{attach}
21912 @tab @code{vAttach}
21915 @item @code{verbose-resume}
21917 @tab Stepping or resuming multiple threads
21923 @item @code{software-breakpoint}
21927 @item @code{hardware-breakpoint}
21931 @item @code{write-watchpoint}
21935 @item @code{read-watchpoint}
21939 @item @code{access-watchpoint}
21943 @item @code{pid-to-exec-file}
21944 @tab @code{qXfer:exec-file:read}
21945 @tab @code{attach}, @code{run}
21947 @item @code{target-features}
21948 @tab @code{qXfer:features:read}
21949 @tab @code{set architecture}
21951 @item @code{library-info}
21952 @tab @code{qXfer:libraries:read}
21953 @tab @code{info sharedlibrary}
21955 @item @code{memory-map}
21956 @tab @code{qXfer:memory-map:read}
21957 @tab @code{info mem}
21959 @item @code{read-sdata-object}
21960 @tab @code{qXfer:sdata:read}
21961 @tab @code{print $_sdata}
21963 @item @code{read-spu-object}
21964 @tab @code{qXfer:spu:read}
21965 @tab @code{info spu}
21967 @item @code{write-spu-object}
21968 @tab @code{qXfer:spu:write}
21969 @tab @code{info spu}
21971 @item @code{read-siginfo-object}
21972 @tab @code{qXfer:siginfo:read}
21973 @tab @code{print $_siginfo}
21975 @item @code{write-siginfo-object}
21976 @tab @code{qXfer:siginfo:write}
21977 @tab @code{set $_siginfo}
21979 @item @code{threads}
21980 @tab @code{qXfer:threads:read}
21981 @tab @code{info threads}
21983 @item @code{get-thread-local-@*storage-address}
21984 @tab @code{qGetTLSAddr}
21985 @tab Displaying @code{__thread} variables
21987 @item @code{get-thread-information-block-address}
21988 @tab @code{qGetTIBAddr}
21989 @tab Display MS-Windows Thread Information Block.
21991 @item @code{search-memory}
21992 @tab @code{qSearch:memory}
21995 @item @code{supported-packets}
21996 @tab @code{qSupported}
21997 @tab Remote communications parameters
21999 @item @code{catch-syscalls}
22000 @tab @code{QCatchSyscalls}
22001 @tab @code{catch syscall}
22003 @item @code{pass-signals}
22004 @tab @code{QPassSignals}
22005 @tab @code{handle @var{signal}}
22007 @item @code{program-signals}
22008 @tab @code{QProgramSignals}
22009 @tab @code{handle @var{signal}}
22011 @item @code{hostio-close-packet}
22012 @tab @code{vFile:close}
22013 @tab @code{remote get}, @code{remote put}
22015 @item @code{hostio-open-packet}
22016 @tab @code{vFile:open}
22017 @tab @code{remote get}, @code{remote put}
22019 @item @code{hostio-pread-packet}
22020 @tab @code{vFile:pread}
22021 @tab @code{remote get}, @code{remote put}
22023 @item @code{hostio-pwrite-packet}
22024 @tab @code{vFile:pwrite}
22025 @tab @code{remote get}, @code{remote put}
22027 @item @code{hostio-unlink-packet}
22028 @tab @code{vFile:unlink}
22029 @tab @code{remote delete}
22031 @item @code{hostio-readlink-packet}
22032 @tab @code{vFile:readlink}
22035 @item @code{hostio-fstat-packet}
22036 @tab @code{vFile:fstat}
22039 @item @code{hostio-setfs-packet}
22040 @tab @code{vFile:setfs}
22043 @item @code{noack-packet}
22044 @tab @code{QStartNoAckMode}
22045 @tab Packet acknowledgment
22047 @item @code{osdata}
22048 @tab @code{qXfer:osdata:read}
22049 @tab @code{info os}
22051 @item @code{query-attached}
22052 @tab @code{qAttached}
22053 @tab Querying remote process attach state.
22055 @item @code{trace-buffer-size}
22056 @tab @code{QTBuffer:size}
22057 @tab @code{set trace-buffer-size}
22059 @item @code{trace-status}
22060 @tab @code{qTStatus}
22061 @tab @code{tstatus}
22063 @item @code{traceframe-info}
22064 @tab @code{qXfer:traceframe-info:read}
22065 @tab Traceframe info
22067 @item @code{install-in-trace}
22068 @tab @code{InstallInTrace}
22069 @tab Install tracepoint in tracing
22071 @item @code{disable-randomization}
22072 @tab @code{QDisableRandomization}
22073 @tab @code{set disable-randomization}
22075 @item @code{startup-with-shell}
22076 @tab @code{QStartupWithShell}
22077 @tab @code{set startup-with-shell}
22079 @item @code{environment-hex-encoded}
22080 @tab @code{QEnvironmentHexEncoded}
22081 @tab @code{set environment}
22083 @item @code{environment-unset}
22084 @tab @code{QEnvironmentUnset}
22085 @tab @code{unset environment}
22087 @item @code{environment-reset}
22088 @tab @code{QEnvironmentReset}
22089 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22091 @item @code{set-working-dir}
22092 @tab @code{QSetWorkingDir}
22093 @tab @code{set cwd}
22095 @item @code{conditional-breakpoints-packet}
22096 @tab @code{Z0 and Z1}
22097 @tab @code{Support for target-side breakpoint condition evaluation}
22099 @item @code{multiprocess-extensions}
22100 @tab @code{multiprocess extensions}
22101 @tab Debug multiple processes and remote process PID awareness
22103 @item @code{swbreak-feature}
22104 @tab @code{swbreak stop reason}
22107 @item @code{hwbreak-feature}
22108 @tab @code{hwbreak stop reason}
22111 @item @code{fork-event-feature}
22112 @tab @code{fork stop reason}
22115 @item @code{vfork-event-feature}
22116 @tab @code{vfork stop reason}
22119 @item @code{exec-event-feature}
22120 @tab @code{exec stop reason}
22123 @item @code{thread-events}
22124 @tab @code{QThreadEvents}
22125 @tab Tracking thread lifetime.
22127 @item @code{no-resumed-stop-reply}
22128 @tab @code{no resumed thread left stop reply}
22129 @tab Tracking thread lifetime.
22134 @section Implementing a Remote Stub
22136 @cindex debugging stub, example
22137 @cindex remote stub, example
22138 @cindex stub example, remote debugging
22139 The stub files provided with @value{GDBN} implement the target side of the
22140 communication protocol, and the @value{GDBN} side is implemented in the
22141 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22142 these subroutines to communicate, and ignore the details. (If you're
22143 implementing your own stub file, you can still ignore the details: start
22144 with one of the existing stub files. @file{sparc-stub.c} is the best
22145 organized, and therefore the easiest to read.)
22147 @cindex remote serial debugging, overview
22148 To debug a program running on another machine (the debugging
22149 @dfn{target} machine), you must first arrange for all the usual
22150 prerequisites for the program to run by itself. For example, for a C
22155 A startup routine to set up the C runtime environment; these usually
22156 have a name like @file{crt0}. The startup routine may be supplied by
22157 your hardware supplier, or you may have to write your own.
22160 A C subroutine library to support your program's
22161 subroutine calls, notably managing input and output.
22164 A way of getting your program to the other machine---for example, a
22165 download program. These are often supplied by the hardware
22166 manufacturer, but you may have to write your own from hardware
22170 The next step is to arrange for your program to use a serial port to
22171 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22172 machine). In general terms, the scheme looks like this:
22176 @value{GDBN} already understands how to use this protocol; when everything
22177 else is set up, you can simply use the @samp{target remote} command
22178 (@pxref{Targets,,Specifying a Debugging Target}).
22180 @item On the target,
22181 you must link with your program a few special-purpose subroutines that
22182 implement the @value{GDBN} remote serial protocol. The file containing these
22183 subroutines is called a @dfn{debugging stub}.
22185 On certain remote targets, you can use an auxiliary program
22186 @code{gdbserver} instead of linking a stub into your program.
22187 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22190 The debugging stub is specific to the architecture of the remote
22191 machine; for example, use @file{sparc-stub.c} to debug programs on
22194 @cindex remote serial stub list
22195 These working remote stubs are distributed with @value{GDBN}:
22200 @cindex @file{i386-stub.c}
22203 For Intel 386 and compatible architectures.
22206 @cindex @file{m68k-stub.c}
22207 @cindex Motorola 680x0
22209 For Motorola 680x0 architectures.
22212 @cindex @file{sh-stub.c}
22215 For Renesas SH architectures.
22218 @cindex @file{sparc-stub.c}
22220 For @sc{sparc} architectures.
22222 @item sparcl-stub.c
22223 @cindex @file{sparcl-stub.c}
22226 For Fujitsu @sc{sparclite} architectures.
22230 The @file{README} file in the @value{GDBN} distribution may list other
22231 recently added stubs.
22234 * Stub Contents:: What the stub can do for you
22235 * Bootstrapping:: What you must do for the stub
22236 * Debug Session:: Putting it all together
22239 @node Stub Contents
22240 @subsection What the Stub Can Do for You
22242 @cindex remote serial stub
22243 The debugging stub for your architecture supplies these three
22247 @item set_debug_traps
22248 @findex set_debug_traps
22249 @cindex remote serial stub, initialization
22250 This routine arranges for @code{handle_exception} to run when your
22251 program stops. You must call this subroutine explicitly in your
22252 program's startup code.
22254 @item handle_exception
22255 @findex handle_exception
22256 @cindex remote serial stub, main routine
22257 This is the central workhorse, but your program never calls it
22258 explicitly---the setup code arranges for @code{handle_exception} to
22259 run when a trap is triggered.
22261 @code{handle_exception} takes control when your program stops during
22262 execution (for example, on a breakpoint), and mediates communications
22263 with @value{GDBN} on the host machine. This is where the communications
22264 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22265 representative on the target machine. It begins by sending summary
22266 information on the state of your program, then continues to execute,
22267 retrieving and transmitting any information @value{GDBN} needs, until you
22268 execute a @value{GDBN} command that makes your program resume; at that point,
22269 @code{handle_exception} returns control to your own code on the target
22273 @cindex @code{breakpoint} subroutine, remote
22274 Use this auxiliary subroutine to make your program contain a
22275 breakpoint. Depending on the particular situation, this may be the only
22276 way for @value{GDBN} to get control. For instance, if your target
22277 machine has some sort of interrupt button, you won't need to call this;
22278 pressing the interrupt button transfers control to
22279 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22280 simply receiving characters on the serial port may also trigger a trap;
22281 again, in that situation, you don't need to call @code{breakpoint} from
22282 your own program---simply running @samp{target remote} from the host
22283 @value{GDBN} session gets control.
22285 Call @code{breakpoint} if none of these is true, or if you simply want
22286 to make certain your program stops at a predetermined point for the
22287 start of your debugging session.
22290 @node Bootstrapping
22291 @subsection What You Must Do for the Stub
22293 @cindex remote stub, support routines
22294 The debugging stubs that come with @value{GDBN} are set up for a particular
22295 chip architecture, but they have no information about the rest of your
22296 debugging target machine.
22298 First of all you need to tell the stub how to communicate with the
22302 @item int getDebugChar()
22303 @findex getDebugChar
22304 Write this subroutine to read a single character from the serial port.
22305 It may be identical to @code{getchar} for your target system; a
22306 different name is used to allow you to distinguish the two if you wish.
22308 @item void putDebugChar(int)
22309 @findex putDebugChar
22310 Write this subroutine to write a single character to the serial port.
22311 It may be identical to @code{putchar} for your target system; a
22312 different name is used to allow you to distinguish the two if you wish.
22315 @cindex control C, and remote debugging
22316 @cindex interrupting remote targets
22317 If you want @value{GDBN} to be able to stop your program while it is
22318 running, you need to use an interrupt-driven serial driver, and arrange
22319 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22320 character). That is the character which @value{GDBN} uses to tell the
22321 remote system to stop.
22323 Getting the debugging target to return the proper status to @value{GDBN}
22324 probably requires changes to the standard stub; one quick and dirty way
22325 is to just execute a breakpoint instruction (the ``dirty'' part is that
22326 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22328 Other routines you need to supply are:
22331 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22332 @findex exceptionHandler
22333 Write this function to install @var{exception_address} in the exception
22334 handling tables. You need to do this because the stub does not have any
22335 way of knowing what the exception handling tables on your target system
22336 are like (for example, the processor's table might be in @sc{rom},
22337 containing entries which point to a table in @sc{ram}).
22338 The @var{exception_number} specifies the exception which should be changed;
22339 its meaning is architecture-dependent (for example, different numbers
22340 might represent divide by zero, misaligned access, etc). When this
22341 exception occurs, control should be transferred directly to
22342 @var{exception_address}, and the processor state (stack, registers,
22343 and so on) should be just as it is when a processor exception occurs. So if
22344 you want to use a jump instruction to reach @var{exception_address}, it
22345 should be a simple jump, not a jump to subroutine.
22347 For the 386, @var{exception_address} should be installed as an interrupt
22348 gate so that interrupts are masked while the handler runs. The gate
22349 should be at privilege level 0 (the most privileged level). The
22350 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22351 help from @code{exceptionHandler}.
22353 @item void flush_i_cache()
22354 @findex flush_i_cache
22355 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22356 instruction cache, if any, on your target machine. If there is no
22357 instruction cache, this subroutine may be a no-op.
22359 On target machines that have instruction caches, @value{GDBN} requires this
22360 function to make certain that the state of your program is stable.
22364 You must also make sure this library routine is available:
22367 @item void *memset(void *, int, int)
22369 This is the standard library function @code{memset} that sets an area of
22370 memory to a known value. If you have one of the free versions of
22371 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22372 either obtain it from your hardware manufacturer, or write your own.
22375 If you do not use the GNU C compiler, you may need other standard
22376 library subroutines as well; this varies from one stub to another,
22377 but in general the stubs are likely to use any of the common library
22378 subroutines which @code{@value{NGCC}} generates as inline code.
22381 @node Debug Session
22382 @subsection Putting it All Together
22384 @cindex remote serial debugging summary
22385 In summary, when your program is ready to debug, you must follow these
22390 Make sure you have defined the supporting low-level routines
22391 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22393 @code{getDebugChar}, @code{putDebugChar},
22394 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22398 Insert these lines in your program's startup code, before the main
22399 procedure is called:
22406 On some machines, when a breakpoint trap is raised, the hardware
22407 automatically makes the PC point to the instruction after the
22408 breakpoint. If your machine doesn't do that, you may need to adjust
22409 @code{handle_exception} to arrange for it to return to the instruction
22410 after the breakpoint on this first invocation, so that your program
22411 doesn't keep hitting the initial breakpoint instead of making
22415 For the 680x0 stub only, you need to provide a variable called
22416 @code{exceptionHook}. Normally you just use:
22419 void (*exceptionHook)() = 0;
22423 but if before calling @code{set_debug_traps}, you set it to point to a
22424 function in your program, that function is called when
22425 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22426 error). The function indicated by @code{exceptionHook} is called with
22427 one parameter: an @code{int} which is the exception number.
22430 Compile and link together: your program, the @value{GDBN} debugging stub for
22431 your target architecture, and the supporting subroutines.
22434 Make sure you have a serial connection between your target machine and
22435 the @value{GDBN} host, and identify the serial port on the host.
22438 @c The "remote" target now provides a `load' command, so we should
22439 @c document that. FIXME.
22440 Download your program to your target machine (or get it there by
22441 whatever means the manufacturer provides), and start it.
22444 Start @value{GDBN} on the host, and connect to the target
22445 (@pxref{Connecting,,Connecting to a Remote Target}).
22449 @node Configurations
22450 @chapter Configuration-Specific Information
22452 While nearly all @value{GDBN} commands are available for all native and
22453 cross versions of the debugger, there are some exceptions. This chapter
22454 describes things that are only available in certain configurations.
22456 There are three major categories of configurations: native
22457 configurations, where the host and target are the same, embedded
22458 operating system configurations, which are usually the same for several
22459 different processor architectures, and bare embedded processors, which
22460 are quite different from each other.
22465 * Embedded Processors::
22472 This section describes details specific to particular native
22476 * BSD libkvm Interface:: Debugging BSD kernel memory images
22477 * Process Information:: Process information
22478 * DJGPP Native:: Features specific to the DJGPP port
22479 * Cygwin Native:: Features specific to the Cygwin port
22480 * Hurd Native:: Features specific to @sc{gnu} Hurd
22481 * Darwin:: Features specific to Darwin
22482 * FreeBSD:: Features specific to FreeBSD
22485 @node BSD libkvm Interface
22486 @subsection BSD libkvm Interface
22489 @cindex kernel memory image
22490 @cindex kernel crash dump
22492 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22493 interface that provides a uniform interface for accessing kernel virtual
22494 memory images, including live systems and crash dumps. @value{GDBN}
22495 uses this interface to allow you to debug live kernels and kernel crash
22496 dumps on many native BSD configurations. This is implemented as a
22497 special @code{kvm} debugging target. For debugging a live system, load
22498 the currently running kernel into @value{GDBN} and connect to the
22502 (@value{GDBP}) @b{target kvm}
22505 For debugging crash dumps, provide the file name of the crash dump as an
22509 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22512 Once connected to the @code{kvm} target, the following commands are
22518 Set current context from the @dfn{Process Control Block} (PCB) address.
22521 Set current context from proc address. This command isn't available on
22522 modern FreeBSD systems.
22525 @node Process Information
22526 @subsection Process Information
22528 @cindex examine process image
22529 @cindex process info via @file{/proc}
22531 Some operating systems provide interfaces to fetch additional
22532 information about running processes beyond memory and per-thread
22533 register state. If @value{GDBN} is configured for an operating system
22534 with a supported interface, the command @code{info proc} is available
22535 to report information about the process running your program, or about
22536 any process running on your system.
22538 One supported interface is a facility called @samp{/proc} that can be
22539 used to examine the image of a running process using file-system
22540 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22543 On FreeBSD systems, system control nodes are used to query process
22546 In addition, some systems may provide additional process information
22547 in core files. Note that a core file may include a subset of the
22548 information available from a live process. Process information is
22549 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22556 @itemx info proc @var{process-id}
22557 Summarize available information about a process. If a
22558 process ID is specified by @var{process-id}, display information about
22559 that process; otherwise display information about the program being
22560 debugged. The summary includes the debugged process ID, the command
22561 line used to invoke it, its current working directory, and its
22562 executable file's absolute file name.
22564 On some systems, @var{process-id} can be of the form
22565 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22566 within a process. If the optional @var{pid} part is missing, it means
22567 a thread from the process being debugged (the leading @samp{/} still
22568 needs to be present, or else @value{GDBN} will interpret the number as
22569 a process ID rather than a thread ID).
22571 @item info proc cmdline
22572 @cindex info proc cmdline
22573 Show the original command line of the process. This command is
22574 supported on @sc{gnu}/Linux and FreeBSD.
22576 @item info proc cwd
22577 @cindex info proc cwd
22578 Show the current working directory of the process. This command is
22579 supported on @sc{gnu}/Linux and FreeBSD.
22581 @item info proc exe
22582 @cindex info proc exe
22583 Show the name of executable of the process. This command is supported
22584 on @sc{gnu}/Linux and FreeBSD.
22586 @item info proc files
22587 @cindex info proc files
22588 Show the file descriptors open by the process. For each open file
22589 descriptor, @value{GDBN} shows its number, type (file, directory,
22590 character device, socket), file pointer offset, and the name of the
22591 resource open on the descriptor. The resource name can be a file name
22592 (for files, directories, and devices) or a protocol followed by socket
22593 address (for network connections). This command is supported on
22596 This example shows the open file descriptors for a process using a
22597 tty for standard input and output as well as two network sockets:
22600 (gdb) info proc files 22136
22604 FD Type Offset Flags Name
22605 text file - r-------- /usr/bin/ssh
22606 ctty chr - rw------- /dev/pts/20
22607 cwd dir - r-------- /usr/home/john
22608 root dir - r-------- /
22609 0 chr 0x32933a4 rw------- /dev/pts/20
22610 1 chr 0x32933a4 rw------- /dev/pts/20
22611 2 chr 0x32933a4 rw------- /dev/pts/20
22612 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22613 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22616 @item info proc mappings
22617 @cindex memory address space mappings
22618 Report the memory address space ranges accessible in a process. On
22619 Solaris and FreeBSD systems, each memory range includes information on
22620 whether the process has read, write, or execute access rights to each
22621 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22622 includes the object file which is mapped to that range.
22624 @item info proc stat
22625 @itemx info proc status
22626 @cindex process detailed status information
22627 Show additional process-related information, including the user ID and
22628 group ID; virtual memory usage; the signals that are pending, blocked,
22629 and ignored; its TTY; its consumption of system and user time; its
22630 stack size; its @samp{nice} value; etc. These commands are supported
22631 on @sc{gnu}/Linux and FreeBSD.
22633 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22634 information (type @kbd{man 5 proc} from your shell prompt).
22636 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22639 @item info proc all
22640 Show all the information about the process described under all of the
22641 above @code{info proc} subcommands.
22644 @comment These sub-options of 'info proc' were not included when
22645 @comment procfs.c was re-written. Keep their descriptions around
22646 @comment against the day when someone finds the time to put them back in.
22647 @kindex info proc times
22648 @item info proc times
22649 Starting time, user CPU time, and system CPU time for your program and
22652 @kindex info proc id
22654 Report on the process IDs related to your program: its own process ID,
22655 the ID of its parent, the process group ID, and the session ID.
22658 @item set procfs-trace
22659 @kindex set procfs-trace
22660 @cindex @code{procfs} API calls
22661 This command enables and disables tracing of @code{procfs} API calls.
22663 @item show procfs-trace
22664 @kindex show procfs-trace
22665 Show the current state of @code{procfs} API call tracing.
22667 @item set procfs-file @var{file}
22668 @kindex set procfs-file
22669 Tell @value{GDBN} to write @code{procfs} API trace to the named
22670 @var{file}. @value{GDBN} appends the trace info to the previous
22671 contents of the file. The default is to display the trace on the
22674 @item show procfs-file
22675 @kindex show procfs-file
22676 Show the file to which @code{procfs} API trace is written.
22678 @item proc-trace-entry
22679 @itemx proc-trace-exit
22680 @itemx proc-untrace-entry
22681 @itemx proc-untrace-exit
22682 @kindex proc-trace-entry
22683 @kindex proc-trace-exit
22684 @kindex proc-untrace-entry
22685 @kindex proc-untrace-exit
22686 These commands enable and disable tracing of entries into and exits
22687 from the @code{syscall} interface.
22690 @kindex info pidlist
22691 @cindex process list, QNX Neutrino
22692 For QNX Neutrino only, this command displays the list of all the
22693 processes and all the threads within each process.
22696 @kindex info meminfo
22697 @cindex mapinfo list, QNX Neutrino
22698 For QNX Neutrino only, this command displays the list of all mapinfos.
22702 @subsection Features for Debugging @sc{djgpp} Programs
22703 @cindex @sc{djgpp} debugging
22704 @cindex native @sc{djgpp} debugging
22705 @cindex MS-DOS-specific commands
22708 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22709 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22710 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22711 top of real-mode DOS systems and their emulations.
22713 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22714 defines a few commands specific to the @sc{djgpp} port. This
22715 subsection describes those commands.
22720 This is a prefix of @sc{djgpp}-specific commands which print
22721 information about the target system and important OS structures.
22724 @cindex MS-DOS system info
22725 @cindex free memory information (MS-DOS)
22726 @item info dos sysinfo
22727 This command displays assorted information about the underlying
22728 platform: the CPU type and features, the OS version and flavor, the
22729 DPMI version, and the available conventional and DPMI memory.
22734 @cindex segment descriptor tables
22735 @cindex descriptor tables display
22737 @itemx info dos ldt
22738 @itemx info dos idt
22739 These 3 commands display entries from, respectively, Global, Local,
22740 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22741 tables are data structures which store a descriptor for each segment
22742 that is currently in use. The segment's selector is an index into a
22743 descriptor table; the table entry for that index holds the
22744 descriptor's base address and limit, and its attributes and access
22747 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22748 segment (used for both data and the stack), and a DOS segment (which
22749 allows access to DOS/BIOS data structures and absolute addresses in
22750 conventional memory). However, the DPMI host will usually define
22751 additional segments in order to support the DPMI environment.
22753 @cindex garbled pointers
22754 These commands allow to display entries from the descriptor tables.
22755 Without an argument, all entries from the specified table are
22756 displayed. An argument, which should be an integer expression, means
22757 display a single entry whose index is given by the argument. For
22758 example, here's a convenient way to display information about the
22759 debugged program's data segment:
22762 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22763 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22767 This comes in handy when you want to see whether a pointer is outside
22768 the data segment's limit (i.e.@: @dfn{garbled}).
22770 @cindex page tables display (MS-DOS)
22772 @itemx info dos pte
22773 These two commands display entries from, respectively, the Page
22774 Directory and the Page Tables. Page Directories and Page Tables are
22775 data structures which control how virtual memory addresses are mapped
22776 into physical addresses. A Page Table includes an entry for every
22777 page of memory that is mapped into the program's address space; there
22778 may be several Page Tables, each one holding up to 4096 entries. A
22779 Page Directory has up to 4096 entries, one each for every Page Table
22780 that is currently in use.
22782 Without an argument, @kbd{info dos pde} displays the entire Page
22783 Directory, and @kbd{info dos pte} displays all the entries in all of
22784 the Page Tables. An argument, an integer expression, given to the
22785 @kbd{info dos pde} command means display only that entry from the Page
22786 Directory table. An argument given to the @kbd{info dos pte} command
22787 means display entries from a single Page Table, the one pointed to by
22788 the specified entry in the Page Directory.
22790 @cindex direct memory access (DMA) on MS-DOS
22791 These commands are useful when your program uses @dfn{DMA} (Direct
22792 Memory Access), which needs physical addresses to program the DMA
22795 These commands are supported only with some DPMI servers.
22797 @cindex physical address from linear address
22798 @item info dos address-pte @var{addr}
22799 This command displays the Page Table entry for a specified linear
22800 address. The argument @var{addr} is a linear address which should
22801 already have the appropriate segment's base address added to it,
22802 because this command accepts addresses which may belong to @emph{any}
22803 segment. For example, here's how to display the Page Table entry for
22804 the page where a variable @code{i} is stored:
22807 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22808 @exdent @code{Page Table entry for address 0x11a00d30:}
22809 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22813 This says that @code{i} is stored at offset @code{0xd30} from the page
22814 whose physical base address is @code{0x02698000}, and shows all the
22815 attributes of that page.
22817 Note that you must cast the addresses of variables to a @code{char *},
22818 since otherwise the value of @code{__djgpp_base_address}, the base
22819 address of all variables and functions in a @sc{djgpp} program, will
22820 be added using the rules of C pointer arithmetics: if @code{i} is
22821 declared an @code{int}, @value{GDBN} will add 4 times the value of
22822 @code{__djgpp_base_address} to the address of @code{i}.
22824 Here's another example, it displays the Page Table entry for the
22828 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22829 @exdent @code{Page Table entry for address 0x29110:}
22830 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22834 (The @code{+ 3} offset is because the transfer buffer's address is the
22835 3rd member of the @code{_go32_info_block} structure.) The output
22836 clearly shows that this DPMI server maps the addresses in conventional
22837 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22838 linear (@code{0x29110}) addresses are identical.
22840 This command is supported only with some DPMI servers.
22843 @cindex DOS serial data link, remote debugging
22844 In addition to native debugging, the DJGPP port supports remote
22845 debugging via a serial data link. The following commands are specific
22846 to remote serial debugging in the DJGPP port of @value{GDBN}.
22849 @kindex set com1base
22850 @kindex set com1irq
22851 @kindex set com2base
22852 @kindex set com2irq
22853 @kindex set com3base
22854 @kindex set com3irq
22855 @kindex set com4base
22856 @kindex set com4irq
22857 @item set com1base @var{addr}
22858 This command sets the base I/O port address of the @file{COM1} serial
22861 @item set com1irq @var{irq}
22862 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22863 for the @file{COM1} serial port.
22865 There are similar commands @samp{set com2base}, @samp{set com3irq},
22866 etc.@: for setting the port address and the @code{IRQ} lines for the
22869 @kindex show com1base
22870 @kindex show com1irq
22871 @kindex show com2base
22872 @kindex show com2irq
22873 @kindex show com3base
22874 @kindex show com3irq
22875 @kindex show com4base
22876 @kindex show com4irq
22877 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22878 display the current settings of the base address and the @code{IRQ}
22879 lines used by the COM ports.
22882 @kindex info serial
22883 @cindex DOS serial port status
22884 This command prints the status of the 4 DOS serial ports. For each
22885 port, it prints whether it's active or not, its I/O base address and
22886 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22887 counts of various errors encountered so far.
22891 @node Cygwin Native
22892 @subsection Features for Debugging MS Windows PE Executables
22893 @cindex MS Windows debugging
22894 @cindex native Cygwin debugging
22895 @cindex Cygwin-specific commands
22897 @value{GDBN} supports native debugging of MS Windows programs, including
22898 DLLs with and without symbolic debugging information.
22900 @cindex Ctrl-BREAK, MS-Windows
22901 @cindex interrupt debuggee on MS-Windows
22902 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22903 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22904 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22905 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22906 sequence, which can be used to interrupt the debuggee even if it
22909 There are various additional Cygwin-specific commands, described in
22910 this section. Working with DLLs that have no debugging symbols is
22911 described in @ref{Non-debug DLL Symbols}.
22916 This is a prefix of MS Windows-specific commands which print
22917 information about the target system and important OS structures.
22919 @item info w32 selector
22920 This command displays information returned by
22921 the Win32 API @code{GetThreadSelectorEntry} function.
22922 It takes an optional argument that is evaluated to
22923 a long value to give the information about this given selector.
22924 Without argument, this command displays information
22925 about the six segment registers.
22927 @item info w32 thread-information-block
22928 This command displays thread specific information stored in the
22929 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22930 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22932 @kindex signal-event
22933 @item signal-event @var{id}
22934 This command signals an event with user-provided @var{id}. Used to resume
22935 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22937 To use it, create or edit the following keys in
22938 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22939 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22940 (for x86_64 versions):
22944 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22945 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22946 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22948 The first @code{%ld} will be replaced by the process ID of the
22949 crashing process, the second @code{%ld} will be replaced by the ID of
22950 the event that blocks the crashing process, waiting for @value{GDBN}
22954 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22955 make the system run debugger specified by the Debugger key
22956 automatically, @code{0} will cause a dialog box with ``OK'' and
22957 ``Cancel'' buttons to appear, which allows the user to either
22958 terminate the crashing process (OK) or debug it (Cancel).
22961 @kindex set cygwin-exceptions
22962 @cindex debugging the Cygwin DLL
22963 @cindex Cygwin DLL, debugging
22964 @item set cygwin-exceptions @var{mode}
22965 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22966 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22967 @value{GDBN} will delay recognition of exceptions, and may ignore some
22968 exceptions which seem to be caused by internal Cygwin DLL
22969 ``bookkeeping''. This option is meant primarily for debugging the
22970 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22971 @value{GDBN} users with false @code{SIGSEGV} signals.
22973 @kindex show cygwin-exceptions
22974 @item show cygwin-exceptions
22975 Displays whether @value{GDBN} will break on exceptions that happen
22976 inside the Cygwin DLL itself.
22978 @kindex set new-console
22979 @item set new-console @var{mode}
22980 If @var{mode} is @code{on} the debuggee will
22981 be started in a new console on next start.
22982 If @var{mode} is @code{off}, the debuggee will
22983 be started in the same console as the debugger.
22985 @kindex show new-console
22986 @item show new-console
22987 Displays whether a new console is used
22988 when the debuggee is started.
22990 @kindex set new-group
22991 @item set new-group @var{mode}
22992 This boolean value controls whether the debuggee should
22993 start a new group or stay in the same group as the debugger.
22994 This affects the way the Windows OS handles
22997 @kindex show new-group
22998 @item show new-group
22999 Displays current value of new-group boolean.
23001 @kindex set debugevents
23002 @item set debugevents
23003 This boolean value adds debug output concerning kernel events related
23004 to the debuggee seen by the debugger. This includes events that
23005 signal thread and process creation and exit, DLL loading and
23006 unloading, console interrupts, and debugging messages produced by the
23007 Windows @code{OutputDebugString} API call.
23009 @kindex set debugexec
23010 @item set debugexec
23011 This boolean value adds debug output concerning execute events
23012 (such as resume thread) seen by the debugger.
23014 @kindex set debugexceptions
23015 @item set debugexceptions
23016 This boolean value adds debug output concerning exceptions in the
23017 debuggee seen by the debugger.
23019 @kindex set debugmemory
23020 @item set debugmemory
23021 This boolean value adds debug output concerning debuggee memory reads
23022 and writes by the debugger.
23026 This boolean values specifies whether the debuggee is called
23027 via a shell or directly (default value is on).
23031 Displays if the debuggee will be started with a shell.
23036 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23039 @node Non-debug DLL Symbols
23040 @subsubsection Support for DLLs without Debugging Symbols
23041 @cindex DLLs with no debugging symbols
23042 @cindex Minimal symbols and DLLs
23044 Very often on windows, some of the DLLs that your program relies on do
23045 not include symbolic debugging information (for example,
23046 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
23047 symbols in a DLL, it relies on the minimal amount of symbolic
23048 information contained in the DLL's export table. This section
23049 describes working with such symbols, known internally to @value{GDBN} as
23050 ``minimal symbols''.
23052 Note that before the debugged program has started execution, no DLLs
23053 will have been loaded. The easiest way around this problem is simply to
23054 start the program --- either by setting a breakpoint or letting the
23055 program run once to completion.
23057 @subsubsection DLL Name Prefixes
23059 In keeping with the naming conventions used by the Microsoft debugging
23060 tools, DLL export symbols are made available with a prefix based on the
23061 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
23062 also entered into the symbol table, so @code{CreateFileA} is often
23063 sufficient. In some cases there will be name clashes within a program
23064 (particularly if the executable itself includes full debugging symbols)
23065 necessitating the use of the fully qualified name when referring to the
23066 contents of the DLL. Use single-quotes around the name to avoid the
23067 exclamation mark (``!'') being interpreted as a language operator.
23069 Note that the internal name of the DLL may be all upper-case, even
23070 though the file name of the DLL is lower-case, or vice-versa. Since
23071 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
23072 some confusion. If in doubt, try the @code{info functions} and
23073 @code{info variables} commands or even @code{maint print msymbols}
23074 (@pxref{Symbols}). Here's an example:
23077 (@value{GDBP}) info function CreateFileA
23078 All functions matching regular expression "CreateFileA":
23080 Non-debugging symbols:
23081 0x77e885f4 CreateFileA
23082 0x77e885f4 KERNEL32!CreateFileA
23086 (@value{GDBP}) info function !
23087 All functions matching regular expression "!":
23089 Non-debugging symbols:
23090 0x6100114c cygwin1!__assert
23091 0x61004034 cygwin1!_dll_crt0@@0
23092 0x61004240 cygwin1!dll_crt0(per_process *)
23096 @subsubsection Working with Minimal Symbols
23098 Symbols extracted from a DLL's export table do not contain very much
23099 type information. All that @value{GDBN} can do is guess whether a symbol
23100 refers to a function or variable depending on the linker section that
23101 contains the symbol. Also note that the actual contents of the memory
23102 contained in a DLL are not available unless the program is running. This
23103 means that you cannot examine the contents of a variable or disassemble
23104 a function within a DLL without a running program.
23106 Variables are generally treated as pointers and dereferenced
23107 automatically. For this reason, it is often necessary to prefix a
23108 variable name with the address-of operator (``&'') and provide explicit
23109 type information in the command. Here's an example of the type of
23113 (@value{GDBP}) print 'cygwin1!__argv'
23114 'cygwin1!__argv' has unknown type; cast it to its declared type
23118 (@value{GDBP}) x 'cygwin1!__argv'
23119 'cygwin1!__argv' has unknown type; cast it to its declared type
23122 And two possible solutions:
23125 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23126 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23130 (@value{GDBP}) x/2x &'cygwin1!__argv'
23131 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23132 (@value{GDBP}) x/x 0x10021608
23133 0x10021608: 0x0022fd98
23134 (@value{GDBP}) x/s 0x0022fd98
23135 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23138 Setting a break point within a DLL is possible even before the program
23139 starts execution. However, under these circumstances, @value{GDBN} can't
23140 examine the initial instructions of the function in order to skip the
23141 function's frame set-up code. You can work around this by using ``*&''
23142 to set the breakpoint at a raw memory address:
23145 (@value{GDBP}) break *&'python22!PyOS_Readline'
23146 Breakpoint 1 at 0x1e04eff0
23149 The author of these extensions is not entirely convinced that setting a
23150 break point within a shared DLL like @file{kernel32.dll} is completely
23154 @subsection Commands Specific to @sc{gnu} Hurd Systems
23155 @cindex @sc{gnu} Hurd debugging
23157 This subsection describes @value{GDBN} commands specific to the
23158 @sc{gnu} Hurd native debugging.
23163 @kindex set signals@r{, Hurd command}
23164 @kindex set sigs@r{, Hurd command}
23165 This command toggles the state of inferior signal interception by
23166 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23167 affected by this command. @code{sigs} is a shorthand alias for
23172 @kindex show signals@r{, Hurd command}
23173 @kindex show sigs@r{, Hurd command}
23174 Show the current state of intercepting inferior's signals.
23176 @item set signal-thread
23177 @itemx set sigthread
23178 @kindex set signal-thread
23179 @kindex set sigthread
23180 This command tells @value{GDBN} which thread is the @code{libc} signal
23181 thread. That thread is run when a signal is delivered to a running
23182 process. @code{set sigthread} is the shorthand alias of @code{set
23185 @item show signal-thread
23186 @itemx show sigthread
23187 @kindex show signal-thread
23188 @kindex show sigthread
23189 These two commands show which thread will run when the inferior is
23190 delivered a signal.
23193 @kindex set stopped@r{, Hurd command}
23194 This commands tells @value{GDBN} that the inferior process is stopped,
23195 as with the @code{SIGSTOP} signal. The stopped process can be
23196 continued by delivering a signal to it.
23199 @kindex show stopped@r{, Hurd command}
23200 This command shows whether @value{GDBN} thinks the debuggee is
23203 @item set exceptions
23204 @kindex set exceptions@r{, Hurd command}
23205 Use this command to turn off trapping of exceptions in the inferior.
23206 When exception trapping is off, neither breakpoints nor
23207 single-stepping will work. To restore the default, set exception
23210 @item show exceptions
23211 @kindex show exceptions@r{, Hurd command}
23212 Show the current state of trapping exceptions in the inferior.
23214 @item set task pause
23215 @kindex set task@r{, Hurd commands}
23216 @cindex task attributes (@sc{gnu} Hurd)
23217 @cindex pause current task (@sc{gnu} Hurd)
23218 This command toggles task suspension when @value{GDBN} has control.
23219 Setting it to on takes effect immediately, and the task is suspended
23220 whenever @value{GDBN} gets control. Setting it to off will take
23221 effect the next time the inferior is continued. If this option is set
23222 to off, you can use @code{set thread default pause on} or @code{set
23223 thread pause on} (see below) to pause individual threads.
23225 @item show task pause
23226 @kindex show task@r{, Hurd commands}
23227 Show the current state of task suspension.
23229 @item set task detach-suspend-count
23230 @cindex task suspend count
23231 @cindex detach from task, @sc{gnu} Hurd
23232 This command sets the suspend count the task will be left with when
23233 @value{GDBN} detaches from it.
23235 @item show task detach-suspend-count
23236 Show the suspend count the task will be left with when detaching.
23238 @item set task exception-port
23239 @itemx set task excp
23240 @cindex task exception port, @sc{gnu} Hurd
23241 This command sets the task exception port to which @value{GDBN} will
23242 forward exceptions. The argument should be the value of the @dfn{send
23243 rights} of the task. @code{set task excp} is a shorthand alias.
23245 @item set noninvasive
23246 @cindex noninvasive task options
23247 This command switches @value{GDBN} to a mode that is the least
23248 invasive as far as interfering with the inferior is concerned. This
23249 is the same as using @code{set task pause}, @code{set exceptions}, and
23250 @code{set signals} to values opposite to the defaults.
23252 @item info send-rights
23253 @itemx info receive-rights
23254 @itemx info port-rights
23255 @itemx info port-sets
23256 @itemx info dead-names
23259 @cindex send rights, @sc{gnu} Hurd
23260 @cindex receive rights, @sc{gnu} Hurd
23261 @cindex port rights, @sc{gnu} Hurd
23262 @cindex port sets, @sc{gnu} Hurd
23263 @cindex dead names, @sc{gnu} Hurd
23264 These commands display information about, respectively, send rights,
23265 receive rights, port rights, port sets, and dead names of a task.
23266 There are also shorthand aliases: @code{info ports} for @code{info
23267 port-rights} and @code{info psets} for @code{info port-sets}.
23269 @item set thread pause
23270 @kindex set thread@r{, Hurd command}
23271 @cindex thread properties, @sc{gnu} Hurd
23272 @cindex pause current thread (@sc{gnu} Hurd)
23273 This command toggles current thread suspension when @value{GDBN} has
23274 control. Setting it to on takes effect immediately, and the current
23275 thread is suspended whenever @value{GDBN} gets control. Setting it to
23276 off will take effect the next time the inferior is continued.
23277 Normally, this command has no effect, since when @value{GDBN} has
23278 control, the whole task is suspended. However, if you used @code{set
23279 task pause off} (see above), this command comes in handy to suspend
23280 only the current thread.
23282 @item show thread pause
23283 @kindex show thread@r{, Hurd command}
23284 This command shows the state of current thread suspension.
23286 @item set thread run
23287 This command sets whether the current thread is allowed to run.
23289 @item show thread run
23290 Show whether the current thread is allowed to run.
23292 @item set thread detach-suspend-count
23293 @cindex thread suspend count, @sc{gnu} Hurd
23294 @cindex detach from thread, @sc{gnu} Hurd
23295 This command sets the suspend count @value{GDBN} will leave on a
23296 thread when detaching. This number is relative to the suspend count
23297 found by @value{GDBN} when it notices the thread; use @code{set thread
23298 takeover-suspend-count} to force it to an absolute value.
23300 @item show thread detach-suspend-count
23301 Show the suspend count @value{GDBN} will leave on the thread when
23304 @item set thread exception-port
23305 @itemx set thread excp
23306 Set the thread exception port to which to forward exceptions. This
23307 overrides the port set by @code{set task exception-port} (see above).
23308 @code{set thread excp} is the shorthand alias.
23310 @item set thread takeover-suspend-count
23311 Normally, @value{GDBN}'s thread suspend counts are relative to the
23312 value @value{GDBN} finds when it notices each thread. This command
23313 changes the suspend counts to be absolute instead.
23315 @item set thread default
23316 @itemx show thread default
23317 @cindex thread default settings, @sc{gnu} Hurd
23318 Each of the above @code{set thread} commands has a @code{set thread
23319 default} counterpart (e.g., @code{set thread default pause}, @code{set
23320 thread default exception-port}, etc.). The @code{thread default}
23321 variety of commands sets the default thread properties for all
23322 threads; you can then change the properties of individual threads with
23323 the non-default commands.
23330 @value{GDBN} provides the following commands specific to the Darwin target:
23333 @item set debug darwin @var{num}
23334 @kindex set debug darwin
23335 When set to a non zero value, enables debugging messages specific to
23336 the Darwin support. Higher values produce more verbose output.
23338 @item show debug darwin
23339 @kindex show debug darwin
23340 Show the current state of Darwin messages.
23342 @item set debug mach-o @var{num}
23343 @kindex set debug mach-o
23344 When set to a non zero value, enables debugging messages while
23345 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23346 file format used on Darwin for object and executable files.) Higher
23347 values produce more verbose output. This is a command to diagnose
23348 problems internal to @value{GDBN} and should not be needed in normal
23351 @item show debug mach-o
23352 @kindex show debug mach-o
23353 Show the current state of Mach-O file messages.
23355 @item set mach-exceptions on
23356 @itemx set mach-exceptions off
23357 @kindex set mach-exceptions
23358 On Darwin, faults are first reported as a Mach exception and are then
23359 mapped to a Posix signal. Use this command to turn on trapping of
23360 Mach exceptions in the inferior. This might be sometimes useful to
23361 better understand the cause of a fault. The default is off.
23363 @item show mach-exceptions
23364 @kindex show mach-exceptions
23365 Show the current state of exceptions trapping.
23369 @subsection FreeBSD
23372 When the ABI of a system call is changed in the FreeBSD kernel, this
23373 is implemented by leaving a compatibility system call using the old
23374 ABI at the existing number and allocating a new system call number for
23375 the version using the new ABI. As a convenience, when a system call
23376 is caught by name (@pxref{catch syscall}), compatibility system calls
23379 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23380 system call and catching the @code{kevent} system call by name catches
23384 (@value{GDBP}) catch syscall kevent
23385 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23391 @section Embedded Operating Systems
23393 This section describes configurations involving the debugging of
23394 embedded operating systems that are available for several different
23397 @value{GDBN} includes the ability to debug programs running on
23398 various real-time operating systems.
23400 @node Embedded Processors
23401 @section Embedded Processors
23403 This section goes into details specific to particular embedded
23406 @cindex send command to simulator
23407 Whenever a specific embedded processor has a simulator, @value{GDBN}
23408 allows to send an arbitrary command to the simulator.
23411 @item sim @var{command}
23412 @kindex sim@r{, a command}
23413 Send an arbitrary @var{command} string to the simulator. Consult the
23414 documentation for the specific simulator in use for information about
23415 acceptable commands.
23420 * ARC:: Synopsys ARC
23422 * M68K:: Motorola M68K
23423 * MicroBlaze:: Xilinx MicroBlaze
23424 * MIPS Embedded:: MIPS Embedded
23425 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23426 * PowerPC Embedded:: PowerPC Embedded
23429 * Super-H:: Renesas Super-H
23433 @subsection Synopsys ARC
23434 @cindex Synopsys ARC
23435 @cindex ARC specific commands
23441 @value{GDBN} provides the following ARC-specific commands:
23444 @item set debug arc
23445 @kindex set debug arc
23446 Control the level of ARC specific debug messages. Use 0 for no messages (the
23447 default), 1 for debug messages, and 2 for even more debug messages.
23449 @item show debug arc
23450 @kindex show debug arc
23451 Show the level of ARC specific debugging in operation.
23453 @item maint print arc arc-instruction @var{address}
23454 @kindex maint print arc arc-instruction
23455 Print internal disassembler information about instruction at a given address.
23462 @value{GDBN} provides the following ARM-specific commands:
23465 @item set arm disassembler
23467 This commands selects from a list of disassembly styles. The
23468 @code{"std"} style is the standard style.
23470 @item show arm disassembler
23472 Show the current disassembly style.
23474 @item set arm apcs32
23475 @cindex ARM 32-bit mode
23476 This command toggles ARM operation mode between 32-bit and 26-bit.
23478 @item show arm apcs32
23479 Display the current usage of the ARM 32-bit mode.
23481 @item set arm fpu @var{fputype}
23482 This command sets the ARM floating-point unit (FPU) type. The
23483 argument @var{fputype} can be one of these:
23487 Determine the FPU type by querying the OS ABI.
23489 Software FPU, with mixed-endian doubles on little-endian ARM
23492 GCC-compiled FPA co-processor.
23494 Software FPU with pure-endian doubles.
23500 Show the current type of the FPU.
23503 This command forces @value{GDBN} to use the specified ABI.
23506 Show the currently used ABI.
23508 @item set arm fallback-mode (arm|thumb|auto)
23509 @value{GDBN} uses the symbol table, when available, to determine
23510 whether instructions are ARM or Thumb. This command controls
23511 @value{GDBN}'s default behavior when the symbol table is not
23512 available. The default is @samp{auto}, which causes @value{GDBN} to
23513 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23516 @item show arm fallback-mode
23517 Show the current fallback instruction mode.
23519 @item set arm force-mode (arm|thumb|auto)
23520 This command overrides use of the symbol table to determine whether
23521 instructions are ARM or Thumb. The default is @samp{auto}, which
23522 causes @value{GDBN} to use the symbol table and then the setting
23523 of @samp{set arm fallback-mode}.
23525 @item show arm force-mode
23526 Show the current forced instruction mode.
23528 @item set debug arm
23529 Toggle whether to display ARM-specific debugging messages from the ARM
23530 target support subsystem.
23532 @item show debug arm
23533 Show whether ARM-specific debugging messages are enabled.
23537 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23538 The @value{GDBN} ARM simulator accepts the following optional arguments.
23541 @item --swi-support=@var{type}
23542 Tell the simulator which SWI interfaces to support. The argument
23543 @var{type} may be a comma separated list of the following values.
23544 The default value is @code{all}.
23559 The Motorola m68k configuration includes ColdFire support.
23562 @subsection MicroBlaze
23563 @cindex Xilinx MicroBlaze
23564 @cindex XMD, Xilinx Microprocessor Debugger
23566 The MicroBlaze is a soft-core processor supported on various Xilinx
23567 FPGAs, such as Spartan or Virtex series. Boards with these processors
23568 usually have JTAG ports which connect to a host system running the Xilinx
23569 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23570 This host system is used to download the configuration bitstream to
23571 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23572 communicates with the target board using the JTAG interface and
23573 presents a @code{gdbserver} interface to the board. By default
23574 @code{xmd} uses port @code{1234}. (While it is possible to change
23575 this default port, it requires the use of undocumented @code{xmd}
23576 commands. Contact Xilinx support if you need to do this.)
23578 Use these GDB commands to connect to the MicroBlaze target processor.
23581 @item target remote :1234
23582 Use this command to connect to the target if you are running @value{GDBN}
23583 on the same system as @code{xmd}.
23585 @item target remote @var{xmd-host}:1234
23586 Use this command to connect to the target if it is connected to @code{xmd}
23587 running on a different system named @var{xmd-host}.
23590 Use this command to download a program to the MicroBlaze target.
23592 @item set debug microblaze @var{n}
23593 Enable MicroBlaze-specific debugging messages if non-zero.
23595 @item show debug microblaze @var{n}
23596 Show MicroBlaze-specific debugging level.
23599 @node MIPS Embedded
23600 @subsection @acronym{MIPS} Embedded
23603 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23606 @item set mipsfpu double
23607 @itemx set mipsfpu single
23608 @itemx set mipsfpu none
23609 @itemx set mipsfpu auto
23610 @itemx show mipsfpu
23611 @kindex set mipsfpu
23612 @kindex show mipsfpu
23613 @cindex @acronym{MIPS} remote floating point
23614 @cindex floating point, @acronym{MIPS} remote
23615 If your target board does not support the @acronym{MIPS} floating point
23616 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23617 need this, you may wish to put the command in your @value{GDBN} init
23618 file). This tells @value{GDBN} how to find the return value of
23619 functions which return floating point values. It also allows
23620 @value{GDBN} to avoid saving the floating point registers when calling
23621 functions on the board. If you are using a floating point coprocessor
23622 with only single precision floating point support, as on the @sc{r4650}
23623 processor, use the command @samp{set mipsfpu single}. The default
23624 double precision floating point coprocessor may be selected using
23625 @samp{set mipsfpu double}.
23627 In previous versions the only choices were double precision or no
23628 floating point, so @samp{set mipsfpu on} will select double precision
23629 and @samp{set mipsfpu off} will select no floating point.
23631 As usual, you can inquire about the @code{mipsfpu} variable with
23632 @samp{show mipsfpu}.
23635 @node OpenRISC 1000
23636 @subsection OpenRISC 1000
23637 @cindex OpenRISC 1000
23640 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23641 mainly provided as a soft-core which can run on Xilinx, Altera and other
23644 @value{GDBN} for OpenRISC supports the below commands when connecting to
23652 Runs the builtin CPU simulator which can run very basic
23653 programs but does not support most hardware functions like MMU.
23654 For more complex use cases the user is advised to run an external
23655 target, and connect using @samp{target remote}.
23657 Example: @code{target sim}
23659 @item set debug or1k
23660 Toggle whether to display OpenRISC-specific debugging messages from the
23661 OpenRISC target support subsystem.
23663 @item show debug or1k
23664 Show whether OpenRISC-specific debugging messages are enabled.
23667 @node PowerPC Embedded
23668 @subsection PowerPC Embedded
23670 @cindex DVC register
23671 @value{GDBN} supports using the DVC (Data Value Compare) register to
23672 implement in hardware simple hardware watchpoint conditions of the form:
23675 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23676 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23679 The DVC register will be automatically used when @value{GDBN} detects
23680 such pattern in a condition expression, and the created watchpoint uses one
23681 debug register (either the @code{exact-watchpoints} option is on and the
23682 variable is scalar, or the variable has a length of one byte). This feature
23683 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23686 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23687 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23688 in which case watchpoints using only one debug register are created when
23689 watching variables of scalar types.
23691 You can create an artificial array to watch an arbitrary memory
23692 region using one of the following commands (@pxref{Expressions}):
23695 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23696 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23699 PowerPC embedded processors support masked watchpoints. See the discussion
23700 about the @code{mask} argument in @ref{Set Watchpoints}.
23702 @cindex ranged breakpoint
23703 PowerPC embedded processors support hardware accelerated
23704 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23705 the inferior whenever it executes an instruction at any address within
23706 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23707 use the @code{break-range} command.
23709 @value{GDBN} provides the following PowerPC-specific commands:
23712 @kindex break-range
23713 @item break-range @var{start-location}, @var{end-location}
23714 Set a breakpoint for an address range given by
23715 @var{start-location} and @var{end-location}, which can specify a function name,
23716 a line number, an offset of lines from the current line or from the start
23717 location, or an address of an instruction (see @ref{Specify Location},
23718 for a list of all the possible ways to specify a @var{location}.)
23719 The breakpoint will stop execution of the inferior whenever it
23720 executes an instruction at any address within the specified range,
23721 (including @var{start-location} and @var{end-location}.)
23723 @kindex set powerpc
23724 @item set powerpc soft-float
23725 @itemx show powerpc soft-float
23726 Force @value{GDBN} to use (or not use) a software floating point calling
23727 convention. By default, @value{GDBN} selects the calling convention based
23728 on the selected architecture and the provided executable file.
23730 @item set powerpc vector-abi
23731 @itemx show powerpc vector-abi
23732 Force @value{GDBN} to use the specified calling convention for vector
23733 arguments and return values. The valid options are @samp{auto};
23734 @samp{generic}, to avoid vector registers even if they are present;
23735 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23736 registers. By default, @value{GDBN} selects the calling convention
23737 based on the selected architecture and the provided executable file.
23739 @item set powerpc exact-watchpoints
23740 @itemx show powerpc exact-watchpoints
23741 Allow @value{GDBN} to use only one debug register when watching a variable
23742 of scalar type, thus assuming that the variable is accessed through the
23743 address of its first byte.
23748 @subsection Atmel AVR
23751 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23752 following AVR-specific commands:
23755 @item info io_registers
23756 @kindex info io_registers@r{, AVR}
23757 @cindex I/O registers (Atmel AVR)
23758 This command displays information about the AVR I/O registers. For
23759 each register, @value{GDBN} prints its number and value.
23766 When configured for debugging CRIS, @value{GDBN} provides the
23767 following CRIS-specific commands:
23770 @item set cris-version @var{ver}
23771 @cindex CRIS version
23772 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23773 The CRIS version affects register names and sizes. This command is useful in
23774 case autodetection of the CRIS version fails.
23776 @item show cris-version
23777 Show the current CRIS version.
23779 @item set cris-dwarf2-cfi
23780 @cindex DWARF-2 CFI and CRIS
23781 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23782 Change to @samp{off} when using @code{gcc-cris} whose version is below
23785 @item show cris-dwarf2-cfi
23786 Show the current state of using DWARF-2 CFI.
23788 @item set cris-mode @var{mode}
23790 Set the current CRIS mode to @var{mode}. It should only be changed when
23791 debugging in guru mode, in which case it should be set to
23792 @samp{guru} (the default is @samp{normal}).
23794 @item show cris-mode
23795 Show the current CRIS mode.
23799 @subsection Renesas Super-H
23802 For the Renesas Super-H processor, @value{GDBN} provides these
23806 @item set sh calling-convention @var{convention}
23807 @kindex set sh calling-convention
23808 Set the calling-convention used when calling functions from @value{GDBN}.
23809 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23810 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23811 convention. If the DWARF-2 information of the called function specifies
23812 that the function follows the Renesas calling convention, the function
23813 is called using the Renesas calling convention. If the calling convention
23814 is set to @samp{renesas}, the Renesas calling convention is always used,
23815 regardless of the DWARF-2 information. This can be used to override the
23816 default of @samp{gcc} if debug information is missing, or the compiler
23817 does not emit the DWARF-2 calling convention entry for a function.
23819 @item show sh calling-convention
23820 @kindex show sh calling-convention
23821 Show the current calling convention setting.
23826 @node Architectures
23827 @section Architectures
23829 This section describes characteristics of architectures that affect
23830 all uses of @value{GDBN} with the architecture, both native and cross.
23837 * HPPA:: HP PA architecture
23838 * SPU:: Cell Broadband Engine SPU architecture
23846 @subsection AArch64
23847 @cindex AArch64 support
23849 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23850 following special commands:
23853 @item set debug aarch64
23854 @kindex set debug aarch64
23855 This command determines whether AArch64 architecture-specific debugging
23856 messages are to be displayed.
23858 @item show debug aarch64
23859 Show whether AArch64 debugging messages are displayed.
23863 @subsubsection AArch64 SVE.
23864 @cindex AArch64 SVE.
23866 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23867 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23868 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23869 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23870 @code{$vg} will be provided. This is the vector granule for the current thread
23871 and represents the number of 64-bit chunks in an SVE @code{z} register.
23873 If the vector length changes, then the @code{$vg} register will be updated,
23874 but the lengths of the @code{z} and @code{p} registers will not change. This
23875 is a known limitation of @value{GDBN} and does not affect the execution of the
23880 @subsection x86 Architecture-specific Issues
23883 @item set struct-convention @var{mode}
23884 @kindex set struct-convention
23885 @cindex struct return convention
23886 @cindex struct/union returned in registers
23887 Set the convention used by the inferior to return @code{struct}s and
23888 @code{union}s from functions to @var{mode}. Possible values of
23889 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23890 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23891 are returned on the stack, while @code{"reg"} means that a
23892 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23893 be returned in a register.
23895 @item show struct-convention
23896 @kindex show struct-convention
23897 Show the current setting of the convention to return @code{struct}s
23902 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23903 @cindex Intel Memory Protection Extensions (MPX).
23905 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23906 @footnote{The register named with capital letters represent the architecture
23907 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23908 which are the lower bound and upper bound. Bounds are effective addresses or
23909 memory locations. The upper bounds are architecturally represented in 1's
23910 complement form. A bound having lower bound = 0, and upper bound = 0
23911 (1's complement of all bits set) will allow access to the entire address space.
23913 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23914 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23915 display the upper bound performing the complement of one operation on the
23916 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23917 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23918 can also be noted that the upper bounds are inclusive.
23920 As an example, assume that the register BND0 holds bounds for a pointer having
23921 access allowed for the range between 0x32 and 0x71. The values present on
23922 bnd0raw and bnd registers are presented as follows:
23925 bnd0raw = @{0x32, 0xffffffff8e@}
23926 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23929 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23930 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23931 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23932 Python, the display includes the memory size, in bits, accessible to
23935 Bounds can also be stored in bounds tables, which are stored in
23936 application memory. These tables store bounds for pointers by specifying
23937 the bounds pointer's value along with its bounds. Evaluating and changing
23938 bounds located in bound tables is therefore interesting while investigating
23939 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23942 @item show mpx bound @var{pointer}
23943 @kindex show mpx bound
23944 Display bounds of the given @var{pointer}.
23946 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23947 @kindex set mpx bound
23948 Set the bounds of a pointer in the bound table.
23949 This command takes three parameters: @var{pointer} is the pointers
23950 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23951 for lower and upper bounds respectively.
23954 When you call an inferior function on an Intel MPX enabled program,
23955 GDB sets the inferior's bound registers to the init (disabled) state
23956 before calling the function. As a consequence, bounds checks for the
23957 pointer arguments passed to the function will always pass.
23959 This is necessary because when you call an inferior function, the
23960 program is usually in the middle of the execution of other function.
23961 Since at that point bound registers are in an arbitrary state, not
23962 clearing them would lead to random bound violations in the called
23965 You can still examine the influence of the bound registers on the
23966 execution of the called function by stopping the execution of the
23967 called function at its prologue, setting bound registers, and
23968 continuing the execution. For example:
23972 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23973 $ print upper (a, b, c, d, 1)
23974 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23976 @{lbound = 0x0, ubound = ffffffff@} : size -1
23979 At this last step the value of bnd0 can be changed for investigation of bound
23980 violations caused along the execution of the call. In order to know how to
23981 set the bound registers or bound table for the call consult the ABI.
23986 See the following section.
23989 @subsection @acronym{MIPS}
23991 @cindex stack on Alpha
23992 @cindex stack on @acronym{MIPS}
23993 @cindex Alpha stack
23994 @cindex @acronym{MIPS} stack
23995 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23996 sometimes requires @value{GDBN} to search backward in the object code to
23997 find the beginning of a function.
23999 @cindex response time, @acronym{MIPS} debugging
24000 To improve response time (especially for embedded applications, where
24001 @value{GDBN} may be restricted to a slow serial line for this search)
24002 you may want to limit the size of this search, using one of these
24006 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
24007 @item set heuristic-fence-post @var{limit}
24008 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
24009 search for the beginning of a function. A value of @var{0} (the
24010 default) means there is no limit. However, except for @var{0}, the
24011 larger the limit the more bytes @code{heuristic-fence-post} must search
24012 and therefore the longer it takes to run. You should only need to use
24013 this command when debugging a stripped executable.
24015 @item show heuristic-fence-post
24016 Display the current limit.
24020 These commands are available @emph{only} when @value{GDBN} is configured
24021 for debugging programs on Alpha or @acronym{MIPS} processors.
24023 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24027 @item set mips abi @var{arg}
24028 @kindex set mips abi
24029 @cindex set ABI for @acronym{MIPS}
24030 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24031 values of @var{arg} are:
24035 The default ABI associated with the current binary (this is the
24045 @item show mips abi
24046 @kindex show mips abi
24047 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
24049 @item set mips compression @var{arg}
24050 @kindex set mips compression
24051 @cindex code compression, @acronym{MIPS}
24052 Tell @value{GDBN} which @acronym{MIPS} compressed
24053 @acronym{ISA, Instruction Set Architecture} encoding is used by the
24054 inferior. @value{GDBN} uses this for code disassembly and other
24055 internal interpretation purposes. This setting is only referred to
24056 when no executable has been associated with the debugging session or
24057 the executable does not provide information about the encoding it uses.
24058 Otherwise this setting is automatically updated from information
24059 provided by the executable.
24061 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
24062 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
24063 executables containing @acronym{MIPS16} code frequently are not
24064 identified as such.
24066 This setting is ``sticky''; that is, it retains its value across
24067 debugging sessions until reset either explicitly with this command or
24068 implicitly from an executable.
24070 The compiler and/or assembler typically add symbol table annotations to
24071 identify functions compiled for the @acronym{MIPS16} or
24072 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
24073 are present, @value{GDBN} uses them in preference to the global
24074 compressed @acronym{ISA} encoding setting.
24076 @item show mips compression
24077 @kindex show mips compression
24078 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24079 @value{GDBN} to debug the inferior.
24082 @itemx show mipsfpu
24083 @xref{MIPS Embedded, set mipsfpu}.
24085 @item set mips mask-address @var{arg}
24086 @kindex set mips mask-address
24087 @cindex @acronym{MIPS} addresses, masking
24088 This command determines whether the most-significant 32 bits of 64-bit
24089 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24090 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24091 setting, which lets @value{GDBN} determine the correct value.
24093 @item show mips mask-address
24094 @kindex show mips mask-address
24095 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24098 @item set remote-mips64-transfers-32bit-regs
24099 @kindex set remote-mips64-transfers-32bit-regs
24100 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24101 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24102 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24103 and 64 bits for other registers, set this option to @samp{on}.
24105 @item show remote-mips64-transfers-32bit-regs
24106 @kindex show remote-mips64-transfers-32bit-regs
24107 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24109 @item set debug mips
24110 @kindex set debug mips
24111 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24112 target code in @value{GDBN}.
24114 @item show debug mips
24115 @kindex show debug mips
24116 Show the current setting of @acronym{MIPS} debugging messages.
24122 @cindex HPPA support
24124 When @value{GDBN} is debugging the HP PA architecture, it provides the
24125 following special commands:
24128 @item set debug hppa
24129 @kindex set debug hppa
24130 This command determines whether HPPA architecture-specific debugging
24131 messages are to be displayed.
24133 @item show debug hppa
24134 Show whether HPPA debugging messages are displayed.
24136 @item maint print unwind @var{address}
24137 @kindex maint print unwind@r{, HPPA}
24138 This command displays the contents of the unwind table entry at the
24139 given @var{address}.
24145 @subsection Cell Broadband Engine SPU architecture
24146 @cindex Cell Broadband Engine
24149 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24150 it provides the following special commands:
24153 @item info spu event
24155 Display SPU event facility status. Shows current event mask
24156 and pending event status.
24158 @item info spu signal
24159 Display SPU signal notification facility status. Shows pending
24160 signal-control word and signal notification mode of both signal
24161 notification channels.
24163 @item info spu mailbox
24164 Display SPU mailbox facility status. Shows all pending entries,
24165 in order of processing, in each of the SPU Write Outbound,
24166 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24169 Display MFC DMA status. Shows all pending commands in the MFC
24170 DMA queue. For each entry, opcode, tag, class IDs, effective
24171 and local store addresses and transfer size are shown.
24173 @item info spu proxydma
24174 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24175 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24176 and local store addresses and transfer size are shown.
24180 When @value{GDBN} is debugging a combined PowerPC/SPU application
24181 on the Cell Broadband Engine, it provides in addition the following
24185 @item set spu stop-on-load @var{arg}
24187 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24188 will give control to the user when a new SPE thread enters its @code{main}
24189 function. The default is @code{off}.
24191 @item show spu stop-on-load
24193 Show whether to stop for new SPE threads.
24195 @item set spu auto-flush-cache @var{arg}
24196 Set whether to automatically flush the software-managed cache. When set to
24197 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24198 cache to be flushed whenever SPE execution stops. This provides a consistent
24199 view of PowerPC memory that is accessed via the cache. If an application
24200 does not use the software-managed cache, this option has no effect.
24202 @item show spu auto-flush-cache
24203 Show whether to automatically flush the software-managed cache.
24208 @subsection PowerPC
24209 @cindex PowerPC architecture
24211 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24212 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24213 numbers stored in the floating point registers. These values must be stored
24214 in two consecutive registers, always starting at an even register like
24215 @code{f0} or @code{f2}.
24217 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24218 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24219 @code{f2} and @code{f3} for @code{$dl1} and so on.
24221 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24222 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24225 @subsection Nios II
24226 @cindex Nios II architecture
24228 When @value{GDBN} is debugging the Nios II architecture,
24229 it provides the following special commands:
24233 @item set debug nios2
24234 @kindex set debug nios2
24235 This command turns on and off debugging messages for the Nios II
24236 target code in @value{GDBN}.
24238 @item show debug nios2
24239 @kindex show debug nios2
24240 Show the current setting of Nios II debugging messages.
24244 @subsection Sparc64
24245 @cindex Sparc64 support
24246 @cindex Application Data Integrity
24247 @subsubsection ADI Support
24249 The M7 processor supports an Application Data Integrity (ADI) feature that
24250 detects invalid data accesses. When software allocates memory and enables
24251 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24252 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24253 the 4-bit version in every cacheline of that data. Hardware saves the latter
24254 in spare bits in the cache and memory hierarchy. On each load and store,
24255 the processor compares the upper 4 VA (virtual address) bits to the
24256 cacheline's version. If there is a mismatch, the processor generates a
24257 version mismatch trap which can be either precise or disrupting. The trap
24258 is an error condition which the kernel delivers to the process as a SIGSEGV
24261 Note that only 64-bit applications can use ADI and need to be built with
24264 Values of the ADI version tags, which are in granularity of a
24265 cacheline (64 bytes), can be viewed or modified.
24269 @kindex adi examine
24270 @item adi (examine | x) [ / @var{n} ] @var{addr}
24272 The @code{adi examine} command displays the value of one ADI version tag per
24275 @var{n} is a decimal integer specifying the number in bytes; the default
24276 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24277 block size, to display.
24279 @var{addr} is the address in user address space where you want @value{GDBN}
24280 to begin displaying the ADI version tags.
24282 Below is an example of displaying ADI versions of variable "shmaddr".
24285 (@value{GDBP}) adi x/100 shmaddr
24286 0xfff800010002c000: 0 0
24290 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24292 The @code{adi assign} command is used to assign new ADI version tag
24295 @var{n} is a decimal integer specifying the number in bytes;
24296 the default is 1. It specifies how much ADI version information, at the
24297 ratio of 1:ADI block size, to modify.
24299 @var{addr} is the address in user address space where you want @value{GDBN}
24300 to begin modifying the ADI version tags.
24302 @var{tag} is the new ADI version tag.
24304 For example, do the following to modify then verify ADI versions of
24305 variable "shmaddr":
24308 (@value{GDBP}) adi a/100 shmaddr = 7
24309 (@value{GDBP}) adi x/100 shmaddr
24310 0xfff800010002c000: 7 7
24317 @cindex S12Z support
24319 When @value{GDBN} is debugging the S12Z architecture,
24320 it provides the following special command:
24323 @item maint info bdccsr
24324 @kindex maint info bdccsr@r{, S12Z}
24325 This command displays the current value of the microprocessor's
24330 @node Controlling GDB
24331 @chapter Controlling @value{GDBN}
24333 You can alter the way @value{GDBN} interacts with you by using the
24334 @code{set} command. For commands controlling how @value{GDBN} displays
24335 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24340 * Editing:: Command editing
24341 * Command History:: Command history
24342 * Screen Size:: Screen size
24343 * Output Styling:: Output styling
24344 * Numbers:: Numbers
24345 * ABI:: Configuring the current ABI
24346 * Auto-loading:: Automatically loading associated files
24347 * Messages/Warnings:: Optional warnings and messages
24348 * Debugging Output:: Optional messages about internal happenings
24349 * Other Misc Settings:: Other Miscellaneous Settings
24357 @value{GDBN} indicates its readiness to read a command by printing a string
24358 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24359 can change the prompt string with the @code{set prompt} command. For
24360 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24361 the prompt in one of the @value{GDBN} sessions so that you can always tell
24362 which one you are talking to.
24364 @emph{Note:} @code{set prompt} does not add a space for you after the
24365 prompt you set. This allows you to set a prompt which ends in a space
24366 or a prompt that does not.
24370 @item set prompt @var{newprompt}
24371 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24373 @kindex show prompt
24375 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24378 Versions of @value{GDBN} that ship with Python scripting enabled have
24379 prompt extensions. The commands for interacting with these extensions
24383 @kindex set extended-prompt
24384 @item set extended-prompt @var{prompt}
24385 Set an extended prompt that allows for substitutions.
24386 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24387 substitution. Any escape sequences specified as part of the prompt
24388 string are replaced with the corresponding strings each time the prompt
24394 set extended-prompt Current working directory: \w (gdb)
24397 Note that when an extended-prompt is set, it takes control of the
24398 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24400 @kindex show extended-prompt
24401 @item show extended-prompt
24402 Prints the extended prompt. Any escape sequences specified as part of
24403 the prompt string with @code{set extended-prompt}, are replaced with the
24404 corresponding strings each time the prompt is displayed.
24408 @section Command Editing
24410 @cindex command line editing
24412 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24413 @sc{gnu} library provides consistent behavior for programs which provide a
24414 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24415 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24416 substitution, and a storage and recall of command history across
24417 debugging sessions.
24419 You may control the behavior of command line editing in @value{GDBN} with the
24420 command @code{set}.
24423 @kindex set editing
24426 @itemx set editing on
24427 Enable command line editing (enabled by default).
24429 @item set editing off
24430 Disable command line editing.
24432 @kindex show editing
24434 Show whether command line editing is enabled.
24437 @ifset SYSTEM_READLINE
24438 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24440 @ifclear SYSTEM_READLINE
24441 @xref{Command Line Editing},
24443 for more details about the Readline
24444 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24445 encouraged to read that chapter.
24447 @node Command History
24448 @section Command History
24449 @cindex command history
24451 @value{GDBN} can keep track of the commands you type during your
24452 debugging sessions, so that you can be certain of precisely what
24453 happened. Use these commands to manage the @value{GDBN} command
24456 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24457 package, to provide the history facility.
24458 @ifset SYSTEM_READLINE
24459 @xref{Using History Interactively, , , history, GNU History Library},
24461 @ifclear SYSTEM_READLINE
24462 @xref{Using History Interactively},
24464 for the detailed description of the History library.
24466 To issue a command to @value{GDBN} without affecting certain aspects of
24467 the state which is seen by users, prefix it with @samp{server }
24468 (@pxref{Server Prefix}). This
24469 means that this command will not affect the command history, nor will it
24470 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24471 pressed on a line by itself.
24473 @cindex @code{server}, command prefix
24474 The server prefix does not affect the recording of values into the value
24475 history; to print a value without recording it into the value history,
24476 use the @code{output} command instead of the @code{print} command.
24478 Here is the description of @value{GDBN} commands related to command
24482 @cindex history substitution
24483 @cindex history file
24484 @kindex set history filename
24485 @cindex @env{GDBHISTFILE}, environment variable
24486 @item set history filename @var{fname}
24487 Set the name of the @value{GDBN} command history file to @var{fname}.
24488 This is the file where @value{GDBN} reads an initial command history
24489 list, and where it writes the command history from this session when it
24490 exits. You can access this list through history expansion or through
24491 the history command editing characters listed below. This file defaults
24492 to the value of the environment variable @code{GDBHISTFILE}, or to
24493 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24496 @cindex save command history
24497 @kindex set history save
24498 @item set history save
24499 @itemx set history save on
24500 Record command history in a file, whose name may be specified with the
24501 @code{set history filename} command. By default, this option is disabled.
24503 @item set history save off
24504 Stop recording command history in a file.
24506 @cindex history size
24507 @kindex set history size
24508 @cindex @env{GDBHISTSIZE}, environment variable
24509 @item set history size @var{size}
24510 @itemx set history size unlimited
24511 Set the number of commands which @value{GDBN} keeps in its history list.
24512 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24513 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24514 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24515 either a negative number or the empty string, then the number of commands
24516 @value{GDBN} keeps in the history list is unlimited.
24518 @cindex remove duplicate history
24519 @kindex set history remove-duplicates
24520 @item set history remove-duplicates @var{count}
24521 @itemx set history remove-duplicates unlimited
24522 Control the removal of duplicate history entries in the command history list.
24523 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24524 history entries and remove the first entry that is a duplicate of the current
24525 entry being added to the command history list. If @var{count} is
24526 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24527 removal of duplicate history entries is disabled.
24529 Only history entries added during the current session are considered for
24530 removal. This option is set to 0 by default.
24534 History expansion assigns special meaning to the character @kbd{!}.
24535 @ifset SYSTEM_READLINE
24536 @xref{Event Designators, , , history, GNU History Library},
24538 @ifclear SYSTEM_READLINE
24539 @xref{Event Designators},
24543 @cindex history expansion, turn on/off
24544 Since @kbd{!} is also the logical not operator in C, history expansion
24545 is off by default. If you decide to enable history expansion with the
24546 @code{set history expansion on} command, you may sometimes need to
24547 follow @kbd{!} (when it is used as logical not, in an expression) with
24548 a space or a tab to prevent it from being expanded. The readline
24549 history facilities do not attempt substitution on the strings
24550 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24552 The commands to control history expansion are:
24555 @item set history expansion on
24556 @itemx set history expansion
24557 @kindex set history expansion
24558 Enable history expansion. History expansion is off by default.
24560 @item set history expansion off
24561 Disable history expansion.
24564 @kindex show history
24566 @itemx show history filename
24567 @itemx show history save
24568 @itemx show history size
24569 @itemx show history expansion
24570 These commands display the state of the @value{GDBN} history parameters.
24571 @code{show history} by itself displays all four states.
24576 @kindex show commands
24577 @cindex show last commands
24578 @cindex display command history
24579 @item show commands
24580 Display the last ten commands in the command history.
24582 @item show commands @var{n}
24583 Print ten commands centered on command number @var{n}.
24585 @item show commands +
24586 Print ten commands just after the commands last printed.
24590 @section Screen Size
24591 @cindex size of screen
24592 @cindex screen size
24595 @cindex pauses in output
24597 Certain commands to @value{GDBN} may produce large amounts of
24598 information output to the screen. To help you read all of it,
24599 @value{GDBN} pauses and asks you for input at the end of each page of
24600 output. Type @key{RET} when you want to see one more page of output,
24601 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24602 without paging for the rest of the current command. Also, the screen
24603 width setting determines when to wrap lines of output. Depending on
24604 what is being printed, @value{GDBN} tries to break the line at a
24605 readable place, rather than simply letting it overflow onto the
24608 Normally @value{GDBN} knows the size of the screen from the terminal
24609 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24610 together with the value of the @code{TERM} environment variable and the
24611 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24612 you can override it with the @code{set height} and @code{set
24619 @kindex show height
24620 @item set height @var{lpp}
24621 @itemx set height unlimited
24623 @itemx set width @var{cpl}
24624 @itemx set width unlimited
24626 These @code{set} commands specify a screen height of @var{lpp} lines and
24627 a screen width of @var{cpl} characters. The associated @code{show}
24628 commands display the current settings.
24630 If you specify a height of either @code{unlimited} or zero lines,
24631 @value{GDBN} does not pause during output no matter how long the
24632 output is. This is useful if output is to a file or to an editor
24635 Likewise, you can specify @samp{set width unlimited} or @samp{set
24636 width 0} to prevent @value{GDBN} from wrapping its output.
24638 @item set pagination on
24639 @itemx set pagination off
24640 @kindex set pagination
24641 Turn the output pagination on or off; the default is on. Turning
24642 pagination off is the alternative to @code{set height unlimited}. Note that
24643 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24644 Options, -batch}) also automatically disables pagination.
24646 @item show pagination
24647 @kindex show pagination
24648 Show the current pagination mode.
24651 @node Output Styling
24652 @section Output Styling
24658 @value{GDBN} can style its output on a capable terminal. This is
24659 enabled by default on most systems, but disabled by default when in
24660 batch mode (@pxref{Mode Options}). Various style settings are available;
24661 and styles can also be disabled entirely.
24664 @item set style enabled @samp{on|off}
24665 Enable or disable all styling. The default is host-dependent, with
24666 most hosts defaulting to @samp{on}.
24668 @item show style enabled
24669 Show the current state of styling.
24671 @item set style sources @samp{on|off}
24672 Enable or disable source code styling. This affects whether source
24673 code, such as the output of the @code{list} command, is styled. Note
24674 that source styling only works if styling in general is enabled, and
24675 if @value{GDBN} was linked with the GNU Source Highlight library. The
24676 default is @samp{on}.
24678 @item show style sources
24679 Show the current state of source code styling.
24682 Subcommands of @code{set style} control specific forms of styling.
24683 These subcommands all follow the same pattern: each style-able object
24684 can be styled with a foreground color, a background color, and an
24687 For example, the style of file names can be controlled using the
24688 @code{set style filename} group of commands:
24691 @item set style filename background @var{color}
24692 Set the background to @var{color}. Valid colors are @samp{none}
24693 (meaning the terminal's default color), @samp{black}, @samp{red},
24694 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24697 @item set style filename foreground @var{color}
24698 Set the foreground to @var{color}. Valid colors are @samp{none}
24699 (meaning the terminal's default color), @samp{black}, @samp{red},
24700 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24703 @item set style filename intensity @var{value}
24704 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24705 (the default), @samp{bold}, and @samp{dim}.
24708 The style-able objects are:
24711 Control the styling of file names. By default, this style's
24712 foreground color is green.
24715 Control the styling of function names. These are managed with the
24716 @code{set style function} family of commands. By default, this
24717 style's foreground color is yellow.
24720 Control the styling of variable names. These are managed with the
24721 @code{set style variable} family of commands. By default, this style's
24722 foreground color is cyan.
24725 Control the styling of addresses. These are managed with the
24726 @code{set style address} family of commands. By default, this style's
24727 foreground color is blue.
24732 @cindex number representation
24733 @cindex entering numbers
24735 You can always enter numbers in octal, decimal, or hexadecimal in
24736 @value{GDBN} by the usual conventions: octal numbers begin with
24737 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24738 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24739 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24740 10; likewise, the default display for numbers---when no particular
24741 format is specified---is base 10. You can change the default base for
24742 both input and output with the commands described below.
24745 @kindex set input-radix
24746 @item set input-radix @var{base}
24747 Set the default base for numeric input. Supported choices
24748 for @var{base} are decimal 8, 10, or 16. The base must itself be
24749 specified either unambiguously or using the current input radix; for
24753 set input-radix 012
24754 set input-radix 10.
24755 set input-radix 0xa
24759 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24760 leaves the input radix unchanged, no matter what it was, since
24761 @samp{10}, being without any leading or trailing signs of its base, is
24762 interpreted in the current radix. Thus, if the current radix is 16,
24763 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24766 @kindex set output-radix
24767 @item set output-radix @var{base}
24768 Set the default base for numeric display. Supported choices
24769 for @var{base} are decimal 8, 10, or 16. The base must itself be
24770 specified either unambiguously or using the current input radix.
24772 @kindex show input-radix
24773 @item show input-radix
24774 Display the current default base for numeric input.
24776 @kindex show output-radix
24777 @item show output-radix
24778 Display the current default base for numeric display.
24780 @item set radix @r{[}@var{base}@r{]}
24784 These commands set and show the default base for both input and output
24785 of numbers. @code{set radix} sets the radix of input and output to
24786 the same base; without an argument, it resets the radix back to its
24787 default value of 10.
24792 @section Configuring the Current ABI
24794 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24795 application automatically. However, sometimes you need to override its
24796 conclusions. Use these commands to manage @value{GDBN}'s view of the
24802 @cindex Newlib OS ABI and its influence on the longjmp handling
24804 One @value{GDBN} configuration can debug binaries for multiple operating
24805 system targets, either via remote debugging or native emulation.
24806 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24807 but you can override its conclusion using the @code{set osabi} command.
24808 One example where this is useful is in debugging of binaries which use
24809 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24810 not have the same identifying marks that the standard C library for your
24813 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24814 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24815 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24816 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24820 Show the OS ABI currently in use.
24823 With no argument, show the list of registered available OS ABI's.
24825 @item set osabi @var{abi}
24826 Set the current OS ABI to @var{abi}.
24829 @cindex float promotion
24831 Generally, the way that an argument of type @code{float} is passed to a
24832 function depends on whether the function is prototyped. For a prototyped
24833 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24834 according to the architecture's convention for @code{float}. For unprototyped
24835 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24836 @code{double} and then passed.
24838 Unfortunately, some forms of debug information do not reliably indicate whether
24839 a function is prototyped. If @value{GDBN} calls a function that is not marked
24840 as prototyped, it consults @kbd{set coerce-float-to-double}.
24843 @kindex set coerce-float-to-double
24844 @item set coerce-float-to-double
24845 @itemx set coerce-float-to-double on
24846 Arguments of type @code{float} will be promoted to @code{double} when passed
24847 to an unprototyped function. This is the default setting.
24849 @item set coerce-float-to-double off
24850 Arguments of type @code{float} will be passed directly to unprototyped
24853 @kindex show coerce-float-to-double
24854 @item show coerce-float-to-double
24855 Show the current setting of promoting @code{float} to @code{double}.
24859 @kindex show cp-abi
24860 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24861 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24862 used to build your application. @value{GDBN} only fully supports
24863 programs with a single C@t{++} ABI; if your program contains code using
24864 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24865 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24866 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24867 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24868 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24869 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24874 Show the C@t{++} ABI currently in use.
24877 With no argument, show the list of supported C@t{++} ABI's.
24879 @item set cp-abi @var{abi}
24880 @itemx set cp-abi auto
24881 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24885 @section Automatically loading associated files
24886 @cindex auto-loading
24888 @value{GDBN} sometimes reads files with commands and settings automatically,
24889 without being explicitly told so by the user. We call this feature
24890 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24891 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24892 results or introduce security risks (e.g., if the file comes from untrusted
24896 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24897 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24899 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24900 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24903 There are various kinds of files @value{GDBN} can automatically load.
24904 In addition to these files, @value{GDBN} supports auto-loading code written
24905 in various extension languages. @xref{Auto-loading extensions}.
24907 Note that loading of these associated files (including the local @file{.gdbinit}
24908 file) requires accordingly configured @code{auto-load safe-path}
24909 (@pxref{Auto-loading safe path}).
24911 For these reasons, @value{GDBN} includes commands and options to let you
24912 control when to auto-load files and which files should be auto-loaded.
24915 @anchor{set auto-load off}
24916 @kindex set auto-load off
24917 @item set auto-load off
24918 Globally disable loading of all auto-loaded files.
24919 You may want to use this command with the @samp{-iex} option
24920 (@pxref{Option -init-eval-command}) such as:
24922 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24925 Be aware that system init file (@pxref{System-wide configuration})
24926 and init files from your home directory (@pxref{Home Directory Init File})
24927 still get read (as they come from generally trusted directories).
24928 To prevent @value{GDBN} from auto-loading even those init files, use the
24929 @option{-nx} option (@pxref{Mode Options}), in addition to
24930 @code{set auto-load no}.
24932 @anchor{show auto-load}
24933 @kindex show auto-load
24934 @item show auto-load
24935 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24939 (gdb) show auto-load
24940 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24941 libthread-db: Auto-loading of inferior specific libthread_db is on.
24942 local-gdbinit: Auto-loading of .gdbinit script from current directory
24944 python-scripts: Auto-loading of Python scripts is on.
24945 safe-path: List of directories from which it is safe to auto-load files
24946 is $debugdir:$datadir/auto-load.
24947 scripts-directory: List of directories from which to load auto-loaded scripts
24948 is $debugdir:$datadir/auto-load.
24951 @anchor{info auto-load}
24952 @kindex info auto-load
24953 @item info auto-load
24954 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24958 (gdb) info auto-load
24961 Yes /home/user/gdb/gdb-gdb.gdb
24962 libthread-db: No auto-loaded libthread-db.
24963 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24967 Yes /home/user/gdb/gdb-gdb.py
24971 These are @value{GDBN} control commands for the auto-loading:
24973 @multitable @columnfractions .5 .5
24974 @item @xref{set auto-load off}.
24975 @tab Disable auto-loading globally.
24976 @item @xref{show auto-load}.
24977 @tab Show setting of all kinds of files.
24978 @item @xref{info auto-load}.
24979 @tab Show state of all kinds of files.
24980 @item @xref{set auto-load gdb-scripts}.
24981 @tab Control for @value{GDBN} command scripts.
24982 @item @xref{show auto-load gdb-scripts}.
24983 @tab Show setting of @value{GDBN} command scripts.
24984 @item @xref{info auto-load gdb-scripts}.
24985 @tab Show state of @value{GDBN} command scripts.
24986 @item @xref{set auto-load python-scripts}.
24987 @tab Control for @value{GDBN} Python scripts.
24988 @item @xref{show auto-load python-scripts}.
24989 @tab Show setting of @value{GDBN} Python scripts.
24990 @item @xref{info auto-load python-scripts}.
24991 @tab Show state of @value{GDBN} Python scripts.
24992 @item @xref{set auto-load guile-scripts}.
24993 @tab Control for @value{GDBN} Guile scripts.
24994 @item @xref{show auto-load guile-scripts}.
24995 @tab Show setting of @value{GDBN} Guile scripts.
24996 @item @xref{info auto-load guile-scripts}.
24997 @tab Show state of @value{GDBN} Guile scripts.
24998 @item @xref{set auto-load scripts-directory}.
24999 @tab Control for @value{GDBN} auto-loaded scripts location.
25000 @item @xref{show auto-load scripts-directory}.
25001 @tab Show @value{GDBN} auto-loaded scripts location.
25002 @item @xref{add-auto-load-scripts-directory}.
25003 @tab Add directory for auto-loaded scripts location list.
25004 @item @xref{set auto-load local-gdbinit}.
25005 @tab Control for init file in the current directory.
25006 @item @xref{show auto-load local-gdbinit}.
25007 @tab Show setting of init file in the current directory.
25008 @item @xref{info auto-load local-gdbinit}.
25009 @tab Show state of init file in the current directory.
25010 @item @xref{set auto-load libthread-db}.
25011 @tab Control for thread debugging library.
25012 @item @xref{show auto-load libthread-db}.
25013 @tab Show setting of thread debugging library.
25014 @item @xref{info auto-load libthread-db}.
25015 @tab Show state of thread debugging library.
25016 @item @xref{set auto-load safe-path}.
25017 @tab Control directories trusted for automatic loading.
25018 @item @xref{show auto-load safe-path}.
25019 @tab Show directories trusted for automatic loading.
25020 @item @xref{add-auto-load-safe-path}.
25021 @tab Add directory trusted for automatic loading.
25024 @node Init File in the Current Directory
25025 @subsection Automatically loading init file in the current directory
25026 @cindex auto-loading init file in the current directory
25028 By default, @value{GDBN} reads and executes the canned sequences of commands
25029 from init file (if any) in the current working directory,
25030 see @ref{Init File in the Current Directory during Startup}.
25032 Note that loading of this local @file{.gdbinit} file also requires accordingly
25033 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25036 @anchor{set auto-load local-gdbinit}
25037 @kindex set auto-load local-gdbinit
25038 @item set auto-load local-gdbinit [on|off]
25039 Enable or disable the auto-loading of canned sequences of commands
25040 (@pxref{Sequences}) found in init file in the current directory.
25042 @anchor{show auto-load local-gdbinit}
25043 @kindex show auto-load local-gdbinit
25044 @item show auto-load local-gdbinit
25045 Show whether auto-loading of canned sequences of commands from init file in the
25046 current directory is enabled or disabled.
25048 @anchor{info auto-load local-gdbinit}
25049 @kindex info auto-load local-gdbinit
25050 @item info auto-load local-gdbinit
25051 Print whether canned sequences of commands from init file in the
25052 current directory have been auto-loaded.
25055 @node libthread_db.so.1 file
25056 @subsection Automatically loading thread debugging library
25057 @cindex auto-loading libthread_db.so.1
25059 This feature is currently present only on @sc{gnu}/Linux native hosts.
25061 @value{GDBN} reads in some cases thread debugging library from places specific
25062 to the inferior (@pxref{set libthread-db-search-path}).
25064 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
25065 without checking this @samp{set auto-load libthread-db} switch as system
25066 libraries have to be trusted in general. In all other cases of
25067 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
25068 auto-load libthread-db} is enabled before trying to open such thread debugging
25071 Note that loading of this debugging library also requires accordingly configured
25072 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25075 @anchor{set auto-load libthread-db}
25076 @kindex set auto-load libthread-db
25077 @item set auto-load libthread-db [on|off]
25078 Enable or disable the auto-loading of inferior specific thread debugging library.
25080 @anchor{show auto-load libthread-db}
25081 @kindex show auto-load libthread-db
25082 @item show auto-load libthread-db
25083 Show whether auto-loading of inferior specific thread debugging library is
25084 enabled or disabled.
25086 @anchor{info auto-load libthread-db}
25087 @kindex info auto-load libthread-db
25088 @item info auto-load libthread-db
25089 Print the list of all loaded inferior specific thread debugging libraries and
25090 for each such library print list of inferior @var{pid}s using it.
25093 @node Auto-loading safe path
25094 @subsection Security restriction for auto-loading
25095 @cindex auto-loading safe-path
25097 As the files of inferior can come from untrusted source (such as submitted by
25098 an application user) @value{GDBN} does not always load any files automatically.
25099 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25100 directories trusted for loading files not explicitly requested by user.
25101 Each directory can also be a shell wildcard pattern.
25103 If the path is not set properly you will see a warning and the file will not
25108 Reading symbols from /home/user/gdb/gdb...done.
25109 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25110 declined by your `auto-load safe-path' set
25111 to "$debugdir:$datadir/auto-load".
25112 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25113 declined by your `auto-load safe-path' set
25114 to "$debugdir:$datadir/auto-load".
25118 To instruct @value{GDBN} to go ahead and use the init files anyway,
25119 invoke @value{GDBN} like this:
25122 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25125 The list of trusted directories is controlled by the following commands:
25128 @anchor{set auto-load safe-path}
25129 @kindex set auto-load safe-path
25130 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25131 Set the list of directories (and their subdirectories) trusted for automatic
25132 loading and execution of scripts. You can also enter a specific trusted file.
25133 Each directory can also be a shell wildcard pattern; wildcards do not match
25134 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25135 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25136 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25137 its default value as specified during @value{GDBN} compilation.
25139 The list of directories uses path separator (@samp{:} on GNU and Unix
25140 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25141 to the @env{PATH} environment variable.
25143 @anchor{show auto-load safe-path}
25144 @kindex show auto-load safe-path
25145 @item show auto-load safe-path
25146 Show the list of directories trusted for automatic loading and execution of
25149 @anchor{add-auto-load-safe-path}
25150 @kindex add-auto-load-safe-path
25151 @item add-auto-load-safe-path
25152 Add an entry (or list of entries) to the list of directories trusted for
25153 automatic loading and execution of scripts. Multiple entries may be delimited
25154 by the host platform path separator in use.
25157 This variable defaults to what @code{--with-auto-load-dir} has been configured
25158 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25159 substitution applies the same as for @ref{set auto-load scripts-directory}.
25160 The default @code{set auto-load safe-path} value can be also overriden by
25161 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25163 Setting this variable to @file{/} disables this security protection,
25164 corresponding @value{GDBN} configuration option is
25165 @option{--without-auto-load-safe-path}.
25166 This variable is supposed to be set to the system directories writable by the
25167 system superuser only. Users can add their source directories in init files in
25168 their home directories (@pxref{Home Directory Init File}). See also deprecated
25169 init file in the current directory
25170 (@pxref{Init File in the Current Directory during Startup}).
25172 To force @value{GDBN} to load the files it declined to load in the previous
25173 example, you could use one of the following ways:
25176 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25177 Specify this trusted directory (or a file) as additional component of the list.
25178 You have to specify also any existing directories displayed by
25179 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25181 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25182 Specify this directory as in the previous case but just for a single
25183 @value{GDBN} session.
25185 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25186 Disable auto-loading safety for a single @value{GDBN} session.
25187 This assumes all the files you debug during this @value{GDBN} session will come
25188 from trusted sources.
25190 @item @kbd{./configure --without-auto-load-safe-path}
25191 During compilation of @value{GDBN} you may disable any auto-loading safety.
25192 This assumes all the files you will ever debug with this @value{GDBN} come from
25196 On the other hand you can also explicitly forbid automatic files loading which
25197 also suppresses any such warning messages:
25200 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25201 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25203 @item @file{~/.gdbinit}: @samp{set auto-load no}
25204 Disable auto-loading globally for the user
25205 (@pxref{Home Directory Init File}). While it is improbable, you could also
25206 use system init file instead (@pxref{System-wide configuration}).
25209 This setting applies to the file names as entered by user. If no entry matches
25210 @value{GDBN} tries as a last resort to also resolve all the file names into
25211 their canonical form (typically resolving symbolic links) and compare the
25212 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25213 own before starting the comparison so a canonical form of directories is
25214 recommended to be entered.
25216 @node Auto-loading verbose mode
25217 @subsection Displaying files tried for auto-load
25218 @cindex auto-loading verbose mode
25220 For better visibility of all the file locations where you can place scripts to
25221 be auto-loaded with inferior --- or to protect yourself against accidental
25222 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25223 all the files attempted to be loaded. Both existing and non-existing files may
25226 For example the list of directories from which it is safe to auto-load files
25227 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25228 may not be too obvious while setting it up.
25231 (gdb) set debug auto-load on
25232 (gdb) file ~/src/t/true
25233 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25234 for objfile "/tmp/true".
25235 auto-load: Updating directories of "/usr:/opt".
25236 auto-load: Using directory "/usr".
25237 auto-load: Using directory "/opt".
25238 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25239 by your `auto-load safe-path' set to "/usr:/opt".
25243 @anchor{set debug auto-load}
25244 @kindex set debug auto-load
25245 @item set debug auto-load [on|off]
25246 Set whether to print the filenames attempted to be auto-loaded.
25248 @anchor{show debug auto-load}
25249 @kindex show debug auto-load
25250 @item show debug auto-load
25251 Show whether printing of the filenames attempted to be auto-loaded is turned
25255 @node Messages/Warnings
25256 @section Optional Warnings and Messages
25258 @cindex verbose operation
25259 @cindex optional warnings
25260 By default, @value{GDBN} is silent about its inner workings. If you are
25261 running on a slow machine, you may want to use the @code{set verbose}
25262 command. This makes @value{GDBN} tell you when it does a lengthy
25263 internal operation, so you will not think it has crashed.
25265 Currently, the messages controlled by @code{set verbose} are those
25266 which announce that the symbol table for a source file is being read;
25267 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25270 @kindex set verbose
25271 @item set verbose on
25272 Enables @value{GDBN} output of certain informational messages.
25274 @item set verbose off
25275 Disables @value{GDBN} output of certain informational messages.
25277 @kindex show verbose
25279 Displays whether @code{set verbose} is on or off.
25282 By default, if @value{GDBN} encounters bugs in the symbol table of an
25283 object file, it is silent; but if you are debugging a compiler, you may
25284 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25289 @kindex set complaints
25290 @item set complaints @var{limit}
25291 Permits @value{GDBN} to output @var{limit} complaints about each type of
25292 unusual symbols before becoming silent about the problem. Set
25293 @var{limit} to zero to suppress all complaints; set it to a large number
25294 to prevent complaints from being suppressed.
25296 @kindex show complaints
25297 @item show complaints
25298 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25302 @anchor{confirmation requests}
25303 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25304 lot of stupid questions to confirm certain commands. For example, if
25305 you try to run a program which is already running:
25309 The program being debugged has been started already.
25310 Start it from the beginning? (y or n)
25313 If you are willing to unflinchingly face the consequences of your own
25314 commands, you can disable this ``feature'':
25318 @kindex set confirm
25320 @cindex confirmation
25321 @cindex stupid questions
25322 @item set confirm off
25323 Disables confirmation requests. Note that running @value{GDBN} with
25324 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25325 automatically disables confirmation requests.
25327 @item set confirm on
25328 Enables confirmation requests (the default).
25330 @kindex show confirm
25332 Displays state of confirmation requests.
25336 @cindex command tracing
25337 If you need to debug user-defined commands or sourced files you may find it
25338 useful to enable @dfn{command tracing}. In this mode each command will be
25339 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25340 quantity denoting the call depth of each command.
25343 @kindex set trace-commands
25344 @cindex command scripts, debugging
25345 @item set trace-commands on
25346 Enable command tracing.
25347 @item set trace-commands off
25348 Disable command tracing.
25349 @item show trace-commands
25350 Display the current state of command tracing.
25353 @node Debugging Output
25354 @section Optional Messages about Internal Happenings
25355 @cindex optional debugging messages
25357 @value{GDBN} has commands that enable optional debugging messages from
25358 various @value{GDBN} subsystems; normally these commands are of
25359 interest to @value{GDBN} maintainers, or when reporting a bug. This
25360 section documents those commands.
25363 @kindex set exec-done-display
25364 @item set exec-done-display
25365 Turns on or off the notification of asynchronous commands'
25366 completion. When on, @value{GDBN} will print a message when an
25367 asynchronous command finishes its execution. The default is off.
25368 @kindex show exec-done-display
25369 @item show exec-done-display
25370 Displays the current setting of asynchronous command completion
25373 @cindex ARM AArch64
25374 @item set debug aarch64
25375 Turns on or off display of debugging messages related to ARM AArch64.
25376 The default is off.
25378 @item show debug aarch64
25379 Displays the current state of displaying debugging messages related to
25381 @cindex gdbarch debugging info
25382 @cindex architecture debugging info
25383 @item set debug arch
25384 Turns on or off display of gdbarch debugging info. The default is off
25385 @item show debug arch
25386 Displays the current state of displaying gdbarch debugging info.
25387 @item set debug aix-solib
25388 @cindex AIX shared library debugging
25389 Control display of debugging messages from the AIX shared library
25390 support module. The default is off.
25391 @item show debug aix-thread
25392 Show the current state of displaying AIX shared library debugging messages.
25393 @item set debug aix-thread
25394 @cindex AIX threads
25395 Display debugging messages about inner workings of the AIX thread
25397 @item show debug aix-thread
25398 Show the current state of AIX thread debugging info display.
25399 @item set debug check-physname
25401 Check the results of the ``physname'' computation. When reading DWARF
25402 debugging information for C@t{++}, @value{GDBN} attempts to compute
25403 each entity's name. @value{GDBN} can do this computation in two
25404 different ways, depending on exactly what information is present.
25405 When enabled, this setting causes @value{GDBN} to compute the names
25406 both ways and display any discrepancies.
25407 @item show debug check-physname
25408 Show the current state of ``physname'' checking.
25409 @item set debug coff-pe-read
25410 @cindex COFF/PE exported symbols
25411 Control display of debugging messages related to reading of COFF/PE
25412 exported symbols. The default is off.
25413 @item show debug coff-pe-read
25414 Displays the current state of displaying debugging messages related to
25415 reading of COFF/PE exported symbols.
25416 @item set debug dwarf-die
25418 Dump DWARF DIEs after they are read in.
25419 The value is the number of nesting levels to print.
25420 A value of zero turns off the display.
25421 @item show debug dwarf-die
25422 Show the current state of DWARF DIE debugging.
25423 @item set debug dwarf-line
25424 @cindex DWARF Line Tables
25425 Turns on or off display of debugging messages related to reading
25426 DWARF line tables. The default is 0 (off).
25427 A value of 1 provides basic information.
25428 A value greater than 1 provides more verbose information.
25429 @item show debug dwarf-line
25430 Show the current state of DWARF line table debugging.
25431 @item set debug dwarf-read
25432 @cindex DWARF Reading
25433 Turns on or off display of debugging messages related to reading
25434 DWARF debug info. The default is 0 (off).
25435 A value of 1 provides basic information.
25436 A value greater than 1 provides more verbose information.
25437 @item show debug dwarf-read
25438 Show the current state of DWARF reader debugging.
25439 @item set debug displaced
25440 @cindex displaced stepping debugging info
25441 Turns on or off display of @value{GDBN} debugging info for the
25442 displaced stepping support. The default is off.
25443 @item show debug displaced
25444 Displays the current state of displaying @value{GDBN} debugging info
25445 related to displaced stepping.
25446 @item set debug event
25447 @cindex event debugging info
25448 Turns on or off display of @value{GDBN} event debugging info. The
25450 @item show debug event
25451 Displays the current state of displaying @value{GDBN} event debugging
25453 @item set debug expression
25454 @cindex expression debugging info
25455 Turns on or off display of debugging info about @value{GDBN}
25456 expression parsing. The default is off.
25457 @item show debug expression
25458 Displays the current state of displaying debugging info about
25459 @value{GDBN} expression parsing.
25460 @item set debug fbsd-lwp
25461 @cindex FreeBSD LWP debug messages
25462 Turns on or off debugging messages from the FreeBSD LWP debug support.
25463 @item show debug fbsd-lwp
25464 Show the current state of FreeBSD LWP debugging messages.
25465 @item set debug fbsd-nat
25466 @cindex FreeBSD native target debug messages
25467 Turns on or off debugging messages from the FreeBSD native target.
25468 @item show debug fbsd-nat
25469 Show the current state of FreeBSD native target debugging messages.
25470 @item set debug frame
25471 @cindex frame debugging info
25472 Turns on or off display of @value{GDBN} frame debugging info. The
25474 @item show debug frame
25475 Displays the current state of displaying @value{GDBN} frame debugging
25477 @item set debug gnu-nat
25478 @cindex @sc{gnu}/Hurd debug messages
25479 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25480 @item show debug gnu-nat
25481 Show the current state of @sc{gnu}/Hurd debugging messages.
25482 @item set debug infrun
25483 @cindex inferior debugging info
25484 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25485 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25486 for implementing operations such as single-stepping the inferior.
25487 @item show debug infrun
25488 Displays the current state of @value{GDBN} inferior debugging.
25489 @item set debug jit
25490 @cindex just-in-time compilation, debugging messages
25491 Turn on or off debugging messages from JIT debug support.
25492 @item show debug jit
25493 Displays the current state of @value{GDBN} JIT debugging.
25494 @item set debug lin-lwp
25495 @cindex @sc{gnu}/Linux LWP debug messages
25496 @cindex Linux lightweight processes
25497 Turn on or off debugging messages from the Linux LWP debug support.
25498 @item show debug lin-lwp
25499 Show the current state of Linux LWP debugging messages.
25500 @item set debug linux-namespaces
25501 @cindex @sc{gnu}/Linux namespaces debug messages
25502 Turn on or off debugging messages from the Linux namespaces debug support.
25503 @item show debug linux-namespaces
25504 Show the current state of Linux namespaces debugging messages.
25505 @item set debug mach-o
25506 @cindex Mach-O symbols processing
25507 Control display of debugging messages related to Mach-O symbols
25508 processing. The default is off.
25509 @item show debug mach-o
25510 Displays the current state of displaying debugging messages related to
25511 reading of COFF/PE exported symbols.
25512 @item set debug notification
25513 @cindex remote async notification debugging info
25514 Turn on or off debugging messages about remote async notification.
25515 The default is off.
25516 @item show debug notification
25517 Displays the current state of remote async notification debugging messages.
25518 @item set debug observer
25519 @cindex observer debugging info
25520 Turns on or off display of @value{GDBN} observer debugging. This
25521 includes info such as the notification of observable events.
25522 @item show debug observer
25523 Displays the current state of observer debugging.
25524 @item set debug overload
25525 @cindex C@t{++} overload debugging info
25526 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25527 info. This includes info such as ranking of functions, etc. The default
25529 @item show debug overload
25530 Displays the current state of displaying @value{GDBN} C@t{++} overload
25532 @cindex expression parser, debugging info
25533 @cindex debug expression parser
25534 @item set debug parser
25535 Turns on or off the display of expression parser debugging output.
25536 Internally, this sets the @code{yydebug} variable in the expression
25537 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25538 details. The default is off.
25539 @item show debug parser
25540 Show the current state of expression parser debugging.
25541 @cindex packets, reporting on stdout
25542 @cindex serial connections, debugging
25543 @cindex debug remote protocol
25544 @cindex remote protocol debugging
25545 @cindex display remote packets
25546 @item set debug remote
25547 Turns on or off display of reports on all packets sent back and forth across
25548 the serial line to the remote machine. The info is printed on the
25549 @value{GDBN} standard output stream. The default is off.
25550 @item show debug remote
25551 Displays the state of display of remote packets.
25553 @item set debug separate-debug-file
25554 Turns on or off display of debug output about separate debug file search.
25555 @item show debug separate-debug-file
25556 Displays the state of separate debug file search debug output.
25558 @item set debug serial
25559 Turns on or off display of @value{GDBN} serial debugging info. The
25561 @item show debug serial
25562 Displays the current state of displaying @value{GDBN} serial debugging
25564 @item set debug solib-frv
25565 @cindex FR-V shared-library debugging
25566 Turn on or off debugging messages for FR-V shared-library code.
25567 @item show debug solib-frv
25568 Display the current state of FR-V shared-library code debugging
25570 @item set debug symbol-lookup
25571 @cindex symbol lookup
25572 Turns on or off display of debugging messages related to symbol lookup.
25573 The default is 0 (off).
25574 A value of 1 provides basic information.
25575 A value greater than 1 provides more verbose information.
25576 @item show debug symbol-lookup
25577 Show the current state of symbol lookup debugging messages.
25578 @item set debug symfile
25579 @cindex symbol file functions
25580 Turns on or off display of debugging messages related to symbol file functions.
25581 The default is off. @xref{Files}.
25582 @item show debug symfile
25583 Show the current state of symbol file debugging messages.
25584 @item set debug symtab-create
25585 @cindex symbol table creation
25586 Turns on or off display of debugging messages related to symbol table creation.
25587 The default is 0 (off).
25588 A value of 1 provides basic information.
25589 A value greater than 1 provides more verbose information.
25590 @item show debug symtab-create
25591 Show the current state of symbol table creation debugging.
25592 @item set debug target
25593 @cindex target debugging info
25594 Turns on or off display of @value{GDBN} target debugging info. This info
25595 includes what is going on at the target level of GDB, as it happens. The
25596 default is 0. Set it to 1 to track events, and to 2 to also track the
25597 value of large memory transfers.
25598 @item show debug target
25599 Displays the current state of displaying @value{GDBN} target debugging
25601 @item set debug timestamp
25602 @cindex timestampping debugging info
25603 Turns on or off display of timestamps with @value{GDBN} debugging info.
25604 When enabled, seconds and microseconds are displayed before each debugging
25606 @item show debug timestamp
25607 Displays the current state of displaying timestamps with @value{GDBN}
25609 @item set debug varobj
25610 @cindex variable object debugging info
25611 Turns on or off display of @value{GDBN} variable object debugging
25612 info. The default is off.
25613 @item show debug varobj
25614 Displays the current state of displaying @value{GDBN} variable object
25616 @item set debug xml
25617 @cindex XML parser debugging
25618 Turn on or off debugging messages for built-in XML parsers.
25619 @item show debug xml
25620 Displays the current state of XML debugging messages.
25623 @node Other Misc Settings
25624 @section Other Miscellaneous Settings
25625 @cindex miscellaneous settings
25628 @kindex set interactive-mode
25629 @item set interactive-mode
25630 If @code{on}, forces @value{GDBN} to assume that GDB was started
25631 in a terminal. In practice, this means that @value{GDBN} should wait
25632 for the user to answer queries generated by commands entered at
25633 the command prompt. If @code{off}, forces @value{GDBN} to operate
25634 in the opposite mode, and it uses the default answers to all queries.
25635 If @code{auto} (the default), @value{GDBN} tries to determine whether
25636 its standard input is a terminal, and works in interactive-mode if it
25637 is, non-interactively otherwise.
25639 In the vast majority of cases, the debugger should be able to guess
25640 correctly which mode should be used. But this setting can be useful
25641 in certain specific cases, such as running a MinGW @value{GDBN}
25642 inside a cygwin window.
25644 @kindex show interactive-mode
25645 @item show interactive-mode
25646 Displays whether the debugger is operating in interactive mode or not.
25649 @node Extending GDB
25650 @chapter Extending @value{GDBN}
25651 @cindex extending GDB
25653 @value{GDBN} provides several mechanisms for extension.
25654 @value{GDBN} also provides the ability to automatically load
25655 extensions when it reads a file for debugging. This allows the
25656 user to automatically customize @value{GDBN} for the program
25660 * Sequences:: Canned Sequences of @value{GDBN} Commands
25661 * Python:: Extending @value{GDBN} using Python
25662 * Guile:: Extending @value{GDBN} using Guile
25663 * Auto-loading extensions:: Automatically loading extensions
25664 * Multiple Extension Languages:: Working with multiple extension languages
25665 * Aliases:: Creating new spellings of existing commands
25668 To facilitate the use of extension languages, @value{GDBN} is capable
25669 of evaluating the contents of a file. When doing so, @value{GDBN}
25670 can recognize which extension language is being used by looking at
25671 the filename extension. Files with an unrecognized filename extension
25672 are always treated as a @value{GDBN} Command Files.
25673 @xref{Command Files,, Command files}.
25675 You can control how @value{GDBN} evaluates these files with the following
25679 @kindex set script-extension
25680 @kindex show script-extension
25681 @item set script-extension off
25682 All scripts are always evaluated as @value{GDBN} Command Files.
25684 @item set script-extension soft
25685 The debugger determines the scripting language based on filename
25686 extension. If this scripting language is supported, @value{GDBN}
25687 evaluates the script using that language. Otherwise, it evaluates
25688 the file as a @value{GDBN} Command File.
25690 @item set script-extension strict
25691 The debugger determines the scripting language based on filename
25692 extension, and evaluates the script using that language. If the
25693 language is not supported, then the evaluation fails.
25695 @item show script-extension
25696 Display the current value of the @code{script-extension} option.
25701 @section Canned Sequences of Commands
25703 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25704 Command Lists}), @value{GDBN} provides two ways to store sequences of
25705 commands for execution as a unit: user-defined commands and command
25709 * Define:: How to define your own commands
25710 * Hooks:: Hooks for user-defined commands
25711 * Command Files:: How to write scripts of commands to be stored in a file
25712 * Output:: Commands for controlled output
25713 * Auto-loading sequences:: Controlling auto-loaded command files
25717 @subsection User-defined Commands
25719 @cindex user-defined command
25720 @cindex arguments, to user-defined commands
25721 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25722 which you assign a new name as a command. This is done with the
25723 @code{define} command. User commands may accept an unlimited number of arguments
25724 separated by whitespace. Arguments are accessed within the user command
25725 via @code{$arg0@dots{}$argN}. A trivial example:
25729 print $arg0 + $arg1 + $arg2
25734 To execute the command use:
25741 This defines the command @code{adder}, which prints the sum of
25742 its three arguments. Note the arguments are text substitutions, so they may
25743 reference variables, use complex expressions, or even perform inferior
25746 @cindex argument count in user-defined commands
25747 @cindex how many arguments (user-defined commands)
25748 In addition, @code{$argc} may be used to find out how many arguments have
25754 print $arg0 + $arg1
25757 print $arg0 + $arg1 + $arg2
25762 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25763 to process a variable number of arguments:
25770 eval "set $sum = $sum + $arg%d", $i
25780 @item define @var{commandname}
25781 Define a command named @var{commandname}. If there is already a command
25782 by that name, you are asked to confirm that you want to redefine it.
25783 The argument @var{commandname} may be a bare command name consisting of letters,
25784 numbers, dashes, and underscores. It may also start with any predefined
25785 prefix command. For example, @samp{define target my-target} creates
25786 a user-defined @samp{target my-target} command.
25788 The definition of the command is made up of other @value{GDBN} command lines,
25789 which are given following the @code{define} command. The end of these
25790 commands is marked by a line containing @code{end}.
25793 @kindex end@r{ (user-defined commands)}
25794 @item document @var{commandname}
25795 Document the user-defined command @var{commandname}, so that it can be
25796 accessed by @code{help}. The command @var{commandname} must already be
25797 defined. This command reads lines of documentation just as @code{define}
25798 reads the lines of the command definition, ending with @code{end}.
25799 After the @code{document} command is finished, @code{help} on command
25800 @var{commandname} displays the documentation you have written.
25802 You may use the @code{document} command again to change the
25803 documentation of a command. Redefining the command with @code{define}
25804 does not change the documentation.
25806 @kindex dont-repeat
25807 @cindex don't repeat command
25809 Used inside a user-defined command, this tells @value{GDBN} that this
25810 command should not be repeated when the user hits @key{RET}
25811 (@pxref{Command Syntax, repeat last command}).
25813 @kindex help user-defined
25814 @item help user-defined
25815 List all user-defined commands and all python commands defined in class
25816 COMAND_USER. The first line of the documentation or docstring is
25821 @itemx show user @var{commandname}
25822 Display the @value{GDBN} commands used to define @var{commandname} (but
25823 not its documentation). If no @var{commandname} is given, display the
25824 definitions for all user-defined commands.
25825 This does not work for user-defined python commands.
25827 @cindex infinite recursion in user-defined commands
25828 @kindex show max-user-call-depth
25829 @kindex set max-user-call-depth
25830 @item show max-user-call-depth
25831 @itemx set max-user-call-depth
25832 The value of @code{max-user-call-depth} controls how many recursion
25833 levels are allowed in user-defined commands before @value{GDBN} suspects an
25834 infinite recursion and aborts the command.
25835 This does not apply to user-defined python commands.
25838 In addition to the above commands, user-defined commands frequently
25839 use control flow commands, described in @ref{Command Files}.
25841 When user-defined commands are executed, the
25842 commands of the definition are not printed. An error in any command
25843 stops execution of the user-defined command.
25845 If used interactively, commands that would ask for confirmation proceed
25846 without asking when used inside a user-defined command. Many @value{GDBN}
25847 commands that normally print messages to say what they are doing omit the
25848 messages when used in a user-defined command.
25851 @subsection User-defined Command Hooks
25852 @cindex command hooks
25853 @cindex hooks, for commands
25854 @cindex hooks, pre-command
25857 You may define @dfn{hooks}, which are a special kind of user-defined
25858 command. Whenever you run the command @samp{foo}, if the user-defined
25859 command @samp{hook-foo} exists, it is executed (with no arguments)
25860 before that command.
25862 @cindex hooks, post-command
25864 A hook may also be defined which is run after the command you executed.
25865 Whenever you run the command @samp{foo}, if the user-defined command
25866 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25867 that command. Post-execution hooks may exist simultaneously with
25868 pre-execution hooks, for the same command.
25870 It is valid for a hook to call the command which it hooks. If this
25871 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25873 @c It would be nice if hookpost could be passed a parameter indicating
25874 @c if the command it hooks executed properly or not. FIXME!
25876 @kindex stop@r{, a pseudo-command}
25877 In addition, a pseudo-command, @samp{stop} exists. Defining
25878 (@samp{hook-stop}) makes the associated commands execute every time
25879 execution stops in your program: before breakpoint commands are run,
25880 displays are printed, or the stack frame is printed.
25882 For example, to ignore @code{SIGALRM} signals while
25883 single-stepping, but treat them normally during normal execution,
25888 handle SIGALRM nopass
25892 handle SIGALRM pass
25895 define hook-continue
25896 handle SIGALRM pass
25900 As a further example, to hook at the beginning and end of the @code{echo}
25901 command, and to add extra text to the beginning and end of the message,
25909 define hookpost-echo
25913 (@value{GDBP}) echo Hello World
25914 <<<---Hello World--->>>
25919 You can define a hook for any single-word command in @value{GDBN}, but
25920 not for command aliases; you should define a hook for the basic command
25921 name, e.g.@: @code{backtrace} rather than @code{bt}.
25922 @c FIXME! So how does Joe User discover whether a command is an alias
25924 You can hook a multi-word command by adding @code{hook-} or
25925 @code{hookpost-} to the last word of the command, e.g.@:
25926 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25928 If an error occurs during the execution of your hook, execution of
25929 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25930 (before the command that you actually typed had a chance to run).
25932 If you try to define a hook which does not match any known command, you
25933 get a warning from the @code{define} command.
25935 @node Command Files
25936 @subsection Command Files
25938 @cindex command files
25939 @cindex scripting commands
25940 A command file for @value{GDBN} is a text file made of lines that are
25941 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25942 also be included. An empty line in a command file does nothing; it
25943 does not mean to repeat the last command, as it would from the
25946 You can request the execution of a command file with the @code{source}
25947 command. Note that the @code{source} command is also used to evaluate
25948 scripts that are not Command Files. The exact behavior can be configured
25949 using the @code{script-extension} setting.
25950 @xref{Extending GDB,, Extending GDB}.
25954 @cindex execute commands from a file
25955 @item source [-s] [-v] @var{filename}
25956 Execute the command file @var{filename}.
25959 The lines in a command file are generally executed sequentially,
25960 unless the order of execution is changed by one of the
25961 @emph{flow-control commands} described below. The commands are not
25962 printed as they are executed. An error in any command terminates
25963 execution of the command file and control is returned to the console.
25965 @value{GDBN} first searches for @var{filename} in the current directory.
25966 If the file is not found there, and @var{filename} does not specify a
25967 directory, then @value{GDBN} also looks for the file on the source search path
25968 (specified with the @samp{directory} command);
25969 except that @file{$cdir} is not searched because the compilation directory
25970 is not relevant to scripts.
25972 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25973 on the search path even if @var{filename} specifies a directory.
25974 The search is done by appending @var{filename} to each element of the
25975 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25976 and the search path contains @file{/home/user} then @value{GDBN} will
25977 look for the script @file{/home/user/mylib/myscript}.
25978 The search is also done if @var{filename} is an absolute path.
25979 For example, if @var{filename} is @file{/tmp/myscript} and
25980 the search path contains @file{/home/user} then @value{GDBN} will
25981 look for the script @file{/home/user/tmp/myscript}.
25982 For DOS-like systems, if @var{filename} contains a drive specification,
25983 it is stripped before concatenation. For example, if @var{filename} is
25984 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25985 will look for the script @file{c:/tmp/myscript}.
25987 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25988 each command as it is executed. The option must be given before
25989 @var{filename}, and is interpreted as part of the filename anywhere else.
25991 Commands that would ask for confirmation if used interactively proceed
25992 without asking when used in a command file. Many @value{GDBN} commands that
25993 normally print messages to say what they are doing omit the messages
25994 when called from command files.
25996 @value{GDBN} also accepts command input from standard input. In this
25997 mode, normal output goes to standard output and error output goes to
25998 standard error. Errors in a command file supplied on standard input do
25999 not terminate execution of the command file---execution continues with
26003 gdb < cmds > log 2>&1
26006 (The syntax above will vary depending on the shell used.) This example
26007 will execute commands from the file @file{cmds}. All output and errors
26008 would be directed to @file{log}.
26010 Since commands stored on command files tend to be more general than
26011 commands typed interactively, they frequently need to deal with
26012 complicated situations, such as different or unexpected values of
26013 variables and symbols, changes in how the program being debugged is
26014 built, etc. @value{GDBN} provides a set of flow-control commands to
26015 deal with these complexities. Using these commands, you can write
26016 complex scripts that loop over data structures, execute commands
26017 conditionally, etc.
26024 This command allows to include in your script conditionally executed
26025 commands. The @code{if} command takes a single argument, which is an
26026 expression to evaluate. It is followed by a series of commands that
26027 are executed only if the expression is true (its value is nonzero).
26028 There can then optionally be an @code{else} line, followed by a series
26029 of commands that are only executed if the expression was false. The
26030 end of the list is marked by a line containing @code{end}.
26034 This command allows to write loops. Its syntax is similar to
26035 @code{if}: the command takes a single argument, which is an expression
26036 to evaluate, and must be followed by the commands to execute, one per
26037 line, terminated by an @code{end}. These commands are called the
26038 @dfn{body} of the loop. The commands in the body of @code{while} are
26039 executed repeatedly as long as the expression evaluates to true.
26043 This command exits the @code{while} loop in whose body it is included.
26044 Execution of the script continues after that @code{while}s @code{end}
26047 @kindex loop_continue
26048 @item loop_continue
26049 This command skips the execution of the rest of the body of commands
26050 in the @code{while} loop in whose body it is included. Execution
26051 branches to the beginning of the @code{while} loop, where it evaluates
26052 the controlling expression.
26054 @kindex end@r{ (if/else/while commands)}
26056 Terminate the block of commands that are the body of @code{if},
26057 @code{else}, or @code{while} flow-control commands.
26062 @subsection Commands for Controlled Output
26064 During the execution of a command file or a user-defined command, normal
26065 @value{GDBN} output is suppressed; the only output that appears is what is
26066 explicitly printed by the commands in the definition. This section
26067 describes three commands useful for generating exactly the output you
26072 @item echo @var{text}
26073 @c I do not consider backslash-space a standard C escape sequence
26074 @c because it is not in ANSI.
26075 Print @var{text}. Nonprinting characters can be included in
26076 @var{text} using C escape sequences, such as @samp{\n} to print a
26077 newline. @strong{No newline is printed unless you specify one.}
26078 In addition to the standard C escape sequences, a backslash followed
26079 by a space stands for a space. This is useful for displaying a
26080 string with spaces at the beginning or the end, since leading and
26081 trailing spaces are otherwise trimmed from all arguments.
26082 To print @samp{@w{ }and foo =@w{ }}, use the command
26083 @samp{echo \@w{ }and foo = \@w{ }}.
26085 A backslash at the end of @var{text} can be used, as in C, to continue
26086 the command onto subsequent lines. For example,
26089 echo This is some text\n\
26090 which is continued\n\
26091 onto several lines.\n
26094 produces the same output as
26097 echo This is some text\n
26098 echo which is continued\n
26099 echo onto several lines.\n
26103 @item output @var{expression}
26104 Print the value of @var{expression} and nothing but that value: no
26105 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26106 value history either. @xref{Expressions, ,Expressions}, for more information
26109 @item output/@var{fmt} @var{expression}
26110 Print the value of @var{expression} in format @var{fmt}. You can use
26111 the same formats as for @code{print}. @xref{Output Formats,,Output
26112 Formats}, for more information.
26115 @item printf @var{template}, @var{expressions}@dots{}
26116 Print the values of one or more @var{expressions} under the control of
26117 the string @var{template}. To print several values, make
26118 @var{expressions} be a comma-separated list of individual expressions,
26119 which may be either numbers or pointers. Their values are printed as
26120 specified by @var{template}, exactly as a C program would do by
26121 executing the code below:
26124 printf (@var{template}, @var{expressions}@dots{});
26127 As in @code{C} @code{printf}, ordinary characters in @var{template}
26128 are printed verbatim, while @dfn{conversion specification} introduced
26129 by the @samp{%} character cause subsequent @var{expressions} to be
26130 evaluated, their values converted and formatted according to type and
26131 style information encoded in the conversion specifications, and then
26134 For example, you can print two values in hex like this:
26137 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26140 @code{printf} supports all the standard @code{C} conversion
26141 specifications, including the flags and modifiers between the @samp{%}
26142 character and the conversion letter, with the following exceptions:
26146 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26149 The modifier @samp{*} is not supported for specifying precision or
26153 The @samp{'} flag (for separation of digits into groups according to
26154 @code{LC_NUMERIC'}) is not supported.
26157 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26161 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26164 The conversion letters @samp{a} and @samp{A} are not supported.
26168 Note that the @samp{ll} type modifier is supported only if the
26169 underlying @code{C} implementation used to build @value{GDBN} supports
26170 the @code{long long int} type, and the @samp{L} type modifier is
26171 supported only if @code{long double} type is available.
26173 As in @code{C}, @code{printf} supports simple backslash-escape
26174 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26175 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26176 single character. Octal and hexadecimal escape sequences are not
26179 Additionally, @code{printf} supports conversion specifications for DFP
26180 (@dfn{Decimal Floating Point}) types using the following length modifiers
26181 together with a floating point specifier.
26186 @samp{H} for printing @code{Decimal32} types.
26189 @samp{D} for printing @code{Decimal64} types.
26192 @samp{DD} for printing @code{Decimal128} types.
26195 If the underlying @code{C} implementation used to build @value{GDBN} has
26196 support for the three length modifiers for DFP types, other modifiers
26197 such as width and precision will also be available for @value{GDBN} to use.
26199 In case there is no such @code{C} support, no additional modifiers will be
26200 available and the value will be printed in the standard way.
26202 Here's an example of printing DFP types using the above conversion letters:
26204 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26209 @item eval @var{template}, @var{expressions}@dots{}
26210 Convert the values of one or more @var{expressions} under the control of
26211 the string @var{template} to a command line, and call it.
26215 @node Auto-loading sequences
26216 @subsection Controlling auto-loading native @value{GDBN} scripts
26217 @cindex native script auto-loading
26219 When a new object file is read (for example, due to the @code{file}
26220 command, or because the inferior has loaded a shared library),
26221 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26222 @xref{Auto-loading extensions}.
26224 Auto-loading can be enabled or disabled,
26225 and the list of auto-loaded scripts can be printed.
26228 @anchor{set auto-load gdb-scripts}
26229 @kindex set auto-load gdb-scripts
26230 @item set auto-load gdb-scripts [on|off]
26231 Enable or disable the auto-loading of canned sequences of commands scripts.
26233 @anchor{show auto-load gdb-scripts}
26234 @kindex show auto-load gdb-scripts
26235 @item show auto-load gdb-scripts
26236 Show whether auto-loading of canned sequences of commands scripts is enabled or
26239 @anchor{info auto-load gdb-scripts}
26240 @kindex info auto-load gdb-scripts
26241 @cindex print list of auto-loaded canned sequences of commands scripts
26242 @item info auto-load gdb-scripts [@var{regexp}]
26243 Print the list of all canned sequences of commands scripts that @value{GDBN}
26247 If @var{regexp} is supplied only canned sequences of commands scripts with
26248 matching names are printed.
26250 @c Python docs live in a separate file.
26251 @include python.texi
26253 @c Guile docs live in a separate file.
26254 @include guile.texi
26256 @node Auto-loading extensions
26257 @section Auto-loading extensions
26258 @cindex auto-loading extensions
26260 @value{GDBN} provides two mechanisms for automatically loading extensions
26261 when a new object file is read (for example, due to the @code{file}
26262 command, or because the inferior has loaded a shared library):
26263 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26264 section of modern file formats like ELF.
26267 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26268 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26269 * Which flavor to choose?::
26272 The auto-loading feature is useful for supplying application-specific
26273 debugging commands and features.
26275 Auto-loading can be enabled or disabled,
26276 and the list of auto-loaded scripts can be printed.
26277 See the @samp{auto-loading} section of each extension language
26278 for more information.
26279 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26280 For Python files see @ref{Python Auto-loading}.
26282 Note that loading of this script file also requires accordingly configured
26283 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26285 @node objfile-gdbdotext file
26286 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26287 @cindex @file{@var{objfile}-gdb.gdb}
26288 @cindex @file{@var{objfile}-gdb.py}
26289 @cindex @file{@var{objfile}-gdb.scm}
26291 When a new object file is read, @value{GDBN} looks for a file named
26292 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26293 where @var{objfile} is the object file's name and
26294 where @var{ext} is the file extension for the extension language:
26297 @item @file{@var{objfile}-gdb.gdb}
26298 GDB's own command language
26299 @item @file{@var{objfile}-gdb.py}
26301 @item @file{@var{objfile}-gdb.scm}
26305 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26306 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26307 components, and appending the @file{-gdb.@var{ext}} suffix.
26308 If this file exists and is readable, @value{GDBN} will evaluate it as a
26309 script in the specified extension language.
26311 If this file does not exist, then @value{GDBN} will look for
26312 @var{script-name} file in all of the directories as specified below.
26314 Note that loading of these files requires an accordingly configured
26315 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26317 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26318 scripts normally according to its @file{.exe} filename. But if no scripts are
26319 found @value{GDBN} also tries script filenames matching the object file without
26320 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26321 is attempted on any platform. This makes the script filenames compatible
26322 between Unix and MS-Windows hosts.
26325 @anchor{set auto-load scripts-directory}
26326 @kindex set auto-load scripts-directory
26327 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26328 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26329 may be delimited by the host platform path separator in use
26330 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26332 Each entry here needs to be covered also by the security setting
26333 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26335 @anchor{with-auto-load-dir}
26336 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26337 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26338 configuration option @option{--with-auto-load-dir}.
26340 Any reference to @file{$debugdir} will get replaced by
26341 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26342 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26343 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26344 @file{$datadir} must be placed as a directory component --- either alone or
26345 delimited by @file{/} or @file{\} directory separators, depending on the host
26348 The list of directories uses path separator (@samp{:} on GNU and Unix
26349 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26350 to the @env{PATH} environment variable.
26352 @anchor{show auto-load scripts-directory}
26353 @kindex show auto-load scripts-directory
26354 @item show auto-load scripts-directory
26355 Show @value{GDBN} auto-loaded scripts location.
26357 @anchor{add-auto-load-scripts-directory}
26358 @kindex add-auto-load-scripts-directory
26359 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26360 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26361 Multiple entries may be delimited by the host platform path separator in use.
26364 @value{GDBN} does not track which files it has already auto-loaded this way.
26365 @value{GDBN} will load the associated script every time the corresponding
26366 @var{objfile} is opened.
26367 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26368 is evaluated more than once.
26370 @node dotdebug_gdb_scripts section
26371 @subsection The @code{.debug_gdb_scripts} section
26372 @cindex @code{.debug_gdb_scripts} section
26374 For systems using file formats like ELF and COFF,
26375 when @value{GDBN} loads a new object file
26376 it will look for a special section named @code{.debug_gdb_scripts}.
26377 If this section exists, its contents is a list of null-terminated entries
26378 specifying scripts to load. Each entry begins with a non-null prefix byte that
26379 specifies the kind of entry, typically the extension language and whether the
26380 script is in a file or inlined in @code{.debug_gdb_scripts}.
26382 The following entries are supported:
26385 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26386 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26387 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26388 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26391 @subsubsection Script File Entries
26393 If the entry specifies a file, @value{GDBN} will look for the file first
26394 in the current directory and then along the source search path
26395 (@pxref{Source Path, ,Specifying Source Directories}),
26396 except that @file{$cdir} is not searched, since the compilation
26397 directory is not relevant to scripts.
26399 File entries can be placed in section @code{.debug_gdb_scripts} with,
26400 for example, this GCC macro for Python scripts.
26403 /* Note: The "MS" section flags are to remove duplicates. */
26404 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26406 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26407 .byte 1 /* Python */\n\
26408 .asciz \"" script_name "\"\n\
26414 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26415 Then one can reference the macro in a header or source file like this:
26418 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26421 The script name may include directories if desired.
26423 Note that loading of this script file also requires accordingly configured
26424 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26426 If the macro invocation is put in a header, any application or library
26427 using this header will get a reference to the specified script,
26428 and with the use of @code{"MS"} attributes on the section, the linker
26429 will remove duplicates.
26431 @subsubsection Script Text Entries
26433 Script text entries allow to put the executable script in the entry
26434 itself instead of loading it from a file.
26435 The first line of the entry, everything after the prefix byte and up to
26436 the first newline (@code{0xa}) character, is the script name, and must not
26437 contain any kind of space character, e.g., spaces or tabs.
26438 The rest of the entry, up to the trailing null byte, is the script to
26439 execute in the specified language. The name needs to be unique among
26440 all script names, as @value{GDBN} executes each script only once based
26443 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26447 #include "symcat.h"
26448 #include "gdb/section-scripts.h"
26450 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26451 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26452 ".ascii \"gdb.inlined-script\\n\"\n"
26453 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26454 ".ascii \" def __init__ (self):\\n\"\n"
26455 ".ascii \" super (test_cmd, self).__init__ ("
26456 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26457 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26458 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26459 ".ascii \"test_cmd ()\\n\"\n"
26465 Loading of inlined scripts requires a properly configured
26466 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26467 The path to specify in @code{auto-load safe-path} is the path of the file
26468 containing the @code{.debug_gdb_scripts} section.
26470 @node Which flavor to choose?
26471 @subsection Which flavor to choose?
26473 Given the multiple ways of auto-loading extensions, it might not always
26474 be clear which one to choose. This section provides some guidance.
26477 Benefits of the @file{-gdb.@var{ext}} way:
26481 Can be used with file formats that don't support multiple sections.
26484 Ease of finding scripts for public libraries.
26486 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26487 in the source search path.
26488 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26489 isn't a source directory in which to find the script.
26492 Doesn't require source code additions.
26496 Benefits of the @code{.debug_gdb_scripts} way:
26500 Works with static linking.
26502 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26503 trigger their loading. When an application is statically linked the only
26504 objfile available is the executable, and it is cumbersome to attach all the
26505 scripts from all the input libraries to the executable's
26506 @file{-gdb.@var{ext}} script.
26509 Works with classes that are entirely inlined.
26511 Some classes can be entirely inlined, and thus there may not be an associated
26512 shared library to attach a @file{-gdb.@var{ext}} script to.
26515 Scripts needn't be copied out of the source tree.
26517 In some circumstances, apps can be built out of large collections of internal
26518 libraries, and the build infrastructure necessary to install the
26519 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26520 cumbersome. It may be easier to specify the scripts in the
26521 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26522 top of the source tree to the source search path.
26525 @node Multiple Extension Languages
26526 @section Multiple Extension Languages
26528 The Guile and Python extension languages do not share any state,
26529 and generally do not interfere with each other.
26530 There are some things to be aware of, however.
26532 @subsection Python comes first
26534 Python was @value{GDBN}'s first extension language, and to avoid breaking
26535 existing behaviour Python comes first. This is generally solved by the
26536 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26537 extension languages, and when it makes a call to an extension language,
26538 (say to pretty-print a value), it tries each in turn until an extension
26539 language indicates it has performed the request (e.g., has returned the
26540 pretty-printed form of a value).
26541 This extends to errors while performing such requests: If an error happens
26542 while, for example, trying to pretty-print an object then the error is
26543 reported and any following extension languages are not tried.
26546 @section Creating new spellings of existing commands
26547 @cindex aliases for commands
26549 It is often useful to define alternate spellings of existing commands.
26550 For example, if a new @value{GDBN} command defined in Python has
26551 a long name to type, it is handy to have an abbreviated version of it
26552 that involves less typing.
26554 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26555 of the @samp{step} command even though it is otherwise an ambiguous
26556 abbreviation of other commands like @samp{set} and @samp{show}.
26558 Aliases are also used to provide shortened or more common versions
26559 of multi-word commands. For example, @value{GDBN} provides the
26560 @samp{tty} alias of the @samp{set inferior-tty} command.
26562 You can define a new alias with the @samp{alias} command.
26567 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26571 @var{ALIAS} specifies the name of the new alias.
26572 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26575 @var{COMMAND} specifies the name of an existing command
26576 that is being aliased.
26578 The @samp{-a} option specifies that the new alias is an abbreviation
26579 of the command. Abbreviations are not shown in command
26580 lists displayed by the @samp{help} command.
26582 The @samp{--} option specifies the end of options,
26583 and is useful when @var{ALIAS} begins with a dash.
26585 Here is a simple example showing how to make an abbreviation
26586 of a command so that there is less to type.
26587 Suppose you were tired of typing @samp{disas}, the current
26588 shortest unambiguous abbreviation of the @samp{disassemble} command
26589 and you wanted an even shorter version named @samp{di}.
26590 The following will accomplish this.
26593 (gdb) alias -a di = disas
26596 Note that aliases are different from user-defined commands.
26597 With a user-defined command, you also need to write documentation
26598 for it with the @samp{document} command.
26599 An alias automatically picks up the documentation of the existing command.
26601 Here is an example where we make @samp{elms} an abbreviation of
26602 @samp{elements} in the @samp{set print elements} command.
26603 This is to show that you can make an abbreviation of any part
26607 (gdb) alias -a set print elms = set print elements
26608 (gdb) alias -a show print elms = show print elements
26609 (gdb) set p elms 20
26611 Limit on string chars or array elements to print is 200.
26614 Note that if you are defining an alias of a @samp{set} command,
26615 and you want to have an alias for the corresponding @samp{show}
26616 command, then you need to define the latter separately.
26618 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26619 @var{ALIAS}, just as they are normally.
26622 (gdb) alias -a set pr elms = set p ele
26625 Finally, here is an example showing the creation of a one word
26626 alias for a more complex command.
26627 This creates alias @samp{spe} of the command @samp{set print elements}.
26630 (gdb) alias spe = set print elements
26635 @chapter Command Interpreters
26636 @cindex command interpreters
26638 @value{GDBN} supports multiple command interpreters, and some command
26639 infrastructure to allow users or user interface writers to switch
26640 between interpreters or run commands in other interpreters.
26642 @value{GDBN} currently supports two command interpreters, the console
26643 interpreter (sometimes called the command-line interpreter or @sc{cli})
26644 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26645 describes both of these interfaces in great detail.
26647 By default, @value{GDBN} will start with the console interpreter.
26648 However, the user may choose to start @value{GDBN} with another
26649 interpreter by specifying the @option{-i} or @option{--interpreter}
26650 startup options. Defined interpreters include:
26654 @cindex console interpreter
26655 The traditional console or command-line interpreter. This is the most often
26656 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26657 @value{GDBN} will use this interpreter.
26660 @cindex mi interpreter
26661 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26662 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26663 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26667 @cindex mi3 interpreter
26668 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26671 @cindex mi2 interpreter
26672 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26675 @cindex mi1 interpreter
26676 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26680 @cindex invoke another interpreter
26682 @kindex interpreter-exec
26683 You may execute commands in any interpreter from the current
26684 interpreter using the appropriate command. If you are running the
26685 console interpreter, simply use the @code{interpreter-exec} command:
26688 interpreter-exec mi "-data-list-register-names"
26691 @sc{gdb/mi} has a similar command, although it is only available in versions of
26692 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26694 Note that @code{interpreter-exec} only changes the interpreter for the
26695 duration of the specified command. It does not change the interpreter
26698 @cindex start a new independent interpreter
26700 Although you may only choose a single interpreter at startup, it is
26701 possible to run an independent interpreter on a specified input/output
26702 device (usually a tty).
26704 For example, consider a debugger GUI or IDE that wants to provide a
26705 @value{GDBN} console view. It may do so by embedding a terminal
26706 emulator widget in its GUI, starting @value{GDBN} in the traditional
26707 command-line mode with stdin/stdout/stderr redirected to that
26708 terminal, and then creating an MI interpreter running on a specified
26709 input/output device. The console interpreter created by @value{GDBN}
26710 at startup handles commands the user types in the terminal widget,
26711 while the GUI controls and synchronizes state with @value{GDBN} using
26712 the separate MI interpreter.
26714 To start a new secondary @dfn{user interface} running MI, use the
26715 @code{new-ui} command:
26718 @cindex new user interface
26720 new-ui @var{interpreter} @var{tty}
26723 The @var{interpreter} parameter specifies the interpreter to run.
26724 This accepts the same values as the @code{interpreter-exec} command.
26725 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26726 @var{tty} parameter specifies the name of the bidirectional file the
26727 interpreter uses for input/output, usually the name of a
26728 pseudoterminal slave on Unix systems. For example:
26731 (@value{GDBP}) new-ui mi /dev/pts/9
26735 runs an MI interpreter on @file{/dev/pts/9}.
26738 @chapter @value{GDBN} Text User Interface
26740 @cindex Text User Interface
26743 * TUI Overview:: TUI overview
26744 * TUI Keys:: TUI key bindings
26745 * TUI Single Key Mode:: TUI single key mode
26746 * TUI Commands:: TUI-specific commands
26747 * TUI Configuration:: TUI configuration variables
26750 The @value{GDBN} Text User Interface (TUI) is a terminal
26751 interface which uses the @code{curses} library to show the source
26752 file, the assembly output, the program registers and @value{GDBN}
26753 commands in separate text windows. The TUI mode is supported only
26754 on platforms where a suitable version of the @code{curses} library
26757 The TUI mode is enabled by default when you invoke @value{GDBN} as
26758 @samp{@value{GDBP} -tui}.
26759 You can also switch in and out of TUI mode while @value{GDBN} runs by
26760 using various TUI commands and key bindings, such as @command{tui
26761 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26762 @ref{TUI Keys, ,TUI Key Bindings}.
26765 @section TUI Overview
26767 In TUI mode, @value{GDBN} can display several text windows:
26771 This window is the @value{GDBN} command window with the @value{GDBN}
26772 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26773 managed using readline.
26776 The source window shows the source file of the program. The current
26777 line and active breakpoints are displayed in this window.
26780 The assembly window shows the disassembly output of the program.
26783 This window shows the processor registers. Registers are highlighted
26784 when their values change.
26787 The source and assembly windows show the current program position
26788 by highlighting the current line and marking it with a @samp{>} marker.
26789 Breakpoints are indicated with two markers. The first marker
26790 indicates the breakpoint type:
26794 Breakpoint which was hit at least once.
26797 Breakpoint which was never hit.
26800 Hardware breakpoint which was hit at least once.
26803 Hardware breakpoint which was never hit.
26806 The second marker indicates whether the breakpoint is enabled or not:
26810 Breakpoint is enabled.
26813 Breakpoint is disabled.
26816 The source, assembly and register windows are updated when the current
26817 thread changes, when the frame changes, or when the program counter
26820 These windows are not all visible at the same time. The command
26821 window is always visible. The others can be arranged in several
26832 source and assembly,
26835 source and registers, or
26838 assembly and registers.
26841 A status line above the command window shows the following information:
26845 Indicates the current @value{GDBN} target.
26846 (@pxref{Targets, ,Specifying a Debugging Target}).
26849 Gives the current process or thread number.
26850 When no process is being debugged, this field is set to @code{No process}.
26853 Gives the current function name for the selected frame.
26854 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26855 When there is no symbol corresponding to the current program counter,
26856 the string @code{??} is displayed.
26859 Indicates the current line number for the selected frame.
26860 When the current line number is not known, the string @code{??} is displayed.
26863 Indicates the current program counter address.
26867 @section TUI Key Bindings
26868 @cindex TUI key bindings
26870 The TUI installs several key bindings in the readline keymaps
26871 @ifset SYSTEM_READLINE
26872 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26874 @ifclear SYSTEM_READLINE
26875 (@pxref{Command Line Editing}).
26877 The following key bindings are installed for both TUI mode and the
26878 @value{GDBN} standard mode.
26887 Enter or leave the TUI mode. When leaving the TUI mode,
26888 the curses window management stops and @value{GDBN} operates using
26889 its standard mode, writing on the terminal directly. When reentering
26890 the TUI mode, control is given back to the curses windows.
26891 The screen is then refreshed.
26895 Use a TUI layout with only one window. The layout will
26896 either be @samp{source} or @samp{assembly}. When the TUI mode
26897 is not active, it will switch to the TUI mode.
26899 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26903 Use a TUI layout with at least two windows. When the current
26904 layout already has two windows, the next layout with two windows is used.
26905 When a new layout is chosen, one window will always be common to the
26906 previous layout and the new one.
26908 Think of it as the Emacs @kbd{C-x 2} binding.
26912 Change the active window. The TUI associates several key bindings
26913 (like scrolling and arrow keys) with the active window. This command
26914 gives the focus to the next TUI window.
26916 Think of it as the Emacs @kbd{C-x o} binding.
26920 Switch in and out of the TUI SingleKey mode that binds single
26921 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26924 The following key bindings only work in the TUI mode:
26929 Scroll the active window one page up.
26933 Scroll the active window one page down.
26937 Scroll the active window one line up.
26941 Scroll the active window one line down.
26945 Scroll the active window one column left.
26949 Scroll the active window one column right.
26953 Refresh the screen.
26956 Because the arrow keys scroll the active window in the TUI mode, they
26957 are not available for their normal use by readline unless the command
26958 window has the focus. When another window is active, you must use
26959 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26960 and @kbd{C-f} to control the command window.
26962 @node TUI Single Key Mode
26963 @section TUI Single Key Mode
26964 @cindex TUI single key mode
26966 The TUI also provides a @dfn{SingleKey} mode, which binds several
26967 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26968 switch into this mode, where the following key bindings are used:
26971 @kindex c @r{(SingleKey TUI key)}
26975 @kindex d @r{(SingleKey TUI key)}
26979 @kindex f @r{(SingleKey TUI key)}
26983 @kindex n @r{(SingleKey TUI key)}
26987 @kindex o @r{(SingleKey TUI key)}
26989 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26991 @kindex q @r{(SingleKey TUI key)}
26993 exit the SingleKey mode.
26995 @kindex r @r{(SingleKey TUI key)}
26999 @kindex s @r{(SingleKey TUI key)}
27003 @kindex i @r{(SingleKey TUI key)}
27005 stepi. The shortcut letter @samp{i} stands for ``step Into''.
27007 @kindex u @r{(SingleKey TUI key)}
27011 @kindex v @r{(SingleKey TUI key)}
27015 @kindex w @r{(SingleKey TUI key)}
27020 Other keys temporarily switch to the @value{GDBN} command prompt.
27021 The key that was pressed is inserted in the editing buffer so that
27022 it is possible to type most @value{GDBN} commands without interaction
27023 with the TUI SingleKey mode. Once the command is entered the TUI
27024 SingleKey mode is restored. The only way to permanently leave
27025 this mode is by typing @kbd{q} or @kbd{C-x s}.
27029 @section TUI-specific Commands
27030 @cindex TUI commands
27032 The TUI has specific commands to control the text windows.
27033 These commands are always available, even when @value{GDBN} is not in
27034 the TUI mode. When @value{GDBN} is in the standard mode, most
27035 of these commands will automatically switch to the TUI mode.
27037 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27038 terminal, or @value{GDBN} has been started with the machine interface
27039 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27040 these commands will fail with an error, because it would not be
27041 possible or desirable to enable curses window management.
27046 Activate TUI mode. The last active TUI window layout will be used if
27047 TUI mode has prevsiouly been used in the current debugging session,
27048 otherwise a default layout is used.
27051 @kindex tui disable
27052 Disable TUI mode, returning to the console interpreter.
27056 List and give the size of all displayed windows.
27058 @item layout @var{name}
27060 Changes which TUI windows are displayed. In each layout the command
27061 window is always displayed, the @var{name} parameter controls which
27062 additional windows are displayed, and can be any of the following:
27066 Display the next layout.
27069 Display the previous layout.
27072 Display the source and command windows.
27075 Display the assembly and command windows.
27078 Display the source, assembly, and command windows.
27081 When in @code{src} layout display the register, source, and command
27082 windows. When in @code{asm} or @code{split} layout display the
27083 register, assembler, and command windows.
27086 @item focus @var{name}
27088 Changes which TUI window is currently active for scrolling. The
27089 @var{name} parameter can be any of the following:
27093 Make the next window active for scrolling.
27096 Make the previous window active for scrolling.
27099 Make the source window active for scrolling.
27102 Make the assembly window active for scrolling.
27105 Make the register window active for scrolling.
27108 Make the command window active for scrolling.
27113 Refresh the screen. This is similar to typing @kbd{C-L}.
27115 @item tui reg @var{group}
27117 Changes the register group displayed in the tui register window to
27118 @var{group}. If the register window is not currently displayed this
27119 command will cause the register window to be displayed. The list of
27120 register groups, as well as their order is target specific. The
27121 following groups are available on most targets:
27124 Repeatedly selecting this group will cause the display to cycle
27125 through all of the available register groups.
27128 Repeatedly selecting this group will cause the display to cycle
27129 through all of the available register groups in the reverse order to
27133 Display the general registers.
27135 Display the floating point registers.
27137 Display the system registers.
27139 Display the vector registers.
27141 Display all registers.
27146 Update the source window and the current execution point.
27148 @item winheight @var{name} +@var{count}
27149 @itemx winheight @var{name} -@var{count}
27151 Change the height of the window @var{name} by @var{count}
27152 lines. Positive counts increase the height, while negative counts
27153 decrease it. The @var{name} parameter can be one of @code{src} (the
27154 source window), @code{cmd} (the command window), @code{asm} (the
27155 disassembly window), or @code{regs} (the register display window).
27158 @node TUI Configuration
27159 @section TUI Configuration Variables
27160 @cindex TUI configuration variables
27162 Several configuration variables control the appearance of TUI windows.
27165 @item set tui border-kind @var{kind}
27166 @kindex set tui border-kind
27167 Select the border appearance for the source, assembly and register windows.
27168 The possible values are the following:
27171 Use a space character to draw the border.
27174 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27177 Use the Alternate Character Set to draw the border. The border is
27178 drawn using character line graphics if the terminal supports them.
27181 @item set tui border-mode @var{mode}
27182 @kindex set tui border-mode
27183 @itemx set tui active-border-mode @var{mode}
27184 @kindex set tui active-border-mode
27185 Select the display attributes for the borders of the inactive windows
27186 or the active window. The @var{mode} can be one of the following:
27189 Use normal attributes to display the border.
27195 Use reverse video mode.
27198 Use half bright mode.
27200 @item half-standout
27201 Use half bright and standout mode.
27204 Use extra bright or bold mode.
27206 @item bold-standout
27207 Use extra bright or bold and standout mode.
27210 @item set tui tab-width @var{nchars}
27211 @kindex set tui tab-width
27213 Set the width of tab stops to be @var{nchars} characters. This
27214 setting affects the display of TAB characters in the source and
27219 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27222 @cindex @sc{gnu} Emacs
27223 A special interface allows you to use @sc{gnu} Emacs to view (and
27224 edit) the source files for the program you are debugging with
27227 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27228 executable file you want to debug as an argument. This command starts
27229 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27230 created Emacs buffer.
27231 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27233 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27238 All ``terminal'' input and output goes through an Emacs buffer, called
27241 This applies both to @value{GDBN} commands and their output, and to the input
27242 and output done by the program you are debugging.
27244 This is useful because it means that you can copy the text of previous
27245 commands and input them again; you can even use parts of the output
27248 All the facilities of Emacs' Shell mode are available for interacting
27249 with your program. In particular, you can send signals the usual
27250 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27254 @value{GDBN} displays source code through Emacs.
27256 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27257 source file for that frame and puts an arrow (@samp{=>}) at the
27258 left margin of the current line. Emacs uses a separate buffer for
27259 source display, and splits the screen to show both your @value{GDBN} session
27262 Explicit @value{GDBN} @code{list} or search commands still produce output as
27263 usual, but you probably have no reason to use them from Emacs.
27266 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27267 a graphical mode, enabled by default, which provides further buffers
27268 that can control the execution and describe the state of your program.
27269 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27271 If you specify an absolute file name when prompted for the @kbd{M-x
27272 gdb} argument, then Emacs sets your current working directory to where
27273 your program resides. If you only specify the file name, then Emacs
27274 sets your current working directory to the directory associated
27275 with the previous buffer. In this case, @value{GDBN} may find your
27276 program by searching your environment's @code{PATH} variable, but on
27277 some operating systems it might not find the source. So, although the
27278 @value{GDBN} input and output session proceeds normally, the auxiliary
27279 buffer does not display the current source and line of execution.
27281 The initial working directory of @value{GDBN} is printed on the top
27282 line of the GUD buffer and this serves as a default for the commands
27283 that specify files for @value{GDBN} to operate on. @xref{Files,
27284 ,Commands to Specify Files}.
27286 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27287 need to call @value{GDBN} by a different name (for example, if you
27288 keep several configurations around, with different names) you can
27289 customize the Emacs variable @code{gud-gdb-command-name} to run the
27292 In the GUD buffer, you can use these special Emacs commands in
27293 addition to the standard Shell mode commands:
27297 Describe the features of Emacs' GUD Mode.
27300 Execute to another source line, like the @value{GDBN} @code{step} command; also
27301 update the display window to show the current file and location.
27304 Execute to next source line in this function, skipping all function
27305 calls, like the @value{GDBN} @code{next} command. Then update the display window
27306 to show the current file and location.
27309 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27310 display window accordingly.
27313 Execute until exit from the selected stack frame, like the @value{GDBN}
27314 @code{finish} command.
27317 Continue execution of your program, like the @value{GDBN} @code{continue}
27321 Go up the number of frames indicated by the numeric argument
27322 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27323 like the @value{GDBN} @code{up} command.
27326 Go down the number of frames indicated by the numeric argument, like the
27327 @value{GDBN} @code{down} command.
27330 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27331 tells @value{GDBN} to set a breakpoint on the source line point is on.
27333 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27334 separate frame which shows a backtrace when the GUD buffer is current.
27335 Move point to any frame in the stack and type @key{RET} to make it
27336 become the current frame and display the associated source in the
27337 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27338 selected frame become the current one. In graphical mode, the
27339 speedbar displays watch expressions.
27341 If you accidentally delete the source-display buffer, an easy way to get
27342 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27343 request a frame display; when you run under Emacs, this recreates
27344 the source buffer if necessary to show you the context of the current
27347 The source files displayed in Emacs are in ordinary Emacs buffers
27348 which are visiting the source files in the usual way. You can edit
27349 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27350 communicates with Emacs in terms of line numbers. If you add or
27351 delete lines from the text, the line numbers that @value{GDBN} knows cease
27352 to correspond properly with the code.
27354 A more detailed description of Emacs' interaction with @value{GDBN} is
27355 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27359 @chapter The @sc{gdb/mi} Interface
27361 @unnumberedsec Function and Purpose
27363 @cindex @sc{gdb/mi}, its purpose
27364 @sc{gdb/mi} is a line based machine oriented text interface to
27365 @value{GDBN} and is activated by specifying using the
27366 @option{--interpreter} command line option (@pxref{Mode Options}). It
27367 is specifically intended to support the development of systems which
27368 use the debugger as just one small component of a larger system.
27370 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27371 in the form of a reference manual.
27373 Note that @sc{gdb/mi} is still under construction, so some of the
27374 features described below are incomplete and subject to change
27375 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27377 @unnumberedsec Notation and Terminology
27379 @cindex notational conventions, for @sc{gdb/mi}
27380 This chapter uses the following notation:
27384 @code{|} separates two alternatives.
27387 @code{[ @var{something} ]} indicates that @var{something} is optional:
27388 it may or may not be given.
27391 @code{( @var{group} )*} means that @var{group} inside the parentheses
27392 may repeat zero or more times.
27395 @code{( @var{group} )+} means that @var{group} inside the parentheses
27396 may repeat one or more times.
27399 @code{"@var{string}"} means a literal @var{string}.
27403 @heading Dependencies
27407 * GDB/MI General Design::
27408 * GDB/MI Command Syntax::
27409 * GDB/MI Compatibility with CLI::
27410 * GDB/MI Development and Front Ends::
27411 * GDB/MI Output Records::
27412 * GDB/MI Simple Examples::
27413 * GDB/MI Command Description Format::
27414 * GDB/MI Breakpoint Commands::
27415 * GDB/MI Catchpoint Commands::
27416 * GDB/MI Program Context::
27417 * GDB/MI Thread Commands::
27418 * GDB/MI Ada Tasking Commands::
27419 * GDB/MI Program Execution::
27420 * GDB/MI Stack Manipulation::
27421 * GDB/MI Variable Objects::
27422 * GDB/MI Data Manipulation::
27423 * GDB/MI Tracepoint Commands::
27424 * GDB/MI Symbol Query::
27425 * GDB/MI File Commands::
27427 * GDB/MI Kod Commands::
27428 * GDB/MI Memory Overlay Commands::
27429 * GDB/MI Signal Handling Commands::
27431 * GDB/MI Target Manipulation::
27432 * GDB/MI File Transfer Commands::
27433 * GDB/MI Ada Exceptions Commands::
27434 * GDB/MI Support Commands::
27435 * GDB/MI Miscellaneous Commands::
27438 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27439 @node GDB/MI General Design
27440 @section @sc{gdb/mi} General Design
27441 @cindex GDB/MI General Design
27443 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27444 parts---commands sent to @value{GDBN}, responses to those commands
27445 and notifications. Each command results in exactly one response,
27446 indicating either successful completion of the command, or an error.
27447 For the commands that do not resume the target, the response contains the
27448 requested information. For the commands that resume the target, the
27449 response only indicates whether the target was successfully resumed.
27450 Notifications is the mechanism for reporting changes in the state of the
27451 target, or in @value{GDBN} state, that cannot conveniently be associated with
27452 a command and reported as part of that command response.
27454 The important examples of notifications are:
27458 Exec notifications. These are used to report changes in
27459 target state---when a target is resumed, or stopped. It would not
27460 be feasible to include this information in response of resuming
27461 commands, because one resume commands can result in multiple events in
27462 different threads. Also, quite some time may pass before any event
27463 happens in the target, while a frontend needs to know whether the resuming
27464 command itself was successfully executed.
27467 Console output, and status notifications. Console output
27468 notifications are used to report output of CLI commands, as well as
27469 diagnostics for other commands. Status notifications are used to
27470 report the progress of a long-running operation. Naturally, including
27471 this information in command response would mean no output is produced
27472 until the command is finished, which is undesirable.
27475 General notifications. Commands may have various side effects on
27476 the @value{GDBN} or target state beyond their official purpose. For example,
27477 a command may change the selected thread. Although such changes can
27478 be included in command response, using notification allows for more
27479 orthogonal frontend design.
27483 There's no guarantee that whenever an MI command reports an error,
27484 @value{GDBN} or the target are in any specific state, and especially,
27485 the state is not reverted to the state before the MI command was
27486 processed. Therefore, whenever an MI command results in an error,
27487 we recommend that the frontend refreshes all the information shown in
27488 the user interface.
27492 * Context management::
27493 * Asynchronous and non-stop modes::
27497 @node Context management
27498 @subsection Context management
27500 @subsubsection Threads and Frames
27502 In most cases when @value{GDBN} accesses the target, this access is
27503 done in context of a specific thread and frame (@pxref{Frames}).
27504 Often, even when accessing global data, the target requires that a thread
27505 be specified. The CLI interface maintains the selected thread and frame,
27506 and supplies them to target on each command. This is convenient,
27507 because a command line user would not want to specify that information
27508 explicitly on each command, and because user interacts with
27509 @value{GDBN} via a single terminal, so no confusion is possible as
27510 to what thread and frame are the current ones.
27512 In the case of MI, the concept of selected thread and frame is less
27513 useful. First, a frontend can easily remember this information
27514 itself. Second, a graphical frontend can have more than one window,
27515 each one used for debugging a different thread, and the frontend might
27516 want to access additional threads for internal purposes. This
27517 increases the risk that by relying on implicitly selected thread, the
27518 frontend may be operating on a wrong one. Therefore, each MI command
27519 should explicitly specify which thread and frame to operate on. To
27520 make it possible, each MI command accepts the @samp{--thread} and
27521 @samp{--frame} options, the value to each is @value{GDBN} global
27522 identifier for thread and frame to operate on.
27524 Usually, each top-level window in a frontend allows the user to select
27525 a thread and a frame, and remembers the user selection for further
27526 operations. However, in some cases @value{GDBN} may suggest that the
27527 current thread or frame be changed. For example, when stopping on a
27528 breakpoint it is reasonable to switch to the thread where breakpoint is
27529 hit. For another example, if the user issues the CLI @samp{thread} or
27530 @samp{frame} commands via the frontend, it is desirable to change the
27531 frontend's selection to the one specified by user. @value{GDBN}
27532 communicates the suggestion to change current thread and frame using the
27533 @samp{=thread-selected} notification.
27535 Note that historically, MI shares the selected thread with CLI, so
27536 frontends used the @code{-thread-select} to execute commands in the
27537 right context. However, getting this to work right is cumbersome. The
27538 simplest way is for frontend to emit @code{-thread-select} command
27539 before every command. This doubles the number of commands that need
27540 to be sent. The alternative approach is to suppress @code{-thread-select}
27541 if the selected thread in @value{GDBN} is supposed to be identical to the
27542 thread the frontend wants to operate on. However, getting this
27543 optimization right can be tricky. In particular, if the frontend
27544 sends several commands to @value{GDBN}, and one of the commands changes the
27545 selected thread, then the behaviour of subsequent commands will
27546 change. So, a frontend should either wait for response from such
27547 problematic commands, or explicitly add @code{-thread-select} for
27548 all subsequent commands. No frontend is known to do this exactly
27549 right, so it is suggested to just always pass the @samp{--thread} and
27550 @samp{--frame} options.
27552 @subsubsection Language
27554 The execution of several commands depends on which language is selected.
27555 By default, the current language (@pxref{show language}) is used.
27556 But for commands known to be language-sensitive, it is recommended
27557 to use the @samp{--language} option. This option takes one argument,
27558 which is the name of the language to use while executing the command.
27562 -data-evaluate-expression --language c "sizeof (void*)"
27567 The valid language names are the same names accepted by the
27568 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27569 @samp{local} or @samp{unknown}.
27571 @node Asynchronous and non-stop modes
27572 @subsection Asynchronous command execution and non-stop mode
27574 On some targets, @value{GDBN} is capable of processing MI commands
27575 even while the target is running. This is called @dfn{asynchronous
27576 command execution} (@pxref{Background Execution}). The frontend may
27577 specify a preferrence for asynchronous execution using the
27578 @code{-gdb-set mi-async 1} command, which should be emitted before
27579 either running the executable or attaching to the target. After the
27580 frontend has started the executable or attached to the target, it can
27581 find if asynchronous execution is enabled using the
27582 @code{-list-target-features} command.
27585 @item -gdb-set mi-async on
27586 @item -gdb-set mi-async off
27587 Set whether MI is in asynchronous mode.
27589 When @code{off}, which is the default, MI execution commands (e.g.,
27590 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27591 for the program to stop before processing further commands.
27593 When @code{on}, MI execution commands are background execution
27594 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27595 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27596 MI commands even while the target is running.
27598 @item -gdb-show mi-async
27599 Show whether MI asynchronous mode is enabled.
27602 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27603 @code{target-async} instead of @code{mi-async}, and it had the effect
27604 of both putting MI in asynchronous mode and making CLI background
27605 commands possible. CLI background commands are now always possible
27606 ``out of the box'' if the target supports them. The old spelling is
27607 kept as a deprecated alias for backwards compatibility.
27609 Even if @value{GDBN} can accept a command while target is running,
27610 many commands that access the target do not work when the target is
27611 running. Therefore, asynchronous command execution is most useful
27612 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27613 it is possible to examine the state of one thread, while other threads
27616 When a given thread is running, MI commands that try to access the
27617 target in the context of that thread may not work, or may work only on
27618 some targets. In particular, commands that try to operate on thread's
27619 stack will not work, on any target. Commands that read memory, or
27620 modify breakpoints, may work or not work, depending on the target. Note
27621 that even commands that operate on global state, such as @code{print},
27622 @code{set}, and breakpoint commands, still access the target in the
27623 context of a specific thread, so frontend should try to find a
27624 stopped thread and perform the operation on that thread (using the
27625 @samp{--thread} option).
27627 Which commands will work in the context of a running thread is
27628 highly target dependent. However, the two commands
27629 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27630 to find the state of a thread, will always work.
27632 @node Thread groups
27633 @subsection Thread groups
27634 @value{GDBN} may be used to debug several processes at the same time.
27635 On some platfroms, @value{GDBN} may support debugging of several
27636 hardware systems, each one having several cores with several different
27637 processes running on each core. This section describes the MI
27638 mechanism to support such debugging scenarios.
27640 The key observation is that regardless of the structure of the
27641 target, MI can have a global list of threads, because most commands that
27642 accept the @samp{--thread} option do not need to know what process that
27643 thread belongs to. Therefore, it is not necessary to introduce
27644 neither additional @samp{--process} option, nor an notion of the
27645 current process in the MI interface. The only strictly new feature
27646 that is required is the ability to find how the threads are grouped
27649 To allow the user to discover such grouping, and to support arbitrary
27650 hierarchy of machines/cores/processes, MI introduces the concept of a
27651 @dfn{thread group}. Thread group is a collection of threads and other
27652 thread groups. A thread group always has a string identifier, a type,
27653 and may have additional attributes specific to the type. A new
27654 command, @code{-list-thread-groups}, returns the list of top-level
27655 thread groups, which correspond to processes that @value{GDBN} is
27656 debugging at the moment. By passing an identifier of a thread group
27657 to the @code{-list-thread-groups} command, it is possible to obtain
27658 the members of specific thread group.
27660 To allow the user to easily discover processes, and other objects, he
27661 wishes to debug, a concept of @dfn{available thread group} is
27662 introduced. Available thread group is an thread group that
27663 @value{GDBN} is not debugging, but that can be attached to, using the
27664 @code{-target-attach} command. The list of available top-level thread
27665 groups can be obtained using @samp{-list-thread-groups --available}.
27666 In general, the content of a thread group may be only retrieved only
27667 after attaching to that thread group.
27669 Thread groups are related to inferiors (@pxref{Inferiors and
27670 Programs}). Each inferior corresponds to a thread group of a special
27671 type @samp{process}, and some additional operations are permitted on
27672 such thread groups.
27674 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27675 @node GDB/MI Command Syntax
27676 @section @sc{gdb/mi} Command Syntax
27679 * GDB/MI Input Syntax::
27680 * GDB/MI Output Syntax::
27683 @node GDB/MI Input Syntax
27684 @subsection @sc{gdb/mi} Input Syntax
27686 @cindex input syntax for @sc{gdb/mi}
27687 @cindex @sc{gdb/mi}, input syntax
27689 @item @var{command} @expansion{}
27690 @code{@var{cli-command} | @var{mi-command}}
27692 @item @var{cli-command} @expansion{}
27693 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27694 @var{cli-command} is any existing @value{GDBN} CLI command.
27696 @item @var{mi-command} @expansion{}
27697 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27698 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27700 @item @var{token} @expansion{}
27701 "any sequence of digits"
27703 @item @var{option} @expansion{}
27704 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27706 @item @var{parameter} @expansion{}
27707 @code{@var{non-blank-sequence} | @var{c-string}}
27709 @item @var{operation} @expansion{}
27710 @emph{any of the operations described in this chapter}
27712 @item @var{non-blank-sequence} @expansion{}
27713 @emph{anything, provided it doesn't contain special characters such as
27714 "-", @var{nl}, """ and of course " "}
27716 @item @var{c-string} @expansion{}
27717 @code{""" @var{seven-bit-iso-c-string-content} """}
27719 @item @var{nl} @expansion{}
27728 The CLI commands are still handled by the @sc{mi} interpreter; their
27729 output is described below.
27732 The @code{@var{token}}, when present, is passed back when the command
27736 Some @sc{mi} commands accept optional arguments as part of the parameter
27737 list. Each option is identified by a leading @samp{-} (dash) and may be
27738 followed by an optional argument parameter. Options occur first in the
27739 parameter list and can be delimited from normal parameters using
27740 @samp{--} (this is useful when some parameters begin with a dash).
27747 We want easy access to the existing CLI syntax (for debugging).
27750 We want it to be easy to spot a @sc{mi} operation.
27753 @node GDB/MI Output Syntax
27754 @subsection @sc{gdb/mi} Output Syntax
27756 @cindex output syntax of @sc{gdb/mi}
27757 @cindex @sc{gdb/mi}, output syntax
27758 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27759 followed, optionally, by a single result record. This result record
27760 is for the most recent command. The sequence of output records is
27761 terminated by @samp{(gdb)}.
27763 If an input command was prefixed with a @code{@var{token}} then the
27764 corresponding output for that command will also be prefixed by that same
27768 @item @var{output} @expansion{}
27769 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27771 @item @var{result-record} @expansion{}
27772 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27774 @item @var{out-of-band-record} @expansion{}
27775 @code{@var{async-record} | @var{stream-record}}
27777 @item @var{async-record} @expansion{}
27778 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27780 @item @var{exec-async-output} @expansion{}
27781 @code{[ @var{token} ] "*" @var{async-output nl}}
27783 @item @var{status-async-output} @expansion{}
27784 @code{[ @var{token} ] "+" @var{async-output nl}}
27786 @item @var{notify-async-output} @expansion{}
27787 @code{[ @var{token} ] "=" @var{async-output nl}}
27789 @item @var{async-output} @expansion{}
27790 @code{@var{async-class} ( "," @var{result} )*}
27792 @item @var{result-class} @expansion{}
27793 @code{"done" | "running" | "connected" | "error" | "exit"}
27795 @item @var{async-class} @expansion{}
27796 @code{"stopped" | @var{others}} (where @var{others} will be added
27797 depending on the needs---this is still in development).
27799 @item @var{result} @expansion{}
27800 @code{ @var{variable} "=" @var{value}}
27802 @item @var{variable} @expansion{}
27803 @code{ @var{string} }
27805 @item @var{value} @expansion{}
27806 @code{ @var{const} | @var{tuple} | @var{list} }
27808 @item @var{const} @expansion{}
27809 @code{@var{c-string}}
27811 @item @var{tuple} @expansion{}
27812 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27814 @item @var{list} @expansion{}
27815 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27816 @var{result} ( "," @var{result} )* "]" }
27818 @item @var{stream-record} @expansion{}
27819 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27821 @item @var{console-stream-output} @expansion{}
27822 @code{"~" @var{c-string nl}}
27824 @item @var{target-stream-output} @expansion{}
27825 @code{"@@" @var{c-string nl}}
27827 @item @var{log-stream-output} @expansion{}
27828 @code{"&" @var{c-string nl}}
27830 @item @var{nl} @expansion{}
27833 @item @var{token} @expansion{}
27834 @emph{any sequence of digits}.
27842 All output sequences end in a single line containing a period.
27845 The @code{@var{token}} is from the corresponding request. Note that
27846 for all async output, while the token is allowed by the grammar and
27847 may be output by future versions of @value{GDBN} for select async
27848 output messages, it is generally omitted. Frontends should treat
27849 all async output as reporting general changes in the state of the
27850 target and there should be no need to associate async output to any
27854 @cindex status output in @sc{gdb/mi}
27855 @var{status-async-output} contains on-going status information about the
27856 progress of a slow operation. It can be discarded. All status output is
27857 prefixed by @samp{+}.
27860 @cindex async output in @sc{gdb/mi}
27861 @var{exec-async-output} contains asynchronous state change on the target
27862 (stopped, started, disappeared). All async output is prefixed by
27866 @cindex notify output in @sc{gdb/mi}
27867 @var{notify-async-output} contains supplementary information that the
27868 client should handle (e.g., a new breakpoint information). All notify
27869 output is prefixed by @samp{=}.
27872 @cindex console output in @sc{gdb/mi}
27873 @var{console-stream-output} is output that should be displayed as is in the
27874 console. It is the textual response to a CLI command. All the console
27875 output is prefixed by @samp{~}.
27878 @cindex target output in @sc{gdb/mi}
27879 @var{target-stream-output} is the output produced by the target program.
27880 All the target output is prefixed by @samp{@@}.
27883 @cindex log output in @sc{gdb/mi}
27884 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27885 instance messages that should be displayed as part of an error log. All
27886 the log output is prefixed by @samp{&}.
27889 @cindex list output in @sc{gdb/mi}
27890 New @sc{gdb/mi} commands should only output @var{lists} containing
27896 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27897 details about the various output records.
27899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27900 @node GDB/MI Compatibility with CLI
27901 @section @sc{gdb/mi} Compatibility with CLI
27903 @cindex compatibility, @sc{gdb/mi} and CLI
27904 @cindex @sc{gdb/mi}, compatibility with CLI
27906 For the developers convenience CLI commands can be entered directly,
27907 but there may be some unexpected behaviour. For example, commands
27908 that query the user will behave as if the user replied yes, breakpoint
27909 command lists are not executed and some CLI commands, such as
27910 @code{if}, @code{when} and @code{define}, prompt for further input with
27911 @samp{>}, which is not valid MI output.
27913 This feature may be removed at some stage in the future and it is
27914 recommended that front ends use the @code{-interpreter-exec} command
27915 (@pxref{-interpreter-exec}).
27917 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27918 @node GDB/MI Development and Front Ends
27919 @section @sc{gdb/mi} Development and Front Ends
27920 @cindex @sc{gdb/mi} development
27922 The application which takes the MI output and presents the state of the
27923 program being debugged to the user is called a @dfn{front end}.
27925 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27926 to the MI interface may break existing usage. This section describes how the
27927 protocol changes and how to request previous version of the protocol when it
27930 Some changes in MI need not break a carefully designed front end, and
27931 for these the MI version will remain unchanged. The following is a
27932 list of changes that may occur within one level, so front ends should
27933 parse MI output in a way that can handle them:
27937 New MI commands may be added.
27940 New fields may be added to the output of any MI command.
27943 The range of values for fields with specified values, e.g.,
27944 @code{in_scope} (@pxref{-var-update}) may be extended.
27946 @c The format of field's content e.g type prefix, may change so parse it
27947 @c at your own risk. Yes, in general?
27949 @c The order of fields may change? Shouldn't really matter but it might
27950 @c resolve inconsistencies.
27953 If the changes are likely to break front ends, the MI version level
27954 will be increased by one. The new versions of the MI protocol are not compatible
27955 with the old versions. Old versions of MI remain available, allowing front ends
27956 to keep using them until they are modified to use the latest MI version.
27958 Since @code{--interpreter=mi} always points to the latest MI version, it is
27959 recommended that front ends request a specific version of MI when launching
27960 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27961 interpreter with the MI version they expect.
27963 The following table gives a summary of the the released versions of the MI
27964 interface: the version number, the version of GDB in which it first appeared
27965 and the breaking changes compared to the previous version.
27967 @multitable @columnfractions .05 .05 .9
27968 @headitem MI version @tab GDB version @tab Breaking changes
27985 The @code{-environment-pwd}, @code{-environment-directory} and
27986 @code{-environment-path} commands now returns values using the MI output
27987 syntax, rather than CLI output syntax.
27990 @code{-var-list-children}'s @code{children} result field is now a list, rather
27994 @code{-var-update}'s @code{changelist} result field is now a list, rather than
28006 The output of information about multi-location breakpoints has changed in the
28007 responses to the @code{-break-insert} and @code{-break-info} commands, as well
28008 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
28009 The multiple locations are now placed in a @code{locations} field, whose value
28015 If your front end cannot yet migrate to a more recent version of the
28016 MI protocol, you can nevertheless selectively enable specific features
28017 available in those recent MI versions, using the following commands:
28021 @item -fix-multi-location-breakpoint-output
28022 Use the output for multi-location breakpoints which was introduced by
28023 MI 3, even when using MI versions 2 or 1. This command has no
28024 effect when using MI version 3 or later.
28028 The best way to avoid unexpected changes in MI that might break your front
28029 end is to make your project known to @value{GDBN} developers and
28030 follow development on @email{gdb@@sourceware.org} and
28031 @email{gdb-patches@@sourceware.org}.
28032 @cindex mailing lists
28034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28035 @node GDB/MI Output Records
28036 @section @sc{gdb/mi} Output Records
28039 * GDB/MI Result Records::
28040 * GDB/MI Stream Records::
28041 * GDB/MI Async Records::
28042 * GDB/MI Breakpoint Information::
28043 * GDB/MI Frame Information::
28044 * GDB/MI Thread Information::
28045 * GDB/MI Ada Exception Information::
28048 @node GDB/MI Result Records
28049 @subsection @sc{gdb/mi} Result Records
28051 @cindex result records in @sc{gdb/mi}
28052 @cindex @sc{gdb/mi}, result records
28053 In addition to a number of out-of-band notifications, the response to a
28054 @sc{gdb/mi} command includes one of the following result indications:
28058 @item "^done" [ "," @var{results} ]
28059 The synchronous operation was successful, @code{@var{results}} are the return
28064 This result record is equivalent to @samp{^done}. Historically, it
28065 was output instead of @samp{^done} if the command has resumed the
28066 target. This behaviour is maintained for backward compatibility, but
28067 all frontends should treat @samp{^done} and @samp{^running}
28068 identically and rely on the @samp{*running} output record to determine
28069 which threads are resumed.
28073 @value{GDBN} has connected to a remote target.
28075 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
28077 The operation failed. The @code{msg=@var{c-string}} variable contains
28078 the corresponding error message.
28080 If present, the @code{code=@var{c-string}} variable provides an error
28081 code on which consumers can rely on to detect the corresponding
28082 error condition. At present, only one error code is defined:
28085 @item "undefined-command"
28086 Indicates that the command causing the error does not exist.
28091 @value{GDBN} has terminated.
28095 @node GDB/MI Stream Records
28096 @subsection @sc{gdb/mi} Stream Records
28098 @cindex @sc{gdb/mi}, stream records
28099 @cindex stream records in @sc{gdb/mi}
28100 @value{GDBN} internally maintains a number of output streams: the console, the
28101 target, and the log. The output intended for each of these streams is
28102 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28104 Each stream record begins with a unique @dfn{prefix character} which
28105 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28106 Syntax}). In addition to the prefix, each stream record contains a
28107 @code{@var{string-output}}. This is either raw text (with an implicit new
28108 line) or a quoted C string (which does not contain an implicit newline).
28111 @item "~" @var{string-output}
28112 The console output stream contains text that should be displayed in the
28113 CLI console window. It contains the textual responses to CLI commands.
28115 @item "@@" @var{string-output}
28116 The target output stream contains any textual output from the running
28117 target. This is only present when GDB's event loop is truly
28118 asynchronous, which is currently only the case for remote targets.
28120 @item "&" @var{string-output}
28121 The log stream contains debugging messages being produced by @value{GDBN}'s
28125 @node GDB/MI Async Records
28126 @subsection @sc{gdb/mi} Async Records
28128 @cindex async records in @sc{gdb/mi}
28129 @cindex @sc{gdb/mi}, async records
28130 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28131 additional changes that have occurred. Those changes can either be a
28132 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28133 target activity (e.g., target stopped).
28135 The following is the list of possible async records:
28139 @item *running,thread-id="@var{thread}"
28140 The target is now running. The @var{thread} field can be the global
28141 thread ID of the the thread that is now running, and it can be
28142 @samp{all} if all threads are running. The frontend should assume
28143 that no interaction with a running thread is possible after this
28144 notification is produced. The frontend should not assume that this
28145 notification is output only once for any command. @value{GDBN} may
28146 emit this notification several times, either for different threads,
28147 because it cannot resume all threads together, or even for a single
28148 thread, if the thread must be stepped though some code before letting
28151 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28152 The target has stopped. The @var{reason} field can have one of the
28156 @item breakpoint-hit
28157 A breakpoint was reached.
28158 @item watchpoint-trigger
28159 A watchpoint was triggered.
28160 @item read-watchpoint-trigger
28161 A read watchpoint was triggered.
28162 @item access-watchpoint-trigger
28163 An access watchpoint was triggered.
28164 @item function-finished
28165 An -exec-finish or similar CLI command was accomplished.
28166 @item location-reached
28167 An -exec-until or similar CLI command was accomplished.
28168 @item watchpoint-scope
28169 A watchpoint has gone out of scope.
28170 @item end-stepping-range
28171 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28172 similar CLI command was accomplished.
28173 @item exited-signalled
28174 The inferior exited because of a signal.
28176 The inferior exited.
28177 @item exited-normally
28178 The inferior exited normally.
28179 @item signal-received
28180 A signal was received by the inferior.
28182 The inferior has stopped due to a library being loaded or unloaded.
28183 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28184 set or when a @code{catch load} or @code{catch unload} catchpoint is
28185 in use (@pxref{Set Catchpoints}).
28187 The inferior has forked. This is reported when @code{catch fork}
28188 (@pxref{Set Catchpoints}) has been used.
28190 The inferior has vforked. This is reported in when @code{catch vfork}
28191 (@pxref{Set Catchpoints}) has been used.
28192 @item syscall-entry
28193 The inferior entered a system call. This is reported when @code{catch
28194 syscall} (@pxref{Set Catchpoints}) has been used.
28195 @item syscall-return
28196 The inferior returned from a system call. This is reported when
28197 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28199 The inferior called @code{exec}. This is reported when @code{catch exec}
28200 (@pxref{Set Catchpoints}) has been used.
28203 The @var{id} field identifies the global thread ID of the thread
28204 that directly caused the stop -- for example by hitting a breakpoint.
28205 Depending on whether all-stop
28206 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28207 stop all threads, or only the thread that directly triggered the stop.
28208 If all threads are stopped, the @var{stopped} field will have the
28209 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28210 field will be a list of thread identifiers. Presently, this list will
28211 always include a single thread, but frontend should be prepared to see
28212 several threads in the list. The @var{core} field reports the
28213 processor core on which the stop event has happened. This field may be absent
28214 if such information is not available.
28216 @item =thread-group-added,id="@var{id}"
28217 @itemx =thread-group-removed,id="@var{id}"
28218 A thread group was either added or removed. The @var{id} field
28219 contains the @value{GDBN} identifier of the thread group. When a thread
28220 group is added, it generally might not be associated with a running
28221 process. When a thread group is removed, its id becomes invalid and
28222 cannot be used in any way.
28224 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28225 A thread group became associated with a running program,
28226 either because the program was just started or the thread group
28227 was attached to a program. The @var{id} field contains the
28228 @value{GDBN} identifier of the thread group. The @var{pid} field
28229 contains process identifier, specific to the operating system.
28231 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28232 A thread group is no longer associated with a running program,
28233 either because the program has exited, or because it was detached
28234 from. The @var{id} field contains the @value{GDBN} identifier of the
28235 thread group. The @var{code} field is the exit code of the inferior; it exists
28236 only when the inferior exited with some code.
28238 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28239 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28240 A thread either was created, or has exited. The @var{id} field
28241 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28242 field identifies the thread group this thread belongs to.
28244 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28245 Informs that the selected thread or frame were changed. This notification
28246 is not emitted as result of the @code{-thread-select} or
28247 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28248 that is not documented to change the selected thread and frame actually
28249 changes them. In particular, invoking, directly or indirectly
28250 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28251 will generate this notification. Changing the thread or frame from another
28252 user interface (see @ref{Interpreters}) will also generate this notification.
28254 The @var{frame} field is only present if the newly selected thread is
28255 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28257 We suggest that in response to this notification, front ends
28258 highlight the selected thread and cause subsequent commands to apply to
28261 @item =library-loaded,...
28262 Reports that a new library file was loaded by the program. This
28263 notification has 5 fields---@var{id}, @var{target-name},
28264 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28265 opaque identifier of the library. For remote debugging case,
28266 @var{target-name} and @var{host-name} fields give the name of the
28267 library file on the target, and on the host respectively. For native
28268 debugging, both those fields have the same value. The
28269 @var{symbols-loaded} field is emitted only for backward compatibility
28270 and should not be relied on to convey any useful information. The
28271 @var{thread-group} field, if present, specifies the id of the thread
28272 group in whose context the library was loaded. If the field is
28273 absent, it means the library was loaded in the context of all present
28274 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28277 @item =library-unloaded,...
28278 Reports that a library was unloaded by the program. This notification
28279 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28280 the same meaning as for the @code{=library-loaded} notification.
28281 The @var{thread-group} field, if present, specifies the id of the
28282 thread group in whose context the library was unloaded. If the field is
28283 absent, it means the library was unloaded in the context of all present
28286 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28287 @itemx =traceframe-changed,end
28288 Reports that the trace frame was changed and its new number is
28289 @var{tfnum}. The number of the tracepoint associated with this trace
28290 frame is @var{tpnum}.
28292 @item =tsv-created,name=@var{name},initial=@var{initial}
28293 Reports that the new trace state variable @var{name} is created with
28294 initial value @var{initial}.
28296 @item =tsv-deleted,name=@var{name}
28297 @itemx =tsv-deleted
28298 Reports that the trace state variable @var{name} is deleted or all
28299 trace state variables are deleted.
28301 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28302 Reports that the trace state variable @var{name} is modified with
28303 the initial value @var{initial}. The current value @var{current} of
28304 trace state variable is optional and is reported if the current
28305 value of trace state variable is known.
28307 @item =breakpoint-created,bkpt=@{...@}
28308 @itemx =breakpoint-modified,bkpt=@{...@}
28309 @itemx =breakpoint-deleted,id=@var{number}
28310 Reports that a breakpoint was created, modified, or deleted,
28311 respectively. Only user-visible breakpoints are reported to the MI
28314 The @var{bkpt} argument is of the same form as returned by the various
28315 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28316 @var{number} is the ordinal number of the breakpoint.
28318 Note that if a breakpoint is emitted in the result record of a
28319 command, then it will not also be emitted in an async record.
28321 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28322 @itemx =record-stopped,thread-group="@var{id}"
28323 Execution log recording was either started or stopped on an
28324 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28325 group corresponding to the affected inferior.
28327 The @var{method} field indicates the method used to record execution. If the
28328 method in use supports multiple recording formats, @var{format} will be present
28329 and contain the currently used format. @xref{Process Record and Replay},
28330 for existing method and format values.
28332 @item =cmd-param-changed,param=@var{param},value=@var{value}
28333 Reports that a parameter of the command @code{set @var{param}} is
28334 changed to @var{value}. In the multi-word @code{set} command,
28335 the @var{param} is the whole parameter list to @code{set} command.
28336 For example, In command @code{set check type on}, @var{param}
28337 is @code{check type} and @var{value} is @code{on}.
28339 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28340 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28341 written in an inferior. The @var{id} is the identifier of the
28342 thread group corresponding to the affected inferior. The optional
28343 @code{type="code"} part is reported if the memory written to holds
28347 @node GDB/MI Breakpoint Information
28348 @subsection @sc{gdb/mi} Breakpoint Information
28350 When @value{GDBN} reports information about a breakpoint, a
28351 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28356 The breakpoint number.
28359 The type of the breakpoint. For ordinary breakpoints this will be
28360 @samp{breakpoint}, but many values are possible.
28363 If the type of the breakpoint is @samp{catchpoint}, then this
28364 indicates the exact type of catchpoint.
28367 This is the breakpoint disposition---either @samp{del}, meaning that
28368 the breakpoint will be deleted at the next stop, or @samp{keep},
28369 meaning that the breakpoint will not be deleted.
28372 This indicates whether the breakpoint is enabled, in which case the
28373 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28374 Note that this is not the same as the field @code{enable}.
28377 The address of the breakpoint. This may be a hexidecimal number,
28378 giving the address; or the string @samp{<PENDING>}, for a pending
28379 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28380 multiple locations. This field will not be present if no address can
28381 be determined. For example, a watchpoint does not have an address.
28384 If known, the function in which the breakpoint appears.
28385 If not known, this field is not present.
28388 The name of the source file which contains this function, if known.
28389 If not known, this field is not present.
28392 The full file name of the source file which contains this function, if
28393 known. If not known, this field is not present.
28396 The line number at which this breakpoint appears, if known.
28397 If not known, this field is not present.
28400 If the source file is not known, this field may be provided. If
28401 provided, this holds the address of the breakpoint, possibly followed
28405 If this breakpoint is pending, this field is present and holds the
28406 text used to set the breakpoint, as entered by the user.
28409 Where this breakpoint's condition is evaluated, either @samp{host} or
28413 If this is a thread-specific breakpoint, then this identifies the
28414 thread in which the breakpoint can trigger.
28417 If this breakpoint is restricted to a particular Ada task, then this
28418 field will hold the task identifier.
28421 If the breakpoint is conditional, this is the condition expression.
28424 The ignore count of the breakpoint.
28427 The enable count of the breakpoint.
28429 @item traceframe-usage
28432 @item static-tracepoint-marker-string-id
28433 For a static tracepoint, the name of the static tracepoint marker.
28436 For a masked watchpoint, this is the mask.
28439 A tracepoint's pass count.
28441 @item original-location
28442 The location of the breakpoint as originally specified by the user.
28443 This field is optional.
28446 The number of times the breakpoint has been hit.
28449 This field is only given for tracepoints. This is either @samp{y},
28450 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28454 Some extra data, the exact contents of which are type-dependent.
28457 This field is present if the breakpoint has multiple locations. It is also
28458 exceptionally present if the breakpoint is enabled and has a single, disabled
28461 The value is a list of locations. The format of a location is decribed below.
28465 A location in a multi-location breakpoint is represented as a tuple with the
28471 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28472 number of the parent breakpoint. The second digit is the number of the
28473 location within that breakpoint.
28476 This indicates whether the location is enabled, in which case the
28477 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28478 Note that this is not the same as the field @code{enable}.
28481 The address of this location as an hexidecimal number.
28484 If known, the function in which the location appears.
28485 If not known, this field is not present.
28488 The name of the source file which contains this location, if known.
28489 If not known, this field is not present.
28492 The full file name of the source file which contains this location, if
28493 known. If not known, this field is not present.
28496 The line number at which this location appears, if known.
28497 If not known, this field is not present.
28499 @item thread-groups
28500 The thread groups this location is in.
28504 For example, here is what the output of @code{-break-insert}
28505 (@pxref{GDB/MI Breakpoint Commands}) might be:
28508 -> -break-insert main
28509 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28510 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28511 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28516 @node GDB/MI Frame Information
28517 @subsection @sc{gdb/mi} Frame Information
28519 Response from many MI commands includes an information about stack
28520 frame. This information is a tuple that may have the following
28525 The level of the stack frame. The innermost frame has the level of
28526 zero. This field is always present.
28529 The name of the function corresponding to the frame. This field may
28530 be absent if @value{GDBN} is unable to determine the function name.
28533 The code address for the frame. This field is always present.
28536 The name of the source files that correspond to the frame's code
28537 address. This field may be absent.
28540 The source line corresponding to the frames' code address. This field
28544 The name of the binary file (either executable or shared library) the
28545 corresponds to the frame's code address. This field may be absent.
28549 @node GDB/MI Thread Information
28550 @subsection @sc{gdb/mi} Thread Information
28552 Whenever @value{GDBN} has to report an information about a thread, it
28553 uses a tuple with the following fields. The fields are always present unless
28558 The global numeric id assigned to the thread by @value{GDBN}.
28561 The target-specific string identifying the thread.
28564 Additional information about the thread provided by the target.
28565 It is supposed to be human-readable and not interpreted by the
28566 frontend. This field is optional.
28569 The name of the thread. If the user specified a name using the
28570 @code{thread name} command, then this name is given. Otherwise, if
28571 @value{GDBN} can extract the thread name from the target, then that
28572 name is given. If @value{GDBN} cannot find the thread name, then this
28576 The execution state of the thread, either @samp{stopped} or @samp{running},
28577 depending on whether the thread is presently running.
28580 The stack frame currently executing in the thread. This field is only present
28581 if the thread is stopped. Its format is documented in
28582 @ref{GDB/MI Frame Information}.
28585 The value of this field is an integer number of the processor core the
28586 thread was last seen on. This field is optional.
28589 @node GDB/MI Ada Exception Information
28590 @subsection @sc{gdb/mi} Ada Exception Information
28592 Whenever a @code{*stopped} record is emitted because the program
28593 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28594 @value{GDBN} provides the name of the exception that was raised via
28595 the @code{exception-name} field. Also, for exceptions that were raised
28596 with an exception message, @value{GDBN} provides that message via
28597 the @code{exception-message} field.
28599 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28600 @node GDB/MI Simple Examples
28601 @section Simple Examples of @sc{gdb/mi} Interaction
28602 @cindex @sc{gdb/mi}, simple examples
28604 This subsection presents several simple examples of interaction using
28605 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28606 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28607 the output received from @sc{gdb/mi}.
28609 Note the line breaks shown in the examples are here only for
28610 readability, they don't appear in the real output.
28612 @subheading Setting a Breakpoint
28614 Setting a breakpoint generates synchronous output which contains detailed
28615 information of the breakpoint.
28618 -> -break-insert main
28619 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28620 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28621 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28626 @subheading Program Execution
28628 Program execution generates asynchronous records and MI gives the
28629 reason that execution stopped.
28635 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28636 frame=@{addr="0x08048564",func="main",
28637 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28638 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28639 arch="i386:x86_64"@}
28644 <- *stopped,reason="exited-normally"
28648 @subheading Quitting @value{GDBN}
28650 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28658 Please note that @samp{^exit} is printed immediately, but it might
28659 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28660 performs necessary cleanups, including killing programs being debugged
28661 or disconnecting from debug hardware, so the frontend should wait till
28662 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28663 fails to exit in reasonable time.
28665 @subheading A Bad Command
28667 Here's what happens if you pass a non-existent command:
28671 <- ^error,msg="Undefined MI command: rubbish"
28676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28677 @node GDB/MI Command Description Format
28678 @section @sc{gdb/mi} Command Description Format
28680 The remaining sections describe blocks of commands. Each block of
28681 commands is laid out in a fashion similar to this section.
28683 @subheading Motivation
28685 The motivation for this collection of commands.
28687 @subheading Introduction
28689 A brief introduction to this collection of commands as a whole.
28691 @subheading Commands
28693 For each command in the block, the following is described:
28695 @subsubheading Synopsis
28698 -command @var{args}@dots{}
28701 @subsubheading Result
28703 @subsubheading @value{GDBN} Command
28705 The corresponding @value{GDBN} CLI command(s), if any.
28707 @subsubheading Example
28709 Example(s) formatted for readability. Some of the described commands have
28710 not been implemented yet and these are labeled N.A.@: (not available).
28713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28714 @node GDB/MI Breakpoint Commands
28715 @section @sc{gdb/mi} Breakpoint Commands
28717 @cindex breakpoint commands for @sc{gdb/mi}
28718 @cindex @sc{gdb/mi}, breakpoint commands
28719 This section documents @sc{gdb/mi} commands for manipulating
28722 @subheading The @code{-break-after} Command
28723 @findex -break-after
28725 @subsubheading Synopsis
28728 -break-after @var{number} @var{count}
28731 The breakpoint number @var{number} is not in effect until it has been
28732 hit @var{count} times. To see how this is reflected in the output of
28733 the @samp{-break-list} command, see the description of the
28734 @samp{-break-list} command below.
28736 @subsubheading @value{GDBN} Command
28738 The corresponding @value{GDBN} command is @samp{ignore}.
28740 @subsubheading Example
28745 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28746 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28747 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28755 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28756 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28757 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28758 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28759 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28760 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28761 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28762 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28763 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28764 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28769 @subheading The @code{-break-catch} Command
28770 @findex -break-catch
28773 @subheading The @code{-break-commands} Command
28774 @findex -break-commands
28776 @subsubheading Synopsis
28779 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28782 Specifies the CLI commands that should be executed when breakpoint
28783 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28784 are the commands. If no command is specified, any previously-set
28785 commands are cleared. @xref{Break Commands}. Typical use of this
28786 functionality is tracing a program, that is, printing of values of
28787 some variables whenever breakpoint is hit and then continuing.
28789 @subsubheading @value{GDBN} Command
28791 The corresponding @value{GDBN} command is @samp{commands}.
28793 @subsubheading Example
28798 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28799 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28800 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28803 -break-commands 1 "print v" "continue"
28808 @subheading The @code{-break-condition} Command
28809 @findex -break-condition
28811 @subsubheading Synopsis
28814 -break-condition @var{number} @var{expr}
28817 Breakpoint @var{number} will stop the program only if the condition in
28818 @var{expr} is true. The condition becomes part of the
28819 @samp{-break-list} output (see the description of the @samp{-break-list}
28822 @subsubheading @value{GDBN} Command
28824 The corresponding @value{GDBN} command is @samp{condition}.
28826 @subsubheading Example
28830 -break-condition 1 1
28834 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28835 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28836 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28837 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28838 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28839 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28840 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28841 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28842 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28843 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28847 @subheading The @code{-break-delete} Command
28848 @findex -break-delete
28850 @subsubheading Synopsis
28853 -break-delete ( @var{breakpoint} )+
28856 Delete the breakpoint(s) whose number(s) are specified in the argument
28857 list. This is obviously reflected in the breakpoint list.
28859 @subsubheading @value{GDBN} Command
28861 The corresponding @value{GDBN} command is @samp{delete}.
28863 @subsubheading Example
28871 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28872 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28873 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28874 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28875 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28876 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28877 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28882 @subheading The @code{-break-disable} Command
28883 @findex -break-disable
28885 @subsubheading Synopsis
28888 -break-disable ( @var{breakpoint} )+
28891 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28892 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28894 @subsubheading @value{GDBN} Command
28896 The corresponding @value{GDBN} command is @samp{disable}.
28898 @subsubheading Example
28906 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28913 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28914 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28915 line="5",thread-groups=["i1"],times="0"@}]@}
28919 @subheading The @code{-break-enable} Command
28920 @findex -break-enable
28922 @subsubheading Synopsis
28925 -break-enable ( @var{breakpoint} )+
28928 Enable (previously disabled) @var{breakpoint}(s).
28930 @subsubheading @value{GDBN} Command
28932 The corresponding @value{GDBN} command is @samp{enable}.
28934 @subsubheading Example
28942 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28943 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28944 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28945 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28946 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28947 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28948 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28949 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28950 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28951 line="5",thread-groups=["i1"],times="0"@}]@}
28955 @subheading The @code{-break-info} Command
28956 @findex -break-info
28958 @subsubheading Synopsis
28961 -break-info @var{breakpoint}
28965 Get information about a single breakpoint.
28967 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28968 Information}, for details on the format of each breakpoint in the
28971 @subsubheading @value{GDBN} Command
28973 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28975 @subsubheading Example
28978 @subheading The @code{-break-insert} Command
28979 @findex -break-insert
28980 @anchor{-break-insert}
28982 @subsubheading Synopsis
28985 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28986 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28987 [ -p @var{thread-id} ] [ @var{location} ]
28991 If specified, @var{location}, can be one of:
28994 @item linespec location
28995 A linespec location. @xref{Linespec Locations}.
28997 @item explicit location
28998 An explicit location. @sc{gdb/mi} explicit locations are
28999 analogous to the CLI's explicit locations using the option names
29000 listed below. @xref{Explicit Locations}.
29003 @item --source @var{filename}
29004 The source file name of the location. This option requires the use
29005 of either @samp{--function} or @samp{--line}.
29007 @item --function @var{function}
29008 The name of a function or method.
29010 @item --label @var{label}
29011 The name of a label.
29013 @item --line @var{lineoffset}
29014 An absolute or relative line offset from the start of the location.
29017 @item address location
29018 An address location, *@var{address}. @xref{Address Locations}.
29022 The possible optional parameters of this command are:
29026 Insert a temporary breakpoint.
29028 Insert a hardware breakpoint.
29030 If @var{location} cannot be parsed (for example if it
29031 refers to unknown files or functions), create a pending
29032 breakpoint. Without this flag, @value{GDBN} will report
29033 an error, and won't create a breakpoint, if @var{location}
29036 Create a disabled breakpoint.
29038 Create a tracepoint. @xref{Tracepoints}. When this parameter
29039 is used together with @samp{-h}, a fast tracepoint is created.
29040 @item -c @var{condition}
29041 Make the breakpoint conditional on @var{condition}.
29042 @item -i @var{ignore-count}
29043 Initialize the @var{ignore-count}.
29044 @item -p @var{thread-id}
29045 Restrict the breakpoint to the thread with the specified global
29049 @subsubheading Result
29051 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29052 resulting breakpoint.
29054 Note: this format is open to change.
29055 @c An out-of-band breakpoint instead of part of the result?
29057 @subsubheading @value{GDBN} Command
29059 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29060 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29062 @subsubheading Example
29067 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29068 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29071 -break-insert -t foo
29072 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29073 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29077 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29078 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29079 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29080 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29081 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29082 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29083 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29084 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29085 addr="0x0001072c", func="main",file="recursive2.c",
29086 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29088 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29089 addr="0x00010774",func="foo",file="recursive2.c",
29090 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29093 @c -break-insert -r foo.*
29094 @c ~int foo(int, int);
29095 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29096 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29101 @subheading The @code{-dprintf-insert} Command
29102 @findex -dprintf-insert
29104 @subsubheading Synopsis
29107 -dprintf-insert [ -t ] [ -f ] [ -d ]
29108 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29109 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29114 If supplied, @var{location} may be specified the same way as for
29115 the @code{-break-insert} command. @xref{-break-insert}.
29117 The possible optional parameters of this command are:
29121 Insert a temporary breakpoint.
29123 If @var{location} cannot be parsed (for example, if it
29124 refers to unknown files or functions), create a pending
29125 breakpoint. Without this flag, @value{GDBN} will report
29126 an error, and won't create a breakpoint, if @var{location}
29129 Create a disabled breakpoint.
29130 @item -c @var{condition}
29131 Make the breakpoint conditional on @var{condition}.
29132 @item -i @var{ignore-count}
29133 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29134 to @var{ignore-count}.
29135 @item -p @var{thread-id}
29136 Restrict the breakpoint to the thread with the specified global
29140 @subsubheading Result
29142 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29143 resulting breakpoint.
29145 @c An out-of-band breakpoint instead of part of the result?
29147 @subsubheading @value{GDBN} Command
29149 The corresponding @value{GDBN} command is @samp{dprintf}.
29151 @subsubheading Example
29155 4-dprintf-insert foo "At foo entry\n"
29156 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29157 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29158 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29159 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29160 original-location="foo"@}
29162 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29163 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29164 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29165 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29166 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29167 original-location="mi-dprintf.c:26"@}
29171 @subheading The @code{-break-list} Command
29172 @findex -break-list
29174 @subsubheading Synopsis
29180 Displays the list of inserted breakpoints, showing the following fields:
29184 number of the breakpoint
29186 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29188 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29191 is the breakpoint enabled or no: @samp{y} or @samp{n}
29193 memory location at which the breakpoint is set
29195 logical location of the breakpoint, expressed by function name, file
29197 @item Thread-groups
29198 list of thread groups to which this breakpoint applies
29200 number of times the breakpoint has been hit
29203 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29204 @code{body} field is an empty list.
29206 @subsubheading @value{GDBN} Command
29208 The corresponding @value{GDBN} command is @samp{info break}.
29210 @subsubheading Example
29215 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29216 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29217 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29218 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29219 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29220 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29221 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29222 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29223 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29225 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29226 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29227 line="13",thread-groups=["i1"],times="0"@}]@}
29231 Here's an example of the result when there are no breakpoints:
29236 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29237 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29238 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29239 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29240 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29241 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29242 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29247 @subheading The @code{-break-passcount} Command
29248 @findex -break-passcount
29250 @subsubheading Synopsis
29253 -break-passcount @var{tracepoint-number} @var{passcount}
29256 Set the passcount for tracepoint @var{tracepoint-number} to
29257 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29258 is not a tracepoint, error is emitted. This corresponds to CLI
29259 command @samp{passcount}.
29261 @subheading The @code{-break-watch} Command
29262 @findex -break-watch
29264 @subsubheading Synopsis
29267 -break-watch [ -a | -r ]
29270 Create a watchpoint. With the @samp{-a} option it will create an
29271 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29272 read from or on a write to the memory location. With the @samp{-r}
29273 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29274 trigger only when the memory location is accessed for reading. Without
29275 either of the options, the watchpoint created is a regular watchpoint,
29276 i.e., it will trigger when the memory location is accessed for writing.
29277 @xref{Set Watchpoints, , Setting Watchpoints}.
29279 Note that @samp{-break-list} will report a single list of watchpoints and
29280 breakpoints inserted.
29282 @subsubheading @value{GDBN} Command
29284 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29287 @subsubheading Example
29289 Setting a watchpoint on a variable in the @code{main} function:
29294 ^done,wpt=@{number="2",exp="x"@}
29299 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29300 value=@{old="-268439212",new="55"@},
29301 frame=@{func="main",args=[],file="recursive2.c",
29302 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29306 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29307 the program execution twice: first for the variable changing value, then
29308 for the watchpoint going out of scope.
29313 ^done,wpt=@{number="5",exp="C"@}
29318 *stopped,reason="watchpoint-trigger",
29319 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29320 frame=@{func="callee4",args=[],
29321 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29322 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29323 arch="i386:x86_64"@}
29328 *stopped,reason="watchpoint-scope",wpnum="5",
29329 frame=@{func="callee3",args=[@{name="strarg",
29330 value="0x11940 \"A string argument.\""@}],
29331 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29332 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29333 arch="i386:x86_64"@}
29337 Listing breakpoints and watchpoints, at different points in the program
29338 execution. Note that once the watchpoint goes out of scope, it is
29344 ^done,wpt=@{number="2",exp="C"@}
29347 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29348 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29349 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29350 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29351 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29352 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29353 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29354 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29355 addr="0x00010734",func="callee4",
29356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29357 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29359 bkpt=@{number="2",type="watchpoint",disp="keep",
29360 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29365 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29366 value=@{old="-276895068",new="3"@},
29367 frame=@{func="callee4",args=[],
29368 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29369 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29370 arch="i386:x86_64"@}
29373 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29374 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29375 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29376 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29377 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29378 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29379 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29380 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29381 addr="0x00010734",func="callee4",
29382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29383 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29385 bkpt=@{number="2",type="watchpoint",disp="keep",
29386 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29390 ^done,reason="watchpoint-scope",wpnum="2",
29391 frame=@{func="callee3",args=[@{name="strarg",
29392 value="0x11940 \"A string argument.\""@}],
29393 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29394 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29395 arch="i386:x86_64"@}
29398 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29399 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29400 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29401 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29402 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29403 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29404 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29405 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29406 addr="0x00010734",func="callee4",
29407 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29408 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29409 thread-groups=["i1"],times="1"@}]@}
29414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29415 @node GDB/MI Catchpoint Commands
29416 @section @sc{gdb/mi} Catchpoint Commands
29418 This section documents @sc{gdb/mi} commands for manipulating
29422 * Shared Library GDB/MI Catchpoint Commands::
29423 * Ada Exception GDB/MI Catchpoint Commands::
29426 @node Shared Library GDB/MI Catchpoint Commands
29427 @subsection Shared Library @sc{gdb/mi} Catchpoints
29429 @subheading The @code{-catch-load} Command
29430 @findex -catch-load
29432 @subsubheading Synopsis
29435 -catch-load [ -t ] [ -d ] @var{regexp}
29438 Add a catchpoint for library load events. If the @samp{-t} option is used,
29439 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29440 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29441 in a disabled state. The @samp{regexp} argument is a regular
29442 expression used to match the name of the loaded library.
29445 @subsubheading @value{GDBN} Command
29447 The corresponding @value{GDBN} command is @samp{catch load}.
29449 @subsubheading Example
29452 -catch-load -t foo.so
29453 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29454 what="load of library matching foo.so",catch-type="load",times="0"@}
29459 @subheading The @code{-catch-unload} Command
29460 @findex -catch-unload
29462 @subsubheading Synopsis
29465 -catch-unload [ -t ] [ -d ] @var{regexp}
29468 Add a catchpoint for library unload events. If the @samp{-t} option is
29469 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29470 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29471 created in a disabled state. The @samp{regexp} argument is a regular
29472 expression used to match the name of the unloaded library.
29474 @subsubheading @value{GDBN} Command
29476 The corresponding @value{GDBN} command is @samp{catch unload}.
29478 @subsubheading Example
29481 -catch-unload -d bar.so
29482 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29483 what="load of library matching bar.so",catch-type="unload",times="0"@}
29487 @node Ada Exception GDB/MI Catchpoint Commands
29488 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29490 The following @sc{gdb/mi} commands can be used to create catchpoints
29491 that stop the execution when Ada exceptions are being raised.
29493 @subheading The @code{-catch-assert} Command
29494 @findex -catch-assert
29496 @subsubheading Synopsis
29499 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29502 Add a catchpoint for failed Ada assertions.
29504 The possible optional parameters for this command are:
29507 @item -c @var{condition}
29508 Make the catchpoint conditional on @var{condition}.
29510 Create a disabled catchpoint.
29512 Create a temporary catchpoint.
29515 @subsubheading @value{GDBN} Command
29517 The corresponding @value{GDBN} command is @samp{catch assert}.
29519 @subsubheading Example
29523 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29524 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29525 thread-groups=["i1"],times="0",
29526 original-location="__gnat_debug_raise_assert_failure"@}
29530 @subheading The @code{-catch-exception} Command
29531 @findex -catch-exception
29533 @subsubheading Synopsis
29536 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29540 Add a catchpoint stopping when Ada exceptions are raised.
29541 By default, the command stops the program when any Ada exception
29542 gets raised. But it is also possible, by using some of the
29543 optional parameters described below, to create more selective
29546 The possible optional parameters for this command are:
29549 @item -c @var{condition}
29550 Make the catchpoint conditional on @var{condition}.
29552 Create a disabled catchpoint.
29553 @item -e @var{exception-name}
29554 Only stop when @var{exception-name} is raised. This option cannot
29555 be used combined with @samp{-u}.
29557 Create a temporary catchpoint.
29559 Stop only when an unhandled exception gets raised. This option
29560 cannot be used combined with @samp{-e}.
29563 @subsubheading @value{GDBN} Command
29565 The corresponding @value{GDBN} commands are @samp{catch exception}
29566 and @samp{catch exception unhandled}.
29568 @subsubheading Example
29571 -catch-exception -e Program_Error
29572 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29573 enabled="y",addr="0x0000000000404874",
29574 what="`Program_Error' Ada exception", thread-groups=["i1"],
29575 times="0",original-location="__gnat_debug_raise_exception"@}
29579 @subheading The @code{-catch-handlers} Command
29580 @findex -catch-handlers
29582 @subsubheading Synopsis
29585 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29589 Add a catchpoint stopping when Ada exceptions are handled.
29590 By default, the command stops the program when any Ada exception
29591 gets handled. But it is also possible, by using some of the
29592 optional parameters described below, to create more selective
29595 The possible optional parameters for this command are:
29598 @item -c @var{condition}
29599 Make the catchpoint conditional on @var{condition}.
29601 Create a disabled catchpoint.
29602 @item -e @var{exception-name}
29603 Only stop when @var{exception-name} is handled.
29605 Create a temporary catchpoint.
29608 @subsubheading @value{GDBN} Command
29610 The corresponding @value{GDBN} command is @samp{catch handlers}.
29612 @subsubheading Example
29615 -catch-handlers -e Constraint_Error
29616 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29617 enabled="y",addr="0x0000000000402f68",
29618 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29619 times="0",original-location="__gnat_begin_handler"@}
29623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29624 @node GDB/MI Program Context
29625 @section @sc{gdb/mi} Program Context
29627 @subheading The @code{-exec-arguments} Command
29628 @findex -exec-arguments
29631 @subsubheading Synopsis
29634 -exec-arguments @var{args}
29637 Set the inferior program arguments, to be used in the next
29640 @subsubheading @value{GDBN} Command
29642 The corresponding @value{GDBN} command is @samp{set args}.
29644 @subsubheading Example
29648 -exec-arguments -v word
29655 @subheading The @code{-exec-show-arguments} Command
29656 @findex -exec-show-arguments
29658 @subsubheading Synopsis
29661 -exec-show-arguments
29664 Print the arguments of the program.
29666 @subsubheading @value{GDBN} Command
29668 The corresponding @value{GDBN} command is @samp{show args}.
29670 @subsubheading Example
29675 @subheading The @code{-environment-cd} Command
29676 @findex -environment-cd
29678 @subsubheading Synopsis
29681 -environment-cd @var{pathdir}
29684 Set @value{GDBN}'s working directory.
29686 @subsubheading @value{GDBN} Command
29688 The corresponding @value{GDBN} command is @samp{cd}.
29690 @subsubheading Example
29694 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29700 @subheading The @code{-environment-directory} Command
29701 @findex -environment-directory
29703 @subsubheading Synopsis
29706 -environment-directory [ -r ] [ @var{pathdir} ]+
29709 Add directories @var{pathdir} to beginning of search path for source files.
29710 If the @samp{-r} option is used, the search path is reset to the default
29711 search path. If directories @var{pathdir} are supplied in addition to the
29712 @samp{-r} option, the search path is first reset and then addition
29714 Multiple directories may be specified, separated by blanks. Specifying
29715 multiple directories in a single command
29716 results in the directories added to the beginning of the
29717 search path in the same order they were presented in the command.
29718 If blanks are needed as
29719 part of a directory name, double-quotes should be used around
29720 the name. In the command output, the path will show up separated
29721 by the system directory-separator character. The directory-separator
29722 character must not be used
29723 in any directory name.
29724 If no directories are specified, the current search path is displayed.
29726 @subsubheading @value{GDBN} Command
29728 The corresponding @value{GDBN} command is @samp{dir}.
29730 @subsubheading Example
29734 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29735 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29737 -environment-directory ""
29738 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29740 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29741 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29743 -environment-directory -r
29744 ^done,source-path="$cdir:$cwd"
29749 @subheading The @code{-environment-path} Command
29750 @findex -environment-path
29752 @subsubheading Synopsis
29755 -environment-path [ -r ] [ @var{pathdir} ]+
29758 Add directories @var{pathdir} to beginning of search path for object files.
29759 If the @samp{-r} option is used, the search path is reset to the original
29760 search path that existed at gdb start-up. If directories @var{pathdir} are
29761 supplied in addition to the
29762 @samp{-r} option, the search path is first reset and then addition
29764 Multiple directories may be specified, separated by blanks. Specifying
29765 multiple directories in a single command
29766 results in the directories added to the beginning of the
29767 search path in the same order they were presented in the command.
29768 If blanks are needed as
29769 part of a directory name, double-quotes should be used around
29770 the name. In the command output, the path will show up separated
29771 by the system directory-separator character. The directory-separator
29772 character must not be used
29773 in any directory name.
29774 If no directories are specified, the current path is displayed.
29777 @subsubheading @value{GDBN} Command
29779 The corresponding @value{GDBN} command is @samp{path}.
29781 @subsubheading Example
29786 ^done,path="/usr/bin"
29788 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29789 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29791 -environment-path -r /usr/local/bin
29792 ^done,path="/usr/local/bin:/usr/bin"
29797 @subheading The @code{-environment-pwd} Command
29798 @findex -environment-pwd
29800 @subsubheading Synopsis
29806 Show the current working directory.
29808 @subsubheading @value{GDBN} Command
29810 The corresponding @value{GDBN} command is @samp{pwd}.
29812 @subsubheading Example
29817 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29822 @node GDB/MI Thread Commands
29823 @section @sc{gdb/mi} Thread Commands
29826 @subheading The @code{-thread-info} Command
29827 @findex -thread-info
29829 @subsubheading Synopsis
29832 -thread-info [ @var{thread-id} ]
29835 Reports information about either a specific thread, if the
29836 @var{thread-id} parameter is present, or about all threads.
29837 @var{thread-id} is the thread's global thread ID. When printing
29838 information about all threads, also reports the global ID of the
29841 @subsubheading @value{GDBN} Command
29843 The @samp{info thread} command prints the same information
29846 @subsubheading Result
29848 The result contains the following attributes:
29852 A list of threads. The format of the elements of the list is described in
29853 @ref{GDB/MI Thread Information}.
29855 @item current-thread-id
29856 The global id of the currently selected thread. This field is omitted if there
29857 is no selected thread (for example, when the selected inferior is not running,
29858 and therefore has no threads) or if a @var{thread-id} argument was passed to
29863 @subsubheading Example
29868 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29869 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29870 args=[]@},state="running"@},
29871 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29872 frame=@{level="0",addr="0x0804891f",func="foo",
29873 args=[@{name="i",value="10"@}],
29874 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29875 state="running"@}],
29876 current-thread-id="1"
29880 @subheading The @code{-thread-list-ids} Command
29881 @findex -thread-list-ids
29883 @subsubheading Synopsis
29889 Produces a list of the currently known global @value{GDBN} thread ids.
29890 At the end of the list it also prints the total number of such
29893 This command is retained for historical reasons, the
29894 @code{-thread-info} command should be used instead.
29896 @subsubheading @value{GDBN} Command
29898 Part of @samp{info threads} supplies the same information.
29900 @subsubheading Example
29905 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29906 current-thread-id="1",number-of-threads="3"
29911 @subheading The @code{-thread-select} Command
29912 @findex -thread-select
29914 @subsubheading Synopsis
29917 -thread-select @var{thread-id}
29920 Make thread with global thread number @var{thread-id} the current
29921 thread. It prints the number of the new current thread, and the
29922 topmost frame for that thread.
29924 This command is deprecated in favor of explicitly using the
29925 @samp{--thread} option to each command.
29927 @subsubheading @value{GDBN} Command
29929 The corresponding @value{GDBN} command is @samp{thread}.
29931 @subsubheading Example
29938 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29939 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29943 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29944 number-of-threads="3"
29947 ^done,new-thread-id="3",
29948 frame=@{level="0",func="vprintf",
29949 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29950 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29955 @node GDB/MI Ada Tasking Commands
29956 @section @sc{gdb/mi} Ada Tasking Commands
29958 @subheading The @code{-ada-task-info} Command
29959 @findex -ada-task-info
29961 @subsubheading Synopsis
29964 -ada-task-info [ @var{task-id} ]
29967 Reports information about either a specific Ada task, if the
29968 @var{task-id} parameter is present, or about all Ada tasks.
29970 @subsubheading @value{GDBN} Command
29972 The @samp{info tasks} command prints the same information
29973 about all Ada tasks (@pxref{Ada Tasks}).
29975 @subsubheading Result
29977 The result is a table of Ada tasks. The following columns are
29978 defined for each Ada task:
29982 This field exists only for the current thread. It has the value @samp{*}.
29985 The identifier that @value{GDBN} uses to refer to the Ada task.
29988 The identifier that the target uses to refer to the Ada task.
29991 The global thread identifier of the thread corresponding to the Ada
29994 This field should always exist, as Ada tasks are always implemented
29995 on top of a thread. But if @value{GDBN} cannot find this corresponding
29996 thread for any reason, the field is omitted.
29999 This field exists only when the task was created by another task.
30000 In this case, it provides the ID of the parent task.
30003 The base priority of the task.
30006 The current state of the task. For a detailed description of the
30007 possible states, see @ref{Ada Tasks}.
30010 The name of the task.
30014 @subsubheading Example
30018 ^done,tasks=@{nr_rows="3",nr_cols="8",
30019 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30020 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30021 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30022 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30023 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30024 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30025 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30026 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30027 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30028 state="Child Termination Wait",name="main_task"@}]@}
30032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30033 @node GDB/MI Program Execution
30034 @section @sc{gdb/mi} Program Execution
30036 These are the asynchronous commands which generate the out-of-band
30037 record @samp{*stopped}. Currently @value{GDBN} only really executes
30038 asynchronously with remote targets and this interaction is mimicked in
30041 @subheading The @code{-exec-continue} Command
30042 @findex -exec-continue
30044 @subsubheading Synopsis
30047 -exec-continue [--reverse] [--all|--thread-group N]
30050 Resumes the execution of the inferior program, which will continue
30051 to execute until it reaches a debugger stop event. If the
30052 @samp{--reverse} option is specified, execution resumes in reverse until
30053 it reaches a stop event. Stop events may include
30056 breakpoints or watchpoints
30058 signals or exceptions
30060 the end of the process (or its beginning under @samp{--reverse})
30062 the end or beginning of a replay log if one is being used.
30064 In all-stop mode (@pxref{All-Stop
30065 Mode}), may resume only one thread, or all threads, depending on the
30066 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30067 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30068 ignored in all-stop mode. If the @samp{--thread-group} options is
30069 specified, then all threads in that thread group are resumed.
30071 @subsubheading @value{GDBN} Command
30073 The corresponding @value{GDBN} corresponding is @samp{continue}.
30075 @subsubheading Example
30082 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30083 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30084 line="13",arch="i386:x86_64"@}
30089 @subheading The @code{-exec-finish} Command
30090 @findex -exec-finish
30092 @subsubheading Synopsis
30095 -exec-finish [--reverse]
30098 Resumes the execution of the inferior program until the current
30099 function is exited. Displays the results returned by the function.
30100 If the @samp{--reverse} option is specified, resumes the reverse
30101 execution of the inferior program until the point where current
30102 function was called.
30104 @subsubheading @value{GDBN} Command
30106 The corresponding @value{GDBN} command is @samp{finish}.
30108 @subsubheading Example
30110 Function returning @code{void}.
30117 *stopped,reason="function-finished",frame=@{func="main",args=[],
30118 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30122 Function returning other than @code{void}. The name of the internal
30123 @value{GDBN} variable storing the result is printed, together with the
30130 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30131 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30133 arch="i386:x86_64"@},
30134 gdb-result-var="$1",return-value="0"
30139 @subheading The @code{-exec-interrupt} Command
30140 @findex -exec-interrupt
30142 @subsubheading Synopsis
30145 -exec-interrupt [--all|--thread-group N]
30148 Interrupts the background execution of the target. Note how the token
30149 associated with the stop message is the one for the execution command
30150 that has been interrupted. The token for the interrupt itself only
30151 appears in the @samp{^done} output. If the user is trying to
30152 interrupt a non-running program, an error message will be printed.
30154 Note that when asynchronous execution is enabled, this command is
30155 asynchronous just like other execution commands. That is, first the
30156 @samp{^done} response will be printed, and the target stop will be
30157 reported after that using the @samp{*stopped} notification.
30159 In non-stop mode, only the context thread is interrupted by default.
30160 All threads (in all inferiors) will be interrupted if the
30161 @samp{--all} option is specified. If the @samp{--thread-group}
30162 option is specified, all threads in that group will be interrupted.
30164 @subsubheading @value{GDBN} Command
30166 The corresponding @value{GDBN} command is @samp{interrupt}.
30168 @subsubheading Example
30179 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30180 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30181 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30186 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30190 @subheading The @code{-exec-jump} Command
30193 @subsubheading Synopsis
30196 -exec-jump @var{location}
30199 Resumes execution of the inferior program at the location specified by
30200 parameter. @xref{Specify Location}, for a description of the
30201 different forms of @var{location}.
30203 @subsubheading @value{GDBN} Command
30205 The corresponding @value{GDBN} command is @samp{jump}.
30207 @subsubheading Example
30210 -exec-jump foo.c:10
30211 *running,thread-id="all"
30216 @subheading The @code{-exec-next} Command
30219 @subsubheading Synopsis
30222 -exec-next [--reverse]
30225 Resumes execution of the inferior program, stopping when the beginning
30226 of the next source line is reached.
30228 If the @samp{--reverse} option is specified, resumes reverse execution
30229 of the inferior program, stopping at the beginning of the previous
30230 source line. If you issue this command on the first line of a
30231 function, it will take you back to the caller of that function, to the
30232 source line where the function was called.
30235 @subsubheading @value{GDBN} Command
30237 The corresponding @value{GDBN} command is @samp{next}.
30239 @subsubheading Example
30245 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30250 @subheading The @code{-exec-next-instruction} Command
30251 @findex -exec-next-instruction
30253 @subsubheading Synopsis
30256 -exec-next-instruction [--reverse]
30259 Executes one machine instruction. If the instruction is a function
30260 call, continues until the function returns. If the program stops at an
30261 instruction in the middle of a source line, the address will be
30264 If the @samp{--reverse} option is specified, resumes reverse execution
30265 of the inferior program, stopping at the previous instruction. If the
30266 previously executed instruction was a return from another function,
30267 it will continue to execute in reverse until the call to that function
30268 (from the current stack frame) is reached.
30270 @subsubheading @value{GDBN} Command
30272 The corresponding @value{GDBN} command is @samp{nexti}.
30274 @subsubheading Example
30278 -exec-next-instruction
30282 *stopped,reason="end-stepping-range",
30283 addr="0x000100d4",line="5",file="hello.c"
30288 @subheading The @code{-exec-return} Command
30289 @findex -exec-return
30291 @subsubheading Synopsis
30297 Makes current function return immediately. Doesn't execute the inferior.
30298 Displays the new current frame.
30300 @subsubheading @value{GDBN} Command
30302 The corresponding @value{GDBN} command is @samp{return}.
30304 @subsubheading Example
30308 200-break-insert callee4
30309 200^done,bkpt=@{number="1",addr="0x00010734",
30310 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30315 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30316 frame=@{func="callee4",args=[],
30317 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30318 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30319 arch="i386:x86_64"@}
30325 111^done,frame=@{level="0",func="callee3",
30326 args=[@{name="strarg",
30327 value="0x11940 \"A string argument.\""@}],
30328 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30329 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30330 arch="i386:x86_64"@}
30335 @subheading The @code{-exec-run} Command
30338 @subsubheading Synopsis
30341 -exec-run [ --all | --thread-group N ] [ --start ]
30344 Starts execution of the inferior from the beginning. The inferior
30345 executes until either a breakpoint is encountered or the program
30346 exits. In the latter case the output will include an exit code, if
30347 the program has exited exceptionally.
30349 When neither the @samp{--all} nor the @samp{--thread-group} option
30350 is specified, the current inferior is started. If the
30351 @samp{--thread-group} option is specified, it should refer to a thread
30352 group of type @samp{process}, and that thread group will be started.
30353 If the @samp{--all} option is specified, then all inferiors will be started.
30355 Using the @samp{--start} option instructs the debugger to stop
30356 the execution at the start of the inferior's main subprogram,
30357 following the same behavior as the @code{start} command
30358 (@pxref{Starting}).
30360 @subsubheading @value{GDBN} Command
30362 The corresponding @value{GDBN} command is @samp{run}.
30364 @subsubheading Examples
30369 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30374 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30375 frame=@{func="main",args=[],file="recursive2.c",
30376 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30381 Program exited normally:
30389 *stopped,reason="exited-normally"
30394 Program exited exceptionally:
30402 *stopped,reason="exited",exit-code="01"
30406 Another way the program can terminate is if it receives a signal such as
30407 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30411 *stopped,reason="exited-signalled",signal-name="SIGINT",
30412 signal-meaning="Interrupt"
30416 @c @subheading -exec-signal
30419 @subheading The @code{-exec-step} Command
30422 @subsubheading Synopsis
30425 -exec-step [--reverse]
30428 Resumes execution of the inferior program, stopping when the beginning
30429 of the next source line is reached, if the next source line is not a
30430 function call. If it is, stop at the first instruction of the called
30431 function. If the @samp{--reverse} option is specified, resumes reverse
30432 execution of the inferior program, stopping at the beginning of the
30433 previously executed source line.
30435 @subsubheading @value{GDBN} Command
30437 The corresponding @value{GDBN} command is @samp{step}.
30439 @subsubheading Example
30441 Stepping into a function:
30447 *stopped,reason="end-stepping-range",
30448 frame=@{func="foo",args=[@{name="a",value="10"@},
30449 @{name="b",value="0"@}],file="recursive2.c",
30450 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30460 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30465 @subheading The @code{-exec-step-instruction} Command
30466 @findex -exec-step-instruction
30468 @subsubheading Synopsis
30471 -exec-step-instruction [--reverse]
30474 Resumes the inferior which executes one machine instruction. If the
30475 @samp{--reverse} option is specified, resumes reverse execution of the
30476 inferior program, stopping at the previously executed instruction.
30477 The output, once @value{GDBN} has stopped, will vary depending on
30478 whether we have stopped in the middle of a source line or not. In the
30479 former case, the address at which the program stopped will be printed
30482 @subsubheading @value{GDBN} Command
30484 The corresponding @value{GDBN} command is @samp{stepi}.
30486 @subsubheading Example
30490 -exec-step-instruction
30494 *stopped,reason="end-stepping-range",
30495 frame=@{func="foo",args=[],file="try.c",
30496 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30498 -exec-step-instruction
30502 *stopped,reason="end-stepping-range",
30503 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30504 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30509 @subheading The @code{-exec-until} Command
30510 @findex -exec-until
30512 @subsubheading Synopsis
30515 -exec-until [ @var{location} ]
30518 Executes the inferior until the @var{location} specified in the
30519 argument is reached. If there is no argument, the inferior executes
30520 until a source line greater than the current one is reached. The
30521 reason for stopping in this case will be @samp{location-reached}.
30523 @subsubheading @value{GDBN} Command
30525 The corresponding @value{GDBN} command is @samp{until}.
30527 @subsubheading Example
30531 -exec-until recursive2.c:6
30535 *stopped,reason="location-reached",frame=@{func="main",args=[],
30536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30537 arch="i386:x86_64"@}
30542 @subheading -file-clear
30543 Is this going away????
30546 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30547 @node GDB/MI Stack Manipulation
30548 @section @sc{gdb/mi} Stack Manipulation Commands
30550 @subheading The @code{-enable-frame-filters} Command
30551 @findex -enable-frame-filters
30554 -enable-frame-filters
30557 @value{GDBN} allows Python-based frame filters to affect the output of
30558 the MI commands relating to stack traces. As there is no way to
30559 implement this in a fully backward-compatible way, a front end must
30560 request that this functionality be enabled.
30562 Once enabled, this feature cannot be disabled.
30564 Note that if Python support has not been compiled into @value{GDBN},
30565 this command will still succeed (and do nothing).
30567 @subheading The @code{-stack-info-frame} Command
30568 @findex -stack-info-frame
30570 @subsubheading Synopsis
30576 Get info on the selected frame.
30578 @subsubheading @value{GDBN} Command
30580 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30581 (without arguments).
30583 @subsubheading Example
30588 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30589 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30590 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30591 arch="i386:x86_64"@}
30595 @subheading The @code{-stack-info-depth} Command
30596 @findex -stack-info-depth
30598 @subsubheading Synopsis
30601 -stack-info-depth [ @var{max-depth} ]
30604 Return the depth of the stack. If the integer argument @var{max-depth}
30605 is specified, do not count beyond @var{max-depth} frames.
30607 @subsubheading @value{GDBN} Command
30609 There's no equivalent @value{GDBN} command.
30611 @subsubheading Example
30613 For a stack with frame levels 0 through 11:
30620 -stack-info-depth 4
30623 -stack-info-depth 12
30626 -stack-info-depth 11
30629 -stack-info-depth 13
30634 @anchor{-stack-list-arguments}
30635 @subheading The @code{-stack-list-arguments} Command
30636 @findex -stack-list-arguments
30638 @subsubheading Synopsis
30641 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30642 [ @var{low-frame} @var{high-frame} ]
30645 Display a list of the arguments for the frames between @var{low-frame}
30646 and @var{high-frame} (inclusive). If @var{low-frame} and
30647 @var{high-frame} are not provided, list the arguments for the whole
30648 call stack. If the two arguments are equal, show the single frame
30649 at the corresponding level. It is an error if @var{low-frame} is
30650 larger than the actual number of frames. On the other hand,
30651 @var{high-frame} may be larger than the actual number of frames, in
30652 which case only existing frames will be returned.
30654 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30655 the variables; if it is 1 or @code{--all-values}, print also their
30656 values; and if it is 2 or @code{--simple-values}, print the name,
30657 type and value for simple data types, and the name and type for arrays,
30658 structures and unions. If the option @code{--no-frame-filters} is
30659 supplied, then Python frame filters will not be executed.
30661 If the @code{--skip-unavailable} option is specified, arguments that
30662 are not available are not listed. Partially available arguments
30663 are still displayed, however.
30665 Use of this command to obtain arguments in a single frame is
30666 deprecated in favor of the @samp{-stack-list-variables} command.
30668 @subsubheading @value{GDBN} Command
30670 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30671 @samp{gdb_get_args} command which partially overlaps with the
30672 functionality of @samp{-stack-list-arguments}.
30674 @subsubheading Example
30681 frame=@{level="0",addr="0x00010734",func="callee4",
30682 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30683 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30684 arch="i386:x86_64"@},
30685 frame=@{level="1",addr="0x0001076c",func="callee3",
30686 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30687 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30688 arch="i386:x86_64"@},
30689 frame=@{level="2",addr="0x0001078c",func="callee2",
30690 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30691 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30692 arch="i386:x86_64"@},
30693 frame=@{level="3",addr="0x000107b4",func="callee1",
30694 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30695 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30696 arch="i386:x86_64"@},
30697 frame=@{level="4",addr="0x000107e0",func="main",
30698 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30699 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30700 arch="i386:x86_64"@}]
30702 -stack-list-arguments 0
30705 frame=@{level="0",args=[]@},
30706 frame=@{level="1",args=[name="strarg"]@},
30707 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30708 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30709 frame=@{level="4",args=[]@}]
30711 -stack-list-arguments 1
30714 frame=@{level="0",args=[]@},
30716 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30717 frame=@{level="2",args=[
30718 @{name="intarg",value="2"@},
30719 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30720 @{frame=@{level="3",args=[
30721 @{name="intarg",value="2"@},
30722 @{name="strarg",value="0x11940 \"A string argument.\""@},
30723 @{name="fltarg",value="3.5"@}]@},
30724 frame=@{level="4",args=[]@}]
30726 -stack-list-arguments 0 2 2
30727 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30729 -stack-list-arguments 1 2 2
30730 ^done,stack-args=[frame=@{level="2",
30731 args=[@{name="intarg",value="2"@},
30732 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30736 @c @subheading -stack-list-exception-handlers
30739 @anchor{-stack-list-frames}
30740 @subheading The @code{-stack-list-frames} Command
30741 @findex -stack-list-frames
30743 @subsubheading Synopsis
30746 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30749 List the frames currently on the stack. For each frame it displays the
30754 The frame number, 0 being the topmost frame, i.e., the innermost function.
30756 The @code{$pc} value for that frame.
30760 File name of the source file where the function lives.
30761 @item @var{fullname}
30762 The full file name of the source file where the function lives.
30764 Line number corresponding to the @code{$pc}.
30766 The shared library where this function is defined. This is only given
30767 if the frame's function is not known.
30769 Frame's architecture.
30772 If invoked without arguments, this command prints a backtrace for the
30773 whole stack. If given two integer arguments, it shows the frames whose
30774 levels are between the two arguments (inclusive). If the two arguments
30775 are equal, it shows the single frame at the corresponding level. It is
30776 an error if @var{low-frame} is larger than the actual number of
30777 frames. On the other hand, @var{high-frame} may be larger than the
30778 actual number of frames, in which case only existing frames will be
30779 returned. If the option @code{--no-frame-filters} is supplied, then
30780 Python frame filters will not be executed.
30782 @subsubheading @value{GDBN} Command
30784 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30786 @subsubheading Example
30788 Full stack backtrace:
30794 [frame=@{level="0",addr="0x0001076c",func="foo",
30795 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30796 arch="i386:x86_64"@},
30797 frame=@{level="1",addr="0x000107a4",func="foo",
30798 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30799 arch="i386:x86_64"@},
30800 frame=@{level="2",addr="0x000107a4",func="foo",
30801 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30802 arch="i386:x86_64"@},
30803 frame=@{level="3",addr="0x000107a4",func="foo",
30804 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30805 arch="i386:x86_64"@},
30806 frame=@{level="4",addr="0x000107a4",func="foo",
30807 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30808 arch="i386:x86_64"@},
30809 frame=@{level="5",addr="0x000107a4",func="foo",
30810 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30811 arch="i386:x86_64"@},
30812 frame=@{level="6",addr="0x000107a4",func="foo",
30813 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30814 arch="i386:x86_64"@},
30815 frame=@{level="7",addr="0x000107a4",func="foo",
30816 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30817 arch="i386:x86_64"@},
30818 frame=@{level="8",addr="0x000107a4",func="foo",
30819 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30820 arch="i386:x86_64"@},
30821 frame=@{level="9",addr="0x000107a4",func="foo",
30822 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30823 arch="i386:x86_64"@},
30824 frame=@{level="10",addr="0x000107a4",func="foo",
30825 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30826 arch="i386:x86_64"@},
30827 frame=@{level="11",addr="0x00010738",func="main",
30828 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30829 arch="i386:x86_64"@}]
30833 Show frames between @var{low_frame} and @var{high_frame}:
30837 -stack-list-frames 3 5
30839 [frame=@{level="3",addr="0x000107a4",func="foo",
30840 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30841 arch="i386:x86_64"@},
30842 frame=@{level="4",addr="0x000107a4",func="foo",
30843 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30844 arch="i386:x86_64"@},
30845 frame=@{level="5",addr="0x000107a4",func="foo",
30846 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30847 arch="i386:x86_64"@}]
30851 Show a single frame:
30855 -stack-list-frames 3 3
30857 [frame=@{level="3",addr="0x000107a4",func="foo",
30858 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30859 arch="i386:x86_64"@}]
30864 @subheading The @code{-stack-list-locals} Command
30865 @findex -stack-list-locals
30866 @anchor{-stack-list-locals}
30868 @subsubheading Synopsis
30871 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30874 Display the local variable names for the selected frame. If
30875 @var{print-values} is 0 or @code{--no-values}, print only the names of
30876 the variables; if it is 1 or @code{--all-values}, print also their
30877 values; and if it is 2 or @code{--simple-values}, print the name,
30878 type and value for simple data types, and the name and type for arrays,
30879 structures and unions. In this last case, a frontend can immediately
30880 display the value of simple data types and create variable objects for
30881 other data types when the user wishes to explore their values in
30882 more detail. If the option @code{--no-frame-filters} is supplied, then
30883 Python frame filters will not be executed.
30885 If the @code{--skip-unavailable} option is specified, local variables
30886 that are not available are not listed. Partially available local
30887 variables are still displayed, however.
30889 This command is deprecated in favor of the
30890 @samp{-stack-list-variables} command.
30892 @subsubheading @value{GDBN} Command
30894 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30896 @subsubheading Example
30900 -stack-list-locals 0
30901 ^done,locals=[name="A",name="B",name="C"]
30903 -stack-list-locals --all-values
30904 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30905 @{name="C",value="@{1, 2, 3@}"@}]
30906 -stack-list-locals --simple-values
30907 ^done,locals=[@{name="A",type="int",value="1"@},
30908 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30912 @anchor{-stack-list-variables}
30913 @subheading The @code{-stack-list-variables} Command
30914 @findex -stack-list-variables
30916 @subsubheading Synopsis
30919 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30922 Display the names of local variables and function arguments for the selected frame. If
30923 @var{print-values} is 0 or @code{--no-values}, print only the names of
30924 the variables; if it is 1 or @code{--all-values}, print also their
30925 values; and if it is 2 or @code{--simple-values}, print the name,
30926 type and value for simple data types, and the name and type for arrays,
30927 structures and unions. If the option @code{--no-frame-filters} is
30928 supplied, then Python frame filters will not be executed.
30930 If the @code{--skip-unavailable} option is specified, local variables
30931 and arguments that are not available are not listed. Partially
30932 available arguments and local variables are still displayed, however.
30934 @subsubheading Example
30938 -stack-list-variables --thread 1 --frame 0 --all-values
30939 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30944 @subheading The @code{-stack-select-frame} Command
30945 @findex -stack-select-frame
30947 @subsubheading Synopsis
30950 -stack-select-frame @var{framenum}
30953 Change the selected frame. Select a different frame @var{framenum} on
30956 This command in deprecated in favor of passing the @samp{--frame}
30957 option to every command.
30959 @subsubheading @value{GDBN} Command
30961 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30962 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30964 @subsubheading Example
30968 -stack-select-frame 2
30973 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30974 @node GDB/MI Variable Objects
30975 @section @sc{gdb/mi} Variable Objects
30979 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30981 For the implementation of a variable debugger window (locals, watched
30982 expressions, etc.), we are proposing the adaptation of the existing code
30983 used by @code{Insight}.
30985 The two main reasons for that are:
30989 It has been proven in practice (it is already on its second generation).
30992 It will shorten development time (needless to say how important it is
30996 The original interface was designed to be used by Tcl code, so it was
30997 slightly changed so it could be used through @sc{gdb/mi}. This section
30998 describes the @sc{gdb/mi} operations that will be available and gives some
30999 hints about their use.
31001 @emph{Note}: In addition to the set of operations described here, we
31002 expect the @sc{gui} implementation of a variable window to require, at
31003 least, the following operations:
31006 @item @code{-gdb-show} @code{output-radix}
31007 @item @code{-stack-list-arguments}
31008 @item @code{-stack-list-locals}
31009 @item @code{-stack-select-frame}
31014 @subheading Introduction to Variable Objects
31016 @cindex variable objects in @sc{gdb/mi}
31018 Variable objects are "object-oriented" MI interface for examining and
31019 changing values of expressions. Unlike some other MI interfaces that
31020 work with expressions, variable objects are specifically designed for
31021 simple and efficient presentation in the frontend. A variable object
31022 is identified by string name. When a variable object is created, the
31023 frontend specifies the expression for that variable object. The
31024 expression can be a simple variable, or it can be an arbitrary complex
31025 expression, and can even involve CPU registers. After creating a
31026 variable object, the frontend can invoke other variable object
31027 operations---for example to obtain or change the value of a variable
31028 object, or to change display format.
31030 Variable objects have hierarchical tree structure. Any variable object
31031 that corresponds to a composite type, such as structure in C, has
31032 a number of child variable objects, for example corresponding to each
31033 element of a structure. A child variable object can itself have
31034 children, recursively. Recursion ends when we reach
31035 leaf variable objects, which always have built-in types. Child variable
31036 objects are created only by explicit request, so if a frontend
31037 is not interested in the children of a particular variable object, no
31038 child will be created.
31040 For a leaf variable object it is possible to obtain its value as a
31041 string, or set the value from a string. String value can be also
31042 obtained for a non-leaf variable object, but it's generally a string
31043 that only indicates the type of the object, and does not list its
31044 contents. Assignment to a non-leaf variable object is not allowed.
31046 A frontend does not need to read the values of all variable objects each time
31047 the program stops. Instead, MI provides an update command that lists all
31048 variable objects whose values has changed since the last update
31049 operation. This considerably reduces the amount of data that must
31050 be transferred to the frontend. As noted above, children variable
31051 objects are created on demand, and only leaf variable objects have a
31052 real value. As result, gdb will read target memory only for leaf
31053 variables that frontend has created.
31055 The automatic update is not always desirable. For example, a frontend
31056 might want to keep a value of some expression for future reference,
31057 and never update it. For another example, fetching memory is
31058 relatively slow for embedded targets, so a frontend might want
31059 to disable automatic update for the variables that are either not
31060 visible on the screen, or ``closed''. This is possible using so
31061 called ``frozen variable objects''. Such variable objects are never
31062 implicitly updated.
31064 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31065 fixed variable object, the expression is parsed when the variable
31066 object is created, including associating identifiers to specific
31067 variables. The meaning of expression never changes. For a floating
31068 variable object the values of variables whose names appear in the
31069 expressions are re-evaluated every time in the context of the current
31070 frame. Consider this example:
31075 struct work_state state;
31082 If a fixed variable object for the @code{state} variable is created in
31083 this function, and we enter the recursive call, the variable
31084 object will report the value of @code{state} in the top-level
31085 @code{do_work} invocation. On the other hand, a floating variable
31086 object will report the value of @code{state} in the current frame.
31088 If an expression specified when creating a fixed variable object
31089 refers to a local variable, the variable object becomes bound to the
31090 thread and frame in which the variable object is created. When such
31091 variable object is updated, @value{GDBN} makes sure that the
31092 thread/frame combination the variable object is bound to still exists,
31093 and re-evaluates the variable object in context of that thread/frame.
31095 The following is the complete set of @sc{gdb/mi} operations defined to
31096 access this functionality:
31098 @multitable @columnfractions .4 .6
31099 @item @strong{Operation}
31100 @tab @strong{Description}
31102 @item @code{-enable-pretty-printing}
31103 @tab enable Python-based pretty-printing
31104 @item @code{-var-create}
31105 @tab create a variable object
31106 @item @code{-var-delete}
31107 @tab delete the variable object and/or its children
31108 @item @code{-var-set-format}
31109 @tab set the display format of this variable
31110 @item @code{-var-show-format}
31111 @tab show the display format of this variable
31112 @item @code{-var-info-num-children}
31113 @tab tells how many children this object has
31114 @item @code{-var-list-children}
31115 @tab return a list of the object's children
31116 @item @code{-var-info-type}
31117 @tab show the type of this variable object
31118 @item @code{-var-info-expression}
31119 @tab print parent-relative expression that this variable object represents
31120 @item @code{-var-info-path-expression}
31121 @tab print full expression that this variable object represents
31122 @item @code{-var-show-attributes}
31123 @tab is this variable editable? does it exist here?
31124 @item @code{-var-evaluate-expression}
31125 @tab get the value of this variable
31126 @item @code{-var-assign}
31127 @tab set the value of this variable
31128 @item @code{-var-update}
31129 @tab update the variable and its children
31130 @item @code{-var-set-frozen}
31131 @tab set frozeness attribute
31132 @item @code{-var-set-update-range}
31133 @tab set range of children to display on update
31136 In the next subsection we describe each operation in detail and suggest
31137 how it can be used.
31139 @subheading Description And Use of Operations on Variable Objects
31141 @subheading The @code{-enable-pretty-printing} Command
31142 @findex -enable-pretty-printing
31145 -enable-pretty-printing
31148 @value{GDBN} allows Python-based visualizers to affect the output of the
31149 MI variable object commands. However, because there was no way to
31150 implement this in a fully backward-compatible way, a front end must
31151 request that this functionality be enabled.
31153 Once enabled, this feature cannot be disabled.
31155 Note that if Python support has not been compiled into @value{GDBN},
31156 this command will still succeed (and do nothing).
31158 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31159 may work differently in future versions of @value{GDBN}.
31161 @subheading The @code{-var-create} Command
31162 @findex -var-create
31164 @subsubheading Synopsis
31167 -var-create @{@var{name} | "-"@}
31168 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31171 This operation creates a variable object, which allows the monitoring of
31172 a variable, the result of an expression, a memory cell or a CPU
31175 The @var{name} parameter is the string by which the object can be
31176 referenced. It must be unique. If @samp{-} is specified, the varobj
31177 system will generate a string ``varNNNNNN'' automatically. It will be
31178 unique provided that one does not specify @var{name} of that format.
31179 The command fails if a duplicate name is found.
31181 The frame under which the expression should be evaluated can be
31182 specified by @var{frame-addr}. A @samp{*} indicates that the current
31183 frame should be used. A @samp{@@} indicates that a floating variable
31184 object must be created.
31186 @var{expression} is any expression valid on the current language set (must not
31187 begin with a @samp{*}), or one of the following:
31191 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31194 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31197 @samp{$@var{regname}} --- a CPU register name
31200 @cindex dynamic varobj
31201 A varobj's contents may be provided by a Python-based pretty-printer. In this
31202 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31203 have slightly different semantics in some cases. If the
31204 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31205 will never create a dynamic varobj. This ensures backward
31206 compatibility for existing clients.
31208 @subsubheading Result
31210 This operation returns attributes of the newly-created varobj. These
31215 The name of the varobj.
31218 The number of children of the varobj. This number is not necessarily
31219 reliable for a dynamic varobj. Instead, you must examine the
31220 @samp{has_more} attribute.
31223 The varobj's scalar value. For a varobj whose type is some sort of
31224 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31225 will not be interesting.
31228 The varobj's type. This is a string representation of the type, as
31229 would be printed by the @value{GDBN} CLI. If @samp{print object}
31230 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31231 @emph{actual} (derived) type of the object is shown rather than the
31232 @emph{declared} one.
31235 If a variable object is bound to a specific thread, then this is the
31236 thread's global identifier.
31239 For a dynamic varobj, this indicates whether there appear to be any
31240 children available. For a non-dynamic varobj, this will be 0.
31243 This attribute will be present and have the value @samp{1} if the
31244 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31245 then this attribute will not be present.
31248 A dynamic varobj can supply a display hint to the front end. The
31249 value comes directly from the Python pretty-printer object's
31250 @code{display_hint} method. @xref{Pretty Printing API}.
31253 Typical output will look like this:
31256 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31257 has_more="@var{has_more}"
31261 @subheading The @code{-var-delete} Command
31262 @findex -var-delete
31264 @subsubheading Synopsis
31267 -var-delete [ -c ] @var{name}
31270 Deletes a previously created variable object and all of its children.
31271 With the @samp{-c} option, just deletes the children.
31273 Returns an error if the object @var{name} is not found.
31276 @subheading The @code{-var-set-format} Command
31277 @findex -var-set-format
31279 @subsubheading Synopsis
31282 -var-set-format @var{name} @var{format-spec}
31285 Sets the output format for the value of the object @var{name} to be
31288 @anchor{-var-set-format}
31289 The syntax for the @var{format-spec} is as follows:
31292 @var{format-spec} @expansion{}
31293 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31296 The natural format is the default format choosen automatically
31297 based on the variable type (like decimal for an @code{int}, hex
31298 for pointers, etc.).
31300 The zero-hexadecimal format has a representation similar to hexadecimal
31301 but with padding zeroes to the left of the value. For example, a 32-bit
31302 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31303 zero-hexadecimal format.
31305 For a variable with children, the format is set only on the
31306 variable itself, and the children are not affected.
31308 @subheading The @code{-var-show-format} Command
31309 @findex -var-show-format
31311 @subsubheading Synopsis
31314 -var-show-format @var{name}
31317 Returns the format used to display the value of the object @var{name}.
31320 @var{format} @expansion{}
31325 @subheading The @code{-var-info-num-children} Command
31326 @findex -var-info-num-children
31328 @subsubheading Synopsis
31331 -var-info-num-children @var{name}
31334 Returns the number of children of a variable object @var{name}:
31340 Note that this number is not completely reliable for a dynamic varobj.
31341 It will return the current number of children, but more children may
31345 @subheading The @code{-var-list-children} Command
31346 @findex -var-list-children
31348 @subsubheading Synopsis
31351 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31353 @anchor{-var-list-children}
31355 Return a list of the children of the specified variable object and
31356 create variable objects for them, if they do not already exist. With
31357 a single argument or if @var{print-values} has a value of 0 or
31358 @code{--no-values}, print only the names of the variables; if
31359 @var{print-values} is 1 or @code{--all-values}, also print their
31360 values; and if it is 2 or @code{--simple-values} print the name and
31361 value for simple data types and just the name for arrays, structures
31364 @var{from} and @var{to}, if specified, indicate the range of children
31365 to report. If @var{from} or @var{to} is less than zero, the range is
31366 reset and all children will be reported. Otherwise, children starting
31367 at @var{from} (zero-based) and up to and excluding @var{to} will be
31370 If a child range is requested, it will only affect the current call to
31371 @code{-var-list-children}, but not future calls to @code{-var-update}.
31372 For this, you must instead use @code{-var-set-update-range}. The
31373 intent of this approach is to enable a front end to implement any
31374 update approach it likes; for example, scrolling a view may cause the
31375 front end to request more children with @code{-var-list-children}, and
31376 then the front end could call @code{-var-set-update-range} with a
31377 different range to ensure that future updates are restricted to just
31380 For each child the following results are returned:
31385 Name of the variable object created for this child.
31388 The expression to be shown to the user by the front end to designate this child.
31389 For example this may be the name of a structure member.
31391 For a dynamic varobj, this value cannot be used to form an
31392 expression. There is no way to do this at all with a dynamic varobj.
31394 For C/C@t{++} structures there are several pseudo children returned to
31395 designate access qualifiers. For these pseudo children @var{exp} is
31396 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31397 type and value are not present.
31399 A dynamic varobj will not report the access qualifying
31400 pseudo-children, regardless of the language. This information is not
31401 available at all with a dynamic varobj.
31404 Number of children this child has. For a dynamic varobj, this will be
31408 The type of the child. If @samp{print object}
31409 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31410 @emph{actual} (derived) type of the object is shown rather than the
31411 @emph{declared} one.
31414 If values were requested, this is the value.
31417 If this variable object is associated with a thread, this is the
31418 thread's global thread id. Otherwise this result is not present.
31421 If the variable object is frozen, this variable will be present with a value of 1.
31424 A dynamic varobj can supply a display hint to the front end. The
31425 value comes directly from the Python pretty-printer object's
31426 @code{display_hint} method. @xref{Pretty Printing API}.
31429 This attribute will be present and have the value @samp{1} if the
31430 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31431 then this attribute will not be present.
31435 The result may have its own attributes:
31439 A dynamic varobj can supply a display hint to the front end. The
31440 value comes directly from the Python pretty-printer object's
31441 @code{display_hint} method. @xref{Pretty Printing API}.
31444 This is an integer attribute which is nonzero if there are children
31445 remaining after the end of the selected range.
31448 @subsubheading Example
31452 -var-list-children n
31453 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31454 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31456 -var-list-children --all-values n
31457 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31458 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31462 @subheading The @code{-var-info-type} Command
31463 @findex -var-info-type
31465 @subsubheading Synopsis
31468 -var-info-type @var{name}
31471 Returns the type of the specified variable @var{name}. The type is
31472 returned as a string in the same format as it is output by the
31476 type=@var{typename}
31480 @subheading The @code{-var-info-expression} Command
31481 @findex -var-info-expression
31483 @subsubheading Synopsis
31486 -var-info-expression @var{name}
31489 Returns a string that is suitable for presenting this
31490 variable object in user interface. The string is generally
31491 not valid expression in the current language, and cannot be evaluated.
31493 For example, if @code{a} is an array, and variable object
31494 @code{A} was created for @code{a}, then we'll get this output:
31497 (gdb) -var-info-expression A.1
31498 ^done,lang="C",exp="1"
31502 Here, the value of @code{lang} is the language name, which can be
31503 found in @ref{Supported Languages}.
31505 Note that the output of the @code{-var-list-children} command also
31506 includes those expressions, so the @code{-var-info-expression} command
31509 @subheading The @code{-var-info-path-expression} Command
31510 @findex -var-info-path-expression
31512 @subsubheading Synopsis
31515 -var-info-path-expression @var{name}
31518 Returns an expression that can be evaluated in the current
31519 context and will yield the same value that a variable object has.
31520 Compare this with the @code{-var-info-expression} command, which
31521 result can be used only for UI presentation. Typical use of
31522 the @code{-var-info-path-expression} command is creating a
31523 watchpoint from a variable object.
31525 This command is currently not valid for children of a dynamic varobj,
31526 and will give an error when invoked on one.
31528 For example, suppose @code{C} is a C@t{++} class, derived from class
31529 @code{Base}, and that the @code{Base} class has a member called
31530 @code{m_size}. Assume a variable @code{c} is has the type of
31531 @code{C} and a variable object @code{C} was created for variable
31532 @code{c}. Then, we'll get this output:
31534 (gdb) -var-info-path-expression C.Base.public.m_size
31535 ^done,path_expr=((Base)c).m_size)
31538 @subheading The @code{-var-show-attributes} Command
31539 @findex -var-show-attributes
31541 @subsubheading Synopsis
31544 -var-show-attributes @var{name}
31547 List attributes of the specified variable object @var{name}:
31550 status=@var{attr} [ ( ,@var{attr} )* ]
31554 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31556 @subheading The @code{-var-evaluate-expression} Command
31557 @findex -var-evaluate-expression
31559 @subsubheading Synopsis
31562 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31565 Evaluates the expression that is represented by the specified variable
31566 object and returns its value as a string. The format of the string
31567 can be specified with the @samp{-f} option. The possible values of
31568 this option are the same as for @code{-var-set-format}
31569 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31570 the current display format will be used. The current display format
31571 can be changed using the @code{-var-set-format} command.
31577 Note that one must invoke @code{-var-list-children} for a variable
31578 before the value of a child variable can be evaluated.
31580 @subheading The @code{-var-assign} Command
31581 @findex -var-assign
31583 @subsubheading Synopsis
31586 -var-assign @var{name} @var{expression}
31589 Assigns the value of @var{expression} to the variable object specified
31590 by @var{name}. The object must be @samp{editable}. If the variable's
31591 value is altered by the assign, the variable will show up in any
31592 subsequent @code{-var-update} list.
31594 @subsubheading Example
31602 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31606 @subheading The @code{-var-update} Command
31607 @findex -var-update
31609 @subsubheading Synopsis
31612 -var-update [@var{print-values}] @{@var{name} | "*"@}
31615 Reevaluate the expressions corresponding to the variable object
31616 @var{name} and all its direct and indirect children, and return the
31617 list of variable objects whose values have changed; @var{name} must
31618 be a root variable object. Here, ``changed'' means that the result of
31619 @code{-var-evaluate-expression} before and after the
31620 @code{-var-update} is different. If @samp{*} is used as the variable
31621 object names, all existing variable objects are updated, except
31622 for frozen ones (@pxref{-var-set-frozen}). The option
31623 @var{print-values} determines whether both names and values, or just
31624 names are printed. The possible values of this option are the same
31625 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31626 recommended to use the @samp{--all-values} option, to reduce the
31627 number of MI commands needed on each program stop.
31629 With the @samp{*} parameter, if a variable object is bound to a
31630 currently running thread, it will not be updated, without any
31633 If @code{-var-set-update-range} was previously used on a varobj, then
31634 only the selected range of children will be reported.
31636 @code{-var-update} reports all the changed varobjs in a tuple named
31639 Each item in the change list is itself a tuple holding:
31643 The name of the varobj.
31646 If values were requested for this update, then this field will be
31647 present and will hold the value of the varobj.
31650 @anchor{-var-update}
31651 This field is a string which may take one of three values:
31655 The variable object's current value is valid.
31658 The variable object does not currently hold a valid value but it may
31659 hold one in the future if its associated expression comes back into
31663 The variable object no longer holds a valid value.
31664 This can occur when the executable file being debugged has changed,
31665 either through recompilation or by using the @value{GDBN} @code{file}
31666 command. The front end should normally choose to delete these variable
31670 In the future new values may be added to this list so the front should
31671 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31674 This is only present if the varobj is still valid. If the type
31675 changed, then this will be the string @samp{true}; otherwise it will
31678 When a varobj's type changes, its children are also likely to have
31679 become incorrect. Therefore, the varobj's children are automatically
31680 deleted when this attribute is @samp{true}. Also, the varobj's update
31681 range, when set using the @code{-var-set-update-range} command, is
31685 If the varobj's type changed, then this field will be present and will
31688 @item new_num_children
31689 For a dynamic varobj, if the number of children changed, or if the
31690 type changed, this will be the new number of children.
31692 The @samp{numchild} field in other varobj responses is generally not
31693 valid for a dynamic varobj -- it will show the number of children that
31694 @value{GDBN} knows about, but because dynamic varobjs lazily
31695 instantiate their children, this will not reflect the number of
31696 children which may be available.
31698 The @samp{new_num_children} attribute only reports changes to the
31699 number of children known by @value{GDBN}. This is the only way to
31700 detect whether an update has removed children (which necessarily can
31701 only happen at the end of the update range).
31704 The display hint, if any.
31707 This is an integer value, which will be 1 if there are more children
31708 available outside the varobj's update range.
31711 This attribute will be present and have the value @samp{1} if the
31712 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31713 then this attribute will not be present.
31716 If new children were added to a dynamic varobj within the selected
31717 update range (as set by @code{-var-set-update-range}), then they will
31718 be listed in this attribute.
31721 @subsubheading Example
31728 -var-update --all-values var1
31729 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31730 type_changed="false"@}]
31734 @subheading The @code{-var-set-frozen} Command
31735 @findex -var-set-frozen
31736 @anchor{-var-set-frozen}
31738 @subsubheading Synopsis
31741 -var-set-frozen @var{name} @var{flag}
31744 Set the frozenness flag on the variable object @var{name}. The
31745 @var{flag} parameter should be either @samp{1} to make the variable
31746 frozen or @samp{0} to make it unfrozen. If a variable object is
31747 frozen, then neither itself, nor any of its children, are
31748 implicitly updated by @code{-var-update} of
31749 a parent variable or by @code{-var-update *}. Only
31750 @code{-var-update} of the variable itself will update its value and
31751 values of its children. After a variable object is unfrozen, it is
31752 implicitly updated by all subsequent @code{-var-update} operations.
31753 Unfreezing a variable does not update it, only subsequent
31754 @code{-var-update} does.
31756 @subsubheading Example
31760 -var-set-frozen V 1
31765 @subheading The @code{-var-set-update-range} command
31766 @findex -var-set-update-range
31767 @anchor{-var-set-update-range}
31769 @subsubheading Synopsis
31772 -var-set-update-range @var{name} @var{from} @var{to}
31775 Set the range of children to be returned by future invocations of
31776 @code{-var-update}.
31778 @var{from} and @var{to} indicate the range of children to report. If
31779 @var{from} or @var{to} is less than zero, the range is reset and all
31780 children will be reported. Otherwise, children starting at @var{from}
31781 (zero-based) and up to and excluding @var{to} will be reported.
31783 @subsubheading Example
31787 -var-set-update-range V 1 2
31791 @subheading The @code{-var-set-visualizer} command
31792 @findex -var-set-visualizer
31793 @anchor{-var-set-visualizer}
31795 @subsubheading Synopsis
31798 -var-set-visualizer @var{name} @var{visualizer}
31801 Set a visualizer for the variable object @var{name}.
31803 @var{visualizer} is the visualizer to use. The special value
31804 @samp{None} means to disable any visualizer in use.
31806 If not @samp{None}, @var{visualizer} must be a Python expression.
31807 This expression must evaluate to a callable object which accepts a
31808 single argument. @value{GDBN} will call this object with the value of
31809 the varobj @var{name} as an argument (this is done so that the same
31810 Python pretty-printing code can be used for both the CLI and MI).
31811 When called, this object must return an object which conforms to the
31812 pretty-printing interface (@pxref{Pretty Printing API}).
31814 The pre-defined function @code{gdb.default_visualizer} may be used to
31815 select a visualizer by following the built-in process
31816 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31817 a varobj is created, and so ordinarily is not needed.
31819 This feature is only available if Python support is enabled. The MI
31820 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31821 can be used to check this.
31823 @subsubheading Example
31825 Resetting the visualizer:
31829 -var-set-visualizer V None
31833 Reselecting the default (type-based) visualizer:
31837 -var-set-visualizer V gdb.default_visualizer
31841 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31842 can be used to instantiate this class for a varobj:
31846 -var-set-visualizer V "lambda val: SomeClass()"
31850 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31851 @node GDB/MI Data Manipulation
31852 @section @sc{gdb/mi} Data Manipulation
31854 @cindex data manipulation, in @sc{gdb/mi}
31855 @cindex @sc{gdb/mi}, data manipulation
31856 This section describes the @sc{gdb/mi} commands that manipulate data:
31857 examine memory and registers, evaluate expressions, etc.
31859 For details about what an addressable memory unit is,
31860 @pxref{addressable memory unit}.
31862 @c REMOVED FROM THE INTERFACE.
31863 @c @subheading -data-assign
31864 @c Change the value of a program variable. Plenty of side effects.
31865 @c @subsubheading GDB Command
31867 @c @subsubheading Example
31870 @subheading The @code{-data-disassemble} Command
31871 @findex -data-disassemble
31873 @subsubheading Synopsis
31877 [ -s @var{start-addr} -e @var{end-addr} ]
31878 | [ -a @var{addr} ]
31879 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31887 @item @var{start-addr}
31888 is the beginning address (or @code{$pc})
31889 @item @var{end-addr}
31892 is an address anywhere within (or the name of) the function to
31893 disassemble. If an address is specified, the whole function
31894 surrounding that address will be disassembled. If a name is
31895 specified, the whole function with that name will be disassembled.
31896 @item @var{filename}
31897 is the name of the file to disassemble
31898 @item @var{linenum}
31899 is the line number to disassemble around
31901 is the number of disassembly lines to be produced. If it is -1,
31902 the whole function will be disassembled, in case no @var{end-addr} is
31903 specified. If @var{end-addr} is specified as a non-zero value, and
31904 @var{lines} is lower than the number of disassembly lines between
31905 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31906 displayed; if @var{lines} is higher than the number of lines between
31907 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31912 @item 0 disassembly only
31913 @item 1 mixed source and disassembly (deprecated)
31914 @item 2 disassembly with raw opcodes
31915 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31916 @item 4 mixed source and disassembly
31917 @item 5 mixed source and disassembly with raw opcodes
31920 Modes 1 and 3 are deprecated. The output is ``source centric''
31921 which hasn't proved useful in practice.
31922 @xref{Machine Code}, for a discussion of the difference between
31923 @code{/m} and @code{/s} output of the @code{disassemble} command.
31926 @subsubheading Result
31928 The result of the @code{-data-disassemble} command will be a list named
31929 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31930 used with the @code{-data-disassemble} command.
31932 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31937 The address at which this instruction was disassembled.
31940 The name of the function this instruction is within.
31943 The decimal offset in bytes from the start of @samp{func-name}.
31946 The text disassembly for this @samp{address}.
31949 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31950 bytes for the @samp{inst} field.
31954 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31955 @samp{src_and_asm_line}, each of which has the following fields:
31959 The line number within @samp{file}.
31962 The file name from the compilation unit. This might be an absolute
31963 file name or a relative file name depending on the compile command
31967 Absolute file name of @samp{file}. It is converted to a canonical form
31968 using the source file search path
31969 (@pxref{Source Path, ,Specifying Source Directories})
31970 and after resolving all the symbolic links.
31972 If the source file is not found this field will contain the path as
31973 present in the debug information.
31975 @item line_asm_insn
31976 This is a list of tuples containing the disassembly for @samp{line} in
31977 @samp{file}. The fields of each tuple are the same as for
31978 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31979 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31984 Note that whatever included in the @samp{inst} field, is not
31985 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31988 @subsubheading @value{GDBN} Command
31990 The corresponding @value{GDBN} command is @samp{disassemble}.
31992 @subsubheading Example
31994 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31998 -data-disassemble -s $pc -e "$pc + 20" -- 0
32001 @{address="0x000107c0",func-name="main",offset="4",
32002 inst="mov 2, %o0"@},
32003 @{address="0x000107c4",func-name="main",offset="8",
32004 inst="sethi %hi(0x11800), %o2"@},
32005 @{address="0x000107c8",func-name="main",offset="12",
32006 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32007 @{address="0x000107cc",func-name="main",offset="16",
32008 inst="sethi %hi(0x11800), %o2"@},
32009 @{address="0x000107d0",func-name="main",offset="20",
32010 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32014 Disassemble the whole @code{main} function. Line 32 is part of
32018 -data-disassemble -f basics.c -l 32 -- 0
32020 @{address="0x000107bc",func-name="main",offset="0",
32021 inst="save %sp, -112, %sp"@},
32022 @{address="0x000107c0",func-name="main",offset="4",
32023 inst="mov 2, %o0"@},
32024 @{address="0x000107c4",func-name="main",offset="8",
32025 inst="sethi %hi(0x11800), %o2"@},
32027 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32028 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32032 Disassemble 3 instructions from the start of @code{main}:
32036 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32038 @{address="0x000107bc",func-name="main",offset="0",
32039 inst="save %sp, -112, %sp"@},
32040 @{address="0x000107c0",func-name="main",offset="4",
32041 inst="mov 2, %o0"@},
32042 @{address="0x000107c4",func-name="main",offset="8",
32043 inst="sethi %hi(0x11800), %o2"@}]
32047 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32051 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32053 src_and_asm_line=@{line="31",
32054 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32055 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32056 line_asm_insn=[@{address="0x000107bc",
32057 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32058 src_and_asm_line=@{line="32",
32059 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32060 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32061 line_asm_insn=[@{address="0x000107c0",
32062 func-name="main",offset="4",inst="mov 2, %o0"@},
32063 @{address="0x000107c4",func-name="main",offset="8",
32064 inst="sethi %hi(0x11800), %o2"@}]@}]
32069 @subheading The @code{-data-evaluate-expression} Command
32070 @findex -data-evaluate-expression
32072 @subsubheading Synopsis
32075 -data-evaluate-expression @var{expr}
32078 Evaluate @var{expr} as an expression. The expression could contain an
32079 inferior function call. The function call will execute synchronously.
32080 If the expression contains spaces, it must be enclosed in double quotes.
32082 @subsubheading @value{GDBN} Command
32084 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32085 @samp{call}. In @code{gdbtk} only, there's a corresponding
32086 @samp{gdb_eval} command.
32088 @subsubheading Example
32090 In the following example, the numbers that precede the commands are the
32091 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32092 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32096 211-data-evaluate-expression A
32099 311-data-evaluate-expression &A
32100 311^done,value="0xefffeb7c"
32102 411-data-evaluate-expression A+3
32105 511-data-evaluate-expression "A + 3"
32111 @subheading The @code{-data-list-changed-registers} Command
32112 @findex -data-list-changed-registers
32114 @subsubheading Synopsis
32117 -data-list-changed-registers
32120 Display a list of the registers that have changed.
32122 @subsubheading @value{GDBN} Command
32124 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32125 has the corresponding command @samp{gdb_changed_register_list}.
32127 @subsubheading Example
32129 On a PPC MBX board:
32137 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32138 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32139 line="5",arch="powerpc"@}
32141 -data-list-changed-registers
32142 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32143 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32144 "24","25","26","27","28","30","31","64","65","66","67","69"]
32149 @subheading The @code{-data-list-register-names} Command
32150 @findex -data-list-register-names
32152 @subsubheading Synopsis
32155 -data-list-register-names [ ( @var{regno} )+ ]
32158 Show a list of register names for the current target. If no arguments
32159 are given, it shows a list of the names of all the registers. If
32160 integer numbers are given as arguments, it will print a list of the
32161 names of the registers corresponding to the arguments. To ensure
32162 consistency between a register name and its number, the output list may
32163 include empty register names.
32165 @subsubheading @value{GDBN} Command
32167 @value{GDBN} does not have a command which corresponds to
32168 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32169 corresponding command @samp{gdb_regnames}.
32171 @subsubheading Example
32173 For the PPC MBX board:
32176 -data-list-register-names
32177 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32178 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32179 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32180 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32181 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32182 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32183 "", "pc","ps","cr","lr","ctr","xer"]
32185 -data-list-register-names 1 2 3
32186 ^done,register-names=["r1","r2","r3"]
32190 @subheading The @code{-data-list-register-values} Command
32191 @findex -data-list-register-values
32193 @subsubheading Synopsis
32196 -data-list-register-values
32197 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32200 Display the registers' contents. The format according to which the
32201 registers' contents are to be returned is given by @var{fmt}, followed
32202 by an optional list of numbers specifying the registers to display. A
32203 missing list of numbers indicates that the contents of all the
32204 registers must be returned. The @code{--skip-unavailable} option
32205 indicates that only the available registers are to be returned.
32207 Allowed formats for @var{fmt} are:
32224 @subsubheading @value{GDBN} Command
32226 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32227 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32229 @subsubheading Example
32231 For a PPC MBX board (note: line breaks are for readability only, they
32232 don't appear in the actual output):
32236 -data-list-register-values r 64 65
32237 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32238 @{number="65",value="0x00029002"@}]
32240 -data-list-register-values x
32241 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32242 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32243 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32244 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32245 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32246 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32247 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32248 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32249 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32250 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32251 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32252 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32253 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32254 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32255 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32256 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32257 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32258 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32259 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32260 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32261 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32262 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32263 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32264 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32265 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32266 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32267 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32268 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32269 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32270 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32271 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32272 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32273 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32274 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32275 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32276 @{number="69",value="0x20002b03"@}]
32281 @subheading The @code{-data-read-memory} Command
32282 @findex -data-read-memory
32284 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32286 @subsubheading Synopsis
32289 -data-read-memory [ -o @var{byte-offset} ]
32290 @var{address} @var{word-format} @var{word-size}
32291 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32298 @item @var{address}
32299 An expression specifying the address of the first memory word to be
32300 read. Complex expressions containing embedded white space should be
32301 quoted using the C convention.
32303 @item @var{word-format}
32304 The format to be used to print the memory words. The notation is the
32305 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32308 @item @var{word-size}
32309 The size of each memory word in bytes.
32311 @item @var{nr-rows}
32312 The number of rows in the output table.
32314 @item @var{nr-cols}
32315 The number of columns in the output table.
32318 If present, indicates that each row should include an @sc{ascii} dump. The
32319 value of @var{aschar} is used as a padding character when a byte is not a
32320 member of the printable @sc{ascii} character set (printable @sc{ascii}
32321 characters are those whose code is between 32 and 126, inclusively).
32323 @item @var{byte-offset}
32324 An offset to add to the @var{address} before fetching memory.
32327 This command displays memory contents as a table of @var{nr-rows} by
32328 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32329 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32330 (returned as @samp{total-bytes}). Should less than the requested number
32331 of bytes be returned by the target, the missing words are identified
32332 using @samp{N/A}. The number of bytes read from the target is returned
32333 in @samp{nr-bytes} and the starting address used to read memory in
32336 The address of the next/previous row or page is available in
32337 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32340 @subsubheading @value{GDBN} Command
32342 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32343 @samp{gdb_get_mem} memory read command.
32345 @subsubheading Example
32347 Read six bytes of memory starting at @code{bytes+6} but then offset by
32348 @code{-6} bytes. Format as three rows of two columns. One byte per
32349 word. Display each word in hex.
32353 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32354 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32355 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32356 prev-page="0x0000138a",memory=[
32357 @{addr="0x00001390",data=["0x00","0x01"]@},
32358 @{addr="0x00001392",data=["0x02","0x03"]@},
32359 @{addr="0x00001394",data=["0x04","0x05"]@}]
32363 Read two bytes of memory starting at address @code{shorts + 64} and
32364 display as a single word formatted in decimal.
32368 5-data-read-memory shorts+64 d 2 1 1
32369 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32370 next-row="0x00001512",prev-row="0x0000150e",
32371 next-page="0x00001512",prev-page="0x0000150e",memory=[
32372 @{addr="0x00001510",data=["128"]@}]
32376 Read thirty two bytes of memory starting at @code{bytes+16} and format
32377 as eight rows of four columns. Include a string encoding with @samp{x}
32378 used as the non-printable character.
32382 4-data-read-memory bytes+16 x 1 8 4 x
32383 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32384 next-row="0x000013c0",prev-row="0x0000139c",
32385 next-page="0x000013c0",prev-page="0x00001380",memory=[
32386 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32387 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32388 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32389 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32390 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32391 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32392 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32393 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32397 @subheading The @code{-data-read-memory-bytes} Command
32398 @findex -data-read-memory-bytes
32400 @subsubheading Synopsis
32403 -data-read-memory-bytes [ -o @var{offset} ]
32404 @var{address} @var{count}
32411 @item @var{address}
32412 An expression specifying the address of the first addressable memory unit
32413 to be read. Complex expressions containing embedded white space should be
32414 quoted using the C convention.
32417 The number of addressable memory units to read. This should be an integer
32421 The offset relative to @var{address} at which to start reading. This
32422 should be an integer literal. This option is provided so that a frontend
32423 is not required to first evaluate address and then perform address
32424 arithmetics itself.
32428 This command attempts to read all accessible memory regions in the
32429 specified range. First, all regions marked as unreadable in the memory
32430 map (if one is defined) will be skipped. @xref{Memory Region
32431 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32432 regions. For each one, if reading full region results in an errors,
32433 @value{GDBN} will try to read a subset of the region.
32435 In general, every single memory unit in the region may be readable or not,
32436 and the only way to read every readable unit is to try a read at
32437 every address, which is not practical. Therefore, @value{GDBN} will
32438 attempt to read all accessible memory units at either beginning or the end
32439 of the region, using a binary division scheme. This heuristic works
32440 well for reading accross a memory map boundary. Note that if a region
32441 has a readable range that is neither at the beginning or the end,
32442 @value{GDBN} will not read it.
32444 The result record (@pxref{GDB/MI Result Records}) that is output of
32445 the command includes a field named @samp{memory} whose content is a
32446 list of tuples. Each tuple represent a successfully read memory block
32447 and has the following fields:
32451 The start address of the memory block, as hexadecimal literal.
32454 The end address of the memory block, as hexadecimal literal.
32457 The offset of the memory block, as hexadecimal literal, relative to
32458 the start address passed to @code{-data-read-memory-bytes}.
32461 The contents of the memory block, in hex.
32467 @subsubheading @value{GDBN} Command
32469 The corresponding @value{GDBN} command is @samp{x}.
32471 @subsubheading Example
32475 -data-read-memory-bytes &a 10
32476 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32478 contents="01000000020000000300"@}]
32483 @subheading The @code{-data-write-memory-bytes} Command
32484 @findex -data-write-memory-bytes
32486 @subsubheading Synopsis
32489 -data-write-memory-bytes @var{address} @var{contents}
32490 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32497 @item @var{address}
32498 An expression specifying the address of the first addressable memory unit
32499 to be written. Complex expressions containing embedded white space should
32500 be quoted using the C convention.
32502 @item @var{contents}
32503 The hex-encoded data to write. It is an error if @var{contents} does
32504 not represent an integral number of addressable memory units.
32507 Optional argument indicating the number of addressable memory units to be
32508 written. If @var{count} is greater than @var{contents}' length,
32509 @value{GDBN} will repeatedly write @var{contents} until it fills
32510 @var{count} memory units.
32514 @subsubheading @value{GDBN} Command
32516 There's no corresponding @value{GDBN} command.
32518 @subsubheading Example
32522 -data-write-memory-bytes &a "aabbccdd"
32529 -data-write-memory-bytes &a "aabbccdd" 16e
32534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32535 @node GDB/MI Tracepoint Commands
32536 @section @sc{gdb/mi} Tracepoint Commands
32538 The commands defined in this section implement MI support for
32539 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32541 @subheading The @code{-trace-find} Command
32542 @findex -trace-find
32544 @subsubheading Synopsis
32547 -trace-find @var{mode} [@var{parameters}@dots{}]
32550 Find a trace frame using criteria defined by @var{mode} and
32551 @var{parameters}. The following table lists permissible
32552 modes and their parameters. For details of operation, see @ref{tfind}.
32557 No parameters are required. Stops examining trace frames.
32560 An integer is required as parameter. Selects tracepoint frame with
32563 @item tracepoint-number
32564 An integer is required as parameter. Finds next
32565 trace frame that corresponds to tracepoint with the specified number.
32568 An address is required as parameter. Finds
32569 next trace frame that corresponds to any tracepoint at the specified
32572 @item pc-inside-range
32573 Two addresses are required as parameters. Finds next trace
32574 frame that corresponds to a tracepoint at an address inside the
32575 specified range. Both bounds are considered to be inside the range.
32577 @item pc-outside-range
32578 Two addresses are required as parameters. Finds
32579 next trace frame that corresponds to a tracepoint at an address outside
32580 the specified range. Both bounds are considered to be inside the range.
32583 Line specification is required as parameter. @xref{Specify Location}.
32584 Finds next trace frame that corresponds to a tracepoint at
32585 the specified location.
32589 If @samp{none} was passed as @var{mode}, the response does not
32590 have fields. Otherwise, the response may have the following fields:
32594 This field has either @samp{0} or @samp{1} as the value, depending
32595 on whether a matching tracepoint was found.
32598 The index of the found traceframe. This field is present iff
32599 the @samp{found} field has value of @samp{1}.
32602 The index of the found tracepoint. This field is present iff
32603 the @samp{found} field has value of @samp{1}.
32606 The information about the frame corresponding to the found trace
32607 frame. This field is present only if a trace frame was found.
32608 @xref{GDB/MI Frame Information}, for description of this field.
32612 @subsubheading @value{GDBN} Command
32614 The corresponding @value{GDBN} command is @samp{tfind}.
32616 @subheading -trace-define-variable
32617 @findex -trace-define-variable
32619 @subsubheading Synopsis
32622 -trace-define-variable @var{name} [ @var{value} ]
32625 Create trace variable @var{name} if it does not exist. If
32626 @var{value} is specified, sets the initial value of the specified
32627 trace variable to that value. Note that the @var{name} should start
32628 with the @samp{$} character.
32630 @subsubheading @value{GDBN} Command
32632 The corresponding @value{GDBN} command is @samp{tvariable}.
32634 @subheading The @code{-trace-frame-collected} Command
32635 @findex -trace-frame-collected
32637 @subsubheading Synopsis
32640 -trace-frame-collected
32641 [--var-print-values @var{var_pval}]
32642 [--comp-print-values @var{comp_pval}]
32643 [--registers-format @var{regformat}]
32644 [--memory-contents]
32647 This command returns the set of collected objects, register names,
32648 trace state variable names, memory ranges and computed expressions
32649 that have been collected at a particular trace frame. The optional
32650 parameters to the command affect the output format in different ways.
32651 See the output description table below for more details.
32653 The reported names can be used in the normal manner to create
32654 varobjs and inspect the objects themselves. The items returned by
32655 this command are categorized so that it is clear which is a variable,
32656 which is a register, which is a trace state variable, which is a
32657 memory range and which is a computed expression.
32659 For instance, if the actions were
32661 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32662 collect *(int*)0xaf02bef0@@40
32666 the object collected in its entirety would be @code{myVar}. The
32667 object @code{myArray} would be partially collected, because only the
32668 element at index @code{myIndex} would be collected. The remaining
32669 objects would be computed expressions.
32671 An example output would be:
32675 -trace-frame-collected
32677 explicit-variables=[@{name="myVar",value="1"@}],
32678 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32679 @{name="myObj.field",value="0"@},
32680 @{name="myPtr->field",value="1"@},
32681 @{name="myCount + 2",value="3"@},
32682 @{name="$tvar1 + 1",value="43970027"@}],
32683 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32684 @{number="1",value="0x0"@},
32685 @{number="2",value="0x4"@},
32687 @{number="125",value="0x0"@}],
32688 tvars=[@{name="$tvar1",current="43970026"@}],
32689 memory=[@{address="0x0000000000602264",length="4"@},
32690 @{address="0x0000000000615bc0",length="4"@}]
32697 @item explicit-variables
32698 The set of objects that have been collected in their entirety (as
32699 opposed to collecting just a few elements of an array or a few struct
32700 members). For each object, its name and value are printed.
32701 The @code{--var-print-values} option affects how or whether the value
32702 field is output. If @var{var_pval} is 0, then print only the names;
32703 if it is 1, print also their values; and if it is 2, print the name,
32704 type and value for simple data types, and the name and type for
32705 arrays, structures and unions.
32707 @item computed-expressions
32708 The set of computed expressions that have been collected at the
32709 current trace frame. The @code{--comp-print-values} option affects
32710 this set like the @code{--var-print-values} option affects the
32711 @code{explicit-variables} set. See above.
32714 The registers that have been collected at the current trace frame.
32715 For each register collected, the name and current value are returned.
32716 The value is formatted according to the @code{--registers-format}
32717 option. See the @command{-data-list-register-values} command for a
32718 list of the allowed formats. The default is @samp{x}.
32721 The trace state variables that have been collected at the current
32722 trace frame. For each trace state variable collected, the name and
32723 current value are returned.
32726 The set of memory ranges that have been collected at the current trace
32727 frame. Its content is a list of tuples. Each tuple represents a
32728 collected memory range and has the following fields:
32732 The start address of the memory range, as hexadecimal literal.
32735 The length of the memory range, as decimal literal.
32738 The contents of the memory block, in hex. This field is only present
32739 if the @code{--memory-contents} option is specified.
32745 @subsubheading @value{GDBN} Command
32747 There is no corresponding @value{GDBN} command.
32749 @subsubheading Example
32751 @subheading -trace-list-variables
32752 @findex -trace-list-variables
32754 @subsubheading Synopsis
32757 -trace-list-variables
32760 Return a table of all defined trace variables. Each element of the
32761 table has the following fields:
32765 The name of the trace variable. This field is always present.
32768 The initial value. This is a 64-bit signed integer. This
32769 field is always present.
32772 The value the trace variable has at the moment. This is a 64-bit
32773 signed integer. This field is absent iff current value is
32774 not defined, for example if the trace was never run, or is
32779 @subsubheading @value{GDBN} Command
32781 The corresponding @value{GDBN} command is @samp{tvariables}.
32783 @subsubheading Example
32787 -trace-list-variables
32788 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32789 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32790 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32791 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32792 body=[variable=@{name="$trace_timestamp",initial="0"@}
32793 variable=@{name="$foo",initial="10",current="15"@}]@}
32797 @subheading -trace-save
32798 @findex -trace-save
32800 @subsubheading Synopsis
32803 -trace-save [ -r ] [ -ctf ] @var{filename}
32806 Saves the collected trace data to @var{filename}. Without the
32807 @samp{-r} option, the data is downloaded from the target and saved
32808 in a local file. With the @samp{-r} option the target is asked
32809 to perform the save.
32811 By default, this command will save the trace in the tfile format. You can
32812 supply the optional @samp{-ctf} argument to save it the CTF format. See
32813 @ref{Trace Files} for more information about CTF.
32815 @subsubheading @value{GDBN} Command
32817 The corresponding @value{GDBN} command is @samp{tsave}.
32820 @subheading -trace-start
32821 @findex -trace-start
32823 @subsubheading Synopsis
32829 Starts a tracing experiment. The result of this command does not
32832 @subsubheading @value{GDBN} Command
32834 The corresponding @value{GDBN} command is @samp{tstart}.
32836 @subheading -trace-status
32837 @findex -trace-status
32839 @subsubheading Synopsis
32845 Obtains the status of a tracing experiment. The result may include
32846 the following fields:
32851 May have a value of either @samp{0}, when no tracing operations are
32852 supported, @samp{1}, when all tracing operations are supported, or
32853 @samp{file} when examining trace file. In the latter case, examining
32854 of trace frame is possible but new tracing experiement cannot be
32855 started. This field is always present.
32858 May have a value of either @samp{0} or @samp{1} depending on whether
32859 tracing experiement is in progress on target. This field is present
32860 if @samp{supported} field is not @samp{0}.
32863 Report the reason why the tracing was stopped last time. This field
32864 may be absent iff tracing was never stopped on target yet. The
32865 value of @samp{request} means the tracing was stopped as result of
32866 the @code{-trace-stop} command. The value of @samp{overflow} means
32867 the tracing buffer is full. The value of @samp{disconnection} means
32868 tracing was automatically stopped when @value{GDBN} has disconnected.
32869 The value of @samp{passcount} means tracing was stopped when a
32870 tracepoint was passed a maximal number of times for that tracepoint.
32871 This field is present if @samp{supported} field is not @samp{0}.
32873 @item stopping-tracepoint
32874 The number of tracepoint whose passcount as exceeded. This field is
32875 present iff the @samp{stop-reason} field has the value of
32879 @itemx frames-created
32880 The @samp{frames} field is a count of the total number of trace frames
32881 in the trace buffer, while @samp{frames-created} is the total created
32882 during the run, including ones that were discarded, such as when a
32883 circular trace buffer filled up. Both fields are optional.
32887 These fields tell the current size of the tracing buffer and the
32888 remaining space. These fields are optional.
32891 The value of the circular trace buffer flag. @code{1} means that the
32892 trace buffer is circular and old trace frames will be discarded if
32893 necessary to make room, @code{0} means that the trace buffer is linear
32897 The value of the disconnected tracing flag. @code{1} means that
32898 tracing will continue after @value{GDBN} disconnects, @code{0} means
32899 that the trace run will stop.
32902 The filename of the trace file being examined. This field is
32903 optional, and only present when examining a trace file.
32907 @subsubheading @value{GDBN} Command
32909 The corresponding @value{GDBN} command is @samp{tstatus}.
32911 @subheading -trace-stop
32912 @findex -trace-stop
32914 @subsubheading Synopsis
32920 Stops a tracing experiment. The result of this command has the same
32921 fields as @code{-trace-status}, except that the @samp{supported} and
32922 @samp{running} fields are not output.
32924 @subsubheading @value{GDBN} Command
32926 The corresponding @value{GDBN} command is @samp{tstop}.
32929 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32930 @node GDB/MI Symbol Query
32931 @section @sc{gdb/mi} Symbol Query Commands
32935 @subheading The @code{-symbol-info-address} Command
32936 @findex -symbol-info-address
32938 @subsubheading Synopsis
32941 -symbol-info-address @var{symbol}
32944 Describe where @var{symbol} is stored.
32946 @subsubheading @value{GDBN} Command
32948 The corresponding @value{GDBN} command is @samp{info address}.
32950 @subsubheading Example
32954 @subheading The @code{-symbol-info-file} Command
32955 @findex -symbol-info-file
32957 @subsubheading Synopsis
32963 Show the file for the symbol.
32965 @subsubheading @value{GDBN} Command
32967 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32968 @samp{gdb_find_file}.
32970 @subsubheading Example
32974 @subheading The @code{-symbol-info-function} Command
32975 @findex -symbol-info-function
32977 @subsubheading Synopsis
32980 -symbol-info-function
32983 Show which function the symbol lives in.
32985 @subsubheading @value{GDBN} Command
32987 @samp{gdb_get_function} in @code{gdbtk}.
32989 @subsubheading Example
32993 @subheading The @code{-symbol-info-line} Command
32994 @findex -symbol-info-line
32996 @subsubheading Synopsis
33002 Show the core addresses of the code for a source line.
33004 @subsubheading @value{GDBN} Command
33006 The corresponding @value{GDBN} command is @samp{info line}.
33007 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33009 @subsubheading Example
33013 @subheading The @code{-symbol-info-symbol} Command
33014 @findex -symbol-info-symbol
33016 @subsubheading Synopsis
33019 -symbol-info-symbol @var{addr}
33022 Describe what symbol is at location @var{addr}.
33024 @subsubheading @value{GDBN} Command
33026 The corresponding @value{GDBN} command is @samp{info symbol}.
33028 @subsubheading Example
33032 @subheading The @code{-symbol-list-functions} Command
33033 @findex -symbol-list-functions
33035 @subsubheading Synopsis
33038 -symbol-list-functions
33041 List the functions in the executable.
33043 @subsubheading @value{GDBN} Command
33045 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33046 @samp{gdb_search} in @code{gdbtk}.
33048 @subsubheading Example
33053 @subheading The @code{-symbol-list-lines} Command
33054 @findex -symbol-list-lines
33056 @subsubheading Synopsis
33059 -symbol-list-lines @var{filename}
33062 Print the list of lines that contain code and their associated program
33063 addresses for the given source filename. The entries are sorted in
33064 ascending PC order.
33066 @subsubheading @value{GDBN} Command
33068 There is no corresponding @value{GDBN} command.
33070 @subsubheading Example
33073 -symbol-list-lines basics.c
33074 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33080 @subheading The @code{-symbol-list-types} Command
33081 @findex -symbol-list-types
33083 @subsubheading Synopsis
33089 List all the type names.
33091 @subsubheading @value{GDBN} Command
33093 The corresponding commands are @samp{info types} in @value{GDBN},
33094 @samp{gdb_search} in @code{gdbtk}.
33096 @subsubheading Example
33100 @subheading The @code{-symbol-list-variables} Command
33101 @findex -symbol-list-variables
33103 @subsubheading Synopsis
33106 -symbol-list-variables
33109 List all the global and static variable names.
33111 @subsubheading @value{GDBN} Command
33113 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33115 @subsubheading Example
33119 @subheading The @code{-symbol-locate} Command
33120 @findex -symbol-locate
33122 @subsubheading Synopsis
33128 @subsubheading @value{GDBN} Command
33130 @samp{gdb_loc} in @code{gdbtk}.
33132 @subsubheading Example
33136 @subheading The @code{-symbol-type} Command
33137 @findex -symbol-type
33139 @subsubheading Synopsis
33142 -symbol-type @var{variable}
33145 Show type of @var{variable}.
33147 @subsubheading @value{GDBN} Command
33149 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33150 @samp{gdb_obj_variable}.
33152 @subsubheading Example
33157 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33158 @node GDB/MI File Commands
33159 @section @sc{gdb/mi} File Commands
33161 This section describes the GDB/MI commands to specify executable file names
33162 and to read in and obtain symbol table information.
33164 @subheading The @code{-file-exec-and-symbols} Command
33165 @findex -file-exec-and-symbols
33167 @subsubheading Synopsis
33170 -file-exec-and-symbols @var{file}
33173 Specify the executable file to be debugged. This file is the one from
33174 which the symbol table is also read. If no file is specified, the
33175 command clears the executable and symbol information. If breakpoints
33176 are set when using this command with no arguments, @value{GDBN} will produce
33177 error messages. Otherwise, no output is produced, except a completion
33180 @subsubheading @value{GDBN} Command
33182 The corresponding @value{GDBN} command is @samp{file}.
33184 @subsubheading Example
33188 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33194 @subheading The @code{-file-exec-file} Command
33195 @findex -file-exec-file
33197 @subsubheading Synopsis
33200 -file-exec-file @var{file}
33203 Specify the executable file to be debugged. Unlike
33204 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33205 from this file. If used without argument, @value{GDBN} clears the information
33206 about the executable file. No output is produced, except a completion
33209 @subsubheading @value{GDBN} Command
33211 The corresponding @value{GDBN} command is @samp{exec-file}.
33213 @subsubheading Example
33217 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33224 @subheading The @code{-file-list-exec-sections} Command
33225 @findex -file-list-exec-sections
33227 @subsubheading Synopsis
33230 -file-list-exec-sections
33233 List the sections of the current executable file.
33235 @subsubheading @value{GDBN} Command
33237 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33238 information as this command. @code{gdbtk} has a corresponding command
33239 @samp{gdb_load_info}.
33241 @subsubheading Example
33246 @subheading The @code{-file-list-exec-source-file} Command
33247 @findex -file-list-exec-source-file
33249 @subsubheading Synopsis
33252 -file-list-exec-source-file
33255 List the line number, the current source file, and the absolute path
33256 to the current source file for the current executable. The macro
33257 information field has a value of @samp{1} or @samp{0} depending on
33258 whether or not the file includes preprocessor macro information.
33260 @subsubheading @value{GDBN} Command
33262 The @value{GDBN} equivalent is @samp{info source}
33264 @subsubheading Example
33268 123-file-list-exec-source-file
33269 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33274 @subheading The @code{-file-list-exec-source-files} Command
33275 @findex -file-list-exec-source-files
33277 @subsubheading Synopsis
33280 -file-list-exec-source-files
33283 List the source files for the current executable.
33285 It will always output both the filename and fullname (absolute file
33286 name) of a source file.
33288 @subsubheading @value{GDBN} Command
33290 The @value{GDBN} equivalent is @samp{info sources}.
33291 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33293 @subsubheading Example
33296 -file-list-exec-source-files
33298 @{file=foo.c,fullname=/home/foo.c@},
33299 @{file=/home/bar.c,fullname=/home/bar.c@},
33300 @{file=gdb_could_not_find_fullpath.c@}]
33304 @subheading The @code{-file-list-shared-libraries} Command
33305 @findex -file-list-shared-libraries
33307 @subsubheading Synopsis
33310 -file-list-shared-libraries [ @var{regexp} ]
33313 List the shared libraries in the program.
33314 With a regular expression @var{regexp}, only those libraries whose
33315 names match @var{regexp} are listed.
33317 @subsubheading @value{GDBN} Command
33319 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33320 have a similar meaning to the @code{=library-loaded} notification.
33321 The @code{ranges} field specifies the multiple segments belonging to this
33322 library. Each range has the following fields:
33326 The address defining the inclusive lower bound of the segment.
33328 The address defining the exclusive upper bound of the segment.
33331 @subsubheading Example
33334 -file-list-exec-source-files
33335 ^done,shared-libraries=[
33336 @{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"@}]@},
33337 @{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"@}]@}]
33343 @subheading The @code{-file-list-symbol-files} Command
33344 @findex -file-list-symbol-files
33346 @subsubheading Synopsis
33349 -file-list-symbol-files
33354 @subsubheading @value{GDBN} Command
33356 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33358 @subsubheading Example
33363 @subheading The @code{-file-symbol-file} Command
33364 @findex -file-symbol-file
33366 @subsubheading Synopsis
33369 -file-symbol-file @var{file}
33372 Read symbol table info from the specified @var{file} argument. When
33373 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33374 produced, except for a completion notification.
33376 @subsubheading @value{GDBN} Command
33378 The corresponding @value{GDBN} command is @samp{symbol-file}.
33380 @subsubheading Example
33384 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33390 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33391 @node GDB/MI Memory Overlay Commands
33392 @section @sc{gdb/mi} Memory Overlay Commands
33394 The memory overlay commands are not implemented.
33396 @c @subheading -overlay-auto
33398 @c @subheading -overlay-list-mapping-state
33400 @c @subheading -overlay-list-overlays
33402 @c @subheading -overlay-map
33404 @c @subheading -overlay-off
33406 @c @subheading -overlay-on
33408 @c @subheading -overlay-unmap
33410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33411 @node GDB/MI Signal Handling Commands
33412 @section @sc{gdb/mi} Signal Handling Commands
33414 Signal handling commands are not implemented.
33416 @c @subheading -signal-handle
33418 @c @subheading -signal-list-handle-actions
33420 @c @subheading -signal-list-signal-types
33424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33425 @node GDB/MI Target Manipulation
33426 @section @sc{gdb/mi} Target Manipulation Commands
33429 @subheading The @code{-target-attach} Command
33430 @findex -target-attach
33432 @subsubheading Synopsis
33435 -target-attach @var{pid} | @var{gid} | @var{file}
33438 Attach to a process @var{pid} or a file @var{file} outside of
33439 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33440 group, the id previously returned by
33441 @samp{-list-thread-groups --available} must be used.
33443 @subsubheading @value{GDBN} Command
33445 The corresponding @value{GDBN} command is @samp{attach}.
33447 @subsubheading Example
33451 =thread-created,id="1"
33452 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33458 @subheading The @code{-target-compare-sections} Command
33459 @findex -target-compare-sections
33461 @subsubheading Synopsis
33464 -target-compare-sections [ @var{section} ]
33467 Compare data of section @var{section} on target to the exec file.
33468 Without the argument, all sections are compared.
33470 @subsubheading @value{GDBN} Command
33472 The @value{GDBN} equivalent is @samp{compare-sections}.
33474 @subsubheading Example
33479 @subheading The @code{-target-detach} Command
33480 @findex -target-detach
33482 @subsubheading Synopsis
33485 -target-detach [ @var{pid} | @var{gid} ]
33488 Detach from the remote target which normally resumes its execution.
33489 If either @var{pid} or @var{gid} is specified, detaches from either
33490 the specified process, or specified thread group. There's no output.
33492 @subsubheading @value{GDBN} Command
33494 The corresponding @value{GDBN} command is @samp{detach}.
33496 @subsubheading Example
33506 @subheading The @code{-target-disconnect} Command
33507 @findex -target-disconnect
33509 @subsubheading Synopsis
33515 Disconnect from the remote target. There's no output and the target is
33516 generally not resumed.
33518 @subsubheading @value{GDBN} Command
33520 The corresponding @value{GDBN} command is @samp{disconnect}.
33522 @subsubheading Example
33532 @subheading The @code{-target-download} Command
33533 @findex -target-download
33535 @subsubheading Synopsis
33541 Loads the executable onto the remote target.
33542 It prints out an update message every half second, which includes the fields:
33546 The name of the section.
33548 The size of what has been sent so far for that section.
33550 The size of the section.
33552 The total size of what was sent so far (the current and the previous sections).
33554 The size of the overall executable to download.
33558 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33559 @sc{gdb/mi} Output Syntax}).
33561 In addition, it prints the name and size of the sections, as they are
33562 downloaded. These messages include the following fields:
33566 The name of the section.
33568 The size of the section.
33570 The size of the overall executable to download.
33574 At the end, a summary is printed.
33576 @subsubheading @value{GDBN} Command
33578 The corresponding @value{GDBN} command is @samp{load}.
33580 @subsubheading Example
33582 Note: each status message appears on a single line. Here the messages
33583 have been broken down so that they can fit onto a page.
33588 +download,@{section=".text",section-size="6668",total-size="9880"@}
33589 +download,@{section=".text",section-sent="512",section-size="6668",
33590 total-sent="512",total-size="9880"@}
33591 +download,@{section=".text",section-sent="1024",section-size="6668",
33592 total-sent="1024",total-size="9880"@}
33593 +download,@{section=".text",section-sent="1536",section-size="6668",
33594 total-sent="1536",total-size="9880"@}
33595 +download,@{section=".text",section-sent="2048",section-size="6668",
33596 total-sent="2048",total-size="9880"@}
33597 +download,@{section=".text",section-sent="2560",section-size="6668",
33598 total-sent="2560",total-size="9880"@}
33599 +download,@{section=".text",section-sent="3072",section-size="6668",
33600 total-sent="3072",total-size="9880"@}
33601 +download,@{section=".text",section-sent="3584",section-size="6668",
33602 total-sent="3584",total-size="9880"@}
33603 +download,@{section=".text",section-sent="4096",section-size="6668",
33604 total-sent="4096",total-size="9880"@}
33605 +download,@{section=".text",section-sent="4608",section-size="6668",
33606 total-sent="4608",total-size="9880"@}
33607 +download,@{section=".text",section-sent="5120",section-size="6668",
33608 total-sent="5120",total-size="9880"@}
33609 +download,@{section=".text",section-sent="5632",section-size="6668",
33610 total-sent="5632",total-size="9880"@}
33611 +download,@{section=".text",section-sent="6144",section-size="6668",
33612 total-sent="6144",total-size="9880"@}
33613 +download,@{section=".text",section-sent="6656",section-size="6668",
33614 total-sent="6656",total-size="9880"@}
33615 +download,@{section=".init",section-size="28",total-size="9880"@}
33616 +download,@{section=".fini",section-size="28",total-size="9880"@}
33617 +download,@{section=".data",section-size="3156",total-size="9880"@}
33618 +download,@{section=".data",section-sent="512",section-size="3156",
33619 total-sent="7236",total-size="9880"@}
33620 +download,@{section=".data",section-sent="1024",section-size="3156",
33621 total-sent="7748",total-size="9880"@}
33622 +download,@{section=".data",section-sent="1536",section-size="3156",
33623 total-sent="8260",total-size="9880"@}
33624 +download,@{section=".data",section-sent="2048",section-size="3156",
33625 total-sent="8772",total-size="9880"@}
33626 +download,@{section=".data",section-sent="2560",section-size="3156",
33627 total-sent="9284",total-size="9880"@}
33628 +download,@{section=".data",section-sent="3072",section-size="3156",
33629 total-sent="9796",total-size="9880"@}
33630 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33637 @subheading The @code{-target-exec-status} Command
33638 @findex -target-exec-status
33640 @subsubheading Synopsis
33643 -target-exec-status
33646 Provide information on the state of the target (whether it is running or
33647 not, for instance).
33649 @subsubheading @value{GDBN} Command
33651 There's no equivalent @value{GDBN} command.
33653 @subsubheading Example
33657 @subheading The @code{-target-list-available-targets} Command
33658 @findex -target-list-available-targets
33660 @subsubheading Synopsis
33663 -target-list-available-targets
33666 List the possible targets to connect to.
33668 @subsubheading @value{GDBN} Command
33670 The corresponding @value{GDBN} command is @samp{help target}.
33672 @subsubheading Example
33676 @subheading The @code{-target-list-current-targets} Command
33677 @findex -target-list-current-targets
33679 @subsubheading Synopsis
33682 -target-list-current-targets
33685 Describe the current target.
33687 @subsubheading @value{GDBN} Command
33689 The corresponding information is printed by @samp{info file} (among
33692 @subsubheading Example
33696 @subheading The @code{-target-list-parameters} Command
33697 @findex -target-list-parameters
33699 @subsubheading Synopsis
33702 -target-list-parameters
33708 @subsubheading @value{GDBN} Command
33712 @subsubheading Example
33715 @subheading The @code{-target-flash-erase} Command
33716 @findex -target-flash-erase
33718 @subsubheading Synopsis
33721 -target-flash-erase
33724 Erases all known flash memory regions on the target.
33726 The corresponding @value{GDBN} command is @samp{flash-erase}.
33728 The output is a list of flash regions that have been erased, with starting
33729 addresses and memory region sizes.
33733 -target-flash-erase
33734 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33738 @subheading The @code{-target-select} Command
33739 @findex -target-select
33741 @subsubheading Synopsis
33744 -target-select @var{type} @var{parameters @dots{}}
33747 Connect @value{GDBN} to the remote target. This command takes two args:
33751 The type of target, for instance @samp{remote}, etc.
33752 @item @var{parameters}
33753 Device names, host names and the like. @xref{Target Commands, ,
33754 Commands for Managing Targets}, for more details.
33757 The output is a connection notification, followed by the address at
33758 which the target program is, in the following form:
33761 ^connected,addr="@var{address}",func="@var{function name}",
33762 args=[@var{arg list}]
33765 @subsubheading @value{GDBN} Command
33767 The corresponding @value{GDBN} command is @samp{target}.
33769 @subsubheading Example
33773 -target-select remote /dev/ttya
33774 ^connected,addr="0xfe00a300",func="??",args=[]
33778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33779 @node GDB/MI File Transfer Commands
33780 @section @sc{gdb/mi} File Transfer Commands
33783 @subheading The @code{-target-file-put} Command
33784 @findex -target-file-put
33786 @subsubheading Synopsis
33789 -target-file-put @var{hostfile} @var{targetfile}
33792 Copy file @var{hostfile} from the host system (the machine running
33793 @value{GDBN}) to @var{targetfile} on the target system.
33795 @subsubheading @value{GDBN} Command
33797 The corresponding @value{GDBN} command is @samp{remote put}.
33799 @subsubheading Example
33803 -target-file-put localfile remotefile
33809 @subheading The @code{-target-file-get} Command
33810 @findex -target-file-get
33812 @subsubheading Synopsis
33815 -target-file-get @var{targetfile} @var{hostfile}
33818 Copy file @var{targetfile} from the target system to @var{hostfile}
33819 on the host system.
33821 @subsubheading @value{GDBN} Command
33823 The corresponding @value{GDBN} command is @samp{remote get}.
33825 @subsubheading Example
33829 -target-file-get remotefile localfile
33835 @subheading The @code{-target-file-delete} Command
33836 @findex -target-file-delete
33838 @subsubheading Synopsis
33841 -target-file-delete @var{targetfile}
33844 Delete @var{targetfile} from the target system.
33846 @subsubheading @value{GDBN} Command
33848 The corresponding @value{GDBN} command is @samp{remote delete}.
33850 @subsubheading Example
33854 -target-file-delete remotefile
33860 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33861 @node GDB/MI Ada Exceptions Commands
33862 @section Ada Exceptions @sc{gdb/mi} Commands
33864 @subheading The @code{-info-ada-exceptions} Command
33865 @findex -info-ada-exceptions
33867 @subsubheading Synopsis
33870 -info-ada-exceptions [ @var{regexp}]
33873 List all Ada exceptions defined within the program being debugged.
33874 With a regular expression @var{regexp}, only those exceptions whose
33875 names match @var{regexp} are listed.
33877 @subsubheading @value{GDBN} Command
33879 The corresponding @value{GDBN} command is @samp{info exceptions}.
33881 @subsubheading Result
33883 The result is a table of Ada exceptions. The following columns are
33884 defined for each exception:
33888 The name of the exception.
33891 The address of the exception.
33895 @subsubheading Example
33898 -info-ada-exceptions aint
33899 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33900 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33901 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33902 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33903 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33906 @subheading Catching Ada Exceptions
33908 The commands describing how to ask @value{GDBN} to stop when a program
33909 raises an exception are described at @ref{Ada Exception GDB/MI
33910 Catchpoint Commands}.
33913 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33914 @node GDB/MI Support Commands
33915 @section @sc{gdb/mi} Support Commands
33917 Since new commands and features get regularly added to @sc{gdb/mi},
33918 some commands are available to help front-ends query the debugger
33919 about support for these capabilities. Similarly, it is also possible
33920 to query @value{GDBN} about target support of certain features.
33922 @subheading The @code{-info-gdb-mi-command} Command
33923 @cindex @code{-info-gdb-mi-command}
33924 @findex -info-gdb-mi-command
33926 @subsubheading Synopsis
33929 -info-gdb-mi-command @var{cmd_name}
33932 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33934 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33935 is technically not part of the command name (@pxref{GDB/MI Input
33936 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33937 for ease of use, this command also accepts the form with the leading
33940 @subsubheading @value{GDBN} Command
33942 There is no corresponding @value{GDBN} command.
33944 @subsubheading Result
33946 The result is a tuple. There is currently only one field:
33950 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33951 @code{"false"} otherwise.
33955 @subsubheading Example
33957 Here is an example where the @sc{gdb/mi} command does not exist:
33960 -info-gdb-mi-command unsupported-command
33961 ^done,command=@{exists="false"@}
33965 And here is an example where the @sc{gdb/mi} command is known
33969 -info-gdb-mi-command symbol-list-lines
33970 ^done,command=@{exists="true"@}
33973 @subheading The @code{-list-features} Command
33974 @findex -list-features
33975 @cindex supported @sc{gdb/mi} features, list
33977 Returns a list of particular features of the MI protocol that
33978 this version of gdb implements. A feature can be a command,
33979 or a new field in an output of some command, or even an
33980 important bugfix. While a frontend can sometimes detect presence
33981 of a feature at runtime, it is easier to perform detection at debugger
33984 The command returns a list of strings, with each string naming an
33985 available feature. Each returned string is just a name, it does not
33986 have any internal structure. The list of possible feature names
33992 (gdb) -list-features
33993 ^done,result=["feature1","feature2"]
33996 The current list of features is:
33999 @item frozen-varobjs
34000 Indicates support for the @code{-var-set-frozen} command, as well
34001 as possible presense of the @code{frozen} field in the output
34002 of @code{-varobj-create}.
34003 @item pending-breakpoints
34004 Indicates support for the @option{-f} option to the @code{-break-insert}
34007 Indicates Python scripting support, Python-based
34008 pretty-printing commands, and possible presence of the
34009 @samp{display_hint} field in the output of @code{-var-list-children}
34011 Indicates support for the @code{-thread-info} command.
34012 @item data-read-memory-bytes
34013 Indicates support for the @code{-data-read-memory-bytes} and the
34014 @code{-data-write-memory-bytes} commands.
34015 @item breakpoint-notifications
34016 Indicates that changes to breakpoints and breakpoints created via the
34017 CLI will be announced via async records.
34018 @item ada-task-info
34019 Indicates support for the @code{-ada-task-info} command.
34020 @item language-option
34021 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
34022 option (@pxref{Context management}).
34023 @item info-gdb-mi-command
34024 Indicates support for the @code{-info-gdb-mi-command} command.
34025 @item undefined-command-error-code
34026 Indicates support for the "undefined-command" error code in error result
34027 records, produced when trying to execute an undefined @sc{gdb/mi} command
34028 (@pxref{GDB/MI Result Records}).
34029 @item exec-run-start-option
34030 Indicates that the @code{-exec-run} command supports the @option{--start}
34031 option (@pxref{GDB/MI Program Execution}).
34032 @item data-disassemble-a-option
34033 Indicates that the @code{-data-disassemble} command supports the @option{-a}
34034 option (@pxref{GDB/MI Data Manipulation}).
34037 @subheading The @code{-list-target-features} Command
34038 @findex -list-target-features
34040 Returns a list of particular features that are supported by the
34041 target. Those features affect the permitted MI commands, but
34042 unlike the features reported by the @code{-list-features} command, the
34043 features depend on which target GDB is using at the moment. Whenever
34044 a target can change, due to commands such as @code{-target-select},
34045 @code{-target-attach} or @code{-exec-run}, the list of target features
34046 may change, and the frontend should obtain it again.
34050 (gdb) -list-target-features
34051 ^done,result=["async"]
34054 The current list of features is:
34058 Indicates that the target is capable of asynchronous command
34059 execution, which means that @value{GDBN} will accept further commands
34060 while the target is running.
34063 Indicates that the target is capable of reverse execution.
34064 @xref{Reverse Execution}, for more information.
34068 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34069 @node GDB/MI Miscellaneous Commands
34070 @section Miscellaneous @sc{gdb/mi} Commands
34072 @c @subheading -gdb-complete
34074 @subheading The @code{-gdb-exit} Command
34077 @subsubheading Synopsis
34083 Exit @value{GDBN} immediately.
34085 @subsubheading @value{GDBN} Command
34087 Approximately corresponds to @samp{quit}.
34089 @subsubheading Example
34099 @subheading The @code{-exec-abort} Command
34100 @findex -exec-abort
34102 @subsubheading Synopsis
34108 Kill the inferior running program.
34110 @subsubheading @value{GDBN} Command
34112 The corresponding @value{GDBN} command is @samp{kill}.
34114 @subsubheading Example
34119 @subheading The @code{-gdb-set} Command
34122 @subsubheading Synopsis
34128 Set an internal @value{GDBN} variable.
34129 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34131 @subsubheading @value{GDBN} Command
34133 The corresponding @value{GDBN} command is @samp{set}.
34135 @subsubheading Example
34145 @subheading The @code{-gdb-show} Command
34148 @subsubheading Synopsis
34154 Show the current value of a @value{GDBN} variable.
34156 @subsubheading @value{GDBN} Command
34158 The corresponding @value{GDBN} command is @samp{show}.
34160 @subsubheading Example
34169 @c @subheading -gdb-source
34172 @subheading The @code{-gdb-version} Command
34173 @findex -gdb-version
34175 @subsubheading Synopsis
34181 Show version information for @value{GDBN}. Used mostly in testing.
34183 @subsubheading @value{GDBN} Command
34185 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34186 default shows this information when you start an interactive session.
34188 @subsubheading Example
34190 @c This example modifies the actual output from GDB to avoid overfull
34196 ~Copyright 2000 Free Software Foundation, Inc.
34197 ~GDB is free software, covered by the GNU General Public License, and
34198 ~you are welcome to change it and/or distribute copies of it under
34199 ~ certain conditions.
34200 ~Type "show copying" to see the conditions.
34201 ~There is absolutely no warranty for GDB. Type "show warranty" for
34203 ~This GDB was configured as
34204 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34209 @subheading The @code{-list-thread-groups} Command
34210 @findex -list-thread-groups
34212 @subheading Synopsis
34215 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34218 Lists thread groups (@pxref{Thread groups}). When a single thread
34219 group is passed as the argument, lists the children of that group.
34220 When several thread group are passed, lists information about those
34221 thread groups. Without any parameters, lists information about all
34222 top-level thread groups.
34224 Normally, thread groups that are being debugged are reported.
34225 With the @samp{--available} option, @value{GDBN} reports thread groups
34226 available on the target.
34228 The output of this command may have either a @samp{threads} result or
34229 a @samp{groups} result. The @samp{thread} result has a list of tuples
34230 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34231 Information}). The @samp{groups} result has a list of tuples as value,
34232 each tuple describing a thread group. If top-level groups are
34233 requested (that is, no parameter is passed), or when several groups
34234 are passed, the output always has a @samp{groups} result. The format
34235 of the @samp{group} result is described below.
34237 To reduce the number of roundtrips it's possible to list thread groups
34238 together with their children, by passing the @samp{--recurse} option
34239 and the recursion depth. Presently, only recursion depth of 1 is
34240 permitted. If this option is present, then every reported thread group
34241 will also include its children, either as @samp{group} or
34242 @samp{threads} field.
34244 In general, any combination of option and parameters is permitted, with
34245 the following caveats:
34249 When a single thread group is passed, the output will typically
34250 be the @samp{threads} result. Because threads may not contain
34251 anything, the @samp{recurse} option will be ignored.
34254 When the @samp{--available} option is passed, limited information may
34255 be available. In particular, the list of threads of a process might
34256 be inaccessible. Further, specifying specific thread groups might
34257 not give any performance advantage over listing all thread groups.
34258 The frontend should assume that @samp{-list-thread-groups --available}
34259 is always an expensive operation and cache the results.
34263 The @samp{groups} result is a list of tuples, where each tuple may
34264 have the following fields:
34268 Identifier of the thread group. This field is always present.
34269 The identifier is an opaque string; frontends should not try to
34270 convert it to an integer, even though it might look like one.
34273 The type of the thread group. At present, only @samp{process} is a
34277 The target-specific process identifier. This field is only present
34278 for thread groups of type @samp{process} and only if the process exists.
34281 The exit code of this group's last exited thread, formatted in octal.
34282 This field is only present for thread groups of type @samp{process} and
34283 only if the process is not running.
34286 The number of children this thread group has. This field may be
34287 absent for an available thread group.
34290 This field has a list of tuples as value, each tuple describing a
34291 thread. It may be present if the @samp{--recurse} option is
34292 specified, and it's actually possible to obtain the threads.
34295 This field is a list of integers, each identifying a core that one
34296 thread of the group is running on. This field may be absent if
34297 such information is not available.
34300 The name of the executable file that corresponds to this thread group.
34301 The field is only present for thread groups of type @samp{process},
34302 and only if there is a corresponding executable file.
34306 @subheading Example
34310 -list-thread-groups
34311 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34312 -list-thread-groups 17
34313 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34314 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34315 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34316 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34317 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34318 -list-thread-groups --available
34319 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34320 -list-thread-groups --available --recurse 1
34321 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34322 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34323 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34324 -list-thread-groups --available --recurse 1 17 18
34325 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34326 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34327 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34330 @subheading The @code{-info-os} Command
34333 @subsubheading Synopsis
34336 -info-os [ @var{type} ]
34339 If no argument is supplied, the command returns a table of available
34340 operating-system-specific information types. If one of these types is
34341 supplied as an argument @var{type}, then the command returns a table
34342 of data of that type.
34344 The types of information available depend on the target operating
34347 @subsubheading @value{GDBN} Command
34349 The corresponding @value{GDBN} command is @samp{info os}.
34351 @subsubheading Example
34353 When run on a @sc{gnu}/Linux system, the output will look something
34359 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34360 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34361 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34362 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34363 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34365 item=@{col0="files",col1="Listing of all file descriptors",
34366 col2="File descriptors"@},
34367 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34368 col2="Kernel modules"@},
34369 item=@{col0="msg",col1="Listing of all message queues",
34370 col2="Message queues"@},
34371 item=@{col0="processes",col1="Listing of all processes",
34372 col2="Processes"@},
34373 item=@{col0="procgroups",col1="Listing of all process groups",
34374 col2="Process groups"@},
34375 item=@{col0="semaphores",col1="Listing of all semaphores",
34376 col2="Semaphores"@},
34377 item=@{col0="shm",col1="Listing of all shared-memory regions",
34378 col2="Shared-memory regions"@},
34379 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34381 item=@{col0="threads",col1="Listing of all threads",
34385 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34386 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34387 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34388 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34389 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34390 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34391 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34392 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34394 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34395 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34399 (Note that the MI output here includes a @code{"Title"} column that
34400 does not appear in command-line @code{info os}; this column is useful
34401 for MI clients that want to enumerate the types of data, such as in a
34402 popup menu, but is needless clutter on the command line, and
34403 @code{info os} omits it.)
34405 @subheading The @code{-add-inferior} Command
34406 @findex -add-inferior
34408 @subheading Synopsis
34414 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34415 inferior is not associated with any executable. Such association may
34416 be established with the @samp{-file-exec-and-symbols} command
34417 (@pxref{GDB/MI File Commands}). The command response has a single
34418 field, @samp{inferior}, whose value is the identifier of the
34419 thread group corresponding to the new inferior.
34421 @subheading Example
34426 ^done,inferior="i3"
34429 @subheading The @code{-interpreter-exec} Command
34430 @findex -interpreter-exec
34432 @subheading Synopsis
34435 -interpreter-exec @var{interpreter} @var{command}
34437 @anchor{-interpreter-exec}
34439 Execute the specified @var{command} in the given @var{interpreter}.
34441 @subheading @value{GDBN} Command
34443 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34445 @subheading Example
34449 -interpreter-exec console "break main"
34450 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34451 &"During symbol reading, bad structure-type format.\n"
34452 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34457 @subheading The @code{-inferior-tty-set} Command
34458 @findex -inferior-tty-set
34460 @subheading Synopsis
34463 -inferior-tty-set /dev/pts/1
34466 Set terminal for future runs of the program being debugged.
34468 @subheading @value{GDBN} Command
34470 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34472 @subheading Example
34476 -inferior-tty-set /dev/pts/1
34481 @subheading The @code{-inferior-tty-show} Command
34482 @findex -inferior-tty-show
34484 @subheading Synopsis
34490 Show terminal for future runs of program being debugged.
34492 @subheading @value{GDBN} Command
34494 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34496 @subheading Example
34500 -inferior-tty-set /dev/pts/1
34504 ^done,inferior_tty_terminal="/dev/pts/1"
34508 @subheading The @code{-enable-timings} Command
34509 @findex -enable-timings
34511 @subheading Synopsis
34514 -enable-timings [yes | no]
34517 Toggle the printing of the wallclock, user and system times for an MI
34518 command as a field in its output. This command is to help frontend
34519 developers optimize the performance of their code. No argument is
34520 equivalent to @samp{yes}.
34522 @subheading @value{GDBN} Command
34526 @subheading Example
34534 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34535 addr="0x080484ed",func="main",file="myprog.c",
34536 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34538 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34546 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34547 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34548 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34549 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34553 @subheading The @code{-complete} Command
34556 @subheading Synopsis
34559 -complete @var{command}
34562 Show a list of completions for partially typed CLI @var{command}.
34564 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
34565 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
34566 because @value{GDBN} is used remotely via a SSH connection.
34570 The result consists of two or three fields:
34574 This field contains the completed @var{command}. If @var{command}
34575 has no known completions, this field is omitted.
34578 This field contains a (possibly empty) array of matches. It is always present.
34580 @item max_completions_reached
34581 This field contains @code{1} if number of known completions is above
34582 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
34583 @code{0}. It is always present.
34587 @subheading @value{GDBN} Command
34589 The corresponding @value{GDBN} command is @samp{complete}.
34591 @subheading Example
34596 ^done,completion="break",
34597 matches=["break","break-range"],
34598 max_completions_reached="0"
34601 ^done,completion="b ma",
34602 matches=["b madvise","b main"],max_completions_reached="0"
34604 -complete "b push_b"
34605 ^done,completion="b push_back(",
34607 "b A::push_back(void*)",
34608 "b std::string::push_back(char)",
34609 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
34610 max_completions_reached="0"
34612 -complete "nonexist"
34613 ^done,matches=[],max_completions_reached="0"
34619 @chapter @value{GDBN} Annotations
34621 This chapter describes annotations in @value{GDBN}. Annotations were
34622 designed to interface @value{GDBN} to graphical user interfaces or other
34623 similar programs which want to interact with @value{GDBN} at a
34624 relatively high level.
34626 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34630 This is Edition @value{EDITION}, @value{DATE}.
34634 * Annotations Overview:: What annotations are; the general syntax.
34635 * Server Prefix:: Issuing a command without affecting user state.
34636 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34637 * Errors:: Annotations for error messages.
34638 * Invalidation:: Some annotations describe things now invalid.
34639 * Annotations for Running::
34640 Whether the program is running, how it stopped, etc.
34641 * Source Annotations:: Annotations describing source code.
34644 @node Annotations Overview
34645 @section What is an Annotation?
34646 @cindex annotations
34648 Annotations start with a newline character, two @samp{control-z}
34649 characters, and the name of the annotation. If there is no additional
34650 information associated with this annotation, the name of the annotation
34651 is followed immediately by a newline. If there is additional
34652 information, the name of the annotation is followed by a space, the
34653 additional information, and a newline. The additional information
34654 cannot contain newline characters.
34656 Any output not beginning with a newline and two @samp{control-z}
34657 characters denotes literal output from @value{GDBN}. Currently there is
34658 no need for @value{GDBN} to output a newline followed by two
34659 @samp{control-z} characters, but if there was such a need, the
34660 annotations could be extended with an @samp{escape} annotation which
34661 means those three characters as output.
34663 The annotation @var{level}, which is specified using the
34664 @option{--annotate} command line option (@pxref{Mode Options}), controls
34665 how much information @value{GDBN} prints together with its prompt,
34666 values of expressions, source lines, and other types of output. Level 0
34667 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34668 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34669 for programs that control @value{GDBN}, and level 2 annotations have
34670 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34671 Interface, annotate, GDB's Obsolete Annotations}).
34674 @kindex set annotate
34675 @item set annotate @var{level}
34676 The @value{GDBN} command @code{set annotate} sets the level of
34677 annotations to the specified @var{level}.
34679 @item show annotate
34680 @kindex show annotate
34681 Show the current annotation level.
34684 This chapter describes level 3 annotations.
34686 A simple example of starting up @value{GDBN} with annotations is:
34689 $ @kbd{gdb --annotate=3}
34691 Copyright 2003 Free Software Foundation, Inc.
34692 GDB is free software, covered by the GNU General Public License,
34693 and you are welcome to change it and/or distribute copies of it
34694 under certain conditions.
34695 Type "show copying" to see the conditions.
34696 There is absolutely no warranty for GDB. Type "show warranty"
34698 This GDB was configured as "i386-pc-linux-gnu"
34709 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34710 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34711 denotes a @samp{control-z} character) are annotations; the rest is
34712 output from @value{GDBN}.
34714 @node Server Prefix
34715 @section The Server Prefix
34716 @cindex server prefix
34718 If you prefix a command with @samp{server } then it will not affect
34719 the command history, nor will it affect @value{GDBN}'s notion of which
34720 command to repeat if @key{RET} is pressed on a line by itself. This
34721 means that commands can be run behind a user's back by a front-end in
34722 a transparent manner.
34724 The @code{server } prefix does not affect the recording of values into
34725 the value history; to print a value without recording it into the
34726 value history, use the @code{output} command instead of the
34727 @code{print} command.
34729 Using this prefix also disables confirmation requests
34730 (@pxref{confirmation requests}).
34733 @section Annotation for @value{GDBN} Input
34735 @cindex annotations for prompts
34736 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34737 to know when to send output, when the output from a given command is
34740 Different kinds of input each have a different @dfn{input type}. Each
34741 input type has three annotations: a @code{pre-} annotation, which
34742 denotes the beginning of any prompt which is being output, a plain
34743 annotation, which denotes the end of the prompt, and then a @code{post-}
34744 annotation which denotes the end of any echo which may (or may not) be
34745 associated with the input. For example, the @code{prompt} input type
34746 features the following annotations:
34754 The input types are
34757 @findex pre-prompt annotation
34758 @findex prompt annotation
34759 @findex post-prompt annotation
34761 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34763 @findex pre-commands annotation
34764 @findex commands annotation
34765 @findex post-commands annotation
34767 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34768 command. The annotations are repeated for each command which is input.
34770 @findex pre-overload-choice annotation
34771 @findex overload-choice annotation
34772 @findex post-overload-choice annotation
34773 @item overload-choice
34774 When @value{GDBN} wants the user to select between various overloaded functions.
34776 @findex pre-query annotation
34777 @findex query annotation
34778 @findex post-query annotation
34780 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34782 @findex pre-prompt-for-continue annotation
34783 @findex prompt-for-continue annotation
34784 @findex post-prompt-for-continue annotation
34785 @item prompt-for-continue
34786 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34787 expect this to work well; instead use @code{set height 0} to disable
34788 prompting. This is because the counting of lines is buggy in the
34789 presence of annotations.
34794 @cindex annotations for errors, warnings and interrupts
34796 @findex quit annotation
34801 This annotation occurs right before @value{GDBN} responds to an interrupt.
34803 @findex error annotation
34808 This annotation occurs right before @value{GDBN} responds to an error.
34810 Quit and error annotations indicate that any annotations which @value{GDBN} was
34811 in the middle of may end abruptly. For example, if a
34812 @code{value-history-begin} annotation is followed by a @code{error}, one
34813 cannot expect to receive the matching @code{value-history-end}. One
34814 cannot expect not to receive it either, however; an error annotation
34815 does not necessarily mean that @value{GDBN} is immediately returning all the way
34818 @findex error-begin annotation
34819 A quit or error annotation may be preceded by
34825 Any output between that and the quit or error annotation is the error
34828 Warning messages are not yet annotated.
34829 @c If we want to change that, need to fix warning(), type_error(),
34830 @c range_error(), and possibly other places.
34833 @section Invalidation Notices
34835 @cindex annotations for invalidation messages
34836 The following annotations say that certain pieces of state may have
34840 @findex frames-invalid annotation
34841 @item ^Z^Zframes-invalid
34843 The frames (for example, output from the @code{backtrace} command) may
34846 @findex breakpoints-invalid annotation
34847 @item ^Z^Zbreakpoints-invalid
34849 The breakpoints may have changed. For example, the user just added or
34850 deleted a breakpoint.
34853 @node Annotations for Running
34854 @section Running the Program
34855 @cindex annotations for running programs
34857 @findex starting annotation
34858 @findex stopping annotation
34859 When the program starts executing due to a @value{GDBN} command such as
34860 @code{step} or @code{continue},
34866 is output. When the program stops,
34872 is output. Before the @code{stopped} annotation, a variety of
34873 annotations describe how the program stopped.
34876 @findex exited annotation
34877 @item ^Z^Zexited @var{exit-status}
34878 The program exited, and @var{exit-status} is the exit status (zero for
34879 successful exit, otherwise nonzero).
34881 @findex signalled annotation
34882 @findex signal-name annotation
34883 @findex signal-name-end annotation
34884 @findex signal-string annotation
34885 @findex signal-string-end annotation
34886 @item ^Z^Zsignalled
34887 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34888 annotation continues:
34894 ^Z^Zsignal-name-end
34898 ^Z^Zsignal-string-end
34903 where @var{name} is the name of the signal, such as @code{SIGILL} or
34904 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34905 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34906 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34907 user's benefit and have no particular format.
34909 @findex signal annotation
34911 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34912 just saying that the program received the signal, not that it was
34913 terminated with it.
34915 @findex breakpoint annotation
34916 @item ^Z^Zbreakpoint @var{number}
34917 The program hit breakpoint number @var{number}.
34919 @findex watchpoint annotation
34920 @item ^Z^Zwatchpoint @var{number}
34921 The program hit watchpoint number @var{number}.
34924 @node Source Annotations
34925 @section Displaying Source
34926 @cindex annotations for source display
34928 @findex source annotation
34929 The following annotation is used instead of displaying source code:
34932 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34935 where @var{filename} is an absolute file name indicating which source
34936 file, @var{line} is the line number within that file (where 1 is the
34937 first line in the file), @var{character} is the character position
34938 within the file (where 0 is the first character in the file) (for most
34939 debug formats this will necessarily point to the beginning of a line),
34940 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34941 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34942 @var{addr} is the address in the target program associated with the
34943 source which is being displayed. The @var{addr} is in the form @samp{0x}
34944 followed by one or more lowercase hex digits (note that this does not
34945 depend on the language).
34947 @node JIT Interface
34948 @chapter JIT Compilation Interface
34949 @cindex just-in-time compilation
34950 @cindex JIT compilation interface
34952 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34953 interface. A JIT compiler is a program or library that generates native
34954 executable code at runtime and executes it, usually in order to achieve good
34955 performance while maintaining platform independence.
34957 Programs that use JIT compilation are normally difficult to debug because
34958 portions of their code are generated at runtime, instead of being loaded from
34959 object files, which is where @value{GDBN} normally finds the program's symbols
34960 and debug information. In order to debug programs that use JIT compilation,
34961 @value{GDBN} has an interface that allows the program to register in-memory
34962 symbol files with @value{GDBN} at runtime.
34964 If you are using @value{GDBN} to debug a program that uses this interface, then
34965 it should work transparently so long as you have not stripped the binary. If
34966 you are developing a JIT compiler, then the interface is documented in the rest
34967 of this chapter. At this time, the only known client of this interface is the
34970 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34971 JIT compiler communicates with @value{GDBN} by writing data into a global
34972 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34973 attaches, it reads a linked list of symbol files from the global variable to
34974 find existing code, and puts a breakpoint in the function so that it can find
34975 out about additional code.
34978 * Declarations:: Relevant C struct declarations
34979 * Registering Code:: Steps to register code
34980 * Unregistering Code:: Steps to unregister code
34981 * Custom Debug Info:: Emit debug information in a custom format
34985 @section JIT Declarations
34987 These are the relevant struct declarations that a C program should include to
34988 implement the interface:
34998 struct jit_code_entry
35000 struct jit_code_entry *next_entry;
35001 struct jit_code_entry *prev_entry;
35002 const char *symfile_addr;
35003 uint64_t symfile_size;
35006 struct jit_descriptor
35009 /* This type should be jit_actions_t, but we use uint32_t
35010 to be explicit about the bitwidth. */
35011 uint32_t action_flag;
35012 struct jit_code_entry *relevant_entry;
35013 struct jit_code_entry *first_entry;
35016 /* GDB puts a breakpoint in this function. */
35017 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35019 /* Make sure to specify the version statically, because the
35020 debugger may check the version before we can set it. */
35021 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35024 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35025 modifications to this global data properly, which can easily be done by putting
35026 a global mutex around modifications to these structures.
35028 @node Registering Code
35029 @section Registering Code
35031 To register code with @value{GDBN}, the JIT should follow this protocol:
35035 Generate an object file in memory with symbols and other desired debug
35036 information. The file must include the virtual addresses of the sections.
35039 Create a code entry for the file, which gives the start and size of the symbol
35043 Add it to the linked list in the JIT descriptor.
35046 Point the relevant_entry field of the descriptor at the entry.
35049 Set @code{action_flag} to @code{JIT_REGISTER} and call
35050 @code{__jit_debug_register_code}.
35053 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35054 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35055 new code. However, the linked list must still be maintained in order to allow
35056 @value{GDBN} to attach to a running process and still find the symbol files.
35058 @node Unregistering Code
35059 @section Unregistering Code
35061 If code is freed, then the JIT should use the following protocol:
35065 Remove the code entry corresponding to the code from the linked list.
35068 Point the @code{relevant_entry} field of the descriptor at the code entry.
35071 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35072 @code{__jit_debug_register_code}.
35075 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35076 and the JIT will leak the memory used for the associated symbol files.
35078 @node Custom Debug Info
35079 @section Custom Debug Info
35080 @cindex custom JIT debug info
35081 @cindex JIT debug info reader
35083 Generating debug information in platform-native file formats (like ELF
35084 or COFF) may be an overkill for JIT compilers; especially if all the
35085 debug info is used for is displaying a meaningful backtrace. The
35086 issue can be resolved by having the JIT writers decide on a debug info
35087 format and also provide a reader that parses the debug info generated
35088 by the JIT compiler. This section gives a brief overview on writing
35089 such a parser. More specific details can be found in the source file
35090 @file{gdb/jit-reader.in}, which is also installed as a header at
35091 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35093 The reader is implemented as a shared object (so this functionality is
35094 not available on platforms which don't allow loading shared objects at
35095 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35096 @code{jit-reader-unload} are provided, to be used to load and unload
35097 the readers from a preconfigured directory. Once loaded, the shared
35098 object is used the parse the debug information emitted by the JIT
35102 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35103 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35106 @node Using JIT Debug Info Readers
35107 @subsection Using JIT Debug Info Readers
35108 @kindex jit-reader-load
35109 @kindex jit-reader-unload
35111 Readers can be loaded and unloaded using the @code{jit-reader-load}
35112 and @code{jit-reader-unload} commands.
35115 @item jit-reader-load @var{reader}
35116 Load the JIT reader named @var{reader}, which is a shared
35117 object specified as either an absolute or a relative file name. In
35118 the latter case, @value{GDBN} will try to load the reader from a
35119 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35120 system (here @var{libdir} is the system library directory, often
35121 @file{/usr/local/lib}).
35123 Only one reader can be active at a time; trying to load a second
35124 reader when one is already loaded will result in @value{GDBN}
35125 reporting an error. A new JIT reader can be loaded by first unloading
35126 the current one using @code{jit-reader-unload} and then invoking
35127 @code{jit-reader-load}.
35129 @item jit-reader-unload
35130 Unload the currently loaded JIT reader.
35134 @node Writing JIT Debug Info Readers
35135 @subsection Writing JIT Debug Info Readers
35136 @cindex writing JIT debug info readers
35138 As mentioned, a reader is essentially a shared object conforming to a
35139 certain ABI. This ABI is described in @file{jit-reader.h}.
35141 @file{jit-reader.h} defines the structures, macros and functions
35142 required to write a reader. It is installed (along with
35143 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35144 the system include directory.
35146 Readers need to be released under a GPL compatible license. A reader
35147 can be declared as released under such a license by placing the macro
35148 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35150 The entry point for readers is the symbol @code{gdb_init_reader},
35151 which is expected to be a function with the prototype
35153 @findex gdb_init_reader
35155 extern struct gdb_reader_funcs *gdb_init_reader (void);
35158 @cindex @code{struct gdb_reader_funcs}
35160 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35161 functions. These functions are executed to read the debug info
35162 generated by the JIT compiler (@code{read}), to unwind stack frames
35163 (@code{unwind}) and to create canonical frame IDs
35164 (@code{get_Frame_id}). It also has a callback that is called when the
35165 reader is being unloaded (@code{destroy}). The struct looks like this
35168 struct gdb_reader_funcs
35170 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35171 int reader_version;
35173 /* For use by the reader. */
35176 gdb_read_debug_info *read;
35177 gdb_unwind_frame *unwind;
35178 gdb_get_frame_id *get_frame_id;
35179 gdb_destroy_reader *destroy;
35183 @cindex @code{struct gdb_symbol_callbacks}
35184 @cindex @code{struct gdb_unwind_callbacks}
35186 The callbacks are provided with another set of callbacks by
35187 @value{GDBN} to do their job. For @code{read}, these callbacks are
35188 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35189 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35190 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35191 files and new symbol tables inside those object files. @code{struct
35192 gdb_unwind_callbacks} has callbacks to read registers off the current
35193 frame and to write out the values of the registers in the previous
35194 frame. Both have a callback (@code{target_read}) to read bytes off the
35195 target's address space.
35197 @node In-Process Agent
35198 @chapter In-Process Agent
35199 @cindex debugging agent
35200 The traditional debugging model is conceptually low-speed, but works fine,
35201 because most bugs can be reproduced in debugging-mode execution. However,
35202 as multi-core or many-core processors are becoming mainstream, and
35203 multi-threaded programs become more and more popular, there should be more
35204 and more bugs that only manifest themselves at normal-mode execution, for
35205 example, thread races, because debugger's interference with the program's
35206 timing may conceal the bugs. On the other hand, in some applications,
35207 it is not feasible for the debugger to interrupt the program's execution
35208 long enough for the developer to learn anything helpful about its behavior.
35209 If the program's correctness depends on its real-time behavior, delays
35210 introduced by a debugger might cause the program to fail, even when the
35211 code itself is correct. It is useful to be able to observe the program's
35212 behavior without interrupting it.
35214 Therefore, traditional debugging model is too intrusive to reproduce
35215 some bugs. In order to reduce the interference with the program, we can
35216 reduce the number of operations performed by debugger. The
35217 @dfn{In-Process Agent}, a shared library, is running within the same
35218 process with inferior, and is able to perform some debugging operations
35219 itself. As a result, debugger is only involved when necessary, and
35220 performance of debugging can be improved accordingly. Note that
35221 interference with program can be reduced but can't be removed completely,
35222 because the in-process agent will still stop or slow down the program.
35224 The in-process agent can interpret and execute Agent Expressions
35225 (@pxref{Agent Expressions}) during performing debugging operations. The
35226 agent expressions can be used for different purposes, such as collecting
35227 data in tracepoints, and condition evaluation in breakpoints.
35229 @anchor{Control Agent}
35230 You can control whether the in-process agent is used as an aid for
35231 debugging with the following commands:
35234 @kindex set agent on
35236 Causes the in-process agent to perform some operations on behalf of the
35237 debugger. Just which operations requested by the user will be done
35238 by the in-process agent depends on the its capabilities. For example,
35239 if you request to evaluate breakpoint conditions in the in-process agent,
35240 and the in-process agent has such capability as well, then breakpoint
35241 conditions will be evaluated in the in-process agent.
35243 @kindex set agent off
35244 @item set agent off
35245 Disables execution of debugging operations by the in-process agent. All
35246 of the operations will be performed by @value{GDBN}.
35250 Display the current setting of execution of debugging operations by
35251 the in-process agent.
35255 * In-Process Agent Protocol::
35258 @node In-Process Agent Protocol
35259 @section In-Process Agent Protocol
35260 @cindex in-process agent protocol
35262 The in-process agent is able to communicate with both @value{GDBN} and
35263 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35264 used for communications between @value{GDBN} or GDBserver and the IPA.
35265 In general, @value{GDBN} or GDBserver sends commands
35266 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35267 in-process agent replies back with the return result of the command, or
35268 some other information. The data sent to in-process agent is composed
35269 of primitive data types, such as 4-byte or 8-byte type, and composite
35270 types, which are called objects (@pxref{IPA Protocol Objects}).
35273 * IPA Protocol Objects::
35274 * IPA Protocol Commands::
35277 @node IPA Protocol Objects
35278 @subsection IPA Protocol Objects
35279 @cindex ipa protocol objects
35281 The commands sent to and results received from agent may contain some
35282 complex data types called @dfn{objects}.
35284 The in-process agent is running on the same machine with @value{GDBN}
35285 or GDBserver, so it doesn't have to handle as much differences between
35286 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35287 However, there are still some differences of two ends in two processes:
35291 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35292 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35294 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35295 GDBserver is compiled with one, and in-process agent is compiled with
35299 Here are the IPA Protocol Objects:
35303 agent expression object. It represents an agent expression
35304 (@pxref{Agent Expressions}).
35305 @anchor{agent expression object}
35307 tracepoint action object. It represents a tracepoint action
35308 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35309 memory, static trace data and to evaluate expression.
35310 @anchor{tracepoint action object}
35312 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35313 @anchor{tracepoint object}
35317 The following table describes important attributes of each IPA protocol
35320 @multitable @columnfractions .30 .20 .50
35321 @headitem Name @tab Size @tab Description
35322 @item @emph{agent expression object} @tab @tab
35323 @item length @tab 4 @tab length of bytes code
35324 @item byte code @tab @var{length} @tab contents of byte code
35325 @item @emph{tracepoint action for collecting memory} @tab @tab
35326 @item 'M' @tab 1 @tab type of tracepoint action
35327 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35328 address of the lowest byte to collect, otherwise @var{addr} is the offset
35329 of @var{basereg} for memory collecting.
35330 @item len @tab 8 @tab length of memory for collecting
35331 @item basereg @tab 4 @tab the register number containing the starting
35332 memory address for collecting.
35333 @item @emph{tracepoint action for collecting registers} @tab @tab
35334 @item 'R' @tab 1 @tab type of tracepoint action
35335 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35336 @item 'L' @tab 1 @tab type of tracepoint action
35337 @item @emph{tracepoint action for expression evaluation} @tab @tab
35338 @item 'X' @tab 1 @tab type of tracepoint action
35339 @item agent expression @tab length of @tab @ref{agent expression object}
35340 @item @emph{tracepoint object} @tab @tab
35341 @item number @tab 4 @tab number of tracepoint
35342 @item address @tab 8 @tab address of tracepoint inserted on
35343 @item type @tab 4 @tab type of tracepoint
35344 @item enabled @tab 1 @tab enable or disable of tracepoint
35345 @item step_count @tab 8 @tab step
35346 @item pass_count @tab 8 @tab pass
35347 @item numactions @tab 4 @tab number of tracepoint actions
35348 @item hit count @tab 8 @tab hit count
35349 @item trace frame usage @tab 8 @tab trace frame usage
35350 @item compiled_cond @tab 8 @tab compiled condition
35351 @item orig_size @tab 8 @tab orig size
35352 @item condition @tab 4 if condition is NULL otherwise length of
35353 @ref{agent expression object}
35354 @tab zero if condition is NULL, otherwise is
35355 @ref{agent expression object}
35356 @item actions @tab variable
35357 @tab numactions number of @ref{tracepoint action object}
35360 @node IPA Protocol Commands
35361 @subsection IPA Protocol Commands
35362 @cindex ipa protocol commands
35364 The spaces in each command are delimiters to ease reading this commands
35365 specification. They don't exist in real commands.
35369 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35370 Installs a new fast tracepoint described by @var{tracepoint_object}
35371 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35372 head of @dfn{jumppad}, which is used to jump to data collection routine
35377 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35378 @var{target_address} is address of tracepoint in the inferior.
35379 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35380 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35381 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35382 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35389 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35390 is about to kill inferiors.
35398 @item probe_marker_at:@var{address}
35399 Asks in-process agent to probe the marker at @var{address}.
35406 @item unprobe_marker_at:@var{address}
35407 Asks in-process agent to unprobe the marker at @var{address}.
35411 @chapter Reporting Bugs in @value{GDBN}
35412 @cindex bugs in @value{GDBN}
35413 @cindex reporting bugs in @value{GDBN}
35415 Your bug reports play an essential role in making @value{GDBN} reliable.
35417 Reporting a bug may help you by bringing a solution to your problem, or it
35418 may not. But in any case the principal function of a bug report is to help
35419 the entire community by making the next version of @value{GDBN} work better. Bug
35420 reports are your contribution to the maintenance of @value{GDBN}.
35422 In order for a bug report to serve its purpose, you must include the
35423 information that enables us to fix the bug.
35426 * Bug Criteria:: Have you found a bug?
35427 * Bug Reporting:: How to report bugs
35431 @section Have You Found a Bug?
35432 @cindex bug criteria
35434 If you are not sure whether you have found a bug, here are some guidelines:
35437 @cindex fatal signal
35438 @cindex debugger crash
35439 @cindex crash of debugger
35441 If the debugger gets a fatal signal, for any input whatever, that is a
35442 @value{GDBN} bug. Reliable debuggers never crash.
35444 @cindex error on valid input
35446 If @value{GDBN} produces an error message for valid input, that is a
35447 bug. (Note that if you're cross debugging, the problem may also be
35448 somewhere in the connection to the target.)
35450 @cindex invalid input
35452 If @value{GDBN} does not produce an error message for invalid input,
35453 that is a bug. However, you should note that your idea of
35454 ``invalid input'' might be our idea of ``an extension'' or ``support
35455 for traditional practice''.
35458 If you are an experienced user of debugging tools, your suggestions
35459 for improvement of @value{GDBN} are welcome in any case.
35462 @node Bug Reporting
35463 @section How to Report Bugs
35464 @cindex bug reports
35465 @cindex @value{GDBN} bugs, reporting
35467 A number of companies and individuals offer support for @sc{gnu} products.
35468 If you obtained @value{GDBN} from a support organization, we recommend you
35469 contact that organization first.
35471 You can find contact information for many support companies and
35472 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35474 @c should add a web page ref...
35477 @ifset BUGURL_DEFAULT
35478 In any event, we also recommend that you submit bug reports for
35479 @value{GDBN}. The preferred method is to submit them directly using
35480 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35481 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35484 @strong{Do not send bug reports to @samp{info-gdb}, or to
35485 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35486 not want to receive bug reports. Those that do have arranged to receive
35489 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35490 serves as a repeater. The mailing list and the newsgroup carry exactly
35491 the same messages. Often people think of posting bug reports to the
35492 newsgroup instead of mailing them. This appears to work, but it has one
35493 problem which can be crucial: a newsgroup posting often lacks a mail
35494 path back to the sender. Thus, if we need to ask for more information,
35495 we may be unable to reach you. For this reason, it is better to send
35496 bug reports to the mailing list.
35498 @ifclear BUGURL_DEFAULT
35499 In any event, we also recommend that you submit bug reports for
35500 @value{GDBN} to @value{BUGURL}.
35504 The fundamental principle of reporting bugs usefully is this:
35505 @strong{report all the facts}. If you are not sure whether to state a
35506 fact or leave it out, state it!
35508 Often people omit facts because they think they know what causes the
35509 problem and assume that some details do not matter. Thus, you might
35510 assume that the name of the variable you use in an example does not matter.
35511 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35512 stray memory reference which happens to fetch from the location where that
35513 name is stored in memory; perhaps, if the name were different, the contents
35514 of that location would fool the debugger into doing the right thing despite
35515 the bug. Play it safe and give a specific, complete example. That is the
35516 easiest thing for you to do, and the most helpful.
35518 Keep in mind that the purpose of a bug report is to enable us to fix the
35519 bug. It may be that the bug has been reported previously, but neither
35520 you nor we can know that unless your bug report is complete and
35523 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35524 bell?'' Those bug reports are useless, and we urge everyone to
35525 @emph{refuse to respond to them} except to chide the sender to report
35528 To enable us to fix the bug, you should include all these things:
35532 The version of @value{GDBN}. @value{GDBN} announces it if you start
35533 with no arguments; you can also print it at any time using @code{show
35536 Without this, we will not know whether there is any point in looking for
35537 the bug in the current version of @value{GDBN}.
35540 The type of machine you are using, and the operating system name and
35544 The details of the @value{GDBN} build-time configuration.
35545 @value{GDBN} shows these details if you invoke it with the
35546 @option{--configuration} command-line option, or if you type
35547 @code{show configuration} at @value{GDBN}'s prompt.
35550 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35551 ``@value{GCC}--2.8.1''.
35554 What compiler (and its version) was used to compile the program you are
35555 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35556 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35557 to get this information; for other compilers, see the documentation for
35561 The command arguments you gave the compiler to compile your example and
35562 observe the bug. For example, did you use @samp{-O}? To guarantee
35563 you will not omit something important, list them all. A copy of the
35564 Makefile (or the output from make) is sufficient.
35566 If we were to try to guess the arguments, we would probably guess wrong
35567 and then we might not encounter the bug.
35570 A complete input script, and all necessary source files, that will
35574 A description of what behavior you observe that you believe is
35575 incorrect. For example, ``It gets a fatal signal.''
35577 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35578 will certainly notice it. But if the bug is incorrect output, we might
35579 not notice unless it is glaringly wrong. You might as well not give us
35580 a chance to make a mistake.
35582 Even if the problem you experience is a fatal signal, you should still
35583 say so explicitly. Suppose something strange is going on, such as, your
35584 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35585 the C library on your system. (This has happened!) Your copy might
35586 crash and ours would not. If you told us to expect a crash, then when
35587 ours fails to crash, we would know that the bug was not happening for
35588 us. If you had not told us to expect a crash, then we would not be able
35589 to draw any conclusion from our observations.
35592 @cindex recording a session script
35593 To collect all this information, you can use a session recording program
35594 such as @command{script}, which is available on many Unix systems.
35595 Just run your @value{GDBN} session inside @command{script} and then
35596 include the @file{typescript} file with your bug report.
35598 Another way to record a @value{GDBN} session is to run @value{GDBN}
35599 inside Emacs and then save the entire buffer to a file.
35602 If you wish to suggest changes to the @value{GDBN} source, send us context
35603 diffs. If you even discuss something in the @value{GDBN} source, refer to
35604 it by context, not by line number.
35606 The line numbers in our development sources will not match those in your
35607 sources. Your line numbers would convey no useful information to us.
35611 Here are some things that are not necessary:
35615 A description of the envelope of the bug.
35617 Often people who encounter a bug spend a lot of time investigating
35618 which changes to the input file will make the bug go away and which
35619 changes will not affect it.
35621 This is often time consuming and not very useful, because the way we
35622 will find the bug is by running a single example under the debugger
35623 with breakpoints, not by pure deduction from a series of examples.
35624 We recommend that you save your time for something else.
35626 Of course, if you can find a simpler example to report @emph{instead}
35627 of the original one, that is a convenience for us. Errors in the
35628 output will be easier to spot, running under the debugger will take
35629 less time, and so on.
35631 However, simplification is not vital; if you do not want to do this,
35632 report the bug anyway and send us the entire test case you used.
35635 A patch for the bug.
35637 A patch for the bug does help us if it is a good one. But do not omit
35638 the necessary information, such as the test case, on the assumption that
35639 a patch is all we need. We might see problems with your patch and decide
35640 to fix the problem another way, or we might not understand it at all.
35642 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35643 construct an example that will make the program follow a certain path
35644 through the code. If you do not send us the example, we will not be able
35645 to construct one, so we will not be able to verify that the bug is fixed.
35647 And if we cannot understand what bug you are trying to fix, or why your
35648 patch should be an improvement, we will not install it. A test case will
35649 help us to understand.
35652 A guess about what the bug is or what it depends on.
35654 Such guesses are usually wrong. Even we cannot guess right about such
35655 things without first using the debugger to find the facts.
35658 @c The readline documentation is distributed with the readline code
35659 @c and consists of the two following files:
35662 @c Use -I with makeinfo to point to the appropriate directory,
35663 @c environment var TEXINPUTS with TeX.
35664 @ifclear SYSTEM_READLINE
35665 @include rluser.texi
35666 @include hsuser.texi
35670 @appendix In Memoriam
35672 The @value{GDBN} project mourns the loss of the following long-time
35677 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35678 to Free Software in general. Outside of @value{GDBN}, he was known in
35679 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35681 @item Michael Snyder
35682 Michael was one of the Global Maintainers of the @value{GDBN} project,
35683 with contributions recorded as early as 1996, until 2011. In addition
35684 to his day to day participation, he was a large driving force behind
35685 adding Reverse Debugging to @value{GDBN}.
35688 Beyond their technical contributions to the project, they were also
35689 enjoyable members of the Free Software Community. We will miss them.
35691 @node Formatting Documentation
35692 @appendix Formatting Documentation
35694 @cindex @value{GDBN} reference card
35695 @cindex reference card
35696 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35697 for printing with PostScript or Ghostscript, in the @file{gdb}
35698 subdirectory of the main source directory@footnote{In
35699 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35700 release.}. If you can use PostScript or Ghostscript with your printer,
35701 you can print the reference card immediately with @file{refcard.ps}.
35703 The release also includes the source for the reference card. You
35704 can format it, using @TeX{}, by typing:
35710 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35711 mode on US ``letter'' size paper;
35712 that is, on a sheet 11 inches wide by 8.5 inches
35713 high. You will need to specify this form of printing as an option to
35714 your @sc{dvi} output program.
35716 @cindex documentation
35718 All the documentation for @value{GDBN} comes as part of the machine-readable
35719 distribution. The documentation is written in Texinfo format, which is
35720 a documentation system that uses a single source file to produce both
35721 on-line information and a printed manual. You can use one of the Info
35722 formatting commands to create the on-line version of the documentation
35723 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35725 @value{GDBN} includes an already formatted copy of the on-line Info
35726 version of this manual in the @file{gdb} subdirectory. The main Info
35727 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35728 subordinate files matching @samp{gdb.info*} in the same directory. If
35729 necessary, you can print out these files, or read them with any editor;
35730 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35731 Emacs or the standalone @code{info} program, available as part of the
35732 @sc{gnu} Texinfo distribution.
35734 If you want to format these Info files yourself, you need one of the
35735 Info formatting programs, such as @code{texinfo-format-buffer} or
35738 If you have @code{makeinfo} installed, and are in the top level
35739 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35740 version @value{GDBVN}), you can make the Info file by typing:
35747 If you want to typeset and print copies of this manual, you need @TeX{},
35748 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35749 Texinfo definitions file.
35751 @TeX{} is a typesetting program; it does not print files directly, but
35752 produces output files called @sc{dvi} files. To print a typeset
35753 document, you need a program to print @sc{dvi} files. If your system
35754 has @TeX{} installed, chances are it has such a program. The precise
35755 command to use depends on your system; @kbd{lpr -d} is common; another
35756 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35757 require a file name without any extension or a @samp{.dvi} extension.
35759 @TeX{} also requires a macro definitions file called
35760 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35761 written in Texinfo format. On its own, @TeX{} cannot either read or
35762 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35763 and is located in the @file{gdb-@var{version-number}/texinfo}
35766 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35767 typeset and print this manual. First switch to the @file{gdb}
35768 subdirectory of the main source directory (for example, to
35769 @file{gdb-@value{GDBVN}/gdb}) and type:
35775 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35777 @node Installing GDB
35778 @appendix Installing @value{GDBN}
35779 @cindex installation
35782 * Requirements:: Requirements for building @value{GDBN}
35783 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35784 * Separate Objdir:: Compiling @value{GDBN} in another directory
35785 * Config Names:: Specifying names for hosts and targets
35786 * Configure Options:: Summary of options for configure
35787 * System-wide configuration:: Having a system-wide init file
35791 @section Requirements for Building @value{GDBN}
35792 @cindex building @value{GDBN}, requirements for
35794 Building @value{GDBN} requires various tools and packages to be available.
35795 Other packages will be used only if they are found.
35797 @heading Tools/Packages Necessary for Building @value{GDBN}
35799 @item C@t{++}11 compiler
35800 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35801 recent C@t{++}11 compiler, e.g.@: GCC.
35804 @value{GDBN}'s build system relies on features only found in the GNU
35805 make program. Other variants of @code{make} will not work.
35808 @heading Tools/Packages Optional for Building @value{GDBN}
35812 @value{GDBN} can use the Expat XML parsing library. This library may be
35813 included with your operating system distribution; if it is not, you
35814 can get the latest version from @url{http://expat.sourceforge.net}.
35815 The @file{configure} script will search for this library in several
35816 standard locations; if it is installed in an unusual path, you can
35817 use the @option{--with-libexpat-prefix} option to specify its location.
35823 Remote protocol memory maps (@pxref{Memory Map Format})
35825 Target descriptions (@pxref{Target Descriptions})
35827 Remote shared library lists (@xref{Library List Format},
35828 or alternatively @pxref{Library List Format for SVR4 Targets})
35830 MS-Windows shared libraries (@pxref{Shared Libraries})
35832 Traceframe info (@pxref{Traceframe Info Format})
35834 Branch trace (@pxref{Branch Trace Format},
35835 @pxref{Branch Trace Configuration Format})
35839 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35840 default, @value{GDBN} will be compiled if the Guile libraries are
35841 installed and are found by @file{configure}. You can use the
35842 @code{--with-guile} option to request Guile, and pass either the Guile
35843 version number or the file name of the relevant @code{pkg-config}
35844 program to choose a particular version of Guile.
35847 @value{GDBN}'s features related to character sets (@pxref{Character
35848 Sets}) require a functioning @code{iconv} implementation. If you are
35849 on a GNU system, then this is provided by the GNU C Library. Some
35850 other systems also provide a working @code{iconv}.
35852 If @value{GDBN} is using the @code{iconv} program which is installed
35853 in a non-standard place, you will need to tell @value{GDBN} where to
35854 find it. This is done with @option{--with-iconv-bin} which specifies
35855 the directory that contains the @code{iconv} program. This program is
35856 run in order to make a list of the available character sets.
35858 On systems without @code{iconv}, you can install GNU Libiconv. If
35859 Libiconv is installed in a standard place, @value{GDBN} will
35860 automatically use it if it is needed. If you have previously
35861 installed Libiconv in a non-standard place, you can use the
35862 @option{--with-libiconv-prefix} option to @file{configure}.
35864 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35865 arrange to build Libiconv if a directory named @file{libiconv} appears
35866 in the top-most source directory. If Libiconv is built this way, and
35867 if the operating system does not provide a suitable @code{iconv}
35868 implementation, then the just-built library will automatically be used
35869 by @value{GDBN}. One easy way to set this up is to download GNU
35870 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35871 source tree, and then rename the directory holding the Libiconv source
35872 code to @samp{libiconv}.
35875 @value{GDBN} can support debugging sections that are compressed with
35876 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35877 included with your operating system, you can find it in the xz package
35878 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35879 the usual place, then the @file{configure} script will use it
35880 automatically. If it is installed in an unusual path, you can use the
35881 @option{--with-lzma-prefix} option to specify its location.
35885 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35886 library. This library may be included with your operating system
35887 distribution; if it is not, you can get the latest version from
35888 @url{http://www.mpfr.org}. The @file{configure} script will search
35889 for this library in several standard locations; if it is installed
35890 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35891 option to specify its location.
35893 GNU MPFR is used to emulate target floating-point arithmetic during
35894 expression evaluation when the target uses different floating-point
35895 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35896 will fall back to using host floating-point arithmetic.
35899 @value{GDBN} can be scripted using Python language. @xref{Python}.
35900 By default, @value{GDBN} will be compiled if the Python libraries are
35901 installed and are found by @file{configure}. You can use the
35902 @code{--with-python} option to request Python, and pass either the
35903 file name of the relevant @code{python} executable, or the name of the
35904 directory in which Python is installed, to choose a particular
35905 installation of Python.
35908 @cindex compressed debug sections
35909 @value{GDBN} will use the @samp{zlib} library, if available, to read
35910 compressed debug sections. Some linkers, such as GNU gold, are capable
35911 of producing binaries with compressed debug sections. If @value{GDBN}
35912 is compiled with @samp{zlib}, it will be able to read the debug
35913 information in such binaries.
35915 The @samp{zlib} library is likely included with your operating system
35916 distribution; if it is not, you can get the latest version from
35917 @url{http://zlib.net}.
35920 @node Running Configure
35921 @section Invoking the @value{GDBN} @file{configure} Script
35922 @cindex configuring @value{GDBN}
35923 @value{GDBN} comes with a @file{configure} script that automates the process
35924 of preparing @value{GDBN} for installation; you can then use @code{make} to
35925 build the @code{gdb} program.
35927 @c irrelevant in info file; it's as current as the code it lives with.
35928 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35929 look at the @file{README} file in the sources; we may have improved the
35930 installation procedures since publishing this manual.}
35933 The @value{GDBN} distribution includes all the source code you need for
35934 @value{GDBN} in a single directory, whose name is usually composed by
35935 appending the version number to @samp{gdb}.
35937 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35938 @file{gdb-@value{GDBVN}} directory. That directory contains:
35941 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35942 script for configuring @value{GDBN} and all its supporting libraries
35944 @item gdb-@value{GDBVN}/gdb
35945 the source specific to @value{GDBN} itself
35947 @item gdb-@value{GDBVN}/bfd
35948 source for the Binary File Descriptor library
35950 @item gdb-@value{GDBVN}/include
35951 @sc{gnu} include files
35953 @item gdb-@value{GDBVN}/libiberty
35954 source for the @samp{-liberty} free software library
35956 @item gdb-@value{GDBVN}/opcodes
35957 source for the library of opcode tables and disassemblers
35959 @item gdb-@value{GDBVN}/readline
35960 source for the @sc{gnu} command-line interface
35963 There may be other subdirectories as well.
35965 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35966 from the @file{gdb-@var{version-number}} source directory, which in
35967 this example is the @file{gdb-@value{GDBVN}} directory.
35969 First switch to the @file{gdb-@var{version-number}} source directory
35970 if you are not already in it; then run @file{configure}. Pass the
35971 identifier for the platform on which @value{GDBN} will run as an
35977 cd gdb-@value{GDBVN}
35982 Running @samp{configure} and then running @code{make} builds the
35983 included supporting libraries, then @code{gdb} itself. The configured
35984 source files, and the binaries, are left in the corresponding source
35988 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35989 system does not recognize this automatically when you run a different
35990 shell, you may need to run @code{sh} on it explicitly:
35996 You should run the @file{configure} script from the top directory in the
35997 source tree, the @file{gdb-@var{version-number}} directory. If you run
35998 @file{configure} from one of the subdirectories, you will configure only
35999 that subdirectory. That is usually not what you want. In particular,
36000 if you run the first @file{configure} from the @file{gdb} subdirectory
36001 of the @file{gdb-@var{version-number}} directory, you will omit the
36002 configuration of @file{bfd}, @file{readline}, and other sibling
36003 directories of the @file{gdb} subdirectory. This leads to build errors
36004 about missing include files such as @file{bfd/bfd.h}.
36006 You can install @code{@value{GDBN}} anywhere. The best way to do this
36007 is to pass the @code{--prefix} option to @code{configure}, and then
36008 install it with @code{make install}.
36010 @node Separate Objdir
36011 @section Compiling @value{GDBN} in Another Directory
36013 If you want to run @value{GDBN} versions for several host or target machines,
36014 you need a different @code{gdb} compiled for each combination of
36015 host and target. @file{configure} is designed to make this easy by
36016 allowing you to generate each configuration in a separate subdirectory,
36017 rather than in the source directory. If your @code{make} program
36018 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36019 @code{make} in each of these directories builds the @code{gdb}
36020 program specified there.
36022 To build @code{gdb} in a separate directory, run @file{configure}
36023 with the @samp{--srcdir} option to specify where to find the source.
36024 (You also need to specify a path to find @file{configure}
36025 itself from your working directory. If the path to @file{configure}
36026 would be the same as the argument to @samp{--srcdir}, you can leave out
36027 the @samp{--srcdir} option; it is assumed.)
36029 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36030 separate directory for a Sun 4 like this:
36034 cd gdb-@value{GDBVN}
36037 ../gdb-@value{GDBVN}/configure
36042 When @file{configure} builds a configuration using a remote source
36043 directory, it creates a tree for the binaries with the same structure
36044 (and using the same names) as the tree under the source directory. In
36045 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36046 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36047 @file{gdb-sun4/gdb}.
36049 Make sure that your path to the @file{configure} script has just one
36050 instance of @file{gdb} in it. If your path to @file{configure} looks
36051 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36052 one subdirectory of @value{GDBN}, not the whole package. This leads to
36053 build errors about missing include files such as @file{bfd/bfd.h}.
36055 One popular reason to build several @value{GDBN} configurations in separate
36056 directories is to configure @value{GDBN} for cross-compiling (where
36057 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36058 programs that run on another machine---the @dfn{target}).
36059 You specify a cross-debugging target by
36060 giving the @samp{--target=@var{target}} option to @file{configure}.
36062 When you run @code{make} to build a program or library, you must run
36063 it in a configured directory---whatever directory you were in when you
36064 called @file{configure} (or one of its subdirectories).
36066 The @code{Makefile} that @file{configure} generates in each source
36067 directory also runs recursively. If you type @code{make} in a source
36068 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36069 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36070 will build all the required libraries, and then build GDB.
36072 When you have multiple hosts or targets configured in separate
36073 directories, you can run @code{make} on them in parallel (for example,
36074 if they are NFS-mounted on each of the hosts); they will not interfere
36078 @section Specifying Names for Hosts and Targets
36080 The specifications used for hosts and targets in the @file{configure}
36081 script are based on a three-part naming scheme, but some short predefined
36082 aliases are also supported. The full naming scheme encodes three pieces
36083 of information in the following pattern:
36086 @var{architecture}-@var{vendor}-@var{os}
36089 For example, you can use the alias @code{sun4} as a @var{host} argument,
36090 or as the value for @var{target} in a @code{--target=@var{target}}
36091 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36093 The @file{configure} script accompanying @value{GDBN} does not provide
36094 any query facility to list all supported host and target names or
36095 aliases. @file{configure} calls the Bourne shell script
36096 @code{config.sub} to map abbreviations to full names; you can read the
36097 script, if you wish, or you can use it to test your guesses on
36098 abbreviations---for example:
36101 % sh config.sub i386-linux
36103 % sh config.sub alpha-linux
36104 alpha-unknown-linux-gnu
36105 % sh config.sub hp9k700
36107 % sh config.sub sun4
36108 sparc-sun-sunos4.1.1
36109 % sh config.sub sun3
36110 m68k-sun-sunos4.1.1
36111 % sh config.sub i986v
36112 Invalid configuration `i986v': machine `i986v' not recognized
36116 @code{config.sub} is also distributed in the @value{GDBN} source
36117 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36119 @node Configure Options
36120 @section @file{configure} Options
36122 Here is a summary of the @file{configure} options and arguments that
36123 are most often useful for building @value{GDBN}. @file{configure}
36124 also has several other options not listed here. @inforef{Running
36125 configure scripts,,autoconf.info}, for a full
36126 explanation of @file{configure}.
36129 configure @r{[}--help@r{]}
36130 @r{[}--prefix=@var{dir}@r{]}
36131 @r{[}--exec-prefix=@var{dir}@r{]}
36132 @r{[}--srcdir=@var{dirname}@r{]}
36133 @r{[}--target=@var{target}@r{]}
36137 You may introduce options with a single @samp{-} rather than
36138 @samp{--} if you prefer; but you may abbreviate option names if you use
36143 Display a quick summary of how to invoke @file{configure}.
36145 @item --prefix=@var{dir}
36146 Configure the source to install programs and files under directory
36149 @item --exec-prefix=@var{dir}
36150 Configure the source to install programs under directory
36153 @c avoid splitting the warning from the explanation:
36155 @item --srcdir=@var{dirname}
36156 Use this option to make configurations in directories separate from the
36157 @value{GDBN} source directories. Among other things, you can use this to
36158 build (or maintain) several configurations simultaneously, in separate
36159 directories. @file{configure} writes configuration-specific files in
36160 the current directory, but arranges for them to use the source in the
36161 directory @var{dirname}. @file{configure} creates directories under
36162 the working directory in parallel to the source directories below
36165 @item --target=@var{target}
36166 Configure @value{GDBN} for cross-debugging programs running on the specified
36167 @var{target}. Without this option, @value{GDBN} is configured to debug
36168 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36170 There is no convenient way to generate a list of all available
36171 targets. Also see the @code{--enable-targets} option, below.
36174 There are many other options that are specific to @value{GDBN}. This
36175 lists just the most common ones; there are some very specialized
36176 options not described here.
36179 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36180 @itemx --enable-targets=all
36181 Configure @value{GDBN} for cross-debugging programs running on the
36182 specified list of targets. The special value @samp{all} configures
36183 @value{GDBN} for debugging programs running on any target it supports.
36185 @item --with-gdb-datadir=@var{path}
36186 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36187 here for certain supporting files or scripts. This defaults to the
36188 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36191 @item --with-relocated-sources=@var{dir}
36192 Sets up the default source path substitution rule so that directory
36193 names recorded in debug information will be automatically adjusted for
36194 any directory under @var{dir}. @var{dir} should be a subdirectory of
36195 @value{GDBN}'s configured prefix, the one mentioned in the
36196 @code{--prefix} or @code{--exec-prefix} options to configure. This
36197 option is useful if GDB is supposed to be moved to a different place
36200 @item --enable-64-bit-bfd
36201 Enable 64-bit support in BFD on 32-bit hosts.
36203 @item --disable-gdbmi
36204 Build @value{GDBN} without the GDB/MI machine interface
36208 Build @value{GDBN} with the text-mode full-screen user interface
36209 (TUI). Requires a curses library (ncurses and cursesX are also
36212 @item --with-curses
36213 Use the curses library instead of the termcap library, for text-mode
36214 terminal operations.
36216 @item --with-libunwind-ia64
36217 Use the libunwind library for unwinding function call stack on ia64
36218 target platforms. See http://www.nongnu.org/libunwind/index.html for
36221 @item --with-system-readline
36222 Use the readline library installed on the host, rather than the
36223 library supplied as part of @value{GDBN}.
36225 @item --with-system-zlib
36226 Use the zlib library installed on the host, rather than the library
36227 supplied as part of @value{GDBN}.
36230 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36231 default if libexpat is installed and found at configure time.) This
36232 library is used to read XML files supplied with @value{GDBN}. If it
36233 is unavailable, some features, such as remote protocol memory maps,
36234 target descriptions, and shared library lists, that are based on XML
36235 files, will not be available in @value{GDBN}. If your host does not
36236 have libexpat installed, you can get the latest version from
36237 `http://expat.sourceforge.net'.
36239 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36241 Build @value{GDBN} with GNU libiconv, a character set encoding
36242 conversion library. This is not done by default, as on GNU systems
36243 the @code{iconv} that is built in to the C library is sufficient. If
36244 your host does not have a working @code{iconv}, you can get the latest
36245 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36247 @value{GDBN}'s build system also supports building GNU libiconv as
36248 part of the overall build. @xref{Requirements}.
36251 Build @value{GDBN} with LZMA, a compression library. (Done by default
36252 if liblzma is installed and found at configure time.) LZMA is used by
36253 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36254 platforms using the ELF object file format. If your host does not
36255 have liblzma installed, you can get the latest version from
36256 `https://tukaani.org/xz/'.
36259 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36260 floating-point computation with correct rounding. (Done by default if
36261 GNU MPFR is installed and found at configure time.) This library is
36262 used to emulate target floating-point arithmetic during expression
36263 evaluation when the target uses different floating-point formats than
36264 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36265 to using host floating-point arithmetic. If your host does not have
36266 GNU MPFR installed, you can get the latest version from
36267 `http://www.mpfr.org'.
36269 @item --with-python@r{[}=@var{python}@r{]}
36270 Build @value{GDBN} with Python scripting support. (Done by default if
36271 libpython is present and found at configure time.) Python makes
36272 @value{GDBN} scripting much more powerful than the restricted CLI
36273 scripting language. If your host does not have Python installed, you
36274 can find it on `http://www.python.org/download/'. The oldest version
36275 of Python supported by GDB is 2.6. The optional argument @var{python}
36276 is used to find the Python headers and libraries. It can be either
36277 the name of a Python executable, or the name of the directory in which
36278 Python is installed.
36280 @item --with-guile[=GUILE]'
36281 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36282 if libguile is present and found at configure time.) If your host
36283 does not have Guile installed, you can find it at
36284 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36285 can be a version number, which will cause @code{configure} to try to
36286 use that version of Guile; or the file name of a @code{pkg-config}
36287 executable, which will be queried to find the information needed to
36288 compile and link against Guile.
36290 @item --without-included-regex
36291 Don't use the regex library included with @value{GDBN} (as part of the
36292 libiberty library). This is the default on hosts with version 2 of
36295 @item --with-sysroot=@var{dir}
36296 Use @var{dir} as the default system root directory for libraries whose
36297 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36298 @var{dir} can be modified at run time by using the @command{set
36299 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36300 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36301 default system root will be automatically adjusted if and when
36302 @value{GDBN} is moved to a different location.
36304 @item --with-system-gdbinit=@var{file}
36305 Configure @value{GDBN} to automatically load a system-wide init file.
36306 @var{file} should be an absolute file name. If @var{file} is in a
36307 directory under the configured prefix, and @value{GDBN} is moved to
36308 another location after being built, the location of the system-wide
36309 init file will be adjusted accordingly.
36311 @item --enable-build-warnings
36312 When building the @value{GDBN} sources, ask the compiler to warn about
36313 any code which looks even vaguely suspicious. It passes many
36314 different warning flags, depending on the exact version of the
36315 compiler you are using.
36317 @item --enable-werror
36318 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36319 to the compiler, which will fail the compilation if the compiler
36320 outputs any warning messages.
36322 @item --enable-ubsan
36323 Enable the GCC undefined behavior sanitizer. This is disabled by
36324 default, but passing @code{--enable-ubsan=yes} or
36325 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36326 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36327 It has a performance cost, so if you are looking at @value{GDBN}'s
36328 performance, you should disable it. The undefined behavior sanitizer
36329 was first introduced in GCC 4.9.
36332 @node System-wide configuration
36333 @section System-wide configuration and settings
36334 @cindex system-wide init file
36336 @value{GDBN} can be configured to have a system-wide init file;
36337 this file will be read and executed at startup (@pxref{Startup, , What
36338 @value{GDBN} does during startup}).
36340 Here is the corresponding configure option:
36343 @item --with-system-gdbinit=@var{file}
36344 Specify that the default location of the system-wide init file is
36348 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36349 it may be subject to relocation. Two possible cases:
36353 If the default location of this init file contains @file{$prefix},
36354 it will be subject to relocation. Suppose that the configure options
36355 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36356 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36357 init file is looked for as @file{$install/etc/gdbinit} instead of
36358 @file{$prefix/etc/gdbinit}.
36361 By contrast, if the default location does not contain the prefix,
36362 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36363 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36364 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36365 wherever @value{GDBN} is installed.
36368 If the configured location of the system-wide init file (as given by the
36369 @option{--with-system-gdbinit} option at configure time) is in the
36370 data-directory (as specified by @option{--with-gdb-datadir} at configure
36371 time) or in one of its subdirectories, then @value{GDBN} will look for the
36372 system-wide init file in the directory specified by the
36373 @option{--data-directory} command-line option.
36374 Note that the system-wide init file is only read once, during @value{GDBN}
36375 initialization. If the data-directory is changed after @value{GDBN} has
36376 started with the @code{set data-directory} command, the file will not be
36380 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36383 @node System-wide Configuration Scripts
36384 @subsection Installed System-wide Configuration Scripts
36385 @cindex system-wide configuration scripts
36387 The @file{system-gdbinit} directory, located inside the data-directory
36388 (as specified by @option{--with-gdb-datadir} at configure time) contains
36389 a number of scripts which can be used as system-wide init files. To
36390 automatically source those scripts at startup, @value{GDBN} should be
36391 configured with @option{--with-system-gdbinit}. Otherwise, any user
36392 should be able to source them by hand as needed.
36394 The following scripts are currently available:
36397 @item @file{elinos.py}
36399 @cindex ELinOS system-wide configuration script
36400 This script is useful when debugging a program on an ELinOS target.
36401 It takes advantage of the environment variables defined in a standard
36402 ELinOS environment in order to determine the location of the system
36403 shared libraries, and then sets the @samp{solib-absolute-prefix}
36404 and @samp{solib-search-path} variables appropriately.
36406 @item @file{wrs-linux.py}
36407 @pindex wrs-linux.py
36408 @cindex Wind River Linux system-wide configuration script
36409 This script is useful when debugging a program on a target running
36410 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36411 the host-side sysroot used by the target system.
36415 @node Maintenance Commands
36416 @appendix Maintenance Commands
36417 @cindex maintenance commands
36418 @cindex internal commands
36420 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36421 includes a number of commands intended for @value{GDBN} developers,
36422 that are not documented elsewhere in this manual. These commands are
36423 provided here for reference. (For commands that turn on debugging
36424 messages, see @ref{Debugging Output}.)
36427 @kindex maint agent
36428 @kindex maint agent-eval
36429 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36430 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36431 Translate the given @var{expression} into remote agent bytecodes.
36432 This command is useful for debugging the Agent Expression mechanism
36433 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36434 expression useful for data collection, such as by tracepoints, while
36435 @samp{maint agent-eval} produces an expression that evaluates directly
36436 to a result. For instance, a collection expression for @code{globa +
36437 globb} will include bytecodes to record four bytes of memory at each
36438 of the addresses of @code{globa} and @code{globb}, while discarding
36439 the result of the addition, while an evaluation expression will do the
36440 addition and return the sum.
36441 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36442 If not, generate remote agent bytecode for current frame PC address.
36444 @kindex maint agent-printf
36445 @item maint agent-printf @var{format},@var{expr},...
36446 Translate the given format string and list of argument expressions
36447 into remote agent bytecodes and display them as a disassembled list.
36448 This command is useful for debugging the agent version of dynamic
36449 printf (@pxref{Dynamic Printf}).
36451 @kindex maint info breakpoints
36452 @item @anchor{maint info breakpoints}maint info breakpoints
36453 Using the same format as @samp{info breakpoints}, display both the
36454 breakpoints you've set explicitly, and those @value{GDBN} is using for
36455 internal purposes. Internal breakpoints are shown with negative
36456 breakpoint numbers. The type column identifies what kind of breakpoint
36461 Normal, explicitly set breakpoint.
36464 Normal, explicitly set watchpoint.
36467 Internal breakpoint, used to handle correctly stepping through
36468 @code{longjmp} calls.
36470 @item longjmp resume
36471 Internal breakpoint at the target of a @code{longjmp}.
36474 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36477 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36480 Shared library events.
36484 @kindex maint info btrace
36485 @item maint info btrace
36486 Pint information about raw branch tracing data.
36488 @kindex maint btrace packet-history
36489 @item maint btrace packet-history
36490 Print the raw branch trace packets that are used to compute the
36491 execution history for the @samp{record btrace} command. Both the
36492 information and the format in which it is printed depend on the btrace
36497 For the BTS recording format, print a list of blocks of sequential
36498 code. For each block, the following information is printed:
36502 Newer blocks have higher numbers. The oldest block has number zero.
36503 @item Lowest @samp{PC}
36504 @item Highest @samp{PC}
36508 For the Intel Processor Trace recording format, print a list of
36509 Intel Processor Trace packets. For each packet, the following
36510 information is printed:
36513 @item Packet number
36514 Newer packets have higher numbers. The oldest packet has number zero.
36516 The packet's offset in the trace stream.
36517 @item Packet opcode and payload
36521 @kindex maint btrace clear-packet-history
36522 @item maint btrace clear-packet-history
36523 Discards the cached packet history printed by the @samp{maint btrace
36524 packet-history} command. The history will be computed again when
36527 @kindex maint btrace clear
36528 @item maint btrace clear
36529 Discard the branch trace data. The data will be fetched anew and the
36530 branch trace will be recomputed when needed.
36532 This implicitly truncates the branch trace to a single branch trace
36533 buffer. When updating branch trace incrementally, the branch trace
36534 available to @value{GDBN} may be bigger than a single branch trace
36537 @kindex maint set btrace pt skip-pad
36538 @item maint set btrace pt skip-pad
36539 @kindex maint show btrace pt skip-pad
36540 @item maint show btrace pt skip-pad
36541 Control whether @value{GDBN} will skip PAD packets when computing the
36544 @kindex set displaced-stepping
36545 @kindex show displaced-stepping
36546 @cindex displaced stepping support
36547 @cindex out-of-line single-stepping
36548 @item set displaced-stepping
36549 @itemx show displaced-stepping
36550 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36551 if the target supports it. Displaced stepping is a way to single-step
36552 over breakpoints without removing them from the inferior, by executing
36553 an out-of-line copy of the instruction that was originally at the
36554 breakpoint location. It is also known as out-of-line single-stepping.
36557 @item set displaced-stepping on
36558 If the target architecture supports it, @value{GDBN} will use
36559 displaced stepping to step over breakpoints.
36561 @item set displaced-stepping off
36562 @value{GDBN} will not use displaced stepping to step over breakpoints,
36563 even if such is supported by the target architecture.
36565 @cindex non-stop mode, and @samp{set displaced-stepping}
36566 @item set displaced-stepping auto
36567 This is the default mode. @value{GDBN} will use displaced stepping
36568 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36569 architecture supports displaced stepping.
36572 @kindex maint check-psymtabs
36573 @item maint check-psymtabs
36574 Check the consistency of currently expanded psymtabs versus symtabs.
36575 Use this to check, for example, whether a symbol is in one but not the other.
36577 @kindex maint check-symtabs
36578 @item maint check-symtabs
36579 Check the consistency of currently expanded symtabs.
36581 @kindex maint expand-symtabs
36582 @item maint expand-symtabs [@var{regexp}]
36583 Expand symbol tables.
36584 If @var{regexp} is specified, only expand symbol tables for file
36585 names matching @var{regexp}.
36587 @kindex maint set catch-demangler-crashes
36588 @kindex maint show catch-demangler-crashes
36589 @cindex demangler crashes
36590 @item maint set catch-demangler-crashes [on|off]
36591 @itemx maint show catch-demangler-crashes
36592 Control whether @value{GDBN} should attempt to catch crashes in the
36593 symbol name demangler. The default is to attempt to catch crashes.
36594 If enabled, the first time a crash is caught, a core file is created,
36595 the offending symbol is displayed and the user is presented with the
36596 option to terminate the current session.
36598 @kindex maint cplus first_component
36599 @item maint cplus first_component @var{name}
36600 Print the first C@t{++} class/namespace component of @var{name}.
36602 @kindex maint cplus namespace
36603 @item maint cplus namespace
36604 Print the list of possible C@t{++} namespaces.
36606 @kindex maint deprecate
36607 @kindex maint undeprecate
36608 @cindex deprecated commands
36609 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36610 @itemx maint undeprecate @var{command}
36611 Deprecate or undeprecate the named @var{command}. Deprecated commands
36612 cause @value{GDBN} to issue a warning when you use them. The optional
36613 argument @var{replacement} says which newer command should be used in
36614 favor of the deprecated one; if it is given, @value{GDBN} will mention
36615 the replacement as part of the warning.
36617 @kindex maint dump-me
36618 @item maint dump-me
36619 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36620 Cause a fatal signal in the debugger and force it to dump its core.
36621 This is supported only on systems which support aborting a program
36622 with the @code{SIGQUIT} signal.
36624 @kindex maint internal-error
36625 @kindex maint internal-warning
36626 @kindex maint demangler-warning
36627 @cindex demangler crashes
36628 @item maint internal-error @r{[}@var{message-text}@r{]}
36629 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36630 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36632 Cause @value{GDBN} to call the internal function @code{internal_error},
36633 @code{internal_warning} or @code{demangler_warning} and hence behave
36634 as though an internal problem has been detected. In addition to
36635 reporting the internal problem, these functions give the user the
36636 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36637 and @code{internal_warning}) create a core file of the current
36638 @value{GDBN} session.
36640 These commands take an optional parameter @var{message-text} that is
36641 used as the text of the error or warning message.
36643 Here's an example of using @code{internal-error}:
36646 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36647 @dots{}/maint.c:121: internal-error: testing, 1, 2
36648 A problem internal to GDB has been detected. Further
36649 debugging may prove unreliable.
36650 Quit this debugging session? (y or n) @kbd{n}
36651 Create a core file? (y or n) @kbd{n}
36655 @cindex @value{GDBN} internal error
36656 @cindex internal errors, control of @value{GDBN} behavior
36657 @cindex demangler crashes
36659 @kindex maint set internal-error
36660 @kindex maint show internal-error
36661 @kindex maint set internal-warning
36662 @kindex maint show internal-warning
36663 @kindex maint set demangler-warning
36664 @kindex maint show demangler-warning
36665 @item maint set internal-error @var{action} [ask|yes|no]
36666 @itemx maint show internal-error @var{action}
36667 @itemx maint set internal-warning @var{action} [ask|yes|no]
36668 @itemx maint show internal-warning @var{action}
36669 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36670 @itemx maint show demangler-warning @var{action}
36671 When @value{GDBN} reports an internal problem (error or warning) it
36672 gives the user the opportunity to both quit @value{GDBN} and create a
36673 core file of the current @value{GDBN} session. These commands let you
36674 override the default behaviour for each particular @var{action},
36675 described in the table below.
36679 You can specify that @value{GDBN} should always (yes) or never (no)
36680 quit. The default is to ask the user what to do.
36683 You can specify that @value{GDBN} should always (yes) or never (no)
36684 create a core file. The default is to ask the user what to do. Note
36685 that there is no @code{corefile} option for @code{demangler-warning}:
36686 demangler warnings always create a core file and this cannot be
36690 @kindex maint packet
36691 @item maint packet @var{text}
36692 If @value{GDBN} is talking to an inferior via the serial protocol,
36693 then this command sends the string @var{text} to the inferior, and
36694 displays the response packet. @value{GDBN} supplies the initial
36695 @samp{$} character, the terminating @samp{#} character, and the
36698 @kindex maint print architecture
36699 @item maint print architecture @r{[}@var{file}@r{]}
36700 Print the entire architecture configuration. The optional argument
36701 @var{file} names the file where the output goes.
36703 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36704 @item maint print c-tdesc
36705 Print the target description (@pxref{Target Descriptions}) as
36706 a C source file. By default, the target description is for the current
36707 target, but if the optional argument @var{file} is provided, that file
36708 is used to produce the description. The @var{file} should be an XML
36709 document, of the form described in @ref{Target Description Format}.
36710 The created source file is built into @value{GDBN} when @value{GDBN} is
36711 built again. This command is used by developers after they add or
36712 modify XML target descriptions.
36714 @kindex maint check xml-descriptions
36715 @item maint check xml-descriptions @var{dir}
36716 Check that the target descriptions dynamically created by @value{GDBN}
36717 equal the descriptions created from XML files found in @var{dir}.
36719 @anchor{maint check libthread-db}
36720 @kindex maint check libthread-db
36721 @item maint check libthread-db
36722 Run integrity checks on the current inferior's thread debugging
36723 library. This exercises all @code{libthread_db} functionality used by
36724 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36725 @code{proc_service} functions provided by @value{GDBN} that
36726 @code{libthread_db} uses. Note that parts of the test may be skipped
36727 on some platforms when debugging core files.
36729 @kindex maint print dummy-frames
36730 @item maint print dummy-frames
36731 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36734 (@value{GDBP}) @kbd{b add}
36736 (@value{GDBP}) @kbd{print add(2,3)}
36737 Breakpoint 2, add (a=2, b=3) at @dots{}
36739 The program being debugged stopped while in a function called from GDB.
36741 (@value{GDBP}) @kbd{maint print dummy-frames}
36742 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36746 Takes an optional file parameter.
36748 @kindex maint print registers
36749 @kindex maint print raw-registers
36750 @kindex maint print cooked-registers
36751 @kindex maint print register-groups
36752 @kindex maint print remote-registers
36753 @item maint print registers @r{[}@var{file}@r{]}
36754 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36755 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36756 @itemx maint print register-groups @r{[}@var{file}@r{]}
36757 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36758 Print @value{GDBN}'s internal register data structures.
36760 The command @code{maint print raw-registers} includes the contents of
36761 the raw register cache; the command @code{maint print
36762 cooked-registers} includes the (cooked) value of all registers,
36763 including registers which aren't available on the target nor visible
36764 to user; the command @code{maint print register-groups} includes the
36765 groups that each register is a member of; and the command @code{maint
36766 print remote-registers} includes the remote target's register numbers
36767 and offsets in the `G' packets.
36769 These commands take an optional parameter, a file name to which to
36770 write the information.
36772 @kindex maint print reggroups
36773 @item maint print reggroups @r{[}@var{file}@r{]}
36774 Print @value{GDBN}'s internal register group data structures. The
36775 optional argument @var{file} tells to what file to write the
36778 The register groups info looks like this:
36781 (@value{GDBP}) @kbd{maint print reggroups}
36794 This command forces @value{GDBN} to flush its internal register cache.
36796 @kindex maint print objfiles
36797 @cindex info for known object files
36798 @item maint print objfiles @r{[}@var{regexp}@r{]}
36799 Print a dump of all known object files.
36800 If @var{regexp} is specified, only print object files whose names
36801 match @var{regexp}. For each object file, this command prints its name,
36802 address in memory, and all of its psymtabs and symtabs.
36804 @kindex maint print user-registers
36805 @cindex user registers
36806 @item maint print user-registers
36807 List all currently available @dfn{user registers}. User registers
36808 typically provide alternate names for actual hardware registers. They
36809 include the four ``standard'' registers @code{$fp}, @code{$pc},
36810 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36811 registers can be used in expressions in the same way as the canonical
36812 register names, but only the latter are listed by the @code{info
36813 registers} and @code{maint print registers} commands.
36815 @kindex maint print section-scripts
36816 @cindex info for known .debug_gdb_scripts-loaded scripts
36817 @item maint print section-scripts [@var{regexp}]
36818 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36819 If @var{regexp} is specified, only print scripts loaded by object files
36820 matching @var{regexp}.
36821 For each script, this command prints its name as specified in the objfile,
36822 and the full path if known.
36823 @xref{dotdebug_gdb_scripts section}.
36825 @kindex maint print statistics
36826 @cindex bcache statistics
36827 @item maint print statistics
36828 This command prints, for each object file in the program, various data
36829 about that object file followed by the byte cache (@dfn{bcache})
36830 statistics for the object file. The objfile data includes the number
36831 of minimal, partial, full, and stabs symbols, the number of types
36832 defined by the objfile, the number of as yet unexpanded psym tables,
36833 the number of line tables and string tables, and the amount of memory
36834 used by the various tables. The bcache statistics include the counts,
36835 sizes, and counts of duplicates of all and unique objects, max,
36836 average, and median entry size, total memory used and its overhead and
36837 savings, and various measures of the hash table size and chain
36840 @kindex maint print target-stack
36841 @cindex target stack description
36842 @item maint print target-stack
36843 A @dfn{target} is an interface between the debugger and a particular
36844 kind of file or process. Targets can be stacked in @dfn{strata},
36845 so that more than one target can potentially respond to a request.
36846 In particular, memory accesses will walk down the stack of targets
36847 until they find a target that is interested in handling that particular
36850 This command prints a short description of each layer that was pushed on
36851 the @dfn{target stack}, starting from the top layer down to the bottom one.
36853 @kindex maint print type
36854 @cindex type chain of a data type
36855 @item maint print type @var{expr}
36856 Print the type chain for a type specified by @var{expr}. The argument
36857 can be either a type name or a symbol. If it is a symbol, the type of
36858 that symbol is described. The type chain produced by this command is
36859 a recursive definition of the data type as stored in @value{GDBN}'s
36860 data structures, including its flags and contained types.
36862 @kindex maint selftest
36864 @item maint selftest @r{[}@var{filter}@r{]}
36865 Run any self tests that were compiled in to @value{GDBN}. This will
36866 print a message showing how many tests were run, and how many failed.
36867 If a @var{filter} is passed, only the tests with @var{filter} in their
36870 @kindex maint info selftests
36872 @item maint info selftests
36873 List the selftests compiled in to @value{GDBN}.
36875 @kindex maint set dwarf always-disassemble
36876 @kindex maint show dwarf always-disassemble
36877 @item maint set dwarf always-disassemble
36878 @item maint show dwarf always-disassemble
36879 Control the behavior of @code{info address} when using DWARF debugging
36882 The default is @code{off}, which means that @value{GDBN} should try to
36883 describe a variable's location in an easily readable format. When
36884 @code{on}, @value{GDBN} will instead display the DWARF location
36885 expression in an assembly-like format. Note that some locations are
36886 too complex for @value{GDBN} to describe simply; in this case you will
36887 always see the disassembly form.
36889 Here is an example of the resulting disassembly:
36892 (gdb) info addr argc
36893 Symbol "argc" is a complex DWARF expression:
36897 For more information on these expressions, see
36898 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36900 @kindex maint set dwarf max-cache-age
36901 @kindex maint show dwarf max-cache-age
36902 @item maint set dwarf max-cache-age
36903 @itemx maint show dwarf max-cache-age
36904 Control the DWARF compilation unit cache.
36906 @cindex DWARF compilation units cache
36907 In object files with inter-compilation-unit references, such as those
36908 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36909 reader needs to frequently refer to previously read compilation units.
36910 This setting controls how long a compilation unit will remain in the
36911 cache if it is not referenced. A higher limit means that cached
36912 compilation units will be stored in memory longer, and more total
36913 memory will be used. Setting it to zero disables caching, which will
36914 slow down @value{GDBN} startup, but reduce memory consumption.
36916 @kindex maint set dwarf unwinders
36917 @kindex maint show dwarf unwinders
36918 @item maint set dwarf unwinders
36919 @itemx maint show dwarf unwinders
36920 Control use of the DWARF frame unwinders.
36922 @cindex DWARF frame unwinders
36923 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36924 frame unwinders to build the backtrace. Many of these targets will
36925 also have a second mechanism for building the backtrace for use in
36926 cases where DWARF information is not available, this second mechanism
36927 is often an analysis of a function's prologue.
36929 In order to extend testing coverage of the second level stack
36930 unwinding mechanisms it is helpful to be able to disable the DWARF
36931 stack unwinders, this can be done with this switch.
36933 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36934 advisable, there are cases that are better handled through DWARF than
36935 prologue analysis, and the debug experience is likely to be better
36936 with the DWARF frame unwinders enabled.
36938 If DWARF frame unwinders are not supported for a particular target
36939 architecture, then enabling this flag does not cause them to be used.
36940 @kindex maint set profile
36941 @kindex maint show profile
36942 @cindex profiling GDB
36943 @item maint set profile
36944 @itemx maint show profile
36945 Control profiling of @value{GDBN}.
36947 Profiling will be disabled until you use the @samp{maint set profile}
36948 command to enable it. When you enable profiling, the system will begin
36949 collecting timing and execution count data; when you disable profiling or
36950 exit @value{GDBN}, the results will be written to a log file. Remember that
36951 if you use profiling, @value{GDBN} will overwrite the profiling log file
36952 (often called @file{gmon.out}). If you have a record of important profiling
36953 data in a @file{gmon.out} file, be sure to move it to a safe location.
36955 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36956 compiled with the @samp{-pg} compiler option.
36958 @kindex maint set show-debug-regs
36959 @kindex maint show show-debug-regs
36960 @cindex hardware debug registers
36961 @item maint set show-debug-regs
36962 @itemx maint show show-debug-regs
36963 Control whether to show variables that mirror the hardware debug
36964 registers. Use @code{on} to enable, @code{off} to disable. If
36965 enabled, the debug registers values are shown when @value{GDBN} inserts or
36966 removes a hardware breakpoint or watchpoint, and when the inferior
36967 triggers a hardware-assisted breakpoint or watchpoint.
36969 @kindex maint set show-all-tib
36970 @kindex maint show show-all-tib
36971 @item maint set show-all-tib
36972 @itemx maint show show-all-tib
36973 Control whether to show all non zero areas within a 1k block starting
36974 at thread local base, when using the @samp{info w32 thread-information-block}
36977 @kindex maint set target-async
36978 @kindex maint show target-async
36979 @item maint set target-async
36980 @itemx maint show target-async
36981 This controls whether @value{GDBN} targets operate in synchronous or
36982 asynchronous mode (@pxref{Background Execution}). Normally the
36983 default is asynchronous, if it is available; but this can be changed
36984 to more easily debug problems occurring only in synchronous mode.
36986 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36987 @kindex maint show target-non-stop
36988 @item maint set target-non-stop
36989 @itemx maint show target-non-stop
36991 This controls whether @value{GDBN} targets always operate in non-stop
36992 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36993 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36994 if supported by the target.
36997 @item maint set target-non-stop auto
36998 This is the default mode. @value{GDBN} controls the target in
36999 non-stop mode if the target supports it.
37001 @item maint set target-non-stop on
37002 @value{GDBN} controls the target in non-stop mode even if the target
37003 does not indicate support.
37005 @item maint set target-non-stop off
37006 @value{GDBN} does not control the target in non-stop mode even if the
37007 target supports it.
37010 @kindex maint set per-command
37011 @kindex maint show per-command
37012 @item maint set per-command
37013 @itemx maint show per-command
37014 @cindex resources used by commands
37016 @value{GDBN} can display the resources used by each command.
37017 This is useful in debugging performance problems.
37020 @item maint set per-command space [on|off]
37021 @itemx maint show per-command space
37022 Enable or disable the printing of the memory used by GDB for each command.
37023 If enabled, @value{GDBN} will display how much memory each command
37024 took, following the command's own output.
37025 This can also be requested by invoking @value{GDBN} with the
37026 @option{--statistics} command-line switch (@pxref{Mode Options}).
37028 @item maint set per-command time [on|off]
37029 @itemx maint show per-command time
37030 Enable or disable the printing of the execution time of @value{GDBN}
37032 If enabled, @value{GDBN} will display how much time it
37033 took to execute each command, following the command's own output.
37034 Both CPU time and wallclock time are printed.
37035 Printing both is useful when trying to determine whether the cost is
37036 CPU or, e.g., disk/network latency.
37037 Note that the CPU time printed is for @value{GDBN} only, it does not include
37038 the execution time of the inferior because there's no mechanism currently
37039 to compute how much time was spent by @value{GDBN} and how much time was
37040 spent by the program been debugged.
37041 This can also be requested by invoking @value{GDBN} with the
37042 @option{--statistics} command-line switch (@pxref{Mode Options}).
37044 @item maint set per-command symtab [on|off]
37045 @itemx maint show per-command symtab
37046 Enable or disable the printing of basic symbol table statistics
37048 If enabled, @value{GDBN} will display the following information:
37052 number of symbol tables
37054 number of primary symbol tables
37056 number of blocks in the blockvector
37060 @kindex maint set check-libthread-db
37061 @kindex maint show check-libthread-db
37062 @item maint set check-libthread-db [on|off]
37063 @itemx maint show check-libthread-db
37064 Control whether @value{GDBN} should run integrity checks on inferior
37065 specific thread debugging libraries as they are loaded. The default
37066 is not to perform such checks. If any check fails @value{GDBN} will
37067 unload the library and continue searching for a suitable candidate as
37068 described in @ref{set libthread-db-search-path}. For more information
37069 about the tests, see @ref{maint check libthread-db}.
37071 @kindex maint space
37072 @cindex memory used by commands
37073 @item maint space @var{value}
37074 An alias for @code{maint set per-command space}.
37075 A non-zero value enables it, zero disables it.
37078 @cindex time of command execution
37079 @item maint time @var{value}
37080 An alias for @code{maint set per-command time}.
37081 A non-zero value enables it, zero disables it.
37083 @kindex maint translate-address
37084 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37085 Find the symbol stored at the location specified by the address
37086 @var{addr} and an optional section name @var{section}. If found,
37087 @value{GDBN} prints the name of the closest symbol and an offset from
37088 the symbol's location to the specified address. This is similar to
37089 the @code{info address} command (@pxref{Symbols}), except that this
37090 command also allows to find symbols in other sections.
37092 If section was not specified, the section in which the symbol was found
37093 is also printed. For dynamically linked executables, the name of
37094 executable or shared library containing the symbol is printed as well.
37098 The following command is useful for non-interactive invocations of
37099 @value{GDBN}, such as in the test suite.
37102 @item set watchdog @var{nsec}
37103 @kindex set watchdog
37104 @cindex watchdog timer
37105 @cindex timeout for commands
37106 Set the maximum number of seconds @value{GDBN} will wait for the
37107 target operation to finish. If this time expires, @value{GDBN}
37108 reports and error and the command is aborted.
37110 @item show watchdog
37111 Show the current setting of the target wait timeout.
37114 @node Remote Protocol
37115 @appendix @value{GDBN} Remote Serial Protocol
37120 * Stop Reply Packets::
37121 * General Query Packets::
37122 * Architecture-Specific Protocol Details::
37123 * Tracepoint Packets::
37124 * Host I/O Packets::
37126 * Notification Packets::
37127 * Remote Non-Stop::
37128 * Packet Acknowledgment::
37130 * File-I/O Remote Protocol Extension::
37131 * Library List Format::
37132 * Library List Format for SVR4 Targets::
37133 * Memory Map Format::
37134 * Thread List Format::
37135 * Traceframe Info Format::
37136 * Branch Trace Format::
37137 * Branch Trace Configuration Format::
37143 There may be occasions when you need to know something about the
37144 protocol---for example, if there is only one serial port to your target
37145 machine, you might want your program to do something special if it
37146 recognizes a packet meant for @value{GDBN}.
37148 In the examples below, @samp{->} and @samp{<-} are used to indicate
37149 transmitted and received data, respectively.
37151 @cindex protocol, @value{GDBN} remote serial
37152 @cindex serial protocol, @value{GDBN} remote
37153 @cindex remote serial protocol
37154 All @value{GDBN} commands and responses (other than acknowledgments
37155 and notifications, see @ref{Notification Packets}) are sent as a
37156 @var{packet}. A @var{packet} is introduced with the character
37157 @samp{$}, the actual @var{packet-data}, and the terminating character
37158 @samp{#} followed by a two-digit @var{checksum}:
37161 @code{$}@var{packet-data}@code{#}@var{checksum}
37165 @cindex checksum, for @value{GDBN} remote
37167 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37168 characters between the leading @samp{$} and the trailing @samp{#} (an
37169 eight bit unsigned checksum).
37171 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37172 specification also included an optional two-digit @var{sequence-id}:
37175 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37178 @cindex sequence-id, for @value{GDBN} remote
37180 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37181 has never output @var{sequence-id}s. Stubs that handle packets added
37182 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37184 When either the host or the target machine receives a packet, the first
37185 response expected is an acknowledgment: either @samp{+} (to indicate
37186 the package was received correctly) or @samp{-} (to request
37190 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37195 The @samp{+}/@samp{-} acknowledgments can be disabled
37196 once a connection is established.
37197 @xref{Packet Acknowledgment}, for details.
37199 The host (@value{GDBN}) sends @var{command}s, and the target (the
37200 debugging stub incorporated in your program) sends a @var{response}. In
37201 the case of step and continue @var{command}s, the response is only sent
37202 when the operation has completed, and the target has again stopped all
37203 threads in all attached processes. This is the default all-stop mode
37204 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37205 execution mode; see @ref{Remote Non-Stop}, for details.
37207 @var{packet-data} consists of a sequence of characters with the
37208 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37211 @cindex remote protocol, field separator
37212 Fields within the packet should be separated using @samp{,} @samp{;} or
37213 @samp{:}. Except where otherwise noted all numbers are represented in
37214 @sc{hex} with leading zeros suppressed.
37216 Implementors should note that prior to @value{GDBN} 5.0, the character
37217 @samp{:} could not appear as the third character in a packet (as it
37218 would potentially conflict with the @var{sequence-id}).
37220 @cindex remote protocol, binary data
37221 @anchor{Binary Data}
37222 Binary data in most packets is encoded either as two hexadecimal
37223 digits per byte of binary data. This allowed the traditional remote
37224 protocol to work over connections which were only seven-bit clean.
37225 Some packets designed more recently assume an eight-bit clean
37226 connection, and use a more efficient encoding to send and receive
37229 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37230 as an escape character. Any escaped byte is transmitted as the escape
37231 character followed by the original character XORed with @code{0x20}.
37232 For example, the byte @code{0x7d} would be transmitted as the two
37233 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37234 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37235 @samp{@}}) must always be escaped. Responses sent by the stub
37236 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37237 is not interpreted as the start of a run-length encoded sequence
37240 Response @var{data} can be run-length encoded to save space.
37241 Run-length encoding replaces runs of identical characters with one
37242 instance of the repeated character, followed by a @samp{*} and a
37243 repeat count. The repeat count is itself sent encoded, to avoid
37244 binary characters in @var{data}: a value of @var{n} is sent as
37245 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37246 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37247 code 32) for a repeat count of 3. (This is because run-length
37248 encoding starts to win for counts 3 or more.) Thus, for example,
37249 @samp{0* } is a run-length encoding of ``0000'': the space character
37250 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37253 The printable characters @samp{#} and @samp{$} or with a numeric value
37254 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37255 seven repeats (@samp{$}) can be expanded using a repeat count of only
37256 five (@samp{"}). For example, @samp{00000000} can be encoded as
37259 The error response returned for some packets includes a two character
37260 error number. That number is not well defined.
37262 @cindex empty response, for unsupported packets
37263 For any @var{command} not supported by the stub, an empty response
37264 (@samp{$#00}) should be returned. That way it is possible to extend the
37265 protocol. A newer @value{GDBN} can tell if a packet is supported based
37268 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37269 commands for register access, and the @samp{m} and @samp{M} commands
37270 for memory access. Stubs that only control single-threaded targets
37271 can implement run control with the @samp{c} (continue), and @samp{s}
37272 (step) commands. Stubs that support multi-threading targets should
37273 support the @samp{vCont} command. All other commands are optional.
37278 The following table provides a complete list of all currently defined
37279 @var{command}s and their corresponding response @var{data}.
37280 @xref{File-I/O Remote Protocol Extension}, for details about the File
37281 I/O extension of the remote protocol.
37283 Each packet's description has a template showing the packet's overall
37284 syntax, followed by an explanation of the packet's meaning. We
37285 include spaces in some of the templates for clarity; these are not
37286 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37287 separate its components. For example, a template like @samp{foo
37288 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37289 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37290 @var{baz}. @value{GDBN} does not transmit a space character between the
37291 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37294 @cindex @var{thread-id}, in remote protocol
37295 @anchor{thread-id syntax}
37296 Several packets and replies include a @var{thread-id} field to identify
37297 a thread. Normally these are positive numbers with a target-specific
37298 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37299 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37302 In addition, the remote protocol supports a multiprocess feature in
37303 which the @var{thread-id} syntax is extended to optionally include both
37304 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37305 The @var{pid} (process) and @var{tid} (thread) components each have the
37306 format described above: a positive number with target-specific
37307 interpretation formatted as a big-endian hex string, literal @samp{-1}
37308 to indicate all processes or threads (respectively), or @samp{0} to
37309 indicate an arbitrary process or thread. Specifying just a process, as
37310 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37311 error to specify all processes but a specific thread, such as
37312 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37313 for those packets and replies explicitly documented to include a process
37314 ID, rather than a @var{thread-id}.
37316 The multiprocess @var{thread-id} syntax extensions are only used if both
37317 @value{GDBN} and the stub report support for the @samp{multiprocess}
37318 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37321 Note that all packet forms beginning with an upper- or lower-case
37322 letter, other than those described here, are reserved for future use.
37324 Here are the packet descriptions.
37329 @cindex @samp{!} packet
37330 @anchor{extended mode}
37331 Enable extended mode. In extended mode, the remote server is made
37332 persistent. The @samp{R} packet is used to restart the program being
37338 The remote target both supports and has enabled extended mode.
37342 @cindex @samp{?} packet
37344 Indicate the reason the target halted. The reply is the same as for
37345 step and continue. This packet has a special interpretation when the
37346 target is in non-stop mode; see @ref{Remote Non-Stop}.
37349 @xref{Stop Reply Packets}, for the reply specifications.
37351 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37352 @cindex @samp{A} packet
37353 Initialized @code{argv[]} array passed into program. @var{arglen}
37354 specifies the number of bytes in the hex encoded byte stream
37355 @var{arg}. See @code{gdbserver} for more details.
37360 The arguments were set.
37366 @cindex @samp{b} packet
37367 (Don't use this packet; its behavior is not well-defined.)
37368 Change the serial line speed to @var{baud}.
37370 JTC: @emph{When does the transport layer state change? When it's
37371 received, or after the ACK is transmitted. In either case, there are
37372 problems if the command or the acknowledgment packet is dropped.}
37374 Stan: @emph{If people really wanted to add something like this, and get
37375 it working for the first time, they ought to modify ser-unix.c to send
37376 some kind of out-of-band message to a specially-setup stub and have the
37377 switch happen "in between" packets, so that from remote protocol's point
37378 of view, nothing actually happened.}
37380 @item B @var{addr},@var{mode}
37381 @cindex @samp{B} packet
37382 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37383 breakpoint at @var{addr}.
37385 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37386 (@pxref{insert breakpoint or watchpoint packet}).
37388 @cindex @samp{bc} packet
37391 Backward continue. Execute the target system in reverse. No parameter.
37392 @xref{Reverse Execution}, for more information.
37395 @xref{Stop Reply Packets}, for the reply specifications.
37397 @cindex @samp{bs} packet
37400 Backward single step. Execute one instruction in reverse. No parameter.
37401 @xref{Reverse Execution}, for more information.
37404 @xref{Stop Reply Packets}, for the reply specifications.
37406 @item c @r{[}@var{addr}@r{]}
37407 @cindex @samp{c} packet
37408 Continue at @var{addr}, which is the address to resume. If @var{addr}
37409 is omitted, resume at current address.
37411 This packet is deprecated for multi-threading support. @xref{vCont
37415 @xref{Stop Reply Packets}, for the reply specifications.
37417 @item C @var{sig}@r{[};@var{addr}@r{]}
37418 @cindex @samp{C} packet
37419 Continue with signal @var{sig} (hex signal number). If
37420 @samp{;@var{addr}} is omitted, resume at same address.
37422 This packet is deprecated for multi-threading support. @xref{vCont
37426 @xref{Stop Reply Packets}, for the reply specifications.
37429 @cindex @samp{d} packet
37432 Don't use this packet; instead, define a general set packet
37433 (@pxref{General Query Packets}).
37437 @cindex @samp{D} packet
37438 The first form of the packet is used to detach @value{GDBN} from the
37439 remote system. It is sent to the remote target
37440 before @value{GDBN} disconnects via the @code{detach} command.
37442 The second form, including a process ID, is used when multiprocess
37443 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37444 detach only a specific process. The @var{pid} is specified as a
37445 big-endian hex string.
37455 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37456 @cindex @samp{F} packet
37457 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37458 This is part of the File-I/O protocol extension. @xref{File-I/O
37459 Remote Protocol Extension}, for the specification.
37462 @anchor{read registers packet}
37463 @cindex @samp{g} packet
37464 Read general registers.
37468 @item @var{XX@dots{}}
37469 Each byte of register data is described by two hex digits. The bytes
37470 with the register are transmitted in target byte order. The size of
37471 each register and their position within the @samp{g} packet are
37472 determined by the @value{GDBN} internal gdbarch functions
37473 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37475 When reading registers from a trace frame (@pxref{Analyze Collected
37476 Data,,Using the Collected Data}), the stub may also return a string of
37477 literal @samp{x}'s in place of the register data digits, to indicate
37478 that the corresponding register has not been collected, thus its value
37479 is unavailable. For example, for an architecture with 4 registers of
37480 4 bytes each, the following reply indicates to @value{GDBN} that
37481 registers 0 and 2 have not been collected, while registers 1 and 3
37482 have been collected, and both have zero value:
37486 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37493 @item G @var{XX@dots{}}
37494 @cindex @samp{G} packet
37495 Write general registers. @xref{read registers packet}, for a
37496 description of the @var{XX@dots{}} data.
37506 @item H @var{op} @var{thread-id}
37507 @cindex @samp{H} packet
37508 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37509 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37510 should be @samp{c} for step and continue operations (note that this
37511 is deprecated, supporting the @samp{vCont} command is a better
37512 option), and @samp{g} for other operations. The thread designator
37513 @var{thread-id} has the format and interpretation described in
37514 @ref{thread-id syntax}.
37525 @c 'H': How restrictive (or permissive) is the thread model. If a
37526 @c thread is selected and stopped, are other threads allowed
37527 @c to continue to execute? As I mentioned above, I think the
37528 @c semantics of each command when a thread is selected must be
37529 @c described. For example:
37531 @c 'g': If the stub supports threads and a specific thread is
37532 @c selected, returns the register block from that thread;
37533 @c otherwise returns current registers.
37535 @c 'G' If the stub supports threads and a specific thread is
37536 @c selected, sets the registers of the register block of
37537 @c that thread; otherwise sets current registers.
37539 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37540 @anchor{cycle step packet}
37541 @cindex @samp{i} packet
37542 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37543 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37544 step starting at that address.
37547 @cindex @samp{I} packet
37548 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37552 @cindex @samp{k} packet
37555 The exact effect of this packet is not specified.
37557 For a bare-metal target, it may power cycle or reset the target
37558 system. For that reason, the @samp{k} packet has no reply.
37560 For a single-process target, it may kill that process if possible.
37562 A multiple-process target may choose to kill just one process, or all
37563 that are under @value{GDBN}'s control. For more precise control, use
37564 the vKill packet (@pxref{vKill packet}).
37566 If the target system immediately closes the connection in response to
37567 @samp{k}, @value{GDBN} does not consider the lack of packet
37568 acknowledgment to be an error, and assumes the kill was successful.
37570 If connected using @kbd{target extended-remote}, and the target does
37571 not close the connection in response to a kill request, @value{GDBN}
37572 probes the target state as if a new connection was opened
37573 (@pxref{? packet}).
37575 @item m @var{addr},@var{length}
37576 @cindex @samp{m} packet
37577 Read @var{length} addressable memory units starting at address @var{addr}
37578 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37579 any particular boundary.
37581 The stub need not use any particular size or alignment when gathering
37582 data from memory for the response; even if @var{addr} is word-aligned
37583 and @var{length} is a multiple of the word size, the stub is free to
37584 use byte accesses, or not. For this reason, this packet may not be
37585 suitable for accessing memory-mapped I/O devices.
37586 @cindex alignment of remote memory accesses
37587 @cindex size of remote memory accesses
37588 @cindex memory, alignment and size of remote accesses
37592 @item @var{XX@dots{}}
37593 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37594 The reply may contain fewer addressable memory units than requested if the
37595 server was able to read only part of the region of memory.
37600 @item M @var{addr},@var{length}:@var{XX@dots{}}
37601 @cindex @samp{M} packet
37602 Write @var{length} addressable memory units starting at address @var{addr}
37603 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37604 byte is transmitted as a two-digit hexadecimal number.
37611 for an error (this includes the case where only part of the data was
37616 @cindex @samp{p} packet
37617 Read the value of register @var{n}; @var{n} is in hex.
37618 @xref{read registers packet}, for a description of how the returned
37619 register value is encoded.
37623 @item @var{XX@dots{}}
37624 the register's value
37628 Indicating an unrecognized @var{query}.
37631 @item P @var{n@dots{}}=@var{r@dots{}}
37632 @anchor{write register packet}
37633 @cindex @samp{P} packet
37634 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37635 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37636 digits for each byte in the register (target byte order).
37646 @item q @var{name} @var{params}@dots{}
37647 @itemx Q @var{name} @var{params}@dots{}
37648 @cindex @samp{q} packet
37649 @cindex @samp{Q} packet
37650 General query (@samp{q}) and set (@samp{Q}). These packets are
37651 described fully in @ref{General Query Packets}.
37654 @cindex @samp{r} packet
37655 Reset the entire system.
37657 Don't use this packet; use the @samp{R} packet instead.
37660 @cindex @samp{R} packet
37661 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37662 This packet is only available in extended mode (@pxref{extended mode}).
37664 The @samp{R} packet has no reply.
37666 @item s @r{[}@var{addr}@r{]}
37667 @cindex @samp{s} packet
37668 Single step, resuming at @var{addr}. If
37669 @var{addr} is omitted, resume at same address.
37671 This packet is deprecated for multi-threading support. @xref{vCont
37675 @xref{Stop Reply Packets}, for the reply specifications.
37677 @item S @var{sig}@r{[};@var{addr}@r{]}
37678 @anchor{step with signal packet}
37679 @cindex @samp{S} packet
37680 Step with signal. This is analogous to the @samp{C} packet, but
37681 requests a single-step, rather than a normal resumption of execution.
37683 This packet is deprecated for multi-threading support. @xref{vCont
37687 @xref{Stop Reply Packets}, for the reply specifications.
37689 @item t @var{addr}:@var{PP},@var{MM}
37690 @cindex @samp{t} packet
37691 Search backwards starting at address @var{addr} for a match with pattern
37692 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37693 There must be at least 3 digits in @var{addr}.
37695 @item T @var{thread-id}
37696 @cindex @samp{T} packet
37697 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37702 thread is still alive
37708 Packets starting with @samp{v} are identified by a multi-letter name,
37709 up to the first @samp{;} or @samp{?} (or the end of the packet).
37711 @item vAttach;@var{pid}
37712 @cindex @samp{vAttach} packet
37713 Attach to a new process with the specified process ID @var{pid}.
37714 The process ID is a
37715 hexadecimal integer identifying the process. In all-stop mode, all
37716 threads in the attached process are stopped; in non-stop mode, it may be
37717 attached without being stopped if that is supported by the target.
37719 @c In non-stop mode, on a successful vAttach, the stub should set the
37720 @c current thread to a thread of the newly-attached process. After
37721 @c attaching, GDB queries for the attached process's thread ID with qC.
37722 @c Also note that, from a user perspective, whether or not the
37723 @c target is stopped on attach in non-stop mode depends on whether you
37724 @c use the foreground or background version of the attach command, not
37725 @c on what vAttach does; GDB does the right thing with respect to either
37726 @c stopping or restarting threads.
37728 This packet is only available in extended mode (@pxref{extended mode}).
37734 @item @r{Any stop packet}
37735 for success in all-stop mode (@pxref{Stop Reply Packets})
37737 for success in non-stop mode (@pxref{Remote Non-Stop})
37740 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37741 @cindex @samp{vCont} packet
37742 @anchor{vCont packet}
37743 Resume the inferior, specifying different actions for each thread.
37745 For each inferior thread, the leftmost action with a matching
37746 @var{thread-id} is applied. Threads that don't match any action
37747 remain in their current state. Thread IDs are specified using the
37748 syntax described in @ref{thread-id syntax}. If multiprocess
37749 extensions (@pxref{multiprocess extensions}) are supported, actions
37750 can be specified to match all threads in a process by using the
37751 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37752 @var{thread-id} matches all threads. Specifying no actions is an
37755 Currently supported actions are:
37761 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37765 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37768 @item r @var{start},@var{end}
37769 Step once, and then keep stepping as long as the thread stops at
37770 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37771 The remote stub reports a stop reply when either the thread goes out
37772 of the range or is stopped due to an unrelated reason, such as hitting
37773 a breakpoint. @xref{range stepping}.
37775 If the range is empty (@var{start} == @var{end}), then the action
37776 becomes equivalent to the @samp{s} action. In other words,
37777 single-step once, and report the stop (even if the stepped instruction
37778 jumps to @var{start}).
37780 (A stop reply may be sent at any point even if the PC is still within
37781 the stepping range; for example, it is valid to implement this packet
37782 in a degenerate way as a single instruction step operation.)
37786 The optional argument @var{addr} normally associated with the
37787 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37788 not supported in @samp{vCont}.
37790 The @samp{t} action is only relevant in non-stop mode
37791 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37792 A stop reply should be generated for any affected thread not already stopped.
37793 When a thread is stopped by means of a @samp{t} action,
37794 the corresponding stop reply should indicate that the thread has stopped with
37795 signal @samp{0}, regardless of whether the target uses some other signal
37796 as an implementation detail.
37798 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37799 @samp{r} actions for threads that are already running. Conversely,
37800 the server must ignore @samp{t} actions for threads that are already
37803 @emph{Note:} In non-stop mode, a thread is considered running until
37804 @value{GDBN} acknowleges an asynchronous stop notification for it with
37805 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37807 The stub must support @samp{vCont} if it reports support for
37808 multiprocess extensions (@pxref{multiprocess extensions}).
37811 @xref{Stop Reply Packets}, for the reply specifications.
37814 @cindex @samp{vCont?} packet
37815 Request a list of actions supported by the @samp{vCont} packet.
37819 @item vCont@r{[};@var{action}@dots{}@r{]}
37820 The @samp{vCont} packet is supported. Each @var{action} is a supported
37821 command in the @samp{vCont} packet.
37823 The @samp{vCont} packet is not supported.
37826 @anchor{vCtrlC packet}
37828 @cindex @samp{vCtrlC} packet
37829 Interrupt remote target as if a control-C was pressed on the remote
37830 terminal. This is the equivalent to reacting to the @code{^C}
37831 (@samp{\003}, the control-C character) character in all-stop mode
37832 while the target is running, except this works in non-stop mode.
37833 @xref{interrupting remote targets}, for more info on the all-stop
37844 @item vFile:@var{operation}:@var{parameter}@dots{}
37845 @cindex @samp{vFile} packet
37846 Perform a file operation on the target system. For details,
37847 see @ref{Host I/O Packets}.
37849 @item vFlashErase:@var{addr},@var{length}
37850 @cindex @samp{vFlashErase} packet
37851 Direct the stub to erase @var{length} bytes of flash starting at
37852 @var{addr}. The region may enclose any number of flash blocks, but
37853 its start and end must fall on block boundaries, as indicated by the
37854 flash block size appearing in the memory map (@pxref{Memory Map
37855 Format}). @value{GDBN} groups flash memory programming operations
37856 together, and sends a @samp{vFlashDone} request after each group; the
37857 stub is allowed to delay erase operation until the @samp{vFlashDone}
37858 packet is received.
37868 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37869 @cindex @samp{vFlashWrite} packet
37870 Direct the stub to write data to flash address @var{addr}. The data
37871 is passed in binary form using the same encoding as for the @samp{X}
37872 packet (@pxref{Binary Data}). The memory ranges specified by
37873 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37874 not overlap, and must appear in order of increasing addresses
37875 (although @samp{vFlashErase} packets for higher addresses may already
37876 have been received; the ordering is guaranteed only between
37877 @samp{vFlashWrite} packets). If a packet writes to an address that was
37878 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37879 target-specific method, the results are unpredictable.
37887 for vFlashWrite addressing non-flash memory
37893 @cindex @samp{vFlashDone} packet
37894 Indicate to the stub that flash programming operation is finished.
37895 The stub is permitted to delay or batch the effects of a group of
37896 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37897 @samp{vFlashDone} packet is received. The contents of the affected
37898 regions of flash memory are unpredictable until the @samp{vFlashDone}
37899 request is completed.
37901 @item vKill;@var{pid}
37902 @cindex @samp{vKill} packet
37903 @anchor{vKill packet}
37904 Kill the process with the specified process ID @var{pid}, which is a
37905 hexadecimal integer identifying the process. This packet is used in
37906 preference to @samp{k} when multiprocess protocol extensions are
37907 supported; see @ref{multiprocess extensions}.
37917 @item vMustReplyEmpty
37918 @cindex @samp{vMustReplyEmpty} packet
37919 The correct reply to an unknown @samp{v} packet is to return the empty
37920 string, however, some older versions of @command{gdbserver} would
37921 incorrectly return @samp{OK} for unknown @samp{v} packets.
37923 The @samp{vMustReplyEmpty} is used as a feature test to check how
37924 @command{gdbserver} handles unknown packets, it is important that this
37925 packet be handled in the same way as other unknown @samp{v} packets.
37926 If this packet is handled differently to other unknown @samp{v}
37927 packets then it is possile that @value{GDBN} may run into problems in
37928 other areas, specifically around use of @samp{vFile:setfs:}.
37930 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37931 @cindex @samp{vRun} packet
37932 Run the program @var{filename}, passing it each @var{argument} on its
37933 command line. The file and arguments are hex-encoded strings. If
37934 @var{filename} is an empty string, the stub may use a default program
37935 (e.g.@: the last program run). The program is created in the stopped
37938 @c FIXME: What about non-stop mode?
37940 This packet is only available in extended mode (@pxref{extended mode}).
37946 @item @r{Any stop packet}
37947 for success (@pxref{Stop Reply Packets})
37951 @cindex @samp{vStopped} packet
37952 @xref{Notification Packets}.
37954 @item X @var{addr},@var{length}:@var{XX@dots{}}
37956 @cindex @samp{X} packet
37957 Write data to memory, where the data is transmitted in binary.
37958 Memory is specified by its address @var{addr} and number of addressable memory
37959 units @var{length} (@pxref{addressable memory unit});
37960 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37970 @item z @var{type},@var{addr},@var{kind}
37971 @itemx Z @var{type},@var{addr},@var{kind}
37972 @anchor{insert breakpoint or watchpoint packet}
37973 @cindex @samp{z} packet
37974 @cindex @samp{Z} packets
37975 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37976 watchpoint starting at address @var{address} of kind @var{kind}.
37978 Each breakpoint and watchpoint packet @var{type} is documented
37981 @emph{Implementation notes: A remote target shall return an empty string
37982 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37983 remote target shall support either both or neither of a given
37984 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37985 avoid potential problems with duplicate packets, the operations should
37986 be implemented in an idempotent way.}
37988 @item z0,@var{addr},@var{kind}
37989 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37990 @cindex @samp{z0} packet
37991 @cindex @samp{Z0} packet
37992 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37993 @var{addr} of type @var{kind}.
37995 A software breakpoint is implemented by replacing the instruction at
37996 @var{addr} with a software breakpoint or trap instruction. The
37997 @var{kind} is target-specific and typically indicates the size of the
37998 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37999 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38000 architectures have additional meanings for @var{kind}
38001 (@pxref{Architecture-Specific Protocol Details}); if no
38002 architecture-specific value is being used, it should be @samp{0}.
38003 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
38004 conditional expressions in bytecode form that should be evaluated on
38005 the target's side. These are the conditions that should be taken into
38006 consideration when deciding if the breakpoint trigger should be
38007 reported back to @value{GDBN}.
38009 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
38010 for how to best report a software breakpoint event to @value{GDBN}.
38012 The @var{cond_list} parameter is comprised of a series of expressions,
38013 concatenated without separators. Each expression has the following form:
38017 @item X @var{len},@var{expr}
38018 @var{len} is the length of the bytecode expression and @var{expr} is the
38019 actual conditional expression in bytecode form.
38023 The optional @var{cmd_list} parameter introduces commands that may be
38024 run on the target, rather than being reported back to @value{GDBN}.
38025 The parameter starts with a numeric flag @var{persist}; if the flag is
38026 nonzero, then the breakpoint may remain active and the commands
38027 continue to be run even when @value{GDBN} disconnects from the target.
38028 Following this flag is a series of expressions concatenated with no
38029 separators. Each expression has the following form:
38033 @item X @var{len},@var{expr}
38034 @var{len} is the length of the bytecode expression and @var{expr} is the
38035 actual commands expression in bytecode form.
38039 @emph{Implementation note: It is possible for a target to copy or move
38040 code that contains software breakpoints (e.g., when implementing
38041 overlays). The behavior of this packet, in the presence of such a
38042 target, is not defined.}
38054 @item z1,@var{addr},@var{kind}
38055 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38056 @cindex @samp{z1} packet
38057 @cindex @samp{Z1} packet
38058 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38059 address @var{addr}.
38061 A hardware breakpoint is implemented using a mechanism that is not
38062 dependent on being able to modify the target's memory. The
38063 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
38064 same meaning as in @samp{Z0} packets.
38066 @emph{Implementation note: A hardware breakpoint is not affected by code
38079 @item z2,@var{addr},@var{kind}
38080 @itemx Z2,@var{addr},@var{kind}
38081 @cindex @samp{z2} packet
38082 @cindex @samp{Z2} packet
38083 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38084 The number of bytes to watch is specified by @var{kind}.
38096 @item z3,@var{addr},@var{kind}
38097 @itemx Z3,@var{addr},@var{kind}
38098 @cindex @samp{z3} packet
38099 @cindex @samp{Z3} packet
38100 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38101 The number of bytes to watch is specified by @var{kind}.
38113 @item z4,@var{addr},@var{kind}
38114 @itemx Z4,@var{addr},@var{kind}
38115 @cindex @samp{z4} packet
38116 @cindex @samp{Z4} packet
38117 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38118 The number of bytes to watch is specified by @var{kind}.
38132 @node Stop Reply Packets
38133 @section Stop Reply Packets
38134 @cindex stop reply packets
38136 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38137 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38138 receive any of the below as a reply. Except for @samp{?}
38139 and @samp{vStopped}, that reply is only returned
38140 when the target halts. In the below the exact meaning of @dfn{signal
38141 number} is defined by the header @file{include/gdb/signals.h} in the
38142 @value{GDBN} source code.
38144 In non-stop mode, the server will simply reply @samp{OK} to commands
38145 such as @samp{vCont}; any stop will be the subject of a future
38146 notification. @xref{Remote Non-Stop}.
38148 As in the description of request packets, we include spaces in the
38149 reply templates for clarity; these are not part of the reply packet's
38150 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38156 The program received signal number @var{AA} (a two-digit hexadecimal
38157 number). This is equivalent to a @samp{T} response with no
38158 @var{n}:@var{r} pairs.
38160 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38161 @cindex @samp{T} packet reply
38162 The program received signal number @var{AA} (a two-digit hexadecimal
38163 number). This is equivalent to an @samp{S} response, except that the
38164 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38165 and other information directly in the stop reply packet, reducing
38166 round-trip latency. Single-step and breakpoint traps are reported
38167 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38171 If @var{n} is a hexadecimal number, it is a register number, and the
38172 corresponding @var{r} gives that register's value. The data @var{r} is a
38173 series of bytes in target byte order, with each byte given by a
38174 two-digit hex number.
38177 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38178 the stopped thread, as specified in @ref{thread-id syntax}.
38181 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38182 the core on which the stop event was detected.
38185 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38186 specific event that stopped the target. The currently defined stop
38187 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38188 signal. At most one stop reason should be present.
38191 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38192 and go on to the next; this allows us to extend the protocol in the
38196 The currently defined stop reasons are:
38202 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38205 @item syscall_entry
38206 @itemx syscall_return
38207 The packet indicates a syscall entry or return, and @var{r} is the
38208 syscall number, in hex.
38210 @cindex shared library events, remote reply
38212 The packet indicates that the loaded libraries have changed.
38213 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38214 list of loaded libraries. The @var{r} part is ignored.
38216 @cindex replay log events, remote reply
38218 The packet indicates that the target cannot continue replaying
38219 logged execution events, because it has reached the end (or the
38220 beginning when executing backward) of the log. The value of @var{r}
38221 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38222 for more information.
38225 @anchor{swbreak stop reason}
38226 The packet indicates a software breakpoint instruction was executed,
38227 irrespective of whether it was @value{GDBN} that planted the
38228 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38229 part must be left empty.
38231 On some architectures, such as x86, at the architecture level, when a
38232 breakpoint instruction executes the program counter points at the
38233 breakpoint address plus an offset. On such targets, the stub is
38234 responsible for adjusting the PC to point back at the breakpoint
38237 This packet should not be sent by default; older @value{GDBN} versions
38238 did not support it. @value{GDBN} requests it, by supplying an
38239 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38240 remote stub must also supply the appropriate @samp{qSupported} feature
38241 indicating support.
38243 This packet is required for correct non-stop mode operation.
38246 The packet indicates the target stopped for a hardware breakpoint.
38247 The @var{r} part must be left empty.
38249 The same remarks about @samp{qSupported} and non-stop mode above
38252 @cindex fork events, remote reply
38254 The packet indicates that @code{fork} was called, and @var{r}
38255 is the thread ID of the new child process. Refer to
38256 @ref{thread-id syntax} for the format of the @var{thread-id}
38257 field. This packet is only applicable to targets that support
38260 This packet should not be sent by default; older @value{GDBN} versions
38261 did not support it. @value{GDBN} requests it, by supplying an
38262 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38263 remote stub must also supply the appropriate @samp{qSupported} feature
38264 indicating support.
38266 @cindex vfork events, remote reply
38268 The packet indicates that @code{vfork} was called, and @var{r}
38269 is the thread ID of the new child process. Refer to
38270 @ref{thread-id syntax} for the format of the @var{thread-id}
38271 field. This packet is only applicable to targets that support
38274 This packet should not be sent by default; older @value{GDBN} versions
38275 did not support it. @value{GDBN} requests it, by supplying an
38276 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38277 remote stub must also supply the appropriate @samp{qSupported} feature
38278 indicating support.
38280 @cindex vforkdone events, remote reply
38282 The packet indicates that a child process created by a vfork
38283 has either called @code{exec} or terminated, so that the
38284 address spaces of the parent and child process are no longer
38285 shared. The @var{r} part is ignored. This packet is only
38286 applicable to targets that support vforkdone events.
38288 This packet should not be sent by default; older @value{GDBN} versions
38289 did not support it. @value{GDBN} requests it, by supplying an
38290 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38291 remote stub must also supply the appropriate @samp{qSupported} feature
38292 indicating support.
38294 @cindex exec events, remote reply
38296 The packet indicates that @code{execve} was called, and @var{r}
38297 is the absolute pathname of the file that was executed, in hex.
38298 This packet is only applicable to targets that support exec events.
38300 This packet should not be sent by default; older @value{GDBN} versions
38301 did not support it. @value{GDBN} requests it, by supplying an
38302 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38303 remote stub must also supply the appropriate @samp{qSupported} feature
38304 indicating support.
38306 @cindex thread create event, remote reply
38307 @anchor{thread create event}
38309 The packet indicates that the thread was just created. The new thread
38310 is stopped until @value{GDBN} sets it running with a resumption packet
38311 (@pxref{vCont packet}). This packet should not be sent by default;
38312 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38313 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38314 @var{r} part is ignored.
38319 @itemx W @var{AA} ; process:@var{pid}
38320 The process exited, and @var{AA} is the exit status. This is only
38321 applicable to certain targets.
38323 The second form of the response, including the process ID of the
38324 exited process, can be used only when @value{GDBN} has reported
38325 support for multiprocess protocol extensions; see @ref{multiprocess
38326 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38330 @itemx X @var{AA} ; process:@var{pid}
38331 The process terminated with signal @var{AA}.
38333 The second form of the response, including the process ID of the
38334 terminated process, can be used only when @value{GDBN} has reported
38335 support for multiprocess protocol extensions; see @ref{multiprocess
38336 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38339 @anchor{thread exit event}
38340 @cindex thread exit event, remote reply
38341 @item w @var{AA} ; @var{tid}
38343 The thread exited, and @var{AA} is the exit status. This response
38344 should not be sent by default; @value{GDBN} requests it with the
38345 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38346 @var{AA} is formatted as a big-endian hex string.
38349 There are no resumed threads left in the target. In other words, even
38350 though the process is alive, the last resumed thread has exited. For
38351 example, say the target process has two threads: thread 1 and thread
38352 2. The client leaves thread 1 stopped, and resumes thread 2, which
38353 subsequently exits. At this point, even though the process is still
38354 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38355 executing either. The @samp{N} stop reply thus informs the client
38356 that it can stop waiting for stop replies. This packet should not be
38357 sent by default; older @value{GDBN} versions did not support it.
38358 @value{GDBN} requests it, by supplying an appropriate
38359 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38360 also supply the appropriate @samp{qSupported} feature indicating
38363 @item O @var{XX}@dots{}
38364 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38365 written as the program's console output. This can happen at any time
38366 while the program is running and the debugger should continue to wait
38367 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38369 @item F @var{call-id},@var{parameter}@dots{}
38370 @var{call-id} is the identifier which says which host system call should
38371 be called. This is just the name of the function. Translation into the
38372 correct system call is only applicable as it's defined in @value{GDBN}.
38373 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38376 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38377 this very system call.
38379 The target replies with this packet when it expects @value{GDBN} to
38380 call a host system call on behalf of the target. @value{GDBN} replies
38381 with an appropriate @samp{F} packet and keeps up waiting for the next
38382 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38383 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38384 Protocol Extension}, for more details.
38388 @node General Query Packets
38389 @section General Query Packets
38390 @cindex remote query requests
38392 Packets starting with @samp{q} are @dfn{general query packets};
38393 packets starting with @samp{Q} are @dfn{general set packets}. General
38394 query and set packets are a semi-unified form for retrieving and
38395 sending information to and from the stub.
38397 The initial letter of a query or set packet is followed by a name
38398 indicating what sort of thing the packet applies to. For example,
38399 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38400 definitions with the stub. These packet names follow some
38405 The name must not contain commas, colons or semicolons.
38407 Most @value{GDBN} query and set packets have a leading upper case
38410 The names of custom vendor packets should use a company prefix, in
38411 lower case, followed by a period. For example, packets designed at
38412 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38413 foos) or @samp{Qacme.bar} (for setting bars).
38416 The name of a query or set packet should be separated from any
38417 parameters by a @samp{:}; the parameters themselves should be
38418 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38419 full packet name, and check for a separator or the end of the packet,
38420 in case two packet names share a common prefix. New packets should not begin
38421 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38422 packets predate these conventions, and have arguments without any terminator
38423 for the packet name; we suspect they are in widespread use in places that
38424 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38425 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38428 Like the descriptions of the other packets, each description here
38429 has a template showing the packet's overall syntax, followed by an
38430 explanation of the packet's meaning. We include spaces in some of the
38431 templates for clarity; these are not part of the packet's syntax. No
38432 @value{GDBN} packet uses spaces to separate its components.
38434 Here are the currently defined query and set packets:
38440 Turn on or off the agent as a helper to perform some debugging operations
38441 delegated from @value{GDBN} (@pxref{Control Agent}).
38443 @item QAllow:@var{op}:@var{val}@dots{}
38444 @cindex @samp{QAllow} packet
38445 Specify which operations @value{GDBN} expects to request of the
38446 target, as a semicolon-separated list of operation name and value
38447 pairs. Possible values for @var{op} include @samp{WriteReg},
38448 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38449 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38450 indicating that @value{GDBN} will not request the operation, or 1,
38451 indicating that it may. (The target can then use this to set up its
38452 own internals optimally, for instance if the debugger never expects to
38453 insert breakpoints, it may not need to install its own trap handler.)
38456 @cindex current thread, remote request
38457 @cindex @samp{qC} packet
38458 Return the current thread ID.
38462 @item QC @var{thread-id}
38463 Where @var{thread-id} is a thread ID as documented in
38464 @ref{thread-id syntax}.
38465 @item @r{(anything else)}
38466 Any other reply implies the old thread ID.
38469 @item qCRC:@var{addr},@var{length}
38470 @cindex CRC of memory block, remote request
38471 @cindex @samp{qCRC} packet
38472 @anchor{qCRC packet}
38473 Compute the CRC checksum of a block of memory using CRC-32 defined in
38474 IEEE 802.3. The CRC is computed byte at a time, taking the most
38475 significant bit of each byte first. The initial pattern code
38476 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38478 @emph{Note:} This is the same CRC used in validating separate debug
38479 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38480 Files}). However the algorithm is slightly different. When validating
38481 separate debug files, the CRC is computed taking the @emph{least}
38482 significant bit of each byte first, and the final result is inverted to
38483 detect trailing zeros.
38488 An error (such as memory fault)
38489 @item C @var{crc32}
38490 The specified memory region's checksum is @var{crc32}.
38493 @item QDisableRandomization:@var{value}
38494 @cindex disable address space randomization, remote request
38495 @cindex @samp{QDisableRandomization} packet
38496 Some target operating systems will randomize the virtual address space
38497 of the inferior process as a security feature, but provide a feature
38498 to disable such randomization, e.g.@: to allow for a more deterministic
38499 debugging experience. On such systems, this packet with a @var{value}
38500 of 1 directs the target to disable address space randomization for
38501 processes subsequently started via @samp{vRun} packets, while a packet
38502 with a @var{value} of 0 tells the target to enable address space
38505 This packet is only available in extended mode (@pxref{extended mode}).
38510 The request succeeded.
38513 An error occurred. The error number @var{nn} is given as hex digits.
38516 An empty reply indicates that @samp{QDisableRandomization} is not supported
38520 This packet is not probed by default; the remote stub must request it,
38521 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38522 This should only be done on targets that actually support disabling
38523 address space randomization.
38525 @item QStartupWithShell:@var{value}
38526 @cindex startup with shell, remote request
38527 @cindex @samp{QStartupWithShell} packet
38528 On UNIX-like targets, it is possible to start the inferior using a
38529 shell program. This is the default behavior on both @value{GDBN} and
38530 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38531 used to inform @command{gdbserver} whether it should start the
38532 inferior using a shell or not.
38534 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38535 to start the inferior. If @var{value} is @samp{1},
38536 @command{gdbserver} will use a shell to start the inferior. All other
38537 values are considered an error.
38539 This packet is only available in extended mode (@pxref{extended
38545 The request succeeded.
38548 An error occurred. The error number @var{nn} is given as hex digits.
38551 This packet is not probed by default; the remote stub must request it,
38552 by supplying an appropriate @samp{qSupported} response
38553 (@pxref{qSupported}). This should only be done on targets that
38554 actually support starting the inferior using a shell.
38556 Use of this packet is controlled by the @code{set startup-with-shell}
38557 command; @pxref{set startup-with-shell}.
38559 @item QEnvironmentHexEncoded:@var{hex-value}
38560 @anchor{QEnvironmentHexEncoded}
38561 @cindex set environment variable, remote request
38562 @cindex @samp{QEnvironmentHexEncoded} packet
38563 On UNIX-like targets, it is possible to set environment variables that
38564 will be passed to the inferior during the startup process. This
38565 packet is used to inform @command{gdbserver} of an environment
38566 variable that has been defined by the user on @value{GDBN} (@pxref{set
38569 The packet is composed by @var{hex-value}, an hex encoded
38570 representation of the @var{name=value} format representing an
38571 environment variable. The name of the environment variable is
38572 represented by @var{name}, and the value to be assigned to the
38573 environment variable is represented by @var{value}. If the variable
38574 has no value (i.e., the value is @code{null}), then @var{value} will
38577 This packet is only available in extended mode (@pxref{extended
38583 The request succeeded.
38586 This packet is not probed by default; the remote stub must request it,
38587 by supplying an appropriate @samp{qSupported} response
38588 (@pxref{qSupported}). This should only be done on targets that
38589 actually support passing environment variables to the starting
38592 This packet is related to the @code{set environment} command;
38593 @pxref{set environment}.
38595 @item QEnvironmentUnset:@var{hex-value}
38596 @anchor{QEnvironmentUnset}
38597 @cindex unset environment variable, remote request
38598 @cindex @samp{QEnvironmentUnset} packet
38599 On UNIX-like targets, it is possible to unset environment variables
38600 before starting the inferior in the remote target. This packet is
38601 used to inform @command{gdbserver} of an environment variable that has
38602 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38604 The packet is composed by @var{hex-value}, an hex encoded
38605 representation of the name of the environment variable to be unset.
38607 This packet is only available in extended mode (@pxref{extended
38613 The request succeeded.
38616 This packet is not probed by default; the remote stub must request it,
38617 by supplying an appropriate @samp{qSupported} response
38618 (@pxref{qSupported}). This should only be done on targets that
38619 actually support passing environment variables to the starting
38622 This packet is related to the @code{unset environment} command;
38623 @pxref{unset environment}.
38625 @item QEnvironmentReset
38626 @anchor{QEnvironmentReset}
38627 @cindex reset environment, remote request
38628 @cindex @samp{QEnvironmentReset} packet
38629 On UNIX-like targets, this packet is used to reset the state of
38630 environment variables in the remote target before starting the
38631 inferior. In this context, reset means unsetting all environment
38632 variables that were previously set by the user (i.e., were not
38633 initially present in the environment). It is sent to
38634 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38635 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38636 (@pxref{QEnvironmentUnset}) packets.
38638 This packet is only available in extended mode (@pxref{extended
38644 The request succeeded.
38647 This packet is not probed by default; the remote stub must request it,
38648 by supplying an appropriate @samp{qSupported} response
38649 (@pxref{qSupported}). This should only be done on targets that
38650 actually support passing environment variables to the starting
38653 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38654 @anchor{QSetWorkingDir packet}
38655 @cindex set working directory, remote request
38656 @cindex @samp{QSetWorkingDir} packet
38657 This packet is used to inform the remote server of the intended
38658 current working directory for programs that are going to be executed.
38660 The packet is composed by @var{directory}, an hex encoded
38661 representation of the directory that the remote inferior will use as
38662 its current working directory. If @var{directory} is an empty string,
38663 the remote server should reset the inferior's current working
38664 directory to its original, empty value.
38666 This packet is only available in extended mode (@pxref{extended
38672 The request succeeded.
38676 @itemx qsThreadInfo
38677 @cindex list active threads, remote request
38678 @cindex @samp{qfThreadInfo} packet
38679 @cindex @samp{qsThreadInfo} packet
38680 Obtain a list of all active thread IDs from the target (OS). Since there
38681 may be too many active threads to fit into one reply packet, this query
38682 works iteratively: it may require more than one query/reply sequence to
38683 obtain the entire list of threads. The first query of the sequence will
38684 be the @samp{qfThreadInfo} query; subsequent queries in the
38685 sequence will be the @samp{qsThreadInfo} query.
38687 NOTE: This packet replaces the @samp{qL} query (see below).
38691 @item m @var{thread-id}
38693 @item m @var{thread-id},@var{thread-id}@dots{}
38694 a comma-separated list of thread IDs
38696 (lower case letter @samp{L}) denotes end of list.
38699 In response to each query, the target will reply with a list of one or
38700 more thread IDs, separated by commas.
38701 @value{GDBN} will respond to each reply with a request for more thread
38702 ids (using the @samp{qs} form of the query), until the target responds
38703 with @samp{l} (lower-case ell, for @dfn{last}).
38704 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38707 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38708 initial connection with the remote target, and the very first thread ID
38709 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38710 message. Therefore, the stub should ensure that the first thread ID in
38711 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38713 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38714 @cindex get thread-local storage address, remote request
38715 @cindex @samp{qGetTLSAddr} packet
38716 Fetch the address associated with thread local storage specified
38717 by @var{thread-id}, @var{offset}, and @var{lm}.
38719 @var{thread-id} is the thread ID associated with the
38720 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38722 @var{offset} is the (big endian, hex encoded) offset associated with the
38723 thread local variable. (This offset is obtained from the debug
38724 information associated with the variable.)
38726 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38727 load module associated with the thread local storage. For example,
38728 a @sc{gnu}/Linux system will pass the link map address of the shared
38729 object associated with the thread local storage under consideration.
38730 Other operating environments may choose to represent the load module
38731 differently, so the precise meaning of this parameter will vary.
38735 @item @var{XX}@dots{}
38736 Hex encoded (big endian) bytes representing the address of the thread
38737 local storage requested.
38740 An error occurred. The error number @var{nn} is given as hex digits.
38743 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38746 @item qGetTIBAddr:@var{thread-id}
38747 @cindex get thread information block address
38748 @cindex @samp{qGetTIBAddr} packet
38749 Fetch address of the Windows OS specific Thread Information Block.
38751 @var{thread-id} is the thread ID associated with the thread.
38755 @item @var{XX}@dots{}
38756 Hex encoded (big endian) bytes representing the linear address of the
38757 thread information block.
38760 An error occured. This means that either the thread was not found, or the
38761 address could not be retrieved.
38764 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38767 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38768 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38769 digit) is one to indicate the first query and zero to indicate a
38770 subsequent query; @var{threadcount} (two hex digits) is the maximum
38771 number of threads the response packet can contain; and @var{nextthread}
38772 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38773 returned in the response as @var{argthread}.
38775 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38779 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38780 Where: @var{count} (two hex digits) is the number of threads being
38781 returned; @var{done} (one hex digit) is zero to indicate more threads
38782 and one indicates no further threads; @var{argthreadid} (eight hex
38783 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38784 is a sequence of thread IDs, @var{threadid} (eight hex
38785 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38789 @cindex section offsets, remote request
38790 @cindex @samp{qOffsets} packet
38791 Get section offsets that the target used when relocating the downloaded
38796 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38797 Relocate the @code{Text} section by @var{xxx} from its original address.
38798 Relocate the @code{Data} section by @var{yyy} from its original address.
38799 If the object file format provides segment information (e.g.@: @sc{elf}
38800 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38801 segments by the supplied offsets.
38803 @emph{Note: while a @code{Bss} offset may be included in the response,
38804 @value{GDBN} ignores this and instead applies the @code{Data} offset
38805 to the @code{Bss} section.}
38807 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38808 Relocate the first segment of the object file, which conventionally
38809 contains program code, to a starting address of @var{xxx}. If
38810 @samp{DataSeg} is specified, relocate the second segment, which
38811 conventionally contains modifiable data, to a starting address of
38812 @var{yyy}. @value{GDBN} will report an error if the object file
38813 does not contain segment information, or does not contain at least
38814 as many segments as mentioned in the reply. Extra segments are
38815 kept at fixed offsets relative to the last relocated segment.
38818 @item qP @var{mode} @var{thread-id}
38819 @cindex thread information, remote request
38820 @cindex @samp{qP} packet
38821 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38822 encoded 32 bit mode; @var{thread-id} is a thread ID
38823 (@pxref{thread-id syntax}).
38825 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38828 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38832 @cindex non-stop mode, remote request
38833 @cindex @samp{QNonStop} packet
38835 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38836 @xref{Remote Non-Stop}, for more information.
38841 The request succeeded.
38844 An error occurred. The error number @var{nn} is given as hex digits.
38847 An empty reply indicates that @samp{QNonStop} is not supported by
38851 This packet is not probed by default; the remote stub must request it,
38852 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38853 Use of this packet is controlled by the @code{set non-stop} command;
38854 @pxref{Non-Stop Mode}.
38856 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38857 @itemx QCatchSyscalls:0
38858 @cindex catch syscalls from inferior, remote request
38859 @cindex @samp{QCatchSyscalls} packet
38860 @anchor{QCatchSyscalls}
38861 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38862 catching syscalls from the inferior process.
38864 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38865 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38866 is listed, every system call should be reported.
38868 Note that if a syscall not in the list is reported, @value{GDBN} will
38869 still filter the event according to its own list from all corresponding
38870 @code{catch syscall} commands. However, it is more efficient to only
38871 report the requested syscalls.
38873 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38874 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38876 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38877 kept for the new process too. On targets where exec may affect syscall
38878 numbers, for example with exec between 32 and 64-bit processes, the
38879 client should send a new packet with the new syscall list.
38884 The request succeeded.
38887 An error occurred. @var{nn} are hex digits.
38890 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38894 Use of this packet is controlled by the @code{set remote catch-syscalls}
38895 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38896 This packet is not probed by default; the remote stub must request it,
38897 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38899 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38900 @cindex pass signals to inferior, remote request
38901 @cindex @samp{QPassSignals} packet
38902 @anchor{QPassSignals}
38903 Each listed @var{signal} should be passed directly to the inferior process.
38904 Signals are numbered identically to continue packets and stop replies
38905 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38906 strictly greater than the previous item. These signals do not need to stop
38907 the inferior, or be reported to @value{GDBN}. All other signals should be
38908 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38909 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38910 new list. This packet improves performance when using @samp{handle
38911 @var{signal} nostop noprint pass}.
38916 The request succeeded.
38919 An error occurred. The error number @var{nn} is given as hex digits.
38922 An empty reply indicates that @samp{QPassSignals} is not supported by
38926 Use of this packet is controlled by the @code{set remote pass-signals}
38927 command (@pxref{Remote Configuration, set remote pass-signals}).
38928 This packet is not probed by default; the remote stub must request it,
38929 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38931 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38932 @cindex signals the inferior may see, remote request
38933 @cindex @samp{QProgramSignals} packet
38934 @anchor{QProgramSignals}
38935 Each listed @var{signal} may be delivered to the inferior process.
38936 Others should be silently discarded.
38938 In some cases, the remote stub may need to decide whether to deliver a
38939 signal to the program or not without @value{GDBN} involvement. One
38940 example of that is while detaching --- the program's threads may have
38941 stopped for signals that haven't yet had a chance of being reported to
38942 @value{GDBN}, and so the remote stub can use the signal list specified
38943 by this packet to know whether to deliver or ignore those pending
38946 This does not influence whether to deliver a signal as requested by a
38947 resumption packet (@pxref{vCont packet}).
38949 Signals are numbered identically to continue packets and stop replies
38950 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38951 strictly greater than the previous item. Multiple
38952 @samp{QProgramSignals} packets do not combine; any earlier
38953 @samp{QProgramSignals} list is completely replaced by the new list.
38958 The request succeeded.
38961 An error occurred. The error number @var{nn} is given as hex digits.
38964 An empty reply indicates that @samp{QProgramSignals} is not supported
38968 Use of this packet is controlled by the @code{set remote program-signals}
38969 command (@pxref{Remote Configuration, set remote program-signals}).
38970 This packet is not probed by default; the remote stub must request it,
38971 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38973 @anchor{QThreadEvents}
38974 @item QThreadEvents:1
38975 @itemx QThreadEvents:0
38976 @cindex thread create/exit events, remote request
38977 @cindex @samp{QThreadEvents} packet
38979 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38980 reporting of thread create and exit events. @xref{thread create
38981 event}, for the reply specifications. For example, this is used in
38982 non-stop mode when @value{GDBN} stops a set of threads and
38983 synchronously waits for the their corresponding stop replies. Without
38984 exit events, if one of the threads exits, @value{GDBN} would hang
38985 forever not knowing that it should no longer expect a stop for that
38986 same thread. @value{GDBN} does not enable this feature unless the
38987 stub reports that it supports it by including @samp{QThreadEvents+} in
38988 its @samp{qSupported} reply.
38993 The request succeeded.
38996 An error occurred. The error number @var{nn} is given as hex digits.
38999 An empty reply indicates that @samp{QThreadEvents} is not supported by
39003 Use of this packet is controlled by the @code{set remote thread-events}
39004 command (@pxref{Remote Configuration, set remote thread-events}).
39006 @item qRcmd,@var{command}
39007 @cindex execute remote command, remote request
39008 @cindex @samp{qRcmd} packet
39009 @var{command} (hex encoded) is passed to the local interpreter for
39010 execution. Invalid commands should be reported using the output
39011 string. Before the final result packet, the target may also respond
39012 with a number of intermediate @samp{O@var{output}} console output
39013 packets. @emph{Implementors should note that providing access to a
39014 stubs's interpreter may have security implications}.
39019 A command response with no output.
39021 A command response with the hex encoded output string @var{OUTPUT}.
39023 Indicate a badly formed request.
39025 An empty reply indicates that @samp{qRcmd} is not recognized.
39028 (Note that the @code{qRcmd} packet's name is separated from the
39029 command by a @samp{,}, not a @samp{:}, contrary to the naming
39030 conventions above. Please don't use this packet as a model for new
39033 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39034 @cindex searching memory, in remote debugging
39036 @cindex @samp{qSearch:memory} packet
39038 @cindex @samp{qSearch memory} packet
39039 @anchor{qSearch memory}
39040 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39041 Both @var{address} and @var{length} are encoded in hex;
39042 @var{search-pattern} is a sequence of bytes, also hex encoded.
39047 The pattern was not found.
39049 The pattern was found at @var{address}.
39051 A badly formed request or an error was encountered while searching memory.
39053 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39056 @item QStartNoAckMode
39057 @cindex @samp{QStartNoAckMode} packet
39058 @anchor{QStartNoAckMode}
39059 Request that the remote stub disable the normal @samp{+}/@samp{-}
39060 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39065 The stub has switched to no-acknowledgment mode.
39066 @value{GDBN} acknowledges this reponse,
39067 but neither the stub nor @value{GDBN} shall send or expect further
39068 @samp{+}/@samp{-} acknowledgments in the current connection.
39070 An empty reply indicates that the stub does not support no-acknowledgment mode.
39073 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39074 @cindex supported packets, remote query
39075 @cindex features of the remote protocol
39076 @cindex @samp{qSupported} packet
39077 @anchor{qSupported}
39078 Tell the remote stub about features supported by @value{GDBN}, and
39079 query the stub for features it supports. This packet allows
39080 @value{GDBN} and the remote stub to take advantage of each others'
39081 features. @samp{qSupported} also consolidates multiple feature probes
39082 at startup, to improve @value{GDBN} performance---a single larger
39083 packet performs better than multiple smaller probe packets on
39084 high-latency links. Some features may enable behavior which must not
39085 be on by default, e.g.@: because it would confuse older clients or
39086 stubs. Other features may describe packets which could be
39087 automatically probed for, but are not. These features must be
39088 reported before @value{GDBN} will use them. This ``default
39089 unsupported'' behavior is not appropriate for all packets, but it
39090 helps to keep the initial connection time under control with new
39091 versions of @value{GDBN} which support increasing numbers of packets.
39095 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39096 The stub supports or does not support each returned @var{stubfeature},
39097 depending on the form of each @var{stubfeature} (see below for the
39100 An empty reply indicates that @samp{qSupported} is not recognized,
39101 or that no features needed to be reported to @value{GDBN}.
39104 The allowed forms for each feature (either a @var{gdbfeature} in the
39105 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39109 @item @var{name}=@var{value}
39110 The remote protocol feature @var{name} is supported, and associated
39111 with the specified @var{value}. The format of @var{value} depends
39112 on the feature, but it must not include a semicolon.
39114 The remote protocol feature @var{name} is supported, and does not
39115 need an associated value.
39117 The remote protocol feature @var{name} is not supported.
39119 The remote protocol feature @var{name} may be supported, and
39120 @value{GDBN} should auto-detect support in some other way when it is
39121 needed. This form will not be used for @var{gdbfeature} notifications,
39122 but may be used for @var{stubfeature} responses.
39125 Whenever the stub receives a @samp{qSupported} request, the
39126 supplied set of @value{GDBN} features should override any previous
39127 request. This allows @value{GDBN} to put the stub in a known
39128 state, even if the stub had previously been communicating with
39129 a different version of @value{GDBN}.
39131 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39136 This feature indicates whether @value{GDBN} supports multiprocess
39137 extensions to the remote protocol. @value{GDBN} does not use such
39138 extensions unless the stub also reports that it supports them by
39139 including @samp{multiprocess+} in its @samp{qSupported} reply.
39140 @xref{multiprocess extensions}, for details.
39143 This feature indicates that @value{GDBN} supports the XML target
39144 description. If the stub sees @samp{xmlRegisters=} with target
39145 specific strings separated by a comma, it will report register
39149 This feature indicates whether @value{GDBN} supports the
39150 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39151 instruction reply packet}).
39154 This feature indicates whether @value{GDBN} supports the swbreak stop
39155 reason in stop replies. @xref{swbreak stop reason}, for details.
39158 This feature indicates whether @value{GDBN} supports the hwbreak stop
39159 reason in stop replies. @xref{swbreak stop reason}, for details.
39162 This feature indicates whether @value{GDBN} supports fork event
39163 extensions to the remote protocol. @value{GDBN} does not use such
39164 extensions unless the stub also reports that it supports them by
39165 including @samp{fork-events+} in its @samp{qSupported} reply.
39168 This feature indicates whether @value{GDBN} supports vfork event
39169 extensions to the remote protocol. @value{GDBN} does not use such
39170 extensions unless the stub also reports that it supports them by
39171 including @samp{vfork-events+} in its @samp{qSupported} reply.
39174 This feature indicates whether @value{GDBN} supports exec event
39175 extensions to the remote protocol. @value{GDBN} does not use such
39176 extensions unless the stub also reports that it supports them by
39177 including @samp{exec-events+} in its @samp{qSupported} reply.
39179 @item vContSupported
39180 This feature indicates whether @value{GDBN} wants to know the
39181 supported actions in the reply to @samp{vCont?} packet.
39184 Stubs should ignore any unknown values for
39185 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39186 packet supports receiving packets of unlimited length (earlier
39187 versions of @value{GDBN} may reject overly long responses). Additional values
39188 for @var{gdbfeature} may be defined in the future to let the stub take
39189 advantage of new features in @value{GDBN}, e.g.@: incompatible
39190 improvements in the remote protocol---the @samp{multiprocess} feature is
39191 an example of such a feature. The stub's reply should be independent
39192 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39193 describes all the features it supports, and then the stub replies with
39194 all the features it supports.
39196 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39197 responses, as long as each response uses one of the standard forms.
39199 Some features are flags. A stub which supports a flag feature
39200 should respond with a @samp{+} form response. Other features
39201 require values, and the stub should respond with an @samp{=}
39204 Each feature has a default value, which @value{GDBN} will use if
39205 @samp{qSupported} is not available or if the feature is not mentioned
39206 in the @samp{qSupported} response. The default values are fixed; a
39207 stub is free to omit any feature responses that match the defaults.
39209 Not all features can be probed, but for those which can, the probing
39210 mechanism is useful: in some cases, a stub's internal
39211 architecture may not allow the protocol layer to know some information
39212 about the underlying target in advance. This is especially common in
39213 stubs which may be configured for multiple targets.
39215 These are the currently defined stub features and their properties:
39217 @multitable @columnfractions 0.35 0.2 0.12 0.2
39218 @c NOTE: The first row should be @headitem, but we do not yet require
39219 @c a new enough version of Texinfo (4.7) to use @headitem.
39221 @tab Value Required
39225 @item @samp{PacketSize}
39230 @item @samp{qXfer:auxv:read}
39235 @item @samp{qXfer:btrace:read}
39240 @item @samp{qXfer:btrace-conf:read}
39245 @item @samp{qXfer:exec-file:read}
39250 @item @samp{qXfer:features:read}
39255 @item @samp{qXfer:libraries:read}
39260 @item @samp{qXfer:libraries-svr4:read}
39265 @item @samp{augmented-libraries-svr4-read}
39270 @item @samp{qXfer:memory-map:read}
39275 @item @samp{qXfer:sdata:read}
39280 @item @samp{qXfer:spu:read}
39285 @item @samp{qXfer:spu:write}
39290 @item @samp{qXfer:siginfo:read}
39295 @item @samp{qXfer:siginfo:write}
39300 @item @samp{qXfer:threads:read}
39305 @item @samp{qXfer:traceframe-info:read}
39310 @item @samp{qXfer:uib:read}
39315 @item @samp{qXfer:fdpic:read}
39320 @item @samp{Qbtrace:off}
39325 @item @samp{Qbtrace:bts}
39330 @item @samp{Qbtrace:pt}
39335 @item @samp{Qbtrace-conf:bts:size}
39340 @item @samp{Qbtrace-conf:pt:size}
39345 @item @samp{QNonStop}
39350 @item @samp{QCatchSyscalls}
39355 @item @samp{QPassSignals}
39360 @item @samp{QStartNoAckMode}
39365 @item @samp{multiprocess}
39370 @item @samp{ConditionalBreakpoints}
39375 @item @samp{ConditionalTracepoints}
39380 @item @samp{ReverseContinue}
39385 @item @samp{ReverseStep}
39390 @item @samp{TracepointSource}
39395 @item @samp{QAgent}
39400 @item @samp{QAllow}
39405 @item @samp{QDisableRandomization}
39410 @item @samp{EnableDisableTracepoints}
39415 @item @samp{QTBuffer:size}
39420 @item @samp{tracenz}
39425 @item @samp{BreakpointCommands}
39430 @item @samp{swbreak}
39435 @item @samp{hwbreak}
39440 @item @samp{fork-events}
39445 @item @samp{vfork-events}
39450 @item @samp{exec-events}
39455 @item @samp{QThreadEvents}
39460 @item @samp{no-resumed}
39467 These are the currently defined stub features, in more detail:
39470 @cindex packet size, remote protocol
39471 @item PacketSize=@var{bytes}
39472 The remote stub can accept packets up to at least @var{bytes} in
39473 length. @value{GDBN} will send packets up to this size for bulk
39474 transfers, and will never send larger packets. This is a limit on the
39475 data characters in the packet, including the frame and checksum.
39476 There is no trailing NUL byte in a remote protocol packet; if the stub
39477 stores packets in a NUL-terminated format, it should allow an extra
39478 byte in its buffer for the NUL. If this stub feature is not supported,
39479 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39481 @item qXfer:auxv:read
39482 The remote stub understands the @samp{qXfer:auxv:read} packet
39483 (@pxref{qXfer auxiliary vector read}).
39485 @item qXfer:btrace:read
39486 The remote stub understands the @samp{qXfer:btrace:read}
39487 packet (@pxref{qXfer btrace read}).
39489 @item qXfer:btrace-conf:read
39490 The remote stub understands the @samp{qXfer:btrace-conf:read}
39491 packet (@pxref{qXfer btrace-conf read}).
39493 @item qXfer:exec-file:read
39494 The remote stub understands the @samp{qXfer:exec-file:read} packet
39495 (@pxref{qXfer executable filename read}).
39497 @item qXfer:features:read
39498 The remote stub understands the @samp{qXfer:features:read} packet
39499 (@pxref{qXfer target description read}).
39501 @item qXfer:libraries:read
39502 The remote stub understands the @samp{qXfer:libraries:read} packet
39503 (@pxref{qXfer library list read}).
39505 @item qXfer:libraries-svr4:read
39506 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39507 (@pxref{qXfer svr4 library list read}).
39509 @item augmented-libraries-svr4-read
39510 The remote stub understands the augmented form of the
39511 @samp{qXfer:libraries-svr4:read} packet
39512 (@pxref{qXfer svr4 library list read}).
39514 @item qXfer:memory-map:read
39515 The remote stub understands the @samp{qXfer:memory-map:read} packet
39516 (@pxref{qXfer memory map read}).
39518 @item qXfer:sdata:read
39519 The remote stub understands the @samp{qXfer:sdata:read} packet
39520 (@pxref{qXfer sdata read}).
39522 @item qXfer:spu:read
39523 The remote stub understands the @samp{qXfer:spu:read} packet
39524 (@pxref{qXfer spu read}).
39526 @item qXfer:spu:write
39527 The remote stub understands the @samp{qXfer:spu:write} packet
39528 (@pxref{qXfer spu write}).
39530 @item qXfer:siginfo:read
39531 The remote stub understands the @samp{qXfer:siginfo:read} packet
39532 (@pxref{qXfer siginfo read}).
39534 @item qXfer:siginfo:write
39535 The remote stub understands the @samp{qXfer:siginfo:write} packet
39536 (@pxref{qXfer siginfo write}).
39538 @item qXfer:threads:read
39539 The remote stub understands the @samp{qXfer:threads:read} packet
39540 (@pxref{qXfer threads read}).
39542 @item qXfer:traceframe-info:read
39543 The remote stub understands the @samp{qXfer:traceframe-info:read}
39544 packet (@pxref{qXfer traceframe info read}).
39546 @item qXfer:uib:read
39547 The remote stub understands the @samp{qXfer:uib:read}
39548 packet (@pxref{qXfer unwind info block}).
39550 @item qXfer:fdpic:read
39551 The remote stub understands the @samp{qXfer:fdpic:read}
39552 packet (@pxref{qXfer fdpic loadmap read}).
39555 The remote stub understands the @samp{QNonStop} packet
39556 (@pxref{QNonStop}).
39558 @item QCatchSyscalls
39559 The remote stub understands the @samp{QCatchSyscalls} packet
39560 (@pxref{QCatchSyscalls}).
39563 The remote stub understands the @samp{QPassSignals} packet
39564 (@pxref{QPassSignals}).
39566 @item QStartNoAckMode
39567 The remote stub understands the @samp{QStartNoAckMode} packet and
39568 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39571 @anchor{multiprocess extensions}
39572 @cindex multiprocess extensions, in remote protocol
39573 The remote stub understands the multiprocess extensions to the remote
39574 protocol syntax. The multiprocess extensions affect the syntax of
39575 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39576 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39577 replies. Note that reporting this feature indicates support for the
39578 syntactic extensions only, not that the stub necessarily supports
39579 debugging of more than one process at a time. The stub must not use
39580 multiprocess extensions in packet replies unless @value{GDBN} has also
39581 indicated it supports them in its @samp{qSupported} request.
39583 @item qXfer:osdata:read
39584 The remote stub understands the @samp{qXfer:osdata:read} packet
39585 ((@pxref{qXfer osdata read}).
39587 @item ConditionalBreakpoints
39588 The target accepts and implements evaluation of conditional expressions
39589 defined for breakpoints. The target will only report breakpoint triggers
39590 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39592 @item ConditionalTracepoints
39593 The remote stub accepts and implements conditional expressions defined
39594 for tracepoints (@pxref{Tracepoint Conditions}).
39596 @item ReverseContinue
39597 The remote stub accepts and implements the reverse continue packet
39601 The remote stub accepts and implements the reverse step packet
39604 @item TracepointSource
39605 The remote stub understands the @samp{QTDPsrc} packet that supplies
39606 the source form of tracepoint definitions.
39609 The remote stub understands the @samp{QAgent} packet.
39612 The remote stub understands the @samp{QAllow} packet.
39614 @item QDisableRandomization
39615 The remote stub understands the @samp{QDisableRandomization} packet.
39617 @item StaticTracepoint
39618 @cindex static tracepoints, in remote protocol
39619 The remote stub supports static tracepoints.
39621 @item InstallInTrace
39622 @anchor{install tracepoint in tracing}
39623 The remote stub supports installing tracepoint in tracing.
39625 @item EnableDisableTracepoints
39626 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39627 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39628 to be enabled and disabled while a trace experiment is running.
39630 @item QTBuffer:size
39631 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39632 packet that allows to change the size of the trace buffer.
39635 @cindex string tracing, in remote protocol
39636 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39637 See @ref{Bytecode Descriptions} for details about the bytecode.
39639 @item BreakpointCommands
39640 @cindex breakpoint commands, in remote protocol
39641 The remote stub supports running a breakpoint's command list itself,
39642 rather than reporting the hit to @value{GDBN}.
39645 The remote stub understands the @samp{Qbtrace:off} packet.
39648 The remote stub understands the @samp{Qbtrace:bts} packet.
39651 The remote stub understands the @samp{Qbtrace:pt} packet.
39653 @item Qbtrace-conf:bts:size
39654 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39656 @item Qbtrace-conf:pt:size
39657 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39660 The remote stub reports the @samp{swbreak} stop reason for memory
39664 The remote stub reports the @samp{hwbreak} stop reason for hardware
39668 The remote stub reports the @samp{fork} stop reason for fork events.
39671 The remote stub reports the @samp{vfork} stop reason for vfork events
39672 and vforkdone events.
39675 The remote stub reports the @samp{exec} stop reason for exec events.
39677 @item vContSupported
39678 The remote stub reports the supported actions in the reply to
39679 @samp{vCont?} packet.
39681 @item QThreadEvents
39682 The remote stub understands the @samp{QThreadEvents} packet.
39685 The remote stub reports the @samp{N} stop reply.
39690 @cindex symbol lookup, remote request
39691 @cindex @samp{qSymbol} packet
39692 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39693 requests. Accept requests from the target for the values of symbols.
39698 The target does not need to look up any (more) symbols.
39699 @item qSymbol:@var{sym_name}
39700 The target requests the value of symbol @var{sym_name} (hex encoded).
39701 @value{GDBN} may provide the value by using the
39702 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39706 @item qSymbol:@var{sym_value}:@var{sym_name}
39707 Set the value of @var{sym_name} to @var{sym_value}.
39709 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39710 target has previously requested.
39712 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39713 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39719 The target does not need to look up any (more) symbols.
39720 @item qSymbol:@var{sym_name}
39721 The target requests the value of a new symbol @var{sym_name} (hex
39722 encoded). @value{GDBN} will continue to supply the values of symbols
39723 (if available), until the target ceases to request them.
39728 @itemx QTDisconnected
39735 @itemx qTMinFTPILen
39737 @xref{Tracepoint Packets}.
39739 @item qThreadExtraInfo,@var{thread-id}
39740 @cindex thread attributes info, remote request
39741 @cindex @samp{qThreadExtraInfo} packet
39742 Obtain from the target OS a printable string description of thread
39743 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39744 for the forms of @var{thread-id}. This
39745 string may contain anything that the target OS thinks is interesting
39746 for @value{GDBN} to tell the user about the thread. The string is
39747 displayed in @value{GDBN}'s @code{info threads} display. Some
39748 examples of possible thread extra info strings are @samp{Runnable}, or
39749 @samp{Blocked on Mutex}.
39753 @item @var{XX}@dots{}
39754 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39755 comprising the printable string containing the extra information about
39756 the thread's attributes.
39759 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39760 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39761 conventions above. Please don't use this packet as a model for new
39780 @xref{Tracepoint Packets}.
39782 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39783 @cindex read special object, remote request
39784 @cindex @samp{qXfer} packet
39785 @anchor{qXfer read}
39786 Read uninterpreted bytes from the target's special data area
39787 identified by the keyword @var{object}. Request @var{length} bytes
39788 starting at @var{offset} bytes into the data. The content and
39789 encoding of @var{annex} is specific to @var{object}; it can supply
39790 additional details about what data to access.
39795 Data @var{data} (@pxref{Binary Data}) has been read from the
39796 target. There may be more data at a higher address (although
39797 it is permitted to return @samp{m} even for the last valid
39798 block of data, as long as at least one byte of data was read).
39799 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39803 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39804 There is no more data to be read. It is possible for @var{data} to
39805 have fewer bytes than the @var{length} in the request.
39808 The @var{offset} in the request is at the end of the data.
39809 There is no more data to be read.
39812 The request was malformed, or @var{annex} was invalid.
39815 The offset was invalid, or there was an error encountered reading the data.
39816 The @var{nn} part is a hex-encoded @code{errno} value.
39819 An empty reply indicates the @var{object} string was not recognized by
39820 the stub, or that the object does not support reading.
39823 Here are the specific requests of this form defined so far. All the
39824 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39825 formats, listed above.
39828 @item qXfer:auxv:read::@var{offset},@var{length}
39829 @anchor{qXfer auxiliary vector read}
39830 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39831 auxiliary vector}. Note @var{annex} must be empty.
39833 This packet is not probed by default; the remote stub must request it,
39834 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39836 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39837 @anchor{qXfer btrace read}
39839 Return a description of the current branch trace.
39840 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39841 packet may have one of the following values:
39845 Returns all available branch trace.
39848 Returns all available branch trace if the branch trace changed since
39849 the last read request.
39852 Returns the new branch trace since the last read request. Adds a new
39853 block to the end of the trace that begins at zero and ends at the source
39854 location of the first branch in the trace buffer. This extra block is
39855 used to stitch traces together.
39857 If the trace buffer overflowed, returns an error indicating the overflow.
39860 This packet is not probed by default; the remote stub must request it
39861 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39863 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39864 @anchor{qXfer btrace-conf read}
39866 Return a description of the current branch trace configuration.
39867 @xref{Branch Trace Configuration Format}.
39869 This packet is not probed by default; the remote stub must request it
39870 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39872 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39873 @anchor{qXfer executable filename read}
39874 Return the full absolute name of the file that was executed to create
39875 a process running on the remote system. The annex specifies the
39876 numeric process ID of the process to query, encoded as a hexadecimal
39877 number. If the annex part is empty the remote stub should return the
39878 filename corresponding to the currently executing process.
39880 This packet is not probed by default; the remote stub must request it,
39881 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39883 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39884 @anchor{qXfer target description read}
39885 Access the @dfn{target description}. @xref{Target Descriptions}. The
39886 annex specifies which XML document to access. The main description is
39887 always loaded from the @samp{target.xml} annex.
39889 This packet is not probed by default; the remote stub must request it,
39890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39892 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39893 @anchor{qXfer library list read}
39894 Access the target's list of loaded libraries. @xref{Library List Format}.
39895 The annex part of the generic @samp{qXfer} packet must be empty
39896 (@pxref{qXfer read}).
39898 Targets which maintain a list of libraries in the program's memory do
39899 not need to implement this packet; it is designed for platforms where
39900 the operating system manages the list of loaded libraries.
39902 This packet is not probed by default; the remote stub must request it,
39903 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39905 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39906 @anchor{qXfer svr4 library list read}
39907 Access the target's list of loaded libraries when the target is an SVR4
39908 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39909 of the generic @samp{qXfer} packet must be empty unless the remote
39910 stub indicated it supports the augmented form of this packet
39911 by supplying an appropriate @samp{qSupported} response
39912 (@pxref{qXfer read}, @ref{qSupported}).
39914 This packet is optional for better performance on SVR4 targets.
39915 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39917 This packet is not probed by default; the remote stub must request it,
39918 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39920 If the remote stub indicates it supports the augmented form of this
39921 packet then the annex part of the generic @samp{qXfer} packet may
39922 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39923 arguments. The currently supported arguments are:
39926 @item start=@var{address}
39927 A hexadecimal number specifying the address of the @samp{struct
39928 link_map} to start reading the library list from. If unset or zero
39929 then the first @samp{struct link_map} in the library list will be
39930 chosen as the starting point.
39932 @item prev=@var{address}
39933 A hexadecimal number specifying the address of the @samp{struct
39934 link_map} immediately preceding the @samp{struct link_map}
39935 specified by the @samp{start} argument. If unset or zero then
39936 the remote stub will expect that no @samp{struct link_map}
39937 exists prior to the starting point.
39941 Arguments that are not understood by the remote stub will be silently
39944 @item qXfer:memory-map:read::@var{offset},@var{length}
39945 @anchor{qXfer memory map read}
39946 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39947 annex part of the generic @samp{qXfer} packet must be empty
39948 (@pxref{qXfer read}).
39950 This packet is not probed by default; the remote stub must request it,
39951 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39953 @item qXfer:sdata:read::@var{offset},@var{length}
39954 @anchor{qXfer sdata read}
39956 Read contents of the extra collected static tracepoint marker
39957 information. The annex part of the generic @samp{qXfer} packet must
39958 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39961 This packet is not probed by default; the remote stub must request it,
39962 by supplying an appropriate @samp{qSupported} response
39963 (@pxref{qSupported}).
39965 @item qXfer:siginfo:read::@var{offset},@var{length}
39966 @anchor{qXfer siginfo read}
39967 Read contents of the extra signal information on the target
39968 system. The annex part of the generic @samp{qXfer} packet must be
39969 empty (@pxref{qXfer read}).
39971 This packet is not probed by default; the remote stub must request it,
39972 by supplying an appropriate @samp{qSupported} response
39973 (@pxref{qSupported}).
39975 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39976 @anchor{qXfer spu read}
39977 Read contents of an @code{spufs} file on the target system. The
39978 annex specifies which file to read; it must be of the form
39979 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39980 in the target process, and @var{name} identifes the @code{spufs} file
39981 in that context to be accessed.
39983 This packet is not probed by default; the remote stub must request it,
39984 by supplying an appropriate @samp{qSupported} response
39985 (@pxref{qSupported}).
39987 @item qXfer:threads:read::@var{offset},@var{length}
39988 @anchor{qXfer threads read}
39989 Access the list of threads on target. @xref{Thread List Format}. The
39990 annex part of the generic @samp{qXfer} packet must be empty
39991 (@pxref{qXfer read}).
39993 This packet is not probed by default; the remote stub must request it,
39994 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39996 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39997 @anchor{qXfer traceframe info read}
39999 Return a description of the current traceframe's contents.
40000 @xref{Traceframe Info Format}. The annex part of the generic
40001 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40003 This packet is not probed by default; the remote stub must request it,
40004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40006 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40007 @anchor{qXfer unwind info block}
40009 Return the unwind information block for @var{pc}. This packet is used
40010 on OpenVMS/ia64 to ask the kernel unwind information.
40012 This packet is not probed by default.
40014 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40015 @anchor{qXfer fdpic loadmap read}
40016 Read contents of @code{loadmap}s on the target system. The
40017 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40018 executable @code{loadmap} or interpreter @code{loadmap} to read.
40020 This packet is not probed by default; the remote stub must request it,
40021 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40023 @item qXfer:osdata:read::@var{offset},@var{length}
40024 @anchor{qXfer osdata read}
40025 Access the target's @dfn{operating system information}.
40026 @xref{Operating System Information}.
40030 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40031 @cindex write data into object, remote request
40032 @anchor{qXfer write}
40033 Write uninterpreted bytes into the target's special data area
40034 identified by the keyword @var{object}, starting at @var{offset} bytes
40035 into the data. The binary-encoded data (@pxref{Binary Data}) to be
40036 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
40037 is specific to @var{object}; it can supply additional details about what data
40043 @var{nn} (hex encoded) is the number of bytes written.
40044 This may be fewer bytes than supplied in the request.
40047 The request was malformed, or @var{annex} was invalid.
40050 The offset was invalid, or there was an error encountered writing the data.
40051 The @var{nn} part is a hex-encoded @code{errno} value.
40054 An empty reply indicates the @var{object} string was not
40055 recognized by the stub, or that the object does not support writing.
40058 Here are the specific requests of this form defined so far. All the
40059 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40060 formats, listed above.
40063 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40064 @anchor{qXfer siginfo write}
40065 Write @var{data} to the extra signal information on the target system.
40066 The annex part of the generic @samp{qXfer} packet must be
40067 empty (@pxref{qXfer write}).
40069 This packet is not probed by default; the remote stub must request it,
40070 by supplying an appropriate @samp{qSupported} response
40071 (@pxref{qSupported}).
40073 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40074 @anchor{qXfer spu write}
40075 Write @var{data} to an @code{spufs} file on the target system. The
40076 annex specifies which file to write; it must be of the form
40077 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40078 in the target process, and @var{name} identifes the @code{spufs} file
40079 in that context to be accessed.
40081 This packet is not probed by default; the remote stub must request it,
40082 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40085 @item qXfer:@var{object}:@var{operation}:@dots{}
40086 Requests of this form may be added in the future. When a stub does
40087 not recognize the @var{object} keyword, or its support for
40088 @var{object} does not recognize the @var{operation} keyword, the stub
40089 must respond with an empty packet.
40091 @item qAttached:@var{pid}
40092 @cindex query attached, remote request
40093 @cindex @samp{qAttached} packet
40094 Return an indication of whether the remote server attached to an
40095 existing process or created a new process. When the multiprocess
40096 protocol extensions are supported (@pxref{multiprocess extensions}),
40097 @var{pid} is an integer in hexadecimal format identifying the target
40098 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40099 the query packet will be simplified as @samp{qAttached}.
40101 This query is used, for example, to know whether the remote process
40102 should be detached or killed when a @value{GDBN} session is ended with
40103 the @code{quit} command.
40108 The remote server attached to an existing process.
40110 The remote server created a new process.
40112 A badly formed request or an error was encountered.
40116 Enable branch tracing for the current thread using Branch Trace Store.
40121 Branch tracing has been enabled.
40123 A badly formed request or an error was encountered.
40127 Enable branch tracing for the current thread using Intel Processor Trace.
40132 Branch tracing has been enabled.
40134 A badly formed request or an error was encountered.
40138 Disable branch tracing for the current thread.
40143 Branch tracing has been disabled.
40145 A badly formed request or an error was encountered.
40148 @item Qbtrace-conf:bts:size=@var{value}
40149 Set the requested ring buffer size for new threads that use the
40150 btrace recording method in bts format.
40155 The ring buffer size has been set.
40157 A badly formed request or an error was encountered.
40160 @item Qbtrace-conf:pt:size=@var{value}
40161 Set the requested ring buffer size for new threads that use the
40162 btrace recording method in pt format.
40167 The ring buffer size has been set.
40169 A badly formed request or an error was encountered.
40174 @node Architecture-Specific Protocol Details
40175 @section Architecture-Specific Protocol Details
40177 This section describes how the remote protocol is applied to specific
40178 target architectures. Also see @ref{Standard Target Features}, for
40179 details of XML target descriptions for each architecture.
40182 * ARM-Specific Protocol Details::
40183 * MIPS-Specific Protocol Details::
40186 @node ARM-Specific Protocol Details
40187 @subsection @acronym{ARM}-specific Protocol Details
40190 * ARM Breakpoint Kinds::
40193 @node ARM Breakpoint Kinds
40194 @subsubsection @acronym{ARM} Breakpoint Kinds
40195 @cindex breakpoint kinds, @acronym{ARM}
40197 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40202 16-bit Thumb mode breakpoint.
40205 32-bit Thumb mode (Thumb-2) breakpoint.
40208 32-bit @acronym{ARM} mode breakpoint.
40212 @node MIPS-Specific Protocol Details
40213 @subsection @acronym{MIPS}-specific Protocol Details
40216 * MIPS Register packet Format::
40217 * MIPS Breakpoint Kinds::
40220 @node MIPS Register packet Format
40221 @subsubsection @acronym{MIPS} Register Packet Format
40222 @cindex register packet format, @acronym{MIPS}
40224 The following @code{g}/@code{G} packets have previously been defined.
40225 In the below, some thirty-two bit registers are transferred as
40226 sixty-four bits. Those registers should be zero/sign extended (which?)
40227 to fill the space allocated. Register bytes are transferred in target
40228 byte order. The two nibbles within a register byte are transferred
40229 most-significant -- least-significant.
40234 All registers are transferred as thirty-two bit quantities in the order:
40235 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40236 registers; fsr; fir; fp.
40239 All registers are transferred as sixty-four bit quantities (including
40240 thirty-two bit registers such as @code{sr}). The ordering is the same
40245 @node MIPS Breakpoint Kinds
40246 @subsubsection @acronym{MIPS} Breakpoint Kinds
40247 @cindex breakpoint kinds, @acronym{MIPS}
40249 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40254 16-bit @acronym{MIPS16} mode breakpoint.
40257 16-bit @acronym{microMIPS} mode breakpoint.
40260 32-bit standard @acronym{MIPS} mode breakpoint.
40263 32-bit @acronym{microMIPS} mode breakpoint.
40267 @node Tracepoint Packets
40268 @section Tracepoint Packets
40269 @cindex tracepoint packets
40270 @cindex packets, tracepoint
40272 Here we describe the packets @value{GDBN} uses to implement
40273 tracepoints (@pxref{Tracepoints}).
40277 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40278 @cindex @samp{QTDP} packet
40279 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40280 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40281 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40282 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40283 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40284 the number of bytes that the target should copy elsewhere to make room
40285 for the tracepoint. If an @samp{X} is present, it introduces a
40286 tracepoint condition, which consists of a hexadecimal length, followed
40287 by a comma and hex-encoded bytes, in a manner similar to action
40288 encodings as described below. If the trailing @samp{-} is present,
40289 further @samp{QTDP} packets will follow to specify this tracepoint's
40295 The packet was understood and carried out.
40297 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40299 The packet was not recognized.
40302 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40303 Define actions to be taken when a tracepoint is hit. The @var{n} and
40304 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40305 this tracepoint. This packet may only be sent immediately after
40306 another @samp{QTDP} packet that ended with a @samp{-}. If the
40307 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40308 specifying more actions for this tracepoint.
40310 In the series of action packets for a given tracepoint, at most one
40311 can have an @samp{S} before its first @var{action}. If such a packet
40312 is sent, it and the following packets define ``while-stepping''
40313 actions. Any prior packets define ordinary actions --- that is, those
40314 taken when the tracepoint is first hit. If no action packet has an
40315 @samp{S}, then all the packets in the series specify ordinary
40316 tracepoint actions.
40318 The @samp{@var{action}@dots{}} portion of the packet is a series of
40319 actions, concatenated without separators. Each action has one of the
40325 Collect the registers whose bits are set in @var{mask},
40326 a hexadecimal number whose @var{i}'th bit is set if register number
40327 @var{i} should be collected. (The least significant bit is numbered
40328 zero.) Note that @var{mask} may be any number of digits long; it may
40329 not fit in a 32-bit word.
40331 @item M @var{basereg},@var{offset},@var{len}
40332 Collect @var{len} bytes of memory starting at the address in register
40333 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40334 @samp{-1}, then the range has a fixed address: @var{offset} is the
40335 address of the lowest byte to collect. The @var{basereg},
40336 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40337 values (the @samp{-1} value for @var{basereg} is a special case).
40339 @item X @var{len},@var{expr}
40340 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40341 it directs. The agent expression @var{expr} is as described in
40342 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40343 two-digit hex number in the packet; @var{len} is the number of bytes
40344 in the expression (and thus one-half the number of hex digits in the
40349 Any number of actions may be packed together in a single @samp{QTDP}
40350 packet, as long as the packet does not exceed the maximum packet
40351 length (400 bytes, for many stubs). There may be only one @samp{R}
40352 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40353 actions. Any registers referred to by @samp{M} and @samp{X} actions
40354 must be collected by a preceding @samp{R} action. (The
40355 ``while-stepping'' actions are treated as if they were attached to a
40356 separate tracepoint, as far as these restrictions are concerned.)
40361 The packet was understood and carried out.
40363 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40365 The packet was not recognized.
40368 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40369 @cindex @samp{QTDPsrc} packet
40370 Specify a source string of tracepoint @var{n} at address @var{addr}.
40371 This is useful to get accurate reproduction of the tracepoints
40372 originally downloaded at the beginning of the trace run. The @var{type}
40373 is the name of the tracepoint part, such as @samp{cond} for the
40374 tracepoint's conditional expression (see below for a list of types), while
40375 @var{bytes} is the string, encoded in hexadecimal.
40377 @var{start} is the offset of the @var{bytes} within the overall source
40378 string, while @var{slen} is the total length of the source string.
40379 This is intended for handling source strings that are longer than will
40380 fit in a single packet.
40381 @c Add detailed example when this info is moved into a dedicated
40382 @c tracepoint descriptions section.
40384 The available string types are @samp{at} for the location,
40385 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40386 @value{GDBN} sends a separate packet for each command in the action
40387 list, in the same order in which the commands are stored in the list.
40389 The target does not need to do anything with source strings except
40390 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40393 Although this packet is optional, and @value{GDBN} will only send it
40394 if the target replies with @samp{TracepointSource} @xref{General
40395 Query Packets}, it makes both disconnected tracing and trace files
40396 much easier to use. Otherwise the user must be careful that the
40397 tracepoints in effect while looking at trace frames are identical to
40398 the ones in effect during the trace run; even a small discrepancy
40399 could cause @samp{tdump} not to work, or a particular trace frame not
40402 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40403 @cindex define trace state variable, remote request
40404 @cindex @samp{QTDV} packet
40405 Create a new trace state variable, number @var{n}, with an initial
40406 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40407 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40408 the option of not using this packet for initial values of zero; the
40409 target should simply create the trace state variables as they are
40410 mentioned in expressions. The value @var{builtin} should be 1 (one)
40411 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40412 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40413 @samp{qTsV} packet had it set. The contents of @var{name} is the
40414 hex-encoded name (without the leading @samp{$}) of the trace state
40417 @item QTFrame:@var{n}
40418 @cindex @samp{QTFrame} packet
40419 Select the @var{n}'th tracepoint frame from the buffer, and use the
40420 register and memory contents recorded there to answer subsequent
40421 request packets from @value{GDBN}.
40423 A successful reply from the stub indicates that the stub has found the
40424 requested frame. The response is a series of parts, concatenated
40425 without separators, describing the frame we selected. Each part has
40426 one of the following forms:
40430 The selected frame is number @var{n} in the trace frame buffer;
40431 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40432 was no frame matching the criteria in the request packet.
40435 The selected trace frame records a hit of tracepoint number @var{t};
40436 @var{t} is a hexadecimal number.
40440 @item QTFrame:pc:@var{addr}
40441 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40442 currently selected frame whose PC is @var{addr};
40443 @var{addr} is a hexadecimal number.
40445 @item QTFrame:tdp:@var{t}
40446 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40447 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40448 is a hexadecimal number.
40450 @item QTFrame:range:@var{start}:@var{end}
40451 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40452 currently selected frame whose PC is between @var{start} (inclusive)
40453 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40456 @item QTFrame:outside:@var{start}:@var{end}
40457 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40458 frame @emph{outside} the given range of addresses (exclusive).
40461 @cindex @samp{qTMinFTPILen} packet
40462 This packet requests the minimum length of instruction at which a fast
40463 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40464 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40465 it depends on the target system being able to create trampolines in
40466 the first 64K of memory, which might or might not be possible for that
40467 system. So the reply to this packet will be 4 if it is able to
40474 The minimum instruction length is currently unknown.
40476 The minimum instruction length is @var{length}, where @var{length}
40477 is a hexadecimal number greater or equal to 1. A reply
40478 of 1 means that a fast tracepoint may be placed on any instruction
40479 regardless of size.
40481 An error has occurred.
40483 An empty reply indicates that the request is not supported by the stub.
40487 @cindex @samp{QTStart} packet
40488 Begin the tracepoint experiment. Begin collecting data from
40489 tracepoint hits in the trace frame buffer. This packet supports the
40490 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40491 instruction reply packet}).
40494 @cindex @samp{QTStop} packet
40495 End the tracepoint experiment. Stop collecting trace frames.
40497 @item QTEnable:@var{n}:@var{addr}
40499 @cindex @samp{QTEnable} packet
40500 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40501 experiment. If the tracepoint was previously disabled, then collection
40502 of data from it will resume.
40504 @item QTDisable:@var{n}:@var{addr}
40506 @cindex @samp{QTDisable} packet
40507 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40508 experiment. No more data will be collected from the tracepoint unless
40509 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40512 @cindex @samp{QTinit} packet
40513 Clear the table of tracepoints, and empty the trace frame buffer.
40515 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40516 @cindex @samp{QTro} packet
40517 Establish the given ranges of memory as ``transparent''. The stub
40518 will answer requests for these ranges from memory's current contents,
40519 if they were not collected as part of the tracepoint hit.
40521 @value{GDBN} uses this to mark read-only regions of memory, like those
40522 containing program code. Since these areas never change, they should
40523 still have the same contents they did when the tracepoint was hit, so
40524 there's no reason for the stub to refuse to provide their contents.
40526 @item QTDisconnected:@var{value}
40527 @cindex @samp{QTDisconnected} packet
40528 Set the choice to what to do with the tracing run when @value{GDBN}
40529 disconnects from the target. A @var{value} of 1 directs the target to
40530 continue the tracing run, while 0 tells the target to stop tracing if
40531 @value{GDBN} is no longer in the picture.
40534 @cindex @samp{qTStatus} packet
40535 Ask the stub if there is a trace experiment running right now.
40537 The reply has the form:
40541 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40542 @var{running} is a single digit @code{1} if the trace is presently
40543 running, or @code{0} if not. It is followed by semicolon-separated
40544 optional fields that an agent may use to report additional status.
40548 If the trace is not running, the agent may report any of several
40549 explanations as one of the optional fields:
40554 No trace has been run yet.
40556 @item tstop[:@var{text}]:0
40557 The trace was stopped by a user-originated stop command. The optional
40558 @var{text} field is a user-supplied string supplied as part of the
40559 stop command (for instance, an explanation of why the trace was
40560 stopped manually). It is hex-encoded.
40563 The trace stopped because the trace buffer filled up.
40565 @item tdisconnected:0
40566 The trace stopped because @value{GDBN} disconnected from the target.
40568 @item tpasscount:@var{tpnum}
40569 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40571 @item terror:@var{text}:@var{tpnum}
40572 The trace stopped because tracepoint @var{tpnum} had an error. The
40573 string @var{text} is available to describe the nature of the error
40574 (for instance, a divide by zero in the condition expression); it
40578 The trace stopped for some other reason.
40582 Additional optional fields supply statistical and other information.
40583 Although not required, they are extremely useful for users monitoring
40584 the progress of a trace run. If a trace has stopped, and these
40585 numbers are reported, they must reflect the state of the just-stopped
40590 @item tframes:@var{n}
40591 The number of trace frames in the buffer.
40593 @item tcreated:@var{n}
40594 The total number of trace frames created during the run. This may
40595 be larger than the trace frame count, if the buffer is circular.
40597 @item tsize:@var{n}
40598 The total size of the trace buffer, in bytes.
40600 @item tfree:@var{n}
40601 The number of bytes still unused in the buffer.
40603 @item circular:@var{n}
40604 The value of the circular trace buffer flag. @code{1} means that the
40605 trace buffer is circular and old trace frames will be discarded if
40606 necessary to make room, @code{0} means that the trace buffer is linear
40609 @item disconn:@var{n}
40610 The value of the disconnected tracing flag. @code{1} means that
40611 tracing will continue after @value{GDBN} disconnects, @code{0} means
40612 that the trace run will stop.
40616 @item qTP:@var{tp}:@var{addr}
40617 @cindex tracepoint status, remote request
40618 @cindex @samp{qTP} packet
40619 Ask the stub for the current state of tracepoint number @var{tp} at
40620 address @var{addr}.
40624 @item V@var{hits}:@var{usage}
40625 The tracepoint has been hit @var{hits} times so far during the trace
40626 run, and accounts for @var{usage} in the trace buffer. Note that
40627 @code{while-stepping} steps are not counted as separate hits, but the
40628 steps' space consumption is added into the usage number.
40632 @item qTV:@var{var}
40633 @cindex trace state variable value, remote request
40634 @cindex @samp{qTV} packet
40635 Ask the stub for the value of the trace state variable number @var{var}.
40640 The value of the variable is @var{value}. This will be the current
40641 value of the variable if the user is examining a running target, or a
40642 saved value if the variable was collected in the trace frame that the
40643 user is looking at. Note that multiple requests may result in
40644 different reply values, such as when requesting values while the
40645 program is running.
40648 The value of the variable is unknown. This would occur, for example,
40649 if the user is examining a trace frame in which the requested variable
40654 @cindex @samp{qTfP} packet
40656 @cindex @samp{qTsP} packet
40657 These packets request data about tracepoints that are being used by
40658 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40659 of data, and multiple @code{qTsP} to get additional pieces. Replies
40660 to these packets generally take the form of the @code{QTDP} packets
40661 that define tracepoints. (FIXME add detailed syntax)
40664 @cindex @samp{qTfV} packet
40666 @cindex @samp{qTsV} packet
40667 These packets request data about trace state variables that are on the
40668 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40669 and multiple @code{qTsV} to get additional variables. Replies to
40670 these packets follow the syntax of the @code{QTDV} packets that define
40671 trace state variables.
40677 @cindex @samp{qTfSTM} packet
40678 @cindex @samp{qTsSTM} packet
40679 These packets request data about static tracepoint markers that exist
40680 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40681 first piece of data, and multiple @code{qTsSTM} to get additional
40682 pieces. Replies to these packets take the following form:
40686 @item m @var{address}:@var{id}:@var{extra}
40688 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40689 a comma-separated list of markers
40691 (lower case letter @samp{L}) denotes end of list.
40693 An error occurred. The error number @var{nn} is given as hex digits.
40695 An empty reply indicates that the request is not supported by the
40699 The @var{address} is encoded in hex;
40700 @var{id} and @var{extra} are strings encoded in hex.
40702 In response to each query, the target will reply with a list of one or
40703 more markers, separated by commas. @value{GDBN} will respond to each
40704 reply with a request for more markers (using the @samp{qs} form of the
40705 query), until the target responds with @samp{l} (lower-case ell, for
40708 @item qTSTMat:@var{address}
40710 @cindex @samp{qTSTMat} packet
40711 This packets requests data about static tracepoint markers in the
40712 target program at @var{address}. Replies to this packet follow the
40713 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40714 tracepoint markers.
40716 @item QTSave:@var{filename}
40717 @cindex @samp{QTSave} packet
40718 This packet directs the target to save trace data to the file name
40719 @var{filename} in the target's filesystem. The @var{filename} is encoded
40720 as a hex string; the interpretation of the file name (relative vs
40721 absolute, wild cards, etc) is up to the target.
40723 @item qTBuffer:@var{offset},@var{len}
40724 @cindex @samp{qTBuffer} packet
40725 Return up to @var{len} bytes of the current contents of trace buffer,
40726 starting at @var{offset}. The trace buffer is treated as if it were
40727 a contiguous collection of traceframes, as per the trace file format.
40728 The reply consists as many hex-encoded bytes as the target can deliver
40729 in a packet; it is not an error to return fewer than were asked for.
40730 A reply consisting of just @code{l} indicates that no bytes are
40733 @item QTBuffer:circular:@var{value}
40734 This packet directs the target to use a circular trace buffer if
40735 @var{value} is 1, or a linear buffer if the value is 0.
40737 @item QTBuffer:size:@var{size}
40738 @anchor{QTBuffer-size}
40739 @cindex @samp{QTBuffer size} packet
40740 This packet directs the target to make the trace buffer be of size
40741 @var{size} if possible. A value of @code{-1} tells the target to
40742 use whatever size it prefers.
40744 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40745 @cindex @samp{QTNotes} packet
40746 This packet adds optional textual notes to the trace run. Allowable
40747 types include @code{user}, @code{notes}, and @code{tstop}, the
40748 @var{text} fields are arbitrary strings, hex-encoded.
40752 @subsection Relocate instruction reply packet
40753 When installing fast tracepoints in memory, the target may need to
40754 relocate the instruction currently at the tracepoint address to a
40755 different address in memory. For most instructions, a simple copy is
40756 enough, but, for example, call instructions that implicitly push the
40757 return address on the stack, and relative branches or other
40758 PC-relative instructions require offset adjustment, so that the effect
40759 of executing the instruction at a different address is the same as if
40760 it had executed in the original location.
40762 In response to several of the tracepoint packets, the target may also
40763 respond with a number of intermediate @samp{qRelocInsn} request
40764 packets before the final result packet, to have @value{GDBN} handle
40765 this relocation operation. If a packet supports this mechanism, its
40766 documentation will explicitly say so. See for example the above
40767 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40768 format of the request is:
40771 @item qRelocInsn:@var{from};@var{to}
40773 This requests @value{GDBN} to copy instruction at address @var{from}
40774 to address @var{to}, possibly adjusted so that executing the
40775 instruction at @var{to} has the same effect as executing it at
40776 @var{from}. @value{GDBN} writes the adjusted instruction to target
40777 memory starting at @var{to}.
40782 @item qRelocInsn:@var{adjusted_size}
40783 Informs the stub the relocation is complete. The @var{adjusted_size} is
40784 the length in bytes of resulting relocated instruction sequence.
40786 A badly formed request was detected, or an error was encountered while
40787 relocating the instruction.
40790 @node Host I/O Packets
40791 @section Host I/O Packets
40792 @cindex Host I/O, remote protocol
40793 @cindex file transfer, remote protocol
40795 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40796 operations on the far side of a remote link. For example, Host I/O is
40797 used to upload and download files to a remote target with its own
40798 filesystem. Host I/O uses the same constant values and data structure
40799 layout as the target-initiated File-I/O protocol. However, the
40800 Host I/O packets are structured differently. The target-initiated
40801 protocol relies on target memory to store parameters and buffers.
40802 Host I/O requests are initiated by @value{GDBN}, and the
40803 target's memory is not involved. @xref{File-I/O Remote Protocol
40804 Extension}, for more details on the target-initiated protocol.
40806 The Host I/O request packets all encode a single operation along with
40807 its arguments. They have this format:
40811 @item vFile:@var{operation}: @var{parameter}@dots{}
40812 @var{operation} is the name of the particular request; the target
40813 should compare the entire packet name up to the second colon when checking
40814 for a supported operation. The format of @var{parameter} depends on
40815 the operation. Numbers are always passed in hexadecimal. Negative
40816 numbers have an explicit minus sign (i.e.@: two's complement is not
40817 used). Strings (e.g.@: filenames) are encoded as a series of
40818 hexadecimal bytes. The last argument to a system call may be a
40819 buffer of escaped binary data (@pxref{Binary Data}).
40823 The valid responses to Host I/O packets are:
40827 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40828 @var{result} is the integer value returned by this operation, usually
40829 non-negative for success and -1 for errors. If an error has occured,
40830 @var{errno} will be included in the result specifying a
40831 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40832 operations which return data, @var{attachment} supplies the data as a
40833 binary buffer. Binary buffers in response packets are escaped in the
40834 normal way (@pxref{Binary Data}). See the individual packet
40835 documentation for the interpretation of @var{result} and
40839 An empty response indicates that this operation is not recognized.
40843 These are the supported Host I/O operations:
40846 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40847 Open a file at @var{filename} and return a file descriptor for it, or
40848 return -1 if an error occurs. The @var{filename} is a string,
40849 @var{flags} is an integer indicating a mask of open flags
40850 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40851 of mode bits to use if the file is created (@pxref{mode_t Values}).
40852 @xref{open}, for details of the open flags and mode values.
40854 @item vFile:close: @var{fd}
40855 Close the open file corresponding to @var{fd} and return 0, or
40856 -1 if an error occurs.
40858 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40859 Read data from the open file corresponding to @var{fd}. Up to
40860 @var{count} bytes will be read from the file, starting at @var{offset}
40861 relative to the start of the file. The target may read fewer bytes;
40862 common reasons include packet size limits and an end-of-file
40863 condition. The number of bytes read is returned. Zero should only be
40864 returned for a successful read at the end of the file, or if
40865 @var{count} was zero.
40867 The data read should be returned as a binary attachment on success.
40868 If zero bytes were read, the response should include an empty binary
40869 attachment (i.e.@: a trailing semicolon). The return value is the
40870 number of target bytes read; the binary attachment may be longer if
40871 some characters were escaped.
40873 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40874 Write @var{data} (a binary buffer) to the open file corresponding
40875 to @var{fd}. Start the write at @var{offset} from the start of the
40876 file. Unlike many @code{write} system calls, there is no
40877 separate @var{count} argument; the length of @var{data} in the
40878 packet is used. @samp{vFile:write} returns the number of bytes written,
40879 which may be shorter than the length of @var{data}, or -1 if an
40882 @item vFile:fstat: @var{fd}
40883 Get information about the open file corresponding to @var{fd}.
40884 On success the information is returned as a binary attachment
40885 and the return value is the size of this attachment in bytes.
40886 If an error occurs the return value is -1. The format of the
40887 returned binary attachment is as described in @ref{struct stat}.
40889 @item vFile:unlink: @var{filename}
40890 Delete the file at @var{filename} on the target. Return 0,
40891 or -1 if an error occurs. The @var{filename} is a string.
40893 @item vFile:readlink: @var{filename}
40894 Read value of symbolic link @var{filename} on the target. Return
40895 the number of bytes read, or -1 if an error occurs.
40897 The data read should be returned as a binary attachment on success.
40898 If zero bytes were read, the response should include an empty binary
40899 attachment (i.e.@: a trailing semicolon). The return value is the
40900 number of target bytes read; the binary attachment may be longer if
40901 some characters were escaped.
40903 @item vFile:setfs: @var{pid}
40904 Select the filesystem on which @code{vFile} operations with
40905 @var{filename} arguments will operate. This is required for
40906 @value{GDBN} to be able to access files on remote targets where
40907 the remote stub does not share a common filesystem with the
40910 If @var{pid} is nonzero, select the filesystem as seen by process
40911 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40912 the remote stub. Return 0 on success, or -1 if an error occurs.
40913 If @code{vFile:setfs:} indicates success, the selected filesystem
40914 remains selected until the next successful @code{vFile:setfs:}
40920 @section Interrupts
40921 @cindex interrupts (remote protocol)
40922 @anchor{interrupting remote targets}
40924 In all-stop mode, when a program on the remote target is running,
40925 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40926 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40927 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40929 The precise meaning of @code{BREAK} is defined by the transport
40930 mechanism and may, in fact, be undefined. @value{GDBN} does not
40931 currently define a @code{BREAK} mechanism for any of the network
40932 interfaces except for TCP, in which case @value{GDBN} sends the
40933 @code{telnet} BREAK sequence.
40935 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40936 transport mechanisms. It is represented by sending the single byte
40937 @code{0x03} without any of the usual packet overhead described in
40938 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40939 transmitted as part of a packet, it is considered to be packet data
40940 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40941 (@pxref{X packet}), used for binary downloads, may include an unescaped
40942 @code{0x03} as part of its packet.
40944 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40945 When Linux kernel receives this sequence from serial port,
40946 it stops execution and connects to gdb.
40948 In non-stop mode, because packet resumptions are asynchronous
40949 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40950 command to the remote stub, even when the target is running. For that
40951 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40952 packet}) with the usual packet framing instead of the single byte
40955 Stubs are not required to recognize these interrupt mechanisms and the
40956 precise meaning associated with receipt of the interrupt is
40957 implementation defined. If the target supports debugging of multiple
40958 threads and/or processes, it should attempt to interrupt all
40959 currently-executing threads and processes.
40960 If the stub is successful at interrupting the
40961 running program, it should send one of the stop
40962 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40963 of successfully stopping the program in all-stop mode, and a stop reply
40964 for each stopped thread in non-stop mode.
40965 Interrupts received while the
40966 program is stopped are queued and the program will be interrupted when
40967 it is resumed next time.
40969 @node Notification Packets
40970 @section Notification Packets
40971 @cindex notification packets
40972 @cindex packets, notification
40974 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40975 packets that require no acknowledgment. Both the GDB and the stub
40976 may send notifications (although the only notifications defined at
40977 present are sent by the stub). Notifications carry information
40978 without incurring the round-trip latency of an acknowledgment, and so
40979 are useful for low-impact communications where occasional packet loss
40982 A notification packet has the form @samp{% @var{data} #
40983 @var{checksum}}, where @var{data} is the content of the notification,
40984 and @var{checksum} is a checksum of @var{data}, computed and formatted
40985 as for ordinary @value{GDBN} packets. A notification's @var{data}
40986 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40987 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40988 to acknowledge the notification's receipt or to report its corruption.
40990 Every notification's @var{data} begins with a name, which contains no
40991 colon characters, followed by a colon character.
40993 Recipients should silently ignore corrupted notifications and
40994 notifications they do not understand. Recipients should restart
40995 timeout periods on receipt of a well-formed notification, whether or
40996 not they understand it.
40998 Senders should only send the notifications described here when this
40999 protocol description specifies that they are permitted. In the
41000 future, we may extend the protocol to permit existing notifications in
41001 new contexts; this rule helps older senders avoid confusing newer
41004 (Older versions of @value{GDBN} ignore bytes received until they see
41005 the @samp{$} byte that begins an ordinary packet, so new stubs may
41006 transmit notifications without fear of confusing older clients. There
41007 are no notifications defined for @value{GDBN} to send at the moment, but we
41008 assume that most older stubs would ignore them, as well.)
41010 Each notification is comprised of three parts:
41012 @item @var{name}:@var{event}
41013 The notification packet is sent by the side that initiates the
41014 exchange (currently, only the stub does that), with @var{event}
41015 carrying the specific information about the notification, and
41016 @var{name} specifying the name of the notification.
41018 The acknowledge sent by the other side, usually @value{GDBN}, to
41019 acknowledge the exchange and request the event.
41022 The purpose of an asynchronous notification mechanism is to report to
41023 @value{GDBN} that something interesting happened in the remote stub.
41025 The remote stub may send notification @var{name}:@var{event}
41026 at any time, but @value{GDBN} acknowledges the notification when
41027 appropriate. The notification event is pending before @value{GDBN}
41028 acknowledges. Only one notification at a time may be pending; if
41029 additional events occur before @value{GDBN} has acknowledged the
41030 previous notification, they must be queued by the stub for later
41031 synchronous transmission in response to @var{ack} packets from
41032 @value{GDBN}. Because the notification mechanism is unreliable,
41033 the stub is permitted to resend a notification if it believes
41034 @value{GDBN} may not have received it.
41036 Specifically, notifications may appear when @value{GDBN} is not
41037 otherwise reading input from the stub, or when @value{GDBN} is
41038 expecting to read a normal synchronous response or a
41039 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41040 Notification packets are distinct from any other communication from
41041 the stub so there is no ambiguity.
41043 After receiving a notification, @value{GDBN} shall acknowledge it by
41044 sending a @var{ack} packet as a regular, synchronous request to the
41045 stub. Such acknowledgment is not required to happen immediately, as
41046 @value{GDBN} is permitted to send other, unrelated packets to the
41047 stub first, which the stub should process normally.
41049 Upon receiving a @var{ack} packet, if the stub has other queued
41050 events to report to @value{GDBN}, it shall respond by sending a
41051 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41052 packet to solicit further responses; again, it is permitted to send
41053 other, unrelated packets as well which the stub should process
41056 If the stub receives a @var{ack} packet and there are no additional
41057 @var{event} to report, the stub shall return an @samp{OK} response.
41058 At this point, @value{GDBN} has finished processing a notification
41059 and the stub has completed sending any queued events. @value{GDBN}
41060 won't accept any new notifications until the final @samp{OK} is
41061 received . If further notification events occur, the stub shall send
41062 a new notification, @value{GDBN} shall accept the notification, and
41063 the process shall be repeated.
41065 The process of asynchronous notification can be illustrated by the
41068 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41071 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41073 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41078 The following notifications are defined:
41079 @multitable @columnfractions 0.12 0.12 0.38 0.38
41088 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41089 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41090 for information on how these notifications are acknowledged by
41092 @tab Report an asynchronous stop event in non-stop mode.
41096 @node Remote Non-Stop
41097 @section Remote Protocol Support for Non-Stop Mode
41099 @value{GDBN}'s remote protocol supports non-stop debugging of
41100 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41101 supports non-stop mode, it should report that to @value{GDBN} by including
41102 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41104 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41105 establishing a new connection with the stub. Entering non-stop mode
41106 does not alter the state of any currently-running threads, but targets
41107 must stop all threads in any already-attached processes when entering
41108 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41109 probe the target state after a mode change.
41111 In non-stop mode, when an attached process encounters an event that
41112 would otherwise be reported with a stop reply, it uses the
41113 asynchronous notification mechanism (@pxref{Notification Packets}) to
41114 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41115 in all processes are stopped when a stop reply is sent, in non-stop
41116 mode only the thread reporting the stop event is stopped. That is,
41117 when reporting a @samp{S} or @samp{T} response to indicate completion
41118 of a step operation, hitting a breakpoint, or a fault, only the
41119 affected thread is stopped; any other still-running threads continue
41120 to run. When reporting a @samp{W} or @samp{X} response, all running
41121 threads belonging to other attached processes continue to run.
41123 In non-stop mode, the target shall respond to the @samp{?} packet as
41124 follows. First, any incomplete stop reply notification/@samp{vStopped}
41125 sequence in progress is abandoned. The target must begin a new
41126 sequence reporting stop events for all stopped threads, whether or not
41127 it has previously reported those events to @value{GDBN}. The first
41128 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41129 subsequent stop replies are sent as responses to @samp{vStopped} packets
41130 using the mechanism described above. The target must not send
41131 asynchronous stop reply notifications until the sequence is complete.
41132 If all threads are running when the target receives the @samp{?} packet,
41133 or if the target is not attached to any process, it shall respond
41136 If the stub supports non-stop mode, it should also support the
41137 @samp{swbreak} stop reason if software breakpoints are supported, and
41138 the @samp{hwbreak} stop reason if hardware breakpoints are supported
41139 (@pxref{swbreak stop reason}). This is because given the asynchronous
41140 nature of non-stop mode, between the time a thread hits a breakpoint
41141 and the time the event is finally processed by @value{GDBN}, the
41142 breakpoint may have already been removed from the target. Due to
41143 this, @value{GDBN} needs to be able to tell whether a trap stop was
41144 caused by a delayed breakpoint event, which should be ignored, as
41145 opposed to a random trap signal, which should be reported to the user.
41146 Note the @samp{swbreak} feature implies that the target is responsible
41147 for adjusting the PC when a software breakpoint triggers, if
41148 necessary, such as on the x86 architecture.
41150 @node Packet Acknowledgment
41151 @section Packet Acknowledgment
41153 @cindex acknowledgment, for @value{GDBN} remote
41154 @cindex packet acknowledgment, for @value{GDBN} remote
41155 By default, when either the host or the target machine receives a packet,
41156 the first response expected is an acknowledgment: either @samp{+} (to indicate
41157 the package was received correctly) or @samp{-} (to request retransmission).
41158 This mechanism allows the @value{GDBN} remote protocol to operate over
41159 unreliable transport mechanisms, such as a serial line.
41161 In cases where the transport mechanism is itself reliable (such as a pipe or
41162 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41163 It may be desirable to disable them in that case to reduce communication
41164 overhead, or for other reasons. This can be accomplished by means of the
41165 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41167 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41168 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41169 and response format still includes the normal checksum, as described in
41170 @ref{Overview}, but the checksum may be ignored by the receiver.
41172 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41173 no-acknowledgment mode, it should report that to @value{GDBN}
41174 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41175 @pxref{qSupported}.
41176 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41177 disabled via the @code{set remote noack-packet off} command
41178 (@pxref{Remote Configuration}),
41179 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41180 Only then may the stub actually turn off packet acknowledgments.
41181 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41182 response, which can be safely ignored by the stub.
41184 Note that @code{set remote noack-packet} command only affects negotiation
41185 between @value{GDBN} and the stub when subsequent connections are made;
41186 it does not affect the protocol acknowledgment state for any current
41188 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41189 new connection is established,
41190 there is also no protocol request to re-enable the acknowledgments
41191 for the current connection, once disabled.
41196 Example sequence of a target being re-started. Notice how the restart
41197 does not get any direct output:
41202 @emph{target restarts}
41205 <- @code{T001:1234123412341234}
41209 Example sequence of a target being stepped by a single instruction:
41212 -> @code{G1445@dots{}}
41217 <- @code{T001:1234123412341234}
41221 <- @code{1455@dots{}}
41225 @node File-I/O Remote Protocol Extension
41226 @section File-I/O Remote Protocol Extension
41227 @cindex File-I/O remote protocol extension
41230 * File-I/O Overview::
41231 * Protocol Basics::
41232 * The F Request Packet::
41233 * The F Reply Packet::
41234 * The Ctrl-C Message::
41236 * List of Supported Calls::
41237 * Protocol-specific Representation of Datatypes::
41239 * File-I/O Examples::
41242 @node File-I/O Overview
41243 @subsection File-I/O Overview
41244 @cindex file-i/o overview
41246 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41247 target to use the host's file system and console I/O to perform various
41248 system calls. System calls on the target system are translated into a
41249 remote protocol packet to the host system, which then performs the needed
41250 actions and returns a response packet to the target system.
41251 This simulates file system operations even on targets that lack file systems.
41253 The protocol is defined to be independent of both the host and target systems.
41254 It uses its own internal representation of datatypes and values. Both
41255 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41256 translating the system-dependent value representations into the internal
41257 protocol representations when data is transmitted.
41259 The communication is synchronous. A system call is possible only when
41260 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41261 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41262 the target is stopped to allow deterministic access to the target's
41263 memory. Therefore File-I/O is not interruptible by target signals. On
41264 the other hand, it is possible to interrupt File-I/O by a user interrupt
41265 (@samp{Ctrl-C}) within @value{GDBN}.
41267 The target's request to perform a host system call does not finish
41268 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41269 after finishing the system call, the target returns to continuing the
41270 previous activity (continue, step). No additional continue or step
41271 request from @value{GDBN} is required.
41274 (@value{GDBP}) continue
41275 <- target requests 'system call X'
41276 target is stopped, @value{GDBN} executes system call
41277 -> @value{GDBN} returns result
41278 ... target continues, @value{GDBN} returns to wait for the target
41279 <- target hits breakpoint and sends a Txx packet
41282 The protocol only supports I/O on the console and to regular files on
41283 the host file system. Character or block special devices, pipes,
41284 named pipes, sockets or any other communication method on the host
41285 system are not supported by this protocol.
41287 File I/O is not supported in non-stop mode.
41289 @node Protocol Basics
41290 @subsection Protocol Basics
41291 @cindex protocol basics, file-i/o
41293 The File-I/O protocol uses the @code{F} packet as the request as well
41294 as reply packet. Since a File-I/O system call can only occur when
41295 @value{GDBN} is waiting for a response from the continuing or stepping target,
41296 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41297 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41298 This @code{F} packet contains all information needed to allow @value{GDBN}
41299 to call the appropriate host system call:
41303 A unique identifier for the requested system call.
41306 All parameters to the system call. Pointers are given as addresses
41307 in the target memory address space. Pointers to strings are given as
41308 pointer/length pair. Numerical values are given as they are.
41309 Numerical control flags are given in a protocol-specific representation.
41313 At this point, @value{GDBN} has to perform the following actions.
41317 If the parameters include pointer values to data needed as input to a
41318 system call, @value{GDBN} requests this data from the target with a
41319 standard @code{m} packet request. This additional communication has to be
41320 expected by the target implementation and is handled as any other @code{m}
41324 @value{GDBN} translates all value from protocol representation to host
41325 representation as needed. Datatypes are coerced into the host types.
41328 @value{GDBN} calls the system call.
41331 It then coerces datatypes back to protocol representation.
41334 If the system call is expected to return data in buffer space specified
41335 by pointer parameters to the call, the data is transmitted to the
41336 target using a @code{M} or @code{X} packet. This packet has to be expected
41337 by the target implementation and is handled as any other @code{M} or @code{X}
41342 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41343 necessary information for the target to continue. This at least contains
41350 @code{errno}, if has been changed by the system call.
41357 After having done the needed type and value coercion, the target continues
41358 the latest continue or step action.
41360 @node The F Request Packet
41361 @subsection The @code{F} Request Packet
41362 @cindex file-i/o request packet
41363 @cindex @code{F} request packet
41365 The @code{F} request packet has the following format:
41368 @item F@var{call-id},@var{parameter@dots{}}
41370 @var{call-id} is the identifier to indicate the host system call to be called.
41371 This is just the name of the function.
41373 @var{parameter@dots{}} are the parameters to the system call.
41374 Parameters are hexadecimal integer values, either the actual values in case
41375 of scalar datatypes, pointers to target buffer space in case of compound
41376 datatypes and unspecified memory areas, or pointer/length pairs in case
41377 of string parameters. These are appended to the @var{call-id} as a
41378 comma-delimited list. All values are transmitted in ASCII
41379 string representation, pointer/length pairs separated by a slash.
41385 @node The F Reply Packet
41386 @subsection The @code{F} Reply Packet
41387 @cindex file-i/o reply packet
41388 @cindex @code{F} reply packet
41390 The @code{F} reply packet has the following format:
41394 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41396 @var{retcode} is the return code of the system call as hexadecimal value.
41398 @var{errno} is the @code{errno} set by the call, in protocol-specific
41400 This parameter can be omitted if the call was successful.
41402 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41403 case, @var{errno} must be sent as well, even if the call was successful.
41404 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41411 or, if the call was interrupted before the host call has been performed:
41418 assuming 4 is the protocol-specific representation of @code{EINTR}.
41423 @node The Ctrl-C Message
41424 @subsection The @samp{Ctrl-C} Message
41425 @cindex ctrl-c message, in file-i/o protocol
41427 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41428 reply packet (@pxref{The F Reply Packet}),
41429 the target should behave as if it had
41430 gotten a break message. The meaning for the target is ``system call
41431 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41432 (as with a break message) and return to @value{GDBN} with a @code{T02}
41435 It's important for the target to know in which
41436 state the system call was interrupted. There are two possible cases:
41440 The system call hasn't been performed on the host yet.
41443 The system call on the host has been finished.
41447 These two states can be distinguished by the target by the value of the
41448 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41449 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41450 on POSIX systems. In any other case, the target may presume that the
41451 system call has been finished --- successfully or not --- and should behave
41452 as if the break message arrived right after the system call.
41454 @value{GDBN} must behave reliably. If the system call has not been called
41455 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41456 @code{errno} in the packet. If the system call on the host has been finished
41457 before the user requests a break, the full action must be finished by
41458 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41459 The @code{F} packet may only be sent when either nothing has happened
41460 or the full action has been completed.
41463 @subsection Console I/O
41464 @cindex console i/o as part of file-i/o
41466 By default and if not explicitly closed by the target system, the file
41467 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41468 on the @value{GDBN} console is handled as any other file output operation
41469 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41470 by @value{GDBN} so that after the target read request from file descriptor
41471 0 all following typing is buffered until either one of the following
41476 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41478 system call is treated as finished.
41481 The user presses @key{RET}. This is treated as end of input with a trailing
41485 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41486 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41490 If the user has typed more characters than fit in the buffer given to
41491 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41492 either another @code{read(0, @dots{})} is requested by the target, or debugging
41493 is stopped at the user's request.
41496 @node List of Supported Calls
41497 @subsection List of Supported Calls
41498 @cindex list of supported file-i/o calls
41515 @unnumberedsubsubsec open
41516 @cindex open, file-i/o system call
41521 int open(const char *pathname, int flags);
41522 int open(const char *pathname, int flags, mode_t mode);
41526 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41529 @var{flags} is the bitwise @code{OR} of the following values:
41533 If the file does not exist it will be created. The host
41534 rules apply as far as file ownership and time stamps
41538 When used with @code{O_CREAT}, if the file already exists it is
41539 an error and open() fails.
41542 If the file already exists and the open mode allows
41543 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41544 truncated to zero length.
41547 The file is opened in append mode.
41550 The file is opened for reading only.
41553 The file is opened for writing only.
41556 The file is opened for reading and writing.
41560 Other bits are silently ignored.
41564 @var{mode} is the bitwise @code{OR} of the following values:
41568 User has read permission.
41571 User has write permission.
41574 Group has read permission.
41577 Group has write permission.
41580 Others have read permission.
41583 Others have write permission.
41587 Other bits are silently ignored.
41590 @item Return value:
41591 @code{open} returns the new file descriptor or -1 if an error
41598 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41601 @var{pathname} refers to a directory.
41604 The requested access is not allowed.
41607 @var{pathname} was too long.
41610 A directory component in @var{pathname} does not exist.
41613 @var{pathname} refers to a device, pipe, named pipe or socket.
41616 @var{pathname} refers to a file on a read-only filesystem and
41617 write access was requested.
41620 @var{pathname} is an invalid pointer value.
41623 No space on device to create the file.
41626 The process already has the maximum number of files open.
41629 The limit on the total number of files open on the system
41633 The call was interrupted by the user.
41639 @unnumberedsubsubsec close
41640 @cindex close, file-i/o system call
41649 @samp{Fclose,@var{fd}}
41651 @item Return value:
41652 @code{close} returns zero on success, or -1 if an error occurred.
41658 @var{fd} isn't a valid open file descriptor.
41661 The call was interrupted by the user.
41667 @unnumberedsubsubsec read
41668 @cindex read, file-i/o system call
41673 int read(int fd, void *buf, unsigned int count);
41677 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41679 @item Return value:
41680 On success, the number of bytes read is returned.
41681 Zero indicates end of file. If count is zero, read
41682 returns zero as well. On error, -1 is returned.
41688 @var{fd} is not a valid file descriptor or is not open for
41692 @var{bufptr} is an invalid pointer value.
41695 The call was interrupted by the user.
41701 @unnumberedsubsubsec write
41702 @cindex write, file-i/o system call
41707 int write(int fd, const void *buf, unsigned int count);
41711 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41713 @item Return value:
41714 On success, the number of bytes written are returned.
41715 Zero indicates nothing was written. On error, -1
41722 @var{fd} is not a valid file descriptor or is not open for
41726 @var{bufptr} is an invalid pointer value.
41729 An attempt was made to write a file that exceeds the
41730 host-specific maximum file size allowed.
41733 No space on device to write the data.
41736 The call was interrupted by the user.
41742 @unnumberedsubsubsec lseek
41743 @cindex lseek, file-i/o system call
41748 long lseek (int fd, long offset, int flag);
41752 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41754 @var{flag} is one of:
41758 The offset is set to @var{offset} bytes.
41761 The offset is set to its current location plus @var{offset}
41765 The offset is set to the size of the file plus @var{offset}
41769 @item Return value:
41770 On success, the resulting unsigned offset in bytes from
41771 the beginning of the file is returned. Otherwise, a
41772 value of -1 is returned.
41778 @var{fd} is not a valid open file descriptor.
41781 @var{fd} is associated with the @value{GDBN} console.
41784 @var{flag} is not a proper value.
41787 The call was interrupted by the user.
41793 @unnumberedsubsubsec rename
41794 @cindex rename, file-i/o system call
41799 int rename(const char *oldpath, const char *newpath);
41803 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41805 @item Return value:
41806 On success, zero is returned. On error, -1 is returned.
41812 @var{newpath} is an existing directory, but @var{oldpath} is not a
41816 @var{newpath} is a non-empty directory.
41819 @var{oldpath} or @var{newpath} is a directory that is in use by some
41823 An attempt was made to make a directory a subdirectory
41827 A component used as a directory in @var{oldpath} or new
41828 path is not a directory. Or @var{oldpath} is a directory
41829 and @var{newpath} exists but is not a directory.
41832 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41835 No access to the file or the path of the file.
41839 @var{oldpath} or @var{newpath} was too long.
41842 A directory component in @var{oldpath} or @var{newpath} does not exist.
41845 The file is on a read-only filesystem.
41848 The device containing the file has no room for the new
41852 The call was interrupted by the user.
41858 @unnumberedsubsubsec unlink
41859 @cindex unlink, file-i/o system call
41864 int unlink(const char *pathname);
41868 @samp{Funlink,@var{pathnameptr}/@var{len}}
41870 @item Return value:
41871 On success, zero is returned. On error, -1 is returned.
41877 No access to the file or the path of the file.
41880 The system does not allow unlinking of directories.
41883 The file @var{pathname} cannot be unlinked because it's
41884 being used by another process.
41887 @var{pathnameptr} is an invalid pointer value.
41890 @var{pathname} was too long.
41893 A directory component in @var{pathname} does not exist.
41896 A component of the path is not a directory.
41899 The file is on a read-only filesystem.
41902 The call was interrupted by the user.
41908 @unnumberedsubsubsec stat/fstat
41909 @cindex fstat, file-i/o system call
41910 @cindex stat, file-i/o system call
41915 int stat(const char *pathname, struct stat *buf);
41916 int fstat(int fd, struct stat *buf);
41920 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41921 @samp{Ffstat,@var{fd},@var{bufptr}}
41923 @item Return value:
41924 On success, zero is returned. On error, -1 is returned.
41930 @var{fd} is not a valid open file.
41933 A directory component in @var{pathname} does not exist or the
41934 path is an empty string.
41937 A component of the path is not a directory.
41940 @var{pathnameptr} is an invalid pointer value.
41943 No access to the file or the path of the file.
41946 @var{pathname} was too long.
41949 The call was interrupted by the user.
41955 @unnumberedsubsubsec gettimeofday
41956 @cindex gettimeofday, file-i/o system call
41961 int gettimeofday(struct timeval *tv, void *tz);
41965 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41967 @item Return value:
41968 On success, 0 is returned, -1 otherwise.
41974 @var{tz} is a non-NULL pointer.
41977 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41983 @unnumberedsubsubsec isatty
41984 @cindex isatty, file-i/o system call
41989 int isatty(int fd);
41993 @samp{Fisatty,@var{fd}}
41995 @item Return value:
41996 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42002 The call was interrupted by the user.
42007 Note that the @code{isatty} call is treated as a special case: it returns
42008 1 to the target if the file descriptor is attached
42009 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42010 would require implementing @code{ioctl} and would be more complex than
42015 @unnumberedsubsubsec system
42016 @cindex system, file-i/o system call
42021 int system(const char *command);
42025 @samp{Fsystem,@var{commandptr}/@var{len}}
42027 @item Return value:
42028 If @var{len} is zero, the return value indicates whether a shell is
42029 available. A zero return value indicates a shell is not available.
42030 For non-zero @var{len}, the value returned is -1 on error and the
42031 return status of the command otherwise. Only the exit status of the
42032 command is returned, which is extracted from the host's @code{system}
42033 return value by calling @code{WEXITSTATUS(retval)}. In case
42034 @file{/bin/sh} could not be executed, 127 is returned.
42040 The call was interrupted by the user.
42045 @value{GDBN} takes over the full task of calling the necessary host calls
42046 to perform the @code{system} call. The return value of @code{system} on
42047 the host is simplified before it's returned
42048 to the target. Any termination signal information from the child process
42049 is discarded, and the return value consists
42050 entirely of the exit status of the called command.
42052 Due to security concerns, the @code{system} call is by default refused
42053 by @value{GDBN}. The user has to allow this call explicitly with the
42054 @code{set remote system-call-allowed 1} command.
42057 @item set remote system-call-allowed
42058 @kindex set remote system-call-allowed
42059 Control whether to allow the @code{system} calls in the File I/O
42060 protocol for the remote target. The default is zero (disabled).
42062 @item show remote system-call-allowed
42063 @kindex show remote system-call-allowed
42064 Show whether the @code{system} calls are allowed in the File I/O
42068 @node Protocol-specific Representation of Datatypes
42069 @subsection Protocol-specific Representation of Datatypes
42070 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42073 * Integral Datatypes::
42075 * Memory Transfer::
42080 @node Integral Datatypes
42081 @unnumberedsubsubsec Integral Datatypes
42082 @cindex integral datatypes, in file-i/o protocol
42084 The integral datatypes used in the system calls are @code{int},
42085 @code{unsigned int}, @code{long}, @code{unsigned long},
42086 @code{mode_t}, and @code{time_t}.
42088 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42089 implemented as 32 bit values in this protocol.
42091 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42093 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42094 in @file{limits.h}) to allow range checking on host and target.
42096 @code{time_t} datatypes are defined as seconds since the Epoch.
42098 All integral datatypes transferred as part of a memory read or write of a
42099 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42102 @node Pointer Values
42103 @unnumberedsubsubsec Pointer Values
42104 @cindex pointer values, in file-i/o protocol
42106 Pointers to target data are transmitted as they are. An exception
42107 is made for pointers to buffers for which the length isn't
42108 transmitted as part of the function call, namely strings. Strings
42109 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42116 which is a pointer to data of length 18 bytes at position 0x1aaf.
42117 The length is defined as the full string length in bytes, including
42118 the trailing null byte. For example, the string @code{"hello world"}
42119 at address 0x123456 is transmitted as
42125 @node Memory Transfer
42126 @unnumberedsubsubsec Memory Transfer
42127 @cindex memory transfer, in file-i/o protocol
42129 Structured data which is transferred using a memory read or write (for
42130 example, a @code{struct stat}) is expected to be in a protocol-specific format
42131 with all scalar multibyte datatypes being big endian. Translation to
42132 this representation needs to be done both by the target before the @code{F}
42133 packet is sent, and by @value{GDBN} before
42134 it transfers memory to the target. Transferred pointers to structured
42135 data should point to the already-coerced data at any time.
42139 @unnumberedsubsubsec struct stat
42140 @cindex struct stat, in file-i/o protocol
42142 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42143 is defined as follows:
42147 unsigned int st_dev; /* device */
42148 unsigned int st_ino; /* inode */
42149 mode_t st_mode; /* protection */
42150 unsigned int st_nlink; /* number of hard links */
42151 unsigned int st_uid; /* user ID of owner */
42152 unsigned int st_gid; /* group ID of owner */
42153 unsigned int st_rdev; /* device type (if inode device) */
42154 unsigned long st_size; /* total size, in bytes */
42155 unsigned long st_blksize; /* blocksize for filesystem I/O */
42156 unsigned long st_blocks; /* number of blocks allocated */
42157 time_t st_atime; /* time of last access */
42158 time_t st_mtime; /* time of last modification */
42159 time_t st_ctime; /* time of last change */
42163 The integral datatypes conform to the definitions given in the
42164 appropriate section (see @ref{Integral Datatypes}, for details) so this
42165 structure is of size 64 bytes.
42167 The values of several fields have a restricted meaning and/or
42173 A value of 0 represents a file, 1 the console.
42176 No valid meaning for the target. Transmitted unchanged.
42179 Valid mode bits are described in @ref{Constants}. Any other
42180 bits have currently no meaning for the target.
42185 No valid meaning for the target. Transmitted unchanged.
42190 These values have a host and file system dependent
42191 accuracy. Especially on Windows hosts, the file system may not
42192 support exact timing values.
42195 The target gets a @code{struct stat} of the above representation and is
42196 responsible for coercing it to the target representation before
42199 Note that due to size differences between the host, target, and protocol
42200 representations of @code{struct stat} members, these members could eventually
42201 get truncated on the target.
42203 @node struct timeval
42204 @unnumberedsubsubsec struct timeval
42205 @cindex struct timeval, in file-i/o protocol
42207 The buffer of type @code{struct timeval} used by the File-I/O protocol
42208 is defined as follows:
42212 time_t tv_sec; /* second */
42213 long tv_usec; /* microsecond */
42217 The integral datatypes conform to the definitions given in the
42218 appropriate section (see @ref{Integral Datatypes}, for details) so this
42219 structure is of size 8 bytes.
42222 @subsection Constants
42223 @cindex constants, in file-i/o protocol
42225 The following values are used for the constants inside of the
42226 protocol. @value{GDBN} and target are responsible for translating these
42227 values before and after the call as needed.
42238 @unnumberedsubsubsec Open Flags
42239 @cindex open flags, in file-i/o protocol
42241 All values are given in hexadecimal representation.
42253 @node mode_t Values
42254 @unnumberedsubsubsec mode_t Values
42255 @cindex mode_t values, in file-i/o protocol
42257 All values are given in octal representation.
42274 @unnumberedsubsubsec Errno Values
42275 @cindex errno values, in file-i/o protocol
42277 All values are given in decimal representation.
42302 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42303 any error value not in the list of supported error numbers.
42306 @unnumberedsubsubsec Lseek Flags
42307 @cindex lseek flags, in file-i/o protocol
42316 @unnumberedsubsubsec Limits
42317 @cindex limits, in file-i/o protocol
42319 All values are given in decimal representation.
42322 INT_MIN -2147483648
42324 UINT_MAX 4294967295
42325 LONG_MIN -9223372036854775808
42326 LONG_MAX 9223372036854775807
42327 ULONG_MAX 18446744073709551615
42330 @node File-I/O Examples
42331 @subsection File-I/O Examples
42332 @cindex file-i/o examples
42334 Example sequence of a write call, file descriptor 3, buffer is at target
42335 address 0x1234, 6 bytes should be written:
42338 <- @code{Fwrite,3,1234,6}
42339 @emph{request memory read from target}
42342 @emph{return "6 bytes written"}
42346 Example sequence of a read call, file descriptor 3, buffer is at target
42347 address 0x1234, 6 bytes should be read:
42350 <- @code{Fread,3,1234,6}
42351 @emph{request memory write to target}
42352 -> @code{X1234,6:XXXXXX}
42353 @emph{return "6 bytes read"}
42357 Example sequence of a read call, call fails on the host due to invalid
42358 file descriptor (@code{EBADF}):
42361 <- @code{Fread,3,1234,6}
42365 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42369 <- @code{Fread,3,1234,6}
42374 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42378 <- @code{Fread,3,1234,6}
42379 -> @code{X1234,6:XXXXXX}
42383 @node Library List Format
42384 @section Library List Format
42385 @cindex library list format, remote protocol
42387 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42388 same process as your application to manage libraries. In this case,
42389 @value{GDBN} can use the loader's symbol table and normal memory
42390 operations to maintain a list of shared libraries. On other
42391 platforms, the operating system manages loaded libraries.
42392 @value{GDBN} can not retrieve the list of currently loaded libraries
42393 through memory operations, so it uses the @samp{qXfer:libraries:read}
42394 packet (@pxref{qXfer library list read}) instead. The remote stub
42395 queries the target's operating system and reports which libraries
42398 The @samp{qXfer:libraries:read} packet returns an XML document which
42399 lists loaded libraries and their offsets. Each library has an
42400 associated name and one or more segment or section base addresses,
42401 which report where the library was loaded in memory.
42403 For the common case of libraries that are fully linked binaries, the
42404 library should have a list of segments. If the target supports
42405 dynamic linking of a relocatable object file, its library XML element
42406 should instead include a list of allocated sections. The segment or
42407 section bases are start addresses, not relocation offsets; they do not
42408 depend on the library's link-time base addresses.
42410 @value{GDBN} must be linked with the Expat library to support XML
42411 library lists. @xref{Expat}.
42413 A simple memory map, with one loaded library relocated by a single
42414 offset, looks like this:
42418 <library name="/lib/libc.so.6">
42419 <segment address="0x10000000"/>
42424 Another simple memory map, with one loaded library with three
42425 allocated sections (.text, .data, .bss), looks like this:
42429 <library name="sharedlib.o">
42430 <section address="0x10000000"/>
42431 <section address="0x20000000"/>
42432 <section address="0x30000000"/>
42437 The format of a library list is described by this DTD:
42440 <!-- library-list: Root element with versioning -->
42441 <!ELEMENT library-list (library)*>
42442 <!ATTLIST library-list version CDATA #FIXED "1.0">
42443 <!ELEMENT library (segment*, section*)>
42444 <!ATTLIST library name CDATA #REQUIRED>
42445 <!ELEMENT segment EMPTY>
42446 <!ATTLIST segment address CDATA #REQUIRED>
42447 <!ELEMENT section EMPTY>
42448 <!ATTLIST section address CDATA #REQUIRED>
42451 In addition, segments and section descriptors cannot be mixed within a
42452 single library element, and you must supply at least one segment or
42453 section for each library.
42455 @node Library List Format for SVR4 Targets
42456 @section Library List Format for SVR4 Targets
42457 @cindex library list format, remote protocol
42459 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42460 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42461 shared libraries. Still a special library list provided by this packet is
42462 more efficient for the @value{GDBN} remote protocol.
42464 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42465 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42466 target, the following parameters are reported:
42470 @code{name}, the absolute file name from the @code{l_name} field of
42471 @code{struct link_map}.
42473 @code{lm} with address of @code{struct link_map} used for TLS
42474 (Thread Local Storage) access.
42476 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42477 @code{struct link_map}. For prelinked libraries this is not an absolute
42478 memory address. It is a displacement of absolute memory address against
42479 address the file was prelinked to during the library load.
42481 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42484 Additionally the single @code{main-lm} attribute specifies address of
42485 @code{struct link_map} used for the main executable. This parameter is used
42486 for TLS access and its presence is optional.
42488 @value{GDBN} must be linked with the Expat library to support XML
42489 SVR4 library lists. @xref{Expat}.
42491 A simple memory map, with two loaded libraries (which do not use prelink),
42495 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42496 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42498 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42500 </library-list-svr>
42503 The format of an SVR4 library list is described by this DTD:
42506 <!-- library-list-svr4: Root element with versioning -->
42507 <!ELEMENT library-list-svr4 (library)*>
42508 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42509 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42510 <!ELEMENT library EMPTY>
42511 <!ATTLIST library name CDATA #REQUIRED>
42512 <!ATTLIST library lm CDATA #REQUIRED>
42513 <!ATTLIST library l_addr CDATA #REQUIRED>
42514 <!ATTLIST library l_ld CDATA #REQUIRED>
42517 @node Memory Map Format
42518 @section Memory Map Format
42519 @cindex memory map format
42521 To be able to write into flash memory, @value{GDBN} needs to obtain a
42522 memory map from the target. This section describes the format of the
42525 The memory map is obtained using the @samp{qXfer:memory-map:read}
42526 (@pxref{qXfer memory map read}) packet and is an XML document that
42527 lists memory regions.
42529 @value{GDBN} must be linked with the Expat library to support XML
42530 memory maps. @xref{Expat}.
42532 The top-level structure of the document is shown below:
42535 <?xml version="1.0"?>
42536 <!DOCTYPE memory-map
42537 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42538 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42544 Each region can be either:
42549 A region of RAM starting at @var{addr} and extending for @var{length}
42553 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42558 A region of read-only memory:
42561 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42566 A region of flash memory, with erasure blocks @var{blocksize}
42570 <memory type="flash" start="@var{addr}" length="@var{length}">
42571 <property name="blocksize">@var{blocksize}</property>
42577 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42578 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42579 packets to write to addresses in such ranges.
42581 The formal DTD for memory map format is given below:
42584 <!-- ................................................... -->
42585 <!-- Memory Map XML DTD ................................ -->
42586 <!-- File: memory-map.dtd .............................. -->
42587 <!-- .................................... .............. -->
42588 <!-- memory-map.dtd -->
42589 <!-- memory-map: Root element with versioning -->
42590 <!ELEMENT memory-map (memory)*>
42591 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42592 <!ELEMENT memory (property)*>
42593 <!-- memory: Specifies a memory region,
42594 and its type, or device. -->
42595 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42596 start CDATA #REQUIRED
42597 length CDATA #REQUIRED>
42598 <!-- property: Generic attribute tag -->
42599 <!ELEMENT property (#PCDATA | property)*>
42600 <!ATTLIST property name (blocksize) #REQUIRED>
42603 @node Thread List Format
42604 @section Thread List Format
42605 @cindex thread list format
42607 To efficiently update the list of threads and their attributes,
42608 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42609 (@pxref{qXfer threads read}) and obtains the XML document with
42610 the following structure:
42613 <?xml version="1.0"?>
42615 <thread id="id" core="0" name="name">
42616 ... description ...
42621 Each @samp{thread} element must have the @samp{id} attribute that
42622 identifies the thread (@pxref{thread-id syntax}). The
42623 @samp{core} attribute, if present, specifies which processor core
42624 the thread was last executing on. The @samp{name} attribute, if
42625 present, specifies the human-readable name of the thread. The content
42626 of the of @samp{thread} element is interpreted as human-readable
42627 auxiliary information. The @samp{handle} attribute, if present,
42628 is a hex encoded representation of the thread handle.
42631 @node Traceframe Info Format
42632 @section Traceframe Info Format
42633 @cindex traceframe info format
42635 To be able to know which objects in the inferior can be examined when
42636 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42637 memory ranges, registers and trace state variables that have been
42638 collected in a traceframe.
42640 This list is obtained using the @samp{qXfer:traceframe-info:read}
42641 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42643 @value{GDBN} must be linked with the Expat library to support XML
42644 traceframe info discovery. @xref{Expat}.
42646 The top-level structure of the document is shown below:
42649 <?xml version="1.0"?>
42650 <!DOCTYPE traceframe-info
42651 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42652 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42658 Each traceframe block can be either:
42663 A region of collected memory starting at @var{addr} and extending for
42664 @var{length} bytes from there:
42667 <memory start="@var{addr}" length="@var{length}"/>
42671 A block indicating trace state variable numbered @var{number} has been
42675 <tvar id="@var{number}"/>
42680 The formal DTD for the traceframe info format is given below:
42683 <!ELEMENT traceframe-info (memory | tvar)* >
42684 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42686 <!ELEMENT memory EMPTY>
42687 <!ATTLIST memory start CDATA #REQUIRED
42688 length CDATA #REQUIRED>
42690 <!ATTLIST tvar id CDATA #REQUIRED>
42693 @node Branch Trace Format
42694 @section Branch Trace Format
42695 @cindex branch trace format
42697 In order to display the branch trace of an inferior thread,
42698 @value{GDBN} needs to obtain the list of branches. This list is
42699 represented as list of sequential code blocks that are connected via
42700 branches. The code in each block has been executed sequentially.
42702 This list is obtained using the @samp{qXfer:btrace:read}
42703 (@pxref{qXfer btrace read}) packet and is an XML document.
42705 @value{GDBN} must be linked with the Expat library to support XML
42706 traceframe info discovery. @xref{Expat}.
42708 The top-level structure of the document is shown below:
42711 <?xml version="1.0"?>
42713 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42714 "http://sourceware.org/gdb/gdb-btrace.dtd">
42723 A block of sequentially executed instructions starting at @var{begin}
42724 and ending at @var{end}:
42727 <block begin="@var{begin}" end="@var{end}"/>
42732 The formal DTD for the branch trace format is given below:
42735 <!ELEMENT btrace (block* | pt) >
42736 <!ATTLIST btrace version CDATA #FIXED "1.0">
42738 <!ELEMENT block EMPTY>
42739 <!ATTLIST block begin CDATA #REQUIRED
42740 end CDATA #REQUIRED>
42742 <!ELEMENT pt (pt-config?, raw?)>
42744 <!ELEMENT pt-config (cpu?)>
42746 <!ELEMENT cpu EMPTY>
42747 <!ATTLIST cpu vendor CDATA #REQUIRED
42748 family CDATA #REQUIRED
42749 model CDATA #REQUIRED
42750 stepping CDATA #REQUIRED>
42752 <!ELEMENT raw (#PCDATA)>
42755 @node Branch Trace Configuration Format
42756 @section Branch Trace Configuration Format
42757 @cindex branch trace configuration format
42759 For each inferior thread, @value{GDBN} can obtain the branch trace
42760 configuration using the @samp{qXfer:btrace-conf:read}
42761 (@pxref{qXfer btrace-conf read}) packet.
42763 The configuration describes the branch trace format and configuration
42764 settings for that format. The following information is described:
42768 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42771 The size of the @acronym{BTS} ring buffer in bytes.
42774 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42778 The size of the @acronym{Intel PT} ring buffer in bytes.
42782 @value{GDBN} must be linked with the Expat library to support XML
42783 branch trace configuration discovery. @xref{Expat}.
42785 The formal DTD for the branch trace configuration format is given below:
42788 <!ELEMENT btrace-conf (bts?, pt?)>
42789 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42791 <!ELEMENT bts EMPTY>
42792 <!ATTLIST bts size CDATA #IMPLIED>
42794 <!ELEMENT pt EMPTY>
42795 <!ATTLIST pt size CDATA #IMPLIED>
42798 @include agentexpr.texi
42800 @node Target Descriptions
42801 @appendix Target Descriptions
42802 @cindex target descriptions
42804 One of the challenges of using @value{GDBN} to debug embedded systems
42805 is that there are so many minor variants of each processor
42806 architecture in use. It is common practice for vendors to start with
42807 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42808 and then make changes to adapt it to a particular market niche. Some
42809 architectures have hundreds of variants, available from dozens of
42810 vendors. This leads to a number of problems:
42814 With so many different customized processors, it is difficult for
42815 the @value{GDBN} maintainers to keep up with the changes.
42817 Since individual variants may have short lifetimes or limited
42818 audiences, it may not be worthwhile to carry information about every
42819 variant in the @value{GDBN} source tree.
42821 When @value{GDBN} does support the architecture of the embedded system
42822 at hand, the task of finding the correct architecture name to give the
42823 @command{set architecture} command can be error-prone.
42826 To address these problems, the @value{GDBN} remote protocol allows a
42827 target system to not only identify itself to @value{GDBN}, but to
42828 actually describe its own features. This lets @value{GDBN} support
42829 processor variants it has never seen before --- to the extent that the
42830 descriptions are accurate, and that @value{GDBN} understands them.
42832 @value{GDBN} must be linked with the Expat library to support XML
42833 target descriptions. @xref{Expat}.
42836 * Retrieving Descriptions:: How descriptions are fetched from a target.
42837 * Target Description Format:: The contents of a target description.
42838 * Predefined Target Types:: Standard types available for target
42840 * Enum Target Types:: How to define enum target types.
42841 * Standard Target Features:: Features @value{GDBN} knows about.
42844 @node Retrieving Descriptions
42845 @section Retrieving Descriptions
42847 Target descriptions can be read from the target automatically, or
42848 specified by the user manually. The default behavior is to read the
42849 description from the target. @value{GDBN} retrieves it via the remote
42850 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42851 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42852 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42853 XML document, of the form described in @ref{Target Description
42856 Alternatively, you can specify a file to read for the target description.
42857 If a file is set, the target will not be queried. The commands to
42858 specify a file are:
42861 @cindex set tdesc filename
42862 @item set tdesc filename @var{path}
42863 Read the target description from @var{path}.
42865 @cindex unset tdesc filename
42866 @item unset tdesc filename
42867 Do not read the XML target description from a file. @value{GDBN}
42868 will use the description supplied by the current target.
42870 @cindex show tdesc filename
42871 @item show tdesc filename
42872 Show the filename to read for a target description, if any.
42876 @node Target Description Format
42877 @section Target Description Format
42878 @cindex target descriptions, XML format
42880 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42881 document which complies with the Document Type Definition provided in
42882 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42883 means you can use generally available tools like @command{xmllint} to
42884 check that your feature descriptions are well-formed and valid.
42885 However, to help people unfamiliar with XML write descriptions for
42886 their targets, we also describe the grammar here.
42888 Target descriptions can identify the architecture of the remote target
42889 and (for some architectures) provide information about custom register
42890 sets. They can also identify the OS ABI of the remote target.
42891 @value{GDBN} can use this information to autoconfigure for your
42892 target, or to warn you if you connect to an unsupported target.
42894 Here is a simple target description:
42897 <target version="1.0">
42898 <architecture>i386:x86-64</architecture>
42903 This minimal description only says that the target uses
42904 the x86-64 architecture.
42906 A target description has the following overall form, with [ ] marking
42907 optional elements and @dots{} marking repeatable elements. The elements
42908 are explained further below.
42911 <?xml version="1.0"?>
42912 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42913 <target version="1.0">
42914 @r{[}@var{architecture}@r{]}
42915 @r{[}@var{osabi}@r{]}
42916 @r{[}@var{compatible}@r{]}
42917 @r{[}@var{feature}@dots{}@r{]}
42922 The description is generally insensitive to whitespace and line
42923 breaks, under the usual common-sense rules. The XML version
42924 declaration and document type declaration can generally be omitted
42925 (@value{GDBN} does not require them), but specifying them may be
42926 useful for XML validation tools. The @samp{version} attribute for
42927 @samp{<target>} may also be omitted, but we recommend
42928 including it; if future versions of @value{GDBN} use an incompatible
42929 revision of @file{gdb-target.dtd}, they will detect and report
42930 the version mismatch.
42932 @subsection Inclusion
42933 @cindex target descriptions, inclusion
42936 @cindex <xi:include>
42939 It can sometimes be valuable to split a target description up into
42940 several different annexes, either for organizational purposes, or to
42941 share files between different possible target descriptions. You can
42942 divide a description into multiple files by replacing any element of
42943 the target description with an inclusion directive of the form:
42946 <xi:include href="@var{document}"/>
42950 When @value{GDBN} encounters an element of this form, it will retrieve
42951 the named XML @var{document}, and replace the inclusion directive with
42952 the contents of that document. If the current description was read
42953 using @samp{qXfer}, then so will be the included document;
42954 @var{document} will be interpreted as the name of an annex. If the
42955 current description was read from a file, @value{GDBN} will look for
42956 @var{document} as a file in the same directory where it found the
42957 original description.
42959 @subsection Architecture
42960 @cindex <architecture>
42962 An @samp{<architecture>} element has this form:
42965 <architecture>@var{arch}</architecture>
42968 @var{arch} is one of the architectures from the set accepted by
42969 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42972 @cindex @code{<osabi>}
42974 This optional field was introduced in @value{GDBN} version 7.0.
42975 Previous versions of @value{GDBN} ignore it.
42977 An @samp{<osabi>} element has this form:
42980 <osabi>@var{abi-name}</osabi>
42983 @var{abi-name} is an OS ABI name from the same selection accepted by
42984 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42986 @subsection Compatible Architecture
42987 @cindex @code{<compatible>}
42989 This optional field was introduced in @value{GDBN} version 7.0.
42990 Previous versions of @value{GDBN} ignore it.
42992 A @samp{<compatible>} element has this form:
42995 <compatible>@var{arch}</compatible>
42998 @var{arch} is one of the architectures from the set accepted by
42999 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
43001 A @samp{<compatible>} element is used to specify that the target
43002 is able to run binaries in some other than the main target architecture
43003 given by the @samp{<architecture>} element. For example, on the
43004 Cell Broadband Engine, the main architecture is @code{powerpc:common}
43005 or @code{powerpc:common64}, but the system is able to run binaries
43006 in the @code{spu} architecture as well. The way to describe this
43007 capability with @samp{<compatible>} is as follows:
43010 <architecture>powerpc:common</architecture>
43011 <compatible>spu</compatible>
43014 @subsection Features
43017 Each @samp{<feature>} describes some logical portion of the target
43018 system. Features are currently used to describe available CPU
43019 registers and the types of their contents. A @samp{<feature>} element
43023 <feature name="@var{name}">
43024 @r{[}@var{type}@dots{}@r{]}
43030 Each feature's name should be unique within the description. The name
43031 of a feature does not matter unless @value{GDBN} has some special
43032 knowledge of the contents of that feature; if it does, the feature
43033 should have its standard name. @xref{Standard Target Features}.
43037 Any register's value is a collection of bits which @value{GDBN} must
43038 interpret. The default interpretation is a two's complement integer,
43039 but other types can be requested by name in the register description.
43040 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43041 Target Types}), and the description can define additional composite
43044 Each type element must have an @samp{id} attribute, which gives
43045 a unique (within the containing @samp{<feature>}) name to the type.
43046 Types must be defined before they are used.
43049 Some targets offer vector registers, which can be treated as arrays
43050 of scalar elements. These types are written as @samp{<vector>} elements,
43051 specifying the array element type, @var{type}, and the number of elements,
43055 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43059 If a register's value is usefully viewed in multiple ways, define it
43060 with a union type containing the useful representations. The
43061 @samp{<union>} element contains one or more @samp{<field>} elements,
43062 each of which has a @var{name} and a @var{type}:
43065 <union id="@var{id}">
43066 <field name="@var{name}" type="@var{type}"/>
43073 If a register's value is composed from several separate values, define
43074 it with either a structure type or a flags type.
43075 A flags type may only contain bitfields.
43076 A structure type may either contain only bitfields or contain no bitfields.
43077 If the value contains only bitfields, its total size in bytes must be
43080 Non-bitfield values have a @var{name} and @var{type}.
43083 <struct id="@var{id}">
43084 <field name="@var{name}" type="@var{type}"/>
43089 Both @var{name} and @var{type} values are required.
43090 No implicit padding is added.
43092 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
43095 <struct id="@var{id}" size="@var{size}">
43096 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43102 <flags id="@var{id}" size="@var{size}">
43103 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43108 The @var{name} value is required.
43109 Bitfield values may be named with the empty string, @samp{""},
43110 in which case the field is ``filler'' and its value is not printed.
43111 Not all bits need to be specified, so ``filler'' fields are optional.
43113 The @var{start} and @var{end} values are required, and @var{type}
43115 The field's @var{start} must be less than or equal to its @var{end},
43116 and zero represents the least significant bit.
43118 The default value of @var{type} is @code{bool} for single bit fields,
43119 and an unsigned integer otherwise.
43121 Which to choose? Structures or flags?
43123 Registers defined with @samp{flags} have these advantages over
43124 defining them with @samp{struct}:
43128 Arithmetic may be performed on them as if they were integers.
43130 They are printed in a more readable fashion.
43133 Registers defined with @samp{struct} have one advantage over
43134 defining them with @samp{flags}:
43138 One can fetch individual fields like in @samp{C}.
43141 (gdb) print $my_struct_reg.field3
43147 @subsection Registers
43150 Each register is represented as an element with this form:
43153 <reg name="@var{name}"
43154 bitsize="@var{size}"
43155 @r{[}regnum="@var{num}"@r{]}
43156 @r{[}save-restore="@var{save-restore}"@r{]}
43157 @r{[}type="@var{type}"@r{]}
43158 @r{[}group="@var{group}"@r{]}/>
43162 The components are as follows:
43167 The register's name; it must be unique within the target description.
43170 The register's size, in bits.
43173 The register's number. If omitted, a register's number is one greater
43174 than that of the previous register (either in the current feature or in
43175 a preceding feature); the first register in the target description
43176 defaults to zero. This register number is used to read or write
43177 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43178 packets, and registers appear in the @code{g} and @code{G} packets
43179 in order of increasing register number.
43182 Whether the register should be preserved across inferior function
43183 calls; this must be either @code{yes} or @code{no}. The default is
43184 @code{yes}, which is appropriate for most registers except for
43185 some system control registers; this is not related to the target's
43189 The type of the register. It may be a predefined type, a type
43190 defined in the current feature, or one of the special types @code{int}
43191 and @code{float}. @code{int} is an integer type of the correct size
43192 for @var{bitsize}, and @code{float} is a floating point type (in the
43193 architecture's normal floating point format) of the correct size for
43194 @var{bitsize}. The default is @code{int}.
43197 The register group to which this register belongs. It can be one of the
43198 standard register groups @code{general}, @code{float}, @code{vector} or an
43199 arbitrary string. Group names should be limited to alphanumeric characters.
43200 If a group name is made up of multiple words the words may be separated by
43201 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43202 @var{group} is specified, @value{GDBN} will not display the register in
43203 @code{info registers}.
43207 @node Predefined Target Types
43208 @section Predefined Target Types
43209 @cindex target descriptions, predefined types
43211 Type definitions in the self-description can build up composite types
43212 from basic building blocks, but can not define fundamental types. Instead,
43213 standard identifiers are provided by @value{GDBN} for the fundamental
43214 types. The currently supported types are:
43219 Boolean type, occupying a single bit.
43227 Signed integer types holding the specified number of bits.
43235 Unsigned integer types holding the specified number of bits.
43239 Pointers to unspecified code and data. The program counter and
43240 any dedicated return address register may be marked as code
43241 pointers; printing a code pointer converts it into a symbolic
43242 address. The stack pointer and any dedicated address registers
43243 may be marked as data pointers.
43246 Single precision IEEE floating point.
43249 Double precision IEEE floating point.
43252 The 12-byte extended precision format used by ARM FPA registers.
43255 The 10-byte extended precision format used by x87 registers.
43258 32bit @sc{eflags} register used by x86.
43261 32bit @sc{mxcsr} register used by x86.
43265 @node Enum Target Types
43266 @section Enum Target Types
43267 @cindex target descriptions, enum types
43269 Enum target types are useful in @samp{struct} and @samp{flags}
43270 register descriptions. @xref{Target Description Format}.
43272 Enum types have a name, size and a list of name/value pairs.
43275 <enum id="@var{id}" size="@var{size}">
43276 <evalue name="@var{name}" value="@var{value}"/>
43281 Enums must be defined before they are used.
43284 <enum id="levels_type" size="4">
43285 <evalue name="low" value="0"/>
43286 <evalue name="high" value="1"/>
43288 <flags id="flags_type" size="4">
43289 <field name="X" start="0"/>
43290 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43292 <reg name="flags" bitsize="32" type="flags_type"/>
43295 Given that description, a value of 3 for the @samp{flags} register
43296 would be printed as:
43299 (gdb) info register flags
43300 flags 0x3 [ X LEVEL=high ]
43303 @node Standard Target Features
43304 @section Standard Target Features
43305 @cindex target descriptions, standard features
43307 A target description must contain either no registers or all the
43308 target's registers. If the description contains no registers, then
43309 @value{GDBN} will assume a default register layout, selected based on
43310 the architecture. If the description contains any registers, the
43311 default layout will not be used; the standard registers must be
43312 described in the target description, in such a way that @value{GDBN}
43313 can recognize them.
43315 This is accomplished by giving specific names to feature elements
43316 which contain standard registers. @value{GDBN} will look for features
43317 with those names and verify that they contain the expected registers;
43318 if any known feature is missing required registers, or if any required
43319 feature is missing, @value{GDBN} will reject the target
43320 description. You can add additional registers to any of the
43321 standard features --- @value{GDBN} will display them just as if
43322 they were added to an unrecognized feature.
43324 This section lists the known features and their expected contents.
43325 Sample XML documents for these features are included in the
43326 @value{GDBN} source tree, in the directory @file{gdb/features}.
43328 Names recognized by @value{GDBN} should include the name of the
43329 company or organization which selected the name, and the overall
43330 architecture to which the feature applies; so e.g.@: the feature
43331 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43333 The names of registers are not case sensitive for the purpose
43334 of recognizing standard features, but @value{GDBN} will only display
43335 registers using the capitalization used in the description.
43338 * AArch64 Features::
43342 * MicroBlaze Features::
43346 * Nios II Features::
43347 * OpenRISC 1000 Features::
43348 * PowerPC Features::
43349 * RISC-V Features::
43350 * S/390 and System z Features::
43356 @node AArch64 Features
43357 @subsection AArch64 Features
43358 @cindex target descriptions, AArch64 features
43360 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43361 targets. It should contain registers @samp{x0} through @samp{x30},
43362 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43364 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43365 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43368 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43369 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43370 through @samp{p15}, @samp{ffr} and @samp{vg}.
43372 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43373 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43376 @subsection ARC Features
43377 @cindex target descriptions, ARC Features
43379 ARC processors are highly configurable, so even core registers and their number
43380 are not completely predetermined. In addition flags and PC registers which are
43381 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43382 that one of the core registers features is present.
43383 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43385 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43386 targets with a normal register file. It should contain registers @samp{r0}
43387 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43388 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43389 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43390 @samp{ilink} and extension core registers are not available to read/write, when
43391 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43393 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43394 ARC HS targets with a reduced register file. It should contain registers
43395 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43396 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43397 This feature may contain register @samp{ilink} and any of extension core
43398 registers @samp{r32} through @samp{r59/acch}.
43400 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43401 targets with a normal register file. It should contain registers @samp{r0}
43402 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43403 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43404 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43405 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43406 registers are not available when debugging GNU/Linux applications. The only
43407 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43408 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43409 ARC v2, but @samp{ilink2} is optional on ARCompact.
43411 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43412 targets. It should contain registers @samp{pc} and @samp{status32}.
43415 @subsection ARM Features
43416 @cindex target descriptions, ARM features
43418 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43420 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43421 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43423 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43424 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43425 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43428 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43429 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43431 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43432 it should contain at least registers @samp{wR0} through @samp{wR15} and
43433 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43434 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43436 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43437 should contain at least registers @samp{d0} through @samp{d15}. If
43438 they are present, @samp{d16} through @samp{d31} should also be included.
43439 @value{GDBN} will synthesize the single-precision registers from
43440 halves of the double-precision registers.
43442 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43443 need to contain registers; it instructs @value{GDBN} to display the
43444 VFP double-precision registers as vectors and to synthesize the
43445 quad-precision registers from pairs of double-precision registers.
43446 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43447 be present and include 32 double-precision registers.
43449 @node i386 Features
43450 @subsection i386 Features
43451 @cindex target descriptions, i386 features
43453 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43454 targets. It should describe the following registers:
43458 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43460 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43462 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43463 @samp{fs}, @samp{gs}
43465 @samp{st0} through @samp{st7}
43467 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43468 @samp{foseg}, @samp{fooff} and @samp{fop}
43471 The register sets may be different, depending on the target.
43473 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43474 describe registers:
43478 @samp{xmm0} through @samp{xmm7} for i386
43480 @samp{xmm0} through @samp{xmm15} for amd64
43485 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43486 @samp{org.gnu.gdb.i386.sse} feature. It should
43487 describe the upper 128 bits of @sc{ymm} registers:
43491 @samp{ymm0h} through @samp{ymm7h} for i386
43493 @samp{ymm0h} through @samp{ymm15h} for amd64
43496 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43497 Memory Protection Extension (MPX). It should describe the following registers:
43501 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43503 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43506 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43507 describe a single register, @samp{orig_eax}.
43509 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43510 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43512 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43513 @samp{org.gnu.gdb.i386.avx} feature. It should
43514 describe additional @sc{xmm} registers:
43518 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43521 It should describe the upper 128 bits of additional @sc{ymm} registers:
43525 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43529 describe the upper 256 bits of @sc{zmm} registers:
43533 @samp{zmm0h} through @samp{zmm7h} for i386.
43535 @samp{zmm0h} through @samp{zmm15h} for amd64.
43539 describe the additional @sc{zmm} registers:
43543 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43546 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43547 describe a single register, @samp{pkru}. It is a 32-bit register
43548 valid for i386 and amd64.
43550 @node MicroBlaze Features
43551 @subsection MicroBlaze Features
43552 @cindex target descriptions, MicroBlaze features
43554 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43555 targets. It should contain registers @samp{r0} through @samp{r31},
43556 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43557 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43558 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43560 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43561 If present, it should contain registers @samp{rshr} and @samp{rslr}
43563 @node MIPS Features
43564 @subsection @acronym{MIPS} Features
43565 @cindex target descriptions, @acronym{MIPS} features
43567 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43568 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43569 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43572 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43573 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43574 registers. They may be 32-bit or 64-bit depending on the target.
43576 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43577 it may be optional in a future version of @value{GDBN}. It should
43578 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43579 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43581 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43582 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43583 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43584 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43586 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43587 contain a single register, @samp{restart}, which is used by the
43588 Linux kernel to control restartable syscalls.
43590 @node M68K Features
43591 @subsection M68K Features
43592 @cindex target descriptions, M68K features
43595 @item @samp{org.gnu.gdb.m68k.core}
43596 @itemx @samp{org.gnu.gdb.coldfire.core}
43597 @itemx @samp{org.gnu.gdb.fido.core}
43598 One of those features must be always present.
43599 The feature that is present determines which flavor of m68k is
43600 used. The feature that is present should contain registers
43601 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43602 @samp{sp}, @samp{ps} and @samp{pc}.
43604 @item @samp{org.gnu.gdb.coldfire.fp}
43605 This feature is optional. If present, it should contain registers
43606 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43610 @node NDS32 Features
43611 @subsection NDS32 Features
43612 @cindex target descriptions, NDS32 features
43614 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43615 targets. It should contain at least registers @samp{r0} through
43616 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43619 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43620 it should contain 64-bit double-precision floating-point registers
43621 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43622 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43624 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43625 registers are overlapped with the thirty-two 32-bit single-precision
43626 floating-point registers. The 32-bit single-precision registers, if
43627 not being listed explicitly, will be synthesized from halves of the
43628 overlapping 64-bit double-precision registers. Listing 32-bit
43629 single-precision registers explicitly is deprecated, and the
43630 support to it could be totally removed some day.
43632 @node Nios II Features
43633 @subsection Nios II Features
43634 @cindex target descriptions, Nios II features
43636 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43637 targets. It should contain the 32 core registers (@samp{zero},
43638 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43639 @samp{pc}, and the 16 control registers (@samp{status} through
43642 @node OpenRISC 1000 Features
43643 @subsection Openrisc 1000 Features
43644 @cindex target descriptions, OpenRISC 1000 features
43646 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43647 targets. It should contain the 32 general purpose registers (@samp{r0}
43648 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43650 @node PowerPC Features
43651 @subsection PowerPC Features
43652 @cindex target descriptions, PowerPC features
43654 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43655 targets. It should contain registers @samp{r0} through @samp{r31},
43656 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43657 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43659 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43660 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43662 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43663 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43664 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43665 through @samp{v31} as aliases for the corresponding @samp{vrX}
43668 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43669 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43670 combine these registers with the floating point registers (@samp{f0}
43671 through @samp{f31}) and the altivec registers (@samp{vr0} through
43672 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43673 @samp{vs63}, the set of vector-scalar registers for POWER7.
43674 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43675 @samp{org.gnu.gdb.power.altivec}.
43677 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43678 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43679 @samp{spefscr}. SPE targets should provide 32-bit registers in
43680 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43681 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43682 these to present registers @samp{ev0} through @samp{ev31} to the
43685 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43686 contain the 64-bit register @samp{ppr}.
43688 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43689 contain the 64-bit register @samp{dscr}.
43691 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43692 contain the 64-bit register @samp{tar}.
43694 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43695 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43698 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43699 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43700 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43701 server PMU registers provided by @sc{gnu}/Linux.
43703 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43704 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43707 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43708 contain the checkpointed general-purpose registers @samp{cr0} through
43709 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43710 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43711 depending on the target. It should also contain the checkpointed
43712 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43715 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43716 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43717 through @samp{cf31}, as well as the checkpointed 64-bit register
43720 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43721 should contain the checkpointed altivec registers @samp{cvr0} through
43722 @samp{cvr31}, all 128-bit wide. It should also contain the
43723 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43726 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43727 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43728 will combine these registers with the checkpointed floating point
43729 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43730 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43731 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43732 @samp{cvs63}. Therefore, this feature requires both
43733 @samp{org.gnu.gdb.power.htm.altivec} and
43734 @samp{org.gnu.gdb.power.htm.fpu}.
43736 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43737 contain the 64-bit checkpointed register @samp{cppr}.
43739 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43740 contain the 64-bit checkpointed register @samp{cdscr}.
43742 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43743 contain the 64-bit checkpointed register @samp{ctar}.
43746 @node RISC-V Features
43747 @subsection RISC-V Features
43748 @cindex target descriptions, RISC-V Features
43750 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43751 targets. It should contain the registers @samp{x0} through
43752 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43753 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43756 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43757 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43758 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43759 architectural register names, or the ABI names can be used.
43761 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43762 it should contain registers that are not backed by real registers on
43763 the target, but are instead virtual, where the register value is
43764 derived from other target state. In many ways these are like
43765 @value{GDBN}s pseudo-registers, except implemented by the target.
43766 Currently the only register expected in this set is the one byte
43767 @samp{priv} register that contains the target's privilege level in the
43768 least significant two bits.
43770 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43771 should contain all of the target's standard CSRs. Standard CSRs are
43772 those defined in the RISC-V specification documents. There is some
43773 overlap between this feature and the fpu feature; the @samp{fflags},
43774 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43775 expectation is that these registers will be in the fpu feature if the
43776 target has floating point hardware, but can be moved into the csr
43777 feature if the target has the floating point control registers, but no
43778 other floating point hardware.
43780 @node S/390 and System z Features
43781 @subsection S/390 and System z Features
43782 @cindex target descriptions, S/390 features
43783 @cindex target descriptions, System z features
43785 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43786 System z targets. It should contain the PSW and the 16 general
43787 registers. In particular, System z targets should provide the 64-bit
43788 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43789 S/390 targets should provide the 32-bit versions of these registers.
43790 A System z target that runs in 31-bit addressing mode should provide
43791 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43792 register's upper halves @samp{r0h} through @samp{r15h}, and their
43793 lower halves @samp{r0l} through @samp{r15l}.
43795 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43796 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43799 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43800 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43802 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43803 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43804 targets and 32-bit otherwise. In addition, the feature may contain
43805 the @samp{last_break} register, whose width depends on the addressing
43806 mode, as well as the @samp{system_call} register, which is always
43809 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43810 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43811 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43813 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43814 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43815 combined by @value{GDBN} with the floating point registers @samp{f0}
43816 through @samp{f15} to present the 128-bit wide vector registers
43817 @samp{v0} through @samp{v15}. In addition, this feature should
43818 contain the 128-bit wide vector registers @samp{v16} through
43821 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43822 the 64-bit wide guarded-storage-control registers @samp{gsd},
43823 @samp{gssm}, and @samp{gsepla}.
43825 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43826 the 64-bit wide guarded-storage broadcast control registers
43827 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43829 @node Sparc Features
43830 @subsection Sparc Features
43831 @cindex target descriptions, sparc32 features
43832 @cindex target descriptions, sparc64 features
43833 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43834 targets. It should describe the following registers:
43838 @samp{g0} through @samp{g7}
43840 @samp{o0} through @samp{o7}
43842 @samp{l0} through @samp{l7}
43844 @samp{i0} through @samp{i7}
43847 They may be 32-bit or 64-bit depending on the target.
43849 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43850 targets. It should describe the following registers:
43854 @samp{f0} through @samp{f31}
43856 @samp{f32} through @samp{f62} for sparc64
43859 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43860 targets. It should describe the following registers:
43864 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43865 @samp{fsr}, and @samp{csr} for sparc32
43867 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43871 @node TIC6x Features
43872 @subsection TMS320C6x Features
43873 @cindex target descriptions, TIC6x features
43874 @cindex target descriptions, TMS320C6x features
43875 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43876 targets. It should contain registers @samp{A0} through @samp{A15},
43877 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43879 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43880 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43881 through @samp{B31}.
43883 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43884 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43886 @node Operating System Information
43887 @appendix Operating System Information
43888 @cindex operating system information
43894 Users of @value{GDBN} often wish to obtain information about the state of
43895 the operating system running on the target---for example the list of
43896 processes, or the list of open files. This section describes the
43897 mechanism that makes it possible. This mechanism is similar to the
43898 target features mechanism (@pxref{Target Descriptions}), but focuses
43899 on a different aspect of target.
43901 Operating system information is retrived from the target via the
43902 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43903 read}). The object name in the request should be @samp{osdata}, and
43904 the @var{annex} identifies the data to be fetched.
43907 @appendixsection Process list
43908 @cindex operating system information, process list
43910 When requesting the process list, the @var{annex} field in the
43911 @samp{qXfer} request should be @samp{processes}. The returned data is
43912 an XML document. The formal syntax of this document is defined in
43913 @file{gdb/features/osdata.dtd}.
43915 An example document is:
43918 <?xml version="1.0"?>
43919 <!DOCTYPE target SYSTEM "osdata.dtd">
43920 <osdata type="processes">
43922 <column name="pid">1</column>
43923 <column name="user">root</column>
43924 <column name="command">/sbin/init</column>
43925 <column name="cores">1,2,3</column>
43930 Each item should include a column whose name is @samp{pid}. The value
43931 of that column should identify the process on the target. The
43932 @samp{user} and @samp{command} columns are optional, and will be
43933 displayed by @value{GDBN}. The @samp{cores} column, if present,
43934 should contain a comma-separated list of cores that this process
43935 is running on. Target may provide additional columns,
43936 which @value{GDBN} currently ignores.
43938 @node Trace File Format
43939 @appendix Trace File Format
43940 @cindex trace file format
43942 The trace file comes in three parts: a header, a textual description
43943 section, and a trace frame section with binary data.
43945 The header has the form @code{\x7fTRACE0\n}. The first byte is
43946 @code{0x7f} so as to indicate that the file contains binary data,
43947 while the @code{0} is a version number that may have different values
43950 The description section consists of multiple lines of @sc{ascii} text
43951 separated by newline characters (@code{0xa}). The lines may include a
43952 variety of optional descriptive or context-setting information, such
43953 as tracepoint definitions or register set size. @value{GDBN} will
43954 ignore any line that it does not recognize. An empty line marks the end
43959 Specifies the size of a register block in bytes. This is equal to the
43960 size of a @code{g} packet payload in the remote protocol. @var{size}
43961 is an ascii decimal number. There should be only one such line in
43962 a single trace file.
43964 @item status @var{status}
43965 Trace status. @var{status} has the same format as a @code{qTStatus}
43966 remote packet reply. There should be only one such line in a single trace
43969 @item tp @var{payload}
43970 Tracepoint definition. The @var{payload} has the same format as
43971 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43972 may take multiple lines of definition, corresponding to the multiple
43975 @item tsv @var{payload}
43976 Trace state variable definition. The @var{payload} has the same format as
43977 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43978 may take multiple lines of definition, corresponding to the multiple
43981 @item tdesc @var{payload}
43982 Target description in XML format. The @var{payload} is a single line of
43983 the XML file. All such lines should be concatenated together to get
43984 the original XML file. This file is in the same format as @code{qXfer}
43985 @code{features} payload, and corresponds to the main @code{target.xml}
43986 file. Includes are not allowed.
43990 The trace frame section consists of a number of consecutive frames.
43991 Each frame begins with a two-byte tracepoint number, followed by a
43992 four-byte size giving the amount of data in the frame. The data in
43993 the frame consists of a number of blocks, each introduced by a
43994 character indicating its type (at least register, memory, and trace
43995 state variable). The data in this section is raw binary, not a
43996 hexadecimal or other encoding; its endianness matches the target's
43999 @c FIXME bi-arch may require endianness/arch info in description section
44002 @item R @var{bytes}
44003 Register block. The number and ordering of bytes matches that of a
44004 @code{g} packet in the remote protocol. Note that these are the
44005 actual bytes, in target order, not a hexadecimal encoding.
44007 @item M @var{address} @var{length} @var{bytes}...
44008 Memory block. This is a contiguous block of memory, at the 8-byte
44009 address @var{address}, with a 2-byte length @var{length}, followed by
44010 @var{length} bytes.
44012 @item V @var{number} @var{value}
44013 Trace state variable block. This records the 8-byte signed value
44014 @var{value} of trace state variable numbered @var{number}.
44018 Future enhancements of the trace file format may include additional types
44021 @node Index Section Format
44022 @appendix @code{.gdb_index} section format
44023 @cindex .gdb_index section format
44024 @cindex index section format
44026 This section documents the index section that is created by @code{save
44027 gdb-index} (@pxref{Index Files}). The index section is
44028 DWARF-specific; some knowledge of DWARF is assumed in this
44031 The mapped index file format is designed to be directly
44032 @code{mmap}able on any architecture. In most cases, a datum is
44033 represented using a little-endian 32-bit integer value, called an
44034 @code{offset_type}. Big endian machines must byte-swap the values
44035 before using them. Exceptions to this rule are noted. The data is
44036 laid out such that alignment is always respected.
44038 A mapped index consists of several areas, laid out in order.
44042 The file header. This is a sequence of values, of @code{offset_type}
44043 unless otherwise noted:
44047 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
44048 Version 4 uses a different hashing function from versions 5 and 6.
44049 Version 6 includes symbols for inlined functions, whereas versions 4
44050 and 5 do not. Version 7 adds attributes to the CU indices in the
44051 symbol table. Version 8 specifies that symbols from DWARF type units
44052 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
44053 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
44055 @value{GDBN} will only read version 4, 5, or 6 indices
44056 by specifying @code{set use-deprecated-index-sections on}.
44057 GDB has a workaround for potentially broken version 7 indices so it is
44058 currently not flagged as deprecated.
44061 The offset, from the start of the file, of the CU list.
44064 The offset, from the start of the file, of the types CU list. Note
44065 that this area can be empty, in which case this offset will be equal
44066 to the next offset.
44069 The offset, from the start of the file, of the address area.
44072 The offset, from the start of the file, of the symbol table.
44075 The offset, from the start of the file, of the constant pool.
44079 The CU list. This is a sequence of pairs of 64-bit little-endian
44080 values, sorted by the CU offset. The first element in each pair is
44081 the offset of a CU in the @code{.debug_info} section. The second
44082 element in each pair is the length of that CU. References to a CU
44083 elsewhere in the map are done using a CU index, which is just the
44084 0-based index into this table. Note that if there are type CUs, then
44085 conceptually CUs and type CUs form a single list for the purposes of
44089 The types CU list. This is a sequence of triplets of 64-bit
44090 little-endian values. In a triplet, the first value is the CU offset,
44091 the second value is the type offset in the CU, and the third value is
44092 the type signature. The types CU list is not sorted.
44095 The address area. The address area consists of a sequence of address
44096 entries. Each address entry has three elements:
44100 The low address. This is a 64-bit little-endian value.
44103 The high address. This is a 64-bit little-endian value. Like
44104 @code{DW_AT_high_pc}, the value is one byte beyond the end.
44107 The CU index. This is an @code{offset_type} value.
44111 The symbol table. This is an open-addressed hash table. The size of
44112 the hash table is always a power of 2.
44114 Each slot in the hash table consists of a pair of @code{offset_type}
44115 values. The first value is the offset of the symbol's name in the
44116 constant pool. The second value is the offset of the CU vector in the
44119 If both values are 0, then this slot in the hash table is empty. This
44120 is ok because while 0 is a valid constant pool index, it cannot be a
44121 valid index for both a string and a CU vector.
44123 The hash value for a table entry is computed by applying an
44124 iterative hash function to the symbol's name. Starting with an
44125 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
44126 the string is incorporated into the hash using the formula depending on the
44131 The formula is @code{r = r * 67 + c - 113}.
44133 @item Versions 5 to 7
44134 The formula is @code{r = r * 67 + tolower (c) - 113}.
44137 The terminating @samp{\0} is not incorporated into the hash.
44139 The step size used in the hash table is computed via
44140 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
44141 value, and @samp{size} is the size of the hash table. The step size
44142 is used to find the next candidate slot when handling a hash
44145 The names of C@t{++} symbols in the hash table are canonicalized. We
44146 don't currently have a simple description of the canonicalization
44147 algorithm; if you intend to create new index sections, you must read
44151 The constant pool. This is simply a bunch of bytes. It is organized
44152 so that alignment is correct: CU vectors are stored first, followed by
44155 A CU vector in the constant pool is a sequence of @code{offset_type}
44156 values. The first value is the number of CU indices in the vector.
44157 Each subsequent value is the index and symbol attributes of a CU in
44158 the CU list. This element in the hash table is used to indicate which
44159 CUs define the symbol and how the symbol is used.
44160 See below for the format of each CU index+attributes entry.
44162 A string in the constant pool is zero-terminated.
44165 Attributes were added to CU index values in @code{.gdb_index} version 7.
44166 If a symbol has multiple uses within a CU then there is one
44167 CU index+attributes value for each use.
44169 The format of each CU index+attributes entry is as follows
44175 This is the index of the CU in the CU list.
44177 These bits are reserved for future purposes and must be zero.
44179 The kind of the symbol in the CU.
44183 This value is reserved and should not be used.
44184 By reserving zero the full @code{offset_type} value is backwards compatible
44185 with previous versions of the index.
44187 The symbol is a type.
44189 The symbol is a variable or an enum value.
44191 The symbol is a function.
44193 Any other kind of symbol.
44195 These values are reserved.
44199 This bit is zero if the value is global and one if it is static.
44201 The determination of whether a symbol is global or static is complicated.
44202 The authorative reference is the file @file{dwarf2read.c} in
44203 @value{GDBN} sources.
44207 This pseudo-code describes the computation of a symbol's kind and
44208 global/static attributes in the index.
44211 is_external = get_attribute (die, DW_AT_external);
44212 language = get_attribute (cu_die, DW_AT_language);
44215 case DW_TAG_typedef:
44216 case DW_TAG_base_type:
44217 case DW_TAG_subrange_type:
44221 case DW_TAG_enumerator:
44223 is_static = language != CPLUS;
44225 case DW_TAG_subprogram:
44227 is_static = ! (is_external || language == ADA);
44229 case DW_TAG_constant:
44231 is_static = ! is_external;
44233 case DW_TAG_variable:
44235 is_static = ! is_external;
44237 case DW_TAG_namespace:
44241 case DW_TAG_class_type:
44242 case DW_TAG_interface_type:
44243 case DW_TAG_structure_type:
44244 case DW_TAG_union_type:
44245 case DW_TAG_enumeration_type:
44247 is_static = language != CPLUS;
44255 @appendix Manual pages
44259 * gdb man:: The GNU Debugger man page
44260 * gdbserver man:: Remote Server for the GNU Debugger man page
44261 * gcore man:: Generate a core file of a running program
44262 * gdbinit man:: gdbinit scripts
44263 * gdb-add-index man:: Add index files to speed up GDB
44269 @c man title gdb The GNU Debugger
44271 @c man begin SYNOPSIS gdb
44272 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44273 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44274 [@option{-b}@w{ }@var{bps}]
44275 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44276 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44277 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44278 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44279 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44282 @c man begin DESCRIPTION gdb
44283 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44284 going on ``inside'' another program while it executes -- or what another
44285 program was doing at the moment it crashed.
44287 @value{GDBN} can do four main kinds of things (plus other things in support of
44288 these) to help you catch bugs in the act:
44292 Start your program, specifying anything that might affect its behavior.
44295 Make your program stop on specified conditions.
44298 Examine what has happened, when your program has stopped.
44301 Change things in your program, so you can experiment with correcting the
44302 effects of one bug and go on to learn about another.
44305 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44308 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44309 commands from the terminal until you tell it to exit with the @value{GDBN}
44310 command @code{quit}. You can get online help from @value{GDBN} itself
44311 by using the command @code{help}.
44313 You can run @code{gdb} with no arguments or options; but the most
44314 usual way to start @value{GDBN} is with one argument or two, specifying an
44315 executable program as the argument:
44321 You can also start with both an executable program and a core file specified:
44327 You can, instead, specify a process ID as a second argument, if you want
44328 to debug a running process:
44336 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44337 named @file{1234}; @value{GDBN} does check for a core file first).
44338 With option @option{-p} you can omit the @var{program} filename.
44340 Here are some of the most frequently needed @value{GDBN} commands:
44342 @c pod2man highlights the right hand side of the @item lines.
44344 @item break [@var{file}:]@var{function}
44345 Set a breakpoint at @var{function} (in @var{file}).
44347 @item run [@var{arglist}]
44348 Start your program (with @var{arglist}, if specified).
44351 Backtrace: display the program stack.
44353 @item print @var{expr}
44354 Display the value of an expression.
44357 Continue running your program (after stopping, e.g. at a breakpoint).
44360 Execute next program line (after stopping); step @emph{over} any
44361 function calls in the line.
44363 @item edit [@var{file}:]@var{function}
44364 look at the program line where it is presently stopped.
44366 @item list [@var{file}:]@var{function}
44367 type the text of the program in the vicinity of where it is presently stopped.
44370 Execute next program line (after stopping); step @emph{into} any
44371 function calls in the line.
44373 @item help [@var{name}]
44374 Show information about @value{GDBN} command @var{name}, or general information
44375 about using @value{GDBN}.
44378 Exit from @value{GDBN}.
44382 For full details on @value{GDBN},
44383 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44384 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44385 as the @code{gdb} entry in the @code{info} program.
44389 @c man begin OPTIONS gdb
44390 Any arguments other than options specify an executable
44391 file and core file (or process ID); that is, the first argument
44392 encountered with no
44393 associated option flag is equivalent to a @option{-se} option, and the second,
44394 if any, is equivalent to a @option{-c} option if it's the name of a file.
44396 both long and short forms; both are shown here. The long forms are also
44397 recognized if you truncate them, so long as enough of the option is
44398 present to be unambiguous. (If you prefer, you can flag option
44399 arguments with @option{+} rather than @option{-}, though we illustrate the
44400 more usual convention.)
44402 All the options and command line arguments you give are processed
44403 in sequential order. The order makes a difference when the @option{-x}
44409 List all options, with brief explanations.
44411 @item -symbols=@var{file}
44412 @itemx -s @var{file}
44413 Read symbol table from file @var{file}.
44416 Enable writing into executable and core files.
44418 @item -exec=@var{file}
44419 @itemx -e @var{file}
44420 Use file @var{file} as the executable file to execute when
44421 appropriate, and for examining pure data in conjunction with a core
44424 @item -se=@var{file}
44425 Read symbol table from file @var{file} and use it as the executable
44428 @item -core=@var{file}
44429 @itemx -c @var{file}
44430 Use file @var{file} as a core dump to examine.
44432 @item -command=@var{file}
44433 @itemx -x @var{file}
44434 Execute @value{GDBN} commands from file @var{file}.
44436 @item -ex @var{command}
44437 Execute given @value{GDBN} @var{command}.
44439 @item -directory=@var{directory}
44440 @itemx -d @var{directory}
44441 Add @var{directory} to the path to search for source files.
44444 Do not execute commands from @file{~/.gdbinit}.
44448 Do not execute commands from any @file{.gdbinit} initialization files.
44452 ``Quiet''. Do not print the introductory and copyright messages. These
44453 messages are also suppressed in batch mode.
44456 Run in batch mode. Exit with status @code{0} after processing all the command
44457 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44458 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44459 commands in the command files.
44461 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44462 download and run a program on another computer; in order to make this
44463 more useful, the message
44466 Program exited normally.
44470 (which is ordinarily issued whenever a program running under @value{GDBN} control
44471 terminates) is not issued when running in batch mode.
44473 @item -cd=@var{directory}
44474 Run @value{GDBN} using @var{directory} as its working directory,
44475 instead of the current directory.
44479 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44480 @value{GDBN} to output the full file name and line number in a standard,
44481 recognizable fashion each time a stack frame is displayed (which
44482 includes each time the program stops). This recognizable format looks
44483 like two @samp{\032} characters, followed by the file name, line number
44484 and character position separated by colons, and a newline. The
44485 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44486 characters as a signal to display the source code for the frame.
44489 Set the line speed (baud rate or bits per second) of any serial
44490 interface used by @value{GDBN} for remote debugging.
44492 @item -tty=@var{device}
44493 Run using @var{device} for your program's standard input and output.
44497 @c man begin SEEALSO gdb
44499 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44500 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44501 documentation are properly installed at your site, the command
44508 should give you access to the complete manual.
44510 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44511 Richard M. Stallman and Roland H. Pesch, July 1991.
44515 @node gdbserver man
44516 @heading gdbserver man
44518 @c man title gdbserver Remote Server for the GNU Debugger
44520 @c man begin SYNOPSIS gdbserver
44521 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44523 gdbserver --attach @var{comm} @var{pid}
44525 gdbserver --multi @var{comm}
44529 @c man begin DESCRIPTION gdbserver
44530 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44531 than the one which is running the program being debugged.
44534 @subheading Usage (server (target) side)
44537 Usage (server (target) side):
44540 First, you need to have a copy of the program you want to debug put onto
44541 the target system. The program can be stripped to save space if needed, as
44542 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44543 the @value{GDBN} running on the host system.
44545 To use the server, you log on to the target system, and run the @command{gdbserver}
44546 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44547 your program, and (c) its arguments. The general syntax is:
44550 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44553 For example, using a serial port, you might say:
44557 @c @file would wrap it as F</dev/com1>.
44558 target> gdbserver /dev/com1 emacs foo.txt
44561 target> gdbserver @file{/dev/com1} emacs foo.txt
44565 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44566 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44567 waits patiently for the host @value{GDBN} to communicate with it.
44569 To use a TCP connection, you could say:
44572 target> gdbserver host:2345 emacs foo.txt
44575 This says pretty much the same thing as the last example, except that we are
44576 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44577 that we are expecting to see a TCP connection from @code{host} to local TCP port
44578 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44579 want for the port number as long as it does not conflict with any existing TCP
44580 ports on the target system. This same port number must be used in the host
44581 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44582 you chose a port number that conflicts with another service, @command{gdbserver} will
44583 print an error message and exit.
44585 @command{gdbserver} can also attach to running programs.
44586 This is accomplished via the @option{--attach} argument. The syntax is:
44589 target> gdbserver --attach @var{comm} @var{pid}
44592 @var{pid} is the process ID of a currently running process. It isn't
44593 necessary to point @command{gdbserver} at a binary for the running process.
44595 To start @code{gdbserver} without supplying an initial command to run
44596 or process ID to attach, use the @option{--multi} command line option.
44597 In such case you should connect using @kbd{target extended-remote} to start
44598 the program you want to debug.
44601 target> gdbserver --multi @var{comm}
44605 @subheading Usage (host side)
44611 You need an unstripped copy of the target program on your host system, since
44612 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44613 would, with the target program as the first argument. (You may need to use the
44614 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44615 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44616 new command you need to know about is @code{target remote}
44617 (or @code{target extended-remote}). Its argument is either
44618 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44619 descriptor. For example:
44623 @c @file would wrap it as F</dev/ttyb>.
44624 (gdb) target remote /dev/ttyb
44627 (gdb) target remote @file{/dev/ttyb}
44632 communicates with the server via serial line @file{/dev/ttyb}, and:
44635 (gdb) target remote the-target:2345
44639 communicates via a TCP connection to port 2345 on host `the-target', where
44640 you previously started up @command{gdbserver} with the same port number. Note that for
44641 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44642 command, otherwise you may get an error that looks something like
44643 `Connection refused'.
44645 @command{gdbserver} can also debug multiple inferiors at once,
44648 the @value{GDBN} manual in node @code{Inferiors and Programs}
44649 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44652 @ref{Inferiors and Programs}.
44654 In such case use the @code{extended-remote} @value{GDBN} command variant:
44657 (gdb) target extended-remote the-target:2345
44660 The @command{gdbserver} option @option{--multi} may or may not be used in such
44664 @c man begin OPTIONS gdbserver
44665 There are three different modes for invoking @command{gdbserver}:
44670 Debug a specific program specified by its program name:
44673 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44676 The @var{comm} parameter specifies how should the server communicate
44677 with @value{GDBN}; it is either a device name (to use a serial line),
44678 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44679 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44680 debug in @var{prog}. Any remaining arguments will be passed to the
44681 program verbatim. When the program exits, @value{GDBN} will close the
44682 connection, and @code{gdbserver} will exit.
44685 Debug a specific program by specifying the process ID of a running
44689 gdbserver --attach @var{comm} @var{pid}
44692 The @var{comm} parameter is as described above. Supply the process ID
44693 of a running program in @var{pid}; @value{GDBN} will do everything
44694 else. Like with the previous mode, when the process @var{pid} exits,
44695 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44698 Multi-process mode -- debug more than one program/process:
44701 gdbserver --multi @var{comm}
44704 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44705 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44706 close the connection when a process being debugged exits, so you can
44707 debug several processes in the same session.
44710 In each of the modes you may specify these options:
44715 List all options, with brief explanations.
44718 This option causes @command{gdbserver} to print its version number and exit.
44721 @command{gdbserver} will attach to a running program. The syntax is:
44724 target> gdbserver --attach @var{comm} @var{pid}
44727 @var{pid} is the process ID of a currently running process. It isn't
44728 necessary to point @command{gdbserver} at a binary for the running process.
44731 To start @code{gdbserver} without supplying an initial command to run
44732 or process ID to attach, use this command line option.
44733 Then you can connect using @kbd{target extended-remote} and start
44734 the program you want to debug. The syntax is:
44737 target> gdbserver --multi @var{comm}
44741 Instruct @code{gdbserver} to display extra status information about the debugging
44743 This option is intended for @code{gdbserver} development and for bug reports to
44746 @item --remote-debug
44747 Instruct @code{gdbserver} to display remote protocol debug output.
44748 This option is intended for @code{gdbserver} development and for bug reports to
44751 @item --debug-file=@var{filename}
44752 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
44753 This option is intended for @code{gdbserver} development and for bug reports to
44756 @item --debug-format=option1@r{[},option2,...@r{]}
44757 Instruct @code{gdbserver} to include extra information in each line
44758 of debugging output.
44759 @xref{Other Command-Line Arguments for gdbserver}.
44762 Specify a wrapper to launch programs
44763 for debugging. The option should be followed by the name of the
44764 wrapper, then any command-line arguments to pass to the wrapper, then
44765 @kbd{--} indicating the end of the wrapper arguments.
44768 By default, @command{gdbserver} keeps the listening TCP port open, so that
44769 additional connections are possible. However, if you start @code{gdbserver}
44770 with the @option{--once} option, it will stop listening for any further
44771 connection attempts after connecting to the first @value{GDBN} session.
44773 @c --disable-packet is not documented for users.
44775 @c --disable-randomization and --no-disable-randomization are superseded by
44776 @c QDisableRandomization.
44781 @c man begin SEEALSO gdbserver
44783 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44784 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44785 documentation are properly installed at your site, the command
44791 should give you access to the complete manual.
44793 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44794 Richard M. Stallman and Roland H. Pesch, July 1991.
44801 @c man title gcore Generate a core file of a running program
44804 @c man begin SYNOPSIS gcore
44805 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44809 @c man begin DESCRIPTION gcore
44810 Generate core dumps of one or more running programs with process IDs
44811 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44812 is equivalent to one produced by the kernel when the process crashes
44813 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44814 limit). However, unlike after a crash, after @command{gcore} finishes
44815 its job the program remains running without any change.
44818 @c man begin OPTIONS gcore
44821 Dump all memory mappings. The actual effect of this option depends on
44822 the Operating System. On @sc{gnu}/Linux, it will disable
44823 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44824 enable @code{dump-excluded-mappings} (@pxref{set
44825 dump-excluded-mappings}).
44827 @item -o @var{prefix}
44828 The optional argument @var{prefix} specifies the prefix to be used
44829 when composing the file names of the core dumps. The file name is
44830 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44831 process ID of the running program being analyzed by @command{gcore}.
44832 If not specified, @var{prefix} defaults to @var{gcore}.
44836 @c man begin SEEALSO gcore
44838 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44839 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44840 documentation are properly installed at your site, the command
44847 should give you access to the complete manual.
44849 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44850 Richard M. Stallman and Roland H. Pesch, July 1991.
44857 @c man title gdbinit GDB initialization scripts
44860 @c man begin SYNOPSIS gdbinit
44861 @ifset SYSTEM_GDBINIT
44862 @value{SYSTEM_GDBINIT}
44871 @c man begin DESCRIPTION gdbinit
44872 These files contain @value{GDBN} commands to automatically execute during
44873 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44876 the @value{GDBN} manual in node @code{Sequences}
44877 -- shell command @code{info -f gdb -n Sequences}.
44883 Please read more in
44885 the @value{GDBN} manual in node @code{Startup}
44886 -- shell command @code{info -f gdb -n Startup}.
44893 @ifset SYSTEM_GDBINIT
44894 @item @value{SYSTEM_GDBINIT}
44896 @ifclear SYSTEM_GDBINIT
44897 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44899 System-wide initialization file. It is executed unless user specified
44900 @value{GDBN} option @code{-nx} or @code{-n}.
44903 the @value{GDBN} manual in node @code{System-wide configuration}
44904 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44907 @ref{System-wide configuration}.
44911 User initialization file. It is executed unless user specified
44912 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44915 Initialization file for current directory. It may need to be enabled with
44916 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44919 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44920 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44923 @ref{Init File in the Current Directory}.
44928 @c man begin SEEALSO gdbinit
44930 gdb(1), @code{info -f gdb -n Startup}
44932 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44933 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44934 documentation are properly installed at your site, the command
44940 should give you access to the complete manual.
44942 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44943 Richard M. Stallman and Roland H. Pesch, July 1991.
44947 @node gdb-add-index man
44948 @heading gdb-add-index
44949 @pindex gdb-add-index
44950 @anchor{gdb-add-index}
44952 @c man title gdb-add-index Add index files to speed up GDB
44954 @c man begin SYNOPSIS gdb-add-index
44955 gdb-add-index @var{filename}
44958 @c man begin DESCRIPTION gdb-add-index
44959 When @value{GDBN} finds a symbol file, it scans the symbols in the
44960 file in order to construct an internal symbol table. This lets most
44961 @value{GDBN} operations work quickly--at the cost of a delay early on.
44962 For large programs, this delay can be quite lengthy, so @value{GDBN}
44963 provides a way to build an index, which speeds up startup.
44965 To determine whether a file contains such an index, use the command
44966 @kbd{readelf -S filename}: the index is stored in a section named
44967 @code{.gdb_index}. The index file can only be produced on systems
44968 which use ELF binaries and DWARF debug information (i.e., sections
44969 named @code{.debug_*}).
44971 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44972 in the @env{PATH} environment variable. If you want to use different
44973 versions of these programs, you can specify them through the
44974 @env{GDB} and @env{OBJDUMP} environment variables.
44978 the @value{GDBN} manual in node @code{Index Files}
44979 -- shell command @kbd{info -f gdb -n "Index Files"}.
44986 @c man begin SEEALSO gdb-add-index
44988 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44989 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44990 documentation are properly installed at your site, the command
44996 should give you access to the complete manual.
44998 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44999 Richard M. Stallman and Roland H. Pesch, July 1991.
45005 @node GNU Free Documentation License
45006 @appendix GNU Free Documentation License
45009 @node Concept Index
45010 @unnumbered Concept Index
45014 @node Command and Variable Index
45015 @unnumbered Command, Variable, and Function Index
45020 % I think something like @@colophon should be in texinfo. In the
45022 \long\def\colophon{\hbox to0pt{}\vfill
45023 \centerline{The body of this manual is set in}
45024 \centerline{\fontname\tenrm,}
45025 \centerline{with headings in {\bf\fontname\tenbf}}
45026 \centerline{and examples in {\tt\fontname\tentt}.}
45027 \centerline{{\it\fontname\tenit\/},}
45028 \centerline{{\bf\fontname\tenbf}, and}
45029 \centerline{{\sl\fontname\tensl\/}}
45030 \centerline{are used for emphasis.}\vfill}
45032 % Blame: doc@@cygnus.com, 1991.